n Feature Article Morphological Characteristics of Posterolateral Articular Fragments in Tibial Plateau Fractures Gao Xiang, MD; Pan Zhi-Jun, MD; Zheng Qiang, MD; Li Hang, MD abstract Full article available online at Healio.com/Orthopedics. Search: 20130920-16 Treatment of posterolateral tibial plateau fractures is controversial, and information regarding this specific fracture pattern is lacking. The purpose of this study was to elucidate the frequency and morphological features of posterolateral articular fragments in tibial plateau fractures. A retrospective radiographic and chart review was performed on a consecutive series of patients who sustained tibial plateau fractures between May 2008 and August 2012. The articular surface area, maximum posterior cortical height, sagittal fracture angle, and amount of displacement were measured on computed tomography scans using the Picture and Archiving Communication System. Thirty-six (15%) of 242 injuries demonstrated a posterolateral fracture fragment comprising a mean 14.3% of the articular surface of the total tibial plateau (range, 8% to 32%). Mean major articular fragment angle was 23° (range, 62° to 243°), mean maximum posterior cortical height was 29 mm (range, 18 to 42 mm), and mean sagittal fracture angle was 77° (range, 58° to 97°). The posterolateral plateau articular fracture fragment has morphological characteristics of a conically shaped fragment with a relatively small articular surface area and sagittal fracture angle. Recognizing these morphological features will help the clinician formulate an effective surgical plan. Figure: Axial computed tomography scan at the subchondral level showing a posterolateral (PL) articular fragment. Point O is the center of the knee (midpoint of 2 tibial spines), point A is the anterior tibial tuberosity, point B is the posterior sulcus of the tibial plateau, point C is the most anterior point of the fibular head (F), and point D is the posteromedial (PM) ridge of the proximal tibia. Although a fracture line exists in the posteromedial quadrant (black arrow), the posteromedial cortex remains intact and a posteromedial fracture was excluded. Abbreviations: AL, anterolateral; AM, anteromedial. The authors are from the Department of Orthopaedic Surgery, the Second Affiliated Hospital, Medical School of Zhejiang University, Hangzhou, China. The authors have no relevant financial relationships to disclose. Correspondence should be addressed to: Pan Zhi-Jun, MD, Department of Orthopaedic Surgery, the Second Affiliated Hospital, Medical School of Zhejiang University, 88 Jie Fang Rd, Hangzhou, Zhejiang, 310009, China ([email protected]). doi: 10.3928/01477447-20130920-16 e1256 ORTHOPEDICS | Healio.com/Orthopedics Posterolateral Articular Fragment in Tibial Plateau Fractures | Xiang et al P osterolateral tibial plateau fractures are difficult to recognize, and, even when recognized, treatment is dif1 ficult. Information about this specific fracture pattern is lacking because the condition has been previously underreported. This is clinically relevant because it is difficult to detect fracture lines in the posterolateral corner region on plain radiography due to the overlapping bony shadows of the tibial plateau.2 Because the posterolateral fragments are often covered by the fibular head and the mass of muscle and tissue are medial to the fibula, the operative treatment of this fracture pattern remains a challenge to most surgeons. Visualization and manipulation of posterolateral plateau fracture patterns are difficult when using an anterolateral or anteromedial approach. To address this problem, a posterolateral transfibular approach was developed by Solomon et al.3 In addition to fibular osteotomy, an additional dissection of the posterolateral ligamentous structures is required. To minimize soft tissue damage and favor the posterior buttress plate, Carlson1 and Chang et al4 introduced a posterior approach and, more recently, Frosch et al5 described a posterolateral approach that does not involve fibular head osteotomy. However, an important disadvantage to all of these approaches is that they are associated with a risk of iatrogenic injury to the anterior tibial artery and cannot be extended distally. Selection of optimal and rational surgical approaches to various patterns is controversial.6 The lateral plateau is smaller and higher than the medial plateau and bears relatively little stress.7 Clinically, stability in flexion may be one of the main complications associated with not reducing this fracture, which may induce