Dual-Tendon Transfer for Chronic Extensor Pollicis Longus Ruptures: Augmented Extensor Indicis Proprius Transfer with Proximal EPL Stump Lengthening.

Background: Extensor indicis proprius (EIP) transfer augmented with proximal extensor pollicis longus (EPL) stump lengthening restores thumb extension and optimizes function in cases of chronic EPL tendon ruptures, which impair hand dexterity and fine motor skills. Traditional EIP-to-EPL transfers often disrupt the natural oblique course of the EPL around the Lister tubercle, leading to functional deficits^1-3. This dual-tendon transfer preserves anatomical alignment and improves thumb biomechanics, enhancing extension strength and the adduction moment arm at the carpometacarpal (CMC) joint.

Description: The procedure involves 3 incisions over the index finger metacarpal neck, Lister tubercle, and dorsal thumb metacarpophalangeal joint. The EIP tendon is harvested, its distal stump is sutured to the extensor digitorum communis, and the proximal stump is withdrawn for transfer. The distal and proximal EPL stumps are exposed, and the proximal EPL is lengthened with use of an L-shaped radial incision, retaining a 1-cm pedicle for turnover. Both the EIP and lengthened EPL tendons are passed subcutaneously and coapted to the distal EPL with use of a Pulvertaft weave and augmentation techniques. The procedure is performed under wide-awake local anesthesia (WALANT), enabling dynamic intraoperative adjustments. A splint is applied postoperatively for 4 weeks, followed by 4 to 8 weeks in a removable splint, with discontinuation at 12 weeks.

Alternatives: Surgical alternatives include extensor carpi radialis brevis to EPL transfer, extensor digiti minimi to EPL transfer, brachioradialis to EPL transfer, and EPL repair with use of a palmaris longus graft.

Rationale: Compared with other tendon transfers, EIP transfer offers anatomical proximity, and minimal donor-site morbidity. However, standalone EIP transfers may reduce extension strength and range of motion as a result of a misaligned vector^4-7. The presently described dual-transfer technique addresses these limitations by retaining the native path of the EPL, reducing adhesions, and improving biomechanical efficiency. This technique is particularly advantageous in patients who require a high level of thumb function, preserving fine motor control and extension strength while reducing residual deficits.

Expected outcomes: This procedure provides improved thumb extension, thumb adduction, and overall hand function. Stirling et al.1 demonstrated that EIP-to-EPL transfer improves QuickDASH (shortened version of the Disabilities of the Arm, Shoulder and Hand questionnaire) scores (from 29.7 to 15.2; p = 0.05), with high patient satisfaction and no complications. Our augmented approach builds on these results by reducing biomechanical loss, preserving angular alignment, and minimizing adhesion risk, aiming for superior total active motion and functional recovery. In our study of 15 patients, the outcome was rated as Good in 11 patients and Fair in 4, with a mean DASH score of 5.5.

Important tips: Preserve a 1-cm pedicle in the EPL lengthening to maintain vascularity and facilitate turnover.Avoid overtightening to prevent interphalangeal joint stiffness.Ensure a smooth subcutaneous tunnel to minimize friction and adhesions.Avoid misalignment of the EPL course, which compromises extension and thumb adduction.

Acronyms and abbreviations: EPL = extensor pollicis longusCMC = carpometacarpalEIP = extensor indicis propriusECRB = extensor carpi radialis brevisEDM = extensor digiti minimiBR = brachioradialisTAM = total active motionMCP = metacarpophalangealIP = interphalangealWALANT = wide-awake local anesthesiaEDC = extensor digitorum communis.