Posterior tibial plateau impaction fractures are not associated with increased knee instability: a quantitative pivot shift analysis

Abstract

PurposeThis study aimed to evaluate posterolateral tibial plateau impaction fractures and how they contribute to rotatory knee laxity using quantitative pivot shift analysis. It was hypothesised that neither the presence of nor the degree of involvement of the plateau would affect rotatory knee laxity in the ACL‐deficient knee. MethodsA retrospective review of prospectively collected data on 284 patients with complete anterior cruciate ligament (ACL) injuries was conducted. Posterolateral tibial plateau impaction fractures were identified on preoperative MRI. The patients were divided into two cohorts: “fractures” or “no fractures”. The cohort with fractures was further categorised based on fracture morphology: “extra‐articular”, “articular‐impaction”, or “displaced‐articular fragment”. All data were collected during examination under anaesthesia performed immediately prior to ACL reconstruction. This included a standard pivot shift test graded by the examiner and quantitative data including anterior tibial translation (mm) via Rolimeter, quantitative pivot shift (QPS) examination (mm) via PIVOT tablet technology, and acceleration (m/sec2) during the pivot shift test via accelerometer. Quantitative examinations were compared with the contralateral knee. ResultsThere were 112 patients with posterolateral tibial plateau impaction fractures (112/284, 39%). Of these, 71/112 (63%) were “extra‐articular”, 28/112 (25%) “articular‐impaction”, and 13/112 (12%) “displaced‐articular”. Regarding the two groups with or without fractures, there was no difference in subjective pivot shift (2 ± 0 vs 2 ± 0, respectively, n.s.), QPS (2.4 ± 1.6 mm vs 2.7 ± 2.2 mm, respectively, n.s.), anterior tibial translation measurements (6 ± 3 mm vs 5 ± 3 mm, respectively, n.s.), or acceleration of the knee during the pivot (1.7 ± 2.3 m/s2 vs 1.8 ± 3.1 m/s2, respectively, n.s.). When the fractures were further subdivided, subgroup analysis revealed no significant differences noted in any of the measured examinations between the fracture subtypes. ConclusionThis study showed that the posterolateral tibial plateau impaction fractures are commonly encountered in the setting of ACL tears; however, contrary to previous reports, they do not significantly increase rotatory knee laxity. This suggests that this type of concomitant injury may not need to be addressed at the time of ACL reconstruction. Level of evidenceLevel III.

Letter to the editor of: “posterior tibial plateau impaction fractures are not associated with increased knee instability: a quantitative pivot shift analysis”

“…With great interest we have read the recent publication of Godshaw et al and their analysis of the association of the posterolateral tibial impression fracture (PLIF) and the pivot shift phenomenon [1]. As the authors highlight, this topic has come into recent focus due to an increased understanding of posterolateral tibial plateau fractures and their potential association with outcome of anterior cruciate ligament (ACL) ruptures.…”

“…The fracture group was defined as “articular‐impaction” or “displaced‐articular fragment” with a displacement of at least 2 mm. The authors found no statistical difference among the three groups with respect to ap translation or pivot shift acceleration [1].…”

Response to letter to the editor of “posterior tibial plateau impaction fractures are not associated with increased knee instability: a quantitative pivot shift analysis”

“…We would like to thank Krause et al [8] for reading our work and commenting on our study [5]. The main purpose of our study [5] was to evaluate rotatory knee instability in patients with posterolateral tibial plateau impaction fractures, ones that are frequently seen in patients with ACL injuries, utilizing objective, quantifiable data.…”

“…This development has uniquely positioned our research team to study rotatory knee instability. Therefore, the aim of our study was to use quantifiable data to further evaluate the true effect of these posterolateral tibial plateau impaction fractures commonly seen at the time of ACL injury in the general population [5].…”

“…We would like to thank Krause et al [8] for reading our work and commenting on our study [5]. The main purpose of our study [5] was to evaluate rotatory knee instability in patients with posterolateral tibial plateau impaction fractures, ones that are frequently seen in patients with ACL injuries, utilizing objective, quantifiable data. We focused on impaction fractures caused from the pivot shift phenomenon [5], and not large posterior tibial plateau fractures caused by trauma or high‐speed collisions [4], as these are most commonly seen at the time of ACL injuries in the general population.…”