The purpose of this study was to evaluate the efficacy of autologous cancellous bone grafting (ABG) for the treatment of long bone fracture non-unions. Patients who were treated with ABG for fracture non-unions of the lower extremities were identified from our prospectively entered database. Non-union was defined as failure of the fracture to unite within a period of 9 months. Demographics, comorbidities, medications, complications and surgical outcomes were all recorded and subsequently analysed. Chi square test was used to analyse the results.

In total 82(54 male) patients met the inclusion criteria. The mean age was 43.6 years (range 18–78). Ten patients were diagnosed with femoral and 72 with tibial fracture non-unions. Fifty three (64.6%) were open fractures at presentation. In the tibial non-union group, initially, 67 fractures were stabilised with IM nailing and 5 with plating. During revision surgery, 33 patients underwent exchanged nailing and ABG whereas 34 received ABG without revision of the metal work.

All five tibial plantings required re-plating and ABG. In the femoral non-union group, five fractures were initially stabilised with IM nailing and the rest with plating. During revision surgery, six patients underwent change of fixation (exchange nailing) and ABG and four received only ABG. Overall 73/82 patients progress uneventfully to union and the success rate was 89%. A second and a third attempt of ABG was made for 6/86 patients (7.31%) and 2/82 patients (2.44%) respectively, till clinical and radiological union. All but one of the patients united their fractures. One patient underwent amputation due to underlying osteomyelitis.

The mean time to union following the ABG procedures was 8.4 months (range 3–18). Autologous bone grafting is an effective method of treating fracture non-unions. Success rates of as high as 89% can be achieved as seen in this series of patients.

The epidemiology of adult fractures is changing rapidly. The longevity of the population continues to extend with increasing incidence of fragility fractures. The aim of this study was to map the epidemiology of fractures in patients 90 years and older.

A retrospective review of all orthopaedic trauma patients over the age of 89 years attending Edinburgh Royal Infirmary in 2000 was performed. All inpatients and outpatients were included. These patients were identified using a prospectively complied database held by the senior author. Patient notes were used to confirm place of residence, mobility, co-morbidity, management, length of admission and place of discharge.

236 fractures (4% of all fractures) were identified. There were 209 (89%) female patients. All were secondary to low energy trauma. More than 50% of the patients were admitted from home and mobilised independently or with a stick. 124 (53%) patients had nil or one co-morbidity, the commonest being dementia and hypertension. Of the 133 neck of femur (NOF) fractures 11 (8%) died as inpatients, and of the 66 patients residing independently in their own home only 5 (8%) returned with the other 61 needing step-up care. The average length of stay in hospital for NOF fractures was 13 days.

The majority of patients are female and reside at home, being independently mobile and have limited co-morbidity. The length of stay is relatively long and few patients’ return directly home following a NOF fracture. This, with the ever-growing super-elderly population, will have substantial financial implications in the future.

Mountain biking is increasing in popularity worldwide. The injury patterns associated with elite level and competitive mountain biking are known. This study analysed the incidence, spectrum and risk factors for injuries sustained during recreational mountain biking.

The injury rate was 1.54 injuries per 1000 biker exposures. Males were more commonly injured than females, with those aged 30–39 years at highest risk. The commonest types of injury were wounding, skeletal fracture and musculoskeletal soft tissue injury. Joint dislocations occurred more commonly in older mountain bikers. The limbs were more commonly injured than the axial skeleton. The highest hospital admission rates were observed with head, neck and torso injuries. Protective body armour, clip-in pedals and the use of a full-suspension bicycle confer a significant protective effect.

The aim of this study is to prepare for the introduction of the world’s first nationwide registry of all rotator cuff tears proceeding to operative management.

Patient’s are scored pre-operatively and again at six and 12 months post-op using the Flex SF functional scale, pain scales and work and activity levels. A questionnaire is filled out by the operating surgeon on the day of surgery detailing pathology and the operative methods used.

This study is a New Zealand Shoulder and Elbow Society initiative begun in 2007. New Zealand is ideally suited with a small, cohesive group of orthopaedic surgeons. Rotator cuff surgery is advancing rapidly with changes in surgical approach from open to arthroscopic, and repair methods from bone tunnels to various choices of anchors. A wide range of surgical methods are used within New Zealand, presenting an opportunity to use the large numbers generated by a registry to give valuable information guiding future treatment.

