Influence of Surgeon Technique on Screw Pullout Strength in Spinal Fusion Surgery
fusion surgery relies on surgical implants such as pedicle screws for fusion of bone
around the affected areas of the spine. Failure modes on these surgeries include high
rates of the surgical implants loosening and in other cases hardware breakage. Existing
studies for these failures demonstrate that the pullout strength of these pedicle screws
is influenced by various factors ... read moresuch as the design of the implants, the screw
trajectory and bone quality but also the experience level and technique of the surgeon.
The objective of this study was to characterize these surgeon profiles using metrics
based on their interaction with the pedicle screws. During the pedicle screw insertion,
wobble, generated by the surgeon, alters the path for proper placement leading to
failure rates post implantation. Using foam blocks that match various levels of bone
quality ranging from young healthy bone to that which mimics osteoporotic bone, pedicle
screws are inserted by health care professionals in surgical simulations. During these
insertions, surgical profiles are generated in the form of screw insertion angle and
maximum handle diameter, and then correlation to the pullout strength of these pedicle
screws is sought. In all cases with lower bone density, the average pullout strength
differed when surgeon techniques of health care professionals were compared to a novice
with little to no experience in pedicle screw placement. Amongst the surgeons, the
pullout forces were within 95% Confidence Interval of expected values and as such the
maximum handle diameter during the insertion did not provide a correlation. The screw
insertion angle did however correlate with pullout strength data, only in the lower
density bone. The thesis explores the various challenges to this pedicle screw insertion
tracking and provides suggestions for further tracking post data
Thesis (M.S.)--Tufts University, 2017.
Submitted to the Dept. of Mechanical Engineering.
Advisor: Robert White.
Committee: Gary Leisk, and Jarred Sakakeeny.
Keywords: Mechanical engineering, Biomechanics, and Surgery.read less