Greg Anderson, M. Home Physicians D. He completed his residency training at the University of California in Irvine and his fellowship at Thomas Jefferson University. Office Locations Office. Professional Profile Education. Prior to becoming a physician assistant, Kevin worked as a certified athletic trainer at the collegiate level. Kevin has since joined Rothman Orthopaedic Institute and works with Dr. David Greg Anderson who specializes in orthopaedic spine surgery.
Kevin has an interest in fracture prevention and treat patients with osteoporosis. Arthritis Rheum. J Neurosurg Spine. Correlation of C2 fractures and vertebral artery injury. Spine Phila Pa Eur Spine J , Nov; 18 11 Epub May Injury of the posterior ligamentous complex of the thoracolumbar spine: a prospective evaluation of the diagnostic accuracy of magnetic resonance imaging. Spine, Nov 1;34 23 :E Clinical survey: patterns of utilization of lumbar epidural steroid injections by a cohort of spinal surgeons. The management of spinal injuries in patients with ankylosing spondylitis or diffuse idiopathic skeletal hyperostosis: a comparison of treatment methods and clinical outcomes.
J Spinal Disord Tech. Primary bovine intervertebral disc cells transduced with adenovirus overexpressing 12 BMPs and Sox9 maintain appropriate phenotype. Am J Phys Med Rehabil. Trends in surgical management for type II odontoid fracture: 20 years of experience at a regional spinal cord injury center. Osmolarity and intracellular calcium regulate aquaporin2 expression through TonEBP in nucleus pulposus cells of the intervertebral disc.
J Bone Miner Res. Neurosurg Focus. Spine J. J of Orthop Sci , Spinal injuries after falls from hunting tree stands. Percutaneous instrumentation of the thoracic and lumbar spine. Orthop Clin North Am. Minimally invasive techniques for lumbar interbody fusions. Minimally invasive spine surgery: a historical perspective. Short-term comparison of cervical fusion with static and dynamic plating using computerized motion analysis. Assessment of injury to the thoracolumbar posterior ligamentous complex in the setting of normal-appearing plain radiography. Epub Jan Characterization of neurophysiologic alerts during anterior cervical spine surgery.
Anderson DG. Image guidance in spinal surgery. Instr Course Lect. Cytokine assay of the epidural space lavage in patients with lumbar intervertebral disk herniation and radiculopathy. Assessment of injury to the posterior ligamentous complex in thoracolumbar spine trauma. Interobserver and intraobserver reliability of maximum canal compromise and spinal cord compression for evaluation of acute traumatic cervical spinal cord injury. A report of two cases. Seminars in Spine Surgery , 17 2 , Spine J , 5 6 Suppl :S, A new classification of thoracolumbar injuries: the importance of injury morphology, the integrity of the posterior ligamentous complex, and neurologic status.
Epub Dec Spine , 30 17 Suppl : S2, Spine , 30 17 Suppl :S, J Spinal Disrd Tech , 18 3 , J Neurosurg Spine, 2 5 , Spine , 30 14 :E, The inclusion criteria were:. The study of patients operated with Dynesys was retrospective, the assessment of outcome was performed by an independent observer. The study of patients operated with DIAM was prospective.
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Concerning the results of FE simulations, the mobility values shown in Fig 4 were obtained. Regarding flexion, Fig 4A shows similar behaviour between the healthy and interspinous device model along all the vertebrae. A Flexion. B Extension. C Lateral bending. D Axial rotation.
In extension movement Fig 4B , the DYNESYS device provided a higher movement as pre compression of the cord favoured this type movement whereas for the interspinous model a higher mobility was developed at superior segments L1 and L2. Regarding lateral bending movement in undeformed and deformed shapes, the DYNESYS model had a marked higher movement compared to the other models. Concerning rotation axial movement Fig 4D , lower amplitude was observed compared to previous movements.
Table 3 summarises all the results concerning the implanted models compared with the healthy model. Consequently, movement compared to the healthy model was limited. Conversely, DIAM increased movement along all the vertebrae during extension. Vertebra L5 1. Compared to the healthy model, the DYNESYS device produced higher variations in the degree of motion, reaching a maximum value during lateral bending.
Flexion and extension produced the same range of variations. The same range of percentages is reached for rotation movement. In summary, vertebra L4 Interdiscal pressure IDP was measured as compressive stresses minimum principal stress at the instrumented and adjacent levels Fig 5. Results concerning the simulated movements are post processed at L3-L4-L5 in terms of von Mises stress, as Fig 6 shows. The von Mises criterion was used for comparison purposes only, and it cannot be used as failure criterion for bone, which has a brittle behavior.
