Triceps surae eccentric exercise is more effective than concentric exercise for treating Achilles tendinopathy, however the mechanisms underpinning these effects are unclear. This study compared the biomechanical characteristics of eccentric and concentric exercises to identify differences in the tendon load response. Eleven healthy volunteers performed eccentric and concentric exercises on a force plate, with ultrasonography, motion tracking, and EMG applied to measure Achilles tendon force, lower limb movement, and leg muscle activation. Tendon length was ultrasonographically tracked and quantified using a novel algorithm. The Fourier transform of the ground reaction force was also calculated to investigate for tremor, or perturbations. Tendon stiffness and extension did not vary between exercise types (P = .43). However, tendon perturbations were significantly higher during eccentric than concentric exercises (25%–40% higher, P = .02). Furthermore, perturbations during eccentric exercises were found to be negatively correlated with the tendon stiffness (R 2 = .59). The particular efficacy of eccentric exercise does not appear to result from variation in tendon stiffness or extension within a given session. However, varied perturbation magnitude may have a role in mediating the observed clinical effects. This property is subject-specific, with the source and clinical timecourse of such perturbations requiring further research.
Saira Chaudhry, Dylan Morrissey, Roger C. Woledge, Dan L. Bader and Hazel R.C. Screen
Adam B. Rosen, Jupil Ko, Kathy J. Simpson and Cathleen N. Brown
Patellar tendinopathy is often managed with a patellar tendon strap, however, their effectiveness is unsubstantiated. The purpose of this study was to determine if straps altered pain or lower extremity kinetics of individuals with patellar tendinopathy during landing. Thirty participants with patellar tendinopathy and 30 controls completed drop jumps with and without patellar tendon straps. Wearing the strap, tendinopathy participants demonstrated significantly decreased pain and reduced knee adductor moment; all participants displayed significantly decreased anterior ground reaction force while wearing a strap. Patellar tendon strapping may reduce pain due to alterations in direction and magnitude of loading.
Caroline Nicol and Paavo V. Komi
Magnitude of the reflex contribution to force enhancement was investigated in vivo during passive stretches of the Achilles tendon (AT) of one female subject. Thirty passive (5 × 6) dorsiflexions were induced by a motorized ankle ergometer. Achilles tendon force (ATF) was sensed by a buckle transducer applied surgically around the right AT. Single passive stretches resulted in a low but rather linear ATF increase in the absence of EMG (surface electrodes) activity. In the presence of reflexes, a clear ATF enhancement occurred 13–15 ms after the beginning of the EMG reflex responses. In double dorsiflexions at either 1.2 or 1.9 rad · s-1, which were separated by a maintained stretched position of either 40 or 90 ms, the first stretch resulted in initial linear ATF increase, followed by an additional force enhancement during the plateau phase. This reflexly induced increase represented 94 ± 4 N and 184 ± 1 N, respectively, for the 40 and the 90 ms plateaus, corresponding to 210 ± 85% and 486 ± 177% enhancements as compared to the first passive stretch effect. The results suggest further that timing of the stretch during the twitch response influences the magnitude and rate of force potentiation.
Oscar Martel, Juan F. Cárdenes, Gerardo Garcés and José A. Carta
Anterior cruciate ligament (ACL) reconstruction is one of the most important aspects of knee surgery. For this purpose, several fixation devices have been developed, although the interference screw is the most frequently used. The most typical biomechanical test of these devices consists of placing them in a testing machine and subjecting them to a pull-out test. However, insufficient attention has been paid to the influence of the displacement test rate on the mechanical properties of the fixation system. The aim of this study is to compare the influence of the crosshead rate in the biomechanical test of two different devices for the fixation of ACL tendon grafts. One hundred in vitro tests were performed using porcine tibiae and bovine tendons. The fixation devices used were (1) an interference screw and (2) a new expansion device. All ACL reconstructions were subjected to pull-out test to failure. Five crosshead rates were employed in a range from 30 mm/min to 4000 mm/min. Statistical analyses of the results show that, for the two devices, the rate has a significant effect on both maximum force and stiffness. Moreover, the new expansion device showed lesser dependency on the crosshead rate than the interference screw.
