Effectiveness of bone grafting versus cannulated screw fixation in the treatment of posterolateral tibial plateau compression fractures with concomitant ACL injury: a comparative study

Posterolateral tibial plateau compression fractures (PTPCF), accounting for only 7–15% of all tibial plateau fractures, are closely associated with anterior cruciate ligament (ACL) injuries or ACL attachment avulsion fractures [1‐4]. The posterolateral tibial plateau plays a crucial role in knee flexion stability, and fractures in this region are often accompanied by an increased posterior inclination angle or an increased lateral inclination angle of the lateral plateau [5, 6]. An increased posterior inclination angle or lateral inclination angle of the lateral plateau can lead to increased load on the ACL during knee joint motion, closely related to ACL injuries, and is one of the significant factors leading to knee instability and ACL reconstruction failure after ACL reconstruction surgery [7]. Therefore, to achieve satisfactory clinical outcomes and reduce the failure rate of ACL reconstruction, the treatment of PTPCF with concomitant ACL injury should not be limited to ACL reconstruction alone; equal attention should be given to the treatment of PTPCF [8, 9]. While addressing PTPCF in patients with concomitant ACL injuries, some surgeons use arthroscopic-assisted reduction and cannulated screw fixation [10]. Other orthopedists perform arthroscopic-assisted reduction and fixation with bone grafting only [11]. Nevertheless, the effectiveness of fixation for these fracture types without the use of metal implants is yet to be conclusively established. Therefore, this study retrospectively analyzed patients who had concomitant ACL injuries and PTPCF to investigate whether the fixation with isolated bone grafting is stable enough for the treatment of PTPCF with concomitant ACL injuries. The hypothesis of this study was that fixation with isolated bone grafting for PTPCF with concomitant ACL injuries can get a stable fixation as well as satisfactory clinical and radiological outcomes compared to fixation with cannulated screws.

This retrospective study analyzed patients treated for concomitant ACL injuries and PTPCF in authors’ institution between June 1, 2017, and May 31, 2022.

Inclusion criteria: (1) preoperative knee joint magnetic resonance imaging (MRI) showing ACL injury or ACL attachment avulsion fractures, with three-dimensional computed tomographs (3DCT) confirming PTPCF; (2) articular step-off of posterolateral tibial plateau fractures ≥ 2 mm or lateral tibial plateau posterior inclination angle greater than or equal to 17°, with patients undergoing arthroscopic surgery for tibial plateau fracture reduction; (3) age ≥ 18 years; (4) follow-up duration ≥ 12 months; and (5) complete preoperative and postoperative imaging data.

Exclusion criteria: (1) intraoperative confirmation of no ACL injury; (2) patients undergoing isolated ACL reconstruction or ACL avulsion fracture reduction and fixation; (3) multiple injury patients; (4) cases of open fractures; (5) patients with severe osteoarthritis; (6) age < 18 years; (7) follow-up duration less than 12 months; and (8) patients treated conservatively.

This study included a total of 53 patients (21 males and 32 females) with an average age of 47.43 ± 14.71 years (range 18–72 years). The patients were diagnosed with concomitant ACL injuries and PTPCF with ACL reconstruction and tibial plateau fracture reduction and fixation as a one-stage procedure. Patients were divided into two groups based on whether the PTPCF was internally fixed with cannulated screws during the procedure: the cannulated screw fixation group (30 cases, 13 males, and 17 females) and the bone grafting fixation group (23 cases, 8 males, and 15 females) (Table 1). This study was approved by the Medical Ethics Committee of Taizhou Hospital in Zhejiang Province, and all enrolled patients were informed and signed informed consent.

Baseline data, including patient age, gender composition, BMI, operated side, diabetes, hypertension, and follow-up time, did not differ significantly between the two groups (P > 0.05) (Table 1). Peroneal nerve injury was not observed in either group, and no cases of ACL reconstruction failure were noted. There were no significant differences between the two groups regarding knee joint periarticular soft tissue injuries (meniscus injuries, medial collateral ligament injuries), major tibial plateau inclination types, or incidence of deep venous thrombosis of lower extremity (P > 0.05) (Table 1).

