Residency · Residency · Plastic Surgery

Extensor Tendon Injuries and Reconstruction

Overview

Extensor tendon injuries are more common than flexor tendon injuries but historically received less attention. The complex anatomy of the extensor mechanism, with its thin flat tendons and intricate lateral band system, makes repair technically demanding and adherence to zone-specific treatment protocols essential for optimal outcomes. ---

Extensor Tendon Zones

Odd Zones Over Joints, Even Zones Between Joints (Fingers)

Thumb Zones

T1: IP joint. T2: proximal phalanx. T3: MCP joint. T4: metacarpal. T5: wrist (dorsal compartment I). ---

Zone I Injuries: Mallet Finger

Mechanism

Forced flexion of an actively extended DIP joint. Results in terminal tendon rupture (closed) or laceration (open). May have associated avulsion fracture of the dorsal base of the distal phalanx.

Classification

Type I: closed, tendinous disruption (no fracture). Type II: open laceration of the terminal tendon. Type III: deep abrasion with loss of skin and tendon substance. Type IV: fracture subtypes.

IVa: transepiphyseal (pediatric). IVb: fracture involving <1/3 of articular surface. IVc: fracture involving >1/3 of articular surface (may have volar subluxation of the distal phalanx).

Treatment

Closed, no fracture or small fracture without subluxation: continuous splinting of DIP in slight hyperextension (0-5 degrees) for 6-8 weeks, followed by 4 weeks of nighttime splinting. Stack splint or custom thermoplastic splint; PIP joint left free. Open injuries: surgical repair with figure-of-eight or mattress sutures (4-0 or 5-0 nonabsorbable). Large fracture (>1/3 articular surface) with volar subluxation: ORIF with extension block pinning (Ishiguro technique) or open reduction.

Key Points

If the DIP is allowed to flex even once during the splinting period, the 6-8 week clock resets. Chronic mallet finger (>3 months) may require Fowler tenotomy (central slip release at PIP) or spiral oblique retinacular ligament (SORL) reconstruction. ---

Zone III Injuries: Boutonniere Deformity

Mechanism

Disruption of the central slip at the PIP joint. The lateral bands gradually sublux volar to the PIP axis of rotation. Results in PIP flexion (loss of central slip extension) and DIP hyperextension (lateral band tightening).

Pathoanatomy

Central slip rupture -- PIP cannot actively extend. Triangular ligament attenuates -- lateral bands migrate volarly. Transverse retinacular ligaments contract -- fix the lateral bands in a volar position. Oblique retinacular ligaments tighten -- produce DIP hyperextension.

Diagnosis

Elson test: flex PIP to 90 degrees over table edge; ask patient to extend against resistance. Central slip intact: strong PIP extension, DIP remains floppy. Central slip disrupted: weak PIP extension, DIP becomes rigid (lateral bands are sole extensors). Boutonniere deformity may not be immediately apparent -- often develops over 2-3 weeks.

Treatment

Acute, closed: PIP extension splinting for 6 weeks (DIP left free and encouraged to flex actively to stretch lateral bands dorsally). Acute, open: surgical repair of the central slip. Chronic, passively correctable: serial casting or dynamic splinting; may require extensor mechanism reconstruction. Chronic, fixed contracture: staged approach -- first achieve passive PIP extension with serial casting, then surgical reconstruction (central slip reconstruction using lateral band rerouting).

<image>Three-panel medical illustration showing the progression of boutonniere deformity. Panel 1: normal extensor mechanism with central slip intact and lateral bands dorsal to the PIP axis. Panel 2: acute central slip rupture with initial volar migration of the lateral bands (arrow showing volar subluxation past the PIP axis of rotation). Panel 3: established boutonniere deformity showing the complete pathoanatomy -- PIP flexion, DIP hyperextension, volar lateral bands, attenuated triangular ligament, and contracted transverse retinacular ligaments. Each structure labeled clearly.</image>

Zone V Injuries: Sagittal Band Disruption

Anatomy

Sagittal bands stabilize the extensor tendon centrally over the MCP joint. Radial sagittal band rupture is more common (especially at the middle finger).

Mechanism

"Boxer's knuckle": direct impact or forceful resisted flexion. Closed rupture or attritional in rheumatoid arthritis.

Presentation

Extensor tendon subluxation or dislocation (usually to the ulnar side with radial sagittal band rupture). Pain at the MCP joint with snapping during flexion/extension. May present with pseudotriggering.

Classification (Rayan and Murray)

Type I: contusion without instability. Type II: subluxation of the extensor tendon (tendon can be reduced). Type III: dislocation of the extensor tendon (irreducible).

Treatment

Type I and II: buddy splinting with MCP in extension for 4-6 weeks. Type III: surgical repair of the sagittal band (direct suture or reconstruction using juncturae tendinum or extensor retinaculum). ---

Zones VI-VIII: Dorsal Hand, Wrist, and Forearm

Zone VI (Dorsum of Hand)

Tendons are more round and accessible. Direct repair with core sutures (modified Kessler or figure-of-eight). Juncturae tendinum may mask a complete tendon laceration (maintain extension via interconnection with adjacent tendon). Splint in wrist extension 30-40 degrees, MCP extension for 4-6 weeks.

Zone VII (Wrist Level)

Tendons beneath the extensor retinaculum. Repair tendons first, then partially close or leave open the retinaculum to prevent bowstringing while avoiding adhesions. High adhesion potential due to retinacular confinement.

