Traditionally, spinal surgeons placed radiographs on viewing boxes in a manner (PA) to replicate the view they would have at surgery. The introduction of digital Picture Archiving and Communications System (PACS) appears to have had marked impact upon this convention. Some Units have the ability to lock digital radiographs such that they are always viewed in the same manner and cannot be reversed.

Following ‘two near misses’ we carried out a survey to confirm the previous practice with radiographs; to ascertain the current practice with PACS and to find out whether the variation in practice could lead to clinical mishaps and harm to patients.

Questionnaires were completed by practicing spinal surgeons.

Previous and current practice of viewing radiographs. Either actual or potential wrong side surgery. Opinions as to whether a single convention was important were recorded.

78 % Spine surgeons used to flip radiographs over prior to introduction of PACS. With PACS, 56 % spine surgeons flip the radiographs over in clinic and 72 % in theatre so to resemble viewing spine from behind. 56% Surgeons had nearly operated on the wrong side of the spine while 94 % have seen or heard of a patient operated on the wrong side. 72 % Spine surgeons agree that the radiographs should be flipped over so as to resemble the spine as viewed intraoperatively.

There is need for a single convention in spine surgery to view radiographs to avoid potential clinical mistakes.

There is evidence that various anatomical structures have altered morphology with ageing, and anecdotal evidence of changing lumbar spinous process (LSP) morphology with age. This study aims to clarify the influence of age on LSP morphology, and on lumbar spine alignment.

200 CT scans of the abdomen were reformatted with bone windows allowing precise measurement of LSP dimensions and lumbar lordosis. Observers were blinded to patient demographics. Inter-observer reliability was confirmed.

The smallest LSP is at L5. The male LSP is on average 2-3mm higher and 1mm wider than the female LSP. LSP height increases significantly with age at every level in the lumbar spine (P<10^-5 at L2). The LSPs increase in height by 2-5mm between 20-85 years of age (P<10^-6), which was as much as 31% at L5 (P<10^-8). Width increases proportionally more, by 3-4mm or greater than 50% at each lumbar level (P<10^-11). Lumbar lordosis decreases in relation to increasing LSP height (P<10^-4) but is independent of increasing LSP width (P=0.2).

The height and width of the spinous processes increases with age. Increases in spinous process height are related to a loss of lumbar lordosis and may contribute to sagittal plane imbalance.

Auckland City Hospital, Auckland, New Zealand.

To show that the spinous processes (SPs) increase in size with age.

To investigate the incidence of SP abutment, relationship to disc degeneration and age related kyphosis.

Describe patterns of SP neoarticulation in relation to back pain and intersegmental axial rotation and deformity.

We reviewed 200 Abdominal CTs, CT myelograms and 100 standing x-rays (age 18-90 years).

We measured SP size, interspinous gap, patterns of neoarticulation, disc height, lumbar lordosis and axial rotation.

We compared symptomatic and asymptomatic groups.

A 30-50% increase in SP size coupled combined with a loss of disc height leads to increasing rates of SP abutment after the age of 35 years. 30% of people over the age of 60 years have SP abutment.

There is a 15 degree increase in standing lumbar kyphosis with age.

Four patterns of SP neoarticulation are seen. Degenerative changes in the SP articulation increase by more than 80% in a symptomatic cohort.

Oblique SP articulation is 2.5 times more likely in symptomatic individuals and associated with a rotational intersegmental deformity.

Ageing is accompanied by SP enlargement and abutment, contributing to a loss of lumbar lordosis.

Patterns of neoarticulation and degeneration appear associated with back pain and rotational deformity.

We aimed (1) to determine the factors which influence outcome after surgery for CES and (2) to study CES MRI measurements. 56 patients with evidence of a sphincteric disturbance who underwent urgent surgery (1994-2002) were identified and invited to clinic. 31 MRIs were available for analysis and randomised with 19 MRIs of patients undergoing discectomy for persistent radiculopathy. Observers estimated the percentage of spinal canal compromise and indicated whether they thought the scan findings could produce CES and whether the discs looked degenerate. Measurements were repeated after two weeks.

