Neuraxial anaesthesia may be preferred as an alternative to general anaesthesia for the patients with AS to be performed by perineum and lower extremity surgery. However, ossification of the interspinous ligaments and ligamentum flavum, the formation of bone bridges between vertebrae enforce insertion of the epidural or spinal needle
2,3,7. Regional anaesthesia may be contraindicated for three reasons. First; ossification of the interspinous ligaments and bone bridge formation can make impossible needle or catheter to be placed, second; a higher incidence of vertebral fractures, and the third; complications of regional anaesthesia such as intravenous injection, requires airway manipulation under difficult conditions
8.
In a retrospective study neuraxial anaesthesia was applied 19.5% of 82 patients with AS. Success was achieved in 76.2% of these patients, all epidural anaesthesia attempts were failed9. In an another study, spinal anaesthesia, that can not be performed with approach from midline, with lateral approach was successfully applied in 3 patients5. In our 2nd case, when two attempts of spinal anaesthesia application with approach from midline was not successful, a successful block was provided with lateral approach.
Hoffman et al.10 have planned epidural analgesia for the purpose of labor analgesia in patient with severe AS. Despite two successful placements of lumbar epidural catheters, adequate rostral spread of local anesthesia to control labour pain was never achieved via the epidural route. Thus, continuous spinal analgesia was used, which provided effective labour analgesia in this patient. They stated that posterior longitudinal ligament is calcified, prevents local anaesthetic agent to spread.
In the recent studies, it's been shown that conventional sitting and lateral positions were modified by combining; block application success is high in head up (semi-sitting) lateral positions and hemodynamics progresses more stable11. We have also seamlessly performed spinal anaesthesia application in our first case in head up (semi-sitting) lateral position and intraoperative hemodynamic change was not observed. In the second case, we were successful with the lateral approach after unsuccessful spinal anaesthesia attempt with midline approach again in sitting position.
In conclusion; in the patients with AS, it should be considered that spinal anaesthesia can be applied more easily with midline approach in lateral semi-sitting position or lateral approach in sitting-position, without insisting on the midline technique in cases where the midline technique is difficult to be performed.
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