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Outcome of the Contralateral Hip in Rapidly Destructive Arthrosis After Total Hip Arthroplasty
The Journal of Arthroplasty Vol. 21 No. 7 2006
Outcome of the Contralateral Hip in Rapidly Destructive Arthrosis After Total Hip Arthroplasty A Preliminary Report Goro Motomura, MD, PhD, Takuaki Yamamoto, MD, PhD, Yasuharu Nakashima, MD, PhD, Toshihide Shuto, MD, PhD, Seiya Jingushi, MD, PhD, and Yukihide Iwamoto, MD, PhD
Abstract: We investigated the outcome of the contralateral hip in patients with rapidly destructive arthrosis of the hip after total hip arthroplasty. Twenty-four patients were included, and the mean duration of radiographic follow-up was 7.0 years (range, 3.8-17.8 years). To assess the capable parameters for predicting the development of osteoarthritis, we evaluated the receiver operating characteristic curves. Three (12.5%) of 24 patients developed osteoarthritis and underwent total hip arthroplasty within 3.8 to 6.5 years. In these 3 patients, both the acetabular-head index and the center-edge angle were significantly lower than those in patients without osteoarthritis ( P b .005). Based on the receiver operating characteristic curves, both an acetabular-head index of less than 72% and a center-edge angle of less than 168 were considered to be associated with the development of osteoarthritis. Key words: rapidly destructive arthrosis of the hip, contralateral hip, total hip arthroplasty, osteoarthritis, acetabular dysplasia. n 2006 Elsevier Inc. All rights reserved.
the etiology of RDA [2-4]; however, to the best of our knowledge, no study has yet shown the outcome of the contralateral hip after THA. The purpose of this study was to investigate the outcome of the contralateral hip in patients with RDA after THA.
Rapidly destructive arthrosis (RDA) of the hip generally occurs in the elderly and causes painful disabilities of the hip joint. Most of the RDA cases are unilateral involvement, and the rates have been reported to be around 89% [1]. Because of the rapid destruction of the hip joint and severe pain, the majority of patients with RDA are treated by total hip arthroplasty (THA) [2]. Many previous studies have focused on the affected hip joint for the purpose of investigating
Patients and Methods Patients Between January 1986 and December 1999, 27 patients underwent THA in our institution based on the previously reported criteria of RDA [1-3,5]: a clinical history of hip pain of 1 to 6 months’ duration, a radiographic appearance of rapid joint space narrowing (N2 mm in 1 year or 50% joint space narrowing in 1 year) and progression of bone destruction involving the femoral head and the acetabulum with minimal osteophyte formation, and the absence of clinical or laboratory evidence
From the Department of Orthopaedic Surgery, Kyushu University, Fukuoka, Japan. Submitted September 17, 2004; accepted August 2, 2005. This work is supported in part by a Grant-in-Aid in Scientific Research (No. 15591587) from JSPS and a grant from Uehara Memorial Foundation. Reprint requests: Takuaki Yamamoto, MD, PhD, Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 8128582, Japan. n 2006 Elsevier Inc. All rights reserved. 0883-5403/06/1906-0004$32.00/0 doi:10.1016/j.arth.2005.08.007
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Outcome of the Contralateral Hip in RDA After THA ! Motomura et al
of sepsis and neurological disease. None of the 27 patients had ever had contralateral hip pain and radiographic evidence of contralateral hip osteoarthritis, which was defined based on minimum joint spaces of 2.5 mm or less and the absence of osteophytes and subchondral cysts [6]. Patients with rheumatoid arthritis, osteonecrosis, or chondrocarcinosis were excluded. For each subject, the sex, age at the initial THA for RDA, height, weight, body mass index (calculated as weight [kg] divided by height [m] squared), side of contralateral hip, and a previous history of TKA were recorded. Study Protocol A supine anteroposterior radiograph of the hips was obtained at 1 month after the initial THA and at every 1-year follow-up visit. Radiographs were taken using the same technique throughout this study period, on which the standardized position of the beam and radiographic penetration were adopted. Every follow-up radiograph on the contralateral hip was evaluated for joint space width and the presence of osteoarthritis. The development of osteoarthritis was evaluated based on the clinical symptoms and radiographic evidence of joint space narrowing [7]. Total hip arthroplasty in the contralateral hip was used as the end point of the radiographic follow-up. In addition, each initial radiograph (taken 1 month after the initial THA) was evaluated quantitatively for radiographic parameters, including the center-edge (CE) angle, acetabular-head index (AHI), pelvic tilt, and joint space width (initial joint space width). All radiographs were