What Role Does Equinus Play In Heel Pain?

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Although equinus has been recognized for centuries, are podiatrists failing to consider it as a possible contributing factor in heel pain cases? In a provocative article, these authors combine their insights with a review of the literature and speculate about the emerging role of endoscopic gastrocnemius recession in treating complex heel pain cases.

     Equinus is one of the earliest published topics when it comes to surgery of the lower extremity. However, there still remains considerable controversy within podiatric medicine and surgery in regard to the recognition and treatment of equinus.

     Equinus is the number one risk factor for the development of heel pain.¹ Plantar fasciosis is the foot pathology most commonly associated with gastrocnemius equinus. ²

     While a recent online Podiatry Today survey on equinus and heel pain was not a scientifically constructed questionnaire, it does provide some interesting information on how our profession is dealing with this condition. Out of the 267 respondents who completed the survey, nearly 22 percent said they diagnose equinus in less than 10 percent of heel pain cases. Yet over 84 percent of the respondents almost always recommend calf stretching exercises for patients with heel pain. More than half of the respondents never surgically treat equinus. Only 1.5 percent surgically treat equinus greater than 50 percent of the time.

     Although heel pain can be complex and difficult to treat, there is a tendency to assume that we know everything about heel pain. We also often hear the podiatric dogma that 90 percent of heel pain cases “resolve with the most minimal of treatment.” ³ This type of individual and profession-wide complacency may lead to less than desirable results in many cases for any foot condition, especially complex heel pain.

     In July 2007, Rocco and colleagues reported a 93.6 percent cure rate with gastrocnemius recession in patients with isolated chronic plantar fasciitis (fasciosis). ⁴ They reported no significant complications and even reported success in patients with BMIs of greater than 30. In the senior author’s opinion, this is a very significant and important advancement for treating plantar heel pain.

     In combination with the existing body of knowledge regarding the relationship between plantar heel pain and equinus, the work by Rocco and colleagues may have application to other foot pathology. With integration into advanced surgical training residency programs, we will likely see more emphasis placed on the diagnostic and therapeutic considerations of a tight gastrocnemius.

A Closer Look At The Connection Between Equinus And Heel Pain

There is still some debate as to how we define equinus and what is normal. Ten degrees of dorsiflexion and 20 degrees of plantarflexion of the ankle are considered the minimum amount necessary for normal range of motion during gait. ⁵ There is still skepticism on whether equinus contributes [10]
biomechanically to any foot condition. However, Subotnick is credited with the statement that equinus “is the greatest symptom producer in the foot.” ^6,7

     Subotnick had the incredible understanding and courage to state in his 1971 article that one needs to treat the gastrocnemius contracture in patients with forefoot manifestations in addition to the surgical correction of the forefoot pathology. ⁷ In children with cerebral palsy, Holstein observed the development of hallux valgus in the foot with equinovalgus with no evidence of the deformity prior to walking. ⁸

     The three greatest risk factors for developing plantar fasciosis are: limitation of ankle joint dorsiflexion (equinus), obesity and the amount of time spent weightbearing. ¹ Equinus is the single biggest risk factor with a 23.3-fold odds ratio for the development of plantar fasciosis in comparison with the control group, which had at least 10 degrees of dorsiflexion. ¹

     As a profession, why are we largely ignoring the single greatest risk factor (equinus) and probably one of the most pervasive etiological factors of foot pathology? ^5,9,10

     We know there are four simple and general classifications of equinus. These classifications include: gastrocnemius, soleal, gastrocsoleal and osseous. We also know the most frequent cause of limitation at the level of the ankle joint is caused by a tight gastrocnemius muscle. Equinus is not a difficult condition to diagnose and it is well understood in biomechanical context. DiGiovanni’s 2002 study showed that 88 percent of patients with foot pathology have equinus. ⁶

     In one study, researchers found that out of 209 consecutive patients who presented at the Kaiser Permanente clinics over a six-week period with foot pain, 96.5 percent had equinus. ¹¹ Of the 63 patients who complained of heel pain, all but one had limitation of ankle joint dorsiflexion and researchers described that patient as having traumatically [11]
induced plantar fasciitis. Bowers and Castro clinically observed a 50 to 60 percent incidence of equinus in all patients examined for any foot or ankle problem. ²

