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© 1999 The Journal of Bone and Joint Surgery, Inc. The Effects of Surface Roughness and Polymethylmethacrylate Precoating on the Radiographic and Clinical Results of the Iowa Hip Prosthesis. A Study of Patients Less Than Fifty Years Old* , IOWA CITY , WEST DES MOINES, IOWA CITY, IOWAInvestigation performed at the Iowa Methodist Medical Center, West Des Moines, and the University of Iowa College of Medicine, Iowa City
Background: The purpose of the present study was to compare the results associated with two different surface finishes (bead-blasted and grit-blasted) for Iowa femoral components used in total hip arthroplasties performed between January 1979 and June 1991 in patients who were less than fifty years old. Methods: Between January 1979 and December 1985, thirty-six primary total hip replacements were performed in twenty-five patients with insertion of a bead-blasted Iowa femoral component (average surface roughness, 0.8 micrometer) with cement and insertion of a titanium-backed acetabular component (thirty-five hips) or non-metal-backed acetabular component (one hip) with cement. Between January 1986 and June 1991, forty-five primary total hip replacements were performed in thirty-seven patients with use of a precoated grit-blasted Iowa femoral component (average surface roughness, 2.1 micrometers) and a Harris-Galante-I porous ingrowth acetabular component (forty-one hips) or an Osteonics component (four hips). The only change in the design of the femoral component (other than the surface finish) between the two consecutive series was the addition of polymethylmethacrylate precoating to the proximal third of all forty-five grit-blasted stems and modularity of the femoral head of the last eight grit-blasted stems. Results: No hip was lost to follow-up. The duration of radiographic follow-up of the hips treated with the bead-blasted component averaged 11.3 years (range, ten to sixteen years) postoperatively, whereas that of the hips treated with the precoated grit-blasted component averaged 8.2 years (range, five to eleven years). Two (6 percent) of the bead-blasted femoral components were revised because of aseptic loosening compared with eight (18 percent) of the precoated grit-blasted components. Four bead-blasted components (11 percent) were either radiographically loose or were revised because of loosening compared with eleven precoated grit-blasted components (24 percent). Kaplan-Meier survivorship curves evaluated with log-rank analysis revealed that the bead-blasted Iowa femoral components were revised because of aseptic loosening (p = 0.0184) and were radiographically loose (p = 0.0068) less often than the precoated grit-blasted Iowa femoral components. Conclusions: The findings of the present study have led the senior ones of us to resume using femoral components with a polished surface and fixed with cement.
The durability of any total hip arthroplasty construct can best be evaluated in patients who place high demands on the prosthesis. Hence, over the years the senior two of us (J. J. C. and R. C. J.) have been most interested in the results of total hip arthroplasty in younger patients—that is, those less than fifty years old22. During the more than twenty-five years that the senior one of us (R. C. J.) performed operations on the hip, he initially used the Charnley prosthesis (Thackray, Leeds, England, and Zimmer, Warsaw, Indiana) with cement, from 1970 through 1978; followed by the Iowa prosthesis (Zimmer), from 1979 through 1985; and finally by the precoated Iowa prosthesis (Zimmer), when it became available in 19863,21,22. He and his colleagues reported excellent results with the Charnley prosthesis fixed with cement, even in younger patients21,22. In addition, he noted no dramatic change in the durability of the implant after he switched to the initial Iowa femoral component, which had a bead-blasted surface finish. This Iowa femoral component had a minimally roughened matte finish (average surface roughness, 0.8 micrometer), which at that time was the standard surface finish for most femoral components designed to be inserted with cement. The next version of the stem had an increased average surface roughness (2.1 micrometers) and was precoated with polymethylmethacrylate because it was believed that the increased bonding of the stem to the cement would improve the long-term results. The senior one of us hypothesized that the increase in surface roughness along with the proximal polymethylmethacrylate precoat on the femoral stem would increase the long-term durability of the prosthesis. However, early follow-up revealed an increase in the prevalence of loosening of precoated grit-blasted Iowa components with rapid radiographic evidence of osseous destruction (osteolysis)15. The purpose of the present study was to compare the results, with regard to long-term durability, of total hip arthroplasty performed with the bead-blasted Iowa femoral component without a precoat with those of arthroplasty performed with the grit-blasted Iowa femoral component with a proximal polymethylmethacrylate precoat in a group of younger patients.
