Aims. The aims of this study were: 1) to describe extended restricted kinematic alignment (E-rKA), a novel alignment strategy during robotic-assisted total knee arthroplasty (RA-TKA); 2) to compare residual medial compartment tightness following virtual surgical planning during RA-TKA using mechanical alignment (MA) and E-rKA, in the same set of osteoarthritic varus knees; 3) to assess the requirement of soft-tissue releases during RA-TKA using E-rKA; and 4) to compare the accuracy of surgical plan execution between knees managed with adjustments in component positioning alone, and those which require additional soft-tissue releases. Methods. Patients who underwent RA-TKA between January and December 2022 for primary varus osteoarthritis were included. Safe boundaries for E-rKA were defined. Residual medial compartment tightness was compared following virtual surgical planning using E-rKA and MA, in the same set of knees. Soft-tissue releases were documented. Errors in postoperative alignment in relation to planned alignment were compared between patients who did (group A) and did not (group B) require soft-tissue releases. Results. The use of E-rKA helped restore all knees within the predefined boundaries, with appropriate soft-tissue balancing. E-rKA compared with MA resulted in reduced residual medial tightness following surgical planning, in full extension (2.71 mm (SD 1.66) vs 5.16 mm (SD 3.10), respectively; p < 0.001), and 90° of flexion (2.52 mm (SD 1.63) vs 6.27 mm (SD 3.11), respectively; p < 0.001). Among the study population, 156 patients (78%) were managed with minor adjustments in component positioning alone, while 44 (22%) required additional soft-tissue releases. The mean errors in postoperative alignment were 0.53 mm and 0.26 mm among patients in group A and group B, respectively (p = 0.328). Conclusion. E-rKA is an effective and reproducible alignment strategy during RA-TKA, permitting a large proportion of patients to be managed without soft-tissue releases. The execution of minor alterations in component positioning within predefined multiplanar boundaries is a better starting point for gap management than soft-tissue releases. Cite this article: Bone Jt Open 2024;5(8):628–636

Aims. Between 15% and 20% of patients remain dissatisfied following total knee arthroplasty (TKA). The SAIPH knee system (MatOrtho, Surrey, United Kingdom) is a medial ball and socket TKA that has been designed to replicate native knee kinematics in order to maximize the range of movement, stability, and function. This system is being progressively introduced in a stepwise fashion, with this study reporting the mid-term clinical and radiological outcomes. Patients and Methods. A retrospective review was undertaken of the first 100 consecutive patients with five-year follow-up following SAIPH TKA performed by the senior authors. The data that were collected included the demographics of the patients, clinical findings, the rate of intraoperative ligamentous release, patient-reported outcome measures (PROMS), radiological assessment, complications, and all-cause revision. Revision data were cross-checked with a national registry. Results. A total of 100 TKAs in 92 patients were included. Three patients died (three TKAs) and a further two TKAs were revised. Of the remaining 95 TKAs, five-year follow-up data were available for 81 TKAs (85%) in 87 patients. There were significant improvements in all PROMs and high satisfaction. The mean ROM at final follow-up was from 0° (full extension) to 124° flexion. There were seven major complications (7%): one infection, two deep vein thromboses, one cerebrovascular event, and two patients with stiffness requiring a manipulation under anaesthesia. Two patients required a lateral retinacular release to optimize patellar tracking in valgus knees; no additional ligament releases were performed in any patient. Radiological analysis demonstrated no evidence of implant-related complications. Conclusion. These results demonstrate satisfactory clinical and radiological outcomes at five years following a medial ball and socket TKA. The complication and revision rates are consistent with those previously reported for patients undergoing TKA. These results demonstrate the safety and efficacy of the SAIPH Knee TKA system and support its wider use

