SYMMETRY OF THE FEMORAL NOTCH WIDTH INDEX

A small femoral notch width index has been reported as a predictive fa ctor for anterior cruciate ligament injury and implicated in the highe r incidence of anterior cruciate ligament injuries in female athletes. Notch-plasty has been recommended for the unaffected knees of patient s who have torn one anterior cruciate ligament and whose notch width i ndex falls one standard deviation below ''normal.'' However, the symme try of the notch width index has not been specifically studied. We com pared the notch width index in both knees of 40 male and 40 female pat ients. Half of the patients in each group had anterior cruciate ligame nt injuries, all from a noncontact mechanism. We found that the notch width indexes of the right and left knees of the same patient are esse ntially symmetrical, regardless of sex or anterior cruciate ligament s tatus. Although the female patients tended to have smaller notch width indexes than the male patients, the difference was not statistically significant. Moreover, the ranges of notch width indexes in male and f emale patients overlapped considerably. Finally, there was no differen ce in notch width index between patients with and without anterior cru ciate ligament tears. These findings suggest that the notch width inde x alone is not the critical etiologic factor in the patient with a uni lateral anterior cruciate ligament tear. Furthermore, the increased in cidence of anterior cruciate ligament tears in female patients compare d with male patients in the same sports cannot be attributed to notch width index alone.