Aims. Blood transfusion and postoperative anaemia are complications of total knee arthroplasty (TKA) that are associated with substantial healthcare costs, morbidity, and mortality. There are few data from large datasets on the risk factors for these complications. Methods. We retrospectively reviewed the records of TKA patients from a single tertiary care institution from February 2016 to December 2020. There were a total of 14,901 patients in this cohort with a mean age of 67.9 years (SD 9.2), and 5,575 patients (37.4%) were male. Outcomes included perioperative blood transfusion and postoperative anaemia, defined a priori as haemoglobin level < 10 g/dl measured on the first day postoperatively. In order to establish a preoperative haemoglobin cutoff, we investigated a preoperative haemoglobin level that would limit transfusion likelihood to ≤ 1% (13 g/dl) and postoperative anaemia likelihood to 4.1%. Risk factors were assessed through multivariable Poisson regression modelling with robust error variance. Results. In multivariable analyses, each gram of tranexamic acid reduced transfusion likelihood by 39% (adjusted risk ratio (ARR) 0.61 (95% confidence interval (CI) 0.47 to 0.78)). Risk factors associated with an increased risk of transfusion included operating time (ARR 2.07 (95% CI 1.54 to 2.77)) and drain use (ARR 1.73 (95% CI 1.34 to 2.24)). Conclusion. In this study, we found that increased tranexamic acid dosing, decreased operating time, and decreased drain use may reduce transfusions following TKA. We also established a single preoperative haemoglobin cutoff of 13 g/dl that could help minimize transfusions and reduce postoperative complete blood counts. Cite this article: Bone Joint J 2023;105-B(10):1086–1093

Aims. The primary objective of this registry-based study was to compare patient-reported outcomes of cementless and cemented medial unicompartmental knee arthroplasty (UKA) during the first postoperative year. The secondary objective was to assess one- and three-year implant survival of both fixation techniques. Methods. We analyzed 10,862 cementless and 7,917 cemented UKA cases enrolled in the Dutch Arthroplasty Registry, operated between 2017 and 2021. Pre- to postoperative change in outcomes at six and 12 months’ follow-up were compared using mixed model analyses. Kaplan-Meier and Cox regression models were applied to quantify differences in implant survival. Adjustments were made for patient-specific variables and annual hospital volume. Results. Change from baseline in the Oxford Knee Score (OKS) and activity-related pain was comparable between groups. Adjustment for covariates demonstrated a minimally greater decrease in rest-related pain in the cemented group (β = -0.09 (95% confidence interval (CI) -0.16 to -0.01)). Cementless fixation was associated with a higher probability of achieving an excellent OKS outcome (> 41 points) (adjusted odds ratio 1.2 (95% CI 1.1 to 1.3)). The likelihood of one-year implant survival was greater for cemented implants (adjusted hazard ratio (HR) 1.35 (95% CI 1.01 to 1.71)), with higher revision rates for periprosthetic fractures of cementless implants. During two to three years’ follow-up, the likelihood of implant survival was non-significantly greater for cementless UKA (adjusted HR 0.64 (95% CI 0.40 to 1.04)), primarily due to increased revision rates for tibial loosening of cemented implants. Conclusion. Cementless and cemented medial UKA led to comparable improvement in physical function and pain reduction during the initial postoperative year, albeit with a greater likelihood of achieving excellent OKS outcomes after cementless UKA. Anticipated differences in early physical function and pain should not be a decisive factor in the choice of fixation technique. However, surgeons should consider the differences in short- and long-term implant survival when deciding which implant to use. Cite this article: Bone Jt Open 2024;5(5):401–410

Aims. The primary aim of this study was to compare the migration of the femoral and tibial components of the cementless rotating platform Attune and Low Contact Stress (LCS) total knee arthroplasty (TKA) designs, two years postoperatively, using radiostereometric analysis (RSA) in order to assess the risk of the development of aseptic loosening. A secondary aim was to compare clinical and patient-reported outcome measures (PROMs) between the designs. Methods. A total of 61 TKAs were analyzed in this randomized clinical RSA trial. RSA examinations were performed one day and three, six, 12, and 24 months postoperatively. The maximal total point motion (MPTM), translations, and rotations of the components were analyzed. PROMs and clinical data were collected preoperatively and at six weeks and three, six, 12, and 24 months postoperatively. Linear mixed effect modelling was used for statistical analyses. Results. The mean MTPM two years postoperatively (95% confidence interval (CI)) of the Attune femoral component (0.92 mm (0.75 to 1.11)) differed significantly from that of the LCS TKA (1.72 mm (1.47 to 2.00), p < 0.001). The Attune femoral component subsided, tilted (anteroposteriorly), and rotated (internal-external) significantly less. The mean tibial MTPM two years postoperatively did not differ significantly, being 1.11 mm (0.94 to 1.30) and 1.17 mm (0.99 to 1.36, p = 0.447) for the Attune and LCS components, respectively. The rate of migration in the second postoperative year was negligible for the femoral and tibial components of both designs. The mean pain-at-rest (numerical rating scale (NRS)-rest) in the Attune group was significantly less compared with that in the LCS group during the entire follow-up period. At three months postoperatively, the Knee injury and Osteoarthritis Outcome Physical Function Shortform score, the Oxford Knee Score, and the NRS-activity scores were significantly better in the Attune group. Conclusion. The mean MTPM of the femoral components of the cementless rotating platform Attune was significantly less compared with that of the LCS design. This was reflected mainly in significantly less subsidence, posterior tilting, and internal rotation. The mean tibial MTPMs were not significantly different. During the second postoperative year, the components of both designs stabilized and low risks for the development of aseptic loosening are expected. Cite this article: Bone Joint J 2023;105-B(2):148–157

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. Methods. This retrospective study included 255 patients who underwent 305 OUKAs with cementless tibial components. There were 52 males and 203 females. Their mean age was 73.1 years (47 to 91), and the mean follow-up was 1.9 years (1.0 to 2.0). In 217 knees in 187 patients in the conventional group, tibial cuts were made orthogonally to the tibial axis. The varus group included 88 knees in 68 patients, and tibial cuts were made slightly varus using a new osteotomy guide. Anterior and posterior KCDs and the origins of fracture lines were assessed using 3D CT scans one week postoperatively. The KCDs and rate of fracture were compared between the two groups. Results. Medial tibial fractures occurred after surgery in 15 patients (15 OUKAs) in the conventional group, but only one patient (one OUKA) had a tibial fracture after surgery in the varus group. This difference was significant (6.9% vs 1.1%; p = 0.029). The mean posterior KCD was significantly shorter in the conventional group (5.0 mm (SD 1.7)) than in the varus group (6.1 mm (SD 2.1); p = 0.002). Conclusion. In OUKA, the distance between the keel and posterior tibial cortex was longer in our patients with slight varus alignment of the tibial component, which seems to decrease the risk of postoperative tibial fracture. Cite this article: Bone Joint J 2022;104-B(10):1118–1125

Aims. MRI has been suggested as an objective method of assessing anterior crucate ligament (ACL) graft “ligamentization” after reconstruction. It has been proposed that the MRI appearances could be used as an indicator of graft maturity and used as part of a return-to-sport assessment. The aim of this study was to evaluate the correlation between MRI graft signal and postoperative functional scores, anterior knee laxity, and patient age at operation. Methods. A consecutive cohort of 149 patients who had undergone semitendinosus autograft ACL reconstruction, using femoral and tibial adjustable loop fixations, were evaluated retrospectively postoperatively at two years. All underwent MRI analysis of the ACL graft, performed using signal-to-noise quotient (SNQ) and the Howell score. Functional outcome scores (Lysholm, Tegner, International Knee Documentation Committee (IKDC) subjective, and IKDC objective) were obtained and all patients underwent instrumented side-to-side anterior laxity differential laxity testing. Results. Two-year postoperative mean outcome scores were: Tegner 6.5 (2 to 10); Lysholm 89.8 (SD 10.4; 52 to 100); and IKDC subjective 86.8 (SD 11.8; 51 to 100). The objective IKDC score was 86% A (128 patients), 13% B (19 patients), and 1% C (two patients). Mean side-to-side anterior laxity difference (134 N force) was 0.6 mm (SD 1.8; -4.1 to 5.6). Mean graft SNQ was 2.0 (SD 3.5; -14 to 17). Graft Howell scores were I (61%, 91 patients), II (25%, 37 patients), III (13%, 19 patients), and IV (1%, two patients). There was no correlation between either Howell score or SNQ with instrumented anterior or Lysholm, Tegner, and IKDC scores, nor was any correlation found between patient age and ACL graft SNQ or Howell score. Conclusion. The two-year postoperative MRI appearances of four-strand, semitendinosus ACL autografts (as measured by SNQ and Howell score) do not appear to have a relationship with postoperative functional scores, instrumented anterior laxity, or patient age at surgery. Other tools for analysis of graft maturity should be developed. Cite this article: Bone Jt Open 2021;2(8):569–575

Aims. It remains difficult to diagnose early postoperative periprosthetic joint infection (PJI) following total knee arthroplasty (TKA). We aimed to validate the optimal cutoff values of ESR, CRP, and synovial fluid analysis for detecting early postoperative PJI in a large series of primary TKAs. Methods. We retrospectively identified 27,066 primary TKAs performed between 2000 and 2019. Within 12 weeks, 169 patients (170 TKAs) had an aspiration. The patients were divided into two groups: those evaluated ≤ six weeks, or between six and 12 weeks postoperatively. The 2011 Musculoskeletal Infection Society (MSIS) criteria for PJI diagnosis in 22 TKAs. The mean follow-up was five years (two months to 17 years). The results were compared using medians and Mann-Whitney U tests and thresholds were analyzed using receiver operator characteristic curves. Results. Within six weeks, the median CRP (101 mg/l vs 35 mg/l; p = 0.011), synovial WBCs (58,295 cells/μl vs 2,121 cells/μl; p ≤ 0.001), percentage of synovial neutrophils (91% vs 71% (p < 0.001), and absolute synovial neutrophil count (ANC) (50,748 cells/μl vs 1,386 cells/μl (p < 0.001) were significantly higher in infected TKAs. Between six and 12 weeks, the median CRP (85 mg/l vs 5 mg/l (p < 0.001)), ESR (33 mm/hr vs 14 mm/hr (p = 0.015)), synovial WBCs (62,247 cells/μl vs 620 cells/μl (p < 0.001)), percentage of synovial neutrophils (93% vs 54% (p < 0.001)), and ANC (55,911 cells/μl vs 326 cells/μl (p < 0.001)) were also significantly higher in infected TKAs. Optimal thresholds at ≤ six weeks were: CRP ≥ 82 mg/l (sensitivity 70%, specificity 77%), synovial WBCs ≥ 8,676 cells/μl (83%, 90%), percentage of synovial neutrophils ≥ 88% (67%, 78%), and ANC ≥ 8,346 cells/μl (83%, 91%). Between six and 12 weeks, thresholds were: CRP ≥ 34 mg/l (90%, 93%), synovial WBCs ≥ 1,983 cells/μl (80%, 85%), percentage of synovial neutrophils ≥ 76% (80%, 81%), and ANC ≥ 1,684 cells/μl (80%, 87%). Conclusion. Early PJI after TKA should be suspected within six weeks if the CRP is ≥ 82 mg/l, synovial WBCs are ≥ 8,676 cells/μl, the percentage of synovial neutrophils is ≥ 88%, and/or the ANC is ≥ 8,346 cells/μl. Between six and 12 weeks, thresholds include a CRP of ≥ 34 mg/l, synovial WBC of ≥ 1,983 cells/μl, a percentage of synovial neutrophils of ≥ 76%, and/or an ANC of ≥ 1,684 cells/μl. Cite this article: Bone Joint J 2021;103-B(6 Supple A):177–184

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. In total knee arthroplasty (TKA), blood loss continues internally after surgery is complete. Typically, the total loss over 48 postoperative hours can be around 1,300 ml, with most occurring within the first 24 hours. We hypothesize that the full potential of tranexamic acid (TXA) to decrease TKA blood loss has not yet been harnessed because it is rarely used beyond the intraoperative period, and is usually withheld from ‘high-risk’ patients with a history of thromboembolic, cardiovascular, or cerebrovascular disease, a patient group who would benefit greatly from a reduced blood loss. Methods. TRAC-24 was a prospective, phase IV, single-centre, open label, parallel group, randomized controlled trial on patients undergoing TKA, including those labelled as high-risk. The primary outcome was indirect calculated blood loss (IBL) at 48 hours. Group 1 received 1 g intravenous (IV) TXA at the time of surgery and an additional 24-hour postoperative oral regime of four 1 g doses, while Group 2 only received the intraoperative dose and Group 3 did not receive any TXA. Results. Between July 2016 and July 2018, 552 patients were randomized to either Group 1 (n = 241), Group 2 (n = 243), or Group 3 (n = 68), and 551 were included in the final analysis. The blood loss did differ significantly between the two intervention groups (733.5 ml (SD 384.0) for Group 1 and 859.2 ml (SD 363.6 ml) for Group 2; mean difference -125.8 ml (95% confidence interval -194.0 to -57.5; p < 0.001). No differences in mortality or thromboembolic events were observed in any group. Conclusion. These data support the hypothesis that in TKA, a TXA regime consisting of IV 1 g perioperatively and four oral 1 g doses over 24 hours postoperatively significantly reduces blood loss beyond that achieved with a single IV 1 g perioperative dose alone. TXA appears safe in patients with history of thromboembolic, cardiovascular, and cerebrovascular disease. Cite this article: Bone Joint J 2021;103-B(10):1595–1603

Aims. Robotic-assisted total knee arthroplasty (RA-TKA) has been introduced to provide accurate bone cuts and help achieve the target knee alignment, along with symmetric gap balancing. The purpose of this study was to determine if any early clinical benefits could be realized following TKA using robotic-assisted technology. Methods. In all, 140 consecutive patients undergoing RA-TKA and 127 consecutive patients undergoing conventional TKA with minimum six-week follow-up were reviewed. Differences in visual analogue scores (VAS) for pain at rest and with activity, postoperative opiate usage, and length of stay (LOS) between the RA-TKA and conventional TKA groups were compared. Results. Patients undergoing RA-TKA had lower average VAS pain scores at rest (p = 0.001) and with activity (p = 0.03) at two weeks following the index procedure. At the six-week interval, the RA-TKA group had lower VAS pain scores with rest (p = 0.03) and with activity (p = 0.02), and required 3.2 mg less morphine equivalents per day relative to the conventional group (p < 0.001). At six weeks, a significantly greater number of patients in the RA-TKA group were free of opioid use compared to the conventional TKA group; 70.7% vs 57.0% (p = 0.02). Patients in the RA-TKA group had a shorter LOS; 1.9 days versus 2.3 days (p < 0.001), and also had a greater percentage of patient discharged on postoperative day one; 41.3% vs 20.5% (p < 0.001). Conclusion. Patients undergoing RA-TKA had lower pain levels at both rest and with activity, required less opioid medication, and had a shorter LOS

Aims. The use of vitamin E-infused highly crosslinked polyethylene (HXLPE) in total knee prostheses is controversial. In this paper we have compared the clinical and radiological results between conventional polyethylene and vitamin E-infused HXLPE inserts in total knee arthroplasty (TKA). Patients and Methods. The study included 200 knees (175 patients) that underwent TKA using the same total knee prostheses. In all, 100 knees (77 patients) had a vitamin E-infused HXLPE insert (study group) and 100 knees (98 patients) had a conventional polyethylene insert (control group). There were no significant differences in age, sex, diagnosis, preoperative knee range of movement (ROM), and preoperative Knee Society Score (KSS) between the two groups. Clinical and radiological results were evaluated at two years postoperatively. Results. Differences in postoperative ROM and KSS were not statistically significant between the study and control groups. No knee exhibited osteolysis, aseptic loosening, or polyethylene failure. Additionally, there was no significant difference in the incidence of a radiolucent line between the two groups. One patient from the study group required irrigation and debridement, due to deep infection, at six months postoperatively. Conclusion. Clinical results were comparable between vitamin E-infused HXLPE inserts and conventional polyethylene inserts at two years after TKA, without any significant clinical failure. Cite this article: Bone Joint J 2019;101-B:559–564

Aims. Adductor canal block (ACB) has emerged as an alternative to femoral nerve block (FNB) for analgesia after total knee arthroplasty (TKA). The optimal duration of maintenance of the ACB is still questionable. The purpose of this study was to compare the analgesic benefits and physiotherapy (PT) outcomes of single-shot ACB to two different regimens of infusion of the continuous ACB, 24-hour and 48-hour infusion. Patients and Methods. This was a prospective, randomized, unblinded study. A total of 159 American Society of Anesthesiologists (ASA) physical status I to III patients scheduled for primary TKA were randomized to one of three study groups. Three patients did not complete the study, leaving 156 patients for final analysis. Group A (n = 53) was the single-shot group (16 female patients and 37 male patients with a mean age of 63.9 years (. sd. 9.6)), group B (n = 51) was the 24-hour infusion group (22 female patients and 29 male patients with a mean age of 66.5 years (. sd. 8.5)), and group C (n = 52) was the 48-hour infusion group (18 female patients and 34 male patients with a mean age of 62.2 years (. sd. 8.7)). Pain scores, opioid requirements, PT test results, and patient-reported outcome instruments were compared between the three groups. Results. The proportion of patients reporting severe pain, defined as a pain score of between 7 and 10, on postoperative day number 2 (POD 2) were 21% for the single-shot group, 14% for the 24-hour block group, and 12% for the 48-hour block group (p = 0.05). Cumulative opioid requirements after 48 hours were similar between the groups. Functional outcomes were similar in all three groups in POD 1 and POD 2. Conclusion. There was no clear benefit of the 24-hour or 48-hour infusions over the single-shot ACB for the primary endpoint of the study. Otherwise, there were marginal benefits for keeping the indwelling catheter for 48 hours in terms of reducing the number of patients with moderate pain and improving the quality of pain management. However, all three groups had similar opioid usage, length of hospital stay, and functional outcomes. Further studies with larger sample sizes are needed to confirm these findings. Cite this article: Bone Joint J 2019;101-B:340–347

The administration of heparin during operation has been reported to enhance the efficacy of thromboprophylaxis in patients undergoing total hip replacement. We have performed a small pilot study in which intraoperative doses of heparin were given in addition to the usual postoperative thromboprophylaxis with enoxaparin in 32 patients undergoing total knee replacement. The primary endpoint was deep-vein thrombosis (DVT) as demonstrated by bilateral venography on 6 ± 2 days after operation. Sixteen patients developed DVT; in two the thrombosis was proximal as well as distal and in one the occurrence was bilateral. There was one major haemorrhage. These results are similar to those obtained with the use of postoperative thromboprophylaxis with enoxaparin alone. They do not provide support for the initiation of a larger randomised trial of this approach to management

We carried out an audit on the result of achieving early walking in total knee replacement after instituting a new rehabilitation protocol, and assessed its influence on the development of deep-vein thrombosis as determined by Doppler ultrasound scanning on the fifth post-operative day. Early mobilisation was defined as beginning to walk less than 24 hours after knee replacement.

Between April 1997 and July 2002, 98 patients underwent a total of 125 total knee replacements. They began walking on the second post-operative day unless there was a medical contraindication. They formed a retrospective control group. A protocol which allowed patients to start walking at less than 24 hours after surgery was instituted in August 2002. Between August 2002 and November 2004, 97 patients underwent a total of 122 total knee replacements. They formed the early mobilisation group, in which data were prospectively gathered. The two groups were of similar age, gender and had similar medical comorbidities. The surgical technique and tourniquet times were similar and the same instrumentation was used in nearly all cases. All the patients received low-molecular-weight heparin thromboprophylaxis and wore compression stockings post-operatively.