(1) 42 patients attended (mean follow up 60 months; range 25–114). Mean age at onset was 41 years (range 24–67). 26 patients were operated on within 48 hours of onset. Acute onset of sphincteric symptoms and the time to operation did not influence the outcomes. Leg weakness at onset persisted in a significant number at follow-up (p<0.005). Bowel disturbance at presentation was associated with sexual problems (<0.005) at follow-up. Urinary disturbance at presentation did not affect the outcomes. The 13 patients who failed their post-operative trial without catheter had worse outcomes. The SF36 scores at follow-up were reduced compared to age-matched norms in the population. The mean ODI was 29, LBOS 42 and VAS 4.5.

(2) No significant correlations were found between MRI canal compromise and clinical outcome. There was moderate to substantial agreement for intra- and inter-observer reproducibility.

Background: The Lumbar Spinous Processes (LSP) have an important anatomical and biomechanical function. They also influence access to the spinal canal for neural decompressive surgical procedures. There is evidence that various anatomical structures have altered morphology with ageing, and there is anecdotal evidence of changing LSP morphology with age. This study aims to clarify the influence of age on LSP morphology, and on lumbar spine alignment.

Method: 200 CT scans of the abdomen were reformatted with bone windows allowing precise measurement of LSP dimensions, and Lumbar Lordosis. Observers were blinded to patient demographics. Inter-observer reliability was confirmed.

Results: The smallest LSP is at L5. The male LSP is on average 2–3mm higher and 1mm wider than the female LSP. LSP height increases significantly with age at every level in the lumbar spine (P< 10-5 at L2). The LSPs increase in height by 2–5mm between 20–85 years of age (P< 10-6), which was as much as 31% at L5 (P< 10-8). Width increases proportionally more, by 3–4mm or greater than 50% at each lumbar level (P< 10-11). Lumbar lordosis decreases in relation to increasing LSP height (P< 10-4) but is independent of increasing LSP width (P=0.2).

Conclusions: The height and width of the spinous processes increases with age. Increases in spinous process height are related to a loss of lumbar lordosis and may contribute to sagittal plane imbalance.

Conflicts of Interest: None

Source of Funding: None

The Lumbar Spinous Processes (LSP) have an important anatomical and biomechanical function protecting the neural structures in the spinal canal, and as an anchor for the inter and supraspinous ligaments, and the inter-segmental paraspinal muscles. They also influence access to the spinal canal for neural decompressive surgical procedures. More recently the LSPs have attracted increased interest as a site for surgical device attachment in an attempt to both decrease the symptoms of spinal stenosis, and as a site for intersegmental stabilization without formal fusion. There is evidence that various anatomical structures have altered morphology with ageing, and there is anecdotal evidence of changing LSP morphology with age. This study aims to clarify the influence of age on LSP morphology, and on lumbar spine alignment.

200 CT scans of the abdomen were reformatted with bone windows in sagittal and coronal planes allowing precise measurement of LSP dimensions, and Lumbar Lordosis. Observers were blinded to patient demographics. Inter-observer reliability was examined. Data was analysed by an independent statistician.

The smallest LSP is at L5. The male LSP is on average 2–3mm higher and 1mm wider than the female LSP. LSP height increases significantly with age at every level in the lumbar spine (p< 10-5 at L2). The LSPs increase in height by 2–5mm between 20–85 years of age (p< 10-6), which was as much as 31% at L5 (p< 10-8). Width increases proportionally more, by 3–4mm or greater than 50% at each lumbar level (p< 10–11). Lumbar lordosis decreases in relation to increasing LSP height (p< 10-4) but is independent of increasing LSP width (p=0.2).

This study demonstrates that the dimensions of the LSP change with age. Increases in LSP height occur with age. More impressive increases in LSP width occur with advancing age. This study suggests that loss of lumbar lordosis is correlated with changing LSP morphology.

