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The Journal of Bone and Joint Surgery (American). 2008;90:404-418. doi:10.2106/JBJS.G.00965 © 2008 The Journal of Bone and Joint Surgery, Inc.
Operative Treatment for Peroneal Tendon Disorders
1 Department of Orthopaedic Surgery, University of North Carolina at Chapel Hill, 3135 Bioinformatics Building, CB #7055, Chapel Hill, NC 27599-7055. E-mail address for S.G. Parekh: selene.parekh{at}gmail.com
Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.
Peroneal tendon disorders are rare, are frequently missed, and can be a source of lateral ankle pain. Magnetic resonance imaging is the standard method of radiographic evaluation of peroneal tendon disorders; however, diagnosis and treatment are based primarily on the history and physical examination. Peroneal tenosynovitis typically responds to conservative therapy, and operative treatment is reserved for refractory cases. Operative treatment is frequently required for peroneal tendon subluxation and consists of anatomic repair or reconstruction of the superior peroneal retinaculum with or without deepening of the retromalleolar groove. Operative treatment of peroneal tendon tears is based on the amount of remaining viable tendon. Primary repair and tubularization is indicated for tears involving <50% of the tendon, and tenodesis is indicated for tears involving >50% of the tendon.
Peroneal tendon disorders are relatively uncommon but frequently underdiagnosed injuries that can be a source of lateral ankle pain. The three primary categories of peroneal tendon disorders include tendinitis and tenosynovitis, tendon subluxation and dislocation, and tendon tears and ruptures. Typically, these conditions respond to nonoperative treatment such as physical therapy, use of nonsteroidal anti-inflammatory drugs, and immobilization; however, severe or refractory cases may require operative intervention. Many operative procedures have been described for the treatment of peroneal tendon disorders. Unfortunately, the literature consists largely of retrospective series and case reports, with no Level-I or II reports available to support treatment recommendations. In this article, we review the epidemiology, relevant anatomy, biomechanical considerations, mechanisms of injury, diagnostic work-up, and options for treatment of peroneal tendon disorders.
Peroneal tendon disorders are an uncommon, underappreciated source of lateral hindfoot pain and dysfunction that are often overlooked because it can be difficult to distinguish them from lateral ankle ligament injuries1. In a study by Dombek et al., only 60% (twenty-four) of forty peroneal tendon disorders were accurately diagnosed at the first clinical evaluation2. When untreated, peroneal tendon disorders can lead to persistent lateral ankle pain and substantial functional problems3,4. Peroneal tendinitis and tenosynovitis usually result from prolonged or repetitive activity, particularly following a period of relative inactivity1. These disorders frequently cause chronic ankle pain in runners and ballet dancers5, and they have been reported in up to 77% of patients (forty-seven of sixty-one) with chronic lateral ankle instability6. Isolated peroneal tendon tears and ruptures are rare, and most result from ankle inversion injuries7-9. The prevalence of incidental peroneus brevis splits found in cadaver specimens has ranged from 11% (fourteen of 124) to 37% (twenty-one of fifty-seven)10, whereas peroneus longus tears occur less frequently11. Tears of both peroneal tendons have been reported in up to 38% of patients (twenty-eight of seventy-three) treated operatively for peroneal tendon tears12. Dombek et al. found a peroneus brevis tear in 88% (thirty-five) and a peroneus longus tear in 13% (five) of forty patients treated operatively for a peroneal tendon tear(s)2. Ankle and hindfoot alignment is an important factor predisposing an individual to peroneal tendinopathy. A cavovarus foot position may cause overloading of the peroneal tendons during activity, leading to tendinosis and tears, particularly of the peroneus longus tendon13. Peroneal tendon tears and ruptures are frequently associated with other disorders, such as chronic tenosynovitis, severe ankle sprains, ankle fractures, or chronic ankle instability3. Among patients treated operatively for peroneal tendon tears, up to 33% (thirteen of forty) also have lateral ankle instability requiring primary ligament reconstruction, 20% (eight of forty) have documented peroneal tendon subluxation, 10% (four of forty) have insufficiency of the retromalleolar groove, 33% (thirteen of forty) have a low-lying peroneus brevis muscle belly2, and 32% (nine of twenty-eight) to 82% (eighteen of twenty-two) have a cavovarus hindfoot posture12,13. Peroneal tendon tears have also been reported in association with foot and ankle fractures2 and tophaceous gout14. Subluxation of the peroneal tendons is a relatively uncommon disorder that was first described in a ballet dancer in 180315 and is frequently associated with sports requiring cutting maneuvers, especially skiing16,17. Peroneal tendon subluxations can be acute or chronic, and they are frequently underdiagnosed as a component of ankle sprains3,18,19. Patients with chronic peroneal tendon subluxation often have concomitant lateral ankle instability20-23, a longitudinal split of the peroneus brevis tendon16,24, or congenital conditions such as laxity of the superior peroneal retinaculum or a shallow retromalleolar groove25-27.
