INTRODUCTION

Lateral epicondylitis, or tennis elbow, is the most common affliction of the elbow.

The origin of the extensor carpi radialis brevis (ECRB) has been implicated as the source of pathology in this condition.^2,^5,^{7–10,13–16}^,18 Reported histopathologic findings in the affected tendon origin include vascular proliferation and hyaline degeneration, which are consistent with a chronic, degenerative process.^10,^14,^18,²⁰ Most commonly, surgical treatment is directed at excision of this pathologic tissue through an open approach or more recently arthroscopic methods.^1,^3,^5,^6,^11,^15,^17,^19,^21,²²

This chapter covers the anatomy of the extensor tendon origins at the humeral epicondyle based on anatomic dissections.⁴ The location of the ECRB tendon origin is defined relative to intra-articular landmarks. Using these data, a technique for arthroscopic lateral epicondylitis surgery is presented with early clinical results.

ANATOMY

The extensor carpi radialis longus (ECRL) and the ECRB have a unique relationship at the level of the elbow. The ECRL overlies the proximal portion of the ECRB such that the ECRL must be elevated anteriorly in order to visualize the superficial surface of the ECRB. A thin film of areolar connective tissue separates these two structures.

The origin of the ECRL is entirely muscular along the lateral supracondylar ridge of the humerus (Fig. 41-1). The muscle origin has a triangular configuration, with the apex pointing proximally. In contrast, the origin of the ECRB is entirely tendinous. Although it blends with the origin of the extensor digitorum communis (EDC), when dissected from a distal to proximal direction and using the tendon undersurface, it can be separated from the EDC back to the humerus (Fig. 41-2). The anatomic origin of the ECRB is located just beneath the distal most tip of the lateral supracondylar ridge (Fig. 41-3). The footprint is diamond shaped, measuring approximately 13 by 7 mm (Fig. 41-4). At the level of the radiocapitellar joint, the ECRB is intimate with the underlying anterior capsule of the elbow joint, but it is easily separable at this level.⁴

FIGURE 41-1 Anatomic specimen showing the footprint of the extensor carpi radialis lonugs tendon. This origin is principally muscular originating off of the supracondylar ridge of the humerus.

FIGURE 41-2 A, Lateral view of cadaveric specimen. The extensor carpi radialis longus (ECRL) has been reflected anteriorly and the extensor carpi ulnaris posteriorly revealing the common extensor tendon origin of the extensor carpi radialis brevis (ECRB) and extensor digitorum communis (EDC). These are indistinguishable when viewed from the outer surface. B, The muscles and tendons have been reflected proximally. The origins of the ECRB anteriorly and the EDC posteriorly are identifiable on the undersurface of the extensor origin. C, Close-up view of the two tendons that can be separated back to their origins. Note the underlying lateral collateral ligament (probe).

FIGURE 41-3 A, The extensor digitorum communis has been removed allowing better visualization of the bony extensor carpi radialis brevis (ECRB) origin on the humerus. B, The ECRB footprint is identified with elevation of the tendon from the humerus.

FIGURE 41-4 Schematic diagram depicting the relationship between the extensor carpi radialis brevis (ECRB) origin at the humerus and bony landmarks. Note that the ECRB footprint origin is diamond shaped and located between the midline of the joint and the top of the humeral capitellum beneath the most distal extent of the supracondylar ridge. The tendon does not originate on the epicondyle specifically. Note the relationship between the ECRB origin and the underlying lateral collateral ligament.

In an effort to develop a strategy for arthroscopic identification and release of the tendon origins, we performed a cadaveric study. The ECRB was identified at the level of the radiocapitellar joint by first separating the ECRL anteriorly from the extensor aponeurosis posteriorly (Fig. 41-5). The EDC origin was then dissected from anterior to posterior to expose the underlying ECRB tendon. The anterior and posterior borders of the ECRB were marked with intra-articular 18-gauge needles, and the ECRL/EDC interval and the skin were repaired (Fig. 41-5).

FIGURE 41-5 A, Cadaveric specimen depicting the junction between the muscular extensor carpi radialis longus (ECRL) anteriorly and the extensor aponeurosis posteriorly, which has been opened. B, The aponeurosis and tendons have been reflected posteriorly off of the ECRL, revealing the undersurface of the extensor carpi radialis brevis (ECRB) tendon. C, The extensor digitorum communis has been dissected off of the underlying ECRB, revealing the anterior and posterior margins of the ECRB tendon.

