Hallym University Sacred Heart Hospital

Dr. Jae-Hyuk Shin and his team of the Spine Center at Hangang Sacred Heart Hospital has recently demonstrated that the optimal insertion angle on the axial surgical plane for a iliac screw insertion was divergently 30 degrees. He disclosed his research finding in his article, “The Trajectory of Iliac Screw in the Axial Plane in 200 Korean Patients” which was published in the latest edition of Asian Spine Journal (2010 vol.4), the official medical journal of Korean Society of Spine Surgery (KSSS).

In spine fusion surgeries for spinal stenosis, degenerative spondylosis and scoliosis, screws must be inserted stably into each vertebra in order to achieve secure fixation and successful fusion. The insertion trajectory into the cervical, thoracic, and lumbar spine have been diversely studied. Iliac screw system has been recently gaining popularity for augmenting the stability of lumbar fusion. “When a patient bends his back anteriorly after long level spine fusion, load increases at the lower spine segment and screw is at risk of coming off the bone” Dr. Shin explained. The insertion trajectory of the iliac screw, however, has never been studied.

From analysis of CT image of 200 normal individuals, the study demonstrated that the optimal insertion angle of the iliac screws turned out to be divergently 30 degrees on the axial plane.

Conventional insertion trajectory guideline suggested divergently 45 degrees. But the study demonstrated that iliac screw inserted divergently 45 degrees on the axial plane could cause breakage of the outer-wall of the iliac bone and protrusion into the buttock, causing pain.

“When we drive the screw into a pelvis at a 30-degree divergently on the axial plane, it will navigate through the intercortical plane of the iliac bone, which is the exact trajectory for the surgeon,” Dr. Shin added.

By Sung-won Lee, Int’l Operations Team, HUMC (sungwon@hallym.or.kr)