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 aim is to assess the cost-effectiveness of patellofemoral arthroplasty (PFA) in comparison with total knee arthroplasty (TKA) for the treatment of isolated patellofemoral osteoarthritis (OA) based on prospectively collected data on health outcomes and resource use from a blinded, randomized, clinical trial. Methods. A total of 100 patients with isolated patellofemoral osteoarthritis were randomized to receive either PFA or TKA by experienced knee surgeons trained in using both implants. Patients completed patient-reported outcomes including EuroQol five-dimension questionnaire (EQ-5D) and 6-Item Short-Form Health Survey questionnaire (SF-6D) before the procedure. The scores were completed again after six weeks, three, six, and nine months, and again after one- and two-year post-surgery and yearly henceforth. Time-weighted outcome measures were constructed. Cost data were obtained from clinical registrations and patient-reported questionnaires. Incremental gain in health outcomes (quality-adjusted life-years (QALYs)) and incremental costs were compared for the two groups of patients. Net monetary benefit was calculated assuming a threshold value of €10,000, €35,000, and €50,000 per QALY and used to test the statistical uncertainty and central assumptions about outcomes and costs. Results. The PFA group had an incremental 12 month EQ-5D gain of 0.056 (95% confidence interval (CI) 0.01 to 0.10) and an incremental 12 month cost of minus €328 (95% CI 836 to 180). PFA therefore dominates TKA by providing better and cheaper outcomes than TKA. The net monetary benefit of PFA was €887 (95% CI 324 to 1450) with the €10,000 threshold, and it was consistently positive when different measures of outcomes and different cost assumptions were used. Conclusion. This study provides robust evidence that PFA from a one-year hospital management perspective is cheaper and provides better outcomes than TKA when applied to patients with isolated patellofemoral osteoarthritis and performed by experienced knee surgeons. Cite this article: Bone Joint J 2020;102-B(4):449–457

Instability is the reason for revision of a primary total knee replacement (TKR) in 20% of patients. To date, the diagnosis of instability has been based on the patient’s symptoms and a subjective clinical assessment. We assessed whether a measured standardised forced leg extension could be used to quantify instability. A total of 25 patients (11 male/14 female, mean age 70 years; 49 to 85) who were to undergo a revision TKR for instability of a primary implant were assessed with a Nottingham rig pre-operatively and then at six and 26 weeks post-operatively. Output was quantified (in revolutions per minute (rpm)) by accelerating a stationary flywheel. A control group of 183 patients (71 male/112 female, mean age 69 years) who had undergone primary TKR were evaluated for comparison. . Pre-operatively, all 25 patients with instability exhibited a distinctive pattern of reduction in ‘mid-push’ speed. The mean reduction was 55 rpm (. sd. 33.2). Post-operatively, no patient exhibited this pattern and the reduction in ‘mid-push’ speed was 0 rpm. The change between pre- and post-operative assessment was significant (p < 0.001). No patients in the control group exhibited this pattern at any of the intervals assessed. The between-groups difference was also significant (p < 0.001). This suggests that a quantitative diagnostic test to assess the unstable primary TKR could be developed. Cite this article: Bone Joint J 2014;96-B:1339–43

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 primary aim of this study was to assess whether the postoperative Oxford Knee Score (OKS) demonstrated a ceiling effect at one and/or two years after total knee arthroplasty (TKA). The secondary aim was to identify preoperative independent predictors for patients that achieved a ceiling score after TKA. Methods. A retrospective cohort of 5,857 patients undergoing a primary TKA were identified from an established arthroplasty database. Patient demographics, body mass index (BMI), OKS, and EuroQoL five-dimension (EQ-5D) general health scores were collected preoperatively and at one and two years postoperatively. Logistic regression analysis was used to identify independent preoperative predictors of patients achieving postoperative ceiling scores. Receiver operating characteristic curve was used to identify a preoperative OKS that predicted a postoperative ceiling score. Results. The ceiling effect was 4.6% (n = 272) at one year which increased significantly (odds ratio (OR) 40.3, 95% confidence interval (CI) 30.4 to 53.3; p < 0.001) to 6.2% (n = 363) at two years, when defined as those with a maximal score of 48 points. However, when the ceiling effect was defined as an OKS of 44 points or more, this increased to 26.3% (n = 1,540) at one year and further to 29.8% (n = 1,748) at two years (OR 21.6, 95% CI 18.7 to 25.1; p < 0.001). A preoperative OKS of 23 or more and 22 or more were predictive of achieving a postoperative ceiling OKS at one and two years when defined as a maximal score or a score of 44 or more, respectively. Conclusion. The postoperative OKS demonstrated a small ceiling effect when defined by a maximal score, but when defined by a postoperative OKS of 44 or more the ceiling effect was moderate and failed to meet standards. The preoperative OKS was an independent predictor of achieving a ceiling score. Cite this article: Bone Joint J 2020;102-B(11):1519–1526

