2002 - University of Washington Bone and Joint Sources

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Is the Absence of an Ipsilateral Fibular Fracture Predictive of Tibial Pilon Fracture Severity DAVID P. BAREI, M.D., F.R.C.S.(C), SEAN E. NORK, M.D., CARLO BELLABARBA, M.D, AND BRUCE J. SANGEORZAN, M.D. The management of tibial pilon fractures remains controversial and challenging. Axial-loading, particularly from motor vehicle collisions or falls from significant heights, is a common mechanism of injury. Principles of operative treatment include reconstruction of the distal tibial articular surface followed by restoration of mechanical axes. Anatomic reduction of the articular surface along with stable fixation allowing early motion has been shown to be the most important predictor of satisfactory outcome, and should be prioritized. The ability to obtain anatomic reduction with stable fixation, however, decreases with increasing comminution of the articular surface. Fibular fractures are commonly associated with tibial pilon injuries, particularly those caused by shearingtype mechanisms. Other fracture patterns, however, do not demonstrate this associated feature. The absence of an ipsilateral fibular fracture in patients with tibial pilon injuries may predict a more severe injury pattern to the tibial plafond. Presumably, the injurious energy is completely absorbed by the tibial plafond resulting in more severe epiphyseal and metaphyseal injury, precluding accurate reduction and worse outcomes. Further, the deleterious effects of mechanical impact at the chondrocyte level may also lead to joint degeneration despite an accurate reduction. The purpose of this study is to evaluate the difference in the radiographic severity of tibial plafond injuries with fibular fractures as compared to those without fibular fractures. MATERIALS AND METHODS Between January 1997 and February 2000, 20 consecutive tibial pilon injuries without associated fibular fractures were retrospectively identified using a prospectively gathered trauma database. Over the same time period, an age and gender matched cohort of 20 tibial pilon injuries with fibular fractures were randomly selected. A computer-based image editing software program was used to digitize and conceal the fibula on the initial anteroposterior (AP) and lateral radiographs on all 40 injuries. Care was taken to completely eliminate any fibular fracture, and associated fibular malalignment, on both the AP and lateral views. Every effort was made to minimize concealment of the tibial plafond while maximizing the concealment of the fibula. Radiographs were then independently rank ordered (1 = least severe, 40 = most severe) by three orthopaedic traumatologists according to the severity of tibial plafond injury. Observers ranked all fractures taking into consideration all the radiographic factors they believe are important in the assessment of tibial pilon fracture severity. The observers were not given any specific guidelines regarding ranking, but relied on their significant clinical experience in managing these fractures. Injuries were also classified according to AO/OTA guidelines, which assigns fractures an alpha-numeric code according to body region and fracture location. Fractures affecting the metaphyseal and epiphyseal portions are divided into A, B, or C-type groupings, indicating an extra-articular fracture, partial articular fracture, or complete articular fracture, respectively. The premise is that the increasing alpha assignment indicates a more severe fracture pattern, and ultimately a worse prognosis. RESULTS Inter-observer agreement was assessed using the weighted Kappa statistic (k=0.6). Mean rank scores for pilon injuries with fibula fractures was 24.4 while those without fibula fractures was 16.7 (T-test = 0.02). Rank order was repeated for only AO/OTA C-type pilon injuries and demonstrated a mean of 10.3 for those with fibular fractures and 8.7 for those without fibular fracture (T-test = 0.5). Mean rank order for AO/OTA B-type injuries was 11.1 whereas the mean rank order for C-type injuries was 24.5 (T-test = 0.001). The proportion of fibula fractures in B-type versus C-type pilon injuries was assessed using the Chisquare statistic (p = 0.006). DISCUSSION Operative treatment of tibial pilon fractures is controversial. Evidence suggests that increasing comminution leads to a worse result for a variety of reasons. Identifying factors that are associated with a given outcome aid in clinical decision making. It has been theorized that the absence of fibular fractures in association with ipsilateral tibial pilon injuries may be associated with a poor outcome. Two different potential scenarios are suggested: the first is that the injurious energy is of lower magnitude and is insufficient to injure the fibula, or conversely, the energy is significant but is completely absorbed by the tibial plafond. To evaluate this theory, we used the rank order technique with experienced traumatologists blinded to the presence or absence of a fibular injury, who then independently assessed the radiographic severity of the tibial pilon fracture. The kappa statistic demonstrated satisfactory correlation, consistent with other published material on interobserver reliability of the AO/OTA fracture classification system. This study demonstrates that, overall, tibial pilon injuries with fibular fractures are more severe than those without fibular fractures. Complete articular (C-type) injuries, with or without fibular fractures, are equally severe. Supporting the OTA classification, C-type injuries were consistently ranked as significantly more severe than B-type injuries. The presence of a fibular fracture was more frequently associated with C-type injury than B-type. This data suggests that the presence of an intact fibula in not predictive of a more severe injury to the tibial pilon, but is predictive of a less severe, B-type, injury. 2002 ORTHOPAEDIC RESEARCH REPORT 7
(A) (A) (B) (B) Figure 1: Representative example of a type 43 C3 distal tibial articular fracture with an associated fibular fracture. Figure 2: Representative example of a type 43 C3 distal tibial articular fracure with an intact fibula. Note the significant shortening and joint impaction. RECOMMENDED READING Swiontkowski, M.F.; Sands, A.K.; Agel, J.; Diab, M.; Schwappach, J.R.; Kreder, H.J.: Interobserver variation in the AO/ OTA fracture classification system for pilon fractures: is there a problem J Orthop Trauma, 11(7): 467-470., 1997. Martin, J.S.; Marsh, J.L.; Bonar, Susan K.; et al.: Assessment of the AO/ASIF fracture classification for the distal tibia. J Orthop Trauma, 11(7): 477-483., 1997. Kellam, J.F.; Waddell, J.P.: Fractures of the distal tibial metaphysis with intraarticular extension – the distal tibial explosion fracture. J Trauma, 19: 593- 601., 1979. Sirkin, M.; Sanders, R.; DiPasquale, T,; Herscovici, D.: A staged protocol for soft tissue management in the treatment of complex pilon fractures. J Orthop Trauma, 13(2): 78-84., 1999. Decoster, T.A.; Willis, M.C.; Marsh, J.L.; et al.: Rank order analysis of tibial plafond fractures: does injury or reduction predict outcome Foot Ankle Int, 20(1): 44-9., 1999. 8 2002 ORTHOPAEDIC RESEARCH REPORT
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2002 - University of Washington Bone and Joint Sources

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