Preoperative assessment of medial acetabular wall bone stock in dysplastic deformation

Abstract

Acetabular reconstruction remains to be one of the crucial aspects of total hip replacament in developmental dysplasia of the hip (DDH) that provides endoprosthesis’ long-term stability and general success of the operation. Among the parameters that influence surgical technique of acetabular reconstruction, medial wall bone stock of the endoprosthesis’ bed zone should be taken into consideration. Purpose of the work to assess medial wall bone stock in the site of acetabular component’s bony bed in normal and dysplastic deformed hips and to define correlation with indices of sphericity and sectoral deficiency of the acetabulum based on MSCT-morphomerty. Materials and methods. A complex comparative MSCT-mophometric investigation of 32 normal hips and 65 hips with DDH (Crowe I – 26 hips (40.0 %), Crowe II – 23 hips (35.4 %), Crowe III – 16 hips (24.6 %)) was performed. There were assessed width of the medial wall bone stock in the projection of the crucial ligament’s and acetabular component’s bony beds according to the proposed method; their correlation with indices of femoral head’s cranial migration and acetabular horizontal sphericity angle. Results. It has been revealed that measurements in he site of the crucial ligament’s bony bed based on pelvic images obtained by a conventional biplanar X-ray remains to be biased and doesn’t correspond to true width of medial acetabular wall bone stock. Absolute width of the medial acetabular wall in sites of the crucial ligament’s / acetabular component’s bony beds carried out through the special MSCT-recontruction methodic was defined as: 4.3 mm [3.3; 4.8]/7,2 mm [6.2; 7.8] for normal hips, 9.95 mm [7.5; 11.6]/11.85 mm [9.8; 13.5] for Crowe I hips,15 mm [11.7; 17.3]/15,7 mm [13,5; 17,3] for Crowe II hips and 15.45 mm [13.7; 19.8]/16.05 mm [12.8; 20.2] for Crowe III hips, respectively. Correlations between medial acetabular wall bone stock in site of acetabular component’s bony bed and indices of femoral head’s cranial migration and acetabular horizontal sphericity angle were defined as: r = 0.36 (P = 0.006); r = 0.36 (P = 0.007), respectively. Conclusions. Weak correlation of medial acetabular wall bone stock with indices of acetabular sphericity and sectoral deficiency requires the necessity of independent evaluation of this index during preoperative planning. Due to the impossibility of the index assessment based on the conventional pelvic X-ray, application of elaborated MSCT-morphometric methodic seems to be clinically valuable and should be applied during preoperative examination of patients with DDH.