Diagnostic Wrist Arthroscopy

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CHAPTER 20 Diagnostic Wrist Arthroscopy

During the past 20 years, wrist arthroscopy has evolved into one of the most reliable and productive means of diagnosing, qualifying, and treating wrist pathology. As the arthroscopic surgeon’s instrumentation and technical ability improves, wrist arthroscopy is increasingly being presented as a necessary, routine, and safe procedure.¹ Although it is a relatively new modality, it is an easily learned skill with ever-increasing indications.

An arthroscopic view allows excellent access to the articular surfaces of the carpal bones and ligaments that is not possible with arthrotomy.² However, a thorough knowledge of wrist anatomy is essential for the safe arthroscopic identification and treatment of wrist pathology. This chapter emphasizes the standard elements of a diagnostic arthroscopic evaluation of the wrist.

ANATOMY

The standard portals for wrist arthroscopy are located on the dorsum of the wrist, primarily because of the lack of neurovascular structures at risk in this area. The dorsal portals are named by their location in relation to the six dorsal compartments of the wrist. The 1-2 portal lies between the first extensor compartment, which includes the extensor pollicis brevis (EPB) and the abductor pollicis longus (APL), and the second dorsal compartment, which contains the extensor carpi radialis brevis (ECRB) and longus (ECRL). The 3-4 portal, which is the primary viewing portal, is located between the third dorsal compartment, which contains the extensor pollicis longus (EPL) tendon, and the fourth dorsal compartment, which contains the extensor digitorum communis (EDC) tendon. The bony landmark for this portal is Lister’s tubercle, which is approximately 1 cm proximal to the wrist joint. The 4-5 portal is located between the EDC and the extensor digiti minimi (EDM). The 6-R portal lies on the radial side of the extensor carpi ulnaris (ECU) tendon, and the 6-U portal is located on the ulnar side of the ECU.

Two primary portals and two accessory portals have been described for use in the midcarpal space. The portal most commonly used for viewing is the radial midcarpal (RMC), which is located approximately 1 cm distal to the 3-4 radiocarpal portal and in line with the third metacarpal. The ulnar midcarpal portal is located on the midaxial line of the fourth metacarpal, approximately 1 to 1.5 cm distal to the 4-5 portal, enters the joint at the four-corner intersection between the lunate, triquetrum, hamate, and capitate. One of the two accessory portals is on the radial side of the midcarpal space and enters the scaphotrapeziotrapezoid (STT) joint. It is located just ulnar to the EPL tendon, at the level of the articular surface on the distal pole of the scaphoid. Staying on the ulnar side of this tendon usually maintains a safe margin between the portal and the radial artery at this level. Another accessory portal can be used, entering the triquetrohamate joint just ulnar to the ECU tendon, for a probe or instrument to access the joint or proximal pole of the hamate.³

PATIENT EVALUATION

History and Physical Examination

A thorough history is essential. This should include the patient’s medical and surgical history; medications; allergies; family history; trauma history, including duration of symptoms, location, intensity, and any aggravating or relieving factors; and the effects of various treatment modalities already used. Contact sports and noncontact sports with repetitive activity should be identified. The mechanism of injury should be fully detailed, and specifics such as position of the hand, direction of force, and resultant area of pain should be kept in mind during the diagnostic evaluation.

The patient’s age and sex should be considered when evaluating a painful wrist. The young patient (<40 years) is more prone to post-traumatic carpal injuries, whereas the older patient is more susceptible to the late effects of systemic and degenerative processes. The patient’s medical history and the family medical history are helpful for diagnosing patients with many of the systemic and hereditary disorders that can manifest in the wrist. Laboratory values combined with this history is often helpful in this situation. Knowledge of the effect of the wrist pain on the patient’s daily activities, including work and leisure activities, is also essential for treatment planning.⁴

The physical examination begins with a careful inspection for specific areas of swelling, erythema, warmth, nodules, skin lesions, and obvious deformities or prior surgical incisions. If possible, tenderness is localized to a specific anatomic structure. Wrist range of motion should be examined, paying careful attention to any snapping or clicking. Clicks, which may indicate carpal instability, can sometimes be felt throughout the wrist range of motion but are usually not significant unless they reproduce the patient’s clinical symptoms.

