Background. The surgical management of musculoskeletal tumours is a challenging problem, particularly in pelvic and diaphyseal tumour resection where accurate determination of bony transection points is extremely important to optimise oncologic, functional and reconstructive options. The use of computer assisted navigation in these cases could improve surgical precision. Materials and methods. We resected musculoskeletal tumours in fifteen patients using commercially available computer navigation software (Orthomap 3D). Results. Of the eight pelvic tumours, three underwent biological reconstruction with extra corporeal irradiation, three endoprosthetic replacement (EPR) and two required no bony reconstruction. Four diaphyseal tumours had biological reconstruction. Two patients with proximal femoral sarcoma underwent extra-articular resection and EPR. One soft tissue sarcoma of the adductor compartment involving the femur was resected with EPR. Histological examination of the resected specimens revealed tumour free margins in all cases. Post-operative radiographs and CT show resection and reconstruction as planned in all cases. Several learning points were identified related to juvenile bony anatomy and intra-operative registration. Discussion. The use of computer navigation in musculoskeletal oncology allows integration of local anatomy and tumour extent to identify resection margins accurately. Furthermore, it can aid in reconstruction following tumour resection. Our experience thus far has been encouraging

Surgical training has been greatly affected by the challenges of reduced training opportunities, shortened working hours, and financial pressures. There is an increased need for the use of training system in developing psychomotor skills of the surgical trainee for fracture fixation. The training system was developed to simulate dynamic hip screw fixation. 12 orthopaedic senior house officers performed dynamic hip screw fixation before and after the training on training system. The results were assessed based on the scoring system that included the amount of time taken, accuracy of guide wire placement and the number of exposures requested to complete the procedure. The result shows a significant improvement in amount of time taken, accuracy of fixation and the number of exposures after the training on simulator system. This was statistically significant using paired student t-test (p-value <0.05).

Computer navigated training system appears to be a good training tool for young orthopaedic trainees The system has the potential to be used in various other orthopaedic procedures for learning of technical skills aimed at ensuring a smooth escalation in task complexity leading to the better performance of procedures in the operating theatre.

To confirm whether developmental dysplasia of the hip has a risk of hip impingement, we analysed maximum ranges of movement to the point of bony impingement, and impingement location using three-dimensional (3D) surface models of the pelvis and femur in combination with 3D morphology of the hip joint using computer-assisted methods. Results of computed tomography were examined for 52 hip joints with DDH and 73 normal healthy hip joints. DDH shows larger maximum extension (p = 0.001) and internal rotation at 90° flexion (p < 0.001). Similar maximum flexion (p = 0.835) and external rotation (p = 0.713) were observed between groups, while high rates of extra-articular impingement were noticed in these directions in DDH (p < 0.001). Smaller cranial acetabular anteversion (p = 0.048), centre-edge angles (p < 0.001), a circumferentially shallower acetabulum, larger femoral neck anteversion (p < 0.001), and larger alpha angle were identified in DDH. Risk of anterior impingement in retroverted DDH hips is similar to that in retroverted normal hips in excessive adduction but minimal in less adduction. These findings might be borne in mind when considering the possibility of extra-articular posterior impingement in DDH being a source of pain, particularly for patients with a highly anteverted femoral neck.

Cite this article: Bone Joint J 2014;96-B:580–9.

We have investigated the benefits of patient specific instrument guides, applied to osteotomies around the knee. Single, dual and triple planar osteotomies were performed on tibias or femurs in 14 subjects. In all patients, a detailed pre-operative plan was prepared based upon full leg standing radiographic and CT scan information. The planned level of the osteotomy and open wedge resection was relayed to the surgery by virtue of a patient specific guide developed from the images. The mean deviation between the planned wedge angle and the executed wedge angle was 0° (-1 to 1, sd 0.71) in the coronal plane and 0.3° (-0.9 to 3, sd 1.14) in the sagittal plane. The mean deviation between the planned hip, knee, ankle angle (HKA) on full leg standing radiograph and the post-operative HKA was 0.3° (-1 to 2, sd 0.75). It is concluded that this is a feasible and valuable concept from the standpoint of pre-operative software based planning, surgical application and geometrical accuracy of outcome.

Cite this article: Bone Joint J 2013;95-B, Supple A:153–8.

Abstract. Introduction. Component mal-positioning in total hip replacement (THR) and total knee replacement (TKR) can increase the risk of revision for various reasons. Compared to conventional surgery, relatively improved accuracy of implant positioning can be achieved using computer assisted technologies including navigation, patient-specific jigs, and robotic systems. However, it is not known whether application of these technologies has improved prosthesis survival in the real-world. This study aimed to compare risk of revision for all-causes following primary THR and TKR, and revision for dislocation following primary THR performed using computer assisted technologies compared to conventional technique. Methods. We performed an observational study using National Joint Registry data. All adult patients undergoing primary THR and TKR for osteoarthritis between 01/04/2003 to 31/12/2020 were eligible. Patients who received metal-on-metal bearing THR were excluded. We generated propensity score weights, using Sturmer weight trimming, based on: age, gender, ASA grade, side, operation funding, year of surgery, approach, and fixation. Specific additional variables included position and bearing for THR and patellar resurfacing for TKR. For THR, effective sample sizes and duration of follow up for conventional versus computer-guided and robotic-assisted analyses were 9,379 and 10,600 procedures, and approximately 18 and 4 years, respectively. For TKR, effective sample sizes and durations of follow up for conventional versus computer-guided, patient-specific jigs, and robotic-assisted groups were 92,579 procedures over 18 years, 11,665 procedures over 8 years, and 644 procedures over 3 years, respectively. Outcomes were assessed using Kaplan-Meier analysis and expressed using hazard ratios (HR) and 95% confidence intervals (CI). Results. For THR, analysis comparing computer-guided versus conventional technique demonstrated HR of 0.771 (95%CI 0.573–1.036) p=0.085, and 0.594 (95%CI 0.297–1.190) p=0.142, for revision for all-causes and dislocation, respectively. When comparing robotic-assisted versus conventional technique, HR for revision for all-causes was 0.480 (95%CI 0.067 –3.452) p=0.466. For TKR, compared to conventional surgery, HR for all-cause revision for procedures performed using computer guidance and patient-specific jigs were 0.967 (95% CI 0.888–1.052) p=0.430, and 0.937 (95% CI 0.708–1.241) p=0.65, respectively. HR for analysis comparing robotic-assisted versus conventional technique was 2.0940 (0.2423, 18.0995) p = 0.50. Conclusions. This is the largest study investigating this topic utilising propensity score analysis methods. We did not find a statistically significant difference in revision for all-causes and dislocation although these analyses are underpowered to detect smaller differences in effect size between groups. Additional comparison for revision for dislocation between robotic-assisted versus conventionally performed THR was not performed as this is a subset of revision for all-causes and wide confidence intervals were already observed for that analysis. It is also important to mention this NJR analysis study is of an observational study design which has inherent limitations. Nonetheless, this is the most feasible study design to answer this research question requiring use of a large data set due to revision being a rare outcome. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Study design. Literature review of the best available evidence on the accuracy of computer assisted pedicle screw insertion. Background. Pedicle screw misplacement rates with the conventional insertion technique and adequate postoperative CT examination have ranged from 5 to 29 % in the cervical spine, from 3 to 58 % in the thoracic spine, and from 6 to 41% in the lumbosacral region. Despite these relatively high perforation rates, the incidence of reported screw-related complications has remained low. Interestingly, the highest rates of neurovascular injuries have been reported from the lumbosacral spine in up to 17% of the patients. Gertzbein and Robbins introduced a 4-mm “safe zone” in the thoracolumbar spine for medial encroachment, consisting of 2-mm of epidural and 2-mm of subarachnoid space. Later, several authors have found the safety margins to be significantly smaller, suggesting that the “safe zone” thresholds of Gertzbein and Robbins do not apply to the thoracic spine, and seem to be too high even for the lumbar spine. The midthoracic and midcervical spine, as well as the thoracolumbar junction set the highest demands for accuracy in pedicle screw insertion, with no room for either translational or rotational error at e.g. T5 level. Computer assisted pedicle screw insertion (navigation) was introduced in the early 90's to increase the accuracy and safety of pedicle screw insertion. Material. PubMed literature search revealed two randomized controlled trials (RCT) comparing the in vivo accuracy of conventional and computer assisted pedicle screw insertion techniques. Three meta-analyses have assessed the published reports on the accuracy of pedicle screw insertion with or without computer assistance, one additional meta-analysis concentrated on the functional outcome of computer assisted pedicle screw insertion. Results. The RCTs by Laine et al and Rajasekaran et al achieved significantly higher screw placement accuracy with computer assistance than with the conventional techniquebased on anatomical landmarks. In a degenerative patient population, Laine et al reported a misplacement rate of 4.6% with computer assistance compared to 13.4% with the conventional technique. In addition to this quantitative difference, a qualitative difference in the misplaced screws was noticed: in the conventional group, 28 out of 37 misplaced screws were either inferior or medial, whereas in the computer assisted group, 1 out of 10 misplaced screws was situated in these ”danger zones”. In deformity surgery, Rajasekaran et al reported a 2% pedicle screw misplacement rate with a computer assisted technique compared to 23% with the conventional technique. Interestingly, in their study, the average screw insertion time in the computer assisted group was significantly shorter than with the conventional technique. The three meta-analyses, assessing up to 37 337 pedicle screws, reported significantly higher accuracy in the placement of pedicle screws with computerassistance compared with the conventional methods. The superiority of the computer assisted technique was even more obvious with abnormal surgical anatomy. CT-based and 3D-fluoroscopy-based navigation methods provided better accuracy compared to 2Dfluoroscopy-based navigation. No statistically significant benefit with computer assistance in the incidence of neuro-vascular complications, or in functional outcome was demonstrated. Conclusion. High pedicle screw misplacement rates have been reported with the conventional technique based on anatomical landmarks and intraoperative fluoroscopy. The concept of ”safe zone” is hypothetical, and underestimates the true risks of misplaced pedicle screws. Computer assistance significantly improves the accuracy and safety of pedicle screw insertion. It will, however, be difficult to correlate this increased accuracy to improved patient outcomes

Background: The use of sacro-iliac screws to restore the stability of posterior pelvic ring dissociations has become a standard technique. Several methods are described including fluoroscopy, CT and computer assisted techniques. Fluoroscopically assisted insertion is the standard technique. Multiple exposures of ionising radiation permit acquisition of a target in sequential planes, requiring a process of interpolation for 3-D localisation. A computer assisted technique facilitates the simultaneous visualisation of multiple planes following a single image intensifier acquisition and registration process in each plane. The purpose of this study is to demonstrate the accuracy of a computer assisted surgery technique and quantify the predicted reduction in radiation exposure. Methods: 10 embalmed human cadavers were used. In each specimen, a sacro-iliac screw was simulated by passing a 5mm reamer over a 3.2mm guide wire. The index track was formed with a closely sheathed 4.8mm drill and was inserted with the standard fluoroscopically assisted technique in the left hemipelvis and a computer assisted technique(Vector Vision trauma) on the right. Registration of the system is achieved by the placement of infra red reflective arrays on all tracked objects. These include the right and left hemi-pelvis, the fluoroscope, the drill guide and the driver unit. The system is an open platform which registers arrays of known geometry whilst permitting the registration of instruments by means of an instrument calibration matrix. The pelvic T and Y pattern fiducials are fixed rigidly to inter-table threaded pins at the level of the gluteal tuberosities. The standard acquisition projections are inlet and outlet views for both techniques with the addition of lateral projections although the latter were not directly used for navigation. Postoperative CT scans demonstrate the actual tracks and analysis is facilitated by means of a digital mapping technique. Results: The accuracy of the fluoroscopically assisted and computer assisted techniques is identical. The procedure time was significantly longer for the computer assisted technique although most of the additional time was accounted for by the “line of sight” registration process. There was a reduction in both the total screening time and the measured radiation dose in the case of the computer assisted technique although this did not reach statistical significance as the sample size is relatively small. Conclusions: The navigation of sacro-iliac screw tracks by means of both fluoroscopically assisted and computer assisted techniques proves equally accurate in a human cadaveric model

Introduction: Obesity [Body Mass Index (BMI) > 30] is seen in a growing percentage of patients seeking joint replacement surgery. Recent studies have shown no clear influence of obesity on the five-year, clinical outcome of total knee replacement; except for the morbidly obese (BMI > 40). Computer navigation has shown improved consistency of prosthetic component alignment. However, this aid does significantly increase operation time. Aims:. To compare tourniquet times of standard and computer assisted total knee arthroplasty in patients with BMI more than 30. To evaluate the change in this variable as a surgeon gained experience over a three year period. Methods and Results: A retrospective analysis of 82, obese, total knee replacements performed by a single surgeon, at a dedicated arthroplasty centre, was undertaken. Conventional knee replacement instrumentation (Plus Orthopaedics, UK) was used in 42 cases and computer assisted navigation (Galileo- Plus Orthopaedics) in 39 cases. The patients were divided into three equal sized groups (1, 2 & 3), in chronological order. Each group comprised fourteen knees undertaken using standard surgical technique and thirteen knees using computer assisted navigation. Group1 had average tourniquet times of 95.69 and 111.67 minutes in the standard and computer assisted groups respectively (p 0.01). Group 2 tourniquet times were 80.75 and 92.33 minutes (p 0.05). Group 3 tourniquet times were 84.5 and 87.5 minutes; these were not significantly different. Conclusions: As the surgeon acquired experience of computer assisted navigation, his tourniquet times decreased and by the end of our study period, there was no longer any difference between the tourniquet times for conventional and computer assisted knee replacement in this subgroup of obese patients. We hypothesise that in obese patients, computer assisted navigation helps the surgeon to overcome jig alignment uncertainty and thus improves accuracy of component alignment without any significant time penalty

Computer assisted surgical techniques in total knee arthroplasty have demonstrated increased accuracy of alignment and decreased risk of outliers. Some studies have also demonstrated improved early functional results and pain scores in comparison to traditional surgical methods. Studies have also shown a slightly increased surgical time for computer assisted surgery. A learning curve for computer assisted surgery is recognized, and there may be different outcomes for cases performed initially during the learning phase. This study reports on a single surgeon’s experience with the initial 261 computer assisted total knee arthroplasties. A single experienced, fellowship trained surgeon performed computer assisted total knee arthroplasty utilizing either the BrainLab or Ci intraoperative navigation system and either the LCS Complete Mobile Bearing Knee System (DePuy) or Sigma PFC Rotating Platform (DePuy). Preoperative and postoperative data was recorded prospectively (DePuy Captureware) of the initial 261 consecutive cases at minimum of one year follow-up. SAS 9.1 was used to perform univariate and multivariate analyses of four groups of patients: patients 1–77, patients 78–135, patients 136–211 and patients 212–261. Multivariate analyses were performed to control for body mass index, age, sex, implant type, pre-operative range of motion, preoperative function and preoperative pain scores. Multivariate analysis of these four groups demonstrated that there was no statistically significant difference in the improvement of postoperative function (p=0.29) and pain scores (p=0.28) among the patients in the four groups at minimum one year follow-up. There was a statistically significant difference in improvement of postoperative extension (p=0.0022) and flexion (p=0.0139) scores with subsequent surgeries, however the range of improvement for the groups was not clinically significant (extension ranging from 1.97 to 5.92 degrees gained in the four groups, and flexion loss of 0.67 degrees to gain of 6.18 degrees in the four groups). The number of patients requiring a hospitalization greater than two days decreased with each subsequent group which was clinically significant (p=0.021, p=0.001, p< 0.0001 for the second, third and fourth groups, respectively). For an experienced reconstructive surgeon incorporating computer assisted surgery into his total knee arthroplasty practice, there is no significant learning curve in regards to intermediate term outcomes. Patients undergoing computer assisted total knee arthroplasty have similar intermediate outcomes whether performed earlier in that surgeon’s experience or later. Patients did initially have shorter hospitalization stays in subsequent groups. However, at an intermediate follow-up period of one year, there is no significant difference in patients’ postoperative improvement in function, pain score, knee flexion and knee extension

We present minimum 20 year results of a randomized, prospective double blinded trial (RCT) of cross-linked versus conventional polyethylene (PE), using a computer assisted method of PE wear measurement. After Ethics Committee approval, 122 patients were enrolled into an RCT comparing Enduron (non cross-linked PE) and highly cross-linked Marathon PE (DePuy, Leeds, UK). Other than the PE liners, identical components were used, a Duraloc 300 metal shell with one screw, a 28mm CoCr femoral head and a cemented Charnley Elite femoral stem. All patients were followed with anteroposterior (A∼P) and lateral radiographs at 3 days, 6 weeks, 3 months, 6 months, 1, 2, 3, 4, 5, 10 and 20 years. PE wear was measured with PolyMig, which has a phantom validated accuracy of ± 0.09mm. At minimum 20 year follow-up, 47 patients had died, 5 of which had been revised prior to their death. Another 32 patients were revised and alive, leaving 43 patients unrevised and alive (15 Enduron, 28 Marathon). No patients were lost to follow-up, but 2 were not able to be radiographed (dementia), leaving 41 patients (15 Enduron, 26 Marathon) available for PE wear measurement. After the bedding-in period, Enduron liners had a wear rate of 0.182 mm/year, and Marathon liners had a wear rate of 0.028 mm/year. At 20 years follow-up, 37 patients had required revision. Patients with conventional PE had three times the revision rate (28/37) of those who received XLPE (9/37). This is the longest term RCT showing substantially improved clinical and radiological results when XLPE is used as the bearing surface

Since 2000 we have performed TKR with the aid of a computer assisted navigation system (PiGalileo). Over this time we have made more than 2000 TKR, while continuing to monitor results from both standard technique and computer navigated TKR. As we began to work with the computer assisted navigation system, we ran a comparison trial to ascertain the accuracy of mechanical axis calculation. The trial comprised of 32 patients. The accuracy of the calculation in both techniques was measured by paralax-free X-ray. The computer assisted navigation group showed a deviation of 0.9°–2.5°, whereas the standard technique group showed a deviation of 3.5°–4.6°. A second comparison was conducted involving 186 patients. The TKR were performed from August 2000 to December 2001. All patients received the same implant (TC-Solution). All operations were performed by the hospital’s two most senior surgeons. Cases involving deviations from our standard TKR (such as patellar replacement) were eliminated from the trial. Two groups were created randomly:. Group A (88 patients) standard technique. Group B (98 patients) technique with the aid of computer assisted navigation system. All patients were examined by an independent doctor, in accordance with a clearly defined protocol. Preoperative and postoperative clinical examinations with X-rays were made. Check ups with valuation of the KSS score (Insall) and HSS Knee score (Ranavate and Shine) followed after 3,6,12,24 and 60 months. Both groups have comparable biometric data. In the post-surgery checks we found noticeable differences in the axis positions of the legs and the ventral cutting plane in favour of group B. This group showed better clinical results and patient satisfaction. There was no difference in the outcome in case of retropatelar problems, as the first generation software did not permit rotation assessment of the prosthesis. The current version of the system allows this assessment. The results of our clincal observations confirm the advantage of computer navigated TKR. It has become our standard operating method. The navigation system is reliable, warrants better axis and rotation positioning of the prosthesis; exact cutting planes, and consequently, exact setting of the implants. Through progressive development of the navigation system and refined surgical techniques in relation to computer assisted TKR, we have reduced the average TKR operating time

Background. Limb length discrepancy after total hip replacement is one of the possible complications of suboptimal positioning of the implant and cause of patients dissatisfaction. Computer assisted navigation become affirmed in last years for total hip replacement surgery and it is also used for the evaluation of the intra-operative limb length discrepancy. The purpose of this study is to verify the reliability of a navigation system with a dedicated software in intraoperative evaluation of limb lengthening and offset as compared with manual technique. Methods. Forty patients who underwent a Total Hip Arthroplasty in our institution were entrolled in this study. Twenty patients were evaluated with pre operative manual planning (group A) and treated with hand positioning of femoral stem. Twenty Patient were evaluated with preoperative manual planning and treated with Computer assisted navigation of Stem (group B). Mean operating time and blood loss were analyzed. Radiological and clinical follow up was made at 1, 3, 6 and 12 months postoperative to assess any mismatch of implant, complications and clinical results that was measured with Harris Hip Score. Results. In the evaluation of the limb length and offset in group A there wasn't significance difference between pre and postoperative measurements obtained with manual planning. Also in group B there wasn't a significance difference between the measurement obtained intraoperative with computer assisted navigation and the one obtainedafter surgery and preoperative with manual planning. In any case we noted a limb length discrepancy in this series. No statistically significance difference was noted between the two groups in relations to the others parameters investigated. Conclusions. Based on our study the computer navigation system is a simple and reliable for the evaluation of limb length discrepancy and offset in total hip replacement. This Navigation system can offer to the surgeon a valid intraoperative information that can reduce possible errors in stem positioning and can reduce rate of length discrepancy

Background. Stress fractures at tracker after computer navigated total knee replacement are rare. Periprosthetic fracture after Minimally Invasive Plate Osteosynthesis (MIPO) of stress fracture through femoral tracker is unique in orthopaedic literature. We are reporting this unique presentation of periprosthetic fractures after MIPO for stress fracture involving femoral pin site track in computer assisted total knee arthroplasty, treated by reconstruction nail (PFNA). Methods. A 75-year old female, who had computer navigated right total knee replacement, was admitted 6 weeks later with increasing pain over distal thigh for 3 weeks without trauma. Prior to onset of pain, she achieved a range of movements of 0–105 degrees. Perioperative radiographs did not suggest obvious osteoporosis, pre-existent benign or malignant lesion, or fracture. Radiographs demonstrated transverse fracture of distal third of femur through pin site track. We fixed the fracture with 11-hole combihole locking plate by MIPO technique. Eight weeks later, she was readmitted with periprosthetic fracture through screw hole at the tip of MIPO Plate and treated by Reconstruction Nail (PFNA), removal of locking screws and refixation of intermediate segment with unicortical locking screws. Then she was protected with plaster cylinder for 4 weeks and hinged brace for 2 months. Results. Retrograde nail for navigation pin site stress fracture entails intraarticular approach with attendant risks including scatches to prosthesis and joint infection. So we opted to fix by MIPO technique. Periprosthetic fracture at the top of MIPO merits fixation with antegrade nail in conjunction with conversion of screws in the proximal part of the plate to unicortical locking screws. Overlap of at least 3cms offers biomechanical superiority. She made an uneventful recovery and was started on osteoporosis treatment, pending DEXA scan. Conclusion. Reconstruction Nail (PFNA), refixation of intermediate segment with unicortical locking screws constitutes a logical management option for the unique periprosthetic fracture after MIPO of stress fracture involving femoral pin site track in computer assisted total knee replacement

