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PubMed2006

Variations in the cerebral venous anatomy and pitfalls in the diagnosis of cerebral venous sinus thrombosis: low field MR experience.

BACKGROUND: Knowledge of variations in the cerebral venous anatomy and apparent signal abnormalities seen on Magnetic resonance (MR) angiography are essential to avoid over-diagnosis of cerebral venous sinus thrombosis (CVST), while interpreting the MR angiograms. AIMS: To evaluate the variations of cerebral venous anatomy and signal abnormalities by using 3D phase contrast MR angiography performed in a 0.5 Tesla MRI scanner. MATERIALS AND METHODS: One hundred patients who underwent MR imaging and MR angiography examinations at our institution from March 2004 to February 2005, with normal MR imaging of brain were studied retrospectively. Patients with clinical suspicion of CVST and patients who underwent color doppler evaluation for suspected deep vein thrombosis were excluded. RESULTS: The superior sagittal, straight sinus and the internal cerebral veins were visualized in all patients. There was hypoplasia of the right transverse sinus in 13 patients, left transverse sinus in 35 patients, right sigmoid sinus in 6 patients and left sigmoid sinus in 19 patients. Absence of transverse sinus on left side was observed in one patient and absence of sigmoid sinus in 2 patients on left side. Flow gaps were observed in non-dominant transverse sinus, sigmoid sinus as well as transverse sigmoid sinus junctions. The occipital sinus was visualized in 17 patients. CONCLUSIONS: MR angiography done at low field strengths is also a reliable method, for assessing cerebral venous sinuses. Awareness of the normal anatomical variations of venous sinuses and apparent MR angiographic flow gaps prevent misdiagnosis of cerebral venous sinus thrombosis.

Adolescent↗

PubMed2000

Computed tomographic cephalometric analysis of Chinese patients with obstructive sleep apnoea.

Variations of craniofacial and upper airway structures are recognized to contribute to the phenomenon of obstructive sleep apnoea (OSA). Most previous cephalometric studies were performed using erect lateral radiographs in Caucasian patients. The present project aims to determine cephalometric measurements, utilizing CT, in normal Chinese subjects and in Chinese patients with OSA. Computed tomography of 25 patients with OSA (proven using overnight polysomnography), and of 25 age-, sex-, height-, bodyweight- and body mass index (BMI)-matched control subjects were prospectively performed. Thirteen standard bony and soft-tissue measurements were obtained from the CT lateral scout view of the head and neck, taken with each subject in the neutral supine position. The cross-sectional area was calculated at two axial levels (velopharynx and hypopharynx). The measurements in the two groups, OSA and control subjects, were compared. The measurements for hyoid position (P = 0.00), nasal cavity length (P = 0.01), mandibular prognathism (P = 0.05), tongue size (P = 0.02), oropharyngeal airway space (P = 0.02), posterior tongue airway space (P = 0.04) and cross-sectional areas at the level of the velopharynx (P = 0.00) and hypopharynx (P = 0.01) differed significantly between the two groups. In conclusion, CT cephalometric measurements show that certain anatomical variations in the head and neck are likely to contribute to the pathogenesis of OSA in Chinese patients.

Adult↗

PubMed2003

Angiographic manifestations and operative findings with 70 cases of hemifacial spasm: relation of common trunk anomalies.

The relations between angiographic manifestations and operative findings of hemifacial spasm were studied in 70 cases between 1988 and 2001. Vertebral angiography was performed, and Towne, straight AP, and lateral projections were routinely examined. The dominant anterior inferior cerebellar artery (AICA) directly compressed the facial nerve root exit zone in 26 cases, the dominant posterior inferior cerebellar artery (PICA) in 20, the AICA in 13, the PICA in 2, and the vertebral artery (VA) in 9. Compression by multiple vessels was observed in 11 cases. Anatomical variations of the affected AICA and PICA were classified into 3 groups according to their origins and distributions of blood supply: normal distribution of AICA and PICA in 18%, common trunk anomaly with dominant AICA (basilar artery origin) in 48% and common trunk anomaly with dominant PICA (vertebral artery origin) in 34%. Analyses of the angiograms revealed significantly increased numbers of common trunk anomalies compared with cases with normal angiograms. In 18 of the 20 cases of unilateral common trunk anomalies, facial nerves were compressed by the dominant artery. Preoperative vertebral angiograms may clarify the offending vessels and their sites in most hemifacial spasm cases, thus increasing the safety of surgical interventions.

Adult↗

PubMed1997

Rat strain and vendor differences in collateral anastomoses.

