Introduction: Deep Venous Thrombosis (DVT) and pulmonary embolism (PE) cause significant morbidity and mortality in orthopaedic surgical practice, although the incidence following surgery to the lumbosacral spine is less than following lower limb surgery. Our objective was to compare our rate of thromboembolic complications with those published elsewhere and investigate whether the adoption of additional pharmacological and physical measures had reduced the incidence of clinically evident deep venous thrombosis (DVT) and pulmonary embolism (PE).

Materials and Method: This study was undertaken to investigate the incidence of DVT/PE during the 10 years from 1/1/1985 to 31/12/1994, and then to assess the effectiveness of an anticoagulant policy introduced during 1995 using low dose aspirin or LMH in high risk cases. All records for spinal operations were reviewed for thromboembolic complications by reference to the Scottish Morbidity Record form SMR1. To ensure that all patients were compliant with the policy, data for the whole of 1995 was omitted and the period 1/1/1996 to 31/12/2003 was taken to assess its effectiveness.

Surgery was done with the patient in the kneeling, seated prone position which leaves the abdomen free and avoids venous kinking in the legs.

Results: Records of a total of 1111 lumbar spine operations were performed from 1/1/1985 to 31/12/2004 were reviewed. The overall incidence of thromboembolic complications was 0.29%. A total of 697 operations were performed from 1/1/1985 to 311994 with two cases of DVT and no cases of PE giving thromboembolic complication rate of 0.29%. During the period 1/1/1996 to 31/12/2003, 414 operations resulted in one case of DVT and no cases of PE, a rate 0f 0.24%.

Conclusion: The incidence of thromboembolic complications is low whether or not anticoagulation is used. We believe that the kneeling, seated prone operating position is a significant contributing factor.

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.

Purpose: To evaluate the changes in lumbar spine kinematics and clinical outcomes of patients with spinal stenosis 2 years after implantation of the X Stop interspinous decompression device.

Methods: 10 patients (6 males; 4 females) underwent X Stop procedure. Age ranged from 57 years to 71 years. 15 levels were operated (5 single levels: L_2-3 - 1, L_4-5 - 4; 5 double levels: L_3-4 +L_4-5 – 4; L_4-5+L₅S₁ – 1). A 0.6 Tesla Upright MRI scanner was used to acquire images in seated (flexion, extension, and neutral) and erect postures at preoperative, 6 months, and 2 years after surgery. The total range of motion of the lumbar spine and the operated segments were measured, along with changes in disc height, areas of the exit foramens, and dural sac. Clinical outcomes were assessed by Zurich Claudication Questionnaire before and 3, 6, 12, and 24 months after surgery.

Results: Mean Zurich Claudication Scores (n=10)

At 6 months, there was a significant increase in the spinal canal and foraminal dimension. However at 2 years there was a reduction in these dimensions such that there was no significant difference from the preop-erative measurements.

Conclusion: The results of this prospective observational study indicate that X Stop offers significant short-term improvement. It is a safe, effective, and less invasive alternative for treatment of lumbar spinal stenosis. The maximum clinical benefit and mechanical efficacy seems to be realized in the early stages postoperatively with gradual reduction thereafter over 2 years. Co-existing co-morbidities such as obesity and osteoarthritis in the lower limbs may influence the clinical results.

Background: It has been demonstrated that a relationship exists between pro-inflammatory cytokine levels and psychological distress. Psychological distress commonly co-exists with back pain and may be detrimental to rehabilitation in such patients undergoing surgery. We aim to establish whether a link exists between psychological distress and increased levels of Interleukin- 6 (IL-6) and it’s soluble receptor (sIL-6r) in patients undergoing surgery for low back pain.

Methods: All individuals selected for spinal fusion or stabilisation surgery, in whom low back pain was the predominant feature, were eligible for inclusion. Participants completed both the Distress and Risk Assessment Method (DRAM) and Hospital Anxiety and Depression Score (HADS) questionnaires pre-operatively. Blood samples for serum IL-6, sIL-6r and high sensitivity C-Reactive Protein (CRP) levels were extracted at recruitment and results were compared with questionnaire findings.

Results: 63 patients were recruited of whom 90.5% had some degree of measurable psychological distress. Patients were divided into two groups based upon the degree of their distress.

Mean IL-6 levels were higher in groups of patients with more distress measured by the DRAM and HADS depression component but were lower in patients with more anxiety. IL-6 receptor levels were higher in patients with raised DRAM and HADS anxiety scores.

No significant correlation between questionnaire responses and cytokine levels was found. A correlation exists between IL-6 and CRP levels even at normal levels of CRP.

