Aggrecan: a new biomarker for acute type A aortic dissection.

Acute type A aortic dissection (ATAAD) constitutes a life-threatening aortic pathology with significant morbidity and mortality. Without surgical intervention the usual mortality rate averages between 1 and 2% per hour. Thus, an early diagnosis of ATAAD is of pivotal importance to direct the affected patients to the appropriate treatment. Preceding tests to find an appropriate biomarker showed among others an increased aggrecan (ACAN) mRNA expression in aortic tissue of ATAAD patients. As a consequence, we investigated whether ACAN is a potential biomarker for diagnosing ATAAD. Mean ACAN protein concentration showed a significantly higher plasma concentration in ATAAD patients (38.59 ng/mL, n = 33) compared to plasma of patients with thoracic aortic aneurysms (4.45 ng/mL, n = 13), patients with myocardial infarction (11.77 ng/mL, n = 18) and healthy volunteers (8.05 ng/mL, n = 12). Cardiac enzymes like creatine kinase MB and cardiac troponin T showed no correlation with ACAN levels in ATAAD patients. Receiver-operator characteristics (ROC) curve analysis for ATAAD patients versus control subjects an optimum discrimination limit of ACAN plasma levels at 14.3 ng/mL with a corresponding sensitivity of 97% and specificity of 81%. According to our findings ACAN is a reliable potential biomarker in plasma samples to detect ATAAD with high sensitivity and specificity.

Reactivation of the Nkx2.5 cardiac enhancer after myocardial infarction does not presage myogenesis.

Aims: The contribution of resident stem or progenitor cells to cardiomyocyte renewal after injury in adult mammalian hearts remains a matter of considerable debate. We evaluated a cell population in the adult mouse heart induced by myocardial infarction (MI) and characterized by an activated Nkx2.5 enhancer element that is specific for multipotent cardiac progenitor cells (CPCs) during embryonic development. We hypothesized that these MI-induced cells (MICs) harbour cardiomyogenic properties similar to their embryonic counterparts. Methods and results: MICs reside in the heart and mainly localize to the infarction area and border zone. Interestingly, gene expression profiling of purified MICs 1 week after infarction revealed increased expression of stem cell markers and embryonic cardiac transcription factors (TFs) in these cells as compared to the non-mycoyte cell fraction of adult hearts. A subsequent global transcriptome comparison with embryonic CPCs and fibroblasts and in vitro culture of MICs unveiled that (myo-)fibroblastic features predominated and that cardiac TFs were only expressed at background levels. Conclusions: Adult injury-induced reactivation of a cardiac-specific Nkx2.5 enhancer element known to specifically mark myocardial progenitor cells during embryonic development does not reflect hypothesized embryonic cardiomyogenic properties. Our data suggest a decreasing plasticity of cardiac progenitor (-like) cell populations with increasing age. A re-expression of embryonic, stem or progenitor cell features in the adult heart must be interpreted very carefully with respect to the definition of cardiac resident progenitor cells. Albeit, the abundance of scar formation after cardiac injury suggests a potential to target predestinated activated profibrotic cells to push them towards cardiomyogenic differentiation to improve regeneration.

Development and validation of an improved mechanical thorax for simulating cardiopulmonary resuscitation with adjustable chest stiffness and simulated blood flow.

Investigations of compressive frequency, duty cycle, or waveform during CPR are typically rooted in animal research or computer simulations. Our goal was to generate a mechanical model incorporating alternate stiffness settings and an integrated blood flow system, enabling defined, reproducible comparisons of CPR efficacy. Based on thoracic stiffness data measured in human cadavers, such a model was constructed using valve-controlled pneumatic pistons and an artificial heart. This model offers two realistic levels of chest elasticity, with a blood flow apparatus that reflects compressive depth and waveform changes. We conducted CPR at opposing levels of physiologic stiffness, using a LUCAS device, a motor-driven plunger, and a group of volunteers. In high-stiffness mode, blood flow generated by volunteers was significantly less after just 2min of CPR, whereas flow generated by LUCAS device was superior by comparison. Optimal blood flow was obtained via motor-driven plunger, with trapezoidal waveform.

Impairment of an atrophic mandible by preparation of the implant cavity: a biomechanical study.

