Alterations in mechanical properties of the patellar tendon is associated with pain in athletes with patellar tendinopathy

PURPOSE

To compare tendon strain and stiffness between athletes with patellar tendinopathy and healthy controls, and explore whether the intensity of pain and dysfunction were related to the mechanical properties of the tendon.

METHODS

Thirty-four male athletes with patellar tendinopathy and 13 healthy controls matched by age and activity levels were recruited. The in vivo mechanical properties of the patellar tendon were examined by ultrasonography and dynamometry. In subjects with patellar tendinopathy, the intensities of self-perceived pain (maximal pain in the past 7 days and pain during a single-legged declined-squat test) using the visual analogue scale and the assessment of functional disability using the Victorian Institute of Sport Assessment-patellar questionnaire, were collected.

RESULTS

In subjects with patellar tendinopathy, tendon strain was significantly reduced by 22% (8.9 ± 3.7 vs. 14.3 ± 4.7%, P = 0.005) when compared with healthy controls. There was no significant group difference in tendon stiffness (P = 0.27). Significant negative correlations between tendon strain and the maximal self-perceived pain over 7 days (r = -0.37, P = 0.03), and pain during a single-legged declined-squat test (r = -0.37, P = 0.03) were detected. A trend of significant positive correlation was found between tendon stiffness and pain during a single-legged declined-squat test (r = 0.30, P = 0.09).

CONCLUSION

Our findings show that tendon strain is reduced in athletes with patellar tendinopathy, and a lower tendon strain is associated with a greater magnitude of pain perceived.

Intrinsic foot muscle volume in experienced runners with and without chronic plantar fasciitis

OBJECTIVES

Plantar fasciitis, a common injury in runners, has been speculated to be associated with weakness of the intrinsic foot muscles. A recent study reported that atrophy of the intrinsic forefoot muscles might contribute to plantar fasciitis by destabilizing the medial longitudinal arch. However, intrinsic foot muscle volume difference between individuals with plantar fasciitis and healthy counterparts remains unknown. This study examined the relationship of intrinsic foot muscle volume and incidence of plantar fasciitis.

DESIGN

Case-control study.

METHODS

20 experienced (≥5 years) runners were recruited. Ten of them had bilateral chronic (≥2 years) plantar fasciitis while the others were healthy characteristics-matched runners. Intrinsic muscle volumes of the participants' right foot were scanned with a 1.5T magnetic resonance system and segmented using established methods. Body-mass normalized intrinsic foot muscle volumes were compared between runners with and without chronic plantar fasciitis.

RESULTS

There was significant greater rearfoot intrinsic muscle volume in healthy runners than runners with chronic plantar fasciitis (Cohen's d=1.13; p=0.023). A similar trend was also observed in the total intrinsic foot muscle volume but it did not reach a statistical significance (Cohen's d=0.92; p=0.056). Forefoot volume was similar between runners with and without plantar fasciitis.

CONCLUSIONS

These results suggest that atrophy of intrinsic foot muscles may be associated with symptoms of plantar fasciitis in runners. These findings may provide useful information in rehabilitation strategies of chronic plantar fasciitis.

Comparison between an accelerometer and a three-dimensional motion analysis system for the detection of movement

OBJECTIVE

To examine the reliability and concurrent validity of an accelerometer compared with a three-dimensional (3D) motion analysis system for measuring the motor reaction time of the lower limbs, to validate a simple method for objective clinical assessment of movement onset.

DESIGN

Timing of the onset of knee extension movement in response to an audio signal was measured simultaneously with an accelerometer and a 3D VICON motion analysis system.

PARTICIPANTS

Twelve able-bodied subjects with a mean age of 26 (standard deviation 2.3) years.

RESULTS

Good reliability was found for both instruments, although the intraclass correlation coefficient (ICC) was higher for the accelerometer (ICC₃,₁=0.739; P<0.001). The mean motor reaction time measured by the accelerometer and the VICON system was 205.0 and 196.9 mseconds, respectively. Good agreement was found between the paired measurements (mean ICC=0.774), and the average 95% limits of agreement were -56.4 to 72.5 mseconds.

