Sheldon Lin, Karl Bergmann, Vikrant Azad, Virak Tan, Enyi Okereke, and Siddhant Mehta
DEFINITION
Subluxation or dislocation of the peroneal tendon is a relatively uncommon injury, with the majority of the cases attributed to a traumatic event. Chronic subluxation has also been reported without any history of a specific event. Numerous surgical procedures have been described for the treatment of peroneal tendon subluxation, which may be classified into three categories: primary repair, soft tissue augmentation, and bony reconstruction. Primary repair of the superior peroneal retinaculum (SPR) is a commonly used surgical procedure. However, the effectiveness of primary repair depends upon the quality of the retinaculum and its ability to contain the peroneal tendons. When the SPR tissue is deficient or insufficient, then other procedures are necessary.
Soft tissue procedures other than primary repair involve the augmentation of tissue already present or the rerouting of tissue from other structures to recreate the SPR.
Bony procedures attempt to recreate a more stable fibular sulcus by deepening the fibular groove or extending the fibular rim. In this chapter we present a soft tissue augmentation procedure using a periosteal-based flap of the retrofibular sulcus.
ANATOMY
Along the lateral aspect of the lower leg there are two muscles in the lateral compartment, the peroneus longus (PL) and peroneus brevis (PB). These two muscles arise at the proximal fibula and become tendinous before crossing the ankle.
The peroneal tendons are contained in a single sheath located posterior and immediately distal to the fibula. Roughly at the level of the peroneal tubercle on the lateral calcaneus, the tendons separate into separate sheaths. The PB muscle belly extends more distal than the PL, and it becomes tendinous about 1.5 cm before the tip of the fibula. The PB tendon lies directly posterior to the fibula and anteromedial to the PL tendon as the two tendons course behind the fibula.
The peroneal tendon sheath comprises the SPR, the calcaneofibular ligament (CFL), and the fibular sulcus. Respectively, the fibular sulcus represents the anterior border, the SPR the lateral border, portions of the SPR and CFL the posterior border, and portions of the CFL and posterior talofibular ligament the medial border of the peroneal tendon sheath.12
The PB inserts on the dorsal base of the fifth metatarsal, while the PL courses lateral to medial on the plantar aspect of the foot and inserts on the lateral sides of the base of the first metatarsal and medial cuneiform bones.
The SPR is the primary restraint against subluxation of the peroneal tendons within the fibular groove. The SPR can have an extremely varied anatomy, with differences in width, thickness, and insertional patterns. Most commonly, the SPR inserts into both the Achilles tendon and the calcaneus.3 There is no distinct insertion point of the SPR; instead, it blends into the periosteum of the fibula.
The anatomy of the fibula is varied as well. About 50% of fibulae have a bony ridge about 2 to 4 mm that augments the fibular sulcus.2 A cadaveric study by Edwards5 found that 82% of the time a sulcus was present at the posterior edge of the distal fibula. The average sulcus dimension was 3 mm deep and 6 mm wide. He found that 11% of the cadavers had no groove and that 7% of the cadavers had a convex fibula. A fibrocartilaginous rim was deficient in 48% of all cadavers and was absent in 30%.
PATHOGENESIS
According to Zoellner and Clancy,16 in acute injury, the peroneal tendons tend to dislocate anteriorly over the lateral malleolus in people who have an anatomic predisposition. The fibular groove that serves as the pulley for the tendons can be shallow or convex, and the SPR may be absent or lax. A lowlying PB muscle belly can also cause subluxation (FIG 1). In a study of the effect of a low-lying PB muscle belly, Geller et al7 measured the location of the musculotendinous junction (MTJ) in 30 cadaveric specimens with respect to the fibula tip and peroneal tubercle, and also the width of the PB tendon.
FIG 1 • A, B. Anatomic dissection of a peroneus muscle belly that is too distal. Note the distance to the fibular tip. The PB MTJ was significantly more distal and the tendons had a significantly greater diameter in torn (4/30) versus untorn (26/30) specimens (Table 1). The authors suggested that the location of the peroneus brevis MTJ may have an influence on the development of degenerative tears.
Recurrent dislocations are the result of an inciting acute traumatic episode of forceful ankle dorsiflexion with a simultaneous powerful contraction of the peroneal muscles that causes failure of the SPR. The dorsiflexion causes the SPR to tighten, thereby decreasing its diameter. This force is theorized to cause the retinaculum to be avulsed from its periosteal attachment. Eckert and Davis4 stated that the SPR's attachment on the edge of the fibula does not adhere to a strong band of collagen, but instead blends into the periosteum of the lateral malleolus. They proposed that this weak insertion point is responsible for tendon dislocation secondary to avulsion of the fibular fibrocartilaginous lip and stripping of the SPR from the fibula.