The isolated bone grafting group achieved satisfactory levels of Rasmussen score (28.22 ± 0.85) and HSS knee joint function scores (95.57 ± 1.97). Similarly, the cannulated screw fixation group had a Rasmussen knee joint function score of 28.70 ± 0.92, and a HSS knee joint function score of 96.07 ± 1.93. There was no statistically significant difference in knee joint function scores between the two groups (P > 0.05) (Table 2).

To further assess the reliability of maintaining articular surface reduction after bone grafting fixation, a comparison of posterior inclination angle and lateral inclination angle of the lateral tibial plateau was performed for patients before surgery, postoperatively, and at the final follow-up. It was found that there was no statistically significant difference in the posterior inclination angle and lateral inclination angle of the lateral tibial plateau at both the postoperative and final follow-up time points.

The cannulated screw fixation group had a mean posterior inclination angle reduction loss of 0.20° ± 1.11°, while the bone grafting group had a reduction loss of 0.18° ± 1.01°, with no statistically significant difference between the groups (P > 0.05). The cannulated screw fixation group had a lateral inclination angle reduction loss of 0.01° ± 0.37°, and the bone grafting group had a reduction loss of 0.03° ± 0.43°, with no statistically significant difference between the groups (P > 0.05) (Table 3).

The outcome of this study shows that the isolated bone grafting for the treatment of PTPCF could achieve a satisfactory range of motion of knee joint (a mean extension of 0.65° ± 1.72° and a mean flexion of 124.78° ± 7.46°) and HSS scores (95.57 ± 1.9) and Rasmussen score (28.22 ± 0.85). Furthermore, the fixation with isolated bone grafting for the treatment of PTPCF could get a relatively stable fixation without significantly loss of reduction compare to fixation with cannulated screws with similar posterior inclination angle reduction loss and lateral inclination angle reduction loss.

ACL injuries are often accompanied by tibial plateau fractures [9, 13, 14]. A meta-analysis of knee MRIs in 1047 cases of ACL injuries revealed that early knee MRIs can detect bone contusion signal changes in up to 78% of patients [15]. The presence of tibial plateau bone contusion or fractures on MRI, and even impaction fractures of the tibial plateau and femoral lateral condyle, usually signifies severe knee joint trauma caused by violent force leading to knee joint subluxation [2]. Tibial plateau bone contusions or impaction fractures, often combined with femoral lateral condyle injuries, are believed to occur during the process of ACL injury, which involves knee joint flexion, external rotation, and valgus force. During the reduction process after knee joint subluxation, the impact between the lateral femoral condyle and the tibial plateau's posterolateral aspect is responsible for this injury. A typical tibial plateau impaction fracture manifests as a coronal plane defect in the posterolateral tibial plateau, hence it has been termed the "bitten apple" fracture [16, 17].

Bernholt et al. categorized tibial plateau compression fractures into three major classes based on the MRI presentation of the lateral tibial plateau: posterior cortical fractures of the tibial plateau that do not involve the articular surface, posterior cortical fractures of the tibial plateau that affect the articular surface, and posterior split fractures of the tibial plateau [18]. Building upon this classification, Menzdorf and colleagues employed the posterior horn of the lateral meniscus as a reference point to aid in the reclassification of surgical guidelines, though the substantial individual variability of meniscus morphology led to a reduction in classification reliability [17].

