The Bicontact cementless primary total hip arthroplasty: long-term results

Long term results of the Bicontact D stem in dysplastic osteoarthritis: a 10-15 year follow-up study

PURPOSE

The purpose of the present study was to investigate the results of total hip arthroplasty (THA) using the Bicontact D stem with a minimum 10 year follow-up that focused on patients with developmental dysplasia of the hip (DDH).

METHODS

One hundred five patients with osteoarthritis due to DDH who underwent primary THA were included in this study. The mean final follow-up period was 12.7 ± 1.2 years (range 10-15 years). All cases were evaluated both clinically and radiographically, and Kaplan-Meier survivorship was determined as stem revision for any reason as the end point.

RESULTS

Modified Harris hip score averaged 89.0 ± 1.1 (range 60-98) at the final follow-up. The survivorship was 99.0% (95% confidence interval 93.4-99.9%) at 15.0 years, and only one hip with a well-fixed stem required stem revision due to recurrent dislocations. Cortical hypertrophy (CH) was observed in 40 of 105 hips (38.1%), and stress shielding (SS) progressed to grade 3 or 4 in six hips (6 of 105 hips: 5.7%) during the study period. Among the six hips with progressed SS, Dorr type C proximal femoral geometry was seen in five hips.

CONCLUSION

This study of 105 THAs using the Bicontact D stem that focused on DDH patients with a minimum 10 year follow-up period achieved satisfactory clinical and radiological outcomes. Dorr type C proximal femoral geometry could be considered a risk factor for progressed SS.

The Implant Proteome—The Right Surgical Glue to Fix Titanium Implants In Situ

Titanium implants are frequently applied to the bone in orthopedic and trauma surgery. Although these biomaterials are characterized by excellent implant survivorship and clinical outcomes, there are almost no data available on the initial protein layer binding to the implant surface in situ. This study aims to investigate the composition of the initial protein layer on endoprosthetic surfaces as a key initiating step in osseointegration. In patients qualified for total hip arthroplasty, the implants are inserted into the femoral canal, fixed and subsequently explanted after 2 and 5 min. The proteins adsorbed to the surface (the implant proteome) are analyzed by liquid chromatography–tandem mass spectrometry (LC-MS/MS). A statistical analysis of the proteins’ alteration with longer incubation times reveals a slight change in their abundance according to the Vroman effect. The pathways involved in the extracellular matrix organization of bone, sterile inflammation and the beginning of an immunogenic response governed by neutrophils are significantly enriched based on the analysis of the implant proteome. Those are generally not changed with longer incubation times. In summary, proteins relevant for osseointegration are already adsorbed within 2 min in situ. A deeper understanding of the in situ protein–implant interactions in patients may contribute to optimizing implant surfaces in orthopedic and trauma surgery.

Straight stem and threaded cup in patients under 60 years of age: 28.8-30.2 years of follow-up

Purpose

The aim of this retrospective observational study of one cohort was to evaluate the long-term outcome in patients younger than 60 years after total hip arthroplasty using a straight uncemented stem and an uncemented threaded cup.

Methods

Between 1986 and 1987, 75 hips of 75 patients (mean age, 53.35 ± 6.17 years) were consecutively implanted with an Alloclassic Zweymüller/Alloclassic SL stem and an Alloclassic CSF cup. Forty-four patients had died over the last 30 years. The remaining 31 patients (mean age, 82.9 ± 6.4 years) were reinvited for follow-up examinations. Clinical and radiographic evaluations were carried out.

Results

At a mean follow-up of 29.5 (28.8–30.2), 4 patients (5.3%) were lost to follow-up.

For the endpoint aseptic loosening (defined as the removal of stem or the cup for 2 cases), the overall survival rate is 97.3%. For the endpoint revision for any reason (22 patients), the survival rate is 70.6%. Eleven patients needed an exchange of head and liner, caused by wear. The average time from implantation until change of head and liner was 21.44 years (SD 5.92). Other reasons for revision surgery were septic loosening (3 cases), aseptic loosening of stem and cup (1 case), aseptic loosening of stem (1 case), periprosthetic calcification (2 cases), implant fracture (1 case), periprosthetic fracture (1 case), intraoperative fissure of stem (1 case), and total wear of liner including cup (1 case).

