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Soft Tissue Repair in Supination-External Rotation IV Ankle Fractures

Donders, Johanna C.E. MD; Gausden, Elizabeth B. MD; Levack, Ashley E. MD, MAS; Helfet, David L. MD; Lorich, Dean G. MD

Techniques in Foot & Ankle Surgery: September 2017 - Volume 16 - Issue 3 - p 136–140
doi: 10.1097/BTF.0000000000000155
Special Focus: Soft Tissue Reconstruction in the Foot and Ankle

Achieving optimal functional outcomes while preventing posttraumatic ankle arthritis in patients with unstable ankle fractures remains challenging for orthopedic surgeons. The rate of syndesmotic malreduction is alarmingly high after transsyndesmotic screw fixation. The senior author introduced an alternative to transsyndesmotic screw fixation with anatomic approach to bone and ligament repair. Here we review the development of this approach and present the technique of repairing soft tissue structures in unstable ankle fractures.

Department of Orthopedic Trauma Surgery, Hospital for Special Surgery, New York Presbyterian Hospital, and Weill Cornell Medicine, New York, NY

The authors declare no conflict of interest.

Address correspondence and reprint requests to Johanna C.E. Donders, MD, Department of Orthopedic Trauma Service, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021. E-mail: dondersj@hss.edu.

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HISTORICAL PERSPECTIVE

Ankle fractures are among the most common musculoskeletal injuries.1,2 Ankle fractures range from simple closed fractures to complex open injuries. The Lauge-Hansen classification categorizes ankle fracture injuries according to the mechanism of injury, and all patterns are further classified by stage according to the severity of the injury and the anatomic structures that are involved. The supination-external rotation (SER) injury begins laterally (fractured fibula) then proceeds to disrupt the posterior structures [posterior inferior tibiofibular ligament (PITFL) or posterior malleolus] and then finally concludes with a medial-sided injury (medial malleolus fracture or deltoid ligament injury). When the injury involves injury to the PITFL or deltoid ligament rather than medial or posterior malleolar fractures, the pattern is classified as an “equivalent” injury. We believe that every fibular fracture involves a component of the ligaments that stabilize the syndesmosis. However the injury to the syndesmosis is a gradation of injury and instability. The objective and indications for treatment are dependent on the extent of the rotational injury in pronation-external rotation (PER) and SER patterns. Although it is generally accepted that SERIV fractures involving a fibula fracture and a medial malleolus fracture require surgical fixation of both the lateral and medial structures, the surgical treatment of the ligamentous equivalent counterparts remains controversial.

The standard approach to ligamentous injuries in ankle fractures has been benign neglect, and most surgeons do not directly address PITFL or deltoid injuries.1,3–7 The standard treatment for persistent syndesmotic instability after fixation of the ankle fracture is transsyndesmotic screws. However, in recent years multiple studies have demonstrated high rates of syndesmotic malreduction after ankle fracture fixation with these methods, which has been correlated with worse clinical outcomes.2,8–15 With use of transsyndesmotic screw fixation, rates of syndesmotic malreduction have been reported from 22% to 52%.8,14,15 Maintenance of intact transsyndesmotic implants has been associated with poorer functional outcomes and decreased range of motion.16,17

Given the shortcomings of the standard methods for treating ankle fractures with this approach and using transsyndesmotic screws, the senior author developed anatomic-specific fixation.12

With the assumption that all SERIV ankle fractures have a syndesmotic injury, surgical treatment of the complete complex of ankle injury to include bone and soft tissue is required to assess the reduction and stability. This approach placed increased emphasis on anatomic fixation of both ligamentous and bony injuries in SERIV equivalent ankle fracture patterns through anatomic repair of both the deltoid ligament and/or the PITFL in addition to fixation of all fractures regardless of size.

