Citations

Background: Surgeons often recommend weight loss for patients with obesity before total knee arthroplasty (TKA). However, it is unknown whether preoperative weight loss affects outcomes. The goals of this study were to determine how many patients with obesity lost weight before TKA, to identify weight loss predictors, and to evaluate if preoperative weight loss affected postoperative outcomes. Methods: Among 23,726 primary TKAs performed between 2002 and 2019, we identified 3,665 patients who had a body mass index (BMI) of ≥30 kg/m 2 measured 1 to 24 months before surgery and had a weight measured at surgery. The mean patient age was 68 years, and 59% of patients were female. The mean patient BMI was 36 kg/m 2 . Univariable linear regressions evaluated weight loss predictors. Univariable and multivariable logistic regressions and Cox proportional hazards models evaluated the impact of preoperative weight change on discharge, operative time, periprosthetic joint infections (PJIs), complications, revisions, and reoperations. The mean follow-up was 6 years. Results: Overall, 20% of patients gained ≥5 pounds (1 pound = 0.45 kg), 39% maintained weight, 17% lost 5 to <10 pounds, 15% lost 10 to <20 pounds, and 9% lost ≥20 pounds before TKA. Male patients lost slightly more weight (−4.6 pounds) than female patients (−4.3 pounds) (p = 0.05). In univariable analyses, gaining >5 pounds was associated with increased odds of extended hospital length of stay (odds ratio [OR], 1.4; p = 0.01) and risk of complications (hazard ratio [HR], 1.7; p < 0.01). Losing 10 to <20 pounds was associated with increased risks of revision (HR, 2.0; p = 0.01), PJI (HR, 3.1; p < 0.01), and complications (HR, 1.6; p = 0.03). In multivariable analyses, compared with maintaining weight, losing 10 to <20 pounds was associated with an increased risk of PJI (HR, 2.6; p = 0.01), whereas gaining >5 pounds was associated with an increased risk of complications (HR, 1.5; p = 0.03). Conclusions: Few patients with obesity lost substantial weight before primary TKA, and reaching common preoperative weight loss goals was not associated with improved outcomes. Although a healthy weight is important for general health, weight loss before TKA may not be sufficient to improve postoperative outcomes for most patients with obesity. Level of Evidence: Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Aims The use of jumbo femoral heads, defined as those with a diameter of ≥ 40 mm, in primary total hip arthroplasty (THA) has gained popularity, to mitigate dislocation. The aim of this study was to determine the risk of dislocation, implant survival, and clinical outcomes of a large cohort of primary THAs with jumbo femoral heads. Methods We conducted a retrospective analysis of 1,828 primary THAs with jumbo femoral heads, which were undertaken for osteoarthritis, in 1,578 patients between January 2000 and December 2022, at a single academic medical centre. The femoral head diameter was 40 mm in 1,584 THAs (87%) and 44 mm in 244 THAs (13%). The outer diameter of the acetabular component ranged from 52 mm to 72 mm in those with 40 mm heads, and from 54 mm to 78 mm in those with 44 mm heads. The types of bearing included ceramic-on-highly cross-linked polyethylene (1,229 THAs; 67%) and metal-on-polyethylene (599 THAs; 33%). Elevated liners were used in 472 THAs (26%) and 1,083 (59%) were lateralized. The most common operative approach was posterior (1,388 THAs; 76%). Outcomes of interest included the rate of dislocation, revision for dislocation, any revision, any reoperation, and the Harris Hip Score (HHS). The mean age of the patients at the time of THA was 64 years (8 to 94); 1,477 (81%) were male, and their mean BMI was 28 kg/m² (5 to 55). The mean follow-up was six years (2 to 14). Results The ten-year survival free of dislocation was 97% (95% CI 96 to 98; 97% for 40 mm heads (95% CI 95 to 98) and 99% for 44 mm heads (95% CI 97 to 100) (hazard ratio 3 (95% CI 1 to 14); p = 0.106)). The ten-year survival free of revision for dislocation was 99.6% (95% CI 99 to 100) (99.5% for 40 mm heads (95% CI 98 to 100) and 100% for 44 mm heads (p = 0.546)). The ten-year survival free of any revision and any reoperation was 95% (95% CI 94 to 97) and 93% (95% CI 91 to 95), respectively. There were no significant differences in survival free of any revision (p = 0.746) or any reoperation (p = 0.762) between the two groups. Conclusion In this large single-centre study of the use of jumbo femoral heads in primary THAs, the ten-year survival free of dislocation was 97%, with extremely few revisions for dislocation. These results highlight the potential for jumbo femoral heads to reduce the risk of dislocation and enhance implant longevity without compromising other clinical outcomes. Cite this article: Bone Joint J 2025;107-B(7):698–706.

