Introduction: Dual mobility implants have been successful in reducing postoperative hip dislocation but mid-term results of cup migration and polyethylene wear are missing in the literature.... Show moreIntroduction: Dual mobility implants have been successful in reducing postoperative hip dislocation but mid-term results of cup migration and polyethylene wear are missing in the literature. Therefore, we measured migration and wear at 5-year follow-up using radiostereometric analysis (RSA). Materials and methods: A cohort of 44 patients (mean age 73, 36 female) with heterogeneous indications for hip arthroplasty but all with a high risk of hip dislocation received total hip replacement (THA) with The Anatomic Dual Mobility X3 monoblock acetabular construct and a highly crosslinked polyethylene liner.RSA images and Oxford Hip Scores were obtained perioperatively and 1, 2, and 5 years postoperatively. Cup migration and polyethylene wear were calculated using RSA. Results: Mean 2-year proximal cup translation was 0.26 mm (95% CI 0.17; 0.36). Proximal cup translation was stable from 1- to 5-year follow-up. Mean 2-year cup inclination (z-rotation) was 0.23 degrees (95% CI - 0.22; 0.68) and was greater in patients with osteoporosis compared to patients without osteoporosis (p = 0.04). Using 1-year follow-up as baseline, the 3D polyethylene wear rate was 0.07 mm/year (0.05; 0.10).Oxford hip scores improved 19 (95% CI 14; 24) points from mean 21 (range 4; 39) at baseline, to 40 (9; 48) 2 years postoperatively. There were no progressive radiolucent lines > 1 mm. There was 1 revision for offset correction. Conclusions: Anatomic Dual Mobility monoblock cups were well-fixed, the polyethylene wear rate was low, and the clinical outcomes were good until 5-year follow-up suggesting good implant survival in patients of different age groups and with heterogeneous indications for THA. Show less
Background Radiostereometric Analysis (RSA) is used to measure fixation of joint prosthesis. This study compared radiation dose and image quality of a digital radiography (DR) RSA system and a... Show moreBackground Radiostereometric Analysis (RSA) is used to measure fixation of joint prosthesis. This study compared radiation dose and image quality of a digital radiography (DR) RSA system and a computed radiography (CR) RSA system in a clinical setting. Methods RSA recordings of 24 hips and shoulders were analyzed. We compared two systems: (1) Arcoma T0 with ST-VI image plates and Profect CR-IR 363 reader to (2) AdoraRSA with CXDI-70C wireless DR detectors in a clinical uniplanar RSA set-up with a +/- 20 degrees tube angulation and 35 cm x 43 cm detectors. Effective dose was calculated using dedicated software. Image quality was evaluated using calibration errors as calculated by the RSA software. Results The mean dose for hips was 0.14 (SD 0.04) mSv in the CR system and 0.05 (SD 0.02) mSv in the DR system. The mean dose for shoulders was 0.16 (SD 0.07) mSv in the CR system and 0.09 (SD 0.03) mSv in the DR system. Radiation dose was 64% (p < 0.001) and 43% (p = 0.03) lower in the DR system compared with the CR system for hip and shoulder RSA, respectively. Image quality was better for the DR system with 60-80% less calibration errors compared to the CR system. Conclusion Owing to highly efficient detectors and added filtration at the x-ray tubes, the DR system considerably reduced radiation dose compared with the CR system without compromising image quality. Based on the findings in this study, we recommend replacing CR RSA systems with DR RSA systems. Registration Patients were selected from clinical studies performed on the two systems and approved by the local ethics committee [20060165, M-20100112, M-20070082, M-20110224, and 20070258] and registered with ClinicalTrials.gov [NCT00408096, NCT01289834, NCT00913679, NCT02311179, and NCT00679120]. Show less
Background: Investigation of polyethylene liner movement in total hip arthroplasty requires bead-marking for radiographic visibility of the liner. However, occlusion of markers poses a challenge... Show moreBackground: Investigation of polyethylene liner movement in total hip arthroplasty requires bead-marking for radiographic visibility of the liner. However, occlusion of markers poses a challenge for marker registration in radiographs.Methods: The polyethylene of a dual mobility acetabular system was marked with twelve 1-mm tantalum markers (four groups of three markers) using a custom-made drill guide. Liner motion in a phantom and a patient was investigated with dynamic radiostereometry analysis (dRSA) at 1-year follow-up and static radiostereometry analysis (sRSA) postoperatively and at 1- and 2-year follow-up. A combined marker configuration (CMC) model was calculated from the registered positions of the liner markers and the femoral head in several images. Furthermore, the CMC model and the theoretic marker positions from computer-assisted models of the drill guide were combined in a hybrid model.Results: The CMC model included eleven markers in the phantom and nine markers in the patient, which was sufficient for dRSA. Liner movement in the phantom followed liner contact with the femoral neck, while liner movement in the patient was independent. The hybrid model was necessary to determine liner orientation in sRSA recordings, which clearly changed from postoperative to 1- and 2-year follow-up even though the patient was positioned similarly.Conclusion: Polyethylene liner motion in dual mobility hip prosthesis can be assessed with CMC models in dRSA recordings. In sRSA, the liner position between follow-ups is unpredictable and analysis requires inclusion of all markers in the model, accomplished with a hybrid marker model. Show less
The longevity of total knee implants may be impaired by aseptic loosening of the components within the bone. Aseptic loosening remains the leading cause of revision surgery. In the past decades,... Show moreThe longevity of total knee implants may be impaired by aseptic loosening of the components within the bone. Aseptic loosening remains the leading cause of revision surgery. In the past decades, many implant design aspects and surgical techniques have been changed in an attempt to decrease the risk of loosening. Given that radiostereometric analysis (RSA) is a highly accurate method to detect early implant migration which is predictive for late loosening, new implant designs should ideally be tested with RSA before widespread introduction onto the market. In this thesis, we present the results of four randomized controlled trials studying the effect of such changes in design on implant migration with use of RSA. We also pooled several RSA studies to be able to analyze the effect of other possible risk factors, including patient characteristics and surgical technique. We show that slight changes in implant design may increase the risk of loosening considerably, while other factors that are often thought to be associated with an increased risk (such as a high body mass index) do not appear to have a large effect. Show less
Hansen, L.; Raedt, S. de; Jorgensen, P.B.; Mygind-Klavsen, B.; Kaptein, B.; Stilling, M. 2018
As the number of hip fracture patients has increased dramatically over the years, the need for high quality, multidisciplinary and patient centred fracture treatment continues to grow. The first... Show moreAs the number of hip fracture patients has increased dramatically over the years, the need for high quality, multidisciplinary and patient centred fracture treatment continues to grow. The first aim of this thesis is to provide better understanding of fracture patterns and classification in hip fractures. Secondly, we investigated what fracture, patient or surgeons' characteristics may lead to improvement of hip fracture care? In Chapters 2 to 6 increased insight in the fracture anatomy was intended and the reliability of the most frequently used classifications for proximal femur fractures were studied. Rotational instability appears to play a significant role in fixation failure. In Chapter 7 the amount of rotational instability in hip fractures, related to type of fracture and modern implants was studied with the use of radiostereometric analysis (RSA). Chapter 8 presents the results of a retrospective cohort study concerning the pre- and post-operative radiographic fracture characteristics in relation to patient age and the occurrence of reoperation. The surgeons' intra-operative estimations of the femoral anteversion angle during placement of a hemi-arthroplasty for femoral neck fractures was studied in Chapter 9 and in Chapter 10 a systematic review regarding the treatment dilemmas in non-displaced femoral neck fracture is described. Show less
