Posterior C1-C2 transarticular screw fixation for atlantoaxial arthrodesis

OBJECTIVE: To assess the outcomes associated with C1-C2 transarticular screw fixation. METHODS: The clinical outcomes of 121 patients treated with posterior C1-C2 transarticular screws and wired posterior C1-C2 autologous bone struts were evaluated prospectively. Atlantoaxial instability was caused by rheumatoid arthritis in 48 patients, C1 or C2 fractures in 45, transverse ligament disruption in 11, os odontoideum in 9, tumors in 6, and infection in 2. RESULTS: Altogether, 226 screws were placed under lateral fluoroscopic guidance. Bilateral C1-C2 screws were placed in 105 patients; each of 16 patients had only one screw placed because of an anomalous vertebral artery (n = 13) or other pathological abnormality. Postoperatively, each patient underwent radiography and computed tomography to assess the position of the screw and healing. Most screws (221 screws, 98%) were positioned satisfactorily. Five screws were malpositioned (2%), but none were associated with clinical sequelae. Four malpositioned screws were reoperated on (one was repositioned, and three were removed). No patients had neurological complications, strokes, or transient ischemic attacks. Long-term follow-up (mean, 22 mo) of 114 patients demonstrated a 98% fusion rate. Two nonunions (2%) required occipitocervical fixation. In comparison, our C1-C2 fixations with wires and autograft (n = 74) had an 86% union rate. CONCLUSION: Rigidly fixating C1-C2 instability with transarticular screws was associated with a significantly higher fusion rate than that achieved using wired grafts alone. The risk of screw malpositioning and catastrophic vascular or neural injury is small and can be minimized by assessing the position of the foramen transversaria on preoperative computed tomographic scans and by using intraoperative fluoroscopy and frameless stereotaxy to guide the screw trajectory.     

Anatomic study for ideal and safe posterior C1-C2 transarticular screw fixation

STUDY DESIGN: Directions of the C1-C2 posterior transarticular screw trajectories making the longest path or violating the transverse foramen were measured by using an objective measuring method. OBJECTIVES: To clarify the directions of the screw trajectory marking the longest paths without violating the transverse foramen. To achieve this, diverse directions of the screw trajectories were objectified by measuring the locations of the points of screw intersection on the superior articular surface of C2. SUMMARY OF BACKGROUND DATA: The principal limitation of posterior C1-C2 transarticular screw fixation is the location of the vertebral artery. Because of the lack of an objective measuring method, surgical unsuitability has been decided on the basis of individual experiences as reported in 18% to 23% of cases. METHODS: Sagittal reconstructed computed tomographic images were made at 3.5 mm and 6 mm from the spinal canal. C1-C2 transarticular screw trajectories making the longest path or violating the transverse foramen (dangerous trajectory) were drawn, and their points of screw intersection on the superior articular surface of C2 were measured from the posterior rim of the superior articular surface of C2. When the space available for the screw behind the points of screw intersection by the dangerous trajectory was equal to or less than 3.5 mm, the case was defined as "unacceptable"; when the space available for the screw was more than 3.5 mm but equal to or less than 4.5 mm, it was defined as "risky" for the placement of the screw. RESULTS: Trajectories make the longest paths when they pass an average of 3.6 mm and 2.8 mm anterior to the posterior rim of the posterior articular surface of C2 at 3.5-mm lateral images and 6-mm lateral images, respectively. Four of 64 cases were unacceptable or risky unilaterally on 3.5-mm lateral images, and 21 cases were unacceptable or risky on 6-mm lateral images. A sigmoid-shaped increment curve of the risk was noted as the increasing forward inclination of the screw trajectories increased. CONCLUSIONS: The areas on the superior articular surface of C2 intersected by the trajectories making the longest paths without violating the transverse foramen are clarified as a guide to the ideal and safe trajectories. The theoretical minimal risk and usual risk of the posterior C1-C2 transarticular screw fixation are presented as well.     

Preoperative oblique axial computed tomographic imaging for C1-C2 transarticular screw fixation: technical note

C1-C2 transarticular screw fixation is an increasingly popular surgical method of treating atlantoaxial instability. When properly performed, it can safely provide fusion rates near 100%. However, the technique of screw insertion into this region allows only a small margin for error. Preoperative radiological assessment is essential to analyze the morphology of the region, assess for vertebral bony and vascular anomalies, and define the tolerances for the transarticular screws along their planned trajectory. As an adjunct to the preoperative planning of C1-C2 transarticular screw fixation, a unique, easily obtainable method of computed tomographic imaging, using thin-section oblique axial computed tomographic images of the C1-C2 region, is described.     

