The intervertebral disc is a cartilaginous structure that resembles articular cartilage in its biochemistry, but morphologically it is clearly different. It shows degenerative and ageing changes earlier than does any other connective tissue in the body. It is believed to be important clinically because there is an association of disc degeneration with back pain. Current treatments are predominantly conservative or, less commonly, surgical; in many cases there is no clear diagnosis and therapy is considered inadequate. New developments, such as genetic and biological approaches, may allow better diagnosis and treatments in the future.

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Degeneration of the intervertebral disc

Study design A biomechanical study was performed using cadaveric cervical spine specimens. Objective To determine the effect of cervical spine fusion on adjacent-level intradiscal pressure. Summary of background data Clinical studies have reported that patients with spinal fusion are at greater risk of pathology and early disc degeneration at adjacent levels. It is hypothesized that eliminating motion at one level leads to hypermobility and increased forces at adjacent levels, thus increasing the rate of disc degeneration. Methods Six cadaveric cervical spine specimens were tested. Specimens were stabilized at T1 and loaded at C3 to 20 degrees of flexion and 15 degrees of extension. Intradiscal pressures and segmental motion at C4-C5 and C6-C7 were recorded first on intact specimens, and then after anterior cervical plating at C5-C6. Changes in intradiscal pressure and segmental motion were calculated and statistically analyzed using a paired Student t test. Results Intradiscal pressures were significantly increased during flexion at both adjacent levels. The pressure increased by 73.2% at C4-C5 (P = 0.002), and by 45.3% at C6-C7 (P = 0.006). Intradiscal pressures increased at both adjacent levels during extension, but not significantly. During flexion, segmental motion increased at both adjacent levels, with greater increases at C4-C5. During extension, segmental motion increased at both adjacent levels, with greater increases at C6-C7. Conclusions Clinical studies have reported increased rates of disc degeneration at levels adjacent to fusion. It is believed that eliminating motion through fusion shifts the load to the adjacent levels, causing earlier disc degeneration. This study has shown that significant increases in intradiscal pressure and segmental motion occur at levels adjacent to fusion during normal range of motion. These results may partially explain the mechanism of early disc degeneration at levels adjacent to cervical spine fusion.

Biomechanical Study on the Effect of Cervical Spine Fusion on Adjacent-Level Intradiscal Pressure and Segmental Motion

Background: Surgical site infections are not uncommon following spinal operations, and they can be associated with serious morbidity, mortality, and increased resource utilization. The accurate identification of risk factors is essential to develop strategies to prevent these potentially devastating infections. We conducted a case-control study to determine independent risk factors for surgical site infection following orthopaedic spinal operations.

Methods: We performed a retrospective case-control study of patients who had had an orthopaedic spinal operation performed at a university-affiliated tertiary-care hospital from 1998 to 2002. Forty-six patients with a superficial, deep, or organ-space surgical site infection were identified and compared with 227 uninfected control patients. Risk factors for surgical site infection were determined with univariate analyses and multivariate logistic regression.

Results: The overall rate of spinal surgical site infection during the five years of the study was 2.0% (forty-six of 2316). Univariate analyses showed serum glucose levels, preoperatively and within five days after the operation, to be significantly higher in patients in whom surgical site infection developed than in uninfected control patients. Independent risk factors for surgical site infection that were identified by multivariate analysis were diabetes (odds ratio = 3.5, 95% confidence interval = 1.2, 10.0), suboptimal timing of prophylactic antibiotic therapy (odds ratio = 3.4, 95% confidence interval = 1.5, 7.9), a preoperative serum glucose level of >125 mg/dL (>6.9 mmol/L) or a postoperative serum glucose level of >200 mg/dL (>11.1 mmol/L) (odds ratio = 3.3, 95% confidence interval = 1.4, 7.5), obesity (odds ratio = 2.2, 95% confidence interval = 1.1, 4.7), and two or more surgical residents participating in the operative procedure (odds ratio = 2.2, 95% confidence interval = 1.0, 4.7). A decreased risk of surgical site infection was associated with operations involving the cervical spine (odds ratio = 0.3, 95% confidence interval = 0.1, 0.6).

