Principles Of Deformity -Tsf

Front 1

List the four deformity components

Back 1

angulation
rotation
translation
length

Front 2

Explain why a TSF corrects for 6 axis deformity or you need 6 deformity parameters to define a single bone deformity

Back 2

Deformity b/w two bone segments can be characterized by three angles (rotations in x/y/z plane) and three displacements (transplations in x/y/z plane)

Front 3

where is the master tab always located on the TSF and which direction does it face

Back 3

-always on the proximal ring
-always faces anterior
-b/w struts 1-2

Front 4

Numbered struts: counterclockwise or clockwise

Back 4

-counterclockwise for the PATIENT

Front 5

where is the anti-master tab

Back 5

-empty distal tab b/w struts 1/2

Front 6

when is the anti master tab a "virtual tab"

Back 6

- in a distal 2/3 ring construct (because there is no ring distal to 1/2 strut)

Front 7

List out the 6 deformity parameters to fully define a clinical deformity

Back 7

1. AP plane angulation (varus/valgus)
2. Lateral plane angulation
(recurvatum/procurvatum)
3. Axial plane angulation
(int/ext rotation)
4. AP Plane translation
(medial/lateral)
5. Lateral Plane translation
(Ant/post)
6. Axial Plane translation
(long/short)

Hint 7

Basically:
AP Angulation / Translation
Lateral Ang/Trans
Axial Ang/Trans

Front 8

what type of TSF construct would you need for correcting a two level deformity

Back 8

3 ring; with 6 struts b/w each pair of rings (12 struts total)

Front 9

to treat a deformity with a TSF; what are three parameters that need to be defined (for computer input)

Back 9

-Frame parameters (struts used, size of rings)
-Deformity parameters
-Mounting parameters

Front 10

what do deformity parameters define

Back 10

-define the angulation and translations (6 parameters) of the origin on the reference segment and its CP on the corresponding segment

Front 11

list the 6 deformity parameters you need to enter into a TSF program

Back 11

1. AP angulation and translation (varus/valgus and med/lat)
2. Lateral or Sagittal ang/trans (procurvatum/recurvatum and ant/post)
3. Axial ang/trans (rotation and long/short)

Front 12

which deformity parameter is measured from radiograph and which is measured from clinical exam

Back 12

- Axial is the only one not measured from radiograph
-can use clinical measurement or CT measurement

Front 13

what do mounting parameters define

Back 13

-postion of the CENTER of the reference ring to the assigned origin

Front 14

what info is needed for mounting parameters to be entered into a TSF program (4)

Back 14

1. AP frame offset (frame is med or lateral to origin)
2. Lateral frame offset (ant/post)
3. Axial frame offset (proximal/distal and int/ext rotated)

Front 15

when defining axial frame offset for mounting parameters; what points are used

Back 15

rotational offset b/w the master tab (prox reference) or the anti master tab

Front 16

The intent is to place a frame in the neutral position with no offset (mounting parameters). However, if rotational offset isnt accounted (or the frame is offset for better ST clearance) for in the TSF program; what can occur

Back 16

-secondary deformity will be created
-Ex: varus deformity with int rotation offset not accounted for will result in recurvatum deformity bc the frame is corrected for the varus in the oblique plane not an AP plane

Front 17

list the modes of correction in TSF

Back 17

1. chronic deformity
2. residual deformity
3. total residual deformity (MC)

Front 18

Chronic deformity mode of correction

Back 18

-frame matches the deformity
-frame is then slowly corrected back to a neutral or home position and the deformity should be corrected
-"crooked frame on a similarly crooked bone"

Front 19

Total residual deformity mode of correction

Back 19

-"crooked frame and a differently crooked frame"

Front 20

placing a ring orthogonal to the proximal bone axis is crucial for Ilizarov frames, is it for TSF

Back 20

-no, but a orthogonal reference rings make planning easier bc you dont have to account for the offset in mounting parameters

Front 21

There are 5 methods of planning;
1. Fracture (Taylor)
2. CORAgin (Paley/Hertzenberg)
3. CORAsponding point (Paley/Hertz)
4. virtual hinge (Standard)
5. LOCA (Taylor)
Describe Fracture method

Back 21

Fracture method: two corresponding points on opp ends of the fracture (end of a spike and where it fits on the opp fx fragment - origin and CP
-cant be used with congential, developmental or post traumatic residual deformities bc no fx line is visible

Front 22

CORAgin method

Back 22

1. the origin is chosen as CORA
2. the CP is determined by using extrinsic data( local length analysis or LLD)
-local length analysis is used when desired correction is a pure neutral wedge, the amt of shortening is added to determine the location of the CP

Front 23

Local length analysis method

Back 23

1. measure distance from CORA (the origin) to to convex surface of the deformity (line W)
2. this line is then projected to the moving fragments axis (prox frag) at a 90 degree angle
3. the W line is then translated downt the moving fragments axis until it contacts the original W line, this point is the CP
-these deformity parameters can then be entered into TSF program
-see pic on next slide

Front 24

Extrinsic method of CORAgin (LLD)

Back 24

-add the amt of shortening that the pt has to the moving segment axis line (prox seg) in a direction towards the reference fragment
see pic

Front 25

describe the CORAsponding point method of planning

Back 25

1. CP is assigned to be at CORA instead of the origin at CORA
2. CP will be on the prox reference line, extending this line to account for a short limb will give the EO or extrinsic origin

Front 26

Virtual Hinge Method

Back 26

-Origin and CP are placed at the same location in space creating a virtual axis of correction (or a virtual hinge)
-ideal position of the hinge is at CORA
-can be used to create a PURE open wedge osteotomy

Front 27

where is the osteotomy located for the LOCA Method of planning (Line of closest approach)

Back 27

-w/ chronic deformities (malunions, etc) CORA on AP view may not correspond to CORA on Lateral view; bc ang and trans are in diff planes
-correcting the deformity at LOCA is the level at which translation b/w fragments is least

Front 28

How do you perform the LOCA method of planning

Back 28

1. assign two levels on the ends of the bone in the AP and lat (same level on both views)
2. determine the translations b/w the reference and deformed fragements at both levels
3. these two values are then plotted on a graph representing the axial plane
4. a perpendicular line is then drawn on the axial graph from ref frag to deformed frag (this line is LOCA and the point it intersects the deformed fragment is LOCA point - also the CP)
-osteotomy is chosen at level of LOCA

Front 29

when using a distal reference; what frame marker is used for rotational mounting parameters

Back 29

-anti master tab (master tab is used for proximal references)

Front 30

how do you choose which ring to use as a reference ring

Back 30

-the most orthogonal one
-or the juxta articular one

Front 31

Define SAR

Back 31

-structure at risk
-can be peroneal nerve or concave side of the bone on a osteotomy