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© 1999 The Journal of Bone and Joint Surgery, Inc. Primary Hybrid Total Hip Replacement, Performed with Insertion of the Acetabular Component without Cement and a Precoat Femoral Component with Cement. An Average Ten-Year Follow-up Study*  , BOSTON, MASSACHUSETTSInvestigation performed at the Orthopaedic Biomechanics Laboratory and the Adult Reconstructive Service, Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston
One hundred and twenty-one primary hybrid total hip replacements were performed in 107 patients. A titanium, porous-coated, hemispherical acetabular component was fixed with screws, and a collared, chromium-cobalt femoral stem, with a roughened surface and a thin layer of methylmethacrylate on the proximal third, was inserted with contemporary cementing techniques (that is, use of a femoral medullary plug, a cement gun, and centrifugation and pressurization of the cement). Fifteen patients (fifteen hips) died before a minimum duration of follow-up of seven years, four patients (four hips) were too ill for a detailed follow-up examination at the time of the study, and two patients (two hips) refused to be evaluated at the time of the latest follow-up. None of these twenty-one hips had had a revision or a reoperation at the time of the latest follow-up. Eighty-six patients (100 hips) were available for clinical follow-up at an average of 120 months (range, eighty-four to 153 months) and for radiographic follow-up at an average of 118 months (range, eighty-four to 153 months). The average age of the patients at the time of the index arthroplasty was sixty-five years (range, forty-five to eighty-seven years). Three acetabular components were revised because of dissociation of the liner in association with a fracture of a locking tine. One well fixed acetabular component was revised because of pelvic osteolysis, and the femoral stem in the same patient was revised because of aseptic loosening. None of the ninety-six remaining acetabular components migrated, was classified as radiographically loose, or was revised because of aseptic loosening. Osteolytic lesions were identified adjacent to five acetabular components, and one of them was treated with bone-grafting around the well fixed acetabular shell. Two hips had a continuous radiolucent line at the interface between the acetabular implant and the bone. Three femoral stems had evidence of radiographic debonding (a radiolucent line that was one millimeter wide or less between the cement and the prosthesis), and they were classified as radiographically loose despite excellent clinical results. Seven hips had osteolytic areas located in the proximal aspect of the most proximal zones of Gruen et al., and five had small osteolytic regions in more distal areas. The Harris hip score for the eighty-two patients (ninety-six hips) who did not have a revision improved from 48 points (range, 22 to 70 points) preoperatively to 92 points (range, 53 to 100 points) at the most recent follow-up examination. Eighty-one patients had no, slight, or mild pain in the hip, and they were satisfied with the clinical result. In the present study, the hybrid total hip replacement with use of the Harris-Galante acetabular component and the Precoat femoral stem continued to provide an excellent result for most patients at an average of approximately ten years after the operation.
The hybrid total hip replacement7,15,16,26,31 combines insertion of an acetabular component without cement and a femoral component with cement. Fixation of the acetabular component without cement was developed in response to the problem of late loosening associated with cemented acetabular components9,32,37,38,42, which was not substantially alleviated by contemporary cementing techniques, such as pressurization and centrifugation. However, those techniques improved the durability of femoral components fixed with cement1,20-25. Thus, hybrid total hip replacement involves different, site-specific strategies for the fixation of the femoral component and the acetabular component in an effort to maximize the durability of fixation and the longevity of the implant15. Many reports on primary hybrid total hip replacement after short-term and intermediate-term follow-up have demonstrated excellent results2,11,22,31,34. Nevertheless, longer-term follow-up is essential to assess the longevity of fixation and the clinical performance of replacements inserted with this technique. In the present report of a prospective, consecutive series of 121 primary hybrid total hip replacements, we present the clinical and radiographic results, with emphasis on the 100 hips that were followed for a minimum of seven years (average duration of radiographic follow-up, 118 months; average duration of clinical follow-up, 120 months). Some of these patients were included in previous reports after a short duration of follow-up (average, 3.5 years)15 and after an intermediate duration of follow-up (average, 6.5 years)31.
