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Types of shoulder arthritis include osteoarthritis, inflammatory arthritis such as rheumatoid arthritis, and the other arthritides such as gout and pseudogout.
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Common to all forms of shoulder arthritis is shoulder pain that has worsened over time as well as stiffness, weakness, grinding, or clicking with movement and functional limitation of the affected arm.
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Nonoperative management strategies should be exhausted before choosing surgical options.
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Surgical options include arthroscopic shoulder debridement, with or without capsular release; humeral hemiarthroplasty, with or without interpositional arthroplasty of the glenoid; total shoulder arthroplasty (TSA); and reverse shoulder arthroplasty.
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Rehabilitation is a standard component of postoperative management and varies according to the specific procedure performed.
Arthritis is a general term used to describe a wide range of pathologic conditions that result in loss of cartilage at the joint surfaces. The shoulder (i.e., glenohumeral joint) is the third most commonly affected large joint, after the hip and knee. There are many etiologies of glenohumeral arthritis, but in some cases the exact cause remains unclear. In general, arthritis can be thought of in the following broad categories: osteoarthritis (OA), inflammatory arthritis, and other arthritides ( Box 109-1 ).
Osteoarthritis
Primary
Secondary
Post-traumatic
Postsurgical
Instability
Hypoplastic glenoid
Systemic Inflammatory Diseases
Rheumatoid arthritis
Ankylosing spondylitis
Psoriatic arthritis
Inflammatory bowel disease
Other Arthritides
Rotator cuff tear arthropathy
Crystalline arthropathy
Gout
Pseudogout
Osteonecrosis
Idiopathic
Corticosteroid induced
Alcoholism
Post-traumatic
Gaucher’s disease
Postirradiation necrosis
Hemaglobinopathies: sickle cell disease, hemophilia, hemachromatosis
Neuropathic arthropathy
Syringomyelia
Peripheral neuropathy
Infectious
Septic arthritis
Lyme arthritis
Arthritis associated with acromegaly
OA can be divided into primary and secondary types. Primary OA is without an identifiable etiology. Examples of secondary OA include post-traumatic (i.e., instability or intra-articular fracture) and postsurgical (i.e., capsulorrhaphy) arthritis. Inflammatory arthritides are systemic diseases in which rheumatoid arthritis (RA) represents the most common form. Arthritis from inflammatory bowel disease, ankylosing spondylitis, and psoriatic arthritis are also in the family of inflammatory arthritides.
The category of other arthritides encompasses a wide range of diagnoses. Crystal deposition diseases, such as gout and pseudogout, can involve the shoulder. Additional types of glenohumeral arthritis include arthritis associated with acromegaly, glenohumeral dysplasia, neuropathic arthropathy, and septic arthropathy. Atraumatic osteonecrosis or avascular necrosis (AVN) can result in humeral head subchondral bone collapse and may be secondary to systemic corticosteroid use, alcoholism, Gaucher’s disease, sickle cell disease, and irradiation. Rotator cuff tear arthropathy (RCTA) is a unique form of arthritis with well-known pathoanatomy but poorly understood etiology.
Although shoulder arthritis entails a broad range of pathogeneses, the focus of this chapter is to discuss the surgical management of the more common conditions: OA, RA, and RCTA. Many of the surgical principles discussed are also applicable to other causes of glenohumeral arthritis.
Investigation
The majority of patients with glenohumeral arthritis can be diagnosed based on history, physical examination, and plain radiographs. At times, computed tomography (CT) and magnetic resonance imaging (MRI) may be of value. Consideration should be given to the list of differential diagnoses, which includes cervical spine disease, cardiac or pulmonary etiologies, diaphragmatic irritation, Charcot’s arthropathy, tumors, and acute trauma.
Specific clinical features of shoulder arthritis presenting in a particular individual are dependent on the type of arthritis. However, in general, there is a predominant symptom of shoulder pain that has worsened over time. Initially, the pain occurs with use of the joint and is relieved by rest. With disease progression, the pain and discomfort can be brought on by minimal activity and may even occur at rest and at nighttime. In addition to the pain, other symptoms usually include stiffness, weakness, grinding, and clicking with movement and functional limitation of the affected arm. Patients with inflammatory arthritis may specifically report morning stiffness that improves throughout the day and swelling around the shoulder.
