Vertical Jump Test as a Functional Test after Anterior Cruciate Ligament Reconstruction

OBJECTIVES: Among the various functional tests to determine the return to sports after anterior cruciate ligament reconstruction (ACLR), the most popular one is single leg hop for distance due to its convenience to perform in clinic based offices. Although its popularity, not many clinicians can actually assess with this test because it requires a spacious room to jump across, and another investigator to check the hopped distance, manually. The purpose of this study is to compare vertical jump test which can be assessed easily with a computerized system in a smaller room, with other functional tests, which are used widely as a guide for determining return to sport, and to assess the validity of vertical jump test as a functional performance test after ACLR. METHODS: Seventy five ACL reconstructed patients (Mean age: 29.5±9.2 years, Mean height: 172.2±8.2 cm, Mean weight: 72.3±11.0 kg, Mean time since surgery: 27.5±6.1 months) completed subjective questionnaires (International Knee Documentation Committee (IKDC), Tegner and Lysholm scores) and functional performance tests; Single leg hop for distance, vertical jump test and three other functional performance tests (Cocontraction, Shuttle run, Carioca tests). Instability was measured with KT-2000. Peak torque/body weight ratio (PT/BW ratio) of extensor and flexor muscle is used to compensate the individual differences in the absolute values of isokinetic muscle strength. Limb symmetry index (LSI, %) was calculated for single leg hop for distance and vertical jump test which were tested separately in each limb. Correlation coefficients between LSI for vertical jump test and other measurements were analyzed. RESULTS: LSI for vertical jump test was correlated to LSI for single leg hop for distance (r=0.354, p=0.002), cocontraction (r=-0.351, p=0.002), shuttle run (r=-0.358, p=0.002), Carioca test(r=-0.285, p=0.013), IKDC (r=0.316, p=0.006) and Tegner scores (r=0.237, p=0.041). There were no correlations with KT-2000 (p=0.626) and Lysholm score(p=0.198). In isokinetic strength tests, extensor PT/BW ratio (60 deg/sec: r=0.298, p=0.009; 180 deg/sec: r=0.247, p=0.033) and extensor strength deficit (60 deg/sec: r=-0.412, p<0.001; 180 deg/sec: r=-0.306, p=0.007) were correlated to LSI for vertical jump test, whereas flexor PT/BW ratio and flexor strength deficit were not. CONCLUSION: As the degrees of functional performance, subjective outcome scores and recovery of extensor strength are correlated with LSI for vertical jump test which clinician can easily assess with a computerized system in clinical offices, we suggest vertical jump test as a functional test after ACLR to determine the return to sports.