Periprosthetic femoral bone loss in total hip arthroplasty: systematic analysis of the effect of stem design

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

BACKGROUND

Hydroxyapatite-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.

METHODS

This 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.

RESULTS

There 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.

CONCLUSIONS

The 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 EVIDENCE

Therapeutic Level III.

Periprosthetic fractures are osteoporotic fractures: missed opportunities for osteoporosis diagnosis

Joint replacement surgery is common in older adults, leading to increasing periprosthetic fracture (PPFx) occurrence. We reviewed all PPFx seen over a 4-year period at an academic hospital. Clinical osteoporosis could be diagnosed based on existing data in 104 (67%) at the time of PPFx. Periprosthetic fractures are generally osteoporosis-related.

PURPOSE

Periprosthetic fractures (PPFx) cause morbidity, mortality, and cost. This study's purpose was to describe osteoporosis-related data available at the time of PPFx.

METHODS

The electronic medical record (EMR) of PPFx patients seen over 4 years in a university orthopedic practice were reviewed. Demographic data and osteoporosis relevant parameters were collected. Prior DXA studies were reviewed, and L1 Hounsfield unit (HU) measurements were performed on CT scans obtained within 2 years before PPFx. Clinical osteoporosis was defined as prior diagnosis, prescribed osteoporosis treatment, T-score ≤  - 2.5, HU ≤ 100, or prior fracture.

RESULTS

Records of 156 PPFx patients (115 F/41 M), mean (SD) age 75.4 (11.9), were reviewed. Almost all 153/156 (98%) of these fractures were femoral. Falls caused 139 (89%); 12 (8%) were spontaneous. Mean time post-arthroplasty was 7.9 (6.3) years. Prior fragility fracture(s) occurred in 72 (46%); 14 were PPFx. Osteoporosis was previously diagnosed in 45 (29%) and medications prescribed in 41 (26%). Prior to PPFx, DXA data were available in 62, mean (SD) lowest T-score was - 1.9 (0.9) and was ≤  - 2.5 in 19. CT data were available in 46; mean (SD) L1 HU was 79.0 (29.4) and was ≤ 100 in 35. Based on existing data, clinical osteoporosis could have been diagnosed in 104 (67%) at the time of PPFx.

CONCLUSION

Periprosthetic fractures are osteoporosis-related. They occur in older adults, often female, and result from falls; BMD, when assessed, is low. Data available at the time of PPFx often allows osteoporosis diagnosis; this should prompt evaluation and pharmacologic treatment consideration.

Slightly reduced early subsidence with similar outcomes and complications rate in collared stems - A systematic review of randomized clinical trials

Background

There is a growing trend towards using femoral stems with a medial calcar collar during total hip arthroplasty (THA).

Purpose

Systematically review the literature comparing a femoral collared stem and femoral collarless stem on subsidence, patient-reported outcomes (PROs), and revision rate.

Study design

Systematic Review, Level of Evidence 1.

Methods

A literature search of Pubmed and Medline was according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Randomized controlled trials that evaluated collared and collarless stems, subsidence and PROs for adult patients undergoing total hip arthroplasty (THA) were included. Additional data collection included patient demographics, stem-calcar contact, canal-fill ratio (CFR), stem orientation, surgical approach, Dorr Type, complications, and revisions.

Results

Five studies met inclusion criteria. 674 patients (704 hips) were included. Mean patient ages ranged 58.5-72.4 years old, and mean BMI ranged 26.6-29.8 kg/m2. Mean reported follow-up of the included clinical trials ranged 1-9.6 years. Two studies reported mean early subsidence at two weeks postoperatively, which was 0.36, 0.99 mm for collared stems and 0.52, 3.22 mm for collarless stems, proving to be statistically significant (P = 0.023), (P = 0.05). All studies demonstrated improved PROs at most recent follow-up. Revision rates ranged from 4 to 11.3 %, but these were not statistically significant.

Conclusions

Implantation of collared stems compared to collarless may reduce early post-operative subsidence, while no substantial effect on aseptic loosening, thigh pain, proximal femoral fracture, and revision is seen. When measuring patient-reported outcomes, the collared femoral stem was not superior to the collarless femoral stem as both resulted in similar improvement preoperatively to postoperative state.

Evaluation of Proximal Femoral Bone Mineral Density in Cementless Total Hip Arthroplasty: A 3-Arm Prospective Randomized Controlled Trial

BACKGROUND

Femoral stem design affects periprosthetic bone mineral density (BMD), which may impact long-term survival of cementless implants in total hip arthroplasty (THA). The aim of this study was to examine proximal femoral BMD in 3 morphologically different uncemented femoral stem designs to investigate whether any particular design resulted in better preservation of BMD.

METHODS

A total of 119 patients were randomized to receive a proximally coated collarless dual-taper wedge stem, a proximally coated collarless anatomic stem, or a fully coated collarless triple-taper stem. All surgeries were performed via the posterior approach, with mobilization on the day of surgery. Dual x-ray absorptiometry scans (Lunar iDXA, GE Healthcare) assessed BMD across the 7 Gruen zones preoperatively and at 6 weeks and 2 years postoperatively; if available, the native contralateral femur was also assessed as a control. Patient-reported outcomes of pain, function, and health were also assessed at these follow-ups.

RESULTS

Averaged across all stems, BMD increased in zones 1 (2.5%), 2 (17.1%), 3 (13.0%), 5 (10%), and 6 (17.9%) at 2 years. Greater preservation of BMD was measured on the lateral cortex (zone 2) for both the dual-taper wedge and anatomic stems (p = 0.019). The dual-taper wedge stem also demonstrated preservation of BMD in the medial calcar (zone 7), while the anatomic and triple-taper stems declined in this region; however, the difference did not reach significance (p = 0.059). Averaged across all stems, BMD decreased in the mid-diaphysis region, distal to the stem tip (zone 4). All stems performed similarly at the time of final follow-up with respect to the patient-reported outcomes.

CONCLUSIONS

This study demonstrated maintenance of femoral BMD after use of 3 different cementless femoral stem designs, with all achieving excellent improvements in patient-reported outcomes. The stems designed to load the proximal metaphyseal region resulted in higher BMD in that region. No significant stress-shielding was observed; however, longer follow-up is required to elucidate the impact of this finding on implant survivorship.

LEVEL OF EVIDENCE

Therapeutic Level I . See Instructions for Authors for a complete description of levels of evidence.

Biomechanical analysis of different THA cementless femoral stem designs in physiological and osteoporotic bone during static loading conditions

BACKGROUND

The influence of THA stem design on periprosthetic femoral fractures (PFFs) risk is subject of debate. This study aims to compare the effects of different cementless stem designs on stress-strain distributions in both physiological and osteoporotic femur under various loading conditions.

MATERIALS

A biomechanical study using finite-element analysis was conducted. Four models were developed: three with implanted femurs and a native one chosen as control. Each model was analyzed for both healthy and osteoporotic bone. The following stem designs were examined: short anatomical stem with femoral neck preservation, double-wedge stem, and anatomical standard stem. Three loading conditions were assessed: gait, sideways falling, and four-point bending.

RESULTS

During gait in physiological bone, the anatomical stem and the short anatomical stem with femoral neck preservation showed stress distribution similar to the native model. The double-wedge stem reduced stress in the proximal area but concentrated it in the meta-diaphysis. In osteoporotic bone, the double-wedge stem design increased average stress by up to 10%. During sideways falling, the double-wedge stem exhibited higher stresses in osteoporotic bone. No significant differences in average stress were found in any of the studied models during four-point bending.

