Flexor Digitorum Profundus Tendon Tension During Finger Manipulation - A Study in Human Cadaver Hands

Principal Investigator: Peter C. Amadio, M.D.
Project Coordinator: Chunfeng Zhao, M.D. — zhao.chunfeng@mayo.edu

Early mobilization after tendon repair is widely recognized as the most practical means of preventing adhesion formation. However, early motion, if too aggressive, may also have the detrimental effect of contributing to gap formation or suture rupture. However, if not aggressive enough, the digit may move but the tendon may not glide, as the passive forces applied to the tendon may not overcome the internal resistance to gliding with the tendon sheath. The purpose of this study was to compare the tendon tension during commonly used rehabilitation protocols after flexor tendon injury, by simultaneously measuring the flexor digitorum profundus tendon tension in zone II and digit angle during joint manipulations which simulate those protocols. Eight human cadaver specimens were used for the analysis. Various wrist and finger joint configurations were studied.

The wrist position had a large effect on tendon tension for any finger position. Digit motion with the wrist flexed 60° resulted in significantly lower tendon tension compared to motion with the wrist extended. The MCP joint position also had a large effect on tendon tension. Generally, the tendon tension in the zone II region was lower with MCP joint flexion and higher with MCP joint extension. The effect of MCP joint position was significant. The tension applied to the tendon increased with MCP joint extension.

For example, there was no tension with the finger fully flexed with the wrist extended (synergistic motion), but the tendon force reached 1.77 N with the MCP joint hyper extended 45° and the DIP and PIP joints flexed. Based on our study, we have designed a clinical 'modified synergistic' therapy protocol, which is a combination of synergistic motion and MCP joint hyperextension with DIP and PIP joint flexion.