What is the treatment for a palmar laceration overlying the abductor pollicis brevis muscle?

Treatment of Palmar Laceration Overlying the Abductor Pollicis Brevis Muscle

A palmar laceration overlying the abductor pollicis brevis muscle requires immediate surgical exploration, meticulous layered repair, and careful assessment for associated neurovascular and tendon injuries, as this muscle is critical for thumb opposition and palmar abduction.

Initial Assessment and Exploration

Examine for associated injuries before closure, as the anatomical location places multiple critical structures at risk:

• Assess the palmar branch of the median nerve, which traverses an orifice near the tendinous slip from palmaris longus to the abductor pollicis brevis and becomes superficial in this region 1
• Evaluate for injury to the superficial palmar branch of the radial artery (SPBRA), which normally pierces through the thenar muscles but can have a subcutaneous course superficial to the abductor pollicis brevis in rare anatomical variations 2
• Inspect for damage to the abductor pollicis brevis muscle belly and its tendinous insertions, as this muscle is the most significant thenar intrinsic for providing palmar abduction and pronation of the thumb 3
• Check for involvement of the palmaris longus tendon slip, which provides a tendinous contribution to the abductor pollicis brevis 1

Surgical Repair Technique

Perform layered closure with specific attention to muscle and fascial integrity:

• Repair the abductor pollicis brevis muscle if lacerated, as even clinically acceptable function may be limited in its absence, and full opposition (thumb tip to base of small finger) requires an intact muscle 3
• Approximate muscle fibers with absorbable sutures to restore the muscular hilum along the lateral border, which contains important neurovascular structures in 40% of cases 1
• Preserve or repair any tendinous slips from the palmaris longus or abductor pollicis longus, as these contribute to the muscle's function in abducting the first metacarpal in the sagittal plane 1
• Use fascial closure techniques that maintain the anatomical compartment boundaries to prevent postoperative complications

Neurovascular Management

Address nerve and arterial injuries identified during exploration:

• Primary repair of the palmar branch of the median nerve should be performed if transected, using microsurgical technique with 8-0 or 9-0 nylon sutures under loupe magnification
• Repair or ligate the SPBRA if injured; if the artery has an aberrant subcutaneous course causing symptoms, consider arterial transposition by splitting the abductor pollicis brevis muscle 2
• Document sensory and motor function before and after repair to establish baseline for follow-up

Wound Closure and Infection Prevention

Close the skin after ensuring hemostasis and adequate deep layer repair:

• Irrigate the wound copiously before closure, as routine abdominal irrigation reduces surgical site infection in other contexts 4
• Use new gloves and instruments for closure, as this practice is recommended to reduce surgical site infection 4
• Close skin with non-absorbable sutures (4-0 or 5-0 nylon) to allow for adequate healing time given the high-stress location on the palm

Postoperative Management

Immobilize the thumb in a position that protects the repair while allowing early controlled motion:

• Apply a thumb spica splint for 7-10 days to protect the abductor pollicis brevis repair while allowing finger motion
• Begin gentle range-of-motion exercises at 10-14 days to prevent adhesions while protecting the repair
• Advance to strengthening exercises at 4-6 weeks once tissue healing is adequate
• Monitor for signs of infection, nerve dysfunction, or loss of thumb opposition at follow-up visits

Common Pitfalls to Avoid

Be aware of anatomical variations and potential complications:

• Do not close the wound without exploring for deeper injuries, as the superficial appearance may not reflect underlying damage to critical structures 1, 2
• Avoid excessive tension on the repair, as the palm is a high-motion area and tension can lead to dehiscence or poor functional outcomes
• Do not overlook rare anatomical variations such as subcutaneous course of the SPBRA or abnormal tendon insertions that may complicate the repair 2, 5
• Ensure adequate anesthesia and muscle relaxation during repair to allow proper visualization and approximation of tissues