The reliability of the lateral radiograph in determination of the optimal transarticular C1-C2 screw length

STUDY DESIGN: This study assessed the value of using lateral radiographs in evaluating the optimal screw length in transarticular C1-C2 screw fixation. OBJECTIVES: To assess the reliability of the lateral radiograph in determining the optimal transarticular C1-C2 screw length. SUMMARY OF BACKGROUND DATA: Transarticular C1-C2 screw placement is usually performed using anatomic landmarks and fluoroscopy. A lateral fluoroscopic image is valuable when directing screws in the sagittal plane, but its exact role in determining screw length has not been investigated. METHODS: Eight cervical spine specimens were used in this study. Screw placements were performed in each specimen, fixed in the exact lateral position and under direct visualization. After each placement, a lateral radiograph was taken. The odontoid process was divided into three equal portions. Another portion anterior to the odontoid process was called the anterior tubercle region. The number of screw tips appearing in each portion on the radiograph was then recorded for each placement. In addition, 30 C1 specimens were measured to evaluate the anterior part of C1. RESULTS: The results showed that 12.5% of the screws placed 2 mm short of reaching the ventral cortex and 0 mm overpenetrating the ventral cortex of the lateral mass of C1 projected in the radiograph on the anterior tubercle region, 37.5% on the anterior region of the odontoid process, and 50% on the middle region of the odontoid process. Twenty-five percent of the screws that were placed to overpenetrate, by 2 or 4 mm, the ventral cortex of the lateral mass of C1 were projected on the anterior tubercle region in the radiograph, and 50% and 62.5% were projected on the anterior region of the odontoid process, respectively. The mean vertical distance between the anteriormost point of the anterior tubercle of the anterior ring and the middle of the ventral cortex of the lateral in all specimens was 5.6 +/- 1 mm, and the mean transverse angle of the anterior ring relative to the frontal plane was 21.1 +/- 3.5 degrees. CONCLUSIONS: This results in this study indicate that a lateral radiograph may not be reliable in determining the optimal screw length, although it is valuable in directing accurate screw angle in the sagittal plane. Preoperative computed tomographic evaluation of the C1-C2 region may be helpful in estimating the location of the screw tip on the lateral radiograph during surgery.     

Biomechanical comparison of C1-C2 posterior fixations. Cable, graft, and screw combinations

STUDY DESIGN: Four combinations of cable-graft-screw fixation at C1-C2 were compared biomechanically in vitro using nondestructive flexibility testing. Each specimen was instrumented successively using each fixation combination. OBJECTIVES: To determine the relative amounts of movement at C1-C2 after instrumentation with various combinations of one or two transarticular screws and a posterior cable-secured graft. Also to determine the role of each component of the construct in resisting different types of loading. SUMMARY OF BACKGROUND DATA: Spinal stiffness increases after instrumentation with two transarticular screws plus a posterior wire-graft compared with a wire-graft alone. Other C1-C2 cable-graft-screw combinations have not been tested. METHODS: Eight human cadaveric occiput-C3 specimens were loaded nondestructively with pure moments, and nonconstrained motion at C1-C2 was measured. The instrumented states tested were a C1-C2 interposition graft attached with multistranded cable; a cable-graft plus one transarticular screw; two transarticular screws alone; and a cable-graft plus two transarticular screws. RESULTS: The transarticular screws prevented lateral bending and axial rotation better than the posterior cable-graft. The cable-graft prevented flexion and extension better than the screws. Increasing the number of fixation points often significantly decreased the rotation and translation (paired t test; P < 0.05). Axes of rotation shifted from their normal location toward the hardware. CONCLUSIONS: It is mechanically advantageous to include as many fixation points as possible when atlantoaxial instability is treated surgically.     

