In this chapter we summarize the use of partial resurfacing options for the treatment of glenohumeral cartilage lesions. We discuss the evaluation of patients, surgical indications, surgical techniques, and results of current resurfacing options. Partial resurfacing is an excellent option in younger patients with limited cartilage lesions.
Partial resufacing may be approached through a standard deltopectoral approach or more limited approaches depending on the location of the lesion.
It is important to place the guide wire in the center of the defect to ensure uniform coverage with the implant.
When performing a total resurfacing, it is important to consider implant height as well as version to ensure proper positioning of the implant
In a partial resurfacing, the implant is placed within the surrounding native cartilage. As long as the implant is recessed to an appropriate level, this minimizes issues of implant height and version.
Arthritis of the glenohumeral joint has become a common cause of disability, especially in older populations. Several studies have found the incidence of shoulder-related problems to be as high as 20% in the elderly population, with glenohumeral arthritis accounting for almost half of these. Over the last century, many advances have been made in joint replacements, especially in relation to the shoulder. The concept of an anatomic replacement has led to the development of implants that preserve bone stock as well as the relation of the humeral head and the glenoid. This is especially true in younger patients and those with milder disease.
Although relatively new in comparison to traditional arthroplasty, resurfacing of the humeral head has become popular in select patient populations. Indications for resurfacing are similar to that for traditional arthroplasty, with a new articulating surface placed over the existing damaged humeral head. Advantages of resurfacing to traditional arthroplasty include preserving bone stock as well as avoiding complications related to the placement of a stem down the humeral shaft.
In some instances, patients may become symptomatic from isolated and well-localized chondral lesions. The incidence of Outerbridge grade II to IV lesions on arthroscopic evaluation has been found to be about 5%. Nonoperative management, including nutritional supplementation (such as chondroitin sulfate and glucosamine sulfate), nonsteroidal anti-inflammatory medications, physical therapy, and corticosteroid/visco-supplementation injections, may provide significant pain relief in some patients.
Surgical options for patients who fail nonoperative management include debridement, microfracture, autologous chondrocyte implantation/mosaioplasty, and reconstructive procedures such as biologic or prosthetic resurfacing. This chapter focuses on prosthetic partial resurfacing of these lesions. Partial resurfacing provides the ability to address isolated cartilage lesions in patients with a by and large healthy joint while preserving the overall anatomy of the glenohumeral articulation and maintaining good cartilage and bone. This chapter explores the advantages and indications and discusses surgical techniques of partial glenohumeral prosthetic resurfacing.
HISTORY AND DEVELOPMENT OF PARTIAL SURFACE REPLACEMENT
The first shoulder arthroplasty was most likely performed by Themistocles Gluck in the early 1890s, using a prosthesis made of ivory. The first documented metal shoulder arthroplasty was performed by Jules Emile Péan in 1893, using a platinum implant in a patient with life-threatening tuberculous septic arthritis. This patient performed relatively well but developed a draining sinus requiring revision surgery 2 years later.
The development of modern-day arthroplasty began with Neer in the early 1950s with the design of a stemmed vitallium implant to be used in the management of complex proximal humerus fractures. The implant was intended to replace the articular surface while allowing the reattachment of the tuberosities. The original prosthesis was made in three sizes to accommodate for anatomic variations. Nine years later, a second report expanded the indications of the implant for degenerative arthritis, and added a fourth, longer stem as well as proximal perforations for proximal ingrowth. Over the next 10 years, several authors, including Neer, described the use of polyethylene to resurface the glenoid.
In the early 1990s, the importance of anatomic reconstruction was stressed by several authors. In particular, failure to match the shape, size, version, and inclination of the proximal humerus was found to have serious biomechanical consequences due to malposition of the joint line and lack of restoration of the instant center of rotation of the glenohumeral complex. This, in turn, has led to development of implants that more closely match the natural anatomy of the glenohumeral joint in an effort to maximize the biomechanical advantage of the prosthesis.
