Preoperative Diagnosis and Treatment Outcomes of Incarcerated Inferiorly Displaced Flap Tear of the Medial Meniscus: Comparison between Flap Tears with and without Incarcerated Fragment

Abstract

The purpose of this study was to compare preoperative variables and postoperative outcomes between flap tears with and without incarceration of inferiorly displaced fragments of medial meniscus and find distinct features of incarcerated flap tear of medial meniscus to improve preoperative diagnosis. 79 patients who underwent partial meniscectomy for flap tear of medial meniscus were classified into two groups: group U, usual flap tear without incarcerated fragment; group I, flap tear with incarcerated inferiorly displaced fragment. Patient characteristics and preoperative variables including duration of symptom aggravation were investigated. A comprehensive physical examination including joint line tenderness was performed. Magnetic resonance imaging (MRI) examination was carried out on all patients. Clinical assessments were performed with functional scores including visual analogue scale (VAS), and radiologic evaluation was conducted. Preoperative values and postoperative outcomes measured at the minimum follow-up duration of 2 years were compared between the groups. The groups did not differ significantly regarding postoperative outcomes by functional and radiological evaluations (p > 0.05). In making preoperative diagnosis, sensitivity of diagnosis based solely on MR images was significantly lower in group I (68.8%) than that in group U (90.5%) (p = 0.040). The following clinical features differed significantly between the groups: Patients in group I had higher scores in preoperative VAS (group U = 6.6; group I = 7.7) (p = 0.011) and shorter duration of symptom aggravation (group U = 13.8 weeks; group I = 3.9 weeks) (p < 0.001). Joint line tenderness was positive more distinctly in group I (100%) than in group U (74.6%). If displaced flap tear was properly resected, improved outcomes did not differ regardless of incarceration of flap tear. In diagnosing incarcerated inferiorly displaced flap tear, sensitivity of diagnosis based solely on MR images could be low. Distinguishing clinical findings would be helpful in obtaining a more appropriate diagnosis.

Figure 1

Flowchart of patient inclusion in the study.

Figure 2

MRI of a 33-year-old male patient with an incarcerated inferiorly displaced flap tear of medial meniscus. (a) A coronal T2-weighted image and (b) a sagittal T2-weighted image of the most medial aspect of the knee showed that the displaced fragment (arrow) was located inferomedial to the tibial plateau and extended deep between tibia and medial collateral ligament.

Figure 3

Arthroscopic findings of the same patient as Figure 2 with an inferiorly displaced flap tear of medial meniscus. (a) The incarcerated meniscal fragment was not seen before exploration. (b & c) The large torn fragment (arrow) was found when the medial meniscus was elevated with a probe. (d) The fragment was resected with an arthroscopic basket punch. (e) Arthroscopic partial meniscectomy was performed.