The increased width of the LSP with age influences access to the spinal canal, particularly if midline-preserving approaches are attempted in the ageing population. There is increased bone volume for bone grafting procedures with increasing age. The reduced distance between LSPs with age may influence design of implants that stabilize this region of the spine, and occur not only as a result of disc space narrowing, but also as a consequence of increased LSP dimensions.

Methods: A Ring Fixator (Taylor Spatial Frame (TSF); Smith & Nephew, Memphis, TN), was used in the treatment of 5 patients (ages 11 to 16 years) with proximal tibial growth arrest following trauma.

Results: The mean corrections were 14.2° (max 28°, min 0°) in the saggital plane and 14° (max 38°, min 2°) in the coronal plane. Leg length discrepancy was also corrected (max 1cm). The average time in frame was 17.8 weeks, with an average correction time of 29.8 days. Knee Society Clinical Rating System (KSCRS) scores post operatively ranged from 95 to 100. All patients returned to full activity, and would accept the same treatment if offered again. The circular fixator is an effective, minimally invasive method for treating the complex deformities arising from this rare injury. Patients remain active during treatment, encouraging a rapid return to school/work activities.

A Ring Fixator (Taylor Spatial Frame (TSF); Smith & Nephew, Memphis, TN), was used in the treatment of 5 patients (ages 11 to 16 years) with proximal tibial growth arrest following trauma. The mean corrections were 14.20 (max 280, min 00) in the saggital plane and 140 (max 380, min 20) in the coronal plane. Leg length discrepancy was also corrected (max 1 cm). The average time in frame was 17.8 weeks, with an average correction time of 29.8 days. Knee Society Clinical Rating System (KSCRS) scores post operatively ranged from 95 to 100. All patients returned to full activity, and would accept the same treatment if offered again.

The circular fixator is an effective, minimally invasive method of treatment for post-traumatic proximal tibial deformity. Patients remain active during treatment encouraging a rapid return to school/work activities.

Survivors of meningococcal septicaemia often develop progressive skeletal deformity secondary to physeal damage at multiple sites, particularly in the lower limb. Distal tibial physeal arrest typically occurs with sparing of the distal fibular physis leading to a rapidly progressive varus ankle deformity. There is no previous literature reporting this ankle deformity following meningococcal septicaemia.

We report the management of this deformity in 13 ankles in 10 consecutive patients 36 months after meningococcal septicaemia. Plain radiographs and MRI were used to define the deformity and the extent of growth plate involvement.

The Taylor Spatial Frame (TSF) with a distal tibial metaphyseal osteotomy was used to restore the distal tibio-fibular joint. Distal fibular epiphysiodesis was performed in all ankles at the initial procedure. Distal tibial epiphysiodesis was performed at the time of fixator removal.

The age at operation ranged from 3–14 years (mean 8). The preoperative ankle varus deformity ranged from 9–29 degrees (mean 19). The differential shortening of the tibia with respect to fibula was on average 1.2 cms. The mean time in frame was 136 days. After a mean follow-up of 1.7 years results were excellent in all patients with complete correction of deformity and shortening. Mechanincal axis was corrected in all patients.

Complications included, 4 superficial pin site infections, 1 lateral peroneal nerve palsy which recovered completely. There were no major nerve or vascular complications.

We consider that this approach provides a powerful method of correction for this difficult group of patients.

Introduction: Intra-Discal Electrothermal Therapy (IDET) has been used to treat chronic discogenic low back pain. Proposed mechanisms of action include denervation of the posterior annulus and collagen denaturation. Previous authors have reported on changes in internal disc mechanics following IDET including reduction in stress concentrations possibly leading to a more even distribution of load across the end-plate¹. A novel intradiscal decompression catheter has been developed to reduce local disc bulging in cases of contained prolapse. This new catheter is inserted percutaneously into a disc and advanced under radiographic control into a postero-lateral position targeting the herniation. The decompression catheter uses more focused heating and higher temperatures than previous devices and is intended to provide a local decompression of the disc through a thermally-mediated reduction in nuclear volume. The purpose of this study was to investigate changes in internal stress profiles following use of the new catheter.

