Restoring Rotation Center in Total Hip Arthroplasty for Developmental Dysplasia of the Hip with the Assistance of Three Dimensional Printing Technology: A Pilot Study

Abstract

Objective To develop a new method to restore hip rotation center exactly and rapidly in total hip arthroplasty (THA) with the assistance of three dimensional (3D) printing technology and evaluate its clinical and radiological outcomes. Methods From March 2014 to July 2018, a total of 17 patients (five hips of four men and 16 hips of 13 women) with end‐stage osteoarthritis secondary to developmental dysplasia of the hip who underwent THA were analyzed and followed up retrospectively. The average age is 58.00 ± 8.12 years (range from 45 to 71 years). Simulated operations were performed on 3D printed hip models for preoperative planning. The morphology of Harris fossa and acetabular notches were recognized and restored to locate the acetabular center. The size of bone defect was measured by the bone wax method. The agreement on the size of acetabular cup and bone defect between simulated operations and actual operations were analyzed. Harris Hip Score (HHS) was used to evaluate the recovery of hip joint function. The vertical distance and horizontal distance of the rotation center on the pelvis plain radiograph were measured, which were used to assess the efficacy of restoring hip rotation center and acetabular cup migration. Results The mean sizes of bone defect in simulated operations and THA were 4.58 ± 2.47 cm2 and 4.55 ± 2.57 cm2 respectively. There was no significant difference statistically between the sizes of bone defect in simulated operations and the actual sizes of bone defect in THA (t = 0.03, P = 0.97). The sizes of the acetabular cup of simulated operations on 3D print models showed a high rate of coincidence with the actual sizes in the operations (ICC = 0.93). All 17 patients were available for clinical and radiological follow‐up. The average follow‐up time was 18.35 ± 6.86 months (range, 12–36 months. The average HHS of the patients was improved from (38.33 ± 6.07) preoperatively to the last follow‐up (88.61 ± 3.44) postoperatively. The mean vertical and horizontal distances of hip rotation center on the pelvic radiographs were restored to 15.12 ± 1.25 mm and 32.49 ± 2.83 mm respectively. No case presented dislocation or radiological signs of loosening until last follow‐up. Conclusions The application of 3D printing technology facilitates orthopedists to recognize the morphology of Harris fossa and acetabular notches, locate the acetabular center and restore the hip rotation center rapidly and accurately.

How to Determine the Orientation of Acetabular Prosthesis in Total Hip Arthroplasty by Refering to the Anatomical landmarker of acetabular notches?

“…The acetabular center was located according to the method proposed by Heng Zhang et al [13] , that is, the acetabular center was located at 25-31 mm (mean 28.7 mm, depended on the size of the acetabulum) above the intersection point of the perpendicular bisector and acetabular anterior and posterior notches' line. During the process of acetabulum reaming, the anteversion was controlled at 15°, while the inclination was 40°, and the depth was the bottom of acetabular fossa.…”

“…Therefore, we speculated the acetabular notches and acetabular fossa were proper anatomical landmarkers of acetabular prosthesis localization. In previous studies, we located the acetabular center in THA using the acetabular fossa and acetabular notches as the landmarks and restored the rotation center exactly, even in DDH and revision THA cases [11][12][13] .…”

How to Develope a Novel 3D Printed Integral Customized Anatomical Acetabular Prosthesis in Hip Arthroplasty for Crowe Type II and III Developmental Dysplasia of the Hip?

“…The area of bone defect was measured by the Photoshop method(Fig. 3G) (6). The surface of bone wax which contacted with the cup was covered with gauze precisely.…”

“…The morphology of acetabulum in Crowe type II and III developmental dysplasia of the hip(DDH)present to be disc-shaped and shell-shaped , shallow socket, increased anteversion and inclination, a large number of osteophytes proliferate and segmental bone defects in the superior and posterior parts (1)(2)(3). These changes pose challenges for anatomical installation of acetabular prosthesis, precise reconstruction of bone defects and realization of good initial stability of the implants in total hip arthroplasty (THA) (4)(5)(6). How to realize anatomical reconstruction of the acetabulum in patients with Crowe type II/III DDH duirng THA and avoid postoperative hip instability, dislocation, lower limb length discrepancy , as well as reduce wear rate and recover hip function are difficult problems confronted by orthopedic surgeons.…”

“…However, it is impossible to avoid the improvement of biological stress of the hip joint , the increase of wear rate of the prosthesis, the secondary complications of lower limb length discrepancy, impingement, gluteus medius fatigue, gait changes, dislocation due to the upward migration of the hip rotation center (7)(8)(9). Currently, more and more scholars (6,10,11) proposed anatomical restoration of rotation center in THA for patients with Crowe type II/III DDH, which is beneficial to balance the stress of ligaments and muscles surrounding the hip joint, reduce the wear rate and loosening of the hip prosthesis, whereas it is difficult to restore the hip rotation center and reconstruct the bone defect during the operation.…”