Are all Schatzker Type-II tibial plateau fractures alike? A retrospective study

Introduction Lateral tibial plateau is the commonest area to encounter the malunion inspite of surgical intervention. Limitation in fracture understanding has role to play and currently available classications are lacking information about the morphological description of the fracture and injury to the associated ligaments/meniscus. Aims, Hypothesis and Methodology In an attempt to add the information to Schatzker's type-II fracture, we propose a technical tip for detailed injury characterization. Clinical and radiological records of 20 patients with Schatzker's-II fracture tibial plateau were evaluated to identify heterogeneity of fracture. Results Four displacement patterns of depression were seen, with varying severity of comminution involving the depressed fragment. The cortical split was in multiple planes in 55% of cases and associated injury to meniscus and MCL were identied in 40% of cases. Conclusion-Tibial


Introduction
Schatzker [1] classi ed proximal tibial plateau fracture into 6 principal types and type II is being the most common variety. This entity consists of depression involving the articular surface into the soft cancellous bone and split in the cortical rim. In current practice, routine use of the computer tomography (CT) scan led to the development of multiple CT-based classi cations, which has made it possible to identify the coronal plane fracture and localize the fracture with respect to the quadrants [2,3]. Yet, it is not very infrequent to encounter signi cant malunion after surgical management of split and depression lateral tibial plateau fracture, which mandates revision surgery or conversion to the arthroplasty [4,5].
Meulenkemp et al [6] also reported that the lateral tibial plateau is the commonest area to encounter malunion and incidence may range 23 to 77%. A recent systematic review has also pointed out the limitations of tibial plateau fracture classi cation; as the CT scan-based classi cation is lacking information about the morphological description of the fracture and injury to the associated ligaments/meniscus [7].
We propose a prede ned checklist, to further extend the understanding of the knee injuries classi ed as Schatzker's Type-II tibial plateau fracture. The primary objective of the current study was to reveal the heterogeneity of knee injuries classi ed as Schatzker's type-II tibial plateau fracture.

Materials And Methods
We identi ed 20 cases of Schatzker type II fractures operated from January 2014 -December 2019. Demographic data, mode of injury, operative details, and radiological records (pre-operative radiographs, multiplanar CT scan images) were collected. All records were evaluated based on a prede ned checklist to describe the depression fragment, split, and associated injuries to meniscus/ligaments Table-1, which includes the following criteria-Displacement pattern of Depression fragment - The displacement de ned by axial displacement of both edge of depression fragment in sagittal and coronal plane in relation to the intact articular surface. Information obtained as per checklist to describe the details of fracture character were recorded in Excel sheet and variation were analysed in percentages.

Results
Radiological and surgical records of the 20 patients were evaluated. Following the fracture characterization checklist. The Angulation type of displacement were most encountered; sagittal plane 60% (12/20) and coronal plane depression 55% (11/20). Pure axial depression was seen in 4 and 3 cases on coronal plane and sagittal axis, respectively. Complex pattern of displacement was seen in 4 cases on sagittal plane and 6 cases on coronal plane. The angulation displacement on the coronal plane was lateral tilt type in 9 cases versus 1 case had medial angulation. Whereas angulation displacement on the sagittal plane was anterior type in 9 cases and posterior in 4 cases.
Con guration of the depressed articular fragment was noted to be, either a single osteochondral chunk in 9 cases or multifragmentary in 11 cases. In 54% of the case with multifragmentary osteochondral fragment had complex displacement pattern in both sagittal and coronal plane (36%) or in one of the planes (18%). 9 cases were having single split 4 in sagittal plane and 5 in the coronal plane. However, all single-coronal-plane fracture was involving the anterolateral quadrant. 7 patients were having dual plane split fracture [9] and 4 were having multiple plane split.
Injury to meniscus or ligament were seen in 8 cases; 4 cases had grade 3 medial collateral ligament (MCL) injury which was diagnosed on the clinical examination combined with stress radiography (Figure 3) and the other 4 cases had a longitudinal tear of the lateral meniscus injury which was diagnosed during open reduction in 2 cases and on arthroscopic examination in 2 cases (Table-2).

Discussion
In our case series of split and depression type of tibial plateau fractures, we were able to identify the wide heterogeneity under various subheadings. Therefore, with the available information, it would not be wrong to say that the knee injuries classi ed as Schatzker type-II fracture are a group of morphologically split and depression types of lateral tibial plateau fracture with variation in the pattern of displacement, fracture location, and associated injuries. Millar et al [7] in their recent systematic review proposed that it is imperative to evaluate the tibial plateau fracture morphologically, topographically, the pattern of displacement, and associated injury to ligaments for comprehensive understanding.
Morphologically all the Schatzker-II fractures are having a cortical split of the lateral tibial plateau and depression of the articular surface. McGonangle et al [10] using the fracture mapping identi ed that 72% of the lateral tibial plateau fracture has a fracture in the sagittal plane (±22 ), amenable to xation with lateral angle stable plate. On the contrary, looking in our series, the classical sagittal plane cortical split was seen in only 20% (n=4) of the cases. However, the other 5 cases having anterolateral quadrant split fracture were also amenable to anterolateral xation. 55% of the cases were having a dual plane or multiplane split. Having multiple cortical splits involving the anterolateral and posterolateral quadrant, indicate the frequent need for multicolumn xation or the need for a Hoop plate to stabilize such fracture [11,12, 13].
The possible reason could be explained by the higher velocity of injury in our series. As, classically split and depression fracture is a type of low-velocity trauma [14], whereas all our cases sustained this fracture as a consequence of road tra c accident (RTA) of varying severity, which explains a higher amount of comminution involving the depression fragment and frequent encounter of multiple cortical splits. However, with increasing road tra c accidents, it is a need for time to understand the multiple dimensions of the fracture. Similarly, 40% of the patients were having an injury to either lateral meniscus or grade III injury of the MCL also corroborative to higher velocity of injury [15].
Identi cation of injuries to meniscus and ligament can be missed in the fracture setting and having a checklist will draw obvious attention. Moreover, this could be helpful to overcome the limitations of the available classi cations [7]. In the current study, we were having the intraoperative data to identify the injury to the ligament or meniscus. In the future wherever possible having a preoperative MRI would be more appropriate for detailed and pre-emptive surgical planning [15].
Moreover, the Depression of articular fracture was heterogeneous in regard to the pattern of displacement in the sagittal and coronal plane, comminution, and location in relation to the quadrants. The angular displacement of the articular surface in a sagittal plane not only identi es the varying pattern but also hints at the varying positions of the knee exion in combination with valgus force leading to lateral tibial plateau fracture [3].
Our study has some limitations because of the retrospective study design and a lesser number of cases. However, our primary objective was limited to identify the heterogeneity of Schatzker type-II fracture. Institute ethics committee given permission for publication and all author agree to consent for publication of this manuscript.
Availability of data and material: This is to declare that the corresponding author has the possession of all the relevant data and material which was required for the formulation and assessment of this manuscript Competing Interests: The authors have no competing interests Funding NO funding was obtained from any outside sources including any institute/ NGO/society or company during the course of the study.

Author's Contribution
First and corresponding author designed the study protocol and has written the manuscript.
Second author has done the independent documentation of the radiological record.
Third Author has scrutinized and provided the radiological records.
Fourth author has helped in study protocol design, guided the manuscript writing and data analysis.