An anteromedial stabilization procedure has the most protective effect on the anterior cruciate ligament in tibial external rotation. A human knee model study.

INTRODUCTION: Anterior cruciate ligament (ACL) reconstruction remains associated with the risk of re-rupture and persisting rotational instability. Additional extraarticular anterolateral stabilization procedures stabilize the tibial internal rotation and lead to lower ACL failure rate and improved knee stability. However, data for additional stabilization of tibial external rotation is lacking and the importance of an anteromedial stabilization procedure is less well evaluated. Aim of this study is to investigate the influence of an extraarticular anteromedial stabilization procedure for the stabilization of the tibial external rotation and protection of the ACL from these rotational forces. METHODS: Internal and external rotations of the tibia were applied to a finite element (FE) model with anatomical ACL, posterior cruciate ligament (PCL), lateral collateral ligament (LCL), medial collateral ligament (MCL) and intact medial and lateral meniscus. Five additional anatomic structures (Anteromedial stabilization/anteromedial ligament, AML, augmented superficial medial collateral ligament, sMCL, posterior oblique ligament, POL, anterolateral ligament, ALL, and popliteal tendon, PLT) were added to the FE model separately and then combined. The force histories within all structures were measured and determined for each case. RESULTS: The anteromedial stabilization or imaginary AML was the main secondary stabilizer of tibial external rotation (90% of overall ACL force reduction). The AML reduced the load on the ACL by 9% in tibial external rotation which could not be achieved by an augmented sMCL (-1%). The AML had no influence in tibial internal rotation (-1%). In the combined measurements with all additional structures (AML, ALL, PLT, POL) the load on the ACL was reduced by 10% in tibial external rotation. CONCLUSION: This study showed that an additional anteromedial stabilization procedure secures the tibial external rotation and has the most protective effect on the ACL during these external rotational forces.

Long-term results of arthroscopic capsulolabral revision repair for failed anterior shoulder instability repair using suture anchors at a minimum of 10 years follow-up.

INTRODUCTION: Arthroscopic revision anterior shoulder instability repair has been proposed, and early clinical results have been promising. However, long-term results after this procedure and the probable risk factors for failure have not been sufficiently discussed in the literature. MATERIALS AND METHODS: Thirty-eight patients who were diagnosed with recurrent anteroinferior shoulder instability after failed Bankart repair, treated with ACRR between September 1998 and November 2003 and able to be contacted were included. Of these patients, 2 were excluded from the study due to the use of SureTak anchors for fixation, and 5 other patients refused to participate in the study due to lack of interest (3 patients) or lack of time (2 patients). The remaining shoulders were clinically examined at a minimum of ten years after surgery via the ASES, Constant, AAOS, Rowe, Dawson and VAS scores for pain and stability. Degenerative arthropathy was assessed with the modified Samilson-Prieto score. RESULTS: All 31 remaining shoulders were evaluated at a mean time of 11.86 years (142.4 months) after surgery. Six patients (19.35%) reported redisolcation after the revision procedure, 4 of whom were affected by a new significant shoulder trauma. The ROWE and Constant scores improved significantly. Moderate to severe dislocation arthropathy was observed in 19.4% of patients. Five patients (16.2%) were not satisfied with the procedure. CONCLUSION: Long-term follow-up after ACRR shows predictable results, with a high degree of patient satisfaction, good to excellent patient-reported outcome scores and minimal radiological degenerative changes. However, with an average recurrence rate of 19.3% after 11.86 years, the redislocation rate appears high. With careful patient selection, recurrence rates can be significantly reduced.

The lack of retropatellar resurfacing at index surgery is significantly associated with failure in patients following patellofemoral inlay arthroplasty: a multi-center study of more than 260 patients.

