Procedure 58 Skier’s Thumb
Repair of Acute Thumb Metacarpophalangeal Joint Ulnar Collateral Ligament Injury
See Video 40: Repair of Acute Thumb MCP Joint Ulnar Collateral Ligament Injury
See Video 41: Thumb Radial Collateral Ligament Repair
Examination/Imaging
Clinical Examination
In the acute presentation, the patient typically has a swollen painful thumb MCP joint. Occasionally, a lump may be palpated on the ulnar side of the thumb MCP joint, representing the avulsed and retracted UCL stump.
Stress testing of the UCL is performed by applying a valgus force to the extended MCP joint while holding the head of the metacarpal fixed. If the joint deviates more than 30 degrees total or 15 degrees more than the contralateral uninjured thumb, it represents a complete UCL tear. A significant deviation in extension represents a more comprehensive injury that includes the dorsal capsule in addition to the UCL. A similar deviation of 30 degrees of flexion represents an injury to the UCL in isolation. If it deviates less than 25 degrees, it may represent a ligamentous strain that would be amenable to nonoperative treatment. (Fig. 58-1 shows clinical and fluoroscopic examination demonstrating significant ulnar collateral ligament laxity on stress testing.)
Imaging
Standard anteroposterior and lateral radiographs of the thumb should be obtained to check for an avulsion fracture of the proximal phalanx. Volar subluxation of the proximal phalanx suggesting a dorsal capsular tear that might need repair can be seen on the lateral radiograph. Comparison views of the opposite uninjured thumb can be obtained to ensure that subluxation is pathologic and not due to the patient’s inherent ligamentous laxity.
In the absence of a fracture, radiographic stress testing can be performed to evaluate joint laxity; however, this is not necessary because the clinical examination is usually sufficient. This may require a local anesthetic block in order for the patient to cooperate with the examination (see Fig. 58-1).
Surgical Anatomy
The MCP joint has characteristics of both a condyloid and a ginglymus joint, which allow a relatively large range of motion. Consequently, there is little inherent stability in the bony architecture.
A Stener lesion results from a forceful radial deviation of the proximal phalanx, resulting in a distal avulsion of the UCL from its insertion on the proximal phalanx. Because of the extensive radial deviation of the proximal phalanx, the UCL becomes displaced from its insertion point deep to the adductor aponeurosis and comes to lie superficial and proximal to the adductor aponeurosis, which prevents the ligament from anatomic alignment. The lesion is created with forced radial deviation of the proximal phalanx with displacement of the UCL superficial to the adductor aponeurosis to prevent its anatomic alignment (Fig. 58-2).
