Intradiscal electrothermal therapy: a treatment option in patients with internal disc disruption

STUDY DESIGN

A literature review was conducted.

OBJECTIVES

To review the anatomy, pathophysiology, diagnosis, procedure, and clinical results of intradiscal electrothermal therapy (IDET).

SUMMARY OF BACKGROUND DATA

Low back pain is a major physical and socioeconomic entity. A significant percentage of low back pain is attributable to internal disc disruption. The management of internal disc disruption has traditionally been limited to either conservative treatment or spinal fusion. IDET has been performed as an alternative to these therapies.

METHODS

The available literature was reviewed.

RESULTS

Scientific data regarding the pathophysiology, biologic effects, and clinical results are relatively scarce. Early biomechanical and histologic investigations into the effects of IDET are conflicting. However, in early prospective human trials, IDET seems to provide some benefit with little risk.

CONCLUSIONS

IDET is potentially beneficial treatment for internal disc disruption in carefully selected patients as an alternative to spinal fusion. More basic science and clinical research with long-term follow-up evaluation is necessary.

Effects of slip severity and loading directions on the stability of isthmic spondylolisthesis: a finite element model study

STUDY DESIGN

Using a validated finite element model, the biomechanical effects of pars defect in a lumbar segment with and without different degrees of slip (up to 50% slip) were studied.

OBJECTIVES

To study the effects of slip severity and loading parameters on the stability of the lytic and adjacent motion segments. Better knowledge of the biomechanics of spondylolisthesis may help formulate treatment strategies such as bracing or spinal implants.

SUMMARY OF THE BACKGROUND DATA

Clinically, spondylolisthesis exists in varying grades of anterior slip, and the biomechanical stability of the motion segments at the lytic defect and adjacent level probably varies as well. In vitro studies of L4-L5 and L5-S1 isthmic spondylolisthesis slips have concluded that an L4-L5 pars defect is more unstable than an L5-S1 pars defect. Comparing the stability of lytic motion segments with different grades of spondylolisthesis is difficult to do experimentally and therefore has not been done. Further assessing the stresses in the bone and intervertebral discs at or adjacent to a lytic defect is also difficult to study experimentally, so no data are available.

METHODS

A finite element model of L4-S1 was validated with and without a pars defect at L5. The model was then revised to represent different degrees of slip at L5, and six different moment loadings were applied.

RESULTS

The current study showed larger decrease in stiffness with increasing percent slip. The decrease in disc stiffness and increase in disc stresses with increasing percent slip were larger at the level of spondylolisthesis as compared to the changes in the adjacent segment. Lateral bending moment and torsion load showed the largest decrease in stiffness due to slip. At 50% slip, the maximum increase in motion (as compared to motion in an intact segment) was seen under lateral bending moment load (about 55% at L4/L5 and 250% at L5/S1). Lateral bending also produced the largest increase in stresses due to 50% slip in the anulus and endplates (300% increase in anular stress and 190% increase in endplate stress) at L5/S1.

CONCLUSIONS

The stiffness of a spondylolisthetic motion segment decreases as the slip increases. Lateral bending and torsion are moment directions causing the greatest resulting motions.

Percutaneous computed tomographic stabilization of the pathologic sacroiliac joint

Metastases to the sacroiliac joint region can be a source of significant pain in many patients who are terminally ill. Six patients with metastatic lesions in the sacroiliac region who presented with significant posterior pelvic pain were treated with computed tomography-guided insertion of iliosacral screws. All patients reported excellent pain control in the early postoperative period. Computed tomography-guided insertion of iliosacral screws in an area of relatively preserved bone stock provides good purchase of the screws. It is a safe percutaneous procedure and it helps alleviate pain in patients with sacroiliac metastases.