The operation day questionnaire includes information on tear size, surgical approach, repair methods, biceps and AC joint pathology and rehabilitation.

More than 100 patients have already been registered in the pilot study and a number have completed the six month questionnaire. These early results will be presented, along with important information for the large number of surgeons who will become involved when the nationwide registry commences.

Dislocation of the elbow with associated fractures of the radial head and the coronoid process of the ulna have been referred to as the “terrible triad of the elbow” because of the difficulties in treating this injury and the poor outcomes.

The orthopaedic database, Orthoscope, was used to identify all patients with dislocation of the ulnohumeral joint and fracture of both the head of the radius and the coronoid process of the ulna, seen and treated at Auckland City Hospital since 1998.

All patients were invited to follow up appointments to evaluate the outcomes achieved. The research protocol was approved by the local research committee. Follow up appointments consisted of clinic al examination, assessing the range of elbow motion, an elbow radiograph and a functional assessment, using the DASH score and the American Shoulder and Elbow Society scoring systems.

There were 32 patients identified, from Orthoscope, and invited for follow up. Six patients, who had moved overseas, were lost to follow up and two others declined follow up. 23 patients (24 elbows) remained for evaluation. All patients returned for the described assessment protocol. There were 10 male patients and 13 female patients, with a mean age of 46.9 (range, 29 to 67 years). The average arc of ulnohumeral motion was 122 degrees (range; 110 degrees to 140 degrees) and that of forearm rotation was 138 degrees (range, 35 degrees to 170 degrees).

The radial head component was fixed in a standard fashion with repair, or replacement, and no radial head excisions were undertaken. Coronoid fractures were treated with screw fixation or suturing, with drill holes or anchors. To augment stability, a lateral ligament repair was undertaken in most patients. All patients, except one, would undergo the procedure again if needed.

Elbow fracture-dislocations are historically very unstable and are prone to numerous complications. With operative treatment of the radial head, with repair or replacement, to restore stability through radiocapitellar contact, coronoid and lateral ligament repair, good range of movement and stability can be achieved.

To illustrate the incidence and epidemiology of fractures due to football.

All inpatient and outpatient fractures from a prospectively collected database for a defined population in 2000 were retrospectively analysed.

There were 396 football fractures, 96% male. Football caused 39% of the 1022 sports fractures in 2000. This represented 5% of the 8151 fractures in total. The incidence was 61/105. 115/105 in males and 5 /105 in females. The average age was 22.9 years; 22.8 in males and 26.6 in females. 77% of fractures were treated as outpatients. The top five fractures representing 84% of the injuries were Radius+Ulna 30%, Phalanx 19%, Tibial+Fibula 18%, Metacarpal 11% and Clavicle 5%. 71% were upper-limb fractures. The busiest two months were October and May 17% and 14% respectively. The quietest two months were February and December at 5%.

Although the epidemiology of football injuries will vary amongst different populations, these results can be generalized to similar population bases. Results will be valuable to medical professionals supporting football teams, enabling them to focus their attention on treating the most common injuries, the majority being treated as outpatients.

Football is the most common cause of fractures in sport. As participation increases, the incidence of fractures is likely to reflect this. Upper limb fractures account for over 2/3 rd of fractures with radius+ulna fractures accounting for up to a 1/3rd of fractures; the majority can be treated as an outpatient. Therefore medical teams should be familiar with standard treatment regimes, possible impact on players’ futures and time out of sport.

Aim: To compare the outcomes of autologous versus no drainage in patients undergoing primary hip and knee arthroplasty.

Methods: Retrospective review of patients undergoing primary total hip or knee arthroplasty within our unit was carried out. There were 4 groups, each consisting of 20 patients. These were; total hip arthroplasty with and without the use of autologous drains, and total knee arthroplasty with and without the use of autologous drains. Outcome measures were- requirement for homologous (banked) blood, post-operative drop in haemoglobin and length of stay in hospital.

Results: For the knee arthroplasty groups, the homologous transfusion rate was 25% in non-drain patients compared with 5% in patients with drains. The average drop in Hb was 3.3 g/dl in the no-drain group compared with 2.7 in the drain group. The average length of stay was 6.35 days in the no-drain group compared with 6.75 days in the drain group. For the hip arthroplasty groups, the homologous transfusion rate was 10% in the non-drain group compared with 15% in the drain group. The average drop in Hb was 3.9 in the no drain group compared with 3.3 in the drain group. The average length of stay was 6.8 days in the no-drain group compared with 6.9 days in the drain group.

