Muscle strength and function before and after anterior cruciate ligament reconstruction using semitendonosus and gracilis

Abstract

This study assessed the quadriceps and hamstring strength before and 6 months after anterior cruciate ligament (ACL) reconstructive surgery using the hamstrings and related the findings to functional performance. Six months after surgery is a critical time for assessment as this is when players are returning to sport. Maximum isokinetic strength of 31 patients with complete unilateral ACL ruptures was measured at speeds of 60° and 120° per second. Functional assessment included the single hop, the triple hop, the shuttle run, side-step and carioca tests. All patients underwent a controlled quadriceps emphasized home-based physiotherapy program both before and after surgery. Results show that before surgery there was a 7.3% quadriceps strength deficit at 60° per second compared to the uninjured leg but no hamstring strength deficit. After surgery there was a statistically significant but relatively small loss of muscle strength. The quadriceps strength deficit had increased to 12% and there was a 10% hamstring deficit. Post-operatively there was an 11% and 6.3% improvement in the hop tests, a 9% (P<0.01) improvement in the shuttle run, a 15% (P<0.001) improvement in the side step and a 24% (P<0.001) improvement in the carioca tests (P<0.001) despite the loss of muscle strength.

Introduction

Rupture of the anterior cruciate ligament (ACL) is a disabling sporting injury and clinicians are continually seeking to provide optimal surgical and rehabilitation strategies. For the past decade the gold standard in reconstruction has been to use a bone-patellar tendon-bone graft from the middle third of the patellar tendon. However, loss of quadriceps strength following the harvesting of the middle third of the patellar tendon has long been a concern of the clinician [1]. Although the stability achieved post-operatively using this method is very satisfactory [2], many authors have described profound quadriceps strength losses with maximum deficits of up to 41% [3], 28% [4], 21% [5] and 18% [6]. Only minimal hamstring strength losses are recorded with this surgical technique [1], [4]. Some surgeons no longer recommend harvesting a graft from the patellar tendon [1] as it is considered that following patellar tendon reconstruction for cases of chronic instability it is impossible to regain pre-injury quadriceps strength [7].

For this reason, and because of the high donor site morbidity [8] associated with patellar tendon reconstructions, there has been a shift in practice by many surgeons to use quadruple hamstring tendons from semitendonosus and gracilis (STG) as a graft source. With this procedure, it may be anticipated that a lesser quadriceps, and greater hamstring deficit would exist. However, it could also be argued that quadriceps strength would still be subject to the inhibition associated with the surgery [7] and to the effect of restricting certain quadriceps activity post-operatively in order to minimize exercise generated shear that could stretch the graft [9], [10]. In fact, several studies [11], [12], [13], [14], [15] have shown a greater deficit in the quadriceps than the hamstrings following reconstruction using a graft from the hamstrings. For instance, Carter [12] found a 21.9% quadriceps strength deficit and an 18% hamstring strength deficit measured isokinetically at movement speeds of 180° per second as compared to the uninjured leg, 6 months post-surgery. In a longer term study, Maeda [11] showed that a 10.3% quadriceps and a 0% hamstring strength loss measured at 60° per second persisted between 2 and 4 years after surgery. As no data were reported by these authors, the degree of quadriceps strength deficits pre-operatively is unknown. No study reporting strength deficits associated with reconstruction using a hamstring graft has assessed both pre- and post-operative torque with a view to improving pre-operative strength or final outcomes. Nor has functional performance before and after surgery been compared or related to strength and post-operative stability.

The aim of this study therefore, was to assess the nature of the strength deficits in the quadriceps and hamstring muscles in a group of 31 patients prior to and after undergoing STG graft reconstructions and relate these findings to functional performance. The patients were assessed 1 week before surgery and at 6 months post-surgery. The 6 month data collection for post-operative measures was considered to be a critical time to assess strength and function as this is often when surgeons recommend that patients return to sport.