In all patients with glenohumeral arthritis, physical examination will demonstrate decreased active motion and crepitus, and there may be generalized atrophy of the shoulder girdle muscles secondary to disuse. Other physical findings are more specific to the disease process.
The basic minimal radiographs for shoulder arthritis should include an anteroposterior (AP) view in the scapular plane in both internal and external rotation and an axillary view. The major indication for using CT is to quantitate posterior glenoid erosion, most often seen in either primary or secondary OA. CT can also assist in evaluating glenoid bone stock, central erosion, and version.
At present, MRI is the preferred imaging method in the setting of inflammatory arthritis. It is accurate and noninvasive and may provide additional information regarding intra-articular pathology. Moreover, MRI is helpful in quantifying cuff tear size, retraction, muscle atrophy, and fatty degeneration, which may be helpful in preoperative planning. MRI is most useful in inflammatory arthritides and RCTA.
Specific Arthritides Affecting the Shoulder
Osteoarthritis (OA)
OA is the most common ailment affecting human joints. Most people have some pathologic changes in their weight-bearing joints by age 40, and about 80% of people will have radiographic evidence of OA by age 55. In general, patients with OA of the shoulder joint are younger and more active than patients with lower extremity arthritis. This is particularly true when the arthritis is related to instability or trauma. Although many data exist regarding the epidemiology of OA in general, very little, if any, relates specifically to the glenohumeral joint.
When searching for causes of OA, two major hypotheses surface. One emphasizes the role of physical forces causing failure of articular cartilage. The other hypothesis implicates a failure of the regulation between degradation and repair of articular cartilage. The common theme between these two theories is eventual cartilage breakdown. Other well-documented factors that have been associated with the development of OA include aging, trauma, and genetic factors. Primary OA of the shoulder is likely to have a similar etiology and pathogenesis as other joints in the body. Although not typically a weight-bearing joint, the muscles about the shoulder can generate significant forces across the joint.
Physical examination of patients with OA reveals a symmetrical restriction of both active and passive motions, with a greater loss of external rotation compared with internal rotation secondary to anterior soft tissue contractures. There may be a slight prominence of the coracoid process and loss of normal shoulder contour due to a posteriorly subluxated humeral head in the setting of posterior glenoid wear. Localized posterior joint line tenderness is also common.
The cardinal radiographic features of glenohumeral OA ( Fig. 109-1 ) are asymmetrical joint-space narrowing, subchondral sclerosis, subchondral cyst formation, and osteophyte formation. Osteophyte formation is commonly seen on the inferior aspect of the humeral head and neck. The axillary view is better than the AP view for evaluating glenohumeral joint-space narrowing and can often show humeral head flattening that is not always appreciated on the AP view. The axillary view can also give a rough estimate of posterior glenoid wear and humeral head subluxation.
Unless there are contraindications (relative or absolute), TSA is generally the standard surgical treatment for glenohumeral arthritis.
Rheumatoid Arthritis
Rheumatoid arthritis is a chronic, progressive inflammatory disease that affects multiple organ systems, including the musculoskeletal system. Although its etiology is not clearly defined, there are data to suggest an antigen-driven mechanism, which results in activation of immune pathways to cause tissue destruction, especially in and around synovial joints. There are probably multiple stimuli that can trigger the cascades of inflammatory response, some of which may be infectious, cross-reactivity, and autoimmunity. This constellation may help explain the wide variations in clinical presentation and the severity of involvement of the disease in different individuals.
The incidence of RA has been reported to be between 20 and 40 per 100,000 white adults, with a prevalence rate of 0.5% to 2%. There is a twofold to fourfold higher frequency in women. The disease prevalence also increases with age. It is believed that there is a genetic predisposition to the development of RA because there is an increased frequency of the disease among first-degree relatives. The prevalence of RA in a sibling of someone who has RA is four to eight times higher than the prevalence in the general population.