Conclusion: These results demonstrate improvements in the transfusion requirements as well as post-operative Hb drop in knee arthroplasty, but not hip arthroplasty when autologous re-transfusion drains were used. The length of stay was not significantly altered by the usage of drains. Based on these results, we would therefore recommend the use of autologous drains in primary total knee arthroplasty but not in primary total hip arthroplasty.

At the New Zealand Shoulder and Elbow Society Meeting in 2005, it was decided to set up a national registry to look at the outcomes of rotator cuff repair in New Zealand. National Joint Registries have produced very powerful information on the performance of joint replacements, not just in the hands of the designer but for all surgeons. The patient numbers in these Registries have allowed powerful information to be derived which has had a significant impact on local practice.

A nationwide registry on rotator cuff repair in New Zealand has the potential to provide similar powerful information. This is an area in which there has been rapid change over the last five years particularly with regard to surgical approach whether it be open, mini-open or arthroscopic and uncertainty remains as to what is best ‘best practice’. Surgeons are unwilling to invest time and effort into mastering sometimes difficult new procedures unless significant benefit can be demonstrated. Aspects addressed include anchors v. traditional drill holes in bone, anchor type, suture type and configuration, length of immobilisation, post-operative regime, effects of smoking and NSAIDs, on outcome and outcome versus size of tear.

A pilot study is being undertaken to ensure the questionnaires are workable and the system will run smoothly. Early results of the pilot study will be presented.

Nanometre-sized particles of ultra-high molecular weight polyethylene have been identified in the lubricants retrieved from hip simulators. Tissue samples were taken from seven failed Charnley total hip replacements, digested using strong alkali and analysed using high-resolution field emission gun-scanning electron microscopy to determine whether nanometre-sized particles of polyethylene debris were generated in vivo. A randomised method of analysis was used to quantify and characterise all the polyethylene particles isolated.

We isolated nanometre-sized particles from the retrieved tissue samples. The smallest identified was 30 nm and the majority were in the 0.1 μm to 0.99 μm size range. Particles in the 1.0 μm to 9.99 μm size range represented the highest proportion of the wear volume of the tissue samples, with 35% to 98% of the total wear volume comprised of particles of this size. The number of nanometre-sized particles isolated from the tissues accounted for only a small proportion of the total wear volume. Further work is required to assess the biological response to nanometre-sized polyethylene particles.

Introduction: The cause for Subungual Exostosis remains unknown, although relationships with trauma, infection and irritation have all been suggested. We report the case of a 23 year old female who developed this condition after Zadek’s procedure done for an in growing toe nail.

Case Report: A 23-year-old woman presented to us with an infected ingrowing great toenail of 1 month duration. An X-ray was performed to rule out osteomyelitis (Figures 1a and 2a), and the patient was put on oral antibiotics to control infection. 12 weeks later, the patient underwent a Zadek’s procedure with uneventful post op. recovery. However, 4 months later the patient came back with increasing pain and swelling in the operated toe. Clinically, there was a shiny nodule measuring 0.5 x 0.5cm over the dorso-medial aspect of the nail bed which was tender to touch, hard in consistency and appeared to be arising from the bone. X-ray’s confirmed it as Subungual Exostosis (Figures 1b and 2b). She successfully underwent excision of the tumour and was symptom free with no signs of recurrence at six-month follow up

Discussion: Our case highlights the fact that Subungual Exostosis may be triggered off by damage to the nail bed during surgeries for ingrowing toe nails and that extreme care must be taken during nail removal to avoid injury to the nail bed. This complication is more pronounced in the presence of pre-existing infection. Excision appears to be the treatment of choice and a biopsy report is always needed for confirmation before discharging the patient from the clinic.

Conclusion: Careful handling of nail bed is necessary during surgery and this unusual complication can be included when taking consent for Zadek’s procedure.

The use of arthroplasty registers was initiated by Sweden in 1979. The practice has been adopted globally as best practice for recording the outcome of joint replacement surgery and for identifying early problems. The Trent and Wales Arthroplasty Audit Group began in 1990 and have recently produced outcome results. We have analysed the short-term outcomes of arthroplasty procedures at a DGH in order to assess comparability to this “gold-standard”.

