Studies in flexor tendon wound healing: neutralizing antibody to TGF-beta1 increases postoperative range of motion

The postoperative outcome of hand flexor tendon repair remains limited by tendon adhesions that prevent normal range of motion. Recent studies using in situ hybridization techniques have implicated transforming growth factor beta-1 (TGF-beta1) in both intrinsic and extrinsic mechanisms of repair. TGF-beta1 is a growth factor that plays multiple roles in wound healing and has also been implicated in the pathogenesis of excessive scar formation. The purpose of this study was to examine the effect of neutralizing antibody to TGF-beta1 in a rabbit zone II flexor tendon wound-healing model. Twenty-two adult New Zealand White rabbits underwent complete transection of the middle digit flexor digitorum profundus tendon in zone II. The tendons were immediately repaired and received intraoperative infiltration of one of the following substances: (1) control phosphate-buffered saline; (2) 50 microg neutralizing antibody to TGF-beta1; (3) 50 microg each of neutralizing antibody to TGF-beta1 and to TGF-beta2. Eight rabbits that had not been operated on underwent analysis for determination of normal flexion range of motion at their proximal and distal interphalangeal joints, using a 1.2-N axial load applied to the flexor digitorum profundus tendon. All rabbits that had been operated on were placed in casts for 8 weeks to allow maximal tendon adhesion and were then killed to determine their flexion range of motion. Statistical analysis was performed using the Student's unpaired t test. When a 1.2-N load was used on rabbit forepaws that had not been operated on, normal combined flexion range of motion at the proximal and distal interphalangeal joints was 93+/-6 degrees. Previous immobilization in casts did not reduce the range of motion in these forepaws (93+/-4 degrees). In the experimental groups, complete transection and repair of the flexor digitorum profundus tendon with infiltration of control phosphate-buffered saline solution resulted in significantly decreased range of motion between the proximal and distal phalanges [15+/-6 degrees (n = 8)]. However, in the tendon repairs infiltrated with neutralizing antibody to TGF-beta1, flexion range of motion increased to 32+/-9 degrees (n = 7; p = 0.002). Interestingly, a combination of neutralizing antibody to TGF-beta1 and that to TGF-beta2 did not improve postoperative range of motion [18+/-4 degrees (n = 7; p = 0.234)]. These data demonstrate that (1) the rabbit flexor tendon repair model is useful for quantifying tendon scar formation on the basis of degrees of flexion between proximal and distal phalanges; (2) intraoperative infiltration of neutralizing antibody to TGF-beta1 improves flexor tendon excursion; and (3) simultaneous infiltration of neutralizing antibody to TGF-beta2 nullifies this effect. Because TGF-beta1 is thought to contribute to the pathogenesis of excessive scar formation, the findings presented here suggest that intraoperative biochemical modulation of TGF-beta1 levels limits flexor tendon adhesion formation.     

Staged reconstruction of flexor tendons with a silicone rod and a "pedicled" sublimis transfer

We report the results in 11 cases of secondary flexor tendon reconstruction, employing a silicone rubber rod and a sublimis/profundus tenorrhaphy in the first stage, then hinging out the sublimis tendon on the profundus motor at the second stage. Achievement of a healed proximal tenorrhaphy before the second stage allows (1) inspection of the proximal tenorrhaphy (with assessment of its location, apperance, and strength) and (2) early postoperative motion in a controlled range (with greater confidence in the proximal tenorrhaphy, as rupture after free tendon grafting is not uncommon. The functional results attained were comparable to those in other series of secondary flexor tendon reconstructions.     