Safe lateral-mass screw lengths in the Roy-Camille and Magerl techniques. An anatomic study

STUDY DESIGN: Investigation of the mean safe lateral-mass screw lengths in the Roy-Camille and Magerl screw techniques in cadaveric cervical specimens. OBJECTIVES: To report the mean screw path length and to evaluate the relation of the screw trajectory to the nerve root in the Roy-Camille and Magerl screw techniques. SUMMARY OF BACKGROUND DATA: Potential injury to the cervical nerve root caused by too long a screw remains a major concern. Few studies regarding proper screw length and its relation to the adjacent nerve root are available. METHODS: Fourteen cervical spines were used for this study. Each lateral mass from C3 to C7 was drilled according to the techniques described by Roy-Camille (right side) and Magerl (left side). The cervical spines were harvested from the cadavers, and the anterior aspect of the lateral mass and spinal nerve were exposed. The screw path length between the dorsal and ventral cortices of the lateral mass were measured. An additional measurement was taken from the ventral aspect of the lateral mass to the nerve root along the screw path. RESULTS: The mean screw path length in the Roy-Camille technique decreased consistently from C3 (15.7 +/- 1.7 mm) to C7 (11.3 +/- 0.8 mm). The mean distance from the ventral cortex to the nerve root ranged from 1.2 to 2.3 mm, and the smallest value was at C7. The mean screw path length in the Magerl technique also decreased from cephelad to caudal, with a range of 15-16 mm at C3-C6 and a mean value of 13.8 mm at C7. CONCLUSIONS: A safe screw length is 14-15 mm in the Roy-Camille technique and 15-16 mm in the Magerl technique at C3-C6. A short screw may be used at C7 if desired.     

Pedicle screw fixation for arthrodesis of the lumbosacral spine in the elderly. An outcome study

STUDY DESIGN: An analysis of the outcome and effectiveness of instrumented arthrodesis of the lumbosacral spine in elderly patients conducted using a review of records, assessment of fusion via plain radiographs, and a two-part questionnaire. OBJECTIVE: To ascertain the outcome and efficacy of instrumented arthrodesis of the lumbosacral spine in patients 60 years of age and older. BACKGROUND DATA: From 1987 to 1991, 38 patients of at least 60 years of age underwent instrumented arthrodesis of the lumbosacral spine using the Wiltse or Selby pedicle screw fixation system (Advanced Spine Fixation Systems, Inc., Irvine, CA). Patients were considered for surgery only after attempts at conservative management, including physical therapy, medication, injection blocks, and home exercises, had proven unsuccessful. METHODS: Follow-up examinations were performed 3 months, 6 months, 1 year, and 2 years after surgery. Fusion was assessed using plain radiographs, including flexion-extension films. Inpatient and outpatient records were reviewed, and a two-part questionnaire was used to establish the effect of surgery on function and lifestyle. Thirty patients responded to the questionnaire. Follow-up observation of the patients ranged from 25 to 56 months. The mean age was 73.8 years (range, 60-90 years). RESULTS: The mean co-morbidity was 1.7. Based on the authors' method of evaluation of fusion, the fusion rate was 92%. Fifty-seven percent of the patients reported excellent or good results, 26% reported fair results, and 17% reported poor results. Functional gains of 50% or more were reported by 71% of the respondents. Female patients had significantly more complications than male patients, but reported comparable outcomes. CONCLUSION: Despite the increase in age, co-morbidity, and associated risk of perioperative complications inherent in this population, an outcome comparable with that of younger patients is reported.     

Radiologic prevalence of advanced lateral C1-C2 osteoarthritis

STUDY DESIGN: The lateral C1-C2 (atlantoaxial) joints were evaluated retrospectively in 355 patients referred for radiographs of the paranasal sinuses. OBJECTIVES: To determine the radiologic prevalence of advanced lateral atlantoaxial osteoarthritis. SUMMARY OF BACKGROUND DATA: Previous studies have shown a relation between atlantoaxial osteoarthritis and referred pain in the suboccipital region. However, the radiologic prevalence of this degenerative disorder is unknown. METHODS: Five hundred radiographs of the paranasal sinuses were evaluated retrospectively. Both lateral atlantoaxial joints were clearly visible on occipitofrontal projections in 355 examinations. Each lateral atlantoaxial joint was considered severely degenerated when advanced narrowing or obliteration of the joint space, subchondral sclerosis, and/or osteophytosis were present. RESULTS: Atlantoaxial osteoarthritis was found in 4.8% of the patients. The radiologic prevalence of advanced degenerative changes at the lateral atlantoaxial joint(s) was found to increase with age, ranging from 5.4% in the sixth decade to 18.2% in the ninth decade of life. CONCLUSION: Because advanced degenerative changes at the lateral atlantoaxial joints can cause suboccipital neck pain, these findings should be included in the differential diagnosis in older patients with this symptom.     

