The research questions this study aims to answer are as follows:

Primary research question:

"Do primary total hip arthroplasties for patients with OA, hip fracture or osteonecrosis with the 150mm Lubinus SPII hip stem have better mortality and stem revision rates than primary total hip arthroplasties with the 130mm hip stem?"

Secondary aims include:

• How does line-to-line cementation, compare to undersized cementation in primary total hip arthroplasty for patients with OA, hip fracture, or osteonecrosis when comparing equal size Lubinus SPII hip stems implanted with different cementation techniques?
• Does the Lubinus SPII 150mm hip stem perform equal to the Lubinus SPII 130mm hip stem in primary total hip arthroplasties for patients with OA, hip fracture or osteonecrosis when comparing patient reported outcome measures?

To answer these questions, this study has been allowed use of registered data from the LROI (dutch arthroplasty registry) and the SAR (swedish arthroplasty registry). After exclusion of patients who did not meet inclusion criteria between 2007-2020, approximately 110000 patients remain eligible for analysis.

Inclusion Criteria:

• Listed in registry for primary hip arthroplasty.

  • Listed in registry with an indication of osteoarthritis, osteonecrosis or hip fracture.
  • Received the Lubinus SPII hip stem, 130mm or 150mm, for their primary hip arthro- plasty.
  • End point listed in registry (Alive, Deceased or revision).

Exclusion Criteria:

• Patients who received the Lubinus SPII 150 XL conus stem.

All patients incorporated in the LROI and SAR databases between 2007 and 2020 were included, if they satisfied the in- and exclusion criteria.