Pedicle screw-based posterior dynamic stabilisation of the lumbar spine: in vitro cadaver investigation and a finite element study.

Pedicle screw-based dynamic constructs either benefit from a dynamic (flexible) interconnecting rod or a dynamic (hinged) screw. Both types of systems have been reported in the literature. However, reports where the dynamic system is composed of two dynamic components, i.e. a dynamic (hinged) screw and a dynamic rod, are sparse. In this study, the biomechanical characteristics of a novel pedicle screw-based dynamic stabilisation system were investigated and compared with equivalent rigid and semi-rigid systems using in vitro testing and finite element modelling analysis. All stabilisation systems restored stability after decompression. A significant decrease in the range of motion was observed for the rigid system in all loadings. In the semi-rigid construct the range of motion was significantly less than the intact in extension, lateral bending and axial rotation loadings. There were no significant differences in motion between the intact spine and the spine treated with the dynamic system (P>0.05). The peak stress in screws was decreased when the stabilisation construct was equipped with dynamic rod and/or dynamic screws.

Application of an asymmetric finite element model of the C2-T1 cervical spine for evaluating the role of soft tissues in stability.

Different finite element models of the cervical spine have been suggested for evaluating the roles of ligaments, facet joints, and disks in the stability of cervical spine under sagittal moments. However, no comprehensive study on the response of the full cervical spine that has used a detailed finite element (FE) model (C2-T1) that considers the asymmetry about the mid-sagittal plane has been reported. The aims of this study were to consider asymmetry in a FE model of the full cervical spine and to investigate the influences of ligaments, facet joints, and disk nucleus on the stability of the asymmetric model during flexion and extension. The model was validated against various published in vitro studies and FE studies for the three main loading planes. Next, the C4-C5 level was modified to simulate different cases to investigate the role of the soft tissues in segmental stability. The FE model predicted that excluding the interspinous ligament (ISL) from the index level would cause excessive instability during flexion and that excluding the posterior longitudinal ligament (PLL) or the ligamentum flavum (LF) would not affect segmental rotation. During extension, motion increased when the facet joints were excluded. The model without disk nucleus was unstable compared to the intact model at lower loads and exhibited a similar rotation response at higher loads.

A novel approach to the surgical treatment of lumbar disc herniations: indications of simple discectomy and posterior transpedicular dynamic stabilization based on carragee classification.

Surgery of lumbar disc herniation is still a problem since Mixter and Barr. Main trouble is dissatisfaction after the operation. Today there is a debate on surgical or conservative treatment despite spending great effort to provide patients with satisfaction. The main problem is segmental instability, and the minimally invasive approach via microscope or endoscope is not necessarily appropriate solution for all cases. Microsurgery or endoscopy would be appropriate for the treatment of Carragee type I and type III herniations. On the other hand in Carragee type II and type IV herniations that are prone to develop recurrent disc herniation and segmental instability, the minimal invasive techniques might be insufficient to achieve satisfactory results. The posterior transpedicular dynamic stabilization method might be a good solution to prevent or diminish the recurrent disc herniation and development of segmental instability. In this study we present our experience in the surgical treatment of disc herniations.

Biomechanics of posterior dynamic stabilization systems.

Spinal rigid instrumentations have been used to fuse and stabilize spinal segments as a surgical treatment for various spinal disorders to date. This technology provides immediate stability after surgery until the natural fusion mass develops. At present, rigid fixation is the current gold standard in surgical treatment of chronic back pain spinal disorders. However, such systems have several drawbacks such as higher mechanical stress on the adjacent segment, leading to long-term degenerative changes and hypermobility that often necessitate additional fusion surgery. Dynamic stabilization systems have been suggested to address adjacent segment degeneration, which is considered to be a fusion-associated phenomenon. Dynamic stabilization systems are designed to preserve segmental stability, to keep the treated segment mobile, and to reduce or eliminate degenerative effects on adjacent segments. This paper aimed to describe the biomechanical aspect of dynamic stabilization systems as an alternative treatment to fusion for certain patients.

