Increased cortical remodeling after osteotomy causes posttraumatic osteopenia

Sagittal support rather than medial cortical support matters in geriatric intertrochanteric fracture: A finite element analysis study

Hip fracture, increasing exponentially with age, is osteoporosis's most severe clinical consequence. Intertrochanteric fracture, one of the main types of hip fracture, is associated with higher mortality and morbidity. The current research hotspots lay in improving the treatment effect and optimizing the secondary stability after intertrochanteric fracture surgery. Cortex buttress reduction is a widely accepted method for treating intertrochanteric fracture by allowing the head-neck fragment to slide and rigidly contact the femoral shaft's cortex. Medial cortical support is considered a more effective option in treating young patients. However, osteo-degenerations features, including bone weakness and cortical thickness thinning, affect the performance of cortex support in geriatric intertrochanteric fracture treatment. Literature focusing on the age-specific difference in cortex performance in the fractured hip is scarce. We hypothesized that this osteo-19 degenerative feature affects the performance of cortex support in treating intertrochanteric fractures between the young and the elderly. We established twenty models for the old and the young with intertrochanteric fractures and performed static and dynamic simulations under one-legged stance and walking cycle conditions. The von Mises stress and displacement on the femur, proximal femoral nail anti-rotation (PFNA) implant, fracture plane, and the cutting volume of cancellous bone of the femur were compared. It was observed that defects in the anterior and posterior cortical bone walls significantly increase the stress on the PFNA implant, the displacement of the fracture surface, and cause a greater volume of cancellous bone to be resected. We concluded that ensuring the integrity and alignment of the anterior and posterior cortical bones is essential for elderly patients, and sagittal support is recommended. This finding suggests that the treatment method for intertrochanteric fracture may differ, considering the patient's age difference.

Osteopenia in Scaphoid Fracture: An Indicator of Good Prognosis or Is it Cause for Concern?: A Case Report

CASE

A 32-year-old man sustained a scaphoid waist fracture and was managed nonoperatively in a short-arm cast. Radiographic follow-up at 6 weeks showed marked loss of radiodensity of the whole scaphoid, although the fracture was clinically united. Patchy ossification at 3 months was followed by the complete restoration of radiodensity and trabecular pattern by 20 weeks. The patient had an uneventful and full functional recovery.

CONCLUSION

This, perhaps unreported, finding seems to be an indicator of preserved vascularity in scaphoid fractures. Further research/reporting of this radiological pattern in these fractures will help improve their understanding and management.

Time dependent loss of trabecular bone in human tibial plateau fractures

We investigated if time between injury and surgery affects cancellous bone properties in patients suffering tibial plateau fractures (TPF), in terms of structural integrity and gene expression controlling bone loss. A cohort of 29 TPF, operated 1-17 days post-injury, had biopsies from the fracture and an equivalent contralateral limb site, at surgery. Samples were assessed using micro-computed tomography and real-time RT-PCR analysis for the expression of genes known to be involved in bone remodeling and fracture healing. Significant decreases in the injured vs control side were observed for bone volume fraction (BV/TV, -13.5 ± 6.0%, p = 0.011), trabecular number (Tb.N, -10.5 ± 5.9%, p = 0.041) and trabecular thickness (Tb.Th, -4.6 ± 2.5%, p = 0.033). Changes in these parameters were more evident in patients operated 5-17 days post-injury, compared to those operated in the first 4 days post-injury. A significant negative association was found between Tb.Th (r = -0.54, p < 0.01) and BV/TV (r = -0.39, p < 0.05) in relation to time post-injury in the injured limb. Both BV/TV and Tb.Th were negatively associated with expression of key molecular markers of bone resorption, CTSK, ACP5, and the ratio of RANKL:OPG mRNA. These structure/gene expression relationships did not exist in the contralateral tibial plateau of these patients. This study demonstrated that there is a significant early time-dependent bone loss in the proximal tibia after TPF. This bone loss was significantly associated with altered expression of genes typically involved in the process of osteoclastic bone resorption but possibly also bone resorption by osteocytes. The mechanism of early bone loss in such fractures should be a subject of further investigation. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2865-2875, 2018.

Can the contra-lateral limb be used as a control with respect to analyses of bone remodelling?

Bone loss may result from remodelling initiated by implant stress protection. Quantifying remodelling requires bone density distributions which can be obtained from computed tomography scans. Pre-operative scans of large animals however are rarely possible. This study aimed to determine if the contra-lateral bone is a suitable control for the purpose of quantifying bone remodelling. CT scans of 8 pairs of ovine tibia were used to determine the likeness of left and right bones. The deviation between the outer surfaces of the bone pairs was used to quantify geometric similarity. The density differences were determined by dividing the bones into discrete volumes along the shaft of the tibia. Density differences were also determined for fractured and contra-lateral bone pairs to determine the magnitude of implant related remodelling. Left and right ovine tibiae were found to have a high degree of similarity with differences of less than 1.0mm in the outer surface deviation and density difference of less than 5% in over 90% of the shaft region. The density differences (10-40%) as a result of implant related bone remodelling were greater than left-right differences. Therefore, for the purpose of quantifying bone remodelling in sheep, the contra-lateral tibia may be considered an alternative to a pre-operative control.

A Biomechanical Evaluation of Orthopaedic Implants for Hip Fractures by Finite Element Analysis and In-Vitro Tests

The aim of this study was to test the hypothesis that a reinforced gamma nail for the fixation of subtrochanteric fractures would experience less stress during loading compared with a common gamma nail. The issue of whether the use of the stronger implant would result in more stress shielding in the surrounding bone was also addressed.

A finite element analysis (FEA) of a synthetic bone was employed to calculate the stress distribution in implant and bone for two fracture types (AO 31-A3.1 and AO 31-A3.3). The FEA was validated by mechanical tests on six synthetic femurs. To test the hypothesis in vitro, mechanical tests on six pairs of fresh-frozen human femurs were conducted. The femurs were supplied with a common or a reinforced gamma nail in a cross-over study design. Strains were measured on the nail shaft to quantify the loading of the nail.

The FEA resulted in 3—51 per cent lower stresses for the reinforced gamma nail. No increase in stress shielding could be observed. In the in-vitro tests, the reinforced gamma nail experienced less strain during loading ( p < 0.016). The study demonstrated the benefit of a reinforced gamma nail in subtrochanteric fractures. It experienced less stress but did not result in more stress shielding.