Causes / typical injury mechanism: Köhler disease was first described by Alban Köhler in 1908 as avascular necrosis of the navicular bone of the foot. It is an idiopathic, self-limiting compression and subsequent avascular necrosis of the watershed area of the navicular bone, which is particularly consequential if it happens before ossification is complete. It primarily affects the pediatric population as they increase in stature and weight. Additional suggested etiologies include infection, inflammation, endocrine imbalance, and lack of nutrition.

Classic history and presentation: Köhler disease is typically unilateral; however, it can present bilaterally in up to 25% of cases. Children will present with a history of gradually worsening medial-sided foot pain, swelling of the dorsomedial foot, and/or a limp.

Prevalence:

• Age – Usual onset is between ages 4 and 7 years, but some individuals have presented as early as age 2 years.
• Sex / gender – Mainly males (80%); Köhler disease is 5 times more likely to affect males than females.

Pathophysiology: The pathophysiology is related to mechanical consequences of delayed ossification of the navicular bone, as it is the last to ossify, after the talus and cuneiforms that border the navicular bone. As children grow, the navicular bone is compressed between the talus and cuneiform bones. The blood supply (perichondral ring of blood vessels) is compressed, leading to ischemia (lack of blood supply) to the bone and eventually avascular necrosis (death of bone secondary to lack of blood supply) to the trabecular bone. Despite the lack of direct blood supply, individuals with Köhler disease fare well because of the radial distribution of vasculature.

The navicular bone has dual blood supply, with a branch of the dorsalis pedis artery supplying the dorsal aspect of the bone and the medial plantar branch of the posterior tibial artery supplying the plantar aspect of the bone. These two blood supplies branch and then supply the medial and lateral thirds of the navicular bone. The central portion of the bone is thus avascularized, relying on supply from the vascular foramina, which are found on the dorsal, plantar, medial, and lateral surfaces of the navicular bone. The idea is that compression of the vascular foramina during ossification of the adjacent bones leads to decreased blood flow and potential avascular necrosis of the navicular bone.

Ossification of the navicular bone is complete between ages 18 and 24 months in females and between ages 30 and 36 months in males. The delayed ossification of this bone lends itself to the belief that it is weaker than other tarsal bones.