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Abstract

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.

Keywords

all-inside biomechanics inside-out meniscal repair primary fixation

Intact menisci are essential for normal knee biomechanics. Meniscal load distribution over an increased tibiofemoral contact area and greater joint congruity reduces contact pressure on the articular surface.¹⁰ Meniscal tears are common knee injuries, especially in young, physically active patients.^11-13 Early primary repair with preservation of meniscal tissue is essential for successful healing and results in better long-term patient-reported outcomes, sooner return to the previous activity levels, and less progression of osteoarthritic changes compared with partial meniscectomy.^14,20,22,29

In addition to the biological healing environment, successful meniscus healing mainly depends on stable surgical fixation of the torn meniscus to avoid loosening during repetitive, cyclic loading.^2,4,17,21,23 In traditional inside-out (IO) meniscal repair, a suture with 2 flexible needles is passed through the meniscus and secured with extra-articular knot fixation over the posterior capsule.^8,17,27 A new generation all-inside meniscal repair applies 2 suture sheaths on the capsule peripheral to the meniscus. Under tension, the repair suture deploys the sheaths as compact suture anchors (SAs), which act as fixation points for the repair suture across the tear to reapproximate the torn meniscus. All-inside meniscal repair devices have optimized arthroscopic repair by reducing the risk of neurovascular injury with a reduced operative time while achieving similar meniscal healing or functional outcomes as IO repair.^8,17,27 Although IO devices create smaller meniscal defects,⁶ further reduction in outer needle diameter and optimized anchor profiles for meniscal passage and all-inside fixation may positively influence defect size and biomechanical performance.²⁶ Additional information about the meniscal defect and anchor may help better understand implant-related deficiencies in meniscal repair stabilization.⁷

Along with the continued development of meniscal repair implants, numerous studies have reported on the biomechanical performance of various devices.^2,4,17,21,23 Recent biomechanical studies have shown greater fixation strength of all-inside repairs with SAs than traditional polyether ether ketone (PEEK) anchors (PA) or IO repairs.^1,2 Stepwise adjustable tensioning of individual loops provided a higher initial load at the time of surgical meniscal reapproximation for a knotless SA implant compared with single-tensioned PA implants and IO repair.¹ Given the existing knowledge gap in the meniscal repair fixation using the latest all-inside devices, it is crucial to obtain biomechanical data to evaluate the primary fixation under prolonged cyclic loading conditions.

This study aimed to (1) investigate the diameter of the iatrogenic meniscal defect and the size and shape of the deployed anchor; and (2) evaluate the initial repair load and relief displacement after primary fixation, gap formation, stiffness behavior during over 10,000 load cycles, and ultimate load and stiffness during failure testing of 3 different devices for repairing longitudinal meniscal tears using human menisci. It was hypothesized that (1) the contact area of an SA would compensate for the iatrogenic meniscal defect caused by needle insertion better than a PA, (2) adjustable tensioning for all-inside meniscus repair fixation would lead to a higher initial repair load, and (3) stiffer constructs would decrease secondary displacement during cyclic loading.

Methods

The present study used microscopic imaging and biomechanical testing protocols to evaluate 3 different meniscal repair techniques. Overall, 39 adult human cadaveric menisci (medial and lateral sides) were isolated from 20 paired knees (10 men and 10 women; mean ± SD = 59.6 ± 6.2 years). The meniscocapsular tissue was released, and the meniscal roots were dissected at their tibial attachments. All specimens were obtained from the Science Care donor bank and underwent visual inspection after harvesting to ensure structural integrity without tears or noticeable degenerative changes.

For all-inside meniscal repair evaluation with 2 in-line anchors completely encased in the needle cannula, a PA device (n = 15) consisting of the Fast-Fix Flex implant (Smith & Nephew), and a knotless SA device (n = 15), the FiberStitch 1.5 implant (Arthrex Inc) were used (Figure 1). The PAs are connected with a No. 2-0 braided ultrahigh molecular weight polyethylene suture and secured with a pretied sliding knot, and the SAs are connected with a 2-0 coreless FiberWire (Arthrex) suture. An IO device (n = 15) using preloaded suture tape (IO-ST) repair needles (2-0 Mini SutureTape Meniscus Repair Needles; Arthrex) served as a reference for baseline comparison. Each meniscus was stored in a freezer at −18°C and defrosted overnight in a refrigerator at 4°C before testing.

