Objectives. Normal sagittal spine-pelvis-lower extremity alignment is crucial in humans for maintaining an ergonomic upright standing posture, and pathogenesis in any segment leads to poor balance. The present study aimed to investigate how this sagittal alignment can be affected by severe knee osteoarthritis (KOA), and whether associated changes corresponded with symptoms of lower back pain (LBP) in this patient population. Methods. Lateral radiograph films in an upright standing position were obtained from 59 patients with severe KOA and 58 asymptomatic controls free from KOA. Sagittal alignment of the spine, pelvis, hip and proximal femur was quantified by measuring several radiographic parameters. Global balance was accessed according to the relative position of the C7 plumb line to the sacrum and femoral heads. The presence of chronic LBP was documented. Comparisons between the two groups were carried by independent samples t-tests or chi-squared test. Results. Patients with severe KOA showed significant backward femoral inclination (FI), hip flexion, forward spinal inclination, and higher prevalence of global imbalance (27.1% versus 3.4%, p < 0.001) compared with controls. In addition, patients with FI of 10° (n = 23) showed reduced lumbar lordosis and significant forward spinal inclination compared with controls, whereas those with FI > 10° (n = 36) presented with significant pelvic anteversion and hip flexion. A total of 39 patients with KOA (66.1%) suffered from LBP. There was no significant difference in sagittal alignment between KOA patients with and without LBP. Conclusions. The sagittal alignment of spine-pelvis-lower extremity axis was significantly influenced by severe KOA. The lumbar spine served as the primary source of compensation, while hip flexion and pelvic anteversion increased for further compensation. Changes in sagittal alignment may not be involved in the pathogenesis of LBP in this patient population. Cite this article: W. J. Wang, F. Liu, Y.W. Zhu, M.H. Sun, Y. Qiu, W. J. Weng. Sagittal alignment of the spine-pelvis-lower extremity axis in patients with severe knee osteoarthritis: A radiographic study. Bone Joint Res 2016;5:198–205. DOI:10.1302/2046-3758.55.2000538

Introduction

The aim of this study was to evaluate the effects of posterior tibial slope (PTS) and posterior condylar offset (PCO) on patient-reported pain and function one year after TKA.

Aims. This study aimed to evaluate the association between the sagittal alignment of the femoral component in total knee arthroplasty (TKA) and new Knee Society Score (2011KSS), under the hypothesis that outliers such as the excessive extended or flexed femoral component were related to worse clinical outcomes. Methods. A group of 156 knees (134 F:22 M) in 133 patients with a mean age 75.8 years (SD 6.4) who underwent TKA with the cruciate-substituting Bi-Surface Knee prosthesis were retrospectively enrolled. On lateral radiographs, γ angle (the angle between the distal femoral axis and the line perpendicular to the distal rear surface of the femoral component) was measured, and the patients were divided into four groups according to the γ angle. The 2011KSSs among groups were compared using the Kruskal-Wallis test. A secondary regression analysis was used to investigate the association between the 2011KSS and γ angle. Results. According to the mean and SD of γ angle (γ, 4.0 SD 3.0°), four groups (Extended or minor flexed group, −0.5° ≤ γ < 2.5° (n = 54)), Mild flexed group (2.5° ≤ γ < 5.5° (n = 63)), Moderate flexed group (5.5° ≤ γ < 8.5° (n = 26)), and Excessive flexed group (8.5° ≤ γ (n = 13)) were defined. The Excessive flexed group showed worse 2011KSSs in all subdomains (Symptoms, Satisfaction, Expectations, and Functional activities) than the Mild flexed group. Secondary regression showed a convex upward function, and the scores were highest at γ = 3.0°, 4.0°, and 3.0° in Satisfaction, Expectations, and Functional activities, respectively. Conclusion. The groups with a sagittal alignment of the femoral component > 8.5° showed inferior clinical outcomes in 2011KSSs. Secondary regression analyses showed that mild flexion of the femoral component was associated with the highest score. When implanting the Bi-Surface Knee prosthesis surgeons should pay careful attention to avoiding flexing the femoral component extensively during TKA. Our findings may be applicable to other implant designs. Cite this article: Bone Joint J 2020;102-B(6 Supple A):36–42

