Identification of a soluble form of a ligand for the lymphocyte homing receptor.

Lymphocytes are engaged in constant trafficking from the blood into secondary lymphoid tissues, such as peripheral lymph nodes (PLN), mesenteric lymph nodes (MLN), and Peyer's patches (PP). The initial step in this process is the binding of lymphocytes to high endothelial venules (HEV), and in the case of trafficking of cells to the PLN, it is required that they bear the L-selectin surface receptor. Using a chimeric protein, combining the extracellular domains of L-selectin with a human immunoglobulin (Ig) G1 Fc region (L-selectin-IgG), we have probed the expression of ligands for this receptor on HEV and in cell lysates. Two sulfated glycoproteins of 50 and 90 kD have been identified in lysates from PLN and MLN, but not PP. Here we show that the 50-kD molecule is secreted in organ cultures in vitro and is present in the blood of normal animals. Indeed, normal serum inhibits lymphocyte binding to HEV by approximately 50% in an in vitro assay. This inhibitory activity can be removed by passage of the serum over an L-selectin-IgG column and has a molecular mass of approximately 50 kD. We speculate on the possible reasons for secretion of a homing receptor ligand.

Hardware failure in an unconstrained lumbar pedicle screw system. A 2-year follow-up study.

STUDY DESIGN: A consecutive study of patients who underwent lumbar spinal arthrodesis with an unconstrained pedicle screw system. OBJECTIVES: To determine the rate of arthrodesis and of clinical success and to examine and characterize the cases of hardware failure with the AO/Dynamic Compression Plate system (Synthes, Paoli, PA). SUMMARY OF BACKGROUND DATA: Although the advantages and disadvantages of nonconstrained versus constrained systems have been studied extensively, instrumentation failure has not. Additionally, the association between pseudarthrosis and hardware failure per se is unclear. METHODS: Seventy-four consecutive cases of lumbar spinal fusion are reviewed. Standard outcome scores based on pain relief and medication usage were tabulated, along with pertinent demographic data. The patients were observed at five intervals after surgery for at least 2 years (range, 24 to 35 months; mean, 27 months). Standard statistical analyses were used to analyze data. Status of the arthrodesis was determined by standard radiographic criteria. RESULTS: The overall fusion rate was 61%. At final follow-up, 60% of patients believed that their back pain had improved, whereas 70% believed that their limb pain had improved. The presence of a solid fusion (r = 3.3, P = 0.010) was correlated positively with a successful clinical outcome; the presence of pseudarthrosis and preoperative narcotic use were negatively correlated with a successful clinical outcome. Twenty-two percent of patients (16) experienced hardware failure. Twelve of the 16 had pseudarthrosis; in the majority of these patients, hardware failure occurred at the level of the pseudarthrosis. CONCLUSIONS: The results of this study demonstrate an extremely high rate of hardware failure and pseudarthrosis using an unconstrained pedicle screw system. Interestingly, the initial rate of pain relief was higher and declined over time and was quite possibly associated with loosening of the hardware. Based on these data, it is difficult to recommend the use of an unconstrained fixation system in the lumbar spine.

Peridiscal vascular anatomy of the lower lumbar spine. An endoscopic perspective.

STUDY DESIGN: An analysis of the vascular anatomy relative to the underlying discs in the lower lumbar spine performed by using radiologic studies. OBJECTIVE: To define better the vascular anatomy of this region from the perspective of the endoscopic spine surgeon, and to draw conclusions regarding surgical accessibility of the lower lumbar intervertebral discs. SUMMARY OF BACKGROUND DATA: Cadaveric studies have highlighted the high degree of anatomic variability among the vascular structures overlying the anterior elements of the lower lumbar spine. An endoscopic approach to the intervertebral disc at these levels often is limited by arterial or venous structures. The growth of laparoscopic techniques to approach the intervertebral disc has renewed interest in the vascular anatomy of this region. METHODS: A computer-generated series of abdominal vascular studies performed for unrelated indications were scrutinized to ensure clear demarcation of the overlying vascular structures and underlying bony anatomy of the lumbar spine in a true anteroposterior plane. For analysis, 21 arterial (abdominal angiograms) and 22 venous (venograms) studies were selected. For the arterial data, level of aortic bifurcation and course of common iliac vessels were determined. The venous data were analyzed in a similar manner using the confluence of the common iliac veins as the major landmark. To draw conclusions about anterior surgical accessibility of the disc, the location of vessels was measured with respect to intervertebral disc spaces. RESULTS: The bifurcation level of the abdominal aorta was quite variable, occurring anteriorly to the L3 vertebral body in 3 of 21 studies (14%), and anteriorly to L4 and L5 in 10 (48%) and 7 (38%) of the studies, respectively. The cranial half of L5 was the most common single area of bifurcation (in one third of the studies). Venous anatomy was more consistent, with 86% of the patients displaying an iliac vein confluence at L5, and 14% having a confluence overlying L4. From an arterial perspective the L3-L4, L4-L5, and L5-S1 discs were readily accessible in 10%, 38%, and 95% of the studies, respectively. From a venous perspective, these levels were accessible in 100%, 73%, and 60% of the studies, respectively. CONCLUSIONS: The results of this study suggest that a laparoscopic approach to the L3-L4 intervertebral disc will seldom be accomplished without significant retraction of the aorta. Access to the L4-L5 space will be accomplished readily in approximately one third of the patients. In the others, it will require significant vascular dissection. The L5-S1 space, conversely, will be readily accessible by the authors' definitions without significant vessel dissection in the majority of patients.

