The use of physical biomodelling in complex spinal surgery

Abstract

Prior studies have suggested that biomodels enhance patient education, preoperative planning and intra-operative stereotaxy; however, the usefulness of biomodels compared to regular imaging modalities such as X-ray, CT and MR has not been quantified. Our objective was to quantify the surgeon's perceptions on the usefulness of biomodels compared to standard visualisation modalities for preoperative planning and intra-operative anatomical reference. Physical biomodels were manufactured for a series of 26 consecutive patients with complex spinal pathologies using a stereolithographic technique based on CT data. The biomodels were used preoperatively for surgical planning and customising implants, and intra-operatively for anatomical reference. Following surgery, a detailed biomodel utility survey was completed by the surgeons, and informal telephone interviews were conducted with patients. Using biomodels, 21 deformity and 5 tumour cases were performed. Surgeons stated that the anatomical details were better visible on the biomodel than on other imaging modalities in 65% of cases, and exclusively visible on the biomodel in 11% of cases. Preoperative use of the biomodel led to a different decision regarding the choice of osteosynthetic materials used in 52% of cases, and the implantation site of osteosynthetic material in 74% of cases. Surgeons reported that the use of biomodels reduced operating time by a mean of 8% in tumour patients and 22% in deformity procedures. This study supports biomodelling as a useful, and sometimes essential tool in the armamentarium of imaging techniques used for complex spinal surgery.

Fig. 1

3D CT reconstruction of lower thoracic spine in a 22-month-old child (Case 21), who presented with severe thoracic kyphosis due to a suspected hemivertebra at T10/11

Fig. 2

MRI sagittal slice of lower thoracic hemivertebra (Case 21) indicating that there may have been two hemivertebrae

Fig. 3

Lateral view of biomodel of lower thoracic hemivertebrae (Case 21) illustrating the two incomplete vertebral segments whose finer details were not clearly demonstrated with either the 3D CT or MRI examinations

Fig. 4

Postoperative sagittal X-ray after excision of both hemivertebrae (Case 21) and posterior instrumented fusion from T4-L3. During anterior surgery, the anatomical accuracy of the biomodel facilitated confident excision of both hemivertebrae, one of which was difficult to visualise within the intra-operative field. This allowed good surgical correction to be achieved

Fig. 5

Sagittal X-ray of cervical spine of child (Case 20) with spondyloepiphyseal dysplasia congenita (SEDC) with atlanto-axial instablility and early neurological signs of spinal cord compression

Fig. 6

Posterior view of biomodel of cervical spine (SEDC in Case 20) illustrating the posterior bony deficits, which were not clearly demonstrated by other investigations. The biomodel allowed safer exposure of the spinal cord and facilitated the placement of posterior instrumentation to achieve fusion

Fig. 7

Sagittal and posteroanterior X-ray views (Case 20) after decompression and posterior instrumented fusion from occiput-T5

Fig. 8

Sagittal 3D CT reconstruction (Case 20) 6 months postsurgical instrumented fusion