67 and 68 - Flatfoot Surgery I and II Flashcards
Goals
- Distinguish components of clinical and radiographic evaluation of pathologically pronated foot
- Recognize the indications for various conservative and surgical treatments
- Identify level of deformity
- Differentiate the mechanics of corrective osteotomies before attempting to memorize historic names of procedures
Is Pronation Good or Bad?
Depends on if it is physiologic or pathologic pronation
Physiologic Pronation
o Necessary for shock absorption
o Movement is decelerated by muscle function
o Balanced by normal supination through GRF & muscle function based on axis position and orientation
Pathologic Pronation
o Joints, tendons, and ligaments are forced to function beyond their physiologic limits
o Net Result: Subluxation, dislocation, degeneration
o Flexible or Rigid
o Arch may be high, low or average
o Compensation for equinus or other deformities
Triplane movement – Pronation
Open Chain
o Eversion
o Abduction
o Dorsiflexion
Closed Chain
o Eversion
o Internal leg rotation
o Plantar flexion of the hind foot on the forefoot
Pronation
- Starts at heel strike and should end at mid-stance
- Major mechanism of shock absorption
- Muscle activity required to slow pronation
- Inefficient and degenerative if excessive
o Joint subluxation and degeneration
o Tendon degeneration
Pathologic pronation
- Arch height is not the primary determinant o Arch may be high, low or average - Hallmarks of Pathologic Pronation o Progressive subluxation o Soft tissue degeneration o Postural symptoms of foot, ankle, calf, knee, back o Joint degeneration - May be primary o Due to laxity or axis anatomy - Or secondary to compensation for static deformity or kinematic abnormality o MTA o Equinus
Conditions associated with pathologic compensatory pronation
Non structural o Heel pain & Plantar fasciitis o Shin splints o Medial Peri-Tendonitis o Knee pain (Patello-Femoral Syndrome) o Low back pain o Decreased endurance
Structural o HAV & Hammer toes o Mid foot subluxation o Tendinosis / PTTD o Degenerative arthritis o Stress fracture
Over pronation leads to:
- Medial stretching
- Lateral jamming
- Excess muscle energy expenditure
- Joint degeneration
- Secondary deformities
- Increases the demands on the leg muscles, knee, hip and back
Joints moving beyond their physiologic limits
- Left image: normal foot position
- Right image: pronated foot position
Goal of surgery to correct flatfoot
- Achieve rotational equilibrium
Indications for flatfoot correction
- Restore proper biomechanics to the foot and the lower extremity
- Improve stability and function
- Halt progression
- Treat painful symptoms
- To alleviate or prevent structural and non-structural associated conditions
Flatfoot correction options
Posterior Muscle/Tendon Lengthening
o Reduces the pronatory force on the foot
o The foot pronates (dorsilexes at the midfoot) to compensate for the lack of ankle dorsiflexion
Calcaneal Osteotomy
o Realigns the subtalar and midtarsal axis
o Increases the supination force medial to the STJ axis
o Permanently reduces pronation and subluxation
Medial arch reconstruction required if secondary degeneration or tendon rupture has occurred
Correction of secondary deformities
Surgical correction principles
Primary correction
o Changes the axis alignment of the STJ / MTJ complex which results in improved stability and reduces secondary changes
o Removes compensatory forces
Secondary correction
o Repairs structures damaged by the pathologic pronation
Physical exam for flatfoot
Open Kinetic Exam
o Hypermobile STJ/MTJ with subluxation
o Normal muscle strength all groups
o Ankle ROM: DF -15 degrees, PF 50 degrees
Closed kinetic exam o RCSP 9 degrees everted o Medial TN subluxation o Patella internally rotated o Abducted forefoot
Questions regarding flatfoot correction
- In which plane is this foot deformed? All 3 – it is a tri-plane deformity
- How many procedures will be needed to realign the foot? ONE
- Does each plane need to be addressed individually? NO
Rotational equilibrium
- You can figure out the right procedure if you understand rotational equilibrium
- Remove deforming forces (i.e. equinus)
- Move GRF medial relative to effective STJ axis
o Pick the most effective site
o Structural alteration results in multi-plane correction - Treat secondarily degenerative joints and tendons
- Give stability where there is instability
What are the procedure choices?