CONCLUSION

In conclusion, the accelerometer had good reliability for the measurement of movement onset time. Agreement between the measurements from the accelerometer and the VICON system was high. However, the limits of agreement covered a wide range, so absolute timings for movement onset derived from these methods should not be used interchangeably.

Parameter optimization for the visco-hyperelastic constitutive model of tendon using FEM

Numerous constitutive models describing the mechanical properties of tendons have been proposed during the past few decades. However, few were widely used owing to the lack of implementation in the general finite element (FE) software, and very few systematic studies have been done on selecting the most appropriate parameters for these constitutive laws. In this work, the visco-hyperelastic constitutive model of the tendon implemented through the use of three-parameter Mooney-Rivlin form and sixty-four-parameter Prony series were firstly analyzed using ANSYS FE software. Afterwards, an integrated optimization scheme was developed by coupling two optimization toolboxes (OPTs) of ANSYS and MATLAB for estimating these unknown constitutive parameters of the tendon. Finally, a group of Sprague-Dawley rat tendons was used to execute experimental and numerical simulation investigation. The simulated results showed good agreement with the experimental data. An important finding revealed that too many Maxwell elements was not necessary for assuring accuracy of the model, which is often neglected in most open literatures. Thus, all these proved that the constitutive parameter optimization scheme was reliable and highly efficient. Furthermore, the approach can be extended to study other tendons or ligaments, as well as any visco-hyperelastic solid materials.

Biofeedback exercise improved the EMG activity ratio of the medial and lateral vasti muscles in subjects with patellofemoral pain syndrome

Patellofemoral pain syndrome (PFPS) is usually due to weakness of vastus medialis obliquus (VMO) resulting in abnormal patellar tracking. One of the objectives of rehabilitation is to strengthen the VMO so as to counterbalance the vastus lateralis (VL) action during normal activities. This study compared the effects of an 8-week exercise program with and without EMG biofeedback on the relative activations of VMO and VL. Twenty-six subjects with PFPS were randomly allocated into an "exercise" group (Group 1) and a "biofeedback+exercise" group (Group 2). Both groups performed the same exercise program but subjects in Group 2 received real time EMG biofeedback information on the relative activations of VMO and VL during the exercises. After 8 weeks of training, Group 1 had insignificant changes in their VMO/VL EMG ratio (p=0.355), whereas Group 2 had significantly greater VMO/VL EMG ratio (p=0.017) when performing normal activities throughout a 6-h assessment period. The present result reveals that the incorporation of an EMG biofeedback into a physiotherapy exercise program could facilitate the activation of VMO muscle such that the muscle could be preferentially recruited during daily activities.

The double peak-to-peak analysis for determining EMG onset of muscle contraction

PURPOSE

Identification of the onset of muscle contraction with EMG signal amplitude double of the baseline value (DP-P) has been recently reported for determining the temporal parameters of muscular activity. Due to its convenience, it is suitable for clinical application. However, there is a lack of report on the reliability and comparability of this method to other established methods. Therefore, this study examined the test-retest reliability of the DP-P method and compared it with an established method that used the mean + 3 standard deviations (mean + 3 s.d.) over the baseline value for muscles of the knee.

METHODS

The onset of contraction of vastus medialis obliquus (VMO) and vastus lateralis (VL) of eleven able-bodied volunteers performing isometric knee extension at 50%, 75% and 100% of MVC in 30-minute and 7-day intervals were analyzed with both the DP-P and mean + 3 s.d. methods.

RESULTS

The ICC for within-day measurements of DP-P method ranged from 0.64 to 0.86 and that for between-day measurements ranged from 0.63-0.81. The ICC values were higher with submaximal than maximal contractions. There was a consistent delay of about 3 ms in EMG onset detection with the DP-P as compared to the mean + 3 s.d method.

CONCLUSION

The DP-P method is a reliable method for muscle onset determination but the absolute onset time of muscle contraction obtained from this method should not be directly compared with other methods such as the mean + 3 s.d.

Running exercises improve the strength of a partially ruptured Achilles tendon

OBJECTIVES

To examine the effects of running and swimming exercises on the functional performance and mechanical strength of a recovering Achilles tendon.

