Summary Peroneal Tendon Tears and Instability represent a spectrum of traumatic injuries to the lateral ankle that include tenosynovitis, tendinopathy, tendon tears and/or tendon instability. Diagnosis is made clinically with subfibular ankle pain with the sensation of apprehension or subluxation with active dorsiflexion and eversion against resistance. MRI studies can help identify the size of peroneal tendon tear and identify concomitant injuries to nearby structures. Treatment may be nonoperative or operative depending on patient activity demands, chronicity of injury, and peroneal instability. Epidemiology Incidence peroneal tendon tears seen in 23-77% of all cases of lateral ankle instability Prevalence peroneal tendon tears comprise 4% of all ankle injuries Demographics tendon instability seen in young, athletic populations Etiology Pathophysiology mechanism of injury rapid forced dorsiflexion of the inverted foot will cause strain through the contracted peroneal muscles, leading to superior peroneal retinaculum (SPR) tear login to view 1 more bullet if superior peroneal retinaculum tears, tendons will become unstable and subluxate or completely dislocate Associated conditions lateral ligamentous instability (ATFL, CFL) cavovarus hindfoot alignment Charcot-Marie Tooth low-lying muscle belly of peroneus brevis enlarged peroneal tubercle (29% of population) accessory peroneus quartus or quintus (10-34% of population) flat or convex retromalleolar sulcus (18% of population) os peroneum calcaneal malunion and subfibular impingement Anatomy Muscle innervation and biomechanics peroneus brevis (PB) innervated by the superficial peroneal nerve, S1 acts as primary evertor of the foot tendinous about 2-4cm proximal to the tip of the fibula lies anterior and medial to the peroneus longus at the level of the lateral malleolus peroneus longus (PL) innervated by superficial peroneal nerve, S1 primarily a plantar flexor and foot and first metatarsal can have an ossicle (os peroneum) located within the tendon body near the calcaneocuboid joint Space & compartment peroneal tendons contained within a common synovial sheath that splits at the level of the peroneal tubercle the sheath runs in the retromalleolar groove on the fibula peroneus brevis is directly posterior to the fibula at the level of the groove peroneus longus is directly posterior to peroneus brevis at the level of the groove deepened by a fibrocartilaginous rim (still only about 5 millimeters deep) covered by superior peroneal retinaculum (SPR) login to view 3 more bullets at the level of the peroneal tubercle of the calcaneus peroneus longus is inferior peroneus brevis is superior both tendons covered by inferior peroneal retinaculum Blood supply supplied by branches of the anterior and posterior tibial arteries via vincula system entirety of both tendons are vascularized early descriptions of avascular zones disproven Classification Anatomic Classification of Superior Peroneal Retinaculum (SPR) Tears Grade 1 The SPR is partially elevated off of the fibula (fibrocartilaginous ridge remains intact) allowing for subluxation of both tendons Grade 2 The SPR is separated from the cartilofibrous ridge of the lateral malleolus, allowing the tendons to subluxate between the SPR and the fibrocartilaginous ridge Grade 3 There is a cortical avulsion of the SPR off of the fibula, allowing the subluxated tendons to move underneath the cortical fragment Grade 4 The SPR is torn from the calcaneus, not the fibula Raikin Classification of Intra-sheath subluxation Type 1 PL tendon lies deep in relation to the PB tendon Type 2 PL tendon subluxated through a PB tear Redfern and Meyerson Peroneal Tendon Tear Classification Type I Both tendons intact but with partial tearing Type II One tendon is intact but other is majority torn Type IIIa Both tendons are majority torn (unusable) and muscle belly has no excursion Type IIIb Both tendons are majority torn (unusable) but muscle belly has excursion Presentation History report feeling a pop with a distinct dorsiflexion ankle injury feelings of instability in lateral ankle sensation of stepping on a pebble if os peroneum is symptomatic Symptoms location lateral or posterolateral ankle pain may be more distal towards the fibular tip aggravating/alieving factors active eversion and/or plantarflexion passive dorsiflexion Physical exam inspection swelling posterior to the lateral malleolus tenderness over the tendons cavovarus hindfoot alignment 'pseudotumor' over the peroneal tendons voluntary subluxation of the tendons +/- a popping sound provocative tests apprehension tests login to view 1 more bullet compression test login to view 1 more bullet active circumduction login to view 1 more bullet ankle drawer testing login to view 1 more bullet Imaging Radiographs recommended views standard weightbearing series optional views Harris view best to visualize peroneal tubercle morphology findings "Fleck sign" login to view 1 more bullet plantarflexed first metatarsal and high Meary's angle indicating cavovarus deformity proximal migration of the os peroneum is indicative of a peroneus longus rupture Ultrasound indications high degree of suspicion for tendon tears or instability findings dynamic view of tendon subluxation intra-sheath tendon subluxation sensitivity and specificity 90% accuracy for tendon tears user-dependent CT indications calcaneus malunion and lateral wall/subfibular impingement concern for retromalleolar groove abnormality