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Intravascular imaging (IVI), including intravascular ultrasound (IVUS) and optical coherence tomography (OCT), is clinically useful for assessing the luminal size, lesion length, and plaque characteristics, as well as for evaluating stent deployment; however, it is not designed to estimate myocardial ischemia accurately. Thus, several types of IVI-derived fractional flow reserve (FFR) (IVI-derived FFR) have been developed and reported. In general, the algorithms of virtual FFR are based on basic fluid dynamics equations (mainly Poiseuille and Borda–Carnot equations) and original microvascular models (fixed velocity or calculating coronary flow reserve). Although the models and assumptions used in the past reports were mostly based on the standard population (not independent patient data), the developed software calculated FFR with high accuracy (88% to 94%) with strong correlations between IVI-derived FFR and wire-based FFR (0.69 to 0.89). Given several other less invasive virtual FFR methods currently available for clinical use, IVI-derived FFR would be limited for the sole use of pre-percutaneous coronary intervention (PCI) physiological evaluation; however, it may play a unique role at PCI guidance and optimization, potentially allowing comprehensive and time/cost-saving assessment of both anatomical and physiological lesion properties using a single diagnostic device. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Mechanically robust hydrogels are promising biomaterials as artificial supportive tissue. These applications require selective and robust bonding of the hydrogels to living tissue. Recently, we achieved strong in vivo bone bonding of a tough double network (DN) hydrogel, a potential material for use as artificial cartilage and tendon, by hybridizing osteoconductive hydroxyapatite (HAp) in the gel surface layer. In this work, we report micro patterning of HAp at the surface of the DN hydrogel for selective osteoconduction. Utilizing the dissolution of HAp in an acidic environment, the soft lithography technique using an acid gel stamp was adopted to form a high-resolution HAp pattern on the gel. The HAp-patterned gel showed well-regulated migration and adhesion of cells in vitro. Moreover, the HAp-patterned gel showed selective and robust bonding to the rabbit bone tissue in vivo. This HAp soft lithography technique allows for simple and quick preparation of tailor-made osteoconductive hydrogels and can be applied to other hydrogels for selective bone bonding. Statement of Significance Hydrogels, preserving large amount of water, have been studied for next-generation artificial soft tissues. However, fixation of hydrogels to living tissue was unsolved issue for clinical application. Recently, we achieved robust bonding of a tough double network gel to bone in vivo by coating of osteoconductive hydroxyapatite in the gel surface layer. For further progress for practical use, we report the micro patterning of HAp at the surface of the DN hydrogel by using soft lithography technique, to perform selective bonding to only objective area without unnecessary coalescence. The HAp lithography technique is simple, quick and non-toxic method to prepare tailor-made osteoconductive hydrogels and has universality of species of hydrogels. [ABSTRACT FROM AUTHOR]

Abstract A hemi–closing-wedge and hemi–opening-wedge, inverted V–shaped high tibial osteotomy with local bone graft has been reported to be an effective surgical procedure for medial osteoarthritis of the knee. In this procedure, an inverted V–shaped osteotomy is made and a thin wedged bone block is resected from the lateral side and implanted in the medial opening space created after valgus correction. This procedure can provide sufficient valgus correction of the knee with severe varus deformity more easily than can closing-wedge high tibial osteotomy. The inverted V–shaped osteotomy does not change the posterior tibial slope, the patellar height, or the length of the lower limb at all because the center of tibial alignment correction by the inverted V–shaped osteotomy is located near the center of rotation of angulation of the lower-limb deformity. We recently modified this procedure by performing biplanar osteotomy, developing useful cutting guides, and fixing the tibia with a lateral locking compression plate. The surgical technique is described to enable the reproducible creation of the hemi–closing-wedge and hemi–opening-wedge, inverted V–shaped osteotomy with the locking plate for medial osteoarthritic knees with moderate or severe varus deformity. [ABSTRACT FROM AUTHOR]

Preservation of the anterior cruciate ligament (ACL) remnant tissue has attracted notice in ACL reconstruction. Remnant preservation has been expected to have several potential advantages to improve postoperative knee stability such as enhanced graft coverage, accelerated cell repopulation, and revascularization. Recently, we have developed a new remnant-preserving technique for anatomical double-bundle ACL reconstruction using the semitendinosus tendon. The anterior laxity values and the results of the pivot-shift test were significantly better in the remnant tissue–preserving procedure than in the remnant tissue–resecting procedure. The arthroscopic evaluation showed that the remnant-preserving procedure was significantly better than the remnant-resecting procedure concerning postoperative laceration or tear of the grafts as well as synovial and fibrous tissue coverage of the grafts. However, to establish the clinical use of remnant tissue preservation, further randomized clinical studies are needed to objectively examine the effects on rotatory stability and the long-term survival of graft function. [ABSTRACT FROM AUTHOR]

