A 3-portal approach for arthroscopic subtalar arthrodesis

The patient is placed in the prone position. A tourniquet is inflated around the thigh. A triangular-shaped pad is placed under the lower leg to provide unconstrained motion of the ankle joint during surgery (Fig. 1). A lateral support is placed against the ipsilateral hip and the operating table is tilted towards the ipsilateral side. Following prepping and draping, the Achilles tendon and the lateral and medial malleolus are identified. The two standard posterior portals for hindfoot endoscopy are created using the technique as described before [12]. First the posterolateral portal is made at the level or slightly above the tip of the lateral malleolus, just lateral to the Achilles tendon with the foot in the neutral position (Fig. 1). After making a longitudinal skin incision, the subcutaneous layer is split using a mosquito clamp. The mosquito clamp is pointed anteriorly, in the direction of the interdigital webspace between the first and second toe. When the tip of the clamp touches bone, it is exchanged for a 4.5 mm arthroscope shaft with the blunt trocar pointing in the same direction. By palpating the bone in the sagittal plane, the level of the ankle joint and subtalar joint most often can be identified because the prominent posterior talar process can be felt in between the joints. The blunt trocar remains extra-articular at the level of the ankle joint. Subsequently, the posteromedial portal is created just medial to the Achilles tendon at the same level as the posterolateral portal (Fig. 1). After making the longitudinal skin incision, a mosquito clamp is introduced and directed straight towards the arthroscope shaft. When the mosquito clamp touches the shaft, it is used as a guide to move the mosquito clamp over the shaft towards the ankle joint. All the way down to the ankle joint, the tip of the mosquito clamp has to touch the arthroscope shaft until the tip touches the bone. The blunt trocar is then exchanged for a 30° 4.0 mm arthroscope. The arthroscope is slightly pulled back until the tip of the mosquito clamp comes into view. The clamp is used to spread the extra-articular soft tissues in front of the tip of the arthroscope. In case of scar tissue or adhesives, the mosquito clamp is exchanged for a 5.0 mm full-radius shaver. The fatty tissue overlying the capsule of the subtalar joint is removed. After removal of the joint capsule of the subtalar joint, the posterior compartment of the subtalar joint is visualized. The posterior talar process can be freed from scar tissue and the flexor hallucis longus (FHL) tendon is identified medially. The FHL tendon is an important anatomic landmark in hindfoot endoscopy, as the posteromedial neurovascular bundle is located medially from the FHL tendon. Release of the flexor retinaculum from the posterior talar process is performed to have better access to the subtalar joint. Via the posterior portals the cartilage of the posterior facet of the subtalar joint is now removed using ring curettes. In case of a talocalcaneal coalition, the working area in the posterior subtalar joint is restricted due to the bar between the talus and calcaneus. A talocalcaneal coalition is a congenital osteofibrous, cartilaginous, or osseous union of the talus and calcaneus. A talocalcaneal coalition ossifies either completely or incompletely between 12 and 16 years of age [10]. To open up the posterior subtalar joint, an accessory sinus tarsi portal is created for introduction of a large diameter blunt trocar. A small skin incision is made at the level of the sinus tarsi. (Fig. 2). A spinal needle is introduced via the sinus tarsi portal and is directed towards the tip of the lateral malleolus. At the level of the subtalar joint the spinal needle is pointing posteriorly. The arthroscope is used to check the position of the needle. Following removal of the spinal needle, the large diameter blunt trocar (4.0 mm) is inserted through the sinus tarsi portal and is manoeuvred towards the posterior subtalar joint. For the purpose of opening up the joint, the blunt trocar is now forced into the subtalar joint. Since the direction of the blunt trocar is almost parallel to the subtalar joint space it can be forced in a sidewards direction into the joint from laterally. The sideward movement prevents the trocar of making a false route into the subchondral bone (Fig. 3a). In case of a talocalcaneal coalition, the talus and calcaneus are connected by the talocalcaneal bar that is located at the medial side. A small size chisel (4.0 or 6.0 mm) is placed through the posteromedial or posterolateral portal into the area of the bar. An attempt can be made to remove the bar by using the small size chisel in order to further open up the joint (Fig. 3b). Removal of the articular cartilage of the posterior subtalar joint using ring curettes is performed by changing portals (Fig. 3c–e). After removal of the articular cartilage, the subchondral bone is entered to expose the highly vascular cancellous bone. Using the small size chisel, a number of approximately 2.0 mm deep longitudinal grooves are made in the subchondral cancellous bone of the talus and calcaneus (Fig. 3f). A vertical skin incision is made at the tip of the heel for introduction of two lag screws. Using fluoroscopy, the 6.5 mm lag screws are placed across the posterior subtalar joint. The estimated length and direction of the two screws can be preoperatively planned on the lateral weightbearing radiograph of the ankle. Before insertion of the two screws it is important to check the alignment of the hindfoot. Coaptation of the posterior subtalar joint surfaces can be checked arthroscopically when tightening the screws (Fig. 3g). The skin is closed using non-resorbable sutures. A non-weightbearing lower leg cast is provided for 4 weeks, followed by a walker boot for another 2 weeks. At 6 weeks following surgery, anteroposterior and lateral weightbearing ankle radiographs are made. With radiographic signs of union of the subtalar arthrodesis, the patient is allowed full weightbearing without further support. For patient comfort, the walker boot can be applied for another 2 weeks.

From March 2006 to July 2006, three subsequent female patients with a painful talocalcaneal coalition (two left and one right foot) were operated on by the senior author using the technique as described. Computed tomography (CT) scanning of the hindfoot confirmed the presence of a medially located coalition between the talus and calcaneus. (Fig. 4). As conservative treatment eventually failed, the decision was made to perform an arthroscopic isolated subtalar arthrodesis using the 3-portal technique as described. Resection of the talocalcaneal coalition was not considered since the patients were skeletally mature and the coalition was of larger extent [5, 9, 10]. In all patients joint opening and distraction using the large diameter blunt trocar introduced via the sinus tarsi portal, was sufficient to create enough working space to remove the articular cartilage from the posterior subtalar joint surfaces. The duration of surgery was on average 60 min (range, 52–65 min). Patients were discharged from the hospital the day after surgery. Post-operative radiographs 6 weeks following surgery, showed bony union of the subtalar arthrodesis in all three patients (Fig. 5). At time of follow-up (range, 24–28 months), none of the patients had any complaints with ambulation and all were satisfied with the results. No complications had occurred.