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PubMed1998

Extracranial nerves in the posterior part of the head. Anatomic variations and their possible clinical significance.

STUDY DESIGN: An anatomic study of the peripheral nerves innervating the occipital region. OBJECTIVES: To study the topography of the extracranial occipital nerves, to define optimal locations for anesthetic nerve blockades, to provide guidelines to use with the suboccipital surgical approach, and to search for structures with putative pathogenetic implications in cases of unilateral headache. SUMMARY OF BACKGROUND DATA: There is little consensus in the literature concerning the sensory innervation of the scalp. Previous clinical and morphologic studies have not proven the existence of an entrapment mechanism in cases of unilateral head pain. Specific sites for anesthetic blockades have been defined only partly with reference to topographic landmarks. METHODS: The topography of the greater occipital (n = 20), the minor occipital (n = 19), and the greater auricular nerves (n = 17) was studied by dissection of 10 embalmed cadavers. Measurements of internerve distances and distances to defined landmarks were supplemented by drawings and photographs. RESULTS: A great variability in nerve topography was seen interindividually and intraindividually. The greater occipital nerve ascended between 5 mm and 28 mm from the midline along the intermastoid line. The minor occipital nerve was found between 32 mm and 90 mm from the midline along the same landmark. In most cases, both the greater occipital nerve and the minor occipital nerve pierced the aponeurosis after branching. Thirteen greater occipital nerves and eight minor occipital nerves also were embedded in this tissue. Twelve of the 20 greater occipital nerves formed a rich network around the occipital artery. However, anatomic structures with an imminent risk of causing entrapment were not observed. CONCLUSION: The results of this study suggest that optimal locations for blockade techniques should be reconsidered. The acquired knowledge concerning greater auricular and minor occipital nerves behind the sternocleidomastoid muscle may aid in preventing intraoperative injuries.

Female↗
PubMed1999

The ligaments and annulus fibrosus of human adult cervical intervertebral discs.

STUDY DESIGN: Descriptive, microdissection study. OBJECTIVE: To determine the morphology of the human adult cervical intervertebral disc and its ligaments. SUMMARY OF BACKGROUND DATA: Some studies indicate that the cervical disc is distinctly different from the lumbar intervertebral disc, yet most clinical and anatomic texts appear content with extrapolating data from the lumbar spine. A detailed three-dimensional description of the cervical intervertebral disc and its surrounding ligaments is currently unavailable. METHODS: Whole cervical spinal columns were freed from 12 human adult embalmed cadavers, and the posterior elements and soft tissues were removed. Using microdissection, the longitudinal ligaments and the fibrous components of 59 cervical intervertebral disc were resected systematically. The orientation, location, and attachments of each stripped bundle of collagen were recorded photographically and in sketches. RESULTS: The cervical anulus fibrosus does not consist of concentric laminae of collagen fibers as in lumbar discs. Instead, it forms a crescentic mass of collagen thick anteriorly and tapering laterally toward the uncinate processes. It is essentially deficient posterolaterally and is represented posteriorly only by a thin layer of paramedian, vertically orientated fibers. The anterior longitudinal ligament covers the front of the disc, and the posterior longitudinal ligament reinforces the deficient posterior anulus fibrosus with longitudinal and alar fibers. CONCLUSIONS: The three-dimensional architecture of the cervical anulus fibrosus is more like a crescentic anterior interosseous ligament than a ring of fibers surrounding the nucleus pulposus.

Adult↗
PubMed1999

Attachments of the posterior layer of lumbar fascia.

