Session 1: Hip


  • A 2-year model-based Roentgen Stereophotogrammetry Analysis (RSA) Randomized Control Trial evaluating the stability of the cementless Taperloc hip stem

Ruben Y. Kok1,2, Lennard A. Koster2 MSc, Bart L. Kaptein2 PhD, Marta Fiocco3,4 PhD, S.B. Keizer1 MD.1 Department of Orthopaedic Surgery, Haaglanden Medical Center, The Hague, the Netherlands.2 Biomechanics and Imaging Group, Department of Orthopaedic Surgery, Leiden University Medical Center, Leiden, the Netherlands.3 Department of Medical Statistics and Bioinformatics, Leiden University Medical Center, Leiden, the Netherlands.4 Mathematical Institute, Leiden University, Leiden, The Netherlands.


The Taperloc Complete hip is the successor of the Taperloc hip, aiming to increase range of motion and optimizing femoral fit with intermediate stem sizes. To evaluate these design changes, this RSA study compares 2-year migration profiles.

Material and method

In this prospective, multi-arm study, 100 patients were randomized to cementless Total Hip Arthroplasty with Taperloc Complete full profile (TCFP), Taperloc Complete reduced distal (TCRD), Taperloc full profile (TFP) or Taperloc reduced distal (TRD). Migration was measured with Model-based RSA post-operatively, and after 3, 12 and 24 months.


RSA was impossible due to RSA technical issues in 24 patients and no surgery in 2 patients. Results based on mixed-model analysis on 2-year PO RSA data from 74 patients, showed similar subsidence in all stems in the first 3 months (Mean (mm (CI)) TCFP: -0.44 (-0.69; -0.20), TCRD: -0.91 (-1.42; -0.40), TFP: -0.71 (-1.19; -0.22), TRD: -1.25 (-1.91; -0.58)) and stabilization afterwards.

The TCFP showed significantly less retroversion at 2-year PO compared to the other stems ((Mean (deg (CI)) TCFP: -0.13 (-0.64; 0.38), TCRD: 0.84 (0.35; 1.33), TFP: 0.56 (0.12; 1.00), TRD: 0.37 (-0.35; 1.09)).

Interpretation and conclusion

As expected in successful uncemented THA, RSA shows stabilization after initial subsidence. Based on these results the Taperloc Complete stem is expected to have similar excellent long-term clinical outcomes compared to the Taperloc stems.

The reduced distal groups have larger, but non-significant, migration compared to the Taperloc Complete full profile group, which could be due to implantation in less feasible femur types (Dorr B, C). It appears that we should consider the femur shape for choosing between a full profile or reduced distal stem in order to minimize migration.


  • Impact of Implant Design on Femoral Stem Migration Following Direct Anterior and Direct Lateral Primary Total Hip Arthroplasty

Jennifer S. Polus1,2,5, Maxwell E. Perelgut1,2, Edward M. Vasarhelyi5, Brent A. Lanting4,5, Matthew G. Teeter1-5
1Robarts Research Institute; 2School of Biomedical Engineering; Depts. of 3Medical Biophysics, and 4Surgery, Western University; 5Lawson Health Research Institute, London ON, Canada

Introduction:Total hip arthroplasty (THA) is one of the most common orthopaedic procedures, with a continuous demand to further optimize patient recovery and lower healthcare costs. Recently, the muscle-sparing direct anterior approach (DAA) has increased in popularity compared to the intramuscular direct lateral approach (DLA). Both surgical approaches utilize collared and collarless femoral stem designs. The purpose of this study is to compare implant migration between surgical approaches and implant designs.

Patients undergoing primary THA performed using either a DAA or DLA were recruited and randomized to receive either a collared or a collarless femoral stem. On the day of surgery (DOS) and at six follow-up visits through to one-year postoperatively, patients underwent supine radiostereometric analysis (RSA) imaging.

Seventy-nine patients were assessed through one-year post-operation. Forty-nine patients underwent the DAA (n=23 received collared, n=26 received collarless) and thirty patients underwent the DLA (n=13 received collared, n=17 received collarless). Surgical approach had a significant effect on subsidence for both collared stems (p = 0.031) and collarless stems (p= 0.002). Stems within the DA group subsided more than stems in the DL group from the DOS to two-weeks post-operation (mean difference = 0.786 mm, p = 0.020 for collared stems and mean difference = 3.136 mm, p = 0.001 for collarless stems) but stabilized in both groups thereafter. Subsidence was significantly lower for collared stems compared to collarless stems within the DA group (p = 0.010) but was not different in the DL group (p = 0.894).

