A bed of sclerotic bone and osseous deficiencies in the superior and medial portions of the acetabulum often gradually develop after a cup arthroplasty. Such changes can compromise the fixation of an acetabular component that is inserted with cement in a subsequent total hip arthroplasty. The purpose of the present study was to determine the long-term outcome, after a minimum of ten years, of total hip arthroplasty with cement in patients who had had a previous cup arthroplasty.
*Although none of the authors have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this article, benefits have been or will be received but are directed solely to a research fund, foundation, educational institution, or other non-profit organization with which one or more of the authors are associated. No funds were received in support of this study.
†Department of Orthopaedic Surgery, University of Iowa College of Medicine, Iowa City, Iowa 52242. Please address requests for reprints to Dr. Callaghan.
‡Des Moines Orthopaedic Surgeons, 6001 Westown Parkway, West Des Moines, Iowa 50266.
Ninety-six cup arthroplasties in eighty-three patients were converted to total hip arthroplasties with cement by the senior one of us (R. C. J.) between July 1970 and August 1982 at the Iowa Methodist Medical Center in Des Moines, Iowa. A Charnley hip prosthesis, consisting of a stainless-steel polished stem with a 22.25-millimeter-diameter head (Charles F. Thackray, Leeds, England, or Zimmer, Warsaw, Indiana) and an all-polyethylene acetabular component with an outer diameter of forty or forty-four millimeters, was used in ninety-four hips. An Iowa prosthesis was used in one of the remaining hips, and a trapezoidal-28 prosthesis (Zimmer) was used in the other. Simplex-P cement (Northhill Plastics, Great Britain, or Howmedica, Rutherford, New Jersey) was used in all hips.
All of the operations were performed through a lateral approach with an osteotomy of the greater trochanter. A complete capsulectomy was done routinely. The acetabular component was placed as far medially and inferiorly as possible; a low hip center was achieved by filling any defect that remained after the previous cup arthroplasty with a cement mantle. No acetabular bone grafts were used. All loose cancellous bone was removed from the proximal end of the femur, and the cement was hand-packed, in the doughy phase into the acetabulum and, separately, into the femoral canal (until 1976). After 1976, a cement plug was placed in the distal aspect of the femoral canal and cement was delivered into the canal with an injection gun. The trochanter was reattached as far laterally as possible. The operation was performed in a standard (1950-vintage) operating room until 1976. No antibiotics were given systemically and no body-exhaust systems were used until 1980.
Postoperatively, the extremity on the side of the operation was placed in balanced suspension for four to seven days. The patients walked with crutches for six weeks after discharge from the hospital and then used a cane for an additional two to six months, until they could walk well without support. Preoperatively, all patients were evaluated with regard to pain, gait, level of activity, range of motion of the hip, and ability to perform activities of daily living. Most patients were followed at regular time-intervals (yearly initially and then every two to three years).
We attempted to contact all eighty-three patients or their families. The surviving patients were asked to return for clinical and radiographic evaluation; those who were unable to return were asked to send current radiographs. All living patients were evaluated clinically in person or by telephone with use of the standard system of terminology for reporting results described previously12. Family members of patients who had died were interviewed to determine the patient's level of function at the time of death. At the time of the most recent follow-up, fifty patients (fifty-eight hips) were alive and twenty-nine (thirty-three hips) had died. Four patients (five hips) were lost to follow-up, but two of the hips in these patients had been followed clinically and radiographically for at least ten years. Thus, the status of ninety-one (95 per cent) of the original ninety-six hips was known at the time of the most recent follow-up.
The present study includes only those hips that were followed for a minimum of ten years (or to failure after a shorter interval), except for the purpose of survivorship analysis, which includes all of the hips. Sixteen men (sixteen hips) and thirty-four women (forty-two hips) were followed clinically and radiographically for a minimum of ten years or to failure. The average age of the patients was forty-six years (range, fifteen to sixty-six years) at the time of the cup arthroplasty and fifty-eight years (range, thirty-two to seventy-four years) at the time of the total hip arthroplasty.
