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Calcaneal fractures result in an altered function of the gastrocnemius medialis.
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Elastic and contractile components require different time spans to recover.
•
Dynamic ultrasound provides relevant information on muscle function after foot trauma.
Abstract
Background
Calcaneal fractures result in severe functional impairments and walking restrictions. Postoperative evaluation mainly focusses on the restoration of calcaneal anatomy while ankle plantar flexor insufficiency remains largely neglected. This study aims to investigate biomechanical and morphologic adaptions of elastic and contractile components of the gastrocnemius medialis after unilateral calcaneal fracture.
Methods
20 Patients (BMI: 27.6 ± 3.1 kgm−2, Age: 50 ± 12 years) were measured using gait analysis and portable ultrasound over a follow-up of three, six and twelve months after surgery. Data comparison was performed using 20 matched healthy controls (BMI: 26.2 ± 2.9 kgm−2, Age: 48 ± 11 years). Static and dynamic behavior of the gastrocnemius muscle tendon unit, muscle fascicle and the serial-elastic element as well ankle joint kinematics and kinetics were analyzed.
Findings
Within patients, a significant (p < 0.05) increase in fascicle length (by 67%) during single support and a decrease of serial elastic element shortening (by 20%) during push off was found between three and twelve months follow-up comparisons. Patients showed differences for fascicle lengthening and pennation angle increase during single support after three and six months compared to healthy controls. A smaller shortening of the serial-elastic element (by 29%) and muscle-tendon unit (by 16%) persisted even for the twelve month comparisons.
Interpretation
Patients with calcaneal fracture showed an incomplete restoration of the medial gastrocnemius dynamic morphological behavior. While muscle fascicle contraction almost recovered, the serial elastic component still showed restrictions regarding its shortening behavior. Limited foot mobility and plantarflexor strength as well as lowered responsiveness of elastic tissues to mechanical loading are regarded as key mechanisms.
Fractures of the calcaneus can cause severe restrictions of dynamic foot function which often lead to large periods of working disability and considerable socioeconomic costs (
Radiographic and functional outcomes after displaced intra-articular calcaneal fractures: a comparative cohort study among the traditional open technique (ORIF) and percutaneous surgical procedures (PS).
). Although great efforts in the treatment of calcaneal fractures (CF) have been made, the functional outcome often remains unsatisfying with considerable restrictions of dynamic foot mobility and insufficiency of plantar flexor muscles (
Do changes in dynamic plantar pressure distribution, strength capacity and postural control after intra-articular calcaneal fracture correlate with clinical and radiological outcome?.
). While clinicians primarily focus on anatomical restoration of the calcaneus using radiography, pathologic structural adaptions of the plantar flexors remain unconsidered. Even two years after a CF dynamic ankle plantar flexion power has not been completely recovered (
). This insufficiency and an altered mechanical behavior of the triceps surae play an important role in the healing process and regaining foot mobility.
Immobilization is a major determinant for the development of musculoskeletal changes after trauma. However, there seems to be an inequality in the time ratio between tissue quality loss and regeneration. Restoration of muscle and tendon morphology is slow and it is unclear whether a normal state can be completely regained (
). Muscle atrophy is widely observed due to prolonged immobilization after surgical interventions. Patients with CF follow long immobilization periods including cast immobilization and non-weightbearing of up to twelve weeks after surgery (
Functional outcome and patient satisfaction after displaced intra-articular calcaneal fractures: a comparison among open, percutaneous, and nonoperative treatment.
). This often results into high rates of calf muscle atrophy (reductions by up to 3 cm of calf circumference) that persist even one year after trauma, indicating that the restoration of musculoskeletal tissue remains decreased or might even tend to deteriorate (
Do changes in dynamic plantar pressure distribution, strength capacity and postural control after intra-articular calcaneal fracture correlate with clinical and radiological outcome?.
Displaced intra-articular fractures of the calcaneus treated non- operatively. Clinical results and analysis of motion and ground-reaction and temporal forces.
