ACL Avulsion Injuries
Abstract & Commentary
Synopsis: Proper treatment of tibial spine avulsions appeared to restore both stability and proprioception, although problems exist with the study methodology.
Source: Ahmad CS, et al. Anterior cruciate ligament function after tibial eminence fracture in skeletally mature patients. Am J Sports Med. 2001;29(3):339-345.
Tibial spine avulsions of the ACL insertion are far more common in adolescents than in adults. It is well accepted that surgical fixation of avulsions in skeletally immature patients yields good results. However, fixation of avulsions in adults is less predictable because of potential intrinsic stretch of the ligament in addition to the bony injury. Ahmad and colleagues analyzed 10 skeletally mature patients with ACL avulsions and compared them to 10 patients with ACL reconstructions and 10 patients with ACL deficient knees who had physical therapy only. We are not told how these other 2 groups of patients were selected or the length of follow-up from surgery or injury. The avulsion group was analyzed at an average of 5 years. All patients were assessed for laxity with KT-2000 arthrometry, outcome with the Lysholm questionnaire, and for proprioception using a modification of a method referenced only once before.
Ahmad and colleagues found that proprioception was restored equally with both the ACL reconstructed and the repaired avulsion groups. There were no significant differences in laxity between these 2 groups either. However, the ACL-deficient group was significantly more lax and had inferior proprioception. They conclude that repair of tibial spine avulsions in adults can restore stability and proprioception.
Comment by David R. Diduch, MS, MD
ACL avulsion injuries of sufficient bone to repair occur quite rarely in adults. This paper supports repair of the avulsed ligament and goes against the concept of stretch within the ligament preventing a stable knee. Ahmad et al also make a case for restored proprioception. However, there are serious methodological problems with this study that makes me question their conclusions.
Most importantly, this is a retrospective study of a small group of patients with no power analysis provided to determine proper sample size. Actually, the group of 10 patients with avulsions includes 2 patients who were left completely untreated (and displaced). I have no idea why they were included in the paper at all. For the remaining 8 patients, 3 were minimally displaced and treated with a cast, while only 5 were treated surgically with varied techniques, both open and arthroscopically, by different surgeons. Essentially, this paper looks at these 5 patients with a mixed group of repair techniques and compares them to reconstructed and deficient knees that were selected by unknown means. I cannot imagine that a group of 5 comes anywhere close to sufficient power to generate statistical significance. In addition, the Lysholm scores are only provided for the avulsion group and not for the other groups for comparison. Lastly, the proprioception testing method is an adaptation of a method only referenced once before, and validation of the method or its modification is not provided.
The fact that only 5 patients with surgical treatment of these avulsions were collected over 5 years at a major teaching hospital in New York should tell us that this is a carefully selected group in terms of indications with an uncommon injury. For patients with adequate bone for stable fixation, the results probably are good. However, for patients with comminuted or small-avulsed fragments, I would be cautious to attempt a repair. Reconstruction is a more established and predictable option. Unfortunately, this paper does not provide a strong enough case to prove that ligament stretch will not compromise the results of repair.
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