The Function of the Midtarsal Joint

1
The Function of the Midtarsal Joint

• J L Tweed BSc
• R J Thompson BSc BA MSc
• Prof J A Campbell
• Dr M J Curran
• The University of Northampton

2
Introduction

• Two axes model (MTJt) joint - theory of
  convenience to explain clinical observation.
• MTJt moves in more complex manner.
• Hypothesised that MTJt - one triplanar axis of
  motion
• How does triplanar motion affect MTJt function in
  gait?
• Implications on podiatric treatment?

3
The Midtarsal Joint

• Combined articulations of TN CC joints.
• Represents the functional articulation between
  the rearfoot midfoot
• Composed of 2 separate anatomic articulations but
  is described as single functional unit.

4
Problems with the Two-Axes Model

• Theory of convenience to explain clinical
  observation?
• Determined using methods that are deemed today to
  be scientifically unacceptable.
• No reliable evidence of the existence of these
  axes.
• Early assessment was cadaver based
• A more accurate explanation of midtarsal joint
  motion has become possible as techniques have
  advanced.

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The Single Triplanar Axis Model

• Nester et al (2002) studied the kinematics of
  MTJt as single functional unit during standing
  leg rotation.
• They described a single instantaneous triplanar
  axis of rotation.
• Over time this axis varies in position
  orientation.

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The Mean Axis of Rotation of the MTJt from the
Transverse Plane
Mean axis of rotation of the midtarsal joint,
reproduced from Nester et al Kinematics of the
Midtarsal Joint during Standing Leg Rotation
JAPMA 92277, 2002
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Similarities Between Motion of TN Joint MTJt

• TN joint has
• Ball socket structure.
• Considerable freedom of movement.
• Triplanar motion similar to that hypothesised for
  MTJt axis.

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Does the STJt Influence MTJt Motion?

• Motion of TN joint could be greater than that of
  STJt during tibial rotation.
• May indicate that MTJt functions independently of
  STJt
• Further research required in this area

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Can the MTJt Pronate?

• Triplanar motion of MTJt could allow for
  pronatory supinatory motion of forefoot on
  rearfoot.
• Van Ghelewe et als (2006) description of
  retrograde, or late phase pronation.
• Clinically can be seen as hypermobile forefoot.

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Conclusion

• Motion at MTJt is triplanar around a single axis.
  
• MTJt axis similar to that approximated to TN Jt.
• Evidence of retrograde pronation-could be
  consistent with pronation at MTJt axis.
• Not yet been established whether motion MTJt is
  independent of STJt.
• Current practise should reflect these new
  theories.

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Implications for practise

• New approach to orthotic and insole therapy?
• Consider midtarsal joint as well as STJt in
  orthotic prescription?
• Full length insoles with forefoot support?

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Thank you
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References

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• Van Gheluwe B et al. Effects of hallux limitus
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