Recently we observed inter- and intrastrain differences in cortical infarct volumes after middle cerebral artery (MCA) occlusion. Variations in the anastomoses providing collateral blood supply could account for different lesion sizes. Our objectives were to compare number and internal diameters of the MCA-anterior cerebral artery (MCA-ACA) anastomoses and to determine if the lesion extended beyond branches of the MCA territory into the field of the ACA in the rat strains/lines. Sprague-Dawley rats and Wistar rats from Simonsen Laboratories (SLSD and SLWIS) and Sprague-Dawley rats from Taconic Laboratories (TLSD) and Charles River Laboratories (CRSD) were anesthetized and injected with papaverine and Vultex (white latex) for arterial visualization. Some rats were also subjected to MCA occlusion. Significantly fewer anastomoses were present in SLSD and SLWIS than in CRSD and TLSD (p < 0.05). The mean internal diameters of the anastomoses were not significantly different between the strains/lines (p < 0.05). After MCA occlusion, significantly more (p < 0.05) TLSD and CRSD than SLSD had lesions extending from the MCA field beneath the anastomoses and into the region supplied by the ACA. Neither the number, luminal diameter, nor density of MCA-ACA anastomoses appears to be the limiting factor that differentiates lesion size following MCA occlusion in these particular rat strains/lines. Therefore, factors other than anatomical variations probably account for different lesion sizes.

Animals↗

PubMed2026

Failure modes and effects analysis for clinical implementation of online adaptive radiotherapy: A systematic review.

BACKGROUND: The accuracy of radiotherapy is limited by anatomical variations occurring over time scales ranging from sub-seconds to days. Online Adaptive Radiotherapy (OART) addresses this by enabling daily plan adaptation based on real-time imaging. While OART offers improved dose conformity, its dynamic, time-constrained workflow introduces novel failure modes that challenge traditional quality assurance protocols. PURPOSE: This study aims to synthesize the existing literature on Failure Modes and Effects Analysis (FMEA) for OART to systematically catalog risks and identify mitigation strategies. METHODS: A systematic literature search was conducted to identify studies applying FMEA to OART workflows. Eleven studies were included, covering MR-guided (ViewRay MRIdian, Elekta Unity), CBCT-guided (Varian Ethos), and MR-enhanced C-arm linac systems. To address heterogeneity in risk scoring methodologies (e.g., TG-100 10-point scales vs. 5-point rankings), extracted failure modes were harmonized into a standardized three-tier risk classification system (Class I: Low, Class II: Intermediate, Class III: High). RESULTS: A total of 300 unique failure modes were identified, with 49.6 percent classified as high-risk (Class III). Analysis revealed that the majority of high-risk failures were concentrated in the online treatment delivery phase, specifically within human-computer interactions and anatomical contouring steps. CONCLUSIONS: This study supports the development of tailored, robust QA frameworks that prioritize human factors and process consistency to guide safe implementation in diverse clinical settings.

Humans↗

PubMed1987

Regional resistivity variations in lens homogenates.

The response of the lens to changes in the distribution and concentration of electrolytes can be measured by characterizing the changes in resistivity that occur secondary to variations in intracellular composition. Regional intracellular cytoplasmic resistivities of lens fiber cells can be approximated by homogenates isolated from the cortex and nucleus of the lens. The cortical, transitional, and nuclear calf lens homogenate resistivities at physiologic water concentrations were established to be 186.04 +/- 12.79, 297.69 +/- 18.95, and 421.74 +/- 69.64 omega cm respectively. The physiologic water content of the calf lens is 70.25 +/- 0.94% in the cortex and 54.33 +/- 1.28% in the nucleus. These data suggest that the increasing cortico-nuclear resistivity gradient is accompanied by a decreasing electrolyte concentration and a progressive cortico-nuclear dehydration. The corresponding mature bovine cortical and nuclear homogenate resistivities are 204.82 +/- 13.92 and 628.30 +/- 111.81 omega cm. When compared with calf homogenates the mature bovine cortical resistivity is nearly identical; while the elevated nuclear resistivity is attributable to a continual nuclear dehydration that occurs secondary to aging. Resistivity measurements performed on decapsulated lens homogenates reveal a close correspondence between calf and human lenses. Whereas, the elevated resistivity of the mature bovine decapsulated lens homogenate is attributable to a progressively dehydrated nucleus that increases in size with age. Supplementary data gathered from hydration and dehydration experiments performed on cortical and nuclear homogenates were used to characterize anatomical variations in resistivity as a function of total water content. These data indicate that the resistivity of the cortical homogenate is inversely proportional to the electrolyte concentration, whereas the resistivity of the nuclear homogenate is primarily dependent upon the mobilities of the electrolyte species with the highest concentrations. As the water concentration of the nuclear homogenate is increased to non-physiologic levels the resistivity becomes concentration-dependent, and is no longer is no longer dominated by the mobility.

