Document Title: Wojtys-AJSM-May00.shtml

Article Title: Longitudinal effects of anterior-cruciate-ligament injury and patellar-tendon autograft reconstruction on neuromuscular performance

Authors: Edward M. Wojtys, Laura J. Huston.

Publication: The American Journal of Sports Medicine

ISSN: 03635465

Date: May-June 2000.

(Figures included. Reference-denoting numbers appear in the same point size as document text.)

Volume: 28

Issue: 3

Pages: 336-344

Key Words: Knee, patellar tendon, graft, ACL, neuromuscular, proprioceptive.

Comments: This penetratingly insightful article is one which everyone who has ever fully torn an ACL should read, as it is both a carefully-done study and an excellent overview of previous research. This study clearly illustrates the protracted neuromuscular consequences of ACL injury. (When the ACL is torn, the embedded nerve endings are lost as well. These nerve endings normally keep the brain apprised of the goings-on in the ligament and, by implication, in the limb in general. Although some regrowth of these nerve endings may occur in a reconstructed ACL over time, one wonders how likely it is for these nerve endings to actually become reconnected to the brain in a meaningful fashion.) Wojtys found that even at 12-18 months post-ACL-reconstruction, significant deficits in muscle performance (most notably reaction time) remained. It was found that quadriceps and hamstring reaction times were the best objective indicators of subjective knee functioning. (Also noted was that the central nervous system seems to limit affected-leg muscle output to about 70% of that of the contralateral limb. Because the knee-surrounding musculature (in particular the hamstrings) is so essential in protecting the knee against certain modes of abnormal forcing (most notably twisting and anterior-drawer forcing), these deficits likely mean that the ACL-reconstructed athlete is effectively more vulnerable to knee reinjury (as compared to a never-injured knee). Wojtys quotes the 1996 study by McDonald, which found that even at 50 months post-op, proprioception had not fully returned. Wojtys points out that "it remains to be seen if these deficiencies can be rectified over time." Note that because Wojtys' findings indicate that the full-ACL-tearing-and-subsequent-reconstruction affects both the hamstring and quadriceps groups, it is reasonable to conclude that the neuromuscular-functioning deficits he studied will exist with any type of ACL reconstruction. Wojtys also notes that in certain sports the knee can be exposed to impact forces 20 times the body's static weight (BW), and that the fact that 85% of ACL injuries are accompanied by articular-cartilage damage (i.e. bone-bruising) could have repercussions with regards to how well the ACL-injury-history knee can deal with the dynamic loadings of high-impact activities.

ABSTRACT

We examined persons after anterior cruciate ligament injury and for 1.5 years after anterior cruciate ligament reconstruction to analyze changes in anterior knee laxity, lower extremity muscle strength, endurance, and several parameters of neuromuscular function. Sixteen men and nine women (average age, 23.8 years) were evaluated preoperatively, then underwent intraarticular autogenous patellar tendon anterior cruciate ligament reconstruction by the same surgeon and were evaluated at 6, 12, and 18 months postoperatively. Muscle strength was measured isokinetically and neuromuscular function was quantified with simultaneous anterior tibial translation and surface electromyography tests. Forty subjects (26 men and 14 women; average age, 23.5 years) with no known knee abnormalities served as the control group. Subjective questionnaire results showed that by 18 months postoperatively, 20 subjects (80%) believed they had regained their preoperative levels of function. Unfortunately, muscle function in most subjects had not returned to normal. At 12 to 18 months postoperatively, when knee rehabilitation was terminated, significant deficiencies in muscle performance persisted in most patients. Interestingly, in this group of stable knees, quadriceps and hamstring muscle reaction times appeared to be the best objective indicators of subjective knee function.

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