We have developed a novel hydroxyapatite (HAp)-coated double-network (DN) hydrogel (HAp/DN gel). The purpose of this study was to determine details of the cell and tissue responses around the implanted HAp/DN gel and to determine how quickly and strongly the HAp/DN gel bonds to the bone in a rabbit osteochondral defect model. Immature osteoid tissue was formed in the space between the HAp/DN gel and the bone at 2 weeks, and the osteoid tissue was mineralized at 4 weeks. The push-out load of the HAp/DN gel averaged 37.54 N and 42.15 N at 4 and 12 weeks, respectively, while the push-out load of the DN gel averaged less than 5 N. The bonding area of the HAp/DN gel to the bone was above 80% by 4 weeks, and above 90% at 12 weeks. This study demonstrated that the HAp/DN gel enhanced osseointegration at an early stage after implantation. The presence of nanoscale structures in addition to osseointegration of HAp promoted osteoblast adhesion onto the surface of the HAp/DN gel. The HAp/DN gel has the potential to improve the implant-tissue interface in next-generation orthopaedic implants such as artificial cartilage. Statement of Significance Recent studies have reported the development of various hydrogels that are sufficiently tough for application as soft supporting tissues. However, fixation of hydrogels on bone surfaces with appropriate strength is a great challenge. We have developed a novel, tough hydrogel hybridizing hydroxyapatite (HAp/DN gel), which is directly bondable to the bone. The present study demonstrated that the HAp/DN gel enhanced osseointegration in the early stage after implantation. The presence of nanoscale structures in addition to the osseointegration ability of hydroxyapatite promoted osteoblast adhesion onto the surface of the HAp/DN gel. The HAp/DN gel has the potential to improve the implant-tissue interface in next-generation orthopaedic implants such as artificial cartilage. [ABSTRACT FROM AUTHOR]

The purpose of this study was to clarify fundamental mechanical properties and biological responses of the sodium hyaluronate-containing double network (HA-DN) gel and chondroitin sulfate-containing double network (CS-DN) gel, which were newly developed using the molecular stent method. This study discovered the following facts. First, these hydrogels had high mechanical performance comparable to the native cartilage tissue, and the mechanical properties were not affected by immersion in the saline solution for 12 weeks. Secondly, the mechanical properties of the CS-DN gel were not significantly reduced at 12 weeks in vivo, while the mechanical properties of the HA-DN gel were significantly deteriorated at 6 weeks. Thirdly, the degree of inflammation around the HA-DN gel was the same as that around the negative control. The CS-DN gel showed a mild but significant foreign body reaction, which was significantly greater than the negative control and less than the positive control at 1 week, while the inflammation was reduced to the same level as the negative control at 4 and 6 weeks. Fourthly, these gels induced differentiation of the ATDC5 cells into chondrocytes in the culture with the insulin-free maintenance medium. These findings suggest that these tough hydrogels are potential biomaterials for future application to therapeutic implants such as artificial cartilage. Statement of Significance The present study reported fundamental biomaterial properties of the sodium hyaluronate-containing double network (HA-DN) gel and chondroitin sulfate-containing double network (CS-DN) gel, which were newly developed using the molecular stent method. Both the HA- and CS-DN gels had high mechanical properties comparable to the cartilage tissue and showed the ability to induce chondrogenic differentiation of ATDC5 cells in vitro. They are potential biomaterials that may meet the requirements of artificial cartilage concerning the material properties. Further, these DN gels can be also applied to the implantable inducer for cell-free cartilage regeneration therapy. [ABSTRACT FROM AUTHOR]

