Aims. We compared the accuracy, operating time and radiation exposure of the introduction of iliosacral screws using O-arm/Stealth Navigation and standard fluoroscopy. Materials and Methods. Iliosacral screws were introduced percutaneously into the first sacral body (S1) of ten human cadavers, four men and six women. The mean age was 77 years (58 to 85). Screws were introduced using a standard technique into the left side of S1 using C-Arm fluoroscopy and then into the right side using O-Arm/Stealth Navigation. The radiation was measured on the surgeon by dosimeters placed under a lead thyroid shield and apron, on a finger, a hat and on the cadavers. Results. There were no neuroforaminal breaches in either group. The set-up time for the O-Arm was significantly longer than for the C-Arm, while total time for placement of the screws was significantly shorter for the O-Arm than for the C-Arm (p = 0.001). The mean absorbed radiation dose during fluoroscopy was 1063 mRad (432.5 mRad to 4150 mRad). No radiation was detected on the surgeon during fluoroscopy, or when he left the room during the use of the O-Arm. The mean radiation detected on the cadavers was significantly higher in the O-Arm group (2710 mRem standard deviation (. sd. ) 1922) than during fluoroscopy (11.9 mRem . sd 14.8). (p < 0.01). Conclusion. O-Arm/Stealth Navigation allows for faster percutaneous placement of iliosacral screws in a radiation-free environment for surgeons, albeit with the same accuracy and significantly more radiation exposure to cadavers, when compared with standard fluoroscopy. Take home message: Placement of iliosacral screws with O-Arm/Stealth Navigation can be performed safely and effectively. Cite this article: Bone Joint J 2016;98-B:696–702

Accurate evaluation of lower limb coronal alignment is essential for effective pre-operative planning of knee arthroplasty. Weightbearing hip-knee-ankle (HKA) radiographs are considered the gold standard. Mako SmartRobotics uses CT-based navigation to provide intra-operative data on lower limb coronal alignment during robotic assisted knee arthroplasty. This study aimed to compare the correlation between the two methods in assessing coronal plane alignment. Patients undergoing Mako partial (PKA) or total knee arthroplasty (TKA) were identified from our hospital database. The hospital PACS system was used to measure pre-operative coronal plane alignment on HKA radiographs. This data was correlated to the intraoperative deformity assessment during Mako PKA and TKA surgery. 443 consecutive Mako knee arthroplasties were performed between November 2019 and December 2021. Weightbearing HKA radiographs were done in 56% of cases. Data for intraoperative coronal plane alignment was available for 414 patients. 378 knees were aligned in varus, and 36 in valgus. Mean varus deformity was 7.46° (SD 3.89) on HKA vs 7.13° (SD 3.56) on Mako intraoperative assessment, with a moderate correlation (R= 0.50, p<0.0001). Intraoperative varus deformity of 0-4° correlated to HKA measured varus (within 3°) in 60% of cases, compared to 28% for 5-9°, 17% for 10-14°, and in no cases with >15° deformity. Mean valgus deformity was 6.44° (SD 4.68) on HKA vs 4.75° (SD 3.79) for Mako, with poor correlation (R=0.18, p=0.38). In this series, the correlation between weightbearing HKA radiographs and intraoperative alignment assessment using Mako SmartRobotics appears to be poor, with greater deformities having poorer correlation

We report on the 5 year results of a randomized study comparing TKR performed using conventional instrumentation versus electromagnetic computer-assisted surgery. This study analysed patient reported outcome measures (PROMs) at 5 years utilising the American Knee Society Score (AKSS), Oxford Knee Score (OKS), the Short Form 36 score and range of motion (ROM). Of the 200 patients enrolled 125 completed 5 year follow up, 62 in the navigated group and 63 in the conventional group. There were 28 deceased patients, 29 withdrawals and 16 lost to follow-up. There was improvement in clinical function in most PROMs from 1-5 year follow up across both groups. OKS improved from a mean of 26.6 (12–55) to 35.1 (5–48). AKSS increased from 75.3 (0–100) to 78.4 (−10–100), SF36 from 58.9 (2.5–100) to 53.2 (0–100). ROM improved by an average 7 degrees from 110 degrees to 117 degrees (80–135). There was no statistically significant difference in PROMs between the groups at 5 years. Patients undergoing revision surgery were identified from the dataset and global PACS. There were no revisions within 5 years in the navigated group and 3 revisions in the conventional group, two for infection and one for mid-flexion instability, giving an all cause revision rate of 3.06% at 5 years for this group. There appears to be no significant advantage in clinical function for patients undergoing TKR for OA of the knee with electromagnetic navigation when compared to conventional techniques. There may be an advantage in reducing early revision rates using this technology