Aims. Porous metaphyseal cones can be used for fixation in revision total knee arthroplasty (rTKA) and complex TKAs. This metaphyseal fixation has led to some surgeons using shorter cemented stems instead of diaphyseal engaging cementless stems with a potential benefit of ease of obtaining proper alignment without being beholden to the diaphysis. The purpose of this study was to evaluate short term clinical and radiographic outcomes of a series of TKA cases performed using 3D-printed metaphyseal cones. Methods. A retrospective review of 86 rTKAs and nine complex primary TKAs, with an average age of 63.2 years (SD 8.2) and BMI of 34.0 kg/m. 2. (SD 8.7), in which metaphyseal cones were used for both femoral and tibial fixation were compared for their knee alignment based on the type of stem used. Overall, 22 knees had cementless stems on both sides, 52 had cemented stems on both sides, and 15 had mixed stems. Postoperative long-standing radiographs were evaluated for coronal and sagittal plane alignment. Adjusted logistic regression models were run to assess malalignment hip-knee-ankle (HKA) alignment beyond ± 3° and sagittal alignment of the tibial and femoral components ± 3° by stem type. Results. No patients had a revision of a cone due to aseptic loosening; however, two had revision surgery due to infection. In all, 26 (27%) patients had HKA malalignment; nine (9.5%) patients had sagittal plane malalignment, five (5.6%) of the tibia, and four (10.8%) of the femur. After adjusting for age, sex, and BMI, there was a significantly increased risk for malalignment when a cone was used and both the femur and tibia had cementless compared to cemented stems (odds ratio 3.19, 95% confidence interval 1.01 to 10.05). Conclusion. Porous 3D-printed cones provide excellent metaphyseal fixation. However, these central cones make the use of offset couplers difficult and may generate malalignment with cementless stems. We found 3.19-times higher odds of malalignment in our TKAs performed with metaphyseal cones and both femoral and tibial cementless stems. Cite this article: Bone Joint J 2021;103-B(6 Supple A):150–157

Aims. The aims of this study were to determine the effect of osteophyte excision on deformity correction and soft tissue gap balance in varus knees undergoing computer-assisted total knee arthroplasty (TKA). Methods. A total of 492 consecutive, cemented, cruciate-substituting TKAs performed for varus osteoarthritis were studied. After exposure and excision of both cruciates and menisci, it was noted from operative records the corrective interventions performed in each case. Knees in which no releases after the initial exposure, those which had only osteophyte excision, and those in which further interventions were performed were identified. From recorded navigation data, coronal and sagittal limb alignment, knee flexion range, and medial and lateral gap distances in maximum knee extension and 90° knee flexion with maximal varus and valgus stresses, were established, initially after exposure and excision of both cruciate ligaments, and then also at trialling. Knees were defined as ‘aligned’ if the hip-knee-ankle axis was between 177° and 180°, (0° to 3° varus) and ‘balanced’ if medial and lateral gaps in extension and at 90° flexion were within 2 mm of each other. Results. Of 50 knees (10%) with no soft tissue releases (other than cruciate ligaments), 90% were aligned, 81% were balanced, and 73% were aligned and balanced. In 288 knees (59%) only osteophyte excision was performed by subperiosteally releasing the deep medial collateral ligament. Of these, 98% were aligned, 80% were balanced, and 79% were aligned and balanced. In 154 knees (31%), additional procedures were performed (reduction osteotomy, posterior capsular release, and semimembranosus release). Of these, 89% were aligned, 68% were balanced, and 66% were aligned and balanced. The superficial medial collateral ligament was not released in any case. Conclusion. Two-thirds of all knees could be aligned and balanced with release of the cruciate ligaments alone and excision of osteophytes. Excision of osteophytes can be a useful step towards achieving deformity correction and gap balance without having to resort to soft tissue release in varus knees while maintaining classical coronal and sagittal alignment of components. Cite this article: Bone Joint J 2020;102-B(6 Supple A):49–58

