INTRODUCTION

Throwing places unique demands on the elbow, resulting in predictable injury patterns. Many of these injuries are treated successfully with arthroscopy. Appreciation of elbow biomechanics relevant to throwing assists the clinician in accurate diagnosis, nonoperative treatment, surgical indications, and surgical technique. In the acceleration phase of throwing, the elbow reaches an angular velocity of 3000 deg/sec as it extends from 110 to 20 degrees of flexion, which corresponds to 64N-m valgus torque. The combination of the valgus torque and rapid extension generates three major forces on the elbow: a tensile stress along the medial aspect (ulnar collateral ligament [UCL], flexor pronator mass, medial epicondyle), a shear stress in the posterior aspect (posteromedial tip of olecranon and olecranon fossa), and compression forces in the lateral aspect (radiocapitellar joint).

On the medial side, the repetitive tensile forces challenge the ultimate strength of the UCL, creating the well known injury risk to the ligament. Patients who develop valgus instability and continue to throw may initiate and exacerbate pathology in the posterior and lateral aspects of the elbow. In the posterior compartment, throwing repeatedly drives the olecranon into the olecranon fossa. The combination of valgus and extension forces creates shear forces on the medial aspect of the olecranon tip and olecranon fossa may cause injury and development of osteophytes (Fig. 39-1). This constellation of injuries has earned the term “valgus extension overload syndrome.” The relationship between the posterior compartment of the elbow and the UCL is evident in a series of professional baseball players who underwent olecranon débridement. Twenty-five percent of these athletes developed valgus instability and eventually required UCL reconstruction. This observation suggests that both the olecranon and the UCL contribute to valgus stability, and the authors believed that they may have missed UCL injuries in many of these patients. A cadaver study supports this theory and has demonstrated that UCL injury results in contact pressure alterations in the posterior compartment that explains the formation of osteophytes on the posteromedial olecranon.¹ Another cadaver biomechanical study demonstrated that sequential partial resection of the posteromedial aspect of the olecranon increases elbow valgus angulation.¹⁴ Another cadaver study confirmed that strain in the UCL is increased with increasing posteromedial olecranon resection beyond 3 mm.¹⁵ These last two studies conclude that overaggressive olecranon resection used to treat posteromedial impingement puts the UCL at risk for injury. In summary, patients with posteromedial impingement pain from valgus extension overload should be critically evaluated for suspected concomitant UCL injuries and avoid overaggressive olecranon resection.

FIGURE 39-1 Throwing creates valgus torque on the elbow that results in (A) medial tension, (B) lateral compression, and (C) posterior shear forces.

In the lateral compartment, compression forces calculated as high as 500 N may result in injuries that has been referred to as radiocapitellar overload syndrome. The syndrome occurs often in combination with medial ligament instability and valgus extension overload. Persistent repetitive radiocapitellar compression may eventually result in chondral or osteochondral fracture and the production of intra-articular loose bodies. In skeletally immature athletes, this is in part the proposed etiology of capitellar osteochondritis dissecans.

VALGUS EXTENSION OVERLOAD

Patients report posteromedial elbow pain that occurs during the deceleration phase of throwing as the elbow reaches terminal extension. Patients also report limited extension, which results from impinging posterior osteophytes or locking and catching resulting from loose bodies. Physical examination demonstrates crepitus and tenderness over the posteromedial olecranon, and pain is reproduced when forcing the elbow into extension. Valgus stress testing, milking maneuver, and moving valgus stress tests are important to assess the status of the UCL. Anteroposterior, lateral, oblique, and axillary views of the elbow may reveal posteromedial olecranon osteophytes and/or loose bodies (Fig. 39-2). Magnetic resonance imaging (MRI) can further assess osteophytes and soft tissues (Fig. 39-3). Computed tomography with two-dimensional reconstruction and three-dimensional surface rendering may best visualize the bony pathology in addition to MRI.

FIGURE 39-2 Radiograph demonstrating osteophyte on posteromedial aspect of olecranon.

FIGURE 39-3 Magnetic resonance imaging scan demonstrating osteophyte on posteromedial olecranon.

Surgical treatment is indicated for those patients who maintain symptoms of posteromedial impingement despite nonoperative management. A relative contraindication to performing isolated olecranon débridement is the presence of UCL insufficiency. UCL insufficiency may become symptomatic following posteromedial decompression. Therefore, careful history, physical examination, and advanced imaging must be performed to avoid missed UCL injuries or valgus instability.

Surgical options include arthroscopic débridement or limited incision arthrotomy to decompress the posterior compartment. Arthroscopy offers the advantages of limited morbidity and complete diagnostic assessment of the elbow. The patient may be positioned supine, prone, or lateral decubitus. If concomitant UCL reconstruction is anticipated, the supine position may be preferred to avoid repositioning of the patient following the arthroscopy. Alternatively, the arthroscopy may be performed in the lateral position, followed by repositioning and repeat prepping and draping for the UCL reconstruction.

Evaluation of the posterior compartment uses direct posterior and posterolateral portals. Diagnostic arthroscopy evaluates presence of osteophytes on the posteromedial aspect of the olecranon, loose bodies, and any evidence of chondromalacia. Figure 39-4 illustrates removal of the olecranon osteophyte with a small osteotome placed at the margin of the osteophyte and normal olecranon (Fig. 39-5A). The motorized burr introduced through either the direct posterior portal or posterolateral portal may further contour the olecranon tip, as shown in Figure 39-5B. A lateral radiograph may be obtained intraoperatively to ensure adequate bone removal and that no bone debris remains in the soft tissues surrounding the elbow. It is important to remove only the osteophyte and not normal olecranon to prevent increased strain on the UCL during valgus loading.¹⁵ Once the osteophyte has been removed from the olecranon, the trochlea and olecranon fossa should be examined for osteophytes or kissing lesions, which should also be removed. It is important to recognize that the osteophytes occur on both the ulna and the humerus. Some nonthrowing athletes have a major component of direct extension overload without significant valgus stress. For these patients, the risk of developing UCL insufficiency following posterior decompression is much less compared with that of the throwing athletes and, therefore, débridement can be more aggressive, if necessary.

FIGURE 39-4 Arthroscopic removal of olecranon osteophytes. Note direct posterior and posterolateral portal placement and ulnar nerve.

(Redrawn with permission from ElAttrache, N. S., and Ahmad, C. S.: Valgus extension overload and olecranon stress fractures. Sports Med. Arthrosc. Rev. 11:25, 2003.)

FIGURE 39-5 Posteromedial impingement. A, Osteotome to remove osteophyte, B, Olecranon tip contoured with motorized burr.

(From Ahmad, C. S., and ElAttrache, N. S.: Posteromedial decompression of valgus extension overload syndrome. In Yamaguchi, K., O’Driscoll, S., King, G., and McKee, M. [eds.]: Advanced Reconstruction: Elbow. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2007, p. 56.)

Care should be taken to avoid injury to the ulnar nerve, which lies in the cubital tunnel, by avoiding suction and use of burrs adjacent to the nerve, which may wrap up soft tissues. If concern exists for ulnar nerve injury, the nerve should be explored through an open incision and protected during the débridement.

Postoperative rehabilitation consists of early active elbow flexion and extension exercises. Emphasis is placed on restoring flexor-pronator strength. At 6 weeks, a progressive throwing program is begun. During this time, plyometric exercises and neuromuscular training is enhanced. Endurance exercises are progressed and return to competition is typically achieved at 3 to 4 months postoperatively.

OSTEOCHONDRITIS DISSECANS