Clinical guidance for treatment strategie of modified MSU classification(MMSU) for lumbar disc herniation in minimally invasive spinal surgery

English Keywords:Lumbar disc herniation  MSU classification  Modify  Minimally invasive spine surgery

English Abstract:

  【Abstract】 Objectives: To compare the clinical consistency between Michigan State University(MSU) classification and modified MSU(MMSU) classification of intervertebral disc herniation, and to investigate the clinical guidance for treatment strategies of MMSU classification in minimally invasive spinal surgery. Methods: A retrospective analysis was conducted on the clinical data of 84 patients with lumbar disc herniation admitted to the Department of Orthopedics, Air Force Medical Center from January to December 2023, including 48 males and 36 females, aged 20 to 69 years(mean, 44.37±12.85 years). After defining the line connecting the peak of the bilateral upper articular processes as line-a and the line connecting the peak of the bilateral lower articular processes as line-b, MMSU grading was defined as: protrusion not exceeding line-a was grade-1, protrusion between line-a and b was grade-2, protrusion exceeding line-b was grade-3. After drawing two parallel vertical lines with the vertices of the bilateral inferior articular processes perpendicular to the transverse axis of the intervertebral disc, where the area between was the spinal canal, MMSU zones was defined by dividing the spinal cannal into three equal quarters along the bilateral intra-facet line, with zone A in the middle and zone B on both sides; Drawing two vertical lines along the outer edges of the bilateral superior articular processes with the zone C inside, which was the intervertebral foramen area; The outer side of the two lines was zone D, which was the extremely outer zone. Eight attending physicians in spinal surgery who were familiar with the two types of classification reviewed the lumbar MRI films of 84 patients and classified them into MSU and MMSU zones and grades, respectively. Data were collected for statistical analysis and consistency rates of the two types of classification were compared(the consistency ratio of the two classification for each MRI image), including average consistency rate, 100% consistency rate cases(same classification in all 8 doctors), >50% consistency rate cases(same classification in at least 5 doctors, excluding same classification in all 8 doctors), ≤50% consistency rate cases(same classification in no more than 4 doctors). Results: MMSU classification was better than MSU classification in the average consistency rate[(71.13±17.15)% vs (61.00±17.67)%], number of cases with 100% consistency rate[10(11.9%) vs 1(1.90%)], and number of cases with ≤50% consistency rate[14(16.67%) vs 33(39.29%)], and the differences were statistically significant(P＜0.05). There was no statistically significant difference in the number of cases with a consistency rate of＞50%[60(71.43%) vs 50(59.52%)] between the MMSU and MSU classification(P＞0.05). Conclusions: The MMSU classification of lumbar disc herniation has refined the grading and zoning of protrusion, highlighted the direction, position and degree of protrusion on the axis position through naming methods, increased the grading degree of sagittal upward or downward shift, therefore is of clinical importance for surgical plans in minimally invasive spinal surgery and useful in communication among spine surgeons.