Aims. This study was designed to develop a model for predicting bone mineral density (BMD) loss of the femur after total hip arthroplasty (THA) using artificial intelligence (AI), and to identify factors that influence the prediction. Additionally, we virtually examined the efficacy of administration of bisphosphonate for cases with severe BMD loss based on the predictive model. Methods. The study included 538 joints that underwent primary THA. The patients were divided into groups using unsupervised time series clustering for five-year BMD loss of Gruen zone 7 postoperatively, and a machine-learning model to predict the BMD loss was developed. Additionally, the predictor for BMD loss was extracted using SHapley Additive exPlanations (SHAP). The patient-specific efficacy of bisphosphonate, which is the most important categorical predictor for BMD loss, was examined by calculating the change in predictive probability when hypothetically switching between the inclusion and exclusion of bisphosphonate. Results. Time series clustering allowed us to divide the patients into two groups, and the predictive factors were identified including patient- and operation-related factors. The area under the receiver operating characteristic (ROC) curve (AUC) for the BMD loss prediction averaged 0.734. Virtual administration of bisphosphonate showed on average 14% efficacy in preventing BMD loss of zone 7. Additionally, stem types and preoperative triglyceride (TG), creatinine (Cr), estimated glomerular filtration rate (eGFR), and creatine kinase (CK) showed significant association with the estimated patient-specific efficacy of bisphosphonate. Conclusion. Periprosthetic BMD loss after THA is predictable based on patient- and operation-related factors, and optimal prescription of bisphosphonate based on the prediction may prevent BMD loss. Cite this article: Bone Joint Res 2024;13(4):184–192

Introduction. Several short femoral stems have been introduced in primary total hip arthroplasty, supposedly in order to save proximal bone stock. We intended to analyse primary stability, changes in periprosthetic bone mineral density (BMD), and clinical outcome after insertion of the uncemented collum femoris preserving (CFP)-femoral device. Methods. A prospective cohort study on 30 patients scheduled for receiving the CFP-stem combined with an uncemented cup was carried out. Stem migration was analysed by radiostereometry (RSA). Preoperative total hip BMD and postoperative periprosthetic BMD in Gruen zones 1–7 was investigated by DXA, and the Harris hips score (HHS) was determined. The patients were followed up to 12 months. Results. 2 patients were intraoperatively excluded because their proximal femur was found to be unsuitable for insertion of the studied implant, 1 patient was later revised due to a deep infection. This left 27 patients for final analysis. RSA showed that only very little migration of the implant occurred, with the largest amplitude found in rotation around the y-axis (1.8°, SD 0.6, after 12 mths), representing minimal stem retroversion. DXA after 12 mths demonstrated substantial BMD loss in Gruen zones 7 (−30.8%), 6 (−19.1%) and 2 (−13.3%, p-values for all described changes <0.001 when comparing with baseline BMD determined immediately postoperatively). There was a moderate correlation of low preoperative total hip BMD with a higher amount of bone loss in Gruen zones 2 (Pearson correlation coefficient r = 0.6, p = 0.001), 6 (r = 0.5, p = 0.005) and 7 (r = 0.6, p = 0.003). In contrast, we found no correlation of periprosthetic bone loss in any of the Gruen zones 1–7 with logarithmically transformed maximal total point translation (MTPT) of the stem (p > 0.05 for all regions), neither after 3 nor after 12 mths. The mean HHS increased from 49 (SD 15) preoperatively to 99 (SD 2) after 12 mths. Interpretation. Based on these short-term data, we conclude that i) the studied implant seems to be stable within the first year, ii) substantial loss in periprosthetic BMD - with a predominance in the calcar region - occurs, iii) low preoperative total hip BMD predisposes towards greater loss of periprosthetic BMD after 12 months, iv) postoperative loss in periprosthetic BMD does not correlate with increased stem migration. Clinical results are excellent so far. Continuing follow-up will reveal whether this novel stem remains stable in the medium and long term, and whether the loss in BMD in the regions mentioned above can be recovered with time or whether it continues