STUDY DESIGN: Superficial and deep laminae of the posterior layer of lumbar fascia were dissected. The lumbar portion was measured for evidence of segmental thickenings. Superior attachments were dissected, documented, and photographed. OBJECTIVES: To verify the existence of posterior accessory ligaments and establish the superior attachments and fiber angles of the posterior layer of lumbar fascia. SUMMARY OF BACKGROUND DATA: There have been two small dissection studies on the posterior layer. Their findings are conflicting in several areas of clinical significance. Thickenings in the lumbar region were described in one study, but have not been verified. The superior attachments of the posterior layer have not been formally documented. METHODS: Study 1: In 21 embalmed cadavers, the lumbar region of the posterior layer was dissected. The lumbar spinous processes and adjacent fascia were marked. The fascia was removed and examined, and its thickness measured with a manual micrometer. Results were statistically analyzed. Study 2: Superior attachments of the posterior layer in 20 cadavers were dissected and photographed. Capacity to transmit tension was estimated and documented photographically, and fiber angles measured in situ. RESULTS: Study 1: There was no evidence of macroscopic segmental thickening in the posterior layer. Study 2: The superficial lamina was continuous superiorly with the rhomboids, and the deep lamina with the tendons of splenius cervices and capitis. These previously undocumented attachments were of variable thickness and fibrosity, and capable of transmitting tension. CONCLUSIONS: Both superficial and deep laminae of the posterior layer are more extensive superiorly than previously thought. This may have implications for certain tests used in assessment and management of low back pain such as the slump and "nonorganic" tests. The thickness of the superior attachments is variable. Their capacity for load bearing is yet to be quantified.

Aged↗
PubMed2001

The risk of foraminal violation and nerve root impingement after anterior placement of lumbar interbody fusion cages.

STUDY DESIGN: Three groups of six embalmed cadaver spines underwent placement of lumbar interbody fusion cages centered either at midline, 10% lateral of midline, or 20% lateral of midline. The spines were evaluated for evidence of neuroforamen violation or nerve root impingement. OBJECTIVES: To determine the potential for foraminal violation or nerve root impingement after correct placement and lateral misplacement of lumbar interbody fusion cages. SUMMARY OF BACKGROUND DATA: Radicular symptoms after anterior cage placement have raised some concern about the potential for inadvertent device-related foraminal violation not adequately appreciated by intraoperative fluoroscopy. METHODS: Preoperative computed tomography scanning and plain radiography was used to measure endplate dimensions at L4-L5 and to template the appropriately sized interbody fusion cages. The cadaveric specimens were randomly divided into three groups of six (Groups I-III) and instrumented at L4-L5 either at midline (I) or 10% (II) or 20% (III) lateral of midline. Postoperative computed tomography and plain radiography was evaluated for evidence of neuroforamen violation, followed by dissection of the specimens. RESULTS: Foraminal violation occurred in one of six spines in group II (10% off midline) and in three of six spines in group III (20% off midline). Two of the three cadavers in group III with foraminal violation also were noted to have nerve root abutment on computed tomography scans and spinal dissection. CONCLUSIONS: Excessive lateral placement of lumbar interbody fusion cages may result in foraminal violation and possible nerve encroachment. The "safe zone" for centering the cages extends approximately 5 mm on either side of midline.

Foramen Magnum↗
PubMed2001

An experimental study on the interface strength between titanium mesh cage and vertebra in reference to vertebral bone mineral density.