Aims. Although bone cement is the primary mode of fixation in total knee arthroplasty (TKA), cementless fixation is gaining interest as it has the potential of achieving lasting biological fixation. By 3D printing an implant, highly porous structures can be manufactured, promoting osseointegration into the implant to prevent aseptic loosening. This study compares the migration of cementless, 3D-printed TKA to cemented TKA of a similar design up to two years of follow-up using radiostereometric analysis (RSA) known for its ability to predict aseptic loosening. Methods. A total of 72 patients were randomized to either cementless 3D-printed or a cemented cruciate retaining TKA. RSA and clinical scores were evaluated at baseline and postoperatively at three, 12, and 24 months. A mixed model was used to analyze the repeated measurements. Results. The mean maximum total point motion (MTPM) at three, 12, and 24 months was 0.33 mm (95% confidence interval (CI) 0.25 to 0.42), 0.42 mm (95% CI 0.33 to 0.51), and 0.47 mm (95% CI 0.38 to 0.57) respectively in the cemented group, versus 0.52 mm (95% CI 0.43 to 0.63), 0.62 mm (95% CI 0.52 to 0.73), and 0.64 mm (95% CI 0.53 to 0.75) in the cementless group (p = 0.003). However, using three months as baseline, no difference in mean migration between groups was found (p = 0.497). Three implants in the cemented group showed a > 0.2 mm increase in MTPM between one and two years of follow-up. In the cementless group, one implant was revised due to pain and progressive migration, and one patient had a liner-exchange due to a deep infection. Conclusion. The cementless TKA migrated more than the cemented TKA in the first two-year period. This difference was mainly due to a higher initial migration of the cementless TKA in the first three postoperative months after which stabilization was observed in all but one malaligned and early revised TKA. Whether the biological fixation of the cementless implants will result in an increased long-term survivorship requires a longer follow-up. Cite this article: Bone Joint J 2020;102-B(8):1016–1024

Aims. We report the natural course of Baker’s cysts following total knee arthroplasty (TKA) at short- and mid-term follow-up. Methods. In this prospective case series, 105 TKA patients were included. All patients who received surgery had a diagnosis of primary osteoarthritis and had preoperatively presented with a Baker’s cyst. Sonography and MRI were performed to evaluate the existence and the gross size of the cyst before TKA, and sonography was repeated at a mean follow-up time of 1.0 years (0.8 to 1.3; short-term) and 4.9 years (4.0 to 5.6; mid-term) after TKA. Symptoms potentially attributable to the Baker’s cyst were recorded at each assessment. Results. At the one-year follow-up analysis, 102 patients were available. Of those, 91 patients were available for the 4.9-year assessment (with an 86.7% follow-up rate (91/105)). At the short- and mid-term follow-up, a Baker’s cyst was still present in 87 (85.3%) and 30 (33.0%) patients, respectively. Of those patients who retained a Baker’s cyst at the short-term follow-up, 31 patients (35.6%) had popliteal symptoms. Of those patients who continued to have a Baker’s cyst at the mid-term follow-up, 17 patients (56.7%) were still symptomatic. The mean preoperative cyst size was 14.5 cm. 2. (13.1 to 15.8). At the short- and mid-term follow-up, the mean cyst size was 9.7 cm. 2. (8.3 to 11.0) and 10.4 cm. 2. (9.8 to 11.4), respectively. A significant association was found between the size of the cyst at peroperatively and the probability of resolution, with lesions smaller than the median having an 83.7% (36/43) probability of resolution, and larger lesions having a 52.1% (25/48) probability of resolution (p < 0.001). At the mid-term follow-up, no association between cyst size and popliteal symptoms was found. Conclusion. At a mean follow-up of 4.9 years (4.0 to 5.6) after TKA, the majority (67.0%, 61/91) of the Baker’s cysts that were present preoperatively had disappeared. The probability of cyst resolution was dependent on the size of the Baker’s cyst at baseline, with an 83.7% (36/43) probability of resolution for smaller cysts and 52.1% (25/48) probability for larger cysts. Cite this article: Bone Joint J. 2020;102-B(1):132–136

