The incidence of avascular necrosis following a cohort of treated developmental dysplasia of the hip in a single tertiary centre

PURPOSE: Avascular necrosis (AVN) may occur following treatment for developmental dysplasia of the hip (DDH). The primary aim of this study was to identify the incidence of AVN in a cohort of patients treated for DDH. Secondary aims were to classify AVN using available classification systems, analyze the correlation between the systems and investigate their relationship with the age at diagnosis of DDH. METHODS: An 11-year retrospective study was carried out at a single tertiary centre, using data from the clinical portal (patient records database) and IMPAX (system used to store plain radiographic images). Clinical details (patient demographics and outcomes) and plain radiographic images were used to identify cases of DDH and categorize cases of AVN using available classification systems: Tonnis and Kuhlmann, Kalamchi and McEwen, Bucholz and Ogden and Salter. Severin was used to assess final clinical outcome. RESULTS: In total, 405 (522 hips) cases of DDH were identified, of which 213 resolved without treatment, 93 were treated conservatively and 99 surgically. Only treated cases were included in the analysis (n = 192). AVN (45/99; 45.5%) was found to occur only postoperatively. A positive correlation was present between age at presentation and severity of AVN as classified according to Salter’s criteria (chi-squared p value < 0.01). CONCLUSION: AVN incidence was 23.4% (45/192) and only occurred in surgically treated patients. Older age at diagnosis was associated with a higher incidence of AVN, as defined according to Salter’s criteria. The classification systems appeared to show no correlation amongst each other (p-value < 0.01). LEVEL OF EVIDENCE: III - Retrospective cohort study