Arthroscopic Masterclass: Evaluation and Treatment of Scapholunate and Lunotriquetral Ligament Disruptions

Fellows, welcome to the operating theater. Today, we're tackling a complex and often challenging area of wrist surgery: the arthroscopic evaluation and treatment of scapholunate (SLIL) and lunotriquetral (LTIL) ligament disruptions. These injuries, while seemingly subtle, can lead to devastating long-term carpal instability and degenerative changes if not accurately diagnosed and appropriately managed. Our goal is not just to fix the immediate problem, but to preserve wrist function and prevent the relentless progression of carpal collapse.

Understanding the Pathology: The Foundation of Treatment

Let's begin by revisiting the fundamental understanding of these injuries. Mayfield and colleagues, in their seminal work, postulated that scapholunate disruption is often the initial component of the lesser arc perilunate injury pattern. This typically occurs when a significant force is applied to the thenar area with the wrist in extension, supination, and ulnar deviation. These interosseous ligament tears are common, occurring either in isolation or as part of a broader perilunate injury pattern. With advances in imaging and, critically, arthroscopy, we are diagnosing these injuries with increasing frequency. However, their management remains a difficult clinical problem. While surgical intervention has shown reliability in pain relief, altering the natural history of carpal degeneration remains a significant challenge. SLIL injuries can range from simple sprains to partial or complete tears, sometimes accompanied by injuries to the crucial extrinsic ligament stabilizers.

Comprehensive Surgical Anatomy: Navigating the Carpus

Before we make any incisions, a thorough understanding of wrist anatomy is paramount. The wrist is a complex kinematic chain, and the intrinsic and extrinsic ligaments are its primary stabilizers.

The Scapholunate Complex

The scapholunate complex is subjected to immense loads because the scaphoid is the only carpal bone that spans both the proximal and distal carpal rows. This unique position makes it a critical link in carpal kinematics. The proximal carpal row, as you know, flexes with radial deviation and extends with ulnar deviation. The scaphoid inherently "wants" to flex, while the triquetrum "wants" to extend. The lunate, acting as the intercalated segment, is tethered precariously between these two opposing forces. This creates a large amount of potential energy within the proximal carpal row, making it susceptible to instability when its ligamentous constraints are compromised.

Stability to the scapholunate complex is provided primarily by the intrinsic scapholunate interosseous ligament (SLIL), but also significantly by several extrinsic capsular ligaments. These extrinsic stabilizers include:
* Dorsal Radiocarpal (DRC) ligament: A crucial dorsal stabilizer.
* Dorsal Intercarpal (DIC) ligament: Connects the scaphoid, lunate, and triquetrum dorsally.
* Volar Radioscaphocapitate (RSC) ligament: A strong volar stabilizer.
* Scaphotrapezium-Trapezoid (STT) ligaments: Provide stability to the distal scaphoid.

The SLIL itself is a C-shaped structure. It comprises a stronger dorsal ligamentous portion, typically 2 to 3 mm thick, which is the most critical for stability. There's also a volar ligamentous portion, about 1 mm thick, and a proximal fibrocartilaginous (membranous) portion. When we talk about SLIL tears, they often fail at the bone-ligament interface off the scaphoid. Arthroscopic evaluations have revealed associated SLIL injuries in up to 30% of intra-articular distal radius fractures, highlighting the importance of a comprehensive assessment even in seemingly straightforward fractures.

The Lunotriquetral Complex

The lunotriquetral complex is similarly stabilized by an intrinsic lunotriquetral ligament (LTIL) and its surrounding extrinsic volar and dorsal capsular ligaments. The LTIL is also C-shaped, analogous to the SLIL, with dorsal and volar ligamentous portions and a membranous proximal portion. However, a key difference here is that the volar ligamentous portion of the LTIL is stronger and more functionally significant than its dorsal counterpart, in contrast to the SLIL.

