Subaxial Region Research Articles

Posterior Spinal Screw Fixation Techniques and Trajectories: General Overview and an Analysis of How Often They Are Used

Abstract Background: There is a great variety of techniques (translaminar, transfacet, and extrapedicular screws) apart from the traditional pedicle screw in posterior spinal instrumentation. The latter technique is the most widely used around the world (except from the cervical region) since it tends to obtain very good results with a simple approach with fewer complications.Therefore, other trajectories are usually reserved for more specific cases in which the insertion of these purely pedicle screws is not possible. Objective: The objective of this study was to review and analyze the use of different techniques and trajectories of posterior spinal instrumentation by different spinal surgeons around the world. Material and Methods: We developed a survey including posterior spinal screw techniques and trajectories. In this article, we present the data resulting from 122 answers from different spinal surgeons (neuro, orthopedic surgery). Results: Despite advances in the development of new technologies such as neuronavigation (17%) and robotic (1%) available on the market, nowadays, the gold-standard technique for spinal screw insertion is the fluoroscopy-assisted freehand approach (54%). The lumbar spine is the most instrumented spinal region (31%), with a clear preference for purely transpedicular screws. Thoracic and sacroiliac areas presented a greater diversity of screw trajectories. In the cervical spine, there is a clear tendency toward the insertion of lateral mass screws (85% in the atlantoaxial region and 70% in the subaxial region), as opposed to the use of pedicular screws. This is mainly due to the complexity of this area and the risk of damaging important neurovascular structures relatively close to the pedicles. Unexpectedly, two additional techniques were presented: cortical bone trajectory for lumbar screw fixation (for osteoporotic patients) and S2-alar-iliac screw fixation (more used than iliac screws alone). Conclusions: This survey demonstrates that the most used spinal trajectory in the thoracolumbar spinal region is the traditional pedicle screw insertion. Lateral mass was the most common place to insert screws in the subaxial cervical region. The use of robotic systems can improve the position of the screws of more complex techniques. We consider that the different techniques should be known since every surgery will be adapted to the patient’s anatomy and needs.

Spinal Post-traumatic Deformity: An International Expert Survey Among AO Spine Knowledge Forum Members.

Survey among spine experts. To investigate the different views and opinions of clinically relevant spinal post-traumatic deformity (SPTD). There is no clear definition of clinically relevant SPTD. This leads to a wide variation in characteristics used for diagnosis and treatment indications of SPTD. To understand the current concepts of SPTD a survey was conducted among spine trauma surgeons. Members of the AO Spine Knowledge Forum Trauma participated in an online survey. The survey was divided in 4 domains: Demographics, criteria to define SPTD, risk factors, and management. The data were collected anonymously and analyzed using descriptive statistics, absolute, and relative frequencies. Consensus on dichotomous outcomes was set to 80% of agreement. Fifteen members with extensive experience in treatment of spinal trauma participated, representing the 5 AO Spine Regions. Back pain was the only criterion for definition of SPTD with complete agreement. Consensus (≥80%) was reached for kyphotic angulation outside normative ranges and impaired function. Eighty-seven percent and 100% agreed that a full-spine conventional radiograph was necessary in diagnosing and treating SPTD, respectively. The "missed B-type injury" was rated at most important by all but 1 participant. There was no agreement on other risk factors leading to clinically relevant SPTD. Concerning the management, all participants agreed that an asymptomatic patient should not undergo surgical treatment and that neurological deficit is an absolute surgical indication. For most of the participants the preferred surgical treatment of acute injury in all spine regions but the subaxial region is posterior fixation. Some consensus exists among leading experts in the field of spine trauma care concerning the definition, diagnosis, risk factors, and management of SPTD. This study acts as the foundation for a Delphi study among the global spine community.

Subaxial Spine Fractures: A Comparison of Patient-reported Outcomes and Complications Between Anterior and Posterior Surgery.

