LEA: Accessory Bone Conference
Terms in this set (26)
what qualifies as an accessory bone
1. sesamoid bone
2. Developmental division of one bone into two smaller ossicles
3. a bone formed from an additional ossification center
what can help you determine whether a bone is an accessory bone or a fracture
x-ray the other foot. Accessory bones can be bilateral, whereas fractures usually are not
characteristics of a sesamoid bone
1. within the substance of a tendon
2. one surface is articualr
3. enclosed in joint capsule
purpose of sesamoid bone
1. protects tendon by reducing pressure and supporting blood supply
2. lifts tendon away form underlying bone and can create mechanical advantage
do sesamoids always show up on x ray
not all ossifty but can present as completely or partially cartilaginous or fibrous. So yes
lateral and medial sesamoid of flexor hallucis brevis tendon.
These are located on the planter surface of the head of the MT 1.
when do the constant sesamoids of MT 1 ossify
10-12 years old
how do you tell the difference, radiographically, between a bipartite and fractured sesamoid
bipartite portions are uneven in size and the portions have rounded edges
a fractured sesamoid has portions even in size which have jagged edges
which sesamoid of the MT 1 is more likely to be bipartite
common sesamoid embedded in fibularis longus tendon (peroneus longus).
It is located in peroneal notch of cuboid
what are some variations to the os peroneum
can be bipartite os peroneum.
can be multicentric os peroneum (three portions).
Os trigonum (talus accessorius)
Sesamoid in 2-8% of population.
the lateral tubercle of the posterior process of the talus.
Os Tibiale externum (os naviculare accessorium)
sesamoid found in 3-12 % of the population
accessory bone on the dorsum of the foot in 1% of population. It is found in a fossa at the union of the medial and intermediate cuneiforms.
Os talonaviculare dorsale/ supranaviculare/ Pirie's Bone
accessory bone on dorsum of the foot of 11-15% of poplulation.
Found between the navicular and head of talus at the midpoint of the articulation between the two bones.
Os Intermetatarsal I
accessory bone on the dorsum of the foot.
Found between MT 1, MT 2, and the medial cuneiform
1-10% of population
Os Calcaneus secondarius
accessory bone on the lateral/dorsal surface of the foot
found at junction of navicular, talus, calcaneus, and cuboid in 2-11% of population
lies just anterior to the sustentaculum tali
believed to be associated with the rare calcaneonavicualr bar or coalition
Os vesalianum pedis
accessory bone on the lateral surface of the foot
just proximal to the MT 5 tuberosity / styloid process
accessory bone of the medial surface of the foot in 2-3% of population
located on the posterior aspect of sustentaculum tali, usually fused to it.
often related to a bar (coalition) spanning the talocalcaneal joint
accessory bone of the medial surface of the foot.
On medial side of talus posterior process
Pars peronea metatarsalis I
accessory bone on the plantar surface of the foot
Located between MT 1 and medial cuneiform
rare. Fibularis longus tendon
Os cuboides secondarius
accessory bone on the plantar surface of the foot in 2-11%
located between the navicular and cuboid
if fused, more commonly to navicular
articulates with talus
Typical pattern of weight distribution in the human foot during walking
ititial contact, foot flat, heel off, toe off
Initial contact: touch down is usually on lateral margin of heel
foot flat: contact proceeds to MT 5 followed by the medial MTs and lastly the lateral toes and hallux
heel off: the heel is the first to leave the ground followed by MT 5 and other MTs
Toe off: Hallux or second digit is the last to leave the ground
If pressure at initial contact from stepping off curb and touching down on a plantarflexed and inverted foot what occurs
if during foot flat to heel off: repetitive and high magnitude force placed on the metatarsals (military marching)
MT stress/march fractures, also Jones fracture
if during heel off to toe off : greater than 50% of body weight is transmitted through MTPJ 1 Joint. What bones are especially susceptible to injury