Wrist arthroscopy allows for a precise visual examination of the carpal joint surfaces and wrist ligaments, areas often inadequately viewed during open surgery. It is a less invasive procedure compared to traditional arthrotomy. First described by Chen in 1979, this technique has been in use ever since.
The indications for a wrist arthroscopy can be either diagnostic or therapeutic.
Wrist arthroscopy portals include radiocarpal, midcarpal, distal radioulnar, and volar portals.
Traditionally, viewing portals are described by their relationship to the six extensor compartments of the wrist. Typically, eleven historical portals are used: five radiocarpal, four midcarpal, and two distal radioulnar portals. Two additional volar portals are gaining popularity.
The radiocarpal portals are 3-4, 4-5, 6-R, 6-U, and 1-2. Radiocarpal portals provide access to smooth carpal joints, whereas midcarpal portals reveal more irregular articulations. Portals are named for the interval between the extensor compartments. For example, the 3-4 portal separates the third and fourth extensor compartments. The 6-R and 6-U portals are named for their relationship to the extensor carpi ulnaris (ECU) tendon, with 6-R on the radial side and 6-U on the ulnar side. Palpation between these compartments reveals soft spots, which are the least traumatic entry points into the joint.
The 3-4 portal is typically the first portal established and the primary viewing portal. It is bounded radially by the extensor pollicis longus (EPL) and extensor carpi radialis brevis (ECRB), ulnarly by the extensor digitorum communis (EDC), proximally by the distal radius, and distally by the scapholunate ligament. It is located 1 cm distal to Lister’s tubercle, between the ulnar border of the ECRB and the radial edge of the EDC, in line with the radial border of the long finger. This is the soft spot between the third and fourth compartments. A spinal needle is then inserted parallel to the radial joint surface at an angle of about 10 degrees, matching the volar tilt. This is the workhorse portal for standard wrist arthroscopy, providing a wide view of most of the radiocarpal joint. The portal is relatively safe, as the superficial branch of the radial nerve (SBRN) averages 16 mm away, and the radial artery averages 26.3 mm away.
The 4-5 portal is bounded radially by the EDC, ulnarly by the extensor digiti minimi (EDM), proximally by the radius and TFCC, and distally by the lunate. Due to the radial tilt, it is located 1 cm ulnar and slightly more proximal than the 3-4 portal. It can be found by palpating the soft spot directly ulnar to the EDC. A spinal needle should then be placed just proximal to the lunate. Instruments introduced through this portal are placed directly next to the mid-portion of the TFCC. It is typically the main working portal for instrumentation on the ulnar side of the wrist and can also serve as a viewing portal for ulnar-sided structures. This portal carries minimal neurovascular risk, unless an aberrant branch of the SBRN is present.
Often used as an alternative to the 4-5 portal, the 6-R portal is bounded radially by the EDM, ulnarly by the ECU, proximally by the TFCC, and distally by the lunotriquetral joint. It enters the wrist directly distal to the ulnar attachment of the TFCC. This portal is located using the proximal edge of the triquetrum as a landmark instead of the distal ulna to avoid damaging the TFCC. It is established under arthroscopic guidance by inserting a needle directly radial to the ECU tendon. The 6-R portal is typically used for instrumentation or outflow. It also provides visualization of the TFCC, the ulnolunate, ulnotriquetral, and interosseous lunotriquetral ligaments. The 6-R portal has an average distance of 8.2 mm from the dorsal sensory branch of the ulnar nerve (DBUN).
The 6-U portal is created on the volar side of the ECU tendon but is not routinely used due to its proximity to the DBUN. The skin incision can be made up to the volar aspect of the dorsal edge of the ECU tendon. The portal enters the wrist through the prestyloid recess between the ECU tendon and the ulnar styloid. It is located distal to the TFCC and dorsal-ulnar to the ulnotriquetral ligament. The 6-U portal is typically used for the inflow or outflow cannula. It can be used as an accessory portal for viewing ulnar structures or for instrumentation during TFCC repairs. The average distance of this portal to the DBUN is 4.5 mm, but in some patients, the nerve may have multiple branches.