Aims. The aim of this study was to compare any differences in the primary outcome (biphasic flexion knee moment during gait) of robotic arm-assisted bi-unicompartmental knee arthroplasty (bi-UKA) with conventional mechanically aligned total knee arthroplasty (TKA) at one year post-surgery. Methods. A total of 76 patients (34 bi-UKA and 42 TKA patients) were analyzed in a prospective, single-centre, randomized controlled trial. Flat ground shod gait analysis was performed preoperatively and one year postoperatively. Knee flexion moment was calculated from motion capture markers and force plates. The same setup determined proprioception outcomes during a joint position sense test and one-leg standing. Surgery allocation, surgeon, and secondary outcomes were analyzed for prediction of the primary outcome from a binary regression model. Results. Both interventions were shown to be effective treatment options, with no significant differences shown between interventions for the primary outcome of this study (18/35 (51.4%) biphasic TKA patients vs 20/31 (64.5%) biphasic bi-UKA patients; p = 0.558). All outcomes were compared to an age-matched, healthy cohort that outperformed both groups, indicating residual deficits exists following surgery. Logistic regression analysis of primary outcome with secondary outcomes indicated that the most significant predictor of postoperative biphasic knee moments was preoperative knee moment profile and trochlear degradation (Outerbridge) (R. 2. = 0.381; p = 0.002, p = 0.046). A separate regression of alignment against primary outcome indicated significant bi-UKA femoral and tibial axial alignment (R. 2. = 0.352; p = 0.029), and TKA femoral sagittal alignment (R. 2. = 0.252; p = 0.016). The bi-UKA group showed a significant increased ability in the proprioceptive joint position test, but no difference was found in more dynamic testing of proprioception. Conclusion. Robotic arm-assisted bi-UKA demonstrated equivalence to TKA in achieving a biphasic gait pattern after surgery for osteoarthritis of the knee. Both treatments are successful at improving gait, but both leave the patients with a functional limitation that is not present in healthy age-matched controls. Cite this article: Bone Joint J 2022;103-B(4):433–443

Objectives. Unicompartmental knee arthroplasty (UKA) is one surgical option for treating symptomatic medial osteoarthritis. Clinical studies have shown the functional benefits of UKA; however, the optimal alignment of the tibial component is still debated. The purpose of this study was to evaluate the effects of tibial coronal and sagittal plane alignment in UKA on knee kinematics and cruciate ligament tension, using a musculoskeletal computer simulation. Methods. The tibial component was first aligned perpendicular to the mechanical axis of the tibia, with a 7° posterior slope (basic model). Subsequently, coronal and sagittal plane alignments were changed in a simulation programme. Kinematics and cruciate ligament tensions were simulated during weight-bearing deep knee bend and gait motions. Translation was defined as the distance between the most medial and the most lateral femoral positions throughout the cycle. Results. The femur was positioned more medially relative to the tibia, with increasing varus alignment of the tibial component. Medial/lateral (ML) translation was smallest in the 2° varus model. A greater posterior slope posteriorized the medial condyle and increased anterior cruciate ligament (ACL) tension. ML translation was increased in the > 7° posterior slope model and the 0° model. Conclusion. The current study suggests that the preferred tibial component alignment is between neutral and 2° varus in the coronal plane, and between 3° and 7° posterior slope in the sagittal plane. Varus > 4° or valgus alignment and excessive posterior slope caused excessive ML translation, which could be related to feelings of instability and could potentially have negative effects on clinical outcomes and implant durability. Cite this article: K. Sekiguchi, S. Nakamura, S. Kuriyama, K. Nishitani, H. Ito, Y. Tanaka, M. Watanabe, S. Matsuda. Bone Joint Res 2019;8:126–135. DOI: 10.1302/2046-3758.83.BJR-2018-0208.R2

Introduction. The relationship between sagittal component alignment on clinical outcomes has not fully evaluated after TKA. This study evaluated the effect of sagittal alignment of the components on patient function and satisfaction as well as kinematics and kinetics. Methods. This study included 148 primary TKAs with cruciate-substituting prosthesis for primary OA. With post-operative lateral radiograph, femoral component flexion angle (γ) and tibial component posterior slope angle (90-σ) was measured. The patients was classified into multiple groups by every three degrees. Patient satisfaction in 2011KSS among groups were analyzed using one-way analysis of variance. By representing the component position which showed poor clinical outcomes, computer simulation analysis was performed, in which kinematics and kinetics in squatting activity were investigated. Results. The femoral component flexion angle was 4.3 ± 3.3°, and tibial component posterior slope angle was 4.5 ± 3.4°, in average. Patients whose femoral component was implanted more than 9 degrees flexion showed lower satisfaction (Figure). There was no difference in satisfaction according to tibial component angle. Computer simulation analysis showed that excessive flexed position caused no remarkable abnormal kinematics, but increased maximum contact force in medial compartment (1097 N to 1711 N), and femoral component down-size did not fully decrease the contact force (1330 N). Similarly, increase of the maximum ligament force in medial collateral ligament (MCL) (188 N to 671 N) was observed in excessive flexed position, and femoral component downsize (343 N) did not fully recovered the ligament force. Conclusion. Excessive flexion of the femoral component showed poor satisfaction. In computer simulation, increase of the contact force of the medial compartment and MCL was observed in computer simulation. For figures, tables, or references, please contact authors directly

