Periprosthetic Bone Mineral Density Changes Research Articles

The assessment of canal flare index and proximal femoral bone density can improve stem selection for peri-prosthetic bone maintenance after total hip arthroplasty.

Bone maintenance after total hip arthroplasty (THA) is important for implant success. This study aimed to investigate the relationship between patient characteristics and periprosthetic bone maintenance after THA for better implant selection. This retrospective cohort study enrolled 112 consecutive patients who underwent THA using full hydroxyapatite (HA) compaction with short (n = 55) or short-tapered wedge (n = 61) stems. Periprosthetic bone mineral density (BMD) was compared between the two groups after propensity score matching, and the relationship between periprosthetic BMD changes and patient background was analyzed. Both groups showed similar periprosthetic BMD changes after adjusting for patient background using propensity score matching. Canal flare index > 3.7 in patients that underwent THA using tapered-wedge stem (odds ratio (OR), 3.2; 95% confidence interval (CI), 1.3-7.9, p = 0.013) and baseline zone 1 BMD > 0.65 in patients that received with short HA compaction stems (OR, 430.0; 95% CI 1.3-1420, p = 0.040) were associated with proximal periprosthetic bone maintenance after THA. Considering their predictive value, canal flare index and zone 1 BMD assessment might be useful strategies for implant selection during THA.

No Impact of Contact Between the Medial Collar of a Hydroxyapatite-Coated Triple-Tapered Stem and the Femoral Neck on Periprosthetic Bone Mineral Density

BackgroundHydroxyapatite-coated, triple-tapered, shorter-length stems with a medial collar have been reported with good results for a few years. We investigated whether contact between the medial collar and femoral neck affects clinical outcomes and changes in bone mineral density (BMD) in patients who have this type of stem in their total hip arthroplasty construct. MethodsThis was a retrospective, single-center study involving 62 patients scheduled for unilateral total hip arthroplasty using a hydroxyapatite-coated, triple-tapered, shorter-length stem who were followed for at least 1 year postoperatively. All patients had a Dorr type B femoral canal shape. Contact between the medial collar and the femoral neck was evaluated by computed tomography at the third postoperative month, and patients were classified into 2 groups. Postoperative clinical outcomes were investigated by the Western Ontario and McMaster Universities Arthritis Index and the Japanese Orthopaedic Association scores; radiological evaluation included stem fixation, spot welds and cortical hypertrophy, postoperative 3-dimensional stem alignment, and periprosthetic BMD changes. ResultsThere were 51 patients in the Contact + group (collar and neck contact) and 11 in the Contact-group (no contact). There were no differences between the 2 groups in the improvement of Western Ontario and McMaster Universities Arthritis Index and Japanese Orthopaedic Association scores, stem fixation, occurrence of cortical hypertrophy, or 3-dimensional stem alignment. Radiolucent lines were present in zones 3, 4, and 5 in 6 patients (12%) in the Contact + group only, who had no statistical difference between the 2 groups. Bone mineral density (BMD) decreased most in zone 7 in both groups, with no difference between the 2 groups. ConclusionsThe presence or absence of contact between the medial collar and femoral neck did not affect postoperative BMD changes or radiological or clinical results. Level of EvidenceTherapeutic Level III.

Comparison study of periprosthetic bone remodeling between simultaneous bilateral total hip arthroplasty and unilateral total hip arthroplasty: a matched cohort study.

The load-bearing pattern of periprosthetic bone may differ between patients who underwent simultaneous bilateral and unilateral total hip arthroplasty (THA). We investigated the differences in periprosthetic bone remodeling after simultaneous bilateral total hip arthroplasty and unilateral total hip arthroplasty. This retrospective cohort study enrolled 154 consecutive patients undergoing THA using full hydroxyapatite (HA) compaction short stems. Patient characteristics including age, body mass index, University of California Los Angeles (UCLA) activity score, and bone shape of the proximal femur were adjusted by propensity score matching. Subsequently, periprosthetic bone mineral density changes were compared between simultaneous bilateral and unilateral THA. We found that bone mineral density loss in the simultaneous bilateral THA group was significantly higher in zones 6 and 7 at 24 months after THA (zone 6, p = 0.019; zone 7, p = 0.041). Periprosthetic bone mineral density loss was not associated with clinical factors, including age, body mass index, and daily activity. Additionally, we demonstrated that periprosthetic bone mineral density loss was higher in zones 1, 4, 6, and 7 of patients with a normal hip on the contralateral side after unilateral THA (zone 1, p = 0.041; zone 4, p = 0.041; zone 6, p = 0.037; zone7, p = 0.019). The postoperative periprosthetic bone remodeling was lower in patients who underwent simultaneous bilateral THA than in those who underwent unilateral THA, even though patient characteristics were adjusted by propensity matching. Further observation of periprosthetic bone mineral density loss is needed to clarify the differences between the groups.

