Background

Carbon fibre (CF) instrumentation is known to be radiolucent and has a tensile strength similar to metal. A specific use could be primary or oligometastatic cancer where regular surveillance imaging and Stereotactic Radiotherapy are required.

CT images are inherently more prone to artefacts which affect Hounsfield unit (HU) measurements. Titanium (Ti) screws scatter more artefacts. Until now it has been difficult to quantify how advantageous the radiolucency of carbon fibre pedicle screws compared to titanium or metallic screws actually is.

Objective

From our series of 570 Dynesys flexible stabilisation procedures, we studied two prospective series of patients with a minimum one-year follow-up comparing uncoated and hydroxyapatite-coated (HA) screws.

We have studied two matching cohorts of patients treated by Dynesys flexible stabilisation with and without hydroxyapatite (HA) coating of the pedicle screws.

From our series of 570 Dynesys procedures, we studied patients with HA coated screws with a minimum one year follow-up.

Patients were entered prospectively and followed up at 6 weeks, 3, 6, and 12 months and annually thereafter. Plain radiographs were obtained annually. 58 patients (26 males, 32 females, mean age 55 years at surgery) underwent Dynesys stabilisation with HA coated screws. The data was compared with 69 patients who underwent Dynesys stabilisation with non-coated pedicle screws between 2004 and 2006 (26 male, 53 female, mean age 54 years). Outcome measures were screw loosening, breakage, implant removal or revision.

A total of 320 HA coated pedicle screws were inserted. 12 patients were lost to follow-up. 2 patients underwent subsequent level extension, and 2 had their implants removed. There were four screw breakages in three patients, all affecting S1 screws. There was no evidence of screw loosening in any patient. In the non-HA coated group 354 pedicle screws were inserted. 5 patients required revision or subsequent surgery. 12 patients had screw loosening and required implant removal. There was a significant improvement of anchorage of the HA coated screws.

Change to HA coating was investigated because of high loosening in plain screws. The improvement has been highly significant. Flexible stabilisation is a better model than fusion because the implant remains under constant load.

Disclosure: The authors did not receive any outside funding in support of preparation of this work.

Introduction

The change of position of the distal pedicle screws with growing rods in relation to vertebral bodies was described as pedicle screws migration. Pedicle screws are subjected to serial distractive forces pushing them down with every distraction; additionally there is continuous growth of the vertebral bodies during the treatment period. These two factors can affect the change of position of the pedicle screws in relation to the vertebrae during the use of growing rods. To our knowledge, this finding has never been studied, confirmed, or quantified.

Different methods of lateral mass(LM) screw placement in the cervical spine have been described. In the axial plane, 30 degrees is the recommended angle to avoid neurovascular injury. The estimation of this angle remains arbitrary and operator dependant.

To assess how accurately the lateral trajectory angle (LTA) for cervical LM screws is achieved by visual estimation amongst experienced spinal surgeons.

A sawbone model of cervical spine with simulated lordosis was used. Five spinal consultants and five senior spinal fellows were asked to insert 1.6 mm K wires into lateral masses of C3 to C6 bilaterally to simulate screws. The LTA in transverse plane was measured using a customised protractor. Basic statistical analyses of all the data were obtained. Using all the angles derived, a virtual screw trajectory was drawn in the lateral plane, on a normal axial Computerised Tomography scan of cervical spine of an anonymous patient using PACS system.

The overall mean LTA for the group was 25.15 degrees, that of the fellows 24.4 and consultants 26.2 degrees. Mean deviation from 30 degrees for fellows was 5.2 and 6.4 degrees for consultants. Overall standard deviation was 4.78, for fellows and consultants it was 3.3 and 5.8 respectively. Two episodes of vertebral artery injury occurred at 15 and 16 degrees with simulated angles on CT.

A moderate variability in visual estimation of the trajectory angle exists even amongst experienced surgeons during insertion of cervical LM screws. An anatomical landmark would be useful to improve the reliability of the procedure.

During the last decade or more, the anchors used for instrumentation in scoliosis surgery are predominantly transpedicular screws, according to Suk. The long term radiographical feature of screw fixation after scoliosis surgery is not previously studied.

