Objective: Calcified thoracic disc herniations (CTDH) represent a challenging pathology. Several surgical techniques have been described with various degrees of success. Aim of this study is to present our experience in treating CTDH via a Minimally Invasive Retropleural rib Sparing Transthoracic direct lateral (MIRST) approach and lessons learnt.

Method: A 10 year retrospective review (2015-2025) of all Anterolateral approaches for thoracic disc herniation was performed at our unit. A total of 31 patients were operated of which 26 had giant calcified disc. Preoperatively CT guided placement of a pedicle marker was used to localise the level. Surgical technique involved the MIRST approach. Patient demographics, clinicopathological presentation, neuromonitoring data, surgical technique and followup outcomes (upto 2 years) are presented.

Results The mean age was 54 years (range 24 to 78 years) with a female predominance. All patients had progressive thoracic myelopathy ongoing for 2 weeks to 1 year. Six patients (20%) presented acutely, 45% were located between T6 - T9 level and 70% centrally based. Four (12%) had intradural extension. Intraop monitoring dropped in 5 of initial 15 patients who were all worse immediately post-surgery. No changes in monitoring occurred in the last 16 consecutive cases which we attribute to technical considerations that included creation of a larger gutter in the vertebral body and the learning curve. Complications occurred in 4 patents with chest infection (n=2), hernia(n=1) and one patient needed to return to theatre for revision discectomy. At discharge, 4 patients were unchanged and the remaining 27 patients were all improved. 23(75%) presented with Nurick grade 4 or worse and at discharge 25(80%) were Nurick 3 or better. All 5 patients with intraop monitoring changes showed improvement at time of discharge as compared to their immediate postop function.

Conclusion: The predominately central anatomical location of CTDH makes the anterior approach ideal enabling minimal retraction of the spinal cord. There

is a learning curve and the MIRST approach offers a safe and reliable corridor for anterolateral excision of thoracic disc herniation.