Conclusion: There does not appear to be a significant relationship between IL-6 and sIL-6r levels and psychological distress in back pain patients.

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.

Introduction: This prospective observational study reports on the clinical efficacy of a complete case series of patients who have had X STOP interspinous device insertion for the treatment of lumbar spinal stenosis.

Methods: 60 patients were enrolled and asked to complete the ZCQ, ODI, SF-36 and VAS questionnaire’s pre-operatively, and at 3-, 6- and 12 months post-operatively. Clinical significance with the ZCQ is accepted as improvement in 2 of the 3 domains (where the changes correspond to a mean decrease of 0.42 or 0.46 for symptom severity or physical function respectively, or there is a mean patient satisfaction score of 2.4 or less). Changes in ZCQ were measured at each time point and compared to pre-operative levels.

Results: The mean age was 70 (range 54–90), M:F 29:30. Two of the 59 patients were withdrawn due to intra-operative spinous process fracture and unrelated death. 60% underwent single level and 40% double level insertion.

The ZCQ, ODI, SF-36 and VAS were completed preoperatively and at 12 months by 54, 50, 52, 52 respectively.

Thirty-nine patients completed all questionnaires at all time points and the maximal clinical efficacy was evident 3 months post-operatively. Clinical significant improvement was maintained at the 6- and 12 month post-operative follow-ups despite a minimal loss of clinical efficacy in absolute mean values.

Overall, clinically significant response was achieved in 65%. Seventy-one per cent of double level patients and 61% of single level patients as determined by the ZCQ, had a clinically significant response. Corresponding changes were seen in VAS and ODI and SF-36.

Ten patients (18%) required caudal epidural for recurrence of symptoms and 1 patient required perifacet injections for back pain.

Conclusion: X STOP offers a safe reversible treatment for symptomatic spinal stenosis. Clinically significant improvement is present at three months and is maintained at 12 months.

Introduction: The effect of the X-STOP on sagittal kinematics and spinal canal and neural foraminal area are reported when this interspinous device is used for the treatment of neurogenic claudication.

Methods: Patients underwent Positional MRI scanning pre-operatively and 6 months post-operatively in the erect, flexed seated and extended and neutral positions. Anterior and posterior disc heights were measured on the erect images, endplate angle and the L1S1 angle on flexion and extension images at the operated and adjacent levels. Spinal canal and neural foraminal area were measured on all images. Measurements were made using the Osiris 4.17 program and statistical analysis using the Wilcoxon sign rank test.

Results: Fifty-two patients were enrolled. M:F 26:26. Single level: Double level insertion 29:20. Three patients withdrawn, one died of unrelated causes, one intra-operative spinous process fracture, one lost to follow-up.

Single Level: Spinal canal and neural foramina areas were increased in all positions with canal area significantly increased on standing (p=0.024) and sitting neutral (p=0.036). There was no significant effect on endplate angle, segmental range of movement, L1S1 angle or disc height.

Double Level: Spinal canal area was significantly increased in the cranial segment on standing (p=0.002) and extension (p=0.016) and the caudal segment in extension (p=0.016). Foraminal area was significantly increased at the right cranial (p=0.019) and caudal (p= 0.045) segments in flexion and left cranial (p=0.017) and caudal segments (p=0.004) in extension. A significant change was observed at the endplate angles in flexion (p=0.028) and extension (p=0.026) at the upper level. The L1S1 angle was significantly reduced in extension (p=0.017). The caudal anterior disc height was reduced (p=0.023). There was no significant effect on segmental range of movement or sagittal kinematics at adjacent levels.

Conclusion: X-STOP insertion has minimal effect on the sagittal kinematics of the lumbar spine but does increase canal and neural foraminal area.

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.

Purpose: To measure the effect of the X-Stop interspinous distraction device on spinal canal, exit foramina, and disc height dimensions at the operated level; and adjacent segment endplate angle, and lumbar spine movement in patients with symptomatic lumbar spinal stenosis using upright MRI.

Methods /Results: 14 patients (9 M;5 F) were scanned before and six months after operation. Age ranged from 57 to 88 years. All had symptomatic lumbar spinal stenosis- single level- 9 (L2/3-1; L3/4-1; L4/5-7); double level 5 (L3/4, L4/5).

Images were taken in sitting flexed, extended, neutral, and standing. The total range of motion of the lumbar spine and of the individual segments were measured, along with changes in disc height, areas of the exit foramina, and dural sac.