In the early mobilisation group 90 patients (92.8%) began walking successfully within 24 hours of their operation. The incidence of deep-vein thrombosis fell from 27.6% in the control group to 1.0% in the early mobilisation group (chi-squared test, p < 0.001). There was a difference in the incidence of risk factors for deep-vein thrombosis between the two groups. However, multiple logistic regression analysis showed that the institution of an early mobilisation protocol resulted in a 30-fold reduction in the risk of post-operative deep-vein thrombosis when we adjusted for other risk factors.

Aims. To evaluate whether low-intensity pulsed ultrasound (LIPUS) accelerates bone healing at osteotomy sites and promotes functional recovery after open-wedge high tibial osteotomy (OWHTO). Methods. Overall, 90 patients who underwent OWHTO without bone grafting were enrolled in this nonrandomized retrospective study, and 45 patients treated with LIPUS were compared with 45 patients without LIPUS treatment in terms of bone healing and functional recovery postoperatively. Clinical evaluations, including the pain visual analogue scale (VAS) and Japanese Orthopaedic Association (JOA) score, were performed preoperatively as well as six weeks and three, six, and 12 months postoperatively. The progression rate of gap filling was evaluated using anteroposterior radiographs at six weeks and three, six, and 12 months postoperatively. Results. The pain VAS and JOA scores significantly improved after OWHTO in both groups. Although the LIPUS group had better pain scores at six weeks and three months postoperatively, there were no significant differences in JOA score between the groups. The lateral hinge united at six weeks postoperatively in 34 (75.6%) knees in the control group and in 33 (73.3%) knees in the LIPUS group. The progression rates of gap filling in the LIPUS group were 8.0%, 15.0%, 27.2%, and 46.0% at six weeks and three, six, and 12 months postoperatively, respectively, whereas in the control group at the same time points they were 7.7%, 15.2%, 26.3%, and 44.0%, respectively. There were no significant differences in the progression rate of gap filling between the groups. Conclusion. The present study demonstrated that LIPUS did not promote bone healing and functional recovery after OWHTO with a locking plate. The routine use of LIPUS after OWHTO was not recommended from the results of our study. Cite this article: Bone Jt Open 2022;3(11):885–893

Aims. The aim of this study was to evaluate whether achieving medial joint opening, as measured by the change in the joint line convergence angle (∆JLCA), is a better predictor of clinical outcomes after high tibial osteotomy (HTO) compared with the mechanical axis deviation, and to find individualized targets for the redistribution of load that reflect bony alignment, joint laxity, and surgical technique. Methods. This retrospective study analyzed 121 knees in 101 patients. Patient-reported outcome measures (PROMs) were collected preoperatively and one year postoperatively, and were analyzed according to the surgical technique (opening or closing wedge), postoperative mechanical axis deviation (deviations above and below 10% from the target), and achievement of medial joint opening (∆JLCA > 1°). Radiological parameters, including JLCA, mechanical axis deviation, and the difference in JLCA between preoperative standing and supine radiographs (JLCA. PD. ), an indicator of medial soft-tissue laxity, were measured. Cut-off points for parameters related to achieving medial joint opening were calculated from receiver operating characteristic (ROC) curves. Results. Patients in whom the medial joint opening was achieved had significantly better postoperative PROMs compared with those without medial opening (all p < 0.05). Patients who were outliers with deviation of > 10% from the target mechanical axis deviation had significantly similar PROMs compared with patients with an acceptable axis deviation (all p > 0.05). Medial joint opening was affected by postoperative mechanical axis deviation and JLCA. PD. The influence of JLCA. PD. on postoperative axis deviation was more pronounced in a closing wedge than in an opening wedge HTO. Conclusion. Medial joint opening rather than the mechanical axis deviation determined the clinical outcome in patients who underwent HTO. The JLCA. PD. identified the optimal postoperative axis deviation necessary to achieve medial joint opening. For patients with increased laxity, lowering the target axis deviation is recommended to achieve medial joint opening. The target axis deviation should also differ according to the technique of undergoing HTO. Cite this article: Bone Joint J 2024;106-B(3):240–248

Aims. The metabolic equivalent of task (MET) score examines patient performance in relation to energy expenditure before and after knee arthroplasty. This study assesses its use in a knee arthroplasty population in comparison with the widely used Oxford Knee Score (OKS) and EuroQol five-dimension index (EQ-5D), which are reported to be limited by ceiling effects. Methods. A total of 116 patients with OKS, EQ-5D, and MET scores before, and at least six months following, unilateral primary knee arthroplasty were identified from a database. Procedures were performed by a single surgeon between 2014 and 2019 consecutively. Scores were analyzed for normality, skewness, kurtosis, and the presence of ceiling/floor effects. Concurrent validity between the MET score, OKS, and EQ-5D was assessed using Spearman’s rank. Results. Postoperatively the OKS and EQ-5D demonstrated negative skews in distribution, with high kurtosis at six months and one year. The OKS demonstrated a ceiling effect at one year (15.7%) postoperatively. The EQ-5D demonstrated a ceiling effect at six months (30.2%) and one year (39.8%) postoperatively. The MET score did not demonstrate a skewed distribution or ceiling effect either at six months or one year postoperatively. Weak-moderate correlations were noted between the MET score and conventional scores at six months and one year postoperatively. Conclusion. In contrast to the OKS and EQ-5D, the MET score was normally distributed postoperatively with no ceiling effect. It is worth consideration as an arthroplasty outcome measure, particularly for patients with high expectations. Cite this article: Bone Jt Open 2023;4(3):129–137

Aims. The aim of this study was to compare the preinjury functional scores with the postinjury preoperative score and postoperative outcome scores following anterior cruciate ligament (ACL) reconstruction surgery (ACLR). Methods. We performed a prospective study on patients who underwent primary ACLR by a single surgeon at a single centre between October 2010 and January 2018. Preoperative preinjury scores were collected at time of first assessment after the index injury. Preoperative (pre- and post-injury), one-year, and two-year postoperative functional outcomes were assessed by using the Knee injury and Osteoarthritis Outcome Score (KOOS), Lysholm Knee Score, and Tegner Activity Scale. Results. We enrolled 308 males and 263 females of mean age 27 years (19 to 46). The mean preinjury and preoperative post-injury Lysholm Knee Scores were 94 (73 to 100) and 63 (25 to 85), respectively, while the respective mean scores at one and two years postoperatively were 84 (71 to 100) and 89 (71 to 100; p < 0.001). The mean Tegner preinjury and preoperative post-injury scores were 7 (3 to 9) and 3 (0 to 6), respectively, while the respective mean scores at one and two years postoperatively were 6 (1 to 8) and 6 (1 to 9) (p < 0.001). The mean KOOS scores at preinjury versus two years postoperatively were: symptoms (96 vs 84); pain (94 vs 87); activities of daily living (97 vs 91), sports and recreation function (84 vs 71), and quality of life (82 vs 69), respectively (p < 0.001). Conclusion. Functional scores improved following ACLR surgery at two years in comparison to preoperative post-injury scores. However, at two-year follow-up, the majority of patients failed to achieve their preinjury scores. The evaluation of ACLR outcomes needs to consider the preinjury scores rather than the immediate preoperative score that is usually collected. Cite this article: Bone Jt Open 2023;4(1):46–52

Aims. The aim of this study was to describe and compare joint-specific and generic health-related quality of life outcomes of the first versus second knee in patients undergoing staged bilateral total knee arthroplasty (BTKA) for osteoarthritis. Methods. This retrospective cohort study used Australian national arthroplasty registry data from January 2013 to January 2021 to identify participants who underwent elective staged BTKA with six to 24 months between procedures. The primary outcome was Oxford Knee Score (OKS) at six months postoperatively for the first TKA compared to the second TKA, adjusted for age and sex. Secondary outcomes compared six-month EuroQol five-dimension five-level (EQ-5D-5L) domain scores, EQ-5D index scores, and the EQ visual analogue scale (EQ-VAS) between knees at six months postoperatively. Results. The cohort included 635 participants (1,270 primary procedures). Preoperative scores were worse in the first knee compared to the second for all instruments; however, comparing the first knee at six months postoperatively with the second knee at six months postoperatively, the mean between-knee difference was minimal for OKS (-0.8 points; 95% confidence interval (CI) -1.4 to -0.2), EQ-VAS (3.3; 95% CI 1.9 to 4.7), and EQ-5D index (0.09 points; 95% CI 0.07 to 0.12). Outcomes for the EQ-5D-5L domains ‘mobility’, ‘usual activities’, and ‘pain/discomfort’ were better following the second TKA. Conclusion. At six months postoperatively, there were no clinically meaningful differences between the first and second TKA in either the joint-specific or overall generic health-related quality of life outcomes. However, individual domain scores assessing mobility, pain, and usual activities were notably higher after the second TKA, likely reflecting the cumulative improvement in quality of life after both knees have been replaced. Cite this article: Bone Jt Open 2024;5(3):202–209

Aims. While mechanical alignment (MA) is the traditional technique in total knee arthroplasty (TKA), its potential for altering constitutional alignment remains poorly understood. This study aimed to quantify unintentional changes to constitutional coronal alignment and joint line obliquity (JLO) resulting from MA. Methods. A retrospective cohort study was undertaken of 700 primary MA TKAs (643 patients) performed between 2014 and 2017. Lateral distal femoral and medial proximal tibial angles were measured pre- and postoperatively to calculate the arithmetic hip-knee-ankle angle (aHKA), JLO, and Coronal Plane Alignment of the Knee (CPAK) phenotypes. The primary outcome was the magnitude and direction of aHKA, JLO, and CPAK alterations. Results. The mean aHKA and JLO increased by 0.1° (SD 3.4°) and 5.8° (SD 3.5°), respectively, from pre- to postoperatively. The most common phenotypes shifted from 76.3% CPAK Types I, II, or III (apex distal JLO) preoperatively to 85.0% IV, V, or VI (apex horizontal JLO) postoperatively. The proportion of knees with apex proximal JLO increased from 0.7% preoperatively to 11.1% postoperatively. Among all MA TKAs, 60.0% (420 knees) were changed from their constitutional alignments into CPAK Type V, while 40.0% (280 knees) either remained in constitutional Type V (5.0%, 35 knees) or were unintentionally aligned into other CPAK types (35.0%; 245 knees). Conclusion. Fixed MA targets in TKA lead to substantial changes from constitutional alignment, primarily a significant increase in JLO. These findings enhance our understanding of alignment alterations resulting from both unintended changes to knee phenotypes and surgical resection imprecision. Cite this article: Bone Jt Open 2024;5(2):109–116

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. Methods. Patients who underwent TKA from September 2020 to September 2021 were prospectively included. Inclusion criteria were primary end-stage osteoarthritis (Kellgren-Lawrence stage IV) of the knee. Exclusion criteria were missed follow-up visit, post-traumatic pathologies of the foot, and neurological disorders. Radiological angles measured included the mTFA, hindfoot alignment view angle, and TT. The Foot Function Index (FFI) score was assessed. Gait analyses were conducted to measure mediolateral changes of the gait line and ankle laxity was tested using an ankle arthrometer. All parameters were acquired one week pre- and three months postoperatively. Results. A total of 69 patients (varus n = 45; valgus n = 24) underwent TKA and completed the postoperative follow-up visit. Of these, 16 patients (23.2%) reported the onset or progression of ankle symptoms. Varus patients with increased ankle symptoms after TKA had a significantly higher pre- and postoperative TT. Valgus patients with ankle symptoms after TKA showed a pathologically lateralized gait line which could not be corrected through TKA. Patients who reported increased ankle pain neither had a decreased ROM of the subtalar joint nor increased ankle laxity following TKA. The preoperative mTFA did not correlate with the postoperative FFI (r = 0.037; p = 0.759). Conclusion. Approximately one-quarter of the patients developed ankle pain after TKA. If patients complain about ankle symptoms after TKA, standing radiographs of the ankle and a gait analysis could help in detecting a malaligned TT or a pathological gait. Cite this article: Bone Joint J 2023;105-B(11):1159–1167

Aims. The aims of this study were to assess mapping models to predict the three-level version of EuroQoL five-dimension utility index (EQ-5D-3L) from the Oxford Knee Score (OKS) and validate these before and after total knee arthroplasty (TKA). Methods. A retrospective cohort of 5,857 patients was used to create the prediction models, and a second cohort of 721 patients from a different centre was used to validate the models, all of whom underwent TKA. Patient characteristics, BMI, OKS, and EQ-5D-3L were collected preoperatively and one year postoperatively. Generalized linear regression was used to formulate the prediction models. Results. There were significant correlations between the OKS and EQ-5D-3L preoperatively (r = 0.68; p < 0.001) and postoperatively (r = 0.77; p < 0.001) and for the change in the scores (r = 0.61; p < 0.001). Three different models (preoperative, postoperative, and change) were created. There were no significant differences between the actual and predicted mean EQ-5D-3L utilities at any timepoint or for change in the scores (p > 0.090) in the validation cohort. There was a significant correlation between the actual and predicted EQ-5D-3L utilities preoperatively (r = 0.63; p < 0.001) and postoperatively (r = 0.77; p < 0.001) and for the change in the scores (r = 0.56; p < 0.001). Bland-Altman plots demonstrated that a lower utility was overestimated, and higher utility was underestimated. The individual predicted EQ-5D-3L that was within ± 0.05 and ± 0.010 (minimal clinically important difference (MCID)) of the actual EQ-5D-3L varied between 13% to 35% and 26% to 64%, respectively, according to timepoint assessed and change in the scores, but was not significantly different between the modelling and validation cohorts (p ≥ 0.148). Conclusion. The OKS can be used to estimate EQ-5D-3L. Predicted individual patient utility error beyond the MCID varied from one-third to two-thirds depending on timepoint assessed, but the mean for a cohort did not differ and could be employed for this purpose. Cite this article: Bone Jt Open 2022;3(7):573–581

Aims. The aim of this study was to compare a bicruciate-retaining (BCR) total knee arthroplasty (TKA) with a posterior cruciate-retaining (CR) TKA design in terms of kinematics, measured using fluoroscopy and stability as micromotion using radiostereometric analysis (RSA). Methods. A total of 40 patients with end-stage osteoarthritis were included in this randomized controlled trial. All patients performed a step-up and lunge task in front of a monoplane fluoroscope one year postoperatively. Femorotibial contact point (CP) locations were determined at every flexion angle and compared between the groups. RSA images were taken at baseline, six weeks, three, six, 12, and 24 months postoperatively. Clinical and functional outcomes were compared postoperatively for two years. Results. The BCR-TKA demonstrated a kinematic pattern comparable to the natural knee’s screw-home mechanism in the step-up task. In the lunge task, the medial CP of the BCR-TKA was more anterior in the early flexion phase, while laterally the CP was more posterior during the entire movement cycle. The BCR-TKA group showed higher tibial migration. No differences were found for the clinical and functional outcomes. Conclusion. The BCR-TKA shows a different kinematic pattern in early flexion/late extension compared to the CR-TKA. The difference between both implants is mostly visible in the flexion phase in which the anterior cruciate ligament is effective; however, both designs fail to fully replicate the motion of a natural knee. The higher migration of the BCR-TKA was concerning and highlights the importance of longer follow-up. Cite this article: Bone Joint J 2023;105-B(1):35–46

Aims. The aim of this study was to describe the prevalence and patterns of neuropathic pain over one year in a cohort of patients with chronic post-surgical pain at three months following total knee arthroplasty (TKA). Methods. Between 2016 and 2019, 363 patients with troublesome pain, defined as a score of ≤ 14 on the Oxford Knee Score pain subscale, three months after TKA from eight UK NHS hospitals, were recruited into the Support and Treatment After Replacement (STAR) clinical trial. Self-reported neuropathic pain and postoperative pain was assessed at three, nine, and 15 months after surgery using the painDETECT and Douleur Neuropathique 4 (DN4) questionnaires collected by postal survey. Results. Symptoms of neuropathic pain were common among patients reporting chronic pain at three months post-TKA, with half reporting neuropathic pain on painDETECT (191/363; 53%) and 74% (267/359) on DN4. Of those with neuropathic pain at three months, half continued to have symptoms over the next 12 months (148/262; 56%), one-quarter had improved (67/262; 26%), and for one-tenth their neuropathic symptoms fluctuated over time (24/262; 9%). However, a subgroup of participants reported new, late onset neuropathic symptoms (23/262; 9%). Prevalence of neuropathic symptoms was similar between the screening tools when the lower cut-off painDETECT score (≥ 13) was applied. Overall, mean neuropathic pain scores improved between three and 15 months after TKA. Conclusion. Neuropathic pain is common in patients with chronic pain at three months after TKA. Although neuropathic symptoms improved over time, up to half continued to report painful neuropathic symptoms at 15 months after TKA. Postoperative care should include screening, assessment, and treatment of neuropathic pain in patients with early chronic postoperative pain after TKA. Cite this article: Bone Joint J 2024;106-B(6):582–588

Aims. The mid-term results of kinematic alignment (KA) for total knee arthroplasty (TKA) using image derived instrumentation (IDI) have not been reported in detail, and questions remain regarding ligamentous stability and revisions. This paper aims to address the following: 1) what is the distribution of alignment of KA TKAs using IDI; 2) is a TKA alignment category associated with increased risk of failure or poor patient outcomes; 3) does extending limb alignment lead to changes in soft-tissue laxity; and 4) what is the five-year survivorship and outcomes of KA TKA using IDI?. Methods. A prospective, multicentre, trial enrolled 100 patients undergoing KA TKA using IDI, with follow-up to five years. Alignment measures were conducted pre- and postoperatively to assess constitutional alignment and final implant position. Patient-reported outcome measures (PROMs) of pain and function were also included. The Australian Orthopaedic Association National Joint Arthroplasty Registry was used to assess survivorship. Results. The postoperative HKA distribution varied from 9° varus to 11° valgus. All PROMs showed statistical improvements at one year (p < 0.001), with further improvements at five years for Knee Osteoarthritis Outcome Score symptoms (p = 0.041) and Forgotten Joint Score (p = 0.011). Correlation analysis showed no difference (p = 0.610) between the hip-knee-ankle and joint line congruence angle at one and five years. Sub-group analysis showed no difference in PROMs for patients placed within 3° of neutral compared to those placed > 3°. There were no revisions for tibial loosening; however, there were reports of a higher incidence of poor patella tracking and patellofemoral stiffness. Conclusion. PROMs were not impacted by postoperative alignment category. Ligamentous stability was maintained at five years with joint line obliquity. There were no revisions for tibial loosening despite a significant portion of tibiae placed in varus; however, KA executed with IDI resulted in a higher than anticipated rate of patella complications. Cite this article: Bone Jt Open 2022;3(8):656–665

