Purpose: The purpose of this study was to compare directly the total work of flexion (TWOF) and the intrasynovial work of flexion (IWOF) of human flexor digitorum profundus tendons and to analyze the ratio of the IWOF to the TWOF of human flexor digitorum profundus tendons. These factors may be important clinically in understanding the role of different methods of postoperative tendon rehabilitation for different types of tendon repairs, especially at the early stage after tendon repair.
Methods: Two different tendon repairs, the modified Kessler and the Massachusetts General Hospital, were used in 18 digits from 6 freshly frozen human cadaver hands. The TWOF and the IWOF were tested by using a digit-resistance testing device.
Results: After tendon repair the TWOF increased 11.2% and 26.9% for the modified Kessler and MGH groups, respectively. The differences in increase between the 2 groups were significant. The IWOF increased 126.8% and 308.8% for the modified Kessler and Massachusetts General Hospital groups, respectively. The IWOF accounted for 16.4% of the TWOF for the intact tendon; this percentage was 28.6% and 45.0% for the modified Kessler and Massachusetts General Hospital groups, respectively.
Conclusions: The IWOF accounts for 16% of the TWOF of normal human cadaver digits but it accounts for a much higher fraction after tendon repair. The ratio of the work of flexion within the synovial sheath to the TWOF varies depending on the type of repair chosen.