The open section effect in a long bone with a longitudinal defect - a theoretical modeling study

Application of allograft and absorbable screws in the reconstruction of a massive bone defect following resection of giant osteochondroma: A retrospective study

Background

This study aims to introduce a reconstruction method of applying allografts and absorbable screws to repair large bone defects caused by the resection of giant osteochondroma.

Methods

A retrospective study of a series of patients who underwent the resection of giant osteochondroma reconstructed by allografts and absorbable screws was conducted from February 2020 to September 2021. Their demographic data, location site, area of bone defect, and pertinent operative details were recorded. The reconstruction modality of allografts was elaborated on. In the follow-up, radiographic images were utilized to determine bone union, and the Musculoskeletal Tumor Society score was used to evaluate postoperative limb function.

Results

A total of seven patients were included, including three males and four females with an average age of 16.6 ± 6.5 years. Among them, three cases of tumors occurred in the humerus and four cases occurred in the femur. The average follow-up time was 11.3 ± 3.0 months. The average area of bone defect was 25.9 ± 8.3 cm². No complications such as infection, nonunion, and allograft bone fracture were found during the follow-up period. Six months after the operation, the average Musculoskeletal Tumor Society score was 26.4 ± 1.6, with acceptable postoperative function.

Conclusions

The cooperative application of absorbable screw fixation and allografts including mixed cortical bone and cancellous bone, which yielded satisfactory functional outcomes and acceptable postoperative complications, is an effective reconstruction method for a massive bone defect after the resection of giant osteochondroma.

Association of the Anterolateral Thigh Osteomyocutaneous Flap With Femur Structural Integrity and Assessment of Prophylactic Fixation

Importance

The chimeric anterolateral thigh osteomyocutaneous (ALTO) free flap is a recently described microvascular option for head and neck osseous defects associated with complex soft-tissue requirements. To date, the association of ALTO flap harvest with femur structural integrity and the need for routine prophylactic fixation following harvest has been incompletely described.

Objective

To investigate the association of ALTO flap harvest, with and without prophylactic fixation, on femur structural integrity as measured by 4-point bend and torsional biomechanical testing.

Design and Setting

At a research laboratory, 24 synthetic fourth-generation composite femurs with validated biomechanical properties underwent 10-cm-long, 30% circumferential osteotomies at the proximal middle third of the femur; 6 femurs served as controls. Osteotomized femurs with and without fixation underwent torsional and 4-point bend biomechanical testing. Femur fixation consisted of intramedullary nail and distal interlock screw placement.

Main Outcomes and Measures

Force and torque to fracture (expressed in kilonewtons [kN] and Newton meters [N∙m], respectively) were compared between controls, osteotomized femurs without fixation, and osteotomized femurs with fixation. Additional outcome measures included femur stiffness and fracture patterns.

Results

On posterior to anterior (PA) 4-point bend testing, force to fracture of osteotomized femurs was 22% of controls (mean difference, 8.3 kN; 95% CI, 6.6-10.0 kN). On torsional testing the torque to fracture of osteotomized femurs was 12% of controls (mean difference, 351.1 N∙m; 95% CI, 307.1-395.1 N∙m). Following fixation there was a 67% improvement in PA force to fracture and a 37% improvement in torque to fracture. However, osteotomized femurs with fixation continued to have a reduced PA force to fracture at 37% of controls (mean difference, 6.8 kN; 95% CI, 4.5-9.2 kN) and torque to fracture at 16% of controls (mean difference, 333.7 N∙m; 95% CI, 306.8-360.6 N∙m). On torsional testing, all osteotomized femurs developed similar spiral fractures through a corner of the distal osteotomy site. This fracture pattern changed after prophylactic fixation with femurs developing nondisplaced fractures through the proximal osteotomy site. There were no underlying hardware failures during testing of osteotomized femurs with fixation.

Conclusions and Relevance

Anterolateral thigh osteomyocutaneous flap harvest results in significant changes in the structural integrity of the femur. Postoperative stabilization should be strongly considered, with future research directed at investigating the clinical significance of residual biomechanical changes following femur fixation.