Most subsidence occurred from the DOS exam to two-weeks post-operation and stabilized thereafter, suggesting adequate fixation and a low risk for aseptic loosening in both groups. The DAA experienced greater implant subsidence from DOS to two-weeks compared to the DLA for both implant designs, with the collared design mitigating the subsidence experienced.

Keywords: total hip arthroplasty, surgical approach, implant design.


  • The early migration behavior of the collared Corail femoral stem. A randomized trial of 61 hips using model-based RSA with 2-year follow-up

Jonsson1, Gjertsen1, Stokke2, Haugan3, Furnes1, Hallan. 1Department of Orthopaedic Surgery, Haukeland University Hospital, Bergen, Norway.2Department of Radiology, Haukeland University Hospital, Bergen, Norway.3Orthopaedic Research Center, Trondheim University Hospital, Trondheim, Norway.


The well-documented Corail stem is the most commonly used cementless femoral component in Norway. This fully hydroxyapatite-coated tapered press-fit femoral component is available in both a collared and a collarless edition. The migration pattern of the collarless stem has been reported earlier, but no reports exist on the migration behavior of the collared stem. We therefore aimed to compare the migration pattern of the standard Corail stem with its collared counterpart in a randomized controlled trial over 2 years using radiostereometric analysis (RSA).

Materials and method:

61 patients under the age of 70 years with osteoarthritis scheduled for primary total hip arthroplasty (THA), were randomized to receive either a collared or a collarless Corail stem with standard offset.  The patients were followed for 2 years with repeated RSA examinations (postoperatively, at 3 months, 1 and 2 years) and clinical outcome measures were evaluated at each follow-up interval.


For the collared stem we observed a mean subsidence of 0.1 mm and a mean retroversion of 1°. The corresponding values for the collarless stem were 0.8 mm and 1.2°, respectively. The differences between the 2 stem types did not reach a statistical significance. The migration of both stem types had stabilized at 3 months and after that no further migration was detected. The initial pattern of migration was similar for both stem types.

Interpretation and conclusion:

The collared Corail femoral component demonstrated a small degree of initial migration before achieving stability within 3 months of implantation in THA patients less than 70 years followed with RSA for 2 years. The early migration behavior of the collared Corail is similar to its well-proven collarless counterpart.


  • Randomized controlled trial comparing the CFP with the Corail stem, a five-year report.

Karin RILBY1, Maziar MOHADDES1 & Johan KÄRRHOLM1 . 1 Department of Orthopaedics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Sweden.

Introduction: The CFP stem has been on the market in its current design since the 90ies. It is often classified as a short stem with metaphyseal anchorage. The design aims to preserve proximal bone in order to facilitate later revision. Few studies have been performed evaluating clinical outcome, subsidence and bone mineral density loss.

Material and methods: 81 patients eligible for hip replacement were recruited from the outpatient clinic at Sahlgenska Hospital, Mölndal. They were assessed using several different clinical outcome scores, plain radiographs, RSA and DXA.

Results: There were no significant difference between groups regarding patient reported outcome measures. Both groups reported high patient satisfaction and a well-functioning hip implant. RSA analysis showed median subsidence of -0.2 (CFP, range -1 to 0.2) and -0.1 (Corail, -6 to 0.3) at 2 years without any significant difference with little or no further subsidence between 2 and 5 years. Median subsidence between 2 and 5 years was -0,098 (CFP, range -0,29-0,55) and -0,05 (Corail, range -0,53-0,29). Neck resorption was evident in 9 patients in the CFP group, none of the Corail stems showed any neck resorption. DXA showed a marked loss of BMD in the proximal Gruen zones in the CFP stems. (Mean changes in BMD, 95% CI, Gruen zone 1; CFP -9.51, -14.84- -4.17, Corail 1.02, -3.37- 5.41, Gruen zone 7; CFP -23.0, -29.4- -16.6, Corail -7.24, -15.87- 1.39) The difference was clinical significant compared to the Corail stem. 2 CFP stems were revised due to loosening before the 2 year follow up, between 2 and 5 years 1 Corail was revised due to late chronic infection.