PURPOSE: To evaluate the clinical outcomes of patients with a minimum 2-year follow-up following contemporary patellofemoral inlay arthroplasty (PFIA) and to identify potential risk factors for failure in a multi-center study. METHODS: All patients who underwent implantation of PFIA between 09/2009 and 11/2016 at 11 specialized orthopedic referral centers were enrolled in the study and were evaluated retrospectively at a minimum 2-year follow-up. Clinical outcomes included the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, the Knee Injury and Osteoarthritis Outcome Score (KOOS), the Tegner Scale, the visual analogue scale (VAS) for pain, and subjective patient satisfaction. Pre- and perioperative risk factors were compared among failures and non-failures to determine potential risk factors. RESULTS: A total of 263 patients (85% follow-up rate) could be enrolled. The mean age at the time of index surgery was 49 ± 12 years with a mean postoperative follow-up of 45 ± 18 months. The overall failure rate was 11% (28 patients), of which 18% (5 patients) were patients with patella resurfacing at index surgery and 82% (23 patients) were patients without initial patella resurfacing. At final follow-up, 93% of the patients who did not fail were satisfied with the procedure with a mean transformed WOMAC Score of 84.5 ± 14.5 points, a mean KOOS Score of 73.3 ± 17.1 points, a mean Tegner Score of 3.4 ± 1.4 points and a mean VAS pain of 2.4 ± 2.0 points. An increased BMI was significantly correlated with a worse postoperative outcome. Concomitant procedures addressing patellofemoral instability or malalignment, the lack of patellofemoral resurfacing at the index surgery and a high BMI were significantly correlated with failure in our patient cohort. CONCLUSION: Patellofemoral inlay arthroplasty shows high patient satisfaction with good functional outcomes at short-term follow-up and thus can be considered a viable treatment option in young patients suffering from isolated patellofemoral arthritis. Patellar resurfacing at index surgery is recommended to decrease the risk of failure. LEVEL OF EVIDENCE: Retrospective case series, Level IV.

Assessment of popliteal neurovascular safety during all-inside suturing of the posterior horn of the lateral meniscus using Upright MRIs of the knee joint.

BACKGROUND: To examine the risk of injury to the popliteal neurovascular bundle (pNVB) during all-inside repair of the posterior horn of the lateral meniscus (PHLM) using Upright-MRIs. METHODS: Upright-MRIs of 61 knees in extension (ext) and 90°-flexion (flex) were included. Distance D from the PHLM to the pNVB was compared between extended and 90°-flexed position, subgroups with/without joint-effusion and evaluated according to demographics. Portal safety was assessed simulating suturing of the PHLM via four arthroscopy portals. Distance d (shortest space from the simulated suturing-device trajectory lines to the pNVB) was compared among portals in increasing distances from the posterior cruciate ligament (PCL). RESULTS: D is longer in flex (17.3 ± 6.0 mm) than in ext (11.3 ± 4.2 mm, p < 0.0001). MRIs with joint-effusion displayed longer values of D than scans without joint-effusion (flex: 20.4 ± 7.1 mm vs. 16.1 ± 5.2 mm, p = 0.012). Shorter distances are associated with female gender, lower body weight and lower BMI. At 0 mm from the PCL, the 1 cm-lateral portal was the safest (p < 0.0001) whereas at 3 mm/6mm/9mm/12 mm the 1 cm-medial portal showed the longest d values (p < 0.0001 each). CONCLUSION: All-inside suturing of the PHLM is safer in 90°-flexion, in presence of intraarticular fluid and in male patients with increasing weight/BMI. Sutures of the PHLM at 0 mm from the PCL are safer from a 1 cm-lateral portal whereas for tears located ≥ 3 mm from the PCL a 1 cm-medial portal involves a lower neurovascular risk. Upright-MRI proves excellent for preoperative planning to minimize neurovascular risks.

[Cartilage repair procedures for early osteoarthritis]. / Stellenwert der chirurgischen Knorpeltherapie bei Früharthrose.

BACKGROUND: Commonly used cartilage repair procedures have been established for focal cartilage lesions; however, degenerative lesions with accompanying changes of other intraarticular structures are much more common in clinical practice. This stage, in which classic radiological signs of osteoarthritis are absent, is called early osteoarthritis and is characterized by impaired joint homeostasis with biomechanical and biochemical changes that can have a negative effect on regenerative cartilage therapy procedures. INDICATION: Cartilage repair procedures are indicated for symptomatic focal early osteoarthritis, defined as cartilage degeneration ICRS grades I or II around a focal cartilage defect ICRS grades III or IV. In more advanced osteoarthritis with significant narrowing of the joint space, cartilage repair procedures are generally contraindicated. THERAPY: The most studied cartilage repair procedure for early osteoarthritis is autologous chondrocyte implantation, which has shown acceptable results in case series, although higher failure rates are to be expected compared to focal, traumatic cartilage lesions. The use of bone marrow-stimulating techniques seems to be limited in early osteoarthritis and should only be used in cases of lesion < 2 cm2 and very little surrounding cartilage degeneration. Concomitant surgical procedures, especially unloading osteotomies, are very important.

All-Arthroscopic Hydrogel-Based Autologous Chondrocyte Transplantation in the Knee Joint: Good Clinical and Magnetic Resonance Imaging Outcome After 24 Months.

