Extraperiosteal Plating of Pronation-Abduction Ankle Fractures

Siegel, Jodi MD; Tornetta, Paul III MD

Journal of Bone & Joint Surgery - American Volume:
doi: 10.2106/JBJS.E.00987
Scientific Articles
Abstract

Background: Pronation-abduction ankle fractures frequently are associated with substantial lateral comminution and have been reported to be associated with the highest rates of nonunion among indirect ankle fractures. The purpose of the present study was to report the technique for and outcomes of extraperiosteal plating in a series of patients with pronation-abduction ankle fractures.

Methods: Thirty-one consecutive patients with an unstable comminuted pronation-abduction ankle fracture were managed with extraperiosteal plating of the fibular fracture. The average age of the patients was forty-four years. There were nineteen bimalleolar and twelve lateral malleolar fractures with an associated deltoid ligament injury. No attempt to reduce the comminuted fragments was made as this area was spanned by the plate. The patients were evaluated functionally (with use of the American Orthopaedic Foot and Ankle Society score), radiographically, and clinically (with range-of-motion testing).

Results: Immediate postoperative and final follow-up radiographs showed that all patients had a well-aligned ankle mortise on the fractured side as compared with the normal side on the basis of standardized measurements. All fractures healed without displacement. At a minimum of two years after the injury, the average American Orthopaedic Foot and Ankle Society score (available for twenty-one patients) was 82. The range of motion averaged 13° of dorsiflexion and 31° of plantar flexion, with one patient not achieving dorsiflexion to neutral. There were no deep infections, and one patient had an area of superficial skin breakdown that healed without operative intervention.

Conclusions: Extraperiosteal plating of pronation-abduction ankle fractures is an effective method of stabilization that leads to predictable union of the fibular fracture. The results of this procedure are at least as good as those of other techniques of open reduction and internal fixation of the ankle, although specific results for pronation-abduction injuries have not been previously reported, to our knowledge.

Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

Author Information

1 Department of Orthopaedic Surgery, Boston University Medical Center, 850 Harrison Avenue, D2N, Boston, MA 02118. E-mail address for P. Tornetta: ptornetta@pol.net

Article Outline

Ankle fractures are one of the most common types of injuries treated by orthopaedic surgeons1. Several radiographic classification systems are used to describe these injuries. The Danis-Weber classification system is based on the level of the fibular fracture in relation to the tibial plafond. This classification scheme may be used for research and documentation as applied in the Orthopaedic Trauma Association (OTA) fracture compendium2. However, many mechanisms of injury can lead to the same classification grouping. For this reason, this scheme is not useful for predicting whether the initial injury was rotational or translational, for determining what reduction force will be required, or for determining the location of the most appropriate type of fixation to offset the instability. The Lauge-Hansen system correlates the radiographic features of the fractures with the mechanism of injury and then subsequently classifies the fractures on the basis of this proposed mechanism3. Within this classification system, the deforming force causing a pronation-abduction fracture is translational rather than rotational. The pronated foot is subjected to an abduction stress, and the fracture occurs in three stages. The medial structures are first placed under tension, causing either a disruption of the deltoid ligament or an avulsion-type fracture of the medial malleolus. A stage-2 pronation-abduction injury will proceed to either an impaction injury of the lateral tibial plafond or a disruption of the syndesmosis. The translational force exits at the fibula in the third stage, resulting in a transverse fracture that is often comminuted laterally, consistent with a bending failure (Fig. 1). The displacement of the talus is lateral, rather than more posterolateral, as is the case with other Weber type-C injuries that occur in rotation. The reduction and fixation of this particular injury should be distinguished from those of other suprasyndesmotic fractures on the basis of the direction of instability. At our institution, stage-3 pronation-abduction ankle fractures account for <9% of all ankle fractures. Substantial lateral comminution of the fibula makes the operative treatment of this type of ankle fracture challenging. Traditional subperiosteal plating techniques strip the remaining soft tissue from the fracture, making the fragments extremely difficult to align and stabilize with a lateral plate, which has led some authors to recommend bone-grafting for comminuted fractures4,5. Extraperiosteal fixation techniques, which preserve the periosteum and indirectly reduce comminution, have been used for the treatment of other long bones6-8. The purpose of the present study was to report the technique for and outcomes of extraperiosteal plating of the fibula for the treatment of unstable pronation-abduction ankle fractures.

