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Archive for the ‘Foot Anatomy’ Category

Heel pain is an incredibly common condition and there are very few Podiatrists who won’t see it on a daily basis in their clinics.  There are numerous different causes of heel pain, (not all mechanical), but the area that this blog entry is going to focus on in particular is the plantar calcaneal/heel spur.  It is yet another source of controversy, with no definitive agreement on the relationship of the spur and the surrounding tissues, or the actual source of the symptoms (if any) seen clinically.

Historically, it has been commonly accepted that heel spur formation is an abnormal finding and very closely correlated with the symptoms of heel pain.  It was reported that excessive traction (pulling) of the plantar fascia on its attachment at the heel resulted in chronic inflammation, which in turn resulted in a reactive ossification and subsequent extra bone forming in the shape of a ‘spur’. 1-3 This is perhaps why heel spurs and ‘plantar fasciitis’ are still to this day thought by many to be one entity.  Causation has been a point of confusion; does the traction and inflammation cause a heel spur, or does a heel spur cause tissue inflammation?  A chicken and egg scenario.  It is not uncommon to see statements that ‘plantar fasciitis’ is caused by heel spurs (admittedly this is on websites rather than academic journals), but is this factually correct?

The plantar calcaneal spur has been classically described as a bone outgrowth localised just anterior to the medial tuberosity of the calcaneus.4 This can not often be palpated clinically, but only seen radiologically as shown in the x-ray on the right above.

Another long term belief has been that individuals with heel pain are more likely to have pronated (flat) feet.5,6 As research has shown that lowering of the medial longitudinal arch of the foot increases plantar fascial tension7 it is easy to see how the connection between foot pronation, heel pain and heel spurs has been made.  However the concern is that any individual who presents to a specialist with heel pain and ‘flat feet’ could be hastily assigned a diagnosis of “plantar fasciitis caused by a heel spur”.  This is clearly unacceptable, and a specialist should have a much more thorough understanding of the research behind the pathological process.  So, how common are heel spurs?  Are they always problematic? Are they actually caused by traction? And what is their relationship with the plantar fascia?

How common are heel spurs?

Studies have shown that heel spurs are more common in pain free individuals than first thought, and it has been reported that anywhere between 11 and 27% of the population have radiographic evidence of a spur.5,8-13 Clearly this suggests they are not always associated with symptoms, and are not necessarily considered as ‘abnormal’ as once thought.  Interestingly, even a study performed over 45 years ago on 323 patients concluded that the plantar calcaneal spur was never the cause of pain and probably a normal manifestation of the aging process.14

However, the research does suggest that calcaneal spurs do seem to be over-represented in certain groups, such as females,10,11,13 individuals with osteoarthritis15,16 and older people.11,13,15,16 Calcaneal spurs have also found to be more common in those who are overweight.17

Where are heel spurs?

MRI of heel spur (arrow). PF=plantar fascia. M=1st layer of foot muscles

As I have already mentioned, it has long been thought that heel spurs and plantar fascia problems were undeniably linked.  Google ‘heel spurs’ and the term ‘plantar fasciitis’ is never far behind.  However, it is interesting to hear how the anatomic studies report the actual location of the bony protrusion.  Far from agreeing it resides solely within the plantar fascia as once thought, many studies found it can also be found above the plantar fascia.4,12,18 Some found it was much more commonly located in the other intrinsic musculature, (namely Flexor Digitorum Brevis and Abductor Digiti Minimi)4,18,19 and one study was as bold to firmly conclude that spurs do not develop within the plantar fascia.20

What is clear is that there is huge variability in the location of heel spur formation, and if we cannot unequivocally state that the spur is within the fascia (which we cannot) then the validity of its link with ‘plantar fasciitis’ is questionable.

What causes heel spurs?

