Evaluation of femoral head bone quality by Hounsfield units: A predictor of implant failure for intertrochanteric fractures after intramedullary nail fixation

Osteoporosis Assessment Using Bone Density Measurement in Hounsfield Units in the Femoral Native CT Cross-Section: A Comparison with Computed Tomography X-Ray Absorptiometry of the Hip

Background/Objectives: Bone mineral density (BMD) loss leads to osteoporosis, significantly increasing fracture risk in both the axial and peripheral skeleton. The extent to which it is possible to estimate the degree of osteoporosis in the hip by determining the density in Hounsfield Unit (HU) measurements derived from computed tomography (CT) scans and to calculate quantitative BMD and T values from the HU values should be examined. Methods: A total of 240 patients (mean age: 64.9 ± 13.1 years, BMI: 26.8 ± 6.8 kg/m2) underwent CT-based BMD assessments using CTXA-Hip. Subregions of the proximal femur, including the femoral head, femoral neck, and intertrochanteric region, were analyzed for cancellous density in HUs using circular and irregular region-of-interest (ROI) measurements. Correlations between HU values and DEXA-equivalent BMD (mg/cm2) and T values were computed. Predictive power for osteoporosis was evaluated using ROC curve analysis. Results: Cancellous bone density in the proximal femur showed a significant decline with increasing age and decreasing BMI (p < 0.05). The median BMD for the entire hip was 0.684 mg/cm2, and the median HU value for the proximal femur was 123.15. Strong correlations were observed between HU values and BMD (R2 = 0.904, p < 0.001) and T values (R2 = 0.911, p < 0.001). A T value of -2.5 corresponded to an HU value of 95.79 in the entire femur. ROC analysis demonstrated high sensitivity (0.92) and specificity (0.93) for HU-based osteoporosis prediction. Conclusions: HU measurements provide a reliable method for estimating BMD and T values in the proximal femur, offering a valuable diagnostic tool for osteoporosis. The highest predictive accuracy was achieved when using an irregular ROI from the entire proximal femoral region.

CT Hounsfield units in assessing bone and soft tissue quality in the proximal femur: A systematic review focusing on osteonecrosis and total hip arthroplasty

BACKGROUND

Computed tomography (CT) Hounsfield Units (HU) offer valuable insights into the changes in bone and soft tissue densities, playing a crucial role in the diagnosis and management of various proximal femur conditions. This systematic review aims to consolidate the application of HU in assessing tissue quality in the proximal femur, with a special focus on osteonecrosis of the femoral head (ONFH) and implications for total hip arthroplasty (THA), thereby addressing unresolved issues in these areas.

METHODS

We conducted a comprehensive literature search on MEDLINE/PubMed, EMBASE, Google Scholar, SpringerLink, Scops, Web of Science, and Bentham Science Publishers from inception to January 2024, following the PRISMA guidelines, to retrieve all studies relevant to the application of HU in assessing both bone and soft tissue quality of the proximal femur, particularly in the context of ONFH and THA. We systematically evaluated the key findings extracted from the included articles.

RESULTS

This systematic review included a total of 58 studies, involving 15,668 patients. The sample sizes ranged from 50 to 685, with the CT slice thickness varying from 0.5 mm to 10 mm. The results mainly focused on three areas: (1) the relationship between HU and the density of proximal femoral tissues (n = 33); (2) the assessment of HU in predicting the risk of femoral head collapse (n = 10); (3) the application of HU during the perioperative period of THA (n = 15).

CONCLUSION

(1) HU can effectively contribute to the evaluation of bone and soft tissue densities in the proximal femur, and reflect local stress changes. (2) In ONFH patients, bone density does not decrease in the necrotic area of the femoral head before collapse. However, abnormally elevated HU at the outer boundary of the necrotic lesion are significant in assessing collapse risk. (3) HU can be used to preoperatively assess hip bone quality for THA, guide surgical approaches, predict intraoperative fractures, monitor postoperative bone ingrowth or absorption, identify and quantitatively evaluate periprosthetic loosening, and guide postoperative rehabilitation.

Long vs short intramedullary nails for reverse pertrochanteric fractures: A biomechanical study

There is currently no definitive evidence for the implant of choice for the treatment of reverse pertrochanteric fractures. Here, we aimed to compare the stability provided by two implant options: long and short intramedullary nails. We performed finite element simulations of different patterns of reverse pertrochanteric fractures with varying bone quality, and compared the short vs long nail stabilization under physiological loads. For each variable combination, the micromotions at the fracture site, bone strain, and implant stress were computed. Mean micromotions at the fracture surface and absolute and relative fracture surface with micromotions >150 µm were slightly lower with the short nail (8%, 3%, and 3%, respectively). The distal fracture extension negatively affected the stability, with increasing micromotions on the medial side. Bone strain above 1 % was not affected by the nail length. Fatigue stresses were similar for both implants, and no volume was found above the yield and ultimate stress in the tested conditions. This simulation study shows no benefit of long nails for the investigated patterns of reverse pertrochanteric fractures, with similar micromotions at the fracture site, bone strain, and implant stress.

Mapping the Spatial Evolution of Proximal Femur Osteoporosis: A Retrospective Cross-Sectional Study Based on CT Scans

Purpose

The purpose of this study was to quantify the modifications occurring in osteoporosis at the level of the human proximal femur throughout the trabecular structure, along with the identification of certain anatomic regions preferentially affected by osteoporosis. Another goal was to map the evolution of the radiodensity of the trabecular bone as osteoporosis progresses to an advanced stage.

Methods

The study included CT scans (right femur) from 51 patients, out of which 40 had various degrees of osteoporosis, but no other local pathology. Ten regions of interest in two orthogonal slices have been identified and the differences in radiodensity as well as their evolution have been statistically analyzed in terms of relative and absolute changes.

Results

A detailed spatial map showing the evolution of osteoporosis was obtained. As osteoporosis evolved, the relative decrease in radiodensity was inversely correlated to the radiodensity of the healthy bone. In particular, the region covering the Ward triangle decreased the most, by an average 61-62% in osteopenia and 101-106% in advanced osteoporosis, while the principal compressive group was affected the least, showing a decrease by an average 14-15% in osteopenia and 29-32% in advanced osteoporosis. The absolute decrease in radiodensity was not correlated to the radiodensity of the healthy bone and was shifted to the inferior-posterior edge of the femur. Inside the femoral head, the upper region was affected the most in absolute terms, while the greater trochanter was less affected than the femoral neck. The maximum metaphyseal cortical bone density was unaffected by the progression of osteoporosis.

Conclusion

Significant differences were noticed in terms of the absolute and relative osteoporotic changes in radiodensity related to different anatomical regions of the human femoral bone. These differences become more pronounced as the disease progresses.