3D-printed navigation template in proximal femoral osteotomy for older children with developmental dysplasia of the hip

Abstract

To explore the feasibility of 3D-printed navigation template in proximal femoral varus rotation and shortening osteotomy for older children with developmental dysplasia of the hip (DDH). Between June 2014 and May 2015, navigation templates were designed and used for 12 DDH patients. Surgical information and outcomes were compared to 13 patients undergoing the same surgery but without navigation template. In template-guided patient group, operation time (21.08 min vs. 46.92 min), number of X-ray exposures (3.92 vs. 6.69), and occurrence of femoral epiphysis damage (0 vs. 0.92) were significantly decreased (P < 0.05). Furthermore, after 12-18 months follow-up, 66.7% and 16.7% of the hips in template-guided group were rated as excellent or good, respectively, according to the McKay criteria; 83.3% and 16.7% by using the Severin criteria respectively. By contrast, 46.2% and 23.1% of the hips in traditional operation group were classed as excellent or good, respectively, using the McKay criteria; 46.2% and 30.8% by using the Severin criteria respectively. The template-guided group achieved a better outcome; however, there was no significant difference. Application of the navigation template for older DDH children can reduce the operation time, radiation exposure, and epiphysis damage, which also simplifies surgery and improves precision.

Figure 1. Preoperative design and template preparation.

(A) DICOM data were imported into Mimics software for 3D reconstruction. (B) The bone cutting plane and needle insertion channel were simulated; the navigation template was designed with reverse modeling. A Boolean operation was used to acquire femoral surface morphology, and the 3D navigation template model was set up with the insertion channel for the Kirschner wire. (C,D) The navigation template includes all the operation parameters and steps for proximal femoral varus rotation and shortening osteotomy: (a) is the shortening length of bone cutting, (b) is the needle insertion angle on the femoral neck (b = LCP-PHP angle + varus angle), and (c) is the rotation angle of bone cutting. (E) The osteotomy process was simulated using the navigation template in Mimics software using the Kirschner wire as a lever.

Figure 2. Simulated operation with the 3D-printed model and navigation template.

(A) The navigation template was matched to verify the degree of surface feature matching. (B) The Kirschner wire needle was placed according to the navigation hole. (C,D) The bridge part of the navigation template and femoral model was removed according to the bone cutting plane in the navigation template, and the cutting section and navigation template were removed. (E) The Kirschner wire needle was used as a lever through the LCP-PHP corresponding screw hole to complete the varus rotating and shortening osteotomy. (F) The positioning needles were removed one by one using the Kirschner wire needle pinhole as the screw nail hole, screwing the screw to the preoperative predicted length and completing internal fixation. (G,H) After the simulation was complete, postoperative angles of femoral anteversion and neck-shaft and shortening length were consistent with the preoperative plans.

Figure 3. The navigation template applied in the operation on a 9-year-old girl with left DDH.

(A) Preoperative X-ray of the pelvis. (B–G) According to the simulation steps, the steps of the intraoperative process were completed as performed in the simulated operation. (H–J) Intraoperative use of C-arm X-ray to verify the direction of the needle and bone cutting form, consistent with preoperative planning (only 3 X-ray exposures). (K) X-ray of the pelvis one week after surgery. (L) X-ray of the pelvis 14 months after surgery.