Introduction. Robotic technology has been applied to unicompartmental knee arthroplasty (UKA) in order to improve surgical precision in prosthetic component placement, restore knee anatomic surfaces, and provide a more physiologic ligament tensioning throughout the knee range of motion. Recent literature has demonstrated the reliability of robotic assisted UKA over manual UKA in component placement and executing a soft-tissue tensioning plan. The purpose of this multicenter study was to determine the correlation between 3D component positioning and soft-tissue tensioning with short-term clinical results following robotic assisted medial UKA. Methods. Between 2013 and 2016, 349 patients (381 knees) underwent robotic assisted fixed bearing metal backed medial UKAs at two centres. Follow-up was performed at 12 months minimum. Pre- and post-operatively, patients were administered Knee Injury and Osteoarthritis Score (KOOS), Forgotten Joint Score 12 (FJS), and Short-Form summary scale (SF-12) surveys. Clinical results for every score were stratified as ‘excellent’, ‘mild’ and ‘insufficient’. Post-operative complications were recorded. Failure mechanisms, reoperations and post-operative knee pain were also assessed. Intra-operative robotic data relative to femoral and tibial component placement in the coronal, sagittal and horizontal plane, as well as femoro-tibial gaps at different knee flexion angles were also collected. Results. A total of 338 robotic assisted medial UKAs (309 patients) were assessed at an average follow-up of 33.5 months post-operatively (89% follow-up rate). Three implants were revised, resulting in a survivorship of 99.0% (C.I. 97.0%–99.7%), one for prosthetic joint infection and two for tibial aseptic loosening. All clinical post-operative scores were significantly improved from the pre-operative scores. The following statistically significant correlations were found between intra-operative robotic data and outcomes considered individually: femoral component coronal alignment influenced KOOS Symptoms, Pain and Quality of Life (p<0.05), sagittal alignment influenced KOOS Symptoms and Pain (p<0.05), and femoro-tibial gaps at 20°–30° knee flexion influenced KOOS Pain and Function in Activities of Daily Living (p<0.05). Both, tibial sagittal alignment and femoro-tibial gaps at 80°–90° knee flexion were found to correlate with SF-12 Physical Status and presence of post-operative pain (p<0.01). ‘Excellent’ clinical outcomes were reported by those patients who, on average, had the femur placed in neutral alignment in the coronal and horizontal planes (0.2°±1.5 and 0.6°±1.4 respectively) as well as avoided excessive flexion in the sagittal plane (3.7°±3.2). When considering the tibia, better results were reported by patients with the tibial component placed in slight external rotation (2.2°±1.7), varus coronal alignment (1.5°±1.7) and no more than 5° of posterior slope (5.0°±1.0). Regarding femoro-tibial gaps, ‘excellent’ clinical outcomes were reported by patients who were slightly loose between 20°–30° and 80°–90° of knee flexion. Conclusion. In the present study, survivorship and clinical outcomes of a large cohort of 309 patients with medial robotic assisted UKA were contacted with at a mean 3-years. The overall survivorship was found to be 99%, with tibial component failure as the most common reason for UKA revision. The significant difference between pre- and post-operative clinical scores highlights the efficacy of robotic assisted UKA in restoring knee function and relieving pain. Differences in components’ positioning and soft-tissue tensioning demonstrated significant correlation with post-operative clinical outcomes

