Comparison of axial-rotational postoperative periprosthetic fracture of the femur in composite osteoporotic femur versus human cadaveric specimens: A validation study

Lessons learned from biomechanical studies on cephalomedullary nails for the management of intertrochanteric fractures. A scoping review

INTRODUCTION

The increasing socioeconomic need for optimal treatment of hip fractures in combination with the high diversity of available implants has raised numerous biomechanical questions. This study aims to provide a comprehensive overview of biomechanical research on the treatment of intertrochanteric fractures using cephalomedullary devices.

METHODS

Following the PRISMA-P guidelines, a systematic literature search was performed on 31.12.2022. The databases PubMed/MEDLINE and Web of Science were searched. Scientific papers published between 01.01.2000 - 31.12.2022 were included when they reported data on implant properties related to the biomechanical stability for intertrochanteric fractures. Data extraction was undertaken using a synthesis approach, gathering data on criteria of implants, sample size, fracture type, bone material, and study results.

RESULTS

The initial search identified a total of 1459 research papers, out of which forty-three papers were considered for final analysis. Due to the heterogeneous methods and parameters used in the included studies, meta-analysis was not feasible. A comprehensive assessment of implant characteristics and outcome parameters was conducted through biomechanical analysis. Various factors such as proximal and distal locking, nail diameter and length, fracture model, and bone material were thoroughly evaluated.

CONCLUSION

This scoping review highlights the need for standardization in biomechanical studies on intertrochanteric fractures to ensure reliable and comparable results. Strategies such as avoiding varus, maintaining a sufficient tip-apex-distance, cement augmentation, and optimizing lesser trochanteric osteosynthesis enhance construct stability. Synthetic alternatives may offer advantages over cadaveric bone. Further research and meta-analyses are required to establish standardized protocols and enhance reliability.

Biomechanical properties of artificial bones made by Sawbones: A review

Biomedical engineers and physicists frequently use human or animal bone for orthopaedic biomechanics research because they are excellent approximations of living bone. But, there are drawbacks to biological bone, like degradation over time, ethical concerns, high financial costs, inter-specimen variability, storage requirements, supplier sourcing, transportation rules, etc. Consequently, since the late 1980s, the Sawbones® company has been one of the world's largest suppliers of artificial bones for biomechanical testing that counteract many disadvantages of biological bone. There have been many published reports using these bone analogs for research on joint replacement, bone fracture fixation, spine surgery, etc. But, there exists no prior review paper on these artificial bones that gives a comprehensive and in-depth look at the numerical data of interest to biomedical engineers and physicists. Thus, this paper critically reviews 25 years of English-language studies on the biomechanical properties of these artificial bones that (a) characterized unknown or unreported values, (b) validated them against biological bone, and/or (c) optimized different design parameters. This survey of data, advantages, disadvantages, and knowledge gaps will hopefully be useful to biomedical engineers and physicists in developing mechanical testing protocols and computational finite element models.

Study protocol: biomechanical testing, finite element analysis and prospective, randomized, clinical study of single screw cephalomedullary nailing versus integrated dual interlocking screw fixation for unstable (31A21-3) intertrochanteric fractures in patients > 70 years old

BACKGROUND

Hip fractures are an increasingly common consequence of falls in older people that are associated with a high risk of death and reduced function. The vast majority of intertrochanteric fractures require surgical treatment to withstand early mobilization and weight bearing, which prevents complications due to prolonged bed rest and aids in fracture healing.

METHODS

This study is compromised by two parts, the experimental study and the clinical part. In the first part, a standard 130° nail will be used with the appropriate lag screw(s) and dynamic distal locking in synthetic osteoporotic femurs and the transmission of forces in the proximal femur, measured by a cortical surface-strain distribution, will be evaluated using digital image correlation. Finite element parametric models of the bone, the nails and their interface will be also developed. Finite element computations of surface strains in implanted femurs, after being validated against biomechanical testing measurements, will be used to assist the comparison of the nails by deriving important data on the developed stress and strain fields, which cannot be measured through biomechanical testing. In the other part, will set up a prospective, randomized, comparative clinical study among the Gamma3 and IT cephalomedullary nailing, in order to investigate if there are any statistical important differences in the main radiological measurements and functional status in closed unstable intertrochanteric fractures (A21-3) in patients aged over 70 years old at the 24-week follow-up evaluation using patient reported disease-specific outcomes.

DISCUSSION

This study will be the first to compare clinical, radiological and biomechanical measurements of the two different cephalomedullary nails. Our main hypothesis is that the IT nail would provide better radiological outcome and probably better clinical results than the Gama3 nail. Clinical trial registration International Standard Randomized Controlled Trial Number (ISRCTN): https://doi.org/10.1186/ISRCTN15588442 , registered on 19/4/2022.

Optimizing fixation methods for stable and unstable intertrochanteric hip fractures treated with sliding hip screw or cephalomedullary nailing: A comparative biomechanical and finite element analysis study

BACKGROUND

Despite recent advances in implants and surgical techniques, catastrophic and clinical failures in the treatment of intertrochanteric fractures continue to occur, with dire consequences in an overall frail population subset. The aim of the current study is to evaluate the effect of the factors under the surgeons' control, namely fracture reduction and implant selection, on the biomechanical behavior of fracture fixation constructs.

MATERIAL-METHODS

An experimental protocol was conducted with the use of instrumented sawbones, in order to validate the finite element models. The implants used were the Gamma3®and DHS systems. Subsequently, a series of scenaria were considered, including various reduction and implant angle combinations. Data were retrieved concerning the peak cancellous bone stresses around the hip screw and the volume of cancellous bone in the femoral head stressed at critical levels, as well as implant stresses and stresses on the cortical bone of the distal fragment.

RESULTS

All stable fracture models displayed significantly decreased cancellous bone stresses and implant stresses compared to their unstable counterparts, regardless of implant used. The effect of increasing implant angle led to a decrease in implant stresses in all models studied, but had a beneficial effect on the stresses in the cancellous bone of the proximal fragment only in the subgroups of stable fractures with both implants and unstable fractures treated with a cephalomedullary nail (CMN). In unstable fractures anatomically reduced, the use of CMN led to significantly lower peak stresses in the cancellous bone and a smaller volume of bone stressed at critical levels. Increasing the reduction angle by 5 ° led to a significant decrease in both peak stresses and volume of bone stressed at critical levels, more prominent in the sliding hip screw (SHS) models. Decreasing the reduction angle into varus by 5 or 10 ° led to a significant increase in bone and implant stresses regardless of implant used.

CONCLUSIONS

In stable two-part (AO31.A2) fractures the use of the SHS appears to be biomechanically equivalent to CMN. In unstable, anatomically reduced fractures, the use of CMN leads to significantly reduced cancellous bone stresses and decreased rotation of the proximal fragment during loading. A reduction in varus should be avoided at all costs. In unstable fractures treated with SHS a reduction in slight valgus appears to be biomechanically beneficial. The highest implant angle that allows for proper screw position and trajectory in the femoral head should be used for stable fractures with both implants and unstable fractures treated with Gamma3®.