Transmetatarsal Amputation Using Calcium Sulfate Antibiotic-Loaded Pellets in Diabetic Patients:

Development of a Novel Model for the Assessment of Dead-Space Management in Soft Tissue

Following extensive surgical debridement in the treatment of infection, a “dead space” can result following surgical closure that can fill with hematoma, an environment conducive to bacterial growth. The eradication of dead space is essential in order to prevent recurrent infection. This study describes a novel small animal model to investigate dead-space management in muscle tissue. Two absorbable test materials were implanted in each animal; beads of calcium sulfate alone, and beads loaded with vancomycin and tobramycin. In-life blood samples and radiographs were taken from each animal following implantation. Animals were sacrificed at 1, 7, 21, 42, and 63 days post-operatively (n = 4), and implant sites were analysed by micro-computed tomography, histology and immunohistochemistry. Complete resorption was confirmed radiographically at 3 weeks post-implantation. Histologically, the host tissue response to both materials was identical, and subsequent healing at the implant sites was observed with no dead space remaining. Vancomycin was not detected in blood serum. However, peak tobramycin levels were detected in all animals at 6 hours post-implantation with no detectable levels in any animals at 72 hours post implantation. Serological inflammatory cytokine expression for IL-6, TNF-α and IL-1β indicated no unusual inflammatory response to the implanted materials or surgical procedure. The model was found to be convenient and effective for the assessment of implant materials for management of dead space in muscle tissue. The two materials tested were effective in resolving the surgically created dead space, and did not elicit any unexpected adverse host response.

Risk factors for failure of transmetatarsal amputation in diabetic patients: a cohort study

INTRODUCTION

This study analysed the factors affecting wound healing of a transmetatarsal amputation (TMA) in patients with diabetes.

MATERIALS AND METHODS

Twenty-one patients who failed a TMA and were revised to transtibial amputation (TTA) within the first year were compared with a matched cohort of 21 successful TMA's. The factors compared included demographics, systemic issues, and local conditions in the foot. Chi-square comparisons were used for group data, and Analysis of Variance (ANOVA) for numeric data.

RESULTS

Blood glucose control as measured by HbA1c was the most important single factor predicting the success of TMA. Need for debridement after TMA was also found to be a significant predictor of failure of TMA. There was a trend towards duration of ulcer prior to TMA and smoking being significant. All other variables, including vascular status or renal failure were not significantly different between the two groups.

CONCLUSION

The primary factor determining the success of a TMA was the quality of glucose control. The results of this study can be extrapolated to diabetic patients undergoing other types of surgery, with preoperative diabetic control as measured by HbA1c being an important determinant of the outcome of surgery. As a result of this study we currently do not perform any elective, trauma or emergency surgery on diabetic patients with an HbA1c of over 8 unless the need for surgery is to save life or limb.

Outcome of transmetatarsal amputations in diabetics using antibiotic beads

BACKGROUND

Diabetic patients with transmetatarsal amputation (TMA) for chronic forefoot ulceration or necrosis are at high risk for postoperative skin breakdown and subsequent amputation. Locally applied antibiotics may reduce the revision rate and improve the outcome.

MATERIAL AND METHODS

In a retrospective comparative study, 60 diabetic patients (65 feet) with forefoot ulceration or necrosis were treated with TMA by three surgeons in three hospitals. In the "beads group'' (46 patients, 49 feet) TMA was combined with local application of bioabsorbable, tobramycin impregnated calcium sulphate beads (OsteoSet-T beads, Wright Medical, Memphis, TN) as a single-stage procedure. The remaining 16 patients had transmetatarsal amputation without beads at the surgeon's discretion and acted as a control group. For all patients, time to healing, length of hospital stay, number of revisions for wound breakdown and conversions to a higher-level amputation were retrospectively reviewed. Of the 60 patients 17 had died and three were lost to followup, leaving 40 patients available for latest followup at 29 months. The Foot & Ankle Outcome Score, Foot Function index, SF-36, and Comorbidity score were recorded.

RESULTS

The revision rate for wound breakdown after TMA was 8.2% (4/49) in the beads group, and 25% (4/16) in the control group (p<0.05). At latest followup, 27% (13/49) in the beads group, and 25% (4/16) in the control group had to be converted to transtibial amputation. Patients in the beads group scored worse for activities of daily living in the FAOS and SF-36 (p < 0.05), and demonstrated more health problems in the Comorbidity scores (not significant), indicating sicker individuals in the beads group.

CONCLUSION

Bioabsorbable calcium sulphate antibiotic beads may be a useful addition for TMA for patients with non-healing diabetic ulcerations of the forefoot. The single-stage procedure could have a significant impact on the management of diabetic forefoot ulcerations by preventing additional hospital stays, improving the patient's quality of life and minimizing cost.