Aims. Simultaneous bilateral total knee arthroplasty (TKA) has been used due to its financial advantages, overall resource usage, and convenience for the patient. The training model where a trainee performs the first TKA, followed by the trainer surgeon performing the second TKA, is a unique model to our institution. This study aims to analyze the functional and clinical outcomes of bilateral simultaneous TKA when performed by a trainee or a supervising surgeon, and also to assess these outcomes based on which side was done by the trainee or by the surgeon. Methods. This was a retrospective cohort study of all simultaneous bilateral TKAs performed by a single surgeon in an academic institution between May 2003 and November 2017. Exclusion criteria were the use of partial knee arthroplasty procedures, staged bilateral procedures, and procedures not performed by the senior author on one side and the trainee on another. Primary clinical outcomes of interest included revision and re-revision. Primary functional outcomes included the Oxford Knee Score (OKS) and patient satisfaction scores. Results. In total, 315 patients (630 knees) were included for analysis. Of these, functional scores were available for 189 patients (378 knees). There was a 1.9% (n = 12) all-cause revision rate for all knees. Overall, 12 knees in ten patients were revised, and both right and left knees were revised in two patients. The OKS and patient satisfaction scores were comparable for trainees and supervising surgeons. A majority of patients (88%, n = 166) were either highly likely (67%, n = 127) or likely (21%, n = 39) to recommend bilateral TKAs to a friend. Conclusion. Simultaneous bilateral TKA can be used as an effective teaching model for trainees without any significant impact on patient clinical or functional outcomes. Excellent functional and clinical outcomes in both knees, regardless of whether the performing surgeon is a trainee or supervising surgeon, can be achieved with simultaneous bilateral TKA. Cite this article: Bone Jt Open 2022;3(1):29–34

Aims. The aim of this meta-analysis was to determine the pooled incidence of postoperative urinary retention (POUR) following total hip and knee arthroplasty (total joint replacement (TJR)) and to evaluate the risk factors and complications associated with POUR. Methods. Two authors conducted searches in PubMed, Embase, Web of Science, and Scopus on TJR and urinary retention. Eligible studies that reported the rate of POUR and associated risk factors for patients undergoing TJR were included in the analysis. Patient demographic details, medical comorbidities, and postoperative outcomes and complications were separately analyzed. The effect estimates for continuous and categorical data were reported as standardized mean differences (SMDs) and odds ratios (ORs) with 95% CIs, respectively. Results. A total of 31 studies were included in the systematic review. Of these, 29 studies entered our meta-analysis, which included 3,273 patients diagnosed with POUR and 11,583 patients without POUR following TJR. The pooled incidence of POUR was 28.06%. Demographic risk factors included male sex (OR 1.81, 95% CI 1.26 to 2.59), increasing age (SMD 0.16, 95% CI 0.04 to 0.27), and American Society of Anesthesiologists grade 3 to 4 (OR 1.39, 95% CI 1.10 to 1.77). Patients with a history of benign prostatic hyperplasia (OR 1.99, 95% CI 1.41 to 2.83) and retention (OR 3.10, 95% CI 1.58 to 6.06) were more likely to develop POUR. Surgery-related risk factors included spinal anaesthesia (OR 1.44, 95% CI 1.19 to 1.74) and postoperative epidural analgesia (OR 2.82, 95% CI 1.65 to 4.82). Total hip arthroplasty was associated with higher odds of POUR compared to total knee arthroplasty (OR 1.10, 95% CI 1.02 to 1.20). Postoperatively, POUR was associated with a longer length of stay (SMD 0.21, 95% CI 0.02 to 0.39). Conclusion. Our meta-analysis demonstrated key risk variables for POUR following TJR, which may assist in identifying at-risk patients and direct patient-centered pathways to minimize this postoperative complication. Cite this article: Bone Jt Open 2024;5(7):601–611

