The glenopolar angle assesses the rotational alignment of the glenoid and may provide prognostic information and aid the management of scapula fractures. We have analysed the effect of the anteroposterior (AP) shoulder radiograph rotational offset on the glenopolar angle in a laboratory setting and used this to assess the accuracy of shoulder imaging employed in routine clinical practice. Fluoroscopic imaging was performed on 25 non-paired scapulae tagged with 2 mm steel spheres to determine the orientation of true AP views. The glenopolar angle was measured on all the bony specimens rotated at 10° increments. The mean glenopolar angle measured on the bone specimens in rotations between 0° and 20° and thereafter was found to be significantly different (p < 0.001). We also obtained the AP radiographs of the uninjured shoulder of 30 patients treated for fractures at our centre and found that none fitted the criteria of a true AP shoulder radiograph. The mean angular offset from the true AP view was 38° (10° to 65°) for this cohort. Radiological AP shoulder views may not fully project the normal anatomy of the scapular body and the measured glenopolar angle. The absence of a true AP view may compromise the clinical management of a scapular fracture.

Cite this article: Bone Joint J 2013;95-B:1114–20.

Background:

During the past two decades the medial Patellofemoral ligament has come to the fore as the essential lesion of acute patella dislocation and its reconstruction in cases of chronic instability seems logical. The femoral insertion of the medial Patellofemoral ligament (MPFL) is key to the isometry or desired anisometry of the reconstruction. Radiographic landmarks for the femoral insertion has been described in literature most notably by Schottle et al. AJSM 2007. We examined the consistency of these landmarks of the femoral insertion of the MPFL.

There is little evidence examining the relationship between anatomical landmarks, radiological placement of the tunnels and long-term clinical outcomes following anterior cruciate ligament (ACL) reconstruction. The aim of this study was to investigate the reproducibility of intra-operative landmarks for placement of the tunnels in single-bundle reconstruction of the ACL using four-strand hamstring tendon autografts.

Isolated reconstruction of the ACL was performed in 200 patients, who were followed prospectively for seven years with use of the International Knee Documentation Committee forms and radiographs. Taking 0% as the anterior and 100% as the posterior extent, the femoral tunnel was a mean of 86% (sd 5) along Blumensaat’s line and the tibial tunnel was 48% (sd 5) along the tibial plateau. Taking 0% as the medial and 100% as the lateral extent, the tibial tunnel was 46% (sd 3) across the tibial plateau and the mean inclination of the graft in the coronal plane was 19° (sd 5.5).

The use of intra-operative landmarks resulted in reproducible placement of the tunnels and an excellent clinical outcome seven years after operation. Vertical inclination was associated with increased rotational instability and degenerative radiological changes, while rupture of the graft was associated with posterior placement of the tibial tunnel. If the osseous tunnels are correctly placed, single-bundle reconstruction of the ACL adequately controls both anteroposterior and rotational instability.

Introduction Central placement of a total disc arthroplasty (TDA) in the coronal plane will result in equivalent facet joint loading, less tendency for lateral core migration, optimum kinematics, and better outcomes. This study was performed to determine which of the radiographic markers – the vertebral body, the pedicles, or the spinous process – provides the most accurate guide to the coronal midline, so to optimise coronal TDA. The coronal midline was defined as the perpendicular bisector of a line drawn between the midpoints of the two facet joints.

Methods Axial CT images were reconstructed from 35 abdominal CT’s to show the relevant anatomy at L4, L5, and S1. Measurements were taken comparing the consistency of the midpoints of the vertebral body, the pedicles, and the spinous processes, in relation to the coronal midline.

Results The mean distance from the coronal midline to the vertebral body midpoint was 0.55mm (SD 0.45), to the interpedicular midpoint was 0.19mm (SD 0.40), and to the spinous process midpoint was and 1.30mm (SD 1.30). 16% of the distances from the coronal midline to the spinous process midpoint were greater than or equal to 3mm, compared with 0% of the distances to the interpedicular midpoint or the vertebral body midpoint. The interpedicular midpoint was significantly closer to the coronal midline than the spinous process midpoint or the vertebral body midpoint at all levels (p< 0.001).

Discussion The interpedicular midpoint is the most accurate guide to the coronal midline. We recommend this landmark be used in preference to the spinous processes or the vertebral body midpoint when placing the implant in TDA. The close location of the interpedicular midpoint to the implant, compared with the more posteriorly located spinous process, means the likelihood of parallax error, by rotation of the patient or the C arm, is reduced using the interpedicular midpoint.