A consecutive series of 81 cases with AIS operated on with an all screw construct has been studied by means of low dose CT postoperatively and at 2 years postoperatively. There were 67 females and 14 males, with a mean age of 18.3 ± 3 years.

In 26 / 81 (32 %) there were signs of loosing of one or more screws, at a maximum 3 screws. We observed loosened screws in the upper thoracic region in 16 cases, in the thoracolumbar 6 and in lumbar area in 4. Mean pre-op Cobb angle was 56 in cases of loosening and 53 of intact screw fixation (n.s.), the correction rate was 69% in loosened vs 70% among intact screws (n.s.). In males there were signs of loosening in 8/14 (57%) and in females 18/67 (27%). Among cases with loosening, 14% had suboptimal screw positioning postoperatively, in intact cases it was observed in 11% (n.s.). In the whole group there were signs of suboptimal screw positioning 12%. Clinically, 1 case had a loosened L4 screw replaced; and at all 21/26 had no complaints and 5/26 reported minor pain or discomfort. 1/26 had a minor proximal junctional kyphosis about 10°, in 3/26 there was a pull-out of some few mms. With plain radiography loosening could be observed in 11/26 cases; 5 were in the lumbar region.

In a consecutive series of 81 adolescents with idiopathic scoliosis who had underwent scoliosis surgery according to Suk, one third showed, 2 years after the intervention, some minor screw loosening, assessed by low dose CT. One patient had one lumbar screw replaced and only 5 patients reported minor discomfort. Males were more prone to develop screw loosening.

To define how pre-operative evaluation guides surgical planning in patients with atlanto-axial subluxation secondary to rheumatoid arthritis and to measure clinical outcome for the same group.

Prospective evaluation of a consecutive cohort of 26 patients undergoing C1/2 fusion over 5 years (2004-2009).

Pre-operative evaluation of posterior atlanto-dens interval (PADI), C1 lateral mass and C2 pedicle dimensions.

Pre- and post-op Ranawat scores and visual analogue scores for neck and C2 pain

C1/2 instability resulted from rheumatoid arthritis (21), trauma (4) and infection (1).

C1 lateral mass mean height 4.4mm, C2 pedicle mean height 5.1mm and mean width 3.4mm (30% width <3mm).

Ranawat scale improved Grade II to Grade I (p=0.07). Neck pain (pre-op mean 5.5, s.d. 2.8; post-op mean 1.6, s.d. 2.1, t<0.05) and C2 pain (pre-op mean 2.1, s.d. 3.3; post-op mean 0.5, s.d. 1.2, t<0.05) improved.

No instrumentation failure. In the rheumatoid group, 17/21 patients had C1 lateral mass and C1/2 transarticular screws. 1 patient had a cranio-cervical fusion and 3 patients had other constructs.

3 patients had C2 numbness. No other neurological deficit.

In a rheumatoid population, pre-operative evaluation often precludes the use of C2 pedicle screws. Rigid fixation with a C1 lateral mass and C1/2 transarticular polyaxial screw-rod system is associated with good clinical outcomes.

Introduction

Recently published results suggest insertion of shorter screws in L5/S1 stand-alone anterior interbody fusion, fearing S1 nerve root violation. However, insertion of shorter screws led to screw fixation failure and new onset of S1 body fractures.

Introduction

Thoracic pedicle screws have been proven to be safe and effective in the treatment of adolescent idiopathic scoliosis (AIS). However, the effect of the instrumentation alloy has not yet been investigated. We aimed to compare segmental versus non segmental thoracic pedicle screw instrumentation in patients with AIS.

Study design

Prospective clinical and radiological analysis of children with complex cervical deformities for the safety of cervical pedicle screw insertion.

Introduction

We aimed to determine the midterm effect of pedicle screw instrumentation on sagittal plane alignment, compared with a hybrid alignment, in the treatment of thoracic adolescent idiopathic scoliosis (AIS).

To determine if there is a safe osseous corridor for trans-sacroiliac screw fixation of U-type sacral fractures using fluoroscopic landmarks.

