Computer-aided design and rapid prototyping technique for individualized artificial semi-knee joint prosthesis: Establishment of three-dimensional model of femoral condyle

Yong TENG; Zhen WANG; Dichen LI; Yi HUAN; Yunyu HU; Feng ZHANG

ABSTRACT

BACKGROUND:

At present, there are several limb-preserving methods,such as xenogenic bone joint replacement, artificial metal prothesis replacement and inactivation and replantation of tumor bone segment, etc.Each method has its advantages and disadvantages. In addition, mismatch of xenogenic and autogeneic joints and articular cartilage necrosis in the late stage, which affects joint function, are two important problems for large frozen bone-joint allograft at ultra-low temperature in repair of bone defect following bone tumor resections in extremities.

OBJECTIVE:

To evaluate a method to obtain outline information on the cartilage surface through spiral CT scanning data, so as to lay foundation for study on individualized artifical semi-knee joint based on rapid prototyping (RP) technique.

DESIGN:

Open experiment.

SETTING:

First Department of Trauma, Urumqi General Hospital of Lanzhou Military Area Command of Chinese PLA.MATERIALS This experiment was carried out at Institute of Orthopaedics, Xijing Hospital, Fourth Military Medical University of Chinese PLA, and Institute of Advanced Manufacturing, Xi'an Jiaotong University from September 2001 to May 2003. CT scanning subject was a 25-year-old healthy male volunteer.

METHODS:

Distal femur was performed 1 mm in thickness scanning with Picker 6 000 spiral CT. Three-dimensional volume reconstruction was conducted at the Voxel Q Image workstation on Picker 6000 CT, then, two-dimensional tomography image of reconstruction data were downloaded with spacing of 0.1 mm. Data format converter software was self-developed. The downloaded image was treated through smoothing, de-noise and so on.Vector data of two-dimensional borderline outline of tomography image was calculated and input into Surfacer 9.0 software (American Imageware company) for vectorial three-dimensional reconstruction. According to recognition of articular cartilage outline and request of prothesis design, the threedimensional images of interested articular cartilage surface outline were extracted and used in the computer-aided design for individualized artificial semi-knee joint.MAIN OUTCOME

MEASURES:

Vector converting of CT image and vector image of three-dimensional reconstruction of femoral condyle.

RESULTS:

Vector converting of CT image dafa had been come true using self-developed medical image vector converter software. Three-dimensional solid model of individualized femoral condyle was constructed with Surfacer9.0 three-dimensional processing software and edited according to design request. Three-dimensional model of articular cartilage requested by artifical semi-knee joint prothesis was extracted for computer-aided design. The constructed articular surface outline could be treated further to complete computer-aided design of artificial semi-knee joint prothesis; The file format was .stl, which could be recognized by RP software and used in engineering.

CONCLUSION:

Vector reconstruction of articular cartilage outline is performed based on spiral CT data that can obtain precise three-dimensional solid model of articular cartilage outline. The three-dimensional model can be edited, which lays foundation for computer-aided design and RP manufacturing of artificial semi-knee joint prothesis compounded with large segment xenogenic bone; It is easy and practicable in vector converting of medical image information with this method, and it also has good application prospect in biomanufacturing field in orthopaedic and oral maxillofacial surgery.