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Materials and Methods

Over a seventy-two-month period, thirty-one skeletally mature patients with a closed, unstable pronation-abduction ankle fracture were managed at a level-I trauma center by a single surgeon (P.T. III). Routine ankle radiographs, including anteroposterior, lateral, and mortise views, were made. In all cases, the fibular fracture extended to within 2 cm of the tibiotalar joint, precluding the use of syndesmotic fixation only.

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Surgical Procedure

Once the soft tissues were amenable to surgical intervention, the planned procedure was undertaken. If a medial malleolar fracture was present, the first step was to open the medial fracture site, to reduce the fragment or fragments, and then to stabilize the fracture with lag screws. If the medial injury was a deltoid rupture, it was not addressed surgically. Subsequently, a direct lateral incision was utilized to access the fibular fracture. A careful extraperiosteal dissection was performed, with the soft-tissue sleeve surrounding the comminuted fracture fragments being left as intact as possible. A nonlocking, one-third tubular plate was precontoured to fit the anatomy of the lateral aspect of the distal part of the fibula. Through fixation of the medial malleolar fracture (when present) and manipulation of the foot, a tentative indirect reduction of the fibula was obtained. As the lateral ankle ligaments, particularly the calcaneofibular ligament, are intact in this injury pattern, reduction of the talus under the plafond pulled the distal part of the fibula out to length in most cases. Length was confirmed by means of radiographic comparison with the normal side with use of standard radiographic landmarks such as the fibular notch and the talocrural angle. If length was not restored, then a bone tenaculum was used to directly pull the distal part of the fibula distally, restoring length. In these cases, a Kirschner wire was used to hold the fibula in position until fixation in the fragment was placed through the plate. The plate was then placed against the fibula, superficial to the periosteum. Radiographs that were made at this time often revealed mild residual lateral fracture displacement (Fig. 2-A). In all cases, fibular length was reestablished prior to proximal fixation. Screws typically were placed sequentially through the plate from proximal to distal in the proximal fragment, which allowed the plate to be utilized as a reduction tool, with the distal part of the fibula being pushed medially as the screws were placed (Fig. 2-B).

In five ankles, screws were placed in the distal fragment to help to maintain length. After fixation was achieved, fibular length was again confirmed radiographically by visualization of the fibular fracture fragments and by comparison with the other ankle. In particular, the talocrural angle was used to confirm the accurate restoration of fibular length and the congruence of the ankle mortise (Fig. 3)9. Additionally, the medial clear space and the tilt of the talus in the mortise were compared between sides. If intraoperative evaluation following lateral fixation demonstrated that the syndesmosis was unstable, syndesmotic screws were placed through the plate, which acts as a substitute lateral cortex in order to stabilize the syndesmosis (Figs. 4-A and 4-B). If the medial injury was ligamentous, instability was identified by measuring the medial clear space and the syndesmotic space or by identifying any lateral subluxation of the talus radiographically with the application of an abduction stress on the ankle. If medial fixation had been performed, then a laterally directed force was applied with use of a clamp placed on the fibula to test for syndesmotic instability, which was defined as the occurrence of >2 mm of lateral translation of the fibula with respect to the tibia at the syndesmotic notch with the foot held in a neutral position. If syndesmotic fixation was placed, the patient was given the option of removal at a minimum of three months. There was no attempt to reduce the comminuted fibular fracture fragments. The plate simply spanned the comminution of the fibula, analogous to “bridge plating” in other long bones10. No bone-grafting was performed. All patients were managed with a cast postoperatively and were kept nonweight-bearing.

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Results

The study group included sixteen men and fifteen women with an average age of forty-four years (range, nineteen to seventy-six years). The average time for fibular fixation was sixteen minutes (range, ten to thirty-two minutes) from incision to fixation. There were nineteen bimalleolar fractures (OTA type 44C2.2) and twelve lateral malleolar fractures with an associated deltoid ligament injury (OTA type 44C2.1). Eighteen patients had medial-sided fixation, and twenty-three (including fourteen of the nineteen with a bimalleolar fracture and nine of the twelve with a lateral malleolar fracture) had placement of syndesmotic screws. One patient with an anterior collicular fracture and poor medial skin had nonoperative treatment of a medial malleolar fracture, which went on to a painless, fibrous union.