The peroneal muscles reside in the lateral compartment of the leg and are innervated by the superficial peroneal nerve. The peroneus longus originates from the lateral condyle of the tibia and the head of the fibula, and the peroneus brevis originates from the middle third of the fibula and the intermuscular septum. Both peroneal tendons enter a common synovial sheath approximately 4 cm proximal to the tip of the lateral malleolus. They course posterior to the lateral malleolus through a fibro-osseous tunnel called the retromalleolar groove, with the peroneus longus tendon lying posterolateral to the peroneus brevis tendon. The retromalleolar groove is formed by the superior peroneal retinaculum posterolaterally, the fibula anteriorly, and the posterior talofibular, calcaneofibular, and posterior-inferior tibiofibular ligaments medially1,28. This sulcus is lined with fibrocartilage and varies in depth and shape. The superior peroneal retinaculum is the primary restraint to tendon subluxation at the ankle29. It is a fibrous band of tissue approximately 1 to 2 cm wide that originates from the posterolateral aspect of the distal part of the fibula and has a variable insertion. Five distinct insertional variations have been described. The most common type was found in 47% (fourteen) of thirty cadaver specimens and comprised two bands: a superior band that inserts on the anterior aspect of the Achilles tendon sheath and an inferior band that inserts on the lateral aspect of the calcaneus at the peroneal tubercle30. Distal to the ankle, the tendon sheath bifurcates around the peroneal tubercle as the peroneal tendons traverse the lateral aspect of the calcaneus. The peroneal tendons pass through the inferior peroneal retinaculum approximately 2 to 3 cm distal to the tip of the fibula. The peroneus brevis tendon continues directly to its insertion onto the tuberosity of the fifth metatarsal. The peroneus longus tendon turns medially between the cuboid groove and the long plantar ligament and inserts onto the plantar surface of the base of the first metatarsal and the lateral aspect of the medial cuneiform. The os peroneum is located within the substance of the peroneus longus tendon at the level of the calcaneocuboid joint. It is estimated that the os peroneum is ossified in approximately 20% of the population (forty-five of 225)31,32; however, this figure has not been well established in a large radiographic study. The peroneal tendons receive their blood supply through separate vincula that arise from the posterior peroneal artery and branches of the medial tarsal artery. These vincula penetrate the posterolateral aspect of each tendon throughout their course in the retromalleolar groove33. It has been proposed that the peroneal tendons have critical avascular zones that may contribute to tendinopathy34. Petersen et al. described three distinct avascular zones: one in the peroneus brevis tendon at the turn around the lateral malleolus and two in the peroneus longus35. The first peroneus longus avascular zone extends from the turn around the lateral malleolus, and the second occurs where the tendon turns around the cuboid35. These avascular zones correspond with the most frequent locations of peroneal tendinopathy35. However, the presence of avascular zones has been refuted by several authors33; thus, the microvasculature of the peroneal tendons remains a subject of controversy. Several anatomic variations are thought to predispose individuals to peroneal tendon disorders. The retromalleolar sulcus varies in size and shape, potentially affecting the stability of the peroneal tendons as they pass posterior to the fibula. Examination of 178 fibulae in a cadaver study revealed that 82% had a concave retromalleolar sulcus, 11% were flat, and 7% had a convex surface36. The sulcus averages 6 to 7 mm in width and 2 to 4 mm in depth and is enhanced by a fibrocartilage ridge. The shape of the groove is determined by this cartilaginous ridge rather than by the concavity of the fibula itself37,38. A shallow or narrow retromalleolar groove may contribute to tendon subluxation and subsequent peroneal tendon disorders36,39,40 (Fig. 1).
The peroneus brevis musculotendinous junction normally lies proximal to the superior peroneal retinaculum; however, this junction can occur distally within the retromalleolar groove. Furthermore, an accessory peroneus quartus muscle may lie within the retromalleolar groove. The prevalence of this muscle is reported to be between 10% (fourteen of 136 cases) and 22% (twenty-seven of 124 cases), and it typically originates from the peroneus brevis muscle belly and inserts onto the peroneal tubercle of the calcaneus41,42. The presence of either a low-lying peroneus brevis muscle belly43 or a peroneus quartus muscle39,41,42,44 can cause stenosis within the retromalleolar groove and attenuation of the superior peroneal retinaculum, thereby increasing the risk of peroneal tendon disorders. Hypertrophy of the peroneal tubercle has also been implicated as a cause of peroneal tendon disorders, and it was reported in 29% (thirty) of 103 calcanei45. This variation increases mechanical stress on the peroneal tendons, potentially leading to tendinopathy and restriction of normal gliding within the tendon sheaths39,46-49. A cavovarus hindfoot places both peroneal tendons at a mechanical disadvantage by reducing their moment arm and increasing frictional forces at the lateral malleolus, peroneal tubercle, and cuboid notch13,50. Higher mechanical stress on the peroneal tendons can increase the likelihood of peroneal tendon disorders.
