Summary
Patients with unstable tear on discoid lateral meniscus and lateral meniscus demonstrated large hiatus width that should carefully be evaluated in meniscus repair around the popliteal hiatus.
Abstract
Introduction
Previous studies have shown that the widening of the popliteal hiatus of the lateral meniscus (LM) on magnetic resonance imaging (MRI) led to recurrent subluxation of LM. Discoid lateral meniscus (DLM) has a high rate of peripheral rim instability, high predisposition to tear, and common mechanical symptoms. However, MRI studies evaluating the popliteal hiatus of DLM and LM have rarely been reported. This study aimed to evaluate the association between popliteal hiatus width on MRI, torn DLM, and LM tears.
Materials And Methods
We included 193 lateral meniscal disorder knees (mean age, 34.6 ± 14.2 years) treated with arthroscopic meniscus repair or partial meniscectomy by senior surgeon from January 2011 to August 2020. The inclusion criteria were as follows; 1) torn DLM 2) LM tear, and 3) a stable knee. In addition, 50 subjects with normal knees were enrolled as controls. All patients were divided into four groups of lateral meniscal disorders: 1) torn DLM (Group A; N=52; mean age, 29.6 ± 15.6 years), 2) lateral meniscal tear without subluxation (Group B; N=114; mean age, 38.6 ± 12.6 years), 3) lateral meniscal tear with subluxation (Group C: N=27; mean age, 27.6 ± 12.8 years), 4) normal meniscus (Group D: N=50; mean age, 24.0 ± 13.7 years). The popliteal hiatus width and the ratio between the popliteal hiatus and the lateral tibial plateau were measured on both the coronal and sagittal planes on preoperative MRI for all groups. The comparisons of preoperative popliteal hiatus width on MRI were performed among the repair group around the popliteal hiatus (N=69), the repair group but not around the popliteal hiatus (N=33), and partial meniscectomy group (N=91).
Results
The coronal and sagittal popliteal hiatus widths from group A (coronal: 3.8mm ± 3.8, sagittal: 2.6mm ± 2.0), group B (coronal: 1.9mm ± 1.5, sagittal: 1.8mm ± 1.4), and group C (coronal: 2.0mm ± 1.5, sagittal:1.8mm ± 1.3) were significantly different compared with those of group D (coronal:1.1mm ± 0.9 , sagittal: 1.0mm ± 1.2) (P<0.05). Significant differences in the coronal and sagittal widths of the popliteal hiatus were observed between group A and B along with group A and C (P<0.05), while there were no differences between groups B and C. Considering popliteal hiatus width of >5mm as positive, the group A patients showed the highest incidence of positive findings (26.9%), while only 5.3%, 3.7%, and 0% of patients were found to be positive in group B, C, and D, respectively. Furthermore, the coronal and sagittal popliteal hiatus widths on preoperative MRI in patients who underwent arthroscopic meniscus repair around the popliteal hiatus (coronal: 3.2mm ± 3.5 , sagittal: 2.4mm ± 1.8) were significantly larger than those in patients who underwent partial meniscectomy (coronal: 2.0mm ± 1.4, sagittal:1.9mm ± 1.5) and arthroscopic meniscus repair not around the popliteal hiatus (coronal: 1.8mm ± 1.8, sagittal: 1.6mm ± 1.3).
Conclusion
Patients with unstable tears on the DLM and LM showed a large popliteal hiatus width that should be carefully evaluated for meniscus repair around the popliteal hiatus.