evaluated by 2 observers, and all demarcations and reference points were decided by consensus. The radiographs were masked for clinically identifying information and were arranged in random order. Measurement Methods Center-Edge Angle. The CE angle (Fig. 1A) is formed by (1) a vertical line drawn from the center of the femoral head at right angles to the teardrop line and (2) a line from the center of the femoral head to the lateral edge of the acetabular roof [8]. The center of the femoral head was determined with concentric circles engraved on a transparent device. Acetabular-Head Index. The AHI (Fig. 1B) is the percentage that is calculated by dividing the horizontal distance of part of the femoral head (a), which is from the innermost surface of the head to
1027
the edge of the acetabulum, by the total horizontal width of the femoral head (b) and multiplying by 100: (a/b) 100 [9]. Joint Space Width. The joint space width (Fig. 1C) is determined by a vertical line going through the femoral head center at right angles to the teardrop line [10]. The joint space width was measured using a transparent ruler with a 0.5-mm graduation. Pelvic Tilt. We measured the angle of pelvic tilt on the anteroposterior radiograph using the method of Konishi and Mieno [11]. The formula for the estimation of the angle of pelvic tilt (backward tilt from neutral position [158]) from the height of the obturator foramen and teardrop distance is as follows: angle of pelvic tilt (in degrees) = height of obturator foramen/(teardrop distance A B), where A = 207.0 and B = 32.0 in a female subject and A = 137.4 and B = 23.1 in a male subject. Statistical Analysis Patients were divided into 2 groups based on the development of contralateral hip osteoarthritis. Univariate analyses between the prevalence of osteoarthritis and the nonprevalence of osteoarthritis groups were performed by means of Fisher exact probability test in proportion of sex and Student t test for numerical data of age, height, weight, body mass index, CE angle, AHI, pelvic tilt, and initial joint space width. To further assess the capable parameters for predicting the development of contralateral hip osteoarthritis, we used the receiver operating characteristic (ROC) curves [12]. In these ROC curves, the circumscribed areas (the area under the curve) give an estimate of the parameter’s diagnostic efficiency (in our study, the diagnostic efficiency of the development of contralateral hip osteoarthritis). This analysis involves plotting the true-positive rate (sensitivity) against the falsepositive rate (1 specificity) for possible cutoff scores. Each point on the ROC plot represents a sensitivity/specificity pair corresponding to a particular decision threshold. The higher the ROC curve is skewed toward the upper-left corner, the better the discriminatory capacity of the parameters. The areas under the curve were compared using the Mann-Whitney U test [13]. A Kaplan-Meier curve was produced with a threshold level, which was defined as the highest sensitivity/specificity combination based on the ROC curve for the most capable parameter for predicting the development of contralateral hip
1028 The Journal of Arthroplasty Vol. 21 No. 7 October 2006
Fig. 1. (A) The CE angle. (B) The AHI: (a/b) 100. (C) Joint space width.
osteoarthritis, dividing the parameter into 2 groups. Total hip arthroplasty in the contralateral hip was used as the end point. Statistical significance was evaluated by the log rank test. P values less than .05 were considered significant.
Results Twenty-four of 27 patients were followed (followup rate, 89%). Two cases died and one case dropped out. They consisted of 8 males and 16 females. The mean age at the initial THA for RDA was 71.0 years (range, 52-88 years). The mean duration of radiographic follow-up was 7.0 years (range, 3.817.8 years). The contralateral side at the time of initial THA was right in 8 and left in 16. Three (12.5%) of 24 patients developed contralateral hip osteoarthritis during the course of this
study, whereas the other 21 patients demonstrated no development of osteoarthritis in the contralateral hip. All of the 3 patients who developed contralateral osteoarthritis underwent THA within a mean of 5.4 years (3.8, 6.0, 6.5 years). One of the patients had a rapid progression of contralateral hip osteoarthritis without any obvious proliferative changes, whose original joint space width (N3 mm) was lost within 1.1 years (Fig. 2), whereas the other patients did not demonstrate such a rapid destruction of the hip joint. None of the patients had a previous history of total knee arthroplasty. Two of the 3 patients underwent revision THA in the RDA hip because of a failed femoral component during this study period. One of them had a revision 1 month before the contralateral THA, and the other, who had a rapid progression of contralateral hip osteoarthritis, required a revision 11 months after the contralateral THA.
