The suprascapular nerve and its articular branch to the acromioclavicular joint: an anatomic study.

HYPOTHESIS: The suprascapular nerve and its articular branch innervate the acromioclavicular (AC) joint. Documenting the detailed anatomy of this innervation in the AC joint, including the pertinent surgical and anatomic relationships of the suprascapular nerve and its branches to the AC joint, will aid in the prevention of injury and the reduction of risk of denervation during shoulder surgery. MATERIALS AND METHODS: Twelve shoulders from 6 embalmed human cadavers were bilaterally dissected to study the course of the suprascapular nerve and its motor and sensory branches. RESULTS: The sensory branch runs superiorly to the supraspinatus muscle towards the AC joint. The average distance from the supraglenoid tubercle to the nerve at the coracoid base was 15 mm. The average distance from the coracoclavicular ligaments to the nerve at the coracoid base was 6 mm. The average distance from the spinoglenoid notch to the sensory branch at the suprascapular notch was 22 mm. The average length of the sensory branch was 30 mm. In half of the specimen shoulders, the suprascapular artery accompanied the nerve at the suprascapular notch under the transverse scapular ligament. DISCUSSION: The innervation of the AC joint by the suprascapular nerve has been described, along with pertinent distances to anatomic landmarks. The sensory branch of the suprascapular nerve, which passed through the scapular notch inferior to the transverse scapular ligament, was found in 100% of the study specimens. CONCLUSION: The sensory branch of the suprascapular nerve runs superiorly to the supraspinatus muscle towards the AC joint. The detailed information can be used to help decrease the risk of nerve injury during shoulder surgery and to aid in effectively diagnosing and treating AC joint-related disorders.

Anatomical considerations of the internal iliac artery in association with the ilioinguinal approach for anterior acetabular fracture fixation.

INTRODUCTION: Vascular injury may be encountered during an anterior approach to the pelvis or acetabulum-be it due to hematoma decompression, clot dislodgement during fracture manipulation, or iatrogenic. This can be associated with significant bleeding, hemodynamic instability, and subsequent morbidity. If the exact source of bleeding cannot be easily identified, compression of the internal iliac artery may be a lifesaving procedure. MATERIALS AND METHODS: We describe an extension of the lateral window of the ilioinguinal (or Olerud) approach elaborated on cadavers. RESULTS: The approach allows emergent access the internal iliac artery and intraoperative cross-clamping of the internal iliac vessels to control bleeding. CONCLUSION: The approach allows rapid access to the internal iliac artery. The surgeon should be familiar, however, with the surgical anatomy of this region to avoid potential injury to the ureter, peritoneum, lymphatics, and sympathetic nerves overlying the vessels when using the approach described.

Retro-cardiac esophageal mobility and deflection to prevent thermal injury during atrial fibrillation ablation: an anatomic feasibility study.

BACKGROUND: Atrial fibrillation (AF) ablation often causes minor esophageal (ESO) injury, and sometimes lethal posterior left atria (PLA)-ESO fistula. Avoidance techniques (energy reduction and/or complete target avoidance) provide questionable ESO protective value, and are likely associated with increased AF recurrence. METHODS AND RESULTS: Potential independent mobility, deflectability and age-related anatomic factors, assessed by multi-position, and age-progressive thoracic computed tomography scans, show (1) mobility of the retro-cardiac ESO-PLA juxtaposition, (2) age-related increased thermal ablation vulnerability; and also, age-increased potential for retro-cardiac ESO mobility and deflectability to avoid collateral injury; and that (3) the retro-cardiac vertebral bodies and the descending aorta create a patient-specific esophageal corridor which defines the resting supine esophageal position and the subsequent PLA-ESO crossing points. CONCLUSION: A small, 1-3 mm, increase in separation of the ESO relative to the PLA occurs when moving the patient from supine to lateral and from supine to prone position. Because of the concave spine; the PLA-ESO area of apposition increases. Patient rotation of 90° and 180° does not create enough passive PLA-ESO separation to avoid collateral ESO thermal energy; but, active repositioning lateral and out of ESO corridor appears feasible.

Scapular muscle activity in overhead athletes with symptoms of secondary shoulder impingement during closed chain exercises.