CONCLUSION

In physiological bone, anatomical stems demonstrated stress distribution comparable to the native model. The double-wedge stem showed uneven stress distribution, which may contribute to long-term stress shielding. In the case of osteoporotic bone, the double-wedge stem design resulted in a significant increase in average stress during both gait and sideways falling, potentially indicating a higher theoretical risk of PFF.

Roles of inflammatory cell infiltrate in periprosthetic osteolysis

Classically, particle-induced periprosthetic osteolysis at the implant-bone interface has explained the aseptic loosening of joint replacement. This response is preceded by triggering both the innate and acquired immune response with subsequent activation of osteoclasts, the bone-resorbing cells. Although particle-induced periprosthetic osteolysis has been considered a foreign body chronic inflammation mediated by myelomonocytic-derived cells, current reports describe wide heterogeneous inflammatory cells infiltrating the periprosthetic tissues. This review aims to discuss the role of those non-myelomonocytic cells in periprosthetic tissues exposed to wear particles by showing original data. Specifically, we discuss the role of T cells (CD3+, CD4+, and CD8+) and B cells (CD20+) coexisting with CD68+/TRAP- multinucleated giant cells associated with both polyethylene and metallic particles infiltrating retrieved periprosthetic membranes. This review contributes valuable insight to support the complex cell and molecular mechanisms behind the aseptic loosening theories of orthopedic implants.

Bone remodeling and cortical thinning distal to the femoral stem: a retrospective review

INTRODUCTION

There is a paucity of information on the bone remodeling that occurs distal to the femoral stem following total hip arthroplasty as most previous studies have focused on proximal changes. In this study, we report the cortical thinning that occur distal to the femoral stem after primary total hip arthroplasty.

METHODS

A retrospective review was performed at one institution over a 5-year period. 156 primary total hip arthroplasty procedures were included. The Cortical Thickness Index (CTI) was measured on both operative and non-operative hips at 1 cm, 3 cm and 5 cm below the prosthetic stem tip on anteroposterior radiographic images pre-operatively as well as at 6 months, 12 months and 24 months post-operatively. The difference in average CTI was measured using paired t-tests.

RESULTS

There were statistically significant decreases in CTI distal to the femoral stem at 12 months and 24 months (-1.3% and -2.8%, respectively). Greater losses were seen in female patients, patients older than 75, and patients with BMI less than 35 at 6 months postoperative. There were no differences in CTI at any time point on the non-operative side.

CONCLUSION

The current study demonstrates that patients undergo bone loss as measured by CTI distal to the stem in the first 2 years following total hip arthroplasty. Comparison to the contralateral non-operative side confirms that this change is greater than expected for the natural aging process. A greater understanding of these changes will help optimize post-operative management and direct future innovations in implant design.

Stress shielding effect after total hip arthroplasty varies between combinations of stem design and stiffness-a comparing biomechanical finite element analysis

PURPOSE

Total hip arthroplasty (THA) has become a highly frequent orthopaedic procedure. Multiple approaches have been made to design the femoral component for THA with a mechanical behaviour as close as possible to a natural femur. The aim of this study was to compare different combinations of design and biomechanical properties of THA prostheses and their impact on stress shielding of the periprosthetic bone.

METHODS

Virtual implantation of different stem designs (straight standard stem, straight short stem, anatomical short stem) by finite element analysis based on in vivo data from computer tomography was performed. For each stem, three grades of stiffness were generated, followed by a strain analysis.

RESULTS

Reduction of stem stiffness led to less stress shielding. Implantation of an anatomical short-stem prosthesis with low stiffness provided the most physiological strain-loading effect (p < 0.001).

CONCLUSION

A combination of a short and an anatomically designed stem with a low stiffness might provide a more physiological strain transfer during THA. Biomechanical properties of the femoral component for THA should be considered as a multifactorial function of dimensions, design, and stiffness.

Wear estimation of hip implants with varying chamfer geometry at the trunnion junction: a finite element analysis

The hip joint helps the upper body to transfer its weight to lower body. Along with age, there are various reasons for the degeneration of the hip joint. The artificial hip implant replaces the degenerated hip. Wear between the joints is the primary cause of the hip implant becoming loose. The wear can occur due to various reasons. Due to this revision surgery are most common in young and active patients. In the design phase of the implant if this is taken care then life expectancy of the implant can be improved. Small design changes can significantly enhance the implant's life. In this work, elliptical-shaped hip implant stem is designed, and linear wear is estimated at trunnion junction. In this work, a 28 mm diameter femoral head with a 4 mm thick acetabular cup and a 2 mm thick backing cup is used. The top surface taper radiuses are changed. Solid works was used to create the models. Ansys was used to perform the analysis. It was found that as the radius of the TTR decreased, the wear rate decreased. The least wear rate was found in 12/14 mm taper with a value of 1.15E^-02mm year^-1for the first material combination and with a value of 1.23E^-02mm year^-1for the second material combination. In the comparison between the models with 1 mm chamfer and no chamfer, it was found that the wear rate was lower for the models with 1 mm chamfer. When the chamfer was increased (more than 1 mm), the linear wear increased. Wear is the main reason for the loosening of hip implants, which leads to a revision of an implant. It was found that with a decrease in TTR, there was a small increase in the linear wear rate. Overall, the implant with TTR 6 mm and a chamfer of 1 mm was found to have the least wear rate. To validate these results, the implant can be 3D printed and tested on a hip simulator.

Biomechanical Properties of Bionic Collum Femoris Preserving Hip Prosthesis: A Finite Element Analysis

OBJECTIVE

Compared with total hip replacement, conventional collum femoris preserving prosthesis has a better bone retention effect. However, damage to the trabecular bone of the proximal femur leads to inevitable abnormal stress distribution, which leads to increased risks of femoral neck bone absorption, periprosthetic fracture, prosthesis loosening, rotation, and sinking. Thus, we compare the biomechanical properties of collum femoris preserving (CFP) and bionic collum femoris preserving (BCFP) hip prostheses.

METHODS

The Sawbone digital model (#3503, left, medium) was selected as the research object. We used the Mimics 21.0 software to reconstruct the digital model of the femur and the SolidWorks 2019 software to build and assemble the three-dimensional models of CFP and BCFP prostheses. With the ANSYS Workbench 2021R1 software, the models were meshed and assigned values to simulate the load of a single foot under slow walking. We measured the mechanical distribution of the whole model and obtained the stress nephogram.

RESULTS

For CFP prosthesis, the peak stresses of the medial interface of the stem neck, the lateral interface of the stem neck, and the end of the stem were 64.894, 32.199, and 8.578 MPa, respectively; the peak stresses of the medial surface of the femoral shaft, the lateral surface of femoral shaft, the medial femoral neck bone-prosthesis interface (osteotomy interface), the lateral femoral neck bone-prosthesis interface (basal area), the lateral femoral neck bone-prosthesis interface (osteotomy interface), and the greater trochanter area were 28.093, 24.790, 14.388, 5.118, 4.179, and 8.245 MPa, respectively; the valley stress of the greater trochanter area was 1.134 MPa. For BCFP prosthesis, the peak stresses of the medial interface of the stem neck, the lateral interface of the stem neck, and the end of the stem were 47.015, 26.771, and 47.593 MPa, respectively; the peak stress of tension screw was 15.739 MPa; the peak stresses of the medial surface of the femoral shaft, the lateral surface of femoral shaft, the medial femoral neck bone-prosthesis interface (osteotomy interface), the lateral femoral neck bone-prosthesis interface (basal area), the lateral femoral neck bone-prosthesis interface (osteotomy interface) and the greater trochanter area were 28.581, 25.364, 15.624, 6.434, 4.986, and 8.796 MPa, respectively; the valley stress of the greater trochanter area was 1.419 MPa; the peak stress of bone-metal interface between the tension screw and the lateral surface of the femur was 5.858 MPa.

