Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine
-
Proc Inst Mech Eng H · Sep 2020
Biomechanical analysis of transverse acetabular fracture fixation in the elderly via the posterior versus the anterior approach with and without a total hip arthroplasty.
This study provides the first biomechanical comparison of the fixation constructs that can be created to treat transverse acetabular fractures when using the "gold-standard" posterior versus the anterior approach with and without a total hip arthroplasty in the elderly. Synthetic hemipelvises partially simulating osteoporosis (n = 24) were osteotomized to create a transverse acetabular fracture and then repaired using plates/screws, lag screws, and total hip arthroplasty acetabular components in one of four ways: posterior approach (n = 6), posterior approach plus a total hip arthroplasty acetabular component (n = 6), anterior approach (n = 6), and anterior approach plus a total hip arthroplasty acetabular component (n = 6). All specimens were biomechanically tested. ⋯ Adding a total hip arthroplasty acetabular component increased ultimate mechanical failure load for posterior (2904.4 vs. 3652.3 N, p = 0.005) and anterior (3204.9 vs. 4396.0 N, p = 0.000) approaches. Adding a total hip arthroplasty acetabular component also substantially reduced interfragmentary sliding for posterior (3.08 vs. 0.50 mm, p = 0.002) and anterior (2.17 vs. 0.29 mm, p = 0.024) approaches. Consequently, the anterior approach with a total hip arthroplasty may provide the best biomechanical stability for elderly patients, since this fixation group had the highest mechanical failure load and least interfragmentary sliding, while providing equivalent stiffness, clinical failure load, and gapping compared to other surgical options.
-
Proc Inst Mech Eng H · Dec 2019
Use of virtual reality for pre-surgical planning in separation of conjoined twins: A case report.
We describe the use of virtual reality technology for surgical planning in the successful separation of thoracopagus conjoined twins. Three-dimensional models were created from computed tomography angiograms to simulate the patient's anatomy on a virtual stereoscopic display. ⋯ The virtual stereoscopic display was critical for the surgical team to successfully separate the twins and provides a useful case study for the use of virtual reality technology in surgical planning. Both twins survived the operation and were subsequently discharged from the hospital.
-
Proc Inst Mech Eng H · Sep 2019
Stability of femoral neck fracture fixation: A finite element analysis.
Femoral neck fractures represent a relatively uncommon injury in the non-elderly population often resulting from high-energy trauma. Clinical outcome in these patients can be improved by optimizing surgical procedures and selecting appropriate fixation methods. The aim of this study was to develop a numerical fracture model to investigate the influence of critical mechanical factors on the stability of fixation methods for femoral neck fractures. ⋯ Considering a consolidated fracture and full weight-bearing load case, average displacements of fracture fragments were obtained of about 1.5, 3 and 70 µm for dynamic hip screw with de-rotational screw, proximal femoral locking plate and cannulated screws methods, respectively. In terms of interfragmentary movements at the fracture site, outcomes of this study demonstrated that, in agreement with our previous experimental research, the dynamic hip screw with de-rotational screw implant is a more effective choice than cannulated screws and proximal femoral locking plate techniques for vertical femoral neck fractures in young patients. Thus, one may conclude that the use of dynamic hip screw with de-rotational screw, particularly during the early stages of bone healing, could provide suitable mechanical environments that facilitate direct bone formation and shorter healing times.
-
The intervertebral disc exhibits a complex inelastic response characterized by relaxation, hysteresis during cyclic loading and rate dependency. All these inelastic phenomena depend on osmotic interactions between disc tissues and their surrounding chemical environment. Coupling between osmotic and inelastic effects is not fully understood, so this article aimed to study the influence of chemical conditions on the inelastic behaviour of the intervertebral disc in response to different modes of loading. ⋯ Analysis of variance showed that saline concentration significantly influenced inelastic effects in tension and especially in compression (p < 0.05), but not in torsion. Opposite effects were seen in tension and compression. An interpretation of the underlying osmo-inelastic mechanisms is proposed in which two sources of inelastic effects are identified, that is, extracellular matrix rearrangements and fluid exchange created by osmosis.
-
Proc Inst Mech Eng H · Mar 2019
Comparative StudyBiomechanical comparison of screw-based zones of a spatial subchondral support plate for proximal humerus fractures.
Stabilisation of proximal humerus fractures remains a surgical challenge. Spatial subchondral support (S3) plate promises to overcome common complications associated with conventional proximal humerus plates. This study compared the biomechanical performance of S3 plate with a fixed-angle hybrid blade (Equinoxe Fx) plate and a conventional fixed-angle locking plate (PHILOS). ⋯ Stability of humeri treated with S3 plate depends on screws' number, orientation and location. Varus stiffness of S3 plate construct (10.54 N/mm) was higher than that of PHILOS (6.61 N/mm) and Fx (7.59 N/mm) plate constructs. We attribute this to S3 plates' thicker cross section, the 135° inclination of its screws with respect to the humeral shaft and the availability of pegs for subchondral support.