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.
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
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.
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