A clinical explosive pivot shift, graded 2 or 3, it’s strongly correlated with lesions of the anterolateral complex, and can be a reliable method to select patient for performing an additional lateral procedure
Anterolateral rotatory knee instability has been described as a result of a combined injury of ACL and secondary restraints of lateral compartment (anterolateral complex). The Pivot-Shift test remains the most used and reliable tool to evaluate and measure the degree of such a kind of instability. As in chronic ACL deficient knee the amount of involvement of anterolateral complex can be difficult to assess due to the scar tissue formation, the acute setting seems to be the best scenario to investigate possible correlation between actual injury of anterolateral complex and Pivot-shift test. The aim of this study was to investigate the correlation between the degree of the Pivot-shift and lesions of anterolateral complex in patients undergoing ACL reconstruction for an apparently isolated acute ACL tear.
A consecutive series of 75 cases to be operated for an acute (within 10 days) apparently isolated ACL tear were selected. Patients with previous surgery, chronic instability or multiligamentous injuries as revealed by clinical tests or MRI were excluded. Under anaesthesia, all patients were examined and Pivot-shift evaluated as negative, grade 1 (glide), grade 2 (jerk) grade 3 (subluxation) by the same senior surgeon. At surgery, besides a standard arthroscopic assisted ACL reconstruction with hamstrings, a lateral incision was performed and lateral compartment accurately exposed under the iliotibial tract. Injuries of the anterolateral complex were identified, recorded, classified and photographed.
A post-hoc power analysis, performed using G*Power 3 software (Heinrich-Heine-University, Dusseldorf, Germany), with an alpha error of 0.5 and a total sample size of 75 patients showed a power (1-beta) of 0.99. Correlation between variables of the study (type of lesion detected and pre-operative degree of pivot-shift) was performed with Pearson's chi-square test for independent variables and with Spearman's test for dependent variables.
The pivot shift was positive in all cases and graded as grade 1 in 9/75 patients, grade 2 in 37/75 and grade 3 in 29/75 cases.
Macroscopic tear of the anterolateral complex were found in 68/75 patients and classified as follow:
Type I, (multilevel rupture with individual layers torn at different levels with macroscopic haemorrhage involving the area of Antero Lateral Ligament (ALL) and extended to Antero Lateral capsule only): 20/75
Type II ( multilevel rupture with individual layers torn at different levels with macroscopic haemorrhage extended from the area of ALL and capsule to PL capsule) : 23/75
Type III, complete transverse tear involving the area of ALL near its insertion to the lateral tibial plateau, distal to lateral meniscus; 15/60
Type IV, bony avulsion (Segond’s fracture);6/60
Statistical analysis showed a positive correlation between presence of lesion and a pre-operative 2 or 3 degree of pivot-shift (p<0.001).
The results of the present study suggest a positive correlation between lesions of the lateral compartment, regardless of the type described, and a pivot-shift graded 2 or 3. However, a direct correlation between every single type of lesion and the degree of the pivot-shift phenomenon was not found
In conclusion, a clinical explosive pivot shift, graded 2 or 3, it’s strongly correlated with lesions of the anterolateral complex, and can be a reliable method to select patient for performing an additional lateral procedure.