Shin Miyatake

An In Vivo Biomechanical Study on the Tension–Versus–Knee Flexion Angle Curves of 2 Grafts in Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction: Effects of Initial Tension and Internal Tibial Rotation

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.

Randomized clinical comparisons of diclofenac concentration in the soft tissues and blood plasma between topical and oral applications

AIMS To compare tissue concentrations of diclofenac resulting from topical and oral applications of diclofenac according to clinically recommended prescriptions. METHODS Diclofenac sodium was applied to 14 subjects (four male and 10 female), who were scheduled to undergo knee arthroplasty due to osteoarthritis, according to the oral or topical prescription (a capsule containing 37.5 mg diclofenac sodium or two tapes containing a total of 30 mg diclofenac sodium). At 12 h after prescription, the diclofenac concentration in the fat, muscle and synovial tissues was measured with liquid chromatography and mass analysis. RESULTS The diclofenac concentration in the muscle was significantly higher (P = 0.0196) after topical application (average 9.29 ng ml(-1)) than after oral application (0.66 ng ml(-1)), whereas there was no significant difference in the plasma diclofenac level (4.70 and 6.63 ng ml(-1)) between the two applications. The concentration in the synovial membrane was significantly (P = 0.0181) lower in the topical application (4.99 ng ml(-1)) than in the oral application (15.07 ng ml(-1)). CONCLUSIONS Whereas plasma levels resulting from topical and oral applications of diclofenac according to clinically recommended prescriptions were comparable, concentration levels in the muscle and synovial tissues were different.

Biomechanical Comparisons Between 4-Strand and Modified Larson 2-Strand Procedures for Reconstruction of the Posterolateral Corner of the Knee

Background: The posterolateral corner (PLC) resists tibial varus angulation, external rotation, and, to a lesser extent, posterior translation. It is important that reconstructions of posterolateral knee injuries restore joint laxity and patient function, but residual laxities are often observed. Hypothesis: The knee laxity after a new 4-strand PLC reconstruction would be closer to normal than after a 2-strand “modified Larson” reconstruction. Study Design: Controlled laboratory study. Methods: Fourteen intact cadaveric knees were mounted in a 6 degrees of freedom rig and subjected to the following external loading conditions: a 90-N posterior tibial force, a 5-N·m external rotation torque, and 5-N·m varus moment. Knee kinematics were recorded with an active optical tracking system for the intact, PLC-deficient, modified Larson PLC reconstruction and 4-strand PLC reconstruction. Results: With external tibial torque, the rotational laxity in 4-strand reconstruction was significantly less than in the PLC-deficient (P < .0001) and modified Larson reconstruction (P = .0112) and did not differ significantly from intact laxity at any angle of flexion. In response to posterior load, posterior translation did not change in any of the tested conditions, while the coupled external rotation laxity in 4-strand PLC reconstruction was significantly less than in the PLC-deficient (P < .0001) and modified Larson reconstruction (P < .0486) and was not significantly different from the intact movements for both reconstructions. The varus angulation-versus-flexion curves were significantly different between the PLC-deficient and both PLC reconstructions (P < .0001). The varus laxity was not significantly different between the modified Larson reconstruction, the 4-strand reconstruction, and the intact knee. Conclusion: This study showed that the rotational knee laxity in response to both external rotation and posterior translation load were significantly better after the 4-strand PLC reconstruction than after the modified Larson reconstruction, although significant differences were not found between the 2 procedures for varus laxity. Clinical Relevance: The 4-strand PLC reconstruction may produce a better biomechanical outcome, especially during external rotation and posterior translation tibial load. The authors suggest that this relates to load sharing among 4 graft strands crossing the joint.

Effects of Remnant Tissue Preservation on the Tendon Graft in Anterior Cruciate Ligament Reconstruction: A Biomechanical and Histological Study

Background: There is controversy regarding the efficacy of remnant tissue preservation on graft healing in anterior cruciate ligament (ACL) reconstruction. Hypothesis: The preserved remnant tissue will (1) adhere to the graft surface and undergo a remodeling process, (2) accelerate graft revascularization, (3) increase the number of graft mechanoreceptors by 4 weeks, and (4) improve anteroposterior knee laxity and structural properties of the graft by 12 weeks. Study Design: Controlled laboratory study. Methods: Forty-two sheep were randomly divided into 2 groups of 21 animals. In group I, the ACL was completely removed. In group II, the ACL was transected at the midsubstance but not debrided. ACL reconstruction was performed using a semitendinosus tendon autograft in both groups. Histological changes of the grafted tendon and the remnant tissue were evaluated at 4 and 12 weeks after surgery. Biomechanically, anterior translation and knee joint stiffness under an anterior drawer force and the structural properties of the femur-graft-tibia complex were evaluated. Results: The preserved remnant tissue was histologically distinct from the graft at 4 weeks, while the tissue partially adhered to the graft surface at 12 weeks. The ACL remnant tissue significantly accelerated revascularization in the grafted tendon at 4 weeks and significantly increased the number of mechanoreceptors at 4 and 12 weeks. In addition, remnant preservation significantly improved anterior translation (9.3 ± 2.1 mm and 5.4 ± 1.7 mm at 60° of knee flexion in groups I and II, respectively) and knee joint stiffness at 12 weeks. However, there were no significant differences in the structural properties between the 2 groups at 4 and 12 weeks after surgery. Conclusion: Preservation of the ACL remnant tissue in ACL reconstruction enhanced cell proliferation, revascularization, and regeneration of proprioceptive organs in the reconstructed ACL and reduced anterior translation. However, remnant preservation did not improve the structural properties of the graft. Clinical Relevance: These results imply that preservation of the ACL remnant tissue may improve graft healing after ACL reconstruction.

