Today, THAs are undertaken in greater numbers of younger and more active patients than ever before; at the same time, the total number of yearly applied THAs is slightly increasing.
This development means that the annual number of total hip revisions is also increasing yearly. In a meta-analysis consisting of 27 studies, Phedy et al. compared cemented THA to cementless THA and found that cemented fixation was superior over cementless (Phedy et al.
2017). In a systematic review study where 5399 MoM HRAs and 3244 THAs were analysed, the overall revision rate for MoM THAs was 4.7% after 6.9 years and for HRA it was 5.9% after 5.7 years (Ras Sørensen et al. 2016). In a 15-year follow-up study, the cumulative revision rate of 1429 MoM HRAs for all causes was 19.5% (Matharu et al. 2016).
Revision causes of LDH MoM arthroplasties can be divided into seven categories; the most common cause of revision in both THA and HRA is aseptic loosening, with rates of 47.6% and 37.7% (Ras Sørensen et al. 2016). Other reasons for revision in THA and HRA were peri-prosthetic fracture (THA 7.7% vs. HRA 19.6%), metal reactions (THA 7.7% vs. HRA 26.9%), infection (THA 12.1% vs. HRA 6.5%), instability (THA 9.1% vs. HRA 2.7%) and a small number of manufacturer defects and miscellaneous reasons (Ras Sørensen et al. 2016). The incidence of revision caused by aseptic loosening varies a lot depending on what devices have been used and how the follow-up has been undertaken. In a large analysis using worldwide registers, Sadoghi et al. found that one in every 13 patients has to be revised due to aseptic loosening (Sadoghi et al. 2013). The cumulative incidence of infection revision after primary THA was 0.86% and 1.03% in one- and five-year follow-ups, respectively (Gundtoft 2017). In a large series of 623,253 index THAs, the prevalence of revision due PJI was 0.4% and after revision surgery was 1.6% (Lenguerrand et al. 2017).
Acetabulum component revision is the most common THA revision; the main reasons leading to revision are aseptic loosening of the component due to wear debris from bearing surfaces and hip instability (Kim 2017). There are several options for revision surgery of the acetabulum component. Common treatment options include acetabular liner exchange, the use of a large cementless cup, reinforcement cage or trabecular metal cup cage, or in some cases the use of a cemented cup (Kim 2017). The optimal treatment depends on the degree of acetabulum discontinuity and the amount of available bone stock. Achieving stable acetabulum component fixation with a proper choice of method is mandatory for successful acetabulum cup revision. Acetabulum reconstruction by using a cementless tantalum acetabulum component gives excellent clinical results with a ten-year survivorship of 92%
(Konan et al. 2016).
Most femoral components with stem failure due to aseptic loosening and are often revised with a cementless long revision stem (Reikerås et al. 2006). The HRA femoral component is quite easy to revise and convert to conventional type femur components by cutting the femoral collum beneath the femoral implant.
3 Aims of the study
The aims of the present study were to:
1. Examine the midterm survival rate of large diameter head total hip arthroplasties and hip resurfacing arthroplasties and compare complications and revision rates between these devices (I).
2. Investigate the incidence and risk factors of intraoperative calcar fracture in cementless total hip arthroplasties (II).
3. Evaluate possible denominators related to early aseptic loosening of the cementless hemispherical monoblock acetabular components (III).
4. Examine the incidence and evaluate patient-dependent demographic and radiographic risk factors for the dislocation of large diameter head total hip arthroplasty and hip resurfacing arthroplasty (IV).
4 Materials and methods
4.1 STUDY DESIGN AND DEMOGRAPHIC DATA
This was a retrospective multicentre study. The participating university hospitals were Kuopio University Hospital (KYS) and Helsinki University Central Hospital (HYKS) and Turku University Hospital (TYKS). A total of 4038 THAs and HRAs with MoM bearing surfaces were operated between January 2004 and December 2009. These patients formed a study population which consisted of 3207 THAs in 2912 patients and 831 HRAs in 757 patients. Smaller sample size subgroups were formed from this study population for more accurate analysis and these study populations were as follows:
Study I.
The midterm survival of LDH THA and HRA were evaluated and the population consisted of a total of 3860 hip arthroplasties in 3491 patients; in this population, there were 3029 THAs (head size ≥ 38 mm) in 2734 patients and 831 HRAs in 757 patients.
Study II.
The incidence and risk factors of intraoperative calcar fracture in cementless THAs were investigated; there was a total of 3207 THAs in 2912 patients.
Study III.
The early aseptic loosening of the hemispherical monoblock MoM acetabular components were evaluated and the study population consisted of 3209 THAs in 2912 patients and 834 HRAs in 757 patients.
Study IV.
The incidence of the LDH MOM THA and HRA dislocation were evaluated and patient depended demographic and radiographic risk factors affecting dislocation were analysed. This study population consisted of a total of 4038 hips with 3207 THAs in 2912 patients and 831 HRAs in 757 patients.
Total number of THAs and HRAs in each hospital are given in Figure 9. The mean age of the patients in TYKS was 61.8 (SD 10.998, range, 18 - 96) years, in HYKS 55.2 (SD 9.405, range, 17 - 86) years and in KYS 60.8 (SD 9.245, range, 25 - 90) years (p = 0.001), respectively.
