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
Hansen, L.; Raedt, S. de; Jorgensen, P.B.; Mygind-Klavsen, B.; Romer, L.; Kaptein, B.; ... ; Stilling, M. 2022
Purpose: Dynamic radiostereometric analysis (dRSA) enables precise non-invasive three-dimensional motion-tracking of bones for assessment of joint kinematics. Hereby, the biomechanical effects of... Show morePurpose: Dynamic radiostereometric analysis (dRSA) enables precise non-invasive three-dimensional motion-tracking of bones for assessment of joint kinematics. Hereby, the biomechanical effects of arthroscopic osteochondroplasty of the hip (ACH) can be evaluated in patients with femoroacetabular impingement (FAI). The aim was to investigate the pre- and postoperative range of motion (ROM) and the CT bone volume removed (BV) after ACH. We hypothesize increase in ROM 1 year after surgery. Methods: Thirteen patients (6 female) with symptomatic FAI were included prospectively. The patient's hips were CT-scanned and CT-bone models were created. Preoperative dRSA recordings were acquired during passive flexion to 90 degrees, adduction, and internal rotation (FADIR). ACH was performed, CT and dRSA were repeated 3 months and 1 year postoperatively. Hip joint kinematics before, and 3 months and 1 year after ACH were compared pairwise. The bone volume removal was quantified and compared to change in ROM. Results: Mean hip internal rotation, adduction and flexion were all unchanged after ACH at 1-year follow-up (p > 0.84). HAGOS scores revealed improvement of quality of life (QOL) from 32 to 60 (p = 0.02). The BV was between 406 and 1783 mm(3) and did not correlate to post-operative ROM. Conclusions: ACH surgery in FAI patients had no impact of ROM at 1-year follow-up. QOL improved significantly. This indicates that the positive clinical effects reported after ACH might be a result of reduced labral stress and cartilage pressure during end-range motion rather than increased ROM. Show less
Background and purpose - Dual-mobility hip arthroplasty utilizes a freely rotating polyethylene acetabular liner to protect against dislocation. As liner motion has not been confirmed in vivo, we... Show moreBackground and purpose - Dual-mobility hip arthroplasty utilizes a freely rotating polyethylene acetabular liner to protect against dislocation. As liner motion has not been confirmed in vivo, we undertook this using dynamic radio-stereometry (RSA). Patients and methods - 6 patients with Anatomical Dual Mobility acetabular components were included.Markers were implanted in the liners using a drill guide. Static RSA recordings and patient-reported outcome measures were obtained postoperatively and at 1-year follow-up. Dynamic RSA recordings were obtained at 1-year follow-up during passive hip movement: abduction/external rotation, adduction/internal rotation (modified FABER-FADIR), to end-range and at 45 degrees hip flexion. Liner and neck movements were described as anteversion, inclination, and rotation.Results - Liner movement during modified FABER-FADIR was detected in 12 of 16 patients. Median (range) absolute liner movements were: anteversion 10 degrees (5-20), inclination 6 degrees (2-12), and rotation 11 degrees (5-48) relative to the cup. Median absolute change in the resulting liner/neck angle (small articulation) was 28 degrees (12-46) and in liner/cup angle (larger articulation) was 6 degrees (4-21). Static RSA showed changes in median liner anteversion from 7 degrees (-12 to 23) postoperatively to 10 degrees (-3 to 16) at 1-year follow-up and inclination from 42 degrees (35-66) postoperatively to 59 degrees (46-80) at 1-year follow-up. Liner/neck contact was associated with high initial liner anteversion (p = 0.01).Interpretation - The polyethylene liner moves over time. 1 year after surgery the liner can move with or without liner/neck contact. The majority of movement is in the smaller articulation between head and liner. 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
Jurgens-Lahnstein, J.H.; Petersen, E.T.; Laursen, M.; Iversen, C.H.; Kaptein, B.L.; Lindgren, L.; Stilling, M. 2021
Radiostereometric analysis (RSA) is an accurate and precise radiographic method that can be used to measure micromotion of implants and study joint kinematics in vivo. A calibration cage with... Show moreRadiostereometric analysis (RSA) is an accurate and precise radiographic method that can be used to measure micromotion of implants and study joint kinematics in vivo. A calibration cage with radiopaque markers is used to calibrate the RSA images; however, the thickness (250 mm) of the calibration cage restricts the available area for the patient and equipment during RSA recordings. A thinner calibration cage would increase the recording area, facilitate handling of the cage, and ease integration of the cage with the RSA system. We developed a thinner calibration cage without compromise of accuracy and precision. First, we performed numerical simulations of an RSA system, and showed that the calibration cage thickness could be decreased to 140 mm maintaining accuracy and precision using 40 fiducial and 30 control markers. Second, we constructed a new calibration cage (NRT cage) according to the simulation results. Third, we validated the new calibration cage against two state-of-the-art calibration cages (Umeaa cage and Leiden cage) in a phantom study. All cages performed similar for marker-based analysis, except for y-rotation, where the Umeaa cage (SD = 0.064 mm) was less precise compared to the NRT (SD = 0.038 mm) and Leiden cages (0.042 mm) (p = .01). For model-based analysis the NRT cage had superior precision for translations (SD <= 0.054 mm) over the Leiden cage (SD <= 0.118 mm) and Umeaa cage (SD <= 0.093 mm) (p < .01). The combined study confirmed that the new and thinner calibration cage maintained accuracy and precision at the level of existing thicker calibration cages. Show less
Background and purpose - Hydroxyapatite (HA)-coated implants have been associated with high polyethylene wear in hip arthroplasties. HA coating as a promoter of wear in knee arthroplasties has not... Show moreBackground and purpose - Hydroxyapatite (HA)-coated implants have been associated with high polyethylene wear in hip arthroplasties. HA coating as a promoter of wear in knee arthroplasties has not been investigated. We compared the wear-rate of the polyethylene bearing for cemented and cementless HA-coated Oxford medial unicondylar knee arthroplasties (UKA). Secondarily, we investigated whether wear-rates were influenced by overhang or impingement of the bearing. Patients and methods - 80 patients (mean age 64 years), treatment-blinded, were randomized to 1 of 3 Oxford medial UKA versions: cemented with double-pegged or single-pegged femoral component or cementless HA-coated with double-pegged femoral component (ratios 1:1:1). We compared wear between the cemented (n = 55) and cementless group (n = 25) (ratio 2:1). Wear, impingement, and overhang were quantified between surgery and 5-year follow-up using radiostereometry. Clinical outcome was evaluated with the Oxford Knee Score. Results - The mean wear-rate for patients without bearing overhang was 0.04 mm/year (95% CI 0.02-0.07) for the cemented group and 0.05 mm/year (CI 0.02-0.08) for the cementless group. The mean difference in wear was 0.008 mm/year (CI -0.04 to 0.03). No impingement was identified. Half of the patients had medial bearing overhang, mean 2.5 mm (1-5). Wear increased by 0.014 mm/year for each mm increment in overhang. The mean Oxford Knee Score was 39 for the cementless group and 38 for the cemented group at the 5-year follow-up. Interpretation - The wear-rates were similar for the 2 fixation methods, which supports further use of the cementless Oxford medial UKA. However, a caveat is a relatively large 95% CI of the mean difference in wear-rate. Component size and position is important as half of the patients presented with an additional increase in wear-rate due to medial bearing overhang. Show less
Nielsen, E.T.; Stentz-Olesen, K.; Raedt, S. de; Jorgensen, P.B.; Sorensen, O.G.; Kaptein, B.; ... ; Stilling, M. 2018
