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Excessive MMP activity may impair tendon-to-bone healing. However, little is known about the effect of joint motion on MMP activity after ACL reconstruction. The aim of this study was to determine the effect of different durations of knee immobilization on MMP activity in a mouse ACL reconstruction model using a fluorescent MMP probe which detects MMP 2, 3, 9, and 13 and near-infra red in vivo imaging. Sixty C57BL male mice underwent ACL reconstruction. Post-operatively, the animals were treated with free cage activity (Group 1), or with the use of an external fixator to restrict knee motion and weight bearing for 5 days (Group 2), 14 days (Group 3), and 28 days (Group 4). At days 3, 7, 16, 23, and 30, five mice underwent IVIS imaging. At days 3, 7, 16, and 30, histological analysis was also performed. Probe signal intensity in the whole limb peaked at day 7, followed by a decrease at day 16, and maintenance up to day 30. There was no significant difference among groups at any time point based on IVIS, but histologic localization of MMP probe signal showed significantly less activity in Group 2 and Group 3 compared to Group 4 in the bone tunnel at day 30. We demonstrated that short-term immobilization led to less MMP activity around the bone tunnel compared with prolonged immobilization. A short period of immobilization after ACL reconstruction might enhance graft-bone interface healing by mitigating excess MMP expression. These findings have implications for post-operative rehabilitation protocols following ACL reconstruction. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:325-334, 2019.

Background: Animal models that use open surgical transection of the anterior cruciate ligament (ACL) do not accurately simulate the clinical condition regarding the pivot-shift mechanism and the associated inflammatory response that occurs before reconstruction. Purpose/Hypothesis: The purpose was to characterize a reproducible manual, nonsurgical method to mimic an isolated ACL tear in a clinically relevant model and to evaluate the development of progressive posttraumatic osteoarthritis due to ACL injury. It was hypothesized that the ACL could be reproducibly torn with minimal damage to other ligaments and that there would be progressive development of degenerative joint disease after ACL injury. Study Design: Controlled laboratory study. Methods: A total of 37 mice (strain C57BL/6) were used to compare the manual procedure with sham surgery (sham group; n = 10) and with the established surgical ACL transection (ACLT) procedure (surgical group; n = 27). In the sham group, a closed manual procedure was performed on the right knee and sham surgery on the left knee. In the surgical group, the closed manual procedure was performed on the right knee and surgical ACLT on the left knee. Dissection using India ink, histological assessment with safranin O and hematoxylin-eosin staining, radiological evaluation through radiographs and microfocus computed tomography scans, and gait analyses were performed to assess cartilage/ligament status. Osteoarthritis Research Society International (OARSI) and synovitis scores, anterior tibial translation, range of motion, bone microstructure, osteophyte volume, and pain were assessed at 2, 4, and 8 weeks postoperatively. Results: The manual procedure successfully resulted in an ACL rupture and associated meniscal injury. The posterior cruciate, lateral collateral, and medial collateral ligaments were intact in all dissected knees. Two weeks after ACL tear, the surgical group showed a significantly higher synovitis score, whereas 8 weeks after ACL tear, the manual group showed a significantly higher volume of osteophytes. No significant differences were found between the groups in terms of OARSI score, anterior tibial translation, range of motion, bone microstructure computed tomography values, and stride distance/irregularity. Conclusion: This procedure can be used to create an ACL tear model without causing grossly evident injuries to other ligaments and avoiding the risk of cartilage damage from surgical instruments. Clinical Relevance: This procedure offers a more clinically relevant ACL tear model and facilitates simple, inexpensive, and reproducible development of posttraumatic osteoarthritis. [ABSTRACT FROM AUTHOR]

PurposeTo investigate the use of kartogenin (KGN) in augmenting healing of the repaired enthesis after rotator cuff repair in a murine model.MethodsSeventy-two C57BL/6 wild-type mice underwent unilateral detachment and transosseous repair of the supraspinatus tendon augmented with either fibrin sealant (control group; n = 36) or fibrin sealant containing 100 μmol/L of KGN (experimental group; n = 36) applied at the repair site. Postoperatively, mice were allowed free cage activity without immobilization. Mice were humanely killed at 2 and 4 weeks postoperatively. Repair site integrity was evaluated histologically through fibrocartilage formation and collagen fiber organization and biomechanically through load-to-failure testing of the supraspinatus tendon-bone construct.ResultsAt 2 weeks, no differences were noted in percent area of fibrocartilage, collagen organization, or ultimate strength between groups. At 4 weeks, superior collagen fiber organization (based on collagen birefringence [17.3 ± 2.0 vs 7.0 ± 6.5 integrated density/μm2; P