Observational study on prospectively collected data. The aim of this study was to compare long-term patient-reported outcomes and complications after anterior or posterior cervical spine surgery for subaxial fractures. There is no consensus in the literature regarding the optimal surgical approach when treating spine fractures in the subaxial region. A total of 200 individuals who had been treated with either anterior or posterior surgery due to a subaxial single segment, or single vertebra, injury between 2006 and 2016 and had at least 1 year follow-up were identified in the Swedish Spine register. Cases were matched 1:1 for age (±5 years). Outcomes were Neck Disability Index (NDI) and EQ-5D-3L, and reoperations, mortality, and surgeon- and patient-reported wound complications within 90 days. t Tests and χ2 tests were used statistical comparisons. At follow-up, NDI was 23 (21) in the anterior group and 29 (21) in the posterior group (P = 0.07). EQ-5D-3L index was 0.62 (0.37) in the anterior group and 0.54 (0.39) in the posterior group (P = 0.13). Patient satisfaction was higher in the anterior group (89% vs. 73%, P = 0.03). No deaths occurred within the first 90 days after surgery, six individuals in the anterior group and three individuals in the posterior group were reoperated (P = 0.31), and five individuals in the anterior group and 24 in the posterior group suffered a wound infection (P < 0.001). Anterior surgery and posterior surgery were associated with similar neck disability and general quality of life at follow-up, whereas anterior surgery was associated with higher patient satisfaction and lower infection rates.Level of Evidence: 3.

Occipitocervical Fixation: General Considerations and Surgical Technique.

Study Design:Narrative literature review.Objective:To review and present details on the occipitocervical fixation (OCF) technique as well as considerations for planning the procedure.Methods:We present the surgical technique of OCF in a step-by-step didactic and practical manner with surgical tips and tricks, including C1 and C2 screw fixation techniques. Additionally, we discuss complications, the extension of fusion, types of OCF, and how to avoid common side effects associated with OCF.Results:The complex and mobile anatomy of the craniocervical junction, when requiring fixation and fusion, warrants rigid instrumentation that can be achieve using a modern screw-plate-rod construct. Indications for OCF are craniocervical instability, and atlantoaxial instability when selective atlantoaxial fusion is not feasible. OCF generally involves occiput-C2 fusion. C1 fixation is generally unnecessary, since it increases the surgical time and is associated with the risk of vascular complications. Selective occiput-C2 fusion is recommended when there is no need for including the cervical subaxial region (eg, when stenosis or fractures coexist in the subaxial spine), and good fixation is achieved at C2. Most instrumentation systems now have occipital plates that are not pre-integrated to rods, making fixation much simpler. Surgical steps, from position to wound closure, are presented in detail, with pearls for practice and discussion of cervical alignment.Conclusions:OCF is a challenging procedure, with potential risk of severe adverse effects. Understanding the surgical indications, as well as the nuances of the surgical technique, is required to improve patient outcomes and avoid complications.

Outcomes following attempted en bloc resection of cervical chordomas in the C-1 and C-2 region versus the subaxial region: a multiinstitutional experience.

Chordomas involving the mobile spine are ideally managed via en bloc resection with reconstruction to optimize local control and possibly offer cure. In the cervical spine, local anatomy poses unique challenges, limiting the feasibility of aggressive resection. The authors present a multi-institutional series of 16 cases of cervical chordomas removed en bloc. Particular attention was paid to clinical outcome, complications, and recurrence. In addition, outcomes were assessed according to position of tumor at the C1-2 level versus the subaxial (SA) spine (C3-7). The authors reviewed cases involving patients who underwent en bloc resection of cervical chordoma at 4 large spine centers. Patients were included if the lesion epicenter involved the C-1 to C-7 vertebral bodies. Demographic data and details of surgery, follow-up course, exposure to adjuvant therapy, and complications were obtained. Outcome was correlated with presence of tumor in C1-2 versus subaxial spine via a Student t-test. Sixteen patients were identified (mean age at presentation 55 ± 14 years). Seven cases (44%) cases involved C1-2, and 16 involved the subaxial spine. Median survival did not differ significantly different between the C1-2 (72 months) and SA (60 months) groups (p = 0.65). A combined (staged anteroposterior) approach was used in 81% of the cases. Use of the combined approach was significantly more common in treatment of subaxial than C1-2 tumors (100% vs 57%, p = 0.04). En bloc resection was attempted via an anterior approach in 6% of cases (C1-2: 14.3%; SA: 0%; p = 0.17) and a posterior approach in 13% of cases (C1-2: 29%; SA: 0%; p = 0.09). The most commonly reported margin classification was marginal (56% of cases), followed by violated (25%) and wide (19%). En bloc excision of subaxial tumors was significantly more likely to result in marginal margins than excision of C1-2 tumors (C1-2: 29%; SA: 78%; p = 0.03). C1-2 tumors were associated with significantly higher rates of postoperative complications (C1-2: 71%; SA: 22%; p = 0.03). Both local and distant tumor recurrence was greatest for C1-2 tumors (local C1-2: 29%; local SA: 11%; distant C1-2: 14%; distant SA: 0%). Statistical analysis of tumor recurrence based on tumor location was not possible due to the small number of cases. There was no between-groups difference in exposure to postoperative adjuvant radiotherapy. There was no difference in median survival between groups receiving proton beam radiotherapy or intensity-modulated radiotherapy versus no radiation therapy (p = 0.8). Compared with en bloc resection of chordomas involving the subaxial cervical spine, en bloc resection of chordomas involving the upper cervical spine (C1-2) is associated with poorer outcomes, such as less favorable margins, higher rates of complications, and increased tumor recurrence. Data from this cohort do not support a statistically significant difference in survival for patients with C1-2 versus subaxial disease, but larger studies are needed to further study survival differences.