Introduction: Continous periprosthetic bone loss after uncemented THA may lead to proximal femoral atrophy and increase the risk for aseptic loosening or peripros-thetic femoral fracture in the long-term. Little is known about the extent and the pattern of bone remodeling around stable, straight uncemented stems after 15 years. Patients and Methods: In a prospective longitudinal study, bone mineral density (BMD) was measured in 131 patients with 146 stable, uncemented, double- tapered, grit- blasted stems (CLS Spotorno, Zimmer, Warsaw, USA) using dual- energy x-ray absorptiometry (DEXA) after a mean of 12 years (range:10–15, t1) postoperatively. Patients were followed with radiographs and Harris hip scores (HHS), and a second and third DEXA were performed at a mean follow-up of 17 years (range: 15–20, t2) and 22 years (range: 20–25, t3) using the identical protocol. Results: We obtained a complete prospective set of data of three consecutive DEXA measurements for 37 hips (32 patients, 14 male, 18 female). In all cases regular bone ongrowth did occur and on radiographic evaluation there were no signs of loosening and no significant change in periprosthetic bone formation. There was no case of severe bone loss and no case of diaphyseal cortical hypertrophy. We analyzed the differences in overall femoral BMD (netavg) and in BMD in zones 1–7 according Gruen. There was no significant change in overall netavg BMD for both male and female patients (p> 0,05) comparing t1 and t3. We found a significant change in periprosthetic BMD in zone 7 (−6,62%, p< 0,05) in male patients and in zones 1, 6 and 7 (−8,7%/−5,1%/−14,2%, p< 0,01/0,05/0,01) in female patients. Discussion and Conclusion: The results of our study suggest that there are no clinically relevant changes in overall periprosthetic BMD around stable, uncemented straight stems in the long- term. However, continuous bone remodeling with slow but steady proximal bone loss occurs, predominantly in female patients. Once osseous integration is observed, stress shielding remains moderate and changes in periprosthetic BMD are limited to the metaphyseal region

Objectives. Our primary aim was to describe migration of the Exeter stem with a 32 mm head on highly crosslinked polyethylene and whether this is influenced by age. Our secondary aims were to assess functional outcome, satisfaction, activity, and bone mineral density (BMD) according to age. Patients and Methods. A prospective cohort study was conducted. Patients were recruited into three age groups: less than 65 years (n = 65), 65 to 74 years (n = 68), and 75 years and older (n = 67). There were 200 patients enrolled in the study, of whom 115 were female and 85 were male, with a mean age of 69.9 years (sd 9.5, 42 to 92). They were assessed preoperatively, and at three, 12 and, 24 months postoperatively. Stem migration was assessed using Einzel-Bild-Röntgen-Analyse (EBRA). Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Harris Hip Score (HHS), Hip Disability and Osteoarthritis Outcome Score (HOOS), EuroQol-5 domains questionnaire (EQ-5D), short form-36 questionnaire (SF-36,) and patient satisfaction were used to assess outcome. The Lower Extremity Activity Scale (LEAS), Timed Up and Go (TUG) test, and activPAL monitor (energy expelled, time lying/standing/walking and step count) were used to assess activity. The BMD was assessed in Gruen and Charnley zones. Results. Mean varus/valgus tilt was -0.77⁰ and axial subsidence was -1.20 mm. No significant difference was observed between age groups (p ⩾ 0.07). There was no difference according to age group for postoperative WOMAC (p ⩾ 0.11), HHS (p ⩾ 0.06), HOOS (p ⩾ 0.46), EQ-5D (p ⩾ 0.38), patient satisfaction (p ⩾ 0.05), or activPAL (p ⩾ 0.06). Patients 75 years and older had a worse SF-36 physical function (p = 0.01) and physical role (p = 0.03), LEAS score (p < 0.001), a shorter TUG (p = 0.01), and a lower BMD in Charnley zone 1 (p = 0.02). Conclusion. Exeter stem migration is within normal limits and is not influenced by age group. Functional outcome, patient satisfaction, activity level, and periprosthetic BMD are similar across all age groups. Cite this article: N. D. Clement, M. Bardgett, K. Merrie, S. Furtado, R. Bowman, D. J. Langton, D. J. Deehan, J. Holland. Cemented Exeter total hip arthroplasty with a 32 mm head on highly crosslinked polyethylene: Does age influence functional outcome, satisfaction, activity, stem migration, and periprosthetic bone mineral density? Bone Joint Res 2019;8:275–287. DOI: 10.1302/2046-3758.86.BJR-2018-0300.R1

The pattern and magnitude of pelvic periprosthetic bone loss around cementless metal-backed acetabular implants have previously been described. The pattern of periprosthetic BMD change around cemented all-polyethylene acetabular implants is unreported. The aims of this study were to determine the precision of pelvic BMD measurements around the Charnley cup and to examine the longitudinal pattern of BMD change over the first 2 years after surgery. 19 subjects who had previously received a Charnley cup for osteoarthritis underwent duplicate measurements of pelvic BMD after repositioning using an Hologic QDR 4500A densitometer. Scan analysis was carried out using a 4-region of interest model according to a protocol previously described. In-vivo precision was expressed as coefficient of variation (CV%) for each region of interest. The precision of pelvic periprosthetic BMD measurements were 7.7%, 9.8%, 10.8%, and 9.9% for regions 1 to 4, respectively. Longitudinal BMD changes were measured over a 2 year period in 32 patients (mean age 74 years; 22 women) undergoing cemented THA for unilateral osteoarthritis (17 right-sided). Transient decreases in BMD were observed in regions 2 and 3 (behind the dome of the implant) at 3 months (−9.0% and −13.2%, respectively; P< 0.05) and at 1 year (−8.1% and −9.3%; P< 0.05). By 2 years there had been some recovery in bone mass (BMD−6.9% and −2.6% respectively). No significant changes in BMD for regions 1 and 4 (located at the rim of the implant) were found. The precision of pelvic periprosthetic BMD measurements for the cemented Charnley cup are poorer than those we have previously reported for cementless cups and may be due, in part, to cement artifact. The pattern of BMD change observed for the Charnley implant suggests that load transfer between the implant and the pelvis occurs principally at the implant rim. The magnitude of bone loss is similar to that we have previously reported for cementless metal-backed acetabular implants