Synovial cyst at the C1-C2 junction and spondyloarthropathy

A spinal synovial cyst is a rare extradural benign tumor generally located at the lumbar spine, arising at the facet joint capsule, and usually associated with degenerative changes. We describe a 64-year-old woman with a synovial cyst involving the quadrate ligament of the odontoid process, which caused neurologic signs. Her family history was positive for spondyloarthropathy. The radiologic investigations, preoperative differential diagnosis, and association of spondyloarthropathy with this rare benign foramen magnum tumor are of particular interest.     

Vertebral artery injury in C1-2 transarticular screw fixation: results of a survey of the AANS/CNS section on disorders of the spine and peripheral nerves. American Association of Neurological Surgeons/Congress of Neurological Surgeons

OBJECTIVES: The goal of this study was to investigate the possible role of transesophageal echocardiography in the evaluation of patients with clinical pacemaker syndrome. BACKGROUND: Several reports on transthoracic echocardiographic features of ventricular pacing were described; however, no previous study of transesophageal echocardiography has been undertaken in patients at the severe end of pacemaker syndrome who need reprogramming of dual-chamber pacing for symptom relief. METHODS: Twelve patients with ventricular-inhibited pacemakers (VVI) with clinical symptomatic pacemaker syndrome (group I) and 10 patients with VVI without pacemaker syndrome (group II) were prospectively studied. The two groups were pacemaker dependent and had persistent ventriculoatrial conduction. Transesophageal echocardiographic parameters were assessed in group II and within 6 hours before reprogramming to the DDD mode in group I. Follow-up transesophageal echocardiographic study was performed 28+/-5 days after reprogramming in group I. RESULTS: All patients in group I had subjective improvements of symptoms after DDD reprogramming. The atrial reverse flow velocities of pulmonary veins in group I before reprogramming were significantly higher in group II (39.3+/-11.4 versus 15.7+/-13.5 cm/sec, p < 0.0001). Spontaneous echo contrast in the descending aorta was detected in all patients from group I before reprogramming. The prevalence of significant mitral regurgitation (> or = moderate) was significantly higher in group I before reprogramming than in group II (67% versus 8%, p = 0.01). Significant mitral regurgitation and spontaneous echo contrast in the descending aorta in group I disappeared after reprogramming to the DDD mode. CONCLUSIONS: Transesophageal echocardiography provides physiologic, pacemaker-related hemodynamic changes in paced patients. Significantly higher atrial reverse flow velocities of pulmonary veins, increased frequency of spontaneous echo contrast in the descending aorta, and significant mitral regurgitation are peculiar echocardiographic findings in patients with VVI with clinical pacemaker syndrome.     

The ideal position of sacral transpedicular endplate screws in Jackson's intrasacral fixation. An anatomic study of 50 sacral specimens

STUDY DESIGN: This study directly measures the ideal point of insertion and direction of sacral screws in the Jackson intrasacral fixation. OBJECTIVE: To design a template for safe positioning of transpedicular endplate screws that does not require fluoroscopy. SUMMARY OF BACKGROUND DATA: Screw and rod insertion into the sacrum as described by Jackson requires careful intraoperative fluoroscopic or radiographic control. The technique can *be difficult and demanding, especially in the case of severe pelvic obliquity. No anatomic data based on cadaveric studies are available to aid in the described technique for screw insertion. METHODS: Fifty dry sacrums were used. On each bone, the length of the intrasacral portion and the ideal direction of transpedicular endplate pins introduced at the originally described point of insertion were measured in reference to the plane formed by the two posterior sacral foramen and the posterior arch of S1. The limit angles in each direction, where the pin perforated the cortex outside of the S1 endplate, were noted. Then, the point of insertion of a pin with the ideal angles was progressively modified to determine the limits of the safe insertion area. The 95% confidence interval was reduced to the smallest safe angle. RESULTS: The safe angles were 54.3 degrees to 57.9 degrees for the sagittal plane, 47 degrees to 50 degrees for the coronal plane, and between 46.9 degrees and 49.7 degrees for the horizontal plane. CONCLUSIONS: A "cylinder of safety" for the transpedicular endplate screws was determined. Its coordinates are related to the sacrum and not to the sacral position. This allowed for a template to be designed, the efficiency of which will have to be confirmed by anatomic and clinical studies.     