The 1-2 portal is not frequently used. It is located between the first and second extensor compartments, 1 to 2 mm distal to the radial styloid. It is found by palpating the soft spot between the first extensor compartment (containing the abductor pollicis longus and extensor pollicis brevis) and the second compartment (containing the extensor carpi radialis longus and brevis tendons) along the most ulnar part of the anatomical snuffbox. It is located just proximal to the waist of the scaphoid. The radial artery is located on the volar and radial side of the anatomical snuffbox. This portal must be placed as dorsally as possible to avoid injury to the artery. The 1-2 portal provides access to the radial styloid, the scaphoid, and the articular surface of the distal radius but offers only a limited view of the lunate. Placing this portal carries significant risk. Two branches of the SBRN are an average distance of 3 mm radially and 5 mm ulnarly from the portal, and the radial artery averages 3 mm from the portal.
Assessment of the midcarpal joint should be a routine part of wrist arthroscopy. The four midcarpal portals are the midcarpal radial, midcarpal ulnar, triquetrohamate, and triscaphe portals. The radial and ulnar midcarpal portals are most commonly used. The very limited space in the midcarpal area requires special caution when entering the joint. Once established, these portals should be maintained to minimize the difficulty of re-establishment due to fluid extravasation. Typically, there is no communication between the radiocarpal and midcarpal spaces. The assessment of wrist instability is better with midcarpal arthroscopy than with radiocarpal arthroscopy alone. Visualization of the scaphotrapeziotrapezoid (STT) joint, the extrinsic ligaments of the midcarpal joint, the capitolunate joint, and the articular surfaces of the metacarpals is enhanced by midcarpal arthroscopy. Midcarpal arthroscopy can be quickly mastered and adds minimal time to wrist arthroscopy. It has a low morbidity rate and should be used routinely for a thorough examination of the wrist.
The midcarpal radial portal is the most commonly used midcarpal portal. It is bounded radially by the ECRB, ulnarly by the EDC, proximally by the scapholunate ligament, and distally by the capitate. It should be placed in line with the radial border of the third metacarpal, 1 cm distal to the 3-4 portal. A soft spot can be palpated on the radial side of the proximal capitate between the base of the third metacarpal and the dorsal rim of the distal radius. The arthroscope is introduced between the capitate and the scaphoid. This allows assessment of the midcarpal space, as well as the scapholunate, lunotriquetral, and STT articulations. This portal is relatively safe, with branches of the SBRN found radially at an average distance of 15.8 mm.
The midcarpal ulnar portal is bounded radially by the EDC, ulnarly by the EDM, proximally by the lunotriquetral joint, and distally by the hamate-capitate joint. It is in line with the center of the fourth metacarpal. Like the midcarpal radial portal, it is placed about 1 cm distal to the 4-5 portal and at approximately the same level as the midcarpal radial portal. This portal enters through the interval between the capitate, hamate, triquetrum, and lunate. It is primarily used for instrumentation within the midcarpal joint. The risk when establishing this portal is minimal, as the SBRN branches are usually distant.
The triquetrohamate portal is made on the ulnar side of the wrist, distal to the triquetrum and ulnar to the midcarpal ulnar portal. The EDM borders it on the radial side, and the ECU tendon on its ulnar side. It enters the triquetrohamate joint directly ulnar to the ECU tendon. It provides excellent access for an inflow or outflow cannula and can be used for instrumentation within the triquetrohamate joint.
The triscaphe (STT) portal is located on the radial side of the midcarpal space. It is made ulnar to the EPL or radial to the abductor pollicis longus, in line with the radial border of the second metacarpal at the level of the distal pole of the scaphoid. The STT portal provides an additional view and access to the STT joint. Staying ulnar to the EPL helps avoid the radial artery. The ulnar part of the ECRL tendon can be used to verify the location of this portal, as the EPL is quite mobile at the level of the STT joint. Care must be taken when establishing the STT portal to prevent radial deviation of the tendon to protect the radial artery. The STT joint can be entered directly through this portal, which is primarily used for instrumentation in this joint. Care should be taken to avoid the small terminal branches of the SBRN.
