Site-Specific Differences in Bone Mineral Density of Proximal Femur Correlate with the Type of Hip Fracture

Tensile Yield Strain of Human Cortical Bone from the Femoral Diaphysis Is Constant among Healthy Adults and across the Anatomical Quadrants

The literature suggests that the yield strain of cortical bone is invariant to its stiffness (elastic modulus) and strength (yield stress). However, data about intra-individual variations, e.g., the influence of different collagen/mineral organisations observed in bone aspects withstanding different habitual loads, are lacking. The hypothesis that the yield strain of human cortical bone tissue, retrieved from femoral diaphyseal quadrants subjected to different habitual loads, is invariant was tested. Four flat dumbbell-shaped specimens were machined from each quadrant of the proximal femoral diaphysis of five adult donors for a total of 80 specimens. Two extensometers attached to the narrow specimen region were used to measure deformation during monotonic tensile testing. The elastic modulus (linear part of the stress-strain curve) and yield strain/stress at a 0.2% offset were obtained. Elastic modulus and yield stress values were, respectively, in the range of 12.2-20.5 GPa and 75.9-136.6 MPa and exhibited a positive linear correlation. All yield strain values were in the narrow range of 0.77-0.87%, regardless of the stiffness and strength of the tissue and the anatomical quadrant. In summary, the results corroborate the hypothesis that tensile yield strain in cortical bone is invariant, irrespective also of the anatomical quadrant. The mean yield strain value found in this study is similar to what was reported by inter-species and evolution studies but slightly higher than previous reports in humans, possibly because of the younger age of our subjects. Further investigations are needed to elucidate a possible dependence of yield strain on age.

Evolving trends in hip fracture patterns among the elderly from 2001 to 2022

INTRODUCTION

Hip fractures among the elderly exhibit diverse patterns. Differences regarding treatment and prognosis of displaced versus undisplaced intracapsular fractures are well established. Unstable extracapsular fractures are associated with considerably higher rates of complications than stable fractures, including cutout failures, non-unions, wound complications and hardware related problems. The purpose of this study was to identify trends in the distribution of various types of hip fractures and their complexity between 2001 and 2022.

METHODS

This retrospective study compared hip fractures treated in the years 2001, 2006, 2010, 2014, 2018, and 2022, excluding patients under 60 years old and those with pathological or peri‑prosthetic fractures. Radiographs were reviewed and fracture patterns were categorized as stable extracapsular, unstable extracapsular, subtrochanteric or intracapsular.

RESULTS

Out of 2646 patients admitted with proximal femoral fractures during these years, 2277 patients (69.5 % women) were available for analysis. Over the initial decade, the mean patient age gradually increased from 80 to 82, subsequently stabilizing. Gender distribution remained consistent, and the proportion of intracapsular fractures showed minimal variation (36-38 %). The most significant finding was the marked decrease in the proportion of stable-to-unstable extracapsular fractures during the first decade from 51 % to 31 %, followed by stabilization after 2010. Subgroup analysis by age revealed that while the proportion change between stable and unstable fractures remained insignificant in younger age groups (p = 0.41 for sexagenarians and 0.12 for septuagenarians), a significant change was observed in older patients (p = 0.002 for octogenarians and 0.04 for nonagenarians and older patients).

DISCUSSION

This study reveals a surge in unstable peritrochanteric fractures between 2001 and 2010, particularly pronounced in patients over 80. This trend plateaued in the following decade, aligning with the stabilization of the cohort's mean age at 82. Numerous factors, from bone morphology to systemic markers, influence hip fracture types. Evolutions in osteoporosis screening and treatment over the last three decades may have contributed to the observed shifts in fracture pattern distribution.

CONCLUSION

Understanding these trends enriches treatment strategies and underscores the need for further exploration of the interplay between demographic and anatomical factors in the etiology of specific fracture patterns.