A computer database of all operations performed at the Iowa Methodist Medical Center was used to identify all patients who had been managed, when they were less than fifty years old, with a primary total hip arthroplasty with an Iowa femoral component by the senior one of us. Between January 1979 and December 1985, thirty-six primary total hip replacements were performed in twenty-five patients younger than fifty years old with use of a bead-blasted Iowa femoral component and a titanium-backed or non-metal-backed acetabular cup. Both the femoral and the acetabular component were fixed with cement. Between January 1986 and June 1991, the senior one of us performed forty-five primary hybrid total hip replacements (with an ingrowth acetabular component fixed without cement and a femoral component fixed with cement) in thirty-seven patients who were younger than the age of fifty years. A grit-blasted Iowa femoral component with a proximal polymethylmethacrylate precoat was inserted with cement and a Harris-Galante-I porous ingrowth acetabular component (Zimmer) was inserted without cement in forty-one hips. An Osteonics dual-geometry porous ingrowth acetabular component (Osteonics, Allendale, New Jersey) was used with the same femoral component in four hips. We reviewed the results in these two consecutive, nonselected series of patients who were younger than fifty years old at the time of the primary operation. All of the patients of the senior one of us had fixation of the femoral component with cement during the interval that was studied. The Iowa femoral components were made of cobalt-chromium alloy. The ingrowth acetabular components were fixed with two screws (forty-three hips) or occasionally with three screws (two hips) placed through the acetabular shell. The operative records were evaluated to determine the approach that had been used; whether a trochanteric osteotomy had been performed and, if so, the method of reattachment; and the cementing technique. Thirty-five of the bead-blasted femoral components were used with a titanium-backed acetabular component (TiBac; Zimmer), and one was used with an all-polyethylene component. A modular polyethylene liner was held in place by tines located around the mouth of the hemispherical shell of the Harris-Galante-I components. All of the prosthetic components were placed by the senior one of us (R. C. J.). A standard lateral approach was used in all hips except three. Two hips, which had a hybrid replacement (that is, a replacement involving the grit-blasted component), were treated through an anterolateral approach, and one was treated through an anterior approach. An osteotomy of the greater trochanter was used in thirty-four of the thirty-six hips treated with the bead-blasted component and in forty-two of the forty-five treated with the grit-blasted component. Cable was used for trochanteric reattachment in eighteen of the hips treated with the bead-blasted component, and wire was used in sixteen. The greater trochanter was reattached with wire in all of the hips that had a grit-blasted component. Simplex-P cement (Howmedica, Rutherford, New Jersey) was used for femoral fixation and was incorporated with use of contemporary cementing techniques, which included pulsatile lavage, drying of the femoral canal, placement of a distal cement plug, and delivery of the cement with a pressurization gun8. The porosity of the cement was reduced by means of centrifugation for the arthroplasties performed with the precoated grit-blasted component2. A complete capsulectomy was performed in all hips. In the hybrid arthroplasties (those involving the grit-blasted components), the acetabular component was inserted after so-called line-to-line reaming of the acetabulum. The acetabular components that were inserted with cement (those used with the bead-blasted components) were placed as far medially and inferiorly as possible with an attempt to maximize osseous contact without compromising the anterior and posterior acetabular walls. No bone graft was used for structural or filler support in the acetabula in which no cement was used. The greater trochanter was reattached as far laterally as possible and advanced as distally as possible. Systemic antibiotics were used perioperatively for one or two days. The operations were performed in an operating room with laminar airflow, and the operating team wore body-exhaust systems. Postoperatively, the patients were managed with balanced suspension for two to seven days and subsequently were taught to walk with crutches. The patients walked with crutches for six weeks after discharge and then used a cane for an additional two to four months, until they could walk well without support. According to the manufacturer, there was no change in the design or in the milling of the cobalt-chromium femoral components, with the exception of the polymethylmethacrylate precoat (Zimmer) being applied to the proximal third of the grit-blasted stems and the change in the surface