Discussion
Although knee dislocations with multiligamentous involvement are rare, their outcomes can be poor. Fortunately, the principles of managing these complex injuries in the acute stage are becoming clearer. In a systematic review, Levy and colleagues18 found that operative treatment of a dislocated knee within 3 weeks after injury, compared with nonoperative or delayed treatment, resulted in improved functional outcomes. Ligament repair and reconstruction yielded similar outcomes, though repair of the posterolateral corner had a comparatively higher rate of failure. For associated lateral injuries, Shelbourne and colleagues17 advocated en masse repair in which the healing tissue complex is reattached to the tibia nonanatomically, without dissecting individual structures—a technique used in the original repair of our patient’s injuries.
Originally designed for other joints, hinged external fixators are now occasionally used for rehabilitation after traumatic knee injury. Stannard and colleagues9 recently confirmed the utility of the HEF as a supplement to ligament reconstruction for recovery from acute knee dislocation.9 Compared with postoperative use of a hinged-knee brace, HEF use resulted in fewer failed ligament reconstructions as well as equivalent joint ROM and Lysholm and IKDC scores at final follow-up. This clinical outcome is supported by results of kinematic studies of these hinged devices, which are capable of rigid fixation in all planes except sagittal and can reduce stress on intra-articular and periarticular ligaments when placed on the appropriate flexion-extension axis of the knee.19,20Unfortunately, the situation is more complicated for subacute or chronic tibial subluxation than for acute subluxation. Maak and colleagues16 described 3 operative steps that are crucial in obtaining desired outcomes in this setting: complete release of scar tissue, re-creation of knee axis through ACL and PCL reconstruction, and postoperative application of a HEF or knee brace. These recommendations mimic the management course described by Richter and Lobenhoffer13 and Simonian and colleagues,14 who treated chronic fixed posterior tibial subluxations with arthrolysis, ligament reconstruction, and use of HEFs for 6 weeks, supporting postoperative rehabilitation. All cases maintained reduction at follow-up after fixator removal.
It is also possible for small fixed anterior or posterior tibial subluxations to be managed nonoperatively. Strobel and colleagues15 described a series of 109 patients with fixed posterior subluxations treated at night with posterior tibial support braces. Mean subluxation was reduced from 6.93 mm to 2.58 mm after an average treatment period of 180 days. Although 60% of all subluxations were completely reduced, reductions were significantly more successful for those displaced <10 mm.
Management of subacute or chronic fixed coronal tibial subluxations is yet to be described. In this article, we have reported on acceptable reduction of a subacute medial tibial subluxation with use of a HEF for 6 weeks after arthroscopic débridement of a deformed subacute bucket-handle lateral meniscus tear. Our case report is unique in that it describes use of a HEF alone for the reduction of a subacute tibial subluxation in any plane without the need for more extensive ligament reconstruction.
The injury here was primarily a lateral ligamentous injury. In the nonanatomical repair that was performed, the LCL and the iliotibial band were reattached to the proximal-lateral tibia. Had we started treating this injury from the time of the patient’s accident, then, depending on repair integrity, we might have considered acute augmentation of the anatomical repair of LCL with Larson-type reconstruction of the LCL and the popliteofibular ligament. Alternatively, acute reconstruction of the LCL and popliteus would be considered if the lateral structures were either irreparable or of very poor quality. In addition, had we initially seen the coronal instability/translation, we might have acutely considered either a staged procedure of a multiplanar external fixator or a HEF.
Given the narrowed lateral joint space, the débridement of the lateral meniscus, and the risk of developing posttraumatic arthritis, our patient will probably need total knee arthroplasty (TKA) at some point. We informed her that she had advanced lateral compartment joint space narrowing and arthritic progression and that she would eventually need TKA based on pain or dysfunction. We think the longevity of that TKA will be predictable and good, as she now had improved tibiofemoral alignment and stability of the collateral ligamentous structures. If she had been allowed to maintain the coronally subluxed position, it would have led to medial ligamentous attenuation and would have compromised the success and longevity of the TKA. In essence, a crucial part of the utility of the HEF was improved coronal tibiofemoral alignment and, therefore, decreased abnormal forces on both the repaired lateral ligaments and the native medial ligamentous structures. Although temporary external fixation issues related to infection risk and patient discomfort are recognized,21-23 use of HEF alone can be part of the treatment considerations for fixed tibial subluxations in any plane when they present after treatment for multiligamentous injury.
Am J Orthop. 2016;45(7):E497-E502. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.