Risk factors for early redislocation after primary treatment of developmental dysplasia of the hip: Is there a protective influence of the ossific nucleus?

BACKGROUND: Re-dislocation after primary treatment of developmental dysplasia of the hip is a serious complication. We analyzed the various risk factors that contribute to re-dislocation, and whether the bony ossific nucleus (ON) confers increased stability against re-dislocation. MATERIALS AND METHODS: Fifty-five children (60 hips) were classified into three treatment groups: Closed reduction (CR) in 15 children (17 hips), open reduction (OR) in 26 children (28 hips), and OR with bony surgery (ORB) in 14 children (15 hips). The mean age at initial treatment was 16 months (range 6–36 months). Fifty-one hips and 9 hips were Tonnis Grade 4 and 3, respectively. The mean preoperative acetabular index (AI) was 44.82° (range 32°–56°) for the study group. At initial treatment, bony ON was absent in 8 hips and present in 52 hips. RESULTS: No hip developed stiffness and pain after primary treatment. Although the AI index, Tonnis grade, and absence of ossific nucleus were higher in the re-dislocated groups, this was not statistically significant. Excluding the re-dislocations, four children had a fair outcome, 11 had good outcome, and 36 had excellent outcome as per McKay's criteria. In the CR group (17 hips), two children (2 hips) with absent ON had re-dislocation. In the OR group (28 hips), three re-dislocations were seen (three children) at 3, 5, and 7 months, respectively. Two of these had an absent bony ON. In the ORB group (15 hips), one late sub-luxation occurred in a child with absent ON. The mean preoperative AI for the re-dislocated and located group was 44.66° (range 42°–48°) and 44.53° (range 39°–56°), respectively. The postoperative AI was 34.53. CONCLUSION: The experience of the treating surgeon and technical factors play an overwhelming role in preventing early dislocation. The absence of ON should perhaps alert the surgeon for enhanced spica care, postoperative splinting, and meticulous intra-operative management.