METHODS

30 Sprague-Dawley rats had surgical transection of their right medial Achilles tendon. The rats were divided into running (n = 11), swimming (n = 10), and control (n = 9) groups. The running and swimming groups were given daily exercise training, starting from the fifth day after the injury; the control group did not exercise throughout the period of the experiment. An Achilles functional index (AFI) was recorded before the operation and on the third, 10th, and 30th days after the operation. On the 30th day, the rats were killed and their Achilles tendons harvested for biomechanical testing of load relaxation properties, stiffness, and ultimate tensile strength (UTS). The AFI data were analysed by two way analysis of variance; load relaxation, stiffness, and UTS data were analysed by multivariate analysis, with alpha at 0.05.

RESULTS

The UTS of the running group was higher than in the control group (p = 0.015), while there was no significant difference between the swimming and control groups (p = 0.228). Differences in stiffness and load relaxation were non-significant (p = 0.823 and 0.633, respectively). The AFI results did not differ among the three groups (p = 0.242).

CONCLUSIONS

Running exercises can improve the strength of partially ruptured Achilles tendons at 30 days after injury.

Combined treatment of therapeutic laser and herbal application improves the strength of repairing ligament

The present study investigated the effects of combined therapeutic laser and herbal medication protocols on injured medial collateral ligaments (MCLs) of rat knees. Fully 36 rats were evenly divided into 9 groups. Right MCLs of groups 1 to 6 and 8 were transected, while that of groups 7 and 9 remained intact. After surgery, group 1 was treated with 1 session of high-dosed laser; group 2 with 9 sessions of low-dosed laser; group 3 with an herbal plaster; groups 4 and 5 received combined treatments of groups 1 and ss and 2, and 3 respectively; groups 6 and 7 received only bandaging; groups 8 and 9 received placebo laser and no treatment, respectively. All MCLs were subjected to biomechanical testing at 3 weeks postsurgery. Results revealed significant differences among groups in ultimate tensile strength (UTS) and stiffness (p < 0.01). Combination of multiple low-dosed laser treatment with herbal treatment (group 5) resulted in higher UTS than either no treatment (groups 6 and 8), single high-dosed laser treatment (group 1), multiple low-dosed laser treatment (group 2), or herbal treatment (group 2) alone. We concluded that combined applications of laser and herb can enhance further biomechanical properties of repairing rat MCLs than separate applications at 3 weeks postinjury.

Herbal remedies improve the strength of repairing ligament in a rat model

Herbal remedies have been reported to be effective in controlling inflammation for acute soft tissue injuries. There exist, however, no reports of their effects on collagen production and remodeling; thus mechanical strength studies of the tissues have not been reported. This study tested the effects of a herbal remedy on the strength of healing medial collateral ligaments (MCL) in rats. Sixteen rats receiving surgical transection to their right MCLs and eight receiving sham operation were tested. Eight of the MCL-injured animals were treated with an adhesive herbal plaster application to their right knees, while the other eight in the MCL injured group and the sham group were treated with plain adhesive plaster to their right knees. The MCLs were harvested and tested at either 3 or 6 weeks post-operation. The ultimate tensile strength (UTS) and stiffness normalized to the uninjured side of each animal of the herb and sham groups were significantly larger than those of the control at both 3 and 6 weeks (p = 0.001). No significant difference was found in stiffness between the herb and sham groups (p > 0.05). We concluded that the herbal remedy improves the UTS and stiffness of repairing MCLs at 3 and 6 weeks after injury.

Comparison of therapeutic ultrasound and exercises for augmenting tendon healing in rats

We compared therapeutic ultrasound (US) and exercises on Achilles tendon healing in 49 mature male rats. The medial Achilles tendon of the right leg was transected and the rats were divided into five groups: 1. control (n = 9), 2. 1 W/cm(2) US (n = 9), 3. 2 W/cm US (n = 10), 4. running (n = 11) and 5. swimming (n = 10). All animals were treated daily, starting from postsurgical day 5, according to their group assignment, except for group 1 control. Achilles functional index (AFI) was recorded pre- and postoperatively. On day 30, the Achilles tendons were biomechanically tested. Results revealed that groups 3 and 4 had higher tensile strength than the controls (p = 0.037 and 0.034), but groups 2 and 5 were not different from the controls. No significant difference in stiffness (p = 0.21) or AFI (p = 0.22) was found. These findings suggest that therapeutic US treatment at 2 W/cm(2) and running exercise improved the strength of repairing Achilles tendon.

