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      Single leg hop for distance symmetry masks lower limb biomechanics: time to discuss hop distance as decision criterion for return to sport after ACL reconstruction?

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          Abstract

          Background

          We evaluated the lower limb status of athletes after anterior cruciate ligament reconstruction (ACLR) during the propulsion and landing phases of a single leg hop for distance (SLHD) task after they had been cleared to return to sport. We wanted to evaluate the biomechanical components of the involved (operated) and uninvolved legs of athletes with ACLR and compare these legs with those of uninjured athletes (controls).

          Methods

          We captured standard video-based three-dimensional motion and electromyography (EMG) in 26 athletes after ACLR and 23 healthy controls during SLHD and calculated lower limb and trunk kinematics. We calculated lower limb joint moments and work using inverse dynamics and computed lower limb muscle forces using an EMG-constrained musculoskeletal modelling approach. Between-limb (within ACLR athletes) and between-group differences (between ACLR athletes and controls) were evaluated using paired and independent sample t-tests, respectively.

          Results

          Significant differences in kinematics (effect sizes ranging from 0.42 to 1.56), moments (0.39 to 1.08), and joint work contribution (0.55 to 1.04) were seen between the involved and uninvolved legs, as well as between groups. Athletes after ACLR achieved a 97%±4% limb symmetry index in hop distance but the symmetry in work done by the knee during propulsion was only 69%. During landing, the involved knee absorbed less work than the uninvolved, while the uninvolved knee absorbed more work than the control group. Athletes after ACLR compensated for lower knee work with greater hip work contribution and by landing with more hip flexion, anterior pelvis tilt, and trunk flexion.

          Conclusion

          Symmetry in performance on a SLHD test does not ensure symmetry in lower limb biomechanics. The distance hopped is a poor measure of knee function, and largely reflects hip and ankle function. Male athletes after ACLR selectively unload the involved limb but outperform controls on the uninvolved knee.

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          Most cited references 24

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          Return to the preinjury level of competitive sport after anterior cruciate ligament reconstruction surgery: two-thirds of patients have not returned by 12 months after surgery.

          An athlete's desire to return to sport after anterior cruciate ligament (ACL) injury is a major indication for ACL reconstruction surgery. Typical clearance to return is 6 to 12 months postoperatively. To investigate the return-to-sport rate and participation level of a large cohort at 12 months after ACL reconstruction surgery. Case series; Level of evidence, 4. Data were analyzed for 503 patients who participated in competitive-level Australian football, basketball, netball, or soccer after ACL reconstruction surgery using a quadruple-strand hamstring autograft. Inclusion criteria included participation in competitive sport before the ACL injury and clearance from the orthopaedic surgeon to return to sport postoperatively. Patients completed a self-report questionnaire regarding preoperative and postoperative sports participation and the Cincinnati Sports Activity Scale. The International Knee Documentation Committee (IKDC) knee evaluation form and hop tests were used to evaluate knee function. Sixty-seven percent of patients attempted some form of sports activity by 12 months postoperatively; 33% attempted competitive sport. Of those who did not attempt any sports activity by 12 months, 47% indicated that they were planning to return. Men were significantly more likely than women to return. Patients who played sports with a seasonal competition, versus a year-round competition, were significantly more likely to return by 12 months. Patients with normal postoperative knee function (IKDC category A), versus those with nearly normal function (IKDC category B), were no more likely to return, but patients with good hop test results (≥85% limb symmetry index) were more likely to return than patients with poor results (<85%). People may require a longer postoperative rehabilitation period than that typically advocated to facilitate a successful return to competitive sport after ACL reconstruction surgery. The relationship between postoperative knee function and return-to-sport outcomes at 12 months after surgery was inconclusive.
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            Limb Symmetry Indexes Can Overestimate Knee Function After Anterior Cruciate Ligament Injury.

            Study Design Prospective cohort. Background The high risk of second anterior cruciate ligament (ACL) injuries after return to sport highlights the importance of return-to-sport decision making. Objective return-to-sport criteria frequently use limb symmetry indexes (LSIs) to quantify quadriceps strength and hop scores. Whether using the uninvolved limb in LSIs is optimal is unknown. Objectives To evaluate the uninvolved limb as a reference standard for LSIs utilized in return-to-sport testing and its relationship with second ACL injury rates. Methods Seventy athletes completed quadriceps strength and 4 single-leg hop tests before anterior cruciate ligament reconstruction (ACLR) and 6 months after ACLR. Limb symmetry indexes for each test compared involved-limb measures at 6 months to uninvolved-limb measures at 6 months. Estimated preinjury capacity (EPIC) levels for each test compared involved-limb measures at 6 months to uninvolved-limb measures before ACLR. Second ACL injuries were tracked for a minimum follow-up of 2 years after ACLR. Results Forty (57.1%) patients achieved 90% LSIs for quadriceps strength and all hop tests. Only 20 (28.6%) patients met 90% EPIC levels (comparing the involved limb at 6 months after ACLR to the uninvolved limb before ACLR) for quadriceps strength and all hop tests. Twenty-four (34.3%) patients who achieved 90% LSIs for all measures 6 months after ACLR did not achieve 90% EPIC levels for all measures. Estimated preinjury capacity levels were more sensitive than LSIs in predicting second ACL injuries (LSIs, 0.273; 95% confidence interval [CI]: 0.010, 0.566 and EPIC, 0.818; 95% CI: 0.523, 0.949). Conclusion Limb symmetry indexes frequently overestimate knee function after ACLR and may be related to second ACL injury risk. These findings raise concern about whether the variable ACL return-to-sport criteria utilized in current clinical practice are stringent enough to achieve safe and successful return to sport. Level of Evidence Prognosis, 2b. J Orthop Sports Phys Ther 2017;47(5):334-338. Epub 29 Mar 2017. doi:10.2519/jospt.2017.7285.
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              Quantitative assessment of functional limitations in normal and anterior cruciate ligament-deficient knees.

              The purpose of this study was to evaluate the effectiveness of five hopping, jumping, and cutting-type (shuttle run) tests in determining lower extremity functional limitations in anterior cruciate ligament- (ACL) deficient knees. Ninety-three normal subjects were tested. No statistical significance was found between right and left lower limb scores (limb symmetry index) as related to sports activity level, gender, or dominant side. This allowed an overall symmetry index score to be established for the population as a whole. An 85% symmetry index score was found in more than 90% of the normal population for the one-legged hop for distance test and the one-legged timed hop test. Thirty-five patients with ACL-deficient knees were tested. The patients also had KT-1000 and Cybex testing and completed questionnaires rating symptoms, sports activity levels, and sports functional limitations. The cutting-type tests and the vertical jump test did not detect functional limitations in a reliable manner. In the one-legged hop tests, 50% of the patients performed normally, however, all reported giving-way episodes with sports, indicating a lack of sensitivity of these tests in defining functional limitations. Patients with abnormal one-legged hop test scores were considered at serious risk for giving way and limitations during sports activities. Statistically significant relationships were found among abnormal scores on the one-legged hop-type tests and (1) self-assessed difficulty with pivoting, cutting, and twisting, (2) quadriceps weakness (Cybex), and (3) patellofemoral compression pain.
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                Author and article information

                Contributors
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                Journal
                British Journal of Sports Medicine
                Br J Sports Med
                BMJ
                0306-3674
                1473-0480
                March 09 2021
                : bjsports-2020-103677
                Article
                10.1136/bjsports-2020-103677
                © 2021

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