In 2004, 231 primary arthroplasties were performed, by the two senior authors, at Musgrove Park Hospital (149 THR, 82 TKR). There was an overall complication rate of 8.7%. There was 1 periprosthetic infection in a THR that required revision (0.043%). 9 patients developed wound complications, principally superficial infections and haematoma formation. 2 patients, both THR developed, thromboembolic complications, one DVT and one pulmonary embolus. There was one periprosthetic fracture around a THR. The dislocation rate for THR was 3.35% (5/149). 3 of these were performed through a posterior approach and 2 through an anterolateral. 3 have required revision surgery.

We have demonstrated comparable results following joint arthroplasty to published teaching hospital series. We have shown that adequate infrastructure can exist in smaller units to accurately record outcome data following arthroplasty surgery.

Femoral neck fractures in the elderly has a devastating impact on health and resources. Past trends suggest pinning un-displaced fractures in the more active elderly patients and resorting to arthroplasty in those less active. In our study the failure rate for un-displaced fractures (18.4%) was greater than that quoted in the literature and greater than the failure rate of fractures treated with arthroplasty (7.4%). Failures consisted of AVN (5), nonunion/malunion (1) and loss of fixation (1). This data suggests that arthroplasty would decrease the failure rate in our study group.

To evaluate the outcome of ORIF for un-displaced femoral neck fractures in the elderly at a tertiary care teaching hospital.

ORIF of femoral neck fractures in the elderly at our institution resulted in higher failure rates than quoted in the literature. A large multi-center randomized controlled trial is warranted to establish clear guidelines in the management of these injuries.

In our study the failure rate for undisplaced fractures was greater than fractures treated with arthroplasty. The clinical relevance of this data suggests that not all un-displaced fractures go on to uneventful union.

Of the forty-five patients that met the inclusion criteria for un-displaced femoral neck fracture, seven of which were originally treated at our institution failed, resulting in 18.4% failure rate. In comparison, our complication rates for displaced femoral neck fractures treated with arthroplasty results in a 7.4% failure rate. Failures consisted of AVN (5), nonunion/malunion (1) and loss of fixation (1).

Retrospective study. Patients sixty-five to eighty years of age with un-displaced femoral neck fractures repaired by cannulated screw fixation from 1995 to 2001. X-ray confirmation was done when fracture was not described in the chart. Failure of pinning was defined as requiring re-operation or arthroplasty.

Recent studies argue in favor of arthroplasty for most displaced femoral neck fractures. Despite the limitations of our study, the failure rate of the un-displaced femoral neck fracture is higher than that quoted in the literature, and suggests that arthroplasty would decrease the failures in our study group.

Introduction: Cobalt-chrome particles from metal hip implants can accumulate in the liver, spleen, lymph nodes and bone marrow of patients. This is a concern as studies have reported neoplastic changes in cells of patients with metal implants. The aims of this study were to determine the effect of wear particles generated by metal-on-metal and ceramic-on-metal implants from hip simulations upon the viability of L929 cells and to determine their genotoxic potential when cultured with primary human fibroblasts.

Methods: Particles were generated in a 10 station Prosim hip simulator run with water as lubricant under microseparation and standard conditions. Bearings comprised medical grade HIPed ‘BIOLOX Forte’ alumina ceramic femoral heads against Ultima metal CoCr acetabular cups (CoM) and wrought CoCr alloy ASTM F1537 femoral heads and acetabular cups (MoM). Particles were sterilised at 1800C for 4 hours and cultured with L929 fibroblasts at particle volume(μm3):cell number ratios of 500:1, 100:1, 50:1, 5:1, 0.5:1, 0.05:1, 0.005:1 and 0.0005:1. Camptothecin (1 and 2μg.ml-1) and latex beads (100μm3 per cell) were used as positive and negative controls. Cultures were for 0, 1, 2, 3, 4 and 5 days at 37oC in 5%(v/v) CO2 in air. Cell viability was assessed using the ATPlite assay. Sterile particles were cultured with primary human fibroblasts at particle volume (μm3):cell number ratios of 50:1, 5:1 and 0.5:1. Cells were exposed to 30%(v/v) H2O2 (positive control) and latex beads (50μm3 per cell; negative control). Cells were cultured for 24 hours and 5 days at 37oC in 5%(v/v) CO2 in air. Genotoxicity was assessed using the comet assay. Statistical analysis between the cell-only negative controls and the cells with the particles at various concentrations, were determined by ANOVA and calculating the minimum significant difference (MSD;p< 0.05) using the T-method.

