Influence of muscle loading on early-stage bone fracture healing

The relationship between the expression of serum asprosin and miR-21 in patients with osteoporosis and delayed healing after OVCF surgery

Objective: To explore the relationship between serum asprosin, microRNA-21 (miR-21) expression, and delayed healing after surgery in patients with osteoporotic vertebral compression fractures (OVCF), and to construct a nomogram model. Methods: A prospective study inducted 300 OVCF patients treated with percutaneous vertebroplasty (PVP) from June 2022 to June 2024. Serum asprosin and miR-21 were measured preoperatively, and fracture healing was assessed via X-ray 3 months post-surgery. Patients were categorized into delayed healing and normal healing groups based on outcomes. The least absolute shrinkage and selection algorithm (LASSO) regression identified factors influencing delayed healing, followed by binary logistic regression analysis. A nomogram model was constructed to predict delayed healing, and its predictive value was evaluated using the receiver operating curve (ROC) analysis. Results: Results showed higher rates of delayed weight-bearing (58.11% vs 33.19%), diabetes prevalence (52.70% vs 42.48%), bone cement injection volume (4.68 ± 1.14 mL vs 3.81 ± 1.09 mL), and serum asprosin levels (4.09 ± 1.39 ng/mL vs 3.14 ± 1.07 ng/mL) in the delayed healing group compared to the normal healing group. Serum miR-21 levels were lower in the delayed healing group (0.69 ± 0.19) than in the normal group (0.92 ± 0.31) (p < 0.05). Bone density T scores in OVCF patients correlated positively with asprosin (r = 0.281, p < 0.001) and negatively with miR-21 (r = -0.184, p = 0.001). The LASSO regression identified five factors associated with delayed healing: bone cement volume, delayed weight-bearing, diabetes, and serum asprosin (risk factors), while high miR-21 was protective. Logistic regression indicated significant risk factors with an overall C-index of 0.867 and AUC of 0.868 (sensitivity 0.892, specificity 0.686). After 3 months of treatment, serum Asprosin [(3.46 ± 1.22) ng/ml] in OVCF patients was lower than that before treatment [(3.03 ± 1.03) ng/ml], and serum miR-21 (0.85 ± 0.30) was higher than that before treatment [(0.99 ± 0.33)] (t = 4.039, 4.318, p < 0.05). Conclusion: Serum asprosin and miR-21 levels are closely related to delayed healing after surgery in patients with OVCF. Additionally, the bone cement injection volume, delayed weight-bearing, and concomitant diabetes mellitus are also important factors affecting fracture healing in patients. The nomogram model based on these factors can effectively predict the risk of delayed healing in patients with OVCF after surgery.

Understanding recurrent groin pain following periacetabular osteotomy: assessment of psoas tendon mechanics using discrete element analysis

Recurrent groin pain following periacetabular osteotomy (PAO) is a challenging problem. The purpose of our study was to evaluate the position and dynamics of the psoas tendon as a potential cause for recurrent groin pain following PAO. A total of 386 PAO procedures, performed between January 2013 and January 2020, were identified from a single surgeon series. Thirteen patients (18 hips) had a psoas tendinopathy, as confirmed with relief of symptoms following a diagnostic injection into the psoas tendon. All patients underwent computed tomography (CT) scans pre- and post-operatively. The data from CT scan was used to manually segment bony structures and create 3D models using Mimics software (Materialise NV). A validated discrete element analysis model using rigid body springs was used to predict psoas tendon movement during hip circumduction and walking. The distance of the iliopsoas tendon to any bony abnormality was calculated. All computational analyses were performed using MATLAB software. Thirteen hips (13/18) showed bony malformations (spurs, hypertrophic callus or delayed union and malunion) secondary to callus at the superior pubic ramus. The mean minimal distance of the iliopsoas tendon to osteotomy site was found to be 13.73 mm (σ = 3.09) for spurs, 10.99 mm (σ = 2.85) for hypertrophic callus and 11.91 mm (σ = 2.55) for canyon type. In normal bony healing, the mean minimal distance was 18.55 mm (σ = 4.11). Using a validated computational modelling technique, this study has demonstrated three different types of malformation around the superior pubic osteotomy site, which are associated with psoas impingement. In all of the cases, the minimal distance of the iliopsoas tendon to the osteotomy site was reduced by 59-74%, as compared with the normal anatomy.