Introduction. Post traumatic arthritis of the knee can be a conseguence of distal femur fracture and retained hardware can complicate any further surgical option including arthroplasty. Both staged surgical procedures to remove before the hardware or simultaneous procedure of arthroplasty and removal of hardware have been indicated with an increased risk of complications. Aim of this study is to present a consecutive series of TKA following distal femur fracture using a computer assisted technique without the removal of retained hardware assessing both the efficacy of navigation in managing these complex cases as “routinary” primary arthroplasties. Material and Methods. A consecutive series of 16 patients treated with a computer assisted TKR following femoral fracture and with retained hardware were included in the study (group A). The interval between the fracture and operation averaged 5.8 years (range 1–12 years), the retained hardwares was an intramedullary nail in 6 cases, distal lateral plates in 7 cases and screws in 4 cases. All patients in group A were matched with a patient who had undergone to a computer assisted TKR using the same implant and software because of atraumatic knee arthritis in the same period (group B). Patients were matched in terms of age, gender, pre-operative range of motion, pre-operative arthritis severity according to Albaack classification, type and grade of deformity and implant features (cruciate retaining or sacrificing). There were 10 male and 6 female for each group, the mean pre-operative age was 64.3 years (range: 54–72) for the group A and 65.4 years (range: 53–74) for the group B. The mean pre-operative flexion was 85.5 degrees (range: 65–115) and 88.1 degrees (range: 70–115) for the post traumatic group and the matched group respectively. Results. There were no statistical significant differences in surgical time, hospital staying, intra/post operative complications. Likewise at a mean follow-up of 47 months no statistically significant difference was seen for the Knee Society, Functional, GIUM and WOMAC scores between the 2 groups. Implant alignment was similar between the 2 groups with similar radiological parameters. Conclusions. The results of this study demonstrated that knee arthritis following distal femoral fracture can be safely managed using computer assisted TKA without any need of hardware removal and obvious costs savings. The Authors achieved both same results and same complication rate of similar uncomplicated primary TKR

To prospectively evaluate the accuracy as well as patient outcome of computer-assisted total knee replacement in a multi-centric randomised study. Two hundred and ninety-five patients in six European centers were randomised between two groups: One hundred and forty-seven in the conventional surgery group and one hundred and forty-eight in the computer assisted surgery. Radiological as well as clinical data (SF-36 and KSS scores) were collected preoperatively as well as six weeks and six months postoperatively. A multilevel mixed-effects linear regression for nested variable with random-effects was used to estimate the effect of the independent variable (type of surgery: conventional surgery vs computer assisted surgery) on each of the dependent variables at six weeks and six months post-operatively. Mechanical axis was statistically better in the navigation group at six weeks (p=0,01) and six months (p=0,04). Similar results are found for the femoral component at six months (p=0,001). At six months, there were statistically greater improvements in the following SF-36 scales for the computer assisted group: bodily pain (p=0,03), role emotional (p=0,03), mental health (p< 0,001), physical health dimension (p=0,01), mental health dimension (p=0,005) and global SF36 score (p=0,002). While a difference in operating time was noted (p< 10-5), the blood losses where similar for both groups (p=0.8). Computer assisted surgery improves the accuracy in total knee arthroplasty, especially for the mechanical axis and the femoral component orientation. These improvements result in better quality of life for the patient at six months postoperatively. Level of Evidence: I – High-quality randomised controlled trial with statistically significant difference

Objective:. Periacetabular spherical osteotomy for the treatment of dysplastic hip is effective but technically demanding. To help surgeons perform this difficult procedure reliably and safely, a computer assisted navigation technique has been developed and evaluated. Methods:. Computed tomographic scans of 5 cadaveric pelvises were obtained and three-dimensional models were generated. The osteotomy was planned preoperatively. The pelvises were registered using an optimized algorithm. Periacetabular spherical osteotomy was performed at one side of each pelvis with navigation and at another side without navigation. The deviation of the real osteotomized surface from the planned surface was measured. Results:. The computer assisted navigation system supported preoperative planning and provided real time display of the surgical procedure. The deviation of the real osteotomized surface from the planned surface was 1.59 ± 0.18 mm in the group with navigation, while 4.81 ± 1.67 mm in the group without navigation. The difference of the deviations has statistical significance (p < 0.003). Conclusion:. A computer assisted navigation technique is able to help increase accuracy and safety of periacetabular spherical osteotomy, and thus facilitate performing this difficult procedure

Introduction: There has been significant development in computer technology in recent years and this has led to applications in orthopaedic surgery. Of particular interest is computer assisted joint arthroplasty to enable accurate insertion of the components based on CT generated images of the patient’s bones. Methods: Twenty-five patients have undergone computer assisted total knee arthroplasty using a computer guidance system (Vector Vision, Brain Lab, Munich) implanting a PFC cruciate retaining total knee replacement (TKR) (Depuy, Leeds). Pre-operative CT scans were obtained from each patient and alignment and sizing were calculated before surgery. Intra-operatively, an infrared camera tracked the instruments and the patient’s limb was accurately mapped in space by surface matching the bone and comparing it with the CT scan. For the purpose of the study the computer generated alignments and sizing were evaluated along with the use of traditional instruments and stored in a database. Results: These have been evaluated comparing computer assisted and instrumented knee arthroplasty. Variables measured include the AP femoral cuts, rotational femoral alignment, and tibial axis alignment in AP and lateral planes. Conclusions: Computer assisted orthopaedic surgery has undergone a rapid development in the last 18 months to enable real-time intra-operative images to be viewed in a moving limb with a degree of accuracy previously not possible. The use of this technology may lead to more accurate alignment of hip and knee prostheses and therefor help to reduce wear in the long-term

To determine the precision of conventional versus computer assisted techniques for positioning the acetabular component in total hip arthroplasty (THA). Malposition of the acetabular component during THA increases the occurrence of impingement, reduces range of motion, and increases the risk of dislocation and long-term wear. To prevent malpositioned hip implants, an increasing number of computer assisted surgery systems have been described, but their accuracy is not well established. Using a lateral approach, 150 cups were placed by 10 different surgeons in 10 identical plastic pelvis models. Only the immediate operating field was visible. Pre-operative planning was performed with a computerised tomography scan. Fifty cups were placed free hand, 50 others with the standard cup positioner, and the remaining 50 cups using computer-assisted orthopaedic surgery (Medivision). The accuracy of cup abduction and anteversion was assessed with an electromagnetic system (Fastrak™). Using conventional techniques, free hand placement revealed a mean precision of cup anteversion and abduction of 10° (range 5.5 to 14) and 3.5° (2.5 to 5) respectively. With the cup positioner, these angles measured 8° (5 to 10.5) and 4° (3 to 5.5) respectively, and using the computer assisted method, the mean cup anteversion precision was 1.5° (1 to 2) and mean cup abduction measured 2.5° (2 to 3.5). Computer assisted cup placement is a very accurate and reproducible technique during THA. It is clearly more precise than either of the two traditional methods of cup positioning, even for well-trained surgeons

Two computer assisted techniques (CT and a fluoro-guide based system) were used to insert the femoral component of the Oxford Unicompartmental Knee arthroplasty. The accuracy and variability of component positioning were compared. Clinical data was collected pre-operatively and is being collected post-operatively. Standing AP and lateral knee X-rays as well as skyline X-rays were collected pre-operatively and post-operative full length AP and lateral femur X-rays were completed in order to measure alignment of the femoral component. Results are showing accurate insertions of the Oxford knee femoral component using both systems. To review two computer-assisted techniques for inserting Oxford Unicompartmental Knee arthroplasties. CT based and fluro based techniques were compared with regards to accuracy and variability of component positioning. Currently we are able to use either a CT based system or a fluro based system to accurately insert the femoral component of the Oxford Unicompartmental Knee arthroplasty. Computer assist techniques are allowing us to perform minimally invasive arthroplasty procedures with great accuracy. Patients were all seen in a pre-admission clinic where pre-operative clinical survey data were collected. All patients had standing AP and lateral knee X-rays as well as skyline X-rays pre-operatively. Post-perative full length AP and lateral femur X-rays were completed in order to measure alignment of the femoral component. Patients are being followed post-operatively with SF-36, WOMAC, Knee Society Scores, and X-rays. Patients being operated on with the CT based system had pre operative CT scans. Intra-operatively a DRB was fixed to the patient’s femur and the chosen computer assisted technique was used to direct the rotation of the tibial cut as well as the alignment of the femoral cutting jig. To date we have completed seventeen computer assisted Oxford Unicompartmental Knee Arthroplasties. The average error in the AP plane using CT based system was 3.2 degrees and 2.1 degrees for the lateral plane. The average error in the AP plane using the fluro-based system was 2.2 degrees and 1.3 degree for the lateral plane. Funding: NSERC, IRIS, ORDCF

Two computer assisted techniques (CT and a fluoro-guide based system) were used to insert the femoral component of the Oxford Unicompartmental Knee arthroplasty. The accuracy and variability of component positioning were compared. Clinical data was collected pre-operatively and is being collected post-operatively. Standing AP and lateral knee X-rays as well as skyline X-rays were collected pre-operatively and post-operative full length AP and lateral femur X-rays were completed in order to measure alignment of the femoral component. Results are showing accurate insertions of the Oxford knee femoral component using both systems. To review two computer-assisted techniques for inserting Oxford Unicompartmental Knee arthroplasties. CT based and fluro based techniques were compared with regards to accuracy and variability of component positioning. Currently we are able to use either a CT based system or a fluro based system to accurately insert the femoral component of the Oxford Unicompartmental Knee arthroplasty. Computer assist techniques are allowing us to perform minimally invasive arthroplasty procedures with great accuracy. Patients were all seen in a pre-admission clinic where pre-operative clinical survey data were collected. All patients had standing AP and lateral knee X-rays as well as skyline X-rays pre-operatively. Post-perative full length AP and lateral femur X-rays were completed in order to measure alignment of the femoral component. Patients are being followed post-operatively with SF-36, WOMAC, Knee Society Scores, and X-rays. Patients being operated on with the CT based system had pre operative CT scans. Intra-operatively a DRB was fixed to the patient’s femur and the chosen computer assisted technique was used to direct the rotation of the tibial cut as well as the alignment of the femoral cutting jig. To date we have completed seventeen computer assisted Oxford Unicompartmental Knee Arthroplasties. The average error in the AP plane using CT based system was 3.2 degrees and 2.1 degrees for the lateral plane. The average error in the AP plane using the fluro-based system was 2.2 degrees and 1.3 degree for the lateral plane. Funding: NSERC, IRIS, ORDCF

Stereotactic principles used primarily for brain surgery have been developed further and introduced into spine surgery at the beginning of the 1990’s. The system solutions available consist of three components: the surgical object (vertebra), the virtual object (CT-image data of the vertebra), and the navigatorallowing the surgeon to localise the position of the instrument inside the surgical object in real-time. Optoelectronic systems using infrared light emitting diodes and magnetic field based navigators are in use. Lumbar pedicle screw insertion was the first clinical application for this technique. Screws can be positioned safely following a preplanned optimal trajectory or according to the anatomic situation utilising the real-time module intraoperatively. The effectiveness of this new technique has been shown in prospective studies (Schwarzenbach et al 1997, Laine et al 1997, 1999). In a a prospective randomised clinical trial one-hundred consecutive patients were randomly allocated for either conventional (Group 1) or computer assisted (Group 2) pedicle screw insertion. From the computer assisted group nine patients were dropped out. There was no statistical difference between the groups. CT-based optoelectronic navigation was used for screw insertion in Group 2. The screw position in the pedicle was assessed postoperatively by an independent observer with CT. The pedicle perforation rate was 13.4% (37/277 screws) in the conventional group and 4.6% (10/219 screws) in the computer assisted group (P=0.006). The majority of perforations was less than 4 mm. A pedicle perforation of 4 to 6 mm was found in 1.4% (4/277) of the screws in Group 1, and none in Group 2. Intraoperatively, eleven screws were repositioned in Group 1 and none in Group 2. There were no postoperative complications related to screw placement. We conclude that higher accuracy of pedicle screw insertion with computer assisted navigation than with conventional methods could be demonstrated under clinical conditions in a randomised controlled clinical trial. At present CAOS Systems are used also for localisation of intraosseous pathologic processes during biopsies in spine and pelvis, sacroiliac screw fixation and vertebral osteotomies. Refinement of the method for use in minimal invasive and percutaneous procedures is in progress

To describe our experience with computer assisted combined anterior cruciate ligament (ACL) reconstruction and osteotomy. It may provide long-term symptom relief and improved function in patients with medial knee arthrosis and ACL-deficiency, while delaying or possibly eliminating the need for further surgical intervention such as arthroplasty. Two patients who had medial unicompartmental arthrosis and chronic ACL-deficient knees underwent ACL reconstruction along with femoral osteotomy in one case and upper tibial osteotomy in the other. We used Orthopilot software to perform computer assisted combined anterior cruciate ligament (ACL) reconstruction and osteotomy. Subjective evaluation at postoperatively indicated significant improvement compared to preoperative evaluation and better scores for patients who obtained normal knee range of motion. Objective evaluation by International Knee Documentation Committee showed improved score postoperatively. Both had minor complications occurred in the immediate postoperative period. The average correction angle of the osteotomy was 7 degrees (7–10). Computer assisted ACL reconstruction and osteotomy may provide long-term symptomatic pain relief, increased activity and improved function. Only Anterior cruciate ligament reconstruction may not effectively provide pain relief to the ACL-deficient knee with degenerative medial arthrosis. The results of this study suggest that combined high tibial or femoral osteotomy and ACL reconstructions are effective in the surgical treatment of varus, ACL-deficient knees with symptomatic medial compartment arthritis. Computer aided surgery allows precise correction of the axial deformity and tunnel orientation intraoperatively

Computer navigation was introduced in Australia in 2000, initially with the use of pre-operative computer scans and then later with image free systems. In 2003 the AOA – NJRR began collecting data for knee replacement performed with computer navigation. Meta analysis of the literature has shown better coronal and sagittal plane alignment in total knee arthroplasty performed with computer navigation as opposed to standard instrumented knee replacement. At present, however, there is no data on improved outcomes or reduced revision rates. Information was requested from the AOA – NJRR on the use of computer navigation for both uni-compartmental and total knee replacements. This included numbers of navigated knees done per year as well as revision rates and reasons for revisions of knees performed by computer navigation surgery. Since data collection began there has been 2,651 computer assisted total knee replacements performed which is 4.1% of the total number of knee replacements in this time period. There has been a steady increase in the last three years in the use of computer navigation. There has been an increased number of computer navigated knees performed in the private hospital sector as opposed to the public hospitals and there is a state by state variation in the uptake of navigation. The revision rate per 100 observed ‘component’ years at three years is 2.8 for non computer assisted and 2.5 computer assisted surgery. This is not statistically significant. There is no difference in the early complication rate leading to revision. The use of computer navigation could be expected to reduce the long term revision rates of knee arthroplasty due to better alignment and potentially less wear. In the short term there is no significant revision rate between the two methods of performing TKR particularly with regard to infection or fracture

Aims: To determine the precision of conventional versus computer assisted techniques for positioning the acetab-ular component in total hip arthroplasty (THA). Methods: Using a lateral approach, 150 cups were placed by 10 different surgeons in 10 identical plastic pelvis models. Only the immediate operating þeld was visible. Preoperative planning was performed with a computerized tomographic scan. Fifty cups were placed free hand, 50 others with the standard cup ancillary, and the remaining 50 cups using computer-assisted orthopaedic surgery. The accuracy of cup abduction and ante-version was assessed with an electromagnetic system. Results: Using conventional techniques, free hand placement revealed a mean precision of cup anteversion and abduction of 10¡ [range: 5.5–14] and 3.5¡ [2.5–5] respectively. With the cup positioner, these angles measured 8¡ [5–10.5] and 4¡ [3–5.5] respectively, and using the computer assisted method, the mean cup anteversion precision was 1.5¡ [1–2] and mean cup abduction measured 2.5¡ [2–3.5]. Conclusions: Computer assisted cup placement is a very accurate and reproducible technique during THA. It is clearly more precise than either of the two traditional methods of cup positioning, even for well-trained surgeons

Minimally invasive total hip replacement surgery not only decreases the number of visual cues necessary for proper acetabular component position, the small incision makes it technically more difficult to use traditional mechanical alignment guides. Furthermore, traditional mechanical guides have been shown to be unable to accurately predict component position as determined by intraoperative computer measurements.[ 1,2 ] Computer assisted intraoperative navigation can enable minimally invasive surgery by giving the surgeon immediate intra-operative feedback of actual component position. We wished to compare the intraoperative computer determined measurement of acetabular inclination with the postoperative radiographic measurement of inclination in order to validate the results of the computer assisted measurements in the clinical setting. To determine whether computer assisted navigation of the acetabular component allows the surgeon to accurately place the prosthesis in minimally invasive hip replacement and to compare the results of intraoperative navigation with the postoperative radiograph. 42 consecutive patients underwent a minimally invasive posterior approach for total hip arthroplasty with the assistance of CT based intraoperative navigation with the BrainLAB VectorVision software. Preoperative surgical planning was performed after acquisition of a CT scan. All components were templated to be placed in 45 degrees of inclination and 25 degrees of anteversion. Intraoperatively, cementless acetabular components were aligned with the computer navigation at these values prior to implant impaction. Because of the press fit nature and limited soft tissue exposure, many components would shift during impaction. Final component position was then verified and values recorded by detecting points on the acetabular surface. If the prosthesis was felt to be in an acceptable position, no attempt was made to modify component position to the predetermined values in order to avoid potentially compromising component fixation. Postoperative supine AP pelvis radiography was then used to determine final inclination. Measurements were made by drawing a line perpendicular to the acetabular teardrop and parallel to the acetabular component and measured with a standard goniometer. These data were then placed in an SPSS database and analyzed by an independent statistician. Assessing acetabular component position in routine total hip arthroplasty has been shown to be unreliable even with experienced surgeons with mechanical alignment guides. [1,3] In minimally invasive total hip arthroplasty, routine visual cues are limited and mechanical instruments are difficult to place in the small operative wounds making an already difficult task even more difficult. CT based image guided surgery can has been shown to improve the acetabular component position intraoperatively 2. However, postoperative validation studies comparing the intraoperative computer assessment with the postoperative radiographic measurement are scarce. [ 2 ] In this consecutive series, which represents the author’s first experience with this technology, several conclusions can be made. First, the act of impacting a solid, porous coated, hemispherical cementless acetabular component in minimally invasive hip surgery often leads to a final component position different from the intended position. Second, computer generated determination of implant position is reliable but care must be taken to make sure the reference arrays do not lose fixation during the procedure or spurious results can occur. Third, routine AP pelvis radiographic measurements are not accurate enough to determine whether the computer determined values are accurate. In spite of these measurement inaccuracies, the computer determined results and the radiographic results were within 10 degress 95 % of the time which is far more accurate than results obtained with mechanical alignment tools 3. Finally, further validation studies need to be done with postoperative CT scanning to determine the accuracy of the intraoperative computerized measurements and determine the measurement errors inherent in the clinical setting. Given these limitations, computer assisted navigation improves the accuracy and reliability of acetabular component position over traditional mechanical instruments and can be utilized in minimally invasive hip surgery to assist in the appropriate placement of the acetabular prosthesis

Introduction: The purpose of this study was to compare two methods for the quantification of bone marrow edema (BME) of the knee. Materials and Methods: Forty-one patients with Bone Marrow Edema (BME) of the knee due to osteonecrosis, osteoarthritis, bone bruise or stress were included in the study. Coronal STIR images of the affected knees were obtained using either a 1.0 Tesla or a 1.5 Tesla Magnetic Resonance (MR) scanner. To monitor the BME’s progression, every knee was examined twice at a 3-month interval. Size and signal intensity of BME were semi-quantitatively assessed in consensus by two radiologists and two orthopaedic surgeons. Independently, size and signal intensity were calculated using a new computer assisted method based on grey value analysis and calculation of a threshold value between normal and edematous bone marrow. The results of the semi-quantitative method were correlated with those of the computer assisted method. Results: The correlation coefficient was 0.89 (ìstrongî) for BME size and 0.72 (ìmedium to strongî) for BME signal intensity. For the progression of size and signal intensity, correlation coefficients of 0.78 (ìstrongî) and 0.67 (ìmediumî) were found. Conclusion: Good correlation between semi-quantitative and quantitative methods of assessment of both size and intensity of BME was found. While the computer assisted method is time-consuming and reserved for scientific purposes, the semi-quantitative method is simple and offers to the experienced examiner a fast and simple means for BME recording in clinical practice

Purpose: Use of six-axis analysis and computer assisted deformity correction via a circular external fixator is a new method for deformity correction. We investigated its accuracy and safety in reconstruction of femoral deformity in children and young adults. Method: We retrospectively reviewed all cases including the indications for use and the methodology of application of the computer assisted six-axis analysis and circular external fixator for reconstruction of 22 femora in 20 patients. Twelve patients were female, and 8 were male. The average age was 13.9 (range, 5.9–24.6). Etiology included traumatic (7), idiopathic (6), multiple enchondromatosis (2), rickets (2), congenital femoral deficiency (2), spondyloepiphyseal dysplasia (1), congenital pseudohypoparathyroidisim (1), and multifocal osteomyelitis (1). Clinical and radiographic data were analyzed. Results: Average follow-up was 14.4 months (range, 4.5–32). Average time in frame was 6.2 months (range, 2.6–19). Bone lengthening of 3.9 cm (range, 1–8.5) was performed in 12 femora. In genu valgum patients, the mLDFA improved from a mean of 73.7° to a mean of 89°. In genu varum patients, the mLDFA improved from a mean of 99.8° to a mean of 89.5°. Complications included pin tract infection in 6, knee stiffness in 3, delayed union in 2, skin irritation in 1, posterior knee subluxation in 2, both of which had stable knees preoperatively. One patient was lost to follow-up and returned back with deformity. No complications occurred in 8 patients. Conclusion: Computer assisted femoral deformity correction with six-axis analysis and application of circular external fixator is a useful technique with the advantage of managing multiplanar deformities in children and young adults. It has the potential complications of the use of any external fixator. Close follow-up is necessary to avoid subluxation of the knee joint even in patients with stable knees. Accurate and safe correction can be achieved in almost all patients