abnormal function of the knee joint.8 However, data on the biomechanical changes of the knee, such as stress distribution and kinematics behavior, following this fracture pattern are lacking. The current authors believe that establishing the frequency, size, and displacement of the posterolateral articular frag- OCTOBER 2013 | Volume 36 • Number 10 ment should lead to a better awareness of this injury and improved treatment. They conducted a retrospective radiographic and chart review of a consecutive series of patients with posterolateral tibial plateau fractures using computed tomography (CT) scans. The study data may be used to better model this fragment and may be useful in formulating and executing a surgical plan for this injury pattern. Materials and Methods Between May 2008 and August 2012, a consecutive series of patients with tibial plateau fractures were identified for a retrospective radiographic and chart review. The Picture and Archiving Communication System (PACS) was used to review the radiographic records. A total of 278 patients had 281 tibial plateau fractures. Thirty-nine fractures with CT scans unavailable for review were excluded. The remaining 242 tibial plateau fractures formed the study group. The tibial plateau can be anatomically classified into the following 4 quadrants on an axial CT image at the subchondral level, as previously proposed by Luo et al9: anterolateral, posterolateral, anteromedial, and posteromedial (Figure 1). In the current study, the posterolateral fracture fragment was defined as any separate posterolateral quadrant–based articular fracture fragment with extension of the fracture line to the posterolateral cortex (ie, a break from the posterolateral wall of the tibial plateau). Using this criterion, 36 patients with tibial plateau fractures had an identifiable posterolateral fracture fragment. The mechanisms of injury were a fall in 9 patients, electric scooter injury in 8 patients, motor vehicle accident in 13 patients, blow by a heavy object in 2 patients, and other causes (unknown) in 4 patients. The fracture type was classified according to the AO/OTA classification, which is dependent on the appearance of anteroposterior radiographs.10 Patients’ demographic data and fracture classifications are presented in Table 1. 1 Figure 1: Axial computed tomography scan at the subchondral level showing a posterolateral (PL) articular fragment. Point O is the center of the knee (midpoint of 2 tibial spines), point A is the anterior tibial tuberosity, point B is the posterior sulcus of the tibial plateau, point C is the most anterior point of the fibular head (F), and point D is the posteromedial (PM) ridge of the proximal tibia. Although a fracture line exists in the posteromedial quadrant (black arrow), the posteromedial cortex remains intact and a posteromedial fracture was excluded. Abbreviations: AL, anterolateral; AM, anteromedial. Morphological Assessment The morphological parameters in the current study were previously proposed by Barei et al11 and Higgins et al12 and were determined using PACS software. These parameters included the major articular fracture angle, surface area of the fracture fragment as a percentage of the whole plateau, posterior sagittal fracture angle, maximum posterior cortical height, and amount of displacement. Axial Images To better describe the morphology of the articular fracture line, an axial CT scan was obtained for further investigation. A quadrant fracture was considered only if the fracture line extended to the relevant quadrant cortex at the subchondral level (Figure 1). The posterior femoral condylar axis was used as a reference line to assess the rotation of the lower extremity on the CT scan. The posterior femoral condylar axis was developed by a connecting line tangential to the most posterior aspects of the femoral condyles (Figure 2A). The major articular fracture angle was calcu- e1257 n Feature Article lated by the major posterolateral articular fracture line and the posterior femoral condylar axis at the subchondral level (Figure 2B). The major articular fracture angle was considered positive if it was internally rotated relative to the posterior femoral condylar axis and negative if it was externally rotated relative to the posterior femoral condylar axis. The surface areas of the posterolateral articular fracture fragment and entire tibial plateau were determined at the same level on the axial CT slice, and the posterolateral fragment area was divided by the whole plateau area to obtain a percentage (percent surface