Primary opponensplasty in toe transfers provides active restoration of thumb opposition and significantly better restoration of tripod pinch than does static opposition with osteosynthesis , research suggests.
Chih-Hung Lin (Chang Gung Memorial Hospital and University, Taoyuan, Taiwan) and colleagues therefore recommend that primary opponensplasty is performed at the time of toe transfer in such injuries.
Lin et al analyzed 19 toe-to-thumb transfers proximal to the metacarpophalangeal level with concomitant thenar muscle damage. All patients underwent either pedicled groin flap (n=16) or free flap (n=3) surgery for amputation stump resurfacing.
Nine of the transferred toes were operated on using a static opposition procedure with osteosynthesis by rotation of 30-60°, while 10 transferred toes were operated on using additional simultaneous opponensplasty to provide dynamic opposition.
For the procedure involving osteosynthesis alone, osteosynthesis of the proximal phalangeal base of the transferred toe was performed to the first metacarpal stump.
For the procedure involving additional simultaneous opponensplasty, the flexor digitorum was the chosen donor tendon, with its pivot point on the flexor carpi ulnaris using a loop of the flexor carpi ulnaris as a pulley. Tensioning of the opponensplasty was performed with the wrist in 30° of flexion and the thumb ray at an approximate 90° arc intraoperatively.
Overall, seven of nine individuals who had a static opposition procedure with osteosynthesis achieved opposable basic hand function and lateral pinch compared with all of those who underwent an additional simultaneous opponensplasty.
Only three of nine individuals who underwent static opposition with osteosynthesis regained tripod pinch grip compared with nine of 10 individuals who underwent additional simultaneous opponensplasty, corresponding to a statistically significant difference.
The authors explain in Plastic and Reconstructive Surgery that thumb amputations proximal to the metacarpophalangeal joint inevitably result in destruction of the thenar musculature and secondary loss of opposition.
They add that pronation osteosynthesis is the traditional method of restoring opposition, but that simultaneous opponensplasty turns this static process into a dynamic one.
"This study demonstrates that in toe transfers for proximal thumb injuries lacking thenar musculature, primary opponensplasty provides a statistically significant increase in the ability to perform tripod pinch, one of the fundamental goals in thumb reconstruction.
"It is therefore suggested that pronation osteosynthesis alone is inadequate for achieving a prehensile opposable hand function, as the restoration of tripod pinch is comparatively poor," Lin et al write.
"This provides level III evidence to support the use of primary opponensplasty," they conclude.
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