Introduction The aim of this study was to compare the new technique of computer assisted knee arthroplasty (CAK) against the conventional jig based technique (JBK). Methods Seventy-five consecutive patients underwent knee replacement and were randomly allocated to either the CAK or JBK group. Post-operative CT scans were performed according to the Perth CT Knee Arthroplasty protocol to assess the accuracy of alignment. This measures seven parameters of alignment to an accuracy of one degree. Pre and post-operative Maquet views of the limb were also performed. Intra-operative soft tissue release together with post-operative pain scores and blood loss where also assessed. Results CT scans performed show a statistically significant improvement in component alignment when using computer assisted surgery for femoral varus/valgus (p=0.032),femoral rotation (p=0.001),tibial varus/valgus (p=0.047) tibial posterior slope (p=0.0001), tibial rotation (p=0.011) and femoraltibial mismatch (p=0.037). Standing Maquet limb alignment was also improved (p=0.004) as was blood loss (p=0.0001). CAK surgery took longer, a mean increase of 13 minutes (p=0.0001). Conclusions This is the first controlled study to assess all seven alignment characteristics of knee arthroplasty and use them to compare outcomes in conventional and computer assisted operations. It shows a clear improvement in component alignment with computer navigation. In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source

The aim of the study was to determine the precision of conventional versus computer-assisted techniques for positioning the acetabular component in total hip arthroplasty (THA). Malposition of the acetabular component during THA increases the occurrence of impingement, reduces range of motion, and increases the risk of dislocation and long-term wear. To prevent malpositioned hip implants, an increasing number of computer assisted surgery systems have been described, but their accuracy is not well established. Using a lateral approach, 150 cups were placed by 10 different surgeons in 10 identical plastic pelvis models. Only the immediate operating field was visible. Pre-operative planning was performed with a computerised tomography scan. Fifty cups were placed free hand, 50 others with the standard cup positioner, and the remaining 50 cups using computer-assisted orthopaedic surgery (Medivision). The accuracy of cup abduction and anteversion was assessed with an electromagnetic system (Fastrak™). Using conventional techniques, free hand placement revealed a mean precision of cup anteversion and abduction of 10° [range 5.5 to 14] and 3.5° [2.5 to 5] respectively. With the cup positioner, these angles measured 8° [5 to 10.5] and 4° [3 to 5.5] respectively, and using the computer assisted method, the mean cup anteversion precision was 1.5° [1 to 2] and mean cup abduction measured 2.5° [2 to 3.5]. Computer assisted cup placement is a very accurate and reproducible technique during THA. It is clearly more precise than either of the two traditional methods of cup positioning, even for well-trained surgeons

The most reported benefit of TKA navigation technologies has been the reduction in limb and component alignment outliers. This improvement has not been shown to effect clinical outcomes. This study was designed to compare the functional outcomes between computer assisted techniques and manual techniques. Each group had 60 patients with similar demographics. The average functional outcomes (SF-36, WOMAC, range of motion, pain relief, and knee society score) were the same. The average scores of the SF-36, Knee Society Score, WOMAC were similar for the two groups. However, fewer patients in Group II reported visual analog pain scores greater than 40 at 6 wks, 3 mos and 6 mos. At 1 yr, the pain scores of the two groups were similar. Fewer patients in Group II had KSS scores less than 70 at 3 months, 80 at 6 months, and 90 at one year, than those in Group I. The average range of motion in Group II was greater by 8 degrees at 4 wks and 3 mos, but equal to the average ROM in Group I at 6 and 12 mos. However, the number of patients with less than 90 degrees of motion at each follow-up period was less in Group II than in Group I at each follow-up period. There were fewer superficial wound infections in Group II than in Group I. The average functional outcomes were similar; the results indicate a consistent reduction in outliers in most measured parameters of functional outcomes. In particular, the guidelines for administering pain medication and providing physical therapy were similar for the two groups. The results of this study are parallel to the radiographic results comparing TKA’s performed with manual and computer assisted instrumentation. In those studies, a reduction in outliers was consistently associated with the use of computer assisted techniques

Unicompartment knee arthroplasty (UKA) was proven to be one of the standard treatments of medial compartment osteoarthritis. The key to success was restoration of pre-operative alignment. Overcorrection of coronal (AP) alignment may predispose to early osteoarthritis in the contralateral compartment, change in post-operative tibial slope may predispose to proximal tibial bone collapse and loosening of tibial prosthesis. Minimally invasive surgery (MIS) in UKA was developed quickly in the last ten years. However, MIS has limited access to visualize the surgical field and limb alignment. Computer navigation may help the surgeon to place the component in more accurate position. We aim to study the radiological alignment of computer assisted MIS UKA. Eighteen patients with UKA (PreservationTM, all poly tibia, DePuy Orthopaedics Inc, Warsaw, IN) implanted using MIS technique were studied prospectively. The CiTM system (DePuy International Ltd, Warsaw IN) were used for computer navigation. Five male and 13 female patients were studied. The mean age of the patients was 58.2 (range, 45 to 70). All patients had medial compartment osteoarthritis with varus deformity. The postoperative coronal (AP) alignment and tibial slope of the operated limb were compared with the pre-operative alignment for any significant difference. The mean pre-operative and post-operative radiographic coronal (AP) alignment of the operated limb were 8.4° varus (range, 2° to 12°) and 7.2° varus (range, 1° to 15°) respectively, the difference was not significant (p = 0.537). The mean pre-operative and post-operative tibial slope were 6.8° (range, 3° to 11°) and 5.8° (range, 3° to 10°) respectively, the difference was not significant (p = 0.066). The post-operative tibial slope correlated well with the intra-operative tibial slope recorded by computer after bone cut was made (Cronbach’s Alpha = 0.771). The mean tourniquet time was 124 minutes (range, 94 to 140 minutes). There was no significant difference in pre-operative and post-operative coronal alignment of the operated limb. Computer assisted MIS UKA could reproduce the pre-operative coronal alignment and tibial slope. Restoration of the pre-operative limb alignment in coronal plane and tibial slope was crucial to the survival of UKA. Computer navigation could help the surgeon to position the component during minimally invasive surgery. However, the learning curve of computer assisted MIS UKA was steep

Computer assisted navigation (CAN) has been shown to significantly improve the overall alignment obtained after total knee arthroplasty (TKA). Human error and the use of conventional jigs may be the reasons for the inaccuracy of conventional TKA. The impact of computer assisted equipment in surgeon training has not yet been established. Three orthopaedic trainees participated in this prospective study to assess the impact of CAN upon intraoperative alignment. Each trainee’s first five (early group) and last five (late group) TKA’s were included in the study during their three month training period. A total of 30 patients were included in the study. The accuracy of conventional jig positioning was assessed simultaneously using navigation equipment. After this assessment, the actual bony resection was performed using CAN equipment. There was a consistent trend towards improved accuracy between the early and late groups in the majority of parameters assessed. In the early group, the coronal plane tibial alignment was found to be outside the acceptable three degree range in 11 out of 15. In the late group this improved to two out of 15 (p< 0.05). An average of 2.8 degrees of tibial jig deviation during pinning was noted in the early group which improved to one degree in late group. The accuracy of jig placement in both groups was improved by CAN. Computer assisted navigation is helpful in improving the accuracy of trainee surgeons and should prove a useful adjunct in training. Surgical accuracy using conventional jig based systems can be improved with training. Deviation of conventional tibial alignment jig during pinning is a significant factor. This aspect has not been appreciated fully in the past and can be minimised by the use of the navigation equipment. As shown in previous studies, the overall alignment using CAN is superior to what would have been obtained using conventional jigs for TKA

Aims: Computer guidance has improved the accuracy and safety of pedicle screw insertion. The aim of this study was to evaluate whether CT-based computer assisted pedicle screw insertion enhances the clinical results of lumbar fusion. Methods: 100 lumbo- and thora-columbosacral operations were randomized either into i) conventional pedicle screw insertion (Group 1) or into ii) computer assisted technique using the SurgiGATE Spine 2.1 optoelectronic navigation system (Group 2). Clinical results were analyzed using the Oswestry index. Radiological analysis was performed by an independent radiologist. Results: 95 patients completed the follow-up. Three had died and two were lost. Thus, there were 48 patients (265 screws) in Group 1, 38 patients (201 screws) in Group 2, and 9 dropouts from the original randomization. There was no statistical difference between the groups regarding age, gender, diagnosis, type of operation, operating time or number of screws per patient. The follow-up time was 24.2 ± 1.6 months. The preoperative Oswestry score in Group 1 was 47.7 ± 16.6, and in Group 2 51.4 ± 16.3 (NS). The postoperative scores were, respectively, 27.1 ± 19.1 and 30.8 ± 22.7 (NS). The fusion rate in Group 1 was 85.1%, and in Group 2 92.1% (NS). In Group 1 4.5% of the screws were loose or broken as compared to 7.0% in Group 2 (NS). Conclusions: Despite superior accuracy, at 2-year follow-up no clinical benefit from computer assisted pedicle screw insertion could be demonstrated in this randomized controlled clinical study

Introduction: Computer navigated total knee replacement does not require the use of intramedullary alignment rods, and is thus less invasive than traditional methods. One previous study has suggested that the computer-assisted technique may reduce blood loss in comparison to traditional methods. This study (. Kalairajah et al, 2005. ) used blood volume loss from drainage bottles as a primary outcome measure (n=60). Hidden (internal) blood losses were not accounted for. Our study uses a more accurate method of assessing blood loss, and the sample size is larger (n=136; 68 standard TKR versus 68 computer assisted TKR). Methods: 136 TKR patients were included, of which 68 had standard TKR and 68 computer assisted. Patients were matched such that in each group half had BMI in the range 20–30, and half had BMI between 30–40. Patients were also matched for gender. All patients had Tranexamic acid at the start of the procedure. Total body blood volume was calculated using the formula of . Nadler, Hidalgo & Bloch (1962). This was then used, together with haematocrit and volume re-infused or transfused, to calculate true blood loss, as described by . Sehat, Evans, and Newman (2004). This method is considered to be more reliable than measuring drain output, as it takes account of “hidden” losses. The navigated and non-navigated groups were compared using Student’s t-test. Results: The average blood loss was 583ml in the standard TKR group, and 442ml in the computer assisted TKR group. This difference was statistically significant (p=0.003). Conclusions: A previous study found reduced blood loss when performing total knee replacement using computer navigation, compared with traditional methods. Our study confirmed this finding, using a larger sample size, and a more reliable method of assessing blood loss. Our study found that overall blood loss was less for both groups, when compared to the findings of Kalairajah Y et al. We suspect that this difference was due to our departmental policy that all patients receive tranexamic acid at the start of joint replacement procedure

Studies suggest that specialty hospitals and high surgical volume decrease adverse outcomes related to hip arthroplasty. Little is known, however, concerning the influence of imageless computer navigation systems on a surgeon’s experience and subsequent placement of implants in the setting of hip resurfacing arthroplasty. A retrospective review of 71 consecutive hip resurfacing arthroplasties placed with computer assisted navigation during 2006 and 2007 was performed. Forty-seven operative days encompassing the surgeon’s entire experience with hip resurfacing were analysed. Within this single surgeon series, operative time, intraoperative cup inclination and femoral stem/shaft angles, as well as postoperative cup inclination and femoral stem/shaft angles were measured and compared over three discreet, sequential operative time intervals. Intraoperative cup inclination angles were comparable to postoperative radiographic values as there was no significant difference (p=.059). Computer assisted navigation produced consistent values despite different levels of surgeon experience in the setting of intraoperative cup inclination (42.8°, 43.5°, and 40.1°) and postoperative cup (46.1°, 43.9°, and 42.9°) and femoral stem (147.9°, 146.5°, and 144.0°) radiographic alignment. A statistically significant difference existed between intraoperative femoral stem/shaft angles compared to postoperative radiographs measurements (p< .001), however, all means maintained a valgus orientation compared to the native neck angle. There was a correlation between evolving surgeon experience and intraoperative stem placement (143.5°, 142.1°, and 138.0°, respectively) despite the mean values remaining well clustered (p< .001). Operative times significantly decreased (p< .001) with surgeon experience, showing the largest decrease after the 1. st. sequence interval (109.6, 97.8, and 94.8 min, respectively). No femoral notching (0/71) occurred throughout the series. Computer assisted navigation provides a dependable method of accurate hip resurfacing arthroplasty component positioning as measured by cup inclination, in addition to a reliable technique for valgus stem placement and avoidance of notching. Furthermore, computer navigation allows for consistency and offers a protective effect on component alignment independent of surgeon procedural experience

INTRODUCTION. Despite clear clinical advantages Unicompartimetal Knee Replacement (UKR) still remain a high demanding and less forgiving surgical procedure. Different Authors in literature pointed out how in coronal tibial malalignment beyond 3° as well as tibial slope beyond 7° increase the rate of aseptic failure. Likewise, overcorrection in the coronal plain is a well recognised cause of failure because of an overweighting on the controlateral compartment. Furthermore it has been shown how in UKR surgery even using short narrow intramedullary guide this can cause errors in both coronal planes. Computer assisted surgery has been proposed to improve implant positioning in joint replacement surgery with no need of intramedullary guide. Likewise more recently Patient Specific Instrumentation (PSI) has been suggested as a new technology capable of new advantages such as shorter surgical times and lower blood losses maintaining at least the same accuracy. Aim of this prospective study is to present comparing 2 groups of UKRs using either a computer assisted technique or a CT based PSI. MATERIALS AND METHODS. Since January 2010 54 patients undergoing UKR because of medial compartment arthritis were prospectively enrolled in the study. Before surgery patients were alternatively assigned to either computer-assisted alignment (group A) or PSI group (group B). In the group A (27 knees) the implant (Sigma, Depuy Orthopaedics Inc, Warsaw, Indiana, USA) was positioned using a CT-free computer assisted alignment system specifically created for UKR surgery (OrthoKey, Delaware, USA USA). In group B (27knees) the implant (GMK uni, Medacta, Castel San Pietro, Switzerland) was performed using a CT-Based PSI technology (MyKnee, Medacta, Castel San Pietro, Switzerland). In both the groups all the implants were cemented and using always a fixed metal backed tibial component. The duration of surgery and all the complications according to Kim classification were documented in all cases. Six months after surgery each patient had long-leg standing anterior-posterior radiographs and lateral radiographs of the knee. The radiographs were assessed to determine the Frontal Femoral Component angle (FFC), the Frontal Tibial Component angle (FTC), the Hip-Knee-Ankle angle (HKA) and the sagittal orientation (slope) of both tibial and femoral component. The number and percentage of outliners for each parameter was determined. In addition the percentage of patients from each group with all 5 parameters within the desired range was calculated. Furthermore at the latest follow-up the 2 groups were clinically assessed using KSS and Functional score. RESULTS. At the last assessments there were no differences in the clinical outcome. The mean surgical time was longer in the navigated group of a mean of 5.9 minutes without any statistical differences in complications. The mechanical axis, tibial slope the FTC angle were significantly better aligned in the navigated group. A statistically significant higher number of outliners was seen in the PSI group. The number of implants with all 5 radiological parameters aligned within the desired range was statistically higher in the navigated group. All the implants in the navigated group were correctly aligned in all the planned parameters. DISCUSSION. To our knowledge this is the first prospective study in literature assessing navigation compared to PSI technique in UKR surgery. Despite a slight not significant longer surgical time in the navigated group, at a short follow-up the results could not demonstrate any clinical diffences between the 2 technologies However according to their results the Authors indicate navigation as more helpful in UKR surgery compared to PSI technology in terms of accuracy

Introduction. Total hip arthroplasty has become an increasingly common procedure. Improper cup position contributes to bearing surface wear, pelvic osteolysis, dislocations, and revision surgery. The incidence of cup malposition outside of the safe zone (40° ± 10° abduction and 15° ± 10° anteversion) using traditional techniques has been reported to be as high as 50%. Our hypothesis is that computer assisted navigation will improve cup placement in total hip arthroplasty compared with traditional techniques. Methods. This study retrospectively evaluated the position of 425 consecutive cups placed during primary total hip arthroplasty performed over a two-year period, from 8/1/2012 to 8/1/2014. All cups were placed with a direct-anterior muscle-sparing approach with computer-assisted imageless navigation by a single surgeon. Real-time intraoperative “screen shots” were taken of cup placement. Standard antero-posterior postoperative radiographs of the pelvis were taken within 6 weeks of surgery in the operating surgeon's office using the same standardized protocol for each patient. The radiographs were evaluated by two separate investigators for final abduction and anteversion utilizing the same method as other studies. Statistics were descriptive in nature. Results. Intraoperative navigation screenshots from 425 hips showed that 100% were within the safe zone for abduction and anteversion. Postoperative radiographic review showed that 97% were within the safe zone for abduction (Mean 41 degrees, Range 29–54 degrees), 96% were within the safe zone for anteversion (Mean 16 degrees, Range 4–38 degrees) and 94% were within the safe zone for both abduction and anteversion. Conclusion. In our series, computer assisted navigation improved cup placement in total hip arthroplasty compared with traditional techniques as reported in current literature. Cup position in our study, was within the safe zone for abduction and version at a comparable rate to similar studies examining THA's performed with navigation

INTRODUCTION. Nowadays, longevity of total knee arthroplasties is very acceptable. Survivorship analyses demonstrate a success in a range of 80% to more than 95% over a period of more than ten years (1–4). However, long-term results largely depend, amongst other factors, on restoration of physiological alignment of the lower limb (5–11). Jeffery et al. (12) reported a three percent loosening rate over eight years when knees were correctly aligned whereas insufficient alignment lead to prosthetic loosening in 24 percent. Rand and Coventry (13) found a 90 percent survivorship rate at ten years when the mechanical axis was aligned in a range from nought to four degrees of valgus. Valgus position of more than four degrees or varus alignment resulted in only 71 percent and 73 percent of survivorship respectively. Recently, computer aided instrumentation systems (14,15) became available and preliminary results of small series were reported (16–17). The purpose of this study was to assess the accuracy of computer integrated instrumentation for knee alignment. MATERIAL AND METHOD. The OrthoPilot. ®. represents a computer controlled image supported alignment system. A 3-D Optotrak™ camera localizes infra-red diodes fixed to rigid bodies within the surgical field. Thereby a spatial coordinate reference system is provided. The localizer is linked to a UNIX work station which performs the operative protocol using a graphical interface and a foot pedal. The rigid bodies are fixed to the bones by bicortical screws. An intraoperative kinematic analysis and various additional landmarks lead to definition of the centres of hip, ankle and knee joint and sizing of endoprosthetic components. With the use of LED-equipped alignment instruments the femoral and tibial resection planes are determined. The OrthoPilot. ®. navigation system is not dependant on CT data and no additional preoperative planning is therefore necessary. A prospective comparative multicentre study in five institutions, four in Germany and one in France, was carried out. 821 patients with primary tricompartimental knee arthroplasty using the SEARCH LC knee (B|Braun AESCULAP) were included in the study. The OrthoPilot. ®. Navigation system was used in 555 cases and 266 knees were implanted with the use of conventional instrumentation. At the three months follow-up alignment was assessed using standardized one leg stance radiographs with regard to the mechanical axis and the femoral and tibial angels in the coronal plane. For the lateral femoral and tibial angels standard lateral x-rays were used. Prosthetic alignment was verified by an independent observer. RESULTS. The radiographically assessed results were subdivided into three groups. An error of ± one degree in the radiographical measurements and small deviations caused by the play of surgical instruments have to be considered. With respect to the femoral and tibial angels in the ap and lateral view the group of very good clinical results was, therefore, defined in the range between ninty degrees and ± two degrees. Deviations of three and four degrees from the optimum were classified as being clinically acceptable. Aberrations of more than four degrees were classified as outliers. When measuring the mechanical axis deviations from fully precise femoral and tibial angels may add up. For this reason zero degrees ± three degrees were rated as a very good result, deviations of four to five degrees were considered to be acceptable and alignment beyond five degrees from the optimum was classified as an unsatisfactory result. Mechanical axis:. 35. 2% of the navigated cases were aligned at exactly zero degrees. This was achieved in only 24. 4% of the manual cases. 88. 6% of cases using navigation and 72. 2% in the manual group showed zero degrees and varus or valgus angles of up to three degrees. 8. 9% and 18. 1% of cases respectively showed deviations of four or five degrees of valgus or varus alignment representing an acceptable clinical result. In only 2. 5% of the navigation group aberrations of more than five degrees occurred. The rate of dissatisfying results was 9. 8% in the manual group. Femoral axis (coronal plane):. In the navigation group 48. 1% of cases showed an alignment at exactly 90 degrees which was the case in only 33. 5% of the control group. Altogether, in 89. 4% of the navigated cases a very good result was observed. In the conventionally instrumented cases only 77. 1% very good results were found. There were 1. 6% outliers beyond the limits of four degrees in the navigation group in comparison to 4. 9% amongst the control cases. Femoral axis (sagittal plane):. Very good results with up to two degrees of deviation from a ninety degree position were obtained in 75. 5% of navigated cases and 70. 7% of manual cases. 37. 3% and 34. 6% respectively showed an ideal alignment of exactly ninety degrees. Unsatisfactory results were observed in 9. 5% of the navigated cases and 9. 4% of the manual cases. Tibial axis (coronal plane):. 58. 7% of the computer assisted and 40. 6% of the reference cases were exactly aligned at rectangles. All in all, in 91. 9% navigated and only 83. 5% manual cases a very good result was obtained. Only 1. 1% outliers had to be observed in the navigation group whereas 3. 4% unsatisfactory results were registered with manual technique. Tibial axis (sagittal plane):. 44. 3% of the navigated cases and only 26. 7% of cases in the control group were aligned perpendicular to the dorsal tibial cortex, thus showing no posterior slope. Altogether, 81. 3% could be classified as very good clinical results in the computer assisted group. The corresponding rate of the manual group was 69. 9%. Equivalent values of 8. 6% in the navigation group and 8. 3% in the reference group were registered beyond the limits of four degrees deviation. The additional operation time for the use of the navigation system is calculated between eight and ten minutes after having passed through the learning curve. CONCLUSIONS. Knee navigation facilitates proper alignment of endoprosthetic components and with the use of the Ortho-Pilot. ®. system results are clearly more favourable in comparison to conventional instrumentation technique. In addition, the data obtained from literature demonstrate that the use of this navigation system contributes to reducing outliers in number. With the learning curve the OrthoPilot. ®. alignment system proved to gain in reliability. Deviations from perfect alignment are still difficult to be classified into surgical or technical deficiencies. Many technical and software improvements which were introduced in the meantime will, in addition, contribute to reliability and time saving. Comparative studies with different navigation systems are not yet available. They might allow an even more profound insight into the possibilities and advantages or disadvantages of computer assisted knee alignment. LITERATURE. (1) Knutson K, Lindstrand A, Lidgren L. Survival of knee arthroplasties, a nation-wide multicenter investigation of 8000 cases. J Bone Joint Surg. 1986; 68B: 795-803 . (2) Scuderi GR, Insall JN, Windsor RE, Moran MC. Survivorship of cemented knee replacement. J Bone Joint Surg. 1989; 798-409 . (3) Nafei A, Kristensen O, Knudson HM, Hvid I, Jensen J. Survivorship analysis of cemented total condylar knee arthoplasty. J Arthoplasty 11, 1996;07-10 . (4) Ranawat CS, Flynn WF, Saddler S, Hansraj KH, Maynhard MJ. Long-term results of total condylar knee arthroplasty. A 15-years survivorship study. Clin Orthop 1993; 286:94-102 . (5) Lotke PA, Ecker ML. Influence of positioning of prosthesis in total knee replacement. J Bone Joint Surg 1977;59-A:77-79 . (6) Hood RW, Vanni M, Insall JN. The correction of knee alignment in 225 consecutive total condylar knee replacements. Clin Orthop 1981;160:94-105 . (7) Bargren JH, Blaha JD, Freeman MAR. Alignment in total knee arthroplasty. Clin Orthop 1983;173:178-183. . (8) Hvid I, Nielsen S. Total condylar knee arthroplasty. Acta Orthop Scand 1984;55:160-165 . (9) Tew M, Waugh W. Tibial-femoral alignment and the results of knee replacement. J Bone Joint Surg 1985;67-B:551-556 . (10) Jonsson B, Astrom J. Alignment and long-term clinical results of a semi-constrained knee prosthesis. Clin Orthop 1988;226:124-128 . (11) Ritter MA, Faris PM, Keating EM, Meding JB. Postoperative alignment of total knee replacement its effect on survival. Clin Orthop 1994;299:153-156 . (12) Jeffery RS, Morris RW, Denham RA. Coronal alignment after total knee replacement. J Bone Joint Surg 1991;73-B:709-714 . (13) Rand JA, Coventry MB. Ten-year evaluation of geometric total knee arthroplasty. 1988;232:168-173 . (14) Leitner F, Picard F, Minfelde R, Schulz HJ, Clinquin P, Saragaglia D. Computer assisted knee surgical total replacement. In: CVRMed-MRCAS. Troccaz J, Grimson E, Mösges R (Eds). 1997; 630-638, Springer . (15) Delp SL, Stulberg SD, Davies BL, Picard F, Leitner F. Computer assisted knee replacement. Clin Orthop 1998; 354:49-56 . (16) Picard F, Saragaglia D, Montbarbon E, Chaussard C, Leitner F, Raoult O. Computer assisted knee arthroplasty - preliminary clinical results with the Ortho-Pilot System. Abstract, 4th International CAOS Symposium, Davos, Switzerland, 1999 . (17) Miehlke RK, Clemens U, Jens J-H, Kershally S. Navigation in der Knieendoprothetik - vorläufige klinische Erfahrungen und prospektiv vergleichende Studie gegenüber konventioneller Implantationstechnik, Z Orthop 2001; 139: 109-116

