[Effects of trabecular metal augments for the reconstruction of Paprosky type Ⅲ acetabulum bone defects]

Objective: To investigate the methods and short-time clinical results of reconstruction of Paprosky type Ⅲ acetabulum bone defects by using tantalum augments. Methods: A total of 17 patients (17 hips) with Paprosky type Ⅲ acetabulum bone defects, treated with tantalum augments in revision of total hip arthroplasty at Department of Orthopedics Surgery in General Hospital of Chinese People's Liberation Army were retrospectively analyzed from March 2014 to May 2016.There were 6 males and 11 females aged from 23 to 74 years with an average of (50.2±16.3) years. Tantalum augments or TM-Cup augment (the cup-on-cup technique) were used to reconstruct the defects.The TM-Cup augment was the tantalum revision cup which was removed titanium ring. The cup-on-cup technique combined TM-Cup augment and biological acetabulum cup. Augments were served as the nonresorptive structural allograft in revision of total hip arthroplasty. Harris hip score was used to evaluate clinical effects. The vertical position of the rotation center was measured and analyzed. Radiographic assessments of the acetabular components were performed by DeLee-Charnley and the Anderson criteria and recorded postoperative complications. Results: All the patients were followed up from 3 to 29 months with an average of (16.2±5.4) months, tantalum augments and biological acetabulum cup were used in 13 patients, the TM-Cup augment and biological acetabulum cup were used in 4 patients. At the time of the latest follow-up, the mean Harris hip score increased compared to preoperatively (86.8±8.3 vs. 30.0±12.0) (t=12.78, P<0.01), the average vertical location of the center of rotation was decreased ((25.3±9.8) mm vs.(47.6±10.5)) mm (t=4.95, P<0.01). All the tantalum augments and biological acetabulum cups were stable, there were no infection, dislocation and other complications. Conclusions: The use of tantalum augments could be considered as an effective management of Paprosky type Ⅲ defects providing good clinical and radiographic outcomes in the short term.The cup-on-cup technique which was used in reconstruction of severe superior-invagination acetabular bone defects and restoration relatively normal center of rotation had special application value.