A recently published biomechanical study in the Journal of Hand Therapy looks at immobilization of the partially torn or repaired ulnar collateral ligament of the thumb.
The researchers investigated the stability provided by a radially based thumb MCP joint orthosis, leaving the CMC and IP joints free. Previous studies have examined the efficacy of forearm based thumb immobilization orthoses.
- Partial ligament injuries of the ulnar collateral ligament are typically treated with 4 weeks of immobilization.
- Complete ulnar collateral ligament injuries are treated with surgery and post-operative immobilization, for up to 10-12 weeks to allow for adequate ligament to bone healing.
However, if properly immobilized with a minimalistic orthosis, individuals might be able to resume activities with their hands sooner.
The researchers studied the effects of applying valgus load (20, 40, 60, 80 and 100 N) forces, pushing the cadaver thumb MCP joints into abduction. Each thumb was custom fit with a radial based MCP orthosis made from 1/16” thermoplastic material. K-wires were placed in the first metacarpal and also protruding from the proximal phalanx. The displacement angle between these two wires was measured after the application of force was applied.
The results of this experimental study indicate that a MCP immobilization orthosis is able to stabilize the thumb UCL ligament and limit abduction up to 100 N. The authors point out that they previously investigated the maximum load to failure of a repaired UCL ligament to be 84 N. Therefore this orthosis adequately protects the repaired UCL up to at least 100 N.
The above findings are important for therapists treating patients following injury and/or surgery of the ulnar collateral ligament of the thumb. A simple radial based thumb MCP joint immobilization orthosis can help protect the injured and/or repaired ligament. It does not need to include the CMC and IP joints. This simple design may allow earlier return to functional and work activities.
Further studies might look at dynamically applied forces, the effect of the dynamic thumb stabilizers in real patients and the maximum force at which the orthosis fails to protect the ligament.
Orfit thermoplastic materials for excellent fabrication of the radial based thumb MCP joint immobilization orthoses include the following:
Orfit Classic 1/16”, 1/12”, 3/32”
Orfit NS 1/16”, 1/12”, 3/32”
Orfit Natural NS 1/16”, 1/12”, 3/32”
Orfit Colors NS 1/12”
Orfilight 1/16”, 3/32”
Orfilight Atomic Blue NS 1/16”, 3/32”
Orfilight Black NS 1/16”, 3/32”
Orficast 6 cm
Orficast More 6 cm, 12 cm, 15 cm
 (Gil, J. A., Ebert, K., Blanchard, K., Goodman, A. D., Crisco, J. J., & Katarincic, J. A. (2017). Efficacy of a radial-based thumb metacarpophalangeal-stabilizing orthosis for protecting the thumb metacarpophalangeal joint ulnar collateral ligament. Journal of Hand Therapy.)
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