Extent Of Bone Removal Research Articles

C7 Fracture as a Complication of C7 Dome-Like Laminectomy : Impact on Clinical and Radiological Outcomes and Evaluation of the Risk Factors.

ObjectiveCervical expansive laminoplasty is an effective surgical method to address multilevel cervical spinal stenosis. During surgery, the spinous processes of C2 and C7 are usually preserved to keep the insertion points of the cervical musculature and nuchal ligament intact. In this regard, dome-like laminectomy (undercutting of C7 lamina) instead of laminoplasty is performed on C7 in selected cases. However, resection of the lamina can weaken the C7 lamina, and stress fractures may occur, but this complication has not been characterized in the literature. The objective of the present study was to investigate the incidence and risk factors for C7 laminar fracture after C7 dome-like laminectomy and its impact on clinical and radiological outcomes. MethodsPatients who underwent cervical open-door laminoplasty combined with C7 dome-like laminectomy (n=123) were classified according to the presence of C7 laminar fracture. Clinical parameters (neck/arm pain score and neck disability index) and radiologic parameters (C2–7 angle, C2–7 sagittal vertical axis, and C7–T1 angle) were compared between the groups preoperatively and at postoperatively at 3, 6, 12, and 24 months. Risk factors for complications were evaluated, and a formula estimating C7 fracture risk was suggested. ResultsC7 lamina fracture occurred in 32/123 (26%) patients and occurred at the bilateral isthmus in 29 patients and at the spinolaminar junction in three patients. All fractures appeared on X-ray within 3 months postoperatively, but patients did not present any neurological deterioration. The fracture spontaneously healed in 27/32 (84%) patients at 1 year and in 29/32 (91%) at 2 years. During follow-up, clinical outcomes were not significantly different between the groups. However, patients with C7 fractures showed a more lordotic C2–7 angle and kyphotic C7–T1 angle than patients without C7 fractures. C7 fracture was significantly associated with the extent of bone removal. By incorporating significant factors, the probability of C7 laminar fracture could be assessed with the formula 'Risk score = 1.08 × depth (%) + 1.03 × length (%, of the posterior height of C7 vertebral body)', and a cut-off value of 167.9% demonstrated a sensitivity of 90.3% and a specificity of 65.1% (area under the curve, 0.81). ConclusionC7 laminar fracture can occur after C7 dome-like laminectomy when a substantial amount of lamina is resected. Although C7 fractures may not cause deleterious clinical outcomes, they can lead to an unharmonized cervical curvature. The chance of C7 fracture should be discussed in the shared decision-making process.

Comparison of unilateral rostral, middle and caudal segmental mandibulectomies as an alternative treatment for unilateral temporomandibular joint ankylosis in cats: an ex vivo study.

Temporomandibular joint ankylosis (TMJA) is the partial or complete inability to open the mouth due to intra- or extra-articular fibrous, bony or fibro-osseous tissue proliferation. Surgical procedures such as gap arthroplasty, condylectomy or wide extra-articular osteotomy have been recommended to treat this condition; these techniques are challenging, time-consuming and have been occasionally associated with postoperative recurrence, severe periarticular neurovascular iatrogenic trauma and death. Segmental mandibulectomy had previously been recommended as an alternative option for unilateral TMJA, but the location of mandibulectomy and extent of bone removal from the mandible region have not been mentioned in the literature. This study aimed to validate the area of the mandibular body (rostral, middle or caudal) and amount of bony tissue that should be osteotomized during a segmental mandibulectomy for treatment of unilateral TMJA in cats. In this block study, 30 cadaver heads of domestic shorthair cats were randomly divided into three groups of 10 specimens each based on the mandibular region that would undergo segmental mandibulectomy (rostral, middle and caudal). The size of the removed mandibular segment and pre- and postoperative vertical range of mandibular motion were compared for statistical purposes. A significant statistical difference was observed between the pre- and postoperative vertical range of mandibular motion between the rostral, middle and caudal segmental mandibulectomies (P <0.001). The mean postoperative recovered range of mandibular motion for the rostral, middle and caudal segmental mandibulectomies was 50.4%, 81.9% and 90.4%, respectively. The caudal segmental mandibulectomy showed the highest postoperative vertical range of mandibular motion. The removal of a minimum of 1.2 cm of the caudal mandibular body was required to achieve nearly full recovery of presurgical mouth opening in the specimens of this study. The caudal segmental mandibulectomy may eliminate the risk of iatrogenic periarticular neurovascular damage inherent to more invasive surgeries performed at the temporomandibular joint area. When performed unilaterally, the caudal segmental mandibulectomy is a viable surgical alternative that may show a similar outcome to other surgical techniques.

