Summary

Hamstring weakness and proprioceptive deficits seen following ACL reconstruction are not evident following primary augmented ACL repair at mean four years post-operatively

Abstract

Anterior cruciate ligament (ACL) reconstruction has been associated with loss of proprioception and donor site morbidity in the form of knee extension or flexion weakness. ACL repair, where the ligament is re-attached and augmented with suture tape negates the need for graft harvest, maintaining native anatomy. The aim of this study was to compare outcomes including strength and proprioception following ACL repair and reconstruction surgery.

Nineteen ACL repair and nineteen hamstring ACL reconstruction patients (mean 4 years post-operatively) were recruited post-operatively, along with twenty healthy volunteers. Patient reported outcome measures (PROMs) were collected. Knee stability was measured using Rolimeter for Lachman and anterior drawer (AD) tests. Maximal isometric quadriceps and hamstring strength at 90° knee flexion was measured using a fixed myometer. Knee angles were measured using a 16-camera Vicon 3D motion capture system. Range of movement (ROM) was recorded, and joint position sense (JPS) was assessed actively at 15° and 50° flexion. Participants performed a single leg hop test battery and limb symmetry index (LSI) was calculated as operated to uninjured side.

There were no differences in patient factors between groups; mean age 29, 64% male, Tegner 6.4. There was a trend towards higher PROM scores for the repair group compared to reconstruction. There was no difference in LSI for quadriceps peak torque or for hamstrings in the volunteer or repair group. There was hamstring weakness of the operated side (p<0.001) in the reconstruction group. The LSI was greater for hamstring strength in the repair group (95%) than the reconstruction group (81%) (p=0.009). Hamstring strength of the reconstructed legs was lower than healthy volunteers by 0.29 Nm/kg (p=0.002), but the repair group showed no significant weakness. Stability tests showed no difference between groups for Lachman but AD had greater displacements for reconstructions than healthy volunteers (4.5mm volunteer, 4.6mm repair, 5.6mm reconstruction p=0.04). Mean ROM was 7° less for the reconstructed knees than healthy volunteers (p<0.05), while no difference existed for the repair group. The mean error for JPS at 15° was 3.4 ±2°, 3.2 ±1° and 3.4 ±2°, while at 50° was 4.1 ±3°, 4.1 ±3° and 5.9 ±4° for volunteers, repair and reconstruction groups respectively. At 15° the mean error difference between operated and uninjured knees was 0.4° higher (p=0.8) and at 50° was 3.3° higher for reconstruction than repair (p=0.03). No significant difference was evident for hop tests, however, means tended toward the repair group being closer to symmetry.

Hamstring weakness and proprioceptive deficits seen following ACL reconstruction are not evident following ACL repair at mean 4 years post-operatively. This asymmetry could contribute to re-injury and influence functional performance. Longer term altered loads across the knee may lead to development of osteoarthritis. The absence of these deficits in the repair group is an encouraging finding for the outcome of these patients. Furthermore, ACL repair patients performed as well as or better in PROMs, stability, movement and hop tests than matched patients following reconstruction, supporting the theory that this technique may be suitable for use in clinical practice.