This study aimed to A) establish a protocol for measuring periprosthetic bone mineral density (BMD) of the proximal humerus following implant arthroplasty, and B) compare the differences in the periprosthetic BMD values 4–9 years after surface replacement and stemmed arthroplasties of the proximal humerus. The study design was of retrospective independent samples cohorts, of patients who had received a proximal humeral arthroplasty between January 1992 and December 1996 in a tertiary referral shoulder unit of a UK hospital. The exclusion criteria were A) patient unavailable for study, B) patient refusal, C) inadequate information of dependent and independent variables, or D) obvious measurement errors. All available patients underwent DEXA scanning of the proximal humerus using a Lunar DPXL scanner fitted with Orthopaedic Hip software version 1.3. Replicable patient positioning with a special jig was used. On a predetermined format of Gruen equivalent zones and sub-zones, BMD values in gm/cm. 2. were plotted. Cortical thickness on plain radiographs was recorded for each zone. Femoral neck DEXA scan was performed to obtain a proportionate value of BMD of the proximal humerus, in order to eliminate the effect of confounding variables. Confounding variables accounted for were age, gender, height, weight, activity level, indication for surgery, duration of implantation, dominance, type of arthroplasty (hemi or total) and use of cemented or uncemented stemmed implants. Statistical analysis was performed using Microsoft excel as well as SPSS software. Initially, 58 shoulders in 52 patients were recruited. 6 patients declined to participate for ill health, 6 had moved out of the area and 8 did not attend or reply. Of the remaining 31 shoulders in 25 patients, 2 patients had an obviously erroneous DEXA reading. 29 shoulders in 23 patients were finally analysed, which included 10 male and 19 female shoulders. Average age was 67.5 years and average time since surgery was 6 years 2 months. Indications for surgery were RA in 14, OA in 8 and other reasons in 7. Of 29 shoulders, 20 received a total replacement, 9 a hemiarthroplasty. The inevitable obliquity of the image caused some difficulties in maintaining accuracy and difficulties were observed due to limitation of the software to measure thin cortices and to distinguish between the cement and bone. There was no significant correlation between gross cortical thickness and BMD values, and the average periprosthetic BMD was 0.54 g/cm. 2. Surface replacement implants were associated with relative preservation of proximal medial cortex and higher BMD values in this region. BMD values were consistently higher at the level of stem tip for the stemmed implants. No such phenomenon was observed for the surface replacement prostheses. Hemiarthroplasty was associated with relatively higher BMD values in the proximal medial cortical region than total arthroplasty

Aims. Modular dual mobility (DM) prostheses in which a cobalt-chromium liner is inserted into a titanium acetabular shell (vs a monoblock acetabular component) have the advantage of allowing supplementary screw fixation, but the potential for corrosion between the liner and acetabulum has raised concerns. While DM prostheses have shown improved stability in patients deemed ‘high-risk’ for dislocation undergoing total hip arthroplasty (THA), their performance in young, active patients has not been reported. This study’s purpose was to assess clinical outcomes, metal ion levels, and periprosthetic femoral bone mineral density (BMD) in young, active patients receiving a modular DM acetabulum and recently introduced titanium, proximally coated, tapered femoral stem design. Patients and Methods. This was a prospective study of patients between 18 and 65 years of age, with a body mass index (BMI) < 35 kg/m. 2. and University of California at Los Angeles (UCLA) activity score > 6, who received a modular cobalt-chromium acetabular liner, highly crosslinked polyethylene mobile bearing, and cementless titanium femoral stem for their primary THA. Patients with a history of renal disease and metal hardware elsewhere in the body were excluded. A total of 43 patients (30 male, 13 female; mean age 52.6 years (. sd. 6.5)) were enrolled. All patients had a minimum of two years’ clinical follow-up. Patient-reported outcome measures, whole blood metal ion levels (ug/l), and periprosthetic femoral BMD were measured at baseline, as well as at one and two years postoperatively. Power analysis indicated 40 patients necessary to demonstrate a five-fold increase in cobalt levels from baseline (alpha = 0.05, beta = 0.80). A mixed model with repeated measures was used for statistical analysis. Results. Mean Harris Hip Scores improved from 54.1 (. sd. 20.5) to 91.2 (. sd. 10.8) at two years postoperatively (p < 0.001). All patients had radiologically well-fixed components, no patients experienced any instability, and no patients required any further intervention. Mean cobalt levels increased from 0.065 ug/l (. sd. 0.03) preoperatively to 0.30 ug/l (. sd. 0.51) at one year postoperatively (p = 0.01) but decreased at two years postoperatively to 0.16 ug/l (. sd. 0.23; p = 0.2). Four patients (9.3%) had a cobalt level outside the reference range (0.03 ug/l to 0.29 ug/l) at two years postoperatively, with values from 0.32 ug/l to 0.94 ug/l. The mean femoral BMD ratio was maintained in Gruen zones 2 to 7 at both one and two years postoperatively using this stem design. At two years postoperatively, mean BMD in the medial calcar was 101.5% of the baseline value. Conclusion. Use of a modular DM prosthesis and cementless, tapered femoral stem has shown encouraging results in young, active patients undergoing primary THA. Elevation in mean cobalt levels and the presence of four patients outside the reference range at two years postoperatively demonstrates the necessity of continued surveillance in this cohort. Cite this article: Bone Joint J 2019;101-B:365–371