Methods: Five cadaveric lumbar ‘motion segments’ were dissected from two spines (age 64–84 yrs). Each segment was compressed, normally to 1 kN, while a miniature pressure transducer was withdrawn from posterior to anterior across the mid-sagittal diameter of the disc producing a baseline stress profile. A decompression catheter was inserted into the disc and its position confirmed with plain radiography. The temperature of the catheter was increased to 90°c over a period of 14 minutes. Stress profiles were then repeated.

Results: Stress profiles in three of the five segments showed changes consistent with degenerative change. In these discs stress profiles following ‘treatment’ showed up to a 35% reduction in the magnitude of stress peaks in the posterior annulus. There was very little change in the distribution of stress in the two non-degenerate discs. Stress in the nucleus appeared unchanged in all discs.

Conclusions: Treatment of degenerate discs with the decompression catheter lead to a measurable alteration annular stress peaks that have been associated with degenerative disc disease, while non-degenerate discs were unaffected. These preliminary findings of an ongoing study suggest that the novel decompression catheter has a biomechanical effect in certain classes of disc.

Introduction: Dynesys is a novel, dynamic stabilization system designed for the treatment of degenerative conditions of the lumbar spine that present with unstable motion segments. This system uses pedicle screws with a modular spacer mounted on a stabilising cord, which controls movement of the instrumented segment in all planes. The purpose of this study was to investigate changes in the biomechanic response of the intervertebral disc (IVD) under normal, flexed and extended loading conditions before and after Dynesys is applied. The IVDs of both the instrumented (bridged) and the adjacent (floating) segment were studied.

Methods: Twelve L3-5 cadaveric segments were dissected and compressed to 1kN in 6° flexion, neutral and 4° extension. The test was done without spacers and with spacers measured to +2mm, neutral and −2mm, where neutral equates to the normal distance between the pedicle screws without an applied load. The stress distribution in the mid-sagittal and posterolateral diameters of both the bridged and floating discs was measured using a miniature pressure transducer. This resulted in greater than 300 stress profiles per specimen. Disc movement and segment motion during loading were recorded using ultrasound imaging and infra-red reflection respectively.

Results: Without stabilization, stress peaks observed in the anterior annulus increased by more than 85% as the specimen was loaded from 4° extension to 6°flexion. With the application of Dynesys, these anterior stress peaks were reduced across the bridged segment. This was most pronounced in 6° flexion where anterior stress peaks of greater than 1 MPa were reduced by 100% in the bridged segment in more than 90% of specimens.

Conclusions: The degree of flexion or extension of the specimen during loading influences the peak stresses generated in the annulus. Dynesys has the potential to relieve peak stresses in the anterior annulus which is most pronounced when the specimen is loaded in flexion.

Introduction: The diagnosis of Achilles tendon rupture must be made promptly and reliably to prevent avoidable morbidity. The calf squeeze test (CST) offers a simple clinical test with high sensitivity. However, in our clinical practice we have noticed a lack of clarity in the medical notes. We believe there is confusion regarding what constitutes a positive CST. Movement of the foot being positive or lack of movement of the foot indicating the test is positive. The purpose of this study was to assess the degree of error and to determine whether this is due to lack of knowledge, an inability to perform or correctly interpret and record the result of the CST. We assessed SHO’s , Registrars and Consultants in the Accident & Emergency and Orthopaedic Departments.

Method: Ninety one doctors completed a supervised questionaire. They were asked four questions 1) What tests they chose to diagnose Achilles tendon rupture. 2) How they would perform a CST. 3) What they considered a positive CST to mean . 4) How they would record the diagnosis of a ruptured Achilles tendon.

