Introduction: Restoration of vertebral height for burst fractures can be achieved either anteriorly, posteriorly or combined.

Aim: To biomechanically assess and compare stiffness of 1) posterior pedicle screws with Synex, 2) Synex+ Double screw+rod Ventrofix 3) Synex+ Double screw+ Single rod and 4) Synex+ Single screw+ Single rod in reconstructing an unstable burst fracture following anterior corpectomy.

Method: Fresh frozen calf lumbar spines (L3–L5) were dissected and L4 corpectomy performed. L3 and L5 were mounted on a plate and fixed. Loads were applied as a dead weight of 2Nm. The range of movement was measured using the Qualisys motion analysis system using external marker clusters attached to L3 and L5. Bony landmarks were identified with marker clusters as baseline. The movement was measured between the 2 marker clusters.

Five specimens were implanted for each group 1) with pedicle screw (into L3 and L5) and tested with/without Synex (expandable) cage anteriorly, 2) implanted with a Synex cage and Double screw+rod Ventrofix system, 3) Synex cage and Double screw+ Single rod Ventrofix construct and 4) Synex cage and Single screw+ Single rod Ventrofix system.

Results: Reconstruction of the anterior column with the combination of Synex and double rod Ventrofix produces a stiffer construct than the pedicle screw system in all planes of movement (p= 0.001 in rotation).

The double screw/ single rod system is less effective than the Ventrofix System but is comparable to the pedicle screw construct.

The single screw/ single rod construct leads to unacceptable movement about the axis of the inferior screw particularly in extension with a ROM much greater than the intact spine (p< 0.001)

Conclusion: Thus biomechanically we recommend Synex and double rod Ventrofix construct to reconstruct the anterior vertebral column following corpectomy for unstable burst fractures.

Introduction The precise contribution of the posterior longitudinal ligament (PLL) and disc annulus in the burst fracture setting and their potential relative roles during intra operative reduction manoeuvres remains unclear. The anatomical attachments of the posterosuperior fragment most often associated with canal occlusion and potential neurological compromise are not well described in a reproducible model.

Methods Burst fractures were induced using a pendulum impact tester. The jig allowed for accurate positioning in all planes and for precise delivery of both the magnitude and vector of the impact force. This allowed for creation of fracture all three major groups of the AO classification. The A3 (burst fracture) was produced in 10 cadaveric sheep spines by delivering a neutral force vector on a physiologically flexed spine. The morphology of the fracture was confirmed by CT. Subsequent laminectomy was performed and the anatomical attachments of the large fragments were identified.

Results The PLL was identified following laminectomy in each case. In six of the ten spines there had been significant disruption of the longitudinal structure of the PLL .In a further two cases there had been stripping of the PLL from the posterior aspect of the vertebral body in association with the retropulsed canal fragment. Subsequent excision of the PLL from the posterior aspects of vertebral body and discs did not compromise the attachment of the retropulsed fragment to the disc annulus in any case.

Discussion This study confirms the anatomical relationship between disc fragment and disc annulus in the burst fracture setting. The strong attachment between fragment and disc facilitate rotation of the fragment about this hinge and into the canal. Subsequent intraoperative reduction of this fragment by restoration of disc height may require contribution both from this annular attachment and from tension set up in an intact PLL. The relative contributions of each of these structures in the reduction manoeuvre remains unclear.

Introduction A tertiary referral centre for spinal injuries will receive referrals from many different centres. The format and quality of imaging that accompanies these patients varies considerably.

Methods Two cases are reported where initial imaging demonstrated unstable cervical spine injuries that were subsequently found to be normal. The cases and images are presented.

Results A 19-year old female was transferred to our unit having fallen off a wall and sustaining a neck injury. The accompanying CT scan showed a C6 vertebral body fracture with bilateral fracture-subluxations of the facet joints. As there was a discrepancy with the clinical findings, a repeat fine cut CT scan was performed which was completely normal. The previous appearances were entirely due to artifact throughout the scan.

A 46-year old male fell down stairs sustaining a neck injury and loss of consciousness. A CT scan of his cervical spine demonstrated an odontoid peg fracture (type II). Subsequent imaging showed the odontoid peg was completely normal. The initial CT appearances were entirely due to artifact caused by the patients’ tongue piercing!

Discussion CT scans are used with increasing frequency in the assessment of cervical spine injuries. In both these case the abnormalities present on the initial scans were entirely due to artifact that was reciprocated through the entire CT scans. Reporting these cases reinforces the importance of careful clinical examination and correlation with appropriate investigations. If there is a discrepancy between the clinical and radiological findings then it is essential that further imaging is performed.

