Leg Length Inequality, Scoliosis and Back Pain

Leg length inequality, scoliosis, and back pain… what a title, and where shall we begin? It is common for chiropractors and other manual therapists to tell their patients that they have one leg shorter than the other, but what is the impact of a shorter leg on the spine? How does one acquire a short leg? Can it be measured or quantified? And what can be done about it? There is a lot to unpack to answer these questions, so hold on to your socks as we explore the interesting and controversial topic of leg length inequality, scoliosis, and back pain in this blog post.

For some people (manual therapists included), what I am about to tell you is controversial and the subject of much disagreement. The reason for this controversy is the misunderstanding of some practitioners that think dysfunction and misalignment of the sacroiliac joint alone can cause leg length inequality. This sentence might land me in a lot of trouble with some of these practitioners, but please bear with me and let me explain this misunderstanding. We have discussed in great detail in a previous blog post the anatomy and biomechanics of the sacroiliac joint, where we discussed the evidence that shows the sacroiliac joint is incapable of such a large amount of movement. I will refer you to my previous blog post on the sacroiliac joint that summarises the literature and points out that even manipulation of the sacroiliac joint under 3D x-ray has failed to show any change in the sacrum or sacroiliac joint comparing pre- and post-manipulation¹.

The main premise that must be accepted from the start of this discussion: if both legs are the same length, and the person is standing with both knees straight and on a flat surface, the human pelvis is incapable of the movement in the figure below.

Figure 1

Stand up and give it a try. At this point, some of you will already be bending one knee and coming to the same realisation. Remember, we have already established that the sacroiliac joint is not capable of such dramatic motions to result in this pelvic movement without serious pathology or injury in our previous blog post. If you haven’t read it already, I recommend it as the sacroiliac joint is an amazing areas of anatomy.

To achieve this level and type of movement, a more significant issue is necessary. An anatomically short leg is one example that will achieve this movement of the pelvis. One sided fallen medial longitudinal arche of the foot with ankle pronation and valgus of the same knee could also result in this movement. It is well-established that an short leg is a possible complication of hip replacement surgery (arthroplasty) ^2,3. I have seen several in my clinical career that have suffered the complication of leg length inequality, leading to scoliosis and back pain. These cases can be difficult to manage if the diagnosis of a leg length inequality is not found prior to commencing treatment.

Other causes of an anatomically short leg include fractures of the femur or the tibia (the fibula is not a weight bearing bone, therefore changes in its length following fracture will result in issues with knee and ankle function, but it is unlikely to affect the length of the limb itself). Following fracture of the femur or tibia, the two fracture fragments must find one-another to repair. This might happen naturally, or it might require surgical intervention. Regardless of how it heals, there is a chance that the fractured bone may heal longer or shorter than it was before the injury.

Another possible cause for an anatomically short leg is asymmetrical growth of one limb compared to the other during childhood and adolescent growth. Heuter-Volkman’s law states that increased or excessive pressure on a bone’s growth plate will stunt its growth, leading to asymmetrical length of limbs, or asymmetrically shaped vertebrae in the spine. Heuter-Volkman’s law is a consequence of Wolff’s law of bone adaptation to stress generated potentials. Asymmetrical vertebras are often called wedge shaped vertebrae and are typically seen in patients with scoliosis and kyphoscoliosis as the malformed vertebrae resulting in the global deformity of the spine.

How Can Leg Length Inequality be Measured?

There are several ways of accurately measuring and quantifying an anatomically short leg with pelvic tilt. This is where I get myself into more trouble with my fellow clinicians and colleagues. Whilst the initial assumption of a leg length inequality can be picked up during a good quality physical examination of the patient, it is not possible to quantify how short the leg is without standing x-rays of the patients lumbar spine and pelvis. I know some clinicians who claim to be able to do this without x-rays, but this claim has never been substantiated and means that any recommendations of a heel lift or an orthotic can be incorrect the patient.

There are two methods of quantifying how short the leg is, both have their pros and cons. The first is to x-ray the full length of both legs and measure the lengths of the tibias and femurs. This is logical, but time consuming requires between two and four images of the patient. Also, if you suffer from the same issue as I do, where the x-ray machine is a standing unit only and does not allow for the cassette to reach as low as the ankle with the standing patient, this option simply isn’t possible.

The second method is to perform a standing x-ray of the patient’s pelvis, known as a Ferguson projection (Fig. 2) and this is the chosen option here at Spriggs Chiropractic. The great thing about this projection is it removes the requirement to x-ray the length of both legs and it turns the issue of standing x-ray machine into a positive. This projection also becomes simply part of the patients’ x-ray examination of their lumbar spine, so no need to obtain additional views. The downside is the lateral (side) projection of the patients’ lumbar spine is required, as the x-ray tube need to be tilted to match the patients’ sacral base angle, which can only be obtained with a lateral view of their lumbar spine. Another downside to this projection is the patient must be standing in the centre of the film, with both feet hip width apart and no alteration of their standing posture can influence their positioning. It can be tricky to get right, which is something I always explain to my patients before obtaining this view.