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. Methods. A total of 74 primary TKAs were included in this single-blind RCT. RSA examinations were performed, and PROMs and clinical outcomes were collected immediate postoperatively, and at three, six, 12, 24, and 60 months’ follow-up. Radiolucent lines (RLLs) were measured in standard anteroposterior radiographs at six weeks, and 12 and 60 months postoperatively. Results. At five-year follow-up, RSA data from 61 patients were available and the mean maximum total point motion (MTPM) of the femoral components were: ATTUNE: 0.96 mm (95% confidence interval (CI) 0.79 to 1.14) and PFC-Sigma 1.37 mm (95% CI 1.18 to 1.59) (p < 0.001). The PFC-Sigma femoral component migrated more in the first postoperative year, but stabilized thereafter. MPTM of the tibial components were comparable at five-year follow-up: ATTUNE 1.12 mm (95% CI 0.95 to 1.31) and PFC-Sigma 1.25 mm (95% CI 1.07 to 1.44) (p = 0.438). RLL at the medial tibial implant-cement interface remained more prevalent for the ATTUNE at five-year follow-up compared to the PFC-Sigma (20% vs 3%). RLL did not progress over time, and varied between patients at different timepoints for both TKA systems. Clinical outcomes and PROMs improved compared with preoperative scores, and were not different between groups. Conclusion. MTPM migration at five-year follow-up of the femoral and tibial component of the ATTUNE were similar and as low as that of the PFC-Sigma. MTPM migration of both knee implants did not significantly change from one year post-surgery, indicating stable fixation. Long-term ATTUNE performance may be expected to be comparable to the clinically well-performing PFC-Sigma. We have not found evidence of increased tibial component migration as measured by RSA to support concerns about cement debonding and a higher risk of aseptic loosening with the ATTUNE TKA. Cite this article: Bone Joint J 2023;105-B(11):1168–1176

Aims. Robotic arm-assisted surgery offers accurate and reproducible guidance in component positioning and assessment of soft-tissue tensioning during knee arthroplasty, but the feasibility and early outcomes when using this technology for revision surgery remain unknown. The objective of this study was to compare the outcomes of robotic arm-assisted revision of unicompartmental knee arthroplasty (UKA) to total knee arthroplasty (TKA) versus primary robotic arm-assisted TKA at short-term follow-up. Methods. This prospective study included 16 patients undergoing robotic arm-assisted revision of UKA to TKA versus 35 matched patients receiving robotic arm-assisted primary TKA. In all study patients, the following data were recorded: operating time, polyethylene liner size, change in haemoglobin concentration (g/dl), length of inpatient stay, postoperative complications, and hip-knee-ankle (HKA) alignment. All procedures were performed using the principles of functional alignment. At most recent follow-up, range of motion (ROM), Forgotten Joint Score (FJS), and Oxford Knee Score (OKS) were collected. Mean follow-up time was 21 months (6 to 36). Results. There were no differences between the two treatment groups with regard to mean change in haemoglobin concentration (p = 0.477), length of stay (LOS, p = 0.172), mean polyethylene thickness (p = 0.065), or postoperative complication rates (p = 0.295). At the most recent follow-up, the primary robotic arm-assisted TKA group had a statistically significantly improved OKS compared with the revision UKA to TKA group (44.6 (SD 2.7) vs 42.3 (SD 2.5); p = 0.004) but there was no difference in the overall ROM (p = 0.056) or FJS between the two treatment groups (86.1 (SD 9.6) vs 84.1 (4.9); p = 0.439). Conclusion. Robotic arm-assisted revision of UKA to TKA was associated with comparable intraoperative blood loss, early postoperative rehabilitation, functional outcomes, and complications to primary robotic TKA at short-term follow-up. Robotic arm-assisted surgery offers a safe and reproducible technique for revising failed UKA to TKA. Cite this article: Bone Joint J 2024;106-B(7):680–687

Aims. The aim of this study was to compare the migration of the femoral component, five years postoperatively, between patients with a highly cross-linked polyethylene (HXLPE) insert and those with a conventional polyethylene (PE) insert in an uncemented Triathlon fixed insert cruciate-retaining total knee arthroplasty (TKA). Secondary aims included clinical outcomes and patient-reported outcome measures (PROMs). We have previously reported the migration and outcome of the tibial components in these patients. Methods. A double-blinded randomized controlled trial was conducted including 96 TKAs. The migration of the femoral component was measured with radiostereometry (RSA) at three and six months and one, two, and five years postoperatively. PROMs were collected preoperatively and at all periods of follow-up. Results. There was no clinically relevant difference in terms of migration of the femoral component or PROMs between the HXLPE and PE groups. The mean difference in migration (maximum total point motion), five years postopeatively, was 0.04 mm (95% CI -0.06 to 0.16) in favour of the PE group. Conclusion. There was no clinically relevant difference in migration of the femoral component, for up to five years between the two groups. These findings will help to establish a benchmark for future studies on migration of femoral components in TKA. Cite this article: Bone Joint J 2024;106-B(8):826–833

Aims. Implantation of ultra-purified alginate (UPAL) gel is safe and effective in animal osteochondral defect models. This study aimed to examine the applicability of UPAL gel implantation to acellular therapy in humans with cartilage injury. Methods. A total of 12 patients (12 knees) with symptomatic, post-traumatic, full-thickness cartilage lesions (1.0 to 4.0 cm. 2. ) were included in this study. UPAL gel was implanted into chondral defects after performing bone marrow stimulation technique, and assessed for up to three years postoperatively. The primary outcomes were the feasibility and safety of the procedure. The secondary outcomes were self-assessed clinical scores, arthroscopic scores, tissue biopsies, and MRI-based estimations. Results. No obvious adverse events related to UPAL gel implantation were observed. Self-assessed clinical scores, including pain, symptoms, activities of daily living, sports activity, and quality of life, were improved significantly at three years after surgery. Defect filling was confirmed using second-look arthroscopy at 72 weeks. Significantly improved MRI scores were observed from 12 to 144 weeks postoperatively. Histological examination of biopsy specimens obtained at 72 weeks after implantation revealed an extracellular matrix rich in glycosaminoglycan and type II collagen in the reparative tissue. Histological assessment yielded a mean overall International Cartilage Regeneration & Joint Preservation Society II score of 69.1 points (SD 10.4; 50 to 80). Conclusion. This study provides evidence supporting the safety of acellular UPAL gel implantation in facilitating cartilage repair. Despite being a single-arm study, it demonstrated the efficacy of UPAL gel implantation, suggesting it is an easy-to-use, one-step method of cartilage tissue repair circumventing the need to harvest donor cells. Cite this article: Bone Joint J 2023;105-B(8):880–887

Aims. The rate of day-case total knee arthroplasty (TKA) in the UK is currently approximately 0.5%. Reducing length of stay allows orthopaedic providers to improve efficiency, increase operative throughput, and tackle the rising demand for joint arthroplasty surgery and the COVID-19-related backlog. Here, we report safe delivery of day-case TKA in an NHS trust via inpatient wards with no additional resources. Methods. Day-case TKAs, defined as patients discharged on the same calendar day as surgery, were retrospectively reviewed with a minimum follow-up of six months. Analysis of hospital and primary care records was performed to determine readmission and reattendance rates. Telephone interviews were conducted to determine patient satisfaction. Results. Since 2016, 301/7350 TKAs (4.1%) in 290 patients at our institution were discharged on the day of surgery. Mean follow-up was 31.4 months (6.2 to 70.0). In all, 28 patients (9.3%) attended the emergency department or other acute care settings within 90 days of surgery, most often with wound concerns or leg swelling; six patients (2.0%) were readmitted. No patients underwent a subsequent revision procedure, and there were no periprosthetic infections. Two patients (0.7%) underwent secondary patella resurfacing, and one patient underwent arthroscopic arthrolysis after previous manipulation under anaesthetic (MUA). Three patients (1.0%) underwent MUA alone. Primary care consultation records, available for 206 patients, showed 16 patients (7.8%) contacted their general practitioner within two weeks postoperatively; two (1.0%) were referred to secondary care. Overall, 115/121 patients (95%) telephoned stated they would have day-case TKA again. Conclusion. Day-case TKA can be safely delivered in the NHS with no additional resources. We found low incidence of contact with primary and secondary care in the postoperative period, and high patient satisfaction. Cite this article: Bone Jt Open 2023;4(8):621–627

Aims. The aim of this study was to report the meaningful values of the EuroQol five-dimension three-level questionnaire (EQ-5D-3L) and EuroQol visual analogue scale (EQ-VAS) in patients undergoing primary knee arthroplasty (KA). Methods. This is a retrospective study of patients undergoing primary KA for osteoarthritis in a university teaching hospital (Royal Infirmary of Edinburgh) (1 January 2013 to 31 December 2019). Pre- and postoperative (one-year) data were prospectively collected for 3,181 patients (median age 69.9 years (interquartile range (IQR) 64.2 to 76.1); females, n = 1,745 (54.9%); median BMI 30.1 kg/m. 2. (IQR 26.6 to 34.2)). The reliability of the EQ-5D-3L was measured using Cronbach’s alpha. Responsiveness was determined by calculating the anchor-based minimal clinically important difference (MCID), the minimal important change (MIC) (cohort and individual), the patient-acceptable symptom state (PASS) predictive of satisfaction, and the minimal detectable change at 90% confidence intervals (MDC-90). Results. The EQ-5D-3L demonstrated good internal consistency with an overall Cronbach alpha of 0.75 (preoperative) and 0.88 (postoperative), respectively. The MCID for the Index score was 0.085 (95% confidence interval (CI) 0.042 to 0.127) and EQ-VAS was 6.41 (95% CI 3.497 to 9.323). The MIC. COHORT. was 0.289 for the EQ-5D and 5.27 for the EQ-VAS. However, the MIC. INDIVIDUAL. for both the EQ-5D-3L Index (0.105) and EQ-VAS (-1) demonstrated poor-to-acceptable reliability. The MDC-90 was 0.023 for the EQ-5D-3L Index and 1.0 for the EQ-VAS. The PASS for the postoperative EQ-5D-3L Index and EQ-VAS scores predictive of patient satisfaction were 0.708 and 77.0, respectively. Conclusion. The meaningful values of the EQ-5D-3L Index and EQ-VAS scores can be used to measure clinically relevant changes in health-related quality of life in patients undergoing primary KA. Cite this article: Bone Joint Res 2022;11(9):619–628

Aims. Despite new technologies for total knee arthroplasty (TKA), approximately 20% of patients are dissatisfied. A major reason for dissatisfaction and revision surgery after TKA is persistent pain. The radiological grade of osteoarthritis (OA) preoperatively has been investigated as a predictor of the outcome after TKA, with conflicting results. The aim of this study was to determine if there is a difference in the intensity of pain 12 months after TKA in relation to the preoperative radiological grade of OA alone, and the combination of the intensity of preoperative pain and radiological grade of OA. Methods. The preoperative data of 300 patients who underwent primary TKA were collected, including clinical information (age, sex, preoperative pain), psychological variables (depression, anxiety, pain catastrophizing, anticipated pain), and quantitative sensory testing (temporal summation, pressure pain thresholds, conditioned pain modulation). The preoperative radiological severity of OA was graded according to the Kellgren-Lawrence (KL) classification. Persistent pain in the knee was recorded 12 months postoperatively. Generalized linear models explored differences in postoperative pain according to the KL grade, and combined preoperative pain and KL grade. Relative risk models explored which preoperative variables were associated with the high preoperative pain/low KL grade group. Results. Pain 12 months after TKA was not associated with the preoperative KL grade alone. Significantly increased pain 12 months after TKA was found in patients with a combination of high preoperative pain and a low KL grade (p = 0.012). Patients in this group were significantly more likely to be male, younger, and have higher preoperative pain catastrophizing, higher depression, and lower anxiety (all p ≤ 0.05). Conclusion. Combined high preoperative pain and low radiological grade of OA, but not the radiological grade alone, was associated with a higher intensity of pain 12 months after primary TKA. This group may have a more complex cause of pain that requires additional psychological interventions in order to optimize the outcome of TKA. Cite this article: Bone Joint J 2022;104-B(11):1202–1208

Aims. With up to 40% of patients having patellofemoral joint osteoarthritis (PFJ OA), the two arthroplasty options are to replace solely the patellofemoral joint via patellofemoral arthroplasty (PFA), or the entire knee via total knee arthroplasty (TKA). The aim of this study was to assess postoperative success of second-generation PFAs compared to TKAs for patients treated for PFJ OA using patient-reported outcome measures (PROMs) and domains deemed important by patients following a patient and public involvement meeting. Methods. MEDLINE, EMBASE via OVID, CINAHL, and EBSCO were searched from inception to January 2022. Any study addressing surgical treatment of primary patellofemoral joint OA using second generation PFA and TKA in patients aged above 18 years with follow-up data of 30 days were included. Studies relating to OA secondary to trauma were excluded. ROB-2 and ROBINS-I bias tools were used. Results. A total of nine studies were included, made up of four randomized controlled trials (domain 1) and five cohort studies (domain 2). PROMs and knee function specific scores developed for reporting TKA were unable to detect any difference between PFA and TKA. There was no significant difference in complications between PFA and TKA. PFAs were found to have a better postoperative range of motion. Conclusion. TKA and PFA are both viable options for patients with primary PFJ OA. Over time, we have seen an emphasis on patient satisfaction and better quality of life. Recommending sacrificing healthy medial and lateral compartments to treat patellofemoral joint arthritis should be given further thought. Cite this article: Bone Jt Open 2023;4(12):948–956

Aims. Obtaining solid implant fixation is crucial in revision total knee arthroplasty (rTKA) to avoid aseptic loosening, a major reason for re-revision. This study aims to validate a novel grading system that quantifies implant fixation across three anatomical zones (epiphysis, metaphysis, diaphysis). Methods. Based on pre-, intra-, and postoperative assessments, the novel grading system allocates a quantitative score (0, 0.5, or 1 point) for the quality of fixation achieved in each anatomical zone. The criteria used by the algorithm to assign the score include the bone quality, the size of the bone defect, and the type of fixation used. A consecutive cohort of 245 patients undergoing rTKA from 2012 to 2018 were evaluated using the current novel scoring system and followed prospectively. In addition, 100 first-time revision cases were assessed radiologically from the original cohort and graded by three observers to evaluate the intra- and inter-rater reliability of the novel radiological grading system. Results. At a mean follow-up of 90 months (64 to 130), only two out of 245 cases failed due to aseptic loosening. Intraoperative grading yielded mean scores of 1.87 (95% confidence interval (CI) 1.82 to 1.92) for the femur and 1.96 (95% CI 1.92 to 2.0) for the tibia. Only 3.7% of femoral and 1.7% of tibial reconstructions fell below the 1.5-point threshold, which included the two cases of aseptic loosening. Interobserver reliability for postoperative radiological grading was 0.97 for the femur and 0.85 for the tibia. Conclusion. A minimum score of 1.5 points for each skeletal segment appears to be a reasonable cut-off to define sufficient fixation in rTKA. There were no revisions for aseptic loosening at mid-term follow-up when this fixation threshold was achieved or exceeded. When assessing first-time revisions, this novel grading system has shown excellent intra- and interobserver reliability. Cite this article: Bone Joint J 2024;106-B(5):468–474

Aims. This study investigates whether primary knee arthroplasty (KA) restores health-related quality of life (HRQoL) to levels expected in the general population. Methods. This retrospective case-control study compared HRQoL data from two sources: patients undergoing primary KA in a university-teaching hospital (2013 to 2019), and the Health Survey for England (HSE; 2010 to 2012). Patient-level data from the HSE were used to represent the general population. Propensity score matching was used to balance covariates and facilitate group comparisons. A propensity score was estimated using logistic regression based upon the covariates sex, age, and BMI. Two matched cohorts with 3,029 patients each were obtained for the adjusted analyses (median age 70.3 (interquartile range (IQR) 64 to 77); number of female patients 3,233 (53.4%); median BMI 29.7 kg/m. 2. (IQR 26.5 to 33.7)). HRQoL was measured using the three-level version of the EuroQol five-dimension questionnaire (EQ-5D-3L), and summarized using the Index and EuroQol visual analogue scale (EQ-VAS) scores. Results. Patients awaiting KA had significantly lower EQ-5D-3L Index scores than the general population (median 0.620 (IQR 0.16 to 0.69) vs median 0.796 (IQR 0.69 to 1.00); p < 0.001). By one year postoperatively, the median EQ-5D-3L Index score improved significantly in the KA cohort (mean change 0.32 (SD 0.33); p < 0.001), and demonstrated no clinically relevant differences when compared to the general population (median 0.796 (IQR 0.69 to 1.00) vs median 0.796 (IQR 0.69 to 1.00)). Compared to the general population cohort, the postoperative EQ-VAS was significantly higher in the KA cohort (p < 0.001). Subgroup comparisons demonstrated that older age groups had statistically better EQ-VAS scores than matched peers in the general population. Conclusion. Patients awaiting KA for osteoarthritis had significantly poorer HRQoL than the general population. However, within one year of surgery, primary KA restored HRQoL to levels expected for the patient’s age-, BMI-, and sex-matched peers. Cite this article: Bone Joint J 2023;105-B(4):365–372

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. Intra-articular administration of antibiotics during primary total knee arthroplasty (TKA) may represent a safe, cost-effective strategy to reduce the risk of acute periprosthetic joint infection (PJI). Vancomycin with an aminoglycoside provides antimicrobial cover for most organisms isolated from acute PJI after TKA. However, the intra-articular doses required to achieve sustained therapeutic intra-articular levels while remaining below toxic serum levels is unknown. The purpose of this study is to determine the intra-articular and serum levels of vancomycin and tobramycin over the first 24 hours postoperatively after intra-articular administration in primary cementless TKA. Methods. A prospective cohort study was performed. Patients were excluded if they had poor renal function, known allergic reaction to vancomycin or tobramycin, received intravenous vancomycin, or were scheduled for same-day discharge. All patients received 600 mg tobramycin and 1 g of vancomycin powder suspended in 25 cc of normal saline and injected into the joint after closure of the arthrotomy. Serum from peripheral venous blood and drain fluid samples were collected at one, four, and 24 hours postoperatively. All concentrations are reported in µg per ml. Results. A total of 22 patients were included in final analysis. At one, four, and 24 hours postoperatively, mean (95% confidence interval (CI)) serum concentrations were 2.4 (0.7 to 4.1), 5.0 (3.1 to 6.9), and 4.8 (2.8 to 6.9) for vancomycin and 4.9 (3.4 to 6.3), 7.0 (5.8 to 8.2), and 1.3 (0.8 to 1.8) for tobramycin; intra-articular concentrations were 1,900.6 (1,492.5 to 2,308.8), 717.9 (485.5 to 950.3), and 162.2 (20.5 to 304.0) for vancomycin and 2,105.3 (1,389.9 to 2,820.6), 403.2 (266.6 to 539.7), and 98.8 (0 to 206.5) for tobramycin. Conclusion. Intra-articular administration of 1 g of vancomycin and 600 mg of tobramycin as a solution after closure of the arthrotomy in primary cementless TKA achieves therapeutic intra-articular concentrations over the first 24 hours postoperatively and does not reach sustained toxic levels in peripheral blood. Cite this article: Bone Joint J 2021;103-B(11):1702–1708

