Septic Arthritis of the Shoulder: Treating an Atypical Case

Thomas L. Pommering, DO; Randall R. Wroble, MD

In Brief: A wrestler developed septic arthritis in his glenohumeral joint. His case is unusual because septic arthritis most commonly affects weight-bearing joints and is usually seen in the very young, the very old, and people who are immunocompromised. Other risk factors include concurrent infection, endocarditis, invasive procedures, and intra-articular corticosteroid injection. Disease onset is usually insidious. Nonspecific findings include restricted motion, mild pain, and joint effusions; systemic signs of toxicity are often mild or absent. Diagnosis is confirmed with joint aspiration and analysis and culture of synovial fluids; definitive treatment often involves arthroscopic debridement followed by 2 to 6 weeks of antibiotics.

Septic arthritis in the shoulder is uncommon in otherwise healthy, active adults. Usually, other factors contribute, like chronic disease resulting in immune compromise, advanced age, local tissue abnormalities such as ongoing local infections, or the use of intra-articular corticosteroid injections.

Diagnosis is typically delayed because of minimal symptoms at onset and nonspecific laboratory findings. In addition, septic arthritis—also called pyarthrosis—often mimics other common shoulder injuries related to overuse or athletic injury. We present the case of a young adult wrestler who had shoulder pyarthrosis that initially appeared to be a rotator cuff tear.

Case Report

A 19-year-old college wrestler had a history of dull, diffuse shoulder pain in his dominant right arm that was exacerbated with overhead positions. He could recall no shoulder trauma or injury. His pain subsided briefly after conservative treatment by his athletic trainer with stretching, ultrasound, and ibuprofen.

Two weeks after the initial onset, however, his pain returned after a wrestling match. At that point the pain became more constant, increasing in severity and sometimes occurring at night, and conservative therapy did not alleviate it. In addition, he experienced shoulder weakness and pain in all directions of motion as well as some symptoms of general malaise.

Except for having asthma, for which he was being treated with oral prednisone, the patient had an unremarkable medical history. He had no history of corticosteroid injections. His wrestling requirements included daily practice and weight loss of approximately 15 lb off his preseason weight to achieve his weight class.

Initial examination by a physician 4 weeks after the onset of his symptoms showed diffuse swelling and tenderness about the shoulder without atrophy. He exhibited painful range of motion, both passively and actively, in all directions. He also had significant weakness with abduction, forward flexion, and external and internal rotation.

Radiographs revealed inferior subluxation of the humeral head on the anteroposterior view (figure 1a), but the humeral head appeared to be in the glenoid cavity on axillary view. Rotator cuff disease was considered. Because of the severity of his symptoms, however, a magnetic resonance image (MRI) was obtained the same day and revealed a large effusion in the glenohumeral joint accompanied by a subtle finding of capsulosynovial thickening without evidence of rotator cuff disease (figures 1b and 1c).

The patient returned the next day for therapeutic aspiration of 30 mL of yellow, cloudy fluid from his glenohumeral joint. Synovial fluid analysis revealed protein at 5.9 g/dL, glucose, 48 mg/dL; red blood cell (RBC) count, 2,000/microliter; white blood cell (WBC) count and differential, 7,000/microliter, 97% neutrophils; good mucin clot; and no crystals. Gram stain showed many WBCs and RBCs but no organisms. Culture later revealed methicillin-sensitive Staphylococcus aureus.

Serum laboratory studies were relatively nonspecific: RBCs, 4,080,000/microliter; WBCs 10,000/microliter, with 71% granulocytes and 19% lymphocytes; hemoglobin, 11.9 g/dL; and hematocrit, 35.4%. Plasma glucose was 94 mg/dL. Electrolytes and renal function tests were within normal limits. Reexamination by an infectious disease consultant did not reveal a cardiac murmur or peripheral stigmata of endocarditis.

When the patient was taken to surgery within 48 hours, a yellow-brown, cloudy fluid was initially expressed from the joint during arthroscopy. The patient subsequently underwent extensive arthroscopic debridement of the shoulder with synovectomy and irrigation of the joint with 9 L of Ringer's lactate containing 80 mg of gentamicin per liter. He was discharged after an uneventful 48-hour hospital stay.

The patient was placed on 2 g per day of intravenous ceftriaxone sodium during 4 weeks of home antibiotic therapy, followed by another 2 weeks of oral cefadroxil 500 mg twice per day. He also underwent physical therapy to regain his strength and range of motion.

The patient progressed rapidly through his outpatient rehabilitation program and was able to return to competitive wrestling in 8 weeks. At 8 months follow-up, he remained asymptomatic with no expected permanent sequelae. He exhibited full range of motion and approximately 90% strength compared with the unaffected side. Plain radiographs of his shoulder revealed a normal relationship between the humeral head and the glenoid (figure 2).

Septic Arthritis: Common and Uncommon Aspects

This case presents several noteworthy points. Some of them are typical for the presentation of septic arthritis in the shoulder, while others are unusual.