Aims. Sagittal plane imbalance (SPI), or asymmetry between extension and flexion gaps, is an important issue in total knee arthroplasty (TKA). The purpose of this study was to compare SPI between kinematic alignment (KA), mechanical alignment (MA), and functional alignment (FA) strategies. Methods. In 137 robotic-assisted TKAs, extension and flexion stressed gap laxities and bone resections were measured. The primary outcome was the proportion and magnitude of medial and lateral SPI (gap differential > 2.0 mm) for KA, MA, and FA. Secondary outcomes were the proportion of knees with severe (> 4.0 mm) SPI, and resection thicknesses for each technique, with KA as reference. Results. FA showed significantly lower rates of medial and lateral SPI (2.9% and 2.2%) compared to KA (45.3%; p < 0.001, and 25.5%; p < 0.001) and compared to MA (52.6%; p < 0.001 and 29.9%; p < 0.001). There was no difference in medial and lateral SPI between KA and MA (p = 0.228 and p = 0.417, respectively). FA showed significantly lower rates of severe medial and lateral SPI (0 and 0%) compared to KA (8.0%; p < 0.001 and 7.3%; p = 0.001) and compared to MA (10.2%; p < 0.001 and 4.4%; p = 0.013). There was no difference in severe medial and lateral SPI between KA and MA (p = 0.527 and p = 0.307, respectively). MA resulted in thinner resections than KA in medial extension (mean difference (MD) 1.4 mm, SD 1.9; p < 0.001), medial flexion (MD 1.5 mm, SD 1.8; p < 0.001), and lateral extension (MD 1.1 mm, SD 1.9; p < 0.001). FA resulted in thinner resections than KA in medial extension (MD 1.6 mm, SD 1.4; p < 0.001) and lateral extension (MD 2.0 mm, SD 1.6; p < 0.001), but in thicker medial flexion resections (MD 0.8 mm, SD 1.4; p < 0.001). Conclusion. Mechanical and kinematic alignment (measured resection techniques) result in high rates of SPI. Pre-resection angular and translational adjustments with functional alignment, with typically smaller distal than posterior femoral resection, address this issue. Cite this article: Bone Jt Open 2024;5(8):681–687

Aims. Tibial fixation in revision total knee arthroplasty (rTKA) can present surgical challenges. It has been suggested that appropriate fixation in at least two of the three anatomical zones (epiphysis, metaphysis, and diaphysis) is essential for implant survival. However, supporting clinical data are lacking. In this retrospective case-control study, we investigated the relationship between zonal fixation of hybrid rTKA tibial components and re-revision total knee arthroplasty for aseptic loosening (rrTKA-AL). Methods. All consecutive rTKAs with hybrid tibial components (May 2006 to December 2020) were screened for subsequent rrTKA-AL. A control group was randomly selected from the remaining cohort. Postoperative radiographs of rTKAs were scored in random order by three blinded observers for zonal fixation in the epiphysis (bone resection level below, at, or above fibular head; 0 to 2), metaphysis (number of sufficiently cemented zones; 0 to 4), and diaphysis (canal filling ratio (CFR); %). The intraclass correlation coefficient (ICC) was calculated to quantify the agreement between observers. Multivariate logistic regression analysis was performed to assess the relationship between zonal fixation and rrTKA-AL. Results. Overall, 33 patients underwent a further rrTKA-AL from a total of 1,173 rTKAs where hybrid tibial components (2.8%) were used. Patients requiring rrTKA-AL had a significantly lower epiphyseal bone resection level (OR 0.43; 95% CI 0.23 to 0.76; p = 0.006), lower number of adequately cemented zones (OR 0.50; 95% CI 0.30 to 0.79; p = 0.004), but no difference in CFR (p = 0.858). Furthermore, patients needing rrTKA-AL had more frequently previous revisions (p = 0.047), a higher rate of a prior use of a stemmed tibial component (p = 0.011), and a higher Anderson Orthopaedic Research Institute classification (p < 0.001). Agreement of zonal fixation between observers was good (ICC 0.79 to 0.87). Conclusion. Patients in need of subsequent rrTKA-AL had lower epiphyseal bone resection levels and a lower number of sufficiently metaphyseal cemented zones following rTKA. These results emphasize the importance of appropriate metaphyseal fixation at rTKA. With this information, orthopaedic surgeons can identify patients at greater risk for rrTKA-AL and optimize their surgical technique in revision knee arthroplasty surgery. Cite this article: Bone Joint J 2025;107-B(1):65–71

Aims. The transepicondylar axis is a well-established reference for the determination of femoral component rotation in total knee arthroplasty (TKA). However, when severe bone loss is present in the femoral condyles, rotational alignment can be more complicated. There is a lack of validated landmarks in the supracondylar region of the distal femur. Therefore, the aim of this study was to analyze the correlation between the surgical transepicondylar axis (sTEA) and the suggested dorsal cortex line (DCL) in the coronal plane and the inter- and intraobserver reliability of its CT scan measurement. Methods. A total of 75 randomly selected CT scans were measured by three experienced surgeons independently. The DCL was defined in the coronal plane as a tangent to the dorsal femoral cortex located 75 mm above the joint line in the frontal plane. The difference between sTEA and DCL was calculated. Descriptive statistics and angulation correlations were generated for the sTEA and DCL, as well as for the distribution of measurement error for intra- and inter-rater reliability. Results. The external rotation of the DCL to the sTEA was a mean of 9.47° (SD 3.06°), and a median of 9.2° (IQR 7.45° to 11.60°), with a minimum value of 1.7° and maximum of 16.3°. The measurements of the DCL demonstrated very good to excellent test-retest and inter-rater reliability coefficients (intraclass correlation coefficient 0.80 to 0.99). Conclusion. This study reveals a correlation between the sTEA and the DCL. Overall, 10° of external rotation of the dorsal femoral cortical bone to the sTEA may serve as a reliable landmark for initial position of the femoral component. Surgeons should be aware that there are outliers in this study in up to 17% of the measurements, which potentially could result in deviations of femoral component rotation. Cite this article: Bone Jt Open 2024;5(12):1067–1071

