The Journal of Arthroplasty

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1 The Journal of Arthroplasty 29 (2014) Contents lists available at ScienceDirect The Journal of Arthroplasty journal homepage: The 27 to 29-Year Outcomes of the PCA Total Hip Arthroplasty in Patients Younger Than 50 Years Old Young-Hoo Kim, MD, Jang-Won Park, MD, Jeong-Soo Park, MD The Joint Replacement Center Ewha Womans University School of Medicine, Seoul, Republic of Korea article info abstract Article history: Received 14 January 2014 Accepted 6 February 2014 Keywords: long-term outcomes PCA total hip arthroplasty young patients We previously reported our six and 19.4-year results of arthroplasty with the PCA total hip prosthesis. We now report on the performance of this prosthesis at years. Eighty-eight consecutive primary THAs using a PCA total hip system were performed in 70 patients (mean age, 45.6 ± 11.1 years). The mean followup was 28.4 years (27 29). The mean Harris hip score was 89 points at final follow-up. Thigh pain was reported in 22 hips (25%). The mean annual polyethylene wear was ± 0.03 mm. There were 75 acetabular (85%) and 40 femoral (45%) osteolysis. The rate of survival after 28.4 years as the end point of revision was 66% for the acetabular component and 90% for the femoral component Elsevier Inc. All rights reserved. Mechanical failure due to aseptic loosening is the most common long-term complication of total hip arthroplasty (THA) with cement [1 5] andis the mostcommonindicationforsurgery [6]. One strategy for avoiding such loosening is the use of porous-coated implants that are designed to achieve stable biological fixation without cement. Few mid-term studies of so-called first-generation cementless hip prostheses have been reported [7 10]. The results associated with these first-generation stems have been mixed. One first-generation cementless total hip prosthesis, the porous-coated anatomic hip prosthesis (PCA; Howmedica, Rutherford, New Jersey) was extensively investigated in the early 1980s, and 15-year, 19.4-year, and 23-year results have been reported [11 14]. Mid-term results of PCA total hip arthroplasty clearly confirmed that polyethylene wear and periacetabular osteolysis, and thigh pain were major problems [11 14]. However, there is no reported longer than 25 years results of PCA femoral stem, to our knowledge. Although the PCA total hip prosthesis has not been used for three decades, study of the long-term data may establish principles which could be applied to modern implants. The purpose of this study was to assess: (1) the clinical outcomes; (2) mechanical fixation of the PCA prosthesis; (3) polyethylene wear and osteolysis; and (4) the survival rates of the components after an average of 28.4 years, in a consecutive series of patients treated with a first generation, PCA cementless total hip prosthesis. The Conflict of Interest statement associated with this article can be found at dx.doi.org/ /j.arth Reprint requests: Young-Hoo Kim, MD, The Joint Replacement Center Ewha Womans University MokDong Hospital, 911 1, MokDong, YangChun-Ku, Seoul, Republic of Korea ( ). Materials and Methods Between January 1984 and January 1986, 108 PCA hip prostheses were implanted in 88 consecutive patients who were younger than 50 years of age by one surgeon. We followed-up every patient and their clinical and radiographic data were stored in the computer. The data were analyzed retrospectively. The current study of which the latter included postoperative computed tomographic (CT) evaluation was approved by our institutional review board, and all patients gave informed consent. Nine patients (10 hips) died of unrelated causes before 10 years elapsed after the operation. All had well-functioning THAs until they died. Nine patients (10 hips) were lost to follow-up before 10 years after the operation. All of these patients had well functioning THAs until they were lost to follow-up. The remaining 70 patients (88 hips) were included in the study. All had radiography at a minimum of 27 years after operation. The average age at the time of the arthroplasty was ± 11.1 years (range, years). Eighteen patients underwent staged bilateral THA (from 2 to 3 weeks apart). The primary diagnosis was osteonecrosis of the femoral head in 24 hips (27%), developmental dysplastic hips in 17 (19%), osteoarthritis secondary to childhood septic arthritis in 15 (17%), osteoarthritis secondary to childhood tuberculous arthritis in 13 (15%), osteoarthritis in 12 (14%), posttraumatic arthritis in 4 (5%), and rheumatoid arthritis in 3 (3%). Table 1 gives details of the components used in 88 PCA hips. The mean duration of follow-up was 28.4 years (range, years). Clinical Evaluation Clinical and radiographic evaluation was performed preoperatively and postoperatively at three months, one year, and annually thereafter. Clinical evaluation was performed by two observers (SML / 2014 Elsevier Inc. All rights reserved.