Posterior dynamic stabilization in the treatment of lumbar degenerative disc disease: 2-year follow-up.

BACKGROUND: A prospective pilot study was designed to evaluate the role of a posterior dynamic stabilization technique in the surgical treatment of degenerative disc disease. Posterior dynamic stabilization with a hinged screw is a new concept in the surgical treatment of degenerative disc disease of the lumbar spine. The traditional surgical treatment is to apply a fusion procedure. However, numerous reports showed unsatisfactory clinical outcomes even when patients have satisfactory radiological outcomes following fusion procedures. MATERIAL AND METHODS: The study included patients who were surgically treated with a dynamic stabilization technique due to painful degenerative disc disease. Clinical and radiological findings for the 20 participating patients were analyzed in a 2-year follow-up study. Preoperative and postoperative data at the 3 (rd), 12 (th) and 24 (th) month were collected for both clinical and radiological outcomes. Statistical analyses between preoperative and postoperative data were performed using the Wilcoxon test. RESULTS: The clinical outcome measurements (VAS, ODI) showed significant improvement in all postoperative measurements compared to preoperative values. The mean preoperative visual analogue score (VAS, 7.9) and Oswestry Disability Index (ODI 59.2) significantly decreased to 0.8 for VAS and 9.2 for ODI, at 2 years post-operation (p<0.05). The radiological studies showed no significant changes between pre- and postoperative values, in all parameters. There was no mortality or morbidity. CONCLUSIONS: The results of this pilot study are encouraging. Dynamic stabilization may be an effective technique in the surgical treatment of painful degenerative disc disease. A larger series study, with longer follow-up periods and with control groups is needed to determine the success and safety of posterior dynamic stabilization in the surgical treatment of degenerative disc disease.

Endoscopic treatment of trans-sellar trans-sphenoidal encephalocele associated with morning glory syndrome presenting with non-traumatic cerebrospinal fluid rhinorrhea.

Basal encephaloceles are rare, accounting for about 1.5% of all encephaloceles. The trans-sellar trans-sphenoidal encephalocele variety is the rarest. Morning glory syndrome is often associated with basal encephalocele. Spontaneous cerebrospinal fluid (CSF) rhinorrheas are the least common of these, accounting for only 3% to 5% of all CSF rhinorrheas. The authors describe the outcome of a 10-year follow-up study of a 26-year-old male patient with a spontaneous CSF rhinorrhea occurring trans-sphenoidal encephalocele associated with bilateral morning glory syndrome that was treated with an endoscopic endonasal approach. Endoscopic exploration of the sella floor was performed and closed with abdomen fat packing and muscle fascia. The postoperative course was uneventful. A follow-up magnetic resonance (MR) image at 6 months postoperatively showed extension of encephalocele in the sphenoidal sinus, which was repaired. The patient had no further CSF rhinorrhea and showed no ophthalmologic changes over a follow-up period of over 10 years. Ophthalmologic findings such as strabismus, in association with anomalies of the optic nerve, should alert the physician to the possible presence of an unrecognized skull base midline defect and encephalocele before CSF leakage is seen. The authors believe that a surgeon who has equal confidence in performing the endoscopic endonasal and conventional microscopic trans-sphenoidal approaches should choose the less invasive surgery.

Endoscopic resection of a retroperitoneal schwannoma: case report.

INTRODUCTION: Retroperitoneal schwannomas are rare tumors. The symptoms are usually non-specific and these lesions can only be demonstrated with advanced radiological methods. Posterior and anterior approaches can be used to remove retroperitoneal schwannomas. Traditional techniques carry significant risks. CASE REPORT: A 35-year-old man was admitted with a history of right leg pain of 3 months duration. He had received conservative treatment and physical therapy but none of these measures had been helpful. Findings on physical and neurological examinations were all within normal limits. Magnetic resonance imaging revealed a retroperitoneal mass lesion medial to the right psoas muscle at the level of the S1 vertebra. The tumor was removed using an endoscopic transabdominal approach. CONCLUSION: The endoscopic transabdominal approach is a safe, efficient and minimally invasive procedure compared to traditional methods also to remove retroperitoneal schwannomas in selected cases.