The immediate effects of tension of counterforce forearm brace on neuromuscular performance of wrist extensor muscles in subjects with lateral humeral epicondylosis

STUDY DESIGN

Within-subject repeated-measures study.

OBJECTIVES

To examine the immediate effects of counterforce forearm brace on isokinetic strenght stretch reflex, passive stretching pain threshold of the wrist extensors, and proprioception of the wrist in subjects with lateral humeral epicondylosis for different strap tensions of a forearm brace.

BACKGROUND

Counterforce forearm bracing has been used for treating lateral humeral epicondylosis, but the effect of brace tension has not been well reported.

METHODS AND MEASURES

Fifteen subjects diagnosed with lateral humeral epicondylosis on their dominant arm were tested under 4 randomized conditions: (1) no brace, (2) brace with minimal tension, (3) brace with 25-N tension, and (4) brace with 50-N tension. The tests included isokinetic wrist extensors strength, passive stretching force in wrist flexion to elicit pain in the wrist extensors, wrist proprioception, and stretch reflex latency of the extensor carpi ulnari. A repeated-measures MANOVA was used to analyze the data and significant results were further analyzed with post hoc linear contrasts (alpha = .05).

RESULTS

Among the 4 conditions, significant differences were found in wrist proprioception P = .032) and pain threshold to passive stretching of the wrist extensors (P = .05), but were not found in wrist extension isokinetic strength and stretch reflex latency of the extensor carpi ulnaris.

CONCLUSION

A forearm counterforce brace, as applied in this study, affects wrist joint proprioception and increases the pain threshold to passive stretching of the wrist extensors in subjects with lateral humeral epicondylosis, but it has no effect on wrist extensor strength and stretch reflex latency of the extensor carpi ulnaris.

Investigation of the collagen fibril distribution in the medial collateral ligament in a rat knee model

This study compared the collagen fibril diameter distribution among six anatomical sites of the rat medial collateral ligament (MCL). Ultrathin MCL sections from 4 male Sprague-Dawley rats were examined electron microscopically. With an automated quantitation method, 41,638 fibrils were measured and compared among the periphery and core regions of the femoral, middle, and tibial portions of the MCL. Results demonstrated significant difference (p < .0033) in mean fibril diameter distribution among the six sites. The mass-averaged diameters of the core and peripheral fibrils were between 175.53 to 190.82 nm and 88.47 to 109.18 nm, respectively, with the peripheral fibrils more homogeneous in size. The fibrils occupied 36.7% to 57.1% of the cross-sectional area of the ligament. About 50% of the fibrils had an oblique factor of 0.8-1.0, implying that most fibrils were aligned longitudinally. This study has provided a detailed profile of the collagen fibril distributions in rat MCL.

Effects of herbal application on the ultrastructural morphology of repairing medial collateral ligament in a rat model

The present study investigated the effects of an external herbal application on the ultrastructural morphology of repairing medial collateral ligament (MCL) in a rat model. Eight MCL-transected/herb-treated rats (group 1) were compared with 8 MCL-transected/placebo-treated controls (group 2) and 8 MCL-intact/placebo-treated rats (group 3). At 3 and 6 weeks posttransection, MCL specimens were examined under electron microscope. With analysis of 370,709 collagen fibrils, all herb-treated animals had significantly larger fibrils than the controls (p < .001) at 6 weeks postinjury. The mean diameter of those peripheral collagen fibrils of group 1 was larger than the sham group (p < .001). The mass-averaged diameters of group 1 (50.49 to 143.07 nm) and group 3 (59.69 to 188.88 nm) were larger than group 2 (50.59 to 121.94 nm). The area coverage by collagen fibrils ranged from 46.86 to 94.97% for group 1 and 43.70 to 68.08%f or group 3 as compared with 40.01 to 50.77% for group 2. Mode obliquity was 0.56 to 0.84 among groups. We concluded that herbal remedy increases collagen fibril size of healing rat MCLs homogeneously at 6 weeks posttransection.