Bachmaier, Samuel

Background: Complex repairs of radial meniscal tears have shown increased fixation strength compared to conventional sutures. A simplified 2-suture hybrid and a novel dual tie-grip repair with interconnected vertical mattress sutures spanning the tear were tested and compared to all-inside double-horizontal and tie-grip repairs. Hypothesis: The dual tie-grip repair would increase the initial compression load across the tear and show the least cyclic displacement and highest failure strength. Study Design: Controlled laboratory study. Methods: A total of 40 porcine medial menisci were assigned to 4 repair groups: double-horizontal, hybrid, tie-grip, and dual tie-grip (10 per group). Results from tie-grip repairs were used to assess the effect of vertical mattress suture interconnection. After suture placement according to the described technique and fixation, the initial compressive load, stiffness, and relief displacement were measured. The repaired specimens underwent cyclic loading between 5 and 30 N over 1000 cycles (0.75 Hz), while cyclic stiffness and displacement were measured. Ultimate stiffness and load-to-failure were analyzed at 3.15 mm/s. Results: Analysis of variance revealed that dual tie-grip and hybrid repairs showed higher initial compressive load and relief displacement than the other techniques, with dual tie-grip repair reaching the highest values for both metrics (load: 19.3 ± 2.3 N [ P < .001]; displacement: 0.75 ± 0.19 mm [ P < .001]). The double-horizontal repair had the lowest initial stiffness ( P < .001). Cyclic displacement was lowest for the dual tie-grip repair and highest for the double-horizontal repair (both P < .001). All repaired specimens stiffened during cycling without intergroup differences. Analysis of covariance for stiffness over displacement revealed higher stabilization ( P < .040) with dual tie-grip repair and reduced stabilization ( P < .001) with double-horizontal repair. Despite comparable ultimate stiffness across groups, the dual tie-grip repair failed predominantly by suture rupture at the highest ultimate load (275.5 ± 26.2 N; P < .001), whereas the double-horizontal repair failed by tissue rupture the earliest (127.2 ± 15.9 N; P < .001). Conclusion: The dual tie-grip repair provided the highest initial compression across the radial meniscal tear, the lowest cyclic displacement, and the greatest load-to-failure among all techniques in a porcine cadaveric model. The simplified 2-suture hybrid repair showed higher initial compression than other repairs and comparable cyclic stability to the tie-grip repair. Clinical Relevance: The dual tie-grip repair provided high compression across the radial tear and strong resistance to cyclic displacement. Future clinical series assessing differences in healing rates among different repair groups are warranted.

Background: Optimized surgical fixation and meniscal stabilization during rehabilitation increase healing success. However, the latest generation of all-inside devices has not yet been biomechanically compared with inside-out suture tape (IO-ST) repair. Hypothesis: (1) The contact area of a suture anchor (SA) would compensate for a meniscal defect better than polyether ether ketone anchors (PA); (2) adjustable tensioning for all-inside meniscal repair fixation would result in higher initial load than IO-ST repair; and (3) stiffer constructs would decrease secondary displacement. Study Design: Controlled laboratory study. Methods: This study investigates human menisci (N = 39) via microscopic imaging and a biomechanical testing protocol. For the imaging protocol, needles of an all-inside SA or PA device and an IO-ST device were inserted after staining to measure the iatrogenic defect created by the needle insertion (n = 20) and the length, width, and meniscus contact area of deployed all-inside anchors (n = 6). For biomechanical testing, menisci with longitudinal bucket handle tears were prepared, and single stitches were repaired (each n = 9). After suture tensioning (50 N) and fixation, initial load, initial stiffness, and relief displacement were measured. Constructs underwent cyclic loading between 2 and 20 N, with 10,000 cycles (0.75 Hz), and stiffness and displacement were measured. Ultimate stiffness and load-to-failure were analyzed at 3.15 mm/sec. Results: All-inside needles created greater iatrogenic meniscal defects ( P < .001) than IO-ST repair. While PAs were longer ( P < .001), SAs were wider with a greater meniscal contact area (both P < .001). IO-ST repair resulted in the lowest initial load ( P < .001) and relief displacement ( P < .001), whereas SA repair resulted in a higher initial load ( P < .007) and stiffness ( P < .023) than PA repair. The overall stiffer SA fixation ( P < 001) significantly reduced cyclic displacement compared with other repairs ( P < .044). The PA group failed due to an anchor fracture at a significantly lower load (84.3 ± 10.7 N; P < .001) than the IO-ST (136.4 ± 10.5 N) and the SA repair (122.1 ± 17.5 N), with a suture-based failure mode. The ultimate stiffness of SA constructs was higher ( P < .045) than that of other repairs. Conclusion: While all-inside devices showed improved primary stability, the IO-ST construct demonstrated the highest load-to-failure. In a human cadaveric model, meniscal repair with a more compact and conforming SA was stiffer and reduced cyclic displacement compared with PA and IO-ST repair. Clinical Relevance: All-inside SA repair improved primary stability. Future clinical series will define the overall significance of healing rates.

