Summary of Extensor Tendon Injuries of the Hand

## Introduction Extensor tendon injuries of the hand present in many clinical forms depending on injury location, chronicity, and tissue loss. This material focuses on practical decision points, treatment principles, and rehabilitation strategies for specific zones and clinical scenarios (closed and open injuries, delayed presentations, and reconstructions). It avoids basic anatomy and broad overviews covered elsewhere and emphasizes applied management and outcomes. > Definition: Extensor tendon injuries are disruptions or dysfunctions of the dorsal tendon structures of the hand that impair finger or thumb extension and may produce deformity, weakness, or joint subluxation. ## Classification by location and clinical relevance Understanding the injury location guides treatment choices. Below are major clinical zones and the key management considerations for each. ### Zone 1 — Distal phalanx (terminal tendon) - Common presentation: mallet deformity with DIP flexion and loss of active DIP extension. - Key decision factors: degree of extensor lag, tendon continuity, open vs closed injury, timing (acute vs delayed). Practical approach - Splinting is effective for many closed injuries of short duration. - For delayed presentations up to ~6 months with extensor lag <35–40°, Fowler central slip tenotomy (used in certain contexts) may help correct compensatory mechanics (note: this method reduces PIP extension moment). - Larger extensor lags (>45°) or complete tendon discontinuity with retraction often require reconstructive procedures such as spiral oblique retinacular ligament (ORL) reconstruction or tendon grafting. Example: A patient with a closed mallet thumb and intact tendon continuity may be managed with a DIP extension splint similar to type I mallet finger protocols; if the tendon is open and retracted, surgical repair or ORL reconstruction may be needed. ### Zone 2 — Middle phalanx (lateral bands and triangular ligament) - Lacerations here often involve one or both lateral bands or the triangular ligament. - Clinical rule: One functioning lateral band can preserve DIP extension; injuries involving ≤50% of the extensor mechanism can sometimes be managed nonoperatively. Management summary - Minor partial lacerations: local wound care for 1–2 weeks then early active motion. - Lacerations >50%: primary repair using fine running suture (e.g., 5-0 Prolene running + cross-stitch) because core sutures are not feasible (tendon too thin). - Postoperative protection: static splint or pin DIP in extension for ~6 weeks, permit PIP motion. - Chronic defects: tendon grafts or ORL reconstruction techniques can restore function. Did you know that in zone 2 the tendon is too thin for core sutures, so repairs typically use fine running and cross-stitch techniques to avoid bunching and achieve smooth gliding? ### Zone 3 — Proximal interphalangeal (PIP) joint (central slip and lateral bands) - Injuries here can produce boutonnière deformity (PIP flexion with DIP hyperextension) if the central slip is disrupted and lateral bands migrate volarly. - Early diagnosis: use the Elson test to detect central slip disruption. Acute management - Splint the PIP joint in full extension for ~6 weeks to allow central slip healing. - Prescribe active DIP flexion exercises hourly during immobilization to help realign lateral bands and reduce tone. - If a bony avulsion is present, treat nondisplaced small fragments nonoperatively; displaced or unstable fragments may need fixation. Postoperative care - When repair is performed, consider an oblique Kirschner wire across the PIP in full extension for 5–6 weeks, then begin ROM with interval splinting for 2–4 weeks. Some centers use early motion or dynamic splints depending on repair strength and compliance. Chronic boutonnière - Classification (practical): Stage I (supple/correctable), Stage II (fixed contracture with contracted lateral bands), Stage III (fixed with joint fibrosis and