STUDY DESIGN: Using human cadaver spines, the authors investigated mechanical properties of the interface between titanium mesh cage and vertebra in respect to vertebral bone mineral density. OBJECTIVES: The objective of this study is to examine the effects of the size of the mesh cage and an internal end ring system on interface mechanical properties in reference to vertebral bone mineral density. SUMMARY OF BACKGROUND DATA: A titanium mesh cage has recently been developed for anterior spinal reconstruction. The cage provides immediate postoperative stability and facilitates bony union with cancellous bone packed in the cage itself. Mechanical properties of the interface between the cage and vertebra, however, are yet to be clarified in osteoporotic spine. METHODS: Twenty-five lumbar vertebrae harvested from embalmed human cadavers (n = 20) were used. The vertebrae were divided into four experimental groups according to the applied cage conditions: Phi25 mm cage without internal end ring (L-), Phi19 mm cage without internal end ring (S-), Phi25 mm cage with internal end ring (L+), and Phi19 mm cage with internal end ring (S+). Bone mineral density of whole vertebral body was measured by dual energy radiograph absorptiometer (DXA). Peripheral quantitative computed tomography was used to determine local bone mineral density of subchondral cancellous bone of vertebral body. Each cage was compressed on vertebral endplate via a specially designed device connected to a material testing machine. Maximum load and stiffness of the interface between the cage and vertebra were measured from load-deformation data in quasi-static compression loading with a loading rate of 0.5 mm/min. Relationships between the mechanical properties and vertebral bone mineral densities were evaluated. In 11 specimens acoustic emission during compression loading was measured and simultaneously recorded in load-deformation data. After the mechanical test microradiograms of midsagittal sections of the vertebrae were taken to observe failure patterns of endplate or trabecular bone. RESULTS: Vertebrae compressed with large cages (group: L- or L+) showed greater maximum load than those compressed with small cages (group: S- or S+). The internal end ring contributed to higher maximumload. The size of the cage or the internal end ring, however, did not have any effect on stiffness. Maximum load and stiffness were positively correlated with whole vertebral bone mineral density measured by dual energy radiograph absorptiometer or local cancellous bone mineral density of subchondral bone measured by peripheral quantitative computed tomography. Correlation coefficient and P value were more significant in the association of the mechanical properties and subchondral bone mineral density measured by peripheral quantitative computed tomography than in the association of the parameters and whole vertebral bone mineral density measured by DXA. A load-deformation curve with an acoustic emission event count rate showed that significant acoustic emission signals were generated around maximum load. On microradiographic study most vertebrae compressed with the cage showed encroachment of the cage spikes into the endplate or trabecular structure, preserving structures of the most central portion of the vertebrae. CONCLUSION: A titanium mesh cage with larger diameter and/or augmentation of internal end ring produces a significant increase of the interface strength between the cage and the vertebra. A positive correlation between the interface strength and vertebral bone mineral density suggests that vertebral bone mineral density is an important parameter for successful spinal reconstruction, and also implies that in severe osteoporotic spine the stability of the cage is declined, and other instrumentation should be combined.

Aged↗
PubMedDate not supplied

Ultrasound-guided facet joint injections in the middle to lower cervical spine: a CT-controlled sonoanatomic study.

OBJECTIVES: The aim of this study was to investigate the efficacy of ultrasound as a guiding tool for simulated cervical facet joint injections in cadavers. METHODS: A total of 40 ultrasound examinations at 5 levels (C6-7 to C2-3) were performed on 4 embalmed cadavers. The zygapophyseal joints were located with ultrasound. First, the transverse processes of C6 and C7 were established and the facet joint of C6-7 was demonstrated. The midpoint of this joint space, defined as the middle of its cranio-caudal extension on its lateral surface, was taken as a reference point. Ipsilateral distances (A, B, C, and D) between this point and each one of the 4 facet joints of the cervical spine up to the facet joints C2-3 were then computed. Subsequently, coronal computed tomography (CT) scans were taken to verify these distances. In a second experiment, a spinal needle was advanced under ultrasound guidance to the zygapophyseal joints from C2-3 to C6-7 on both sides of 1 cadaver. The exact placement of the needle tips was again verified by CT. RESULTS: In 4 attempts, a depiction of the joint space was not possible. Ultrasound and CT provided the same mean measurements of 1.2+/-0.2 cm, 2.0+/-0.3 cm, 3.0+/-0.2, and 4.0+/-0.5 cm for distances A, B, C, and D, respectively. All 10 needle tips were located in the joint space during simulated facet joint injections, as also verified by CT. DISCUSSION: This preclinical study suggests that ultrasound is a useful guiding tool for facet joint injections in the cervical spine.

Cervical Vertebrae↗
PubMed2003

The proximal tibiofibular joint: an anatomic study.