The diagnosis before the cup arthroplasty was osteoarthrosis in twenty-three hips, degenerative osteoarthrosis secondary to congenital dysplasia of the hip in twenty hips, slipped capital femoral epiphysis in three, degenerative osteoarthrosis secondary to previous fracture-dislocation in three, ankylosing spondylitis in two, childhood septic arthritis in two, rheumatoid arthritis in two, new fracture in two, and aseptic necrosis secondary to fracture in one. The diagnosis before the total hip arthroplasty was pain at the site of the cup arthroplasty in fifty-seven hips and stiffness of one hip (without pain) secondary to ankylosing spondylitis.
An operation had been performed before the cup arthroplasty in twelve (21 per cent) of the fifty-eight hips. Two of these hips had had more than one procedure: one had been treated with Smith-Petersen nailing and a subsequent varus osteotomy, and the other, with pinning of a slipped capital femoral epiphysis and subsequent removal of the pins. The other previous procedures included Shantz osteotomy for congenital dislocation of the hip, bone-grafting for a cyst of the femoral head, open reduction for congenital dislocation of the hip, soft-tissue release, proximal femoral osteotomy for a slipped capital femoral epiphysis, subtrochanteric osteotomy for septic arthritis, insertion of an Austin Moore prosthesis, open reduction of an acetabular fracture, placement of an unspecified prosthesis, and one other unspecified procedure. The cup arthroplasties had lasted an average of eleven years (range, one to thirty-nine years).
Radiographic Evaluation
Observations and measurements were made on anteroposterior radiographs of the pelvis that had been made for all patients in the early postoperative period and at the time of the most recent examination. In addition, interval radiographs were used to determine when various radiographic changes had occurred. Correction for magnification was performed with use of a template with measured concentric circles: the known size of the femoral head of the implant was compared with that measured on the radiograph. No lateral femoral or Judet acetabular radiographs were used; this is a possible limitation of the study.
Preoperative radiographs were used to evaluate the acetabular deficiencies that were present at the time of the index total hip arthroplasty. The deficiencies were assessed according to the criteria described by The American Academy of Orthopaedic Surgeons Committee on the Hip3. Radiographs that were made immediately after the operation were used to determine the cementing technique on the femoral side according to the criteria proposed by Barrack et al. In addition, the amount of cement that had been used to fill any deficiencies in the superior and medial portions of the acetabulum was recorded in centimeters.
Loosening of the femoral component was defined according to the criteria described by Harris et al.8,9,19. Definite loosening was defined as subsidence of the femoral component, a fracture of the cement or stem, or a radiolucent line between the stem and the cement that had not been present on the radiograph made immediately after the operation. (This final criterion was modified so that a progressive radiolucent line of more than one millimeter between the stem and the cement was considered to indicate definite loosening.) Probable loosening was defined as a continuous radiolucent line along the entire bone-cement interface, and possible loosening, as a radiolucent line at the bone-cement interface that encompassed more than 50 but less than 100 per cent of the circumference of the stem on at least one radiograph.
Subsidence of the femoral component was determined with the method of Loudon and Charnley. A vertical line that was drawn through two measured mid-points on the distal (straight) part of the stem defined the central axis of the stem. Lines were drawn perpendicular to this axis, at the distal tip of the stem and at the point where the trochanteric wire passed through the lateral femoral cortex. The distance between these two horizontal lines was measured on the initial postoperative and most recent follow-up radiographs. Subsidence was defined as a difference in the measured values (after correction for magnification) of more than five millimeters, a fracture of the cement, or a radiolucent line of more than one millimeter at the superolateral cement-prosthesis interface.
Migration of the acetabular component was evaluated according to the criteria of Massin et al. On each radiograph, the vertical distance between the center of the cup and the line joining the two teardrops was measured. The horizontal distance between the center of the cup and a vertical line drawn through the teardrop also was measured. A variation of these distances of more than five millimeters between the early postoperative and most recent follow-up radiographs, or any crack in the cement mantle around the prosthesis, was defined as migration of the acetabular component. Definite loosening of the acetabular component was defined as migration of that component or the presence of any new fracture of the cement mantle; probable loosening, as a complete circumferential radiolucent line at the bone-cement interface; and possible loosening, as a radiolucent line that encompassed 50 to 99 per cent of the bone-cement interface10,19.