J. Bone Joint Surgery - Series A.1994; 76: 1531-1540
). Trauma and disuse could also have a significant effect on mechanical tendon properties. In this context, decreased stiffness of lower limb tendons and aponeuroses (up to 67%) as well as reduced tendon force (up to 36%) was found after several weeks of immobilization (
). Reductions of tendon stiffness could result in a relevant decrease of muscle strength and the ability of muscle fascicles to transfer force to the tendon. However, the investigation of the dynamic behavior of muscle structural tissues after trauma is rare and practically nothing is known about potential biomechanical adaptions that occur due to muscular deficits after CF.
Sonographic measurements of dynamic muscle structure behavior have demonstrated that an almost isometric contraction of fascicles during mid-stance and simultaneous stretch-shortening behavior of serial-elastic tissues are a main mechanism for generating an efficient power output during walking (
). Clinically, abnormal behavior of muscle structure will have a large impact on force potential, and decreased tissue quality might even lead to permanent muscle damage (
). However, it is unclear if and to what extent the interaction between fascicles and elastic tissue during movement is altered and whether structural changes can be completely restored during the healing process after trauma.
The main research objective of this study is to provide information regarding dynamic structural adaptions of the gastrocnemius medialis as a main ankle plantar flexor, after CF. We want to know, how muscle fascicles and serial elastic components contribute to the limited function of the ankle plantar flexors during walking. We hypothesize that during a follow-up period of three, six and twelve months, a difference in static and dynamic muscle structure behavior of the gastrocnemius medialis in patients after unilateral CF is observed. We further hypothesize that patients with CF show an altered dynamic behavior of muscle-tendon components when compared to healthy controls.
2. Methods
2.1 Participants
A total of 20 patients (2 female, 18 male) with unilateral CF were analyzed. Thirteen patients were affected on the right side while seven patients were diagnosed with a fracture of the left side. All patients were part of a larger ongoing clinical study that analyses the biomechanical and functional outcome after calcaneal fractures (
Gait characteristics and functional outcomes during early follow-up are comparable in patients with calcaneal fractures treated by either the sinus tarsi or the extended lateral approach.
). Sanders fracture classification revealed ten patients with a type II fracture consisting of one primary fracture line while the remaining patients had a type III fracture consisting of two main fracture lines (
). Subsequently, patients received a standardized aftercare protocol including 20 kg partial weight bearing with a lower limb cast (VACOped, OPED GmbH, Valley, DE) for eight weeks followed by an in-house rehabilitation program (three weeks) including physical therapy, sports therapy and manual lymph drainage. Written informed consent was obtained from all patients prior to study enrollment. The study was approved by the local ethics committee (Bayerische Landesärztekammer BLÄK, Munich, Germany, Nr. 11041, German Clinical Trials Registry Number: DRKS00003485) according to the guidelines of the Declaration of Helsinki of the World Medical Association. For comparison with normative gait data a group of twenty age and gender matched healthy controls was analyzed. Patient and control group anthropometrics are presented in Table 1.
Table 1Anthropometrics with mean (standard deviation) values and levels of significance (p, Student's t-test) for calcaneus fracture patients and healthy controls.
2.2 Ankle biomechanics and muscle structure measurements
To investigate structural muscle properties after CF, patients were investigated at approximately three (107 days, range: 91–132 days), six (209 days, range: 182–255 days) and twelve months (383 days, range: 360–434 days) after surgical treatment. To enable muscle structure analysis, a portable ultrasound system (MicroUS, Telemed, Vilnius, LT) with a 7.5 MHz linear scanner (Image width: 65 mm, Image depth: 60 mm, sampling frequency: 95 Hz) was used. Accurate fixation of the linear scanner was achieved using a custom made hard-rubber cast with two adjustable straps. To enable reproducible imaging of the longitudinal fascicle plane at the gastrocnemius mid belly, probe positioning was adjusted using transversal images while the patients lay prone (
). The ultrasound receiver was fixed to the patients back using a custom made portable transport box (Fig. 1). Each measurement for patients and healthy controls consisted of static and dynamic analyses of the involved side and one randomized side, respectively. Calf circumference was measured 15 cm below the knee joint gap using a tape measure. Static muscle thickness, fascicle length and pennation angle at the mid-belly position (half-way between muscle-tendon junction and popliteal crease) of the medial gastrocnemius were obtained from ultrasound images during seated rest with a knee flexion angle of 90 degrees.
