1 Introduction

Tibial plateau fractures occur in approximately 10 per 100,000 persons annually, with the highest incidence in patients between 40 and 60 years of age.¹ The fracture pattern is determined by the direction and energy of the impact, and quality of the bone.^2,3 Bicondylar tibial plateau (BTP) fractures are a severe subset of these injuries and occur in approximately 32 % of cases.^1,4,5 The standard treatment for most BTP fractures is open reduction and internal fixation (ORIF).

Bicondylar tibial plateau fractures can be classified using the AO/OTA, Schatzker, and Moore classification systems; however, some fracture patterns do not fit these systems.^4,6–8 One such pattern has been described as a BTP fracture-dislocation with an intact anterolateral (AL) cortical rim.^9–11 This pattern may be similar to the Type IV-P described by Kfuri and Schatzker, but is differentiated by the lack of any medial articular surface attached to the metaphysis.⁶ This fracture pattern may present with significant lateral joint impaction, but the intact AL cortical rim makes access to the lateral plateau and joint restoration challenging.¹¹ Several series have proposed techniques to access the lateral plateau when the lateral rim is intact including an all medial approach,¹⁰ an intra-articular osteotomy of the lateral tibial plateau,¹¹ and a standard dual incision approach for dual plating with creation of a cortical window.⁹

Despite multiple descriptions of this fracture entity and proposed surgical strategies, the prevalence of this fracture pattern is not known, and outcomes are limited to small case series.^9–14 The primary aim of this study was to determine the prevalence of BTP fractures with an intact anterolateral cortical rim in a large multicenter cohort. The secondary aims were to evaluate fracture characteristics and determine complication rates after ORIF.

2 Methods

Patients: After Institutional Review Board approval, all adult patients with a BTP fracture (AO/OTA 41C) were retrospectively identified from a prospectively maintained institutional database of two academic Level 1 centers between January 2010 and December 2023. Patients were identified using International Classification of Diseases, Tenth Revision (ICD-10) codes S82.141, S82.142, S82.143 for bicondylar tibial plateau fractures and Current Procedural Terminology (CPT) code 27,536 for open treatment of an intra-articular (plateau) tibial fracture. Patients with BTP fractures were screened for those with an intact anterolateral cortical rim. Eligibility of patients was confirmed through chart review and review of radiographs and Computed Tomography (CT) scans. Patients with any medial joint surface in continuity with the shaft were excluded and considered to have a posterior shearing pattern. Patients with periprosthetic fractures, without an available pre-operative CT scan, and with <3 months follow-up were excluded.

Outcome variables: Demographic, injury, and treatment characteristics, and surgical outcome variables were obtained from electronic medical records through chart review. Demographic variables included age, sex, body mass index (BMI), and American Society of Anesthesiologists (ASA) score. Injury characteristics included injury mechanism energy (low energy was fall from standing, all others high energy), Gustilo Anderson (GA) classification,¹⁵ quadrants compromised (anterolateral, anteromedial, posteromedial, posterolateral), lateral depression in millimeters and proportion of lateral plateau involvement <50 or >50 % (measured on preoperative axial CT scan), preoperative neurovascular injury, and meniscal injury (as documented intra-operatively). Treatment characteristics included use of external fixation, fasciotomy, surgical approach, osteotomy, number and anatomic location of plates, meniscal repair, and use of bone void filler. Outcome variables included reoperation, infection, conversion to total knee arthroplasty (TKA), time to weightbearing as tolerated (WBAT), and knee range of motion (ROM) at final follow-up. Deep infection was defined as requiring reoperation for incision and drainage (I&D).

