Leg Length Inequality Following Total Hip Replacement

Management of Leg Length Inequality following Total Hip Arthroplasty

Total Hip Arthroplasty (THA) or Total Hip Replacement (THR) was introduced in the 1960’s, and was considered the “operation of the century”, because it revolutionized the management of elderly patients who were crippled with arthritis of the hip joints.1 Patients who suffered from hip fractures, or osteonecrosis of the femoral head have also benefited. Through the past 40 plus years many advancements in the technology of the hip prosthesis, pre-operative and intra-operative measurement techniques, and surgical procedures have resulted in much better outcomes in regard to hospital stays, better range of motion, improved gait, and durability of the prosthesis itself.

The major goal in total hip arthroplasty is to restore the biomechanics of the hip and minimize leg length inequality (LLI).

Leg length inequality is a common occurrence2 as the operated hip is usually lengthened with the placement of the femoral component of the prosthesis. In the 70’s one study revealed that the average leg lengthening following total hip arthroplasty was 15.9mm in 27% of the cases studied and required heel lifts on the opposite leg to help correct the problem.3 Another study revealed that revision hip surgery was required for symptomatic limb length discrepancy. The mean limb-length discrepancy at the time of the revision was 4 cm (range, 2 to 7 cm).4 4 cm being the equivalent to approximately a little over 1.5 inches. Studies have been done which reveal that 5mm of leg deficiency is significant and can cause low back and other related symptoms.5 Another point that needs to be considered is that some patients have leg deficiency, acquired or congenital, prior to hip arthroplasty, and the surgery can either aggravate or ameliorate this discrepancy.

Why does leg lengthening occur during this type of procedure?

In the literature, we find an emphasis on developing a systematic and reproducible approach to pre-operatively evaluating patients for leg length discrepancy before undergoing THA. A pre-operative x-ray will establish any pre-existing leg deficiency. Then an operative plan can established, but intra-operative evaluation must also be done based upon the components available and the final components after being implanted. Intraoperative objective measurement of limb length is critical to avoid over-lengthening. The surgeon has at his/her disposal several hip prosthesis to choose from during surgery based upon what conditions he/she finds during the procedure. For instance, the patient may need a certain type of shaft to improve stability because of the condition of the femur. Even with all the pre-examination, with x-rays, CT’s or MRI’s, the final decision on the size and type of prosthesis comes when the surgeon can actually view what he/she has to work with.

Techniques are being developed in digital templating and image guided surgery that may provide better accuracy and improved outcomes concerning LLI, but for now what is needed to keep leg length inequality minimal, is a good pre-operative plan, attention to detail, intra-operative measurements referencing the well leg after the components are implanted, and then post-operative measurements some weeks following the surgery. Even with those measures there will be cases of significant leg length inequality, but the post-op measurement will discern the amount, and simple procedures such as the addition of shoe lifts or heel lifts can reduce or eliminate LLI before related problems occur.

What are some of the problems that occur with leg deficiency following THA?

Some of the problems that occur are a limp, leg pain, hip and/or back pain, hip joint instability, paraesthesia in the lower extremity, disc problems, osteoarthritis of the knee, poor oxygen consumption while walking, and vertigo due to alteration of the postural control system.6, 7, 8, 9, 10, 11, 12
What can be done to help remedy the problem should it occur?

Post-operatively a standing x-ray should be taken with the heels 8 inches apart and the knees extended. The primary ray should be at the level of the umbilicus and collimated to 14 X 17 inches. This film will reveal any leg deficiency, pelvic deficiency, sacral deficiency, or L5 deficiency.

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More on Why, When, and How to Determine Whether You Should Use Heel Lifts - for clinical advice on diagnosing and measuring leg length discrepancy. Also, indirect examination using a calibrated foot support can be useful. If the measured deficiency is 2 cm or less a heel lift or shoe lift will certainly reduce if not eliminate the problem.

Should the deficiency be greater that 2 cm. and problems severe, further consultation with the orthopedist should be considered to assess other options.

Citations

1 Learmonth ID, Young C, Rorabeck C “The operation of the century: total hip replacement” Lancet. 2007 Oct 27;370(9597):1508-19

2 Maloney WJ, Keeney JA. “Leg length discrepancy after total hip arthroplasty” J. Arthroplasty. 2004 Jun;19(4 Suppl 1):108-10.

3 Williamson JA, Reckling FW, “Limb length discrepancy and related problems following total hip joint replacement” Clin Orthop 1978 Jul;134:135-138

4 Parvizi J, Sharkey PF, Bissett GA, Rothman RH, Hozack WJ “Surgical treatment of limb-length discrepancy following total hip arthroplasty” J Bone Joint Surg Am. 2003 Dec;85-A(12):2310-7.

5 Friberg O, “Clinical Symptoms and Biomechanics of Lumbar Spine and Hip Joint in Leg Length Inequality” Spine. Vol 8 Number 6 Pages 643-649

6 Austin MS, Hozack WJ, Sharkey PF, Rothman RH, “Stability and leg length equality in total hip arthroplasty” J Arthroplasty. 2003 Apr;18(3 Suppl 1):88-90.

7 Friberg O, “Clinical symptoms and biomechanics of lumbar spine and hip joint in leg length inequality” Spine. 1983 Sep;8(6):643-51.

8 ten Brinke A, van der Aa HE, van der Palen J, Oosterveld F, “Is leg length discrepancy associated with the side of radiating pain in patients with a lumbar herniated disc?” Spine 1999 Apr 1;24(7):684-6

9 Golightly YM, Allen KD, Renner JB, Helmick CG, Salazar A, Jordan JM “Relationship of limb length inequality with radiographic knee and hip osteoarthritis” Osteoarthritis Cartilage. 2007 Jul;15(7):824-9. Epub 2007 Feb 22

10 Williamson JA, Reckling FW, “Limb length discrepancy and related problems following total hip joint replacement” Clin Orthop 1978 Jul;134:135-138

11 Irvin RE. “The origin and relief of common pain” J Back Musculoskeletal Rehabil. 1998;11(2):89-130

12 Gurney B. “Leg length discrepancy” Gait Posture. 2002 Apr;15 (2):195-206.

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