Effect of implant composition on periprosthetic bone mineral density after total hip arthroplasty.

The severity of bone mineral density (BMD) loss after total hip arthroplasty (THA) depends on both implant- and patient-related factors. While implant fixation type is an important factor, but few studies have considered the effect of material composition on the same implant fixation type. In particular, differences in mechanical stiffness due to material composition are of great interest. Here, we compared changes in periprosthetic BMD after THA using proximal fixation concept stems comprising different titanium alloys, i.e., β titanium alloys stem and α + β titanium alloys stem. This retrospective cohort included 122 patients (β titanium alloys stem, 61 cases; α + β titanium alloys stem, 61 cases) who underwent primary THA between January 2009 and December 2019. The primary outcome was the change in periprosthetic BMD from base line. Age, body mass index, diagnosis, stem size, canal flare index, surgical approach, pre-operative lumbar BMD, and pre-operative activity scores were reviewed and changes in periprosthetic BMD between the two groups were compared using analysis of covariance. The secondary outcome was radiographic response after THA. There was significant difference in periprosthetic BMD in zone 6 and 7 at 2years (p < 0.05) between the two groups. There was no significant difference in other zones. A significant difference in radiographic response was noted only for the Engh classification. α + β titanium alloys stem resulted in a significantly higher rate of BMD loss in zones 6 and 7 compared with the β titanium alloys stem. These results may be due to differences in mechanical stiffness due to the different titanium alloy composition of the prosthetics.

Peri-prosthetic bone remodeling of hydroxyapatite-coated compaction short stem was not affected by stem alignment

BackgroundTo improve implant survival through accelerated early bone remodeling during total hip arthroplasty (THA), hydroxyapatite (HA) is widely used as a bioactive coating, which is believed to enhance initial fixation by osseointegration. We aimed to investigate the relationship between stem insertion alignment and postoperative bone mineral density (BMD) changes in patients with full hydroxyapatite-coated (HA) compaction short stem and short tapered-wedge stem.MethodsThis retrospective cohort study enrolled 115 consecutive patients (115 joints) undergoing THA using the full HA compaction short (n = 59) and short tapered-wedge (n = 56) stems. Stem alignment, including anteversion, valgus, and anterior tilt were measured by a three-dimensional template using computed tomography data. Post-operative peri-prosthetic BMD was measured by dual-energy X-ray absorptiometry. The relationship between stem alignment and BMD changes in the stems was analyzed.ResultsPatterns of peri-prosthetic BMD changes were similar in both groups. Stem insertion alignments of anteversion, valgus, and anterior tilt were different between the two stem types. Stem alignment of valgus and anterior tilt did not affect peri-prosthetic BMD in either of the stem type. An absolute anteversion difference between stem anteversion and original canal anteversion caused significant peri-prosthetic BMD loss in Gruen zones one and seven in the tapered-wedge stem. However, stem alignment of absolute anteversion difference did not affect BMD changes in the HA compaction stem.ConclusionsPeri-prosthetic bone remodeling remained unaffected by stem alignment after THA with the new short full HA compaction stem.

Component migration, bone mineral density changes, and bone turnover markers in cementless and cemented total knee arthroplasty: a prospective randomized RSA study in 53 patients with 2-year follow-up.