Conclusions: Diabetes was associated with the highest independent risk of spinal surgical site infection, and an elevated preoperative or postoperative serum glucose level was also independently associated with an increased risk of surgical site infection. The role of hyperglycemia as a risk factor for surgical site infection in patients not previously diagnosed with diabetes should be investigated further. Administration of prophylactic antibiotics within one hour before the operation and increasing the antibiotic dosage to adjust for obesity are also important strategies to decrease the risk of surgical site infection after spinal operations.

Level of Evidence: Prognostic Level III. See Instructions to Authors for a complete description of levels of evidence.

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Risk factors for surgical site infection following orthopaedic spinal operations.

Degenerative disc and facet joint disease of the lumbar spine is common in the ageing population, and is one of the most frequent causes of disability Lumbar spondylosis may result in mechanical back pain, radicular and claudicant symptoms, reduced mobility and poor quality of life Surgical interbody fusion of degenerative levels is an effective treatment option to stablize the painful motion segment, and may provide indirect decompression of the neural elements, restore lordosis and correct deformity The surgical options for interbody fusion of the lumbar spine include: posterior lumbar interbody fusion (PLIF), transforaminal lumbar interbody fusion (TLIF), minimally invasive transforaminal lumbar interbody fusion (MI-TLIF), oblique lumbar interbody fusion/anterior to psoas (OLIF/ATP), lateral lumbar interbody fusion (LLIF) and anterior lumbar interbody fusion (ALIF) The indications may include: discogenic/facetogenic low back pain, neurogenic claudication, radiculopathy due to foraminal stenosis, lumbar degenerative spinal deformity including symptomatic spondylolisthesis and degenerative scoliosis In general, traditional posterior approaches are frequently used with acceptable fusion rates and low complication rates, however they are limited by thecal sac and nerve root retraction, along with iatrogenic injury to the paraspinal musculature and disruption of the posterior tension band Minimally invasive (MIS) posterior approaches have evolved in an attempt to reduce approach related complications Anterior approaches avoid the spinal canal, cauda equina and nerve roots, however have issues with approach related abdominal and vascular complications In addition, lateral and OLIF techniques have potential risks to the lumbar plexus and psoas muscle The present study aims firstly to comprehensively review the available literature and evidence for different lumbar interbody fusion (LIF) techniques Secondly, we propose a set of recommendations and guidelines for the indications for interbody fusion options Thirdly, this article provides a description of each approach, and illustrates the potential benefits and disadvantages of each technique with reference to indication and spine level performed

Lumbar interbody fusion: techniques, indications and comparison of interbody fusion options including PLIF, TLIF, MI-TLIF, OLIF/ATP, LLIF and ALIF.

Object. The objective of this study was to identify specific independent risk factors for surgical site infections (SSIs) occurring after laminectomy or spinal fusion. Methods. The authors performed a retrospective case-control study of data obtained in patients between 1996 and 1999 who had undergone laminectomy and/or spinal fusion. Forty-one patients with SSI or meningitis were identified, and data were compared with those acquired in 178 uninfected control patients. Risk factors for SSI were determined using univariate analyses and multivariate logistic regression. The spinal surgery—related SSI rate (incisional and organ space) during the 4-year study period was 2.8%. Independent risk factors for SSI identified by multivariate analysis were postoperative incontinence (odds ratio [OR] 8.2, 95% confidence interval [CI] 2.9–22.8), posterior approach (OR 8.2, 95% CI 2–33.5), procedure for tumor resection (OR 6.2, 95% CI 1.7–22.3), and morbid obesity (OR 5.2, 95% CI 1.9–14.2). In patients with SSI the pos...

