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Orthotics Q&A

Limb Length Discrepancy: Pertinent Insights On Diagnosis And Treatment Through Lifts And Orthotic Therapy

Although the consequences of limb length discrepancies (LLDs) are far-reaching, possibilities for biomechanical management of this condition are equally as expansive. With this in mind, the panelists share their experiences in optimal evaluation for LLD and discuss what aspects of orthotics and lifts they use to treat this pathology. 

Q:

In your experience, what do you find to be the most effective and reliable way to assess a limb length discrepancy (LLD)? 

A:

In his early practice, Joseph D’Amico, DPM assessed the presence of LLD through clinical and radiographic measurements. This included measurement and/or assessment of anterior and posterior iliac spine levels, pelvic brim obliquity, asymmetry of skin folds, asymmetry of calcaneal stance position and ranges of motion, anterior superior iliac spine (ASIS) or umbilicus to medial malleolus measurements and standing radiographs when indicated. 

“With experience. I realized that none of these methods assessed symmetry in function,” notes Dr. D’Amico. “Since observational gait analysis has proven to be an unreliable indicator of foot and limb function, I began to assess limb asymmetry via computer-assisted gait analysis.”1,2 

The indices Dr. D’Amico finds most important and reliable include a comparison of temporal parameters, plantar pressures and center of force trajectories. He says he emphasizes computer-assisted gait analysis for these assessments as other diagnostic methods cannot evaluate these forces that occur under the foot and inside the shoe. The data from the computer-assisted gait analysis helps providers make a more accurate determination of whether the individual is functioning symmetrically, according to Dr. D’Amico. 

“Much like tires on a car, the goal is to have both wheels properly aligned and spinning at the same speed for the same amount of time, and generating the same pressure,” describes Dr. D’Amico. 

Stanley Beekman, DPM points out that it is necessary to perform a more complete examination than just measuring limb lengths. 

“The length of one leg compared to another is meaningless without looking at it in context with the rest of the body,” maintains Dr. Beekman. 

For instance, if a patient has a long leg compensated for by a posterior innominate dysfunction of the iliosacral joint, then functionally, there is no shortage. For this reason, Dr. Beekman recommends evaluating the anterior superior iliac spines to the ground in both neutral and relaxed positions and the posterior superior iliac spines to the ground in both neutral and relaxed positions, ankle dorsiflexion and gait. 

“If the patient has unilateral foot or leg symptoms, I automatically put leg length discrepancy in my differential diagnosis,” adds R. Daryl Phillips, DPM. 

However, Dr. Phillips emphasizes the importance of a thorough history. When it comes to patients he suspects of having LLD, he asks about a history of back pain, muscle fatigue, sacroiliac joint pain and whether symptoms are worse when standing or walking. If the patient answers yes, Dr. Phillips says podiatrists should evaluate further for functional or anatomical leg length discrepancy. 

Dr. Phillips no longer utilizes a tape measure to assess the length of the various limb segments due to difficulty in precisely identifying the relevant landmarks. Instead, he first does a non-weightbearing estimation with the patient supine and then positions the trunk and the legs in such a manner that one could conceivably draw a straight line from the nose through the manubrium sternae to the symphysis pubis and a point where the knees or the malleoli touch. 

“Then with equal tension on both legs, I look to see if the bottom of the heels are at the same distal level or whether the bottom of one heel is more distal than the other,” says Dr. Phillips. “This is not an exact measurement but it indicates a possible difference.” 

Dr. Phillips subsequently has the patient stand comfortably and looks for asymmetry in arch height or the medial prominence of the navicular and medial malleolus and/or calcaneal eversion. He also looks for asymmetry in popliteal space tension, which indicates whether one knee is more flexed than the other. Lastly, he looks for equality of the pelvic brim height. If the physical exam indicates a leg length discrepancy, then Dr. Phillips may order a radiographic leg length discrepancy study with the patient standing to determine the exact anatomical parameters. 

Q:

What factors do you use to determine whether to treat an identified LLD? 

A:

Some studies show that possibly over 90 percent of the population has some degree of limb asymmetry, shares Dr. D’Amico, who notes the average discrepancy is reportedly less than one-half inch (1.1 cm) and usually people easily compensate for this.3-5 In cases with a larger LLD, Dr. D’Amico says a patient’s presenting concern could be recurrent asymmetric symptoms, especially those affecting the low back. 

