Introduction

Growing rods are used in the treatment of early-onset scoliosis. The aim of this technique is to achieve deformity correction while maintaining spinal growth. Gradual stiffening or spontaneous fusion of the spine can interfere with the ability to lengthen. Furthermore, diminished acquired length with serial distraction is common and needs to be evaluated and quantified. The purpose of this prospective study was to measure the forces and amount of distraction over time in patients with early-onset scoliosis treated with growing rods.

Introduction: Cement augmentation of osteoporotic vertebral fractures by vertebroplasty can alleviate pain, possibly by restoring normal load-sharing to the affected motion segment. Fracture is known to decrease vertebral compressive stiffness (1), and also affects the compressive stress distribution acting on the vertebral body, causing stress concentrations to appear in the adjoining intervertebral discs (2). We hypothesise that vertebro-plasty can reverse these fracture-induced changes.

Methods: Nineteen cadaver thoraco-lumbar motion segments (64–90 yrs) were used. Each was mounted on a hydraulic materials testing machine and induced to fracture by compressive overload in moderate flexion. Vertebroplasty was performed by injecting 7 cc of poly-methylmethacrylate cement (Simplex P, Stryker Howmedica, NJ) into the fractured vertebral body. Specimens were then creep loaded at 1.5 kN for 1 hour to allow consolidation. Before and after each procedure, profiles of the compressive stress distribution were obtained by pulling a miniature pressure transducer along the mid-sagittal diameter of the intervertebral disc whilst it was compressed at 1.5kN. Using these profiles, stress peaks in the anterior and posterior annulus were measured by subtracting the nucleus pressure from the peak stress in each region (2). Compressive stiffness of the motion segment was also measured before and after vertebroplasty from the tangent of the load-displacement curve at 1 kN. Changes were compared using ANOVA.

Results: Following fracture, motion segment compressive stiffness was reduced by 37% from 2478 N/mm, STD 966N/mm, to 1583 N/mm, STD 585 N/mm (p = 0.0001), stress peaks in the posterior annulus were increased by 139% from 0.24 MPa, STD 0.24 MPa, to 0.57 MPa, STD 0.47 MPa (p = 0.016), and stress peaks in the anterior annulus showed no significant change. The decrease in compressive stiffness was significantly correlated with the increase in the size of the posterior stress peak (Rsq = 0.65, p< 0.001). Following vertebroplasty and subsequent creep loading, compressive stiffness was increased to 2156 N/mm, STD 718 N/mm, and stress peaks in the posterior annulus were reduced to 0.31 MPa, STD 0.43 MPa. These changes were again highly correlated with each other (Rsq = 0.68, p< 0.001). Both compressive stiffness and the size of posterior stress peaks after vertebroplasty showed no significant difference when compared to pre-fracture values.

Discussion: Fracture reduces the ability of vertebrae to resist deformation, thereby decreasing compressive stiffness. These changes impair the disc’s ability to press evenly on the vertebral body, giving rise to increased stress peaks in the posterior annulus. Vertebroplasty can reverse these fracture induced changes by increasing vertebral compressive stiffness which acts to restore pressure in the nucleus. This enables the disc to press more evenly on the vertebral body and thereby reduces the size of stress peaks in the posterior annulus. This restoration of normal load-sharing may possibly contribute to pain relief in patients undergoing this procedure.

Study Design: An analysis of patients admitted with cervical trauma, comparing: those managed with rigid collars until definitive management; rigid collar usage overnight; and no rigid collar usage from outset.

Objectives: To determine the safety of omitting a rigid collar following cervical trauma, whilst awaiting definitive management.

Summary of Background Data: The use of a rigid collar can result in pain, occipital sores, as well as raised intracranial pressure in head injured patients.

Subjects: Fifty one patients with proven cervical fractures were analysed. Three groups of patients were identified with respect to their initial management after admission to the ward until definitive management: 1) Hard collar, sandbags and bed rest 2) Hard collar in situ overnight and then sandbags and bed rest. 3) Sandbags and bed rest. All patients had full spinal care and precautions, with rigid collars used for any transfers. The spectrum of injury severity was similar throughout all 3 groups.

Outcome measures: Loss of alignment, neurological compromise and complications related to the rigid collar.

Results: There was no loss of reduction or progression of neurological deficit in any group. There were compliance issues in the rigid collar group. Two patients developed occipital skin problems following rigid collar use. All groups proceeded to definitive management successfully.

Conclusion: No significant adverse events were noted in any group. Management without a rigid collar depends on good nursing care. It is more comfortable for the patient and avoids the potential problems encountered with rigid collar use. In compliant patients not requiring immediate definitive management the omission of the rigid collar did not result in loss of reduction or neurological compromise. We feel such collars should be for transport and extrication only.

Introduction: Cement augmentation of osteoporotic vertebral fractures by vertebroplasty can alleviate pain, although the mechanism remains unknown. We hypothesise that vertebral fracture reduces loading by the vertebral body, and that vertebroplasty reverses this effect.