In the first stage of the current study, 14 fresh specimens from above-the-knee amputations were examined by magnetic resonance imaging arthrography. In the second part of the study, these amputation specimens and 38 embalmed knees from cadavers were dissected. The types of the joint and insertion of the biceps femoris tendon and the other structures were observed. Of 14 fresh specimens from above-the-knee amputations examined by magnetic resonance imaging arthrography, nine had a clear communication between the proximal tibiofibular joint and the knee. It was difficult to distinguish the anterior tibiofibular ligament in 30 specimens as a separate band because it was fused intimately with the biceps femoris tendon. Of these specimens, 24 had an oblique type of joint. Because of this communication, the proximal tibiofibular joint might be construed as the fourth compartment of the knee to explain subtle knee problems.

Amputation, Surgical↗
PubMed2005

Standard multiplanar fluoroscopy versus a fluoroscopically based navigation system for the percutaneous insertion of iliosacral screws: a cadaver model.

OBJECTIVES: To compare the safety and efficiency of standard multiplanar fluoroscopy (StdFluoro) and virtual fluoroscopy (VirtualFluoro) for use in the percutaneous insertion of iliosacral screws. DESIGN: : Human cadaver study comparing 2 imaging modalities during iliosacral screw insertion; imaging randomized from side to side. SETTING: Bioskills laboratory in a medical school. PARTICIPANTS: Twenty-nine embalmed whole human cadavers without prior hip or pelvic surgery. INTERVENTION: Iliosacral screws were inserted into the S1 bodies using a percutaneous insertion technique. Screws were inserted on one side using StdFluoro, and on the other side, screws were placed using VirtualFluoro. MAIN OUTCOME MEASUREMENTS: Time necessary for imaging preparation, screw insertion, and actual fluoroscopy were recorded. Accuracy and safety of screw placement was assessed using computed tomography and an anatomic dissection of the pelvis. RESULTS: : Fifty-six of 58 iliosacral screws were placed within the desired bony corridor of the posterior pelvis. One screw placed using each method was inserted erroneously, but both were relatively minor deviations. There were no obvious injuries to major vessels or nerve roots. The total surgical time required for preparation of imaging and screw insertion averaged 7.3 minutes using StdFluoro and 6.7 minutes using VirtualFluoro (P = 0.4). Although the time necessary for screw insertion using VirtualFluoro averaged only 3.5 minutes, compared to 7.0 minutes for StdFluoro (P < 0.05), this time savings was offset by that required for application and calibration of tracking devices when using VirtualFluoro. The average fluoroscopy time using StdFluoro method was 26 seconds, whereas that for the VirtualFluoro was only 6 seconds (P < 0.01). CONCLUSIONS: Most of the percutaneous iliosacral screws were safely inserted using StdFluoro and VirtualFluoro, and total surgical times were similar using both methods. As VirtualFluoro continues to evolve, improved efficiency in operative times may be expected. Currently, the most beneficial aspect of using VirtualFluoro during the insertion of percutaneous iliosacral screws appears to be significantly decreased use of fluoroscopy when compared to StdFluoro.

Aged↗
PubMed2005

The effect of locked distal screws in retrograde nailing of osteoporotic distal femur fractures: a laboratory study using cadaver femurs.

