Kinematic analysis of scapulothoracic movements in the shoulder girdle: a whole cadaver study.

Background: Existing kinematic studies of the shoulder girdle focus on humerothoracic movements. Isolated scapulothoracic movements are also performed during daily activities and rehabilitation but kinematic values are lacking. Methods: A kinematic analysis was performed in 14 cadaveric shoulders during protraction, retraction, and shrug. An optical navigation system was used to analyze sternoclavicular, scapulothoracic, and acromioclavicular motions. Results: In the sternoclavicular joint, shrug and retraction caused a posterior clavicular rotation of 5° (standard deviation [SD] 6°) and 3° (SD 2°), while protraction induced an anterior rotation of 3° (SD 2°). Shrug caused a large clavicular elevation of 25° (SD 5°). Shrug and retraction caused an increase in retraction of 17° (SD 5°) and 9° (SD 2°). Protraction induced an increase of 10° (SD 2°) toward protraction. In the scapulothoracic joint, shrug induced an increase of 3° (SD 2°) in anterior scapular tilt, and a lateral rotation of 26° (SD 4°). Retraction caused a lateral rotation of 4° (SD 3°). Protraction caused an increase of 7° (SD 2°) in the scapular protraction position, while shrug and retraction demonstrated a decrease of 9° (SD 2°) and 6° (SD 5°). In the acromioclavicular joint, posterior tilting of the scapula compared to the clavicle increased 23° (SD 6°) during shrug, while during protraction an increase of only 4° (SD 3°) was seen. During shrug, relative lateral rotation increased 13° (SD 4°). The protraction movement decreased the relative protraction position with 3° (SD 2°). Conclusion: This study provided normative kinematic values of scapulothoracic movements in the shoulder girdle.

Biomechanical Evaluation of a Tubular Braided Construct for Primary Deep Flexor Tendon Surgery.

PURPOSE: Immediate postoperative mobilization has been shown to avoid adhesion formation and improve range of motion after flexor tendon repair. A tubular braided construct was designed to allow for these rehabilitation protocols. METHODS: In this ex vivo study, 92 ovine flexor tendons were divided randomly into 2 equal groups. After creating a transection, the tendons of the first group were repaired using a tubular braided construct. This construct, consisting of a tubular braid of polypropylene and polyethylene terephthalate fibers, exerts a grasping effect on the tendon ends. The control group received a multistrand modified Kessler repair with a looped polydioxanone suture (PDS) 4-0 suture and a Silfverskiöld epitendinous repair using an Ethilon 6-0 suture. After the repair, a static and an incremental cyclic tensile test was performed until failure. RESULTS: During the static test, the tubular braid resulted in a significantly higher load at 3 mm gap formation (86.3 N ± 6.0 vs 50.1 N ± 11.6), a higher ultimate load at failure (98.3 N ± 12.7 vs 63 N ± 11.1), higher stress at ultimate load (11.8 MPa ± 1.2 vs 8.1 MPa ± 3.1), and higher stiffness (7.1 N/mm ± 2.9 vs 8.7 N/mm ± 2.2). For the cyclic tests, survival analyses for 1-, 2- and 3-mm gap formation and failure demonstrated significant differences in favor of the tubular braided construct. CONCLUSION: The tubular braided construct withstands the required loads for immediate rehabilitation not only in static tests, but also during cyclic tests. This is in contrast with the control group, where sufficient strength is reached during static tests, but failures occur below the required loads during cyclic testing. CLINICAL RELEVANCE: The tubular braided construct provides a larger safety margin for immediate intensive rehabilitation protocols.

Acromioclavicular reconstruction techniques after acromioclavicular joint injuries: A systematic review of biomechanical studies.

BACKGROUND: Residual horizontal instability after surgical treatment for acromioclavicular joint injuries is seen as a potential cause of suboptimal clinical outcomes. Biomechanical studies have demonstrated that the acromioclavicular capsule/ligaments are the primary restraints for anteroposterior translation. However, limited studies have addressed the biomechanics of a reconstruction of the acromioclavicular capsule/ligaments. The aim of this systematic review was to evaluate the biomechanical role of acromioclavicular capsule/ligament reconstruction techniques after an acromioclavicular joint injury. METHODS: A search was carried out on the databases Medline and EMBASE, and was conducted according to the PRISMA guidelines. Biomechanical studies addressing horizontal and vertical displacement or joint stiffness after reconstructing the acromioclavicular capsule/ligament with or without coracoclavicular ligament reconstruction, were included. FINDINGS: Nineteen studies were included in this review after screening and eligibility assessment. Five of them investigated different sole acromioclavicular capsule/ligament reconstruction techniques. In 10 studies, a sole coracoclavicular ligament reconstruction was compared to a coracoclavicular ligament reconstruction with additional acromioclavicular capsule/ligament reconstruction. The remaining 4 studies compared different acromioclavicular capsule/ligament with coracoclavicular reconstruction techniques with each other. INTERPRETATION: Several testing protocols to evaluate acromioclavicular capsule/ligament reconstruction have been described and can make it difficult to compare the results of the different studies. Acromioclavicular capsule/ligament reconstruction may provide increased anteroposterior and rotational stability but an optimal reconstruction technique, which mimics all biomechanical characteristics of the native joint is not yet available.