Aims. The primary aim of this study was to compare the knee-specific functional outcome of patellofemoral arthroplasty with total knee arthroplasty (TKA) in the management of patients with patellofemoral osteoarthritis. Patients and Methods. A total of 54 consecutive Avon patellofemoral arthroplasties were identified and propensity-score-matched to a group of 54 patients undergoing a TKA with patellar resurfacing for patellofemoral osteoarthritis. The Oxford Knee Score (OKS), the 12-Item Short-Form Health Survey (SF-12), and patient satisfaction were collected at a mean follow up of 9.2 years (8 to 15). Survival was defined by revision or intention to revise. Results. There was no significant difference in the mean OKS (p > 0.60) or SF-12 scores (p > 0.28) between the groups. There was a lower rate of satisfaction at the final follow-up for the TKA group (78% vs 87%) but this was not statistically significant (odds ratio 0.56, p = 0.21). Length of stay was significantly shorter (p = 0.008) for the Avon group (difference 1.8 days, 95% confidence interval (CI) 0.4 to 3.2). The ten-year survival for the Avon group was 92.3% (95% CI 87.1 to 97.5) and for the TKA group was 100% (95% CI 93.8 to 100). This difference was not statistically significant (log-rank test, p = 0.10). Conclusion. Patients undergoing an Avon patellofemoral arthroplasty have a shorter length of stay, and a functional outcome and rate of satisfaction that is equal to that of TKA. The benefits of the Avon arthroplasty need to be balanced against the increased rate of revision when compared with TKA

Aims. There is little literature about total knee arthroplasty (TKA) after distal femoral osteotomy (DFO). Consequently, the purpose of this study was to analyze the outcomes of TKA after DFO, with particular emphasis on: survivorship free from aseptic loosening, revision, or any re-operation; complications; radiological results; and clinical outcome. Patients and Methods. We retrospectively reviewed 29 patients (17 women, 12 men) from our total joint registry who had undergone 31 cemented TKAs after a DFO between 2000 and 2012. Their mean age at TKA was 51 years (22 to 76) and their mean body mass index 32 kg/m. 2. (20 to 45). The mean time between DFO and TKA was ten years (2 to 20). The mean follow-up from TKA was ten years (2 to 16). The prostheses were posterior-stabilized in 77%, varus-valgus constraint (VVC) in 13%, and cruciate-retaining in 10%. While no patient had metaphyseal fixation (e.g. cones or sleeves), 16% needed a femoral stem. Results. The ten-year survivorship was 95% with aseptic loosening as the endpoint, 88% with revision for any reason as the endpoint, and 81% with re-operation for any reason as the endpoint. Three TKAs were revised for instability (n = 2) and aseptic tibial loosening (n = 1). No femoral component was revised for aseptic loosening. Patients under the age of 50 years were at greater risk of revision for any reason (hazard ratio 7; p = 0.03). There were two additional re-operations (6%) and four complications (13%), including three manipulations under anaesthetic (MUA; 10%). The Knee Society scores improved from a mean of 50 preoperatively (32 to 68) to a mean of 93 postoperatively (76 to 100; p < 0.001). Conclusion. A cemented posterior-stabilized TKA has an 88% ten-year survivorship with revision for any reason as the endpoint. No femoral component was revised for aseptic loosening. Patients under the age of 50 years have a greater risk of revision. The clinical outcome was significantly improved but balancing the knee was challenging in 13% of TKAs requiring VVC. Overall, 10% of TKAs needed an MUA, and 6% of TKAs were revised for instability. Cite this article: Bone Joint J 2019;101-B:660–666

Aims. The aim of this study was to characterize the factors leading to transfemoral amputation after total knee arthroplasty (TKA), as well as the rates of mortality and functional independence after this procedure in these patients. Patients and Methods. This was a multicentre retrospective review with a prospective telephone survey for the assessment of function. All patients with a TKA who subsequently required transfemoral amputation between January 2001 and December 2015 were included. Demographic information, medical comorbidities, and postoperative mortality data were collected. A 19-item survey was used for the assessment of function in surviving patients. Results. A total of 111 patients were included. Their mean age was 61.0 years (42.0 to 88.0) at the time of TKA, with a subsequent mean of 3.7 operations (0 to 15) over a mean period of 6.1 years (0.05 to 30.1) before amputation. The indication for amputation was chronic infection in 97 patients (87.4%). The rate of five-year survival was 51.7%, and advanced age (p = 0.001) and renal failure (p = 0.045) were associated with an increased risk of mortality. Of the 62 surviving patients, 34 completed the survey; 32 (94.1%) owned a prosthesis but only 19 (55.9%) used it; 19 (55.9%) primarily used a wheelchair for mobility; 27 (79.5%) had phantom pain; and 16 (47.1%) required chronic pain medication. Only 18 patients (52.9%) were satisfied with the quality of life. Conclusion. Patients with complications after TKA, in whom transfemoral amputation is considered, should be made aware of the high rate of mortality and the poor functional outcome in the survivors. Alternative forms of treatment including arthrodesis of the knee should be investigated

