59 STG Deformity 2024 PDF

Deforming Forces!! Sean T. Grambart DPM FACFAS Associate Dean of Clinical Affairs, DMU-CPMS Attending, IMMC Foot and Ankle Surgical Residency, Des Moines IA AO Fellow Past-President, ACFAS 1 1 What is “Normal”? 2 3 4 5 In Order to Understand the Abnormal, You Must Identify the Normal… 6 Importance o...

Deforming Forces!! Sean T. Grambart DPM FACFAS Associate Dean of Clinical Affairs, DMU-CPMS Attending, IMMC Foot and Ankle Surgical Residency, Des Moines IA AO Fellow Past-President, ACFAS 1 1 What is “Normal”? 2 3 4 5 In Order to Understand the Abnormal, You Must Identify the Normal… 6 Importance of Radiographs Static evaluation is the basis for surgery Trauma Charcot reconstruction Hindfoot and ankle arthrodesis Flat foot/cavus foot reconstruction Lateral Ankle Instability Long Bone Deformity correction Combined Deformities Preoperative planning Osseous vs. soft tissue deformities Assess for joint laxity and congruity Intra-operative decisions 7 Importance of Radiographs Static evaluation is the basis for surgery 8 Importance of Radiographs Pre-operative planning 9 Importance of Radiographs Osseous versus soft tissue deformities 10 Importance of Radiographs Intra-operative decision making 11 Normal Alignment Calcaneal inclination angle (CIA) is the angle formed by the plantar surface of the calcaneus and the weightbearing surface of the foot (normal, 18° [13–23°]) Navicular height is the perpendicular distance from the floor to the plantar-most portion of the navicular (normal, 4 cm [3–5 cm])M Metatarsal declination angle is the angle formed by the weightbearing surface of the foot and mid-diaphyseal line of the first metatarsal shaft (normal, 23° [20–26°]) The lateral Meary’s angle is formed by the talar neck bisector line and the mid-diaphyseal line of the first metatarsal (normal, 6° [2–10°]) 12 Normal Alignment The tibio-talar angle is the angle formed by the mid-diaphyseal line of the tibia and the line that bisects the talar neck (normal, 68° [64–72°]) The lateral process of the talus should be located along the tibial mid-diaphyseal line (normal, 3 mm anterior [±3 mm from tibial mid-diaphyseal line]) 13 Radiology of the “Normal” Foot 14 Normal Alignment Metatarsal parabola angle is the angle formed by one line connecting the most distal aspect of the first metatarsal and the most distal aspect of the second metatarsal and another line connecting the most distal aspect of the fifth and second metatarsal (normal, 140° [135–145°]) The relationship between the talar bisector line and the mid-diaphyseal line of the first metatarsal is known as the anteroposterior view Meary’s angle (normal, 7° [3–11°]) 15 Radiology of the “Normal” Foot 16 Normal Alignment The center of the talar dome is a bisector line drawn halfway between the medial and lateral aspects of the trochlea of the talus. The center of the talar dome is slightly lateral to the tibial mid-diaphyseal line Plafond malleolar angle (PMA) is the relationship between the tibial plafond and the transmalleolar axis (tip of the medial malleolus to the tip of the lateral malleolus) (normal, 15° [13–17°]) 17 Normal Alignment Tibial-calcaneal distance Hindfoot alignment view (Saltzman view), the calcaneal bisector is 10 mm lateral (6–14 mm lateral) to the tibial mid-diaphyseal line This is called the (Table 2) Shenton’s line of the ankle is a congruent space that exists between the medial talus, medial malleolus, and extends across the tibiotalar joint space to the fibular-talar space The tibial-calcaneal angle is the angle formed by the calcaneal bisector line and the tibial middiaphyseal line (normal, 2° valgus [± 3°] 18 Radiology of the “Normal” Ankle 19 Radiology of the “Normal” Foot 20 Deforming Forces of the Flatfoot 21 Equinus 22 Equinus 23 Pathomechanics Normal Equinus AAFF Inverter Everter 24 Pathomechanics Equinus Pronation 25 Pathomechanics Equinus Pronation Increased Load PTT Spring Ligament 26 Pathomechanics Equinus Pronation Increased Load PTT Spring Ligament Unlocking MTJ 