T General Anato m y and Setup 1

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hough wrist arthroscopy was first introduced in 1979, it did not become an accepted method of diagnosis until the mid-1980s. As our technical abilities and technologies improved, wrist arthroscopy became a therapeutic modality as well as a diagnostic one.¹It is useful in the diagnosis and treatment of triangular fibrocartilage complex (TFCC) pathology, ligamentous injuries, carpal instability, chondral defects, arthritis, carpal and radial fractures, ganglia, synovitis, and loose bodies. There is little doubt that arthroscopy will continue to play a larger role in the diagnosis and treatment of wrist pathology.

A complete understanding of the anatomy as well as appropriately sized instrumentation facilitates visualization. Precise placement of portals and adequate traction are required in wrist arthroscopy due to the small space available within the wrist joint. Once these techniques have been learned, arthroscopy can be used to treat a tremendous array of wrist pathology.

SURGICAL TECHNIQUE

Although arthroscopy without traction has been described, traction is usually recommended.² Several methods of traction are available. A traction tower allows precise modulation of the traction through a gear- ing mechanism (Figures 1.1 and 1.2). The forearm is stabilized while the traction is applied vertically through finger-traps, which permits 360-degree access to the wrist. If a traction tower is not available, a shoulder holder can be used to hold the arm vertically with a countertraction band around the arm proximal to the elbow. Weights can be added to the countertraction to adjust the tension. Finally, the wrist can be positioned horizontally on a hand table (Figure 1.3).

Finger traps are placed on the index, long, and ring fin- gers, with 10 pounds of weight suspended over the end of the table. A bar or pulley is used to provide countertraction. The advantage of this last method is its simplicity and ease of setup.

The development of diagnostic and therapeutic in- dications for wrist arthroscopy would not have been possible without the development of smaller arthroscopy equipment in the 1980s. Small-bore arthroscopes and shavers are either 2.7 or 2.9 mm in dia-

meter.³ Arthroscopes are available with either a 30- degree or 70-degree viewing angle. An appropriately sized wrist probe is essential to fully examine the con- tents of the joint. A variety of hand-held graspers and punches have been developed that have expanded our ability to treat TFCC and ligament tears. A video printer is also helpful to document identified pathology and demonstrate treatments performed.

Thorough understanding of wrist anatomy is the most crucial aspect of wrist arthroscopy. Proper portal placement, identification of pathology, and suc- cessful treatment all rely on a complete understanding of the structures at risk and the ability to recognize the abnormalities present.^1,2,4–7Placement of the portals either too proximal or too distal can cause articular cartilage injury. It is important to mark the por- tal sites after traction is applied, so that the relationships of surface landmarks are not altered. Pal- pation and marking of the index, middle, and ring metacarpal bases provide good landmarks for the distal edge of the carpus. The surgeon’s fingertip can be rolled over the distal edge of the radius to identify the

“soft spot” of the radiocarpal joint. Additionally the extensor digitorum communis, extensor pollicis longus, and extensor carpi ulnaris are all palpable if the wrist is not markedly swollen.

The portal locations are identified relative to the extensor compartments between which they pass (Fig- ure 1.4A,B). The 3-4 portal is between the third and fourth compartment, and the cannula passes radial to the extensor digitorum communis tendon to the index finger and ulnar to the extensor pollicis longus tendon.

Bony landmarks for this portal include Lister’s tubercle, which is approximately 1 cm proximal to the wrist joint; and the radial aspect of the long finger, which is in line with the 3-4 portal. The surgeon should place a fingertip on Lister’s tubercle and then roll the finger over the distal edge of the radius into the soft spot of the 3-4 portal. The surgeon who uses the fingernail for part of this last step can feel the extensor tendons on either side of the 3-4 portal (Figure 1.5).

The 4-5 portal passes ulnar to the extensor digitorum communis tendon to the ring finger and radial to the extensor digiti minimi tendon. The fourth compartment is palpated, and the finger is rolled over ulnarly over the tendons until it falls into the soft spot 1

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on the ulnar side of the fourth compartment (Figure 1.6). Because of the radial inclination of the distal radius, the 4-5 portal is usually slightly proximal to the 3-4 portal (and never distal to the 3-4 portal). The 6-R portal lies radial to the extensor carpi ulnaris tendon and ulnar to the extensor digiti minimi tendon and can be found by moving the finger over the palpable fifth compartment. Alternatively, the surgeon can locate the prominent extensor carpi ulnaris (ECU) tendon of the sixth dorsal compartment and palpate the soft spot just radial to it and distal to the edge of the radius.