One hundred and twenty-one consecutive primary hybrid total hip replacements were performed in 107 patients between January 1984 and December 1987 by the senior one of us (W. H. H.). Each arthroplasty was performed with insertion of a porous-coated acetabular component (Harris-Galante; Zimmer, Warsaw, Indiana) with screw fixation19 and a femoral component (Precoat; Zimmer) with use of contemporary cementing techniques (Figs. 1-A, 1-B, and 1-C). The Precoat femoral component is a modular, collared, chromium-cobalt stem that has a roughened surface and a thin (fifty-micrometer) layer of methylmethacrylate (Precoat) added to the surface on approximately the proximal one-third of the stem, below the collar. The initial Precoat stems had a surface roughness (Ra) of about thirty microinches that was generated by bead-blasting. Subsequently, the manufacturing process was changed to a grit-blasting technique, which produced a surface roughness of about sixty microinches. Hips that needed structural bone-grafting of the acetabulum or the use of a CDH Precoat femoral component (Zimmer) were excluded from the series. During this same time-period, total hip replacements without cement were also being performed, primarily in younger patients. Those results have been reported separately10,33,39.
Fifteen patients (fifteen hips) died before the minimum duration of follow-up of seven years. Four patients (four hips) were too ill to return for the latest follow-up evaluation of the study. Three of these patients were completely bedridden and, according to family members, had no pain in the hip, and one patient reported moderate intermittent pain in the hip. Two patients (two hips) refused to be evaluated at the time of the most recent follow-up. At the time of the latest follow-up examination, at an average of thirty-eight months (range, three to eighty-two months) postoperatively, all twenty-one hip replacements were well fixed without evidence of osteolysis and none of the hips had had a reoperation. The remaining eighty-six patients (100 hips), including fourteen patients who had had a bilateral total hip arthroplasty, were available for clinical and radiographic review after a minimum duration of follow-up of seven years and are the primary focus of the present study. The average duration of radiographic follow-up was 118 months (range, eighty-four to 153 months), and the average duration of clinical follow-up was 120 months (range, eighty-four to 153 months). Forty-two patients were men, and forty-four were women. The average age at the time of the index operation was sixty-five years (range, forty-five to eighty-seven years). The average weight of the patients was seventy kilograms (range, forty-eight to ninety-seven kilograms), and the average height was 170 centimeters (range, 147 to 188 centimeters). The diagnosis was osteoarthritis for seventy-four hips, congenital dislocation for eight, osteonecrosis for six, posttraumatic osteoarthritis for four, Paget disease for three, rheumatoid arthritis for three, and nonunion of the femoral neck for two. A posterolateral approach was used in all hips. Eleven hips had a trochanteric osteotomy in order to improve exposure (eight hips) or to optimize the tension in the abductor muscles (three hips). A titanium hemispherical HGP (Harris-Galante porous-coated) acetabular component (HGP-1 [eighty-five hips] or HGP-2 [fifteen hips]) with sintered titanium fiber-mesh at the implant-bone interface was used for all hips. The HGP-2 differs from the HGP-1 component by virtue of its thicker shell, the increased number of tines with its larger sizes, and the greater diameter of the cancellous-bone screws that are used with it (6.5 millimeters compared with 5.1 millimeters for the screws that are used with the HGP-1 component). The multiple screw-holes in the shell were used for screw fixation in all hips. The polyethylene liner was held in place with tines located around the mouth of the acetabular shell. In ninety-four hips, the acetabular bed was prepared with hemispherical reamers in the so-called line-to-line fashion; that is, the nominal outer diameter of the acetabular component was equal to the nominal outer diameter of the last reamer that was used. In the remaining six hips, the acetabular component was press-fit after underreaming of the acetabulum by two millimeters; that is, the nominal outer diameter of the acetabular component was two millimeters larger than the nominal outer diameter of the final reamer. An average of three screws (range, two to six screws) were used for fixation. No structural bone grafts were used, but autogenous bone from reaming was used for grafting at the site of acetabular cystic defects in forty-seven hips. The diameter of the prosthetic femoral head was twenty-six millimeters in sixty-six hips, twenty-eight millimeters in twenty hips, twenty-two millimeters in ten hips, and thirty-two millimeters in four hips. The femoral canal was broached to the appropriate size, and the medial portion of the femoral neck was prepared with the calcar planer. The femoral canal was occluded with a methylmethacrylate plug in all hips except one, which had insertion of a bone plug. Loose cancellous bone was removed from the medullary canal with a curet, and the canal was irrigated with a pulsatile lavage system. The canal was then dried and