PURPOSE: To evaluate subjective and objective clinical and magnetic resonance imaging-based radiologic outcomes after short-term follow-up in patients with focal full-size cartilage lesions of the knee joint treated with all-arthroscopic hydrogel-based autologous chondrocyte transplantation. METHODS: A retrospective study on patients with isolated focal cartilage defects of the knee joint who were treated with arthroscopically conducted matrix-induced autologous chondrocyte transplantation was performed. Clinical scores were assessed at baseline and final follow-up using the Tegner Score, visual analog scale, the International Knee Documentation Committee, and the 5 subscales of the Knee Injury and Osteoarthritis Outcome Score. Magnetic resonance imaging scans of the treated knee joints were evaluated with the updated MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue) 2.0 scoring system at follow-up. RESULTS: Twenty-nine consecutive patients were included in the study. Mean time to follow-up was 24.9 ± 1.1 months. Average visual analog scale decreased significantly from 6.5 ± 3.1 preoperatively to 2.3 ± 1.6 at follow-up (P < .0001). Tegner score increased from 3.1 ± 1.3 to 4.3 ± 1.2 (P < .0001) and the International Knee Documentation Committee from 43.8 ± 21.9 to 64.9 ± 18.9 (P < .0001). Also, all Knee Injury and Osteoarthritis Outcome Score subscales displayed significant improvements. Patients showed similar improvements of nearly all clinical scores independent of the defect size. Average MOCART2.0 score was 70.0 ± 13.6 and 20 patients scored ≥70 points. All 8 patients with large defects (>5 cm2) scored ≥75 points. CONCLUSIONS: In this small study, injectable matrix-induced autologous chondrocyte transplantation therapy in the knee joint led to favourable clinical and radiologic short-term results with significant improvements in all clinical scores and MOCART2.0 scores, confirming morphologic integrity of the transplanted chondrocytes. Therefore, this minimally invasive procedure represents a promising operative technique for cartilage regeneration, even for large-diameter lesions. LEVEL OF EVIDENCE: IV, therapeutic case series.

Predictors for an unsuccessful conservative treatment of patients with medial patellar plica syndrome.

INTRODUCTION: In several cases persistent medial knee pain remains after conservative treatment in patients with medial patellar plica syndrome. In recent literature accepted criteria for surgical indication are lacking. In this retrospective study patients after conservative treatment were evaluated to identify predictors for an unsuccessful outcome. MATERIALS AND METHODS: 117 Patients with medial patellar plica syndrome between 2016 and 2019 were retrospectively evaluated. All patients received conservative treatment for three months. Surgery was indicated due to failed conservative treatment (n = 76) with persistent medial knee pain and restriction of activity after 3 months. Preoperative MRI analysis, Lysholm score, pain by the visual analog scale (VAS), postoperative sports participation (RTS) and Tegner activity score were collected at least 12 months after definite treatment. Statistical analysis was performed to evaluate differences between patients with successful and unsuccessful conservative treatment. RESULTS: There were significant differences in the clinical and radiological findings between patients with successful and unsuccessful conservative treatment. Patients with failed conservative treatment showed a significant larger diameter of the medial patellar plica (0.8 ± 0.3 mm vs. 1.6 ± 0.4 mm; p < 0.05) and a significant higher rate of contact of the plica to the adjacent cartilage. Furthermore, these patients reported a significant higher rate of medial knee pain from flexion to extension and snapping symptoms. At final follow-up the patient-reported outcome by means of Lysholm score (96.25 vs. 95.93), RTS (96.2% vs. 97%) and Tegner activity score (6.0 vs. 6.01) was excellent after conservative and surgical treatment. There were no statistical differences in the preoperative and postoperative outcomes between both. CONCLUSIONS: The diameter of a medial patellar plica and contact of the plica to the retropatellar cartilage as well as clinical signs like persistent medial knee pain from flexion to extension with snapping symptoms might be predictors for an unsuccessful conservative treatment and the need for surgical intervention in patients with painful medial patellar plica syndrome.

Autologous Chondrocyte Transplantation in Femoroacetabular Impingement Syndrome: Growth and Redifferentiation Potential of Chondrocytes Harvested from the Femur in Cam-Type Deformities.

