What Are They, Causes, and More
Author: Corinne Tarantino, MPH
Editors: Alyssa Haag, Józia McGowan, DO, FACOI, FNAOME, CS
Illustrator: Jillian Dunbar
Copyeditor: Joy Mapes
What are saber shins?
Saber shins are a deformity of the tibia, the bone located in the front of the lower leg. In saber shins, the tibial bone has a pronounced anterior bowing (i.e., bends forward), so the shape of the lower leg resembles a saber, a sword with a curved blade. Saber shins are most frequently described as a symptom of congenital syphilis; however, they may also indicate other diseases, such as rickets.
What causes saber shins?
Congenital syphilis is one source of saber shins. Syphilis is a bacterial infection caused by the bacterium Treponema pallidum, and congenital syphilis is passed from a pregnant individual who has untreated syphilis to their fetus. When an infant is born with syphilis, the infection may spread throughout their body. As bones continue to grow throughout childhood, the infection may alter the bone growth in the tibia, thereby causing saber shins.
Rickets, the softening and weakening of the bones in childhood, is another cause of saber shins. Rickets is a result of prolonged vitamin D deficiency, most often due to lack of exposure to sunlight or foods containing vitamin D (e.g., fish, milk), and it can lead to impaired or abnormal bone growth.
What are the signs and symptoms associated with saber shins?
Saber shins may be associated with other symptoms of congenital syphilis or rickets. Early symptoms of congenital syphilis include runny nose, canker sores in the mouth, tenderness of the bones, and yellowing of skin and eyes (i.e., jaundice). After one year of age, symptoms may include deafness, as well as joint pain and swelling. When symptoms present after the child turns two years old (i.e., late-onset congenital syphilis), symptoms may include Hutchinson’s teeth, which are small, spaced apart, and may have an uneven shape; “mulberry” molars, which feature rounded cusps or bumps on the chewing surface; saddle nose, in which the nasal bridge collapses in; saber shins; and additional characteristic symptoms.
How are saber shins diagnosed and treated?
Saber shins are often diagnosed through a clinical examination, including review of the child’s symptoms and the gestational parent’s medical history. Following the clinical exam, blood tests are often conducted in order to diagnose the underlying cause. Blood tests typically include an assessment of the individual’s vitamin D levels and presence of syphilis antibodies. X-ray imaging can confirm the presence of saber shins and assess for any changes in bone density. Occasionally, a lumbar puncture, in which a needle is inserted into the spinal column to retrieve cerebrospinal fluid, is performed to confirm the presence of T. pallidum.
Saber shins caused by syphilis are treated with penicillin G, an antibiotic. Penicillin G is typically administered as an injection into the shoulder muscle of children with congenital syphilis who are at least two years old. Rickets is treated with vitamin D supplements, often accompanied by calcium supplements.
Saber shins can be prevented by testing pregnant individuals for syphilis early in their pregnancy and treating indicated syphilis infections accordingly.
What are the most important facts to know about saber shins?
Saber shins are a malformation of the tibia that presents with anterior bowing of the tibia, usually caused by congenital syphilis or rickets. If caused by syphilis, saber shins typically appear along with other symptoms of syphilis, such as Hutchinson’s teeth and mulberry molars. If caused by rickets, saber shins may be accompanied by additional bone deformities, like thick wrists and ankles. Diagnosis generally involves a clinical examination, blood tests, and an X-Ray. Injection of penicillin G into the shoulder muscle is the typical treatment for congenital syphilis, while vitamin D supplementation is needed to treat rickets.
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Resources for research and reference
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Bringhurst, F., Demay, M. B., & Kronenberg, H. M. (2018). Bone and mineral metabolism in health and disease. In J. L. Jameson, A. Fauci, D. Kasper, S. Hauser, D. Longo, & J. Loscalzo (Eds.), Harrison's principles of internal medicine (20th ed.). McGraw-Hill.
Fitzgerald, P. A. (2021). Rickets & osteomalacia. In M. Papadakis, S. McPhee, & M. Rabow (Eds.), Current medical diagnosis & treatment 2021. McGraw-Hill.
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