We reviewed the sacral anatomy of patients who underwent Computed Tomography (CT) investigations between October and December 2009. Agfa-IPMAX Version 5.2 software was used to determine if there was a trans-sacroiliac osseous corridor in the S1 and S2 vertebrae from one ilium to the other.

76 patients were in the study, 38 male and 38 female. Exclusion criteria were patients under 18 years old; patients with degenerate lumbar spine and lumbo-sacral junction; CT imaging slices greater than 2.5mm.

We measured various parameters including the dimensions of the S1 and S2 mid-sagittal vertebral body; cross-sectional areas of the S1 and S2 corridor; location of the centre of the S1 and S2 corridor.

The mean cross-sectional area for S1 and S2 corridors in males and females are 21mm² and 15mm² respectively. The mean cross-sectional area for the S2 corridor in males and females were 15mm² and 11mm² respectively. The centre of the S1 and S2 corridor is located in the centre of both S1 and S2 vertebrae.

Two-thirds of males and females have a complete osseous corridor to pass a trans-sacroiliac S1 screw. The S2 corridor was present in all males but only in 87% of females. Before placement of trans-sacroiliac screws, the surgeon should review the CT sacral anatomy to determine if the trans-sacroiliac osseous corridor is present.

Ethics Approval: None – Audit Interest Statement: None

Introduction

We report the outcomes of minimally invasive technique for posterior lumbar interbody fusion (PLIF) procedure using Hollow Modular Anchorage (HMA) screws supplemented by routine pedicle screw fixation (Dynesis).

Introduction

With the use of each pedicle screw for surgical correction of adolescent idiopathic scoliosis (AIS), there is an increase in instrumentation-related costs, operative time, risk of neural injury, and overall health-care expenses. As such, alternate level screw strategy (ALSS) has been reported as a potential alternative to contiguous multilevel screw strategy (CMSS). Moreover, studies have shown the importance in accounting for the flexibility of the curve based on the fulcrum bending radiograph when assessing postoperative curve correction. Therefore, this study addressed a radiographic and cost analysis comparing CMSS with ALSS for the treatment of thoracic AIS with titanium screws and rod application.

Aims

The aim of this study was to assess the accuracy of pedicle screw placement, as well as intraoperative factors, radiation exposure, and complication rates in adult patients with degenerative disorders of the thoracic and lumbar spines who have undergone robotic-navigated spinal surgery using a contemporary system.

Aims. Loosening of pedicle screws is a major complication of posterior spinal stabilisation, especially in the osteoporotic spine. Our aim was to evaluate the effect of cement augmentation compared with extended dorsal instrumentation on the stability of posterior spinal fixation. Materials and Methods. A total of 12 osteoporotic human cadaveric spines (T11-L3) were randomised by bone mineral density into two groups and instrumented with pedicle screws: group I (SHORT) separated T12 or L2 and group II (EXTENDED) specimen consisting of T11/12 to L2/3. Screws were augmented with cement unilaterally in each vertebra. Fatigue testing was performed using a cranial-caudal sinusoidal, cyclic (1.0 Hz) load with stepwise increasing peak force. Results. Augmentation showed no significant increase in the mean cycles to failure and fatigue force (SHORT p = 0.067; EXTENDED p = 0.239). Extending the instrumentation resulted in a significantly increased number of cycles to failure and a significantly higher fatigue force compared with the SHORT instrumentation (EXTENDED non-augmented + 76%, p < 0.001; EXTENDED augmented + 87%, p < 0.001). Conclusion. The stabilising effect of cement augmentation of pedicle screws might not be as beneficial as expected from biomechanical pull-out tests. Lengthening the dorsal instrumentation results in a much higher increase of stability during fatigue testing in the osteoporotic spine compared with cement augmentation. Cite this article: Bone Joint J 2016;98-B:1099–1105

