PROSPECTIVE ISOKINETIC ASSESSMENT OF MUSCLE RECOVERY AFTER HAMSTRING RECONSTRUCTION OF THE ANTERIOR CRUCIATE LIGAMENT

Abstract

Purpose: We studied early recovery of knee muscles after harvesting the hamstrings for arthroscopic reconstruction of the anterior cruciate ligament (ACL) using an isokinetic testing device (Biodex®).

Material: This prospective consecutive series included 22 athletes (twelve amateur athletes and ten competition level athletes) who presented a full thickness tear of the ACL without associated lesions. Intra-articular and extra-articular ligamentoplasty using the gracilis and semi-tendinous was performed arthroscopically by the same surgeon. The same rehabilitation program was prescribed for all patients.

Method: The flexor and extensor system of both knees was assessed for each patient using the Biodex® device operating in concentric isokinetic mode. Tests were performed at two speeds 90 and 180°/s and at three times: preoperatively, and four and seven months postoperatively. The peak couple and mean power during a series of six flexion-extension movements were retained for this analysis.

Mean values remained unchanged for the three test times for the healthy knees. We therefore chose the preoperative values obtained for the healthy knee as the paired reference value for each patient. The values obtained for the operated knees were compared with these control values using two-way analysis of variance for paired variables.

Results: At four months postop, flexor and extensor muscles exhibited significant (p < 0.05) and equivalent diminution. However, 25% of the patients had already achieved 80% recovery, sufficient for renewed sports activities. At seven months postop, the extensors had totally recovered and the flexors remained significantly diminished (related to hamstring harvesting); 65% of the patients had reached 80% recovery, but 90% of the competition level athletes had recovered more than 80%. The statistical analysis demonstrated a positive correlation between muscle recovery at seven months and preoperative muscle level: the patients with higher preop levels having the higher postop levels.

Discussion: These results suggest the following: preoperative rehabilitation exercises (to start with a higher preop level), more work on the flexors (limiting factor), new recovery objectives (80% at four months, 100% at seven months). Currently, we authorise renewed sports activities on the basis of muscle recovery as assessed by isokinetic tests which are performed at four months for competition level athletes and seven months for amateur athletes.