Purpose. The purpose of this study was to evaluate periprosthetic bone mineral density (BMD) changes around a cementless short tapered-wedge stem and determine correlations between BMD changes and various clinical factors, including daily activity, after total hip arthroplasty (THA) with a short tapered-wedge stem. Methods. The study included 65 patients (65 joints) who underwent THA with a TriLock stem. At baseline, and 6, 12, and 24 months postoperatively, BMDs of the seven Gruen zones were evaluated using dual-energy X-ray absorptiometry. Correlations were determined between BMD changes and clinical factors, including the Harris hip score, body mass index, University of California at Los Angeles (UCLA) activity rating score, age at surgery, and initial lumbar BMD. Results. Minimal BMD changes were noted in the distal femur (Gruen zones 3, 4, and 5). However, significant BMD loss was noted in zone 7 at each time point. BMD loss was also noted in zone 1 at 6 and 12 months postoperatively, but BMD recovered after 18 months. Significant positive correlations were noted between BMD changes and the UCLA activity rating score in zones 1, 6, and 7. Additionally, negative correlations were noted between BMD changes and initial spine BMD in zones 2 and 3. Table legends. Table 1 Background of the patients. Table 2 Bone mineral density changes (%) at 6, 12, and 24 months postoperatively in the seven Gruen zones. Columns represent mean ± standard deviation. ※indicates P < 0.05 compared with baseline bone mineral density. Table 3 Correlations between periprosthetic bone mineral density changes and clinical factors (the Harris hip score, body mass index, University of California at Los Angeles activity rating score, age at surgery, and initial lumbar bone mineral density) in the seven Gruen zones at 24 months postoperatively. Correlation coefficients and P-values are presented. Boldface indicates P < 0.05. Conclusion. Periprosthetic BMD was maintained in the proximal femur, especially Gruen zone 1, with a short tapered stem. Daily activity may reflect improvements in periprosthetic bone quality after THA with a short tapered stem; however, this stem is not recommended in patients with low bone quality. To view tables, please contact authors directly

Purpose. The study aim was to assess how the periprosthetic bone density of the MiniHip™ changed in the course of the first year. Is there a correlation between the decrease in bone density with CCD angle or stem size? Are there other variables influencing the changes in bone density?. Material and Methods. 62 patients aged 25–78 years (34 women, 28 men) were implanted with a MiniHip total hip replacement during 2011 and 2012 through an anterolateral minimally invasive (ALMI) approach. Pre-operative diagnosis was osteoarthritis in 49 patients, dysplasia in 7, femoral necrosis in 4 and femoral neck fracture in 2 cases. As a primary variable the periprosthetic bone mineral density (BMD) was measured postoperatively within the first 2 weeks as a baseline measurement. Follow-up measurements were performed at 3, 6 and 12 months postoperatively. Statistical analysis was conducted to show any differences. Results. There is an initial post-operative loss of BMD in the first 3 months due to surgery and inactivity, with a significant decrease in the periprosthetic BMD proximally in Gruen Zones 1 (10.05%), 2 (12.37%) and 7 (10.05%) and distally in Gruen Zone 4 (6.9%). The density in the remaining Gruen regions also decreased but was not significant. In the following 3 months, the decrease in this Gruen regions continues without being significant. But after 6 months the bone mineral density shows a regeneration. At 12 months compared with the 6 months results there is an increase in BMD in Gruen Zones 1 (5.09%) and 7 (2.82%), also an increase in Gruen Zone 3 (1.75%) and 4 (1.78%) [Fig. 1]. A significant correlation between stem size and proximally bone loss in Gruen zones 1 & 7 was seen. In Gruen zone 1, there is also a correlation between bone loss and femoral neck angle, whereas this correlation was not significant in Gruen zone 7, but showing the same tendency. The analysis of covariables showed no dependencies of the results to sex, diagnosis or bearing surfaces. Conclusion. The MiniHip shows a loss of bone mineral density immediately post-operatively. After the initial decrease there was an increase especially in the proximal Gruen zones 1 and 7. Compared to other cementless short stems there was a lower bone density decrease [Fig. 2]. MiniHip™ loads the proximal femur in a more physiological way, which may preserve more bone in zones 1 and 7

