Radiologic and anatomic evaluation of the anterior sacral foramens and nerve grooves.

STUDY DESIGN: The present study evaluated the anterior sacral foramen using plain radiographs and projected the positions of S1-S3 anterior sacral foramen and corresponding nerve root groove on the posterior aspect of the sacrum. OBJECTIVES: To evaluate the plain radiographs of anteroposterior, inlet, and outlet views regarding the sacral foramen, and to determine quantitatively the location of the anterior sacral foramens on the posterior aspect of the sacrum. SUMMARY OF BACKGROUND DATA: Injury to the sacral nerve roots associated with posterior sacral screw placement remains a potential hazard. Few studies regarding the evaluation of the anterior sacral foramen and its projection on the posterior sacral surface are available. METHODS: Six bony pelves were harvested from preserved cadavers. The superior aspects of the sacral alae, the openings of the anterior and posterior foramens of S1-S2, were marked by outlining them with K-wires. Anteroposterior, inlet, and outlet plain radiographs were taken. The bony sacra were further disarticulated from the above six pelvic specimens. K-wires were drilled through the sacra to project the dimensions of the anterior foramens and nerve grooves of S1-S3 onto the posterior sacral surface. The dimensions between the perimeter of the projection and the corresponding posterior foramen were measured. RESULTS: The plain radiographs show that the shape and relative position between the anterior and posterior foramens vary with different projections. It was believed that outlet projection is the best view of plain and radiographs in the evaluation of the sacral foramens and corresponding pedicles. The approximate boundaries of the anterior sacral foramens' projections were 6 mm superior, 10 mm lateral, 3 mm inferior, and 3 mm medial to the corresponding margins of the posterior foramens. CONCLUSIONS: The outlet projection is the most useful view in plain radiographs for the evaluation of sacral foramens and pedicles. Quantitative data of the anterior sacral foramen's anatomic position on the dorsal aspect of the sacrum may be helpful in the sacral pedicle screw placement.

Sacroiliac joint injection: a cadaveric study.

Eleven bony pelves were studied in an attempt to find an ideal approach for needle placement into the sacroiliac joint and to describe the unique anatomy of the sacroiliac joint relative to sacroiliac joint injection. A posterior approach starting 2 cm to 3 cm inferior to the posterior superior iliac spine, angled 20 degrees to 30 degrees laterally, relative to the sagittal plane, and 10 degrees to 20 degrees inferiorly, relative to the transverse plane, was found to be the best approach to the intra-articular portion of the sacroiliac joint.

Computed tomographic evaluation of length of screw paths for anterior cervical plating.

Thirty patients' computed tomographic (CT) scans of the cervical spine were used to measure screw path lengths with respect to anterior plating. The results indicated that all screw paths were longer in men than in women, and the majority of lengths differed significantly by sex (P < or = .05). The mean length of the sagittal, parasagittal, and convergent screw paths for both men and women was 16 mm. The mean length of the safe divergent screw path was 15 mm. Therefore, the safe screw length may be 16 mm for convergent placement and 15 mm for divergent placement. Convergent screw placement is recommended. Preoperative CT or magnetic resonance imaging evaluation and measurement of the intended screw trajectories are recommended.

The relationship of lumbosacral plexus to the sacrum and the sacroiliac joint.

