STrain Analysis and Mapping of the Plantar Surface (STAMPS): A novel technique of plantar load analysis during gait.

Diabetic foot ulceration is driven by peripheral neuropathy, resulting in abnormal foot biomechanics and elevated plantar load. Plantar load comprises normal pressure and tangential shear stress. Currently, there are no in-shoe devices measuring both components of plantar load. The STAMPS (STrain Analysis and Mapping of the Plantar Surface) system was developed to address this and utilises digital image correlation (DIC) to determine the strain sustained by a plastically deformable insole, providing an assessment of plantar load at the foot-surface interface during gait. STAMPS was developed as a multi-layered insole, comprising a deformable mid-layer, onto which a stochastic speckle pattern film is applied. A custom-built imaging platform is used to obtain high resolution pre- and post-walking images. Images are imported into commercially available DIC software (GOM Correlate, 2020) to obtain pointwise strain data. The strain and displacement data are exported and post-processed with custom analysis routines (MATLAB, Mathworks Inc.), to obtain the resultant global and regional peak strain (SMAG), antero-posterior strain (SAP) and medio-lateral strain (SML). To validate the core technique an experimental test process used a Universal Mechanical Tester (UMT) system (UMT TriboLab, Bruker) to apply controlled vertical and tangential load regimes to the proposed multi-layer insole. A pilot study was then conducted to assess the efficacy of using the STAMPS system to measure in-shoe plantar strain in three healthy participants. Each participant walked 10 steps on the STAMPS insole using a standardised shoe. They also walked 10 m in the same shoe using a plantar pressure measurement insole (Novel Pedar®) to record peak plantar pressure (PPP) as a gold-standard comparator. The results of the experimental validation tests show that with increased normal force, at a constant shear distance, SMAG increased in a linear fashion. Furthermore, they showed that with increased shear distance, at a constant force, SMAG increased. The results of the pilot study found participant 1 demonstrated greatest SMAG in the region toes 3-5 (15.31%). The highest mean SMAG for participant 2 was at the hallux (29.31%). Participant 3 exhibited highest strain in the regions of the first and second metatarsal heads (58.85% and 41.62% respectively). Increased PPP was strongly associated with increased SMAG with a Spearman's correlation coefficient 0.673 (p < 0.0001). This study has demonstrated the efficacy of a novel method to assess plantar load across the plantar surface of the foot. Experimental testing validated the sensitivity of the method to both normal pressure and tangential shear stress. This technique was successfully incorporated into the STAMPS insole to reliably measure and quantify the cumulative degree of strain sustained by a plastically deformable insole during a period of gait, which can be used to infer plantar loading patterns. Future work will explore how these measures relate to different pathologies, such as regions at risk of diabetic foot ulceration.

Plantar shear stress in the diabetic foot: A systematic review and meta-analysis.

AIMS: Diabetic foot ulceration (DFU) is a multifactorial process involving undetected, repetitive trauma resulting in inflammation and tissue breakdown. Shear stress forms a major part of plantar load, the aim of this review is to determine whether elevated shear stress results in ulceration. METHODS: A systematic review of the Ovid Medline, EMBASE, CINAHL and Cochrane library databases was performed. Studies involving patients with diabetes who underwent plantar shear stress assessment were included. The primary outcome was plantar shear stress in patients with diabetes who had a current/previous DFU compared with those with no prior ulceration. Meta-analysis was performed comparing shear stress between those with a current or previous DFU and those without, and those with diabetes and healthy controls. RESULTS: The search strategy identified 1461 potentially relevant articles, 16 studies met the inclusion criteria, involving a total of 597 patients. Comparing shear stress between the current/previous DFU group and those without: Standardised mean difference (SMD) 0.62 (95% CI -0.01 to 1.25), in favour of greater shear stress within the DFU group, p = 0.05. Comparing shear stress between people with diabetes and healthy controls: 0.36 (95% CI -0.31 to 1.03), in favour of greater shear stress within the diabetes group, p = 0.29. CONCLUSION: This review suggests that that patients with diabetes and a history of ulceration exhibit greater shear stress than their ulcer-free counterparts. This strengthens the premise that development of systems to measure shear stress may be helpful in DFU prediction and prevention.