Gregory J. Steele, Rod A. Harter and Arthur J. Ting
The purpose of our study was to evaluate the functional outcomes of two methods of surgical treatment of acute closed raptures of the Achilles tendon, specifically, the primary open repair and the percutaneous repair techniques, utilizing (a) isokinetic plantar flexion strength, (b) midcalf girth, (c) ankle joint proprioception, and (d) ankle range of motion values. As a secondary purpose, the frequency of reruptures and postsurgical complications were compared between techniques. Twenty male patients (mean age, 43.8 ± 9.4 years) who sustained complete, closed ruptures of the Achilles tendon participated in this study. Results of paired t tests revealed significant differences between postsurgical and contralateral normal limbs for 6 of 12 variables. Results of the ANOVAs revealed no significant differences between the open repair group and percutaneous repair group for any of the evaluative parameters. The significant deficits in postoperative isokinetic plantar flexion strength and midcalf girth measurements, irrespective of surgical technique, suggest an incompleteness of rehabilitation or, more likely, the physiological inability to regain these characteristics postoperatively.
Gulcan Harput, H. Erkan Kilinc, Hamza Ozer, Gul Baltaci and Carl G. Mattacola
There is lack of information related to quadriceps and hamstring strength recovery during the early period of rehabilitation after anterior cruciate ligament reconstruction (ACLR) using hamstring-tendon graft (HTG).
To investigate quadriceps and hamstring isometric strength at 4-, 8-, and 12-wk time points after ACLR and to document the strength changes of these muscles over time.
24 patients (age 28.1 ± 8.1 y) who underwent unilateral single-bundle anatomic ACLR with 4-strand semitendinosus and gracilis tendon graft.
Main Outcome Measures:
The isometric strength of quadriceps and hamstring muscles was measured on an isokinetic dynamometer at a 60° knee-flexion angle 4, 8, and 12 wk after surgery.
Quadriceps and hamstring strength significantly increased over time for both the involved limb (quadriceps F 2,46 = 58.3, P < .001; hamstring F 2,46 = 35.7, P < .001) and uninvolved limb (quadriceps F 2,46 = 17.9, P < .001; hamstring F 2,46 = 56.9, P = .001). Quadriceps and hamstring indexes significantly changed from 4 wk (QI 57.9, HI 54.4) to 8 wk (QI 78.8, HI 69.9) and from 8 wk to 12 wk (QI 82, HI 75.7) (P < .001); however, there was no difference between indexes at the 12-wk time point (P = .17).
The results of this study serve as a reference for clinicians while directing a rehabilitation protocol for HTG ACLR patients to better appreciate expected strength changes of the muscles in the early phase of recovery.
Michael R. McCarthy, Barton P. Buxton and Carlan K. Yates
Continuous passive motion (CPM) is a modality used in the treatment, management, and rehabilitation of a variety of orthopedic problems. Recently, CPM devices have been therapeutically employed immediately after autogenous patellar tendon reconstruction of the anterior cruciate ligament (ACL). Whereas the concept of early motion is indicated, there is a concomitant concern that the implementation of immediate passive motion may stretch or rupture the graft. Twenty subjects scheduled to undergo ACL reconstruction were randomized into two groups (10 CPM and 10 non-CPM). All subjects performed the same postoperative rehabilitation with the exception of the CPM. Objective anterior tibial translation measurements were recorded with a KT-1000 for a 30-1b (133.5-N) Lachman test at 1 year postreconstruction. The results of this study indicated that the implementation of immediate continuous passive motion did not have any deleterious effects on the stability of the ligament reconstruction.