AimsTo characterize the effects of varying experimental parameters of transforming growth factor-beta 1 (TGF-β1) in primary knee fibroblasts as an in vitro model of arthrofibrosis.MethodsPrimary knee fibroblasts were isolated from one patient undergoing primary total knee arthroplasty (TKA) and one patient undergoing revision TKA for arthrofibrosis, respectively. Fibroblasts were stimulated with varying concentrations and durations of the pro-fibrotic cytokine TGF-β1. Picrosirius red staining (PSR) was conducted to assess collagen deposition, and real-time quantitative polymerase chain reaction (RT-qPCR) and western blotting were performed to determine cellular gene expression levels. A collagen gel contraction assay was used to assess TGF-β1-induced fibroblast contraction.ResultsIn our experiments, TGF-β1-mediated collagen deposition was consistent across a vast concentration range (0.5 to 40 ng/ml). While α-smooth muscle actin (ACTA2) protein levels and SMAD2 phosphorylation were induced by low concentrations (1 ng/ml), robust ACTA2 transcription required higher concentrations (5 ng/ml) of TGF-β1. Evaluation of TGF-β1-mediated cell and cytoskeletal contractility shows that in the measured fibroblasts, this process occurs within three hours following TGF-β1 administration. Of note, TGF-β1-differentiated myofibroblasts exhibited greater contractile properties than naïve fibroblasts in the presence of TGF-β1.ConclusionTaken together, this study elucidates key TGF-β1 experimental parameters that will inform the development and interpretation of in vitro models of arthrofibrosis.Cite this article: Bone Joint Res 2025;14(6):527–538.

Aims An angular proximal femoral deformity, in association with osteoarthritis (OA) of the hip, considerably increases the technical complexity of primary total hip arthroplasty (THA). The aims of this study were to determine the long-term implant survival, the risk factors for failure, complications, and clinical outcomes of contemporary primary THA in this difficult group of patients. Methods Our institutional total joint registry was used to identify 119 primary THAs performed in 108 patients with an angular proximal femoral deformity, between January 1997 and September 2017. The deformity was related to a previous femoral osteotomy in 102 THAs (86%), and developmental or metabolic disorders in 17 THAs (14%). A total of 62 hips (53%) had a predominantly varus deformity. The mean age of the patients was 44 years (SD 13), their mean BMI was 29 kg/m 2 (SD 6), and 70 (59%) were female. An uncemented femoral component with metaphyseal fixation was used in 35 THAs (30%), an uncemented femoral component with diaphyseal fixation in 34 (29%), an uncemented modular femoral component with a metaphyseal fixation sleeve in 29 (24%), and a cemented femoral component in 21 (18%). Simultaneous corrective femoral osteotomy was performed in 22 THAs (18%). Kaplan-Meier survival and Harris Hip Scores (HHSs) were reported. The mean follow-up was eight years (2 to 22). Results The ten-year survival free of femoral loosening, any femoral revision, any revision and any reoperation was 95%, 93%, 90%, and 88%, respectively. A total of 13 revisions were undertaken, for aseptic femoral loosening in three, fracture of the femoral component in two, dislocation in two, aseptic acetabular loosening in two, polyethylene liner exchange in two, and infection in two. A preoperative varus deformity was associated with a higher risk of any revision (hazard ratio (HR) 12.5, p = 0.020), and those with a simultaneous osteotomy had a higher risk of any reoperation (HR 3.6, p = 0.023). The mean HHSs improved significantly from 52 preoperatively to 82 at ten years (p < 0.001). Conclusion In the largest series to date of primary THAs in patients with hip OA and an angular proximal femoral deformity, we found a good ten-year survival free from any revision. Varus deformities, particularly those treated with a simultaneous osteotomy due to the magnitude or location of the deformity, had a higher rate of further surgery. Cite this article: Bone Joint J 2025;107-B(6 Supple B):101–108.

