Acute and long-term response of the meniscus to partial meniscectomy using the holmium: YAG laser.

The purpose of this study was to evaluate the histological effects of holmium:YAG laser partial meniscectomy in an in vivo rabbit model and compare it with scalpel partial meniscectomy at selected time intervals. Twenty-four adult male New Zealand rabbits underwent bilateral partial medial meniscectomies through the avascular zone. In the right knee, partial medial meniscectomy was performed using a standard surgical blade; in the left knee, an anatomically similar partial medial meniscectomy was performed using a Ho:YAG laser (Coherent, Santa Clara, CA). All animals were randomized and three animals were killed at postoperative days I and 3, and postoperative weeks 1, 2, 3, 4, 6, and 10. Samples of all medial and lateral menisci, with attached synovium and vascular rim, from both knees were harvested and submitted for histological and/or ultrastructural examination. The results indicate that (1) at all time periods, laser cut menisci had more cell loss and matrix degradation; (2) synovial necrosis was more common in laser-treated knees; (3) the Ho:YAG laser creates three zones of damage in the meniscal fibrocartilage: a zone of fibrin and debris at the incision site, a zone of necrosis characterized by degeneration of the collagen and loss of viable cells, and a zone of thermal change characterized by collagen degeneration. The zone of thermal change, with its histological injury was thought at the time of surgery to be the viable border. The zone of thermal change may act as a barrier to delay healing, and the scalpel produced a consistently straighter cut.

The effect of a wrist brace on injury patterns in experimentally produced distal radial fractures in a cadaveric model.

We compared patterns of bony and ligamentous injury with distal radial fractures in braced and unbraced wrists using 20 paired fresh cadaveric upper extremities. A commercially available wrist brace was placed on one wrist in each pair. Specimens were then placed in a fast-loading gravity-driven device and subjected to loads averaging 16 kg from an average height of 78 cm. Postfracture radiographs were obtained, the specimens were dissected, and fracture patterns and ligamentous integrity were assessed. The following fracture types were produced: distal radial fractures (eight unbraced, seven braced) and intraarticular (seven unbraced, four braced). Radiographically, seven unbraced wrists demonstrated carpal bone fracture and one braced wrist demonstrated carpal fractures. Eight unbraced and three braced wrists sustained carpal intrinsic ligament injuries, four unbraced and one braced wrists demonstrated extrinsic ligament injuries. More capsular tears occurred in the unbraced group (N = 8) than in the braced group (N = 1). This model demonstrated a difference in the patterns of injury in unbraced and braced wrists subjected to the same mechanical conditions, which suggests that use of a wrist brace may alter patterns of wrist injury.

A method for radiographic evaluation of pedicle screw violation of the vertebral endplate. Technique.

STUDY DESIGN: This study evaluated the utility of intraoperative radiographs for minimizing the risk of pedicle screw tip violation of the superior vertebral endplate. OBJECTIVES: An intraoperative radiographic technique is demonstrated that ensures that a screw has not penetrated the intervertebral disk. SUMMARY OF BACKGROUND DATA: Although methods to avoid penetration of the medial pedicle cortex and the anterior body cortex have been described, no study has discussed screw penetration of the superior endplate and disc. METHODS: Pedicle screws were inserted into 11 cadaveric lumbar spines, randomly, with the tip interior to the endplate, at the endplate, and through the endplate. Radiographs were evaluated to measure the penetration, if any, of the screws. Spine segments were dissected and evaluated anatomically. The anatomic and radiographic results were then compared. RESULTS: The overall error rate for radiographs was 22/312 (7%). Oblique radiographs gave a much higher error rate. CONCLUSIONS: A true lateral or anteroposterior radiographic view of the vertebra provides a high degree of certainty that the screw has not crossed the endplate when a "safe zone" of 3 mm remains superior to the screw tip. Intraoperative radiography can reduce concern about violation of the superior vertebral endplate.

The tibiofibular syndesmosis. Evaluation of the ligamentous structures, methods of fixation, and radiographic assessment.