As previously mentioned, the traditional theory for formation of plantar calcaneal spurs is what Menz and colleagues16 refer to as the longitudinal traction hypothesis, i.e. the plantar fascia pulling on the heel bone and causing the formation of a spur.  Despite the anatomical studies showed that the spur is far from consistently found in the fascia, it has been suggested that there could be an element of tensile force exerted on the calcaneus from a variety of the other structures which attach to it.4,19

An alternative theory, termed the vertical compression hypothesis16 and was proposed by Kumai and Benjamin in 2002.20 This theory suggests that calcaneal spurs are outgrowths which form in response to repetitive vertical stress in an attempt to protect against microfractures.  This idea is supported by histological studies which show that the bony trabeculae are NOT aligned in the direction of soft tissue traction.16,18 Li and Muehleman18 found that the direction of the trabeculae suggested that the force causing the pathological response was consistent with the external ground reaction force vector.

Conclusions

So what does all this mean in plain English?  It means that we used to think a spur was caused by the plantar fascia pulling on the bone.  This is highly unlikely as the spur is seldom found in the plantar fascia.  If traction is the cause it is more likely to be caused by other musculature such as Flexor Digitorum Brevis or Abductor Digiti Minimi.  However these bony protrusions could instead be caused by the repetitive vertical loading (the heel continuously hitting the floor, and the floor of course hitting it back) with the spur forming as a protective mechanism.  Of course we cannot overlook the fact that there may be a combination of both traction and compression present in the aetiology of spur development.  We also know that anywhere up to a quarter of the population may have a heel spur, but this will not always be problematic.

So, in summary:

The pathophysiology of plantar calcaneal heel spurs is poorly understood.

The presence of a plantar calcaneal spur does not always lead to the development of heel pain.

Plantar calcaneal spurs do appear to be associated with obesity, osteoarthritis and the aging process.

It is unclear whether spur formation is due to longitudinal traction of the plantar tissues or an adaptive response to vertical loading/compression (or both).

It is erroneous to assume there is a causal relationship between plantar calcaneal spurs and ‘plantar fasciitis’.

References

  1. DuVries, H.L. (1957). Heel spur (calcaneal spur). Archives of Surgery, 74: 536-542.
  2. Furey, J.G. (1975). Plantar fasciitis: the painful heel syndrome. Journal of Bone and Joint Surgery Am, 57: 672-673.
  3. Bergmann, J.N. (1990). History and mechanical control of heel spur pain. Clinics in Podiatric Medicine and Surgery, 7: 243-259.
  4. Abreu, M.R., Chung, C.B., Mendes, L. et al. (2003). Plantar calcaneal enthesophytes: new observations regarding sites of origin based on radiographic, MR imaging, anatomic, and paleopathologic analysis. Skeletal Radiology, 32: 13-21.
  5. Prichasuk, S., Subhadrabandhu, T. (1994). The relationship of pes planus and calcaneal spur to plantar heel pain. Clinical Orthopaedics and Related Research, 306: 192-196.
  6. Irving, D.B., Cook, J.L., Young, M.A. et el. (2007). Obesity and pronated foot type may increase the risk of chronic plantar heel pain: a matched case-control study. BMC Musculoskeletal Disorders, 8: 41.
  7. Kogler, G.F., Solomonidis, S.E., Paul, J.P. (1996). Biomechanics of longitudinal arch support mechanisms in foot orthoses and their effect on plantar aponeurosis strain. Clinical Biomechanics, 11: 243-252.
  8. Rubin, G., Witten, M. (1963). Plantar calcaneal spurs. American Journal of Orthopaedics, 5: 38-41.
  9. McCarthy, D.J., Gorecki, G.E. (1979). Anatomical basis of inferior calcaneal lesions: a cryomicrotomy study. Journal of the American Podiatric Medical Association, 69: 527-536.
  10. Shama, S.S., Kominsky, S.J., Lemont, H. (1983). Prevalence of non-painful heel spur and its relation to postural foot position. Journal of the American Podiatric Medical Association, 73: 122-123.
  11. Banadda, B.M., Gona, O., Vas, R., et al. (1992). Calcaneal spurs in a black African population. Foot & Ankle, 13: 352-354.
  12. Barrett, S.L., Day, S.V., Pignetti, T.T. et al. (1995). Endoscopic heel anatomy: analysis of 200 fresh frozen specimens. Journal of Foot & Ankle Surgery, 34: 51-56.
  13. Riepert, T., Drechsler, T., Schild, H. et al. (1996). Estimation of sex on the basis of radiographs of the calcaneus. Forensic Science International, 77: 133-140.
  14. Lapidus, P.W., Guidotti, F.P. (1965). Painful heel: report of 323 patients with 364 painful heels. Clinical Orthopaedics and related Research, 39: 178-186.
  15. Gerster, J.C., Vischer, T.L., Bennani, A. et al. (1977). The painful heel. Comparative study in rheumatoid arthritis, ankylosing spondylitis, Reiter’s syndrome, and generalised osteoarthritis. Annals of the Rheumatic Diseases, 36: 343-348.
  16. Menz, H.B., Zammit, G.V., Landorf, K.B. et al. (2008). Plantar calcaneal spurs in older people: longitudinal traction or vertical compression? Journal of Foot & Ankle Research, 1:7.
  17. Sadat-Ali, M. (1998). Plantar fasciitis/calcaneal spur among security forces personnel. Military Medicine, 163: 56-57.
  18. Li, J., Muehleman, C. (2007). Anatomic Relationship of Heel Spur to Surrounding Soft Tissues: Greater variability than previously reported. Clinical Anatomy, 20: 950-955.
  19. Smith, S., Tinley, P., Gilheany, M. et al. (2007). The inferior calcaneal spur – Anatomical and histological considerations. The Foot, 17: 25-31.
  20. Kumai, T., Benjamin, M. (2002). Heel spur formation and the subcalcaneal enthesis of the plantar fascia. The Journal of Rheumatology, 29: 1957-1964.
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It is often stated that the human foot has 3 arches; two longitudinal arches and the transverse arch (sometimes also referred to as the metatarsal arch).1 Whereas the presence of longitudinal arches are unanimously accepted, the transverse metatarsal arch of the foot is considered to be quite controversial.  Believe it or not its existence has been debated since last century.  But what is the transverse metatarsal arch?  And what does the research actually tell us about it?

