Introduction
Recent literature has focused on new classification systems that help surgeons with the decision-making process of choosing the appropriate surgical approach and intraoperative evaluation of the reduction quality [
1,
2]. The 10-segment classification system as introduced by Krause et al. has been utilized in anatomical studies to evaluate the visualization of the different segments via various surgical approaches [
3]. The classic anterior-lateral approach allows to reach only 36.6% of the anterior-lateral as well as the lateral articular surface but has very limited in visualization of the central lateral segments [
3]. In this regard, type 41-B3 and 41-C3 fractures according to AO/OTA (Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association) classification [
4] are most common and difficult to treat as they often evolve the central lateral segments, namely the postero-latero-central (PLC) and antero-latero-central (ALC) segment [
1,
5]. Meulenkamp et al. reported about a malreduction rate of 16.6 and 41.4% in tibial plateau fractures that were approached via an anterolateral approach and submeniscal arthrotomy or fluoroscopy alone [
6]. These malreductions were heavily weighted to the posterior half of the ALC and whole PLC segment. An additional osteotomy of the lateral femoral epicondyle may be carried out in order to visualize almost all of the lateral joint line (more than 80%) [
3,
7‐
9]. However, the modified posterolateral approach provides access to the posterior convex aspect of the articular surface (19.0% [
3]), but visualization of the anterior aspect of the PLC and ALC remains limited [
3]. The importance of an accurate reduction of the articular surface has been highlighted by clinical and biomechanical studies that demonstrated poorer clinical results and increased joint contact pressure if the intraarticular joint irregularity was higher than 2 mm [
5,
10,
11].
Suboptimal intraoperative visualization has been described to be a main reason for inferior results [
6,
12]. Fracturoscopy has been reported to be superior to fluoroscopy [
12], but visualization of the central lateral segments can still be challenging.
The main scope of this study was a validation of additional methods to improve visualization in tibial plateau fractures involving the central lateral segments. Fractures were treated by an anterolateral or modified posterior-lateral approach and reduced in a “stepwise approach” by improving the visualization by (1) the additional usage of a standard 4 mm, 30-degree-angled arthroscope, (2) a 1.9-mm straight nanoscope and (3) lateral epicondyle osteotomy. We hypothesize that the AL and PL approaches both fail to properly reduce the ALC and PLC/ALC intersegmental area. We further hypothesize that additional visualization aids are necessary in this type of fractures and that by improved visualization the reduction quality of the central lateral segment can be optimized.
Discussion
The main result of this study was that neither an anterolateral nor the modified posterolateral approach were able to control the reduction of the ALC and ALC/PLC intersegmental area with the sole use of fluoroscopy. Video-assisted reduction significantly improved the reduction within this area resulting in less than 2 mm irregularity of the articular surface. In this regard, nanoscopy was more effective as visualization of the entire plateau was possible regardless of the approach used. ECO achieved optimal reduction of the latero-central segments in all cases, but only allows limited possibility for direct reduction in the posterior half of the PLC when performed as an AL approach.
Optimal surgical reduction of tibial plateau fractures demands a strategy that takes both visualization and accessibility for direct or indirect reduction into account. Direct visualization of the articular surface has been described as a perquisite for anatomical reduction, particularly in fractures including the latero-central segments [
3,
6]. By using the classic anterolateral approach only, the anterolateral third of the articular surface can be exposed [
3]. In line with this, we were not able to properly reduce the ALC and ALC/PLC intersegmental area in this study following fluoroscopic control of reduction. This finding was described preciously in a clinical study, in which postoperative malreductions were heavily weighted to the posterior half of the ALC and PLC segment when using an AL approach and fluoroscopic control [
6]. The PL approach yielded slightly better reduction of the ALC/PLC intersegmental area, which certainly demands on the fracture morphology of the PLC fragment. If the fragment is angulated posteriorly and exceeds far posterior in the PLC segment, it can be controlled better by the posterior window of the PL approach [
15]. However, as mentioned by others, fluoroscopy could not overcome the issue of insufficient visualization in our study [
6,
12,
16,
17]. Alternatively, intraoperative 3D imaging can be utilized, but it only offers a sort of snapshot in time, that cannot be used during active reduction [
17]. As this study was designed as a proof-of-concept study, we aimed for anatomical reduction, while aware, that steps or gaps smaller than 2 mm may likely not be clinically relevant [
5,
6]. A recent biomechanical study, again, corroborated the importance of proper fracture reduction demonstrating that a fracture step-off of 2 mm increases the joint pressure [
11]. The importance of insufficient fracture reduction was shown in an analysis that evaluated postoperative CT scans, in which the authors demonstrated that insufficient intraoperative visualization may be a major reason of failure in complex tibial plateau fractures [
6].