Conclusion

The combination of a straight stem (Alloclassic) and a screw cup (CSF) shows excellent results in young patients under the age of 60 at ultra-long-term follow-up at 30 years. Revisions due to wear of the polyethylene liner are more likely than in the older patients.

Radiological Evaluation of the Relationship Between Cortical Hypertrophy and Stress Shielding After Total Hip Arthroplasty Using a Cementless Stem

Background

Unloading of the proximal medial femoral cortex is usually associated with an increased bone strain at the distal part of the prosthesis, which may cause distal femoral cortical hypertrophy (CH). The objective of this study was to determine the factors that may be considered a predisposition to distal femoral CH and its effect on the stress shielding (SS) or durability of the fixation of the stem.

Methods

A total of 240 total hip arthroplasties were performed between January 2006 and December 2016, with all hips implanted with a Bicontact stem. The minimum follow-up period was more than 2 years, and the mean follow-up period was 7.2 years. The radiographic outcome was assessed on an anteroposterior hip radiograph. CH and SS were assessed on postoperative radiographs in the Gruen zone. We defined CH that appeared in zone 3 or 5 as ‘the focal type’ and defined CH that appeared in zones 2, 3, 4, 5, and 6 as ‘the diffuse type.’ SS followed the procedures from the Engh classification.

Results

CH was found in 72 hips (30% of the 240 hips), the focal type was found in 23 hips (9.6% of the 240 hips), and the diffuse type was found in 49 hips (20.4% of the 240 hips). SS was found in 41 hips (17.1% of 240 hips), including 32 hips with SS, which was found after the development of CH. One hip was from the focal-type CH and 31 hips were from the diffuse-type CH. SS, which is typically found in Engh classification types 1 and 2 developed in 13 hips, and SS, which is widely seen in Engh classification types 3 and 4 developed in 19 hips. All 19 hips with progressed SS were found after the diffuse-type CH had developed. In addition, among the 19 hips with progressed SS, Dorr type A was found in 0 hips, Dorr type B in 8 hips, and Dorr type C in 11 hips.

Conclusions

According to the results of our radiological evaluation, development of the diffuse-type CH after total hip arthroplasty using Bicontact stems is one of the critical causes of the later development of SS and could be predicted to progress to SS. To prevent the development of the diffuse-type CH, the indication to choose a Bicontact stem for a Dorr type C with osteoporotic bone should be considered.

Is the strain pattern of conventional stems negatively affected by a previously short stem THA? An experimental study in cadavaric bone

BACKGROUND

A short stem hip arthroplasty can be revised in many cases using a conventional stem. Furthermore, in some cases the implantation of a short stem is intended, but intraoperatively reasons may lead to the decision to implant a conventional stem after previous preparation of a short stem.

OBJECTIVE

In both cases it is questionable if the anchorage of a conventional stem is negatively affected by the previous preparation of a short stem. In clinical practice mid- or long-term follow up for these special cases hardly exist.

METHODS

The strain patterns for the conventional Bicontact stem in primary implantation and after preparation of the proximal femur for a METHA short stem were tested biomechanically in three pairs of cadaveric femora.

RESULTS

The strain patterns for the conventional Bicontact after preparation of the METHA short stem were similar to conditions after testing the conventional stem in primary conditions.

CONCLUSIONS

These data lead to the consequence that in clinical practise the implantation of a conventional stem after preparation of a short stem and even after revision of a short stem is possible without increased risk of loosening or long-term stress-shielding.

Intrasurgical Protein Layer on Titanium Arthroplasty Explants: From the Big Twelve to the Implant Proteome

PURPOSE

Aseptic loosening in total joint replacement due to insufficient osteointegration is an unsolved problem in orthopaedics. The purpose of the study is to obtain a picture of the initial protein adsorption layer on femoral endoprosthetic surfaces as the key to the initiation of osseointegration.

EXPERIMENTAL DESIGN

The paper describes the first study of femoral stem explants from patients for proteome analysis of the primary protein layer. After 2 min in situ, the stems are explanted and frozen in liquid nitrogen. Proteins are eluted under reducing conditions and analyzed by LC-MS/MS.

RESULTS

After exclusion of proteins identified by a single peptide, the implant proteome is found to consist of 2802 unique proteins. Of these, 77% are of intracellular origin, 9% are derived from the plasma proteome, 8% from the bone proteome, and four proteins with highest specificity score could be assigned to the bone marrow proteome (transcriptome). The most abundant protein in the adsorbed total protein layer is hemoglobin (8-11%) followed by serum albumin (3.6-6%).

