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insertion into bone
insertions into bone
70
Anatomy
Graduate
11/07/2013

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Term
how big is the transition of ligament/tendon/capsular tissue into bone?
Definition
<1mm
Term
describe the stress concentration at insertion sites
Definition
stress concentration occurs becase the bone is stronger/stiffer than the soft tissue
Term
what helps to reduce stress concentration at insertion sites?
Definition
transition zones
Term
what are the 2 major types of insertions
Definition
direct, indirect
Term
which type of insertion site is deeper?
Definition
direct insertions
Term
describe direct insertion structure
Definition
has 5 zones of deep fiber groups
Term
describe direct insertion zone I
Definition
tendon/ligament proper, some capillaries and fibroblasts - more cartilage
Term
describe direct insertion zone II
Definition
fibrocartilage, flat fibroblasts and oval chondrocytes with a little more fibrocartilage overall
Term
describe the structure of direct insertion zone III
Definition
mineralized fibrocartilage with tidemark line between zones II and III - mineralized fibrocartilage
Term
describe the structure of direct insertion zone IV
Definition
bone with inserting collagen fibers blending into bone
Term
what is the main component of zone 1
Definition
cartilage
Term
what is the main component of zone 2
Definition
fibrocartilage.
Term
what is the main component of zone 3
Definition
mineralized fibrocartilage.
Term
what is the main component of zone IV
Definition
bone.
Term
what are the 2 transitional zones of direct insertions
Definition
2, 3
Term
in what zones are we unlikely to see failure?
Definition
2, 3
Term
why are ruptures rare in zones 2, 3?
Definition
because the transition is so smooth and amazing
Term
describe indirect insertions
Definition
Superficial collagen fibers blend with the periosteum while some deep fibers go intobone without transitional fibrocartilage zones.
Term
how does the deep osteogenic layer of indirect insertions attach to the bone?
Definition
the deep osteogenic layer attaches to the subperiosteal bone via Sharpey's fibers.
Term
describe Sharpey's fibers
Definition
collagen fibers that originate in periosteum and perforate into subperiosteal bone. They are like nails that come up to anchor the inserting fibers from the soft tissue into the bone
Term
are there any superficial fibers in direct insertion sites?
Definition
yes, there are a few superifical fibers that blend with the periosteum, but most are deep fibers that pass through the 4 zones
Term
what types of attachments tend to have direct insertions?
Definition
proximal attachments of collateral ligaments tend to be direct
Term
what types of attachments tend to have indirect insertions?
Definition
distal attachments of ligaments
Term
are tendon insertions direct or indirect?
Definition
it varies
Term
are the direct insertion's transitional zones vascular or avascular
Definition
avascular
Term
what is the function of ligament/tendon/capsule insertions into bone?
Definition
transmit force from soft tissue to stiff bone without injury from stress concentration
Term
what is the singlemost powerful soft tissue force in the body?
Definition
patellar tendon force
Term
which component of the patellar tendon force puts tensile stress on the ACL?
Definition
anteriorly directed component
Term
how does the ACL elevation angle change as you go through knee flexion to extension?
Definition
when the knee goes into extension, the ACL elevation angle increases to become more vertical
Term
what is the orientation of the trabeculae in the tibial plateau?
Definition
vertical
Term
if you have failure of the ACL in knee flexion, what fails and why?
Definition
the bone fails because the ACL is emitting tensile stress along a line that is not parallel to the trabeculae.
Term
if you have failure of the ACL in knee extension what fails and why?
Definition
ACL; the ACL is pulling more along the line of the collagen fibers in the trabeculae of the bone so the bone is stronger. Also, the line of the pull of the patellar tendon compared to the tibia is greatest when the knee is in extension because they are closest to parallel in this position (the angle is smallest.) Therefore, if there is a lot of force in the patellar tendon, the anteriorly directed component of the patellar tendon is also strong. But in extension, the ACL is vertically oriented and not in a good position to resist the anteriorly directed patellar tendon force. It takes a lot of force from the ACL to match the anteriorly direced component of the patellar tendon force, the ACL will fail.
Term
is the ACL more likely to fail when the quads are contracted and why?
Definition
yes; the quads produce a greater anteriorly directed force of the patellar tendon, which the ACL is not good at resisting
Term
why are girls more at risk for ACL rupture than boys?
Definition
girls land with more extended knees compared to boys. Also, girls patellas are more anterior, increasing the anteriorly directed force of the patellar tendon
Term
how does a faster strain rate affect the location of failure?
Definition
faster strain rates tend to cause mid-substance failures
Term
what area is most likely to fail in general?
Definition
mid-substance failure is more common than avulsion fracture because the bone is generally stronger than the soft tissue
Term
why is it uncommon to see insertion site failures in zones 2 and 3?
Definition
they are effective transition zones in minimizing stress concentration
Term
what are the effects of immobilization on insertion sites?
Definition
decrease in ultimate strength, stiffness, and energy at failure
Term
is bone or ligament more likely to fail after immobilization?
