Etiology, Diagnosis, and Nonoperative Treatment of the Arthritic Shoulder

CHAPTER PREVIEW

CHAPTER SYNOPSIS:

Glenohumeral arthritis is a painful condition with a wide spectrum of etiologies. The most common etiologies and their characteristic clinical presentations are discussed in this chapter. Keys to the appropriate evaluation of the arthritic shoulder, as well as approaches to nonoperative management, are also presented.

IMPORTANT POINTS:

1

The etiology of glenohumeral arthritis impacts treatment and outcomes, underscoring the importance of accurate diagnoses.
2

Nonoperative management is the mainstay of treatment for glenohumeral arthritis and should be, at minimum, considered in each case prior to discussion of surgical intervention.

CLINICAL/SURGICAL PEARLS:

1

Findings from a comprehensive history, physical examination, and radiographic evaluation can assist in distinguishing the major categories of glenohumeral arthritis.
2

Multidisciplinary care, particularly in rheumatoid arthritis patients, is essential to yield better outcomes and clinical monitoring of the disease progression.

CLINICAL/SURGICAL PITFALLS:

Failure to achieve a detailed history or physical examination may lead to missed diagnoses of systemic or neuromuscular etiologies.

VIDEO AVAILABLE:

Not applicable.

Shoulder arthritis is a painful condition that requires special attention across myriad specialties. Damage and degeneration of the articular cartilage surfaces of the glenoid labrum or humeral head compromise the normal smooth congruency of the joint. This often results in glenohumeral joint arthritis. Although shoulder arthritis occurs less commonly than arthritis of the hip, knee, or hands, the potential impact on function and lifestyle affirms understanding of the involved anatomy, possible etiologies, appropriate clinical evaluation, and treatment options as a master tool for musculoskeletal clinicians.

Normal function of the shoulder has been characterized by authors in terms of motion, stability, strength, and articular surface smoothness. Glenohumeral joint motion is influenced by coordinated laxity and tension of the surrounding capsule and resulting translation movements within the joint. Asymmetric tension of the capsuloligamentous structures can result in shearing moments and subsequent degeneration. The stability of the shoulder is conferred by a combination of static and dynamic restraints. Instability caused by a deficiency of any of these restraint mechanisms can lead to imbalanced joint loading and resulting wear. Shoulder strength is determined by the contracting forces of the rotator cuff muscles and the deltoid, with weakness or injuries to the musculature manifesting as abnormal function and range of motion. Finally, the smooth articular surface of a normal shoulder is provided by a synovial fluid layer within the joint that minimizes friction and allows for an appropriate shoulder arc range of motion. When there is chondral injury or loss of a space for an adequate synovial layer, resistance increases between the two surfaces, causing progressive wear and degeneration.

Thus, multiple different mechanisms, acute and chronic, can lead to shoulder arthritis ( Table 1-1 ). Among them are primary osteoarthritis, inflammatory arthritides (such as rheumatoid arthritis [RA]), posttraumatic arthritis, rotator cuff arthropathy, osteonecrosis, infection, and arthritis resulting from instability. Pinpointing the etiology of glenohumeral arthritis becomes an essential component of clinical evaluation because each one is associated with particular characteristics that affect selection of treatments as well as outcomes.

TABLE 1-1

Etiologies of Glenohumeral Arthritis and Their Relevant Clinical Features

Etiology	Clinical Features
*Primary osteoarthritis*	Women affected more than men. Elderly affected more than young people. Slow progression. Osteophyte formation and posterior glenoid wear.
*Inflammatory Arthritides/RA*	Multiple joints affected. Proximal joints affected later in disease. Effusion and local tenderness. Central glenoid wear, cystic changes and bony erosions.
*Posttraumatic Arthritis*	Secondary arthritis after trauma, fracture, or instability. Affects younger patients. Associated with soft tissue and bony abnormalities from the injury.
*Cuff-Tear Arthropathy*	Arthritis caused by cascade of events resulting from severe rotator cuff disease. Findings similar to primary arthritis with addition of rotator cuff deficiency.
*Capsularrhapy Arthropathy*	Associated with soft tissue imbalance after surgical treatment of instability, most commonly excessive capsule tightening. Deficient external rotation causes abnormal posterior forces and wear.
*Osteonecrosis*	Traumatic or nontraumatic. Multiple causes, including alcoholism and steroid use. Presents with stiffness and eventual bone collapse. MRI helpful 8 weeks or more after injury.
*Infection*	Immunocompromised host is major risk factor. Acute process. Erythema, warmth, and drainage clinical clues. Results from joint aspirate confirm diagnosis.
*Neuropathic Arthritis*	Joint destruction after loss of protective innervation, but patients still present with pain. At end stage, may mimic infection, osteonecrosis, or Milwaukee shoulder radiographically.

