Tibial tubercule osteotomy during medial approach to difficult knee arthroplasties.

INTRODUCTION

Osteotomy of the anterior tibial tubercle (TT) is well known as the approach to difficult knees, in particular those with a low patella, but it has a poor reputation.

PATIENTS AND METHODS

This technique was used 21 times in 20 patients (10 males and 10 females) with a mean age of 71 years (range, 42-90 years) for 14 prosthesis revisions (three for septic loosening, 11 for aseptic loosening) and seven knees that had not anteriorly received prior implants (three osteotomies, one synovectomy). The surgical technique included a long (7 cm), thick (>1 cm) fragment retaining its lateral muscle hinge with compression fixation using two screws. In cases with a low patella, the TT was proximally displaced, with amplitude limited by the tibial baseplate. Follow-up was clinical and radiological, lasting a mean 54 months (range, 8-195 months). The clinical results were assessed using the IKS score and the radiological results using the measurement of the patellar index according to the protocol described during the Lyon Knee Days.

RESULTS

The mean preoperative IKS scores were: knee, 57.5±22.4; function, 42.6±21.5 (total, 100±33.9); postoperative scores: knee, 84±11.6; function 65±28 (total, 149±32.9). The joint range of motion increased from 73±34.9 to 88±21.1 for a mean gain of 15±23.1. We found a traumatic nondisplaced tibia fracture around a tibial stem, treated conservatively, two stress fractures of the immediate proximal part overhanging the TT with no consequences, one case of stiffness (not related to the osteotomy), and one case of localized skin necrosis on a knee that had undergone several surgeries (secondary scarring). No cases of malunion or migration of the TT were noted. The mean deliberate proximal migration obtained was 13 mm±6 (range, 8-33 mm). The patellar index increased from 0.18±0.20 (range, -0.39 to 0.57) to 0.33±0.19 (range, -0.13 to 0.60).

DISCUSSION

This series shows that the indications are rare but invaluable, facilitating the approach and most particularly making it possible to modify the position of the patella, thus contributing to increasing the joint range of motion. Fixation with two screws carries no risk of disassembly if the technique is rigorous. Patellar translation is limited by the tibial tray.