OBJECTIVE: To determine the amount of muscle activation in 4 scapular muscles in overhead athletes with and without a history of secondary shoulder impingement, during 3 upper extremity closed chain exercises. DESIGN: One-between (group), one-within (exercise) repeated measures. SETTING: Controlled laboratory study. PARTICIPANTS: Overhead athletes (n=15; mean age +/- SD, 21.0+/-2.5 y; mean height +/- SD, 176.0+/-7.8 cm; mean weight +/- SD, 76.1+/-13.4 kg) demonstrating with symptoms of shoulder impingement and overhead athletes (n=15; mean age +/- SD, 20.4+/-3.8 y; mean height +/- SD, 174.1+/-9.7 cm; mean weight +/- SD, 73.3+/-11.7 kg) with no shoulder pathologies. INTERVENTIONS: Subjects completed 5 individual trials of a standard push-up, a push-up on an unstable surface, and a revolution on a shoulder rehabilitation device while electromyography (EMG) recorded muscle activity of the serratus anterior, upper trapezius, middle trapezius, and lower trapezius. MAIN OUTCOME MEASURES: The mean EMG data for the 4 muscles from the standard push-up, push-up on an unstable surface, and shoulder rehabilitation device trials were normalized as a percentage of a maximum voluntary isometric contraction for each muscle. RESULTS: There was a statistically significant interaction for the middle trapezius (F(2,56)=3.856; P=.027). The shoulder impingement push-up on an unstable surface (33.76%+/-26.45%) had significantly greater activation compared with the shoulder impingement standard push-up (25.88%+/-13.76%), the shoulder impingement shoulder rehabilitation device (9.40%+/-5.86%), and the nonpathology push-up on an unstable surface (19.49%+/-7.73%). The shoulder impingement standard push-up had significantly greater activation compared with the shoulder impingement shoulder rehabilitation device and nonpathology standard push-up (17.99%+/-7.31%). The nonpathology standard push-up and nonpathology push-up on an unstable surface had significantly greater activation compared with the nonpathology shoulder rehabilitation device (7.95%+/-4.30%). CONCLUSIONS: These results suggest that the muscle activation of the middle trapezius differs in overhead athletes with a history of secondary shoulder impingement compared with those who lack this history during closed chain exercise, as well as within the 3 closed chain exercises. The levels of muscle activation of the serratus anterior and upper trapezius during these closed chain exercises were similar between the 2 groups. These results support the use of closed chain exercises in the rehabilitation process of overhead athletes with secondary shoulder impingement. However, clinicians should consider the muscle(s) of interest when selecting an exercise.

Anatomical basis of the vascular risk related to the circumflex scapular artery during posterior approach to the scapula.

PURPOSE: The vasculature and anastomosis around the scapula is extremely intricate making surgical treatment complicated. We aimed to determine the "at risk area" for the circumflex scapular artery and its anastomosis with the suprascapular artery during posterior approach to the scapula. METHODS: Sixteen shoulders from eight embalmed adult cadavers were dissected through posterior approach to the scapula to study the relationship of the circumflex scapular artery and its anastomosis with the suprascapular artery to bony landmarks of the posterior scapula. Three measurements were obtained: from inferior glenoid rim to the point of the bony groove of the circumflex scapular artery; from the posterior glenoid rim to the spinoglenoid notch; and from the spinoglenoid notch to the circumflex scapular artery. RESULTS: The circumflex scapular was identified at a distance of 2.9 cm from the inferior glenoid rim and at a distance of 4.6 cm from the spinoglenoid notch, as it winds around the lateral border of the scapula to enter the infraspinous fossa. The suprascapular neurovascular bundle was identified at the spinoglenoid notch 1.8 cm from the posterior glenoid rim. CONCLUSIONS: We were able to identify the relationship of the circumflex scapular artery to the anatomic landmarks of the scapula and to define the "at risk area" for the ascending branch of the circumflex scapular artery and its anastomosis with the suprascapular artery. We believe our anatomical study may aid in the avoidance of vascular complications during internal fixation of scapular fractures.

An evaluation of halo pin insertion torque on outer table penetration in elderly patients.

