Bi-Metric Stem Research Articles

Intra-operative Clodronate Rinsing Improves the Integration of the Femoral Stem in a Prospective, Double-blinded, Randomized, Placebo-controlled Clinical RSA-study

Background: Periprosthetic bone loss after Total Hip Arthroplasty (THA), detected as an early migration of the prosthesis may predict later loosening of the implant. Objective: We hypothesized that intra-operative bisphosphonate rinsing would reduce bone resorption after THA. It might therefore be possible to achieve better early fixation of the implant. Methods: Nineteen patients suffering from arthrosis were recruited in a prospective, double-blinded, randomized, placebo-controlled clinical pilot trial. Patients were operated with an uncemented Bimetric stem using tantalum markers. The femoral proximal intramedullary canal was rinsed with 1mM clodronate in nine patients and with saline in 10 patients. These patients were followed for two years using radiostereometric analysis (RSA), dual energy x-ray absorptiometry (DXA) and the Harris Hip Score (HHS). Results: We did not found any significant differences between the study groups with regards to the primary output measures (maximum total point motion, MTPM). However, there was evidence that clodronate could affect periprosthetic bone quality; a beneficial effect in BMD in Gruen zone 3 during the two-year follow-up was observed, BMD decreased less in the clodronate group (p = 0.02). The maximal x-translation of the stem at 3-24 months was significantly two-fold, being higher in the placebo group (p = 0.02). The baseline BMD and the maximal total point motion (MTPM) at 3-24 months showed a positive correlation in the clodronate group and a negative correlation in the placebo group. Conclusion: In conclusion, further studies with larger patient groups and longer follow-up periods are needed to estimate the clinical importance of these findings and further to prove if an intraoperative clodronate rinsing prior to application of femoral stem during THA can prevent periprosthetic bone loss. Clinical Trial Registration No.: NCT03803839

Migration of the uncemented Echo Bi-Metric and Bi-Metric THA stems: a randomized controlled RSA study involving 62 patients with 24-month follow-up

Background and purpose — Despite the good results after total hip arthroplasty (THA), new implants are continuously being developed to improve durability. The Echo Bi-Metric (EBM) THA stem is the successor to the Bi-Metric (BM) THA stem. The EBM stem includes many of the features of the BM stem, but minor changes in the design might improve the clinical performance. We compared the migration behavior with radiostereometric analysis (RSA) of the EBM stem and the BM stem at 24 months and evaluated the clinical outcome. Patients and methods — We randomized 62 patients with osteoarthritis (mean age 64 years, female/male 28/34) scheduled for an uncemented THA to receive either an EBM or a BM THA stem. We performed RSA within 1 week after surgery and at 3, 6, 12, and 24 months. The clinical outcome was evaluated using Harris Hip Score (HHS) and Oxford Hip Score (OHS). Results — At 24 months, we found no statistically significant differences in migration between the two implants. During the first 3 months both the EBM and the BM stems showed visible subsidence (2.5 mm and 2.2 mm respectively), and retroversion (2.5° and 2.2° respectively), but after 3 months this stabilized. The expected increase in HHS and OHS was similar between the groups. Interpretation — The EBM stem showed a migration at 24 months not different from the BM stem, and both stems display satisfying clinical results.

Higher early proximal migration of hemispherical cups with electrochemically applied hydroxyapatite (BoneMaster) on a porous surface compared with porous surface alone: a randomized RSA study with 53 patients