Restoring the overall mechanical alignment to neutral has been the gold standard since the 1970s and remains the current standard of knee arthroplasty today. Recently, there has been renewed interest in alternative alignment goals that place implants in a more “physiologic” position with the hope of improving clinical outcomes. Anywhere from 10 – 20% of patients are dissatisfied after knee replacement surgery and while the cause is multifactorial, some believe that it is related to changing native alignment and an oblique joint line (the concept of constitutional varus) to a single target of mechanical neutral alignment. In addition, recent studies have challenged the long held belief that total knee placed outside the classic “safe zone” of +/− 3 degrees increases the risk of mechanical failure which theoretically supports investigating alternative, more patient specific, alignment targets. From a biomechanical, implant retrieval, and clinical outcomes perspective, mechanical alignment should remain the gold standard for TKA. Varus tibias regardless of overall alignment pattern show increased polyethylene wear and varus loading increases the risk of posteromedial collapse. While recently questioned, the evidence states that alignment does matter. When you combine contemporary knee designs placed in varus with an overweight population (which is the majority of TKA patients) the failure rate increases exponentially when compared to neutral alignment. A recent meta-analysis on mechanical alignment and survivorship clearly demonstrated reduced survivorship for varus-aligned total knees. The only way to justify the biomechanical risks associated with placing components in an alternative alignment target is a significant clinical outcome benefit but the evidence is lacking. A randomised control trial comparing mechanical alignment (MA) and kinematic alignment (KA) found a significant improvement in clinical outcomes and knee function in KA patients at 2 year follow-up. In contrast, Young et al. recently published a randomised control trial comparing PSI KA and computer assisted mechanical TKA and found no difference in any clinical outcome measure. Why were the clinical outcomes scores in the MA patients so different: One potential explanation is that different surgical techniques were used. In the Dosset study, the femur was cut at 5 degrees valgus in all patients and femoral component rotation was always set at 3 degrees externally rotated to the posterior condylar axis. We know from several studies that this method leads to inaccuracies in both coronal plane and axial plane in some patients. Young et al. used computer assisted navigation to align his distal femur cut with the mechanical axis and adjusted femoral component rotation to the transepicondylar axis. The results suggest that a well performed mechanical aligned total knee replacement has excellent clinical performance equal to that of kinematic alignment without any of the long term risks of implant failure. Most contemporary TKA implants are designed to be loaded perpendicular to the polyethylene surface and placing them in shear without extensive biomechanical testing to support this alignment target may put patients at long term risk for an unproven benefit. Have we not learned our lesson?

INTRODUCTION. Total knee replacement is mostly done with alignment rods in order to achieve a proper Varus / Valgus alignement. Other techniques are computer assisted navigation or MRI based preoperative planning. iASSIST™ is a computer assisted stereotaxic surgical instrument system to assist the surgeon in the positioning of the orthopaedic implant system components intra-operatively. It is imageless and the communication between the PC and the “Pod's” does not require any direct camera view, it is a bluethooth comunication system. This study presents preliminary results utilizing iASSIST™. The aim of this study was to test and compare radiographic alignment, functional outcomes, and perioperative morbidity of the iASSIST™ Knee system versus conventional total knee arthroplasty. METHODS. In a prospective randomized trial we investigated 60 patients with osteoarthritis of the knee joint. Each surgical procedure was conducted by highly experienced surgeons. In both groups the implant Legacy LPS-Flex Fixed Bearing Knee was used (Zimmer®, Warsaw, Indiana). The groups were equally divided and randomized by hazard. For clinical evaluation, the Short Form-36 and Knee Society Score were obtained. For the radiological assessment mediCAD® Classic, a digital measurement system, was used. The aim of the study was the comparison of results after 3 months. Results. 2 patients refused any further participation, and 5 cases required a switch to a conventional alignement technique intraoperatively due to technical problems. Average BMI and average age did not differ in both groups. Surgical time in the iASSIST™ group amounted to 100 minutes, in the conventional group to 76 min. Postoperative functional outcomes were statistically insignificant, showing slight improvements of the Combined Knee Society Score, Knee Society Knee Score, and Knee Society Function Score favouring the iASSIST method, and slight improvements of knee flexion. Short Form-36 physical scales slightly favoured the conventional method but not significantly. The mean deviation from neutral mechanical axis was 1.68°±1.9° within the iASSIST group, and 2.73°±2.1° within the conventional TKA group. Conclusion. IASSIST™ is a valuable computer navigation system. The 5 technical troubles were due to the learning curve. The clinical results after 3 months did not differ significantly, the radiological assessment showed a tendency of improved alignement in the iASSIST™ group

Computer assisted orthopaedic surgery (CAOS) is an emerging and expanding filed. There are some old classification systems that are too comprehensive to cover all new CAOS tools and hybrid devises that are currently present and others that are expected to appear in the near future. Based on our experience and on the literature review, we grouped CAOS devises on the basis of their functionality and clinical use into 6 categories, which are then sub-grouped on technical basis. In future, new devices can be added under new categories or subcategories. This grouping scheme is meant to provide a simple guide on orthopaedic systems rather than a comprehensive classification for all computer assisted systems in surgical practice. For example, the number and diversity of tasks of surgical robots is enormous, up to 159 surgical robots with different mechanisms and functions reported in the literature. These can be classified according to their tasks, mechanism of actions, degree of freedom and level of activity but for the purpose of simplicity we subcategorised the orthopaedic robots to only industrial, hand-held and bone-mounted. Table 1 shows the classification system with the 6 categories and other subcategories

Introduction. Recently, tibial insert design of cruciate-substituting (CS) polyethylene insert is employed and widely used. However, in vivo kinematics of using CS polyethylene insert is still unclear. In this study, it is hypothesized that CS polyethylene insert leads to stability of femoro-tibial joint as well as posterior-stabilized (PS) polyethylene insert, even if PCL is sacrificed after TKA. The purpose of this study is an investigation of in vivo kinematics of femoro-tibial joint with use of CS polyethylene insert before and after PCL resction using computer assisted navigation system and tensor device intra-operatively in TKA. Materials and Methods. Sixty-one consecutive patients who had knees of osteoarthritis with varus deformity were investigated in this study. All TKAs (Triathlon, Stryker) were performed using computer assisted navigation system. During surgery, using a tensor device, after bony cut of femur and tibia, joint gaps were assessed in 0 and 90 degrees in flexion. Then, CS polyethylene tibial trial insert were inserted after trial implantation of femoral and tibial components, before and after resection of PCL, respectively. The kinematic parameters of the soft-tissue balance, and amount of coronal and sagittal relative movement between femur and tibia were obtained by interpreting kinematics, which display tables throughout the range of motion (ROM) in the navigation system. In each ROM (30, 45, 60, 90, max degrees), the data were analyzed with a ANOVA test, and mean values were compared by the multiple comparison test (Turkey HSD test) (p< 0.05). Results. Joint gap assessment revealed significant enlargement in both of extension and 90 degrees in flexion after PCL resection compared with before resection. In kinematic analyses in navigation system, regarding to amount of sagittal movement of tibia, there were significances between before and after PCL resection in 60 and 90 degrees in flexion, 1.2mm difference in 60 degrees, and 2.3mm difference in 90 degrees in flexion. There were no significance between before and after PCL resection in the other degrees in flexion. Regarding to the other analyses, varus/ valgus and rotation, there were no differences between before and after resection of PCL. In addition, concerning ROM, maximum extension angle is significantly lower, and maximum flexion angle is significantly higher after than before PCL resection. Discussion. These results demonstrated that CS polyethylene insert might have a stability of femoro-tibial joint nearly after PCL resection as well as before PCL resection. The main design feature of Triathlon CS insert is single radius and rotary arc, in addition, the posterior lip is same as that of Triathlon CR, which can be the factor to avoid paradoxical anterior movement and to permit internal and external rotation between femoral and tibial component. Due to the design features and benefits, there is a high possibility that use of CS insert without PCL can lead same stability as PCL remained, and improvement of ROM. Based on these backgrounds, it is suggested that CS insert may have an additional choice of PCL resection in case of tight gap of flexion in TKA

Introduction. Computer assisted total knee replacement (CATKR) has been shown to give reproducible and accurate alignment of the mechanical axis. The benefits of the reproducible technique has been demonstrated in literature but there is little evidence of benefits in training junior surgeons in a clinical setting. We show our experience of CATKR performed by junior staff under supervision by the senior author, looking at component alignment and patient reported outcome measures. Objectives. Assess radiological and clinical outcomes of Computer Assisted Total Knee Replacements performed by trainees. Methods. Pre-operative Knee Society Scores (KSS) were recorded and all patients underwent CATKR by a trainee who was supervised by the senior author. The Stryker navigation system was used and a Triatholon Total Knee replacement was implanted. Post-operatively patients had long leg Maquet views to assess component alignment and Post-operative Knee Society Scores at a minimum of 5 years were recorded. Results. Pre-operatively the KSS score was 45.6 (24–59) and function 54 (42–65) with post operative scores for KSS 80.0 (55–94) and function 81 (55–100). Post-operatively the average mechanical tibio-femoral angle for the CATKR group was 1.88 degrees varus, the tibial component angle was 90.63 degrees and the femoral component angle was 89.88 degrees. Conclusions. This is the first study of its kind, looking at the medium term outcome of computer assisted total knee replacements performed by trainee surgeons. Our study demonstrates that satisfactory patient outcomes can be achieved by trainee surgeons undertaking Computer Assisted TKR. Despite the learning curve associated with component positioning, trainees were able to achieve satisfactory alignment using the navigation system

The advantages of computer navigated total knee replacement are well documented in the literature, however, increased surgical time and cost issues remain the major deterrent for the wide use of this technology. Placement of cutting jigs under computer guidance forms a major aspect of computer assisted knee replacement surgery. The use of a motorized mini-robotic cutting jig allows for a more precise and time efficient execution of the femoral cuts under computer guidance. We present a preliminary report on our experience using standard computer assisted surgery (CAS) jigs and mini robotic motorized jigs in computer navigated knee replacement. Methods:. We compared our experience using standard jigs and mini-robotic jigs in knee replacement. A cohort of patients involved in a study comparing navigated and standard total knee replacements received TKA using a Bi-Cruciate Stabilised Knee System. A pilot cohort of patients received total knee replacement using standard computer navigation by the pi galileo system without the mini-robots while awaiting acquisition of the mini robot system. We compared our experience using the same pi galileo system with mini robotic cutting jigs to the cohort without the mini-robotic cutting guides. Results:. Reduction in surgical time was statistically significant when using the motorized mini robotic jigs. Blood loss was identical in both cohorts, and cut precision was better in the cohort with the motorized mini robotic jigs. Conclusion:. The use of the mini robot in navigated knee replacements allows for shorter surgical time, as well as more accurate and precise positioning of the cutting jigs. We believe this is a useful technological addition to navigated knee replacement and deserves further attention and research

There have been mixed reports of the contribution of the anterior cruciate ligament (ACL) to the overall envelope of tibial rotational stability. The effect of single bundle ACL reconstruction on the separate components of internal and external rotational stability respectively is also unclear. We determined the internal and external rotation, and antero-posterior movement of the knee before and after single bundle computer assisted reconstruction of the anterior cruciate ligament (ACL) in 57 patients. The Orthopilot. ®. ACL (v2) software (BBraun, Aesculap) was used. The mean overall range of tibial rotation was also significantly reduced from 30.5 degrees to 16 degrees (p< 0.0001). The mean internal rotation was significantly reduced from 16 degrees to 8 degrees (p< 0.0001). Mean external rotation was also significantly reduced from 15 degrees to 8 degrees (p< 0.0001). Unlike previous studies we did not find a greater reduction of internal rotation compared with external rotation. The mean antero-posterior movement of the tibia was significantly reduced from 12mm to 4mm (p< 0.0001). The results of this study seem to indicate that computer assisted single bundle ACL reconstruction results in a significant intraoperative improvement in both internal and external rotatory stability as well as a significant improvement in antero-posterior stability

Computer assisted surgical navigation has played an increasingly central role in total knee arthroplasty (TKA). Given the recognized importance of subtle component position changes in knee function, navigation has emerged as a promising tool for reducing the occurrence of significant malalignment. The ability of this technology to reliably measure multiple parameters intraoperatively allows analysis to possibly identify a correlation between intraoperative computer assisted surgical navigation data and functional outcomes of patients undergoing elective total knee arthroplasty. Intraoperative navigation data was collected for 121 patients undergoing cemented, posterior stabilized TKA. Three forward stepwise regression analyses were performed to associate intraoperative coronal alignment correction, tibiofemoral external rotation, and alignment under varus and valgus stress with one year outcomes, including range of motion, Oxford and SF-36 scores. The amount of alignment correction and the maximum flexion achieved intraoperatively were significantly correlated (p <0.05, R-sq = 13%) with clinically measured maximum flexion at one year. Maximum flexion achieved intraoperatively, external tibiofemoral rotation and maximum varus under stress were also significantly associated (p < 0.05, R-sq = 31%) with the physical component of the SF-36 outcome score. Analyses of computer navigation in TKA to date have primarily focused on precision of sagittal plane correction. Alternatively we have identified four intraoperative parameters that correlate with functional outcome at one year. Correct intraoperative interpretation of navigation data may allow surgeons to make subtle changes in real time to produce superior short-term outcomes for patients

Introduction. Recently, tibial insert design of cruciate-substituting (CS) polyethylene insert is employed. However, in vivo kinematics of using CS polyethylene insert is still unclear. In this study, it is hypothesized that CS polyethylene insert leads to stability of femolo-tibial joint as well as posterior-stabilized (PS) polyethylene insert, even if PCL is sacrificed after TKA. The purpose of this study is an investigation of in vivo kinematics of femolo-tibial joint with use of CS polyethylene insert before and after PCL resction using computer assisted navigation system intra-operatively in TKA. Materials and Methods. Twenty-four consecutive patients who had knees of osteoarthritis with varus deformity were investigated in this study. All TKAs (Triathlon, Stryker) were performed using computer assisted navigation system. In all patients, difference between extension and flexion gap was under 3mm after bony cut of femur and tibia. During surgery, CS polyethylene tibial trial insert were inserted after trial implantation of femoral and tibial components, before and after resection of PCL, respectively. The kinematic parameters of the soft-tissue balance, and amount of coronal (valgus/varus), sagittal (anterior/posterior) and rotational relative movement between femur and tibia were obtained by interpreting kinematics, which display tables throughout the range of motion (ROM) (Figure1). During record of kinematics, the surgeon gently lifted the experimental thigh three times, flexing the hip and knee. In each ROM (30, 45, 60, 90, max degrees), the data were analyzed with paired t-test, and an ANOVA test, and mean values were compared by the multiple comparison test (Turkey HSD test) (p < 0.05). Results. In coronal (valgus/varus) movement, there are no difference between before and after resection of PCL in all ROM. Regarding to amount of sagittal movement of tibia, tibia was slightly shifted approximately 0.75mm posteriorly in 60 degrees of flexion (p=0.013). There are no significance between before and after PCL resection in the other ROM. In addition, concerning ROM, maximum extension angle is significantly lower, and maximum flexion angle is significantly higher after than before PCL resection. Discussion. These results demonstrated that CS polyethylene insert might have a stability of femoro-tibial joint nearly after PCL resection as well as before PCL resection. The main design feature of Triathlon CS insert is single radius and rotary arc, in addition, the posterior lip is same as that of Triathlon CR, which can be the factor to avoid paradoxical anterior movement and to permit internal and external rotation between femoral and tibial component. This study was localized at point of certain situation that difference between extension and flexion gap is under 3mm after bony cut of femur and tibia during surgery. Due to the design features and benefits, there is a high possibility that use of CS insert without PCL can lead same stability as PCL remained, and improvement of ROM. Based on these backgrounds, it is suggested that CS insert may have an additional choice of PCL resection in case of tight gap of flexion in TKA

Reconstructive knee arthroplasty in patients with limb deformity can be a daunting and complex task. These patients are often younger and so post traumatic osteoarthritis poses a real challenge. In view of their relative youth, bone preservation would be favourable; however accurate implantation of components is essential. Formulation of a well calculated plan and accurate execution is essential for successful surgery. We report on a novel method which combines 3D CT joint analysis and computer navigation to define the deformity present pre-operatively and determine whether the proposed reconstruction is feasible. If the reconstructive surgery is feasible, an accurate calculation the correction required is performed. The planned surgery is executed using computer aided navigation surgery. Eight patients have benefited from the technique. Four patients presented with isolated medial compartment osteoarthritis and intact anterior cruciate ligament. These patients underwent 3D CT joint analysis and computer assisted navigation surgery to accurately implant unicondylar knee replacements. Four Patients presented with two or three compartment disease. These patients underwent similar 3D CT analysis and navigated Total Knee Replacement. The series demonstrates the merits of 3D CT joint analysis to accurately define deformity and therefore determine pre-operatively feasibility of corrective surgery proposed. The technique is then complimented by computer assisted navigation surgery to ensure the proposed surgical plan is accurately executed

This preliminary study concerns the results of THR using a minimally invasive computer assisted technique: We use the Siguier and Judet procedure. The patient is in supine position and we use an orthopedic table. The skin incision is 6 to 8 cm long and we dont cut any muscle during the approach. The first 30 cases are studied: The navigation system is scanner free and allows different controls: cup inclination and anteversion, center of rotation, laterality, lengh of the lower limb. The acetabular implant is a cementless impacted cup and the femoral implant is either cemented or cementless. The first results are rapported and the technical modifications are descreibed. A randomized study of 50 patients with CAS and 50 without CAS is now begining to determine if the risk of bad positionning the implants in MIS decreases when we use computer assisted surgery

Recent studies suggest the use of computer navigation during TKA can reduce intraoperative blood loss. The purpose of this study was to assess if navigation affected blood loss after TKA in the morbidly obese patient (BMI> 40). Total body blood loss was calculated from body weight, height and haemotocrit change, using a model which accurately assess true blood loss. The computer navigated group comprised of 60 patients, 30 with BMI > 40 and 30 with BMI< 30. The matched conventional knee arthroplasty group consisted of 62 consecutive patients, 31 with BMI> 40 and 31 with BMI< 30 The groups were matched for age, gender, diagnosis and operative technique. Following TKA, the mean total loss was 1014mls (521-1942, SD 312) in the computer assisted group and 1287mls (687-2356, SD 330) in the conventional group. This difference was statistically different (p< 0.001). The mean calculated loss of haemoglobin was 19 g/dl in the navigated group versus 25 g/dl in the conventional group; this was also significant at p< 0.01. The mean total loss was 1105mls in patients with a BMI> 40 in the navigated group compared to 1300mls in the conventional group (p< 0.01). A significant correlation was found between total blood loss and BMI (r=0.2, p< 0.05). This study confirms a highly significant reduction in total body blood loss and calculated Hb loss between computer assisted and conventional TKA in obese patients. Therefore navigation-assisted TKA could present an effective and safe method for reducing blood loss and preventing blood transfusion in obese patients undergoing TKA