CONCLUSION

Compared with the CFP prosthesis, the design of the BCFP prosthesis is based on the lever balance theory. With the bionic reconstruction of tension trabeculae, BCFP prosthesis makes up for the defects of CFP prosthesis design, optimizes the stress distribution, and reduces the stress shelter effect of the proximal femur, which has better biomechanical properties.

Bionic reconstruction of tension trabeculae in short-stem hip arthroplasty: a finite element analysis

BACKGROUND

Short-stem hip arthroplasty (SHA) is characterized by metaphyseal load transfer that effectively preserves the bone stock, but still suffers from stress shielding in the proximal femur. We designed a tension screw to mimic tension trabeculae in the new bionic collum femoris preserving (BCFP) short stem for bionic reconstruction, aiming to restore the biomechanics of hip joint.

METHODS

Native femur finite element model was constructed to investigate the biomechanics of hip joint based on computed tomography (CT) data. The maximum absolute principal stress/strain cloud chart allowed the direction of stress/strain to be assessed. Six BCFP models with different screw angles (5°, 10°, 15°, 20°, 25°, and 30°) and the Corail model were created. The stress/strain distribution and overall stiffness were compared between each of the BCFP and Corail implanted models.

RESULTS

The native model visualized the transfer pathways of tensile and compressive stress. The BCFP stems showed significantly higher stress and strain distribution in the greater trochanteric region compared to conventional total hip arthroplasty (THA). In particular, the BCFP-5° stem demonstrated the highest average strain in both medial and lateral regions and the overall stiffness was closest to the intact femur.

CONCLUSIONS

Stress transfer pathways of trabecular architecture provide biomechanical insight that serves as the basis for bionic reconstruction. The tension screw improves load transfer pattern in the proximal femur and prevents stress reduction in the greater trochanteric region. The BCFP-5° stem minimizes the stress shielding effect and presents a more bionic mechanical performance.

Poly (Ether-Ether-Ketone) for Biomedical Applications: From Enhancing Bioactivity to Reinforced-Bioactive Composites-An Overview

The global orthopedic market is forecasted to reach US$79.5 billion by the end of this decade. Factors driving the increase in this market are population aging, sports injury, road traffic accidents, and overweight, which justify a growing demand for orthopedic implants. Therefore, it is of utmost importance to develop bone implants with superior mechanical and biological properties to face the demand and improve patients' quality of life. Today, metallic implants still hold a dominant position in the global orthopedic implant market, mainly due to their superior mechanical resistance. However, their performance might be jeopardized due to the possible release of metallic debris, leading to cytotoxic effects and inflammatory responses in the body. Poly (ether-ether-ketone) (PEEK) is a biocompatible, high-performance polymer and one of the most prominent candidates to be used in manufacturing bone implants due to its similarity to the mechanical properties of bone. Unfortunately, the bioinert nature of PEEK culminates in its diminished osseointegration. Notwithstanding, PEEK's bioactivity can be improved through surface modification techniques and by the development of bioactive composites. This paper overviews the advantages of using PEEK for manufacturing implants and addresses the most common strategies to improve the bioactivity of PEEK in order to promote enhanced biomechanical performance.

Selecting a Press-fit Stem for Total Hip Arthroplasty: The Rationale and Evolution of the Modern Femoral Prosthesis

Noncemented press-fit femoral stems predominate in total hip arthroplasty for all age groups with generally excellent long-term survivorship. The 2021 American Joint Replacement Registry reports that 96% of all elective primary total hip arthroplasties used noncemented femoral implant fixation. 1 Today, there are many styles of press-fit stems, each with supposed benefits, based on a range of design philosophies. Design aspects to consider when selecting a stem are numerous, including stem geometry, stem length, collared or collarless, material properties, and surface structure. Although most stem designs demonstrate excellent results, the differences in stem designs are intimately linked to additional factors such as ease of use/implantation, percentage of surface osseointegration, overall bone removal versus bone stock preservation, subsequent femoral stress shielding, and consideration of complexity of later revision. A surgeon with a broad understanding and appreciation of femoral stem designs should be prepared to select between the multitude of options to best serve individual patients.

A randomized controlled trial comparing two modern total wrist arthroplasties : improved function with stable implants, but high complication rates in non-rheumatoid wrists at two years

AIMS

To analyze the short-term outcome of two types of total wrist arthroplasty (TWA) in terms of wrist function, migration, and periprosthetic bone behaviour.

METHODS

A total of 40 patients suffering from non-rheumatoid wrist arthritis were enrolled in a randomized controlled trial comparing the ReMotion and Motec TWAs. Patient-rated and functional outcomes, radiological changes, blood metal ion levels, migration measured by model-based radiostereometric analysis (RSA), bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DXA), complications, loosening, and revision rates at two years were compared.

RESULTS

Patient-Rated Wrist and Hand Evaluation (PRWHE) scores, abbreviated version of the Disabilities of the Arm, Shoulder and Hand questionnaire scores, and pain improved similarly and significantly in both groups. Wrist motion improved significantly in the Motec group only, and forearm rotation in the ReMotion group only. Cobalt (Co) and chromium (Cr) blood ion levels were significantly higher in the metal-on-metal (MoM) Motec group than in the metal-on-polyethylene (MoP) ReMotion group. Mean total translation was 0.65 mm (95% confidence interval (CI) 0.26 to 1.12) and 0.27 mm (95% CI 0.14 to 0.47) for the ReMotion carpal and radial components, and 0.32 mm (95% CI 0.22 to 0.45) and 0.26 mm (95% CI 0.20 to 0.34) for the Motec metacarpal and radial components, respectively. Apart from dorsal and volar tilts, which were significantly higher for the radial ReMotion than for the Motec component, no significant differences in absolute migration occurred. BMD around the radial components never returned to baseline. Almost one-third of patients required reoperation due to complications. Two ReMotion implants were revised to Motec TWAs due to carpal component loosening, and three Motec MoM articulations were revised to metal-on-polyether ether ketone due to painful synovitis.

CONCLUSION

Both implants provided matched function and were stable at short-term follow-up, but with a high complication rate. This procedure should be restricted to specialist centres undertaking prospective analysis until its role is clarified.Cite this article: Bone Joint J 2022;104-B(10):1132-1141.

Effects of denosumab treatment on the expression of receptor activator of nuclear kappa-B ligand (RANKL) and TNF-receptor TNFRSF9 after total hip arthroplasty-results from a randomized placebo-controlled clinical trial

We investigated whether the drug denosumab modulates the inflammatory response after total hip arthroplasty in a randomized controlled trial. Significantly increased expression of RANKL was found in patients treated with denosumab. This could provide an explanation for the rebound effect with rapid loss of BMD seen after discontinuation of denosumab treatment.

PURPOSE

To evaluate whether denosumab, a human monoclonal antibody directed against receptor activator of nuclear factor kappa-B ligand (RANKL), modulates the inflammatory response after cementless total hip arthroplasty (THA) in patients with osteoarthritis of the hip.

METHODS

Sixty-four patients operated with cementless THA were randomized to two doses of 60-mg denosumab or placebo 1-3 days and 6 months postoperatively. Serum samples were analyzed by a multiplex extension assay detecting 92 inflammation-related proteins. Bone turnover markers were assessed. Proteins were analyzed using linear mixed effect models. Validation of conspicuous findings was performed with ELISA.

