2025 ISAKOS Biennial Congress ePoster
A Large Medial Posterior Tibial Slope Leads To Worse Rotational Instability After Anterior Cruciate Ligament Reconstruction Over Time
Kensaku Abe, MD, PhD, Nagoya JAPAN
Masahiro Nozaki, MD, PhD, Nagoya, Aichi JAPAN
Hiroaki Fukushima, MD, PhD, Nagoya, Aichi JAPAN
Shunta Hanaki, MD, Nagoya, Aichi JAPAN
Kyohei Ota, MD, Nagoya, Aichi JAPAN
Makoto Kobayashi, MD, PhD, Nagoya, Aichi JAPAN
Yusuke Kawanishi, Nagoya, Aichi JAPAN
Jiro Kato, Nagoya, Aichi JAPAN
Hideki Murakami, MD, PhD, Nagoya JAPAN
Department of Orthopaedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi, JAPAN
FDA Status Not Applicable
Summary
An increase in MPTS may contribute to the worsening of rotational instability, which may not be apparent intraoperatively but could become more pronounced over time.
Abstract
Purpose
In recent years, posterior tibial slope (PTS) has garnered attention as a risk factor for anterior cruciate ligament (ACL) injuries and graft failure following ACL reconstruction (ACLR). This study aims to evaluate the impact of PTS on preoperative and postoperative instability and to assess the changes in instability after surgery.
Methods
This study included 100 knees selected from 614 cases that underwent initial ACLR at our department between 2016 and 2022. These 100 cases were chosen from high activity (Tegner activity scale ≥ 7) 151 knees of 227 knees that underwent hardware removal and second-look arthroscopy, excluding those with concomitant ligament injuries, osteotomies, or incomplete data. Medial and lateral PTS (MPTS and LPTS, respectively) were measured using MRI, and these values, along with other parameters, were used as explanatory variables. The objective variables included anterior tibial translation (ATT), pivot shift grade (PSG), acceleration, and external rotational angular velocity (ERAV), measured preoperatively, intraoperatively (during temporary graft fixation), and at the time of hardware removal. The changes in these objective variables from intraoperatively to the time of hardware removal were also evaluated. Acceleration and ERAV were measured by an inertial sensor during the pivot shift test. ATT was recorded as a side-to-side difference, where tibial acceleration and ERAV were defined as the side-to-side ratio of the injured knee to the intact contralateral knee. Based on previous studies, MPTS and LPTS were categorized at 9.05° and 9.55°, respectively. PSG was divided into grades 0 and 1 versus grades 2 and 3 preoperatively, and into grade 0 versus grades 1 and 2 for other PSG assessments. Continuous variables were split into two groups at the median. Statistical analyses were performed using Fisher’s exact test and logistic regression analysis.
Results
The mean MPTS and LPTS were 5.6 ± 2.8° and 9.0 ± 2.8°, respectively. Preoperatively, an increase in MPTS was associated with an increase in ATT (p = 0.024). During surgery, no significant differences due to PTS were observed. However, at the time of hardware removal, an increase in MPTS was associated with an increase in PSG (p = 0.013) and acceleration (p = 0.027). The degree of change indicated that an increase in MPTS led to an increase in PSG (p = 0.013), acceleration (p = 0.025) and ERAV (p = 0.037).
Discussion
Large MPTS influenced anteroposterior instability preoperatively, while there was no correlation for MPTS to influence intraoperative or postoperative rotational instability. On the other hand, large MPTS showed a tendency to affect the degree of change in postoperative rotational instability. These findings suggest that an increase in MPTS may contribute to the worsening of rotational instability, which may not be apparent intraoperatively but could become more pronounced over time.