L3 was discharged which is related with the onset of screw loosening. The DIAM implant developed a similar behaviour to the healthy model but overloading the apophyses of L4. L3 had a noticeable increase of stress compared to the healthy model, with a different distribution and higher values near to the back vertebral body. The DIAM device exhibited a similar distribution to the healthy model, except at the apophyses of L4 which exhibited a stress concentration and at L3 where a slight decrease was observed Fig 6D.
Between the years and , 46 patients were operated on, 3 of them with a double device in L4-L5 and L5-S1. The ages range from 26—43 years with an average of The follow-up time ranges from 5 years to 8 months with an average of 3. Three of them have been reoperated due to persistent low back pain despite conservative treatment. Two at the two-year DIAM placement and another at 14 months, all were treated with lumbar arthrodesis. Of the remaining 43 patients, 6 had lumbar pain and were treated by rhizolysis, and the symptomatology disappeared.
The remaining 37 patients We have not had any breakage of spinous apophyses nor any displacement of the device. There are no clinical or radiographic signs of ASD in the adjacent segments. We reviewed 12 patients operated between and , ranging in age from 28—41 years with an average of The follow-up time ranges from 10 years to 6. Of these 12 patients, 7 are asymptomatic We have not detected any pulling of the screws, or breakage of the material.
The incidence of clinically symptomatic adjacent segment disease SASD is lower compared to radiographic adjacent segment disease RASD , because radiographic changes in adjacent segments do not necessarily imply functional impairment in patients with Arthrodesis [ 46 ]. The stiffness of the implant and the number of fixed segments in lumbar fusion has been associated with an increased incidence of ASD [ 47 ].
Nevertheless, fusion produces a significant increase in stress of the adjacent segments, particularly in the facet joints which is considered to provoke a degenerative cumulative process leading to ASD [ 48 ].
So as to avoid or minimize the occurrence of ASD, dynamic fixation systems have emerged, becoming a popular alternative to arthrodesis in the treatment of degenerative disc disease. DF reduces IDP at the instrumented levels by unloading the discs [ 49 ]. Consequently, an improvement is obtained on the MRI images of the degenerated disc by increasing the proportion of glycosaminoglycans [ 27 ]. Dynamic fixations were designed to prevent abnormal motions, yielding to a better physiological load transmission.
Posterior motion-sparing devices intend to off-load facet joints and fibrous annulus enabling the damaged discs to repair themselves [ 50 ] if the degenerative process is not very advanced. They improve lumbar pain and reduce the stress on adjacent segments. Computational biomechanical research has confirmed that dynamic systems protect adjacent levels from excessive motion [ 51 ].
Important clinical symptoms and clear signs of disc degeneration were confirmed by MRI, but without instability or degeneration of the facet joints in young and active patients. As floating fusion entails a high risk for ASD [ 53 ], this technique is considered to be a good alternative.
The four principal movements were simulated. ROM was different in both systems. The results obtained in the present study with DIAM are in agreement with other works [ 22 ]. With respect to the stresses, although neither fixation device produced a significant rise on adjacent vertebrae, they both generated stress concentrations at their locations. Therefore, DYNESYS underwent this increase at the insertion zones of the screws, according to a previous study [ 54 ]; the stress concentration can provoke the pull-out of the screws in the medium or long term [ 21 ].
The obtained results showed the insertions at vertebra L4 as the most loaded whereas vertebra L3 was discharged, suggesting possible problems related to screw loosening at this level.
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In our clinical experience, we have not observed any pulling or loosening of the screws. The DIAM device increased the stresses at the spinous apophyses of the instrumented level. This complication, already described [ 26 ], can cause its own fracture. In the 46 operated cases we did not suffer any fracture of the spinous apophyses, although we must consider the follow-up time is not especially long. The obtained results are in accordance with Wu [ 26 ], exhibiting peak stress values at the apophyses of L4 during extension, flexion and lateral bending above all.
As a result vertebra L4 remained as the most loaded one.
Neither significant increase in mobility in the L5-S1 level nor an increase on the stress were found, considering that a dynamic fixation floating was simulated, like those of our clinical cases. Conversely, the minimum stress values were obtained for axial rotation with the DIAM model exhibiting lower stresses. Regarding DIAM, contradictory published results have reported: a decrease in IDP at instrumented level and adjacent discs [ 48 ], a decrease in IDP at instrumented level with no significant changes in the IDP at the adjacent levels [ 55 ], and only a decrease in IDP during extension at the instrumented level [ 56 ].
