Abstract
OBJECTIVES: Recently, the interest in the anterolateral knee anatomy and tears of the anterolateral structures following anterior cruciate ligament (ACL) injury has brought back interest in extra articular procedures in an attempt to aid reestablishing normal rotational laxity to the ACL deficient knee. However, the contribution of an extra articular tenodesis combined to the ACL reconstruction, as well as the role of the lateral capsule of the knee in the knee stability, are poorly understood. The objective of this study was to determine the effect of anterolateral capsule injury and extra-articular tenodesis on the intact, ACL-deficient, and ACL-reconstructed knees. Our hypothesis was that the extra articular tenodesis associated with ACL-reconstruction would be necessary to reestablish intact knee kinematics exclusively when an anterolateral capsule injury is associated with an ACL tear. METHODS: Seven knees from whole lower extremity fresh-frozen human cadavers (mean age: 60 years) were utilized in the study. Three Orthopedic surgeons performed the pivot shift test and one surgeon applied maximal anterior load at 30° of knee flexion and maximal rotatory torques (internal and external rotations) at 30° and 90° of knee flexion. Three trials of each examination were recorded in seven knee states (Table 1). Injury to the anterolateral capsule was created by making a 2 cm incision at the level of the joint line starting 5 mm anterior to lateral collateral ligament. Extra articular tenodesis was performed by a modified Lemaire procedure. An electromagnetic tracking system (Nest of Birds, Ascension Technology) was used to measure the kinematics of the knee (accuracy: 0.5 mm and 0.5°). Tibial and femoral coordinate systems were determined in the Grood-Suntay joint coordinate system and anterior tibial translation and rotations were determined with respect to the femur. The Kruskal-Wallis test was used since the data was non-Normally distributed. RESULTS: Anterior tibial translation (ATT) during the pivot shift test (Figure 1) significantly increased from 8.0 ± 5.2 mm to 12.7 ± 6.2 mm (p = .006), and internal rotation (IR) significantly increased from 12.6 ± 6.1° to 16.4 ± 6.9° (p = .04) after injuring the lateral capsule in an ACL deficient knee. There was no difference in knee kinematics when an extra articular tenodesis was performed in a knee with intact lateral capsule. Significant difference was found in ATT (decreased from 7.0 ± 3.4 mm to 4.4 ± 2.7 mm, p = .014) and IR (decreased from 13.4 ± 6.8° to 8.4 ± 4.3°, p = .01) when the extra articular procedure was performed after the ACL reconstruction in a lateral capsule injured knee. When evaluating the maximum manual loads, the effects of injuring the capsule and adding the extra articular tenodesis were less relevant then when evaluating a dynamic test like the pivot shift. CONCLUSION: An extra articular tenodesis was beneficial in reestablishing the normal knee kinematics only when a lateral capsule lesion was present. Moreover, This study may aid in developing guidelines regarding the proper indication of an extra articular tenodesis following an ACL reconstruction.