The peroneus brevis abducts and everts the foot and plantar flexes the ankle. The peroneus longus everts the foot, plantar flexes the first ray, functions as a secondary plantar flexor of the ankle, and stabilizes the medial column of the foot during stance. The peroneal muscles are antagonists to the posterior tibialis, flexor hallucis longus, flexor digitorum longus, and anterior tibialis muscles. Together they provide 63% of the total hindfoot eversion strength, with the peroneus longus contributing 35% and the peroneus brevis contributing 28%. The peroneals are relatively weak plantar flexors, providing only 4% of the total plantar flexion strength compared with 87% provided by the gastrocnemius-soleus complex50. The peroneal tendons are also dynamic stabilizers of the lateral ankle ligament complex. Peroneal tendinitis and tenosynovitis involve inflammation of the tendon or tendon sheath that is precipitated by prolonged or repetitive activity, particularly following a period of relative inactivity1. Other causes include severe sprains, chronic ankle instability, direct trauma, and fractures of the ankle or calcaneus7,39,51-55. Hypertrophy of the peroneal tubercle has been reported to cause peroneal tenosynovitis32,46,49,56. Several authors have reported this hypertrophy secondary to an osteochondroma57-59. Mechanical trauma to the tendon from pressure or tension causes inflammation and thickening of the sheath and can subsequently prevent free excursion of the tendons60. Peroneal tendon tears and ruptures can result from either acute or chronic injuries. Acute inversion ankle sprain, chronic ankle instability, and peroneal tendon subluxation have all been implicated as mechanisms of peroneus brevis tendon tears2,4,22,54. During inversion ankle injuries, impingement of the peroneus brevis tendon between the overlying peroneus longus tendon and the posterior aspect of the fibula may lead to peroneus brevis split tears5,61. Peroneus brevis tears can also result from stenosis in the retrofibular groove caused by a low-lying peroneus brevis muscle belly, a peroneus quartus, or peroneal tenosynovitis41. A recent magnetic resonance imaging study confirmed that patients with a peroneus brevis tear had a substantially shorter distance between the musculotendinous junction and the tip of the fibula62. Alternatively, incompetence of the superior peroneal retinaculum and peroneal tendon subluxation may result in attritional split tears of the peroneus brevis over the posterolateral edge of the fibula61. Acute tears of the peroneus longus tendon usually result from sports injuries, lateral ankle instability, peroneal subluxation, or traumatic injuries such as tendon avulsion at the os perineum and traumatic tendon laceration4,9,11,34,40,51,54,63-67. Furthermore, anatomic variations, including a shallow retromalleolar groove, a low-lying peroneus brevis muscle belly, a peroneus quartus muscle, incompetence of the superior peroneal retinaculum, posterolateral fibular spurring, and a cavovarus position of the foot, may predispose an individual to peroneal tendon tears4,13,40,42. Longitudinal split tears of the peroneus brevis are usually found within the retromalleolar sulcus (Fig. 2), indicating that they are likely due to mechanical trauma in this region10. Less frequently, ruptures of the peroneus brevis tendon may occur just proximal to its insertion on the fifth metatarsal following sudden inversion of the foot against a contracting peroneus brevis muscle34,66.
Peroneus longus ruptures usually occur at the level of the cuboid, at the os peroneum, at the peroneal tubercle, or at the tip of the lateral malleolus45,68. They can be associated with a fracture through the os peroneum, as they are in patients with painful os peroneum syndrome11,32,69-71; however, the presence of an os peroneum does not predispose an individual to peroneus longus tears, nor is the os peroneum involved in most tears65,72. High shear stresses as the tendon passes around the peroneal tubercle and through the cuboid tunnel may be a major factor in the mechanics of longitudinal tears. Brandes and Smith defined three anatomic zones where injuries of the peroneus longus tendon are likely to occur13. Zone A extends from the distal end of the superior peroneal retinaculum to the tip of the lateral malleolus, Zone B is near the lateral calcaneal trochlear process, and Zone C begins at the cuboid notch and extends distally to the tendon insertion. In the study by Brandes and Smith, 77% (seventeen) of twenty-two peroneus longus injuries occurred in Zone C (at the cuboid notch), with all six complete tears occurring in that zone, and eight of nine partial tears occurred in Zone B (at the lateral calcaneal trochlear process )13. Peroneal tendon subluxation occurs when the tendons displace from the retromalleolar groove during tendon loading. The most common mechanisms involve the sudden, reflexive contraction of the peroneal muscles either during an acute inversion injury to the dorsiflexed ankle37 or during forced dorsiflexion of the everted foot18. This leads to disruption of the superior peroneal retinaculum and allows the peroneal tendons to subluxate anteriorly over the lateral malleolus27,28. Rupture of the superior peroneal retinaculum occurs infrequently38. Peroneal tendon subluxation is commonly associated with lateral ankle instability, since disruption of the lateral ligamentous complex places considerable strain on the superior peroneal retinaculum16,24. An inadequate retromalleolar groove, laxity of the superior peroneal retinaculum due to a calcaneovalgus foot or neuromuscular disease, and congenital absence of the superior peroneal retinaculum all may contribute to the mechanism of subluxation19,51,73. In a cadaver study, Bassett and Speer found that the position of the foot may determine the type of disorder resulting from inversion ankle injuries5. With ankle inversion and plantar flexion of <15°, the superior peroneal retinaculum is injured with resulting peroneal tendon subluxation. With plantar flexion of between 15° and 25°, the peroneal tendons are perched along the lateral malleolus and are at risk for tears. With plantar flexion of >25°, the peroneal tendons are well seated in the retromalleolar groove and are protected from injury. Varus hindfoot alignment is a common predisposing factor for both ankle inversion injuries and chronic overload of the peroneal tendons, and patients with peroneal tendinopathy are frequently found to have a cavovarus foot posture.
