Resurfacing Shoulder Arthroplasty
Curtis R. Noel, MD
Preserving humeral bone with short stems and stemless implants is a recent trend in total shoulder arthroplasty (TSA), but the first and most bone-conserving implant, the humeral head resurfacing (HHR), evolved from the hip resurfacing experience over 40 years ago.1 Copeland’s development of his humeral resurfacing design began in 1979, and it was first implanted in 1986.2 Since then, a variety of systems and implants have been developed.
The benefits of HHR are well documented. It is the most bone conserving shoulder arthroplasty option, even with the development of newer stemless and short-stem implant designs. By eliminating humeral canal reaming, HHR is a more streamlined surgery with decreased blood loss and decreased operative time.3 In addition, because the HHR avoids violating the canal, the threat of a periprosthetic humeral diaphyseal fracture is greatly diminished,2 as is the threat of infection violating the humeral shaft. As HHR is not bound by the humeral canal, it has the freedom of expanded inclination and version options and potentially is a more anatomic shoulder replacement.4 Finally, with minimal bone removal and with a less aggressive implant, revision of an HHR to a stemmed implant is much less complicated (VIDEO 16.1).
In general, HHR is indicated in many of the same cases considered for a hemiarthroplasty or TSA. These broad categories include primary and secondary osteoarthritis, rheumatoid and other inflammatory arthritis, posttraumatic and instability-related arthritis, osteonecrosis, and cuff tear arthropathy.1,2,3 For those who cannot have a stemmed implant because of humeral deformity (genetic or posttraumatic) or previous surgery (elbow arthroplasty or previous open reduction internal fixation), HHR may also be the best option.
More specifically, HHR is often considered for the young, active patient with arthritis or osteonecrosis.1,5 In these younger patients, conserving humeral bone for future surgeries and avoiding a glenoid implant that may eventually fail is often the most prudent option. Younger patients with significant Hill-Sachs impression fractures from shoulder dislocations may also benefit from HHR when other options are contraindicated. However, the HHR can also be considered in older patients with concentric osteoarthritis or with cuff tear arthropathy when a reverse total shoulder is contraindicated.2
Multiple comparative studies have reported superior outcomes with TSA over hemiarthroplasties.6,7 Therefore, addressing the glenoid while performing an HHR is often desired. In HHR, the humeral head is reshaped and not resected, which makes exposure of the glenoid much more challenging. Success in performing a resurfacing TSA is increased by careful patient selection. Thinner patients with concentric glenoid wear (Walch A)8 and whose shoulder range of motion is somewhat maintained are better candidates for a combined glenoid and humerus resurfacing. Having decreased soft tissue mass to retract, having absent or decreased glenoid retroversion, and having less joint stiffness allows for improved retraction of the humerus and better exposure of the glenoid.
HHR is contraindicated in all circumstances in which a standard TSA is contraindicated; ie, active infections, nerve injury, and neuropathic arthropathy. In addition, HHR is contraindicated in cases where the proximal humerus bone will not support a nonstemmed implant owing to extreme proximal humeral bone loss (greater than 60% of the humeral head), excessively soft bone, or bone containing large cysts.2 Those patients with acute proximal humerus fractures or chronic humeral neck fracture nonunions are also not candidates for HHR.2,3,9
Relative contraindications to preforming a resurfacing TSA include conditions that make glenoid exposure difficult or impossible. These conditions include patients with significant retroversion (Walch B or C glenoids),8 obese or well-muscled patients, and patients with advanced arthritis with significant loss of motion and joint contracture.
Relative contraindications for an HHR include conditions that make hemiarthroplasties more likely to fail. These include excessive glenoid bone loss leading to instability or predisposing the glenoid to rapid medial wear. These are situations in which biconcave glenoids (Walch B2)8 and posterior humeral head subluxation lead to decreased implant survival.10
The operating room setup and positioning for HHR is the same as that of any TSA. Unless contraindicated, all patients receive a regional block along with general anesthesia. In addition to the block, complete muscle paralysis may improve retraction and aid in difficult glenoid exposures. Once asleep, the patient is placed in the beach chair position with the head secured in the head rest and the operative arm freely mobile either on a Mayo stand or in an arm positioner.
A standard deltopectoral approach is routinely used (FIGURE 16.1), but an anterosuperior approach, preferred by Copeland and Levy, could also be utilized.11
The subscapularis can be approached in a variety of ways. I prefer to do a subscapularis peel, but a tenotomy or lesser tuberosity osteotomy can also be performed with equal efficacy. Savoie has described a partial subscapularis sparing approach, which only releases the lower portion of the subscapularis.5,12 In this approach, the tendinous portion of the upper subscapularis remains intact while the more muscular inferior portion of the subscapularis is removed along with the inferior capsule. The humerus is then abducted and externally rotated to slide under the intact upper subscapularis (FIGURE 16.2). This approach can make visualizing the superior aspect of the humerus more challenging as the subscapularis lays across the top of the humerus, but it can allow for a more aggressive rehabilitation and quicker recovery because the important tendinous portion of the upper subscapularis remains intact.5,12
FIGURE 16.2 A and B, Savoie’s subscapularis sparing approach: removing the bottom portion of the tendon and tucking the humeral head under the intact upper border of the subscapularis.
Regardless of how the subscapularis is addressed, it is critical to perform ample soft tissue releases, especially if the glenoid is going to be resurfaced. The subscapularis and capsular release must proceed down the inferior and medial aspect of the humeral neck continuing all the way to the posterior aspect of the humerus, making sure to protect the axillary nerve. Some authors prefer to excise the capsule, but I prefer to do an aggressive capsular release off the humerus and glenoid, leaving the remaining capsule attached to the undersurface of the subscapularis. I feel this decreases trauma to the subscapularis and adds mass to the tendon improving its repair.