The mean area of the dural sac at the operated levels increased from 62.46mm2 to 77.69mm2 (p=0.004) in the standing posture and from 70.85mm2 to 94.62mm2 (p=0.019) in extension postoperatively. The area of the exit foramina in extension increased from 83.57mm2 to 107.88mm2 (p=0.002) on the left side and from 83.77mm2 to 108.69mm2 (p=0.012) on the right. The overall changes in the range of movement of the individual segments or of the lumbar spine were statistically insignificant.

Conclusions: This is the first study carried out using an upright MRI scanner in patients with lumbar spinal stenosis. 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.

Purpose Of The Study: This study measures the changes in the lumbar spine in different postures, pre- and after insertion of the device.

Material-Method-Results: All the 25 patients, with chronic back pain, had discography preoperatively a positional MRI scans pre-op and nine months postoperatively in different postures.

The patients were divided into two groups. The Group-A with 14 patients in which only Dynesys was used and Group-B with 11 patients in which Dynesys was combined with fused levels.

The operated levels were 51, 13 of which were fused. The results showed that the mean range of movement of the lumbosacral angle reduced by 10.28° (Preop=39.21°, Postop=28.93°) (p=0.016) in group-A. In group-B it reduced by 13.73° (Preop=36.18°, Postop=22.45°) (p=0.02).

The range of movement of the end plate angle at the instrumented segments in group-A reduced by 2.96° (Preop=5.56°, Postop=2.60°) (p=0.016) while in group-Bit reduced by 4.23° (Preop=6.69°, Postop=2.46°)(p=0.008).

The mean range of movement of the end plate angle at adjacent level in group-A reduced by 1.58° (Preop=8.7°, Postop=7.21°)(p=0.427) while in group-B it increased by 1.73° (Preop=6.91°, Postop=8.64°) (p=0.149)

The mean anterior disc height in group-A reduced by 1.18mm (Preop=10.05mm, Postop=8.87mm) (p< 0.005), and the posterior one was increased by 0.6mm (Preop=6.51mm, Postop=8.87mm) (p=0.013). In group-B, the anterior disc height was reduced by 1.11mm (Preop= 10.44mm, Postop=9.33mm) (p=0.049) and the posterior one by 0.16mm (Preop=6.98mm Postop=6.82mm) (p=0.714)

Conclusion: Dynesys stabilizing system allows movement at the instrumented levels, with no significant increased mobility in the adjacent levels. Also the device acted to compress the more the anterior annulus than to distract the posterior.

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.

Cement pressurisation is recognised as critical to achieving optimal results in cemented arthroplasty of the hip, but relatively little data exists on the pressures generated by different cement introduction systems. An in vitro experiment was consequently undertaken to measure the mean pressures developed by three such systems: the Howmedica Mark 1 and DePuy Cemvac retrograde cementation systems, and a novel antegrade system consisting of a simple 60ml catheter-tipped syringe and a Miller proximal femoral seal (Zimmer Ltd).

Plastic femoral models (Sawbones Europe) were prepared as for hip arthroplasty, and had a series of three transducers attached to their medial wall. Pressure was recorded continuously during cement introduction and pressurisation, before implanting a hip prosthesis and allowing the cement to cure. The experiment was repeated on ten models for each of the three systems. After cement curing, the femora were split in the coronal plane and examined for air-bubble defects in 7 zones analogous to Gruen’s radiographic zones.

Mean pressure was significantly higher for the syringe system (161.45 ± 28.9 kPa) than the Mark 1 (103.51 ± 22.0 kPa) or Cemvac (92.65 ± 30.7 kPa) systems (p=0.0001, ANOVA). The antegrade syringe system also generated a statistically different distribution of pressure in comparison to the two retrograde systems, with particularly high proximal pressurisation in the former. The median number of zones with defects was 1 (interquartile range 1,2) using the syringe system, 3 (IQR 2,4) with the Mark 1 system, and 3 (IQR1,3) using the Cemvac system. These differences were also statistically significant (p=0.0256, Kruskal-Wallis).

These results have relevance for clinical practice and cement system design, and the various design features of the different systems are discussed.

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

Cement pressurisation is recognised as critical to achieving optimal results in cemented arthroplasty of the hip, but relatively little data exists on the pressures generated by different cement introduction systems. An in vitro experiment was consequently undertaken to measure the mean pressures developed by three such systems: the Howmedica Mark 1 and DePuy Cemvac retrograde cementation systems, and a novel antegrade system consisting of a simple 60ml catheter-tipped syringe and a Miller proximal femoral seal (Zimmer Ltd).