Electromagnetic navigation versus conventional Total Knee Arthroplasty: Clinical improvements Optical and electromagnetic (EM) tracking systems are widely used commercially. However in orthopaedic applications optical systems dominate the market. Optical systems suffer from deficiencies due to line of sight. EM trackers are smaller but are affected by metal. The accuracy of the two tracker systems has been seen to be comparable1. Recent advancements in optical navigated TKA have shown improved overall limb alignment, implant placement and reduce outliers when compared to conventional TKA2-4. This study is the first RCT to compare EM and conventional TKA. Two groups of 100 patients underwent TKA using either the EM navigation system or the conventional method. Frontal, sagittal and rotational alignment was analysed from a CT scan. Clinical scores including Oxford Knee Score (OKS) and Knee/Function American Knee Society Score (AKSS) were recorded pre-op, and at 3 and 12 months post-op. 3 month data presented includes 180 patients (n = 90). The 12 months data presented includes 140 (n = 70). The two groups had similar mean mechanical axis alignments (EM 0.31o valgus, conventional 0.15o valgus). The mechanical axis alignment was improved in the EM group with 92% within +/-3o of neutral compared to 84% of the conventional group (p = 0.90). The alignment of the EM group was improved in terms of frontal femoral, frontal tibial, sagittal femoral, sagittal tibial and tibial rotation alignment. However, only the sagittal femoral alignment was significantly improved in the EM group (p = 0.04). Clinically, both TKA groups showed significant improvements in OKS and AKSS scores between both pre-op to 3 month post-op and 3 months to 12 months post-op (p<0.001). The OKS and the AKSS knee score for the EM group was significantly better at 3 months post-op (OXS p = 0.02, AKSS knee p = 0.04). However there was no difference between the groups at 12 months. The mean pre-op range of motion (ROM) for both groups was 105o. This decreased to 102o in the EM group and 99o in the conventional group at 3 months. There was a significant improvement at 12 months post-op, EM = 113o (p = 0.012) and conventional = 112o (p = 0.026). There was no significant difference in ROM between the two groups at 3 or 12 months post-op. Therefore the alignment outcome of the EM TKA group was improved compared to the conventional group. The EM group also showed clinical improvements at 3 months post-op however these were not seen again at 12 months post-op. ROM was seen to decrease at 3 months post-op but then significantly improve by 12 month post-op

Background. Navigation in total knee replacement is controversially discussed in the literature. In our previous study, femoral component positioning was more accurate with computed navigation than with conventional implantation techniques, however tibial positioning showed similar results. Moreover there were no differences between image-free and image-based navigation techniques. To what extent more accurate femoral positioning has an impact on the clinical mid-term follow up is not known. Methods. At a mean follow-up interval of 5.3 years, seventy-one patients (84.5%) returned for a review and were examined clinically and radiographically, with use of a methodology identical to that used preop and at 2 years, using the subjective value, the Knee Society Score (KSS), and a.p. and true lateral standard radiographs respectively. Complications, re-operations, persisting pain and resulting range of motion were registered. Results. Four patients in the image-based (2x late-onset infection, 1x femoral impingement, 1x component malalignment), 2 in the conventional group (2x component malalignment) and 1 patient in the image-free navigated group (arthoscopic debridement for arthrofibrosis) needed reoperation in the mean time. 59 of the 71 patients were very satisfied and satisfied at 5.3 years folllow up: (conventional: 19 of 25 (77±8 years); image-based navigation: 18 of 22 (77±10 years); image-free navigation: 22 of 24 (78±7 years)). The mean average of the Knee Society Score was 92.3(range 47 to 98). Compared to the conventional (KSS: 93.9±8,0) and image-free (KSS: 94.0±6,43) group, the KSS in the image-based group was insignificantly lower (KSS: 90±13,6) (p< 0,05). Radiographically, two patients in the conventional group showed a lysis on the lateral and medial tibia plateau of <1 mm without any clinical significance. There was no need for reintervention. There were no significant differences concerning remainig pain (conventional: 24%; image-based 18%; image-free: 8,5%), ROM and ligamental stability. Conclusion. Radiographical and clinical mid-term results after TKA yielded good and excellent results independent of the computed navigation and its type. Even a more accurate femoral component positioning in the patients cohort has been shown, we couldn't find a significant difference concerning the clinical outcome 5.3 years after conventional, image-based and image-free total knee arthroplasty. Despite of increased costs and time for navigated techniques we cannot show a mid-term benefit in functional and subjectiv outcome compared to conventional techniques