Peroneal tendon injuries are frequently overlooked as a cause of lateral ankle pain, and they are often misdiagnosed as ankle sprains1. Therefore, a thorough history and physical examination are essential to correctly diagnose peroneal tendon disorders. The differential diagnosis of peroneal tendinopathy is broad and includes lateral ankle instability; sinus tarsi syndrome; fracture of the fifth metatarsal, cuboid, or fibula; calcaneal stress fracture; calcaneocuboid syndrome; talar osteochondral lesions; ankle or subtalar loose bodies; degenerative joint disease; tarsal coalition; sural neuritis; radiculopathy; malignant tumor; and accessory muscle or bone19. Peroneal tendinitis may be precipitated by repetitive overuse injuries or acute trauma. This is particularly true for patients with varus hindfoot alignment, which places increased stress on the peroneal tendons and can predispose patients to ankle inversion injuries and chronic peroneal tendinosis. Tendinitis is defined as acute if symptoms have been present for less than two weeks, subacute if they have been present for two to six weeks, and chronic if they have persisted for more than six weeks1. Patients with acute peroneal tendinitis present with pain posterior or distal to the lateral malleolus, usually within days after the injury. Chronic tendinitis is characterized by the insidious onset of posterolateral ankle pain over weeks to months. Peroneus brevis tendinitis is often associated with symptoms extending distally from the lateral malleolus to the insertion of the tendon on the base of the fifth metatarsal, while peroneus longus tendinitis usually causes symptoms over the lateral calcaneus that extend distally to the cuboid groove34. The examiner should assess for swelling and warmth along the course of the peroneal tendons. These findings are a hallmark of acute tendinitis, but they are less severe with chronic tendinitis. Forefoot and hindfoot alignment should be noted, since a cavovarus foot is associated with an increased rate of peroneal tendon disorders. A Coleman block test74 can be useful to determine whether the varus hindfoot is the primary problem or if it is secondary to forefoot valgus or a dropped first ray. Making this distinction enables the clinician to select the correct orthotic device for a patient with a cavovarus foot. Tenderness along the peroneal tendon sheath and palpable thickening within the tendons distinguish peroneal tendon disorders from other sources of lateral ankle pain. Pain is exacerbated by passive hindfoot inversion and ankle plantar flexion or by active resisted hindfoot eversion and ankle dorsiflexion. Muscle strength may or may not be decreased. Peroneal tendon tears typically present with severe posterolateral ankle pain and swelling along the peroneal tendon sheath4. These symptoms are usually more severe in younger patients, whereas elderly patients may be completely asymptomatic75. Patients may also describe a history of recurrent ankle sprains and chronic ankle instability51. The surgeon should suspect a tendon tear in a patient diagnosed with recalcitrant peroneal tenosynovitis. Peroneus longus ruptures usually present with pain in the cuboid groove or near the tendon's distal insertion on the plantar aspect of the foot. Pain may also be present in the medial aspect of the foot, imitating dysfunction of the posterior tibial tendon. On examination, swelling over the peroneal tendons is the most consistent finding in patients with split tears1,2. Peroneal muscle strength is often decreased; however, absence of notable peroneal weakness does not rule out a tendon tear or rupture, since the peroneus tertius, extensor digitorum longus, and extensor hallucis longus can provide some compensatory eversion function76. The peroneal tunnel compression test is used to evaluate peroneus brevis tears. This maneuver involves applying manual pressure along the peroneal tendon sheath in the retromalleolar groove with the knee flexed 90° and the foot in a resting plantar flexed position40. Loss or limitation of plantar flexion of the first ray may indicate a peroneus longus rupture. Peroneal tendon subluxation usually follows an acute injury with rupture or attenuation of the superior peroneal retinaculum; however, some patients have a chronic presentation without a definite traumatic event. Patients describe pain posterior to the fibula or above the joint line18. Occasionally, patients experience a painful snapping or popping sensation in the lateral aspect of the ankle. Physical examination generally reveals good muscle strength. Pain is elicited by active dorsiflexion and eversion of the ankle or by active circumduction of the foot. Palpable clicking, snapping, or crepitus of the tendons may also be evident during these maneuvers. Peroneal tendon subluxation can be visualized when the patient walks29. Patients with acute peroneal tendon subluxation demonstrate substantial swelling, tenderness, and ecchymosis posterior to the lateral malleolus. Safran et al. described an examination method in which the patient is positioned prone with the knees flexed 90° and active resisted dorsiflexion and eversion are used to elicit dynamic tendon instability18. Positive anterior drawer or talar tilt tests indicate injury to both the superior peroneal retinaculum and the lateral ligamentous complex. A detailed history should include the presence of associated conditions. Rheumatoid arthritis, psoriasis, hyperparathyroidism, diabetic neuropathy, calcaneal fracture, fluoroquinolone use, and local steroid injections have all been reported to increase the prevalence of peroneal tendon dysfunction77-82.