RESULTS

Two proteins were significantly affected by denosumab treatment: RANKL and tumor necrosis factor receptor super family member 9 (TNFRSF9). Serum levels of RANKL were more than twice as high in the denosumab than in the placebo group 3 months after surgery (ratio 2.10, p<0.001). Six and 12 months after surgery, the expression of RANKL was still elevated in the denosumab-treated group (ratios 1.50, p < 0.001; 1.47, p =0.002). The expression of TNFRSF9 was lower in the denosumab group at 3 months (ratio 0.68, p<0.001). In the denosumab group, concentrations of bone turnover markers were substantially reduced after 3 months, remained suppressed after 6 and 12 months, but increased above baseline at 24 months after surgery.

CONCLUSION

Two subcutaneous denosumab injections 6 months apart increase RANKL and depress TNFRSF9 after THA. This provides a possible explanation for the rebound effect on bone turnover markers as well as bone mineral density (BMD) upon withdrawal of denosumab. None of the other measured markers of inflammation was influenced by denosumab treatment.

Analysis of Bone Loss around Cemented and Biologic Prostheses after Hemiarthroplasty

Objective. To perform hemiarthroplasty (HA) on elderly patients with femoral neck fractures using cemented and biologic prostheses and then compare the bone loss around the two types of prostheses after surgery. Methods. A total of 60 patients aged over 75 years (with a mean age of 83.5 years) and suffering from femoral neck fracture (Garden types III and IV) from January 2018 to December 2020 were selected; they were randomly divided into group A ( $n=30$ , cemented prostheses) and group B ( $n=30$ , biologic prostheses) and received HA. At 1 month, 6 months, and 12 months after surgery, Harris Hip Scale (HHS) was adopted for patient evaluation, and patients’ bone mineral density (BMD) of the 7 Gruen zones around the prostheses was measured by dual-energy X-ray absorptiometry (DEXA scan). Results. Both groups achieved satisfactory results postoperatively, and the Harris scores of the hips increased gradually over time, which were better in group A than in group B. Gruen zones in group A showed a slower trend of decreasing BMD than group B, and the differences were significant at zones 2, 3, and 4 ( $P<0.05$ ). Conclusion. For elderly patients with femoral neck fractures, selecting cemented prosthesis for HA better recovers the hip function and has a low rate of bone loss around the prosthesis.

The insidious risk of periprosthetic fracture in clinically functional total hip arthroplasties: A biomechanical study of willed joints

Femoral bone quality is a major risk factor of periprosthetic fracture after total hip arthroplasty (THA), which has mortality similar to native hip fractures but higher short-term morbidity. The goal of this study was to quantify cortical strains at the site of expected Vancouver Type-B periprosthetic fracture as a function of bone mineral density, femoral stem material, and fixation method using a series of 29 autopsy-retrieved, clinically asymptomatic hip joints with THA. Periprosthetic bone mineral content and density was assessed using dual-energy X-ray absorptiometry by Gruen Zone. Specimens then underwent combined cyclic axial and torsional loading, increasing incrementally from 100 N and ±1 Nm to peaks of 700 N and ±5 Nm. All specimens experienced significantly higher strains on the lateral surface than on the anterior surface, indicating that the bending loads in the frontal plane, rather than axial/torsional loads, had the predominant effect. Multiple significant relationships (p = 0.04, p = 0.02) were found between predicted periprosthetic strains calculated from radiographic measurements and observed principal strains. Though THA in the present study were in successful clinical service, the produced results indicated that some femurs with rigid cemented or noncemented implants were potentially at high risk for Vancouver Type-B fractures, which may be predicted radiographically.

Optimal configuration of a three-rod ortho-bridge system in the treatment of Vancouver type B1 periprosthetic femoral fractures: A finite element analysis

Introduction and Aim

Periprosthetic femoral fractures (PFF) represent an increasing clinical and economic burden. This study aims to determine the optimal configuration of a bridge-combined internal fixation system in the treatment of Vancouver type B1 PFF, using finite element analysis.

Materials and methods

A three-rod ortho-bridge system (OBS) fixation model was used to evaluate the optimal configuration of four target parameters: position of the third rod; intersection angle between the proximal screws; connecting rod diameter; and number of screws used. Femoral displacement and the maximum von Mises stress of the OBS were used as the evaluation indices, to analyze the PFF and to determine the optimal use of an OBS. For each parameter, various candidate options were tested.

Results

Finite element analysis revealed that the rate of femoral displacement and the maximum von Mises stress of the OBS were at a minimum when there was a 35 mm downward movement of the third rod from the baseline. Therefore, the optimal position of third rod fixation was 35 mm below the fovea capitis of the femur. The optimal intersection angles between the proximal screws were found to be 71.92° or 84°. A 6 mm diameter connecting rod proved to be most effective. Configuration d, utilizing 7 screws, represented the most clinically appropriate screw number configuration, despite configuration f, utilizing 9 screws, eliciting the best evaluation indices.

Conclusion

An OBS used in the above-described configuration is well suited to the characteristics of PFF and provides an effective and reliable means for their treatment.

How to Prevent Aseptic Loosening in Cementless Arthroplasty: A Review

Aseptic loosening is the main late postoperative complication of cementless total hip arthroplasties (THAs), leading to pain and functional impairment. This article aims to update the orthopedic surgeon on the various methods by which the aseptic loosening rate can be reduced. We performed a systematic review by searching the PubMed database for hip aseptic loosening. We included meta-analysis, randomized controlled trials, reviews, and systematic reviews in the last 10 years, which provided information on techniques that can prevent aseptic loosening in total hip arthroplasty. From a total of 3205 articles identified, 69 articles (2%) met the inclusion criteria, leading to a total of 36 recommendations. A lot of research has been conducted in terms of septic loosening in the last decade. Currently, we have various techniques by which we can reduce the rate of aseptic loosening. Nevertheless, further randomized clinical trials are needed to expand the recommendations for aseptic loosening prevention.

Preserved periprosthetic bone stock at 5 years post-operatively with uncemented short hip stem in both collared and collarless version

INTRODUCTION

Previous bone density studies have generally shown bone resorption around both cemented and uncemented total hip arthroplasty (THA) stems. This is presumed to be due to stress shielding. Short stems have been introduced partly to preserve bone in the proximal femur by a more physiological loading of the bone. The purpose of this study was to evaluate bone remodeling around a short, fully hydroxyapatite-coated titanium stem that comes in a collared and collarless version.

PATIENTS AND METHODS

A prospective cohort of 50 patients included in a study evaluating the Furlong Evolution stem has been followed for 5 years. Examination was done with dual energy X-ray absorptiometry (DXA) postoperatively, at 1, 2 and 5 years. Clinical outcome was followed with radiography and both general and hip specific outcome measures.

RESULTS

The two versions of the stem behaved similarly regarding bone remodeling. After an initial decrease up to 1 year, bone mineral density (BMD) increased in all Gruen zones up to 2 years and at 5 years bone stock was still preserved compared with postoperatively (net BMD + 1.2% (95% CI - 0.4 to 2.8)). Increase in BMD occurred mainly in the greater trochanter and distally around the stem with a decrease in the calcar area. Both versions showed excellent clinical outcome up to 5 years.

CONCLUSION

This short stem seems to preserve proximal bone stock up to 5 years, exhibiting similar behaviour both with and without a collar.

TRIAL REGISTRATION NUMBER AND DATE OF REGISTRATION

ClinicalTrials.gov, (identifier: NCT01894854). July 10, 2013.

Short-term success of proximal bone stock preservation in short hip stems: a systematic review of the literature

Total hip arthroplasty is performed more frequently in younger patients nowadays, making long-term bone stock preservation an important topic. A mechanism for late implant failure is periprosthetic bone loss, caused by stress shielding around the hip stem due to different load distribution. Short stems are designed to keep the physical loading in the proximal part of the femur to reduce stress shielding. The aim of this review is to give more insight into how short and anatomic stems behave and whether they succeed in preservation of proximal bone stock.