The existence of a transverse arch at the metatarsal region would require the pressure to be greatest at the areas beneath the 1st and 5th metatarsal heads, and the area of the 2nd, 3rd and 4th metatarsal heads to be elevated relative to this.  This gives us the ‘tripod’ like weight distribution of the foot which was first described by Kapandji in 1970.2 However, the first descriptions of the transverse metatarsal arch date back as far as 100 years prior to Kapandji’s work3 and several papers published in Germany between 1882 and 1927 actually concluded that no transverse arch of the foot was usually present.4-7 Much of the research produced following Kapandji’s work concurs with these conclusions regarding the transverse metatarsal arch being a misnomer.

So if the presence of a transverse metatarsal arch has long been questioned, why have so many authors, and indeed medical professionals, subscribed to this theory for so long (and continue to do so) in spite of growing evidence against it?

The conception of the foot bearing its weight on three points must be quite attractive in order to persist (Jones, 1941)8

When a patient presents with diffuse pain across the forefoot, what should be performed is thorough examination of the region, identification of the anatomical structure which is involved, and then a management plan directed towards reducing the symptoms with the most appropriate treatment available.  However, all too often a clinician will diagnose ‘metatarsalgia’ (NOT a diagnosis, but we’ll save that for another blog) caused by ‘dropped metatarsals’ or ‘a fallen metatarsal arch’.  It’s very quick and very easy, and you can see how it doesn’t require too much thinking.  For these clinicians to accept that a transverse metatarsal arch does not exist would require them to change their entire clinical practice, and for many this sort of paradigm shift in thinking is too uncomfortable to accept, so instead they continue as they are.

So, 100 year old journal articles written in German aside, lets look at some of the more current research which has looked at the mythical transverse metatarsal arch.

In 1997, Daentzer et al.9 performed a study on 100 feet.  The age range of the participants in the study was between 10-72 years old.  None of the participants had any foot deformity or symptoms.  Ultrasonography was performed at the level of the metatarsal heads in both non weight bearing and weightbearing.  Barefoot plantar pressure measurements were recorded using a force plate.  Their findings/conclusions: Pressures are usually highest underneath the 2nd, 3rd and 4th metatarsal heads, there is no transverse metatarsal arch, and the forefoot is normally flat at the level of the metatarsal heads.

