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Cédric Barrey, Patrick Mertens, Claude Rumelhart, François Cotton, Jérôme Jund and Gilles Perrin

Object. The purpose of this study was to assess human cervical spine pullout force after lateral mass fixation involving two different techniques: the Roy-Camille and the Magerl techniques. Although such comparisons have been conducted previously, because of the heterogeneity of results and the importance of this procedure in clinical practice, it is essential to have data derived from a prospective and randomized biomechanical study involving a sufficient sample of human cervical spines. The authors also evaluated the influence of the sex, the vertebral level, the bone mineral density (BMD), the length of bone purchase, and the thickness of the anterior cortical purchase.

Methods. Twenty-one adult cervical spines were harvested from fresh human cadavers. Computerized tomography was performed before and after placing 3.5-mm titanium lateral mass screws from C-3 to C-6. Pullout forces were evaluated using a material testing machine. The load was applied until the pullout of the screw was observed. A total of 152 pullout tests were available, 76 for each type of screw fixation. The statistical analysis was mainly performed using the Kaplan—Meier survival method.

The mean pullout force was 266 ± 124 N for the Roy-Camille technique and 231 ± 94 N for the Magerl technique (p < 0.025). For the C3–4 specimen group, Roy-Camille screws were demonstrated to exert a significantly higher resistance to pullout forces (299 ± 114 N) compared with Magerl screws (242 ± 97 N), whereas no difference was found between the two techniques for the C5–6 specimen group (Roy-Camille 236 ± 122 N and Magerl 220 ± 86 N). Independent of the procedure, pullout strengths were greater at the C3–4 level (271 ± 114 N) than the C5–6 level (228 ± 105 N) (p < 0.05).

No significant correlation between the cancellous BMD, the thickness of the anterior cortical purchase, the length of bone purchase, and maximal pullout forces was found for either technique.

Conclusions. The difference between pullout forces associated with the Roy-Camille and the Magerl techniques was not as significant as has been previously suggested in the literature. It was interesting to note the influence of the vertebral level: Roy-Camille screws demonstrated greater pullout strength (23%) at the C3–4 vertebral level than Magerl screws but no significant difference between the techniques was observed at C5–6.

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Cédric Barrey, Thomas Mosnier, Jérôme Jund, Gilles Perrin and Wafa Skalli

Object

Few biomechanical in vitro studies have reported the effects of disc replacement on motion and kinematics of the cervical spine. The purpose of this study was to analyze motion through 3D load-displacement curves before and after implantation of a ball-and-socket cervical disc prosthesis with cranial geometric center; special focus was placed on coupled motion, which is a well-known aspect of normal cervical spine kinematics.

Methods

Six human cervical spines were studied. There were 3 male and 3 female cadaveric specimens (mean age at death 68.5 ± 5 years [range 54–74 years]). The specimens were evaluated sequentially in 2 different conditions: first they were tested intact; then the spinal specimens were tested after implantation of a ball-and-socket cervical disc prosthesis, the Discocerv, at the C5–6 level. Pure moment loading was applied in flexion/extension, left and right axial rotation, and left and right lateral bending. All tests were performed under load control with a 3D measurement system.

Results

No differences were found to be statistically significant after comparison of range of motion between intact and instrumented spines for all loading conditions. The mean range of motion for intact spines was 10.3° in flexion/extension, 5.6° in lateral bending, and 5.4° in axial rotation; that for instrumented spines was 10.4, 5.2, and 4.8°, respectively. No statistical difference was observed for the neutral zone nor stiffness between intact and instrumented spines. Finally, the coupled motions were also preserved during axial rotation and lateral bending, with no significant difference before and after implantation.

Conclusions

This study demonstrated that, under specific testing conditions, a ball-and-socket joint with cranial geometrical center can restore motion in the 3 planes after discectomy in the cervical spine while maintaining physiological coupled motions during axial rotation and lateral bending.

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Mahmoud Messerer, Juan Carlos De battista, Gérald Raverot, Sebouh Kassis, Julie Dubourg, Veronique Lapras, Jacqueline Trouillas, Gilles Perrin and Emmanuel Jouanneau

Object

Because of their size and lateral extension, total removal of nonfunctioning pituitary adenomas (NFPAs) remains a challenge and postoperative tumor remnants are frequent. Endoscopy has improved the surgeon's view; however, its superiority in terms of surgical outcome remains undetermined. The authors' aim in this study was to compare the clinical results and morbidity between microscopic and endoscopic techniques in 164 patients with NFPAs.

