Harukazu Tohyama

Effects of local administration of vascular endothelial growth factor on mechanical characteristics of the semitendinosus tendon graft after anterior cruciate ligament reconstruction in sheep.

Background Vascular endothelial growth factor (VEGF) is a potent mediator of angiogenesis. Hypothesis An application of VEGF may enhance angiogenesis in the grafted tendon in anterior cruciate ligament (ACL) reconstruction, and the application may affect mechanical characteristics of the ACL graft. Study Design Controlled laboratory study. Methods Eighteen sheep were divided into groups I and II. In group I, the harvested semitendinosus tendon was soaked in VEGF solution, and the right knee then underwent ACL reconstruction using this tendon. In group II, the right knee underwent identical procedures to those of group I except that the harvested tendon was soaked in phosphate-buffered saline. All animals were sacrificed 12 weeks after ACL reconstruction. Results Histologic findings showed that newly formed vessels and infiltrative fibroblasts were more abundant in group I than in group II. The anterior-posterior translation of the knee during an anterior-posterior force of ±100 N was significantly larger in group I than in group II by 2.58 mm (95% confidence interval, -1.76 mm to 1.76 mm) (P =. 002). The linear stiffness of the femur-graft-tibia complex in group I was significantly lower than that in group II by 41.5 N/mm (95% confidence interval, -32.2 N/mm to 32.2 N/mm) (P=. 017). Conclusion This study has revealed that VEGF as administered in this study promotes angiogenesis in the ACL graft and significantly reduces the stiffness of the ACL graft with increased knee laxity at 12 weeks after ACL reconstruction. Clinical Relevance Exogenous VEGF application for ACL reconstruction can induce an increase in knee laxity and a decrease in the stiffness of the grafted tendon at least temporarily after ACL reconstruction. These potentially negative mechanical effects need to be taken into account when considering clinical use of VEGF.

The Effect of Cyclic Displacement On the Biomechanical Characteristics of Anterior Cruciate Ligament Reconstructions

This study was conducted to clarify the influence of cyclic displacement on the structural properties of four types of femur-graft-tibia complexes used to reconstruct the anterior cruciate ligament. Forty hindlimbs from pigs were used. In two groups, bone-patellar tendon-bone grafts were secured with interference screws (group A) or the suture-post technique (group B). In two groups, multistrand flexor tendons were fixed using the tape-staple technique (group C) or the sutures-tied-over-a-button technique (group D). In each group, five femur-graft-tibia complexes underwent tensile failure tests without cyclic displacement. The other five complexes underwent 5000 cycles of cyclic elongation for 2 mm, and then underwent the tensile failure tests. The initial stiffness significantly decreased after cyclic displacement in each group, although there were no significant differences in the linear stiffness and the ultimate failure load between the tests with and without cyclic displacement. These findings suggest that 5000 cycles of repetitive elongation of the femur-graft-tibia complex by 2 mm does not jeopardize the graft fixed with the procedures used in this study, despite a slight but significant increase of an anterior-posterior laxity of the knee.

The Effect of Growth Factors on Biomechanical Properties of the Bone–Patellar Tendon–Bone Graft After Anterior Cruciate Ligament Reconstruction A Canine Model Study

Background No studies have dealt with the effect of growth factors on the free tendon autograft in anterior cruciate ligament reconstruction. Hypothesis Application of exogenous transforming growth factor-β and epidermal growth factor may affect the structural properties and histology of the bone-patellar tendon-bone autograft after anterior cruciate ligament reconstruction. Study Design Controlled laboratory study. Methods Twenty dogs underwent anterior cruciate ligament reconstruction with the autogenous bone-patellar tendon-bone graft in bilateral knees. In 10 animals, 12 ng transforming growth factor-β and 300 ng epidermal growth factor mixed with fibrin sealant of 0.6 mL were applied to the left knee. In the remaining 10 dogs, fibrin sealant alone was applied to the left knee. No additional treatments were applied to the right knee. Results The growth factor application increased the stiffness and maximum failure load of the femur-graft-tibia complex at 12 weeks (P = .016 and P = .012, respectively); the sham treatment did not significantly affect them. Histologically, most of the cells in the grafts treated with growth factors had spindle-shaped nuclei; cells in the other grafts had round-shaped nuclei. Conclusions Application of transforming growth factor-β and epidermal growth factor improves the structural properties of the autograft after anterior cruciate ligament reconstruction in the canine model. Clinical Relevance Application of growth factors is a possible strategy to prevent graft deterioration in anterior cruciate ligament reconstruction.

