Proximal Row Carpectomy: An Intraoperative Masterclass for Wrist Degeneration

Introduction and Epidemiology

Proximal row carpectomy (PRC) is a highly durable, motion-preserving excisional arthroplasty of the wrist. First described by Stamm in 1944, the procedure involves the extirpation of the scaphoid, lunate, and triquetrum. By removing the proximal carpal row, the complex link-joint mechanics of the carpus are converted into a simplified, hinge-like radiocapitate articulation. The primary surgical objective is to alleviate pain secondary to advanced radiocarpal or intercarpal arthrosis while maintaining a functional arc of motion, making it a highly favorable alternative to total wrist arthrodesis in appropriately selected patients.

Epidemiologically, the most frequent indications for PRC are Scaphoid Nonunion Advanced Collapse (SNAC) and Scapholunate Advanced Collapse (SLAC). These degenerative cascades represent the most common patterns of wrist osteoarthritis, typically originating from untreated traumatic injuries such as scaphoid fractures or scapholunate interosseous ligament (SLIL) ruptures. Other indications include advanced Kienböck disease (avascular necrosis of the lunate), chronic perilunate dislocations, and Preiser disease. The fundamental prerequisite for a successful PRC is the absolute preservation of the articular cartilage on the lunate fossa of the distal radius and the proximal head of the capitate. Without a pristine radiocapitate articulation, the procedure is destined for early failure.

Surgical Anatomy and Biomechanics

A profound understanding of carpal osteology, ligamentous restraints, and wrist kinematics is mandatory for executing a PRC and anticipating postoperative biomechanical alterations.

Carpal Osteology and Articulations

The carpus consists of eight bones divided into proximal and distal rows. The proximal row (scaphoid, lunate, triquetrum) functions as an intercalated segment. It possesses no direct tendinous insertions, moving entirely in response to mechanical forces exerted by the surrounding ligaments and the distal carpal row. The scaphoid acts as a critical mechanical bridge between the proximal and distal rows, stabilizing the midcarpal joint. The lunate articulates proximally with the lunate fossa of the radius and distally with the capitate head. The triquetrum articulates with the triangular fibrocartilage complex (TFCC) and the hamate.

The distal carpal row (trapezium, trapezoid, capitate, hamate) is tightly bound by robust interosseous ligaments and functions essentially as a single biomechanical unit, moving synchronously with the metacarpals. The capitate is the keystone of the carpus, and its proximal articular geometry is paramount in the post-PRC wrist.

Ligamentous Anatomy and Stability

Carpal stability is governed by a sophisticated network of intrinsic and extrinsic ligaments.
* Intrinsic Ligaments: The SLIL and the lunotriquetral interosseous ligament (LTIL) are the primary stabilizers of the proximal row. SLIL insufficiency initiates the SLAC cascade, leading to dorsal intercalated segmental instability (DISI) and subsequent arthrosis.
* Extrinsic Ligaments: The volar extrinsic ligaments are stout, intracapsular structures that are critical for carpal stability. The radioscaphocapitate (RSC) ligament, the long radiolunate (LRL), and the short radiolunate (SRL) ligaments form a critical volar sling.
* The Role of the RSC in PRC: During a PRC, the integrity of the volar extrinsic ligaments—specifically the RSC—must be meticulously preserved. The RSC acts as a volar buttress that prevents palmar subluxation of the capitate head out of the lunate fossa. Iatrogenic transection of the RSC during scaphoid excision will lead to catastrophic radiocapitate instability.

Post-Proximal Row Carpectomy Biomechanics

Normal carpal kinematics distribute axial loads approximately 80% through the radiocarpal joint and 20% through the ulnocarpal joint. Within the radiocarpal joint, the scaphoid fossa bears roughly 60% of the load, and the lunate fossa bears 40%.

Following PRC, the biomechanical environment is radically altered. The capitate head is seated directly into the lunate fossa of the radius. Because the radius of curvature of the capitate head is smaller than that of the lunate fossa, the initial articulation is incongruent, resulting in point-contact loading rather than physiologic load distribution. Over time, adaptive remodeling occurs, but the joint remains subjected to elevated contact stresses. Despite this biomechanical mismatch, clinical outcomes demonstrate that the radiocapitate joint is surprisingly resilient, provided the initial cartilage was healthy. Postoperatively, patients typically retain 50% to 60% of their normal flexion-extension arc and achieve 70% to 80% of their contralateral grip strength.