The clinical hallmark of RA is morning joint stiffness and polyarticular arthritis. The shoulders are not commonly symptomatic early in the inflammatory disease process, with only 4% of rheumatoid patients initially presenting with shoulder symptoms. However, with progression of the disease, as many as 91% of patients report shoulder symptoms. When the glenohumeral joint is involved, it is often bilateral and is usually associated with deformities of the hand and elbow. The rheumatoid process may affect the entire shoulder girdle, including the bursae, tendons, and all four articulations of the shoulder.
Examination of a rheumatoid shoulder is likely to reveal boggy synovitis, generalized atrophy, and decreased active and passive ranges of motion. In contrast to OA, the loss of active motion in RA is often greater than the loss of passive motion. Because of a higher prevalence of dysfunctional or torn rotator cuffs, there may also be weakness and spinatus atrophy.
The radiographic features of a rheumatoid shoulder parallel those of any joint affected by RA. There is regional osteopenia, symmetrical joint-space narrowing, and juxta-articular erosions. These erosions are best seen at the synovial reflection on the superior aspect of the humeral head. Osteophytes are not a prominent feature, but may be present. Central glenoid erosion may also be present on the AP view, seen as medialization of the glenoid joint surface as far as the base of the coracoid process and beyond. Additionally, in the case of rotator cuff insufficiency, the AP view will help determine superior migration of the humerus, which contributes to superior glenoid erosion. The axillary view is the best way to estimate joint-space narrowing as well as medial erosion of the glenoid surface with respect to the coracoid process ( Fig. 109-2A ). The extent of humeral head deformity associated with juxta-articular erosions is best evaluated with the axillary view and can be verified on MRI ( Fig. 109-2B ).
Surgical management of a rheumatoid shoulder depends on the stage of disease. For early disease, patients may benefit from joint debridement, bursectomy, and synovectomy. For later stage disease, hemiarthroplasty is often indicated because of significant bone loss or proximal humeral migration associated with rotator cuff dysfunction. However, when glenoid bone stock is adequate and the humeral head can be centered on the glenoid by a functional cuff, TSA provides pain relief superior to that with hemiarthroplasty.
RCTA
The clinical features of RCTA have been described in the literature since the 19th century; however, its pathogenesis remains elusive. Two main theories have been proposed to explain this distinct clinical entity of severe glenohumeral joint destruction that occurs in association with a chronic massive rotator cuff defect. One theory points to mechanical and nutritional factors as being causative and the other implicates crystal deposition as the inciting factor.
In 1981, McCarty and colleagues introduced the term Milwaukee shoulder to describe four patients with glenohumeral degenerative joint disease and rotator cuff defects whose joint fluid contained active collagenase, neutral proteinase, and hydroxyapatite crystals. These authors postulated that the syndrome begins with capsular, synovial, or cartilage damage, which in turn precipitates hydroxyapatite crystal deposition. The crystals are then phagocytized by macrophage-like synoviocytes. Phagocytosis of the crystals stimulates the synoviocytes to release collagenase and protease that attack all the periarticular tissues, including articular cartilage, the rotator cuff, and adjacent soft tissues. The tissue damage leads to further crystal deposition and perpetuates the cycle of joint destruction. In a more recent study, Antoniou and colleagues showed a significant relationship between the presence of crystals and glenohumeral arthritis with massive rotator cuff tears. However, it is not clear which developed first, the massive cuff defect and abnormal joint mechanics that cause the crystals to appear in the synovial fluid or the deposition of apatite crystals that generate cytokines that lead to a massive tear. Regardless of the sequence, the presence of apatite crystals in synovial fluid leads to the production of inflammatory mediators, which is detrimental to the glenohumeral joint.
In 1983, Neer and colleagues put forth the concept that mechanical and nutritional factors lead to RCTA. They postulated that a small percentage of untreated, chronic, full-thickness cuff tears progress to RCTA. The mechanical factors cited are gross instability of the humeral head, proximal migration against the coracoacromial arch, and rupture or dislocation of the long head of the biceps, resulting in further impingement and instability. Nutritional factors included decreased perfusion of nutrients into the articular cartilage because of leakage of synovial fluid from the joint. In addition, disuse of the joint alters water and glycosaminoglycan concentration of the articular cartilage causing softening and collapse. These authors believed that the combination of instability, inactivity and disuse, proximal humeral migration, and poor nutrition ultimately lead to subchondral bone collapse on both the humeral head and glenoid.
