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

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

Background. The posterior slope of the tibial component in total knee arthroplasty (TKA) has been reported to vary widely even with computer assisted surgery. In the present study, we analyzed the influence of posterior tibial slope on one-year postoperative clinical outcome after posterior-stabilized (PS) -TKA to find out the optimal posterior slope of tibial component. Materials and Method. Seventy-three patients with varus type osteoarthritic (OA) knees underwent PS-TKA (Persona PS. R. ) were involved in this study. The mean age was 76.6 years old and preoperative HKA angle was 14.3 degrees in varus. Tibial bone cut was performed using standard extra-medullary guide with 7 degrees of posterior slope. The tibial slopes were radiographically measured by post-operative lateral radiograph with posterior inclination in plus value. The angle between the perpendicular line of the proximal fibular shaft axis and the line drawn along the superior margin of the proximal tibia represented the tibial slope angle. We assessed one-year postoperative clinical outcomes including active range of motion (ROM), patient satisfaction and symptoms scores using 2011 Knee Society Score (2011 KSS). The influences of posterior tibial slope on one-year postoperative parameters were analyzed using simple linear regression analysis (p<0.05). Results. The average posterior tibial slope was 6.4 ± 2.0 °. The average active ROM were −2.4 ± 6.6 ° in extension and 113.5± 12.6 ° in flexion. The mean one-year postoperative patient satisfaction and symptom scores were 29.3 ± 6.4 and 19.6 ± 3.9 points respectively. The active knee extension, satisfaction and symptom scores were significantly negatively correlated to the posterior tibial slope (r = −0.25, −0.31, −0.23). Discussion. In the present study, we have found significant influence of the posterior tibial slope on the one-year postoperative clinical outcomes in PS-TKA. The higher posterior slope would induce flexion contracture and deteriorate patient satisfaction and symptom. We had reported that the higher tibial posterior slope increased flexion gap and the component gap change during knee flexion in PS-TKA. Furthermore, another study reported that increase of the posterior tibia slope reduced the tension in the collateral ligaments and resulted in the knee laxity at flexion. The excessive posterior slope of tibial component would result in flexion instability, and adversely affected the clinical results including patient satisfaction and symptom. Conclusion. In the PS-TKA for varus type OA knees, excessive tibial posterior slope was found to adversely affect one-year postoperative knee extension and clinical outcome including patient satisfaction and symptom. Surgeons should aware of the importance of tibial slope on one-year postoperative clinical results and pay more attentions to the posterior tibial slope angle not to be excessive

INTRODUCTION. Variability in placement of total shoulder arthroplasty (TSA) glenoid implants has led to the increased use of 3D CT preoperative planning software. Computer assisted surgery (CAS) offers the potential of improved accuracy in TSA while following a preoperative plan, as well as the flexibility for intraoperative adjustment during the procedure. This study compares the accuracy of implantation of reverse total shoulder arthroplasty (rTSA) glenoid implants using a CAS TSA system verses traditional non-navigated techniques in 30 cadaveric shoulders relative to a preoperative plan from 3D CT software. METHODS. High resolution 1mm slice thickness CT scans were obtained on 30 cadaveric shoulders from 15 matched pair specimens. Each scan was segmented and the digital models were incorporated into a preoperative planning software. Five fellowship trained orthopedic shoulder specialists used this software to virtually place a rTSA glenoid implant as they deemed best fit in six cadavers each. The specimens were randomized with respect to side and split into a cohort utilizing the CAS system and a cohort utilizing conventional instrumentation, for a total of three shoulders per cohort per surgeon. A BaSO. 4. PEEK surrogate implant identical in geometry to the metal implant used in the preoperative plan was used in every specimen, to maintain high CT resolution while minimizing CT artifact. The surgeons were instructed to implant the rTSA implants as close to their preoperative plans as possible for both cohorts. In the CAS cohort, each surgeon used the system to register the native cadaveric bones to each respective CT, perform the TSA procedure, and implant the surrogate rTSA implant. The surgeons then performed the TSA procedure on the opposing side of the matched pair using conventional instrumentation. Postoperatively, CT scans were repeated on each specimen and segmented to extract the digital models. The pre- and postoperative scapulae models were aligned using a best fit match algorithm, and variance between the virtual planned position of the implant and the executed surgical position of the implant was calculated [Fig 1]. RESULTS. For version and inclination, implants in the CAS cohort showed significantly less deviation from preoperative plan than those in the non-navigated cohort (Version: 1.9 ± 1.9° vs 5.9 ± 3.5°; p < .001; Inclination: 2.4 ± 2.5° vs 6.3 ± 6.2°; p = .031). No significant difference was noted between the two cohorts regarding deviation from the preoperative plan in anterior-posterior and superior-inferior positioning on the glenoid face (1.5 ± 1.0mm CAS cohort, 2.4 ± 1.3mm non- navigated cohort; p = .055). No significant difference was found for deviation from preoperative plan for reaming depth (1.1. ± 0.7mm CAS cohort, 1.3 ± 0.9mm non-navigated cohort; p =.397). CONCLUSION. The results of this study demonstrate that this CAS navigation system facilitates a surgeon's ability to more accurately reproduce their intended glenoid implant version and inclination (with respect to their preoperative plan), compared to conventional non-navigated techniques. Future work will determine if more accurate and precise implant placement is associated with improved clinical outcomes. For any figures or tables, please contact the authors directly

