Introduction to Wrist Arthroscopy
The evolution of arthroscopy from a purely diagnostic endeavor to a highly advanced therapeutic field represents one of the most significant paradigm shifts in modern orthopedic surgery. While the foundational principles of arthroscopic joint stabilization—such as capsulolabral plication, suture anchor biomechanics, and advanced knot-tying techniques—were largely pioneered in the shoulder (as extensively documented by pioneers like Altchek, Andrews, Burkhart, and Caspari), these exact paradigms have been meticulously adapted to the micro-anatomy of the wrist.
Today, wrist arthroscopy is the gold standard for evaluating and treating intra-articular pathology of the radiocarpal, midcarpal, and distal radioulnar joints (DRUJ). It offers unparalleled visualization of the articular cartilage, intrinsic and extrinsic carpal ligaments, and the triangular fibrocartilage complex (TFCC), allowing for minimally invasive interventions that preserve the critical proprioceptive and stabilizing structures of the wrist capsule.
Biomechanics and Pathoanatomy
A profound understanding of carpal kinematics is mandatory before undertaking wrist arthroscopy. The wrist is not a single joint but a complex articulation comprising the radiocarpal joint, the midcarpal joint, and the DRUJ.
The Radiocarpal and Midcarpal Joints
The proximal carpal row (scaphoid, lunate, triquetrum) acts as an intercalated segment. Its motion is entirely dependent on the mechanical forces exerted by the surrounding ligaments and the articular contours of the radius and distal carpal row.
* Extrinsic Ligaments: The volar extrinsic ligaments (radioscaphocapitate [RSC], long radiolunate [LRL], and short radiolunate [SRL]) are the primary stabilizers of the radiocarpal joint. They are visualized arthroscopically as stout, distinct bands in the volar capsule.
* Intrinsic Ligaments: The scapholunate (SL) and lunotriquetral (LT) interosseous ligaments are critical for synchronous carpal motion. Disruption of these ligaments leads to dissociative carpal instability (e.g., DISI or VISI deformities).
The Triangular Fibrocartilage Complex (TFCC)
The TFCC is the primary stabilizer of the DRUJ and the ulnar carpus. It acts as a shock absorber, transmitting approximately 20% of the axial load from the carpus to the ulna. The complex consists of the articular disc, the dorsal and volar radioulnar ligaments, the meniscus homologue, the ulnar collateral ligament, and the sheath of the extensor carpi ulnaris (ECU).
CLINICAL PEARL:
When evaluating the TFCC arthroscopically, the "trampoline test" is essential. A normal articular disc will bounce back when probed. A loss of this tension indicates a peripheral tear or detachment, necessitating repair to restore DRUJ stability.
Indications for Wrist Arthroscopy
The indications for wrist arthroscopy have expanded exponentially, mirroring the trajectory of shoulder arthroscopy over the past three decades.
Diagnostic Indications
- Unexplained chronic wrist pain unresponsive to conservative management.
- Evaluation of suspected chondral lesions or occult carpal instability not definitively diagnosed on MRI or MR arthrography.
Therapeutic Indications
- TFCC Pathology: Debridement of central tears (Palmer 1A) or repair of peripheral tears (Palmer 1B, 1C, 1D).
- Carpal Instability: Debridement, thermal shrinkage, or arthroscopic-assisted reduction and pinning of SL or LT ligament tears (Geissler Grades I-III).
- Fracture Management: Arthroscopic-assisted reduction of intra-articular distal radius fractures to ensure anatomic restoration of the articular surface and to treat concomitant soft-tissue injuries.
- Synovial Disease: Synovectomy for rheumatoid arthritis or inflammatory arthropathies.
- Ganglion Cysts: Arthroscopic excision of dorsal or volar carpal ganglions via stalk resection.
Operating Room Setup and Patient Positioning
Meticulous setup is the foundation of successful wrist arthroscopy. The procedure is typically performed under regional anesthesia (brachial plexus block) with a proximal arm tourniquet.