Assessment of fracture risk in proximal tibia with tumorous bone defects by a finite element method

There has not been a satisfying method to predict the fracture risk in tumorous bone lesions. To tackle this challenge, we used a finite element method to assess the fracture risk in the proximal tibia (pT) when the size and location of the tumorous defects are varied in bone. Towards this end, the circular cortical defects, mimicking the tumorous lesions by forming cortical window defects, with a diameter (Ф) of 20, 30, 40, or 50 mm, are structured on the anteromedial, lateral, posterior wall of pT, which is located 5, 15, and 25 mm below articular margin, respectively. We found that under walking conditions, the Von Mises Stress of each defective tibia model was larger than that of the intact tibia model and also showed a positive linear correlation with the sizes of the defects. A notable fracture risk was not observed until the defect was Ф30 mm or larger. When the defect emerged, the anteromedial wall resisted fracture risk more than the rest of wall. Our results show that the size and location of the bone tumors are important factors affecting the fracture risk of pT. Our findings will be beneficial to clinicians when deciding what treatment to use for pT lesions.

Biomechanics of Fractures

BACKGROUND

This video presents the digitized, original, reel-to-reel footage of Victor Frankel's groundbreaking 1960s experiments demonstrating the viscoelastic properties and fracture mechanics of loaded bone. As can be seen, novel instrumentation was used that resulted in an easily reproducible method of controlling bone loading rates. The innovation, and associated experiments, radically advanced our understanding of the mechanisms of acute fractures and bone's response to energy.

METHODS

Using the "Standard Torsion Testing Machine" that he helped design, the author explains how the mechanical and functional properties of bone are affected by various defects. Examples used include an intact dog femur, a femur with a hole in the cortex, and a femur with an open section defect. Slow motion depiction allows the viewer to appreciate the potential soft tissue damage associated with bone fragmentation and how this varies with energy input. The video concludes with a demonstration of the effect of torsional motion on the vasculature.

RESULTS

Graphs produced by the torsion tester display torque versus angular deformation plots for each experiment. These illustrate the relationship between bone structure, fracture, and energy. The x-ray contrast segment provides an example of associated arterial damage secondary to a fracture.

CONCLUSION

This previously unreleased piece of orthopaedic history provides viewers with perspective on the early days of biomechanical study and an easy-to-understand tutorial on acute fracture mechanics and the role of energy in injury.

Combining mesenchymal stem cell sheets with platelet-rich plasma gel/calcium phosphate particles: a novel strategy to promote bone regeneration

Background

Promotion of bone regeneration is important for successful repair of bony defects. This study aimed to investigate whether combining bone marrow-derived mesenchymal stem cell (BMSC) sheets with platelet-rich plasma (PRP) gel/calcium phosphate particles could promote bone formation in the femoral bone defects of rats.

Methods

The proliferation and differentiation of BMSCs or BMSC sheets cultured with calcium phosphate particles and/or PRP were investigated in in vitro. In vivo, 36 2.5 × 5 mm bone defects were randomly divided into groups and treated with either BMSCs/PRP gel, calcium phosphate particles, PRP gel/calcium phosphate particles, a BMSC sheet/calcium phosphate particles, a BMSC sheet/PRP gel/calcium phosphate particles, or were left untreated (n = 6/group). A further 15 bone defects were treated with chloromethyl-benzamidodialkylcarbocyanine (CM-Dil)-labelled BMSC sheet/PRP gel/calcium phosphate particles and observed using a small animal in vivo fluorescence imaging system to trace the implanted BMSCs at 1 day, 3 days, 7 days, 2 weeks, and 4 weeks after surgery.

Results

The expression of collagen type I and osteocalcin genes of BMSCs or BMSC sheets treated with PRP and calcium phosphate particles was significantly higher than that of BMSCs or BMSC sheets treated with calcium phosphate particles or the controls (P <0.05). PRP can promote gene expression of collagen III and tenomodulin by BMSCs and in BMSC sheets. The VEGF, collagen I and osteocalcin gene expression levels were higher in the BMSC sheet than in cultured BMSCs (P <0.05). Moreover, alizarin red staining quantification, ALP quantification and calcein blue fluorescence showed the osteogenic potential of BMSCs treated with PRP and calcium phosphate particles The implanted BMSCs were detectable at 1 day, 3 days, 7 days, 2 weeks and 4 weeks after surgery by a small animal in vivo fluorescence imaging system and were visualized in the defect zones by confocal microscopy. At 4 weeks after implantation, the defects treated with the BMSC sheet/PRP gel/calcium phosphate particles showed significantly more bone formation than the other five groups.

