Leg Length Discrepancy



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


2.  Lower back pain / scoliosis


THR LLDTHR LLD with secondary scoliosis


3.  Abnormal gait


2 - 4 cm discrepancy

- significant increase in oxygen consumption

- also risk of falls


Assessment of LLD






Functional LLD

- blocks


Apparent LLD

- umbilicus to medial malleolus


True LLD

- ASIS to medial malleolus


Apparent shortening

- FFD & adduction hip


Apparent lengthening

- abduction contracture 

- scoliosis, fixed pelvic tilt




Very important

- must mention LLD


X-ray Assessment


AP pelvis 

- both femurs IR 15o

- compensate for anteversion




THR Template LLDTHR Leg Length Ischial LineCentre of Rotation Ranawat Method


1.  Establish Centre of rotation


Acetabular Templating

A.  Ilioischial line / Inter-tear drop line / Superior edge acetabulum

B.  Ranawat

- intersection of ilioishial and shenton's

- 5 mm laterally

- 1/5 pelvis up and 1/5 pelvis in

C.  Rule of thumb

- 2 cm horizontal and 4 cm vertical from teardrop


2.  Calculate LLD

- draw line LT / ischial tuberosity / inferior teardrop

- up to centre of femoral head / centre of rotation

- beware adducted hip on x-ray / false shortening


LLD with hip adduction


3.  Femoral Templating


A.  Size implant

B.  Determine offset

C.  Determine femoral osteotomy from lesser trochanter to restore LLD




1.  Leg to leg comparison


Careful patient positioning

- ASIS perpendicular to floor and patient stable

- ability to palpate both knees and feet

- small pillow to prevent adduction of superior leg

- feel LLD before surgery in this position

- upper femur often feels 1 cm short even if no LLD due to adduction

- aim to reduce LLD to normal after reduction of THR at end of case


2.  Intra-operative measurement



- proximal pin in superoacetabular region

- distally diathermy mark in vas lateralis

- calliper measures horizontal distance (LLD) and vertical distance (offset)

- must place leg in similar position each time to measure leg distance


3.  Tests


Shuck test

- distract femoral head from acetabulum

- should be only few mm of shuck with correct tension


Drop Kick Test

- with thigh extended, knee should remain flexed

- if tension too tight, knee will extend



- if hip tension too tight, ROM especially IR / ER / extension is limited




Transient Perception of LLD

- 14% patients

- usually passes

- may have had LLD before which has been adjusted

- will then feel that leg is longer / which is true



- may get back pain



- abductor weakness

- even dislocation




Delay using shoe lift for 6/12

- allows perceived LLD to resolve


Rarely revision surgery is required

- persistent neurological pain

- beware instability