Leg Length Discrepancy

 

THR LLDTHR LLD with secondary scoliosis

 

Complications of LLD

 

1.  Abnormal gait / risk of falls

 

2.  Lower back pain / scoliosis

 

3.  Nerve palsy

- sciatic nerve - tolerate average 4.4cm lengthening

- common peroneal nerve - tolerate average 2.7 cm lengthening

 

4.  Instability / dislocation

 

Pre-operative assessment

 

Examination

 

True LLD

- anatomical discrepancy in leg lengths

- ASIS to medial malleolus

 

Apparent / Perceived LLD

- altered mechanics

- scoliosis and pelvic obliquity

- hip fixed flexion deformity (FFD) & adduction - apparent shortening

- abduction contracture - apparent lengthening

- umbilicus to medial malleolus

- can measure with blocks

 

X-ray templating

 

AP pelvis 

- both femurs IR 15o / compensate for anteversion

- symmetrical abduction / adduction of femurs

 

LLD with hip adduction

Abnormal femur position

 

Pelvic landmarks

- inferior aspect of ischial tuberosities

- tear drop

- center of rotation

 

Femoral landmarks

- lesser tuberosity

 

THR Minimal LLD Template

 

THR Template Severe LLDCentre of Rotation Ranawat Method

 

Intra-operative assessment

 

1.  Leg to leg comparison

 

Careful patient positioning

- ASIS perpendicular to floor and patient stable

- place both legs in same position i.e. flexion / adduction

- supine - palpate medial malleolus

- lateral - palpate heels

 

2.  Tests

 

Shuck test

- distract femoral head from acetabulum

 

Drop Kick Test

- with thigh extended, knee should be able to flex past 90 degrees

- if tension too tight, knee will extend

 

ROM

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

 

3.  Intra-operative measurement

 

Mechanical referencing / Pins

 

Pin LLD

 

Technique

- pin in pelvis / pin in femur

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

- measure horizontal distance (LLD) and vertical distance (offset)

 

Chen et al Front Surg 2022

- comparison study of mechanical vs freehand

- mechanical reduces incidence of LLD

 

Fluoroscopy

 

THA fluroTHA fluoro

 

Sun et al Arch Orthop Trauma Surg 2024

- meta-analysis of use of intra-operative fluoroscopy versus conventional navigation in THA

- fluoroscopy reduces incidence of LLD

 

Image-less Navigation

 

Imageless LLD

Smith&Nephew RI Hip Navigation

 

Migliorini et al J Orthop Traumatol 2022

- meta-analysis of image-less versus conventional THA

- image-less reduces LLD

 

CT navigation

 

Mako 1

Stryker Mako Hip System

 

Migliorini et al Eur J Med Res 2023

- meta-analysis of CT navigation versus conventional in THA

- CT navigation reduces LLD

 

Postoperative LLD

 

Incidence

 

Transient perception of LLD common

- usually apparent leg lengthening

 

Cause

- leg was slightly short, now normal length

- contracture releases

 

Typically resolves over 6 months

 

Management

 

Nonoperative

 

Delay using shoe lift for 6/12

- allows apparent LLD to resolve

 

Shoe insert for opposite leg

 

Operative

 

Parvizi et al JBJS Am 2004

- 21 cases of LLD mean 4 cm following THA

- treated with revision

- LLD restored to within 1 cm in all cases