Extrinsic stabilizers for the LTIL include:
* Volar Ulnotriquetral (UT) ligament
* Ulnolunate (UL) ligament
* Ulnocapitate (UC) ligament
* Dorsal Radiocarpal (DRC) ligament
* Dorsal Intercarpal (DIC) ligament

LTIL disruption can be traumatic or atraumatic. Traumatic ruptures may occur as the final component of a greater or lesser arc perilunate injury pattern. Isolated LTIL tears can result from a fall on an outstretched hand in extension, pronation, and radial deviation (a "reverse perilunate injury") or from a dorsally applied force on a flexed wrist. Atraumatic ruptures may be secondary to inflammatory arthritis or ulnar impaction syndrome.

Neurovascular Risks and Portal Anatomy

When establishing our portals, we must be acutely aware of the superficial neurovascular structures.
* Dorsal Sensory Branch of the Ulnar Nerve: Lies subcutaneously on the ulnar side, susceptible to injury during 6R and 6U portal placement.
* Superficial Radial Nerve: Courses radially, at risk with 1-2 and 3-4 portal placement.
* Extensor Tendons: All dorsal wrist portals are placed between specific extensor compartments. Careful blunt dissection is crucial to avoid tendon laceration or fraying. For instance, the 3-4 portal is between EPL (extensor pollicis longus) and EDC (extensor digitorum communis) tendons, the 4-5 portal between EDC and EDM (extensor digiti minimi), and the 6R/6U portals are ulnar to the EDM.

SURGICAL WARNING: Always use blunt dissection with a hemostat or mosquito clamp to spread tissues after skin incision for portal creation. Never blindly stab with a sharp trocar. This minimizes the risk of neurovascular or tendinous injury.

Natural History and Instability Patterns

Tears of the SLIL or LTIL, with or without extrinsic ligamentous injury, can lead to various degrees of carpal instability:
* Predynamic instability: Subtle changes, often only seen on stress views or arthroscopy.
* Dynamic instability: Instability evident with provocative maneuvers or stress radiographs, but static alignment is normal.
* Static instability: Frank carpal malalignment visible on standard radiographs.

These instabilities alter normal carpal mechanics and kinematics, inevitably leading to early degenerative changes in the radiocarpal and midcarpal joints.

• SLIL Tears and DISI Deformity: A complete SLIL tear is associated with the development of a Dorsal Intercalated Segment Instability (DISI) deformity. In this pattern, the scaphoid flexes, and the lunate is pulled by the triquetrum into extension. This can be dynamic or static; static DISI usually indicates additional injury to the extrinsic ligaments, particularly the dorsal intercarpal (DIC) ligament. As a DISI deformity forms, abnormal radiocarpal contact loading occurs due to the shift in proximal carpal bone positions and loss of congruency. Over time, abnormal flexion and hypermobility of the scaphoid lead to degenerative changes of the radioscaphoid and capitolunate joints, culminating in Scapholunate Advanced Collapse (SLAC) wrist degeneration. These degenerative changes have been documented to begin as early as 3 months post-injury, underscoring the urgency of early diagnosis and intervention.

• LTIL Tears and VISI Deformity: A complete LTIL tear is associated with the development of a Volar Intercalated Segment Instability (VISI) deformity. In this case, the lunate and scaphoid flex volarly relative to the capitate. Isolated injuries to the LTIL are usually insufficient for the development of static instability; presence of a static deformity indicates additional injury to extrinsic ligamentous structures (volar ulnotriquetral, ulnolunate, and ulnocapitate ligaments or the dorsal radiocarpal and intercarpal ligaments).

The natural history of partial tears of either the SLIL or LTIL is currently poorly defined. However, these partial injuries can still cause chronic, activity-related wrist pain even in the absence of obvious radiographic findings.

Preoperative Planning: Setting the Stage for Success

Preoperative planning is not merely a formality; it's a critical phase that dictates the intraoperative strategy. A careful review of the patient’s history, physical findings, and all available static and stress radiographs provides us with a reasonable impression of the pathology and what will be required.

Patient History and Physical Findings

Fellows, always start with a detailed history. Dorsoradial or ulnar-sided wrist pain, particularly with a history of a fall, sudden loading, or twisting, should immediately raise suspicion for an SLIL or LTIL tear, respectively. However, do not be surprised if the patient denies any significant injury; some presentations are insidious. Patients frequently complain of weakness, swelling, and loss of wrist range of motion. A sensation of instability or "giving way" is often reported, sometimes associated with a painful clunk.

