DRUJ Anatomy and Sauvé-Kapandji (Kapandji) Procedure

MS Orthopaedics - 20 Marks Answer

PART I: ANATOMY OF THE DISTAL RADIOULNAR JOINT (DRUJ)

1. Introduction

2. Bony Anatomy

• The ulnar head articulates with the sigmoid notch (ulnar notch) of the distal radius.
• The sigmoid notch is a shallow, concave facet on the medial aspect of the distal radius. Its arc of curvature (~47°) is smaller than the arc of the ulnar head (~165°), creating inherent bony instability - only about one-quarter of the ulnar circumference is in contact with the notch at any given time.
• This geometric mismatch means the DRUJ relies heavily on soft tissue stabilizers.

• The depth and shape of the sigmoid notch varies (flat, ski-slope, C-type, S-type) and influences native stability.
• Ulnar variance (positive or negative) alters load transmission: at neutral variance, 80% of compressive loads pass through the radius and 20% through the ulna. At -2 mm negative variance, load through the ulna drops to 40%; positive variance increases the ulnar load and is associated with ulnar impaction syndrome and TFCC degeneration.

3. Joint Capsule and Ligamentous Stabilizers

• These are the most important static stabilizers of the DRUJ.
• They arise from the margins of the sigmoid notch and converge on the fovea at the base of the ulnar styloid (deep limb) and the ulnar styloid tip (superficial limb).
• The volar (palmar) radioulnar ligament is taut in supination.
• The dorsal radioulnar ligament is taut in pronation.
• The deep fibers inserting at the fovea are the most biomechanically significant; foveal disruption causes complete DRUJ instability.

• The distal oblique bundle (DOB) of the IOM provides secondary stabilization to the DRUJ.
• The IOM also plays a critical role in longitudinal forearm stability (disrupted in Essex-Lopresti injury).

• The ECU tendon, running in the 6th extensor compartment within its own subsheath, acts as a dynamic stabilizer of the DRUJ, particularly against dorsal ulnar head subluxation.
• ECU subsheath disruption from forceful hypersupination + ulnar deviation contributes to DRUJ instability.

• This deep muscle is a dynamic stabilizer that compresses and stabilizes the DRUJ during active forearm rotation.

4. The Triangular Fibrocartilage Complex (TFCC)

1. Articular disc (TFC proper) - fibrocartilaginous disc; base attaches to the medial margin of the sigmoid notch of the radius; apex attaches to the base of the ulnar styloid and the fovea
2. Dorsal radioulnar ligament (deep + superficial limbs)
3. Volar (palmar) radioulnar ligament (deep + superficial limbs)
4. Meniscus homologue - fibrous tissue between the ulnar head and triquetrum/pisiform
5. Ulnotriquetral ligament
6. Ulnolunate ligament
7. ECU subsheath (floor of 6th extensor compartment)
8. Ulnar capsule (distal ulnocarpal ligaments)

• Peripheral 20% of the disc (near ulnar styloid) is vascularized - from the ulnar artery branches. Hence peripheral tears are amenable to repair.
• Central zone is avascular - central tears do not heal and require debridement.
• The anterior and posterior interosseous arteries supply the DRUJ itself.

• During forearm rotation, the radius rotates around the fixed ulna. The TFCC disc remains attached to the ulna and rotates with the radius, acting as a load-bearing tether.
• The TFC transmits ~20% of axial load from the carpus to the ulna at neutral variance.

5. Biomechanics of the DRUJ

• The radius rotates around the ulna (which is largely stationary) during pronosupination. The range is ~75-80° each of pronation and supination.
• The ulnar head translates: dorsally in pronation and volarly in supination relative to the sigmoid notch.
• DRUJ stability depends on form closure (bony congruity), force closure (ligament tension), and muscle action (ECU, pronator quadratus).
• Disruption of the deep fibers of the radioulnar ligaments at the fovea is the key lesion causing complete DRUJ instability.

6. Clinical Correlations - DRUJ Conditions

PART II: THE SAUVÉ-KAPANDJI PROCEDURE

1. Historical Background

2. Concept and Rationale

• Fusing the DRUJ eliminates painful articular cartilage, provides a stable ulnocarpal support, and preserves the TFCC attachments and ulnar carpal ligaments.
• Resecting a segment of ulna proximal to the fusion creates the "pseudarthrosis" that allows the radius (and hand) to rotate freely during pronosupination - because the fused DRUJ (now part of the radius) rotates around the still-mobile proximal ulnar stump.
• Unlike the Darrach procedure, the distal ulna is preserved as a structural support for the carpus.

3. Indications

1. Rheumatoid arthritis with DRUJ destruction (preferred over Darrach in younger, active patients because it preserves ulnocarpal support)
2. Post-traumatic DRUJ osteoarthritis (from distal radius malunion, TFCC disruption, ulnar styloid nonunion)
3. Fixed DRUJ subluxation with concomitant joint destruction following intraarticular fractures of the distal radius
4. Failed previous DRUJ surgery (including failed Darrach)
5. Painful DRUJ from various chronic conditions where joint-preserving surgery is not possible

4. Contraindications

• Active infection
• Soft tissue deficiency precluding closure
• Essex-Lopresti injury (longitudinal forearm instability) - arthrodesis without IOM repair would worsen proximal migration