Results: Particle volume(μm3):cell ratios of 500:1, 100:1 and 50:1 caused a significant decrease in cell viability over 5 days. Wear particles from MoM implants under microseparation wear conditions were also significantly reduced viability at particle volume(μm3):cell ratios of 5:1 over 5 days. Particles from MoM implants under standard wear conditions and CoM implants under both wear conditions resulted in increases in tail length and tail moment relative to the cells only negative control for all treatment groups after 24 hours. These decreased by day 5. Tail length and tail moment were increased at 24 hours relative to day 5 for each of the three particle types. Particles generated by MoM implants under microseparation conditions had different effects upon cells. Tail lengths increased between days 1and 5 for all particle concentrations. A significant increase in tail moments between days 1 and 5 was recorded.

Discussion: This study has shown that metal particles can cause cytotoxic effects and immediate DNA damage to fibroblasts in vitro. Particles were found to reduce cell viability over 5 days and this may account for the decreases in tail length and moments between 1 and 5 days for three particle types. This is of concern as MoM and CoM implants are designed to be implanted into young patients and, despite their low wear rates generate circa 10¹³ particles per mm3 of wear.

Introduction and Aims: The aim was to prospectively assess shoulder hemiarthroplasty for un-reconstructable proximal humeral fractures at a minimum of 12 months and identify factors that aid prognosis.

Method: Inclusion criteria were patients with a displaced fracture requiring shoulder hemiarthroplasty. Constant scoring was done at a minimum follow-up of one year. Patients were treated using a Neer or Osteonics prosthesis, the decision for hemiarthroplasty being made at the time of surgery. Post-operative management was standardised. An independent functional assessment, record review establishing a physiological index according to co-morbidities, and radiological analysis were carried out. Survival analysis was performed for one and five-year results and data was analysed by linear regression to identify prognostic factors.

Results: From 163 patients there were 138 fitting the criteria, 42 males and 96 females, average age of 68.5 (range 30–90) years and follow-up of 6.3 (range 1–15) years. The fracture pattern was three and four part in 133 cases and five head split fractures; 58 were associated with dislocation. Survival was 96.4 percent at one year and 93.6 percent at five years, with no significant difference between prostheses. There were eight revisions, (one deep infection, four dislocations and three peri-prosthetic fractures), by 12 months. The average Constant score was 67.1 at one year.

Conclusion: Prognostic factors on presentation were age of the patient and their physiological index, and at three months any complication, the position of the implant, tuberosity union and persistent neurological deficit. Overall optimum outcome was in patients aged 55 to 60, with minimal co-morbidities and uncomplicated recovery.

Elbow contracture is a recognized sequel of elbow trauma. We aim at reviewing the clinical outcome of surgical capsulectomy and elbow debridement.

The operative notes as well as pre and post-operative clinical records were reviewed for 15 patients who sustained an elbow trauma which resulted in elbow contracture and were managed with open capsulectomy and debridement. In addition two patients had anterior transfer of the ulnar nerve, twohad removal of loose bodies, two had excision of heterotopic bone, one patient had reconstruction of the medial collateral ligament and one patient had repair of the lateral collateral ligament .

These patients were followed up for a mean of 21 months (6 to 37).

Elbow flexion contracture improved from a mean of 37° (10° to 55°), to a mean of 10° (0° to 25°). Elbow flex-ion improved from a mean of 125° (95° to 140°) to a mean of 129° (90° to 140°). There were no major complications. Two patients underwent repeat debridement due to recurrence of contracture. One patient developed serious collection that settled gradually.

We conclude that open capsulectomy and debridement is a satisfactory way of management of post-traumatic elbow contracture in the short and intermediate term.

Introduction The aim of this study was to assess shoulder hemiarthroplasty for non-reconstructable proximal humeral fractures at a minimum of 12 months and identify factors that aid prognosis.