Percutaneous endoscopic discectomy for far lateral lumbar disc herniations: prospective study and outcome of 66 patients.

BACKGROUND: Extraforaminal disc herniations represent up to 11% of all lumbar herniated discs. Numerous surgical approaches have been described. Percutaneous endoscopic discectomy (PED) is one of the minimally invasive techniques; after mastering this procedure it is a practical method that is used for treatment of foraminal or extraforaminal disc herniation. The outcome of PED for treatment of foraminal or extraforaminal disc herniation has been studied. METHOD: A total of 66 patients with foraminal or extraforaminal lumbar disc herniation was treated by applying the PED technique between January 1998 and June 2005. The positions of the herniated disc levels were L2-3 (n=5, 8%), L3-4 (n=19, 28%) and L4-5 (n=42; 64%). The selected patients had no previous surgery, appropriate conservative therapies were done before the operations, and MRI was the main diagnostic method with the clinical findings. Evaluation of the patients with clinical examinations, visual analogue pain scale (VAS) and Oswestry scale was performed preoperatively, on postoperative day 7 and in the postoperative 6-12 months period. RESULTS: In two patients (n=1, L4-5 and n=1, L3-4) disc material could not be removed with PED, so discectomy was performed with microscopic visualization during the same session. Three patients (n=3, L4-5) were reoperated on three to six months after primary surgery due to recurring disc problems with microscope visualization. In two patients (n=2, L4-5) root nerves were partially damaged, and in two patients (n=2, L4-5) root nerves were impinged by the working channel. These 4 patients had dysesthesias from just after surgery to a mean of 45 days after surgery. One of recurrent cases was among these patients. Neurological examinations showed minimal muscle weakness of the quadriceps femoris and diminished sensation of the L4 dermatomal area in patients with partial nerve root damage. This patient improved and the neurologic examination became normal with disappearance of the dysesthesia. There was no sign of reflex sympathetic dystrophy (RDS). With these two patients VAS and Oswestry scales scores decreased significantly early in the postoperative follow-up. The postoperative 6-month average scores are favourable in comparison with the average score at postoperative day 7. The postoperative 12-month scores showed no significant differences to those of postoperative month 1. CONCLUSION: Percutaneous endoscopic discectomy is a minimally invasive method and offers many benefits to the patient, but extensive surgical practice is needed to become a capable surgeon. Consequently this technique can only be a treatment option on appropriate patients. This study reconfirmed that the removal of fragmented disc material is achieved and offers a pain-free status.

Giant supratentorial atypical teratoid/rhabdoid tumor presentation: a case of a five-year-old child with favorable outcome and review of the literature.

Atypical teratoid/rhabdoid tumor of the central nervous system is a highly malignant neoplasm and that usually arises in the posterior fossa, survival from this is frequently poor. We present a unique case in a 21-month-old girl who had an atypical teratoid/rhabdoid tumor with cystic components located in the right fronto-parietal lobe. The patient underwent radical surgical intervention followed by chemotherapy. It consisted of five chemotherapeutic agents, but the patient did not receive any radiotherapy. The postoperative course was uneventful and the patient was followed-up by cranial magnetic resonance imaging every 3 months. Two years later at the last follow-up visit, there was no evidence of a tumor relapse on MRI, and the examination was symptom free. It is possible the favorable outcome of the patient resulted from a rapid diagnosis, prompt management, radical surgical intervention and aggressive chemotherapy.

Open-window laparotomy during a transperitoneal approach to the lower lumbar vertebrae: new method for reducing complications.