Wear of the acetabular component was determined with the technique of Livermore et al. The rate of linear wear was determined by measuring, on the most recent follow-up and initial postoperative radiographs, the thickness of the acetabular cup along the shortest line from the center of the femoral head to the acetabular cup-cement interface. The thickness of the cup was measured with a caliper to an accuracy of 0.025 millimeter. The difference between the measured values, after correction for magnification, determined the distance of linear migration of the femoral head.
Any cystic-appearing loss of bone in the periacetabular region was recorded, as was any localized loss of endosteal cortex of the femur. The position of the stem was recorded as varus, valgus, or neutral on each radiograph, by extension of the previously described line along the central axis of the stem distally; it then could be determined whether this line was parallel to (neutral), divergent from (valgus), or convergent toward (varus) a line drawn along the endosteal lateral cortex distally. Heterotopic ossification, when present, was graded with the method of Brooker et al.
Radiolucent lines at the bone-cement interface were recorded in the three acetabular zones of DeLee and Charnley and the seven femoral zones of Gruen et al.
Statistical Analysis
Clinical and radiographic findings were analyzed with the Fisher exact test when both variables were categorical and with the Wilcoxon rank-sum method when one variable was continuous. Kaplan-Meier survivorship curves, with corresponding confidence intervals, were calculated with failure defined according to one of three end points: revision or resection of all or part of the original prosthesis; aseptic loosening of the acetabular component necessitating revision; and radiographic evidence of definite or probable loosening of the acetabular component, or aseptic loosening of the acetabular component necessitating revision5,6. The log-rank test was used to compare survivorship curves.
Clinical Results
Fifty-eight hips (nine of which were revised for aseptic loosening of the acetabular component) were followed clinically and radiographically for a minimum of ten years (or to failure after a shorter interval). A deep infection developed in eight other hips at an average of four years (range, eight months to seven years) after the index total hip arthroplasty.
Before the total hip arthroplasty, there had been no pain in one hip, mild pain in eight, moderate pain in thirty-three, and severe pain in sixteen. At the time of the most recent examination, there was no pain in thirty-six hips; slight, occasional pain in seventeen; and moderate pain that necessitated modification of activities in five. No patient had severe pain with important functional limitation.
Before the total hip arthroplasty, eleven hips had been in patients who could perform light labor; thirty-five, in those who could perform light housework; and twelve, in those whose activity was minimum. No patient was bedridden. At the time of the most recent follow-up evaluation, thirty-two hips were in patients who could perform at least light labor on a regular basis; twenty-five, in patients who were semi-sedentary; and one, in a patient who was bedridden.
Before the total hip arthroplasty, seventeen hips were in patients who were able to walk without support; thirteen, in those who used a cane; eight, in those who used two canes; and twenty, in those who used two crutches. At the time of the most recent follow-up examination, thirty hips were in patients who were able to walk without support; thirteen, in those who walked with a cane part-time; fourteen, in those who walked with an aid full-time; and one, in one who was unable to walk. Only eleven patients (eleven hips) needed a walking aid solely because of the hip. Twenty-four hips were in patients who were able to walk without limitation; ten, in those who could walk for thirty to sixty minutes; ten, in those who could walk for ten to less than thirty minutes; eight, in those who could walk for two to less than ten minutes; and five, in those who could walk for less than two minutes. As mentioned, one patient (one hip) was unable to walk.
