Using a patella reduced technique while balancing a TKA results in restored physiological strain in the collateral ligaments: an ex vivo kinematic analysis.

INTRODUCTION: Poor soft tissue balance in total knee arthroplasty (TKA) often results in patient dissatisfaction and reduced joint longevity. Patella-in-place balancing (PIPB) is a novel technique which aims to restore native collateral ligament behavior without collateral ligament release, while restoring post-operative patellar position. This study aimed to assess the effectiveness of this novel technique through a detailed ex vivo biomechanical analysis by comparing post-TKA tibiofemoral kinematics and collateral ligament behavior to the native condition. MATERIALS AND METHODS: Eight fresh-frozen cadaveric legs (89.2 ± 6 years) were tested on a validated dynamic knee simulator, following computed tomography imaging. Specimens were subjected to passive flexion (10-120°), squatting (35-100°), and varus/valgus laxity testing (10 Nm at 0°, 30°, 60°, 90° flexion). An optical motion capture system recorded markers affixed rigidly to the femur, tibia, and patella, while digital extensometers longitudinally affixed to the superficial medial collateral ligament (MCL) and lateral collateral ligament (LCL) collected synchronized strain data. Following native testing, a Stryker Triathlon CR TKA (Stryker, MI, USA) was performed on each specimen and the identical testing protocol was repeated. Statistical analyses were performed using a linear mixed model for functional motor tasks, while Wilcoxon signed-rank test was used for laxity tests (p < 0.05). RESULTS: Postoperative laxity was lower than the native condition at all flexion angles while post-operative ligament strain was lowered only for MCL at 30° (p = 0.017) and 60° (p = 0.011). Postoperative femoral rollback patterns were comparable to the native condition in passive flexion but demonstrated a more pronounced medial pivot during squatting. CONCLUSIONS: Balancing a TKA with the PIPB technique resulted in reduced joint laxity, while restoring collateral ligament strains. The technique also seemed to restore kinematics and strains, especially in passive flexion.

Influence of outpatient total knee arthroplasty compared to inpatient surgery on medical and economic outcomes.

Firstly, this study compared the rate of readmission after a total knee arthroplasty between selected out- patients (no hospitalization, directly sent home after surgery) and inpatients (3 days hospitalization) at 6 weeks. Secondly, it examined the mobility and the complications in the two groups after the same period of time. The rate of readmission, complications and knee mobility of 32 outpatients (M-age : 61 years ± 10 ; 10 females), were compared against those of 32 birth- matched inpatients (M-age : 64 years ± 8.6 ; 10 females). No patient was re-admitted in either group. Post- surgical complications included one hematoma resorbed at 6 weeks in the outpatient group and three joint effusions in the inpatient group. There were no instances of deep venous thrombosis, failure of primary fixation, infection, or wound dehiscence. Knee mobility was identical between the two groups. This is the first study to compare inpatient and outpatient total knee arthroplasty in a Belgian setting. Our study suggests that day-care total knee arthroplasty in selected patients is possible without increasing the rate of re-admission and complications, and without affecting the mobility at 6 weeks. However, the Belgian financial incentives do not seem to currently promote this surgical approach. These results should be confirmed with a larger sample to define the adequate length of stay after a total knee arthroplasty.