Weight-bearing anteroposterior and lateral radiographs of the ankle and foot should be made for all patients with lateral ankle pain. Radiographs are useful for evaluating acute osseous injuries, such as fractures of the calcaneus, lateral malleolus, or os peroneum, or chronic conditions, such as lateral ankle impingement, hypertrophy of the peroneal tubercle, spurring of the retromalleolar groove, and exostoses, arthrosis, and tumors of the ankle and hindfoot. Foot radiographs should be evaluated for fractures of the base of the fifth metatarsal, which can indicate avulsion of the peroneus brevis tendon. The presence of an os peroneum should be noted, as proximal migration or fracture of this accessory ossicle correlates with partial or complete rupture of the peroneus longus tendon83. The peroneal tubercle and retromalleolar groove are best evaluated with a Harris heel radiograph32,46. Ankle radiographs may reveal a small avulsion fracture of the lateral malleolus. This has been termed a fleck sign and indicates a Grade-III injury of the superior peroneal retinaculum84 (Fig. 3). The fleck sign is commonly overlooked; however, it is pathognomonic for an acute dislocation of the peroneal tendon. A hindfoot alignment radiograph is helpful to identify a cavovarus foot position as a predisposing factor for peroneal tendinopathy as well as to guide subsequent treatment of the varus malalignment85.
Computed tomography is a valuable tool for further defining osseous abnormalities associated with peroneal tendon disorders, such as hypertrophy of the peroneal tubercle or retrotrochlear eminence and fractures of the calcaneus, os peroneum, or lateral malleolus. However, poor soft-tissue resolution limits the usefulness of computed tomography scans for identifying intrinsic tendon disorders53. Ultrasonography for the evaluation of peroneal tendon disorders is gaining popularity. It is relatively inexpensive and noninvasive, and it does not expose the patient to ionizing radiation. Abnormalities associated with peroneal tendon disorders, including peritendinous fluid, tendon thickening, and partial or complete tendon ruptures, are all easily evaluated with use of ultrasonography. Dynamic high-resolution ultrasonography offers so-called real-time imaging, which allows identification of episodic peroneal subluxation and associated tendon splits that may be missed on magnetic resonance imaging. The positive predictive value of ultrasonography for detecting peroneal subluxation has been reported to be 100%86,87. Ultrasonography can identify peroneal tendon tears with 90% to 100% accuracy, 85% to 100% specificity, and 100% sensitivity68,86,88,89. The primary limitations of ultrasonography are a high degree of technician dependence and a substantial learning curve90. Nevertheless, when performed by experienced operators, ultrasonography may be capable of detecting more subtle injuries than can be identified with magnetic resonance imaging. In a prospective study comparing ultrasonography with magnetic resonance imaging for the diagnosis of peroneal tendon tears, Rockett et al. found that ultrasonography had a sensitivity of 100%, a specificity of 90%, and an accuracy of 94%, while magnetic resonance imaging had a sensitivity of 23%, a specificity of 100%, and an accuracy of 66%88. Magnetic resonance imaging is the standard method for evaluating tendon disorders91. It provides detailed multiplanar imaging without ionizing radiation, and its excellent soft-tissue contrast allows superior visualization of peroneal tenosynovitis and midsubstance or subtle longitudinal split tears92, grading of injuries of the superior peroneal retinaculum, diagnosis of ligamentous disorders, determination of the morphology of the retromalleolar groove, and preoperative planning72,93-95. Axial cuts with the foot in slight plantar flexion provide the best definition of tendon contours, synovial sheath contents, and surrounding structures such as the superior peroneal retinaculum and the retromalleolar groove93,96. If peroneal tendon subluxation is suspected, static magnetic resonance imaging with the ankle dorsiflexed may demonstrate tendon displacement95. Peroneus longus tears can be further assessed with oblique coronal magnetic resonance images. The findings on magnetic resonance imaging of peroneal tendinitis include fluid accumulation within the tendon sheath on T2-weighted images and tendon thickening1 (Fig. 4). Kijowski et al. found that an intermediate T2 signal within the peroneal tendons has a sensitivity of 92% and a specificity of 79% for detecting peroneal tendinopathy, and circumferential fluid within the peroneal tendon sheath in excess of 3 mm in diameter has a sensitivity of 17% and a specificity of 100% for detecting peroneal tenosynovitis97. However, detecting peroneal tendinitis and tenosynovitis with magnetic resonance imaging can sometimes be difficult since fluid within the peroneal tendon sheath can also be seen in asymptomatic patients67. One study demonstrated a sensitivity of only 38% when magnetic resonance imaging was used to diagnose peroneal tenosynovitis in patients with chronic lateral ankle instability6. This may be partially explained by the so-called magic-angle phenomenon, which refers to the appearance of an artifactual intratendinous signal when the fibers are oriented 55° to the magnetic field axis67,98.
Peroneal tendon tears are also readily visualized with magnetic resonance imaging. A peroneus brevis tear may appear as a c-shaped or bisected tendon or as increased intratendinous T2 signal93 (Fig. 5). A peroneus longus tear may demonstrate a linear or round area of increased signal within the tendon99, a fluid-filled tendon sheath, marrow edema along the lateral calcaneal wall, or a hypertrophied peroneal tubercle72. In a recent study, magnetic resonance imaging used to diagnose peroneus brevis tears demonstrated a sensitivity of 83% and a specificity of 75% when compared with intraoperative findings39. Steel and DeOrio reported the specificity of magnetic resonance imaging to be 80% for the detection of peroneus brevis tears, 100% for the detection of peroneus longus tears, and 60% for the detection of tears of both tendons; however, they found magnetic resonance imaging to be less useful for diagnosing anatomic abnormalities such as a low-lying peroneus brevis or a peroneus quartus muscle100. DiGiovanni et al. found the accuracy of magnetic resonance imaging to be 80% (twelve of fifteen) for diagnosing peroneus brevis tears, but there were two correct and three false-positive diagnoses of peroneus longus tears6. Some authors have reported that magnetic resonance imaging underestimates peroneal tendon disorders, particularly peroneus longus tendon tears, when compared with intraoperative findings2,4,12. However, Brandes and Smith found that magnetic resonance imaging tended to overestimate peroneal tendon disorders13. Therefore, although magnetic resonance imaging may facilitate the evaluation of peroneal tendon disorders, definitive diagnosis and treatment should be based primarily on the history and physical examination12.