OBJECTIVES: To examine the effects of locked distal screws in retrograde nails used in unstable osteopenic distal femur fractures. DESIGN: Biomechanical testing of paired human cadaveric femurs. INTERVENTION: Seven matched pairs of embalmed, moderately osteopenic cadaver femurs were instrumented with 12-mm intramedullary nails in a statically locked, retrograde fashion. One femur of each pair had locked distal screws and the other femur had unlocked distal screws. A 2.5-cm gap of bone was cut nine centimeters from the distal condyles to simulate an unstable fracture. The locked distal screw nails were compared to unlocked distal screw nails for collapse of the fracture gap, medial-lateral and anterior-posterior translation of the nail within the fracture site, and fracture angulation. The femurs were axially loaded, cycled, and then loaded to failure. MAIN OUTCOME MEASURES: Motion at the fracture site with axial cyclic loading and site of failure when loaded to failure. RESULTS: After cycling, both locked distal screw and unlocked distal screw nails demonstrated several millimeters medial and anterior translation within the fracture site and approximately 1 mm collapse of the fracture gap. Although no statistically significant differences were found, the locked distal screw nails had less anterior and medial translation, angulation, and collapse of the fracture gap after cycling. Loads to failure were similar for both locked distal screw and unlocked distal screw nails. It was noted that proximal femur failure occurred at the level of the proximal screw hole in the nail at the subtrochanteric level in 7 (4 locked distal screws and 3 unlocked distal screw groups) of the 14 samples. Four other samples failed through the intertrochanteric region (2 locked distal screw and 2 unlocked distal screw groups) and the remainder within the distal fragment by fracture of the femur along the medial cortex. CONCLUSIONS: Although most differences in fixation stability were not significant, the locked distal screw nails exhibited less fracture collapse and anterior and medial translation of the nail at the fracture site than the unlocked distal screw nails. The degree of varus angulation after cyclic loading was also less for the locked distal screw nails. The length of the nail chosen should avoid having proximal locking screws distal to the lesser trochanter, thus averting proximal femur stress risers and fractures.

Bone Screws↗
PubMed2005

Impaired forearm rotation after tension-band-wiring fixation of olecranon fractures: evaluation of the transcortical K-wire technique.

The tension-band-wiring technique is a well-accepted method of internal fixation of olecranon fractures. In addition, it is suggested that transcortical placement of the k-wires results in lower rates wire migration. We encountered two clinical cases in which transcortical placement of the k-wires led to impairment of forearm rotation. An anatomic study was conducted to study the effect of transcortical wire placement to avoid similar future complications. Using specimens from 10 embalmed cadavers, we found that transcortical wires inserted in <30 degrees of ulnar angulation in the coronal plane to the medial ridge of the olecranon, impinged on the radial neck, supinator muscle, or biceps tendon. This was avoided in all 10 specimens when the wires were inserted, with the forearm in supination, at 30 degrees of ulnar angulation. We recommend this technique to be adopted to avoid forearm rotation impairment.

Bone Wires↗
PubMedDate not supplied

A critical analysis of the eccentric starting point for trochanteric intramedullary femoral nailing.

OBJECTIVES: Antegrade femoral intramedullary nailing through a greater trochanteric insertion site has been proposed for the treatment of subtrochanteric fractures. The currently available trochanteric nails have dissimilar characteristics, and the most appropriate insertion site for satisfactory subtrochanteric fracture alignment has not been determined. This study is an analysis of 5 different trochanteric femoral nails and 3 different insertion sites using a cadaveric model of a reverse obliquity subtrochanteric femur fracture to determine the optimal trochanteric entry site. SETTING: OSHA-approved cadaveric laboratory with an OEC 9800 (General Electric Company, Fairfield, CT) fluoroscopic C-arm. METHODS: Twenty-one embalmed human cadaveric femurs were stripped of soft tissues. Three different starting points on the anteroposterior radiograph were used: at the tip of the greater trochanter, and 2 to 3 mm medial and lateral to the tip. A reverse obliquity subtrochanteric fracture was created. The Trochanteric Antegrade Nail (TAN), Gamma nail (2nd and 3rd generations), Trochanteric Fixation Nail (TFN), and the Holland Nail were then inserted. The proximal bend and radius of curvature were calculated for each nail. Varus and valgus angulation as well as lateral gapping were measured on radiographs; also calculated were the mean, range, and standard deviation. Statistical analysis was performed on angulation and gapping at the fracture site by using Fisher least significant differences analysis, based on a 2-way ANOVA test. RESULTS: The Holland nail had a proximal bend of 10 degrees and a radius of 300 cm. TAN was 5 degrees and 350 cm, TFN was 6 degrees and 150 cm, Gamma 2 was 4 degrees and 300 cm, and Gamma 3 was 4 degrees and 200 cm. The tip starting point led to the most neutral alignment regardless of nail. The lateral starting point led to varus with all nails. The medial starting point led to valgus of >6 degrees with the Holland and TFN; Gamma and TAN had better alignment with <4 degrees of valgus. Gapping of the lateral cortex was greatest with a lateral starting point. CONCLUSIONS: An analysis of 5 trochanteric intramedullary nails with different proximal bends and 3 different starting points in the greater trochanter showed that the tip of the trochanter is close to the "universal" starting point. In this cadaveric subtrochanteric fracture model, the tip starting point led to the most neutral alignment regardless of nail used. The lateral starting point led to varus and gapping of the lateral cortex with all nails. CLINICAL RELEVANCE: Subtrochanteric fractures treated with a trochanteric antegrade nail should have an acceptable reduction before nail insertion. The tip of the trochanter, or even slightly medial, on anteroposterior fluoroscopy is recommended as the universal starting point for these nails. However, slight deviations from this point and nail geometry can cause fracture site malalignment. A lateral starting point led to varus alignment and should be avoided.

