Neurolysis

Distal Surgical Neurolysis of the First Branch of the Lateral Plantar Nerve in Twelve FeetSteven G. Tillett, D.P.M., Terry M. Kennedy, D.P.M. ABSTRACT Twelve heels (11 patients) with chronic heel pain underwent a surgical neurolysis of the first branch of the lateral plantar nerve. Clinically these patients all demonstrated an area of maximal tenderness where the first branch of the lateral plantar nerve (nerve to the abductor digiti quinti) is compressed between the taut deep fascia of the abductor hallucis muscle and the medial caudal margin of the quadratus plantae muscle. Preoperatively, the patient’s average duration of heel-pain symptoms was 19 months (range 3 months to 60 months). Post-operatively all twelve heels were deemed as a excellent or good result with eight patients relating 100% relief of pain on an average of 4.1 months (range 8 weeks – 11 months), and the other four patients relating 80% or better improvement. All patients were evaluated on a ‘Verbal Descriptive Scale’ for pain as follows: 0-1 No pain, 2-3 Mild pain, 4-5 Discomforting – moderate pain, 6-7 Distressing – severe pain, 8-9 Intense – very severe pain, 10 Unbearable pain.” Heel pain as a general rule is best treated through conservative means. In patients, however, with chronic heel pain, an entrapment syndrome of the mixed nerve supplying the first branch of the lateral plantar nerve (nerve to the abductor digiti quinti) is an important differential diagnosis, and should be suspected. Surgical release of the first branch of the lateral plantar nerve has shown to be a successful treatment for this type of chronic heel pain syndrome. INTRODUCTION Plantar heel pain is one of the most common complaints seen in the foot. Most patients with heel pain are diagnosed with Plantar Fasciitis, and respond to conservative therapy modalities designed to decrease the inflammation, support the arch and to prevent problems in the future. However, there are a number of patients whose heel pain is recalcitrant to conservative therapy. One must consider other etiologies, which have a similar presentation, to the chronic heel pain caused by plantar fasciitis (an enthesiopathy of the insertion of the plantar fascia into the calcaneus). The complexity of the heel’s anatomy makes the clinical assessment of chronic heel pain a challenge. One must consider a differential diagnosis that also includes: plantar fascial rupture, Heel pain syndrome (HPS), fat pad atrophy, Tendonitis (of the flexor hallucis longus, flexor digitorum longus, or both), stress fracture of the calcaneus, tumor, painful piezogenic Heel Papules, and notably Nerve entrapment: {a} tarsal tunnel syndrome, {b} first branch of the lateral plantar nerve. [1, 13-22] In 1956, Henry Duvries [12] produced his paper on heel pain, helping to dispel prior conceptions regarding its etiology. He elucidated the indicators for a sub acute inflammatory process at the insertion of the plantar fascia into the calcaneus, noted by an area of decreased radiolucency. With his article, he also helped dispel the prior mindset that heel pain was a result of an infectious process. However, there are a number of patients whose heel pain is recalcitrant to conservative therapy. One must consider other etiologies, which have a similar presentation, to the chronic heel pain caused by plantar fasciitis (an enthesiopathy of the insertion of the plantar fascia into the calcaneus). The complexity of the heel’s anatomy makes the clinical assessment of chronic heel pain a challenge. One must consider a differential diagnosis that also includes: plantar fascial rupture, Heel pain syndrome (HPS), fat pad atrophy, Tendonitis (of the flexor hallucis longus, flexor digitorum longus, or both), stress fracture of the calcaneus, tumor, painful piezogenic Heel Papules, and notably Nerve entrapment: {a} tarsal tunnel syndrome, {b} first branch of the lateral plantar nerve. [1, 13-22] In 1956, Henry Duvries [12] produced his paper on heel pain, helping to dispel prior conceptions regarding its etiology. He elucidated the indicators for a sub acute inflammatory process at the insertion of the plantar fascia into the calcaneus, noted by an area of decreased radiolucency. With his article, he also helped dispel the prior mindset that heel pain was a result of an infectious process. Then in 1960, Kopell and Thompson [11], in there article on “Peripheral Entrapment Neuropathies of the Lower Extremities,” stated that: “the reason for the persistent pain of a severe heel bruise and the basis of many complaints of heel pain, was an entrapment process of the medial and lateral plantar nerves as they pass through the fibrous opening in the origin of the abductor