Assessing LLD And Whether Shoe Lifts Can Have An Impact

Author(s): 
David Levine, DPM, CPed

While most of the published research on leg length discrepancy (LLD) focuses on surgical intervention, conservative care may be helpful in this regard. Accordingly, this author discusses the assessment of LLD and how shoe lifts can be beneficial.

When it comes to leg length discrepancies (LLDs), the literature has infrequently described a practical approach — namely conservative use of footwear as part of the solution — although etiologies and surgical treatments have been well documented. The majority of the LLD literature is geared toward surgical intervention, perhaps because quantifying the efficacy of conservative treatment is fairly subjective. There are so many variables to consider, including the activity level of the person, the body type and the way to truly assess the amount of difference present.

   While the causes of LLDs are divided into functional and structural etiologies, the simple fact remains that the person who has a LLD is functioning every day and every step with one leg longer than the other. Add scoliosis into the equation or a pelvic tilt, and significant asymmetry results. Regardless of the cause, treatment should start conservatively.

   We see clues on a daily basis as to the prevalence of LLD. In fact, it is estimated that 1 to 2 percent of adolescents and 50 percent of people over 60 have a LLD.1 Asymmetric structural findings, such as asymmetric hallux limitus, are the first clue to indicate that a LLD may be present. Over time with feet having to compensate for the leg length inequality, one foot will be forced to pronate more than the other. This constant driving of the first ray into the ground, whether this is on the longer or shorter side, will contribute to an early breakdown of the first metatarsophalangeal joint (MPJ). That is not to say that every hallux limitus is the result of a LLD but if hallux limitus is an asymmetric finding and it is not traumatically induced, looking for a LLD is simple, quick and worthwhile.

   If one is planning surgery, identifying this difference preoperatively becomes especially important in ensuring a satisfactory outcome. If one does not identify and address the LLD sufficiently, it is quite possible to see either rapid recurrence of the problem or a failed procedure.

   Leg length discrepancy could result in recurrent bunion deformities, failed hallux limitus surgery, Charcot arthropathy, reconstructive rearfoot or ankle surgery, and many other difficult to explain phenomena. These are just the podiatric implications. These do not include hip and knee joint replacements, spinal fusions and other lower extremity problems that are common to the general population.

   A clear analogy is the front end of a car. If it is not aligned properly, the car will constantly pull to one side. When this occurs, repair is needed. Unfortunately, our patients do not always realize they need repair and continue to function and cause further damage. In less severe cases, maybe only the front tires will wear unevenly. However, if one just replaces the tires, this is analogous to treating only the symptoms. After several hundred miles, the same exact thing can happen again.

   Another analogy is the foundation of a building where symmetry is critical. You would never want to build upward on a crooked foundation. That would be a cause for instability, breakdown and disaster. The bottom line is that mechanical symmetry is critical for a machine to run smoothly and efficiently, or for a building to be stable. This is no less important for the human body.

   There are many specialties that are forced to deal with LLDs. We as podiatrists often deal with the condition in the form of heel lifts in the shoe or heel lifts that one can add to orthotic devices. This is often inadequate and unsuccessful in fully addressing what the patient actually needs. Physical therapists and chiropractors will often try and address discrepancies with adjustment of the hips and spine. Although this can work well, it may only be temporary, sometimes lasting until the patient gets up from the exam table. Then there are differences of opinion from time to time. Some specialists believe that regular adjustment will address it adequately but others see this only as practice management.

   Orthopedists and neurosurgeons see LLDs in their practices regularly. However, they may not feel the need to treat or even look for discrepancies unless the difference is large or the cause of symptoms is obvious. Often the orthopedist’s best intervention is on the operating table in the form of sizing joint implants properly. Unfortunately, the table or even the radiographic view does not always correlate with the way a person functions. When a patient is supine, scoliosis or pelvic tilt issues may not be as easy to appreciate. The key is assessing how the person functions.