Magnetic resonance imaging of acute Maisonneuve fractures.

Magnetic resonance imaging (MRI) studies were performed on five patients with acute Maisonneuve fractures. All patients had sustained a twisting injury to their ankles and complained of ankle pain and pain over their proximal fibula. High quality images with excellent visualization of all the ankle ligamentous structures were obtained. MRI showed that the anterior inferior tibiofibular ligament was disrupted in all patients and the posterior inferior tibiofibular ligament was intact in three of five patients. Also, the anterior talofibular ligament was disrupted in all patients and the calcaneofibular ligament was ruptured in two of five patients. This raises the question of whether patients with Maisonneuve fractures have lateral ankle instability at long-term follow-up. Although the superficial deltoid ligament was disrupted in all patients, the deep deltoid ligament was intact in one patient, partially disrupted in one patient, and completely disrupted in three patients. The interosseous ligament was disrupted at the ankle in all patients, while the interosseous membrane was disrupted in the leg in all patients except one. This patient had an intact interosseous membrane despite rupture of the interosseous ligament at the ankle and the presence of a proximal one third fibula fracture.

Ablation rates of human meniscal tissue with the Ho:YAG laser: the effects of varying fluences.

To further define the operating parameters for Holmium laser meniscectomy, an in vitro experimental was set up to specifically measure ablation rates and the concomitant thermal injury. Using an experiment set-up with a laser fiber penetrating through meniscal tissue slices, energy levels were varied between 167 and 927 Joules (J)/cm2 per pulse to measure meniscal ablation rates. Following each experiment the adjacent thermal effects were evaluated with hematoxylin and eosin and trichrome staining. The fastest ablation rate was found at 927 J/cm2 per pulse. The increase in ablation rates was directly proportional to the increases in energy levels. Histological examination showed the average lateral thermal change to be 400 to 500 microns, with no demonstrated relation to the pulse level of energy. At these laser parameters the higher levels of energy per pulse showed better ablation of human meniscal tissue without increasing thermal effects in adjacent tissue. Higher energy levels and fluences appeared desirable for more efficient arthroscopic meniscectomy with the Holmium laser.

Bone suture anchors versus the pullout button for repair of distal profundus tendon injuries: a comparison of strength in human cadaveric hands.

Avulsion or distal tendon laceration of flexor digitorum profundus (FDP) is classically repaired to the base of the distal phalanx via a pullout suture over a button. Bone suture anchors, used extensively in other surgical areas, have recently been proposed for reattachment of the FDP to the distal phalanx. The FDP tendons of the index, long, and ring fingers in 9 fresh frozen cadeveric hands were randomized to 1 of 3 repair techniques after simulated distal avulsion injuries. These were the pullout button using 3-0 monofilament nylon in a 2-strand Bunnell suture pattern, the 1.8 mm Mini QuickAnchor (Mitek Products, Norwood, MA) using 3-0 braided polyester in a 2-strand Bunnell suture pattern, and the Mitek micro anchor using 3-0 braided polyester with a modified 4-strand Becker suture pattern. Nine specimens were loaded to failure, noting maximum load and mode of failure. The 1.3 mm Micro QuickAnchor (Mitek) technique (69.6 +/- 10.8 N) was significantly stronger than the pullout button (43.3 +/- 4.8 N) or the Mini anchor technique (44.6 +/- 12.7 N). The Micro bone suture anchor provides a stronger tendon to bone repair than the pullout button or the Mini anchor. Given the disadvantages of the pullout button, the Micro bone suture anchor with the modified Becker technique is worth consideration as an alternative method to repair distal FDP avulsions.