A New Classification System for Acetabular Bone Defect Evaluation in Posttraumatic Acetabular Nonunion and Malunion.

Introduction: There is no distinct classification system to evaluate the bone defect in previously managed acetabular fractures. We propose a new classification system for bone defect evaluation in a previously managed acetabular fracture that will be helpful for total hip arthroplasty (THA). Materials and Methods: The preoperative pelvis radiographs of 99 THA patients with previous acetabular fractures with at least 2 years of follow-up were evaluated by 10 experienced surgeons (Paprosky and new classification systems). As per the new classification system, the five types of bone defects are circumferential, posterior wall, posterior column, both column defect, and anterior column. The interobserver and intraobserver reliability was calculated, and a consensus management plan based on the recommendation of the observers was formulated. Results: There was fair interobserver reliability for Paprosky classification (alpha coefficient 0.39) and substantial interobserver reliability for the new classification (alpha co-efficient 0.71). There was a substantial intraobserver agreement for the new classification (kappa value 0.80) and moderate intraobserver agreement for Paprosky classification (kappa value 0.55). Sixty-nine patients who were treated as per the management plan of the observers reported significant improvement in modified Harris hip score (improved from 25 to 85.88, Conclusions: The new classification system for bone defect evaluation in previously treated acetabular fractures is valid and reliable. The proposed surgical plan for the management of bone defects in THA provided good to excellent outcomes.