An important complication during insertion of implants in atrophic mandibles is the fracture that can be induced by preparation of the cavity. We designed this study to identify which configuration of cavities in the interforaminal region was the least likely to fracture. An electromechanical testing machine was used to measure breaking loads of specifically-designed synthetic models of atrophic mandibles. The implant cavities correlated with the common clinical patterns. Intact atrophied synthetic mandibles broke at a mean (SD) load of 729.48 (59.94) N (control group). Models with four different configurations of cavities fractured as follows: two short, wide cavities (8 x 4.2mm) at a mean (SD) load of 569.17 (67.7) N; two long, thin cavities (15 x2.8mm) at a load of 563.40 (62.0) N; four short, wide cavities (8 x 4.2mm) at a load of 667.01 (71.89) N; and four long, thin cavities (15 x 2.8mm) at a load of 409.50 (43.61) N. Biomechanical findings showed that there was a greater risk of fracture of atrophic mandibular models in long, thin implant cavities with more preparation sites. Each cavity prepared for an implant increased the risk of fracture in an atrophic mandible. The risk of fracture is greatest with long, thin cavities.

Cardiopulmonary resuscitation using electrically driven devices: a review.

In the treatment of sudden cardiac arrest (SCA) immediate resuscitation with chest compressions and ventilation is crucial for survival. As manual resuscitation is associated with several drawbacks, mechanical resuscitation devices have been developed to support resuscitation teams. These devices are able to achieve better perfusion of heart and brain in laboratory settings, but real world experience showed no significant improved survival in comparison to manual resuscitation. This review will focus on two mechanical resuscitation devices, the Lund University Cardiac Assist System (LUCAS) and AutoPulse devices and the actual literature available. In conclusion, the general use of mechanical resuscitation devices cannot be recommended at the moment.

Locking versus nonlocking plates in mandibular reconstruction with fibular graft--a biomechanical ex vivo study.

OBJECTIVES: The main goal of the present study was to compare the biomechanical stability of locking plates and conventional miniplate combinations in human mandibles reconstructed with fibular grafts. MATERIALS AND METHODS: A specially developed and well-proven testing device reproduced the in vivo loading conditions on the mandible. Cadaveric human mandibles (n = 12) reconstructed with harvested human fibular bone grafts were divided into two groups, and different osteosynthesis systems were applied using two lines of plates per osteotomy. On the test apparatus, the specimens were stressed to failure, and interfragmentary movement was monitored and quantified with a contact-free optical measurement system. RESULTS: The relevant interfragmentary movement results from a Euclidean summary calculation which considered all three spatial angles around the axes. Using values up to a maximum load of 300 N, the conventional six-hole miniplates (profile 1.0) had an average value of 7.45° ± 1.46°, and the locking six-hole plates (profile 1.3) had an average value of 12.16° ± 2.37° for rotational interfragmentary movement. The miniplate system exhibited a significantly superior performance in fixation compared to the fixed-angle system (p < 0.05). CONCLUSION: According to these biomechanical experiments, both osteosynthesis devices provided sufficient stabilization at loads of up to 300 N. The six-hole miniplate system provided better stabilization of the osteotomy gap for mandibles reconstructed with fibular grafts. CLINICAL RELEVANCE: The osteosynthesis system is essential for primary stability and the avoidance of pseudarthrosis formation. This study demonstrates that the miniplates provide sufficient stabilization and offers a method to improve fixation in reconstructed mandibles.

Apolipoprotein E genotype, TNF-α 308G/A and risk for cardiac surgery associated-acute kidney injury in Caucasians.

