26/01/2023
Just published in “The Spine Journal” 🔥
Can we predict resorption of lumbar disc herniations in symptomatic patients? 🤔
👉 Lumbar disc herniation (LDH), is a common cause of LBP, commonly manifesting as pain with or with-out radiation to the leg, paresthesia, sensory deficits, muscle weakness, and other neurologic signs [https://www.nejm.org/doi/10.1056/NEJMcp1512658, https://www.nejm.org/doi/10.1056/NEJMcp1512658, https://onlinelibrary.wiley.com/doi/10.1111/j.1533-2500.2010.00370.x]
👉 Herniation occurs when the intervertebral disc protrudes, extrudes, or is sequestrated from its usual anatomic position and compresses a nearby nerve root [https://www.nejm.org/doi/10.1056/NEJMcp1512658]. In the majority of cases, LDHs are caused by patient-specific factors, such as age-related disc degeneration, genetic predisposition, bio-mechanical factors, sedentary lifestyle, and trauma [https://link.springer.com/article/10.1007/s12178-017-9441-4, https://www.annualreviews.org/doi/10.1146/annurev.bioeng.4.092101.122107, https://www.cmaj.ca/content/188/4/284].
👉 Nonoperative management is initially recommended in the majority of cases, leading to significant improvement in symptoms within 3 to 6 months from initial herniation [https://onlinelibrary.wiley.com/doi/10.1111/j.1533-2500.2010.00370.x, https://jamanetwork.com/journals/jama/fullarticle/204281, https://pubmed.ncbi.nlm.nih.gov/15834338/, https://journals.lww.com/spinejournal/Abstract/1990/07000/The_Natural_History_of_Lumbar_Intervertebral_Disc.13.aspx].
👉 Conservative management relies on the body’s natural ability to spontaneously “resorb” the herniated disc fragment as part of a phenomenon of “self-healing”. Although the exact mechanism of action is under debate, a recent meta-analysis noted that spontaneous resorption after an LDH occurs in 67% of cases within 1 year [https://pubmed.ncbi.nlm.nih.gov/28072796/] and up to 96% in disc sequestration [https://pubmed.ncbi.nlm.nih.gov/25009200/].
🤷♂️ But at the moment we don´t know exactly the predictive factors of resorption. To answer this question, Hornung et al.[ https://www.thespinejournalonline.com/article/S1529-9430(22)00959-7/fulltext] followed 93 patients with symptomatic disc herniation up to 1 year after in a prospective study.
📊 Baseline assessment of patient demographics (eg, smoking status, height, weight, etc.), herniation characteristics (eg, the initial level of herniation, the direction of herniation, prevalence of multiple herniations, etc.) and MRI phenotypes (eg, Modic changes, end plate abnormalities, disc degeneration, vertebral body dimensions, etc.) were collected for further analysis. Lumbar MRIs were performed approximately every 3 months for 1 year from time of enrollment to assess disc integrity.
📊 All patients (93/93; 100%) experienced resorption within 1 year. 23 patients exhibited complete resorption < 3 months after initial evaluation and were classified to the “early resorption group”, whereas the others patients were categorized to the late resorption groups.
⛔ All patients were treated with gabapentin, acupuncture, and education on avoidance of inflammatory-modulating medications. This regimen was developed based on the idea that inflammation and neovascularization are integral to disc resorption, and this response may be altered by NSAIDs or corticosteroids as they have the potential to limit our bodies’ naturally selected mechanisms for resorbing herniated discs [https://www.thespinejournalonline.com/article/S1529-9430(22)00959-7/fulltext , https://arthritis-research.biomedcentral.com/articles/10.1186/s13075-018-1743-4].
💡 3 baseline factors (s. figure) predicted an early resorption after LDH (precision (0.75), specificity (0.92), sensitivity (0.67)):
1. greater L4 posterior vertebral height,
2. greater sacral slope (SS), and
3. greater herniated volume
While the reason behind a faster resorption with a greater posterior vertebral height are unclear, the authors speculate, that a greater SS (greater than 35˚) could lead to lower strain on the disc and biomechanical stress, potentially influence the likelihood of early resorption. [https://josr-online.biomedcentral.com/articles/10.1186/s13018-018-0838-6]
💡 Moreover, the advantage of greater initial herniation size maybe a product of differential access to nutrients and hydration to facilitate resorption, as larger herniations may pe*****te the annulus fibrosus and the posterior longitudinal ligament and become exposed to epidural vascular supply, whereas smaller herniations remain dependent on the adjacent end plate and its relatively lower capacity for metabolic transport [https://journals.lww.com/spinejournal/Abstract/2006/05150/Determinants_of_Spontaneous_Resorption_of.12.aspx, https://journals.lww.com/spinejournal/Abstract/2021/04010/Association_Between_Vertebral_Dimensions_and.3.aspx].
According to the authors, this hypothesis is particularly interesting in the context of this study, as restricting anti-inflammatory medications to permits natural inflammation may have enabled greater neovascularization [https://arthritis-research.biomedcentral.com/articles/10.1186/s13075-018-1743-4, https://www.sciencedirect.com/science/article/pii/S1878875011004992?via%3Dihub] and contributed to accelerated resorption of larger herniations.
📣 In any case, we should pass on a great message to patients: A larger disc herniation seems to favour early complete resorption.
And one more important side note to this study: There were no differences in onset of symptoms, cessation of radicular symptoms, or VAS scores at follow-up between the early and late resorption group! So resorption does not equal symptom reduction.