area) (Figure 2C). Sagittal Images The sagittal fracture angle was subtended by the major posterolateral sagittal fracture line and a line parallel to the posterolateral articular surface (Figure 2D). The maximum posterior cortical height was measured from the articular surface to the most distal aspect of the posterolateral fracture fragment (Figure 2E). Displacement was defined as the maximum depth between the posterolateral articular fragment and the remainder of the lateral joint at the joint surface on the sagittal images. The displacement was considered major if it was greater than 5 mm and minor if it was less than 5 mm (Figure 2F). Statistical Analysis All data analyses were performed using SPSS version 16.0 statistical software (SPSS Inc, Chicago, Illinois). The 1-sample Kolmogorov-Smirnov test was used to test for normality of the distribution. Descriptive statistics were used to determine morphologic data. Associated fibular head fractures were statistically compared with respect to the degree of displacement. A P value less than .05 was considered statistically significant. Results Thirty-six of 242 patients with tibial plateau fractures had an identifiable pos- e1258 terolateral articular fragment, and posterolateral fractures accounted for 15% of all tibial plateau fractures. The fracture had major displacement in 31 patients and minor displacement in 5 patients, and average size of the displacement was 10.565.2 mm (range, 2 to 19 mm). The posterolateral articular fragment has a relatively small articular surface area, and average size of the fragment relative to the surface area of the plateau was 14.3%66.3% (range, 8% to 32%). Average major articular fracture angle of the posterolateral fracture fragment plane was 23°624° (range, 62° to 243°), which implied a coronal fracture line (Figure 3). Average height of the fragment was 2967 mm (range, 18 to 42 mm; 90th percentile538 mm) (Figure 4). Average sagittal angle was 77°612° (range, 58° to 97°) (Figure 5). Nine patients demonstrated an associated fibular head fracture, which were significantly associated with displacement of the posterolateral fracture fragment (independent samples t test, P,.05). Given the high-energy nature of associated fibular head fractures compared with intact fibular heads, the ob- Table Patient Demographics and Fracture Classification Patient No./ Sex/Age, y Side AO/OTA Classification10 Quadrant Involved 1/F/56 R C1.2 PL, AL 2/F/58 L C1.2 PL, AL 3/F/63 R B1.1 PL, AL 4/M/43 R B3.1 PL 5/F/70 L B3.1 PL, AL 6/F/58 R B3.1 PL 7/F/65 L B3.1 PL, AL 8/F/49 L C2.2 PL, AL, AM 9/M/53 R B3.1 PL, AL 10/F/45 R B3.1 PL, AL 11/M/33 R B3.1 PL, AL 12/M/42 L B3.3 PL, AM 13/F/49 L C3.1 PL ,AL,AM 14/F/68 L B3.1 PL 15/M/58 L B3.1 PL, AL 16/F/21 R C3.2 PL, AM,PM 17/F/65 L B3.1 PL, AL 18/F/69 L B3.1 PL, AL 19/M/37 R B3.1 PL, AL 20/M/57 L B3.3 PL, AM 21/M/60 R C3.1 PL, AL, AM 22/M/46 R B3.1 PL 23/F/33 R C1.3 PL, PM 24/M/49 L C3.1 PL, AL, PM 25/F/54 L B3.1 PL, AL 26/M/40 R B3.1 PL 27/M/36 R B1.1 PL 28/M/65 L B1.1 PL, AL 29/F/66 R C2.2 PL, PM 30/F/66 R B3.1 PL, AL 31/M/44 R B3.3 PL, AL 32/F/45 L B3.1 PL, AL 33/F/50 L B3.1 PL 34/F/53 L B3.1 PL, AL 35/M/46 R B3.1 PL, AL 36/M/43 R C2.2 PL, AM, PM Abbreviations: AL, anterolateral; AM, anteromedial; L, left; PL, posterolateral; PM, posteromedial; R, right. ORTHOPEDICS | Healio.com/Orthopedics Posterolateral Articular Fragment in Tibial Plateau Fractures | Xiang et al 2A 2D 2B 2E 2C 2F Figure 2: Axial (A-C) and sagittal (D-F) computed tomography scans showing the methods of measuring the posterior femoral condylar axis (A), major articular fragment angle (B), articular surface area (C), sagittal fracture angle (D), maximum fracture height (E), and displacement (F). Abbreviations: PFCA, posterior femoral condylar axis. served difference in the displacement rates is unsurprising. Discussion The morphological characteristics of posterolateral tibial plateau fractures have not been widely reported in the literature. The findings of the current study may provide new insight into this specific fracture pattern. The frequency of the posterolateral articular fracture fragment identified in the current study was 15% of tibial plateau fractures (36/242), and most of these fragments had major displacement. Clinicians should be aware that the posterolateral articular fragment is not uncommon in tibial plateau fractures. Posterolateral plateau injuries are difficult to assess radiographically on anteroposterior and lateral views, and full assessment of the fracture morphology requires a CT scan.2 This fracture OCTOBER 