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

Aims. The primary aim of this study was to assess whether non-fatal postoperative venous thromboembolism (VTE) within six months of surgery influences the knee-specific functional outcome (Oxford Knee Score (OKS)) one year after total knee arthroplasty (TKA). Secondary aims were to assess whether non-fatal postoperative VTE influences generic health and patient satisfaction at this time. Methods. A study of 2,393 TKAs was performed in 2,393 patients. Patient demographics, comorbidities, OKS, EuroQol five-dimension score (EQ-5D), and Forgotten Joint Score (FJS) were collected preoperatively and one year postoperatively. Overall patient satisfaction with their TKA was assessed at one year. Patients with VTE within six months of surgery were identified retrospectively and compared with those without. Results. A total of 37 patients (1.5%) suffered a VTE and were significantly more likely to have associated comorbidities of stroke (p = 0.026), vascular disease (p = 0.026), and kidney disease (p = 0.026), but less likely to have diabetes (p = 0.046). In an unadjusted analysis, patients suffering a VTE had a significantly worse postoperative OKS (difference in mean (DIM) 4.8 (95% confidence interval (CI) 1.6 to 8.0); p = 0.004) and EQ-5D (DIM 0.146 (95% CI 0.059 to 0.233); p = 0.001) compared with patients without a VTE. After adjusting for confounding variables VTE remained a significant independent predictor associated with a worse postoperative OKS (DIM -5.4 (95% CI -8.4 to -2.4); p < 0.001), and EQ-5D score (DIM-0.169 (95% CI -0.251 to -0.087); p < 0.001). VTE was not independently associated with overall satisfaction after TKA (odds ratio 0.89 (95% CI 0.35 to 2.07); p = 0.717). Conclusion. Patients who had a VTE within six months of their TKA had clinically significantly worse knee-specific outcome (OKS) and general health (EQ-5D) scores one year postoperatively, but the overall satisfaction with their TKA was similar to those patients who did not have a VTE. Cite this article: Bone Joint J 2021;103-B(7):1254–1260

Aims. The aim of this study was to establish consensus statements on medial patellofemoral ligament (MPFL) reconstruction, anteromedialization tibial tubercle osteotomy, trochleoplasty, and rehabilitation and return to sporting activity in patients with patellar instability, using the modified Delphi process. Methods. This was the second part of a study dealing with these aspects of management in these patients. As in part I, a total of 60 surgeons from 11 countries contributed to the development of consensus statements based on their expertise in this area. They were assigned to one of seven working groups defined by subtopics of interest. Consensus was defined as achieving between 80% and 89% agreement, strong consensus was defined as between 90% and 99% agreement, and 100% agreement was considered unanimous. Results. Of 41 questions and statements on patellar instability, none achieved unanimous consensus, 19 achieved strong consensus, 15 achieved consensus, and seven did not achieve consensus. Conclusion. Most statements reached some degree of consensus, without any achieving unanimous consensus. There was no consensus on the use of anchors in MPFL reconstruction, and the order of fixation of the graft (patella first versus femur first). There was also no consensus on the indications for trochleoplasty or its effect on the viability of the cartilage after elevation of the osteochondral flap. There was also no consensus on postoperative immobilization or weightbearing, or whether paediatric patients should avoid an early return to sport. Cite this article: Bone Joint J 2023;105-B(12):1265–1270

Aims. The aim of this study was to compare the clinical outcomes of robotic arm-assisted bi-unicompartmental knee arthroplasty (bi-UKA) with conventional mechanically aligned total knee arthroplasty (TKA) during the first six weeks and at one year postoperatively. Methods. A per protocol analysis of 76 patients, 43 of whom underwent TKA and 34 of whom underwent bi-UKA, was performed from a prospective, single-centre, randomized controlled trial. Diaries kept by the patients recorded pain, function, and the use of analgesics daily throughout the first week and weekly between the second and sixth weeks. Patient-reported outcome measures (PROMs) were compared preoperatively, and at three months and one year postoperatively. Data were also compared longitudinally and a subgroup analysis was conducted, stratified by preoperative PROM status. Results. Both operations were shown to offer comparable outcomes, with no significant differences between the groups across all timepoints and outcome measures. Both groups also had similarly low rates of complications. Subgroup analysis for preoperative psychological state, activity levels, and BMI showed no difference in outcomes between the two groups. Conclusion. Robotic arm-assisted, cruciate-sparing bi-UKA offered similar early clinical outcomes and rates of complications to a mechanically aligned TKA, both in the immediate postoperative period and up to one year following surgery. Further work is required to identify which patients with osteoarthritis of the knee will derive benefit from a cruciate-sparing bi-UKA. Cite this article: Bone Joint J 2021;103-B(10):1561–1570

Aims. The primary objective of this study was to compare the five-year tibial component migration and wear between highly crosslinked polyethylene (HXLPE) inserts and conventional polyethylene (PE) inserts of the uncemented Triathlon fixed insert cruciate-retaining total knee arthroplasty (TKA). Secondary objectives included clinical outcomes and patient-reported outcome measures (PROMs). Methods. A double-blinded, randomized study was conducted including 96 TKAs. Tibial component migration and insert wear were measured with radiostereometric analysis (RSA) at three, six, 12, 24, and 60 months postoperatively. PROMS were collected preoperatively and at all follow-up timepoints. Results. There was no clinically relevant difference in terms of tibial component migration, insert wear, and PROMs between the HXLPE and PE groups. The mean difference in tibial component migration (maximal total point migration (MTPM)) was 0.02 mm (95% confidence interval (CI) -0.07 to 0.11), which is below the value of 0.2 mm considered to be clinically relevant. Wear after five years for HXLPE was 0.16 mm (95% CI 0.05 to 0.27), and for PE was 0.23 mm (95% CI 0.12 to 0.35). The mean difference in wear rate was 0.01 mm/year (95% CI -0.02 to 0.05) in favour of the HXLPE group. Wear is mainly present on the medial side of the insert. Conclusion. There is no clinically relevant difference in tibial component migration and insert wear for up to five years between the HXLPE conventional PE inserts. For the implant studied, the potential advantages of a HXLPE insert remain to be proven under clinical conditions at longer-term follow-up. Cite this article: Bone Joint J 2023;105-B(5):518–525

Aims. Unicompartmental knee arthroplasty (UKA) is the preferred treatment for anterior medial knee osteoarthritis (OA) owing to the rapid postoperative recovery. However, the risk factors for UKA failure remain controversial. Methods. The clinical data of Oxford mobile-bearing UKAs performed between 2011 and 2017 with a minimum follow-up of five years were retrospectively analyzed. Demographic, surgical, and follow-up data were collected. The Cox proportional hazards model was used to identify the risk factors that contribute to UKA failure. Kaplan-Meier survival was used to compare the effect of the prosthesis position on UKA survival. Results. A total of 407 patients who underwent UKA were included in the study. The mean age of patients was 61.8 years, and the mean follow-up period of the patients was 91.7 months. The mean Knee Society Score (KSS) preoperatively and at the last follow-up were 64.2 and 89.7, respectively (p = 0.001). Overall, 28 patients (6.9%) with UKA underwent revision due to prosthesis loosening (16 patients), dislocation (eight patients), and persistent pain (four patients). Cox proportional hazards model analysis identified malposition of the prostheses as a high-risk factor for UKA failure (p = 0.007). Kaplan-Meier analysis revealed that the five-year survival rate of the group with malposition was 85.1%, which was significantly lower than that of the group with normal position (96.2%; p < 0.001). Conclusion. UKA constitutes an effective method for treating anteromedial knee OA, with an excellent five-year survival rate. Aseptic loosening caused by prosthesis malposition was identified as the main cause of UKA failure. Surgeons should pay close attention to prevent the potential occurrence of this problem. Cite this article: Bone Jt Open 2023;4(12):914–922

Aims. Knowledge on total knee arthroplasties (TKAs) in patients with a history of poliomyelitis is limited. This study compared implant survivorship and clinical outcomes among affected and unaffected limbs in patients with sequelae of poliomyelitis undergoing TKAs. Methods. A retrospective review of our total joint registry identified 94 patients with post-polio syndrome undergoing 116 primary TKAs between January 2000 and December 2019. The mean age was 70 years (33 to 86) with 56% males (n = 65) and a mean BMI of 31 kg/m. 2. (18 to 49). Rotating hinge TKAs were used in 14 of 63 affected limbs (22%), but not in any of the 53 unaffected limbs. Kaplan-Meier survivorship analyses were completed. The mean follow-up was eight years (2 to 19). Results. The ten-year survivorship free from revision was 91% (95% confidence interval (CI) 81 to 100) in affected and 84% (95% CI 68 to 100) in unaffected limbs. There were six revisions in affected limbs: three for periprosthetic femoral fractures and one each for periprosthetic joint infection (PJI), patellar clunk syndrome, and instability. Unaffected limbs were revised in four cases: two for instability and one each for PJI and tibial component loosening. The ten-year survivorship free from any reoperation was 86% (95% CI 75 to 97) and 80% (95% CI 64 to 99) in affected and unaffected limbs, respectively. There were three additional reoperations among affected and two in unaffected limbs. There were 12 nonoperative complications, including four periprosthetic fractures. Arthrofibrosis occurred in five affected (8%) and two unaffected limbs (4%). Postoperative range of motion decreased with 31% achieving less than 90° knee flexion by five years. Conclusion. TKAs in post-polio patients are complex cases associated with instability, and one in four require constraint on the affected side. Periprosthetic fracture was the main mode of failure. Arthrofibrosis rates were high and twice as frequent in affected limbs. Cite this article: Bone Joint J 2023;105-B(6):635–640

Aims. To perform an incremental cost-utility analysis and assess the impact of differential costs and case volume on the cost-effectiveness of robotic arm-assisted unicompartmental knee arthroplasty (rUKA) compared to manual (mUKA). Methods. This was a five-year follow-up study of patients who were randomized to rUKA (n = 64) or mUKA (n = 65). Patients completed the EuroQol five-dimension questionnaire (EQ-5D) preoperatively, and at three months and one, two, and five years postoperatively, which was used to calculate quality-adjusted life years (QALYs) gained. Costs for the primary and additional surgery and healthcare costs were calculated. Results. rUKA was associated with a relative 0.012 QALY gain at five years, which was associated with an incremental cost per QALY of £13,078 for a unit undertaking 400 cases per year. A cost per QALY of less than £20,000 was achieved when ≥ 300 cases were performed per year. However, on removal of the cost for a revision for presumed infection (mUKA group, n = 1) the cost per QALY was greater than £38,000, which was in part due to the increased intraoperative consumable costs associated with rUKA (£626 per patient). When the absolute cost difference (operative and revision costs) was less than £240, a cost per QALY of less than £20,000 was achieved. On removing the cost of the revision for infection, rUKA was cost-neutral when more than 900 cases per year were undertaken and when the consumable costs were zero. Conclusion. rUKA was a cost-effective intervention with an incremental cost per QALY of £13,078 at five years, however when removing the revision for presumed infection, which was arguably a random event, this was no longer the case. The absolute cost difference had to be less than £240 to be cost-effective, which could be achieved by reducing the perioperative costs of rUKA or if there were increased revision costs associated with mUKA with longer follow-up. Cite this article: Bone Jt Open 2023;4(11):889–898

Aims. The aim was to assess whether robotic-assisted total knee arthroplasty (rTKA) had greater knee-specific outcomes, improved fulfilment of expectations, health-related quality of life (HRQoL), and patient satisfaction when compared with manual TKA (mTKA). Methods. A randomized controlled trial was undertaken (May 2019 to December 2021), and patients were allocated to either mTKA or rTKA. A total of 100 patients were randomized, 50 to each group, of whom 43 rTKA and 38 mTKA patients were available for review at 12 months following surgery. There were no statistically significant preoperative differences between the groups. The minimal clinically important difference in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain score was defined as 7.5 points. Results. There were no clinically or statistically significant differences between the knee-specific measures (WOMAC, Oxford Knee Score (OKS), Forgotten Joint Score (FJS)) or HRQoL measures (EuroQol five-dimension questionnaire (EQ-5D) and EuroQol visual analogue scale (EQ-VAS)) at 12 months between the groups. However, the rTKA group had significantly (p = 0.029) greater improvements in the WOMAC pain component (mean difference 9.7, 95% confidence interval (CI) 1.0 to 18.4) over the postoperative period (two, six, and 12 months), which was clinically meaningful. This was not observed for function (p = 0.248) or total (p = 0.147) WOMAC scores. The rTKA group was significantly (p = 0.039) more likely to have expectation of ‘Relief of daytime pain in the joint’ when compared with the mTKA group. There were no other significant differences in expectations met between the groups. There was no significant difference in patient satisfaction with their knee (p = 0.464), return to work (p = 0.464), activities (p = 0.293), or pain (p = 0.701). Conclusion. Patients undergoing rTKA had a clinically meaningful greater improvement in their knee pain over the first 12 months, and were more likely to have fulfilment of their expectation of daytime pain relief compared with patients undergoing mTKA. However, rTKA was not associated with a clinically significant greater knee-specific function or HRQoL, according to current definitions. Cite this article: Bone Joint J 2024;106-B(5):450–459

Aims. Cementless total knee arthroplasty (TKA) offers the potential for strong biological fixation compared with cemented TKA where fixation is achieved by the mechanical integration of the cement. Few mid-term results are available for newer cementless TKA designs, which have used additive manufacturing (3D printing). The aim of this study was to present mid-term clinical outcomes and implant survivorship of the cementless Stryker Triathlon Tritanium TKA. Methods. This was a single institution registry review of prospectively gathered data from 341 cementless Triathlon Tritanium TKAs at four to 6.8 years follow-up. Outcomes were determined by comparing pre- and postoperative Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS JR) scores, and pre- and postoperative 12-item Veterans RAND/Short Form Health Survey (VR/SF-12) scores. Aseptic loosening and revision for any reason were the endpoints which were used to determine survivorship at five years. Results. At mid-term follow-up, the mean KOOS JR score improved significantly from 33.14 (0 t0 85, standard deviation (SD) 21.88) preoperatively to 84.12 (15.94 to 100, SD 20.51) postoperatively (p < 0.001), the mean VR/SF-12 scores improved significantly from physical health (PH), 31.21 (SD 5.32; 23.99 to 56.77) preoperatively to 42.62 (SD 10.72; 19.38 to 56.82) postoperatively (p < 0.001) and the mental health (MH), 38.15 (SD 8.17; 19.06 to 60.75) preoperatively to 55.09 (SD 9.64; 19.06 to 66.98) postoperatively (p < 0.001). A total of 11 revisions were undertaken, with an overall revision rate of 2.94%, including five for periprosthetic joint infection (1.34%), three for loosening (0.80%), two for instability (0.53%), and one for pain (0.27%). The overall survivorship was 97.06% and survivorship for aseptic loosening as the endpoint was 98.40%, with a 99.5% survivorship of the 3D-printed tibial component. Conclusion. This 3D-printed cementless total knee system shows excellent survivorship at mid-term follow-up. This design and the ability to obtain cementless fixation offers promise for excellent long-term durability. Cite this article: Bone Joint J 2021;103-B(6 Supple A):32–37

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. Methods. In total, 34 patients (13 female, 21 male; mean age 62 years (41 to 79); BMI 29.7 kg/m. 2. (23.6 to 42.1)) with 38 medial Oxford partial UKAs (20 left, 18 right; 19 cementless, 14 cemented, and five hybrid) were prospectively followed with sequential 99mTc-hydroxymethane diphosphonate single photon emission CT (SPECT)/CT preoperatively, and at one and two years postoperatively. Changes in mean osteoblastic activity were investigated using a tracer localization scheme with volumes of interest (VOIs), reported by normalized mean tracer values. A SPECT/CT registration platform additionally explored cortical tracer evolution in zones of interest identified by previous experimental research. Results. Significant reduction of tracer activity from the preoperative situation was found in femoral and anteromedial tibial VOIs adjacent to the UKA components. Temporarily increased osteoblastic bone activity was observed in VOIs comprising the UKA keel structure at one year postoperatively compared to the preoperative activity. Persistent higher tracer uptake was found in the posterior tibial cortex at final follow-up. Multivariate analysis showed no statistical difference in osteoblastic bone activity underneath cemented or cementless components. Conclusion. Well-functioning medial mobile-bearing UKAs showed distinct changes in patterns of normalized bone tracer activity in the different VOIs adjacent to the prosthetic components, regardless of their type of fixation. Compared to the preoperative situation, persistent high bone activity was found underneath the keel and the posterior tibial cortex at final follow-up, with significant reduced activity only being identified in femoral and anteromedial tibial VOIs. Cite this article: Bone Joint J 2022;104-B(1):34–44

Aims. Spinal anaesthesia has seen increased use in contemporary primary total knee arthroplasties (TKAs). However, controversy exists about the benefits of spinal in comparison to general anaesthesia in primary TKAs. This study aimed to investigate the pain control, length of stay (LOS), and complications associated with spinal versus general anaesthesia in primary TKAs from a single, high-volume academic centre. Methods. We retrospectively identified 17,690 primary TKAs (13,297 patients) from 2001 to 2016 using our institutional total joint registry, where 52% had general anaesthesia and 48% had spinal anaesthesia. Baseline characteristics were similar between cohorts with a mean age of 68 years (SD 10), 58% female (n = 7,669), and mean BMI of 32 kg/m. 2. (SD 7). Pain was evaluated using oral morphine equivalents (OMEs) and numerical pain rating scale (NPRS) data. Complications including 30- and 90-day readmissions were studied. Data were analyzed using an inverse probability of treatment weighted model based on propensity score that included many patient and surgical factors. Mean follow-up was seven years (2 to 18). Results. Patients treated with spinal anaesthesia required fewer postoperative OMEs (p < 0.001) and had lower NPRS scores (p < 0.001). Spinal anaesthesia also had fewer cases of altered mental status (AMS; odds ratio (OR) 1.3; p = 0.044), as well as 30-day (OR 1.4; p < 0.001) and 90-day readmissions (OR 1.5; p < 0.001). General anaesthesia was associated with increased risk of any revision (OR 1.2; p = 0.021) and any reoperation (1.3; p < 0.001). Conclusion. In the largest single institutional report to date, we found that spinal anaesthesia was associated with significantly lower OME use, lower risk of AMS, and lower overall 30- and 90-day readmissions following primary TKAs. Additionally, spinal anaesthesia was associated with reduced risk of any revision and any reoperation after accounting for numerous patient and operative factors. When possible and safe, spinal anaesthesia should be considered in primary TKAs. Cite this article: Bone Joint J 2022;104-B(11):1209–1214

Aims. To identify the responsiveness, minimal clinically important difference (MCID), minimal clinical important change (MIC), and patient-acceptable symptom state (PASS) thresholds in the 36-item Short Form Health Survey questionnaire (SF-36) (v2) for each of the eight dimensions and the total score following total knee arthroplasty (TKA). Methods. There were 3,321 patients undergoing primary TKA with preoperative and one-year postoperative SF-36 scores. At one-year patients were asked how satisfied they were and “How much did the knee arthroplasty surgery improve the quality of your life?”, which was graded as: great, moderate, little (n = 277), none (n = 98), or worse. Results. Physical function, role limitations due to physical problems (‘role physical’), bodily pain, and the total score SF-36 scores demonstrated the greatest effect sizes (> 0.9). The MCID for each of SF-36 dimensions ranged from 1.7 for role emotional to 6.4 for bodily pain. The MICs for a cohort of patients ranged from -1.0 for general health to 11.1 for bodily pain. The MICs for an individual patient were marginally greater (one to two points) compared to those for a cohort, and ranging from 0.0 for general and mental health to 13.5 for physical function. The lowest PASS score threshold was associated with physical function (> 34 points) whereas the greatest threshold (> 69 points) was associated with mental health. Conclusion. The SF-36 is a responsive tool, and the estimates for MCID, MIC, and PASS thresholds that can be used to power studies, assess whether there has been a meaningful change in patients’ health-related quality of life, and can be used as a marker of achieving patient satisfaction following TKA. Cite this article: Bone Joint Res 2022;11(7):477–483

