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BMSc - mine > Rami's Paper > Flashcards

Rami's Paper Flashcards

1
Q

What is biomechanics?

A

The study of normal mechanics (kinetics and kinematics) of the musculoskeletal system

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2
Q

During the stance phase of gait, what impact should the lower extremity have on the forces involved?

A

It should distribute and dissipate compressive, tensile, shearing, and rotatory forces. Inadequate distribution of these forces can lead to abnormal movement, which in turn produces excessive stress which can result in the breakdown of soft tissue and muscle

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3
Q

How many bones and joints does the foot contain?

A

26 bones (7 tarsals, 5 metatarsals, and 14 phalanges) and 6 joints (ankle, subtalar, midtarsal, tarsometatarsal, metatarsophalangeal (MTP), and interphalangeal (IP) joints). These make up the 4 segments of the foot - hindfoot, midfoot, forefoot and the phalanges

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4
Q

What bones are in the hindfoot?

A

Talus and calcaneus

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5
Q

What is the function of the talus?

A

The 3 parts of the talus (body, neck and head) are orientated to transmit reactive forces from the foot through the ankle joint to the leg. Lying between the calcaneus and tibia, it communicates thrust from one to the other

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6
Q

What is the function of the calcaneus?

A

Located as the most posterior bone in the foot, it provides a lever arm for the insertion of the Achilles tendon, which is one of the largest and most powerful tendons in the body. Through it, the gastrocnemius and soleus impart powerful plantarflexion forces to the foot

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7
Q

What bones are in the midfoot?

A

Navicular, the cuboid and the 3 cuneiforms make up the midfoot

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8
Q

What are the articulations of the navicular bone?

A

The navicular is medial to the cuboid and articulates with the head of the talus proximally and the 3 cuneiforms distally. It is the key stone at the top of the medial longitudinal arch

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9
Q

What does the cuboid bone articulate with?

A

The calcaneus proximally and the 4th and 5th metatarsals distally

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10
Q

What is the shape of the 3 cuneiforms?

A

The 3 cuneiforms are convexly shaped on their broad dorsal aspect whilst the plantar surface is concave and wedge shaped so that the apex of each bone points inferiorly. They articulate with the 1st-3rd metatarsals and the navicular

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11
Q

What bones make up the forefoot?

A

The 5 metatarsals make up the forefoot

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12
Q

What does the first metatarsal articulate with?

A

It articulates with the 1st phalange distally and the medial cuneiform proximally. It is the shortest and widest of the metatarsals. Its base that articulates proximally is somewhat cone shaped. Additionally, the head of the first metatarsal articulates with 2 sesamoids on its plantar articular surface

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13
Q

Why is the 2nd metatarsal the most stable?

A

The 2nd metatarsal extends beyond the 1st proximally and articulates with the intermediate cuneiform as well as the medial and lateral ones to form a “key-like” configuration. This renders it the stiffest and most stable part of the foot, making it key in stabilising foot posture after hallux surgery

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14
Q

What is the shape of the 3rd-5th metatarsals? What is different about the shape of the 5th?

A

They are broad at the base, narrow at the shaft and have dome-shaped heads. The 5th has a prominent styloid, laterally and proximally at its base, on which the peroneus brevis tendon inserts

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15
Q

What can commonly lead to avulsion fractures of the styloid?

A

Avulsion fractures of the styloid commonly occur when the foot is inverted against the contracted peroneus brevis muscle

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16
Q

What is the shape of the proximal and middle phalanges?

A

They have trochlear shaped heads which allow for greater stability

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17
Q

Function of the phalanges?

A

Contribute to weight bearing and load distribution and also effect propulsion during the push-off phase of gait

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18
Q

When is the foot considered to be supinated?

A

When it is simultaneously adducted, inverted and plantarflexed. Opposite for pronated

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19
Q

How many planes of motion do each of the joints of the foot have?

A

The midtarsal, MTP and IP joints have 2 planes of motion (Dorsiflexion-Plantarflexion and Adduction-Abduction).
The others all have 1 plane of motion

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20
Q

Plane of motion of the ankle joint?

A

The ankle joint is the articulation between the distal tibia and the talus body. It permits dorsiflexion-plantarflexion of the foot around its axis of motion which passes obliquely from lateral-plantar-posterior to medial-dorsal-anterior

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21
Q

What is the minimum range of ankle joint motion required for normal locomotion?

A

10 degrees of dorsiflexion and 20 of plantarflexion

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22
Q

What is the composite joints that make up the subtalar joint?