Over the last decade, there has been renewed interest in bone-preserving procedures, especially in younger patients with mild but activity-limiting disease. In order to address the issue of anatomic restoration as well as bone preservation, there has been increasing interest in resurfacing options for the humeral head. Several authors have demonstrated results comparable to hemiarthroplasty and total shoulder arthroplasty with resurfacing of the humeral head without a stemmed component.
Partial replacement was developed with the goal of replacing isolated cartilage and bone defects of the glenohumeral joint. By definition, these implants would preserve the natural joint line as well as the natural mechanics of the joint, as the implant would remain recessed within the face of the native joint surface. Although we still only have short-term follow-up of these studies due to the relative novelty of these implants, early results have shown promise in regard to restoring function in select patient populations.
DESIGN RATIONAL OF PARTIAL HUMERAL RESURFACING
One important difference between partial and total resurfacing is the preservation of the natural anatomy of the joint. Total resurfacing options, while still a bone-preserving procedure, may still result in a change in the natural joint line, especially in regard to the version, inclination, and height of the articulating surface. This is in part due to the fact that the overall shape of the articular surface has to be changed in order to fit a resurfacing cap over it. If not performed properly, this may result in an articular surface that is raised or improperly inclined and may change the natural biomechanics of the joint. Partial resurfacing, on the other hand, relies on the natural anatomy of the joint and recesses the implant within the native anatomy. As a result, the overall shape, inclination, and height of the articular surface remain unchanged.
In order to properly address the complex relationship of the glenohumeral joint, it is important to consider the anatomy of the humeral head. As our ability to image the humeral head has improved, so has the understanding of the true anatomy of the glenohumeral joint. Although the humeral head is spherical in its central portion, it becomes less so along its edges. These anatomic findings may result in radii of curvature that are different when examined in two orthogonal planes. When performing a partial resurfacing, it is important to address these different radii of curvatures of the humeral head in order to restore the true anatomic congruity of the glenohumeral joint.
Current designs for partial surface replacements stress this important difference in radius of curvatures of the humeral articular surface, especially as lesions near the periphery. Current jigs are made to determine the offset of the articular defect in orthogonal planes (e.g., superior-inferior and medial-lateral). As a result, the replacement closely approximates the overall shape of the articular surface it is intended to replace and results in a smooth transition from native cartilage to implant.
INDICATIONS AND CONTRAINDICATIONS
Indications for partial resurfacing arthroplasty include patients with focal chondral defects and progressive shoulder pain that have been refractory to conservative management. In general, these defects are the results of posttraumatic degenerative disease or avascular necrosis. It is important that the patient have sufficient bone stock to support loading. The rotator cuff should be intact or reconstructable.
Patient selection factors are also important when considering partial resurfacing. Patients should be healthy enough to undergo surgery and should be able and willing to cooperate with postoperative physical therapy as well as comply with activity restrictions.
Absolute contraindications for partial resurfacing include infection or sepsis. Patients with known sensitivities to the metal alloys used in the prosthesis (mainly cobalt-chromium and titanium alloys) are also not good candidates for partial resurfacing. Relative contraindications include uncooperative patients or patients incapable of following preoperative and postoperative instructions; patients with metabolic disorders that may impair the formation or healing of bone; patients with infections at remote sites that may spread to the implant site; rapid joint destruction or bone resorption visible on roentgenograms; and patients with known chronic instability or deficient soft tissue structures, including muscular, vascular, and other supporting structures.
Another relative contraindication for partial resurfacing includes patients with defects that are not well localized and defects that are discontinuous. Patients with inflammatory arthropathies such as rheumatoid arthritis may also not be good candidates for a partial resurfacing due to the global effect on cartilage that these conditions cause. However, this operation has been performed at our institution in patients with well-contained defects due to inflammatory arthritis. It is also worth mentioning that the partial resurfacing implant used for this operation does have the option of converting from a partial resurfacing to a total resurfacing implant. As such, this versatility provides the surgeon the ability to gage the status of the humeral head and make an intraoperative decision as to whether to perform a partial or total resurfacing.