hallucis.” In 1963, Tanz [10] demonstrated through cadaveric dissection a branch of the lateral plantar nerve as it passed around the inferior medial border of the heel and despite no clinical material proposed that entrapment of this nerve was an overlooked cause of chronic heel pain. Then in 1965, Lapidus and Guiudotti reported on 323 patients with 364 cases of heel pain. They found that 50% of their patients had bilateral heel spurs however had unilateral heel pain, and that 46% of their patients had no radiographic evidence of a calcaneal spur. Their conclusion that the actual infra-calcaneal spur was not the cause of heel pain but a “coincidental occurrence,” helped prompt the evolution to the understanding of the etiology of heel pain. [9] Later in 1981, Przylucki and Jones [8] related relief of heel pain symptoms in three patients in which they surgically removed this lateral plantar nerve branch, which they demonstrated to innervate the abductor digiti quinti muscle and noted that it traveled just anterior to the medial tuberosity of the calcaneus as it coursed across the heel. Subsequently in 1982 Baxter was the first to report successful relief of chronic heel pain symptoms by surgically releasing the first branch of the lateral plantar nerve (nerve to the abductor digiti quinti). Which he presented at the Second Annual Meeting of the orthopaedic Foot Club, in New Orleans. [Baxter, D.E.: Nerve entrapment as cause of heel pain. Presented at the Second Annual Meeting of the orthopaedic Foot Club, New Orleans, May 15, 1982]. Then again, in 1984 Baxter and Thigpen released their results of 32 heels with “good results”, of the 34 heels operated on through a release of this nerve entrapment. [7] Baxter and Thigpen also, challenged the traditional description of the anatomic location of the nerve to the abductor digiti quinti in 1984. They found the literature misleading and inexact regarding the nerve distribution about the heel. They also, found through cadaveric and amputated specimen dissection the nerve to the abductor digiti quinti to branch off the lateral plantar nerve more proximal than in most anatomy textbooks and noted it to accompany the medial and lateral plantar nerves as they enter beneath the abductor hallucis muscle. They related that the relationship of the nerve to medial calcaneal tuberosity and the muscle and fascial insertions into the calcaneus predisposed the nerve to compression syndromes – entrapment. [7]. Dr. Baxter’s work with this condition has earned the honor of referral of the nerve to the abductor digiti quinti as “Baxter’s nerve”[3]. In 1986, Rondhuis and Huson [5] redefined this nerve as a mixed type, consisting of sensory fibers for the calcaneal periosteum and the long plantar ligament as well as the motor fibers for the quadratus plantae, flexor digitorum brevis and abductor digiti quinti muscles. They also, elucidated that the exact site of entrapment was where the nerve passes between the deep taut fascia of the abductor hallucis muscle and the medial caudal margin of the medial head of the quadratus plantae muscle. This article will discuss the results of an isolated neurolysis of the mixed nerve supplying first branch of the lateral plantar nerve (nerve to the abductor digiti quinti), where it passes between the abductor hallucis muscle and the medial ridge of the calcaneus. CONSERVATIVE CARE All patients in this study received non-steroidal anti-inflammatories, biomechanical assistants (Low-dye strapping and subsequent foot orthosis), as well as steroid injections. All patients were also placed on a strict regimen of home physical therapy to include: icing, gastroc-complex stretches, decreased activity, patients were advised not to walk barefooted or without supportive appropriate shoe gear. Twelve heels were operated on with preoperative symptoms ranging between 6 months (one patient 3 months) and 5 years. Conservative treatment was rendered for a minimum of 6 months with the one exception. SURGICAL TECHNIQUE The distal neurolysis is performed under regional or general anesthesia. Hemostasis is accomplished with a pneumatic tourniquet placed about the thigh. An approximate 4.5 cm in length linear incision is made starting below the laciniate ligament, coursing distally, and posteriorly stopping just short of the juncture between the plantar and dorsal skin transition. The incision is centered over the nerve or area of maximal tenderness, which is defined and marked with a surgical pen prior to anesthesia. The course noted to be consistent with the anatomical location of the first branch of the lateral plantar nerve (Baxter’s nerve), also known as the distal tarsal tunnel, however more accurately