Pelvic tumor is one of the more complex and difficult types of bone tumor surgery, and the removal of tumor can lead to large bone loss. The anatomical structure and morphology of the pelvis is relatively complex compared to other areas. Moreover, pelvis is adjacent to important organs in the abdominal cavity with many surrounding soft tissue structures , so there are considerable challenges in both preoperative planning and intraoperative management.
In the preoperative design of the prosthesis, the resection area needs to be reasonably designed according to the patient’s morbidity, and then the reconstruction of the affected area and the implantation of the prosthesis need to be planned according to the resection area.
The difficulty in designing a “pelvic tumor prosthesis” lies not only in the complex anatomical shape of the pelvis but also the fact that the patient’s predilection sites varies from person to person, so how to design the prosthesis that can better match patient’s need and achieve best surgical results is a key factor in the success of the operation.
LDK engineers assess each patient’s individual morphological differences, the area of bone loss and the mechanical environment in which the prosthesis will live, “Personalize” the reconstructed area and carry out a computer simulation of the fitting and a mock-up to ensure that the prosthesis can be implanted intraoperatively. In this article, we have selected 6 representative tumor prosthesis designs for different pelvic tumor subdivisions in the last 5 years for reference and discussion.
1 region I Pelvis tumor
This case is a tumor of the pelvic region I with involvement of the sacroiliac joint. The proximal end was osteotomized via the sacroiliac joint at the outer edge of the sacral foramen, and the distal end was osteotomized horizontally from the acetabular apex upwards. A customised pelvic prosthesis was used to reconstruct the defective iliac wing. The shape and size of the prosthesis was customized to the patient’s defect, and the prosthesis-bone interface (contacting sacral and iliac bones) was machined to mimic the porous mesh of the bone trabeculae to facilitate bone ingrowth and achieve long term fixation of the prosthesis. The posterior wall of the acetabulum has a one-piece printed steel plate and a nail bar system can be attached to the posterior side of the prosthesis to improve the stability of the prosthesis.
2 Region II Pelvis tumor
The patient had a small lesion and only a partial acetabular resection was performed, with a vertical osteotomy in the patient’s acetabulum and a horizontal osteotomy at the superior edge of the acetabulum, with removal of the pubic bone and preservation of the sciatic branch. A customised pelvic prosthesis was printed in one piece, with the prosthesis-bone interface machined to mimic the porous mesh of the trabeculae. The outer diameter of the patient’s acetabulum was measured and a cemented acetabular cup matching the patient’s acetabular dimensions was determined to be the base for reconstruction, with the plate printed in one piece on the outside of the prosthesis. This solution maximised the preservation of the sciatic branch and part of the acetabulum for the patient and achieved a precise resection and reconstruction.
3 Region I + II pelvis tumor
In this case, tumor occurred at Region I + II, the lateral sacral osteotomy cut the sacroiliac joint. the pubic and sciatic branches were preserved according to the intraoperative situation. The contact surface of the customised pelvic prosthesis with the sacrum was machined into a porous mesh imitating bone trabeculae, with a stopper designed to rest on the inner side of the sacrum. The customised iliac support and the acetabular cup are assembled separately and are adjustable intraoperatively for easy and reliable attachment. Two rows of nail holes are reserved for the attachment of the retained pubic and sciatic branches.
4 Region I + II pelvis tumor
In this case, tumor occurred at Region I + II, the lateral sacral osteotomy cut the sacroiliac joint. the pubic and sciatic branches were preserved according to the intraoperative situation. The contact surface of the customised pelvic prosthesis with the sacrum was machined into a porous mesh imitating bone trabeculae, The posterior side of the prosthesis can be connected to a nail bar system, the length and orientation of the screws at the sacrum are customized from patient’s CT data and the outer edge of the prosthesis is designed with a row of suture holes to facilitate the fixation of soft tissue
5 Region II + III pelvis tumor
This case is a tumor on pelvis II + III with a horizontal osteotomy from the superior acetabular rim. The prosthesis is made up of a customised pelvis and a pubic bone attachment plate. The size of the contact surface of the customised pelvis prosthesis is designed according to the shape of the osteotomy surface and is reinforced by an external one-piece printed plate. The pubic bone attachment plate is customised to the patient’s original pubic bone shape and is attached to the healthy side of the pubic bone.
6 Region IV pelvis tumor
In this case, tumor occurred on region IV, the right and left sides were osteotomized from the sacroiliac joint, preserving part of the olecranon, and the prosthesis was attached to the iliac bone on both sides and to the lower end of the fifth vertebra. The customised pelvic prosthesis is printed in one piece and has screws for the lumbar vertebrae and the right and left sides respectively, with the possibility of attaching a staple system on the posterior side.
Post time: Feb-21-2023