INTRODUCTION:

A discrepancy exists between biomechanical and clinical outcome studies when comparing cruciate-retaining (CR) versus posterior stabilized (PS) component designs. The purpose of this study is to re-evaluate experimental model results using half-body specimens with intact extensor mechanisms and navigation to evaluate PS and CR component gaps though an entire range of motion.

Aim of the study: To define the dimensions of the radial head, as well as the radiocapitellar and proximal radio-ulnar joints. The most congruent portions of the radial head articulations were determined.

Materials & Methods: Computed tomography scans of twenty-two cadaveric adult elbows were obtained in three forearm positions – supination, neutral, pronation. The radial head dimensions, the radiocapitellar joints, and the proximal radioulnar joints were also measured. Multivariate analysis of variance was used to determine which portions of each articulation were the most congruent.

Results: At the level of the radial trough, the maximum diameter was 22.3 mm, the minimum diameter was 20.9 mm, and the diameter difference was 1.4 mm. This difference represented only 6.3% of the overall maximum diameter. The depth of curvature of the radial head trough was 2.3 mm, the radial head length was 9.8 mm, and the radial neck length was 10.7 mm. At the isthmus of medullary canal, the maximum diameter was 9.7 mm, the minimum diameter was 8.2 mm, and the diameter difference was 1.5 mm. This difference represented 15.6% of the maximum diameter. The average radiocapitellar distance at the radial lip was 4.0 mm, the trough 2.4 mm, and the ulnar lip 2.2 mm. Thus, the radial head tended to become uncovered at the radial lip (p < 0.0001). The radiocapitellar joint was tighter in pronation than in supination (p = 0.0008). The proximal radioulnar joint was most congruent at the MPRUJ (middle proximal radioulnar joint), at the midportion and posterior aspects, rather than the anterior aspect (p < 0.0001). The PRUJ coverage was between 69.0 and 79.2 degrees.

Conclusions: Prosthesis trial sizing should be judged by the articulations providing the most congruency –

1) the ulnar lip or trough of the radiocapitellar joint in pronation and

Video-assisted thoracoscopic surgery (VATS) has been in use since the 1980s for surgery of the spine. Initially it was used for anterior release of the thoracic spine in order to facilitate posterior instrumentation. With increasing experience, it has been applied to perform definitive correction and instrumentation. Video-assisted thoracoscopic spine surgery allows the surgeon to perform anterior thoracic spine operations with fewer levels of instrumentation, reducing the crankshaft effect and removing the morbidity associated with thoracotomy. From 1996 to November 2000, our center performed 19 such operations. 18 of them were completed successfully endoscopically and one was converted to an open procedure. An initial group of 10 patients underwent thoracoscopic anterior release and fusion followed by same day posterior instrumentation and fusion. Subsequently, 6 patients underwent anterior discectomies, fusion with instrumentation via thoracoscopic approach.

For the initial 10 patients, the average operative time was 190 minutes. The average post-operative correction was 62 % and blood loss was 350 mLs. For the 6 patients who underwent anterior discectomies, fusion and instrumentation via the thoracoscopic approach, the average operative time was 360 minutes; average post-operative correction was 70% and blood loss was 400 mLs.

Complications encountered were minor and included one case ofcontralateral pneumothorax, one patient complained of transient limb numbness which resolved within 6 weeks. It is our conclusion that thoracoscopic anterior spinal surgery, though with learning curve, a safe and effective procedure.