Aims. The purpose of this study was to use pharmacogenetics to determine the frequency of genetic variants in our total knee arthroplasty (TKA) patients that could affect postoperative pain medications. Pharmacogenetic testing evaluates patient DNA to determine if a drug is expected to have a normal clinical effect, heightened effect, or no effect at all on the patient. It also predicts whether patients are likely to experience side effects from medicine. We further sought to determine if changing the multimodal programme based on these results would improve pain control or reduce side effects. Methods. In this pilot study, buccal samples were collected from 31 primary TKA patients. Pharmacogenetics testing examined genetic variants in genes OPRM1, CYP1A2, CYP2B6, CYP2C19, CYP3A4, CYP2C9, and CYP2D6. These genes affect the pharmacodynamics and pharmacokinetics of non-steroidal anti-inflammatory drugs and opioids. We examined the frequency of genetic variants to any of the medications we prescribed including celecoxib, hydrocodone, and tramadol. Patients were randomized to one of two groups: the control group received the standard postoperative pain regimen, and the study group received a customized regimen based on the pharmacogenetic results. For the first ten postoperative days, patients recorded pain scores, medication, and side effects. Results. Genetic variants involving one or more medications in the multimodal pain protocol occurred in 13 of the 31 patients (42%). In total, eight patients (26%) had variants affecting more than one of the medications. For the 25 patients who recorded pain and medication logs, the mean pain levels and morphine equivalents (MEQs) consumed in the first ten days were higher in the control group than in the custom-guided group (p = 0.019 for pain and p = 0.655 for MEQ). Conclusion. Overall, 42% of patients had a variant involving one of the pain medications prescribed in our perioperative pain program for TKA. Ongoing research will help determine if using these data to modify a patient’s medication will improve outcomes. Cite this article: Bone Joint J 2020;102-B(6 Supple A):73–78

Aims. To evaluate the influence of discharge timing on 30-day complications following total knee arthroplasty (TKA). Patients and Methods. We identified patients aged 18 years or older who underwent TKA between 2005 and 2016 from the American College of Surgeons’ National Surgical Quality Improvement Program (NSQIP) database. We propensity score-matched length-of-stay (LOS) groups using all relevant covariables. We used multivariable regression to determine if the rate of complications and re-admissions differed depending on LOS. Results. Our matched cohort consisted of 76 246 TKA patients (mean age 67 years . (sd. 9)). Patients whose LOS was zero and four days had an increased risk of major complications by an odds ratio (OR) of 1.8 (95% confidence interval (CI) 1.0 to 3.2) and 1.5 (95% CI 1.2 to 1.7), respectively, compared with patients whose LOS was two days. Patients whose LOS was zero, three, and four days had an increased risk of minor complications (OR 1.8 (95% CI 1.3 to 2.7), 1.2 (95% CI 1.0 to 1.4), and 1.6 (95% CI 1.4 to 1.9), respectively), compared with patients whose LOS was two days. In addition, a LOS of three days increased the risk of re-admission by an OR of 1.2 (95% CI 1.0 to 1.3), and a LOS of four days increased the risk of re-admission by an OR of 1.5 (95% CI 1.3 to 1.6), compared with a LOS of two days. Conclusion. Patients discharged on days one to two postoperatively following TKA appear to have reduced major and minor complications compared with discharge on the day of surgery, or on days three to four. Prospective clinical data are required to confirm these findings. Cite this article: Bone Joint J 2019;101-B(7 Supple C):70–76

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

The strain on clinic and surgeon resources resulting from a rise in demand for total knee replacement (TKR) requires reconsideration of when and how often patients need to be seen for follow-up. Surgeons will otherwise require increased paramedical staff or need to limit the number of TKRs they undertake. We reviewed the outcome data of 16 414 primary TKRs undertaken at our centre to determine the time to re-operation for any reason and for specific failure mechanisms. Peak risk years for failure were determined by comparing the conditional probability of failure, the number of failures divided by the total number of TKRs cases, for each year. The median times to failure for the most common failure mechanisms were 4.9 years (interquartile range (IQR) 1.7 to 10.7) for femoral and tibial loosening, 1.9 years (IQR 0.8 to 3.9) for infection, 3.1 years (IQR 1.6 to 5.5) for tibial collapse and 5.6 years (IQR 3.4 to 9.3) for instability. The median time to failure for all revisions was 3.3 years (IQR 1.2 to 8.5), with an overall revision rate of 1.7% (n = 282). Results from our patient population suggest that patients be seen for follow-up at six months, one year, three years, eight years, 12 years, and every five years thereafter. Patients with higher pain in the early post-operative period or high body mass index (≥ 41 kg/m. 2. ) should be monitored more closely. Cite this article: Bone Joint J 2013;95-B:1484–9