Cementless tibial components migrate initially until osseointegration and preserve periprosthetic bone. Cemented tibial components are fixed from surgery but loose periprosthetic bone. Little is known about bone formation and resorption biomarkers in relation to component fixation and bone mineral density (BMD) changes of cementless and cemented total knee arthroplasty. We hypothesize a similar migration of cemented and cementless tibial components between 1- and 2-year follow-up indicating a stable long-term fixation. In a prospective patient-blinded randomized study, we compared cementless (n = 27) and cemented (n = 26) tibial components with radiostereometry measured migration (MTPM = Maximum Total Point Motion: point of component that migrates the most) and changes in BMD and biochemical bone turnover markers (BTMs) until 24months after surgery. The mean MTPM between 12 and 24months were similar between groups with -0.06mm (95% CI -0.23; 0.11) in the cementless group compared to 0.02mm (95% CI -0.07; 0.11) in the cemented group. However, there was a higher proportion of cementless components (16/25) than cemented components (7/24) with continuous migration (MTPM > 0.2mm) (p = 0.02). In the medial and anterior region below the tibial components, the BMD increased by mean 1.8% and 7.4% for cementless components and decreased by mean 8.6% and 4.2% for cemented components until 24-month follow-up. In both groups, BTMs initially showed increased bone resorption (CTx) and bone formation (P1NP) followed by normalization to pre-operative levels at 6months post-surgery. More cementless components than cemented components showed continues migration which suggest a higher risk of early revision. Bone turnover increased post-surgery in both groups, but did not explain the difference in change in periprosthetic BMD. I.

Continuous periprosthetic bone loss but preserved stability for a collum femoris-preserving stem: follow-up of a prospective cohort study of 21 patients with dualenergy X-ray absorptiometry and radiostereometric analysis with minimum 8 years of follow-up.

Background and purposeWe previously described a decrease in bone mineral density (BMD) in the calcar region 2 years after insertion of the collum femoris-preserving (CFP) stem, but the implants were stable. Now we have examined the long-term changes in periprosthetic BMD and stability of the CFP stem.Patients and methodsWe conducted a minimum 8-year follow-up of 21 patients from our original investigation. We examined periprosthetic BMD by dual-energy X-ray absorptiometry (DEXA) and implant stability by radiostereometric analysis (RSA).ResultsBetween 2 and 8 years 1 stem was revised due to aseptic loosening. Between 2 and 8 years we found a 14% (95% confidence interval [CI] 9–19) reduction in BMD in Gruen zone 6 and 17% (CI 6–28) in Gruen zone 7. From baseline the reduction in BMD was 30% (CI 23–36) in Gruen zone 6, 39% (CI 31–47) in Gruen zone 7, and 19% (CI 14–23) in Gruen zone 2. Between 2 and 8 years, RSA (n = 17) showed a mean translation along the stem axis of 0.02 mm (CI –0.02 to 0.06) and a mean rotation around the stem axis of 0.08° (CI –0.26 to 0.41). From baseline mean subsidence was 0.07 mm (CI –0.16 to 0.03) and mean rotation around the stem axis was 0.23° (CI –0.23 to 0.68) at 8 years.InterpretationThere was continuous loss of proximomedial BMD at 8 years while the CFP stem remained stable. Proximal periprosthetic bone loss cannot be prevented by this stem.

Hydroxyapatite-coated compaction short stem represents a characteristic pattern of peri-prosthetic bone remodelling after total hip arthroplasty.

We aimed to investigate the differences in peri-prosthetic bone remodelling between the full hydroxyapatite (HA)-collared compaction short stem and the short tapered-wedge stem. This retrospective cohort study enrolled 159 consecutive patients (159 joints) undergoing total hip arthroplasty (THA) using the full HA compaction short (n = 64) and short tapered-wedge (n = 95) stems. Body mass index (BMI), peri-prosthetic bone mineral density (BMD), and clinical factors, including the Japanese Orthopaedic Association score and the University of California Los Angeles (UCLA) activity score were assessed and compared. Stem related complications were seen in three cases. Both groups showed similar peri-prosthetic BMD changes. Peri-prosthetic BMD was almost maintained in the distal femur and Gruen zone 6 with both type of stems, but significant BMD loss was found in zones 1 and 7 in both groups and in zone 2 of the full HA compaction stem group. No significant correlations were found between the proximal femoral BMD changes and the age, BMI, and UCLA score in both the full HA compaction and tapered-wedge stem groups. Femoral bone shape affected the peri-prosthetic BMD changes in the tapered-wedge stem group but not in the full HA compaction group. The stem collar of the full HA compaction stem did not affect peri-prosthetic BMD, but unique bone remodelling in the calcar region was observed in 27.6% cases. A significant difference in the peri-prosthetic BMD changes at Gruen zone 2 was found in patients with or without thigh pain. Peri-prosthetic bone remodelling remained unaffected by clinical and radiographic factors after THA with the new short full HA compaction stem. Therefore, this new stem may be useful in a variety of cases.

