Purpose

The purpose of the study was to determine the rate of conversion from RSA to THR in a number of Canadian centers performing resurfacings

Objective

To identify any difference in clinical outcome between Intra-Capsular facet (IF) and Peri-facet (PF) injections in patients with low back pain (LBP). IF and PF joint steroid injections have been used for treatment of LBP with varied reports of pain relief for many years.

Purpose: Recently, there has been concern raised on the occurrence of pseudotumors after metal on metal hip resurfacing. A pseudotumor is defined as a local soft tissue mass associated with localized bony and/or tissue (muscle) destruction. The primary purpose of this study is to determine the incidence of this complication in several high volume Canadian academic centres.

Method: Nine of the 11 Canadian academic centres who perform metal on metal hip resurfacings were surveyed. The number of metal on metal hip resurfacing arthroplasties performed at each centre was first determined, as were the number of those who have presented with a pseudotumour, and subsequently gone on to revision surgery. The basic demographics of the group were recorded, as were the radiographic and implant design variables for those cases presenting with a pseudotumour.

Results: A sample of 3,400 hip resurfacing arthroplasties performed between 2002 and December 2008 were surveyed. Demographics were tabulated for a sub-sample of these patients. 76% were male, the mean length of follow-up was 3.02 years, mean BMI was 28.65, and mean age was 52.10 years. Three of 3,400 cases presented with a pseudotumour, an incidence of .09%.

Conclusion: Although pseudotumors remain a concern after metal on metal hip resurfacing, the incidence at short to mid term follow-up is very low in this multi-centre academic survey. This information is significantly lower than what other groups have recently reported. Continued close monitoring is required in order to determine what clinical factors are at play.

Purpose: Correlation of clinical outcome of X stop interspinous process decompression in patients with symptomatic lumbar spinal stenosis is made with spinal canal area change on positional MRI.

Method and Results: Clinical outcome was assessed by ZCQ, ODI, SF36 and VAS scores. There is clinically significant improvement if two ZCQ domains improved > threshold or patients were satisfied. Dural sac area was measured standing erect and sitting, neutral, flexion and extension preoperatively and at 2 years. Increased dural sac area was taken as radiological improvement.

Thirty-six patients had MRI at 2 years. Using paired t test we noted statistically significant increase in mean dural sac area in all four positions mentioned above. There was clinical improvement in 26 and some or no improvement in 10 patients. Number with increase in canal cross sectional area was 28 and that with reduced area was 8. Clinical and canal area improvement was seen in 20 (56%) patients and clinical improvement with reduced canal area was seen in 5 (14%). Some or no clinical improvement with canal area improvement occurred in 8 (22%) patients and no significant clinical or canal area improvement in 3 (8%).

Conclusions:

Majority of patients (56%) showed clinical and cross sectional area improvement at 2 years.

Interest statement: Commercial/industry support: Medtronics

Purpose: Correlation of the clinical outcome of X stop interspinous process decompression (IPD) in patients with symptomatic lumbar spinal stenosis (LSS) is made with their preoperative disc heights.

Method: 45 patients, who had clinical follow-up at 2 years, had pre-operative erect positional MRI scans. Clinical outcome was assessed by Zurich Claudication Questionnaire,ODI,SF36 and VAS scores.ZCQ is the most condition specific for LSS and was used. There is clinically significant improvement if two ZCQ domains improved > threshold (SS> 0.46, PF> 0.42, PS< 2.4) or patients were satisfied. Disc heights were measured in the standing erect posture. Osiris 4.17 software program was used for measurements. Statistics used was Chi-Square test with cross tabulation.

Results: There was clinical improvement in 33 and some or no improvement in 12 patients. Overall preoperative range of disc heights was 1.8 to 10.05 mm, median 5.93. Disc height was less than or equal to 5mm in 21 patients and it was > 5 mm in 24 patients.19 patients who had initial disc height of > 5 mm and 14 patients who had disc height of less than or equal to 5 mm had clinically significant improvement. In the group of patients who had some or no improvement the numbers were 5 and 7 respectively. We found a difference between the groups with bigger and smaller preoperative disc heights and a larger proportion of patients with bigger preoperative disc height had better clinical outcome. This difference was not statistically significant, P = 0.350.