Kambin's triangle: definition and new classification schema.

Kambin's triangle is an anatomical corridor used to access critical structures in a variety of spinal procedures. It is considered a safe space because it is devoid of vascular and neural structures of importance. Nonetheless, there is currently significant variation in the literature regarding the exact dimensions and anatomical borders of Kambin's triangle. This confusion was originally caused by leaving the superior articular process (SAP) unassigned in the description of the working triangle, despite Kambin identifying that structure in his original report. The SAP is the most relevant structure to consider when accessing the transforaminal corridor. Leaving the SAP unassigned has led to an open-handed application of the term "Kambin's triangle." That single eponym currently has two potential meanings, one meaning for endoscopic surgeons working through a corridor in the intact spine and a second meaning for surgeons accessing the disc space after a complete or partial facetectomy. Nevertheless, an anatomical corridor should have one consistent definition to clearly communicate techniques and use of instrumentation performed through that space. As such, the authors propose a new surgically relevant classification of this corridor. Assigning the SAP a border requires adding another dimension to the triangle, thereby transforming it into a prism. The term "Kambin's prism" indicates the assignment of a border to all relevant anatomical structures, allowing for a uniform definition of the 3D space. From there, the classification scheme considers the expansion of the corridor and the extent of bone removal, with a particular focus on the SAP.

Pure Endoscopic Lateral Orbitotomy Approach to the Cavernous Sinus, Posterior, and Infratemporal Fossae: Anatomic Study.

Objective The aim of this anatomic study is to describe a fully endoscopic lateral orbitotomy extradural approach to the cavernous sinus, posterior, and infratemporal fossae. Material and Methods Three prefixed latex-injected head specimens (six orbital exposures) were used in the study. Before and after dissection, a computed tomography scan was performed on each cadaver head and a neuronavigation system was used to guide the approach. The extent of bone removal and the area of exposure of the targeted corridor were evaluated with the aid of OsiriX software (Pixmeo, Bernex, Switzerland). Results The lateral orbital approach offers four main endoscopic extradural routes: the anteromedial, posteromedial, posterior, and inferior. The anteromedial route allows a direct route to the optic canal by removal of the anterior clinoid process, whereas the posteromedial route allows for exposure of the lateral wall of the cavernous sinus. The posterior route is targeted to Meckel's cave and provides access to the posterior cranial fossa by exposure and drilling of the petrous apex, whereas the inferior route gives access to the pterygopalatine and infratemporal fossae by drilling the floor of the middle cranial fossa and the bone between the second and third branches of the trigeminal nerve. Conclusion The lateral orbitotomy endoscopic approach provides direct access to the cavernous sinus, posterior, and infratemporal fossae. Advantages of the approach include a favorable angle of attack, minimal brain retraction, and the possibility of dissection within the two dural layers of the cavernous sinus without entering its neurovascular compartment.

A Modified Microsurgical Endoscopic-Assisted Transpedicular Corpectomy of the Thoracic Spine Based on Virtual 3-Dimensional Planning

The main difficulties of transpedicular corpectomies are lack of space for vertebral body replacement in the neighborhood of critical structures, the necessity for sacrifice of nerve roots in the thoracic spine. and the extent of hemorrhage due to venous epidural bleeding. We present a modified technique of transpedicular corpectomy by using an endoscopic-assisted microsurgical technique performed through a single posterior approach. A 3-dimensional (3D) preoperative reconstruction could be helpful in the planning for this complex anatomic region. Surface and volume 3D reconstruction were performed by Amira or the Dextroscope. The clinical experience of this study includes 7 cases, 2 with an unstable burst fracture and 5 with metastatic destructive vertebral body disease, all with significant retropulsion and obstruction of the spinal canal. We performed a comparison with a conventional cohort of transpedicular thoracic corpectomies. Qualitative parameters of the 3D virtual reality planning included degree of bone removal and distance from critical structures such as myelon and implant diameter. Parameters were met in each case, with demonstration of optimal positioning of the implant without neurological complications. In all patients, the endoscope was a significant help in identifying the origins of active bleeding, residual tumor, extent of bone removal, facilitating cage insertion in a minimally invasive way, and helping to avoid root sacrifice on both sides. Microsurgical endoscopic-assisted transpedicular corpectomy may prove valuable in enhancing the safety of corpectomy in destructive vertebral body disease. The 3D virtual anatomic model greatly facilitated the preoperative planning.