Figure 1.

(A) Meniscal repair devices with exemplary images of the deployed (B) PAs and (C) SAs after implant placement with illustrated primary outcome parameters (length, width, meniscal contact area) and created meniscal defects after (D) all-inside and (E) inside-out needle insertion. PA, polyether ether ketone anchor; SAs, suture anchors.

Implant and Meniscus Imaging

A digital caliper was used to measure the maximum outer diameter of the needle tip of all devices (n = 15 in each group). For the imaging part, the paired menisci of 6 knees were used. Medial menisci were used to insert the implant device needles horizontally without rotation during needle tip penetration and anchor deployment. The needle tip of each device was dipped in methylene blue before insertion to stain the meniscal tissue interface preferentially and visualize the microtrauma. The anchors of all-inside devices were completely encased in the cannula; thus, their nondeployment should not have affected the defect created by each needle puncture. The defects (n = 20) were placed in line with the fibers in pairs of 2, approximately 4 mm apart radially and 6 mm longitudinally from each other.⁶

The lateral menisci were used to place horizontal all-inside repairs (each n = 6) with anchors spaced approximately 10 mm longitudinally and tensioned according to the manufacturer’s guidelines. A final manual tension of 50 N was applied to the tightening suture for 5 seconds using a digital force gauge (Mark-10 M7-50; Bronx-Systems) and an arthroscopic knot pusher to simulate intraoperative single-hand tensioning with counter-tension applied.¹ Reproducible repair tensioning ensured proper anchor seating on the meniscus with the fully deployed SAs.

The iatrogenic meniscal defects caused by needle insertion and deployed anchors were imaged and measured with a microscope (Nikon SMZ25) using the same calibration setting based on a known 1.0-mm calibration slide for all specimens. The menisci with iatrogenic needle defects and deployed anchors were divided into 3 and 2 parts, respectively, with each part manually aligned flat on the microscope stage for accurate measurements from the top view. For deployed SAs and PAs, the length, width, and meniscal contact area were analyzed (Figure 1, B and C). Each meniscal defect was measured multidirectionally, with the greatest defect length (Figure 1, D and E) used for comparative analysis.⁶ While the outer dimensions of the PA determined the outcome parameters (Figure 1B), the SA length represented the arithmetic mean of the 2 anchor leg lengths, and the maximum anchor width was measured near the needle exit point (Figure 1C). A single investigator (S.B.) used the microscope software to obtain all measurements of meniscal defects and all-inside anchors. The investigator was not blinded to the device during the measurement and imaging portions of the study. Using a single investigator to obtain all measurements ensured consistency and accuracy using the microscope and imaging software.

Meniscal Preparation and Repair Fixation

Paired medial and lateral menisci were equally distributed in a balanced incomplete block design. There was no statistical difference in age between the 3 groups for primary repair fixation and cyclic testing of various repairs. A longitudinal vertical tear was created 3 mm from the peripheral rim, starting from the midpoint of the meniscus, separating the central third of the meniscus portion along the circumferential fiber orientation toward the anterior and posterior horns.¹ A single vertical mattress repair was placed at the midpoint of the meniscus, with suture passes placed 3 mm away from the tear and directed toward the capsule. After repair, the meniscal tear was completely repaired through vertical resection involving both the anterior and posterior horns. All tears were repaired with single stitches.

The peripheral and central portions of the meniscus were secured using custom clamps with textured surfaces to minimize slippage, with the center of the meniscus in a central position to align the vertical repair with the actuator axis (Figure 2). The clamps were mounted at the bottom and top of the baseplate and the test machine actuator (ElectroPuls E10000; Instron), respectively. The actuator was adjusted to achieve an initial 5 mm distance between the 2 meniscal parts, as measured along the repair using a caliper. All-inside meniscal repair devices were tensioned similar to the imaging section, with a final manual 50 N pull on the tightening suture applied over 5 seconds and counter-tension applied over an arthroscopic knot-pusher (Figure 2A).¹ Suture fixation of IO-ST samples followed a similar procedure, with 50 N traction on each of the 4 alternating counteractive half-hitch knots using an arthroscopic knot-pusher on the capsular side of the meniscus. Reproducible repair tensioning with the actuator locked in position ensured proper time-zero fixation for comparative analysis and reduced settling effects before cyclic testing.