Regardless of the exact pathogenesis, RCTA is characterized by rotator cuff insufficiency, degenerative changes of the glenohumeral joint, superior migration of the humeral head, and recurrent (often hemorrhagic) effusions. The most significant physical finding in RTCA is the lack of or limited active elevation of the shoulder ( Fig. 109-3 ). This loss of motion is not only related to the rotator cuff deficiency, but also to the glenohumeral incongruity that resulted from the high-riding humeral head. There is marked atrophy of the supra- and infraspinatus muscles, and patients may also have recurrent swelling (i.e., Codman’s “fluid sign”). In the setting of an incompetent coracoacromial arch as a static humeral head restraint, patients will have superior escape of the humeral head and “pseudoparalysis” of the arm.
Typically, radiographs show osteopenia, proximal humeral head migration, narrowing or obliteration of the acromiohumeral space, acromion erosions, and superior glenoid bone loss ( Fig. 109-4 ). Humeral head collapse, osteophytes, cyst formation, and subchondral sclerosis may also be seen. The axillary view is useful for evaluating glenoid erosion and medial migration. In addition, anterior subluxation on the axillary view suggests anterosuperior escape.
Surgical management of RCTA has mainly entailed hemiarthroplasty with an anatomic, slightly oversized or hooded humeral component. More recently, the reverse shoulder arthroplasty has emerged as a promising procedure and may even have a larger role in the near future as more experience is gained.
Management
Once all nonoperative management strategies have been exhausted, there are several surgical options available to patients with glenohumeral arthritis. In general, the surgical armamentarium includes arthroscopic joint debridement, with or without capsular release; humeral hemiarthroplasty, with or without interpositional arthroplasty of the glenoid; TSA ; and reverse shoulder arthroplasty. Arthrodesis has a limited role in the treatment of glenohumeral OA; however, discussion of this topic is beyond the focus of this chapter.
Debridement and Capsular Release
In active, high-demand, young patients (usually younger than age 40) with mild to moderate glenohumeral arthritis, joint debridement can be a useful procedure for pain relief. A nonconcentric or incongruent joint is a relative contraindication to debridement because the results have been poor. Although the debridement can be done by open technique, most are performed arthroscopically. Furthermore, arthroscopy can be both diagnostic and therapeutic for early-stage arthritis, especially in cases in which there are small focal lesions that are not easily seen by imaging studies.
Surgical Technique
Shoulder arthroscopy is performed in the beach-chair or lateral position. Standard posterior viewing and anterior working portals are used. After diagnostic arthroscopy, chondral lesions are debrided of loose fragments until a stable edge is obtained. Any degenerative or frayed labrum is also debrided to a stable rim with a shaver. In the presence of substantial stiffness and the absence of severe bone deformity, capsular release may increase postoperative range of motion. Release of the rotator interval and anterior capsule down to the 4-o’clock position is achieved with an electrocautery probe. This is an important step to gain external rotation. Further release of the axillary pouch and posterior capsule can also be done with an arthroscopic punch, depending on the restriction in preoperative motion. Loose bodies that are encountered in the axillary pouch and small inferior osteophytes off the humeral head can be removed to alleviate mechanical symptoms. At the completion of debridement of the glenohumeral joint, the arthroscope is removed and manipulation of the shoulder may be performed to ensure that adequate capsular releases have been achieved. The arthroscope is then inserted into the subacromial space through the posterior portal. A bursectomy is performed to assess the rotator cuff. As clinically warranted, subacromial decompression and/or distal clavicle resection can be done accordingly. In cases of inflammatory arthritis, a thorough synovectomy and bursectomy are essential for pain relief.