finish. All femoral components were monolithic in design except for the last eight grit-blasted implants, which had a modular femoral head. A twenty-eight-millimeter femoral head was used in all hips. Fourteen women (twenty-two hips) and eleven men (fourteen hips) were managed with a bead-blasted component. The average age of these patients at the time of the arthroplasty was 37.8 years (range, eighteen to forty-nine years). Fourteen components were inserted in patients who were in their forties; fourteen, in patients in their thirties; seven, in patients in their twenties; and one, in an eighteen-year-old patient. The diagnoses before the primary total hip arthroplasties included congenital dislocation of the hip (fifteen hips), avascular necrosis (nine), rheumatoid arthritis (seven), primary osteoarthritis (three), Legg-Calvé-Perthes disease (one), and traumatic injury with secondary degenerative osteoarthritis (one). Nineteen arthroplasties were done on the right hip, and seventeen were performed on the left. Eighteen women (twenty-three hips) and nineteen men (twenty-two hips) were managed with a grit-blasted component. The average age at the time of the arthroplasty was 41.0 years (range, twenty-six to forty-nine years). Twenty-seven components were inserted in patients who were in their forties; fifteen, in patients in their thirties; and three, in patients in their twenties. The diagnoses before the arthroplasties included primary degenerative arthritis (five hips), congenital dislocation of the hip (ten), slipped capital femoral epiphysis (seven), achondroplasia (two), juvenile rheumatoid arthritis (four), traumatic injury with secondary degenerative osteoarthritis (four), avascular necrosis (five), Legg-Calvé-Perthes disease (three), Morquio syndrome (two), spastic hemiparesis with degenerative changes (one), and metaphyseal chondrodysplasia (two). Nineteen arthroplasties were done on the right hip, and twenty-six arthroplasties were performed on the left hip. Between January 1979 and December 1985 the senior one of us fixed both components with cement in all hips, and between January 1986 and June 1991 he used hybrid fixation in all hips. Hence, the study represents a nonselected consecutive series of primary hip arthroplasties performed by the senior one of us in this age-group. Attempts were made to contact all of the patients in the two groups. The surviving patients were asked to return for clinical and radiographic evaluation. Those who were unable to return to the clinic were asked to have radiographs made locally and sent to the office of the senior one of us. Four patients who had a bead-blasted prosthesis and five who had a grit-blasted prosthesis had radiographs made at an outside facility. Anteroposterior radiographs of the pelvis that included the tip of the femoral component, as well as Judet radiographs when possible, were reviewed. All patients were evaluated clinically in person or by telephone with use of the standard system of terminology for reporting results as described by the senior one of us (R. C. J.) and colleagues9. All of the telephone questionnaires were completed by another one of us (S. M. S.). If a patient had died, family members were interviewed to determine the patient's functional status at the time of death. The latest available anteroposterior pelvic radiograph that included the tip of the femoral component was compared with the initial postoperative radiograph made in the office as well as with subsequent radiographs, which had been made every one to two years for most patients. In addition, Judet radiographs were examined whenever possible to further evaluate radiolucent lines around the acetabular component. All radiographs were examined by two of us (S. M. S. and J. J. C.), and a consensus was reached regarding the findings. Radiographic measurements were adjusted for magnification by comparing the actual width of the femoral head with the measured size on each radiograph according to the technique of Livermore et al.11. The acetabular components were evaluated radiographically in order to assess the placement of the hip center, radiolucent lines at the metal-bone or metal-cement interface, migration of the component, breakage of screws (in the Harris-Galante-I components), osteolysis, and linear and volumetric wear. Migration of the cup was defined as more than five millimeters of variation in the vertical distance between the center of the cup and a line joining the teardrops or as more than five millimeters of variation in the horizontal distance between the center of the cup and a vertical line through the ipsilateral teardrop13. Linear and volumetric wear of the acetabular component was determined according to a modification of the technique of Livermore et al.11 by the one of us (J. P. O.) who was the most experienced with this method. The femoral components were evaluated for radiolucency at the cement-bone interface, subsidence, and osteolysis around the construct. Any nonlinear