Fig. 1Study Participant equipped with the portable/backpack ultrasound system and retro-reflective markers for instrumented gait analysis.
For dynamic measurements, sagittal ankle range of motion and the maximum ankle joint moment during gait were obtained by instrumented gait analysis using eight infrared cameras (Vicon Nexus 1.7, Oxford, UK) and two embedded force plates (AMTI, Watertown, USA). Each study participant was equipped with 15 retroreflective skin markers at predefined anatomical landmarks according to the Conventional Gait Model (
). For synchronization of gait and muscle ultrasound data, a software-based cineloop-input function (Telemed Echowave II, Vilnius, LT) with a trigger switch was implemented. Gait measurements were performed over a 15 m walkway while a total of five valid measurements (single foot contact on force plate) were used for further analysis. To evaluate muscle structure behavior from ultrasound images, a software-based semi-automatic tracking method (MATLAB, Natick, USA) with subsequent manual frame-wise inspection was used (
). For image analysis, one clearly visible fascicle as well as the deeper aponeurosis within the ultrasound image was manually tracked. Outcome parameters for dynamic measurements were fascicle length, pennation angle, serial elastic element length and muscle tendon complex length (
. Serial elastic element length was determined by calculation of the difference between the muscle tendon complex length and the fascicle length with respect the fascicle pennation angle (
). Ipsilateral and contralateral foot contact events were used to determine these gait phases. To control for effects of gait speed on muscle structure behavior and ankle joint biomechanics, walking velocity for healthy controls was adjusted to those of the patients. This was realized by direct analysis of movement speed of the sacrum marker during walking measurements.
2.3 Statistical analysis
A previously performed power analysis (G*power, Version 3.1, Düsseldorf, DE) revealed a sample size of 20 patients required to detect changes in the geometry of muscle parameters of about 75% of the standard deviation with a power of 90% and an effect size of 0.77 (
). Static and dynamic data was tested for normal distribution using the Saphiro-Wilk test. For within group comparisons for the healthy control group Student's t-test for dependent samples (normally distributed data) or the Wilcoxon-test for (non-normally distributed data) were used. Within group comparisons of patients were performed using ANOVA for repeated measures (normally distributed data) or Friedman test (non-normally distributed data). For between-group comparisons the t-test for independent samples (normally distributed data) or the Mann-Whitney test (non-normally distributed data) was used. Bonferroni correction was used for post-hoc comparisons. Differences were considered as significant at p < 0.05. For significant within-group and between-group differences of walking parameters and dynamic muscle structure data, effect sizes were calculated using Cohen's f and Cohen's d (
Patients with CF demonstrated average walking velocities of 0.9 ± 0.2 m/s, 1.1 ± 0.2 m/s and 1.1 ± 0.1 m/s after the three, six and twelve month follow-up. Since velocities between six and twelve month follow-up were similar, gait data using two velocities of the healthy control group were analyzed for further comparison. The first velocity (vel1) was adjusted to the average gait speed of patients after the three months follow-up. The second velocity (vel2) was adjusted to patient speed during the six and twelve month follow-up.
3.2 Gait kinematics
Regarding ankle joint kinematics and kinetics, largest differences were observed for the three month follow-up comparisons between patients and healthy controls (Fig. 2).