packed with a sponge that had been soaked in a dilute adrenaline solution. Simplex-P bone cement (Howmedica, Rutherford, New Jersey) was centrifuged to reduce porosity, and then it was injected in a retrograde fashion with a cement gun14. The cement was then pressurized with use of the cement gun and a proximal seal27. Care was taken to insert the femoral component in a central position, but proximal and distal centralizers were not used. All patients received warfarin as prophylaxis against deep-vein thrombosis. The Harris hip score13 was determined preoperatively and at the most recent follow-up examination in order to evaluate the function of the hip. All patients were followed prospectively. At the time of the latest follow-up, twenty-seven patients (thirty hips) were evaluated with a personal interview, a physical examination, and a review of the current radiographs. The remaining fifty-nine patients (seventy hips) were evaluated with use of a written questionnaire followed by a telephone interview and a review of the radiographs. An anteroposterior radiograph of the pelvis and hips, a frog-leg lateral radiograph, and a true lateral radiograph were made preoperatively and at each follow-up examination. In addition, seventy-one patients had a Judet radiograph of the pelvis, made at the latest follow-up examination. Preoperative, immediate postoperative, and all intermediate radiographs as well as those made at the latest follow-up visit were analyzed by a fully trained orthopaedic surgeon, other than the operating surgeon, who was skilled in total joint arthroplasty. The abduction angle of the acetabular component in relation to the interteardrop line was recorded. Acetabular coverage was estimated as the percentage of the shell covered with host bone as seen on the anteroposterior radiograph of the pelvis. The position of the acetabular component was determined by measurement of the vertical and horizontal locations of the center of that component as previously described29. The acetabular component was classified as migrated if there was a change of at least four millimeters in the horizontal or vertical position of the center of the component compared with that seen on the immediate postoperative anteroposterior radiograph of the pelvis29. The acetabular interface on the anteroposterior radiograph was divided into three zones as described by DeLee and Charnley8. Specific attention was directed toward the interface between the acetabular component and the host bone. Regions in which the surface of the acetabular component was not in contact with bone on the immediate postoperative radiographs were classified as gaps, to distinguish them from radiolucent lines that appeared on subsequent radiographs in areas where no gaps had existed initially30. The apparent thickness of the polyethylene was determined by comparing the shortest distance between the outer edge of the femoral head and the outer edge of the acetabular component as measured on the radiograph made at the latest follow-up examination with that measurement made in the same direction on the immediate postoperative radiograph, as previously reported17. All measurements were corrected for magnification. The annual average rate of polyethylene wear was determined by subtracting the polyethylene thickness measured on the radiographs made at the latest follow-up examination from that seen on the immediate postoperative radiographs, after correction for magnification, and dividing the value by the duration of follow-up (in years). Heterotopic ossification was graded according to the system of Brooker et al.4. The initial position (varus, valgus, or neutral) of the femoral stem was noted, and the presence or absence of contact between the collar of the prosthesis and the calcar of the femoral neck was determined from the immediate postoperative radiographs. Coverage of the calcar was defined as the percentage of the medial cortex of the femoral neck that was covered by the collar of the prosthesis. The cementing of the femoral stem was graded according to the method described by Barrack et al.1 and modified by Mulroy et al.25. Grade A indicated that the cement mantle had no voids, defects, or thin areas (areas that were less than one millimeter thick) in the diaphyseal region and no evidence of a radiolucent line between the cement and the femoral cortex (a so-called whiteout) (Fig. 1-C). Grade B indicated that there were no voids, defects, or thin areas in the cement mantle but there was a radiolucent line between the cement and the cortex in some portion of the diaphysis. Grade C1 indicated that the cement mantle had a void or an extensive radiolucent line (involving more than 50 percent of the interface) between the cement and the cortical bone. Grade C2 indicated that the cement mantle had a thin area or a defect. Grade D indicated that the cement mantle had gross deficiencies, including multiple defects or larger voids; was grossly inadequate; or did not extend at least ten millimeters distal to the tip of the prosthesis. It is important to note that all views of the femur from all sets of postoperative radiographs were used to assess thin areas (a C2 deformity) in the femoral cement mantle because, in some instances, the angle of projection of the image on a subsequent radiograph revealed a defect in the mantle that had not