Risk factors for surgical site infection in spinal surgery

STUDY DESIGN: A study of the transforaminal lumbar interbody fusion and the posterior lumbar interbody fusion techniques was performed. OBJECTIVES: To describe the transforaminal lumbar interbody fusion technique, and to compare operative data, including blood loss and operative time, with data from posterior lumbar interbody fusion technique. SUMMARY OF BACKGROUND DATA: The evolution of posterior lumbar fusion combined with anterior interbody fusion has resulted in increased fusion rates as well as improved reductions and stability. The transforaminal lumbar interbody fusion technique pioneered by Harms and Jeszensky offers potential advantages and provides a surgical alternative to more traditional methods. METHODS: In 13 consecutive months, two spinal surgeons performed 40 transforaminal lumbar interbody fusions and 34 posterior lumbar interbody fusion procedures. Data regarding blood loss, operative times, and length of hospital stay were recorded. These data were analyzed using analysis of variance to show any significant differences between the two techniques. To determine whether differences in measured variables were dependent on patient gender or number of levels fused, epsilon(chi2) analysis was used. RESULTS: No significant differences were found between transforaminal and posterior lumbar interbody fusions in terms of blood loss, operative time, or duration of hospital stay when a single-level fusion was performed. Significantly less blood loss occurred when a two-level fusion was performed using the transforaminal approach instead of the posterior approach (P < 0.01). Differences in measured variables for the two procedures were independent of patient age, gender, and the number of levels fused. There were no complications with the transforaminal approach, but the posterior approach resulted in multiple complications. CONCLUSIONS: In this comparison of patients receiving transforaminal lumbar interbody fusion versus posterior lumbar interbody fusion, no complications occurred with the transforaminal approach, whereas multiple complications were associated with the posterior approach. Similar operative times, blood loss, and duration of hospital stay were obtained in single-level fusions, but significantly less blood loss occurred with the transforaminal lumbar interbody approach in two-level fusions. The transforaminal procedure preserves the interspinous ligaments of the lumbar spine and preserves the contralateral laminar surface as an additional surface for bone graft. It may be performed at all lumbar levels because it avoids significant retraction of the dura and conus medullaris.

Comparison of posterior and transforaminal approaches to lumbar interbody fusion.

Lumbar fusion is commonly performed to relieve pain from degenerative conditions, including spinal stenosis and spondylolisthesis. While clinical studies have reported favorable fusion rates with limited complications, few have investigated the effect of fusion on the adjacent motion segment. A solid fusion alters the biomechanics at the adjacent level, resulting in increased mechanical demands. There have been reports of increased rates of adjacent-level pathologic lesions after fusion, but these have not accounted for the natural history of degenerative changes. Biomechanical and radiographic studies have shown increased forces, mobility, and intradiscal pressure in adjacent segments after fusion. It has been hypothesized that these changes lead to an acceleration in pathologic changes.

Adjacent-segment degeneration after lumbar fusion : a review of clinical, biomechanical, and radiologic studies

Study Design. A retrospective review of 20 patients with incidental durotomy treated without mandatory bed rest. Objectives. To determine whether patients with incidental durotomy can be treated effectively without multiple days of bed rest. Summary of Background Data. Incidental durotomy can cause postural headaches, nausea, vomiting, dizziness, photophobia, tinnitus, and vertigo. These symptoms are believed to result from a decrease in cerebrospinal fluid pressure, leading to traction on the supporting structures of the brain. Traditional management includes bed rest for up to 7 days to eliminate traction and reduce hydrostatic pressure during the healing process. Methods. Twenty incidental durotomies were repaired intraoperatively with dural stitches and fibrin glue. Patients were allowed to ambulate according to the natural course after surgery without mandatory bed rest. Symptoms were monitored closely for 1 week, and long-term follow-up assessments were obtained at a minimum of 10 months. Results. Of the 20 patients in this study, 75% had no symptoms after repair of the incidental durotomy. Each of the dural tears was 1–3 mm in length. Two patients reported headache, two reported nausea, and one reported tinnitus; no patients experienced vomiting. One patient (5%) had stitch loosening requiring revision surgery. There were no additional serious complications. Conclusions. This study has shown that the majority of patients with incidental durotomy can be treated effectively with dural stitches and fibrin glue. Patients can be permitted to ambulate immediately after surgery but should be cautioned to lay flat if they develop symptoms. This will reduce the costs related to the hospital stay and missed work.