NI-18 * MULTIMODAL NAVIGATION IN ENDOSCOPIC TRANS-SPHENOIDAL RESECTION OF PITUITARY TUMORS USING IMAGE-BASED VASCULAR AND CRANIAL NERVE SEGMENTATION: A PROSPECTIVE VALIDATION STUDY

Trans-Sphenoidal surgery (TSS) is a well-known approach for treatment of pituitary tumors. However, in inexperienced hands, the risk of lateral misdirection and vascular damage, intraoperative CSF leakage, and optic nerve injury are all well-known complications of this procedure. This prospective study was conducted to validate the accuracy of image-based segmentation in localization of neurovascular structures during TSS. METHODS: Eight patients with pituitary tumor underwent preoperative 3TMRI, which included thin sectioned 3D space T2, 3D Time of Flight and MPRAGE sequences. Images were reviewed by an expert independent neuroradiologist. Imaging sequences were loaded in BrainLab iPlanNet (6/8) and Stryker (2/8) for segmentation and pre-op planning. After patient registration to the intra-op neuronavigation system and surgical exposure, each segmented neural or vascular element was validated by manual placement of the navigation probe. The pulses of the bilateral ICA were confirmed using micro-Doppler. RESULTS: Pre-operative segmentation of the ICA and cavernous sinus matched with the intra-operative endoscopic and micro-Doppler findings in all cases (Dice-coefficient =1). This information reassured surgeons regarding the lateral extent of bone removal at the sellar floor and the limits of lateral explorations. Perfect correspondence between image-based segmentation and endoscopic view was also found at the surface of the tumor and tumor-normal gland interfaces. This helped in preventing unnecessary removal of the normal pituitary gland. Image-guidance helped surgeon to localize the optic nerve and chiasm in 63% of case and Diaphragma sella in 50% of cases, which helped to determine the limits of upward exploration and decrease the risk of CSF leakage. CONCLUSION: Image-based pre-operative vascular and neural element segmentation especially with 3D reconstruction is highly informative preoperatively and helps young and inexperienced neurosurgeons to prevent vascular and neural injury during trans-Sphenoidal surgeries. This novel preliminary study is encouraging for future prospective intraoperative validation with larger numbers of patients.

Retrograde approach and soft wall reconstruction in surgery for congenital cholesteatoma

Conclusions: A retrograde approach and soft wall reconstruction is thought to be an effective surgical approach for patients with good eustachian tube function and good mastoid development such as in congenital cholesteatoma. Objective: To analyze the usefulness of a retrograde approach and soft wall reconstructive surgical treatment for congenital cholesteatoma. Methods: Data from 24 patients (25 ears in total) who underwent surgical intervention for congenital cholesteatoma at Kanazawa University Hospital between January 2001 and July 2011 were retrospectively reviewed. We had used a retrograde approach for congenital cholesteatomas in which bone is removed as necessary in a retrograde manner from the external auditory canal side. The extent of bone removal was determined according to the location of the cholesteatoma. The posterior walls of the external auditory canals were reconstructed with soft tissue using temporal fascia. Results: Good preoperative mastoid development was identified in 83% of the patients. Postoperative recurrence was seen in 1 of 25 ears. Analysis of pre- and postoperative hearing ability showed significant improvement in both pure tone audiogram air conduction and pure tone audiogram air–bone gaps.

