Medial Meniscal Ramp Lesion Repair Concomitant With Anterior Cruciate Ligament Reconstruction Did Not Contribute to Better Anterior Knee Stability and Structural Properties After Cyclic Loading: A Porcine Model

Morphological and histological evaluation of the tendon-bone junction in porcine shoulders to create a rotator cuff tear and repair model

BACKGROUND

This study aimed to morphologically and histologically examine whether pig is useful as models for rotator cuff tear (RCT).

METHODS

The morphology of the scapula and humerus bones was evaluated by taking X-ray and three-dimensional computed tomography (3D CT) scans of the right shoulders of five female pigs (age: 4 months). The rotator cuff (RC) footprint at the humeral insertion of these was observed and its shape was measured. Next, they underwent general anesthesia and an acute rotator cuff tear/rotator cuff repair (RCT/RCR) model was created using a deltoid split approach. Four weeks after surgery, the animals were euthanized, the shoulder joints were harvested, and the repaired RC was evaluated by hematoxylin and eosin staining and toluidine blue staining.

RESULTS

The scapula of the pig had a vestigial acromion, in contrast to that in humans. The supraspinatus and infraspinatus tendons were connected so as to overlap each other and attached to the postero-superior part of the greater tuberosity. These tendons were located extra-articularly, separate from the joint capsule. The average antero-posterior length of the foot print was 17.4 ± 0.7 mm on the medial margin and 19.1 ± 2.2 mm on the lateral margin. The maximum medial-to-lateral width of it was 5.1 ± 0.5 mm. In all RCT/RCR models at 4 weeks after surgery, the repaired RC compound tendon was visually confirmed to be continuous with the footprint. Histologically, it was confirmed that regeneration of the four-layer structure of the bone-tendon junction had occurred.

CONCLUSION

Porcine supraspinatus and infraspinatus attachment to the greater tuberosity have a structure similar to that of sheep and dogs, which is advantageous for creating the RCT/RCR model. It might be used for future in vivo studies of shoulder joint diseases.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

Pigs could potentially serve as a viable model for rotator cuff tears.

Relationship Between Achilles Tendon Stiffness Using Myoton PRO and Translation Using a Tensile Testing Machine: A Biomechanical Study of a Porcine Model

Background Achilles tendinopathy is a common ankle disorder in both the general population and athletes. This condition can alter the mechanical characteristics of the Achilles tendon (AT) by decreasing tendon stiffness. Achilles tendinopathy is primarily treated conservatively; however, few monitoring tools exist for evaluating the condition of the AT. The Myoton PRO (Myoton AS, Tallinn, Estonia) device is a handheld tool used to evaluate tissue stiffness. However, no basic studies have examined the validity of Myoton PRO for assessing the AT. This study aimed to assess the validity of Myoton PRO using animal ATs and to examine its clinical applicability. Methods We used 28 fresh porcine ankles and evaluated AT stiffness at the calcaneus insertion site (AT0) and 2.0 cm above the calcaneus (AT2) using Myoton PRO. We also measured changes in the AT length using a tensile testing machine during the cyclic loading test. We investigated the correlation between dynamic stiffness and length change. Furthermore, we assessed the difference in stiffness between AT0 and AT2. Results The dynamic stiffness was 717.6 ± 183.1 N/m at AT0 and 467.4 ± 152.3 N/m at AT2. The change in length during the cyclic loading test was 1.8 ± 0.7 mm. The correlation between dynamic stiffness and length change was as follows: AT0, r=-0.61; AT2, r=-0.64 (P<0.001). The dynamic stiffness at AT0 was significantly greater than that at AT2 (P<0.001). Conclusions AT assessment using Myoton PRO has potential clinical utility as an indicator of tissue stiffness.

Comparison of Electrothermal Ablation and Electrolyte Plasmalization Devices Based on the Mechanical Properties of Anterior Cruciate Ligament Femoral Attachment Following Partial Debridement: A Biomechanical Study Using a Porcine Model

Purpose This study aimed to clarify whether differences in ablation devices used in the knee joint during partial debridement of the proximal end of the femoral attachment of the anterior cruciate ligament (ACL) affect the mechanical properties of the femur-ACL-tibia complex. Methods Electrothermal ablation was generated from Vulcan for the left knees, and radiofrequency ablation was generated from Werewolf Flow 50 Wand for the right knees. The probes were set to the default setting of 120 W and 150 W for Vulcan and Werewolf Flow 50 Wand, respectively. To mimic partial debridement in remnant tissue-preserving (RTP) ACL reconstruction, the bipolar ablation mode and serpentine movements were employed while in contact with the femoral fan-like extension fibers of the ACL. To simulate the arthroscopic environment, the model was immersed in a saline solution. The probes were applied for 60 s, and their biomechanical properties were evaluated. Results A significant difference was observed in the upper yield load between the two groups (Vulcan group, 107.1 ± 93.4 N; Werewolf group, 177.9 ± 108.8 N; P = 0.045). However, no significant differences were noted in linear stiffness (Vulcan group, 47.6 ± 30.9 N/mm; Werewolf group, 50.1 ± 30.5 N/mm; P = 0.85), maximum load (Vulcan group, 276.2 ± 171.8 N; Werewolf group, 397.7 ± 150.8 N; P = 0.26), or elongation at failure (Vulcan group, 6.1 ± 0.9 mm; Werewolf group, 11.6 ± 10.4 mm; P = 0.20) between the two groups. Conclusion The mechanical properties of the ACL after partial ACL femoral attachment debridement for RTP-ACL reconstruction were better when an electrolyte plasmalization device was used. When performing RTP-ACL reconstruction, surgeons must consider that the device used for partial femoral ACL stump debridement may affect the mechanical properties of the ACL remnant tissue. Clinical relevance When performing RTP-ACL reconstruction, surgeons must consider that the device used for partial femoral ACL stump debridement may affect the mechanical properties of the ACL remnant tissue.

Suture Augmentation Does Not Change Biomechanical Properties and Histological Remodeling of Tendon Graft in Anterior Cruciate Ligament Reconstruction: A Study in a Porcine Model

PURPOSE

To evaluate the initial safety of the combined use of ultra-high molecular weight polyethylene (UHMWPE) sutures for suture augmentation (SA) in a porcine ACL reconstruction model and examine whether the procedure can affect the anterior knee laxity and structural properties of the tendon graft itself, influence histological remodeling, and cause a foreign body-induced inflammation.

METHODS

Ten pigs were divided into SA and non-SA Groups to undergo ACL reconstruction using an autologous semitendinosus tendon with and without SA, respectively. At 12 weeks postoperatively, the tibial fixation of the grafted tendon and SA was removed, and the anterior knee laxity and structural characteristics of the grafted tendon were evaluated for mechanical testing. Histological evaluation, including the ligament tissue maturation index (LTMI) score and the presence or absence of foreign-body reaction, was evaluated.

RESULTS

There was no significant difference in anterior laxity between the two groups (SA Group, 1.19 ± 0.78 mm; non-SA Group, 1.08 ± 0.42 mm; P = 1). There were no significant differences in maximum load failure, yield strength, stiffness, elongation at failure, and the LTMI score between the two groups (P = 0.31, 1, 1, 1, and 0.24, respectively). All grafted tendons showed no foreign-body reactions.

CONCLUSION

Suture augmentation did not have significant effect on the anterior knee laxity and the structural properties of the grafted tendon, interfere with histological remodeling, or cause foreign body-induced reactions.

CLINICAL RELEVANCE

The results of our study may lay the foundation for further clinical studies to verify the usefulness of ACL reconstruction with SA.