OBJECTIVES: Acute kidney injury following cardiac surgery depicts a severe clinical problem that is strongly associated with adverse short- and long-term outcome. We analyzed two common genetic polymorphisms that have previously been linked to renal failure and inflammation, and have been supposed to be associated with cardiac surgery associated-acute kidney injury (CSA-AKI). METHODS: A total of 1415 consecutive patients who underwent elective cardiac surgery with CPB at our institution were prospectively enrolled. Patients were genotyped for Apolipoprotein E (ApoE E2,E3,E4) (rs429358 and rs7412) and TNF-α-308 G > A (rs1800629). RESULTS: Demographic characteristics and procedural data revealed no significant differences between genotypes. No association between ApoE (E2,E3,E4) and TNF-α-308 G > A genotypes and the RIFLE criteria could be detected. Several multiple linear regression analyses for postoperative creatinine increase revealed highly significant associations for aortic cross clamp time (p < 0.001), CPB-time (p < 0.001), norepinephrine (p < 0.001), left ventricular function (p = 0.004) and blood transfusion (p < 0.001). No associations were found for ApoE (E2,E3,E4) and TNF-α-308 G > A genotypes or baseline creatinine. When the sample size is 1415, the multiple linear regression test of R(2 )= 0 for seven covariates assuming normal distribution will have at least 99% power with significance level 0.05 to detect an R(2) of 0.108 or 0.107 as observed in the data. CONCLUSIONS: ApoE (E2,E3,E4) polymorphism and the TNF-α-308 G > A polymorphism are not associated with renal injury after CPB.

COMT-Val158Met-polymorphism is not a risk factor for acute kidney injury after cardiac surgery.

BACKGROUND: Cardiac surgery-associated acute kidney injury (CSA-AKI) depicts a major complication after cardiac surgery using cardiopulmonary bypass (CPB). OBJECTIVE: CSA-AKI has clearly been linked to increased perioperative morbidity and mortality. Dysregulations of vasomotor tone are assumed to be causal for CSA-AKI. While catechol-O-methyltransferase (COMT) is involved in metabolizing catecholamines, a single-nucleotide polymorphism (SNP) in the COMT gene leads to different enzyme activities according to genotype. Pilot studies found associations between those COMT genotypes and CSA-AKI. METHODS: We prospectively included 1741 patients undergoing elective cardiac surgery using cardiopulmonary bypass (CPB). Patients were genotyped for COMT-Val158Met-(G/A) polymorphism (rs4680). RESULTS: Demographic characteristics and procedural data revealed no significant differences between genotypes. No association between COMT genotypes and the RIFLE criteria could be detected. A multiple linear regression analysis for postoperative creatinine increase revealed highly significant associations for aortic cross-clamp time (P < 0.001), CPB time (P < 0.001), norepinephrine (P < 0.001), and age (P < 0.001). No associations were found for COMT genotypes or baseline creatinine. With an R (2) = 0.39 and a sample size of 1741, the observed power of the regression analysis was >99%. CONCLUSIONS: Based on our results, we can rule out an association between the COMT-Val158Met-(G/A) polymorphism and the appearance of CSA-AKI.

Development of an Exergame for individual rehabilitation of patients with cardiovascular diseases.

An Exergame prototype for improved and patient-adapted rehabilitation was developed. A target heart rate for individual users was defined and tracked using a chest belt. Physical activity was tracked by two 3-axis accelerometers, fixed to both wrists. Dependent on the recorded heart rate and by means of a supporting factor and linear regression the movement of the user within the game was supported or hindered. The Exergame was evaluated on 15 healthy users regarding entertaining aspects, physical effort, and impressions concerning the handling of the whole setup. The support factor algorithm to reach the target heart rate was reliable in all subjects.

Long-term outcome and structural integrity following open repair of massive rotator cuff tears.

BACKGROUND: Surgical repair of massive rotator cuff tears is associated with less favorable clinical results and a higher retear rate than repair of smaller tears, which is attributed to irreversible degenerative changes of the musculotendinous unit. MATERIALS AND METHODS: During the study period, 25 consecutive patients with a massive rotator cuff tear were enrolled in the study and the tears were repaired with an open suture anchor repair technique. Preoperative and postoperative clinical assessments were performed with the Constant score, the simple shoulder test (SST) and a pain visual analog scale (VAS). At the final follow-up, rotator cuff strength measurement was evaluated and assessment of tendon integrity, fatty degeneration and muscle atrophy was done using a standardized magnetic resonance imaging protocol. RESULTS: The mean follow-up period was 70 months. The mean constant score improved significantly from 42.3 to 73.1 points at the final follow-up. Both the SST and the pain VAS improved significantly from 5.3 to 10.2 points and from 6.3 to 2.1, respectively. The overall retear rate was 44% after 6 years. Patients with an intact repair had better shoulder scores and rotator cuff strength than those with a failed repair, and also the retear group showed a significant clinical improvement (each P<0.05). Rotator cuff strength in all testing positions was significantly reduced for the operated compared to the contralateral shoulder. Muscle atrophy and fatty infiltration of the rotator cuff muscles did not recover in intact repairs, whereas both parameters progressed in retorn cuffs. CONCLUSIONS: Open repair of massive rotator tears achieved high patient satisfaction and a good clinical outcome at the long-term follow-up despite a high retear rate. Also, shoulders with retorn cuffs were significantly improved by the procedure. Muscle atrophy and fatty muscle degeneration could not be reversed after repair and rotator cuff strength still did not equal that of the contralateral shoulder after 6 years. LEVEL OF EVIDENCE: Level IV.

