BRIEF HISTORY AND PHYSICAL EXAMINATION
A 65-year-old female recreational skier with no significant medical or family history presented for evaluation of a constant, aching pain along the anterior medial arch of her right foot. Symptoms began 7 months before without clear inciting event. Symptoms are aggravated by walking downhill and alleviated by rest without radiation or paresthesias. She has been utilizing rest, activity modification, ice, nonsteroidal anti-inflammatory medication, and self-prescribed banded stretching with minimal improvement. She has not participated in formal physical therapy for this issue.
On physical examination, there is notable tenderness to palpation along the dorsomedial tibiotalar joint extending distally to the medial cuneiform and first metatarsal base. The patient is otherwise nontender to palpation throughout her right foot and ankle. The patient ambulates without visible abnormality or antalgic gait; however, concordant right foot anterior medial arch pain is significantly aggravated by heel-walking. Manual muscle testing revealed 5/5 strength throughout the right lower extremity, although there is significant aggravation of symptoms with dorsiflexion strength testing. Examination is otherwise nonrevealing.
What is the differential diagnosis for pain along the dorsomedial foot?
From a bony standpoint, acute or chronic fractures of the navicular or medial cuneiform can elicit pain in the area of interest. In addition, degenerative conditions, such as arthrosis of the first tarsometatarsal joint, medial naviculocuneiform joint and talonavicular joint, can also elicit dorsomedial foot pain. Soft tissue injury in this region can include ligamentous sprain of the deltoid ligament, smaller ligaments of the foot, including between the navicular and medial/intermediate cuneiform bones, as well as the intercuneiform ligament. Several tendons traverse the medial aspect of the foot as well, including the tibialis anterior (TA), tibialis posterior, flexor digitorum, and flexor hallucis longus tendons. Injury to intrinsic foot muscles, notably, the abductor hallucis, which sits on the medial plantar aspect of the foot, can also reproduce this pain. Nerve injuries should also be considered in the differential, including the medial plantar nerve and the saphenous nerve.
What additional testing can be ordered to narrow the differential diagnosis in this patient?
DIAGNOSTIC RESULTS AND APPROACH TO MANAGEMENT
The patient saw an orthopedic surgeon 2 months before presentation, who ordered magnetic resonance imaging (MRI), which demonstrated a focal distal TA tendinopathy with a partial thickness tear (Supplemental Fig. 1, Supplemental Digital Content 1, https://links.lww.com/PHM/B848). She was then referred to a sports medicine specialist for further evaluation and nonsurgical treatment. In clinic, musculoskeletal ultrasound (US) demonstrated significant thickening of the TA tendon proximal to its insertion on the medial cuneiform and hypoechoic fusiform enlargement without tendon fiber disruption (Fig. 1). After reviewing the MRI and US images, the decision was made to proceed with a US-guided prolotherapy injection to the distal TA tendon. The patient was then discharged and referred to physical therapy.
Unfortunately, at the 8-week follow-up visit, the patient had developed worsening of her usual pain in the dorsomedial aspect of the foot. The decision was made to pursue US-guided percutaneous tenotomy and debridement (Fig. 2) followed by a postprocedure rehabilitation protocol of physical therapy with transition to home exercise program.
The TA tendon materializes from the central body of the TA muscle, passing below the superior and inferior extensor retinaculum and attaching onto the first metatarsal base and the medial aspect of the medial cuneiform.1 The primary action of the TA is to dorsiflex the ankle, particularly during the swing phase of gait, and invert the foot.1
Accurate assessment of the incidence and prevalence of TA tendinopathy is difficult, as it has only been discussed in case reports and low-volume case series. The most common site of TA tendinopathy occurs at the extensor retinaculum, as the tendon passes over the tibiocrual joint; however, distal TA tendinopathy, as seen in the case presented here, can be seen near the insertional site. Acutely, TA tendinopathy is a result of indirect trauma caused by supination of the ankle joint and an applied abrupt plantarflexion force against resistance. Chronic TA tendinopathy can be seen in runners, presenting as anterior ankle pain that results from an overuse injury.2 Because of a lack of research into this clinical entity, the natural history of distal TA tendinopathy is unknown. Delay in the diagnosis of TA tendinopathy can result in continued pain and possibly TA tendon rupture.