Peroneal tenography is an invasive and highly user-dependent imaging technique that is currently of limited use for diagnosing peroneal tendon disorders, as it has largely been replaced by magnetic resonance imaging19.
Painful os peroneum syndrome is a term coined by Sobel et al. to describe a spectrum of posttraumatic conditions of the peroneal tendons32. The syndrome includes an acute fracture of the os peroneum or diastasis of a multipartite os peroneum, a chronic fracture of the os peroneum associated with stenosing tenosynovitis of the peroneus longus, partial or complete rupture of the peroneus longus tendon near the os peroneum, or entrapment of the peroneus longus tendon and the os peroneum by a hypertrophied peroneal tubercle32. Peroneal tendinopathy should initially be treated nonoperatively. Conservative measures consist of nonsteroidal anti-inflammatory medications, rest, ice, compression, and modification of activity. Physical therapy that includes stretching, strengthening, and proprioceptive exercises can be beneficial. Management with an orthotic device is based on the foot alignment as determined by the Coleman block test. A lateral heel wedge may be helpful for primary hindfoot varus deformities, whereas a lateral forefoot post is more beneficial when forefoot valgus is the primary deformity. For refractory cases, immobilization in a rigid ankle-foot orthosis, a controlled-ankle-motion (CAM) boot, or a short leg walking cast for six weeks may be attempted. Corticosteroid injections should be used with caution to avoid iatrogenic tendon rupture56. Conservative treatment of painful os peroneum syndrome is similar to that of peroneal tendinitis and includes immobilization in a weight-bearing cast and possibly corticosteroid injections. Persistent pain following prolonged conservative treatment and radiographic evidence of a peroneal tendon disorder may indicate the need for operative intervention32,46,56,57,59. Operative treatment of refractory peroneal tendinitis usually involves an open tendon débridement and tenosynovectomy. A lateral incision, starting approximately 1 cm posterior to the tip of the fibula and following the course of the peroneals to approximately 1 cm proximal to the base of the fifth metatarsal, is used for this procedure. During the approach, care should be taken not to injure the sural nerve, which is located in the retromalleolar area midway between the lateral malleolus and the Achilles tendon1. The peroneal tendon sheath is opened longitudinally, each tendon is inspected, and any areas of erythema, attenuation, synovitis, and granulation tissue are débrided. The peroneus longus tendon should be explored distally to the cuboid groove. A peroneus quartus muscle, if present, can be excised. If the peroneal tubercle is prominent, it can be excised. Associated tendon split tears should be repaired primarily with a tubularization technique. The tendon sheath may or may not be reapproximated. The postoperative course depends on the extent of the pathological involvement of the tendon. Initial immobilization in a short leg cast with the foot plantar flexed and everted allows tendon healing. Following isolated tenosynovectomy, weight-bearing may be allowed after two to three weeks, and the cast can be removed and range-of-motion and strengthening exercises can be initiated at four to six weeks19. Operative treatment of painful os peroneum syndrome should include excision of the os peroneum and hypertrophied peroneal tubercle, if present, along with primary repair or tenodesis of the peroneus longus tendon101. Nonoperative treatment of peroneal tenosynovitis is usually successful. For refractory cases, operative débridement and tenosynovectomy, along with correction of any associated anatomic or biomechanical abnormalities, provide excellent relief of symptoms. Improper or delayed diagnosis and treatment of peroneal tenosynovitis may lead to persistent inflammation, which in turn may result in progression of the tenosynovitis to peroneal tendon rupture1, ultimately limiting the benefit of nonoperative treatment. Furthermore, associated disorders are frequently missed at the time of surgery. Failure to address cavovarus hindfoot alignment, a hypertrophic peroneal tubercle, a painful os peroneum, a peroneus quartus or low-lying peroneus brevis muscle belly, a peroneal tendon tear, or lateral ankle instability may result in incomplete pain relief1. Gray and Alpar reported on the outcomes of operative decompression for chronic peroneal tenosynovitis in nineteen patients, and found that sixteen were symptom-free at eight weeks60. Peacock et al. described a single case of painful os peroneum syndrome in which a fractured os peroneum associated with a peroneus longus rupture was repaired primarily with sutures passed through drill holes70. The patient had only mild discomfort and tenderness at the time of a twelve-month follow-up. Unfortunately, the treatment recommendations (Table I) for peroneal tenosynovitis and painful os peroneum syndrome are based primarily on case series and expert opinion (Table II).
Subluxation or dislocation of the peroneal tendons is frequently associated with injury to the superior peroneal retinaculum. Acute disorders of the superior peroneal retinaculum leading to peroneal tendon instability were first classified by Eckert and Davis38 into three grades of severity, and later Oden102 described a fourth grade (Table III). Unfortunately this classification scheme has little utility for guiding the treatment of these injuries since the injury pattern cannot be accurately determined preoperatively28.
