Introduction: Lumbar disc herniations (LDH) are amongst the most common spinal pathologies worldwide.  As part of a “self-healing” phenomenon, patients often undergo spontaneous LDH resorption. However, the mechanism of this process remains poorly understood, particularly in the context of multiple herniations. The current study therefore aimed to identify specific patient characteristics, MRI findings, and resorption features associated multiple herniations and LDH resorption.  We hypothesized patients with multiple LDH herniations will (1) demonstrate distinct patient characteristics, (2) exhibit discrete MRI findings, and (3) experience longer resorption times compared to those with a single herniation.

Methods: A one-year prospective study was conducted of patients presenting with acute symptomatic LDH. All patients were managed by a single clinician between 2017 and 2019. All included patients (1) were >18 years of age, (2) exhibited MRI findings of acute LDH, and (3) had symptomatic radiculopathy. Baseline assessment encompassed patient demographics, herniation characteristics (e.g., herniation location), and MRI phenotypes (e.g., disc degeneration, endplate abnormalities, vertebral body dimensions). Treatment consisted of gabapentin, acupuncture, and avoidance of inflammatory-modulating medications in all patients. MRIs were performed approximately every 3 months after initial evaluation to assess disc integrity. P-values <0.05 were deemed statistically significant.

Results: Ninety patients were included (n=73 single herniation, n=17 multi-herniation) with a mean age of 48.7±11.9 years. Baseline demographics did not differ between single- and multi-herniation groups apart from body mass index (BMI), as the multi-herniation group consisted of patients with higher BMI (p<0.001). Moreover, the frequency of multiple herniations was similar between males (9 of 44, 20.5%) and females (8 of 46, 17.4%). Those with multiple herniations were more likely to have greater initial disc size (axially) compared to those with only a single herniation (p=0.012). No other baseline herniation characteristics differed between groups (e.g., initial size of herniation, location of herniation, or sagittal maximal measurement), nor did vertebral dimensions, Cobb angle (CA), sacral slope (SS) or CA:SS. Patients with multiple herniations were more like to have L3/L4 inferior endplate changes (p=0.001), L4/L5 superior endplate changes (p=0.012) and L4/L5 inferior endplate changes (p=0.020). No other differences in MRI phenotypes (e.g., Modic changes, osteophytes, etc.) existed between groups. Furthermore, no differences in resorption rate or time to resolution were observed between those with single and multiple herniations.

Discussion: In the first study of its kind, compared to those with single-level LDH, patients with multiple herniations are more likely to have a higher BMI, greater initial axial measurements, and endplate changes at the inferior L3/L4, superior L4/L5, and inferior L4/L5 levels. Patients of both groups, all managed conservatively, experienced similar rates of resorption and times to symptom resolution. Taken together, these results indicate conservative management represents an effective strategy for managing patients with LDH regardless of the number of affected levels, and they may assist clinicians in prognosticating recovery within this specific patient population.