Combined tears of the subscapularis and supraspinatus tendon: clinical outcome, rotator cuff strength and structural integrity following open repair.

BACKGROUND: Anterosuperior rotator cuff tears involving the subscapularis and supraspinatus tendons are less common than other tears of the rotator cuff. The purpose of this study was to report the clinical outcome, rotator cuff strength and structural integrity of open repair of combined anterosuperior rotator cuff tears. PATIENTS AND METHODS: Forty-eight patients at an average age of 58 years underwent open repair of a combined supraspinatus and subscapularis tendon tear. The follow-up evaluation included clinical scores, rotator cuff strength testing with a custom-made force measurement plate (FMP) and postoperative MRI to evaluate repair integrity and muscle cross-sectional area. RESULTS: After a mean follow-up of 49 months the average Constant score improved from 43 points preoperatively to 79 points postoperatively. The SST and the pain VAS were significantly improved by the procedure (each <0.05). The combined tear group with partial subscapularis tears (G1) did not achieve significantly better score results than the combined tear group with a full-thickness subscapularis tear (G2) (p > 0.05). Strength for all rotator cuff components was reduced significantly (p < 0.05) compared with the contralateral shoulder in both groups. MRI revealed a retear-rate of 4% for the subscapularis and a retear-rate of 19% for the supraspinatus. Postoperative muscle cross-sectional area of all rotator cuff muscles did not differ significantly between G1 and G2 (p > 0.05). CONCLUSION: Open repair of combined anterosuperior rotator cuff tears achieved good postoperative results despite a residual rotator cuff strength deficit. Combined supraspinatus-/full-thickness subscapularis tears achieved equal clinical and radiographic results compared with supraspinatus-/partial-thickness subscapularis tears.

New method for determining in vitro structure stiffness of ceramic acetabular liners under different impact conditions.

Increasing both patient mobility and prosthesis life span requires improvements in the range of motion and wear behavior of the liner. With the use of new composite alumina-zirconia ceramic materials, the same stability of the liner can be achieved at lower wall thickness than it is possible with alumina-only materials. The aim of this study was developing a method for determining the in vitro structure stiffness of ceramic acetabular liners against impact stresses. The first trials were performed with a common alumina acetabular liner type (Ceramtec; Biolox forte; diameter 28 mm; thickness 7 mm) and a new type of alumina-zirconia (Ceramtec Biolox delta; same dimensions) liner. The clinically established alumina liner was reproducibly damaged using worst case Separation/subluxation equivalent to one-fourth or half of the head diameter, and an impact load of 15 J. The liners containing the new alumina-zirconia material were not damaged in any of the trials up to an impact load of 20 J and half head diameter offset.

Pulsatile ex vivo perfusion of human saphenous vein grafts under controlled pressure conditions increases MMP-2 expression.

BACKGROUND: The use of human saphenous vein grafts (HSVGs) as a bypass conduit is a standard procedure in the treatment of coronary artery disease while their early occlusion remains a major problem. METHODS: We have developed an ex vivo perfusion system, which uses standardized and strictly controlled hemodynamic parameters for the pulsatile and non-static perfusion of HSVGs to guarantee a reliable analysis of molecular parameters under different pressure conditions. Cell viability of HSVGs (n = 12) was determined by the metabolic conversion of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) into a purple formazan dye. RESULTS: Under physiological flow rates (10 mmHg) HSVGs remained viable for two weeks. Their exposure to arterial conditions (100 mmHg) was possible for one week without important reduction in viability. Baseline expression of matrix metalloproteinase-2 (MMP-2) after venous perfusion (2.2 ± 0.5, n = 5) was strongly up-regulated after exposure to arterial conditions for three days (19.8 ± 4.3) or five days (23.9 ± 6.1, p < 0.05). Zymographic analyses confirmed this increase on the protein level. Our results suggest that expression and activity of MMP-2 are strongly increased after exposure of HSVGs to arterial hemodynamic conditions compared to physiological conditions. CONCLUSION: Therefore, our system might be helpful to more precisely understand the molecular mechanisms leading to an early failure of HSVGs.