Background and purpose — BoneMaster (BM) is an electrochemically deposited hydroxyapatite (HA) implant-coating, which is evenly distributed, thin, and quickly resorbed. It is designed to stimulate osseointegration and early implant stability and alleviate longer-term HA-induced third-body polyethylene wear. This study evaluates early cup migration and functional outcomes of cementless porous-coated hemispherical cups with or without BM.Patients and methods — In a patient-blinded, randomized, controlled trial 53 patients at mean 64 years (55–75) with coxarthritis were operated with an Exceed cup (Zimmer Biomet) and Bi-Metric stem (Zimmer Biomet) with porous and BM coating (PBM) or with porous coating alone (P). Follow-ups were performed postoperatively and at 3, 6, 12, and 24 months. Effect measures were cup migration measured with RSA and PROMs.Results — At 6-month follow-up, proximal cup migration in the PBM group (0.09 mm, 95% CI 0.02–0.20) was higher than in the P group (0.25 mm, CI 0.15–0.35). At 1- and 2-year follow-up, cup migration in all 6 degrees of freedom was similar between groups (p > 0.2). From before surgery to 2-year follow-up, Oxford Hip Score (OHS) increased by 17 points (CI 14–20). Hip disability and Osteoarthritis Outcome Score (HOOS) increased in all sub-scores, but was more pronounced for PBM cups compared with P cups in the Symptoms sub-score (p = 0.04).Interpretation — Contrary to expectations, PBM cups had higher early migration than P cups. At 2-year follow-up, migration was similar between groups. There seems to be no early benefit of BM coating on acetabular cups.

Effect of stem alignment on long-term outcomes of total hip arthroplasty with cementless Bi-Metric femoral components

We investigated the effects of varus-valgus alignment on the long-term outcomes after cementless total hip arthroplasty (THA) using a porous coated version of Bi-Metric® femoral stems. The Kaplan-Meier survival analysis was performed in 71 hips. The survival rate with femoral revision for aseptic loosening as the end point was 100% at 17 years. Nevertheless, the initial stem alignment was more valgus in patients with the Engh grade III–IV stress shielding than patients with the Engh grade I–II. Our results suggest that valgus misalignment of cementless Bi-Metric stem might be a potential risk factor for the progression of stress shielding.

Preparation of the femoral bone cavity in cementless stems: broaching versus compaction

Background and purpose — Short-term experimental studies have confirmed that there is superior fixation of cementless implants inserted with compaction compared to broaching of the cancellous bone.Patients and methods — 1-stage, bilateral primary THA was performed in 28 patients between May 2001 and September 2007. The patients were randomized to femoral bone preparation with broaching on 1 side and compaction on the other side. 8 patients declined to attend the postoperative follow-up, leaving 20 patients (13 male) with a mean age of 58 (36–70) years for evaluation. The patients were followed with radiostereometric analysis (RSA) at baseline, at 6 and 12 weeks, and at 1, 2, and 5 years, and measurements of periprosthetic bone mineral density (BMD) at baseline and at 1, 2, and 5 years. The subjective part of the Harris hip score (HHS) and details of complications throughout the observation period were obtained at a mean interval of 6.3 (3.0–9.5) years after surgery.Results — Femoral stems in the compaction group had a higher degree of medio-lateral migration (0.21 mm, 95% CI: 0.03–0.40) than femoral stems in the broaching group at 5 years (p = 0.02). No other significant differences in translations or rotations were found between the 2 surgical techniques at 2 years (p > 0.4) and 5 years (p > 0.7) postoperatively. There were no individual stems with continuous migration. Periprosthetic BMD in the 7 Gruen zones was similar at 2 years and at 5 years. Intraoperative femoral fractures occurred in 2 of 20 compacted hips, but there were none in the 20 broached hips. The HHS and dislocations were similar in the 2 groups at 6.3 (3.0–9.5) years after surgery.Interpretation — Bone compaction as a surgical technique with the Bi-Metric stem did not show the superior outcomes expected compared to conventional broaching. Furthermore, 2 periprosthetic fractures occurred using the compaction technique, so we cannot recommend compaction for insertion of the cementless Bi-Metric stem.

Arthroplasty with Cement Resulted in Better Functioning Than Arthroplasty without Cement in Older Patients with Displaced Femoral Neck Fracture.

