12 Superficialis Transfer for Rupture of the Flexor Pollicis Longus Tendon

10.1055/b-0040-177427

12 Superficialis Transfer for Rupture of the Flexor Pollicis Longus Tendon

Alexandria L. Case, R. Glenn Gaston, and Joshua M. Abzug

Abstract

Flexor pollicis longus (FPL) tendon ruptures are observed as a result of Mannerfelt lesions in patients with rheumatoid arthritis (RA) and are also associated with excessive tendon wear following distal radius fractures requiring open reduction and internal fixation. These tendon ruptures present clinically as a thumb with normal motion except for active flexion at the interphalangeal (IP) joint, although in patients with RA or those with limited functionality of the thumb at baseline, these injuries are more difficult to identify. Radiographic views of the hand and wrist should be taken as a part of the clinical examination to identify any causes of attrition to the tendon and to aid in preoperative planning, as bony deformities may need to be addressed during the procedure to avoid future rupture of the transferred tendon. The procedure may also be performed for patients with an anterior interosseous nerve (AIN) palsy, thus causing the FPL to become nonfunctional. The ruptured tendon will need to be debrided to allow for adequate motion of the transferred tendon. The flexor digitorum superficialis (FDS) tendon of either the long or ring finger is commonly the source of the tendon for transfer during this procedure. The source tendon is tagged and withdrawn through the wrist into an incision in the forearm, then transferred to the thumb where it is secured to finalize the transfer. In cases of an AIN palsy, the FDS to the ring finger should be utilized, although this procedure is not an option for high median palsies.

12.1 Preoperative Work-up

Flexor pollicis longus (FPL) tendon ruptures are marked by full passive range of motion with no active flexion of the interphalangeal (IP) joint of the thumb. ¹ The remainder of the digit typically demonstrates normal abduction, adduction, extension, and strength. ¹ The use of a tenodesis test or forearm squeeze test (in addition to assessing flexor digitorum profundus [FDP] function of the index and long finger) can help differentiate anterior interosseous nerve (AIN) palsy from FPL rupture. Closed FPL ruptures are often associated with distal radius fractures, particularly those with internal fixation in which the plate is fixed too distally to the watershed line as the raised profile of the hardware can cause excessive wear on the tendon ² ^, ³ ^, ⁴ (► Fig. 12.1). In addition, FPL tendon ruptures are also observed in patients with rheumatoid arthritis (RA), as bony deformity typically at the scaphotrapeziotrapezoid (STT) joint may contribute to unusual amounts of tendon wear and predispose the patient to tendon rupture. ⁵ ^, ⁶ Given the pathology, preventative care in patients with RA is crucial. Detailed inspection of rheumatoid hands and wrists for signs of tenosynovitis should be completed as part of the physical examination, as tenosynovitis may be indicative of a rupture in a low or nonfunctional rheumatoid hand. ⁵ Three radiographic views of the hand and wrist should be ordered to assess for any bony deformation or displacement that may have caused attrition of the tendon. Additionally, imaging of the thumb IP joint is important to assess for arthritic change as this may influence a decision for IP arthrodesis in lieu of tendon reconstruction. In patients with RA, bony spicules can form on the scaphoid and lead to increased wear of the tendon. Similarly, volar displacement of the scaphoid can also contribute to tendon attrition and should be noted during radiographic assessment.

**Fig. 12.1** Flexor pollicis longus (FPL) tendon rupture. (Image credit: R. Glenn Gaston, MD.)

12.1.1 Indications and Contraindications

Indications for a tendon transfer include tendon rupture or an AIN palsy. The procedure is ideal for patients with these conditions who desire functional improvements. Alternative treatments to tendon transfer include nonoperative management, tendon reconstruction, two-stage tendon reconstruction, bridge graft, and arthrodesis. In cases where the thumb is stable, and the carpometacarpal (CMC) and metacarpophalangeal (MCP) joints are functioning normally, particularly in the elderly population, it is appropriate to manage the rupture conservatively. If the FPL rupture is identified within 4 to 6 weeks of initial rupture, it may be feasible to perform a tendon grafting procedure, provided that the IP joint has satisfactory motion and that no myostatic contracture of the FPL muscle is observed. ⁶ If both tendon ends can be identified at the level of the wrist in an RA patient and these ends are in good condition, a bridge graft with simultaneous resection of the offending bony pathology may be performed. ⁵ In patients with severe scarring of the tendon sheath bed and/or destruction of the pulley system, an arthrodesis or a two-stage tendon reconstruction would be a better approach than a tendon transfer. ⁵

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