23 - Abnormal Subtalar Joint

Question 1

STJ axis is comprised of movement in the…

Answer 1

o Sagittal Plane (very little motion occurs here)
o **Transverse Plane (MOST of motion)
o **Frontal Plane (MOST of motion)

NOTE: Due to the anatomical position of the axis, very little NORMAL movement occurs in the sagittal plane

Question 2

Normal position of STJ axis

Answer 2

o 16° from the sagittal plane
o 42° from the transverse plane
o 48° from the frontal plane

Question 3

Describe the position of the STJ axis in the sagittal plane

Answer 3

• Uses longitudinal axis of foot which passes through 2nd met
• Ends just medial to 2nd metatarsal in the 1st interspace
• Begins proximally at lateral posterior aspect of calcaneus

Question 4

Angular deviations of the STJ axis

Answer 4

• We are only able to accurately describe TWO angular deviations of teh STJ axis
  o Sagittal plane deviations
  o Transverse plane deviations
  o Usually both sagittal plane and transverse plane deviations exist in same foot

NOTE: this is not the same as identifying how much movement occurs in each plane

Question 5

What motion arises from sagittal and transverse plane deviations of the STJ axis?

Answer 5

• This gives us movement primarily in two planes – frontal plane (inversion/eversion of STJ) and transverse plane (abduction/adduction of STJ)

Question 6

What 3 forces act on the position of the STJ axis during weightbearing?

Answer 6

• Proximal forces
• Distal forces
• Intrinsic/extrinsic muscle forces

Question 7

Proximal forces

Answer 7

Proximal forces act on the talus through movements of the leg.
o Internal rotation of the leg causes the STJ to pronate (due to talar adduction)
o External rotation of the leg causes the STJ to supinate (due to talus abduction)
o As leg rotates, it pulls the talus with it, causing STJ pronation or supination

Question 8

Distal forces

Answer 8

Distal forces act on the talus through movement and position/shape of the calcaneus (ground reactive forces)

Question 9

Intrinisic and extrinsic muscle forces

Answer 9

Intrinsic and extrinsic muscle function of the foot also determine position of STJ

Question 10

STJ pitch

Answer 10

• STJ Pitch = the location from the transverse plane
• Normal pitch ranges from 35-45° (42° is the average value)
• Above normal = high pitch, below normal = low pitch

Question 11

The more vertical the STJ axis is…

Answer 11

o Less STJ inversion and eversion in response to rotation of the leg
o More abduction and adduction of the foot in response to internal and external rotation of the leg
o More postural and leg complaints

Notes

• The more vertical the STJ axis (the higher the pitch), the more motion (abduction/adduction) occurs in the horizontal or transverse plane
• The more horizontal the STJ axis (the lower the pitch), the more motion occurs in the frontal plane
• Notice that motion is occurring in either the transverse or frontal plane, NOT sagittal - VERY little sagittal plane motion (dorsiflexion, plantarflexion)

Question 12

What determines the pitch of the STJ?

Answer 12

The most important factor is the anatomical shape of the facets in the subtalar joint

Therefore, changes in the arrangement and shape of the STJ will result in changes of the STJ axis from normal and lead to different positions of the foot on the floor
o E.g.: a foot with a more vertical axis to the STJ, will have a chance for more adduction/abduction of the foot; while a foot with a lower axis will have a chance for more inversion/eversion of the foot

Question 13

Bruckner theory

Answer 13

• A man named Bruckner realized that the pitch of the STJ is
  determined by the anatomical shape of the facets of the STJ
• He found that there were 4 basic arrangements of the
  facets of the subtalar joint
• The arrangement of the facets dictates the shape of the
  STJ and therefore the type of motion it will have (high pitch
  vs low pitch)

Question 14

How can we determine whether STJ axis is high or low clinically?

Answer 14

With the foot in STJ neutral, a high axis exists if the examiner can move the heel with more adduction/abduction than inversion/eversion

High axis
o Examiner finds MORE transverse plane motion (abduction/adduction) than frontal plane motion (inversion/eversion)
Low axis
o Examiner finds MORE frontal plane motion (inversion/eversion) than transverse plane motion (abduction/adduction)

Question 15

How reliable is determining STJ axis pitch clinically?