Acetabular cup placement in total hip replacement surgery is often difficult to assess, especially in the lateral position and using the posterior approach. On table control X-Rays are not always accessible, especially in the government sector. Conventional techniques and computer assisted surgery (CAS), are currently the two most popular methods for proper placement of the acetabular cup in Lewinnek's safe zone of orientation (anteversion 15°–10° and lateral inclination 40°±10°). We developed a simple way to get accurate cup placement using Smartphone technology. Methods:. A spirit level application was downloaded to the Smartphone. The acetabulum inclination was measured on the pre-operative X-Rays. The phone is placed in a sterile bag and then used intra-operatively, to measure and set our acetabular cup orientation to our pre-operative measurements. The inclination level was measured before and after final placement of the acetabular cup. This was compared to the acetabular cup inclination in our post-operative X-Rays. Results:. In our series of 50 cup placements we found high accuracy. The results show less than 5° deviation between our pre-, intra- and post-operative measurements. Conclusions:. Smartphone technology proves to be good alternative to conventional methods and CAS, to improve Acetabular Cup placement in Total Hip Arthroplasty

Conventional total knee arthroplasty aims to place the joint line perpendicular to the mechanical axis, despite the fact that the normal knee is inclined approximately 3 degrees, resulting in a medial proximal tibial angle of 87 degrees. The goal of a neutral mechanical axis is based largely on historical biomedical studies and the fact that it is easier to make a neutral tibial cut with conventional jigs and the eye. In order to balance the flexion and extension gap to accommodate a neutral tibial cut, in most patients, asymmetrical distal and posterior femoral cuts are required. The resulting position of the femoral component could be considered to be “mal-rotated” with respect to the patient's soft tissue envelope. Soft tissue releases are often required. The target of neutral mechanical axis, or “straight and narrow,” represents a compromise position with respect to the kinematics of the knee. Neutral mechanical alignment may not confer any befits with respect to survivorship but dissatisfaction rates are high globally, with approximately 20% of patients being dissatisfied after total knee arthroplasty in multiple studies. Computer assisted surgery and shape matching allow for consideration of placing total knee components to match an individual's anatomy, as opposed to forcing the knee into an unnatural neutral mechanical alignment