Aging↗

PubMed2007

Piriformis muscle: clinical anatomy and consideration of the piriformis syndrome.

Patients with lumbosacral and buttock pain provide tacit support for recognizing the piriformis muscle as a contributing factor to the pain (piriformis syndrome). One hundred and twelve cadaveric specimens were observed to elucidate the anatomical variations of the piriformis muscle referred to the diagnostic and treatment of the piriformis syndrome. The distance between the musculotendinous junction and the insertion was measured and the piriformis categorized into three types: Type A (71, 63.39%): long upper and short lower muscle belly; Type B (40, 35.71%): short upper and long lower muscle belly; Type C (1, 0.9%): fusion of both muscle bellies at the same level. The diameter of the piriformis tendon at the level of the musculotendinous junction ranged from 3 to 9 mm (mean: 6.3 mm). The piriformis showed the following possible fusions with adjacent tendons. In type one (60, 53.57%) a rounded tendon of the piriformis reached the upper border of the greater trochanter. In type two (33, 29.46%) it first joined into the gemellus superior tendon and at last both fused with the obturator internus tendon and inserted into the medial surface of the greater trochanter. A fusion of the piriformis, obturator internus and gluteus medius tendon with the same insertion area as above was observed in type three (15, 13.39%) and finally in type four (4, 3.57%) the tendon fused with the gluteus medius to reach the upper surface of the greater trochanter. Based on this survey anatomical causes for the piriformis syndrome are rare and a more precise workup is necessary to rule out more common diagnosis.

Adult↗

PubMed2007

Anatomy of the clavicle and the intramedullary nailing of midclavicular fractures.

Intramedullary fixation is used increasingly to treat clavicular fractures. Anatomical variations in the clavicle of relevance to this procedure are analyzed. The length, diameters and curvature of the clavicle were measured in 196 specimens from the dissecting room. The calcium bone density was analyzed in 300 cross-sectional samples of 100 specimens. The thickness of cortical and medullary bone of 70 slices was analyzed from freshly plastinated clavicles with implants in place. The female clavicle was shorter, less curved, and had a lower concentration of calcium than the male clavicle. Measurement of cortical thickness showed a mean value of 1.05 +/- 0.23 mm at the most sternal measuring point, 2.05 +/- 0.29 mm at the midpoint of the clavicle, and 0.95 +/- 0.35 mm at the acromial end. The thinnest regions were the medial ventral cortex and the dorsal acromial cortex. These measurements explain clinical observations on nail perforation. The diameter of the medullary canal measured 6.7 +/- 2.6 mm at its narrowest part, so that reaming (i.e., predrilling the medullary canal) prior to 3.5 mm titanium nail insertion is not necessary. The main difficulties encountered when placing a nail are secondary to the S-curvature of the clavicle. In 80% of fractures, the break is located at the narrowest diameter of the medullary canal. Thus, the clavicle displays definite gender- and side-specific anatomical features in terms of length, diameter, curvature, and calcium concentration. These should be considered when performing intramedullary fixation.

Adult↗

PubMed2002

Depicting cerebral veins by three-dimensional CT angiography before surgical clipping of aneurysms.

BACKGROUND AND PURPOSE: Cerebral veins show wide variation, and unexpected veins occasionally limit surgical procedures for clipping of cerebral aneurysms. This study was undertaken to assess the utility of three-dimensional CT angiography (3D-CTA) in the evaluation of venous anatomy before surgical clipping of cerebral aneurysms. METHODS: 3D-CTA was performed in 19 patients before pterional craniotomy. The venous anatomy visualized by use of 3D-CTA was compared retrospectively with intraoperative findings. RESULTS: 3D-CTA clearly depicted the superficial sylvian veins (SSVs) in 17 of 19 cases. In three of these 17 cases, 3D-CTA failed to reveal the additional connecting veins from SSVs to the midportion of the sphenoid wing. 3D-CTA also depicted bridging veins from: 1) the basal vein of Rosenthal to the sphenoparietal sinus (SPS) (three cases); 2) a junction of the anterior cerebral vein and the deep middle cerebral vein to the SPS (two cases); 3) the anterior cerebral vein into the cavernous sinus (one case); and 4) the deep middle cerebral vein to the cavernous sinus in one case. Surgical findings corresponded well with the angiographic findings. 3D-CTA depicted bridging veins from the frontal base into the SPS in two cases; retraction of the frontal lobe was severely limited in these cases. 3D-CTA also exhibited anatomic variation of deep cerebral veins, which suggests the utility of 3D-CTA in evaluating the risks carried by sacrifice of some bridging veins. In two patients, aneurysmal dissection was restricted because of adhering veins. 3D-CTA depicted these cerebral veins to be lying in contact with the aneurysm. In one case, the contiguous vein was hidden behind a large middle cerebral artery aneurysm; 3D-CTA was helpful for visualization of this vein. CONCLUSION: 3D-CTA can clearly depict the venous anatomy of the brain and is useful for surgical planning of a pterional or temporopolar approach for cerebral aneurysms.

