[Patella in Place Balancer: Technique for total knee arthroplasty]

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.

Preliminary results of a new surgical technique in total knee arthroplasty (TKA) using the native ligament tension for femoral implant positioning in varus osteoarthritis

PURPOSE

Individual implant alignment in total knee arthroplasty (TKA) has seen growing interest over the past years. This study therefore aimed to develop a surgical technique for implant alignment based on native ligament tension, and to present the results obtained using this technique.

METHODS

25 patients were included in this prospective study. Patient-specific instrumentation (PSI) was used for the resection of the extension gap. Ligament tension was measured after the removal of all accessible osteophytes. In the event of asymmetry, the distal femur resection was adjusted up to 2.5° using an adjustable cutting block. The aim was to achieve a symmetrical extension gap without release, not a neutral leg axis. Femoral rotation was aligned on the basis of ligament tension. Patients were followed up to 3 months postoperatively.

RESULTS

The postoperative whole-leg axis was 2.8° ± 1.6° varus. Patients achieved a flexion of 118° ± 9°, a Knee Score of 91.5 ± 3.2 and a Function Score of 86.8 ± 8.3 points.

CONCLUSION

For the first time, the new surgical technique described here permits a ligament tension based femoral implant alignment together with PSI. It was shown to be safe, with encouraging clinical and radiological results.

LEVEL OF EVIDENCE

Therapeutic study level IV.