Purpose The purpose was to clarify the load-bearing functions of the fibers of the femoral anterior cruciate ligament (ACL) attachment in resisting tibial anterior drawer and rotation. Methods A sequential cutting study was performed on 8 fresh-frozen human knees. The femoral attachment of the ACL was divided into a central area that had dense fibers inserting directly into the femur and anterior and posterior fan-like extension areas. The ACL fibers were cut sequentially from the bone: the posterior fan-like area in 2 stages, the central dense area in 4 stages, and then the anterior fan-like area in 2 stages. Each knee was mounted in a robotic joint testing system that applied tibial anteroposterior 6-mm translations and 10° or 15° of internal rotation at 0° to 90° of flexion. The reduction of restraining force or moment was measured after each cut. Results The central area resisted 82% to 90% of the anterior drawer force; the anterior fan-like area, 2% to 3%; and the posterior fan-like area, 11% to 15%. Among the 4 central areas, most load was carried close to the roof of the intercondylar notch: the anteromedial bundle resisted 66% to 84% of the force and the posterolateral bundle resisted 16% to 9% from 0° to 90° of flexion. There was no clear pattern for tibial internal rotation, with the load shared among the posterodistal and central areas near extension and mostly the central areas in flexion. Conclusions Under the experimental conditions described, 66% to 84% of the resistance to tibial anterior drawer arose from the ACL fibers at the central-proximal area of the femoral attachment, corresponding to the anteromedial bundle; the fan-like extension fibers contributed very little. This work did not support moving a single-bundle ACL graft to the side wall of the notch or attempting to cover the whole attachment area if the intention was to mimic how the natural ACL resists tibial displacements. Clinical Relevance There is ongoing debate about how best to reconstruct the ACL to restore normal knee function, including where is the best place for ACL graft tunnels. This study found that the most important area on the femur, in terms of resisting displacement of the tibia, was in the central-anterior part of the femoral ACL attachment, near the roof of the intercondylar notch. The testing protocol did not lead to data that would support using a large ACL graft tunnel that attempts to cover the whole natural femoral attachment area. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to clarify the changes in the kinematics of the knee that result from isolated deficiency of the anteromedial (AM) or posterolateral (PL) bundle. Methods: Fourteen cadaveric knees were mounted in a 6-df rig and tested using the following 5 loading conditions: 90-N anterior and posterior tibial loads, 5-Nm internal and external tibial torques, and a simulated pivot-shift test. Tibiofemoral kinematics during flexion-extension was recorded with an optical tracking system for (1) intact knees, (2) knees in which the isolated AM bundle was cut, (3) knees in which the isolated PL bundle was cut, and (4) anterior cruciate ligament (ACL)-deficient knees. The distances between the femoral and tibial attachments of the AM and PL bundles of the ACL were also calculated. Results: Anterior translation laxity under an anterior tibial load, rotational laxity under an internal tibial torque, and anterior translation laxity under pivot-shift loading were significantly different between the knees with AM and PL bundle deficiencies (P < .024), but the changes were small: less than 3 mm or 1.5°. The AM bundle distance increased significantly more after an AM bundle tear (P = .004) than after a PL bundle tear in flexion. Cutting the PL bundle did not have a significant effect on the lengths between the bundle attachments. Conclusions: An isolated AM or PL bundle tear caused a small increase in laxity (<3 mm or <1.5°). Clinical Relevance: If there is a clinically identifiable increase in laxity, then--in addition to the isolated tear of the AM or PL bundle--there must also be a tear of the other bundle of the ACL, or at least a partial tear. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this pilot study was to evaluate the preliminary results of an anatomic double-bundle anterior cruciate ligament (ACL) reconstruction procedure with ligament remnant tissue preservation. Methods: By use of the transtibial technique, 2 doubled semitendinosus tendons were grafted into 4 tunnels created at the center of each bundle attachment, penetrating the ACL remnant tissue. In total, 44 patients (27 male and 17 female patients) with an isolated ACL injury underwent ACL reconstruction with this procedure. The mean age of the patients was 29 years (range, 17 to 58 years). Postoperative clinical evaluations were performed at 16.6 months on average (range, 12 to 23 months). Radiologic evaluations were also performed to evaluate the tunnel location in the femur and the tibia. Results: The mean operation time was 86 minutes (range, 72 to 96 minutes) in the cases with ACL reconstruction only. Postoperatively, the mean anterior laxity was 0.7 mm. The postoperative pivot-shift test was negative in 81.8% of the patients, whereas there were no patients evaluated as ++. No patients showed any extension or flexion deficit. There were no patients evaluated as “nearly abnormal” or “abnormal” according to the International Knee Documentation Committee evaluation. The tunnel angles of the 4 tunnels were identical to those reported in a previous study. Conclusions: The minimal 1-year clinical results of anatomic double-bundle ACL reconstruction with ligament remnant tissue preservation were comparable to previously reported results of anatomic double-bundle reconstruction without remnant tissue preservation. Level of Evidence: Level IV, therapeutic case series. [Copyright &y& Elsevier]

Purpose: The purpose of this biomechanical study was to compare the structural properties of the flexor tendon graft connected to the EndoButton CL BTB (ECL-BTB) (Smith & Nephew Endoscopy, Andover, MA), which is newly developed to fix the bone-tendon-bone graft, with those of the same graft connected to the EndoButton CL (ECL) (Smith & Nephew Endoscopy), which is commonly used as a standard fixation device. Methods: We randomly divided 40 porcine flexor digitorum profundus tendons into 4 groups. An ECL and an ECL-BTB were attached to the doubled tendon measuring 6 mm in diameter in groups I and II, respectively. An ECL and an ECL-BTB were attached to the doubled tendon measuring 7 mm in diameter in the same manner in groups III and IV, respectively. Tensile testing was performed with a tensile tester. Results: The linear stiffness of the tendon-device composite (mean ± SD) was 131.8 ± 18.3 N/mm, 109.7 ± 14.9 N/mm, 132.4 ± 20.5 N/mm, and 123.8 ± 10.7 N/mm in groups I, II, III, and IV, respectively. The 2-way analysis of variance (ANOVA) showed a significant difference (P = .0058) between the ECL and the ECL-BTB. Concerning the maximum load and the elongation at failure of the tendon-device composite, the 2-way ANOVA showed no significant difference between the 2 fixation devices. Regarding the cross-sectional area, the 2-way ANOVA indicated no significant difference between the 2 fixation devices. Conclusions: This study has shown that the maximum load of the flexor tendon graft connected to the ECL-BTB is similar to that of the ECL whereas the stiffness of the ECL-BTB is inferior to that of the ECL. Clinical Relevance: This study has suggested that patients should not be permitted to perform vigorous activities in the early period after anterior cruciate ligament reconstruction by use of the ECL-BTB fixation technique, because of its low stiffness compared with the ECL device. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the behavior of chondrogenic ATDC5 cells on synthetic polymer gels with various charge densities: negatively charged poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) gel, neutral poly(dimethylacrylamide) (PDMAAm) gel, and copolymer gels of 2-acrylamido-2-methyl-1-propanesulfonic acid and dimethylacrylamide P(AMPS-co-DMAAm) with different compositions (molar fractions of AMPS, F =0.25, 0.5, 0.75). In insulin-free maintenance medium, the ATDC5 cells cultured on the highly negatively charged gels – PAMPS gel and the P(AMPS-co-DMAAm) copolymer gels (F =0.75) – spread and became confluent at day 7, and interestingly formed nodules at day 14, expressing type II collagen and proteoglycan. This result demonstrates that the highly negatively charged gels can induce chondrogenic differentiation of ATDC5 cells even in insulin-free maintenance medium, in which the ATDC5 cells cultured on the standard polystyrene dish cannot differentiate into chondrocytes. In insulin-supplemented differentiation medium, ATDC5 cells cultured on the PDMAAm gel made focal adhesions, rapidly aggregated and formed large nodules within 7days, expressing significantly greater levels of type II collagen and proteoglycan than cells cultured on the polystyrene dish and the negatively charged gels. These results showed that the neutral gel accelerated chondrogenic differentiation of ATDC5 cells cultured in the differentiation medium. We suggest that the highly negatively charged PAMPS gel and the neutral PDMAAm gel are interesting biomaterials for cartilage tissue engineering as a scaffold with the potential to induce chondrogenic differentiation. [Copyright &y& Elsevier]

