Complete posterior dislocation of fractured lateral condyle of tibia with disruption of proximal tibiofibular joint: Technical note

Abstract

Tibial plateau fracture-dislocations are relatively uncommon injuries. They represent instability patterns due to injured collateral ligaments or extensive condylar depression. Medial and lateral subluxations of the fractured fragments represent the majority of these injuries. Posterior dislocations with the tibial plateau fractures are extremely rare injuries. Moreover, isolated posterior dislocations of the tibial condyles with a normally maintained position of the remaining tibia have not been reported in literature. We describe a difficult case scenario in which whole of the articular segment of the lateral condyle of the tibia was separated from its anterolateral rim and completely dislocated posteriorly, with no contact with the lateral condyle of the femur. Besides this, there was a complete disruption of the proximal tibiofibular joint as well. To further add to the problem, the distal pulses in the affected limb had a reduced volume. Stepwise management of all aspects of this injury has been described in this technical note along with a six-month follow-up.

1. Introduction

Displaced tibial plateau fractures belong to the high-velocity trauma. The management of these fractures has never been simple and is often fraught with long term complications like post-traumatic arthritis. The vast literature regarding the management of tibial plateau fractures focuses on the classification, surgical approaches, and factors influencing the radiological and functional outcomes. The methods and technical aspects concerning the optimum reduction in complex fractures are among the least addressed aspects of the displaced tibial plateau fractures. A large number of approaches for the different columns of the tibial plateau have been described with all of them having some advantages and limitations.¹ The posterolateral approaches advocated for the fixation of posterolateral fragments can provide access to the posterolateral fragments. However, the working zone for plate fixation is less than 5 cm which is limited by the bifurcation of the popliteal artery into the posterior tibial artery and anterior tibial artery.² The safe working zone in this region can be as small as 27 mm and any aggressive manipulation in this zone can potentially injure these vessels. Thus, for small fragments, mini-fragment buttress plates can be applied; but for the larger fragments, longer buttress plates are out of the question. A more severe variety of tibial plateau fractures are the fracture-dislocations. They account for the medial and lateral subluxations or dislocations of fractured segments of the tibial plateau fractures. Posterior dislocation of the knee with tibial plateau fracture is extremely rare. A high index of suspicion for vascular injury should be considered in such cases.³ In so far reported fracture dislocations of knee, the subluxated or dislocated articular segment of tibial plateau is in direct continuity with rest of tibia. They could be reduced to appropriate position by manoeuvring the remaining tibia.^{4, 5, 6} Isolated dislocations of condylar fragments in the medial and lateral direction have also been described.⁷ However, no case with complete posterior dislocation of the fractured tibial plateau as a whole or its single fractured condyle has been discussed or reported in the literature. We describe a difficult case scenario in which whole of the articular segment of the lateral condyle of the tibia was fractured off its anterolateral rim and completely dislocated posteriorly. Besides this, there was a complete disruption of the proximal tibiofibular joint as well. To further add to the problem, the distal pulses in the affected limb had a reduced volume. Stepwise management of all aspects of this injury has been described in this technical note along with a six-month follow-up.

