Thomas A. Gruen

Modes of failure of cemented stem-type femoral components : a radiographic analysis of loosening

In view of the increasing incidence of stem-type femoral component loosening, a detailed retrospective radiographic zonal analysis of 389 total hip replacements indicated a 19.5% incidence (76 hips) of radiological evidences of mechanical looseness, i.e., fractured acrylic cement and/or a radiolucent gap at the stem-cement or cement-bone interfaces. Detailed serial radiographic examination demonstrated progressive loosening in 56 of the 76 hips and these were categorized into mechanical modes of failure. The 4 modes of failure characterizing stem-type component progressive loosening mechanisms consisted of stem pistoning within the acrylic (3.3%), cement-embedded stem pistoning with the femur (5.1%), medial midstem pivot (2.5%), calcar pivot (0.7%) and bending (fatigue) cantilever (3.3%).

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.

Revision of failed total hip arthroplasties with uncemented porous-coated anatomic components.

This series represents a relatively short follow-up study of patients who were treated with cementless revisions for failed previous arthroplasties. Many of these cases required extensive bone grafting to the acetabulum and often to the femur. Despite extensive bone grafting, there were no infections. There has been but a single graft resorption after a hemiarthroplasty conversion for recurrent dislocations. To date, all other grafts have remained intact and have shown signs of union. Even though the acetabular components were not anchored in place by adjuvant fixation devices such as screws, migration of the acetabular component has not been a problem. All other components have remained stable, and the supporting grafts appear to have united successfully. Femoral revision has been more technically demanding because the largest stem possible should be placed within the femur to prevent subsidence and provide good stabilization in the proximal metaphyseal area. These short-term results compared favorably with similar series of cemented revisions. Patient selection is important and there are definite candidates for cemented femoral components, particularly with first-time revisions in elderly patients. If there is massive osteolysis in the femur, cemented revision is probably not indicated. Long stems should not be used unless necessary. Cortical defects at the tip of the standard stem obviously would require bypassing the stress riser with a longer stem. If, however, the cortex is intact in this region and stability can be achieved, revision should be carried out with a relatively short stem. Techniques for cementless revision are demanding, but with meticulous attention to detail and technical perfection, the method has a most encouraging prognosis. Longer follow-up evaluations will be necessary to make an accurate evaluation of graft incorporation, but short-term results are encouraging to both surgeons and patients.

Clinical and Radiographic Results of Metal-on-Metal Hip Resurfacing with a Minimum Ten-Year Follow-up

BACKGROUND There was a need for information about the long-term performance of the modern generation of hip resurfacing implants. A retrospective review of the first 100 hips that had implantation of one resurfacing design and had been followed for a minimum of ten years was performed. METHODS Between 1996 and 1998, 100 CONSERVE PLUS hip resurfacing devices were implanted by a single surgeon in eighty-nine patients. The mean age of the patients was 49.1 years, and fifty-nine patients were male. Primary osteoarthritis was the etiology for sixty-four hips. All patients were assessed clinically and radiographically. RESULTS The mean duration of follow-up was 11.7 years (range, 10.8 to 12.9 years). Two patients were lost to follow-up, and five patients died of causes unrelated to the surgery. Eleven hips had conversion to total hip arthroplasty because of loosening of the femoral component (eight), a femoral neck fracture (one), recurrent subluxation (one), and late infection (one). The Kaplan-Meier survivorship was 88.5% at ten years. None of the resurfacing arthroplasties failed in the twenty-eight hips that had a femoral component of >46 mm and no femoral head cystic or necrotic defects of >1 cm. Five hips had narrowing of the femoral neck, three had radiolucent zones interpreted as osteolysis, and twenty had signs of neck-socket impingement. Five hips had radiolucencies around the metaphyseal stem (two partial and three complete) that had been stable for 7.8 to 10.2 years. The mean scores on the University of California at Los Angeles (UCLA) system at the time of the latest follow-up were 9.5 points for pain, 9.3 points for walking, 8.9 points for function, and 6.8 points for activity; the mean scores on the physical and mental components of the Short Form-12 (SF-12) were 47.3 and 50.5 points, respectively; and the mean Harris hip score was 90 points. CONCLUSIONS The results of the present series constitute a reference point to which subsequent series should be compared. These ten-year results in a group of young patients are satisfactory, and the low rate of osteolysis is encouraging, but longer follow-up is required for comparison with conventional total hip arthroplasty.