The prototypical mechanism is in skiers as they forcefully contract the peroneal muscles to grab the ski edge into the snow.
Eckert and Davis4 classified SPR injury into three different grades according to severity:
Normally, the peroneal tendons are contained within the fibular sulcus by the SPR.
Grade 1 injury: Separation of the retinaculum from the cartilaginous lip and the lateral malleolus
Grade 2 injury: The distal 1- to 2-cm dense fibrous lip is elevated along with the SPR.
Grade 3 injury: Avulsion of a thin fragment of bone along with the collagenous lip attached to the deep surface of the SPR and deep fascia. (Radiographically, this may be represented by a “fleck sign.”)
In grade 1 injuries the peroneal tendons are easily reducible and are unstable under tension only.
In grade 2 and 3 injuries the peroneal tendons fail to remain reduced even without tension.
FIG 2 • The split peroneus brevis tendon, with the peroneus longus running more posterior.
NATURAL HISTORY
Based on our experience, symptomatic recurrent subluxation does not resolve spontaneously.
Often, peroneal tendon dislocation continues to be misdiagnosed as a chronic ankle sprain. As the tendons dislocate and relocate, direct tendon injury occurs due to repetitive trauma.
Zone 1 tendon injuries occur at the fibular groove and usually involve the PB tendon. The action of the PB tendon snapping over the sharp ridge of the fibula leads to a longitudinal tear within the tendon substance (FIG 2).
Zone 2 injuries occur distal to the fibular tip, usually affecting the PL tendon. These injuries are caused by the PL coursing over the lateral wall of the calcaneus and turning 45 degrees at the cuboid facet. As the tears propagate, an inflammatory response may lead to tenosynovitis, tendinopathy, and potential tendon rupture. Peroneal tendon subluxation and dislocation is thought to accentuate the symptoms.
PATIENT HISTORY AND PHYSICAL FINDINGS
The patient may not be able to recall a traumatic event preceding the usual complaints of lateral ankle swelling and pain posterior to the lateral malleolus. Most patients report that the pain radiates proximally. Patients complain of persistent lateral ankle pain and swelling with a sensation of snapping or popping and may note a “pop” laterally before the tendon gives way.
On physical examination, the lateral ankle will be swollen and tender and may be ecchymotic in the acute setting. This can easily be confused with a lateral ankle sprain (Table 2), but the location of the pain may be used to differentiate between the two. Tenderness posterior to the fibula is indicative of peroneal tendinopathy; in contrast, tenderness at the anterior distal fibula suggests an anterior talofibular ligament injury (ankle sprain). However, since the CFL is the floor of the peroneal tendon sheath, there may still be some confusion with more severe ankle sprains. A negative anterior drawer test and pain experienced when the foot is stressed against resisted eversion are more indicative of an injury to the SPR.
Peroneal tendon subluxation test: In the prone position, with the knee flexed to 90 degrees, ankle dorsiflexion and forced hindfoot eversion against resistance is performed. Apprehension and peroneal tendon subluxation or dislocation with this provocative maneuver typically confirms the diagnosis.8
Acutely dislocated peroneal tendons are occasionally seen on physical examination, but more commonly the tendons are reduced upon presentation and are dislocated only with the peroneal tendon subluxation test.
Likewise, chronic peroneal tendon subluxation or dislocation may not present with the tendons frankly dislocated. Chronic subluxation and dislocation are generally best diagnosed by testing the ankle through a range of motion of inversion and plantarflexion to maximum eversion and dorsiflexion with resistance.
Peroneal compression test: Direct compression of the peroneal tendon sheath to identify peroneal tendon injury
IMAGING AND OTHER DIAGNOSTIC STUDIES
Standard weight-bearing ankle radiographs (AP, lateral, and mortise) define the bony ankle anatomy alignment. In cases of peroneal tendon subluxation, radiographs are usually negative. In a grade 3 injury a “fleck” of bone can be seen off the posterior distal fibula and is considered pathognomonic of an SPR injury (FIG 3).
MRI affords detail of the soft tissues. Injury to the SPR, the peroneal tendons, or other supporting tissues may be identified: anomalous structures such as the peroneus quartus or a low-lying PB muscle belly may be suggested (FIG 4). A MRI is useful for preoperative planning, as other pathology (PB tear, low-lying MJT, fibular sulcus) may also need to be surgically addressed concomitant with repair of the subluxation or dislocating peroneal tendons. We also use MRI to define the morphology of the fibular sulcus. While MRI may identify dislocated or subluxated peroneal tendons, the tendons are often reduced while the patient is relaxed in the MRI scanner; however, occasionally dislocated tendons may be identified on axial MRI views.