radiolucency of more than five millimeters in width was considered osteolysis. Subsidence of the femoral component was defined, according to the method of Loudon and Charnley12, as an increase of at least five millimeters in the vertical distance from the tip of the femoral component to the drill-hole in the lateral cortex for the trochanteric reattachment wire. When trochanteric wire had not been used, the proximal aspect of the lesser trochanter was used as a reference. Debonding was noted as separation of the stem from the surrounding cement, usually in zone I of Gruen et al.7. Radiographic loosening was classified according to the criteria of Harris and McGann8. Definite loosening was defined as migration of the component, fracture of the cement, or a radiolucent line at the stem-cement interface that had not been present on the radiograph made immediately postoperatively. Probable loosening was defined as a continuous radiolucent line at the cement-bone interface without migration of the component. Possible loosening was defined as an incomplete radiolucent line involving 50 to 99 percent of the femoral component, the metal-bone interface of the ingrowth acetabular component, or the metal-cement interface of the cemented acetabular component. Heterotopic ossification was classified with use of the system of Brooker et al.1. The technique for cementing of the femoral component was graded on the first postoperative radiograph with use of the criteria of Schmalzried and Harris20. Grade A indicates a whiteout—that is, no radiolucency between the bone and the cement; grade B, cancellous bone between the cortex and the cement; grade C1, voids in the cement mantle; grade C2, defects in the cement mantle or a cement mantle of less than one millimeter in thickness; and grade D, no cement around the distal part of the stem. Significant differences between the two groups were determined with use of a Student t test for continuous variables, and a chi-square test was utilized for discrete variables. Kaplan-Meier survivorship curves10 were created for both groups and were compared with use of a Wilcoxon rank-sum test.
At the time of the most recent follow-up, one patient (two hips) of the twenty-five who had a bead-blasted component had died from an acute myocardial infarction and one patient (two hips) of the thirty-seven who had a grit-blasted component had died. These two patients were included in the analysis as they had been followed clinically and radiographically for at least five years. Consequently, all of the total hip arthroplasties performed by the senior one of us at the Iowa Methodist Medical Center between 1979 and 1991 in patients who were less than fifty years old were followed with use of both a clinical questionnaire and radiographic evaluation.
Radiographic Results In the group treated with the grit-blasted component, the patient (with two involved hips) who had died was included in the radiographic analysis as the last radiograph had been made seven years postoperatively. Therefore, a radiograph was made from five to eleven years (average, 8.2 years) postoperatively for all forty-five hips. The initial postoperative radiographs demonstrated grade-A cementing technique in twenty-five hips (56 percent), grade-B in thirteen (29 percent), grade-C1 in three (7 percent), and grade-C2 in four (9 percent)20.
Femoral Constructs
Two (6 percent) of the thirty-three bead-blasted femoral components had evidence of definite loosening (Table I) according to the criteria of Harris and McGann8. No other component demonstrated probable or possible loosening, and there was no femoral radiolucency. Osteolysis of at least five millimeters in width was detected in zone I in one hip (3 percent), in zone II in five hips (15 percent), in zone III in three hips (9 percent), in zone IV in one hip (3 percent), in zone V in two hips (6 percent), in zone VI in one hip (3 percent), and in zone VII in seventeen hips (52 percent). Kaplan-Meier survivorship curves10 demonstrated ten-year rates of survival of 93 and 91 percent, with revision of the femoral component because of aseptic loosening and loosening of the femoral component (with or without revision) as the respective end points (Figs. 1-A and 1-B).
Eight grit-blasted femoral components (18 percent) in seven patients were revised because of loosening (Table II). All eight hips demonstrated rapid failure with osteolysis once debonding (radiolucency in zone I of the stem-cement interface) had occurred (Figs. 2-A, 2-B, 2-C and 2-D). One of the eight components with a modular head and seven of the thirty-seven monolithic stems were revised. Excluding the eight hips that were revised for aseptic loosening, the radiographic analysis of the femoral construct included thirty-seven hips. One hip in which an extended acetabular liner was inserted because of postoperative recurrent dislocation was included as the acetabular shell and the femoral component were not removed at the time of the revision procedure.
