Acetabular screw rings and surface treatment

Effects of a roughened femoral head and the locus of grafting on the wear resistance of the phospholipid polymer-grafted acetabular liner

Although laboratory tests and mid-term clinical outcomes show the clinical safety and remarkable wear resistance of the highly cross-linked polyethylene (HXLPE) acetabular liner with a nanometer-scaled graft layer of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), the wear resistance of the layer under severe abrasive conditions is concerning. We evaluated the effects of a roughened femoral head and the grafting locus on the wear resistance of the PMPC-grafted HXLPE liner and the effect of PMPC grafting on wear resistance of the HXLPE substrate by removing the PMPC-grafted layer using a severely roughened femoral head. Against a moderately roughened femoral head, the PMPC-grafted HXLPE liner showed negative wear, although an untreated HXLPE liner increased the wear by 154.1% compared with wear against a polished femoral head, confirming that PMPC grafts were unaffected. Against a severely roughened femoral head, the PMPC-grafted layer of the head contact area might be removed under severe conditions. However, the wear rate was reduced by 52.5% compared to that of untreated HXLPE liners. Moreover, the head non-contact area-modified PMPC-grafted HXLPE liner against a polished femoral head reduced the wear by 76.8% compared with untreated HXLPE liner; thus, this area may be also important in the development of fluid-film lubrication. STATEMENT OF SIGNIFICANCE: Here we describe effects of a roughened femoral head and the locus of grafting on the wear-resistance of the phospholipid polymer grafted highly cross-linked polyethylene (PMPC-HXLPE) liner. Against a moderately roughened femoral head, the PMPC-HXLPE liner showed negative wear, confirming that PMPC grafts were unaffected. After removing the PMPC layer of the head contact area using a severely roughened femoral head, the wear rate not only exceeded that of untreated HXLPE liners, but was reduced by 52.5%, confirming that PMPC grafting does not affect the wear-resistance of the HXLPE substrate. In addition, the head non-contact area-modified PMPC-HXLPE liner reduced the wear by 76.8%. Thus, this area may also may be important in the development of fluid-film lubrication.

Treatment of the Fixation Surface Improves Glenoid Prosthesis Longevity in vitro

Many commercial cemented glenoid components claim superior fixation designs and increased survivability. However, both research and clinical studies have shown conflicting results and it is unclear whether these design variations do improve loosening rates. Part of the difficulty in investigating fixation failure is the inability to directly observe the fixation interface, a problem addressed in this study by using a novel experimental set-up. Cyclic loading-displacement tests were carried out on 60 custom-made glenoid prostheses implanted into a bone substitute. Design parameters investigated included treatment of the fixation surface of the component resulting in different levels of back-surface roughness, flat-back versus curved-back, keel versus peg and more versus less conforming implants. Visually-observed failure and ASTM-recommended rim-displacements were recorded throughout testing to investigate fixation failure and if rim displacement is an appropriate measure of loosening. Roughening the implant back (R_a>3µm) improved resistance to failure (P<0.005) by an order of magnitude with the rough and smooth groups failing at 8712±5584 cycles (mean±SD) and 1080±1197 cycles, respectively. All other design parameters had no statistically significant effect on the number of cycles to failure. All implants failed inferiorly and 95% (57/60) at the implant/cement interface. Rim-displacement correlated with visually observed failure. The most important effect was that of roughening the implant, which strengthened the polyethylene-cement interface. Rim-displacement can be used as an indicator of fixation failure, but the sensitivity was insufficient to capture subtle effects.

LEVEL OF EVIDENCE

Basic Science Study, Biomechanical Analysis.

Surveillance of Arc2f polyethylene after 15 years of implantation

BACKGROUND

To investigate the behavior of Arc2f polyethylene (PE) component after a minimum of 15 years post implantation and its possible reasons for failure.

METHODS

Between January 1988 and March 1995, 557 cementless total hip arthroplasties were performed in 578 patients. A total of 435 patients (450 hips) were followed up for 18.6 years (range 15-22).