A systematic approach is essential for palpation of the wrist. All joints must be palpated and appropriately stressed with the use of some of the many provocative tests that have been described. Radially, carpometacarpal thumb arthritis can be assessed with the grind test. Just proximal to this, the STT joint should be palpated to assess for arthritis. Anatomic snuff box tenderness may indicate scaphoid or scapholunate ligament pathology. This ligament can be further assessed by Watson’s scaphoid shift test.⁵ The distal pole of the scaphoid is stabilized to restrict palmer flexion while the wrist is moved from ulnar to radial deviation. Dorsal wrist pain indicates subluxation of the scaphoid and scapholunate ligament instability. Ulnarly, lunotriquetral instability can be assessed by manipulating the two bones relative to each other (i.e., shear or ballottement test). Ulnocarpal abutment and triangular fibrocartilage complex (TFCC) tears are tested by axial loading and ulnar wrist deviation. Pain just distal to the ulnar styloid and reproduction of symptoms with this maneuver indicate these conditions.

Instability of the midcarpal joint is suggested by the catch-up clunk, which is produced when the wrist is moved from radial to ulnar deviation during axial loading. The clunk is produced by sudden change in position of the proximal carpal row from a flexed position to an extended position as the triquetrum engages the hamate without the synchronizing effect of the attenuated ulnar ligaments. A painful response or crepitation on compressing the distal radioulnar joint (DRUJ) suggests instability or arthritic changes of the joint. Volarly, tenderness with palpation of the pisiform or hook of the hamate may represent pisotriquetral arthritis or hamate fracture, respectively.⁶

To complete the wrist examination, the tendons are palpated and stressed to rule out tenosynovitis on the dorsal and volar aspects. The nerves are evaluated to rule out compressive neuropathies, and the vascular status is assessed by evaluating capillary refill along with Allen’s test to rule out insufficiency or thrombosis.

Diagnostic Imaging

Unless otherwise indicated by clinical evaluation, the initial radiographic evaluation should consist of standard posteroanterior, oblique, and lateral views of the wrist. They should be examined for bony disruptions such as fractures, alignment and congruence of joint spaces, and evidence of arthritic changes and mineralization. The lateral view is important for assessment of the carpal alignment. A scapholunate angle of greater than 60 degrees suggests possible scapholunate instability, and an angle of less than 30 degrees suggests ulnar-sided wrist instability. Additional radiographs may be needed depending on the clinical scenario. The clenched fist view is valuable for better visualization of possible scapholunate dissociation, and a carpal tunnel view can better elucidate the bony tubercles of the carpal tunnel.

Musculoskeletal ultrasound may be useful for the evaluation of soft tissue abnormalities, such as tendinopathy, ganglia, and synovial cysts. However, it is highly operator dependent.

Arthrography is useful to evaluate the integrity of capsular structures and interosseous ligaments, especially the scapholunate, lunotriquetral, and triangular fibrocartilage (TFC).² It may show localized synovitis or abnormal leaks between normally compartmentalized spaces.

Computed tomography (CT) is useful to evaluate osseous and articular morphology. It is most effective in the evaluation of bone healing in the carpus after fracture or surgery, and CT can provide images in any plane needed (e.g., oblique axis of the scaphoid). Likewise, because fractures of the hook of the hamate are difficult to visualize with plain radiographs, CT provides clear detail to assist with decision making and treatment.⁶

Magnetic resonance imaging (MRI) provides important information about the soft tissues of the wrist and the vascularity of the bones. Avascular necrosis of the carpal bones, such as the lunate and scaphoid, and occult ganglions, soft tissue tumors, tendonitis, and joint effusions are well visualized using MRI. It is also the most accurate modality for evaluating bone bruises and microfractures. MRI has a sensitivity of 90% in evaluating the integrity of the TFCC. The accuracy of MRI for identifying tears of the scapholunate ligament has also approached 90%, but it drops significantly to 50% for lunotriquetral tears.⁶

To evaluate the bony architecture and overall wrist alignment, we prefer the use of standard radiographs, usually with additional radiographic views based on clinical presentation. This is commonly followed by standard MRI to further evaluate the wrist for occult fractures, avascular necrosis, and soft tissue pathology.