Aims. The purpose of this multicentre observational study was to investigate the association between intraoperative component positioning and soft-tissue balancing on short-term clinical outcomes in patients undergoing robotic-arm assisted unicompartmental knee arthroplasty (UKA). Patients and Methods. Between 2013 and 2016, 363 patients (395 knees) underwent robotic-arm assisted UKAs at two centres. Pre- and postoperatively, patients were administered Knee Injury and Osteoarthritis Score (KOOS) and Forgotten Joint Score-12 (FJS-12). Results were stratified as “good” and “bad” if KOOS/FJS-12 were more than or equal to 80. Intraoperative, post-implantation robotic data relative to CT-based components placement were collected and classified. Postoperative complications were recorded. Results. Following exclusions and losses to follow-up, 334 medial robotic-arm assisted UKAs were assessed at a mean follow-up of 30.0 months (8.0 to 54.9). None of the measured parameters were associated with overall KOOS outcome. Correlations were described between specific KOOS subscales and intraoperative, post-implantation robotic data, and between FJS-12 and femoral component sagittal alignment. Three UKAs were revised, resulting in 99.0% survival at two years (95% confidence interval (CI) 97.9 to 100.0). Conclusion. Although little correlation was found between intraoperative robotic data and overall clinical outcome, surgeons should consider information regarding 3D component placement and soft-tissue balancing to improve patient satisfaction. Reproducible and precise placement of components has been confirmed as essential for satisfactory clinical outcome. Cite this article: Bone Joint J 2019;101-B:435–442

Background. Advanced technologies, like robotics, provide enhanced precision for implanting total knee arthroplasty (TKA) components; however, optimal component position and limb alignment remain unknown. This study purpose was to identify the ideal target sagittal component position and coronal limb alignment that produce optimal clinical outcomes. Methods. A retrospective review of 1,091 consecutive TKAs was performed. All TKAs were PCL retaining or sacrificing with anterior lipped (49.4%) or conforming bearings (50.6%) performed with modern perioperative protocols. Posterior tibial slope, femoral flexion, and tibiofemoral limb alignment were measured with a standardized protocols. Patients were grouped by the ‘how often does your knee feel normal?’ outcome score at latest follow-up. Machine learning algorithms were used to identify optimal alignment zones which predicted improved outcomes scores. Results. Mean age and BMI were 66 years and 34 kg/m. 2. with 67% female. Demographics and relevant covariates did not affect outcomes (p≥0.145) except for BMI (p=0.077) but the difference was not clinically significant. For sagittal alignment, approximating native tibial slope within 0 to +2° with some amount of femoral flexion within 0 to +3° (possibly up to +9°) was predictive of knees always feeling normal. For knees in preoperative varus or neutral, knees were more likely to always feel normal when postoperative tibiofemoral alignment was in varus (>−1°). Knees aligned in valgus preoperatively were more likely to always feel normal in valgus (<−7°) or varus (>−4°) postoperatively. Conclusion. Superior patient-reported outcomes correlated with approximating native tibial slope and incorporating some femoral flexion while maintaining similar preoperative coronal limb alignment. Excessive deviation from native tibial slope, excessive femoral flexion or any femoral component extension, or coronal alignment overcorrection beyond the preoperative limb alignment correlated with worse outcomes

Introduction. Porous metaphyseal cones are increasingly used for fixation in revision total knee arthroplasty (RTKA). Both cemented shorter length stems and longer diaphyseal engaging stems are currently utilized with metaphyseal cones with no clear evidence of superiority. The purpose of this study was to evaluate our experience with 3D printed titanium metaphyseal cones with both short cemented and longer cementless stems from a clinical and radiographic perspective. Methods. In total 136 3D printed titanium metaphyseal cones were implanted. The mean patient age was 63 and 48% were female. The mean BMI was 33 and the mean ASA class was 2.5. There were 42 femoral cones in which 28 cemented and 14 cementless stems were utilized. There were 94 tibial cones in which 67 cemented and 27 cementless stems were utilized. The choice for stem fixation was surgeon dependent and in general cones were utilized for AORI type 2 and 3 bone defects on the femur and tibia. The most common fixation scenario was short cemented stems on both the femur and tibia followed by cemented stem fixation on the tibia and cementless fixation on the femur. Clinical data such as revision, complication, and PRO was collected at last follow-up (minimum follow-up 1 year). Radiographic analysis included cone bony ingrowth and coronal and sagittal alignment on long-standing radiographs. Descriptive statistics were used to compare demographics between patients who had malalignment (HKA beyond +/− 3 degrees and flexion/extension beyond +/− 3 degrees). Adjusted logistic regression models were run to assess malalignment risk by stem type. Results. Patient reported outcomes demonstrated modest improvements with Pre-op KOOS improving from 44 pre-op to 59 post -op and PF-CAT improving from 33 to 37 post-op. PROMIS pain scores decreased significantly from 54 to 44 post-op. 36% of patients had malalignment in either the coronal or sagittal plane. Patients with malalignment were more likely to be female (66.7% vs 40.4%, p-value=0.02). After adjusting for age, sex and BMI, there was a significantly increased risk for coronal plane malalignment when both the femur and tibia had cementless compared to cemented stems (odds ratio=5.54, 95%CI=1.15, 26.80). There was no significantly increased risk when comparing patients with mixed stems to patients with cemented stems. Sagittal plane malalignment was more common with short cemented stems although both coronal plane and sagittal plane malalignment with either stem type was not associated with inferior clinical outcome. Overall cone survivorship was excellent with only two cones removed for infection. Conclusion. Metaphyseal titanium cones provide reliable fixation in revision TKA. However, PROs in this complex patient population show only modest improvement consistent with other variables such as co-morbidities and poor baseline physical function. Small cone inner diameter may adversely influence cementless stem position leading to coronal plane malalignment. Short cemented stems are subject to greater sagittal plane malalignment with no apparent influence on clinical outcome

