[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Spine](https://durgical.com/en/anatomy/region/spine/) › L5 vertebra [Skeletal system](https://durgical.com/en/anatomy/system/skeletal-system/) · [Spine](https://durgical.com/en/anatomy/region/spine/) # L5 vertebra L5 is the lowest lumbar vertebra, wedge-shaped, sitting on the sacrum; it passes the weight of the upper body to the [pelvis](https://durgical.com/en/anatomy/region/pelvis/). Official name: L5 [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=spine&select=l5&side=r) Opens in the Durgical app, no sign-up needed. ## What it is The lowest lumbar vertebra, wedge-shaped, sitting on the sacrum at the base of the [spine](https://durgical.com/en/anatomy/region/spine/). ## What it does Passes the weight of the whole upper body onto the sacrum and pelvis. ## Key points - Isthmic spondylolisthesis at L5–S1 traps the exiting [L5 nerve root](https://durgical.com/en/anatomy/l5/) in the foramen, while an L5–S1 disc herniation usually hits the traversing [S1 nerve root](https://durgical.com/en/anatomy/s1/) - Scottie dog on oblique X-rays: the pars interarticularis is the dog's neck, and a dark collar across it is spondylolysis - Meyerding grades slip in quarters of the S1 width: I up to 25%, II 25–50%, III 50–75%, IV 75–100%, V complete slip (spondyloptosis) - A transitional L5 (sacralization) or a lumbarized S1 shifts level numbering; counting from C2 on MRI avoids wrong-level surgery ## Key facts **Joints with** L4 above (disc, facet joints); sacrum (S1) below (L5–S1 disc and facet joints); tied to ilium by iliolumbar ligament **Landmarks** Largest body, wedge-shaped (taller in front), forming the lumbosacral angle; thick conical transverse processes; smallest lumbar spine; commonest site of spondylolysis ## Relations **In front** The left [common iliac vein](https://durgical.com/en/anatomy/common-iliac-vein/) crosses in front of L5 under the right [common iliac artery](https://durgical.com/en/anatomy/common-iliac-artery/); the [superior hypogastric plexus](https://durgical.com/en/anatomy/superior-hypogastric-plexus/) and [median sacral artery](https://durgical.com/en/anatomy/median-sacral-artery/) lie on the front of the [L5–S1 disc](https://durgical.com/en/anatomy/l5-s1/) **Lateral** The [iliolumbar ligament](https://durgical.com/en/anatomy/iliolumbar-ligament/) runs from the thick transverse process to the iliac crest; the L5 ventral ramus joins L4 to form the lumbosacral trunk across the sacral ala **Behind** [Low-back facet joints](https://durgical.com/en/anatomy/zygapophysial-joints-spine-and-pelvis/) set more coronally than above, resisting forward shear on the sloping [sacrum](https://durgical.com/en/anatomy/sacrum/); the pars interarticularis between upper and lower facets **Below** Sacrum: the L5–S1 disc on the sacral promontory, the most wedge-shaped disc ## How to find it The L5 spine is the last lumbar spine felt in the midline, a little below the line across the iliac crests, just above the sacrum. The [skin](https://durgical.com/en/anatomy/skin/) dimples over the posterior superior iliac spines lie lower, at about S2. ## Examination - One-leg hyperextension (stork) test: standing on one leg and arching back reproduces pain from a pars stress fracture, usually on the standing side ## On imaging Oblique views show the Scottie dog; a lateral view grades the slip and the slip angle. CT shows the pars gap; MRI shows an early stress reaction before a gap appears. On the AP view an enlarged L5 transverse process meeting the sacrum marks a transitional vertebra (Castellvi types). ## Common problems - Spondylolysis: a stress fracture of the bony bridge at the back (pars), common in young athletes who arch the back (gymnasts, football linemen). - Isthmic spondylolisthesis: L5 slips forward on the sacrum after a pars fracture. - L5-S1 disc herniation pressing on the S1 root. ## How it is diagnosed X-rays (including oblique and flexion-extension views) show slipping; CT shows a pars