The spine journal : official journal of the North American Spine Society 2011 Jul
Authors: Savage JW, Limthongkul W, Park HS, Zhang LQ, Karaikovic EE
Several fusion techniques are used to treat atlantoaxial instability. Recent literature suggests that intralaminar screw (LS) fixation and pedicle screw (PS) fixation offer similar stability and comparable pullout strength. No studies have compared these characteristics after cyclic loading.
To compare the stability and pullout strength of intra-LSs and PSs in a C1-C2 instability model after 1,000 cycles of axial loading.
In vitro biomechanical study.
Stability in axial rotation and screw pullout strength after cyclic loading.
Six fresh-frozen human cadaveric cervical spines (C1-C2) were used in this study. C1-C2 instability was mimicked via odontoidotomy at its base and posterior soft-tissue release, including the supraspinous ligaments and facet joint capsules. Specimens were tested to 1,000 cycles after stabilization with two fixation constructs: C1 lateral mass (LM) screws and C2 intra-LSs (C1LM-C2LS) and C1 LM screws and C2 PSs (C1LM-C2PS). Angular motion was recorded for right and left axial rotation using an Optotrak 3020 system (Northern Digital, Waterloo, Ontario, Canada). Tensile loading to failure was then performed collinear to the longitudinal axis of the screw, and the data were recorded as peak pullout strength in newtons.
There was no statistically significant difference in stability (measured in degrees of rotation) between the intra-LS and PS constructs at 250, 500, 750, and 1,000 cycles of axial rotation. Furthermore, there was no significant difference in stability at 250 cycles versus 1,000 cycles for the LS (1.30 vs. 1.49, p = .80) or PS (0.84 vs. 0.85, p = .96). Pedicle screws had higher pullout strength when compared with the intra-LSs (757.5 ± 239 vs. 583.4 ± 472 N); however, high standard deviation precluded statistical significance (p = .44).
Our data suggest that a C1LM and C2LS construct has similar biomechanical stability when compared with a C1LM and C2PS construct after 1,000 cycles of axial rotation. Furthermore, PSs had higher pullout strength when compared with LSs; however, this result was not statistically significant.
PMID: 21640660 [PubMed – as supplied by publisher]
Spine 2010 Mar 01
Authors: Karaikovic EE, Rattner Z, Bilimoria MM, Sener SF, McGee JP, Metrick LB, Szokol JW, Limthongkul W
To emphasize the role that interventional radiology can perform in stemming bleeding to vascular structures injured during spine surgery without altering patient position.
Injury to the lumbar artery or aorta may occur during lumbar disc surgery. Occasionally the site of bleeding may not be readily identifiable or accessible through the surgical incision. Interventional radiology techniques may be employed to help locate and stop these difficult to locate vascular structures without changing a patient position.
A 48-year-old woman undergoing L4-L5 lumbar hemilaminectomy and discectomy secondary to a herniated disc sustained an injury to a right L3 lumbar artery. Several liters of blood were lost in an attempt to surgically locate and repair the injury to the lumbar artery. A literature search identified the potential severity and treatment options.
An interventional radiologist was called for and he was able to angiographically locate the source of bleeding and stem its source using coil embolization of the lumbar artery.
Whenever there is bleeding from an inaccessible site, consultation with an interventional radiologist to perform an intraoperative coil embolization of the injured vessel should be done especially if a resort to an anterior abdominal approach would permit uncontrolled bleeding.
PMID: 20147872 [PubMed – as supplied by publisher]
The spine journal : official journal of the North American Spine Society 2010 Feb
Authors: Limthongkul W, Karaikovic EE, Savage JW, Markovic A
During the last decade, vertebral augmentation techniques with cement (kyphoplasty and vertebroplasty) have revealed that 75% to 100% of individuals with osteoporotic vertebral compression fractures have good to moderate pain relief postoperatively, as well as adequate restoration of the vertebral body height. The volume of cement injected into a vertebra varied in different reports. To our knowledge, there are no studies that report on the physiological distribution of thoracic and lumbar vertebrae body volumes.
The purpose of this study was to quantitatively evaluate thoracic and lumbar vertebral body volumes.
Forty computed tomography (CT) scans of the thoracic and lumbar spines were used to measure a volume of each vertebral body.