Effect of a reduction of the atlanto-axial angle on the cranio-cervical and subaxial angles following atlanto-axial arthrodesis in rheumatoid arthritis

We retrospectively investigated the radiographic findings in patients with atlanto-axial subluxation (AAS) due to rheumatoid arthritis, and clarified the effect of reduction of the atlanto-axial angle (AAA) on the cranio-cervical and subaxial angles. Forty-one patients, consisting of 29 females and 12 males, with AAS treated by surgery were reviewed. The average patient age at surgery was 61.0years, and the average follow-up period was 4.0years. We investigated the AAA at the neutral position in lateral cervical radiographs before surgery and at the last follow-up. In addition, we also investigated the clivo-axial angle (CAA) and the subaxial angle (SAA) at the neutral position before and after surgery. Due to pre-operative AAA, the patients were classified into three groups as follows: (1) the kyphotic group (K group), (2) the neutral group (N group), and (3) the lordotic group (L group). The average AAA values at the neutral position in the K group before and after surgery were 6.0° and 18.1°, respectively (P<0.001). In the N group 19.7° and 21.7°, respectively (P<0.05), and in the L group 31.6° and 27.0°, respectively (P<0.01). However, no significant differences in the average CAA values were found before and after surgery in all groups. Furthermore, no significant differences in the SAA values were seen before and after surgery in all groups. A proper reduction of the AAA did not affect the cranial angles or induce kyphotic malalignment of the subaxial region after atlanto-axial arthrodesis. However, if we can obtain a significant and large reduction of AAA in patients showing kyphosis before surgery, then this reduction will be offset in the atlanto-occipital joint and we should therefore pay special attention to its morphology after surgery.

Mean subaxial space available for the cord index as a novel method of measuring cervical spine geometry to predict the chronic stinger syndrome in American football players

The chronic stinger syndrome is a distinct entity from acute stingers and has been shown to have its own pathophysiology that, unlike acute stingers, may reflect long-standing geometrical changes of the subaxial spinal canal and chronic irritation/degeneration of the exiting nerve root complex. There is no method available, however, to accurately predict these symptoms in athletes. The mean subaxial cervical space available for the cord (MSCSAC) is a novel alternative to the Torg ratio for predicting neurological symptoms caused by cervical spondylosis in elite athletes. It is the goal of this study to determine critical values for this measurement index and to retrospectively correlate those values to neurological symptoms. Magnetic resonance images obtained in 103 male athletes participating in the 2005 and 2006 National Football League Scouting Combine and a control group of 42 age-matched male nonathletes were retrospectively reviewed. The Torg ratio and SAC values were calculated in triplicate at each cervical level from C3-6 by using lateral radiographs and midsagittal T2-weighted MR images of the cervical spine, respectively. These values were then averaged for each individual to produce mean subaxial cervical Torg ratio (MSCTR) and MSCSAC values. Receiver operating characteristic curves were constructed for each measurement technique and were compared based on their respective area under the curves (AUCs). The MSCSAC difference between athletes with and without chronic stingers was statistically significant (p < 0.01). The difference between athletes with and without chronic stingers compared with controls was also statistically significant (p < 0.001 and p < 0.001, respectively). The AUC for the MSCSAC was 0.813, which was significantly greater than the AUC for both the MSCTR (p = 0.0475) and the individual Torg ratio (p = 0.0277). The MSCTR had the second largest AUC (0.676) and the conventional method of measuring individual Torg ratio values produced the lowest AUC (0.661). It was found that using the MSCSAC with a critical value of 5.0 mm produced a sensitivity of 80% and a negative likelihood ratio of 0.23 for predicting chronic stingers. Lowering the cutoff value to 4.3 mm for the MSCSAC resulted in a possible confirmatory test with a specificity of 96% and a positive likelihood ratio of 13.25. A critical value of 5.0 mm for the MSCSAC provides the clinician with a screening test for chronic stingers and anything < 4.3 mm adds additional confidence as a confirmatory test. These results are approximately 20% more accurate than the classic Torg ratio based on our AUC analysis. It was found that measuring the spinal geometry throughout the length of the subaxial cervical spine produced a more reliable method by which to predict neurological symptoms than the traditional approach of measuring individual levels. This shows that the underlying pathogenesis of the chronic stinger syndrome is best characterized as a process that involves the entire subaxial region uniformly.