CONCLUSIONS

A detailed knowledge of the initial protein film deposited onto the implants, as demonstrated here for the first time, may help to understand and predict the response of the osseous microenvironment to implant surfaces.

Does Proximally Coated Single-Wedge Cementless Stem Work Well in Dorr Type C Femurs? Minimum 10-year Followup

BACKGROUND

Total hip arthroplasty (THA) with a proximally coated single-wedge (PSW) cementless stem had been generally considered not to be suitable for Dorr Type C femurs. This study compares the long term outcomes of PSW stem according to the type of proximal femoral geometry.

MATERIALS AND METHODS

307 primary THAs in 247 patients were performed with PSW cementless stem and followed up for over 10 years in this retrospective study. According to Dorr's criteria, 89 femurs were classified as Type A, 156 as Type B, and 62 as Type C. They were followed up for an average of 13.2 years (range 10.0-17.3 years). All the hips were evaluated clinically and radiologically.

RESULTS

There was no significant difference in stem survivorship and clinical outcomes including the incidence of thigh pain and the mean postoperative Harris hip score (HHS) in all three groups. No significant differences were observed in osteolysis, pedestal formation, or cortical hypertrophy among the groups. Radiolucent lines <2 mm in thickness in Gruen zone 4 and 7 (P = 0.003 and P = 0.044, respectively), spot-weld (P < 0.001), and stress shielding (P = 0.010) of proximal femur were more pronounced in Dorr C type femora than in Type A or B. Fifty-six intraoperative fractures were identified among 307 hips with PSW stems. The incidence of intraoperative or postoperative femoral fractures was not significantly different among the groups.

CONCLUSIONS

From over a 10-year followup, the PSW stem provided a recommendable option with satisfactory outcomes and excellent stem survivorship regardless of the Dorr type.

Comparison of Specific Femoral Short Stems and Conventional-Length Stems in Primary Cementless Total Hip Arthroplasty

There are several reported disadvantages with conventional-length femoral stems in cementless total hip arthroplasty (THA). Therefore, various efforts have been made to develop a specific femoral short stem to improve physiologic bone remodeling at the femoral aspect of a cementless THA. However, there are potential disadvantages with specific femoral short stems, such as malalignment, inadvertent subsidence, and potential proximal femoral fracture. Therefore, the authors quantitatively compared radiographic and clinical outcomes as well as component-specific complications between 2 groups of patients following primary cementless THA. A matched comparison was made between specific femoral short stems (n=50) and conventional-length femoral stems (n=50) in cementless THA procedures performed between January 2008 and January 2012. Patients were matched for age, sex, body mass index, height, surgical approach, and surgeon. No significant differences were found between the 2 groups in mean postoperative radiographic outcomes, functional outcomes, or complications. Both groups showed satisfactory performance at 5-year follow-up. Specific femoral short stems resulted in a higher incidence of malalignment and subsidence and a lower incidence of thigh pain and proximal bone resorption compared with conventional-length femoral stems. Although longer follow-up is required, specific femoral short stems may have clinical and radiographic advantages with equivalent perioperative complications relative to conventional-length femoral stems. However, this technique requires proper patient selection in combination with careful preoperative planning and meticulous surgical technique.

Three-Dimensional Analysis of the Contact Pattern between the Cortical Bone and Femoral Prosthesis after Cementless Total Hip Arthroplasty

The cementless stem Excia (B. Braun, Melsungen, Germany) implant has a rectangular cross-sectional shape with back-and-forth flanges and a plasma-sprayed, dicalcium phosphate dihydrate coating from the middle to proximal portion to increase initial fixation and early bone formation. Here, the conformity of the Excia stem to the femoral canal morphology was three-dimensionally assessed using computed tomography. Forty-three patients (45 hips) were examined after primary total hip arthroplasty with a mean follow-up of 27 ± 3 months (range: 24–36 months). Spot welds occurred at zone 2 in 16 hips and at zone 6 in 24 hips, with 83% (20/24 hips) of those occurring within 3 months after surgery. First- (n = 12 hips), second- (n = 32), and third- (n = 1) degree stress shielding were observed. The stem was typically in contact with the cortical bone in the anterolateral mid-portion (100%) and posteromedial distal portions (85%). Stress shielding did not progress, even in cases where the stems were in contact with the distal portions. The anterior flange was in contact with the bone in all cases. The stability of the mid-lateral portion with the dicalcium phosphate dihydrate coating and the anterior flange may have inhibited the progression of stress shielding beyond the second degree.

