The Journal of Diabetic Foot Complications Transmetatarsal amputation in an at-risk diabetic population: a retrospective study Authors: Merribeth Bruntz, DPM, MS* 1,2, Heather Young, MD 3,4, Robert W. Belknap, MD 3,4, Timothy C. Jenkins, MD 3,4, Connie S. Price, MD 3,4 The Journal of Diabetic Foot Complications, 2014; Volume 6, Issue 3, No. 3, Pages 72-77 All rights reserved. Abstract: Key words: Diabetic Comorbidities, Osteomyelitis, Peripheral Artery Disease, Prosthesis, Transmetatarsal Amputation This study evaluated the success rate of Transmetatarsal Amputations (TMAs) performed on patients with diabetes in a safety-net hospital system. We conducted a retrospective study of diabetic patients who underwent TMAs between 2004 and 2012. All patients were diagnosed with either osteomyelitis or peripheral vascular disease. The same surgeon performed all amputations using the same method. The patients with peripheral vascular disease were revascularized prior to amputation, and all patients in the study received antimicrobial therapy based upon bone biopsy and infection at the surgical margin. In all cases comorbidities, social history, hemoglobin A1c, and access to prosthesis were evaluated. Sixty patients underwent TMAs. Eight of these patients had a below-knee amputation (BKA) for an overall success rate of 86.7%, with an average healing time of 4.3 months. There was significant risk of BKA if the patient did not acquire a toe filler prosthesis (p-value < 0.01) or had coronary artery disease (p-value < 0.01). Risk of subsequent BKA was not statistically significant when compared to other comorbidities (i.e., end-stage renal disease, hypertension), social history (i.e., smoking, alcohol abuse, drug abuse) and hemoglobin A1c. Based upon these findings we conclude that the transmetatarsal amputation can be successful in at-risk patients with diabetes if there is both a commitment to several months of post-operative healing and if a toe filler prosthesis is acquired. Corresponding author * Merribeth Bruntz, DPM, MS 777 Bannock Street Denver, Colorado 80204 Email: merribeth.bruntz@dhha.org INTRODUCTION Transmetatarsal Amputation (TMA) is a procedure used for limb salvage in diabetic patients who have substantial tissue loss or an infection in the toes or distal metatarsals. This procedure is likely underutilized because of challenges with predicting healing. Several studies have shown that patients whose amputations healed early and remained ambulatory were unlikely to require additional amputations. This suggests amputations should be pursued in patients with good rehabilitation potential. 3,6 Using appropriate footwear postoperatively is a significant predictor of healing. 4 The literature has historically reported a range of healing rates. In the classic paper describing the TMA for diabetic patients, McKittrick et al. reported a healing rate of 72%. 5 From a literature review of published healing Affiliations 1. Department of Orthopedic Surgery, Denver Health Medical Center, Denver, Colorado 2. Department of Orthopedic Surgery, University of Colorado Denver, Aurora, Colorado 3. Department of Medicine and Division of Infectious Diseases, Denver Health Medical Center, Denver, Colorado 4. Department of Medicine and Division of Infectious Diseases, University of Colorado Denver, Aurora, Colorado rates between 1977 and 2005, Nguyen et al. reported ranges between 43% and 78%. 6 More recently, published literature states healing rates ranging between 44% and 91.6%. These rates are shown in Table 1. 1,3,4,6,7,10 Table 1. Published healing rates of transmetatarsal amputation Year Healing Rate (Percent) Number of Patients Author 2006 44 52 Anthony et al. 1 2006 57 33 Nguyen et al. 6 2006 57.4 101 Pollard et al. 8 2009 64.7 68 Younger et al. 10 2011 53 57 Landry et al. 3 2012 91.6 12 McCallum et al. 4 2013 73.6 1,205 O Brien et al. 7 72
The Journal of Diabetic Foot Complications, 2014; Volume 6, Issue 3, No. 3, Pages 72-77 Significant predictors of failure include poor blood glucose control, tobacco smoking for greater than 20 years, dialysis-dependent renal failure, need for further debridement, nonindependent living, and the need for preoperative revascularization. 3,6,10 The purpose of this study was to describe our experience with TMAs over a 9-year period and evaluate factors associated with poor outcomes. MATERIALS AND METHODS Study Design and Population This study was a retrospective review of 60 consecutive patients with diabetes who underwent TMAs between 2004 and 2012. Merribeth Bruntz, DPM, MS, affiliated with the Denver Health Medical Center, a Level 1 Trauma Center and public safety-net hospital serving the metropolitan Denver area, performed the surgical procedure. All patients were diagnosed with either osteomyelitis, peripheral vascular disease, or both. Standard Treatment Protocol All patients in the study received antimicrobial therapy based upon bone biopsy and infection at the surgical margin. Intravenous or oral antibiotics with substantial bone penetration was utilized. Patients with evidence of osteomyelitis at the resection margin were treated with antibiotics for six weeks, and patients without evidence of osteomyelitis at the resection margin received two weeks of antibiotics. Patients without palpable pedal pulses underwent vascular studies. If necessary, patients were revascularized prior to TMA using endovascular or surgical bypass techniques. Variables of Interest and Statistical