Conclusions

Incorporation of an BMSC sheet into the PRP gel/calcium phosphate particles greatly promoted bone regeneration. These BMSC sheet and tissue engineering strategies offer therapeutic opportunities for promoting bone defect repair clinically.

Pathological fracture prediction in patients with metastatic lesions can be improved with quantitative computed tomography based computer models

PURPOSE

In clinical practice, there is an urgent need to improve the prediction of fracture risk for cancer patients with bone metastases. The methods that are currently used to estimate fracture risk are dissatisfying, hence affecting the quality of life of patients with a limited life expectancy. The purpose of this study was to assess if non-linear finite element (FE) computer models, which are based on Quantitative Computer Tomography (QCT), are better than clinical experts in predicting bone strength.

MATERIALS AND METHODS

Ten human cadaver femurs were scanned using QCT. In one femur of each pair a hole (size 22, 40, or 45 mm diameter) was drilled at the anterior or medial side to simulate a metastatic lesion. All femurs were mechanically tested to failure under single-limb stance-type loading. The failure force was calculated using non-linear FE-models, and six clinical experts were asked to rank the femurs from weak to strong based on X-rays, gender, age, and the loading protocol. Kendall Tau correlation coefficients were calculated to compare the predictions of the FE-model with the predictions of the clinicians.

RESULTS

The FE-failure predictions correlated strongly with the experimental failure force (r(2)=0.92, p<0.001). For the clinical experts, the Kendall Tau coefficient between the experimental ranking and predicted ranking ranged between tau=0.39 and tau=0.72, whereas this coefficient was considerably higher (tau=0.78) for the FE-model.

CONCLUSION

This study showed that the use of a non-linear FE-model can improve the prediction of bone strength compared to the prediction by clinical experts.

Femoral fracture through a previous pin site after computer-assisted total knee arthroplasty

Computer-assisted total knee arthroplasty has been gaining popularity given the proposed benefits of increased accuracy of the femoral and tibial cuts, quantitative feedback on soft tissue balancing, and the potential for performing the procedure through smaller incisions with decreased soft tissue trauma. Most navigation systems require femoral and tibial threaded pin insertion for placement of guidance trackers, which when removed leave behind defects in the bone that may act as stress risers. We present 2 cases of a femoral fracture through a previous pin site where a guidance tracker had been placed for computer-assisted total knee arthroplasty. Both patients were informed that data concerning the cases would be submitted for publication. To our knowledge, this complication has not previously been reported for this procedure.

Torsional strength estimates of femoral diaphyses with endosteal lytic lesions: dual-energy X-ray absorptiometry study

Pathologic fracture is a significant problem for individuals with metastatic bone disease. Current guidelines for prophylactic internal fixation are neither reliable nor easily applied. The purpose of this study was to validate dual-energy X-ray absorptiometry (DXA) as an accurate method for estimating torsional bone strength of diaphyseal bone with endosteal lytic lesions. Endosteal lesions of varying sizes were simulated in the diaphyses of 12 adult cadaveric femurs. Unaltered contralateral femurs served as matched controls. Machined lesions ranged from 3 to 6.5 cm in length, 1 to 3 cm in width, 15 to 48 cm(2) in elliptical area, with 10% to 100% removal of the cortical thickness. Morphology and density data obtained from DXA images were used to estimate torsional strength. All femora were mechanically tested to failure in torsion. Physically measured torsional strength was not significantly correlated to lesion elliptical area (r = 0.542, p > 0.05) or percentage cortical thickness removed (r = 0.257, p > 0.05). Measured torsional strength was significantly correlated to DXA-based torsional strength estimates (r = 0.855, p < 0.01). Lesion size alone did not correlate with the strength of bones with simulated endosteal lytic lesions. In contrast, calculations based on DXA (morphology, density) did correlate with torsional strength. This is the first step in the development of a DXA-based tool for objectively estimating bone strength in the presence of endosteal lytic lesions.

Prediction of torsional failure in 22 cadaver femora with and without simulated subtrochanteric metastatic defects: a CT scan-based finite element analysis

BACKGROUND

In metastatic bone disease, prophylactic fixation of impending long bone fracture is preferred over surgical treatment of a manifest fracture. There are no reliable guidelines for prediction of pathological fracture risk, however. We aimed to determine whether finite element (FE) models constructed from quantitative CT scans could be used for predicting pathological fracture load and location in a cadaver model of metastatic bone disease.