Results: 92%(84/91) of doctors overall chose to use a CST. 88%(80/91) performed the CST correctly. The CST was interpreted incorrectly by 41%(15/37) and 26%(14/54) of A + E and Orthopaedic doctors respectively. Also 32%(12/37) of A + E and 19%(10/54) of Orthopaedic department doctors mistakenly thought that the diagnosis of an Achilles tendon rupture was consistent with a negative test.

Conclusion: The results suggest that the recording of AT rupture may be inaccurate in as many as 32%(12/37) when patients present to the A + E department. This error is not a result of lack of knowledge or performance of the CST but of interpretation and recording. We would strongly discourage the recording of the CST in terms of a positive or negative result. The result should be described in words, for example ‘No movement of the foot on squeezing the calf muscle.’ We suggest that all SHOs and Registrars who may be called upon to assess patients with suspected Achilles tendon rupture are informed of this source of error.

Introduction: (1) Determine whether initial MRI findings correlate with clinical outcome.(2) Study the reproducibility of MRI measurements of large disc prolapses.(3) Estimate the ability to predict CES based on MRI alone.(4) Does CES only occur in degenerate discs?

Method: 31 patients with CES were identified and invited to attend clinic. 19 patients who underwent discectomy were identified. Digital photographs of all 50 MRIs were obtained. Observers: 1 Radiologist, 2 Spinal Surgeons and 1 Trainee did not know the number of patients in each group. Observers estimated the percentage spinal canal compromise on each view (0–100%), indicated whether they thought the scan findings could produce CES and commented on disc degeneration. Measurements were repeated after 2 weeks.

Results: 26 patients attended clinic – mean follow up 51 months (range 25–97). 12 of the 26 patients with CES had, on average, > 75% canal compromise. No significant correlations were found between MRI canal compromise and clinical outcome. Kappa values for intra-observer reproducibility of measurements ranged from 0.4–0.85 and inter-observer 0.63–5. Based on MRI, the correct identification of CES has sensitivity 68%, specificity 78%, positive predictive value 84% and negative predictive value 58%. Over 80% of the CES causing discs were degenerate.

Discussion: Canal compromise does not appear to predict clinical outcome. MRI measurement reproducibility has substantial agreement. CES is a clinical diagnosis supported by an MRI scan. In less clear cases the presence of a large disc on an MRI scan supports a diagnosis of CES (PPV 84%). CES occurs in degenerate discs.

Introduction: To determine the factors which influence outcome after surgery for cauda equina syndrome.

Method: 56 patients with evidence of sphincteric disturbance who underwent urgent surgery between 1994 and 2002 were identified and invited to follow up. Outcomes consisted of history and examination, and several validated questionnaires.

Results: 42 patients attended with a mean follow up of 60 months (range 25–114). Mean age at onset was 41 years (range 24–67) with 23 males and 19 females. 26 patients were operated on within 48 hours of onset. Urinary disturbance at presentation did not affect the outcomes. Bowel disturbance at presentation was associated with sexual problems (< 0.005) and abnormal rectal tone (p< 0.05) at follow up. There was a weak association between delay to operation and bowel disturbance (p< 0.05) at follow up. Eight patients had faecal soiling and faecal incontinence at follow up and this was associated with sudden onset of symptoms, initial abnormal rectal tone and time to operation (p< 0.05). The 12 patients who failed their postoperative trial without catheter had worse outcomes. The SF36 scores at follow up were reduced compared to age matched norms in the population. The mean ODI was 29, LBOS 42 and VAS 4.5.

Discussion: In our series the duration of symptoms and speed of onset prior to surgery appears to influence bowel but not bladder outcome two years after surgery. Based on the SF36, LBOS and ODI scores, patients who have had CES do not return to a normal status.

Introduction: Current evidence suggests that CES should be operated within 48 hours from onset of sphincteric symptoms in order to maximise chances of recovery. Measurement reproducibility of large disc prolapses and clinical correlations have not previously been studied.