Biomechanical Evaluation of a Novel Application of a Fixation Device for Bone-Tendon-Bone Graft (EndoButton CL BTB) to Soft-Tissue Grafts in Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction

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.

Biomechanical Characteristics of 3 Pivot-Shift Maneuvers for the Anterior Cruciate Ligament–Deficient Knee In Vivo Evaluation With an Electromagnetic Sensor System

Background: A disadvantage of pivot-shift maneuvers is that the examiner has to subjectively evaluate the degree of pivot shift observed. It is unknown whether the various maneuvers are biomechanically identical. Purpose: To compare biomechanical features of 3 clinical maneuvers for the anterior cruciate ligament (ACL)–deficient knee: the pivot-shift test, the jerk test, and the N-test. Study Design: Controlled laboratory study. Methods: A total of 28 patients with an isolated ACL injury were examined by use of 3 pivot-shift maneuvers (pivot-shift test, jerk test, and N-test). An electromagnetic sensor system was used to evaluate the 3-dimensional knee kinematics of each patient’s injured and uninjured knees during each maneuver. Peak coupled anterior tibial translation (pCAT) and maximal acceleration of posterior translation (APT) were measured relative to results during a flexion-extension motion in each test. Results: The pCAT of the pivot-shift test was significantly greater than that of both the jerk test and the N-test (P = .0020 and P < .0001, respectively); there was no statistical difference in pCAT between the jerk test and the N-test. The APT of the N-test was significantly greater than that of both the pivot-shift test and the jerk test (P < .0001), while there was no statistical difference between the pivot-shift and the jerk tests. There was no correlation between pCAT and APT in each test. Conclusion: The pivot-shift test, jerk test, and N-test have different biomechanical characteristics to induce the pivot-shift phenomenon in the ACL-deficient knee. The pivot-shift test produced the largest side-to-side difference in pCAT, whereas the N-test provoked the largest side-to-side difference in APT. Clinical Relevance: The biomechanical differences in pivot-shift maneuvers are caused by technical differences, and clinicians should understand these biomechanical differences while practicing the maneuvers. The electromagnetic sensor system is clinically useful for quantifying the pivot-shift phenomenon.

Stress deprivation from the patellar tendon induces apoptosis of fibroblasts in vivo with activation of mitogen-activated protein kinases

The effect of stress deprivation on the tendon tissue has been an important focus in the field of biomechanics. However, less is known about the in vivo effect of stress deprivation on fibroblast apoptosis as of yet. This study was conducted to test a hypothesis that complete stress deprivation of the patellar tendon induces fibroblast apoptosis in vivo with activation of Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38) within 24 h after treatment. A total of 35 mature rabbits were divided into stress-shielded (n=15), sham-operated (n=15), and control (n=5) groups. To completely shield the patellar tendon from stress, we used an established surgical method. Animals were sacrificed at 24 h, and 2, 4, 7, and 14 days after the treatment. Tendon specimens underwent TUNEL assay and immunohistological examinations of active caspase-3, JNK, and p38. Both the number and the ratio of TUNEL-positive and caspase-3-positive cells were significantly greater (p<0.0001) in the stress-shielded group than in the sham group at 24 h, 2, 4, and 7 days. Concerning JNK and p38, both the number and the ratio were significantly greater (p<0.0001) in the stress-shielded group than in the sham group at 24 h, 2, and 4 days. This study demonstrated that complete stress deprivation induces fibroblast apoptosis in vivo with activation of JNK and p38 within 24 h. This fact suggested that the fibroblast apoptosis caused by stress deprivation is induced via the mitogen-activated protein kinase signaling pathway.

Deficiency of macrophage migration inhibitory factor gene delays healing of the medial collateral ligament : A biomechanical and biological study

The role played by macrophage migration inhibitory factor (MIF) in the process of wound healing is controversial. Besides, there have been no reports that investigated the expression or the role of MIF in the repair process after ligament injury. In this study, we hypothesized that the deficiency in MIF gene might delay ligament healing in mice. The aim of this study was to clarify this hypothesis using MIF gene-deficient mice (MIFKO) and murine model of injury to the medial collateral ligament (MCL). Biomechanical testing showed that the levels of mechanical properties were significantly lower in MIFKO than in wild-type mice (WT) on day 28 after injury. Levels of matrix metalloproteinase (MMP)-2 and -13 mRNA in the healing tissue were significantly lower in MIFKO than in WT on day 28 and on day 7, respectively. Histologically, healing tissues in MIFKO exhibited prolonged hypertrophy, poor vascularity, and prolonged increase in cell number compared with those in WT. Taken together, it was suggested that MIFKO exhibited delayed healing of the MCL, which might be caused by lower mRNA expression of MMP-2 and -13.