The lumbosacral plexus was dissected bilaterally in 20 adult cadavers to define the anatomic relationship of the lumbosacral plexus to the sacrum and the sacroiliac joint. All results are mean values +/- standard deviation. The length of the nerve roots of the lumbosacral plexus gradually decreased from L-4 to S-3 (from 93.8 +/- 6.9 mm in males and 108.7 +/- 7.7 mm in females at L-4 to 43.7 +/- 4.3 mm in males and 49.0 +/- 7.6 mm in females at S-3). The angle projected by the nerve roots of the lumbosacral plexus with respect to the sagittal plane gradually increased from L-4 to S-3 (from 14.3 degrees +/- 3.4 degrees in males and 16.7 degrees +/- 4.8 degrees in females at L-4 to 51.8 degrees +/- 9.0 degrees in males and 57.8 degrees +/- 9.1 degrees in females at S-3). The width of the nerve roots of the lumbosacral plexus was greatest at S-1 (9.8 +/- 1.8 mm in males, 8.6 +/- 1.5 mm in females). The L-5 nerve root was the thickest in males (4.4 +/- 0.5 mm), and the S-1 nerve root was thickest in females (4.3 +/- 0.4 mm). The lumbosacral trunk was 30.0 +/- 9.0 mm in length in males and 32.0 +/- 6.0 mm in females; 11.4 +/- 1.8 mm wide in males and 11.2 +/- 1.5 mm in females; and 4.4 +/- 0.5 mm thick in males and 4.0 +/- 0.6 mm in females. The fifth lumbar nerve root and lumbosacral trunk coursed across the sacroiliac at a level 2.0 +/- 0.2 cm below the pelvic brim and were relatively fixed to the sacral ala with fibrous connective tissue.

Anterior approach to the cervical spine: surgical anatomy.

While performing the anterior approach to the cervical vertebral bodies, injury to important anatomic structures in the vicinity of the dissection represents a serious risk. The midportion of the recurrent laryngeal nerve and the external branch of the superior laryngeal nerve are encountered in the anterior approach to the lower cervical spine. The recurrent laryngeal nerve is vulnerable to injury on the right side, especially if ligation of inferior thyroid vessels is performed without paying sufficient attention to the course and position of the nerve, and the external branch of the superior laryngeal nerve is vulnerable to injury during ligature and division of the superior thyroid artery. Avoiding injury to the recurrent laryngeal nerve (especially on the right side) and superior laryngeal nerve is a major consideration in the anterior approach to the lower cervical spine. The sympathetic trunk is situated in close proximity to the medial border of the longus colli at the C6 level (the longus colli diverge laterally, whereas the sympathetic trunk converges medially). The damage leads to the development of Horner's syndrome with its associated ptosis, meiosis, and anhydrosis. Awareness of the regional anatomy of the sympathetic trunk may help in identifying and preserving this important structure while performing anterior cervical surgery or during exposure of the transverse foramen or uncovertebral joint at the lower cervical levels. Finally, the spinal accessory nerve (embedded in fibroadipose tissue in the posterior triangle of the neck) is prone to injury. Its damage will result in an obvious shoulder droop, loss of shoulder elevation, and pain. Prevention of inadvertant injury to the accessory nerve is critical in the neck dissection.

Cancer pain management.

The management of cancer-related pain is often quite different from the management of chronic benign pain (see companion article by Thomas Elliott, M.D., page 28). As cancer therapy becomes increasingly complex, the management of pain and other symptoms requires more innovative approaches as well. This article begins with a basic overview of how to evaluate the patient with cancer pain, offers simple opiate use guidelines, and discusses newer agents for neuropathic and somatic pain. Finally, it discusses how future pain management strategies may hinge on research and cites examples of studies being performed in Minnesota.

Postoperative pain management following bilateral lung volume reduction surgery for severe emphysema.

This study was conducted to audit the clinical management of a continuous local anaesthetic infusion delivered by a fluoroscopically placed thoracic epidural catheter in conjunction with supplemental intravenous opioid patient controlled analgesia for postoperative pain control following bilateral lung volume reduction surgery for severe emphysema. This retrospective case series involved a random sample of 43 patients from a possible 65 patients. The mean dose of epidural bupivacaine 0.15% was 6.7 ml/h (SD 1.5), while the mean daily dose of morphine or hydromorphone was 22.5 mg/day (SD 17.9) and 4.3 mg/day (SD 3.1), respectively. Inadequate analgesia was reported by 19 (44%) patients during the first two postoperative days, but was successfully treated by individual titration of these medications. The incidence of atrial fibrillation (n = 6), premature epidural catheter dislodgement (n=6) or respiratory failure (n=3) appeared to be greater among patients who had inadequate analgesia at some stage. One patient developed excessive sedation; otherwise, there were no major complications. The use of an epidural bupivacaine infusion in conjunction with intravenous opioid patient controlled analgesia proved to be a safe and effective pain medication regimen when accompanied by individual titration of these agents in response to acute exacerbations of postoperative pain.

