Infection, how it inhibits wound healing, and that it is an integral part of evaluating a patient with a non-healing wound, have been discussed in previous posts; however, there are some distinct infections that warrant further discussion.  Osteomyelitis, or infection of the bone, derives its name from osteo (meaning bone) and myelo (relating to myeloid tissue in the bone marrow). Osteomyelitis can be acute (diagnosed within 2 weeks of onset of signs and symptoms) or chronic (reoccurs in a patient with a history of osteomyelitis).[1] It can be further classified as hematogenous (caused by pathogens carried in the blood stream from sites of infection in other parts of the body) or exogenous (caused by pathogens that enter from outside the body, eg, from open fractures, surgical sites, and penetrating wounds). Acute hematogenous osteomyelitis occurs most frequently in children, especially those with sickle cell disease, and affects the long bones (femur, tibia, humerus, pelvis). Chronic osteomyelitis occurs most frequently in adults, especially those with diabetes, open fractures, implanted hardware, and vascular insufficiency. In the diabetic population with vascular insufficiency, the bones most affected are the small bones in the foot.¹

The sequence of osteomyelitis involves the following stages: Stage 1—the pathogen, usually Staphylococcus aureus, invades the medullary canal of the bone and becomes a nidus of infection; Stage 2, the acute phase—the infection results in pus from the inflammatory process and spreads to the vascular channels in the bone; and Stage 3, the chronic phase—the inflammatory process obliterates the vascular channels with subsequent ischemia and bone necrosis.¹ The pieces of necrotic bone may separate from the healthy bone (termed sequestrum), and can occur on any infected bone.

        Clinical Presentation

Acute hematogenous osteomyelitis usually presents with focal tenderness, swelling, or difficulty with weight-bearing activities, especially in the lower extremities. The clinical diagnosis is supported by acute inflammatory serum studies (including white blood cell count, erythrocyte sedimentation rate, C-reactive protein) along with radiologic studies.¹ MRI studies and technetium 99m bone scans are very sensitive, and a definitive diagnosis is made with biopsies. Although x-rays may not be definitive until 10–14 days after onset of symptoms, they will show edema in the adjacent soft tissue and areas of sclerosis.

Osteomyelitis in adult patients usually occurs with surgical reduction and internal fixation of fractures, prosthetic devices, open fractures, and soft tissue infections. The symptoms will usually occur about 1 month after introduction of the pathogen, and include low-grade fever, drainage, pain, and loss of bone stability. The overlying soft tissue may be edematous (resulting in a “sausage toe” appearance, erythematous, or necrotic. (See attached photo)  Exposed bone in the wound bed, a positive “probe-to-bone” test, or a wound more than 2 cm² on the foot of a patient with diabetes is very suspicious of underlying osteomyelitis.[2]  Bone biopsy confirms osteomyelitis and identifies the specific pathogen; however, increased leukocyte count, ESR greater than 70 mm/h, and plain films provide 89% sensitivity and 88% specificity.[3]

        Medical Management

The mainstay of treatment for all cases of osteomyelitis is identification of the pathogen, through biopsy or surgical debridement, and specific antibiotics for at least 6 weeks. For patients with diabetes, antibiotics for up to 12 weeks have been recommended.¹ Surgical debridement is advised for a wound that includes tissue invasion, abscess, open purulence, fistulae, or acute osteomyelitis, all of which could lead to sepsis. Amputation, foot reconstruction, osteotomies, or musculocutaneous flaps may be required in severe cases of chronic osteomyelitis. A thorough vascular assessment is vital for any patient with a history of peripheral vascular disease.

        Wound Management

Wounds are treated with standard moist wound care both before and after surgical debridement, which may include topical antimicrobial dressings, absorbent dressings until drainage abates, and off-loading strategies for any plantar foot wound. Negative pressure wound therapy may be used for post-surgical open wounds with adequate vascular supply, and hyperbaric oxygen therapy may be helpful for patients with diabetes and marginal blood supply.

[1] Groll ME, Woods T, Salcido R.  Osteomyelitis: a context for wound management.  Adv Skin Wound Care.  2018;31(6):253-262.

[2] Lavery LA, Armstrong DG, Peters EJ, Lipsky BA. Probe-to-bone test for diagnosing diabetic foot osteomyelitis: reliable or relic?  Diabetes Care. 2007;30(2):270-274.

[3] Goldman RJ, Delaeon JM, Popescu A, Salcido R.  Chronic wounds. In: Cifu DX, ed. Braddom’s Physical Medicine and Rehabilitation. 5^th edition. New York, NY: Elsevier Health Sciences. 2015.