INCISION AND JOINT EXPOSURE

Two incisions are used for the surgical approach to the ankle. The first is a medial incision made between the notch of the malleolus and the anterior tibial tendon, over a 2.5-cm length. On the lateral aspect of the ankle, the interspace between the peroneus tertius tendon and the fibula is identified, lateral to the lateral cutaneous branch of the superficial peroneal nerve, which is retracted medially with the peroneus tertius tendon. On the medial aspect of the ankle the incision is deepened through subcutaneous tissue through the capsule, which is incised down to the periosteum, and a retractor is inserted. Stripping the anterior distal periosteum off the tibia is helpful; then the articular debris, osteophytes, and loose bodies should be removed. Both gutters should be debrided extensively, with a focus on the lateral gutter between the talus and the fibula. I pay a lot of attention to obtaining an arthrodesis between the medial and lateral aspects of the talus and the medial malleolus and the fibula. Either a rongeur or a smooth nontoothed laminar spreader is inserted in the medial incision, followed by insertion of a toothed laminar spreader laterally (Figure 37-2).

Figure 37-2 The mini-arthrotomy approach to ankle arthrodesis: A, the incisions; B, exposure of the joint with a retractor; and C, alternation of the retractor with a laminar spreader between the medial and the lateral incisions. D, The medial and lateral gutters are debrided with a rongeur. E, The first guide pin is placed through the medial malleolus. F, The second guide pin is inserted adjacent to the Achilles tendon and directed into the head of the talus toward the sinus tarsi, avoiding the posterior facet.

The goal of joint debridement is to remove the joint surface down to bleeding bone. With use of the laminar spreader alternating between the medial and the lateral aspects of the joint, the articular surface of the talus and tibia is completely denuded. I use copious irrigation to ensure that good articular apposition is obtained and that good bleeding cancellous bone is present. One of the most significant changes in my preparation of the joint over recent years has been the creation of broad bleeding bone surfaces with use of a 5-mm osteotome, as well as thoroughly perforating the joint surfaces with a 2-mm drill bit. Before fixation, I check the alignment of the ankle fluoroscopically to ensure good bone-to-bone apposition. Large bone gaps are to be avoided; ideally, the prepared bone surfaces should give the appearance that the joint is already fused.

SCREW FIXATION

Crossing the plane of the screws is important. No screw construct should be created in which all of the screws are perpendicular to the axis of the joint. Parallel screw fixation should be avoided, because this technique is ineffective in controlling torsion and rotational forces. The fixation is performed with three screws placed over cannulated guide pins. The first guide pin is inserted from the medial malleolus to extend obliquely down toward the anterior aspect of the sinus tarsi. Why insertion in the medial malleolus first? I find that this is a more predictable placement that affords good compression of the joint. This screw is introduced from the medial aspect of the medial malleolus and extends down inferolaterally into the lateral body of the talus, directly above the lateral process of the talus. The screw must not enter the subtalar joint, and I rarely use a screw longer than 40 mm here. The foot can then be held in position while the second guide pin is introduced from the posterior leg adjacent to the Achilles tendon between the tendon and the sural nerve. The posterior axial screw is introduced next, from the posterior aspect of the tibia into the anteromedial neck of the talus; a 7.0-mm partially threaded screw, usually approximately 65 mm in length, is used.

The insertion point for the third screw is variable and depends on the anterolateral bone shape. If a ridge is observed on the distal lateral tibia, then the third screw is inserted from the anterolateral tibia immediately adjacent to the fibula into the distal medial talus. If no shoulder is present on the distal tibia, then one or two smaller screws can be inserted from the fibula into the talus, but these screws are not my preference (Figure 37-3).

Figure 37-3 The standard screw location as seen on anteroposterior (A) and lateral (B) plain radiographs. Note that there is no screw in the fibula, and the lateral screw is inserted from the anterolateral tibia.

In complex cases and when the bone quality is poor, the arthrodesis can be extended up into the syndesmosis, with insertion of a few extra screws from the fibula into the tibia (Figures 37-4 and 37-5). Sometimes the second posterior-to-anterior screw does not go in smoothly and hits the first medial screw. In such instances, a more lateral starting point is preferable, with the guide pin inserted through the posterolateral tibia. The three screws ideally should go through the tibia into the talus, rather than through the fibula. If, however, placement through the fibula is necessary, it should be drilled through to allow the screw to compress the fibula against the tibia. I like to use compression here if at all possible. Clearly, the first medially inserted screw gives the most compression, with less afforded with each subsequent screw, despite the use of partially threaded screws. If the bone quality is very poor, I forego compression; after making sure that the joint surfaces are very well debrided, I then use fully threaded screws (Figure 37-6).