Purpose: The purposes of this study were to determine the relation between the graft tension and the knee flexion angle in the anteromedial (AM) and posterolateral (PL) bundles of a clinically simulated anatomic double-bundle anterior cruciate ligament (ACL) reconstruction procedure and to clarify the effect of initial tension on the tension-versus-flexion curve of each graft, as well as the effect of internal rotation of the tibia on the tension of the 2 grafts. Methods: During ACL reconstruction in 30 patients, 2 suture anchors with a No. 1 polyester suture were firmly screwed into the center of the anatomic attachment of the AM and PL bundles on the femur, respectively, and each graft tension was measured with a strain gauge-type tensiometer attached at the end of the suture under 2 conditions of initial tension. Results: The averaged tension-versus-flexion curves were significantly different between the AM and PL grafts under each initial tension condition (P < .0001). The initial tension applied at 30 degrees of knee flexion significantly affected the absolute values of each graft tension at each knee flexion angle (P < .0001) but did not significantly affect the tension-versus-flexion curve pattern of each graft. The maximal internal rotation of the tibia significantly increased the tension on both the AM and PL grafts at knee flexion angles of less than 60 degrees under each initial tension condition (P < .0001). Conclusions: The tension-versus-flexion curves of the 2 sutures, which mimicked the AM and PL grafts reconstructed clinically with the anatomic double-bundle ACL reconstruction procedure, were significantly different in the tension values. Differences in initial tension applied to the 2 grafts significantly affected the absolute values of each graft tension at each knee flexion angle but did not significantly affect the tension-versus-flexion curve pattern. The maximal internal rotation of the tibia significantly increased the tension on both the AM and PL suture grafts at knee flexion angles of less than 60 degrees . Level Of Evidence: Level I, testing of previously developed diagnostic criteria in series of consecutive patients with universally applied gold standard. [ABSTRACT FROM AUTHOR]

Abstract: Background: No studies have been conducted to clarify an in vivo remodeling of the radiofrequency-treated lesion of the anterior cruciate ligament. The purpose was to determine in vivo effects of radiofrequency shrinkage on mechanical properties of the anterior cruciate ligament. Methods: Thirty skeletally mature rabbits were used. In each group, radiofrequency energy set at non-ablative levels was applied to the posterolateral bundle of the anterior cruciate ligament with a bipolar radiofrequency generator. All animals were sacrificed at 0, 6, and 12 weeks after surgery, respectively. In each group, 7 and 3 out of the 10 specimens were used for biomechanical and histological evaluations. Findings: After shrinkage treatment, the anterior–posterior translation of the knee and the length of the posterolateral bundle were significantly reduced immediately after surgery, but that this effect disappeared at 6 weeks. The tensile strength and the tangent modulus of the treated bundle were significantly lower than that of the normal control bundle at each period. In addition, the tensile strength and the tangent modulus measured at 12 weeks were significantly lower than that at 0 week. Histological examination showed granulation-like tissues with numerous plump fibroblasts and inflammatory cells were dominantly found in the midsubstance of the posterolateral bundle at 12 weeks. Interpretations: This result suggested that the anterior cruciate ligament tissue shortened with the radiofrequency treatment is elongated gradually over time. The mechanical properties of the posterolateral bundle of the anterior cruciate ligament reduced by the radiofrequency shrinkage are not restored in vivo, but significantly deteriorated with time. [Copyright &y& Elsevier]

Purpose: The purpose of this study was to test the hypothesis that both the anteromedial and posterolateral bundles may be clearly visible after anatomic double-bundle reconstruction, as well as that a strong relation may exist between the appearance of the 2 bundles and the clinical evaluation. Methods: A prospective study was performed based on 178 consecutive patients who underwent anatomic double-bundle anterior cruciate ligament reconstruction with 2 hamstring tendon autografts in the unilateral knee. To develop arthroscopic diagnostic criteria, clinical evaluations were carried out at 1 to 2 years concerning the anterior laxity, the pivot-shift test, the Lysholm knee score, and the International Knee Documentation Committee evaluation, and 136 of the 178 patients underwent second-look arthroscopy shortly before or after the clinical examinations that are the basis of this study. The focus of the second-look arthroscopy was on graft thickness, apparent tension, and synovium coverage of the bundle. Results: Second-look arthroscopy showed that the anteromedial bundle was evaluated as excellent in 79.5% of the knees, fair in 16.7%, and poor in 3.8% and the posterolateral bundle was evaluated as excellent in 75.8%, fair in 21.2%, and poor in 3.0%. There was a significant difference in the anterior laxity and the pivot-shift test among the arthroscopically observed categories. Between the knees with second-look arthroscopy and those without it, there were no significant differences in all clinical evaluations. Conclusions: Both the anteromedial and posterolateral bundles were clearly visible after the anatomic double-bundle anterior cruciate ligament reconstruction at 1 to 2 years after surgery. There was a significant difference in the anterior laxity and pivot-shift test in patients in category I, which comprised those who had excellent anteromedial and posterolateral bundles, compared with those in category II or III, which comprised those in whom either 1 or both of the bundles was scored as less than excellent. Level Of Evidence: Level II, development of diagnostic criteria on the basis of consecutive patients with universally applied reference gold standard. [ABSTRACT FROM AUTHOR]