TREATMENT

Indications and Contraindications

Wrist arthroscopy is a useful tool for diagnosis in patients who present with wrist pain, motion loss, and weakness, for which noninvasive diagnostic and treatment protocols have failed. It is also useful in patients with well-defined pathology such as nonunions, Kienbock’s disease, and scapholunate or lunotriquetral dissociations, for which evaluation of the articular surfaces is of prognostic and therapeutic importance.

Many forms of wrist pathology, such as cartilage flaps or tears of the (TFC), can be treated during arthroscopy.¹ Wrist arthroscopy is a useful adjunct in the reduction of intra-articular fractures of the distal radius and percutaneous pinning of scaphoid fractures. Innovative surgeons have described partial carpal resections for post-traumatic arthritis and arthroscopically guided capitolunate fusions. Using the midcarpal, DRUJ, and volar portals has further expanded the arthroscope’s use as a tool for evaluation and treatment of midcarpal chondral lesions of the hamate, articular damage to the ulnar head or surrounding synovitis, and improved visualization of volar articular surfaces and dorsal capsular structures.⁷

Contraindications to wrist arthroscopy are limited mainly to conditions of trauma or swelling that distorts the normal anat omy or significantly damages capsular integrity, leading to fluid extravasation.

Conservative Management

Before operative management, nonoperative measures should be exhausted. Depending on the pathology, temporarily immobilizing the wrist in a splint or brace and administering anti-inflammatory medication may be the only treatment necessary. Diagnostic and therapeutic injections can be helpful. A small amount of local anesthetic may confirm the source of pain and provide relief for the patient. A structured therapy regimen for wrist range of motion and strengthening may help in treating certain types of wrist pathology.

Arthroscopic Technique

Regional or general anesthesia may be used. The patient is positioned supine, with the operative extremity on an arm table. A tourniquet is placed proximally on the upper arm. A 2.5- or 3-mm, 30-degree arthroscope; small joint arthroscopic instruments; and gravity flow are used for the procedure. The operating table is angled so that the surgeon is positioned above the arm table and near the patient’s head, and the assistant is positioned directly across the arm table within the patient’s axilla.

After preparing and draping, the arm is exsanguinated before inflation of the tourniquet and placed in position in the traction tower. We prefer a sterile traction tower with nylon finger traps to provide convenient application of wrist distraction in flexion, extension, and radial and ulnar deviation. We use soft nylon finger traps to secure the index and long finger to the tower in a sterile fashion for most procedures. However, for ulnar-sided pathology, we frequently use the index and ring fingers. Five to ten pounds of traction is adequate for most procedures.

Radiocarpal Evaluation

Diagnostic wrist arthroscopy begins with the 3-4 portal and is the primary viewing portal. Palpation and spinal needle localization of this portal are essential before the skin incision is made. Through the 3-4 portal, a needle is inserted, and the joint is distended with 5 to 7 mL of saline. The skin is incised with a no. 15 or 11 blade, and a small hemostat is used spread the soft tissues. Next, the blunt trocar should be inserted at approximately a 20-degree proximal angle to match the distal radius articular slope. This angle can avoid damaging the dorsal articular surface.²^,⁸^,⁹ Only blunt trocars are used in establishing portals. The inflow and outflow are interchangeable and can be maintained through the arthroscopic cannula or a separate 6-U portal established under direct arthroscopic visualization. We prefer the inflow through the arthroscope to push debris away instead of pulling it toward the camera. After a 3-4 portal is established, a diagnostic radiocarpal arthroscopy is performed.

The radial styloid and radial capsule are examined first. The scaphoid superiorly and the radial styloid inferiorly can be evaluated for signs of arthritic change or articular injury (Fig. 20-1). The proximal border of the radial facet is examined, as are the volar extrinsic ligaments, the radioscaphocapitate ligament, and long radiolunate ligament (Fig. 20-2). The long radiolunate ligament is a wide structure usually two to three times the width of the radioscaphocapitate ligament.⁹^,¹⁰ The ligaments should be taut on probing because of the traction applied to the wrist. Ulnar to these is the radioscapholunate ligament, also called the ligament of Testut, which is a vascularized tuft of tissue without any significant structural integrity. This tuft marks the scapholunate interval and sagittal ridge.¹⁰^–¹² Blood vessels are frequently seen along this ligament, and there is a natural redundancy to this ligament that should not be mistaken for a tear.

