Imaging Quiz Answer: Perplexing Shin Pain
Edward G. McFarland, MD; Eva H. KrausTHE PHYSICIAN AND SPORTSMEDICINE - VOL 25 - NO. 4 - APRIL 97
The plain radiographs revealed a destructive lesion, 3 to 4 cm in length, of the anterior tibial cortex in the distal tibia (figure 3). Inside the lesion was a faint area of sclerotic bone. The CT scan showed a focally destructive lesion in the anterior tibial cortex with sclerotic bone consistent with a sequestrum (figure 4). A bone scan showed increased uptake around the lesion but no other lesions. These findings pointed to a differential diagnosis of osteomyelitis versus osteoid osteoma.
Under sterile procedures, an incision was made in the anterior aspect of the lesion. The cortex was opened with a curette, and an area of abscess with a sequestrum was revealed. A portion of this tissue was sent for frozen section, and the diagnosis of osteomyelitis was made. Cultures for aerobic, anaerobic, fungal, and tuberculous organisms were taken for microbiology. A high-speed burr was used to remove all the reactive and abnormal bone. The wound was irrigated liberally with normal saline and closed primarily.
Cultures identified the organism as Salmonella typhi. Blood and stool cultures were negative. Ampicillin was prescribed but was switched to ceftriaxone because of sensitivities and ease of administration. The patient's leg was then placed in a cast, windowed over his wound, with a toe-touch weight-bearing status. Intravenous antibiotics were continued for 6 weeks.
Radiographs at 6 weeks showed early healing of the incisional biopsy site. Twelve weeks after surgery the patient was allowed full weight bearing. He eventually returned to play as a minor league baseball pitcher with no limitations.
Shin pain is common in athletes. The most frequently reported causes are "shin splints," stress fractures, and stress reactions. Tumors and infections rarely present as shin pain in athletes (1).
In our patient, shin splints were unlikely since they are not usually associated with warmth or swelling. The physical findings did not readily distinguish his infection from a stress fracture. His symptoms were not specific, and an osteoid osteoma had to be excluded (1).
After plain radiographs revealed the bony lesion, further imaging was used to elucidate the extent of the lesion and to confirm the diagnosis. Although the patient's lesion appeared to be solitary, bone scanning helps to eliminate multifocal lesions. CT scanning is not always necessary, but assists in distinguishing cortical lesions of bone.
Hematogenous infection of long bones is uncommon in adulthood (2). When it occurs, Staphylococcus aureus is the most common pathogen (3). Salmonella is an uncommon cause of osteomyelitis (4-6); one estimate is that it causes 5% of cases (7). When salmonella is the pathogen, the patient usually has a history of salmonella infection (6,8,9), such as gastroenteritis, enteric fever, or bacteremia (8,10). With S typhi, a previous episode with gastroenteritis is the rule (9). From their intestinal habitat, the pathogens are disseminated via the bloodstream (7). This is the most common pathway for bone infection by salmonella species (5,10,11). The most common sites for salmonella infection in bone are the diaphyses of the femur, tibia, and humerus (9,10).
Although uncommon overall, salmonella osteomyelitis is common in patients with sickle cell disease or other preexisting illnesses (2,4,7,9,10,12). Bennett and Namnyak (12) reported that salmonella species occur in 71% of sickle cell patients who have osteomyelitis.
Trauma and age can also play a role in the development of bone infection. Salmonella osteomyelitis has been reported in children with closed fractures (13,14); this may be due to the different vascular anatomy in bones during childhood. Adeyokonnu and Hendrickse (2) found younger patients generally more susceptible to salmonella osteomyelitis than older patients.
Where the causative agent entered our patient's bloodstream is unknown, but the site is presumed to have been the gastrointestinal tract. Blood and stool cultures, however, were negative, indicating that the patient was not a carrier for S typhi. Identification of the pathogen was possible only by open biopsy.
The antibiotics normally used for treatment of salmonella osteomyelitis are chloramphenicol, ampicillin, and trimethoprim-sulfamethoxazole (2,10,13,15). The patient in this case was treated with 1 g of ceftriaxone twice a day because it has been reported to be a successful antibiotic for multidrug-resistant salmonella osteomyelitis (16 ).Concurrent antibiotic and surgical treatment is important for preventing recurrence of the bone infection and promoting complete healing.
Watch for the Unusual
Although this is rare, osteomyelitis can present as shin pain in athletes. Skeletal pain in athletes should be evaluated with radiographs or other scans if it does not improve with treatment. The diagnosis of salmonella infection should be considered in individuals at risk.
Dr McFarland is an assistant professor in the department of orthopaedic surgery, section of sports medicine, at Johns Hopkins University in Baltimore. Ms Kraus is a medical student at the University of Freiburg in Freiburg, Germany. Address correspondence to Edward G. McFarland, MD, Johns Hopkins University, Section of Sports Medicine, 2360 West Joppa Rd, Suite 205, Baltimore, MD 21093.
Copyright (C) 1997. The McGraw-Hill Companies. All Rights Reserved