Poor outcome in ACL reconstruction is often related to tunnel position. This study investigates the use of surgical navigation to improve outcome. Improving accuracy of tunnel position will lead to improved outcome. In a prospective randomised controlled trial 60 ACL plasties with quadruple-loop semi-tendinosus and gracilis tendon were randomised to either standard instrumentation or computer assisted guides to position the tibial and femoral tunnels. The results were evaluated on clinical outcome based on IKDC laxity measurements and radiologic assessment of anterior drawer at 150 and 200N as well as radiological assessment of the tunnel positions. No complications were observed in either group. IKDC laxity was level A in 22 knees in the conventional group (average 1.5 mm (0-6) at 200N) compared with 26 navigated knees (average laxity 1.3mm (0-5)). Laxity was less than 2 mm in 96.7% of the navigated group (83% in conventional group). The variability of laxity in the navigated group was significantly less than the conventional group, with the standard deviation of the navigated group being smaller than the conventional group standard deviation (p = 0.0003 at 150N and 0.0005 at 200N TELOS). A significant difference (p=0.03) was found between the groups in the ATB value characterising the sagittal position of the tibial tunnel (negative ATB values imply graft impingement in extension). In the conventional group mean ATB was -1.2 (-5-+4) while it was 0.4 (0 - 3) in Group II. There were no negative ATB values in the Navigated Group. The use of computer assisted navigation creates a more consistently accurate tibial tunnel position than using conventional techniques. It is suggested that this should reduce impingement and improve graft longevity

Introduction. This community Arthroplasty Register is an individual initiative to document arthroplasty procedures performed from 2007 to date in a sample area in Cairo, Egypt. Currently, there is no published study or official documentation of the indications for arthroplasty, types of implants or the rate of total hip and knee arthroplasty (THA & TKA). Although the population of Egypt reached 80,394,000, the unofficial estimate of the rate of joint replacement is less than 10,000 per year. This rate is less than 10% of what is currently done in UK, a country with similar or even less population than Egypt. This indicates the unmet need for TKA in Egypt, where the knee OA is prevailing and there is a call for documentation and a registry. Methods. The registry sheet is 3 pages; pre-, intra- and post-operative. It is available in printed format and online as demonstrated below . www.knee-hip.com. During the registry period, there were 282 cases collected prospectively and 206 collected retrospectively. This initial analysis included only prospectively collected data of 157 TKA and 125 THA. Results. For THA, the mean age was 48 years ranging from (19–86). Female to male ratio was 1.15:1. The rate of uncemented THA was 84.8%, Cemented was 10.2% and hybrid THA was 5%. We have observed significant growth in the uncemented type of fixation. The rate of primary was 54.4 % (complex primary 26.4%), Conventional THA techniques were done for 56.15%, while computer assisted surgery was used in 43.85% of cases. For TKA, there was 71.33% primary and 19.7% complex primary, 8.97% revision arthroplasty. A female to male ratio was 2.92:1. The main indication for TKA was OA in 87.26%. Preoperative radiographic evaluation showed that 47% had severe varus and 15% had significant bone defect. Conventional TKA techniques were done for 73.2%, while computer assisted surgery was sued in 26.8 % of cases

Introduction. Proper alignment of the components and soft tissue balance are the two factors that determine the long term outcome of total knee arthroplasty (TKA). On the femoral side a distal cut made perpendicular to the MA will restore the MA of the leg. Different methods are commonly used to resect the femur perpendicular to its MA. In uncomplicated cases, most surgeons routinely use a fixed valgus cut angle (VCA) of 5° or 6°. Various studies have questioned the use of fixed valgus angle resection to restore the mechanical axis. The purpose of this prospective study is to analyze the variability in the valgus angle following computer assisted TKA. Materials and methods. Twenty-three patients who underwent computer assisted TKA in our institution in 2009 were involved in the study. A total of 40 knees were available for analysis. All the knees underwent a CT scanogram postoperatively. Each scanogram was analyzed using the Amrita medvision(r) software. The angle subtended between the mechanical axis and the distal femoral anatomic axis is the valgus angle. Two independent observers calculated all the values and the interobserver reliability was calculated. Results. The average age of the patients was 65.6 years. The kappa coefficient of agreement was 0.8, which shows good interobserver reliability. The average angle formed by the femoral component with the mechanical axis was 91.6. 0. and the average valgus angle calculated was 7.41. 0. 14 knees out of 40 (35%) were lying within the range of 4 - 7 degrees. In 25 knees (65%) valgus angle was more than 7 degrees. In one case the valgus angle was less than 4 degrees. Conclusions. Fixed valgus angle resection is not reliable in restoring mechanical axis in total knee arthroplasty. In the absence of facilities for surgical navigation, a pre operative planning with long leg films is extremely important to achieve long-term success

Introduction. Pedicle screw fixation is considered gold standard as it provides stable and adequate fixation of all the three columns of spine. Mal-placement of screws in dorso-lumbar region, using fluoroscopic control only, varies from 15% to 30 %. The aim of this study was to determine whether accuracy of pedicle screw placement can be improved using CT based navigation technique. Material & methods. 15 patients with fracture of D12 in 4 patients, L1 in 6 patients, L2 in 4 patients, and L4 in 1 patient underwent pedicle screw fixation using CT based navigation. Each fracture was fixed with 4 pedicle screws, 2 each in one level above and one level below the fractured vertebrae. A total of 60 pedicle screws was inserted. A pre-operative 1mm slice planning CT scan was taken from two levels above to two levels below the fractured vertebrae. It was loaded into the workstation and pre-operative planning was made of screw trajectory and screw size i.e. thickness and length, according to the dimensions of the pedicle and vertebral body. Screws were then inserted using opto-electronic navigation system. Screw placement was analysed in all patients using post-operative CT scan and graded according to the Laine's system. Results. The average time for matching was 10.8 minutes and average time for screw insertion was 4.3 minutes (range 2-8 minutes). One screw in right sided pedicle of L2 perforated the lateral cortex (1.66%). There was no neuro-vascular complication. Conclusion. The incidence of a misplaced screw in the present study is only 1.66% which is much less than reported with conventional technique, reflecting enhanced accuracy with computer assisted navigation. Thus computer assisted navigation is a potent tool in the hands of a spine surgeon in improving the accuracy of pedicle screw placement

Soft tissue management is a critical factor in total knee arthroplasty especially in valgus knees. The stepwise release has been based upon surgeon’s experience until now. Computer assisted surgery gained increasing scientific interest in recent times and allows the intraoperative measurement of leg axis and gap size in extension and flexion. We therefore aimed to analyse the effect of the sequential lateral soft tissue release and the resulting change in the a.p. limb axis on the one hand and the tibiofemoral gaps on the other hand as well in extension as in flexion in 8 cadaveric knees. Measurements were obtained using a CT-free navigation system. In extension the highest increase compared to the previous release step was found for the first (iliotibial band, p=0.002), second (popliteus muscle, p=0.0003), third (LCL, 0.007) and the sixth (entire PCL, p=0.001) release step. In 90° flexion all differences of the lateral release steps were statistically significant (p< 0.004). Massive progression of the lateral gap in flexion was found after the second (popliteus muscle, p=0.004) and third (LCL, 0.007) release step. Computer assisted surgery allows to measure the effect of each release step of the sequential lateral release sequence and helps the surgeon to asses the result better

We have assessed the bone cuts achieved at surgery compared to the planned cuts produced during computer assisted surgery (CAS) using a CT free navigation system. In addition, two groups of matched patients were compared to assess the post-operative mechanical alignment achieved: 14 patients received a LCS total knee replacement (TKR) using the VectorVision module and 14 received a TKR using a conventional method of extramedullary alignment jigs The deviation in each plane (valgus-varus, flexion-extension and proximal-distal) was calculated. For the tibia the mean deviation in the coronal plane was 0.21 degrees of Varus (SD = 1.37) and in the sagittal plane was 1.29 degrees of flexion (SD = 3.73) and 0.24 mm of resection distal to the anticipated cut (SD = 2.14). For the femur the mean deviation in the coronal plane was 0.88 degrees (SD = 2.2) of valgus and in the sagittal plane the mean deviation was 0.3 degrees (SD = 2.91) of extension. In the transverse plane there was a mean deviation of 0.07 degrees (SD = 1.57) of external rotation. There was mean deviation of 2.33 mm of proximal resection (SD = 2.9) and 1.05 mm of anterior shift (SD = 2.81). On comparing the two groups, no statistically significant differences were found for the angles between the femoral component and the femoral mechanical axis, the tibial component and the tibial mechanical axis, the femoral and tibial mechanical axis and the femoral and tibial anatomical axis. We have demonstrated variation in the true bone cuts obtained using computer assisted surgery from those suggested by the software and have not demonstrated significant improvement in post-operative alignment. Justification for the extra cost, time and morbidity associated with this technology must be provided in the form of improved clinical outcomes in the future

Computer navigated total knee arthroplasty (TKA) has several proposed benefits including reduced post operative blood loss. We compared the total blood volume loss in a cohort of morbidly obese (BMI> 40) patients undergoing computer navigated (n=30) or standard intramedullary techniques (n=30) with a cohort of matched patients with a BMI< 30 also undergoing navigated (n=31) or standard TKA (n=31). Total body blood loss was calculated from body weight, height and haemotocrit change, using a model which accurately assesses true blood loss as was maximum allowable blood loss. The groups were matched for age, gender, diagnosis and operative technique. The mean true blood volume loss was significantly (p< 0.001) less in the computer assisted group (1014±312mls) compared to the conventional group (1287±330mls). Patients with a BMI > 40 and a computer navigated procedure (1105 ±321mls) had a significantly lower (p< 0.001) blood volume loss compared to those who underwent a conventional TKA (1399±330mls). There was no significant difference in the transfusion rate or those reaching the maximum allowable blood loss between groups. This study confirms a significant reduction in total body blood loss between computer assisted and conventional TKA in morbidly obese patients. However computer navigation did not affect the transfusion rate or those reaching the transfusion trigger in the morbidly obese group. Therefore computer navigation may reduce blood loss in the morbidly obese patient but this may not be clinically relevant to transfusion requirements as previously suggested

An intelligent bone cutting tool as well as a navigation system is of high potential to provide great assistance for the surgeons in computer assisted orthopedic surgery. In this paper we designed a coordinated controller for the surgical robot to perform bone cutting more safely, easily and fast compared with being performed by manual bone saw. Coordinated control is in an outer control loop and determines suitable parameters of the inner control loop of the robot. The inner control loop is an admittance controller for the master site and a compliance controller for the slave site. Coordinated control consists of three modes, i.e. automated cutting, cautious cutting and automated prevention depending on bone cutting conditions and human intention. In automated cutting mode, the coordinated control will set larger admittance gain and smaller compliance gain to provide an assistant force to the human for completion of bone cutting. In cautious cutting mode, smaller admittance gain and larger compliance gain will be set and a resistant force will be provided to the operator for micro progress of bone cutting. In emergence mode, the robot will stop the cutter going forward. Experimental result shows that in automated mode of the proposed coordinated control was able to assist bone cutting at the same time to avoid undesired large cutting force and cutter breakage. The moving speed of cutter slowed down as the cutting forces increased due to the cutter hitting harder bone, thus alleviated sawblade bouncing up and achieved less deviation from designed cutting plane. In cautious cutting mode the cutting forces were magnified to be felt by the operator. The operator was able to perform micro progress of bone cutting with intensive monitoring of the cutting forces. This functionality is especially useful as the cutter approaches the critical area where the surgeon regards as dangerous region. The emergent mode was also successfully triggered by calculating the defined apparent admittance. The apparent admittance is more reliable than using the cutting force only in detection of cutting boundary. A hand's on robot under coordinated control is demonstrated in conjunction with surgical navigation system in computer assisted orthopedic surgery. This paper experimentally showed that the coordinated control can effective provide assistive and resistant forces to achieve safe and accurate bone cutting in total knee arthroplasty

Background: During the past decade, there has been a resurgence of interest in hip resurfacing as a mode of treatment for the younger patient with hip disease since major disadvantages of previous resurfacing systems have been overcome. The purpose of the presented study was to clarify if an imageless navigation system will allow precise placement of the femoral component. Methods: Between September 2004 and May 2006, 50 metal-on-metal surface arthroplasties each were performed either using an imageless navigation system or the conventional technique. The inclination and the axial alignment of the femoral component were determined by two independend examiners and compared to the values presented by the navigation system. Results: In the preoperative x-rays a mean CCD-Angle of 129.2 degrees (Control group: 127.5°) was measured. The mean femoral shaft angle was 137.5 degrees (Control group 133°) postoperatively with a mean deviation of 2.1 degrees compared to the values shown by the system. In the computer assisted group the mean deviation from the ideal placement in the axial plane was 2.9 degrees compared to 4.8° when using the conventional technique. Conclusion: The use of a navigation system was associated with only an average time loss of 7 minutes for surface data acquisition und mounting of the reference base. The computer assisted technique appears to be helpful to avoid notching during the femoral bone preparation and improve implant positioning which might improve durability

Introduction. Computer hexapod assisted orthopaedic surgery (CHAOS) has previously been shown to provide a predictable and safe method for correcting multiplanar femoral deformity. We report the outcomes of tibial deformity correction using CHAOS, as well as a new cohort of femoral CHAOS procedures. Materials and Methods. Retrospective review of medical records and radiographs for patients who underwent CHAOS for lower limb deformity at our tertiary centre between 2012–2020. Results. There were 70 consecutive cases from 56 patients with no loss to follow-up. Mean age was 40 years (17 to 77); 59% male. There were 48 femoral and 22 tibial procedures. Method of fixation was intramedullary nailing in 47 cases and locking plates in 23. Multiplanar correction was required in 43 cases. The largest correction of rotation was 40 degrees, and angulation was 28 degrees. Mean mechanical axis deviation reduction per procedure was 17.2 mm, maximum 89 mm. Deformity correction was mechanically satisfactory in all patients bar one who was under-corrected, requiring revision. Complications from femoral surgery included one under-correction, two cases of non-union, and one pulmonary embolism. Complications from tibial surgery were one locking plate fatigue failure, one compartment syndrome, one pseudoaneurysm of the anterior tibial artery requiring stenting, and one transient neurapraxia of the common peroneal nerve. There were no deaths. Conclusions. CHAOS can be used for reliable correction of complex deformities of both the femur and tibia. The risk profile appears to differ between femoral and tibial surgeries

Computer navigation systems enable precise measurement and intra- operative knee range of movement analysis. We present a series of five knees that demonstrated unusual kinematics. Five of 80 computer navigated knee replacements that were part of a prospective randomised trial were found to have unusual joint lines. Range of motion assessment was performed with computer assisted navigation after exposure and registration of bony landmarks and before bony resection was commenced. This revealed valgus alignment in extension that drifted into varus with knee flexion. We referred to these unusual patterns as ‘oblique joint lines’. The data from the navigation log files of these five knees was analysed in detail. Average age of patients in this series was 68years and all were female. The average pre- operative angle between femoral axis and distal femoral articular surface was 101 degrees. All five knees had a tibial varus with average angle between the tibial axis and articular surface being 85 degrees. In two knees, more bone was resected from the medial posterior femoral condyle using 4 degrees external rotation. These two knees showed improved kinematics and horizontal joint line post- operatively. Computer assisted navigation provides a precise understanding of the pre- operative knee kinematics. Bony cuts can be tailored to suit the pre- operative deformity. Increased external rotation of the femur with adequate medial soft tissue release is an alternate approach for difficult knees with ‘oblique joint lines’

Introduction. The authors performed a short term prospective study of unicompartmental knee replacement (UKR) associated to patella-femoral arthroplasty (PFA) for the treatment of bicompartmental symptomatic knee arthritis. At the latest follow-up all the implants were matched to a similar computer assisted Total Knee Replacements (CAS-TKR) group implanted for the same indications. Hypothesis of the study was that this bicompartimental implants could achieve comparable outcomes to TKR with a more conservative surgery and a higher joint function. Materials and Methods. 19 cases of anteriomedial (12) or anterolateral (7) arthritis in 19 stable knees were prospectively involved in the study. All the knees underwent to a selective reconstruction using simultaneously both UKR and PFR using the same surgical technique. All bicompartmental implants were performed by the same surgeon. Surgical time, hospital staying and all intra and post operative complications were registered. At a minimum follow-up of 20 months, every single case was marched to a similar case where had been implanted a computer assisted cruciate retaining TKR. Criteria of matching were: sex, age, pre-operative range of motion and arthritis grade. In both the groups all the cases were assessed clinically using WOMAC, KKS and GIUM scores. All the knees were radiologically investigated using the same radiological protocol. Results. Intra operatively we did not registered any complication. No revision in both groups. The mean surgical time was 86 minutes (range: 78–121) in UKR+PFR group and 81 minutes (range: 71–112) in CAS-TKR group. There were no statistical significant differences in the hospital stay. No statistically significant difference was seen for the Knee Society, Functional and GIUM scores between the 2 groups. Statistically significant better WOMAC Function/Stiffness indexes were registered for the UKR+PFR group. CAS-TKR implants achieved a statistically better aligned mechanical axes. Conclusions. The results of this prospective short term prospective study suggest that UKR+PFR implant is a viable option for bicompartmental anteromedial arthritis at least as well as TKR but maintaining an higher level of function

Genu recurvatum deformity is uncommon in arthritic knees undergoing total knee arthroplasty (TKA). We retrospectively analysed radiographs and navigation data to determine the clinical and radiographic results of computer-assisted TKA in knee arthritis with recurvatum deformity. Based on alignment data obtained during computer assisted (CAS) TKA, 40 arthritic knees (36 patients) with a recurvatum deformity of at least 5° were identified. The mean recurvatum deformity was 8.7° (6° to 14°). On preoperative standing hip-ankle radiographs, 23 limbs (57.5%) had a mean varus deformity of 169.4° (153° to 178°) and 17 limbs had a mean valgus deformity of 189.2° (182° to 224°). The intraoperative navigation data showed mean tibial resection of 7.5mm (4.6 to 13.4mm) and distal femur resection of 7.5mm (3.3 to 13mm) with a mean final extension gap of 21.2mm and a flexion gap at 90° of 21.1mm and on extension. On table, the mean knee deformity in sagittal plane was 3° flexion (1.5° to 4.5° flexion). Postoperatively, the mean HKA angle on standing hip-ankle radiographs was 179.2° (177° to 182°). On postoperative lateral radiographs, joint line in extension was moved distally in 35 limbs by 2.3mm (0.3 to 4mm) and proximally in 5 limbs by 2.2mm (2.2 to 2.4mm); the mean preoperative posterior femoral offset of 28.7 mm changed to 27.9 mm postoperatively. At a mean follow up 28 months (14- 48 months) the knee, function, and pain scores improved by 61, 48, and 28 points, respectively and there was no recurrence of recurvatum deformity at final follow up. Genu recurvatum is a notoriously difficult condition to address at TKA. The challenges are to be able to detect it at surgery and take appropriate measures in terms of resection and releases to correct it satisfactorily. Computer assisted TKA helps to achieve excellent deformity correction, limb alignment, gap balancing and function in patients with recurvatum deformity by accurately quantifying and helping to modify the amount of bone cuts and titrate soft tissue release

The ligament balancing technique involves precise measurement and equalisation of flexion and extension gaps. A force tension distractor that has separate arms for the medial and lateral joint compartments was used. We describe our experience of 40 total knee replacements (TKR) using this technique. We undertook a prospective randomised trial using computer assisted navigation in TKRs applying two different soft tissue balancing techniques. The aim was to see how balancing techniques help us achieve a rectangular flexion extension gap. The 40 TKR that underwent the ligament balancing procedure were part of this trial. The distractor used was derived from the Freeman-Swanson knee instrumentation which measures the gap and tension in the medial and lateral compartments. The options to make the gap rectangular were: 1. adjustment of femoral cut by change in external rotation (for the flexion gap); 2. soft- tissue release or 3. a combination of both. Using computer assisted navigation it was possible to perform real time motion analysis during surgery. We found that three degrees of external rotation for the femoral component was adhered to in only 16 out of 40 knees. The remaining 60% had external rotation of femoral component varying between two and eight degrees. No maltracking of the patella resulted in any of the TKR with increased rotation of the femoral component. The axis of movement was plotted on a graph at the end of the surgery by passive extension to flexion to which the operating surgeon was blinded. Varying external rotation of femoral component might be an option in balancing difficult knees. Computer navigation enables precise tailoring of bony resection to suit different deformities

Introduction: Previous reports have described the potentially compromising effect of a high tibial osteotomy (HTO) on the results of a subsequent total knee arthroplasty (TKA). Although the reasons are not clear, some authors reported of problems in soft tissue balancing in TKA following a previous HTO. Method: In a prospective study 22 patients with an average interval of 5.8 years after closed wedge HTO, were operated for TKA. All surgeries were performed with the BrainLAB CT-free navigation system and measurements of the extension and flexion gap were assessed. The intraoperative data were compared to a control group of 100 consecutive computer assisted TKA without previous HTO. Results: In the study group a highly significant shift towards a medial opening of the flexion gap between the posterior condylar line and the tibial resection (study group 0.4° +/− 4.7° medial opening vs. control group 3.4° +/− 3.3° lateral opening, p< 0.001) was observed. 45% in the study group showed a medial opening of the flexion gap compared to 11% in the control group. Conclusion: Surgeons should be aware of difficulties in soft-tissue balance in TKA following HTO, especially for the flexion gap configuration and the axial femoral component orientation. The computer assisted technique is helpful to identify soft tissue imbalance

Purpose. The surgical treatment of scaphoid fractures consists of reduction of the fracture followed by stable internal fixation using a headless compression screw. Proper positioning of the screw remains technically challenging and therefore computer assisted surgery may have an advantage. Navigation assisted surgery requires placement and registration of stable reference markers which is technically impossible in a small bone like the scaphoid. Custom made wrist-positioning devices with built-in reference markers have been developed for this purpose. The purpose of this study was to evaluate a different method of navigation assisted scaphoid fracture fixation. Temporary stabilisation with a pin of the scaphoid to the radius enables placement of the reference markers on the radius. Our hypothesis was that this method will achieve precise fracture fixation, superior to the standard free hand technique. Methods. In 20 identical saw bone models with mobile scaphoids, the scaphoid was stabilised to the radius using one Kirschner wire (KW). An additional KW representing the fixating screw was placed either using the Mazor Renaissance Robotic System (MAZOR Surgical Technologies, Israel) or standard free hand technique. CT scans were performed prior to fixation and after fixation in order to plan the location of the KW and compare this planned location with the final result. Results. No significant difference was found between the measures of KW location between groups and in comparison with the planned location, including entry and exit points of the KW, length of KW through the scaphoid (mean axis length of 28.7 mm [SD 1.5] with the robot system versus 29.6 mm [SD 2.1] with the free hand technique) and difference in angle of fixation with the planned axis of fixation (mean of 1.7 degrees [SD 5.5] with the robot versus 3.8 degrees [SD 5.6] free hand). Significant differences were found between exposure to radiation (mean of 0.07 Rad [SD 0.04] with the robot system versus 13.9 Rad [SD 18.4] with the free hand technique; p=0.04) and the number of attempts in placing the KW (mean of 1.1 attempts [SD 0.32] with the robot versus 8 attempts [SD 6.65] free hand; p=0.01). Conclusion. Computer assisted fixation of a scaphoid fracture was found to be as accurate as the free hand technique, after fixation of the scaphoid to the radius, without the need for a custom splint. It was also shown to be superior by decreasing the exposure to radiation and number of attempts of KW placement