Bone Nails↗
PubMed2006

Fixation of periprosthetic femoral shaft fractures associated with cemented femoral stems: a biomechanical comparison of locked plating and conventional cable plates.

UNLABELLED: To determine which of 2 techniques for the treatment of periprosthetic femoral shaft fractures is of greater stiffness. DESIGN: A laboratory study using 8 pairs of matched, embalmed femurs. METHODS: Femurs implanted with a cemented total hip prosthesis had a simulated periprosthetic femur fracture created distal to the implant. Fractures were fixed with a plate with locked screws or a plate with cables (Ogden construct). Fixation stability was compared in various loading modalities before and after cycling. Failure in torsional loading was then determined. The cement mantle was tested for crack propagation that may have occurred secondary to locked screw insertion and loading. OUTCOME MEASUREMENTS: Fixation stiffness (the ratio of applied load to displacement at the fracture site), torsional strength, mode of failure for each system, and cement mantle evaluation for cracks after screw insertion. RESULTS: Locked plating was stiffer than the Ogden construct in pre- and post-cyclic axial loading and torsion. There was no difference in lateral bending stability or torsional failure loads. CONCLUSIONS: Locked plating constructs were stiffer than the Ogden construct in axial loading and torsion. Although no differences in loads to failure during torsion were noted, locked plating constructs exhibited catastrophic failure not observed with the Ogden construct.

Arthroplasty, Replacement, Hip↗
PubMed2002

Image-guided spine surgery: a cadaver study comparing conventional open laminoforaminotomy and two image-guided techniques for pedicle screw placement in posterolateral fusion and nonfusion models.

