INTRODUCTION TO DORSAL SYNOVECTOMY

Dorsal synovectomy of the wrist is a cornerstone procedure in the operative management of inflammatory arthropathies, most notably rheumatoid arthritis (RA). The rheumatoid wrist is frequently the epicenter of aggressive synovial hypertrophy, which, if left unchecked, leads to progressive capsular distension, ligamentous attenuation, and enzymatic degradation of the extensor tendons.

The primary objective of a dorsal synovectomy is prophylactic: to eradicate the invasive pannus, decompress the extensor compartments, and prevent attritional or ischemic tendon ruptures—classically culminating in Vaughan-Jackson syndrome. Furthermore, the procedure aims to restore the biomechanical vectors of the wrist by addressing distal radioulnar joint (DRUJ) instability and relocating the subluxated extensor carpi ulnaris (ECU).

This comprehensive guide delineates the postgraduate-level surgical technique, biomechanical rationale, and postoperative protocols required to execute a successful dorsal synovectomy, incorporating extensor retinaculum transposition and distal ulnar management.

PATHOPHYSIOLOGY AND BIOMECHANICAL CONSIDERATIONS

To master the surgical technique, the operating surgeon must possess a profound understanding of the pathoanatomy of the rheumatoid wrist.

The Caput Ulnae Syndrome

Chronic synovitis of the DRUJ leads to attenuation of the triangular fibrocartilage complex (TFCC) and the dorsal radioulnar ligaments. This results in the classic "caput ulnae" deformity, characterized by:
* Dorsal subluxation of the distal ulna.
* Volar subluxation and supination of the carpus.
* Palmar displacement of the ECU tendon.

Biomechanics of the Extensor Carpi Ulnaris (ECU)

In a healthy wrist, the ECU resides in the sixth dorsal compartment and acts as a primary wrist extensor and ulnar deviator. In the rheumatoid wrist, destruction of the ECU subsheath allows the tendon to subluxate volar to the axis of wrist flexion-extension.
* Pathologic Conversion: Once displaced volarly, the ECU biomechanically converts from a wrist extensor to a wrist flexor.
* Deformity Amplification: This aberrant vector exacerbates palmar flexion and ulnar deviation of the carpus, accelerating the characteristic rheumatoid wrist deformity. Relocation of the ECU to the dorsum of the wrist is therefore a mandatory step in restoring coronal and sagittal balance.

Mechanisms of Tendon Rupture

Extensor tendon rupture in the rheumatoid wrist occurs via two primary mechanisms:
1. Mechanical Attrition: The dorsally prominent, arthritic distal ulna acts as a saw against the overlying extensor tendons (typically beginning with the extensor digiti minimi [EDM] and progressing radially to the extensor digitorum communis [EDC]).
2. Ischemic/Enzymatic Degradation: Proliferative tenosynovium invades the tendon substance, releasing matrix metalloproteinases (MMPs) and compromising the intrinsic microvascular supply, leading to spontaneous rupture.

INDICATIONS AND PREOPERATIVE PREPARATION

Surgical Indications

• Refractory Tenosynovitis: Persistent dorsal wrist swelling and tenosynovitis lasting greater than 6 months despite optimal medical management (including Disease-Modifying Antirheumatic Drugs [DMARDs] and biologic therapies).
• Impending Tendon Rupture: Clinical signs of severe attrition, such as a prominent, unstable distal ulna with overlying crepitus.
• Caput Ulnae Syndrome: Painful DRUJ instability with restricted forearm rotation.
• Early Tendon Rupture: Rupture of one or two extensor tendons requiring simultaneous synovectomy and tendon transfer/grafting.

💡 Clinical Pearl: The "Tuck Sign"

Before proceeding to surgery, carefully evaluate the patient for silent tendon ruptures. A loss of active extension at the metacarpophalangeal (MCP) joint with preserved tenodesis effect suggests tendon rupture rather than MCP joint subluxation or posterior interosseous nerve (PIN) palsy.

Preoperative Setup

• Anesthesia: Regional block (axillary or supraclavicular brachial plexus block) is preferred, supplemented with intravenous sedation or general anesthesia.
• Positioning: The patient is positioned supine with the operative arm extended on a radiolucent hand table.
• Tourniquet: A well-padded pneumatic tourniquet is applied to the proximal arm and inflated to 250 mmHg (or 100 mmHg above systolic blood pressure) after exsanguination with an Esmarch bandage.

SURGICAL TECHNIQUE: STEP-BY-STEP

1. Incision and Superficial Dissection

Meticulous handling of the soft tissues is paramount, as rheumatoid skin is notoriously fragile and prone to necrosis.

• Incision Design: Make a dorsal longitudinal incision, centered over the wrist joint. The incision may be curved only slightly ulnarward to provide adequate exposure of the distal ulna and the extensor retinaculum.
• Flap Viability: Avoid curving the incision sharply or creating acute angles. Broad-based flaps are essential to preserve the subdermal vascular plexus and prevent marginal skin necrosis.
• Nerve Preservation: Carefully dissect through the subcutaneous tissue. Identify, mobilize, and protect the larger dorsal veins. Meticulously preserve all identifiable sensory nerves, specifically the dorsal sensory branch of the ulnar nerve (DSBUN) medially and the superficial branch of the radial nerve (SBRN) laterally.

