| Summary: | ABSTRACT
A group of 133 hips with developmental dysplasia of the hip (DDH) are reviewed in the form of a clinical audit. The aim of the study is to determine the relevance of measuring the ossific nucleus centre edge angle (ONCEA) to determine if this measurement can be used to predict the final outcome and the need for a secondary procedure at an earlier age than currently determined. The ONCEA is defined as an approximation of the lowest centre edge angle within six months of removal of the Batchelor POP, following reduction (mean age 24.1 months). It is measured earlier than the centre edge angle (CEA), which is generally used from the age of five years.
The ONCEA was divided into three groups:
- Reduced (>=10°) – Group A
- Mild subluxation (-9° to 9°) – Group B
- Severe subluxation (<=-10°) – Group C
The significance of the ONCEA was confirmed using the ONCEA/AI ratio, which was also divided into three groups:
- Reduced (>0.5) – Group A
- Mild subluxation (0 to 0.5) – Group B
- Severe subluxation (<0) – Group C
Outcome was assessed radiologically by way of the Severin score: In group C there were only 1/13 hips (8%) with an excellent result, in group B there were 20/44 hips (45%) with an excellent result and in group A there were 39/76 hips (51%) with an excellent result. Using Fisher’s exact test, a statistically significant association was shown between each group and subsequent outcome (p=0.001). A significant result was also shown in a comparison of the three ONCEA groups using the McKay classification (a clinical outcome measurement).
The ONCEA/AI ratio was also used to include the degree of acetabular coverage. It had similar statistically significant results as described for the above ONCEA results, thus confirming the findings.
In conclusion, the ONCEA or ONCEA/AI ratio can be used at an early age (within six months following removal of POP after reduction, at a mean of 18 months of age) for two purposes:
1. To prognosticate the medium and long-term outcome of the patient.
2. To enable the clinician to determine whether a secondary procedure should be performed at an earlier age than usual. A prospective study will be necessary to confirm this.
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