Des Moines University Surgery/Biomechanics CPMS 23: Deformities I&II PDF

Surgery/Biomechanics CPMS 23: Deformities I&II Sean T. Grambart DPM FACFAS Syllabus Objectives Demonstrate Demonstrate the knowledge of types of forefoot varus and valgus Identify Identify pathomechanics associated with forefoot varus and valgus deformities Demonstrate Demonstrate knowledge of struc...

Surgery/Biomechanics CPMS 23: Deformities I&II Sean T. Grambart DPM FACFAS Syllabus Objectives Demonstrate Demonstrate the knowledge of types of forefoot varus and valgus Identify Identify pathomechanics associated with forefoot varus and valgus deformities Demonstrate Demonstrate knowledge of structural and functional mechanics 2 Distal one-third leg is vertical 17% of patients fitting Root’s normal criteria Posterior calcaneal bisection vertical Knee, ankle, subtalar joint parallel with floor (in transverse plane) Plantar forefoot parallels plantar rearfoot, both parallel with ground Metatarsals 2, 3, and 4 dorsiflexed position, all parallel with ground Metatarsal heads 1 and 5 in same plane as heads of 2, 3, and 4 THE JOURNAL OF ORTHOPAEDIC AND SPORTS PHYSICAL Importance of Radiographs Static evaluation is the basis for surgery Talue very vaurs Reinvatum 4 Importance of Radiographs finding apex of Deform bylooking forefoot to rear foot relation Pre-operative Rearfoot Bisect talus planning Fortfoot Bisect first met apex fd TMT Congenital maimed Importance of Radiographs Osseous versus soft tissue deformities 6 Importance of Radiographs Intra-operative decision making position of takedatproless should line up w eib on lateral eras hindfood Alignment bisect calf and tib 7 Alignment Planning 8 Normal Frontal Plane Alignment Mechanical Axis Fem head to of Ankle joint Defined as a line connecting the center of the femoral head with the center of the ankle joint In a normal limb, the mechanical axis should pass through the zone that lies between 3 mm medial to the center of the knee joint and 3 mm lateral to the center of the knee joint Perfect alignment is defined as when the mechanical axis passes through the center of the knee. In other words, collinearity of the hip, knee, and ankle represents perfect alignment The mechanical axis allows for a direct analysis of limb alignment Anatomic Axis Defined as the middiaphyseal line of the bone and can be a straight line or a curved line Segment of bone toDistal Joint 9 Mechanical Axis Deviation Mechanical Axis Deviation (MAD) The mechanical axis passes outside of the normal zone Valgus Deformity The mechanical axis is lateral to the center of the knee Varus Deformity The mechanical axis is medial to the center of the knee 10 Anatomical Axis gnatonis axis on Mid-diaphyseal line of the bone CNET.fi Straight line or tion curved line 11 Deformitycorrection Joint LinesKILEY Each joint has a defined line that represents that joint’s position The intersection of the mechanical and anatomic axes with the joint lines creates joint angles To form joint angles, draw the mechanical or anatomic axes of the femur or tibia so that they intersect the joint lines. Each angle has an average and range of values that is considered to be normal based on average population values ankle look for shoulders of talus 12 Putting it Together The intersection of the mechanical and anatomic axes with the joint lines creates joint angles To form joint angles, draw the mechanical or anatomic axes of the femur or tibia so that they intersect the joint lines. Each angle has an average and range of values that is considered to be normal based on average population values a me A 13 Naming Joint Angles in Frontal Plane 5 components a or m: designates whether the anatomic (a) or mechanical (m) axis is being used M or L: designates whether the angle is medial (M) or lateral (L) to the axis P or D: designates whether the angle is located at the proximal (P) or distal (D) end of the axis F or T: designates whether the femur (F) or tibia (T) is being measured A: Stands for angle (A) 14 Why is the Tibia Different In a normal tibia, the mechanical and anatomic axes are essentially the same axis The anatomic and mechanical joint angles of the tibia do not need to be differentiated Referred to simply as: Medial proximal tibial angle (MPTA) Lateral distal tibial angle (LDTA) 15 Alignment in the Sagittal Plane seegenurecurvature Sagittal plane has a and orGen Valsum mechanical axis of the limb that extends from the center of the femoral head to the center of the ankle This mechanical axis should pass slightly anterior to the hinge point of the knee Within the range of normal if it stays within the zone that lies between the hinge point of the knee and the anterior confines of the distal femur 16 Alignment in the Sagittal Plane When the mechanical axis of the limb passes slightly anterior to the hinge point of the knee, the knee can “lock” when the lower limb is fully extended, which allows the quadriceps muscle to rest during prolonged standing If the lower extremity has a “fixed flexion” deformity at the knee and the mechanical axis is posterior to the hinge point of the knee, then the individual will have to activate the quadriceps muscle constantly This constant activation of the quadriceps muscle can result in fatigue, patella-femoral pain, and gait disturbance If the mechanical axis of the limb passes anterior to the confines of the distal femur, a hyperextension deformity is present geaupvosouvatumgenureiuvu at it 17 Alignment in the Sagittal Plane To draw the modified mechanical axis of the tibia Draw the proximal tibial joint line. Then place a point on the proximal tibial joint