Biomechanical effects of muscle loading on early healing of femoral stem fractures: a combined musculoskeletal dynamics and finite element approach

Femoral stem fractures (FST) are often accompanied by muscle injuries, however, what muscle injuries affect fracture healing and to what extent is unknown. The purpose of this study was to analyze the extent to which different muscles affect FST healing through a combined musculoskeletal dynamics and finite element approach. Modeling the lower extremity musculoskeletal system for 12 different muscle comprehensives. Muscle and joint reaction forces on the femur were calculated and these data were used as boundary conditions input to the FSTs model to predict the degree of muscle influence on fracture healing. Finally, we will investigate the extent to which muscle influences FST healing during knee flexion. Muscle and joint forces are highly dependent on joint motion and have a significant biomechanical influence on interfragmentary strain (IFS) healing. The psoas major (PM), gastrocnemius lateralis (GL) and gastrocnemius medialis (GM) muscles play a major role in standing, with GM > PM > GL, whereas the gluteus medius posterior (GMP), vastus intermedius (VI), vastus medialis (VM), vastus lateralis superior (VLS), and adductor magnus distalis (AMD) muscles play a major role in knee flexion, with VLS > VM > VI > AMD > GMP. Mechanical stimulus-controlled healing can be facilitated when the knee joint is flexed less than 20°. Different muscles exert varying degrees of influence on the healing of fractures. Therefore, comprehending the impact of particular muscles on fracture site tissue FST healing can aid orthopedic surgeons in formulating improved surgical and rehabilitation strategies.

Fracture healing research: Recent insights

Bone has the rare capability of scarless regeneration that enables the complete restoration of the injured bone area. In recent decades, promising new technologies have emerged from basic, translational and clinical research for fracture treatment; however, 5-10 % of all bone fractures still fail to heal successfully or heal in a delayed manner. Several comorbidities and risk factors have been identified which impair bone healing and might lead to delayed bone union or non-union. Therefore, a considerable amount of research has been conducted to elucidate molecular mechanisms of successful and delayed fracture healing to gain further insights into this complex process. One focus of recent research is to investigate the complex interactions of different cell types and the action of progenitor cells during the healing process. Of particular interest is also the identification of patient-specific comorbidities and how these affect fracture healing. In this review, we discuss the recent knowledge about progenitor cells for long bone repair and the influence of comorbidities such as diabetes, postmenopausal osteoporosis, and chronic stress on the healing process. The topic selection for this review was made based on the presented studies at the 2022 annual meeting of the European Calcified Tissue Society (ECTS) in Helsinki.

Influence of knee flexion on early femoral fracture healing: A combined analysis of musculoskeletal dynamics and finite elements

BACKGROUND AND OBJECTIVES

Knee flexion causes a certain amount of misalignment and relative movement of the fractured ends of the femur fracture, and if the flexion angle is too large it will affect the stability of the fracture and the healing process, making it challenging to design a safe range of flexion. However, due to a lack of basic understanding of the effect of knee flexion on the mechanical environment at the fracture site, clinicians are often unable to provide an objective and safe range of motion in flexion based on subjective experience. The aim of this study was to evaluate the effect of knee flexion on plate and fracture healing using finite element analysis (FEA).

METHODS

A human musculoskeletal model was constructed based on CT scan data, and the mechanical properties of the fracture site were changed by adjusting the knee flexion angle. The joint forces, muscle forces and moments acting on the femur were obtained by inverse dynamics analysis, and the biomechanical properties of the fracture-plate system were analyzed using finite elements. A finite element model of the fracture-plate system without muscle loading was also constructed. The effect of knee flexion on the safety of plate fixation and fracture healing was evaluated in terms of the biomechanical properties of the plate and the interfragmentary motion of the fracture.

RESULTS

As the knee flexion angle increases, the von Mises stress of the locked compression plate (LCP) first increases, then decreases, then increases again. The deformation from compression bending to tension twisting occurs simultaneously. At 30° of flexion, shear interfragmentary motion (SIM) was dominant and inhibited fracture healing; at more than 45° of flexion, the plate was twisted and deformed to the lateral side of the body, and the fracture site underwent greater misalignment and relative motion, with destructive effects on bone scabs and healing tissues. If muscle loading is not taken into account, the plate will undergo predominantly bending deformation and will overestimate the interfragmentary strain in the far and near cortex.

CONCLUSIONS

Knee flexion causes the plate to deform from compression bending to extension and torsion, which has an important impact on the safety and healing process of the fracture, and this study provides a biomechanical basis to guide the clinician in the post-operative rehabilitation of femoral fractures in the clinical setting.