CHANGES IN THE FLEXIBILITY CHARACTERISTICS OF THE ANKLE COMPLEX DUE TO DAMAGE TO THE LATERAL COLLATERAL LIGAMENTS - AN IN-VITRO AND IN-VIVOSTUDY

This study was part of a long-term effort to develop a reliable diagno stic procedure for ankle ligament injuries. Earlier efforts led to the development and validation of a six-degrees-of-freedom instrumented l inkage capable of measuring the flexibility characteristics of the ank le complex in vitro and in vivo. The major goal of the present study w as to determine if these flexibility measurements are sufficiently sen sitive to detect the presence of damage to the lateral collateral liga ments of the ankle joint both in vitro and ill vivo. the anterior talo fibular ligament and the calcaneofibular ligament. The flexibility in inversion-eversion, anterior drawer, and internal-external rotation wa s measured before and after resection of the ligaments. The in vivo te sting was conducted on five patients with unilateral injuries to the a nkle ligament. The flexibility evaluation used for ii? vitro specimens was also performed on both the injured and the intact ankles. For the in vitro testing, the data analysis was based on comparison of flexib ility values before and after resection of the ligaments, whereas the data analysis for the in vivo testing was based on comparison of the f lexibility of the injured joint with that of the intact contralateral joint. The results of the in vitro study indicated that both an isolat ed rupture of the anterior talofibular ligament and combined damage of the anterior talofibular and calcaneofibular ligaments produce statis tically significant changes in flexibility. Furthermore, the most sens itive parameters to the presence of ligament injuries were found to be early flexibility in anterior drawer, early flexibility in inversion, and the amount of coupling between internal rotation and inversion. T hese parameters provided a basis for differentiating between an isolat ed injury to the anterior talofibular ligament and a combined anterior talofibular and calcaneofibular ligament injury. For an isolated ante rior talofibular ligament injury. a significant increase in flexibilit y in anterior drawer was present, whereas the increase in inversion fl exibility or in the amount of coupling was insignificant. However, the increases in inversion flexibility and the amount of coupling became significant when both ligaments were involved. The results of the in v ivo study indicated that significant changes in flexibility can be det ected in patients with lateral ankle injuries. Finally, both the in vi tro and ill vivo results suggest that development of a reliable diagno stic test for ankle ligament injury based an changes in passive flexib ility may be possible.