Methods

Tumoral (3D MR imaging), endocrinological, and ophthalmological results and morbidity were compared between 2 groups of 82 patients with newly diagnosed NFPAs surgically treated via either a sublabial microscopic approach (Group B) or a fully endonasal endoscopic technique (Group A).

Results

The groups showed no difference in terms of clinical features, tumor size, or cavernous sinus invasion (p > 0.05). One year postoperatively, the quality of resection was significantly improved in Group A (gross-total removal [GTR]: 74% vs 50% in Group B, p = 0.002) with greater control of lateral extension (Knosp Grade 2: GTR 88.2% vs 47.8% in Group B, p = 0.02; Knosp Grade 3: 67.9% vs 16.7% in Group B, p < 0.001) and suprasellar extension (tumor height 20–30 mm: GTR 76% vs 53% in Group B, p = 0.01). Endocrinological outcome in patients with a partial deficiency in anterior pituitary function preoperatively was significantly better in Group A (improvement 56% vs 25% in Group B, stabilization 22% vs 46%, and aggravation 22% vs 29%; p = 0.01). Among the ophthalmologically symptomatic patients, 100% from Group A improved compared with 93% in Group B (p = 0.35). Lastly, no significant difference was found regarding morbidity. These data were supported by the literature in which the GTR rate is consistently higher for endoscopy compared with microscopy.

Conclusions

In this large series of patients with NFPAs, endoscopy improved the quality of resection and endocrinological outcome. Larger studies focusing on the impact of these promising results on the long-term recurrence of NFPAs are warranted.

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Jacqueline Trouillas, Laurent Daniel, Marie-Paule Guigard, Soutsakhone Tong, Joanny Gouvernet, Emmanuel Jouanneau, Michel Jan, Gilles Perrin, Georges Fischer, Antoine Tabarin, Geneviève Rougon and Dominique Figarella-Branger

Object. Pituitary adenomas are usually benign tumors; however, some behave aggressively and metastasize. Until now, no specific marker of aggressive behavior or malignancy has been found. The polysialylated neural cell adhesion molecule (NCAM), which is highly expressed in embryonic tissues such as the brain and pituitary, is detected in some neuronal and neuroendocrine tumors. Because polysialylation has been implicated in the regulation of cell growth and migration, polysialylated NCAM expression has been considered as a prognostic marker in such tumors.

Methods. In the present study, the authors analyzed polysialylated NCAM expression in 82 pituitary tumors from humans: 49 secreting adenomas, 32 nonfunctioning adenomas, and one growth hormone and prolactin—secreting carcinoma associated with acromegaly and spinal and liver metastases. Based on immunohistochemical analyses, the tumors were classified as somatotropic (22 tumors), prolactinoma (14 tumors), corticotropic (17 tumors), and gonadotropic or so-called null cell adenomas (28 tumors). Assessment of polysialylated NCAM was performed using three different methods (immunohistochemical analysis, Western blot analysis, and enzyme-linked immunosorbent assay) with a specific mouse monoclonal immunoglobulin M (Men B) that recognizes polysialic acid on NCAM. Tumoral NCAM expression was also evaluated with the aid of immunohistochemical analysis. Using this method, NCAM and polysialylated NCAM were studied in six healthy pituitaries. In addition, corrrelations were investigated using three statistical methods (chi-square test, nonparametric Mann—Whitney U-test, and principal component analysis) to compare tumoral polysialylated NCAM expression and seven parameters (tumor size and type, intrasphenoidal or cavernous sinus invasion, Ki-67 index, mitoses, and patient age and sex).

Neural cell adhesion molecules were expressed in the healthy anterior pituitary and in all tumors. In contrast, polysialylated NCAM was not found in the healthy pituitary gland, but was expressed in 46.3% of typical pituitary tumors and in 85% of the tumors selected as highly aggressive, including one carcinoma and three tumors with histological characteristics that raised suspicion of malignancy. There was no significant correlation between polysialylated NCAM expression and tumor size, tumor type, Ki-67 index, mitoses, or patient age and sex. In contrast, the expression of polysialylated NCAM, which was sensitive to endoneuraminidase-N treatment, was strongly correlated with tumor invasion (p < 0.0001).

Conclusions. In pituitary tumors in humans, expression of polysialylated NCAM is strongly related to tumor invasion and confirms the clinical diagnosis of aggressiveness.