Aim: Stress-shielding is a common problem after uncemented THA that may lead to proximal femoral atrophy and consecutive aseptic loosening. Methods: In 143 patients with 154 uncemented CLS-stems periprosthetic bone mineral density (BMD) was measured using DXA after a mean of 12 years (10–15) postoperatively (T1). Five years later the same group of patients was examined at a mean of 17 years (range: 15–20) (T2) using the identical protocol. Results: We obtained a complete prospective set of data of two consecutive DXA measurements in 76 cases (32 men, 44 women). In all cases regular bone ongrowth did occur and there were no signs of radiographic loosening (T1 and T2). On radiographic evaluation there was no significant change in periprosthetic bone formation in all Gruen zones between T1 and T2. There was no significant change in activity and BMD. In male patients we found no significant changes in periprosthetic BMD (netavg T1–T2: −1,19%, p< 0,01), in female patients there was no significant difference either (netavg T1–T2: −1,32%,p< 0,01). We analyzed the differences in BMD in all Gruen zones (zone 1–7) comparing T1 and T2 and found no significant differences in any zone (p< 0,01). Conclusion: This study showed that there is no significant change in periprosthetic bone mineral density in the long term using the uncemented CLS stem. There was not a single case of stress shielding in the long term. Once osseous integration has occurred the periprostethic BMD changes remain minimal in the long term

Purpose. Use of a large femoral head metal-on-metal bearing in total hip arthroplasty may offer an advantage in terms of dislocation rates and more natural joint kinematics. The acetabular component is more rigid however in these prostheses and if not placed accurately can lead to increased levels of metal ion release. A prospective randomized controlled trial was conducted to quantify bone mineral density on the acetabular side, as well as compare metal ion levels from a standard metal-on-polyethylene bearing to a large head metal-on-metal bearing in primary total hip arthroplasty. Method. Fifty patients were randomized to receive total hip arthroplasty with either the CONSERVE A-Class Total Hip with BFH femoral head or the Lineage acetabular component with polyethylene insert and cobalt chrome femoral head. There were 27 females (11 BFH) and 23 males (14 BFH), with a mean overall age of 61.6 (range 47.7–73.2). Serum levels of cobalt, chromium, and titanium were measured at regular intervals up to two years. Harris Hip Score, WOMAC, UCLA, and RAND-36 were completed at these same intervals. Standard radiographs as well as periprosthetic BMD were performed. Results. Bone mineral density in acetabular zones II, III, and IV was greater in the BFH group compared with the metal on poly group (p= 0.030, 0.046, and 0.019 respectively). Serum levels of cobalt (2.31 microg/mL vs 0.23 microg/mL, p=<0.001) and chromium (1.53 microg/mL vs 0.21 microg/mL, p=<0.001) were statistically higher in the BFH group compared with the metal-on-polyethylene group at one year post-op. There was no significant difference in serum titanium levels between groups. Conclusion. At short term follow up the load transfer to the acetabular bony bed differed between the two groups, with the more rigid shells demonstrating increased BMD in certain zones when compared with metal on poly. Serum levels of certain ions were 7–15 fold higher in the metal-on-metal large femoral head design compared with a standard metal-on-polyethylene. We await results on any clinical differences in performance and complications in this group of patients. Systemic implications of these ion levels are not known and further study is warranted

Periprosthetic bone loss is identified after inserting a hip prosthesis and is many times a result of stress shielding or altered loading of the proximal femur. Depending on the severity, the bone loss may threaten the prosthesis survival. The current study investigated the effect of cyclic etidronate therapy on periprosthetic and contralateral bone mineral density (BMD) in an one-year, prospective, randomized, double-blind study on 46 patients after cemented hip arthroplasty. Etidronate was administered orally in a regimen repeated every 14 weeks and periprosthetic BMD was measured with dual energy X-ray absorptiometry (DXA) in the total periprosthetic area and in the seven Gruen Zones at 1 week (baseline), 6 weeks, 3 months, 6 months, and 12 months postoperatively. In the etidronate group there were significant temporal BMD decreases measured in Gruen Zones 2, 3, 6, and 7 as well as in the entire proximal femur; the greatest decrease was 11.1% and was measured in Zone 2 at 12 months. Also in the etidronate group, there was a significant 3.4% increase in BMD of the spine at 12 months. In the placebo group there were significant temporal BMD decreases measured in Gruen Zones 1, 2, 3, 4, 6, and 7 as well as in the entire proximal; the greatest decrease was 16.4% and was measured in Zone 7 at 12 months. There were no significant differences between the mean BMD measurements of the etidronate and placebo groups with the exception of the mean percent change in the spine at 6 months and 12 months, and in Gruen Zone 3 at 6 months; in all three cases the etidronate group had significantly greater mean values. These findings suggest that cyclic etidronate therapy has no significant effect in surpressing the periprosthetic bone loss following cemented hip arthroplasty