Epidural clonidine after cesarean section. Appropriate dose and effect of prior local anesthetic.

Epidurally administered clonidine represents a new approach to postcesarean section pain therapy, yet the appropriate bolus dose and infusion to provide effective pain relief have not been defined. In addition, whether 2-chloroprocaine, a commonly used local anesthetic for intraoperative anesthesia, interferes with clonidine's analgesia, as it does with that of opioids, has not been examined. In this study, using a randomized, blinded design, 63 women received either bupivacaine or 2-chloroprocaine for epidural anesthesia for cesarean section and then received, upon request for analgesia in the recovery room, epidural clonidine 400 micrograms or 800 micrograms bolus, each followed by a 24-h infusion of 40 micrograms/h, or an equivalent volume bolus and infusion of saline. In the bupivacaine group, both clonidine doses produced equivalent analgesia, as determined by pain scores and time to first supplemental intravenous morphine request, and sustained analgesia was produced by clonidine infusion, as measured by need for supplemental morphine. In contrast, 2-chloroprocaine diminished analgesia from 800 micrograms by 21% and abolished analgesia from 400 micrograms clonidine. After 2-chloroprocaine, sustained analgesia from continuous clonidine infusion was present only in the group who had received 800 micrograms clonidine. Clonidine did not alter resolution of residual local anesthetic sensory blockade, as measured by 2- or 4-segment regression following either local anesthetic, but did prolong duration of motor blockade in women receiving bupivacaine. Clonidine produced small decreases in heart rate and blood pressure. One patient received iv fluids for hypotension; one had asymptomatic bradycardia resolving without therapy; and one had mild hypoxemia with snoring during clonidine-induced sedation, responding to supplemental oxygen.(ABSTRACT TRUNCATED AT 250 WORDS)

Location of the extraforaminal lumbar nerve roots. An anatomic study.

Twelve cadavers were used to determine the anatomic location of the extraforaminal lumbar nerve root in the intertransverse space. After exposure of the transverse processes of the lumbar spine and the extraforaminal lumbar nerve roots, direct measurements, including the nerve root angle, nerve root diameter, distance to the superior facet, and the intertransverse space, were made bilaterally. The results showed that the extraforaminal nerve root angle and diameter and the distance between the superior facet and lateral limit of the nerve root consistently increased from cephalad to caudal. The largest dimension for height and width of the intertransverse space was found at the level of L3-4, and the smallest was found at the level of L5-S1. This information may be helpful in minimizing the incidence of injury to the lumbar nerve root during a posterolateral approach to lumbar disc.

Lumbosacral plexus: a histological study.