Inngul C, Blomfeldt R, Ponzer S, Enocson A. Cemented versus uncemented arthroplasty in patients with a displaced fracture of the femoral neck: a randomised controlled trial. Bone Joint J. 2015 Nov;97-B(11):1475-80. ### Question: In patients >65 years of age with a displaced femoral neck fracture, should a cemented or uncemented femoral stem be used? ### Design: Randomized (allocation concealed), unblinded, controlled trial with 4 and 12 months of follow-up. ### Setting: A large Swedish trauma center. ### Patients: 141 patients >65 years of age (mean age, 81 years; 70% women) who presented within 48 hours after acute displaced fracture of the femoral neck due to low-energy trauma and had total hip arthroplasty (65 to 79 years of age) or hemiarthroplasty (HA) (≥80 years of age). The exclusion criteria were severe cognitive dysfunction, alcohol or drug abuse, rheumatoid arthritis, osteoarthritis, residence in an institution, or inability to walk independently. ### Intervention: Cemented Exeter stem with gentamicin bone cement (n = 67) or uncemented hydroxyapatite Bimetric stem (n …

Short-term Outcomes With a Second-Generation Uncemented Stem in Total Hip Arthroplasty.

An uncemented stem has been used successfully in total hip arthroplasty for 2 decades, and some implants have been updated. The authors have used second-generation uncemented proximal porous coating stems, the Echo Bi-Metric Full Proximal Profile stem (Echo FPP; Biomet, Warsaw, Indiana) and the Echo Reduced Proximal Profile stem (Echo RPP; Biomet). This article reports short-term outcomes with these stems compared with their predecessor, the Bi-Metric stem (Biomet). The authors reviewed 1280 Echo FPP stems, 366 Echo RPP stems, and 1497 Bi-Metric stems. With more than 5 years of follow-up, both the Echo FPP and the Echo RPP stems had 100% survivorship with stem revision as the endpoint, and the Bi-Metric stems also had 100% survivorship for more than 20 years. Average Harris Hip Scores for the Echo FPP, the Echo RPP, and the Bi-Metric stems were 53.3, 49.7, and 51.5 preoperatively, 93.8, 94.6, and 95.2 at 1 year, and 94.0, 95.8, and 95.4 at 3 years postoperatively, respectively. Dislocation after surgery was significantly lower with the Echo FPP and the Echo RPP stems than with the Bi-Metric stems, but this was more relevant to the surgical approach and head size. All radiographs of the Echo FPP, the Echo RPP, and the Bi-Metric stems showed proximal femoral remodeling consistent with osseous ingrowth. Distal cortical hypertrophy around the implanted stem and spot-welding were comparably observed in all 3 cohorts. The short-term outcomes of the updated uncemented stems were as excellent as the previously used stem regarding survivorship, complications, and radiographic assessment.

Dual mobility total hip replacement in a high risk population.

Objective: The purpose of the study was to evaluate results of dual mobility total replacement in a high risk population who take hip into hyperflexed position while sitting and praying on the floor. Method: The study included 65 (35 primary total replacement and 30 complex total hip replacement) cases of total hip replacement using avantage privilege dual mobility cup system from biomet. A cemented acetabular component and on femoral side a bimetric stem, either cemented or uncemented used depending on the canal type. Ten cases were examined fluoroscopically in follow up. Result: There was dislocation in one patient undergoing complex hip replacement. Fluoroscopy study showed no impingement between the neck of prosthesis and acetabular shell at extremes of all movements. Conclusion: The prevalence of dislocation is low in our high risk population and we consider it preferred concept for patients undergoing complex total hip replacement.

Cemented versus uncemented arthroplasty in patients with a displaced fracture of the femoral neck: a randomised controlled trial.

The aim of this randomised controlled study was to compare functional and radiological outcomes between modern cemented and uncemented hydroxyapatite coated stems after one year in patients treated surgically for a fracture of the femoral neck. A total of 141 patients aged > 65 years were included. Patients were randomised to be treated with a cemented Exeter stem or an uncemented Bimetric stem. The patients were reviewed at four and 12 months. The cemented group performed better than the uncemented group for the Harris hip score (78 vs 70.7, p = 0.004) at four months and for the Short Musculoskeletal Function Assesment Questionnaire dysfunction score at four (29.8 vs 39.2, p = 0.007) and 12 months (22.3 vs 34.9, p = 0.001). The mean EQ-5D index score was better in the cemented group at four (0.68 vs 0.53, p = 0.001) and 12 months (0.75 vs 0.58, p = < 0.001) follow-up. There were nine intra-operative fractures in the uncemented group and none in the cemented group. In conclusion, our data do not support the use of an uncemented hydroxyapatite coated stem for the treatment of displaced fractures of the femoral neck in the elderly.