27 Pathomechanics Equinus Pronation Dorsolateral Peritalar Subluxation Increased Load PTT Spring Ligament Unlocking MTJ 28 Dorsolateral Peritalar Subluxation Refers to the position of the navicular to the talus 29 Pathomechanics Equinus Pronation Dorsolateral Peritalar Subluxation Increased Load PTT Spring Ligament Unlocking MTJ 30 Pathomechanics Equinus Valgus Rearfoot STJ Eversion Ground Reactive Force Dorsolateral Peritalar Subluxation Pronation Increased Load PTT Spring Ligament Unlocking MTJ 31 Ground Reactive Forces Calcaneus is position lateral to the talus and leg STJ is forced into everted position Equinus Causes Eversion of the Calcaneus 32 Pathomechanics AAFF Normal Everter Inverter 33 Pathomechanics Equinus Valgus Rearfoot STJ Eversion Ground Reactive Force Dorsolateral Peritalar Subluxation Pronation Increased Stress PTT Spring Ligament Unlocking MTJ 34 Dysfunction of the PTT Overpull of the PB Radiology of the Flatfoot 35 Radiology of the Flatfoot 36 Radiology of the Flatfoot 37 Radiology of the Flatfoot 38 The Cavus Foot 39 What is a Cavovarus Foot? 40 Foot Tripod 41 Foot Tripod 42 What is the Ground Reactive Force Going to Do? What Muscle is Going to Overwork? What Muscle will be recruited? What Will That Lead Too… 43 Peroneal Longus Overdrive 44 Foot Tripod 45 Peroneal Longus Overdrive 46 Radiographic Findings Increased calcaneal pitch Increased angle of Meary’s Angle Increased Navicular Height A posterior fibula with a flattopped talus 47 Radiographic Findings 48 Hindfoot deformity with normal ankle 49 Compensation 50 Key Concept “The amount of compensation for a deformity at an adjacent joint is dependent on the mobility of that adjacent joint.” 51 How Does the Body Compensate for Equinus?? 52 Compensation Pronation Lumbar Lordosis Hip Flexion Genu Recurvatum 53 Compensation for Frontal Plane Deformity Frontal plane deformity of the distal tibia and ankle is commonly compensated by motion in the subtalar joint The subtalar joint normally allows for up to 30° of inversion and 10° of eversion In the frontal plane, valgus deformity of the distal tibia is tolerated better than varus deformity because a greater amount of subtalar joint motion is available The subtalar joint compensates for a valgus ankle deformity by inversion The subtalar joint compensates for a varus ankle deformity by eversion 54 Compensation for Frontal Plane Deformity Distal tibial varus deformities that exceed the amount of compensation that is available at the subtalar joint result in compensatory midfoot pronation The increased plantarflexion of the first ray increases the arch height, thus decreasing the weightbearing surface of the foot. This results in a cavus deformity 55 Compensation for Frontal Plane Deformity Distal tibial valgus with inadequate subtalar joint inversion compensation, the forefoot supinates and the first ray dorsiflexes Flattens the arch and increases the weightbearing surface of the foot. 56 Compensation for Sagittal Plane Deformity Distal tibial recurvatum is more joint destructive because the talar articular surface is uncovered and the talus is displaced anteriorly Typically, this is not painful early on and is recognized only after the condition has significantly progressed Recurvatum of the distal tibia displaces the center of rotation of the ankle joint anteriorly, thus increasing the anterior lever arm of the foot The triceps surae counter these forces by placing the foot in equinus and decreasing the plantarflexor push off of the foot 57 Compensation for Sagittal Plane Deformity Distal tibial procurvatum is typically more painful because limited dorsiflexion compensation is available through the ankle joint Distal tibial procurvatum results in anterior ankle joint impingement 58 Deformity Planning/Assessment CORA Normal ADTA 59 Case Patient presents with a 15 tibial Varum The ankle has 25 degrees of plantarflexion and 15 degrees of dorsflexion The STJ has 17 degrees of inversion and 8 degrees of eversion How does the patient try and compensate? 60