Methods: Nineteen thoracolumbar motion segments (64 – 90 yrs) were used. Specimens were compressed at 1.5kN in moderate flexion and extension while intradis-cal stress profiles were obtained by pulling a miniature pressure transducer along the mid-sagittal diameter of the disc (1). Vertebral fracture was induced by compressive overload in moderate flexion. Vertebroplasty was then performed by injecting polymethylmethacry-late cement into the anterior vertebral body. Stress profiles were repeated after fracture, and after vertebroplasty.

Stress concentration in the annulus was calculated by subtracting the nuclear pressure from the maximum stress in the annulus. Neural arch compressive load was obtained by subtracting the disc compressive force, calculated by integrating intradiscal stress over area, from the applied 1.5kN (1).

Results: Fracture increased the stress concentration in the annulus from 0.21 to 0.58MPa in flexion (p< 0.01) and from 0.02 to 0.20MPa in extension (p< 0.05). It also increased neural arch load bearing from 9% to 27% of the applied load in flexion (p< 0.01), and from 53% to 70% in extension (p< 0.01). Following vertebroplasty, these changes were largely reversed: in flexion, stress concentrations in the annulus decreased to 0.36MPa and neural arch load-bearing fell to 5% (p< 0.01). Similar, non-significant trends were observed in extension.

Discussion: Vertebral fracture reduces load-bearing by the vertebral body, and increased compressive loading of the neural arch. Vertebroplasty goes some way to reversing these effects, and significantly decreased stress concentration in the annulus and loading of the neural arch in flexion. This could contribute to pain relief in patients undergoing this procedure.

Recent years have seen the popularization of minimally invasive approaches to the spine.

However, the use of the balloon assisted retroperitoneal approach has not been widely described, moreover there has been no direct comparison between this mini-ALIF (anterior lumbar interbody fusion) and the conventional open method in the literature.

Comparison of peri and intra-operative parameters between the rnini-ALIF (using the balloon assisted dissector and Synframe retractor system) and the open midline approach for single and double level anterior lumbar interbody fusions in order to assess the efficacy of this procedure.

An independent retrospective evaluation of 35 patients who underwent single or double level ALIF under the care of the senior author at the University Hospital, Nottingham during the period from 1997 to 2000. The patients were split between those undergoing a mini-ALIF (balloon assisted retroperitoneal dissection) or the conventional approach via a larger midline incision. The groups were matched for age, sex and number of levels. Data was collated from the medical notes with regards to intra-operative blood loss, operative time, intra-operative complications, PCA requirements, time to mobilisation and length of hospital stay.

A statistically significant (p=0. 01) reduction in time to mobilisation (mean 2. 1 days vs 3. 9 days) and operative time (mean 175mins vs 265mins) was found for the single level mini-ALIF. This reflects the greater number of L5/SI fusions in this group. The number of vascular injuries was also greater in the approach to L4/5.

No difference was found between the two groups for double level procedures.

The immediate advantages of a less invasive approach both to the patient and hospital do not appear to be borne out by this study. Cosmesis was not assessed and the long term functional outcome awaits later confirmation.

Numerous studies have examined the biomechanical properties of the vertebral body following PMMA cement augmentation for the treatment of osteoporotic vertebral body fractures. To date there is no published literature reporting the effects of Vertebroplasty on internal intervertebral disc biomechanics which in turn have been shown to reflect loading patterns of the vertebral column.

To study effects of PMMA cement augmentation of vertebral body fractures on intervertebral disc biomechanics using stress prolifometry to assess differential anterior and posterior vertebral column loading.

Eight cadaveric motion segments were individually loaded on a hydraulically powered materials testing machine under 1.5kN of axial compression. Following fracture induction the lower vertebral body underwent Vertebroplasty.

Profiles of the vertically acting compressive stress were obtained by pulling a pressure sensitive transducer along the mid-sagittal diameter of the intervertebral disc. “Stress profile” measurements were obtained before fracture, following fracture, and after vertebro-plasty both in extension and flexion.

Stress profiles were integrated over area to calculate the compressive force across the disc. The compressive load acting on the neural arch was calculated by subtracting the disc force from the applied 1.5kN load.

In flexed postures posterior column loading increased from 17.1% to 42.2% following fracture (p< 0.01) and then decreased significantly from 42.2% to 23.68% following vertebroplasty (p< 0.03). There was no significant difference between pre-fracture and post-vertebroplasty status (p=0.11). In extended posture, fracture produced increased posterior column loading 72.9% vs 51.8% (p< 0.005) and following vertebroplasty there was no significant change (p=0.2).

In moderate degrees of flexion, vertebroplasty produces normalisation of load bearing through the anterior vertebral column and hence offloads the posterior elements to a significant degree. This could be postulated, to partly account for the analgesic effect seen following vertebroplasty in the clinical setting.

Objective: A clear definition of cauda equina syndrome (CES) following herniated discs was not available from the literature. Some define CES as a total paralysis of the pelvic viscera1 while others consider any dysfunction as sufficient evidence of CES2. An extensive search of the literature also demonstrated a lack of a disease specific outcome measure for CES. We aimed to classify CES in the above spectrum and validate a new outcome score for CES.