Reduction quality was determined on the first post-operative radiograph or second post-operative radiograph in cases where a knee immobilizer obstructed measurement (n = 2). Measurements included articular step or gap at the joint (<2 mm, 2–5 mm, or >5 mm),⁹ condylar width,¹⁶ medial proximal tibial angle (MPTA), and posterior proximal tibial angle (PPTA). The acceptable ranges for the MPTA and PPTA are 87 ± 5° and 9 ± 5°, respectively.^17,18

Statistical Analysis: Variables are presented as frequencies with percentages for categorical variables and as medians with interquartile range (IQR) for continuous variables. Radiographic measurements of reduction quality were compared between patients with less than or greater than 50 % lateral joint involvement and between patients with and without a lateral submeniscal arthrotomy using Fisher's exact test for categorical variables and Wilcoxon rank sum test for continuous variables. Non-parametric analyses were used for continuous variables due to non-normal distribution on histograms and limited sample size within groups. All statistical analyses were performed using R (Version 4.3.0.21, Vienna, Austria).

3 Results

Patient and Injury Characteristics: In total, 46/455 patients (10 %) who presented with BTP fractures with an intact anterolateral cortical rim and posterolateral joint impaction met inclusion criteria (Table 1 and Fig. 1). The majority of fractures resulted from a high energy injury mechanism (71 %) and all fractures were closed. The median posterolateral joint depression was 9.0 mm (IQR: 6.0–12.0), 18 fractures (39 %) had >50 % lateral joint involvement, and one meniscus tear was identified and repaired (2.2 %) through a lateral submeniscal arthrotomy (Table 1). The overall rate of lateral submeniscal arthrotomy was 13/46 cases (28 %). There were 2 (4.3 %) pre-operative neurovascular injuries, specifically one peroneal nerve palsy and one anterior tibial artery injury with distal reconstitution, both of which did not require operative intervention. The median follow-up was 11 months (IQR: 6–27).

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Fig. 1 Bicondylar tibial plateau fracture with an intact anterolateral cortical rim and posterolateral joint impaction.

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Treatment Characteristics: Twelve patients (26 %) underwent temporary external fixation and 6 patients (13 %) required prophylactic fasciotomy (n = 5) or therapeutic fasciotomy for compartment syndrome (n = 1) (Table 2). A single-incision approach was used in 38 cases (83 %), either posteromedial, anteromedial, or direct medially (63 %), midline anterior (11 %), posterior (4.3 %), or lateral (4.3 %). Combined medial and lateral incisions were used in 8 cases (17 %). A lateral submeniscal arthrotomy was performed 6/8 (75 %) of these cases. In 13 cases (28 %), a lateral cortical window was made and in 1 case (2.2 %) a tamp was introduced through the medial fracture line to elevate depressed joint segments. Bone void filler was used in 18 cases (39 %). Single medial plating was performed for 27 fractures (59 %), dual medial plating for 10 fractures (21 %), combined medial and lateral plating for 7 fractures (15 %), and single lateral plating for 2 fractures (4.3 %). One fracture required plating on the posterior, posteromedial, and medial aspect of the tibia plateau.

Clinical Outcomes: Eight patients (17 %) required reoperation, most commonly for removal of symptomatic hardware (n = 6), I&D for infection (n = 2), and manipulation under anesthesia (n = 1) (Table 3). Two patients developed deep infection and underwent subsequent I&D and vacuum assisted closure of the wound. One patient ultimately required a gastrocnemius flap. All patients requiring reoperation healed at the final follow-up. One patient underwent total knee arthroplasty 3.3 years after the index procedure. Median flexion at final follow-up was 128° (IQR: 110–130) and median time to WBAT was 12 weeks (IQR: 10–15).

Reduction Quality: The median MPTA was 88° (IQR: 86–89) and was within satisfactory range for 45/46 cases (98 %) (Table 4). The median PPTA was 9° (IQR: 7–11) and was within satisfactory range for all cases. There was no difference in the MPTA (87 vs. 89°, P = .088) or PPTA (9.5 vs. 7.5°, P = .300) between patients with less than or greater than 50 % lateral joint involvement, respectively. Additionally, there was no difference in the MPTA (89 vs. 87°, P = .283) or PPTA (10° vs. 9°, P = .320) between patients with and without a submeniscal arthrotomy, respectively. The median tibial to femoral condylar width ratio was 0.91 (IQR: 0.90–0.95). The articular step or gap was <2 mm for 59 % of cases, 2–5 mm for 30 % of cases, and >5 mm for 11 % of cases post-operatively as measured on initial post-operative x-rays.

