Alexander Kress

Periacetabular bone changes after uncemented total hip arthroplasty evaluated by quantitative computed tomography

Background There are few dual X-ray absorptiometry (DXA) studies on periacetabular bone density changes after cup implantation. This study was designed to analyze the load-transfer mechanism and stress pattern of periacetabular cortical and cancellous bone after implantation of a ihemispherical titanium alloy press-fit cup with alumina-alumina pairing in vivo. We introduced a novel method of computed tomography (CT)-assisted osteodensitometry. Method We investigated 26 hips (26 patients) with osteoarthritis using conventional sequential CT examinations performed within the first 10 days after implantation, and after a mean period of 1.1 years postoperatively. Bone density of full, cancellous and cortical bone (mgCaHA/mL) was measured. Results At the time of follow-up, the mean bone density values of the cortical bone cranial to the cup increased by 3.6% (p = 0.03) while the cancellous bone density decreased by 18%. Cancellous bone loss was greater in the region ventral to the cup (–35%) than in the dorsal region (–30%). Cortical bone density decreased ventral to the cup (–6.4%). All these changes were statistically significant. The bone density changes in the dorsal cortical region were not significant. Interpretation The method presented is an excellent tool for detailed measurement of bone density changes around the cup after total hip arthroplasty, and allows a thorough assessment of stress shielding phenomena in vivo. The hemispherical titanium alloy press-fit cup is a rigid implant which stress shields cancellous bone and enhances load transfer to the cranial cortical bone. Further investigations will demonstrate the impact these factors have on the long-term results of the implant, and may allow a type-related predictable prognosis of the longevity of the prosthesis.

Modes of periacetabular load transfer to cortical and cancellous bone after cemented versus uncemented total hip arthroplasty: a prospective study using computed tomography-assisted osteodensitometry.

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 = 21) versus noncemented (n = 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 (−45 to −53%). After cemented cup fixation, significant cortical BD decrease was seen ventral to the cup (−11 to −20%). Cancellous BD decrased only ventral (−21 to −31%) and in two scans cranial (−11 and −12%) 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.

Inter- and intraobserver assessment of periacetabular osteodensitometry after cemented and uncemented total hip arthroplasty using computed tomography

IntroductionThis study was initiated to evaluate the reproducibility of a novel method for measuring the periacetabular bone density after insertion of cemented and uncemented acetabular cups using CT in vivo.Materials and methodsCT scans were obtained from 20 patients after cemented polyethylene cup implantation (ZCA, Zimmer, USA) and 20 patients after uncemented titanium alloy cup fixation (Cerafit, Ceraver, France). A manual segmentation of cancellous and cortical pelvic bone ventral, dorsal and cranial to the cup was undertaken. Values are given in Hounsfield units. Inter- and intraobserver studies were conducted using a special analysis software tool. To define the reproducibility of the method, all measurements were evaluated according to Bland and Altman.ResultsFor both cemented and uncemented acetabular cups, reproducibility of bone density measurement for cortical and cancellous bone cranial, ventral and dorsal to the cup was high. There was no significant difference between the intraobsever study (two repeated measurements) and the interobserver study (two investigators), indicating the reproducibility of the method independent of the investigator.ConclusionIn conclusion, the periacetabular bone density measurement as conducted in this CT study is a new reproducible method for in vivo evaluation of cortical and cancellous pelvic bone after cemented and uncemented acetabular cup implantation. In vivo CT measurements will allow a thorough assessment of periacetabular stress-shielding phenomena.

Progressive femoral cortical and cancellous bone density loss after uncemented tapered-design stem fixation

Background Aseptic implant loosening and periprosthetic bone loss are major problems after total hip arthroplasty (THA). We present an in vivo method of computed tomography (CT) assisted osteodensitometry after THA that differentiates between cortical and cancellous bone density (BD) and area around the femoral component. Method Cortical and cancellous periprosthetic femoral BD (mg CaHA/mL), area (mm2) and contact area between the prothesis and cortical bone were determined prospectively in 31 patients 10 days, 1 year, and 6 years after uncemented THA (mean age at implantation: 55 years) using CT-osteodensitometry. Results 6 years postoperatively, cancellous BD had decreased by as much as 41% and cortical BD by up to 27% at the metaphyseal portion of the femur; this decrease was progressive between the 1-year and 6-year examinations. Mild cortical hypertrophy was observed along the entire length of the diaphysis. No statistically significant changes in cortical BD were observed along the diaphysis of the stem. Interpretation Periprosthetic CT-assisted osteodensitometry has the technical ability to discriminate between cortical and cancellous bone structures with respect to strain-adapted remodeling. Continuous loss of cortical and cancellous BD at the femoral metaphysis, a homeostatic cortical strain configuration, and mild cortical hypertrophy along the diaphysis suggest a diaphyseal fixation of the implanted stem. CT-assisted osteodensitometry has the potential to become an effective instrument for quality control in THA by means of in vivo determination of periprosthetic BD, which may be a causal factor in implant loosening after THA.

