A Five-Year Metal-on-Metal Retrospective Clinical Study

Study Overview
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Brief Summary
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This retrospective study will review the Anderson Orthopaedic Institute's initial experience among a consecutive series of 126 patients who had primary total hip arthroplasty using a metal-on-metal articulation consisting of a DePuy Pinnacle cup with an Ultamet liner coupled with a 36-mm cobalt-chrome alloy femoral head. The relationship between metal ion levels, cup orientation, osteolysis, radiographic implant stability and clinical outcome measures including component revision, complications, patient satisfaction and Harris Hip Scores will be evaluated.

Detailed Description
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Metal-on-metal bearings for total hip arthroplasty are an alternative to traditional polyethylene bearing surfaces and hip simulators studies have shown that metal-on-metal bearings have lower wear than metal-on-polyethylene bearings. In addition, simulator studies indicate that the amount of wear decreases as head size increases allowing the use of larger head diameters than possible with other bearing surfaces. Since dislocation is currently the most common reason for reoperation in the United States, representing 22.5% of hip revisions, the combination of low wear and larger head sizes to reduce dislocation hold the promise of improving outcome among total hip arthroplasty patients. While there are potential advantages to metal-on-metal bearings, a few concerns have been noted in the literature. Although the total volume of wear is low with these bearings, the articulation generates metal debris that may be related to patient and surgical factors such as implant positioning. Despite a reduced wear volume, there is also the possibility that an increased bioreactivity associated with metal debris might induce an osteolytic response or local tissue hypersensitivity reaction. This study will retrospectively review the outcome of a consecutive series of 126 patients who had 131 primary THAs performed between April 2001 and November 2002 at the Anderson Clinic with a Pinnacle acetabular cup, an Ultamet insert and a 36-mm cobalt-chrome alloy femoral head. These total hip arthroplasties represent the Anderson Orthopaedic Institute's in initial experience with this implant. The relationship between metal ion levels, cup orientation, osteolysis, radiographic implant stability and clinical outcome measures including component revision, complications, patient satisfaction and Harris Hip Scores will be evaluated. The outcome data from our analysis will also be compared with the data from other published series with metal-on-metal bearing surfaces. Serial radiographs obtained as part of routine post-operative care will be used to evaluate osteolysis, implant stability and radiographic complications such as periprosthetic fracture. The area of each osteolytic region will be measured on the AP pelvic x-ray using Martell's Hip Analysis Suite. Computed tomography (CT) scans obtained as part of routine follow-up will be also analyzed to identify regions of acetabular osteolysis. The volume and location of each osteolytic defect identified on CT will be evaluated using three-dimensional image analysis software (Analyze, Biomedical Imaging Resource, Rochester, MN). A three-dimensional (3D) reconstruction of the pelvis, cup and acetabular osteolytic lesions will also be generated from the CT image data. This reconstruction will be oriented to simulate the AP pelvic radiographic view. Cobalt and chromium ion level data will be compiled for patients who had blood drawn to evaluate metal ion levels. The mean and median blood metal-ion levels for these patients will be calculated and the results will be compared to the metal-ion levels reported in the literature.

Official Title
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A Five-Year Metal-on-Metal Retrospective Clinical Study

Conditions
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Osteoarthritis

Intervention / Treatment
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* Device: Metal-on-metal primary total hip arthroplasty (DePuy )


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Primary total hip arthroplasty patients who had surgery between April 2001 and November 2002 who were implanted with a Pinnacle acetabular cup, an Ultamet metal-on-metal insert and a 36mm cobalt-chrome alloy femoral head Exclusion Criteria: Revision total hip arthroplasties Primary total hip arthroplasties using Ultamet liners coupled with 28-mm femoral heads

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Metal-on-Metal Total Hip Arthroplasties<br>Consecutive series of patients who had metal-on-metal primary total hip arthroplasty performed with DePuy Pinnacle cups, Ultamet metal liners and 36-mm cobalt-chromium alloy femoral heads. | Device: Metal-on-metal primary total hip arthroplasty (DePuy )<br>* Replacement of a patient's native hip with an artificial implant featuring a metal-on-metal articulation<br>* Other names: DePuy 36-mm femoral head;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Metal Ion Levels Per Participant | Metal ion levels include cobalt and chromium ion levels determined from tests of blood samples. Metal ion levels are reported per participant since blood samples were taken from individual participants who could have had one or both hips replaced. | At a mean of 4.2 years after primary total hip arthroplasty | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Cup Orientation Per Hip | Cup orientation including abduction and anteversion is determined using follow-up radiographs. Since a participant with both hips replaced could have different cup orientations for each hip, cup abduction and anteversion angles are reported per hip. | On the first post-operative anteroposterior pelvic radiograph after primary total hip arthroplasty | 
| Harris Hip Score Per Hip | Harris Hip Scores are derived from a patient questionnaire and physical examination. Since a participant with both hips replaced could have different Harris Hip Scores for each hip, the Harris Hip Scores are reported per hip. | At a mean of 5.6 years after primary total hip arthroplasty | 
| Osteolysis Per Hip | Osteolysis is defined as localized areas of peri-prosthetic bone loss that did not exist prior to surgery and is evaluated using radiographs and CT scans. Since a participant with both hips replaced could have a osteolysis present or absent for each hip, osteolysis is reported per hip. | At a mean of 5.6 years after primary total hip arthroplasty | 
| Implant Stability Per Hip | Implant stability is classified and stable/bone ingrown, fibrous fixed or loose and evaluated using conventional radiographs. Since a participant with both hips replaced could have a different type of stability for each hip, implant stability is reported per hip. | At a mean of 5.6 years after primary total hip arthroplasty | 
| Component Revision Per Hip | For implants that require a component revision, the reason for the revision is determined based on the pre-operative history and operative findings at the time of revision. Since a participant with both hips replaced could have a revision of each hip, component revision is reported per hip. | At a mean of 6.7 years after primary total hip arthroplasty | 
| Patient Satisfaction Per Hip | Whether or not an individual is satisfied with the outcome of their hip arthroplasty is evaluated using a questionnaire. Since a participant with both hips replaced could have a different level of satisfaction for each hip, patient satisfaction is reported per hip. | At a mean of 5.6 years after primary total hip arthroplasty | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Hip replacement, Metal-on-metal bearings, Osteolysis, Metal ion levels, Outcome