nerve palsy

Undercorrection /  loss of correction 

Most important factor in good results and duration of results

- must correct to 8^o of valgus

- mechanical axis must pass through lateral joint line

Causes

- inadequate initial correction

Issue

Most common reason for litigation against orthopaedic surgeons in THR

Usually from lengthening

Complications of LLD

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