Epidemiology of severe cervical spinal trauma in the north area of São Paulo City: a 10-year prospective study

The main objective was to study the epidemiological data obtained in patients with cervical spinal trauma (CST) in the north area of São Paulo City between 1997 and 2006. All patients with severe CST in the north area of São Paulo City were studied. The data analyzed were age, sex, incidence, causes of trauma, level of trauma, morbidity, deaths, and complications. Analytical tests were performed to study risks of trauma and complications. The chi-square and analysis of variance tests were used for analytical data (significance level p < 0.05). The study population consisted of 217 patients who were hospitalized for CST. The average incidence rate was 21.6 cases annually or 1.8 cases monthly. The mean patient age was 36.75 years. The 20-40-year-old age bracket was found to be most highly represented, corresponding to 52.6% of total patients. Patients were predominantly male; 191 patients (88.01%) were male compared with only 26 female patients (11.99%). The ratio of men to women was 7.35:1. Injuries in the craniocervical region corresponded to 43 (19.8%) of the cases; injuries in the cervical subaxial region corresponded to 174 (80.2%) of the cases and were associated with worse neurological lesions. Additionally, 40.6% of patients presented with complications in other organs and systems; several patients presented with multiple complications, and 33 patients (15.02%) died. During the hospitalization period, 4 patients presenting as Grade A on the American Spinal Injury Association (ASIA) Scale evolved to Grade C, 1 patient presenting as ASIA Grade A evolved to Grade B, and 2 patients evolved to Grade E. Two patients who had been admitted without neurological lesions evolved to ASIA Grade C (1 patient postsurgery and 1 patient post-traction). Two patients presenting initially as ASIA Grade E evolved to Grade D, and another to central cord syndrome. On average, patients with incomplete lesions improved 1 grade in ASIA classification during hospitalization. Data from severe CST observed in the current study suggest many differences in the characteristics described in the majority of published epidemiological studies and those found in patients in the north area of São Paulo City. It is likely that these differences reflect the urban and cultural habits and behaviors of the population specific to this area.

Toomey et al. reply

Replying to: S. S. Singh & K. C. Macdonald , 10.1038/nature07887 (2009) We think that the Singh and Macdonald 1 description of the experimental uncertainties in our data2 is a misrepresentation of what we have done, and that they are incorrect in stating that our results2 on the structure of the uppermost mantle in the subaxial region beneath the East Pacific Rise are unconstrained by data.

Preoperative Evaluation of Extension Capacity of the Occipitoatlantoaxial Complex in Patients with Rheumatoid Arthritis

The authors devised a new method, the hyomental distance ratio (HMDR), for preoperatively identifying patients with a reduced occipitoatlantoaxial extension capacity, which was defined as the ratio of the hyomental distance in head extension position to that in the neutral position. They compared the accuracy of the HMDR with that of the Bellhouse test in 40 patients with rheumatoid arthritis. Each patient wearing goggles on which a goniometer was mounted sat upright with the head in the neutral position and then extended the head maximally. The angle of the goggles and the hyomental distance were measured in the two head positions, and a lateral cervical radiograph was taken simultaneously. The Bellhouse angle was defined as a difference in the angles of the goggles between these positions. Median values of the radiologic occipitoatlantoaxial extension angle and the Bellhouse angle were 11.2 degrees and 24.9 degrees , respectively. In 21 of 40 patients, the radiologic occipitoatlantoaxial extension angle was less than 12 degrees (reduced occipitoatlantoaxial extension capacity). In these patients, extension of the median angle of 16.4 degrees occurred at the subaxial regions and was greater than that of 8.5 degrees in patients with a radiologic occipitoatlantoaxial extension angle of 12 degrees or more (P < 0.01). As a result, a strong relation between the Bellhouse angle and radiologic occipitoatlantoaxial extension angle was not established (P < 0.01, r = 0.48). In contrast, the HMDR correlated well with the radiologic occipitoatlantoaxial extension angle (P < 0.0001, r = 0.88). The areas under the receiver operating characteristic curve of the Bellhouse test and the HMDR were 0.72 and 0.95, respectively. The HMDR was a good predictor of a reduced occipitoatlantoaxial extension capacity in patients with rheumatoid arthritis, but the Bellhouse test was not a clinically reliable method.