Biomechanical in vitro validation of intramedullary cortical button fixation for distal biceps tendon repair: a new technique.

BACKGROUND: Extramedullary cortical button-based fixation for distal biceps tendon ruptures exhibits maximum load to failure in vitro but cannot restore the anatomic footprint and has the potential risk for injury to the posterior interosseous nerve. HYPOTHESIS: Double intramedullary cortical button fixation repair provides superior fixation strength to the bone when compared with single extramedullary cortical button-based repair. STUDY DESIGN: Controlled laboratory study. METHODS: The technique of intramedullary cortical button fixation with 1 or 2 buttons was compared with single extramedullary cortical button-based repair using 12 paired human cadaveric elbows. All specimens underwent computed tomography analysis to determine intramedullary dimensions of the radial tuberosity as well as the thickness of the anterior and posterior cortices before biomechanical testing. Maximum load to failure and failure modes were recorded. For baseline measurements, the native tendon was tested for maximum load to failure. RESULTS: The intramedullary area of the radial tuberosity provides sufficient space for single or double intramedullary cortical button implantation. The mean thickness of the anterior cortex was 1.13 ± 0.15 mm, and for the posterior cortex it was 1.97 ± 0.48 mm (P < .001). We found the highest loads to failure for double intramedullary cortical button fixation with a mean load to failure of 455 ± 103 N, versus 275 ± 44 N for single intramedullary cortical button fixation (P < .001) and 305 ± 27 N for single extramedullary cortical button-based technique (P = .003). There were no statistically significant differences between single intramedullary and single extramedullary button fixation repair (P = .081). The mean load to failure for the native tendon was 379 ± 87 N. CONCLUSION: Double intramedullary cortical button fixation provides the highest load to failure in the specimens tested. CLINICAL RELEVANCE: Double intramedullary cortical button fixation provides reliable fixation strength to the bone for distal biceps tendon repair and potentially minimizes the risk of posterior interosseous nerve injury. Further, based on a 2-point-fixation, this method may offer a wider, more anatomic restoration of the distal biceps tendon to its anatomic footprint.

Subscapularis function and structural integrity after arthroscopic repair of isolated subscapularis tears.

BACKGROUND: Results of arthroscopic repair of isolated subscapularis tendon tears have not been widely studied. A detailed evaluation of subscapularis function with subscapularis strength quantification has not been performed to date. PURPOSE: To evaluate postoperative subscapularis muscle function and to assess the clinical outcome and structural tendon integrity with postoperative magnetic resonance imaging after arthroscopic repair of isolated subscapularis tears. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: In a prospective study, isolated subscapularis tendon tears in 21 patients were treated with an all-arthroscopic repair. The average age of the study population was 43 years. The mean interval between trauma and surgery was 5.8 months. In 19 patients, a traumatic event caused the onset of symptoms. Subscapularis muscle function was assessed with specific clinical tests and the Constant scoring system. Postoperative subscapularis strength was evaluated with a custom-made electronic force measurement plate. All patients underwent postoperative magnetic resonance imaging to assess structural integrity of the repair. RESULTS: The average duration of follow-up was 27 months. The Constant score increased from 50 points preoperatively to 82 points postoperatively (P < .01). Most positive preoperative lift-off and belly-press tests were reversed by surgery, with a rate of 5 (24%) persistent positive tests after surgery. In operated shoulders, subscapularis strength in the belly-press (65 vs 87 N; P < .05) and the lift-off position (44 vs 68 N; P < .05) was significantly reduced compared with the contralateral shoulder. Magnetic resonance imaging revealed an intact repair in 20 patients. Atrophy of the upper subscapularis muscle portion was present in about one-fourth of the patients and in all patients with a positive postoperative belly-press test. CONCLUSION: Arthroscopic repair of isolated subscapularis tendon tears achieves substantial improvement of shoulder function and a low rerupture rate. Despite excellent clinical results, a significant postoperative subscapularis strength deficit compared with the contralateral shoulder persists that can be quantified with use of the force measurement plate. Atrophy of the upper subscapularis muscle is present in 25% of the patients in the postoperative course.