STUDY DESIGN: An experimental anatomic study performed on elderly cadaveric skulls. OBJECTIVES: (1) To determine the pin penetration depths in outer table of skull at different torques in the elderly population during halo pin insertion and (2) to validate a safe range of torque for use in this population. SUMMARY OF BACKGROUND DATA: The elderly are at an increased risk of falls, which can lead to cervical fractures. The halo pins used to stabilize these injuries present unique problems in this population owing to osteoporosis, and intracranial pin penetration should always be avoided. METHODS: A halo ring was used to insert pins in 4 standard positions on 10 elderly cadaveric skulls. Incremental torques were used to drive the pin into the outer table, and the penetration of each pin was measured using computed tomography imaging at each stage. RESULTS: Eight to Twelve in-lb of torque was not sufficient to fully penetrate the outer table of the skull. Only at 16 in-lb of torque was the outer table penetrated, and only anterolaterally, hence the posterolateral outer table is more resistant to penetration than the anterolateral outer table. CONCLUSIONS: Despite age-related bone changes in the elderly, it is still safe to use 8 in-lb of torque when inserting pins for a halo vest. However, as the anterolateral outer table is weaker than the posterolateral outer table, a new pin design with broader shoulders should be used anterolaterally to ensure maximal patient safety.

Comparison of angled versus AP view radiography for post-operative evaluation of lumbosacral spondylolisthesis: a cadaveric study.

BACKGROUND: The objective of this study was to investigate if angled radiographic views of the L5-S1 junction result in quantitatively better images in patients with lumbosacral spondylolisthesis compared to conventional AP view. METHODS: Grade I lumbosacral spondylolisthesis was simulated in cadaveric specimens and repaired using pedicle screws and posterolateral bone grafting. Angled view AP radiographs were taken at different angles and analyzed at both grade I spondylolisthesis and complete reduction (to normal). RESULTS: The results indicated that angled view radiographs provide better visualization of intervertebral disc height, area, and posterolateral bone graft area compared with true AP views. The optimal view was at 40 degrees for grade I spondylolisthesis, and at 25 degrees -35 degrees for complete reduction. CONCLUSION: In addition to the dynamic radiographs currently used for evaluation of patients post-spondylolisthesis repair, an additional angled view radiograph (at 40 degrees or 25-35 degrees ) is recommended to evaluate intervertebral disc height, intervertebral area, bone graft area, and pedicle screw position.

Morphometric analyses of the cervical superior facets and implications for facet dislocation.

The articular facets of the cervical spine have been well addressed; however, little information is available on the relationship of the superior facets of the cervical spine to traumatic dislocation in the literature. Morphometric analyses of the superior facets of 30 dried cervical spines from C3 to C7 were performed to determine any morphological differences. The angle of the superior facet with respect to the transverse plane was also measured on computed tomography (CT) scans of 30 patients having neck injury without fracture/dislocation. The vertical and surface lengths of the superior facet were significantly lower (P < 0.01) at C6-C7 levels than at C3-5 levels. The anteroposterior diameter of the superior facet was smaller (P < 0.05) at C6 and C7 levels compared to C3-5 levels. Although the superior facet joint surface is in a more coronal orientation in lower cervical vertebrae, the inclination of the superior facet is more horizontal relative to the transverse plane when measured in vivo. A combination of lower height, smaller anteroposterior diameter of the superior facet, and a more horizontally oriented superior facet at C6 and C7 levels in vivo may explain the predilection of translation relative to one another in the lower cervical spine.

The effect of removing the lateral part of the pars interarticularis on stress distribution at the neural arch in lumbar foraminal microdecompression at L3-L4 and L4-L5: anatomic and finite element investigations.

STUDY DESIGN: The assessment of L3 and L4 pars interarticularis thickness and finite element analysis of stress distribution across L3 and L4 pars interarticularis. OBJECTIVE: To quantify the morphology of the region of the L3 and L4 pars interarticularis and to assess the stress increase as a function of access size using the finite element lumbar spine model. SUMMARY OF BACKGROUND DATA: Inadequate decompression and traction of the nerve structures are several causes of the unsatisfactory outcomes in patients after foraminal stenosis decompression and far lateral disc herniation removal by extraforaminal exposure. Enlarging the access of the foraminal exposure by the removal of the lateral aspect of the pars interarticularis may be able to diminish the inadequate decompression and traction of the nerve structures; however, it may lead to increase stress and fracture of the neural arch. METHODS: We used 15 human cadaver L3 and L4 lumbar vertebrae for measuring the thickness of the pars interarticularis. The ventral and dorsal surfaces were subdivided into 4 equal parts, and the thickness of each part was measured using a digital caliper. An experimentally validated 3-dimensional nonlinear finite element model of the intact L3-S1 segment was used to simulate the lateral removal of one fourth and one half of the L3 and L4 pars interarticularis. RESULTS: The mean thicknesses of the pars interarticularis showed a gradual increase toward the lateral edge. Finite element model analyses predicted stresses increased to 35% and 40% after removal of one half of the lateral part of the L3 and L4 pars interarticularis, respectively, and were much closer to the intact spine after removal of one fourth of the lateral part of the pars interarticularis. CONCLUSION: The removal of one fourth of the lateral aspect of the pars interarticularis has minimal influence on the stresses in the remaining L3 and L4 neural arches. The lateral half of the pars has the largest thickness, and its removal leads to considerable stress increases.

