Short summary

A periprosthetic fracture after knee arthroplasty is an invalidating injury in where the number of fractures is projected to increase within the next decades. Essential background information on the epidemiology, outcome and especially patient related qualitative outcome is unknown. The aim of this thesis is to investigate periprosthetic fracture after knee arthroplasties on a nationwide basis in Denmark. Risk, epidemiology, mortality, treatment and reoperation outcomes is investigated based on

Rationale

Periprosthetic knee fracture (PPKF) is a serious complication after both primary knee arthroplasty and revision knee arthroplasty. A continuous increase in primary knee arthroplasties has been registered since 1997, and in the last two years there has been an annual increase of 14% culminating in 11,124 primary knee arthroplasties in Denmark in 2019 (1). Furthermore, projections from the United States of America (USA) estimates an 85% increase in total knee arthroplasties (TKA) during 2014-2030 (2). With an increase in knee arthroplasties and a longer life expectancy an increase in the total number of PPKF is to be expected (3).

Contemporary treatment options of PPKF includes: non-operative treatment, open reduction and internal fixation (ORIF) with either locking compression plate or intramedullary nailing and revision knee arthroplasty including distal femoral replacement/arthroplasty (4-10).

Only one large single-center study examining PPFK after total knee arthroplasties (TKA) exist (11). This study (11) is based on data from the Mayo Clinic (USA) and reports risk and predictors of PPFK after 17,633 primary and 3,286 revision TKA's from 1987-2008. The reported cumulative risk of PPKF was 1,1% (n=188) after primary TKA and 2,5% (n=104) after revision TKA with a follow-up of 6,3 and 5,1 years. The reported risk factors of PPKF were, age <60 after primary TKA and high comorbidity burden as well as indication for revision (infection, non-union) after revision TKA.

Only smaller retrospective studies (n<75) have previously examined outcomes after treatment of PPKF (5,8,9,10,12,13) and limited data exist on patient reported outcome measures (PROM's) after PPKF (4,9,12). Darrith et al (4) and Tandon et al (12) found a postoperative Oxford Knee Score (OKS) of 27-29 points regardless of type of treatment whereas Verma et al. (9) found improved OKS (40 points) for revision TKA and tibial ORIF compared to other treatment options.

Hence, no study examining predictors and risk of PPKF in a European nationwide setting exists. Risk of PPKF after all types of knee arthroplasty including the increasingly used unicompartmental knee arthroplasties have not been reported previously. No large quantity study examining choice of treatment, reoperation rates and mortality after treatment of PPKF exist. Furthermore, no data exist on qualitative outcomes quality of life after surgical treatment of PPKF.

The aim of this thesis is to investigate periprosthetic fractures after knee arthroplasties on a nationwide basis in Denmark. In specifics, we will examine the risk of periprosthetic knee fractures (PPKF) after knee arthroplasty and demographics of the patients having PPKF including analysis of risk factors. Furthermore, mortality and reoperation risk after treatment of PPKF will be analyzed. Finally, we will report knee function, quality of life and qualitative outcome after treatment of PPKF.

Description of the cohort

Indekspopulationen til studiet er alle patienter med procedurekoder for knæalloplastik, både primær og sekundær i perioden 1997-2021. Forventet antal er ca. 150.000 primære operationer og 15.000 revisioner Patienterne skal være bosiddende i Danmark på operationsdatoen (indexoperationsdatoen), personer der er bosiddende i Grønland skal eksluderes. Hvis samme patient er opereret i begge knæ eller er blevet re-opereret vil patienten indgå flere gange i populationen Alle operationskoder skal fremgå.

Vi ønsker at berige data på populationen med data fra Dansk Knæalloplastik Register. Dokumentation for variable fra Dansk Knæalloplastik Register er medsendt ansøgningen. I studie 2 vil indexpopulationen fra studie blive koblet op på frakturkoder omkring samme knæ som indexoperationen er foretaget på. Derfor skal alle frakturkoder også med.

Studie 3 og 4 vil bestå af patienter fra den oprindelige indekspopulation udvalgt til at danne en heterogen patientgruppe

Data and biological material

for Study 1 and 2: Demografic data, diagnosis, treatment, data from the patient journal and data from national patient registry For study 3: PROM's and Interviews

Collaborating researchers and departments

Department of Orthopedic Surgery and Traumatology, Odense University Hospital

• Martin Lindberg-Larsen, Consultant Orthopaedic Surgeon, PhD, Ass. Professor, Head of Orthopedic research unit
• Bjarke Viberg, PhD, Consultant at Department of Orthopedic Surgery and Traumatology, Odense University Hospital & Ass. Professor

Department of Orthopedic Surgery and Traumatology, Hospital Lillebaelt

• Charlotte Skov Abrahamsen, PhD, MHS, Assistant Professor

Department of Orthopaedic Surgery and Traumatology, Rigshospitalet

• Anders Odgaard, Professor, Consultant Orthopaedic Surgeon, DMSc, FRCS(Eng)