01406nas a2200253   4500000000100000008004100001260001300042653002800055653001700083653001100100653001200111653003000123653002300153653001400176653001200190653001000202100001700212700001800229245004100247300001000288490000600298520083400304022001401138       1982                            d  c1982 Jul10aBiomechanical Phenomena10aFinger Joint10aHumans10aleprosy10aMetacarpophalangeal Joint10aModels, Biological10aParalysis10aTendons10aThumb1 aSrinivasan H1 aLandsmeer J M00aInternal stabilization in the thumb.  a371-50 v73 a<p>An analysis of the thumb as an articular chain, with the biarticular tendon displacement used as a model, is presented. Comparison of the extensor pollicis longus/flexor pollicis longus (EPL/FPL) tendon displacement ratios at the three joints, as determined from cadaver studies, shows that the thumb will be unstable, with a persistent tendency to extend at the carpometacarpal (CMC) joint and flex at the interphalangeal (IP) joint when it is under the exclusive control of the EPL and FPL muscles. In addition, according to the model, with stabilization of the CMC joint, the MCP joint will tend to extend and the IP joint will flex. Clinical data from thumbs of leprosy patients with thenar paralyses largely confirm these predictions and the validity of this approach in studying the functional behavior of the thumb.</p>  a0363-5023