described as the “Lateral Plantar Tunnel.” Caution must be taken to identify and protect sensory branches of the medial calcaneal nerve identified during dissection (encountered just superficial to the deep fascia). Subsequent dissection yields visualization of the superficial fascia over abductor hallucis muscle. A small puncture hole is created through the superficial fascia with a freer elevator, so that it can be separated from the muscle belly. The superior portion of the fascia is then released with a fifteen blade. The abductor is then retracted superiorly and the remainder of the fascia is released in a similar fashion. Once the superficial fascia is completely released, a retractor is used to reflect the muscle plantarly – this will expose the deep fascia of the abductor hallucis muscle. The deep fascia is then separated from the underlying tissues. Again, this tissue is undermined and then sharply released. A retractor is then utilized to reflect the muscle superiorly, exposing the remainder of the deep fascia of the abductor hallucis muscle, which is then released in a similar fashion. Self-retaining retractors are then introduced into the surgical site and the neurovascular bundle is then inspected, which includes the first branch of the lateral plantar nerve. Careful inspection, as well as palpation is utilized to ensure complete release of all tight, possibly impending structures around the nerve. After reflecting the muscle superiorly, approximately 5 mm of the interface between the deep fascia of the abductor hallucis and the plantar fascia is also released. The abductor hallucis muscle belly is left in tact. Once the nerve has been released and the wound flushed, the pneumatic tourniquet is deflated for identification of any bleeders and to evaluate for immediate hyperemic response. Subsequently, subcutaneous and skin closure is performed. Post operatively a compressive dressing is applied to prevent wound dehiscence until sutures are removed at the 2-3 week period, and the patients are maintained on limited 3 point ambulation. Anti-inflammatories and foot orthosis are continued post-operatively as well. MATERIALS AND METHODS This article is a retrospective clinical study of 12 heels (11 patients) with calcodynia who underwent surgical release of the nerve to the abductor digiti quinti, at least 2 years prior to evaluation of the results. The 11 patients represent all patients treated by the senior author of this article, by this modality. Clinical presentation of these 12 heels, was consistent with maximal tenderness over the course of the nerve on the plantar medial aspect of the foot where it is compressed between the taut deep fascia of the abductor hallucis muscle and the medial caudal margin of the quadratus plantae muscle, as described by Baxter and Pfeffer in 1992 [4]. Surgical intervention was based upon recalcitrant heel pain of at least 3 months. Preoperatively, the patient’s average duration of heel-pain symptoms was 19 months (range 3 months to 60 months). The charts of patients seen in the Sr. authors office were reviewed for those patients who had undergone a surgical release of Baxter’s nerve. Post-operatively all charts were reviewed for the following: duration of symptoms, conservative care rendered, patient’s age, sex, side involved and surgical results and complications. RESULTS This study was performed as a retrospective analysis of twelve heels with recalcitrant calcodynia in eleven patients. Eight of the patients were females and three males: one patient with bilateral involvement, the rest were all unilateral. Six were right and six were left. The average age of the patient was 45 years (range 31 -59 years). The average follow up was 5.7 months (range 9 weeks – 11.5 months). All patients were followed by the senior author for a minimum of 9 weeks and dismissed as they became asymptomatic or were satisfied with the surgical results and were lost to follow up. Eleven patients (twelve heels), who had underwent a unilateral Distal Tarsal Tunnel Release (DTTR), between 1998 to 2000, were evaluated. All of these procedures were performed either by or under the direct supervision of the senior author. The criteria utilized to assess a “excellent or good result” meant that the patient had at least 80% improvement from preoperative pain, with no functional impairment. A “poor result” meant that the patient experienced some improvement from the preoperative condition, however, not beyond 80%. A “bad result” meant that the heel pain was not improved or worse than the preoperative condition. All twelve heels were deemed as an excellent or good result with eight patients relating 100% relief of pain on an average of 