The anatomy of the wrist is among the most complex in the human body. A large number of flexor and extensor tendons pass from the forearm across the wrist to the hand. In order to help delineate the myriad extensor tendons within this anatomic region, anatomists have organized them into six compartments (Table 74.1). It is at the intersection of the first and second extensor compartments, which contain the extensor carpi radialis longus, the extensor carpi radialis brevis, the extensor pollicis brevis, and the abductor pollicis longus tendons and associated muscles that a painful tenosynovitis known as intersection syndrome, or ice axe wrist, can occur (Fig. 74.1). The inflammation responsible for the pain and functional disability associated with intersection syndrome is due to repetitive flexion and extension of the wrist when performing activities such as cross-country skiing, sculling, rowing, and weight lifting. Often confused with other radial-sided wrist pain syndromes including de Quervain tenosynovitis, cheiralgia paresthetica (Wartenberg syndrome), and arthritis of the first metacarpal joint, intersection syndrome tends to occur more dorsally and proximally than these other conditions (Table 74.2).

The pain of intersection syndrome will be exacerbated by flexion or extension of the affected wrist. Palpation at the site of tendon intersection may reveal tenderness, color, and swelling. A positive creaking tendon sign is often present if there is significant inflammation (Fig. 74.2). The examiner may appreciate what has been named “wet leather” crepitus with flexion and extension of the wrist.

Plain radiographs of the wrist are indicated in all patients suspected of suffering from intersection syndrome to rule out occult bony pathology and to identify calcific tendonitis. Based on the patient’s clinical presentation, additional testing may be indicated, including complete blood cell count, uric acid, sedimentation rate, and antinuclear antibody testing. Magnetic resonance imaging and ultrasound imaging of the wrist are indicated to assess the status of the extensor carpi radialis longus, the extensor carpi radialis brevis, the extensor pollicis brevis, and the abductor pollicis longus tendons and tendon sheaths as well as to identify other occult pathology including coexistent bursitis, arthritis, and gout involving the first metacarpal joint, cheiralgia paresthetica, and/or de Quervain tenosynovitis (Figs. 74.3 and 74.4).

The key landmarks when performing ultrasound-guided injection for intersection syndrome are Lister tubercle and the intersection of the extensor carpi radialis longus, the extensor carpi radialis brevis, the extensor pollicis brevis, and the abductor pollicis longus tendons and tendon sheaths (Fig. 74.5). Passing obliquely over the extensor carpi radialis brevis and extensor carpi radialis longus tendons of the second compartment, the abductor pollicis longus and extensor pollicis brevis of the first compartment intersect at their musculotendinous junctions. This intersection is just proximal to the extensor retinaculum, which serves to tether down the tendons and may contribute to the evolution of intersection syndrome (see Fig. 74.5).

The benefits, risks, and alternative treatments are explained to the patient, and informed consent is obtained. The patient is then placed in the sitting position with the elbow flexed to about 100 degrees and the forearm resting comfortably with the hand in neutral position palm down against a padded bedside table (Fig. 74.6). With the patient in the above position, the Lister tubercle of the radius is identified by palpation (Fig. 74.7). Identification of the affected tendons is facilitated by having the patient extend the wrist against examiner resistance. At the level of Lister tubercle, a high-frequency linear ultrasound transducer is placed in a transverse position over the intersection of the extensor carpi radialis longus, the extensor carpi radialis brevis, the extensor pollicis brevis, and the abductor pollicis longus tendons (Figs. 74.8 and 74.9). The tendons will appear as the hyperechoic “hole” in the hypoechoic tendon sheath. The ultrasound transducer may be turned into the
longitudinal axis to further delineate the point of intersection (Fig. 74.10). When the point of intersection is identified, the skin overlying the area beneath the ultrasound transducer is then prepped with antiseptic solution. A sterile syringe containing 1.0 mL of 0.25% preservative-free bupivacaine and 40 mg of methylprednisolone is attached to a 1½-inch, 22-gauge needle using strict aseptic technique. The needle is placed through the skin just above the superior border of the transversely placed transducer and is then advanced using an out-of-plane approach with the needle trajectory adjusted under real-time ultrasound guidance so that the needle tip ultimately rests in proximity to the point of intersection but outside the substance of the tendons themselves (Fig. 74.11). When the tip of the needle is thought to be in satisfactory position, after careful aspiration, a small amount of local anesthetic and steroid is injected under real-time ultrasound guidance to confirm that the needle tip is in the proper position. After proper needle tip placement is confirmed, the remainder of the contents of the syringe are slowly injected. There should be minimal resistance to injection.