Postoperative Rehabilitation
Rehabilitation begins with passive shoulder range of motion (ROM) on the first postoperative day. The sling is discontinued within 2 to 3 days, as tolerated. Active shoulder motion is started according to pain tolerance, and patients are allowed to return to their regular recreational activities after 4 to 6 weeks.
Results
In 1986, Ogilvie-Harris and Wiley reported on 54 patients undergoing arthroscopic shoulder debridement for degenerative arthritis. Nearly two thirds of their patients with mild disease achieved a successful result, whereas only 30% of those with moderate to severe disease had a good result.
Weinstein and colleagues noted good to excellent outcomes in 80% of patients undergoing arthroscopic debridement for early glenohumeral OA. The average age of the group was 46 years, and all patients reported at least some improvement in pain. At final follow-up (12 to 63 months), only two patients had reported return of pain to preoperative levels. There was a trend toward increasing severity of articular cartilage damage and unfavorable results.
In 2002, Cameron and colleagues reported on arthroscopic debridement of grade 4 glenohumeral articular lesions and noted pain relief for at least 28 months in their patients. They found that chondral lesions greater than 2 cm 2 were predictive of ultimate failure of the debridement. Similarly, Kerr and McCarty concluded that the grade of the chondral lesion did not influence outcome scores, but patients with articular changes on both sides of the joint had lower scores.
Hemiarthroplasty
Although the procedure of choice for most patients with glenohumeral arthritis is a TSA, there are several scenarios when replacing just the humeral side of the joint (i.e., hemiarthroplasty) is indicated. First, in the young patient who has isolated humeral head arthrosis (i.e., uninvolved glenoid) and an intact rotator cuff (such as in AVN or post-traumatic arthropathy), hemiarthoplasty is a good option because it preserves glenoid bone stock. In certain instances, even when there is arthritic involvement of the glenoid, a hemiarthroplasty with concentric glenoid reaming and/or biological resurfacing may be beneficial ( Fig. 109-5 ).
Another indication for shoulder hemiarthroplasty is when the arthritis occurs in the setting of an irreparable rotator cuff tear and proximal humeral head migration. Typically, this can be seen with RCTA, OA, or RA. The use of a prosthetic glenoid component under these circumstances has been associated with premature glenoid loosening; therefore, hemiarthroplasty is a better choice. Inadequate glenoid bone stock to accept a prosthesis is yet another reason to select hemiarthroplasty over total shoulder replacement.
Surgical Technique and Postoperative Rehabilitation
Since the surgical technique and postoperative rehabilitation for a shoulder hemiarthroplasty are similar to those of a TSA, they are presented under that section.
Results
In 2006, Wirth and colleagues reported the results of 64 hemiarthroplasties done for primary or secondary glenohumeral arthritis. Fifty shoulders were followed for a minimum of 5 years (mean, 7.5 years), and the average age of the patients was 63 years. The authors included patients with nonconcentric glenoids as long as concentricity could be achieved with reaming and patients with humeral head subluxation that was correctable by soft tissue balancing. Postoperatively, these patients were found to have improvement in the pain score and the shoulder range of motion. Kaplan-Meier analysis estimated a 98.4% survival rate at 8 years. The authors concluded that in carefully selected patients, shoulder hemiarthroplasty provided good-to-excellent pain relief and functional improvement that was sustained at 5 to 10 years postoperatively.
In a prospective study, Lynch and colleagues reported on 37 consecutive patients (38 shoulders) who underwent uncemented humeral hemiarthroplasty combined with reaming of the glenoid to a diameter 2 mm larger than the prosthetic head. Of the 35 shoulders that were followed for 2 years or longer, 26 had primary and 4 secondary OA, and 5 had capsulorrhaphy arthritis. According to patient self-assessment ratings, 32 shoulders demonstrated improved comfort and function, one demonstrated no change from the preoperative level, and two had worse function postoperatively.
Several authors presented their results of biological glenoid resurfacing and humeral head replacement as an alternative to total shoulder replacement. Krishnan and colleagues reported on 36 shoulders in which they concluded that biological resurfacing of the glenoid can provide pain relief similar to TSA and recommended Achilles tendon allograft as their material of choice for this procedure. Nicholson and colleagues concluded that glenoid resurfacing with lateral meniscus allograft was not perfect but did provide significant pain relief, increased range of motion, and patient satisfaction in the short term.