Analysis For all cases the patient s comorbidities (i.e., hypertension, coronary artery disease, end-stage renal disease), social history (i.e., smoking, alcohol abuse, drug abuse), hemoglobin A1c, and access to prosthesis were evaluated. TMA failure was defined as progression to BKA. Descriptive statistics were used to summarize data and clinical outcomes. Associations between TMA success and independent variables were analyzed using Analysis of Variance and Fisher exact tests. The study was approved by the Colorado Multiple Institutional Review Board. Operative Procedure The TMA procedure was performed using a fishmouth incision placed just proximal to the nonviable soft tissue (Figure 1). In general, the dorsal and plantar transverse incisions were made with a longer plantar flap; however, if there was extensive plantar soft tissue damage then the flaps were closer to the same length. If there was a plantar wound, then a V-to-T flap closure was used. Occasionally, soft tissue damage required the rotation of the dorsal/plantar flap medially or laterally (Figure 2). Figure 1. A TMA incision. Figure 2. A rotational flap closure. 73
The Journal of Diabetic Foot Complications, 2014; Volume 6, Issue 3, No. 3, Pages 72-77 Transverse bone cuts of all metatarsals were made along the shafts, just distal to the bases maintaining the natural parabola of the forefoot (Figure 3). All remaining tendons were excised, and the wound was pulse lavaged using 3-6 liters of saline mixed with bacitracin. The tourniquet was then deflated, and all bleeding vessels were cauterized. A strip of iodoform packing was placed across the bone stumps and extended out of the incision to act as a drain (Figure 4). This remained in place for 3-6 days post-operatively when the first dressing change was performed. The wound was closed using absorbable deep and subcutaneous sutures, as well as with nonabsorbable suture to close the skin. Subcutaneous closure consisted of a running suture technique, and cutaneous closure was achieved with a simple suture technique. Postoperative Course All patients were placed in a walking boot that extended just distal to the knee. They were instructed to wear the boot at all times when ambulating. If it became evident that the patient might not be wearing the boot for ambulation, then they were placed in a nonremovable totalcontact cast that was changed weekly. The dressings were changed weekly with suture removal at 3-4 weeks (Figure 5). Upon healing, the patients remained in the walking boot until diabetic shoes with a toe filler to accommodate the amputation were fabricated. These were high-top shoes with a rocker-bottom sole which reduced the force on the amputation stump during propulsion (Figure 6). Figure 3. Bone cut through metatarsals. Figure 5. A healed TMA. Figure 4. A closure with an iodoform drain. Figure 6. Diabetic shoes with a toe filler to accommodate a TMA. 74
The Journal of Diabetic Foot Complications, 2014; Volume 6, Issue 3, No. 3, Pages 72-77 RESULTS Table 2. Demographic data N Male 47 (78.3%) Female 13 (21.7%) Osteomyelitis 49 (81.7%) PVD 11 (18.3%) Table 3. Clinical characteristics Mean (Range) Age 55 (37-81) Month of Follow-up 23.3 (1-80) Months Healing 4.3 (1-18) HgbA1c 8.5 (4.8-16.8) Table 4. Comparisons between successful and unsuccessful TMAs Successful TMA Unsuccessful TMA (Range and (Range and Percent) Percent) p-value Average Age 55 (37-81) 59 (44-77) 0.155 Ave Months F/U 25.4 (1,80) 9.6 (2, 33) 0.257 Acquired Prosthesis 46 (97.9%) 1 (2.1%) 0.001 Smoking History 39 (84.8%) 7 (15.2%) 0.667 EtOH Abuse 22 (88%) 3 (12%) 1.000 Drug Abuse 14 (93.3%) 1 (6.7%) 0.666 CAD 25 (75.8%) 8 (24.2%) 0.006 ESRD 15 (83.3%) 3 (16.7%) 0.686 8.3 (4.8-13.4) 9.9 (5.1-16.8) 0.264 Ave HgbA1c 75
The Journal of Diabetic Foot Complications, 2014; Volume 6, Issue 3, No. 3, Pages 72-77 DISCUSSION 1 2,4 76
The Journal of Diabetic Foot Complications, 2014; Volume 6, Issue 3, No. 3, Pages 72-77 DISCUSSION (cont.) References 1. Anthony T, Roberts J, et al. Transmetatrsal amputation: assessment of current selection criteria. Am J Surg. 2006;192:e8-e11. 2. Fontaine JL, Brown D, et al. New and recurrent ulcerations after percutaneous achilles tendon lengthening in transmetatarsal amputation. J Foot & Ankle Surg. 2008;47(3):225-229. 3. Landry GJ, Silverman DA, et al. Predictors of healing and functional outcome following transmetatarsal amputations. Arch Surg. 2011;146:1005-1009. 4. McCallum R, Tagoe M. Transmetatarsal amputation: a case series and review of the literature. J Aging Res. 2012;79218:1-6. 5. McKittrick LS, McKittrick JB, et al. Transmetatarsal amputation for infection or gangrene in patients with diabetes mellitus. Ann of Surg. 1949;130(4):826-840. 6. Nguyen TH, Gordon IL, et al. Transmetatrsal amputation: predictors of healing. Am Surg. 2006;72(10):973-977. 7. O Brien PJ, Cox MW, et al. Risk factors for early failure of surgical amputations: an analysis of 8,878 isolated lower extremity amputation procedures. J Am Coll Surg. 2013;216(4):836-842. 8. Pollard J, Hamilton GA, et al. Mortality and morbidity after transmetatarsal amputation: retrospective review of 101 cases. J Foot & Ankle Surg. 2006;45(2):91-97. 9. Thomas SRYW, Perkins JMT, et al. Transmetatarsal amputation: an 8-year experience. Ann R Coll Surg Engl. 2001;83:164-166. 10. Younger ASE, Awwad MA, et al. Risk factors for failure of transmetatarsal amputation in diabetic patients: a cohort study. Foot Ankle Int. 2009;30:1177-1182. 77