Hinged External Fixator

External fixator elbow 1External Fixator Elbow 2

 

Indications

 

1.  Persistent instability despite ORIF and LCL repair

 

2.  Gross acute instability, not suitable for surgery

 

3.  Delayed treatment > 4 weeks

 

Compass hinge  / S&N

 

Compass Hinge Lateral XrayCompass Hinge AP Xray

 

Compass HInge Medial ClinicalCompass Hinge Clinical

 

Set up

- two incomplete rings proximal and distal

- hinge in centre

- can be used actively or passively

- adjustment wheel is medial (to use with other hand)

- rings posterior, open anteriorly

- rings compatible with ilizarov equipment

- hinge can also be adjusted in the varus valgus plane

- do so that distal ring is perpendicular to plane of ulna

 

Compass Hinge Centre of Rotation

 

Key is distal humeral axis

- imagine axis is in spool at end of humerus

- open laterally to identify capitellum

- open medially to identify trochlea

- confirm centre of rotation on lateral

 

A. Insert medial and lateral 3.5 mm pins partially

- place external fixator over pins but this can be difficult

- adjust pins so hinge slides easily over them

- insert pins 2mm

 

B.  Insert a single pin through axis of rotation

- slightly easier to apply the external hinge over the pin

- may not have to open the medial side as much

- only slight to identify and protect the ulna nerve

 

Medial Humeral half pin

- posterior to ulna nerve

- ensure proximal ring is perpendicular to humerus

- use two hole rancho cube with centering sleeve

- drop off undersurface off ring

- insert 5mm pin (drill, measure, insert HA pin by hand)

- need bicortical fixation

 

Lateral humeral pin

- anterior to radial nerve

- 2 hole post with single hole rancho

- allows angulation of pin from proximal to distal

- also angle posterior to anterior

 

Ulna pins

- 4mm pins into subcutaneous border

- must reduce elbow first and hold reduced whilst inserting pins

- ring must be perpendicular to ulna

- usually put elbow in 90 degrees of flexion

- proximal pin off proximal side of ring wth rancho cube

- bicortical usually into coronoid

- check is stable reduction

- insert second +/- third pin distally