23 - Abnormal Subtalar Joint Flashcards
STJ axis is comprised of movement in the…
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
Normal position of STJ axis
o 16° from the sagittal plane
o 42° from the transverse plane
o 48° from the frontal plane
Describe the position of the STJ axis in the sagittal plane
- 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
Angular deviations of the STJ axis
- 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
What motion arises from sagittal and transverse plane deviations of the STJ axis?
- This gives us movement primarily in two planes – frontal plane (inversion/eversion of STJ) and transverse plane (abduction/adduction of STJ)
What 3 forces act on the position of the STJ axis during weightbearing?
- Proximal forces
- Distal forces
- Intrinsic/extrinsic muscle forces
Proximal forces
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
Distal forces
Distal forces act on the talus through movement and position/shape of the calcaneus (ground reactive forces)
Intrinisic and extrinsic muscle forces
Intrinsic and extrinsic muscle function of the foot also determine position of STJ
STJ pitch
- 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
The more vertical the STJ axis is…
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)
What determines the pitch of the STJ?
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
Bruckner theory
- 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)
How can we determine whether STJ axis is high or low clinically?
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)
How reliable is determining STJ axis pitch clinically?
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)
High pitched STJ axis
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
Low pitched STJ axis
Pitch
Signs and symptoms of a low pitch axis
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
Normal transverse plane orientation
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”
Abnormal transverse plane deviation
- 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
Plotting the STJ axis
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)
STUDY: Intra-tester Reliability in Determining the STJ Axis Using the Palpation Technique (Kirby Method)
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
Medially deviated STJ axis
- 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
Symptoms of medially deviated STJ axis
- 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
Laterally deviated STJ axis
- 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
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: 1, 3 – this means a high pitch, which leads to more abduction/adduction (transverse plane motion)
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: 1, 4 – the axis will always be opposite to the plane the motion occurs in
Positional displacement of the calcaneus
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
Normal alignment of tibia, talus, calcaneus
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”)
Normal calcaneal position
- 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
Pathologic calcaneal position
- 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)
Flatfoot correction
- 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
Koutsogiannis osteotomy notes
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)
Cavus foot correction
- 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
Notes on Dwyer osteotomy
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
Conclusion
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
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
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Focus
KNOW THE TWO PROCEDURES