Hydroxyapatite coating does not improve uncemented stem survival after total hip arthroplasty!

Background and purpose — It is still being debated whether HA coating of uncemented stems used in total hip arthroplasty (THA) improves implant survival. We therefore investigated different uncemented stem brands, with and without HA coating, regarding early and long-term survival. Patients and methods — We identified 152,410 THA procedures using uncemented stems that were performed between 1995 and 2011 and registered in the Nordic Arthroplasty Register Association (NARA) database. We excluded 19,446 procedures that used stem brands less than 500 times in each country, procedures performed due to diagnoses other than osteoarthritis or pediatric hip disease, and procedures with missing information on the type of coating. 22 stem brands remained (which were used in 116,069 procedures) for analysis of revision of any component. 79,192 procedures from Denmark, Norway, and Sweden were analyzed for the endpoint stem revision. Unadjusted survival rates were calculated according to Kaplan-Meier, and Cox proportional hazards models were fitted in order to calculate hazard ratios (HRs) for the risk of revision with 95% confidence intervals (CIs). Results — Unadjusted 10-year survival with the endpoint revision of any component for any reason was 92.1% (CI: 91.8–92.4). Unadjusted 10-year survival with the endpoint stem revision due to aseptic loosening varied between the stem brands investigated and ranged from 96.7% (CI: 94.4–99.0) to 99.9% (CI: 99.6–100). Of the stem brands with the best survival, stems with and without HA coating were found. The presence of HA coating was not associated with statistically significant effects on the adjusted risk of stem revision due to aseptic loosening, with an HR of 0.8 (CI: 0.5–1.3; p = 0.4). The adjusted risk of revision due to infection was similar in the groups of THAs using HA-coated and non-HA-coated stems, with an HR of 0.9 (CI: 0.8–1.1; p = 0.6) for the presence of HA coating. The commonly used Bimetric stem (n = 25,329) was available both with and without HA coating, and the adjusted risk of stem revision due to aseptic loosening was similar for the 2 variants, with an HR of 0.9 (CI: 0.5–1.4; p = 0.5) for the HA-coated Bimetric stem. Interpretation — Uncemented HA-coated stems had similar results to those of uncemented stems with porous coating or rough sand-blasted stems. The use of HA coating on stems available both with and without this surface treatment had no clinically relevant effect on their outcome, and we thus question whether HA coating adds any value to well-functioning stem designs.

Effects of hydroxyapatite coating on survival of an uncemented femoral stem

Background and purpose Hydroxyapatite (HA) is widely used as a coating for uncemented total hip arthroplasty components. This has been suggested to improve implant ingrowth and long-term stability. However, the evidence behind the use of HA coating on femoral stems is ambiguous. We investigated survival of an uncemented, tapered titanium femoral stem that was available either with or without HA coating (Bi-Metric).Patients and methods The stem had been used in 4,772 total hip arthroplasties (THAs) in 4,169 patients registered in the Swedish Hip Arthroplasty Register between 1992 and 2009. 59% of the stems investigated were coated with HA and 41% were uncoated. Kaplan-Meier survival analysis and a Cox regression model with adjustment for age, sex, primary diagnosis, and the type of cup fixation were used to calculate survival rates and adjusted risk ratios (RRs) of the risk of revision for various reasons.Results The 10-year survival rates of the HA-coated version and the uncoated version were about equal when we used revision for any reason as the endpoint: 98% (95% CI: 98–99) and 98% (CI: 97–99), respectively. A Cox regression model adjusting for the covariates mentioned above showed that the presence of HA coating did not have any influence on the risk of stem revision for any reason (RR = 1.0, 95% CI: 0.6–1.6) or due to aseptic loosening (RR = 0.5, CI: 0.2–1.5). There was no effect of HA coating on the risk of stem revision due to infection, dislocation, or fracture.Interpretation The uncemented Bi-Metric stem showed excellent 10-year survival. Our findings do not support the use of HA coating on this stem to enhance implant survival.