Different Types of Syringomyelia and Their Management

Surgical Procedures Posterior Fossa Decompression There are many ways to perform posterior fossa decompression (PFD), although indications for each technique are not clear, and its application depends on clinical manifestations, radiologic findings, dynamics of cerebrospinal fluid (CSF) and especially, the surgeon’s preference. OccipitalCraniectomy.This is the simplest procedure, and it consists of performinganoccipital craniectomywide enough to allow for both decompression and maintenance of the posterior fossaneural elements. The extent of bone removal is very important, because performing a wide occipital window has a high risk of formation of a pseudomeningocele and the socalled cerebellar ptosis; in these cases, symptomsmaynot only recur but even become associated with other cerebellar manifestations. Themost recommendedaverage size for the craniectomy is approximately 2.5 to 3 cm on each side of the midline immediately below the inionup to the foramenmagnumand, depending on the extension of cerebellar tonsillar herniation, it is usually associated with resection of the posterior arch of C1 and sometimes, the lamina of C2 (Figure 1). Most patients with type I Chiari malformation experience improvement in their symptomswith this simpleprocedure. This improvement is because pathologic analysis has shown an increase in collagen fibers, hyaline nodules, and calcification in thedural band of the craniovertebral junction, so bone removal promotes liberationof all these elements andallows restorationofCSF flow. However, if this procedure is chosen as the only treatment, it Different Types of Syringomyelia and Their Management: Part II

Surgical management of foramen magnum meningiomas

The objective of the study is to describe our experience in the surgical management of foramen magnum meningiomas with regard to the clinical-radiological findings, the surgical approach and the outcomes after mid-term follow up. Over a 5-year period, 15 patients presenting with meningiomas of the foramen magnum underwent surgical treatment. The medical records were reviewed in order to analyze the clinical-radiological aspects, as well as the surgical approach and the outcomes. Based on the preoperative magnetic resonance imaging exams, the tumors were classified as anterior or anterolateral in the axial slices and clivospinal or spinoclival in the sagittal slices. The lateral approach was used in all cases. However, the extent of bone removal and the management of the vertebral artery were tailored to each patient. Fourteen patients were females, and one was male, ranging in age from 42 to 74 years (mean 55,9 years). The occipital condyle was partially removed in eight patients, and in seven patients, removal was not necessary. Total removal of the tumor was achieved in 12 patients, subtotal in two, and partial resection in one patient. Postoperative complications occurred in two patients. Follow-up ranged from 6 to 56 months (mean 23.6 months).There was no surgical mortality in this series. The extent of the surgical approach to foramen magnum meningiomas must be based on the main point of dural attachment and tailored individually case-by-case. The differentiation between the clivospinal and spinoclival types, as well as anterior and anterolateral types, is crucial for the neurosurgical planning of foramen magnum meningiomas.

Preoperative localization of herniated thoracic discs using myelo-CT guided transpleural puncture: technical note

In recent years, video-assisted thoracoscopic microdiscectomy has gained acceptance as a minimally invasive, safe, and efficient technique suited for herniated thoracic discs from T4T5 until T11T12. However, correct localization is difficult and wrong level exploration is an ever-present threat. We present a reliable and time-efficient localizing technique. In 86 consecutive cases, 1 day preoperatively intrathecal contrast was administered and a computed tomography (CT) scan was performed in prone position. Using local anesthesia, a hollow needle was advanced above the corresponding rib and through the pleura. The inner wire and corresponding pathological level were easily identified endoscopically. Myelo-CT provides detailed anatomical information, which is often helpful in determining the side of operative approach and the extent of bone removal needed. Needle localization obviates fluoroscopy, saves OR time, and allows the surgeon to focus on the technically demanding procedure. Furthermore, it is a relatively simple and safe technique.

