APPROACH ALTERNATIVES FOR TREATMENT OF OSTEOCHONDRAL LESIONS OF THE TALUS
January 16th, 2002
David O. Navid, DO, and Mark S. Myerson, MD
Osteochondral lesions of the ankle joint can pose a diagnostic as well as a therapeutic challenge for the treating physician. This article reviews the current operative management approaches to these lesions of the talar dome. Indications for arthroscopic and open procedures are reviewed along with surgical techniques. Potential complications and pitfalls are discussed.
The terms osteochondral dissecans (OCD), transchondral fracture, osteochondral fracture, and osteochondral defect are used in the literature to describe the separation of a segment of articular cartilage in combination with a varying amount of subchondral bone.2,6,41 Numerous theories have been postulated as to the underlying etiology of the disease, including traumatic, ischemic, defective ossification, and genetic etiologies.6,7,13,14,36 (Ferkel, R.D., Cheng, M.S., and Applegate, G. A new method of radiologic and arthroscopic staging for osteochondral lesions of the talus. Presented at the Annual meeting of the American Academy of Orthopaedic Surgeons, Orlando, Florida, February 17, 1995) (Frey C.C., Laimins, P., Morgan, C.D., and Stone, J.W..Ankle and Subtalar Arthroscopy. Presented at the 65th Annual meeting of the American Academy of Orthopaedic Surgeons, New Orleans, Louisiana, March 19-23, 1998). With osteochondral lesions of the talus, surgery is performed only in symptomatic cases since the lesions show little tendency for progression and do not typically lead to osteoarthritis.6,29 This paper focuses on OCD lesions of the talus, and in particular on surgical approaches to treat these defects of the superior talar dome.
In a review of papers on osteochondral lesions of the talus between 1947 and 1983, Flick and Gould found the overall sex distribution to be 72% male and 28% female.16 Most of the patient population was in the age range of 20 to 35 years. Lesions were reported with approximately equal frequency in the right and the left ankle. Lateral dome lesions were located primarily in the anterior half of the talus, whereas medial dome lesions were generally located in the posterior half. A history of trauma was noted in approximately 98% of the patients with lateral dome lesions and in 70% of those with medial dome lesions.
Berndt and Harty 6 preferred the term transchondral fracture of the dome of the talus because it is specific for anatomical location and traumatic etiology. They reproduced the lesion in two sites in cadavers. Strong inversion of the foot with the ankle dorsiflexed produced a lesion of the lateral part of the talar dome, and inversion, plantar flexion, and lateral rotation of the tibia on the talus produced a lesion of the medial surface. These authors described four stages of the lesion: stage I, compression of the border of the talus; stage II, rupture of the ligaments with partial separation of a bone fragment; stage III, complete separation of the fragment without displacement; and stage IV, displacement of the fragment. The four stages may be seen in either the lateral or the medial side.
Ferkel et al. developed a computed tomography (CT) staging classification: stage I, cystic lesion within dome of talus; stage IIA, cystic lesion with communication to talar dome surface; stage IIB, open articular surface lesion with overlying nondisplaced fragment; stage III, nondisplaced lesion with lucency; and stage IV, displaced fragment (Fig. 1).15 Nonsurgical treatment is recommended for stages I and II with 6 to 12 weeks of casting. Surgery is advocated for failed conservative treatment and for all symptomatic stage III and IV lesions.38,40,41
Magnetic resonance imaging (MRI) has been used to determine the stage of osteochondral lesions, but it does not define the bone cortex as well as CT. CT and MRI yield similar results, though MRI showed a slight diagnostic advantage in a study by Anderson and associates.4 Studies comparing CT, MRI, and arthroscopic staging found that CT is preferred if an osteochondral lesion has been diagnosed.12 If radiographs and clinical findings are not diagnostic, MRI may be more useful.
Several surgical treatment options have been well described in the literature, including arthroscopic debridement with abrasion arthroplasty, subchondral drilling, and microfracture.1,8,10,18 Osteochondral fixation of lesions involving greater than 25%-30% of the articular surface with screws, biodegradable pins, and fibrin glues has been described.24,35,42 More recently osteochondral autograft and allograft procedures have been advocated for larger refractory lesions.9,19-23,27 (Kim, C., and Bugbee,W..Ankle osteochondral allografts. Presented at the Winter Meeting of the American Orthopaedic Foot and Ankle Society, Anaheim, California, February 7, 1999).
