Nonanatomic Placement of Posteromedial Meniscal Root Repairs: A Finite Element Study

Accurate tibial tunnel position in transtibial pullout repair for medial meniscus posterior root tears delays the progression of medial joint space narrowing

PURPOSE

This study aimed to evaluate the association between the progression of medial joint space (MJS) narrowing, medial meniscus extrusion (MME) and clinical scores and the tibial tunnel position in pullout repairs for medial meniscus posterior root tears (MMPRTs).

METHODS

This retrospective study examined 54 patients. Changes in MJS (ΔMJS), MME (ΔMME) and clinical scores and their relationship with the tibial tunnel position were evaluated using correlation coefficients. The distance from the anatomical to technical attachment position in the tibial tunnel position was measured in the anterior and medial directions, and the direct distance was measured using the Pythagorean theorem.

RESULTS

The mean ΔMJS and ΔMME were 0.6 ± 0.8 and 1.3 ± 1.3 mm, respectively, and the mean anterior, medial and direct distances were 1.4 ± 2.3, 2.2 ± 1.7 and 3.4 ± 1.7 mm, respectively. ΔMJS had a significant positive correlation with the medial (r = 0.580, p < 0.001) and direct (r = 0.559, p < 0.001) distances, while ΔMME had a significant positive correlation with direct distance (r = 0.295, p = 0.030). Several clinical scores were significantly negatively correlated with these distances.

CONCLUSION

In transtibial pullout repair for MMPRTs, accurate tibial tunnel position delayed the progression of MJS narrowing and MME, leading to improved clinical outcomes. The progression of MJS narrowing was associated with the mediolateral direction of the tibial tunnel position, while the clinical scores were associated with the anteroposterior direction of the tibial tunnel position. These findings indicate the need to orient the tip of the guide in a more posterolateral direction when creating the tibial tunnel.

LEVEL OF EVIDENCE

Level IV.

The modified Nice knot has improved mechanical performance compared to the cinch stitch for meniscal root repair

PURPOSE

According to previous biomechanical studies, the success of meniscus root repair depends on the suture-meniscus interface and optimisation of this procedure seems to be critical. A progressive, reliable and adjustable knot has numerous advantages in meniscal repair since the surgeon can adapt and meticulously tune the final strength of the fixation. We hypothesised that a single passage of one tape at two different points of the posterior meniscal root with a modified Nice knot configuration may allow similar or superior fixation for root repair compared to the cinch stitch suture technique.

METHODS

Posterior root repair of medial and lateral meniscus was performed on 26 porcine knees. In group (A), two simple cinch stitches were applied, and in group (B), a modified Nice knot was used in a crossmatch configuration. For both groups, two passages through the meniscus with a 2-mm braided tape were used, and a single transosseous tibial tunnel technique was performed and tested in pull-out conditions.

RESULTS

The modified Nice knot showed an improved biomechanical performance considering the maximum failure load for both the medial (600.7 ± 77.5 N) and lateral (686.1 ± 83.5 N) (p = 0.006) posterior root fixation when compared to a double cinch stitch (558.0 ± 123.9 N) and (629.0 ± 110.2 N) (p = 0.178) for medial and lateral fixation, respectively. The maximum stiffness was also higher for the modified Nice knot configuration for both medial (17.1 ± 1.5 vs. 13.3 ± 1.6 N/mm) and lateral meniscus (20.0 ± 2.6 vs. 13.8 ± 2.3 N/mm), being this difference statistically significative (p = 0.001).

CONCLUSIONS

The modified Nice knot allowed better adaptation in the pull-out tests and presented higher fixation strength, stiffness and reproducibility, with lower standard deviation, being at the same time economically advantageous, since only one tape is needed.

LEVEL OF EVIDENCE

Level III.

Effect of meniscus modelling assumptions in a static tibiofemoral finite element model: importance of geometry over material

Finite element studies of the tibiofemoral joint have increased use in research, with attention often placed on the material models. Few studies assess the effect of meniscus modelling assumptions in image-based models on contact mechanics outcomes. This work aimed to assess the effect of modelling assumptions of the meniscus on knee contact mechanics and meniscus kinematics. A sensitivity analysis was performed using three specimen-specific tibiofemoral models and one generic knee model. The assumptions in representing the meniscus attachment on the tibia (shape of the roots and position of the attachment), the material properties of the meniscus, the shape of the meniscus and the alignment of the joint were evaluated, creating 40 model instances. The values of material parameters for the meniscus and the position of the root attachment had a small influence on the total contact area but not on the meniscus displacement or the force balance between condyles. Using 3D shapes to represent the roots instead of springs had a large influence in meniscus displacement but not in knee contact area. Changes in meniscus shape and in knee alignment had a significantly larger influence on all outcomes of interest, with differences two to six times larger than those due to material properties. The sensitivity study demonstrated the importance of meniscus shape and knee alignment on meniscus kinematics and knee contact mechanics, both being more important than the material properties or the position of the roots. It also showed that differences between knees were large, suggesting that clinical interpretations of modelling studies using single geometries should be avoided.

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.

Distal Fixation of Meniscal Root Repair by Transtibial Pullout Technique via Transtibial Tubercle Fixation Without Hardware

The meniscal roots are critical in maintaining the normal shock-absorbing function of the meniscus. If a meniscal root tear is left untreated, meniscal extrusion can occur, rendering the meniscus nonfunctional, resulting in degenerative arthritis. Preservation of meniscal tissue with restoration of meniscal continuity is becoming the standard for meniscal root pathology. Not all patients are candidates for root repair; however, repair is indicated in active patients after acute or chronic injury with no significant osteoarthritis and malalignment. Two main repair techniques have been described: suture anchor (direct fixation) and transtibial pullout (indirect fixation). The most common root repair technique is a transtibial technique. In this technique, sutures are placed into the torn meniscal root and then shuttled down through the tunnel in the tibia to tie the repair distally. The option adopted in our technique is to fix the meniscal root distally by wrapping threads of FiberTape (Arthrex) around the tibial tubercle through a transverse tunnel posterior to the tibial tubercle with buried knots inside the transverse tunnel without the use of metal buttons or anchors. This technique provides secure tension for repair without loosening of knots and tension that occur when using metal buttons and avoiding irritation caused by metal buttons and knots in patients.

Arthroscopic Medial Meniscal Posterior Root Repair With Transtibial Luggage-Tag and Horizontal Mattress Sutures

Medial meniscal posterior root repair techniques have shown positive yet varied results in the literature. The decision to perform repair has improved clinical outcomes in many situations, although the healing rate is approximately 64% and the repair strength is roughly one-third of the native root strength, with meniscal extrusion being common. We present a technique based on biomechanical evidence to obtain a strong anatomic posterior root repair to restore nearly normal knee mechanics, combining an increased size of footprint under the lateral aspect of the medial meniscal horn for healing and a luggage-tag suture with a posteriorly placed horizontal mattress suture. The horizontal mattress suture is passed to capture the circumferential fibers of the meniscus and the luggage-tag suture is passed to capture the radial fibers of the meniscal body, through a single transtibial tunnel. The aim of this repair is to restore the normal meniscal function.