Posterior lumbar interbody fusion using non resorbable poly-ether-ether-ketone versus resorbable poly-l-lactide-co-d,l-lactide fusion devices. Clinical outcome at a minimum of 2-year follow-up

Previous papers on resorbable poly-l-lactide-co-d,l-lactide (PLDLLA) cages in spinal fusion have failed to report adequately on patient-centred clinical outcome measures. Also comparison of PLDLLA cage with a traditionally applicable counterpart has not been previously reported. This is the first randomized prospective study that assesses clinical outcome of PLDLLA cage compared with a poly-ether-ether-ketone (PEEK) implant. Twenty-six patients were randomly assigned to undergo instrumented posterior lumbar interbody fusion (PLIF) whereby either a PEEK cage or a PLDLLA cage was implanted. Clinical outcome based on visual analogue scale scores for leg pain and back pain, as well as Oswestry Disability Index (ODI) and SF-36 questionnaires were documented and analysed. When compared with preoperative values, all clinical parameters have significantly improved in the PEEK group at 2 years after surgery with the exception of SF-36 general health, SF-36 mental health and SF-36 role emotional scores. No clinical parameter showed significant improvement at 2 years after surgery compared with preoperative values in the PLDLLA patient group. Only six patients (50%) in the PLDLLA group showed improvement in the VAS scores for leg and back pain as well as the ODI, as opposed to 10 patients (71%) in the PEEK group. One-third of the patients in the PLDLLA group actually reported worsening of their pain scores and ODI. Three cases of mild to moderate osteolysis were seen in the PLDLLA group. Following up on our preliminary report, these 2-year results confirm the superiority of the PEEK implant to the resorbable PLDLLA implant in aiding spinal fusion and alleviating symptoms following PLIF in patients with degenerative spondylolisthesis associated with either canal stenosis or foramen stenosis or both and emanating from a single lumbar segment

Predictability of the spontaneous lumbar curve correction after selective thoracic fusion in idiopathic scoliosis

In this study we tried to achieve a better understanding of the biodynamic mechanism of balance in the scoliotic spine. Therefore we focused on the pre- and postoperative spine of patients with idiopathic scoliosis with a primary thoracic curve and a secondary lumbar curve. Several studies showed that the lumbar curve spontaneously corrects and improves after selective thoracic fusion. We try to understand and describe this spontaneous compensatory lumbar curve correction after selective thoracic correction and fusion. We performed a retrospective examination of pre- and postoperative radiographs of the spine of 38 patients with idiopathic scoliosis King type II and III. Frontal Cobb angles of the thoracic and lumbar curves were assessed on pre- and postoperative antero-posterior and side bending radiographs. We determined the postoperative corrections of the thoracic and lumbar curves. Relative (%) corrections and correlations of the postoperative corrections were calculated. The group was divided in three subgroups, depending on lumbar curve modifier, according to Lenkes classification system. The calculations were done for the whole group as for each subgroup. As expected, significant correlations were present between the relative correction of the main thoracic and the lumbar curve (mean R = 0.590; P = 0.001). The relation between relative thoracic and lumbar correction decreased with the lumbar modifier type. This study shows a highly significant correlation between the relative corrections of the main thoracic curve and the lumbar curve after selective thoracic fusion in idiopathic scoliosis. This correlation depends on lumbar curve modifier type. This new classification system seems to be of great predictable value for the spontaneous correction of the lumbar curve. Depending on the curve-type, a different technique for predicting the outcome should be used. The lumbar curve correction does not occur throughout the whole lumbar curve. Most correction is achieved in the upper part of the curve. The distal lumbar curve seems to be more rigid and less important in the spontaneous curve correction

The effect of starting point placement technique on thoracic transverse process strength: an ex vivo biomechanical study