STUDY DESIGN: A randomized comparison of conventional and image-guided technology techniques for pedicle screw placement was performed. OBJECTIVE: To evaluate the accuracy of thoracolumbosacral pedicle screw placement in simulated posterior fusion and nonfusion models via conventional and image-guided surgical techniques. SUMMARY OF BACKGROUND DATA: Computer-assisted image-guided technology has been promoted as a means for theoretically improving the accuracy of spinal instrumentation placement, especially when visual landmarks are obscured. METHODS: Seven embalmed cadaveric spines were cleared of all posterior soft tissue and mounted. The posterior elements of four spines were obscured so as to simulate a fusion mass using a synthetic bone cement. Three nonobscured spines also were instrumented. Pedicle screws were placed from T6 to S1 in two obscured specimens (24 screws) using a computer-assisted image-guided system, in one obscured specimen from T6 to S1 (12 screws) using a fluoroscopically assisted system, and in one obscured specimen from T6 to S1 (14 screws) using a conventional open laminoforaminotomy technique. In addition, pedicle screws were placed from T6 to S1 using a fluoroscopically assisted technique in two unobscured specimens (36 screws), and from from T6 to S1 (14 screws) via a laminoforaminotomy technique in one unobscured specimen. Pedicle violation was assessed by computed tomography scanning and direct visual inspection. The degree of screw misplacement noted visually was quantified with an electronic caliper. RESULTS: Pedicle screws placed via open laminoforaminotomy resulted in a pedicle cortex breach rate of 21.43% in fused specimens and 14.29% in nonfused specimens. Screws placed in the nonfused model (two cadavers) via fluoroscopically assisted methods had pedicle cortical breaches, respectively, in 6.25% and 10% of the specimens, whereas the same method was noted to have a 8.33% violation rate in the fusion model. Finally, computed tomography-based image-guided placement through a simulated fusion mass resulted in no pedicle wall violations. CONCLUSIONS: Accuracy of pedicle screw placement in the thoracolumbosacral spine is improved with the use of image-guided methods, particularly guidance by computed tomography. This is especially relevant clinically when the anatomy is obscured or altered as a result of inflammatory spondyloarthropathy (e.g., ankylosing spondylitis in which spontaneous fusions obscure surgical landmarks for pedicle access), or when used postsurgically in the setting of a posterolateral fusion.

Bone Screws↗
PubMed2004

Tensile transmission across the lumbar fasciae in unembalmed cadavers: effects of tension to various muscular attachments.

STUDY DESIGN: Traction was applied to muscles attaching to the posterior and middle layers of lumbar fascia (PLF, MLF). Effects on fasciae were determined via tensile force measures and movement of markers. OBJECTIVES: To document tensile transmission to the PLF and MLF when traction was applied to latissimus dorsi (LD), gluteus maximus (GM), external and internal oblique (EO, IO), and transversus abdominis (TrA) in unembalmed cadavers. SUMMARY OF BACKGROUND DATA: A previous study on embalmed cadavers applied traction to muscle attachments while monitoring fascial movement but did not test TrA or the MLF. METHODS: The PLF and MLF were dissected then marked on eight unembalmed cadavers. A strain gauge was inserted through fascia at L3; 10N traction was applied to each muscle attachment while photographs and tension measures were taken. Movement of fascial markers was detected photographically. Fascial widths were also measured. RESULTS: Tension was clearly transmitted to fascial vertebral attachments. Tensile forces and fascial areas affected were highest for traction on LD and TrA in the PLF and for TrA in the MLF. Movement of PLF markers from tension on LD and TrA occurred bilaterally between T12 and S1. Effects from other muscles were variably bilateral, with those from GM and IO occurring below L3 and those from EO occurring above L3. Tensile forces were relatively high in the MLF and its width was less than half that of the PLF. CONCLUSIONS: Low levels of tension are effectively transmitted between TrA and the MLF or PLF. Via them, TrA may influence intersegmental movement.

Aged↗
PubMed2004

The anterior dural (Hofmann) ligaments.

STUDY DESIGN: A dissection-based study of 18 embalmed cadavers (7 male, 11 female), mean age 84 (+/-8.4) years. OBJECTIVE: To determine the morphology and morphometry of the anterior dural (Hofmann) ligaments. SUMMARY OF BACKGROUND DATA: The attachment of the posterior longitudinal ligament to the dura mater is poorly understood. Anterior dural ligaments connect the anterior dura to the deep layer of the posterior longitudinal ligament, but appear to be limited to the lumbar region and have been observed to have a craniocaudal orientation. Their function is reported to help in supporting and protecting the dural sac and spinal cord. METHODS: The spinal canal was opened exposing the dural sac, the spinal nerve roots incised, and spinal cord removed to mobilize the dural sac and gain access to Hofmann ligaments. The extent, orientation, length, and level of origin and insertion of the ligaments were documented. RESULTS: The orientation of the ligaments changed from caudocranial (dura to posterior longitudinal ligament) at upper thoracic levels to transverse at the level of T8-T9 to craniocaudal at lower thoracic and lumbar levels, often with multiple ligaments being present at a single level. Ligament length varied from 0.5 to 28.8 mm and was positively correlated with vertebral level and negatively correlated with orientation. CONCLUSIONS: Hofmann ligaments are present at most levels between C7 and L5; although most ligaments were limited to a single vertebral segment, some were observed to cross several segments.

