George K. Triantafyllopoulos

Posterior Spinal Fusion Using Pedicle Screws

Few clinical studies have reported polyetheretherketone (PEEK) rod pedicle screw spinal instrumentation systems (CD-Horizon Legacy PEEK rods; Medtronic, Minneapolis, Minnesota). This article describes a clinical series of 52 patients who underwent posterior spinal fusion using the PEEK Rod System between 2007 and 2010. Of the 52 patients, 25 had degenerative disk disease, 10 had lateral recess stenosis, 6 had degenerative spondylolisthesis, 6 had lumbar spine vertebral fracture, 4 had combined lateral recess stenosis and degenerative spondylolisthesis, and 1 had an L5 giant cell tumor. Ten patients had 1-segment fusion, 29 had 2-segment fusion, and 13 had 3-segment fusion. Mean follow-up was 3 years (range, 1.5-4 years); no patient was lost to follow-up. Clinical evaluation was performed using the Oswestry Disability Index and a low back and leg visual analog pain scale. Imaging evaluation of fusion was performed with standard and dynamic radiographs. Complications were recorded. Mean Oswestry Disability Index scores improved from 76% preoperatively (range, 52%-90%) to 48% at 6 weeks postoperatively, and to 34%, 28%, and 30% at 3, 6, and 12 months postoperatively, respectively. Mean low back and leg pain improved from 8 and 9 points preoperatively, respectively, to 6 and 5 points immediately postoperatively, respectively, and to 2 points each thereafter. Imaging union of the arthrodesis was observed in 50 (96%) patients by 1-year follow-up. Two patients sustained screw breakage: 1 had painful loss of sagittal alignment of the lumbar spine and underwent revision spinal surgery with pedicle screws and titanium rods and the other had superficial wound infection and was treated with wound dressing changes and antibiotics for 6 weeks. No adjacent segment degeneration was observed in any patient until the time of this writing.

PEEK rod systems for the spine

Abstract Traditional materials for the spine such as titanium and stainless steel have produced satisfying long-term fusion rates, mainly due to their strength and stiffness. However, although fixation with titanium rods leads to high fusion rates, increased stiffness of titanium constructs may also contribute to stress shielding and adjacent segment degeneration. Dynamic and flexible materials such as the Dynesys system allow better stress distribution to all of the spinal columns, but increase the rate of complications including screw loosening, infection, back and leg pain, and endplate vertebral fracture. Semi-rigid instrumentation systems using rods made from synthetic polymers such as the polyetheretherketone (PEEK) have been recently introduced as an alternative biomaterial for the spine. PEEK is a fully biocompatible and inert semi-crystalline thermoplastic polymer with minimal toxicity; it has a modulus of elasticity between that of cortical and cancellous bone, and significantly lower than titanium. However, there are very few clinical studies with small sample size and short-term follow-up using PEEK rod-pedicle screw spinal instrumentation systems. Additionally, their results are conflicting. To enhance the literature, this review discusses the effect of this medical for the spine and summarizes the results of the most important related series.

Whiplash Associated Disease

Whiplash associated disorder is the name given to a collection of symptoms including pain in the neck, head, shoulder and arms following rear end collisions. The classic explanation is that the head is suddenly jerked back and forth beyond its normal limits after a collision or car crash, causing the muscles and ligaments supporting the neck to be injured. More precisely, an upward force on the cervical spine causes abnormal movements of the lower cervical spine with damage to the zygapophyseal and other joints between the vertebrae, at least in some cases. The injury may or may not cause acute symptoms. Those symptoms may be contrived; they may be mild; or they may be serious. The treatment may or may not be effective and many patients may develop chronic problems. The outcome of the natural history of this condition is not predictable and thus Whiplash disease may be the reason for many legal proceedings. The Quebec classification is the most common grading system of Whiplash disease and is based primarily on pathoanatomy.

Traumatic Spondylolisthesis of the Axis (Hangman’s Fracture)

This injury refers to a fracture of both pedicles or pars inter-articularis of the axis vertebra (C2). Apart from hangings, the mechanism of injury – a sudden forceful hyperextension centred just under the chin – occurs mainly with deceleration injuries in which the victim’s face or chin strike an unyielding object with the neck in extension. The most recent and most useful classification is the four types classification proposed by Levine and Edwards, which is essentially a modification of Effendi and associates three types classification.

Ossification of the Posterior Longitudinal Ligament (OPLL)

This clinical situation, which comprises high prevalence in Japanese population, is characterized by hyperplasia of cartilage cells with eventual endochondral ossification of the posterior longitudinal ligament. As the most common site of ossification of the PLL is in the cervical cord, cervical myelopathy is the most common presentation. However, clinically significant ossification of the ligament has also been noted to occur in the thoracic and lumbar spine. Ossification of the PLL can present with pain, neurological deficit, or with acute neurological injury (even after a minor injury). However, given the prevalence of ossified PLL, the majority of patients with OPLL remain without significant symptoms.

Lower Cervical Spine Injuries

The scheme proposed by Argenson et al. which derived from a study of 255 trauma patients, follows on from previous classifications devised by Allen and, Harris. The previous schemes were based upon the assumption that injuries to the lower cervical spine (LCS) are produced by multiple simultaneous forces, with one force vector predominant. In this scheme, compression, flexion-extension-distraction and rotation were considered to be the main force vectors, which occur with equal frequency. Within each of these vector groups, the injuries produced are graded into three subgroups, as a function of the intensity of the trauma-producing force.

Atlanto-Occipital Dislocations

The incidence of atlanto-occipital dislocation has been encountered in 1 % of alive or dead victims of cervical spine injuries. The mechanism of injury includes extension and traction of the head which results to disruption of the ligaments around the Atlanto-Occipital region. The symptoms include severe neck pain and neurologic presentation which can range from no deficits to quadriplegia with ventilator dependency. Cranial nerve palsies of the fifth, sixth, ninth and eleventh nerves may be present. The classification describing this rare type of injury was proposed in 1986 by Traynelis et al and is based on the position of the Occipital condyles in relation to C1 (Atlas) vertebra.

Myelopathy: Nurick Grading System

The classic presentation of myelopathy is numbness and clumsiness of the hands in association with a stiff, spastic unsteady gait. Acute myelopathy can occur spontaneously or after minor or major trauma. The common presentation is a central spinal cord syndrome with pain. The neurologic loss is that of lower motor abnormalities in arms and hands with hyperreflexia and spasticity on the legs. Attempts at grading myelopathy have focused on the effects on patients’ performance. A six grade system (0–5) based on the ‘difficulty in walking’ was published by S. Nurick in Brain in 1972.

American Spinal Injury Association - ASIA - Impairment Scale for Neurological Deficit

Spinal cord injuries are classified as complete and incomplete by the American Spinal Injury Association (ASIA) classification. The ASIA scale grades patients based on their functional impairment as a result of the injury, grading a patient from A to E.

Occipital Condyle Fractures

Occipital Condyle Fractures (OCFs) can easily be missed because the clinical manifestation is highly variable and the results of physical examination are usually nonspecific. The most widely used classification system is the one proposed in 1988 by Anderson and Montesano who divided OCFs into three types, depending on their morphology and mechanism of injury.