Volar portals are increasingly popular for completing the view in diagnostic wrist arthroscopy and providing access for procedures not feasible from dorsal entry points. Bain and colleagues proposed a box approach for wrist arthroscopy. Using portals around the entire wrist improves visualization and access to all surfaces. Viewing and working portals can then be adapted to the specific diagnostic or therapeutic procedure. Volar portals allow for improved treatment of dorsal pathologies, such as dorsal rim fractures of the distal radius, dorsal rheumatoid synovial proliferation, and volar segment tears of the scapholunate and lunotriquetral interosseous ligaments.
To place the volar radial (VR) portal, a mini-open technique is used over the flexor carpi radialis tendon on the radial side of the volar proximal wrist crease. An anatomical study identified a safe zone encompassing the width of the flexor carpi radialis and at least 3 mm in all directions at this level from the palmar cutaneous branch of the median nerve (ulnarly) and the radial artery (radially). Due to this safe zone, a 2 cm transverse incision can be made over the flexor carpi radialis tendon. The transverse incision provides an excellent cosmetic result while minimizing risk to volar structures. The tendon sheath is incised, the radial artery is retracted radially, and the flexor carpi radialis and median nerve are retracted ulnarly. The radiocarpal joint is identified with a spinal needle, and the portal is opened with a blunt instrument. This portal is used to assess the dorsal side of the scapholunate interosseous ligament and the dorsal radiocarpal ligament.
The volar ulnar portal is also placed using a mini-open technique. A 2 cm longitudinal incision is made centrally over the proximal wrist crease along the ulnar edge of the common flexors. The interval between the flexor carpi ulnaris and the common flexor tendons is then used. The common flexors are retracted radially, and the flexor carpi ulnaris and ulnar nerve are retracted ulnarly. The joint space is identified with a spinal needle, and the capsule is opened bluntly. As there is no truly safe zone for the volar ulnar portal, careful dissection and spreading technique are required. This portal provides access for reduction of a distal radius fracture and a view of the dorsal articular surfaces and dorsal ligaments.
The distal radioulnar joint (DRUJ) is difficult to examine, and wrist arthroscopy is not frequently used in these cases. The proximal and distal DRUJ portals are named for their location proximal and distal to the ulnar head, respectively. The DRUJ portals are bounded radially by the EDC and ulnarly by the ECU. Access to the joint is at the base of the DRUJ, bordered by the radius and ulna. The proximal portal is placed in this line directly proximal to the DRUJ. The forearm is supinated to relax the dorsal capsule, and the arthroscope is then introduced between the radius and ulna below the TFCC and proximal to the articular surface. The radioulnar articular surfaces are then visible. Pronation and supination increase the available surface area during examination. The distal portal is not always accessible. This portal allows the surgeon to examine the distal articular surface of the ulna and the underside of the TFCC. The DRUJ portal uses a mini-open approach. It is located very near the TFCC, and care must be taken to stay below the TFCC to prevent injury to this structure. There is some risk to the posterior interosseous nerve. The risk to sensory nerves is minimal, as the nearest distance is 17.5 mm distally.
Due to the relative absence of major neurovascular structures, the dorsal aspect of the wrist is most commonly used for wrist arthroscopy. Only the deep branch of the radial artery and the superficial dorsal sensory branches of the radial, ulnar, and lateral antebrachial cutaneous nerves are located on the dorsum of the wrist. Injury to these structures can cause numbness and, in the worst case, a painful neuroma and complex regional pain syndrome. Certain portals carry a higher risk of iatrogenic neurovascular damage. The greatest risk to the radial artery and branches of the sensory radial and ulnar nerves is with the 1-2, 6R, and 6U portals. The midcarpal portals, 3-4, 4-5, and distal radioulnar joint portals are relatively safe. However, even in safe portals, a risk exists due to aberrant sensory nerve branches that can be dangerously close. This necessitates longitudinal skin incisions made by pulling the skin over a blade and bluntly dissecting through the subcutaneous tissue. Only a blunt trocar should be used when piercing the capsule. This technique helps protect structures between the dermis and capsule from injury.
A newer technique has been attempted where arthroscopic wrist procedures are performed without irrigation. Proponents claim that arthroscopy without water offers benefits, including limiting tendon loss and compartment syndrome. Another potential advantage is the possibility of performing open procedures without soft tissue infiltration. Researchers also suggest that there may be less pain and swelling after surgery. No prospective studies have evaluated these reported benefits, and this technique is still in its early stages.