OBJECTIVE: Cam-type femoroacetabular impingement (FAI) syndrome is one of the most frequent reasons for cartilage damage in the hip. Autologous chondrocyte transplantation has proven high success rates in the treatment of focal chondral defects; however, harvesting of chondrocytes in the hip has been reported but not specifically from the region of femoral cam lesions. Therefore, the goal of this study was to analyze the growth and redifferentiation potential of cartilage samples harvested from the cam deformities in patients with FAI. DESIGN: Cartilage samples were gained from 15 patients with cam-type FAI undergoing arthroscopic femoral cam resection. Healthy (hyaline cartilage of the hip and knee joint, n = 12) and arthritic control groups (degenerative changes in cartilage of the hip joint, n = 8) were also analyzed. Chondrocytes were initially cultured under monolayer, and subsequently under pellet conditions. A comparative representation of the groups was performed by Mankin score classification, immunohistochemistry (IHC) (Col1, Col2, aggrecan), and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) (Col1, Col2, Col10, Sox9, RunX2). RESULTS: Mankin score of FAI-samples (4.1±3.1, Range 0-10) showed a wide variation but was significant lower (P = 0.0244) when compared with the arthritic control (7.5 ± 2.7, range 4-12). IHC showed an increased deposition of Col2 (P = 0.0002) and aggrecan (P = 0.0261) after pellet culture compared with deposition after monolayer culture in all groups. In qRT-PCR, FAI samples showed after pellet culture increased Col2 (P = 0.0050) and Col10 expression (P = 0.0006) and also Mankin score correlated increasing gene-expression of Col10 (r = 0.8108, P = 0.0341) and RunX2 (r = 0.8829, P = 0.123). CONCLUSIONS: Cartilage samples of patients with cam-type FAI showed sufficient but heterogeneous composition relating to histological quality and chondrogenic potential. However, harvesting of chondrocytes from the cam lesion might be a valid option especially if a cartilage lesion is noted in a diagnostic arthroscopy and individual preexisting stage of cartilage degeneration and appropriate pellet-culturing conditions are considered.

Effects of focal metallic implants on opposing cartilage - an in-vitro study with an abrasion test machine.

BACKGROUND: For focal cartilage defects, biological repair might be ineffective in patients over 45 years. A focal metallic implant (FMI) (Hemi-CAP Arthrosurface Inc., Franklin, MA, USA) was designed to reduce symptoms. The aim of this study was to evaluate the effects of a FMI on the opposing tibial cartilage in a biomechanical set-up. It is hypothesized that a FMI would not damage the opposing cartilage under physiological loading conditions. METHODS: An abrasion machine was used to test the effects of cyclic loading on osteochondral plugs. The machine applied a compressive load of 33 N and sheared the samples 10 mm in the anteroposterior direction by 1 Hz. Tibial osteochondral plugs from porcine knees were placed in opposition to a FMI and cycled for 1 or 6 h. After testing each plug was fixed, stained and evaluated for cartilage damage. RESULTS: After 1 h of loading (n = 6), none of the osteochondral plugs showed histologic signs of degradation. After 6 h of loading (n = 6) three samples had histologic signs of injury in the tangential zone (grade 1) and one had signs of injury in the transitional and deep zones (grade 2). Exploration for 6 h resulted in significant more cartilage damage compared to the shorter exploration time (p = 0.06). However, no significant difference between saline and hyaluronic acid was evident (p = 0.55). CONCLUSION: Under physiologic loading conditions, contact with a FMI leads to cartilage damage in the opposing articular cartilage in six hours. In clinical practice, a thorough analysis of pre-existing defects on the opposing cartilage is recommended when FMI is considered.

The Forced Active Buckling Sign: A New Clinical Test for the Diagnosis of ACL Insufficiency.

Although insufficiency of the anterior cruciate ligament (ACL) is a frequent result of an injury, validated tests are associated with unsatisfying validity. Moreover, some of these tests are not easy to perform and patient's muscular resistance often limits their reliability. Therefore, with this study, we want to design an accurate test to diagnose an ACL insufficiency, which is independent of the assessor's skills and overcome any muscular resistance. Fifty patients with an isolated ACL rupture (group A; age 26.4 years ± 14.9 standard deviation [SD]; female, n = 15) and additional 50 patients with an intact ACL but meniscal lesions (group B; age 45.4 years ± 12.9 SD; female, n = 23) were consecutively included in this study. The integrity of the ACL and the menisci were evaluated by magnetic resonance imaging and verified arthroscopically. Two orthopaedic surgeons performed a pivot shift test, a Lachman's test, and our new "forced active buckling" (FAB)-sign test in all patients. The surgeons were blinded for the pathology of the knee and we randomized the tests for each patient and examiner. The sensitivity, specificity, positive predictive value, negative predictive value, and positive and negative likelihood ratios with confidence intervals were calculated and compared. With a prevalence of 0.5, the FAB-sign test revealed the best overall sensitivity of 0.78 compared with the Lachman's and pivot shift tests of 0.74 and 0.46, respectively. Also, the overall specificity of the FAB-sign test of 0.95 was higher than the Lachman's test of 0.83, however, comparable to the pivot shift test of 0.96. The FAB-sign test demonstrated the best positive and negative predictive values of 0.94 and 0.81. There was no significant difference between the two examiners concerning the accuracy of results in each test (p = 0.83). This study shows that the introduced FAB-sign test can detect an ACL insufficiency more sensitive and more specific compared to the pivot shift and Lachman's tests in the subacute phase. This is a randomized controlled diagnostic study, level 1b.