Experimental determination of forces transmitted through the patello-femoral joint

Tensions in the quadriceps tendon and infrapatellar ligament were measured as a function of flexion angle in eight cadaver knees using a load cell of a materials tester to determine the quadriceps force and a spring balance to quantify the patellar tendon force. The ratio between the tensions in the quadriceps tendon and the patellar tendon (FQ/FP) ranged from 1.55 at 70 degrees of flexion to 0.86 at 10 degrees of flexion. The patello-femoral joint reaction (PFJR) force for extension against resistance was maximal at 60 degrees. No change in the quadriceps force required to extend the knee occurred with changes of the Q-angle of +/- 5 degrees. This study demonstrates that FQ does not equal FP as several authors have reported (Bandi, 1972; Barry, 1979; Ficat and Hungerford, 1977; Hungerford and Barry, 1979; Reilly and Martens, 1972; Smidt, 1973). Furthermore, the difference in FQ and FP influences both the magnitude and direction of PFJR. Studies that assess the influence of surgical procedures which alter the patello-femoral joint or the extensor mechanism must take these differences into account.     

Effect of vascular endothelial growth factor on rat Achilles tendon healing

This study evaluated the effect of exogenous vascular endothelial growth factor (VEGF) on tendon healing and regulation of other growth factors in a rat Achilles tendon model. Fifty Sprague-Dawley rats were used. In the experimental group, the left Achilles tendon was transected and repaired with the modified Kessler suture technique, and the right Achilles tendon was transected and repaired with resection of plantaris tendon. VEGF, 100 mul (50 mug/ml), was injected into each tendon at the repair site. The same surgical procedures were performed in the control group, with the same volume of saline injected into the repair sites. At intervals of 1, 2, and 4 weeks, the animals were killed and the tendons were harvested and evaluated for tensile strength (1, 2, and 4 weeks) and gene expression (postoperative day 4). At 1 week postoperatively, when plantaris tendon was preserved, the tensile strength of the repaired tendons with VEGF treatment (3.63 +/- 0.62 MPa) was significantly higher than the tensile strength of the repaired tendons with saline treatment (2.20 +/- 0.36 MPa). There was no difference in tensile strength between the two groups without the plantaris tendon support. At 2 weeks postoperatively, the tensile strength was 11.34 +/- 3.89 MPa in the group with VEGF treatment and plantaris tendon preservation, which was significantly higher than the tensile strength in the other groups. There was no significant difference in tensile strength among the groups at 4 weeks postoperatively. The gene expression showed that transforming growth factor-beta in the VEGF-treated tendon was up-regulated in the early stage of tendon healing, whereas expression of platelet-derived growth factor, basic fibroblast growth factor, and insulin-like growth factor-1 was not significantly different among the groups. In conclusion, administration of exogenous VEGF can significantly improve tensile strength early in the course of the rat Achilles tendon healing and was associated with increased expression of transforming growth factor-beta.     

Effects of knee flexion on the structural properties of the rabbit femur-anterior cruciate ligament-tibia complex (FATC)

Many studies have been conducted to determine the biomechanical properties of the anterior cruciate ligament (ACL). The method of holding the femur-ACL-tibia complex (FATC) test specimen, the strain rate applied, the angle of knee flexion and the direction of the applied loads have an important effect on the outcome. It is felt that the tensile properties and strength of the ligament should be measured by applying the tensile force along the axis of the ligament. A versatile clamp was designed to accomplish this purpose. Fifty-seven rabbit knee specimens were tested at angles of flexion of 0 degrees, 30 degrees or 90 degrees. In addition, a comparative study of 25 pairs of rabbit legs were performed, whereby loading was either along the ligament or along the tibial axis. Cyclic hysteresis, ultimate load, energy absorbed, and stiffness were determined. The ultimate load values for the FATC decreased with increased knee flexion for those loaded along the tibial axis, while no such change was detected for FATC tested along the ligament axis. Other structural properties measured followed similar trends. It is concluded that the structural properties of the rabbit FATC change minimally with knee flexion (from 0 to 90 degrees) when loaded along the ligament axis, but decrease significantly with knee flexion when loaded along the axis of the tibia. Therefore, the data obtained in this field of study can be compared only if the direction of loading with respect to the ACL is similar.     

