Image Quiz

Suprapubic Pain Following Strenuous Physical Activity (continued)

Answer: Osteomyelitis of the pubis.

Fig. 1

Fig. 1 Pelvic radiograph showing sclerosis and cortical irregularity of the right pubic ramus. Osteopenia and cortical reabsorption of the left pubic ramus is also noted.

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Fig. 2

Fig. 2 Technetium-99m bone scan demonstrates increased uptake in the symphysis pubis and the left pubic ramus.

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Fig. 3

Fig. 3 An axial computed tomography scan through the symphysis pubis demonstrates the same findings with greater detail. Osteopenia with patchy bone reabsorption of the left pubic ramus as well as sclerosis and patchy cortical reabsorption of the right pubic ramus are well delineated. Soft-tissue swelling overlying the symphysis pubis is also noted.

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The needle aspiration from the left pubic ramus performed prior to antibiotic treatment yielded purulent fluid. A gram stain revealed numerous gram-positive cocci and polymorphonuclear cells. Bacterial culture yielded a pure heavy growth of methicillin-sensitive Staphylococcus epidermidis. Repeated blood cultures were negative. The patient was treated with intravenous cloxacillin for six weeks, with resolution of the pain and fever and resumption of physical activity. The patient was free of symptoms at the one-year follow-up examination.

Discussion

We found eighteen reported cases of pubic osteomyelitis in athletes, including our patient, in a review of the literature. A summary of the clinical data is provided in the electronic Appendix of the original case report¹. Seventeen cases occurred in men. The average age (and standard deviation) was 25 ± 10 years (range, twelve to forty-eight years). All patients were active athletes who participated in strenuous physical activity. However, a specific traumatic event was noted for only two of the eighteen patients. In addition, only three patients had specific skin lesions that may have been a port for bacteremia.

The major clinical symptom is pain in the groin or adjacent areas that radiates to the thigh. Limitation of motion is common, and local tenderness and swelling may occur. A high temperature is usually noted. An elevated erythrocyte sedimentation rate and leukocytosis, although common, are not always evident.

In most of the eighteen patients, the diagnosis was delayed. The average time from the start of symptoms to diagnosis was thirteen days (range, one to thirty days). Changes in plain radiographs of the pubic bone usually appear only several weeks after the clinical presentation of osteomyelitis and therefore are not reliable in making the diagnosis. Typical changes include pubic rarefaction and osteolysis. Sclerosis may appear later. A technetium bone scan shows increased uptake and may facilitate an earlier diagnosis. In three patients, the diagnosis was made only after aspiration and culture.

Blood cultures may be positive; however, in patients with a highly suspicious case, early bone aspiration or biopsy will facilitate the diagnosis. In most of the cases reviewed, the infectious agent was identified (see Appendix). The most common pathogen was Staphylococcus aureus, which was identified in cultures of blood or local aspiration.

The main differential diagnosis of pubic osteomyelitis is osteitis pubis. Osteitis pubis is a painful, noninfectious, self-limited inflammatory condition of the pubic bone associated mainly with genitourinary surgery, but it also occurs following minor trauma or as a manifestation of overuse in athletes. Whereas the initial clinical symptoms of the two entities may be similar, the presence of fever and progressive clinical deterioration favors an infectious process and emphasizes the need for repeated cultures.

The cornerstone of treatment is antibiotic therapy. In the cases reviewed, the duration of treatment varied from four weeks to six months. Six weeks of antibiotic treatment typically resulted in a good clinical response without complications. Surgical treatment should be considered in patients with a complicated course that does not respond to antibiotic treatment.

Two other groups at risk for the development of pubic osteomyelitis are intravenous drug abusers and patients undergoing genitourinary surgery. The clinical presentation, contributing factors for the development of osteomyelitis, the pathogens, and the treatment seem to be distinct for the three groups. The clinical symptoms and signs, in particular a high fever, are almost always present in athletes, but they are frequently absent in patients who have development of pubic osteomyelitis after genitourinary surgery. In athletes, minor skin abrasion allowing bacteremia with seeding to the pubic bone is the putative reason that Staphylococcus aureus is the predominant pathogen. In intravenous drug abusers, the most common pathogen is Pseudomonas aeruginosa, associated with hematogenous seeding. In patients after genitourinary surgery, the infection usually follows some technical complication of the procedure and the pathogens, gram-negative bacteria, stem from contamination of the surgical wound. The therapeutic approach is also different among the groups. In athletes and drug abusers, antibiotics are usually sufficient, whereas patients who have had surgery frequently require some form of surgical intervention in order to minimize complications.

It is still unclear why athletes are at risk for the development of this rare condition. This entity commonly occurs in specific athletic endeavors, such as football or running, that involve strenuous physical exercise and may produce excessive stress to the pelvis. In addition, it has been suggested that the immune system in athletes may be compromised during strenuous exercise, which perhaps increases their susceptibility to transient bacteremia caused by minor skin trauma; however, this issue is debatable. Finally, a preexisting subclinical osteitis pubis may make the athletes locally susceptible to osteomyelitis. In our patient, Staphylococcus epidermidis grew on a culture of fluid from the bone aspiration. To our knowledge, as of the time of publication of the original case report (May 2004), Staphylococcus epidermidis has not been previously reported as a cause of pubic osteomyelitis. Repeated local irritation of the chronic Leishmania skin lesions in our patient could have served as a port of entry and predisposed the patient to transient bacteremia.

In conclusion, pubic osteomyelitis should be suspected in athletic individuals with sudden groin pain and fever. The pathogenesis is obscure and is possibly due to local trauma of the pubic bone caused by stress combined with minor skin trauma causing seeding of the bacteria. The clinical diagnosis depends on a high index of suspicion. Radiographic changes are delayed; early findings may be seen in bone scans. The diagnosis should be established by blood culture or needle aspiration of the pubic bone. Treatment with intravenous antibiotics should be started early and continued for six weeks, with a high expectation that the infection will resolve.

Reference

1. Meirovitz A, Gotsman I, Lilling M, Bogot NR, Fridlender Z, Wolf DG. Osteomyelitis of the pubis after strenuous exercise. A case report and review of the literature. J Bone Joint Surg Am. 2004;86:1057-60.