What are the implications of a flexor pollicis longus (FPL) tendon rupture?

From the Guidelines

Flexor pollicis longus (FPL) rupture requires prompt surgical repair for optimal outcomes, as it significantly impairs pinch grip and hand function, particularly for precision tasks requiring thumb dexterity. The FPL is a critical tendon that allows flexion of the thumb's distal joint, and ruptures typically occur from trauma, rheumatoid arthritis, or after distal radius fractures. According to the study by 1, MRI is ideal for evaluating tendon injuries and helping with surgical planning, with a sensitivity of 92% and specificity of 100% for diagnosis of flexor tendon injuries.

Diagnosis and Treatment

• The diagnosis of FPL rupture can be made using MRI, which allows for direct visualization of the tendon and assessment of the level of tendon retraction, the quality of the tendon stump, and associated injuries, including pulley injuries 1.
• Treatment involves surgical repair within 4-6 weeks of injury for primary tendon repair, though delayed cases may require tendon grafting.
• Post-surgery, patients follow a structured rehabilitation protocol starting with protected immobilization in a thumb spica cast for 2-3 weeks, followed by controlled motion in a removable splint for another 3-4 weeks.
• Physical therapy focuses on progressive range of motion exercises, strengthening, and functional activities over 8-12 weeks.

Pain Management

• Pain management typically includes acetaminophen (500-1000mg every 6 hours) or NSAIDs like ibuprofen (400-600mg every 6-8 hours) for 1-2 weeks.
• Without proper repair, patients lose the ability to flex the thumb's distal joint (positive Mannerfelt sign), significantly impairing pinch grip and hand function, particularly for precision tasks requiring thumb dexterity.

Importance of Prompt Repair

• Prompt surgical repair is crucial to prevent long-term morbidity and mortality, as well as to improve quality of life, as it allows for optimal recovery of thumb function and reduces the risk of complications, such as contractures or joint laxity 1.

From the Research

Implications of FPL Tendon Rupture

The implications of a flexor pollicis longus (FPL) tendon rupture can be significant, with potential effects on thumb function and overall hand strength. Some of the key implications include:

• Reduced active interphalangeal joint flexion and thumb opposition, as seen in studies 2, 3
• Comparable power grip and key pinch strength to the contralateral hand, despite reduced thumb range of motion 2, 3
• Excellent functional results reported by patients, despite some residual deficits in thumb function 2, 3

Surgical Treatment Options

Several surgical treatment options are available for FPL tendon rupture, including:

• Reconstruction with a palmaris longus interposition graft, which has been shown to be a viable treatment option with lower donor site morbidity than tendon transfer surgery 2, 3
• Primary repair of the FPL tendon, which can be challenging if not done within the first few days after injury, and may require early active mobilization to prevent rupture 4, 5
• Reconstruction with an allograft tendon, which can be used to restore FPL tendon continuity in cases where primary repair is not possible 6

Postoperative Outcomes

Postoperative outcomes for FPL tendon rupture repair can vary, but generally include:

• Reduced thumb range of motion, with mean active interphalangeal joint flexion and thumb opposition significantly reduced compared to the opposite side 2, 3
• Comparable power grip and key pinch strength to the contralateral hand, with mean values reported in the range of 32 kg and 8 kg, respectively 2, 3
• Excellent functional results reported by patients, with mean DASH scores and Visual Analogue Scale for pain indicating good overall hand function 2, 3