MATERIAL AND METHODS

Subject-specific FE models were constructed from quantitative CT scans of 11 pairs of human femora. To simulate a metastatic defect, a transcortical hole was made in the subtrochanteric region in one femur of each pair. All femora were experimentally loaded in torsion until fracture. FE simulations of the experimental set-up were performed and torsional stiffness and strain energy density (SED) distribution were determined.

RESULTS

In 15 of the 22 cases, locations of maximal SED fitted with the actual fracture locations. The calculated torsional stiffness of the entire femur combined with a criterion based on the local SED distribution in the FE model predicted 82% of the variance of the experimental torsional failure load.

INTERPRETATION

In the future, CT scan-based FE analysis may provide a useful tool for identification of impending pathological fractures requiring prophylactic stabilization.

Stress Analysis and Optimizing of Osteoinductive Ca-P Ceramics and Net-Cage-Structured Titanium Alloy in Dog Segmental Femoral Defect Reparation

The purpose of this study was to develop a feasible technique for bone reparation and further explore the possible applications of Ca-P ceramics in segmental load-bearing bone reparation. HA/TCP ceramics sintered at 1250oC were fabricated into tube-like columns of Φ15mm×30mm with a central canal of Φ4mm. Bone-like apatite was precipitated on the ceramics before implantation. 12 male dogs were used in this study, and a 30mm long segmental bone defect was made in the middle of one femur of each dog. Supported by the fixation of net-cage-structured TC4, the osteoinductive Ca-P ceramic cylinder was used to repair the segmental defect in dog femur. Stress was analyzed by ANSYS. The morphology recovery, function restoration, gait analyses and bone regeneration were evaluated. After implantation at 2, 4 and 8 months, the specimens were harvested respectively. The specimens were evaluated with morphological observation and mechanical testing. Stress analysis showed that the thickness of TC4 net cage was 0.3mm. The morphology recovery of the experimental animal was good and function was restored after 2 months gradually. Aided by stress analysis and by optimizing the design and fixation of implants, Ca-P materials with excellent osteoinductivity could be applied in repairing segmental bone defects.

The effect of shoulder arthroplasty on humeral strength: an in vitro biomechanical investigation

BACKGROUND

Periprosthetic humeral fractures are a serious complication of shoulder arthroplasty. While adequate reaming of the canal and insertion of an oversized implant optimizes fit, such maneuvers also weaken the bone and predispose it to fracture.

METHODS

The impact of the humeral arthroplasty was assessed in vitro on human cadaveric specimens. Strain gauges were attached to the distal diaphyses and the specimens were mounted in a torsion-loading fixture throughout the tests. An initial series examined the effect of reaming of the canal to its clinically appropriate diameter using uniaxial strain gauges. A second series utilized strain rosettes to evaluate the cumulative effects of reaming, broaching, and implant insertion.

FINDINGS

Reaming of the canal to its clinically appropriate diameter significantly increased (P=0.007) uniaxial strain measurements by a mean of 30% with five of eight specimens showing increases of over 49% on at least one of four diaphyseal locations. In the second series, the surface strain was significantly affected by arthroplasty (P<0.008). Post-hoc analysis showed that the maximum in-plane shear strain following implant insertion was significantly increased relative to strain levels following reaming and broaching (P<0.009). The direction of the principal strain axes did not significantly change (P>0.46). Unexpected decreases in some strain measurements were observed as the arthroplasty procedure progressed perhaps reflecting overt mechanical failure within the humeral shaft.

INTERPRETATION

The strain increase following reaming suggests a reduction in torsional strength by over 33% which is further reduced following broaching and implant insertion. For the practicing surgeon, post-operative strength can be adversely affected by both canal preparation and implant insertion.

