Weintraub, Matthew T.

Aims Two-stage exchange arthroplasty with an antibiotic-eluting cement spacer remains the predominant strategy in the USA for managing chronic periprosthetic joint infection (PJI) following total hip arthroplasty (THA). The aim of this study was to evaluate a commercially available, partially intraoperatively fabricated articulating high-dose antibiotic cement spacer, focusing on survival, complications, and patient-reported outcomes. Methods A total of 298 patients (302 THAs) underwent two-stage exchange arthroplasty for PJI using a specific articulating antibiotic spacer between August 2005 and May 2022. Patients with a previous failed two-stage exchange were excluded, although 121 THAs (302, 40%) had undergone previous PJI-related procedures. The mean age of the patients was 65 years (SD 11), the mean BMI was 32 kg/m 2 (SD 7), and 116 (38%) were female. Most patients were classified as McPherson host B (158; 52%) and limb grade 2 (165; 55%), and 265 (88%) met the 2011 Musculoskeletal Infection Society criteria. The mean follow-up was six years (2 to 16). Results At five years after reimplantation, survival free of reinfection, aseptic rerevision, any rerevision, or any reoperation were 89% (95% CI 85.2 to 93.1), 93% (95% CI 89.3 to 96.1), 86% (95% CI 81.3 to 90.3), and 80% (95% CI 74.7 to 84.9), respectively. Dislocation accounted for most aseptic rerevisions (15/20). McPherson host C (HR 3.7 (95% CI 1.4 to 9.6); p = 0.007) and limb grade 3 (HR 3.3 (95% CI 1.0 to 11.1); p = 0.049) were significantly associated with an increased risk of reinfection. The mean Harris Hip Score at the latest follow-up was 76 (29 to 100). A total of 17 patients underwent revision or removal of a spacer for concerns about persistent infection and two for dislocation of the spacer. Eight patients underwent a non-rerevision reoperation during the spacer interval for wound drainage (n = 5), dislocation of the spacer (n = 2), and perispacer fracture (n = 1). A total of 26 spacer-related complications were treated nonoperatively (15 perispacer fractures, 11 dislocations). Dislocation of the spacer was strongly associated with dislocation after reimplantation (HR 6.2 (95% CI 2.3 to 16.9); p < 0.001). Conclusion This commercially available, partially intraoperatively fabricated articulating spacer showed excellent reinfection-free five-year survival (89%). Spacer-related fracture and dislocation each occurred in 5% of patients. Dislocation of the spacer significantly increased the risk of dislocation following reimplantation, supporting the use of higher-stability bearings in these high-risk patients. Cite this article: Bone Joint J 2026;108-B(9):1104–1112.

Aims Reliable assessment of joint stiffness is essential for studying arthrofibrosis in preclinical animal models. This study presents a new dedicated biomechanics device for measuring knee stiffness in mouse, rat, and rabbit models of arthrofibrosis, with the aim of validating its performance and comparing it to a previously validated device. Methods The new system integrates a torque load cell, stepper motor, and absolute encoder in a through-hole, unified configuration for precise continuous torque-angle measurement, with custom limb brackets ensuring species-specific alignment at the joint’s centre of rotation. To validate this device and compare it to a previously validated device, arthrofibrosis was induced using established models of extra-articular immobilization in mice and intra-articular violation with immobilization in rats and rabbits, followed by defined remobilization periods. Torque-angle curves were recorded ex vivo across species-specific torque ranges, and measurement variability between the new and a previous validated device was statistically compared using Brown-Forsythe’s test. Results The onset of hyperextension in contralateral limbs occurred at mean angles of 152.4° (mice), 154.4° (rats), and 152.8° (rabbits), and at maximum torque, mean flexion angles were 79.2°, 87.3°, and 140.5°, respectively. No significant differences in measurement variability were observed between devices across all species. Conclusion These findings demonstrate that our new device provides reproducible torque-angle data while maintaining the statistical robustness of the previous device and offering improved mechanical design and operational standardization. By enabling standardized, cross-species joint stiffness quantification, this platform improves cross-study comparability and strengthens the translational reliability of preclinical arthrofibrosis research. Cite this article: Bone Joint Res 2026;15(6):716–725.

Aims Total knee arthroplasty (TKA) for end-stage osteonecrosis has historically been associated with concerns regarding aseptic loosening, and long-term data are limited. The purpose of this study was to update and expand our previous series with long-term follow-up, with specific emphasis on implant survivorship, risk factors for failure, complications, and clinical outcomes in a consecutive cohort of TKAs performed for primary and secondary osteonecrosis. Methods We retrospectively identified 295 consecutive TKAs in 266 patients for osteonecrosis performed at a single tertiary care academic institution from January 2002 to July 2022. Of these, 207 TKAs (70%) were performed for primary osteonecrosis, and 88 (30%) for secondary osteonecrosis. The predominant cause of secondary osteonecrosis was steroid use (59%; n = 52), followed by post-traumatic (25%; n = 22), radiation-induced (9%; n = 8), and alcohol-induced (7%; n = 6) osteonecrosis. Implant survivorship was analyzed as a time-to-event outcome using Kaplan-Meier estimation. The mean age was 61 years (18 to 93), with 67% being female (n = 197). The mean follow-up was nine years (2 to 20). Results The 15-year survivorship free of any revision for the entire cohort was 92% (95% CI 87 to 97), with similar rates between primary and secondary osteonecrosis (92% (95% CI 87 to 98) vs 93% (95% CI 87 to 100), respectively; p = 0.459). Varus-valgus constraint implant designs (HR 10.8 (95% CI 2.7 to 43.4); p < 0.001) and tibial stem use (HR 12.0 (95% CI 4.1 to 35.1); p < 0.001) were associated with an increased risk of any revision. The 15-year survivorship free of aseptic loosening was 97% (95% CI 93 to 100) for the entire cohort. Age under 65 years (HR 2.7 (95% CI 1.4 to 5.4); p = 0.005) and secondary osteonecrosis (HR 1.9 (95% CI 1.0 to 3.4); p = 0.044) were associated with an increased risk of any reoperation at 15 years. Conclusion TKA is a durable and reliable option for primary osteonecrosis at long-term follow-up. However, TKAs performed for secondary osteonecrosis carry a higher reoperation risk. Cite this article: Bone Joint J 2026;108-B(4):455–462.