Correlating pre-operative MRI measurements of metatarsal Osteomyelitis with surgical clean margins reveals the need for a one centimeter resection margin

Surgical techniques for Bone Biopsy in Diabetic Foot Infection, and association between results and treatment duration

Surgery is an important part of the management of patients diagnosed with DFO. It consists in some selected patients, to remove all or part of the infected bone(s) or even to amputate all or part of the foot. Despite the use of sophisticated imaging techniques, it is however difficult to remove all the infected tissue while respecting the principles of an economical surgery. Bone biopsy performed at the margins of the resection permits to identify residual osteomyelitis and to adjust the post-surgical antibiotic treatment. Some recent studies have reported the way to perform bone margin biopsies and have assessed the impact of the bone results on the patient's outcome. However, the real impact of a residual osteomyelitis on the risk of recurrent DFO is still debated and questions regarding the interpretation of the results remain to be solved. Similarly, the consequences in terms of choice and duration of the antimicrobial treatment to use in case of positive bone margin are not clearly established.

Utility of Culturing Marginal Bone in Patients Undergoing Lower Limb Amputation for Infection

Guidelines suggest culturing clinically uninfected bone at the margin after surgical resection for osteomyelitis, but little published evidence supports this procedure. To investigate whether culturing marginal bone after completing resection of infected bone affected antibiotic use or further surgical intervention, we collected data on sequential patients undergoing amputation for a foot infection at our tertiary care hospital between January 2014 and May 2015. We recorded patient age, sex, presence of diabetes mellitus, level of amputation, whether marginal bone was sent for culture, microbiology of any marginal bone specimens, type and duration of antibiotic therapy, and any further surgical resection. Among 132 patients, the mean age was 71.9 years, 103 (78.0%) were male, and 79 (59.8%) had diabetes. Treating surgeons sent marginal bone in 58 (43.9%) of these patients, 50 (86.2%) of which were culture positive. Patients with a positive bone culture were significantly more likely to undergo further surgical intervention (20.0% vs 6.1%, p = .047). For patients with diabetes, compared with those without, surgeons did not send marginal bone for culture more often (46% vs 42%, p = .72), nor did they undertake further surgical interventions more frequently (13.4% vs 10.1%, p = .89). Our results suggest that the clinicians used the marginal bone culture findings to make clinical decisions but do not clarify if there is a benefit to performing this procedure. Although patients whose proximal bone specimens were culture positive were more likely to undergo a surgical intervention, the reasons for, and benefit of, this additional surgery were unclear.

Analysis of proximal bone margins in diabetic foot osteomyelitis by conventional culture, DNA sequencing and microscopy

Multiple approaches were employed to detect pathogens from bone margins associated with Diabetic Foot Osteomyelitis (DFO). Intra-operative bone specimens of 14 consecutive subjects with suspected DFO were collected over a six-month study period from Liverpool Hospital. Infected bone and a proximal bone margins presumed to be 'clean/non-infected' were collected. Bone material was subjected to conventional culture, DNA sequencing and microscopy. In total, eight of 14 (57%) proximal bone margins had no growth by conventional culture but were identified in all proximal bone specimens by DNA sequencing. Proximal margins had lower median total microbial counts than infected specimens, but these differences were not statistically significant. Pathogens identified by sequencing in infected specimens were identified in proximal margins and the microbiomes were similar (ANOSIM = 0.02, p = 0.59). Using a combination of SEM and/or PNA-FISH, we visualized the presence of microorganisms in infected bone specimens and their corresponding proximal margins of seven patients (50%) with DFO. We identify that bacteria can still reside in what seems to be proximal 'clean' margins. The significance and implications of clinical outcomes requires further analysis from a larger sample size that incorporates differences in surgical and post-operative approaches, correlating any outcomes back to culture-sequence findings.

Added value of MRI to X-ray in guiding the extent of surgical resection in diabetic forefoot osteomyelitis: a review of pathologically proven, surgically treated cases

OBJECTIVE

This study retrospectively evaluated the added value of MRI over X-ray in guiding the extent of amputation in a cohort of patients with surgically treated, pathologically proven osteomyelitis.

MATERIALS AND METHODS

A database search revealed 32 cases of pathology-proven diabetic forefoot osteomyelitis between 2006 and 2016, in which X-ray, MRI, and surgery occurred within 30 days. Data collection included extent of osteomyelitis reported on imaging and extent of subsequent amputation using a point system. Added value of MRI over X-ray in guiding surgical resection was stated if the X-ray was negative, MRI was positive, and there was MRI-surgical concordance; if both modalities were positive, X-ray was discordant whereas the MRI was concordant; or if MRI detected an abscess. Two-tailed Fisher's exact test compared proportions.

RESULTS

In 9 cases that were positive on both modalities, MRI identified an average of 1.2 additional bone segments of disease. There was surgical agreement with X-ray in 3 out of 31 cases (9.7%, 95%CI 0-20.1) and with MRI in 17 out of 31 cases (55%, 37.3-72.4; p < 0.0001). There was an added value of MRI over X-ray in guiding surgical treatment in 64.5% of cases (95% CI 47.7%-81.4%). MRI added value in 5 out of 9 X-rays positive for osteomyelitis and in 15 out of 22 negative (p value was not significant).

CONCLUSION

Magnetic resonance imaging demonstrated added value over X-ray in guiding surgical management in both X-ray-negative and -positive cases. Although multiple factors are involved in determining the degree of surgical excision, MRI is a clinically useful component of the diagnostic algorithm in patients who undergo surgical treatment.