Neuromuscular Evaluation With Single-Leg Squat Test at 6 Months After Anterior Cruciate Ligament Reconstruction
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Neuromuscular Evaluation With Single-Leg Squat Test at 6 Months After Anterior Cruciate Ligament Reconstruction
Michael P. Hall
Ronald S. Paik
Anthony J. Ware
Karen J. Mohr
Orr Limpisvasti
Los Angeles
California
Background: Criteria for return to unrestricted activity after anterior cruciate ligament (ACL) reconstruction varies, with some using time after surgery as the sole criterion-most often at 6 months. Patients may have residual neuromuscular deficits, which may increase the risk of ACL injury. A single-leg squat test (SLST) can dynamically assess for many of these deficits prior to return to unrestricted activity. Hypothesis: A significant number of patients will continue to exhibit neuromuscular deficits with SLST at 6 months after ACL reconstruction. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Patients using a standardized accelerated rehabilitation protocol at their 6-month follow-up after primary ACL reconstruction were enrolled. Evaluation included bilateral SLST, single-leg hop distance, hip abduction strength, and the subjective International Knee Documentation Committee (IKDC) score. Results: Thirty-three patients were enrolled. Poor performance of the operative leg SLST was found in 15 of 33 patients (45%). Of those 15 patients, 7 (45%) had concomitant poor performance of the nonoperative leg compared with 2 of 18 patients (11%) in those who demonstrated good performance in the operative leg. The poor performers were significantly older (33.6 years) than the good performers (24.2 years) (P ¼ .007). Those with poor performance demonstrated decreased hip abduction strength (17.6 kg operative leg vs 20.5 kg nonoperative leg) (P ¼ .024), decreased single-leg hop distance (83.3 cm operative leg vs 112.3 cm nonoperative leg) (P ¼ .036), and lower IKDC scores (67.9 vs 82.3) (P ¼ .001). Conclusion: Nearly half of patients demonstrated persistent neuromuscular deficits on SLST at 6 months, which is when many patients return to unrestricted activity. Those with poor performance were of a significantly older age, decreased hip abduction strength, decreased single-leg hop distance, and lower IKDC subjective scores. Clinical Relevance: The SLST can be used to identify neuromuscular risk factors for ACL rupture. Many patients at 6 months have persistent neuromuscular deficits on SLST. Caution should be used when using time alone to determine when patients can return to unrestricted activity.
anterior cruciate ligament; return to unrestricted activity; single-leg squat test; neuromuscular evaluation
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Substantial research has supported neuromuscular deficits
to be risk factors for anterior cruciate ligament (ACL)
rupture.24-26,48,54,59 Increased valgus loading of the knee
and deficits in trunk stability have both been shown to
predict ACL injury with high sensitivity and specificity in
female athletes.8,25,26,39,54,58,59 Recent kinematic research
has now supported a link between increased knee
abduction forces and lateral trunk displacement during
noncontact ACL injuries.2,6,26,27 This association has provided a
strong rationale for the development of trunk- and
corebased strengthening programs, which have demonstrated
a decreased risk of ACL injury.17,18,20,23,26,37,56
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In addition to preventing ACL injury, preventing
reinjury after ACL reconstruction is a concern for orthopaedic
surgeons. The risk of ACL rerupture is substantially
higher than it is prior to the initial ACL injury,22,44,47,50,52
and traumatic rerupture after ACL reconstruction is the
most common mechanism of failure in the first 2 years
postoperatively.57 Increasing emphasis is being placed
on postoperative rehabilitation, as increased rerupture
rates have been observed when deficits in postural
stability and hip dynamics are not addressed.22,45
Currently, there is little evidence-based guidance on
appropriate criteria, including in-office screening, for
determining readiness for return to play after ACL
reconstruction. A single-leg squat test (SLST) is used as an
indicator of residual deficits in hip abduction strength and pelvic
stability and has been used in baseball players returning
from shoulder injury.12,34 There is a correlation between
performance on SLST and hip abductor function.5,12,31,35 Hip
abductor weakness increases the risk of AC (...truncated)