Evaluation of skull thickness and insertion torque at the halo pin insertion areas in the elderly: a cadaveric study.

BACKGROUND CONTEXT: The halo skeletal fixator provides the most rigid type of immobilization of all the orthoses that stabilize the cervical spine. Sometimes with older patients (>70 years old), the pin penetrates the cortical and cancellous bone of the skull and enters the intracranial space, which can result in serious complications such as brain injury, infection, hematoma, and loss of cerebrospinal fluid from the subarachnoid space. Currently, there is a lack of relevant literature that examines these concerns. PURPOSE: To evaluate the thickness of the outer table, diploe, and inner table at the anterolateral and posterolateral pin insertion areas of the skull in elderly cadavers by using computed tomography (CT) scans. In addition, insertion torques at the four standard pin insertion areas was determined by applying halo pins at incremental torque in an effort to suggest safe torque levels for the anterolateral and posterolateral pins. STUDY DESIGN/SETTING: A human cadaveric anatomical and biomechanical study relating to thickness and insertion torques at standard pin areas in the elderly. PATIENT SAMPLE: Twenty-one elderly cadaveric skull specimens. OUTCOME MEASURES: Thickness of cortices (tables) and diploe of skull and insertion torque at halo pin insertion areas. METHODS: Aquarius Image software at the CT scanner's TeraRecon Aquarius Workstation was used to make the necessary skull thickness measurements at the pin insertion areas. Six, 8, 12, 18, and 36 inch lb of torque were used to determine penetration of the pins through the inner table at each of the four locations (two anterolateral and two posterolateral). RESULTS: The mean anterolateral thickness was 7.36+/-1.57 mm. The average thickness of the outer table, diploe, and inner table were 2.24+/-0.44 mm, 1.52+/-0.41 mm, and 3.59+/-1.70 mm, respectively. The mean posterolateral thickness was 9.47+/-1.12 mm. The average thickness of the outer table, diploe, and inner table were 4.32+/-0.92 mm, 1.88+/-0.35 mm, and 3.27+/-1.21 mm, respectively. No pin penetration was seen at the traditional 8 inch lb of insertion torque in both the anterolateral and posterolateral pin insertion areas. Eighteen inch lb of torque resulted in penetration in 90.48% (19/21) and in 85.71% (18/21) of specimens in the left anterolateral and right anterolateral pin insertion areas, respectively. No penetration was seen even at 36 inch lb of torque in 80.95% (17/21) of the cadavers in both the left and right posterolateral pin insertion areas. CONCLUSIONS: The current study supported previous research that 8 inch lb of torque is safe for application of halo pins in the elderly. The posterolateral skull is thicker and stronger than the anterolateral skull. The safe maximum torque is 8 inch lb for anterolateral pin insertion area and 18 inch lb for the posterolateral pin insertion area.

Pathomechanism of loss of elasticity and hypertrophy of lumbar ligamentum flavum in elderly patients with lumbar spinal canal stenosis.

