Thumb Ligament Injuries

The MCP joint of the thumb is a condyloid type joint.36 The osteoarticular anatomy of the thumb MP joint provides minimal intrinsic stability.37 The lateral static stabilizers include the proper collateral ligaments and accessory collateral ligaments. Dynamic stability is provided by the abductor and adductor aponeurosis. The proper and accessory collateral ligaments originate from the lateral condylar region of the metacarpal and insert on the volar aspect of the proximal phalanx and the volar plate, respectively.36 Palmar support is provided by a fibrocarti-laginous volar plate, which is further supported by thenar intrinsic muscles. Smith and others emphasized the importance of the dorsal capsule and the accessory collateral ligaments as static stabilizers of the MP joint.38,39

Ulnar Collateral Ligament Injuries

UCL injuries (skier's or gamekeeper's thumb) of the thumb MP joint are seen among athletes participating in ball-handling and contact sports. UCL injuries have been recognized to be more common than radial collateral ligament (RCL) injuries of the thumb.40-42 Ulnar MCP joint injuries are most commonly caused by an abrupt forced radial deviation of the thumb. Athletes usually report a fall onto the outstretched hand with the thumb abducted. Disruption of the UCL usually occurs at its distal insertion on the proximal phalanx.43 Mid-substance tears, although uncommon, can occur. Associated injuries with UCL tears include volar plate and dorsal capsular disruptions. Avulsion fracture at the ulnar base of the proximal phalanx may occur (Fig. 41-11). Complete tears of the UCL can have interposition of the adductor aponeurosis (termed a Stener lesion), whereby the distally avulsed ligament cannot reasonably reapproximate its insertion onto the proximal phalanx.44

Clinical Features and Evaluation

Athletes with UCL injuries usually present with global swelling of the thumb MP joint and point tenderness along the ulnar joint line. In the case of UCL injuries without associated fracture, it is important to distinguish partial versus complete tears. Determination of complete (grade III) and partial (grade I/II) UCL disruptions is largely clinical with the use of a stress test of the thumb MP joint in full extension and 30 degrees of flexion. Loss

Figure 41-12 Significant clinical ulnar-side instability of the thumb middle phalanx joint is demonstrated with loss of endpoint and excessive laxity with radial stress testing.

Figure 41-11 A frontal plane radiograph of a 43-year-old master swimmer who sustained an avulsion fracture of the ulnar proximal phalanx after hitting the pool wall with the thumb in abduction.

of a firm endpoint with radial stress of the MP joint in full extension and greater than 30 degrees of laxity compared to the contralateral side in both extension and flexion are suggestive of a complete UCL tear (Fig. 41-12). Athletes with partial tears demonstrate pain with radial stress but have a firm endpoint and minimal to moderate laxity. The presence of a palpable mass on the ulnar side of the proximal MP joint can suggest a Stener lesion. The use of a local anesthetic block is useful in the evaluation of patients with significant pain or guarding.

Radiographic evaluation should include posteroanterior, oblique, and lateral views to assess for fracture and joint con-gruency. With complete UCL disruption, occasionally volar subluxation occurs as a result of an associated dorsal capsular injury. Stress radiographs confirm a complete tear of the UCL when greater than one third subluxation of the proximal phalanx on the metacarpal head is present.45 It is always important to compare these results to stress radiographs of the contralateral thumb. In certain cases, MRI evaluation of the thumb to assess for a complete tear of the UCL or the presence of a Stener lesion may be a helpful adjunct (Fig. 41-13).46

Treatment Options

Acute partial tears are managed with a hand-based thumb spica splint or cast for 4 weeks. The cast or orthosis is placed with the MCP joint in slight flexion and neutral alignment. Active ROM is initiated 4 weeks after injury with continued splint wear for an additional 2 weeks. Some authors have advocated cast immobilization in the case of complete tears.47 The thumb UCL plays a significant role in the athlete's ability to provide pinch grip. It is for this reason, along with the unpredictability of nonoperative management, that anatomic repair is generally indicated for complete disruption of the UCL in the athlete.

Ulnar Collateral Ligament Thumb
Figure 41-13 Magnetic resonance imaging of the thumb demonstrates a complete disruption of the ulnar collateral ligament with distal avulsion of the ligament.

Surgery: Acute Ulnar Collateral Ligament Repair

A curvilinear incision is made centered over the ulnar aspect of the thumb MP joint. The distal limb skin incision is completed along the mid-axial line of the proximal phalanx. The incision is extended proximally over the dorsoulnar aspect of the joint. Blunt dissection is undertaken within the subcutaneous tissues to identify branches of the superficial radial nerve, which are carefully protected (Fig. 41-14). The adductor aponeurosis is identified and released longitudinally just volar to the extensor

Figure 41-14 The intraoperative photograph demonstrates the approach for repair of the thumb ulnar collateral ligament and a branch of the superficial radial nerve (Freer). Dissection within the subcutaneous tissues should be done with care to avoid injury to branches of the superficial radial nerve, which commonly traverse the surgical field.

