Does cup position differ between trabecular metal and titanium cups? A radiographic propensity score matched study of 300 hips

Inari Laaksonen; Natalie  Hjelmberg; Kirill  Gromov; Antti E  Eskelinen; Ola  Rolfson; Henrik  Malchau; Anders Troelsen; Keijo T  Mäkelä; Maziar  Mohaddes

doi:10.1080/17453674.2020.1788290

Authors

Inari Laaksonen Department of Orthopedics and Traumatology, Turku University Hospital, Turku, Finland, Finnish Arthroplasty Register, Helsinki, Finland
Natalie Hjelmberg Swedish Hip Arthroplasty Register, Department of Orthopaedics, Institute of Surgical Sciences, Sahlgrenska University Hospital, Gothenburg, Sweden
Kirill Gromov Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark; Danish Hip Arthroplasty Register, Aarhus, Denmark
Antti E Eskelinen 5 Coxa Hospital for Joint Replacement, Tampere, Finland, Finnish Arthroplasty Register, Helsinki, Finland
Ola Rolfson Swedish Hip Arthroplasty Register, Department of Orthopaedics, Institute of Surgical Sciences, Sahlgrenska University Hospital, Gothenburg, Sweden
Henrik Malchau Swedish Hip Arthroplasty Register, Department of Orthopaedics, Institute of Surgical Sciences, Sahlgrenska University Hospital, Gothenburg, Sweden; Harris Orthopedic Laboratory, Massachusetts General Hospital, Boston, USA
Anders Troelsen Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark
Keijo T Mäkelä Department of Orthopedics and Traumatology, Turku University Hospital, Turku, Finland, Finnish Arthroplasty Register, Helsinki, Finland
Maziar Mohaddes Swedish Hip Arthroplasty Register, Department of Orthopaedics, Institute of Surgical Sciences, Sahlgrenska University Hospital, Gothenburg, Sweden

DOI:

https://doi.org/10.1080/17453674.2020.1788290

Abstract

Background and purpose — The use of trabecular metal cups in primary total hip arthroplasty (THA) is increasing, despite the survival of Continuum cups being slightly inferior compared with other uncemented cups in registries. This difference is mainly explained by a higher rate of dislocation revisions. Cup malpositioning is a risk factor for dislocation and, being made of a highly porous material, Continuum cups might be more difficult to position. We evaluated whether Continuum cups had worse cup positioning compared with other uncemented cups.

Patients and methods — Based on power calculation, 150 Continuum cups from 1 center were propensity score matched with 150 other uncemented cups from 4 centers. All patients had an uncemented stem, femoral head size of 32 mm or 36 mm, and BMI between 19 and 35. All operations were done for primary osteoarthrosis through a posterior approach. Patients were matched using age, sex, and BMI. Cup positioning was measured from anteroposterior pelvic radiograph using the Martell Hip Analysis Suite software.

Results — There was no clinically relevant difference in mean inclination angle between the study group and the control group (43° [95% CI 41–44] and 43° [CI 42–45], respectively). The study group had a larger mean anteversion angle compared with the control group, 19° (CI 18–20) and 17° (CI 15–18) respectively.

Interpretation — Continuum cups had a greater anteversion compared with the other uncemented cups. However, the median anteversion was acceptable in both groups and this difference does not explain the larger dislocation rate in the Continuum cups observed in earlier studies.