Discussion about different cut-off values of conventional hamstring-to-quadriceps ratio used in hamstring injury prediction among professional male football players.

OBJECTIVE: To measure the sensitivity and specificity of differences cut-off values for isokinetic Hcon/Qcon ratio in order to improve the capacity to evaluate (retrospectively) the injury of hamstring muscles in professional soccer screened with knee isokinetic tests. DESIGN: Retrospective study. METHODS: Medical and biomechanical data of professional football players playing for the same team for at least one season between 2010 and 2016 were analysed. Hamstring strain injury cases and the reports generated via isokinetic testing were investigated. Isokinetic concentric(con) hamstring(H) and quadriceps(Q) absolute strength in addition with Hcon/Qcon ratio were examined for the injured versus uninjured limbs among injured players, and for the injured and non-injured players. 2 x 2 contingency table was used for comparing variables: predicted injured or predicted uninjured with actual injured or actual uninjured. Sensitivity, specificity, accuracy, positive and negative predictive values, and positive and negative likelihood ratio were calculated for three different cut-off values (0.47 vs. 0.6 vs. 0.658) to compare the discriminative power of an isokinetic test, whilst examining the key value of Hcon/Qcon ratio which may indicate the highest level of ability to predispose a player to injury. McNemar's chi2 test with Yates's correction was used to determine agreement between the tests. PQStat software was used for all statistical analysis, and an alpha level of p <0.05 was used for all statistical comparisons. RESULTS: 340 isokinetic test reports on both limbs of 66 professional soccer players were analysed. Eleven players suffered hamstring injuries during the analysed period. None of these players sustained recurrence of hamstring injury. One player sustained hamstring strain injury on both legs, thus the total number of injuries was 12. Application of different cut-off values for Hcon/Qcon significantly affected the sensitivity and specificity of isokinetic test used as a tool for muscle injury detection. The use of 0.47 of Hcon/Qcon as a discriminate value resulted in significantly lower sensitivity when compared to 0.658 threshold (sensitivity of 16.7% vs. 91.7%, respectively; t = 6.125,p = 0.0133). Calculated values of specificity (when three different cut-off were applied) were also significantly different. Threshold of 0.6 of Hcon/Qcon resulted with significantly lower specificity compared to 0.47 value (specificity of 46.9% vs. 94.5%, respectively; t = 153.0,p<0.0001), and significantly higher specificity when compared to 0.658 (specificity of 46.9% vs. 24.1%, respectively; t = 229.0, p<0.0001). CONCLUSION: The use of different cut-off values for Hcon/Qcon significantly affected the sensitivity and specificity of isokinetic testing. The interpretation of usefulness of isokinetic test as a screening tool in a group of male professional football players to predict hamstring injury occurrence within the next 12 months might be therefore significantly biased due to the different threshold values of Hcon/Qcon. Using one "normative" value as a cut-off (e.g. 0.47 or 0.60, or 0.658) to quantify soccer players (or not) to the group with a higher risk of knee injury might result in biased outcomes due to the natural strength asymmetry that is observed within the group of soccer players.

[Postural control strategy in patients with anterior cruciate ligament deficiency]. / Sposoby kontroli postawy u chorych z niestabilnoscia przednia stawu kolanowego.

UNLABELLED: Dysfunction of the knee joint caused by injury of the anterior cruciate ligament is associated not only with mechanical joint destabilization but also damage of receptors in the ligament responsible for joint proprioception. Sensory disorders associated with damage of receptors in the ligaments may produce abnormalities in the posture control. The study aimed at evaluating postural control strategy in patients with chronic anterior cruciate ligament deficiency and determining a relationship between clinical assessment, subjective evaluation of knee joint functioning, and type of postural control. MATERIAL AND METHODS: Postural control with dynamic and static Riva test in one-legged position was assessed in 46 patients (6 women and 40 men), aged between 15 and 52 years (mean 32 years), in whom damage of the anterior cruciate ligament was diagnosed clinically and/or radiologically. Diagnosis was confirmed arthroscopically in all cases. Clinical evaluation was made with the aid of two subjective scales of knee ailments: Lysholm knee scale and subjective knee evaluation form IKDC 2000. Arthrometer Rolimeter by Aircast was used to measure the difference between lower limbs in anterior knee laxity during "anterior drawer" test and Lachman's test. The way of visual proprioceptive control was assessed with both dynamic (DRT) and static (SRT) Riva tests in monopodalic stance. Tests were performed with the DELOS Postural Proprioceptive System (DELOS s.r.l., Corso Lecce, Torino, Italy) in the biomechanical evaluation laboratory at Rehasport Clinic in Poznan. CONCLUSIONS: Strategy of the postural control in both dynamic and static Riva test does not allow differentiating ACL deficient leg from the mechanically stable leg. The obtained results of postural control in dynamic and static Riva test confirm significant value of knee joint mechanical stability for preservation its functional stability. Knee joint extension (hyperextension) may be one of mechanisms maintaining functional knee joint stability.