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Biomedical subjects

Harlan C Amstutz

Publications and source records attributed to Harlan C Amstutz.

At least 19 recordsLinked to original sources
PubMed2006

The value of patient activity level in the outcome of total hip arthroplasty.

Commonly used total hip arthroplasty scores take into account pain, function, walking, and range of motion. The purpose of this study was to evaluate the value of patient activity level as part of the outcome of total hip arthroplasty. Using linear regression analysis, the relationship between patient activity level (University of California Los Angeles activity score), the Harris Hip Score, and the Short Form-12 health survey was evaluated in 152 patients (mean age, 58.7 years) with a mean follow-up 5.2 years (range, 2-21 years). The University of California Los Angeles activity scale had an R(2) value of 0.39 and 0.19 to the Short Form-12 physical and mental components, respectively, and 0.32 to the Harris Hip Score. By evaluating patient activity level, one obtains important qualitative information in assessing the clinical outcome after total hip arthroplasty.

Arthroplasty, Replacement, Hip↗
PubMed2006

Metal-on-metal hybrid surface arthroplasty. Surgical Technique.

BACKGROUND: Following the reintroduction of metal-on-metal articulating surfaces for total hip arthroplasty in Europe in 1988, we developed a surface arthroplasty prosthetic system using a metal-on-metal articulation. The present study describes the clinical and radiographic results of the first 400 hips treated with metal-on-metal hybrid surface arthroplasties at an average follow-up of three and a half years. METHODS: Between November 1996 and November 2000, 400 metal-on-metal hybrid surface arthroplasties were performed in 355 patients. All femoral head components were cemented, but only fifty-nine of the short metaphyseal stems were cemented. The patients had an average age of forty-eight years, 73% were men, and 66% had a diagnosis of osteoarthritis. Clinical and radiographic follow-up was performed at three months postoperatively and yearly thereafter. RESULTS: The majority of the patients returned to a high level of activity, including sports, and 54% had activity scores of >7 on the University of California at Los Angeles activity assessment system. Kaplan-Meier survivorship curves demonstrated that the rate of survival of the components at four years was 94.4%. For patients with a surface arthroplasty risk index score of >3, the rate of survival of the components at four years was 89% compared with a rate of 97% for those with a score of <or=3. The patients with a higher risk index were 4.2 times more likely to undergo revision to a total hip replacement at four years. Twelve hips (3%) had a revision to a total hip replacement. Seven of the twelve hips were revised because of loosening of the femoral component, and three were revised because of a femoral neck fracture. Substantial radiolucencies were seen around sixteen uncemented metaphyseal femoral stems. No femoral radiolucencies were observed among the hips in which the metaphyseal stem was cemented. The most important risk factors for femoral component loosening and substantial stem radiolucencies were large femoral head cysts (p = 0.029), patient height (p = 0.032), female gender (p = 0.005), and smaller component size in male patients (p = 0.005). CONCLUSIONS: The preliminary experience with this hybrid metal-on-metal bearing is encouraging. Optimal femoral bone preparation and component fixation are critical to improving durability. The metal-on-metal hybrid surface arthroplasty is easily revised to a standard femoral component if necessary.

Adolescent↗
PubMed2005

Surface arthroplasty in young patients with hip arthritis secondary to childhood disorders.

Legg-Calvé-Perthes disease (LCP) and slipped capital femoral epiphysis (SCFE) may result in alterations of the proximal femoral morphology, leading to the development of hip osteoarthritis as a young adult. Hip surface arthroplasty presents special technical challenges in these patients because of the abnormal anatomy of the head and neck. The authors reviewed the radiographic and clinical results of patients with a history of LCP or SCFE who underwent hip resurfacing between 1996 and 2002. Despite the challenges in performing hip resurfacing in this patient population and the inability to completely normalize hip anatomy, biomechanics, and leg length discrepancy, the results to date have been encouraging.

Adolescent↗
PubMed2004

Metal-on-metal surface arthroplasty with a cemented femoral component: a 7-10 year follow-up study.

Forty-two McMinn metal-on-metal surface arthroplasties were implanted in 23 males and 16 females, average age 47.5 years old. The overall survivorship at 7 years was 79%; with any reoperation surgery as endpoint, 80%; and 93%; with aseptic loosening of the socket and femoral component, respectively. The average Surface Arthroplasty Risk Index of patients who had failed or were at risk of failing on the femoral side was significantly greater than for the rest of the cohort, 3.9 versus 1.9. The overall survivorship of the McMinn component was unacceptably low, with the majority of failures occurring with the cemented acetabular components. The recent reintroduction of surface arthroplasty of the hip using metal-on-metal bearings and cementless acetabular components may benefit young patients with hip arthritis with appropriate patient selection.