Outcome of the Contralateral Hip in RDA After THA ! Motomura et al
1029
Fig. 2. Radiographs of a 58-year-old woman who was diagnosed with rapidly destructive arthrosis of the left hip. (A) Anteroposterior radiograph obtained at the time of the left THA shows subluxation and flattening of the left femoral head. The right hip joint appears to be normal except for the presence of developmental dysplasia of the acetabulum (AHI, 69%; CE angle, 158). (B) Anteroposterior radiograph of the right hip obtained 2.3 years after THA shows mild joint space narrowing. (C) Anteroposterior radiograph obtained 3.4 years after THA shows a rapid loss of joint space mainly at the superio-lateral portion of the femoral head.
Characteristics of the patients with contralateral hip osteoarthritis and those without osteoarthritis are shown in Table 1. There were no significant differences regarding age, sex, weight, height, body mass index, pelvic tilt, and initial joint space width, but the 2 groups differed significantly with respect to AHI and CE angle. The AHI was 68.3% F 3.1% in the patients with osteoarthritis, whereas it was 82.5% F 5.8% in the patients without osteoarthritis. The CE angle was 14.78 F 0.88 in the patients with osteoarthritis, whereas it was 24.28 F 6.58 in the patients without osteoarthritis. The ROC curves for age, AHI, CE angle, pelvic tilt, and initial joint space width are shown in Fig. 3. Both of the curves for the AHI and CE angle were skewed toward the upper-left corner. The area under the ROC curve for the AHI and CE angle was 0.965 and 0.941, respectively. There were no significant differences in the areas under the ROC
Table 1. Characteristics of the 2 Groups
Age (y)* No. of women/no. of men Weight (kg) Height (m) Body mass index (kg/m2) Acetabular-head index (%) Center-edge angle (8) Pelvic tilt (8)y Initial joint space width (mm)
Osteoarthritis (n = 3)
No osteoarthritis (n = 21)
62.3 F 5.1 2/1
72.3 F 9.9 14/7
.1 1.0
59.5 F 0.7 1.57 F 0.16 24.5 F 5.0
56.0 F 9.0 1.52 F 0.09 24.0 F 2.5
.6 .5 .8
68.3 F 3.1
82.5 F 5.8
.0005
14.7 F 0.8
24.2 F 6.5
.0035
19.3 F 4.4 4.7 F 0.5
20.7 F 8.8 4.9 F 1.0
.99 .7
*Age at the initial THA for RDA of the hip. yBackward tilt from the neutral pelvic tilt (158).
P
1030 The Journal of Arthroplasty Vol. 21 No. 7 October 2006 curve between the AHI and CE angle. In contrast, each of the curves for pelvic tilt and initial joint space width was close to the reference line (0 diagnostic efficiency). The area under the ROC curve for the pelvic tilt and initial joint space width was 0.578 and 0.563, respectively. The area under the curve for the AHI and CE angle was significantly larger than that for the pelvic tilt and initial joint space width ( P b .05). The area under the ROC curve for age was 0.830, and there were no significant differences in the area under the ROC curve between age and the other 4 parameters. Based on the ROC curves in Fig. 3, the cutoff points for AHI and CE angle were statistically defined, corresponding to the highest sensitivity/ specificity combination. The cutoff point for AHI and CE angle was 72% (sensitivity, 100%; specificity, 95%) and 168 (sensitivity, 100%; specificity, 95%), respectively. A Kaplan-Meier curve with a threshold level, which was defined based on the ROC curve for the AHI and CE angle (72% and 168, respectively), is Fig. 4. Kaplan-Meier survival curve of the groups with an AHI of more than 72% or a CE angle of more than 16 degrees, and with an AHI of less than 72% or a CE angle of less than 16 degrees. Total hip arthroplasty in the contralateral hip is used as an end point.
shown in Fig. 4. There was a significant difference in the survival rate between patients with an AHI of more than 72% or a CE angle of more than 168 and those with an AHI of less than 72% or a CE angle of less than 168 ( P b .01).
Discussion
Fig. 3. The ROC curves show each of the curves for the AHI and CE angle is skewed toward the upper-left corner. The arrows on the curves show the optimal cutoff points, corresponding to the highest sensitivity/ specificity combination. Straight line indicates reference line (0 diagnostic efficiency).
Based on a study of patients with osteoarthritis, Ritter et al [7] reported that the probability of developing osteoarthritis in the contralateral hip after THA was 36.5% at 10 years. In our series, 3 (12.5%) of 24 patients with RDA developed osteoarthritis in the contralateral hip. This result suggests that patients with RDA may not have a higher risk of developing osteoarthritis in the contralateral hip after THA than patients with osteoarthritis. In our series, one of 3 patients demonstrated a rapid progression of contralateral hip osteoarthritis around 3 years after THA, such as seen in RDA cases. Although there have been a few published RDA cases in whom the bilateral hips were affected in such a long time interval (3 years), this case may be considered to have bilateral RDA based on the radiographic appearances.