   With the high frequency of joint implantation surgery occurring in the baby boomer age group, checking for LLDs should become a routine part of a biomechanical examination. Often when a patient needs a joint replacement, the affected limb has gone through changes over the years. For example, sometimes when knee replacement is necessary, the affected lower extremity may exhibit genu valgum or varum, which might be asymmetric. Once the joint is replaced, that limb may then be rectus but the other limb might not be. Structurally, the bony segments may measure the same but may not be in the same plane of function.

How To Test For Leg Length Discrepancy

There are simple quick diagnostic tests that one can perform when suspicious of a leg length discrepancy. The literature reports that there is a lack of intratester and intertester consistency, making it difficult to arrive at a definitive amount. There is a sensible solution to this problem. Let the patient decide if there is a significant difference and how much of that difference needs to be addressed. If you suspect a LLD and you are wrong, your patient will tell you. If you are right, the patient will thank you. This will all happen within a week or two at the most. This approach is also a cost effective way of approaching the problem.

   First, have your patients stand in front of you in a relaxed position without shoes on. Talk to them for a bit as you assess their posture and the position in which they are most comfortable standing. If you see a pelvic tilt or a slant to the belt line, this will serve as supportive evidence.

   Then see if their posture changes. For example, some people constantly shift from one foot to the other while others may favor standing on one foot more than the other. When the latter is the case, this is often a clue to which side is shorter. Due to gravity, it is easier to go downhill and stand on the shorter limb than it is to go uphill and stand on the longer side.

   Additionally, if someone does have a leg length discrepancy, he or she is probably not comfortable standing for too long without constantly changing position. They will find themselves consistently changing feet for support. It is all about symmetry. If the legs are equal in length and the foundation stable, using both feet and legs for equal balance will be more comfortable.

   Palpating the anterior superior iliac spine and the pelvic crests is helpful, but not if the patient is obese. In obese patients, those bony landmarks are obscured, making it difficult to objectively assess them. Having the patient supine with knees bent will allow you to see if the femoral or tibial segments differ in length. You can always measure these segments but this is too subjective to be effective or reliable. Measuring also does not take scoliosis or other pelvic issues into account.

Pertinent Pointers On Using Heel Lifts Effectively

Finally, probably the most effective way to assess for LLDs is to observe the patient and rely on the patient’s feedback as well. People can generally perceive 1/8-inch differences. Therefore, the difference will be 1/8 inch, ¼ inch, 3/8 inch and so on. Have these materials of different thicknesses in your exam rooms. Place a piece under one foot. Typically, you should start with a material that is at least ¼ inch. Ask the patient how it feels. Then switch feet. Try to confuse the patient with which foot and the thickness of material while you titrate the amount and the side it works best.

   It is truly amazing how quickly people can perceive balance, even when they have been functioning in an uneven manner for a long time. This can be a fun, rewarding and educational tool to use when discussing treatment with the patient. Within just a couple of minutes, in most cases, you will be able to determine easily and with a high degree of certainty whether there is a leg length discrepancy, which side is shorter and by approximately how much.

   How you interpret and use this information will directly impact your outcomes. The most important concept is to use shoes to your advantage. In general, as I mentioned previously, people perceive 1/8-inch differences. If the difference is only 1/8 inch or you are sure it is not as much as ¼ inch, simply placing a non-compressible heel lift in the shoe will suffice. The material needs to be firm and one should place it under the insole so it is as far from the foot as possible. This way, you don’t have to alter the feel of the shoes yet the shoe will be more comfortable and the patient will be more likely to be adherent.

   If the difference is greater than 1/8 inch, the lift needs to go on the shoe. Unfortunately, this is a concept that is foreign to too many practitioners. For the best outcomes, one needs to raise the entire short side, not just the heel.

   You can do an experiment to prove this yourself. Stand only on a ¼-inch heel lift. Then try standing on a ¼-inch platform of material. It is clearly a lot more efficient to raise the entire side than just the heel. In addition, if you only raise the heel, you are contributing to further asymmetry down the road. Doing this will also have a negative impact on the fit of the shoe. If you try to use more than a heel lift but put it inside of the shoe, then one shoe will be tight with the heel slipping out and the other loose. This is not a comfortable or efficient combination.