Zone VIII (Forearm)

Muscular or musculotendinous junction injuries. Direct repair when possible; may require figure-of-eight suture through muscle. Healing can be challenging due to poor muscle holding capacity. ---

Rehabilitation for Extensor Tendon Repairs

Zones I-IV: Relative Motion Extension Splinting

DIP or PIP immobilized in extension; adjacent joints free. Static splinting for Zone I (6-8 weeks) and Zone III (6 weeks).

Zones V-VIII: Dynamic Extension Splinting / Relative Motion

Relative motion extension (RME) splinting: the repaired digit held in slightly more extension (15-20 degrees) than the adjacent digits; allows composite finger flexion. Gaining popularity over traditional static immobilization. Earlier return of function and reduced adhesion formation. Short arc motion (SAM) protocols for Zones V-VI.

Traditional Approach

Wrist and MCP extension splint for 4-6 weeks. Progressive active flexion beginning at 4-6 weeks. Full activity by 8-12 weeks. ---

Extensor Tendon Reconstruction

Indications

Failed primary repair with extensive adhesions. Tendon loss or segmental defects. Chronic untreated injuries.

Graft Options

Palmaris longus, plantaris, toe extensor tendons. EIP transfer for isolated EPL rupture (most common transfer in hand surgery). Free tendon graft for segmental defects.

EIP to EPL Transfer

Most common tendon transfer in the hand. Indicated for closed EPL rupture (often after distal radius fracture -- attritional rupture at Lister tubercle). EIP harvested at the MCP level, rerouted subcutaneously to the EPL insertion. Pulvertaft weave proximally; tension set with wrist in neutral and thumb in full retropulsion.

Tenolysis

Indicated when adhesions limit tendon gliding despite adequate therapy. Performed under local anesthesia or wide-awake anesthesia (WALANT) to assess active excursion intraoperatively. Aggressive hand therapy within 24-48 hours postoperatively. ---

Special Considerations

Swan Neck Deformity

PIP hyperextension with DIP flexion. Causes: volar plate laxity, FDS rupture/attenuation, intrinsic tightness, mallet finger (secondary). Treatment depends on etiology and flexibility: Flexible: FDS tenodesis (Zancolli lasso), spiral oblique retinacular ligament reconstruction. Fixed: staged PIP capsulotomy then reconstruction. Rheumatoid: intrinsic release, joint arthroplasty.

Extensor Tendon Injuries in Rheumatoid Arthritis

Attritional rupture from synovitis, bony spurs (especially at the Lister tubercle and distal ulna). Vaughan-Jackson syndrome: sequential rupture of extensors from EDM to EDC (ulnar to radial). Treatment: synovectomy, distal ulna excision (Darrach), tendon transfers or grafts.

<image>Dorsal view illustration of the hand showing the extensor zones I through VIII labeled over the finger and hand dorsum, with the six extensor compartments at the wrist labeled (I: APL/EPB, II: ECRL/ECRB, III: EPL, IV: EDC/EIP, V: EDM, VI: ECU). An inset demonstrates the sagittal band anatomy at the MCP joint level (Zone V) with the extensor tendon held centrally over the metacarpal head by the radial and ulnar sagittal bands, and the juncturae tendinum interconnecting adjacent EDC tendons on the dorsum of the hand.</image>

Clinical Pearls

Mallet finger is the most common closed tendon injury in the hand -- continuous DIP extension splinting for 6-8 weeks is highly effective, but the patient must never allow the DIP to flex during the splinting period. Boutonniere deformity may not present immediately after central slip injury -- any PIP joint injury with pain on the dorsum and weak extension should be splinted as a presumed central slip injury and followed closely. The Elson test is the key clinical test for central slip integrity -- a rigid DIP during resisted PIP extension indicates central slip disruption.

Juncturae tendinum can mask a complete EDC laceration in Zone VI -- always examine each tendon independently. EIP to EPL transfer is the workhorse tendon transfer for EPL rupture -- the EIP is identified as the most ulnar tendon to the index finger EDC at the MCP level. Relative motion extension splinting is replacing traditional static extension immobilization for Zone V-VI repairs, allowing earlier motion with comparable or better outcomes. In rheumatoid patients, progressive extensor tendon ruptures (Vaughan-Jackson lesion) require urgent surgical intervention before additional tendons rupture. ---.

References

• Doyle JR. Extensor tendons -- acute injuries. In: Green DP, ed. Green's Operative Hand Surgery. 8th ed. Elsevier; 2022.
• Matzon JL, Bozentka DJ. Extensor tendon injuries. J Hand Surg Am. 2010;35(5):854-861.
• Elson RA. Rupture of the central slip of the extensor hood of the finger. J Bone Joint Surg Br. 1986;68(2):229-231.
• Hanz KR, Saint-Cyr M, Semmler MJ, Rohrich RJ. Extensor tendon injuries: acute management and secondary reconstruction. Plast Reconstr Surg. 2008;121(3):109e-120e.
• Rayan GM, Murray D. Classification and treatment of closed sagittal band injuries. J Hand Surg Am. 1994;19(4):590-594.
• Merritt WH. Relative motion splint for dynamic treatment of extensor lag or extensor tendon repair. J Hand Ther. 2014;27(2):19-25.
• Vaughan-Jackson OJ. Rupture of extensor tendons by attrition at the inferior radio-ulnar joint. J Bone Joint Surg Br. 1948;30(4):528-531.

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