Isolated Medial Patellofemoral Ligament Reconstruction Can Be an Effective Procedure in Patellofemoral Instability with Risk Factors.

Patellofemoral instability is a severe problem in young and active patients. This pathology is influenced by ligamentous, bony, and neuromuscular parameters. The reconstruction of the medial patellofemoral ligament (MPFL) evolved to a primary procedure, but combined procedures were more frequently performed in the past years. However, additional operative procedures are associated with increased morbidity and no absolute indication can be identified in the literature. This study is intended to clarify whether addressing only ligamentous influence factors (MPFL) in chronic patellofemoral instability is sufficient to produce good clinical outcomes, or whether other risk factors influence the results negatively and should also be treated at some point. In 52 patients with chronic patellofemoral instability patellar height according to Caton-Deschamps, trochlear dysplasia according to Dejour, the leg axis, the femoral antetorsion, tibial tubercle (TT)-trochlear groove, and TT-posterior cruciate ligament distance were evaluated. All patients were treated with isolated MPFL reconstruction. After a minimum follow-up period of 24 months (24-36 months), the clinical outcome results were calculated using the scoring system according to Lysholm and Tegner. Correlation between clinical outcome scores and anatomic risk factors were calculated. The analysis was performed using a standard statistical software package (JMP version 12, SAS Institute, Cary, NC). The average postoperative Lysholm score increased significantly from 57.23 ± 19.9 to 85.9 ± 17.2 points (p < 0.0001) after isolated MPFL reconstruction. Moreover, the Tegner and Lysholm scores significantly improved both in patients without and with different risk factors postoperative. There were no significant differences in the outcome sores between the groups. Even the degree of trochlear dysplasia (types I-III) did not influence the results. Finally, there was no significant correlation found between all collected risk factors and the postoperative outcome scores. Isolated MPFL reconstruction can be an effective procedure in patients with patellofemoral instability and mild to moderate risk factors.

Bifunctional Labeling of Rabbit Mesenchymal Stem Cells for MR Imaging and Fluorescence Microscopy.

PURPOSE: Longitudinal imaging studies are important in the translational process of stem cell-based therapies. Small animal imaging models are widely available and practical but insufficiently depict important morphologic detail. In contrary, large animal models are logistically challenging and costly but offer greater imaging quality. In order to combine the advantages of both, we developed an intermediate-sized rabbit animal model for cartilage imaging studies. PROCEDURES: Rabbit mesenchymal stem cells (rMSC) were isolated as primary cultures from the bone marrow of New Zealand white rabbits. rMSC were subsequentially transduced lentivirally with eGFP and magnetically labeled with the iron oxide ferucarbotran. eGFP expression was evaluated by flow cytometry and iron uptake was analyzed by isotope dilution mass spectrometry and Prussian blue staining. Fluorescence microscopy of eGFP-transduced rMSC was performed. Viability and induction of apoptosis were assessed by XTT and caspase-3/-7 measurements. The chondrogenic potential of labeled cells was quantified by glycosaminoglycan contents in TGF-ß3 induced pellet cultures. Labeled and unlabeled cells underwent magnetic resonance imaging (MRI) at 1.5 T before and after differentiation using T1-, T2-, and T2*-weighted pulse sequences. Relaxation rates were calculated. rMSCs were implanted in fibrin clots in osteochondral defects of cadaveric rabbit knees and imaged by 7 T MRI. T2* maps were calculated. Statistical analyses were performed using multiple regression models. RESULTS: Efficiency of lentiviral transduction was greater than 90 %. Fluorescence signal was dose dependent. Cellular iron uptake was significant for all concentrations (p < 0.05) and dose dependent (3.3-56.5 pg Fe/cell). Labeled rMSC showed a strong, dose-dependent contrast on all MR pulse sequences and a significant decrease in T2 and T2* relaxation rates. Compared with non-transduced or unlabeled controls, there were no adverse effects on cell viability, rate of apoptosis, or chondrogenic differentiation. MRI of labeled rMSCs in osteochondral defects showed a significant signal of the transplant with additional high-resolution anatomical information. CONCLUSIONS: This intermediate-sized rabbit model and its bifunctional labeling technique allow for improved depiction of anatomic detail for noninvasive in vivo rMSC tracking with MRI and for immunohistological correlation by fluorescence microscopy.