Background: Recent biomechanical evidence for adjustable suture anchor (ASA)–based posterior medial meniscus root (PMMR) fixation has shown promising results compared with conventional transtibial pull-out repair (TPOR). However, ASA fixation has not been evaluated in human tissue to 100,000 cycles. Hypothesis: ASA repair would lead to increased primary fixation strength and less cyclic displacement than conventional TPORs. Study Design: Controlled laboratory study. Methods: A total of 32 human medial menisci were used, 8 of which were intact specimens and served as native controls. For the others, PMMR tears were created and repaired using 3 different techniques (n = 8 group). Two conventional PMMR repairs were prepared consisting of two No. 2 simple sutures (TSS) and two No. 2 sutures in a Mason-Allen (MA) configuration, all tied over a cortical button. The knotless ASA repair was fixed in MA with repair sutures tensioned at 120 N (MA-120). The repairs’ initial force, stiffness, and relief displacement from the tensioned state toward repair unloading (2 N) were measured after fixation. All repair constructs were loaded for 100,000 cycles, with displacement and stiffness measured, and finally were pulled to failure. Results: The TPORs demonstrated similar primary fixation and cyclic loading behavior except for initial cyclic displacement (cycle 10). The ASA repair provided a higher initial repair load ( P < .001) and stiffness ( P < .001) with relief displacement similar to conventional TPORs. Lower initial cyclic displacement ( P < .011; cycle 10) with overall higher repair stiffness ( P < .011) resulted in significantly lower displacement ( P < .001) throughout testing for ASA repair. Although both TPORs were completely loose after 100,000 cycles, the ASA repair achieved near-native dynamic meniscal stabilization. The TSS repair had lower overall ultimate load ( P < .001) and ultimate stiffness ( P < .023) compared with the ASA repair. All repairs had lower ultimate stiffness and loads than the native meniscus ( P < .001). Conclusion: The ASA repair resulted in improved primary PMMR fixation that was stiffer with less cyclic displacement than conventional TPORs and approached that of the human meniscal function after 100,000 load cycles in a cadaveric model. However, all repair techniques had lower ultimate strength than the native human PMMR. Clinical Relevance: Knotless ASA meniscus root fixation resulted in higher tissue compression and less displacement in a cadaveric model; however, future clinical series with surveillance imaging will define the overall significance of healing rates.