Introduction. The same cup orientation is classically applied to all cases of hip replacement (45° abduction, 20° anteversion). We hypothesize that this orientation must be adapted to the patient's hip range of motion. We tested this hypothesis by means of an experimental study with respect to hip range of motion, comparing the classical orientation (45° and 20°), and the orientation obtained with computer-assisted navigation. Material and Methods. The experimental model included a hemipelvis equipped with a femur whose mobility was controlled for three configurations: stiff (60°/0°, 15°/10°, 10°/10°), average (80°/10°, 35°/30°,35°/25°), mobile (130°/30°, 50°/50°, 45°/35°). The hemipelvis and the cup holder were equipped with an electromagnetic system (Fastrack ™) to measure cup orientation. The Pleos™ navigation system (equipping the hemipelvis, the femur, and the cup holder) guided the cup orientation by detecting the positions risking impingement through a kinematic study of the hip. Nine operators each performed 18 navigation-guided implantations (162 hip abduction, anteversion, and range of movement measurements) in two series scheduled 2 months apart. Results. The model used herein showed intra and interobserver reliability. Compared to the navigation-assisted surgery, the arbitrary orientation gave a mean anteversion error of only 1° ± 6° (−12 to +19°) but 5° ± 8° (−26° to +13°) for abduction. However, 16% of the errors were more than 10° in anteversion (1/2 in the mobile configuration) and 11% of the errors were more than 15° in abduction (for the most part in the mobile configuration). With arbitrary orientation, the errors consisted in excess anteversion and insufficient abduction. Discussion and Conclusion. The experimental model developed was reliable and can be used to evaluate different prosthetic configurations. This study emphasizes that the ideal arbitrary cup orientation cannot be applied to all hips. All the surgeons are very reproducible but the only way to integrate the range of motion in there ‘own way to do’ in vitro, is to use a navigation system witch can guide the surgeon so as to reduce the risk of impingement and instability

Introduction. Patellar tracking in total knee replacements has been extensively studied, but little is known about patellar tracking in isolated patellofemoral replacements. We compared patellar tracking and the position of the patellar groove in the natural knee, followed by implantation of the femoral component of a PFR (patella unresurfaced) and after implantation of the femoral & patellar component of the PFR. Methods. Computer navigation was used to track the patella in eight whole lower extremities of four cadavers in the natural knee, in the same knee with the femoral component of the PFR (PFR-P) and with the femoral and patellar component of the PFR (PFR+P, patella resurfaced) (Depuy Sigma PFR). The form and position of the trochlea in the natural knee and the patellar groove of the femoral component was also analysed. Values are means+/−SD, two tailed Student's t-test for paired samples. Results. With a PFR-P the patella had a slightly more lateral tilt (0.8+/−0.8° to 2.8+/−2.5° at 40–100° of flexion, p<0.05 vs. Nat), this was more pronounced with the PFR+P (2.0+/−0.7° to 4.9+/−1.8° at 20–90° flexion, p<0.05 vs. Nat., p<0.05 vs. PFR-P at 20–80° flexion). No differences in patella rotation were seen between the three groups. In the PFR-P group the patella tracked a little more medially compared to the natural knee (0.6+/− 0.7mm to 1.3+/−2.6mm, p<0.05 at 20°,80°,90° flexion). The difference was more pronounced after patella resurfacing (PFR+P) (2.1+/−2.0mm to 3.0+/−2.2mm, p<0.05 vs. Nat. at 10°–100°, p<0.05 vs. PFR-P from 10–100°). When analysed relative to the patellar groove of the trochlea/femoral component the patella in the natural knee tracked slightly lateral to the groove (2.0+/−1.7mm to 2.9+/−2.0mm at 50–100° p<0.05), so did the patella of PFR-P (2.0+/−2.3mm to 2.3+/−2.3mm at 60–90° flexion, p<0.05), whilst the PFR+P tracked right on the groove (0.6+/−3.7mm medially to 0.6+/−2.9mm laterally, p<0.05 vs Nat at 10–30° & 70–100°, p<0.05 vs. PFR-P at 10–100°). Distance from the patellatot the epicondylar axis was slightly larger in the PFR-P group (0.6+/− 0.7mm to 1.3+/−1.4mm, p<0.05 vs. Natu at 20,80 & 90°. This was more pronounced with patellar resurfacing (2.1+/−2.0 to 3.0+/−2.2mm, p<0.05 vs. Nat at 10–100°, p<0.05 vs. PFR-P at 20–100°) The patella groove on the natural knee and the implanted femoral component of the implanted PFR had the same radius, inclination relative to the femoral mechanical axis, antero-posterior position and medio-lateral orientation. As intended by the designers the groove of the patellar component extended about 13mm further superiorly and 0.5mm more inferiorly. Discussion. The patella groove on the femoral component of the PFR reproduces the natural trochlear anatomy well. Patella tracking in the PFR-P shows only minor differences compared to the natural knee. Resurfacing of the patella in the PFR+P group causes the patella to tilt a little more laterally and track a little more medially, the distance to the epicondylar axis is slightly larger but this allows the patella to engage better in the patellar groove of the femoral component

