Active extensor indicis proprius extension strength after its use as a tendon transfer: 19 cases

Complications following extensor indicis proprius (EIP) tendon transfer are loss of strength, independence and mobility in the index finger in extension. The main goal of this study was to measure the index finger's independent and dependent extension strength after a tendon transfer. Secondary goals were to determine if the index finger retained the ability to extend independently after the transfer and to evaluate second metacarpophalangeal (MCP) joint mobility. Our study consisted of 19 patients in whom the EIP tendon had been divided proximally to the extensor hood. The EIP tendon was retrieved through a proximal approach at the distal radius level and rerouted towards a recipient tendon. At an average follow-up of 41 months, the average independent extension strength was 5.6N versus 11N on the contralateral side and the dependent strength was 10.9N versus 20N. No patient complained of a loss of extension strength and all had retained independent active extension on the operated index finger. The second MCP joint on the operated side had an independent extension lag of 15.3° compared to the contralateral healthy side and a dependent extension lag of 0.2°. Two patients were impaired in their daily activities when moving the operated index finger. Our results show that EIP harvesting for tendon transfer leads to decreased independent and dependent strength as well as decreased active extension of the second MCP joint. However, the functional impact was negligible and should not compromise the use of the EIP as a tendon transfer.

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