Effect of hydrogen peroxide on human tendon allograft

Bacterial contamination of tendon allografts at the completion of processing has historically been about 2 %, with tendons that are found to be culture positive being discarded. Treatment of tendon allograft with hydrogen peroxide at the beginning of tissue processing may reduce bacterial contamination, however, the potential side effects of hydrogen peroxide treatment include hydrolysis of the collagen and this may alter the mechanical properties of the graft. Pairs of human tendons were used. One was washed in 3 % hydrogen peroxide for 5 min and the untreated tendon was used as a control. The ultimate tensile strength of the tendons was determined using a material testing machine. A freeze clamp technique was used to hold the tendons securely at the high loads required to cause tendon failure. There was no statistical difference in the ultimate tensile strength between the treated and untreated tendons. Mean strength ranged from Extensor Hallucis Longus at 588 Newtons to Tibialis Posterior at 2,366 Newtons. Hydrogen peroxide washing may reduce bacterial contamination of tendon allograft and does not affect the strength of the tendon.     

The effect of a lathyritic diet on the sensitivity of tendon to strain rate

While the tensile failure properties of rat-tail tendon depend on strain rate, the sensitivity to strain rate decreases with age, especially during sexual maturation. The object of this study was to determine the effect of an experimental model of chronic lathyrism on age-dependent changes in the sensitivity of developing tendon strength to strain rate. Tensile failure experiments were conducted at high and low strain rate on tendons excised from test and control animals aged 1 to 6 mo. The tensile "yield" response of tendon was significantly affected by the diet resulting in a reduced tensile strength and failure strain. While the sensitivity of tendon failure to strain rate was slightly elevated by the experimental diet, age-dependent changes compared with controls. Since the diet supplement is thought to inhibit covalent crosslinking of collagen in the developing tendon, other factors are likely responsible for decrease in the sensitivity of tendon strength to strain rate during maturation.     

Four Anchor Repair of Jersey Finger

BackgroundVarious surgical techniques for treating avulsions of the flexor digitorum profundus tendon at the distal phalanx have been published but no ideal technique has emerged. We introduce a new all-internal 4-anchor flexor tendon repair technique and evaluate outcomes in three clinical cases.MethodsIn this retrospective case series, we reviewed three patients that sustained an avulsion of the flexor digitorum profundus tendon at the distal phalanx. All patients were surgically treated with the four-anchor repair technique. Two titanium anchors were inserted into the distal phalanx and two all-suture anchors were inserted distal to the first set of anchors. The tendon was then attached to these four anchors using a Krackow stitch pattern and the anchors were sown to each other. Active flexion and extension of the proximal and distal interphalangeal joint were measured at 3-month, 12-month, and 5-year follow-up. Postoperative complications were documented.ResultsAll patients achieved excellent clinical outcomes according to assessment criteria. At 3-month follow-up, all patients regained full flexion; two patients had full extension, while one patient was 3 degrees short of full extension. At 12-month follow-up, all patients had full flexion and extension. Five-year follow-up demonstrated the same results with no loss of function, sensation or grip strength. The repairs healed without rupture, and no complications were reported.ConclusionThe 4-anchor flexor tendon repair is a viable surgical technique for zone 1 flexor digitorum profundus tendon repair or reconstruction. Further studies are needed to replicate these promising results and biomechanically validate this technique.Level of Evidence: IV     

A new testing device for measuring gliding resistance and work of flexion in a digit

In order to move the finger the tendon force must overcome the gliding resistance of the tendon as well as the forces to move the joints, finger inertias, and external load. These sources, combined, make up the work of flexion (WOF) which has been experimentally used to evaluate the finger function. In this study, we have designed a new device, which can measure the forces at the proximal and distal end of the tendon during finger flexion, so that gliding resistance can be isolated from the WOF. Two index fingers from a pair of human cadaver hands were used for testing this device. Preliminary data showed that internal resistance occupied about 10% of WOF with an intact tendon. However, after tendon repair, the gliding resistance increased 31% of WOF for a modified Kessler repair and 50% of WOF for a Becker repair compared to intact tendon. We simulated joint stiffness by injection of saline solution into the proximal interphalangeal joint. This increased the overall WOF but not the gliding resistance. We believe that this testing device provides a useful tool to evaluate finger function after tendon repair in an experimental model.     