Conclusions: The X stop device remains clinically effective at the end of 2 years in the majority of patients. Overall patients who had bigger preoperative disc heights 79% (i.e. 19/24 who had > 5mm initial disc height) had better clinical outcome compared to those with smaller preoperative disc heights.

Interest statement: Commercial/industry support: Medtronics

Aims: To investigate the clinical and radiological (MRI) effectiveness of Nuclear Magnetic Resonance Therapy (NMRT) on mild to moderate degenerative knee osteo-arthrosis (OA).

Methods: A double blind randomised control mono-centric study of 100 volunteer patients with mild to moderated knee OA. All patients underwent clinical examination, pain was recorded on visual analog scale (VAS) and Oxford knee score and WOMAC osteoarthritis index at baseline and at follow up intervals (1 week, 1 month, 3 months and 6 months). The treatment group (n=50) received five sessions of one hour NMRT on five consecutive days. Radiological assessment included baseline standing plain radiograph of the knee joint (AP and Lateral views) and positional MRI scan which was repeated at 3 months. Cartilage thickness in weight bearing areas and bone and cartilage MRI score (BAC-MS) were used to assess response of the cartilage to NMRT. Data was analysed using SPSS 16.0 software and non-parametric tests.

Results: Ninety six patients completed six months follow-up. The treatment and placebo groups were comparable except that the male: female ration was 1:1 and 1:2 respectively. No adverse effect was reported during the study. The treatment group showed mean increase of 4° in the range of movement at 6 six months, which was statistically significant (p=0.01). There was no difference in other outcome variables at any time interval between the two groups.

Radiologically, BAC-MS and cartilage thickness at three months had no significant difference between treatment and placebo groups (p-value = 0.81 and 0.88 respectively). The change in BAC-MS and cartilage thickness at 3 months was also not significant (p-value = 0.09 and 0.41 respectively).

Conclusion: Five 1 hour sessions of NMRT is a safe mode of treatment, but has no radiological (at 3 months) and clinical (6 months) beneficial effect on mild to moderate Knee Joint Osteoathrosis.

Purpose: To see if the symptoms of mild to moderate degenerative knee osteoarthrosis are improved clinically by magnetic resonance therapy (MRT).

Method: This a double blind randamised control mono-centric study involving 100 volunteer patients recruited form the outpatient clinics who met the set inclusion and exclusion criteria of mild to moderate Osteoarthrosis of the knee joint. AD Elektronik GmbH, Wetzlar, Germany supplied the devices for giving MRT, which involved five sessions of one hour each on five consecutive days. These devices work with a coded chip card and only half of the 100 cards were coded to provide MRT. Base line assessment and follow up at 1 week, 1 month, 3 month and 6 months included clinical examination and Oxford and WOMAC Knee scores. Radiological assessment included baseline plain radiographs of the knee joint in standing position (AP and Lateral views) and positional MRI scan. At three months MRI scan was repeated. Data was analysed using SPSS 16.0 software and Mann-Whitney and Chi–square Tests were used.

Results: No adverse effects were reported during the study. The treatment and the placebo groups were comparable except that the male: female ratio was 1: 2. Placebo group had statistically significant improvement in the WOMAC Pain OA index at 3 months (p=0.017). There was statistically significant improvement in the range of movements at 6 months (p=0.010), but this was clinically not significant as the mean increase in Range of Movement was 4°. At the end of 6 months there was not difference between the two groups.

Conclusion: This study has found that five 1 hour sessions of MRT is a safe mode of treatment, but fails to support that it has a beneficial effect on Knee Joint Osteoathrosis.

Background: The X stop interspinous process decompression device has been used effectively in symptomatic lumbar spinal stenosis. It holds the spinal segment in a flexed position maintaining increase in dural sac and foraminal areas.

Aim: To study the effect of X-stop on the lumbar spine kinematics at 24 months post operatively at the instrumented and adjacent levels.

Design: Prospective Observational Study of 48 patients.

Methods: Patients had a positional MRI scan preoperatively, 6 and 24 months post operatively in erect, flexion, extension and neutral positions. Disc heights, endplate angles, segmental and lumbar spine motion were measured at stenosed instrumented and adjacent levels. Osiris 4.17 software program was used for measurements. The data was analysed using paired t test on SPSS ver.15.01.