Plastic femoral models (Sawbones Europe) were prepared as for hip arthroplasty, and had a series of three transducers attached to their medial wall. Pressure was recorded continuously during cement introduction and pressurisation, before implanting a hip prosthesis and allowing the cement to cure. The experiment was repeated on ten models for each of the three systems. After cement curing, the femora were split in the coronal plane and examined for air-bubble defects in 7 zones analogous to Gruen’s radiographic zones.

Mean pressure was significantly higher for the syringe system (161.45 28.9 kPa) than the Mark 1 (103.51 22.0 kPa) or Cemvac (92.65 30.7 kPa) systems (p=0.0001, ANOVA). The antegrade syringe system also generated a statistically different distribution of pressure in comparison to the two retrograde systems, with particularly high proximal pressurisation in the former. The median number of zones with defects was 1 (interquartile range 1,2) using the syringe system, 3 (IQR 2,4) with the Mark 1 system, and 3 (IQR1,3) using the Cemvac system. These differences were also statistically significant (p=0.0256, Kruskal-Wallis).

These results have relevance for clinical practice and cement system design, and the various design features of the different systems are discussed.

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.

Introduction The Dynesys® stabilisation system (Zimmer Spine) uses transpedicular screws linked by a cord and spacers; the advantage claimed is that it allows some motion, in all directions, in the operated levels. In vitro laboratory biomechanical studies show that the movement permitted is similar to rigid fixation systems.

This study measures the changes in the lumbar spine in different postures, pre- and after insertion of the device. Methods In our study 25 patients with dominant low back pain, with or without leg pain, were treated with Dynesys system, 14 females and 11 males with mean age 43.5 yrs. Discography was done to evaluate the symptomatic painful level. All patients had a positional magnetic resonance imaging (pMRI) scans preoperatively and nine months post-operatively in standing; sitting flexion and extension, and left and right bending postures. The patients were initially divided into two groups. The first (Group A) with 14 patients in which only Dynesys was used (disc height 40–90%) and the second (group B) with 11 patients in which Dynesys was used with fusion (disc height < 40 %).

Results The operated levels were 51, 13 of which were fused. The results of the pMRI measurements showed that the mean range of movement of the lumbosacral angle reduced by 10.3° from pre-op of 39.2° to postop. of 28.9° (p= 0.016) in group A while in group B it reduced by 13.7° from 36.2° preop. to 22.5° postoperatively (p= 0.02).

The range of movement of the end plate angle at the instrumented segments in group A reduced from 5.6° preoperatively to 2.6° with a difference of 3.0° (p=0.016) while in group B it reduced from 6.7° to 2.5° postoperatively with a difference of 4.2°(p=0.008). The range of movement of the end plate angle at adjacent level in group A changed from 8.8° preop. to 7.2° with a reduction of 1.6° (p=0.427) while in group B it increased from 6.9° to 8.6°, difference of 1.7° (p=0.149)

The mean anterior disc height in group A reduced by 1.2mm (p< 0.005) from 10.1mm to 8.9mm postoperatively, and the posterior one was increased from 6.5mm to 8.9mm with a difference of 0.6mm (p= 0.013). In group B the anterior disc height was reduced by 1.1mm (pre-op 10.4mm to post-op 9.3mm; p=0.049) and the posterior one by 0.16mm (pre-op 6.98mm to post-op 6.82mm; p=0.714)

Discussion This study shows that in the Dynesys stabilising system allows a 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 more than to distract the posterior annulus.

Introduction Conventional MRI scanners require the patient to lie in a supine position within the bore of the magnet; positional MRI (pMRI) scanners allow patients to be scanned in any position. This is of particular value when patients have postural dependent symptoms.

Here we discuss the evaluation of two spinal devices: Dynesys, a spinal stabilisation system for back pain, and X STOP, an interspinous process distraction device for spinal stenosis.

Materials, Methods & Results For each device, patients underwent pre and post-operative scans in standing, lying and seated in neutral, flexed and extended positions and the ranges of movement at the operated levels and across the whole lumbar were measured.

For Dynesys, 30 patients with lower back pain were recruited. The first 20 patients have completed their 9 month scan, and the results show that the device reduces the range of movement at the operated segments, with a small increase in movement at adjacent segments and an overall reduction in the range of movement of the lumbar spine.

For X STOP, the first 10 of 45 have reached their second scan at 6 months post surgery. The scans demonstrate a net increase in the cross-section of the spinal canal of 21% when flexed to 35% whilst standing, and an increase in the surface area of the exit foramen of 23% flexed and 51% standing at operated levels.

Conclusion These studies demonstrate the value of pMRI for the evaluation of lumbar spine prosthesis. pMRI allows for the assessment of the devices in their functional (i.e. upright) position.