The clinical findings of patients with glenohumeral arthritis may overlap with signs and symptoms of other shoulder pain–invoking conditions, such as adhesive capsulitis. Furthermore, the natural history of cartilaginous injuries in the shoulder is largely unknown and even large degenerative lesions may present with only minimal discomfort and impediment of physical function. Accordingly, when a patient presents with a painful shoulder, the ability to distinguish physical exam and imaging findings specific to glenohumeral arthritis is key in order to obtain an accurate diagnosis and formulate the appropriate treatment plan.

Treatment options for glenohumeral arthritis include a spectrum of nonoperative, conservative management techniques as well as operative intervention. With the improved understanding of glenohumeral arthritis and advancements in prosthetic design, shoulder arthroplasty has gained popularity over the years. The frequency of shoulder arthroplasties increased substantially over the past decade, from approximately 10,000 in 1990 to 20,000 in 2000, with favorable repute stemming from predictable results in terms of pain relief and function. However, the decision to advance away from nonoperative management to surgical intervention is complex and a variety of patient factors must come into play. For example, in one study investigating the long-term outcomes of shoulder arthroplasty in 33 relatively young patients with a mean age of 46 years, arthroplasty provided excellent pain relief; however, the implant survival rate was only 61% at 10 years. Therefore, implementation of nonoperative treatment strategies for younger patients, patients who have not yet attempted conservative management, or individuals who are not candidates for arthroplasty is an important component of managing glenohumeral arthritis.

ETIOLOGY

Primary Osteoarthritis

Primary osteoarthritis of the glenohumeral joint involves wear-and-tear of the articular cartilage of the glenoid labrum and humeral head. The disease process is generally more common in women and in patients over the age of 60. Similar to the development of osteoarthritis in other major joints, the progression of osteoarthritis in the shoulder involves narrowing of the joint space, subchondral sclerosis, and osteophyte formation ( Fig. 1-1 ). Subchondral cystic changes may also be apparent. Complete loss of articular cartilage and bony destruction can occur at later stages. Posterior glenoid wear is characteristic of osteoarthritis, unlike the central glenoid wear typically found in patients with rheumatoid arthritis.

Patients with primary osteoarthritis typically present with the gradual development of anterior shoulder pain and stiffness over a period of months to years. Physical exam findings include local joint line tenderness, painfully restricted external rotation and abduction, and crepitation. Plain radiographs are necessary to confirm the diagnosis because similar symptoms and physical exam findings can be seen in adhesive capsulitis (“frozen shoulder”) as well.

Plain films are typically normal in patients with isolated capsule pathology, whereas cartilaginous wear, osteophytes on the inferior portion of the humeral head, sclerosis of the humeral head, and narrowing of the inferior portion of the glenohumeral articular cartilage are characteristic of osteoarthritis. As the disease progresses, large spurs may form and flattening of the humeral head may be noted as well ( Fig. 1-2 ).

Inflammatory Arthritides

The inflammatory arthritides comprise a significant etiologic category for glenohumeral arthritis. Systemic inflammatory diseases include systemic lupus erythematosus, gout, pseudogout, ankylosising spondylitis, and psoriatic arthritis, with rheumatoid arthritis serving as the classic model. The arthritis seen in inflammatory arthritides is symmetrical. Although the disease may remit in a small subpopulation, uncontrolled inflammation has the potential to progress to destruction of joints due to erosion of cartilage and bone and eventually cause deformity.

Arthritic involvement of the glenohumeral joint is not uncommon in rheumatoid patients. However, because rheumatoid arthritis typically affects distal joints first, involvement of proximal joints, such as the shoulder, tends to presents later in the disease process. A prospective study of 74 patients with RA reported that 55% of patients had developed radiographic evidence of erosive glenohumeral joint disease by their 15-year follow-up end-point. Like osteoarthritis, RA can be associated with osteophyte formation. However, central wear (versus posterior wear) is more common with rheumatoid disease, as are osteopenia, bone erosions, and subchondral cyst formation. Furthermore, whereas osteoarthritis usually involves a single joint, multiple affected joints (polyarthritis) is a clinical indication for the patient to be screened for inflammatory arthritides.

