Stress-shielding and periprosthetic bone loss after total hip arthroplasty (THA) may be clinically relevant for high-demand patients. Analysis of cortical and cancellous bone density (BD) changes in vivo after THA is of interest to basic science researchers and joint reconstruction surgeons. An insufficient periprosthetic bone stock may predispose to migration, early mechanical failure, and major problems in revision surgery. We used computed tomography (CT)-assisted osteodensitometry in two prospectively analyzed cohorts after cemented (n ¼ 21) versus noncemented (n ¼ 23) cup fixation. Periacetabular BD (mgCaHa/mL) was determined in five CT scans cranial and five CT scans at the level of the cup 10 days and 26 months postoperatively. For press-fit cups BD decreased significantly in all CT cans except in four out of the five scans of cortical bone cranial to the cup. The decrease was highest for cancellous bone ventral to the cup (À45 to À53%). After cemented cup fixation, significant cortical BD decrease was seen ventral to the cup (À11 to À20%). Cancellous BD decrased only ventral (À21 to À31%) and in two scans cranial (À11 and À12%) to the cup. The modes of load transfer between cemented and uncemented cups differ fundamentally. Cemented cups especially prevent the loss of cancellous bone of the acetabulum while also cortical BD loss was significantly lower in most CT scans surrounding the cemented cup compared to the press-fit component. Long-term results are required to prove whether third-generation cementing technique protects periprosthetic BD and thereby improve implant survival. Keywords: osteodensitometry; computed tomography; total hip arthroplasty; acetabulum; load transfer Bone is a highly organized tissue that reacts to mechanical load in a typical stress related pattern according to Wolff's law. 1 In the last century increasing knowledge of load transfer mechanisms and stress distribution patterns after total hip replacements was provided. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Most of these studies have focussed on stress shielding mechanisms after femoral stem implantation. [2][3][4][5][6]10 The most common technique to study bone density (BD) changes is dual X-ray absorptiometry (DXA), which is a reproducible two-dimensional measurement technique. [2][3][4][5][6][7]11,[15][16][17] To allow a differentiated three-dimensional analysis of cortical and cancellous bone structures after THA in vivo we have introduced a novel method of CT-assisted osteodensitometry. 9,10,13,14 In a previous study we have provided clear evidences for the reproducibility and validity of our method. 9 Opposed to DXA CT-assisted osteodensitometry allows the separate analysis of cortical and cancellous BD surrounding the prosthesis, which might be a potential advantage in studying mechanical load transfer mechanisms to the ilium after total hip arthroplasty. 13,14 A DXA based study by Sabo et al. 11 showed a decrease of periacetabular BD 24 months after implantation of a rigid press fit cup. T...
CT-osteodensitometry has the technical ability to discriminate between cortical and cancellous bone structures with respect to strain-adapted remodeling: sufficient cancellous and cortical bone stock remained dorsal and cranial to the cup indicative of a balanced load transfer to these regions. CT-osteodensitometry has the potential to become an effective instrument for quality control in THA and the method of choice for in vivo determination of periprosthetic BD. In contrast, plain radiography is more suitable for the early detection of radiolucent lines compared to axial CT scans.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.