Positioning and Traction
- The patient is placed supine with the operative arm extended on a hand table.
- Longitudinal traction is applied using sterile finger traps placed on the index and middle fingers.
- A traction tower or a system of weights over the end of the table is utilized. Approximately 10 to 15 pounds of traction is applied to distract the radiocarpal and midcarpal joints.
- The wrist should be maintained in neutral to slight flexion to open the dorsal radiocarpal space.
Equipment
- Arthroscope: A 2.7-mm or 1.9-mm, 30-degree short-barrel arthroscope is standard.
- Fluid Management: Gravity inflow or a dedicated small-joint pump set to low pressure (30-40 mm Hg) is used to maintain joint distension while minimizing the risk of compartment syndrome.
- Instrumentation: Small joint probes, graspers, punches, and motorized shavers (2.0 mm to 2.9 mm).
SURGICAL WARNING:
Excessive fluid pressure or prolonged surgical times can lead to massive fluid extravasation into the forearm compartments. Always monitor forearm tension throughout the procedure. If the forearm becomes tense, terminate the fluid inflow immediately and assess for compartment syndrome.
Portal Anatomy and Placement
Wrist arthroscopy relies on precise portal placement to avoid iatrogenic injury to the dorsal sensory nerves and extensor tendons. Portals are named according to their relationship with the extensor compartments.
Radiocarpal Portals
- 3-4 Portal: The primary viewing portal. Located between the extensor pollicis longus (EPL, 3rd compartment) and the extensor digitorum communis (EDC, 4th compartment), approximately 1 cm distal to Lister's tubercle.
- 4-5 Portal: The primary working portal. Located between the EDC and the extensor digiti minimi (EDM, 5th compartment).
- 6R Portal: Located immediately radial to the ECU tendon. Useful for viewing the TFCC and ulnar carpus.
- 6U Portal: Located immediately ulnar to the ECU tendon. Used for inflow/outflow or working in the ulnar gutter.
- 1-2 Portal: Located between the first and second extensor compartments. Used for viewing the radial styloid and radioscaphoid joint. Caution: High risk to the superficial branch of the radial nerve (SBRN).
Midcarpal Portals
- Radial Midcarpal (RMC) Portal: Located 1 cm distal to the 3-4 portal, in line with the radial border of the third metacarpal. Provides visualization of the scaphotrapezial-trapezoid (STT) joint and the SL interval.
- Ulnar Midcarpal (UMC) Portal: Located 1 cm distal to the 4-5 portal, in line with the fourth metacarpal. Provides visualization of the capitohamate and LT intervals.
Step-by-Step Surgical Techniques
1. The Diagnostic Sweep
A systematic 14-point diagnostic sweep must be performed in every case to ensure no pathology is missed.
1. Insert the arthroscope into the 3-4 portal.
2. Evaluate the volar capsule and extrinsic ligaments (RSC, LRL, SRL).
3. Assess the radial styloid and scaphoid articular surfaces.
4. Sweep ulnarly to evaluate the SL interosseous ligament.
5. Inspect the lunate facet of the radius and the proximal lunate.
6. Evaluate the LT interosseous ligament.
7. Inspect the TFCC, performing the trampoline test with a probe from the 4-5 portal.
8. Assess the ulnocarpal ligaments and the ulnar gutter.
9. Transition the scope to the midcarpal portals to evaluate the distal carpal row and the midcarpal portions of the SL and LT ligaments.
2. Arthroscopic TFCC Repair (Palmer 1B Tears)
Peripheral tears of the TFCC (Palmer 1B) occur at the highly vascularized capsular attachment, making them amenable to repair. Drawing from the principles of Bankart repairs in the shoulder, TFCC repairs aim to restore capsular tension and DRUJ stability.
- Outside-In Technique: Needles are passed from the ulnar capsule into the joint, capturing the torn edge of the TFCC. Suture loops are retrieved through the 4-5 or 6R portal, tied over the dorsal ulnar capsule, and buried beneath the skin.