Three (8 percent) of the thirty-seven grit-blasted femoral components were definitely loose (Table II) according to the criteria of Harris and McGann8. No components were probably or possibly loose. Two hips demonstrated a radiolucent line along less than 50 percent of the cement-bone interface. The radiolucency was in zone III in one of these hips and in zone II in the other. One hip (3 percent) demonstrated osteolysis of at least five millimeters in zone I; two hips (5 percent), in zone III; three hips (8 percent), in zone IV; two hips (5 percent), in zone V; and thirteen hips (35 percent), in zone VII. In the group treated with the grit-blasted component, male gender was associated with both femoral loosening (with or without revision) (p = 0.002) and femoral revision (p = 0.022). Also, a heavier weight of the patient was associated with femoral loosening (p = 0.0514) and with femoral revision (p = 0.083). Kaplan-Meier survivorship curves10 demonstrated a seven-year rate of survival of 86 and 84 percent, with femoral revision and femoral loosening as the respective end points. Comparison of the Kaplan-Meier curves with use of the Wilcoxon rank-sum test demonstrated an increase in the prevalence of revision because of aseptic loosening (p = 0.0184) and in that of aseptic loosening (with or without revision) (p = 0.0068) for the grit-blasted femoral components compared with the prevalences for the bead-blasted components (Figs. 1-A and 1-B).
Acetabular Constructs The average rate of linear wear of the acetabular components used with the bead-blasted femoral components was 0.14 millimeter per year (range, zero to 0.58 millimeter per year). With the numbers available, no association was detected between the rate of linear wear and the grade of the cementing technique (p = 0.564), the weight of the patient (p = 0.243), or the patient's activity level (p = 0.260) with use of a Wilcoxon rank-sum test. However, there was an association between increased linear wear and male gender (p = 0.036) and a younger age (p = 0.0066). At the time of follow-up of the group treated with the grit-blasted femoral component, no acetabular component had been revised because of aseptic loosening and none had migrated. Radiolucent lines were observed around twenty-two components (49 percent). The lines were seen in zone I of DeLee and Charnley5 in eleven hips (24 percent), zone II in five hips (11 percent), and zone III in fourteen hips (31 percent). Although one hip had radiolucent lines in zones I, II, and III, these lines were noncontiguous and the position of the component had not changed. Osteolysis was observed in two acetabula (4 percent); the osteolysis was in zone II in one and in zones II and III in the other. None of the acetabular components were considered possibly, probably, or definitely loose. The average rate of linear wear of the acetabular components used with the grit-blasted femoral components was determined to be 0.099 millimeter per year (range, zero to 0.362 millimeter per year). The rate was 0.0 to 0.099 millimeter per year in twenty-eight hips, 0.1 to 0.199 millimeter per year in eleven, 0.2 to 0.299 millimeter per year in three, and 0.3 millimeter or more per year in three. With use of Kaplan-Meier ten-year survivorship analysis10 and the Wilcoxon rank-sum test, we detected no significant increase, but we did detect a definite trend toward an increase, in the prevalence of revision because of aseptic loosening (p = 0.0862) and the prevalence of aseptic loosening (with or without revision) (p = 0.0789) for the acetabular cups inserted with cement compared with the prevalences for the cups inserted without cement (p = 0.031) (Figs. 3-A and 3-B). The metal-backed acetabular components inserted with cement were associated with a greater yearly rate of linear wear than the porous ingrowth acetabular components (p = 0.031).