At the time of the most recent follow-up evaluation, forty-five hips were in patients who were able to maintain their own home; nine, in those who lived in their own home with assistance; and four, in those who needed someone to care for them full-time. The result of the total hip arthroplasty was considered by the patient to be satisfactory for fifty-six (97 per cent) of the fifty-eight hips. One patient, who had ankylosing spondylitis, was dissatisfied because of the limited range of motion of the hip. Another patient, who had been satisfied with the original procedure for many years, was dissatisfied with the revision (which had been performed for painful aseptic loosening of the acetabular component) because it had decreased the pain but had not increased the function of the hip. Two additional patients were dissatisfied: one, after removal of the total hip prosthesis because of a deep infection, and the other, after direct-exchange total hip arthroplasty because of a deep infection.
Survival of the Original Prosthesis
At the time of the most recent follow-up of the fifty-eight hips that were followed clinically and radiographically for a minimum of ten years or until failure, nine hips (16 per cent) had been revised because of aseptic loosening of the acetabular component and one (2 per cent) had been revised because of a traumatic fracture of the femoral shaft. No hip had been revised because of loosening of the femoral component. In addition to the fifty-eight hips in which a postoperative infection did not develop, eight (8 per cent) of the original ninety-six hips had septic loosening. Five of these eight hips eventually had a resection arthroplasty; two, a one-stage reimplantation arthroplasty; and one, a two-stage reimplantation arthroplasty. As previously stated, no antibiotics were given prophylactically at the time of the initial hip replacement until 1980.
Aseptic loosening of the acetabular component necessitating revision was significantly more likely to develop in a patient who was less than fifty years old at the time of the conversion of the cup arthroplasty to a total hip arthroplasty (p = 0.01, Fisher exact test), but this complication was not related to the sex of the patient (p = 0.19, Fisher exact test) or to the reported level of activity of the patient (p = 0.76, Wilcoxon rank-sum test).
Radiographic Results
The acetabular deficiencies that were present at the time of the index total hip replacement were classified as superior segmental in thirty-four hips, combined superior segmental and medial cavitary in six, combined superior cavitary and medial cavitary in four, and medial cavitary in one3. Thirteen hips had no acetabular deficiency. In sixteen hips, less than one centimeter of cement was needed to fill the acetabular deficiency proximal to the superolateral corner of the acetabular component; in sixteen, one to less than two centimeters was needed; in twelve, two to less than three centimeters was needed; and in fourteen, three centimeters or more was needed. The femoral cement mantle was classified as grade A in nineteen hips, as grade B in twenty-nine, and as grade C in ten1.
Wear of the acetabular component was measured in the forty-nine hips for which detailed radiographs were available. (Hips that had been revised because of aseptic loosening were excluded.) The average amount of linear wear was 0.057 millimeter per year (range, 0.000 to 0.225 millimeter per year). Femoral osteolysis in zone 7 of Gruen et al. (the medial side of the femoral neck) occurred in twenty-three hips. The rate of wear of the acetabular component was not related to the presence of osteolysis in zone 7 (p = 0.49, Wilcoxon rank-sum test) or to radiographic loosening of the acetabular component (p = 0.80, Wilcoxon rank-sum test). Femoral osteolysis was uncommon in zones 1 through 6; only one hip had such osteolysis. A radiolucent line at the cement-prosthesis interface (so-called debonding) occurred in zone 1 in fourteen hips.
As assessed in the fifty-eight hips according to the modified criteria of Harris et al.8,9,19, and including components that were revised because of aseptic loosening, there was definite loosening of eighteen acetabular components (31 per cent) and one femoral component (2 per cent), probable loosening of two acetabular components (3 per cent) and no femoral components, and possible loosening of eleven acetabular components (19 per cent) and two femoral components (3 per cent). The need for revision of the acetabular component was not significantly greater in hips in which there had been an acetabular deficiency at the time of the index total hip arthroplasty (p > 0.10). In addition, there was no significant association between the amount of cement needed to fill the acetabular deficiency and the need for revision of the acetabular component (p = 0.49) or the radiographic appearance of loosening of the acetabular component (p = 0.08).
Heterotopic ossification was present in eighteen hips; it was grade 1 in ten, grade 2 in two, grade 3 in three, and grade 4 in three2.
