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CORAIL® Collared Hip System collared provides increased protection against risk of femoral fracture, registry analysis backed up by biomechanical study

Isaiah Adekanmbi1, David Horne1, Jonathan N Lamb3, Johanna Baetz2, Philipp Messer-Hannemann2, Michael M Morlock2, Hemant G Pandit3

1. DePuy Synthes Joint reconstruction, Leeds, UK.

2. TUHH, Hamburg University of technology, Institute of Biomechanics, Hamburg, Germany.

3. Leeds Institute of Rheumatic and Musculoskeletal Medicine (LIRMM), School of medicine, University of Leeds, Chapel Allerton Hospital, Leeds, UK

Keywords: Collar, PFF, Joint Registry, Biomechanical testing.




Periprosthetic femoral fracture (PFF) is a complication of THA that occurs in up to 5% of primary THA1 . The risk of PFF is greatest in the early post-operative period and is four-fold higher in cementless versus cemented stems in the first 90 days2. However, the role of the specific design features that are responsible are not known. The aim of the study was to estimate the 90-day risk of revision for PFF associated with design features of cementless femoral stems and the effect of a collar on early PFF risk using a biomechanical in-vitro model.



337 647 primary THAs from the UK National Joint Registry (NJR) were included in a multivariable survival and regression analysis to identify the adjusted risk of PFF revision following primary THA using cementless stems.5 The effect of a collar on early PFF was evaluated in an in-vitro model using paired fresh frozen cadaveric femora. A 32mm CoCr head was fitted to the CORAIL® Stem and loading scenario was applied to the specimen to simulate single leg stance and then a traumatic event. Imaging after fracture was performed to identify fracture patterns.


The overall prevalence of revision for PFF was 0.34% (1180/337647) and 44% occurred (520/1180) within 90 days of surgery. The study indicated that collarless design was associated with the largest increase to risk of revision due to PFF (HR 4.7 (3.5,6.3) P<0.001.5 In the in-vitro PFF modelprior to fracture in all femur pairs a maximum torsional moment was seen to be larger for the collared CORAIL® Implant versus a collarless CORAIL® Implant. The medial calcar collar was seen to improve construct stability and fracture resistance.


Analysis of stem design features in registry data appears to be a useful method to identify potential implant characteristics which may affect the risk of early PFF in cementless femoral stems. The biomechanical testing replicated early in-vivo PFF patterns3,4 and confirmed that a medial calcar collar increased the resistance to PFF. The use of a collar may help to improve the survival of cementless stems in the future by reducing the risk of early periprosthetic fracture.


1. Abdel MP, Watts CD, Houdek MT, Lewallen DG, Berry DJ. Epidemiology of periprosthetic fracture of the femur in 32 644 primary total hip arthroplasties: a 40-year experience. Bone & Joint Journal. 2016;98-B(4):461-7.

2. Lindberg-Larsen M, Jorgensen CC, Solgaard S, Kjersgaard AG, Kehlet H, Lundbeck Fdn Ctr Fast-Track H. Increased risk of intraoperative and early postoperative periprosthetic femoral fracture with uncemented stems 7,169 total hip arthroplasties from 8 Danish centers. Acta Orthopaedica. 2017;88(4):390-4.

3. Gromov K, Bersang A, Nielsen CS, Kallemose T, Husted H, Troelsen A. Risk factors for post-operative periprosthetic fractures following primary total hip arthroplasty with a proximally coated double-tapered cementless femoral component. Bone & Joint Journal. 2017;99-B(4):451-7.

4. Taunton MJ, Dorr LD, Long WT, Dastane MR, Berry DJ. Early Postoperative Femur Fracture After Uncemented Collarless Primary Total Hip Arthroplasty: Characterization and Results of Treatment. Journal of Arthroplasty. 2015;30(11):2008-11.

5. Lamb, JN, Baetz, J, Messer-Hannemann, P et al. (2019) A calcar collar is protective against early periprosthetic femoral fracture around cementless femoral components in primary total hip arthroplasty: a registry study with biomechanical validation. Bone and Joint Journal, 101-B (7). pp. 779-786.



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