Location of the first and second sacral nerve roots in relation to pedicle screw placement

Dissection and measurements of the first 2 sacral nerve roots with regard to the commonly used entrance points for S1 and S2 pedicle screw placement were performed to determine the location of the first 2 sacral nerve roots in relation to the pedicle screw entrance points in the upper 2 sacral vertebrae. The sacral nerve roots, dural sac, and pedicles were exposed after laminectomy. The mean distance from the reference point to the adjacent nerve roots superiorly and inferiorly at the S2 pedicle level was smaller than those at the S1 pedicle level. The medial angle of the sacral nerve roots progressively decreased from L5 to S3. The nerve root passing through the next foramen formed an immediate medial relation to the sacral pedicle rather than the dural sac. Pedicle screw placement in the first 2 sacral vertebral pedicles has been recommended for lumbosacral fusion and internal fixation of sacral fractures. No anatomic study is available regarding the location of the sacral nerve roots relative to the entrance points of sacral pedicle screw placement. Violation of the sacral canal and foramina by a sacral pedicle screw may injure the sacral nerve roots, especially at the level of the S2 pedicle.

Complications in the management of complex Monteggia-equivalent fractures in adults

We report five adult patients with complex Monteggia-equivalent fractures who were surgically treated, all of whom had significant complications. All ulnar fractures and three radial fractures developed nonunion. Three patients required more than two procedures to achieve bony union, and one required a total elbow arthroplasty.

Anterior tibial artery and its actual projection on the lateral aspect of the tibia: a cadaveric study

The anterior tibial artery (ATA) is at risk of injury during high tibial osteotomy, Ilizarov wire placement, pin placement in external fixation, or proximal locking screw insertion, as the artery is not visualized intraoperatively. The ATA is anchored to the oval foramen of the interosseous membrane on the proximal tibia by the deep fascia and recurrent genicular vascular branches. Segment 1 (from the bifurcation of the popliteal artery to the level of the interosseous foramen) and the proximal part of segment 2 (from the interosseous foramen to the level where the artery crosses the anterior border of the tibia) may be damaged when pin, wire or screw placement is directed posterolaterally at that level. Distally, a straight mediolateral pin or Ilizarov wires may lacerate the artery. Segment 2 of the ATA descends against the interosseous membrane in its proximal part, which is projected on the posterior third of the tibia relative to the sagittal plane; in its middle part, it runs close to the lateral cortex of the tibia, it is projected on the middle third of the tibia; in its distal part it runs gradually towards the anterior third of the tibia and contacts with the anterior third of the tibial cortical surface. This information may help reduce risk of injury to the ATA during high tibial osteotomy, external fixation and pin placement or insertion of locking screws.

Cartilage and synovium of the human atlanto-odontoid joint. An anatomic and histological study

The surface area, thickness and composition of articular cartilage of the atlanto-odontoid joints were investigated in twenty human cadaveric cervical spine specimens. The specimens were also examined grossly and by light microscopy to determine the location of the synovium. The anterior arch of the atlas and ventral and dorsal articular surfaces of the dens were covered with hyaline cartilage. The mean values of the articular surface areas on the ventral surface of the dens and anterior arch of the atlas were 55.10 and 58.24 mm2, respectively. The mean thickness of the articular cartilage of the anterior arch of the atlas, ventral and dorsal surfaces of the dens was 0.80, 0.81 and 0.82 mm, respectively. Synovial membranes were associated with the joint capsules and surrounding tissues of both anterior and posterior atlanto-odontoid joint spaces, where the synovial membranes were attached to the margins of the articular surfaces of the dens and anterior arch of the atlas anteriorly and the region of the cruciate ligament immediately peripheral to the cartilage region apposed to the dens and dens cartilage itself, posteriorly.

Nonunion of pelvic fractures

Nonunion of the pelvic bones is uncommon. It may be under-diagnosed because of the difficulty in visualization of the fracture and interpretation with conventional radiography. The authors report four cases of nonunion involving the pelvic bones. Nonunion of the posterior ilium was occult in two patients and was not apparent on routine radiographs. The two patients with nonunion of the anterior iliac crest had major displacement caused by muscle pull. Pain on weight-bearing and awkward gait were common symptoms. All patients required surgical management for symptomatic relief.