been seen on the immediate postoperative radiograph. Femoral osteolysis was defined as areas of endosteal, intracortical, or cancellous loss of bone that were scalloped or had the appearance of destruction of bone rather than disuse osteopenia. Also, a radiolucent zone that was linear but more than two millimeters wide was deemed to be osteolysis25. The dimensions and location of osteolytic lesions were recorded according to the zones of Gruen et al.12. Radiolucent lines at the bone-cement interface of the femoral component that were isolated to the proximal two centimeters of zones 1, 7, 8, and 14, that were parallel to the cement mantle, and that were less than two millimeters thick were not recorded as osteolytic lesions25. The femoral stem was considered to be loose if it had subsided or changed position, if it was associated with a fracture of the cement mantle, if there was a radiolucent line at its interface with the cement (debonding), or if the cement mantle itself had subsided. Any stem that had broken or bent was also considered to be loose. A Kaplan-Meier survivorship analysis18 was performed to assess the life span of the hybrid total hip replacement, the femoral component, and the acetabular component. All patients who had been lost to follow-up were included.
Four (4 percent) of the 100 hips (eighty-six patients) that were followed for an average of ten years subsequently had a revision. Four acetabular components and one femoral component were revised. One of the acetabular components, in a sixty-seven-year-old man who weighed ninety-one kilograms, was revised because of osteolysis. The patient exercised regularly, and we calculated that he walked 4.5 million cycles per year for six years postoperatively, which was approximately twenty-seven million cycles. Major pelvic osteolysis developed around the well fixed acetabular component, and the femoral stem became loose. Both components were revised at seventy-two months. The average rate of penetration by the twenty-eight-millimeter head into the polyethylene liner was calculated to be 0.4 millimeter per year. The volumetric wear measured 460 cubic millimeters, which was calculated to be a rate of seventy-seven cubic millimeters per year. This rate is within the annual range of volumetric wear of twelve to 284 cubic millimeters (average, ninety-four cubic millimeters) for twenty-two other retrieved acetabular components inserted without cement that we measured in a similar fashion17. The other three acetabular components that were revised, at forty-two, eighty-two, and 111 months postoperatively, had failed because of dissociation of the liner associated with fractures of the tines. These three acetabular shells were well fixed with excellent osseous ingrowth. All three components were HGP-1 sockets. The average Harris hip score for the ninety-six hips (eighty-two patients) that did not have a revision improved from 48 points (range, 22 to 70 points) preoperatively to 92 points (range, 53 to 100 points) at the latest follow-up examination. Seventy-five hips had an excellent result (90 to 100 points); nine, a good result (80 to 89 points); seven, a fair result (70 to 79 points); and five, a poor result (less than 70 points). The five patients who had a poor result had additional illness that contributed to the low Harris hip score. Two patients had severe degenerative disease of the lumbar spine, one had difficulties with balance and gait because of a systemic mitochondrial disease, one had severe hemiplegia after a stroke in addition to bilateral osteoarthritis of the knee, and one had a severe neuropathy secondary to adrenoleukodystrophy. Fifty-four patients (sixty-three hips) had no pain, and twenty-seven patients (thirty-two hips) had slight occasional pain or mild pain. One patient (one hip) had moderate pain in the region of the hip, which was thought to be the result of degenerative disease of the lumbar spine. Seventy patients could walk at least six blocks, and seventy-two patients had no limp or only a slight limp. Eighty-one of the eighty-two patients were satisfied with the result of the hip replacement. The average angle of abduction of the ninety-six acetabular components that were in place at the time of the latest follow-up was 35 degrees (range, 28 to 48 degrees). Ninety-four were anteverted, one was in a neutral position, and one was in retroversion. At least 90 percent of the acetabular component was covered with host bone in ninety-two hips, and at least 80 percent was covered in all ninety-six hips. There were no acetabular fractures. One of 264 acetabular screws broke. The average rate of polyethylene wear was 0.09 millimeter per year (range, zero to 0.41 millimeter per year). Four HGP-1 acetabular components had radiographic evidence of a broken tine without dissociation of the liner. In fifty-five hips, there were no gaps at the interface between the bone and the acetabular component on the immediate postoperative anteroposterior radiograph. Twenty-six of these hips had no radiolucent lines at the bone-implant interface on the anteroposterior radiograph made at the most recent follow-up examination, whereas twenty-nine had at least one radiolucent line. Two hips had a continuous 0.5-millimeter-wide radiolucent line. Forty-one hips had at least one gap, which was one millimeter wide or less in all