Immediately postoperatively, all patients had a well-aligned mortise on the fractured side as compared with the normal side on the basis of measurements of the medial, superior, lateral, and syndesmotic spaces, the position of the fibula on the lateral view, and the talocrural angle (which measured within 2° of that on the normal side). All fibular fractures healed without displacement within ten weeks. One patient was lost to follow-up after fracture union had occurred. Of the remaining thirty patients, twenty-one were followed for a minimum of two years (average, 2.3 years; range, two to four years). The average American Orthopaedic Foot and Ankle Society (AOFAS) score for these patients at the time of the latest follow-up was 82 (range, 68 to 100)11. The range of motion averaged 13° of dorsiflexion and 31° of plantar flexion, with one patient having a fixed plantar flexion contracture of 5° (this patient did not return for follow-up for four months and was undergoing a course of serial casting at the time of the most recent follow-up). There were no deep infections, but one elderly patient with type-1 diabetes had minor superficial skin breakdown that healed without operative intervention.

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Discussion

Figure. No caption a...
Figure. No caption a...

Unstable stage-3 pronation-abduction ankle fractures result in laterally comminuted fibular shaft fractures because of the bending moment at the time of fracture. The resultant fragmented bone is challenging to adequately align while maintaining satisfactory vascularity for fracture-healing. A classic direct open fracture reduction and rigid plate fixation will violate the soft-tissue attachments of the fragments and jeopardize the viability of the injured bone12,13. The surgical site is therefore placed at risk for nonunion and infection.

Because the endosteal blood supply is interrupted in association with a comminuted shaft fracture, the vitality of the bone depends on the periosteal vasculature and adjacent musculature, as does fracture-healing. One way to obtain stability while protecting the soft tissue is to apply a plate outside of the periosteum13,14, spanning the fracture fragments, to function as an internal splint. This technique provides stability at the fracture site similar to the level of fixation provided by an intramedullary nail or a cast. It allows micromotion at the fracture site but does not violate the delicate biology necessary for bone-healing; therefore, interfragmentary callus forms and the fracture proceeds to union14,15.

Indirect reduction techniques imply that the fracture site is not directly violated and therefore its soft-tissue envelope remains mostly intact. Ligamentotaxis and utilization of a plate as a reduction tool can be used to assist with the less invasive reduction in order to obtain stable fixation6.

These concepts have been explored extensively in association with femoral fractures. In studies involving cadaveric femora, Farouk et al.16,17 showed that minimally invasive plate osteosynthesis was superior to conventional plate osteosynthesis for preserving arterial femoral vascularity and perfusion. Other investigators have shown that union through callus formation, similar to that achieved with intramedullary fixation, can be obtained safely with a decreased need for bone-grafting and a decreased risk of infection through this minimally invasive, submuscular plating technique7,8,18. This concept has been applied to long-bone fractures of the femoral shaft as well as to periarticular and intra-articular fractures of both the femur7,8 and the tibia19.

In 1987, Limbird and Aaron5 reported on a series of eight laterally comminuted ankle fracture-dislocations in which anatomic reduction of the mortise and restoration of fibular length had been difficult to achieve secondary to discontinuity of the fibula. All of the patients underwent traditional open reduction and internal fixation, which included stripping the periosteum and opening the fracture site. The authors identified comminution of the distal part of the fibula as the cardinal feature of the injury but also reported that the anterior tibiofibular ligament was torn in all cases. Bone-grafting of the fibular defects was performed in six of the eight patients. The two fractures that did not receive bone graft went on to nonunion and required further revision surgery with secondary bone-grafting. These injuries were consistent with a pronation-abduction pattern ankle fracture. Similarly, Ebraheim et al.4 reported on nine Weber type-C, stage-3 pronation-abduction ankle fractures that were treated with traditional open reduction and internal fixation. Five required syndesmotic fixation. There was one delayed union and one nonunion. Those authors also recommend bone-grafting for high-energy fractures with comminution.