pollicis longus. The aponeurosis is reflected volarly to expose the ulnar side of the MP joint. The UCL is identified and most commonly found to be avulsed from the proximal phalanx (Fig. 4115). An arthrotomy of the MP joint is completed and the articular cartilage examined. If there is a small bony fragment still attached to the ligament, it is excised. If the fragment is greater than 15% of the articular surface, attempts should be made to fix the fragment with wire or mini screws. Mid-substance tears can be repaired in an end-to-end fashion. Although pull-out suture technique has been described with good results, we have routinely used bone anchors to secure the avulsed ligament.48 In preparation for placement of the suture anchors, the ulnar volar and dorsal aspect of the proximal phalanx is exposed. Two drill holes are placed into the volar-ulnar and dorsoulnar base of the proximal phalanx (Fig. 41-16). The mini suture anchors, metallic or biodegradable, are placed into the predrilled holes. Most of the mini anchors come prethreaded with a 2-0 Ethibond suture. The distally avulsed ligament is then reapproximated to its insertion via the suture anchors (Fig. 41-17). Sutures are placed to repair the dorsal capsule and reapproximate the volar plate to the most distal aspect of the repaired ligament. A gentle radial stress is applied to assess the adequacy of repair. The adductor aponeurosis is then reattached. The skin is sutured and the hand placed in a thumb spica splint.

For the "weekend athlete," the thumb is immobilized in a hand-based thumb spica cast for 4 weeks postoperatively. ROM exercises are permitted at 1 month with continued protection in an orthosis. Splint wear is discontinued at 6 weeks for most activities. Depending on the sport, protection is recommended for 3 months postoperatively. If the repair is considered adequate, athletes may be converted to a thumb spica orthosis after 2 weeks of cast immobilization as described by Lane.49 This has resulted in a quicker return to sports with good long-term functional outcome. Following repair, the athlete may return to play in a protective playing cast at 2 to 3 weeks. Athletes participating in sports requiring significant pinch strength, such as the throwing hand of a quarterback, may require 6 to 9 weeks prior to return.

Chronic thumb UCL injuries may occur after a missed Stener lesion, failed treatment of an acute complete disruption, or

Figure 41-14 The intraoperative photograph demonstrates the approach for repair of the thumb ulnar collateral ligament and a branch of the superficial radial nerve (Freer). Dissection within the subcutaneous tissues should be done with care to avoid injury to branches of the superficial radial nerve, which commonly traverse the surgical field.

Figure 41-16 The illustration demonstrates the location of the predrilled holes in preparation for placement of mini bone suture anchors. Attempts are made to place the anchors just distal to the articular surface on the volar-ulnar and dorsoulnar aspect of the proximal phalanx.

progressive attenuation. Complete ruptures of the UCL less than 2 months after injury can usually be addressed by careful excision of scar and reinsertion of the retracted ligament.45 Chronic UCL injuries have been treated by using a scarred capsule to create a new ligament, adductor advancement, or reconstruction with a free tendon graft.45,50,51 The postoperative rehabilitation is similar to that for acute repair. However, an additional 1 to 2 weeks of immobilization is recommended. MP arthrodesis may also be considered to address chronic UCL insufficiency.

Radial Collateral Ligament Injuries

Although RCL tears are less common than UCL ruptures, they can become a debilitating injury if unrecognized. Among 100 collateral ligament repairs of the thumb, Melone et al45 identified 40 serious radial-side ligament injuries. The mechanism of injury is an adduction force across the MCP joint. Proximal and distal disruption of the RCL occurs with equal frequency.52 Stener lesions do not occur after complete disruptions of the RCL because of the anatomy of the abductor aponeurosis.

Athletes may present with ecchymosis, pain, and swelling along the radial side of the MP joint. Dorsoradial pain with prominence of the thumb metacarpal head may be seen in complete RCL tears. The prominence occurs as the proximal phalanx shifts volarward and into pronation because of dorsal

Figure 41-17 Bone anchors have been placed into the proximal phalanx. The prethreaded suture on the anchors is then utilized to secure the avulsed UCL ligament back to its insertion.

capsule disruption and an intact UCL. Three views of the thumb should be obtained. Lateral radiographs may demonstrate volar subluxation of the proximal phalanx. It is important to differentiate partial (grade I/II) from full-thickness (grade III) tears. An ulnar stress is applied to the thumb MP joint in full extension and 30 degrees of flexion and compared to the uninjured thumb. The absence of a firm endpoint with ulnar stress and greater than 30 degrees of instability compared to the contralateral side suggest a complete tear. Stress radiographs are consistent with a complete tear when more than one third ulnar subluxation on the metacarpal head is present.45

Partial RCL tears are treated with immobilization in a hand-based thumb spica cast or splint for approximately 4 weeks. Mobilization of the MP joint is initiated at 1 month with continued splinting for an additional 2 weeks. Athletes are protected with splint or taping for 10 to 12 weeks after injury. Both immobilization and early repair have been advocated for the treatment of complete ruptures of the RCL.45,52,53 Physical examination findings consistent with a complete rupture and/or the presence of MP joint subluxation are indications for exploration and repair of the ligament. The postoperative management and return to sports is similar to that for acute repair of the UCL. Chronic RCL injuries can be surgically addressed with mobilization of the scarred ligament or reconstruction with a free tendon graft.

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