Computer assisted surgery (CAS) has gained popularity in orthopaedics for both total knee (TKA) and total hip arthroplasty (THA) in the past decades as a stereotactic device that provides the surgeon with real-time feedback on implant position based on electromagnetic or infrared based instruments. The purpose of this study was to assess the effect of CAS on 30-day complication rates following THA and TKA. The American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database was used to identify all patients that underwent THA and TKA from 2011 to 2013, as well as any complication they had within 30-days of their surgery. Univariate and multivariate regression analysis was used to compare the post-operative complications in patients whose surgery involved the use of CAS with those by conventional surgical techniques. We identified 104,550 patients who had THA (42,275 patients) and TKA (62,275 patients) procedures in the database between 2011 and 2013. Computer Assisted Surgery was used in 1,120 THA and 2,173 TKA procedures. There were higher overall adverse events (OR 1.40, CI: 1.22–1.59) in the Conventional group when compared to CAS for TKA. The rate of overall minor events (OR 1.38, CI: 1.21–1.58) and requirements for blood transfusion (OR 1.44, CI: 1.25–1.67) were higher in the Conventional group compared to the CAS group for TKA. However, rate of re-operation was significantly higher in the CAS group for TKA (OR 1.60, CI: 1.15–2.25). The results also showed higher overall adverse events (OR 2.61, CI: 2.09–3.26) in the Conventional group when compared to CAS for THA. The rate of overall minor events (OR 2.72, CI: 2.16–3.42) and requirements for blood transfusion (OR 3.27, CI: 2.52–4.25) was higher in the Conventional group whereas superficial wound infections (OR 0.46, CI: 0.46–0.81) were shown to be higher in the CAS group. The result also showed slightly longer operative times in CAS for both THA and TKA. This study analysed a large patient database involving multiple institutions and surgeons and found that, overall, the use off CAS in primary total hip and total knee arthroplasty reduced the number of adverse events in the first 30-days postoperatively, compared to conventional surgical techniques. However, CAS was associated with an increased number of reoperations, superficial infections and operating time. The clinical benefits and disadvantages of CAS should be considered by arthroplasty surgeons when determining the potential benefit-cost ratio of this technology

Introduction. The use of a surgical navigation system has been demonstrated to allow to intraoperatively analyze knee kinematics during total knee arthroplasty (TKA), thus providing the surgeon with a quantitative and reproducible estimation of the knee functional behaviour. Recently severak authors used the computer assisted surgery (CAS) for kinematic evaluations during TKA, in particular to evaluate the achievement of a correct joint biomechanics after the prosthesis implantation. The major concern related to CAS is that the movements are usually passively performed, thence without a real active task performed by the subject. Starting from the hypothesis that the passive kinematics may properly describe the biomechanic behaviour of the knee, the main goal of this work was to intra-operatively compare the active kinematics of the limb, analysing a flexion movement actively performed by the patient, and the passive kinematics, manually performed by the surgeon. Methods. The anatomical and kinematic acquisitions were performed on 31 patients TKA using a commercial navigation system (BLU-IGS, Orthokey, USA). All the surgeries were performed under local anesthesia, which specifically allowed to acquire the passive and active kinematics including three flexion movements. Both in pre- and post-implant conditions, internal-external (IE) rotations and anterior-posterior (AP) translations were estimated to track any changes in the kinematic pattern. Results. The IE rotations showed no statistical difference (n.s.) for all the condition under study, in particular no differences existed between the active and the passive kinematics (Figure 1). Similarly, the AP translations (Figure 2) did not show any statistical difference (n.s.) both between active and passive flexion movement, and between pre- and post- implant conditions (n.s.). Conclusions. The use of a navigation system in TKA has beed identified to be extremely useful not only to assist the operator in providing a proper surgical procedure, but also in performing an accurate estimation of the joint kinematics. The performed analysis of the active flexion movement compared to the passive one, demonstrated that the absence of the active muscle contraction did not affect the knee kinematics estimation. The analysis of knee kinematics with CAS could be considered therefore comparable to other techniques which allow to analyse the dynamic control performed by the subject during active tasks, such as fluoroscopy or gait analysis