Two hundred and forty histological paraffin sections were obtained from the midportion of the spinal nerve roots of 20 lumbosacral plexus (from L4 to S3) bilaterally. All microscopic images were digitized using the NIH image software with a Nikon microscope and Sony videocamera. The total, fascicular as well as epineurial cross-sectional areas of the nerve roots in the lumbosacral plexus were determined. The total cross-sectional area of the lumbosacral trunk (LST) was the largest (28.56 +/- 12.28 mm2) followed by the S1 (21.97 +/- 11.22 mm2) and L5 (21.00 +/- 8.79 mm2) nerve roots. The total cross-sectional areas of the L4 (6.93 +/- 3.32 mm2), S2 (13.93 +/- 5.86 mm2) and S3 (6.03 +/- 3.74 mm2) were significantly lower. Statistical differences were found among all absolute values at different levels (p < 0.0001) with the exception of the levels between L4 and S3, L5 and S1, and LST and S1 (p > 0.05). The total areas occupied by the fascicles in L5 (7.78 +/- 3.26 mm2), LST (9.97 +/- 4.01 mm2) and S1 (8.55 +/- 3.27 mm2) nerve roots were greater than those in L4 (2.96 +/- 1.50 mm2), S2 (5.56 +/- 2.34 mm2) and S3 (2.28 +/- 1.14 mm2). However, the percentages of the total cross-sectional areas occupied by the fascicles in the L5 nerve root (38%) and LST (36.4%) were smaller compared to other nerve roots (44.9% at L4, 40.5% at S1, 40.8% at S2 and 41.6% at S3). The cross-sectional areas and percentages of the epineurium were greater in L5 (13.22 +/- 6.48 mm2, 62.0%), LST (18.58 +/- 9.31 mm2, 63.6%) and S1 (13.42 +/- 8.88 mm2, 59.5%) roots. The L5 (12.1 +/- 5.0), LST (27.5 +/- 11.4) and S1 (15.0 +/- 7.3) roots contained more fascicles than L4 (6.3 +/- 3.3), S2 (9.5 +/- 4.1) and S3 (7.1 +/- 2.7). Statistical differences were found among all absolute values at different levels (p < 0.0001) with the exception of the levels between L4 and S3, L5 and S1 and LST and S1 (p > 0.05). No statistical differences were found for percentages among different levels (p > 0.05) with the exception of the levels between L4 and L5, L4 and LST, LST and S1, LST and S2, and LST and S3 (p < or = 0.05). The histological structure of nerve roots of the lumbosacral plexus is identical to that of the peripheral nerve. The midportions of L5 and S1 roots and the LST have a relatively higher epineurial content. These nerve roots also have a greater number of the fasicles, but the total cross-sectional area occupied by the fascicles is less than in L4, S2 and S3 nerve roots.

Anatomic considerations of superior cluneal nerve at posterior iliac crest region.

No previous studies describe the anatomic relationship of the superior cluneal nerve to the posterior iliac crest and thoracolumbar fascia. In the current study, 15 cadavers were dissected to determine the relationship of the superior cluneal nerve to the posterior iliac crest and thoracolumbar fascia. The distances from the medial branch of the superior cluneal nerve to the posterior superior iliac crest and the midline were 64.7 +/- 5.3 mm and 81.0 +/- 9.2 mm, respectively. The distances between the level of the iliac crest and perforating points of the superior cluneal nerve on the thoracolumbar fascia were 5.8 +/- 1.8 mm inferiorly for the medial branch, 2.2 +/- 1.8 mm superiorly for the intermediate branch, and 12.0 +/- 4.4 mm superiorly for the lateral branch, respectively. The proximal dissection above the perforating point of the nerve showed that the medial branch of the superior cluneal nerve is confined within a tunnel consisting of the thoracolumbar fascia and the superior rim of the iliac crest as it passes over the iliac crest. The intermediate and lateral branches of the superior cluneal nerve either pierce the thoracolumbar fascia or pass through an orifice or fissure in the thoracolumbar fascia. In two specimens, the medial branches of the superior cluneal nerve were constricted within the osteofibrous tunnel. The nerve was entrapped between the rigid fibers of the thoracolumbar fascia and the iliac crest.

Cervical intervertebral disc space narrowing and size of intervertebral foramina.

Computer-assisted simulation of C4-C5, C5-C6, and C6-C7 intervertebral disc space narrowing was performed on 16 anatomic specimen cervical spines to determine the relationship of the cross sectional foraminal areas with the degree of narrowing of the cervical intervertebral disc space. Compared with normal foraminal area values, reduction of 20% to 30% of the foraminal area was found after 1 mm narrowing of the intervertebral disc spaces; reduction of 30% to 40% of the foraminal area was found after 2 mm narrowing of the intervertebral disc space; and reduction of 35% to 45% of the foraminal area was found after 3 mm narrowing of the intervertebral disc space. Statistically significant differences were found among the remaining cross sectional foraminal areas after different degrees of intervertebral disc space narrowing. Compression of the nerve root within the intervertebral foramina after the collapse of the intervertebral disc space cannot be ignored, and an appropriate surgical procedure to maintain the normal height of the disc space is essential. The size of the intervertebral foramen is related directly to the height of the intervertebral disc space. A 3-mm vertical reduction of the intervertebral disc space is associated more frequently with severe narrowing of the neuroforamen.