Background: Periprosthetic tibial fractures around a total knee replacement (TKR) remain challenging to manage, with little published information for guidance. The purpose of this study was to review the types, management techniques, and outcomes of periprosthetic tibial fractures in the largest series to date. Methods: We identified 300 periprosthetic tibial fractures (285 patients) around a TKR (43% in primary TKRs and 57% in revision TKRs) sustained between 1996 and 2020. Fractures were classified according to Felix et al. as Type I (tibial plateau), Type II (adjacent to stem), Type III (distal to stem), or Type IV (tibial tubercle), with subtypes A (well-fixed component), B (loose component), and C (intraoperative fracture). Of the fractures in this study, 53% were Type I, 24% were Type II, 16% were Type III, and 8% were Type IV. A total of 46% of fractures occurred intraoperatively, and 54% of fractures occurred postoperatively (61% subtype A, 39% subtype B). The mean patient age at fracture was 67 years, and 64% of patients were female. The mean follow-up was 6 years. Results: The intraoperative fracture incidence was 1.40% in revision TKRs and 0.10% in primary TKRs. Among intraoperative fractures, the 2-year survivorship free from tibial component revision was highest in Type I (100%) and lowest in Type IV (67%) (p < 0.001). For postoperative fractures, the 2-year survivorship free from any reoperation was 29% and the 2-year survivorship free from tibial component revision was 51%. Type-I postoperative fractures had the lowest 2-year survivorship free from tibial component revision (10%), whereas Type-III fractures had the highest survivorship (88%) (p < 0.001). Conclusions: Intraoperative periprosthetic fracture of the tibia was fourteenfold more likely in revision TKRs compared with primary TKRs. Among all intraoperative fractures, Type-I fractures were well-tolerated, with 100% survivorship free from tibial component revision at 2 years. Conversely, Type-I postoperative fractures had only 10% survivorship at 2 years. Level of Evidence: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Background: Total hip arthroplasty (THA) effectively restores mobility, reduces pain, and enhances the quality of life of patients of all ages. Despite its benefits, concerns regarding the long-term effects of high-impact activities and sports on implant longevity require further study. This study investigated the effect of activity level on long-term radiographic wear of highly cross-linked polyethylene (HXLPE) in young patients undergoing THA. Methods: Between 1999 and 2008, 785 patients (909 hips) aged ≤50 underwent primary THA using first-generation HXLPE liners from 4 different vendors with either metal or ceramic heads. Functional activity and participation questionnaires, including the Hip Injury and Osteoarthritis Outcome Score (HOOS Jr), University of California Los Angeles (UCLA) activity scale, and High-Activity Arthroplasty Score (HAAS), were surveyed in 2018 to 2019. The response rate was 44%. Radiographic linear wear rates were measured using the ROMAN software in patients who had completed questionnaires and had radiographs taken at least 10 years apart, leaving a final cohort of 249 patients (284 hips). Multivariate analyses were performed to determine the relationship between HXLPE wear rates and activity scores. Results: At the time of the survey, approximately 10% of the patients performed high-impact activities not-recommended by consensus guidelines. The HXLPE linear wear rate was 0.036 mm/year (SD: 0.026). Patients with higher activity levels, as measured on the continuous UCLA/HAAS activity scale, did not exhibit increased wear (β = -0.0009; p = 0.31). Stair climbing was correlated with increased wear rates (β = 0.0066; p = 0.004), whereas walking (β = 0.0005; p = 0.66) and running (β = 0.0017; p = 0.30) were not significantly correlated. Patients performing nonrecommended activities did not show increased wear rates compared with those performing recommended activities (β = 0.0063; p = 0.19). Conclusions: Linear wear rates of first-generation HXLPE were not related to functional activity or participation in high-impact activities. Future research should include longitudinal assessments of activity levels and data on other potential complications related to high-impact sports to provide robust evidence regarding recommended activity level postoperatively. Level of Evidence: Level III , Retrospective Comparative Study. See Instructions for Authors for a complete description of levels of evidence.