Aims. The outcomes of total knee arthroplasty (TKA) depend on many factors. The impact of implant design on patient-reported outcomes is unknown. Our goal was to evaluate the patient-reported outcomes and satisfaction after primary TKA in patients with osteoarthritis undergoing primary TKA using five different brands of posterior-stabilized implant. Patients and Methods. Using our institutional registry, we identified 4135 patients who underwent TKA using one of the five most common brands of implant. These included Biomet Vanguard (Zimmer Biomet, Warsaw, Indiana) in 211 patients, DePuy/Johnson & Johnson Sigma (DePuy Synthes, Raynham, Massachusetts) in 222, Exactech Optetrak Logic (Exactech, Gainesville, Florida) in 1508, Smith & Nephew Genesis II (Smith & Nephew, London, United Kingdom) in 1415, and Zimmer NexGen (Zimmer Biomet) in 779 patients. Patients were evaluated preoperatively using the Knee Injury and Osteoarthritis Outcome Score (KOOS), Lower Extremity Activity Scale (LEAS), and 12-Item Short-Form Health Survey questionnaire (SF-12). Demographics including age, body mass index, Charlson Comorbidity Index, American Society of Anethesiologists status, sex, and smoking status were collected. Postoperatively, two-year KOOS, LEAS, SF-12, and satisfaction scores were compared between groups. Results. Outcomes were available for 4069 patients (98%) at two years postoperatively. In multiple regression analysis, which separately compared each implant group with the aggregate of all others, there were no clinically significant differences in the change of KOOS score from baseline to two-year follow-up between any of the groups. More than 80% of patients in each group were satisfied at this time in all domains. In a multivariate regression model, patients in the NexGen group were the most likely to be satisfied (odds ratio (OR) 1.63; p = 0.006) and Optetrak Logic patients were the least likely to be satisfied (OR 0.60; p < 0.001). Conclusion. TKA provides improvement in function and satisfaction regardless of the type of implant. We could not demonstrate superiority of one design above others across these groups of implants, and any price premium for one above the other systems may not be justified. Healthcare administrators may find these similarities in outcomes helpful when negotiating purchasing contracts. Cite this article: Bone Joint J 2019;101-B(7 Supple C):48–54

Aims. Responsiveness to clinically important change is a key feature of any outcome measure. Throughout Europe, health-related quality of life following total knee arthroplasty (TKA) is routinely measured with EuroQol five-dimension (EQ-5D) questionnaires. The Patient-Reported Outcomes Measurement Information System 10-Question Short-Form (PROMIS-10 Global Health) score is a new general heath outcome tool which is thought to offer greater responsiveness. Our aim was to compare these two tools. Patients and Methods. We accessed data from a prospective multicentre cohort study in the United Kingdom, which evaluated outcomes following TKA. The median age of the 721 patients was 69.0 years (interquartile range, 63.3 to 74.6). There was an even division of sex, and approximately half were educated to secondary school level. The preoperative EQ-5D, PROMIS-10, and Oxford Knee Scores (OKS) were available and at three, six, and 12 months postoperatively. Internal responsiveness was assessed by standardized response mean (SRM) and effect size (Cohen’s d). External responsiveness was assessed by correlating change scores of the EQ-5D and PROMIS-10, with the minimal clinically important difference (MCID) of the OKS. Receiver operating characteristic (ROC) curves were used to assess the ability of change scores to discriminate between improved and non-improved patients. Results. All measures showed significant changes between the preoperative score and the various postoperative times (p < 0.001). Most improvement occurred during the first three months, with small but significant changes between three and six months, and no further change between six and 12 months postoperatively. SRM scores for EQ-5D, PROMIS-10, and OKS were large (> 0.8). ROC curves showed that both EQ-5D and PROMIS-10 were able to discriminate between patients who achieved the OKS MCID and those who did not (area under the curve (AUC) of 0.7 to 0.82). Conclusion. The PROMIS-10 physical health tool showed greater responsiveness to change than the EQ-5D, most probably due to the additional questions on physical health parameters that are more susceptible to modification following TKA. The EQ-5D was, however, shown to be sensitive to clinically meaningful change following TKA, and provides the additional ability to calculate health economic utility scores. It is likely, therefore, that EQ-5D will continue to be the global health metric of choice in the United Kingdom. Cite this article: Bone Joint J 2019;101-B:832–837