2. Elevation of the Extensor Retinaculum Flap

The extensor retinaculum must be elevated as a continuous sheet to be utilized later for tendon isolation and DRUJ stabilization.

• Transverse Incisions: Make transverse incisions at the proximal and distal margins of the extensor retinaculum.
• Proximal Band Preservation: At the proximal end, make the transverse incision such that a continuous band of retinaculum, approximately 5 to 10 mm wide, is preserved proximally. This intact band acts as a critical pulley to prevent bowstringing of the extensor tendons during active wrist extension postoperatively.
• Longitudinal Release: Connect the transverse, parallel retinacular incisions with a longitudinal incision placed over the sixth dorsal compartment (extensor carpi ulnaris).
• Flap Elevation: Raise the retinacular flap from medial (ulnar) to lateral (radial). As the flap is reflected, sharply divide the vertical septa that separate the six extensor compartments.
• Tendon Protection: Exercise extreme caution to avoid iatrogenic injury to the extensor tendons. The extensor pollicis longus (EPL) in the third compartment is particularly vulnerable as it angles around Lister's tubercle; it is often attenuated and embedded in thick pannus.
• Complete Reflection: Detach the retinaculum from its radial insertion and reflect it ulnarward as a single, intact sheet.

3. Meticulous Tenosynovectomy

With the extensor tendons exposed, the core of the procedure commences.

• Carefully excise the hypertrophic synovium from around the finger extensors (EDC, EIP, EDM) and the radial wrist extensors (ECRL, ECRB).
• Use blunt and sharp dissection, along with fine tenotomy scissors or a rongeur, to peel the pannus off the epitenon.
• If the synovium has invaded the tendon substance, perform a careful intra-tendinous debulking, ensuring the longitudinal continuity of the tendon fibers is maintained.

⚠️ Surgical Warning: Tendon Handling

Rheumatoid tendons are structurally compromised. Avoid excessive traction with forceps. Use moist umbilical tapes or Penrose drains to gently retract the tendons during the synovectomy.

4. Management of the Distal Ulna and DRUJ

The distal ulna is a primary generator of pathology in the rheumatoid wrist.

• Assessment: Evaluate the DRUJ. If the attachments of the distal ulna to the radius and carpus are intact, and the joint is stable without severe arthritic change, do not disturb it. Excise any hypertrophied synovium from the periphery of the DRUJ.
• Distal Ulnar Resection (Darrach Procedure): If the distal ulna is found to be subluxated, unstable, or denuded of cartilage (Caput Ulnae), a resection is indicated.
  • Excise approximately 1 cm of the distal ulna. Resecting more than 1.5 cm increases the risk of radioulnar impingement and stump instability.
  • Smooth the remaining distal ulnar stump meticulously with a rasp to remove any sharp cortical edges that could threaten the overlying tendons.
  • Cover the resected end of the ulna with local periosteum, the volar DRUJ capsule, or a portion of the pronator quadratus to create a soft-tissue interposition barrier.

5. ECU Relocation and Stabilization

Addressing the ECU is critical for restoring coronal balance to the wrist.

• Incise the sheath of the ECU tendon near its attachment to the base of the fifth metacarpal.
• Pathologic Assessment: Evaluate the position of the ECU. If the sheath is disintegrated and the tendon is dislocated palmarward, it has biomechanically become a flexor, driving palmar flexion and ulnar deviation.
• Relocation: Remove the tendon from its volar, subluxated position as needed and physically return it to the dorsum of the wrist.
• Pulley Creation: To maintain the ECU in its corrected dorsal position, create a robust pulley using a strip of the dorsal retinaculum or local capsular tissue. Suture this pulley securely to prevent recurrent volar subluxation during forearm pronation.

6. Tendon Transfers for Radial Deviation

In advanced rheumatoid wrists, the carpus often collapses into ulnar translation and palmar flexion, while the metacarpals deviate radially.

• Indications for Transfer: If, before surgery, the patient could not actively deviate and dorsiflex the wrist from a position of radial deviation, the ulnar-sided extensors are mechanically incompetent.
• ECRL to ECU Transfer: To correct this radial deviation and augment ulnar extension, transfer the insertion of the extensor carpi radialis longus (ECRL) tendon to the extensor carpi ulnaris (ECU) tendon. This rebalances the wrist, providing a strong dorsoulnar corrective force.

7. Radiocarpal and Midcarpal Synovectomy

• While an assistant applies longitudinal traction to the hand to distract the carpus, inspect the radiocarpal and midcarpal joints.
• Use a small rongeur or synovectomy forceps to meticulously remove the invasive pannus from among the carpal bones and the radiocarpal articulation.
• Avoid aggressive debridement of the intrinsic intercarpal ligaments, which could precipitate further carpal collapse.

8. Retinacular Transposition

This step is vital to protect the extensor tendons from future attrition against the carpus and the radiocarpal joint.