A systematic literature search was performed to find all published studies on bone mineral density in short and anatomic hip stems. Results on periprosthetic femoral bone mineral density, measured with dual-energy X-ray absorptiometry (DEXA), were compiled and analysed per Gruen zone in percentual change.

A total of 29 studies were included. In short stems, Gruen 1 showed bone loss of 5% after one year (n = 855) and 5% after two years (n = 266). Gruen 7 showed bone loss of 10% after one year and –11% after two years. In anatomic stems, Gruen 1 showed bone loss of 8% after one year (n = 731) and 11% after two years (n = 227). Gruen 7 showed bone loss of 14% after one year and 15% after two years.

Short stems are capable of preserving proximal bone stock and have slightly less proximal bone loss in the first years, compared to anatomic stems.

Cite this article: EFORT Open Rev 2021;6:1040-1051. DOI: 10.1302/2058-5241.6.210030

The 20-year results of the first 400 Conserve Plus hip resurfacing arthroplasties

AIMS

Adverse local tissue reactions associated with abnormal wear considerably slowed down the general use of metal-on-metal (MoM) hip resurfacing arthroplasty (HRA), now limited to a few specialized centres. In this study, we provide the clinical results of 400 consecutive MoM HRAs implanted more than 20 years ago in one such centre.

METHODS

A total of 355 patients (400 hips) were treated with Conserve Plus HRA between November 1996 and November 2000. There were 96 female (27%) and 259 male patients (73%). Their mean age was 48.2 years (SD 10.9). The University of California, Los Angeles (UCLA) hip scores and 12-item Short Form Survey (SF-12) quality of life scores were reported. Survivorship was assessed using Kaplan-Meier analyses.

RESULTS

The mean follow-up was 16.5 years (0.1 to 24.0), including 34 patients (37 hips) who died. The mean UCLA hip scores were 9.3 (2 to 10), 9.1 (3 to 10), 9.0 (3 to 10), and 6.9 (2 to 10) for pain, walking, function, and activity, respectively. The mean SF-12 scores were 48.4 (16.0 to 62.1) for the physical component and 48.5 (10.5 to 66.5) for the mental component, and did not differ from those of the general population of the USA. A total of 60 hips in 55 patients were revised. Using revision for any indication as the endpoint, the Kaplan-Meier survivorship was 83.5% at 20 years. A diagnosis of developmental dysplasia (hazard ratio (HR) 2.199 (95% confidence interval (CI) 1.140 to 4.239); p = 0.019) and a low BMI (HR 0.931 (95% CI 0.873 to 0.994); p = 0.032) were risk factors for revision. Female sex was a risk factor only because of hip dysplasia and small component size. There were no cases of metal sensitivity associated with revision surgery. Radiological analysis showed persistent fixation in all but one hip.

CONCLUSION

The 83.5% 20-year survivorship of this initial series surpasses that of total hip arthroplasties in use 20 years ago in these young patients, suggesting satisfactory lifelong durability of the device for almost all of the remaining patients. Cite this article: Bone Joint J 2021;103-B(7 Supple B):25-32.

Factors Affecting Periprosthetic Bone Loss after Hip Arthroplasty

Periprosthetic bone loss may lead to major complications in hip arthroplasty, including aseptic loosening, implant migration, and even periprosthetic fracture. Such a complication leads to revision surgeries, which are expensive, technically demanding, and result in a low satisfaction rate. Therefore, a study was conducted of the factors affecting the periprosthetic bone loss around the stem that caused these complications. Factors influencing periprosthetic bone loss include demographic factors such as age, sex, obesity, smoking, and comorbidity including diabetes and osteoporosis. The implant design and fixation method are also factors that are determined before surgery. In addition, there are surgical factors, such as surgical approach and surgical technique, and we wish to investigate the factors affecting periprosthetic bone loss around the stem by comparing the effects of postoperative rehabilitation protocols and osteoporosis drugs.

Bilateral massive osteolysis of uncertain origin after total knee arthroplasty: A case report and review of literature

INTRODUCTION AND IMPORTANCE

Periprosthetic osteolysis (PPOL) is a common complication after total knee arthroplasty (TKA) and is most commonly caused by wear-induced particles.

CASE PRESENTATION

We report an unusual case of massive bilateral PPOL in the posterior flanges of the femur and patellae 4 years after bilateral uncemented TKA without patellar resurfacing in a 71-year old female. Bilateral staged revision surgery including polyethylene exchange and allograft morselized bone impaction was performed to treat the osteolytic lesions. There were no signs of implant malalignment, polyethylene wear or component loosening.

CLINICAL DISCUSSION

Several factors are associated with an increased risk on PPOL (e.g. polyethylene sterilization method, patient age, male gender). Surgical intervention in the context of massive PPOL should include replacement of a potential particle generator (most often polyethylene), correction of potential malalignment, treatment of bone defects and assessment of implant anchorage.

CONCLUSION

This report highlights the available evidence on clinical presentation, associated risk factors and preferred treatment strategy of massive osteolytic lesions after TKA according to available evidence.

Influence of Femoral Component Design on Proximal Femoral Bone Mass After Total Hip Replacement: A Randomized Controlled Trial

BACKGROUND

In this randomized controlled trial (RCT), we compared bone remodeling and bone turnover between 2 total hip arthroplasty implants-the short, proximally porous-coated Tri-Lock Bone-Preservation Stem and a conventional, fully-coated Corail prosthesis-over a 2-year postoperative period.

METHODS

Forty-six participants received the Tri-Lock prosthesis and 40 received the Corail prosthesis. At baseline, the 2 groups had similar demographics, proximal femoral bone mineral density (BMD), bone turnover markers, radiographic canal flare index, and patient-reported outcome measure (PROM) scores. Outcomes were measured at weeks 26, 52, and 104.

RESULTS

Loss of periprosthetic bone, measured by high-sensitivity dual x-ray absorptiometry region-free analysis (DXA-RFA), was identified at the calcar and proximal-lateral aspect of the femur in both prosthesis groups (p < 0.05). However, the conventional prosthesis was associated with a smaller reduction in BMD compared with the bone-preservation prosthesis (p < 0.001). This effect was most prominent in the region of the femoral calcar and greater trochanter. A small gain in BMD was also identified in some areas, and this gain was greater with the conventional than the bone-preservation prosthesis (p < 0.001). The 2 groups had similar changes in bone turnover markers and improvement in PROM scores over the study period (p > 0.05). The adverse-event rate was also similar between the groups (p > 0.05).

CONCLUSIONS

This RCT shows that prostheses intended to preserve proximal femoral bone do not necessarily perform better in this regard than conventional cementless designs. DXA-RFA is a sensitive tool for detecting spatially complex patterns of periprosthetic bone remodeling.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Perioperative patient-specific factors-based nomograms predict short-term periprosthetic bone loss after total hip arthroplasty

BACKGROUND

Although medical intervention of periprosthetic bone loss in the immediate postoperative period was recommended, not all the patients experienced periprosthetic bone loss after total hip arthroplasty (THA). Prediction tools that enrolled all potential risk factors to calculate an individualized prediction of postoperative periprosthetic bone loss were strongly needed for clinical decision-making.

METHODS

Data of the patients who underwent primary unilateral cementless THA between April 2015 and October 2017 in our center were retrospectively collected. Candidate variables included demographic data and bone mineral density (BMD) in spine, hip, and periprosthetic regions that measured 1 week after THA. Outcomes of interest included the risk of postoperative periprosthetic bone loss in Gruen zone 1, 7, and total zones in the 1st postoperative year. Nomograms were presented based on multiple logistic regressions via R language. One thousand Bootstraps were used for internal validation.