Adult↗

PubMed1995

The anatomy of the inferior petrosal sinus, glossopharyngeal nerve, vagus nerve, and accessory nerve in the jugular foramen.

PURPOSE: To define the variations of the courses of the cranial nerves and the inferior petrosal sinuses as they enter and traverse the jugular foramen. METHODS: Thirty-nine cadaveric specimens containing the jugular foramen were scanned with 1-mm contiguous axial and coronal CT sections. Each specimen was dissected to evaluate the position of the cranial nerves and inferior petrosal sinus as they entered the jugular foramen. RESULTS: The glossopharyngeal nerve entered the most superior, anterior, and medial aspect of the jugular foramen and descended in the anterior portion of the jugular foramen, often within a groove. The vagus and accessory nerves could not be separated by CT. They entered the jugular foramen most often anterior or anterior and inferior to the jugular spine of the temporal bone and descended in a position ranging from medial to anterior to the jugular vein. The inferior petrosal sinus most often coursed inferior to the horizontal portion of the glossopharyngeal nerve and entered the jugular system in the jugular foramen, at the exocranial opening or below the skull base. A pars nervosa and pars venosa could be identified only at the endocranial opening, where the jugular spine separated the pars nervosa containing the inferior petrosal sinus and three cranial nerves from the pars venosa containing the jugular vein. CONCLUSION: Our evaluation demonstrated anatomic variation in the area of the jugular foramen.

Accessory Nerve↗

PubMed1999

Circle of Willis collateral flow investigated by magnetic resonance angiography.

BACKGROUND AND PURPOSE: The circle of Willis (CW) is considered an important collateral pathway in maintaining adequate cerebral blood flow in patients with internal carotid artery (ICA) obstruction. We aimed to investigate the anatomic variation of the CW in patients with severe symptomatic carotid obstructive disease and to analyze diameter changes of its components in relation to varying grades of ICA obstruction and in relation to the presence or absence of (retrograde) collateral flow. METHODS: Seventy-five patients with minor disabling neurological deficits and with ICA stenoses or occlusions were categorized into 4 groups according to the severity of ICA obstruction. This patient population reflected a relatively favorable subgroup of cerebral infarction (considering their minor neurological deficits). All subjects underwent magnetic resonance angiography, including magnetic resonance angiography sensitive to flow direction. CW morphology and the size of its components were determined and compared with those values in control subjects (n=100). RESULTS: Compared with control subjects, patients demonstrated a significantly higher percentage of entirely complete CW configurations (55% versus 36%, P=0.02), complete anterior configurations (88% versus 68%, P=0.002), and complete posterior CW configurations (63% versus 47%, P=0.04). Patients with severe ICA stenosis did not show significantly increased CW vessel diameters. Patients with ICA occlusion demonstrated a high prevalence of collateral flow through the anterior CW and significantly increased diameters of the communicating channels. Patients with bilateral ICA occlusion relied on collateral flow via the posterior CW and demonstrated a bilateral increase in posterior communicating artery diameters (P<0.05). CONCLUSIONS: The anatomic and functional configuration of the CW reflects the degree of ICA obstruction.

Adult↗

PubMed1998

Dysversion of the optic disc and axial length measurements in a presumed amblyopic population.