Survivorship Analysis
The Kaplan-Meier method was used to calculate the probability of survival of the original prosthesis from the time of the initial total hip arthroplasty to one of three end points: revision or resection of all or part of the original prosthesis (including hips in which an infection developed); aseptic loosening of the acetabular component necessitating revision (not including hips in which an infection developed); and radiographic evidence of definite or probable loosening of the acetabular component, or aseptic loosening of the acetabular component necessitating revision (not including hips in which an infection developed) (Figs. 1-A, 1-B, and 1-C)
The survivorship curves after total hip replacement for a failed cup arthroplasty were compared with those after Charnley primary total hip replacement as reported by two of us (R. C. J. and J. J. C.) and colleagues20. For all three end points, the rate of survival after revision of a cup arthroplasty was significantly lower. With revision for any reason as the end point, the average probability (with 95 per cent confidence interval) of survival of the prosthesis was 92 ± 6 per cent at ten years and 74 ± 12 per cent at twenty years (p = 0.004, log-rank test) (Fig. 1-A). With aseptic loosening of the acetabular component necessitating revision as the end point, the probability of survival was 84 ± 10 per cent at twenty years; no acetabular component was revised for aseptic loosening in the first ten years (p = 0.07, log-rank test) (Fig. 1-B). With definite or probable loosening of the acetabular component, or aseptic loosening of the acetabular component necessitating revision, as the end point, the probability of survival was 91 ± 6 per cent at ten years and 53 ± 22 per cent at twenty years (p = 0.005, log-rank test) (Fig. 1-C).
We found little published information about the results of total hip arthroplasty after cup arthroplasty. Llinas et al. reported that loosening of the acetabular component occurred more frequently when a cup arthroplasty had been converted to a total hip replacement; the average duration of follow-up in that study was eight years.
The rate of loosening of the femoral component in the present study (2 per cent; one of fifty-eight hips) was lower than that in the previous twenty-year study of Charnley primary total hip arthroplasties (6 per cent; twenty of 319 hips)20; this finding possibly is related to the use of improved cementing techniques in patients who entered the present study beginning in the late 1970's. The rate of radiographic loosening of the acetabular component in the present study (34 per cent; twenty of fifty-eight hips) was significantly higher than that in the previous study (13 per cent; forty-three of 319 hips)20 (p = 0.005), but the rate of revision because of aseptic loosening of the acetabular component in the present study (16 per cent; nine of fifty-eight hips) was not significantly different from that in the previous study (6 per cent; eighteen of 319 hips)20 (p = 0.07). Loosening of the acetabular component probably was minimized by the inferomedial placement of the component (which lowers hip-joint-reaction forces11) and by the use of cement rather than bone graft to fill the large defect in the superior aspect of the acetabulum (which eliminates the risk of failure of the acetabular component due to resorption of the bone graft) (Figs. 2-A, 2-B, and 2-C). The prevalence of pain in the present study (in which thirty-six [62 per cent] of the fifty-eight hips caused no pain) was higher than that in the study of Charnley primary total hip arthroplasties (in which eighty-four [86 per cent] of ninety-eight hips caused no pain)20. This finding is consistent with the history of trauma and soft-tissue damage associated with multiple operations. The rate of infection in the present series (8 per cent; eight of ninety-six hips) was markedly higher than that in the study of Charnley primary total hip arthroplasties (2 per cent; eight of 322 hips)20 and other series (1 per cent; four of 333 hips)13, probably because of the previous operations, the 1950's-vintage operating room used for many of the procedures, and the fact that no antibiotics were used until 1980.
The present study demonstrates that the use of bulk cement—rather than bulk autogenous graft—to fill deficient areas in the superior weight-bearing aspect of the acetabulum can provide durable fixation (Figs. 2-A, 2-B, and 2-C). The study also demonstrates the long-term durability that can be achieved with insertion of a femoral component with cement when an adequate cement mantle is obtained. The results of the present study may be relevant in the reconsideration of the use of cup arthroplasty or its modifications for the treatment of certain conditions, especially in younger patients, in view of problems of loosening due to osteolysis secondary to polyethylene debris14.