Analysis of bone demineralization due to the use of exoprosthesis by comparing Young’s Modulus of the femur in unilateral transfemoral amputees

Abstract

Background: There is a relation between Hounsfield units obtained from computed tomography (CT) scans and bone density. The density of the bones can be used to establish its mechanical properties and therefore to assess the bone mechanical condition using CT images. Objectives: To identify the effect of the transfemoral amputation and the use of external lower limb prosthesis in the bone properties, by comparing Young’s modulus. Study Design: Young’s modulus comparison. Methods: Comparison of bone density between the healthy femur and the amputated bone of 20 unilateral transfemoral amputees was done by generating three histograms of the Hounsfield units at different parts of the femur. The histograms were created based on images obtained by CT and the Hounsfield units were translated to Young’s modulus to establish the comparison. Results: The results show a significant difference ( p-value <0.05) between the mean value of Young’s modulus of healthy and amputated bone. Conclusions: There is clearly a direct association between the use of external prosthesis and the bone demineralization due the stress shielding phenomenon. The Young’s modulus comparison using information from CT images can be a suitable tool to analyze the bone demineralization due to the use of exoprosthesis.

Association Between Combat‐Related Traumatic Injury and Skeletal Health: Bone Mineral Density Loss Is Localized and Correlates With Altered Loading in Amputees: the Armed Services Trauma Rehabilitation Outcome (ADVANCE) Study

“…Sherk and colleagues ( 12 ) first highlighted the possible similarities between BMD loss post‐amputation and BMD loss because of periods of prolonged unloading from scuba diving, ( 35 ) bed rest, ( 36 ) and space travel studies. ( 37 ) Later studies by Bemben and colleagues, ( 13 ) Ramirez and colleagues, ( 14 ) and Flint and colleagues ( 15 ) made similar comparisons and do not equate amputee BMD loss to osteoporosis or osteopenia but rather to physical phenomena such as bone stress shielding by the socket resulting in reduced load transmission through the skeleton. Although the concept of disuse osteopenia is well understood, the activity levels seen in this cohort suggest that the reduced BMD seen is more likely secondary to bone stress shielding through socket design.…”

“…There is some evidence in the literature from studies in older groups, using X-ray data as a surrogate of BMD, few numbers of amputees, without control groups, and without controlling or accounting for differences in activity levels, smoking or body mass index (BMI), that amputee bone loss is commonly localized to the amputated limb. (12)(13)(14)(15) Thus it is postulated that BMD loss in amputees is a mechanical phenomenon, similar to disuse osteopenia, where altered, nonphysiological loading, postamputation, drives progressive bone loss over the course of many remodeling cycles. Literature has suggested this might come from: offloading by the predominantly ischial tuberosity weight bearing prosthetic socket (13) that would be worse for above knee amputees than below knee amputees, bedrest immediately postsurgery, (12) reduced activity as ambulation becomes more challenging, (16,17) and significantly lowered muscle forces from extreme atrophy.…”

Triangular Mechanical Structure of the Proximal Femur

“…After the procedures above, six three‐dimensional reconstruction models of the proximal femur were generated and further imported into Geomagic Studio 14.0 (Geomagic, Inc., Research Triangle Park, NC, USA) in STL format for modification. Using the material function of the FEA module in the Mimics software, the density and elastic modulus of the proximal femoral bone structure were automatically defined according to the CT value of the bone structure 26 , and the Poisson's ratio of all bone structures was defined as 0.3 27 . Finally, these models were imported into Abaqus (Simulia, France) to generate the finite element models.…”

“…The threshold units ranged from 226 to 3071. The "region growing" tool was utilized to split the segmentation as Using the material function of the FEA module in the Mimics software, the density and elastic modulus of the proximal femoral bone structure were automatically defined according to the CT value of the bone structure 26 , and the Poisson's ratio of all bone structures was defined as 0.3 27 . Finally, these models were imported into Abaqus (Simulia, France) to generate the finite element models.…”

Preliminary Results of Size and Slide-Roll Effect on the Kinematics of Total Knee Replacements

“…of commercial knee replacements and supporting telesurgical technologies [1] are available for surgeons to carry out knee operations to restore closely the same kinematics of the physiological knee joint. Multiple, substantial studies have been published about how total knee replacement (TKR) design affects the kinetics [2,3] and kinematics [4] of the knee joint. It is also worth mentioning the indirect changes caused by TKR positioning during operation [5] or the effect of foot impairs in the general health of the knee joint [6].…”