The 6-U portal is just ulnar to the extensor carpi ulnaris tendon, dorsal to the flexor carpi ulnaris, and just distal to the ulnar styloid. Any instruments placed in the 6-U portal should be introduced by “hugging”

the underside of the ECU, thereby avoiding any po- tential injury to the ulnar neurovascular structures.

Midcarpal portals can be placed on the radial and ulnar sides of the capitate approximately 1 cm distal to the 3-4 and 4-5 portals, respectively.⁸

The wrist joint is distended by the introduction of 3 to 5 mL of saline prior to trocar insertion. A sepa- rate inflow cannula can be placed throughout the pro- cedure to keep a constant pressure or flow of the irri-

2 T H O M A S B. H U G H E S, J R. , A N D A R N O L D-P E T E R C. W E I S S

FIGURE 1.1. A specialized tower providing traction significantly aids in instrument placement.

FIGURE 1.2. Diagram of a new traction tower designed by Geissler and Slade (Acumed, Beavertown, OR). The traction bar is off to the side which allows simultaneous arthroscopic and fluoroscopic evaluation of the wrist without having to move the wrist around the traction bar to obtain radiologic evaluation. Also, the traction tower can be set up so the surgeon may arthroscope or perform open surgery to the hand or wrist in either the vertical or horizontal position.

FIGURE 1.3. Alternatively, horizontal traction through finger traps and a pulley system can provide joint distraction. This type of setup is especially useful for arthroscopic treatment of distal radius fractures.

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gant (Figure 1.7) Irrigation pumps are now available that regulate fluid volumes and pressure to avoid extravasation and decrease intraoperative bleeding. In the midcarpal joint, care should be taken to maintain the cannulas in the joint once they are placed, because extravasation of fluid makes reintroduction of the cannulas into this tight joint difficult.

A needle should be placed into the joint at the prospective portal sites prior to skin incision to confirm their location. Longitudinal portal incisions are made to avoid tendon transection by an inadvertently deep incision. Prior to making the incisions, the skin should be pulled taut against the tip of a number 11 blade so that only the skin is cut. This prevents inad- vertent injury to branches of the radial sensory nerve, which run in the immediate subcutaneous tissue.

The 3-4 portal is usually established first, as this is the main viewing portal. A blunt trocar with a cannula is directed volar and proximal at a 30-degree an-

FIGURE 1.4. An illustration in cross-section (A) and frontal view (B) of the main working portals.

FIGURE 1.5. From Lister’s tubercle, the 3-4 portal is found 1 cm distally as a soft spot when palpated by the thumb or finger.

FIGURE 1.6. After rolling the finger over the 4th compartment ten- dons, the 4–5 portal soft spot is identified.

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gle. This technique aligns the cannula with the articular surface of the radiocarpal joint. If one attempts to place the cannula into the joint perpendicular to the wrist, injury to the dorsal articular surface will occur (Figure 1.8). Once the camera is introduced, more precise placement of the remaining portals is possible.

The 4-5 or 6-R portals are commonly used to insert instruments if a therapeutic arthroscopy is planned.

The 6-U portal is used as the inflow portal, while the port on the camera cannula is left open to allow fluid to drain.

Other portals described include the 1-2 portal and anterior portals. The 1-2 portal passes ulnar to the extensor pollicis brevis tendon and radial to the extensor carpi radialis longus tendon. Various anterior portals have been described, but most recently a safe inside- out technique has been described for a portal that is ulnar to the flexor carpi radialis tendon and radial to the median nerve. Though these portals are not used rou- tinely, they may be helpful in certain circumstances.

Examination of the wrist should be systematic to make certain that all areas are inspected and that pathology identified early does not distract from a thorough exam. Frequently the exam is performed be- ginning radially and moving ulnarly. The radial styloid and scaphoid articular surfaces are examined for degeneration as well as for surrounding synovitis. As the camera is moved ulnarly, the extrinsic volar ligaments are visible beyond the scaphoid articular surface. First the radioscaphocapitate ligament comes

FIGURE 1.8. To avoid injury, the normal inclination of the distal radius must always be taken into consideration when entering the joint with a trocar. The usual alignment is with the trocar angled 20 to 30 degrees proximally to match the distal radius articular curve.