Outcome of the Contralateral Hip in RDA After THA ! Motomura et al
We do not consider that only mild hip dysplasia leads to the development of osteoarthritis in the contralateral hip of RDA after THA. Loizeau et al [14] examined 4 postoperative patients who had undergone unilateral THA for end-stage osteoarthritis and noted the presence of some mechanical dysfunction in the nonoperated limb, thus suggesting that THA itself may change the biomechanics of joint loading in the contralateral hip. In our series, 2 cases underwent revision THA in the RDA side, and both of them developed osteoarthritis in the contralateral hip. The condition of initial THA may alter the biomechanics and influence the development of osteoarthritis in the contralateral hip. Moreover, the progression of osteoarthritis in the contralateral hip may have also partially affected the condition of the replaced hip. Regarding age, we found no significant differences between patients with contralateral hip osteoarthritis and those without osteoarthritis, which may be because of the small number of cases examined (n = 3). The area under the ROC curve for age was 0.830, which is considered to be buseful for some purposeQ [15]. We therefore suppose that patient age may be one factor for the development of contralateral hip osteoarthritis in patients with RDA. In this study, we used ROC curves to check the usefulness of the AHI and CE angle, as well as to assess the predictive threshold values of the AHI and CE angle, for predicting the development of contralateral hip osteoarthritis. Although the current analyses suggest that both the AHI and CE angle may be a useful marker for predicting the development of contralateral hip osteoarthritis, it should be noted that they may not be an independent risk factor for the development of osteoarthritis. The chief limitation of this study may be the small number of cases examined (3 cases vs 21). Therefore, further investigations with increased number of cases could elucidate the role of acetabular dysplasia in the development of contralateral hip osteoarthritis. In summary, this study showed that the development of osteoarthritis in the contralateral hip was about 12% in patients with RDA after THA, and that both the AHI and CE angle may be a useful parameter for predicting the possible development of osteoarthritis.
Acknowledgment This work is supported in part by a Grant-in-Aid in Scientific Research (No. 15591587) from JSPS and a grant from Uehara Memorial Foundation.
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We would like to thank Naoko Kinukawa (Department of Medical Informatics, Kyushu University, Fukuoka, Japan) for her helpful advice on the statistical analysis.
References 1. Rosenberg ZS, Shankman S, Steiner GC, et al. Rapid destructive osteoarthritis: clinical, radiographic, and pathologic features. Radiology 1992;182:213. 2. Postel M, Kerboull M. Total prosthetic replacement in rapidly destructive arthrosis of the hip joint. Clin Orthop 1970;72:138. 3. Bock GW, Garcia A, Weisman MH, et al. Rapidly destructive hip disease: clinical and imaging abnormalities. Radiology 1993;186:461. 4. Yamamoto T, Bullough PG. The role of subchondral insufficiency fracture in rapid destruction of the hip joint: a preliminary report. Arthritis Rheum 2000; 43:2423. 5. Boutry N, Paul C, Leroy X, et al. Rapidly destructive osteoarthritis of the hip: MR imaging findings. Am J Roentgenol 2002;179:657. 6. Croft P, Cooper C, Wickham C, et al. Defining osteoarthritis of the hip for epidemiologic studies. Am J Epidemiol 1990;132:514. 7. Ritter MA, Carr K, Herbst SA, et al. Outcome of the contralateral hip following total hip arthroplasty for osteoarthritis. J Arthroplasty 1996;11:242. 8. Fredensborg N. The CE angle of normal hips. Acta Orthop Scand 1976;47:403. 9. Heyman CH, Herndon CH. Legg-Perthes disease; a method for the measurement of the roentgenographic result. J Bone Joint Surg Am 1950;32:767. 10. Reis P, Nahal-Said R, Ravaud P, et al. Are radiological joint space widths of normal hips asymmetrical? Ann Rheum Dis 1999;58:246. 11. Konishi N, Mieno T. Determination of acetabular coverage of the femoral head with use of a single anteroposterior radiograph. A new computerized technique. J Bone Joint Surg Am 1993;75:1318. 12. McNeil BJ, Keller E, Adelstein SJ. Primer on certain elements of medical decision making. N Engl J Med 1975;293:211. 13. Bland M. An introduction to medical statistics. New York: Oxford University Press Inc. 14. Loizeau J, Allard P, Duhaime M, et al. Bilateral gait patterns in subjects fitted with a total hip prosthesis. Arch Phys Med Rehabil 1995;76:552. 15. Swets JA. ROC analysis applied to the evaluation of medical imaging techniques. Invest Radiol 1979; 14:109.