End-point accuracy of kinesthetically and visually based corrections to a mechanically perturbed aiming movement.

12 right-handed females performed a multi-degrees of freedom manual aiming movement which could be unexpectedly perturbed. Ss performed the task in either a full vision (FV) situation or while only the target to be reached was visible (TO). Neither the absolute constant error (ICEI) nor the variable error (VE) of aiming could differentiate the perturbed and unperturbed trials for the Ss submitted to the FV condition. However, significantly larger ICEI and VE were observed for the perturbed trials in the TO condition. This is taken to indicate that the sensorimotor representation of the movement developed through learning is more precise when learning occurs in the presence of more afferent sources. Further, the larger spatial error found in the TO condition for the perturbed trials suggests that, when a learned movement is forced out of its usual trajectory, the kinesthetic feedback available, and/or the corrective motor commands, are less accurate than those available when the movement follows its usual trajectory. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of translation of the C1-C2 on the spinal canal

The stability of the atlantoaxial articulation depends fundamentally on the integrity of the odontoid process and the ligaments. Ligament stability mostly is maintained by two ligaments: the transverse ligament and the alar, apical ligaments. Failure of the transverse ligament can result in anterior translation of the atlas on the axis. The anteroposterior diameter of the ring of the atlas is approximately 3 cm. The spinal cord and the odontoid process are each approximately 1 cm in diameter, approximately 1/3 the diameter of the ring. According to Steel's rule of thirds, the remaining centimeter of free space allows for some degree of pathologic displacement. The current anatomic study showed that the space available for the spinal cord was limited. The sagittal diameter C1-C2 canal is 18.71 +/- 2.88 mm (excluding 10 mm thickness of the dens and 2.91 +/- 0.69 mm thickness of transverse ligament), with the spinal cord occupying 7.73 +/- 0.87 mm of the available space. Space available for spinal cord at the level of the atlas is 3.44 +/- 1.19 mm plus 1.01 +/- 0.20 mm space anterior to the cord (anterior epidural space) and 5.64 +/- 2.22 mm space posterior to the cord (posterior epidural space), which is approximately in agreement with the normal diameter by Steel's rule of thirds.     

A comparative study of fixation techniques in the open Bankart operation using either a cannulated screw or suture-anchors

Neuroendocrine PC12 cells contain small microvesicles that closely resemble synaptic vesicles in their physical and chemical properties. Two defining characteristics of synaptic vesicles are their homogeneous size and their unique protein composition. Since synaptic vesicles arise by endocytosis from the plasma membrane, nerve terminals and PC12 cells must contain the molecular machinery to sort synaptic vesicles from other membrane proteins and pinch off vesicles of the correct diameter from a precursor compartment. A cell-free reconstitution system was developed that generates vesicles from PC12 membrane precursors in the presence of ATP and brain cytosol and is temperature dependent. At 15 degrees C, surface-labeled synaptic vesicle proteins accumulate in a donor compartment, while labeled synaptic vesicles cannot be detected. The block of synaptic vesicle formation at 15 degrees C enables the use of the monoclonal antibody, KT3, a specific marker for the epitope-tagged synaptic vesicle protein, VAMP-TAg, to label precursors in the synaptic vesicle biogenesis pathway. From membranes labeled in vivo at 15 degrees C, vesicles generated in vitro at 37 degreesC had the sedimentation characteristics of neuroendocrine synaptic vesicles on glycerol velocity gradients, and excluded the transferrin receptor. Therefore, vesiculation and sorting can be studied in this cell-free system.     