Once a decision has been made to proceed with surgical treatment of a talar dome lesion, an approach is chosen from among the variety of options available. Several factors should be considered when deciding on a particular surgical approach. Important determining factors include the size and depth of the lesion, the exact location of the lesion (medial vs. lateral, anterior vs. posterior), the history of prior surgical treatment, the stage of the disease, and the viability of the articular cartilage.
IMAGING STUDIES OF THE ANKLE
Radiographic evaluation begins with standard anteroposterior, lateral, and mortise views of the ankle and can be supplemented with lateral plantar flexion and dorsiflexion views. The lateral plantar flexion and dorsiflexion views are an important adjunct to standard imaging, especially if arthrotomy, either anterior or posterior, is contemplated. Imaging studies are obtained in the weightbearing position with the patient leaning backward and forward on the extended limb to visualize the anterior and posterior margin of the talar dome (Fig. 2A and 2B). An open approach to the ankle is sometimes necessary, and appropriate preoperative imaging studies are critical to the ability to choose the least aggressive approach possible. Computed tomography or an MRI study can be of benefit to evaluate the size, depth, and exact location of the lesion and in planning a surgical approach.
An arthroscopic approach to the ankle is ideal for the majority of medial and lateral lesions. Arthroscopic treatment of talar dome lesions has been well described in the literature.5,17,25,30,33 Debridement of lesions, abrasion chondroplasty, subchondral drilling, and microfracture procedures can be performed arthroscopically. Several arthroscopic approaches to the ankle have been described and can be categorized into three groups: anterior, posterior, and transmalleolar. Medial and lateral techniques have also been reported for mechanically distracting the tibiotalar joint. These approaches require pin placement into the tibia proximally and the talus (medial method) or the calcaneus (lateral method) distally.
Most arthroscopic procedures for treatment of talar dome lesions are performed using only anterior portals (anterolateral and anteromedial).30 This is especially true if an external mechanical distraction device is utilized, which creates more space between the tibia and talus and eliminates the need for additional portals. However, use of a posterior portal may be necessary when treating posterior compartment pathology or when triangulation from anterior portals is not possible. The posterolateral portal is the most commonly used posterior approach.
The anterolateral portal is the primary diagnostic portal used for initial placement of the arthroscope. The portal is made 5 mm below the joint line, just lateral to the extensor tendons. The lateral cutaneous branch of the superficial peroneal nerve lies near this portal region and should be protected. The anteromedial portal is created 5 mm distal to the joint line, just medial to the anterior tibial tendon. This portal is initially used for placement of a diagnostic probe or a motorized shaver.
Triangulation may be done by alternately switching the instrument and the arthroscope between these two portals. Surgical instrumentation is generally inserted on the same side as the pathology, with the scope placed from the opposite anterior approach. The anteromedial portal lies close to the terminal branch of the saphenous nerve and great saphenous vein. Transillumination with the arthroscope placed anterolaterally is helpful in locating and avoiding these structures.
The posterolateral portal is made in the triangular space between the Achilles and peroneal tendons. The skin incision should be made adjacent to the lateral border of the Achilles tendon to minimize the risk of injury to the sural nerve and the short saphenous vein. This portal is used primarily for placement of instruments into the posterior compartment and occasionally for fluid inflow or placement of the arthroscope for viewing from behind the joint.
SURGICAL APPROACHES TO THE ANKLE JOINT
Certain procedures may require a formal ankle arthrotomy to allow direct access to a lesion, such as fixation of a large detached transchondral lesion or transfer of an osteochondral autograft or allograft plug. Once a decision has been made to approach the ankle through an arthrotomy, the exact size and location of the lesion becomes important. Most lateral talar dome lesions can be approached through a standard anterolateral incision. Medial dome lesions usually have a more posterior location, and either an osteotomy of the medial malleolus or a posterior ankle arthrotomy is required for visualization. The main advantage of either a tibial or fibular osteotomy is to provide exposure that may be necessary to visualize the full extent of the transchondral fracture.