Outcome of the Contralateral Hip in Rapidly Destructive Arthrosis After Total Hip Arthroplasty A Preliminary Report Goro Motomura, MD, PhD, Takuaki Yamamoto, MD, PhD, Yasuharu Nakashima, MD, PhD, Toshihide Shuto, MD, PhD, Seiya Jingushi, MD, PhD, and Yukihide Iwamoto, MD, PhD
Abstract: We investigated the outcome of the contralateral hip in patients with rapidly destructive arthrosis of the hip after total hip arthroplasty. Twenty-four patients were included, and the mean duration of radiographic follow-up was 7.0 years (range, 3.8-17.8 years). To assess the capable parameters for predicting the development of osteoarthritis, we evaluated the receiver operating characteristic curves. Three (12.5%) of 24 patients developed osteoarthritis and underwent total hip arthroplasty within 3.8 to 6.5 years. In these 3 patients, both the acetabular-head index and the center-edge angle were significantly lower than those in patients without osteoarthritis ( P b .005). Based on the receiver operating characteristic curves, both an acetabular-head index of less than 72% and a center-edge angle of less than 168 were considered to be associated with the development of osteoarthritis. Key words: rapidly destructive arthrosis of the hip, contralateral hip, total hip arthroplasty, osteoarthritis, acetabular dysplasia. n 2006 Elsevier Inc. All rights reserved.
the etiology of RDA [2-4]; however, to the best of our knowledge, no study has yet shown the outcome of the contralateral hip after THA. The purpose of this study was to investigate the outcome of the contralateral hip in patients with RDA after THA.
Rapidly destructive arthrosis (RDA) of the hip generally occurs in the elderly and causes painful disabilities of the hip joint. Most of the RDA cases are unilateral involvement, and the rates have been reported to be around 89% [1]. Because of the rapid destruction of the hip joint and severe pain, the majority of patients with RDA are treated by total hip arthroplasty (THA) [2]. Many previous studies have focused on the affected hip joint for the purpose of investigating
Patients and Methods Patients Between January 1986 and December 1999, 27 patients underwent THA in our institution based on the previously reported criteria of RDA [1-3,5]: a clinical history of hip pain of 1 to 6 months’ duration, a radiographic appearance of rapid joint space narrowing (N2 mm in 1 year or 50% joint space narrowing in 1 year) and progression of bone destruction involving the femoral head and the acetabulum with minimal osteophyte formation, and the absence of clinical or laboratory evidence
From the Department of Orthopaedic Surgery, Kyushu University, Fukuoka, Japan. Submitted September 17, 2004; accepted August 2, 2005. This work is supported in part by a Grant-in-Aid in Scientific Research (No. 15591587) from JSPS and a grant from Uehara Memorial Foundation. Reprint requests: Takuaki Yamamoto, MD, PhD, Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 8128582, Japan. n 2006 Elsevier Inc. All rights reserved. 0883-5403/06/1906-0004$32.00/0 doi:10.1016/j.arth.2005.08.007
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Outcome of the Contralateral Hip in RDA After THA ! Motomura et al
of sepsis and neurological disease. None of the 27 patients had ever had contralateral hip pain and radiographic evidence of contralateral hip osteoarthritis, which was defined based on minimum joint spaces of 2.5 mm or less and the absence of osteophytes and subchondral cysts [6]. Patients with rheumatoid arthritis, osteonecrosis, or chondrocarcinosis were excluded. For each subject, the sex, age at the initial THA for RDA, height, weight, body mass index (calculated as weight [kg] divided by height [m] squared), side of contralateral hip, and a previous history of TKA were recorded. Study Protocol A supine anteroposterior radiograph of the hips was obtained at 1 month after the initial THA and at every 1-year follow-up visit. Radiographs were taken using the same technique throughout this study period, on which the standardized position of the beam and radiographic penetration were adopted. Every follow-up radiograph on the contralateral hip was evaluated for joint space width and the presence of osteoarthritis. The development of osteoarthritis was evaluated based on the clinical symptoms and radiographic evidence of joint space narrowing [7]. Total hip arthroplasty in the contralateral hip was used as the end point of the radiographic follow-up. In addition, each initial radiograph (taken 1 month after the initial THA) was evaluated quantitatively for radiographic parameters, including the center-edge (CE) angle, acetabular-head index (AHI), pelvic tilt, and joint space width (initial joint space width). All radiographs were evaluated by 2 observers, and all demarcations and reference points were decided by consensus. The radiographs were masked for clinically identifying information and were arranged in random order. Measurement Methods Center-Edge Angle. The CE angle (Fig. 1A) is formed by (1) a vertical line drawn from the center of the femoral head at right angles to the teardrop line and (2) a line from the center of the femoral head to the lateral edge of the acetabular roof [8]. The center of the femoral head was determined with concentric circles engraved on a transparent device. Acetabular-Head Index. The AHI (Fig. 1B) is the percentage that is calculated by dividing the horizontal distance of part of the femoral head (a), which is from the innermost surface of the head to