Clinical Results The remainder of the clinical analysis of the group managed with the bead-blasted component excluded the patient (one hip) who had the Girdlestone procedure because of a delayed hematogenous infection. At the time of the latest interview, evaluation of the activity level of the remaining patients revealed that sixteen (67 percent) performed light labor, four (17 percent) performed moderate labor, three (13 percent) were semi-sedentary, and one (4 percent) was bedridden because of a severe stroke nine years postoperatively. Twenty-one (88 percent) of the patients did not need walking aids, one (4 percent) used a cane full-time, and one (4 percent) walked with a cane part-time at the time of the most recent follow-up. The bedridden patient was unable to walk even with assistance. The patient who walked with a cane full-time had had a revision arthroplasty one month before the time of follow-up, and the patient who used a cane part-time did so primarily to help improve her balance and stamina on long walks. With regard to activities of daily living in the group managed with the bead-blasted component, eighteen (75 percent) of the patients had no trouble putting on shoes and socks, four (17 percent) had minor difficulty with this task, and two (8 percent) were unable to put on shoes and socks. To ascend stairs, nineteen patients (79 percent) alternated their feet normally (one over the other), two (8 percent) were able to alternate their feet but needed to hold a banister, and two placed two feet on each step; one patient (4 percent) was unable to ascend stairs. To stand from a sitting position, twenty (83 percent) of the patients did not need to use their upper extremities and three (13 percent) needed to use both upper extremities; one patient (4 percent) was unable to rise from a chair. Nineteen (79 percent) of the patients reported no trouble picking up an object from the floor, two (8 percent) reported some difficulty, one (4 percent) needed support to complete the task, and two were unable to pick up an object from the floor. Twenty-one (88 percent) of the patients reported no limitation with regard to the ability to carry an object, and three (13 percent) reported substantial limitation. These three patients were limited by problems with balance, back pain, or an arthritic joint and not by pain in the involved hip. The one patient who had a poor functional result was bedridden because of multiple cerebral infarctions and was not debilitated secondary to the hip. At the time of the latest interview, seventeen (46 percent) of the thirty-seven patients who had received a grit-blasted component performed light labor, six (16 percent) performed moderate labor, two (5 percent) performed strenuous labor, eleven (30 percent) were capable of light activity, and one (3 percent) performed little activity and was semi-sedentary. Thirty-five (95 percent) of the patients did not need walking aids, one (3 percent) used a cane full-time, and one (3 percent) walked with a cane part-time at the time of the most recent follow-up. The patient who walked with a cane full-time used it primarily to help improve her balance and not because of pain in the hip. With regard to activities of daily living in the group managed with the grit-blasted component, twenty-eight (76 percent) of the patients had no trouble putting on shoes and socks, eight (22 percent) had minor difficulty with this task, and one (3 percent) was unable to put on shoes and socks. To ascend stairs, twenty-four patients (65 percent) alternated their feet normally (one over the other), eight (22 percent) were able to alternate their feet but needed to hold a banister, and five (14 percent) placed two feet on each step. To stand from a sitting position, thirty-two (86 percent) of the patients did not need to use their upper extremities and four (11 percent) needed to use both upper extremities; one patient (3 percent) was unable to rise from a chair. The inability to rise from a chair was due to systemic rheumatoid arthritis with pain in the back, knees, and contrateral hip and not to pain in the treated hip. Twenty-nine (78 percent) of the patients reported no trouble picking up an object from the floor, five (14 percent) reported some difficulty, and three (8 percent) needed support to complete the task. Thirty-one (84 percent) of the patients reported no limitation with regard to the ability to carry an object, and six (16 percent) reported substantial limitation. These six patients were limited by problems with balance, back pain, or an arthritic joint and not by pain in the involved hip. The result of the total hip arthroplasty was considered to be satisfactory for all twenty-four patients managed with the bead-blasted component and for thirty-five (95 percent) of the thirty-seven managed with the grit-blasted component. One patient (one hip) with a grit-blasted component was dissatisfied because of a decreased range of motion compared with that of the contralateral hip as well as difficulty performing activities of daily living. The other patient (two hips) stated that he was dissatisfied because of continued trochanteric bursitis as well as a fear of recurrent dislocation. This was the only patient in the series who had recurrent dislocation following the total hip arthroplasty. He subsequently had an extended-lip acetabular liner inserted six months postoperatively, and he has had no additional complications since that time. All patients who had a bead-blasted component and thirty-five patients (forty-three hips) who had a grit-blasted component believed that their functional status had improved after the operation. The two patients with the grit-blasted component who did not believe that their functional status had improved stated that muscle strength was severely reduced on the side of the operation and that a limited range of motion affected their lifestyle. All patients in both study groups stated that the pain in the hip and the need for medication remained markedly reduced compared with their preoperative condition.
