Background: The use of megaprostheses in nononcologic patients has been associated with complication rates greater than 50%. In patients with prior periprosthetic joint infection (PJI) with subsequent twostage reimplantation, this complication rate may be even higher. This study was to investigate the outcomes of megaprostheses in nononcologic patients undergoing revision hip/knee arthroplasty. Methods: We retrospectively studied patients who underwent megaprosthesis replacements from 1999 to 2017 at 5 hospitals with minimum 24 months of follow-up. Patients were stratified based on history of prior PJI (septic vs aseptic) and location of the megaprosthesis (the hip or knee). Postoperative complications were classified as soft-tissue failure, aseptic loosening, structural failure, and infection. Results: Of the 42 patients, 19 were in the septic cohort and 23 were in the aseptic cohort. The overall complication rate was 28.6%. Complication rates for the septic and aseptic cohorts were 32% and 26%, respectively (P ¼ .74). By anatomic location, there were 2 of 13 (15%) and 10 of 29 (34%) complications in the hip and knee groups, respectively (P ¼ .28). In the septic cohort, there were no (0%) complications in the hip group and 6 of 14 (43%) complications in the knee group (P ¼ .13), all due to infection. In the aseptic cohort, there were 2 of 8 (25%) and 4 of 15 (27%) complications in the hip and knee groups, respectively (P ¼ 1.0). Conclusions: There is no difference in the postoperative complication rates between the septic or aseptic cohorts undergoing revision hip or knee megaprosthesis replacements. In patients with prior PJI, proximal femoral replacements have improved short-term survivorship compared with distal femoral or proximal tibial replacements.

Objectives: To (1) report the thermal changes encountered at the pin/skin interface in a cadaver with a knee-spanning external fixator inside the magnetic resonance imaging (MRI) bore and (2) report on the quality of the MRI sequences collected. Methods: Three commonly used external fixation systems were placed on cadaveric lower extremities to simulate knee external fixation. Fiber optic thermal probes were placed at the pin/skin interface of a femoral and tibial pin. A control probe was embedded in the soft tissues of the thigh. Full knee MRI scans were performed using a 1.5-Tesla magnet. Real-time thermal data were collected. A clinically significant increase in temperature compared with the control was defined as 2°C. Two blinded radiologists evaluated the images for image quality and overall diagnostic utility using a standardized 5-point grading scale. Results: There were statistically significant differences in the temperature changes between the femoral/tibial pin sites and the control probe sites during each phase of the MRI scan. However, there was only one clinically significant difference in temperature change during a single sequence of one MRI scan of one of the external fixator devices. Overall image quality was graded as a 4 for each image set with 100% interobserver agreement (k = 1.0). Conclusions: Despite significant differences in temperature changes between the pin sites and controls over multiple MRI sequences in commonly used external fixator devices, the differences in temperature change are likely not clinically relevant. Overall image quality and interpretability of the images were excellent.

Introduction. Expectations for limb length differences after TKA are important for patient perception and outcomes. Limb length discrepancies may occur due to postoperative leg length increases, which can lead to decreased patient functionality and satisfaction and even possible litigation. The purpose of this study is to examine the frequency and extent of limb lengthening among various preoperative deformities and between two different implant systems. Methods. Preoperative and postoperative full-length standing radiographs were obtained between August 2018 and August 2019 to measure mechanical axis and limb length of operative limbs. Demographic information such as age, sex, and BMI was also collected. Patients were grouped into categories for pre- and postoperative subgroup analysis: valgus, varus, customized implant, and conventional implant. Regression analysis was performed to evaluate significant relationships. Results. Of the 121 primary TKAs analyzed, 62% of the knees showed an increase in limb length after TKA, with an average lengthening of 5.32 mm. Preoperative varus alignment was associated with a mean lengthening of 3.14 mm, while preoperative valgus alignment was associated with a mean lengthening of 16.2 mm. Overall, there were no statistically significant differences in limb lengths pre- and postoperatively ( p  = 0.23) and no significant changes in limb length for any subgroup. Further, no variables were associated with limb length changes ( p  = 0.49), including the use of customized implants ( p  = 0.2). Conclusions. Limb lengthening after TKA is common and, on average, occurs more significantly in valgus knees. No significant difference in limb lengthening could be demonstrated using customized over conventional implants. Preoperative counseling is important to manage patient expectations.

The demand for revision total joint arthroplasties (rTJAs) is expected to increase as the age of the population continues to rise. Accurate cost data regarding hospital expenses for differing age groups are needed to deliver optimal care within value-based healthcare (VBHC) models. The aim of this study was to compare the total in-hospital costs by decadal groups following rTJA and to determine the primary drivers of the costs for these procedures. Time-driven activity-based costing (TDABC) was used to capture granular hospital costs. A total of 551 rTJAs were included in the study, with 294 sexagenarians, 198 septuagenarians, and 59 octogenarians and older. Sexagenarians had a lower ASA classification (2.3 vs. 2.4 and 2.7; p < 0.0001) and were more often privately insured (66.7% vs. 24.2% and 33.9%; p < 0.0001) as compared to septuagenarians and octogenarians and older, respectively. Sexagenarians were discharged to home at a higher rate (85.3% vs. 68.3% and 34.3%; p < 0.0001), experienced a longer operating room (OR) time (199.8 min vs. 189.7 min and 172.3 min; p = 0.0195), and had a differing overall hospital length of stay (2.8 days vs. 2.7 days and 3.6 days; p = 0.0086) compared to septuagenarians and octogenarians and older, respectively. Sexagenarians had 7% and 23% less expensive personnel costs from post-anesthesia care unit (PACU) to discharge (p < 0.0001), and 1% and 24% more expensive implant costs (p = 0.077) compared to septuagenarians and octogenarians and older, respectively. Sexagenarians had a lower total in-hospital cost for rTJAs by 0.9% compared to septuagenarians but 12% more expensive total in-hospital costs compared to octogenarians and older (p = 0.185). Multivariate linear regression showed that the implant cost (0.88389; p < 0.0001), OR time (0.12140; p < 0.0001), personnel cost from PACU through to discharge (0.11472; p = 0.0007), and rTHAs (−0.03058; p < 0.0001) to be the strongest associations with overall costs. Focusing on the implant costs and OR times to reduce costs for all age groups for rTJAs is important to provide cost-effective VBHC.

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