All patients should have undergone a thorough history and physical examination prior to surgery. It is important to ascertain the etiology of the pain in the shoulder. In general, most patients should have undergone a course of conservative management (including anti-inflammatory medications and/or physical therapy) prior to proceeding with operative intervention.
Preoperative imaging should include at least two orthogonal views of the shoulder, including a true anteroposterior (AP) view of the glenohumeral joint as well as an axillary lateral view. The axillary lateral view provides valuable information about the glenoid anatomy, including version, degree of arthritic degeneration, and bone stock. In cases in which further information about the bony anatomy is of importance, a computed tomography (CT) scan may provide crucial information as to glenoid erosion and bone stock and may help in decision making as to whether to address the glenoid at the time of surgery. Finally, magnetic resonance imaging (MRI) may provide useful information as to the state of the rotator cuff and may help identify repairable tears.
In the majority of cases, a standard anterior (deltopectoral) approach may be used and will provide excellent exposure for the procedure. Some authors have advocated the use of a superior approach for resurfacing procedures. We have found that we are able to address all humeral head defects (including posterior defects) with the standard anterior approach and we therefore have not found the need to use the superior approach.
The patient is placed in a beach-chair position, with the back tilted at a 30-degree angle. A hydraulic table may be used to position and hold the arm in the various positions necessary to maximize exposure. An anterior axillary incision is made along Langer lines. After development of the skin flaps, the interval is developed, ensuring to protect the cephalic vein in the center of the interval. The vein may be mobilized either laterally or medially, although laterally is preferred at our institution to allow drainage of the deltoid. After release of any subdeltoid and subacromial adhesion, the deltoid and pectoralis muscles are retracted and may be maintained with the use of a self-retaining retractor. The conjoined tendon is then identified and retracted medially, ensuring to avoid injury to the musculocutaneous nerve by avoiding too vigorous retraction. The bursa overlying the subscapularis muscle is then identified and excised, exposing the underlying anterior humeral circumflex vessels overlying the inferior border of the subscapularis. These vessels are isolated and ligated prior to proceeding, while at the same time identifying and protecting the axillary nerve that lies deep to these vessels and superficial to the subscapularis muscle at the level of the glenoid. The subscapularis is either incised lateral to its musculotendinous junction or osteotomized with the lesser tuberosity and separated bluntly from the underlying capsule. At this point, the rotator interval is also released between the superior edge of the subscapularis and the anterior edge of the supraspinatus.
The glenohumeral joint capsule is incised along the anatomic neck and released from its insertion anteriorly and inferiorly, ensuring to protect the axillary nerve. The capsule must be completely released of the anatomic neck until adequate exposure of the humeral head is achieved. In cases where a posterior defect is to be addressed, it is important to perform an adequate inferior capsular release, making sure to take the capsule directly off of bone to minimize the risk of injury to the axillary nerve.
Depending on the site of the chondral lesion, it may be possible to avoid the morbidity associated with the taking down the insertion of the subscapularis muscle. Next we describe two instances when this may be performed.
In some cases, smaller chondral lesions will be located anteriorly. This may be confirmed both by preoperative imaging and diagnostic arthroscopy. In such cases, a subscapularis splitting approach may be used to expose the lesion for resurfacing, thus avoiding the complications and morbidity associated with taking down this muscle.
The skin and superficial dissection proceeds as previously described. Once the subscapularis tendon has been identified, a horizontal split along the muscle fibers at the junction of the upper two thirds and lower one third is performed. This interval may be used to expose the underlying capsule or may be taken in one layer with the capsule depending on the surgeon’s preference. Once the joint has been exposed, the humeral head and the underlying lesion may be seen through this interval or buttonholed if more exposure is necessary.
In some instances, a small chondral lesion may be seen located superiorly in the humeral head ( Fig. 4-1 ). Again, this may be confirmed by preoperative imaging as well as arthroscopy. The surgeon may once again avoid the morbidity of a subscapularis take down by a superior approach to the lesion.