A REVIEW OF COMPOSITIONS AND TEXTURES OF ABYSSAL PERIDOTITES FROM THE NORTH ATLANTIC AND INDIAN OCEANS. PETROLOGICAL AND GEODYNAMICAL IMPLICATIONS

Abyssal peridotites equilibrated in the spinel lherzolite facies and sampled along ultra-slow, slow and intermediate spreading ridges, at transform faults and on-axis, in the Atlantic and Indian oceans, are compared for available mineralogical / geochemical data, with special emphasis on modal compositions and textures. Large mantle regions (100->1000 km) below the Atlantic and Indian ridges have been highly depleted by partial melting and melt extraction, not always in relation with known nearby hotspots. In those regions, residual harzburgites locally underwent secondary crystallization of clinopyroxene, spinel and olivine as a result of late-stage melt / rock reactions involving dissolution and/or incongruent (re)melting of residual orthopyroxene. In extreme cases, these reactions lead to the formation of secondary lherzolites and/or wehrlites closely associated with dunites. Trace element compositions of the secondary clinopyroxenes, as well of residual clinopyroxenes where some are still present, suggest that reacting melts derived from primary melts generated by partial melting of already depleted upper mantle. Residual peridotites sampled along transform faults are in the whole less depleted than on-axis peridotites. However, they are also characterized by a wide compositional range that includes highly depleted harzburgites. Thus, offaxis more fertile abyssal peridotite compositions probably not reflect a colder thermal regime of the ridge near the transforms. Instead, peridotite compositional variability along the transforms likely results from episodic magmatic activity at slow spreading mid-oceanic ridges, with temporal variations in the degree of melting. Pyroxenes dissolution textures and intergranular igneous clinopyroxenes can also be observed locally in less depleted, residual harzburgites and lherzolites although in much lower amounts than in the highly depleted harzburgites. In all peridotite samples, igneous clinopyroxenes and other minerals produced by melt precipitation and last-stage melt-rock reactions crystallized at the convective – conductive thermal regime transition, such that high temperatures are responsible for near-homogeneous compositions of all textural types of minerals. At a global scale, when regional averages of a large number of samples are considered, modal compositions and mineral chemistry (except sodium and the most incompatible trace elements) are relatively well correlated, and consistent with variable degrees of partial melting (~5-25%) of a lherzolitic source. Nevertheless, at a local scale, each subaxial mantle domain has its own compositional trend indicating variable melting parameters and/or source composition. Furthermore, orthopyroxene contents for a given olivine content allow to define a subgroup of orthopyroxene- rich harzburgites which is characteristically found in the most refractory subaxial mantle regions and whose clinopyroxenes are, in average, richer in sodium and chromium than those from orthopyroxene-poor harzburgites and lherzolites. Such differences in compositions might result from partial melting occurring at higher pressures in the more depleted regions. However, even in taking in account various late magmatic / metamorphic events which could have modified the primary mineral proportions, the present variations in the olivine / orthopyroxene ratios of all abyssal peridotites cannot be explained by any partial melting processes, at a global and regional / local scales. In the eastern region of the Southwest Indian ridge, along-axis compositional variability is as high as in transform zones. The scale of this compositional heterogeneity is correlated with the roughness and irregularity of the rift floor. In contrast with transform zone peridotites, however, mineral compositions and modal compositions do not correlate with each other and classical partial melting indicators are not internally coherent. The most refractory harzburgites clearly underwent metasomatism by fertile, alkali-rich, hydrous, asthenospheric melts, before subridge partial melting and high temperature annealing, while lherzolites appear to be well equilibrated hybrid rocks resulting from refertilization of refractory peridotites by basaltic melts mostly generated in the garnet stability field. Such subaxial mantle may represent heterogeneous upper mantle that upwelled beneath the present ridge and has been preserved because of very low degrees of melting. Alternatively, it may possible that in this very slow spreading / cold environment, thick subaxial lithosphere formed during the previous magmatic episode, was thermochemically eroded during the subsequent (present-day) magmatic event.