Results: 48 patients underwent scans preoperatively. At 2 years 40 patients were scanned (3 patients had removal of X stop and 5 were not scanned). Of these, 38 scans were complete. Mean anterior disc height reduced from 7.2 mm to 5.9 mm (p< 0.001) at 24 months at the instrumented level. There were no significant changes in posterior disc height at instrumented or adjacent levels. The mean lumbar spine motion was 22o and 20o (p=0.366) in single level cases and 24.5o and 22.8o (p=0.547) in double level cases preoperatively and at 24 months. There was no significant change in the segmental range of motion at instrumented or adjacent levels.

Conclusion: X-stop device does not significantly alter the kinematics of lumbar spine at instrumented or adjacent levels at 24 months postoperatively.

Background: X stop interspinous decompression device has been used effectively in symptomatic patients with lumbar canal stenosis. The positional MRI scanner images patients in the erect weight bearing position and is used here to evaluate the efficacy of the X stop in maintaining increase in dural sac and foraminal areas.

Aim: To assess the clinical effectiveness of X stop in patients with lumbar canal stenosis and measure its effect in decompressing the spinal canal two years postoperatively.

Design: Prospective Observational Study.

Methods: Clinical outcome was assessed by ZCQ, VAS, ODI and SF36 questionnaires. Clinical and radiological outcomes were measured preoperatively and at 2 years. Foraminal area was measured in flexion and extension whereas dural sac area was measured in erect, neutral, flexion and extension. Osiris 4.17 software program was used for the measurements. The data was analysed using paired t test on SPSS ver.15.01.

Results: With ZCQ overall 57% of patients had clinically significant improvement at 24 months. The mean ODI and VAS scores showed improvement. The SF-36 improved in four domains. Radiologically we noted increase in mean dural sac area in all positions. There was a small increase in foraminal areas and statistically significant increase in dural sac areas at 24 months.

Conclusion: The X stop device remains clinically effective at the end of 2 years. It is a relatively less invasive procedure without major complications and can be performed as a day case procedure. X stop maintains increase in dural sac and foraminal areas at 24 months postoperatively.

Aim: To measure the effect of X-stop interspinous decompression device on the dural sac and foraminal area at 6 and 24 months post operatively at the instrumented level in patients with symptomatic lumbar canal stenosis.

Design: Prospective Observational Study of 48 patients.

Methods: Patients due to have an X stop procedure were included and had a positional MRI scan preoperatively and 6 & 24 months post operatively. Foraminal area was measured in flexion and extension position whereas dural cross sectional area was measured in erect, neutral, flexion and extension positions. Osiris 4.17 software program was used to measure the canal and foraminal dimensions. The data was analysed using paired t test on SPSS ver.15.01.

Results: Forty-eight patients (25 male and 23 female) underwent scans preoperatively and at six months. Twenty-nine patients had single level and 19 had double level procedures. Three patients had removal of X stop and 5 did not have scan at 24 months leaving 40 patients scanned at 24 months. Of these 38 scans were complete and were included. We noted increase in mean dural sac area in all positions. The mean dural sac area increased from 131 mm2 to 143 mm2 (p=0.144) at 6 months and from 137 mm2 to 202 mm2 (p= 000) at 24 months in standing position. The difference in pre-operative measurements in the six and 24-month measurements is because of the different patient numbers scanned. There were similar increased dural sac areas in the other positions. The mean foraminal areas were measured in flexion and extension and the measurements in extension were increased from 66.58 mm2 to 79.51 mm2 (p=. 001) at 6 months and from 68.10 to 69.57 mm2 (p=0.752) at 24 months on left side; and increased from 63.75 mm2 to 71.65 mm2 (p=0.036) at 6 months, from 65.54 mm2 to 68.01mm2 (p=0.440) at 24 months on right side. Thus there is a small increase in foraminal areas and statistically significant increase in dural sac areas at 24 months.

Conclusion: X-stop interspinous device remains effective in decompressing the stenosed spinal segment by increasing the anatomic dural cross sectional areas and foraminal areas of spinal canal at 24 months post operatively, thus providing symptomatic relief from lumbar canal stenosis.

Aim: To study the effect of X-stop interspinous decompression device on the lumbar spine kinematics at 6 and 24 months post operatively at the instrumented and adjacent levels in patients with symptomatic lumbar canal stenosis.

Design: Prospective Observational Study of 48 patients.