We report the results of revision total knee replacement (TKR) in 26 patients with major metaphyseal osteolytic defects using 29 trabecular metal cones in conjunction with a rotating hinged total knee prosthesis. The osteolytic defects were types II and III (A or B) according to the Anderson Orthopaedic Research Institute (AORI) classification. The mean age of the patients was 72 years (62 to 84) and there were 15 men and 11 women. In this series patients had undergone a mean of 2.34 previous total knee arthroplasties. The main objective was to restore anatomy along with stability and function of the knee joint to allow immediate full weight-bearing and active knee movement. Outcomes were measured using Knee Society scores, Oxford knee scores, range of movement of the knee and serial radiographs. Patients were followed for a mean of 36 months (24 to 49). The mean Oxford knee clinical scores improved from 12.83 (10 to 15) to 35.20 (32 to 38) (p < 0.001) and mean American Knee Society scores improved from 33.24 (13 to 36) to 81.12 (78 to 86) (p < 0.001). No radiolucent lines suggestive of loosening were seen around the trabecular metal cones, and by one year all the radiographs showed good osteo-integration. There was no evidence of any collapse or implant migration. Our early results confirm the findings of others that trabecular metal cones offer a useful way of managing severe bone loss in revision TKR. Cite this article: Bone Joint J 2013;95-B:1069–74

We report ten-year clinical and radiological follow-up data for the Sigma Press Fit Condylar total knee replacement system (Sigma PFC TKR). Between October 1998 and October 1999 a total of 235 consecutive PFC Sigma TKRs were carried out in 203 patients. Patients were seen at a specialist nurse-led clinic seven to ten days before admission and at six and 18 months, three, five and eight to ten years after surgery. Data were recorded prospectively at each clinic visit. Radiographs were obtained at the five- and eight- to ten-year follow-up appointments. Of the 203 patients, 147 (171 knees) were alive at ten years and 12 were lost to follow-up. A total of eight knees (3.4%) were revised, five for infection and three to change the polyethylene insert. The survival at ten years with an endpoint of revision for any reason was 95.9%, and with an endpoint of revision for aseptic failure was 98.7%. The mean American Knee Society Score (AKSS) was 79 (10 to 99) at eight to ten years, compared with 31 (2 to 62) pre-operatively. Of 109 knee with radiographs reviewed, 47 knees had radiolucent lines but none showed evidence of loosening. Cite this article: Bone Joint J 2013;95-B:177–80

Stems improve the mechanical stability of tibial components in total knee replacement (TKR), but come at a cost of stress shielding along their length. Their advantages include resistance to shear, reduced tibial lift-off and increased stability by reducing micromotion. Longer stems may have disadvantages including stress shielding along the length of the stem with associated reduction in bone density and a theoretical risk of subsidence and loosening, peri-prosthetic fracture and end-of-stem pain. These features make long stems unattractive in the primary TKR setting, but often desirable in revision surgery with bone loss and instability. In the revision scenario, stems are beneficial in order to convey structural stability to the construct and protect the reconstruction of bony defects. Cemented and uncemented long stemmed implants have different roles depending on the nature of the bone loss involved. This review discusses the biomechanics of the design of tibial components and stems to inform the selection of the component and the technique of implantation

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

Despite many claims of good wear properties following total knee replacement (TKR) with an oxidised zirconium (OxZr) femoral component, there are conflicting clinical results. We hypothesised that there would be no difference in either the mid-term clinical and radiological outcomes or the characteristics of the polyethylene wear particles (weight, size and shape) in patients using an OxZr or cobalt-chrome (CoCr) femoral component. In all 331 patients underwent bilateral TKR, receiving an OxZr femoral component in one knee and a CoCr femoral component in the other. The mean follow-up was 7.5 years (6 to 8). Following aspiration, polyethylene wear particles were analysed using thermogravimetric methods and scanning electron microscopy. At the most recent follow-up, the mean Knee Society score, Western Ontario and McMaster Universities Osteoarthritis Index score, range of movement and satisfaction score were not significantly different in the two groups. The mean weight, size, aspect ratio and roundness of the aspirated wear particles were similar for each femoral component. Survivorship of the femoral, tibial and patellar components was 100% in both groups. In the absence of evidence of an advantage in the medium term we cannot justify the additional expense of an OxZr femoral component.

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