Palpation and sensations during a lumbar puncture: how Sim&Care takes these aspects into account
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By Héloïse Guillot / 18th August 2021
? The importance of palpation and sensations during a lumbar puncture
Palpation during a lumbar puncture
The success of a lumbar puncture is based on a good knowledge of the anatomical landmarks involved in the procedure. The more the doctor knows what to expect, the more likely the procedure will be successful.
The goal of a lumbar puncture is to insert a needle in the right spot, between two lumbar vertebrates, in order to reach the spinal canal and collect a sample of cerebrospinal fluid. During the first step of the procedure, the doctor identifies the appropriate interspinous space for the needle insertion by palpation of the iliac crests and lumbar spine. The correct levels for the puncture are the interspinous spaces between L3 and L4, L4 and L5 or L5 and the sacrum, as they are located below the termination of the spinal cord. The horizontal line drawn between the two iliac crests helps determine the position of the L4-L5 space and thus identify the puncture point. Usually widest interspace is chosen, that’s why the patient is position in a seated position, or in lateral recumbent position, with the back as bent as possible to widen the space between vertebrates as much as possible and allow the needle passage. The palpation step is an integral part of the lumbar puncture procedure, and is essential for its success. If the puncture site is misidentified, the needle will not be inserted with the correct path, and the puncture will fail.
Once the puncture point has been located, and the area disinfected, the doctor inserts the needle at a range of 15 to 20° in the cranial direction. He then feels the passage of different anatomical structures, each associated with a specific sensation. After passing through the skin, the needle goes through the supraspinous ligament that connects the tips of spinous processes, and then through the thicker interspinous ligament between each spinous processes. The practitioner should then feel a last resistance, corresponding to the ligamentum flavum. After passing this last ligament, the needle is in the spinal canal, and the CSF can be collected. If the trajectory is wrong, the needle may hit a bone, indicating that the needle should be retracted and the insertion angle modified.
Palpation and sensations are crucial aspects of the lumbar puncture, since during the gesture, the doctor cannot see in transparency what he is doing. The success of the gesture therefore depends solely on its knowledge of the anatomical aspects and its ability to recognize the structures through sensations. For a novice student, it can be difficult to grasp these concepts without priori training. If the puncture is not successful, it is particularly difficult for the student to understand the factors that led to the failure, especially if he is convinced to have carried out the gesture correctly in theory. Palpation and sensations must therefore be taken into account when learning the gesture. Medical students should know what to expect and learn the right reflexes before performing their first puncture on a patient.
? How Sim&Care takes these aspects into account
In order to train future practitioners, InSimo takes these fundamental aspects into account in the development of its lumbar puncture simulator, Sim&Care.
The user manipulates the force feedback interface
Our simulator faithfully recreates the behaviour of the virtual patient’s anatomy, including tissue elasticity and resistance to virtual medical interactions. The technical gesture and the sensations associated with crossing each structure are calculated by real-time simulation and transmitted to the haptic interface to reproduce the physical sensations of the real medical gesture, allowing the student to become familiar with the perception of a real lumbar puncture.