1027
the edge of the acetabulum, by the total horizontal width of the femoral head (b) and multiplying by 100: (a/b) 100 [9]. Joint Space Width. The joint space width (Fig. 1C) is determined by a vertical line going through the femoral head center at right angles to the teardrop line [10]. The joint space width was measured using a transparent ruler with a 0.5-mm graduation. Pelvic Tilt. We measured the angle of pelvic tilt on the anteroposterior radiograph using the method of Konishi and Mieno [11]. The formula for the estimation of the angle of pelvic tilt (backward tilt from neutral position [158]) from the height of the obturator foramen and teardrop distance is as follows: angle of pelvic tilt (in degrees) = height of obturator foramen/(teardrop distance A B), where A = 207.0 and B = 32.0 in a female subject and A = 137.4 and B = 23.1 in a male subject. Statistical Analysis Patients were divided into 2 groups based on the development of contralateral hip osteoarthritis. Univariate analyses between the prevalence of osteoarthritis and the nonprevalence of osteoarthritis groups were performed by means of Fisher exact probability test in proportion of sex and Student t test for numerical data of age, height, weight, body mass index, CE angle, AHI, pelvic tilt, and initial joint space width. To further assess the capable parameters for predicting the development of contralateral hip osteoarthritis, we used the receiver operating characteristic (ROC) curves [12]. In these ROC curves, the circumscribed areas (the area under the curve) give an estimate of the parameter’s diagnostic efficiency (in our study, the diagnostic efficiency of the development of contralateral hip osteoarthritis). This analysis involves plotting the true-positive rate (sensitivity) against the falsepositive rate (1 specificity) for possible cutoff scores. Each point on the ROC plot represents a sensitivity/specificity pair corresponding to a particular decision threshold. The higher the ROC curve is skewed toward the upper-left corner, the better the discriminatory capacity of the parameters. The areas under the curve were compared using the Mann-Whitney U test [13]. A Kaplan-Meier curve was produced with a threshold level, which was defined as the highest sensitivity/specificity combination based on the ROC curve for the most capable parameter for predicting the development of contralateral hip
1028 The Journal of Arthroplasty Vol. 21 No. 7 October 2006
Fig. 1. (A) The CE angle. (B) The AHI: (a/b) 100. (C) Joint space width.
osteoarthritis, dividing the parameter into 2 groups. Total hip arthroplasty in the contralateral hip was used as the end point. Statistical significance was evaluated by the log rank test. P values less than .05 were considered significant.
Results Twenty-four of 27 patients were followed (followup rate, 89%). Two cases died and one case dropped out. They consisted of 8 males and 16 females. The mean age at the initial THA for RDA was 71.0 years (range, 52-88 years). The mean duration of radiographic follow-up was 7.0 years (range, 3.817.8 years). The contralateral side at the time of initial THA was right in 8 and left in 16. Three (12.5%) of 24 patients developed contralateral hip osteoarthritis during the course of this
study, whereas the other 21 patients demonstrated no development of osteoarthritis in the contralateral hip. All of the 3 patients who developed contralateral osteoarthritis underwent THA within a mean of 5.4 years (3.8, 6.0, 6.5 years). One of the patients had a rapid progression of contralateral hip osteoarthritis without any obvious proliferative changes, whose original joint space width (N3 mm) was lost within 1.1 years (Fig. 2), whereas the other patients did not demonstrate such a rapid destruction of the hip joint. None of the patients had a previous history of total knee arthroplasty. Two of the 3 patients underwent revision THA in the RDA hip because of a failed femoral component during this study period. One of them had a revision 1 month before the contralateral THA, and the other, who had a rapid progression of contralateral hip osteoarthritis, required a revision 11 months after the contralateral THA.
Outcome of the Contralateral Hip in RDA After THA ! Motomura et al
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Fig. 2. Radiographs of a 58-year-old woman who was diagnosed with rapidly destructive arthrosis of the left hip. (A) Anteroposterior radiograph obtained at the time of the left THA shows subluxation and flattening of the left femoral head. The right hip joint appears to be normal except for the presence of developmental dysplasia of the acetabulum (AHI, 69%; CE angle, 158). (B) Anteroposterior radiograph of the right hip obtained 2.3 years after THA shows mild joint space narrowing. (C) Anteroposterior radiograph obtained 3.4 years after THA shows a rapid loss of joint space mainly at the superio-lateral portion of the femoral head.