The Content of Pre-habilitative Interventions for Patients Undergoing Repair of Abdominal Aortic Aneurysms and Their Effect on Post-Operative Outcomes: A Systematic Review.

OBJECTIVE: Patients requiring abdominal aortic aneurysm (AAA) repair are at risk of post-operative complications due to poor pre-operative state. Pre-habilitation describes the enhancement of functional capacity and tolerance to an upcoming physiological stressor, intended to reduce those complications. The ability to provide such an intervention (physical, pharmacological, nutritional, or psychosocial) between diagnosis and surgery is a growing interest, but its role in AAA repair is unclear. This paper aimed to systematically review existing literature to better describe the effect of pre-habilitative interventions on post-operative outcomes of patients undergoing AAA repair. DATA SOURCES: EMBASE and Medline were searched from inception to October 2020. Retrieved papers, systematic reviews, and trial registries were citation tracked. REVIEW METHODS: Randomised controlled trials (RCTs) comparing post-operative outcomes for adult patients undergoing a period of pre-habilitation prior to AAA repair (open or endovascular) were eligible for inclusion. Two authors screened titles for inclusion, assessed risk of bias, and extracted data. Primary outcomes were post-operative 30 day mortality, composite endpoint of 30 day post-operative complications, hospital length of stay (LOS), and health related quality of life (HRQL) outcomes. The content of interventions was extracted and a narrative analysis of results undertaken. RESULTS: Seven RCTs with 901 patients were included (three exercise based, two pharmacological based, and two nutritional based). Risk of bias was mostly unclear or high and the clinical heterogeneity between the trials precluded data pooling for meta-analyses. The quality of intervention descriptions was highly variable. One exercise based RCT reported significantly reduced hospital LOS and another improved HRQL outcomes. Neither pharmacological nor nutritional based RCTs reported significant differences in primary outcomes. CONCLUSION: There is limited evidence to draw clinically robust conclusions about the effect of pre-habilitation on post-operative outcomes following AAA repair. Well designed RCTs, adhering to reporting standards for intervention content and trial methods, are urgently needed to establish the clinical and cost effectiveness of pre-habilitation interventions.

Preoperative Very Low-Calorie Diet Reduces Technical Difficulty During Laparoscopic Cholecystectomy in Obese Patients.

This study investigates the effectiveness of preoperative very low-calorie diet (VLCD) in laparoscopic cholecystectomy. A prospective observational study of consecutive patients undergoing laparoscopic cholecystectomy was undertaken. At the preoperative visit, all patients were advised to adhere to VLCD for 2 weeks before surgery (<800 kcal/d). Patients were judged to have complied with the VLCD if weight loss >2 kg. Technical difficulty was assessed using questionnaires. A total of 38 patients met the inclusion criteria. Difficulty of visualization and dissection of Calot's triangle in obese patients was twice that of nonobese patients (P=0.01). In 62% of procedures involving obese VLCD noncompliant patients, the surgeon experienced ≥1 area of technical difficulty, compared with 0% of procedures on obese, compliant patients (P=0.018). Difficulty of dissection of the gallbladder bed was 3 times higher in obese, noncompliant patients, compared with obese, compliant patients (P=0.07). Adherence to a 2-week preoperative VLCD may reduce technical difficulty of laparoscopic cholecystectomy in obese patients.

Listeria Infected Pseudoaneurysm of the Superficial Femoral Artery.

We present a unique case of listeria-infected pseudoaneurysm of the superficial femoral artery. Listeria monocytogenes, a gram positive, intracellular bacterium, is widespread in the environment. The manifestation of infection in humans ranges from mild gastroenteritis to life-threatening listeriosis. The incidence in the healthy population is low (0.7 per 100,000) but rises sharply in pregnancy, the immunocompromised and patients with malignancy. Listeria rarely causes mycotic aneurysm formation, with fewer than 40 cases reported in the literature. Further investigation revealed the patient to be diagnosed with a hepatocellular carcinoma. It is likely that the two pathologies were linked. Hence, we would advocate investigation for underlying malignancy in patients presenting with a mycotic aneurysm, particularly those resulting from Listeria infection.