Osteotomies, especially osteotomies of the medial malleolus, must be approached with caution. Nonunion or malunion of the osteotomy may lead to increased loads on the joint, worsening articular disruption, and arthritis (Fig. 3A through 3H).
The operative approach is partly determined based on the size of the lesion and on whether debridement, drilling, microfracture, autograft, allograft, or mosaicplasty is planned as the definitive treatment. If the lesion is extensive and is associated with necrosis and collapse, then debridement may be the only feasible procedure. Drilling and microfracture of the subchondral bone have also been shown to be effective in providing a fibrocartilaginous covering of a dome defect. Under these circumstances, visualization of the lesion via open arthrotomy may be advantageous (Fig. 4).
For certain large lesions, especially those that have not responded to the less invasive procedures, an osteochondral transfer can be considered.
Moderate-sized talar defects can be filled with several small (4 to 10 mm) osteochondral autograft plugs from the ipsilateral knee. Larger defects, and defects involving the medial or lateral talar wall, may require an allograft transfer. To perform an osteochondral autograft procedure successfully, the graft must be inserted perpendicular to the axis of the talar dome. The procedure is difficult to perform for a medial lesion without osteotomy of the medial malleolus, but it can usually be accomplished via anterior arthrotomy for a lateral lesion regardless of lesion size.
An alternative approach to the medial or lateral anterior ankle is via arthrotomy and removal of a small window of the anterior tibia for further exposure. If extended visualization is required, this approach may be extended with an osteotomy of the anterior tibia, followed by replacement of the bone fragment and screw fixation.
Approach to Lateral Talar Dome Lesions
Most lateral lesions have an anterior location, and the standard anterolateral approach to the ankle offers excellent access. The incision begins over the anterolateral aspect of the leg medial to the fibula and 1-2 cm proximal to the ankle joint. The incision is carried distally 1-2 cm over the ankle joint. The intermediate dorsal cutaneous branches of the superficial peroneal nerve should be identified and protected. The extensor retinaculum is incised, the extensor digitorum longus is identified and retracted medially, and the joint capsule is incised in line with the incision. Slight plantar flexion of the ankle will further facilitate exposure for access to debridement or grafting.
Fibular osteotomy is rarely necessary to treat a lateral talar dome lesion and is used only for large lesions located posterior and laterally, which can not be accessed with arthrotomy. Rarely a fibular osteotomy may be required to treat a large lateral talar dome lesion associated with necrosis and collapse (Fig. 5). Davidson et al. described one case in which an oblique fibular osteotomy was performed to provide access to the lesion in a lateral transchondral fracture.11 The osteotomy was subsequently fixed with a self-tapping screw. In a series by Ly and Fallat that focused on talar dome pathology, a sagittal saw was used to create an oblique osteotomy similar in orientation to a Weber B fibular fracture.28 Anatomic reduction was then maintained utilizing a five-hole, one-third tubular plate with screw fixation in the posterolateral aspect of the fibula.
When a fibular osteotomy is required to visualize a lateral dome lesion, we use a 6 cm incision made laterally over the distal fibula, starting from 1 cm distal to the joint and extending proximally. Dissection is carried down to the bone, and the periosteum is elevated anteriorly and posteriorly. Utilizing a microsagittal saw, a cut is then made transversely across the fibula, at a level of approximately 1 cm proximal to the joint. The interosseous ligaments are then incised, and the distal fibula is peeled down and retracted inferiorly to expose the lateral talar dome. At the completion of the intraarticular procedure, the fibular osteotomy is anatomically reduced and held with a lateral or posterolateral plate. The interosseous ligaments should be repaired if possible. The addition of a syndesmotic screw through the plate is necessary and should be performed routinely (Fig. 6A through 6H). In the rare occasion when the lateral lesion has a more central location and cannot be accessed by simply inverting the ankle, an anterolateral tibial osteotomy in addition to the fibular osteotomy can provide excellent visualization of the lesion (Fig. 6B).
The posterolateral approach to the ankle can be useful when the surgeon is faced with a loose body, fragment, or lesion posterolaterally, for example with excision of a large os trigonum. An incision is made posterolaterally, behind the peroneal sheath and anterior to the sural nerve. The incision is then deepened through the subcutaneous tissue. The peroneal retinaculum is incised longitudinally to release the tendons, which are then retracted laterally and anteriorly. The retrocalcaneal fat is then dissected, giving good visualization of the ankle joint.