Assessing a relationship between bone microstructure and growth rate: a fluorescent labelling study in the king penguin chick (Aptenodytes patagonicus)

Microstructure–function relationships remain poorly understood in primary bone tissues. The relationship between bone growth rate and bone tissue type, although documented in some species by previous works, remains somewhat unclear and controversial. We assessed this relationship in a species with extreme adaptations, the king penguin (Aptenodytes patagonicus). These birds have a peculiar growth, interrupted 3 months after hatching by the austral winter. Before this interruption, chicks undergo extremely rapid statural and ponderal growth. We recorded experimentally (by means of fluorescent labelling) the growth rate of bone tissue in four long bones(humerus, radius, femur and tibiotarsus) of four king penguin chicks during their fastest phase of growth (3–5 weeks after hatching) and identified the associated bone tissue types (`laminar', `longitudinal', `reticular' or`radial' fibro-lamellar bone tissue). We found the highest bone tissue growth rate known to date, up to 171 μm day–1 (mean 55 μm day–1). There was a highly significant relationship between bone tissue type and growth rate (P&lt;10–6). Highest rates were obtained with the radial microarchitecture of fibro-lamellar bone, where cavities in the woven network are aligned radially. This result supports the heuristic value of a relationship between growth rate and bone primary microstructure. However, we also found that growth rates of bone tissue types vary according to the long bone considered(P&lt;10–5) (e.g. growth rates were 38% lower in the radius than in the other long bones), a result that puts some restriction on the applicability of absolute growth rate values (e.g. to fossil species). The biomechanical disadvantages of accelerated bone growth are discussed in relation to the locomotor behaviour of the chicks during their first month of life.

Stress and strain distribution in the intact canine femur: finite element analysis

Information regarding the stresses and strains in the canine femur during various activities is important for veterinary orthopaedic surgeons, engineers designing implants for dogs, and researchers of human orthopaedics who use dogs as models. Nevertheless, such information is currently unavailable. The objective of this study is to determine the stress and strain distribution in the canine femur during mid-stance, for two loading scenarios. Three-dimensional finite element models of the canine femur were created. Two loading cases were considered: the hip joint reaction force alone, and the hip joint reaction force with all muscle forces acting on the femur. Force directions and magnitudes were obtained from the literature. Analyses were performed with NASTRAN for Windows software. When all muscle forces were considered, stresses and strains were significantly reduced, peak compressive stresses were found to occur in the medial diaphysis, and peak tensile stresses occurred in the lateral diaphysis. While the canine femur seems to be loaded primarily in bending when only the hip joint reaction force is considered, the bending moment is significantly decreased when all muscle forces are considered as well. Further in vivo and in vitro experiments are needed to validate the results of the calculations described in this paper. It is expected that future studies will be carried out, in which the stress and strain distributions in femora with different types of implants and stems will be compared to those in the normal femur.

The muscle standardized femur: a step forward in the replication of numerical studies in biomechanics

The standardized femur is the computer aided design (CAD) solid model of a synthetic human femur, commonly used in experiments in vitro, available in the public domain through the International Society of Biomechanics Finite Element Mesh Repository. Currently used by hundreds of researchers, it was made available to simplify the experimental cross-validation of numerical studies as well as their replication by other researchers. One aspect that the standardized femur left uncovered is the definition of muscles and ligaments. In particular, for a variety of simulations it would be extremely useful to map on to the femoral surface the insertion of the principal muscles. The aim of the present study was to create a new solid model, called the muscle standardized femur, where the femoral insertion of each muscle is mapped on to the surface of the femur. Published data on muscle insertion morphometry were registered to the model by applying an affine scaling defined on bone landmarks. Good agreement was found with another similar study in which only the insertion centres were defined. The new model will be made available in the public domain for no-profit uses. When combined with published data on the direction and intensity of muscular forces this model is expected to make a useful contribution to the steadily growing library of models and data sets made available to the biomechanical community.

Simple curettage without bone grafting for enchondromata of the hand: with special reference to replacement of the cortical window

We studied 23 patients (25 bones) with enchondromata of the hand which were treated with simple curettage without bone grafting. The cortical window was replaced in 18 bones (group A), whereas it was not replaced in six bones (group B). In one bone, only half of the cortical window was replaced. Local recurrence was not seen in any patient. Although bone grafting was not performed, new bone formation was observed in all the patients. Radiographic and functional results were excellent in most bones. Restoration of the continuity of the cortex was seen at 3 (range, 1.5-4) months in group A and 8 (range, 6-12) months in group B. This restoration is important for the recovery of mechanical strength and we therefore consider that the cortical window should be replaced, unless this is impractical.