TSA
When deciding whether to use a glenoid component in shoulder arthroplasty for arthritis, the surgeon must individualize each case and weigh the risks and benefits of possible improved pain relief versus early glenoid loosening. Nonconstrained humeral and glenoid prostheses are the devices of choice for glenohumeral arthritis with an intact (or reparable), functional rotator cuff. Most arthroplasty systems use a stemmed humeral component in conjunction with a polyethylene glenoid component. However, humeral head resurfacing without an intramedullary stem has proponents, particularly when the glenoid is not being resurfaced. In addition, there is a variety of options for glenoid replacement, including all-polyethylene designs, metal-backed designs, and hybrid designs with metal peg sleeves but no metal backing. There are also options with regard to articular conformity and constraint, in which less conforming radii of curvature yield more physiologic translations and exhibit lower loosening scores than conforming designs. In general, most surgeons use modular humeral components with humeral head offset options and an all-polyethylene cemented glenoid component with some degree of articular mismatch.
Surgical Technique
There are general principles that are applicable to all types of arthritides when arthroplasty is performed for the glenohumeral joint. Some principles are more relevant to specific pathologies seen in the particular form of the arthritis. For example, because of the associated incidence of proximal humeral migration and irreparable rotator cuff insufficiency, coracoacromial arch preservation is more germane in cases of RA and RCTA than in primary OA. The most important principle of patient positioning is to provide adequate access to the humeral shaft during reaming and humeral stem insertion. This requires that the patient be in the beach-chair position with the thorax and pelvis laterally on the operating table so the entire shoulder and arm are unsupported by the table. The arm may then be maximally adducted, extended, and externally rotated to provide unobstructed instrumentation of the intramedullary canal.
Exposure.
An extended deltopectoral approach is used whether the procedure is a hemiarthroplasty or TSA. The skin incision begins at the coracoid process and extends inferolaterally toward the deltoid tuberosity. The interval between the deltoid and pectoralis major is identified and dissected superiorly to the clavicle and inferiorly to the inferior margin of the pectoralis major tendon. The cephalic vein is preserved and may be taken laterally with the deltoid or medially with the pectoralis major. The upper 1.0 to 1.5 cm of the pectoralis major tendon may be released from the humerus for added exposure or correction of severe internal rotation contractures.
The conjoined tendon of the coracobrachialis and short head of the biceps brachii is identified deep to the deltopectoral groove. The clavipectoral fascia is incised lateral to the conjoined tendon. This incision is extended proximally to the coracoacromial ligament, which can be preserved in all cases. The rotator cuff is then inspected. If a full-thickness rotator cuff tear is identified, the surgeon needs to assess whether it is reparable. In most cases of primary or post-traumatic OA, the cuff is intact or can be repaired. In all cases of RCTA and many cases of RA, rotator cuff integrity cannot be restored adequately. The subscapularis tendon is exposed by retracting the conjoined tendon medially. The anterior humeral circumflex vessels are coagulated or ligated, and the axillary nerve is identified and protected throughout the remainder of the case. In addition, the musculocutaneous nerve may enter the posterior surface of the conjoined tendon as close as 1.5 to 2.0 cm distal to the tip of the coracoid. Under these circumstances, excessive traction on the conjoined tendon should be avoided.
The method of subscapularis incision depends on the extent of subscapularis and anterior capsular contracture. If preoperative passive external rotation with the arm at the side is greater than 10 degrees, the subscapularis is incised 1.5 to 2.0 cm medial to its insertion on the lesser tuberosity, or a lesser tuberosity osteotomy is performed. After appropriate capsular release, the subscapularis may be repaired anatomically, either tendon to tendon or via suture osteosynthesis of the lesser tuberosity osteotomy. When preoperative passive external rotation is between 10 degrees and −30 degrees, additional subscapularis length is needed for external rotation. Under these circumstances, the subscapularis is released directly from its insertion on the lesser tuberosity to ensure maximal length. At the time of closure, the subscapularis is reinserted at the level of the humeral osteotomy site. Every 1 cm of medial advancement yields approximately 20 to 30 degrees of external rotation. In the rare case of severe internal rotation contractures (i.e., passive external of less than −30 degrees), subscapularis Z -lengthening may be required. This can be accomplished by direct release of the subscapularis from the lesser tuberosity, followed by separation of the subscapularis from the underlying anterior capsule. After separating these two structures, the anterior capsule is then released from the glenoid, thereby creating a medially based subscapularis flap and a laterally based capsular flap that can be sutured in a lengthened position at the time of closure. However, subscapularis Z -lengthening is difficult and may compromise the strength of the subscapularis repair.
