1 Introduction

Isolated depressed anteromedial rim fracture of medial tibial plateau following hyperextension injuries to the knee is a unique fracture patterns and are not included in the current classification systems.¹ A posteriorly directed force on the anteromedial aspect of the knee (hyperextension and varus) results in an anteromedial impaction fracture with an associated posterolateral corner(PLC) or posterior cruciate ligament (PCL) injury or tension failure of the posterior cortex.^2,3 This results in a sagittal plane deformity in which the normal antero-posterior(AP) slope of the tibial articular surface is decreased or reversed.¹ Tibial slope is an essential factor in normal knee biomechanics owing to its influence on range of motion, stability and load transfer.⁴ Recreating the tibial slope becomes difficult in these unique fracture patterns due to the comminution and depression of fracture fragments. The conventional techniques of proximal tibia fracture management may be less optimal for these rare patterns and the described open reduction techniques for this fracture pattern tend to be time consuming, extensile and/or difficult to replicate. We herein describe a novel indirect reduction manoeuvre for restoring the tibial slope easily in antero-medial tibial plateau fractures following a hyperextension injury which can be followed by the definitive fixation as the fracture necessitates.

2 Case description

2.1

2.1 Case history

A 32 years old female sustained injury to her left knee and was diagnosed with medial tibial condyle fracture(41-B3.1). On further evaluation, it was a depressed anteromedial rim fracture with tension failure of posterior cortex and reversal of the tibial slope. AP tibial slope is measured as the angle between a line perpendicular to the diaphyseal axis of the tibia and the posterior inferior inclination of the tibial plateau in the sagittal plane.⁵ The AP tibial slope was −3.8° (Fig. 1). She was planned for a plate osteosyntheses and the surgery was done as described below.

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Fig. 1 (a): Pre-operative radiographs, (b) coronal and sagittal CT images of the patient showing antero-medial tibial plateau hyperextension fracture (41-B.3.1). (c) Pre-operative AP slope of −3.8°.

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2.2

2.2 Surgical technique

Patient is positioned supine on a standard radiolucent operating table with a rectangular pillow supporting the injured knee and leg. Through a standard antero-medial incision, the medial condylar fracture fragment is exposed to visualise the underlying depressed fragments. Capsulotomy is done to look for intra articular reduction and to rule out meniscal tears. The injured leg is then lifted by an assistant holding it at the ankle. Due to the reversed tibial slope and lack of bony support anteriorly the knee joint goes into hyperextension (Fig. 2a). This manoeuvre essentially brings the leg in same position as it was at the time of injury. Holding the leg in this position, the tibial condyles are transfixed to the femoral condyle using two 2mm K-wires under image intensifier guidance (Fig. 2b). Now, the leg is brought back down to its initial supine position on the pillow. Due to the transfixation, the tibial condyles maintain their reduced position in relation to the femoral condyles while the distal fragment flexes resulting in a gap anteriorly between the tibial condyles and the metaphysis suggesting that the reversed posterior slope (directed postero-superiorly) has been restored to its normal postero-inferior inclination (Fig. 2c). This manoeuvre causes indirect reduction of tibial condyles. The reduction is held with two criss-crossing K-wires (2mm) till the tibial subchondral region. (Fig. 2d). After restoring the slope, the conventional techniques to correct the other parameters such as varus, condylar widening, translation etc. can be carried out to reduce the fracture. The anterior defect needs to be filled with either autograft or allograft depending on the size of the defect and the fixation is completed with a suitable LCP (Fig. 3). After internal fixation, knee joint is assessed for ligamentous instability by stress tests which were negative in our patient. The sequence of reduction manoeuvre is illustrated in Fig. 4.

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Fig. 2 (a) Injured knee is hyper-extended to bring the fractured tibial condyle in alignment with the femoral condyles. (b) Reduced tibial condyle is transfixed to the femoral condyle with two 2mm K-wires. After that, the leg is brought back to neutral position from hyperextension. While the transfixed tibial condyle stays in position restoring the tibial slope, the distal fragment moves into flexion creating an anterior void. (c) The reduction is held temporarily with two criss-cross 2mm K-wires. (d) Transfixing wires are removed, and definitive fixation follows.