Background. The purpose of this study was to assess the overall clinical and radiographic outcomes of unicompartmental knee arthroplasty (UKA) in the 2–10 year postoperative period. The secondary goal was to compare outcomes between fixed- (FB) and mobile-bearing (MB) implant designs. Methods. We performed a retrospective analysis of 237 consecutive primary medial UKAs from a single academic center. All cases were performed by high-volume fellowship-trained arthroplasty surgeons, though UKA comprised <10% of their overall knee arthroplasty practice (<20 medial UKAs per surgeon per year). Clinical outcomes included the Oxford Knee Scores (OKS) and revision rates. Femoral and tibial coronal and sagittal angles (FCA, FSA, TCA, TSA) were radiographically measured. FCA (>±10º deviation from the neutral axis), FSA (>15º flexion), TCA (>±5º deviation from the neutral axis), and TSA (>±5º deviation from 7º) outliers were defined. Far outliers were defined as measurements that fell an additional >±2º outside of these ranges. Outcomes were compared between the FB and MB groups. Results. Overall, OKS scores improved significantly from 18.6 to 34.2 (p<0.0001) following UKA. The overall revision rate at an average 5.5-year follow-up was 14.3%. Only 48.9% and 46.4% of knees simultaneously fell within coronal and sagittal alignment targets for femoral and tibial alignment, respectively. Only 24.1% of all UKAs fell within target alignment in all four measurements. When comparing FB and MB knees, there was no difference in the overall revision rate (12.5% vs. 17.6%, p=0.280), nor were there differences in postoperative OKS (33.6 vs. 35.4, p=0.239) or outlier risk. Conclusions. The proportion of UKA revisions and alignment outliers is greater than expected, even among high-volume surgeons. In general, implant design does not appear to significantly impact clinical outcomes, revision rates, or implant alignment. There was a trend for far outliers to have a higher rate of revision and lower OKS. For figures, tables, or references, please contact authors directly

Aims. The purpose of the present study was to compare patient-specific instrumentation (PSI) and conventional surgical instrumentation (CSI) for total knee arthroplasty (TKA) in terms of early implant migration, alignment, surgical resources, patient outcomes, and costs. . Patients and Methods. The study was a prospective, randomized controlled trial of 50 patients undergoing TKA. There were 25 patients in each of the PSI and CSI groups. There were 12 male patients in the PSI group and seven male patients in the CSI group. The patients had a mean age of 69.0 years (. sd. 8.4) in the PSI group and 69.4 years (. sd. 8.4) in the CSI group. All patients received the same TKA implant. Intraoperative surgical resources and any surgical waste generated were recorded. Patients underwent radiostereometric analysis (RSA) studies to measure femoral and tibial component migration over two years. Outcome measures were recorded pre- and postoperatively. Overall costs were calculated for each group. Results. There were no differences (p > 0.05) in any measurement of migration at two years for either the tibial or femoral components. Movement between one and two years was < 0.2 mm, indicating stable fixation. There were no differences in coronal or sagittal alignment between the two groups. The PSI group took a mean 6.1 minutes longer (p = 0.04) and used a mean 3.4 less trays (p < 0.0001). Total waste generated was similar (10 kg) between the two groups. The PSI group cost a mean CAD$1787 more per case (p < 0.01). Conclusion. RSA criteria suggest that both groups will have revision rates of approximately 3% at five years. The advantages of PSI were minimal or absent for surgical resources used and waste eliminated, and for meeting target alignment, yet had significantly greater costs. Therefore, we conclude that PSI may not offer any advantage over CSI for routine primary TKA cases. Cite this article: Bone Joint J 2019;101-B:565–572

Aims

A fracture of the medial tibial plateau is a serious complication of Oxford mobile-bearing unicompartmental knee arthroplasty (OUKA). The risk of these fractures is reportedly lower when using components with a longer keel-cortex distance (KCDs). The aim of this study was to examine how slight varus placement of the tibial component might affect the KCDs, and the rate of tibial plateau fracture, in a clinical setting.