Purpose:. Correct placement of the acetabular cup is a crucial step in hip replacement to achieve a satisfactory result and remains a challenge with free hand techniques. Imageless navigation may provide a viable alternative to freehand technique and improve placement significantly. The purpose of this project was to assess and validate intra-operative placement values as displayed by an imageless navigation system to postoperative measurement of cup position using high resolution CT scans. Methods:. Thirty-two subjects who underwent primary hip joint arthroplasty using imageless navigation were included. The average age was 66.5 years (range 32–87). 23 non-cemented and 9 cemented acetabular cups were implanted. The desired position for the cup was 45 degrees of inversion and 15 degrees of anteversion. A pelvic CT scan using a multi-slice CT was used to assess the position of the cup radiographically. Results:. Two subjects were excluded because of dislodgement of the tracking pin. Pearson correlation revealed a strong and significant correlation (r=0.68; p<0.006) for cup inclination and a moderate non-significant correlation (r=0.53; p=0.45) between intra-operative readings and cup placement for anteversion. Conclusion:. These findings can be explained with the possible introduction of systematic error. Even though the acquisition of anatomic landmarks is simple, they must be acquired with great precision. An error of 1 cm can result in a mean anteversion error of 6 degrees and inclination error of 2.5 degrees. Whilst computer assisted surgery results in highly accurate cup placements for inclination, anteversion of the cup cannot be

Introduction. Clear operative oncological margins are the main target in malignant bone tumour resections. Novel techniques like patient specific instruments (PSIs) are becoming more popular in orthopaedic oncology surgeries and arthroplasty in general with studies suggesting improved accuracy and reduced operating time using PSIs compared to conventional techniques and computer assisted surgery. Improved accuracy would allow preservation of more natural bone of patients with smaller tumour margin. Novel low-cost technology improving accuracy of surgical cuts, would facilitate highly delicate surgeries such as Joint Preserving Surgery (JPS) that improves quality of life for patients by preserving the tibial plateau and muscle attachments around the knee whilst removing bone tumours with adequate tumour margins. There are no universal guidelines on PSI designs and there are no studies showing how specific design of PSIs would affect accuracy of the surgical cuts. We hypothesised if an increased depth of the cutting slot guide for sawblades on the PSI would improve accuracy of cuts. Methods. A pilot drybone experiment was set up, testing 3 different designs of a PSI with changing cutting slot depth, simulating removal of a tumour on the proximal tibia (figure 1). A handheld 3D scanner (Artec Spider, Luxembourg) was used to scan tibia drybones and Computer Aided Design (CAD) software was used to simulate osteosarcoma position and plan intentioned cuts (figure 1). PSI were designed accordingly to allow sufficient tumour. The only change for the 3 designs is the cutting slot depth (10mm, 15mm & 20mm). 7 orthopaedic surgeons were recruited to participate and perform JPS on the drybones using each design 2 times. Each fragment was then scanned with the 3D scanner and were then matched onto the reference tibia with customized software to calculate how each cut (inferior-superior-vertical) deviated from plan in millimetres and degrees (figure 3). In order to tackle PSI placement error, a dedicated 3D-printed mould was used. Results. Comparing actual cuts to planned cuts, changing the height of the cutting slot guide on the designed PSI did not deviate accuracy enough to interfere with a tumour resection margin set to maximum 10mm. We have obtained very accurate cuts with the mean deviations(error) for the 3 different designs were: [10mm slot: 0.76±0.52mm, 2.37±1.26°], [15mm slot: 0.43±0.40mm, 1.89±1.04°] and [20mm: 0.74±0.65mm, 2.40±1.78°] respectively, with no significant difference between mean error for each design overall, but the inferior cuts deviation in mm did show to be more precise with 15mm cutting slot (p<0.05) (figure 2). Discussion. Simulating a cut to resect an osteosarcoma, none of the proposed designs introduced error that would interfere with the tumour margin set. Though 15mm showed increased precision on only one parameter, we concluded that 10mm cutting slot would be sufficient for the accuracy needed for this specific surgical intervention. Future work would include comparing PSI slot depth with position of knee implants after arthroplasty, and how optimisation of other design parameters of PSIs can continue to improve accuracy of orthopaedic surgery and allow increase of bone and joint preservation. For figures/tables, please contact authors directly.

