Biomechanical consequences of anterior root detachment of the lateral meniscus and its reinsertion

Magnetic Resonance Imaging Indirect Signs for Anterior Instability of the Lateral Meniscus in Pediatric and Adolescent Patients

BACKGROUND

Anterior instability (AI) of the LM is potentially debilitating in young patients. The use of magnetic resonance imaging (MRI) to diagnose AI is limited due to the lack of reliable and accurate MRI findings. The ability to identify AI preoperatively would potentially improve the diagnosis and treatment of this pathology. This study presents a novel MRI finding ("phantom sign") for the detection of AI of the LM and demonstrates its reliability and accuracy.

METHODS

Three independent blinded reviewers performed retrospective review of preoperative MRI for all patients who underwent LM repair between July 1, 2019, and March 31, 2022, at a single center. Positive phantom sign was defined as abnormal signal intensity on MRI of the anterior horn of the LM on the coronal sequence at the anterior tibial insertion of the anterior cruciate ligament (ACL). Preoperative MRI was also evaluated for other signs of LM anterior instability. Intrarater and inter-rater reliability was assessed for rater scoring of presence of pathology on MRI. Predictive ability of each imaging finding with at least good (ICC 0.6 or above) reliability was also evaluated based on documented intraoperative findings.

RESULTS

Fifty-five preoperative MRIs of arthroscopically treated LM tears were reviewed. Median age was 15 years (range 6 to 20), and 21 patients (38.2%) were female. Twenty-seven patients (49.1%) had a discoid meniscus. LM AI was present on arthroscopy for 25 knees (45.45%), and among these, 21 had discoid morphology. Interrater reliability was substantial for phantom sign (ICC 0.71, 97.5% CI: 0.55-0.82), posterior displacement (ICC 0.71, 97.5% CI: 0.55-0.82), and posterior "megahorn" (ICC 0.76, 97.5% CI: 0.62-0.85). On predictive analysis, phantom signs were 98% sensitive and 76.7% specific for LM AI. Posterior displacement and posterior megahorn were specific for AI (both 93.34%), though with limited sensitivity (32% and 28.6%, respectively).

CONCLUSIONS

Phantom sign is a reliable and sensitive MRI finding for anterior instability, even in the absence of frank displacement on preoperative MRI. A positive finding should prompt a thorough arthroscopic evaluation of the anterior horn of the LM.

LEVEL OF EVIDENCE

Level III-case control study.

Better clinical outcomes and return to sport rates with additional medial meniscus root tear repair in high tibial osteotomy for medial compartmental knee osteoarthritis

PURPOSE

This retrospective study aimed to investigate whether the repair of medial meniscus posterior root tears (MMPRTs) is effective for improving clinical outcomes and return to sports rates in young patients (50 years old or younger) with medial compartment knee osteoarthritis (KOA) and MMPRTs.

METHODS

Between 2016 and 2019, 153 patients with KOA and MMPRTs who underwent open-wedge high tibial osteotomy (OWHTO) were retrospectively included. The patients were divided into OWHTO combined with MMPRT repair (n = 73) and isolated OWHTO (n = 80) groups. Lysholm scores, Hospital for Special Surgery (HHS) scores, Tegner scores, flexion contracture, range of knee flexion, return to sports rates and postoperative complications were compared. Radiological outcomes, including hip-knee-ankle angle (HKA), medial proximal tibial angle (MPTA), joint line convergence angle (JLCA) and Kellgren-Lawrence (K-L) grade, were compared between the two groups.

RESULTS

After a mean follow-up of 30.1 ± 3.0 months, the OWHTO + Repair group observed better clinical outcomes compared with the OWHTO group (Lysholm score: 86.7 ± 7.4 vs. 81.6 ± 6.9, p = 0.023. HHS score: 85.4 ± 8.20 vs. 80.5 ± 7.1, p = 0.039). The OWHTO + Repair group had higher Tegner scores and return to sports rates than the OWHTO group (Tegner score: 6 vs. 5, p = 0.020; return to sports rates: 38% vs. 15%, p = 0.001). No fracture or major complications occurred. Radiological outcomes showed no significant differences between the two groups (HKA: 181.1 ± 2.7 vs. 180.1 ± 1.5 n.s; MPTA: 90.1 ± 1.8 vs. 89.2 ± 1.4, n.s; JLCA:1.9 ± 0.7 vs. 2.1 ± 0.7, n.s).

