• Hip and knee surgery

This PhD thesis evaluates periacetabular osteotomy (PAO) for treating hip dysplasia, encompassing a systematic review, a cross-sectional study, and three cohort analyses. Together, these five papers address functional performance and muscle strength before PAO as well as adverse events, patient-reported outcomes, and radiological findings after the surgery.

The first study (Paper I) is a systematic review with meta-analysis investigating the harms and benefits of PAO through a systematic literature search. The paper included studies reporting both adverse events and patient-reported outcomes. Twenty-nine cohort studies were included, estimating a 4.3% (95% confidence interval (95% CI): 3.7;4.9) risk of a major adverse event and a 14.0% (95% CI: 13.0;15.1) risk of a minor adverse event. The benefits of PAO were clinically relevant improvements in patient-reported hip pain and function that persisted for at least 5 years after the surgery.

The second study (Paper II) is a cross-sectional study investigating functional performance and muscle strength deficits in patients with hip dysplasia scheduled for PAO compared to healthy subjects. Compared to healthy subjects, patients with hip dysplasia had significantly worse functional performance and a significant deficit in isometric hip flexion strength. For patients with hip dysplasia, better isometric muscle strength was associated with better functional performance.

The third study (Paper III) is a cohort study investigating the assumed association between the radiographic measurement of the femoral-epiphyseal acetabular roof (FEAR) index and patient-reported outcomes. Patients were divided into two groups defined by their preoperative FEAR index: (1) patients with an unstable hip, defined by a FEAR index >2° and (2) patients with a stable hip, defined by a FEAR index ≤2°. Both groups had clinically relevant improvements in patient-reported hip pain, function and quality of life from preoperative to 6 months after PAO. No differences were found in the improvements between the two groups, and the FEAR index was thus not able to predict patient-reported outcomes after PAO.

The fourth study (Paper IV) is a cohort study investigating sports participation before and after PAO, measured preoperative and 6 months, 2, 5, 10, 15, and 20 years after the surgery. It demonstrated that the number of patients participating in sports increased from 45% (95% CI: 43;48) before PAO to 56% (95% CI: 53;59) 6 months after PAO and 60% (95% CI: 57;63) 2 years after PAO. The number of sports participants remained higher than before the surgery throughout the follow-up period. Being sports-active, having a higher education, and having a better pain score before PAO increased the odds of participating in sports after PAO.

The fifth study (Paper V) is also a cohort study, investigating the registration completeness of the Aarhus PAO-database, which served as the basis for the two above-mentioned cohort studies. The registration completeness between the Aarhus PAO-database and the Danish National Patient Registry was 94.7% (95% CI: 93.3;95.9), confirming its validity as a resource for investigating the effect of PAO.

The findings of this PhD thesis demonstrate that patients with hip dysplasia experience reduced hip function and that their hip function is associated with their hip muscle strength. The research has identified the risks and benefits associated with the PAO procedure, as well as the preoperative factors that affect sports participation after surgery. Additionally, it has been uncovered that the FEAR index does not affect patient-reported outcomes following PAO. These findings highlight the complex effects of PAO on patients with hip dysplasia, providing valuable insights for clinical practice and future research.