Men and women have similar Q angles: a clinical and trigonometric evaluation.

The Q angle is an important determinant of patellar tracking, though its clinical relevance is debatable. One controversy centres around any possible differences in its value between men and women. The accepted, though unproven explanation, for the greater Q angle in women is that a woman has a wider pelvis. However, because of the long distance between the pelvis and patella, relative to the distance from the patella to the tibial tuberosity, large changes in the position of the anterior superior iliac spine are necessary to effect significant changes in the Q angle. In our study of 69 subjects, we did not find such large differences in the position of the anterior superior iliac spine, and found a mean difference of only 2.3 degrees between the Q angles of men and women. Furthermore, we found that men and women of equal height demonstrated similar Q angles, with taller people having slightly smaller Q angles. The slight difference in Q angles between men and women can be explained by the fact that men tend to be taller.

Applied biomechanics of the patella.

Although numerous prominent orthopaedists of the twentieth century considered the patella to be useless, even detrimental, it now is clear that the patella serves an important biomechanical function. It is a complex lever that magnifies the moment arm of the extensor mechanism. The patellofemoral contact area (the fulcrum of the lever) shifts along a proximodistal axis through the knee's arc of motion. As the knee flexes, the force within the patellar tendon diminishes relative to that of the quadriceps tendon. One's interpretation of patellar tracking is dependent on the choice of coordinates. When assessing tracking by way of anatomic coordinates, patellas are seen to be slightly lateralized at 0 degrees flexion and to follow similar paths down the trochlea. The tracking pattern is the result of an elaborate interplay between the quadriceps muscles, patellofemoral ligaments, the geometry of the trochlea, and the quadriceps angle. The articular cartilage of the patella is the thickest in the human body and does not follow the contour of the subchondral bone. Patellar cartilage is softer and more permeable than that of the trochlea. It is insensate. In size, nature, and number, the facets of the patellar articulation vary from person to person.

Anesthesia of six-week-old New Zealand White rabbits for thoracotomy.

Many methods of administering surgical anesthesia to rabbits have been described. We are studying the effects of anterior thoracic spinal procedures on the growth of young rabbit spines. We introduce a method for intubation using direct laryngoscopy without the need for specially manufactured or costly equipment and for administration of anesthesia applicable to six-week-old New Zealand White (NZW) rabbits. Induction of anesthesia was initiated with 5% isoflurane in a sealed plastic anesthesia box. No premedication was given. We performed direct laryngoscopy by using an otoscope. Under direct visualization, a 5-French polypropylene catheter was passed through the speculum of the otoscope and advanced through the vocal cords. The endotracheal tube without the adapter then was advanced over this guide. A vigorous cough reflex was noted as the tube passed through the vocal cords. We have found this cough reflex to be a very reliable indicator of correct placement. Throughout the surgical procedure, anesthesia was maintained with isoflurane delivered from a standard small-animal anesthetic machine using pediatric breathing hoses, y-piece, and ventilator. Recovery after surgery was rapid.

The effect of valproic acid on blood loss in patients with cerebral palsy.

Valproic acid (VPA) is used in the treatment of seizure disorders often present in patients with cerebral palsy. The charts of 114 patients with cerebral palsy were reviewed to evaluate the effect of VPA on blood loss during spine surgery. Forty-one patients had seizure disorders. Of these, 18 were taking VPA as monotherapy (group III) and the remaining 23 patients were taking other antiseizure medications, including two taking VPA (group II). There was a significant increase in the number of patients with abnormal bleeding times and a significant difference (p < 0.001) in blood loss (ml/kg) in patients taking VPA as monotherapy (38.6 ml/kg vs. 30.0 ml/kg). There was also increased blood-product administration postoperatively in the VPA monotherapy patients. Physicians should be aware of this potential association between VPA use and increased blood loss. The routine laboratory tests of complete blood count, prothrombin time, and partial thromboplastin time will not adequately screen for the platelet-mediated effects of VPA.