Indications and Contraindications

Patient selection is the single most critical determinant of success in proximal row carpectomy. The surgeon must carefully evaluate the pattern of arthrosis to ensure the radiocapitate articulation is viable.

Clinical Indications

• Scaphoid Nonunion Advanced Collapse (SNAC): Indicated for Stage II (radioscaphoid and scaphocapitate arthrosis) and Stage III (periscaphoid arthrosis). The lunate fossa and proximal capitate are classically spared in SNAC wrists.
  
• Scapholunate Advanced Collapse (SLAC): Indicated for Stage II (radioscaphoid arthrosis) and early Stage III (capitolunate arthrosis). Note: If capitolunate arthrosis has resulted in significant eburnation or chondromalacia of the capitate head, PRC is contraindicated.
  
• Kienböck Disease: Indicated for Stage IIIb (lunate collapse with fixed carpal rotation/DISI) and Stage IV (pancarpal arthrosis), strictly provided that the capitate head and lunate fossa have not undergone secondary arthritic degeneration.
  
• Chronic Perilunate Dislocations: Utilized as a salvage procedure when open reduction and internal fixation are no longer feasible due to articular damage or chronicity, assuming the radiocapitate joint is intact.
• Preiser Disease: Advanced idiopathic avascular necrosis of the scaphoid with subsequent carpal collapse.

Absolute and Relative Contraindications

• Absolute Contraindications:
  • Lunate Fossa Arthrosis: Any significant chondromalacia, osteochondral defect, or eburnation of the lunate fossa of the distal radius.
  • Capitate Head Arthrosis: Degeneration of the proximal articular surface of the capitate.
  • Inflammatory Arthropathies: Rheumatoid arthritis is generally considered a contraindication due to the progressive nature of the disease, poor bone stock, and inevitable capsuloligamentous attenuation which leads to ulnar translation and volar subluxation of the carpus.
  • Active Infection: Absolute contraindication for any elective arthroplasty.
• Relative Contraindications:
  • Severe ulnar positive variance (may require concomitant ulnar shortening osteotomy to prevent ulnocarpal impaction post-PRC).
  • Heavy manual laborers (due to the theoretical risk of accelerated radiocapitate wear, though this is debated in recent literature).

Preoperative Planning and Patient Positioning

Thorough preoperative evaluation prevents intraoperative surprises and ensures the patient is a true candidate for a motion-preserving procedure versus an arthrodesis.

Clinical Evaluation and Imaging

1. Clinical Assessment: Evaluate active and passive range of motion, grip strength (using a Jamar dynamometer), and perform a comprehensive neurovascular exam. Assess for specific points of tenderness (e.g., anatomic snuffbox, dorsal SL interval).
2. Standard Radiographs: PA, lateral, and scaphoid views. The lateral view is essential for assessing carpal alignment (DISI/VISI) and the degree of carpal collapse.
3. Advanced Imaging:
   • CT Scan: Highly recommended to critically evaluate the subchondral bone of the capitate head and lunate fossa. CT is superior to plain radiographs for detecting subtle osteophytes, subchondral cysts, and joint space narrowing.
   • MRI: Useful for evaluating the vascularity of the carpal bones (e.g., Kienböck or Preiser disease) and assessing the integrity of the interosseous ligaments.

Patient Positioning and Anesthesia

The procedure is typically performed under regional anesthesia (supraclavicular or axillary brachial plexus block) combined with monitored anesthesia care (MAC) or general anesthesia.
* The patient is positioned supine with the operative extremity abducted onto a radiolucent hand table.
* A well-padded pneumatic upper arm tourniquet is applied.
* The arm is prepped and draped in a standard sterile fashion.
* Intraoperative fluoroscopy (C-arm) must be available and positioned parallel to the hand table.

Detailed Surgical Approach and Technique

The surgical execution requires meticulous soft tissue handling to preserve the dorsal capsule for repair and the volar extrinsic ligaments for radiocapitate stability.