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

Gap planning in total knee arthroplasty (TKA) navigation is critically concerned. Osteophyte is one of the contributing factors for gap balancing in TKA. The osteophyte is normally removed before gap planning step. However, the posterior condylar osteophyte of femur is sometimes removed during the flexion gap preparation or may not be removed at all depends on individual case. This study attempts to investigate on how posterior condylar osteophyte affects on gap balancing and limb alignment during operation. The study was conducted on 35 varus osteoarthritis knees with posterior condylar osteophyte and undergone on TKA navigation. All knees were measured by CT scan for the size of posterior condylar osteophyte according to its width. Extension gap, flexion gap width, and limb alignment were measured by using the tension device with distraction force of 98 N on both medial and lateral sides under computer assisted surgery. The measuring of extension gap, flexion gap width, and limb alignment was undertaken before and after the posterior condylar osteophyte removal. This study reveals that the mean of the size of posterior condylar osteophyte after removal is 8.96 mm. The posterior condylar osteophyte has an effect on the increasing of medial extension gap and lateral extension in average 0.74 ± 0.72 mm. and 0.42 ± 0.67 mm. respectively. It also increases 0.71 ± 1.00 mm. in medial flexion gap and 0.97 ± 1.47 mm. in lateral flexion gap. After the posterior condylar osteophyte removal the mean of varus deformity is decreased 0.90° ± 1.14 ° while the mean of extension angle of sagittal limb alignment is increased 1.61°±1.69°. There is also a significant relationship between the size of posterior condylar osteophyte and the increasing of lateral flexion gap and also with the varus deformity decreasing. If the size of posterior condylar osteophyte is increased 10 mm. the lateral flexion gap will be increased 1.15 mm. and varus deformity will be decreased 0.75 degree

Computer assisted surgery (CAS) is used in trauma surgery to reduce radiation and improve accuracy but it is time consuming. Some trials for navigation in small bone fractures were made, but they are still experimental. One major problem is the fixation of the dynamic reference base for navigation. We evaluated the benefit of a new image based guidance-system (Surgix®, Tel Aviv, Israel) for fracture treatment in scaphoid bones compared to the conventional method without navigation. The system consists of a workstation and surgical devices with embedded radio opaque markers. These markers as well as the object of interest must be on the same C-arm shot. If a tool is detected in an image by the attached workstation additional information such as trajectories are displayed in the original fluoroscopic image to serve the surgeon as aiming device. The system needs no referencing and no change of the workflow. For this study 20 synthetic hand models (Synbone®, Malans, Switzerland) were randomised in two groups. Aim of this study was a central guide-wire placement in the scaphoid bone, which was blindly measured by using postoperative CT-scans. Significant distinctions related to the duration of surgery, emission of radiation, radiation dose, and trials of guide-wire positioning were observed. By using the system the surgery duration was with 50 % shortened (p = 0.0054) compared to the conventional group. One reason might be the significant reduction of trials to achieve a central guide-wire placement in the bone (p = 0.0032). Consequently the radiation exposure for the surgeon and the patient could be shortened by reduction of radiation emission (p = 0.0014) and radiation dose (p = 0.0019). By using the imaged based guidance system a reduction of surgery duration, radiation exposure for the patient and the surgeon can be achieved. By a reduced number of trials for achieving a central guide-wire position the risk of weakening the bone structure can be minimised as well by using the system. The system seems helpful where navigation is not applicable up to now. The surgical workflow does not have to be chanced