BACKGROUND & AIM. Most previous studies found that the rate of dislocation following primary THA was 2 to 3 % on average. It is expected that minimally invasive (MI) THA has fewer dislocations after surgery because it causes less muscle damage. To ascertain the risk factors of dislocation, we conducted a retrospective study of the occurrence of dislocation after MI-THA in Japanese patients. METHODS. From June 2003 when we began MI-THA to August 2010 primary MI-THAs were performed on 2,042 hips; 1,997 hips with mini-posterior approach (a mean incision of 7 cm) with the repair of posterior soft tissues and 45 hips with other approaches. The dislocation after MI-THA was studied with respect to age, sex, body mass index, the use of navigation system, femoral head size, cup size and approaches. The period of follow-up was from six weeks to seven years. RESULTS. The numbers of dislocation after MI-THA were 13 hips (0.6%). The numbers of posterior and anterior dislocation after MI-THA were nine and four hips, respectively. In the patients undergoing MI-THA, there was a significant difference between non-dislocated hips and dislocated hips, with respect to the average age (57 years vs. 66 years, p<0.017), the numbers of male patients (181 cases (9%) vs. 4 cases (31%), p<0.024), cup size (50 mm vs. 53 mm, p<0.007) and the numbers of cases which used navigation system (1,932 hips (95%) vs. 10 hips (77%), p<0.023). Whereas there was no significant difference between non-dislocated hips and dislocated hips with respect to the body mass index, femoral head size and approaches. DISCUSSION. Several risk factors of the dislocation after primary THA have been reported. In this study we found that MI-THA had fewer risk of dislocation as compared with historic controls. It is suggested that less soft tissue damage can decrease the risk of the dislocation after surgery. The incidence of dislocation was fewer in the younger and female patients undergoing MI-THA with the navigation system than in the older and male patients undergoing MI-THA without the navigation system. The posterior approach combined with the repair of posterior soft tissues did not increase the risk of dislocation after surgery as compared with other approaches. The position of implants is important to prevent dislocation after surgery, and the navigation system can help to obtain a good position of implants. CONCLUSIONS. We conclude that MI-THA can decrease the risk of dislocation after primary THA. Furthermore the combination of MI-THA and the navigation system is very useful to reduce the incidence of dislocation because the use of the navigation system during surgery can be helpful to acquire the precise position of implants

Background. Computer-assisted navigation systems for total knee arthroplasty (TKA) were introduced to improve implantation accuracy and to optimize ligament balancing. Several comparative studies in the literature confirmed an effect on the component position and other studies could not confirm these results. For ligament balancing most studies found no significant influence on the clinical outcome using a navigation system for TKA. In the literature there were no reports of mid-term results after navigated TKA. With our study we wanted to show if the use of a navigation system for TKA will have an influence on the component's position and on the clinical results at 5-year follow up. Methods. We enrolled 200 patients in a prospective randomized study with a minimum follow up of 5 years. 100 TKA were operated on without using a navigation system (Group A) and 100 surgeries (Group B) were done with computer assistance. Radiological investigation by standard radiographs including a long-leg X-ray was performed with a follow up rate in Group A of 86.2% versus 80.2% in Group B. We measured the mechanical axis of the leg, lateral distal femoral angel (LDFA), medial proximal tibial angle (MPTA), tibial slope and the alpha-angle of the patella. Clinical investigation was performed with a follow up rate in Group A of 85.7% versus 79.8% in Group B including the parameters for the range of motion (ROM), ligament balancing, anterior drawer test, feeling of instability, anterior knee pain, effusion, WOMAC Score, Insall Score and HSS Knee Score. Results. In both groups there was no aseptic loosening or difference in TKA survival rate (Group A 95.4% versus Group B 98.85% 5-year survival rate, p = 0.368). With the navigation technique the mechanical axis of the limb in the frontal plane was improved (p = 0.015; Group B: 1.67 ° ± 1.6° versus 2,44 ° ± 2.2 ° in Group A). 90% of the Group B and 81% of the Group A were within 3 ° varus/valgus deformity of the mechanical axis of the limb (p = 0.157). The accuracy of tibial slope was higher in the Group B (p = 0.001). More patients of the Group B (95% versus 79%) were within a deviation of 3 °, −7 ° tibial slope (p = 0.007). The mean deviation of 90 ° LDFA was higher (p = 0.034) in the Group A (1.89 ° versus 1.36 ° in Group B). Mean deviation of 90 ° MPTA, mean MPTA, mean LDFA and patella alpha angle were similar in both groups (p 0.253). There was no difference in ROM, ligament balancing, anterior drawer test, anterior knee pain or feeling of instability (p 0.058). Insall Knee Score total (181 Group A/191 Group B) and HSS Knee Score total (91 Group A/93 Group B) was higher with the navigated procedure in Group B (p 0.026). WOMAC total and HSS grades were similar in both groups (p 0.070). Conclusions. The accuracy of the mechanical axis of the limb and the tibial slope was higher with the navigated procedure. TKA survival rate and clinical outcomes were similar in both groups at 5-year follow up