Cementless total hip arthroplasty for primary osteoarthritis in patients aged 55 years and older

Background Cemented total hip arthroplasty has been the treatment of choice for elderly patients with osteoarthritis. We analyzed survival rates of the most common cementless designs used in this age group in Finland.Patients and methods Inclusion criteria permitted 10,310 replacements (8 designs) performed in patients aged 55 years or older to be selected for evaluation. The risk of revision of each of the 8 implants was compared with that of a group comprising 3 cemented designs as the reference (9,549 replacements). Survival analyses were performed overall and separately for 3 age cohorts: 55–64 years (6,781 replacements), 65–74 years (8,821 replacements), and 75 years or older (4,257 replacements).Results In all patients aged 55 years or more, the Bi-Metric stem had a higher survival rate for aseptic loosening at 15 years than the cemented reference group: 96% (95% CI: 94–98) vs. 91% (CI: 90–92). However, the 15-year survival rates of the Bi-Metric/Press-Fit Universal (71% (CI: 67–75)) and the Anatomic Mesh/Harris-Galante II (72% (CI: 67–78)) total hip replacements were lower than that of the reference group (86% (CI: 84–87)). Information was scarce for patients aged 75 years or more.Interpretation Cementless proximal porous-coated stems are a good option for elderly patients. Even though biological fixation is a reliable fixation method in THA, polyethylene wear and osteolysis remain a serious problem for cementless cup designs with unplugged screw holes and low-quality liners.

The Bimetric cementless total hip replacement: 7–18 year follow-up assessing the influence of acetabular design on survivorship

The purpose of this study was to evaluate the mid- to long-term survivorship of Bimetric cementless total hip replacement and assess how it is affected by the acetabular design. This was a retrospective analysis of 127 Bimetric cementless total hip replacements in 110 patients with a follow-up of 7-18 years. A single design stem and three different cementless metal-backed acetabular designs were used. Patients were assessed clinically using the Harris hip score and radiologically by independent review of current hip radiographs. There was only one case of aseptic loosening of the femoral stem. The earliest acetabular design showed a high failure rate whilst the latter two designs showed a 96% survivorship at a mean of 9.5 years. We conclude that a combination of the bimetric stem with either of the latter acetabular cup designs has a good mid- to long-term performance.

Comparison of the uncemented Cone and the cemented Bimetric hip prosthesis in young patients with osteoarthritis: An RSA, clinical and radiographic study

Background There is no consensus as to whether uncemented or cemented femoral stems should be used in younger patients. We compared the uncemented Cone stem to the cemented Bimetric stem in young patients with osteoarthritis.Patients and methods We randomized 45 relatively young patients (< 65 years old, mean age 54 years) with osteoarthritis to either an uncemented Cone stem or a cemented Bimetric stem. All patients were followed for 2 years. Outcome was assessed by the Merle d’Aubigné score, conventional radiography and repeated radio-stereometric analysis (RSA). We also followed 81 Cone stems for 8 (7–12) years with revision as endpoint.Results The clinical outcome was excellent. No patient had postoperative thigh pain. The migration was small. The Bimetric stem was stable during the whole observation period, while the Cone stem subsided and rotated to retroversion during the first 3 months post-operatively, and then remained stable. In the follow-up study of 81 Cone stems, 1 stem was revised.Interpretation We conclude that both the cemented Bimetric stem and the uncemented Cone stem are stable and give excellent clinical results after 2 years in relatively young patients with osteoarthritis. Although designed for CDH hips, the Cone stem appears to be suitable also for patients with osteoarthitis. ▪

Uncemented total hip arthroplasty for primary osteoarthritis in young patients: A mid-to long-term follow-up study from the Finnish Arthroplasty Register

