Leg Length Discrepancy Following Knee Replacement Surgery

Overview

Some people have an ?apparent? LLD which may make the affected leg seem longer than the other leg. There are several factors that can contribute to this feeling. Most commonly, contractures or shortening of the muscles surrounding the hip joint and pelvis make the involved leg feel longer, even when both legs are really the same length. Additionally, contractures of the muscles around the lower back from spinal disorders (i.e. arthritis, spinal stenosis), curvatures of the spine from scoliosis, and deformities of the knee or ankle joint can make one leg seem longer or shorter. In the general public, some people have an ?apparent LLD? as long as one half inch but usually don?t notice it because the LLD occurs over time. A ?true? LLD is where one leg is actually longer than the other. Patients can have unequal leg lengths of 1/4? to 1/2? and never feel it too! You can also have combinations of ?True? and ?Apparent? LLDs. During total hip replacement surgery, the surgeon may ?lengthen? the involved leg by stretching the muscles and ligaments that were contracted, as well as by restoring the joint space that had become narrowed from the arthritis. This is usually a necessary part of the surgery because it also provides stability to the new hip joint. Your surgeon takes measurements of your leg lengths on x-ray prior to surgery. Your surgeon always aims for equal leg lengths if at all possible and measures the length of your legs before and during surgery in order to achieve this goal. Occasionally, surgeons may need to lengthen the operable leg to help improve stability and prevent dislocations as well improve the muscle function around the hip.Leg Length Discrepancy

Causes

Some limb-length differences are caused by actual anatomic differences from one side to the other (referred to as structural causes). The femur is longer (or shorter) or the cartilage between the femur and tibia is thicker (or thinner) on one side. There could be actual deformities in one femur or hip joint contributing to leg length differences from side to side. Even a small structural difference can amount to significant changes in the anatomy of the limb. A past history of leg fracture, developmental hip dysplasia, slipped capital femoral epiphysis (SCFE), short neck of the femur, or coxa vara can also lead to placement of the femoral head in the hip socket that is offset. The end-result can be a limb-length difference and early degenerative arthritis of the hip.

Symptoms

Back pain along with pain in the foot, knee, leg and hip on one side of the body are the main complaints. There may also be limping or head bop down on the short side or uneven arm swinging. The knee bend, hip or shoulder may be down on one side, and there may be uneven wear to the soles of shoes (usually more on the longer side).

Diagnosis

Infants, children or adolescents suspected of having a limb-length condition should receive an evaluation at the first sign of difficulty in using their arms or legs. In many cases, signs are subtle and only noticeable in certain situations, such as when buying clothing or playing sports. Proper initial assessments by qualified pediatric orthopedic providers can reduce the likelihood of long-term complications and increase the likelihood that less invasive management will be effective. In most cases, very mild limb length discrepancies require no formal treatment at all.

Non Surgical Treatment

Structural leg length discrepancy can be treated with a heel lift in the shorter leg?s shoe, if the leg length is greater than 5 mm. The use and size of the heel lift is determined by a physical therapist based on how much lift is needed to restore proper lumbopelvic biomechanics. In certain cases, surgical intervention may be needed to either shorten or lengthen the limb. An important component to any surgical procedure to correct leg length discrepancies is physical therapy. Physical therapy helps to stretch muscles and maintain joint flexibility, which is essential in the healing process. For a functional leg length discrepancy no heel lift is required, but proper manual therapy techniques and specific therapeutic exercise is needed to treat and normalize pelvic and lower extremity compensations. The number of treatments needed to hold the pelvis in a symmetrical position is different for each patient based on their presentation and biomechanical dysfunctions in their lower back, pelvis, hip, knee, and foot/ankle. If you have pain in your lower back or lower extremity and possibly a length discrepancy; the two symptoms could be related. A good place to start would be a physical therapy evaluation to determine whether you have a leg length discrepancy and if it could be contributing to your lower back pain, hip pain, knee pain, or leg pain.

Leg Length

Surgical Treatment

Lengthening is usually done by corticotomy and gradual distraction. This technique can result in lengthenings of 25% or more, but typically lengthening of 15%, or about 6 cm, is recommended. The limits of lengthening depend on patient tolerance, bony consolidation, maintenance of range of motion, and stability of the joints above and below the lengthened limb. Numerous fixation devices are available, such as the ring fixator with fine wires, monolateral fixator with half pins, or a hybrid frame. The choice of fixation device depends on the desired goal. A monolateral device is easier to apply and better tolerated by the patient. The disadvantages of monolateral fixation devices include the limitation of the degree of angular correction that can concurrently be obtained; the cantilever effect on the pins, which may result in angular deformity, especially when lengthening the femur in large patients; and the difficulty in making adjustments without placing new pins. Monolateral fixators appear to have a similar success rate as circular fixators, especially with more modest lengthenings (20%).

Write a comment

Comments: 6