<p>Abstract</p> <p>Background</p> <p>The use of thoracic pedicle screws in spinal deformity, trauma, and tumor reconstruction is becoming more common. Unsuccessful screw placement may require salvage techniques utilizing transverse process hooks. The effect of different starting point placement techniques on the strength of the transverse process has not previously been reported. The purpose of this paper is to determine the biomechanical properties of the thoracic transverse process following various pedicle screw starting point placement techniques.</p> <p>Methods</p> <p>Forty-seven fresh-frozen human cadaveric thoracic vertebrae from T2 to T9 were disarticulated and matched by bone mineral density (BMD) and transverse process (TP) cross-sectional area. Specimens were randomized to one of four groups: A, control, and three others based on thoracic pedicle screw placement technique; B, straightforward; C, funnel; and D, in-out-in. Initial cortical bone removal for pedicle screw placement was made using a burr at the location on the transverse process or transverse process-laminar junction as published in the original description of each technique. The transverse process was tested measuring load-to-failure simulating a hook in compression mode. Analysis of covariance and Pearson correlation coefficients were used to examine the data.</p> <p>Results</p> <p>Technique was a significant predictor of load-to-failure (<it>P </it>= 0.0007). The least squares mean (LS mean) load-to-failure of group A (control) was 377 N, group B (straightforward) 355 N, group C (funnel) 229 N, and group D (in-out-in) 301 N. Significant differences were noted between groups A and C, A and D, B and C, and C and D. BMD (0.925 g/cm²[range, 0.624-1.301 g/cm²]) was also a significant predictor of load-to-failure, for all specimens grouped together (<it>P </it>< 0.0001) and for each technique (<it>P <</it>0.05). Level and side tested were not found to significantly correlate with load-to-failure.</p> <p>Conclusions</p> <p>The residual coronal plane compressive strength of the thoracic transverse process is dependent upon the screw starting point placement technique. The funnel technique significantly weakens transverse processes as compared to the straightforward technique, which does not significantly weaken the transverse process. It is also dependent upon bone mineral density, and low failure loads even in some control specimens suggest limited usefulness of the transverse process for axial compression loading in the osteoporotic thoracic spine.</p

The flying buttress construct for posterior spinopelvic fixation: a technical note

<p>Abstract</p> <p>Background</p> <p>Posterior fusion of the spine to the pelvis in paediatric and adult spinal deformity is still challenging. Especially assembling of the posterior rod construct to the iliac screw is considered technically difficult. A variety of spinopelvic fixation techniques have been developed. However, extreme bending of the longitudinal rods or the use of 90-degree lateral offset connectors proved to be difficult, because the angle between the rod and the iliac screw varies from patient to patient.</p> <p>Methods</p> <p>We adopted a new spinopelvic fixation system, in which iliac screws are side-to-side connected to the posterior thoracolumbar rod construct, independent of the angle between the rod and the iliac screw. Open angled parallel connectors are used to connect short iliac rods from the posterior rod construct to the iliac screws at both sides. The construct resembles in form and function an architectural Flying Buttress, or lateral support arches, used in Gothic cathedrals.</p> <p>Results and discussion</p> <p>Three different cases that illustrate the Flying Buttress construct for spinopelvic fixation are reported here with the clinical details, radiographic findings and surgical technique used.</p> <p>Conclusion</p> <p>The Flying Buttress construct may offer an alternative surgical option for spinopelvic fixation in circumstances wherein coronal or sagittal balance cannot be achieved, for example in cases with significant residual pelvic obliquity, or in revision spinal surgery for failed lumbosacral fusion.</p

Comparative analysis between shape memory alloy-based correction and traditional correction technique in pedicle screws constructs for treating severe scoliosis

The three-dimensional correction of severe rigid scoliosis has been improved by segmental pedicle screw instrumentation. However, there can be significant difficulty related to the use of a rigid rod, especially in the apex region of severe scoliosis. This study is a retrospective matched cohort study to evaluate the advantages of Nitinol shape memory alloy (SMA) rod-based correction by comparing the clinical and radiographic results obtained from using a temporary SMA rod and those from a standard rod in the correction of severe scoliosis. From May 2004 to September 2006, patients with matched curve type, ages at surgery, operative methods and fusion levels in our institute and instrumented with either SMA rods (n = 14) or traditional correction techniques (n = 16) were reviewed. In SMA group, the SMA rods served as a temporary intraoperative tool for deformity correction and were replaced by standard rods. The blood loss at surgery averaged 778 ± 285 ml in the traditional group and 585 ± 188 ml in the SMA group (P < 0.05). Operative time averaged 284 ± 53 min in the SMA group and 324 ± 41 min in the traditional group (P < 0.05). In the SMA group, the preoperative major curve was 92.6° ± 13.7° with a flexibility of 25.5 ± 7.3% was corrected to 29.4° ± 5.7° demonstrating a 68.4% immediate postoperative correction. In the traditional group, the preoperative major curve was 88.6° ± 14.6° with a flexibility of 29.3 ± 6.6% was corrected to 37.2° ± 7.3° demonstrating a 57.8% immediate postoperative correction. There was a statistic difference between the SMA group and traditional group in correction rate of the major thoracic curve. In the SMA group, one case suffered from deep infection 2 months postoperatively. In the traditional group, 6 of 16 cases suffered pedicle screw pull out or loosening during placement of the standard rod at the apex vertebrae on the concave side. In three cases, the mono-axial pedicle screws near the apex were abandoned and in five cases replaced with poly-axial pedicle screws. This study shows that the temporary use of SMA rod may reduce the operative time, blood loss, while improve the correction of the coronal plane when compared with standard techniques