Forty CT scans with standard 2.5-mm bone window cuts of the thoracic and lumbar vertebrae (20 men and 20 women) were analyzed to measure the volumetric capacity of vertebral bodies using a BrainLAB Software (iPlan RT image 4.0) program. The software was tested for validity and reliability in two pilot studies. Mean and standard deviations for each vertebral body volume were calculated and recorded. The vertebral body working distance and the so-called “safe zone” were also measured to determine a size of a balloon to be used in kyphoplasty.
Vertebral body volume increased gradually from T1 to L4 with the exception of L5, which measured to be smaller than L4. The mean thoracic vertebrae volume was 15.0 cm(3) (ranged in the absolute values from 5.2 to 39.5 cm(3)), and the mean lumbar vertebrae volume was 35 cm(3) (ranged in the absolute values from 19.7 to 61.5 cm(3)). Men had larger volume vertebral bodies only in the lumbar spine compared with women. The average vertebral body working distances from T1 to T4 was 23.4+/-2.7 mm, from T5 to T9 was 30.3+/-3.6 mm, and from T10 to L5 was 35.5+/-3.9 mm.
Knowing the physiological variability of vertebral body volumes may help prevent complications as a result of underaugmentation or overaugmentation with excessive amount of cement during kyphoplasty or vertebroplasty in osteoporotic compression fractures. We recommend using 10 mm balloons from T1 to T4, 15 mm balloons from T5 to T9, and 20 mm balloons from T10 to L5 for kyphoplasty.
PMID: 20142072 [PubMed – as supplied by publisher]
Load sharing properties of cervical pedicle screw-rod constructs versus lateral mass screw-rod constructs
European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society 2010 May
Authors: Dunlap BJ, Karaikovic EE, Park HS, Sokolowski MJ, Zhang LQ
Lateral mass screws have a history of successful clinical use, but cannot always be used in the subaxial cervical spine. Despite safety concerns, cervical pedicle screws have been proposed as an alternative. Pedicle screws have been shown to be biomechanically stronger than lateral mass screws. No study, however, has investigated the load sharing properties comparing constructs using these screws. To investigate this, 12 fresh-frozen single cervical spine motion segments (C4-5 and C6-7) from six cadavers were isolated. They were randomized to receive either lateral mass or pedicle screw-rod constructs. After preloading, the segments were cyclically loaded with a uniplanar axial load from 0 to 90 N both with and without the construct in place. Pressure data at the disc space were continuously collected using a dynamic pressure sensor. The reduction in disc space pressure between the two constructs was calculated to see if pedicle screw and lateral mass screw-rod constructs differed in their load sharing properties. In both the pedicle screw and lateral mass screw-rod constructs, there was a significant reduction in the disc space pressures from the no-construct to construct conditions. The percentage decrease for the pedicle screw constructs was significantly greater than the percentage decrease for the lateral mass screw constructs for average pressure (p < or = 0.002), peak pressure (p < or = 0.03) and force (p < or = 0.04). We conclude that cervical pedicle screw-rod constructs demonstrated a greater reduction in axial load transfer through the intervertebral disc than lateral mass screw-rod constructs. Though there are dangers associated with the insertion of cervical pedicle screws, their use might be advantageous in some clinical conditions when increased load sharing is necessary.
PMID: 20119837 [PubMed – as supplied by publisher]
Evaluation of the intrinsic properties of pedicle screws: do diameter, manufacturing and screw design affect resistance and/or resistivity
Bosnian journal of basic medical sciences 2009 Oct
Authors: Limthongkul W, Savage J, Nenonene EK, Karaikovic EE
The pedicle screw diameter, composite and design are variables that can affect the threshold of intraoperative electromyographic monitoring. Even though we know that larger diameter objects tend to have less resistance, no study documented the effect that this variable could have on pedicle screw resistance. Using high quality equipment, resistance and resistivity of ten pedicle screws (from four manufacturers) were calculated based on known constant current and measured voltage. Voltage was measured three times for each screw to determine intraobserver measurement variability. Resistance of all screws ranged from 1.4 to 3.9 m ohm (mean = 2.69+/-0.71 m ohm). The screw with largest diameter (7.75 mm) had lower resistance than screws with other diameters. Resistivity of screws ranged from 7.12 to 12.63 micro ohm*m (mean = 9.9+/-1.82 micro ohm*m). Based on the screw design, one manufacturer’s pedicle screws (A) had significantly lower resistivity compared to three other manufacturers (p<0.01). Larger diameter screws (7.75 mm in diameter) had lower resistance. Screw design (polyaxial or monoaxial) had no effect on its resistance. Screws of one manufacturer (A) showed lower resistivity compared to those manufactured by other three companies.