“That is not to say that discrepancies of less than one-half inch will not produce asymmetrical forces and symptomatology since, ideally, all mechanical models work more efficiently and require the least amount of energy when functioning symmetrically,” says Dr. D’Amico. 

He goes on to say that minor discrepancies even as little as one-eighth inch may aggravate, perpetuate or precipitate existing pathology, especially during stress situations such as those in repetitive motion sports such as running. Overall, Dr. D’Amico shares that the demands on and response of the musculoskeletal system will determine whether pathology warrants intervention. 

“With that being said, since symmetrical function is the ideal state, asymmetrical function warrants attention, especially in active individuals,” maintains Dr. D’Amico. 

In his opinion, Dr. Beekman feels the most important determining factors for treatment of a LLD are asymmetric symptoms and associated asymmetry. 

“If a patient presents with a condition associated with a shortage of a leg (i.e. cuboid syndrome, peroneal tendonitis, chronic ankle sprains, Achilles tendonitis, iliotibial band syndrome or trochanteric bursitis), and I find a structural or functional shortage on that side, then correcting the asymmetry would be part of the treatment,” says Dr. Beekman. “However, if an equinus occurs as a result of a functional short leg, eventually this will result in compensation that can mimic pronatory long leg symptoms.” 

Dr. Phillips feels that back pain exacerbated by standing or walking usually warrants podiatric care as part of the solution. 

“I never promise patients that I can help their back pain, only that I might be part of the solution,” says Dr. Phillips. 

He continues to say that identifying the root cause of the problem is vital before deciding how or if to treat. If symptoms are present, though, Dr. Phillips shares that treatment is usually necessary. If an adult patient is asymptomatic in the back, legs and feet, then he usually does not initiate treatment though Dr. Phillips finds these cases are rare. 

Q:

What is the rationale and methodology that you employ in managing LLD? How might you apply this rationale to prescribing and creating orthotics for these patients? 

A:

Dr. D’Amico states he first aims to realign the osseous and soft tissue structures in the foot and ankle by combining the prescription of custom foot orthoses with stretching of tight musculature and strengthening of weak musculature. This is especially important in cases of functional discrepancy, in which the discrepancy resolves once one achieves realignment and improved function. 

Dr. D’Amico initiates in-shoe lift therapy when observing asymmetry by adding a one-quarter inch felt heel lift to the shorter limb and retesting the patient. If this does not achieve symmetry, he adds an additional one-eighth inch before retesting, repeating up to the use of a five-eighths inch lift or a one-half inch heel lift with a one-eighth inch full foot insole. After achieving symmetry, Dr. D’Amico reassesses the patient in three months. Most times, he says one can remove or reduce the size of the lift. 

“Lifts are not forever as the body seems to assimilate the mechanics the lift induces and tries whenever possible to replicate the effect on its own,” notes Dr. D’Amico. 

Dr. Beekman emphasizes using information from the patient history and gait evaluation to determine treatment, including when to refer to an osteopath, chiropractor or physical therapist. One can consider a lift on the side with the low posterior superior iliac spine if none of the aforementioned specialists are available. However he also states that if the asymmetry is due to a restriction of the spine (which one sees by an asymmetry of the level of the head during gait), then the lift will aggravate the condition, adds Dr. Beekman. The lift can be part of the orthoses if there is a pronatory component attributable to the patient’s symptoms, according to Dr. Beekman. 

If both the anterior and posterior superior iliac spines are level and become unlevel when the patient is in the relaxed calcaneal stance position, Dr. Beekman recommends orthoses. When dispensing the devices, he makes sure that the pelvis is level (or at least improved) when the patient stands on them. 

Dr. Beekman goes on to say that if the anterior and posterior superior iliac spines are high on the same side with the patient in neutral calcaneal stance position, then there is a structural leg length issue that a lift may help. If a relaxed calcaneal stance levels the two iliac spines, pronation is a compensation, according to Dr. Beekman. In this situation, Dr. Beekman says orthoses without an appropriate lift will result in proximal pathology. 

