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author:("garfi, Steven")
1.  Regional Myosin Heavy Chains Distribution in Selected Paraspinal Muscles 
Spine  2010;35(13):1265-1270.
Study Design
Cross-sectional study with repeated measures design.
Objective
To compare the myosin heavy chain isoform distribution within and between paraspinal muscles and to test the theory that fiber type gradients exist as a function of paraspinal muscle depth.
Summary of Background Data
There is still uncertainty regarding the fiber type distributions within different paraspinal muscles. It has been previously proposed that deep fibers of the multifidus muscle may contain a higher ratio of type I to type II fibers, because, unlike superficial fibers, they primarily stabilize the spine, and may therefore have relatively higher endurance. Using a minimally invasive surgical approach, utilizing tubular retractors that are placed within anatomic inter-muscular planes, it was feasible to obtain biopsies from the multifidus, longissimus, iliocostalis and psoas muscles at specific predefined depths.
Methods
Under an IRB approved protocol, muscle biopsies were obtained from 15 patients who underwent minimally invasive spinal surgery, using the posterior paramedian (Wiltse) approach or the minimally invasive lateral approach. Myosin heavy chain (MyHC) isoform distribution was analyzed using SDS-PAGE electrophoresis. Since multiple biopsies were obtained from each patient, MyHC distribution was compared using both within- and between-muscle repeated measures analyses.
Results
The fiber type distribution was similar among the posterior paraspinal muscles and was composed of relatively high percentage of type I (63%), compared to type IIA (19%) and type IIX (18%) fibers. In contrast, the psoas muscle was found to contain a lower percentage of type I fibers (42%) and a higher percentage of type IIA (33%) and IIX fibers (26%; P<0.05). No significant difference was found for fiber type distribution among three different depths of the multifidus and psoas muscles.
Conclusion
Fiber type distribution between the posterior paraspinal muscles is consistent and is composed of relatively high percentage of type I fibers, consistent with a postural function. The psoas muscle, on the other hand, is composed of a higher percentage of type II fibers such as in the appendicular muscles. Our data do not support the idea of a fiber type gradient as a function of depth for any muscle studied.
doi:10.1097/BRS.0b013e3181bfcd98
PMCID: PMC2947743  PMID: 20461040
Lumbar multifidus; Muscle mechanics; Lumbar spine
2.  Surgeon Perceptions of Minimally Invasive Spine Surgery 
SAS journal  2008;2(3):145.
Background
Interest in minimally invasive surgery (MIS) of the spine has driven the development of new and innovative techniques to treat an ever wider range of spinal disorders. Despite these new advances, spine surgeons have been slow in adopting MIS into their clinical practice. This study aims to provide a better understanding of the factors that have led to limited incorporation of these procedures into their practices.
Methods
Eighty-seven spine surgeons completed a questionnaire related to their perceptions of MIS. Respondents were asked to comment on their perceptions regarding the limitations and advantages of minimally invasive spine surgery. Survey results were then analyzed for both overall opinions and opinions based on the amount of MIS utilization in the respondents’ current practices.
Results
The top 3 identified limitations of MIS of the spine were technical difficulty, lack of convenient training opportunities, and radiation exposure. Of these respondents, spine surgeons experienced in MIS were concerned more with radiation exposure than the lack of training opportunities. In contrast, spine surgeons with little MIS experience cited the lack of training opportunities as the most significant limitation. There was little concern related to the limited proven clinical efficacy of MIS of the spine.
Discussion
Technical factors, training opportunities, and radiation exposure appear to be the major obstacles to MIS of the spine. Most spine surgeons believe that MIS leads to faster return to daily activities, better long-term function, and decreased hospitalization. This may explain why most surgeons did not cite a lack of proven efficacy as a major limitation to MIS.
These findings indicate that the widespread adoption of MIS of the spine will likely be driven through relatively simple means, such as improved training programs that strive to decrease the technical difficulty and limit radiation exposure of these procedures. It is unlikely that extensive clinical data alone, without such improved training programs, will be sufficient to drive widespread use of minimally invasive spine surgery.
doi:10.1016/S1935-9810(08)70032-X
PMCID: PMC2817980  PMID: 20148184
Surgeon perceptions; minimally invasive spine surgery; survey; limitations
3.  Do design variations in the artificial disc influence cervical spine biomechanics? A finite element investigation 
European Spine Journal  2009;21(Suppl 5):653-662.
Various ball and socket-type designs of cervical artificial discs are in use or under investigation. Many artificial disc designs claim to restore the normal kinematics of the cervical spine. What differentiates one type of design from another design is currently not well understood. In this study, authors examined various clinically relevant parameters using a finite element model of C3–C7 cervical spine to study the effects of variations of ball and socket disc designs. Four variations of ball and socket-type artificial disc were placed at the C5–C6 level in an experimentally validated finite element model. Biomechanical effects of the shape (oval vs. spherical ball) and location (inferior vs. superior ball) were studied in detail. Range of motion, facet loading, implant stresses and capsule ligament strains were computed to investigate the influence of disc designs on resulting biomechanics. Motions at the implant level tended to increase following disc replacement. No major kinematic differences were observed among the disc designs tested. However, implant stresses were substantially higher in the spherical designs when compared to the oval designs. For both spherical and oval designs, the facet loads were lower for the designs with an inferior ball component. The capsule ligament strains were lower for the oval design with an inferior ball component. Overall, the oval design with an inferior ball component, produced motion, facet loads, implant stresses and capsule ligament strains closest to the intact spine, which may be key to long-term implant survival.
doi:10.1007/s00586-009-1211-6
PMCID: PMC3377801  PMID: 19936805
Cervical; Disc replacement; Finite element; Biomechanics; Design variation
4.  Spine surgeons: spine industry 
European Spine Journal  2007;17(6):785-790.
doi:10.1007/s00586-007-0542-4
PMCID: PMC2518994  PMID: 18027002

Results 1-6 (6)