Clinically, patients will typically describe a burning pain, particularly at night, located in the medial midfoot at the insertion site or on the anterior ankle.1,2 Physical examination should include inspection for swelling in the region of the TA insertion, palpation for tenderness over the insertion of the TA on the plantar medial midfoot, and pain that be elicited with resisted dorsiflexion.1 The TA passive stretch test can also be performed by passively stretching the TA tendon through an ankle plantarflexion, hindfoot eversion, midfoot abduction, and pronation force applied to reproduce typical pain at the TA tendon insertion site. The sensitivity of the TA passive stretch test is 90% with specificity of 95%.2
In addition to physical examination maneuvers, diagnostic imaging tests should include a dynamic US examination of the anterior ankle as well as MRI of the affected foot and ankle. US examination provides the advantages of widespread availability, dynamic assessment, low associated costs, and direct and quick comparison of the contralateral limb; for these reasons, US is preferred as a first-line imaging modality.3 Sonographically, the TA tendon is hyperechoic with a fibrillated appearance. In the setting of tendinopathy, the tendon will have a thickened, irregular, hypoechoic appearance. Color Doppler or microvascular imaging can also be used to identify hyperemia of the synovial sheath.3 In addition to US, MRI also allows for detailed examination of the TA muscle and tendon, given the tissue contrast between muscle, joint, and bone planes. MRI findings or TA tendinopathy include focal thickening of the tendon with peritendon and insertional edema/synovitis.2,3
Although there is a dearth of evidence regarding best practices, the initial treatment of distal TA tendinopathy is often conservative. Soft, accommodative, full length, custom ankle foot orthosis or night splints supporting the medial longitudinal arch by maintaining the ankle in a neutral or slightly dorsiflexed position or a CAM boot are recommended.1,2 Current evidence suggests that nonsteroidal anti-inflammatory drugs are effective for treatment of tenosynovitis and soft tissue impingement, but they are not recommended for chronic isolated tendinopathy.4 Targeted physical therapy should focus on eccentric exercises, as several studies on treatment of tendinopathy have revealed long-term pain reduction and improvement in function.5 Isometric exercises may also be helpful, as they seem to be more effective for short-term pain relief.5 Additional modalities can be considered, such as extracorporeal shockwave therapy, which has also shown reduction of pain and improvement of function in tendinopathy.5
Should this initial approach fail, however, surgery can be considered. Surgical techniques described in the literature include TA tendon debridement and reattachment, extensor hallucis longus tendon transfer, or decompressive medial cuneiform exostectomy.1,3 Surgical outcomes, however, are lacking. Associated complications of surgery include failure of the repair, infection, decreased dorsiflexion strength, rerupture, neuroma formation, entrapment of the intermediate branch of the superficial peroneal nerve, and the formation of adhesions between the tendon and extensor retinaculum.1
In the current patient case, conservative measures had been ineffective, which warranted procedural intervention. Given the risks associated with surgery, injection therapy was considered. While corticosteroids can provide short-term pain relief in painful tendinopathy, they also have widely known tenotoxic profile when injected intratendinously, leading to pain, worsening tendiopathy, or permanent injury.6 For these reasons, corticosteroid injection was not considered in this case and the decision was made to perform a prolotherapy injection. In recent years, prolotherapy, the percutaneous injection of an irritant such as dextrose or sodium morrhuate, has been more widely utilized in the treatment of tendon injuries.7 The proposed mechanism posits that the injected irritant will promote localized inflammation, which will prompt a healing response.7 Prolotherapy has been previously used in the treatment of various lower extremity tendon injuries, such as the patellar tendon and Achilles tendon with significant improvements in pain and function.7 However, to the best of the authors’ knowledge, there are no published reports on the treatment of distal TA tendinopathy using prolotherapy.
Unfortunately, despite prolotherapy injection, the patient did not have adequate pain relief; therefore, the decision was made to pursue percutaneous ultrasonic tenotomy (PUT) and debridement of the diseased tendon, a relatively new but promising treatment for chronic tendinopathy of the foot and ankle.8 Given the rationale of healing promotion through controlled inflammation, clinicians have also been leveraging PUT and debridement to promote repair of damaged tendons. PUT is achieved by insertion of an 18-gauge ultrasonic vibrating double lumen needle with a suction and irrigation system through a small incision to phacoemulsify diseased tendon tissue.9 PUT has been previously used successfully in the treatment of tendinopathy at the elbow, hip and pelvis, and knee, with improvement in pain and satisfaction outcomes, as well as in the peroneus brevis tendinopathy with rapid recovery and improvement in pain.10 However, there is a paucity of literature on use of PUT in the treatment of tendon and ligament of the foot and ankle.
After PUT of the diseased distal TA tendon and after nearly 1 year of persistent and debilitating symptoms, the patient experienced complete pain relief at her 8-week postprocedure follow-up and was able to return to preinjury activity levels. This was supported by ultrasonographic evidence of tendon healing. PUT provides an alternative procedural intervention in the setting of failed conservative treatment. In this particular case, multiple conservative approaches were trialed before intervention with a stepwise escalation from least invasive to more invasive. Unfortunately, there are few high-quality studies that exist for the treatment of tendinopathy using PUT. The first case of the treatment of distal TA tendinopathy with PUT is reported here. Future research is needed to establish the use of PUT in the treatment of TA tendinopathy. This study conforms to all American Journal of Physical Medicine & Rehabilitation Resident Fellow Section-CAse REport guidelines and reports the required information accordingly (see Supplementary Checklist, Supplemental Digital Content 2, https://links.lww.com/PHM/B849).
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