Figure 9. Total number of THAs and HRAs in each participated hospital (TYKS =Turku University Hospital, HYKS=Helsinki University Central Hospital, KYS=Kuopio University Hospital).
Demographic data (age, gender, side, indication for surgery, date of surgery) and surgical details (surgical approach, intraoperative complication, type and name of components used) were collected from the medical records. There were 14 different THA femoral components, 14 different THA acetabular components and 6 different HRA (Table 2 and 3). THAs and HRAs were performed according to the manufacturers’ instructions. Surgeons (consultant orthopaedic surgeons/residents) who performed surgeries were identified in the small sample size study groups of studies II and III. Operations were performed by 39 consultant orthopaedic surgeons and by seven residents under the supervision of the consultant orthopaedic surgeon.
Patient-dependent risk factors affecting bone quality (age, gender, diagnosis of osteoporosis, long-term oral cortisone medication for any reason, rheumatoid arthritis, and previous history of alcohol abuse) were analysed from the patient medical records. Other patient-dependent risk factors like developmental dysplasia of the hip, previous childhood hip osteotomies, and acute and previous hip fractures were also evaluated, as well as underlying systemic diseases affecting risk of dislocation (prior diagnosed rheumatoid arthritis, alcohol abuse, neurological disease). Diagnosis of hip dysplasia was collected from the patient medical records and also defined from the radiographs.
Table 2. Types, brands and numbers of THAs of the study population.
n (%)
Total hip arthroplasty 3207 (79.4)
Femur components
Fit and fill -type 2739 (85.4)
Biomet Bi-Metric (Biomet, Warsaw, IN, USA) 2418 (75.4)
Synergy (Smith & Nephew, Memphis, TN, USA) 321 (10)
Tapered 412 (12.9)
Conserve Profemur TL (Wright Medical Technology, Arlington, TN, USA) 188 (5.9)
Metasul CLS (Zimmer, Warsaw, IN, USA) 158 (4.9)
M/L Taper (Zimmer, Warsaw, IN, USA) 46 (1.4)
Corail (DePuy Orthopaedics, Warsaw, IN, USA) 18 (0.6)
Accolade (Stryker, Mahwah, NJ, USA) 2 (0.1)
Other 56 (1.7)
Biomet Reach (Biomet, Warsaw, IN, USA) 31 (1.0)
Biomet CDH (Biomet, Warsaw, IN, USA) 10 (0.3)
Biomet Integral (Biomet, Warsaw, IN, USA) 7 (0.2)
Metalic 5 (0.2)
Mitch Symax (Stryker, Mahwah, NJ, USA) 1 (0.0)
Biomet Balance (Biomet, Warsaw, IN, USA) 1 (0.0)
Biomet Head/Neck (Biomet, Warsaw, IN, USA) 1 (0.0)
Acetabulum components
Biomet ReCap (Biomet, Warsaw, IN, USA) 1851 (57.7)
Biomet M2a38 (Biomet, Warsaw, IN, USA) 469 (14.6)
BHR (Smith & Nephew, Memphis, TN, USA) 247 (7.7)
Conserve (Wright Medical Technology, Arlington, TN, USA) 189 (5.9)
Durom Cup (Zimmer, Warsaw, IN, USA) 184 (5.7)
R3 (Smith & Nephew, Memphis, TN, USA) 75 (2.3)
Biomet Vision (Biomet, Warsaw, IN, USA) 75 (2.3)
Biomet Stanmore (Biomet, Warsaw, IN, USA) 56 (1.7)
Pinnacle (DePuy Orthopaedics, Warsaw, IN, USA) 18 (0.6)
Biomet Universal (Biomet, Warsaw, IN, USA) 15 (0.5)
Morscher Cup (Sulzer/Zimmer GmbH, Winterthur, Switzerland) 14 (0.4)
MMC Cup (Zimmer, Warsaw, IN, USA) 6 (0.2)
Metalic 5 (0.2)
Mitch TRH (Stryker, Mahwah, NJ, USA) 3 (0.1)
Table 3. Types, brands and numbers of HRAs of the study population.
n (%)
Hip resurfacing arthroplasty 831 (21.5)
BHR (Smith & Nephew, Memphis, TN, USA) 467 (56.2)
Biomet ReCap (Biomet, Warsaw, IN, USA) 157 (18.9)
Conserve Plus (Wright Medical Technology, Arlington, TN, USA) 120 (14.4)
Cormet (Corin, Tampa, FL, USA) 44 (5.3)
Durom (Zimmer, Warsaw, IN, USA) 23 (2.8)
ASR (DePuy Orthopaedics, Warsaw, IN, USA) 20 (2.4)
Mean head size of THAs was 45.5 mm (SD 6.489, range, 28 - 60) and HRAs 49.7 mm (SD 3.826, range, 40 - 60) (p = 0.001). THA head sizes were classified in three subgroups: 1) head sizes < 38 mm (n=178), 2) 38 mm (n=492) and 3) > 38 mm (n=2537). Mean head size of HRAs was 46.0 mm (SD 2.766, range, 40 - 54) in females and 51.3 mm (SD 2.963, range, 42 - 60) in males (p = 0.001), respectively.