Anatomic considerations of the principal nutrient foramen and artery on internal surface of the ilium

Direct measurements of the nutrient foramen of thirty dried ilia using digital calipers and observations of the nutrient a. from ten cadaveric specimens were made in the present study. The nutrient foramen was situated 12.5 +/- 2.7 mm lateral to the anterosuperior sacroiliac joint line but perpendicular to this line and 23.5 +/- 5.8 mm above the pelvic brim parallel to the sacroiliac joint line. The nutrient a. originated from the iliolumbar a. as it coursed across the anterosuperior aspect of the sacroiliac joint. The present anatomic study indicates that the nutrient a. on the internal surface of the ilium is prone to injury as a result of traumatic disruption of the sacroiliac joint, sacral alar fractures and during the anterior approach to the sacroiliac joint.

Anatomic basis of lag screw placement in the anterior column of the acetabulum

The projection point of the axis of the anterior column of the acetabulum on the outer table of the iliac wing was determined in 15 adult bony hemipelves. The optimal entry point for lag screw fixation in the anterior column was located 16 +/- 3.9 mm superior to the midpoint of the line connecting the apex of the sciatic notch with the notch between anterior superior iliac spine and anterior inferior iliac spine, and 46 +/- 5.9 mm superior to the acetabular rim. The mean inclination of the projected axis was 90.6 degrees +/- 5.0 degrees in the sagittal plane and 29.0 degrees +/- 4.4 degrees in the transverse plane. These data may facilitate insertion of a lag screw into the anterior acetabular column and minimize the risk of articular violation or cortical penetration because there is a narrow margin of safety. The lag screw placement also may be aided by palpating the anterior column with a finger and by intraoperative fluoroscopy for visualization of the hip joint and the anterior column in the obturator or pelvic outlet views.

Anatomic considerations of the lumbar isthmus

STUDY DESIGN

A morphometric study of lumbar isthmus from L1 to L5 on 30 dried lumbar spines was conducted.

OBJECTIVE

To provide anatomic data about the lumbar isthmus and to quantitatively evaluate structural features of the lumbar isthmus and its relationship to adjacent anatomic structures.

SUMMARY OF BACKGROUND DATA

There are very few anatomic studies about the lumbar isthmus, and no study describes the relationship of the lumbar isthmus to its adjacent structures.

METHODS

Direct measurements using digital calipers and a goniometer were taken from 30 dried lumbar spines. Anatomic evaluation focused on the lumbar isthmus and its related structures, the isthmus pedicle, and superior and inferior facets. Seven linear and four angular parameters of the lumbar isthmus were determined.

RESULTS

The length of the superior edge of the isthmus gradually increased from L2 to L5 (from 8.22 +/- 1.43 mm at L2 to 10.44 +/- 1.90 mm at L5), and that of its inferior edge progressively decreased from L2 to L5 (from 8.67 +/- 1.76 mm at L2 to 6.34 +/- 1.74 mm at L5). The superoinferior diameter of the isthmus decreased from L3 to L5 (from 13.87 +/- 1.77 mm at L3 to 13.26 +/- 2.49 mm at L5). The superior edge of the isthmus was the thinnest at L4 (1.62 +/- 0.58 mm), and its thickness inferiorly increased from L1 to L5 (from 6.71 +/- 1.47 mm at L1 to 7.76 +/- 1.08 mm at L5). The medial and caudal inclination of the isthmus with respect to the pedicle gradually increased from L1 to L5 (from 112.3 degrees +/- 13.8 degrees at L1 to 119.2 degrees +/- 11.2 degrees at L5 medial inclination and from 132.5 degrees +/- 8.8 degrees at L2 to 139.0 degrees +/- 12.1 degrees at L5 caudal inclination, respectively). The dimensions of the lumbar isthmus were positively correlated to dimensions of the pedicle and orientations of the facets.

CONCLUSIONS

This study provides detailed anatomic data of the lumbar isthmus. Anatomic parameters of the lumbar isthmus are related to the vertebral levels and have a significant correlation with the angles of the facets and the dimensions of the pedicles. The vulnerability of the pars interarticularis of the fifth lumbar vertebra has been anatomically confirmed.