Complications In the group managed with the grit-blasted component, one hip that had recurrent dislocation was revised with an extended-lip acetabular liner six months postoperatively, as previously mentioned. Three additional hips had an isolated postoperative dislocation but did not need to be revised. Four hips (9 percent) had trochanteric nonunion without displacement, and two hips (4 percent) had trochanteric nonunion with displacement. Heterotopic ossification was present in seventeen hips (38 percent). It was class I in thirteen hips and class II in four1. All eight patients who were managed with a revision total hip arthroplasty had relief of pain, and none of them had a second revision.
The present study involved a consecutive, non-selected series of primary total hip replacements performed by one surgeon between January 1979 and June 1991 in patients who were less than fifty years old. Unlike many surgeons, the senior one of us (R. C. J.) fixed all femoral components with cement during this time-period. Many other surgeons tended to use cement for femoral fixation in older patients and inserted femoral components without cement in younger patients14,19,20. We consider the fact that we were able to evaluate a nonselected group of patients managed with primary total hip arthroplasty as a strength of the present study. The other strengths were that all of the prostheses were placed by one surgeon and the technique was uniform. The weaknesses of the study include its somewhat retrospective nature, the inherent problems with intraobserver and interobserver variability of radiographic measurements, and the difficulty involved in making reproducible standardized radiographs. Often, only anteroposterior radiographs were available to determine the grade of the cementing technique. Another potential weakness is the fact that the two treatment groups had different acetabular components inserted at the time of the index operation. However, the ingrowth acetabular components that were used with the grit-blasted femoral components showed no evidence of loosening, and none of them were revised. Therefore, we believe that the change in the acetabular component could not account for the increased rate of loosening of the grit-blasted femoral components. After a follow-up period that was three years shorter, the prevalence of revision because of aseptic loosening was threefold higher for the Iowa precoated grit-blasted femoral components than for the Iowa bead-blasted femoral components. The results achieved with use of the bead-blasted Iowa femoral components were slightly inferior to the sixteen to twenty-two-year (average, eighteen-year) results that the senior two of us had with use of Charnley flat-backed polished femoral components cemented with hand-packing techniques in patients less than fifty years old22. Other authors have also demonstrated excellent durability of cemented bead-blasted stems16,17. We believe that the present study demonstrates the potentially deleterious effects of increased surface roughness on the longevity of a cemented femoral component. Not only did the grit-blasted stems have an increased prevalence of loosening, but rapid osseous destruction occurred soon after the stem was noted to have debonded from the cement15. This mechanism of failure (initial loosening of the stem from the cement followed by osseous destruction with or without loosening between the bone and the cement) was found in association with both the bead-blasted and the grit-blasted femoral components (Figs. 2-A, 2-B, 2-C and 2-D, 4-A, and 4-B). Although a modular femoral head was used with only the last eight grit-blasted stems, only one of the eight was revised compared with seven of the thirty-seven monolithic femoral components. As the patients in both treatment groups were young and active, as the two prostheses were of the same design with regard to the stem geometry, offset, and material (cobalt-chromium), and as loosening was initially noted at the prosthesis-cement interface in both groups, we concluded that the difference in the prevalence of loosening was related to the difference in the surface finish.
This phenomenon of increased prevalences of loosening and osteolysis with increased surface roughness has also been demonstrated with other femoral components inserted with cement4,6,18. We hypothesized that a percentage of the cemented femoral components cannot stay bonded to the cement over the long term, even with the use of bond-enhancing surface finishes and other bond-enhancing materials (polymethylmethacrylate precoat). If the stem does debond from the cement, a component with a smooth surface finish (regardless of the geometry or offset of the component) that will not abrade the cement and produce fine particles of debris is probably preferable. These findings have led the senior ones of us to resume using femoral components with a polished surface finish similar to that of the Charnley device, which has worked well in their patients. Although it was not the focus of the present study, the Harris-Galante-I acetabular components inserted without cement also appeared to have increased durability, with less loosening and wear, compared with the metal-backed acetabular components inserted with cement in these active patients.
*One or more of the authors has received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this article. In addition, benefits have been or will be directed to a research fund, foundation, educational institution, or other nonprofit organization with which one or more of the authors is associated. Funds were received in total or partial support of the research or clinical study presented in this article. The funding source was National Institutes of Health Grant AR43314.
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