Arthroscopic Meniscopexy for the Treatment of Nontraumatic Osteochondritis Dissecans in the Knee Joint of Adult Patients.

OBJECTIVE: The etiology of osteochondritis dissecans (OCD) is still uncertain. Recently, it has been hypothesized that instability of the anterior horn of the meniscus is an important cause for the development of a nontraumatic OCD in adolescents with good results after surgical stabilization. This case series aims to evaluate the treatment results after meniscus stabilization in adults with nontraumatic OCD. DESIGN: Ten patients with magnetic resonance imaging (MRI)-confirmed OCD of the knee joint, meniscal instability, and closed epiphyseal plates were enrolled in this study. The instable meniscus was stabilized by direct suturing of the anterior horn of the meniscus. MRI examinations were performed preoperative and 6 and 12 months postoperative. The OCD was classified arthroscopically according to Guhl and according to Hughes in the MRI. The overall knee function was evaluated by the Lysholm score before treatment and 12 months postoperative. RESULTS: Four women and 6 men with a mean age of 20.6 ± 1.9 years were included in this study. Preoperatively 60% of the patients showed a grade II or III lesion arthroscopically and 70% a grade III or IVa lesion in the MRI examination. After arthroscopic meniscus stabilization the Lysholm score increased in average from 48.1 ± 14.12 before treatment to 97.5 ± 3.1 postoperative. At final follow-up after 12 months, an improvement of the OCD in the MRI could be demonstrated in all patients (100%). In 80% of the patients a complete healing of the OCD could be noted. CONCLUSION: The clinical concept of an instable anterior horn of the meniscus as a cause for the development of a nontraumatic OCD seems to be transferable to adults and arthroscopic stabilization can lead to a sufficient healing of this knee pathology.

Influence of Sutures on Cartilage Integrity: Do Meniscus Sutures Harm Cartilage? An Experimental Animal Study.

PURPOSE: To evaluate whether different suture materials in meniscal repair may harm cartilage. METHODS: A preloaded linear friction testing setup including porcine knees with porcine cartilage, porcine meniscus, and different suture materials (braided nonabsorbable, absorbable monofilament) was used. Five groups with different tribological pairs were tested: cartilage on meniscus (control), cartilage on cartilage (control No. 2), and cartilage on different meniscus sutures (3 groups). Cartilage integrity was analyzed macroscopically by the India ink method and histologically using Giemsa-eosin-stained undecalcified methyl methacrylate sections. Cartilage lesions were classified by using a quantitative scoring system. RESULTS: The control groups did not show cartilage damage, either macroscopically or histologically. Loading cartilage with sutured menisci led to significant damage of the superficial radial and transitional zones with braided nonabsorbable (P = .03) and absorbable monofilament (P = .02) sutures at final examination. Menisci sutured with braided nonabsorbable material resulted in deeper damage to the cartilage. However, there were no significant differences between the suture materials. Sutures oriented perpendicular to surface motion led to a larger defect than parallel-oriented sutures. CONCLUSIONS: Braided nonabsorbable and absorbable monofilament suture materials cause significant damage to cartilage during long-term cyclic loading in vitro. The extent of damage depends on suture orientation. CLINICAL RELEVANCE: This study provides data on the extent to which different suture materials in meniscus repair may harm cartilage.

Chemically Modified Messenger RNA: Modified RNA Application for Treatment of Achilles Tendon Defects.