Quantitative measurements of adaptive bone remodeling around the cemented Zimmer\xae segmental stem after tumor resection arthroplasty using dual-energy x-ray absorptiometry

BackgroundLimb salvage surgery (LSS) is the preferred method for treatment of patients with sarcomas and to a greater extent also to patients with metastatic bone disease. The aim of the present study was to evaluate the adaptive remodeling of the periprosthetic cortical bone after insertion of a tumor prosthesis with cemented stem.MethodsA prospective study of 21 patients (F/M = 12/9), mean age 55 years (range 15–81) with metastatic bone disease (n = 9), sarcomas (n = 8) or aggressive benign tumors (n = 4) who underwent bone resection due to a tumor, and reconstruction with a tumor-prosthesis (Zimmer® Segmental 130 mm straight fluted cemented stem with trabecular metal (TM) collars) in the proximal femur (n = 10), distal femur (n = 9) or proximal tibia (n = 2). Measurements of bone mineral density (BMD) (g/cm2) were done postoperatively and after 3, 6, and 12 months using dual-energy X-ray absorptiometry. BMD was measured in 4 regions of interest around the cemented stem and in one region of interest 1 cm proximal from the ankle joint of the affected limb and measurement of the contralateral ankle was used as reference. Repeated measures ANOVA and students paired t-test was used to evaluate BMD changes over time.ResultsAt 1-year follow-up, BMD decreased compared to baseline in all four regions of interest with a statistically significant bone loss of 8–15%. The bone loss was most pronounced (14–15%) in the 2 regions of interest closest to the trabecular metal (TM) collar and lowest (8%) adjacent to the tip of the stem.ConclusionAfter 1 year the decrease in bone mineral density of the ankle on the affected limb was 9% and the contralateral ankle was close to baseline, thus suggesting that the periprosthetic bone mineral density changes during follow-up, mainly are caused by stress shielding and immobilization.Trial registrationThe study was approved by the Scientific Ethical Committee of the Capital Region of Denmark (J. No. H-2-2014-105) and the Danish Data Protection Agency (J. No.:2012–58-00004).

Comparison of bone remodelling around short stem and conventional straight stem in total hip replacement: a prospective randomized radiographic and dual-energy X-ray absorptiometric study.

The aim of study was to evaluate periprosthetic bone mineral density (BMD) changes of proximal femur, osseointegration and clinical outcomes after implantation of short-stemmed and conventional straight-stemmed prostheses. This prospective, randomized study included 50 patients with unilateral total hip replacement. The patients were randomized into 2 cohorts: patients with a cementless short stem Metha (n=25) and patients with a cementless conventional straight stem Bicontact evaluated as the control (n=25). Periprosthetic BMD changes were measured using a DEXA performed at one-week, 3-monts, 6-months and 1-year follow up. Clinical evaluation with Harris hip score (HHS) and radiographic assessment were performed through a 1 year follow up. Compared to 1-week postoperative assessment, there were differences in BMD changes between the groups at the final follow-up in all ROIs, with statistical significances in ROI 1, 2, 3, 6 and 7. The loss of periprosthetic BMD in all ROIs around straight stems at each time-point was observed. There was a tendency towards a regain of BMD in all ROIs at 1-year follow-up compared to the 3-months postoperative assessment with the short stems. Less pronounced bone loss was observed around the short stems that the straight stems in ROI 1 (‒2.9 % % vs ‒16.2 %), 5 (‒4.7 % vs ‒8.9 %) and 7 (‒8.6 % vs ‒20 %). The periprosthetic BMD exceeded baseline values in the short stem cohort in ROI 2 (+4.4 % vs ‒5 %), 3 (+5.6 % vs ‒2.5 %) and 6 (+4.3 % vs ‒10 %). All stems had a radiographically stable fixation. Stress shielding-related bone resorption was markedly lower in the short stem cohort. The HHS score was comparable between the two cohorts. The implant-specific stress shielding altered the proximal loading condition for both stems; however, the results of this study suggest a more physiological strain distribution with the short stems versus the straight stems (Tab. 3, Fig. 3, Ref. 25).