PURPOSE: Our purpose was to evaluate anatomic variations of eyes presumed to be amblyopic. METHOD: Computer imaging and photography of the optic discs of 205 amblyopic subjects were performed and the axial lengths of 183 of the subjects were measured. The paired optic nerve images were evaluated for symmetry of disc contours and orientation of central blood vessels to detect optic nerve head dysversion. Dysversion of the optic nerve head, which is also referred to as segmental hypoplasia, is a congenital disorder characterized by the central retinal vessels emerging temporal to the vertical midline of the disc and being directed nasally or the nerve head tilting in a vertical direction resulting in a downward or oblique tilting of the discs with the blood vessels emerging at the superior or inferior disc rim. RESULTS: Ninety-three subjects had optic nerve dysversion. There was a greater degree of anisometropia (P< or =.004) in subjects with dysversion (anisometropia factor of 2.51+/-2.15) than in the subjects with symmetric discs (anisometropia factor of 1.76+/-1.63). Axial lengths of the amblyopic eyes were significantly smaller (P<.0001) than those of the nonamblyopic eyes. There was no statistical difference (P< or =.879) in length between amblyopic eyes with dysversion and those with symmetric discs. CONCLUSION: Optic disc dysversion was identified in 45.4% of patients who were previously assumed to be amblyopic. There are anatomic malformations in the eyes of a significant proportion of the presumed amblyopic population. This suggests that, in these individuals, congenital peripheral factors rather than impaired cortical development may be responsible for decreased unilateral acuity.

Adolescent↗

PubMedDate not supplied

Foramen tympanicum, or foramen of Huschke: pathologic cases and anatomic CT study.

BACKGROUND AND PURPOSE: A persistent foramen tympanicum, or foramen of Huschke, is an anatomic variation of the tympanic portion of the temporal bone due to a defect in normal ossification in the first 5 years of life. The foramen is located at the anteroinferior aspect of the external auditory canal (EAC), posteromedial to the temporomandibular joint (TMJ). We sought to define its prevalence, location, and size on high-resolution spiral CT (HRCT). METHODS: We prospectively examined 102 consecutive HRCT studies of the temporal bone (204 ears). HRCT was performed by using 120 kV, 400 mAs, an ultra-high-resolution filter, 0.6-mm section thickness, 0.3-mm section increment, 728 x 728 matrix, and 160-mm field of view. We noted the size and location of the foramen tympanicum relative to the tympanic membrane and calculated its prevalence. Patients with focally decreased tympanic bone thickness of <1 mm at the anteroinferior EAC (between the 3- and 6-o'clock positions) were considered separately. RESULTS: We found a foramen tympanicum was found in six (4.6%) of 130 ears. Mean axial diameter was 4.2 mm, and mean sagittal diameter was 3.6 mm. Focally reduced bone thickness in the same location was found in 45 (35%) ears, with a female preponderance (P = .003). CONCLUSION: HRCT is sensitive for detection of the foramen tympanicum because of its thin sections, high spatial resolution, and multiplanar capabilities. Awareness of this anatomic entity may be useful in evaluating patients with transient otorrhea in whom no otologic cause (e.g., ear infection, TMJ disease) is identified.

Adolescent↗

PubMed1995

[Surgical anatomy of the sural nerve].

The sural nerve is generally used as a graft in nervous reconstructions due to its easy access and minimal sequelae after its withdrawal. Although this nerve presents a constancy in its topographical localization, anatomical variations are frequent. Thus, trying to determine the formation pattern of the sural nerve complex, 38 legs from 19 cadaveres were dissected. The data obtained differ from those of the literature as to the frequency of the occurrence of the two classically known patter (pattern I and II). Besides, it was possible to identify two other paterns (pattern III and IV) of the sural nerve formation not yet described The cutaneous nerve and the comunicating peroneal nerve were found in 21% of the cases. In the literature, the frequency is of 65.8% to 80%. Pattern II, where the sural nerve is originated from the medial sural cutaneous nerve, was identified in 52.6% of cases, while in the literature its frequency is of 20 to 34.2%. Pattern III, not yet described in the literature, had the sural nerve coming from the junction between the medial sural cutaneous nerve and the lateral sural cutaneous one, with a frequency of 21% of the cases. Pattern IV, also not yet described in the literature, had the sural nerve originated from the common fibular nerve in 5.2% of patients. It was also possible to identify in the sample the presence of the lateral sural cutaneous nerve (branch of the common fibular nerve) and of the peroneal communicating nerve (branch of the lateral sural cutaneous nerve) with anatomical characteristics indicating them as an alternative source of nerve grafts.

Cadaver↗

PubMed2001

Additional renal arteries: incidence and morphometry.