There are numerous approaches for exploring the lower lumbar vertebrae, and the anterior transperitoneal route is one of the most popular. Like all surgical techniques, this approach has advantages and disadvantages. It provides direct access to the target tissue through a small incision, exposes the anterior portion of the vertebrae well, and permits good visualization of the major vessels, thus reducing risk of vascular injury and life-threatening hemorrhage. However, compared to the extraperitoneal route, the transperitoneal approach carries higher risks for peritoneal complications. This article describes a new practical method for creating an extraperitoneal passageway or "window" during transperitoneal approaches to the lower lumbar vertebrae. Isolation of the peritoneal cavity and its contents with this technique can reduce peri- and postoperative abdominal complications.

Effects of cervical spine posture on axial load bearing ability: a biomechanical study.

OBJECT: The authors conducted a study to assess the effects of cervical posture on the loadbearing ability of the cervical spine. METHODS: Twelve cervical spine specimens obtained in 12 adult sheep were tested. The specimens were randomly separated into two groups. In Group I the specimens were fixed in a lordotic posture, and in Group II they were fixed in a straight posture. Axial compressive loads were applied at a constant rate of 5 cm/minute. Load-to-failure, time-to-failure, piston displacement at failure, and failure modes were recorded. Statistical analyses were performed to detect differences between the groups. There was no significant difference in load-to-failure values between the two groups. However, the time-to-failure and the piston displacement values for the straight spines were significantly less than those for the lordotic spines. Additionally, the straight spines failed predominantly through ventral elements, whereas the lordotic spines predominantly failed dorsally. CONCLUSIONS: It is concluded that a loss of a lordosis increases the risk of injury to the cervical spine following axial loading.

Effects of hole preparation on screw pullout resistance and insertional torque: a biomechanical study.

OBJECT: The authors conducted a study to assess the effect of a pilot hole preparation on screw pullout resistance and screw insertional torque. METHODS: Three different screws were tested: cancellous lateral mass screws, cortical lateral mass screws, and pedicle screws. Synthetic bone blocks were used as the host material. Each screw group was separated into two subgroups. The first subgroup of screws was inserted into the test material following pilot hole preparation. Pilot holes were prepared; a drill bit diameter size smaller than the core diameter of the screws was used. The second group of screws was inserted into the test material without pilot hole preparation (a 3- or 4-mm hole drilled for entrance site preparation only). The insertional torque was measured as the screw was advanced into the material. The screws were axially extracted from the host material at a constant speed of 2.5 mm/minute. The pullout resistances and insertional torques for the pilot hole and the nonpilot hole groups were then statistically compared. The authors found that preparation of a pilot hole caused a significant decrease in the insertional torque. The screws inserted without a pilot hole showed greater pullout resistances compared with those inserted following a pilot hole preparation; however, there was no statistically significant difference. CONCLUSIONS: The optimum screw insertion technique may involve drilling a short pilot hole and using a drill bit with a smaller diameter than the screw core diameter to increase bone-screw purchase. This applies to cancellous and cortical lateral mass screws as well as pedicle screws.

A new surgical technique: open-window corpectomy in the treatment of ossification of the posterior longitudinal ligament and advanced cervical spondylosis: technical note.

OBJECTIVE: To achieve satisfactory cervical spinal cord decompression with minimal removal of bone. METHODS: The open-window corpectomy technique is designed to remove a minimal amount of bone and achieve satisfactory decompression. With the use of a high-speed drill under a surgical microscope, only the dorsal surface of the corpus is removed after appropriate microdiscectomies. This leaves the anterior and the lateral portions of the vertebral corpus intact. RESULTS: In a 15-month period, a total of 11 patients were treated with this technique. Five patients improved, and the remaining six patients remained the same neurologically during a mean follow-up period of 8.3 months. No complications were observed in any patients. CONCLUSION: The open-window corpectomy provides satisfactory spinal cord decompression in a biomechanically sound manner.

