Osteochondral lesions of the talus can be a cause of chronic ankle pain, which does not respond to typical treatment regimens of rest, ice, anti-inflammatory medication, immobilization, bracing, physical therapy and/or orthotic use. Osteochondral lesions can occur in any joint.
These lesions most commonly occur in the knee, elbow and ankle. In the ankle, the cause is usually an ankle sprain. Other non-traumatic causes can be localized bone ischemia due to smoking, steroid use, collagen vascular diseases and various systemic metabolic disorders. There may be some genetic predisposition as well.
Lateral osteochondral lesions of the talus are usually caused by trauma. When there is a traumatic etiology, lateral lesions are caused by inversion-dorsiflexion forces yielding an anterior, shallow, wafer-like defect. A greater percentage of medial osteochondral lesions are not associated with an injury. Plantarflexion-inversion forces cause medial lesions. This will create a cup-like lesion in the central to posterior aspect of the talus with more bone involved than lateral lesions.
Patient symptoms with osteochondral lesions may include joint catching or clicking (which may represent a loose body), swelling, chronic pain and ankle weakness. For lateral lesions, the exam may be consistent with sprain with pain over the lateral ankle ligaments and lateral ankle gutter. For medial lesions, there may be pain with palpation into the anteromedial recess of the ankle and on the posteromedial ankle in the region of the posterior tibial tendon.
Assuming conservative care has failed to resolve pain, one should consider surgery. Lateral lesions are usually straightforward. Since the lesions are anterior and wafer-shaped, excision of the lesion and some curettage or drilling of the bone is generally all that one needs to do. Surgeons can do this arthroscopically or through an anterolateral arthrotomy.
Medial lesions present more surgical planning challenges. Since the lesions tend to be centrally or posteriorly located on the talus, exposure is difficult. A number of options for exposure are available. I am going to provide a step-by-step guide to the procedure for the traditional medial malleolar osteotomy to gain exposure for osteochondral grafting.
The patient should be in a supine position and under general anesthesia. Scrub, prep and drape the foot and leg in the usual manner. I do not use a tourniquet so I will administer 1% lidocaine with epinephrine mixed with 0.5% Marcaine in a 50:50 ratio in a regional fashion. Outline landmarks to include the medial malleolus and the medial gutter.
Make a midline linear incision over the medial malleolus and carry dissection down via standard dissection. Generally, dissection is not complicated by any significant neurovascular structures. One may encounter small traversing veins but the great saphenous vein usually will have tributaries distal to where you are working. After reflecting the fatty tissues off the medial malleolus, I will use fluoroscopy to confirm the exact location of the medial shoulder of the talus. You can use a needle or a Freer elevator.
Use a skin scribe to mark the orientation of the proposed osteotomy. I tend to keep it simple with an oblique osteotomy. Many variations have been proposed and they all work. Insert guide pins for fixation into the tip of the malleolus through the soft tissues. After marking the osteotomy line, make sure the screws will be perpendicular to the osteotomy. Confirm guide pins on fluoroscopy, insert screws in the standard fashion and confirm screw placement once again on fluoroscopy.
Prior to making the osteotomy, remove the screws. I then proceed to make a small puncture into the ankle joint capsule in the anteromedial recess in order to place a mini-Hohmann retractor to protect the talus. Also make a small fascial incision on the posterior medial malleolus to retract the posterior tibial tendon to avoid lacerating it. Use a sagittal saw to make the osteotomy. I will generally stop just short of the far end of the bone and use an osteotome and mallet to finish the osteotomy.
One can then turn down the medial malleolus to expose the medial shoulder of the talus. If there is resistance, then release of some soft tissues may be necessary. Sometimes, the posterior tibial tendon will interfere with mobility of the fragment. You may need to manipulate the bone a little to find the least resistance. One can use a Weitlaner retractor or similar instrument to retract the bone down.
Then inspect the osteochondral lesion. Using a Freer elevator, lift up the cartilaginous defect and curette or drill the underlying bone. Most likely, I will do an osteochondral graft with this type of exposure. A curettage surgery is fine for an arthroscopy procedure or transmalleolar drilling. However, when it comes to a medial malleolar osteotomy, I feel I have to do everything in my power for this to be the final, definitive operation.
The case that I am illustrating is using a fresh frozen talus that was age, gender, size and extremity matched to obtain an osteochondral allograft. A tissue bank can order this for you. Many surgical implant companies have instrumentation one can use to obtain a graft plug to insert into the drilled defect in the patient’s talus.
Determine the diameter of the lesion with a measuring device. Drill a guide pin into the center of the lesion and then place the corresponding sized drill over the guide pin and drill down to at least 10 mm in depth. I will generally use a curette to make sure good bleeding bone is present at that level of drilling. If not, then one can perform deeper drilling.
Set the talus up on a jig for obtaining the graft. Position the drill guide for the appropriate sized plug on the graft to correspond to the exact anatomic area on the patient’s bone. Use the appropriate sized diameter plug cutter and then, using a measuring device, cut an appropriate length.
Press-fit the graft and tamp it in with a special tamp that will not damage the cartilage surface. I tend to leave the graft about 1 mm proud or flush. Internal fixation of the graft is not necessary due to the tightness of the fit and overall stability once you have repaired the medial malleolus.
Then return the medial malleolus to its anatomic position, insert the guide pins into the holes and replace the screws. Remove the guide pins and take final fluoroscopy images to confirm anatomic reduction. Perform deep closure by repairing the capsule at the anterior medial joint line and the fascia of the posterior tibial tendon. I also repair the periosteum on the medial malleolus where I performed the osteotomy. I generally will close the subcutaneous tissues and skin with a running absorbable stitch. Apply a dry sterile dressing and a well padded below knee posterior splint.
The postoperative course includes a minimum of six weeks of non-weightbearing. I will change the dressing at seven to 10 days postoperatively and place an elastic bandage on the ankle and apply a removable fracture boot. The patient can now start some ankle range of motion while in non-weightbearing status. After six weeks or when radiographs are consistent with healed bone, gradual weightbearing in the fracture boot commences. Usually around three months, the patient is back to regular shoes.