RESULTS

At 10 years follow-up no cup needed revision surgery. After 15 years of implantation, we observed massive PE wear in 140 cups (31%) with large osteolytic lesions. A revision procedure was performed in all cases. Exchange only of the PE liner was sufficient in 78 cases, whilst in 59 the cup was also revised. PE insert thickness and the type of prosthetic head were found to be related to PE wear.

CONCLUSIONS

We postulate that the massive failure seen is attributed to the manufacturing of the PE insert. We advocate following all patients that have an implant lasting a decade after implantation for routine monitoring to identify those at risk for accelerated PE wear.

Role of primary stability for successful osseointegration of dental implants: Factors of influence and evaluation

A secure implant primary (mechanical) stability is positively associated with a successful implant integration and long-term successful clinical outcome. Therefore, it is essential to assess the initial stability at different time-points to ensure a successful osseointegration. The present study critically reviews the factors that may play a role in achieving a successful initial stability in dental implants. Databases were searched from 1983 up to and including October 2013 using different combinations of various keywords. Bone quality and quantity, implant geometry, and surgical technique adopted may significantly influence primary stability and overall success rate of dental implants.

High medium-term survivorship and durability of Zweymüller-Plus total hip arthroplasty

BACKGROUND AND PURPOSE

The Zweymüller-Plus system (SL-Plus stem, Bicon-Plus threaded cup) for primary total hip arthroplasty (THA) was introduced in 1993, as a successor of the Alloclassic THA with a few modifications in the conical stem shape and a new biconical threaded cup with a spherical shape. The medium-term performance of this system is not well established. To better understand the potential impact these design changes have had on (1) survivorship, (2) implant stability and (3) periprosthetic osteolysis, we studied patients who underwent THA using the SL-Plus stem and Bicon-Plus.

METHODS

We retrospectively reviewed the cases of 148 patients (153 hips) who underwent Zweymüller-Plus primary THA after an average of 11 years.

RESULTS

With revision for aseptic failure of biological fixation as the endpoint, survivorship was 98% for the stem and 100% for the cup. Focal osteolysis was observed in 6.6% of cups and 29% of stems. Four hips (2.6%) were revised because of aseptic failure of the biologic fixation and three hips (1.95%) for deep infection. As much as 146 stems and 149 cups were evaluated to be stable.

CONCLUSION

Zweymüller-Plus THA resulted in high survivorship and durability at 11 years, although the rate of osteolysis around the stem indicated polyethylene wear.

Clinical outcome study and radiological findings of Zweymuller metal on metal total hip arthroplasty. a follow-up of 6 to 15 years

We report the clinical and radiological outcome of 99 Zweymuller metal on metal total hip arthroplasties in 84 patients followed up prospectively for a mean period of 9.5 (range, 6-15) years. There were 29 (34.5%) male and 55 (65.5%) female patients with a mean age of 62.85 years (range, 50-70 years) at the time of surgery. All patients had osteoarthritis. One acetabular component and one stem were revised due to aseptic loosening. One femoral stem was revised due to a periprosthetic fracture. HHS score improved from a preoperative mean of 62.56 points (SD 8.87) to a final postoperative follow-up mean of 93.48 (SD 7.7). Cumulative success rate for both implants at 13 years, with aseptic loosening as the end point, was 97.05%, while for both implants at 13 years, with revision for any reason as the end point, it was 91.17%. Satisfactory results were observed with the use of this prosthesis.

Long-term results of the threaded Weill cup in primary total hip arthroplasty: a 15-20-year follow-up study

Uncemented, threaded acetabular components with smooth surface treatment were widely used in continental Europe in the 1970s and 1980s for primary total hip arthroplasty (THA). Previously published studies showed high failure rates in the mid-term. In a consecutive series of 116 patients, 127 threaded cups with smooth surface treatment (Weill cup; Zimmer, Winterthur, Switzerland) were implanted in combination with one type of uncemented stem. Patients were followed up clinically and radiographically. Mean time of follow-up was 17 years (range 15-20). At the time of follow-up, the acetabular component had been revised or was awaiting revision in 30 hips (24%). Two hips were revised for infection and 23 for aseptic loosening. Four polyethylene liners were exchanged because of excessive wear. One hip was awaiting revision. The survival rate for all acetabular revisions including one hip awaiting revision was 75% (95%CI: 65-85%) at 17 years. These results support the view that smooth, threaded acetabular components do not provide satisfactory long-term fixation and should be abandoned. It is important to closely monitor patients with these components as the failure rate remains high in the long-term.