Background: Traditional Medicare (TM) claims data are widely used by researchers and registries to report survivorship following total knee arthroplasty (TKA). The purpose of the present study was to investigate whether the mass exodus of patients from TM to Medicare Advantage (MA) has compromised the fidelity of TM data. Methods: We identified 11,717 Medicare-eligible patients (15,282 knees) who had undergone primary TKA from 2000 to 2020 at a single institution. Insurance type was analyzed, and 84% of TKAs were covered by TM. The rates of survivorship free from revision or reoperation were calculated for patients with TM coverage. The same survivorship end points were recalculated after censoring of patients who transitioned to MA after primary TKA, thereby modeling the impact of losing patients from the TM dataset. Differences in survivorship were compared. The mean duration of follow-up was 10 years. Results: From 2000 to 2020, there was a decrease in TM insurance (from 94% to 68%) and a corresponding increase in MA insurance (from 0% to 19%) among patients undergoing TKA. Following TKA, 25% of patients with TM coverage switched to MA. For patients with TM at the time of surgery, the 15-year rates of survivorship free from any reoperation or revision were 90% and 96%, respectively. When patients were censored upon transition from TM to MA, the 15-year rates of survivorship free from any reoperation (92% versus 90%; hazard ratio [HR] = 1.2; p = 0.001) or any revision (97% versus 96%; HR = 1.3; p = 0.002) were significantly higher. Conclusions: One in 4 patients left TM for MA after primary TKA, effectively making them lost to follow-up within TM datasets. The mass exodus of patients out of TM resulted in falsely elevated estimates of survivorship free from reoperation and from revision, with increasing divergence in survivorship over time, when MA data were excluded. As MA continues to grow, efforts to incorporate these data will become increasingly important. Level of Evidence: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Experimental analyses of knee joint contractures have traditionally utilized a 6-month rabbit model as the gold standard. However, this model is time-intensive and costly. The purpose of this study was to develop an abbreviated rabbit model of knee contractures and compare it to the well-established longer model. Twenty female New Zealand White rabbits were divided into two equal groups and prospectively studied to assess knee passive extension angles (PEA), contracture angles (CA), and terminal posterior capsular stiffness. Experimental knees were immobilized for either 4 weeks ( n = 10) with an 8-week remobilization period in the abbreviated model (i.e., 3 months) or for 8 weeks ( n = 10) with a 16-week remobilization period in the standard model (i.e., 6 months). PEAs were assessed at remobilization and several time points using differing vertical forces. At sacrifice, terminal biomechanical data were collected to assess posterior capsular stiffness. Analysis of PEAs in live animals at each torque value and time point demonstrated increased PEAs and decreased CAs in the 3-month abbreviated model as compared to the 6-month standard model. At sacrifice, biomechanical analysis demonstrated that the posterior capsules of the 3-month experimental limbs were significantly more stiff than the contralateral limb (2.4 vs. 0.05 Ncm/°, p < 0.0001), but significantly less stiff compared to the 6-month experimental limbs (2.4 vs. 4.7 Ncm/°, p < 0.0001). Our study suggests that the 6-month standard rabbit knee model of arthrofibrosis should continue to be used in the laboratory assessment of arthrofibrosis. However, the abbreviated model may be beneficial under selected experimental conditions.