CONCLUSIONS

Additional MMPRT repair during OWHTO was associated with better clinical outcomes and higher rates of return to sports in young patients with medial compartment KOA and MMPRTs.

LEVEL OF EVIDENCE

Level III.

Meniscus root tears: state of the art

BACKGROUND

Meniscus root tears represent significant pathology that, historically, has been underdiagnosed and undertreated. However, the recognition of their clinical and functional significance has recently surged, mainly due to their frequent association with anterior cruciate ligament injuries.

AIM

This comprehensive review discusses various aspects of meniscal root tears, including their epidemiology, biomechanics, etiology, clinical and radiological findings, classification, management and surgical techniques.

Age influence on resistance and deformation of the human sutured meniscal horn in the immediate postoperative period

Introduction: To preserve knee function, surgical repair is indicated when a meniscal root disinsertion occurs. However, this surgery has not yet achieved complete recovery of the joint´s natural biomechanics, with the meniscus-suture interface identified as a potentially determining factor. Knowing the deformation and resistance behavior of the sutured meniscal horn and whether these properties are preserved as the patient ages could greatly contribute to improving repair outcomes. Methods: A cadaveric experimental study was conducted on human sutured menisci classified into three n = 22 age groups (young ≤55; 55 < middle-aged ≤75; 75 < old) were subjected to load-to-failure test by suture pulling. Meniscal thickness at the suture hole was measured and the applied traction force and tissue deformation in the suture area in the direction of traction were recorded during the test. The traction load that initiated the meniscal cut-out, F c , maximum load borne by the meniscus, F u , tissue stress at the cut-out initiation, S c , and equivalent stiffness modulus at the suture area, m s , were calculated. Results: At the tissue level, the resistance in terms of S c decrease with age (young: 47.2 MPa; middle-aged: 44.7 MPa; old: 33.8 MPa) being significantly different between the young and the old group (p = 0.015). Mean meniscal thickness increased with age (young: 2.50 mm; middle-aged: 2.92 mm; old: 3.38 mm; p = 0.001). Probably due to thickening, no differences in resistance were found at the specimen level, i.e., in F c (overall mean 58.2 N) and F u (overall mean 73.6 N). As for elasticity, m s was lower in the old group than in the young group (57.5 MPa vs. 113.6 MPa, p = 0.02) and the middle-aged one (57.5 MPa vs. 108.0 MPa, p = 0.04). Conclusion: Regarding the influence of age on the sutured meniscal horn tissue, in vitro experimentation revealed that meniscal horn specimens older than 75 years old had a more elastic tissue which was less resistant to cut-out than younger menisci at the suture hole area. However, a thickening of the meniscal horns with age, which was also found, leveled out the difference in the force that initiated the tear, as well as in the maximum force borne by the meniscus in the load-to-failure test.

Improved tibiofemoral contact restoration after transtibial reinsertion of the anterior root of the lateral meniscus compared to in situ repair: a biomechanical study

PURPOSE

To compare biomechanical behaviour of the anterior root of the lateral meniscus (ARLM) after a transtibial repair (TTR) and after an in situ repair (ISR), discussing the reasons for the efficacy of the more advantageous technique.

METHODS

Eight cadaveric human knees were tested at flexion angles from 0° to 90° in four conditions of their ARLM: intact, detached, reinserted using TTR, and reinserted using ISR. Specimens were subjected to 1000 N of compression, and the contact area (CA), mean pressure (MP), and peak pressure (PP) on the tibial cartilage were computed. For the TTR, traction force on the sutures was registered.

RESULTS

ARLM detachment significantly altered contact biomechanics, mainly at shallow flexion. After ISR, differences compared to the healthy group persisted (extension, CA 22% smaller (p = 0.012); at 30°, CA 30% smaller (p = 0.012), MP 21%, and PP 32% higher (both p = 0.017); at 60°, CA 28% smaller (p = 0.012), MP 32%, and PP 49% higher (both p = 0.025). With TTR, alterations significantly decreased compared to the injured group, with no statistical differences from the intact ones observed, except for CA at extension (15% decrease, p = 0.012) and at 30° (12% decrease, p = 0.017). The suture tension after TTR, given as mean(SD), was 36.46(11.75)N, 44.32(11.71)N, 40.38(14.93)N, and 43.18(14.89)N for the four tested flexion angles.

CONCLUSIONS

Alterations caused by ARLM detachment were partially restored with both ISR and TTR, with TTR showing better results on recovering CA, MP, and PP in the immediate postoperative period. The tensile force was far below the value reported to cause meniscal cut-out in porcine models.