Effect of proximal femoral osteoporosis on cementless hip arthroplasty: A short-term clinical analysis

Effect of proximal femoral osteoporosis on cementless hip arthroplasty: A short-term clinical analysis 1 first-author 2 corresp ‡Corresponding Author ‡Corresponding Author †E-mail:yuh_li2002@hotmail.com †E-mail:yuh_li2002@hotmail.com yuh_li2002@hotmail.com 1 Department of Orthopedics, the First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310003, China Department of Orthopedics, the First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310003, China Department of Anesthesiology, the First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310003, China Department of Anesthesiology, the First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310003, China Objective: 2 The aim of this retrospective investigation was to explore the influence of femoral osteoporosis on short-term curative effects of cementless hip arthroplasty and to evaluate the femoral metaphyseal bone mineral density (BMD) for femoral osteoporosis in order to guide prosthesis choice and rehabilitation. Methods: 2 We performed 127 total arthroplasty operations between June 1999 to February 2003 and investigated 49 cementless hip replacements with the Metalcancellous cementless Lubeck II system being used in all hips. There were twenty men and twenty-nine women whose mean age at the time of the operation was 60 years (range, 52~81 years). The patients were divided into osteoporosis or normal groups according to the femoral metaphyseal BMD measured preoperatively. The average duration of follow-up was 30 months (range, 8~52 months). We evaluated all of the patients from a clinical standpoint with use of a standard-terminology questionnaire with respect to the short-term curative effects and patients’ satisfaction. Hip pain status and functional ability were important indicators of treatment efficacy. Results: 2 Harris hip score and patients’ satisfaction in femoral osteoporosis patients who underwent noncemented hip arthroplasty were lower ( P =0.004, P =0.03) while the incidence of thigh pain was higher ( P =0.03) than the patients with non-osteoporosis. Conclusion: 2 The higher incidence of pain, as well as the decrease in function experienced by the patients in osteoporosis group, supports the case that cementless arthroplasty is not a better choice for those patients and that we had better select prosthesis based on the femoral metaphyseal BMD. Cementless hip arthroplasty Osteoporosis Bone mineral density (BMD) Curative effect INTRODUCTION 1 Cementless total hip arthroplasty (THA) is a reliable procedure for treatment of degenerative joint disease (Engh et al., 2001 2001 ; Xenos et al., 1999 1999 ). The primary advantage of biological fixation of cementless femoral prosthesis with porous prosthesis is the avoidance of use of acrylic cement. Gui et al.( 2002 2002 ) reported that in some cases noncemented prosthesis was preferred because of its initial stability and they found that some patients could resume standing immediately after operations. Gui et al.( 2000a 2000a ) described 121 patients who underwent cementless hip placement in their average 3.5 years follow-up clinical investigation. In their investigation, they found that the cortical index (CI) was lower than 2.2, Harris scores and patients’ satisfactions were lower but pain was more significant and prolonged. They thought CI was a reliable semi-quality parameter for clinical evaluation of femoral quality. In another study (Gui et al., 2002 2002 ), they considered femoral metaphyseal bone mineral density (BMD) was a better parameter for evaluating femoral quality in some circumstances. How the femoral metaphyseal BMD influenced the short-term results of cementless hip replacement of the patients with femoral osteoporosis? The purpose of the study was to investigate the influence of the femoral osteoporosis on short-term curative effects of cementless hip arthroplasty and to evaluate the femoral mataphyseal BMD for the patients with femoral osteoporosis in order to guide prosthesis choice and rehabilitation. MATERIALS AND METHODS 1 Study population 2 We surveyed one hundred twenty-seven patients who had received hip arthroplasty in our hospital from June 1999 to February 2003. Forty-nine patients who had undergone cementless hip arthroplasty were included in this study. The patients were 20 men and 29 women whose average age at the time of arthroplasty was 60 years (range, 52~81 years). The preoperative diagnoses of these patients were fracture of the femoral neck in 24 hips, aseptic femur head necrosis in 12 hips and hip osteoarthritis in 13 hips. The inclusion criteria were primary hip arthroplasty, no perioperative complications, no metabolic changes causing a reduction of BMD, and no previous use of drugs affecting bone metabolism such as steroids, calcitonin, or biphosphonates. All women were postmenopausal. Details of the patients are given in Table 1 1 . Informed consent to the study was obtained from all patients. The average follow-up time was 30 months