Different regenerative medicine approaches for tendon healing exist. Recently, especially gene therapy gained popularity. However, potential mutagenic and immunologic effects might prevent its translation to clinical research. Chemically modified mRNA (cmRNA) might bypass these limitations of gene therapy. Therefore, the purpose of this study was to evaluate the early healing properties of Achilles tendon defects in rats treated with basic fibroblast growth factor (bFGF) cmRNA. Forty male Lewis rats were used for the study and randomly assigned to two study groups: (1) treatment with cmRNA coding for bFGF and (2) noncoding cmRNA control. Protein expression was measured using in vivo bioluminescence imaging at 24, 48, and 72 h, as well as 14 days. Animals were euthanized 2 weeks following surgery. Biomechanical, histological, and immunohistological analyses were performed with the significance level set at p < 0.05. Protein expression was evident for 3 days. At 14 days, bioluminescence imaging revealed only little protein expression. Biomechanically, tendons treated with bFGF cmRNA showed a construct stiffness closer to the healthy contralateral side when compared with the control group (p = 0.034), without any significant differences in terms of load to failure. Hematoxylin and eosin staining detected no side effects of the treatment, as signs of inflammation, or necrosis. Furthermore, it revealed the shape of the nuclei to be more oval in the bFGF group in the tendon midsubstance (p = 0.043) with a reduced cell count (p = 0.035). Immunohistological staining for type I, II, III, and IV collagen did not differ significantly between the two groups. In conclusion, this pilot study demonstrates the feasibility of a novel messenger RNA (mRNA)-based therapy for Achilles tendon defects using chemically modified mRNA coding for bFGF.

Rapid determination of binding parameters of chitin binding domains using chitin-coated quartz crystal microbalance sensor chips.

Chitin present in fungal cell walls has been considered as a diagnostic polymer for the detection of fungal infections. Chitin staining can be achieved with different dyes such as Calcofluor white or Congo red, but these methods have not entered into clinical routine diagnosis due to problems with sensitivity and specificity. More accurate detection can be achieved using chitin binding domains (CBDs) from a large variety of naturally occurring proteins that specifically interact with chitin. The chitin binding properties of most of these proteins have not yet been determined, because chitin is an insoluble fibrillar material rendering accurate determination of chitin binding kinetics challenging. Here we report a quartz crystal microbalance with dissipation monitoring (QCM-D) based method to determine binding constants of CBDs on chitin-coated gold surfaces. For this purpose, chitin was trimethylsilylated and coated onto the sensor chips. After desilylation, regular fibril-like structures with a typical center-to-center spacing of 85 nm were observed by atomic force microscopy. Using different experimental conditions and data evaluation methods for QCM-D measurements, we determined kon and koff and calculated the KD values for binding of a recombinant CBD from Bacillus circulans chitinase A1. Depending on the evaluation method, the KD values ranged between 0.6 and 2.5 µM. The obtained KD values were in good agreement with those measured for other bacterial CBDs usually ranging between 1 to 10 µM. Hence, we propose that the experimental approach developed in this study can be applied to determine yet unknown binding affinities of various CBDs from different origin.

Langmuir Analysis of the Binding Affinity and Kinetics for Surface Tethered Duplex DNA and a Ligand-Apoprotein Complex.

In this work, the hybridization and dehybridization of ssDNA with 20 bases at gold coated sensor surfaces modified with complementary 20 bases capture probe ssDNA was investigated at 18 °C by quartz crystal microbalance measurements with dissipation monitoring (QCM-D). A sequence of 20 base pairs with a melting temperature of about 64 °C was chosen, since in many biosensor studies the target molecules are DNA or RNA oligomers of similar length. It turned out that at the applied experimental conditions the DNA hybridization was irreversible, and therefore the hybridization and dehybridization process could not be described by the Langmuir model of adsorption. Nevertheless, quantitative dehybridization could be achieved by rinsing the sensor surface thoroughly with pure water. When in contrast the hybridization of a target with only 10 bases complementary to the outermost 10 bases of the 20 bases capture probe was studied, binding and unbinding were reversible, and the hybridization/dehybridization process could be satisfactorily described by the Langmuir model. For the 10 base pair sequence, the melting temperature was about 36 °C. Apparently, for Langmuir behavior, it is important that the experiments are applied at a temperature sufficiently close to the melting temperature of the sequence under investigation to ensure that at least traces of the target molecules are unhybridized (i.e., there needs to be an equilibrium between hybridized and dehybridized target molecules). To validate the reliability of our experimental approach we also studied the reconstitution and disassembly of the flavoprotein dodecin at flavin-terminated DNA monolayers, as according to previous studies it is assumed that the apododecin-flavin system can be well described by the Langmuir model. As a result, this assumption could be verified. Using three different approaches, KD values were obtained that differ not more than by a factor of 4.

Flavin Storage and Sequestration by Mycobacterium tuberculosis Dodecin.