Inferior stabilization of cementless compared with cemented dual-mobility cups in elderly osteoarthrosis patients: a randomized controlled radiostereometry study on 60 patients with 2 years’ follow-up

Background and purpose — Elderly patients may benefit from a dislocation low-risk dual-mobility (DM) articulation in total hip arthroplasty, but the best cup fixation method is unknown. We compared cup migration for cemented and cementless DM cups using radiostereometry.Patients and methods — In a patient-blinded randomized trial, 60 patients (33 female) with osteoarthritis were allocated to cemented (n = 30) or cementless (n = 30) Avantage DM cup fixation. Criteria were age above 70 years, and T-score above –4. We investigated cup migration, periprosthetic bone mineral density (BMD), and patient-reported outcome measures (PROMs) until 24 months postoperative follow-up.Results — At 24 months mean proximal cup migration was 0.11 mm (95% CI 0.00–0.23) for cemented cups and 0.09 mm (CI –0.09 to 0.28) for cementless cups. However, cementless cups generally migrated more than cemented cups at 12 and 24 months. Cemented cups had no measurable migration from 3 months’ follow-up, while cementless cups had not yet stabilized at 24 months in all rotations. Cementless cups showed statistically significantly more maximum total point motion (MTPM) at 12- and 24-month follow-up compared with cemented cups in patients with low systemic BMD (p = 0.01). Periprosthetic BMD changes did not statisticially significantly correlate to proximal migration in either cup fixation group (p > 0.05). PROMs improved similarly in both groups.Interpretation — Cemented cups were well fixed at 3 months. The cementless cups migrated more in patients with low BMD, showed an inconsistent pattern of migration, and migrated in different directions during the first and second year without tendency to stabilization. Cemented fixation of the Avantage DM cup seems safer in elderly patients

Short to Midterm Follow-Up of Periprosthetic Bone Mineral Density after Total Hip Arthroplasty with the Ribbed Anatomic Stem.

Background Femoral bone remodeling around hip prosthesis after total hip arthroplasty (THA) is definite but unpredictable in time and place. This study aimed to investigate the implant-specific remodeling and periprosthetic bone mineral density (BMD) changes after implantation of the Ribbed anatomic cementless femoral stem. Methods After power analysis, 41 patients who had undergone primary unilateral THA with the Ribbed anatomic cementless stem were included. BMD of the seven Gruen zones was measured by dual-energy X-ray absorptiometry, and the contact, fitness, and fixation of the femoral stem and proximal femur were analyzed by X-ray. Additional clinical outcome parameters were also recorded. Results Compared with the contralateral unoperated side, significant reductions of BMD were detected in the distal zone (Gruen zone 4: 1.665±0.198 versus 1.568±0.242 g/cm2, P=0.001) and middle distal zone (Gruen zone 5: 1.660±0.209 versus 1.608±0.215 g/cm2, P=0.026) on the prosthetic side, but no significant differences in BMD were detected in other zones (Gruen zones 1, 2, 3, 6, and 7). Subgroups analyses indicated no significant correlation between periprosthetic BMD changes and clinical factors including primary disease and body mass index. Visible areas of bone ingrowth indicated solid fixation of the femoral stem and there was no case of loosening. Clinical and functional outcome scores were excellent with mean HHS of 93.13 points and mean WOMAC score of 5.20 points, and three patients described intermittent mild thigh pain at the final follow-up. Conclusions For the Ribbed femoral stem, the periprosthetic BMD was well maintained in the proximal femur, while periprosthetic BMD was significantly reduced in the distal and middle distal zones of the femur. Further clinical investigations are required to examine the efficacy of the Ribbed stem, particularly with regard to long-term survival. This trial is registered with ChiCTR1800017750.

Periprosthetic Bone Mineral Density Changes After Implantation of a Curved Bone Preserving Hip Stem Compared to a Standard Length Straight Stem: 5-Yr Results of a Prospective, Randomized DXA-Analysis

Introduction: The objective of this prospective, randomized study was to evaluate differences in periprosthetic bone mineral density changes in the proximal femur after implantation of a cementless bone preserving stem (Fitmore) compared to a cementless straight stem (CLS Spotorno). Methodology: Periprosthetic bone mineral density was measured in 140 patients (aged 33–74 yr) before surgery, 7 d, 3, 12, and 60 mo postoperatively, using dual energy X-ray absorptiometry. The 1-yr results have already been published. The results of the first postoperative measurement served as the baseline value. Because of the different length of the 2 implants we used adapted Gruen zones to divide the periprosthetic bone in seven regions of interest with comparable length. Clinical results were recorded using the Western Ontario and McMaster Universities Arthritis Index and the Harris hip score. Results: Clinical findings showed comparable results in both groups at all follow-ups (p > 0.05). A total of 5 yr after surgery, the comparison of periprosthetic bone mineral density changes showed significant differences in regions of interests 3 (CLS −3.9% vs Fitmore −0.2%, p < 0.001) and 5 (CLS −3.6% vs Fitmore −1.3%, p = 0.0028) between both implants. Conclusion: Despite the fact that no exclusive proximal load distribution could be observed, proximal periprosthetic bone loss in the proximal femur was less pronounced after implantation of the bone preserving stem than with the straight stem.