FIGURE 20-1 The radiocarpal joint is viewed from the 3-4 portal, showing the scaphoid superiorly and distal radius inferiorly.

FIGURE 20-2 Volar extrinsic ligaments are viewed from the 3-4 portal, showing the radioscaphocapitate ligament (RSC) and the long radiolunate ligament (LRL).

Following the scaphoid ulnarly, the slightly concave scapholunate interosseous ligament can be examined for tears or scapho lunate diastasis (Fig. 20-3). An intact ligament may not be immediately obvious because it mimics the appearance of cartilage. Complete injury to this ligament, however, allows the arthroscope to pass between the scaphoid and the lunate (i.e., drive-through sign).²

FIGURE 20-3 The convexity of the scapholunate interosseous ligament (asterisk), scaphoid (S), and lunate (L) can be seen.

The proximal surface of the lunate and the distal surface of the radius can be evaluated next. The two fossae of the distal radius, the scaphoid and the lunate fossae, are separated by a sagittal ridge. Fraying or fissuring of this area, suggestive of chondromalacia, should be documented. Normally, in the neutral wrist position, one half of the lunate articulates with the lunate facet, and one half articulates with the TFC.¹⁰

The radial attachment of the TFC is evaluated, as are the volar and dorsal radioulnar ligaments. The lunotriquetral interosseous ligament is evaluated by identifying a sulcus or concavity in the otherwise convex articular surfaces of the lunate and triquetrum.¹³ A probe can be inserted through the 4-5 or 6-R portal to evaluate the integrity of the lunotriquetral ligament. Next, the peripheral attachment of the TFC and the ulnar prestyloid recess should be examined. The TFC is wedge shaped in the coronal plane, with a thickened periphery and a thin radial attachment.¹² A probe can be used to evaluate the tension of the TFCC by ballottement (i.e., trampoline test) (Fig. 20-4).¹¹^,¹³ The TFC, also known as the articular disk, should be taut, and lack of tension raises suspicion of a central or peripheral TFCC tear. The peripheral 15% to 20% of the TFCC is vascularized and therefore has healing potential if torn.² The prestyloid ulnar recess is a normal anatomic finding that is approximately 3 to 4 mm wide, and it should not be mistaken for a peripheral tear.¹⁰ The ulnolunate and ulnotriquetral ligaments may be more easily evaluated by placing the arthroscope in the 4-5 or 6-R portal. These ligaments are identified as capsular thickenings in the volar aspect of the ulnar capsule.

FIGURE 20-4 For the trampoline test, a probe is used to test the tension of the triangular fibrocartilage.

Midcarpal Evaluation

After a complete examination of the radiocarpal joint has been performed, the arthroscope can be used to evaluate the midcarpal space. The radial midcarpal portal, located approximately 1 cm distal to the 3-4 radiocarpal portal, is typically used to establish a diagnostic arthroscopy portal. The midcarpal joint can be distended with 3 to 5 mL of fluid through any of the portals. This allows easier access into the joint with a blunt trocar and minimizes the risk of damaging the articular cartilage.¹⁰ Normally, there is no communication between the radiocarpal and midcarpal spaces.³

Care must be taken when entering the radial midcarpal space, because it is less than one half of the depth of the radiocarpal space.² The ulnar midcarpal portal is created for instrumentation and visualization of the ulnar portion of the midcarpal joint. The arthroscopic evaluation in this area begins with visualization of the convexity of the capitate (superiorly) and the scapholunate joint (inferiorly). The scapholunate joint should be perfectly congruous (Fig. 20-5). The scapholunate ligament is not present on the distal edge of the scapholunate joint, and the joint is best viewed from this perspective. Intraoperatively, the stability of the joint may be assessed by performing Watson’s scaphoid shift test.³^,¹⁴

FIGURE 20-5 The congruent scapholunate joint is viewed from the radial midcarpal portal.

The distal surfaces of the lunate and the triquetrum are then evaluated, as is the concave proximal surface of the hamate (Fig. 20-6). The lunotriquetral joint is also well visualized from this view, and a ballottement test can be performed to assess stability. Within the distal row, the capitate and capitohamate articulation can be examined from this portal. Farther ulnarly, the triquetrohamate joint may be used to establish an accessory portal. The triquetrohamate joint is a saddle-shaped joint that is normally quite tight and difficult to view across unless pathologic laxity exists.³