Aims. For many designs of total knee arthroplasty (TKA) it remains unclear whether cemented or uncemented fixation provides optimal long-term survival. The main limitation in most studies is a retrospective or non-comparative study design. The same is true for comparative trials looking only at the survival rate as extensive sample sizes are needed to detect true differences in fixation and durability. Studies using radiostereometric analysis (RSA) techniques have shown to be highly predictive in detecting late occurring aseptic loosening at an early stage. To investigate the difference in predicted long-term survival between cemented, uncemented, and hybrid fixation of TKA, we performed a randomized controlled trial using RSA. Methods. A total of 105 patients were randomized into three groups (cemented, uncemented, and hybrid fixation of the ACS Mobile Bearing (ACS MB) knee system, implantcast). RSA examinations were performed on the first day after surgery and at scheduled follow-up visits at three months, six months, one year, and two years postoperatively. Patient-reported outcome measures (PROMs) were obtained preoperatively and after two years follow-up. Patients and follow-up investigators were blinded for the result of randomization. Results. RSA secondary stabilization did not show a significant difference between the three types of fixation. A maximum total point motion of less than 0.2 mm in the second postoperative year was shown in each group, which suggests stabilization of the implant. At 24 months after surgery, PROMs significantly improved compared to baseline in all treatment groups. No significant difference was observed between the three groups. Conclusion. Secondary stabilization measurements in this study demonstrated no significant difference between the groups. In all groups migration stabilized after initial settling of the implant. For this implant the long-term outcome is not expected to be influenced by the type of fixation to the bone. Cite this article: Bone Joint J 2021;103-B(1):98–104

Aims. Anterior cruciate ligament (ACL) and multiligament knee (MLK) injuries increase the risk of development of knee osteoarthritis and eventual need for total knee arthroplasty (TKA). There are limited data regarding implant use and outcomes in these patients. The aim of this study was to compare the use of constrained implants and outcomes among patients undergoing TKA with a history of prior knee ligament reconstruction (PKLR) versus a matched cohort of patients undergoing TKA with no history of PKLR. Patients and Methods. Patients with a history of ACL or MLK reconstruction who underwent TKA between 2007 and 2017 were identified in a single-institution registry. There were 223 patients who met inclusion criteria (188 ACL reconstruction patients, 35 MLK reconstruction patients). A matched cohort, also of 223 patients, was identified based on patient age, body mass index (BMI), sex, and year of surgery. There were 144 male patients and 79 female patients in both cohorts. Mean age at the time of TKA was 57.2 years (31 to 88). Mean BMI was 29.7 kg/m. 2. (19.5 to 55.7). Results. There was a significantly higher use of constrained implants among patients with PKLR (76 of 223, 34.1%) compared with the control group (40 of 223, 17.9%; p < 0.001). Subgroup analysis showed a higher use of constrained implants among patients with prior MLK reconstruction (21 of 35, 60.0%) compared with ACL reconstruction (55 of 188, 29.3%; p < 0.001). Removal of hardware was performed in 69.5% of patients with PKLR. Mean operative time (p < 0.001) and tourniquet time (p < 0.001) were longer in patients with PKLR compared with controls. There were no significant differences in rates of deep vein thrombosis, pulmonary embolism, infection, transfusion, postoperative knee range of movement (ROM), or need for revision surgery. There was no significant difference in preoperative or postoperative Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS, JR) scores between groups. Conclusion. Results of this study suggest a history of PKLR results in increased use of constrained implants but no difference in postoperative knee ROM, patient-reported outcomes, or incidence of revision surgery. Cite this article: Bone Joint J 2019;101-B(7 Supple C):77–83

