Examining the Schenck KD I Classification in Patients With Documented Tibiofemoral Knee Dislocations: A Multicenter Retrospective Case Series

Abstract

Background: Acute tibiofemoral knee dislocations (KDs) with a single cruciate ligament remaining intact are rare and can be classified as Schenck KD I. The inclusion of multiligament knee injuries (MLKIs) has contributed to a recent surge in Schenck KD I prevalence and has convoluted the original definition of the classification. Purpose: To (1) report on a series of true Schenck KD I injuries with radiologically confirmed tibiofemoral dislocation and (2) introduce suffix modifications to further subclassify these injuries based on the reported cases. Study Design: Case series; Level of evidence, 4. Methods: A retrospective chart review identified all Schenck KD I MLKIs at 2 separate institutions between January 2001 and June 2022. Single-cruciate tears were included if a concomitant complete disruption of a collateral injury was present or injuries to the posterolateral corner, posteromedial corner, or extensor mechanism. All knee radiographs and magnetic resonance imaging scans were retrospectively reviewed by 2 board-certified orthopaedic sports medicine fellowship-trained surgeons. Only documented cases consistent with a complete tibiofemoral dislocation were included. Results: Of the 227 MLKIs, 63 (27.8%) were classified as KD I, and 12 (19.0%) of the 63 KD I injuries had a radiologically confirmed tibiofemoral dislocation. These 12 injuries were subclassified based on the following proposed suffix modifications: KD I-DA (anterior cruciate ligament [ACL] only; n = 3), KD I-DAM (ACL + medial collateral ligament [MCL]; n = 3), KD I-DPM (posterior cruciate ligament [PCL] + MCL; n = 2), KD I-DAL (ACL + lateral collateral ligament [LCL]; n = 1), and KD I-DPL (PCL + LCL; n = 3). Conclusion: The Schenck classification system should only be used to describe dislocations with bicruciate injuries or with single-cruciate injuries that have clinical and/or radiological evidence of tibiofemoral dislocation. Based on the presented cases, the authors recommend the suffix modifications for subclassifying Schenck KD I injuries with the goal of improving communication, surgical management, and the design of future outcome studies.

Clinical and Functional Outcomes of Documented Knee Dislocation Versus Multiligamentous Knee Injury: A Comparison of KD3 Injuries at Mean 6.5 Years Follow-up

“…2,22 Given that MLKI and KD are often intertwined, it is becoming even more apparent that 2 distinct entities exist along the progressive spectrum of ligamentous knee injuries. 8,20,23 Sustaining a traumatic KD with radiographic evidence of tibiofemoral disarticulation or clinical documentation of a manual reduction of a tibiofemoral KD has been shown by our multi-institutional data to be associated with a poorer clinical outcome and reduced activity capacity at a mean of 6.5 years after injury. Documented KDs likely represent a greater insult to the soft tissue envelope than a nondislocated 3-ligament knee injury.…”

“…4,14,28 Recent studies have shown a higher risk of neurovascular injury in the documented KD as well as misappropriation of the term ''knee dislocation'' for nondislocated MLKIs. 8,14 While it has been stated that up to 50% of MLKIs may have ''spontaneously reduced'' before presentation, 29 this represents a presumptive diagnosis to an entity that has never been documented and has spawned a phrase that may be misused when describing an MLKI without objective evidence of disarticulation. MLKI and KD are often used interchangeably, in spite of the awareness that the latter describes a soft tissue injury of greater severity.…”

“…MLKI and KD are often used interchangeably, in spite of the awareness that the latter describes a soft tissue injury of greater severity. 8,14 It remains unclear whether there is a comparative difference in functional recovery and clinical outcomes of MLKIs based on the presence of a true dislocation.…”

“…KDs are typically described using the Schenck classification system, which outlines the anatomic injury pattern based on the number and location of ligaments torn. 29 Traumatic KDs typically occur with disruption of 2 major stabilizing knee ligaments and rarely are seen with singlecruciate ligament disruption 8 ; however, it has been described that any bicruciate MLKI should be considered to be a KD until proven otherwise, given the need for close assessment of neurovascular injury. 4,6 The knee dislocation-3 (KD3) injury pattern of MLKI consists of tears to both cruciate ligaments and one of the collateral ligaments, is subdivided based on medial (KD3-M) or lateral (KD3-L) involvement, and is the most common pattern of ligamentous injury associated with KD.…”

“…In addition, combining MLKI and KD has presumably obscured the injury and outcome findings of both injury patterns to date. 8 The purpose of this study was to determine whether KD3 with documented tibiofemoral dislocation represents a more severe injury than KD3 without documented dislocation. We hypothesized that patients who had a documented dislocation would have poorer functional outcomes and increased neurovascular morbidity than those who did not.…”