Updated: 6/10/2021

THA Leg Length Discrepancy

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  • summary
    • THA Leg Length Discrepancy is a common finding following THA that may be transient due to weakness of the abductors or permanent due to intentional limb lengthening. 
    • Diagnosis can be made clinically with comparison of the measurement from the anterior superior iliac spine to the medial malleolus. Pelvic radiographs can also be used to determine and compare limb lengths.
    • Treatment is generally observation as most cases resolve with relaxation of the abductor muscles over time. Shoe-lifts may be indicated if leg length discrepancy persists after 6 months.
  • Etiology
    • Mechanism
      • contracture leads to pelvic obliquity
        • ABDuction contracture causes involved hemipelvis to be lower, creating apparent LONG leg
        • ADDuction contracture causes involved hemipelvis to be higher, creating apparent SHORT leg
      • weakness
        • weak abductors may provide the sensation of a long leg in the absence of true LLD
        • usually resolve within 3-6 months post-operatively
    • Prevention
      • pre-operative planning reduces incidence of post-operative discrepancies
  • Presentation
    • Symptoms
      • patient may feel perceived LLD despite anatomic equality
    • Physical exam
      • post-operative assessment of limb-length discrepancy
        • true limb length
          • measured from anterior superior iliac spine to medial malleolus
        • apparent limb length
          • determined by adding effect of soft-tissue contractures and pelvic obliquity
          • difficult to truly measure
  • Imaging
    • Radiographs
      • recommended views
        • AP
      • findings
        • leg length discrepancy
        • increased neck length
        • increasing femoral offset will not increase limb length
  • Treatment
    • Nonoperative
      • shoe-lift
        • indications
          • shoe-lift adequate in most cases
          • wait 6 months until treatment to allow adequate relaxation of muscles
    • Operative
      • revisions THA - rare
        • indications
          • significant LLD that affect quality of life and has not resolved over 6 to 12 months.
          • concern for dislocation with revision surgery especially if attempting to shorten limb

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Questions (3)

(OBQ10.160) All of the following intra-operative techniques may result in lengthening of the operative leg during total hip arthroplasty EXCEPT:

QID: 3248
1

Increasing the femoral neck offset

88%

(2552/2907)

2

Increasing the femoral neck length

1%

(30/2907)

3

Incomplete insertion of a cemented femoral stem

1%

(36/2907)

4

Making a high femoral neck cut just below the femoral head

5%

(151/2907)

5

Bone grafting superior to the acetabulum to seat the cup more inferior

4%

(124/2907)

L 1 C

Select Answer to see Preferred Response

(OBQ06.141) The preoperative pelvic radiograph of a 63-year-old female with osteoarthritis is shown in Figure A. She undergoes an uncomplicated total hip replacement. Six weeks post-operatively she complains that her right leg is longer than her left, and an AP pelvic radiograph is obtained which is shown in Figure B. Physical exam shows normal post-operative range of motion and strength in both hips. What is the most likely etiology for this patients gait impairment?

QID: 327
FIGURES:
1

Hip flexion contracture

3%

(68/2422)

2

Excessive medialization of the acetabular component

1%

(35/2422)

3

Patient's perceived leg length discrepancy

87%

(2119/2422)

4

Hip adduction contracture

6%

(148/2422)

5

Malpositioning of the femoral component

2%

(44/2422)

L 1 C

Select Answer to see Preferred Response

(OBQ05.109) All of the following interventions help restore anatomic limb length following total hip arthroplasty EXCEPT:

QID: 995
1

Preoperative templating

3%

(59/2296)

2

Use of an arthroplasty system incorporating variable neck lengths

4%

(87/2296)

3

Intraoperative assessment of limb length

5%

(120/2296)

4

Use of a modular arthroplasty system that allows variable femoral offset

84%

(1938/2296)

5

Clinical and radiographic preoperative assessment for limb length discrepancy

4%

(83/2296)

L 1 D

Select Answer to see Preferred Response

VIDEOS & PODCASTS (4)
EXPERT COMMENTS (1)
Private Note