By Dr. Mark Hinkes, DPM Unequal limb length (ULL) is a clinical problem that is more common than most clinicians realize and is one for which most patients are rarely evaluated. Common problems associated with unequal limb length include instability in gait, falling, low back pain, sciatica, joint pain, IT Band Syndrome, chronic muscle strain, tendonitis, and failure of diabetic foot wounds to heal. Unequal limb length may be the result of a difference in the length of the leg bones caused by a birth defect, a leg fracture, infection, damage to a growth plate of the bone or as a result of hip or knee joint implant arthroplasty or genu valgum of one leg. ULL may also occur when the legs themselves are the same length, but due to neuromuscular injuries in the pelvis or upper legs, one leg or hip is held higher and tighter than the other. The unequally tightened muscles cause the legs to seem to be different lengths.
Problems caused by ULL typically demonstrate unilateral pathology on the foot on the longer leg. Problems such as heel spur, plantar fasciitis, nerve entrapment syndromes in the heel and forefoot, hallux abducto valgus, digital deformities and ankle or sub talar joint pain are commonly seen. If ULL is unrecognized or undiagnosed, it can be a contributing factor in delaying the healing of diabetic foot ulcers. This problem is especially common under the first metatarsal, where 19% of all diabetic foot ulcers occur and the first or great toe where 24% of all diabetic foot ulcers occur.
When there is an unequal limb length, the foot on the longer leg will tend to pronate or flatten out in an attempt to equalize the unequal limb length. This creates abnormal pressure against the medial side of the foot, and especially under the first metatarsal and great toe. As the foot rolls in and flattens, this causes continued pressure against the ulcer. In essence the ulcer site is not "offloaded," one of the necessary components of wound healing. Even if the patient is in an offloading surgical shoe and permitted to bear weight, the continuous pressure against the ulcer via pronation due to ULL delays the healing.
Typically the difference in limb length in the average patient is small, ranging from 1/8" to 1/4". However, in some cases the difference can be 3/8" up to an inch or more.
Measure your patient for a limb length inequality:
"Eyeball" your patient for a limb length inequality:
Here is how to figure the amount of correction needed to treat unequal limb length:
Once the limb length issue is addressed, most diabetic foot ulcers go on to heal without delay and do not tend to reoccur as the abnormal pressure against them has been removed and the site is offloaded. The body can usually compensate for mild ULL differences, but not always. In these cases, an adhesive felt pad placed under the insole of the heel of the shoe on the short limb will act as a lift and can be a temporary solution. A more permanent solution is to fabricate a custom foot orthotic and have the lift added to the heel of the orthotic. Crepe material works best for this lift. In this way, the correction remains inside the shoe and out of sight.
For cases where the difference is greater than 1/2 inch, a modification to the sole of the shoe may be an option to correct the problem. Podiatrists have an advantage in this area of wound care as they have special training in clinical podiatric biomechanics. This science is a powerful tool that quantifies human locomotion function, and helps to understand issues of gait and ambulation and how foot structure affects its function. So in the case of a patient with diabetes who has a foot or great toe ulcer that fails to heal, faulty biomechanical function as a result of unequal limb length should be considered. A podiatry consultation may be appropriate for a biomechanical evaluation and fabrication of orthotics with a heel lift to control abnormal pronation due to ULL and prevent a recurrence of the ulcer.
About the Author
Dr. Mark Hinkes is the former Chief of the Podiatry Service and Director of Podiatric Medical Education for the Veterans Affairs Medical Centers in Nashville and Murfreesboro, Tennessee, part of the Tennessee Valley Healthcare System. He was Chairman of the Preservation Amputation Care and Treatment (PACT) Program for more than a decade. He is Board Certiﬁed by the American Board of Foot and Ankle Surgery, and the American Professional Wound Care Association, and is a Fellow of the American College of Foot and Ankle Surgeons. Dr. Hinkes spends time consulting, lecturing, and writing about foot health issues on his website, www.dr-mark.net. His most recent book, Healthy Feet for People with Diabetes, is a practical self-care guide designed for patient education.
The views and opinions expressed in this blog are solely those of the author, and do not represent the views of WoundSource, HMP Global, its affiliates, or subsidiary companies.