Dodecins are small flavin binding proteins occurring in archaea and bacteria. They are remarkable for binding dimers of flavins with their functional relevant aromatic isoalloxazine rings deeply covered. Bacterial dodecins are widely spread and found in a large variety of pathogens, among them Pseudomonas aeruginosa, Streptococcus pneumonia, Ralstonia solanacearum, and Mycobacterium tuberculosis ( M. tuberculosis). In this work, we seek to understand the function of dodecins from M. tuberculosis dodecin. We describe flavin binding in thermodynamic and kinetic properties and achieve mechanistic insight in dodecin function by applying spectroscopic and electrochemical methods. Intriguingly, we reveal a significant pH dependence in the affinity and specificity of flavin binding. Our data give insight in M. tuberculosis dodecin function and advance the current understanding of dodecins as flavin storage and sequestering proteins. We suggest that the dodecin in M. tuberculosis may specifically be important for flavin homeostasis during the elaborate lifestyle of this organism, which calls for the evaluation of this protein as drug target.

Detection of intramyocardially injected DiR-labeled mesenchymal stem cells by optical and optoacoustic tomography.

The distribution of intramyocardially injected rabbit MSCs, labeled with the near-infrared dye 1,1'-dioctadecyl-3,3,3',3'-tetramethylindotricarbo-cyanine-iodide (DiR) using hybrid Fluorescence Molecular Tomography-X-ray Computed Tomography (FMT-XCT) and Multispectral Optoacoustic Tomography (MSOT) imaging technologies, was investigated. Viability and induction of apoptosis of DiR labeled MSCs were assessed by XTT- and Caspase-3/-7-testing in vitro. 2 × 106, 2 × 105 and 2 × 104 MSCs labeled with 5 and 10 µg DiR/ml were injected into fresh frozen rabbit hearts. FMT-XCT, MSOT and fluorescence cryosection imaging were performed. Concentrations up to 10 µg DiR/ml did not cause apoptosis in vitro (p > 0.05). FMT and MSOT imaging of labeled MSCs led to a strong signal. The imaging modalities highlighted a difference in cell distribution and concentration correlated to the number of injected cells. Ex-vivo cryosectioning confirmed the molecular fluorescence signal. FMT and MSOT are sensitive imaging techniques offering high-anatomic resolution in terms of detection and distribution of intramyocardially injected stem cells in a rabbit model.

Results of Arthroscopic Bankart Repair for Anterior-Inferior Shoulder Instability at 13-Year Follow-up.

BACKGROUND: Anterior-inferior shoulder instability is a common injury in young patients, particularly those practicing overhead-throwing sports. Long-term results after open procedures are well studied and evaluated. However, the long-term results after arthroscopic repair and risk factors of recurrence require further assessment. HYPOTHESIS: Arthroscopic Bankart repair results are comparable with those of open repair as described in the literature. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: A total of 180 shoulders with anterior-inferior shoulder instability were stabilized arthroscopically, met the inclusion criteria and the patients were able to be contacted at a minimum of 10-year follow-up. Of these patients, 143 agreed to participate in the study. Assessment was performed clinically in 104 patients using the American Shoulder and Elbow Surgeons score, Constant score, American Academy of Orthopaedic Surgeons score, Rowe score, and the Dawson 12-item questionnaire. The Samilson-Prieto score was used to assess degenerative arthropathy in radiographs available for 100 shoulders. Additionally, 15 patients participated through a specific questionnaire and 24 patients through a telephone survey. RESULTS: The overall redislocation rate was 18.18%. Redislocation rates for the different types of fixation devices were as follows: FASTak/Bio-FASTak, 15.1% (17/112); SureTac, 26.3% (5/19); and Panalok, 33.3% (4/12). Concomitant superior labral anterior-posterior repair had no effect on clinical outcome. Redislocation rate was significantly affected by the patient's age and duration of postoperative rehabilitation. Redislocation rate tended to be higher if there had been more than 1 dislocation preoperatively ( P = .098). Severe dislocation arthropathy was observed in 12% of patients, and degenerative changes were significantly correlated with the number of preoperative dislocations, patient age, and number of anchors. The patient satisfaction rate was 92.3%, and return to the preinjury sport level was possible in 49.5%. CONCLUSION: Clinical outcome at a mean follow-up of 13 years after arthroscopic repair of anterior-inferior shoulder instability is comparable with the reported results of open Bankart repair in the literature and allows management of concomitant lesions arthroscopically. Modifiable risk factors of postoperative redislocation and arthropathy must be considered. Stabilization after the first-time dislocation achieves better clinical and radiological outcomes than after multiple dislocations.