Abstract: Background: The purpose of this study is to biomechanically and histologically evaluate the effect of bleeding from bone marrow on remodeling of the in situ frozen-thawed anterior cruciate ligament. Methods: Forty-four rabbits were used. Eight rabbits were used to evaluate the amount of bleeding at days 1–4. Thirty-six rabbits were divided into two groups, after the right anterior cruciate ligament underwent the freeze-thaw treatment. In Group I, no treatments were applied. In Group II, a tunnel was drilled into the bone marrow the femoral intercondylar notch. Each rabbit was sacrificed at 6 or 12 weeks. We examined the mechanical properties, and the histology of the anterior cruciate ligament. Findings: A small amount of blood clot was observed only on the first day in Group I, while a large amount of blood clot was seen around the anterior cruciate ligament for 3 days after surgery in Group II. In the midsubstance, a number of cells were scattered in Group II, no cells were seen in Group I at 6 weeks. The tangent modulus showed some tendency of difference between Groups I and II at each period. Interpretation: Bleeding from the bone marrow obviously enhanced extrinsic cell infiltration into the in situ frozen-thawed anterior cruciate ligament at 6 weeks, and showed some effects on its mechanical properties. This study implied that, in anterior cruciate ligament reconstruction, the blood from a bone tunnel play an important role in graft remodeling. [Copyright &y& Elsevier]

Purpose: The purpose of this study was to clarify femoral and tibial tunnel angles in anatomic double-bundle anterior cruciate ligament (ACL) reconstruction. Methods: A prospective study was performed in 50 consecutive patients who underwent anatomic double-bundle ACL reconstruction via hamstring tendon grafts for chronic ACL deficiency in the unilateral knee. For this procedure, 2 hamstring tendon grafts were secured with EndoButtons (Smith & Nephew Endoscopy, Andover, MA) on the femur and with 2 staples on the tibia. Each patient underwent radiologic examination 1 year after surgery. Results: The tibial tunnel angles of the posterolateral bundle averaged 40.7 degrees in the anteroposterior view and 35.4 degrees in the lateral view. The tibial tunnel angles of the anteromedial bundle averaged 15.6 degrees in the anteroposterior view and 41.4 degrees in the lateral view. The femoral tunnel angles of the posterolateral bundle averaged 44.0 degrees in the anteroposterior view and 52.0 degrees in the lateral view. The femoral tunnel angles of the anteromedial bundle averaged 18.0 degrees in the anteroposterior view and 49.8 degrees in the lateral view. Conclusions: The given data will be useful for surgeons to evaluate the tunnel positions and standardization postoperatively in anatomic double-bundle reconstruction. Level Of Evidence: Level II, development of diagnostic criteria on the basis of consecutive patients with universally applied reference gold standard. [ABSTRACT FROM AUTHOR]

Purpose: To compare the clinical outcome of anatomic double-bundle anterior cruciate ligament (ACL) reconstruction with that of nonanatomic single- and double-bundle reconstructions. Type Of Study: Prospective comparative cohort study. Methods: Seventy-two patients with unilateral ACL-deficient knees were randomly divided into 3 groups. Concerning all background factors, there were no statistical differences among the 3 groups. In group S (n = 24), single-bundle ACL reconstruction was performed. In group N-AD (n = 24), nonanatomic double-bundle reconstruction was carried out. In group AD (n = 24), anatomic double-bundle reconstruction was performed. One surgeon performed all operations using hamstring tendon autografts. Each patient underwent clinical examinations, before surgery and at 2 years. Results: No intraoperative and postoperative complications were experienced in each group. There were no significant differences concerning the time for operation among the 3 groups. The statistical analysis showed a significant difference in the postoperative side-to-side anterior laxity among the 3 groups (P = .006). The laxity was significantly less (P = .002) in group AD (1.1 mm) than in group S (2.8 mm), while there was no significant difference (P = .072) between groups AD and N-AD. Concerning the pivot-shift test, group AD was significantly superior to group S (P = .025). There were no significant differences in the range of knee motion, the muscle torque, and the International Knee Documentation Committee evaluation. Conclusions: On the basis of the KT-2000 measurement, the side-to-side anterior laxity of our anatomic double-bundle ACL reconstruction was significantly better than that of the single-bundle reconstruction with the hamstring tendon graft, although there were no significant differences in the other clinical measures among any of the 3 procedures. Level Of Evidence: Level II. [ABSTRACT FROM AUTHOR]

