Contractures of the intrinsic muscles of the fingers disrupts the delicate and complex balance of the intrinsic and extrinsic muscles. Sometimes, it is called Intrinsic Plus Hand. The hand assumes a posture with a hyper flexed metacarpophalangeal (MCP) joint and a hyperextended proximal interphalangeal (PIP) joint. Contracted interossei and lumbrical muscles deform the natural cascade of the fingers. Severe disability may result because of weakness in grip and pinch strength as well as difficulty in grasping large objects.
Intrinsic Contracture of the hand is caused by trauma, spasticity, ischemia, rheumatological disorders, vascular injuries, and compartment syndrome.
When testing the digit for intrinsic muscle or capsular tightness, you will perform the Bunnell Test. When the MCP joint is in extension, the intrinsic contracture (interosseous and lumbrical muscle contracture) impedes the flexion of the PIP joint. When the MCP joint is flexed, the PIP joint flexion increases.
To treat intrinsic tightness, physical therapy is usually recommended first—passive stretching and orthotics in mild cases. Surgery is performed if the condition is severe or if noticed too late. Surgery will consist of a distal intrinsic release of the oblique fibers and preserving the proximal transverse fibers. Options for surgical management are diverse and decided by the cause and severity of the contracture.
When testing for extrinsic tightness, you will place the MCP join in flexion and try to passively flex the PIP joint. The PIP motion is less with the MCP joint flexed than when it is extended (opposite of intrinsic contracture). Treatment consists of aggressive therapy and tenolysis.
A PIP joint contracture is determined when the loss of motion of the PIP joint is the same with the MCP joint extended or flexed. Intrinsic minus hand, or Claw Hand, is a condition usually secondary to a crush injury caused by contracture of the intrinsic muscles of the hand. Intrinsic minus hand is characterized by the flexion of the PIP and DIP joints as well as the extension of the MCP joint.