Aim of the study: The aim of the study was to register and þnd out the longterm femoral bone response after insertion of femoral stem with or with-out cement. Materials and methods: Seventeen patients (7 men, 10 women) underwent cemented and 22 patients (14 men, 8 women) uncemented total hip arthroplasty (THA). The mean age in the cemented group was 69 (58–74) years and in the uncemented group 58 (46–68) years. Femoral bone mineral density (BMD) was measured using Lunar DPX or Lunar DPX-IQ densitometry according to zones by Gruen (ROI 1–7). BMD measurements were made preoperatively, and postoperatively over four to 14 days, and at 3, 6, 12, 24, and 36 months after THA. Postoperative BMD changes were calculated using the immediate postoperative BMD value as a reference, the change being expressed as a percent. Results: Peri-prosthetic BMD decreased signiþcantly almost in all ROIs during the þrst three months after both cemented (5–18%) and uncemented (3–14%) THA (p-values < 0.05 to p< 0.001). At the end of the þrst year the most remarkable decrease in BMD was found in the calcar (zone 7) in both groups (cemented 25%; uncemented 23%). Low preoperative bone loss predicted higher periprosthetic bone loss in both groups. From one to three year only small changes in periprosthetic BMD were detected after THA. Conclusions: The present study suggests that postoperative bone loss is equal after uncemented and cemented THA. The bone loss is most pronounced during the þrst six months after THA and mainly associated in proximal femoral bone. After the phase of acute bone loss, further loss is minimal after uncomplicated THA, reßecting merely the normal aging of bone. Patients with poor bone quality at baseline are at higher risk to lose bone around the prosthesis after THA

Aseptic loosening arises when periprosthetic bone loss results in mechanical failure at the host-implant interface, and is the main factor limiting implant survival after total hip arthroplasty (THA). The aims of this study were to determine whether genetic variation is a risk factor for loosening, explore the metabolic mechanisms of periprosthetic bone loss, and determine whether bisphosphonates may prevent bone loss and enhance implant mechanical stability after THA. In a genetic association study (. J Bone Mineral Res. 2003. ; . 18. :. 1995. –2001. ) we found that carriage of the −238A allele within the promoter region of the TNF gene was an independent risk factor for aseptic loosening. A subsequent reporter gene assay showed differential TNF gene responsiveness between the –238A and –238G alleles to polyethylene particule stimulation (Calcified Tissue Int 2003; 72: 251-273). In a cross-sectional study (J Orthop Res 2003; 214: 691–696) we found that subjects with aseptic loosening had lower bone mineral density (BMD) in the region of the femoral calcar and higher urinary excretion of cross-linked collagen breakdown products than their counterparts with fixed femoral implants. In a randomised controlled trial we found that a single dose infusion of a bisphosphonate (pamidronate) reduced femoral bone loss over 2 years after THA, but did not affect pelvic bone loss or implant migration (. J Bone Miner Res. 2002. ; . 17. : . 1328. ). Transient increases in bone turnover markers occurred after surgery and were highly predictive of later femoral BMD change. The main predictor of early implant migration was patient age, but not periprosthetic BMD change. In summary, genetic as well as environmental factors affect implant survival after THA. Aseptic loosening is associated with regional changes in bone mass and turnover as well as focal osteolytic lesions. Bisphosphonate therapy is well tolerated after THA and has a clear biological effect. However, the impact of preventing early bone loss on late aseptic loosening remains unclear and awaits long term study. [Winner, Robert Jones Gold Medal and Association Prize, 2003]