Objectives: (1) Determine whether initial MRI findings correlate with clinical outcome (2) Study the reproducibility of MRI measurements of large disc prolapses (3) Estimate the ability to predict CES based on MRI alone.

Study Design: 31 patients with CES were identified, the case notes reviewed and the patients invited to attend clinic. Outcome consisted of history and examination, and several validated questionnaire assessments. 19 patients who underwent discectomy for persistent radiculopathy were identified. None had sphincteric symptoms. All had a significant surgical target. Digital photographs of all 50 MRIs were obtained showing the T2 mid-sagittal image and the axial image with the greatest disc protrusion. The Observers: 1 Consultant Radiologist, 2 Consultant Spinal Surgeons and 1 SHO did not know the number of patients in each group. Observers estimated the percentage spinal canal compromise on each view and indicated whether they thought the scan findings could produce CES. Measurements were repeated after 2 weeks.

Results: 26 patients attended clinic mean follow up 51 months (25 to 97). As expected, the % canal compromise differed significantly between the two groups (p0.001). 12 of the 26 patients with CES had, on average, over75% canal compromise. No significant correlations were found between MRI canal compromise and clinical outcome. Canal compromise did predict whether the patient would fail their Trial Without Catheter (p0.05). Based on MRI alone, the correct identification of CES has sensitivity 68%, specificity 78%, positive predictive value 84% and negative predictive value 58%. Kappa values for intra-observer reproducibility ranged from 0.4 to 0.85 for sagittal compromise, axial compromise and correct prediction of CES. All three interobserver kappa values for these measurements were 0.64.

Conclusions: This is the largest radiological case series of CES with 4 years clinical follow up. Canal compromise on MRI does not appear to directly predict clinical outcome. Reproducibility of MRI measurements of large disc protrusions has substantial agreement. MRI could be of help in equivocal cases if the scan shows a large disc.

Objective: Determine factors influencing outcome after surgery for cauda equina syndrome with particular attention sphincteric recovery. Subjects:56 patients with evidence of a sphincteric disturbance who underwent urgent surgery between 1994 and 2002 were identified and invited for follow up.

Outcome Measures: History and examination, Oswestry Disability Index, Short Form 36, Visual Analogue Score, Low Back Outcome Score, Modified Somatic Perception Score, Modified Zung Depression Score, International Prostate Severity Score, Male Sexual Health Questionnaire and Sheffield Female Pelvic Floor Questionnaire.

Results: 42 patients attended with a mean follow up of 60 months (25 to 114 months). Mean age at onset was 41 years (24 to 67 years) with 23 males and 19 females. 25 patients had sudden onset of symptoms in less than 24 hours. 26 patients were operated on within 48 hours of onset. At presentation urinary retention was associated with acute onset of less than 24 hours (p0.01), leg weakness (p0.01), abnormal leg sensation (p0.05) and abnormal rectal tone (p0.05). Bilateral radiculopathy was associated with leg weakness (p0.005). All patients with abnormal rectal tone (21) had abnormal rectal sensation. At follow up significantly more females had urinary incontinence (p0.001) and bowel disturbance (p0.05), higher VAS scores (p0.05) and lower SF36 Pain and Energy scores (p0.05) than males. Urinary disturbance at presentation did not affect the outcomes. Bowel disturbance at presentation was associated with sexual problems (0.005) and abnormal rectal tone (p0.05) at follow up. Objective reduced perianal sensation at onset persisted in a significant number at follow up (21/32 patients; p0.05) as did leg weakness (14/23; p0.005). There was a weak association between delay to operation and bowel disturbance (p0.05) at follow up. Eight patients had faecal soiling and faecal incontinence at follow up and this was associated with sudden onset of symptoms, initial abnormal rectal tone and time to operation (p0.05). The SF36 scores at follow up were reduced compared to age matched norms in the population. The mean ODI was 29, LBOS 42 and VAS 4.5.

