Revisiting A Proven Approach To Severe Ankle Instability

   Severe, acute or repetitive chronic inversion ankle sprains can often result in lateral instability of the lateral ankle complex. Although one can treat the vast majority of these conditions conservatively, a significant and unresponsive case may require surgical intervention. Over the course of the past two decades, improved soft tissue anchors and arthroscopic procedures have reduced the necessity of traditional open procedures.    However, these procedures can still play a vital role in the surgical management of this condition. Naturally, there are numerous procedures at the surgeon’s disposal, but the Christman and Snook (C.S.) procedure is one of the most widely recognized surgical interventions to address severe instability of the ankle.    Originally described in 1969, the C.S. procedure was originally a modification of a procedure documented by Elmslie in 1934. It involves harvesting a portion of the peroneus brevis tendon to recreate two pseudo-ligaments to stabilize the lateral ankle. The Winfield procedure actually describes this technique more accurately since it was originally devised by simply anchoring the portion of the peroneus brevis tendon into the lateral calcaneus.

Differentiating Between Ligamentous Laxity And True Instability

   The anterior talofibular, the calcaneofibular and the posterior talofibular are the three ligaments that stabilize the lateral ankle. Instability may result from a severe injury or multiple repetitive injuries. Clinically, it is important to differentiate between simple ligamentous laxity and true instability. The patient history will likely indicate an instability on uneven surfaces but patients may occasionally suffer from this instability on flat surfaces as well. In my experience, chronic cases of instability often worsen with activity due to a gradual decrease in muscular splinting secondary to fatigue.    A physical examination may show anterior subluxation of the talus when bracing the tibia and pulling the heel forward. One may also see a deficit just superior to the opening of the sinus tarsi when the patient applies an inversion motion to his or her foot.    Radiographs may or may not provide a definitive diagnosis of this condition. Typically, a decision for surgical intervention is based on clinical exam, patient history and complaints. When one obtains radiographs, a difference of 20 degrees between the affected and unaffected side is usually indicative of significant instability. Avulsion fragments near the distal tip of the fibula may also suggest a significant previous injury.

Pertinent Step-By-Step Pearls

   Although one may perform the procedure while the patient is supine or even prone, a lateral position is the easiest for performing the procedure. I prefer a “hockey stick” incision that begins approximately 6 cm superior and posterior to the distal tip of the fibula, and extends to the base of the fifth metatarsal. One should deepen this incision to the level of the sheath surrounding the peroneal tendons. I often orient myself by first defining the superior and inferior peroneal retinaculums.    Typically the only structure to avoid is the sural nerve. Since this type of incision is very large, I typically find postoperative numbness or nerve entrapment are two of the most common complications. (It is important to have a frank preoperative discussion with the patient about these possibilities.)    The peroneus brevis lies slightly superior and lateral to the peroneus longus. With the aforementioned incision, one can easily trace the peroneus brevis from the fifth metatarsal base. Surgeons can split the brevis longitudinally or harvest the entire brevis. If you harvest the entire brevis, leave it intact distally and suture the proximal stump to the longus tendon. A number of suture techniques are available for securing the end of the brevis to be transferred. With this technique, one should focus on forming the end into a tight cylinder shape that will not fray. Lay the tendon aside and wrap it in a moist gauze.    At this point, one should easily identify the distal tip of the fibula and dissection is not necessary for performing the drill hole. Employing a 4-mm drill is often adequate to accommodate the tendon, but one may adjust this based on the circumference of the tendon harvested. Surgeons should always begin with a small drill and gradually increase the diameter, usually placing it approximately 1 cm superior to the distal tip. One of the most common mistakes in creating the tunnel is moving too far laterally and violating the lateral cortex. If this occurs, I have found employing a soft tissue anchor secures the tendon at this point with no detrimental consequences to the procedure.    A second mistake is directing the drill bit too medially and entering the lateral gutter of the ankle joint. Using intraoperative fluoroscopy is imperative during this portion of the procedure. Then pass the brevis tendon anterior to posterior through the fibula.    Occasionally, surgeons may find there is insufficient length to attach the tendon into the lateral wall of the calcaneus. Often this may be due to insufficient length of the original incision. If this occurs, one may split the tendon longitudinally and secure it with a suture at the point where it passes through the fibula.    Originally, surgeons secured the free end of the brevis into the lateral wall of the calcaneus by creating a drill hole just beneath the cortical wall. Now a soft tissue anchor serves this purpose just as well.

Key Pointers On Postoperative Care

   Immobilization in a short leg cast or splint is usually advisable for four weeks. Some authors recommend six weeks but in my experience, the two extra weeks of strict immobilization contributes to a greater amount of ankle stiffness. Following the initial four weeks, the patient should continue weightbearing in a removable cast walker for an additional four weeks. Physical therapy is at the surgeon’s discretion, but I have often found it helpful with these procedures, due to significant edema and a decreased in ankle joint range of motion.    While the modified Christman and Snook (Winfield) ankle stabilization is an older procedure, it remains a very effective surgical technique for addressing severe ankle instability. Dr. Burks is a Fellow of the American College of Foot and Ankle Surgeons and is board certified in foot and ankle surgery. Dr. Burks practices in Little Rock, Ark. Editor’s Note: For related articles, see “Detecting The Cause Of Chronic Ankle Pain” on page 68 of the March 2002 issue or “How To Manage Lateral Ankle Sprains” on page 56 of the November 2003 issue. Also check out the archives at www.podiatrytoday.com.