Advances in surgical and uro-radiological techniques dictate a reappraisal and definition of renal arterial variations. This retrospective study aimed at establishing the incidence of additional renal arteries. Two subsets were analysed viz.: a) Clinical series--130 renal angiograms performed on renal transplant donors, 32 cadaver kidneys used in renal transplantation b) Cadaveric series--74 en-bloc morphologically normal kidney pairs. The sex and race distribution was: males 140, females 96; African 84, Indian 91, White 43 and "Coloured" 18, respectively. Incidence of first and second additional arteries were respectively, 23.2% (R: 18.6%; L: 27.6%) and 4.5% (R: 4.7%; L: 4.4%). Additional arteries occurred more frequently on the left (L: 32.0%; R: 23.3%). The incidence bilaterally was 10.2% (first additional arteries, only). The sex and race incidence (first and second additional) was: males, 28.0%, 5.1%; females, 16.4%, 3.8% and African 31.1%, 5.4%; Indian 13.5%, 4.5%; White 30.9%, 4.4% and "Coloured" 18.5%, 0%; respectively. Significant differences in the incidence of first additional arteries were noted between sex and race. The morphometry of additional renal arteries were lengths (cm) of first and second additional renal arteries: 4.5 and 3.8 (right), 4.9 and 3.7 (left); diameters: 0.4 and 0.3 (right), 0.3 and 0.3 (left). Detailed morphometry of sex and race were also recorded. No statistically significant differences were noted. Our results of the incidence of additional renal arteries of 27.7% compared favourably to that reported in the literature (weighted mean 28.1%). The study is unique in recording detailed morphometry of these vessels. Careful techniques in the identification of this anatomical variation is important since it impacts on renal transplantation surgery, vascular operations for renal artery stenosis, reno-vascular hypertension, Takayasu's disease, renal trauma and uro-radiological procedures.

Adolescent↗

PubMed1997

Morphologic characteristics of human cervical pedicles.

STUDY DESIGN: Cervical pedicle morphology was investigated using manual and computed tomography measurements. OBJECTIVES: Normal anatomic variations of the cervical pedicles were measured to evaluate their safety as anchors for posterior cervical fixation systems. SUMMARY OF BACKGROUND DATA: There have been no cervical pedicle measurements on a large number of specimens. No study has ever measured the inner pedicle diameter. METHODS: Fifty-three spinal columns (C2-C7) of Euro-American origin identified by age, sex, and height (318 vertebrae or 636 pedicles) were measured using a digital caliper, a goniometer, and computed tomography scanning. RESULTS: The pedicle axis lengths were similar from C3 to C7 (except for shorter C2 pedicles). In the horizontal plane, the medial inclination of the pedicles followed the cervical spinal cord enlargement. In the sagittal plane, the pedicles were directed superiorly in the upper spine and inferiorly in the lower cervical spine. Some pedicles had no medullary canal (i.e., were solid cortical bone: 0.9% C2, 2.8% C3 and C4, and 3.8% C5 pedicles). The outer pedicle width was smaller than the height in most of the pedicles. The inner pedicle width was equal to or smaller than 2 mm in 13.2% C2, 72.6% C3, 67.0% C4, 62.3% C5, 51.9% C6, and 16.0% C7. The outer pedicle width was equal to or smaller than 4 mm in 8.5% C2, 75.5% C3, 35.8% C4, 13.2% C5 and C6, and 6.6% C7 pedicles. The thinnest pedicle cortex was always the lateral cortex, which protects the vertebral artery. Measurements of the posterior pedicle projection also were taken. CONCLUSIONS: These data provide anatomic limitations to pedicle screw use in the cervical spine.

Adult↗

PubMed2005

[Harms technique of C1-C2 fixation with polyaxial screws and rods].