Introduction:. Efforts continue to reduce blood loss in total knee arthroplasty (TKA). Computer assisted surgery (CAS) has been shown to reduce outliers in component position and improve functional outcomes in TKA, yet few studies have reported specifically on blood loss. The primary study objective was to determine whether a modern abbreviated CAS protocol would reduce blood loss in TKA compared to conventional instrumentation. A secondary objective was to assess the effect of CAS on cost and surgical efficiency. Methods:. A retrospective cohort study of 100 consecutive patients was performed comparing an abbreviated and modern CAS protocol versus conventional IM instrumentation. All TKAs utilized an identical surgical technique without any hemostatic agent. Blood loss was determined using drain output, change in hemoglobin, and calculated blood loss. Tourniquet times were recorded as an indicator of procedural efficiency. A cost analysis compared the CAS protocol to the cost associated with tranexamic acid (TXA) to reduce blood loss and long-leg alignment radiographs to optimize component position. Results:. Height, weight, BMI, and preoperative hemoglobin were similar between groups. The CAS group demonstrated a decrease in average hourly drain output (CAS 33.8 ml; conventional 40.5 ml; p = 0.024), decreased change in hemoglobin (CAS 2.2; conventional 3.1; p < 0.001), and estimated total blood loss (CAS 925 ml; conventional 1327 ml; p < 0.001) compared to conventional instrumentation. No patients in either group required a blood transfusion. In non-teaching cases, there was a mean increase of 5 minutes surgical time in the CAS group. Cost-analysis demonstrated CAS was less expensive than using TXA and long-leg alignment radiographs, with a savings of $564 for 200 TKAs annually and $284 for 100 TKAs annually. Conclusion:. AbbreviatedCAS is effective in reducing blood loss in TKA comparable to TXA, likely due to avoidance of the femoral IM canal, with minimal effect on surgical efficiency. Along with proven advantages of accurate component placement and improved functional outcome after TKA, the additional blood conservation supports CAS providing value in healthcare and obviates the need for advanced preoperative imaging and TXA, and can be used in patients regardless of cardiac or thromboembolic risk

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

Introduction. Computer assisted surgery (CAS) systems have been shown to improve alignment accuracy in total knee arthroplasty (TKA), yet concerns regarding increased costs, operative times, pin sites, and the learning curve associated with CAS techniques have limited its widespread acceptance. The purpose of this study was to compare the alignment accuracy of an accelerometer-based, portable navigation device (KneeAlignÒ 2) to a large console, imageless CAS system (AchieveCAS). Our hypothesis is that no significant difference in alignment accuracy will be appreciated between the portable, accelerometer-based system, and the large-console, imageless navigation system. Methods. 62 consecutive patients, and a total of 80 knees, received a posterior cruciate substituting TKA using the Achieve CAS computer navigation system. Subsequently, 65 consecutive patients, and a total of 80 knees, received a posterior cruciate substituting TKA using the KneeAlignÒ 2 to perform both the distal femoral and proximal tibial resections (femoral guide seen in Figure 1, and tibial guide seen in Figure 2). Postoperatively, standing AP hip-to-ankle radiographs were obtained for each patient, from which the lower extremity mechanical axis, tibial component varus/valgus mechanical alignment, and femoral component varus/valgus mechanical alignment were digitally measured. Each measurement was performed by two, blinded independent observers, and interclass correlation for each measurement was calculated. All procedures were performed using a thigh pneumatic tourniquet, and the total tourniquet time for each procedure was recorded. Results. In the KneeAlignÒ 2 cohort, 92.5% of patients had an alignment within 3° of a neutral mechanical axis (vs. 86.3% with AchieveCAS, p<0.01), 96.2% had a tibial component alignment within 2° of perpendicular to the tibial mechanical axis (vs. 97.5% with AchieveCAS, p=0.8), and 94.9% had a femoral component alignment within 2° of perpendicular to the femoral mechanical axis (vs. 92.5% with AchieveCAS, p<0.01). The mean tourniquet time in the KneeAlignÒ 2 cohort was 48.1 + 10.2 minutes, versus 54.1 + 10.5 in the AchieveCAS cohort (p<0.01). The interclass correlation coefficient for measurement of the postoperative tibial alignment was 0.92, for femoral alignment was 0.85, and for overall lower extremity alignment was 0.94. Conclusion. Accelerometer-based, portable navigation can provide the same degree of alignment accuracy as large console, imageless CAS system in TKA, while also decreasing operative times. The KneeAlignÒ 2 successfully combines the benefits and accuracy of large-console, CAS systems, while avoiding the use of extra pin sites, decreasing operative times, and providing a level of familiarity with conventional alignment methods