but one hip, between the bone and the acetabular component on the initial anteroposterior postoperative radiograph. Thirty gaps persisted on the anteroposterior radiograph made at the latest follow-up examination, whereas twenty-one had resolved. During the thirteen-year span of this study, no acetabular component migrated, was classified as radiographically loose, or was revised because of aseptic loosening. Only two hips had a complete radiolucent line at the acetabular bone-implant interface. Anteroposterior radiographs made at the latest follow-up evaluation (available for all ninety-six hips) and Judet radiographs (available for seventy hips) revealed osteolytic lesions adjacent to the acetabular component in five hips. One lesion (ten by fifteen millimeters) was associated with an acetabular screw in zone 1 of DeLee and Charnley8, one (eight by twelve millimeters) involved only zone 2, and two lesions (seventeen by fifteen and nine by eleven millimeters) involved both zones 1 and 2. One hip had discontinuous osteolytic lesions in zones 1, 2, and 3, and it was treated with curettage and bone-grafting around the well fixed acetabular component, exchange of the acetabular liner, and exchange of the femoral head at 136 months. One femoral component, which had been inserted in a neutral position, was revised because of aseptic loosening. Of the remaining ninety-nine femoral components, fifty-seven had been inserted in a neutral position; thirty-two, in a valgus position; and ten, in a varus position. Contact between the collar of the prosthesis and the calcar was seen postoperatively in ninety-three of the ninety-nine hips, and this contact was maintained in seventy of the hips at the time of the latest follow-up. The cementing of the femoral component was grade A in six hips, grade B in twenty-six, grade C1 in thirty-seven, and grade C2 in thirty. No hip had grade-D cementing. The femoral component that was revised because of aseptic loosening had had grade-C1 cementing. Seven femora had areas of focal osteolysis located in the most proximal zones (zones 1, 7, 8, and 14). Two additional lesions (one by three millimeters and four by twenty-five millimeters) were located in zone 3; two (four by twenty-five millimeters and five by fifteen millimeters), in zone 13; and one (two by twenty millimeters), in zone 5. Three hips had a radiolucent line between the cement and the femoral stem that was less than one millimeter thick and, although these patients had no limp or pain and could walk an unlimited distance without support, the stems were considered to have debonded and were therefore classified as loose. One of these stems was associated with a fracture of the cement mantle. The cementing technique was grade C1 for one of these femoral stems and grade C2 for two. Heterotopic ossification was classified as grade 0 or 1 in seventy-one hips, grade 2 in twelve, grade 3 in thirteen, and grade 4 in four. The rate of mechanical failure leading to revision of the femoral stem was 1 percent (one) of 100 hips. Kaplan-Meier survivorship analysis18 with failure defined as revision of either the femoral component or the acetabular component, or both, revealed that the hybrid total hip replacement had a 96 percent chance of survival at 120 months (95 percent confidence interval, 0.93 to 0.98). The probability of survival with failure defined as revision of the acetabular component was also 96 percent at 120 months (95 percent confidence interval, 0.93 to 0.98), and that with failure defined as revision of the femoral component was 99 percent at 120 months (95 percent confidence interval, 0.97 to 1.0). All patients were screened for deep-vein thrombosis with venography before they were discharged. A deep-vein thrombus developed postoperatively in eight patients (8 percent). One patient had a nonfatal pulmonary embolus and one, a nonfatal myocardial infarction. One patient died within ninety days after the hybrid total hip replacement. This patient, an eighty-one-year-old man who had coronary artery disease and aortic stenosis, died on the fifty-eighth day because of bronchopneumonia, which was unrelated to the operation on the hip. The total hip replacement had been performed despite the severe cardiac condition because of marked, unrelenting pain secondary to a nonunion of a fracture of the femoral neck. Six patients had postoperative dislocations that were treated with closed reduction and temporary application of an abduction brace. Five of these patients had no additional dislocations. One patient had two additional dislocations during a ten-year span, but an additional operation was not necessary. Two patients had a trochanteric nonunion, which did not necessitate an operation. One patient had mild sciatic and femoral-nerve palsies that resolved. Another patient had a mild femoral-nerve palsy that resolved, and one patient had a femoral-nerve palsy that resolved except for a partial residual sensory deficit. Another patient had a urinary-tract infection postoperatively. There were no reoperations or readmissions to the hospital except for the four revisions, one of which included a bone-grafting procedure for the treatment of retroacetabular osteolysis, that were already described. There were no deep wound infections and no complications associated with the placement of the acetabular screws.