Answer 15

VERY SUBJECTIVE AND UNRELIABLE – in theory this works, but not clinically
o This is because the calcaneus will not move much at all, making it difficult to distinguish
o Instead, you would use x-rays to determine the vertical axis (high or low pitch)

Question 16

High pitched STJ axis

Answer 16

Pitch > 42-45 degrees*** KNOW THIS

A high pitched axis allows:
o More abduction/adduction and less inversion/inversion
o Patients will generally relate more medial knee pain than foot complaints
o This is because the foot will want to abduct and adduct more than the knee wants to
o This causes tension on the knee, typically medial knee because there is more adduction

Question 17

Low pitched STJ axis

Answer 17

Pitch

Question 18

Signs and symptoms of a low pitch axis

Answer 18

More foot than knee complaints

Often find a keratoma under 2nd and 3rd metatarsal heads
o The more pressure that is placed under the 1st metatarsal, the more the rearfoot rolls into valgus and the 1st metatarsal moves dorsally due to hypermobility
o If the 1st metatarsal moves dorsally (due to the increased pressure), the more the other metatarsal (2, 3 and 4) bear an increased amount of weight
o This is manifested by the formation of calluses

Medial arch strain

Question 19

Normal transverse plane orientation

Answer 19

16 degrees
- When STJ axis is oriented within normal range (through 1st intermetatarsal space),
more of the weight bearing surface of the calcaneus (rearfoot) is medial to the STJ
axis and the more of the weight bearing surface of the forefoot is lateral to the STJ axis
- This can theoretically test this through the Kirby method (unreliable) of pushing on
foot to try to find points of “balanced soft tissue”

Question 20

Abnormal transverse plane deviation

Answer 20

• The STJ axis can be deviated medially or laterally within the
  transverse plane in relation to the plantar weight bearing
  structures of the foot
• If the STJ axis is deviated medially, you cause STJ pronation
• If the STJ axis is deviated laterally, you cause STJ supination

Question 21

Plotting the STJ axis

Answer 21

Kirby method

• Place STJ in neutral and lock MTJ by stabilizing the 5th metatarsal head
• Palpate for the axis by applying force medial and lateral to the STJ axis
• There will be no rotation when directly on the axis
• This is not typically done on a patient (more theoretical/educational)

Question 22

STUDY: Intra-tester Reliability in Determining the STJ Axis Using the Palpation Technique (Kirby Method)

Answer 22

High intra-tester precision was found for determining the axis location
o The same clinician repeating the measurement does get consistent results

However, classification of the spatial position of the axis has large inter-tester variation
o There is tremendous variability between different clinicians examining the same patient

Question 23

Medially deviated STJ axis

Answer 23

• STJ axis is considered medially displaced if the axis is noted
  to lie medial to the 1st intermetatarsal space
• This is important because the foot will lose some of its
  supinatory torques from the calcaneus and gain additional
  pronatory torque from the forefoot’s longer lever arm on the lateral side of the axis
• The foot appears to be REALLY pronated when the STJ axis is medially deviated

Question 24

Symptoms of medially deviated STJ axis

Answer 24

• STJ pronates to its end ROM [i.e., if the deformity(ies) causes the calcaneus to evert past 3°, the calcaneus will continue to evert until it has used up all of its available STJ eversion]
• Forefoot symptoms, arch fatigue, medial midfoot and rearfoot ligamentous strain
• Pathologies of the lower leg, knee, pelvis and spine

Question 25

Laterally deviated STJ axis

Answer 25

• STJ axis is considered laterally displaced if the axis is noted to lie lateral to the 1st
  intermetatarsal space – the result is that you get a supinated foot (high-arched)
• More lateral foot and ankle pain is common

Question 26

As the STJ axis increases its distance from the transverse plane:
o	More abduction occurs
o	More inversion occurs
o	More transverse plane movement occurs
o	Less transverse plane movement occurs

Answer 26

Answer: 1, 3 – this means a high pitch, which leads to more abduction/adduction (transverse plane motion)

Question 27

A patient exhibits a flatfoot with a transverse plane dominance. Which of the following is/are true?
o The axis of motion lies in the frontal and sagittal planes
o The axis of motion lies in the transverse and sagittal planes
o The STJ is more horizontal
o Forefoot abduction will predominate
o Calcaneal eversion will predominate

Answer 27

Answer: 1, 4 – the axis will always be opposite to the plane the motion occurs in

Question 28

Positional displacement of the calcaneus

Answer 28

Just like STJ axis deviation in either the sagittal or transverse planes, calcaneal position, even with a normal STJ axis, can influence foot position
o Position of the calcaneus is most critical in the stance phase of gait
o It changes the applied force to the STJ axis