Fig. 2Average ankle joint kinematics with standard deviations (shaded areas) during gait for patients over the follow-up period (blue: three months, green: six months, red: twelve months) and controls (black) using matched gait velocities (vel1 & vel2). Vertical dotted lines indicate loading response, single support and push off during gait. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
A significant decrease of ankle range of motion during push-off of up to 55% (p < 0.05, Cohen's f = 1.57) as well as maximum ankle moment of up to 36% (p < 0.05, Cohen's f = 1.51) was found between the three month and subsequent follow-up periods as well as for comparisons between six and twelve months. A significantly smaller ankle range of motion during push-off of up to 64% (p < 0.01, Cohen's d = 0.91–1.59) was found in patients for each follow-up comparison with matched controls. For the maximum ankle joint moment, significant differences of up to 35% (p < 0.01, Cohen's d = 1.03–1.46) were found for patients at three and six month follow-up comparisons with healthy controls. No differences were found for between-group comparisons at the twelve month follow-up (Fig. 3). Additional information on raw data is provided as supplemental material (See Fig. S1).
Fig. 3Between-group and follow-up comparisons of average ankle joint range of motion during push-off (left) and maximum ankle joint moment (right). RoM: Range of motion, § significant difference between follow-up for patients, *significant difference between patients and controls.
For static measurements, a significant average increase in calf circumference (3%) and gastrocnemius muscle thickness (8%) were found between the three and twelve months follow-up (p < 0.05). Comparisons between three and six months showed a small but significant average increase of calf circumference by 2% (p = 0.03). Patients at the three months follow-up and had a significanty (p = 0.04) smaller resting pennation angle by 5% than controls (Table 2).
Table 2Muscle specific parameters of the calf and the medial gastrocnemius during rest for patients during follow-up and matched controls.
Patients (n = 20)
Controls (n = 20)
3 Mo
6 Mo
12 Mo
Calf circumference [cm]
37.3 (3.3) §†
37.8 (3)
38.2 (3.3)
38.9 (2.5)
Thickness [% shank length]
4.5 (0.8)†
4.8 (0.6)
4.9 (0.5)
4.8 (0.6)
Fascicle length [% shank length]
9.9 (1.9)
10 (1.9)
10.2 (1.6)
9.1 (1.4)
Pennation angle [°]
27.2 (5)*
28.7 (6.2)
28.5 (5.5)
30.8 (5.5)
§ significant difference with six months follow-up, † significant difference with twelve months follow-up, * significant difference with controls.
Regarding dynamic muscle structure behavior, the patients group showed a larger change in fascicle length during single support which was primarily observed for the three month follow-up. Analogous, pennation angle showed a decrease during single support after three months. Normalized muscle-tendon length showed comparable progressions for patients and matched controls during loading response and single support, while a decreased shortening during push-off could be observed for patients at the three months follow-up. Serial-elastic element length behavior demonstrated the typical stretch-shortening mechanism in both groups. However, during push-off, serial-elastic element shortening was smaller in patients for the three months follow-up when compared to healthy controls (Fig. 4).
Fig. 4Average graph excursions with standard deviations (shaded areas) of structural data of the medial gastrocnemius for patients over the follow-up (blue: three months, green: six months, red: twelve months) and controls (black) using matched gait velocities (vel1 & vel2). Vertical dotted lines indicate loading response, single support and push off during gait. FL: Fascicle length, PA: Pennation angle, MTU: Muscle tendon unit, SEE: Serial elastic element. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Within patients, a significant increase of fascicle length change of 25% (p < 0.05, Cohen's f = 0.55) during loading response and a significant decrease of 67% (p < 0.05, Cohen's f = 0.62) during single support was observed between the three and twelve months follow-up. Similarly, pennation angle change was significantly decreased by 54% (p < 0.05, Cohen's f = 0.47) during single support, while a significant increase of 46% (p < 0.05, Cohen's f = 0.63) was observed during push-off. Muscle tendon unit length change during push-off significantly increased by up to 35% (p < 0.01, Cohen's f = 1.57) over the follow-up period. For the serial elastic element, a significant increase in length change of 26% (p < 0.01, Cohen's f = 0.71) during single support and of 20% (p < 0.01, Cohen's f = 0.61) during push-off was found between the three and twelve month follow-up.