Incision and Superficial Dissection

• A dorsal longitudinal incision is made, centered over Lister's tubercle, extending from the distal radius to the base of the third metacarpal.
  
• Subcutaneous dissection is carried out carefully. The dorsal sensory branch of the radial nerve (radial aspect) and the dorsal sensory branch of the ulnar nerve (ulnar aspect) must be identified and protected. Retraction should be gentle to avoid traction neuropraxia.
• The extensor retinaculum is exposed. The third dorsal compartment is opened, and the extensor pollicis longus (EPL) tendon is transposed radially.
• The interval between the third and fourth dorsal compartments is utilized. The extensor digitorum communis (EDC) and extensor indicis proprius (EIP) tendons are retracted ulnarly. Alternatively, a retinacular flap can be raised.
  
  
  

Capsulotomy and Joint Exposure

• A ligament-sparing capsulotomy (e.g., Berger's dorsal capsular flap) or a straight longitudinal capsulotomy is performed. The capsule is elevated off the radiocarpal and midcarpal joints.
• It is critical to raise full-thickness capsular flaps to ensure a robust closure at the end of the procedure, which is vital for preventing dorsal capitate subluxation.
  

Excision of the Proximal Carpal Row

The removal of the proximal row should be systematic, typically beginning with the scaphoid.
* Scaphoid Excision: The SLIL is divided. The scaphoid is grasped with a towel clip or threaded Joy-stick. Sharp dissection is used to release the dorsal and proximal attachments. Crucial Step: When dissecting the volar pole of the scaphoid, the surgeon must stay strictly subperiosteal or directly on bone to avoid injuring the underlying radioscaphocapitate (RSC) ligament. The scaphoid can be removed en bloc or fragmented with a rongeur if collapsed.

* Lunate Excision: With the scaphoid removed, the lunate is easily visualized. The LTIL is transected. The dorsal radiolunate ligaments are released, and the lunate is excised.

* Triquetrum Excision: The triquetrum is often the most difficult to remove due to its deep ulnar position and strong volar ligamentous attachments. It is sharply dissected free from the hamate and the TFCC.

Articular Preparation and Capitate Reduction

• Once the proximal row is excised, the joint is thoroughly irrigated. The surgeon must now directly inspect the articular cartilage of the lunate fossa and the capitate head.
• If unexpected, severe grade III/IV chondromalacia is encountered on either surface, the surgeon must be prepared to abort the PRC and convert to a total wrist arthrodesis or a four-corner fusion (if the lunate is salvageable and the radiolunate joint is pristine).
  
  
• Radial Styloidectomy (Optional but Recommended): A conservative radial styloidectomy (removing no more than 3-4 mm) is frequently performed to prevent postoperative impingement between the trapezium and the radial styloid during radial deviation. Care must be taken not to detach the origin of the RSC ligament.
• Reduction: Longitudinal traction is released, allowing the capitate head to seat into the lunate fossa. The wrist is taken through a full range of motion under direct vision and fluoroscopy to ensure concentric tracking and absence of impingement.
  

Closure and Stabilization

• Pinning: Routine K-wire fixation is not strictly necessary if the volar ligaments are intact and the capitate seats well. However, if there is concern for instability, a 0.062-inch K-wire can be passed from the dorsal radius into the capitate to hold the joint in neutral alignment for 3-4 weeks.
  
• Capsular Closure: The dorsal capsule is meticulously repaired with interrupted non-absorbable sutures (e.g., 2-0 Ethibond or FiberWire). A watertight, robust closure is essential for dorsal stability.
• The extensor retinaculum is repaired, leaving the EPL transposed subcutaneously to prevent attrition rupture.
• The skin is closed, and the wrist is placed in a bulky dressing and a volar sugar-tong splint in neutral position.

Complications and Management

While PRC is highly reliable, surgeons must be adept at managing potential postoperative complications.

Progressive Radiocapitate Arthrosis

This is the most common long-term complication and the primary reason for PRC failure. It occurs due to the biomechanical mismatch and point-loading of the capitate in the lunate fossa.
* Incidence: Radiographic arthrosis is seen in up to 15-30% of patients at 10-year follow-up, though clinical symptoms often do not correlate with radiographic severity.
* Management: Initial management includes NSAIDs, activity modification, and intra-articular corticosteroid injections.
* Salvage: If conservative measures fail, the definitive salvage procedure is Total Wrist Arthrodesis. Conversion of a failed PRC to a total wrist fusion yields reliable pain relief and functional grip strength, though all radiocarpal motion is sacrificed.