Methods: Patients due to have an X stop procedure were included and had a positional MRI scan preoperatively, 6 and 24 months post operatively in erect, flexion, extension and neutral position. Disc heights, endplate angles, segmental and lumbar spine motion was measured at stenosed instrumented and adjacent levels. Osiris 4.17 software program was used to measure the canal and foraminal dimensions. The data was analysed using paired t test on SPSS ver.15.01.

Results: Forty-eight patients (25 Male and 23 Female) underwent scans preoperatively and at 6 months. Twenty-nine patients had single level and 19 had double level procedures. Three patients had removal of X stop and 5 did not have scan at 24 months, leaving 40 patients scanned at 24 months. Of these, 38 scans were complete and were included. Mean anterior disc height reduced from 7.1 mm to 6.3 mm (p=0.004) from 48 scans at 6 months and from 7.2 mm (pre-operative) to 5.9 mm (at 24 months) – (p=0.000) from 38 scans at 24 months at the instrumented level. We hypothesise that the reduction in anterior disc heights could be a result of the interspinous distraction plus the natural progression of spinal stenosis and ageing. There was no significant change in posterior disc heights at instrumented level or adjacent levels. The mean lumbar spine motion was 22.89o, 21.3 o and 21o (p=0.183) preoperatively, 6 and 24 months respectively. The total range of movements of lumbar spine and individual segments were measured. There was no significant change in the segmental range of motion at instrumented and adjacent levels.

Conclusion: X-stop interspinous device does not significantly alter the kinematics of lumbar spine at instrumented and adjacent levels at 6 and 24 months postoperatively.

Aim: To assess the clinical effectiveness of X stop interspinous decompression device in patients with neurogenic claudication due to lumbar canal stenosis at 24 months post surgery.

Design: Prospective Observational Study of 57 patients with X stop procedure.

Methods: Fifty-seven patients with unilateral or bilateral leg pain due to lumbar canal stenosis, who had significant relief from sitting or flexing the lumbar spine, were treated with X stop.

Clinical outcome was assessed by Zurich claudication questionnaire (ZCQ), visual analogue score (VAS), Oswestery disability index (ODI) and SF36 questionnaires preoperatively and at 2 years. ZCQ has three components- symptom severity, physical function and patient satisfaction. ZCQ is considered the most precise, reliable and condition specific questionnaire for lumbar canal stenosis.

Out of 57 patients, 2 died due to unrelated causes, 3 withdrew from study and 3 had the device removed within 2 years. Forty-five, 44, 42 and 48 completed ZCQ, ODI, SF-36 and VAS respectively at 24 months.

Results: The mean age was 71(53–94) and M: F ratio 29:28. X stop device was inserted at single level in 32 (56%) and double levels in 25(44%) patients. In single level cases, 72% reported improvement in symptom severity, 65% in physical function, 68% were satisfied with the procedure, and overall 55% made a clinically significant improvement at 24 months. In double level cases, the figures were 62%, 68%, 78% and 40% respectively. The threshold for changes in symptom severity was 0.46, physical function was 0.42 and patient satisfaction 2.42. Overall clinically significant improvement requires that a patient achieves at least 2 criteria.

The mean ODI improved by 6.5 in single level and 10.8 in double level cases. The SF-36 showed improvement in physical function, role physical, bodily pain and vitality social domain.

Average hospital stay for the procedure was 1.6 days. One patient stayed for 10 days for investigation unrelated to the procedure. There were no major complications.

Conclusions: The results of our study show that the X stop interspinous decompression device remains clinically effective at the end of 2 years. X stop is a relatively less invasive procedure, especially suitable for patients with other co-morbidities, which can be performed as a day case procedure without major complications.

There is little evidence from the literature regarding the timing of hip fracture surgery for patients who are on the antiplatelet agent clopidogrel bisulphate (Plavix) (1).

We report the results of a retrospective case control study of 40 patients comparing the timing of surgery for patients taking clopidogrel against a control group of those not taking an antiplatelet agent. Time to surgery, length of stay, transfusion requirements, wound problems and other post operative complications were examined.

Within the study group of patients taking clopidogrel, we also compared those who underwent surgery within four days of stopping the clopidogrel and after four days.

The transfusion requirements were greater in those patients on clopidogrel prior to admission. Wound healing and post operative complications were similar between the two groups. Total length of hospital stay and post operative length of stay were longer in the clopidogrel group.