For comparisons with matched controls, fascicle length change as well as pennation angle change was significantly increased by up to 90% (p < 0.01, Cohen's d = 0.71–1.37) in patients during single support at the three and six month follow-up. Muscle tendon unit length change in patients during loading response was 50% smaller (p = 0.04, Cohen's d = 0.64) to controls for the three month follow-up. During push-off, muscle tendon unit length change was up to 41% smaller (p < 0.05, Cohen's d = 0.71–1.42) for follow-up comparisons between patients and controls. A significantly smaller serial-elastic element length change was found for patients at the three, six and twelve month follow-up during single support (up to 32%, p < 0.01, Cohen's d = 0.96–1.28) and push-off (up to 36%, p < 0.01, Cohen's d = 1–1.2) when compared with healthy controls. Data is presented in Table 3.
Table 3Muscle structural data for gait sub-phases for patients and healthy controls at matched gait speeds (Vel1: 3Mo & Vel2: 6Mo/12Mo). Negative values indicate shortening (for FL, MTU, SEE) or decrease (for PA).
Patients (n = 20)
Controls (n = 20)
3 Mo
6 Mo
12 Mo
vel1
vel2
Loading response
FL change [% shank length]
−1.2 (0.5)§†
−1.4 (0.5)
−1.6 (0.6)
−1.3 (2.9)
−1.2 (0.4)
PA change [°]
2.2 (0.8)
2.6 (0.9)
2.5 (1.1)
2.6 (1.4)
2.2 (1.2)
MTU length change [% shank length]
−0.6 (1)*
−1.3 (0.4)
−1.1 (0.8)
−1.2 (0.2)
−1.3 (0.2)
SEE length change [% shank length]
0.9 (0.6)
0.9 (0.8)
1 (0.9)
1.2 (0.5)
0.4 (0.9)
Single support
FL change [% shank length]
1.2 (0.8)*†
0.9 (1.2)*
0.4 (0.7)
0 (0.5)
−0.1 (0.5)
PA change [°]
−2.4 (2)*†
−1.7 (2.5)*
−1.1 (1.7)
0.1 (1.6)
0 (1.6)
MTU length change [% shank length]
3.6 (0.5)
3.6 (0.7)
3.4 (0.5)
3.3 (0.4)
3.6 (0.5)
SEE length change [% shank length]
2.3 (0.8)*†
2.7 (0.8)*
3.1 (0.6)*
3.4 (0.4)
3.7 (0.5)
Push off
FL change [% shank length]
−1.2 (1.5)
−1.5 (1)
−1.8 (0.7)
−1.2 (0.7)
−1.3 (0.6)
PA change [°]
2.3 (1.5)†
3 (1.9)
4.3 (2)
3 (1.5)
3.3 (1.7)
MTU length change [% shank length]
−4.1 (1.3)*§†
−5.5 (1.7)*†
−6.3 (1.3)*
−6.9 (1.2)
−7.3 (1.1)
SEE length change [% shank length]
−3.6 (1.6)*†
−4.2 (1.8)*
−4.5 (1.3)*
−5.6 (1.1)
−5.8 (1.1)
FL: Fascicle length, PA: Pennation angle, MTU: Muscle tendon unit, SEE: Serial elastic element, § significant difference with six month follow-up, † significant difference with twelve month follow-up, * significant difference with controls.
This study investigated the static and dynamic muscle structural behavior and morphological adaptions of the gastrocnemius medialis muscle after surgically treated unilateral CF. Our findings indicate that both, serial-elastic (tendons with aponeuroses) and contractile (muscle fascicles) components recovered in a different way. Twelve months after surgery, fascicles of the medial gastrocnemius showed an almost similar movement behavior compared to healthy controls, while elastic components still demonstrated some considerable differences. Regarding the identification of differences in static and dynamic muscle structure behavior during follow-up (first study hypothesis), only an incomplete recovery towards a physiologic muscle structural behavior could be observed in patients with CF. Regarding the detection of an altered muscle-tendon behavior when compared to healthy controls (second study hypothesis) and supported by strong effect sizes, we could confirm relevant muscle structural differences regarding changes of fascicle length, pennation angle, muscle tendon unit length and serial elastic element length. These differences mainly occurred during supportive and propulsive gait phases such as single support and push-off.