Seismic velocity anisotropy and heterogeneity beneath the Mantle Electromagnetic and Tomography Experiment (MELT) region of the East Pacific Rise from analysis of P and S body waves

We use teleseismic P and S delay times and shear wave splitting measurements to constrain isotropic and anisotropic heterogeneity in the mantle beneath the southern East Pacific Rise (SEPR). The data comprise 462 P and S delay times and 18 shear wave splitting observations recorded during the Mantle Electromagnetic and Tomography (MELT) Experiment. We estimate the mantle melt content (F) and temperature (T) variation from the isotropic velocity variation. Our results indicate that the maximum variation in F beneath our array is between zero and ∼1.2%, and maximum variation in T is between zero and ∼100 K. We favor an explanation having partial contributions from both T and F. We approximate the seismic anisotropy of the upper mantle with hexagonal symmetry, consistent with the assumption of two dimensionality of mantle flow. Our new tomographic technique uses a nonlinear inversion of P and slow S polarization delay times to simultaneously solve for coupled VP and VS heterogeneity throughout the model and for the magnitude of anisotropy within discrete domains. The domain dimensions and the dip of the anisotropy are fixed for each inversion but are varied in a grid search, obtaining the misfit of the models to the body wave delay data and to split times of vertically propagating S waves. The data misfit and the isotropic heterogeneity are sensitive to domain dimensions and dip of anisotropy. In a region centered beneath the SEPR the best average dip of the hexagonal symmetry axis is horizontal or dipping shallowly (&lt;30°) west. Given the resolution of our data, a subaxial region characterized by vertically aligned symmetry axes may exist but is limited to be &lt;80 km deep. We infer that the mantle flow beneath the SEPR is consistent with shallow asthenospheric return flow from the direction of the South Pacific superswell.

Internal structure of uppermost oceanic crust along the Western Blanco Transform Scarp: Implications for subaxial accretion and deformation at the Juan de Fuca Ridge

[1] The uppermost 2 km of oceanic crust created near the southern end of the Juan de Fuca Ridge (∼60 mm/yr, full spreading rate) is exposed in a “tectonic window” created along the north wall of the Blanco Transform Fault. A total of 27 submersible dives transect this escarpment over a distance of >30 km, corresponding to ∼1 m.y. of spreading history. In this exposure, weakly deformed basaltic lavas grade downward into much more intensely fractured lavas cut by basaltic dikes. Lava flow surfaces dip persistently to the northwest (toward the spreading center) and the dikes dip southeast (away from the spreading center). The underlying sheeted dike complex is composed of subparallel dikes that dip moderately to the southeast. Discrete faults and more distributed cataclastic deformation zones separate the panels of sheeted dikes from one another. Disruption of the lava and dike units are interpreted as a result of dramatic, subaxial, vertical mass transport that created the “accommodation space” for the accumulation of a thickness of 1000–1500 m of basaltic lava. The observed patterns of tilting of lavas and dikes imply subsidence beneath the region of active volcanism (∼3 km wide) that is most rapid near the axis and diminishes quickly off-axis. Deformation that accommodates this subsidence has generated extensive fracture porosity in the subaxial region that could strongly influence upper crustal hydrothermal pathways, alteration history, seismic properties, and the distribution of subsurface biological communities.

Surgical management of cervical spine metastatic disease

Metastatic disease to the cervical spine is a relatively infrequent occurrence. Management requires a multidisciplinary approach, and nonoperative treatment is often successful. There are specific indications for surgical intervention for cervical spine metastases, including instability, neurologic deterioration from compression by bone or soft tissue, progressive deformity threatening neurologic compromise, pain unresponsive to nonoperative measures, and the need for biopsy material for tissue diagnosis. Successful surgical strategies take into consideration tumor location, tumor type, medical comorbidities, and overall patient prognosis. Different reconstructive challenges exist in the occipitocervical and subaxial regions. In both regions the surgeon must ensure that the reconstruction accomplishes neurologic decompression and affords enough stability to minimize external immobilization postoperatively and maximize patient function. Newer techniques of instrumentation and alternatives to surgical reconstruction such as vertebroplasty need further evaluation and assessment of intermediate-term results before assuming a prominent role in the treatment of cervical metastatic disease.

