Comparison Of Landmark Versus Ultrasound Guided Lumbar Puncture Technique In Obese Patients Undergoing Total Knee Replacement Surgery Under Spinal Anaesthesia

Subarachnoid Block produces a quick sensory and good motor block through the injection of local anaesthetic to the subarachnoid space. Spinal anaesthesia is traditionally performed using the palpation of bony landmarks to identify the level and point of the needle insertion, together with tactile feedback during needle insertion. The success of traditional lumbar puncture mainly depends on the accurate positioning of the puncture point. The accurate location of the puncture point was mainly based on the anatomical landmarks, through the Tuffler’s line (the transverse line connecting the superior aspects of the iliac crests) and touching the interspace of the spinous process. However, the actual level of Tuffler’s line may vary from the L4 body to the L5 body, the line is insufficient to use for assessing spinal segmental level. If the patient is obese, the subcutaneous fat layer is thickened, the ligament and bony landmarks are not displayed clearly, the traditional lumbar puncture method is more difficult, greatly increasing the possibility of failure. Ultrasound (US) imaging has become an increasingly popular tool among anaesthesiologists to guide neuraxial blockade. Studies have shown that Ultrasonography facilitates the performance of spinal anaesthesia in patients in whom technical difficulties are expected. Ultrasound window provides an enhanced visibility of the neuraxis and surrounding structures. In this prospective, observational study we hypothesized that Ultrasound guided spinal anaesthesia would result in reduced puncture attempts and improved success rates at first attempt when compared with the conventional landmark-guided technique in obese patients