In patients with CF, muscle fascicles during single support showed an increase in fascicle length and a simultaneous decrease of pennation angle after three and six months. During locomotion gastrocnemius fascicles usually follow an almost isometric behavior in order to transfer mechanical energy to the tendon (
). The observed non-isometric fascicle movement in our patients indicated a restricted and energetically inefficient function of the gastrocnemius muscle during locomotion. It might be assumed that an increased dorsiflexion of the ankle joint during single support which would induce a passive stretch on the muscle belly and fascicles might explain our findings (
Displaced intra-articular fractures of the calcaneus treated non- operatively. Clinical results and analysis of motion and ground-reaction and temporal forces.
J. Bone Joint Surgery - Series A.1994; 76: 1531-1540
). However, in our study, maximum ankle dorsiflexion angles as well as ankle range of motion during single support were almost comparable with controls and showed no differences between follow-up measurements in our patients. Therefore, a compensatory ankle joint movement during locomotion may not entirely explain an increased fascicle lengthening during single support phase. In this context, the observed non-physiologic fascicle behavior might be more related to residual strength deficits of the plantar flexors that are frequently observed in patients with CF (
Gait characteristics and functional outcomes during early follow-up are comparable in patients with calcaneal fractures treated by either the sinus tarsi or the extended lateral approach.
). In our study, an indication of the decreased plantar flexor strength could be related to the severely diminished maximum ankle joint moments during the last third of stance phase especially three and six-months after surgery. It might be assumed that less resistance of the gastrocnemius fascicles to the tensile forces during single support resulted in an increased fascicle lengthening. This consequently decreases the amount of elastic energy storage and release in tendinous tissues (
Factors such as posttraumatic immobilization and its effect on fibre type composition (slow – to fast-twitch transformation) and mechanical properties (decrease in stiffness) could also explain the altered muscle structural behavior (
). In this context, our patients followed a standard aftercare protocol of up to eight weeks of cast immobilization with partial weight bearing which could have induced structural remodeling of muscle morphology. This might be an explanation for the increased gastrocnemius fascicle stretch and less compliant elastic tissues that both would contribute to a loss of mechanical power that needs to be transferred to the foot during locomotion (
). In our patients with CF, this effect could be also observed by the lowered serial elastic element elongation during single support and reduced shortening during push-off, which persisted even one year after surgery. Due to this reduced stretch, less recoil of the serial elastic element could be transferred to generate adequate dynamic ankle joint push-off power.
From a biological perspective, de-tensioning also removes the constant mechanotransduction on elastic tissues such as tendons and aponeuroses and therefore might decrease the expression of collagen type I and inflammatory signaling markers which are important for the mechanical adaption to exercise (
). In contrast to muscle fascicle behavior, the decreased serial elastic element lengthening and shortening behavior during walking even persisted after the twelve months when compared to healthy controls. This is supported by previous findings, that elastic tissues such as tendons generally show a different responsiveness to mechanical loading than muscle fascicles, and that a normal function may not be achieved within one year after surgery (M. D.
To counteract these issues, training interventions that increase tendon stiffness and fascicle tensile stress resistance by applying higher loading intensities (> 70% of maximum voluntary contraction) at longer intervention duration (> twelve weeks) in the early rehabilitation phase might serve as a potential therapeutic strategy (
). In this context, interdisciplinary collaboration between orthopedic surgeons, sports technicians and physical therapists is essential to improve muscular recovery in patients with CF.
Nonetheless, other confounding factors such as compensatory unloading of the ankle joint as well as an insufficient calcaneal restoration might contribute to long-lasting or even irreversible effects on elastic components during walking (
Displaced intra-articular fractures of the calcaneus treated non- operatively. Clinical results and analysis of motion and ground-reaction and temporal forces.
J. Bone Joint Surgery - Series A.1994; 76: 1531-1540
). In this context, radiographic parameters, such as Böhler's angle, Gissanes angle, talocalcaneal angle or absolute foot height revealed significant intra-individual differences between the injured (fractured) and uninjured side (
). Future studies might focus on long-term investigations regarding the interaction between dynamic muscle function and restored bony anatomy of the calcaneus.