The clinical presentation of RA is marked by pain, reduced range of motion, stiffness, and muscle weakness. The initial intense synovitis that stimulates absorption of cartilage and bone by the release of cytokines results in the localized pain and swelling that may be evident on examination. Joint effusion and crepitation can also be appreciated on physical exam. Reports of morning stiffness lasting more than 1 hour reflects the severe inflammatory process and is a symptom strongly associated with RA. It is also important to note that RA can be associated with cervical spine instability and myelopathy that may cause referred pain to the acromioclavicular, subacromical, or glenohumeral joint spaces, further complicating the clinical examination.

Radiographs of the affected rheumatoid shoulder can show osteopenia, articular or juxta-articular erosions, and subchondral cyst formation. In advanced disease, central glenoid wear and humeral head elevation may be evident. A large-scale radiographic study of shoulders with rheumatoid glenohumeral arthritis reported that, in general, the shoulders of patients with RA indeed showed statistically significant symmetry and uniform destruction on plain radiographs. Advanced imaging techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI) studies, can be helpful in evaluating the extent of bone erosion and any rotator cuff pathology, and also for planning operative treatment.

Posttraumatic Arthritis

Secondary arthritis is more common than primary osteoarthritis of the shoulder. The term refers to arthritis that occurs as a result of an inciting event, including trauma, fracture, or instability. Fractures may be the result of direct trauma to the humeral head or glenoid or of trauma caused during surgical procedures, such as humeral head osteotomy. Instability leading to arthritic changes may be from untreated atraumatic subluxation or the result of a traumatic dislocation, also known as dislocation arthropathy. Though there are variations between the etiologies, posttraumatic arthritis generally presents with osseous deformities and soft tissue contractures. Accordingly, surgical management of posttraumatic arthritis is complex, and bone and soft tissue abnormalities resulting from the initial insult must be addressed to achieve the best possible outcome.

Static posterior subluxation of the humeral head has recently been reported as a possible etiology of early glenohumeral arthritis in young adults. In a review of young adult male patients with early glenohumeral arthritis (mean age of 40 years), marked static posterior subluxation and increased glenoid retroversion were found. Not amenable to surgical treatment, static posterior subluxation was postulated as a risk for the development of early glenohumeral arthritis. In another study, the incidence of preoperative arthritis was determined in 282 patients with traumatic anterior instability of the shoulder before any surgical intervention was performed. Osteoarthritis was found in radiographs in more than 10% of the patients, while CT imaging revealed arthritic changes in 31% of the population, supporting the potential of traumatic injury to cause early glenohumeral arthritis and its likelihood to be underestimated in radiographic studies.

There are also investigations of specific elite sports as risk factors for the development of early glenohumeral arthritis. A radiographic study of asymptomatic former elite tennis players with no history of prior shoulder surgery reported that the prevalence of glenohumeral osteoarthritis in the dominant shoulder was greater in this group than in sedentary controls. Gymnastics and baseball are two overhead sports that have also been implicated as risk factors for development of shoulder arthritis in younger patients.

Rotator Cuff Arthropathy

Patients with chronic, massive, or irreparable rotator cuff tears are at risk for the development of glenohumeral arthritis. Although there are circulating hypotheses as to the exact cause of arthritis after rotator cuff disease, Neer’s explanation of this phenomenon has been widely accepted. In 1983, Neer et al. applied the diagnosis of cuff-tear arthropathy to patients with radiographic evidence of humeral head collapse following the exclusion of other processes that could involve both degenerative changes of the glenohumeral joint and a tear of the rotator cuff (such as inflammatory arthritides, posttraumatic arthritis, infection, Charcot arthropathy, or metabolic disease). They proposed that following a massive tear, inactivity, leaking of synovial fluid, and instability of the humeral head all contribute to nutritional and mechanical factors that cause articular cartilage atrophy and osteoporosis of the subchondral bone. Furthermore, Neer et al. reported that massive tears allow the humeral head to displace upward, causing subacromial impingement and joint incongruity that can eventually erode the acromion, glenoid, and coracoid.

Glenohumeral arthritis resulting from rotator cuff arthropathy can present at different points in this suggested natural history, with some patients seeking medical attention before evidence of humeral head collapse has developed, and other patients presenting with very advanced loss of glenohumeral bone. Common symptoms of rotator cuff arthropathy include progressive pain and dysfunction. Physical examination, similar to primary arthritis, can demonstrate pain, crepitation, and restricted range of motion. In addition, rotator cuff weakness will be apparent. Radiographic findings span from osteophyte formation and sclerosis to superior migration of the humeral head and erosion of bony surfaces ( Fig. 1-3 ). MRI may be used to characterize the extent of the rotator cuff tear, the amount of retraction (which correlates with functional deficits), muscle atrophy, and fatty degenerative changes, all of which are important factors taken into consideration for treatment planning.