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Roberto Masferrer, Carlos H. Gomez, Dean G. Karahalios and Volker K. H. Sonntag

Object

The goal of this study was to review retrospectively the outcome of 95 patients with various disorders leading to instability of the thoracolumbar and lumbar spine who were treated consecutively via a posterior surgical approach with pedicle screw fixation in which the Texas Scottish Rite Hospital system was used.

Methods

All cases were managed according to the same protocol. Follow-up review averaged 29.6 months. Radiographic evidence of osseous union and the patient's current status were analyzed. Four screws were malpositioned, and there were two dural lacerations of a nerve root and one pedicle fracture. Deep wound infections developed in five patients (5.2%) and three patients had postoperative radicular pain. In one case, the rods disengaged from the screws; in four cases, hardware was removed but there were no broken screws. Neurological deficits improved in 85% of the patients and no patient was worse neurologically after surgery. The rate of osseous union was 96.8%. Three patients developed pseudarthrosis, one of whom was asymptomatic. Back pain improved in 80 patients (85%). A solid bone fusion, however, was not necessarily associated with decreased back pain.

Conclusions

These results support the use of pedicle screw fixation as an effective and safe procedure for fusion of the thoracolumbar and lumbar spine and support the finding that complications can be minimal when a meticulous surgical technique is used. The proper selection of patients for surgery is probably the most important factor associated with good outcomes.

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Paul J. Apostolides, Nicholas Theodore, Dean G. Karahalios and Volker K. H. Sonntag

✓ The authors report the successful treatment of an acute combination atlas—axis fracture in an 85-year-old man using anterior odontoid and C1–2 transarticular facet screw fixation and a Philadelphia collar. Treatment with halo brace immobilization failed, and the patient experienced recurrent episodes of oxygen desaturation when placed partially prone for chest physiotherapy. If a posterior approach is not feasible, an anterior odontoid and C1–2 transarticular facet screw fixation can be considered as a salvage procedure for patients with acute combination atlas—axis fractures.

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Will Forest Beringer, Jean-Pierre Mobasser, Dean Karahalios and Eric Alfred Potts

✓Adult high-grade degenerative spondylolisthesis represents the extreme end of the spectrum for spondylolisthesis and is consequently rarely encountered. Surgical management of high-grade spondylolisthesis requires constructs capable of resisting the shear forces at the slipped L5–S1 interspace. The severity of the slip, sacral inclination, and slip angle may make conventional approaches to 360° fusion difficult or hazardous. Transdiscal pedicle screw fixation, transvertebral fibular graft fusion, and transvertebral cage fixation are techniques that have been developed to establish anterior column load sharing and to resist shear forces at the L5–S1 interspace, given the anatomical constraints accompanying high-grade spondylolisthesis. In this technical note the authors describe the procedure for implanting an in situ anterior L5–S1 transvertebral cage and performing L4–5 anterior lumbar interbody fusion, followed by placement of posterior S1–L5 vertebral body transdiscal pedicle screws for management of high-grade spondylolisthesis.

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Sean A. Salehi, Randall R. McCafferty, Dean Karahalios and Stephen L. Ondra

✓ The management of tumors that metastasize to the sacrum remains controversial. Typically, resection of such tumors and reconstruction of the lumbopelvic junction requires sacrifice of neural elements resulting in neurological dysfunction and prolonged periods of bed rest. This severely affects the quality of life in patients in whom there is frequently a limited life expectancy.

The authors describe three patients who underwent subtotal resection of metastatic sacral tumors. Postoperatively, good outcome was demonstrated in all patients.

The authors present a technique for debulking and reconstruction that provides immediate spinopelvic junction stability and allows for early mobilization. Quality of life is significantly improved compared with that resulting from either medical treatment or traditional surgery.

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Roberto Masferrer, Carlos H. Gomez, Dean G. Karahalios and Volker K. H. Sonntag

Object. The goal of this study was to review retrospectively the outcome of 95 patients with various disorders leading to instability of the thoracolumbar and lumbar spine who were treated consecutively via a posterior surgical approach with pedicle screw fixation in which the Texas Scottish Rite Hospital system was used.

Methods. All cases were managed according to the same protocol. Follow-up review averaged 29.6 months. Radiographic evidence of osseous union and the patient's current status were analyzed. Four screws were malpositioned, and there were two dural lacerations of a nerve root and one pedicle fracture. Deep wound infections developed in five patients (5.2%), and three patients had postoperative radicular pain. In one case, the rods disengaged from the screws; in four cases, hardware was removed but there were no broken screws. Neurological deficits improved in 85% of the surviving patients, and no patient was worse neurologically after surgery. The rate of osseous union was 96.8%. Three patients developed pseudarthrosis, one of whom was asymptomatic. Back pain improved in 80 patients. A solid bone fusion, however, was not necessarily associated with decreased back pain.

Conclusions. These results support the use of pedicle screw fixation as an effective and safe procedure for fusion of the thoracolumbar and lumbar spine and support the finding that complications can be minimal when a meticulous surgical technique is used. The proper selection of patients for surgery is probably the most important factor associated with good outcomes.

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Frank La Marca, Geoffrey Zubay, Thomas Morrison III and Dean Karahalios

Object

The occipital condyle has never been studied as a viable structure that could permit bone purchase by fixation devices for occipitocervical fusion. The authors propose occipital condyle screw placement as a possible alternative to conventional occipitocervical fixation techniques.