1.1. Case presentation and management

A 32-year-old male was presented to our emergency department with a history of a road traffic accident. The described mechanism of injury was an acute axial loading and hyperextension force on the right knee. The patient had marked swelling, multiple deep abrasions over the anterolateral aspect, ecchymosis on the posterolateral aspect of the right knee with the restriction of knee movements. Other systemic and bony injuries were ruled out. The vitals were within normal limits. The clinical assessment revealed associated common peroneal nerve palsy. The pulse volume of the posterior tibial and anterior tibial arteries was reduced compared to the contralateral limb. The change in the position of the knee to flexion of 20–30° restored the pulse volume of both the vessels. An ultrasound doppler evaluation confirmed the integrity of the popliteal vessels. After appropriate analgesia and fluid support, the anteroposterior(AP) and lateral radiographs were ordered (Fig. 1a). The AP radiograph revealed a comminuted fracture of the lateral condyle of the tibia that appeared to be of Schatzker type II. However, the lateral radiograph revealed a visibly different picture of the posteriorly dislocated lateral condyle with disruption of both lateral femoral and proximal fibular articulations. The articular segment of the fractured condyle was visibly intact. A computed tomography (CT) scan was ordered for detailed evaluation. The CT scan revealed a posteriorly dislocated lateral condyle of the tibia separated from its anterolateral rim and its femoral articulation (Fig. 1b and c). The corresponding proximal tibiofibular articulation was also disrupted and the fibular head was displaced into the fracture cavity (Fig. 1c). Utilizing the CT based information, the fracture would be classified as Schatzker type I only, considering the condylar split without any obvious articular depression of the separated lateral condyle. According to the column-based classification of tibial plateau fractures, the fracture line exited through the posteriormost limit of the lateral column and mid portion of the posterior column. The injury can thus be classified as a posterior column injury, in spite of involving the anterior articular component of the lateral condyle. The CT scan also revealed that the lateral condyle was pressing upon the popliteal artery and the inferior spike was close to its bifurcation into posterior tibial and anterior tibial arteries (Fig. 1d). To plan the management of this uncommon fracture-dislocation, a CT scan of an undisplaced lateral condylar split fracture of the proximal tibia was used to compare the relative displacement of the lateral condyle, the correction required to relocate the lateral condyle and to know the relative position of the fibular head which is important to restore the proximal tibiofibular articulation in our case. The vascularity of the limb was constantly monitored and the limb was supported on a Bohler Braun splint. We waited for the local swelling to subside, and then planned and executed our approach, reduction, and fixation under the following steps:

• 1.Under spinal anesthesia, the patient was positioned in a floppy lateral position to assess the anterolateral and posterolateral aspect of the proximal tibia. No tourniquet was used.
• 2.A posterolateral approach through the interval between lateral head of the gastrocnemius and the distal part of biceps femoris was used to expose the posteriorly dislocated lateral condyle of the tibia. The common peroneal nerve was found to be intact and was retracted using a small feeding tube. The inferior lateral genicular vessel was ligated and the soleus muscle was gently elevated from the dislocated lateral condylar fragment. Initially, only the proximal half of the displaced fragment was assessed considering the proximity of the distal fracture spike to the bifurcation of the popliteal artery.
• 3.The capsular attachments of the dislocated fragment were disrupted and the joint capsule was interspersed in the fracture cavity. A varus stress to the knee joint helped in retracting the capsule posteriorly.
• 4.As evident from Fig. 1b, the fibular head was crumpled inside the fracture cavity. This suggested that some of the ligamentous structures of the proximal tibiofibular articulation were intact and were under tension, and thus prevented the outward or posterior migration of the fibular head. Considering the extent of posterior migration of the facet for the fibular head, we anticipated that the proximal tibiofibular ligaments would have been injured and the intact lateral collateral ligament probably prevented the outward migration of the fibular head. It was difficult to push the dislocated fragment back to its original position because the fibular head blocked the same. A 2 mm Kirschner wire was inserted in the fibular head from behind and that was used as a joystick to maneuver the fibular head outwards laterally in order to create space for the reduction of the posteriorly dislocated lateral condyle (Fig. 2a–d). A clamp assisted reduction was performed and the surface matching with the intact posterior bone and the settling of the fibular head into its corresponding fossa on the lateral condyle were considered as the indirect markers of the reduction. Once the reduction of the lateral condyle and the relocation of the fibular head were confirmed in the image intensifier, multiple K wires were spanned through the fracture to temporarily stabilize the reduction(Fig. 2e–f).
• 5.The distal extent of the fracture spike was palpated and it was observed to in close proximity to the bifurcation of the popliteal artery. Thus, a buttress plate long enough to span the fracture spike carried a risk of injuring the vessel. To definitively stabilize the condylar fragment we inserted two 7 mm juxta-articular lag screws from the posterolateral aspect to the anteromedially non-fractured tibial plateau segment (Fig. 2g and h). Another 7 mm lag screw was added from the posterior to the anterior direction for additional stability. A stable reduction of the fibular head was automatically achieved after its settling into the corresponding fossa on the posterolateral aspect of the lateral condyle. The torn posterior capsular attachments were repaired.
• 6.Since it was unsafe to place the buttress plate on the posterior aspect, to secure the fixation to allow early knee mobilization, we planned to stabilize the reduced condylar fragment using an anterolateral locking plate construct. The anterior incision was made a bit more anterior than the conventional anterolateral approach while maintaining a bridge of more than 7 cm from the posterolateral incision. After elevating the tibialis anterior from the anterolateral aspect, an anterolateral plate fixation was achieved (Fig. 2i).
• 7.The reduction was found stable throughout the passive range of motion of the knee joint and the same was confirmed under the image-intensifier guidance. No signs of collateral ligaments insufficiency and cruciate ligaments insufficiency were observed with stress testing immediately following the fixation.