Over the last decade Computer Assisted Orthopaedic Surgery (CAOS) has emerged particularly in the area of minimally invasive Unicompartmental Knee Replacement (UKR) surgery. Image registration is an important aspect in all computer assisted surgeries which is a process of developing a spatial relationship between pre-operative data, such as Computerised Tomography (CT) scans or Magnetic Resonance Imaging (MRI) scans and the physical patient in the operation theatre. It allows the surgeon to visualise the 3D pre-operative scan data in-relation to the patient's anatomy in the operating theatre. Current image registration techniques for CAOS in minimally invasive UKR are achieved by digitising points on the articulating surface of the knee joint using a navigated probe. By using these digitised points a rigid body is formed which is then fitted to the pre-operative scan data using a best fit type minimisation. However, this manual digitisation approach is time consuming and often takes 15–20 minutes and is therefore costly. The rationale for this study was to develop a new, quick, cost effective, contactless shape acquisition technique which could produce an accurate rigid body model in theatre from the ends of the exposed bones using 3D scans taken intra-operatively by a Laser Displacement Sensor. Bespoke and automated 3D laser scanning techniques based on DAVID-Laserscanner have been developed and were used to scan surface geometry of the knee joint in 10 cadaveric legs. The Medial compartments of 9 joints had undergone a UKR procedure post donation but the lateral compartments were unaffected. The 9 legs were CT scanned and then segmented using Mimics 12.01 to generate 3D models of the medial compartments. The 10 legs were also MRI scanned using a 3D FLASH technique to produce 3D models of the lateral articular cartilage. All the samples were then 3D Laser scanned using a tailored plane-less technique and customised positioner assemblies. The CT and MRI generated 3D models were then registered with the corresponding 3D Laser scans in the Geomagic Qualify® package using manual surface registration. This is a type of surface (point based registration or free-form surface matching) registration which works closely on Iterative closest point (ICP) algorithm. Once the models were registered, a best fit alignment was performed between two datasets. Results indicate average best fit alignment errors and standard deviations ranging from 0.2 mm to 0.9 mm with errors normally distributed. Most of the errors could be attributed to calibration errors, segmentation errors and post-processing systematic errors. We have demonstrated the feasibility of using a novel laser scanning technique where by acquiring multiple scans of the tibio-femoral joint in theatre, complete 3D models of the geometry and surface texture can be developed which can be registered with the pre-operative scan. The overall time for scanning, post-processing and the registration requires less than 5 minutes and is a non-invasive, cost-efficient approach. This study has provided proof of concept for a new automated registration technique with the potential for providing a quantitative assessment of the articular cartilage integrity during lower limb arthroplasty