Aim. A retrospective review of the management of adjacent level discectomy and fusion using a Zero-P (Synthes) cage and report of ease of technique and outcomes. Method. Surgical approach to adjacent level cervical disc protrusion with previous anterior cervical discectomy and fusion (ACDF) can be difficult. We review 4 patients who had previous ACDF with cage and plate who developed new onset adjacent level cervical disc prolepses causing myelopathy. A retrospective review of demographic data, symptoms, details of surgery, pre and post operative radiology, pre and postoperative ODI and pain score, length of stay, complications and follow-up data were collected in all patients. Results. Previous ACDF with plate was performed in all 4 patients an average of 11.6 years ago. Two patients had bilateral approaches previously and both had previous vascular injuries. The average duration of current symptoms was 9 months with a mean age of 65 years. All patients presented with myelopathy and two also had radiculopathy. Multiple level ACDF were operated in 2 patients previously. Revision surgery and dissection on the disc level was restricted by the previous plate. Screws from the previous plate fusion were removed adjacent to the level of surgery and discectomy was performed using distractor pins through the screw sites. Following discectomy a Zero-P cage was used to fusion with DBX under image intensifier guidance. The advantage was not to remove the previous plate and keep the dissection over the scar tissue to the minimal. All patients improved in their radicular symptoms with improvement of their hand function in the myelopaths. There was no complication and post operative radiographs were satisfactory. Conclusions. Use of the Zero-P cage for adjacent level discectomy and fusion was safe without disturbing the previous cage and plate fusion or stability

We analysed the complications encountered in 102 consecutive patients who had posterolateral lumbosacral fusion performed with transpedicular screw and rod fixation for non-traumatic disorders after a minimum of two years. Of these, 40 had spondylolysis and spondylolisthesis, 42 a degenerative disorder, 14 instability after previous laminectomy and decompression, and six pain after nonunion of previous attempts at spinal fusion without internal fixation. There were 75 multilevel and 27 single-level fusions. There were 76 individual complications in 48 patients, and none in the other 54. The complications seen were screw misplacement, coupling failure of the device, wound infection, nonunion, permanent neural injury, and loosening, bending and breakage of screws. Screw breakage or loosening was more common in patients with multilevel fusions (p < 0.001). Screws of 5 mm diameter should not be used for sacral fixation. Forty-six patients had at least one further operation for one or several complications, including 20 fusion procedures for nonunion. The high incidence of complications is a disadvantage of this technically-demanding method

Introduction. We present our experience of 22 patients with low grade degenerative lumbar spondylolysthesis with stenosis (21 Grade I and 1 Grade II) who were treated using new stabilization systems {Scient'x IsoBar TTL Dynamic Rod Stabilization and the Inlign™ Multi-Axial pedicle Screws (Disc Motion Technologies - DMT)}. Methodology and Results. The pain intensity was evaluated using the Visual Analogue Score for back pain (VAS-BP) and leg pain (VAS-LP) and functional outcomes using Oswestry Disability Score (ODS). Overall improvement in general patient's health was assessed using the Bodily Pain (SF36-BP) component of the SF -36 questionnaires. Data was analysed with the SPSS 16.0 for Windows (SPSS Inc, Chicago, IL). Statistical significance was designated at p < 0.05 and appropriate parametric (Paired sample t-test) and non parametric tests (Wilcoxon signed-rank test) were used. There were 3 male and 19 female patients and average age at operation was 68.95 years (57-79 years). The average duration of follow up was 16.18 months (8-37 months). Most common level of surgery was L4/5 (n=18). Decompression and instrumentation involved 1 level (7 cases), 2 levels (9 cases), 3 levels (1 case) and 4 levels (5 cases). There was statistically significant improvement in all clinical outcomes. The ODS improved from 49.45 ±14.35 pre-operatively to 22.91 ± 6.38 post operatively (p< 0.001). There was statistically significant improvement noted in VAS-BP (p< 0.001), VAS-LP (p<0.001) and SF36-BP (p=0.002). Conclusion. The recent dynamic stabilisation systems were developed with an intention to stabilise the spondylolisthetic segment and preventing adjacent level degeneration. The study results clearly demonstrate that central decompression and dynamic stabilization using TTL/DMT system for degenerative lumbar spondylolysthesis is a safe, reliable method and offers excellent clinical outcomes. This technique obviates the need of bone graft and hence the graft site pain

Aims

To compare the rates of sagittal and coronal correction for all-pedicle screw instrumentation and hybrid instrumentation using sublaminar bands in the treatment of thoracic adolescent idiopathic scoliosis (AIS).