Pedicle

Medical Terminology Daily (MTD) is a blog sponsored by Clinical Anatomy Associates, Inc. as a service to the medical community. We post anatomical, medical or surgical terms, their meaning and usage, as well as biographical notes on anatomists, surgeons, and researchers through the ages. Be warned that some of the images used depict human anatomical specimens.

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A Moment in History

Jean Louis Petit
(1674 – 1750)

French surgeon and anatomist, Jean Louis Petit was born in Paris in on March 13, 1674. His family rented an apartment at his house to Alexis Littre (1658 – 1726), a French anatomist. Petit became an apprentice of Littre at seven years of age, helping him in the dissections for his lectures and at an early age became the assistant in charge of the anatomic amphitheater.

Because of Petit’s dedication to anatomy and medicine, in 1690 at the age of sixteen, became a disciple of a famous Paris surgeon, Castel.

In 1692, Petit entered the French army and performed surgery in two military campaigns. By 1693 he started delivering lectures and was accepted as a great surgeon, being invited to the most difficult operations. In 1700 he was appointed Chief Surgeon of the Military School in Paris and in the same year he received the degree of Master of Surgery from the Faculty of Paris.

In 1715 he was made a member of the Royal Academy of Sciences and an honorary member of the Royal Society of London. He was appointed by the King as the first Director General of the Royal Academy of Surgery when it was founded in 1731.

Petit’s written works are of historical importance. “Traite des Maladies des Os” ( A Treatise on Bone Diseases); “Traite des Maladies Chirurgicales et des Operation” (A Treatise on Surgical Diseases and their Operations” This last book was published posthumously in 1774. He also published a monograph on hemorrhage, another on lachrymal fistula, and others.

He was one of the first to perform choIecystotomy and mastoidotomy. His original tourniquet design for amputations saved many in the battlefield and the design of the same surgical instrument today has not changed much since its invention by him.

His name is remembered in the lumbar triangle, also called the "triangle of Petit", and the abdominal hernia that can ensue through that area of weakness, the lumbar hernia or "Petit's hernia".

Sources:
1. “Jean Louis Petit – A Sketch of his Life, Character, and Writings” Hayne, AP San Fran Western Lancet 1875 4: 446-454
2. “Oeuvres compl?tes de Jean-Louis Petit” 1837 Imprimerie de F. Chapoulaud
3. Extraits de l'eloge de Jean-Louis Petit Ius dans Ia seance publique de I' Academie royale de chirurgie du 26 mai 1750” Louis A. Chirurgie 2001: 126 : 475- 81

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Pedicle

Published: Thursday, July 30, 2015 07:00 | Written by: Efrain A. Miranda, Ph.D. | Hits: 4646

[UPDATED] The word [pedicle] is a derivative from the Latin [pediculus] meaning “a small foot”, a “stem”, or a “stalk”. The Latin term [pediculus] is itself a derivative of [pes/pedis] meaning “foot”.

[Pedicle] is also used to denote structures that lie at the root of “foot” of an organ, as in the “renal pedicle” (an older anatomical term) or in the pedicle of a sessile tumor. It is also used in surgery, to denote the vascular pedicle or “stalk” of a free tissue graft.

Since a pedicle is also the “foot” of an arch, the term has also been used to denote the base of the vertebral arch. Thus explained, each vertebra has bilateral bony bridges between the vertebral body anteriorly and the laminae posteriorly. These are the vertebral pedicles, which form the lateral walls of the vertebral canal.

The vertebral pedicles have different characteristics (width, length, angulation) depending on their vertebral level. This is important for spine surgery where pedicle screws are used:

• Lumbar vertebra: has a thicker, wider pedicle that tends to angulate posterolaterally
• Thoracic vertebra: has a thinner pedicle that looks almost anteroposteriorly
• Cervical vertebra: the pedicle is very small and thin, angles quite laterally, and forms the medial border of the transverse foramina.

The accompanying image is an inferior view of a thoracic vertebra showing the location of the vertebral pedicles. Click on the image for a larger version.

Additional information: “Vertebral pedicle anatomy in relation to pedicle screw fixation: a cadaver study” Chaynes et al. Surg Rad Anat (2001) 23:2, 85-90
Image property of:CAA.Inc.. Photographer:D.M. Klein.

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