STUDY DESIGN: A histologic, biologic, and immunohistochemical assessment using human samples of lumbar ligamentum flavum. OBJECTIVE: To clarify the pathomechanism of loss of elasticity and hypertrophy of the lumbar ligamentum flavum (LF) in the elderly population. SUMMARY OF BACKGROUND DATA: The most common spinal disorder in elderly patients is lumbar spinal canal stenosis, causing low back and leg pain, and paresis. Canal narrowing, in part, results from hypertrophy of the LF. Although histologic and biologic literature on this topic is available, the pathomechanism of loss of elasticity and hypertrophy of the LF is still unknown. METHODS: One fetus, 5 young, and 5 elderly LF were obtained for histologic study. Hematoxylin and eosin, Alcian blue, Masson Trichrome, and Elastica Van Gieson stains were performed for each LF. Nine LF were collected and were used for biologic study of real time RT-PCR to quantitatively measure mRNA expression of Type I collagen and elastin in each LF. RESULTS: In the LF of the fetus, elastic fibers accounted for about 75% of the entire area. In the dural aspect of the LF in the young and elderly group, the ratio was also around 75%; however, the ratio of the dorsal aspect decreased with age. Almost half of the area showing loss of elastic fibers was shown to be converted to cartilaginous tissue producing Type II collagen and proteoglycan by Alcian blue and Type II collagen immunohistochemistry. The area, which did not stain black with EV nor blue with AB stain, was positively stained blue with T stain, indicating scarring. The area of the normal dural layer was 18.0 +/- 2.3 and 33.8 +/- 4.3 (mm2), for young and elderly group, respectively. Accordingly, it was 3.2 +/- 0.8 and 18.0 +/- 10.2 (mm2), for the dorsal abnormal layer. Elastin mRNA showed a relatively strong correlation (r = 0.44) with age; however, the slope was very gentle. Type I collagen mRNA showed a very strong correlation (r = 0.80) with age. The slope was steeper, and the value reached at 1000% (10-fold) around 65 years old when compared with the LF from younger patient. Elastin mRNA showed a weak correlation (r = 0.36) with thickness, and the slope was gentle. Type I collagen mRNA showed relatively strong correlation (r = 0.52) with thickness. The slope was steeper, and the line reached at 1000% (10-fold) around 6.5 (mm) when compared with a thin LF. CONCLUSION: Decreased elasticity of LF in the elderly is due to the loss of elastic fibers and a concomitant increase of collagenous fibers in the dorsal aspect. LF hypertrophy could be due to the thickening of the normal elastic layer as well as of the abnormal collagenous layer.

Anatomical evaluation and clinical importance of the tibiofibular syndesmosis ligaments.

The aim of this study was to describe the detailed anatomical arrangement of ligaments of the tibiofibular syndesmosis and to highlight the clinical aspects of fracture dislocations. This study was performed on 42 legs of adult human embalmed cadavers. Tibiofibular syndesmosis ligaments attachments and their mutual relationships were described and their dimensions were measured. The anterior tibiofibular ligament is usually composed of three parts. This ligament runs obliquely at laterodistaly direction making 35 degrees angle with horizontal plane and posteriorly 65 degrees angle with sagittal plane. The posterior tibiofibular ligament runs almost horizontally 20 degrees angle with horizontal plane. The mean thicknesses of tibial and fibular attachments are 6.38+/-1.91 mm and 9.67+/-1.74 mm, respectively. The inferior transverse ligament originates from just below the posterior tibiofibular ligament, which has variations on the shape and dimensions due to its attachment points. The average length is 36.60+/-9.51 mm. The network between the fibular notch and the distal fibula has been filled with the interosseous tibiofibular ligament whose fibers follow the laterodistal and anterior direction from the tibia to the fibula. It lies proximally 30-40 mm from the mortise. At the inferior view of the tibiofibular syndesmosis a pyramidal shaped cartilaginous facet was observed which was attached to the fibula. The length of this cartilage was variable. Some of synovial plicas from the ankle joints synovial membrane were observed at this view. We conclude that the results of this study may be useful to both orthopedic surgeons and radiologists for anatomic evaluation of the tibiofibular syndesmosis area.

Quantitative analysis of changes in cervical intervertebral foramen size with vertebral translation.