     Researchers have reported that tension in the plantar fascia is correlative to the tension force transmitted through the Achilles tendon. It is widely believed that some type of mechanical aberration is responsible for degeneration within the plantar fascia. This mechanical aberration is usually described as a tension force but is more likely a shearing type force based on work that has been done with other tendinopathies. ^12-16 Recent work in the histology of inferior calcaneal spurs supports this contention as the authors have noted trabeculae in the spur itself as being perpendicular to the plantar fascia. ¹⁷

A Historical Perspective On Equinus

In 1913, Nutt extensively described the effects of a tight gastrocnemius muscle on the foot and lower extremity. Nutt said this condition may “cause muscular pain from stretching of the calf muscles or pain about the knee from the strain of [12]
supporting the body with the knee slightly flexed … .”

     Alternatively, a short calf muscle complex may lead to “pain at the astragalo-scaphoid articulation from strain of overextension or over the tuberosities of the os calcis from a periostitis set up by strain on the plantar fascia,” according to Nutt. ¹⁸

     Nutt attributed the heel pain to a periostitis and this was a very astute observation at that time. Although we know today that the plantar fascia suffers from degeneration rather than an inflammation, Nutt was able to make the connection of the important role equinus plays in the etiology of plantar fasciosis almost 100 years ago. In his book, he also describes a complex machine he devised to stretch the calf muscle as well as the operative treatment for tendo-Achilles lengthening.18 Interestingly, in the same year, Vulpius described the surgical technique for gastrocnemius recession. ¹⁹

     If we continue down this historic trail of the diagnosis, treatment and understanding of equinus, one can see the bridge from orthopedics to podiatry in the 1960s.

     In the lead author’s opinion, Thomas Sgarlato, DPM, is one of the key members of a very special and brilliant small group of podiatrists who steered the course of our profession to where we know it today. Dr. Sgarlato was critical in our understanding of how important a role gastrocnemius equinus played in the most common foot pathology. ^20-22 Nearly 40 years ago, he was not only teaching and publishing his work on medial gastrocnemius recession, Dr. Sgarlato was seeing the overwhelmingly positive surgical outcomes that we continue to see today with this procedure.

     His work in this subject area is well known in all professions dealing with foot surgery and pathomechanics. In a recent phone conversation, Dr. Sgarlato notes that “the medial gastroc is the culprit” and although equinus is a big deal, the profession overlooks it. Dr. Sgarlato also recalls that he, the late Merton Root, DPM, and some students assessed 5,000 school children in San Francisco in the 1960s and 20 to 25 percent of them had equinus. He extrapolated these findings to suggest that possibly up to one-quarter of humans have equinus. ²³

     Dr. Sgarlato notes that in 1963, Root was doing tendo-Achilles lengthenings and McGlamry was doing tongue in groove gastrocs while Sgarlato discovered he could just release the medial gastroc.

      “Podiatry was in the dark ages then and we did not have the tools to react to it (equinus),” says Dr. Sgarlato.

     Knowing what we know now, why don’t we as a profession today in 2008 diagnose and surgically treat [13]
gastrocnemius equinus more?

      “The problem is training,” says Dr. Sgarlato. “If more podiatric surgeons were trained to do the technique, and especially with the endoscopic approach that we did not have, more people would be helped.”

Is It Time To Redefine ‘Conservative’ Care For Complex Heel Pain Cases?

There are inherent advantages to treating one of the major etiological factors of a condition such as equinus rather than surgically operating on just a “symptom” such as the hammertoe.

     Nothing illustrates this point more than the failed “Morton’s neuroma” excision patient who still has diffuse forefoot pain from beneath the second metatarsal head laterally to the fifth metatarsal head, with hyperkeratosis and contracted lesser digits, but now truly has a recurrent Morton’s neuroma.

