Sesamoid bones – what are they and how do they get injured? By Jackson McCosker
The sesamoids are found under the big toe joint head. Sesamoid injury are responsible for approximately 9% of foot and ankle injuries and 1-2% of running injuries. Sesamoid pain is commonly sesamoids
localised but can be associated with joint aches, sharp stabs or irritating niggles. With respects to medical imaging, plain radiograph is best taken in weight-bearing stance, however a anterio-posterior is capable of illustrating a bipartite sesamoid. CT Scan is capable of helping practitioners diagnose a stress fracture, nonunion or post traumatic changes
The sesamoid complex is responsible for the transition of as little as 50% body weight and more than 300% body weight during propulsion leaving them susceptible to a number of injuries and pathologies including;
Hallux Limitus
Hallux limitus is a functional range of motion pathology secondary to obstruction or destruction of the 1st metatarsal phalangeal joint which significantly affects an individual’s gait and potentially leads to tertiary pathological issues such as bursitis and synovitis. So how does this involve the sesamoids?
It is important to understand that the sesamoids are imbedded within the Flexor Hallucis Brevis tendon which can lead to increased pressures directly upon the first metatarsal if the muscle belly or the tendon itself is taught and restricting extension.
Sesamoiditis
Sesamoiditis is a layman’s term for painful sesamoid associated with overuse/repetitive stress but fail to show changes with medical imaging. Clinically, direct palpation will illicit pain and a patient will present with a plantarflexed first ray or HAV. In the acute stages the use of ice and NSAIDs are advised however, long term results require the use of orthotic devices for anatomical modification or gait changes.
Osteoarthritis
Osteoarthritis of the sesamoid complex is in most cases related to trauma, chronic overuse poor range of motion or secondary to other pathologies related to the first MTPJ. HAV is one of the most common primary range of motion restrictors due to the malformation and misalignments of the joint leading to increased pressures upon the first MTPJ. See here: http://footnotesblogging.com/2015/07/20/osteoarthritis-joint-degeneration/
Nerve Impingement
Both the branches of the medial or lateral plantar nerve can become inflamed for a number of reasons. The medial plantar digital nerve may develop irritation due to restricted range of motion – as discussed earlier or excessive pronation at the mid to forefoot. The lateral plantar nerve is more likely to develop neuritis from the impinging of the fibular sesamoid when enlarged or inflamed leading to displacement.
Sesamoid Fracture
Sesamoid fractures are considered to be high risk whether acute or developed over time from repetitive stress. See:http://footnotesblogging.com/2015/05/07/breaking-bone-an-overview-of-stress-fractures-and-subsequent-management/ for the best information regarding this injury.
Infection
Infection within the sesamoids is rarely seen within healthy patients and more commonly will develop from osteomylitis associated with diabetic wounds. Treatment is aggressive and requires surgical intervention as soon as possible to reduce the risk of further bone infection.
As it can be seen from this brief summary, the sesamoids are important in the propulsion and stabilizing of the human body. These two 4 small bones are responsible for distributing weight evenly and acting as a pully system to increase tension of the Flexor Hallucis Tendon during propulsion of the gait cycle. Due to their high risk status, any injury should be treated seriously as the avascular nature can quickly lead to the development of fracture, necrosis and infection – of course in most health individual the risks is significantly reduced however, best treatment protocols should always be followed.
Article written by our Sports Podiatrist: Jackson McCosker