Design and subjects: We present a retrospective study of 38 patients with a minimum of one-year follow up who presented with an acute cauda equina syndrome. We categorized the patients as complete or incomplete and further sub-classified them as acute or chronic. A total paralysis of the pelvic viscera was considered as complete. Presence of only dysfunction of the pelvic viscera was considered as incomplete. If the presenting episode plateaued within 24 hours or less of onset it was classified as acute and if it plateaued later than 24 hours it was considered as chronic.

Outcome measures: The new 17-item disease specific questionnaire was compared with the Oswestry Disability Index, SF36 and Urodynamic studies.

Results and conclusion: Of the patients studied, 44.7% were complete with acute onset, 21.1% were complete with chronic onset, 10.5% were incomplete with acute onset and 23.7% were incomplete with chronic onset. Outcome score matched the spectrum of our suggested classification.

Objectives: Comparison of peri and intraoperative parameters between mini-ALIF (using balloon assisted dissector and Synframe retractor) and open midline approach for single and double level ALIF.

Methods: Independent, retrospective evaluation of 35 patients split between those undergoing the mini-ALIF or the conventional approach via larger midline incision. Groups matched for age, sex and number of levels. Operations performed at University Hospital, Nottingham between 1997 and 2000.

Outcome measures: Data collated for operative time, intraoperative blood loss, complications, PCA requirements, time to mobilisation and hospital stay.

Results: Statistically significant (p=0.01) reduction in operative time (175 vs 265mins) and time to mobilization (2.1 vs 3.9 days) found for single level mini-ALIF. Complications namely vascular injuries were almost equal in both groups. No difference was found between the two groups for double level procedures.

Conclusion: The immediate advantages of a less invasive approach both to the patient and the hospital do not appear to be borne out by this study. Cosmesis was not assessed and long term functional outcome awaits later review.

Objective: To evaluate the efficacy and safety of an expandable titanium cage for anterior column replacement after partial or total corpectomy in the thoracolumbar spine.

Design: A retrospective study evaluating the clinical and radiographic outcome following insertion of a novel implant.

Subjects: Twenty-three patients with anterior column insufficiency secondary to tumour, fracture, and infection were treated with a vertebral replacement capable of rapid and controlled in-situ expansion. Follow up consisted of a clinical and radiological review at a mean of 15.2 months (range 6–20 months).

Outcome Measures: The clinical outcome was measured by the degree of pain relief post-operatively, the ability to ambulate and the reliance on walking aids. Neurological deficit was measured using the Frankel Grade. Radiological follow-up compared preoperative radiographs with those taken at maximal follow-up. The degree of kyphosis and the degree of subsidence was measured.

Results: Twenty-three patients with a mean age of 43.6 years (range 20–72) underwent surgery. Indications included metastatic tumour in eight, acute fractures in five, infection in four, degenerative conditions in three, post-traumatic kyphosis in two and pseudathrosis in one. Nineteen patients underwent a single-level corpectomy and four patients a two-level corpectomy. Fourteen patients had a significant neurological deficit preoperatively. Supplementary instrumentation was used in 20 of 23 cases (anterior in nine, posterior in eleven). Excellent pain relief was observed in 19. Ten of 14 patients showed neurological improvement. Eleven patients improved their ambulatory status. There was no hardware failure. An average correction of 110 of kyphosis was observed. The average subsidence was 1.3 mm (range 0.2–2.3).

Conclusions: The use of an expandable vertebral body replacement with supplementary instrumentation following corpectomy appears to be safe and efficacious in correcting kyphosis. This implant appears to have a high resistance to subsidence.

Advances in laparoscopic technology have popularised minimally invasive approaches to the anterior lumbar spine. The use of the balloon assisted retroperitoneal approach however has not been widely described; moreover there has been no direct comparison between this mini anterior lumbar interbody fusion (ALIF) and the conventional open method in the literature.

Comparison of peri and intra-operative parameters between the mini-ALIF (using the balloon assisted dissector) and the open midline approach for single and double level anterior lumbar interbody fusions in order to assess the efficacy of this procedure.

An independent retrospective evaluation of 35 patients who underwent single or double level ALIF. A single surgeon at the University Hospital, Nottingham, performed the procedures during the period from 1997 to 2000. The patients were split between those undergoing a mini-ALIF (balloon assisted retroperitoneal dissection) and the conventional approach via a larger midline incision. The groups were matched for age, sex and number of levels. Data was collated from the medical notes with regards to intra-operative blood loss, operative time, intra-operative complications, Patient Controlled Analgesic (PCA) requirements, time to mobilisation and length of hospital stay.

A statistically significant reduction in operative time (mean 178mins Vs 255mins) and time to mobilisation (mean 2.2 days Vs 3.7days) was found for the single level mini-ALIF. No other significant difference was detected for the other criteria between the two groups for either single or double level procedures. Complications in the form of vascular injuries were almost equal in both groups.

Although operating time was significantly shortened using the balloon-assisted dissector other perioperative parameters were not. The question of cosmesis of the surgical scar was not explored in this study, this may have been more favorable in the mini-ALIF group but given the above results one must question whether the added expense of this innovative device is justified when there was no detected difference in all other measured criteria.