Nonetheless, a recent paper has published a rise in IDP and the facet load in adjacent segment with an important stress at the bone-implant interface, similar to the findings in the present work [ 54 ]. IDP decrease and the stabilization of the stresses on adjacent vertebrae is a positive factor in avoiding the appearance of ASD. The obtained results did not detect a stress increase on the adjacent segments, which is in accordance with the published evidence where no incidence was observed on ASD after the implantation of dynamic systems. In the same way, our results through FE simulation confirmed a decrease in IDP without any variations in the adjacent discs.
In the clinical study we did not observe the presence of ASD in the adjacent discs, which is in favor of that there is no increase of IDP, although in the cases of DIAM the follow-up is short. Concerning the increased mobility detected in the adjacent segments, particularly with DYNESYS, it does not appear to have clinical implications in the medium term taking into account the published results [ 21 ]. The mid-term results obtained by our group in the clinical follow-up were very satisfactory and we did not find hypermobility with displacement of adjacent vertebrae in any case, which is a major cause of ASD [ 47 ].
Our clinical results with the use of the DIAM, with But, what is evident is that with both devices we have not detected ASD in the adjacent discs, which is one of the reasons for using dynamic fixations. The obtained results show that the use of dynamic fixations as single systems without vertebral fusion, for low grades of disc degeneration grades II and III of Pfirrmann , which corresponds to slightly affected vertebral endplates but without instability, is an advisable technique which can provide good results. Regardin the controversial published results, the results obtained in the present work are in accordance with the authors who consider both systems capable of maintaining the stability of the lumbar spine DYNESYS [ 20 , 54 , 57 — 60 ] and DIAM [ 50 , 61 — 63 ].
Nonetheless, the follow up period is not long enough to establish definitive conclusions. Both fixations have been used on young patients, and have made it possible to postpone the lumbar spine arthrodesis whenever necessary, as the definitive solution. Additionally, patients have been re-operated after several months of ineffective conservative treatments, recommending a dynamic fixation mainly because of their age.
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The main limitations of this study derive from the small sample of patients and the short follow-up time, both of which need to be broadened. Nevertheless, there is a good correspondence between computational results and the absence of ASD in the radiologic controls of the patients. Nevertheless, it must be noted that the DYNESYS system may have greater long-term stability, whilst also considering that its implementation requires a more aggressive surgery. Accorfing to the obtained results, the dynamic systems anlyzed, used as single systems without vertebral fusion, could be an alternative for the treatment of degenerative disc disease for grade II and grade III of Pfirrmann.
Their major advantage is the possibility they offer to execute a subsequent rigid fixation in case of the failure of the dynamic fixation. In any case, they make it possible to postpone the procedure of lumbar spine arthrodesis. Results of the movement angle at each vertebra. Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field. Abstract Arthrodesis is a recommended treatment in advanced stages of degenerative disc disease. Funding: The authors received no specific funding for this work. Introduction A lot of patients suffer low back pain in some of them with chronic evolution.
Material and methods Computational simulations The present work is based on a previous FE model [ 42 ] validated according to the four basic movements for a healthy spine flexion, extension, lateral bending and axial rotation. Download: PPT. Fig 1. Analyzed devices, their FE models and lateral and posterior view of the operated models. Table 1. Fig 3. Geometrical references for relative movement calculation. Clinical study A total of 58 patients were operated on for degenerative disc disease, 46 patients with a DIAM device and 12 patients with DYNESYS, all of whom were examined to know their evolution and the long-term results of surgical treatment.
The inclusion criteria were: Patients younger than 50 years Persistent chronic low back pain after at least 6 months of conservative treatment Pfirrmann Grade II or III of degenerative disc disease No existence of facet osteoarthritis or instability No previous surgery The exclusion criteria were: Patients older than 50 years Pfirrmann Grade IV or V of Degenerative Disc Disease Existence of facet osteoarthritis or instability Previous surgeries The study of patients operated with Dynesys was retrospective, the assessment of outcome was performed by an independent observer.
Results Results of computational simulations Concerning the results of FE simulations, the mobility values shown in Fig 4 were obtained. Table 3. Fig 5. Fig 6. Results of clinical study DIAM. Discussion The incidence of clinically symptomatic adjacent segment disease SASD is lower compared to radiographic adjacent segment disease RASD , because radiographic changes in adjacent segments do not necessarily imply functional impairment in patients with Arthrodesis [ 46 ].
Supporting information. S1 Fig. Analyzed devices, their FE models and lateral and posterior view the operated models. S2 Fig. S3 Fig. S4 Fig. S5 Fig. S6 Fig. S1 Table. S2 Table. Material properties of every fixation component. S3 Table. References 1. Comprehensive review of epidemiology, scope, and impact of spinal pain.
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