Clinical and Surgical Correlation with MRI Findings in Herniated Lumbar Disc: Towards Clinical and Surgical Application of the Current Classification Oriented Understanding of the Morphology of the Herniated Lumbar Disc

Document Type : Clinical Articles

Authors

Department of Neurosurgery, Ain Shams University, Cairo, Egypt.

Abstract

Background Data: Herniated lumbar discs requiring surgery are evaluated preoperatively by magnetic resonance imaging. This helps the surgeon to appreciate the size, direction and morphology of the herniated disc material and aids planning
the surgical procedure. The currently available MRI based classifications and terminology do correlate clinical, surgical and prognostic information. Purpose: Our study aims to find clinical and/or surgical correlation between the morphology of different disc herniations based on MRI findings with correlation to the clinical and surgical findings. Study Design: Retrospective analysis of 117 patients who had lumbar microdiscectomy for single level herniated lumbar discs.
Patients and Methods: Preoperative MRI was thoroughly examined and the level, laterality, the presence of High Intensity Zone (HIZ) on T2 MRI and Modic changes were recorded. Furthermore, all disc levels were analyzed using the
Michigan University Grading System (MSU), the Pfirmann grading for degree of disc degeneration. We subdivided the fragment according to its base diameter on sagittal MRI into: uniform, protruded, extruded and sequestrated. Noted was the fragment direction. The signal intensity of the herniated material in T2 weighted images was reported. We then correlated using statistical analysis each of the MSU Grade, Pfirmann Grade, fragment morphology, fragment signal and fragment migration with the preoperative duration of symptoms, self-reported Visual Analogue Score for leg pain (VAS), neurological deficit, sphincters dysfunction and straight leg raising, blood loss, incision length, bony work, the amount of disc material removed and the shape of the fragment, length of hospital stay, early postoperative sciatica, unintended durotomy, recurrent sciatica, redo surgery within the first year. Results: The mean age was 39.3 years, 70% were males, 47% were L4-5, and 47.9% were L5-S1. Unilateral left herniation was reported in 52.1%, right in 31.6%, central in 12%, and bilateral in 4.3%. Patients were classified as IIAB in 36, IIB in 28, III AB in 24, HIZ in 7. Caudal migration was reported in 28.2%, straight posterior in 64.1%, and cranial migration in 7.7%. The fragments were dark gray on T2WI in 66 (56.4%) patients. Fragment base was uniform in 53 (45.3%) patients. Most of our surgically treated disc prolapses were Pfirmann, Grade 3 and 4. There was no statistical significance between any of the preoperative clinical or the surgical or the postoperative parameters and Pfrimann grade, MSU grade, fragment base, fragment signal, sagittal extent(P>0.05). Except for a statistically significance between the disc size according to MSU classification and the severity of the preoperative leg pain (VAS) (P=0.01) and the preoperative SLR (P=0.005). There was also a statistically significant correlation between the operative time and the fragment base (P=0.006) Conclusion: Not all disc herniations are similar. On our first attempt to clinically and surgically correlate some of these classifications, we found few clinical and surgical correlations with herniated fragment morphology. A more surgically oriented classification scheme would be useful and applicable for surgeons to anticipate the degree of difficulty of surgery and the plan required for adequate nerve root decompression. (2015ESJ079)

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