Definition
increased incidence of avulsion ffracture, particularly for indirect insertions because of subperiosteal bone resorption. The bone is the more metabolically reactive tissue. The atrophy will be more pronounced in the bone than in the soft tissue, so the bone is the weak link.
Term
describe remobilization of insertion sites after immobilization
Definition
the return of mechanical properties with remobilization can be very, very, very slow and recovery may never happen
Term
how to introduce movement after immobilization?
Definition
remember that the tissue is weak. Gradually reintroduce to exercise
Term
in the primate study in which primates were immobilized and then encouraged to exercise a lot for a year, what was the effect of exercise on bone after one year?
Definition
the bone was stronger than it had been even before the period of immobilizatoin. There will be fewer avulsion fractures than initially
Term
what are the effects of mobilization on insertion sites?
Definition
psotive effect on mechanical properties, but not as extreme as the negative effects of immobilization. Less demonstrable effects on the histologic apeparance of inserting tissues compared with effects of immobilization
Term
is ligament or insertion site recovery faster following immobilization?
Definition
ligament reovery is faster than insertion site recovery after immobilization
Term
how does age affect insertion sites?
Definition
greater incidence of epiphyseal avulsions if plates are still open, more mid-substance failures once plates close, more avulsion fractures in individuals over 50
Term
describe the epiphyseal avulsion that can occur if plates are still open
Definition
Type I Salter Harris = shearing of epiphysis on metaphysis
Term
what might cause an avulsion fracture in a healthy not old adult?
Definition
strain rate, immobilization, loading direction
Term
why is there a greater incidence of avulsion fractures in individuals over 50?
Definition
bone resorption
Term
what to look for in possible avulsion fracture
Definition
tenderness at the insertion site
Term
what is apophysitis
Definition
chronic inflammatory response at apophyseal growth plate where tendon or ligament attaches to bone.
Term
how to treat apophysitis
Definition
rest, ice NSAIDs. Stop the activity for a while.
Term
what causes apophysitis
Definition
too much magnitude, frequency, duration of tugging of tendon or ligament force
Term
what are common locations of apophysitis
Definition
tibial turbecle, humeral epicondyle, ASIS< AIIS, ischial tuberosity, iliac crest, calcaneus, base of the 5th metatarsal
Term
what is the name of apophysitis of the calcaneus
Definition
Sever's disease
Term
describe apophysitis
Definition
The apophyseal palte region where th pwerful soft tissue inserts becomes inflamed and very, very weak. It's painful, limiting. Can cause avulsion because of weakness and a big force.
Term
what to say to a child/parent/coach who has apophysitis
Definition
the child needs to rest. Can't play. Risk of avulsion.
Term
how might a soccer player with apophysitis get an avulsion of rectus femoris?
Definition
trying to kick ball but catching cleat in the ground: distal end can't move, so the proximal end is ripped from the pelvis
Term
what might cause an ischial tuberosity apophyseal traction fracture?
Definition
young gymnats or other athelte secondary to powerful eccentric activation in hamstring muscles
Term
what muscles's powerful eccentric contraction can case base of 5th metatarsal apophyseal tractionf racture
Definition
fibularis brevis
Term
what is a segond fracture
Definition
apophyseal traction fracture at the tibial insertion of LCL with internal rotation and varus
Term
what to look for in someone with Segond fracture
Definition
associated injuries to ACL and meniscus
Term
What might cause an ASIS apophyseal traction fracture
Definition
sartorius or TFL with foreful trunk rotation to the contralateral side resulting in lateral displacement of the avulsion. Could happen in baseball and hitting the ball. Could be rectus with pwoerful hip flexion such as soccer player who kicks the ground
Term
what is Sinding-Larson-Johannson syndrome
Definition
apophysitis at the inferior pole of the patella. Caused by repetitive jumping and landing
Term
what are predisposing factors for apophyseal traction fractures
Definition
MOI with too much magnitude, duration, frequency
Term
what are histological predisposing factors for apophyseal traction fractures
Definition
histological changes at the insertion site as it transitions from cartilaginous plate to mature bone. Just before this transition, there is a replacement of fibrocartilaginous cells to columnated bone cells. This region has decreased ability to resist tensile stress. If there is also an inflammatory process and weakening of the site, the region is predisposed to a traction/avulsion injury.
Term
what are repair strategies for non-displaced apophyseal traction fractures
Definition
often non-surgical. Reduced activity level. No tugging at all. NWB. Muscles must be totally quiet. Recovery must be gradual over a long period of time.
Term
how to repair a displaced apophyseal traction fracture
Definition
surgery
Term
when a skeletally immature patient has a joint injury, what do you need to do
Definition
rule out epiphyseal infjury
Term
when an older individual has an injury related to inserting tissue, what do you need to do
Definition
rule out avulsion fracture
Term
what to consider for insertion sites following periods of immobility
Definition
slow, progressive return to functional loading
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