To compare the new technique of computer assisted knee arthroplasty (CAK) against the current gold standard conventional jig based technique (JBK), 75 consecutive patients underwent knee replacement and were randomly allocated to either the CAK or JBK group. The CAK surgery was performed using a freehand technique that avoids violation of the medullary canal. Pre-and post-operative Knee society scores were collected. Post-operative CT scans were performed according to the Perth CT Knee Arthroplasty protocol and pre-and post-operative Maquet views of the limb performed. Intra-operative soft tissue release together with postoperative pain scores and blood loss were also assessed. CT scans performed show a statistically significant improvement in component alignment when using computer assisted surgery for femoral varus/valgus (p=0.032), femoral rotation (p=0.001), tibial varus/ valgus (p=0.047) tibial posterior slope (p=0.0001), tibial rotation (p=0.011) and femoral-tibial mismatch (p=0.037). Standing Maquet limb alignment was also improved (p=0.004) as was blood loss (p=0.0001). CAK surgery took longer, a mean increase of 13 minutes (p=0.0001). This is the first controlled study to assess all seven-alignment characteristics of knee arthroplasty in these two groups of patients. The improvement in alignment resulted in this trial being stopped prematurely as 6 out of 7 of the initial variables had reached significance. It shows a clear improvement in component alignment with computer navigation. The reduction in blood loss in this surgery through not violating the medullary canal will also be beneficial

Introduction We present our earliest series of computer assisted minimally invasive fixation of intertrochanteric hip fractures using the dynamic hip screw. Methods The first five cases of computer assisted minimally invasive dynamic hip screw fixation of intertro-chanteric femur fracture are presented. We used the Medivision Computer Navigation system. Our operative techniques, pitfalls and tricks are presented. All were performed in the standard lateral approach to the femur on a traction table. The minimally invasive cases had a incision length of 5 cm compared with an average length of 13.9 cm for the conventional procedure. Results Technical difficulties in screw placement exists and screw head positions tends to be superior. There was one case of implant cutout. The others recovered uneventfully. Fluoroscopy time is halved, sparing the surgeon from excessive radiation. Operative time is prolonged by about 20 minutes. Patient satisfaction has been very good. Conclusions Our procedure is safe and predictable. Patient satisfaction is high. The small wound allows for less pain and tissue dissection enabling faster and more effective rehabilitation. The instrumentation is based on the existing DHS system and there is no need to change inventory. The option of day surgery and same day discharges for hip fracture patients using this technique is tantalising

Correct rotational alignment of the femoral prosthesis in total knee arthroplasty is important for correct patella tracking, patellofemoral joint contact forces, varus-valgus positioning in flexion, and the avoidance of anterior femoral notching. But achieving correct femoral rotation can be difficult, and there are reports of highly variable rotational alignment with the use of fixed surgical landmarks to determine femoral rotation. Minimal invasive technics makes it more difficult to identify these surgical landmarks. Computer assisted surgery may increase the accuracy of coronal and sagittal positioning but probably does not increase the accuracy of rotational positioning. We used preoperative MRI to aid us in determining femoral rotation preoperatively and used that information to implant our femoral components and evaluated the results. We measured the angular difference between the surgical epicondylar axis and the posterior condylar axis of twenty patients preoperatively using MRI images and then used that angle to implant the femoral component. For a second group of twenty patients, computer assisted balanced flexion gap technic (Aesculap. Orthopilot system) was used to determine the rotational alignment of femoral components. CT scans were taken postoperatively and the accuracy of the rotational alignment was analyzed for both groups. The ranges of error were as follows;. Preoperative MRI Group, 8degrees (3 degrees IR to 5 degrees ER). Gap technic group, 21degrees (11 degrees IR to 10 degrees ER). If an error of more than 5 degrees from neutral alignment is defined as an outlier, 2 in the pre-operative group and 6 in the GAP method group would fall in the outlier zone. In conclusion, using preoperative MRI to determine the femoral rotational alignment and then using that information to implant the femoral component could aid in avoiding errors in rotation positioning of the femoral prosthesis. It is a simple and effective method to avoid rotational positioning errors with no learning curve

The problem associated with ceramic on ceramic total hip replacement (THR) is audible noise. Squeaking is the most frequently documented sound. The incidence of squeaking has been reported to wide range from 0.7 to 20.9%. Nevertheless there is no study to investigate on incidence of noise in computer assisted THR with ceramic on ceramic bearing. The purpose of this study was to determine the incidence and risks factors associated with noise. We retrospectively reviewed 200 patients (202 hips) whom performed computer assisted THR (Orthopilot, B. Braun, Tuttlingen, Germany) with ceramic on ceramic bearing between March 2009 and August 2012. All procedures underwent uncemented THR with posterior approach by single surgeon. All hips implanted with PLASMACUP and EXIA femoral stem (B. Braun, Tuttlingen, Germany). All cases used BIOLOX DELTA (Ceramtec, AG, Plochingen, Germany) ceramic liner and head. The incidence and type of noise were interviewed by telephone using set of questionnaire. Patient's age, weight, height, body mass index, acetabular cup size, femoral offset size determined from medical record for comparing between silent hips and noisy hips. The acetabular inclination angle, acetabular anteversion angle, femoral offset, hip offset were reviewed to compare difference between silent hips and noisy hips. The audible noise was reported for 13 hips (6.44%). 5 patients (5 hips) reported click (2.47%) and 8 patients (8 hips) squeaked (3.97%). The mean time to first occurrence of click was 13.4 months and squeak was 7.4 months after surgery. Most common frequency of click was less than weekly (60%) and squeak was 1–4 times per week (50%). Most common activity associated with noise was bending; 40% in click and 75% in squeaking. No patients complained for pain or social problem. Moreover, no patient underwent any intervention for the noise. The noise had not self-resolved in any of the patients at last follow up. Age, weight, height and BMI showed no statistically significant difference between silent hips and click hips. In addition, there was also same result between silent hips and squeaking hips. Acetabular cup insert size and femoral offset stem size the results showed that there was no statistically significant difference between silent hips and click hips, also with squeaking hips. Acetabular inclination, angle acetabular anteversion angle, femoral offset, hip offset the results shown that only acetabular anteversion angle differed significantly between silent hips (19.94±7.78 degree) and squeaking hips (13.46±5.54 degree). The results can conclude that incidence of noise after ceramic on ceramic THR with navigation was 6.44 %. Squeaking incidence was 3.97% and click incidence was 2.47%. The only associated squeaking risk factor was cup anteversion angle. In this study, squeaking hip had cup anteversion angle significant less than silent hip

Aim To compare the new technique of computer assisted knee arthroplasty (CAK) against the current gold standard conventional jig based technique (JBK). Methods Seventy-Five consecutive patients underwent knee replacement and were randomly allocated to either the CAK or JBK group. Pre and postoperative Knee society scores were collected. Post-operative CT scans were performed according to the Perth CT Knee Arthroplasty protocol and pre and post operative Maquet views of the limb performed. Intra operative soft tissue release together with post operative pain scores and blood loss where also assessed. Results CT scans performed show a statistically significant improvement in component alignment when using computer assisted surgery for femoral varus/valgus (p=0.032), femoral rotation (p=0.001), tibial varus/valgus (p=0.047) tibial posterior slope (p=0.0001), tibial rotation (p=0.011) and femoraltibial mismatch (p=0.037). Standing Maquet limb alignment was also improved (p=0.004) as was blood loss (p=0.0001). CAK surgery took longer- a mean increase of 13minutes(p=0.0001). Conclusions This is the first controlled study to assess all seven alignment characteristics of knee arthroplasty in these two groups of patients. The improvement in alignment resulted in this trial being stopped prematurely as 6 out of 7 of the initial variables had reached significance. It shows a clear improvement in component alignment with computer navigation

Aims: Various studies could show that computer assisted pedicle screw insertion can reduce pedicle perforation rate. We conducted this study to verify if pedicle screw navigation can also avoid neurological complications. Methods: Within 20 months 112 patients were stabilised with 584 pedicle screws in the thoracolumbar spine (Th1-L5). 333 screws were inserted using a CT-based navigation system, 251 srews with conventional technique. Postoperatively, screw positons were assessed by an independent radiologist using CT-scans. Neurological complications and revision surgery were noted. Results: 47 (14.1%) of navigated screws perforated pedicle wall, 13 (28%) to medial side with 2 screws more than 4 mm. One screw (0.3%) had to be changed due to medial perforation of 6 mm in Th4. In the conventional group 60 (29.9%) screws perforated pedicle wall, 13 (22%) to medial side with 3 screws more than 4 mm. One patient had to be reoperated due to radicular deficit caused by a medial perforated screw in L1 (0.4%)Conclusion: CT-based navigation of pedicle screws decreased pedicle perforation rate significantly. However, considerable medial perforations up to 6 mm could not be avoided entirely. The rate of neurologic complicatons and revision surgery was the same in both computer assisted and conventional group

A major limiting factor for the accuracy in Computer Assisted Surgery (CAS) is the system’s positional knowledge of the patient’s anatomy, derived through the process of registration. In computer assisted Minimally Invasive Surgery (MIS) the registration process is made more difficult by the lack of direct access to a large portion of the surface to be registered. Current experience with a hands-on robotic surgery system, which uses a set of points measured with a mechanical digitiser on the exposed surface of the bone and a surface reconstructed from computer tomography (CT) data, has shown that accurate and robust registration is still possible through an MIS approach. The registration method described here, which was originally developed for robotic assisted total knee arthroplasty (TKA), has successfully been adapted for robotic assisted unicompartmental knee arthroplasty (UKA) and computer assisted hip resurfacing (HR). Results show that good registration can be achieved by registering the bone surfaces through conventional surgical incisions, with two additional stab-wounds required for the UKA procedure. However, experimental results suggest that, because of the limited access resulting from a smaller incision, a good correspondence between the point-set and surface measurements (i.e., better than one millimeter) is necessary for registration accuracy better than two degrees and two millimeters. This degree of correspondence can be expected for a good surface model and an appropriate intra-operative setup, but poses an important constraint on the requirements for a system suitable for this type of procedure, if a registration method based on anatomical features is to be used without the need for additional access

Introduction. Acetabular dysplasia, also known as developmental dysplasia of the hip, has been shown to contribute to the onset of osteoarthritis. Surgical correction involves repositioning the acetabulum in order to improve coverage of the femoral head. However, ideal placement of the acetabular fragment can often be difficult due to inadequate visualization. Therefore, there has been an increased need for pre-operative planning and navigation modalities for this procedure. Methods. PubMed and EBSCO Host databases were queried using keywords (preoperative, pre-op, preop, before surgery, planning, plan, operation, surgery, surgical, acetabular dysplasia, developmental dysplasia of the hip, and Hip Dislocation, Congenital [Mesh]) from 1974 to March 2019. The search generated 411 results. We included all case-series, English, full-text manuscripts pertaining to pre-operative planning for congenital acetabular dysplasia. Exclusion criteria included: total hip arthroplasty (THA) planning, patient population mean age over 35, and double and single case studies. Results. A total of 12 manuscripts met our criteria for a total of 186 hips. Preoperative planning modalities described were: Amira (Thermo Fischer Scientific; Waltham, MA, USA) − 12.9%, OrthoMap (Stryker Orthopaedics; Mahwah, NJ, USA) − 36.5%, Amira + Biomechanical Guidance System (Johns Hopkins University) − 5.9%, Mills et al. method − 16.1%, Klaue et al. method − 16.1%, Armand et al. method − 6.5%, Tsumura et al. method − 3.8%, and Morrita et al. method − 2.2%. Virtual implementation of the Amira software yielded increases in femoral head coverage (p<0.05) and a significant decrease in lateral center edge angle (LCEA) (p<0.05). A significant decrease in post-surgical complications (0.0% navigated group vs. 8.7% non-navigated group, p<0.01) was found with usage of OrthoMap related planning. Conclusion. There was a notable lack of prospective studies demonstrating the efficacy of these modalities, with decreased post-surgical complications being the only added benefit of their use. Additionally, small sample sizes and lack of commercial availability for many of these programs further diminishes their applicability. Future studies are needed to compare computer assisted planning with traditional radiographic assessment of ideal osteotomy orientation. Furthermore, these programs must be readily accessible rather than be solely available to the researchers who wrote the program. For any figures or tables, please contact authors directly

Introduction. Acquiring adaptive soft-tissue balance is one of the most important factors in total knee arthroplasty (TKA). However, there have been few reports regarding to alteration of tolerability of varus/valgus stress between before and after TKA. In particular, there is no enough data about mid-flexion stability. Based on these backgrounds, it is hypothesized that alteration of varus/valgus tolerance may influence post-operative results in TKA. The purpose of this study is an investigation of in vivo kinematic analyses of tolerability of varus/valgus stress before and after TKA, comparing to clinical results. Materials and Methods. A hundred knees of 88 consecutive patients who had knees of osteoarthritis with varus deformity were investigated in this study. All TKAs (Triathlon, Stryker) were performed using computer assisted navigation system. The kinematic parameters of the soft-tissue balance, and amount of coronal relative movement between femur and tibia were obtained by interpreting kinematics, which display graphs throughout the range of motion (ROM) in the navigation system. Femoro-tibial alignments were recorded under the stress of varus and valgus before the procedure and after implantation of all components. In each ROM (0, 30, 60, 90, 120 degrees), the data of coronal relative movement between femur and tibia (tolerability) were analyzed before and after implantation. Furthermore, correlations between tolerability of varus/valgus and clinical improvement revealed by ROM and Knee society score (KSS) were analyzed by logistic regression analysis. Results. Evaluation of soft tissue balance with navigation system revealed that the tolerance of coronal relative movement between femur and tibia (varus/valgus) after implantation was significantly decreased compared with before implantation even in mid-flexion range. There were no significant correlations between tolerability of coronal relative movement and improvement of extension range and KSS. However, mid-flexion tolerability showed negative correlation with flexion range. Discussion. One of the most important principles for ligament balancing in TKA for varus knees is involved that the medial extension gap should be within 1–3mm to avoid flexion contracture and a feeling of instability, the medial flexion gap should be equal or 1–2mm larger to the medial extension gap, and lateral extension laxity up to 5 degrees is acceptable. However, there have been few reports measuring laxity from 30 to 60 degrees. In this study, the tolerance of coronal relative movement was significantly limited even in mid-flexion. However, mid-flexion tightness was not significantly correlated with clinical results except for flexion range. This result might be suggested that high tolerability of coronal relative movement in mid-flexion range may lead to widening of flexion range of motion of the knee after TKA. For any figures or tables, please contact authors directly

Summary. Computer assisted surgery (CAS) during total knee arthroplasty (TKA) is known to improve prosthetic alignment in coronal and sagittal plane. In this systematic review, no evidence is found that CAS also improves axial component orientation when used during TKA. Introduction. Primary total knee arthroplasty (TKA) is a safe and cost-effective treatment for end-stage knee osteoarthritis. Correct prosthesis alignment is essential, since malpositioning of the prosthesis leads to worse functional outcome and increased wear, which compromises survival of the prosthesis. Computer assisted surgery (CAS) has been developed to enhance prosthesis alignment during TKA. CAS significantly improves postoperative coronal and sagittal alignment compared to conventional TKA. However, the influence of CAS on rotational alignment is a matter of debate. Therefore purpose of this review is to assess published evidence on the influence of CAS during TKA on postoperative rotational alignment. Patients and Methods. This review was performed according to the PRISMA Statement. An electronic literature search was performed in Pubmed, Medline and Embase on studies published between 1991 and April 2013. Studies were included when rotational alignment following imageless CAS-TKA was compared to rotational alignment following conventional TKA. At least one of the following outcome measures had to be assessed: 1) rotational alignment of the femoral component, 2) rotational alignment of the tibial component, 3) tibiofemoral mismatch, 4) the amount of rotational outliers of the femoral component, 5) the amount of rotational outliers of the tibial component. Study selection was performed in two stages and data extraction and methodological quality assessment was conducted independently by two reviewers. Standardized mean difference (SMD) with 95% confidence interval (95% CI) was calculated for continuous variables. The SMDs were interpreted according to Cohen: an SMD of 0.2–0.4 was considered a small effect; 0.5–0.7 was considered moderate; and ≥ 0.8 was considered a large effect. For the comparison of the amount of outliers for femoral and tibial component rotation, the Odds ratio (OR) and 95% CI was calculated. The OR represents the odds of outliers occurring in the CAS group compared with the conventional group. An OR of < 1 favors the CAS group. The OR is considered statistically significant when the 95% CI does not include the value of 1. Results. Seventeen studies met the inclusion criteria. One study was considered of high, 15 studies of medium and one study of low methodological quality. SMD for rotation of the femoral component was −0.07 (−0.19–0.04). For rotation of the tibial component, the SMD was 0.11 (−0.01–0.24). Regarding tibiofemoral mismatch, the SMD was −0.27 (−0.57–0.02). For femoral outliers, the OR was 1.05 (0.78–1.43) and for tibial outliers the OR was 1.12 (0.86–1.47). Discussion / Conclusion. Results of this review show no evidence that CAS-TKA leads to better rotational alignment of the femoral or tibial component or tibiofemoral mismatch. Also no evidence was found that CAS results in a decrease of the amount of outliers regarding femoral or tibial component orientation. However, these conclusions have to be interpreted with caution. The number of included studies was low and strong heterogeneity existed between the studies. Of the 17 included studies, only one study was considered of high methodological quality. Moreover, different methods for assessing tibial component rotation have been used in the studies included

Computer navigated total knee replacement is less invasive than traditional methods, as it avoids the use of intramedullary alignment rods. A previous study (Kalairajah et al, 2005) has shown that computer-assisted techniques may reduce blood loss in comparison to traditional methods. Our study uses a more accurate method of assessing blood loss, and the sample size is larger. 136 TKR patients were selected from a prospectively collected database of all those undergoing arthroplasty at our institution; 68 had standard TKR and 68 had a computer assisted TKR. In each group, half had BMI in the range 20–30, and half had BMI between 30–40. There were an equal number of males and females in each group. All patients received a standardised anaesthetic, and had tranexamic acid at the start of the procedure. Total body blood volume was calculated from patient height, weight and sex, using the model described by Nadler, Hidalgo & Bloch (1962). This was then used, together with pre- and post-op haematocrit and volume re-infused or transfused, to calculate true blood loss, as described by Sehat, Evans, and Newman (2004). This method is considered to be more reliable than measuring drain output, as it takes account of “hidden” (internal) losses. The average blood loss was 603ml in the standard TKR group, and 448ml in the computer assisted TKR group. Student’s t-test showed that this difference was statistically significant (p = 0.007). Regression analysis showed no significant difference between obese and non-obese patients, nor a difference between sexes. Blood loss in both groups was lower than in a previous study, which we attribute to our department’s routine use of tranexamic acid. We conclude that computer-assisted total knee replacement leads to significant reduction in blood loss when compared with traditional techniques. This confirms previous reports

Robotic systems for computer assisted surgery have gained a lot of initial interest and several systems to support surgical inventions have been developed over the past ten years. While almost all systems are tailored to specific applications, the technology used may be divided into different groups. One part of the proposed solutions is essentially based on industrial robots, whereas the part relies on specific designs for medical applications. A particular approach which will not be discussed in this contribution is represented by tele-manipulator systems like the daVinci system from Intuitive Surgical Inc. for cardiac applications, and robots for endoscope guidance in abdominal surgery. The operation of these systems is controlled manually by the surgeon based on the visual information of the operating area which he gets by endoscopic cameras. Robotic application in computer assisted surgery, in contrast to tele-manipulator approaches, is based on pre-operative planning and intra-operative registration of the patient anatomy. They principally offer additional advantages compared to pure navigation systems, such as. No problems due to tremor or unintentional slipping of the tool. Surgery will exactly achieve pre-operatively planned targets, resulting in very good reproducibility. Precise drilling or reaming. Overcome ergonomic problems, like difficult hand-eye-coordination or frequent changes of viewing the direction. Definition of “safe areas” – robot will not move tool beyond. Use of novel tool systems which cannot be guided manually. Essential issues: operating mode & “added value” of a robot. It is a major challenge for new solutions of surgical robot system to exploit this potential while avoiding the drawbacks some existing designs which have not gained wider clinical acceptance. The “added value” of robotic systems must be obvious. Important features to achieve this objectives include interactive operating modes which turn the robot into a powerful and versatile assistance system instead of fully automatic system operation

Though the perceived advantages of computer assisted orthopaedic systems (CAOS) have been claimed incessantly over the years, these systems are far from commonplace in most orthopaedic theatres. Here, we present a summary of those very reasons. Health Technology Assessment report elicited no proof of clinical benefits of the Robodoc over conventional procedures. Mazoochian et al were unable to confirm the same accuracy of implant position while using the Caspar. Honl et al found a higher revision and dislocation rate accompanied with longer surgery durations when robotic assisted technology was used. Shortcomings identified in the CT-based navigation systems included an additional CT scan, which represents extra costs for the acquisition as well as additional radiation to the patient. Sistan et al claims that image-free navigational systems in knee arthroplasty do not provide a more reliable means for rotational alignment as compared to traditional techniques. Computer assisted pedicle screw insertion in the spine has also not demonstrated any significant clinical advantages. To date, long term results of computer-guided or robot-assisted implantation of endoprosthetic devices are still lacking. With the unproven long-term clinical and functional results of patients who had computer aided surgery and given the multi-factorial complexities of patient outcome, it is difficult to claim via small scale short term studies that these systems present a significant benefit to the patient or the healthcare providers. Potential benefits of long-term outcome, better implant survival and functional improvement require further investigation and until that information is available this technology must be further developed before its widespread usage can be justified