Methods Patients with a displaced fracture requiring shoulder hemiarthroplasty were studied. Patients were treated using the Neer or Osteonics prosthesis and the decision for hemiarthroplasty was made at the time of surgery. Post-operative management was standardised. An independent functional assessment, record review creating a physiological index on co-morbidities, and a radiological analysis were carried out. Survival analysis was performed for one and five year results and data was analysed by linear regression to identify prognostic factors. From 163 patients there were 138 fitting the criteria, 42 males and 96 females, average age of 68.5 (range 30 to 90) years and follow-up of 6.3 (range 1 to 15) years. The fracture pattern was three or four part in 133 cases and five head split fractures; 58 were associated with dislocation.

Results Survival was 96.4% one year and 93.6% five years, with no significant difference between prostheses. There were eight revisions, (one deep infection, four dislocations and three peri-prosthetic fractures), by 12 months. The average Constant score was 67.1 at one year. Prognostic factors at presentation were patient age and physiological index. At three months factors were implant position, tuberosity union, persistent neurological deficit and any complication.

Conclusion Overall optimum outcome was in patients aged 55 to 60, with minimal co-morbidities and an uncomplicated recovery.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.

Introduction: Enlarging cystic cavitations (syrinxes) form within the spinal cord in up to 28% of spinal cord injured patients. These post-traumatic syrinxes can cause neurological deterioration, and treatment results remain poor. Syrinxes are often found adjacent to regions of arachnoiditis.

The understanding of biological systems is increasingly dependent on modelling and simulations. Numerical simulation is not intended to replace in vivo experimental studies, but to enhance the understanding of biological systems. This study tests the hypothesis that pressure pulses in the SAS are high adjacent to areas of arachnoiditis and investigates the validity of a numerical model by comparison with in vivo experimental findings.

Methods: Experimental Model: Post-traumatic syringomyelia was induced in eight sheep by injection of kaolin into the subarachnoid space (SAS), and excitotoxic amino acid into the spinal cord of the upper thoracic spine. Cerebrospinal fluid (CSF) pressure studies were undertaken at either 3 or 6 weeks. Fibre-optic monitors were used to measure the pressure in the SAS 1 cm rostral and 1 cm caudal to the induced arachnoiditis.

Numerical Model: An axisymmetric fluid-structure interaction model was developed to represent the spinal cord and SAS under normal physiological conditions and in the presence of arachnoiditis. Arachnoiditis was modeled as a porous obstruction in the SAS.

Results: In both models the SAS pressure rostral to the arachnoiditis was found to be higher than the caudal SAS pressure. There was no statistically significant difference between the sheep at 3 and 6 weeks. Under normal conditions, both experimentally and in the numerical model, the pressure drop along the SAS was negligible. In the presence of arachnoiditis, the pressure drop across the arachnoiditis in the experimental model was 1.6 mmHg, whereas the numerical model predicted a pressure difference of 1.3 mmHg.

Discussion: The numerical model accurately predicts CSF pressures in the animal model under both normal and abnormal conditions, allowing predictions to be made to within 20% accuracy. The local increases in SAS CSF pressure demonstrated may act to increase fluid flow through perivascular spaces and be implicated in syrinx formation and enlargement.

Introduction: Modern imaging techniques have demonstrated that up to 28% of patients with spinal cord injury develop syringomyelia. Cyst formation and enlargement are thought to be related to abnormalities of cerebrospinal fluid hydrodynamics, however the exact mechanism and route of entry into the spinal cord remain incompletely understood. Previous work in rats has demonstrated that experimental post-traumatic syrinxes occur more reliably and are larger when the excitotoxic injury is combined with arachnoiditis produced by subarachnoid kaolin injection. A sheep model of post-traumatic syringomyelia (P.T.S.) has been characterised and studies of cerebrospinal fluid dynamics are currently being undertaken. The aim of this study was to assess the effect of focal subarachnoid space blockage on spinal fluid pressures and flow.

Methods: Arachnoiditis was induced in 5 sheep by injection of 1.5 mls of kaolin in the subarachnoid space (SAS) of upper thoracic spinal cord. The animals were left for 6–8 weeks before C.S.F. studies were undertaken. In another 5 sheep, a ligature was passed around the spinal cord to simulate an acute blockage of the subarachnoid space. Fluid-coupled monitors were used to measure blood pressure, central venous pressure and subarachnoid pressure (1cm rostral and 1 cm caudal to the arachnoiditis or ligature). Fiberoptic monitors were used to measure intracranial pressure. In the ligature group, subarachnoid pressures were also measured prior to tying the ligature to obliterate the SAS and served as baseline control pressures. The effects of Valsalva and Queckenstedt manoeuvres on SAS pressures were examined in both groups.

