Hybrid approach in sacral sore management with maggot debridement therapy and flap reconstruction.

Sacral sore is a common problem in patients with spinal cord injury. It leads to prolonged hospitalization and recurrent infections which might require repeated surgery to treat. Flap reconstruction allows soft tissue coverage of sacral sore under the premise of infection-free wound base. Maggot debridement therapy (MDT) has been described as an alternative non-surgical management as opposed to the traditional surgical debridement in case of infected sore, reducing number of surgeries under anaesthesia. However, MDT and surgery are not mutually exclusive. In this article we describe a hybrid approach combining MDT and flap reconstruction with multi-disciplinary effort in management of sacral sore, which accelerates wound healing and prevents morbidities, while lowering the risks associated with repeated surgical debridement at the same time.

Chicken proximal interphalangeal joint as an animal model for human finger joint prosthesis evaluation.

A group of chickens was employed as animal model for evaluation of osteointegration, stability and to a lesser extent, functional recovery potential of a newly designed human finger joint prosthesis under long term implantation. Mechanical and Histological test was conducted. Results in our study suggest that while chicken interphalangeal joint could be a potential model for evaluating surgical operation and osteointegration of human finger joint prosthesis, the effectiveness of evaluation in certain areas are far from ideal especially in functional and mechanical evaluation of the prosthesis. Nevertheless, it is suggested that chicken interphalangeal joint can still be a potential model for evaluating new human finger joint prosthesis if enough anchoring and stabilization could be provided because of the similarity in anatomical structure.

The measured mechanical properties of osteoporotic trabecular bone decline with the increment of deformation volume during micro-indentation.

PURPOSE: Osteoporosis is a critical global health issue. However, the biomechanical properties of osteoporotic trabecular bone have not been well understood due to its hierarchically complex structure mingled with accumulated microcracks. Previous studies indicated the mechanical behaviors of trabecular bone may differ with varying amounts of deformation. Therefore, this study aims to further reveal the relationship between the measured mechanical properties of osteoporotic trabecular bone and various amounts of deformation volume during micro-indentation. METHODS: Two trabecular specimens were dissected transversally and frontally from an osteoporotic lumbar vertebral (L5) cadaver and embedded into Methyl methacrylate. On each specimen, two orthogonal cuts were performed to make a right-angle, followed by five parallel slicing. On each slice, the region of interest was gridded into 16 (4 × 4) sub-regions with the size equal to the microscope field. Within each sub-region, indentations were made on a single trabecula with five different indentation depths (3, 4, 5, 6, 7 µm) to induce different deformation volume. Both the indentation hardness and modulus were computed from the indenting curve for each measurement. The results of the five slices are pooled together to represent the longitudinal and circumferential mechanical characteristics, respectively. Linear regression was performed to investigate the relationship between the measured mechanical properties and various deformation volumes. RESULTS: A total of 1055 indents were made. After eliminating outliers, 840 indents were left for data analysis with 490 indents from transversal slices and 350 indents from frontal slices. Both the hardness and modulus decreased with the increasement of indentation depths. The hardness decreased by slopes of -0.65 (R2 = 0.72, p = 0.044) and -0.869 (R2 = 0.95, p = 0.003) longitudinally and circumferentially while the modulus decreased by slopes of -0.39 (R2 = 0.82, p = 0.02) and -0.348 (R2 = 0.94, p = 0.004) longitudinally and circumferentially. CONCLUSIONS: Mechanical properties of trabecular bone measured by micro-indentation can alter with the variation of deformation volume, which reflects the nonlinear behavior of vertebra from the material perspective.

Biological Evaluation of Flexible Polyurethane/Poly l-Lactic Acid Composite Scaffold as a Potential Filler for Bone Regeneration.

Degradable bone graft substitute for large-volume bone defects is a continuously developing field in orthopedics. With the advance in biomaterial in past decades, a wide range of new materials has been investigated for their potential in this application. When compared to common biopolymers within the field such as PLA or PCL, elastomers such as polyurethane offer some unique advantages in terms of flexibility. In cases of bone defect treatments, a flexible soft filler can help to establish an intimate contact with surrounding bones to provide a stable bone-material interface for cell proliferation and ingrowth of tissue. In this study, a porous filler based on segmented polyurethane incorporated with poly l-lactic acid was synthesized by a phase inverse salt leaching method. The filler was put through in vitro and in vivo tests to evaluate its potential in acting as a bone graft substitute for critical-sized bone defects. In vitro results indicated there was a major improvement in biological response, including cell attachment, proliferation and alkaline phosphatase expression for osteoblast-like cells when seeded on the composite material compared to unmodified polyurethane. In vivo evaluation on a critical-sized defect model of New Zealand White (NZW) rabbit indicated there was bone ingrowth along the defect area with the introduction of the new filler. A tight interface formed between bone and filler, with osteogenic cells proliferating on the surface. The result suggested polyurethane/poly l-lactic acid composite is a material with the potential to act as a bone graft substitute for orthopedics application.