We have investigated the errors in the identification of the transepicondylar axis and the anteroposterior axis between a minimally-invasive and a conventional approach in four fresh-frozen cadaver knees. The errors in aligning the femoral prosthesis were compared with the reference transepicondylar axis as established by CT.

The error in the identification of the transepicondylar axis was significantly higher in the minimal approach (4.5° of internal rotation, sd 4) than in the conventional approach (3° of internal rotation, sd 4; p < 0.001). The errors in identifying the anteroposterior axis in the two approaches were 0° (sd 5) and 1.8° (sd 5) of internal rotation, respectively (p < 0.001).

Aims. This study aims to describe the pre- and postoperative self-reported health and quality of life from a national cohort of patients undergoing elective total conventional hip arthroplasty (THA) and total knee arthroplasty (TKA) in Australia. For context, these data will be compared with patient-reported outcome measures (PROMs) data from other international nation-wide registries. Methods. Between 2018 to 2020, and nested within a nationwide arthroplasty registry, preoperative and six-month postoperative PROMs were electronically collected from patients before and after elective THA and TKA. There were 5,228 THA and 8,299 TKA preoperative procedures as well as 3,215 THA and 4,982 TKA postoperative procedures available for analysis. Validated PROMs included the EuroQol five-dimension five-level questionnaire (EQ-5D-5L; range 0 to 100; scored worst-best health), Oxford Hip/Knee Scores (OHS/OKS; range 0 to 48; scored worst-best hip/knee function) and the 12-item Hip/Knee disability and Osteoarthritis Outcome Score (HOOS-12/KOOS-12; range 0 to 100; scored best-worst hip/knee health). Additional items included preoperative expectations, patient-perceived improvement, and postoperative satisfaction. Descriptive analyses were undertaken. Results. For THA and TKA patients respectively, the patient profile was 2,850 (54.5%) and 4,684 (56.4%) female, mean age 66.8 years (SD 10.6) and 67.5 (SD 8.8), and mean BMI 29.9 kg/m. 2. (SD 7.7) and 32.5 kg/m. 2. (SD 7.0). The proportion of THA and TKA patients who reported their joint as ‘much better’ was 2,946 (92.6%) and 4,020 (81.6%) respectively, and the majority of patients were ‘satisfied’ or ‘very satisfied’ with their procedure (2,754 (86.5%) and 3,981 (80.8%)). There were 311 (9.7%) of THA patients and 516 (10.5%) of TKA patients who reported ‘dissatisfied’ or ‘very dissatisfied’ with their surgery. Conclusion. Large improvements in pain, function, and overall health were evident following primary THA and TKA. Approximately 10% of patients reported dissatisfaction with their surgery. Future analyses will focus on factors contributing to dissatisfaction after arthroplasty. Cite this article: Bone Jt Open 2021;2(6):422–432

Estimates of knee joint loadings were calculated for 12 normal subjects from kinematic and kinetic measures obtained during both level and downhill walking. The maximum tibiofemoral compressive force reached an average load of 3.9 times body-weight (BW) for level walking and 8 times BW for downhill walking, in each instance during the early stance phase. Muscle forces contributed 80% of the maximum bone-on-bone force during downhill walking and 70% during level walking whereas the ground reaction forces contributed only 20% and 30% respectively.

Most total knee designs provide a tibiofemoral contact area of 100 to 300 mm². The yield point of these polyethylene inlays will therefore be exceeded with each step during downhill walking. Future evaluation of total knee designs should be based on a tibiofemoral joint load of 3.5 times BW at 20° knee flexion, 8 times BW at 40° and 6 times BW at 60°.

Maquet's line passes from the centre of the femoral head to the centre of the body of the talus. The distance of this line from the centre of the knee on a long-leg radiograph provides the most accurate measure of coronal alignment. Malalignment causes abnormal forces which may lead to loosening after knee replacement. We report a series of 115 Denham knee replacements performed between 1976 and 1981 using the earliest design of components, inserted with intramedullary guide rods. Patients were assessed clinically and long-leg standing radiographs were taken before operation, soon after surgery and up to 12 years later. In two-thirds of the knees (68%) Maquet's line passed through the middle third of the prosthesis on postoperative films and the incidence of subsequent loosening was 3%. When Maquet's line was medial or lateral to this, an error of approximately +/- 3 degrees, the incidence of loosening at a median period of eight years was 24%. This difference is highly significant (p = 0.001). Accurate coronal alignment appears to be an important factor in prevention of loosening. Means of improving the accuracy of alignment and of measuring it on long-leg radiographs are discussed.

