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Biomechanical analysis of fibular graft techniques for nontraumatic osteonecrosis of the femoral head: a finite element analysis.

ABSTRACT: BACKGROUND:Free vascularized fibula graft (FVFG) techniques have most consistently demonstrated beneficial effects in young patients diagnosed with nontraumatic osteonecrosis of the femoral head (NONFH), and the core track technique (CTT) in particular is the most commonly used technique. As an alternative to CTT, the modified light bulb technique (LBT) has been reported to have a higher success rate. However, its biomechanical outcomes are poorly understood. This study aimed to compare the biomechanical properties of modified LBT with those of CTT in treating NONFH. METHODS:Two types (C1 and C2) of NONFH finite element models were established on the basis of a healthy subject and the Japanese Investigation Committee (JIC) classification system, and the CTT and LBT procedures were simulated in each type of model. The average von Mises stresses and stiffness of the proximal femur were calculated by applying a load of 250% of the body weight on the femoral head to simulate walking conditions. In addition, two patient-specific models were built and simulated under the same boundary conditions to further validate the LBT. RESULTS:In the healthy subject-derived models, both the LBT and CTT resulted in reduced stresses in the weight-bearing area, central femoral head, femoral neck, and trochanteric and subtrochanteric regions and increased structural stiffness after surgery. In the weight-bearing area, the CTT reduced the stress more than the LBT did (36.19% vs 31.45%) for type C1 NONFH and less than the LBT did (23.63% vs 26.76%) for type C2 NONFH. In the patient-specific models, the stiffness and stresses also increased and decreased, respectively, from before to after surgery, which is consistent with the results of healthy subject-derived models. CONCLUSION:The biomechanical effects of the LBT and CTT differ by the JIC type of NONFH. In terms of preventing the collapse of the femoral head, the LBT may be more effective for JIC type C2 NONFH and may be a suitable alternative to the CTT, while for JIC type C1 NONFH, the CTT is still a better choice. Both techniques can improve the biomechanical properties of NONFH by reducing the proximal femoral stress and increasing the structural stiffness.

SUBMITTER: Xu J

PROVIDER: S-EPMC7433362 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

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Biomechanical analysis of fibular graft techniques for nontraumatic osteonecrosis of the femoral head: a finite element analysis.

Xu Jian J Zhan Shi S Ling Ming M Jiang Dajun D Hu Hai H Sheng Jiagen J Zhang Changqing C

Journal of orthopaedic surgery and research 20200817 1

<h4>Background</h4>Free vascularized fibula graft (FVFG) techniques have most consistently demonstrated beneficial effects in young patients diagnosed with nontraumatic osteonecrosis of the femoral head (NONFH), and the core track technique (CTT) in particular is the most commonly used technique. As an alternative to CTT, the modified light bulb technique (LBT) has been reported to have a higher success rate. However, its biomechanical outcomes are poorly understood. This study aimed to compare ...[more]

PMID: 32807218

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Project description:BackgroundOsteonecrosis of the femoral head (ONFH) is a debilitating condition affecting primarily young patients. Free vascularized fibular grafting (FVFG) may provide a durable means to preserve the femoral head. When used in the precollapse stages of ONFH, this treatment may alter the course of disease.Questions/purposesWe asked: (1) In what percentage of patients does FVFG preserve the femoral head beyond 10 years? (2) When long-term preservation is not achieved, what is the duration of femoral head preservation? (3) Do demographic or etiologic factors predict FVFG survivorship? (4) What long-term improvements in function and activity can be anticipated?MethodsWe retrospectively reviewed 61 patients (65 hips) who underwent FVFG for precollapse ONFH. We calculated graft survivorship, SF-12 scores, activity levels, and Harris hip scores. Minimum followup was 10.5 years (mean, 14.4 years; range, 10.5-26 years). Results Forty-nine of 65 hips (75%) had surviving FVFG for at least 10 years. At last followup, 39 of 65 hips (60%) had surviving FVFG, with a mean graft survival time of 15 years (range, 10.5-26.1 years). Twenty-six of the 65 hips with FVFG (40%) underwent conversion to THA at a mean of 8 years postoperatively. Demographic factors, lesion size, additional procedures, and low preoperative function were not associated with changes in graft survivorship. Pain and function were similar in patients with surviving FVFG and patients who had conversion to THA. Patients with surviving FVFG were more likely to engage in impact sports or active events than were patients who had conversion to THA.ConclusionsWhen patients with precollapse ONFH undergo FVFG, the majority have preservation of the hip lasting for greater than 10 years with low levels of pain and reasonable function. In patients who ultimately undergo conversion surgery to THA, the mean duration of hip preservation before conversion is 8 years. We continue to use FVFG for treating patients younger than 50 years with symptomatic, precollapse ONFH.Level of evidenceLevel IV, therapeutic study. See Instructions to Authors for a complete description of levels of evidence.

Project description:BackgroundIn the follow-up after internal fixation of thoracolumbar fractures, the imaging of some patients shows "crater-like" collapse of the superior endplate of the injured vertebra, with variable collapse area and depth, even involving the anterior edge of the vertebral body. Though many papers had described the phenomenon, but nearly no one did biomechanical research about this. So we did this research in a creative way by using finite element model.MethodsA healthy male volunteer was selected. The 64-slice thin-section spiral computed tomography images at the level of T11-L3 were collected. Data were imported into Mimics 15.0 medical image processing software to establish three-dimensional finite element skeletal models of T11 to L3 containing only three-dimensional surface elements without entities. The model was assigned values and verified. Then the pedicle screw-rod system was added to this model, and five models containing the screw-rod system with different defect sizes as well as five models that simulated the removal of the screw-rod system were derived at the same time (the defect volume was 1/5, 2/5, 3/5, 4/5, or 5/5 of the anterior vertebral column, respectively). Biomechanical analysis was then performed on this basis.ResultsAfter the removal of the internal fixator, as defect volume increased, the stress difference between the 4/5 defect group and the 5/5 defect group had the greatest magnitude of combined stress under the seven working conditions. When the volume of the collapse defect reached 4/5 of the anterior column of the vertebral body, the concentration of stress increased significantly, suggesting that the risk of continued compression or even refracture of the injured vertebra increased if the internal fixator was removed at that time.ConclusionsWhen the volume of the defect in the superior endplate of the injured vertebra reaches 4/5 of the anterior column, the removal of the internal fixator should be carefully considered to avoid refracture of the anterior column of the injured vertebra.

Dataset Information

Biomechanical analysis of fibular graft techniques for nontraumatic osteonecrosis of the femoral head: a finite element analysis.

Publications

Biomechanical analysis of fibular graft techniques for nontraumatic osteonecrosis of the femoral head: a finite element analysis.

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