Approach To The Medial Talar Dome Lesions
Medial malleolar osteotomy remains the standard approach for medial talar dome lesions. Various procedures have been proposed in the literature. Regardless of the shape of the osteotomy, visualization can be improved with use of a medial external distractor, valgus manipulation of the foot, and careful planning of the osteotomy. A saw is utilized for three quarters of the osteotomy, and the remainder should be completed with an osteotome to minimize injury to the articular cartilage. In 1947, Ray and Coughlin referred to a transverse osteotomy across the base of the medial malleolus that had been pre-drilled for fixation using a single screw.34 Since then, Davidson et al.,11 Kelikian and Kelikian,26 and Tachdjian39 have described an osteotomy with screw fixation.
OFarrell and Costello reported on the use of a shallow inverted V osteotomy of the medial malleolus to approach medial lesions of the talus in eight patients.31 The fragment was refixed to the tibia with a screw. They noted one case of nonunion, which they attributed to an error in fixation. Other proposed procedures include oblique, crescentic, and step-cut osteotomies and an inverted U osteotomy as described by Oznur.3,32,37,43 In the inverted U osteotomy, the width and height of the arms are planned preoperatively, utilizing MRI or CT images to localize the exact location of the talar lesion.32 This ensures that enough bone is taken to allow access to the lesion (Fig. 7). Most authors recommend predrilling at 90 degrees across the planned osteotomy site. 3,32,37,43
An oblique osteotomy described by Spatt et al. begins proximal to the tibial plafond and ends just distal to it (Fig. 8). 37 One problem with this technique is the potential for malunion, because apposition of the osteotomy where the saw cut is made may not be collinear with respect to the osteotomy cut. This may lead to malunion by creating a shear force at the osteotomy site (Fig. 3E and 3F). At our institution, we have found that the addition of a transverse screw in line with the joint can counter this shearing force and help prevent translation and malunion in cadaver models.
In a transverse approach, the peak of the talar dome may not be readily viewed because it may remain covered by the contour of the tibial plafond. The inverted V or chevron-type osteotomies also have this possible disadvantage. Since the arms of the cut in these osteotomies fall below the joint line, full visualization of the anterior and posterior aspects of the talar dome may not be possible and dorsiflexion or plantar flexion of the talus may be required. In the crescentic osteotomy, as described by Wallen and Fallat,43 the osteotomy is positioned with the apex of the arch at the tibiotalar joint or immediately proximal to it. The crescentic cut conforms to the contour of the talar dome and thus offers better exposure and visualization of the entire articulating surface without any need to maneuver the talus. The disadvantages of this osteotomy are related primarily to instrumentation. The oscillating crescentic blade cuts a wide osteotomy that may cause some shortening of the medial malleolus which may cause tilting of the distal fragment slightly outward or medially when fixated.
A step-cut osteotomy of the medial malleolus was described by Alexander and Watson3 (Fig. 9). They mentioned nonunion or rotation as potential complications and noted that this technique provides excellent inherent stability and broad cancellous surface for rapid healing. In this technique,3 the medial malleolus is exposed through subperiosteal stripping anteriorly and posteriorly approximately 1.5 cm above the joint line. The deltoid ligament is not disrupted. The tibialis posterior tendon is protected at the posteromedial border of the tibia. The medial malleolus is then predrilled with a 2.0 drill bit using the three-hole drill guide. The drill bits are directed proximal and lateral, avoiding violation of the intraarticular space. Prior to starting the osteotomy, a K-wire is inserted into the ankle joint space from anterior to posterior at the junction of the dorsal and medial aspects of the talus. A cut is then made in the transverse plane using a microsagittal saw 1.5 cm above the anterior margin of the distal tibia at the ankle joint. The depth of this cut is to the sagittal (vertical) plane of the intraarticular K-wire. A fine osteotome is then driven from anterior to posterior in line of the intraarticular wire to join the joint space and the transverse cut. With the osteotome used as a lever, the osteotomy is completed and the medial malleolus is reflected plantarward on the deltoid ligament. This exposes the medial aspect of the ankle joint. At the completion of the intraarticular procedure, the malleolus is fixed to its original position using two 4.0 cancellous lag screws.