Improved visualization using standard approaches can be optimized using video-assistance and extension of the surgical approach. Fracturoscopy has shown to be superior to fluoroscopy before, leading to good clinical results [
12,
18]. Depending on the patient’s knee laxity, lateral joint space opening can be 2–4 mm and atraumatic insertion of a 4-mm arthroscope can be challenging if the anterolateral wall is reduced properly. In addition, the opportunity of lateral joint space opening by distinctive varus stress is limited in bicondylar fractures and the 30-degree angulation can further limit visualization. In this study, a 1.9-mm straight nanoscope facilitated visualization of the entire tibia plateau resulting in satisfactory reduction of the remaining ALC and intersegmental area for both approaches used in this study. NS provided a better overview of the joint. All investigators felt that the handling of NS was easier and more convenient, likely due to its straight view (0° degree angulation, compared to the 30° of a standard arthroscope). Similar findings were described for visualization of small joint compartments in the ankle joint when using the nanoscope [
19,
20]. NS-assisted fracture reduction may decrease the necessity of extended approaches in certain cases of complex tibia plateau fractures. Importantly, video-assistance only allows for indirect reduction of punch-like depressed fragments and the degree of preoperative fragment depression may also influence successful reduction using this technique as indicated by Krause et al. [
12]. The authors suggest to critically analyze the fracture morphology of the fragment located in the ALC and ALC/PLC intersegmental area. Isolated ALC fragments with a deep preoperative depression and angulation, particularly 90° deformities, are hard to reduce indirectly and may necessitate an extension of the approach to directly reduce the fragment [
21,
22]. Dislocated fragments that reach the posterior aspect of the PLC may necessitate a PL approach, which can be performed in prone or lateral position depending on the involvement of the medial plateau [
15]. In fractures that only involve the anterior part of the PLC, an AL approach should be favored to spare the need for neurolysis of the peroneal nerve, which is recommended using the PL approach. Distal extension of the approach to reduce distal metaphyseal fractures is more feasible to handle using the anterolateral approach, while care must be taken to distally extend the posterior window of the posterolateral approach due to the trifurcation of the popliteal vessels.
Alternatively, to video-assisted reduction, visualization of the lateral plateau can be improved to 65% (with an isolated osteotomy of the LCL footprint at the distal femur) and 80% (with an osteotomy of both, the LCL and popliteus tendon origins) by an ECO [
3,
9]. ECO in this study enabled anatomical reduction in all types of fractures, which significantly optimized the radiographic reduction quality compared to the fluoroscopic-controlled reduction. However, due to limited accessibility to the PLC and PLL segments when using the AL, larger remaining irregularities were noted at the fracture sites when compared to the PL approach. Similar findings were reported in a cadaveric and a clinical study that examined the radiological and clinical outcome of complex tibial plateau fractures [
15,
23]. The authors acknowledge that the ECO procedure is an invasive procedure and that only short-term clinical results have been described for ECO in tibial plateau fractures [
24]. Therefore, we emphasize the concept of a stepwise intraoperative extension allowing for superior visualization of the joint, if no sufficient reduction can be achieved using other reduction tools [
8].
Clinical studies are needed to validate this proof-of-concept study design. Limitations of this study are the small number of cases, the multi-surgeon design, and a preoperatively fixed reduction sequence. Due to the fact that the sequence of the steps of the surgery was not randomized, the surgeon had the chance to improve the primary result considering a learning curve in each specimen. This may have biased the results in favor of the fracturoscopy/nanoscopy. In addition, the effect of the ECO may have been overestimated due to the reduction in the previous steps. Although matched fractures were used in this study, there are several factors regarding the fracture morphology that influence the reduction quality. Importantly, the severity of impaction and angulation are critical as well as the involvement of the medial plateau. Reduction and fixation of the medial plateau were neglected in this study, but certainly have a major impact on the surgical treatment strategy and patient positioning. However, comminuted lateral plateau fractures often coincide with split fracture types of the medial compartment, that needs separate attention using a medial approach [
25,
26]. With respect to video-assisted reduction, the authors acknowledge that bleeding was absent in this study and frequently limits its application. Osteotomy of the lateral epicondyle requires a solid bone stock and should be performed restrainedly in older patients with poor bone quality. Otherwise, if the screw fixation or bone healing fails, these patients may require a constrained knee prothesis.