A comparative study on extra-corporal circulation control.

Hydraulic models of the human circulatory system allow simulation of hemodynamics in a standardized setting. In this work we use such a model to compare concurrent control strategies for extra-corporal circulation control. Patients suffering from cardio-vascular diseases under extra-corporal circulation can benefit from an automated regulation. The control task is to keep either the pump flow or the pressure in the cardio-vascular system at a constant target value, despite any parameter variations or external perturbations. We implement four control strategies that seem favorable for our task: a Proportional-Integral Controller, a H(∞)-Controller, a PI-Fuzzy Controller and a Model Reference Adaptive Controller. The methods are compared quantitatively and their advantages and drawbacks are discussed.

The dynamic locking screw (DLS) can increase interfragmentary motion on the near cortex of locked plating constructs by reducing the axial stiffness.

BACKGROUND: The plate-screw interface of an angular stable plate osteosynthesis is very rigid. So far, all attempts to decrease the stiffness of locked plating construct, e.g. the bridged plate technique, decrease primarily the bending stiffness. Thus, the interfragmentary motion increases only on the far cortical side by bending the plate. To solve this problem, the dynamic locking screw (DLS) was developed. MATERIALS AND METHODS: Comparison tests were performed with locking screws (LS) and DLS. Axial stiffness, bending stiffness and interfragmentary motion were compared. For measurements, we used a simplified transverse fracture model, consisting of POM C and an 11-hole LCP3.5 with a fracture gap of 3 mm. Three-dimensional fracture motion was detected using an optical measurement device (PONTOS 5 M/GOM) consisting of two CCD cameras (2,448 x 2,048 pixel) observing passive markers. RESULTS: The DLS reduced the axial stiffness by approximately 16% while increasing the interfragmentary motion at the near cortical side significantly from 282 microm (LS) to 423 microm (DLS) applying an axial load of 150 N. CONCLUSION: The use of DLS reduces the stiffness of the plate-screw interface and thus increases the interfragmentary motion at the near cortical side without altering the advantages of angular stability and the strength.

A comparison study of the osseointegration of zirconia and titanium dental implants. A biomechanical evaluation in the maxilla of pigs.

OBJECTIVES: The purpose of the present study was to investigate the osseointegration of microstructured zirconia implants in comparison with sandblasted and acid-etched (SLA) titanium implants in a biomechanical study. MATERIALS: Zirconia implants (4.1 mm in diameter, 10 mm in length) were produced using a new low pressure injection molding technique. After that the implants were acid-etched with hydrofluoric acid. Standard Ti-SLA implants of the exact same shape served as controls. Six months after extraction of incisors 2 and 3, 16 adult pigs received a total of 64 implants in the maxillae. After 4, 8, and 12 weeks the animals were sacrificed, and 59 implants could be analyzed to removal torque (RTQ) testing. RESULTS: The mean RTQ values for zirconia implants were 42.4 Ncm at 4 weeks, 69.6 Ncm at 8 weeks, and 69.3 Ncm at 12 weeks of healing, whereas RTQ values for the Ti-SLA implants were 42.1 Ncm, 75.0 Ncm, and 73.1 Ncm at corresponding time intervals. There is no statistical difference in RTQ values between Ti-SLA and zirconia implants at 8 weeks. CONCLUSIONS: Within the limits of the present study it was concluded that acid-etching of zirconia implants enhances bone apposition resulting in RTQ values which were equivalent to that of Ti-SLA.

Tissue engineering of the anterior cruciate ligament-sodium dodecyl sulfate-acellularized and revitalized tendons are inferior to native tendons.