In order to enhance the acceptance of computer assisted surgery in joint replacement, a development-cooperation with BrainLAB, Germany was set up to develop a user-friendly handheld navigation device. A sterile draped Apple® IPod-Touch which is placed into a hardcover cradle, is used as navigation monitor and touchscreen control. Different instruments, such as navigation-pointer are attached to the cradle. In addition the workflows for TKR and THR procedures have been optimised. Therefore the main focus for TKR is navigation of femoral and tibial resection as well as leg alignment control. For the THR the system enables an intraoperative control of leg-length and femoral-offset measurement in comparison with the preoperative situation. Each step of the procedure is supported by video animations of the specific navigation workflow. Between September and December 2010 the first clinical study on the usability in TKR and THR was performed for 20 cases using a prototype system. The study was approved by the local ethic committee and the “German Federal Institute for Drugs and Medical Devices (BfArM)”. Special interest was taken to the aspects of usability and the necessary time periods for specific steps of the procedure. Usability was measured for specific time periods of the procedure assessment of the usability of the surgical team. In addition postoperative x-rays were evaluated for implant position, leg alignment for TKR and hip joint geometry for THR cases. Throughout the study for each assigned patient the procedure could be performed as planned. Several design inputs were identified for further improvement of the final system. Therefore time measurements of the first five cases were excluded. For the TKR cases the registration process of the last 5 cases was less than 3 minutes. The interval for the tibial resection was between 3 and 7 minutes (aligning tibial cutting block – end of tibial verification). The interval for the distal femur resection was between 7 and 11 minutes (aligning femoral cutting block – end of femoral verification). All 10 Patients showed a final leg alignment on the postoperative standing x-ray within the save-zone of +/− 3° from neutral alignment. For the THR cases the preoperative registration period including the femoral head resection and acetabular registration was between 7 and 12 Minutes. Each final measurement of the hip geometry was done in less than 2 minutes. The evaluation of the pelvic ap-x-ray pre- and postoperative showed equivalent measurements of the new hip geometry compared with the intraoperative measured values. No specific complications occurred throughout the study. In conclusion the BrainLAB–DASH-System has shown a high grade of usability and very short learning curve within this first clinical study. The use of a standard Apple® IPod-touch as a user interface seems to enhance the acceptance of the navigation technique. Equivalent precision compared to standard navigation systems have been demonstrated

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

Over the last decade Computer Assisted Orthopaedic Surgery (CAOS) has emerged particularly in the area of minimally invasive Uni-compartmental Knee Replacement (UKR) surgery. Image registration is an important aspect in all computer assisted surgery including Neurosurgery, Cranio-maxillofacial surgery and Orthopaedics. It is possible for example to visualise the patient's medial or lateral condyle on the tibia in the pre-operated CT scan as well as to locate the same points on the actual patient during surgery using intra-operative sensors or probes. However their spatial correspondence remains unknown until image registration is achieved. Image registration process generates this relationship and allows the surgeon to visualise the 3D pre-operative scan data in-relation to the patient's anatomy in the operating theatre. Current image registration for most CAOS applications is achieved through probing along the articulating surface of the femur and tibial plateau and using these digitised points to form a rigid body which is then fitted to the pre-operative scan data using a best fit type minimisation. However, the probe approach is time consuming which often takes 10–15 minutes to complete and therefore costly. Thus the rationale for this study was to develop a new, cost effective, contactless, automated registration method which would entail much lesser time to produce the rigid body model in theatre from the ends of the exposed bones. This can be achieved by taking 3D scans intra-operatively using a Laser Displacement Sensor. A number of techniques using hand held and automated 3D Laser scanners for acquiring geometry of non-reflective objects have been developed and used to scan the surface geometry of a porcine femur with four holes drilled in it. The distances between the holes and the geometry of the bone were measured using digital vernier callipers as well as measurements acquired from the 3D scans. These distances were measured in an open source package MESHLAB version 1.3.2 used for the interpretation, post-processing and analysis of the 3D meshes. Absolute errors ranging from of 0.1 mm to 0.4 mm and the absolute percentage errors ranging from 0.48% to 0.75% were found. Additionally, a pre-calibrated dental model was scanned using a 650 nm FARO™ Laser arm using the global surface registration approach in Geomagic Qualify package and our 3D Laser scanner. Results indicate an average measurement error of 0.16 mm, with deviations ranging from 0.12mm to −0.13 mm and a standard deviation of 0.2 mm. We demonstrated that by acquiring multiple scans of the targets, complete 3D models along with their surface texture can be developed. The overall scanning process, including time required for the post-processing of the data requires less than 20 minutes and is a cost-efficient approach. Moreover, the majority of that time was used in post processing the acquired data which could be potentially reduced through the use of bespoke application software. This project has provided proof of concept for a new automated, non-invasive and cost efficient registration technique with the potential of providing a quantitative assessment of the articular cartilage integrity during lower limb arthroplasty