Conventional computer navigation systems using bone fixation have been validated in measuring anteroposterior (AP) translation of the tibia. Recent developments in non-invasive skin-mounted systems may allow quantification of AP laxity in the out-patient setting. We tested cadaveric lower limbs (n=12) with a commercial image free navigation system using passive trackers secured by bone screws. We then tested a non-invasive fabric-strap system. The lower limb was secured at 10° intervals from 0° to 60° knee flexion and 100N of force applied perpendicular to the tibial tuberosity using a secured dynamometer. Repeatability coefficient was calculated both to reflect precision within each system, and demonstrate agreement between the two systems at each flexion interval. An acceptable repeatability coefficient of ≤3mm was set based on diagnostic criteria for ACL insufficiency when using other mechanical devices to measure AP tibial translation. Precision within the individual invasive and non-invasive systems measuring AP translation of the tibia was acceptable throughout the range of flexion tested (repeatability coefficient ≤1.6 mm). Agreement between the two systems was acceptable when measuring AP laxity between full extension and 40° knee flexion (repeatability coefficient ≤2.1 mm). Beyond 40° of flexion, agreement between the systems was unacceptable (repeatability coefficient >3 mm). These results indicate that from full knee extension to 40° flexion, non-invasive navigation-based quantification of AP tibial translation is as accurate as the standard invasive system, particularly in the clinically and functionally important range of 20° to 30° knee flexion. This could be useful in diagnosis and post-operative follow-up of ACL pathology

Simulation in surgical training has become a key component of surgical training curricula, mandated by the GMC, however commercial tools are often expensive. As training budgets become increasingly pressurised, low-cost innovative simulation tools become desirable. We present the results of a low-cost, high-fidelity simulator developed in-house for teaching fluoroscopic guidewire insertion. A guidewire is placed in a 3d-printed plastic bone using simulated fluoroscopy. Custom software enables two inexpensive web cameras and an infra-red led marker to function as an accurate computer navigation system. This enables high quality simulated fluoroscopic images to be generated from the original CT scan from which the bone model is derived and measured guidewire position. Data including time taken, number of simulated radiographs required and final measurements such as tip apex distance (TAD) are collected. The simulator was validated using a DHS model and integrated assessment tool. TAD improved from 16.8mm to 6.6mm (p=0.001, n=9) in inexperienced trainees, and time taken from 4:25s to 2m59s (p=0.011). A control group of experienced surgeons showed no improvement but better starting points in TAD, time taken and number of radiographs. We have also simulated cannulated hip screws, femoral nail entry point and SUFE, but the system has potential for simulating any procedure requiring fluoroscopic guidewire placement e.g. pedicle screws or pelvic fixation. The low cost and 3D-printable nature have enabled multiple copies to be built. The software is open source allowing replication by any interested party. The simulator has been incorporated successfully into a higher orthopaedic surgical training program