A Prospective Assessment of Periprosthetic Bone Mineral Density and Osteoimmunological Biomarkers Variations After Total Knee Replacement Surgery

Aseptic loosening is a major cause of premature failure of total knee replacement (TKR). Variations in periprosthetic bone mineral density (BMD) and osteoimmunological biomarkers levels could help to quantify prosthesis osteointegration and predict early aseptic loosening. The gene expression of 5 selected osteoimmunological biomarkers was evaluated in tibial plateau bone biopsies by real-time polymerase chain reaction and changes in their serum levels after TKR were prospectively evaluated with enzyme-linked immunosorbent assay for 1 yr after surgery. These variations were correlated to changes in periprosthetic BMD. Sixteen patients were evaluated. A statistically significant decrease in serum levels of Sclerostin (p = 0.0135) was observed immediately after surgery. A specular pattern was observed between dickkopf-related protein 1 and osteoprotegerin expression. No statistically significant changes were detectable in the other study biomarkers. Periprosthetic BMD did not change significantly across the duration of the follow-up. Prosthetic knee surgery has an impact on bone remodeling, in particular on sclerostin expression. Although not showing statistically significant changes, in the patterns of dickkopf-related protein 1, osteoprotegerin, and the ligand of the receptor activator of nuclear factor kappa-B symmetries and correspondences related to the biological activities of these proteins could be identified. Variation in osteoimmunological biomarkers after TKR surgery can help in quantifying prosthesis osteointegration.

Restoration of proximal periprosthetic bone loss by denosumab in cementless total hip arthroplasty.

Although bone quality is an important issue in elderly osteoporotic patients who underwent total hip arthroplasty (THA) with a cementless stem, periprosthetic bone mineral density (BMD) in the proximal femur has been reported to be decreased by 15-40% postoperatively. Some authors have examined the use of several types of bisphosphonates to prevent decreases in BMD in the proximal femur after cementless THA; however, few reports have demonstrated success in restoring BMD in the proximal medial femoral bone, such as zone 7. We conducted prospective study comparing patients who underwent cementless THA administered with denosumab (10 patients) and without denosumab (10 patients). BMD around the femoral stem were measured using a DEXA immediately after surgery, and at 6months and at 1year after surgery. No difference was found between the two groups referred to the patient's demographic data. We found that denosumab displayed definitive effects in increasing the % change in periprosthetic BMD at zone 7 by an average of 7.3% in patients with cementless THA, compared to control group who were given only vitamin D. Denosumab is one of a number of anti-osteoporotic agents to have a definitive effect on the restoration of proximal periprosthetic bone loss, especially in zone 7, after cementless THA. Denosumab contributed to the restoration of decreased periprosthetic BMD to normal levels. As the decrease in BMD in the proximal femur after THA is considered to be apparent at 6-12months after surgery, it is believed that prevention of the deterioration of bone quality is important in the proximal femur immediately after cementless THA for elderly female patients with osteoporosis.

Difference in Postoperative Periprosthetic Bone Mineral Density Changes Between 3 Major Designs of Uncemented Stems: A 3-Year Follow-Up Study

BackgroundAlthough few studies have examined the direct effect of stress shielding on clinical outcomes, periprosthetic bone loss due to stress shielding is still an issue of concern, especially when physicians perform uncemented total hip arthroplasty (THA) in younger patients. Differences in femoral stem design may affect the degree of postoperative stress shielding. Therefore, the characteristics of the behavior for stress shielding of each type of femoral stem should be determined. This study compares differences in bone mineral density (BMD) change in the femur after primary THA between 3 major types of uncemented stems. MethodsAmong a total of 89 hips, 26 hips received THA with a fit-and-fill type stem (VerSys Fiber Metal MidCoat; Zimmer, Inc, Warsaw, IN), 32 hips received a tapered rectangular Zweymüller-type stem (SL-Plus; Smith & Nephew Inc, Memphis, TN), and 31 received a tapered wedge-type stem (Accolade TMZF; Stryker Orthopaedics, Mahwah, NJ). BMD measurements were performed with a HOLOGIC Discovery device (Hologic Inc, Waltham, MA). ResultsBMD in the medial-proximal femur was maintained for 3 years after THA in the group with the tapered wedge-type stem. BMD in the lateral-proximal femur was maintained for 3 years after THA in the group with the Zweymüller-type stem. There were no significant differences in the Harris Hip Score among the 3 stem groups preoperatively and 1, 2, and 3 years after surgery. ConclusionThere are clear differences in postoperative BMD loss of the proximal femur among these 3 commonly used uncemented stems.