Nonoperative treatment can be used for acute dislocations17,19. In particular, it is indicated for grade-I and possibly grade-III injuries, depending on the degree of displacement of the cortical fragment. Pain is typically the primary reason for treatment19, which involves immobilization in a short leg cast with the foot in neutral to slight inversion to allow the superior peroneal retinaculum to heal to the posterolateral aspect of the fibula19. However, nonoperative treatment of acute peroneal subluxation is associated with a high rate of recurrence, particularly in athletes who subject the peroneal tendons to high stresses; therefore, operative treatment should be considered for high-demand individuals38. Furthermore, operative treatment is required for chronic cases of subluxation or dislocation in order to achieve a satisfactory outcome19,103. Operative treatment has been advocated for young, athletic individuals with either acute or recurrent dislocations103. Several operative procedures have been utilized to treat recurrent subluxations and dislocations, including (1) anatomic reattachment of the retinaculum, (2) bone-block procedures, (3) reinforcement of the superior peroneal retinaculum with local tissue transfers, (4) tendon rerouting behind the calcaneofibular ligament, and (5) groove-deepening procedures16. Regardless of the procedure selected, all associated pathological findings should also be addressed, with measures including the débridement of a low-lying peroneus brevis muscle belly, excision of a peroneus quartus muscle, and correction of varus hindfoot alignment. Despite the number of operative techniques that have been described, we are not aware of any randomized studies that have been conducted to determine which method is superior. The available literature is limited to case series or reports with inadequate evidence to support any specific treatment. Anatomic reattachment of the retinaculum is the proposed method of treatment for acute dislocations with the goal of restoring the primary structure restraining the peroneal tendons16. The procedure involves making an incision in line with the peroneal tendons from approximately 6 cm proximal to the tip of the fibula to 2 cm distal to it. The superior peroneal retinaculum is elevated from the posterolateral aspect of the fibula. An osseous trough is created along the posterolateral aspect of the fibula with an osteotome or burr, and three or four lateral-to-medial drill holes are made along the trough. A nonabsorbable suture is used to secure the retinaculum to the osseous trough. The retinaculum is then tied to the remaining portion of the retinaculum attached to the fibula16,17. Alternatively, the edge of the retinaculum can be secured deep to the inferior edge of the fibular trough, thereby reducing the space available for the tendons and further securing them within the retromalleolar groove. In a series of twenty patients in whom symptomatic dislocation of the peroneal tendons had been treated with the above procedure, Adachi et al. reported no dislocations during a follow-up period of approximately three years17. Fifteen of eighteen patients were able to return to their previous level of athletic activity. In a series of fourteen patients who had undergone repair of the superior peroneal retinaculum with suture anchors, Maffulli et al. reported that no patient had a recurrence of the subluxation or dislocation and all were able to return to their normal activities16. Originally described by Kelly in 1920104, bone-block procedures involve performance of a sagittal osteotomy within the fibula followed by posterior displacement of the lateral fragment to serve as a mechanical block to tendon subluxation. The osteotomy site is typically fixed with screws19,104. Micheli et al. reported excellent results in eleven of twelve patients who had undergone this procedure; the remaining patient, who had had bilateral reconstruction, required reexploration because of recurrence of symptoms105. Problems with nonunion, tendon irritation, and tendon adherence to the underlying bone have been noted with this procedure16,19. Patients with recurrent subluxation can have attenuation or insufficiency of the superior peroneal retinaculum. Local tissue transfers can be utilized to reinforce the retinaculum to prevent future subluxation. To our knowledge, Jones was the first to describe and demonstrate this concept, by using a strip of Achilles tendon anchored to a drill hole in the fibula106. Tan et al. reported the clinical results in four patients in whom a superior peroneal retinaculoplasty had been performed with use of an elevated strip of periosteum from the posterior aspect of the fibula in the region of the peroneal groove23. The flap was used to reinforce the superior peroneal retinaculum and prevent anterior dislocation of the peroneal tendons. Additional transfers, including the use of the plantaris and peroneus brevis tendons to reinforce the superior peroneal retinaculum, have been described17,19. Rerouting the peroneal tendons behind the calcaneofibular ligament has also been performed to prevent subluxation. Various techniques involving division of the calcaneofibular ligament107 or peroneal tendons108 and subsequent transposition of the tendons underneath the calcaneofibular ligament have been described. Steinbock and Pinsger reported good-to-excellent results in eleven of thirteen patients available for follow-up following tendon rerouting; no patient reported recurrence of subluxation following the procedure107. Groove-deepening procedures have also been utilized to treat recurrent subluxation or dislocation with the premise that a shallow posterior groove or a convex surface predisposes an individual to subluxation. Groove-deepening involves incising the superior peroneal retinaculum, dislocating the peroneal tendons anteriorly, and then using an osteotome to raise an osseous flap from the posterolateral aspect of the fibula. The underlying cancellous bone is then removed with use of a burr to a depth of approximately 5 mm. The flap is reduced and is impacted with a bone tamp. The tendons are relocated, and the superior peroneal retinaculum is repaired16,19. Kollias and Ferkel reported the clinical results at a mean of six years following a groove-deepening procedure in twelve ankles in eleven patients with recurrent subluxation20. There were no recurrent subluxations following the procedure, and eleven ankles were rated as excellent. Porter et al. reported no recurrent subluxation in a series of nine athletes, eight of whom were able to return to their prior level of sports activity103. Shawen and Anderson described an indirect groove-deepening technique in which sequential intramedullary reaming is used to thin the posterior fibular cortex109. The retromalleolar groove is then deepened by impaction of the thinned fibular cortex. This method allows preservation of the periosteum and minimizes soft-tissue morbidity. They reported no recurrent subluxations in a series of twenty-eight patients (unpublished data). Outcomes of operative treatment of peroneal tendon subluxation are difficult to report given the number of operative procedures that have been employed to address the condition16,19. Furthermore, the results of each of the techniques are based on Level-IV and V evidence (Table IV). Currently, decisions regarding the operative procedure depend on the surgeon's preference as well as the specific pathological findings encountered in each case.