INTRODUCTION. This study aimed to intra-operatively quantify the improvements in knee stability given both by anatomic double-bundle (ADB) and single-bundle with additional lateral plasty (SBLP) ACL reconstruction using a navigation system. MATERIALS AND METHODS. We prospectively included 35 consecutive patients, with an isolated anterior cruciate ligament injury, that underwent both ADB and SBLP ACL reconstruction (15 ADB, 20 SBLP). The testing protocol included anterior/posterior displacement at 30° and 90° of flexion (AP30–AP90), internal/external rotation at 30° and 90° of flexion (IE 30–IE90) and varus/valgus test at 0° and 30° of flexion (VV0–VV30); pivot-shift (PS) test was used to determine dynamic laxity. The tests were manually performed before and after the ACL reconstruction and the data were acquired by means a surgical navigation system (BLU-IGS, Orthokey, USA). Comparisons of pre- and post-reconstruction laxities were made using paired Student t-test (P=0.05) within the same group; comparison between ADB and SBLP groups was indeed performed using independent Student t-test (P=0.05), analysing both starting pre-operative condition and post-operative one. RESULTS. Statistically significant reduction of the global amount of laxity and global displacement was observed for both reconstructions (p<0.05) in all the performed clinical tests. Statistical differences was found between the two reconstruction considering the recovery (pre-post laxities) due to the each reconstruction, in VV0 (SBLP: 3.7±0.2° and ADB: 2.3±0.5°, p<0.0001) and in IE90 (SBLP: 9.2±3.1° and ADB: 5.0±2.8°, p=0.0022). Statistical differences were also found between the two reconstruction considering the recovery of global displacement, in particular for the lateral compartment during AP90 SBLP: 8.8±1.0 mm, ADB: 6.4±0.4 mm, p<0.0001), for the maximal lateral joint opening during VV0 (SBLP: 4.5±1.2 mm, ADB: 1.2±1.1 mm, p<0.0001) and VV30 (SBLP 3.5±1.3 mm, ADB 1.8±0.1 mm, p=0.0013) and both for the medial and lateral AP displacement during IE90 (in in medial compartment SBLP:5.6±0.6 mm, ADB: 2.7±0.7 mm, p<0.0001, in lateral compartment SBLP:8.2±1.0 mm, ADB: 3.9±0.8 mm, p<0.0001). During PS test ADB patients revealed less “hysteresis” after reconstruction (p=0.0005). Moreover SBLP patients presented more acceleration after the reconstruction compared to ADB and more evident displacement (p=0.0009). DISCUSSION. Both the reconstructions worked similarly for what concerns knee static laxity. The considered extra-articular procedure plays an important role in better controlling lateral tibial compartment displacement in drawer test and in controlling maximal lateral joint opening both at 0° and 30° of flexion. On the other hand the ADB reconstruction better restores the dynamic behaviour of the joint under PS test

Component malalignment has long been implicated in poor implant survival in Total Knee Arthroplasty (TKA). Malalignment can occur in orientation of bony cuts, and in component cementation/implantation. Several systems exist to aid bony cut alignment (navigation, shape matching), but final implantation technique is common to all TKA. Correction of errors in bony cut alignment at cementation/implantation by surgeons has been described. Changes in alignment at this stage are likely to result in asymmetrical cement penetration, which is implicated in early failure. This study reviewed a consecutive series of 150 primary cemented TKAs using an imageless navigation system (aiming for neutral overall limb alignment). Deviation at implantation was calculated by comparing limb alignment recorded using the trial components with limb alignment recorded with the final implanted components, prior to closure. 136 patients (91%) had a final overall limb alignment within 2° of neutral. Three patients (2%) had a final overall limb alignment greater than 3° from neutral. Deviation occurring at implantation is shown in Figure 1 with deviations distributed around zero (mode 0, median 0.3, range −2 to +4,)

Background. Improving positioning and alignment by the use of computer assisted surgery (CAS) might improve longevity and function in total knee replacements. This study evaluates the short term results of computer navigated knee replacements based on data from a national register. Patients and Methods. Primary total knee replacements without patella resurfacing, reported to the Norwegian Arthroplasty Register during the years 2005–2008, were evaluated. The five most common implants and the three most common navigation systems were selected. Cemented, uncemented and hybrid knees were included. With the risk for revision due to any cause as the primary end-point, 1465 computer navigated knee replacements (CAS) were evaluated against 8214 conventionally operated knee replacements (CON). Kaplan-Meier survival analysis and Cox regression analysis with adjustment for age, sex, prosthesis brand, fixation method, previous knee surgery, preoperative diagnosis and ASA category were used. Results. Kaplan-Meier estimated survival at two years was 97.9% (95% CI: 97.5–98.3) in the CON group and 96.4% (95% CI: 95.0–97.8) in the CAS group. The adjusted Cox regression analysis showed a statistically significantly higher risk for revision in the CAS group (relative risk = 1.7, 95% CI: 1.1–2.5, p = 0.019). The LCS complete knees had a significantly higher risk for revision with CAS, compared to CON (relative risk = 2.1 (95% CI 1.3–3.4, p = 0.004)). Mean operating time was 15 minutes longer in the CAS group. Conclusion. Survivorship at two years of computer navigated primary total knee replacements was inferior compared to conventionally operated knees. Therefore, an extensive use of CAS in primary total knee replacement surgery cannot be encouraged until proven superior in long term register studies and clinical trials

