gms | German Medical Science

Objectives: In prevenient studies arthroscopic suture anchor (SA) refixation compared to transosseus pullout (TPO) refixation of meniscal root tears were already evaluated. As current SA techniques require a posterior portal with risk of damage to neurovascular structures and TPO refixation requires an extracortical fixation, a new all-suture anchor refixation was developed. In this technique, an all-suture anchor is pulled-in not requiring an additional posterior portal nor an extracortical fixation nor interfere in a tunnel conflict. Aim of this study was the evaluation of the biomechanical properties of this refixation of meniscal root tears using a new trans-tibial pull-in (TPI) technique in comparison to standard SA and TPO repair. We hypothesized that the biomechanical properties of refixation of meniscal root tears using all-suture anchors in the TPI technique are comparable to current concepts.

Methods: The study was a biomechanical study with thawed porcine fresh frozen proximal tibia. Intact posterior medial meniscus root was sectioned 5mm from the insertion. SA was applied from posterior. For TPI a double loaded all-suture anchor was modified and pulled into the subcortical bone through the tunnel at the meniscal root insertion instead of tapping it in. Drilling was applied transtibial analog to the TPO technique. The meniscus was knotted to the anchor analog to the SA technique. We defined 4 groups (n=10):

1.

native meniscal root (NM),

2.

TPO repair with 2 sutures (#2Hi-Fy, Conmed, USA) and extracortical fliptack fixation (Storz, Germany),

3.

double loaded SA repair (SuperRevo, Conmed, USA),

4.

double loaded new TPI repair (Y-KnotFlex 1.8 mm, Conmed, USA).

Testing was performed using a servohydraulic testing device (Zwick, Germany). The meniscus was clamped to the testing device and the proximal Tibia was potted into an aluminum pot with PMMA. The meniscus was mounted 90° to the testing device (posterior part up). Force was applied in posterior direction to the NM. The meniscus was exposed to cyclic loading with subsequent load to failure (LTF) (preload 2N, 1000 cycles with 5-20N; 0.5Hz) LTF and stiffness (N/mm) were calculated. Significancy was defined as p≤0,05.

Results and conclusion: TPI showed similar elongation during cyclic loading (TPI 2,4 ±0,9mm, SA 2,6±0,3mm, TPO 2,0±1,1mm; n.s.) compared to SA/TPO refixation. TPI showed similar displacement after 1000 cycles (TPI 2,4±0,9mm vs. SA 2,6±0,3mm vs. TPO 2,0±1,1mm; n.s.) and significantly lower stiffness (TPI 13,3±3,8N/mm, SA 24,0±3,3N/mm, TPO 22,7±6,2N/mm; p=0,042) compared with SA/TPO. No significant difference was observed for displacement at failure (TPI 15,1±7,8mm, SA 11,9±3,4mm, TPO 10,1±1,2mm; n.s.). LTF did not differ significantly between groups (TPI 224,9±54,6N, SA 278,9±49,6N, TPO 224,8±35,0N; n.s.). Failure mode was always a suture cut out from the meniscus. The TPI technique showed similar biomechanical properties compared to the TPO/SA technique. All techniques did not reach the biomechanical properties of the NM.