   Another common error is placing more than a 1/8-inch lift on an orthotic device. The function of orthotic devices and the purpose of a lift are different. Trying to combine them may negatively impact each. When adding an additional heel lift to the orthotic, it will alter the purpose of the heel post and change the pitch of the orthotic device. In addition, depending upon the material one selects, it might compress easily, making it difficult to determine how much of a difference really exists.

   The focus needs to be on the shoe. Not only can one add a lift to any shoe, it can happen in a cosmetically appealing way that is barely even noticeable. This way, one can sufficiently elevate the short side to the right level.

   Having the patient try the lift in the shoe for a couple of weeks will determine if you are right. The feedback you obtain after the patient tries it for a few weeks is always helpful. If you made patients worse, you can remove the lift. If you made them better, they will bring you more shoes. If it is not enough, you can modify the lift can be modified further. Just remember, it is always easier to operate on a shoe than it is to operate on a foot. The complications are much easier to deal with.

   The common question asked by patients is whether all shoes have to be modified. The answer is no. Patients should try the lift on just one shoe and wear it consistently for a couple of weeks. If it works, it will be more comfortable and patients will not only want to wear it, but they will recognize the need to wear it.

Final Words

The logistics of utilizing lifts is easier than fabricating orthotic devices. Once you make the recommendation to patients, have them give you a shoe. Send the shoe to a lab of your choice. It will be fixed and returned within a week. This allows you to maintain control of the treatment and effectively monitor the patient's progress.

   Leg length discrepancies are well understood and described in the literature. However, integrating the assessment and conservative treatment of LLDs into your practice is another matter. Look for LLDs in all of your patients with asymmetric findings. Look for it in patients who have undergone joint replacement surgery. Diagnose it with more frequency and start treating it with the modification of shoes. You will be pleasantly surprised how easy and gratifying this treatment can be for you and your patients.

   Dr. Levine is a Fellow of the American Society of Podiatric Surgeons, and the American Academy of Podiatric Sports Medicine. He is in private practice and is the director and owner of the Frederick, Md.-based Walkright and Physician's Footwear, a comprehensive pedorthic facility. For more information or to contact Dr. Levine, visit www.Levinefeet.com .

References

1. O'Brien S, Kernohan G, Fitzpatrick C, Hill J, Beverland D. Perception of imposed leg length inequality in normal subjects. Hip Int. 2010; 20(4):505-11.

2. Mahmood S, Huffman LK, Harris JG. Limb-length discrepancy as a cause of plantar fasciitis. J Am Podiatr Med Assoc. 2010; 100(6):452-5.

3. Harvey WF, Yang M, Cooke TD, Segal NA, Lane N, Lewis CE, Felson DT. Association of leg-length inequality with knee osteoarthritis: a cohort study. Ann Intern Med. 2010; 152(5):287-95.

4. Defrin R, Ben Benyamin S, Aldubi RD, Pick CG. Conservative correction of leg-length discrepancies of 10mm or less for the relief of chronic low back pain. Arch Phys Med Rehabil. 2005; 86(11):2075-80.

5. Brady RJ, Dean JB, Skinner TM, Gross MT. Limb length inequality: clinical implications for assessment and intervention. J Orthop Sports Phys Ther. 2003; 33(5):221-34. Review.

6. McCarthy JJ, MacEwen GD. Management of leg length inequality. J South Orthop Assoc. 2001; 10(2):73-85; discussion 85.

7. Trobisch P, Suess O, Schwab F. Idiopathic scoliosis. Dtsch Arztebl Int. 2010; 107(49):875-83; quiz 884.

8. Brady RJ, Dean JB, Skinner TM, Gross MT. Limb length inequality: clinical implications for assessment and intervention. J Orthop Sports Phys Ther. 2003; 33(5):221-34.

9. Goss DL, Moore JH. Compliance wearing a heel lift during 8 weeks of military training in cadets with limb length inequality. J Orthop Sports Phys Ther. 2004; 34(3):126-31.

   Editor’s note: For a related PodiatryLIVE™ video by Dr. Levine, see http://www.podiatrylive.com/shoe_lift_LLD .

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