Incidence and risk factors for bilateral proximal femoral fractures

Is there a femoral morphology at risk of a cervical or pertrochanteric fracture? Description and validation of the "Neck shaft ratio" and the "Intertrochanteric distal ratio" after analyzing a continuous cohort of 126 bilateral fractures of the proximal femur

BACKGROUND

Proximal femur fractures constitute a public health concern given their high frequency and the aging population. The frequency of a contralateral fracture occurring can reach up to 15% of cases. Certain historical or demographic factors constitute risk factors for refracture, but the type of fracture, either of the femoral neck (FN) or pertrochanteric (PT), cannot be predicted. The objectives of this retrospective study were: firstly, to analyze several anatomical markers in order to determine whether they predispose to a certain type of fracture in the event of contralateral refracture, and secondly, to determine the predictive power of these possible radiological markers for the type of contralateral fracture.

HYPOTHESIS

The hypothesis was that the "Neck shaft ratio" (NSR) and the "Intertrochanteric distal ratio" (ITDR) made it possible to determine a proximal femoral morphology at risk of FN and/or PT fracture in the event of a second fracture.

MATERIAL AND METHODS

This continuous retrospective single-center series from January 2011 to December 2019 of patients who presented with bilateral fractures of the proximal femurs was analyzed. Radiographs, taken after the first fracture, of the contralateral femur were studied. Morphological measurements previously described in the literature were carried out as well as the NSR (ratio of the medial cortical thicknesses of the femoral neck at its narrowest and basicervical level) and the ITDR (ratio of the medial diaphyseal cortical thicknesses at 5mm and 20mm from the distal portion of the lesser trochanter). One hundred and twenty-six patients were included: 46/126 (36.5%) had bilateral FN, 50/126 (39.7%) bilateral PT and 30/126 (23.8%) one of each.

RESULTS

Only NSR and ITDR were significant predictive measures for FN or PT fracture type [0.54±0.11 vs. 0.81±0.16 (p<0.0001) and 0. 85±0.1 vs. 0.68±0.1 (p<0.0001), respectively]. These two ratios had an excellent predictive value for the type of fracture occurring on the contralateral side [NSR: AUC ROC = 0.91 (95% CI; 0.86-0.96); ITDR: AUC ROC = 0.81 (95% CI; %, 0.74-0.89)]. The NSR had excellent intra- and inter-observer reproducibility with an interclass correlation coefficient of 0.93 [95% CI: 0.86-0.97] and 0.91 [95% CI: 0.82-0.96] respectively, the same also applied for the ITDR with interclass correlation coefficient values of 0.93 [95% CI: 0.87-0.97] and 0.86 [95% CI: 0.73-0.93] respectively.

DISCUSSION

The NSR and ITDR ratios offer a simple and reproducible means to predict a morphological predisposition to a certain fracture type, respectively an FN and PT on the side contralateral to an initial osteoporotic proximal femur fracture. A prospective cohort study would be useful in defining a possible prognostic nature on the occurrence and/or time until refracture.

LEVEL OF EVIDENCE

III; retrospective control case.

Development and validation of a predictive nomogram for subsequent contralateral hip fracture in elderly patients within 2 years after hip fracture surgery

Purpose

Contralateral hip refracture following initial hip fracture surgery is life-threatening in the elderly with high incidence and mortality. This study investigated the associated independent risk factors and established a nomogram prediction model.

Methods

Totally 734 elderly patients with hip fractures who underwent surgical treatment (January 2016-December 2020) were enrolled. Following analyses on demographic variables, clinical characteristics, and laboratory examination, independent risk factors of contralateral hip fractures in the elderly were identified through the least absolute shrinkage and selection operator (LASSO) regression, and univariate and multivariate logistic regression. Patients were randomly allocated into training (n = 513) and validation sets (n = 221). A training set-based nomogram prediction model was established and assessed for predictability, discriminatory ability, and clinical applicability using the receiver operating characteristic (ROC) curves, calibration curves, and decision curve analysis (DCA) in both sets.

Results

Contralateral hip refractures occurred in 7.08% (52/734) patients within 2 years after surgery. Age, hemoglobin (Hb), heart disease, neurovascular disease, Parkinson's disease (PD), Alzheimer's disease (AD), chronic obstructive pulmonary disease (COPD), and chronic kidney disease (CKD) were independent risk factors. The nomogram prediction model had a favorable discriminatory ability, as indicated by the areas under the ROC curves (AUC): 0.906 (95% CI, 0.845-0.967) in the training set and 0.956 (95% CI, 0.927-0.985) in the validation set. The calibration curves demonstrated a good consistency between the actual subsequent contralateral hip fracture incidence and the predicted probability. The DCA of the nomogram demonstrated the model's excellent clinical efficacy.

Conclusion

The nomogram model enabled accurate individualized prediction for the occurrence of subsequent contralateral hip fracture in the elderly within 2 years after surgical treatment, which might help clinicians with precise references for appropriate perioperative management and rehabilitation education following initial hip surgery for their patients.

Effect of screw tunnels on proximal femur strength after screw removal: A finite element analysis

BACKGROUND

The presence of screw tunnels in the femoral neck is a problem for patients with proximal femoral fractures after removal of internal fixation. The question of how much does the existence of the screw tunnels affect the strength of the femur and whether the patient needs to be protected with an adjunctive device has been controversial. The objective of this finite element analysis was to determine (1) whether the screw tunnels affects normal weight bearing after removal of internal fixation of a proximal femur fracture, (2) which screw tunnels parameters affect the weight bearing capacity of the entire femur.

HYPOTHESIS

The presence of the screw tunnels reduces the load-bearing capacity of the femur, and the arrangement, diameter and wall thickness of the screw tunnels affect the load-bearing capacity of the femur.

MATERIALS AND METHODS

Twenty patients who underwent surgical treatment for proximal femur fracture at our hospital were included in the study. Computed tomography (CT) values of the screw tunnel wall in the femur after removal of internal fixations were analysed. Mimics v16.0 and Hypermesh v13.0 software programs were used to generate 3-dimensional (3D) tetrahedral finite element models of the proximal femur with different screw tunnel numbers, diameters, thicknesses, and arrangements. An acetabulum exerting a vertical pressure load of 600N on the femoral head was simulated and the force on various parts of the femur in each model was calculated.

RESULTS

There was no difference in the Hounsfield Units of the tunnel walls and cortical bone of the proximal femur (893.48±61.28 vs. 926.34±58.43; p=0.091). In each of the 3D models, the cancellous bone was the first structure to reach maximal stress. The compressive strength of the femur decreased with increasing thickness of the screw tunnel wall and decreased with increasing tunnel diameter. The femoral neck model with the inverted triangle screw tunnel arrangement had the highest compressive strength.

DISCUSSION

The femoral neck with screw tunnels can withstand day-to-day stress without special intervention. For femoral neck fractures fixed with cannulated screws, inverted triangle screws are recommended; For a single screw tunnel in the femoral neck, the larger the diameter of the femoral neck internal screw channel, the weaker the load-bearing capacity of the femur.

LEVEL OF EVIDENCE

III; well-designed computational non-experimental study.