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INDICATION AND CONTRAINDICATIONS

Surgeons must evaluate all patients with ankle fractures for ankle stability, which is determined based on physical examination as well as radiographic findings. Anterior-posterior and lateral radiographs are obtained on all patients with suspected unstable ankle injuries. Manual external rotation stress radiographs are commonly used to assess syndesmotic integrity.18 However, diagnosis of syndesmotic and ligamentous injuries based on plain radiographs, and even based upon external rotation stress test preoperatively, is often inaccurate and can misguide management.19

Identifying ligamentous injuries in ankle fractures is particularly challenging. In “apparent isolated” SERII fibular fractures, 38% to 68% of fractures may also have disruption of the deltoid ligament (SERIV) when diagnosed with plain radiographs.18,20 For this reason, we frequently use axial, coronal, and sagittal T2-weighted magnetic resonance imaging (MRI) images to assess the ligamentous structures and determine ankle stability in patients with ankle fractures. MRI is 100% sensitive and 94% specific in diagnosing ligamentous injuries in the ankle.9

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PREOPERATIVE PLANNING

Radiographs are obtained of all patients with ankle fractures, including 3 views (anteroposterior, mortise, and lateral). In addition, patients undergo MRI to ascertain the extent of the soft tissue injuries, with careful attention to PITFL injury as well as deep deltoid injury.

Rather than indicating fixation of posterior malleolus fractures according to size of the fragment or amount of articular involvement, the decision to address posterior malleolus fractures is contingent upon the stability of the syndesmosis. As the PITFL accounts for 42% (9% superficial and 33% deep posterior inferior tibiofibular) of the strength of the syndesmosis, restoring this posterior structure as the anatomic checkrein against fibular rotation is crucial to reestablishing a stable syndesmosis and functional ankle joint.21 Therefore, even a small posterior malleolus fracture involving <25% of the articular surface often disrupts syndesmotic stability by introducing laxity within the PITFL complex. Even among cases of SERIV and PERIV fracture equivalent patterns, the PITFL is delaminated from the posterior tibia over 90% of the time.6 For this reason, the senior author prefers to address all posterior injuries (either PITFL delaminations or posterior malleolus fractures) with anatomic reduction and restoration of posterior syndesmotic integrity.

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SURGICAL TECHNIQUE

Definitive fixation is delayed as long as necessary to allow for optimization of soft tissue status, including a diminution of swelling about the ankle, resolution of fracture blisters, and sloughing of compromised soft tissue. We frequently apply external fixation on dislocated ankle fractures to maintain length while awaiting soft tissue optimization.

The patient is placed in prone or sloppy lateral position, depending on the pattern of injury, after thoroughly protecting the down body structures. General or regional anesthesia techniques are utilized. The leg is sterilely draped free, and the toes sealed with a plastic adhesive drape. If external fixation was required, the fixator is generally included in the sterile preparation and may be used to help position the leg. Bony landmarks (medial/lateral malleoli and joint line) are localized and identified with a surgical marking pen.

A posterolateral approach to the ankle is performed. The skin incision is marked halfway between the fibula and the Achilles tendon, and the dissection is taken down sharply to the fascia. It is important to identify the sural nerve under the superficial fascial layer. After this, a deep dissection to the bone between the interval of the flexor hallucis longus tendon and peroneal muscles, is performed providing exposure of the fibular fracture (Fig. 1).

After debridement, the fibular fracture is reduced. As the size of the plate has to mimic the cortex it is replacing, a 2.7 or 2.4 recon plate is applied to the posterior fibula in antiglide manner.

After reduction and fixation of the fibula, intraoperative fluoroscopy is used to confirm appropriate anatomic fibular alignment and the stability of the ankle is reassessed. The first intraoperative external stress test under fluoroscopy is performed and the syndesmosis is assessed with the tibiofibular clear space (Fig. 3). The integrity of the deltoid is also assessed by monitoring for talar tilt (Fig. 4).

After this intraoperative testing, attention is turned to the posterior structures. When a posterior malleolus fracture is present, the fracture is reduced and a T-plate is applied in antiglide manner. In cases where no posterior malleolus fracture is present, the PITFL complex is assessed. The most common injury seen is a delamination of the PITFL.6 Once the delaminated PITFL is exposed, it is tensioned and reapproximated to the posterior malleolus. With the foot maximally internally rotated, a 3.5 compression screw with a soft tissue washer is placed in a posterior to anterior direction to reattach the avulsed PITFL off the posterior tibia (Fig. 2B). No suture anchor is used, as malposition of the suture anchor, pullout, and possibility of fracture following the drill holes for the bone tunnels. After PITFL repair, a second intraoperative external rotation stress test under fluoroscopy is performed, and the alignment of the ankle joint, the medial clear space, the tibiofibular clear space, and the degree of talar tilt is again noted. In general, the PITFL repair will stabilize the syndesmosis and restore the tibiofibular clear space (Fig. 3). However, if persistent talar tilt remains, the deep deltoid should be repaired (Fig. 4).