Abstract: Background. No investigators have studied the effects of an application of growth factors on the in vivo tissue regeneration in the tendon after resecting the central portion. The purpose of this study is to clarify whether an application of transforming growth factor (TGF)-beta1 increases the mechanical properties of the regenerated tissue in the patellar tendon after resecting the central portion. Methods. Thirty female rabbits were divided into three groups, after a 3mm wide and 10mm long tendon substance was resected from the central portion in the patellar tendon. In Group I, 5-ng TGF-beta1 dissolved in 0.1-ml saline was injected into the resected portion in the patellar tendon. In Group II, only 0.1-ml saline was injected into the resected portion. In Group III, nothing was injected. All animals were sacrificed at 6weeks after surgery. Mechanical and histological evaluations were made concerning the regenerated tissue and the unresected tendon tissue in the patellar tendon. Findings. Concerning the regenerated tissue, the tangent modulus and the tensile strength of Group I were significantly greater than those of Groups II and III, while there were no significant differences in these parameters between Groups II and III. Interpretation. The application of TGF-beta1 significantly increases the tangent modulus and the tensile strength of the fibrous tissue regenerated in the patellar tendon after resecting the central portion. This study has provided basic important information on the utility of TGF-beta1 in the in vivo tendon regeneration. [Copyright &y& Elsevier]

Purpose: To clarify the effect of transforming growth factor (TGF)-β1 on intraosseous healing of the flexor tendon autograft in anterior cruciate ligament (ACL) replacement. Type of Study: Randomized trial in animals. Methods: Twenty-one adult beagle dogs were divided into 3 groups of 7 animals each. The ACL was replaced with a flexor tendon autograft in the left knee. The distal end of each graft was placed in the tibial bone tunnel. In group I, no treatment was applied in the bone tunnel. In group II, 0.1 mL of fibrin sealant was applied in the tendon-bone gap. In group III, 2 ng of TGF-β1 mixed with 0.1 mL fibrin sealant was applied in the gap. Each animal was euthanized 3 weeks after surgery. Results: In pullout testing, the ultimate load of the graft-tibia complex of group III (188.2 ± 51.4 N) was significantly greater than that of groups I (86.7 ± 36.5 N) and II (99.0 ± 18.7 N) (P = .005). There were no significant differences between groups I and II. Histologically, the perpendicular collagen fibers connecting the tendon to the bone were narrowly seen in groups I and II, whereas the fibers were richly generated in group III. Conclusions: In ACL replacement using flexor tendon autograft, exogenous administration of TGF-β1 significantly increased the bonding strength of the graft to the tunnel wall at 3 weeks, although the long-term effects are unknown. Clinical Relevance: Intraosseous healing of the flexor tendon autograft in ACL reconstruction may be enhanced by a use of some growth factors involving TGF-β1 in the future. [Copyright &y& Elsevier]

Purpose: Posterior cruciate ligament (PCL) reconstruction procedures have not been thoroughly evaluated under cyclic loading conditions. We tested the hypothesis that PCL reconstruction with a quadrupled flexor-tendon graft and fixation using tapes and staples is biomechanically superior to that fixed with sutures, a button, and a post-screw, and is comparable to reconstruction with a bone—patellar tendon—bone (BPTB) graft. Study Design: In vitro biomechanical study. Methods: A total of 45 porcine knees were used. The quadrupled flexor-tendon graft was fixed using the suture/button/post-screw procedure in 15 knees, and with the tape/staples procedure in another 15 knees. The remaining 15 knees underwent reconstruction with a BPTB graft secured with screws as the standard control. In each group of 15 knees, 5 underwent tensile testing without cyclic loading, and 10 underwent the same tensile test after 5,000 cycles of load-controlled or displacement-controlled loading. Results: Each type of cyclic loading produced larger biomechanical changes in the knees fixed with the suture/button/post-screw procedure than in the knees secured using the other 2 procedures. Conclusions: In PCL reconstruction, the tape/staples procedure is biomechanically superior to the suture/button/post-screw procedure, and is comparable to the BPTB/screws procedure with regard to the ultimate failure load. Neither of the procedures using the quadrupled flexor-tendon graft was comparable to the BPTB graft in linear stiffness and the initial displacement after load-controlled cyclic testing. Clinical Relevance: The biomechanical behaviors of PCL-reconstructed knees are significantly different, depending on surgical techniques. [Copyright &y& Elsevier]

Abstract: This study evaluated the wear property of four novel double-network (DN) hydrogels, which was composed of two kinds of hydrophilic polymers, using pin-on-flat wear testing. The gels involve PAMPS–PAAm gel which consists of poly(2-acrylamide-2-metyl-propane sulfonic acid) and polyacrylamide, PAMPS–PDAAAm gel which consists of poly(2-acrylamide-2-metyl-propane sulfonic acid) and poly(N,N′-dimetyl acrylamide), Cellulose/PDMAAm gel which consists of bacterial Cellulose and poly dimetyl-acrylamide, and Cellulose–Gelatin gel which consists of bacterial Cellulose and Gelatin. Ultra-high molecular weight polyethylene (UHMWPE) was used as a control of a clinically available material. Using a reciprocating apparatus, 106 cycles of friction between a flat specimen and ceramic pin were repeated in water under a contact pressure of 0.1MPa. To determine the depth and the roughness of the concave lesion created by wear, a confocal laser microscope was used. As a result, the maximum wear depth of the PAMPS–PDMAAm gel (3.20μm) was minimal in the five materials, while there was no significant difference compared to UHMWPE. There were significant differences between UHMWPE and one of the other three gels. The PAMPS–PAAm gel (9.50μm), the Cellulose–PDMAAm gel (7.80μm), and the Cellulose–Gelatin gel (1302.40μm). This study demonstrated that the PAMPS–PDMAAm DN gel has an amazing wear property as a hydrogel that is comparable to the UHMWPE. In addition, the PAMPS–PAAm and Cellulose–PDMAAm DN gels are also resistant to wear to greater degrees than conventionally reported hydrogels. On the other hand, this study showed that the Cellulose–Gelatin DN gel was not resistant to wear. [Copyright &y& Elsevier]