2 Y.-H. Kim et al. / The Journal of Arthroplasty 29 (2014) Table 1 Components Used in PCA Total Hip Arthroplasties. Femoral Stem and JWP) who were not involved in the operation. Clinical evaluation determined the Harris hip score [15]. The chance corrected kappa coefficient, which was calculated to determine interobserver agreement of Harris hip score was 0.91 and 0.95, indicating excellent reproducibility. A result was considered excellent when the Harris hip score was between 90 and 100 points, good when it was between 80 and 89 points, fair when it was between 70 and 79 points, and poor when it was b70 points. The patients were questioned about thigh pain, and its severity was graded using a ten-point visual analog scale with 0 indicating no pain and 10 severe pain [9]. The postoperative level of activity was assessed using the University of California, Los Angeles (UCLA) score [16]. Radiographic Evaluation Acetabular Component a Size Number Size (mm) Number a Inner diameter 32 mm in all. Standard radiographs included an anteroposterior view of the pelvis and anteroposterior and cross-table lateral views of the proximal part of the femur. Two observers (SML and JWP) who had not been involved in the operation evaluated all radiographs. The isthmus ratio as described by Dorr [17] was assessed on preoperative radiographs and the bone type was classified into type A, B and C. The chance corrected kappa coefficient, which was calculated to determine interobserver agreement of radiographic findings, including subsidence of the component, remodeling of the femur, interfacial radiolucencies, polyethylene wear, osteolysis and component loosening was 0.86 and 0.91, indicating excellent reproducibility. The 3- month postoperative radiograph served as the baseline for identifying subsequent subsidence, remodeling of the femur, interfacial radiolucencies, osteolysis, and component loosening. The radiographs were analyzed for stability of the femoral components. They were classified as osseointegrated, fibrous, or unstable [18]. Components that showed spot welds were considered osseointegrated. On the anteroposterior [19] and lateral [20] radiographs, the femoral component was divided into seven zones. Radiolucencies wider than 1 mm at the boneprosthesis interface was recorded. The measurement of the ratio of the width of the femoral component to that of the femoral canal in the coronal and sagittal plane was performed as described by Kim and Kim [9]. Definite loosening of the acetabular component was defined as a change of angle, vertical or horizontal migration exceeding 2 mm or a continuous radiolucent line wider than 2 mm on both the anteroposterior and the lateral radiographs [9]. Vertical migration was measured between the inferior margin of the cup and the inferior margin of the ipsilateral teardrop and horizontal migration between Köhler s line and the center of the outer shell of the acetabular component [5]. Definite loosening of the femoral component was defined as progressive axial subsidence exceeding 3 mm or varus or valgus migration [21] and possible loosening when a complete radiolucent line surrounded the entire porous-coated surface on both the anteroposterior and lateral radiographs [21]. Osteolysis was recorded in acetabular and femoral zones [19,22]. The extent of osteolysis was estimated by multiplying the longest diameter (cm) by a second diameter perpendicular to the first [13]. We classified the periacetabular osteolytic lesions as small (b1 cm in diameter), large ( 1 cm in diameter), or combined (two or more lesions) in different size categories. We also categorized the lesions according to their location (peripheral, retroacetabular, or ischial). Polyethylene Wear Penetration of the polyethylene liner was measured at 3 months and the final follow-up with Auto CAD 2013 (Auto desk, Sam Rafael, California) by two observers blinded to the clinical results [23]. The observers made three measurements on each radiograph, and the interobserver error was assessed. A ScanMaker 9600XL flatbed scanner (Microtek, Carlson, California) digitized the anteroposterior radiograph of the pelvis as 2-dimensional gray-scale arrays of 12-bit (256-gray level) integers. The scanning resolution was 600 pixels per square inch (PSI). Penetration of the head into the liner was determined annually from anteroposterior radiographs. The amount of penetration on radiographs made 3 months postoperatively was considered the zero position. Osteolysis Computed tomographic (CT) evaluation of osteolysis was performed at the final follow-up. Radiographic evaluation of osteolysis is an indirect measure, therefore the current methodology is insensitive and subject to operator error. A more sensitive CT image set provides 3-dimensional data, but the beam-hardening artifacts from the prosthesis itself make these images difficult to interpret and use. We developed an algorithm to address the beam-hardening artifacts as well as to measure the volume of osteolytic lesions. This algorithm was similar to the previous techniques [24 26]. We then developed a segmentation algorithm to segment the osteolytic lesions from image data and to measure their volumes. CT images were acquired with use of a Siemens scanner (Munich, Germany) with 1-mm collimation, a pitch of 1.5 and a 14 to 22-cm field of view. The raw data were reconstructed for 1-mm slices. The area within 5 cm of the prosthesisbone interface in all directions was evaluated. The volume of osteolysis was calculated with use of a quantitative imaging system (Muscular Skeleton Analysis Software, Virtual Scopics, Rochester, New York). CT images were acquired for all patients at an average follow-up of 28.4 years (range, years). Heterotopic ossification, if present, was graded according to the classification of Brooker et al [27]. Statistical Analysis Survivorship analysis was performed with use of the Kaplan-Meier method [28], with revision for any reason as one end point. We determined differences in continuous variances (Harris hip score and range of motion) between preoperative and postoperative results with use of a Student paired t test, and differences in categorical variances (details of functional evaluation and deformity according to the Harris hip score) and limb length between preoperative and postoperative evaluation with use of a chi-square test. Univariate regression analysis was used to evaluate the relationship, if any, between osteolysis and the variables of age, sex, weight, diagnosis, duration of follow-up, and acetabular inclination and anteversion. Multivariate regression analysis was used to determine the effect, if any, of multiple covariates on revision status (dependent variable). The level of significance was set at P b Results Clinical Results The average Harris hip score increased from 39 ± 14.8 points (range, points) before surgery to 96 ± 3.8 points (range, points) at one year after surgery, 93 ± 6.5 points (range,

3 2258 Y.-H. Kim et al. / The Journal of Arthroplasty 29 (2014) Table 2 Clinical Hip Ratings Showing the Harris Hip Score (Range) and the Distribution of the Score, by Number Percentage of Hips, and Before, and at Two, Ten, Twenty and 28.4 Years After Operation. Follow-Up Interval (Years) Number of Hips Harris Hip Score (Points) Excellent ( Points) Good (80 89 Points) Fair (70 79 Points) Poor (b70 Points) Preoperative (11 56) (85 100) (85 100) (75 100) (45 100) (30 100) points) at 10 years, 89 ± 11.1 points (range, points) at 20 years and 86 ± 13.9 points (range, points) at 28.4 years (Table 2). After 28.4 years, mild thigh pain (visual analog scale, 1 3 points) after vigorous activity was present in 14 hips (16%) since early postoperative period and severe late onset of thigh pain (visual analog scale, 8 10) in 8 (9%). Eight patients with severe thigh pain had aseptic loosening of the femoral component. Preoperative UCLA activity score was missing. The authors were not aware of the UCLA activity score about 30 years ago. The mean UCLA activity score for the patients was 7.9 points (range, 5 10 points) at the time of the latest follow-up. Radiological Findings The Dorr bone type was A in 77 of 88 hips (88%), type B in 7 (8%), and type C in 4 (4%). Eight femoral components (9%) had subsided and these components were undersized. At the most recent follow-up examination, at 28.4 years, the 80 femoral components had osseous growth into the proximal porous surfaces, as seen on anteroposterior and lateral radiographs, without subsidence or additional varus shift (Fig. 1). Eighty of the 