Positions of dorsal root ganglia in the cervical spine. An anatomic and clinical study

STUDY DESIGN: The authors investigated the positions of dorsal root ganglia and the relation of the location to symptoms and to the effects of nerve root infiltration in the cervical spine anatomically and clinically. OBJECTIVES: To clarify normal variation of positions of dorsal root ganglia and the relation of the location of dorsal root ganglia to symptoms and to the effects of nerve root infiltration. SUMMARY OF BACKGROUND DATA: The dorsal root ganglia of the spinal nerve has attracted much attention as an important structure in the mechanisms of radicular symptoms in the lumbar spine. Although the position of the dorsal root ganglia in the lumbar spine has been classified recently, there are few reports regarding the dorsal root ganglia in the cervical spine. METHODS: The positions of dorsal root ganglia were divided into two types: proximally situated and distally situated. The positions of dorsal root ganglia in the anatomic and clinical cases were compared. The relation of the positions of dorsal root ganglia to symptoms and to the clinical effects of nerve root infiltration were analyzed. RESULTS: There was no statistically significant difference in positions of dorsal root ganglia in C6 nerve roots between anatomic and clinical cases. In addition, there was no relation between symptoms and the positions of dorsal root ganglia in clinical cases. However, there was a significant difference in positions of dorsal root ganglia in C7 nerve roots between anatomic and clinical cases. Nerve root infiltration was significantly more effective in the distally situated type of dorsal root ganglia. CONCLUSIONS: This study defined the normal variation of the positions of dorsal root ganglia. The results strongly suggest that some attention should be paid to the position of dorsal root ganglia in the diagnosis and treatment of cervical radiculopathy.     

Odontoid process and C1-C2 corrective osteotomy through a posterior approach: technical case report

OBJECTIVE AND IMPORTANCE: To demonstrate a new posterior approach to the anterior elements of the atlas and the axis including the odontoid process. CLINICAL PRESENTATION: A 36-year-old woman presented with ankylosing spondylitis and severe flexion deformity of the cervical spine. She had sustained a trauma 5 years previously, causing the inability to look forward or to open the jaw adequately. An examination demonstrated fixed flexion and rotation of the cervical spine, with no neurological deficit. Radiologically, there was fusion of C1, C2, and the clivus. TECHNIQUE: The upper cervical vertebrae were exposed via a midline posterior incision, the posterior arch of C1 was excised, and the vertebral arteries were mobilized. A wedge osteotomy was performed through the lateral masses of C1 and subsequently through the odontoid. The head was repositioned, and C1-C2 lateral mass screws and a Ransford loop were inserted. CONCLUSION: It is possible to gain sufficient surgical access to the odontoid process via a posterior approach. The technique described is of benefit when the alternative anterior approaches to the upper cervical spine are technically difficult or impossible.     

The design and performance of an experimental external fixation device with load transducers

It is becoming increasingly common that fracture healing is modelled in the laboratory with an osteotomy in the diaphysis of the ovine tibia. External fixation is often used to hold the bones in these models, presenting the problem that the loads on such devices are poorly understood. To help investigate this, a unilateral device has been developed which is capable of measuring the two components of load considered to be the most important, that of axial compression and bending in the plane of the fixator. The device was found to be a rigid system and easy to apply, with the in-vivo measurements being straightforward. The estimated limits of error of the compression transducer are +37.9 N and -21.4 N and those of the bending transducer are +3.6 Nm and -4.2 Nm. Preliminary measurements showed the maximum load during normal walking to 345 N compression and 28 Nm in-plane bending.     

An anatomic study of the superficial radial nerve and its clinical implications

BACKGROUND: Acetylcholine produces coronary artery (CA) constriction in diabetic patients, suggesting an impairment of endothelium-dependent dilation. In diabetes, multiple metabolic abnormalities may inactivate nitric oxide through oxygen free radical production. METHODS AND RESULTS: To examine the mechanism of this abnormal response, two physiological tests (ie, a cold pressor test [CPT] and coronary flow increase induced by an injection of 10 mg papaverine [PAP] in the distal left anterior descending CA) were performed before and after either intravenous L-arginine (625 mg/min x 10 minutes) or intravenous deferoxamine (50 mg/min x 10 minutes) in 22 normotensive nonsmoking diabetic patients with angiographically normal CAs and normal cholesterol. Coronary surface areas were measured with quantitative angiography. Before the administration of L-arginine or deferoxamine, CPT induced CA constriction in both groups (-14 +/- 10% and -15 +/- 11%, respectively; each P<.001), and PAP injection in distal LAD did not modify significantly proximal LAD dimensions. In the 10 diabetic patients receiving L-arginine, responses to CPT and PAP were not modified. Conversely, in the 12 patients receiving deferoxamine, CA dilated in response to the two tests (+10 +/- 9% after CPT and +22 +/- 7% after PAP, each P<.001). Intracoronary isosorbide dinitrate, an endothelium-independent dilator, produced similar dilation in the two groups (+47 +/- 19% and +41 +/- 15%, respectively; each P<.001). CONCLUSIONS: This study shows that (1) responses of angiographically normal CAs to CPT and to flow increase are impaired in diabetic patients; (2) abnormal responses are not improved by L-arginine, suggesting that a deficit in substrate for nitric oxide synthesis is not involved; and (3) deferoxamine restores a vasodilator response to the two tests, suggesting that inactivation of NO by oxygen species might be partly responsible for the impairment of CA dilation in diabetic patients.     