Long-term results of the threaded Mecron cup in primary total hip arthroplasty : A 15-20-year follow-up study

In the 1970s, high failure rates of cemented acetabular components, especially in young patients, in the middle- and long-term prompted a search for alternatives. The Mecring was one of the most popular first generation uncemented, threaded cups widely used in the 1980s for arthroplasty of the hip. First generation threaded cups commonly had smooth surface treatment and showed unacceptably high failure rates in the mid-term. In a consecutive series of 209 patients, 221 threaded uncemented acetabular cups with smooth surface treatment (Mecring) had been implanted in combination with one type of uncemented stem. Patients were followed up clinically and radiographically. The mean time of follow-up was 17 (range 15-20) years. In 91 (41%) hips the acetabular component had been revised or was awaiting revision: two hips for infection and 84 (38%) for aseptic loosening. Five hips were awaiting revision. The survival rate for all revisions including hips awaiting revision was 49% (95% CI: 41-57%) at 17 years. These results support the view that smooth, threaded acetabular components do not provide satisfactory long-term fixation and should be abandoned. Patients with these components must be closely monitored as the failure rate remains high in the long-term.

THA using metal-on-metal articulation in active patients younger than 50 years

The main concern of patients with longer life expectancies and of patients who are younger and more active is the longevity of their total hip arthroplasty. We retrospectively reviewed 83 cementless total hip arthroplasties in 73 patients implanted with metal-on-metal articulation. All patients were younger than 50 years old (average age, 41 years) at the time of the index procedure, and 80% of the patients had an activity level graded 4 or 5 when measured with the system of Devane et al. A 28-mm Metasul articulation was used with three different cementless titanium acetabular components. At the most recent followup (average, 7.3 years), the average Merle d'Aubigné-Postel score improved from a preoperative 11.1 points to 17.4 points. We observed no radiographic evidence of component loosening. Ten acetabular components had lucency limited to one zone. The 10-year survivorship with the end point of revision (ie, exchange of at least one prosthetic or bearing component) was 100% (95% confidence interval, 90%-100%). Metasul bearings with cementless acetabular components remain promising in this high-risk younger patient population. However, additional followup strategies are recommended to determine any possible long-term deleterious effects associated with the dissemination of metallic ions.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Long-term results of the cementless ALLOCLASSIC hip arthroplasty system using a 28-mm ceramic head: with a retrospective comparison to a 32-mm head

One hundred twenty-four total hip arthroplasties in 119 patients, all performed with the cementless ALLOCLASSIC hip arthroplasty system (SL stem and CSF cup; Centerpulse, Winterthur, Switzerland), were analyzed retrospectively. In all hips, a 28-mm head and an ultrahigh-molecular-weight polyethylene inlay were used. Of the 124 hips, 81 could be investigated clinically and radiologically after an average of 150.6 months (range, 133-169 months). Twenty-six patients (26 hips) died in the interim. One of these patients had septic cup loosening. Seventeen hips (16 patients) were not available for follow-up because of health reasons (12 hips in 11 patients), lack of cooperation (3 hips in 3 patients), or loss to follow-up (2 hips in 2 patients). Of the 124 total hip arthroplasties, 4 cups were removed (2 aseptic and 2 septic loosening). No stem had to be removed. If aseptic loosening is defined as the end point, the survival rate is 98.4% (95% confidence interval, 93.8%-99.6%) for the cup and 100% for the stem after 157 months. If revision for any reason is defined as the end point, the survival rate is 95.6% (95% confidence interval, 90.1%-98.3%). Before operation, the average Harris Hip Score was 36.4 points (21-46). At time of follow-up, the average Harris Hip Score was 89.7 points (54-100). Radiolucent lines and osteolyses were found only seldom (mostly in the proximal stem zones).