Aims. A novel enhanced cement fixation (EF) tibial implant with deeper cement pockets and a more roughened bonding surface was released to market for an existing total knee arthroplasty (TKA) system.This randomized controlled trial assessed fixation of the both the EF (ATTUNE S+) and standard (Std; ATTUNE S) using radiostereometric analysis. Methods. Overall, 50 subjects were randomized (21 EF-TKA and 23 Std-TKA in the final analysis), and had follow-up visits at six weeks, and six, 12, and 24 months to assess migration of the tibial component. Low viscosity bone cement with tobramycin was used in a standardized fashion for all subjects. Patient-reported outcome measure data was captured at preoperative and all postoperative visits. Results. The patient cohort mean age was 66 years (SD seven years), 59% were female, and the mean BMI was 32 kg/m. 2. (SD 6 kg/m. 2. ). Mean two-year subsidence of the EF-TKA was 0.056 mm (95% confidence interval (CI) 0.025 to 0.086) versus 0.006 mm (95% CI -0.029 to 0.040) for the Std-TKA, and the two-year maximum total point motion (MTPM) was 0.285 mm (95% upper confidence limit (UCL) ≤ 0.363) versus 0.346 mm (95% UCL ≤ 0.432), respectively, for a mean difference of -0.061 mm (95% CI -0.196 to 0.074). Inducible displacement also did not differ between groups. The MTPMs between 12 and 24 months for each group was below the published threshold of 0.2 mm for predicting early aseptic loosening (p < 0.001 and p = 0.001, respectively). Conclusion. Both the enhanced fixation and the standard tibial implant design showed fixation with a predicted low risk of long-term aseptic loosening. Cite this article: Bone Jt Open 2024;5(1):20–27

Aims. Revision total knee arthroplasty (rTKA) is a technically challenging and costly procedure. It is well-documented that primary TKA (pTKA) have better survivorship than rTKA; however, we were unable to identify any studies explicitly investigating previous rTKA as a risk factor for failure following rTKA. The purpose of this study is to compare the outcomes following rTKA between patients undergoing index rTKA and those who had been previously revised. Methods. This retrospective, observational study reviewed patients who underwent unilateral, aseptic rTKA at an academic orthopaedic speciality hospital between June 2011 and April 2020 with > one-year of follow-up. Patients were dichotomized based on whether this was their first revision procedure or not. Patient demographics, surgical factors, postoperative outcomes, and re-revision rates were compared between the groups. Results. A total of 663 cases were identified (486 index rTKAs and 177 multiply revised TKAs). There were no differences in demographics, rTKA type, or indication for revision. Multiply revised patients had significantly longer rTKA operative times (p < 0.001), and were more likely to be discharged to an acute rehabilitation centre (6.2% vs 4.5%) or skilled nursing facility (29.9% vs 17.5%; p = 0.003). Patients who had been multiply revised were also significantly more likely to have subsequent reoperation (18.1% vs 9.5%; p = 0.004) and re-revision (27.1% vs 18.1%; p = 0.013). The number of previous revisions did not correlate with the number of subsequent reoperations (r = 0.038; p = 0.670) or re-revisions (r = −0.102; p = 0.251). Conclusion. Multiply revised TKA had worse outcomes, with higher rates of facility discharge, longer operative times, and greater reoperation and re-revision rates compared to index rTKA. Cite this article: Bone Jt Open 2023;4(5):393–398

Aims. Achievement of accurate microbiological diagnosis prior to revision is key to reducing the high rates of persistent infection after revision knee surgery. The effect of change in the microorganism between the first- and second-stage revision of total knee arthroplasty for periprosthetic joint infection (PJI) on the success of management is not clear. Methods. A two-centre retrospective cohort study was conducted to review the outcome of patients who have undergone two-stage revision for treatment of knee arthroplasty PJI, focusing specifically on isolated micro-organisms at both the first- and second-stage procedure. Patient demographics, medical, and orthopaedic history data, including postoperative outcomes and subsequent treatment, were obtained from the electronic records and medical notes. Results. The study cohort consisted of 84 patients, of whom 59.5% (n = 50) had successful eradication of their infection at a mean follow-up of 4.7 years. For the 34 patients who had recurrence of infection, 58.8% (n = 20) had a change in isolated organism, compared to 18% (n = 9) in the infection eradication group (p < 0.001). When adjusting for confound, there was no association when the growth on the second stage was the same as the first (odd ratio (OR) 2.50, 95% confidence interval (CI) 0.49 to 12.50; p = 0.269); however, when a different organism was identified at the second stage, this was independently associated with failure of treatment (OR 8.40, 95% CI 2.91 to 24.39; p < 0.001). There were no other significant differences between the two cohorts with regard to patient demographics or type of organisms isolated. Conclusion. Change in the identified microorganism between first- and second-stage revision for PJI was associated with failure of management. Identification of this change in the microorganism prior to commencement of the second stage may help target antibiotic management and could improve the success of surgery in these patients. Cite this article: Bone Jt Open 2023;4(9):720–727

Aims. The aim of this study was to report patient and clinical outcomes following robotic-assisted total knee arthroplasty (RA-TKA) at multiple institutions with a minimum two-year follow-up. Methods. This was a multicentre registry study from October 2016 to June 2021 that included 861 primary RA-TKA patients who completed at least one pre- and postoperative patient-reported outcome measure (PROM) questionnaire, including Forgotten Joint Score (FJS), Knee Injury and Osteoarthritis Outcomes Score for Joint Replacement (KOOS JR), and pain out of 100 points. The mean age was 67 years (35 to 86), 452 were male (53%), mean BMI was 31.5 kg/m. 2. (19 to 58), and 553 (64%) cemented and 308 (36%) cementless implants. Results. There were significant improvements in PROMs over time between preoperative, one- to two-year, and > two-year follow-up, with a mean FJS of 17.5 (SD 18.2), 70.2 (SD 27.8), and 76.7 (SD 25.8; p < 0.001); mean KOOS JR of 51.6 (SD 11.5), 85.1 (SD 13.8), and 87.9 (SD 13.0; p < 0.001); and mean pain scores of 65.7 (SD 20.4), 13.0 (SD 19.1), and 11.3 (SD 19.9; p < 0.001), respectively. There were eight superficial infections (0.9%) and four revisions (0.5%). Conclusion. RA-TKA demonstrated consistent clinical results across multiple institutions with excellent PROMs that continued to improve over time. With the ability to achieve target alignment in the coronal, axial, and sagittal planes and provide intraoperative real-time data to obtain balanced gaps, RA-TKA demonstrated excellent clinical outcomes and PROMs in this patient population. Cite this article: Bone Jt Open 2022;3(7):589–595

Aims. To investigate the impact of consecutive perioperative care transitions on in-hospital recovery of patients who had primary total knee arthroplasty (TKA) over an 11-year period. Methods. This observational cohort study used electronic health record data from all patients undergoing preoperative screening for primary TKA at a Northern Netherlands hospital between 2009 and 2020. In this timeframe, three perioperative care transitions were divided into four periods: Baseline care (Joint Care, n = 171; May 2009 to August 2010), Function-tailored (n = 404; September 2010 to October 2013), Fast-track (n = 721; November 2013 to May 2018), and Prehabilitation (n = 601; June 2018 to December 2020). In-hospital recovery was measured using inpatient recovery of activities (IROA), length of stay (LOS), and discharge to preoperative living situation (PLS). Multivariable regression models were used to analyze the impact of each perioperative care transition on in-hospital recovery. Results. The four periods analyzed involved 1,853 patients (65.9% female (1,221/1,853); mean age 70.1 years (SD 9.0)). IROA improved significantly with each transition: Function-tailored (0.9 days; p < 0.001 (95% confidence interval (CI) -0.32 to -0.15)), Fast-track (0.6 days; p < 0.001 (95% CI -0.25 to -0.16)), and Prehabilitation (0.4 days; p < 0.001 (95% CI -0.18 to -0.10)). LOS decreased significantly in Function-tailored (1.1 days; p = 0.001 (95% CI -0.30 to -0.06)), Fast-track (0.6 days; p < 0.001 (95% CI -0.21 to -0.05)), and Prehabilitation (0.6 days; p < 0.001 (95%CI -0.27 to -0.11)). Discharge to PLS increased in Function-tailored (77%), Fast-track (91.6%), and Prehabilitation (92.6%). Post-hoc analysis indicated a significant increase after the transition to the Fast-track period (p < 0.001 (95% CI 3.19 to 8.00)). Conclusion. This study highlights the positive impact of different perioperative care procedures on in-hospital recovery of patients undergoing primary TKA. Assessing functional recovery, LOS, and discharge towards PLS consistently, provides hospitals with valuable insights into postoperative recovery. This can potentially aid planning and identifying areas for targeted improvements to optimize patient outcomes. Cite this article: Bone Joint J 2024;106-B(6):573–581

Aims. The use of cementless total knee arthroplasty (TKA) components has increased during the past decade. The initial design of cementless metal-backed patellar components had shown high failure rates due to many factors. The aim of this study was to evaluate the clinical results of a second-generation cementless, metal-backed patellar component of a modern design. Methods. This was a retrospective review of 707 primary TKAs in 590 patients from a single institution, using a cementless, metal-backed patellar component with a mean follow-up of 6.9 years (2 to 12). A total of 409 TKAs were performed in 338 females and 298 TKAs in 252 males. The mean age of the patients was 63 years (34 to 87) and their mean BMI was 34.3 kg/m. 2. (18.8 to 64.5). The patients were chosen to undergo a cementless procedure based on age and preoperative radiological and intraoperative bone quality. Outcome was assessed using the Knee Society knee and function scores and range of motion (ROM), complications, and revisions. Results. A total of 24 TKAs (3.4%) in 24 patients failed and required revision surgery, of which five were due to patellar complications (0.71%): one for aseptic patellar loosening (0.14%) and four for polyethylene dissociation (0.57%). A total of 19 revisions (2.7%) were undertaken in 19 patients for indications which did not relate to the patella: four for aseptic tibial loosening (0.57%), one for aseptic femoral loosening (0.14%), nine for periprosthetic infection (1.3%), one for popliteus impingement (0.14%), and four for instability (0.57%). Knee Society knee and function scores, and ROM, improved significantly when comparing pre- and postoperative values. Survival of the metal-backed patellar component for all-cause failure was 97.5% (95% confidence interval 94.9% to 100%) at 12 years. Conclusion. The second-generation cementless TKA design of metal-backed patellar components showed a 97.5% survival at 12 years, with polyethylene dissociation from the metal-backing being the most common cause of patellar failure. In view of the increased use of TKA, especially in younger, more active, or obese patients, these findings are encouraging at mean follow-up of seven years. Cite this article: Bone Joint J 2023;105-B(12):1279–1285

Aims. Both the femoral and tibial component are usually cemented at revision total knee arthroplasty (rTKA), while stems can be added with either cemented or press-fit (hybrid) fixation. The aim of this study was to compare the long-term stability of rTKA with cemented and press-fitted stems, using radiostereometric analysis (RSA). Methods. This is a follow-up of a randomized controlled trial, initially involving 32 patients, of whom 19 (nine cemented, ten hybrid) were available for follow-up ten years postoperatively, when further RSA measurements were made. Micromotion of the femoral and tibial components was assessed using model-based RSA software (RSAcore). The clinical outcome was evaluated using the Knee Society Score (KSS), the Knee injury and Osteoarthritis Outcome Score (KOOS), and visual analogue scale (pain and satisfaction). Results. The median total femoral translation and rotation at ten years were 0.39 mm (interquartile range (IQR) 0.20 to 0.54) and 0.59° (IQR 0.46° to 0.73°) for the cemented group and 0.70 mm (IQR 0.15 to 0.77) and 0.78° (IQR 0.47° to 1.43°) for the hybrid group. For the tibial components this was 0.38 mm (IQR 0.33 to 0.85) and 0.98° (IQR 0.38° to 1.34°) for the cemented group and 0.42 mm (IQR 0.30 to 0.52) and 0.72° (IQR 0.62° to 0.82°) for the hybrid group. None of these values were significantly different between the two groups and there were no significant differences between the clinical scores in the two groups at this time. There was only one re-revision, in the hybrid group, for infection and not for aseptic loosening. Conclusion. These results show good long-term fixation with no difference in micromotion and clinical outcome between fully cemented and hybrid fixation in rTKA, which builds on earlier short- to mid-term results. The patients all had type I or II osseous defects, which may in part explain the good results. Cite this article: Bone Joint J 2022;104-B(7):875–883

Aims. Meeting preoperative expectations is known to be of major influence on postoperative satisfaction after total knee arthroplasty (TKA). Improved management of expectation, resulting in more realistic expectations can potentially lead to higher postoperative satisfaction. The objective of this study was to assess the effect of an additional preoperative education module, addressing realistic expectations for long-term functional recovery, on postoperative satisfaction and expectation fulfilment. Methods. In total, 204 primary TKA patients with osteoarthritis were enrolled in this randomized controlled trial (RCT). Patients were allocated to either usual preoperative education (control group) or usual education plus an additional module on realistic expectations (intervention group). Primary outcome was being very satisfied (numerical rating scale for satisfaction ≥ 8) with the treatment result at 12 months' follow-up. Other outcomes were change in preoperative expectations and postoperative expectation fulfilment. Results. A total of 187 patients (91.7%) were available for analysis at follow-up. In the intention-to-treat analysis, 58.5% (55/94) of patients were very satisfied with the treatment result in the control group, and 69.9% (65/93) of patients in the intervention group (adjusted odds ratio (AOR) 1.72, 95% confidence interval (CI) 0.90 to 3.29). A per-protocol analysis for patients who attended the education session (92.0%, n = 172) showed that 56.9% (49/86) of patients were very satisfied in the control group and 74.4% (61/86) in the intervention group (AOR 2.44, 95% CI 1.21 to 4.91). After preoperative education, the expectation scores in the intervention group were significantly lower (mean difference -6.9 (95% CI -10.2 to -3.6)) and did not alter in the control group (mean difference 0.5 (95% CI -2.9 to 3.9)). Overall, fulfilment of expectations at 12 months was significantly higher in the intervention group (mean difference 11.4% (95% CI 2.3 to 20.5)). Conclusion. Improved preoperative patient education can modify patient expectations, resulting in higher postoperative fulfilment of expectation and higher satisfaction in the group that attended the preoperative education. This is the first RCT to confirm the potential of improved expectation management on satisfaction after TKA. Cite this article: Bone Joint J 2021;103-B(4):619–626

Aims. Single-shot adductor canal block (ACB) after total knee arthroplasty (TKA) for postoperative analgesia is a common modality. Patients can experience breakthrough pain when the effect of ACB wears off. Local anaesthetic infusion through an intra-articular catheter (IAC) can help manage breakthrough pain after TKA. We hypothesized that combined ACB with ropivacaine infusion through IAC is associated with better pain relief compared to ACB used alone. Methods. This study was a prospective double-blinded placebo-controlled randomized controlled trial to compare the efficacy of combined ACB+ IAC-ropivacaine infusion (study group, n = 68) versus single-shot ACB+ intra-articular normal saline placebo (control group, n = 66) after primary TKA. The primary outcome was assessment of pain, using the visual analogue scale (VAS) recorded at 6, 12, 24, and 48 hours after surgery. Secondary outcomes included active knee ROM 48 hours after surgery and additional requirement of analgesia for breakthrough pain. Results. The study group (mean visual analogue scale (VAS) pain score of 5.5 (SD 0.889)) experienced significant reduction in pain 12 hours after surgery compared to the control group (mean VAS 6.62 (SD 1.356); mean difference = 1.12, 95% confidence interval (CI) -1.46 to 0.67; p < 0.001), and pain scores on postoperative day (POD) 1 and POD-2 were lower in the study group compared to the control group (mean difference in VAS pain = 1.04 (-1.39 to -0.68, 95% CI, p < 0.001). Fewer patients in the study group (0 vs 3 in the control group) required additional analgesia for breakthrough pain, but this was not statistically significant. The study group had significantly increased active knee flexion (mean flexion 86.4° (SD 7.22°)), compared to the control group (mean 73.86° (SD 7.88°), mean difference = 12.54, 95% CI 9.97 to 15.1; p < 0.014). Conclusion. Combined ACB+ ropivacaine infusion via IAC is a safe, reproducible analgesic modality after primary TKA, with superior analgesia compared to ACB alone. Further large volume trials are warranted to generate evidence on clinical significance on analgesia after TKA. Cite this article: Bone Jt Open 2021;2(12):1082–1088

Aims. Liposomal bupivacaine (LB) as part of a periarticular injection protocol continues to be a highly debated topic in total knee arthroplasty (TKA). We evaluated the effect of discontinuing the use of LB in a periarticular protocol on immediate postoperative pain scores, opioid consumption, and objective functional outcomes. Methods. On 1 July 2019, we discontinued the use of intraoperative LB as part of a periarticular injection protocol. A consecutive group of patients who received LB as part of the protocol (Protocol 1) and a subsequent group who did not (Protocol 2) were compared. All patients received the same opioid-sparing protocol. Verbal rating scale (VRS) pain scores were collected from our electronic data warehouse and averaged per patient per 12-hour interval. Events relating to the opiate administration were derived as morphine milligram equivalences (MMEs) per patient per 24-hour interval. The Activity Measure for Post-Acute Care (AM-PAC) tool was used to assess the immediate postoperative function. Results. A total of 888 patients received Protocol 1 and while 789 received Protocol 2. The mean age of the patients was significantly higher in those who did not receive LB (66.80 vs 65.57 years, p = 0.006). The sex, BMI, American Society of Anesthesiologists physical status score, race, smoking status, marital status, operating time, length of stay, and discharge disposition were similar in the two groups. Compared with the LB group, discontinuing LB showed no significant difference in postoperative VRS pain scores up to 72 hours (p > 0.05), opioid administration up to 96 hours (p > 0.05), or AM-PAC scores within the first 24 hours (p > 0.05). Conclusion. The control of pain after TKA with a multimodal management protocol is not improved by the addition of LB compared with traditional bupivacaine. Cite this article: Bone Joint J 2021;103-B(6 Supple A):102–107

Aims. The objective of this study was to compare the two-year migration pattern and clinical outcomes of a total knee arthroplasty (TKA) with an asymmetrical tibial design (Persona PS) and a well-proven TKA with a symmetrical tibial design (NexGen LPS). Methods. A randomized controlled radiostereometric analysis (RSA) trial was conducted including 75 cemented posterior-stabilized TKAs. Implant migration was measured with RSA. Maximum total point motion (MTPM), translations, rotations, clinical outcomes, and patient-reported outcome measures (PROMs) were assessed at one week postoperatively and at three, six, 12, and 24 months postoperatively. Results. A linear mixed-effect model using RSA data of 31 asymmetrical and 38 symmetrical TKAs did not show a difference in mean MTPM migration pattern of the tibial or femoral components. Mean tibial component MTPM at two years postoperative of the asymmetrical TKA design was 0.93 mm and 1.00 mm for the symmetrical design. For the femoral component these values were 1.04 mm and 1.14 mm, respectively. No significant differences were observed in other migration parameters or in clinical and PROM measurements. Conclusion. The TKA design with an asymmetrical tibial component has comparable component migration with the proven TKA with a symmetrical tibial component. This suggests the risk of long-term aseptic loosening of the two designs is comparable. Cite this article: Bone Joint J 2021;103-B(5):855–863