Introduction The survival of total hip arthroplasties (THAs) has been considered to be poor in young patients. We evaluated the population-based survival of uncemented THA for primary osteoarthritis (OA) in patients under 55 years of age and the factors affecting survival.Methods The Finnish Arthroplasty Register was established in 1980. Between that year and 2003, 92,083 primary THAs were entered in the register, 5,607 of which were performed for primary OA in patients under 55 years of age. Using records from these 5,607 THAs, we selected uncemented femoral and acetabular components that had been used in more than 100 operations during the study period. Survival of both components (cup/stem) and their combinations were analyzed separately with the Kaplan-Meier analysis and the Cox regression model.Results All uncemented stems studied showed a survival rate of over 90% at 10 years. The Biomet Bi-Metric stem had a 95% (95% CI 93– 97) survival rate even at 15 years. Overall survival of the extendedly porous-coated Lord Madréporique stem (p = 0.003) and the proximally porous-coated Anatomic Mesh stem (p = 0.0008) were poorer than that of the Biomet Bi-Metric stem. When endpoint was defined as stem revision for any reason, results were generally similar; there was no difference, however, between the survival rates of the Lord Madréporique stem and the Bi-Metric stem.Of the acetabular components, the Biomet Universal, the ABG Il and the Harris-Galante II cups showed < 90% survival rates at 10 years with aseptic loosening as endpoint; at 13 years the corresponding survival rates were 94% (95% CI 91–97) for the Biomet Universal and 95% (95% CI 91–98) for the Harris-Galante II cups with aseptic loosening as endpoint. The PCA Pegged porous-coated uncemented cup showed a poor 13-year survival rate of 68% (95% CI 59–78) with aseptic loosening as endpoint. However, when endpoint was defined as any revision (including exchange of liner), the 10-year survival rates of all brands of cup except Harris-Galante II declined to under 80%.Interpretation Modern second-generation uncemented stems, with proximal circumferential porous- or HA-coating, seem to be a good choice for young patients with primary OA. Similarly, modern press-fit porous- and HA-coated cups appear to have good endurance against aseptic loosening in these young patients. However, liner revisions were common; thus, survival rates of uncemented cups were unsatisfactorily low. Polyethylene wear and unfavorable locking mechanisms between the metal shell and the polyethylene liner and their sequelae remain matters of concern in this young and active group of patients. ▪

Early periprosthetic femoral bone remodelling using different bearing material combinations in total hip arthroplasties: a prospective randomised study

The present study was performed to test the hypothesis that different bearing materials have an impact on femoral bone remodelling within the first year after a total hip arthroplasty. A total of 225 patients with osteoarthrosis of the hip or avascular necrosis of the femoral head were included in this randomised prospective study. All patients had an identical hybrid total hip arthroplasty (cemented BiMetric stem and cementless RingLoc acetabular cup) except for the bearing materials: polyethylene-on-zirconia (n = 78), CoCr-on-CoCr (n = 71), or alumina-on-alumina (n = 76). Bone mineral density (BMD) was measured with Dual-energy X-ray absorptiometry (DEXA) in seven Gruen zones adjacent to the femoral implant. The DEXA scan was performed within one week after surgery and was repeated one year postoperatively. There was no significant difference in periprosthetic BMD change between the three groups. After twelve months the relative BMD decrease was highest in the proximal part of the femur, - 6.2% in the greater trochanter region and - 12.7% in the lesser trochanter region. In the distal zones the relative BMD decrease was -5.3, -4.2, -2.1, -2.3, and -5.6%, respectively. The use of different bearing materials had no significant impact on femoral bone remodelling adjacent to the cemented hip stem within one year after surgery.

Survival of Bi-Metric femoral stems in 77 total hip arthroplasties for juvenile chronic arthritis

The survival of 77 cementless total hip arthroplasties using a Bi-Metric femoral stem and two types of acetabular components was analysed in 55 patients with juvenile chronic arthritis. The patients were treated between 1986 and 1996. Their mean age was 8.0 years at the onset of the disease and 28.1 years at the time of surgery. The mean follow-up period was 9.6 years. Follow-up evaluations were conducted 3 months and 1, 4, 8, 12 and 16 years post-operatively. The endpoints of survival analysis were revision surgery, death of the patient or the end of the year 2002. The 10-year survival was 77.6% for the Romanus cup and 49.1% for the TTAP-ST cup. In contrast to these inadequate outcomes, the cementless Bi-Metric stem yielded excellent results with a survival rate of 100% for aseptic loosening during a mean follow-up period of 10 years.