Fig. 1.

Preoperative radiological assessment of the present case: a) AP and lateral radiographs suggestive of fractured lateral condyle of the tibia with posterior dislocation of the condylar fragment and disruption of the proximal tibiofemoral joint. b) An axial cross-section through the subchondral region of the tibial plateau suggesting a complete posterior dislocation of the articular segment of lateral condyle compared to an undisplaced lateral condyle fracture. c) Three dimensional (3D) reconstruction images suggesting an intact articular surface of the posteriorly dislocated lateral condyle, with fibular head crumpling inside fracture cavity anterior to the dislocated condylar fragment. A comparative interpretation was performed through a 3D CT scan of an undisplaced tibial plateau fracture. d) The popliteal artery is being pressed upon by the dislocated condylar fragment (double arrows) and the terminal spike of the condylar fragment is close to the level of bifurcation of the popliteal artery (red pointer) at a distance of 4.64 cm from the joint line.

Fig. 2.

Steps in reduction and fixation of the posteriorly dislocated condylar: 1. Maneuvering fibular head to create a passage for the dislocated lateral condylar fragment (a,b,c,d). 2. Temporary reduction and stabilization of the lateral condylar fragment using multiple K-wires (e,f). 3. Placement of multiple lag screws to fix the condylar fragment to the intact anterior and medial bone (g,h). 4. Addition of an anterolateral plate to augment the fixation stability (i). Satisfactory healing of both posterolateral and anterior wounds was observed at the time of suture removal(j,k).

Postoperatively, symptomatic and supportive treatment was continued. Gradual active knee mobilization was started from the first postoperative day and a full knee range of motion was achieved in two weeks. Both anterior and the posterior surgical wounds healed without any complications and sutures were removed at two weeks postoperatively (Fig. 2j and k). The common peroneal nerve recovered spontaneously at 3 weeks post-injury, suggesting a neuropraxia. The patient was kept on a non-weight bearing mobilization protocol for two months postoperatively and partial weight-bearing (up to 50%) for the next month. Radiological signs of fracture healing were evident at two months postoperatively. Consolidated radiological union was achieved at three months postoperatively (Fig. 3), following which the patient (a laborer by occupation) resumed all his activities. There were no signs of mediolateral or anteroposterior instability throughout the followup evaluation.

Fig. 3.

Initial postoperative AP and lateral radiographs following fracture fixation (a,b). Consolidated union of the fracture at three months postoperatively (c,d).

2. Discussion

Dislocations of knee joint associated with tibial plateau fractures are rare. The classical patterns of fracture-dislocations associated with tibial plateau fractures were first described by Hohl and Moore in 1983.⁷ Failure of the collateral ligaments to contain the condyles within the mediolateral extent of the knee joint or extensive depression of one or both condyles can result in medial or lateral instability. However, an extreme axial force can dislocate an intact or fractured condyle medially or laterally depending upon the direction of stress. Fracture dislocations of the tibial plateau are usually associated with type IV-VI Schatzker injuries.^8,9 In type IV injury the medial condyle may split off from the remaining tibial plateau and due to varus stress, the lateral condyle may be subluxated or dislocated towards the lateral side.⁵ In type V and VI injuries the condyles may subluxate due to medial or lateral bony disruption or ligamentous failure.