Quantitative Computed Tomography-Assisted Osteodensitometry of the Pelvis After Press-Fit Cup Fixation A Prospective Ten-Year Follow-up

BACKGROUND As a follow-up of a previously reported three-year study, we analyzed the periprosthetic acetabular cortical and cancellous bone density changes at ten years after implantation of a press-fit cup. METHODS Prospective clinical, radiographic, and quantitative computed tomography examinations were performed within ten days and at mean periods of one, three, and ten years after total hip arthroplasty with a press-fit cup, a femoral stem with a tapered design, and alumina-alumina pairing. Periacetabular cortical and cancellous bone density (mg CaHA/mL) in the cranial, ventral, and dorsal regions about the cup were measured for twenty-four hips in vivo. RESULTS All acetabular cups showed radiographic signs of stable ingrowth, and no acetabular component had to be revised. The loss of periacetabular cancellous bone density about the cup was as much as -37% cranially, -60% ventrally, and -71% dorsally; the decrease was progressive between the one-year and three-year examinations only. In contrast, cortical bone density above the dome of the acetabular cup remained constant throughout the ten-year follow-up. A moderate change in cortical bone density of -5% to -18% was seen at the level of the cup ten years postoperatively. CONCLUSIONS Both periacetabular cortical and cancellous bone density changes were nonprogressive between the three-year and ten-year examinations after press-fit cup fixation.

Periacetabular cortical and cancellous bone mineral density loss after press-fit cup fixation: a prospective 7-year follow-up.

The impact of total hip arthroplasty on strain adaptive bone remodeling has been extensively analyzed by dual-energy x-ray absorptiometry. In this study, we present a prospective computed tomography-assisted study of periacetabular cortical and cancellous bone mineral density (in milligrams of calcium hydroxyapatite [CaHA] per milliliter, or mgCaHA/mL) changes 10 days and 1, 3, and 7 years after press-fit cup implantation for 38 hips in vivo. Cancellous bone mineral density decreased by Ø -63% ventral and Ø -85% dorsal to the cup; cortical bone mineral density, by Ø -22% ventral and Ø -18% dorsal to the cup. The presented periacetabular strain adaptive bone mineral density data are the most extensive of the current literature. Even the measured extensive cancellous bone mineral density loss was thus far of no clinical relevance because all cups showed radiographic signs of stable ingrowth.

Comparison of cortical and cancellous bone remodeling of the pelvis after press-fit cup total hip arthroplasty dependent on patient and prosthesis-specific characteristics: a computed tomography-assisted osteodensitometry study in vivo

Abstract Even though periprosthetic bone loss is common after total hip arthroplasty, there is no scientific evidence whether it compromises the survival of the prosthesis. Using quantitative computed tomography-assisted osteodensitometry, we determined the pattern of periacetabular bone density (BD) changes of two different press-fit cups (54 hips) 10 days, 1 year and 3 years post-operatively. We measured cortical and cancellous BD at three points of time and evaluated the effects of patient-specific characteristics [age, gender, body mass index (BMI)], clinical function, and BD at index operation. Cancellous BD decreased in all periacetabular regions by up to -52% (p≤0.001). In contrast, cortical BD above the dome of the cup remained constant while at the level of the cup it decreased by up to -17% (p≤0.001). Older patients had significantly lower cortical (ventral and dorsal) and cancellous (cranial) BD values, obese patients had a higher cortical BD ventral, and patients with excellent clinical results had a higher cancellous BD ventral and dorsal to the cup. Changes in BD suggest high stress shielding of retroacetabular cancellous bone, while load is transmitted to cortical bone above the dome of the cup. Patient-specific characteristics were shown to affect BD, but long-term analysis is needed to show whether these effects are of clinical importance.

Evaluation of Periacetabular Bone Reaction after Total Hip Arthroplasty with Alumina-Alumina Pairing Using Computed Tomography

This study was initiated to evaluate periacetabular bone chan ges i uncemented total hip arthroplasty (THA) with a titanium hemispherical press-fit acetabular component and alumina-alumina pairing using computed tomography-assisted osteodensit metry. We studied the acetabular bone density (BD) changes that occurred in 24 patie nts at 2 weeks and again after 1 year post-operatively. At the time of follow-up the mean bone density values of the cortical bone cranial to the cup increased by 3.6% (p<0.05) while the c ancellous bone density decreased by -18.4% (p<0.001). For the retroacetabular area, both corti cal (-6.4%, p<0.005) and cancellous (-29.6%, p<0.001) bone density decreased. These changes repres ent a response to a decrease in regional bone stress induced by the presenc e of the press-fit implant with aluminia-aluminia pairing and might be considered as retroacetabular stress shielding. Introduction Periprosthetic bone loss is a well known issue in total hip arthroplas ty. Loss of periprosthetic bone mineral density can compromise the long term outcome [1, 2]. Compute d tomography (CT) is a standardized radiological method for the assessment of bone structures with high validity and resolution [3]. CT generates sectional views of the bone surrounding the prosthesis, permitting a separation of cortical and cancellous bone. F init element analysis of periacetabular stress distribution after THA have postulated a B D increase in the cortical bone cephaled to the cup, decrease of the cancellous BD in the same regi on [4] and extensive attenuation of BD medial to the cup [5]. Key Engineering Materials Online: 2003-05-15 ISSN: 1662-9795, Vols. 240-242, pp 863-866 doi:10.4028/www.scientific.net/KEM.240-242.863