Differences between Coracoclavicular, Acromioclavicular, or Combined Reconstruction Techniques on the Kinematics of the Shoulder Girdle.

BACKGROUND: Although the coracoclavicular (CC) ligaments are classically reconstructed after acromioclavicular (AC) joint injuries, biomechanical studies over the past decade have indicated the importance of an additional reconstruction of the AC ligaments. To date, no kinematic study has investigated the kinematic differences between these reconstruction strategies. PURPOSE: To evaluate the restoration of shoulder motion after an AC injury using a CC ligament, an AC ligament, or a combined reconstruction technique. STUDY DESIGN: Controlled laboratory study. METHODS: After creating a Rockwood grade V lesion in 14 cadaveric shoulders, the AC joint injury was treated with either a CC ligament reconstruction using a suspension device, an in situ AC ligament reconstruction using 2 coupled soft tissue anchors, or a combination of these 2 techniques. Joint motions were registered during humerothoracic elevation in the coronal plane and protraction in the intact shoulder in a Rockwood V lesion and after the 3 reconstruction strategies. An optical navigation system measured 3-dimensional rotation in the sternoclavicular and scapulothoracic joints, and both rotation and translation were analyzed in the AC joint. RESULTS: In the sternoclavicular joint, the CC and combined reconstruction techniques adequately restored clavicular axial rotation, while the AC reconstruction technique showed a better correction of clavicular elevation. Scapulothoracic joint rotations were best restored by reconstructing the AC ligaments. In the AC joint, the relative tilting position and the lateral rotation of the scapula compared with the clavicle were best restored by the suspension device and combined reconstruction. The AC ligament reconstruction technique demonstrated a better restoration of the relative protracted position and resulted in a better correction of the translation of the scapula relative to the clavicle. CONCLUSION: This study illustrates that there are kinematic differences between AC, CC, or combined ligament reconstruction strategies. Although each technique was able to restore different elements of the joint kinematics, none of the strategies completely restored the shoulder girdle to its preinjured state. CLINICAL RELEVANCE: Humerothoracic movements after Rockwood V lesions are best restored using the CC reconstruction technique, and scapulothoracic movements are best restored using the AC ligament reconstruction technique.

Flexor tendon repair using a reinforced tubular, medicated electrospun construct.

A reinforced tubular, medicated electrospun construct was developed for deep flexor tendon repair. This construct combines mechanical strength with the release of anti-inflammatory and anti-adhesion drugs. In this study, the reinforced construct was evaluated using a rabbit model. It was compared to its components (a tubular, medicated electrospun polymer without reinforcement and a tubular braid as such) on the one hand to a modified Kessler suture as a control group. Forty New Zealand rabbits were randomly divided into two groups. Surgery was performed in the second and fourth deep flexor tendons of one hind paw of the rabbits in the two groups using four repair techniques. Biomechanical tensile testing and macroscopic and histological evaluations were performed at 3 and 8 weeks postoperatively. A two-way analysis of variance with pairwise comparisons revealed that the three experimental surgical techniques (a reinforced tubular medicated electrospun construct, tubular-medicated construct, and tubular braid as such) showed similar strength as that of a modified Kessler suture repair, which was characterized by a mean load at ultimate failure of 19.85 N (standard deviation [SD] 5.29 N) at 3 weeks and 18.15 N (SD 8.01 N) at 8 weeks. Macroscopically, a significantly different adhesion pattern was observed at the suture knots, either centrally or peripherally, depending on the technique. Histologically, a qualitative assessment showed good to excellent repair at the tendon repair site, irrespective of the applied technique. This study demonstrates that mechanical and biological repair strategies for flexor tendon repair can be successfully combined.

Kinematic Alterations in the Shoulder Complex in Rockwood V Acromioclavicular Injuries During Humerothoracic and Scapulothoracic Movements: A Whole-Cadaver Study.