A Case Series of Total Hip Arthroplasty Using Cementless Hip Stem Customized for Patients of a Specific Race: 10- to 15-Year Results

We report a minimum of 10-year results of patients undergoing total hip arthroplasty (THA) using the cementless BiCONTACT N stem, which was developed to fit the femur in a specific race in which the predominant etiology of hip diseases was developmental dysplasia. A total of 108 hips were evaluated with a mean follow-up of 11.9 ± 1.4 years. The etiology for THA was secondary osteoarthritis due to developmental dysplasia in 90.3% of patients. No evidence of aseptic loosening of the BiCONTACT N stem was observed. The survivorship with the end point as revision surgery for any reason was 94.4% (95% confidence interval 88.7%-97.3%) at 15.0 years postoperatively. BiCONTACT N stem may be an effective alternative for patients with developmental dysplasia of the hip.

Long-term results using the straight tapered femoral cementless hip stem in total hip arthroplasty: a minimum of twenty-year follow-up

We report the first long-term results of a prospective cohort study after total hip arthroplasty using the cementless Bicontact hip stem. Between 1987 and 1990, 250 total hip arthroplasties in 236 patients were performed using the cementless Bicontact hip stem. The average follow-up was 22.8 years (20.4-24.8) and average age at index surgery was 58.1 years. Eighty-one patients died and 9 were lost to follow-up. We noted 11 stem revisions revealing an overall Kaplan Meier survival rate of 95.0% (CI 95%: 91.1-97.2%). The average Harris Hip Score revealed 81 points (range 24-93). The Bicontact hip stem demonstrated high survival rates despite high ages and osteopenic changes, which are equivalent to other long-term reports of cementless stem fixation.

Changes in strain patterns after implantation of a short stem with metaphyseal anchorage compared to a standard stem: an experimental study in synthetic bone

Short stem hip arthroplasties with predominantly metaphyseal fixation, such as the METHA® stem (Aesculap, Tuttlingen, Germany), are recommended because they are presumed to allow a more physiologic load transfer and thus a reduction of stress-shielding. However, the hypothesized metaphyseal anchorage associated with the aforementioned benefits still needs to be verified. Therefore, the METHA short stem and the Bicontact® standard stem (Aesculap, Tuttlingen, Germany) were tested biomechanically in synthetic femora while strain gauges monitored their corresponding strain patterns. For the METHA stem, the strains in all tested locations including the region of the calcar (87% of the non-implanted femur) were similar to conditions of synthetic bone without implanted stem. The Bicontact stem showed approximately the level of strain of the non-implanted femur on the lateral and medial aspect in the proximal diaphysis of the femur. On the anterior and posterior aspect of the proximal metaphysis the strains reached averages of 78% and 87% of the non-implanted femur, respectively. This study revealed primary metaphyseal anchorage of the METHA short stem, as opposed to a metaphyseal-diaphyseal anchorage of the Bicontact stem.

A cementless hip system with a new surface for osseous integration

PURPOSE

The failure of total hip systems caused by wear-particle-induced loosening has focused interest on factors potentially affecting wear rate. Remnants of the blasting material were reported on grit-blasted surfaces for cementless fixation. These particles are believed to cause third-body wear and implant loosening. The purpose of this study was to evaluate the early clinical and radiological outcomes of a cementless hip system with a new, contamination-free, roughened surface with regard to prosthesis-related failures.

METHODS

Between May 2004 and March 2009, 202 consecutive primary total hip arthroplasties (THAs) (192 patients with a mean age of 62.6 years) were performed using a cementless stem (Hipstar®) and a hemispherical acetabular cup (Trident®).

RESULTS

At a minimum follow-up of two years, five revisions (2.5%) due to aseptic loosening of the stem and three (1.5%) of the cup were necessary. The cumulative rate of prostheses survival, counting revision of both components and with aseptic failure as end point, was 92.9% at 8.8 years. Radiolucent lines up to three millimetres were evaluated in the proximal part of the femur in 61% of cases.

CONCLUSIONS

Although the incidence of radiolucent lines was decreased, the revision rate was considerably increased compared to other uncemented hip implants with grit-blasted surfaces in the short- to mid-term follow-up of our study. Subsequent studies are needed to confirm whether these changes in implant material and surface affect the radiological and clinical outcome in the long term.