RESULTS

Five hundred sixty-three patients met the inclusion criteria were enrolled, and the final analysis was performed in 427 patients (195 male and 232 female) after the exclusion. The mean BMD of Gruen zone 1, 7, and total were decreased by 4.1%, 6.4%, and 1.7% at the 1st year after THA, respectively. 61.1% of the patients (261/427) experienced bone loss in Gruen zone 1 at the 1st postoperative year, while there were 58.1% (248/427) in Gruen zone 7 and 63.0% (269/427) in Gruen zone total. Bias-corrected C-index for risk of postoperative bone loss in Gruen zone 1, 7, and total zones in the 1st postoperative year were 0.700, 0.785, and 0.696, respectively. The most highly influential factors for the postoperative periprosthetic bone loss were primary diagnosis and BMD in the corresponding Gruen zones at the baseline.

CONCLUSIONS

To the best of our knowledge, our study represented the first time to use the nomograms in estimating the risk of postoperative periprosthetic bone loss with adequate predictive discrimination and calibration. Those predictive models would help surgeons to identify high-risk patients who may benefit from anti-bone-resorptive treatment in the early postoperative period effectively. It is also beneficial for patients, as they can choose the treatment options based on a reasonable expectation following surgery.

Feasibility of the Inner-Side-Out Use of the LC-DCP for Periprosthetic Femoral Fracture in Total Hip Arthroplasty

BACKGROUND

The optimal technique for plate fixation to treat type B and C periprosthetic femoral fractures (PFFs) is unclear. The purpose of this study is to evaluate the radiographic results of inner-side-out limited contact dynamic compression plate (LC-DCP) to treat PFFs during or after total hip arthroplasty (THA).

METHODS

This retrospective study comprised of four men and six women with an average age of 64.7 years who underwent open reduction and internal fixation with an inner-side-out LC-DCP technique to treat PFFs; the reduction was maintained preliminary with the use of contoured plate and cables, and the grooves on the undersurface of LC-DCP for limited contact was used to hold and prevent the cables from slippage during tightening the cables. There were five intraoperative and five postoperative PFFs after THA. According to the Vancouver classification, the intraoperative PFFs included type B2 in two, B3 in one and C3 in two patients while postoperative PFFs were categorized into type B1 in one, type B2 in two and type C in two patients. The mean follow-up duration was 5.9 years (range 1-10.4). We evaluated radiographic union and complications after index operation.

RESULTS

All patients demonstrated radiographic bone union at an average follow-up duration of 4.4 months (range 3-8). Two patients showed stem subsidence after revision THA and one patient demonstrated a subsequent peri-implant fracture around the distal end of plate after union of the initial PPF; one patient underwent re-revision THA for stem loosening while another patient went through refixation for the peri-implant fracture. There was no nonunion, infection, nerve injury, or dislocation.

CONCLUSION

The inner-side-out LC-DCP technique showed satisfactory radiographic outcome. In certain situations where locking plates are not available, this technique might be a useful alternative for treating type B and C PFFs.

Bone Remodeling of Two Anatomic Stems: Densitometric Study of the Redesign of the ABG-II Stem

Background

Periprosthetic bone remodeling, which is a phenomenon observed in all femoral stems, has a multifactorial origin as it depends on factors related to the patient, the surgical technique, and the design of the implant. To determine the pattern of remodeling produced by 2 models of anatomic cementless implants, we quantified the changes in bone mineral density (BMD) in the 7 areas of Gruen observed at different moments after surgery during the first postoperative year.

Methods

A prospective, comparative, controlled, 1-year follow-up densitometric study was carried out in 2 groups of patients suffering from primary unilateral hip osteoarthritis. In the first group, with 68 patients, an ABG-II stem was implanted. In the second, with 66 patients, the ANATO stem was used. The contralateral, healthy hip was taken as a control.

Results

Both groups showed a decrease in BMD at 3 months in all the areas, which recovered at the end of the study, except in zone 7: there was a 17.7% decrease in the ABG-II group and a 5.9% decrease in the ANATO group. In zones 2 and 6, where more loads are transmitted, conservation of BMD is observed in response to Wolff's law. The differences in the pattern of remodeling between groups were maintained despite the age, gender, and BMI of the patients or the size of the implants.

Conclusion

The ANATO stem achieved a more efficient transmission of loads at the metaphyseal level, which promotes bone preservation at the proximal femur, than the ABG-II stem.

Strain shielding for cemented hip implants

BACKGROUND

Long-term survival of hip implants is of increasing relevance due to the rising life expectancy. The biomechanical effect of strain shielding as a result of implant insertion may lead to bone resorption, thus increasing risk for implant loosening and periprosthetic fractures. Patient-specific quantification of strain shielding could assist orthopedic surgeons in choosing the biomechanically most appropriate prosthesis.

METHODS

Validated quantitative CT-based finite element models of five femurs in intact and implanted states were considered to propose a systematic algorithm for strain shielding quantification. Three different strain measures were investigated and the most appropriate measure for strain shielding quantification is recommended. It is used to demonstrate a practical femur-specific implant selection among three common designs.

FINDINGS

Strain shielding measures demonstrated similar trends in all Gruen zones except zone 1, where the volumetric strain measure differed from von-Mises and maximum principal strains. The volumetric strain measure is in better agreement with clinical bone resorption records. It is also consistent with the biological mechanism of bone remodeling so it is recommended for strain shielding quantification. Applying the strain shielding algorithm on three different implants for a specific femur suggests that the collared design is preferable. Such quantitative biomechanical input is valuable for practical patient specific implant selection.

INTERPRETATION

Volumetric strain should be considered for strain shielding examination. The presented methodology may potentially enable patient-specific pre-operative strain shielding evaluation so to minimize strain shielding. It should be further used in a longitudinal study so to correlate between strain shielding predictions and clinical bone resorption.

Comparison of Bone Preservation in Elderly Patients with Femoral Neck Fracture After Bipolar Hemiarthroplasty Using Shorter Femoral Stem and Standard Femoral Stem

BACKGROUND

This randomized control study was designed to compare the clinical and radiological outcomes, including periprosthetic bone mineral density (BMD) changes, between the short and standard stems after using cementless hemiarthroplasty in elderly patients with femur neck fractures.

MATERIALS AND METHODS

From January 2013 to May 2017, 151 patients (aged ≥ 65 years) underwent hemiarthroplasties due to femoral neck fractures. Patients were randomized into two groups; 77 patients in Group A implanting the short femoral stem and 74 patients in Group B implanting the standard femoral stem. Clinical and radiographic evaluations were performed in all patients.

RESULTS

75 patients (40 patients in Group A and 35 patients in Group B) completed routine follow-up for a minimum of 2 years. The clinical outcomes, including ambulatory functions and thigh pain, were similar in both groups. All the femoral stems acquired radiologic stability. At postoperative one year, BMD values in Gruen zone (G) seven on the standard stem side were significantly lower than those on the short stem side (P = 0.038). At the second year of follow-up, the BMD values of Group A in G1, G3, G4, and G7 were significantly greater than those of Group B (P = 0.007, 0.032, 0.026, and P < 0.000, respectively).

CONCLUSIONS

Both the clinical outcomes and radiologic stability in both group demonstrated similar results in elderly patients with femoral neck fracture at the latest follow-up. In addition, the periprosthetic BMD of the short femoral stems demonstrated better periprosthetic bone preservation at a minimum of 2 years of follow-up.

LEVEL OF EVIDENCES

Therapeutic Level II.

Bone remodelling and integration of two different types of short stem: a dual-energy X-ray - absorptiometry study

PURPOSE

Different kinds of bone preserving hip stems have been created to assure a more physiological distribution of the strengths on the femur. The aim of this research is to evaluate the density reaction of the periprosthetic bone while changing the conformation of the prosthetic implant on dual-energy X-ray - absorptiometry (DXA).