A meticulous physical examination is indispensable:
* Observation: Look for any subtle deformity or swelling.
* Range of Motion: Assess active and passive ROM.
* Grip Strength and Pain: Diminished grip strength correlates with wrist pathology. Pain at the central aspect of the wrist with attempted grip is often associated with scapholunate ligament pathology.
* Specific Ligament Tests:
* Deep palpation of scapholunate interval: Point tenderness indicates SLIL injury, scaphoid injury, or ganglion cyst.
* Watson’s scaphoid shift test: Pain with or without a clunk or catch sensation is highly suggestive of scapholunate instability. This test involves grasping the scaphoid tubercle and applying volar pressure while moving the wrist from ulnar to radial deviation.
* Scaphoid ballottement test: Pain and increased anteroposterior laxity of the scaphoid relative to the lunate are highly suggestive of scapholunate instability.
* Deep palpation of lunotriquetral interval: Point tenderness indicates LTIL injury or triangular fibrocartilage complex (TFCC) pathology.
* Ulnar wrist loading: A painful snap indicates lunotriquetral instability, midcarpal instability, or TFCC complex pathology. This maneuver will also be painful if ulnar impaction is present.
* Triquetrum ballottement test: Pain and increased anteroposterior laxity of the triquetrum relative to the lunate are highly suggestive of lunotriquetral instability.
* “Ulnar snuffbox” tenderness: Pain with or without crepitus indicates lunotriquetral instability, TFCC complex pathology, or triquetrohamate pathology.

Imaging and Diagnostic Studies

• Initial Radiographs: Always include AP and lateral radiographs. If scapholunate pathology is suspected, a bilateral pronated grip anteroposterior (Mayo Clinic) view should be obtained for comparison to the contralateral side.
  • Static Scapholunate Instability:
    • AP view: Increased scapholunate interval (3 mm or more, often called the "Terry Thomas sign"); comparison to the contralateral wrist is crucial. Look for the scaphoid cortical “ring sign” (indicating scaphoid flexion) and a triangular appearance of the lunate (indicating lunate extension).
    • Lateral view: Flexion of the scaphoid and dorsiflexion of the lunate, determined by an increased scapholunate angle (more than 60 degrees) and an increased lunocapitate angle (over 10 degrees) with dorsal translation of the capitate.
  • Static Lunotriquetral Instability: Radiographic findings are often normal.
    • AP view: Proximal translation of the triquetrum or lunotriquetral overlap without gapping, and interruption of Gilula’s arc.
    • Lateral view: Flexion of the scaphoid and lunate, determined by a normal or decreased scapholunate angle (less than 45 degrees), an increased lunocapitate angle (more than 10 degrees) with volar translation of the capitate, and a negative lunotriquetral angle.
• Provocative Views/Videofluoroscopy: Radial-ulnar deviation or flexion-extension views, or videofluoroscopy, can demonstrate asynchronous scapholunate motion (dynamic scapholunate instability) in cases with suspected SLIL injury and normal standard views. Increased, synchronous mobility of the scapholunate complex with diminished motion of the triquetrum can indicate an LTIL injury.
• Wrist Arthrography: While historically used, its sensitivity is only about 60% compared to arthroscopy, and it cannot determine the extent of any tear.
• MRI (with or without arthrography): Has limited value in evaluating interosseous ligament injuries. Reported sensitivity rates for SLIL injuries range from 40% to 65% compared to arthroscopy and is even less reliable for LTIL injuries.
• Arthroscopy: Fellows, this is the gold standard. Arthroscopy (radiocarpal, midcarpal with probing) remains the most accurate method for evaluating SLIL and LTIL injuries, allowing direct visualization and dynamic assessment.

Operative Room Setup and Patient Positioning

Today, we'll be performing arthroscopic procedures for dynamic instability.