At-risk groups. Septic arthritis of the glenohumeral joint is uncommon, accounting for 3% to 12% of septic arthritis of all joints (1-4). In comparison, 61% to 79% of all septic arthritides are found in weight-bearing joints. Our patient's case was unusual in that glenohumeral pyarthrosis is rarely an isolated condition, especially in young, healthy adults (1,5). It is usually seen in specific populations: the very young (6,7); the very old (1,7,8); and patients who are immunocompromised because of other diseases such as neoplastic, hematologic, rheumatologic, renal, or endocrine conditions, or by heavy alcohol or drug use (1,5,7-11).

Local tissue abnormalities such as concurrent infections can also be important (5-7,9). Endocarditis, trauma, prosthetic joint replacement, arthroscopy, or other invasive procedures affecting the shoulder have also been implicated as risk factors (7,9,12).

Another risk factor for developing septic arthritis in the shoulder is previous intra-articular corticosteroid injection (1,5,7,12). In fact, it has been noted that infections in the shoulder were infrequent before the use of such injections (13). At the time of disease onset, our patient was taking oral corticosteroids that might have contributed to some degree of immunocompromise, but we could find no reports citing oral or intramuscular corticosteroids as a sole cause of septic arthritis in the shoulder.

Although reports conflict, intense exercise has been shown to compromise immunity to some degree (14-17). In addition, malnutrition and weight loss have also been shown to impair immune function (18-21). Both of these factors would apply to our patient.

Signs and symptoms. As with our patient, the onset of septic arthritis is usually insidious, leading to delayed diagnosis (1,5,11,22). Nonspecific findings include restricted motion that is usually only mildly painful. Although they are sometimes difficult to detect depending on the patient's size, joint effusions of the shoulder are always present.

Systemic signs of toxicity, such as fever, chills, anorexia, and lethargy, are often mild, if present at all (1,5,7,10,11). In the case of our patient, systemic symptoms may have been suppressed by the oral corticosteroids.

Diagnostic tests. Signs of infection such as leukocytosis and positive blood cultures are often unreliable (1,5,10,11). The erythrocyte sedimentation rate, however, is almost always elevated (1). (The erythrocyte sedimentation rate was not measured in our patient.) As in our patient, septic arthritis of the shoulder often masquerades as rotator cuff disease, which prompted ordering the MRI (13,22).

Radiographic findings can include inferior subluxation of the humeral head, soft-tissue swelling, joint effusion, demineralization, loss of joint space, superior subluxation, and subchondral osseous erosion. Plain radiographs, however, may be normal (7,22,23). Further diagnostic imaging may be necessary at times when the clinical diagnosis is unclear or does not fit the patient's symptoms.

Diagnosis is confirmed with joint aspiration, synovial fluid analysis, and culture. It should be noted that synovial fluid analysis can be unreliable and inconsistent with clinical findings, as it was in our patient, in whom only the neutrophil count was significant. The synovial fluid culture may provide the highest diagnostic yield (24). Staphylococcus aureus is the most common pathogenic organism, although Staphylococcus epidermidis and streptococci are also common (1,7,9,22). Haemophilus organisms, salmonellae, Neisseria gonorrhoeae, mycoplasmas, pseudomonads, Proteus species, Serratia bacteria, Escherichia coli, and Mycobacterium tuberculosis should also be kept in mind (1,5-7,9,11).

Disease management. Treatment strategies have evolved over the years. Intravenous antibiotic therapy and repeated aspirations alone are usually not effective; surgical intervention is considered essential. Arthroscopic debridement is very effective and has few complications (1,5,7,9,25). A 2- to 6-week course of intravenous antibiotic therapy is instituted following surgical intervention (7,9,24). Outcome depends on many variables, including time of diagnosis, virulence of the organism, appropriateness of treatment, and health of the patient.

When to Be Suspicious

Glenohumeral septic arthritis should always be suspected in very young or elderly patients who are immunocompromised and experience painful loss of shoulder motion possibly accompanied by vague systemic symptoms. The index of suspicion should also be raised when a healthy young person reports similar complaints that are inconsistent with physical findings or treatment response. In our case, a highly competitive, healthy young wrestler may have been predisposed to septic arthritis by being relatively immunocompromised from a combination of intense athletic exertion, weight loss with malnutrition, and systemic corticosteroids.

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Dr Pommering is a family practitioner in Pickerington, Ohio, fellowship trained in primary care sports medicine. He is a member of both the American Medical Society for Sports Medicine and the American Academy of Family Physicians. Dr Wroble is an orthopedic surgeon with SportsMedicine Grant in Columbus, Ohio. He is an editorial board member of The Physician and Sportsmedicine. Address correspondence to Thomas L. Pommering, DO, Pickerington Family Practice, Inc, 641 Hill Rd N, Pickerington, OH 43147-1293.

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