Screw placement in the lumbar vertebral isthmus

Anatomic parameters of the isthmus from L1 to L5 were measured in 30 dried lumbar spines. All measured parameters were fairly constant from L1 to L5. The mean values of the core length, thickness of the superior and inferior borders of the isthmus, superoinferior diameter and posterior and medial inclinations of the lumbar isthmus at L5 were 39.9 +/- 2.3 mm, 2.0 +/- 0.9 mm, 8.9 +/- 1.0 mm, 13.2 +/- 2.5 mm, 35.9 degrees +/- 5.7 degrees and 31.8 degrees +/- 6.3 degrees, respectively. This study shows that a 40 mm long, 4 to 5 mm diameter screw should be inserted in the lumbar vertebral isthmus at an angle of 30 degrees laterally and anteriorly.

Management of infected defect nonunion of the metacarpals

A 30-year-old man sustained a displaced closed fracture of the fourth metacarpal bone, which was treated by open reduction and internal fixation with Kirschner wires. Severe postoperative infection led to a segmental defect with shortening of the fourth metacarpal bone and infected defect nonunion of the fifth metacarpal bone. After serial debridements and intravenous antibiotics, the infection was controlled. An AO external minifixator was applied to restore the length of the fourth metacarpal bone and to stabilize the fourth and fifth metacarpals, and iliac bone grafting was performed, leading to complete healing and restoration of normal hand function.

Morphologic considerations of the first sacral pedicle for iliosacral screw placement

STUDY DESIGN

Morphometric, radiographic, and computed tomographic evaluation of the pedicle of the first sacral vertebra was performed, and the pedicle's spatial relation with the posterior surface of the ilium was defined.

OBJECTIVES

To facilitate accurate localization of the entry site of the iliosacral pedicular screw on the posterior surface of the ilium, to provide optimal length and direction of iliosacral screw placement, and to investigate the feasibility of inserting two screws through the first sacral vertebral pedicle for unstable posterior pelvic fixation.

METHODS

Anterior and posterior pedicular height, pedicular depth, alar depth, and posterior alar height of S1 vertebrae were measured in 11 body pelves bilaterally. Sacral pedicular height was also measured on the outlet view radiograph as visualized during intraoperative fluoroscopy, and compared with actual anatomic pedicular height. The distance from the posterior limit of the ilium to the S1 ala, pedicle, and pedicle axis, and the distance between the outer table of the ilium and anterior cortex of the sacrum were measured on axial computed tomography scans. Finally, parasagittal sections of the sacral were made to assess the safety zone for placement of two pedicular screws into the vertebral body.

RESULTS

The mean anterior and posterior pedicular heights were 30.2 and 26.1 mm, respectively. The depths of the pedicle and ala were 27.8 and 45.8 mm, respectively. The mean posterior alar height was 28.7 mm. The mean first sacral pedicular height measured on the outlet-view radiographs was 20 mm, which was significantly less (P < 0.0001) than the actual gross anatomic pedicular height. The mean distance from the posterior limit of the ilium to the pedicle axis projection point on axial computed tomography scans was 32.5 mm, and the mean distance from this point to the greater sciatic notch was 38.6 mm. The mean distance between the outer table of the ilium and the anterior cortex of the sacrum was 105.2 mm. The safety margin for two closely inserted pedicular screws was only 4 to 6 mm.

CONCLUSIONS

This study suggests that placement of one screw through the S1 pedicle into the vertebral body is safer, and routine placement of two sacral pedicular screws may be difficult. The optimal starting point for placement of single iliosacral screw is 3 to 3.5 cm anterior to the posterior border of the iliac bone in the sagittal plans, and 3.5 to 4 cm cephalad to the greater sciatic notch. The screw should be directed perpendicular to the outer surface of the table from this entry point. The safe length of the iliosacral pedicular screw is up to 80 mm.

Anterior iliac crest bone graft. Anatomic considerations

STUDY DESIGN

A morphologic study of the anterior part of the iliac crest was performed.

OBJECTIVE

To define the anatomic characteristics of the anterior part of the ilium and to determine an optimal area to harvest the iliac bone graft from the anterior iliac crest.

SUMMARY OF BACKGROUND DATA

Stress fracture or avulsion fracture of the anterior cut for anterior iliac crest graft have been noted previously. However, there is insufficient published information on the morphology of the anterior part of the ilium relative to the optimal location of harvesting the bone graft.