Neurologic and Soft Tissue Complications

• Neuroma: Injury to the superficial radial nerve (SRN) or dorsal sensory branch of the ulnar nerve (DSBUN) can lead to debilitating neuromas. Prevention through careful superficial dissection is paramount. Management includes desensitization, gabapentinoids, and surgical excision with proximal burying if refractory.
• Weakness and Stiffness: Patients will universally experience a reduction in grip strength (averaging 70% of the contralateral side) and a decrease in ROM. This is an expected outcome of the altered biomechanics rather than a true "complication," and preoperative patient counseling is essential.
• Capitate Subluxation: Volar subluxation occurs if the RSC ligament is violated during scaphoid excision. Dorsal subluxation occurs with inadequate dorsal capsular repair. Both scenarios result in severe pain and mechanical block, often requiring revision to total wrist fusion.

Postoperative Rehabilitation Protocols

A standardized, phased rehabilitation protocol is critical for optimizing functional outcomes and preventing arthrofibrosis.

Phase 1: Acute Immobilization (Weeks 0-3)

• The wrist is immobilized in a short-arm cast or rigid splint in neutral alignment.
• Immediate active range of motion (AROM) of the digits, thumb, elbow, and shoulder is initiated to prevent secondary stiffness.
• Edema control is prioritized through elevation and retrograde massage of the digits.
• If a K-wire was utilized for temporary stabilization, it is typically removed in the clinic at 3 to 4 weeks.

Phase 2: Early Mobilization (Weeks 3-6)

• The rigid cast is discontinued, and the patient is transitioned to a custom thermoplastic removable wrist splint, to be worn between exercise sessions and at night.
• Supervised AROM and active-assisted range of motion (AAROM) of the wrist (flexion, extension, radial/ulnar deviation) are initiated.
• Aggressive passive stretching is avoided in this phase to protect the healing dorsal capsular repair.

Phase 3: Strengthening and Functional Integration (Weeks 6-12)

• Progressive passive range of motion (PROM) is introduced.
• Isometric and progressive isotonic strengthening exercises for the forearm musculature and grip are initiated.
• Dynamic splinting may be considered if significant flexion/extension deficits persist beyond 8 weeks.
• Patients are gradually transitioned to normal activities of daily living (ADLs). Heavy lifting and impact loading are restricted until at least 12 to 16 weeks postoperatively.

Summary of Key Literature and Guidelines

The orthopedic literature heavily debates the superiority of PRC versus Four-Corner Fusion (4CF) for the treatment of SLAC/SNAC wrists.

Long-Term Outcomes and Comparative Studies

• Motion vs. Strength: Meta-analyses (e.g., Strauch et al., 2007) consistently demonstrate that PRC provides a superior arc of motion compared to 4CF (average 60° vs. 45° flexion-extension arc). Conversely, some studies suggest 4CF may preserve slightly better grip strength, though many prospective trials show no statistically significant difference in final grip strength between the two cohorts.
• Complication Profiles: 4CF carries the specific risks of nonunion (up to 5-10%) and hardware-related complications (impingement, migration). PRC eliminates the risk of nonunion but carries a higher long-term risk of progressive radiocapitate arthrosis.
• Revision Rates: Long-term follow-up studies (10-15 years) indicate that PRC has a slightly higher conversion rate to total wrist arthrodesis compared to 4CF, primarily due to the aforementioned radiocapitate degeneration.
• Cost and Operative Time: PRC is significantly faster to perform, requires no hardware (reducing implant costs), and involves a shorter period of postoperative immobilization compared to 4CF.

Clinical Guidelines

Current academic consensus dictates that PRC is the preferred motion-preserving procedure for patients with appropriate indications (SNAC/SLAC II) who are older, have lower functional demands, or prioritize postoperative range of motion. 4CF is often favored in younger, high-demand laborers or in patients with any evidence of capitate head chondromalacia. The ultimate decision must be tailored to the patient

Clinical & Radiographic Imaging