40.1 Goals of Procedure

Arthritic changes of the humeral head articular cartilage may occur through degenerative, inflammatory, traumatic, or iatrogenic mechanisms. ¹ When this occurs in younger patients and broadly affects the articular surface, surgical management is challenging. If possible, in a young patient population, maintenance of the native glenoid is preferred in order to avoid early replacement of the glenoid. ²

The goal of any arthroplasty procedure is to relieve pain and improve function. Humeral head resurfacing achieves these goals by replacing the arthritic or damaged cartilaginous surface. The glenoid is not typically addressed with humeral head resurfacing. However, management of glenoid sided bone and cartilage involvement are not precluded with humeral head resurfacing.

New stemless implants have recently been introduced, which can accomplish the same goal of humeral arthroplasty without the need for stem introduction into the metaphysis or diaphysis. These do, however, require resection of the head and therefore sacrifice more metaphyseal bone than a humeral resurfacing implant. This chapter will focus on humeral resurfacing.

40.2 Advantages

The main advantage of resurfacing the humeral head is the ability to re-create the native anatomy of the proximal humerus independent of the humeral canal. Since the resurfacing component is a shell configuration, it allows for minimal bone resection. The lack of an intramedullary stem allows the surgeon to place the implant in the precise position without being limited by the relationship of the intramedullary canal to the articular surface. The ability to minimize bone resection of the proximal humerus and avoid instrumentation of the humeral canal may facilitate future reconstructive procedures such as arthrodesis or further arthroplasty. ³

40.3 Indications

Humeral head resurfacing is indicated for young patients (<60 years old), who have significant pain and dysfunction from cartilage compromise of the humeral head. It is preferred that the glenoid articular cartilage is maintained and that the humeral head remains concentric on the glenoid on both anteroposterior (AP) and axillary views. Patients with posttraumatic arthritis and disruption of the relationship of the humeral head to the diaphysis also benefit from a resurfacing procedure. When the relationship of the humeral canal and head precludes stemmed arthroplasty, humeral head resurfacing is preferred to tuberosity osteotomy. Avascular necrosis (AVN) with articular collapse involving greater than 40% of the humeral articular surface is another indication for humeral resurfacing. However, in these cases it is important that at least 60% of the subchondral bone be of good quality in order to support the resurfacing prosthesis. ⁴ Finally, a rare indication for resurfacing is a large, engaging Hill–Sachs defect secondary to instability, which takes up more than 40% of the humeral head surface. Generally, these defects may be treated with partial head replacement or allograft reconstruction; however, occasionally a complete resurfacing may be needed.

40.4 Contraindications

Resurfacing of the humeral head should be avoided in patients with deficiency of more than 60% of the humeral head or poor subchondral bone. Resurfacing of the humerus should also be avoided in the setting of acute three- and four-part fractures of the proximal humerus, as the implant will not have appropriate bony support in the face of tuberosity involvement. While glenoid arthrosis is not an absolute contraindication to resurfacing, it should be avoided in this situation as the patient may continue to experience glenoid-based pain. Glenoid resurfacing can be performed in the setting of humeral head resurfacing ( Fig. 40.1 ). However, the retained portion of the humeral head limits glenoid exposure.

40.5 Preoperative Preparation/Positioning

A thorough history and orthopaedic evaluation should be undertaken initially to establish the correct diagnosis. A complete radiographic examination should also be performed including AP views of the glenohumeral joint in the plane of the scapula with the humerus in internal and external rotation as well as an axillary view and a scapular Y view. The AP views help assess the quality of the joint space as well as presence of osteophytes and location of the humerus with respect to the glenoid. The lateral and axillary views are key to evaluate posterior subluxation of the humerus, version of the glenoid, and posterior glenoid wear. A CT scan may also be useful for a more detailed evaluation of the glenoid if there is any concern for extensive disease on the plain radiographs. Finally, if there is any concern for rotator cuff disease, an MRI should be obtained to confirm the integrity of the rotator cuff tendons.

As with other arthroplasty procedures, we prefer to perform the procedure in the beach-chair position in 30 degrees of elevation. Sterile preparation and draping is done in the standard fashion with the arm held in a positioning device ( Fig. 40.2 ).