Preoperative Planning of Total Hip Arthroplasty on Dysplastic Acetabuli
Background: When performing total hip arthroplasty (THA) on a dysplastic hip, proper positioning of the acetabular component in the true acetabulum may not allow for more than 70% coverage. Structural support in the form of an autograft or a high porosity metal augment may be necessary.
Questions/Purposes: What is the value of (1) preoperative templating and (2) deformity classification in predicting cup coverage and the need for structural support.
Methods: Sixty five cases of THA for DDH were retrospectively analyzed. Patients with post-operative radiographs less than 1cm of elevated hip center of rotation and no measurable cup medialization were included. Two observers independently classified each dysplastic hip according to Hartofilakidis and determined the extent of cup coverage via templating software on pre-operative digital AP pelvic radiographs (figure 1a).
Results: Weighted kappa interobserver agreement was 0.68 for cup coverage and 0.76 for Hartofilakidis type. Structural support was necessary in 10 hips. No structural support was necessary in low, Hartofilakidis type-1, dysplasia cases. However, 27-30% of cases with low or high dislocation (types 2 or 3) required structural support. All cases with templated cup coverage of 65% or less required structural support. Templated coverage within 65-75% and over 75% resulted in 20% and 10% of patients receiving structural augmentation, respectively (figure 1b).
Conclusion: Preoperative planning for THA in the setting of hip dysplasia is crucial and can provide valuable insight to the need for column augmentation. The surgeon must always be prepared to face greater technical challenges than anticipated. The three dimensional severity of the deformity may be underestimated in the two dimensional radiographs. A surgeon experienced with difficult hip reconstruction and technically capable to manage severe bone defects would prove beneficial in caring for patients with concomitant dysplastic and arthritic hips.