Association of Hip Strength with the Hip Sports Test: A Functional Test to Measure Athlete’s Ability to Return to Sport Activity after Hip Arthroscopy

OBJECTIVES: Excellent clinical outcomes and high rates of return to pre-operative level of activity has been reported in athletes that underwent hip arthroscopy. However, physicians often struggle to decide whether or not in an athlete is able to return to full activity. The Hip sports test (HST), like the already established knee test, may be a useful assessment tool towards this direction. The purpose of our study was evaluate the the correlation of the hip muscle strength values with the HST performance of athlete (measured on the same day) during the post-operative rehabilitation period. Muscle strength could serve as a complimentary, to sports test, tool in order to evaluate the return to sport ability of the athletes. METHODS: The HST score as well as the muscle strength measurement were obtained on the same day in 115 athletes. Hip muscle strength was assessed using the MicroFET Dynometer pre-operatively and post-operatively. Measurements were made in hip flexion, extension, abduction, adduction, internal rotation, external rotation, gluteus medius and hamstrings. During the HST assessment patients were assessed in single leg squats (single knee bents), lateral agility, diagonal agility exercises as well as in forward single leg lunges in order to obtain their score. The score of 18 or more is considered a passing score for this test. Pre-operatively, 62 tests were performed whereas 53 tests were performed post-operatively. Our data were normally distributed- however, correlation was done non-parametrically using Spearman’s rank correlation coefficient (Spearman’s rho) due to the limited scale of HST. RESULTS: The pre-operative strength change compared to the uninjured hip was -4.8% for flexion, -2.2% for extension, 2.4% for abduction, 0.3% for adduction, -2.1% for internal rotation, -1.7% for external rotation, -1.5% for gluteus medius and 1.3% for hamstring. The pre-operative median HST score was 12.5 (range: 0-20). Post-operative hip strength measurements and the distribution of HTS scores are summarized in the table.The Total HST score performance was correlated with hip muscle strength in extension (rho=0.344; p=0.001) and external Rotation (rho=0.260; p=0.006). CONCLUSION: The HST score performance is correlated with the hip muscle strength of hip extension and hip external rotation.