88 hips (80%) had radiolucency in at least one zone of the nonporous surface of the femoral component. All radiolucencies were b1 mm in width and were not progressive. Polyethylene Wear and Osteolysis Survivorship of the implants yields results for the end-point criteria for any revision. The mean linear wear rate of the polyethylene liner was 5.16 ± 0.75 mm. The mean annual rate of linear wear of the polyethylene liner was ± 0.03 mm. Radiographs and CT scans demonstrated that 75 acetabular (85%) and 40 femoral (45%) osteolysis were detected at the time of the last follow-up. Twenty-eight (37%) acetabular osteolytic lesions were large ( 1 cm in diameter) and the remaining 47 (53%) were small (b1 cm). Twenty-eight (37%) were retroacetabular and ischial osteolysis and 47 (53%) were peripheral osteolytic lesions (Fig. 2A C). The mean acetabular osteolytic lesion volume on CT was 22.1 ± 23.1 cm 3 (standard deviation) (range, cm 3 ). There were new cases of acetabular osteolysis in 27 hips (31%) between 10 and 28.4 years. Femoral osteolysis was observed in 40 hips (45%). Femoral osteolysis was confined in zones 1 and 7 of femur in 31 hips (35%) and the remaining 9 hips (10%) had proximal and distal femoral osteolysis (Fig. 2A C). Wear of polyethylene liner and osteolysis were associated with age under 30 years (Student s t-test, P = ), male gender (chi-squared test, P = 0.031), and acetabular components with an inclination angle of more than 50 (Student s t-test, P = 0.003). Polyethylene wear and osteolysis were not associated with diagnosis (chi-squared test, P = 0.231), weight (Student s t-test, P = 0.235), hip score (Student s t-test, P = 0.16), range of motion (Student s t-test, P = 0.393) or acetabular anteversion (Student s t-test,p =0.298). Revision Rate Fig. 1. Radiographic evaluation of the left hip of 29-year-old man with childhood hip sepsis. Anteroposterior radiograph of the left hip 28 years after surgery, demonstrating that PCA cementless acetabular component and femoral components are fixed in a satisfactory position. There is no evidence of a radiolucent line, polyethylene wear, or osteolysis about the acetabular or the femoral component. Overall, 30 acetabular components (34%) were revised after a mean of 28.4 years (range, years). Twenty-two, well-fixed acetabular components were removed because of extensive periprosthetic osteolysis (Fig. 3) and 6 because of aseptic loosening and osteolysis. Two acetabular components were revised for recurrent dislocation. Nine femoral components (10%) were revised for aseptic loosening and osteolysis. Three acetabular components (3%) were revised between 12 and 14 years after the operation, 10 (11%) were revised between 18 and 20 years and the remaining 17 acetabular components (19%) were revised between 20 and 29 years. Six femoral components (9%) were revised between 8 and 15 years. Multivariate regression analysis with use of revision because of aseptic loosening, age, male gender, time since the operation, inclination angle of the acetabular component and undersized femoral component were the significant covariates for revision status. The rate of survival after 28.4 years as the end point of revision for any reason was 66% (confidence interval, ) for the acetabular and 90% (confidence interval, ) for the femoral component. Eighteen bilateral hips did not require revision at the time of writing. The rate of survival of the acetabular components at 28.4 years in patients

4 Y.-H. Kim et al. / The Journal of Arthroplasty 29 (2014) Survival (%) Acetabular component 95% C.I. Lower limit 95% C.I. Upper limit Femoral Component 95% C.I. Lower limit 95% C.I. Upper limit years Fig. 3. Kaplan-Meier curves show survival rates at 28.4 years with revision of the acetabular and femoral components as the end-points. components was not significantly different (89% versus 91%, P = 0.597) between both genders. In the worst scenario, the rate of survival of both components would be substantially reduced if 20 hips (death or loss to follow-up) are included as failed hips. All of revisions of the acetabular components were performed using a cementless hemispherical cup with alumina forte-on-alumina forte bearing. All revisions of the femoral components were performed using a cementless