Adult↗
PubMed2004

Surface arthroplasty for osteonecrosis of the hip: hemiresurfacing versus metal-on-metal hybrid resurfacing.

Eighty-four hips with Ficat stage III and IV osteonecrosis were treated: 56 with metal-on-metal surface arthroplasty (MMSA) and 28 with hemi-surface arthroplasty (HSA). Average follow-up was 4.9 years. UCLA hip scores were significantly better for MMSA versus HSA for function and activity as well as Harris Hip scores and physical component of the SF-12 scores. In the MMSA group, 2 hips were revised to total hip arthroplasty for femoral loosening, and 5 hips had adverse radiological changes. In the HSA group, 4 hips were revised (1 sepsis and 3 for pain). There was no evidence of any femoral loosening or neck narrowing in the HSA group. Although the functional clinical outcome of MMSA is superior to HSA, long-term follow up of MMSA will determine the reliability of the femoral fixation.

Adolescent↗
PubMed2004

Can metal levels be used to monitor metal-on-metal hip arthroplasties?

In this review, the prospects for using blood, serum, and/or urine metal levels for monitoring the performance of metal-on-metal hip arthroplasty systems are explored. This approach does have substantial potential for serving this function; however, the methodology is technically challenging and the interpretation of the values requires an extensive database with correlative clinical information. At this time, it is premature to recommend metal concentration analysis on a routine clinical basis for patients with metal-on-metal total hip arthroplasties. Nonetheless, metal concentration analysis remains a powerful research tool in the evaluation of metal-on-metal hip arthroplasty systems.

Arthroplasty, Replacement, Hip↗
PubMed2004

Fixation strength of an all-metal acetabular component cemented into an acetabular shell: a biomechanical analysis.

When an acetabular shell is well fixed but the locking mechanism is compromised, cementing a new liner into the existing acetabular component can provide a simple revision solution. The pull-out and torsional fixation strength of cobalt chromium (CoCr) alloy acetabular components cemented into 3 sizes of titanium alloy acetabular components was tested under conditions of 0 or 2 mm cement mantle at the dome and 2 mm cement with the cemented component in 20 degrees of version with respect to the shell. The lowest mean tensile load to failure was 1500 N, and occurred with no cement at the dome of the 54 mm shell, whereas the greatest load was with 2 mm cement thickness. Smallest mean torque to failure was 43 Nm. Version angle did not substantially change failure load. Although not cyclically loaded, fixation strength of metal liners cemented into shells was comparable to that of commonly used locking mechanisms, suggesting sufficient strength for clinical application.

Acetabulum↗
PubMed2004

Prevention and treatment of dislocation after total hip replacement using large diameter balls.

The purpose of this study was to review safety and efficacy of total hip arthroplasty using large-diameter femoral heads in treatment and prevention of dislocation. One hundred forty hips in 135 patients were replaced using femoral heads at least 36 mm in diameter. The average age of the patients was 61.6 years. The patients were grouped into three categories depending on their diagnoses: recurrent dislocations from previous total hip replacements (Group 1; 29 hips); revision surgeries not including revisions for dislocations (Group 2; 54 hips); and primary surgeries (Group 3; 57 hips). The average followup was 5.5 years (range, 1-17 years). A total of 16 hips were revised: six for instability, four for fracture or disassociation of a conventional polyethylene liner, three for aseptic loosening of the socket, and three for sepsis. One hip from Group 1 dislocated at 12.5 years postoperatively, was treated with closed reduction, and since has been nonrecurring. UCLA hip scores all improved significantly. The prevalence of dislocation varied among the three groups, with 13.7% for Group 1, 1.8% for Group 2, and 3.5% for Group 3. The failure in the six cases that required revision for instability was attributable to poor socket orientation. All the hips became stable after revision without the use of a constrained acetabular liner. Large-diameter femoral heads provide additional stability not only for patients with recurrent dislocations, but also for patients having revision. The new, more wear-resistant bearings now enable the surgeon to extend the use of big femoral heads to primary total hip arthroplasty. Metal-on-metal seems to be the material of choice for a bone-conserving reconstruction with large femoral heads.

Adolescent↗
PubMed2004

Cementing a liner into a stable cementless acetabular shell: the double-socket technique.