Aims. Postoperative range of movement (ROM) is an important measure of successful and satisfying total knee arthroplasty (TKA). Reduced postoperative ROM may be evident in up to 20% of all TKAs and negatively affects satisfaction. To improve ROM, manipulation under anaesthesia (MUA) may be performed. Historically, a limited ROM preoperatively was used as the key harbinger of the postoperative ROM. However, comorbidities may also be useful in predicting postoperative stiffness. The goal was to assess preoperative comorbidities in patients undergoing TKA relative to incidence of postoperative MUA. The hope is to forecast those who may be at increased risk and determine if MUA is an effective form of treatment. Methods. Prospectively collected data of TKAs performed at our institution’s two hospitals from August 2014 to August 2018 were evaluated for incidence of MUA. Comorbid conditions, risk factors, implant component design and fixation method (cemented vs cementless), and discharge disposition were analyzed. Overall, 3,556 TKAs met the inclusion criteria. Of those, 164 underwent MUA. Results. Patients with increased age and body mass index (BMI) had decreased likelihood of MUA. For every one-year increase in age, the likelihood of MUA decreased by 4%. Similarly, for every one-unit increase in BMI the likelihood of MUA decreased by 6%. There were no differences in incidence of MUA between component type/design or fixation method. Current or former smokers were more likely to have no MUA. Surprisingly, patients discharged to home health service or skilled nursing facility were approximately 40% and 70% less likely than those discharged home with outpatient therapy to be in the MUA group. MUA was effective, with a mean increased ROM of 32.81° (SD 19.85°; -15° to 90°). Conclusion. Younger, thinner patients had highest incidence of MUA. Effect of discharge disposition on rate of MUA was an important finding and may influence surgeons’ decisions. Interestingly, use of cement and component design (constraint) did not impact incidence of MUA. Level of Evidence II: Prospective cohort study. Cite this article: Bone Joint J 2020;102-B(6 Supple A):66–72

Aims. The primary aim of this study was to assess whether pain in the contralateral knee had a clinically significant influence on the outcome of total knee arthroplasty (TKA) according to the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score. Secondary aims were to: describe the prevalence of contralateral knee pain; identify if it clinically improves after TKA; and assess whether contralateral knee pain independently influences patient satisfaction with their TKA. Methods. A retrospective cohort of 3,178 primary TKA patients were identified from an arthroplasty database. Patient characteristics, comorbidities, and WOMAC scores were collected preoperatively and one year postoperatively for the index knee. In addition, WOMAC pain scores were also collected for the contralateral knee. Overall patient satisfaction was assessed at one year. Preoperative contralateral knee pain was defined according to the WOMAC score: minimal (> 78 points), mild (59 to 78), moderate (44 to 58), and severe (< 44). Multivariate regression analysis was used to adjust for confounding. Results. According to severity there were 1,425 patients (44.8%) with minimal, 710 (22.3%) with mild, 518 (16.3%) with moderate, and 525 (16.5%) with severe pain in the contralateral knee. Patients in the severe group had a greater clinically significant improvement in their functional WOMAC score (9.8 points; p < 0.001). Only patients in the moderate (22.9 points) and severe (37.8 points) groups had a clinically significant improvement in their contralateral knee pain (p < 0.001), but they were significantly less likely to be satisfied with their TKA (moderate: odds ratio (OR) 0.64, 95% confidence interval (CI) 0.4 to 0.92, p = 0.022; severe: OR 0.57, 95% CI 0.39 to 0.82, p = 0.002). Conclusion. Contralateral knee pain did not impair improvement in the WOMAC score after TKA, and patients with the most severe contralateral knee pain had a clinically significantly greater improvement in their functional outcome. More than half the patients presenting for TKA had mild-to-severe contralateral knee pain, most of whom had a clinically meaningful improvement but were significantly less likely to be satisfied with their TKA. Cite this article: Bone Joint J. 2020;102-B(1):125–131