J. Allen Hardin, John A. Guido and Christopher J. Hughes
Due to the likelihood of hamstring dysfunction associated with anterior cruciate ligament (ACL) injury, it is clinically significant to determine if a hamstring weakness exists preoperatively. The purpose of this study was to determine if a hamstring muscle deficit existed at the time of surgery and to determine the time necessary to achieve hamstring strength equal to preoperative measures of the uninvolved extremity during postoperative rehabilitation. Twelve patients who underwent ACL reconstruction using a patellar tendon autograft participated. Each subject underwent a preoperative isometric knee strength evaluation at 60° of knee flexion. Each subject underwent postoperative rehabilitation including hamstring muscle strengthening. Repeat isometric testing was performed on each subject at 21 and 42 days postoperative. There was no statistical difference in hamstring muscle strength, as measured by isometric peak torque, either preoperatively or postoperatively. Therefore, maintaining rather than increasing hamstring strength postoperatively should be emphasized as an integral part of rehabilitation.
Robert J. de Vos, Marinus P. Heijboer, Harrie Weinans, Jan A.N. Verhaar and Hans T.M. van Schie
Chronic midportion Achilles tendinopathy is a common and hard-to-treat disorder characterized by degenerative changes of the tendon matrix. Ultrasonographic tissue characterization (UTC) was successfully used to quantify structural human Achilles tendon changes. This novel and reliable technique could be used in follow-up studies to relate tendon structure to symptoms.
To quantify structural tendon changes and assess clinical change in patients with tendinopathy.
Prospective observational study.
Orthopedic department in a university medical center.
23 patients with chronic midportion Achilles tendinopathy.
The patients performed a 16-wk home-based eccentric exercise program. An experienced researcher performed the ultrasonographic data collection with the UTC procedure. These data were assessed by a blinded observer. The severity of symptoms was established with the validated Victorian Institute of Sport Assessment–Achilles (VISA-A) questionnaire.
Main Outcome Measures:
UTC was performed to quantify tendon structure through measuring the proportion of 4 echo types. Echo types I and II represent more or less organized tendon bundles, and echo types III and IV represent disintegrated tendon structure. On the VISA-A, the total possible score is divided by 100 for a percentage score, with a perfect score of 100. Follow-up was at 2, 8, 16, and 24 wk.
The mean percentage of echo types I and II changed by 0.3% after 24 wk (P = .92, 95% CI −5.8 to 5.3). The mean VISA-A score increased slightly but significantly by 11.3 points after 24 wk (P = .01, 95% CI 2.6–20.0). An increased VISA-A score was not correlated with an increased percentage of echo types I and II (P = .94, r = −.02), and the baseline percentage of echo types I and II did not correlate with an increased VISA-A score (P = .74, r = .07).
There is no short-term increase in organized tendon structure after eccentric exercises. Tendon structure is not related to symptom severity and cannot be used as a predictor of clinical outcome.
Erik Schrödter, Gert-Peter Brüggemann and Steffen Willwacher
To describe the stretch-shortening behavior of ankle plantar-flexing muscle–tendon units (MTUs) during the push-off in a sprint start.
Fifty-four male (100-m personal best: 9.58–12.07 s) and 34 female (100-m personal best: 11.05–14.00 s) sprinters were analyzed using an instrumented starting block and 2-dimensional high-speed video imaging. Analysis was performed separately for front and rear legs, while accounting for block obliquities and performance levels.
The results showed clear signs of a dorsiflexion in the upper ankle joint (front block 15.8° ± 7.4°, 95% CI 13.2–18.2°; rear block 8.0° ± 5.7°, 95% CI 6.4–9.7°) preceding plantar flexion. When observed in their natural block settings, the athletes’ block obliquity did not significantly affect push-off characteristics. It seems that the stretch-shortening-cycle-like motion of the soleus MTU has an enhancing influence on push-off force generation.
This study provides the first systematic observation of ankle-joint stretch-shortening behavior for sprinters of a wide range of performance levels. The findings highlight the importance of reactive-type training for the improvement of starting performance. Nonetheless, future studies need to resolve the independent contributions of tendinous and muscle-fascicle structures to overall MTU performance.