However, the two fracture classifications did not encompass the tibial plateau compression fractures included in this study. Tibial plateau compression fractures, often treated with arthroscopically assisted reduction and cannulated screw fixation involving the use of a metal tamp during the reduction process, exhibit various deficiencies, such as articular surface fracture fragment fragmentation, uneven articular surfaces, inadequate angular reduction, and fracture fragment rotation. To facilitate the use of metal tamp for fracture reduction, the authors categorized compression fractures of the lateral tibial plateau into three types based on the primary direction of articular surface inclination: posterior inclination, lateral inclination, and horizontal compression types [10]. In this study, the main focus was on posterior inclination and lateral inclination types. In contrast to tibial plateau impaction fractures accompanied by ACL injury, which often display the "kissing sign" on knee MRI [19], this sign is less frequent in the MRIs of knee joints with tibial plateau compression fractures associated with ACL injuries. The mechanism behind this difference might be that the lateral tibial plateau compression during the violent process of flexion and external rotation increases the posterior inclination angle or external rotation angle. This increased stress on the ACL eventually leads to ACL injury, even without knee joint subluxation. Tibial plateau articular subsidence and increased posterior inclination angle are closely related to the posterolateral instability of the knee joint and are often associated with a positive pivot-shift test of grade 2 or higher in knee joints [20]. A posterior inclination angle of 17 degrees or more is a significant factor in post-ACL reconstruction failure [21]. Thus, the treatment of tibial plateau compression fractures has attracted considerable attention.

The treatment of tibial plateau compression fractures varies. As arthroscopic technology continues to advance, many orthopedists have adopted arthroscopic reduction and cannulated screw fixation, which has shown good results [11, 12]. However, excessive cannulated screw fixation may interfere with the tibial tunnel for the ACL, affect grafts, risk peroneal nerve damage during the lateral implantation of the cannulated screw fixation, and require a second removal of the cannulated screw fixation [22, 23]. In this retrospective study, we compared the clinical and radiographic results of arthroscopic reduction and cannulated screw fixation and isolated bone grafting for tibial plateau compression fractures. It was found that simply filling and compacting bone under the tibial plateau fracture fragment can achieve a good reduction support effect. There were no significant differences in postoperative knee joint function or reduction loss between two groups. The subchondral bone underlying the fracture fragment in the tibial plateau is characterized by its trabecular composition, imposing rigorous requirements on the strategic placement of cannulated screws. Therefore, it is imperative to position the screws directly beneath the fracture fragment of the articular surface to attain an efficacious support effect (Fig. 3). In this study, increasing the trabecular bone density under the fracture fragment by performing allograft bone or calcium sulfate artificial bone grafting and compaction under the articular surface fracture fragment results in good reduction support, as shown in Fig. 4. Notably, neither the application of one or two cannulated screws nor isolated bone grafting can achieve the level of robust fixation compared with plate fixation [24, 25]. During knee joint movement, the axial load on the lateral tibial plateau is minimal when in the extended position. However, during knee flexion, due to the roll-back effect of the lateral condyle of the femur, the lateral plateau gradually begins to bear axial stress [26, 27]. Therefore, regardless of whether cannulated screw internal fixation is used, early weight-bearing knee flexion exercises should be avoided during postoperative rehabilitation.

In this study, some patients were managed using calcium sulfate artificial bone for grafting. Calcium sulfate artificial bone has good biocompatibility and degradability, while also inducing bone formation and having excellent mechanical properties. Although some degradation and absorption were observed during postoperative follow-up, all fractures achieved good healing, with no reduction loss (Fig. 4). Other patients were under went allograft bone grafting for the fixation of PTPCF. While the mechanical performance of allograft bone is lower than that of calcium sulfate artificial bone, its absorption rate is lower, approximately 10.78% [28]. During the follow-up, the fracture healed well with no significant loss of reduction. In comparison to cannulated screw fixation group, bone grafting fixation have several advantages, including avoiding the use of additional metal implants, reducing the risk of peroneal nerve injury during the fixation process, and eliminating the need for secondary removal surgery.

The use of isolated bone grafting for fixation of PTPCF with accompanying ACL injuries demonstrated no substantial disparities in postoperative knee joint range of motion, Rasmussen score, HSS knee joint function score, or VAS score when contrasted with cannulated screw fixation. In cases of simple PTPCF without lateral wall disruption, filling and compacting the bone defect underneath the tibial plateau fracture fragment can yield satisfactory fixation results, obviating the necessity for supplementary cannulate screw fixation.