[Value of a synthetic osseous model obtained by stereo-lithography for preoperative planning. Correction of a complex femoral deformity caused by fibrous dysplasia].
OBJECTIVE
The authors investigated the application of life-sized bone models obtained by stereolithography in orthopaedics.


METHODS
The method was applied to planify correction of a severe femoral bone deformity secondary to fibrous dysplasia in a 27 years old man. This deformity was responsible for abnormal hip range of motion 70 degrees/-10 degrees (flexion-extension), -20 degrees/60 degrees (abduction-adduction), -30 degrees/60 degrees (external-internal rotation), and restricted walking ability because of lack of abduction and external rotation. A "shepherd-cross" deformity was identified on X-rays. A correction osteotomy was considered but we were unable to planify the angle of osteotomy on plain X-rays. CT scan identified 100 degrees of varus cervical deformity and 90 degrees of cervical antetorsion, but CT scan was helpless to choose the position for the osteosynthesis device.


METHODS
2D pictures obtained by CT scan were introduced and treated on a Silicon Graphics Indigo2 hardware. Mimics software authorized 2D and 3D views of bone which were separated of soft tissue by color separation process. CTM software authorized the 3D bone surface reconstruction (3D files). The 3D files were used to obtain life-sized bone model in 6 hours by stereolithographic process (scale 1/1).


RESULTS
We planified a 70 degrees valgus and 40 degrees derotation and chose the best location for osteosynthesis device considering the fibrous dysplasia (best location was the posterior and superior aspect of the femoral neck). The planified osteotomy was performed and we obtained the stability of a nail-plate in the femoral neck. During surgery, we observed the bone model and the deformed femur had the same shape. Likewise, the model strongly indicated the inside bone structure (ie distribution of fibrous dysplasia tissue). Bone healing was obtained after 5 months with improvement of range of motion [(70/0) (20/30) (30/20)]. Histologic examination diagnosed fibrous dysplasia without malignancy features.


CONCLUSIONS
Computer-generated life-sized bone models are available from computer tomographic data by means of stereolithographic process. This technic was helpful to improve planification of this complex proximal femoral osteotomy. Obtaining life-sized bone models could improve preoperative planning in case of multidirectional deformity, unusual site for osteotomy, or severe deformity impairing the choice for fixation device or its position into bone extremities. The indications for this method should be restricted to unusual and severe bone deformities, with inadequate preoperative assessment by standard X-rays or CT scans. Likewise, this method could be indicated for preoperative planning of technically demanding osteotomies such as oblique plane.
Migaud
H
H
Service d'Orthopédie-Traumatologie B, Hôpital Salengro, C.H.R.U. de Lille.
Cortet
B
B
Assaker
R
R
Fontaine
C
C
Kulik
J F
JF
Duquennoy
A
A
D000328:Adult; D003198:Computer Simulation; D005269:Femur; D005359:Fibrous Dysplasia, Polyostotic / Q000000981:diagnostic imaging* / Q000601:surgery; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008953:Models, Anatomic; D010027:Osteotomy / Q000379:methods*; D016059:Range of Motion, Articular; D014057:Tomography, X-Ray Computed
Intérêt d'un modèle osseux synthétique créé par stéréolithographie pour la planification préopératoire. Correction d'une déformation fémorale complexe dans le cadre d'une dysplasie fibreuse.