Windlass, Hallux Valgus and structural adaptation of the musculoskeletal system

Question 1

What is Halux Valgus

Answer 1

Hallux Valgus is a progressive condition affecting the First Metatarsophalangeal joint. It can be described as a Lateral devation of the Hallux and a medial devation of the first MTP joint (Abduction of the first metatarsal and adduction of the first phalanx.

Question 2

What is the hallux abducts angle

Answer 2

The Hallux abducts angle refers to the angle between the long axes of the first metatarsal and the Proximal phalanx. an angle of 15 degrees or less tends to be asymptamatic but an increase above 15 degrees can result in pain and discomfort.

Question 3

Describe the reverse windlass mechanism

Answer 3

The reverese windlass mechanism refers to flexeion of the mtp joint which unwinds the Plantar Aponeurosis from around the Metatarsal Heads and lowers the longitudinal arch.

Question 4

Explain the association with the reverse windlass mechanism and the gait cycle

Answer 4

The reverse windlass mechanism is a feature of the loading and the single support phase of the gait cycle (Heel strike to foot flat) The rearfoot complex normally pronates which unwinds the PA and lowers the longitudinal arch. This is associated with extension of the miditarsal joint (unlocking the miditarsal)

During Flat foot position ternsion in the PA exerts a flexor moment on the proximal phalanges (pushes pads of the toes against the ground) reducing the pressure on the plantar surfaces of the heads of the metatarsals.

Question 5

Explain the association with the windlass mechanism and the gait cycle

Answer 5

• The Windlass mechanism is a feature of push off in the gait cycle (Heel off to toe off)
• Rearfoot complex supinates (rotate inward) in association with extension of the MTP Joints
• This action raises the longitudinal arch stabalising the foot giving a firm base for push off
• Windlass is associated with flexion of the miditarsal ( locking of the miditarasl joint)

Question 6

What is the arch spring

Answer 6

Arch spring can be described as the arch spanning ligaments that store elastic energy during compression and return it in recoil

Question 7

Describe what happens during prolonged increase of the Hallux Abductus angle

Answer 7

• Displace the line of action of the PA and intrinsic and extrinsic muscles that cross the first MTP Joint
• Displace the seasmoid bones laterally resulting in increased force on the muscles supporting the arch during push off (decreasing the leverage of the windlass)
• Prolonged excessive pressure on the articular surfaces can result in osteoarthritis

Question 8

Explain what structural adaptation of the Musculoskeletal system is

Answer 8

Structural adaptation of the musculoskeletal system referes to the changes and adaptations whcihn take place in the body’s external form (size and shape) and internal architecture (structure) when forces are excreted upon them.

Question 9

Explain Wolf’s Law in regards to structural adaptation of the bone

Answer 9

Wolf Hypothosised that the bone will remodel itself over a period of time when time averaged loads are placed upon it. Internal architecture undergoes adavptive changes folowed by secondary changes to external cortical portion of the bone.

Adaptation to time averaged load is referred to as modelling

Question 10

What is Chondral Modelling

Answer 10

Chondral modeling is a theory which argues that the rate and amount of new bone formed by hyaline cartlidge depends on the amount and kind of load exreted on it

Question 11

What is meant by the term Joint Congruence

Answer 11

The term refers to a visual inspection of how artiucular surfaces mate each other, evaluating the joint capability to distribute an applied load from a purely geometrical stand point