BACKGROUND: During revision hip replacement surgery, the cementless acetabular shell is often well fixed but the locking mechanism may be ineffective. Cementing a new liner into the existing acetabular shell (the double-socket technique) can provide a simple solution. The purposes of the present study were to review our initial clinical results and to define the potential limitations of this technique. METHODS: Thirty-two hips with a preexisting well-fixed acetabular socket that had been in situ for an average of 8.6 years were treated with the insertion of a new polyethylene liner (seventeen hips) or a metal liner (fifteen hips) with use of cement. The indication for this technique was a deficient locking mechanism in twenty-two hips and the unavailability of a matching liner in ten hips. Anteroposterior radiographs of all hips were analyzed by a single independent reviewer. RESULTS: The mean duration of follow-up was 5.1 years. Six hips required a reoperation after a mean of 29.7 months; the reasons for the reoperations included aseptic failure of the acetabular construct (four hips), instability (one hip), and sepsis (one hip). The University of California at Los Angeles hip scores improved significantly (p < 0.001) compared with the preoperative values; specifically, the mean score improved from 6.2 to 9.1 for pain, from 6.3 to 8.3 for walking, from 6.2 to 7.8 for function, and from 4.7 to 5.8 for activity. The prevalence of dislocation was 22%. Kaplan-Meier analysis with revision as the end point revealed a five-year survival rate of 78% (95% confidence interval, 55% to 91%). CONCLUSIONS: The double-socket technique is a good alternative to acetabular socket removal for suitable candidates who have a well-fixed cementless socket with an inner diameter that is larger than the outer diameter of the cemented liner. This technique preserves acetabular bone stock and permits conversion to alternate bearing surfaces. We believe, however, that removal of a well-fixed acetabular shell or the use of a constrained liner should be strongly considered for patients with a history of hip instability.

Acetabulum↗
PubMed2004

Fracture of the neck of the femur after surface arthroplasty of the hip.

BACKGROUND: There are two main modes of failure of the femur following surface arthroplasty of the hip: femoral neck fracture and aseptic loosening. The purpose of the present study was to present our experience with femoral neck fractures that occurred after metal-on-metal hybrid surface arthroplasty and to assess their cause. METHODS: A series of 600 metal-on-metal surface arthroplasties was performed between late 1996 and early 2003. Failures that occurred during this period were assessed radiographically and with implant retrieval analysis to determine their cause. RESULTS: Five femoral neck fractures occurred in this series (prevalence, 0.83%). Four of the five fractures occurred at the component-neck junction within the first five months (average, three months) after surgery. All five fractures were associated with a traumatic episode, but all five also were associated with structural and/or technical risk factors, which we believe weakened the femoral neck. The most important technical deficiency that contributed to three of the five fractures was the failure to cover all of the reamed bone with the component. CONCLUSIONS: It is important to avoid or at least minimize notching of the femoral neck by performing the cylindrical reaming at the recommended angle of 140 degrees and to stop reaming before the reamer touches the lateral cortex. Osteophytes should be removed judiciously only if there is notable impingement when the hip is flexed to 90 degrees and internally rotated. We believe that understanding the factors that contribute to femoral neck fracture after surface arthroplasty may reduce the prevalence of this mode of failure.

Adult↗
PubMed2004

Orientation of the femoral component in surface arthroplasty of the hip. A biomechanical and clinical analysis.

BACKGROUND: Although the orientation of the femoral component has been shown to influence the outcome of total hip replacement, its effect on the clinical outcome of surface arthroplasty has not been studied, to our knowledge. The purpose of this study was to examine the relationship between femoral component positioning and the outcome of a surface arthroplasty of the hip. METHODS: We reviewed the results of ninety-four hybrid metal-on-metal surface arthroplasties in patients who were forty years old or younger at the time of the operation and were followed for a minimum of two years or until the prosthesis failed. Measurements of the hip reconstruction were made on the anteroposterior pelvic radiograph. The correlation between the orientation of the femoral component and the outcome of the arthroplasty was evaluated, as were stresses within the resurfaced femoral head as a function of the orientation of the femoral component. RESULTS: The mean duration of follow-up was 4.2 years. Thirteen hips had an adverse outcome, defined as conversion to a total hip replacement, radiolucency of >1 mm in thickness adjacent to the femoral stem, or narrowing of the femoral neck of >10%. The mean femoral stem-shaft angle in the coronal plane was 138 degrees, with the hips that had an adverse outcome having a significantly lower mean angle than the rest of the cohort (133 degrees compared with 139 degrees, p = 0.03). Hips with an angle of <or=130 degrees had an increase in the relative risk of an adverse outcome by a factor of 6.1 (p < 0.004). In the entire cohort, stresses in the superior aspect of the resurfaced femoral head were substantially lower during slow walking than they were during fast walking (7.1 N/mm(2) compared with 14.2 N/mm(2)). CONCLUSIONS: Optimizing the femoral stem-shaft angle toward a valgus orientation during the preparation of the femoral head is important when a hip is being reconstructed with a surface arthroplasty because the resurfaced hip transmits the load through a narrow critical zone in the femoral head-neck region and the valgus angulation may reduce these stresses.