4 Discussion

Bicondylar tibial plateau fracture-dislocations with an intact anterolateral cortical rim pose a unique surgical challenge due to their medial-shearing pattern with posterolateral plateau involvement that may be difficult to access. Multiple surgical strategies to treat this fracture pattern have been proposed in several small case series.^9,11,19 However, the prevalence of this fracture pattern has not been determined and there is a paucity of data on fracture characteristics and outcomes following surgery.^9,11 This study defines the pattern as a medial-shearing injury where the only portion of uninjured articular surface in continuity with the shaft is located between the tibial tubercle and the anterior aspect of the fibular head. This represents the largest series on this fracture pattern to date and demonstrated a prevalence of 10 % for this fracture pattern among BTP fractures at two Level 1 trauma centers. Rates of meniscal repair and post-operative infection were relatively low using a predominantly medial-only strategy. Radiographic parameters of reduction quality including restoration of condylar width were within range of previously reported values despite low rates of lateral approaches or meniscal repair (Table 4).⁹

Prior literature has not reported the overall prevalence of this specific fracture pattern among BTP fractures. Potocnik et al. reported on postoperative outcomes of posteromedial fracture-dislocations sustained largely from skiing injuries.¹⁰ Their case series included BTP fractures with an intact anterolateral rim as well as some posterior shearing injuries. They proposed a medial-only approach to address posterolateral depression through the medial fracture line. An anteromedial parapatellar arthrotomy was used to address ACL avulsion fragments or anterior horn meniscal injuries. Sciadini et al. performed a lateral metaphyseal osteotomy in a case series of 8 patients (9 fractures) to achieve anatomic reduction for displaced medial tibial plateau fractures with central and posterior impaction of the lateral plateau but an intact lateral cortex.¹¹ Four patients required reoperation for manipulation under anesthesia (n = 3) and fasciotomies (n = 1) and all 9 fractures went on to union. The authors reported lateral meniscus injury in 5/9 fractures (56 %).

Crabtree et al. evaluated radiographic and functional outcomes using their preferred fixation strategy for 8 patients with BTP fracture dislocations with an intact anterolateral cortical rim. They suggested a standard dual incision approach, plating medially first and then using a corticotomy to address posterolateral impaction with a lateral plate applied to raft the elevated articular fragments.⁹ The post-operative articular step or gap was 0–2 mm for 7 patients and 2–5 mm for 1 patient. The mean Knee Injury and Osteoarthritis Outcome Score (KOOS) was 70.9 at a mean follow-up of 6.0 years.

Prior series on the rate of associated meniscal injuries after BTP fractures report rates up to 22 %.^20–22 In the present series, 1 meniscal tear (2.2 %) was repaired, which is lower than Sciadini et al. (5/9 fractures).¹¹ Potocnik et al. and Crabtree et al. did not report the rate of meniscal tear in their series.^9,10 The low rate of meniscal repair in this study suggests that a lateral submeniscal arthrotomy may not be mandatory for these fractures as satisfactory restoration of condylar width was achieved in the majority of fractures in this series without a dedicated lateral approach (Table 4). Further research is needed to determine the actual prevalence of lateral meniscus tears in this injury and when a lateral approach is mandatory.