Aims. The primary aim of this study was to compare the postoperative systemic inflammatory response in conventional jig-based total knee arthroplasty (conventional TKA) versus robotic-arm assisted total knee arthroplasty (robotic TKA). Secondary aims were to compare the macroscopic soft tissue injury, femoral and tibial bone trauma, localized thermal response, and the accuracy of component positioning between the two treatment groups. Methods. This prospective randomized controlled trial included 30 patients with osteoarthritis of the knee undergoing conventional TKA versus robotic TKA. Predefined serum markers of inflammation and localized knee temperature were collected preoperatively and postoperatively at six hours, day 1, day 2, day 7, and day 28 following TKA. Blinded observers used the Macroscopic Soft Tissue Injury (MASTI) classification system to grade intraoperative periarticular soft tissue injury and bone trauma. Plain radiographs were used to assess the accuracy of achieving the planned postioning of the components in both groups. Results. Patients undergoing conventional TKA and robotic TKA had comparable changes in the postoperative systemic inflammatory and localized thermal response at six hours, day 1, day 2, and day 28 after surgery. Robotic TKA had significantly reduced levels of interleukin-6 (p < 0.001), tumour necrosis factor-α (p = 0.021), ESR (p = 0.001), CRP (p = 0.004), lactate dehydrogenase (p = 0.007), and creatine kinase (p = 0.004) at day 7 after surgery compared with conventional TKA. Robotic TKA was associated with significantly improved preservation of the periarticular soft tissue envelope (p < 0.001), and reduced femoral (p = 0.012) and tibial (p = 0.023) bone trauma compared with conventional TKA. Robotic TKA significantly improved the accuracy of achieving the planned limb alignment (p < 0.001), femoral component positioning (p < 0.001), and tibial component positioning (p < 0.001) compared with conventional TKA. Conclusion. Robotic TKA was associated with a transient reduction in the early (day 7) postoperative inflammatory response but there was no difference in the immediate (< 48 hours) or late (day 28) postoperative systemic inflammatory response compared with conventional TKA. Robotic TKA was associated with decreased iatrogenic periarticular soft tissue injury, reduced femoral and tibial bone trauma, and improved accuracy of component positioning compared with conventional TKA. Cite this article: Bone Joint J 2021;103-B(1):113–122

Aims. The Oswestry-Bristol Classification (OBC) is an MRI-specific assessment tool to grade trochlear dysplasia. The aim of this study is to validate clinically the OBC by demonstrating its use in selecting treatments that are safe and effective. Methods. The OBC and the patellotrochlear index were used as part of the Oswestry Patellotrochlear Algorithm (OPTA) to guide the surgical treatment of patients with patellar instability. Patients were assigned to one of four treatment groups: medial patellofemoral ligament reconstruction (MPFLr); MPFLr + tibial tubercle distalization (TTD); trochleoplasty; or trochleoplasty + TTD. A prospective analysis of a longitudinal patellofemoral database was performed. Between 2012 and 2018, 202 patients (233 knees) with a mean age of 24.2 years (SD 8.1), with recurrent patellar instability were treated by two fellowship-trained consultant sports/knee surgeons at The Robert Jones and Agnes Hunt Orthopaedic Hospital. Clinical efficacy of each treatment group was assessed by Kujala, International Knee Documentation Committee (IKDC), and EuroQol five-dimension questionnaire (EQ-5D) scores at baseline, and up to 60 months postoperatively. Their safety was assessed by complication rate and requirement for further surgery. The pattern of clinical outcome over time was analyzed using mixed regression modelling. Results. In all, 135 knees (mean age 24.9 years (SD 9.4)) were treated using a MPFLr. Ten knees (7.4%) required additional surgery. A total of 50 knees (mean age 24.4 years (SD 6.3)) were treated using MPFLr + TTD. Ten (20%) required additional surgery. A total of 20 knees (mean age 19.5 years (SD 3.0)) were treated using trochleoplasty + TTD. Three patients (15%) required additional surgery. In each treatment group, there was a significant improvement in Kujala, IKDC, and EQ-5D at one year postoperatively (p < 0.001) with a recognized level of overall complication rate. Conclusion. The OBC is a valid assessment tool to grade patients with trochlear dysplasia and, when used as part of the OPTA, helps to determine treatments that are safe and effective. This fulfils the requirements for its application in mainstream clinical practice. Cite this article: Bone Joint J 2021;103-B(10):1586–1594

Aims. The aims of this study were to investigate the ability to kneel after total knee arthroplasty (TKA) without patellar resurfacing, and its effect on patient-reported outcome measures (PROMs). Secondary aims included identifying which kneeling positions were most important to patients, and the influence of radiological parameters on the ability to kneel before and after TKA. Methods. This prospective longitudinal study involved 209 patients who underwent single radius cruciate-retaining TKA without patellar resurfacing. Preoperative EuroQol five-dimension questionnaire (EQ-5D), Oxford Knee Score (OKS), and the ability to achieve four kneeling positions were assessed including a single leg kneel, a double leg kneel, a high-flexion kneel, and a praying position. The severity of radiological osteoarthritis (OA) was graded and the pattern of OA was recorded intraoperatively. The flexion of the femoral component, posterior condylar offset, and anterior femoral offset were measured radiologically. At two to four years postoperatively, 151 patients with a mean age of 70.0 years (SD 9.44) were included. Their mean BMI was 30.4 kg/m. 2. (SD 5.36) and 60 were male (40%). They completed EQ-5D, OKS, and Kujala scores, assessments of the ability to kneel, and a visual analogue scale for anterior knee pain and satisfaction. Results. The ability to kneel in the four positions improved in between 29 (19%) and 53 patients (35%) after TKA, but declined in between 35 (23%) and 46 patients (30%). Single-leg kneeling was most important to patients. After TKA, 62 patients (41%) were unable to achieve a single-leg kneel, 76 (50%) were unable to achieve a double-leg kneel, 102 (68%) were unable to achieve a high-flexion kneel and 61 (40%) were unable to achieve a praying position. Posterolateral cartilage loss significantly affected preoperative deep flexion kneeling (p = 0.019). A postoperative inability to kneel was significantly associated with worse OKS, Kujala scores, and satisfaction (p < 0.05). Multivariable regression analysis identified significant independent associations with the ability to kneel after TKA (p < 0.05): better preoperative EQ-5D and flexion of the femoral component for single-leg kneeling; the ability to achieve it preoperatively and flexion of the femoral component for double-leg kneeling; male sex for high-flexion kneeling; and the ability to achieve it preoperatively, anterior femoral offset, and patellar cartilage loss for the praying position. Conclusion. The ability to kneel was important to patients and significantly influenced knee-specific PROMs, but was poorly restored by TKA with equal chances of improvement or decline. Cite this article: Bone Joint J 2021;103-B(9):1514–1525

Aims. To estimate the measurement properties for the Oxford Knee Score (OKS) in patients undergoing revision knee arthroplasty (responsiveness, minimal detectable change (MDC-90), minimal important change (MIC), minimal important difference (MID), internal consistency, construct validity, and interpretability). Methods. Secondary data analysis was performed for 10,727 patients undergoing revision knee arthroplasty between 2013 to 2019 using a UK national patient-reported outcome measure (PROM) dataset. Outcome data were collected before revision and at six months postoperatively, using the OKS and EuroQol five-dimension score (EQ-5D). Measurement properties were assessed according to COnsensus-based Standards for the selection of health status Measurement Instruments (COSMIN) guidelines. Results. A total of 9,219 patients had complete outcome data. Mean preoperative OKS was 16.7 points (SD 8.1), mean postoperative OKS 29.1 (SD 11.4), and mean change in OKS + 12.5 (SD 10.7). Median preoperative EQ-5D index was 0.260 (interquartile range (IQR) 0.055 to 0.691), median postoperative EQ-5D index 0.691 (IQR 0.516 to 0.796), and median change in EQ-5D index + 0.240 (IQR 0.000 to 0.567). Internal consistency was good with Cronbach’s α 0.88 (baseline) and 0.94 (post-revision). Construct validity found a high correlation of OKS total score with EQ-5D index (r = 0.76 (baseline), r = 0.83 (post-revision), p < 0.001). The OKS was responsive with standardized effect size (SES) 1.54 (95% confidence interval (CI) 1.51 to 1.57), compared to SES 0.83 (0.81 to 0.86) for the EQ-5D index. The MIC for the OKS was 7.5 points (95% CI 5.5 to 8.5) based on the optimal cut-off with specificity 0.72, sensitivity 0.60, and area under the curve 0.66. The MID for the OKS was 5.2 points. The MDC-90 was 3.9 points. The OKS did not demonstrate significant floor or ceiling effects. Conclusion. This study found that the OKS was a useful and valid instrument for assessment of outcome following revision knee arthroplasty. The OKS was responsive to change and demonstrated good measurement properties. Cite this article: Bone Joint J 2021;103-B(4):627–634

Aims. The primary objective of this study was to compare migration of the cemented ATTUNE fixed bearing cruciate retaining tibial component with the cemented Press-Fit Condylar (PFC)-sigma fixed bearing cruciate retaining tibial component. The secondary objectives included comparing clinical and radiological outcomes and Patient Reported Outcome Measures (PROMs). Methods. A single blinded randomized, non-inferiority study was conducted including 74 patients. Radiostereometry examinations were made after weight bearing, but before hospital discharge, and at three, six, 12, and 24 months postoperatively. PROMS were collected preoperatively and at three, six, 12, and 24 months postoperatively. Radiographs for measuring radiolucencies were collected at two weeks and two years postoperatively. Results. The overall migration (mean maximum total point motion (MPTM)) at two years was comparable: mean 1.13 mm (95% confidence interval (CI), 0.97 to 1.30) for the ATTUNE and 1.16 mm (95% CI, 0.99 to 1.35) for the PFC-sigma. At two years, the mean backward tilting was -0.43° (95% CI, -0.65 to -0.21) for the ATTUNE and 0.08° (95% CI -0.16 to 0.31), for the PFC-sigma. Overall migration between the first and second postoperative year was negligible for both components. The clinical outcomes and PROMs improved compared with preoperative scores and were not different between groups. Radiolucencies at the implant-cement interface were mainly seen below the medial baseplate: 17% in the ATTUNE and 3% in the PFC-sigma at two weeks, and at two years 42% and 9% respectively (p = 0.001). Conclusion. In the first two postoperative years the initial version of the ATTUNE tibial component was not inferior with respect to overall migration, although it showed relatively more backwards tilting and radiolucent lines at the implant-cement interface than the PFC-sigma. The version of the ATTUNE tibial component examined in this study has subsequently undergone modification by the manufacturer. Level of Evidence: 1 (randomized controlled clinical trial). Cite this article: Bone Joint J 2020;102-B(9):1158–1166

Aims. A limited number of investigations with conflicting results have described perivascular lymphocytic infiltration (PVLI) in the setting of total knee arthroplasty (TKA). The purpose of this study was to determine if PVLI found in TKAs at the time of aseptic revision surgery was associated with worse clinical outcomes and survivorship. Methods. A retrospective review was conducted on 617 patients who underwent aseptic TKA revision who had histological analysis for PVLI at the time of surgery. Clinical and radiological data were obtained pre- and postoperatively, six weeks postoperatively, and then every year thereafter. Results. Within this cohort, 118 patients (19.1%) were found to have PVLI on histological analysis. Re-revision was performed on 83 patients (13.4%) with no significant differences in all-cause or aseptic revisions between groups. A higher incidence of PVLI was noted in female patients (p = 0.037). There was no significant difference in improvement in the range of motion (p = 0.536), or improvement of KSC (p = 0.66), KSP (p = 0.61), or KSF (p = 0.3) clinical outcome scores between PVLI and no PVLI sub-groups. There was a higher incidence of a preoperative diagnosis of pain in the PVLI group compared with patients without PVLI (p = 0.002) present. Conclusion. PVLI found on large-scale histological analysis in TKAs at aseptic revision surgery was not associated with worse clinical outcomes or rates of re-revision. Cite this article: Bone Joint J 2021;103-B(6 Supple A):145–149

Aims. The optimal management of an infrapopliteal deep venous thrombosis (IDVT) following total knee arthroplasty (TKA) remains unknown. The risk of DVT propagation and symptom progression must be balanced against potential haemorrhagic complications associated with administration of anticoagulation therapy. The current study reports on a cohort of patients diagnosed with IDVT following TKA who were treated with aspirin, followed closely for development of symptoms, and scanned with ultrasound to determine resolution of IDVT. Methods. Among a cohort of 5,078 patients undergoing TKA, 532 patients (695 TKAs, 12.6%) developed an IDVT between 1 January 2014 to 31 December 2019 at a single institution, as diagnosed using Doppler ultrasound at the first postoperative visit. Of the entire cohort of 532 patients with IDVT, 91.4% (486/532) were treated with aspirin (325 mg twice daily) and followed closely. Repeat lower limb ultrasound was performed four weeks later to evaluate the status of IDVT. Results. Follow-up Doppler ultrasound was performed on 459/486 (94.4%) patients and demonstrated resolution of IDVT in 445/459 cases (96.9%). Doppler diagnosed propagation of IDVT to the popliteal vein had occurred in 10/459 (2.2%) cases. One patient with an IDVT developed a pulmonary embolus six weeks postoperatively. Conclusion. The results of this study demonstrate a low rate of IDVT propagation in patients managed with aspirin. Additionally, no significant bleeding episodes, wound-related complications, or other adverse events were noted from aspirin therapy. Cite this article: Bone Joint J 2021;103-B(6 Supple A):18–22

Aims. Stemmed tibial components are frequently used in revision total knee arthroplasty (TKA). The purpose of this study was to evaluate patient satisfaction, overall pain, and diaphyseal tibial pain in patients who underwent revision TKA with cemented or uncemented stemmed tibial components. Methods. This is a retrospective cohort study involving 110 patients with revision TKA with cemented versus uncemented stemmed tibial components. Patients who underwent revision TKA with stemmed tibial components over a 15-year period at a single institution with at least two-year follow-up were assessed. Pain was evaluated through postal surveys. There were 63 patients with cemented tibial stems and 47 with uncemented stems. Radiographs and Knee Society Scores were used to evaluate for objective findings associated with pain or patient dissatisfaction. Postal surveys were analyzed using Fisher’s exact test and the independent-samples t-test. Logistic regression was used to adjust for age, sex, and preoperative bone loss. Results. No statistically significant differences in stem length, operative side, or indications for revision were found between the two cohorts. Tibial pain at the end of the stem was present in 25.3% (16/63) of cemented stems and 25.5% (12/47) of uncemented stems (p = 1.000); 74.6% (47/63) of cemented patients and 78.7% (37/47) of uncemented patients were satisfied following revision TKA (p = 0.657). Conclusion. There were no differences in patient satisfaction, overall pain, and diaphyseal tibial pain in cemented and uncemented stemmed tibial components in revision TKA. Patient factors, rather than implant selection and surgical technique, likely play a large role in the presence of postoperative pain. Stemmed tibial components have been shown to be a possible source of pain in revision TKA. There is no difference in patient satisfaction or postoperative pain with cemented or uncemented stemmed tibial components in revision TKA. Cite this article: Bone Joint J 2021;103-B(6 Supple A):165–170

Aims. The purpose is to determine the non-inferiority of a smartphone-based exercise educational care management system after primary knee arthroplasty compared with a traditional in-person physiotherapy rehabilitation model. Methods. A multicentre prospective randomized controlled trial was conducted evaluating the use of a smartphone-based care management system for primary total knee arthroplasty (TKA) and partial knee arthroplasty (PKA). Patients in the control group (n = 244) received the respective institution’s standard of care with formal physiotherapy. The treatment group (n = 208) were provided a smartwatch and smartphone application. Early outcomes assessed included 90-day knee range of movement, EuroQoL five-dimension five-level score, Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS JR) score, 30-day single leg stance (SLS) time, Time up and Go (TUG) time, and need for manipulation under anaesthesia (MUA). Results. Overall, 90-day mean flexion was not significantly different between the control (121° (SD 11.7°)) and treatment groups (121. o. ; p = 0.559); 90-day mean SLS was 22.7 seconds (SD 9.8) in controls and 24.3 seconds (SD 20.8) in treatment (p = 0.519); 90-day mean TUG times were 10.1 seconds (SD 4.8) in control and 9.3 seconds (SD 3.3) in treatment (p = 0.139). Mean KOOS JR scores were significantly different between control group (73.6 (SD 13.4)) and treatment group (70.4 (SD 12.6); p = 0.026). MUAs were performed in nine (3.7%) patients in the control group and four (1.9%) in the treatment group (p = 0.398). Physiotherapy was performed by 230 (94.4%) of control group and 123 (59.3%) of treatment group (p < 0.001). There were no significant differences between groups in postoperative urgent care visits, or readmissions within 90 days, with significantly fewer emergency department visits in the treatment group (16 (8.2%) vs five (2.5%), p = 0.014). Conclusion. The use of the smartwatch/smartphone care platform demonstrated non-inferiority of clinically significant outcomes to traditional care models, while requiring significantly less postoperative physiotherapy and fewer emergency department visits. This platform could aid in decreasing postoperative costs, while improving patient engagement and communication with the healthcare team. Cite this article: Bone Joint J 2021;103-B(6 Supple A):3–12

Aims. The aim of this study was to identify the minimal clinically important difference (MCID), minimal important change (MIC), minimal detectable change (MDC), and patient-acceptable symptom state (PASS) threshold in the Forgotten Joint Score (FJS) according to patient satisfaction six months following total knee arthroplasty (TKA). Methods. During a one-year period 484 patients underwent a primary TKA and completed preoperative and six-month FJS and OKS. At six months patients were asked, “How satisfied are you with your operated knee?” Their response was recorded as: very satisfied, satisfied, neutral, dissatisfied, or very dissatisfied. The difference between patients recording neutral (n = 44) and satisfied (n = 153) was used to define the MCID. MIC for a cohort was defined as the change in the FJS for those patients declaring their outcome as satisfied, whereas receiver operating characteristic curve analysis was used to determine the MIC for an individual and the PASS threshold. Distribution-based methodology was used to calculate the MDC. Results. Using satisfaction as the anchor question, the MCID for the FJS was 16.6 (95% confidence interval (CIs) 8.9 to 24.3; p < 0.001) and when adjusting for confounding this decreased to 13.7 points (95% CI 4.8 to 22.5; p < 0.001). The MIC for the FJS for a cohort of patients was 17.7 points and for an individual patient was 10 points. The MDC90 for the FGS was 12 points; where 90% of patients scoring more than this will have experienced a real change that is beyond measurement error. The PASS was defined as 22 points or more in the postoperative FJS. Conclusion. The estimates for MCID and MIC can be used to assess whether there is clinical difference between two groups and whether a cohort/patient has had a meaningful change in their FJS, respectively. The MDC90 of 12 points suggests a value lower than this may fall within measurement error. A postoperative FJS of 22 or more was predictive of achieving PASS. Cite this article: Bone Joint J 2021;103-B(5):846–854