2013 | Volume 36 • Number 10 pattern results from axial loading with the knee in flexion, and the tibia has a tendency for anterior subluxation on the femur when posterolateral plateau fractures occur. Carlson1 reported that posterior bicondylar tibial plateau fractures have a high association with lateral meniscal pathology and anterior cruciate ligament injuries, whereas Waldrop et al8 noted that the medial static stabilizing structures of the knee may also be involved with more applied forces. Preoperative magnetic resonance imaging evaluation of this fracture pattern would assist with the diagnosis of meniscal pathology and the possibility of ligament instability.13,14 Restoration of articular surface congruity is the goal of treatment for tibial plateau fractures to minimize the longterm risk of posttraumatic arthritis.15,16 Clinically, not reducing this fracture would lead to knee instability and dys- function.8 Because the fragments are often covered by the fibula head and ligamentous structures in the corner region of the popliteus muscle, the question of how to surgically address this fracture remains controversial.1,3-6 The findings of the current study may be useful in formulating a preoperative strategy. The posterolateral fragment is potentially unsecured with the use of a lateral plate and screw fixation because of its conical shape and relatively small articular surface area. Average sagittal fracture angle in this study was 77°, implying a dislocation trend under shear force. A lateral plate and screw cannot guarantee neutralization of this osteoarticular fragment under shear force during knee flexion. From a biomechanical point of view, direct exposure and posterior buttress fixation may be required when managing this injury pattern.17 e1259 n Feature Article 3 Figure 3: Histogram demonstrating distribution of the major posterolateral articular fragment angle (MAFA). Several approaches have been described for direct exposure and buttress plating fixation of posterolateral fracture patterns, and authors have deliberated over the merits of each.1,3-5 However, in all of the described approaches, the distal limit of dissection is the location at which the anterior tibial artery perforates the interosseous membrane. Iatrogenic injury to the anterior tibial artery can result in ischemic muscle necrosis of the compartment and skin loss. In a cadaver study, Heidari et al18 reported that the anterior tibial artery courses through the interosseous membrane at approximately 46 mm distal to the lateral tibial plateau. This morphologic study showed that the average height of the posterolateral articular fragment is 2967 mm (range, 18 to 42 mm).18 The current study found that in most cases, enough distance existed between the fracture and the anterior tibial artery, and iatrogenic injury to the anterior tibial artery could be avoided by careful manipulation intraoperatively. However, the anterior tibial artery is usually near the area of exposure, and careful dissection and placement of retractors is recommended. A good understanding of the surgical anatomy of this region and the morphology of the fracture are essential for a successful outcome. e1260 4 Figure 4: Histogram showing distribution of the maximum fracture height. Maximum knee flexion is 60° and occurs during the swing phase of the gait cycle, and the lateral tibial plateau bears relatively small compressive stress compared with the medial plateau.19,20 The lateral femoral condyle undergoes significant posterior translation, including sliding 5 and rolling, during knee flexion, Figure 5: Histogram demonstrating the distribution of the sagittal fracture angle. and the position of the tibiofemoral contact area varies with the change in facilitate better modeling of this fragment the knee flexion angle.21 Therefore, the for future study. biomechanical role of the posterolateral The frequency of posterolateral fracfragment differs from that of the media ture patterns may be overestimated in the plateau, and knowledge of biomechani- current study. Posterolateral articular fraccal changes, such as stress distribution ture fragments will cause posterolateral and the kinematics behavior at the knee instability of the knee joint if this fracture following posterolateral fracture, is lack- fragment is not reduced. Therefore, the ining. The data in the current study should clusion criteria in this study included any ORTHOPEDICS | Healio.com/Orthopedics Posterolateral Articular Fragment in Tibial Plateau Fractures | Xiang et al separate posterolateral quadrant–based articular fracture fragment. Furthermore, nearly one-quarter of patients (8/36) sustained the fracture in an electric scooter accident, in which a person’s knee was flexed at 90° when riding. This mode of transportation may not be as popular elsewhere. However, the authors do not believe that this limitation presented bias during analysis of the morphological characteristics of this specific fracture. 