PURPOSE OF THE STUDY: The Harms technique of stabilizing C1-C2 by fixation with polyaxial screws and rods is a further option for atlantoaxial fixation from the dorsal approach. Harms and Melcher published this method in 2001, but the operation had first been performed by Harms in August 1997. The aim of this study is to evaluate the first results and try to assign the Harms C1-C2 fixation an appropriate standing in the in broad range of options for stabilization of the atlantoaxial complex. MATERIAL: Between December 2002 and January 2004 we carried out the Harms fixation of C1-C2 on 22 patients admitted to the Department of Spine Surgery, Motol University Hospital, 2nd Medical Faculty in Prague. Out of these, 18 patients were included in this study, 10 men and 8 women between 23 and 84 years of age (average, 55.4 years) followed-up longer than 6 months. In 14 patients we used the Harms technique as a permanent fixation of C1-C2 in order to achieve atlantoaxial arthrodesis and, in four patients, we applied it only for a period of 4 to 6 months without the use of bone grafts or their substitutions. We employed the permanent fixation to treat the following conditions: fracture of the atlas in three patients, type IIA comminuted fracture of the dens base in three patients, fracture of C2 categorized as "other" in two patients, atlantoaxial vertical instability in one patient with rheumatoid arthritis, malunion of the fractured dens in one patient, and complicated trauma to C1-C2 in four patients. The temporary fixation was used for type III displaced fractures of the dens in two and fixed atlantoaxial rotatory dislocations also in two cases. Only one patient showed signs of Frankel C neurological deficit on admission, the rest were without neurological findings. METHODS: All screws were inserted under an image intensifier always in lateral projection. First we retracted the greater occipital nerve in a caudal direction towards C2 with a fine raspatory and, using an awl, marked the entry point in the C1 lateral mass; a pilot hole, reaching through the anterior cortical bone, was made with a 2.5 mm drill. It followed a straight or slightly convergent trajectory in an anterior-posterior direction and parallel to the plane of the C1 posterior arch in the sagittal direction. Individual anatomical variations in the atlantoaxial complex of every patient were respected. The hole was tapped through the entire vertebral body, with the exception of osteoporous bone in which only the posterior cortical bone was treated with a screw tap. At this stage profuse bleeding usually arose from dissection around the epidural venous plexus along the C1-C2 joint. This was effectively controlled by a quick insertion of a screw and compression of the venous plexus with the screw head. To control bleeding by bipolar electrocautery is difficult and is always associated with a risk of nerve injury. Screws 3.5 mm thick, with polyaxial heads, were inserted bicortically into the lateral mass of C1. Subsequently, the intervertebral C2-C3 joint was localized and its medial border in the spinal canal was palpated. The entry point for placement of a C2 pedicle screw was marked with an awl at the point of intersection at a distance of 2 mm from the medial border and 5 mm from the caudal border of the C2 articular process. Under an X-ray intensifier in lateral projection, a hole was drilled approximately parallel to the screws inserted in C1, i. e., at an angle of 20 to 30 degrees cranially, up to and through the anterior cortical bone. In the transversal plane, the screws were situated in a convergent direction at an angle of 20 to 25 degrees. After all screws had been inserted, we reduced the antlantoaxial complex in the correct anatomical position by manipulating the patient's head or by directly adjusting the screws. Connecting 3.0-mm rods were then applied and fastened by cap nuts or inner nuts according to the instrumentation used. RESULTS: Operative time ranged from 35 to 155 min, with an average of 81 min. Intra-operative blood loss ranged from 50 to 1500 ml, with an average of 560 ml. The X-ray intensifier was used for a period of 0.4 to 2.6 min, with an average of 0.9 min. A total of 36 screws were inserted in the atlas; their length ranged from 16 to 34 mm (average, 30.6 mm). All screws were positioned correctly in the C1 lateral mass; two screws did not reach up to the anterior cortical bone and one protruded over it, but without causing clinical problems. Thirty-six screws were inserted in the axis. Their length ranged from 28 to 36 mm (average, 31.7) mm). Twenty-seven screws were correctly applied through the isthmus into the C2 anterior cortical bone, three were too short to reach it and five were placed too close to the vertebral artery canal. Of these, two protruded into the artery canal, but without clinical consequences. One screw inserted too medially passed into the spinal canal, but this also was without clinical response. Of the 36 screws inserted in C2, three (8.3 %) were malpositioned. Bony fusion at C1-C2 was the goal of this operation in 14 patients. At 6 weeks post-operatively, it was achieved in two patients, at 12 weeks in 12 patients and at 6 months in all 14 patients. The C1-C2 segment was stable at 12 weeks in all 18 treated patients. Four patients reported restriction of motion in rotation by 10 to 25 % after removal of the instrumentation. DISCUSSION: Operative time, longer at the beginning than with the Magerl technique, gradually shortened to between 45 and 60 min. Similar trends were seen when intra-operative blood loss and X-ray exposure were evaluated. Using the Harms and Melcher procedure we saved the greater suboccipital nerve. In contrast to these authors, however, we did not resect the atlantoaxial joint. Solid fusion was achieved in all our patients. Of the total of 72 screws inserted, only three (4.2 %) were assessed as malpositioned; however, when related to the 36 screws inserted in C2, this was 8.3 %, which indicates that insertion of screws in C2 was more difficult. We did not observe any clinical consequences in any of these cases. CONCLUSIONS: The Harms fixation of C1-C2 is a very effective technique for stabilizing the atlantoaxial complex. It enables us to provide temporary fixation without damage to atlantoaxial joints and to reduce the vertebrae after the screws and rods had been inserted, which is unique. These advantages compensate for a higher cost of the implant.

Adult↗

PubMedDate not supplied

Congenital lumbar spinal stenosis: a prospective, control-matched, cohort radiographic analysis.