If the anterior and posterior superior iliac spines are high on opposite sides, Dr. Beekman says the patient has a primary iliosacral dysfunction. If there is tenderness of the sinus tarsi on the side of the low posterior superior iliac spine, this is indicative of a lateral talus subluxation. 

“There is an acupuncture point called GB 40,” says Dr. Beekman. “I treat this with a sinus tarsi injection and rotate the needle twice around. This usually corrects the posterior innominate on that side.” 

He agrees that referral to an osteopath, chiropractor or physical therapist may also be beneficial for manipulation or musculotendinous balancing exercises. 

Dr. Beekman uses heel lifts and sole lifts to a height that does not cause a secondary spinal curve or transverse rotation of the pelvis. He says a heel lift could be up to one-quarter to one-half inch inside the shoe. If this is not enough to resolve symptoms, Dr. Beekman says one may have a shoemaker add a heel lift to the outside of the shoes and a sole lift inversely related to the amount of the patient’s equinus. 

Dr. Phillips relates that the standing radiological study can reveal the true length of the legs as well as a lot about function. He notes that sometimes asymmetries in coronal plane hip and leg angles produce a functional leg length difference. If the LLD is functional only, he treats the function only. However, if it is anatomical, then Dr. Phillips may also add some degree of lift under the short side. 

He uses a heel lift when the short leg has less ankle joint dorsiflexion than the long leg. However, if there is equal ankle joint dorsiflexion on both sides, Dr. Phillips may use a lift that runs the entire length of the shoe. 

“The question always arises whether I should use the lift inside or outside of the shoe,” explains Dr. Phillips. “Depending on the shoe depth, one-quarter to one-half inch of heel lift can usually go in the shoe. More than one-half inch usually means that the shoe itself needs modification.” 

If the discrepancy is less than one-half inch and there is little pronation in either foot, Dr. Phillips shares that he may utilize a lift only under the short side. However, he finds that when patients compensate for LLD through pronation of the foot on the long leg more than the short leg, that excess pronation on the long side usually does not autocorrect when lifting the short side. 

“Most of these cases require additional orthotic therapy,” notes Dr. Phillips. “Most of the time, I will add the lift directly to the orthotic so the patient doesn’t have to add lifts inside all of his or her shoes.”  

Dr. Beekman was previously an Assistant Professor of Podopediatrics and Sports Medicine at the Ohio College of Podiatric Medicine (now the Kent State University College of Podiatric Medicine). He was board-certified in both podiatric orthopedics and podiatric surgery. Dr. Beekman is now retired from private practice. 

Dr. Phillips is the Director of the Podiatric Medicine and Surgery Residency at the the Orlando Veterans Affairs Medical Center in Orlando, Fla. He is a Diplomate of the American Board of Foot and Ankle Surgery, and the American Board of Podiatric Medicine. Dr. Phillips is a clinical volunteer Professor of Podiatric Medicine with the College of Medicine at the University of Central Florida. He is also a member of the American Society of Biomechanics. 

Dr. D’Amico is a Professor and Past Chairman in the Division of Orthopedics at the New York College of Podiatric Medicine. He is a Diplomate of the American Board of Podiatric Medicine, a Fellow of the American College of Foot and Ankle Orthopedics, and a Fellow of the American Academy of Podiatric Sports Medicine. Dr. D’Amico is in private practice in New York City. 

Orthotics Q&A
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Guest Clinical Editor: Joseph C. D’Amico, DPM
Panelists: Stanley Beekman, DPM and R. Daryl Phillips, DPM
References

1. Oatis CA. Goals of gait assessment. In: Craik RL, Oatis CA, eds. Gait Analysis. St. Louis:Mosby;1995:328. 

2. Cavanaugh P. The shoe-ground interface in running. In: Mack RP. Symposium on the Foot and Leg in Running Sports. St. Louis:Mosby;1982:30-44. 

3. D’Amico JC, Dinowitz H, Polchanianoff M. Limb length discrepancy: an electrodynographic analysis. J Am Podiatr Med Assoc. 1985;75(12):639-643. 

4. D’Amico JC. Keys to recognizing and treating limb length discrepancy. Podiatry Today 2014;27(5):66-75. 

5. Blustien SM, D’Amico JC. Limb length discrepancy: identification, clinical significance and management. J Am Podiatr Med Assoc. 1985;75(4):200-206. 

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