FIG 3 • “Fleck” sign on a radiograph. The best view to see this on is the mortise view.
FIG 4 • An MRI in the axial plane demonstrating the peroneus brevis tendon splitting over the cartilage lip of the fibula.
CT scan is rarely indicated in preoperative planning of dislocated peroneal tendons.
DIFFERENTIAL DIAGNOSIS
Injury to the lateral ligament complex
Fracture of lateral malleolus, lateral process of the talus, anterior process of the calcaneus, or fracture at the base of the fifth metatarsal
Osteochondral defect on the talar dome
Peroneal tendon pathology
NONOPERATIVE MANAGEMENT
Initial treatment of an acute injury consists of a well-molded, short-leg cast for 6 weeks. Successful outcomes of nonoperative management range from 14% in a study by Eckert and Davis4 to up to 56% as reported by McClennan,9while other investigators have also reported variable outcomes in small case series.6,10,11,14 At best, only half of all patients become better. Therefore, as part of initial injury counseling, it is necessary to inform the patient that an operation will still be necessary, in most instances, despite conservative treatment. For patients with chronic subluxation, nonoperative treatment has not been shown to help; usually pain and symptoms recur once the short-leg cast is removed. In addition, more athletic, higher-demand patients tend to demand more reliable treatment and wish to proceed with operative repair.
SURGICAL MANAGEMENT
Illustrated here is a modified surgical technique for soft tissue augmentation representing an alternative procedure for the treatment of peroneal tendon subluxation. No absolute contraindications exist for the procedure, but relative contraindications include:
The presence of a previous fracture or surgery that alters the local morphology and tissue quality
An Eckert and Davis grade 3 fracture, with a thin fragment of bone along the cartilaginous lip attached to the deep surface of the peroneal retinaculum; the anterior portion of the SPR is already compromised and would not make a good surgical candidate.
Patients with collagen disorders (Marfan, Ehlers-Danlos), where the strength and integrity of the periosteal flap could be suspect
Preoperative Planning
Routine ankle radiographs are essential to identify or rule out a rim fracture of the distal fibula, which occurs in 15% to 50% of all cases of peroneal subluxation.1
Typically, the ankle radiographs appear normal. We routinely obtain an MRI to identify potential peroneal tendon tears, other soft tissue anomalies such as a peroneus quartus, or other causes of lateral ankle pain and instability that need to be addressed concomitant to SPR augmentation.13
MRI axial cuts define the morphology of the fibular sulcus and are helpful in staging a bony procedure if necessary during the superior retinaculoplasty.
Positioning
Either general or regional anesthesia is acceptable for this procedure, and the surgeon's preference determines which anesthetic method to use.
The patient is placed in an oblique lateral position using a beanbag or large support under the ipsilateral hip. Adequate rotation of the limb facilitates access to the posterior fibula.
We routinely use a thigh tourniquet and carefully pad all bony prominences.
An examination under anesthesia with provocative maneuvers such as the anterior drawer and rotary subluxation test may identify associated instability and locking or popping of the unstable peroneal tendons.
Approach
The standard lateral approach is used.
Care should be taken not to injure the sural nerve.
TECHNIQUES
SUPERIOR PERONEAL RETINACULOPLASTY
We use a standard lateral incision along the course of the peroneal tendons, taking care not to injure the sural nerve.
Carry the incision down to the level of the peroneal tendon sheath (TECH FIG 1A).
Inspect the SPR. Usually, it is attenuated and deficient, especially along its anterior border. The retinaculum often is lifted off its fibular attachment, thus allowing the peroneal tendons to subluxate.
Make an incision in the peroneal sheath along the posterior border of the fibula.
TECH FIG 1 • A. Intraoperative photograph of a left ankle (lateral approach) shows the peroneal tendons subluxing anteriorly (brevis is the gray arrow, longus is the white arrow, superior peroneal retinaculum [SPR] is the black arrow). B. The peroneal tendons have been retracted anteriorly by the Penrose drain. Elevation of an anterior-based periosteal flap (outlined by dots) from the fibular groove has been completed. The black arrow shows the remnant of the SPR posteriorly. C. The tendons are relocated, after a groove-deepening procedure, into the recreated groove. The white dots outline the anteriorly based periosteal flap. It is then brought over to the posterior remnant of the SPR (black arrow). D. The flap is sutured to the remnant SPR with nonabsorbable sutures, completing the superior peroneal retinaculoplasty.