Background. Radiofrequency Kyphoplasty (RFK) provides a new minimally invasive procedure to treat vertebral compression fractures (VCF). Purpose. The purpose of this study was to investigate the functional outcomes, safety and radiographic outcomes after the treatment of painful osteolytic vertebral fractures treated with a novel minimally invasive procedure, RFK. Material and Methods. 88 patients (50 females and 38 males) with 158 osteolytic vertebral fractures were treated with RFK using the StabiliT Vertebral Augmentation System (Dfine Inc, San Jose, CA). The StabiliT System provides a navigational osteotome to create a site and size specific cavity prior to delivering ultrahigh viscosity cement with an extended working time (done by applying radiofrequency energy to the cement immediately prior to entering the patient). 12 months follow up in 60 patients (36 females and 24 males) with 110 treated vertebrae are reported. Pre- and postoperative, 3, 6 and 12 months clinical parameters (Visual Analogue Scale, Oswestry Disability Index score), and radiological parameters (vertebral height and kyphotic angle) were measured. Results. The median pain scores (VAS) (p<0.001) and the Oswestry Disability Score (p<0.001) improved significantly from pre- to post-treatment and maintained at 3, 6 and 12 months follow up. Postoperative, 3,6 and 12 months follow-up RFK restored and stabilized the vertebral height and avoided further kyphotic deformity. No symptomatic cement leaks or serious adverse events were seen in the RFK group during 3-months of follow up. In 7 out of 158 vertebrae (4.4%) a cement leakage into the disc or lateral wall could be determined by radiograph postoperatively. Conclusion. Radiofrequency Kyphoplasty is a very safe and effective minimally invasive procedure for the treatment of osteolytic vertebral fractures. Radiofrequency Kyphoplasty shows excellent clinical and radiological results in the 3 and 6 months follow up. Site specific cavity creation and delivery of ultra-high viscosity cement in RF Kyphoplasty with extended working time resulted in the added benefits of height restoration and lower cement leakages intra-operatively

Summary. UC TKA showed similar anteroposterior translation and more femoral external rotation of earlier onset when compared to PS TKA. Introduction. Recently highly conforming ultracongruent TKA has been reintroduced with improved wear characteristics and lower complications. The purpose of the study was to assess kinematics and clinical outcome of posterior stabilized and ultracongruent rotating-platform mobile bearing TKA. Methods. Ninety patients with primary osteoarthritis of the knee were randomized to undergo computer assisted TKA with PS(n = 45) or UC(n = 45) prostheses and were followed up for a minimum 2 years. The passive kinematic evaluation was performed before and after implantation with a navigation system. Three parameters of tibiofemoral relationship (anterior/posterior translation, varus/valgus alignment and rotation) were recorded from 0° to 120° of flexion. The patients were clinically and radiographically evaluated at final follow-up. Results. Paradoxical anterior translation of the femur was observed from 0° to 70° of flexion in PS(8.7mm) and 0° to 85° in UC knees(10.4mm, p = 0.064). The distance of femoral roll-back was 6.7mm and 5.5mm, but never reached the starting point. Paradoxical internal rotation of the femur was found from 0° to 62° of flexion in PS(9.9°) and 0° to 47° in UC knees(5.6°, p = 0.002). UC knees showed more external rotation of the femur during flexion from 0° to 120°(5.7:11.0, p = 0.048). There was no significant difference in the maximal flexion(123.3°:125.5°, p = 0.366), AKS knee scores(95.9:92.0, p = 0.101), AKS function scores(86.2:82.9, p = 0.435) and WOMAC index scores(13.4:15.9, p = 0.268). There was no progressive radiolucent line or loosening in all knees. Discussion and Conclusion. UC TKA showed similar anteroposterior translation and more femoral external rotation of earlier onset when compared to PS TKA. There was no difference in clinical outcome between two designs. UC TKA showed comparable kinematic and clinical results to PS TKA