METHODS

This is a prospective, single-centre study assessing bone remodelling changes after implantation of two short hip stems, dividing the patients in two groups according to the implant used: 20 in group A, Metha (B-Braun), and 16 in group B, SMF (Smith and Nephew). All participants had a pre-operative and a post-operative (24 months) DXA evaluating the changes in bone mass density (BMD) occurred in the five Gruen's zones.

RESULTS

Compared to the pre-operative value, differences in BMD percentage were statistically significant only in ROI 4 (p < 0.05), with an increase in both groups (9 and 18%, respectively). The average increase in BMD was of 7.3% and 7.2% in the 2 groups.

CONCLUSION

According to our study, both stems have proved able to provide good load distribution across the metaphyseal region favouring proper system integration. Nonetheless, is certainly needed to perform other studies with longer follow-up and bigger populations to give strength to these conclusions.

An Ultra-Short Femoral Neck-Preserving Hip Prosthesis: A 2-Year Follow-up Study with Radiostereometric Analysis and Dual X-Ray Absorptiometry in a Stepwise Introduction

BACKGROUND

Total hip arthroplasty (THA) with a diaphyseal stem may risk bone loss. In order to save proximal bone stock in young patients with a high activity level and a long life expectancy, the interest in short stems has evolved. The purpose of this prospective observational cohort study was to evaluate the fixation of, and bone remodeling around, the Primoris femoral neck-preserving hip implant.

METHODS

Fifty younger patients with end-stage osteoarthritis were managed with the Primoris hip implant. We evaluated bone mineral density (BMD) using dual x-ray absorptiometry (DXA) and implant migration using radiostereometric analysis (RSA). A region-of-interest (ROI) protocol for 4 ROIs was applied to assess BMD. The association between BMD and migration was evaluated to determine the fixation of the Primoris implant and bone remodeling in the proximal part of the femur. Follow-up evaluation was performed at regular intervals from day 1 (baseline) until 24 months after surgery.

RESULTS

The major stem migrations were subsidence (Y axis; mean, 0.38 mm) at 6 weeks and varus tilt (rotation) (Z axis; mean, 0.93°) at 6 to 12 months. In ROI4 (the calcar area), a significant gain in bone was found with a mean difference of 4.1% (95% confidence interval [CI], 0.8% to 7.4%; p < 0.02) at 24 months postoperatively. Significant bone loss was found in ROI1 and ROI2, with a mean difference of -4.9% (95% CI, -7.4% to -2.4%; p = 0.0003) and -8.9% (95% CI, -11.5% to -6.2%; p = 0.0001), respectively. Linear regression and multivariate regression analysis showed a significant negative association between maximal total point motion and BMD (p = 0.02, R = 15%; and p < 0.05, R = 26%, respectively).

CONCLUSIONS

The Primoris component showed satisfactory primary stability with promising results at the 24-month follow-up. DXA scans showed limited stress-shielding with the proximal loading pattern of the Primoris. Better bone quality was associated with less implant migration.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Local Mechanical Environment and Spinal Trabecular Volumetric Bone Mineral Density Measured by Quantitative Computed Tomography: A Study on Lumbar Lordosis

OBJECTIVE

There have been some reports on the association between spinal balance parameters and regional bone mineral density (BMD), but the results are controversial. The purpose of this study is to evaluate the relationship between spinopelvic parameters and regional volumetric BMDs (vBMDs) measured by quantitative computed tomography (QCT) in the lumbosacral region of patients undergoing lumbar fusion surgery.

METHODS

The data of consecutive patients undergoing posterior lumbar spinal fusion with preoperative computed tomography was reviewed. QCT measurements were conducted in L1-S1 vertebral trabecular bone. The associations between spinopelvic sagittal parameters and vBMDs were evaluated. Multivariate analyses adjusted with age, gender, race, and body mass index were conducted with vBMD as the response variable.

RESULTS

A total of 144 patients were included in the final analyses. Mean age (± standard deviation) was 65.4 ± 11.8 years. Mean vBMD in L1 (± standard deviation) was 118.3 ± 37.4 mg/cm³. After adjusting by cofactors, lumbar lordosis was negatively associated with vBMDs in all levels from L1 to L5 (% regression coefficients and adjusted R² values: L1, -0.438, 0.268; L2, -0.556, 0.296; L3, -0.608, 0.362; L4, -0.554, 0.228; L5, -0.424, 0.194), but not in S1. Sacral slope was negatively associated with vBMD only at L4 (% coefficient, -0.588; R², 0.208). Other parameters were not significantly associated with vBMDs at any levels.

CONCLUSIONS

Higher lumbar lordosis was associated with lower vBMDs in all lumbar spine levels. Our results suggest that BMD is affected not only by metabolic factors but also by the mechanical environment. Further longitudinal studies are needed to elucidate this effect of vBMD on clinical outcomes.

Periprosthetic Osteolysis: Mechanisms, Prevention and Treatment

Clinical studies, as well as in vitro and in vivo experiments have demonstrated that byproducts from joint replacements induce an inflammatory reaction that can result in periprosthetic osteolysis (PPOL) and aseptic loosening (AL). Particle-stimulated macrophages and other cells release cytokines, chemokines, and other pro-inflammatory substances that perpetuate chronic inflammation, induce osteoclastic bone resorption and suppress bone formation. Differentiation, maturation, activation, and survival of osteoclasts at the bone-implant interface are under the control of the receptor activator of nuclear factor kappa-Β ligand (RANKL)-dependent pathways, and the transcription factors like nuclear factor κB (NF-κB) and activator protein-1 (AP-1). Mechanical factors such as prosthetic micromotion and oscillations in fluid pressures also contribute to PPOL. The treatment for progressive PPOL is only surgical. In order to mitigate ongoing loss of host bone, a number of non-operative approaches have been proposed. However, except for the use of bisphosphonates in selected cases, none are evidence based. To date, the most successful and effective approach to preventing PPOL is usage of wear-resistant bearing couples in combination with advanced implant designs, reducing the load of metallic and polymer particles. These innovations have significantly decreased the revision rate due to AL and PPOL in the last decade.

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.

Stem length in primary cementless total hip arthroplasty: Does it make a difference in bone remodeling?

PURPOSE

Stem design is usually accused for proximal femoral remodeling following total hip arthroplasty (THA). The aim of this prospective study was to compare the in vivo changes in bone mineral density (BMD) of the proximal femur after implantation of cementless THA with two length alternative stems.

METHODS

Between May 2011 and March 2014, 50 patients, who met our selection criteria and received cementless THA, randomized into two groups. Group A received cementless standard femoral stems, while group B received short stems. Harris Hip Score (HHS) and visual analog scale (VAS) were used for clinical assessment. Stem and cup positions and stability were radiologically evaluated. Dual-energy X-ray absorptiometry was used to follow and compare changes in BMD in different zones of proximal femur between both groups.

RESULTS

After a mean follow-up of 21.4 ± 3.53 months, there was a significant (p < 0.05) improvement in mean HHS and VAS with no significant differences (p > 0.05) between groups. There was no significant difference (p > 0.05) between groups regarding radiological results and rates of complications. The mean overall BMD was decreased by 11.26% for group A and 8.68% for group B at the final follow-up (p > 0.05). The greatest loss was found in greater trochanter region for group A and so for group B, but to a lesser extent (p < 0.05).

CONCLUSIONS

Cementless short stem was not able to hold back proximal femoral bone loss, but only can modify or decrease its incidence within limits.

Is a modular dual mobility acetabulum a viable option for the young, active total hip arthroplasty patient?

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/m² 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.

