COMPARATIVE ANALYSIS ON SURGICAL OPERABILITY AND DEGREE OF EXPOSURE OF MICROSURGICAL APPROACHES TO INTRAFORAMINAL LUMBAR DISC HERNIATIONS.

IFDHs (intraforaminal disc herniations) represent a heterogeneous and relatively uncommon disease; their treatment is technically demanding due to the anatomic relationships with nerve roots and vertebral joints. Over time, several approaches have been developed without reaching a consensus about the best treatment strategy. Authors comparatively analyze surgical operability and exposure in terms of quantitative variables between the different microsurgical approaches to intraforaminal lumbar disc herniations (IFDH), defining the impact of each approach on surgical maneuverability and exposure on specific targets. A comparative microanatomical laboratory investigation was conducted. The operability score (OS) was applied for quantitative analysis of surgical operability. Trans-articular and combined translaminar-trans-pars-interarticularis approaches result in providing the best surgical exposure and maneuverability on all targets with surgical controls on both nerve roots, at the expense of a higher risk of iatrogenic instability. Trans-pars-interarticularis approach reaches comparable levels of operability, even limited to the pure foraminal area (lateral compartment); similar findings were recorded for partial facetectomy on the medial compartment. The contralateral interlaminar approach provides good visualization of the foramen without consensual favorable maneuverability, which should be considered as the main drawback. Approach selection has to consider disease location, the possible migration of disc fragments, the degree of nerve root involvement, and risk of iatrogenic instability. According to the findings, authors propose an operative algorithm to tailor the surgical strategy, based both on the precise definition of anatomic boundaries of exposure of each approach, as well as surgical maneuverability on specific targets.