STUDY DESIGN: Simulated translation of the C5 vertebra was performed in 20 embalmed cadaveric cervical spines, and cross-sectional areas of the C4-C5 and C5-C6 intervertebral foramina were measured and compared before and after translation of the C5 vertebra. OBJECTIVE: To determine the relationship of cross-sectional intervertebral foraminal areas to the degrees of vertebral translation. SUMMARY OF BACKGROUND DATA: The common feature of clinical instability and adjacent diseases of the cervical spine is malalignment of the cervical spine (i.e., there is ventral and dorsal translation of vertebral body with respect to the adjacent upper and lower vertebral body, respectively). To our knowledge, no previous study has analyzed the quantitative effect of vertebral translation on the size of the intervertebral foramina. METHODS: The cross-sectional areas of the intervertebral foramina at C4-C5 and C5-C6 were measured on computerized tomography. The images were then transferred to the personal computer, where consecutive dorsal translations of C5 vertebrae with a 1-mm increment from 1 to 5-mm displacements were performed using Microsoft paint software (Microsoft, Corp., Redmond, WA). National Institutes of Health (Bethesda, MD) Image J software (V1.33m) was then used to measure the areas of both sides of C4-C5 and C4-C6 foramina at normal and each displacement level in the computer. RESULTS: Following dorsal translation of C5 vertebra, anterolisthesis of C4 relative to C5 and retrolisthesis of C5 relative to C6 was noted. No significant difference was found between the measured values using Aquarius Image software (Microsoft, Corp.) on computerized tomography and National Institutes of Health image J software on the desktop computer (P > 0.05). When compared with normal values, there was an increase in the C4-C5 intervertebral foraminal area (i.e., 6%, 14%, 18%, 21%, and 26% with anterolisthesis of C4 relative to C5 following 1, 2, 3, 4, and 5-mm dorsal translation of the C5 vertebra, respectively). There was a 12% decrease in the C5-C6 intervertebral foraminal area, with each 1-mm incremental retrolisthesis of C5 relative to C6 vertebra. Statistically significant differences were found among residual cross-sectional foraminal areas following different degrees of dorsal translation (P < 0.05). CONCLUSION: There is a significant increase in size with anterolisthesis and decrease in size with retrolisthesis of upper and lower adjacent vertebral intervertebral foramina, respectively.

Enlarged perforating branch of peroneal artery and extra crural fascia in close relationship with the tibiofibular syndesmosis.

We found an extremely large perforating branch of peroneal artery in an 89-year-old female cadaver's left ankle. The anterior tibial artery could not reach to supply the ankle and dorsum of the foot. The perforating branch of peroneal artery continued as the dorsalis pedis after giving off an anterior lateral malleolar artery branch. The posterior tibial artery was thinner than usual. On the anterior side of the ankle, there was an extra crural fascia in addition to the regular crural fascia, under the anterior crural muscles. This strong fascia was tightly overlying the perforating branch of peroneal artery and anterior tibiofibular ligament. It is important to know the relationship of these vessels to the surrounding structures. Surgeons must be careful while dissecting this area since the perforating branch of peroneal artery might be anomalously enlarged as well as crossing in front of the tibiofibular syndesmosis in order to prevent vascular injury.

Lateral femoral cutaneous nerve: an anatomic study.

The purpose of our study was to determine the location of the lateral femoral cutaneous nerve and its branches at the inguinal ligament and proximal thigh. We think that further defining the location of the nerve and its branches based on certain measurements from known anatomic landmarks would enable us to determine a danger zone that could aid in preventing iatrogenic injury to the lateral femoral cutaneous nerve. The anatomic course of the lateral femoral cutaneous nerve was studied in 29 cadaver specimens and distances from various landmarks were recorded. In addition, the branching pattern of the nerves was recorded. We observed variability in the course and branching patterns of the lateral femoral cutaneous nerve. The lateral femoral cutaneous nerve was found to potentially be at risk as far as 7.3 cm medial to the anterior superior iliac spine along the inguinal ligament and as much as 11.3 cm distal on the sartorius muscle from the anterior superior iliac spine. As many as five branches of the lateral femoral cutaneous nerve were found and in 27.6% of cases the lateral femoral cutaneous nerve branched before traversing the inguinal ligament. We used this information to describe a danger zone, which could be used as a guide to help prevent unnecessary injury during certain procedures.

Value of intraoperative true lateral radiograph of C2 pedicle for C1-2 transarticular screw insertion.

