The aim of this study was to assess the accuracy of pedicle screw placement using NAVITRAK, a system of Computer Assisted Orthopaedic Surgery and conventional fluoroscopic technique.

Twelve porcine lumbar spines were scanned pre-operatively by computer tomography for 3-D reconstruction ( 1 mm slice thickness, 1mm increment and 2.5 mm pitch ).

Computer randomisation divided the specimens between surgeons of different experience, and the two pedicles of each vertebral level between the two surgical techniques. Stainless steel screws (6.5 spongiosa) were inserted.

Post-operatively, fluoroscopic- and CT imaging were blindly assessed for accuracy by two independent observers, and compared to macroscopic dissection of the spinal segments.

Of 168 pedicles in 12 porcine specimens, 166 received a pedicle screw. Two pedicle screw placements were abandoned. Sixyty-one screws (73%) were placed satisfactorily with the CAOS system, 56 (67.5%) in the conventional group.

In 26 pedicles the screws were placed unsatisfactorily (12 pedicles (46.2%) with the NAVITRAK system and 14 pedicles (53.8%) with the conventional technique.

The NAVITRAK system in combination with stainless steel screws showed a difference of 5.5% in misplacement in favour for the computer assisted technique.

The aim of this study was to demonstrate a correlation between FASTRAK readings of spinal movement and established disability scores in-patients undergoing litigation.

A retrospective, blind study was conducted on patients who had been evaluated clinically between January 1994-October 1998. Statistical regression analysis between evaluated Oswestry Disability Score (ODS) and MSPQ/Zung questionnaires and the mean ROM was obtained. 49 patients with soft tissue injuries of the cervical (n = 14) and lumbar (n = 34) spine were assessed. All of them were undergoing litigation.

A standardised Fastrak trace measuring flexion, extension, right and left bending and rotation of the cervical and lumbar spine was recorded. An ODS and MSPQ/Zung questionnaire was filled in under the supervision of a senior physiotherapist.

There was no correlation between the ODS and MSPQ/Zung and mean ROM for the cervical spine. In the lumbar spine, flexion and ODS correlated statistically significantly (p< 0.01) and right rotation with the combined MSPQ/Zung score (p< 0.014).

This preliminary study is encouraging in that it demonstrates a direct correlation between FASTRAK measurements and recognised disability scores in the lumbar spine. Further analysis of non- litigation cohorts will contribute to establish these correlations.

The aim of this study was to assess the accuracy of pedicle screw placement comparing Computer Assisted Orthopaedic Surgery equipment with conventional fluoroscopic technique.

Twelve porcine cervical spines were scanned pre-operatively by computer tomography for 3D reconstruction (1 mm slice thickness, 1mm increment and 1 mm pitch).

Computerised randomisation divided the specimens between surgeons of different experience, and the two pedicles of each vertebral level between the two surgical techniques. Stainless steel screws (6.5 diameter, spongiosa) were inserted. Post-operatively, fluoroscopic imaging was used for accuracy assessment by two independent observers, and findings were compared to macroscopic dissection of the spinal segments.

Of 96 pedicles in 12 porcine specimens, 78 received a pedicle screw, 18 screw placements were abandoned, 38 (39.6%) were satisfactorily placed (19 in each, p> 0.05). 40 screws were misplaced, 18 (45%) with the NAVITRAK system vs. 22 (55%) with the conventional technique. These single factor results (all non-significant), were corroborated using a linear logistic regression model. Some heterogeneity in performance was detected between surgeons, independently of the type of technique used.

Computer assisted surgery is an aiming device and is not advantageous over conventional methods in spines with high bone density.