The infection rate for bicondylar tibial plateau fractures (AO/OTA type 41C) ranges between 2.6 and 15 % and factors such as temporary external fixation and fasciotomies for compartment syndrome have been shown to increase this risk.^23–27 The deep infection rate of the present study (6.5 %) is within this range. Previous series evaluating outcomes of BTP fractures with an intact anterolateral cortical rim did not report any cases of post-operative infection.^9–11

In the present study, reduction quality based on the MPTA and articular stepoff or gap was similar to the results of Crabtree et al.⁹ Condylar width was also measured for patients in this series and was similar to previous CT-based assessment of uninjured knees.²⁸ This suggests that adequate reduction can be achieved with a medial-only strategy, even in patients with >50 % posterolateral joint involvement (Table 4). This strategy is also consistent with Schatzker and Kfuri's proposed management of the posterolateral impaction in the similar Type IV-P injury. These authors state that the posterolateral extension often involves mostly the non-articular part of the lateral condyle, and “thus it is questionable if an anatomic reduction of this non articular portion of the rim is necessary.⁶” The post-operative stepoff or gap was <5 mm in 89 % of cases in this series despite the predominantly medial-only strategy. One patient in this series was converted to TKA but long-term follow up is limited.

There are several limitations to this study. First, the present study lacks long-term follow-up and patient-reported outcomes (PROs). Second, the prevalence of meniscal injuries is likely underestimated due to the high number of medial-only approaches and lack of pre-operative magnetic resonance imaging.^22,29 This requires further study as small prior series have shown higher rates of meniscal injury. Use of a medial-only strategy may be advantageous in the setting of soft tissue compromise and was effective at restoring condylar width in this series but may limit access to posterolateral depression or leave meniscal tears unaddressed. The comparisons of radiographic reduction according to approach and degree of joint involvement are small and underpowered. Larger numbers and longer follow up are needed to determine the effect on patient outcomes. Future multicenter studies that include cohorts of patients from a range of treatment centers will be able to confirm the prevalence and outcomes of this fracture pattern. Future studies should utilize PROs to further evaluate outcomes, as they provide valuable information on patients’ health and are increasingly used in orthopaedic trauma literature.^30,31

5 Conclusion

This study demonstrates that up to 1 in 10 BTP fractures may be classified as a fracture-dislocation of the knee with an intact anterolateral cortical rim. There is a paucity of research on this relatively common fracture pattern. Despite the large proportion with >50 % lateral joint depression, restoration of condylar width was achieved utilizing predominantly medial-only approaches similar to the series by Potocnik et al.¹⁰ The low rate of meniscal repair in this cohort raises an important question about the utility of lateral approaches, which allow meniscal visualization and repair but carry the morbidity of a second incision. Longer follow up is needed to determine the impact on functional outcomes. As more unique variants of bicondylar tibial plateau fractures are identified, exploration of these surgical techniques in combination with fracture mapping will allow for in-depth evaluation of the relative merits of various fixation constructs. Future studies should aim to determine preferred operative strategies based on radiographic and long-term clinical outcomes.

Conflicts of interest and sources of funding

Author Arun Aneja reports research Support from OTA, AONA, AOFAS, and US Department of Defense, speaking fees from AO Trauma North America, and committee membership for OTA and AAOS. For the remaining authors no conflicts of interest were declared. No funding was obtained for this project.

Contributor roles taxonomy per author

JSB: data curation, methodology, visualization, formal analysis, writing - original draft and review & editing, HD: data curation, methodology, visualization, writing - original draft and review & editing, RKW: data curation, formal analysis, methodology, writing - original draft and review & editing, BJ: data curation, methodology, project administration, writing - review & editing, PTG: methodology, validation, project administration, writing - review & editing, SC: methodology, validation, supervision, writing - review & editing, MBH: methodology, supervision, writing - review & editing, AA: methodology. Supervision, writing - original draft and review & editing, TVL: methodology, supervision, project administration, writing - review & editing, MJW: conceptualization, methodology, supervision, writing - review & editing, AVK: conceptualization, methodology, supervision, project administration, writing - original draft and review & editing, DSS: conceptualization, methodology, supervision, project administration, writing - original draft and review & editing, Bicondylar Tibial Plateau Fracture Dislocations with an Intact Anterolateral Cortical Rim: Prevalence, Fracture Characteristics, and Complications.

Funding statement

No funding was received from the commercial or private sector for this project.

Ethical statement

Ethical approval was obtained from Mass General Brigham IRB (Protocol #: 2023P003009).