- Inside-Out Technique: Specialized suture passing devices are used to drive sutures from the intra-articular space through the capsule.
- All-Inside Technique: Utilizing modern micro-suture anchors or specialized deployment devices, the TFCC is repaired directly to the fovea or capsule without external knot tying. This technique minimizes the risk of injury to the dorsal sensory branch of the ulnar nerve (DSBUN).
3. Management of Scapholunate Instability
The Geissler classification is used to grade SL tears arthroscopically:
* Grade I: Attenuation of the ligament; no step-off.
* Grade II: Incongruency of the SL interval; probe can be placed into the gap.
* Grade III: Probe can be passed entirely through the SL interval into the midcarpal joint.
* Grade IV: The arthroscope can be driven through the SL interval (drive-through sign).
Treatment: Grades I and II may be treated with arthroscopic debridement and thermal shrinkage (a technique adapted from shoulder thermal capsulorrhaphy, though used with caution to avoid chondrolysis). Grades III and IV require arthroscopic-assisted reduction, percutaneous K-wire fixation, and potentially open ligamentous reconstruction.
4. Arthroscopic-Assisted Distal Radius Fracture Fixation
Arthroscopy is increasingly utilized as an adjunct to volar locking plate fixation for intra-articular distal radius fractures.
1. Following preliminary fluoroscopic reduction and plate application, the arthroscope is introduced.
2. The joint is flushed of hematoma.
3. Articular step-offs are directly visualized. A step-off greater than 1-2 mm is unacceptable.
4. A probe or elevator is used via a working portal to elevate depressed articular fragments.
5. Subchondral bone graft or substitute can be packed beneath the elevated fragments before final screw fixation.
6. Concomitant TFCC or SL tears (which occur in up to 70% of intra-articular distal radius fractures) are addressed simultaneously.
Complications and Avoidance
While wrist arthroscopy is minimally invasive, the margin for error is exceptionally small due to the proximity of neurovascular structures.
- Nerve Injury: The SBRN and DSBUN are at highest risk. Always use longitudinal skin incisions (never transverse) and blunt dissection with a hemostat down to the capsule. Avoid excessive traction on the soft tissues.
- Tendon Injury: Extensor tendons can be lacerated by trocars or shavers. Ensure portals are placed precisely between compartments. Always visualize the shaver blade and keep it facing away from the capsule and tendons.
- Iatrogenic Cartilage Damage: The radiocarpal space is tight. Forcing the trocar can cause severe scaphoid or lunate chondral scoring. If entry is difficult, increase traction, ensure proper wrist flexion, and use a blunt obturator.
- Fluid Extravasation: As previously noted, monitor forearm compartments continuously.
Postoperative Rehabilitation Protocols
Rehabilitation is dictated by the specific procedure performed:
- Diagnostic Arthroscopy / Debridement: A bulky dressing is applied. Immediate active range of motion (ROM) of the fingers is encouraged. Wrist ROM begins at 3-5 days postoperatively. Strengthening commences at 3-4 weeks.
- TFCC Repair: The wrist and forearm are immobilized in a Muenster-style splint or sugar-tong splint in neutral rotation for 4-6 weeks to protect the DRUJ. Pronation and supination are strictly limited. Gradual ROM begins at 6 weeks, with full unrestricted activity delayed until 3-4 months.
- Arthroscopic-Assisted Fracture Fixation: Early ROM is initiated within 1-2 weeks, relying on the stability of the volar locking plate, while protecting any concomitant ligamentous repairs.
Conclusion
Wrist arthroscopy represents the pinnacle of minimally invasive orthopedic surgery, demanding a rigorous understanding of carpal biomechanics, meticulous surgical technique, and a deep respect for the complex neurovascular anatomy. By applying the advanced principles of capsuloligamentous repair originally developed in larger joints, the modern orthopedic surgeon can achieve anatomic restoration and superior functional outcomes in the treatment of complex wrist pathology. Mastery of these techniques is an essential component of contemporary orthopedic practice.