line that is 1/5 of the total length of the proximal tibial joint line from the anterior cortex Draw the distal tibial joint line by connecting points placed on the anterior and posterior “beaks” of the distal tibia Place a point at the center of the distal tibial joint line Draw the sagittal plane modified mechanical axis of the tibia, connect the point on the proximal joint line to the point on the distal joint line 18 Normal Alignment The anterior distal tibial angle (ADTA) is the angle formed by the modified mechanical axis of the tibia and the joint line of the distal tibia (normal, 80° [78– 82°]) 19 Normal Alignment wantante ftp.tmisline The tibio-talar angle is the angle formed by the middiaphyseal 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 middiaphyseal line]) 20 NormalAlignment 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 middiaphyseal line of the first metatarsal (normal, 6° [2–10°]) 21 Normal Alignment Medial proximal tibial angle (MPTA) is formed by the tibial mid-diaphyseal line and the joint line of the proximal tibia (normal, 87° [85–90°]) The lateral distal tibial angle (LDTA) is formed by the tibial mid-diaphyseal line and the joint line of the distal tibia (normal, 89° [86–92°]) 22 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°]) 23 Normal Alignment Talo-calcaneal angle (TCA or Kite angle) is formed by the talar bisector line and a line drawn along the lateral wall of the calcaneus (normal, 21° [15–27°]) Fourth intermetatarsal angle (IMA) is the angle formed by the mid-diaphyseal line of the fourth metatarsal and the middiaphyseal line of the fifth metatarsal (normal, 9° [6–12°]) First IMA is the angle formed by the mid-diaphyseal line of the first metatarsal and the mid-diaphyseal line of the second metatarsal (normal, 8° [6–10°]) 24 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°]) alar head The relationship between the talar bisector line and the shouldgo mid-diaphyseal line of the first metatarsal is known as the 51 1 hit me anteroposterior view Meary’s angle (normal, 7° [3–11°]) y and eachother thengo 3 z should be 4 2 mm of length w 4 s w 5 being shortest 25 Normal Alignment Hindfoot alignment view (Saltzman view) Tibial-calcaneal-distance is 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°] Calc should be slightly lateral to t.is26 Frontal Plane Deformity Varus or valgus malalignment of the distal tibia, ankle, talus, and calcaneus in isolation or in combination Malalignment in the frontal plane of the ankle joint is evaluated on a weightbearing AP view ankle x-ray and an axial view x-ray (hindfoot alignment view and long leg calcaneal axial view) MTI will Pichens 27 Identifying the Apex on an AP View Ankle X-ray Step 1: Draw the mechanical axis of the tibia Step 2: Draw the joint line of the ankle and measure the LDTA. The LDTA is 84° (abnormal) Step 3: Measure the plafond malleolar angle (13°) Step 4: Create a normal LDTA of 89° from the center of the ankle joint Step 5: Locate the apex of the deformity at the intersection of the two axes Measure the magnitude of the deformity 28 Frontal Plane Deformity LDTA measurements greater than 92° varus position LDTA measurements of less than 86° valgus position Frontal Plane Deformity Hindfoot alignment view The center of the calcaneus with respect to the tibial middiaphyseal line Medial or lateral translation of the calcaneus when compared to the tibial mid-diaphyseal line is a major factor for the evaluation of axial alignment 30 Identifying the Apex on a Hindfoot Alignment View X-ray Step 1: Draw a mid-diaphyseal line of the distal tibia Step 2: Draw a calcaneal bisector line Step 3: Measure the magnitude of the deformity Step 4: Measure the distance between the tibial middiaphyseal line and the calcaneal bisector line at the plantar-most level of the calcaneus Amx tells you whereto work 31 Identifying the Apex on a Hindfoot Alignment View X-ray Step 5: To locate the apex of the deformity, draw a third line (blue dashed line) that is parallel and 1 cm medial to the calcaneal bisector line (solid blue line) The apex (A) is located at the intersection of the tibial mid-diaphyseal line and the blue dashed line 32 How do we Compensate? ? “The amount of compensation for a deformity at an adjacent joint is dependent on the mobility of that adjacent joint.” 33 Compensation for Frontal Plane Deformity youhave more STJinversion turnover 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 34 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 forefoot 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 35 Compensationfor FrontalPlane 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. 36 CompensationforFrontal PlaneDeformity Hindfoot valgus creates an increase in Meary’s angle on the AP view x-ray A valgus hindfoot also causes talar head uncovering and peritalar lateral/ abduction subluxation of the forefoot 37 Compensation for Frontal Plane Deformity In normal gait, the ground reaction force vector (GRFV) passes lateral to the ankle joint and imparts a valgus moment arm on the ankle joint A valgus deformity moves the GRFV more laterally, which further increases the load on the lateral aspect of the ankle joint and laterally shifts the talus into the fibula Varus deformity of the distal tibia or ankle moves the GRFV medially Varus is more symptomatic because the subtalar joint cannot compensate as much in eversion as it can in inversion 38 SagittalPlaneAxisPlanning Sagittal plane deformity is evaluated on a standing lateral view x-ray The inclination angle of the calcaneus can be useful in determining a calcaneus (>23°) or equinus position (