Introduction Far lateral disc prolapse (also known as foraminal or extreme lateral prolapse) make up 10% of all disc herniations. In addition, far lateral disc prolapses tend to affect more proximal levels more frequently than do prolapses in the posterolateral location and they are often associated with greater radicular symptoms than typical posterolateral herniations, most likely due to involvement of the dorsal root ganglion. Surgery for far lateral disc protrusions has been associated with a less favourable outcome, perhaps due to delays in diagnosis, inadequate preoperative imaging, and postoperative instability as a result of excessive bony and facet resection during the surgical approach

Methods Twelve patients with far lateral disc herniations operated on by the senior author (RPW) fulfilled the criteria of having both pre- and postoperative Oswestry Disability Index (ODI) scores recorded at each clinic visit. Results of these cases and those of a cohort of age and sex matched patients undergoing standard posterolateral discectomy undertaken by the same surgeon were analyzed. The presence of radiculopathy pre- and postoperatively, workers compensation status, return to work, length of stay and complications, as well as any prior intervention in the form of nerve root sleeve blocks or surgery were recorded

Results Both groups were well matched in terms of age and sex. Follow up ranged from 4 to 18 months. Herniations at more proximal levels (L2/3 and L3/4) were seen more frequently in the far lateral group than in the posterolateral group. Six patients in the far lateral group had preoperative nerve root sleeve blocks compared with one in the posterolateral group. Two patients in each group had had previous (different level) surgery. Patients in each group had similar preoperative ODI scores. Both groups demonstrated a reduction in the preoperative ODI compared with the preoperative score. The mean improvement was 24 (range −26 to +62) for the far lateral group and 22 (range −6 to +46). There was no significant difference between the groups

Discussion The results of this study are encouraging with respect to surgical treatment of far lateral discs. Recent literature has questioned the efficacy of surgical intervention for this pathology. These results show that with carefully selected patients results are comparable with standard posterolateral discectomy

Controversy exists as to whether the biomechanical properties of a 360 lumbar fusion are influenced by the order in which the anterior and posterior components of the procedure are performed.

The fusion technique used Magerl screws to effect the posterior fusion and a Syncage implant (Stratec) to effect the anterior component of the fusion.

Isolated motion segments from calf spines were tested in each of two groups of five. In the first group the posterior fusion was performed first and in the second group the anterior fusion was performed first. Loads were applied as a dead weight of 2Nm in each range of movement of the spine (flexion/extension, lateral flexion and rotation). The range of movement was measured using the Qualisys motion analysis software linked to a set of five cameras, using external marker clusters attached to the vertebral bodies. Each motion segment was tested prior to instrumentation, post anterior or posterior instrumentation and with both anterior and posterior instrumentation.

Ranges of movement following 360 instrumentation were increased in all planes tested when posterior fixation was performed first; flexion/extension 26% v 55% (p=0.020), lateral flexion 18% v 34% (p=0.382), and rotation 18% v 73% (p=0.034).

It was concluded that posterior fixation should not be performed prior to anterior fixation as this results in a significant loss of stability in both flexion/extension and rotation

Objective: Controversy exists as to whether the biomechanical properties of a 360° lumbar fusion are influenced by the order in which the anterior and posterior components of the procedure are performed.

Methods: The fusion technique used Mager screws to effect the posterior fusion and a Syncage implant (Stratec) to effect the anterior component of the fusion. Isolated motion segments from five calf spines were tested in each of two groups. In the first group the posterior fusion was performed first and in the second group the anterior fusion was performed first. Loads were applied as a dead weight of 2Nm in each range of movement of the spine (flexion/extension, lateral flexion and rotation). The range of movement was measured using the Qualisys motion analysis system, using external marker clusters attached to the vertebral bodies. Each motion segment was tested prior to instrumentation, post anterior or posterior instrumentation and with both anterior and posterior instrumentation.

Results: Ranges of movement following 360° instrumentation were decreased in all planes. When posterior fixation was performed first; flexion/extension reduced to 55% compared to 26% with anterior fixation first (p=0.020), in lateral flexion 34% v 18% (p=0.382), and in rotation 73% v 18%(p=0.034).

Conclusions: The 360° fusion construct has reduced range of movement if the anterior first approach is used as compared to posterior first approach. Posterior fixation should not be performed prior to anterior fixation as this results in a significant loss of stability in both flexion/extension and rotation.