There was an increase in transfusion requirements and post operative length of stay in patients on clopidogrel undergoing early surgery (within 4 days) compared to the group where surgery was delayed.

We conclude that, in this small study, transfusion requirements and length of stay were greater in patients on clopidogrel. Transfusion requirements and post operative length of stay were also greater if surgery was performed within four days of omitting clopidogrel. Further studies are required to determine optimal timing of surgery following discontinuation of clopidogrel.

Aim: To assess the kinematic changes that occur within the lumbar spine 2 years following insertion of the Dynesys Spinal stabilisation implant.

Materials and Methods: Twenty patients who were treated with Dynesys surgical stabilisation for dominant lower back pain underwent positional MRI scanning before and two years following surgery.

The patients were divided into two groups, A and B. The first, Group A, in which only Dynesys was used and the second, Group B, in which Dynesys was used adjacent to one or more fused segments.

Results: The results of the pMRI measurements showed that the range of movement (ROM) of the L1/S1 angle in Group A reduced by 11.8o{pre-op=37.9o, postop=26.1o(p=0.085)} while in Group-B reduced by 12.3o {pre-op=37.8o, postop=25.5o(p=0.017)}.

The ROM of the end plate angle at the instrumented segments in Group A reduced from 5.72^o to 1.44^o{difference 4.28^o(p=0.005)} and in Group B reduced from 6.00^o to 2.17^o,{difference 3.83^o(p=0.001)}.

The ROM of the end plate angle at the level above instrumentation in Group A reduced from 8.2^o to 5.1^o {reduction 3.1^o(p=0.085)}, while in group-B increased from 7.3^o to 7.5^o, a difference of 0.2^o (p=0.877).

The mean anterior disc height in Group A reduced by 2.1mm (p< 0.001) from 9.59mm to 7.44mm. The posterior disc height also reduced from 6.56mm to 6.26mm, a difference of 0.3mm, (p=0.434). In Group B, the anterior disc height reduced by 1.98mm (pre-op=9.04mm, post-op= 7.06mm, p=0.001) and the posterior height by 0.35mm (pre-op 6.14mm to post op 5.79mm, p=0.443)

Discussion: This study shows that the Dynesys stabilisation system allows some movement at the operated segment two years following surgery. The study also confirms that the adjacent segment hypermobility often seen following spinal fusion surgery is eliminated.

Aim: To assess the kinematic changes that occur within the lumbar spine 2 years following insertion of the Dynesys Spinal stabilisation implant.

Materials and Methods: Twenty patients who were treated with Dynesys surgical stabilisation for dominant lower back pain underwent positional MRI scanning before and two years following surgery.

The patients were divided into two groups, A and B. The first, Group A, in which only Dynesys was used and the second, Group B, in which Dynesys was used adjacent to one or more fused segments.

Results: The results of the pMRI measurements showed that the range of movement (ROM) of the L1/S1 angle in Group A reduced by 11.8o{pre-op=37.9o, postop=26.1o(p=0.085)} while in Group-B reduced by 12.3o {pre-op=37.8o, postop=25.5o(p=0.017)}.

The ROM of the end plate angle at the instrumented segments in Group A reduced from 5.72^o to 1.44^o{difference 4.28^o(p=0.005)} and in Group B reduced from 6.00^o to 2.17^o,{difference 3.83^o(p=0.001)}.

The ROM of the end plate angle at the level above instrumentation in Group A reduced from 8.2^o to 5.1^o {reduction 3.1^o(p=0.085)}, while in group-B increased from 7.3^o to 7.5^o, a difference of 0.2^o (p=0.877).

The mean anterior disc height in Group A reduced by 2.1mm (p< 0.001) from 9.59mm to 7.44mm. The posterior disc height also reduced from 6.56mm to 6.26mm, a difference of 0.3mm, (p=0.434). In Group B, the anterior disc height reduced by 1.98mm (pre-op=9.04mm, post-op= 7.06mm, p=0.001) and the posterior height by 0.35mm (pre-op 6.14mm to post op 5.79mm, p=0.443)

Discussion: This study shows that the Dynesys stabilisation system allows some movement at the operated segment two years following surgery. The study also confirms that the adjacent segment hypermobility often seen following spinal fusion surgery is eliminated.

