Tendoscopy

Markus Knupp

V. James Sammarco

INDICATIONS

Surgery for tendon disorders of the posterior foot and ankle are common. Tendons in this area enter a relatively avascular zone as they traverse local fibroosseous tunnels. These avascular zones are also areas of high stress and shear as the tendons undergo marked directional change. Inflammation and synovitis are poorly tolerated due to the tight retinacular structures which direct the tendons and can lead to tears and degenerative conditions of the tendons themselves. Traditional surgical techniques require extensile exposures in this area, and as a result, even simple tenosynovectomy of the ankle tendons can lead to fibrosis, sensory nerve injury, and recurrent symptomatology. Endoscopy of the hindfoot has successfully been used to address articular and periarticular pathologies around the ankle joint and when used for to treat tendons offers the advantage of allowing visualization without disruption of the normal retinacular structures. Endoscopy of tendons and their surrounding structures has been termed tendoscopy. Some tendinopathies can be treated completely endoscopically, but even when open procedures are required, diagnostic tendoscopy can limit the amount of exposure needed. While any tendon can be visualized endoscopically, tendoscopy is particularly useful in addressing the tendons of the tarsal canal and the lateral ankle joint. This chapter will discuss tendoscopic procedures and techniques used for treatment of the peroneal tendons, the posterior tibial tendon, the flexor hallucis longus tendon, and the Achilles tendon. Indications for tendoscopy are diagnostic examination, treatment of tenosynovitis, impingement, degenerative tendon tears, and tendon subluxation.

Peroneal Tendons

Pathologic conditions of the peroneal tendons are common, and MRI may often be ambiguous. We have found tendoscopy to be useful as a diagnostic adjunct in patients with recalcitrant ankle pain localized to the peroneal tendon sheath where definitive diagnosis is lacking. Conditions such as stenosis due to tenosynovitis or an accessory muscle, low lying peroneal muscle bellies, and peroneus quartus tendons can often be treated with tendoscopic debridement alone. Tendoscopic examination facilitates a “mini-open” technique for repair in cases where degeneration is present. Success has also been reported in treating tendon subluxation and dislocation with tendoscopy.¹ Additionally, peroneal tendon disease may be associated with intra-articular pathology and osseous or ligamentous imbalance of the ankle joint.² Open or endoscopic tendon debridement, tendon repair,¹^, ³^, ⁴^, ⁵ and groove deepening⁶ are indicated if the patients fail to improve with conservative treatment. If necessary, concomitant ankle arthroscopy or ligament stabilization may also be performed.

Posterior Tibial Tendon

Posterior tibial tendonitis can progress to significant degeneration if not recognized and treated early. Patients may present with stage I tenosynovitis where there is inflammation, but an intact and functioning tendon. If untreated, this may progress to dysfunction and rupture of the tendon which in turn may require extensive surgery or bracing to control. While most patients respond to a course of immobilization and physical therapy, some will continue to have pain along the course of the tendon which does not improve. In recalcitrant cases, where inflammation and synovitis persist despite conservative management, tendoscopy has been described to halt disease progression and prevent development of adult acquired flatfoot deformity.¹^, ⁷

Flexor Hallucis Longus Tendon

Certain athletic pursuits such as ballet and other forms of dance pose an increased risk for developing pathology of the flexor hallucis longus tendon. Entrapment often occurs at the posterior ankle as the FHL tendon enters the fibroosseous tunnel system posterior to the talus. Anatomic considerations in this area that predispose to entrapment of the tendon include an enlarged posterolateral process of the talus, os trigonum syndrome, and “bottlenecking” of a flexor hallucis longus muscle belly where hypertrophied muscle fibers impinge and become inflamed when they enter the tendon sheath. The FHL tendon sheath is intimate with the posterior ankle capsule and posteromedial ankle ligaments and as a result is very dense and rigid. Stenosis in this area is poorly tolerated and can lead to attritional tears of the tendon. The sheath often communicates with the ankle and/or subtalar joint and can also be a repository for loose bodies from either joint. In our experience, flexor hallucis
longus tendonitis is often associated with a tight flexor retinaculum and thickened tendon sheath that can lead to stenosing tenosynovitis. Symptomatic patients who present with posterior ankle impingement can be treated by endoscopic decompression by FHL myoplasty/synovectomy and retinacular release with or without excision of an os trigonum.⁸

Achilles Tendon

Insertional Achilles tendinopathy is a common condition that often improves with simple eccentric stretching exercises and other physical therapeutic modalities. When symptoms persist despite conservative management, surgical intervention can be considered. Success has been reported with endoscopic decompression for the Achilles insertion by resection of the osseous Haglund deformity and retrocalcaneal bursectomy.⁹^, ¹⁰ The ideal candidate for a limited endoscopic procedure is the patient with no significant ossification of the tendon on plain radiographs and minimal tendon degeneration on magnetic resonance imaging.

PATIENT POSITIONING

Peroneal Tendons

The patient is placed in a lateral decubitus position for isolated endoscopy of the peroneal tendons or supine with a sandbag under the buttock of the affected limb if the tendoscopy is combined with an ankle arthroscopy (Fig. 3-1). After exsanguination of the leg, a pneumatic tourniquet is inflated on the thigh.

Posterior Tibial Tendon

The patient is placed in a supine position. A tourniquet is placed on the thigh of the affected leg. If the endoscopy is combined with an ankle arthroscopy, starting with the ankle will allow removing the leg support prior to the tendoscopy and thereby eases the approach to the tendon.

Flexor Hallucis Longus

The patient is placed in a prone position with a thigh tourniquet. A support is placed under the lower leg with the foot at the edge of the operating table allowing the ankle to move freely (Fig. 3-2).

SURGICAL APPROACHES

Peroneal Tendons

Four portals are described for tendoscopy of the peroneal tendon sheath, although often all are not utilized (Fig. 3-3). The first portal established is between the peroneal tubercle and the tip of the fibula. The tendons are subcutaneous here, and a small nick in the skin with a no. 11 scalpel is all that is needed to allow the tendon sheath to be entered. A blunt trocar is then advanced into
the tendon sheath proximally posterior to the fibula, and a 30-degree 2.7-mm (preferred) or 1.9-mm (for patients with a very tight sheath) arthroscope is introduced to allow visualization. The second portal is then established in a similar manner 3 cm proximal to the tip of the fibula. Visualization of an 18-gauge spinal needle which is passed into the tendon sheath as a trial will help verify position and avoid injury to the tendons as the second portal is established (Fig. 3-4). Most lesions can be treated or diagnosed with these two portals alone. Occasionally, synovitis will extend proximally and further debridement will require a more proximal portal. The inferior peroneal retinaculum can be visualized from proximal to distal. If distal synovectomy or release of the inferior peroneal retinaculum is necessary, a portal distal to the peroneal retinaculum may be established. Neurologic structures at risk in this procedure include the superficial peroneal nerve for the more proximal portals, and the sural nerve which crosses the surgical field distal to the lateral malleolus. The course and branching of these nerves is quite variable but the risk of injury can be minimized by using the “nick and spread” technique, where the skin is nicked with a no. 11 scalpel and the subcutaneous tissue and tendon sheath are spread with a small, pointed hemostat.

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