Adolescent↗
PubMed2004

Preservation of bone mineral density of the proximal femur following hemisurface arthroplasty.

Bone mineral density of the proximal femur was measured in six patients who underwent hemisurface replacement for osteonecrosis of the femoral head. Bone mineral density values in operated and contralateral nonoperated hips were compared. In four patients who had sequential examinations, bone mineral density was compared over time. Average patient age was 34.6 years, average follow-up was 9.1 years, and mean follow-up of bone mineral density measurements was 6.6 years. Average bone mineral density variation was 0.0048 to -0.0264 g/cm2 per year in all five regions in nonoperated hips and -0.012 to -0.0300 g/cm2 in operated hips. These results support bone conservation and preservation with hemiresurfacing arthroplasty in young patients with osteonecrosis of the femoral head.

Adolescent↗
PubMed2004

Metal-on-metal hybrid surface arthroplasty: two to six-year follow-up study.

BACKGROUND: Following the reintroduction of metal-on-metal articulating surfaces for total hip arthroplasty in Europe in 1988, we developed a surface arthroplasty prosthetic system using a metal-on-metal articulation. The present study describes the clinical and radiographic results of the first 400 hips treated with metal-on-metal hybrid surface arthroplasties at an average follow-up of three and a half years. METHODS: Between November 1996 and November 2000, 400 metal-on-metal hybrid surface arthroplasties were performed in 355 patients. All femoral head components were cemented, but only fifty-nine of the short metaphyseal stems were cemented. The patients had an average age of forty-eight years, 73% were men, and 66% had a diagnosis of osteoarthritis. Clinical and radiographic follow-up were performed at three months postoperatively and yearly thereafter. RESULTS: The majority of the patients returned to a high level of activity, including sports, and 54% had activity scores of >7 on the University of California at Los Angeles activity assessment system. Kaplan-Meier survivorship curves demonstrated that the rate of survival of the components at four years was 94.4%. For patients with a surface arthroplasty risk index score of >3, the rate of survival of the components at four years was 89% compared with a rate of 97% for those with a score of </=3. The patients with a higher risk index were 4.2 times more likely to undergo revision to a total hip replacement at four years. Twelve hips (3%) had a revision to a total hip replacement. Seven of the twelve hips were revised because of loosening of the femoral component, and three were revised because of a femoral neck fracture. Substantial radiolucencies were seen around sixteen uncemented metaphyseal femoral stems. No femoral radiolucencies were observed among the hips in which the metaphyseal stem was cemented. The most important risk factors for femoral component loosening and substantial stem radiolucencies were large femoral head cysts (p = 0.029), patient height (p = 0.032), female gender (p = 0.005), and smaller component size in male patients (p = 0.005). CONCLUSIONS: The preliminary experience with this hybrid metal-on-metal bearing is encouraging. Optimal femoral bone preparation and component fixation are critical to improving durability. The metal-on-metal hybrid surface arthroplasty is easily revised to a standard femoral component if necessary. LEVEL OF EVIDENCE: Therapeutic study, Level IV (case series [no, or historical, control group]). See Instructions to Authors for a complete description of levels of evidence.

Adolescent↗
PubMed2004

Risk factors affecting outcome of metal-on-metal surface arthroplasty of the hip.

We evaluated radiologic and clinical features affecting the outcome of hybrid metal-on-metal surface arthroplasty of the hip in 119 hips in patients 40 years and younger. Only the hips that had either failed or had minimum 2-year followup were reviewed. Ninety-four hips in 83 patients with a mean age of 34.2 years (range, 15-40 years) were reviewed. Seventy-one percent of the patients were males and 29% of the patients were females; 14% had previous surgery. The Chandler index and surface arthroplasty risk index were calculated. The mean followup at 3 years (range, 2-5 years) showed that three hips were converted to a total hip replacement at a mean of 27 months (range, 2-50 months) after the original surgery, and 10 hips had significant radiologic changes. The mean surface arthroplasty risk index for these 13 problematic hips versus the remaining hips was significantly higher, 4.7 and 2.6, respectively. The mean angle between the prosthesis stem and femoral shaft in the problematic group was significantly smaller than in the remaining hips: 133 degrees and 139 degrees, respectively. With a surface arthroplasty risk index score greater than 3 the relative risk of early problems is 12 times greater than if surface arthroplasty risk index less than or equal to 3.

Adult↗