Humeral Preparation.
After taking down the subscapularis and capsule, the humeral head is dislocated by simultaneously adducting, extending, and externally rotating the arm. Humeral osteophytes are removed to define the anatomic neck. The humeral osteotomy can be performed in one of two ways. In the first method, the osteotomy can be performed by following the native boundary of the humeral anatomic neck. Theoretically, this technique ensures that the humeral cut reproduces the native humeral retroversion and neck-shaft angle for that particular patient. However, identification of the native anatomic neck can be difficult when the humeral head is deformed. The second method uses a mechanical cutting guide at a predetermined “average” neck-shaft angle. These guides can be intramedullary or extramedullary. Retroversion can be determined using the known average relationship between the distal humeral epicondylar axis and the plane of the articular surface (i.e., 30 degrees of retroversion). The goal of the osteotomy is to permit anatomic placement of the prosthetic head on the cut surface of the humerus.
Once the humeral osteotomy has been performed, the resected head is used for sizing on the back table. The humeral canal is reamed using sequentially larger reamers. In the presence of hard, necrotic bone within the humeral metaphysis (i.e., AVN), initial passage of the reamer can be difficult. In this instance, it is advisable to first drill a hole in the metaphysis as large as the initial reamer to minimize hoop stress on the proximal humeral metaphysis. After adequate drilling, sequential reamers can be passed as usual. An appropriately sized broach is then used to prepare the proximal metaphysis by cutting out channels for the fins of the prosthesis. The broach is left in place to protect the humeral metaphysis during posterior retraction that is required for glenoid exposure. Alternatively, the glenoid can be prepared after the humeral osteotomy but before humeral intramedullary preparation.
A retractor is placed between the humerus and the glenoid to posteriorly displace the humeral metaphysis. The glenoid is inspected, and a decision is made with regard to concentric glenoid reaming or resurfacing. If the native glenoid is to remain and hemiarthroplasty is the choice procedure, the need for concentric glenoid reaming is assessed. Once the glenoid has been concentrically reamed, the next step is soft tissue balancing and trialing of the humeral head component (see the following).
Biologic Glenoid Resurfacing.
If the decision is for biological resurfacing, then preparation of the glenoid is as follows. The labrum is preserved for graft fixation. Any remaining glenoid cartilage is removed with a motorized reamer and reaming is continued until neutral version is achieved (concentric reaming). Drill holes can be placed in the subchondral surface of the glenoid to create a bleeding bed for the biological graft adherence (see Fig. 109-5A ). Absorbable anchors with nonabsorbable sutures are placed at the 12-, 3-, 6-, and 9-o’clock positions on the periphery of the glenoid. The sutures are later used for securing the graft. Alternatively, the biological graft can be sutured to the retained labrum.
Next the biological graft material is prepared. Although several materials can be used for this purpose, including Achilles tendon, meniscal, and human dermis allograft, the general concept is the same: to create an oval dish shape that resembles the glenoid surface. The thickness of the graft material should be approximately 6 to 8 mm, which can be achieved by folding the flat or thin graft material onto itself several times. Sutures are placed in the periphery of the graft to prevent sliding between the layers. For the meniscal allograft, the anterior and posterior horns are sewn together to create the oval. The graft is now inset onto the previously prepared glenoid surface by first passing all sutures from the anchors through the graft using horizontal mattress stitches. Once all sutures are passed, the graft is slid onto the glenoid and the sutures tied. Further fixation can be achieved by suturing the graft to the labrum between the anchors (see Fig. 109-5B ).