The purposes of this review are to explain surgical and biomechanical concepts of anatomic anatomic anterior cruciate ligament (ACL) reconstruction and to introduce our anatomic reconstruction procedure of the anteromedial (AM) and posterolateral (PL) bundles of the ACL using hamstring tendon autografts. According to common medical concept, anatomical ACL reconstruction is defined as the reconstruction in which all 4 ends of 2 tendon grafts are grafted at the center of the anatomical attachment of the AM bundles or the PL bundles, not only on the femur but also on the tibia, because only such a procedure allows for the reconstruction of 2 bundles having an anatomical orientation. On the basis of our anatomic studies on the normal attachments of the ACL, we developed an arthroscopy-assisted anatomic reconstruction procedure of the AM and PL bundles that involves a new method of creating the tibial and femoral tunnels for the posterolateral bundle. To insert a Kirschner wire as a guide into the tibia, we use an originally developed a Wire-navigator, which is a key device for the trans-tibial tunnel technique. To visualize the femoral attachment of the posterolateral bundle, the medial infra-patellar portal is more useful than the lateral one. Biomechanical studies have shown that anatomic double-bundle ACL reconstruction has some biomechanical advantages over a single-bundle reconstruction. In our clinical experience, results of the anatomic reconstruction were superior to those of the one-bundle reconstruction. We believe that the anatomic reconstruction of the AM and PL bundles using hamstring tendon autografts is clinically practical in the treatment for the ACL-deficient knee. [Copyright &y& Elsevier]

Abstract: Objective. To clarify effects of a separate application of TGF-beta1, EGF, and PDGF-BB on the material properties of the in situ frozen–thawed anterior cruciate ligament. Design. Twenty-eight rabbits were divided into four groups after undergoing the in situ freeze–thaw treatment in the right anterior cruciate ligament. In 3 of the 4 groups, 4ng TGF-beta1, 20ng EGF, and 4μg PDGF-BB was applied to the frozen anterior cruciate ligament, respectively. In the remaining sham treatment group, only fibrin sealant as a vehicle was applied. Each animal was sacrificed at 12 weeks after surgery. Background. If the role of growth factors in ligament healing and remodeling is understood, better therapies can be designed for ligament trauma. Methods. The freeze–thaw treatment was performed three times using the originally developed cryo-probe. The cross-sectional area of the anterior cruciate ligament was measured by the optical non-contact method. After preconditioning, each specimen was stretched to failure. The ligament strain was determined with a video dimension analyzer. Results. The tensile strength and the tangent modulus of the anterior cruciate ligament in the TGF-beta1 group was significantly higher than in the sham group, but significantly lower than in the normal control group. There were no significant differences in the strength and the modulus between the EGF group, the PDGF-BB group, and the sham group. Conclusions. In this model, an application of 4ng TGF-beta1 significantly inhibited some of the material deterioration that occurs in the in situ frozen–thawed anterior cruciate ligament, while an application of 20ng EGF or 4μg PDGF-BB did not significantly affect the deterioration.Relevance This information will be useful in the future to develop a new biological therapy for ligament reconstruction to prevent the graft deterioration after transplantation. [Copyright &y& Elsevier]

A high-precision navigation system for Anterior Cruciate Ligament (ACL) reconstruction surgery is presented. In this system, 3D CT data is used to visualize the structure of bones and optical localizer is used to detect the position of femur, tibia and surgical tools. Since CT images are acquired preoperatively and markers are fixed to bones intraoperatively, their relative position has to be initialized. To achieve this initialization, 2D/3D registration method between CT model and X-ray images was developed. The registration is performed by minimizing the difference between contour lines. As ACL reconstruction requires precision, three X-ray images taken from different viewpoints are used for the registration. Experimental registration shows the Fiducial Registration Error (FRE) error to be 1.2 mm. [Copyright &y& Elsevier]

Objective. To biomechanically evaluate a newly devised model for the elongation-type anterior cruciate ligament injury with partial laceration and permanent elongation.Design. Thirty-six rabbits were randomly divided into 4 groups of 9 animals each, after a quantitative injury was given to the right anterior cruciate ligament. The 4 groups were sacrificed at 0, 6, 12, and 24 weeks after surgery, respectively. Biomechanical and histological evaluations were performed at each period.Background. No adequate animal models have been established for the elongation-type anterior cruciate ligament injury in which the mid-substance is permanently elongated with partial laceration.Methods. The anteromedial and posterolateral half of the anterior cruciate ligament was transected at the proximal and distal one-third levels, respectively. Then, the anterior cruciate ligament was stretched by applying an anterior drawer force to the tibia at 90 degrees of knee flexion.Results. The treatment significantly increased the anterior translation of the knee into approximately 150–250% at each period after surgery. The maximum load and the stiffness of the femur–anterior cruciate ligament–tibia complex significantly decreased to 30% or less immediately after surgery, and then gradually increased to 50% at 12 weeks.Conclusions. In this model, this quantitative treatment created serious injuries with partial laceration and permanent elongation in the anterior cruciate ligament to similar degrees. Also, incomplete tissue healing occurred in the anterior cruciate ligament to similar degrees after the treatment.RelevanceThis model will be useful to study new therapeutic methods for the elongation-type anterior cruciate ligament injury. [Copyright &y& Elsevier]