Introduction. It was the purpose to evaluate the biomechanical changes that occur after optimal and non-optimal component placement of a hip resurfacing (SRA) by using a subject specific musculoskeletal model based on CT-scan data. Materials and Methods. Nineteen hips from 11 cadavers were resurfaced with a BHR using a femoral navigation system. CT images were acquired before and after surgery. Grey-value segmentation in Mimics produced contours representing the bone geometry and identifying the outlines of the 3 parts of the gluteus medius. The anatomical changes induced by the procedure were characterised by the translation of the hip joint center (HJCR) with respect to the pelvic and femoral bone. The contact forces during normal gait with ‘optimal’ component placement were calculated for a cement mantle of 3 mm, a socket inclination of 45° and anteversion of 15°. The biomechanical effect of ‘non-optimal placement’ was simulated by varying the positioning of the components. Results. There was a significant (p<0.01) shortening of the muscle length with the ‘optimal’ component placement for all parts of the gluteus medius with the largest shortening of the posterior part by 6mm. This was caused by a significant shortening of the femoral offset by 2.3mm (p<0.01). Because of a significant (p<0.01) medialisation of the HJCR by 4 mm, there was no significant increase in contact force. The hip joint contact forces increased by 0.5% per mm HJCR displacement. Each millimeter of cranial and lateral displacement of the femoral HJCR increased the contact force by 0.5% and 1%, respectively. The contact stresses changed significantly by 0.8% and 0.2% per degree of socket inclination and anteversion. The contact force increased 1% per mm lateral displacement of the acetabular HJCR. Discussion. Optimal placement of the SRA components did not completely restore the biomechanics of the native hip joint. The contact forces were not increased due to the compensatory effect of the medialisation of the acetabular HJCR. This suggests that reaming to the acetabular floor should be conducted in SRA. Femoral component displacement in the cranial and lateral direction significantly increased the hip joint loading. Errors of socket placement in the coronal and sagital plane significantly increased the contact stresses. Accumulative errors of both component displacements could lead to increased contact stresses of 18% to 23% with socket inclinations of 50° and 55°. Surgeons should reconsider continuing the SRA procedure if a neck length loss and lateralisation of the HCJR by >5 mm is anticipated as this would increase the contact stresses by >12%

INTRODUCTION. Computer-aided systems have been developed recently in order to improve the precision of implantation of unicompartmental knee replacement (UKR). Minimal invasive techniques may decrease the surgical trauma related to the prosthesis implantation, but there might be a concern about the potential for a loss of accuracy. Mobile bearing prostheses have been developed to decrease the risk of polyethylene wear, but are technically more demanding. Navigation might help to compensate for these difficulties. We wanted to combine the theoretical advantages of the three different techniques by developing a navigated, minimal invasive, mobile bearing unicompartmental knee prosthesis. MATERIAL AND METHODS. 160 patients have been operated on at our institution with this system. The 81 patients with more than 2 year follow-up have been re-examined. Complications have been recorded. The clinical results have been analyzed according to the Knee Society Scoring System. The subjective results have been analyzed with the Oxford Knee Questionnaire. The accuracy of implantation has been analyzed on post-operative antero-posterior and lateral long leg X-rays. The 2-year survival rate has been calculated. RESULTS. We observed 8 complications related to the implant or the operative technique: 2 cases of meniscus instability (1 revision to TKR, 1 bearing exchange); 2 cases of tibia loosening (revised to TKR), 2 cases of femoral loosening (revised to TKR), 1 case of lateral disease progression (revised to TKR), 1 case of unexplained pain syndrome (revised to TKR). The mean Knee Score was 93 points, 44% had the maximum of 100 points, and only 10% have less than 85 points. The mean pain score was 48 points/50. The mean flexion angle was 128°, and 60% had at least 130° of knee flexion. The mean Function Score was 97 points, 84% have the maximum of 100 points, and only 5% had less than 85 points. The mean Oxford Knee Questionnaire score was 19 points (best result: 12 points, worst result: 60 points). Expected limb axis correction was obtained in 77% of the cases. 62% of the cases had an optimally implanted prosthesis for all studied criteria. The 2-year survival rate was 97%. DISCUSSION. Most of the revision cases were related to technical difficulties during the development phase. Fixation of the implant has been improved, and some imprecise steps of the software have been corrected. Since these changes occurred, no severe early complication related to implant or software has been observed. The current implant is considered reliable, and the current minimal invasive navigated technique is considered reliable as well

Aims

The best method of treating unstable pelvic fractures that involve the obturator ring is still a matter for debate. This study compared three methods of treatment: nonoperative, isolated posterior fixation and combined anteroposterior stabilization.

In the time since Letournel popularised the surgical treatment of acetabular fractures, more than 25 years ago, there have been many changes within the field, related to patients, surgical technique, implants and post-operative care. However, the long-term outcomes appear largely unchanged. Does this represent stasis or have the advances been mitigated by other negative factors? In this article we have attempted to document the recent changes within the surgery of patients with a fracture involving the acetabulum, outline contemporary management, and identify the major problem areas where further research is most needed.

Cite this article: Bone Joint J 2017;99-B:1125–31