• Take the previously elevated, laterally based extensor retinacular flap and pass it deep to the long extensor tendons.
• Suture its detached radial end in place medially, effectively creating a smooth, biological barrier between the rough, arthritic carpal bones/radiocarpal joint below and the extensor tendons above.
• The tendons now glide in the subcutaneous tissue, superficial to the transposed retinaculum, while the preserved 5-10 mm proximal retinacular band prevents bowstringing.

9. Hemostasis and Closure

• Tourniquet Release: Elevate the hand and apply firm manual pressure over the wound. Release the tourniquet prior to closure.
• Hemostasis: Wait 5 to 10 minutes for reactive hyperemia to subside. Achieve meticulous hemostasis using bipolar electrocautery. Hematoma formation is a devastating complication that can lead to wound breakdown, infection, and severe stiffness.
• Drain Placement: Leave a small closed-suction drain or a rubber drain in the wound bed to evacuate postoperative oozing.
• Skin Closure: Close the skin with interrupted, non-absorbable sutures (e.g., 4-0 nylon). Avoid excessive tension on the skin edges.

POSTOPERATIVE CARE AND REHABILITATION

The success of a dorsal synovectomy relies heavily on a disciplined, phased postoperative rehabilitation protocol. The goal is to balance tissue healing with the prevention of peritendinous adhesions.

Phase 1: Immediate Postoperative Period (Days 0–14)

• Immobilization: Apply a bulky, non-adherent compression dressing. Fabricate and apply a volar plaster or fiberglass splint to hold the wrist in a neutral position (0 degrees of flexion/extension).
• Elevation: The limb must be strictly elevated above heart level for the first 48 to 72 hours to minimize edema.
• Early Motion: Active motion of the metacarpophalangeal (MCP) and interphalangeal (IP) joints of the fingers is encouraged immediately on postoperative day one. This is critical to promote independent tendon gliding and prevent adhesions.
• Wound Care: The wound is periodically inspected. Any significant hematoma beneath the skin must be evacuated promptly to prevent flap necrosis.

Phase 2: Suture Removal and Transition (Weeks 2–4)

• At 10 to 14 days, the bulky dressing is removed, and the skin sutures are extracted.
• The patient is transitioned to a custom-molded, removable thermoplastic volar wrist splint.
• Wrist ROM: Gentle, active range of motion (AROM) of the wrist is initiated out of the splint under the guidance of a specialized hand therapist.
• The splint is worn between exercise sessions and at night to protect the ECU stabilization and any tendon transfers.

Phase 3: Strengthening and Weaning (Weeks 4–8)

• At 3 to 4 weeks, the daytime use of the splint is gradually weaned.
• Active-assisted range of motion (AAROM) and gentle passive range of motion (PROM) are introduced.
• If an ECRL to ECU tendon transfer was performed, specific neuromuscular re-education exercises are initiated to train the transfer.
• Light strengthening exercises (e.g., isometric wrist extension, grip strengthening) begin at 6 weeks, progressing to functional activities by 8 to 10 weeks.

COMPLICATIONS AND PITFALLS

Even with meticulous technique, complications can arise in the vulnerable rheumatoid patient population.

• Wound Breakdown and Flap Necrosis: Usually secondary to poor incision design (sharp angles), excessive retraction, or underlying hematoma. Meticulous hemostasis prior to closure is non-negotiable.
• Tendon Bowstringing: Occurs if the proximal 5-10 mm band of the extensor retinaculum is inadvertently resected or fails. This results in a loss of mechanical advantage and weakness in wrist extension.
• Ulnar Stump Instability: Following a Darrach procedure, the distal ulnar stump may become unstable, causing painful impingement against the radius during pronation/supination. Ensuring a conservative resection (<1.5 cm) and robust soft-tissue interposition minimizes this risk.
• Recurrent Synovitis: While synovectomy provides excellent medium-term relief, it does not halt the systemic disease process. Continued rheumatological management with DMARDs/biologics is essential to prevent recurrence.
• Iatrogenic Nerve Injury: Neuroma formation from injury to the SBRN or DSBUN can cause debilitating neuropathic pain, often overshadowing the benefits of the synovectomy. Careful superficial dissection is imperative.

By adhering to these rigorous surgical principles and postoperative protocols, the orthopaedic surgeon can reliably relieve pain, halt progressive tendon destruction, and significantly improve the functional longevity of the rheumatoid wrist.

📚 Medical References

• dorsal synovectomy for the rheumatoid wrist, Hand Clin 7:335, 1991.
• Minami A, Ogino T, Tohyama H: Multiple ruptures of fl exor tendons due to hypertrophic change at the distal radio-ulnar joint: a case report, J Bone Joint Surg 71A:300, 1989.
• Moore JR, Weiland AJ, Valdata L: Tendon ruptures in the rheumatoid hand: analysis of treatment and functional results in 60 patients, J Hand Surg 12A:9, 1987.
• Nalebuff EA: The rheumatoid swan-neck deformity, Hand Clin 5:203, 1989.
• Nalebuff EA, Millender LH: Surgical treatment of the