Introduction: Cervical spine pedicle morphology has been assessed by direct measurement and by CT in cadavers. We have assessed reproducibility and produced data for normal ranges in live subjects from the UK.

Method: 54 axial CT scans were examined. All subjects were scanned for the exclusion of fracture between December 2003 and December 2004. The digitised images were analysed on the Philips PACS system using SECTRA software. 168 individual vertebrae were assessed between C3 and C7. The following were measured; the angle of the pedicle relative to the sagittal plane, the smallest internal and external diameter, the angle of the lamina and the distance from the lateral mass to the anterior vertebral body (LMAVB) in the line of the pedicle. Reproducibility was assessed in a subset of 10 individuals with paired measures using the FDA approved formula for CV%.

Results: Angular measures had a CV% of 3.9%. The re-measurement error for distance was 0.5mm. 338 pedicles were assessed in 25 females and 29 males. Average age was 48.2 years (range 17–85). Our data from live subjects was comparable to previous cadaveric data. Mean pedicle external diameter was 4.9mm at C3 and 6.6mm at C7. Females were marginally smaller than males. Left and right did not significantly differ. Mean LMAVB was 34mm (min 21mm). In no case was the pedicle narrower than 3.2mm. Mean pedicle angle was 130 deg at C3 and 140 deg at C7.

Conclusions: CT measurement has acceptable reproducibility. Previous cadaveric measurements have been validated in live subjects in the UK. Although there is some variation in morphology, instrumentation no wider than 3.0mm and no longer than 20mm is unlikely to prove too large for an adult pedicle.

Introduction: We have assessed the clinical observation that the angle of the contralateral lamina matches the angle required from the sagittal plane for the placement of pedicle screws in the subaxial cervical spine.

Method: 54 axial CT scans were examined. All subjects were scanned for the exclusion of fracture between December 2003 and December 2004. The digitised images were analysed on the Philips PACS system using SECTRA software. 168 individual vertebrae were assessed between C3 and C7. The following were measured; the angle of the pedicle relative to the sagittal plane, the smallest internal and external diameter, the angle of the lamina and the distance from the lateral mass to the anterior vertebral body (LMAVB) in the line of the pedicle. Reproducibility was assessed in a subset of 10 individuals with paired measures using the FDA approved formula for CV%.

Results: Angular measures had a CV% of 3.9%. The re-measurement error for distance was 0.5mm. 336 pedicles were assessed in 25 females and 29 males. Average age was 48.2 years (range 17–85). Our morphologic data from live subjects was comparable to previous cadaveric data. Mean pedicle external diameter was 4.9mm at C3 and 6.6mm at C7. Females were marginally smaller than males. Left and right did not significantly differ. In no case was the pedicle narrower than 3.2mm. Mean pedicle angle was 130 deg at C3 and 140 deg at C7. The laminar angle correlated well at C3,4,5 (R2> 0.7) and was within 1 deg of pedicle angle. At C6,7 it was within 11 deg. In all cases a line parallel to the lamina provided a safe corridor of 3mm for a pedicle implant.

Conclusions: The contralateral lamina provides a reliable intraoperative guide to the angle from the sagittal plane for subaxial cervical pedicle instrumentation in adults.

The management of proximal humeral fractures is determined by fragment displacement. Intra-operative and radiological classification systems have been proposed, namely AO and the Neer classifications to assess therapeutic options.

This study evaluates the usefulness of these classification systems by the creation of physical 3D models using a rapid prototyping technique avoiding the problems associated with 3D illusions on a 2D screen.

Seven consecutive patients with complex fractures of the proximal humerus were investigated using the data from multi-sliced spiral CT scans. Fractures associated with dislocation were excluded. The data from these CTs was segmented to reveal the anatomy of interest and converted to a stereolithographic format from which the physical models could be made of the proximal humerus via a laser guided filament deposition process. Further manipulation with software allowed angulation and displacements of fragments to be measured.

Inter-observer agreement: All models were assessed by three surgeons. A consultant with a special interest in shoulder surgery, a fellowship trained surgeon and a senior house officer in basic surgical training. Independent assessment of the fractures from the models was made using the Neer and AO classifications. In only 1 incidence did all 3 observers agree on the classification, in 5 incidences only two observers agreed and on 8 occasions none of the observers agreed. Indeed there were 9 occasions that at least one observer thought the fracture pattern could not be applied to a classification.

Fracture Patterns: Observation of the individual models together with measurements of angulation and displacement by further software analysis, demonstrated major subtypes namely valgus and varus angulation with minimal displacement of the greater tuberosity. Appreciation of the integrity of the medial hinge and buckling could be made in relation to the different fracture patterns.

This study highlights concerns on the validity of current classification systems. It also questions whether the existing systems reflect the pathophysiological subtypes of these fractures allowing comparison of surgical results in order to evaluate treatment options.