The average ten-year results in the present study continue to be very encouraging. In the entire group of 121 hips, four (3 percent) of the acetabular components and one (1 percent) of the femoral components were revised. For the ninety-six hips (eighty-two patients) that were not revised and that were followed clinically for an average of 120 months, the average Harris hip score improved from 48 points preoperatively to 92 points at the latest follow-up evaluation. Eighty-one patients had no, slight, or mild pain, and only one patient had moderate pain, which was most likely due to concurrent degenerative disease of the lumbar spine. The performance of the acetabular component was excellent in most patients; none of the components were revised because of aseptic loosening, and none were found to be radiographically loose. Only one femoral component was revised because of aseptic loosening. The optimum method for fixation of the acetabular component in primary total hip arthroplasty remains controversial. Late aseptic loosening of acetabular components inserted with cement has been well documented9,23,25,32,37,38,42. The prevalence of such loosening has not been substantially decreased by contemporary cementing techniques20,24,25, and acetabular loosening remains, in the opinion of several investigators, the major problem associated with total hip arthroplasty performed with cement. For example, Schulte et al.32 found that forty-three (13 percent) of 322 acetabular components were loose after an average duration of follow-up of fourteen years, and twenty-two (22 percent) of ninety-eight acetabular components in patients who were still living at twenty years were loose. In a series of 680 hips, García-Cimbrelo and Munuera9 reported that sixty-one acetabular cups that had been inserted with cement were loose after an average duration of follow-up of twelve years and eight months. According to survivorship analysis, the total cumulative probability of loosening at eighteen years postoperatively was 19 percent. After an average of 16.6 years of follow-up, Wroblewski42 found that thirty-six (31 percent) of 116 components had complete demarcation at the bone-cement interface and twenty-five (22 percent) cemented cups had migrated. Mulroy et al.25 reported that, in addition to a rate of revision because of aseptic loosening of 10 percent (eight) of eighty-one cups at fourteen years, 42 percent (twenty-eight) of sixty-seven acetabular components that had been in place for at least fourteen years were radiographically loose, for a total prevalence of loosening of 44 percent. In response to the problem of late loosening of acetabular components inserted with cement, acetabular devices that could be fixed without cement were developed. The clinical and radiographic results associated with different acetabular components inserted without cement have varied widely and appear to depend on the design features of the component. For example, acetabular implants inserted without cement have been associated with variable rates of pelvic osteolysis. Zicat et al.43, in a series of 137 hips, reported an 18 percent rate of pelvic osteolysis associated with the AML (anatomic medullary locking) acetabular cup (DePuy, Warsaw, Indiana) after an average duration of follow-up of 8.8 years, whereas Bono et al.3 reported a 38 percent rate of pelvic osteolysis at an average of 3.5 years after insertion of the AML+ acetabular component (DePuy) with the ACS (acetabular cup system) polyethylene liner (DePuy) in ninety-four hips. In contrast, Tompkins et al.40, in a recent evaluation of 173 HGP-1 acetabular components at seven to ten years, found a rate of pelvic osteolysis of only 4 percent. In the present series of hybrid primary total hip replacements, the performance of the HGP-1 and HGP-2 acetabular components, which had a conventional ultra-high molecular weight polyethylene liner that had been sterilized with gamma irradiation in air, was excellent in most patients. Six (6 percent) of the 100 acetabular components, which were followed radiographically for an average of 118 months or until revision, had an adjacent osteolytic lesion, and only two had a major lesion. Four of the 100 acetabular components were revised: three because of dissociation of the liner in association with fractures of the tines and one because of major retroacetabular osteolysis. In a subsequent version of the Harris-Galante porous-coated acetabular component, the liner-locking tines were replaced by a locking ring. The longevity and clinical performance of femoral components fixed with cement have improved as cementing techniques have been refined. Specifically, plugging of