Summary. Five year migration results of 49 large-head metal-metal (MoM) total hip arthroplasties show good implant stability and no association between implant migration and metal-ions levels, stem and cup position, or femoral bone mineral density. Introduction. The failure mechanism of metal-metal (MoM) total hip arthroplasty has been related to metal wear-debris and pseudotumor, but it is unknown whether implant fixation is affected by metal wear-debris. Patients and Methods. In July-August 2012 41 patients (10 women) at a mean age of 47 (23–63) years with a total of 49 MoM hip arthroplasties (ReCap Shell/M2a-Magnum head/Bi-Metric stem; Biomet Inc.) participated in a 5–7 year follow-up with blood tests (chrome and cobalt serum ions), questionnaires (Oxford Hip Score (OHS) and Harris Hip Score (HHS), measurement of cup and stem position and periprosthetic BMD. Further the patients had been followed with stereo-radiographs post-operative and at 1, 2 and 5 years for analysis of implant migration (Model-Based RSA 3.32). Results. 4 patients (6 hips) had elevated metal-ion levels (>7ug/l). The mean cup inclination was 45°(sd 6), the mean cup anteversion was 17°(sd7), and the mean stem anteversion was 19°(sd7). The difference between genders was statistically insignificant (p>0.09). At 5 years follow-up total translation (TT) for the stems (n=39 hips) was a mean 0.79mm (sd 0.53) and total rotation (TR) was a mean 1.99° (sd 1.53). Between 1–2 years there was no significant difference in mean TT (p=0.49)for the stems and between 2–5 years TT was mean 0.13 mm (sd 0.35) which was significant (p=0.03) but clinically very small and within the precision limits of the method. We found no significant migration along the 3 separate axes. There was no significant association between stem migration and metal ion levels >7ug/l (p=0.55), female gender (p=0.86), stem anteversion > 25° (p=0.29), T-scores < −1 (p=0.23), total OHS < 40 (p=0.19) or total HHS < 90 (p=0.68). Between 1–5 years there was no significant change in neither subsidence (p=0.14) nor in version (p=0.91) of the stems. At 5 years TT for the cups (n=36) was mean 1.21 mm (sd 0.74) and TR was mean 2.63° (sd 1.71). Between 1–2 years cup migration along the z-axis was mean 0.29 (sd 0.73) (p=0.03), which was also within precision limits of the method. There was a positive association between total OHS below 40 (n=4) and cup migration (p=0.04), but no association between cup migration and metal ion levels >7ug/l (p=0.80), female gender (p=0.74), cup inclination > 50° (p=0.93), cup anteversion > 25° (p=0.88) or HHS < 90 (p=0.93). Proximal cup migration at 5 years was mean 0.46 mm (sd 0.47), which was similar to the cup migration at 1 year (p=0.91) and 2 years (p=0.80) follow-up. No patients were revised before the final 5–7 year follow-up. Patient satisfaction was high (94%). Conclusion. All cups and stems were well-fixed between 1–5 years. We found no statistical significant correlation between implant migration and other factors that have been associated with failure of MoM hip arthroplasty such as elevated metal ion levels, component position, and female gender. Cup migration was higher in patients with a total OHS below 40. In conclusion, metal wear-debris does not seem to influence fixation of hip components in large-head MoM articulations at mid-term follow-up

Introduction: Bone resorption in the proximal femur is commonly seen after cementless total hip arthroplasty (THA). One of the main determinants of bone remodeling seems to be prosthesis design. With DXA, the amount of bone mass after THA can be precisely determined. We evaluated the BMD behavior of two different ultra-short implants with proximal load transfer, in order to study how a design can affect femoral bone remodeling. The rationale behind these designs is the experimental evidence that loading the medial and the lateral flare effectively preserves in time metaphyseal bone stock. Moreover, biomechanical tests have confirmed that this kind of stress distribution allows to remove the diaphyseal portion of the stem. Methods: A total of 33 patients operated with a cementless femoral implant were included in this study. Two slightly different designs were tested: Type 1 (Stanmore Orthopaedics), featuring an extremely short distal stem (n=10), and Type 2 (DePuy International Ltd), where distal stem was virtually absent (n=23). All implants were customized based on pre-operative CT data. The main features of these implants were the ultra-short stem and the large lateral flare. The rationale was to preserve bone stock and gain a more physiologic load transfer to the proximal femur thus preventing stress-shielding. DXA examination was performed on all patients 3 years after THA. Due to the peculiar design, a specific protocol of analysis with five regions of interest (ROI) was developed: ROI1 (greater trochanter), ROI2 and ROI4 (respectively lateral and medial of the ultra-short stem), ROI3 (below the tip) and ROI5 (calcar). The same protocol was applied to the non-operated contralateral femur and percentage contralateral BMD was calculated with the following formula: (BMD of operated hip/BMD of contralateral hip)×100. A standard DXA of contralateral hip and lumbar spine was also performed to evaluate the skeletal bone mineralization. Results: No differences were found in the anthropometric data and sex between the two groups. Age was found lower (p=0.001) in Type 2. BMD of lumbar spine and contralateral femur from standard DXA were not different in the two groups. BMD was higher in Type 2 in ROI4 and ROI5 (p< 0.001). The calculated percentage contralateral BMD was higher in Type 2 in ROI2 (p=0.009), ROI4 (p< 0.001) and ROI5 (p=0.01). Conclusions: This study confirms that progressive shortening of femoral stem produces a more proximal loading, which effectively preserves in time metaphyseal bone stock and increases periprosthetic BMD in the medial ROIs. The increased BMD in periprosthetic lateral and medial proximal regions in the operated hip respect to the contralateral femur seems to be due not only to the increased weight-bearing, but also to the specific ultra-short stem design

Aims

Femoral bone preparation using compaction technique has been shown to preserve bone and improve implant fixation in animal models. No long-term clinical outcomes are available. There are no significant long-term differences between compaction and broaching techniques for primary total hip arthroplasty (THA) in terms of migration, clinical, and radiological outcomes.