4. Chang SM, Zheng HP, Li HF, et al. Treatment of isolated posterior coronal fracture of the lateral tibial plateau through posterolateral approach for direct exposure and buttress plate fixation. Arch Orthop Trauma Surg. 2009; 129(7):955-962. 13. Stallenberg B, Gevenois PA, Sintzoff SA Jr, Matos C, Andrianne Y, Struyven J. Fracture of the posterior aspect of the lateral tibial plateau: radiographic sign of anterior cruciate ligament tear. Radiology. 1993; 187(3):821825. 5. Frosch KH, Balcarek P, Walde T, Stürmer KM. A new posterolateral approach without fibula osteotomy for the treatment of tibial plateau fractures. J Orthop Trauma. 2010; 24(8):515-520. 14.Lee J, Papakonstantinou O, Brookenthal KR, Trudell D, Resnick DL. Arcuate sign of posterolateral knee injuries: anatomic, radiographic, and MR imaging data related to patterns of injury. Skeletal Radiol. 2003; 32(11):619-627. Conclusion 7. Martelli S, Pinskerova V. The shapes of the tibial and femoral articular surfaces in relation to tibiofemoral movement. J Bone Joint Surg Br. 2002; 84(4):607-613. Posterolateral plateau fracture patterns have morphological features of a conical shape and relatively small articular surface area and sagittal fracture angle. Recognizing these morphological features will help clinicians formulate an effective surgical plan. References 1.Carlson DA. Posterior bicondylar tibial plateau fractures. J Orthop Trauma. 2005; 19(2):73-78. 2. te Stroet MA, Holla M, Biert J, van Kampen A. The value of a CT scan compared to plain radiographs for the classification and treatment plan in tibial plateau fractures. Emerg Radiol. 2011; 18(4):279-283. 3. Solomon LB, Stevenson AW, Baird RP, Pohl AP. Posterolateral transfibular approach to tibial plateau fractures: technique, results, and rationale. J Orthop Trauma. 2010; 24(8):505-514. OCTOBER 2013 | Volume 36 • Number 10 6. Chang SM. Selection of surgical approaches to the posterolateral tibial plateau fracture by its combination patterns. J Orthop Trauma. 2011; 25(3):32-33. 8. Waldrop JI, Macey TI, Trettin JC, Bourgeois WR, Hughston JC. Fractures of the posterolateral tibial plateau. Am J Sports Med. 1988; 16(5):492-498. 9. Luo CF, Sun H, Zhang B, Zeng BF. Threecolumn fixation for complex tibial plateau fractures. J Orthop Trauma. 2010; 24(11):683-692. 10. Marsh JL, Slongo TF, Agel J, et al. Fracture and dislocation classification compendium–2007: Orthopaedic Trauma Association classification, database and outcomes committee. J Orthop Trauma. 2007; 21(suppl 10):1-133. 11. Barei DP, O’Mara TJ, Taitsman LA, Dunbar RP, Nork SE. Frequency and fracture morphology of the posteromedial fragment in bicondylar tibial plateau fracture patterns. J Orthop Trauma. 2008; 22(3):176-182. 12. Higgins TF, Kemper D, Klatt J. Incidence and morphology of the posteromedial fragment in bicondylar tibial plateau fractures. J Orthop Trauma. 2009; 23(1):45-51. 15. Barei DP, Nork SE, Mills WJ, et al. Functional outcomes of severe bicondylar tibial plateau fractures treated with dual incisions and medial and lateral plates. J Bone Joint Surg Am. 2006; 88(8):1713-1721. 16. Rademakers MV, Kerkhoffs GM, Sierevelt IN, et al. Operative treatment of 109 tibial plateau fractures: five- to 27-year follow-up results. J Orthop Trauma. 2007; 21(1):5-10. 17. Zhang W, Luo CF, Putnis S, Sun H, Zeng ZM, Zeng BF. Biomechanical analysis of four different fixations for the posterolateral shearing tibial plateau fracture. Knee. 2012; 19(2):94-98. 18. Heidari N, Lidder S, Grechenig W, Tesch NP, Weinberg AM. The risk of injury to the anterior tibial artery in the posterolateral approach to the tibia plateau: a cadaver study. J Orthop Trauma. 2013; 27(4):221-225. 19. Freeman MA, Pinskerova V. The movement of the normal tibio-femoral joint. J Biomech. 2005; 38(2):197-208. 20. Koo S, Andriacchi TP. The knee joint center of rotation is predominantly on the lateral side during normal walking. J Biomech. 2008; 41(6):1269-1273. 21. Kozanek M, Hosseini A, Liu F, et al. Tibiofemoral kinematics and condylar motion during the stance phase of gait. J Biomech. 2009; 42(12):1877-1884. e1261
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