Objectives. The use of the haptically bounded saw blades in robotic-assisted total knee arthroplasty (RTKA) can potentially help to limit surrounding soft-tissue injuries. However, there are limited data characterizing these injuries for cruciate-retaining (CR) TKA with the use of this technique. The objective of this cadaver study was to compare the extent of soft-tissue damage sustained through a robotic-assisted, haptically guided TKA (RATKA) versus a manual TKA (MTKA) approach. Methods. A total of 12 fresh-frozen pelvis-to-toe cadaver specimens were included. Four surgeons each prepared three RATKA and three MTKA specimens for cruciate-retaining TKAs. A RATKA was performed on one knee and a MTKA on the other. Postoperatively, two additional surgeons assessed and graded damage to 14 key anatomical structures in a blinded manner. Kruskal–Wallis hypothesis tests were performed to assess statistical differences in soft-tissue damage between RATKA and MTKA cases. Results. Significantly less damage occurred to the PCLs in the RATKA versus the MTKA specimens (p < 0.001). RATKA specimens had non-significantly less damage to the deep medial collateral ligaments (p = 0.149), iliotibial bands (p = 0.580), poplitei (p = 0.248), and patellar ligaments (p = 0.317). The remaining anatomical structures had minimal soft-tissue damage in all MTKA and RATKA specimens. Conclusion. The results of this study indicate that less soft-tissue damage may occur when utilizing RATKA compared with MTKA. These findings are likely due to the enhanced preoperative planning with the robotic software, the real-time intraoperative feedback, and the haptically bounded saw blade, all of which may help protect the surrounding soft tissues and ligaments. Cite this article: Bone Joint Res 2019;8:495–501

Aims. The purpose of this study was to determine the impact of the removal of total knee arthroplasty (TKA) from the Medicare Inpatient Only (IPO) list on our Bundled Payments for Care Improvement (BPCI) Initiative in 2018. Methods. We examined our institutional database to identify all Medicare patients who underwent primary TKA from 2017 to 2018. Hospital inpatient or outpatient status was cross-referenced with Centers for Medicare & Medicaid Services (CMS) claims data. Demographics, comorbidities, and outcomes were compared between patients classified as ‘outpatient’ and ‘inpatient’ TKA. Episode-of-care BPCI costs were then compared from 2017 to 2018. Results. Of the 2,135 primary TKA patients in 2018, 908 (43%) were classified as an outpatient and were excluded from BPCI. Inpatient classified patients had longer mean length of stay (1.9 (SD 1.4) vs 1.4 (SD 1.7) days, p < 0.001) and higher rates of discharge to rehabilitation (17% vs 3%, p < 0.001). Post-acute care costs increased when comparing the BPCI patients from 2017 to 2018, ($5,037 (SD $7,792) vs $5793 (SD $8,311), p = 0.010). The removal of TKA from the IPO list turned a net savings of $53,805 in 2017 into a loss of $219,747 in 2018 for our BPCI programme. Conclusions. Following the removal of TKA from the IPO list, nearly half of the patients at our institution were inappropriately classified as an outpatient. Our target price was increased and our institution realized a substantial loss in 2018 BPCI despite strong quality metrics. CMS should address its negative implications on bundled payment programmes. Cite this article: Bone Joint J 2020;102-B(6 Supple A):19–23