Dual energy X-ray absorptiometry (DXA) is a precise tool for measuring bone mineral density (BMD) around total joint prostheses. The Hologic ‘metal-removal hip’ analysis package (Hologic Inc, Waltham, Massachusetts) is a DOS-based analysis platform that has been previously validated for measurement of pelvic and proximal BMD after total hip arthroplasty (THA). This software has undergone a change in the operating platform to a Windows-based system that has also incorporated changes to DXA image manipulation on-screen. These changes may affect the magnitude of random error (precision) and systematic error (bias) when compared with measurements made using the previously validated DOS-based system. These factors could influence interpretation of longitudinal studies commenced using the DOS system and later completed using the Windows system. The aims of this study were to compare the precision and bias of pelvic and femoral periprosthetic BMD measurements made using the Windows versus the DOS analysis platform of the Hologic ‘metal-removal hip’ software. A total of 29 subjects (17 men and 12 women) with a mean age of 51years (SD±10), who had undergone hybrid THA using a cemented stem and uncemented cup. Subjects underwent duplicate DXA scans of the hemipelvis and proximal femur taken on the same day after a period for repositioning.. Scans were obtained with the patient lying supine in the scanner with the legs in extension and the foot in a neutral position. Scans were carried out using the same Hologic QDR 4500-A fan-beam densitometer in ‘metal-removal hip’ scanning mode. The DXA scan acquisitions were analysed using both the DOS and the Windows versions of the analysis software. The same observer made all analyses (NRS). Pelvic scans were analysed using a four region of interest model and femoral scans were analysed using a seven region of interest model. Precision was expressed as coefficient of variation (CV%) and compared between methods using the F-test. Systematic bias was examined using the Bland and Altman method and paired t-test. The CV% for the pelvic regions of interest (n=4) varied from 3.92 to 8.54 and from 2.36 to 5.96 for the Windows and DOS systems, respectively. The CV% for the net pelvic region was 3.04 and 2.36 for Windows versus DOS, respectively (F- test, p> 0.05). The CV% for the femoral regions of interest (n=7) varied from 1.58 to 4.14 and from 1.84 to 4.65 for the Windows and DOS systems, respectively. The CV% for the net femoral region was 1.75 and 1.51 for Windows versus DOS, respectively (F- test, p> 0.05). Absolute BMD values for the net pelvic region were similar (Bland-Altman, Windows minus DOS value mean = -1.0%, 95% CI −7.5 to 5.6; t-test p.0.05). Absolute BMD values for the net femoral region were also similar (Bland-Altman, Windows minus DOS value mean = 1.3%, 95% CI −8.3 to 10.8; t-test p.0.05). In summary precision of the measurements using the 2 operating systems was similar and there was no systematic bias between methods. These data suggest that scans analysed using each platform may be used interchangeably within the same study subjects, without the need of a calibration correction

To assess clinical outcomes, metal ion levels, and periprosthetic femoral bone mineral density (BMD) in young, active patients receiving a modular dual mobility acetabulum and recently introduced titanium, proximally coated, tapered femoral stem design. This was a prospective study of patients  65 years of age, with a BMI  35 kg/m. 2. , and UCLA activity score > 6 who received a modular cobalt chrome acetabular liner, highly cross-linked polyethylene mobile bearing, and cementless titanium femoral stem for their primary THA. Patients with a history of renal disease and metal hardware elsewhere in the body were excluded. All patients had a minimum of 2-year clinical follow-up. Patient reported outcome measures, whole blood metal ion levels (ug/L), and periprosthetic femur BMD were measured at baseline and at 1- and 2-years postoperatively. 43 patients (30 male, 13 female; mean age 52.6 ± 6.5 years) were enrolled. Harris Hip Scores improved from 54.1 ± 20.5 to 91.2 ± 10.8 at 2 years postoperatively (p<0.001). All patients had radiographically well-fixed components, no patients have sustained an instability event, and no patients have required a return to the operating room or revision procedure. Mean cobalt levels increased from 0.065 ± 0.03 ug/L preoperatively to 0.30 ± 0.51 at 1-year postoperatively (p=0.01), but decreased at 2 years postoperatively to 0.16 ± 0.23 (p=0.2) (Table 1). Four patients (9.3%) had a cobalt level outside the reference range (0.03 to 0.29ug/L) at 2 years postoperatively with values from 0.32 to 0.94. None were symptomatic. The mean femoral BMD ratio was maintained in Gruen zones 2 thru 7 at both 1- and 2-years postoperatively using this stem design (Table 2). At 2 years postoperatively, BMD in the medial calcar was 101.5% of the baseline value. Use of a modular dual mobility prosthesis and cementless, tapered femoral stem has shown encouraging results in young, active patients undergoing primary THA. Elevation in mean cobalt levels and the presence of four patients outside the reference range at 2 years postoperatively demonstrates the necessity of continued surveillance in this cohort. For any figures or tables, please contact authors directly: . barrackr@wustl.edu

The October 2012 Hip & Pelvis Roundup³⁶⁰ looks at: diagnosing the infected hip replacement; whether tranexamic acid has a low complication rate; the relationship between poor cementing technique and early failure of resurfacing; debridement and retention for the infected replacement; triple-tapered stems and bone mineral density; how early discharge can be bad for your sleep; an updated QFracture algorithm to predict the risk of an osteoporotic fracture; and local infiltration analgesia and total hip replacement.