Figure 2

This might be of interest to my fellow clinicians that’s the Ferguson projection has also been found beneficial for the assessment of the sacroiliac joints and sacroiliitis (inflammation of the sacroiliac joints) and of the sacroiliac joints^4–6. As you see from the image above, the Ferguson view brings the sacroiliac joints into view a lot better when compared to the standard pelvic view. The image above is of the same patient and demonstrates the benefit of a true Ferguson view for pelvic imaging. The Ferguson view is becoming more frequently used to assess patients with leg length inequality, scoliosis and back pain with many of my colleagues adopting this view into their clinical practice.

What Is the Impact of Leg Length Inequality on Scoliosis and Back Pain?

A leg length inequality has been associated with the development of low back pain^7–9. It has been found that patients with an anatomically short leg are up to 5.3 times more likely to have low back pain¹⁰.

As a result of Heuter-Volkmans’ and Wolff’s laws, malformed vertebrae are found in patients with anatomically short leg⁹ and accelerated degeneration of the lumbar spine and hip². The tilt of the pelvis shifts the patients centre of mass away from the mid-line towards the side of the short leg, leading to scoliosis of the lumbar spine⁹. This results in an increase in the mechanical loading of the spinal joints, spine discs, sacroiliac joint, hip, and knee joints on the same side as the short leg^11–14. Notwithstanding, excessive loading of the knee on the same side as the short leg leads to accelerated degeneration of the knee joint leading to osteoarthritis¹⁵.

Figure 3. On the left, the initial x-ray of this child’s spine without a heel lift. On the right, the same child with a heel lift correcting the leg length inequality and balancing the pelvis. Image taken from Sheha et al (2018).

Hip Spine Syndrome

Yes, there is such a thing as hip-spine syndrome. Could a leg length inequality or scoliosis be related to their back pain? It is the concurrent appearance of arthritis of the hip and lumbar spine with narrowing (stenosis) of the spinal canal space¹⁶. Murray et al (2017) state that there is a causal relationship between the amount of osteoarthritis of a patients lumbar spine, and hip to the magnitude of the leg length inequality². These findings were also related to the patients age, as in, the severity of the arthritis gets worse as we age. It seems sensible to me at least, to assess the patient’s leg length when a patient presents with low back pain and hip pain.

Treatments

It is probably obvious to you now, that one way to treat this issue is with prescription heel lifts or foot orthotics that aim to correct the leg length inequality and balance the pelvis. These orthotics need to take into account the severity of the leg length inequality and pelvic tilt, meaning that x-rays of the patients lumbar spine and pelvis need to be performed along with a detailed assessment of the patients feet. Here at Spriggs Chiropractic, we work along side an custom orthotics company that manufactures prescription orthotics that are made to take into account the whole patient.

There is always one draw back to prescription orthotics that require a heel lift that needs to be mentioned before ordering a prescription. The size of the heel lift impacts on the types of shoes that can accommodate the orthotic and still have room for your foot. However, 100% correction of the leg length inequality may not be required to improve a patients symptoms. Even a 50% correction can significantly reduce the excessive loading on the spine, pelvis, hip and knee, which can be all it needs to improve the patients’ symptoms. This is something your clinician will discuss with you at your consultation appointment, as it can be a large shift in lifestyle to have orthotics.

I hope this blog post is informative for you. I have been unable to blog much recently due to work commitments. However, the aim is to get back to it over the summer months now that the academic year is over. The next blog will be about my experiences of lecturing and working at London South Bank University. All the best!

Dr Mark Spriggs DC, MChiro, MSc, PGCert, FRCC

References:

1. Tullberg T, Blomberg S, Branth B, Johnsson R. Manipulation does not alter the position of the sacroiliac joint. A roentgen stereophotogrammetric analysis. Spine (Phila Pa 1976). 1998;23:1124-1129.
2. Murray KJ, Molyneux T, Le Grande MR, Castro Mendez A, Fuss FK, Azari MF. Association of Mild Leg Length Discrepancy and Degenerative Changes in the Hip Joint and Lumbar Spine. J Manipulative Physiol Ther. 2017;40(5):320-329. doi:10.1016/j.jmpt.2017.03.001
3. Flecher X, Ollivier M, Argenson JN. Lower limb length and offset in total hip arthroplasty. Orthop Traumatol Surg Res. 2016;102(1 Suppl):S9-S20. doi:10.1016/J.OTSR.2015.11.001
4. Bøcker Puhakka K, Jurik AG, Egund N, et al. Imaging of sacroiliitis in early seronegative spondylarthropathy: Assessment of abnormalities by MR in comparison with radiography and CT. Acta radiol. 2003;44(2):218-229. doi:10.1034/j.1600-0455.2003.00034.x
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