1. Patient Position: The patient is placed in the supine position on the operating table.
2. Hand Table: The affected extremity is placed on a specialized hand table. Ensure the table is stable and allows sufficient space for instrument manipulation and fluoroscopy.
3. Tourniquet: A pneumatic tourniquet is applied to the upper arm. We will inflate it to 250 mmHg after exsanguination to maintain a bloodless field, which is crucial for clear arthroscopic visualization.
4. Distraction Tower: The extremity is then secured in a tower distraction device. We will apply 10 to 12 lb (5 to 6 kg) of distraction. This creates space within the joint for arthroscopic visualization and instrument manipulation. The wrist should be positioned in 12 to 15 degrees of wrist flexion. This flexion helps to open up the dorsal radiocarpal space, facilitating portal placement and scope entry.
   

   
   
   

FIG 1 • A. Positioning for arthroscopy of the wrist.
5. Monitor Placement: The arthroscope monitor is placed on the opposite side of the hand table from the surgeon. This allows for an ergonomic viewing angle without obstructing the surgical field.

Necessary Equipment

Based on our preoperative assessment, we must ensure the following equipment is readily available:
* Arthroscopic Tower: Light source, camera, shaver, irrigation pump.
* Arthroscopes: A 2.7-mm, 30-degree arthroscope is preferred for wrist arthroscopy. A 2.7-mm, 70-degree scope may also be useful for specific angles.
* Instrumentation: Probes, graspers, basket forceps, motorized shaver blades (full radius, aggressive), radiofrequency (RF) probes (e.g., ArthroCare, Stryker), mini C-arm, drills, Kirschner wires of various widths (typically 0.035" and 0.045"), and headless compression screws if RASL or fusion is considered.
* Irrigation: Normal saline, pressurized for continuous flow.

Intraoperative Execution: The Arthroscopic Masterclass

Alright fellows, let's scrub in. We've got our patient positioned, prepped, and draped. The tourniquet is up, and we have a clear, bloodless field.

Establishing Radiocarpal Portals and Initial Evaluation

Our initial approach will be through standard dorsal wrist portals.

1. Joint Distension: First, we'll use an 18-gauge needle to distend the radiocarpal joint with 7 to 10 mL of normal saline. This creates the necessary working space and helps visualize the joint capsule. You'll feel a distinct "pop" as the needle enters the joint.
   

   
   
   

FIG 2 • A. Initial joint distension using an 18-gauge needle through the 3–4 portal.
2. 3-4 Portal Entry: I'll palpate Lister's tubercle and the extensor tendons. The 3-4 portal is located just ulnar to the extensor pollicis longus (EPL) tendon and radial to the extensor digitorum communis (EDC) tendons. After a small skin incision, I'll use a mosquito clamp to spread the subcutaneous tissues and capsule. Then, the blunt trocar and cannula are advanced into the joint.

Midcarpal Portals (if needed)

For a comprehensive evaluation of the LTIL, or if midcarpal pathology is suspected, we'll establish midcarpal portals. A common midcarpal portal is the midcarpal ulnar (MCU) portal, located just distal to the 6R portal, between the triquetrum and capitate. The midcarpal radial (MCR) portal can also be used. The additional use of a radial volar portal through the flexor carpi radialis (FCR) sheath has been advocated for better visualization of the volar portions of the SLIL and LTIL, as well as the DRC and DIC ligaments, but this is less commonly used for routine diagnostic arthroscopy.

Arthroscopic Débridement of SLIL and LTIL Injuries

• Indications: Predynamic or dynamic instability; arthroscopic findings of a partial ligament tear with an unstable tissue flap (Geissler grade II); with or without synovitis. This technique is ideal for patients with mechanical symptoms (pain with crepitance or clicking) attributable to impingement of unstable tissue flaps and resulting synovitis.
• Technique: Using a motorized shaver or basket forceps through the 4-5 working portal, we will meticulously débride any frayed, unstable tissue flaps or hypertrophic synovium. The goal is to smooth out the torn edges and remove any impingement sources.
  

  
  
  

FIG 4 • A. Débridement of an unstable SLIL tear with a motorized shaver.