A detailed and validated three dimensional dynamic model of the patellofemoral joint

A detailed 3D anatomical model of the patellofemoral joint was developed to study the tracking, force, contact and stability characteristics of the joint. The quadriceps was considered to include six components represented by 15 force vectors. The patellar tendon was modeled using four bundles of viscoelastic tensile elements. Each of the lateral and medial retinaculum was modeled by a three-bundle nonlinear spring. The femur and patella were considered as rigid bodies with their articular cartilage layers represented by an isotropic viscoelastic material. The geometrical and tracking data needed for model simulation, as well as validation of its results, were obtained from an in vivo experiment, involving MR imaging of a normal knee while performing isometric leg press against a constant 140 N force. The model was formulated within the framework of a rigid body spring model and solved using forth-order Runge-Kutta, for knee flexion angles between zero and 50 degrees. Results indicated a good agreement between the model predictions for patellar tracking and the experimental results with RMS deviations of about 2 mm for translations (less than 0.7 mm for patellar mediolateral shift), and 4 degrees for rotations (less than 3 degrees for patellar tilt). The contact pattern predicted by the model was also consistent with the results of the experiment and the literature. The joint contact force increased linearly with progressive knee flexion from 80 N to 210 N. The medial retinaculum experienced a peak force of 18 N at full extension that decreased with knee flexion and disappeared entirely at 20 degrees flexion. Analysis of the patellar time response to the quadriceps contraction suggested that the muscle activation most affected the patellar shift and tilt. These results are consistent with the recent observations in the literature concerning the significance of retinaculum and quadriceps in the patellar stability.     

低强度脉冲超声波对肌腱愈合的促进作用

目的:分析低强度脉冲超声波(low intensity pulsed ultrasound,LIPU)对Ⅱ区屈指肌腱愈合的促进作用,并探讨其减少肌腱粘连的临床效果。方法:选取2010年8月至2013年4月在我院接受II区屈指肌腱损伤修复术治疗的患者80例并随机分为两组。LIPU组(33例,共39指),该组患者均接受系统的低强度脉冲超声波进行治疗;对照组(34例,共41指),所有患者在治疗时放置超声探头,但不接通电源。在术后12周,采用视觉模拟评分法(visual analogue scale,VAS)评估患手疼痛程度;采用肌腱总主动活动度(total active motion,TAM)评定标准评价肌腱的功能状况;采用Lovett分级法评价患指屈指肌力。结果:两组术后无肌腱再断裂病例出现。术后12周时,LIPU组与对照组的VAS疼痛评分分别为(1.9±1.8)和(2.3±1.9)(t=0.996,P=0.337)。根据TAM系统评定标准,LIPU组与对照组的优良率分别为94.9%和70.7%,组间差异有统计学意义(X2=12.798,P=0.000),LIPU组显著高于对照组,两组患指屈指肌力恢复正常的发生率分别为100%和95.1%,组间差异无统计学意义(X2=1.951,P=0.162)。结论:LIPU具有促进II区屈指肌腱愈合,改善患指主动活动功能的效果,且不增加肌腱断裂的风险,但其促进肌腱愈合的机制尚需进一步实验研究证实。     

The biomechanical function of the patellar tendon during in-vivo weight-bearing flexion