FIGURE 1.7. A custom inflow cannula placed into the 6U portal provides excellent joint irrigation.

FIGURE 1.9. The radioscaphocapitate and long radiolunate ligaments run side-by-side in a proximal-radial to distal-ulnar orientation.

into view, then the long radiolunate ligament, which is about three times wider (Figure 1.9). Next, the radioscapholunate ligament (ligament of Testut) is seen, which is small and identified by the blood vessels that frequently run upon it (Figure 1.10). This usually marks the scapholunate joint and the intrinsic scapholunate ligament. Complete injury to this ligament allows the arthroscope to pass between the scaphoid and lunate, visualizing the capitate head (known as a “drive-through” sign).^1,9,10Next, the lunate fossa of the radius and the proximal lunate articular surfaces are examined.

Attention is then turned to the triangular fibrocartilage complex (TFCC) and its attachment to the ulnar portion of the distal radius. A probe is used to perform the trampoline test, which involves ballotte- ment of the disk of the TFCC to test the disk’s in- tegrity (Figure 1.11). When the disk is without tension or a break in the smooth contour is noted, a tear must be suspected (Figure 1.12). Both the central and pe-

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ripheral portions of the disk must be inspected, as either can lead to a loss of the tension of the TFCC. In the distal ulnar portion of the TFCC, the ulnar styloid recess can be mistaken for a tear, though it is a normal anatomic finding. The trampoline test can be helpful to confirm that this is not a tear, as the TFCC will remain taut.

Arthroscopy should continue with examination of the lunotriquetral articulation and the ulnocarpal ligaments. The lunotriquetral interosseous ligament has a concave appearance between the 2 bones (Figure 1.13). The ulnocarpal can be best visualized by switch- ing the scope to the 4–5 or 6-R intervals. Capsular

thickenings can be identified volarly that represent the ulnolunate and the ulnotriquetral ligaments.

Following complete examination and treatment of the radiocarpal joint, the arthroscopy should continue with insertion of the arthroscope into the midcarpal joint as described earlier (Figure 1.14). Midcarpal arthroscopy has been shown to contribute to the diagnosis of pathology in 82% to 84% of cases and can significantly impact the treatment protocol.⁸The first landmark identified is usually the convexity of the proximal capitate. The scope is then turned proximally to view the scapholunate joint radially and the lunotriquetral joint ulnarly, and these joints are

FIGURE 1.10. The radioscapholunate ligament (ligament of Tes- tut) is a vascular structure; the distal end marks the scapholunate ligament.

FIGURE 1.11. A probe is used to check for the tightness of the TFC articular disk by the trampoline test.

FIGURE 1.13. A slight concavity marks the lunotriquetral liga- ment.

FIGURE 1.12. Loss of the trampoline effect or an obvious disrup- tion (as in this case) indicates a TFC disk tear.

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probed to detect signs of instability. The scapho- trapeziotrapezoid (STT) joint can be visualized by moving the scope radially and distally around the capitate head, while the capitohamate joint can be viewed by moving the scope distally and ulnarly around the capitate. The articular surfaces should be examined for early arthritic changes. Visualization of a significant amount of the volar capsule between the hamate and the triquetrum is a sign of midcarpal instability.

CONCLUSION

Arthroscopy of the radiocarpal and midcarpal articulation can be performed safely and effectively once the anatomy is mastered and the appropriate equipment is obtained. Its usefulness as a diagnostic and therapeutic modality for pathology of the wrist has been dem- onstrated. As our understanding of wrist pathology and our technical ability increase, arthroscopy will play a larger role in the treatment of disorders of the wrist.

References

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8. Viegas SF. Midcarpal arthroscopy: anatomy and portals. Hand Clin1994;10:577–587.

9. Weiss APC, Akelman E, Lambiase R. Comparison of the find- ings of triple-injection cinearthrography of the wrist with those of arthroscopy. J Bone Joint Surg 1996;78-A:348–356.

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344–349.

FIGURE 1.14. During midcarpal arthroscopy, excellent visualiza- tion of both the scapholunate (shown here) and the lunotriquetral articulations is accomplished.