4.1 months (range 8 weeks – 11 months). One postoperative complication was noted. One patient developed a DVT and was treated successfully with Low dose Heparin – this patient was subsequently worked up by a Hematologist and a Vascular specialist and ruled in for a coagulopathy syndrome. DISCUSSION There has been much discussion on the etiology of heel pain in the Podiatric and Orthopedic literature. Conservative care is still considered the treatment of choice for acute and chronic heel pain. In patients with chronic heel pain, an entrapment syndrome of the mixed nerve supplying the first branch of the lateral plantar nerve (nerve to the abductor digiti quinti) is an important differential diagnosis, and should be suspected. Successful treatment of this chronic heel pain syndrome has been documented through surgically releasing the first branch of the lateral plantar nerve. The diagnosis is done on a clinical basis, noting maximal tenderness in the area where the nerve is compressed between the taut deep fascia of the abductor hallucis muscle and the medial caudal margin of the quadratus plantae muscle [3,6]. Electromyography and nerve conduction studies have not been found to be useful in the diagnosis of this entrapment syndrome [2,4]. The chronic inflammatory changes associated with plantar fasciitis may also predispose a patient to entrapment of the first branch of the lateral plantar nerve. Therefore, entrapment of the first branch of the lateral plantar nerve should always be a part of the differential diagnosis for the patient with heel pain, even when presenting symptoms are clinically consistent with an insertional plantar fasciitis. Glenn B. Pfeffer, Plantar Heel Pain. The Foot and Ankle in Sport, chapter 14:195-206, Mosby 1994. Schon, L.C., MD; Glennon, T.P., MD; Baxter, D.E., MD. Heel Pain Syndrome: Electrodiagnostic Support for Nerve Entrapment. Foot and Ankle. Volume 14(3):129-135, 1993. Schon, L.C., MD. Plantar Fascia and Baxter’s Nerve Release. Current Therapy in Foot and Ankle Surgery. Mark Myerson, MD, Editor. pp 177-182, 1993. Baxter, D.E., MD; Pfeffer, G.B., MD; Treatment of Chronic Heel Pain by Surgical Release of the First Branch of the Lateral Plantar Nerve. Clinical Orthopedics and Related Research. 279:229-236, 1992. Rondhuis, J.J., MD., Huson, A., MD; The First Branch of the Lateral Plantar Nerve and Heel Pain. Acta Morphol. Neerl. Scand. 24:269-279, 1986. 6. Kenzora, J.E., MD; The Painful Heel Syndrome: An Entrapment Neuropathy. BULLETIN of the Hospital for Joint Disease Orthopaedic Institute. Vol. 47(2):178-189, 1987. 7. Baxter, D.E., MD, Thigpen, M.C., MD; Heel Pain-Operative Results. Foot and Ankle. 5(1):16-25, 1984. 8. Przylucki, H., DPM; Jones, C.L., DPM; Entrapment Neuropathy of Muscle Branch of Lateral Plantar Nerve. J. of the American Podiatry Association. 71(3):119-124, 1981. 9. Lapidus, P.W., MD., Guidotti, F.P., MD; Painful Heel: Report of 323 Patients with 364 Painful Heels. Clin. Orthop., 39:178-186, 1965 10. Tanz, S.S., MD., Heel pain. Clin. Orthop. 28:169-177, 1963. 11. Kopell, H.P., MD; Thompson, W.A.L., MD., Peripheral Entrapment Neuropathies of the Lower Extremity. New England Journal of Medicine. Vol. 262(2):56-61, 1960. 12. DuVries, H.L., MD., Heel Spur (Calcaneal Spur. A. M. A. Archives of Surgery. Vol. 74: 536-542, 1956. 13. Davidson, M.R., MD., Copoloff, J.A., MD; Neuromas of the Heel. Clinics in Podiatric Medicine and Surgery. Vol. 7(2):271-288, 1990. 14. Shaw, R., MD; Holt, P.A., MD; Stevens, M.B., MD: Heel Pain in Sarcoidosis. Annals of Internal Medicine., 675-677, 15 October 1988. 15. Lin, E. MD; Ronen, M.; Stampler, D. MD; Suster, S. MD.: Painful Piezogenic Papules. J. of Bone and Joint Surgery. Vol. 67-A(4): 640-641, 1985. 16. Steiner, G., MD; Greenspan, A., MD; Jahs, M., MD; Norman, A., MD., Myxoid Chondrosarcoma of the Os Calcis: A Case Report. Foot and Ankle. Vol. 5(2):84-91, 1984. 17. Gerster, J.C., MD. Planter Fasciitis and Achilles Tendinitis among 150 Cases of Seronegtive Spondarthitis. Rheumatology and Rehabilitiaon. 19:218-222, 1980. 18. Major John T. Quigley, MD.: A Glomus Tumor of the Heel Pad. J. of Bone and Joint Surgery. Vol. 61-A(3):443-444, 1979. 19. Leach, R. MD; Jones, R. MD; Silva, T. MD.: Rupture of the Plantar Fascia in Athletes, J. of Bone and Joint Surgery. Vol. 60-A(4):537-539, 1978. 20. Khermosh, O., MD; Schujman, E., MD., Benign Osteoblastoma of the Calcaneus. Clin. Orhtopaedics and Related Research. Num. 127: 197-199, 1976. 21. Smith, R.W., MD; Smith, C.F., MD. Solitary Unicarmeral Bone Cyst of the Calcaneus. J. of Bone and Joint Surgery. Vol. 56-A(1):49-56, 1974. 22. Cozen, L., MD. Bursitis of the Heel. Am. J. of Orthopedics. Pp. 372-374, 1961. copy right 2000