The Zweymüller threaded cup: a choice in revision? Migration analysis and follow-up after 6 years

Excellent long-term results are reported for threaded cups with an osteointegrable surface in primary interventions. So far, little data are available on the use of such implants in revision cases. We investigated 30 loosened Aesculap PM threaded cups (Tuttlingen, Germany) with a smooth surface, revised with a conical, corundum-blasted Zweymüller threaded cup (Zweymüller Alloclassic CSF cup, Zimmer, Warsaw, Ind). Aseptic radiological loosening was seen in 8% of cases, and a survival rate of 95% was achieved after 6.1 years. Average migration was 1.4 mm cranially and 0.7 mm medially. The Harris hip score improved from 42 points preoperatively to 75 points at follow-up. Good medium-term results are possible after revision using a threaded cup with an osteointegrable surface, but not if segmental acetabular margin defects are present.

Reconstruction of severe acetabular bone-deficiency: the Burch-Schneider antiprotrusio cage in primary and revision total hip arthroplasty

Ninety Burch-Schneider antiprotrusio cages in 87 patients implanted in primary and revision total hip arthroplasty were analyzed. Sixty-seven hips (64 patients) could be examined clinically and radiologically after an average of 50.3 months (minimum 23.6, maximum 131.0 months). Twenty patients (20 hips) died in interim and 3 patients (3 hips) were not available for follow-up. Of the 90 Burch-Schneider antiprotrusio cages, 4 had to be removed and 8 further cages were considered definitely loose. The survival rate is 93.4% (95% confidence interval, 74.3%-96.7%) after 131 months if the endpoint "cage explantation" is used. The average Harris Hip Score was improved from 28.2 preoperatively to 73.5 points at the time of follow-up. Radiolucent lines were often found in the Charnley/DeLee's zones II and III. In contrast, osteolyses were seldom seen.

Cementless Zweymüller hip replacement: a short-term follow-up in Al Razi Hospital, Kuwait

OBJECTIVE

To present initial experience of the first 71 cases of cementless total hip replacement in Al Razi Hospital.

SUBJECT AND METHODS

Between 1996 and 2004, total hip replacement was performed in 71 patients (40 male, 31 female, average age 40.7 years, range 17-74) using Zweymüller cementless prosthesis. The patients were followed clinically and radiologically over an average period of 36 months (range 6-84). The results were assessed according to Merle d'Aubigne clinical score. Radiological assessment included position of the implant, behavior of the prosthesis/bone interface and signs of osteointegration.

RESULTS

Average clinical score during the 3 years' follow-up period was 17.8 points. Most of the implants were in optimal positions. No significant radiological modifications of the implant-bone interface were observed.

CONCLUSION

Zweymüller total hip prosthesis gives excellent clinical and radiological results in short-term follow-up.

Ten to twelve-year results with the Zweymüller cementless total hip prosthesis

Between January 1987 and December 1990, 221 Zweymüller cementless total hip arthroplasties were performed in 211 patients with idiopathic osteoarthritis. A total of 136 patients (142 prostheses) were evaluated at a mean follow-up of 134 months (SD 9.5). The study group consisted of 78 Hochgezogen and 64 Stepless stem prostheses, all with a threaded titanium cup and ceramic head. No clinical and radiological differences were found between the 2 stem prostheses. Seven cups had been revised because of aseptic loosening; 17 cups showed radiolucent lines, osteolysis, or migration. Mean linear polyethylene wear of 105 (74%) cups was 0.46 mm (SD 0.27), with an annual wear of 0.04 mm (SD 0.02). Wear did not correlate with pain, cup migration, radiolucent lines, or osteolysis. Cumulative survival was 96%. Zweymüller cementless total hip arthroplasty showed good midterm results.

Long-term results with the cementless Alloclassic brand hip arthroplasty system

The first 100 Alloclassic (Centerpulse, Winterthur, Switzerland) hip prostheses implanted at Allgemeines Krankenhaus Linz were examined in this study. All cases involved primary total hip arthroplasty. Of these 100, 75 could be followed up clinically and radiologically. All living patients were contacted by telephone. The follow-up period was at least 10 years. If the endpoint is defined as removal of the prosthesis due to aseptic loosening, the survival rate was 96.9% for the cup and 100% for the stem after 132 months. The average Harris Hip Score was 85.4 points. Radiolucent lines and osteolyses were found primarily in the proximal zones of the stem.