Characteristics of the patients with contralateral hip osteoarthritis and those without osteoarthritis are shown in Table 1. There were no significant differences regarding age, sex, weight, height, body mass index, pelvic tilt, and initial joint space width, but the 2 groups differed significantly with respect to AHI and CE angle. The AHI was 68.3% F 3.1% in the patients with osteoarthritis, whereas it was 82.5% F 5.8% in the patients without osteoarthritis. The CE angle was 14.78 F 0.88 in the patients with osteoarthritis, whereas it was 24.28 F 6.58 in the patients without osteoarthritis. The ROC curves for age, AHI, CE angle, pelvic tilt, and initial joint space width are shown in Fig. 3. Both of the curves for the AHI and CE angle were skewed toward the upper-left corner. The area under the ROC curve for the AHI and CE angle was 0.965 and 0.941, respectively. There were no significant differences in the areas under the ROC
Table 1. Characteristics of the 2 Groups
Age (y)* No. of women/no. of men Weight (kg) Height (m) Body mass index (kg/m2) Acetabular-head index (%) Center-edge angle (8) Pelvic tilt (8)y Initial joint space width (mm)
Osteoarthritis (n = 3)
No osteoarthritis (n = 21)
62.3 F 5.1 2/1
72.3 F 9.9 14/7
.1 1.0
59.5 F 0.7 1.57 F 0.16 24.5 F 5.0
56.0 F 9.0 1.52 F 0.09 24.0 F 2.5
.6 .5 .8
68.3 F 3.1
82.5 F 5.8
.0005
14.7 F 0.8
24.2 F 6.5
.0035
19.3 F 4.4 4.7 F 0.5
20.7 F 8.8 4.9 F 1.0
.99 .7
*Age at the initial THA for RDA of the hip. yBackward tilt from the neutral pelvic tilt (158).
P
1030 The Journal of Arthroplasty Vol. 21 No. 7 October 2006 curve between the AHI and CE angle. In contrast, each of the curves for pelvic tilt and initial joint space width was close to the reference line (0 diagnostic efficiency). The area under the ROC curve for the pelvic tilt and initial joint space width was 0.578 and 0.563, respectively. The area under the curve for the AHI and CE angle was significantly larger than that for the pelvic tilt and initial joint space width ( P b .05). The area under the ROC curve for age was 0.830, and there were no significant differences in the area under the ROC curve between age and the other 4 parameters. Based on the ROC curves in Fig. 3, the cutoff points for AHI and CE angle were statistically defined, corresponding to the highest sensitivity/ specificity combination. The cutoff point for AHI and CE angle was 72% (sensitivity, 100%; specificity, 95%) and 168 (sensitivity, 100%; specificity, 95%), respectively. A Kaplan-Meier curve with a threshold level, which was defined based on the ROC curve for the AHI and CE angle (72% and 168, respectively), is Fig. 4. Kaplan-Meier survival curve of the groups with an AHI of more than 72% or a CE angle of more than 16 degrees, and with an AHI of less than 72% or a CE angle of less than 16 degrees. Total hip arthroplasty in the contralateral hip is used as an end point.
shown in Fig. 4. There was a significant difference in the survival rate between patients with an AHI of more than 72% or a CE angle of more than 168 and those with an AHI of less than 72% or a CE angle of less than 168 ( P b .01).
Discussion
Fig. 3. The ROC curves show each of the curves for the AHI and CE angle is skewed toward the upper-left corner. The arrows on the curves show the optimal cutoff points, corresponding to the highest sensitivity/ specificity combination. Straight line indicates reference line (0 diagnostic efficiency).
Based on a study of patients with osteoarthritis, Ritter et al [7] reported that the probability of developing osteoarthritis in the contralateral hip after THA was 36.5% at 10 years. In our series, 3 (12.5%) of 24 patients with RDA developed osteoarthritis in the contralateral hip. This result suggests that patients with RDA may not have a higher risk of developing osteoarthritis in the contralateral hip after THA than patients with osteoarthritis. In our series, one of 3 patients demonstrated a rapid progression of contralateral hip osteoarthritis around 3 years after THA, such as seen in RDA cases. Although there have been a few published RDA cases in whom the bilateral hips were affected in such a long time interval (3 years), this case may be considered to have bilateral RDA based on the radiographic appearances.
