CLDH is a special subtype of disc herniation. Most researches concerning calcified disc concentrated on thoracic and thoracolumbar vertebrae because of the complexity of the surgical procedure and serious consequence if left untreated. The narrower spinal canal limits the manipulating field. Voluminous herniated disc and severe adhesion to thecal sac may result in iatrogenic damage. Beyond that, wide visualization of the lesion is necessary while maintaining the postoperative spinal stability restricts the usage of osteotomy. Traditional laminectomy is not suitable for thoracic and thoracolumbar calcified herniation. But for CLDH attracted less attention because laminectomy and discectomy, TLIF (Transforaminal Lumbar Interbody Fusion) and PLIF (Posterior Lumbar Interbody Fusion) could remove the calcification efficiently and safely. With the prosperity of transforaminal endoscopic surgery, this minimally-invasive, rapid-recovering and cost-saving technique has been widely applied in the treatment of LDH[12, 13]. Is it possible to treat CLDH through transforaminal endoscopy? May it cause severe iatrogenic injury? The feasibility, safety and efficacy of transforaminal endoscopic surgery to treat CLDH should be studied.
We designed a simplified and effective technique of transforaminal endoscopy-PTES.Compared with TESS (Transforaminal Endoscopic Spine Surgery) or YESS (Yeung Endoscopic Spine Surgery), only one anteroposterior fluoroscopy is required to determine the surface projection of targeting segment, and the entrance point locates at the corner of flat back turning to lateral side, which was named “Gu’s Point”. It is not necessary to take the C-arm projection and measure the distance lateral from the midline for determination of the entrance point. This entrance point locates at a more medial position than that of other transforaminal endoscopic techniques, which has three advantages: (1) Avoid injuring the exiting nerve root. Exiting nerve root leaves the foraminal in the direction from superomedial to inferolateral. If the entrance point locates laterally, the foraminotomy procedure may meet and injure the exiting nerve root more possibly and the patient may complain of pain in lower extremities during surgery. (2) Avoid blockage by the high iliac crest for the L5/S1 level. Peak of the iliac crest locates at the lateral side of the waist and the height lowers down when getting closer to the midline. Height of the iliac crest at “Gu’s Point” is relatively lower, reducing the difficulty of puncture and subsequent operation. (3) Avoid injuring abdominal viscera and main blood vessels. Puncture from a lateral entrance point could be dangerous if penetrating into the abdomen. Puncture from “Gu’s Point” is much safer, even if in a large horizontal angle. Tip of the needle could be blocked by bony structure of spine.
During the puncture procedure of PTES, tip of the needle is required to stay at the posterior 1/3 of the intervertebral space or the posterior wall of the disc, making the puncture angle more flexible. When enlarging the foramen, pressing down the cannula docking at the superior articular process to decrease the horizontal angle of the trephine could remove more bones in the ventral part of the articular process, and inserting the cannula into the interspace between disc and dura mater will be much easier. This self-created foraminotomy was called “press-down enlargement of foramen”, which makes it possible to remove the herniated nucleus pulposus compressing dura or contralateral nerve root. Of 209 LDH patients who received PTES surgery, 95.7% showed an excellent or good outcome. For the treatment of CLDH, the extent of pressing down is greater than normal to aim the trephine at the calcification during foraminotomy. Keep drilling until the distal end of the trephine exceeds the midpoint between medial border of the pedicle and the spinous process on anteroposterior view to remove the calcification. Pay close attention to patient’s reaction and stop drilling if patient develops nerve root stimulating symptoms. Preoperative images, intraoperative fluoroscopy and patient’s reaction could guarantee the safety of the operation. Rest of the calcified tissue should be grinded off as completely as possible through trephine, electric drill or ultrasonic bone scalpel under endoscopic vision.
In this study, 44 of 46 CLDH patients indicated a satisfied prognosis two years after surgery and postoperative VAS scores had no statistical difference compared with ULDH patients, proving that PTES could treat CLDH safely and efficiently. Duration of operation and intraoperative frequency of fluoroscopy were slightly more than those of the uncalcified patients, because removing the calcification during foraminotomy needed extra fluoroscopic positioning and using trephine or drill under endoscope may cost more time. We ascribed the low recurrence rate to successful postoperative education. Patients were required to avoid bending down, lifting heavy stuff, maintaining a posture for a long time or focusing force on waist while sneezing or coughing. The removed protruded nucleus pulposus under endoscope is usually fragmentized or sequestrated, and the remaining portion at the intervertebral space is healthy and relatively intact. Generally, the remaining nucleus pulposus could keep stable and will not protrude again. If neglecting postoperative waist maintenance, the intact nucleus pulposus may rupture and protrude again.
CLDH has a frequent morbidity and can be relatively difficult to treat. Though PTES technique is a simple, safe and efficient therapeutic method, in our subsequent researches, we will seek for the clinical characteristics of CLDH patients, such as certain risk factors, and the difference in age, course of disease, pain and limited mobility with uncalcified patients. Revealing the etiologies and mechanism of herniated disc calcification could help preventing and blocking the procedure in early stage. We are intending to collect the data of all the CLDH and ULDH patients of recent ten years to analyze the risk factors of calcification in subsequent studies.