Figure 2.

(A) Experimental test setup with separated meniscus portions secured with riffled metal clamps for tensioning of the single vertical repair with a knot pusher. (B) Cyclic loading was applied in line with the test machine actuator axis.

As the primary tension varied after surgical meniscal repair fixation, the test machine actuator moved to reach a defined time-zero preload position of 2 N, which served as a reference for later elongation analysis and guaranteed similar and reproducible initial testing conditions for all groups (Figure 3). The test machine, using a 1 kN load cell (Instron), acquired the initial load on the repair (F₀, b) after tensioning with corresponding actuator relief displacement to reach the time-zero valley position (2 N) for cyclic testing (s₀, Δbc). The initial stiffness represents the linear inclination between the initial load position and the loading point with 5 N tension on the repair during construct unloading. The actuator relief displacement from the tensioned state after fixation toward repair unloading represents a direct indicator for gap initiation. An absolute greater relief displacement of a device at the time of insertion is equivalent to a higher degree of security against gap initiation. All tests were performed at room temperature, and soft tissue was kept moist with physiological saline solution during preparation and testing.

Figure 3.

Testing protocol with the simulation of intraoperative tensioning (a) for meniscal repair fixation, cyclic loading, and pull to failure. Points of data analysis included initial repair load (F₀, b), initial stiffness (D₀, Δbc), and relief displacement (s₀, Δbc) to reach the time-zero valley position with 2 N load on the repair, gap formation (eg, Δcd, Δcf), and repair stiffness (eg, Δde, Δfg) at defined load cycles, as well as ultimate load and stiffness during pull to failure (Δhi).

Cyclic and Failure Testing

To evaluate the cyclic performance, repetitive loading was applied perpendicular to the tear with the meniscal repair aligned along the actuator axis (Figure 2B). The test was conducted at a frequency of 0.75 Hz over 10,000 cycles, ranging from 2 N to 20 N. These load parameters are consistent with previous meniscal repair studies.^{1,3-5,7,17,23} Valley and peak actuator translation relative to the time-zero valley position at cycles 10, 100, 500, 1000, 5000, and 10,000 were assessed (Figure 3). Mechanical data were continuously recorded at a sampling rate of 500 Hz. Finally, load-to-failure testing was performed at a rate of 3.15 mm/sec with failure mode noted.

Cyclic loading outcome data included gap formation and dynamic stiffness at defined load cycles with ultimate load (F_max) and stiffness (D_UF) determined during pull to failure. Gap formation represents plastic deformation (laxity) with a valley load (2 N) on the repair. Dynamic stiffness represents the linear inclination of the hysteresis valley and peak data in the loading phase. Ultimate failure load (F_max) and stiffness (D_UF) were determined during pull to failure. Stiffness was calculated within the linear portion of the load-displacement curve.

Statistical Analysis

In this study, repair techniques and devices were independent variables (eg, all-inside PA, all-inside SA, and IO-ST). All metrics for comparison were dependent variables. Across all tests, the significance level was set at .05 and was adjusted when appropriate to control for multiple comparisons using Bonferroni correction. The desired power level was set at 0.8. The normal distribution for each variable was tested a priori via the Shapiro-Wilk test. If the variable was not normally distributed, nonparametric tests were performed, equivalent to the below-described parametric versions.

The first hypothesis was tested on 2 levels. First, the length of the iatrogenic meniscal defect created by all-inside and inside-out needles (Figure 1, D and E) was tested using a 1-way analysis of variance (ANOVA) with Holm-Sidak post-hoc tests (SA vs PA vs. IO-ST). In a second step, it was tested whether the contact area of an SA compensates better for a meniscal defect than a PA using an unpaired 1-tailed Student t test. The anchor length, width, and meniscal contact area were investigated between the 2 all-inside devices (SA vs PA).

For the second hypothesis, the initial repair tension (F₀), stiffness, and relief displacement (s₀) were analyzed to indicate the meniscal repair stabilization directly after surgical fixation across all 3 groups (SA vs PA vs OT-ST). Three 1-way ANOVAs with Holm-Sidak post hoc tests were performed.