Aims. The aim of this study was to assess the effect of posterior cruciate ligament (PCL) resection on flexion-extension gaps, mediolateral soft-tissue laxity, fixed flexion deformity (FFD), and limb alignment during posterior-stabilized (PS) total knee arthroplasty (TKA). Patients and Methods. This prospective study included 110 patients with symptomatic osteoarthritis of the knee undergoing primary robot-assisted PS TKA. All operations were performed by a single surgeon using a standard medial parapatellar approach. Optical motion capture technology with fixed femoral and tibial registration pins was used to assess gaps before and after PCL resection in extension and 90° knee flexion. Measurements were made after excision of the anterior cruciate ligament and prior to bone resection. There were 54 men (49.1%) and 56 women (50.9%) with a mean age of 68 years (. sd. 6.2) at the time of surgery. The mean preoperative hip-knee-ankle deformity was 4.1° varus (. sd. 3.4). Results. PCL resection increased the mean flexion gap significantly more than the extension gap in the medial (2.4 mm (. sd. 1.5) vs 1.3 mm (. sd. 1.0); p < 0.001) and lateral (3.3 mm (. sd. 1.6) vs 1.2 mm (. sd. 0.9); p < 0.01) compartments. The mean gap differences after PCL resection created significant mediolateral laxity in flexion (gap difference: 1.1 mm (. sd. 2.5); p < 0.001) but not in extension (gap difference: 0.1 mm (. sd. 2.1); p = 0.51). PCL resection significantly improved the mean FFD (6.3° (. sd. 4.4) preoperatively vs 3.1° (. sd. 1.5) postoperatively; p < 0.001). There was a strong positive correlation between the preoperative FFD and change in FFD following PCL resection (Pearson’s correlation coefficient = 0.81; p < 0.001). PCL resection did not significantly affect limb alignment (mean change in alignment: 0.2° valgus (. sd. 1.2); p = 0.60). Conclusion. PCL resection creates flexion-extension mismatch by increasing the flexion gap more than the extension gap. The increase in the lateral flexion gap is greater than the increase in the medial flexion gap, which creates mediolateral laxity in flexion. Improvements in FFD following PCL resection are dependent on the degree of deformity before PCL resection. Cite this article: Bone Joint J 2019;101-B:1230–1237

Aims. With an ageing population of patients who are infected with hepatitis C virus (HCV), the demand for total knee arthroplasty (TKA) in this high-risk group continues to grow. It has previously been shown that HCV infection predisposes to poor outcomes following TKA. However, there is little information about the outcome of TKA in patients with HCV who have been treated successfully. The purpose of this study was to compare the outcomes of TKA in untreated HCV patients and those with HCV who have been successfully treated and have a serologically confirmed remission. Patients and Methods. A retrospective review of all patients diagnosed with HCV who underwent primary TKA between November 2011 and April 2018 was conducted. HCV patients were divided into two groups: 1) those whose HCV was cured (HCV-C); and 2) those in whom it was untreated (HCV-UT). All variables including demographics, HCV infection characteristics, surgical details, and postoperative medical and surgical outcomes were evaluated. There were 64 patients (70 TKAs) in the HCV-C group and 63 patients (71 TKAs) in the HCV-UT cohort. The mean age at the time of surgery was 63.0 years (. sd. 7.5; 44 to 79) in the HCV-C group and 61.7 years (. sd. 6.9; 47 to 88) in the HCV-UT group. Results. HCV-UT patients had a significantly longer mean hospital stay (3.4 days vs 2.9 days; p = 0.04), were more likely to be transferred to the intensive care unit (14.1% vs 4.3%; p = 0.04), and were significantly more often discharged to a post-acute care facility (39.4% vs 14.3%; p < 0.01). HCV-UT patients had significantly more postoperative infections (15.5% vs 4.3%; p = 0.03), surgical complications (21.1% vs 7.1%; p = 0.02), and revision TKA (12.7% vs 1.4%; p < 0.01) than HCV-C patients. Conclusion. The preoperative treatment of HCV can reduce the risk of complications, including prosthetic joint infection and revision TKA. We recommend that HCV treatment regimens should be integrated into the preoperative optimization protocol for this high-risk group of patients. Cite this article: Bone Joint J 2019;101-B:667–674

Aims. We performed a meta-analysis investigating the association between preoperative psychological distress and postoperative pain and function after total knee arthroplasty (TKA). Materials and Methods. Pubmed/Medline, Embase, PsycINFO, and the Cochrane library were searched for studies on the influence of preoperative psychological distress on postoperative pain and physical function after TKA. Two blinded reviewers screened for eligibility and assessed the risk of bias and the quality of evidence. We used random effects models to pool data for the meta-analysis. Results. Six prospective cohort studies, with a total of 1525 patients, were included. The random effects models showed significantly poorer outcomes in patients who preoperatively had elevated scores on the pain catastrophizing scale, worse 36-Item Short-Form Health Survey (SF-36) mental health score, symptoms of anxiety and/or depression, and somatization dysfunction. After 12 months, the standard mean difference for pain was −0.74 (95% confidence interval (CI) −1.04 to −0.44) and −0.56 (95% CI −0.80 to −0.32) for function. Conclusion. Preoperative pain catastrophizing, mental distress, symptoms of anxiety and/or depression, and somatoform disorders appear to adversely affect pain and function after TKA. Some patients undergoing TKA may therefore need psychological support to improve the outcome and quality of life