Sobel et al. described four grades of peroneus brevis tendon ruptures40. Krause and Brodsky developed an alternate classification for directing treatment on the basis of the cross-sectional area of viable tendon4 (Table V). Nonoperative treatment of peroneal tendon tears includes anti-inflammatory medications, physical therapy, activity modification, and immobilization with a brace or short leg walking cast that limits ankle inversion-eversion. However, symptoms may continue despite nonoperative management, especially with peroneus brevis tendon tears in the setting of chronic ankle laxity4.
Operative treatment of peroneal tendon tears varies depending on the severity of the pathological involvement. Krause and Brodsky proposed that tears involving <50% of the cross-sectional area be treated with excision of the affected area followed by tubularization (Fig. 6) and those involving >50% of the cross-sectional area be treated with tenodesis4. Patients presenting with retrofibular pain and swelling in association with chronic peroneal tendon instability most likely have a peroneal tendon tear and should be treated operatively. Additional factors such as chronic ankle laxity and hindfoot varus deformity are also indications for surgery12.
Redfern and Myerson12 proposed an algorithm for operative management of peroneal tendon tears based on intraoperative pathological findings (Table VI). A tendon graft (a hamstring allograft) is most commonly used for a type-III tear if there is sufficient tendon excursion and minimal scarring of the proximal musculotendinous unit. However, if there is minimal excursion, then a tendon graft is unlikely to be successful and a tendon transfer should be performed12. Transfers of the flexor digitorum longus to the peroneus brevis and of the plantaris to the peroneus longus have been utilized with satisfactory outcomes65,77. The flexor digitorum longus has been utilized as its excursion and work percentage are similar to those of the peroneus brevis. The flexor digitorum longus can be attached to the distal stump of the peroneus brevis or directly to the fifth metatarsal base12,77. A staged reconstruction has been described for treatment of chronic rupture of both peroneal tendons110. The first stage of this technique involves débridement of any remaining tendon and synovial sheath followed by implantation of a Hunter rod into the bed of the peroneal sheath. A delayed transfer of the flexor hallucis longus to the peroneus brevis, performed at three months, completes the reconstruction.
In addition to addressing the pathological condition affecting the peroneal tendon, associated disorders such as chronic ankle instability or a cavovarus hindfoot also must be corrected to increase the likelihood of a successful outcome19. As noted above, outcomes of operative treatment of peroneal tendon tears are difficult to interpret. Results are based on Level-IV and V studies (Table VII). In the study by Redfern and Myerson12, twenty-eight consecutive patients underwent tendon repair, tenodesis, or tendon transfer, as dictated by the authors' treatment algorithm, for concomitant tears of the peroneus longus and brevis tendons. Nine of the patients were noted to have postoperative complications, including a superficial wound infection (three), sural neuritis (two), complex regional pain syndrome (one), failure of repair (one), wound dehiscence (one), and adhesive tendinitis (one). Krause and Brodsky reported that treatment of peroneus brevis tears is primarily operative and must address both the tear within the tendon and the instability to avoid a poor outcome4. In their series of twenty patients, the average American Orthopaedic Foot and Ankle Society score was 85 points, with the majority of patients having a good-to-excellent result. In a series of fourteen patients with a peroneus longus tear, Sammarco found that those with acute symptoms fared better than those with chronic symptoms and those with an isolated tear of the peroneus longus fared better than those with involvement of both tendons65. In a series of seven patients with chronic tears of both peroneal tendons, Wapner et al.111 reported good results of staged reconstruction with use of a Hunter rod. At an average of 8.5 years postoperatively, six of seven patients had complete pain relief and had returned to their preinjury level of function.
Peroneal tendon disorders are an infrequent but underdiagnosed cause of lateral ankle pain and dysfunction. A high suspicion for these injuries with early identification and appropriate initial treatment is essential to obtain a successful outcome. Diagnosis of peroneal tendon disorders relies on a detailed history and physical examination as well as an understanding of injury mechanisms and predisposing anatomic variations. Magnetic resonance imaging is the gold standard for evaluation of suspected peroneal tendon disorders. Although many operative procedures have been described for addressing peroneal tendon disorders, treatment recommendations are currently based on Level-IV and V evidence. Large prospective, randomized, controlled trials are needed to refine operative indications and to clarify the roles of these various procedures in the operative treatment of peroneal tendon disorders. 
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