BackgroundMany orthopaedic surgical procedures involve reattachment of a single tendon to bone. Whether tendon-to-bone healing is better facilitated by tendon fixation within a bone tunnel or on a cortical surface is unknown. The purpose of this study was to evaluate tendon-healing within a bone tunnel compared with that on the cortical surface in a rabbit model of biceps tenodesis.MethodsThirty-two rabbits (24 weeks of age) underwent unilateral proximal biceps tenodesis with tendon fixation within a bone tunnel (BT group) or on the cortical surface (SA [surface attachment] group). Postoperatively, rabbits were allowed free-cage activity without immobilization. All rabbits were killed 8 weeks after surgery. Healing was assessed by biomechanical testing, microcomputed tomography (micro-CT), and histomorphometric analysis.ResultsBiomechanical testing demonstrated no significant difference between the groups in mean failure loads (BT: 56.8 ± 28.8 N, SA: 55.8 ± 14.9 N; p = 0.92) or stiffness (BT: 26.3 ± 16.6 N/mm, SA: 32.3 ± 9.6 N/mm; p = 0.34). Micro-CT analysis demonstrated no significant difference between the groups in mean volume of newly formed bone (BT: 69.3 ± 13.9 mm, SA: 65.5 ± 21.9 mm; p = 0.70) or tissue mineral density of newly formed bone (BT: 721.4 ± 10.9 mg/cm, SA: 698.6 ± 26.2 mg/cm; p = 0.07). On average, newly formed bone within the tunnel represented only 5% of the total new bone formed in the BT specimens. Histological analysis demonstrated tendon-bone interdigitation and early fibrocartilaginous zone formation on the outer cortical surface in both groups. In contrast, minimal tendon-bone bonding was observed within the tunnel in the BT specimens.ConclusionsTendon fixation in a bone tunnel and on the cortical surface resulted in similar healing profiles. For tendons placed within a bone tunnel, intratunnel healing was minimal compared with the healing outside the tunnel on the cortical surface.Clinical relevanceThe creation of large bone tunnels, which can lead to stress risers and increase the risk of fracture, may not be necessary for biceps tenodesis procedures.

The standard grafts used for anterior cruciate ligament (ACL) reconstruction are tendon, either patellar tendon, hamstring, or quadriceps. However, the microstructure and composition of tendon differs from ligament. Ideally, the ACL would be replaced with the same tissue. To evaluate the incorporation of a bone‐ACL‐bone (B‐ACL‐B) graft for ACL reconstruction, we performed a controlled laboratory study in a rabbit model with microcomputed tomography (μCT). Forty‐six New Zealand white rabbits were used, with 17 donor rabbits to harvest bilateral B‐ACL‐B allografts and 29 rabbits undergoing unilateral ACL reconstruction with B‐ACL‐B allograft. Knee specimens were collected for biomechanical testing (n = 14) at 4 and 8 weeks and for μCT analysis (n = 15) at 2, 4, and 8 weeks after surgery. Gross inspection and μCT examination confirmed bone blocks in the appropriate anatomic position. Biomechanical tests revealed no difference in mean load‐to‐failure force for B‐ACL‐B allografts between 4 and 8 weeks. Progressive healing occurred between the bone block and the tunnel as demonstrated by a gradual increase on average bone‐volume fraction and total mineral density (TMD) in both femoral and tibial tunnels. Remodeling of the bone block was evidenced by a significant decrease in TMD of both tibial and femoral bone blocks. This is a report of a novel rabbit B‐ACL‐B allograft reconstruction model demonstrating early signs of graft remodeling and incorporation. Clinical Relevance: This study demonstrates ACL reconstruction using an anatomically matched ACL allograft, rather than a tendon graft, may be possible based on early findings in this lapine model. [ABSTRACT FROM AUTHOR]

With the development of the Internet economy, computer games have developed rapidly in recent years. At the same time, with the increasing prosperity of computer games, many infringement problems have also arisen. The concept and classification of computer games and computer game live broadcasts, as well as computer game screens and computer game live broadcasts need to be distinguished. The article lists common problems in the computer game live broadcast industry, which are mainly manifested in the unclear copyright identification and attribution of computer game live broadcasts, and the unclear legal status of the relevant subjects in the computer game live broadcast. It is concluded that whether the computer game live broadcast is a work needs to be specifically defined in conjunction with the live broadcast content. And further put forward suggestions to improve my country’s related protection system of computer game copyright, and promote the development of computer game live broadcast industry.