Purposes Of The Study-Background Data: Dynesys is claimed that allows motion in the operative levels. This study measures the changes in the lumbar spine in different postures, pre- and after insertion of the device.

Thirty patients with were treated with Dynesys system. All had discography and positional MRI preoperatively and nine months post-operatively.

The patients were divided in to two groups. The first in which only Dynesys was used and the second in which Dynesys was used with fusion.

Results: The operated levels were 63. The results of the pMRI measurements showed that the range of movement(ROM) of the L1/S1 angle in group-A reduced by 11.89^o{pre-op=39.26^o,postop=27.37^o(p=0.008)} while in group-B reduced by 13.73^o {preop=36.18^o,po stop=22.45^o(p=0.002)}.

The ROM of the end plate angle at the instrumented segments in group-A reduced from 5.24^o to 2.18^o{difference 3.06^o(p< 0.005)} and in group-B reduced from 6.69^o to 2.46^o,{difference 4.23^o(p=0.008)}. The ROM of the end plate angle at adjacent level in group-A changed from 8.26^o to 7.0^o {reduction 1.26^o(p=0.388)},while in group-B increased from 6.91^o to 8.64^o, {difference 1.73^o(p=0.149)}

The mean anterior disc height in-group A reduced by 1.43mm (p< 0.005) from 9.75mm to 8.32mm, and the posterior one was increased from 6.27mm to 6.77mm {difference of 0.5mm,(p=0.008)}. In group-B the anterior disc height reduced by 1.11mm (pre-op=10.44mm,post-op= 9.33mm,p=0.049) and the posterior one by 0.16mm (pre-op 6.98mm to post-op 6.82mm,p=0.714).

Conclusion: This study shows that in the Dynesys stabilizing system allows small range of movement at the instrumented levels, with no significant increased mobility in the adjacent levels. Also the device acted to compress the anterior annulus.

A retrospective study of one hundred and nineteen unicompartmental knee arthroplasties was performed. Outcome measures were the Oxford twelve-item knee questionnaire, the Short Musculoskeletal Functional Assessment (SMFA) and the WOMAC. Regression analysis was performed in order to determine predictors of outcome. After an average follow up period of four years, the mean scores indicated a good to excellent functional outcome. The only predictor of outcome identified was gender, with women obtaining a better functional outcome than men. Other variables that did not influence functional outcome included age, weight, stage of disease, previous HTO and bilateral procedures.

The purpose of this study was to determine

the functional outcome of unicompartmental knee arthroplasty and

Although unicompartmental knee arthroplasty is becoming more widely accepted as a treatment option for degenerative osteoarthritis, there are very few studies in the literature that systematically investigate the predictors of outcome for this procedure.

This is a retrospective study of one hundred and nineteen unicompartmental knee arthroplasties perfomed at a university hospital by a single surgeon. The outcome measures used were the Oxford twelve-item knee questionnaire, the Short Musculoskeletal Function Assessment (SMFA) and the Western Ontario and McMaster (WOMAC) functional indices. Multiple regression analysis was performed to determine predictors of outcome from chart derived variables.

After a mean follow-up of four years the mean Oxford Knee Score was thirty-nine and the mean SMFA and WOMAC functional scores were eight and seven respectively, indicating a good to excellent functional outcome. Regression analysis revealed gender as a predictor of outcome however other variables including age (range 49–84 yrs), weight (range 55–225 kgs), previous ORIF, preoperative varus/valgus (range 0–16 degrees), joint subluxation (range 0–13mm), radiographic stage of disease (Kellgren and Lawrence), as well as previous HTO and bilateral (simultaneous or staged) unicompartmental knee arthroplasty were found to not correlate with functional outcome.

Good to excellent functional outcome scores can be achieved with unicompartmental knee replacement. Previous HTO or bilateral procedures as well as weight, pre-operative varus/valgus < sixteen degrees or radiographic stage of disease were not predictive of outcome.

Introduction Symptoms of neurogenic intermittent claudication in spinal stenosis are explained by the narrowing of the spinal canal in the extended (upright) position and widening in the sitting (flexed) position. The XStop inter-spinous process distraction device is a new product that is designed to hold the affected segments in a flexed posture. This prospective study looks at the changes in the lumbar spine in a variety of postures from pre- to post insertion.