Primary Total Hip Arthroplasty with Use of the Modular S-ROM Prosthesis. Four to Seven-Year Clinical and Radiographic Results*

BACKGROUND A multicenter retrospective study was conducted to determine the clinical and radiographic results of primary total hip arthroplasty with insertion of the S-ROM modular femoral stem without cement in a series of patients who had been followed for four to seven years. Four centers participated in the study, with one contributing surgeon at each center. METHODS Two hundred and eight consecutive patients who had a total hip arthroplasty with implantation of the S-ROM femoral prosthesis at one of the four centers during the study period were identified. Twenty-nine patients were lost to follow-up or had incomplete radiographic data, and twenty patients died from causes unrelated to the index arthroplasty. The remaining 159 patients formed the basis of this study. Sixteen of these patients had a bilateral procedure, resulting in 175 hips with complete clinical and radiographic data. The average age of the patients at the time of the index operation was fifty-nine years (range, twenty-two to ninety-three years). The duration of clinical follow-up averaged 5.3 years (range, four to 7.8 years), and the duration of radiographic follow-up averaged 4.9 years (range, four to 7.3 years). RESULTS One patient (0.6 percent) had a failed femoral component, which was evidenced by progressive subsidence and lack of bone ingrowth. In addition, two patients (1 percent) had a revision of the acetabular component. The average Harris hip score increased from 35 points (range, 10 to 76 points) preoperatively to 91 points (range, 52 to 100 points) at the most recent follow-up examination. The radiographic evaluation revealed that 172 hips (98 percent) had stable bone ingrowth, two hips (1 percent) had stable fibrous ingrowth, and one hip (0.6 percent) had unstable fibrous ingrowth. Periprosthetic osteolytic lesions were noted in twelve hips (7 percent). The lesions were observed in the femur in eight hips, in the acetabulum in two hips, and in both the femur and the acetabulum in two hips. All femoral osteolytic lesions were localized within the greater trochanter or the proximal-medial portion of the femoral neck. No osteolytic lesions were evident distal to the stem-sleeve junction. CONCLUSIONS Use of the modular S-ROM femoral prosthesis yielded excellent intermediate-term outcomes with respect to standard radiographic and clinical criteria. The issue regarding the theoretical increase in the rate of osteolysis due to metal debris generated at the modular femoral stem-sleeve junction was specifically addressed. We found that the rate of osteolysis in this series was not notably higher than that in other series reported in the orthopaedic literature. Although many possible factors may influence the rate of osteolysis in total hip arthroplasty, this finding suggests that the potential increase in osteolysis theoretically associated with this modular femoral implant was not observed at intermediate-term follow-up. Although longer follow-up is warranted so that the potential for osteolysis can be evaluated fully, no osteolytic lesions were evident distal to the stem-sleeve interface at the time of intermediate-term follow-up. This finding suggests that there is a circumferential seal at the modular junction of the stem that prevents the distal egress of wear debris.

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.

Hydroxyapatite-coated proximal ingrowth femoral stems. A matched pair control study.

A matched pair study of 2 groups of 42 uncemented total hip replacements were compared retrospectively after a minimum 3-year followup. Forty-two hips were implanted with a hydroxyapatite coating on the proximal femoral patched porous surfaces; 42 hips had patched porous-coated stems without hydroxyapatite. There were no clinical differences between the matched groups by any criteria of measurement. There was no statistically significant difference between the matched groups for femoral stem fixation at all followup intervals. At the 3-year followup, 90% of the femoral stems in the hydroxyapatite porous group, and 83% in the porous control group achieved stable bony fixation. Hydroxyapatite-coated femoral stems demonstrated accelerated bone remodeling characterized by proximal cancellous hypertrophy. The percentage of femoral stems exhibiting cancellous hypertrophy was significantly greater at all followup intervals. This study did not demonstrate any clinical advantage of hydroxyapatite being added to a porous-coated surface. The radiographic changes of bone remodeling seen with hydroxyapatite are not known to improve durability of the hip arthroplasty. This study again condemns the use of patched porous-coating and titanium-bearing surfaces.