femoral stem. Grade 1 heterotopic ossification occurred in 4 hips (5%), and grade 2 heterotopic ossification in 2 hips (2%). No hip had a grade 3 or 4 heterotopic ossification. Discussion Fig. 2. Radiographic evaluation of osteolysis of the left hip of a 45-year-old man with osteonecrosis of the femoral head. (A) Anteroposterior radiograph of the left hip 29 years after surgery, demonstrating the PCA cementless acetabular component and femoral components are embedded in a satisfactory position. Femoral head is positioned eccentrically in the acetabulum due to polyethylene wear. Osteolysis is observed in Zone I and II about the acetabular component. Femoral osteolysis is confined to greater trochanter. Grade 2 heterotopic ossification is found. (B) Anteroposterior radiograph of the left hip taken 11 years after revision of the acetabular component. Revised acetabular component is fixed satisfactorily without having radiolucent line or osteolysis. Grade 2 heterotopic ossification is observed. younger than 30 years old was 53% (confidence interval, ) and 79% (confidence interval, ) in patients older than 30 years old. The rate of survival of the femoral component in both groups was not different significantly (88% versus 92%, P = 0.613). The rate of survival of the acetabular components in male patients was 55% (confidence interval, ) and 77% (confidence interval, ) in female patients. The rate of survival of the femoral The purpose of this study was to evaluate the results at an average of 28.4 years after a PCA cementless THA incorporating an anatomically designed femoral component with a circumferential proximal porous coating and a hemispheric acetabular component with polyethylene sterilized in air. Although the fixation of the femoral stem was good, polyethylene wear and periacetabular osteolysis led to poor results of this PCA total hip system in this young and active patient population. There are some limitation of this study. First, this is a prospectively follow-up of the patients and their data were stored in the computer and retrospectively reviewed but, there is no control group to compare. Second, this particular femoral stem has not been used for three decades, but the principles of this stem could be applied to modern designed femoral stems. Third, this study was based on a single surgeon and single institute study design. Finally, there was a large loss to follow-up, thus there is a potential for underreporting of failures at the final analysis. As result of the disappointing results associated with early proximally coated cementless femoral component such as the Harris-Galante-1 implant (Zimmer, Warsaw, Indiana) [29], newgeneration proximally coated femoral stems were developed. The Harris-Galante-1 femoral component had a relatively small porous surface area that was noncircumferential, resulting in a susceptibility to distal osteolysis [30,31]. The clinical results in the present series, in which a PCA femoral component with a circumferential porous surface was used, compare favorably with those in previous reports on cemented femoral components [32 34] and other successful

5 2260 Y.-H. Kim et al. / The Journal of Arthroplasty 29 (2014) cementless designs [9,35,36]. Therefore, the principle of circumferential porous-coating of the femoral stem is continually applied to the modern cementless femoral component. Bojescul et al [11] were impressed with the longevity of the PCA femoral component particularly as it was a first-generation design and was implanted by surgeons with little experience of cementless hip arthroplasty. In their series, only 4% of hips were revised for aseptic loosening and 7% for loosening and osteolysis. Kim [13] reported longterm results of the PCA total hip prosthesis. At 19.4 years follow-up, 8 of 131 hips (6%) had undergone revision because of loosening and/ or osteolysis of the femoral component. Only 4 femoral components (4%) were revised for isolated aseptic loosening without osteolysis and 2 (2%) for recurrent dislocation. Loughead et al [14] reported the survival rate of the acetabular component was 80% and 95% of the femoral component at 23-year follow-up. Tezuka et al [12] reported the survival rate of the acetabular component was 60% and 82% of the femoral stem at 23-year