- Remove the deforming forces
- Change the GRF
What is equinus?
- Limitation of normal ankle dorsiflexion
o Normal forward ambulation requires dorsiflexion at the ankle.
o When adequate ankle motion is not available the foot is subjected to excessive bending forces. (pathologic pronation) - Most common limiting factor in equinus is tight Achilles tendon
- However the block in motion can be at the ankle joint
o More common in cavus foot
Equinus level
- Gastrocnemius
- Gastrocnemius soleus
- Pseudoequinus
- Osseous equinus
- A combination of the above
Anatomy
- Gastrocnemius and Plantaris are 3 joint muscles
o Cross the knee, ankle and subtalar joints - Soleus is a 2 joint muscle
o Crosses only the ankle and subtalar joints - Gastrocnemius aponeurosis lies on the anterior surface of the muscle
- Soleus aponeurosis lies on the posterior surface of the muscle
- Sural nerve and small saphenous vein are vulnerable
Normal biomechanics
- Maximum ankle dorsiflexion occurs at mid-stance just before heel lift (10 degrees is functional)
- Dorsiflexion of the ankle joint is also important for clearance of the ground during swing phase
Equinus biomechanics
- More rapid entrance and exit into and out of mid-stance
- Reduced step length
- Slower walking velocity
- Increased forefoot pressure
- Pronation of foot to obtain required dorsiflexion
Compensatory mechanisms – What if your ankle can’t dorsiflex?
- Forward torso lean
- Pelvic rotation
- Hip Flexion
- Knee hyperextension
- External rotation of leg
- Subtalar pronation
o Unlocks midtarsal joint
o Dorsiflexion of forefoot on rearfoot
How do we test for equinus?
- Must avoid pronation of the foot
o Pronation will give a false indication of available DF by bending at the midfoot - Holding the foot Slightly SUPINATED is the most accurate way to measure
- Knee Extended & Flexed
o Testing gastroc and soleus
Neutral to supinated is most accurate
- Pronation of the foot increases the measured DF by more than 10 degrees
- This DF does not represent ankle movement
Achilles stretching
- Universally recommended
- Can you “stretch” a tendon?
- Systematic Review
o An average of 2.41 degrees of increased dorsiflexion was seen with extensive BID Achilles stretches
o Is this amount of improvement clinically relevant? NO
Gastroc recession technique options
- Position o Prone o Frog leg o Extended Knee Hemi-lithotomy - Incision Approach o Medial o Midline posterior - Level of cuts - Straight release vs. tongue and groove
In a foot that is compensating for equinus, what happens if you correct the valgus heel without correcting the equinus?
- The deformity will come back – the valgus heel will appear again or it will find a way to induce movement and pathology into a different joint
Goal for flatfoot surgery
The goal is to achieve rotational equilibrium of all forces
o Ground reactive forces (GRF)
o Tendon and muscle forces
Evans anterior calcaneal osteotomy indications
- Flexible Pes valgus o Progressive o Painful - No DJD - Younger patients
What does the Evans procedure accomplish?
- KNOW THIS – UNIPLANE procedure induces TRIPLANE correction*
Static anatomic changes o Lengthens the lateral column o Relocates TN joint o Preloads the plantar fascia o Improves Peroneus longus function
STJ axis changes o Lateral shift o Enlarges the supinatory lever arm of GRF - moves FF medial and moves valgus heel more vertical o More effective MTJ locking o Medializes Achilles o Increases supination of TA
Rotational equilibrium
Why does the calcaneus invert and dorsiflex?