Aims. The aim of this study was to compare ten-year longitudinal healthcare costs and revision rates for patients undergoing unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA). Methods. The Humana database was used to compare 2,383 patients undergoing UKA between 2007 and 2009, who were matched 1:1 from a cohort of 63,036 patients undergoing primary TKA based on age, sex, and Elixhauser Comorbidity Index. Medical and surgical complications were tracked longitudinally for one year following surgery. Rates of revision surgery and cumulative mean healthcare costs were recorded for this period of time and compared between the cohorts. Results. Patients undergoing TKA had significantly higher rates of manipulation under anaesthesia (3.9% vs 0.9%; p < 0.001), deep vein thrombosis (5.0% vs 3.1%; p < 0.001), pulmonary embolism (1.5% vs 0.8%; p = 0.001), and renal failure (4.2% vs 2.2%; p < 0.001). Revision rates, however, were significantly higher for UKA at five years (6.0% vs 4.2%; p = 0.007) and ten years postoperatively (6.5% vs 4.4%; p = 0.002). Longitudinal-related healthcare costs for patients undergoing TKA were greater than for those undergoing UKA at one year ($24,771 vs $22,071; p < 0.001) and five years following surgery ($26,549 vs $25,730; p < 0.001); however, the mean costs of TKA were comparable to UKA at ten years ($26,877 vs $26,891; p = 0.425). Conclusion. Despite higher revision rates, patients undergoing UKA had lower mean healthcare costs than those undergoing TKA up to ten years following the procedure, at which time costs were comparable. In the era of value-based care, surgeons and policymakers should be aware of the costs involved with these procedures. UKA was associated with fewer complications at one year postoperatively but higher revision rates at five and ten years. While UKA was significantly less costly than TKA at one and five years, costs at ten years were comparable with a mean difference of only $14. Lowering the risk of revision surgery should be targeted as a source of cost savings for both UKA and TKA as the mean related healthcare costs were 2.5-fold higher in patients requiring revision surgery. Cite this article: Bone Joint J 2021;103-B(6 Supple A):23–31

Aims. Neither a surgeon’s intraoperative impression nor the parameters of computer navigation have been shown to be predictive of the outcomes following total knee arthroplasty (TKA). The aim of this study was to determine whether a surgeon, with robotic assistance, can predict the outcome as assessed using the Knee Injury and Osteoarthritis Outcome Score (KOOS) for pain (KPS), one year postoperatively, and establish what factors correlate with poor KOOS scores in a well-aligned and balanced TKA. Methods. A total of 134 consecutive patients who underwent TKA using a dynamic ligament tensioning robotic system with a tibia first resection technique and a cruciate sacrificing ultracongruent TKA system were enrolled into a prospective study. Each TKA was graded based on the final mediolateral ligament balance at 10° and 90° of flexion: 1) < 1 mm difference in the thickness of the tibial insert and that which was planned (n = 75); 2) < 1 mm difference (n = 26); 3) between 1 mm to 2 mm difference (n = 26); and 4) > 2 mm difference (n = 7). The mean one-year KPS score for each grade of TKA was compared and the likelihood of achieving an KPS score of > 90 was calculated. Finally, the factors associated with lower KPS despite achieving a high-grade TKA (grade A and B) were analyzed. Results. Patients with a grade of A or B TKA had significantly higher mean one-year KPS scores compared with those with C or D grades (p = 0.031). There was no difference in KPS scores in grade A or B TKAs, but 33% of these patients did not have a KPS score of > 90. While there was no correlation with age, sex, preoperative deformity, and preoperative KOOS and Patient-Reported Outcomes Measurement Information System (PROMIS) physical scores, patients with a KPS score of < 90, despite a grade A or B TKA, had lower PROMIS mental health scores compared with those with KPS scores of > 90 (54.1 vs 50.8; p = 0.043). Patients with grade A and B TKAs with KPS > 90 were significantly more likely to respond with “my expectations were too low”, and with “the knee is performing better than expected” compared with patients with these grades of TKA who had a KPS score of < 90 (40% vs 22%; p = 0.004). Conclusion. A TKA balanced with robotic assistance to within 1 mm of difference between the medial and lateral sides in both flexion and extension had a higher KPS score one year postoperatively. Despite accurate ligament balance information, a robotic system could not guarantee excellent pain relief. Patient expectations and mental status also significantly affected the perceived success of TKA. Cite this article: Bone Joint J 2021;103-B(6 Supple A):67–73

Aims. It has been shown that the preoperative modification of risk factors associated with obesity may reduce complications after total knee arthroplasty (TKA). However, the optimal method of doing so remains unclear. The aim of this study was to investigate whether a preoperative Risk Stratification Tool (RST) devised in our institution could reduce unexpected intensive care unit (ICU) transfers and 90-day emergency department (ED) visits, readmissions, and reoperations after TKA in obese patients. Methods. We retrospectively reviewed 1,614 consecutive patients undergoing primary unilateral TKA. Their mean age was 65.1 years (17.9 to 87.7) and the mean BMI was 34.2 kg/m. 2. (SD 7.7). All patients underwent perioperative optimization and monitoring using the RST, which is a validated calculation tool that provides a recommendation for postoperative ICU care or increased nursing support. Patients were divided into three groups: non-obese (BMI < 30 kg/m. 2. , n = 512); obese (BMI 30 kg/m. 2. to 39.9 kg/m. 2. , n = 748); and morbidly obese (BMI > 40 kg/m. 2. , n = 354). Logistic regression analysis was used to evaluate the outcomes among the groups adjusted for age, sex, smoking, and diabetes. Results. Obese patients had a significantly increased rate of discharge to a rehabilitation facility compared with non-obese patients (38.7% (426/1,102) vs 26.0% (133/512), respectively; p < 0.001). When stratified by BMI, discharge to a rehabilitation facility remained significantly higher compared with non-obese (26.0% (133)) in both obese (34.2% (256), odds ratio (OR) 1.6) and morbidly obese (48.0% (170), OR 3.1) patients (p < 0.001). However, there was no significant difference in unexpected ICU transfer (0.4% (two) non-obese vs 0.9% (seven) obese (OR 2.5) vs 1.7% (six) morbidly obese (OR 5.4); p = 0.054), visits to the ED (8.6% (44) vs 10.3% (77) (OR 1.3) vs 10.5% (37) (OR 1.2); p = 0.379), readmissions (4.5% (23) vs 4.0% (30) (OR 1.0) vs 5.1% (18) (OR 1.4); p = 0.322), or reoperations (2.5% (13) vs 3.3% (25) (OR 1.2) vs 3.1% (11) (OR 0.9); p = 0.939). Conclusion. With the use of a preoperative RST, morbidly obese patients had similar rates of short-term postoperative adverse outcomes after primary TKA as non-obese patients. This supports the assertion that morbidly obese patients can safely undergo TKA with appropriate perioperative optimization and monitoring. Cite this article: Bone Joint J 2021;103-B(6 Supple A):45–50

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. A significant percentage of patients remain dissatisfied after total knee arthroplasty (TKA). The aim of this study was to determine whether the sequential addition of accelerometer-based navigation for femoral component preparation and sensor-guided ligament balancing improved complication rates, radiological alignment, or patient-reported outcomes (PROMs) compared with a historical control group using conventional instrumentation. Methods. This retrospective cohort study included 371 TKAs performed by a single surgeon sequentially. A historical control group, with the use of intramedullary guides for distal femoral resection and surgeon-guided ligament balancing, was compared with a group using accelerometer-based navigation for distal femoral resection and surgeon-guided balancing (group 1), and one using navigated femoral resection and sensor-guided balancing (group 2). Primary outcome measures were Patient-Reported Outcomes Measurement Information System (PROMIS) and Knee injury and Osteoarthritis Outcome (KOOS) scores measured preoperatively and at six weeks and 12 months postoperatively. The position of the components and the mechanical axis of the limb were measured postoperatively. The postoperative range of motion (ROM), haematocrit change, and complications were also recorded. Results. There were 194 patients in the control group, 103 in group 1, and 74 in group 2. There were no significant differences in baseline demographics between the groups. Patients in group 2 had significantly higher baseline mental health subscores than control and group 1 patients (53.2 vs 50.2 vs 50.2, p = 0.041). There were no significant differences in any PROMs at six weeks or 12 months postoperatively (p > 0.05). There was no difference in the rate of manipulation under anaesthesia (MUA), complication rates, postoperative ROM, or blood loss. There were fewer mechanical axis outliers in groups 1 and 2 (25.2%, 14.9% respectively) versus control (28.4%), but this was not statistically significant (p = 0.10). Conclusion. The sequential addition of navigation of the distal femoral cut and sensor-guided ligament balancing did not improve short-term PROMs, radiological outcomes, or complication rates compared with conventional techniques. The costs of these added technologies may not be justified. Cite this article: Bone Joint J 2020;102-B(6 Supple A):24–30

Aims. The aim of this study was to compare robotic arm-assisted bi-unicompartmental knee arthroplasty (bi-UKA) with conventional mechanically aligned total knee arthroplasty (TKA) in order to determine the changes in the anatomy of the knee and alignment of the lower limb following surgery. Methods. An analysis of 38 patients who underwent TKA and 32 who underwent bi-UKA was performed as a secondary study from a prospective, single-centre, randomized controlled trial. CT imaging was used to measure coronal, sagittal, and axial alignment of the knee preoperatively and at three months postoperatively to determine changes in anatomy that had occurred as a result of the surgery. The hip-knee-ankle angle (HKAA) was also measured to identify any differences between the two groups. Results. The pre- to postoperative changes in joint anatomy were significantly less in patients undergoing bi-UKA in all three planes in both the femur and tibia, except for femoral sagittal component orientation in which there was no difference. Overall, for the six parameters of alignment (three femoral and three tibial), 47% of bi-UKAs and 24% TKAs had a change of < 2° (p = 0.045). The change in HKAA towards neutral in varus and valgus knees was significantly less in patients undergoing bi-UKA compared with those undergoing TKA (p < 0.001). Alignment was neutral in those undergoing TKA (mean 179.5° (SD 3.2°)) while those undergoing bi-UKA had mild residual varus or valgus alignment (mean 177.8° (SD 3.4°)) (p < 0.001). Conclusion. Robotic-assisted, cruciate-sparing bi-UKA maintains the natural anatomy of the knee in the coronal, sagittal, and axial planes better, and may therefore preserve normal joint kinematics, compared with a mechanically aligned TKA. This includes preservation of coronal joint line obliquity. HKAA alignment was corrected towards neutral significantly less in patients undergoing bi-UKA, which may represent restoration of the pre-disease constitutional alignment (p < 0.001). Cite this article: Bone Joint J 2020;102-B(11):1511–1518

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. 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. To describe the risk of periprosthetic joint infection (PJI) and reoperation in patients who have an acute, traumatic wound dehiscence following total knee arthroplasty (TKA). Methods. From January 2002 to December 2018, 16,134 primary TKAs were performed at a single institution. A total of 26 patients (0.1%) had a traumatic wound dehiscence within the first 30 days. Mean age was 68 years (44 to 87), 38% (n = 10) were female, and mean BMI was 34 kg/m. 2. (23 to 48). Median time to dehiscence was 13 days (interquartile range (IQR) 4 to 15). The dehiscence resulted from a fall in 22 patients and sudden flexion after staple removal in four. The arthrotomy was also disrupted in 58% (n = 15), including a complete extensor mechanism disruption in four knees. An irrigation and debridement with component retention (IDCR) was performed within 48 hours in 19 of 26 knees and two-thirds were discharged on antibiotic therapy. The mean follow-up was six years (2 to 15). The association of wound dehiscence and the risk of developing a PJI was analyzed. Results. Patients who sustained a traumatic wound dehiscence had a 6.5-fold increase in the risk of PJI (95% confidence interval (CI) 1.6 to 26.2; p = 0.008). With the small number of PJIs, no variables were found to be significant risk factors. However, there were no PJIs in any of the patients who were treated with IDCR and a course of antibiotics. Three knees required reoperation including one two-stage exchange for PJI, one repeat IDCR for PJI, and one revision for aseptic loosening of the tibial component. Conclusion. Despite having a traumatic wound dehiscence, the risk of PJI was low, but much higher than experienced in all other TKAs during the same period. We recommend urgent IDCR and a course of postoperative antibiotics to decrease the risk of PJI. A traumatic wound dehiscence increases risk of PJI by 6.5-fold. Cite this article: Bone Joint J 2021;103-B(6 Supple A):191–195

Aims. Infection complicating primary total knee arthroplasty (TKA) is a common reason for revision surgery, hospital readmission, patient morbidity, and mortality. Increasing incidence of methicillin-resistant Staphylococcus aureus (MRSA) is a particular concern. The use of vancomycin as prophylactic agent alone or in combination with cephalosporin has not demonstrated lower periprosthetic joint infection (PJI) rates, partly due to timing and dosing of intravenous (IV) vancomycin administration, which have proven important factors in effectiveness. This is a retrospective review of a consecutive series of primary TKAs examining incidence of PJI, adverse reactions, and complications using IV versus intraosseous (IO) vancomycin at 30-day, 90-day, and one-year follow-up. Methods. A retrospective review of 1,060 patients who underwent TKA between May 2016 to July 2020 was performed. There were 572 patients in the IV group and 488 in the IO group, with minimal 30 days of follow-up. Patients were followed up at regularly scheduled intervals (two, six, and 12 weeks). No differences between groups for age, sex, BMI, or baseline comorbidities existed. The IV group received an IV dose of 15 mg/kg vancomycin given over an hour preceding skin incision. The IO group received a 500 mg dose of vancomycin mixed in 150 ml of normal saline, injected into proximal tibia after tourniquet inflation, before skin incision. All patients received an additional dose of first generation cephalosporin. Evaluation included preoperative and postoperative serum creatinine values, tourniquet time, and adverse reactions attributable to vancomycin. Results. Incidence of PJI with minimum 90-day follow-up was 1.4% (eight knees) in the IV group and 0.22% (one knee) in IO group (p = 0.047). This preliminary report demonstrated an reduction in the incidence of infection in TKA using IO vancomycin combined with a first-generation cephalosporin. While the study suffers from limitations of a retrospective, multi-surgeon investigation, early findings are encouraging. Conclusion. IO delivery of vancomycin after tourniquet inflation is a safe and effective alternative to IV administration, eliminating the logistical challenges of timely dosing. Cite this article: Bone Joint J 2021;103-B(6 Supple A):13–17

Aims. Many surgeons choose to perform total knee arthroplasty (TKA) surgery with the aid of a tourniquet. A tourniquet is a device that fits around the leg and restricts blood flow to the limb. There is a need to understand whether tourniquets are safe, and if they benefit, or harm, patients. The aim of this study was to determine the benefits and harms of tourniquet use in TKA surgery. Methods. We searched MEDLINE, EMBASE, Cochrane Central Register of Controlled trials, and trial registries up to 26 March 2020. We included randomized controlled trials (RCTs), comparing TKA with a tourniquet versus without a tourniquet. Outcomes included: pain, function, serious adverse events (SAEs), blood loss, implant stability, duration of surgery, and length of hospital stay. Results. We included 41 RCTs with 2,819 participants. SAEs were significantly more common in the tourniquet group (53/901 vs 26/898, tourniquet vs no tourniquet respectively) (risk ratio 1.73 (95% confidence interval (CI) 1.10 to 2.73). The mean pain score on the first postoperative day was 1.25 points higher (95% CI 0.32 to 2.19) in the tourniquet group. Overall blood loss did not differ between groups (mean difference 8.61 ml; 95% CI -83.76 to 100.97). The mean length of hospital stay was 0.34 days longer in the group that had surgery with a tourniquet (95% CI 0.03 to 0.64) and the mean duration of surgery was 3.7 minutes shorter (95% CI -5.53 to -1.87). Conclusion. TKA with a tourniquet is associated with an increased risk of SAEs, pain, and a marginally longer hospital stay. The only finding in favour of tourniquet use was a shorter time in theatre. The results make it difficult to justify the routine use of a tourniquet in TKA surgery. Cite this article: Bone Joint J 2021;103-B(5):830–839

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. Although total knee arthroplasty (TKA) is a highly successful procedure, about 20% of patients remain dissatisfied postoperatively. This proportion is derived from dichotomous models of the assessment of surgical success or failure, which may not reflect the spectrum of outcomes. The aim of this study was to explore differing responses to surgery, and assess whether there are distinct groups of patients with differing patterns of outcome. Methods. This was a secondary analysis of a UK multicentre TKA longitudinal cohort study. We used a group-based trajectory modelling analysis of Oxford Knee Score (OKS) in the first year following surgery with longitudinal data involving five different timepoints and multiple predictor variables. Associations between the derived trajectory groups and categorical baseline variables were assessed, and predictors of trajectory group membership were identified using Poisson regression and multinomial logistic regression, as appropriate. The final model was adjusted for sociodemographic factors (age, sex) and baseline OKS. Results. Data from 731 patients were available for analysis. Three distinct trajectories of outcome were identified: “poor” 14.0%, “modest” 39.1%, and “good” 46.9%. The predicted probability of membership for patients assigned to each trajectory group was high (0.89 to 0.93). Preoperative mental, physical health, and psychosocial factors determined which trajectory is likely to be followed. Poor responders were characterized by a comparatively small number of factors, preoperative expectations of pain and limitations, coping strategies, and a lower baseline physical health status, while the good responders were characterized by a combination of clinical, psychosocial, mental health, and quality of life factors. Conclusion. We identified three distinct response trajectories in patients undergoing TKA. Controlling for baseline score, age, and sex, psychosocial factors such as expectations of pain and limited function and poor coping strategies differentiated the trajectory groups, suggesting a role for preoperative psychosocial support in optimizing the clinical outcome. Cite this article: Bone Joint J 2021;103-B(6):1096–1102

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. Periprosthetic joint infection (PJI) is a devastating complication following total knee arthroplasty (TKA). Two-stage revision has traditionally been considered the gold standard of treatment for established infection, but increasing evidence is emerging in support of one-stage exchange for selected patients. The objective of this study was to determine the outcomes of single-stage revision TKA for PJI, with mid-term follow-up. Methods. A total of 84 patients, with a mean age of 68 years (36 to 92), underwent single-stage revision TKA for confirmed PJI at a single institution between 2006 and 2016. In all, 37 patients (44%) were treated for an infected primary TKA, while the majority presented with infected revisions: 31 had undergone one previous revision (36.9%) and 16 had multiple prior revisions (19.1%). Contraindications to single-stage exchange included systemic sepsis, extensive bone or soft-tissue loss, extensor mechanism failure, or if primary wound closure was unlikely to be achievable. Patients were not excluded for culture-negative PJI or the presence of a sinus. Results. Overall, 76 patients (90.5%) were infection-free at a mean follow-up of seven years, with eight reinfections (9.5%). Culture-negative PJI was not associated with a higher reinfection rate (p = 0.343). However, there was a significantly higher rate of recurrence in patients with polymicrobial infections (p = 0.003). The mean Oxford Knee Score (OKS) improved from 18.7 (SD 8.7) preoperatively to 33.8 (SD 9.7) at six months postoperatively (p < 0.001). The Kaplan-Meier implant survival rate for all causes of reoperation, including reinfection and aseptic failure, was 95.2% at one year (95% confidence interval (CI) 87.7 to 98.2), 83.5% at five years (95% CI 73.2 to 90.3), and 78.9% at 12 years (95% CI 66.8 to 87.2). Conclusion. One-stage exchange, using a strict debridement protocol and multidisciplinary input, is an effective treatment option for the infected TKA. This is the largest single-surgeon series of consecutive cases reported to date, with broad inclusion criteria. Cite this article: Bone Jt Open 2021;2(5):305–313