Question 29

Normal alignment of tibia, talus, calcaneus

Answer 29

There is a normal alignment of the tibia, talus, and calcaneus
o A line that bisects the longitudinal axis of the tibia will pass through the middle of the talus which is locked in the ankle mortise (tibio-talar unit)
o A line that bisects the middle of the calcaneus will almost always lie lateral to the tibio-talar bisection (called the “calcaneal translational displacement”)

Question 30

Normal calcaneal position

Answer 30

• X-ray – instead of the ankle, get more of the leg as well

- The bisection of the calcaneus should lie lateral to the bisection of the tibia and talus

Question 31

Pathologic calcaneal position

Answer 31

• 5-10 mm is the normal amount of lateral displacement, though this may vary according to the size of the leg and the foot and the location of the STJ axis
• If >10 mm lateral to the bisection of the tibia, then ground force causes the heel to evert (body of the heel is lateral to the STJ axis)
• If medial to the bisection of the tibia, then ground force causes heel to invert (body of the heel is medial to the STJ axis)

Question 32

Flatfoot correction

Answer 32

• One of the options to correct a flatfoot is to transpose the body of the
  calcaneus more medially in order to create a supinatory moment of STJ (This is called the Koutsogiannis osteotomy)
• If the body of the calcaneus is more medial to the STJ, itself, you will
  get supination
• Note that the cut is that you are not near the joint, make sure you are
  far from the STJ joint

Question 33

Koutsogiannis osteotomy notes

Answer 33

o You will make an Incision through skin and cut through the calcaneus.
roughly following the lines of perineal tissue on the back of the heel
o Cut on lateral side because there are fewer vital structures (tarsal canal is medially)
o Expose the lateral calcaneus and cut the calcaneus as shown in diagram
o You then take the posterior fragment and move it medially then fixate it with a screw
o This is a common surgical correction for flatfoot deformity
o This procedure is not utilized very often (if ever) to take the heel and move it laterally if it is situated too far medially – this is not done
o You will alter the motion of the STJ by displacing the calcaneus, but you are not touching the joint itself (too risky)

Question 34

Cavus foot correction

Answer 34

• One of the options to correct a cavus foot is to move the body of the calcaneus more laterally in order to create a pronatory moment of the STJ
• Occurs NOT via a transpositional osteotomy of the calcaneus, but by removing a wedge of bone with the base lateral
• In these cases, calcaneus is also inverted and is determined by measuring
  calcaneal tibial angle (Calcaneal Tibial Angle: normal is between 2° varus to 4° valgus)

The treatment for this is a Dwyer osteotomy
o Take out a wedge of bone
o Get rid of the supinatory force
o Give them more pronatory force

Question 35

Notes on Dwyer osteotomy

Answer 35

o The first (proximal) cut you make is the same cut you would make for a Koutsogiannis osteotomy – the incision for the procedure is the same as the Koutsogiannis as well
o The second (distal) cut you make forms the wedge of bone that you will take out
o Typically pes cavus feet have much more than 2° of varus, so we are attempting to correct the deformity so that the calcaneal tibial angle is between 2° varus and 4° valgus
o Before correcting the deformity, you can see that the majority of the body of the calcaneus is medial to the bisection of the calcaneus
o The goal of the Dwyer osteotomy is the bring that body of the calcaneus lateral so that the calcaneal tibial angle is within the normal range
o This “untwists” the bone, gets rid of a supinatory force by realigning the forces in the STJ

Question 36

Conclusion

Answer 36

Planal dominance is determined by the axis of the subtalar joint
o If the STJ axis lies closer to the horizontal (transverse) and sagittal planes, the deformity is frontal plane dominant and there is more inversion-eversion
o If the STJ axis lies closer to the vertical (frontal) and sagittal planes, the deformity is transverse plane dominant and there is more adduction-abduction
o If the STJ axis lies closer to the frontal and horizontal planes, the deformity is sagittal plane dominant and there is more dorsiflexion-plantarflexion

NOTE: Whatever plane the STJ axis does NOT lie in is the plane of the movement

Question 37

A foot that is pronated will have the body of the calcaneus positioned:
o 5 mm lateral to the tibiotalar bisection
o 5mm medial to the tibiotalar bisection
o 5-10 mm lateral to the tibiotalar bisection
o > 10 mm lateral to the tibiotalar bisection
o > 10 mm medial to the tibiotalar bisection

Answer 37

4

Question 38

Focus

Answer 38

KNOW THE TWO PROCEDURES