A

The talocalcaneal joint and the talocalcaneal part of the talocalcaneonavicular joint

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23
Q

What is the axis of motion of the subtalar joint?

A

It passes through the joint obliquely at 42 degrees from the Transverse plane and 16 form the Sp. These motions occur simultaneously

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24
Q

What are the normal motions exhibited by the subtalar joint?

A

Supination and pronation

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25
Q

What joints make up the midtarsal joint?

A

The talonavicular and the calcaneocuboid joints

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26
Q

How many axes of motion does the midtarsal joint have? What types of motion are a result of this joint?

A
  1. A longitudinal (calcaneocuboid) and an oblique one (talonavicular). Because they are at an angle to the 3 planes, supination and pronation result
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27
Q

Most of the tarsometatarsal joints are limited in motion. Which one is the exception to this?

A

Between the 1st MT and the medial cuneiform

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28
Q

How do the MTs fit in the phalanges at the MTPs? What is the ROM of the MTPs like?

A

The rounded heads of the MTs are located in the shallow cavities of the phalanges. Up to 90 degrees of extension is possible in these joints, but only a few degrees of flexion

29
Q

What allows the foot to function as a support and a lever to propel the body during locomotion on nearly any type of surface?

A

It is made possible by a series of bony longitudinal and transverse arches (TAs), maintained by ligaments and muscles

30
Q

What does the medial arch comprise of?

A

The calcaneus, talus, 3 cuneiforms, navicular and 1st-3rd MTs. The pillars of the arch are the tuberosity of the calcaneus posteriorly and the heads of the medial 3 MTs anteriorly

31
Q

What does the lateral arch comprise of?

A

The calcaneus, cuboid and the 2 lateral MTs

32
Q

Which of the two arches is more flexible?

A

The MA and LA are relatively rigid in standing and loosen off in walking. The MA is the more flexible of the two

33
Q

Where are the TAs?

A

A series of TAs exist around the MTP joints. They tend to flatten out during weight bearing

34
Q

How can the muscles of the foot be divided into extrinsic and intrinsic?

A

Extrinsic - arise from lower leg

Intrinsic - arise from within the foot itself

35
Q

The muscles can also be divided into dorsal and plantar groups. What functions are carried out during locomotion by the muscles of the lower limb?

A

All the muscles of the lower limb are actively providing stability and balance during standing and a strong lever arm effect during propulsion

36
Q

How is kinematics studied?

A

Kinematics is related to the measurement of motion irrespective of the forces involved using cine/cameras to observe the inter-segmental relationship of the trunk and the limbs

37
Q

How is kineics studied?

A

Kinetics concentrates on the study of forces associated with motion using force plates, pressure platforms and/or in-shoe sensors providing a direct description/orientation of foot posture

38
Q

What is one full gait cycle (GC) referred to in gait analysis?

A

The time interval between two consecutive heel strikes of the same foot on the ground. This time interval is known as the stride time

39
Q

What % of the gait cycle is taken by the stance phase and what by the swing phase?

A

Stance phase - 60%

Swing phase - 40%

40
Q

What is the term used when both feet are in contact with the ground during the GC?

A

Double support period

41
Q

What are the stages of the GC e.g. for the right side?

A

All right foot:

Heel strike
Forefoot loading
Midstance
Heel off
Toe off
42
Q

How is the ground reaction force countered and controlled?

A

The GRF is countered and controlled by the function of the lower limb muscles which, in conjunction with the bones, joints and tendons of the foot, controls the kinematic and kinetic progression of the foot with the ground

43
Q

For a very short period at and after heel strike (HS), known as the transient period, the GRF is anterior to both the ankle and the knee. How long does this last?

A

10-20ms

44
Q

After the transient period, where does the GRF change location to? What does this create?

A

A location posterior to both the knee and ankle joints which creates an external plantarflexion moment around the ankle joint

45
Q

At this instant, the tibialis anterior, with assistance from the extensor hallucis longus muscle, contracts eccentrically. What moment does this produce?

A

It produces an internal dorsiflexion moment which decelerates the rate of ankle joint plantarflexion

NB: Late firing of the tibialis anterior in diabetics leads to forefoot slap

46
Q

What does the combined synergistic action of these two muscle groups allow?

A

It allows the foot to passively plantarflex in a smooth, regulated manner, such that ankle joint plantarflexion is virtually stopped synchronously with forefoot contacting the ground

47
Q

During the initial movement of the forefoot, which side is the only one to make contact with the ground?