Arthroscopic Débridement and Thermal Shrinkage

• Indications: Predynamic or dynamic instability; arthroscopic finding of a partial ligament tear (Geissler grade I or II). Crucially, the dorsal segment of the SLIL should be intact for this procedure. This technique provides an option for managing lax, redundant ligaments with no frank tear (Geissler grade I) where simple débridement is insufficient.
• Rationale: Thermal shrinkage attempts to increase stability and improve long-term outcomes compared to simple débridement. Radiofrequency probes use a high-frequency alternating current to generate heat, which leads to denaturation (uncoiling) of the collagen triple helix, resulting in a reduction in overall ligament length.
• Technique: After débridement of unstable flaps, we introduce the radiofrequency probe through the working portal. Under direct visualization, we apply the probe to the lax ligamentous tissue, systematically treating the entire length. You'll observe the tissue blanching and shrinking.
  > SURGICAL WARNING: Use of a radiofrequency device is contraindicated in patients with pacemakers or other implantable electronic devices. Also, be extremely careful to avoid excessive heat application or prolonged contact with articular cartilage, as this can lead to chondral damage. Maintain constant irrigation to dissipate heat.
  

  
  
  

FIG 4 • B. Thermal shrinkage of the SLIL.

Arthroscopic Débridement and Percutaneous Pinning

• Indications: Acute or subacute dynamic instability (Geissler grades II and III). This technique aims to induce the formation of fibrous union between the involved carpal bones, providing temporary stabilization while healing occurs.
• Technique (Scapholunate Pinning):
  1. Reduction: First, we must achieve an anatomical reduction of the scapholunate interval. This is often accomplished by direct manual pressure on the scaphoid tubercle and lunate, or by using a small probe to manipulate the bones into alignment. We'll confirm reduction with fluoroscopy.
  2. Pin Placement: We typically use two 0.045-inch Kirschner wires. The first K-wire is usually inserted from the scaphoid, across the scapholunate joint, into the lunate. The entry point on the scaphoid is typically on its dorsal-radial aspect.
  3. Fluoroscopic Guidance: This step is absolutely critical. We'll use the mini C-arm to guide the K-wire placement. We need to ensure the wire is:
     • Intra-articular: Crossing the scapholunate joint without violating the radioscaphoid or capitolunate joint.
     • Central in the bones: Avoiding the edges to prevent breakage and maximize purchase.
     • Parallel: The two wires should be parallel to each other, approximately 2-3 mm apart.
     • Adequate Length: Sufficiently long to engage both the scaphoid and lunate without protruding excessively.
  4. Second Pin: A second K-wire is placed in a similar fashion for rotational stability.
  5. Pin Bending and Capping: Once satisfied with the position on fluoroscopy, the K-wires are cut and bent outside the skin, then capped to prevent migration and skin irritation.
     

     
     
     

FIG 5 • A. Percutaneous pinning of the scapholunate joint using two K-wires.

• Technique (Lunotriquetral Pinning):
  1. Reduction: Reduce the lunotriquetral joint, often by applying pressure to the triquetrum and lunate.
  2. Pin Placement: Two 0.045-inch K-wires are typically inserted from the triquetrum, across the lunotriquetral joint, into the lunate. The entry point on the triquetrum is usually on its dorsal-ulnar aspect.
  3. Fluoroscopic Guidance: Similar to SLIL pinning, ensure intra-articular, central, parallel, and adequate length placement under fluoroscopic control.

Arthroscopic Radial Styloidectomy

• Indications: Early (stage I) scapholunate advanced collapse (SLAC) wrist, characterized by radial styloid–scaphoid impingement or arthritis, with focal and reproducible clinical findings of radial styloid pain exacerbated by wrist flexion and radial deviation. This procedure may provide significant pain relief until a salvage procedure (proximal row carpectomy, scaphoid excision

Additional Intraoperative Imaging & Surgical Steps

REFERENCES

1. Abe Y, Doi K, Hattori Y, et al. Arthroscopic assessment of the volar region of the scapholunate interosseous ligament through a volar portal. J Hand Surg Am 2003;28A:69–73.

2. Berger RA. The gross and histologic anatomy of the scapholunate interosseous ligament. J Hand Surg Am 1996;21A:170–178.

3. Darlis NA, Kaufmann RA, Giannoulis F, et al. Arthroscopic debridement and closed pinning for chronic dynamic scapholunate instability. J Hand Surg Am 2006;31A:418–424.