Periprosthetic Bone Mineral Density Changes after Cementless Total Knee Arthroplasty

Periprosthetic Bone Mineral Density Changes after Cementless Total Knee Arthroplasty

Bone remodelling after femoral short stem implantation in total hip arthroplasty: 1-year results from a randomized DEXA study.

Short stem prostheses have been developed to preserve proximal femoral bone stock. This prospective, randomized study compared periprosthetic bone remodelling following short and straight stem implantation 1 year after surgery. One hundred and forty-four consecutive patients undergoing total hip arthroplasty were randomized to either a Fitmore short or a cementless straight stem (both Zimmer, Winterthur, Switzerland). Periprosthetic bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry performed the day before surgery and at 7 days, 3 months and 1 year postoperatively. Furthermore, the HHS and the WOMAC were obtained. One hundred and thirty-eight patients completed 1-year follow-up. Periprosthetic BMD changes at 1 year were most pronounced in the proximal medial region of interest (ROI) 7 with -17.2% after short stem and -16.7% after straight implantation (p = 0.67). However, there was significantly less BMD reduction in ROI 6 following short (-4.7%) versus straight stem (-10.8%) implantation (p = 0.01). There were no significant differences between the two groups in terms of the HHS and the WOMAC either before or after surgery. One year after surgery, both stems showed an implant-specific periprosthetic bone remodelling. Nevertheless, proximal load transfer was more pronounced after short stem implantation than with a straight stem.

Lower periprosthetic bone loss and good fixation of an ultra-short stem compared to a conventional stem in uncemented total hip arthroplasty

Background and purpose — We hypothesized that an ultra-short stem would load the proximal femur in a more physiological way and could therefore reduce the adaptive periprosthetic bone loss known as stress shielding.Patients and methods — 51 patients with primary hip osteoarthritis were randomized to total hip arthroplasty (THA) with either an ultra-short stem or a conventional tapered stem. The primary endpoint was change in periprosthetic bone mineral density (BMD), measured with dual-energy x-ray absorptiometry (DXA), in Gruen zones 1 and 7, two years after surgery. Secondary endpoints were change in periprosthetic BMD in the entire periprosthetic region, i.e. Gruen zones 1 through 7, stem migration measured with radiostereometric analysis (RSA), and function measured with self-administered functional scores.Results — The periprosthetic decrease in BMD was statistically significantly lower with the ultra-short stem. In Gruen zone 1, the mean difference was 18% (95% CI: −27% to −10%). In zone 7, the difference was 5% (CI: −12% to −3%) and for Gruen zones 1–7 the difference was also 5% (CI: −9% to −2%). During the first 6 weeks postoperatively, the ultra-short stems migrated 0.77 mm more on average than the conventional stems. 3 months after surgery, no further migration was seen. The functional scores improved during the study and were similar in the 2 groups.Interpretation — Up to 2 years after total hip arthroplasty, compared to the conventional tapered stem the ultra-short uncemented anatomical stem induced lower periprosthetic bone loss and had equally excellent stem fixation and clinical outcome.

Bone Mineral Density of the Femur in Autopsy Retrieved Total Knee Arthroplasties

Bone mineral density (BMD), as measured by DEXA, can vary depending on bone rotation and fat content of soft tissues. We performed DEXA measurements, under controlled positioning, on 24 autopsy-retrieved femora from patients who had fully functional and asymptomatic successful TKA to determine periprosthetic BMD changes and compared results to 24 normal cadaveric femora. In TKA specimens, BMD was affected by gender, preoperative diagnosis, and zone under analysis. The lowest mean BMD was in the anterior femoral condylar zone. Males had higher mean BMD at all zones while patients with preoperative diagnosis of osteoarthritis had higher BMD in the posterior condylar zone. The mean BMD in the anterior femoral condylar zone in TKA specimens was significantly lower than in normal specimens without arthroplasties, most likely due to stress shielding.