PMID: 19912122 [PubMed – as supplied by publisher]
American journal of orthopedics (Belle Mead, N.J.) 2009 May
Authors: Mangla J, Young JL, Young JO, Thomas TO, Thomas T, Karaikovic EE
PMID: 19584993 [PubMed – as supplied by publisher]
Preoperative imaging of cervical pedicles: comparison of accuracy of oblique radiographs versus axial CT scans
European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society 2008 Sep
Authors: Sieradzki JP, Karaikovic EE, Lautenschlager EP, Lazarus ML
In spite of concerns about safety during their insertion, cervical spine pedicle screws have demonstrated biomechanical superiority over lateral mass screws in several biomechanical studies. One of the concerns for placement of cervical pedicle screws is their small size. Preoperative planning with computed tomography to assess pedicle width has been shown to be extremely accurate and is recommended by several authors. To date there has been no study assessing the accuracy of oblique radiographs for pedicle measurement. We sought to compare accuracy of the oblique radiographic measurements of cervical pedicle width with axial CT scan measurements. Five fresh-frozen human cadaveric cervical spines C3-C7 were studied. Thin cut 1.25 mm computed tomography axial cuts were made through the pedicle isthmus. Oblique radiographs at 35 degrees , 45 degrees , and 55 degrees angles were taken of the right and left pedicles of each specimen using a standardized technique. Each radiograph contained a pin of known length to correct for magnification. All pedicles were again measured and corrected for magnification using the standard pin. Corrected oblique radiograph measurements were compared to CT for each specimen. The outer pedicle width was measured and agreed upon by consensus. The radiograph measurements were on average significantly larger than CT measurements for the pedicles indicating that the pin standard did not completely correct magnification. Plain radiographic data failed to reveal that one oblique angle was favorable to another in terms of magnification or precision. Plain radiographs at oblique angles do not provide accurate measurements of subaxial cervical pedicles at 35 degrees , 45 degrees , or 55 degrees angles. We recommend that thin cut axial CT scans be obtained on all patients prior to transpedicular fixation in the cervical spine.
PMID: 18661159 [PubMed – as supplied by publisher]
Neurology India 2005 Dec – More
Authors: Dashti H, Lee HC, Karaikovic EE, Gaines RW
PMID: 16565548 [PubMed – as supplied by publisher]
Becker’s Spine Review
Bosnian journal of basic medical sciences 2005 May
Authors: Trebinjac S, Mujic-Skikic E, Ninkovic M, Karaikovic E
The application of extracorporeal shock wave therapy (ESWT) as a treatment for different orthopaedic conditions has experienced a rapid increase over the last several years. However the mechanism of action and the therapeutic effect is not clear. The aim of this study was to review the literature about the efficacy of ESWT in the treatment of plantar fasciitis, lateral epicondylitis, shoulder painful disorders and non-union fractures. Only randomized controlled studies published in the last 5 years were retrieved from electronic database and manual search. Results on efficacy of ESWT are controversial. Studies that have claimed therapeutic benefit did not fulfill scientific criteria and controlled randomized trials were not able to confirm significant improvement after treatment with ESWT.
PMID: 16053451 [PubMed – as supplied by publisher]
Bosnian journal of basic medical sciences 2005 May
Authors: Karaikovic EE, Pacheco HO
A decision for operative versus nonoperative management of thoracolumbar fractures should NEVER be based solely on one factor. Only after a thorough physical, neurological, and spinal examination, and an assessment of a patient’s prior activity, social and educational background and patient’s expectations, one should review the patient’s radiographs and CT scans to determine risks and benefits of operative versus nonoperative care. Both treatment options are discussed in this paper. As a surgical option our preference is short-segment instrumentation and fusion. Careful and appropriate patient selection and an excellent operative technique insure the minimum complications.
PMID: 16053450 [PubMed – as supplied by publisher]
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