HAND/WRIST
“The main purpose of the upper extremity is to assist hand function. An arm without a hand is like a crane without a hook at the end of its cable” -Raoul Tubiana, 1978
A hand without proximal articulations, which are both mobile and stabile, will not be functional. Wrist mobility allows positioning of the hand for grasp, prehension and manipulation tasks. Stability of the wrist allows for engaging in heavier tasks such as lifting, carrying, pushing, pulling and weight bearing. Wrist mobility and stability are dependent upon the carpal bones and ligaments in conjunction with wrist musculature.
The wrist is comprised of a proximal and a distal carpal row. An intricate network of ligaments maintains the stability of these carpal bones. The proximal row has no tendon insertions. Therefore, wrist motion starts at the distal row. As wrist motion progresses, the midcarpal ligaments become taught exerting a compressive load at the midcarpal joint forcing movement at the proximal row. Ligamentous disruption between bones of the proximal carpal row is a frequent cause of wrist instability (scapholunate and lunotriquetral dissociation). These dissociations are often referred to as CID (carpal instability dissociative). Wrist instability can also be caused by disruption of ligaments between carpal rows as seen in ulnar midcarpal instability. This pattern is referred to as CIND (carpal instability nondissociative).
Carpal instability may be due to ligament laxity, traumatic ligament disruption or malunion of distal radius fractures. This laxity causes misalignment of the carpal bones, altering normal wrist kinematics and ability for load bearing. The injury may be due to a high velocity incident or a low energy event. Symptoms may range from vague reports of wrist pain and weakness to significant pain, swelling and weakness. The instability may produce pain with particular wrist motions and a snapping or clunking feel. An athlete may find himself or herself unable to perform a pushup due to wrist pain. A manual laborer may be unable to swing a hammer. Simple tasks such as opening a bottle of water or turning a key may become difficult or impossible. Instability injuries may be static - visible with standard diagnostic imaging, or they can be dynamic and require provocative testing or stress imaging techniques to diagnose.
Due to the complex kinematics of the wrist, a qualified hand practitioner should assess any injury resulting in pain or loss of function. Many injuries are successfully treated with a calculated precise progression of motion after a period of immobilization. There are a variety of wrist supports and taping methodologies available that allow earlier return to work and play. There are various patterns of wrist motion required for all daily activities. Ongoing research of wrist proprioceptive reflexes and neuromuscular actions on the wrist is necessary for continued development of advanced rehab programs. DTM or “dart throwers motion” is a frequently utilized movement pattern in the rehab of instability injuries. This motion involves extension and radial deviation of the wrist (cocking the wrist back in prep for throwing) progressing to flexion and ulnar deviation (bringing the wrist forward and releasing the dart). Research has supported claims that during DTM, there is less scaphoid and lunate motion than during pure flexion/extension and radial/ulnar deviation of the wrist. Additionally, task analysis has shown DTM is a common path of motion in many occupational, recreational and daily activities. Use of DTM has been trialed as a safe and protected range of motion for postoperative radiocarpal surgeries.
Effective diagnosis and treatment of carpal instability continues to be a developing area of practice among hand specialists. Ongoing research is needed to further investigate optimal treatment of all wrist injuries and development of new ways to prevent these injuries.
