Document Title: MacDonald-AJSM-Nov96
Article Title: Proprioception in anterior cruciate ligament-deficient and reconstructed knees
Author: MacDonald, Peter B, Hedden, David Pacin, Ondrej, Sutherland, Kelly
Publication: The American Journal of Sports Medicine
ISSN: 03635465
Date: November-December 1996.
(Figures included. Reference-denoting numbers appear in the same point size as document text.)
Volume: 24
Issue: 6
Pages: 774-778
Key Words: Knee, ligaments, tissue grafts, ACL deficiency, reconstruction.

This study provides a good overview of the ACL's structure, including the various types of neurological detectors present in the ligament. It also notes the ACL-protective hamstring reflex. MacDonald also notes the chilling fact that in 90% of ACL-tear patients, other structures are also damaged, and that this also contributes to proprioceptive loss. (Even the effusion [swelling] resulting from each and every giving-way incident (of a chronically ACL-deficient knee) causes a reduction in neurological output of the sensors in the knee tissues. MacDonald also noted that the well-known fact that chronically ACL-deficient knees are prone to progressive instability [and eventual disability] is partly due to the proprioceptive loss.) In this study, the proprioception testing on the reconstructed knees was done 24 months after surgery (range, 17 to 30 months)...but note that more recent studies (in humans) show that the time frame for nerve-ending-regrowth-and-reconnection is longer than this. (Furthermore, in some people, such regrowth-and-reconnection might not occur at all.) MacDonald concludes (at the post-op time-frames noted) that ACL reconstruction does not improve proprioception in the ACL-deficient knee. (Note that a few of the subjects in this study had ACL reconstructions using hamstring autografting combined with synthetic graft back-up [known as ligament-augmentation devices]. The use of LADs has now fallen into disfavour, given the strain-shielding effect they cause. Conversion of an ACL graft into a bona-fide surrogate ligament requires carefully planned exposure to gradual increases in stresses; only this way can the normal helical parallel orientation of collagen strands [which is essential to the surrogate ACL developing good tensile-load-bearing capabilities] be developed in the nascent ligament. Here we see the importance of a good post-op physiotherapy programme, overseen by a knee-experienced physiotherapist. Note that variations in post-op rehab training were not accounted for by this study.) MacDonald concludes that because of the inherent difficulties and complexities associated with proprioception testing, this study may have missed some proprioceptive-type improvements. (This provides another possible explanation for the fact that Barrack's studies found prioprioceptive improvements following ACL reconstruction and rehabilitation, while MacDonald's study did not.)

ABSTRACT

Proprioceptive function of the knee was quantified and compared in three groups of patients: those with anterior cruciate ligament deficiency, with hamstring tendons-ligament augmentation device anterior cruciate ligament reconstructions, and with bone-patellar tendon-bone anterior cruciate ligament reconstructions. A total of 32 subjects, including 6 uninjured control subjects, were tested for threshold to perception of passive motion of the knee. All other sensory input was neutralized and testing occurred in the 30 degree to 40 degree range of knee flexion. The noninvolved contralateral knee served as a control for each subject. Each leg was moved at 0.5 deg/sec into flexion or extension in a random sequence. The variables of age, KT-1000 arthrometer scores, injury-to-surgery interval, injury-to-follow-up interval, and patient satisfaction were statistically analyzed for correlation with threshold to perception of passive motion of the knee. Control subjects showed no statistically significant differences in threshold between their two knees. The three test groups all showed significantly higher values in the involved knee compared with the noninvolved knee (P < 0.01 ). However, no statistically significant differences were found between the groups, including controls, with respect to mean threshold to perception of passive motion. According to these results, anterior cruciate ligament reconstruction did not improve proprioception in the patients in this study.

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