Retract the peroneal tendons anteriorly (TECH FIG 1B).
Occasionally, a small tear may be noticed in the PB tendon, warranting débridement or repair.
If a shallow or convex fibular groove is present, we typically perform a groove-deepening procedure.
We routinely reinforce the SPR with a soft tissue periosteal flap elevated from the fibular groove from a posterior to anterior direction.
Raise the periosteal flap, measuring about 1.0 × 3.0 cm, sharply, from posterior to anterior. After the flap is raised, a groove-deepening procedure may be performed when indicated.
Use a burr to deepen the groove 6 to 9 mm with all raw bony edges. The groove should extend from the fibular tip to 5 cm proximal. We use bone wax to smooth the groove.
Reduce the peroneal tendons and use the periosteal flap to contain the tendons, with the visceral side of the periosteum facing the tendons (TECH FIG 1C).
Suture the flap to the posterior remnant of the SPR with a series of 3-0 polybraided nonabsorbable sutures (TECH FIG 1D).
Range the ankle to evaluate the soft tissue repair, being sure that the tendons are free to move within the reconstructed peroneal tendon sheath.
Close the skin in usual fashion, and place the leg into appropriate dressings and splints with compressive bandages.
DETAILED SURGICAL TECHNIQUE (COURTESY OF MARK E. EASLEY, MD, AND JAMES K. DEORIO, MD)
Positioning and Approach
Patient positioned in lateral decubitus position
Regional anesthesia
Thigh tourniquet
Posterolateral approach
Immediately posterior to posterior margin of the distal fibula
Expose SPR.
Protect sural nerve.
Release SPR 1 to 2 mm posterior from posterior fibular margin.
Peroneal tendons will be dislocated, so determining exactly where to release SPR will be distorted.
Chronically dislocated tendon may be located in a “pocket” lateral to the distal fibula (TECH FIG 2).
Inspect the tendons, particularly the more anterior peroneus brevis, for a tear.
Peroneal tendon dislocations predispose the tendons to longitudinal split tears as the tendon repeatedly subluxates around the posterolateral fibula.
TECH FIG 2 • Chronically dislocated peroneal tendons. A. Tendons in a pseudogroove on the lateral fibula. B. With peroneal tendons reduced, a “new gliding surface” and pocket of displaced superior peroneal retinaculum is evident.
TRADITIONAL GROOVE-DEEPENING PROCEDURE (“TRAP DOOR TECHNIQUE”)
Creating the “trap door” in the posterior distal fibula
Maintain the peroneal tendons dislocated anteriorly to protect them during the fibular groove deepening.
Using a microsagittal saw, weaken the posterior cortex within the fibular groove (TECH FIG 3A).
While the fibula may be weakened only on the posterolateral margin, it is often necessary to weaken the “hinge” on the posteromedial margin as well (TECH FIG 3B).
The fibular groove also needs to be weakened transversely, at the proximal margin of the trap door (TECH FIG 3C).
Next, the trap door is completed at its distal margin, where the fibular groove rounds the distal fibula (TECH FIG 3D).
TECH FIG 3 • A. Weakening the posterolateral aspect of the fibula to create the “trap door.” B. Weakening the hinge of the trap door. C. Transverse osteotomy to ensure that the trap door can open. D–F.Elevating the trap door. D. Osteotome introduced into distal posterior fibula. E. Posterior fibula elevated at its posteromedial hinge. F. Trap door completely open.
Elevate the trap door and reflect it posteriorly on its hinge (TECH FIG 3E,F). If the hinge should be separated completely, it is not a problem.
Decancellate the distal fibula. We typically use a highspeed burr to evacuate the cancellous bone from the distal fibula (TECH FIG 4), but a curette may also be used.
TECH FIG 4 • High-speed burr is used to remove cancellous bone from distal fibula.
Replace the “trap door” into the deepened fibular groove.
Impact the posterior fibular bone that was elevated, but try to preserve the smooth surface so that the peroneal tendons have a smooth gliding surface with little risk of impingement or creation of adhesions (TECH FIG 5A).
The groove should be deep enough to keep the peroneal tendons reduced without manually restricting them (TECH FIG 5B). If it is not, then further decancellation may be necessary.
Repair the SPR.
With the tendons reduced, repair the SPR by advancing the intact leading edge of the SPR from its posterior position to the posterolateral rim of the distal fibula from which the SPR was displaced by the tendon dislocation and elevated for the surgical exposure (TECH FIG 6A).
We routinely create drill holes in the distal posterolateral fibula to anchor the SPR (TECH FIG 6B).
