Connections between the Tendons of the Musculus flexor digitorum profundus Involving the Synovial Sheaths in the Carpal Tunnel

Abstract

In the carpal tunnel anatomical interconnections between the tendons of the musculus flexor digitorum profundus are systematically present. These interconnections limit the mutual tendon displacements, which decreases finger independence and may be problematic in a musician’s hand. The present study investigates a possible role of the synovial sheaths in the formation of these intertendinous connections in the carpal tunnel. To this end a morphological model is provided which correlates the often distinctly fibrous structure of the deep flexor tendons in the carpal tunnel and the frequent exchange of tendon fibres between the tendons to the different fingers, with the tendency of the synovial membranes to strongly adhere to the tendons. This model is validated by gross dissection results, and by cross sections of the flexor tendons in the carpal tunnel. In agreement with the model, the anatomic data show that the synovial membranes tend to invade and become trapped in tendons made up from individualised tendon strands, and also strongly adhere to the substantial amounts of tendon fibres which may be exchanged between the flexor tendons proximal to the lumbrical origins. These fibres and the synovial membranes may form a strong fabric able to withstand substantial stretching forces of interconnected oppositely pulled flexor tendons.

Coexistence of multiple anomalies in the carpal tunnel

“…Anomalous extra tendons and intertendinous slips of the FPL and FDP have been described by many researchers (Linburg and Comstock, 1979;Leijnse et al, 1997;Steinberg and Szabo, 1996;Lindley and Kleinert, 2003). In 96 cadaveric hands, Linburg and Comstock (1979) found unilateral extra tendon slips in 25% of subjects, an observation fairly equivalent to ours of 20%.…”

Limits to the Control of the Human Thumb and Fingers in Flexion and Extension

“…They can involve connections between tendinous structures (e.g., FPL and FDP;Leijnse 1995;Leijnse et al 1997), but also direct links at a muscle level ("intermuscular" force transmission; see Huijing 2003; see also Chao et al 1989;Kilbreath and Gandevia 1994;Lang and Schieber 2004;Yucesoy et al 2003Yucesoy et al , 2005. Mechanical interactions can produce marked changes in force production when the hand is postured in unusual ways that effectively "disengage" the FDP from the distal joint of the finger (Gandevia and McCloskey 1976;Smith et al 2009).…”

Finger inter-dependence: Linking the kinetic and kinematic variables

“…In particular, both muscle and connective tissues are known to have viscoelastic properties. Such connections between the task finger and other fingers (Leijnse, 1997;Leijnse, Walbeehm, Sonneveld, Hovius, & Kauer, 1997) may be expected to lead to velocity-dependence of forces transmitted to the slave fingers. In our experiments, such dependence was not observed (Figure 6).…”