Efficacy and Reliability of a Novel Intraoperative Rod Angle Measurement Device Compared to Intraoperative X-Rays in Scheuermann Kyphosis Patients who Underwent Posterior Instrumented Fusion
Authors: Kose Kamil Cagri , Caliskan Islam , Bal Emre , Inanmaz Mustafa Erkan 
Published: May 2015

Introductıon

In spinal deformity surgery the gold standard to determine the postanesthesia and postcorection magnitude of the deformity is measurement of Cobb angles in intraoperative X-rays. Taking intraoperative X-rays is a time-consuming procedure which also exposes the patient and the surgical staff to radiation. In kyphotic deformities to our knowledge, there are no means to bend a straight rod to a desired degree as we have rod benders but we do not have an angle measurement device. To decrease the need for intraoperative X-rays and to measure the bending degree of a rod both before and after fixation of the rod to the spine, a new device has been developed. In this study we aimed to determine the efficacy and reliability of this device in measuring the spinal angles using the screw heads or the rod as a reference point.

Materıal and Methods

Between 2010 and 2014 64 patients were operated with the diagnosis of Scheuermann kyphosis. The new rod angle measurement device has been used in 30 patients with Scheuermann kyphosis who underwent posterior instrumented fusion. Ortho roentgens were taken before and after surgery. Also intraoperative X-rays were obtained before and after adaptation of the rods to the pedicle screws. At the same time spinal angles were measured using the new device (1) adapted over the upper and lower end pedicle screw heads and (2) adapted to the upper and lower ends of the rod. Sagittal plane angles and global sagittal balance were measured.

Results

There were 22 males and 8 females with a mean age of 21.7 and 24.1 years, respectively. The mean time of follow-up was 12.2 months. The mean preoperative kyphosis was 71.6 degrees (range, 80–48 degrees) which was corrected to 39.5 degrees (range, 50–24 degrees) postoperative ( p < 0.0005). For both versions of the device: The correlation of the device and intraoperative precorrection X-rays was r = 0.899 and the correlation of the device and the intraoperative X-rays was r = 1.00 which showed excellent correlation of the device with the X-rays. The mean preoperative lordosis was 61.173 degrees (range, 90–42 degrees), which spontaneously corrected to 47.17 degrees (range, 9–30 degrees) postoperative. There was a mean of 14.53 degrees and 23.75% correction ( p < 0.001). There was no correlation between the degree of kyphosis correction and the degree of spontaneous lumbar lordosis correction ( r = 0.0360).

Conclusıon

Intraoperative rod angle measurement device gives similar and comparable results to the current gold standard. It is also possible to give a desired degree of bending to the rods with this device as it enables direct measurement of the angle. This will aid in preventing over or undercorrections originating from too much or inadequate bending of the rod. As this device obviates the need for intraoperative X-rays, it will decrease the operative times and possibly, the bleeding.