Human placental membrane as a wound cover for chronic diabetic foot ulcers: a prospective, postmarket, CLOSURE study.

OBJECTIVE: To evaluate the safety and efficacy of a chorioamniotic allograft, used as a wound cover for chronic foot ulcers, in patients with diabetes. METHODS: A multicentre, prospective, postmarket study where eligible patients received up to 11 weekly wound cover applications. Computerised planimetry was used to calculate the diabetic foot ulcer (DFU) area each week. The primary endpoint of the study was wound closure assessment. Secondary endpoints included DFU recurrence and morbidity. RESULTS: A total of 63 patients with 64 ulcers were enrolled, after successful completion of a two-week run-in period. Patients were predominantly male and had risk factors for delayed healing. Mean baseline DFU area was 3.8cm2 (standard deviation (SD): 4.8). After 12 weeks, a total of 19 (40%) DFUs had closed. Results varied by size category, 'small' (≤2.0cm2), 'medium' (>2.0-4.0 cm2), and 'large' (>4.0-25.0 cm2), with higher percentage closure in the 'small' DFU group, compared with the 'medium' and 'large' DFUs (57%, 33%, and 10%, respectively). Of those DFUs that closed, the average closure time was 6.5 weeks. There were no unanticipated adverse events. CONCLUSION: Known risk factors for healing, including DFU size, location and duration, affected the outcomes. However, the results are in line with the literature and support the use of the chorioamniotic allograft in chronic and complex cases.

Compression forces of internal and external ankle fixation devices with simulated bone resorption.

BACKGROUND: Internal and external fixation techniques have been developed to provide rigidity and stability to a fusion site such as in tibiotalocalcaneal (TTC) arthrodesis. Compression of the fusion site plays an integral role in primary bone healing, though little work has been done to quantify the compressive force values of ankle fixation devices. MATERIALS AND METHODS: Using synthetic and cadaveric bone models, a Newdeal/Integra PantaNail and DePuy VersaNail were tested as compressive intramedullary (IM) nails while an Encore True/Lok and an Ace-Fischer frame were tested as external fixators. RESULTS: The PantaNail experienced maximum compressive loads of 1898 and 1255 N in synthetic and cadaveric constructs, respectively. The VersaNail experienced max compressive loads 388 N during installation. All IM nails tested experienced decreased compressive loads after removal of the external guide and instrumentation. The external fixators were loaded to approximately 1200 N in both synthetic and cadaveric constructs. The decrease in compressive load was recorded as a function of simulated fusion site bone resorption for all devices. The IM nails experienced a 90% reduction in load with less than 1 mm of resorption, while the external fixators held 50% load for over 4 mm of resorption. These data were verified using a simple constitutive model of IM nails and external fixators. CONCLUSION: Intramedullary nails are capable of generating compression, however, are unable to provide sustained compression for any considerable amount of resorption. External fixators are inherently capable of applying and sustaining greater amounts of compression. CLINICAL RELEVANCE: Surgeons who perform TTC arthrodesis procedures should be aware of a device's ability to generate and sustain compression with respect to bone resorption.

Finite element analysis of a pseudoelastic compression-generating intramedullary ankle arthrodesis nail.

Tibio-talo-calcaneal (TTC) arthrodesis is an end-stage treatment for patients with severe degeneration of the ankle joint. This treatment consists of using an intramedullary nail (IM) to fuse the calcaneus, talus, and tibia bones together into one construct. Poor bone quality within the joint prior to surgery is common and thus the procedure has shown complications due to non-union. However, a new FDA-approved IM nail has been released that houses a nickel titanium (NiTi) rod that uses its inherent pseudoelastic material properties to apply active compression across the fusion site. Finite element analysis was performed to model the mechanical response of the NiTi within the device. A bone model was then developed based on a quantitative computed tomography (QCT) image for anatomical geometry and bone material properties. A total bone and device system was modeled to investigate the effect of bone quality change and gather load-sharing properties during gait loading. It was found that during the highest magnitude loading of gait, the load taken by the bone was more than 50% higher than the load taken by the nail. When comparing the load distribution during gait, results from this study would suggest that the device helps to prevent stress shielding by allowing a more even distribution of load between bone and nail. In conditions where bone quality may vary patient-to-patient, the model indicates that a 10% decrease in overall bone modulus (i.e. material stiffness) due to reduced bone mineral density would result in higher stresses in the nail (3.4%) and a marginal decrease in stress for the bone (0.5%). The finite element model presented in this study can be used as a quantitative tool to further understand the stress environment of both bone and device for a TTC fusion. Furthermore, the methodology presented gives insight on how to computationally program and use the unique material properties of NiTi in an active compression state useful for bone fracture healing or fusion treatments.

Demineralized bone matrix: basic science and clinical applications.

Bone grafting with demineralized bone matrix (DBM) is useful in reconstructive surgery to ultimately provide anatomic alignment, restore function, or augment/change the biomechanics of the foot and ankle. DBM should be used in conjunction with a transplant or implant displaying mechanical strength. DBM can augment cortical grafts used for bridging gaps or defects and lengthening procedures by increasing the connectivity of the structural graft with the host bone. Another useful application is providing a biologic boost to patients who have less-than-ideal physiology. Because DBM has higher concentrations of available bone morphogenic proteins, it can aid in the incorporation of other grafts. Other uses include delayed unions, nonunions, packing joints for arthrodesis, filling resected cysts, and filling gaps of debrided infected bone.

Pseudoelastic intramedullary nailing for tibio-talo-calcaneal arthrodesis.

Tibio-talo-calcaneal (TTC) arthrodesis is a procedure to treat severe ankle arthropathy by providing a pain-free and stable fusion. Intramedullary (IM) nails offer a method of internal fixation for TTC arthrodesis by providing compressive stability, as well as shear and torsional rigidity. IM nails have been developed to apply compression to the TTC complex during installation; however, current designs are highly susceptible to a loss of compression when exposed to small amounts of bone resorption and cyclic loading. Nickel titanium (NiTi) is a shape-memory alloy capable of recovering large amounts of deformation via shape-memory or pseudoelasticity. Currently, the next generation of IM nails is being developed to utilize the adaptive, pseudoelastic properties of NiTi and provide a fusion nail that is resistant to loss of compression or loosening. Specifically, the pseudoelastic IM nail contains an internal NiTi compression element that applies sustained compression during the course of fusion, analogous to external fixators.