     When one examines these patients closely, one may find they were never evaluated for equinus. Consequently, the real cause of the forefoot pathology was never really diagnosed and subsequently never treated. Maybe it would have been more “conservative” to simply release the tight [14]
gastrocnemius via a minimally invasive endoscopic technique and then allow time for the forefoot to respond to the decreased plantar pressures and improved tendon balance. We have been able to demonstrate this concept and published this several years ago in JAPMA. ²⁴

     Those who treat heel pain, including 96.4 percent of Podiatry Today survey respondents, accept that stretching exercises are one of the keystones of conservative treatment. However, there has been very little published on the efficacy of stretching to reduce limitation of dorsiflexion of the ankle. ²⁵

     DiGiovanni, et al., was able to show that a plantar fascia specific stretch was statistically significant in the treatment of plantar fasciosis in comparison to the usual calf stretch, which is recommended in nearly every article written on the conservative management of heel pain. ²⁶

     However, in Grady and Saxena’s 1991 study, they were not able to show statistical significance of different durations of stretch and were only able to demonstrate an average of increased flexibility of a few degrees. While it is well established that there are different grades of plantar fasciosis, we know there are significant differences of “limitation of dorsiflexion” from one patient to the next. They also state that “it is recognized that all persons cannot [15]
stretch to the same degree.” ²⁵

     In her 2001 article discussing the clinical outcome of using night splints, Evans showed that only six of 20 patients with heel pain treated from six to 52 weeks demonstrated the ability to reach 10 degrees of dorsiflexion. ²⁷ Clearly in severe cases of heel pain with concomitant severe tightness of the gastrocnemius, one should consider recession as a foundation of treatment.

Current Concepts With The Endoscopic Gastrocnemius Recession

Researchers have described different techniques of endoscopic gastrocnemius recession (EGR). ^9,28 DiDomenico, et al., have reported some interesting observations. They note few complications (as we have observed over the last five years) but there was no delineation of sural nerve complications if there were any. The authors did report transient “weakness” in a few patients. They reported an average increase in dorsiflexion of 18 degrees, which is the equivalent of improved range of motion reported in open type surgery. ²⁸

     While DiDomenico and colleagues used a two-portal technique and similar instrumentation, there is some variation in surgical techniques. They describe sliding the [16]
cannula over the obturator after placement of the “blunt trocar” within the leg.

     This system, originally designed for endoscopic plantar fasciotomy (EPF), was intended to be used with the cannula and obturator coupled together prior to introduction. The surgeon would then remove the obturator, thereby leaving the slotted cannula in proper anatomical placement.

     Their method requires an additional step that one can eliminate by using the instruments as originally designed and obviates use of the intracannular markings, which can be a guide as to how much medial gastrocnemius the surgeon has cut. We also recommend use of the retrograde hook knife, which minimizes the potential for injury to the muscle. Any surgical technique should have the same goals: safety for the patient, efficacy and surgeon reproducibility. We also recognize that the evolution of surgical technique usually improves patient outcomes.

     Clearly, EGR will fail if the limitation is caused by other forms of equinus such as a bony block or a soleal type of equinus. Clinically, it is very easy to determine the type of equinus present with the Silfverskiold maneuver although it is not as easy to evaluate the actual amount of dorsiflexion available. In fact, DiGiovanni developed an “equinometer” and reported on the inability to precisely determine clinically the actual degrees of dorsiflexion of the foot to the ankle. ²⁹

     It is important for the clinician to evaluate the true dorsiflexion (as opposed to compensation) occurring at the level of the midtarsal joint. This sometimes requires slight supination or at least the foot being in a subtalar joint neutral position.

     Endoscopic gastrocnemius recession is indicated as an isolated procedure or in conjunction with other types of planned lower extremity surgical procedures when there is documentation of pathologic gastrocnemius contracture.

A Guide To The EGR Surgical Technique

One would perform the two-portal technique using the Endotrac™ instrumentation (Instratek). The instrumentation is very similar to the instruments surgeons use for the endoscopic plantar fasciotomy (EPF) with the substitution of a special “blunt nose” obturator. With proper training and an understanding of anatomy, the EGR has a relatively small learning curve for the experienced surgeon and is safe for the patient.