Methods

Six adult cadaver heads (12 total occipital condyles) were studied, and the StealthStation image-guidance system was used for preoperative planning of occipital condyle screw placement. Morphometric studies of the occipital condyle were performed. A 3.5-mm Vertex screw was then placed in the occipital condyle with image-guided assistance in 3 specimens. Operations in the remaining 3 specimens proceeded using anatomical markers and calculated degrees of angulation for screw placement with a free-hand technique. Postoperatively the cadaver heads were rescanned and reanalyzed to determine the success of screw placement and its effect on hypoglossal canal volume.

Results

All screws were successfully placed with no sign of lateral or medial cortical breach. Two screws had bicortical purchase. There was no change in hypoglossal canal volume in any specimen.

Conclusions

Occipital condyle screw placement is a safe and viable option for occipitocervical fixation and could be a preferred procedure in selected cases. However, further biomechanical studies are required to compare its reliability to other more established techniques.

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Gregory P. Lekovic, Eric A. Potts, Dean G. Karahalios and Graham Hall

Object

The goal of this study was to compare the accuracy of thoracic pedicle screw placement aided by two different image-guidance modalities.

Methods

The charts of 40 consecutive patients who had undergone stabilization of the thoracic spine between January 2003 and January 2005 were retrospectively reviewed. Three patients were excluded from the study because, on the basis of preoperative findings, small pedicle diameter precluded the use of pedicle screws. Thus, a total of 37 patients had 277 screws placed with the aid of either virtual fluoroscopy or isocentric C-arm 3D navigation. The indications for surgery included trauma, degenerative disease, and tumor, and were similar in both groups. All 37 patients underwent postoperative computed tomography scanning, and an independent reviewer graded all screws based on axial, sagittal, and coronal projections for a full determination of the placement of the screw in the pedicle.

Results

The rate of unintended perforations was found to depend on pedicle diameter (p < 0.0001). There were no statistical differences between groups with regard to rate or grade of cortical perforations. Overall, the rate and grade of perforations was low, and there were no neurological or vascular complications.

Conclusions

The authors have shown that either image-guidance system may be used with a high degree of accuracy and safety. Because both systems were found to be comparably safe and accurate, the choice of image-guidance modality may be determined by the level of surgeon comfort and/or availability of the system.

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Paul Marcotte, Curtis A. Dickman, Volker K. H. Sonntag, Dean G. Karahalios and Janine Drabier

✓ Eighteen patients with atlantoaxial instability were treated with posterior atlantoaxial facet screws to obtain immediate rigid fixation of C1–2. Of these 18 patients, instability occurred due to trauma in nine, rheumatoid arthritis in six, neoplasms in two, and os odontoideum in one. Four patients presented with nonunion after failed C1–2 wire and graft procedures. In all cases in this series the screw fixations were augmented with an interspinous C1–2 strut graft which was wired in place to provide three-point stabilization and to facilitate bone fusion. In every case fixation was satisfactory, and C1–2 alignment and stability were restored without complications due to instrumentation. One patient died 3 months postoperatively from metastatic tumor; the spinal fixation was intact. All 17 surviving patients have developed osseous unions (mean follow-up period 12 months, range 6 to 16 months). Posterior atlantoaxial facet screw fixation provides immediate multidirectional rigid fixation of C1–2 that is mechanically superior to wiring or clamp fixation. This technique maximizes success without the need for a supplemental rigid external orthosis, and is particularly useful for pseudoarthrosis.

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Dean G. Karahalios, Taro Kaibara, Randall W. Porter, Udaya K. Kakarla, Phillip M. Reyes, Ali A. Baaj, Ali S. Yaqoobi and Neil R. Crawford

Object

An interspinous anchor (ISA) provides fixation to the lumbar spine to facilitate fusion. The biomechanical stability provided by the Aspen ISA was studied in applications utilizing an anterior lumbar interbody fusion (ALIF) construct.

Methods

Seven human cadaveric L3–S1 specimens were tested in the following states: 1) intact; 2) after placing an ISA at L4–5; 3) after ALIF with an ISA; 4) after ALIF with an ISA and anterior screw/plate fixation system; 5) after removing the ISA (ALIF with plate only); 6) after removing the plate (ALIF only); and 7) after applying bilateral pedicle screws and rods. Pure moments (7.5 Nm maximum) were applied in flexion and extension, lateral bending, and axial rotation while recording angular motion optoelectronically. Changes in angulation as well as foraminal height were also measured.

Results

All instrumentation variances except ALIF alone reduced angular range of motion (ROM) significantly from normal in all directions of loading. The ISA was most effective in limiting flexion and extension (25% of normal) and less effective in reducing lateral bending (71% of normal) and axial rotation (71% of normal). Overall, ALIF with an ISA provided stability that was statistically equivalent to ALIF with bilateral pedicle screws and rods. An ISA-augmented ALIF allowed less ROM than plate-augmented ALIF during flexion, extension, and lateral bending. Use of the ISA resulted in flexion at the index level, with a resultant increase in foraminal height. Compensatory extension at the adjacent levels prevented any significant change in overall sagittal balance.

Conclusions

When used with ALIF at L4–5, the ISA provides immediate rigid immobilization of the lumbar spine, allowing equivalent ROM to that of a pedicle screw/rod system, and smaller ROM than an anterior plate. When used with ALIF, the ISA may offer an alternative to anterior plate fixation or bilateral pedicle screw/rod constructs.