Aims. The aim of this study was to analyze the true costs associated with preoperative CT scans performed for robotic-assisted total knee arthroplasty (RATKA) planning and to determine the value of a formal radiologist’s report of these studies. Methods. We reviewed 194 CT reports of 176 sequential patients who underwent primary RATKA by a single surgeon at a suburban teaching hospital. CT radiology reports were reviewed for the presence of incidental findings that might change the management of the patient. Payments for the scans, including the technical and professional components, for 330 patients at two hospitals were also recorded and compared. Results. There were 82 incidental findings in 61 CT studies, one of which led to a recommendation for additional testing. Across both institutions, the mean total payment for a preoperative scan was $446 ($8 to $3,870). The mean patient payment was $71 ($0 to $2,690). There was wide variation in payments between the institutions. In Institution A, the mean total payment was $258 ($168 to $264), with a mean patient payment of $57 ($0 to $100). The mean technical payment in this institution was $211 ($8 to $856), while the mean professional payment was $48 ($0 to $66). In Institution B, the mean total payment was $636 ($37 to $3,870), with a mean patient payment of $85 ($0 to $2,690). Conclusion. The total cost of a CT scan is low and a minimal part of the overall cost of the RATKA. No incidental findings identified on imaging led to a change in management, suggesting that the professional component could be eliminated to reduce costs. Further studies need to take into account the patient perspective and the wide variation in total costs and patient payments across institutions and insurances. Cite this article: Bone Joint J 2020;102-B(6 Supple A):79–84

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

Objectives. Little biomechanical information is available about kinematically aligned (KA) total knee arthroplasty (TKA). The purpose of this study was to simulate the kinematics and kinetics after KA TKA and mechanically aligned (MA) TKA with four different limb alignments. Materials and Methods. Bone models were constructed from one volunteer (normal) and three patients with three different knee deformities (slight, moderate and severe varus). A dynamic musculoskeletal modelling system was used to analyse the kinematics and the tibiofemoral contact force. The contact stress on the tibial insert, and the stress to the resection surface and medial tibial cortex were examined by using finite element analysis. Results. In all bone models, posterior translation on the lateral side and external rotation in the KA TKA models were greater than in the MA TKA models. The tibiofemoral force at the medial side was increased in the moderate and severe varus models with KA TKA. In the severe varus model with KA TKA, the contact stress on the tibial insert and the stress to the resection surface and to the medial tibial cortex were increased by 41.5%, 32.2% and 53.7%, respectively, compared with MA TKA, and the bone strain at the medial side was highest among all models. Conclusion. Near normal kinematics was observed in KA TKA. However, KA TKA increased the contact force, stress and bone strain at the medial side for moderate and severe varus knee models. The application of KA TKA for severe varus knees may be inadequate. Cite this article: S. Nakamura, Y. Tian, Y. Tanaka, S. Kuriyama, H. Ito, M. Furu, S. Matsuda. The effects of kinematically aligned total knee arthroplasty on stress at the medial tibia: A case study for varus knee. Bone Joint Res 2017;6:43–51. DOI: 10.1302/2046-3758.61.BJR-2016-0090.R1

Advances in polyethylene (PE) in total hip arthroplasty have led to interest and increased use of highly crosslinked PE (HXLPE) in total knee arthroplasty (TKA). Biomechanical data suggest improved wear characteristics for HXLPE inserts over conventional PE in TKA. Short-term results from registry data and few clinical trials are promising. Our aim is to present a review of the history of HXLPEs, the use of HXLPE inserts in TKA, concerns regarding potential mechanical complications, and a thorough review of the available biomechanical and clinical data. Cite this article: Bone Joint J 2017;99-B:996–1002