     Surgeons usually perform the EGR with the patient in a supine position, which facilitates intraoperative positioning and anesthesia. Any procedure that requires changing a patient from the prone position to a supine position increases intraoperative time and adds risk for the patient. General anesthesia is usually required due to the fact that a thigh tourniquet is required.

     As one can see in the right photo on page 46, preoperative mapping of the topographical anatomy can help to estimate the course of the sural nerve. It is important to note there is a high degree of neuroanatomical variation.

     Several published studies are helpful when it comes to determining the course of the sural nerve. ^18,30 One can easily palpate the insertion of the Achilles tendon. Delineate the gastrocnemius aponeurosis with a surgical marker as it flattens out and widens medially and laterally from where the Achilles tendon begins.

     Tashjian, et al., determined that the sural nerve is approximately 12 mm from the lateral border of the aponeurosis at the gastroc soleal junction. ¹⁸ They were surprised in their cadaveric research that it was this lateral at this proximal level. It is well known that distally at the level of the malleolus, the sural nerve is usually just lateral and anterior to the lateral aspect of the Achilles tendon.

     Unlike the EPF procedure in which cannula placement is absolutely critical for surgical efficacy, there is some latitude for placement of the obturator/cannula instrumentation for EGR as demonstrated by our anatomical cadaveric study. ^31,32

     Postoperative management for EGR performed in conjunction with other procedures such as a Lapidus will be subordinate to the postoperative requirements of the primary procedure. If we perform the EGR procedure alone, we allow patients immediate weightbearing with a walking boot. We advise them to elevate the extremity during the first 48 hours and to keep ambulation even with the boot to a minimum.

     At approximately four weeks, we allow ambulation without the walking boot and a gradual increase of activity to tolerance to the eighth week. High impact athletics may not be possible until 12 to 16 weeks after surgery, depending on the athletic endeavor and the patient’s progress. We have not seen any substantive loss of muscle grade or strength in patients who have had EGR.

Pertinent Insights On Addressing Potential Complications

There is always the possibility with gastrocnemius recession surgery, either open or with endoscopic technique, for injury to the sural nerve. We have noted two serious injuries to sural nerves from the endoscopic technique, which demonstrated amputation neuromata at the time of revision surgery. With any surgical technique, one must analyze the benefits with respect to risks and this is also the case for this surgical technique.

     The sural nerve is solely a cutaneous nerve, which supplies innervation to the skin on the dorsal lateral aspect of the foot and lateral part of the ankle. Upper extremity nerve surgeons frequently use it for nerve grafting, which sheds light on its perceived importance in the lower extremity.

     We have seen far more injuries to the sural nerve from ORIF of malleolar and calcaneal fractures, and lateral ankle stabilization surgery. Occasionally, patients will present postoperatively with what is believed as traction neuropathy of the sural nerve due to the increase in dorsiflexion that EGR achieves. This is almost always transitory and self-limiting by about the sixth to eighth week after surgery.

     If there is any question of sural nerve axontomesis versus a traction neuropathy, implementation of neurosensory testing with the Pressure Specified Sensory Device (PSSD, Sensory Management) in combination with either the presence or absence of a localized or distally migrating Tinel’s sign can give the surgeon insight into the extent and nature of the peripheral nerve injury.

     We have had a couple of hematomas develop after EGR. While some deep vein thromboses have occurred after EGR, we have not seen one in more than five years of performing the surgery. There have been several patients who have reported muscular pain in the calf between the third and eight week postoperatively but these have always been associated with excessive activity and muscle strain. Ice, rest and returning patients to a walking boot have always resolved this condition.

     With very careful attention to the topographical anatomy, consideration of sural nerve anatomical variability and judicious and meticulous surgical technique, the surgeon can usually avoid these complications.

     Even in those rare cases of sural nerve complication, it is usually reported as simply numbness in a small area of the skin on the dorsal lateral aspect of the foot but this rarely acts as a pain generator.

In Summary

The detrimental biomechanical effect of the limitation of ankle joint dorsiflexion on the foot and especially plantar fasciosis has been surgically treated for nearly 100 years.