Conclusions: In our series the duration of symptoms and speed of onset prior to surgery appears to influence bowel but not bladder outcome two years after surgery. Based on the SF36, LBOS and ODI scores, patients who have had CES do not return to a normal status. Patient counselling about this would therefore be appropriate.

Study Design: Cadaveric study on the effects of Dynesys.

Summary of Background Data: Dynesys is a novel form of soft stabilization that utilises pedicle screws and modular spacers mounted on a stabilising cord to control movement of the instrumented segment in all planes. In this way it provides a biomechanical alternative with greater physiological function than spinal fusion and may prevent the penalties of “overworking” adjacent levels.

Objective: The biomechanical response of both the instrumented and adjacent intervertebral discs (IVD) is investigated under compressive loading in flexion and extension. The effects of varying spacer heights on intradiscal pressure distribution are also reported.

Methods: Twelve L3-5 cadaveric lumbar segments were compressed to 1 kN in 6° flexion, neutral and 4° extension. The stress distribution in the mid-sagittal and posterolateral diameters of both the bridged and adjacent discs was measured by withdrawing a miniature pressure transducer across the IVD. Dynesys was applied across a single level and +2mm, neutral and −2mm spacer configurations tested in each position of loading. Over 2500 stress profiles were collected and the data obtained from measurements with and without application of Dynesys was analysed.

Results: In the absence of instrumentation stress peaks in the anterior annulus increased with a greater degree of specimen flexion. In 0° to 6° flexion, Dynesys eliminated the anterior stress peaks observed in the instrumented disc in 80% of specimens tested. In the +2mm to −2mm spacer range tested, posterior stress peaks were generally seen to increase with decreasing spacer height. Little effect is seen with the application of Dynesys to a non-degenerate disc. Preliminary analysis of the data suggests that stress distribution through the adjacent disc appears largely unchanged with instrumentation of the inferior segment.

Conclusions: Dynesys has the potential to relieve peak stresses in the anterior annulus seen particularly in positions of flexion. Spacer size influences the generation of peak stresses seen within the posterior annulus. Initial observations indicate that the IVD of the adjacent motion segment is not biomechanically prejudiced following the application of Dynesys.

Objective: To determine the factors which influence outcome after surgery for cauda equina syndrome. Particular attention has been given to sphincteric recovery.

Study Design: Retrospective cohort study with prospective clinical follow up.

Subjects: 56 patients with evidence of a sphincteric disturbance who underwent urgent surgery between 1994 and 2002 were identified and invited for follow up.

Outcome Measures: History and examination, Oswestry Disability Index, Short Form 36 Health Survey Questionnaire, Visual Analogue Score, Low Back Outcome Score, Modified Somatic Perception Score, Modified Zung Depression Score, International Prostate Severity Score, Male Sexual Health Questionnaire and Sheffield Female Pelvic Floor Questionnaire.

Results: 42 patients attended with a mean follow up of 60 months (Range 25–114 months). Mean age at onset was 41 years (Range 24–67 years) with 23 males and 19 females. 25 patients had sudden onset of symptoms in less than 24 hours. 26 patients were operated on within 48 hours of onset. At presentation urinary retention was associated with acute onset of less than 24 hours (p< 0.01), leg weakness (p< 0.01), abnormal leg sensation (p< 0.05) and abnormal rectal tone (p< 0.05). Bilateral radiculopathy was associated with leg weakness (p< 0.005). All patients with abnormal rectal tone (21) had abnormal rectal sensation.

At follow up significantly more females had urinary incontinence (p< 0.001) and bowel disturbance (p< 0.05), higher VAS scores (p< 0.05) and lower SF36 Pain and Energy scores (p< 0.05) than males. Urinary disturbance at presentation did not affect the outcomes. Bowel disturbance at presentation was associated with sexual problems (< 0.005) and abnormal rectal tone (p< 0.05) at follow up. Objective reduced perianal sensation at onset persisted in a significant number at follow up (21/32 patients; p< 0.05) as did leg weakness (14/23; p< 0.005). There was a weak association between delay to operation and bowel disturbance (p< 0.05) at follow up. Eight patients had faecal soiling and faecal incontinence at follow up and this was associated with sudden onset of symptoms, initial abnormal rectal tone and time to operation (p< 0.05). The SF36 scores at follow up were reduced compared to age matched norms in the population. The mean ODI was 29, LBOS 42 and VAS 4.5.