Background: While posterior medial meniscus root (PMMR) techniques have evolved, there remains a need to both optimize repair strength and improve resistance to cyclic loading. Hypothesis: Adjustable tensioning would lead to higher initial repair strength and reduce displacement with cyclic loading compared with previously described transtibial pull-out repair (TPOR) fixation techniques. Study Design: Controlled laboratory study. Methods: A total of 56 porcine medial menisci were used. Eight intact specimens served as a control for the native meniscus. For the others, PMMR tears were created and repaired with 6 different TPOR techniques (8 in each group). Fixed PMMR repairs were executed using 4 different suture techniques (two No. 2 cinch sutures, two cinch tapes, two No. 2 simple sutures, and two No. 2 sutures in a Mason-Allen configuration) all tied over a cortical button. Adjustable PMMR repairs using Mason-Allen sutures were fixed with an adjustable soft tissue anchor fixation tensioned at either 80 N or 120 N. The initial force, stiffness, and relief displacement of the repairs were measured after fixation. Repair constructs were then cyclically loaded, with cyclic displacement and stiffness measured after 1000 cycles. Finally, the specimens were pulled to failure. Results: The PMMR repaired with the 2 cinch sutures fixed technique afforded the lowest ( P < .001) initial repair load, stiffness, and relief displacement. The adjustable PMMR repairs achieved a higher initial repair load ( P < .001) and relief displacement ( P < .001) than all fixed repairs. The 2 cinch sutures fixed technique showed an overall higher cyclic displacement ( P < .028) and was completely loose compared with the native meniscus functional zone. Repairs with adjustable intratunnel fixation showed displacement with cyclic loading similar to the native meniscus. With cyclic loading, the Mason-Allen adjustable repair with 120 N of tension showed less displacement ( P < .016) than all fixed repairs and a stiffness comparable to the fixed Mason-Allen repair. The fixed Mason-Allen technique demonstrated a higher ultimate load ( P < .007) than the adjustable Mason-Allen techniques. All repairs were less stiff, with lower ultimate failure loads, than the native meniscus root attachment ( P < .0001). Conclusion: Adjustable TPOR led to considerably higher initial repair load and relief displacement than other conventional fixed repairs and restricted cyclic displacement to match the native meniscus function. However, the ultimate failure load of the adjustable devices was lower than that of a Mason-Allen construct tied over a cortical button. All repair techniques had a significantly lower load to failure than the native meniscus root. Clinical Relevance: Knotless adjustable PMMR repair based on soft anchor fixation results in higher tissue compression and less displacement, but the overall clinical significance on healing rates remains unclear.

Background: Primary device fixation and the resistance against gap formation during repetitive loading influence the quality of meniscal repair. There are limited biomechanical data comparing primary tensioning and cyclic behavior of all-inside versus inside-out repair. Hypothesis: All-inside devices provide higher initial load on the meniscal repair than inside-out fixation, and stiffer constructs show higher resistance against gap formation during cyclic loading. Study Design: Controlled laboratory study. Methods: In total, 60 longitudinal bucket-handle tears in human cadaveric menisci were created and repaired with a single stitch and randomly assigned to 4 all-inside groups (TrueSpan, FastFix 360, Stryker AIR, FiberStich) and 2 inside-out groups (suture repair [IO-S], suture tape [IO-ST]). Residual load after repair tensioning (50 N) and relief displacement were measured. Constructs underwent cyclic loading between 2 and 20 N over 500 cycles (0.75 Hz) with cyclic stiffness, gap formation, and final peak elongation measured. Ultimate load and stiffness were analyzed during pull to failure (3.15 mm/s). Results: All-inside repair demonstrated significantly higher primary fixation strength than inside-out repair. The significantly highest load (mean ± SD; 20.1 ± 0.9 N; P < .037) and relief displacement (–2.40 ± 0.32 mm; P < .03) were for the knotless soft anchoring FiberStich group. The lowest initial load (9.0 ± 1.5 N; P < .001) and relief displacement (–1.39 ± 0.26 mm; P < .045) were for the IO-S repair group. The final gap formation (500th cycle) of FiberStich (0.75 ± 0.37 mm; P < .02) was significantly smaller than others and that of the IO-S (1.47 ± 0.33 mm; P < .045) significantly larger. The construct stiffness of the FiberStich and IO-ST groups was significantly greater at the end of cyclic testing (16.7 ± 0.80 and 15.5 ± 1.42 N/mm; P < .042, respectively) and ultimate failure testing (23.4 ± 3.6 and 20.6 ± 2.3 N/mm; P < .005). The FastFix 360 (86.4 ± 4.8 N) and Stryker AIR (84.4 ± 4.6 N) groups failed at a significantly lower load than the IO-S group ( P < .02) with loss of anchor support. The FiberStich (146.8 ± 23.4 N), TrueSpan (142.0 ± 17.8 N), and IO-ST (139.4 ± 7.3 N) groups failed at significantly higher loads ( P < .02) due to suture tearing. Conclusion: Overall, primary fixation strength of inside-out meniscal repair was significantly lower than all-inside repair in this cadaveric tissue model. Although absolute differences among groups were small, meniscal repairs with higher construct stiffness (IO-ST, FiberStich) demonstrated increased resistance against gap formation and failure load. Clinical Relevance: Knotless single-stitch all-inside meniscal repair with a soft anchor resulted in less gapping, but the overall clinical significance on healing rates remains unclear.