     With the recent advent of minimally invasive endoscopic procedures to perform gastrocnemius recessions, emerging research in this area and the increased training of more podiatric surgeons in these techniques, it is likely that more patients will have definitive podiatric surgery which actually addresses one of the most devastating pathogenic forces inflicted on the lower extremity. This is in stark contrast to palliative foot surgery, which merely deals with the symptom at the end of the biomechanical chain.

     Again, we must ask several questions. Are we really doing the patient the greatest good by ignoring and not treating such an elemental and devastating musculoskeletal condition? Is it just due to a lack of training that most foot surgeons are not performing EGR (or open) more commonly? Is this especially true in severe cases in which equinus is so evidently documented?

     Dr. Barrett is a Fellow of the American College of Foot and Ankle Surgeons, and is an Adjunct Associate Professor within the Arizona Podiatric Medicine Program at Midwestern University College of Health Sciences in Glendale, Ariz.

     Mr. Whiting is a third-year student at the Arizona Podiatric Medicine Program at Midwestern University College of Health Sciences.

References:

1. Riddle DL, Pulisic M, Pidcoe P, Johnson RE. Risk factors for plantar fasciitis: a matched case-control study. J Bone Joint Surg Am. 2003 May;85-A(5):872-7.
2. Bowers AL, Castro MD. The mechanics behind the image: foot and ankle pathology associated with gastrocnemius contracture. Semin Musculoskelet Radiol. 2007 Mar;11(1):83-90.
3. Atkins D, Crawford F, Edwards J, Lambert M. A systematic review of treatments for the painful heel. Rheumatology (Oxford). 1999 Oct;38(10):968-73.
4. Chilvers MR, Rocco JJ, Manoli A. Gastrocnemius slide found safe, effective as treatment for chronic plantar fasciitis. Toronto: American Orthopedic Foot and Ankle Society 23rd Annual Summer Meeting, 2007.
5. Lamm BM, Paley D, Herzenberg JE. Gastrocnemius soleus recession: a simpler, more limited approach. J Am Podiatr Med Assoc. 2005 Jan-Feb;95(1):18-25.
6. DiGiovanni CW, Kuo R, Tejwani N, et al. Isolated gastrocnemius tightness. J Bone Joint Surg Am. 2002 Jun;84-A(6):962-70.
7. Subotnick SI. Equinus deformity as it affects the forefoot. J Am Podiatry Assoc. 1971 Nov;61(11):423-7.
8. Holstein A. Hallux valgus--an acquired deformity of the foot in cerebral palsy. Foot Ankle. 1980 Jul;1(1):33-8.
9. DiDomenico LA, Adams HB, Garchar D. Endoscopic gastrocnemius recession for the treatment of gastrocnemius equinus. J Am Podiatr Med Assoc. 2005 Jul-Aug;95(4):410-3.
10. Downey MS, Banks AS. Gastrocnemius recession in the treatment of nonspastic ankle equinus. A retrospective study. J Am Podiatr Med Assoc. 1989 April;79(4):159-74.
11. Hill RS. Ankle equinus. Prevalence and linkage to common foot pathology. J Am Podiatr Med Assoc. 1995 June;85(6):295-300.
12. Erdemir A, Hamel AJ, Fauth AR, Piazza SJ, Sharkey NA. Dynamic loading of the plantar aponeurosis in walking. J Bone Joint Surg Am. 2004 Mar;86-A(3):546-52.
13. Almekinders LC. Tendinitis and other chronic tendinopathies. J Am Acad Orthop Surg. 1998 May-Jun;6(3):157-64.
14. Almekinders LC, Temple JD. Etiology, diagnosis, and treatment of tendonitis: an analysis of the literature. Med Sci Sports Exerc. 1998 Aug;30(8):1183-90.