METHODS

Direct measurements using digital calipers were taken from 30 dried human pelves and 10 cadaveric pelves. The thickness of the anterior part of the ilium was measured, with different starting points on the iliac crest. The length of the bicortical iliac bone graft also was determined.

RESULTS

The thickest portion of the ilium was 18.9 +/- 2.3 mm at the iliac tubercle, which was 45% thicker than at a point 3 cm posterior to the anterior superior iliac spine. The thick region of the anterior iliac crest extended 54.0 +/- 10.2 mm posteriorly from a point 3 cm posterior to the anterior superior iliac spine. The mean length of a 10 mm thick bicortical iliac tubercle bone graft was 36.8 +/- 8.7 mm.

CONCLUSIONS

The region around the iliac tubercle is suitable for harvesting bicortical or tricortical bone graft.

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.

Anatomic considerations for uncovertebral involvement in cervical spondylosis

Morphometric analysis of 54 dry cervical spines from C3 to C7 (a total of 270 cervical vertebrae) and bilateral dissection of 10 anatomic specimen cervical spines were performed. The uncinate processes were significantly higher at C4 to C6 (5.8 +/- 1.1 mm to 6.1 +/- 1.3 mm) levels than at C3 or C7 levels. The anteroposterior diameter of the intervertebral foramina was smaller at the C4, C5, and C6 levels compared with that at the C3 or C7 levels. The length of nerve root between the lateral border of dural tube and medial border of vertebral artery gradually increased from C3 (3.3 +/- 1.1 mm) to C7 (8.1 +/- 2.1 mm). A combination of higher uncinate process, smaller anteroposterior diameter of intervertebral foramina, and longer course of nerve roots in close proximity of the uncovertebral joints at the C4 to C6 levels may explain the predilection of nerve root compression by uncovertebral osteophytes at these levels. The distance from apex of the uncinate process to medial border of the transverse foramen gradually increased from C3 (1.7 +/- 0.8 mm) to C7 (3.3 +/- 1.0 mm), which may predispose the midcervical level to compression of the vertebral artery by laterally projecting uncovertebral osteophytes.

Anatomic considerations for posterior approach to the sacroiliac joint

STUDY DESIGN

This anatomic study describes a new intraosseous, posterior approach to the sacroiliac joint.

OBJECTIVES

To define a transosseous approach to the sacroiliac joint in which a triangular bony window is raised on the posterosuperior aspect of the ilium that provides improved access to the sacroiliac joint for posterior fusion.

SUMMARY OF BACKGROUND DATA

A posterior approach to the sacroiliac joint has been widely used for debridement of infectious diseases and for fusion. Most conventional approaches to the sacroiliac joint are interosseous, and there is a relative lack of information on transiliac approaches.

METHODS

The projection of the sacroiliac joint on the outer table of the ilium and the thickness of the posterior ilium forming part of the sacroiliac joint were determined in 15 cadaveric pelves. A right angle, triangular bony window was raised from the posterior ilium to investigate the suitability of a transiliac approach in performing sacroiliac debridement and arthrodesis. A horizontal reference line 3-3.5 cm in length was drawn between a point 1 cm anterosuperior to the posteroinferior iliac spine and a point 1.5 cm superior to the superior border of the greater sciatic notch. A vertical reference line was extended superiorly for 2-2.5 cm perpendicular to and beginning at the anterior end of the horizontal reference line. The oblique arm of the right triangle was created by joining the superior end of the vertical reference line to the posterior end of the horizontal line.

RESULTS

Thirty percent to fifty percent of the articular surface of the iliac bone was removed with this triangular segment of bone, and a corresponding area of the sacral articular surface was visualized directly. It was possible to remove the rest of the articular cartilage with angled curettes in all specimens.

CONCLUSIONS

This approach facilities improved access to the sacroiliac joint for debridement and arthrodesis with minimal soft tissue dissection and iliac bone resection.