As shown in our study, static measurements of muscle properties only partly reflected morphological adaptions of muscles and did not provide sufficient information about functional adaptions. Static fascicle length measures showed no differences within patients and when compared to healthy controls, while dynamic measures revealed meaningful differences in terms of isometric (healthy) and a non-isometric (CF) fascicle behavior. This generally supports the clinical importance of dynamic muscle structure analysis to evaluate morphological adaptions of muscles and tendons after trauma (
This study has some limitations. Morphologic analyses were only conducted for the medial gastrocnemius and therefore cannot reflect the biomechanical behavior of the entire plantar-flexor muscle group. Differences in the dynamic mechanical behavior between uniarticular (Soleus) and biarticular (Gastrocnemius) muscles were identified in previous studies (
). This indicates that, during walking, single ankle plantar flexors might not be considered as unique synergists during gait especially in clinical populations and that additional information is needed to provide a complete understanding of their morphologic behavior. Using 2D ultrasound in dynamic muscle analysis limits the information on fascicle measures since tracked fascicles tend to rotate and change their curvature during contraction and may move outside of the 2D image plane (
). Although correct probe alignment reduces fascicle misestimations, interpretation of fascicle data is still limited. Muscle tendon unit estimation was only obtained using one static knee and ankle joint moment arm. Since changes in moment arm during gait were not considered, especially knee moment arms might be overestimated and would result in an altered gastrocnemius length (
). Regarding elastic components we only analyzed combined tendon and aponeurosis movement of the medial gastrocnemius which cannot represent isolated tendon (Achilles tendon) behavior during walking. In this context, the Achilles tendon is a complex structure of different subtendons demonstrating inhomogeneous functional loading deformations and intertendon sliding during walking (
). Future research regarding dynamic tendon analysis and posttraumatic adaption is needed to provide a complete understanding about the clinical rehabilitation process in patients with CF or other comparable foot and ankle pathologies.
5. Conclusions
CF resulted in an altered interaction of contractile and elastic components of the medial gastrocnemius during walking. Although a recovery to an almost physiologic movement of fascicles was achieved twelve months after surgical treatment, serial elastic element movement in particular still showed relevant restrictions during its shortening behavior. This implies a diminished ability of tendinous tissues to release elastic energy during forward propulsion in patients after CF. Although restrictions of ankle joint kinematics and kinetics may in some part explain this limited biomechanical function, altered mechanical properties due to structural remodeling of connective tissue after trauma and subsequent immobilization are considered as key factors.
The following is the supplementary data related to this article.
Supplementary Fig. 1Individual Data (patients and controls) for the ankle range of motion (ROM) during push-off and the maximum ankle moment during stance phase. Blue: three months, green: six months, red: twelve months, gray: vel1, black: vel2).
This work was proportionally supported by the Paracelsus Medical Private University Research support fund PMU-FFF (Project no. E-17/26/136-AUG) and the German Social Accident Insurance (Project no. FF-FR 0180). The findings and conclusions in this manuscript are those of the authors and do not necessarily represent the views of the German Social Accident Insurance.
Radiographic and functional outcomes after displaced intra-articular calcaneal fractures: a comparative cohort study among the traditional open technique (ORIF) and percutaneous surgical procedures (PS).
Gait characteristics and functional outcomes during early follow-up are comparable in patients with calcaneal fractures treated by either the sinus tarsi or the extended lateral approach.
Functional outcome and patient satisfaction after displaced intra-articular calcaneal fractures: a comparison among open, percutaneous, and nonoperative treatment.
Do changes in dynamic plantar pressure distribution, strength capacity and postural control after intra-articular calcaneal fracture correlate with clinical and radiological outcome?.
Displaced intra-articular fractures of the calcaneus treated non- operatively. Clinical results and analysis of motion and ground-reaction and temporal forces.
J. Bone Joint Surgery - Series A.1994; 76: 1531-1540
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