Bone Quality Assessment Before Total Hip Arthroplasty: The Role of Densitometry

Abstract

Background Total hip arthroplasty (THA) is effective in the treatment of hip osteoarthritis. Radiographic evaluation, standard in THA planning, is sufficient in examining hip anatomy, although it may not precisely assess bone quality. A routinely implemented method in bone quality assessment is densitometry. The technique allows for a measurement of bone mineral density (BMD). Methodology In the study, we included 26 participants who qualified for THA. All the patients were preoperatively examined with radiographs and densitometry of the affected hip. On the preoperative anteroposterior radiograph, we measured the canal-to-calcar isthmus ratio (CC ratio) and the cortical index (CI). Intraoperatively, during the THA procedure, we measured the thickness of the cortical bone and the diameter of the femoral neck in the line of neck resection. Results The examination with Pearson's correlation coefficient revealed that BMD significantly positively correlates with the intraoperatively measured diameter of the femoral neck (r = 0.5, P = 0.009), and with the measured thickness of the cortical bone (r = 0.47, P = 0.015), CI significantly positively correlates with the intraoperatively measured diameter of the femoral neck (r = 0.6, P = 0.001), and with the CC ratio (r = 0.44, P = 0.024), the intraoperatively measured diameter of the femoral neck significantly positively correlates with the intraoperatively measured thickness of the cortical bone (r = 0.59, P = 0.001). All of the other correlations were not statistically significant. Conclusions BMD measurements can be used in THA planning as they positively correlate with intraoperative measurements. The radiological parameters (CC ratio and CI) may not be as precise in bone quality assessment.

Keywords: densitometry; osteoarthritis; preoperative planning; tha; total hip arthroplasty.

Figure 1. Representation of the radiological measurements taken in the study.

All the measurements were made according to the method previously described by Dorr et al. [10]. In the preoperative AP radiograph of the affected hip, we identified three lines perpendicular to the long axis of the femur: the reference line crossing the apex of the lesser trochanter, the line 3 cm below the reference line, and the line 10 cm below the reference line. On both the line 3 cm and the line 10 cm below the reference line, we identified two points along the endosteal margin of the femur. By connecting the lateral and the medial points of the endosteal margin we identified the lateral and the medial endosteal lines. Next, we identified three distances: the distance (X) between two points of the endosteal margin of the femur on the line 10 cm below the reference line, the distance (Y) between the points where the lateral and the medial endosteal lines cross the reference line and the distance (Z) between two periosteal surfaces on the line 10 cm below the reference line. CC ratio was calculated by dividing the distance (X) by the distance (Y). CI was calculated by dividing the difference between the distance (Z) and the distance (X) by the distance (Z). CI, cortical index; CC, canal-to-calcar isthmus