P53 expression, growth, and spontaneous metastasis of the human GI 101 breast carcinoma in athymic nude mice.

The human GI 101 breast carcinoma cell lines produces spontaneous metastasis to the lungs when xenografted subcutaneously in female athymic nude mice. To establish the time-course of tumor growth and distant metastasis to the lungs and axillary lymph nodes, 5 mm3 of tumor tissue was implanted in the subaxial region of female athymic nude mice. Micrometastases in the lung were first detected 3 weeks after tumor implantation. The incidence of lung metastasis and the number of tumor emboli were correlated with the volume of the primary tumors. Ipsilateral axillary lymph node metastasis was observed within 17 weeks, indicating that metastasis to the lymph node is a later event. Unlike pulmonary micrometastases which were in the form of clusters of four to six tumor cells, metastasis to the lymph nodes were in nodules of poorly differentiated and larger tumor cells. Immunohistochemistry evaluation of p53 oncoprotein in the primary and metastatic tumor cells showed different patterns of subcellular accumulation. Cytoplasmic staining was mainly detected in the primary and secondary tumor cells disseminated to the lungs. In contrast, nuclear staining was only detected in tumor cells infiltrated to the axillary lymph nodes. There was no gain of loss of positivity of p53 accumulation (i.e., qualitative measurements) as the tumor grew in size. The data indicate that the GI 101 tumor cells could be used as a useful model for studying the malignant progression of hormone-independent breast cancer, antimetastatic drugs, and early events in tumor metastasis.

後頭頚椎固定術後の中下位頚椎におけるＸ線学的検討 非慢性関節リウマチ患者について

The effects of the occipito-axial angle on the development of subaxial lesion after occipitocervical fusion are discussed. Twenty-seven patients without rheumatoid arthritis who underwent occipitocervical fusion for irreducible atlantoaxial dislocation were reviewed with an average 4.1 year follow-up. No significant relationship was seen between the abnormal range of the occipito-axial angle, and development of subaxial subluxation was not apparent. The effects of mechanical stress after occipitocervical fusion on the subaxial region were not significant in patients without rheumatoid arthritis.

Petrology and oxygen isotope geochemistry of a fossil seawater hydrothermal system within the Solea graben, northern Troodos ophiolite, Cyprus

Hydrothermal mineral zonations and O isotope patterns of the northern Troodos complex do not parallel the ophiolite pseudostratigraphy, but reflect the convective geometry of an Upper Cretaceous seawater hydrothermal system. Large areas of the sheeted intrusive complex (SIC), including the subaxial region of the Solea graben, are composed of 18O‐rich, subgreenschist mineral assemblages and may represent regions of diffuse seawater recharge. Other areas of the SIC are recrystallized to distinctive epidosite rocks: granular, high‐variance assemblages of epidote + quartz ± chlorite that are depleted in 18O, Al2O3, Na2O, K2O, Zr, Cu, and Zn and are enriched in CaO and Sr compared with other mafic volcanic and dike rocks of the Solea graben. Epidosite alteration occurred at temperatures of ∼310–370°C and involved fluids with δ18O values and salinities similar to those of Upper Cretaceous seawater. The epidosite zones are discordant with earlier, mineral/O isotope zonations and with the axis of spreading in the Solea graben, suggesting a postspreading, off‐axis origin. The seawater hydrothermal system responsible for Solea graben massive sulfide deposits was probably driven by hypabyssal intrusions (not exposed), emplaced in a terminal, failed spreading episode. The geometries of O isotope surfaces within the Solea graben imply that the epidosites formed in fossil upflow and deep recharge conduits. Depletions in base metals show that epidosite alteration liberated Cu and Zn to mineralizing fluids within the fossil upflow zone.

Rheumatoid cervical luxations with fatal neurological complications.

When the cervical spine is involved in primary chronic polyarthritis, this leads in 6–8% of cases to an atlantoaxial dislocation or to luxations in the subaxial region. This may in turn lead to spinal cord compression and to an intermittent vertebral artery insufficiency. The clinical and radiological findings are described in 4 cases and the symptomatology discussed with the aid of the literature. The recognition of such complications in primary chronic polyarthritis is important, since neurosurgical measures for the stabilization of the cervical spine can produce impressive remissions.