Aims. To compare time dependent functional improvement for patients with medial, respectively lateral knee osteoarthritis (OA) after treatment with opening wedge osteotomy relieving the pressure on the osteoarthritic part of the knee. Methods. In all, 49 patients (52 knees) with a mean age of 47 years (31 to 64) underwent high tibial osteotomies (HTO), and 24 patients with a mean age of 48 years (31 to 62) low femoral osteotomies (LFO) with opening wedge technique due to medial, respectively lateral knee OA with malalignment. All osteotomies were stabilized with a Puddu plate and bone grafting performed in the same time period (2000 to 2008). The patients were evaluated by the Knee Injury and Osteoarthritis Outcome Score (KOOS) pre-operatively and at six months, and at one, two, five, and ten years postoperatively. The knee OA was graded according to the Ahlbäck and Kellgren-Lawrence radiological scoring systems. Results. The mean angular corrections were 8.0° (4° to 12°) for the HTO and 9.6° (4° to 20°) for the LFO. Both the pre-operative KOOS and the osteoarthritic gradings were similar for the two patient groups. The five subscores of KOOS increased significantly during the postoperative period (p < 0.001 to 0.029) levelling out after one year in both groups. The KOOS subscore symptoms was significantly higher for patients with HTO than those with LFO at all follow-up times, for sport and recreation in the period one to five years, and for pain and quality of life at two to five years (p < 0.001 to 0.009). Eight HTOs (15%) and five LFOs (21%) were converted to total knee arthroplasty after mean 6.7 years (2.0 to 9.8) and 5.4 years (4.0 to 8.0) respectively. The ten-year osteotomy survival rates were 88% for the HTO and 79% for the LFO (p = 0.745). Conclusion. Patients with unicompartmental knee OA improved after a corrective opening wedge osteotomy, but four of the five subscores of KOOS were significantly higher for those with medial than those with lateral OA in most of the ten-year follow-up period. Cite this article: Bone Joint Open 2020;1-7:346–354

Aims. The aim of this study was to assess the influence of obesity on the clinical outcomes and survivorship ten years postoperatively in patients who underwent a fixed-bearing unicompartmental knee arthroplasty (UKA). Patients and Methods. We prospectively followed 184 patients who underwent UKA between 2003 and 2007 for a minimum of ten years. A total of 142 patients with preoperative body mass index (BMI) of < 30 kg/m. 2. were in the control group (32 male, 110 female) and 42 patients with BMI of ≥ 30 kg/m. 2. were in the obese group (five male, 37 female). Pre- and postoperative range of movement (ROM), Knee Society Score (KSS), Oxford Knee Score (OKS), 36-Item Short-Form Health Survey (SF-36), and survivorship were analyzed. Results. Patients in the obese group underwent UKA at a significantly younger mean age (56.5 years (. sd. 6.4)) than those in the control group (62.4 years (. sd. 7.8); p < 0.001). There was no significant difference in preoperative functional scores. However, those in the obese group had a significantly lower ROM (116° (. sd. 15°) vs 123° (. sd. 17°); p = 0.003). Both groups achieved significant improvement in outcome scores regardless of BMI, ten years postoperatively. All patients achieved the minimal clinically important difference (MCID) for OKS and KSS. Both groups also had high rates of satisfaction (96.3% in the control group and 97.5% in the obese group) and the fulfilment of expectations (94.9% in the control group and 95.0% in the obese group). Multiple linear regression showed a clear association between obesity and a lower OKS two years postoperatively and Knee Society Function Score (KSFS) ten years postoperatively. After applying propensity matching, obese patients had a significantly lower KSFS, OKS, and physical component score (PCS) ten years postoperatively. Seven patients underwent revision to total knee arthroplasty (TKA), two in the control group and five in the obese group, resulting in a mean rate of survival at ten years of 98.6% and 88.1%, respectively (p = 0.012). Conclusion. Both groups had significant improvements in functional and quality-of-life scores postoperatively. However, obesity was a significant predictor of poorer improvement in clinical outcome and an increased rate of revision ten years postoperatively

Aims. The primary aim of the study was to compare the knee-specific functional outcome of robotic unicompartmental knee arthroplasty (rUKA) with manual total knee arthroplasty (mTKA) for the management of isolated medial compartment osteoarthritis. Secondary aims were to compare length of hospital stay, general health improvement, and satisfaction between rUKA and mTKA. Methods. A powered (1:3 ratio) cohort study was performed. A total of 30 patients undergoing rUKA were propensity score matched to 90 patients undergoing mTKA for isolated medial compartment arthritis. Patients were matched for age, sex, body mass index (BMI), and preoperative function. The Oxford Knee Score (OKS) and EuroQol five-dimension questionnaire (EQ-5D) were collected preoperatively and six months postoperatively. The Forgotten Joint Score (FJS) and patient satisfaction were collected six months postoperatively. Length of hospital stay was also recorded. Results. There were no significant differences in the preoperative demographics (p ⩾ 0.150) or function (p ⩾ 0.230) between the groups. The six-month OKS was significantly greater in the rUKA group when compared with the mTKA group (difference 7.7, p < 0.001). There was also a greater six-month postoperative EQ-5D (difference 0.148, p = 0.002) and FJS (difference 24.2, p < 0.001) for the rUKA when compared to the mTKA. No patient was dissatisfied in the rUKA group and five (6%) were dissatisfied in the mTKA, but this was not significant (p = 0.210). Length of stay was significantly (p < 0.001) shorter in the rUKA group (median two days, interquartile range (IQR) 1 to 3) compared to the mTKA (median four days, IQR 3 to 5). Conclusion. Patients with isolated medial compartment arthritis had a greater knee-specific functional outcome and generic health with a shorter length of hospital stay after rUKA when compared to mTKA. Cite this article: Bone Joint Res 2019;9(1):15–22

Aims. The aim of this study was to assess the effectiveness of perioperative essential amino acid (EAA) supplementation to prevent rectus femoris muscle atrophy and facilitate early recovery of function after total knee arthroplasty (TKA). Methods. The study involved 60 patients who underwent unilateral TKA for primary knee osteo-arthritis (OA). This was a double-blind, placebo-controlled, randomized control trial with patients randomly allocated to two groups, 30 patients each: the essential amino acid supplementation (9 g daily) and placebo (lactose powder, 9 g daily) groups. Supplementation and placebo were provided from one week before to two weeks after surgery. The area of the rectus femoris muscle were measured by ultrasound imaging one month before surgery and one, two, three, and four weeks postoperatively. The serum albumin level, a visual analogue knee pain score, and mobility were also measured at each time point. The time to recovery of activities of daily living (ADLs) was recorded. Postoperative nutrition and physiotherapy were identical in both groups. Results. The mean relative change from baseline was as follows for the amino acid group: 116% in rectus femoris muscle area (71% to 206%); 95% in serum albumin (80% to 115%) and 39% in VAS pain (0% to 100%) at four weeks after surgery. These values in the placebo group were: 97% in muscle area (68 to 155); 89% in serum albumin (71% to 100%) and 56% in VAS pain four weeks after surgery (0% to 100%). All changes were statistically significant (p < 0.05). The mean time to recovery of ADLs was shorter in the amino acid group compared with the placebo group (p = 0.005). Conclusion. Perioperative essential amino acid supplementation prevents rectus femoris muscle atrophy and accelerates early functional recovery after TKA. Cite this article: Bone Joint J 2020;102-B(6 Supple A):10–18

Aims. Ideal component sizing may be difficult to achieve in unicompartmental knee arthroplasty (UKA). Anatomical variants, incremental implant size, and a reduced surgical exposure may lead to over- or under-sizing of the components. The purpose of this study was to compare the accuracy of UKA sizing with robotic-assisted techniques versus a conventional surgical technique. Methods. Three groups of 93 medial UKAs were assessed. The first group was performed by a conventional technique, the second group with an image-free robotic-assisted system (Image-Free group), and the last group with an image-based robotic arm-assisted system, using a preoperative CT scan (Image-Based group). There were no demographic differences between groups. We compared six parameters on postoperative radiographs to assess UKA sizing. Incorrect sizing was defined by an over- or under-sizing greater than 3 mm. Results. There was a higher rate of tibial under-sizing posteriorly in the conventional group compared to robotic-assisted groups (47.3% (n = 44) in conventional group, 29% (n = 27) in Image-Free group, 6.5% (n = 6) in Image-Based group; p < 0.001), as well as a higher rate of femoral under-sizing posteriorly (30.1% (n = 28) in conventional group, 7.5% (n = 7) in Image-Free group, 12.9% (n = 12) in Image-Based group; p < 0.001). The posterior femoral offset was more often increased in the conventional group, especially in comparison to the Image-Based group (43% (n = 40) in conventional group, 30.1% (n = 28) in Image-Free group, 8.6% (n = 8) in Image-Based group; p < 0.001). There was no significant overhang of the femoral or tibial implant in any groups. Conclusion. Robotic-assisted surgical techniques for medial UKA decrease the risk of tibial and femoral under-sizing, particularly with an image-based system using a preoperative CT scan. Cite this article: Bone Joint J 2021;103-B(4):610–618

Aims. The aim of this study was to examine whether tourniquet use can improve perioperative blood loss, early function recovery, and pain after primary total knee arthroplasty (TKA) in the setting of multiple-dose intravenous tranexamic acid. Methods. This was a prospective, randomized clinical trial including 180 patients undergoing TKA with multiple doses of intravenous tranexamic acid. One group was treated with a tourniquet during the entire procedure, the second group received a tourniquet during cementing, and the third group did not receive a tourniquet. All patients received the same protocol of intravenous tranexamic acid (20 mg/kg) before skin incision, and three and six hours later (10 mg/kg). The primary outcome measure was perioperative blood loss. Secondary outcome measures were creatine kinase (CK), CRP, interleukin-6 (IL-6), visual analogue scale (VAS) pain score, limb swelling ratio, quadriceps strength, straight leg raising, range of motion (ROM), American Knee Society Score (KSS), and adverse events. Results. The mean total blood loss was lowest in the no-tourniquet group at 867.32 ml (SD 201.11), increased in the limited-tourniquet group at 1024.35 ml (SD 176.35), and was highest in the tourniquet group at 1,213.00 ml (SD 211.48). The hidden blood loss was lowest in the no-tourniquet group (both p < 0.001). There was less mean intraoperative blood loss in the tourniquet group (77.48 ml (SD 24.82)) than in the limited-tourniquet group (137.04 ml (SD 26.96)) and the no-tourniquet group (212.99 ml (SD 56.35); both p < 0.001). Patients in the tourniquet group showed significantly higher levels of muscle damage and inflammation biomarkers such as CK, CRP, and IL-6 than the other two groups (p < 0.05). Outcomes for VAS pain scores, limb swelling ratio, quadriceps strength, straight leg raising, ROM, and KSS were significantly better in the no-tourniquet group at three weeks postoperatively (p < 0.05), but there were no significant differences at three months. No significant differences were observed among the three groups with respect to transfusion rate, thrombotic events, or the length of hospital stay. Conclusion. Patients who underwent TKA with multiple doses of intravenous tranexamic acid but without a tourniquet presented lower total blood loss and hidden blood loss, and they showed less postoperative inflammation reaction, less muscle damage, lower VAS pain score, and better early knee function. Our results argue for not using a tourniquet during TKA. Cite this article: Bone Joint Res 2020;9(6):322–332

Aims. The objectives of this study were to compare postoperative pain, analgesia requirements, inpatient functional rehabilitation, time to hospital discharge, and complications in patients undergoing conventional jig-based unicompartmental knee arthroplasty (UKA) versus robotic-arm assisted UKA. Patients and Methods. This prospective cohort study included 146 patients with symptomatic medial compartment knee osteoarthritis undergoing primary UKA performed by a single surgeon. This included 73 consecutive patients undergoing conventional jig-based mobile bearing UKA, followed by 73 consecutive patients receiving robotic-arm assisted fixed bearing UKA. All surgical procedures were performed using the standard medial parapatellar approach for UKA, and all patients underwent the same postoperative rehabilitation programme. Postoperative pain scores on the numerical rating scale and opiate analgesia consumption were recorded until discharge. Time to attainment of predefined functional rehabilitation outcomes, hospital discharge, and postoperative complications were recorded by independent observers. Results. Robotic-arm assisted UKA was associated with reduced postoperative pain (p < 0.001), decreased opiate analgesia requirements (p < 0.001), shorter time to straight leg raise (p < 0.001), decreased number of physiotherapy sessions (p < 0.001), and increased maximum knee flexion at discharge (p < 0.001) compared with conventional jig-based UKA. Mean time to hospital discharge was reduced in robotic UKA compared with conventional UKA (42.5 hours (. sd 5.9). vs 71.1 hours (. sd. 14.6), respectively; p < 0.001). There was no difference in postoperative complications between the two groups within 90 days’ follow-up. Conclusion. Robotic-arm assisted UKA was associated with decreased postoperative pain, reduced opiate analgesia requirements, improved early functional rehabilitation, and shorter time to hospital discharge compared with conventional jig-based UKA

Aims. Total knee arthroplasty (TKA) using functional alignment aims to implant the components with minimal compromise of the soft-tissue envelope by restoring the plane and obliquity of the non-arthritic joint. The objective of this study was to determine the effect of TKA with functional alignment on mediolateral soft-tissue balance as assessed using intraoperative sensor-guided technology. Methods. This prospective study included 30 consecutive patients undergoing robotic-assisted TKA using the Stryker PS Triathlon implant with functional alignment. Intraoperative soft-tissue balance was assessed using sensor-guided technology after definitive component implantation; soft-tissue balance was defined as intercompartmental pressure difference (ICPD) of < 15 psi. Medial and lateral compartment pressures were recorded at 10°, 45°, and 90° of knee flexion. This study included 18 females (60%) and 12 males (40%) with a mean age of 65.2 years (SD 9.3). Mean preoperative hip-knee-ankle deformity was 6.3° varus (SD 2.7°). Results. TKA with functional alignment achieved balanced medial and lateral compartment pressures at 10° (25.0 psi (SD 6.1) vs 23.1 psi (SD 6.7), respectively; p = 0.140), 45° (21.4 psi (SD 5.9) vs 20.6 psi (SD 5.9), respectively; p = 0.510), and 90° (21.2 psi (SD 7.1) vs 21.6 psi (SD 9.0), respectively; p = 0.800) of knee flexion. Mean ICPD was 6.1 psi (SD 4.5; 0 to 14) at 10°, 5.4 psi (SD 3.9; 0 to 12) at 45°, and 4.9 psi (SD 4.45; 0 to 15) at 90° of knee flexion. Mean postoperative limb alignment was 2.2° varus (SD 1.0°). Conclusion. TKA using the functional alignment achieves balanced mediolateral soft-tissue tension through the arc of knee flexion as assessed using intraoperative pressure-sensor technology. Further clinical trials are required to determine if TKA with functional alignment translates to improvements in patient satisfaction and outcomes compared to conventional alignment techniques. Cite this article: Bone Joint J 2021;103-B(3):507–514

Aims. The purpose of this study was to compare the radiological outcomes of manual versus robotic-assisted medial unicompartmental knee arthroplasty (UKA). Methods. Postoperative radiological outcomes from 86 consecutive robotic-assisted UKAs (RAUKA group) from a single academic centre were retrospectively reviewed and compared to 253 manual UKAs (MUKA group) drawn from a prior study at our institution. Femoral coronal and sagittal angles (FCA, FSA), tibial coronal and sagittal angles (TCA, TSA), and implant overhang were radiologically measured to identify outliers. Results. When assessing the accuracy of RAUKAs, 91.6% of all alignment measurements and 99.2% of all overhang measurements were within the target range. All alignment and overhang targets were simultaneously met in 68.6% of RAUKAs. When comparing radiological outcomes between the RAUKA and MUKA groups, statistically significant differences were identified for combined outliers in FCA (2.3% vs 12.6%; p = 0.006), FSA (17.4% vs 50.2%; p < 0.001), TCA (5.8% vs 41.5%; p < 0.001), and TSA (8.1% vs 18.6%; p = 0.023), as well as anterior (0.0% vs 4.7%; p = 0.042), posterior (1.2% vs 13.4%; p = 0.001), and medial (1.2% vs 14.2%; p < 0.001) overhang outliers. Conclusion. Robotic system navigation decreases alignment and overhang outliers compared to manual UKA. Given the association between component placement errors and revision in UKA, this strong significant improvement in accuracy may improve implant survival. Level of Evidence: III. Cite this article: Bone Jt Open 2021;2-3:191–197

Aims

Adenosine, lidocaine, and Mg²⁺ (ALM) therapy exerts differential immuno-inflammatory responses in males and females early after anterior cruciate ligament (ACL) reconstruction (ACLR). Our aim was to investigate sex-specific effects of ALM therapy on joint tissue repair and recovery 28 days after surgery.

Aims. Tourniquets have potential adverse effects including postoperative thigh pain, likely caused by their ischaemic and possible compressive effects. The aims of this preliminary study were to determine if it is possible to directly measure intramuscular pH in human subjects over time, and to measure the intramuscular pH changes resulting from tourniquet ischaemia in patients undergoing knee arthroscopy. Methods. For patients undergoing short knee arthroscopic procedures, a sterile calibrated pH probe was inserted into the anterior fascial compartment of the leg after skin preparation, but before tourniquet inflation. The limb was elevated for three minutes prior to tourniquet inflation to 250 mmHg or 300 mmHg. Intramuscular pH was recorded at one-second intervals throughout the procedure and for 20 minutes following tourniquet deflation. Probe-related adverse events were recorded. Results. A total of 27 patients were recruited to the study. Mean tourniquet time was 21 minutes (10 to 56). Tourniquet pressure was 300 mmHg for 21 patients and 250 mmHg for six patients. Mean muscle pH prior to tourniquet inflation was 6.80. Muscle pH decreased upon tourniquet inflation, with a steeper fall in the first ten minutes than for the rest of the procedure. Change in muscle pH was significant after five minutes of tourniquet ischaemia (p < 0.001). Mean muscle pH prior to tourniquet release was 6.58 and recovered to 6.75 within 20 minutes following release. No probe related adverse events were recorded. Conclusion. It is possible to directly measure skeletal muscle pH in human subjects over time. Tourniquet ischaemia results in a decrease in human skeletal muscle pH over time during short procedures. Cite this article: Bone Joint Res 2021;10(6):363–369

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The use of high tibial osteotomy (HTO) to delay total knee arthroplasty (TKA) in young patients with osteoarthritis (OA) and constitutional deformity remains debated. The aim of this study was to compare the long-term outcomes of TKA after HTO compared to TKA without HTO, using the time from the index OA surgery as reference (HTO for the study group, TKA for the control group).

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Micromotion of the polyethylene (PE) inlay may contribute to backside PE wear in addition to articulate wear of total knee arthroplasty (TKA). Using radiostereometric analysis (RSA) with tantalum beads in the PE inlay, we evaluated PE micromotion and its relationship to PE wear.

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Tibial tubercle osteotomy (TTO) facilitates surgical exposure and protects the extensor mechanism during revision total knee arthroplasty (rTKA). The purpose of this study was to determine the rates of bony union, complications, and reoperations following TTO during rTKA, to assess the functional outcomes of rTKA with TTO at two years’ minimum follow-up, and to identify the risk factors of failure.

Aims

The aim of this study was to investigate the distribution of phenotypes in Asian patients with end-stage osteoarthritis (OA) and assess whether the phenotype affected the clinical outcome and survival of mechanically aligned total knee arthroplasty (TKA). We also compared the survival of the group in which the phenotype unintentionally remained unchanged with those in which it was corrected to neutral.