The third hypothesis was tested using dynamic stiffness and gap formation at defined load cycles (10, 100, 500, 1000, 5000, and 10,000 cycles) to evaluate the influence of construct stiffness on secondary displacement across all 3 groups. For each defined load cycle, a 1-way ANOVA with Holm-Sidak post hoc tests were performed for significant pairwise analysis of primary outcome variables between groups (SA vs PA vs IO-ST). Differences between the 3 groups in ultimate strength were tested for stiffness (D_UF) and failure load (F_max) during pull-to-failure via 1-way ANOVAs with Holm-Sidak post hoc tests.

Statistical analysis was performed using Sigma Plot Statistics for Windows Version 13.0 (Systat Software). Mechanical testing raw data were analyzed with a custom-written MATLAB script, Version R2019a (MathWorks).

Results

Imaging

The iatrogenic meniscal defects created by all-inside needles were significantly greater than those made by IO-ST (Table 1). Overall, the PAs were longer but had a smaller width and meniscal contact area than the U-shaped SAs.

Table 1

Imaging-Related Outcome Parameters for Deployed All-Inside PEEK, SAs, and Created All-Inside and Inside-Out Iatrogenic Meniscal Defects^a

		All-Inside		Inside-Out
	Groups	PA	SA	IO-ST
Needle	Diameter, ND, mm	1.46 ± 0.01	1.54 ± 0.01	0.76 ± 0.01
Defect	Length, DL, mm	1.91 ± 0.09	1.98 ± 0.12	0.91 ± 0.09^b
	DL/ND, %	1.31	1.29	1.20
Anchor 1	Length, mm	6.25 ± 0.05	5.05 ± 0.05^b	-
	Width, mm	0.94 ± 0.01^b	3.38 ± 0.37	-
	Contact area, mm²	5.89 ± 0.06^b	9.73 ± 0.36	-
	Contact area/DL, mm	3.08	4.91	-
Anchor 2	Length, mm	5.04 ± 0.05	4.41 ± 0.24^b	-
	Width, mm	0.93 ± 0.02^b	2.82 ± 0.22	-
	Contact area, mm²	4.67 ± 0.09^b	8.44 ± 0.61	-
	Contact area/DL, mm	2.44	4.26	-

Data are presented as mean ± SD. DL, defect length; IO-ST, inside-out suture tape; ND, needle diameter; PA, PEEK anchor; PEEK, polyether ether ketone; SA, suture anchor.

Indicates a significant difference compared with other groups (P < .001).

Primary Fixation

The all-inside repairs demonstrated significantly higher (P < .001) initial repair load and relief displacement than IO-ST. While the SA device achieved significantly higher initial load and stiffness than the PA device (Figure 4), knot tying of the IO-ST device resulted in the lowest initial load and relief displacement (0.73 ± 0.30 mm; P < .001). The relief displacement of SA (1.39 ± 0.30 mm) and PA (1.48 ± 0.25 mm) groups was not significantly different (P = .449).

Figure 4.

Boxplot with mean ± standard deviation values of the initial repair load after tension release (50 N) and initial stiffness, with significance indicated between groups via the brackets. IO-ST, inside-out suture tape; PA, PEEK anchor; PEEK, polyether ether ketone; SA, suture anchor.

Cyclic Testing

At the beginning, all groups showed gap formation levels that were not significantly different from one another (cycle 10). However, the gap formation of SA became significantly smaller with continued loading compared with PA (cycle No. 100) and IO-ST (cycle No. 100) (Figure 5). All groups showed construct stiffening during cycling. The SA constructs showed an overall higher stiffness (P < .001) than the other repair groups throughout cyclic loading (Figure 5). The cyclic displacement and stiffness were not significantly different between PA and IO-ST.

Figure 5.

Progression of repair stiffness and displacement throughout testing with final values (italics) at 10,000 cycles (mean ± SD on both axes). The arrow with a symbol indicates significance from the specific load cycle until the end of the test. IO-ST, inside-out suture tape; PA, PEEK anchor; PEEK, polyether ether ketone; SA, suture anchor.

Pull to Failure

All constructs reached the regular test end. The ultimate stiffness of SA was significantly higher than that of PA and IO-ST (Figure 6). The ultimate load of the PA device was significantly lower than that of the SA and IO-ST devices and failed due to loss of anchor fixation (breakage). The IO-ST group failed due to suture rupture. The SA group failed due to either the tearing of the repair suture or the rupture of the anchor connecting suture.

Figure 6.