Conclusions: In our series the duration of symptoms and speed of onset prior to surgery appears to influence bowel but not bladder outcome two years after surgery. Based on the SF36, LBOS and ODI scores, patients who have had CES do not return to a normal status. Patient counselling about this would therefore be appropriate.

Introduction: Dynesys is a novel, dynamic stabilization system designed for the treatment of degenerative conditions of the lumbar spine that present with unstable motion segments. This system uses pedicle screws with a modular spacer mounted on a stabilising cord, which controls movement of the instrumented segment in all planes. The purpose of this study was to investigate changes in the biomechanic response of the intervertebral disc (IVD) under normal, flexed and extended loading conditions before and after Dynesys is applied. The IVDs of both the instrumented (bridged) and the adjacent (floating) segment were studied.

Methods: Eight L3–5 cadaveric segments were dissected and compressed to 1kN in 6° flexion, neutral and 4° extension. The test was done without spacers and with spacers measured to +2mm, neutral and −2mm, where neutral equates to the normal distance between the pedicle screws without an applied load. The stress distribution in the mid-sagittal and postero-lateral diameters of both the bridged and floating discs was measured using a miniature pressure transducer. This resulted in greater than 300 stress profiles per specimen. Disc movement and segment motion during loading were recorded using ultrasound imaging and infrared reflection respectively.

Results: Without stabilization, stress peaks observed in the anterior annulus increased by more than 85% as the specimen was loaded from 4° extension to 6°flexion. With the application of Dynesys, these anterior stress peaks were reduced across the bridged segment. This was most pronounced in 6° flexion where anterior stress peaks of greater than 1 MPa were reduced by 100% in the bridged segment in more than 90% of specimens.

Conclusions: The degree of flexion or extension of the specimen during loading influences the peak stresses generated in the annulus. Dynesys has the potential to relieve peak stresses in the anterior annulus which is most pronounced when the specimen is loaded in flexion.

Introduction: Cadaveric intervertebral discs (IVD) must perform consistently and repeatably with time and cyclic loading if the results from long experimental protocols are to be considered valid. Experiment design should take into account the potential for changes in the biomechanical properties of the intervertebral disc. Changes in the pressure distribution and stress profiles across the IVD along with variation in movement of the anterior annulus during a load cycle give a good indication as to the biomechanic status of the IVD. The purpose of this study was to assess the biomechanic response of the IVD to repeated cyclic loading, in normal, flexed and extended positions over a prolonged period.

Methods: Ten multisegment cadaveric lumbar spine specimens (L3-5 or L1-3) were dissected and compressed to 1kN in 6° flexion, neutral and 4° extension. The anterior annulus was imaged during loading using ultrasound. The stress distribution along the mid-sagittal and antero-postero-lateral (APL) diameters of both discs was measured by withdrawing a miniature pressure transducer from posterior to anterior across the IVD during loading. Stress profilometry and ultrasound imaging was performed over a two day period.

Results: Ultrasound imaging provides an easy method for observing disc movement during compressive loading of a multi-segment specimen through positions of extension and flexion. Anterior disc bulging increased by more than 150% as the specimen is loaded from 4° of extension to 6° flexion. Repeated passes of the pressure transducer across both the mid-sagittal and APL diameter of the discs produced repeatable stress profiles. Similarly, ultrasound imaging of the anterior annulus showed comparable disc movement after cyclic loading.

Conclusions: Preliminary results suggest that the biomechanical behaviour of the IVDs of a multi-segment specimen do not change significantly following prolonged testing and multiple cyclic loading.