Effects of combined administration of transforming growth factor-β1 and epidermal growth factor on properties of the in situ frozen anterior cruciate ligament in rabbits

The mechanical properties of tendon autografts used in reconstruction of the anterior cruciate ligament (ACL) are reduced after surgery. Previous studies showed that growth factors such as transforming growth factor‐β1 (TGF‐β1) and epidermal growth factor (EGF) can stimulate fibroblast proliferation and increase collagen and noncollagenous protein synthesis by these cells. These factors might be useful, therefore, in preventing graft deterioration after transplantation or accelerating mechanical restoration of the deteriorated graft. The purpose of our study, therefore, was to clarify the effects of TGF‐β1 and EGF on biomechanical properties using an in situ freeze‐thaw ACL model in the rabbit. A total of 142 rabbits underwent the freeze‐thaw treatment in the right ACL and were then divided into four groups. Group I served as a freeze‐thaw, but otherwise untreated control. In Group II, a delivery vehicle (fibrin sealant) alone was applied. In Group III, 4‐ng TGF‐β1 and 100‐ng EGF mixed with the vehicle were applied. In Group IV, higher doses (2‐μg TGF‐β1 and 50‐μg EGF) of growth factors were mixed with the vehicle. The groups were compared at 6 and 12 weeks on the basis of mechanical properties, water content, and histological and ultrastructural observations. The cross‐sectional area of Group III (average, 7.1 mm2) was significantly less than that of Groups I, II, and IV (9.0, 8.2, and 9.4 mm2, respectively) at 12 weeks. The tensile strength of Group III (62.2 MPa) was significantly greater than that of Groups I, II, and IV (35.6, 43.7, and 36.9 MPa, respectively) at 12 weeks, while the water content of Group III (70.7%) was significantly lower than that of Group I (75.2%). No other significant differences occurred among Groups I, II, and IV. A unimodal distribution of collagen fibril diameters was noted in Groups I and II, while a bimodal pattern was found in Group III. This study demonstrated that low‐dose application of TGF‐β1 and EGF significantly inhibited not only the increased water content and cross‐sectional area, but also the decreased tensile strength caused by the freeze‐thaw treatment, while a high dose of TGF‐β1 and EGF does not have the same beneficial effects.

Magnetic Resonance Imaging in Stress Fractures and Shin Splints

The purpose of the current study was to determine whether stress fractures and shin splints could be discriminated with MRI in the early phase. Twenty-two athletes, who had pain in the middle or distal part of their leg during or after sports activity, were evaluated with radiographs and MRI scans. Stress fractures were diagnosed when consecutive radiographs showed local periosteal reaction or a fracture line, and shin splints were diagnosed in all the other cases. In all eight patients with stress fractures, an abnormally wide high signal in the localized bone marrow was the most detectable in the coronal fat-suppressed MRI scan. In 11 patients with shin splints, the coronal fat-suppressed MRI scans showed a linear abnormally high signal along the medial posterior surface of the tibia, and in seven patients with shin splints, the MRI scans showed a linear abnormally high signal along the medial bone marrow. No MRI scans of shin splints showed an abnormally wide high signal in the bone marrow as observed on MRI scans of stress fractures. This study showed that fat-suppressed MRI is useful for discrimination between stress fracture and shin splints before radiographs show a detectable periosteal reaction in the tibia.

The Effect of Initial Graft Tension in Anterior Cruciate Ligament Reconstruction on the Mechanical Behaviors of the Femur-Graft-Tibia Complex during Cyclic Loading*

Background Initial graft tension influences clinical results of anterior cruciate ligament reconstruction. Hypothesis Under repetitive loading conditions, the effect of initial graft tension on the biomechanical behavior of the femur-graft-tibia complex may depend on the graft and the fixation. Study Design Ex vivo biomechanical laboratory study. Methods After anterior cruciate ligament reconstruction, initial graft tension of 20, 80, or 140 N was applied to the complex for 2 minutes. Then, a cyclic force-relaxation test was performed for 5000 cycles so that the graft was stretched by 2 mm. Results In a patellar tendon graft with interference screws, the average peak load values at the 5000th cycle were 105, 157, and 205 N for the complexes with initial tension of 20, 80, and 140 N, respectively. In a flexor tendon graft with interference screws, the values were 27, 41, and 39 N. In a flexor tendon graft with Endobutton fixation, the values were 17, 40, and 77 N. Conclusions Considering the tension of the normal anterior cruciate ligament (16 to 87 N), an initial tension of 20 N appears to be high enough for a patellar tendon graft. For a flexor tendon graft with interference screws, an increase in initial tension above 80 N has no biomechanical advantages.

Anterior Drawer Test for Acute Anterior Talofibular Ligament Injuries of the Ankle How Much Load Should be Applied During the Test

Background: There is a lack of consensus regarding the magnitude of load for performing the anterior drawer test in evaluating acute ankle injuries. Purpose: To determine how much load should be applied during the anterior drawer test to detect the integrity of the anterior talofibular ligament. Methods: First, the anterior-posterior load-displacement response of nine cadaveric ankles was measured. Second, anterior displacement of the ankle was measured at 30 and 60 N of anterior load in 14 patients with acute tears of the anterior talofibular ligament. Results: In the cadaver study, the increased displacement by sectioning of the ligament measured at 10, 20, 30, and 40 N of anterior load were significantly greater than those measured at 60 N. In vivo examination of the subjects without anesthesia demonstrated that the injured-to-normal displacement value at 30 N of anterior load was significantly greater than the value at 60 N. Conclusions: This study suggests that a large magnitude of anterior load is not necessary to detect the integrity of the ligament during the anterior drawer test. Clinical Relevance: When evaluating the integrity of the anterior talofibular ligament in cases of acute ankle ligament injury, a relatively low-magnitude load should be applied.