or enlarged peroneal tubercle MRI indications high degree of suspicion for tendon tears or instability, or other concomitant pathology (ATFL/CFL insufficiency and talar OCD) views best evaluated with axial views of a slightly plantarflexed ankle login to view 1 more bullet findings edema and tendon thickening indicating tendinopathy significant circumferential fluid within sheath indicating tenosynovitis intra-substance tendon tears fatty infiltration of the muscle belly "Boomerang sign" as the peroneus brevis wraps around the longus accessory tendons or low-lying PB muscle belly sensitivity and specificity 83-90% sensitivity 72-75% specificity Treatment Nonoperative short leg cast immobilization and protected weight bearing for 6 weeks indications login to view 1 more bullet outcomes login to view 2 more bullets period of activity modification and boot immobilization, followed by physical therapy indications login to view 1 more bullet outcomes login to view 1 more bullet Operative repair of superior peroneal retinaculum and deepening of the retromalleolar groove indications login to view 2 more bullets outcomes login to view 2 more bullets groove-deepening with soft tissue transfer and/or osteotomy indications login to view 2 more bullets outcomes login to view 1 more bullet tenosynovectomy and tendon debridement with tubularization indications login to view 1 more bullet outcomes login to view 1 more bullet tenosynovectomy and tendon debridement without tubularization indications login to view 2 more bullets outcomes login to view 1 more bullet tenodesis of distal and proximal ends of the brevis tendon to the peroneus longus indications login to view 1 more bullet outcomes login to view 1 more bullet debridement of both tendons with interposition auto- or allo-graft indications login to view 1 more bullet outcomes login to view 1 more bullet debridement of both tendons with FHL/FDL transfer indications login to view 1 more bullet outcomes login to view 1 more bullet hindfoot corrective osteotomy indications login to view 1 more bullet outcomes login to view 1 more bullet Techniques Short leg cast immobilization and protected weight bearing for 6 weeks technique tendons must be reduced at the time of immobilization (and able to maintain reduced position) foot placed in slight plantarflexion and inversion Period of activity modification and boot immobilization, followed by physical therapy technique boot immobilization ended and physical therapy started once pain at rest has completely resolved may incorporate shoe orthosis to address hindfoot- or forefoot-driven varus Repair of superior peroneal retinaculum and deepening of the fibular groove approach longitudinal incision over the peroneal tendons technique careful dissection that avoids sural nerve branches SPR can then be split longitudinally leaving cuff of tissue for later repair, or sharply transected from fibula tendons can be evaluated for concomitant tears and groove assessed for morphology if groove deepening chosen, a small burr can be used to deepen groove alternatively, a small drillbit can be drilled retrograde from the fibular tip through the subcortical groove bone login to view 1 more bullet SPR can then be repaired via direct repair, bone tunnels, or suture anchors Groove-deepening with soft tissue transfer and/or osteotomy approach open approach as described above technique treatment focuses on other aspects of peroneal stability involves groove-deepening in addition to soft tissue transfers or bone block osteotomies to further contain the tendons within the sulcus plantaris grafts can be harvested or soft tissue allograft use to reinforce/reconstruct the SPR Tenosynovectomy and tendon debridement without tubularization approach endoscopic/tendonoscopic technique technique first viewing portal started 2cm distal to fibular tip, and second working portal made 3cm proximal to fibular tip tendon can be visualized and synovium/adhesions resected Tenosynovectomy and tendon debridement with tubularization approach open approach as described above technique SPR incised longitudinally and tendon exposed tendon tear location and type assessed and nonviable tissues debrided monofilament suture used to repair edges of remaining tendon to itself to create smooth-gliding tube SPR repaired Debridement of the tendon with tenodesis of distal and proximal ends of the brevis tendon to the peroneus longus approach open approach as described above technique SPR incised longitudinally and tendon exposed PB tendon tear location and type assessed and nonviable tissues debrided proximal end of PB tenodesed to PL in side-to-side fashion approximately 3cm proximal to the fibular tip distal end of PB tenodeses to PL in side-to-side fashion approximately 2cm distal to fibular tip SPR repaired Hindfoot corrective osteotomy approach incision based on osteotomy selected (distractive bone-block subtalar fusion, Dwyer osteotomy etc) technique neutral realignment goal of all surgical techniques Complications Sural neuroma incidence most common complication following surgery given proximity to peroneal tendons Recurrence of peroneal tendon instability risk factors unaddressed ankle malalignment treatment corrective osteotomy with/without soft tissue reconstruction Persistent pain risk factors overtightening of SPR repair causing tendon stenosis Tibial nerve compression incidence seen following FHL transfer prevention release adhesions between FHL and neurovascular bundle