Background

The purpose of the present study is to measure the intraoperative joint gap using tensor device and pre- and, postoperative variation of coronal stability at 0, 30 and 90° of flexion using stress radiograph and identify whether these factors influence patient reported outcome measurement (PROM).

Methods

53 knees with preoperative varus osteoarthritis of the knee were treated with anatomical BCR TKA with oblique 3°angle femorotibial joint line (Journey II XR; Smith& Nephew. Inc. Memphis, TN, USA). The intraoperative joint gap (medial, lateral and varus-valgus) using a tensor device and varus-valgus gap angle were measured using stress radiographs. PROM was also evaluated at 1.5 years postoperatively.

Results

There was no significant difference between pre- and postoperative flexion angle. Intraoperative medial laxity rather than medial tightness from full extension to 140° of flexion angle played an important role in influencing postoperative function of patellofemoral joint. Intraoperative varus laxity at full extension improved postoperative symptom in 2011 Knee Society Score (2011 KSS), while greater postoperative lateral stability at 30 and 90° of flexion with the varus stress test was found to contribute to the patient expectation in 2011 KSS. Greater postoperative valgus laxity at 90° of flexion with the valgus stress test improved the patient expectation and satisfaction in 2011 KSS, stiffness in WOMAC score and FJS-12.

Conclusion

The findings in the present study suggest that the intraoperative joint gap after implantation is not rectangular but trapezoidal gap and greater postoperative varus stability and valgus laxity at 90° of flexion improved patient reported outcome measurement in anatomical BCR TKA.