Several other methods of fixation for these osteotomies have been described, including the use of one or more screws, a combination of screws and K-wire fixation, and a tension band wire technique.43 In the presence of an open epiphysis, fixation can be accomplished with two or three smooth pins, which gain purchase in the lateral tibial cortex.39
In the rare occasion when a medial talar dome lesion has a more anterior location, a standard anteromedial approach can be utilized. Flick and Gould described a technique that allows access to these medial lesions through a standard anteromedial approach, thus avoiding the need for a medial malleolar osteotomy.16 The approach involves a skin incision 0.5 to 1.0 cm lateral to the course of the anterior tibial tendon. The incision begins 3 cm proximal to the ankle joint and extends 2 cm distal to it. The anterior tibial tendon sheath is opened longitudinally throughout the length of the surgical incision. The tendon is then retracted medially from its sheath and the arthrotomy is performed by using sharp dissection through the deep surface of tibialis anterior tendon sheath. The foot is then brought down to maximum equines, and the lesion is identified. To allow access to the entire margin of the lesion, the anteromedial articular surface of the tibia overlying the talar lesion is grooved with a narrow gouge. The area of distal tibial articular surface that is removed is 4 to 5 mm wide anteriorly by 6 to 8 mm deep. This portion of articular surface is not replaced. At the end of the procedure, the capsule, the deep and superficial portions of the tendon sheath are closed with 4-0 absorbable sutures.16
A posteromedial arthrotomy may be indicated for very large posteromedial lesions, in case of prior failed surgeries, or when addressing lesions involving the medial wall of the talus. When a small part of the medial wall of the talus is involved, treatment is usually limited to debridement of the lesion because a graft will not hold in this location. If the entire medial wall is involved, then use of a fresh talar allograft can be considered to replace the entire medial wall. To approach the ankle posteriorly, a standard posteromedial approach to the ankle joint is carried out. The neurovascular bundle is identified and protected by minimizing retraction of the nerve. The flexor hallucis longus tendon is identified posterior to the neurovascular bundle and retracted posteriorly, and the tibial nerve is retracted anteriorly (Fig. 10A and 10B). To improve visualization of the talus, the foot can be passively dorsiflexed and the posterior tibia may be notched, removing a small segment of the posterior articular surface (Fig. 11A and 11B).
CONCURRENT ANKLE LIGAMENT INJURIES
Ankle ligament injuries can be identified concurrent with talar dome lesions. The presence of chronic ankle instability may influence the treatment plan. We approach this problem in a staged manner. The intraarticular pathology is approached first. This allows aggressive physical therapy and early postoperative motion to take place. After adequate rehabilitation, the instability is then addressed through a second surgery, followed by postoperative immobilization and a less aggressive initial therapy program.
Osteochondral lesions of the talus are common injuries, especially in the athletic population. Although multiple etiologies exist, lateral lesions have a higher incidence of association with a specific traumatic event. It has been postulated that lateral lesions are produced when the anterolateral aspect of the talar dome impacts the fibula upon application of an inversion or dorsiflexion stress to the ankle.6 There is general agreement that surgery should be performed only in symptomatic cases, since osteochondral lesions of the talar dome show little tendency to progression and do not seem to lead to osteoarthritis.29,31
Appropriate preoperative imaging is extremely important. Standard radiographs of the ankle supplemented with lateral plantar flexion and dorsiflexion views and CT or MRI can be helpful in evaluating the size, depth and exact location of the lesion. This information is essential in planning the appropriate surgical procedure.
Although many stage I and II lesions respond well to conservative therapy and a period of immobilization, some higher-grade lesions (stage III and IV) eventually require surgical intervention. Most lesions can be approached arthroscopically. Many arthroscopic procedures have been shown to be successful, including debridement with abrasion chondroplasty, subchondral drilling, and microfracture.1,8 10,18 However, certain larger or refractory lesions may require an open approach to the ankle joint to restore the articular cartilage. Most lateral lesions have an anterior location and are easily accessible through a standard anterolateral approach. Most medial lesions are located on the posterior talar dome, and a medial malleolar osteotomy is usually required.
Osteotomies, in particular of the medial malleolus, should be approached carefully. The possible complications of nonunion and malunion can lead to progressive arthritis of the ankle joint.
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