Evaluation of Salter and Pemberton osteotomies in developmental dysplasia of the hip: the role of the congruity index as a prognostic factor

BACKGROUND: The Salter osteotomy (SO) and the Pemberton osteotomy (PO) are common surgical methods for treating paediatric developmental dysplasia of the hip (DDH). Although they each have their own advantages, complications resulting from open surgeries are still relatively common. This study aimed to evaluate the clinical outcomes of SO and PO in the treatment of DDH and to identify prognostic factors associated with postoperative outcomes. METHODS: Between April 2011 and May 2018, we retrospectively reviewed 72 DDH patients who underwent open reduction combined with pelvic osteotomy (SO/PO) at our hospital, and divided them into two groups based on the different surgical procedures: SO and PO. The minimum follow-up duration was 5 years. Subsequently, general patient information, along with clinical and radiographic results, were collected for comparative analysis. We introduced the congruity index, defined as the percentage of femoral head coverage by the acetabulum, to evaluate the prognosis of DDH. The Pearson's chi-square test and Student t tests were used for comparisons of outcomes between the groups. Multivariable logistic regression models were used to analyze factors associated with avascular necrosis (AVN) and with the poorer McKay classification. RESULTS: A total of 65 patients completed the final follow-up. Laterality, duration of follow-up, and preoperative CEA differed significantly between the groups. Patients in the SO group had higher postoperative congruity index than those in the PO group (P < 0.001). According to the Severin and McKay classifications, satisfactory radiographic outcomes (Severin class I or II) were achieved in 88.9% of patients in the SO group and 76.9% of patients in the PO group. Satisfactory clinical outcomes (McKay class I or II) were achieved in 92.6% of patients in the SO group and 84.6% of patients in the PO group. Congruity index was risk factor for AVN (P = 0.007), and the lower congruity index was associated with a poorer McKay classification (P = 0.007). CONCLUSION: Both SO and PO are effective in treating paediatric DDH, with favourable radiographic performance and clinical outcomes. Congruity index played an important role in the poorer McKay classification and the risk of occurrence of AVN.