Numeric simulation of bone remodelling patterns after implantation of a cementless straight stem

PURPOSE

For further development of better bone-preserving implants in total hip arthroplasty (THA), we need to look back and analyse established and clinically approved implants to find out what made them successful. Finite element analysis can help do this by simulating periprosthetic bone remodelling under different conditions. Our aim was thus to establish a numerical model of the cementless straight stem for which good long-term results have been obtained.

METHODS

We performed a numeric simulation of a cementless straight stem, which has been successfully used in its unaltered form since 1986/1987. We have 20 years of experience with this THA system and implanted it 555 times in 2012. We performed qualitative and quantitative validation using bone density data derived from a prospective dual-energy X-ray absorptiometry (DEXA) investigation.

RESULTS

Bone mass loss converged to 9.25% for the entire femur. No change in bone density was calculated distal to the tip of the prosthesis. Bone mass decreased by 46.2% around the proximal half of the implant and by 7.6% in the diaphysis. The numeric model was in excellent agreement with DEXA data except for the calcar region, where deviation was 67.7%.

CONCLUSIONS

The higher deviation in the calcar region is possibly a sign of the complex interactions between the titanium coating on the stem and the surrounding bone. We developed a validated numeric model to simulate bone remodelling for different stem-design modifications. We recommend that new THA implants undergo critical numeric simulation before clinical application.

The cementless Bicontact stem in a prospective dual-energy X-ray absorptiometry study

PURPOSE

The cementless Bicontact total hip arthroplasty (THA) system (AESCULAP AG, Tuttlingen, Germany) was introduced in 1986/1987 and has been in successful clinical use in an unaltered form up to today. Although good long-term results with the Bicontact stem have been published, it is questionable whether the implant provides the criteria for a state-of-the-art stem regarding proximal bone stock preservation. The purpose of the study was to monitor the periprosthetic bone mineral density (BMD) in a prospective two-year follow-up dual-energy X-ray absorptiometry (DEXA) study.

METHODS

After power analysis, a consecutive series of 25 patients with unilateral Bicontact stem implantation was examined clinically and underwent DEXA examinations. Scans of seven regions of interest were taken preoperatively and at one week, six months, and one and two years.

RESULTS

One patient required stem revision due to a deep infection. The Harris Hip Score increased significantly by 44 points. The most significant bone loss was observed in the calcar region (R7) in the first six months (-19.2 %). It recovered in the following 18 months to -8.5 %. The BMD in the greater trochanter dropped significantly after six months and remained stable at this level. BMD exceeded baseline values in distal regions and even more in the lesser trochanter region after two years.

CONCLUSIONS

We conclude that the Bicontact stem provides adequate proximal bone stock preservation. We observed some signs of stress shielding at the tip of the stem, which is inevitable to some degree in THA with cementless straight stems. However, in this prospective DEXA investigation, we showed that proximal off-loading does not occur after THA with the Bicontact system. Thus, we believe that this stem is still a state-of-the-art implant.

Excellent results with cementless total hip arthroplasty and alumina-on-alumina pairing: minimum ten-year follow-up

Ceramic-on-ceramic coupling is thought to be a durable alternative to metal- or alumina-on-polyethylene pairing. No evidence exists suggesting superior clinical and radiological results for hydroxyapatite-coated stems versus uncoated stems. The aim of this study is to report the performance of an alumina-on-alumina bearing cementless total hip arthroplasty and to compare stems with a tapered design with and without hydroxyapatite coating. We prospectively analysed the results of cementless tapered femoral stems (40 hydroxyapatite-coated versus 22 uncoated stems), a metal-backed fibre mesh hydroxyapatite-coated socket and alumina-on-alumina pairing. Of 75 hips studied, 62 were available for follow-up (mean of 10.5 years after surgery). The average Harris hip score was 90. Only one hydroxyapatite-coated stem was revised for aseptic loosening. One instance of non-progressive osteolysis was detected around a screw of a cup. All other components showed radiographic signs of stable ingrowth. Hydroxyapatite coating of the stem had no significant impact on the clinical or radiological results. Total hip arthroplasty with the presented implant and pairing provides a durable standard for all patients requiring hip joint replacement against which all newer generations of cementless implants should be judged.