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Walter R. Frontera, MD, PhD, Editor-in-Chief
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CLINICAL FEATURES OF PLANTAR FASCIITIS
Plantar fasciitis is the most common cause of inferior heel pain in adults.1 Although the actual etiology of plantar fasciitis is still being debated, its high prevalence in runners suggests that overuse or repetitive microtrauma by excessive tension/load on the plantar fascia may be a major contributing factor to this disorder.1,2 Because patients with pes planus and rigid pes cavus are predisposed to the development of plantar fasciitis, improper foot biomechanics may be another key contributing factor.3
The diagnosis of plantar fasciitis is generally based on history and physical examination. The most characteristic complaint is pain and tenderness at or near the proximal insertion of the plantar fascia (attachment to the calcaneal tuberosity area), sometimes along the plantar aspect of the midfoot. Typically, the pain is worst when the patient takes the first few steps after getting out of bed in the morning or after prolonged rest. Plain radiographs often show plantar calcaneal spurs, which may indicate chronic reaction to strain on the fascia-bone interface.4 Along with proper physiatry evaluation, musculoskeletal ultrasound has proven to be very useful in confirming the diagnosis of plantar fasciitis.2,4
ULTRASOUND-GUIDED EXAMINATION AND INJECTION OF PLANTAR FASCIITIS
The plantar fascia is a fibrous aponeurosis deep into the fatty subcutaneous tissue of the plantar aspect of the foot, spanning from the calcaneal tuberosity to the proximal phalanges. The fascia helps support the medial longitudinal arch of the foot and acts as a shock absorber.1 The plantar fascia is best examined with the patient in the prone position, with the affected foot hanging over the edge of the examination table. The ultrasound probe is applied vertically to the plantar aspect of the heel (Fig. 1A). In the long-axis view, the plantar fascia can be readily identified as a linear, fibrillar echogenic structure attached to calcaneal cortex (Fig. 1B, solid arrowheads).4 The entire length of the fascia should be traced carefully to determine its integrity. In severe cases, partial tear or even complete rupture of the fascia can be observed.5 Because the fascia is bulkiest at the proximal end, its thickness is measured at the proximal attachment to the calcaneus (Fig. 1B, blank arrows), which is also the most common site of pathologic changes and often the site of maximal tenderness. Normally, the thickness of the fascia should not exceed 4 mm.2,4 Diagnosis of plantar fasciitis can be verified by (1) fascial thickening greater than 4–5 mm, (2) decreased echogenicity (Fig. 2A) and, sometimes (3) perifascial effusion.2,4,6 In acute plantar fasciitis, hypervascularity involving the fascia and its adjacent soft tissue can be demonstrated on color Doppler.7 Treatment of plantar fasciitis without rupture is primarily nonoperative. It includes rest, activity modification, physical therapy, stretching exercise, nonsteroidal anti-inflammatory drugs, splinting, and prescription of foot orthoses to improve foot biomechanics. However, if conservative treatment is unsuccessful, corticosteroid injection to the inflamed fascia may be indicated.1,4 Although palpation-guided corticosteroid injection is convenient to perform, its accuracy is under question. If the needle is misplaced, injection may lead to heel pad atrophy or fascia rupture.4,5,8 Therefore, with the advancement in technology and reduction in cost, ultrasound-guided corticosteroid injections have been used to improve the accuracy and therapeutic efficacy in the treatment of intractable plantar fasciitis.4,8 The injection is best performed with the patient in the prone position, as if one were examining the plantar fascia.4,8 The needle can be inserted by either posterior approach, medial approach, or anterior approach. The posterior approach has the advantage of allowing easy access to the posterior fascial origin (Fig. 2B).4 A 21- or 23-gauge long needle is preferred because sometimes, the lesion may be anterior to the calcaneal tuberosity. If the lesion is much more anterior (e.g., at the mid-foot level), then medial approach is preferred (Fig. 3A, B). This allows access to both the superficial and the deep layer of the plantar fascia without puncturing the fascia. To provide immediate pain relief before the corticosteroid takes effect, mixing corticosteroid with local anesthetic is a common practice.9 Although most patients experience immediate and long-term relief of symptoms up to 3 mos,3 a minority of patients (about 3.5%) experience postinjection flare-up during the first 24 to 48 hrs.10 Patients should also be informed to avoid any strenuous activity involving the injected region for at least 48 hrs.11 The injection should be followed up with conservative treatment programs such as gentle stretching exercise.1
Musculoskeletal ultrasound is useful in diagnosing and treating plantar fasciitis. Under ultrasound guidance, corticosteroid can be accurately injected into (or around) the inflamed fascia, thus increasing the treatment success rate and decreasing the possible complications.
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2. Chew K, Stevens KJ, Wang T-G, et al.: Introduction to diagnostic musculoskeletal ultrasound: Part 2: Examination of the lower limb. Am J Phys Med Rehabil 2008; 87: 238–48
3. Gill L: Plantar fasciitis: Diagnosis and conservative Management. J Am Acad Orthop Surgeons 1997; 5: 109–17
4. Tsai WC, Wang CL, Tang FT, et al.: Treatment of proximal plantar fasciitis with ultrasound-guided steroid injection. Arch Phys Med Rehabil 2000; 81: 1416–21
5. Sellman JR: Plantar fascia rupture associated with corticosteroid injection. Foot Ankle Int 1994; 15: 376–81
6. Cardinal E, Chhem RK, Beauregard CG, et al.: Plantar fasciitis: Sonographic evaluation. Radiology 1996; 201: 257–9
7. Walther M, Radke S, Kirschner S, et al.: Power Doppler findings in plantar fasciitis. Ultrasound Med Biol 2004; 30: 435–40
8. Tsai WC, Hsu CC, Chen CP, et al.: Plantar fasciitis treated with local steroid injection: Comparison between sonographic and palpation guidance. J Clin Ultrasound 2006; 34: 12–6
9. Jacobs J: How to perform local soft-tissue glucocorticoid injections. Best Pract Res Clin Rheumatol 2009; 23: 193–219
10. Johnson JE, Klein SE, Putnam RM: Corticosteroid injections in the treatment of foot & ankle disorders: An AOFAS survey. Foot Ankle Int 2011; 32: 394–9
11. Tallia AF, Cardone DA: Diagnostic and therapeutic injection of the ankle and foot. Am Fam Physician 2003; 68: 1356–62