5. Advantages over the Darrach Procedure

6. Preoperative Assessment

• Plain X-rays: assess DRUJ, ulnar variance, carpal alignment
• CT scan (bilateral): in neutral, full pronation, full supination - >50% ulnar head translation is abnormal and confirms DRUJ instability
• MRI/arthroscopy: assess TFCC integrity
• Wrist arthroscopy: gold standard for diagnosing TFCC tears and DRUJ pathology

7. Surgical Technique (Sanders/Vincent/Lamey-Fernandez Modification)

1. Supine, arm on hand table, well-padded tourniquet, limb exsanguinated.
2. For rheumatoid patients: Dorsal longitudinal incision (to permit extensor tenosynovectomy + tendon repairs/transfers).
3. For non-rheumatoid patients: Dorsoulnar incision centered over the ulnar head. Protect the dorsal sensory branch of the ulnar nerve throughout.
4. Identify the interval between the extensor carpi ulnaris (ECU) and the extensor digiti minimi (EDM).
5. Open the extensor retinaculum, forming proximal (radial-based) and distal (ulnar-based) flaps.
6. Decorticate the radial and ulnar articular surfaces of the DRUJ with narrow osteotomes and rongeur to prepare the fusion bed.
7. Temporarily stabilize the DRUJ with a 0.045-inch Kirschner wire.
8. Ulnar osteotomy: Proximal to the ulnar neck and just proximal to the DRUJ, perform osteotomy with oscillating saw.
9. Bone resection:
   • Neutral/negative ulnar variance: remove a 15-mm segment of ulna with surrounding periosteum.
   • Positive ulnar variance: remove a larger segment to achieve neutral variance at the arthrodesis site and ensure a ≥15-mm gap for free rotation.
10. Remove temporary K-wire and obtain permanent DRUJ fixation using a 3.5-mm cortical screw with lag technique (washer for poor bone quality). K-wires may be used alternatively.
11. Bone from the resected ulnar segment is used as autograft at the arthrodesis site.
12. The pronator quadratus is secured to the proximal ulnar stump through drill holes to fill the pseudarthrosis gap (Lamey-Fernandez modification: also stabilizes the stump).

• A distally based slip of flexor carpi ulnaris (FCU) is passed through drill holes in the distal end of the proximal ulnar segment - acts as a tenodesis to prevent stump instability.
• The pronator quadratus is placed into the osteotomy (nonunion) site and sutured to the ECU sheath, filling the gap and preventing osseous bridging (which would defeat the purpose of the pseudarthrosis).
• Johnson-Ruby modification: the ulnar portion of pronator quadratus is passed through a drill hole in the proximal ulna.

8. Postoperative Care

• Long arm cast in supination for 4-6 weeks to protect the fusion.
• Sutures and splint removed at ~2 weeks.
• After cast removal: mobilization, physiotherapy with gradual return of pronosupination.
• The arthrodesis typically heals in 6-8 weeks.

9. Complications

• The most significant complication. The proximal stump, now "floating," may become painful and unstable (dorsal migration/subluxation with pronation).
• Incidence reduced with the Lamey-Fernandez modification (FCU tenodesis and pronator quadratus interposition).
• Treatment: repeat stabilization surgery.

• Nonunion of the DRUJ arthrodesis (defeats the purpose)
• Paradoxical osseous bridging of the pseudarthrosis site (also defeats the purpose)
• Dorsal sensory branch of ulnar nerve injury (neuropraxia, neuroma)
• Infection
• Persistent pain

10. Outcomes

• Effective in resolving ulnar-sided wrist pain from DRUJ pathology.
• Forearm rotation is restored or maintained through the pseudarthrosis mechanism.
• Ulnocarpal support is preserved.
• Grip strength improves.
• Particularly favored in rheumatoid arthritis where preservation of the ulnar carpal pillar is important.
• Sanders et al. (1991) reported it as a reliable "salvage operation for the DRUJ."

11. Comparison with Other DRUJ Salvage Procedures

Summary Diagram (Conceptual)

DRUJ Anatomy:
  Sigmoid notch (radius) ←→ Ulnar head
  Stabilizers: Radioulnar ligaments (deep foveal fibers = most important)
               TFCC disc (apex at fovea/styloid; base at sigmoid notch)
               ECU subsheath, Pronator quadratus, Distal IOM

Sauvé-Kapandji:
  Step 1: DRUJ arthrodesis (screw fixation ulnar head to sigmoid notch)
  Step 2: 15mm ulnar segment resection proximal to fusion
  Step 3: Pronator quadratus fills gap → prevents bony bridging
  Step 4: FCU slip tenodesis → stabilizes proximal stump
  Result: Stable DRUJ (fused) + Free forearm rotation (via pseudarthrosis)

• Campbell's Operative Orthopaedics 15th Ed 2026, Chapter 74 (Wrist Disorders) - DRUJ, TFCC, Technique 74.36 (Sauvé-Kapandji)
• Miller's Review of Orthopaedics 9th Edition - DRUJ/TFCC/Wrist Arthroscopy section
• Gray's Anatomy for Students - DRUJ anatomy (pivot-type joint, TFC, sigmoid notch)
• Sanders RA, Frederick HA, Hontas RB. The Sauvé-Kapandji procedure: a salvage operation for the distal radioulnar joint. J Hand Surg Am. 1991;16:1125.
• Lamey DM, Fernandez DL. Results of modified Sauvé-Kapandji procedure in the treatment of chronic posttraumatic derangement of the distal radioulnar joint. J Bone Joint Surg Am. 1998.