In 1999, Luger et al.10 performed a study on 720 feet (the largest study to my knowledge).  The age range of the participants in the study was 18-83 years old.  Interestingly they included individuals with a variety of foot symptoms and abnormalities as well as pain free individuals.  The all had static and dynamic barefoot pressure measurements taken.  Their findings/conclusions: Only 22 feet out of 720 (3%) had a dynamic metatarsal arch whilst walking, and this was only found in the feet classified as having deformity or pain.  Not only was a transverse metatarsal arch rarely seen, but they concluded that it actually indicated a possible pathological deformity (i.e it is an abnormality which may cause problems)

In 2003, Kanatli et al.11 performed a study on 32 feet.  The age range of the participants in the study was 20-30 years old.  All participants were pain free and had no foot deformities.  Barefoot plantar pressure measurements were taken whilst walking.  Their findings/conclusions: Significantly higher pressures were recorded beneath the 2nd and 3rd metatarsal heads, and the transverse metatarsal arch did not exist in normal subjects.

As you can see one of the common findings seen in the research discussed has been that higher pressures are not seen beneath the 1st and 5th metatarsal heads during gait.  Other authors have investigated this employing pressure measurement equipment and found that the pressures in the middle metatarsals are consistently greater than the 1st and 5th metatarsals.12,13 All of the research suggests that the tripod configuration of the foot is completely erroneous, and without this, it is obvious that it is not possible for there to be a transverse metatarsal arch.  Clinicians who continue to talk about the transverse arch, and offer treatments for its ‘collapse’ are either uninformed, bogged down in old habits or in denial.

References

  1. Williams, P.L. et al. (1995) Gray’s Anatomy. 38th Edition, Churchill Livingstone, New York.
  2. Kapandji, L.A. (1970) The Physiology of the Joints. E & S Livingstone, Edinburgh.
  3. Henle, J. (1871) Handbuch der Knochenlehre des Menschen. Vieweg, Braunschweig.
  4. Beely, F. (1882) Zur Mechanik des Stehens. Uber die Bedeutung des Fussgewolbes im Stehen. Arch klin Chir, 27: 457-471.
  5. Momburg, F.A. (1909) Die Stutzpunkte des Fusses beim Gehen und Stehen. Dtsch med Wschr, 4: 148-152.
  6. Frostell, G. (1925) Beitrag zur Kenntnis der vorderen Stutzpunkte des Fusses, sowie des Fusswinkels beim Stehen und Gehen. Z  Orthop Chir, 47: 3-54.
  7. Abramson, E. (1927) Zur Kenntnis der Mechanik des Mittelfusses. Skand Arch Physiol, 51: 175-234.
  8. Jones, R.L. (1941) The Human Foot. An experimental study of its mechanics, and the role of its muscles and ligaments in support of the arch. American Journal of Anatomy, 68: 1-39.
  9. Daentzer, D., Wulker, N., & Zimmermann, U. (1997) Observations concerning the transverse metatarsal arch. Foot and Ankle Surgery, 3: 15-20.
  10. Luger, E.J., Nissan, M., Karpf, A., Steinberg, E.L., & Dekel, S. (1999) Patterns of weight distribution under the metatarsal heads. The Journal of Bone & Joint Surgery (Br), 81: 199-202.
  11. Kanatli, U., Yetkin, H., & Bolukbasi, S. (2003) Evaluation of the transverse metatarsal arch of the foot with gait analysis. Arch Orthop Trauma Surg, 123: 148-150.
  12. Cavanagh, P.R., Rodgers, M.M., & Iiboshi, A. (1987) Pressure distribution under symptom-free feet during barefoot standing. Foot and Ankle, 7: 262-276.
  13. Hennig, E.M., & Milani, T.L. (1993) Die Dreipunktuntersttzung des Fusses. Eine Druckverteilungsanalyse bei statischer und dynamischer Belastung. Z Orthop, 131: 279-284.

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