BACKGROUND CONTEXT: Transarticular C1-2 screws are widely used in posterior cervical spine instrumentation. Injury to the vertebral artery during insertion of transarticular Cl-2 screw remains a serious complication. Use of a computer-assisted surgery system decreases this complication considerably. However, this system encounters problems in ensuring complete accuracy because of positional variations during preoperative and intraoperative imaging generation. Therefore, intraoperative fluoroscopy still is one of the commonly used methods to guide insertion of transarticular Cl-2 screw. Evaluation of a true lateral radiographic view of the C2 pedicle for screw trajectory during C1-2 transarticular screw insertion may help to minimize this potential complication. PURPOSE: To evaluate the value of intraoperative true lateral radiograph of the C2 pedicle for screw trajectory during C1-2 transarticular screw insertion. STUDY DESIGN: To compare the height of the C2 pedicle area allowing instrumentation on true lateral view radiograph of the C2 pedicle and computed tomographic (CT) scan with multiplanar reconstruction. METHODS: Twenty embalmed human cadaveric cervical spine specimens were used to insert a total of 40 C1-2 transarticular screws using Magerl and Seemann technique. One side of the C2 transverse foramen was filled with radiopaque material (lead oxide) to simulate the artery and to demarcate the danger zone for better visualization on radiography. Measurements and calculation of the mean and standard deviation of the height of the area allowing instrumentation of the C2 pedicle were done on true lateral view radiograph of the C2 pedicle, the sagittal and 30 degrees sagittal views relative to the frontal plane passing exactly through the center of the C2 pedicle of CT scans. Student t test was applied to calculate the statistical significance of measured values. Statistical significance was defined as por=.36. Using sagittal CT scan views, the height of pedicles was 7.71+/-0.7 mm (right) and 7.58+/-1.01 mm (left), p>or=.23. On 30 degrees sagittal CT scan views, the height of pedicles was 7.84+/-1.00 mm (right) and 7.76+/-1.02 mm (left), p>or=.27. The p value was >or=.78, >or=.56, and >or=.49 for true lateral radiographic view and sagittal CT scan view, true lateral radiographic view and 30 degrees sagittal CT scan view, and sagittal CT scan view and 30 degrees sagittal CT scan views, respectively. On lateral view of cervical spine, the decline angle of the transarticular screw was 51.3+/-0.50 degrees (right) and 50.68+/-0.41 degrees (left), p>or=.17. Mean decline angle was 51+/-0.43 degrees . On the anteroposterior (AP) view, radiograph median angle was 6.87+/-0.53 degrees (right) and 6.0+/-0.59 degrees (left), p>or=.25. Mean median angle was 6.44+/-0.62 degrees. CONCLUSIONS: True lateral radiographic views of the pedicles provide useful information for defining screw trajectory intraoperatively. Using this view along with AP and lateral view of cervical spine and preoperative three-dimensional CT scan may narrow the margin of error in this delicate area.

Dynamic changes in the contact area of the sacroiliac joint.

Thirty adult dry-bone ilium specimens were used in conjunction with computer analysis to determine the average articular contact area between the sacrum and ilium at the sacroiliac joint. Simulating an unstable pelvic injury, the sacroiliac joint was displaced in three directions by moving the ilium posteriorly, superiorly, and posterosuperiorly. After each displacement, the contact area between the sacrum and ilium at the sacroiliac joint was calculated. The data showed that the average articular surface area of the male sacroiliac joint (1138.3 mm2) was approximately 12.8% greater than the average surface area of the female sacroiliac joint (992.5 mm2). The average articular contact area between the sacrum and ilium at the sacroiliac joint was lowest with the ilium displaced posterosuperiorly compared to equal displacements superiorly or posteriorly. This study quantitatively illustrated the loss of contact surface area between the sacrum and ilium during various displacements of the ilium, thus indicating the clinical cross-section area available for open reduction and internal fixation or fusion.

Extensor hallucis longus innervation: an anatomic study.

Thirty legs from skeletally mature embalmed cadavers were dissected to define the most common pattern and the variants of innervation of the extensor hallucis longus muscle and its clinical significance. Twenty-seven muscles had only one innervating branch (90%). Only three muscles had two innervating branches (10%). Twenty-one of the branches entered the muscles from the fibular side (63.6%), six entered the muscles from the tibial side (18.2%), and six entered the muscles from the anterior edge (18.2%). The branches innervating the extensor hallucis longus from the fibular side had a closer relation with the fibular periosteum than those entering the muscle from the tibial side or the anterior edge. The mean length of these branches between their points of origin and entry in the extensor hallucis longus was 5.0 +/- 1.5 cm. The high risk zone for the iatrogenic injury to the muscular branch of the extensor hallucis longus was located between 5.9 +/- 1.7 and 10.9 +/- 1.7 cm inferior to the most distal palpable point of the fibular head. The current study confirmed that the extensor hallucis longus was supplied mostly by one nerve that usually entered the muscle from the fibular side and had a close relation to the fibular periosteum in the dangerous zone.