Introduction: The long-term results of total hip replacement can be improved by accurate placement of the implants, leading to restoration of hip biomechanics and prevention impingement from of implant malposition. Pelvic obliquity from patient positioning during surgery prevents accurate intra-operative assessment of component placement. Computer navigation assisted total hip replacement can potentially eliminate these problems by providing feedback on prosthetic placement during surgery. The purpose of our study was to assess the accuracy of the component placement in computer navigation assisted THRs performed in our institution. Methods: A total of 154 computer navigation assisted total hip arthroplasties performed between January 2004 and January 2005 were prospectively included in this study. Image free optical based navigation system (Navitrack™) was used. All procedures were performed by the senior author using MIS and open posterior approaches. Two independent observers performed analysis of the position of components and leg length discrepancy from standardized hip radiographs. Navigation values during surgery were compared with postoperative radiographic evaluation. Results: The mean abduction and anteversion angles of acetabular component in postoperative radiographs were 41.4 ± 6.1 and 22.6 ± 3.8 degrees respectively, in comparison to the navigation values of 40.9 ± 4.0 and 22.9 ± 3.6 degrees respectively. The femoral neck offset and leg length discrepancy calculated from navigation were with in a mean of 1.5mm and 2.8mm, respectively. There was one complication consisting of a peri-prosthetic femoral fracture that was recognised during surgery and treated with revision of the femoral component to a long-stem prosthesis. There was no early post-operative dislocation or deep infection in this series. Discussion: This study showed that computer navigation assisted THR provided predictable and reproducible results with accuracy in component placement and restorations of femoral neck offset and leg length

INTRODUCTION:. Despite clear clinical advantages Unicompartimetal Knee Replacement still remain an high demanding and less forgiving surgical procedure. Different Authors in literature pointed out how malalignment increases the rate of aseptic failure even more than in TKR. Computer-assisted surgery has been proposed to improve implant positioning in joint replacement surgery with no need of intramedullary guide despite no still proven clinical advantages. Likewise more recently Patient Specific Instrumentation (PSI) has been suggested, even in partial knee reconstruction, as a new technology capable of new advantages such as shorter surgical times and lower blood losses maintaining at least the same accuracy. Aim of the study is to present a prospective study comparing 2 groups of UKR s using either a computer assisted technique or a CT-based Patient Specific Instrumentation. MATERIALS AND METHODS:. Since January 2010, 54 patients undergoing UKR because medial compartment arthritis were enrolled in the study prospectively. Before surgery patients were alternatively assigned to either computer-assisted alignment (group A) or patient specific instrumentation group (group B). In the group A (27 knees) the implant (Sigma, Depuy Orthopaedics Inc, Warsaw, Indiana, USA) was positioned using a CT-free computer assisted alignment system specifically created for UKR surgery (OrthoKey, Delaware, USA). In group B (27 knees) the implant (GMK Uni, Medacta, Castel San Pietro, Switzerland) was performed using a CT-based PSI technology (MyKnee, Medacta, Castel San Pietro, Switzerland). In both the groups all the implants were cemented and using always a fixed metal backed tibial component. The surgical time and complications were documented in all cases. Six months post-operatively the patients underwent to the same radiological investigation to determine the frontal femoral component angle (FFC), the frontal tibial component angle (FTC), the hip-knee-ankle angle (HKA) and the sagittal orientation (slope) of tibial/femoral components. The number and percentage of outliners for each parameter was determined. In addition the percentage of patients in each group with all 5 parameters within the desired range was calculated. Furthermore the 2 groups were clinically assessed using KSS and Functional score. RESULTS:. There were no differences in the clinical outcome. The mean surgical time was longer in the navigated group of a mean of 5.9 minutes without any statistical differences in complications. The mechanical axes, tibial slope the FTC angle were significantly better aligned in the navigated group. A statistically significant higher number of outliners was seen in the PSI group. The number of implants with all 5 radiological parameters aligned within the desired range was statistically higher in the navigated group. All the implants in the navigated group were correctly aligned in all the planned parameters. Discussion:. To our knowledge this is the first prospective study in literature assessing navigation compared to PSI technique in UKR surgery. Despite a slight not significant longer surgical time in the navigated group, at a short follow-up the results could not demonstrate any clinical differences between the 2 technologies However according to their results the Authors indicate navigation as more helpful in UKR surgery compared to PSI technology in terms of accuracy

Introduction. Recently, tibial insert design of cruciate-substituting (CS) polyethylene insert is employed. However, in vivo kinematics of using CS polyethylene insert is still unclear. In this study, it is hypothesized that CS polyethylene insert leads to stability of femolo-tibial joint as well as posterior-stabilized polyethylene insert, even if posterior cruciate ligament (PCL) is sacrificed after total knee arthroplasty (TKA). The purpose of this study is an investigation of in vivo kinematics of three different tibial insert designs using computer assisted navigation system intra-operatively in TKA. Materials and Methods. Sixty-four consecutive patients who had knees of osteoarthritis with varus deformity were investigated in this study. All TKAs (Triathlon, Stryker, New Jersey, USA) were performed using computer assisted navigation system. During surgery, three different designs of polyethylene tibial trial inserts (PS, CS, and cruciate-retaining (CR) polyethylene insert) were inserted respectively after implantation of femoral and tibial components. The kinematic parameters of the soft-tissue balance were obtained by interpreting kinematics curve, which display bicompartmental gaps throughout the range of motion (ROM) after implantation of each trial insert (Figure. 1). During record of kinematics, the surgeon gently lifted the experimental thigh three times, flexing the hip and knee. Deviation of these three values in each ROM was calculated in each tibial insert in each patient for descriptive analysis. Results. Regarding to values of compartmental gaps, there are no significance between three inserts in both medial and lateral compartments (Figure 2a, b). On medial compartmental gaps, the values of deviations were significantly higher in CR insert than both of PS and CS insert in ROM of over 45 degrees in extension (Fig 3a). In addition, concerning lateral compartmental gaps, the values of deviations were significantly higher in CS insert than both PS and CS insert in all ROM (Fig 3b). Furthermore, there was no significance between PS and CS insert in overall range of motion in both medial and lateral compartmental gaps (Fig 3a, b). Discussion. These results demonstrated that CS polyethylene insert has a stability of femoro-tibial joint nearly as well as PS polyethylene insert. While PS insert may leads to surface damage on open box and has necessity of cutting more bone of femur, some problems involving management of PCL are enumerated in CR inserts. The main design feature of Triathlon CS insert is single radius and rotary arc, in addition, the posterior lip is same as that of Triathlon CR, which can be the factor to avoid paradoxical anterior movement and to permit internal and external rotation between femoral and tibial component. Due to the design features and benefits, there is a high possibility that CS insert can lead same ROM as PS insert, although PS design can produce more ROM than the other type of insert type. Based on these backgrounds, it is suggested that CS insert may have an additional choice in TKA with some advantages especially in concerning of high activity patients like middle aged patients

Purpose of the study: Tibial osteotomy to correct for varus deformity is a well defined procedure. Survival has reached 80% at ten years. Nevertheless, a number of early failures are related to inadequate initial correction. Computer assisted surgery has demonstrated its efficacy for knee arthroplasty. We hypothesised that it could also improve the reliability of correction for tibial osteotomy. Material and method: From 2007, in a prospective case-control study, 34 tibial wedge osteotomies were performed, 17 were computer assisted (Navitrack, Orthosoft) with plate fixation (Tomofix, Synthès) without wedge insertion; the objective was valgus measuring 2 to 5°. Results: The two series were comparable for age (54.2±6 and 55.7±4.5), body mass index (28.9±6.2 and 28.7±5.7), and varus deformity (7.2±3 and 6.2±6) respectively in the standard and navigated groups. Osteoarthritis was more severe in the navigated group, with five patients stage 2 and 12 stage 2 versus one stage 1, 12 stage 2 and 4 stage 3 in the standard group (p=0.0152). The duration of the operation was not longer in the navigation group (p)0.2779). Comparisons were made for alignment at three months, between the groups and in relation to the preoperative data. There was no significant difference between the intraoperative navigation alignment and the alignment measured at 3 months: 3.6±6 and 2.5±3 at 3 months (p=0.2187). At 3 months, there was no significant difference in alignment between the two groups with 3.22 and 2.5±1.6 valgus in the standard and navigation groups respectively (p=0.2136). The objective was achieved in 25 patients: 12 in the standard group and 13 in the navigated group. In the navigation group, there were four failures, no cases of over correction, two cases of insufficient valgus at 1.5, one neutral alignment, and one recurrent varus. In the standard group, there were five failures with two over corrections at 7 and 8, two under corrections at 0 and 1, and 1 recurrent varus at 4. Discussion: We were unable to prove that navigation improves the reliability of the correction but it did appear to avoid important errors, particularly over correction. Few series have compared standard varus navigated osteotomies, and all published series have been small. Our study has the advantage of being monocentric with two comparable series of patients. The sample size nevertheless remains small and the follow-up short

In foot and ankle surgery incorrect placement of implants, or inaccuracy in fracture reduction may remain undiscovered with the use of conventional C-arm fluoroscopy. These imperfections are often only recognized on postoperative computer tomography scans. The apparition of three dimensional (3D) mobile Imaging system has allowed to provide an intraoperative control of fracture reduction and implant placement. Three dimensional computer assisted surgery (CAS) has proven to improve accuracy in spine and pelvic surgery. We hypothesized that 3D-based CAS could improve accuracy in foot and ankle surgery. The purpose of our study was to evaluate the feasibility and utility of a multi-dimensional surgical imaging platform with intra-operative three dimensional imaging and/or CAS in a broad array of foot and ankle traumatic and orthopaedic surgery. Cohort study of patients where the 3D mobile imaging system was used for intraoperative 3D imaging or 3D-based CAS in foot and ankle surgery. The imaging system used was the O-arm Surgical Imaging System and the navigation system was the Medtronic's StealthStation. Surgical procedures were performed according to standard protocols. In case of fractures, image acquisition was performed after reduction of the fracture. In cases of 3D-based CAS, image acquisition was performed at the surgical step before implants placement. At the end of the operations, an intraoperative 3D scan was made. We used the O-arm Surgical Imaging system in 11 patients: intraoperative 3D scans were performed in 3 cases of percutaneus fixation of distal tibio-fibular syndesmotic disruptions; in 2 of the cases, revision of reduction and/or implant placement were needed after the intraoperative 3D scan. Three dimensional CAS was used in 10 cases: 2 open reduction and internal fixation (ORIF) of the calcaneum, 1 subtalar fusion, 2 ankle arthrodesis, 1 retrograde drilling of an osteochondral lesion of the talus, 1 Charcot diabetic reconstruction foot and 1 intramedullary screw fixation of a fifth metatarsal fracture. The guidance was used essentially for screw placement, except in the retrograde drilling of an osteochondral lesion where the guidance was used to navigate the drill tool. Intraoperative 3D imaging showed a good accuracy in implant placement with no need to revision of implants. We report a preliminary case series with use of the O-arm Surgical Imaging System in the field of foot and ankle surgery. This system has been used either as intraoperative 3D imaging control or for 3D-based CAS. In our series, the 3D computer assisted navigation has been very useful in the placement of implants and has shown that guidance of implants is feasible in foot and ankle surgery. Intraoperative 3D imaging could confirm the accuracy of the system as no revisions were needed. Using the O-arm as intraoperative 3D imaging was also beneficial because it allowed todemonstrate intraoperative malreduction or malposition of implants (which were repositioned immediately). Intraoperative 3D imaging system showed very promising preliminary results in foot and ankle surgery. There is no doubt that intraoperative use of 3D imaging will become a standard of care. The exact indications need however to be defined with further studies

Background. Acetabular component malpositioning during hip arthroplasty increases the risk of dislocation, reduces range of motion and can be responsible for early wear and loosening. There have been numerous reports on the optimal orientation of the acetabular component in total hip arthroplasty (THA). Lewinnek et al recommended an abduction angle of 40°±10° and an anteversion of 15°±10° for cup alignment in THA. The purpose of the in vivo study was to compare computer assisted acetabular component insertion versus free-hand placement. The goal of the cadaveric study was to compare in vitro a new tool using ultrasound with the standard percutaneous manual methods for the anterior pelvic plane registration during computer-assisted total hip arthroplasty. Methods. A controlled randomized matched prospective study was performed in two groups of 30 patients. In the first group, cup positioning was assisted by an imageless computer assisted orthopaedics system, based on Bone Morphingâ (CAOS+ group). In the control group, a free-hand cup placement was performed (CAOS- group). A same cementless cup has been used in the two groups. All the patients were operated by the same surgeon through an anterolateral approach. Cup anteversion and abduction angles were measured on three-dimensional CT-scan reconstruction postoperatively for each patient by an independent observer with special cup evaluation software. In vitro, four clinicians were asked to register ten times in a randomly change order the anterior pelvic plane landmarks in four different acquisition conditions: a cutaneous acquisition, a draped cutaneous acquisition, ultrasound acquisition and a direct bone acquisition on two cadavers. The mean and standard deviation of error for each anterior pelvic plane acquisition method were expressed as rotation and tilt about the relevant reference plane and compared. Results. There were 16 males and 14 females in each group, the mean age was 62 years (24–80) and mean Body Mass Index was 25. Mean additional time of the CAOS procedure was 12 minutes (8–20). Intraoperative subjective agreement of the surgeon with the computer guidance system demonstrated a high correlation in 23 cases, weak correlation in 6 cases and a poor correlation in 1 case. There were no statistical differences between the CAOS+ group and the CAOS- group regarding means of the abduction and anteversion angles but a significant heterogeneity of variances, with the lowest variations in the CAOS+ group. In vitro, for the draped cutaneous acquisition method the mean of the rotation and tilt around the reference plane for the two cadavers and the four operators were respectively 3.8 °±0.21° and 19.25 °±4.1°, for the for the ultrasound acquisition method respectively 2.8 °±0.21° and 6.2 °± 4.1°, for the cutaneous acquisition method respectively 2 °±0.21° and 16.2 °±4.1°. Discussion. The in vivo study has shown the accuracy of cup positioning using a CT-free navigation system in a prospective randomized controled protocol. Based on the number of the cadaveric study, ultrasound acquisition of the anterior pelvic plane is more accurate, reliable and reproducible in vitro than actual cutaneous digitization

Malalignment of knee arthroplasty components can lead to abnormal wear, premature loosening and patellofemoral problems. Computer assisted surgery has been developed to improve surgeons ability to achieve correct alignment and thereby improve outcomes. This project compares the accuracy of computer assisted total knee arthroplasty with a conventional jig-assisted technique. A total of 150 patients were recruited. Selection criteria included patients presenting with degenerative or inflammatory joint disease who were candidates for total knee arthroplasty. Patients having revision procedures were excluded as were patients who previously had a corrective osteotomy. Ethics approval was obtained and patients consented for the study. Patients were randomly allocated to either the computer navigated or jig alignment groups via the sealed envelope system. Demographic patient data and intraoperative data were collected. Quality of life and function assessments made using the WOMAC and Knee Society Scores. The component position was assessed using the Perth CT protocol. One hundred and fifty patients were recruited from Dec 2005 to July 2007. Five patients were excluded due to machine malfunction and two others were excluded due to insufficient data collected leaving 143 patients for the study. There was no difference in blood loss, post operative hemoglobin or patient length of hospital stay. There was no difference in the Knee Society knee or function scores at 12 weeks or the knee flexion range either at discharge or at 3 months follow up. There was a significant correlation in duration of surgery (p< 0.05) with the navigated cases taking an average 23 minutes longer. Both the conventional jig alignment and computer navigated techniques produced accurate results in all CT measurements except for the tibial slope where the navigated group (4.8+/−1.6) was closer to the elected posterior slope of 3.5+/− 1.5 than the jig system (6.4+/−2). Statistically significant differences in favour of the navigated group were also found for both femoral component rotation and tibial coronal alignment but the outliers beyond the accepted ideal alignment of 0+/−3 degrees for each parameter were minimal and equivalent for the two groups. Computer navigation in knee replacement surgery is gaining popularity to improve component alignment and consequently the outcome of total knee arthroplasty. This study has shown only marginal benefits in alignment of the navigated group but this needs to be considered against the increased surgical time despite familiarity with the hardware

Introduction. Traditional Total Knee Arthpolasty (TKA) replaces all 3 compartments of the knee for patients diagnosed with OA. There might be functional benefit to replacing only damaged compartments, and retaining the normal ligamentous structures. There is a long history of performing multi-compartment arthroplasty with discrete components. Laskin reported in 1976 that good pain relief and acceptable clinical results were achieved at two years in patients with bi-unicondylar knee replacement [Laskin 1976]. Other authors also have reported on bi-unicompartmental knee arthroplasty achieving successful clinical outcomes [Stockley 1990; Confalonieri 2005]. Banks et al. reported that kinematics of bi-unicompartmental arthroplasties during gait demonstrated some of the basic features of normal knee kinematics [Banks 2005]. These reports suggest that a modular approach to resurfacing the knee can be successful and achieve satisfactory clinical and functional results. Objective. The primary objective of this study is to compare the functional outcomes of three patient groups treated for osteoarthritis. Methods. Subjects received either a modular, multicompartment knee arthroplasty (MKA) implanted with robotic-arm assistance(MAKO Surgical Corp., Fort Lauderdale, FL), a computer assisted TKA (TKA CAS) or a TKA implanted using traditional manual instrumentation (TKA T). Patients that were eligible to receive a TKA were randomly selected to receive computer assisted or traditional surgical technique and blinded to the type of TKA surgical technique utilized. We report post-operative functional outcomes including Range of Motion (ROM), Timed-up and go(TUG), and Quad strength at time intervals of 2 weeks, 6 weeks, 3 months and 6 months. The TUG test is a validated measure of patient mobility where a patient is asked to stand up from a chair, walk three meters turn around and sit back down [Boonstra, 2008]. The Quad strength assessment is measured with a hand held dynamometer (Lafayette Instruments, Lafayette, IN) while patient was seated with leg at 90 degrees flexion. The patient is asked to extend their knee while a physical therapist provides resistive forces to maintain static knee flexion. All tests were administered by one physical therapist. Results. Patients that underwent MKA saw significant increase in ROM post-operatively when compared to TKA CAS patients (P<0.009) and TKA T patients (p<0.003), Figure 1. Patients that underwent MKA also saw an increase in Quad Strength, however this was only statistically significant between the MKA and TKA CAS groups, (P<0.04), Figure 2. Patients that underwent MKA saw a reduction in TUG which indicated an improved mobility post-operatively, Figure 3. The reduced TUG was only statistically significant for MKA patients compared to TKA T patients (P<0.005). There was no statistical significance seen between the two TKA groups for any functional measure. Discussion. Initial findings do indicate a short term improvement in functional outcomes for MKA patients when compared to TKA patients. Additional data clinical and functional data is being collected and enrollment is continuing for this study

Introduction: Much debate exists regarding sparing or sacrificing the posterior cruciate ligament (PCL). The posterior cruciate ligament is said to maintain proprioception and stabilization post knee arthroplasty. Substitution of the PCL can require more femoral bone resection, but is thought to improve range of motion. Release of the PCL can restore extension and enhance flexion through greater femoral rollback. Bicruciate implants potentially offer greater flexion and enhanced stability. Each implant design with mechanical instruments requires a different surgical technique making it difficult to directly compare the patient and surgical outcomes. Computer navigation eliminates the differences in implantation between the various implant designs and theoretically allows a more direct comparison of implants based on design characteristics and not surgical technique. The purpose of this paper is to review four different implant designs implanted by a single surgeon with a computer assisted, gap balancing technique to determine if there was any difference in patient outcome. Methods: A total of 504 implants consisting of posterior cruciate sparing (PFC-RP), PCL substituting (PFC-RPC), PCL sacrificing (LCS) and bicruciate (Journey) implants performed by a single surgeon were reviewed. The PFC-RP group (260) was the largest, followed by the LCS (124), the PFC-RPF (80) and the Journey Knee (40). Outcomes reviewed were range of motion, function, pain and radiographic data to include alignment and evidence of radiolucency. Results: Demographic data of groups compared included 175 men and 329 women. Mean ages ranged from 61 to 74 years. Preoperative scores among all groups were similar with the cruciate substituting group slightly lower in function, flexion and with more pain before surgery. Overall function improved across all groups through two years, with better scores in the Journey and LCS implants (77 and 73 points) versus RPF (47) and PFC retaining group at (68) at one year (A perfect score is 100). Flexion values were comparable between all groups at one and two year intervals with Journey the highest mean flexion (116 degrees) at one year and with the PFC-RP offering the highest mean flexion at the two year mark (115 degrees). The RPF group at the one year mark had more pain overall (28) versus the other three groups (Journey 45, LCS 42, Sigma RP 45). No patients in any group were revised for instability. Other surgical complications were equal in each group. Discussion: While the PCL substituting knee patients (PFC-RPF) had lower pain, function and flexion at 12 months compared to all other groups, they started with lower overall knee scores. After accounting for the differences in patients preoperatively, no difference could be found between implant designs when implanted with a similar surgical technique employing a computer assisted gap balancing protocol

Introduction: The correct position of the knee arthroplasty components is associated with a better result of the prosthesis. In the tibial component, both intramedullar and extramedullar instrumentations have been used for its fiability, but in the femoral component intramedullar guides are more precise than extramedullar ones. The use of the intramedullar guide for the femoral component is not always possible, because a significant deformity of the femoral shaft or when a intramedullar device has been implanted in the femur. We have studied the alineation of the components of computer assisted total knee arthroplasties in a group of patients with femoral deformities or implants. Material and methods: We have used the surgical navigator Stryker-Howmedica for the implantation of a knee arthroplasty in a group of 10 patients in which a endomedullar femoral guide can not be used for femoral shaft severe deformities (6 cases): Paget disease (1 case), previous femoral osteomyelitis (2 cases) or previous femoral fractures (3 cases), or a shaft device was in the femoral shaft (4 cases): long hip femoral stem (3 cases) or a femoral nail (1 case) . We have studied the alineation of femoral and tibial components with a whole-leg X-ray and Computer Tomography. Results: All the femoral and tibial components have been implanted in a good position (90 +/– 2 degrees in the A-P plane and a femorotibial axe 180 +/– 3 degrees. The alineation in the sagital and axial planes have been inside the desired values in all cases also. Discussion: It is generally accepted than intramedullary guides for the femoral component is the gold standard in arthroplasty of the knee. In the last years, the development of computer assisted systems has allowed to obtain femoral and tibial cuts referred to the mechanical axes of the bone, without using mechanical guides for the alineation. In some studies these navigation systems are better than mechanical instruments in terms of alineation of the components in cases without great deformities. In this study, with some cases with severe femoral shaft deformities or with some intramedullary devices that does not allow the use of intramedullary femoral guides, we think that the indication to use a surgical navigator should be nearly absolute