the femoral canal, preparation of the canal with curettage and irrigation, and retrograde injection of cement with a cement gun have resulted in excellent long-term performance of the femoral component20-25. Mulroy et al.25 reported on 162 bead-blasted femoral components inserted with so-called second-generation cementing techniques. At an average of fifteen years, only 2 percent of the femoral components had been revised because of aseptic loosening. Also, of ninety components that had been followed for at least fourteen years (average, fifteen years), only 2 percent had been revised because of aseptic loosening. An additional 7 percent had slight debonding but had not been revised. In addition, Madey et al.20 recently reported on a series of 356 Charnley total hip arthroplasties performed with these same so-called second-generation cementing techniques. The femoral component became loose in 3 percent of the 356 hips and in 5 percent of the 116 hips that had been followed for at least fifteen years. Centralization devices were not used for insertion of the femoral stems in the present series. Only one of the original 121 femoral components in the present study was revised, as already described. Three additional patients had debonding of the stem, but they were asymptomatic. The cementing in two of these patients was grade C2, which has been shown to significantly increase the risk of loosening of the femoral stem (p < 0.05)25. Mohler et al.23 directed attention to the possibility that the surface finish or the surface finish and the precoating on a femoral stem fixed with cement may contribute to loosening. In their study of 1941 hips in which an Iowa femoral component had been inserted with cement, 1.5 percent (twenty-nine hips) had loosening of the femoral component and those femora, which were in a subset of male patients who weighed an average of eighty-seven kilograms, had an increased rate of osteolysis during a ten-year period. By comparison, when two of the surgeons in that report23 used a smooth stem of a different design in an earlier series5,6,32, the rates of loosening and osteolysis were much lower. However, there were a number of other differences between the series, including the available neck lengths and head sizes, the design of the proximal and distal parts of the stem, the type of acetabular component, and possibly the offset of the stem. The results in the current study, in which only one of the 100 Precoat femoral components (in the patient whose daily exercise program resulted in approximately 4.5 million cycles per year) had been revised because of aseptic loosening after an average duration of clinical follow-up of 120 months, indicate that when precoated stems of the same design as that used in our study are well cemented, they will remain well fixed throughout the first decade after the operation. Similar results after a slightly shorter duration of follow-up have been reported by Goldberg et al.11, Berger et al.2, and Oishi et al.28. In a study of 161 hips that had a primary total hip arthroplasty with insertion of a bead-blasted (roughness [Ra], approximately thirty microinches), monoblock, chromium-cobalt femoral stem without precoating, Smith et al.35 reported that 7 percent of the femoral stems had been removed because of aseptic loosening and no others were radiographically loose at an average of eighteen years. Thus, in these two series, stems with a roughened surface performed well for an average of almost twenty years and those that were bead-blasted or grit-blasted and precoated performed well for an average of ten years. In a study of hybrid total hip arthroplasties with use of precoated stems, Trakru and Rubash41 found a high rate of failure because of defects in the cement mantle (grade-C2 cementing technique). Those authors and others37 have reported on the adverse effects of defects in the cement mantle. Trakru and Rubash clearly showed that centralization is an important factor even with contemporary cementing techniques as all of the failures in their series occurred in the hips that did not have centralization and none occurred in those with centralization. Their data also showed that, in some instances, precoating does not afford protection against loosening if there are defects in the cement mantle. Our results show that hybrid total hip arthroplasty with insertion of the Harris-Galante acetabular component without cement and the Precoat femoral component with cement is an effective strategy for primary total hip replacement in older 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 the William H. Harris Foundation.
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