Boxplot with mean ± standard deviation values of the ultimate load (left) and stiffness during pull to failure (right), with significance indicated between groups via the brackets. IO-ST, inside-out suture tape; PA, PEEK anchor; PEEK, polyether ether ketone; SA, suture anchor.

Discussion

The main findings of this study were that (1) all-inside device needles produced larger iatrogenic meniscal defects than IO repair, with the all-inside SA device better compensating for the microtrauma when deployed under tension compared with PA devices, and (2) surgical tensioning of all-inside devices resulted in a significantly higher initial load for meniscal reapproximation compared with the IO repair, and (3) the overall stiffer SA implant achieved significantly lower gap formation and higher ultimate strength compared with the PA implant after repetitive loading of 10,000 cycles in human cadaver menisci. The current literature lacks a comprehensive analysis of how meniscal defects and material-specific anchor designs (eg, size and shape) influence the biomechanical performance of various all-inside meniscal repair implants. This study built upon a multidirectional iatrogenic meniscal defect measurement with the greatest length for “worst-case” comparative analysis across multiple implants.⁶ Significant differences between the latest commercially available SA and PA meniscal repair devices in terms of primary surgical anchor fixation and construct behavior during cyclic and ultimate failure testing were found, providing a better understanding of implant-related deficiencies in meniscal repair stabilization.

In line with a previous study,⁶ smaller-diameter IO needles produced more stellate and less invasive defects than semilunar defects with all-inside needles. Thus, the orientation of the cutting edge of the cannula relative to the meniscus is important; needles were inserted in line with the meniscal fibers and without rotation to avoid excessive laceration of fibers and to reduce the biomechanical effects on the meniscal repair.²⁶ Differences in the needle diameter, shape, and sharpness between the IO and all-inside devices may explain the predominantly different defect patterns. Based on a needle of similar shape, outer diameter, and 2 in-line anchors fully encased in the cannula, no difference in the defect pattern was observed between the 2 all-inside devices. The literature does not indicate a critical size for an iatrogenic meniscal defect caused by needle insertion that would compromise meniscal healing or repair stabilization. While smaller defects may promote better repair and healing due to less surrounding tissue damage, larger defects may allow for improved vascularity by creating fenestration channels, resulting in an optimized biological environment for meniscus healing.^6,26 However, larger meniscal defects with all-inside repair are also associated with meniscal retears, which may affect the number of devices used for meniscal repair.^25,27

Unlike rigid PA implants, all-inside SA implants achieve fixation through anchor deployment by manually pulling on the repair suture. Under tension, the repair suture deploys the sheath as an anchor according to its underlying deployment configuration and acts as a fixation point for the repair suture. This study used a reproducible tension force (50 N) to simulate the meniscal repair's intraoperative tensioning.¹ The greater flexibility of SA compared with rigid PA allows longer anchor sheaths to be placed within a similarly sized device needle, ultimately resulting in a more compact anchor body that better conforms to the meniscal surface around the meniscal defect. The anchor’s material-specific properties and design (size and shape) influence the tissue interaction with the meniscus, the resistance to gap formation during cyclic loading, and, ultimately, the failure strength and mode. Reduced time-zero meniscal tissue compression at the repair site and progressive meniscal repair loosening during cyclic loading are unfavorable for meniscal healing.^18,23,28 While displacement after the first load cycle has not been able to differentiate the primary fixation strength between variable meniscal repairs,^18,21,23,28 significantly increased initial load and relief displacement of all-inside fixation may refine the perspective of primary surgical fixation. A larger conforming SA contact area to support the meniscal suture repair under tension provides optimized load distribution and stable anchor seating with a reduced risk of soft tissue damage during cyclic loading. In the narrower and more elongated PA, the weakest central section of the suture suspension experiences higher bending stress under load. Uneven flexural stress in the PA and the meniscus contact area over a smaller linear anchor support area could cause anchor deflection or subsidence into the meniscus with the cheese-wire cutting of the repair suture through the meniscus, resulting in an iatrogenic retear and/or anchor pullout. In contrast to Müller et al¹⁹ who reported a higher propensity for suture cut-through meniscus failures in stiffer IO and PA constructs after applying 10,000 cycles, none of the specimens in our study exhibited this specific failure mode. A stiffer porcine meniscus compared with the human meniscus used in this study may explain the differences in failure mode. The PA fracture at lower load levels during failure testing may be influenced by cyclic bending fatigue, demonstrating the intended failure mechanism of the more fragile PA. The SA implant failed at significantly higher loads due to a repair or anchor-connecting suture rupture. In the clinical setting, anchor failure or pullout could result in anchor migration into the joint, tissue irritation or damage, swelling, and pain.²⁷