Few studies have investigated the function of the patellar tendon in-vivo. This study quantified the three-dimensional (3D) kinematics of the patellar tendon during weight-bearing flexion. Eleven subjects were imaged using magnetic resonance (MR). Sagittal plane images were outlined to create a 3D model of the patella, tibia, and femur and included the attachment sites of the patellar tendon. Each attachment site was divided into central, medial, and lateral thirds. Next, the subjects were imaged using fluoroscopy from two orthogonal directions while performing a single-leg lunge. The models and fluoroscopic images were used to reproduce the motion of the patella, tibia, and femur. The apparent elongation, sagittal plane angle, and coronal plane angle of each third of the patellar tendon were measured from the relative motion of the attachment sites. All three portions of the patellar tendon deformed similarly with flexion. The length of the patellar tendon significantly from full extension to 30 degrees . From 30 degrees -110 degrees , no significant change in the length of the patellar tendon was observed. The patellar tendon was oriented anteriorly at flexion angles less than 60 degrees and posteriorly thereafter. From full extension to 60 degrees , the medial orientation of the patellar tendon decreased significantly with flexion. These data may have important implications for anterior cruciate ligament reconstruction using patellar tendon autografts and for the design of rehabilitation regimens for patients of patellar tendon repair.     

In vivo tendon force measurement of 2-week duration in sheep

Tendon tension in vivo may be determined indirectly by measuring intratendinous pressure, by using a buckle transducer or by measuring the tendon strain. All of these methods require appropriate calibration, which is highly dependent on various variables. To measure the tendon load in vivo during a period of 2 weeks in sheep, a measurement technique has been developed using a force sensor interposed serially between the humeral head and the tendon end. Within a supporting frame, a flexion-sensitive force transducer is subjected to three-point bending stress. The load is transmitted by sutures from the tendon end through a hole in the sensor frame, orthogonal to the force transducer. In this configuration, the sensor measures the tensile force acting on the tendon, largely independent of the loading direction. The sensor was screwed to the humeral head and connected to the tendon end which was previously released from its insertion site along with a bone chip, using sutures. Connecting wires passed subcutaneously to a skin outlet about 30 cm away from the transducer. The sensor output was linear to the measured load up to 300 N, with maximum hysteresis of 18% full scale. All sensors worked in vivo without drift over a period of up to 14 days with no change in the calibration data. Forces up to 310 N have been recorded in vivo with daily tension measurements. This study shows that serial tendon tension measurement is feasible and allows for reliable, repeatable recording of the absolute tendon tension at the expense of tendon integrity.     

Relationships between stretch-shortening cycle performance and maximum muscle strength

This study aimed to examine the relationships between muscle power output using the stretch-shortening cycle (SSC) and maximum strength, as measured by the 1 RM (1 repetition maximum) test and the isokinetic dynamometer under elbow flexion. Sixteen trained, young adult males pulled a constant load of 40% MVC (maximum voluntary elbow flexion contraction) by ballistic elbow flexion under the following two preliminary conditions: 1) the static relaxed muscle state (SR condition) and 2) using the SSC (SSC condition). Muscle power was determined from the product of the pulling velocity and load mass by a power measurement instrument with a rotary encoder. The 1 RM bench press (1RM BP) and isokinetic maximum strength under elbow flexion with the Cybex-325 were measured as indicators of dynamic maximum strength. 1) The early power output exerted under the SSC condition showed a significant and high correlation with the 1 RM BP (r = 0.83), but only moderate correlation with the isokinetic muscle strength (r = 0.50-0.67). 2) The contribution of the 1 RM BP to the early muscle contraction velocity exerted under the SSC condition was large. These results suggested that muscle power exerted using the SSC shows a stronger relationship with maximum muscle strength measured by a 1 RM test rather than isokinetic maximum strength.     