BACKGROUND CONTEXT: Degenerative lumbar spinal stenosis manifests primarily after the sixth decade of life as a result of facet hypertrophy and degenerative disc disease. Congenital stenosis, on the other hand, presents earlier in age with similar clinical findings but with multilevel involvement and fewer degenerative changes. These patients may have subtle anatomic variations of the lumbar spine that may increase the likelihood of thecal sac compression. However, to the authors' knowledge, no quantitative studies have addressed various radiographic parameters of symptomatic, congenitally stenotic individuals to normal subjects. PURPOSE: To radiographically quantify and compare the anatomy of the lumbar spine in symptomatic, congenitally stenotic individuals to age- and sex-matched, asymptomatic, nonstenotic controlled individuals. STUDY DESIGN/SETTING: A prospective, control-matched, cohort radiographic analysis. PATIENT SAMPLE: Axial and sagittal magnetic resonance imaging (MRI) and lateral, lumbar, plain radiographs of 20 surgically treated patients who were given a clinical diagnosis of congenital lumbar stenosis by the senior author were randomized with images of 20, asymptomatic age- and sex-matched subjects. OUTCOME MEASURES: MRIs and lateral, lumbar, plain radiographs were independently quantitatively assessed by two individuals. Measurements obtained from the axial MRIs included: midline anterior-posterior (AP) vertebral body diameter, vertebral body width, midline AP canal diameter, canal width, spinal canal cross-sectional area, pedicle length, and pedicle width. From the sagittal MRIs, the following measurements were calculated: AP vertebral body diameter, vertebral body height, and AP canal diameter at the mid-vertebral level. On the lateral, lumbar, plain radiograph (L3 level), the AP diameters of the vertebral body spinal canal were measured. METHODS: The images of these 40 individuals were then randomized and distributed in a blinded fashion to five separate spine surgeons who graded the presence and severity of congenital stenosis utilizing a five-tier scale. Images consisting of 15 symptomatic individuals, graded definitely congenitally stenotic (mean age, 51.7 years; range, 43-65 years), and 15 asymptomatic individuals, graded definitely not stenotic (mean age, 50.7 years; range, 41-55 years), were age- and sex-matched and included for further review. From these 30 patients, a lateral, lumbar, plain radiograph and axial and sagittal MRIs (T1/T2 weighted) from L2-L5 were quantitatively analyzed. Rater reliability was assessed by Kappa coefficient testing. RESULTS: The cross-sectional area of the canal was significantly smaller in the congenitally stenotic patients at all lumbar levels measured (L2: 176 mm(2) vs. 259 mm(2), L3: 177 mm(2) vs. 275 mm(2), L4: 183 mm(2) vs. 283 mm(2), L5: 213 mm(2) vs. 323 mm(2), p<.05). Pedicle length was markedly shorter in the stenosis group at each lumbar level (L2: 5.9 mm vs. 8.9 mm, L3: 6.0 mm vs. 8.8 mm, L4: 6.5 mm vs. 9.2 mm, L5: 5.8 mm vs. 9.1 mm, p<.05). Furthermore, midline, axial AP canal diameter, vertebral body width, and sagittal AP canal diameter were all significantly smaller than the control patients (p<.05). A ratio of the AP diameter of the pedicle length to the vertebral body was also noted to be statistically significant on both the lateral plain radiographs (L3: 0.426 vs. 0.704) and sagittal MRI (L2: 0.343 vs. 0.461, L3: 0.361 vs. 0.461, L4: 0.362 vs. 0.481, L5: 0.354 vs. 0.452, p<.05). No difference was noted comparing the AP diameter of the vertebral body (axial and sagittal images), vertebral body height, canal width, and pedicle width. Kappa testing coefficient indicated a strong rater reliability (k=0.81, 95% confidence interval: 0.62-0.94). CONCLUSIONS: Congenital lumbar stenosis has not been clearly defined radiographically. Clinically, congenitally stenotic patients present at a younger age with fewer degenerative changes and multiple levels of involvement. Radiographically, these patients have a shorter pedicular length and as a result a smaller cross-sectional spinal canal area (mean critical values of 6.5 mm and 213 mm(2) were observed, respectively). The mean critical ratios were 0.43 (2:1 AP vertebral body: pedicle length) on the lateral lumbar radiograph and 0.36 on the sagittal MRI. The altered canal anatomy resulting from a decreased pedicle length may anatomically predispose these patients to earlier complaints of symptomatic neurogenic claudication. Identification of the presence of congenital stenosis should increase the treating surgeon's awareness of the potential need for multilevel treatment.

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