The specimens were then mounted, and elbow arthroscopy was performed. Based on pilot studies, a modified lateral portal was established from an inside-out technique. This portal was made several millimeters proximal and anterior to the top of the humeral capitellum. Using a monopolar thermal device (Arthrocare, Austin, TX), the tissue between the two needles was released from the humerus, taking care to use the previously determined intra-articular landmarks for the ECRB origin. The joint capsule was first ablated to expose the undersurface of the ECRB tendon. Above the anterior needle, the muscular origin of the ECRL was identified. The ECRB tendon was then released from its humeral origin and allowed to retract distally. Care was taken to release all the tissue located between the two needles and dissect down to the midline of the radiocapitellar joint as visualized arthroscopically.

The specimens were then removed from the mounting device and individually dissected. The ECRL/EDC interval was opened, and the origin of the ECRB was evaluated to document complete release. The elbow capsule was identified beneath this plane at the joint level. The origin of the lateral collateral ligament was then exposed by reflecting the remaining extensor tendon origin posteriorly. In addition, the posterior interosseous nerve (PIN) was dissected out to document that it was not compromised by the arthroscopic release procedure.

Dissection of the specimens revealed an intact extensor aponeurosis and a complete release of the underlying ECRB in all cases (Fig. 41-6). The capsule was identified as a separate layer beneath the ECRB release. The collateral ligament origin was not violated, and the PIN was well distal to the release and not compromised in any case (see Fig. 41-6). Using these data, an arthroscopic technique was designed for lateral epicondylar release.⁴

FIGURE 41-6 A, Following arthroscopic release of the extensor carpi radialis brevis (ECRB), the specimen is opened documenting a complete release of the ECRB. Note the distal retraction of the tendon edge. B, The posterior interosseous nerve has been exposed as it passes from anterior to posterior (arrow). This is well distal and anterior to the tendon origin release. C, The tendinous origin has been elevated posteriorly revealing the intact lateral collateral ligament (LCL). The ligament is safe as long as the release stays anterior to the midline of the radiocapitellar joint.

TECHNIQUE

The patient is positioned prone, with all bony prominences well padded. We favor regional anesthesia. Bony landmarks are drawn out including the path of the ulnar nerve.

Once the tourniquet is inflated, the elbow is insufflated with an 18-gauge needle introduced through the soft spot of the elbow (midlateral portal).

Next, a standard anteromedial portal is established (Fig. 41-7). This is started several centimeters proximal and anterior to the medial epicondyle and well anterior to the palpable intermuscular septum. Care is taken to slide along the anterior humerus, and the joint is entered with a blunt introducer or a switching stick. This medial portal allows one to view the lateral joint including the radial head, capitellum, and the lateral capsule. It is often helpful at this point to open the inflow to allow distension of the capsule. If visualization is a problem, a retractor can be introduced through a proximal anterolateral portal 2 to 3 cm proximal and just anterior to the lateral supracondylar ridge. A simple freer elevator is useful for this purpose. By tensioning the capsule anteriorly, improved visualization of the lateral capsule and soft tissues can be achieved.

FIGURE 41-7 A, Diagram depicting the medial portal used in visualization for the arthroscopic lateral epicondylar release. B and C, Field of view from the medial portal. D, Diagram depicting the relationship of the extensor tendon origins when viewed intraarticularly. These are located outside (behind) the elbow capsule. E, Needle used to help establish a modified lateral portal. Note how this is begun slightly proximal and anterior to the proximal margin of the humeral capitellum. F, Cannula used to establish the final lateral portal. G, Release of the capsule from the lateral humeral margin allowing visualization of the tendinous origins behind. The extensor carpi radialis longus (ECRL) is more anteriorly located and is muscular. The extensor carpi radialis brevis (ECRB) is more posterior. H, The ECRB is released from the top of the capitellum to the (I) midline of the radiocapitellar joint.

A modified anterolateral portal is established using an inside-out technique. This is started 2 to 3 cm above and anterior to the lateral epicondyle (see Fig. 41-7). The portal is slightly more proximal than a standard anterolateral portal. This allows instrumentation down to the tendon origin rather than entering the joint through the ECRB tendon itself. If lateral synovitis is present, this can be débrided with a resector.

The capsule is next released. Occasionally in epicondylitis, one can find a disruption of the underlying capsule from the humerus (Fig. 41-8). Most commonly, the capsule is intact although small linear tears can be present (Fig. 41-9). We have found it easier to release the lateral soft tissues in layers using a monopolar thermal device. In this way, the capsule is first incised or released from the humerus. When it retracts distally, one can appreciate the ECRB tendon posteriorly and the ECRL, which is principally muscular, more anterior. As noted earlier, the ECRB tendon spans from the top of the capitellum to the midline of the radiocapitellar joint.