The acellularization of tendons using detergents (sodium dodecyl sulfate, Triton-X, tri-nitro-butyl-phosphate) is a new source of scaffolds for tissue engineering in anterior cruciate ligament (ACL) repair. In vitro testing demonstrated that acellular tendon scaffolds are biocompatible and show good biomechanical properties, but in vivo confirmation of these results is not yet available. Therefore, the aim of this study was to see in vivo if an acellular allogenic construct colonized with autologous fibroblasts improves the quality of ACL reconstruction. ACL replacement was performed in 31 New Zealand White rabbits using a standardized model. Fifteen animals received autologous semitendinosus tendon, whereas 16 animals were treated with a tissue-engineered construct. This construct was made by acellularization of allogenic semitendinosus tendons using sodium dodecyl sulfate and subsequent in vitro colonization with autologous fibroblasts. Eight weeks postoperatively, macroscopic, biomechanical (ultimate load to failure, elongation, stiffness; n = 8/9), and histological (n = 5) examinations were performed. Biomechanical testing showed decreasing strength of the constructs at 8 weeks after implantation compared with the direct postsurgical strength. However, tissue-engineered constructs (F = 19.7 +/- 20.3 N) were significantly weaker than autologous tendons (F = 61.2 +/- 31.2 N). Histologically, the autologous tendons showed signs of partial necrosis and tissue remodeling. The tissue-engineered constructs exhibited an inflammatory reaction and showed both repopulated and acellular regions. In conclusion, in vivo results were much more unfavorable than in vitro results had suggested. Further studies have to be performed to test if modifications of the acellularization process yield better results in vivo.

The anatomic reconstruction of acromioclavicular joint dislocations using 2 TightRope devices: a biomechanical study.

BACKGROUND: For the reconstruction of acromioclavicular (AC) joint separation, several operative procedures have been described; however, the anatomic reconstruction of both coracoclavicular ligaments has rarely been reported. PURPOSE: The aim of this biomechanical study is to describe a new procedure for anatomic reconstruction of the AC joint. STUDY DESIGN: Controlled laboratory study. MATERIALS AND METHODS: Forty fresh-frozen cadaveric shoulders were tested. Cyclic loading and a load-to-failure protocol was performed in vertical (native, n = 10; reconstructed, n = 10) and anterior directions (native, n = 10; reconstructed, n = 10) on 20 AC joints and repeated after anatomic reconstruction. Reconstruction of conoid and trapezoid ligaments was achieved by 2 TightRope devices (Arthrex, Naples, Florida). Dynamic, cyclic, and static loading until failure in vertical (n = 5) and horizontal (n = 5) directions were tested in native as well as reconstructed joints in a standardized setting. RESULTS: The native coracoclavicular ligaments in static load for vertical force measured 598 N (range, 409-687), elongation 10 mm (range, 6-14), and stiffness 99 N/mm (range, 67-130); static load for anterior force was 338 N (range, 186-561), elongation 4 mm (range, 3-7), and stiffness 140 N/mm (range, 70-210). The mean maximum static load until failure in reconstruction for vertical force was 982 N (range, 584-1330) (P =.001), elongation 4 mm (range, 3-6) (P < .001), and stiffness 80 N/mm (range, 66.6-105) (P = .091); and for anterior static force 627 N (range, 364-973) (P < .001), elongation 6.5 mm (range, 4-10) (P = .023), and stiffness 78 N/mm (range, 46-120) (P = .009). During dynamic testing of the native coracoclavicular ligaments, the mean amount of repetitions (100 repetitions per stage, stage 0-100 N, 100-200 N, 200-300 N, etc, and a frequency of 1.5 Hz) in native vertical direction was 593 repetitions (range, 426-683) and an average of 552 N (range, 452-683) load until failure. In vertical reconstructed testing, there were 742 repetitions (range, 488-893) (P = .222) with a load until failure of 768 N (range, 486-900) (P = .095). In the anterior direction load, the native ligament failed after an average of 365 repetitions (range, 330-475) and an average load of 360 N (range, 307-411), while reconstructed joints ended in 549 repetitions (range, 498-566) (P = .008) with a load until failure of 547 N (range, 490-585) (P = .008). In all testing procedures, a preload of 5 N was performed. CONCLUSION: The anatomic reconstruction of the AC joint using TightRope is a stable and functional anatomic reconstruction procedure. The reconstruction technique led to favorable in vitro results with equal or even higher forces than native ligaments. CLINICAL RELEVANCE: Through anatomic repair, stable function of the AC joint can be achieved in an anatomic manner.