A. LL Equality
- components equal with no deformity
B. Components equal with bilateral symmetrical deformity
- eg bilateral varus knees
Uncompensated LLD
Most common reason for litigation against orthopaedic surgeons in THR
Usually from lengthening
1. Nerve palsy
Sciatic nerve - tolerate average 4.4cm lengthening
Common peroneal nerve - tolerate average 2.7 cm lengthening
Lengthen by up to 15-20% of the resting nerve length
- but in reality is unknown and multifactorial
11-18 years
Usually severe trauma
Head 5-6 months (1)
GT 2-5 years (5)
LT 9-13 years (9)
Type 1
1. Equal leg lengths
- goal is mild to moderate isolated discrepancy
2. Unequal leg lengths
- goal with paralysis / equinus foot
- aim 1-2 cm short for clearance
3. Level Pelvis
- should use blocks to estimate functional correction
4. Vertical LS Spine
- vertical spine more important than level pelvis