Purpose: Schenck IV knee dislocation patients have dissatisfactory knee function and return‐to‐sport rate with the existing treatment methods. The purpose of this study was to illustrate a one‐stage arthroscopic multiple ligament reconstruction method for treating Schenck IV knee dislocations. Methods: A retrospective case series study was performed. All patients with a history of Schenck IV knee dislocation who underwent one‐stage arthroscopic multi‐ligament reconstruction from 2010 to 2018 were followed for 24 months. The outcomes, including general patient data, Lysholm scores, International Knee Documentation Committee (IKDC) scores, visual analog scale (VAS) pain scores, knee active range of motion, and complications, were reviewed. The data was analyzed with paired‐samples t‐test. Results: A total of 12 patients, comprising nine males and three females, were followed up and reviewed. The mean age at the time of the surgical procedure was 40.3 ± 9.0 (22–57) years. The mean body mass index (BMI) was 24.6 ± 4.9 (15.2–32.5) kg/m2. The mean IKDC score and Lysholm score before surgery were 30.4 ± 6.1 (21–42) and 28.2 ± 6.2 (22–39), respectively. The average operation time was 121.8 minutes. The mean IKDC score and Lysholm score at the 24‐month follow‐up were 80.6 ± 6.5 (68–92) and 82.0 ± 7.5 (72–95), respectively. There were significant differences in the IKDC and Lysholm scores between the preoperative and 24‐month postoperative time points (p < 0.01). The mean knee range of motion was 124.6° ± 6.6° (115°–135°) at the 24‐month follow‐up. No major complications occurred. Conclusions: The results of this retrospective study suggest that the new arthroscopic one‐stage multi‐ligament reconstruction technique is an effective way to treat Schenck IV knee dislocation with satisfactory postoperative knee function. [ABSTRACT FROM AUTHOR]

The relative contributions of sex differences in anatomy, biomechanics, and hormones to the increased risk of anterior cruciate ligament (ACL) injury in female athletes remains unknown. The purpose of this study is to investigate sex differences in anatomy and biomechanics of the native and reconstructed ACL using our established murine model. A total of 140 12‐week‐old wild‐type C57Bl/6 (70 male vs. 70 female) mice were used for this study. ACL reconstruction was performed on 120 mice who were split into four groups: Group 1 (30 males sacrificed at 14 days), Group 2 (30 females sacrificed at 14 days), Group 3 (30 males sacrificed at 28 days), and Group 4 (30 females sacrificed at 28 days). Tendon graft‐to‐bone healing was assessed by biomechanical, histological, and micro‐CT analysis. Twenty mice were used for baseline testing. Females showed significantly higher anterior (p < 0.05) and total displacement (p < 0.05). Males demonstrated a significantly higher load‐to‐failure force of native ACLs compared to females (p < 0.05). There was no significant difference in load‐to‐failure force in the ACL autograft. There were no significant sex differences in histological analysis of graft integration or tibial slope. The increased knee laxity and reduced load‐to‐failure of the native ACL observed in the female mice are consistent with some of the proposed risk factors driving the increased risk of ACL injury in females. Understanding the relative contributions of factors driving sex differences in material properties of the ACL will provide insight into the sex differences in ACL injury and future prevention strategies. [ABSTRACT FROM AUTHOR]

Background: Successful anterior cruciate ligament reconstruction requires secure healing between tendon and bone. Hypothesis: Bone morphogenetic protein-signaling plays an important role in tendon-to-bone healing. rhBMP-2, a powerful osteoinductive agent, can [...]

Background: The underlying cellular and molecular mechanisms involved in the development of tendinopathy due to subacromial supraspinatus tendon (SST) impingement and the response to subsequent removal of impingement remain unknown. Purpose: To investigate the involvement of Indian hedgehog (IHH) signaling in the development of SST tendinopathy and the subsequent healing process after the relief of subacromial impingement in a novel mouse shoulder impingement model. Study Design: Controlled laboratory study. Methods: A total of 48 male wild-type C57BL/6 mice were used in this study. Supraspinatus tendinopathy was induced by inserting a microsurgical clip into the subacromial space bilaterally. Eleven mice were sacrificed at 4 weeks after surgery to establish impingement baseline; 24 mice underwent clip removal at 4 weeks after surgery and then were euthanized at 2 or 4 weeks after clip removal. Thirteen mice without surgical intervention were utilized as the control group. All SSTs were evaluated with biomechanical testing; quantitative histomorphometry after staining with hematoxylin and eosin, Alcian blue, and picrosirius red; and immunohistochemical staining (factor VIII, IHH, Patched1 [PTCH1], and glioma-associated oncogene homolog 1 [GLI1]). Results: The mean failure force and stiffness in the 4-week impingement group decreased significantly compared with the control group (P <.001) and gradually increased at 2 and 4 weeks after clip removal. Histological analysis demonstrated increased cellularity and disorganized collagen fibers in the SST, with higher modified Bonar scores at 4 weeks, followed by gradual improvement after clip removal. The IHH-positive area and PTCH1- and GLI1-positive cell percentages significantly increased after 4 weeks of clip impingement (20.64% vs 2.06%, P <.001; 53.9% vs 28.03%, P =.016; and 30% vs 12.19%, P =.036, respectively) and continuously increased after clip removal. Conclusion: The authors' findings suggest that the hedgehog signaling pathway and its downstream signaling mediator and target GLI1 may play a role in the development and healing process of rotator cuff tendinopathy due to extrinsic rotator cuff impingement. Clinical Relevance: This study suggests the potential for the hedgehog pathway, together with its downstream targets, as candidates for further study as potential therapeutic targets in the treatment of supraspinatus tendinopathy. [ABSTRACT FROM AUTHOR]