The next step is soft tissue balancing and trialing of the humeral head component (see the following).
Prosthetic Glenoid Component.
If adequate bone is available, the rotator cuff is intact and functional, and the patient’s age and activity level are appropriate, glenoid resurfacing with a polyethylene component is preferred. To prepare for the glenoid component, the labrum is circumferentially excised, including the biceps anchor. The long head of the biceps is tenodesed in all cases of shoulder replacement. In cases of greater than 25% posterior subluxation, release of the posterior capsule should be avoided.
The glenoid is prepared with a motorized reamer, correcting the glenoid version to neutral position (perpendicular to the plane of the scapula) as needed by eccentric reaming. The asymmetrical glenoid reaming limit is 0.5 to 1.0 cm. Beyond this degree of reaming, the remaining glenoid bone may be insufficient to safely anchor glenoid component. Therefore, the preoperative CT scan should be reviewed carefully to determine the degree of correction that is possible with reaming alone. If complete correction does not seem possible, a decision must be made to either accept incomplete correction or bone graft the glenoid. The glenoid surface is then prepared to accept either a pegged or keeled component and the component is placed. Although both cemented and cementless designs exist, the most commonly used components are all polyethylene and are cemented into place.
Soft Tissue Balancing and Trialing.
Regardless of whether a glenoid component is implanted, soft tissue balancing is an important step in shoulder arthroplasty. Appropriate tension in the capsule and rotator cuff ensures maximal ROM and stability. Soft tissue tension is assessed by placing a trial humeral head on the broach or the trial stem. A humeral head is selected that approximates the size of the resected native humeral head. With the joint reduced, the humeral head is translated posteriorly. Appropriate soft tissue balance is achieved when the humeral head subluxates approximately 50% of its diameter. In addition, the subscapularis should reach the proposed repair site with enough laxity to allow a minimum of 30 to 40 degrees of external rotation. This may require circumferential release of the subscapularis and excision of the anterior capsule. If the posterior capsule is too lax, a larger humeral head can be placed. However, if the larger head compromises subscapularis length, a posterior capsular shift is performed and the smaller head size is used. This capsulorraphy can be accomplished from the anterior approach “through the joint” with the trial prosthetic humeral head removed. Once a humeral head size has been selected, the trial implant is removed. The final humeral component can be fixed to the humerus using either cemented or cementless techniques.
Closure.
The technique of subscapularis repair depends on how the subscapularis was taken down. If the tendon was incised medial to its insertion, anatomic tendon-to-tendon repair of the subscapularis is performed. Our preference is a lesser tuberosity osteotomy, and this can be repaired anatomically with interfragmentary sutures in addition to rotator interval closure and a suture passed from the neck of the prosthesis through the bone–tendon junction. If the tendon was released directly from the lesser tuberosity, it is reattached through drill holes at the osteotomy site. If Z- lengthening of the subscapularis is planned, then the medially based subscapularis flap is sutured to the laterally based capsular flap in a lengthened position. The subcutaneous tissue and skin are closed in standard fashion over a closed-suction drainage system.
Postoperative Rehabilitation
The rehabilitation program after a shoulder arthroplasty should be individualized according to the patient’s goals, motivation, and physical ability. Those patients with good preoperative rotator cuff function and bone quality can enroll in the standard program, whereas patients with poor preoperative rotator cuff function are placed in a limited goals program. A general scheme of postoperative rehabilitation is outlined in the following.
Phase I.
Rehabilitation begins the first postoperative day with patient education, where they are informed to expect swelling and discoloration and instructed in the use of ice and modalities for edema control. Patients can use their extremity for waist level activities and bring their hand to the mouth with the arm adducted but are to avoid lifting, carrying, pushing, pulling, and leaning on the operated side. Pendulum exercises, supine passive forward elevation, and external rotation are initiated ( Fig. 109-6 ). Patients in the limited goals category can achieve forward flexion by the table slide technique, typically after a period of immobilization or rest. The exercises are performed four to six times daily and are continued until full passive ROM is achieved.
