GENERAL HISTOLOGY

Detailed explanation-1: -The lumbar spinous processes of L3, L4, and L5, and the interspaces between, can usually be directly identified by palpation. The spinal needle can be safely inserted into the subarachnoid space at the L3-4 or L4-5 interspace, since this is well below the termination of the spinal cord in most patients.

Detailed explanation-2: -The ideal insertion point of the spinal needle should be either in the interspinous area between L4 and L5 or L3 and L4. Using these landmarks will avoid inadvertent damage to the conus medullaris, which typically terminates at L1.

Detailed explanation-3: -During the procedure A thin, hollow needle is inserted between the two lower vertebrae (lumbar region), through the spinal membrane (dura) and into the spinal canal. You may feel pressure in your back during this part of the procedure. Once the needle is in place, you may be asked to change your position slightly.

Detailed explanation-4: -A 3.5-inch-long (8.9-cm) LP needle is most often used to perform this procedure in adults; however with the obesity epidemic in the United States, 5 the use of 5-inch-long (12.7 cm) and 7-inch-long (17.8 cm) needles is becoming increasingly common and has been estimated to be necessary in 13.8% of patients.

Detailed explanation-5: -Lumbar puncture is also performed therapeutically in some instances. Standard LP needles come in 1.5, 2.5, 3.5 and 5.0 inch lengths (3.8, 6.4, 8.9, and 12.7 cm, respectively). Selection of LP needle length is typically based on experience; however, an unusually obese or cachectic patient may pose more of a challenge.