Extensor tendon ruptures have been reported in up to 8.8% of patients after volar plating and long screws have been implicated. The dihedral dorsal surface of the distal radius hinders accurate screw length determination using standard radiographic views (lateral; pronation and supination). A ‘dorsal tangential’ view has recently been described, but has not been validated.

To validate this view, we mounted a plate-instrumented sawbone onto a jig. Radiographs at different angles were reviewed independently by 11 individuals. Skyline views clearly demonstrated all screw tips, whereas only 69% of screw tips were identifiable on standard views.

With screws 2mm proud of the dorsal surface, skyline views detected 67% of long screws (sensitivity). The best of the standard views achieved only 11% sensitivity. At 4mm long, skyline sensitivity was 85%, compared with 25% for standard views. At 6mm long, 100% of long screws were detected on skylines, but only 50% of 8mm long screws were detected by standard views. Inter and intra-observer variability was 0.97 (p=0.005).

For dorsal screw length determination of the distal radius, the skyline view is superior to standard views. It is simple to perform and its introduction should reduce the incidence of volar plate-related extensor tendon rupture.

We assessed polyethylene wear and osteolysis in 15 patients (30 hips) undergoing staged bilateral total hip arthroplasty, who had a cemented hip arthroplasty on one side and a hybrid arthroplasty on the other. All factors apart from mode of acetabular component fixation were matched. Wear was measured radiographically using Livermore’s technique.

The mean clinical and radiological follow-up was 11.2 years for the cemented arthroplasties and 10.7 years for the hybrid arthroplasties. Mean annual linear wear rate for the cemented cups was 0.09mm/year, and 0.14mm/year for the uncemented cups. This difference was statistically significant (p=0.03), confirming previous reports that polyethylene wear in uncemented cups is greater than in cemented cups. Polyethylene wear in the uncemented cup exceeded wear in the cemented cup by more than > 0.1mm/year in 5 patients, 4 of whom had a BMI of greater than 30.

No periacetabular osteolysis was noted. Femoral osteolysis was present in 5 hybrid arthroplasties and 2 cemented arthroplasties. Zone 7 femoral osteolysis occurred in 3 patients on the side of the hybrid arthroplasty, multifocal femoral osteolysis not involving zone 7 was seen in 2 patients in both hips.

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.