The Clinical Significance Of Q-angle Measurement Under Different Conditions In Recurrent Patellar Dislocation

Objective To investigate the clinical significance of Q-angle measurement under different conditions in recurrent patellar dislocation.Methods Between August2012and March2012,10female patients (11knees) confirmed with recurrent patellar dislocation by arthoscopy were collected as trial group, which average age was17.4years old (range from16to24years).20female patients (20knees) confirmed with simple meniscus injury were collected as control group at the same time, which average age was19.4years old (range from11to25years). Q-angle of the trial group’s was measured when the knee was at the extension position,30°flexion,30°flexion with correcting patella and the last position as patellar dislocation was corrected in surgical operation. Q-angle of the control group was measured only at the extension position and30°flexion. Then we calculated the changed degree of Q-angle in two groups when the knee was measured at the extension position and30°flexion. Independent sample T-test was used to analyze Q-angle degrees at the extension position,30°flexion and the changed degrees of two groups. The Q-angle, at30°flexion wih correcting patella and in surgical operation, of the trial group was analyzed by paired T-test.RESULTS Q-angle in the trial group was17.2°±3.6°at the extension position, while14.3°±3.0°at the30°flexion position. The changed degree of Q-angle in the trial group was-2.45°±2.62°. Q-angle in the control group was15.2°±3.4°at the extension position, while14.4°±3.5°at the30°flexion position. The changed degree of Q-angle in the control group was-0.75°±1.68°. Q-angle at the extension position of two groups had not statistical differences(t=1.553, P=0.131>0.05). And the same to Q-angle at the30°flexion position(t=-0.101, P=0.920>0.05). But the changed degree of two groups were statistical differences (t=-3.252, P=0.003<0.05). It evidenced The Q-angle at30°flexion position wih correcting patella and in surgical operation of the trial group was higher significantly than the control group. The degree of Q-angle by manual reduction in the trail group was19.8°±3.4°. And the degree of Q-angle by surgical operation was18.9°±3.8°. The degree of two groups had not statistical differences(t=2.193, P=0.053>0.05).Conclusions1. When a female patient’s Q-angle at the30°flexion knee changes obviously than at the extension position, recurrent patellar dislocation should be considered.2. For female patients with recurrent patellar dislocation, the preoperative degree of Q-angle at30°flexion with correcting patella shoule be measured. It can help increasing the accuracy of evaluation whether remote rearrangement should be operatived.