and a retrospective analysis was conducted on those patients with or without osteoporosis in femur. Data are expressed as mean ( SD ) and count as appropriate Variables Normal group ( n =28) Osteoporosis group ( n =21) Age (years) 59 (12) 61 (15) M/F 10/18 10/11 Weight (kg) 60 (13) 56 (11) Follow-up time (months) 31 (5) 29 (7) 3 Stem size ( n ) 100 mm 6 4 110 mm 10 8 120 mm 8 6 130 mm 4 3 Extensively coated stem 16 13 Proximally coated stem 12 9 3 Diseases Femoral neck fracture 14 10 Sepsis femur head necrosis 6 6 Hip osteoarthritis 8 5 Measurement of proximal femur BMD 2 The femoral metaphyseal BMD was determined with dual energy X-ray absorptiometry (DXA) (XR-36, Norland Company, USA). Computer software (prosthetic scanning software version 5.73; Hologic Inc., Waltham, MA, USA) was used to measure the femoral metaphyseal bone mineral content and BMD in the regions of interest. The patients were placed supine on the scan table with standard knee and foot supports to place the femur in a neutral position. In our institution, the precision error of the calculations by DXA was less than 5%. The normal BMD was defined when the femoral metaphyseal BMD was more than 1.06 g/cm referred to the values of 1246 Chinese people in the site obtained by the East Chinese Hospital (Gui et al., 2002 2002 ). All patients were divided into two groups according the BMD (normal group and osteoporosis group). The prostheses used in the operation were the Metalcancellous Cementless Lubeck II system (S & G; ESKA, Lubeck, Gemany) (Matsui et al., 1998 1998 ; Plötz et al., 1992 1992 ; Sugano et al., 1994 1994 ). In the system, the stem and metal socket of the implant are made of cobalt-chrome-molybdenum alloy with a metal cancellous structure. In the operation, either extensively coated stem or proximally coated stems were used. The proximally coated stems had a porous surface applied circumferentially to the proximal 60%. The stem size used for the patients ranged from 100 to 130 mm in length with 10-mm intervals. The cylindrical diameter of the stem at 1 cm above the tip ranged from 9.5 to 13 mm. The operation was performed via a posterolateral approach using standardized techniques by a single hip surgeon. Patients were allowed to start partial weight-bearing at 1 week postoperatively. Full weight-bearing was allowed at 3 week. Harris score for evaluating arthritis of the hip (Harris, 1969 1969 ) 2 The Harris score was developed to assess patients with traumatic arthritis of the hip. It can be used to follow patients over time and to help plan management including the timing for surgical intervention. It can be used to assess patients before and after surgery to determine improvement. The arthritis of hip was assessed in the following four aspects: pain, function, absence of deformity and range of motion including 10 items of pain, limp, support, distance walk, stairs, shoes, sitting, public transportation, absence of deformity and range of motion. The maximum point was 100 (pain 44, function 47, absence of deformity 4 and range of motion 5) and the goal is to have a value as close to 100 as possible. However, the point of more than 80 was defined as excellent when evaluating curative effects after hip arthroplasty in clinical conditions (Gui et al., 2000a 2000a ). We evaluated the thigh pain using Harris pain scale (Table 2 2 ). Finding Points Scale None or ignores it 44 I Slight occasional no compromise in activity 40 I Mild pain no effect on average activities rarely moderate pain with usual activity may take aspirin 30 II Moderate pain tolerable but makes concessions to pain; some limitations of ordinary activity or work; may require occasional pain medicine stronger than aspirin 20 III Marked pain with serious limitation of activity 10 VI Totally disabled crippled pain in bed bedridden 0 VI The patients’ satisfaction was evaluated as good (no problem), moderate (minor problems, but easily managed) or bad (significant problems). Statistical analysis 2 All data were expressed as means ( SD ) and count ( n ) as appropriate except for special indication. Averages were compared by the Mann-Whitney U test and counts or proportions by using the Fisher’s exact test. All statistical analysis was performed using SPSS 11.0 (SPSS Inc., Chicago, IL). A significance level of 0.05 was used for all analysis. RESULTS 1 There were no significant differences between normal and osteoporosis group with regard to the male-female ratio, average patient age, average follow-up time, or weight. We could not detect a significant difference with regard to the stem size and proportion of extensively coated stems to proximally coated stems between the two groups (Table 1 1 ). In addition, no prosthesis loosening was observed in either group at the latest follow-up evaluation. Comparing the two groups, we found that 86% of the patients fall in normal group whose Harris score was more than 80; while there were just 48% of the patients in the osteoporosis group. There was a significant difference ( P =0.004) (Table 3 3 ). There were significant differences