15. Lemont H, Ammirati KM, Usen N. Plantar fasciitis: a degenerative process (fasciosis) without inflammation. J Am Podiatr Med Assoc. 2003 May-Jun;93(3):234-7.
16. Wearing SC, Smeathers JE, Urry SR, Hennig EM, Hills AP. The pathomechanics of plantar fasciitis. Sports Med. 2006; 36(7):585-611.
17. Li J, Muehleman C. Anatomic relationship of heel spur to surrounding soft tissues: greater variability than previously reported. Clin Anat. 2007 Nov;20(8):950-5.
18. Tashjian RZ, Appel AJ, Banerjee R, DiGiovanni CW. Anatomic study of the gastrocnemius-soleus junction and its relationship to the sural nerve. Foot Ankle Int. 2003 Jun;24(6):473-6.
19. Vulpius O, Stoffel A. Tenotomie der end schnen der mm. gastrocnemius el soleus mittels mittels rutschenlassens nach vulpius. In Orthopadische Operationslehre, pg. 29-31, Ferdinard Enke, Stuttgart, 1913.
20. Sgarlato TE. A Compendium of Podiatric Biomechanics. California College of Podiatric Medicine, San Francisco, Calif., 1971.
21. Sgarlato TE. Medial gastrocnemius tenotomy to assist body posture balancing. J Foot Ankle Surg. 1998 Nov-Dec;37(6):546-7.
22. Sgarlato TE, Morgan J, Shane HS, Frenkenberg A. Tendo-Achilles lengthening and its effect on foot disorders. J Am Podiatry Assoc. 1975 Sep;65(9):849-71.
23. Personal communication with Thomas Sgarlato, DPM, 2008.
24. Barrett SL, Jarvis J. Equinus deformity as a factor in forefoot nerve entrapment: treatment with endoscopic gastrocnemius recession. J Am Podiatr Med Assoc. 2005 Sep-Oct;95(5):464-8.
25. Grady JF, Saxena A. Effects of stretching the gastrocnemius muscle. J Foot Surg. 1991 Sep-Oct;30(5):465-9.
26. Digiovanni BF, Nawoczenski DA, Malay DP, et al. Plantar fascia-specific stretching exercise improves outcomes in patients with chronic plantar fasciitis. A prospective clinical trial with two-year follow-up. J Bone Joint Surg Am. 2006 Aug;88(8):1775-81.
27. Evans A. Podiatric medical applications of posterior night stretch splinting. J Am Podiatr Med Assoc. 2001 Jul-Aug;91(7):356-60.
28. Saxena A, Gollwitzer H, Widtfeldt A, DiDomenico LA. Endoscopic gastrocnemius recession as therapy for gastrocnemius equinus. Z Orthop Unfall. 2007 Jul-Aug;145(4):499-504.
29. Digiovanni CW, Holt S, Czerniecki JM, Ledoux WR, Sangeorzan BJ. Can the presence of equinus contracture be established by physical exam alone? J Rehabil Res Dev. 2001 May-Jun;38(3):335-40.
30. Carl T, Barrett SL. Cadaveric assessment of the gastrocnemius aponeurosis to assist in the pre-operative planning of two portal endoscopic gastrocnemius recession (EGR). The Foot. September 2005;15(3):137-40.
31. Barrett SL, Day SV. Endoscopic plantar fasciotomy: two portal endoscopic surgical techniques--clinical results of 65 procedures. J Foot Ankle Surg. 1993 May-Jun;32(3):248-56.
32. Barrett SL, Day SV, Pignetti TT, Egly BR. Endoscopic heel anatomy: analysis of 200 fresh frozen specimens. J Foot Ankle Surg. 1995 Jan-Feb;34(1):51-6.

Additional Reference
33. Brown JB. Case of equino-varus acquisitus successfully treated. Boston Medical and Surgical Journal. 3:57-8, 1844.

For related articles, see “Pertinent Pointers On Equinus Procedures” in the June 2007 issue of Podiatry Today, “Key Insights On The Role Of Equinus In Foot Pain” in the May 2007 issue, “Addressing Tendon Balancing Concerns In Diabetic Patients” in the March 2003 issue and “Roundtable Insights On Adult-Acquired Flatfoot” in the June 2005 issue.

One can also check out the archives or get information regarding reprints by visiting www.podiatrytoday.com [17].