CSF flow was studied at 0 and 10 minutes after injection of the CSF tracer horseradish peroxidase (HRP). Vibratome sections of the spinal cord were processed using tetramethylbenzidine and sections examined under light microscopy.

Results: The mean SAS pressure rostral to the arachnoiditis was found to be greater than the mean caudal SAS pressure by 1.7 mmHg. In the ligature group, the difference was 0.9 mmHg, being higher in the caudal SAS. Queckenstedt manoeuvre exaggerated this difference to 3 mmHg in the Kaolin group and 4 mmHg in the ligature group. The effect of Valsalva was much less marked in both groups.

Perivascular spaces were enlarged in most cases of arachnoiditis and HRP was seen to stain these spaces and the central canal within 10 minutes.

Discussion: Post-traumatic syrinxes are usually juxtaposed to the injury site with 80% occurring rostral, 4% caudal and 15%in both directions. The finding of a higher subarachnoid pressure rostral to the injury site may help explain this phenomenon. We hypothesize that a reduction of compliance in subarachnoid space increases the pulse pressure and hence increases perivascular flow of C.S.F. contributing to the formation and enlargement of PTS. We are currently investigating this hypothesis by measuring subarachnoid space compliance directly in the sheep model of arachnoiditis described above.

INTRODUCTION: Modern imaging techniques have demonstrated that up to 28% of patients with spinal cord injury develop syringomyelia. Cyst formation and enlargement are thought to be related to abnormalities of cerebrospinal fluid hydrodynamics, however the exact mechanism and route of entry into the spinal cord remain incompletely understood. Previous work in rats has demonstrated that experimental post-traumatic syrinxes occur more reliably and are larger when the excitotoxic injury is combined with arachnoiditis produced by subarachnoid kaolin injection. A sheep model of post-traumatic syringomyelia (P.T.S.) has been characterised and studies of cerebrospinal fluid dynamics are currently being undertaken. The aim of this study was to assess the effect of focal subarachnoid space blockage on spinal fluid pressures and flow.

METHODS: Arachnoiditis was induced in five sheep by injection of 1.5 mls of kaolin in the subarachnoid space (SAS) of upper thoracic spinal cord. The animals were left for 6–8 weeks before C.S.F. studies were undertaken. In another five sheep, a ligature was passed around the spinal cord to simulate an acute blockage of the subarachnoid space. Fluid-coupled monitors were used to measure blood pressure, central venous pressure and subarachnoid pressure (1 cm rostral and 1 cm caudal to the arachnoiditis or ligature). Fiberoptic monitors were used to measure intracranial pressure. In the ligature group, subarachnoid pressures were also measured prior to tying the ligature to obliterate the SAS and served as baseline control pressures. The effects of Valsalva and Queckenstedt manoeuvres on SAS pressures were examined in both groups.

CSF flow was studied at 0 and 10 minutes after injection of the CSF tracer horseradish peroxidase (HRP). Vibratome sections of the spinal cord were processed using tetramethylbenzidine and sections examined under light microscopy.

RESULTS: The mean SAS pressure rostral to the arachnoiditis was found to be greater than the mean caudal SAS pressure by 1.7 mmHg. In the ligature group, the difference was 0.9 mmHg, being higher in the caudal SAS. Queckenstedt manoeuvre exaggerated this difference to 3 mmHg in the Kaolin group and 4 mmHg in the ligature group. The effect of Valsalva was much less marked in both groups.

Perivascular spaces were enlarged in most cases of arachnoiditis and HRP was seen to stain these spaces and the central canal within 10 minutes.

DISCUSSION: Post-traumatic syrinxes are usually juxtaposed to the injury site with 80% occurring rostral, 4% caudal and 15% in both directions. The finding of a higher subarachnoid pressure rostral to the injury site may help explain this phenomenon. We hypothesise that a reduction of compliance in subarachnoid space increases the pulse pressure and hence increases peri-vascular flow of C.S.F. contributing to the formation and enlargement of PTS. We are currently investigating this hypothesis by measuring subarachnoid space compliance directly in the sheep model of arachnoiditis described above.