Aims

Total knee arthroplasty (TKA) may provoke ankle symptoms. The aim of this study was to validate the impact of the preoperative mechanical tibiofemoral angle (mTFA), the talar tilt (TT) on ankle symptoms after TKA, and assess changes in the range of motion (ROM) of the subtalar joint, foot posture, and ankle laxity.

Aims

Higher osteoblastic bone activity is expected in aseptic loosening and painful unicompartmental knee arthroplasty (UKA). However, insights into normal bone activity patterns after medial UKAs are lacking. The aim of this study was to identify the evolution in bone activity pattern in well-functioning medial mobile-bearing UKAs.

Aims

Conflicting clinical results are reported for the ATTUNE Total Knee Arthroplasty (TKA). This randomized controlled trial (RCT) evaluated five-year follow-up results comparing cemented ATTUNE and PFC-Sigma cruciate retaining TKAs, analyzing component migration as measured by radiostereometric analysis (RSA), clinical outcomes, patient-reported outcome measures (PROMs), and radiological outcomes.

Recent advancements in optical navigated TKA have shown improved overall limb alignment, implant placement and reduced outliers compared to conventional TKA. This study represents the first RCT comparing EM navigation and conventional TKA. 3D alignment was analysed from CT scans. Clinical scores (Oxford Knee Score (OKS) and American Knee Society Score (AKSS)) were recorded at pre-op, 3 and 12 months post-op. Data presented includes 180 patients (n=90 per group) at 3 months and 140 (n=70 per group) at 12 months. The groups had similar mean mechanical axis alignments (EM 0.31° valgus; conventional 0.15° valgus). Mechanical axis alignment however was improved in the EM group with 92% within +/−3° of neutral compared to 84% of the conventional group (p=0.90). The EM group showed improved coronal and sagittal femoral alignment and improved coronal, sagittal and rotational tibial alignment, which was significant for sagittal femoral alignment (p=0.04). The OKS and AKSS scores were significantly better for the EM group at 3 months post-op (OKS p=0.02, AKSS p=0.04), but there was no difference between groups at 12 months. The mean pre-op range of motion (ROM) for both groups was 105°. This decreased at 3 months to 102° in the EM group and 99° in the conventional group, but there was a significant improvement by 12 months: EM=113° (p=0.012) and conventional=112° (p=0.026). ROM was statistically similar between groups at all assessment phases. Knee alignment was better restored following EM navigated TKA relative to conventional TKA, but the difference was not significant. The EM group showed greater clinical improvements at early follow-up; however this difference was not sustained at 12 months. ROM was seen to decrease at 3 months but then significantly improve by 12 month post-op. Proving cost-effectiveness for navigation systems in TKA remains a challenge

A controlled study, comparing computer- and conventional jig-assisted total knee replacement in six cadavers is presented. In order to provide a quantitative assessment of the alignment of the replacements, a CT-based technique which measures seven parameters of alignment has been devised and used. In this a multi-slice CT machine scanned in 2.5 mm slices from the acetabular roof to the dome of the talus with the subject’s legs held in a standard position. The mechanical and anatomical axes were identified, from three-dimensional landmarks, in both anteroposterior and lateral planes. The coronal and sagittal alignment of the prosthesis was then measured against the axes. The rotation of the femoral component was measured relative to the transepicondylar axis. The rotation of the tibial component was measured with reference to the posterior tibial condyles and the tibial tuberosity. Coupled femorotibial rotational alignment was assessed by superimposition of the femoral and tibial axial images. The radiation dose was 2.7 mSV. The computer-assisted total knee replacements showed better alignment in rotation and flexion of the femoral component, the posterior slope of the tibial component and in the matching of the femoral and tibial components in rotation. Differences were statistically significant and of a magnitude that support extension of computer assistance to the clinical situation