Effects of static stress on the mechanical properties of cultured collagen fascicles from the rabbit patellar tendon

In-vitro tissue culture experiments were performed to study the effects of static stress on the mechanical properties of collagen fascicles obtained from the rabbit patellar tendon. After collagen fascicles having the diameter of approximately 300 microm were cultured for 1 and 2 wk under static stress between 0 and 3 MPa, their mechanical properties and crimp morphology were determined using a micro-tensile tester and a light microscope, respectively. The tensile strength and tangent modulus of the fascicles were significantly decreased by culture under no load compared to control fascicles. A statistically significant correlation, which was described by a quadratic curve, was observed between applied stress and tensile strength. The maximum tensile strength (16.7 MPa) was obtained at the applied stress of 1.2 MPa; the strength was within a range of control values. There was a similar correlation between applied stress and tangent modulus, and the modulus was maintained at control level under 1.3 MPa stress. The stress of 1.2 to 1.3 MPa is equivalent to approximately 50 percent of the peak stress developed in the intact rabbit patellar tendon by running. Strain at failure of cultured collagen fascicles was negatively correlated with applied stress, and that at 1.2 to 1.3 MPa stress was almost the same as the control value. Crimp morphology in the fascicles cultured under about 1.2 MPa stress was similar to that in control fascicles. These results indicate that cultured collagen fascicles change the mechanical properties and structure in response to static tensile stress. In addition, their mechanical properties and structure are maintained at control level if the static stress of 50 percent of in-vivo peak stress is applied.     

PDGF-BB, IGF-I and mechanical load stimulate DNA synthesis in avian tendon fibroblasts in vitro

Resident cells in the surface epitenon and internal compartment of flexor tendons are subjected to cyclic mechanical load as muscle contracts to move limbs or digits. Tendons are largely tensile load bearing tissues and are highly matrix intensive with nondividing cells providing maintenance functions. However, when an injury occurs, tendon cells are stimulated to divide by activated endogenous growth factors and those from platelets and plasma. We hypothesize that tendon cells detect mechanical load signals but do not interpret such signals as mitogenic unless an active growth factor is present. We have used an in vitro mechanical load model, application of cyclic strain to cells cultured on flexible bottomed culture plates, to test the hypothesis that tendon cells require platelet-derived growth factor (PDGF-BB) and insulin-like growth factor-I (IGF-I) in addition to mechanical load to stimulate DNA synthesis. In addition, we demonstrate that in avian tendon cells, load and growth factors stimulate phosphorylation of tyrosine residues in multiple proteins, including pp₆₀src, a protein kinase that phosphorylates receptor protein tyrosine kinases. A lack of mitogenic responsiveness to mechanical load alone by tendon cells may be a characteristic of a regulatory pathway that modulates cell division.     

Calibration and application of an intra-articular force transducer for the measurement of patellar tendon graft forces: an in situ evaluation.

The objective of this study was to evaluate two calibration methods for the "Arthroscopically Implantable Force Probe" (AIFP) that are potentially suitable for in vivo use: (1) a direct, experimentally based method performed by applying a tensile load directly to the graft after it is harvested but prior to implantation (the "pre-implantation" technique), and (2) an indirect method that utilizes cadaver-based analytical expressions to transform the AIFP output versus anterior shear load relationship, which may be established in vivo, to resultant graft load (the "post-implantation" technique). The AIFP outputs during anterior shear loading of the knee joint using these two calibration methods were compared directly to graft force measurements using a ligament cutting protocol and a 6 DOF load cell. The mean percent error (actual-measured)/(actual)* 100) associated with the pre-implantation calibration ranged between 85 and 175 percent, and was dependent on the knee flexion angle tested. The percent error associated with the post-implantation technique was evaluated in two load ranges: loads less than 40 N, and loads greater than 40 N. For graft force values greater than 40 N, the mean percent errors inherent to the post-implantation calibration method ranged between 20 and 29 percent, depending on the knee flexion angle tested. Below 40 N, these errors were substantially greater. Of the two calibration methods evaluated, the post-implantation approach provided a better estimate of the ACL graft force than the pre-implantation technique. However, the errors for the post-implantation approach were still high and suggested that caution should be employed when using implantable force probes for in vivo measurement of ACL graft forces.     