An evaluation of proximal femur bone density in young, active patients undergoing total hip arthroplasty at one year postoperatively

BACKGROUND:

Prior investigations have shown a decrease in periprosthetic bone mineral density (BMD) of the calcar following total hip arthroplasty (THA). The purpose of this investigation was to study proximal femur BMD in a cohort of young, active patients following THA at 1 year postoperatively using a recently introduced stem design.

METHODS:

This was a prospective, IRB-approved investigation of patients with an age <65 years, BMI <35 kg/m², and presymptomatic UCLA score of >6 undergoing a primary THA for a diagnosis of osteoarthritis. All patients received a titanium, proximally coated, tapered cementless femoral stem (ACCOLADE II, Stryker Inc, Mahwah, NJ, USA). Dual energy X-ray absorptiometry scans were performed at 6 weeks, 6 months, and 1 year postoperatively. Bone density was analyzed for 7 traditional Gruen zones with BMD ratios calculated for change in BMD compared with the baseline.

RESULTS:

31 patients (mean age of 52.6 + 6.5 years, BMI of 27.9 + 3.9 kg/m², and UCLA activity score of 7.3 + 1.9) were included. The mean BMD ratio decreased at the 6 months and 1 year interval in zones 1 and 2. However, the mean BMD ratio was maintained in Gruen zones 3 thru 7 with zone 7 (medial calcar) demonstrating 100% maintenance of the baseline BMD at 1 year.

CONCLUSION:

This study demonstrates the maintenance of medial calcar bone density at 1 year postoperatively in young, active patients undergoing THA. Further longitudinal analysis of this stem design is necessary to elucidate the significance of this finding.

Total Hip Arthroplasty Using Hybrid Ceramic Bearing: A Minimum 10-Year Followup Study

BACKGROUND

Contemporary ceramic articulation in total hip arthroplasty (THA) has shown successful clinical and radiologic outcomes at mid-to-long term. Delta ceramic, which includes 24% zirconia, has been developed to reduce the rate of ceramic fracture. However, the phase transformation of the zirconia that might cause surface roughness, ceramic wear, and subsequent osteolysis remains a concern. The purpose of this study was to evaluate clinicoradiological outcomes, ceramic-related complications, and survivorship of THA with the use of hybrid ceramic bearing; BIOLOX delta liner-on-BIOLOX forte head articulation at a minimum followup of 10 years.

MATERIALS AND METHODS

One hundred cementless THAs (85 patients) were performed with the use of 36-mm hybrid ceramic bearing. The thickness of the delta ceramic liner was 4-6 mm. Four patients (4 hips) were lost and six patients (6 hips) died within 10 years after the operation. Thus, the remaining 75 patients (90 hips) were followed up for 10-12 years. There were 43 men and 32 women. The mean age of these patients at the index operation was 58 years (21-78 years).

RESULTS

There were no fractures of ceramic liner or head. There was no measurable ceramic wear, and neither pelvic nor femoral osteolysis was identified. All acetabular and femoral components were bone-ingrown. Three (3/90, 3.3%) patients noted noise of clicking sound. The mean Harris hip score was 87 points (range 72-99 points) at the time of final followup. THA survivorship with revision surgery as an endpoint was 97.8% (95% confidence interval: 91.4%-99.8%).

CONCLUSIONS

The long term result of cementless THA with the use of a large BIOLOX forte head on the BIOLOX delta liner showed an encouraging result. Wear or osteolysis associated with composite of 24% zirconia in the fourth-generation ceramic was not observed at a minimum followup of 10 years.

Bone remodelling of the proximal femur after total hip arthroplasty with 2 different hip implant designs: 15 years follow-up of the thrust plate prosthesis and the Bi-Metric stem

INTRODUCTION

The thrust plate prosthesis (TPP) was introduced to preserve bone in patients undergoing total hip arthroplasty. We assessed the long-term results of hip arthroplasty in patients who received the TPP compared to a traditional intramedullary stem (Bi-Metric).

METHODS

In this prospective observational cohort study, we evaluated bone mineral density (BMD) using dual-energy X-ray absorptiometry (DXA), radiological imaging and clinical outcome using Harris Hip Score (HHS). Twenty patients received the TPP (group A) and 18 patients received the Bi-Metric stem (group B). Baseline was the 1st postoperative day, and subsequent follow-up was performed at 6 months, 1, 2, 8, 12 and 15 years after surgery. A four regions of interest (ROI) protocol was developed to assess BMD.

RESULTS

In ROI1, bone resorption was significantly higher for group A at 6 months with a mean difference of 10% (95% confidence interval [CI], 4-16; p = 0.003) and 8% (95% CI, 1-15; p = 0.03) at 8 years. Regarding ROI4, group A had a lesser decrease in general compared to group B. The radiological findings did not reveal any subsidence or detectable implant migration. HHS improved from 53 (23-69) to 93 (55-100) in group A and from 51 (24-72) to 94 (78-100) in group B.

CONCLUSION

The TPP was not found to be inferior to the Bi-Metric stem regarding bone preservation. The decrease in BMD in ROI4 was greater in group B. Clinical and radiological results also revealed that the TPP was not inferior to the Bi-Metric stem.

Comparison of periprosthetic bone remodeling after implantation of anatomic and tapered cementless femoral stems in total hip arthroplasty: A prospective cohort study protocol

INTRODUCTION

Current total hip arthroplasty (THA) implant usage trends favor cementless fixation, and plenty studies have demonstrated that numbers of cementless femoral stems are associated with excellent long-term survivorship and functional outcomes. Various types of cementless femoral stems have been developed and utilized in multiple applications, including straight, tapered, anatomic, customized, short, and even neck stems. All of these designs aimed to achieve maximal primary stability and promote osseointegration. Nevertheless, stress-shielding and periprosthetic bone loss continue to occur and remain critical issues in promoting long-term survivorship of THA. Considering anatomic and tapered stems are the most popular cementless designs today, this prospective cohort study aimed to investigate the effect of stem design on stress-shielding and periprosthetic bone remodeling after implantation of an anatomic stem with proximal fixation (Ribbed Hip system; Waldemar Link, Hamburg, Germany) and the direct comparison to a fully coated tapered stem (LCU Hip system; Waldemar Link).

MATERIALS AND METHODS

This prospective cohort study will comprise patients who receive primary unilateral THA with the Ribbed anatomic hydroxyapatite (HA)-coated stem or LCU tapered fully HA-coated stem. The changes in periprosthetic bone mineral density after insertion of Ribbed and LCU stem prostheses will be assessed by means of dual-energy X-ray absorptiometry in the periprosthetic region of interest according to Gruen and colleagues. Standard anteroposterior and lateral plain radiography will be performed for qualitative assessment of the periprosthetic bone remodeling. The following items will be analyzed or measured on follow-up radiographs to compare with the initial appearance on the radiographs taken immediately postoperatively: cortical thickness in each Gruen zone, fitness of the distal stem within the isthmus, femoral stem alignment, radiolucent line, reactive line, periosteal bone reactions, and subsidence. Biologic fixation and stability of the cementless implant will be evaluated using Engh grading scale, and heterotopic ossification will be graded according to Brooker classification. Furthermore, Harris hip score and Western Ontario and McMaster Universities Osteoarthritis Index Score will also be assessed for postoperative functional evaluation. These radiologic and clinical assessments will be taken postoperatively, at 6 months, 1, 2, 3, 4, and 5 years after surgery.

ETHICS AND DISSEMINATION

This study was approved by The First Affiliated Hospital of Chongqing Medical University Ethics Committee. The study results will be disseminated at national and international conferences and published in peer-reviewed journals.

STUDY REGISTRATION

Chinese Clinical Trial Registry (http://www.chictr.org.cn): ChiCTR1800017841.