Porous ingrowth fixation of the femoral component in a canine surface replacement of the hip

Prosthetic fixation by growth of bone into porous implants coated with a sintered layer of cobalt chrome beads offers an attractive alternative to acrylic cementation. Experiments on dogs demonstrate that bone ingrowth occurred into the femoral component of a hip surface replacement. Methods of stabilizing prostheses in order to promote bone ingrowth must not interfere with the uniformity of stress transfer at the bone - implant interface. Ingrowth occurred as early as the second week postimplantation. The absence of any fibrous membrane formation in the interface between bone and metal suggests that sintered chrome cobalt is a highly compatible biological system, and that fixation by bone ingrowth is stable and does not promote osteoclasis and progression to a fibrous membrane at the interface.

THARIES surface replacements: a review of the first 100 cases.

The first 100 cases of the 135 THARIES surface replacement procedures with 4--32 months follow-up, are evaluated in terms of clinical results, radiographic information and complications. The short but detailed follow-up suggests that this procedure was an excellent alternative for the younger and more active population. The overall hip ratings (pain, walking and function) and range of motion are comparable to that of stem-type total hip replacements. When the THARIES and conventional hip results are further compared in 34 patients matched by sex and age for 3 major etiological groups (osteoarthritis, osteonecrosis and congenital hip dysplasia), the interim results are essentially comparable for both types. Three cases in the first 100 have required revision. One patient (no. 1) with osteoporosis, chondrolysis and arthrofibrosis following slipped capital femoral epiphysis had loose femoral and acetabular components 24 months postoperatively. He was revised to a T-28 hip replacement. The polyethylene socket in another patient (no. 4), the first dysplastic hip in this series, was 20 nm uncovered superiorly, became loose and was revised 9 months postoperatively. Now 15 months postoperative with a more medial THARIES acetabulum, the patient continues to have a good result. Another patient (no. 12) with bilateral dysplastic hips became progressively more disabled due to heterotopic bone, which was then excised 18 months postoperatively. Radiographic studies of the THARIES sockets demonstrate radiolucent zones at the cement-bone interfaces of the acetabulum in 88 cases, partial in 51 and complete in 37. Three hips were currently considered to have evidence of progressive socket loosening but are active and asymptomatic. There have been no femoral neck fractures in this series which we attribute to the custom fitting ability inherent in the range of components, the reaming protocol and the various remodelling guides. There have been no prosthetic breakages, subluxations, dislocations or sepsis. The complications observed in this series are minor and comparable to that of many other total hip arthroplasty operations. Nerve palsy and trochanteric separation have not been major problems although one existing peroneal nerve dysfunction and one trochanteric migration emphasize the need to minimize these complications by careful handling of the operative leg, and an accurate trochanteric reattachment technique.

Functional results in total hip replacement in patients 65 years and older.

Total hip arthroplasty in patients 65 years and older has been very durable in long term results. Eighty-nine hips in 79 patients were observed for 5 to 9 years to determine the importance of advancing age and deterioration of activity levels to durability of total hip replacement. The age of patients was 65 years or older at the time of surgery. A classification of function was used that graded activity level. During the average 6.24 years of postoperative followup, 22% of the patients died, 38% had medical problems that reduced their functional level, and 10% reduced their function because of their hip surgery. Hip related deterioration occurred only in those patients with a cementless stem. There was decreasing measured wear with increasing age; otherwise, neither age nor activity change in this study was related to loss of fixation of components, osteolysis, or bone remodeling. Increasing age and decreasing activity in patients 65 years and older does not seem to be the primary reason for durability of total hip arthroplasty in these patients. In this age group, the durability of hip replacement is related mostly to the quality of fixation.