Short summary

The purpose of this study is to assess the survival rate of the PAO procedure with the endpoint being THA and presented according to the different types of dysplasia. Methods: Data on all patients treated with PAO at Odense University Hospital between 1997 and 2021 is collected from patient journals. Data on patients undergoing PAO nationwide is collected on procedure code level. Traditional dysplasia, retroversion and Calve-Legg-Perthes are all included. Data is collected from October 2021.

Rationale

Developmental dysplasia of the hip (DDH) is a condition of the hip joint that refers to insufficient development of the acetabulum which results in suboptimal bony coverage of the femoral head. Retroversion is a condition of the hip where the acetabulum is retroverted and the hip has over-coverage anteriorly. Calve-Legg-Perthes is often seen in children, where there is not enough blood flow to the femoral head potentially leading to a deformity of the femoral head. The symptoms of these conditions include hip pain, restricted mobility and can lead to secondary osteoarthritis (OA).

Periacetabular osteotomy (PAO) has become the most common used surgery for DDH and the aim of the PAO is to reorient the acetabulum, to correct abnormal acetabular morphology and improve femoral head coverage. The procedure was first described in 1988 by Ganz et al. and is referred to as a hip-preserving operation. The PAO is considered for young patients with malalignment yet not advanced OA. The aim of the surgery is to reduce hip pain and re-store function resulting in better quality of life, but also to avoid secondary OA, thus postponing a total hip arthroplasty (THA). The patients are often young, and most will outlive an arthroplasty if not postponed to later in life, therefore the goal is an alternative treatment to THA that can last long.

Primary objective:

1) To analyze the risk of reoperation with THA after PAO for patients with traditional dysplasia, retroversion and Calvé-Legg-Perthes visualized with a survivorship curve.

Secondary objectives:

2) To compare the risk of reoperation with THA after PAO in two time periods; from 1997 to 2010 and from 2011 to 2021 to analyze a potential learning curve of the clinic.

3) To evaluate the risk of other reoperations than THA (removal of osteosynthesis material, hip arthroscopy, re-PAO etc.)

4) To evaluate length of hospital-stay and risk of readmission within 90 days after PAO.

5) To compare all secondary outcomes between the cohort of patients from OUH in the period from 1997 to 2021 with a cohort of patients treated in all other hospital in Denmark in the same period (control group).

Description of the cohort

The study population includes all patients undergoing primary PAO at OUH in Odense, Denmark - approximately 1500 patients. The patients were all operated in the period 1997-2021 and the population is identified by specific procedure and diagnosis codes. A control group of patients treated in all other hospitals in Denmark in the same period is identified from Statistics Denmark and analyzed on procedure code level.

Data and biological material

This study is a retrospective cohort study. The population is identified by specific procedures and diagnosis codes from Cosmic (electronic patient file system from Region of Southern Denmark) and in the Danish National Patient Registry (DNPR). Patients treated with PAO at OUH will be investigated on patient file level to analyze whether indication for surgery was traditional dysplasia, retroversion or Calvé-Legg-Perthes as well as to analyze detailed information of postoperative complications (in-hospital complications causing prolonged length of stay and remissions).

Follow-up data on risk of re-operations (including THA) will also be achieved from DNPR via Statistics Denmark on procedure code level. Furthermore, length of hospital stays, readmissions and reoperations from OUH as well as remaining centers performing PAO surgery will be applied for from Statistics Denmark to ensure complete follow-up and a proper control group.