Cementless Primary Total Hip Arthroplasty Using CLS Stem - A Minimum 10-Year Follow-up Study-
- Cementless Primary Total Hip Arthroplasty Using CLS Stem - A Minimum 10-Year Follow-up Study-
- Other Titles
- CLS 대퇴 스템을 이용한 무시멘트 일차성 인공 고관절 전치환술 - 최소 10년 추시 연구 -
- Alternative Author(s)
- Hwang, Kyu-Tae
- Issue Date
- Background: Total hip arthroplasty is one of the most successful interventions in orthopaedics and many long-term follow-up studies have reported favorable clinical results for cementless total hip arthroplasty. However, numbers of failed total hip arthroplasties continue to increase due to the greater numbers of procedures performed. To minimize failures, newly designed implants, alternative bearings, and novel surgical techniques have been exploited. Furthermore, recently, several cementless components and alternative bearings have been successfully used. In particular, clinical outcomes have been greatly improved by the use of titanium alloy, tapered designs, and rough-blasted surfaces for cementless femoral components. The purpose of this study was to evaluate the clinical and radiographic outcomes of cementless primary total hip arthroplasty using a rough-blasted titanium CLS stem and to identify the factors that influence outcomes after a minimum follow-up of 10 years.
Materials and Methods: Between December 1993 and May 1999, 247 total hip arthroplasties were performed using a cementless rough-blasted straight tapered titanium femoral stem combined with a rough-blasted Wagner cup in 206 patients. Of the patients treated, 227 hips in 191 patients with a mean age of 50.2 years (range, 19 to 85 years) were available for clinical and radiographic review at a mean of 12.3 years (range, 10 to 16.1 years) postoperatively. A rough-blasted CLS stem with proximal hydroxyapatite coating was used in 119 hips and a CLS stem without a hydroxyapatite coating in 108 hips. Two types of bearing surfaces were implanted
a metal-on-metal bearing in 180 hips and a ceramic-on-polyethylene bearing in 47. Hips were categorized into three groups, based on stem alignment: neutral, valgus, and varus stem alignment groups. The canal fill index was used as a criterion to determine the adequacy of stem sizing. Clinical and radiographic outcomes were evaluated based on interrelated criteria, namely, stem surface treatment, bearing surface, stem alignment, and canal fill index. Potential patient-related factors, such as, sex, age, and BMI were also evaluated. Defining end points as overall, acetabular, or femoral revision, Kaplan-Meier survivorship analysis was performed to predict long-term outcomes. In addition, periprosthetic tissue specimens from one hip fitted with a metal-on-metal bearing that had undergone revision arthroplasty were subjected to histological and immunohistochemical analyses. Serum cobalt levels were determined in 24 randomly selected patients who had undergone unilateral total hip arthroplasty at 1, 3, and 5 years postoperatively, and in 2 patients who developed postoperative osteolysis at 3 and 5 years postoperatively.
Results: Mean preoperative Harris hip score improved from 50.6 points (range, 45 to 60 points) to 92.1 points (range, 69 to 100 points) at final follow-up. Three patients experienced transient thigh pain within 1 year postoperatively, but the symptom disappeared spontaneously in all cases. Endosteal bone formation was observed in all femoral components without aseptic loosening. Stem subsidence occurred in 7 hips
2 hips with a hydroxyapatite coating and 5 hips with a non-hydroxyapatite coating. However, all stems achieved secondary stability. Focal osteolysis was found at Gruen zones 1 and 7 in 14 hips. Stem alignment was neutral in 194 hips, valgus in 13 hips, and varus in 20 hips. At the final follow-up, no significant differences were evident between the three stem alignment groups in terms of clinical or radiographic results. Furthermore, no significant was observed between the two different surface treatment types or between the two bearing types, and no patient-related factor was found to affect clinical or radiographic outcome. However, a canal fill index of ≤80% at the lesser trochanter level was found to affect cortical remodeling (p=0.031), subsidence (p=0.006), and a change in stem position of ≧
5 degrees (p=0.029). In two hips, acetabular component was revised due to acetabular loosening, and three hips were revised due to a late postoperative periprosthetic fracture following trauma. Overall survival rate at 16.1 years was 92.6% (95% confidence interval, 91% to 97%) when revision for any reason was defined as the end point, and 97.2% (95% CI, 95% to 99%) when femoral revision for any reason was defined as the end point. According to bearing surface type, the survival rate at 16.1 years was 93.8% (95% CI, 89% to 97%) for metal-on-metal bearings and 97.9% (95% CI, 96% to 100%) for ceramic-on-polyethylene bearings, taking revision for any reason as the end point. The survival rate at 16.1 years, taking an end point of acetabular revision for any reason, was 95.3% (95% CI, 92% to 98%) for metal-on-metal bearings, and 100% (95% CI, 100%) for ceramic-on-polyethylene bearings.
Groin pain occured in five patients (5 hips). Two of these patients had focal periacetabular osteolysis with mild groin pain, and continue to be followed. The other three patients rated their pain as moderate to severe. One of the three, with moderate pain, showed periacetabular focal osteolysis, and follow-up radiographs showed an acetabular fracture around the osteolytic lesion, another was revised for unexplained early cup loosening, and the third was revised due to periacetabular osteolysis with aseptic loosening. Histological and immunohistochemical analyses were performed on tissues retrieved from this patient. Histological findings revealed perivascular lymphocytic infiltration and a small number of macrophages engulfing metal debris. Immunohistochemical staining showed admixed CD4- and CD8-positive T cells, and CD68-positive macrophages. Serum cobalt levels in two patients with osteolysis were 0.89㎛/ℓ and 0.65㎛/ℓ at 3 years postoperatively, and 0.72㎛/ℓ and 0.54㎛/ℓ at 5 years postoperatively, which were lower than mean serum cobalt levels (1.19 ± 0.16㎛/ℓ at 3 years and 1.10±0.12㎛/ℓ at 5 years) in randomly selected 24 patients.
Conclusions: After a minimum follow-up of 10 years, the outcomes of cementless primary total hip arthroplasty using CLS stem were found to be excellent with no case of aseptic stem loosening. The main mode of stem failure was periprosthetic fracture. However, when the canal fill index was ≤80%, cortical remodeling, subsidence, and a stem position change of ≧
5 degrees increased significantly, demonstrating that care must be taken not to use an undersized stem. Longer-term follow-up studies would be necessary to determine whether CLS stems maintain this performance after a second decade. In a small percentage (2.2%) of hips with a metal-on-metal bearing, periacetabular osteolysis occurred and revision surgery was necessary. The findings of this study support the contention that early osteolysis in patients with a second-generation metal-on-metal prosthesis is associated with delayed hypersensitivity to metal debris. Further randomized studies are necessary to determine the causes of early osteolysis and the effects of elevated serum metal ion levels.
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