*Article* **Quantitative Three-Dimensional Measurements of Acetabular Fracture Displacement Could Be Predictive for Native Hip Survivorship †**

**Anne M. L. Meesters 1,2 , Miriam G. E. Oldhoff 1,2, Neeltje M. Trouwborst <sup>1</sup> , Nick Assink 1,2 , Joep Kraeima 2,3 , Max J. H. Witjes 2,3, Jean-Paul P. M. de Vries <sup>1</sup> , Kaj ten Duis <sup>1</sup> and Frank F. A. IJpma 1,\***

	- 9713 GZ Groningen, The Netherlands

**Abstract:** This study aims to develop a three-dimensional (3D) measurement for acetabular fracture displacement, determine the inter- and intra-observer variability, and correlate the measurement with clinical outcome. Three-dimensional models were created for 100 patients surgically treated for acetabular fractures. The '3D gap area', the 3D surface between all the fracture fragments, was developed. The association between the 3D gap area and the risk of conversion to a total hip arthroplasty (THA) was determined by an ROC curve and a Cox regression analysis. The 3D gap area had an excellent inter-observer and intra-observer reliability. The preoperative median 3D gap area for patients without and with a THA was 1731 mm<sup>2</sup> versus 2237 mm<sup>2</sup> . The median postoperative 3D gap area was 640 mm<sup>2</sup> versus 845 mm<sup>2</sup> . The area under the curve was 0.63. The Cox regression analysis showed that a preoperative 3D gap area > 2103 mm<sup>2</sup> and a postoperative 3D gap area > 1058 mm<sup>2</sup> were independently associated with a 3.0 versus 2.4 times higher risk of conversion to a THA. A 3D assessment of acetabular fractures is feasible, reproducible, and correlates with clinical outcome. Three-dimensional measurements could be added to the current classification systems to quantify the level of fracture displacement and to assess operative results.

**Keywords:** acetabular fracture; 3D fracture analysis; 3D gap area; three dimensional; three-dimensional measurements; 3DCT