Aged↗
PubMed2005

Extraforaminal ligament attachments of human lumbar nerves.

STUDY DESIGN: An anatomic study of the extraforaminal attachments of the lumbar spinal nerves was performed using human lumbar spinal columns. OBJECTIVES: To identify and describe the existence of ligamentous structures at each lumbar level that attach lumbar spinal nerves to structures at the level of the extraforaminal region. SUMMARY OF BACKGROUND DATA: During the last 120 years, several mechanisms to protect the spinal nerve against traction have been described. All these structures involved are located in the spinal canal, proximal to the intervertebral foramen. METHODS: Five embalmed human lumbar spines (T12-S1) were used. Bilaterally, the extraforaminal region was dissected to describe and measure anatomic structures and their relationships. Histology was performed with staining on the sites of attachment and along the ligament. RESULTS: The levels T12-L2 show bilaterally 2 ligaments, a superior extraforaminal ligament and an inferior extraforaminal ligament. The superior extraforaminal ligament emerges from the joint capsule of the facet joints and inserts in both, the intervertebral disc and the ventral crista of the intervertebral foramen, passing the spinal nerve laterally. In one specimen on level L2-L3, the superior extraforaminal ligament is not attached to the spinal nerve. The inferior extraforaminal ligament emerges from the intervertebral disc, passing the nerve medially and attaching the spinal nerve. At the levels L2-L5, the inferior extraforaminal ligaments are only attached to the intervertebral disc, not to the joint capsule. Histologically, the ligaments consisted of mainly collagenous structures. CONCLUSION: Ligamentous connections exist between lumbar extraforaminal spinal nerves and nearby structures.

Aged, 80 and over↗
PubMed2005

Vibration characteristics of the human spine under axial cyclic loads: effect of frequency and damping.

STUDY DESIGN: A nonlinear finite element model of lumbar spine segment L3-L5 was developed. The effects of upper body mass, nucleus injury, damping, and different vibration frequency loads were analyzed for the whole body vibration. OBJECTIVES: To analyze the influence of whole body vibration on facets of lumbar spine and to analyze the influence of nucleus injury, upper body mass, and damping on the dynamic characteristics of lumbar spine. SUMMARY OF BACKGROUND DATA: Many studies have investigated whole body vibration for lumbar spine. However, very few investigations analyzed the influence of whole body vibration on facets and vibration characteristics of the injured spine. METHODS: The nonlinear finite element model of the L3-L5 segment was constructed based on the embalmed vertebra geometry and validated. Besides static and modal analyses, transient dynamic analyses were also conducted on the model with an upper body mass under damping and different frequency cyclic loads. RESULTS: In the period of human spine vibration, the vibration effects of different regions of the lumbar spine are not the same. Anterior regions of the L3-L5 segment show small vibration amplitudes, but posterior regions show large amplitudes. The vibration amplitude of facet contact force is more than 2.0-fold as large as that of displacement and stress on vertebrae or discs. To decrease the weight of the upper body will increase the resonant frequency. To remove the nucleus will decrease the resonant frequencies. The vibration displacement, stress, and facet contact force will reduce generally by 50% using damping ratio 0.08. CONCLUSIONS: The posterior regions of intervertebral discs of the lumbar spine are easy to injure during long-term whole body vibration compared to anterior regions. The vibration of human spine is more dangerous to facets, especially during whole body vibration approximating a sympathetic vibration, which may lead to abnormal remodeling and disorder of the lumbar spine.

Cadaver↗
PubMed2006

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.

Aged↗