between the two groups with regard to the rate of the patients who had thigh pain (35% for normal group and 71% for osteoporosis group; P =0.03) (Table 4 4 ). Table 5 5 shows that the patients who felt good in normal group were greater than that in osteoporosis group (64% for normal group and 29% for osteoporosis group; P =0.03). P =0.004 2 Group 2 Harris score ≥80 <80 Normal group 24 4 Osteoporosis group * * 10 11 P =0.03 2 Group 4 Harris pain scale I II III IV Normal group 18 6 3 1 Osteoporosis group * * 6 4 8 3 P =0.03 2 Group 3 Patients’ satisfaction Good Moderate Bad Normal group 18 9 1 Osteoporosis group * * 6 12 3 DISCUSSION 1 THA has become a reliable procedure offering pain relief and increase in the range of motion with stability of the hip joint (Callaghan et al., 2000 2000 ; Engh et al., 1997 1997 ; Xenos et al., 1999 1999 ). The implantation of a stem alters the mechanical load environment in the host bone; it takes away a relatively larger share of the load from the femur. Once the stem has been inserted, the stress that would normally be borne by the bone alone is reduced, which leads to proximal femoral bone resorption. This resorption phenomenon around the femoral stem is called “stress shielding”, which is one of the major complications of cementless THA (Bobyn et al., 1992 1992 ; Lord et al., 1988 1988 ). The potential complications resulting from stress shielding include thigh pain, late stem loosing and femoral fracture in the revision surgery. Our finding of reliable short-term curative effects of cementless hip replacement is consistent with the work of Gui et al.( 2000a 2000a ). In 1987, Decker ( 1987 1987 ) inserted a total of 72 cementless isoelastic hip prosthesis in 33 cases of loosening of various prosthesis models and in 39 cases of femoral stem fracture. Aside from one late infection, no renewed loosensings have been observed. Spicer et al.( 2001 2001 ) showed that osteolysis was noted in six patients (7%) undergoing cementless THA but predominantly in relation to the femoral stem. Fecal pelvic osteolytic lesions were rare. All the cups were classified as stable on radiography. There has been some concern regarding cementless THA femoral fixation in the elderly patient population. Berend et al.( 2004 2004 ) investigated the outcomes of a tapered cementless femoral compartment in elderly patients 75 years of age and older and found that no periopeartive deaths or significant orthopedic complications identified at a mean follow-up of 5 year. So they concluded that advanced age is not a contraindication for tapered cementless THA. However, Learmoth and Spirakis ( 1994 1994 ) recommended a cementless hip replacement for the very young, hybrid replacement (cemented stem, uncemented cup) for the middle-aged and a fully cemented replacement for the elderly. In recent studies Roth et al.( 2006 2006 ) and Peter et al.( 2006 2006 ) showed that the cemented prosthesis should be implanted in cases with known severe osteoporosis of the proximal femur. Gui et al.( 2000b 2000b ) investigated the relation between the femoral metaphyseal bone mineral density, Singh index, the bone mineral density of other area and biomechanical properties and found that femoral metaphyseal bone mineral density was highly correlated with other bone mineral density parameters, Singh index and prosthesis stability. They therefore concluded that femoral metaphyseal bone mineral density was a good parameter for evaluating femoral quality. In this study we measured the femoral metaphyseal BMD preoperatively and defined the osteoporosis according to the BMD of this area. This study mainly aimed to explore whether proximal femoral osteoporosis influenced the short-term curative effect of cementless hip arthroplasty. The results showed that Harris score and patients’ satisfaction in femoral osteoporosis patients who underwent noncemented hip arthroplasty were lower while the incidence of thigh pain was higher than the patients with non-osteoporosis, which were consistent with the results of previous study (Gui et al., 2000a 2000a ). Some limitations of our investigation need to be considered. In our first design we planned to survey 80 patients. But it is difficult to enroll more patients and at last we just included 49 patients. Another limitation of the study is that the follow-up was too short for evaluating the long-term treatment effect, which is more important for the patients. Due to the higher incidence of pain, as well as the decrease in function experienced by the patients in osteoporosis group, we concluded that cementless arthroplasty is not a better choice for those patients. 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A prospective study with a minimum of ten years of follow-up 10.1631/jzus.2007.B0076 Project (No. 419200-584602) supported by the Start Foundation for Introducing Talent of Zhejiang University, China 2006-02-13 2006-07-21 2006-12-18 2022-01-05 Copyright © 2007, Journal of Zhejiang University Science 2007 Journal of Zhejiang University-SCIENCE B (Biomedicine and Biotechnology) 01 08