Surgical Technique for Reconstruction of Severe Acetabular Defects During Revision Total Hip Arthroplasty
2019 AWARD WINNER
Acetabular components used to manage severe acetabular bone defects during revision total hip arthroplasty (THA) traditionally are associated with a high rate of rerevision for loosening at mid-term to long-term follow up. This led to the development of specialized revision acetabular components to specifically manage severe bone loss. Of these specialized components, porous tantalum components are associated with the most promising early- to mid-term results with regard to rerevision for loosening. Early translation of acetabular components used during revision THA is a good predictor of loosening, with acetabular components that migrate less than or equal to 1 mm at a follow up of 24 months resulting in the best reported survivorship. Radiostereometric analysis is the most sensitive method to measure implant migration.
This video describes the surgical technique developed at our institution to reconstruct severe acetabular bone defects during revision THA. The surgical approach allows for safe exposure of the pelvis around the acetabulum with particular attention to preservation of the superior gluteal bundle and the abductor muscles. The reconstruction technique also affords a safe, reproducible method for inserting long pubic and ischial screws through the cup for secure inferior fixation of the construct. Failed THA occurred in the patient shown in this video, who underwent the procedure for management of a Paprosky type III acetabular defect and pelvic discontinuity. A porous tantalum, trabecular metal, two cup-and-cage technique with inferior screw fixation is demonstrated. An extensile posterior approach is used to exploit the internervous plane between the gluteus medius and gluteus maximus, preserving the superior gluteal neurovascular bundle and adequately exposing the acetabular bone defect. A revision trabecular metal cup appropriately sized for the reamed superior acetabular defect is customized into a superior augment. Using an additional cup rather than an augment promotes more surface area contact to the limited bone available. After the cup is impacted into the defect, long screws are inserted along the sacroacetabular and ilioacetabular buttresses to secure the augment to the ilium. Exposure of the deep division of the superior gluteal bundle allows for safe placement of retractors and the superior flange of the cage without disrupting or kinking the neurovascular structures. This is critical for good postoperative abductor muscle function. A channel must be cut in the superior aspect of the trabecular metal cup rim and an inferior oversized screw hole must be created before cup insertion to facilitate passing long ischial screws toward the ischial tuberosity and a pubic screw along the length of the superior pubic ramus, respectively. Full weight-bearing is initiated immediately postoperatively.
At our institution, we have used trabecular metal components to reconstruct all Paprosky type III acetabular defects since 2003, and we have used radiostereometric analysis in all patients to measure the stability and migration of the cup postoperatively. Initially, screws were inserted into the ilium only; however, subsequent to the initial review of our radiostereometric analysis results (since 2012), inferior (ischial or pubic) screws were used in all patients in whom adequate press-fit and acetabular component stability could not be achieved intraoperatively. To date, the migration of 55 porous tantalum components used to manage Paprosky type III acetabular defects have been assessed at a mean follow up of 4 years (range, 2 to 13 years). None of the patients lost abductor muscle function postoperatively. Seven of 29 components used before the introduction of inferior screw fixation had migrated more than 1 mm at a follow up of 2 years, whereas none of the 26 components used after the introduction of screw fixation had migrated beyond the threshold at any time point postoperatively. Absolute proximal translation was significantly lower for the components with inferior screws compared with the components without inferior screws (P = 0.04). The extensile posterior approach allows for exposure of the pelvis around the acetabulum to safely remove and reimplant components during revision hip surgery. Careful dissection, especially around the superior gluteal bundle, preserves structures crucial to good abductor muscle function. In addition, customization of the cup allows for safe and accurate placement of long pubic and ischial screws with good bone purchase. Our outcomes demonstrate that the use of inferior screws improved early acetabular component fixation.