The results reported in this study have limited historical comparison, as only a few studies have reported the response to cyclic loading after 10,000 cycles.^19,24 A recent porcine study compared 2 SA implants with a PA implant and an IO repair using a cyclic loading protocol between 10 and 50 N over 200 cycles.² Although the SAs showed less displacement with a similar stiffness to the PA device, no significance was found between the devices during cycling. Using less rigid towel forceps, clamps, and a lower initial preload (10 N over 60 seconds) may have resulted in pronounced settling effects during cyclic loading at a higher peak load, leading to a higher variance in the test result without significant differences. The failure modes between the previous and the current studies were similar. The PA device exhibited anchor failure at a lower load level than the SAs, which experienced suture breakage. Although the failure load range reported in the previous study was narrower in this study, the variance of the SA device was slightly greater (mean, 45 N [min-max, 106-151 N]) compared with the PA device (mean, 27 N [min-max, 73-100 N]) and the IO repair (mean, 34 [min-max, 106-148 N]).

Limitations

We recognize several limitations in the present study. The mean age of the human menisci donors was higher than that of patients undergoing a meniscal repair, which may limit the applicability of our findings to the target clinical population. While patients with meniscal injuries often already experience degeneration of the meniscus, which reduces tissue stability, the menisci used in this study revealed no damage. In this context, the cadaveric specimens utilized may exhibit stability effects contrary to those observed in clinical settings. Therefore, the tissue quality in patients with meniscal tears could be worse than in patients without injuries. The tensile load was applied along the repair to simulate worst-case testing conditions, with the meniscus secured in customized clamps. This setup differs from the knee joint’s highly variable in vivo loading conditions, including rotational and shear forces. Consequently, the current test methodology only approximates an in vivo loading environment. We acknowledge that the obtained functional performance may differ from the clinical behavior of meniscal repair devices.^9,16 The number of specimens available was limited by material availability; therefore, no a priori power calculation was made. However, the sample size was determined based on previous, similar biomechanical studies.^1,4 Variations in knot tying and tensioning, influenced by the surgeon’s experience, could further affect clinical outcomes. While multiple stitches in different meniscal repair configurations are commonly used in practice,¹⁵ this biomechanical work focused solely on the performance of a single repair stitch, without considering its biological effect or the patient’s clinical outcome. In addition, slight differences in the stitching pattern in variable menisci (eg, size and quality) may have affected the mechanical behavior because of the relative length of the repair construct.

Conclusion

Footnotes

Final revision submitted June 3, 2025; accepted June 24, 2025.

One or more of the authors has declared the following potential conflict of interest or source of funding: S.B. and C.A.W. are employees of Arthrex. A.J.K., P.A.S., and A.B. are consultants for Arthrex and have received consulting fees, speaking fees, compensation for services other than consulting, and royalties from Arthrex. A.J.K. has received honoraria from the Joint Restoration Foundation; royalties from Responsive Arthroscopy; and a grant from DJO. P.A.S. has received compensation for services other than consulting from Kairos Surgical and support for education from United Orthopedics. A.B. has received hospitality payments from GE Healthcare; speaking fees from Synthes GmbH; and consulting fees from Collagen Matrix. Arthrex provided research support for this study. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Ethical approval was not sought for the present study.

ORCID IDs

Aaron J. Krych

Romain Seil

Coen A. Wijdicks

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Primary Fixation of Single Stitch All-Inside and Inside-Out Meniscal Devices for Repairing Vertical Longitudinal Meniscal Tears: A Human Microscopic Imaging and Biomechanical Study

Abstract

Background:

Hypothesis:

Study Design:

Methods:

Results:

Conclusion:

Clinical Relevance:

Keywords

Methods

Implant and Meniscus Imaging

Meniscal Preparation and Repair Fixation

Cyclic and Failure Testing

Statistical Analysis

Results

Imaging

Primary Fixation

Cyclic Testing

Pull to Failure

Discussion

Limitations

Conclusion

Footnotes

ORCID IDs

References