Suprameatal Extension of the Retrosigmoid Approach: Microsurgical Anatomy

This study was conducted to determine whether removing the bony prominence located above the porus of the internal acoustic meatus, called the suprameatal tubercle, and surrounding bone using the retrosigmoid approach would aid in the exposure of tumors that are located predominantly in the cerebellopontine angle but that also extend into the middle cranial fossa in the region of Meckel's cave and thus avoid the need for a supratentorial craniotomy. Thirty cerebellopontine angles from 15 cadaveric heads examined using 3 to 40x magnification provided the material for this study. A retrosigmoid craniotomy was completed and the exposure obtained before and after removing the suprameatal tubercle, and the surrounding bone was examined. In some cases, Meckel's cave and the tentorium lateral to the porus of Meckel's cave was opened to aid in the exposure. Removing the suprameatal tubercle and surrounding bone increased the exposure an average of 10.3 mm (range, 8.0-13.0 mm) forward of the exposure, which could be obtained without suprameatal drilling. The extent of bone removal was limited on the lateral side by the posterior and superior semicircular canals and their common crus. The suprameatal extension of the retrosigmoid approach will permit removal of some tumors that are located mainly in the posterior fossa but that extend into the middle fossa in the region of Meckel's cave. The exposure can be increased by opening the superior petrosal sinus as it crosses in the upper margin of the porus of Meckel's cave and by opening the tentorium lateral to Meckel's cave.

Surgical approach to the internal auditory meatus in acoustic neuroma surgery: significance of preoperative high-resolution computed tomography.

To establish a surgical approach that provides better access to the internal auditory meatus (IAM) in acoustic tumor removal via a suboccipital transmeatal route, the anatomic location of the labyrinth with regard to the sigmoid-fundus line and the extent of bone removal from the IAM were evaluated by pre- and postoperative high-resolution computed tomography for 47 patients. The labyrinth was located lateral to the sigmoid-fundus line in 22 cases (lateral type, 46.8%), on the line in 9 (on-the-line type, 19.1%), and medial to the line in 16 (medial type, 34.0%). Postoperative high-resolution computed tomography showed that the mean length of the posterior wall from the fundus was shortened to 5.1 +/- 1.1 mm (n = 27) in the partially resected group and to 2.0 +/- 0.6 mm (n = 20) in the widely opened IAM group. The labyrinth was damaged in four cases from the widely opened IAM group; the preoperative status of the labyrinth was medial to the sigmoid-fundus line in three and on the line in one. The cochlear nerve was preserved in seven (31%) partially resected and in eight (50%) widely opened IAM cases. The overall success rate of hearing preservation was 4 of 22 (18.2%) partially resected and 5 of 16 (31.2%) widely opened cases. Preoperative evaluation of the anatomic relation between the IAM and the labyrinth by high-resolution computed tomography provides an efficient surgical approach to the IAM and contributes to anatomic and functional preservation of the cochlear nerve.

Frameless Stereotactic Guidance

The application of a video-interactive frameless stereotactic guidance system for the treatment of ventral cervicomedullary junction compression is described in a patient with basilar invagination, odontoid dysgenesis, and a Chiari malformation who had irreducible impingement on the ventral brainstem by a partially fused mass of bone made up of the malformed odontoid peg, the inferior clivus, and dorsally protruding osteophytes at the odontoid-clival junction. This technology permitted instantaneous feedback of the surgeon's orientation in all planes, facilitating extensive removal of the dens and clival tip to achieve adequate ventral brainstem decompression. In view of the distortion of the craniovertebral anatomy produced by the patient's anomalies, the ability to visualize three dimensionally the location of the vertebral arteries also added an element of safety to the lateral bone removal. Similarly, the ability to localize the rostral limit of the clivus that needed to be resected and the caudal extent of C2 that needed to be removed to achieve an adequate decompression helped ensure that the extent of bone removal was appropriately tailored to the patient's anatomy. The authors believe this technique represents a significant advance over standard radiographic intraoperative localization techniques during transoral approaches to the ventral cervicomedullary junction for patients in whom the odontoid is fixed in position in relation to the clivus. This is based on the speed with which localization can be obtained, the accuracy of the information provided, the ability to obtain localization in multiple planes simultaneously, and the lack of radiation exposure during the procedure.

Arthroscopic roofplasty: A method for correcting an extension deficit caused by roof impingement of an anterior cruciate ligament graft

Intercondylar roof impingement should be suspected in any patient having difficulty regaining knee extension following an anterior cruciate ligament (ACL) reconstruction. An arthroscopically performed roofplasty can eliminate the clinical complaints. The extent of bone removal can be planted from studying a lateral radiograph taken with the knee in terminal extension. Extension exercises or passive extension devices should not be used in patients with extension deficits caused by roof impingement because they may further damage the graft.