Computer evaluation of second tarsometatarsal joint dislocation

Using computer-assisted techniques, this study analyzes the mean contact area of the articular surface of the second tarsometatarsal joint. The articular contact area decreased proportionate to the displacement in both males and females, but it was consistently greater in males than in females for all simulated displacements. The reduction in the contact area was the highest with dorsolateral displacement compared with the lateral and dorsal displacements. Dorsolateral displacement of the second metatarsal of 3 mm led to 38.6% reduction in the contact area, compared with 33.1% and 20.2% reduction with lateral and dorsal displacements, respectively. This study shows that even minor degrees of displacement not apparent on plain radiographs lead to significant decrease in the contact area of the second tarsometatarsal joint. Careful evaluation of second tarsometatarsal injuries with computed tomography is recommended to detect minor degrees of displacement.

Anatomic considerations of halo pin placement

In the present study, the anatomic location of supraorbital and greater occipital nerves and their branches was quantitatively determined with regard to halo pin placement, and a safe zone for anterolateral and posterolateral halo pins was defined to minimize neurologic damage. The mean distance between the midline and the lateral branches of supraorbital nerve and greater occipital nerve was 3.9 +/- 0.4 cm and 4.8 +/- 0.6 cm on the left side and 3.9 +/- 0.5 cm and 4.8 +/- 0.6 cm on the right, respectively. The mean angles of lateral branches of supraorbital and greater occipital nerves with respect to sagittal plane were 26.0 degrees +/- 6.0 degrees and 38.0 degrees +/- 5.0 degrees on the left side and 25.0 degrees +/- 4.0 degrees and 38.0 degrees +/- 4.0 degrees on the right, respectively. The supraorbital and greater occipital nerves and their branches are safe when the halo pins are placed at sites 4.5 cm and 6.0 cm lateral to the anterior and posterior midlines.

Zone III fractures of the sacrum. A case report

STUDY DESIGN

Case reports.

OBJECTIVES

To define the radiologic characteristics, management, and results of Zone III fractures of the sacrum.

SUMMARY OF BACKGROUND DATA

Zone III fractures of the sacrum are rare. There are few case reports of longitudinal fractures of the sacrum involving Zone III.

METHOD

The authors report eight (four transverse, four longitudinal) Zone III fractures of the sacrum. Seven patients were treated surgically by posterior sacral decompression with or without transiliac bar fixation, and one neurologically intact patient with undisplaced longitudinal fracture was treated conservatively.

RESULTS

Two neurologically compromised patients had return of normal bladder and rectal function, and another had bladder recovery only. The rest continued to show neurogenic bladder and required intermittent self-catheterization. The patient with bilateral foot drop had partial motor recovery and did not require an ankle-foot orthosis.

CONCLUSIONS

These fractures may be difficult to diagnose in polytraumatized patients and require a high index of suspicion. The longitudinal fractures may not be apparent on anteroposterior radiographs, and computed tomography scan may be necessary for establishing the diagnosis. The transverse fractures may show a characteristic step ladder sign on anteroposterior radiographs when the fracture is displaced severely. Proper lateral radiographs often are difficult to obtain, particularly in obese polytraumatized patients. Routine computed tomography scan may overlook the diagnosis. Therefore 2- to 3-mm computed tomography cuts are recommended, which may show double neural foramina in presence of significant anteroposterior displacement and overriding of the fracture fragments. Sagittal computed tomography reconstructions are useful in evaluating the transverse fractures. Posterior sacral decompression is safe and probably promotes nerve root recovery. Longitudinal fractures may be stabilized satisfactorily by transiliac rod fixation.

Anatomic considerations of an anterior approach to the sacroiliac joint

This anatomic study was performed on 25 disarticulated pelves and 10 embalmed cadavers to evaluate an anterior approach to the sacroiliac joint. The angle of inclination of the superior limb of the sacroiliac joint was 15 degrees superolateral to inferomedial in the sagittal plane, and the inferior limb was parallel to the sagittal plane. The cranial lateral part of the ala overlapped the joint space and the adjacent part of the ilium. Elevation of a rectangular bone block on the cranial part of the ala removed the joint space from the superior limb and provided direct access to the joint space of the inferior limb.