Human rectal absorption of short- and medium-chain C2-C10 fatty acids

PURPOSE: To study the effects of running suture adjustment for reduction of astigmatism after penetrating keratoplasty. Suture adjustments performed during surgery and during the early postoperative and late postoperative periods were retrospectively compared. METHODS: We studied 53 patients who received running suture adjustment after penetrating keratoplasty, either intraoperatively (ISA group, n = 18), early (< 2 weeks) postoperatively (EPSA group, n = 19), or late (> 1 month) postoperatively (LPSA group, n = 16). Refractive and topographic astigmatism and corneal topography were examined at 1, 3, and 6 months after surgery. RESULTS: Overall mean refractive astigmatism and topographic astigmatism at 6 months were 2.55 +/- 1.61 D and 3.12 +/- 1.89 D, respectively (mean +/- SD). The mean refractive astigmatism and topographic astigmatism were 1.88 +/- 1.04 D and 2.35 +/- 1.35 D in the ISA group, 2.32 +/- 1.17 D and 2.70 +/- 1.21 D in the EPSA group, and 3.01 +/- 1.62 D and 4.62 +/- 2.51 D in the LPSA group, respectively (mean +/- SD). The LPSA group demonstrated significantly increased topographic astigmatism compared to the ISA group (p = 0.0048) and the EPSA group (p = 0.015). Although 31.6 and 25.0% of the EPSA and LPSA groups, respectively, did not require postoperative suture adjustments, more eyes (10/18 eyes, 55.6%) in the ISA group did not require the procedure. CONCLUSIONS: Early postoperative suture adjustment was more effective than late postoperative adjustment. Intraoperative suture adjustment may further reduce final astigmatism and the necessity for postoperative suture manipulation.     

Translaminar screw fixation of the lumbar and lumbosacral spine. A 5-year follow-up

STUDY DESIGN: In a retrospective study, the long-term results of translaminar facet screw fixation of the lumbar and lumbosacral spine are reviewed. OBJECTIVES: To evaluate the clinical results, fusion rates and complications of this posterior fusion technique in various conditions of the lumbar spine. SUMMARY OF BACKGROUND DATA: Posterior fusion of the lumbar and lumbosacral spine is one of the possible methods to relieve pain and eliminate instability in degenerative conditions. Data in the literature support the use of internal fixation to optimize the rate of fusion. METHODS: Posterior lumbar and lumbosacral fixation with translaminar screws and fusion in 173 patients with degenerative changes with or without compressive syndromes including failed back syndromes, monosegmental hypermobilities, and posttraumatic conditions were investigated. Fixation and fusion with translaminar screws was performed in 57% monosegmentally, in 40% across two segments and in 2% over three segments. Decompressive surgery was performed in addition in 52% and nucleotomy in 30% of the cases. Clinical and radiologic assessment with flexion/extension x-rays was performed in 145 (83%) patients by two independent orthopedic surgeons. After an average follow-up of 68 months (range, 52-83). RESULTS: Ninety-four percent of the patients showed solid bony fusion in the radiologic follow-up. Loosening of the screws was noted in 3%, and two screws were broken without apparent motion on the functional x-rays. Pain scores decreased from 7.6 before surgery to 2.9 after surgery on a 10-point pain scale. The results were further analyzed according to Stauffer and Coventry with 99 good results, 70 satisfactory results, and 4 bad results. CONCLUSIONS: Translaminar screw fixation offers an immediate postoperative stability of the lumbar and lumbosacral spine and enhances fusion. In the present series no neurologic complications were noted. It represents a useful and inexpensive technique for short segment fusion of the nontraumatic lumbar and lumbosacral spine.