A CADAVERIC STUDY OF FOOT TENODESIS EFFECT AND DIGITAL CASCADE

Abstract

Tenodesis effect and digital cascade of the foot were never described in the current literature. However, understanding of these effects are important in the diagnoses and managements of foot flexor tendon rupture and lesser toe deformities. We aim to investigate the presence of these effects in the foot with intact and cut tendons.

Ten fresh frozen cadaveric specimens were used in our study. 2^nd, 3^rdand 4^thtoe metatarsophalangeal joint (MTPJ) and proximal interphalangeal joint (PIPJ) range of motion (ROM) at ankle resting position were measured. Same measurements were repeated with maximum ankle plantarflexion and dorsiflexion. 4^thtoe Flexor Digitorum Longus (FDL) was then identified over plantar aspect of metatarsal shaft and cut transversely. 2^nd, 3^rdand 4^thtoe MTPJ and PIPJ ROM at ankle resting position, maximum plantarflexion and dorsiflexion were then measured.

Mean 4^thtoe MTPJ and PIPJ ROM at ankle dorsiflexion were 13.5 ° of dorsiflexion and 25 ° of plantarflexion respectively, compared with values at ankle plantarflexion which were 35 ° and 25 ° respectively. After 4^thtoe FDL was cut, mean 4^thtoe MTPJ and PIPJ ROM at ankle dorsiflexion were 14 ° and 24 ° respectively and at ankle plantarflexion the values were 34.5 ° and 25 ° respectively. At ankle resting position before 4^thFDL was cut, mean 4^thtoe MTPJ and PIPJ ROM were 22 ° and 31 ° respectively, compared with the values after 4^thFDL was cut, ie 22.5 ° and 30.5 ° respectively.

Tenodesis effect of the foot was shown in our study. However unlike in hand, this effect was only present in MTPJ and was still present following cut FDL. Similarly, digital cascade was still present following cut FDL. The maintenance of tenodesis effect and digital cascade following cut flexor tendon is likely contributed by various soft tissue restraints and intrinsic muscle actions. These findings are important in both the diagnosis and management of foot flexor tendon rupture and help us to better understand the biomechanics of lesser toe deformities and the managements of these deformities.