In the current series, after stabilization of the medial osseous injury (when present), a precontoured plate was placed directly laterally outside of the periosteum, spanning the area of fracture comminution, similar to a bridge plate. The direct lateral location opposes the abduction moment that caused the original injury. The extraperiosteal position precludes the need for bone graft, decreases the risk of infection, and provides the most biologically friendly environment for union. Also, using the plate as the reduction tool allows the softtissue envelope to be preserved while still allowing appropriate length and alignment to be obtained. All fractures in the present series exhibited a well-aligned mortise and went on to union without bone-grafting.

In 1978, Pankovich20 described a series of ankle fractures that included fourteen pronation-abduction injuries (five of which were stage 2 and nine of which were stage 3). Fixation of the medial side only did not restore stability in the patients with stage-2 injuries, and all required syndesmotic fixation. Six of the nine patients with a stage-3 fracture had persistent instability of the ankle after plating of the fibula and required syndesmotic fixation. Eleven of these fourteen patients achieved a painless ankle with a normal or nearly normal range of motion. In the current series, the syndesmosis was stressed after lateral fixation was completed21. When necessary, syndesmotic screws were placed directly through the plate. In such cases, the lateral plate serves as a substitute lateral cortex, which adds greater strength to the syndesmotic fixation as these screws often traverse the comminuted area of the fibula.

The technique of extraperiosteal plating of pronation-abduction fibular fractures has been described previously22. A lateral buttress plate, usually applied outside of the periosteum, bridges the comminuted fragments. The concept of indirect reduction with use of a plate also has been described for the treatment of high fibular fractures associated with a syndesmotic injury22. With this technique, distal fixation is performed first and then the fibula is subsequently pushed out to length before the proximal screws are placed. We prefer to perform proximal fixation first because manipulation of the foot combined with medial fixation, when necessary, generally restores fibular length, obviating the need for distal fibular fixation in most cases. The plate acts as a push plate, reducing the fibula and centering the talus within the mortise. In our series, only five of the thirty-one fractures required distal fibular fixation to maintain length.

There is only limited information regarding the outcomes of unstable ankle fractures. Lindsjo23 reported unlimited functional ability to work in 90%, to do physical activity and play sports in 82%, and to walk in 89% of patients in that series, as well as good range of motion, after surgical treatment of ankle fractures. In a retrospective review in which patients with operatively treated ankle fractures were compared with a group of control subjects, Belcher et al.24 reported functional impairment at eight to twenty-four months postoperatively despite adequate reduction and no radiographic evidence of degenerative changes; however, the study did not address whether these differences significantly impacted the patients' quality of life. Obremskey et al.25 observed that although patients continue to show improvement in function for as long as twenty-four months after surgical fixation, residual physical and functional effects can be expected. The degree to which these residual effects impact the quality of life is low. These reports are consistent with our findings, as all of our radiographs revealed osseous union with a well-aligned mortise and a stable joint and all patients but one had good range of motion.

In the present series, we found extraperiosteal plating to be an effective method for the stabilization of pronation-abduction ankle fractures. The technique allows for accurate reduction of the mortise without stripping the periosteum of the comminuted region of the fracture. In contrast with previous work, bone-grafting was not used and yet all fractures healed. The outcomes were similar to those in other series of ankle fractures after open reduction and internal fixation4,20,23,26, although we believe that the present study represents the first series that has been limited to only pronation-abduction injuries. The technique is easier and faster than standard techniques in which the lateral periosteum is split to facilitate placement of the plate. We recommend this technique for the treatment of comminuted pronation-abduction ankle fractures. Medial fixation, specific attention to restoring the length of the fibula and the fibular position as seen on the lateral radiograph, and evaluation of the syndesmosis after fibular fixation are essential elements of the technique. ▪

Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. A commercial entity (Smith and Nephew) paid or directed in any one year, or agreed to pay or direct, benefits in excess of $10,000 to a research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.

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Investigation performed at the Department of Orthopaedic Surgery, Boston University Medical Center, Boston, Massachusetts

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