A 10-year minimum follow-up of hydroxyapatite-coated threaded cups: clinical, radiographic and survivorship analyses with comparison to the literature

We evaluated the clinical, radiographic, and survivorship outcomes in a series of 418 threaded hydroxyapatite-coated acetabular cups (Arc2f; Osteonics, Allendale, NJ) implanted in a consecutive series of 384 patients undergoing primary total hip arthroplasty. In all cases, the cup was screwed into the prepared acetabulum. Bone screws were used to provide secondary fixation. At a minimum 10-year follow-up, 304 cups were available for analysis. The cumulative survivorship (mechanical failure as endpoint) at that time was 99.43% +/- 0.0104. Two hundred seventy-six hips were available for full clinical and radiographic review at or after the tenth anniversary. No unstable implants were noted; all implant fixation interfaces were classified as "stable bone ingrown," and the cup migration rate was zero. Based on the survivorship achieved with this implant, our results compare favorably with survivorship reported for the best cemented and cementless acetabular implant designs.

Total hip arthroplasty with use of the cementless Zweymüller Alloclassic system. A ten to thirteen-year follow-up study

BACKGROUND

The Zweymüller Alloclassic total hip arthroplasty system is widely used, although few intermediate-term studies have been published. The purpose of the present study was to evaluate the clinical and radiographic results of this system after ten years.

METHODS

One hundred and twenty-four consecutive primary total hip arthroplasties were performed with the Zweymüller Alloclassic cementless system at our institution between February 1988 and March 1991, and 104 hips (ninety-four patients) were retrospectively reviewed after a minimum duration of follow-up of ten years. The mean age of the patients at the time of the arthroplasty was 62.3 years (range, twenty-five to seventy-seven years). The mean duration of follow-up was 11.3 years. Standard radiographs were made for all patients immediately after the operation, at six and twelve months, and annually thereafter for at least ten years. Cox multivariate regression analysis was performed to assess the influence of various factors on survival of the implant.

RESULTS

The cumulative probability of not having a revision of any prosthetic component for any reason was 94.1% (95% confidence interval, 91.9% to 96.3%) at twelve years in the best-case scenario and 85.3% (95% confidence interval, 82.1% to 88.5%) at twelve years in the worst-case scenario for the entire series of 124 hips. Among the 104 hips in the follow-up study, three acetabular components and no stems were revised. Two hips had level-4 pain according to the system of Merle D'Aubigné and Postel. Seven acetabular components (7%) were loose at twelve years, and all stems had radiographic evidence of stable fixation. Acetabular cup loosening was related to a vertical cup angle (p = 0.0008, Student t test), acetabular wear of > or =1 mm (p = 0.001, Fisher exact test), and a 32-mm femoral head (p = 0.001, Fisher exact test). Although femoral osteolysis was seen in eighteen hips (17%) at twelve years, all osteolytic cavities were proximal and focal.

CONCLUSIONS

The Zweymüller Alloclassic prosthesis, particularly its femoral stem, demonstrated good results and durable fixation at a minimum of ten years of follow-up.

Survivorship of rough-surfaced threaded acetabular cups. 382 consecutive primary Zweymüller cups followed for 0.2-12 years

We studied prospectively 382 cementless (Zweymüller stem) and hybrid (cemented stem) primary total hip replacements and used a cementless grit-blasted titanium alloy threaded cup. After a median 5 (0.2-12) year follow-up, 1 cup was exchanged, 2 cups were removed for deep sepsis, and 3 cups showed definite loosening; of these, 2 subsequently required revision. Actuarial calculation methods indicated a 10-year survivorship of 99% with cup retrieval for any cause (clinical failure), definite cup-loosening (radiographic failure), and revision for aseptic cup-loosening as endpoints. These intermediate results exceed those from smooth-surfaced screw rings and compare favorably with those from cemented cups and cementless, press-fit, metal-backed cups.