We reviewed 40 cementless Porous Coated Anatomic knee replacements in 34 consecutive patients. The average follow-up was 12.9 months (range 6 to 36 months). At review, loose beads were identified in 23 knees, in 11 on the femoral side and in 16 on the tibial side (in five knees on both sides). One loose bead was adjacent to the patella. In four knees there were intra-articular beads. Radiolucent lines at the interface between bone and prosthesis were seen in 19 knees, in six on the femoral side and in 16 on the tibial side (in three knees on both sides). In relation to the tibial component loose beads were associated with a radiolucent line in all except one case. Progressive loosening with an increasing number of loose beads was seen in three knees. At this early stage of follow-up there was no correlation between the clinical results and the presence of loose beads.

Between 1969 and 1971 20 prototypes of the Stanmore total knee prosthesis were used to replace severely arthritic knees in 18 patients. Seven patients died before the final follow-up and one had to have her leg amputated because of deep infection; in none of these patients had the prosthesis become loose. Ten patients (11 knees) were reviewed at least 10 years after operation. There was no significant clinical deterioration in 7 of these 11 surviving knees when the results at one year were compared with those at 10 years.

One hundred and three sequential Stanmore knee replacements were reviewed retrospectively on two occasions with a maximal follow-up period of nine years three months. This knee prosthesis, which is hinged, was successful in alleviating pain, stabilising an unstable knee and modestly increasing the arc of flexion. Walking capacity was increased and flexion contractures were reduced. There were seven cases of infection and four of fracture around the prosthesis. All these proved difficult to treat and two knees with both fracture and infection needed amputation. Eight knees were revised for aseptic loosening and a further 14 were found to have radiological signs of loosening. The results have been analysed by the methods advocated by Tew and Waugh and give a cumulative success rate of 80 per cent at seven years, provided success is judged solely by whether the prosthesis is still in situ. The role of the Stanmore knee as a primary arthroplasty is discussed.

Aims. Surgeon and patient reluctance to participate are potential significant barriers to conducting placebo-controlled trials of orthopaedic surgery. Understanding the preferences of orthopaedic surgeons and patients regarding the design of randomized placebo-controlled trials (RCT-Ps) of knee procedures can help to identify what RCT-P features will lead to the greatest participation. This information could inform future trial designs and feasibility assessments. Methods. This study used two discrete choice experiments (DCEs) to determine which features of RCT-Ps of knee procedures influence surgeon and patient participation. A mixed-methods approach informed the DCE development. The DCEs were analyzed with a baseline category multinomial logit model. Results. The proportion of respondents (surgeons n = 103; patients n = 140) who would not participate in any of the DCE choice sets (surgeons = 31%; patients = 40%), and the proportion who would participate in all (surgeons = 18%; patients = 30%), indicated strong views regarding the conduct of RCT-Ps. There were three main findings: for both surgeons and patients, studies which involved an arthroscopic procedure were more likely to result in participation than those with a total knee arthroplasty; as the age (for patients) and years of experience (for surgeons) increased, the overall likelihood of participation decreased; and, for surgeons, offering authorship and input into the RCT-P design was preferred for less experienced surgeons, while only completing the procedure was preferred by more experienced surgeons. Conclusion. Patients and surgeons have strong views regarding participation in RCT-Ps. However, understanding their preferences can inform future trial designs and feasibility assessments with regard to recruitment rates. Cite this article: Bone Joint J 2024;106-B(12):1408–1415

We performed a prospective study of 54 patients (76 knees) who underwent Osteonics series 3000 cruciate-retaining cementless total knee arthroplasty between December 1990 and June 1993. Five patients (seven knees) were lost to follow-up (90.7% completion). One patient required revision at 10.5 years after operation.

The rate of survival was 100% at ten years and 96.7% at 13 years. The mean ten-year knee and function scores were 79 and 59 respectively. Both were significantly better than the pre-operative scores. The range of movement also improved. Although a radiolucent line around the tibial component enlarged in six knees (20.7%) at ten years, the clinical outcome was generally good. In a patient who died after 5.5 years, post-mortem examination of the knee showed no bony ingrowth into the tibial component. Despite poor bony ingrowth, press-fit fixation was satisfactory and good results can be obtained with this cementless, cruciate-retaining prosthesis.