Be sure that the tendons glide well within the new fibular groove and are not stenosed by the repair (TECH FIG 6C,D).
Standard closure
TECH FIG 5 • A. Trap door reduced in deepened fibular groove, with impactor being used to recess the bone and deepen the groove maximally. B. Peroneal tendons remaining reduced, even without repair of the superior peroneal retinaculum.
TECH FIG 6 • A, B. Superior peroneal retinaculum (SPR) repair to posterior fibula. A. Sutures to the posterolateral fibula to advance the SPR. B. Drill holes used to anchor SPR to posterolateral fibula. C, D.Peroneal tendons gliding without being stenosed within new fibular groove. C. Dorsiflexion. D. Plantarflexion.
MODIFIED TECHNIQUE USING A LARGE-DIAMETER DRILL BIT (AS DESCRIBED BY ROBERT B. ANDERSON, MD)
Chronically dislocated peroneal tendons may create a new pocket and even gliding surface on the lateral fibula (TECH FIG 7).
Protect the dislocated tendons and adjacent soft tissues from the drill bit.
From the distal fibular tip, introduce progressively largerdiameter drill bits to weaken the distal fibula and ream away the distal fibular cancellous bone (TECH FIG 8).
While simple impaction of the posterior fibula to deepen the groove is possible at this point, we prefer to first weaken the cortex with a microsagittal saw as described for the traditional fibular groove-deepening procedure (TECH FIG 9A).
To protect the smooth surface on the posterior fibula, a tamp can be placed longitudinally in the groove and impacted so as to avoid disruption of the smooth gliding surface for the peroneal tendons (TECH FIG 9B).
The peroneal tendons should remain reduced without manually restraining them (TECH FIG 10A). If not, then deepen the groove further with a larger-diameter drill bit and perform further impaction of the posterior fibular surface.
Reattach the SPR to the posterolateral fibular margin via drill holes.
Be sure the peroneal tendons glide well without restriction in the deeper fibular groove (TECH FIG 10B).
Standard closure
TECH FIG 7 • Pseudogroove created on lateral fibula. A. Peroneal tendons lateral to fibula. B. With tendons reduced, the pseudogroove is visible, with the displaced and attenuated superior peroneal retinaculum.
TECH FIG 8 • A. Drill bit introduced to decancellate the distal fibula. B, C. Fluoroscopic confirmation of proper drill bit position in distal fibula. B. AP view. C. Lateral view.
TECH FIG 9 • Impaction of the posterior fibula to deepen the fibular groove. A. Weakening the posterolateral margin of the fibula to facilitate impaction. B. Using a tamp longitudinally to protect the gliding surface of the posterior fibula during its impaction.
TECH FIG 10 • A. Peroneal tendons remaining reduced in the deepened fibular groove, even without superior peroneal retinaculum (SPR) repair. B. SPR repaired without stenosis of the peroneal tendons.
POSTOPERATIVE CARE
Postoperatively, the patient is immobilized in a short-leg cast and is kept non–weight-bearing for a total of 6 weeks.
After 4 weeks the cast is removed and the patient is given a removable stiff-ankle rocker-bottom boot and remains non–weight-bearing for an additional 2 weeks while beginning physical therapy with ankle range-of-motion exercises.
At the end of 6 weeks the patient is progressed to weight bearing as tolerated in the brace, after which the patient is weaned from the stiff-ankle boot and is started with ankle strengthening with inversion and eversion exercises.
OUTCOMES
A favorable outcome of the procedure depends not only on how well the surgical procedure is performed but also on the appropriate treatment of other associated conditions. Often tendon injuries coexist with subluxation and dislocation and must be treated simultaneously. If tendon pathology such as a tear or degeneration is present and left untreated, pain may persist after surgery no matter how well the surgery was performed.
In a preliminary study by Tan et al.15 conducted at two centers (University of Pennsylvania and University of Medicine and Dentistry of New Jersey), 10 patients with subluxation or dislocation of the peroneal tendons were treated with this technique. Nine of 10 patients had good to excellent results. One patient required a groove-deepening procedure.
COMPLICATIONS
Peroneal tendon adhesions: Early range-of-motion exercises starting at 4 weeks can minimize this complication.
Stenosing flexor tenosynovitis: Overtightening of the peroneal tendon sheath is unnecessary; the tendons simply need to remain reduced posterior to the fibula.
Sural and superficial peroneal nerve injury The editor and coauthors of this chapter wish to acknowledge the contribution of Dr. Enyi Okereke. Dr. Okereke passed away while on a medical mission to Enugu, Nigeria.
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