A medial incision is then made, beginning at the distal tip of the medial malleolus and extending distally, to expose the avulsed deltoid ligament (Figs. 4A, B). Using a 3.2 drill bit, a pilot hole is created for the 5.0 mm suture anchor (Mitek, Raynham, MA) in the bare area of the medial malleolus. Intraoperative fluoroscopy can be used during this step to ensure that the track remains extra-articular. Using a “pants-over-vest” suture technique, the 2 limbs of FiberWire from the suture anchor are used retension both the superficial and the deep deltoid ligament to its insertion point (Fig. 4C). The suture limbs are then tied and secured to the medial malleolus while the foot is maintained in maximum internal rotation (Fig. 4D).

After deltoid repair, the reduction of the ankle joint is confirmed with fluoroscopy and the external stress test is repeated to confirm maintenance of syndesmotic stability as well as resolution of talar tilt (Fig. 3). Then, the wounds are irrigated copiously and closed. The lateral interval and overlying fascia is closed using #0 absorbable suture (Vicryl; Ethicon, NJ). Next, both the medial and lateral subcutaneous wounds are closed with 3-0 Caprosyn (Covidien, MN) suture and the skin is closed with 4-0 nylon sutures (Ethicon). Nonadherent dressing and sterile gauze are applied to all incision sites and held in position with sterile cast padding. With the ankle neutral dorsiflexion, a short leg posterior splint is applied.

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POSTOPERATIVE MANAGEMENT

Postoperative, active and passive range of motion with a licensed physical therapist is initiated after 2 weeks. Patients are kept non–weight-bearing and in a CAM walking boot for a total of 6 weeks. Evaluation of range of motion and plain radiographs (anteroposterior, lateral, and mortise) are performed at 6 weeks, 3 months, 6 months, and 1 year postoperatively.

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RESULTS

The results of the anatomic-specific technique for approaching ankle fractures are promising. In a cohort study of 45 patients, patients treated with anatomic fixation as described above had significantly better postoperative syndesmotic reduction compared with patients treated with transsyndesmotic screws (7.4% vs. 33.3%, P=0.02), and were less likely to require reoperation (78% to 11%).12

The outcomes following operative fixation of ankle fractures involving a posterior malleolus fracture and/or medial malleolus were compared the outcomes of patients with the ligamentous equivalents, a PITFL delamination and/or deltoid injury. There was no significant difference in SF-36 or FAOS between the 2 groups of patients when patients were treated with the anatomic-specific approach. We believe that regardless of whether the injury is osseous or ligamentous, anatomic repair of posterior and medial structures is important to achieving a stable ankle in SERIV and PERIV fracture patterns.

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COMPLICATIONS

The complications encountered after anatomic fixation of ankle fractures with soft tissue repair are similar to those encountered after all surgical treatment of ankle fractures and include soft tissue complications, infections, and hardware irritation. However, the need for reoperation for hardware removal is lower with this technique compared with transyndesmotic screw fixation, as the screws traversing the syndesmosis are frequently removed.

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POSSIBLE CONCERNS, FUTURE OF THE TECHNIQUE

Although the syndesmotic reduction was improved with the anatomic fixation compared with transyndesmotic repair, the clinical significance of the improved radiographic outcomes continues to be debated in the literature.6,8,12 Further investigation into functional outcomes of these patients and long-term incidence of posttraumatic ankle arthritis is necessary to determine the future clinical impact of this anatomic fixation strategy.

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REFERENCES

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Keywords:

ankle fracture; supination-external rotation type IV; posterior inferior tibiofibular ligament; deltoid ligament; syndesmosis

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