follow-up. The results in the current series showed that 30 of 88 (34%) acetabular components and 9 of 88 (10%) femoral components had undergone revision because of aseptic loosening and/or osteolysis. In our series, most cases (55 patients, 79%) at the final follow-up had age related deterioration in function rather than attributing to the implant failure. The high UCLA activity score for the patients in our study was related to relatively healthy young patients with low comorbidity. In our series, 22 hips (25%) were associated with mildto-severe thigh pain, which was mild in association with 14 hips (16%) and severe and disabling in association with 8 hips. In other series of proximally and fully coated femoral components, the prevalence of thigh pain has been variable ranging from 1.5% to 27% [8,9,14,35 37]. In our study, we confirmed that tight distal stem-bone contact caused an activity related mild thigh pain and aseptic loosening of the femoral component caused a severe thigh pain. Fixation of cementless femoral component was classified by Engh et al [18] as stable with osseous ingrowth, stable with fibrous ingrowth, and unstable. This classification system is dependent on a cylindrical implant and a radiograph made tangential the porous surface. However, it is difficult to use the system for anatomically designed stems with limited ingrowth surfaces. Incomplete sclerotic and radiolucent lines adjacent to the prosthesis do not correlate well with implant stability. Most stems in our series had a radiolucent line at least one zone, however, these lines were generally seen adjacent to the nonporous surface of the implants and were not associated with other changes indicative of stem loosening. In the case of proximally porous-coated femoral components, therefore, radiographic subsidence or a complete radiolucent line is an indicator of loosening, whereas partial radiolucencies that are not adjacent to the ingrowth surface are not. Trabecularization into ingrowth porous surfaces is an indication of osseointegration. Tezuka et al [12] clearly reported that the stem-fitting ratio was significantly associated with femoral component revision surgery. Their poor results for stem survival rate were caused by undersized stem implantation. In the current series, six undersized stems underwent revision. Particulate debris from polyethylene wear and resultant osteolysis remain the primary factors limiting the longevity of hip prosthesis [38]. While the tight seal at the bone-implant interface and stable fixation without motion of the femoral component potentially inhibit or slow migration of the debris to the distal femoral zones, periacetabular osteolysis has become relatively common at intermediate follow-up intervals [8,9,14,35 37]. The femoral osteolysis in our series (in 35% of the 88 hips) was localized to Gruen zones 1 and 7, proximal to the lesser trochanter. Nine hips (10%) had osteolysis distal to the lesser trochanter. However, we identified a 53% rate (47 of 88 hips) of small (b1 cm) periacetabular osteolytic lesions and a 37% rate (28 hips) of large lesions ( 1 cm). Loughead et al [14] showed that the polyethylene thickness strongly predicted the risk of revision. This may explain the high prevalence of periacetabular osteolysis in our patient cohorts as a 32-mm head results in a thin polyethylene insert. Loughead et al [14] observed that there was an expected increase in the rate of osteolysis in young patients, who are more likely to be alive and active, and who have increased polyethylene wear. We observed that the presence of these osteolytic lesions is directly related to polyethylene wear, with acetabular osteolysis more likely to develop in patients with a higher wear rate. The high prevalence of polyethylene wear and periacetabular osteolysis in our series appears to be related to a poor quality of polyethylene liner, sterilized in air, poor locking system, young patients, and long-term follow-up. Patients younger than 30 years of age had a higher prevalence of osteolysis. Given these findings, screening radiographs at annual intervals and early intervention are warranted to prevent the difficult situation that results from advanced osteolysis and loosening. 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