A

The lateral side of the forefoot

48
Q

As weight is transferred to the forefoot, what impact does this have on the tibialis anterior?

A

It is relaxed by the GRF acting on the lateral side of the forefoot, everting the foot. This controlled relaxation of the tibialis anterior facilitates smooth progressive loading of the forefoot from lateral to medial locations

49
Q

Once the tibialis anterior relaxes, and the GRF everts the foot so that full foot contact is achieved, what occurs?

A

The loading of the forefoot is transferred from the lateral to the medial side

50
Q

When do the tibialis posterior, gastrocnemius and soleus contract and what does this contraction cause?

A

After HS and before forefoot contact, they begin to contract. These muscles, which function to collectively decelerate subtalar joint pronation and internal leg rotation continue to contract through the MS phase and relax at HO or very shortly thereafter

51
Q

What happens to the GRF during MS?

A

It begins to move anteriorly along the foot, becoming small and reversing in direction to point anteriorly. GRF is still posterior to the knee but is now anterior to the ankle joint

52
Q

At the beginning of the MS phase, the posterior calf muscle become prime movers which initiates what?

A

Subtalar supination and external leg rotation. Both the tibialis posterior and the soleus have attachments which create significant lever arms relative to the axis of motion of the subtalar joint

53
Q

Foot goes from plantar flexed to neutral to dorsiflexed over the course of the MS phase until the point of HO. Deceleration of tibial momentum also extends the knee in preparation for HO. What muscles are involved in decelerating the tibia’s forward momentum?

A

Those that have significant lever arms for ankle joint plantarflexion - tibialis posterior, soleus, and flexor digitorum longus, with also some late assistance form the peroneus longus

54
Q

In early MS, what muscles stabilise the bones of the lesser tarsus?

A

Soleus, tibialis posterior, peroneus longus and peroneus brevis. The soleus maintains the Sp stability of the cuboid in order to serve as an effective pulley for the function of the peroneus longus. The peroneus longus pulls laterally against the lesser tarsus, whilst the tibialis posterior pulls the lesser tarsal bones medially. Collectively, these opposing actions serve to compress the lesser tarsus in the Tp, thus producing medio-lateral stability

55
Q

What is peroneal spastic flatfoot?

A

In disorders such as cerebral palsy, the entire foot may be pronated into a flat foot position

56
Q

Where is the GRF at HO?

A

Anterior to both ankle and knee joints

57
Q

The GRF anterior to both joints creates an external dorsiflexion moment. How is this balanced?

A

It is opposed by the soleus and gastrocnemius muscles. The peak activity of these muscles coincides with when the peak external moment occurs - just after HO

58
Q

What is the main function of the intrinsic muscles of the foot during the second half of the MS phase?

A

Providing tensile forces necessary to stabilise the bones of the metatarsus and lesser tarsus transversely and posteriorly against one another.
Economy of intrinsic muscle of the foot depends on supination of the foot

59
Q

How does heel rise occur?

A

HR results from the interaction between forward momentum of the body, deceleration of the tibia and passive knee flexion

60
Q

What muscles are responsible for tibial deceleration at this stage?

A

Tibialis posterior, soleus, gastrocnemius, with later assistance from the flexor digitorum longus and peroneus longus

61
Q

What does the gastrocnemius do just before commencement of heel rise?

A

It contracts to halt knee extension and begins to flex it

62
Q

Ankle joint movement during the propulsion phase?

A

It initially dorsiflexes before plantarflexing until TO. The soleus, gastrocnemius, peroneus longus and tibialis posterior all contribute to plantarflexion

63
Q

The final stage of propulsion occurs in the big toe. What two muscles are primarily involved in propulsion at this stage?

A

Peroneus longus and brevis

64
Q

How many degrees must the hallux be able to dorsiflex by on the 1st MT?

A

65-70

65
Q

Where is the GRF just prior to TO?

A

Anterior to the ankle but posterior to the knee joint

66
Q

What action does the tibialis anterior have immediately before TO until the mid-swing phase?

A

It contracts to dorsiflex the foot, allowing clearance of the foot from the ground

67
Q

What type of fracture can occur if there is a compressive axial force down into the ankle joint?

A

Pilon fracture - Tibial plafond fracture

68
Q

If the force involves less axial load and more rotation movement of the talus, what fracture occurs?

A

Malleolar fractures

BMSc - mine (13 decks)

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