Abstract
Background:
Acetabular component malpositioning in total hip arthroplasty increases the risk of dislocations, impingement, and long-term component wear. The purpose of this Sawbones study was to define the efficacy of a novel acetabular imprinting device (AID) with 3D preoperative planning in accurately placing the acetabular component.
Methods:
Four surgeons performed the study on osteoarthritic and dysplastic Sawbone models using 3 different methods for placing the acetabular component (total n = 24). The 3 methods included (1) standard preoperative planning and instrumentation (i.e., standard method), (2) 3D computed tomographic (CT) scan planning and standard instrumentation (i.e., 3D planning method), and (3) 3D CT scan planning combined with an acetabular imprinting device (i.e., AID method). In the AID method, 3D planning software was used to virtually place the acetabular component at 40° of inclination and 22° of anteversion and create a parallel guide pin trajectory. A patient-specific surrogate bone model with a built-in guide pin trajectory was then manufactured as a stereoltihography device (Fig. 1A). The surgeon molded bone cement into the acetabulum imprinting the acetabular features while maintaining the guide pin trajectory (Fig. 1B). Afterward, the AID was removed from the surrogate bone model and placed onto the Sawbone, ensuring a secure fit (Fig. 1C). A guide pin was drilled into the Sawbone along the prescribed trajectory. With the guide pin in place, the surgeon could ream the acetabulum and impact the acetabular component using the guide pin as a visual aid (Fig. 1D). Postoperatively, a CT scan was used to define and compare the actual implant location with the preoperative plan. Statistical analysis was performed as 3 group comparisons using the chi-squared test for categorical data and analysis of variance (ANOVA) for continuous measurements.
Results:
The AID method significantly decreased the mean deviation of acetabular component inclination (3.4°) compared to standard (14.0°) and 3D planning methods (17.4°) (p = 0.003). The mean deviation in version was 10.6° in the standard method, 10.8° in the 3D planning method, and 5.3° in the AID method (p = 0.28). Overall, AID reduced the number of implants malpositioned in excess of 10° from the planned position to 12.5%, compared with 87.5% in the standard method and 75% in the 3D planning method (p = 0.005) (Fig. 2).
Conclusions:
Novel 3D preoperative planning combined with AID allows the surgeon to accurately replicate the preoperative plan using Sawbones models. This proof-of-concept study justifies a clinical trial to compare the AID to standard surgical techniques.
