How tibial tubercle torsion impacts patellar stability: A biomechanics study.

INTRODUCTION: A new factor for patellofemoral instability-external torsion of the tibial tubercle-has recently been described. The primary aim of this biomechanics study was to analyze the consequences of internal torsion tibial tubercle osteotomy (TTO) on an experimentally unstable patella. We hypothesized that internal TTO can stabilize an experimental patellar instability. MATERIALS AND METHODS: This in vitro study was conducted on six fresh anatomical specimens. The knees were flexed to 25°. The patella was destabilized by transecting the patellar retinaculae and the vastus medialis tendon and by applying continuous oblique traction on the quadriceps tendon. A 3D stereovision system was used to record patellar displacement and tilt and to determine whether patellar dislocation occurred. The measurements were done before the osteotomy then repeated on the same knee after a triangular internal torsion 30° TTO was completed, without medialization. RESULTS: There was a significant difference in the patellar displacement and tilt before and after the osteotomy (p<0.05). Patellar dislocation, which was induced by traction on all the knees before osteotomy, did not occur after the osteotomy was performed. DISCUSSION: Internal torsion of the tibial tubercle improves patellar stability, confirming our hypothesis. These findings confirm the stabilizing effect of placing the tibial tuberosity in internal torsion. Although a knee without instability factors is not the perfect model for patellar instability, our findings suggest that tibial tubercle torsion influences patellar stability. Internal TTO may be justified as a surgical treatment of patellofemoral instability.

Revision ACL reconstruction: influence of a lateral tenodesis.

PURPOSE: The aims of this article were to report the objective results of revision ACL reconstruction and to assess the influence of an associated lateral extra-articular tenodesis on knee stability and IKDC score. METHODS: This study focused on revision ACL reconstruction and was conducted over a 10-year period, from 1994 to 2003 with ten French orthopedic centers participating. The minimum follow-up required was 2 years. To be included, patients had to be evaluated at follow-up with the objective International Knee Documenting Committee (IKDC) scoring system. In 2006, 163 patients met the inclusion criteria. RESULTS: The objective IKDC knee score improved significantly after revision ACL reconstruction, with 72% IKDC A + B (26% A). When a lateral tenodesis was performed, 80% had a negative pivot shift, versus 63% without (P = 0.03), but there was no significant difference in the IKDC score. CONCLUSION: This study shows a significant improvement in the IKDC score after revision ACL reconstruction. The association of a lateral extra-articular tenodesis with the intra-articular graft increases knee stability after revision ACL reconstruction; however, this additional procedure does not significantly alter the IKDC score at follow-up. LEVEL OF EVIDENCE: Retrospective case series, Level IV.

Causes for failure of ACL reconstruction and influence of meniscectomies after revision.

The purpose of this multicenter retrospective study was to analyze the causes for failure of ACL reconstruction and the influence of meniscectomies after revision. This study was conducted over a 12-year period, from 1994 to 2005 with ten French orthopaedic centers participating. Assessment included the objective International Knee Documenting Committee (IKDC) 2000 scoring system evaluation. Two hundred and ninety-three patients were available for statistics. Untreated laxity, femoral and tibial tunnel malposition, impingement, failure of fixation were assessed, new traumatism and infection were recorded. Meniscus surgery was evaluated before, during or after primary ACL reconstruction, and then during or after revision ACL surgery. The main cause for failure of ACL reconstruction was femoral tunnel malposition in 36% of the cases. Forty-four percent of the patients with an anterior femoral tunnel as a cause for failure of the primary surgery were IKDC A after revision versus 24% if the cause of failure was not the femoral tunnel (P = 0.05). A 70% meniscectomy rate was found in revision ACL reconstruction. Comparison between patients with a total meniscectomy (n = 56) and patients with preserved menisci (n = 65) revealed a better functional result and knee stability in the non-meniscectomized group (P = 0.04). This study shows that the anterior femoral tunnel malposition is the main cause for failure in ACL reconstruction. This reason for failure should be considered as a predictive factor of good result of revision ACL reconstruction. Total meniscectomy jeopardizes functional result and knee stability at follow-up.