- Supination of the mid foot effectively moves the axis of the STJ lateral
- Lateral shift of the STJ axis increases the supination moment across the STJ from GRF
- GRF produces tri-plane movement of the STJ and MTJ (supination)
Triplane correction
- If we alter one planar component of the foot ground reactive force will then act on the foot to move the joints from the new orientation
- Since the joints are tri plane, moving one segment results in correction of the other planar components by ground reactive force
- The surgery changes the rotational equilibrium and therefore the GRF effect
Triplane compensation
Triplane compensation
- Remember the STJ & MTJ are tri-plane joints
- Movement in one plane is accompanied by the other two planar motions
- **Continuously variable axis, therefore… **
- If the heel is everting to compensate for tibial varus, the talus also plantar flexes and adducts (STJ Pronation)
- We see the first planar compensation, we must imagine the other movements and consider their effect on the patients complaint and on correction
Why fixate the osteotomy
- Loss of lateral column length (primary correction)
o Graft collapse
o Calcaneal collapse - Shift of the anterior fragment
o Dorsal, plantar, medial, lateral - Stability
o Early active ROM Improves rehabilitation
STUDY: Does Locking Plate Prevent Length Loss and Displacement?
- Dayton, Feilmeier, Prins, Smith JFAS 2013
- N= 35
- Without plate (12): Average loss - 2.45 mm (0-9mm) @ 6 mo, visible shift 5 = 23%
- With Plate (23): Average loss - 1.0 mm (0-3mm) @ 6 mo, visible shift 1 = 8%
- Main point: without fixation, we are losing a lot of our correction***
Fixated technique
- Longitudinal incision from the cuboid to the lateral malleolus just dorsal and parallel to the peroneal tendons.
- Full thickness sub-periosteal flap raised with the peroneal tendons.
- Osteotomy vertical 1.5-2 cm from cc, parallel to joint
- Graft placed and fixated with locking plate
- Trapezoid-shaped osteotomy
o Linear advancement of the anterior calcaneus - Wedge-shaped osteotomy
o Larger net medial shift of the midfoot
o Cortical contact maintained medial-plantar
Locking plate vs screw
Locking plate
o Load bearing bridge fixation provides the ideal mechanics for inter-positional bone graft
o Multi-planar stability
Screw
o Does not neutralize angular or compressive forces on the graft
Allograft
- Healing is based on new bone formation around the graft and biologic replacement of the graft
- Incorporation???
- Creeping substitution is replacement of the graft with host bone from the edges inward
- This is a long process that takes many months to fully complete
What does the Evans procedure accomplish?
Lengthens the lateral column
o Relocates TN joint
o Preloads the plantar fascia
o Improves Peroneus longus function
Moves the effective STJ axis lateral o Medializes Achilles o Increases supination of TA o Enlarges the supinatory lever arm GRF o More effective MTJ locking o Increased calcaneal inclination o Reduces valgus heel
Posterior calcaneal displacement osteotomy
- Sliding Calcaneal Osteotomy
- Posterior Calcaneus is slid medially to increase the supinatory ground reactive force
o STJ Axis moves lateral - Posterior calcaneus is slid laterally to decrease the supinatory forces across the STJ
o STJ Axis moves medial - Rotational Equilibrium
Cotton
- Dorsal opening wedge Cuneiform osteotomy
- Used to reduce elevated first ray (forefoot varus)
- Adjunctive procedure to calcaneal osteotomy
- Increase GRF medial to the STJ axis by PF first ray
Triple arthrodesis
- Salvage for chronic pain with DJD
- ALWAYS correct the deformity
- Mobilize and prepare all three joints before fixation
- Congruous anatomic joint surfaces are preferable to planar or wedge fusion of surfaces
- Reduction Sequence: Calcaneus, TN then CC
SUMMARY
Physiologic pronation o Normal motion o Necessary for shock absorption o Arch may be high, low or average o No soft tissue or joint morbidity o Responds well to orthotic / shoe therapy
Pathologic pronation
o Arch may be high, low or average
o Progressive subluxation
o Soft tissue degeneration
o Postural symptoms of foot, ankle, distal & proximal LE
o Joint degeneration
o Secondary to equinus, coalition or other
o Corrective treatment desirable before degenerative changes