Interpretation and conclusion: CFP stem had about equal subsidence and clinical outcome compared to the Corail stem, but the 2 early revisions due to loosening are reason for concern. The more pronounced stress shielding around the CFP stems suggest a diaphyseal anchorage rather than a metaphyseal one.

Keywords: Total hip arthroplasty, Radiostereometric analysis, short stems


  • Very early migration of a neck preserving short stem – What happens between surgery and first weight bearing?

Stefan Budde, Christof Hurschler, Yvonne Noll, Alexander Derksen, Michael Schwarze. All authors: Hannover Medical School, Orthopaedic Department, Hannover, Germany.


Previous studies of short stems have revealed a distinct pattern of migration in cementless short stem THA: Many individual prostheses show an initial migration of around 1mm between post-operative examination and the first follow-up at three months. The RSA-ISO standard recommends the reference examination „within five days, preferably before weight bearing“. Since the usual procedure in our clinic is to allow full weight bearing at the first postoperative day, it is unknown which amount of migration occurs between surgery and the usual examination at the day of discharge. One of the goals of this study was to determine the exact course of the very early postoperative migration within the first three months.

Materials and Methods

Sixty patients were included in the study. The primary endpoint of the study is the difference in migration depending on surface coating and stem shape of the A2 short stem after 24 months and will be determined in late 2022.

RSA examinations were conducted at the day of surgery or in the morning of the post-operative day before any loading of the affected leg, at hospital discharge, 1.5, 3, 6, 12 and 24 months post-operatively. Resulting migration over time was calculated using bone markers and CAD models.


All sixty patients have completed at least the six week examination. Average resulting migration was 0.28mm at discharge and 0.61mm at six weeks. The difference in migration between stem coatings was significant at six weeks, while the difference between stem shapes was not.

Interpretation and Conclusion

There is some migration occurring during the first days of prosthesis usage, that would not be detected when using the radiographs at discharge day as reference. However this migration is only marginal, indicating that the major initial settling of the implant takes place between discharge and six weeks post-operatively.

Keywords Very early migration, THA, short stem, surface coating

Keywords Very early migration, THA, short stem, surface coating


  • Similar clinical results and migration with use of either a new anteverted or a straight standard stem after 2 years: randomized study of 72 Total Hip Arthroplasties (THAs) evaluated with clinical parameters, radiostereometry and DXA up to 2 years

Karin Rilby1, Maziar Mohaddes1, Emma Nauclér2 & Johan Kärrholm1. 1, Department of Orthopaedics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Sweden. 2, Swedish Hip Arthroplasty Register, Gothenburg, Sweden


We evaluated an anatomical uncemented stem, SP-CL, (Static Physiologicus – CementLess) designed to facilitate insertion and to avoid stress concentration at solitary contact points. It has been on the market since 2014 but is still not well documented. We studied its clinical performance, migration and associated bone remodeling in a randomized controlled trial, with use of the Corail stem as control. 

Patients and method

79 patients (80 hips) were primarily recruited and 71 patients (72 hips, 36 SP-CL, 36 Corail) attended the last follow up at 2 years. Several types of PROMs and Harris Hip Score were used for the clinical evaluation with use of Oxford Hip Score (OHS) as primary outcome. In addition, repeated measurements of stem migration, changes in bone mineral density and development of radiolucencies were studied with RSA, DXA and conventional radiography. 


In both groups Oxford hip score had almost doubled at 3 months, continued to increase up to 6 months and was about equal at 2 years (SP-CL; median 46, range 17-48, Corail; median 47 range 19-48, p-value 1.0). At 2 years the SP-CL stems showed a median distal migration of -0.23 range -5.2 – 0.1, and the Corail stems of – 0.11, -4.4 – 0.4, p = 0.2. Between 1 and 2 years there was little further median subsidence, SP-CL -0,02 (range -0,25-0,27) Corail -0,00 (range -0,55-0,47) The SP-CL stems showed slightly more loss of bone mineral density in Gruen region 7 (p = 0.003).

Interpretation and conclusion

At 2 years use of the SP-CL stem was associated similar clinical results and stem migration as for the control stem. Our results support further evaluation of the SP-CL stem in a multi-center setting.