Distribution of nerve fibers in the standard incision for carpal tunnel decompression

Twenty-two paired biopsy specimens of skin and subcutaneous tissue from the proximal and distal halves of the conventional curvilinear incision or carpal tunnel decompression were histologically examined. The specimens were immunohistochemically stained with S100 antibody to highlight the nerve fibers. The mean count of free nerve endings in the proximal biopsy site was 4.42/mm2 (SD, 2.97; range, 1.23-12.27), compared to 4.2/mm2 (SD, 2.71; range, 1.01-10.50) in the distal biopsy specimens. This difference was not statistically significant (p = .20, Wilcoxon's signed ranks [matched pairs] test). The proximal incision site for carpal tunnel decompression did not appear to be more neuroreceptive than the distal incision site, providing no support for the implication of proximal incision sites in proximal scar tenderness.

Calcaneocuboid joint involvement in calcaneal fractures

The charts and radiographs of 48 surgically treated patients who underwent surgery for calcaneal fractures (right in 25 patients, left in 22, and bilateral in 1) between 1987 and 1994 were retrospectively reviewed. Coronal computed tomographic scans alone were obtained in 33 patients, and both coronal and axial computed tomographic scans were obtained in 9 patients. Three fractures exiting close to the calcaneocuboid joint (CCJ), but not involving the joint, were excluded. Nineteen patients (38.7%) had involvement of the CCJ. The extension of the fracture to the CCJ was apparent in anteroposterior or oblique radiographs or both in 18 patients. There was intra-articular fracture displacement of < or = 1 mm in 6 patients, and 13 patients had a step or a gap of > or = 2 mm with or without angulation. Eleven patients had joint depression type fractures, 6 had tongue type fractures, and 2 had comminuted fractures. Extension of the calcaneal fracture into the CCJ was significantly more common with the joint depression type calcaneal fractures (chi-square test; P = 0.008). The coronal computed tomographic images showed significant lateral subluxation of posterior facet fragments in 8 patients and considerable comminution of the lateral calcaneal wall with or without lateral subluxation of posterior facet fragment in 10 patients. These patients also had CCJ involvement, thus establishing a strong correlation between lateral subluxation of the posterior facet fragment or comminution of the lateral calcaneal wall and CCJ involvement. CCJ involvement is more common with joint depression type fractures. Extension of the fracture line into the CCJ should be suspected in presence of significant lateral column comminution or lateral talar subluxation.

Vulnerability of great medullary artery

STUDY DESIGN

The present study describes anatomic observations on great medullary artery and intercostal arteries pertinent to thoracolumbar spinal surgery.

OBJECTIVES

This study reveals the vulnerable course of the great medullary artery and its relationship to the lateral or posterolateral approach to thoracic spine.

SUMMARY OF BACKGROUND DATA

There are no previous anatomic data on the length of the great medullary artery, its intradural course, its relationship with the anterior spinal artery, and the distance between two adjacent intercostal arteries.

METHODS

The location of the intercostal arteries was defined, and the distance between two adjacent arteries was measured at a point on the lateral surface of the vertebra midway between its anteroposterior diameter. The intradural length of the great medullary artery and the angle it formed with the anterior spinal artery at the point of anastomosis were also measured.

RESULTS

The mean intradural length of the great medullary artery was 3.6 cm (range, 1.7-8.1 cm), and it passed over 1-3 disc spaces before joining the anterior spinal artery at a mean angle of 20.1 degrees (range, 12-28 degrees). The average distance between two adjacent intercostal arteries from T6 to L2 was 3.6 cm (range, 2.8-4.0 cm), which provides a safe window through which a herniated thoracic disc may be approached if surgery is indicated.

CONCLUSIONS

The acute angle between the great medullary artery and anterior spinal artery indicates that these two arteries are in close proximity for considerable length and are liable to be compressed together with the intervening vascular collaterals by a space-occupying lesion, such as disc herniation or a fractured fragment. The longer the intradural course of the great medullary artery, the more vulnerable it is to compression by disc herniation or fracture. The intercostal and lumbar arteries are located at the midportion of the lateral aspect of the vertebral bodies rather than at the level of intervertebral discs. Discectomy or decompression of the anterior thoracic canal may be accomplished through a lateral or posterolateral extracavitary approach between two intercostal or lumbar arteries.