Functional, mechanical, and biochemical assessment of ultrasound therapy on tendon healing in the chicken toe

We studied the therapeutic effect of ultrasound treatment on the functional recovery of surgically repaired profundus tendon in the right third toe of mature White Leghorn hens. Ultrasound treatment was given daily for 5 minutes for a total of 20 treatment days, starting immediately after 4 weeks immobilization. Ultrasound (frequency 3.0 mHz; intensity 0.75 W/cm2) was delivered to the right leg by a 5-cm2 probe through distilled water in a bath kept at 35 degrees C. The flexion of the toe was measured preoperatively for 4 consecutive days and daily for 6 weeks after the start of ultrasound treatment for the calculation of percent of functional recovery of the flexor tendon. The non-ultrasound-treated group of birds went through the same manipulations except that no ultrasound was given when the right leg was immersed in the water bath. Ultrasound treatment significantly (p less than 0.01) improved the functional recovery of the repaired tendons (less than 5-mm gap) starting on the third week of treatment (94 +/- 2 percent) compared with the non-ultrasound-treated group (79 +/- 4 percent). Ultrasound treatment had no effect on gap formation or breaking (tensile) strength of the repaired tendons. It is concluded that ultrasound enhanced functional return of repaired flexor tendons in the hen, and the clinical implication is discussed.     

通道辅助微创缝合与两种常用跟腱缝合方式的生物力学研究

目的:通过对比通道辅助跟腱微创缝合方式(CAMIR)与2种临床最常用的跟腱缝合方式的生物力学强度,验证CAMIR微创缝合方式同样能够达到常规缝合方式的力学强度,为临床推广应用提供可靠的理论依据。方法:将27支跟腱样本随机分为3组(每组9支),分别是CAMIR组、经典微创Ma-Griffith组、标准切开Krackow组。所有跟腱样本首先预加载50N,2min。然后以20N-100N,1Hz,循环1000次。如果缝合未失效,则以20 mm/s的速度将样本拉伸至失效。通过实验仪上的传感器自动记录循环1000次时整个缝合结构的伸长量,记录拉伸失效时整个缝合结构的伸长量以及最大负荷,并计算单纯拉伸阶段缝合结构的抗拉伸硬度。结果:CAMIR的循环1000次结束时伸长量(P=0.581)、缝合失效时伸长量(P=0.799)、缝合失效时最大负荷(P=0.278)、单纯拉伸过程中抗应变硬度(P=0.935)与常用的Ma-Griffith、Krackow缝合方式均无明显差异。结论:CAMIR缝合方式强度可靠,为术后进行早期功能康复训练提供力学保障,同时能够有效避免腓肠神经损伤,是临床上值得推荐的微创缝合方式。     

Relationships between muscle power output using the stretch-shortening cycle and eccentric maximum strength

This study aimed to examine the relationships between muscle power output using the stretch-shortening cycle (SSC) and eccentric maximum strength under elbow flexion. Eighteen young adult males pulled up a constant light load (2 kg) by ballistic elbow flexion under the following two preliminary conditions: 1) the static relaxed muscle state (SR condition), and 2) using the SSC with countermovement (SSC condition).Muscle power was determined from the product of the pulling velocity and the load mass by a power measurement instrument that adopted the weight-loading method. We assumed the pulling velocity to be the subject's muscle power parameters as a matter of convenience, because we used a constant load. The following two parameters were selected in reference to a previous study: 1) peak velocity (m x s(-1)) (peak power) and 2) 0.1-second velocity during concentric contraction (m x s(-1)) (initial power). Eccentric maximum strength by elbow flexion was measured by a handheld dynamometer.Initial power produced in the SSC condition was significantly larger than that in the SR condition. Eccentric maximum strength showed a significant and high correlation (r = 0.70) with peak power in the SSC condition but not in the SR condition. Eccentric maximum strength showed insignificant correlations with initial power in both conditions. In conclusion, it was suggested that eccentric maximum strength is associated with peak power in the SSC condition, but the contribution of the eccentric maximum strength to the SSC potentiation (initial power) may be low.