Methods Using a positional magnetic resonance imaging (pMRI) scanner, patients were scanned before and six months after the insertion of the device. Images were taken in sitting flexed and extended, and standing positions. The change in the total range of movement of the lumbar spine and in the individual operated segments was measured along with changes in the surface areas of the exit foramen, the dural sac, and the disc height.

Results 12 patients with 17 levels distracted have been scanned and measured. The cross sectional area of the dural sac at the level of the stenosis has increased from a mean of 77.8 mm² to 93.4 mm² in the standing position (p=0.006) and from 84.56mm² to 107.35mm² on extension (p=0.008). There were no statistically significant changes in the range of movement of the whole lumbar spine, or at levels adjacent to the device.

Discussion This study demonstrates that the X Stop device increases the cross sectional surface area of the spinal canal at the stenosed level, without causing extensive changes in the posture of the lumbar spine.

Introduction The Dynesys device uses transpedicular screws linked by a cord and spacers. It is claimed that the advantage is that it allows some motion, in all directions, in the operative levels. In vitro laboratory biomechanical studies show that the movement permitted is similar to rigid fusions.

This study measures the changes in the lumbar spine in different postures, pre- and after insertion of the device.

Material-method In our study 20 patients with dominant low back pain, with or without leg pain, were treated with Dynesys system. Stress discography was made to evaluate the symptomatic level

All had a positional MRI preoperatively and nine months post-operatively in flexion-extension-lateral bending.

The patients were divided in to two groups:

Group(A) with 8 patients in which Dynesys was used with fusion (disc-height< 40 %)

Group(B) with 12 patients was the Dynesys-only group (disc-height=40–90%).

Results The operated levels were 42, 10 of those were fused levels. The results showed that there was a statistically significant difference in flexion-extension range of movement of the whole lumbar spine (mean= −13.45)(p< 0.005), but it wasn’t significant in the level above (mean=0.056)(p=0.972) and at a single instrumented segment was (mean=−4.06°)(p< 0.05)

The changes in the anterior disc height was (mean= −1.18)(p< 0.05) and to the posterior (mean=0.37)(p=0.134). In bending were (mean=−0.87°)(p=0.18) for left and (mean=−0.24°)(p=0.75) for the right

Discussion This study shows that in the Dynesys stabilizing system allows small range of movement at the instrumented levels, with no significant increased mobility in the adjacent levels. Also the device acted to compress the anterior annulus

Introduction Symptoms of neurogenic intermittent claudication in spinal stenosis are explained by the narrowing of the spinal canal in the extended (upright) position and widening in the sitting (flexed) position. The X-Stop® inter-spinous process distraction device (St. francis Medical Technologies) is a new product designed to hold the affected segments in a flexed posture. This prospective study looks at the changes in the lumbar spine in a variety of postures from pre- to post-insertion.

Method Using positional MRI (pMRI), patients were scanned before and six months after operation. Images were taken in sitting flexed, extended, neutral, and standing positions. The total range of motion of the lumbar spine and of the individual operated segments were measured, along with changes in disc height, areas of the exit foramina, and dural sac.

21 patients (11 males; 10 females) were included in the study. Age ranged from 57 – 88 years. All had symptomatic lumbar spinal stenosis- single level- 13 (L2/3-1; L3/4-3; L4/5-9); double level 8(L3/4, L4/5 – 7; L4/5, L5/ S1 – 1).

Results The mean area of the dural sac at the operated levels increased from 89.25mm2 to 108.96mm2 (p< 0.001) in the standing posture and from 103.96mm2 to 124.94mm2 (p< 0.001) in extension postoperatively. The area of the exit foramina in extension increased from 79.15mm2 to 100.41mm2 (p< 0.001) on the left side and from 80.86mm2 to 98.74mm2 (p< 0.001) on the right side. The overall changes in the range of movement of the individual segments or of the lumbar spine were statistically insignificant.

Discussion Previous, radiologic (Willen J, et al; Spine 1997) and cadaveric studies have demonstrated reduction in area of the dural sac and exit foramina as the lumbar spine moves from flexion into extension. Our study is the first to quantify these changes in symptomatic patients with lumbar spinal stenosis using postional MRI. This study supports previous studies using positional MRI scanner in patients with lumbar spinal stenosis and also demonstrates that the X-Stop device increases the cross-sectional area of the spinal canal and exit foramina by distracting the spinous processes of the operated level without significantly affecting overall posture of the lumbar spine.