Management of incidental durotomy without mandatory bed rest. A retrospective review of 20 cases.

Study Design This study was intended to identify normal degenerative morphologic evolution in the bony foramen in asymptomatic subjects by decade in comparison with symptomatic subjects of like decades Objectives To determine normal degenerative changes in the cervical spine caused by the aging process that predispose a person to foraminal stenosis and radiculopathy Summary of Background Data Cervical radiculopathy is a common problem caused by degenerative changes as people age The characteristics of the foramen that result in stenosis are not known Methods Five to six symptomatic and asymptomatic people in each decade volunteered for magnetic resonance imaging Lordosis, disc heights, and ratio of spinal cord diameter to spinal canal diameter were measured at C4-C5, C5-C6, and C6-C7 from sagittal magnetic resonance images Foraminal heights, widths, and areas were measured at the isthmus of the same foramen from oblique images Results Foraminal heights, widths, and areas were larger in asymptomatic patients than in symptomatic patients Morphologic analysis showed that inferior facet hypertrophy tended to decrease the width of the foramen in aging people Disc heights, lordosis, and ratio of spinal cord diameter to spinal canal diameter showed no significant differences Conclusions Foraminal height affects overall foraminal area but tends to change little with age Width also affects overall area and not only decreases in older people but also significantly affects the available area for the exiting nerve root

The natural history of the cervical foramen in symptomatic and asymptomatic individuals aged 20-60 years as measured by magnetic resonance imaging. A descriptive approach.

Study design A retrospective review of 25 patients who underwent a modified surgical procedure for the treatment of far lateral disc herniation. Objectives To describe a modification of previous surgical techniques for the treatment of far lateral disc herniation and to review the outcomes in resolution of pain and improvement of functional status. Summary of background data Lumbar disc herniations that occur far lateral to the intervertebral facet result in spinal nerve compression at L3-L4 and L4-L5. Previous surgical techniques have resulted in an increased risk of instability or continued postoperative back pain. Methods Twenty-five patients with far lateral disc herniation underwent surgery using an extreme lateral approach. There was no medial facetectomy or disruption of the pars interarticularis. The intertransverse ligament was released from the superior portion of the inferior transverse process, and the nerve was located before removal of the disc. Preoperative and postoperative visual analog pain scale and Oswestry functional status evaluation were reviewed along with complications to evaluate the efficacy of the surgery. Results No serious complications were noted, although transient neuropathic pain was common and was theorized to be caused by manipulation of the dorsal root ganglion during surgery. This pain was usually resolved within 4 to 6 weeks. The mean preoperative and postoperative visual analog scale scores were 7.7 and 4.2, respectively. The mean preoperative and postoperative Oswestry scores were 50.7% and 34.7%, respectively. Both of these improvements were statistically significant (P Conclusions This far lateral approach allowed the nerve and far lateral disc herniations to be easily identified. Also, there was less blood loss and no medial facetectomy or disruption of the pars interarticularis. This is a safe, effective technique with no disruption of spinal stability.

S C Humphreys

Papers

Comparison of posterior and transforaminal approaches to lumbar interbody fusion.

Adjacent-segment degeneration after lumbar fusion : a review of clinical, biomechanical, and radiologic studies

Management of incidental durotomy without mandatory bed rest. A retrospective review of 20 cases.

The natural history of the cervical foramen in symptomatic and asymptomatic individuals aged 20-60 years as measured by magnetic resonance imaging. A descriptive approach.

The surgical treatment of far lateral L3-L4 and L4-L5 disc herniations. A modified technique and outcomes analysis of 25 patients.