Twenty-five fresh-frozen cadaveric specimens were used to evaluate the role of the syndesmotic ligaments when the ankle is loaded with external rotation torque. An apparatus was constructed that allowed pure external-rotation torque to be applied through the ankle with the foot in neutral flexion. The apparatus provided solid fixation of the tibia while allowing free movement of the fibula in all planes. The syndesmotic ligaments were incrementally sectioned, and direct measurements of anatomical diastasis were made. Mortise and lateral radiographs were made at each increment under both loaded (5.0 newton-meters) and unloaded conditions. After all structures of the syndesmosis had been divided, the syndesmosis was reduced and was repaired with one or two screws. The strength of the repair was measured with incremental increases in torque of 1.0 newton-meter. The radiographs were measured by three independent observers in a blind fashion. In order to evaluate intraobserver error, each observer was randomly given forty radiographs to reinterpret. Diastasis and rotation were found to be related to the amount of injury of the ligament (p < 0.0001). After the entire syndesmosis had been divided, application of a 5.0-newton-meter torque resulted in a mean diastasis of 7.3 millimeters. The subsequent repair of the anterior tibiofibular ligament with suture failed at a mean of 2.0 newton-meters (range, 1.0 to 6.0 newton-meters) of torque. Repair with two screws was found to be stronger than repair with one, with the first construct failing at a mean of 11.0 newton-meters (range, 5.0 to 15.0 newton-meters) and the second, at a mean of 6.2 newton-meters (range, 2.0 to 10.0 newton-meters) (p = 0.0005). Failure of the screw fixation was not associated with the maximum previous diastasis (p = 0.13). Measurements of anatomical diastasis were compared with measurements made on the mortise and lateral radiographs. Measurements on the stress mortise radiographs had a weak correlation with diastasis (r = 0.41, p < 0.0001). However, measurements on the stress lateral radiographs had a higher correlation (r = 0.81, p < 0.0001). Additionally, interobserver correlation was significantly higher for the measurements on the lateral radiographs (r = 0.87, p < 0.0001) than for those on the mortise radiographs (r = 0.56, p < 0.0001). Intraobserver correlation for the three observers was poor with regard to the measurements on the mortise radiographs (r = 0.12, 0.42, and 0.25). The respective correlations for the measurements on the lateral radiographs were r = 0.81, 0.90, and 0.89.(ABSTRACT TRUNCATED AT 400 WORDS)

Intrapelvic migration of threaded pins following open reduction and internal fixation of the acetabular fracture.

The subject of this article is intrapelvic migration of threaded pins used in fixation of fracture. A case report is presented along with suggested treatment. A discussion of pin migration follows.

Decreased oxygen uptake with stored blood in the isolated hindlimb.

Storage of red cells in acid-citrate-dextrose (ACD) solution for more than a week has been shown to cause a reduction in red cell 2,3-diphosphoglycerate (2,3-DPG), resulting in a decrease in the half-saturation pressure (P50) of stored blood, thus increasing hemoglobin-oxygen affinity and theoretically decreasing oxygen delivery to the tissues. A method to isolate and perfuse the hindlimb in a dog has been developed and used successfully to compare the difference of oxygen release between banked and fresh ACD blood. Ten dogs were perfused using canine blood collected in standard blood transfusion bags containing ACD and stored at 4 degrees C and fresh blood collected in a similar manner but used immediately. The total oxygen release in the limb during perfusion with fresh blood was significantly greater than during perfusion with stored blood.

Aspiration of blood and pulmonary host defense mechanisms.

The effect of aspiration of blood on pulmonary host defenses was studied in the rat. Sham and experimental rats had 0.2 ml of saline or blood/100 g body weight injected into their tracheas. One or 24 hours after aspiration rats were challenged with aerosolized, radiolabeled ((32)P), S. aureus. Fourteen hours after bacterial challenge, lungs were removed and intrapulmonary bacterial inactivation was quantified. Significant impairment of bacterial inactivation occurred at both 15 and 38 hours after aspiration of blood, but not after saline. The pulmonary consolidation after aspiration of blood was focal in nature. The lung weight increased but fractional water content decreased. Arterial pH, pCO(2), or pO(2) were unaffected by aspiration of blood. The number and viability of macrophages recovered by lavage were similar in control, sham and experimental groups. If similar impairment in pulmonary host defenses occurred in man following aspiration of blood, the patient with aspiration of blood would have an increased susceptibility to bacterial infection.

Effects of biliary obstruction on pulmonary ultrastructure in the rat.

Hypoxemia and respiratory alkalosis have been described in patients with liver disease. Since no pulmonary parenchymal lesions have been related to the abnormal respiratory function, the effects of common bile duct ligation and division on pulmonary alveolar structure were studied in ninety-two 10- to 14-week-old male Wistar rats. In comparison with controls, the rats with ligated common bile ducts (CBD) developed progressive hepatic and pulmonary changes. The hepatic damage consisted of bile duct proliferation, loss of hepatocytes and generalized cirrhosis. Most pronounced pulmonary histologic differences between the CBD and sham-operated rats were thickening of interalveolar septa and generalized increase in cellularity of alveolar walls. With electron microscopy, frequently observed alterations included swelling and increased vacuolization of endothelial and epithelial (Type I) cells, proliferation of Type II alveolar pneumonocytes, and increase in amounts of collagen fibers and edema of the interstitium.