Quantitative Evaluation of Dynamic Lateral Meniscal Extrusion After Radial Tear Repair

Abstract

Background: Radial tears of the lateral meniscus frequently accompany acute anterior cruciate ligament (ACL) injuries and lead to increased joint stress and pathological meniscal extrusion (ME). The dynamic behavior of the lateral meniscus after radial tear repair with respect to ME has not been described. Purpose: To quantitatively assess dynamic lateral ME after all-inside radial tear repair. Study Design: Case series; Level of evidence, 4. Methods: Patients who underwent ACL reconstruction and all-inside radial tear repair of the lateral meniscus and had no history of contralateral knee injuries were included. Magnetic resonance imaging scans were acquired in loaded (50% of body weight) and unloaded conditions of both the injured and noninjured knees. A custom-made pneumatically driven knee brace was used for standardized knee positioning in 10° of flexion and with axial load application. Quantitative measures included the absolute lateral ME, meniscal body extrusion ratio, and Δ extrusion. Preoperative and postoperative unloaded extrusion data were compared by paired t tests. For postoperative data, the concomitant influence of the factors “leg” and “condition” were assessed through factorial analyses of variance. Results: A total of 10 patients with a mean follow-up of 47.9 months were enrolled. The intraclass correlation coefficient (ICC) confirmed good interrater reliability (ICC, 0.898) and excellent intrarater reliability (ICC, 0.976). In the unloaded injured leg, all-inside repair reduced ME from 3.15 ± 1.07 mm to 2.13 ± 0.61 mm (–32.4%; P = .033). Overall, load application led to a significant increase in ME (+0.34 mm [+21.8%]; P = .029). Significantly greater ME was observed in the injured knee (+1.10 mm [+93.2%]; P = .001) than in the noninjured knee. The condition × leg interaction was not significant ( P = .795), suggesting that the compression-associated increase in ME did not differ significantly between the injured and noninjured knees. Conclusion: Lateral ME depends on the knee status and loading condition. All-inside repair of radial meniscal tears led to a reduction of extrusion with no alteration in dynamic lateral ME. Meniscus-preserving therapy is recommended in the case of a radial lateral meniscal tear to preserve its dynamic behavior.

Sonographic evaluation of lateral meniscal extrusion: implementation and validation

“…The main findings of the present study were that US-based measurement of lateral ME (1) yields highly reliable data, provided a standardized measurement protocol is used, but (2) overestimates lateral ME as compared to MRI measurements, resulting in the poor agreement of measurement results. Magnetic resonance imaging, the gold standard for meniscus evaluation [14], is time-consuming, costly and limited in that the acquisition of stress images [6,11,15] is not possible unless sophisticated loading devices are used. US, by contrast, is cost-effective, readily available and easily applicable in the standing position to obtain images under axial knee compression.…”

“…Additionally, ten consecutive patients presenting for a follow-up (FU) examination (minimum 12 months FU) after anterior cruciate ligament reconstruction and all-inside lateral meniscal radial tear repair were asked for participation for validity testing (Group II). Lateral ME measurement is of high interest in patients undergoing radial meniscal tear repair since a correlation between lateral ME and radial meniscal tear healing is assumed [ 15 ]. Both knees were examined in all subjects, so that data of 22 and 20 knees were available in Group I and Group II, respectively (Fig.…”

“…MR images were recorded in both knees of the patients assigned to Group II in an unloaded and loaded condition. Standardized knee positioning and axial load application were achieved using an MRI-compatible, pneumatically driven knee brace device (Ergospect GmbH, Innsbruck, Austria), which has recently been described in detail [ 15 ]. Consistent with the US examinations, neutral rotational alignment of the lower leg and 10° of knee flexion were defined as the standard position for image acquisition.…”

“…Also, the acquisition of MR images may be time-consuming and complex. This particularly holds true for stress images, which require the use of special devices for load application [ 6 , 11 , 15 ]. In clinical practice, ME an indicator of various pathologies needs to be recorded quickly, simply and cost-effectively.…”

Meniscal substitution, a developing and long-awaited demand

“…Meniscal extrusion has gained interest in recent years and can be quantified by MRI or ultrasound [ 24 , 28 , 29 ]. It has been shown, that excessive meniscal extrusion is an indirect sign for radial tears as well as for meniscal root lesions [ 24 , 29 ]. Radial meniscal displacement of > 3 mm is often considered as a cut-off value from physiologic to pathologic extrusion.…”