Use of Bioabsorbable Bone Graft in Osteomyelitis Associated with Ischial Pressure Sores

Abstract

Sir: Traditional surgical principles in pressure sore management include soft-tissue débridement, removal of infected bone, and filling the dead space using local flaps. Antibiotic-impregnated methylmethacrylate beads have been used in chronic osteomyelitis to deliver antibiotics locally in high concentrations. However, once the antibiotics have leached out of the bead, the bead acts as a nidus for infection and requires removal.1 Bone graft substitutes impregnated with antibiotics have been used to replace bone defects in osteomyelitis of the long bones and spine with excellent results.2 However, their use has not been described in pressure sore–associated osteomyelitis. OsteoSet (Wright Medical Group, Inc., Arlington, Tenn.), a bioabsorbable calcium sulfate bone graft substitute, can be impregnated with antibiotics and used to fill the bony cavity.3 The concentration of antibiotics released from calcium sulfate preparations exceeds 100-fold the minimum inhibitory concentration in the first 24 hours and 10-fold the minimum inhibitory concentration for 3 to 4 days, with continued elution of the antibiotic beyond 10 days.4 New bone adheres to the reabsorbing OsteoSet and gradually fills in the defect. Obliteration of the bony dead space by bone graft substitutes reduces the need for extensive flap surgery. Our experience in three patients with ischial pressure sores and infected ischium was successful in curing osteomyelitis and closing wounds without extensive flap, and there was no occurrence of contralateral ischial pressure sores caused by traditional ischiectomy. After soft-tissue débridement, the outer cortex is opened with a dental burr to allow complete débridement of the infected cancellous bone. The remaining cortex is kept intact to provide housing for the bone graft substitute (Fig. 1). Multiple débridements may be required until the wound is clean. Then, OsteoSet antibiotic paste is molded into the bony cancellous defect within the cortical bone envelope, and layered closure of the wound is performed over a suction drain. Its placement should be deep; otherwise, subcutaneous bone formation will occur and can lead to ulceration. Culture-directed intravenous antibiotics are continued for 6 weeks.Fig. 1.: Ischial wound after soft-tissue and bony débridement shows preservation of ischial and pubic ramus bone cortex for placement of bone graft substitute antibiotic paste (above). Healed ischial area in a C7 quadriplegic patient after bone graft substitute and layered closure is seen at 42 months after surgery (below).Our first patient remained healed for 3 years after this procedure. A new area of osteomyelitis was then débrided and treated with OsteoSet. Healthy bone was noted in areas where OsteoSet had been placed initially. A second patient was recurrence free for over 3 years. Incidentally, he failed multiple conventional flap procedures for a contralateral ischial pressure sore that was treated at another institution. Our last patient underwent placement of OsteoSet with an inferior gluteal flap. Two recurrences at 3 and 5 years were managed with débridement, OsteoSet placement, and flap readvancement. The use of antibiotic-impregnated bone graft substitute is a simple and effective technique for pressure sore–associated osteomyelitis. Because recurrence rates can be as high as 69 percent after surgical management of pressure sores,5 it is common to exhaust most local flap options within a few years. Placement of a bone graft substitute obliterates the bony dead space and preserves local tissue to salvage future recurrences that are inevitable in this patient population. DISCLOSURE The authors have no financial interest to declare in relation to the content of this article. Matthias Solomon, M.B.B.S. Division of Plastic Surgery Mayo Clinic Rochester, Minn. Peyton Davis, M.B.Ch.B. Department of Emergency Medicine Oxford University Oxford, United Kingdom Nho V. Tran, M.D. Division of Plastic Surgery Mayo Clinic Rochester, Minn. Michael Rock, M.D. Department of Orthopedic Surgery Mayo Clinic Rochester, Minn.