Outcome of the Contralateral Hip in RDA After THA ! Motomura et al
We do not consider that only mild hip dysplasia leads to the development of osteoarthritis in the contralateral hip of RDA after THA. Loizeau et al [14] examined 4 postoperative patients who had undergone unilateral THA for end-stage osteoarthritis and noted the presence of some mechanical dysfunction in the nonoperated limb, thus suggesting that THA itself may change the biomechanics of joint loading in the contralateral hip. In our series, 2 cases underwent revision THA in the RDA side, and both of them developed osteoarthritis in the contralateral hip. The condition of initial THA may alter the biomechanics and influence the development of osteoarthritis in the contralateral hip. Moreover, the progression of osteoarthritis in the contralateral hip may have also partially affected the condition of the replaced hip. Regarding age, we found no significant differences between patients with contralateral hip osteoarthritis and those without osteoarthritis, which may be because of the small number of cases examined (n = 3). The area under the ROC curve for age was 0.830, which is considered to be buseful for some purposeQ [15]. We therefore suppose that patient age may be one factor for the development of contralateral hip osteoarthritis in patients with RDA. In this study, we used ROC curves to check the usefulness of the AHI and CE angle, as well as to assess the predictive threshold values of the AHI and CE angle, for predicting the development of contralateral hip osteoarthritis. Although the current analyses suggest that both the AHI and CE angle may be a useful marker for predicting the development of contralateral hip osteoarthritis, it should be noted that they may not be an independent risk factor for the development of osteoarthritis. The chief limitation of this study may be the small number of cases examined (3 cases vs 21). Therefore, further investigations with increased number of cases could elucidate the role of acetabular dysplasia in the development of contralateral hip osteoarthritis. In summary, this study showed that the development of osteoarthritis in the contralateral hip was about 12% in patients with RDA after THA, and that both the AHI and CE angle may be a useful parameter for predicting the possible development of osteoarthritis.
Acknowledgment This work is supported in part by a Grant-in-Aid in Scientific Research (No. 15591587) from JSPS and a grant from Uehara Memorial Foundation.
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We would like to thank Naoko Kinukawa (Department of Medical Informatics, Kyushu University, Fukuoka, Japan) for her helpful advice on the statistical analysis.
References 1. Rosenberg ZS, Shankman S, Steiner GC, et al. Rapid destructive osteoarthritis: clinical, radiographic, and pathologic features. Radiology 1992;182:213. 2. Postel M, Kerboull M. Total prosthetic replacement in rapidly destructive arthrosis of the hip joint. Clin Orthop 1970;72:138. 3. Bock GW, Garcia A, Weisman MH, et al. Rapidly destructive hip disease: clinical and imaging abnormalities. Radiology 1993;186:461. 4. Yamamoto T, Bullough PG. The role of subchondral insufficiency fracture in rapid destruction of the hip joint: a preliminary report. Arthritis Rheum 2000; 43:2423. 5. Boutry N, Paul C, Leroy X, et al. Rapidly destructive osteoarthritis of the hip: MR imaging findings. Am J Roentgenol 2002;179:657. 6. Croft P, Cooper C, Wickham C, et al. Defining osteoarthritis of the hip for epidemiologic studies. Am J Epidemiol 1990;132:514. 7. Ritter MA, Carr K, Herbst SA, et al. Outcome of the contralateral hip following total hip arthroplasty for osteoarthritis. J Arthroplasty 1996;11:242. 8. Fredensborg N. The CE angle of normal hips. Acta Orthop Scand 1976;47:403. 9. Heyman CH, Herndon CH. Legg-Perthes disease; a method for the measurement of the roentgenographic result. J Bone Joint Surg Am 1950;32:767. 10. Reis P, Nahal-Said R, Ravaud P, et al. Are radiological joint space widths of normal hips asymmetrical? Ann Rheum Dis 1999;58:246. 11. Konishi N, Mieno T. Determination of acetabular coverage of the femoral head with use of a single anteroposterior radiograph. A new computerized technique. J Bone Joint Surg Am 1993;75:1318. 12. McNeil BJ, Keller E, Adelstein SJ. Primer on certain elements of medical decision making. N Engl J Med 1975;293:211. 13. Bland M. An introduction to medical statistics. New York: Oxford University Press Inc. 14. Loizeau J, Allard P, Duhaime M, et al. Bilateral gait patterns in subjects fitted with a total hip prosthesis. Arch Phys Med Rehabil 1995;76:552. 15. Swets JA. ROC analysis applied to the evaluation of medical imaging techniques. Invest Radiol 1979; 14:109.