Functional Leg-Length Discrepancy Biomechanics

posted on 28 Apr 2015 00:13 by tyler0irwin04
Overview

Differences between the lengths of the upper and/or lower legs are called leg length discrepancies (LLD). A leg length difference may simply be a mild variation between the two sides of the body. This is not unusual in the general population. For example, one study reported that 32 percent of 600 military recruits had a 1/5 inch to a 3/5 inch difference between the lengths of their legs. This is a normal variation. Greater differences may need treatment because a significant difference can affect a patient's well-being and quality of life.Leg Length Discrepancy

Causes

The causes of LLD may be divided into those that shorten a limb versus those that lengthen a limb, or they may be classified as affecting the length versus the rate of growth in a limb. For example, a fracture that heals poorly may shorten a leg slightly, but does not affect its growth rate. Radiation, on the other hand, can affect a leg's long-term ability to expand, but does not acutely affect its length. Causes that shorten the leg are more common than those that lengthen it and include congenital growth deficiencies (seen in hemiatrophy and skeletal dysplasias ), infections that infiltrate the epiphysis (e.g. osteomyelitis ), tumors, fractures that occur through the growth plate or have overriding ends, Legg-Calve-Perthes disease, slipped capital femoral epiphysis (SCFE), and radiation. Lengthening can result from unique conditions, such as hemihypertrophy , in which one or more structures on one side of the body become larger than the other side, vascular malformations or tumors (such as hemangioma ), which cause blood flow on one side to exceed that of the other, Wilm's tumor (of the kidney), septic arthritis, healed fractures, or orthopaedic surgery. Leg length discrepancy may arise from a problem in almost any portion of the femur or tibia. For example, fractures can occur at virtually all levels of the two bones. Fractures or other problems of the fibula do not lead to LLD, as long as the more central, weight-bearing tibia is unaffected. Because many cases of LLD are due to decreased rate of growth, the femoral or tibial epiphyses are commonly affected regions.

Symptoms

Often there are few or no symptoms prior to the age of 25-35. The most common symptom is chronic lower back pain, but also is frequently middle and upper back pain. Same-sided and repeated injury or pain to the hip, knee and/or ankle is also a hallmark of a long-standing untreated LLD. It is not uncommon to have buttock or radiating hip pain that is non-dermatomal (not from a disc) and tends to go away when lying down.

Diagnosis

A qualified musculoskeletal expert will first take a medical history and conduct a physical exam. Other tests may include X-rays, MRI, or CT scan to diagnose the root cause.

Non Surgical Treatment

The treatment of LLD depends primarily on the diagnosed cause, the age of the patient, and the severity of the discrepancy. Non-operative treatment is usually the first step in management and, in many cases, LLD is mild or is predicted to lessen in the future, based on growth rate estimates in the two legs. In such cases, no treatment may be necessary or can be delayed until a later stage of physical maturity that allows for clearer prognostic approximation. For LLD of 2cm to 2.5cm, treatment may be as simple as insertion of a heel lift or other shoe insert that evens out leg lengths, so to speak. For more severe cases, heel lifts can affect patient comfort when walking, decrease ankle stability, and greatly increase the risk of sprains. For infants with congenital shortening of the limb, a prosthetic ? often a custom-fit splint made of polypropylene ? may be successful in treating more severe LLD without surgery. In many instances, however, a surgical operation is the best treatment for LLD.

Leg Length

Surgical Treatment

For discrepancies over five centimeters, more aggressive surgical procedures-specifically leg lengthening procedures-are typically required. The specifics of this operative procedure are beyond the scope of this informational page, but your child's physician will be able to discuss the details in reference to your child's specific problems when considered appropriate.