Atelocollagen-associated autologous chondrocyte implantation for the repair of chondral defects of the knee: a prospective multicenter clinical trial in Japan

BackgroundNew tissue-engineering technology was developed to create a cartilage-like tissue in a three-dimensional culture using atelocollagen gel. The minimum 2-year followup outcome of transplanting autologous chondrocytes cultured in atelocollagen gel for the treatment of full-thickness defects of cartilage in knees was reported from the single institution. The present multicenter study was conducted to determine clinical and arthroscopic outcomes in patients who underwent atelocollagen-associated autologous chondrocyte implantation for the repair of chondral defects of the knees.MethodsAt six medical institutes in Japan, we prospectively evaluated the clinical and arthroscopic outcomes of transplanting autologous chondrocytes cultured in atelocollagen gel for the treatment of full-thickness defects of cartilage in 27 patients (27 knees) with cartilage lesions on a femoral condyle or on a patellar facet over 24 months.ResultsThe Lysholm score significantly increased from 60.0 ± 13.7 points to 89.8 ± 9.5 points (P = 0.001). Concerning the ICRS grade for arthroscopic appearance, 6 knees (24%) were assessed as grade I (normal) and 17 knees (68%) as grade II (nearly normal). There were few adverse features, except for detachment of the graft in two cases.ConclusionsWe concluded that transplanting chondrocytes in a newly formed matrix of atelocollagen gel can promote restoration of the articular cartilage of the knee.

Effects of Local Administration of Vascular Endothelial Growth Factor on Properties of the in Situ Frozen-Thawed Anterior Cruciate Ligament in Rabbits

Background In the autogenous tendon for anterior cruciate ligament reconstruction, intrinsic fibroblasts are necrotized immediately after surgery, and repopulation and revascularization occur. Vascular endothelial growth factor is considered to be a potent mediator of angiogenesis. Hypothesis An application of vascular endothelial growth factor significantly enhances angiogenesis in the in situ frozen anterior cruciate ligament, and the application significantly affects mechanical properties of the in situ frozen anterior cruciate ligament. Study Design Controlled laboratory study. Methods Right anterior cruciate ligaments from 66 rabbits underwent the freeze-thaw treatment, and animals were then divided into 3 groups. Group I served as a freeze-thaw but otherwise untreated control. In group II, 0.2 mL phosphate-buffered saline alone was applied. In group III, 30 µ g vascular endothelial growth factor was applied. The groups were compared on the basis of histologic revascularization examinations using the Chalkley score, an indicator of the microvessel density, and mechanical evaluations, which included the anterior-posterior translation of the tibia relative to the femur during ± 10 N of anterior-posterior load and the mechanical properties of the anteromedial bundle of the anterior cruciate ligament. Results Group IIIs Chalkley score was significantly greater than that of groups I and II. The tensile strength and the tangent modulus of anterior cruciate ligaments in groups I, II, and III were significantly lower than those of a normal anterior cruciate ligament, although there were no significant differences among groups I, II, and III. Conclusion Vascular endothelial growth factor, as administered in this study, significantly promoted angiogenesis in the devitalized anterior cruciate ligament with in situ freeze-thaw treatment, but it did not affect the mechanical properties of the in situ frozen-thawed anterior cruciate ligament in the rabbit model. Clinical Relevance An application of the recombinant anterior cruciate ligament is a potential future strategy to enhance revascularization of the autograft in anterior cruciate ligament reconstruction.

Significance of graft tension in anterior cruciate ligament reconstruction Basic background and clinical outcome

Abstract The purpose of this paper is to review scientific evidence that graft tension affects remodelling of the autograft in ligament reconstruction. The in situ freezing model of the patellar tendon, an ideal patellar tendon autograft model, demonstrated that subsequent cellular proliferation following fibroblast necrosis reduces the mechanical properties of the autograft. Stress shielding enhances reduction of the strength in the once-frozen patellar tendon. The strength of the patellar tendon also changes depending on the degree of stress shielding. Transmission electron micrographs revealed that the number of small-diameter fibrils decreases in the stress-shielded tendons compared with non-stress-shielded tendons after in situ freezing. Restressing essentially restores the mechanical properties of patellar tendon autografts even if the strength has been much reduced by complete stress shielding. The effects of restressing may depend on the period of stress shielding applied before restressing. Unphysiologically high tension significantly reduces the mechanical properties of the in situ frozen anterior cruciate ligament (ACL). Therefore, not only stress-deprivation but also stress-enhancement significantly affect the mechanical properties of tendon autografts. Results of in vivo and in vitro studies suggest that cyclic tensile loading may inhibit the deterioration in mechanical strength of the transplanted tendon. Clinically, our prospective randomized study demonstrated that a relatively high initial tension reduces the postoperative anterior laxity of the knee joint after ACL reconstruction using the doubled autogenous hamstring tendons connected in series with polyester tapes, when the tension applied is less than 80 N. Our experimental and clinical results indicate that the initial tension is one of the significant factors that affect the results of ACL reconstruction, although the optimal initial tension for the other graft materials still remains unknown.