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Fig. 3 No hyperextension at the knee at the end of fixation, suggesting restored AP tibial slope. Restored AP slope is seen in the postoperative Xray achieving a correction of 18.9°.

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Fig. 4 Pictorial representation of the technique of reduction. (a)- AP and lateral views of the varus hyperextension fracture demonstrating a reversal of the tibial slope. (b)- The manoeuvre consists of exaggerating the deformity and hyperextending the leg to restore the tibial slope and transfixing the proximal fragment of the fracture to the femoral condyle with crisscross K-wires. (c)- By lowering the leg the proximal fragment remains in the same position and the distal fragment moves resulting in an anterior defect. The proximal and the distal fragments are fixed with K-wires. (d)- After securing the fracture fragments, the gap is filled with cancellous bone graft. (e)- The K-wires are retained to maintain the reduction and fixation is carried out with an appropriate plate. The K-wires are removed at the end of fixation. (f)- Final fixation with a plate showing restored tibial slope.

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2.3

2.3 Post-operative protocol and follow up

The AP tibial slope measured on lateral radiographs in the immediate post-operative x ray was 15.1° achieving a correction of 18.9°. Active and active assisted range of motion exercises was started from post-operative day one and toe touch weight bearing on day two. Partial weight bearing was started at three weeks and weight bearing was progressively increased to full weight bearing at six weeks. The fracture united at 4.5 months (Fig. 5). At the end of follow-up, she had an excellent functional score of 29 as per the Rasmussen score.⁶

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Fig. 5 (a) AP and lateral radiographs showing uneventful fracture healing at the end of 4 months.

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3 Discussion

Isolated anteromedial tibial plateau fracture following a hyperextension injury is a rare pattern with very few case reports in the literature.^2,3 The hyperextension varus bicondylar tibial plateau fracture is another variant which also follows a similar mechanism injury with the exception that there is a tension failure of the posterior cortex of proximal tibia in place of a ligamentous injury.¹ The key element to the management of these fracture patterns is the restoration of the AP slope of the proximal tibia. Based on lateral radiographs of the knee, the mean tibial slope was found to be 13.6° ± 3.5° in adult Indian population.⁷

Firoozabadi in their study on 23 patients with the hyperextension varus bicondylar proximal tibia fracture described several techniques of open reduction of these fracture patterns.¹ They emphasized on a preliminary stabilisation of the tension failure posteriorly via a posteromedial approach, followed by articular surface reduction and restoration of sagittal balance using Cobbs elevators, laminar spreaders, K-wires as well as plates. Although they aid in achieving an accurate reduction in these rare fracture patterns, they need an extensive exposure and are time consuming. With our indirect reduction technique of hyperextending the knee and exaggerating the deformity, an indirect reduction occurs which can easily be held with K –wires. This technique is easily reproducible to achieve anatomical reduction and restore the sagittal alignment of the proximal tibial with minimal soft tissue stripping.

4 Conclusion

In conclusion, the indirect hyperextension reduction technique is a rapid and easily reproducible manoeuvre for the management of these rare hyperextension fracture patterns of the tibial plateau. Although the overall incidence of these injuries is relatively low, it is important for surgeons to recognize these injuries and treat them appropriately to optimize patient outcome.

CRediT authorship contribution statement

Jayaramaraju Dheenadhayalan: contributed to the study conception, critically reviewed the manuscript. Vasudeva Nagashree: The first draft of the manuscript was written, Reviewing and editing of the manuscript was done. Avinash Mahender: Data curation, analysis were performed by. Azhar Lakhani: Data curation, analysis were performed. Shanmuganathan Rajasekaran: critically reviewed the manuscript, All authors read and approved the final manuscript.

Informed consent

Informed written consent was obtained from the patient for publication of the case report.

Ethics approval

Approval was obtained from the Institutional ethics committee.

Ethical statement

Since it was a case report and the consent was obtained from the patient to publish it, ethical committee clearance was not required.

Funding statement

This research received no grant from any funding agency in the public, commercial, or not-for-profit sectors.