Computer assisted total knee arthroplasty (TKA) is still a relatively novel technique. Surgeons wishing to adopt any new practice undergo a learning curve. The learning curve experienced with navigated TKA, its duration and cost in terms of complications, has not been well defined in the literature. Therefore we set out to analyse the learning curve of a newly appointed consultant with no previous experience of navigated TKA by using a surgeon who has completed over 1000 TKAs in over 10 years of experience with this technique as a baseline. The study used the inexperienced surgeon’s first ever fifty navigated TKAs and the experienced surgeon’s most recent fifty TKAs over the same period in the same theatre using the same CT free navigation system (Orthopilot. ®. ) and prosthesis. Operative time, bone cuts and limb alignment before and after prosthesis implantation were recorded, along with the navigation specific difficulties and complications encountered by the inexperienced surgeon. There was no statistical difference in the accuracy of postoperative limb alignment in either the coronal (p = 0.33) or sagital (p = 0.35) planes between the novice and experienced surgeon. There was also no difference in the executed bone cut angles (tibial p = 0.79, femoral p = 0.92). The operating time showed a difference between the two surgeons with the novice having a median of 80 mins (inter-quartile range of 20 mins) and the experienced surgeon had a median of 70 mins (inter-quartile range of 20 mins), p = 0.001. However there was a statistically significant reduction in operating time between the inexperienced surgeon’s first twenty and last twenty TKAs (p = 0.001). Comparison of the last 20 TKAs for each surgeon showed no difference in the operative time (medians of 70 mins and 75 mins respectively, p = 0.945). The navigation specific difficulties and complications recorded for the novice navigator were all related to the trackers: one loosening, one tibial tracker placed too proximally, one superficial infection in a tibial tracker wound and one incompletely engaged pin-tracker coupling which brought about the only conversion to manual TKA in this series. We conclude that in terms of execution and outcome, a beginner using computer assisted TKA can match the results of an experienced navigator from the outset. The only parameter assessed that underwent a clear learning curve was the operative time, which took approximately 20 procedures to approach the same as the experienced surgeon

Aims: In Revision Total Knee Arthroplasty (RTKA), bone deficiencies and lack of anatomical references make it difficult to understand the normal knee kinematic and adequately plan the intervention. To our knowledge there are no data about computer assisted navigation system specifically developed for RTKA in the literature and existing navigated techniques for RTKA use navigation systems developed for primary TKA. A new computer assisted technique for RTKA is presented. Methods: This technique is based on the use of a navigation system, RTKANav consisting of an optical localizer, a dedicated software and some navigated tools specifically done for RTKA. The system doesn’t use medical images, and patient anatomy model is represented with dots and lines corresponding to acquired landmarks, providing the surgeon with the main references for the intervention monitored in real-time. During the most critical steps of the intervention (soft tissue balancing and the consequent choice of implant size, and joint line height restoration), the system provide the surgeon with graphical and numerical tools to improve the surgical outcome. Several criteria to set each degree of freedom of prosthetic components are considered and compared, and even if some required landmarks can not be identified, the system is always able suggest an intervention plan. The surgeon is provided with tools to analyze and modify the proposed plan, and to reproduce it on the patient. Results: Till now the presented technique was used on five patients by an expert surgeon. Qualitative results, collected after the intervention through a questionnaire on surgeon feelings, in order to assess the functionality, user friendliness and the data visualization criteria implemented were very satisfying. System reliability was assessed intraoperatively analyzing joint line height, limb alignment and knee stability using trial components: based on his experience, the surgeon checked some acceptable components combination and compared the corresponding outcome with the one provided by the implant planned by the system. In three out five cases the suggested implant was considered the best by the surgeon, while in one case he decided to change the tibial insert of one size because of knee instability and in another case he changed the tibial component of one size because the planned one was too small. Final limb alignment evaluated with postoperative x-rays, was satisfactory in all cases. Conclusions: Presented navigation system showed early promising results providing the surgeon with intraoperative quantitative and qualitative information on the main surgical parameters, useful to achieve a satisfactory prosthesis implant. Moreover this system use anatomical patient specific landmarks acquired after prosthesys removal, while navigation systems developed for primary TKA use both reference taken from preoperative x-rays and anatomical references acquired on metal component to be removed. Therefore in this case the operation planning is based on rough anatomical landmarks that do not reflect patients original anatomy

Introduction: Computer assisted knee arthroplasty (CAKA) has been shown in a number of studies to result in improved post-operative alignment of prostheses. However prosthetic alignment is only one part of total knee arthroplasty surgery and outcome is likely to depend on other factors such as soft tissue balancing. Our study compared the functional outcome following knee arthroplasty using CAKA or conventional instrumentation, and investigated whether the theoretical advantage of improved prosthesis alignment with CAKA resulted in improved functional outcome. Materials and Methods: Data on 299 patients have been recorded to date. 139 patients have a minimum one year follow up. No patients were lost to follow up. All patients were operated on by a single surgeon at a dedicated arthroplasty centre and were allocated to one of two groups: Computer assisted navigation using a robot assisted technique (PiGalilieo, Plus Orthopaedics, Rotkreuz, Switzerland), or using conventional instrumentation. In both groups the prosthesis used was the TC-Plus Self-aligning bearing (Plus Orthopaedics). Functional outcome was measured using the Oxford Knee Score (OKS). A power analysis was performed with alpha of 0.05 and power of 80%. In order to detect a difference of 4 points in the OKS, 126 patients were required. This number was exceeded in our study at one year. Results: The mean OKS at one year follow up was 24.9 (range 12 – 54, s.d. 9.8) for the CAKA group and 25.3 (range 12–49, s.d. 9.7) for the control group. There was no significant difference in functional outcome at one year between the two groups (p = 0.41). At two years follow up the mean OKS was 25.39 (range 13 – 53, s.d. 10.3) for the CAKA group and 24.14 (range 12–43, s.d. 9.1) for the control group (p = 0.33). The results for the two year follow up group should be treated with caution as further patient numbers are awaited to obtain adequate power. Conclusions: Although several studies show that use of CAKA results in improved prosthesis alignment, our study indicates that CAKA does not result in improved functional outcome as assessed by the patient at short term follow up. Improved prosthesis alignment is thought to result in improved long term outcome, however long term studies are necessary to show whether the known advantages of CAKA in improved prosthesis alignment results in improved patient satisfaction and increased implant survival. These further studies are important in order to justify the increased costs associated with CAKA

Cadeveric studies showed that single bundle ACL reconstructions were successful in limiting anterior tibial translation but were insufficient to control a combined rotatory load of internal and valgus torque. One possible cause of these condition could be that current single bundle procedures cannot realistically reproduce the complex anatomy of the ACL, especially the different function of its anteromedial(AM)and posterolateral(PL)bundle. The hypothesis of our study is that the addition of the PL bundle to the AM bundle, in an “in vivo” double bundle computer assisted ACL reconstruction, is actually able to reduce the internal rotation of the tibia at 30° degrees of knee flexion. Computer assisted ACL reconstruction has been used because it could be very effective in evaluating the global performance of the reconstructed knee. Ten consecutive doble bundle ACL reconstructions were performed in our Hospital using hamstrings graft and the 2.0OrthoPilot-B. Braun-Aesculap ACLnavigation system. The average age of patients was 27.8 years. The double-looped semitendinosus tendon replicating the AM bundle was fixed first at 60° of knee flexion. Than the gracilis tendon replicating the PL bundle was fixed at 15° of knee flexion. Maximum manual A–P displacement at 30° of flexion, maximum internal and external rotation of the knee were evaluated using the navigation system before surgery and after single(A–M)and double (AM+PL)bundle reconstruction. Statystical anlisys was done using paired T-test. Before ACL reconstruction mean manual maximum AP displacement was 17.2mm;mean manual maximum internal rotation was 19.8mm and mean manual maximum external rotation was 16.8mm. After AM bundle reconstruction mean manual maximum AP displacement was 6.1mm;mean manual maximum internal rotation was 17.0mm and mean manual maximum external rotation was 16.3mm. After AM+PL bundles reconstruction mean manual maximum AP displacement was 5.3mm;mean manual maximum internal rotation was 16.2mm and mean manual maximum external rotation was 14.6mm. There was no statistically significant difference in the tibial internal rotation at 30° after single bundle(AM)and double bundle(AM+PL)reconstruction. In this study the effectiveness of the PL bundle in controlling the internal rotation of the tibia, responsible of rotational instability of the knee, was evaluated in “in vivo” ACL reconstruction. The navigator system allowed us to obtain “in vivo” the real and correct value of AP displacement and internal and external rotation of the tibia before and after reconstruction. Our hypothesis that the addition of the PL bundle to the AM bundle is actually able to reduce the internal rotation of the tibia at 30° degrees of knee flexion, minimizing the pivot shift phenomenon, on the basis of our study has not been confirmed

Patellofemoral complications in total knee arthroplasty (TKA) are common. Patellar tracking can be adversely affected by component positioning, soft tissue imbalance and bony deformity. Lateral patellar release rates reported in the literature vary from 6– 40%. Computer assisted surgery has largely been confined to the tibio-femoral component of total knee replacement. However, with recently developed software, it can be used to visualise and quantify patellar tracking and thus guide the precise extent and site of lateral patellar release. The aim of this early study was to define the diagnostic envelope for identification and quantisation of patella maltracking using a current generation patella navigation system. Our previous prospective analysis of 100 patients undergoing primary TKA identified pre-operative radiographic indices that correlate with maltracking of the patellofemoral joint. 20 cases were subsequently selected for computer assisted total knee replacement surgery. The navigation system (Vector Vision (BrainLab) version 1.6) was used to achieve accurate alignment and position of the femoral and tibial components. All knee replacements were performed using a posterior cruciate-retaining prosthesis. The femoral component was of a ‘patella-friendly’ design with inbuilt 3 degrees external rotation, and the patella was resurfaced in all cases with a biconvex inlay patellar prosthesis. Patellar tracking was assessed intra-operatively using an additional patellar array and patella tracking-specific software. Real-time displays of patella shift, tilt, rotation and circle radii during multiple flexion-extension cycles were obtained. Where necessary, an ‘outside-to-in’ release of the lateral retinacular complex was performed. The navigation system was used to provide contemporaneous feedback on the effect of the soft tissue releases on the tracking characteristics of the patella component on the prosthetic trochlea. Primary outcomes included the sensitivity and specificity of the system for peri-operative patella maltracking; secondary outcomes included the definition of interventional endpoints and correlation of intra-operative tracking data with post-operative x-rays. The demographic data for the 20 patients enrolled in this study was essentially unremarkable. As compared to standard intra-operative clinical evaluation of patella tracking, the computer navigation system is equally sensitive and specific, and it can potentially detect more subtle instances of maltracking that may elude conventional clinical evaluation. We present patterns of patellar tracking during the surgery for patient with and without pre-operative patellar maltracking. However, the significance of this is unknown without longer-term outcome data. Patella shift abnormalities that were detected by the system, but not tilt, correlated with clinical judgement of patella maltracking (p< 0.05). Soft tissue balancing of the patella can now be performed by observing precise changes in shift and tilt. This can be as important as component alignment for optimising patellar tracking and minimising patellofemoral complications

Introduction: Computer assisted knee arthroplasty (CAKA) has been shown in a number of studies to result in better post-operative alignment of prostheses. However good prosthetic alignment is only one part of total knee arthroplasty surgery and outcome is likely to depend on other factors such as soft tissue balancing. Our study aimed to compare the functional outcome following knee arthroplasty using CAKA or conventional instrumentation, and to determine whether the theoretical advantage of improved prosthesis alignment with CAKA resulted in improved functional outcome. Materials and Methods: Data on 299 patients have been recorded to date. 139 patients have a minimum one year follow up. No patients were lost to follow up All patients were operated on by a single surgeon at a dedicated arthroplasty centre and were allocated to one of two groups: Computer assisted navigation using a robot assisted technique (PiGalilieo, Plus Orthopaedics, Rotkreuz, Switzerland), or using conventional instrumentation. In both groups the prosthesis used was the TC-Plus Self-aligning bearing (Plus Orthopaedics). Functional outcome was measured using the Oxford Knee Score (OKS). There was no statistical difference in pre-operative OKS and demographic data between the two groups. A power analysis was performed with alpha of 0.05 and power of 80%. In order to detect a difference of 4 points in the OKS, 126 patients were required. This number was exceeded in our study at one year. Results: The mean OKS at one year follow up was 24.9 (range 12–54, standard deviation (s.d) 9.8) for the CAKA group and 25.3 (range 12– 49, s.d. 9.7) for the control group. There was no significant difference in functional outcome at one year between the two groups (p = 0.41). At two years follow up the mean OKS was 25.39 (range 13–53, s.d. 10.3) for the CAKA group and 24.14 (range 12– 43, s.d. 9.1) for the control group (p = 0.33). The results for the two year follow up group should be treated with caution as further patient numbers are awaited to obtain adequate power. Conclusion: Although several studies show that use of CAKA results in improved prosthesis alignment, our study indicates that CAKA does not result in improved functional outcome as assessed by the patient at short term follow up. Improved prosthesis alignment is thought to result in improved long term outcome, however long-term studies are necessary to show whether the known advantages of CAKA in improved prosthesis alignment results in improved patient satisfaction and increased implant survival in order to justify the increased costs associated with CAKA

Whilst computer assistance enables more accurate arthroplasty to be performed, demonstrating this is difficult. The superior results of CAOS systems have not been widely appreciated because accurate determination of the position of the implants is impossible with conventional radiographs for they give very little information outside their plane of view. We report on the use of low dose (approximately a quarter of a conventional pelvic scan), low cost CT to robustly measure and demonstrate the efficacy of computer assisted hip resurfacing. In this study we demonstrate 3 methods of using 3D CT to measure the difference between the planned and achieved positions in both conventional and navigated hip resurfacing. The initial part of this study was performed by imaging a standard radiological, tissue equivalent phantom pelvis. The 3D surface models extracted from the CT scan were co-registered with a further scan of the same phantom. Subsequently both the femoral and acetabular components were scanned encased in a large block of ice to simulate the equivalent Hounsfield value of human tissue. The CT images of the metal components were then co-registered with their digital images provided by the implant manufactures. The accuracy of the co-registration algorithm developed here was shown to be within 0.5mm. This technique was subsequently used to evaluate the accuracy of component placement in our patients who were all pre-operatively CT scanned. Their surgery was digitally planned by first defining the anterior pelvic plane (APP), which is then used as the frame of reference to accurately position and size the wire frame models of the implant. This plan greatly aids the surgeon in both groups and in the computer assisted arm the Acrobot Wayfinder uses this pre-operative plan to guide the surgeon. Following surgery all patients, in both groups were further CT scanned to evaluate the achieved accuracy. This post-operative CT scan is co-registered to the pre-operative CT based plan. The difference between the planned and achieved implant positions is accurately computed in all three planes, giving 3 angular and 3 translational numerical values for each component. Further analysis of the CT generated results is used to measure the implant intersection volume between the pre-operatively planned and achieved positions. This gives a single numerical value of placement error for each component. These 3D CT datasets have also been used to quantify the volume of bone resected in both groups of patients comparing the simulated resection of the planned position of the implant to that measured on the post-operative CT. This study uses 3D CT as a surrogate outcome measure to demonstrate the efficacy of CAOS systems

Measurements of a patient’s anatomy are often made in two different forms, for instance from a computer tomography (CT) scan and by direct measurement of the anatomy, or when comparing a CT and a magnetic resonance imaging (MRI) scan or at different times. Therefore, it is almost inevitable that the patient will be measured in a different position each time, since the relative position between the patient and the measuring or scanning device will be different. To align the patient’s anatomy between these different measurement systems a process of registration is used. This is necessary in a number of fields including computer assisted navigation, robotic assisted surgery and diagnostics. Computer assisted surgery (CAS) generally involves “patient to modality” registration, as, in any CAS application that involves planning, the relationship between the modeled space (where the procedure is planned) and the patient’s workspace (where the procedure is executed) needs to be established. Patient to modality registration involves the registration of patient-specific anatomy with an image acquired using one of many modalities. It is usually associated with intra-operative registration, where the actual patient’s position needs to be known with respect to a pre-operative or previously acquired image. Even though the acquisition of patient-specific information may itself involve the use of a modality, the purpose of the process is to register the patient’s position against the model. The two co-ordinate systems to be registered belong to the patient and to the modality used to acquire the registration image, respectively. In “image-based” methods, identifiable features, such as fiducial marker screws or anatomical landmarks, are first extracted from the model, which is generally reconstructed from CT images, and then “sensed,” or located, in the operating theatre. This process provides the system with enough positional information for the model’s and patient’s spaces to be registered against a common co-ordinate system. In recent years, the CAS community has seen a shift to “image-free” methods, where both the plan and registration process are carried out without any prior knowledge of the patient’s anatomy. The pre-operative image acquisition stage is avoided altogether, and the planning is executed intra-operatively during surgery. A complete functional model of the patient is reconstructed from anatomical landmarks sensed intra-operatively and, in some instances; intra-operatively acquired surface information is used to “morph” a standard anatomical atlas to resemble that of the patient. Image-free methods offer the prospect of no pre-operative imaging or planning, however their value, in terms of intra-operative workflow and accuracy of outcome, has yet to be assessed when compared to image-based methods

In recent years, there has been a growing interest to incorporate ultrasound into computer assisted orthopaedic surgery procedures in order to provide non-ionizing intra-operative imaging alternative to traditional fluoroscopy. However, identification of bone boundaries still continues to be a challenging process due low signal to noise ratio and imaging artifacts. The quality of the collected images also depends on the orientation of the ultrasound transducer with respect to the imaged bone surface. Shadow region is an important feature indicating the presence of a bone surface in the collected ultrasound data. In this work, we propose a framework for the enhancement of shadow regions from extended field of view spine ultrasound data. First bone surfaces are enhanced using a combination of local phase based image features. The combination of the phase features provides a more compact representation of vertebrae bone surfaces with supressed soft tissue interfaces. These enhanced features are used as an input to a L1 norm based regularisation method which emphasised uncertainty in the shadow regions. Validation on phantom and in vivo experiments achieve a mean dice coefficient value of 0.93 and 0.9 respectively

Aims: The aim of the study was to determine the accuracy of the kinematical determination of the centre of rotation of the hip and to compare the outcome of the Computer assisted surgery (CAS) group versus a control group of patients with conventionally instrumented TKA, in a prospective randomized way. Methods: A prospective, randomized and controlled trial was undertaken with an image based CAS system (ION®), using specific knee software for the GENESIS II®total knee system. Randomization was performed on a consecutive group of 50 primary TKA’s, without exclusion criteria. All computed kinematical centres of rotation of the hip were compared to the anatomic fluoroscopic images. The difference between the kinematical centre of rotation and the anatomic centre of the femoral head was measured in the frontal plane. Coronal alignment was measured on full leg standing films. Validation of the full leg standing films was carried out in comparing the pre-operative measured angle and the computed deformity angle at the beginning of the surgery. Outcome of the CAS group was compared to the conventional group on the following items: tourniquet time, operative time, blood loss, patellar alignment, tibial slope, coronal alignment, range of motion and complications. Results: ACCURACY: The correlation index between pre-op full legs and CAS measured values was excellent: r. 2. =0.997. Difference between kinematical centre of rotation and anatomic centre of the hip: mean deviation between the two points was 1.2 mm (0–4mm), stdv 1.2 mm. This corresponds with a mean angular deviation of 0.17° (0–0.57°). OUTCOME: Tourniquet time: conventional 56 min., CAS 72 min. p=0.002. Operative time: conventional 70 min., CAS 93 min. p< 0.001. Blood loss: conventional 3.3 g/dl, CAS 4 g/dl. Patellar alignment: no tilt > 5°, no subluxation > 3 mm, both groups. Tibial slope: conventional 3.5°, CAS 3°. Post-operative mechanical alignment was between 0 and 2° of deformity for 16 conventional knees, and between 3–4° for 5 conventional knees. In the CAS group, all 21 knees scored between 0° and 2° of mechanical alignment. ROM at 6 weeks: flexion conventional 106°, CAS 105°. Fixed flexion contracture: conventional 2.9, CAS 2.1. Complications: delayed wound healing: conventional 2, CAS 1. Conclusions: Computer assisted kinematical determination of the centre of the hip can be highly accurate. Post-operative coronal alignment in CAS group is excellent, however not significantly better than conventional instrumentation

Many recent studies emphasise the importance of surgical technique for achieving long-lasting, pain-free, optimally functioning TKR. However, little information exists in the accuracy with which each step of the TKR procedure is performed using current instrumentation. This study examines the accuracy with which each step of the TKR procedure using current, intramedullary instrumentation. Twenty primary TKR were performed using a current, intramedullary instrumentation system. The accuracy of each femoral and tibial cut and the accuracy of the final frontal and sagittal limb alignment were measured using an image-free computer assisted navigation system. The system made it possible to measure: 1) frontal femoral implant alignment; 2) sagittal femoral implant alignment; 3) femoral implant rotational alignment; 4) frontal tibial implant alignment; 5) sagittal tibial implant alignment; 6) frontal limb alignment; 7) sagittal limb alignment. Alignment results are expressed in terms of the mechanical axis. Optional results are a frontal and sagittal axis of 90° relative to the mechanical axis. The optimal femoral rotational alignment is 3 degrees externally rotated from the posterior femoral condyles or zero degrees externally rotated from Whitesides line. The alignment results were: 1) frontal femoral alignment: 89° (range 87 to 92°); 2) sagittal femoral alignment: 89 (range 88 to 193°); 3) femoral rotational alignment: 1° external rotation vs. femoral condyle; 2 degrees internally rotated vs. Whitesides line (range 0.5° to 3.5°); 4) frontal tibial alignment: 88° (87° to 93°); 5) sagittal tibial axis: 87° (range 86° to 91°); 6) frontal limb alignment: 179° (range 177 to 181°); 7) sagittal limb alignment 179° (range 174 to 180°). Intramedullary instrumentation allows reasonably accurate and reproducible frontal limb alignment. There is a tendency to leave the limb in slight flexion when using intramedullary instruments. There is also a consistent tendency to internally rotate the femur with current anterior –posterior alignment guides and to excessively posteriorly flex the tibial component, although almost all of the 20 TKR’s resulted in final limb alignment within 3 degrees of frontal and sagittal axes. Very few (4) TKR’s were performed in which all of the measured steps were within 3 degrees of the optimal position. The study emphasises that current intramedullary instrumentation does not result in a high incidence of accuracy when each step of the procedure is measured. Computer assisted techniques permit measurement of the steps of the TKR procedure with a high degree (error < 1°) of accuracy. Longevity, pain-relief and funtion should be related to the total accuracy with which TKR are performed