fracture; MRI shows discs and nerves. ## Treatment - Rest from the sport, physical therapy and sometimes a brace for a new pars fracture. - Disabling slip or nerve pain: decompression and fusion at L5-S1 (posterior or anterior). ## Clinical notes - Bertolotti syndrome: low back pain linked to an enlarged L5 transverse process that forms a false joint with the sacrum or ilium - Anterior approach to L5–S1 works between the common iliac vessels and can injure the superior hypogastric plexus, causing retrograde ejaculation in men - May–Thurner syndrome: the left common iliac vein is squeezed between the right common iliac artery and L5, a cause of left leg deep vein thrombosis ## Anatomical variants - Sacralization of L5 or lumbarization of S1 (lumbosacral transitional vertebrae) are common, with frequencies that vary widely between studies - Spina bifida occulta of L5 or S1: a gap in the lamina, usually without symptoms; a hairy patch or dimple above may mark a deeper defect ## Development Spondylolysis is acquired, not congenital: it is not seen in newborns and appears with upright activity in childhood and adolescence, more often in sports with repeated arching of the back. ## Memory aid Scottie dog: nose = transverse process, eye = pedicle, ear = superior articular process, neck = pars interarticularis, front leg = inferior articular process; a collar on the neck is a pars fracture. ## Related conditions - [Spondylolisthesis](https://durgical.com/en/conditions/spondylolisthesis/) - [Spina bifida (myelomeningocele)](https://durgical.com/en/conditions/spina-bifida/) - [VACTERL association](https://durgical.com/en/conditions/vacterl-association/) - [Lumbar Disc Herniation](https://durgical.com/en/conditions/lumbar-disc-herniation/) ## Test yourself Think of the answer, then tap the question to see it. ## In isthmic spondylolisthesis at L5–S1, which nerve root is trapped, compared with an L5–S1 disc herniation? The exiting L5 nerve root is trapped in the foramen; an L5–S1 disc herniation usually hits the traversing S1 nerve root. ## On an oblique X-ray of the L5 vertebra, what does a collar on the Scottie dog's neck mean? Spondylolysis: the neck is the pars interarticularis, and a dark collar across it is a pars fracture. ## How does the Meyerding system grade a slip of L5 on S1? In quarters of the S1 width: I up to 25%, II 25–50%, III 50–75%, IV 75–100%, V complete slip (spondyloptosis). ## What is May–Thurner syndrome, which involves the L5 vertebra? The left common iliac vein is squeezed between the right common iliac artery and L5, a cause of left leg deep vein thrombosis. ## What is Bertolotti syndrome? Low back pain linked to an enlarged L5 transverse process that forms a false joint with the sacrum or ilium. [Add to my cards (5)](https://durgical.app/estudiar/?add=/en/anatomy/lumbar-vertebra-spine-and-pelvis-l5/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** vertebra lumbalis V TA2 1068 **Official Spanish (DeCS)** Vértebra lumbar L5 DeCS D008159 **English (TA2)** L5 ## Related - [L4–L5 disc](https://durgical.com/en/anatomy/l4-l5/) - [L5–S1 disc](https://durgical.com/en/anatomy/l5-s1/) - [Iliolumbar ligament](https://durgical.com/en/anatomy/iliolumbar-ligament/) - [Iliolumbar vessels](https://durgical.com/en/anatomy/iliolumbar-artery/) - [Anterior longitudinal ligament](https://durgical.com/en/anatomy/anterior-longitudinal-ligament/) - [Endplates](https://durgical.com/en/anatomy/vertebral-endplates/) - [Low-back facet joints](https://durgical.com/en/anatomy/zygapophysial-joints-spine-and-pelvis/) - [Interspinales](https://durgical.com/en/anatomy/interspinales-muscles/) Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=8334&filter=ths_termall&q=V%C3%A9rtebras%20Lumbares); [Anatomy, Back, Lumbar Spine](https://www.ncbi.nlm.nih.gov/books/NBK557616/). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/anatomy/lumbar-vertebra-spine-and-pelvis-l5/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/lumbar-vertebra-spine-and-pelvis-l5/