Posterior dislocation of the knee joint associated with tibial plateau fractures are extremely rare and carries a high risk of vascular injury.⁵ However, these injuries represent more of occult multi ligamentous disruption compared to the bony component. The associated fractures are periarticular rim fractures.^5,10 Isolated posterior dislocation of the fractured condyle, either medial or lateral condyle has not been reported. Such a dislocation would represent a challenging scenario considering the non-continuity of the fractured condyle to the remaining tibia and thus, the conventional techniques of maneuvering tibia may not be helpful. Moreover, in our discussed case, the whole of the articular component of the lateral condyle was dislocated posteriorly. Moreover, it was abutting on the posterior aspect of the lateral femoral condyle making it difficult to reduce. Secondly, due to the tension in the remaining intact ligamentous attachments, especially the lateral collateral ligament, the fibular head got crumpled inside the fracture cavity that represented the original space for the lateral femoral condyle, which again prevented the reduction of the condyle. This fibular position also prevented the reduction of the condyle. The fracture-dislocation injuries represent high energy trauma and the extent of soft tissue may be difficult to estimate. An overenthusiastic attempt to perform an early open reduction may compromise wound healing. The transient reduction in the pulse volume was probably related to the pressure of the dislocated condyle on the popliteal vessels. We kept the limb in 20–30° flexion and constantly monitored the limb saturation and that was very well maintained with this position. The patient was also comfortable in this semi flexed knee position. The ankle-brachial index is a rapid clinical tool for vascular injury assessment in fracture dislocations around knee and should ideally be assessed in such situations.¹¹ However, we had a bedside doppler apparatus available in the emergengy room and that provided a quick assessment of the popliteal vessels.

The mechanism of this injury was described as hyperextension and axial loading injury as per the history provided by the patient. However, considering an isolated lateral condylar dislocation, the valgus load could also have been involved. Similar injuries without complete dislocation of the condylar fragment usually occur in axial loading combined with flexion and valgus force. Thus, the possibility of such an injury cannot be ruled out.

The critical part of the open reduction and internal fixation of this injury is the technique to reduce the condyle back to the original position. A lack of preoperative planning can add to the intraoperative struggle. Considering the previously unreported nature of the injury, we compared the 3D reconstruction images of the injury to a normal tibial plateau image and that helped us in knowing the approximate relations that were needed to be restored. The malalignment and anterior translation of the fibular head were better appreciated in the 3D images. The 3D images helped us in planning the rotational maneuver for the fibular head that indirectly helped in the reduction of the lateral condyle to its original location (Fig. 2a–d). Another important aspect of preoperative planning is the distal extent of the lateral condyle fracture. A distal extension may prevent the placement of the posterior buttress plate due to proximity to the bifurcation of the popliteal artery into the anterior tibial artery and the posterior tibial artery. Posterolateral to anteromedial lag screws supplemented with anterolateral plate fixation can be helpful in such a situation. We used a dual (posterolateral and anterior) approach in this case. However, a transfibular osteotomy based approach can also be planned based on the surgeons experience and expertise. This approach can help in avoiding dual incisions on a compromised soft tissue.

The fibular head was reduced back to the corresponding fossa and was found to be stable following the fixation of the lateral condylar fracture. In the situation of the instability of the fibular head, a lag screw from fibular head to tibial plateau can be added. The stable fixation helped in the early knee mobilization exercises. The wound healing was uneventful and the patient regained full knee range of motion within two weeks. At the final follow up at six months postoperatively, the patient had returned to routine labor work with full weight-bearing and complete range of motion.

3. Conclusion

Unicondylar posterior dislocation of the fractured articular segment of the tibial lateral condyle is a rare injury. A careful CT based preoperative planning and maneuvering of the fibular head to reduce the dislocated lateral condyle and judicious posterior and anterolateral fixation considering the risk of injury to the bifurcation of the popliteal artery with posterior plating can result in favorable radiological and functional outcomes.

Ethics approval

No experimental procedure on human and animal subjects was performed in this study. Ethical approval was not required.

Consent to participate

Appropriate consents were obtained from the patient that underwent surgical intervention.