Objective. To know the temporal changes of the mechanical properties of the regenerated and the residual tissues in the patellar tendon after removal of the central portion.Design. The regenerated and the residual tissues were compared to sham-operated tendons.Background. Although the structural properties of the whole patellar tendon after removal of the central portion have been investigated, no studies have distinguished between the regenerated and the residual tissues.Methods. For 52 skeletally mature rabbits, a full-thick, segmental defect was made at the central portion of the right patellar tendon, while a sham operation performed in the left tendon. At 3, 6, 12, and 24 weeks, we evaluated the mechanical properties and fibroblast density of the regenerated and the residual tissues as well as the blood flow and tissue dimensions of the patellar tendon. In addition, non-treated patellar tendons from six rabbits were served as the control for mechanical testing.Results. The tangent modulus and the tensile strength of the regenerated tissue progressively increased with time. On the other hand, these parameters of the residual tendinous portion decreased until 6 weeks, although they gradually increased thereafter. The tensile strength of the regenerated and the residual tissues at 24 weeks were approximately 80% and 75%, respectively, of the non-treated, control tendon. Abundant blood flow and cell proliferation were observed in the regenerative tissue until 6 weeks.Conclusion. The mechanical properties of the regenerated and the residual tissues after removal of the central portion in the patellar tendon are much different from those of the original tendon.RelevanceThe present study showed inferior mechanical properties of the residual and the regenerated tissues for up to 24 weeks after removal of the central portion in the patellar tendon. Therefore, the aggressive rehabilitation that applies excessive load to the patellar tendon should be avoided at an early stage after harvesting the tendon for ligament reconstruction. [Copyright &y& Elsevier]

One of the future goals in ligament reconstruction is to prevent graft deterioration after transplantation. The aim of this study is to clarify whether an administration of TGF-beta1 and EGF significantly affect biomechanical properties of the in situ frozen-thawed anterior cruciate ligament (ACL), an ACL autograft model, and to elucidate whether the timing of this administration may influence its effect. Rabbits were randomly divided into 4 groups after the freeze-thaw treatment with liquid nitrogen was applied to the right knee. In 2 groups, 4-ng TGF-beta1 and 100-ng EGF mixed with 0.2-ml fibrin sealant were applied around the ACL at 3 and 6 weeks after the treatment, respectively. In the remaining two groups, only 0.2-ml fibrin sealant was applied around the ACL at 3 and 6 weeks, respectively. In each group, all animals were sacrificed at 12 weeks after the freeze-thaw treatment. These growth factors applied at 3 weeks significantly inhibited not only the increase of water content and the cross-sectional area of the ACL but also reduction of the tensile strength and the tangent modulus of the ACL (p<0.0001), which were induced by the freeze-thaw treatment. However, the application at 6 weeks did not significantly affect the changes of these parameters after the treatment. This study demonstrated that the timing of administration of TGF-beta and EGF after the freeze-thaw treatment significantly influences its effect on the biomechanical properties of the frozen-thawed ACL. [Copyright &y& Elsevier]

Objective. To clarify the effect of complete stress deprivation on the mechanical properties of the in situ frozen-thawed semitendinosus tendon, an idealized autograft model.Design. Ninety-six rabbits were divided into three groups. In the frozen group (n=36), we applied the freeze-thaw treatment to the semitendinosus tendon to necrotize fibroblasts in the tendon. In the frozen and stress-shielded group (n=30), after we applied the same freeze-thaw treatment to the tendon, we completely released the tendon from stress. In the sham group (n=30), a sham operation was applied. In each group, 6 rabbits were sacrificed at 0 (only in the frozen group), 1, 2, 3, 6 and 12 weeks after surgery.Background. Previous studies have not clarified remodeling of the semitendinosus autograft in ligament reconstruction or its idealized model.Method. The tendon was frozen with liquid nitrogen. The tendon was released from stress with the originally developed technique using a polyester tape. In each period, 5 out of the 6 rabbits were evaluated with tensile testing, and the remaining rabbit was histologically observed.Result. Complete stress shielding significantly increased the cross-sectional area of the frozen-thawed tendon at 1 and 2 weeks, while it significantly inhibited the increase of the area due to the freeze-thaw treatment at 3 and 6 weeks. Complete stress shielding significantly reduced material properties of the frozen-thawed tendon after 2 weeks.Conclusion. The frozen-thawed semitendinosus tendon has unique remodeling characteristics under a stress-shielded condition, which were not the same as those of the frozen-thawed patellar tendon.Relevance Remodeling of the semitendinosus tendon autograft under stress-shielded conditions may be different from that of the patellar tendon autograft. [Copyright &y& Elsevier]