A novel retractor for the anterior approach to the cervical spine.

Various types of retractors have been used in cervical disc operations. The most frequently used type is the Cloward's retractor. Caspar also designed a new retractor for cervical operations. The presented device is a new instrument for simple cervical disc herniation. It provides a significant surgical exposure area under the surgical microscope. When using this retractor, there is no need to use a vertebral spreader because the retractor itself can be used as a vertebral spreader and it is possible to carry out the Smith Robinson type fusion. This retractor has been used for over two hundred cases and there has not been any complication involving the carotid artery, trachea and esophagus.

Brucellar spondylitis mimicking lumbar disc herniation. Case report.

In this paper, a patient with brucellar spondylitis who was initially diagnosed as having a lumbar disc herniation is presented. As the disc tissue enlarges in the early stages of discitis because of the inflammatory reaction, it may compress the related root(s) mimicking a disc herniation. For this reason infectious discitis, as in our case, should be kept in mind in the differential diagnosis of the radicular symptoms caused by a disc herniation. The crucial role of magnetic resonance imaging in making the differential diagnosis of the case is especially emphasized.

Microvascular decompression in the surgical management of trigeminal neuralgia.

The pathophysiological mechanisms underlying trigeminal neuralgia are not clearly understood and several therapeutic modalities have been advocated. Microvascular decompression (MVD) is a widely used surgical approach for the decompression of the affected root entry zone (REZ) of the fifth cranial nerve. In this paper, we present our experience based on 32 patients with trigeminal neuralgia who were treated with MVD, and discuss the role of this procedure in the surgical management of trigeminal neuralgia. All patients had typical TN pain and had had previous medical management which was unsuccessful. Fourteen patients (44%) had been previously treated with other surgical procedures and had persisting pain at the time of admission. Preoperatively, computerized tomography was obtained in all patients; twelve patients (37.5%) were evaluated with magnetic resonance imaging. These neuroradiological studies revealed an asymmetrical vascular structure at the involved REZ in nine patients (28%). All patients underwent MVD, and a vascular loop causing compression on the REZ of the fifth cranial nerve was demonstrated in each case. No mortality was observed, and the only permanent morbidity was cerebellar infarction in one patient (3%). Symptoms disappeared in all patients in the early postoperative period, and only three recurrences (12%) were observed within the follow-up period (mean: 26 months).

Intradural rupture of cervical vertebral disc.

STUDY DESIGN: The authors discuss their experience with a patient who had cervical intradural disc herniation and relate the case to the relevant literature. OBJECTIVES: The patient was evaluated with direct radiographies, myelography, electromyography, and computerized tomography, as well as with neurologic examination. The follow-up period was 10 months post-operative. SUMMARY OF BACKGROUND DATA: Intradural disc herniation is a rare pathology nearly always confined to the lumbar region. In 1989, Katooka et al reviewed the existing literature and discovered 70 cases. Cervical intradural disc herniation, on the other hand, is much rarer, and there are only five cases in the literature. METHODS: The patient's neurologic, neuroradiologic, and operative findings were evaluated and compared with the cases reported in the literature. CONCLUSIONS: The five patients in the literature had signs of cord compression, but the present patient is the first with root compression.

Sacrococcygeal hydatid cyst: another entity in the differential diagnosis of sacrococcygeal chordoma. Case report.

A case of hydatid disease of the sacrum with severe neurological symptoms, which was misdiagnosed preoperatively as a chordoma, is presented. The patient had significant improvement of the neurological symptoms after evacuation of the cyst. Sacral hydatid cysts must be considered in the differential diagnosis of sacrococcygeal chordoma.

Magnetic resonance imaging in the diagnosis of spinal hydatid cyst disease. Case report.

A very rare case of multiple spinal hydatid disease causing paraplegia is presented. The neuroradiological evaluation included an MRI study. The surgical approach and the medical treatment of the disease is discussed, with a review of the literature.