BACKGROUND: Previous cadaveric kinematic studies on acromioclavicular injuries described mainly rotational differences during humerothoracic movements. Although isolated scapulothoracic movements are also often performed during activities of daily life and can be painful after acromioclavicular injuries, they have not been extensively studied. Further, the analysis of joint translations in kinematic studies has received little attention compared with biomechanical studies. HYPOTHESIS: A kinematic analysis of joint motions in the intact shoulder versus a shoulder with Rockwood V injury would demonstrate a different pattern of kinematic alterations during humerothoracic and scapulothoracic movements. STUDY DESIGN: Descriptive laboratory study. METHODS: A kinematic analysis was performed in 14 cadaveric shoulders during 3 humerothoracic passive movements (coronal and sagittal plane elevation and horizontal adduction) and 3 scapulothoracic passive movements (protraction, retraction, and shrug). An optical navigation system registered rotational motions in the sternoclavicular, scapulothoracic, and acromioclavicular joints in the intact and Rockwood V conditions. In the acromioclavicular joint, mediolateral, anteroposterior, and superoinferior translations were also analyzed. RESULTS: In the Rockwood V condition, a significant increase in clavicular elevation in the sternoclavicular joint during both humerothoracic and scapulothoracic movements was demonstrated, whereas a significant decrease in posterior rotation of the clavicle occurred only during humerothoracic movements. In the scapulothoracic joint, the scapular position changed most significantly during protraction. In the acromioclavicular joint, the scapular tilting position was altered significantly during both humerothoracic and scapulothoracic movements, whereas the scapular rotational position changed only during coronal and sagittal plane elevation. The largest significant changes in the scapular protraction position were seen during protraction movement. Further, in the acromioclavicular joint there was a significant inferior translation of the scapula during all motions, a significant anterior translation during protraction and horizontal adduction, and a significant posterior translation during coronal plane elevation. Mediolaterally, the acromial end of the scapula slid further under the distal clavicle during protraction than during horizontal adduction. CONCLUSION: Large kinematic differences were seen between the intact state and a Rockwood V lesion not only during humerothoracic movements but also during scapulothoracic movements in the cadaveric model. During humerothoracic movements, rotational differences were mainly caused by alterations in the clavicular position. In contrast, during protraction, the alterations in the scapular position were the dominant factor. CLINICAL RELEVANCE: This study demonstrates that protraction induces larger kinematic alterations than horizontal adduction in acromioclavicular injuries and can therefore be included in both clinical examination and kinematic analyses to identify lesions more clearly.

Design and development of a reinforced tubular electrospun construct for the repair of ruptures of deep flexor tendons.

This research aims at developing a more potent solution for deep flexor tendon repair by combining a mechanical and biological approach. A reinforced, multi-layered electrospun tubular construct is developed, composed of three layers: an inner electrospun layer containing an anti-inflammatory component (Naproxen), a middle layer of braided monofilament as reinforcement and an outer electrospun layer containing an anti-adhesion component (hyaluronic acid, HA). In a first step, a novel acrylate endcapped urethane-based precursor (AUP) is developed and characterized by measuring molar mass, acrylate content and thermo-stability. The AUP material is benchmarked against commercially available poly(ε-caprolactone) (PCL). Next, the materials are processed into multi-layered, tubular constructs with bio-active components (Naproxen and HA) using electrospinning. In vitro assays using human fibroblasts show that incorporation of the bio-active components is successful and not-cytotoxic. Moreover, tensile testing using ex vivo sheep tendons prove that the developed multi-layered constructs fulfill the required strength for tendon repair (i.e. 2.79-3.98 MPa), with an ultimate strength of 8.56 ±â€¯1.92 MPa and 8.36 ±â€¯0.57 MPa for PCL and AUP/PCL constructs respectively. In conclusion, by combining a mechanical approach (improved mechanical properties) with the incorporation of bio-active compounds (biological approach), this solution shows its potential for application in deep flexor tendon repair.

Biomechanical evaluation of a new technique for acromioclavicular stabilization.

BACKGROUND: The most commonly used repair techniques to treat an acromioclavicular dislocation imply a suspension mechanism by substituting the supero-inferior oriented coracoclavicular structures with a tight rope mechanism or allograft. Recently, the importance of restoring the antero-posterior stability by addressing the acromioclavicular structures has also been demonstrated. If an in situ repair at the acromioclavicular joint itself could achieve a reposition and would be strong enough, the suspension of the CC structures might become obsolete. Possible advantages would be minimal dissection, lower risk in damaging neurovascular structures, greater stability, reduction of the surgical time and even the possibility of locoregional anesthesia. HYPOTHESIS: In this biomechanical study, the feasibility of different in situ repair techniques is explored thereby testing both compression and translation characteristics. Our hypothesis is that an in situ repair technique results in an adequate repair for the AC joint. METHODS AND MATERIALS: Polyurethane foam blocks will be used as a model for the acromioclavicular joint and the repair techniques will be done by using a combination of sutures and bone anchors or using a transosseous technique. Compression will be measured by means of a Tekscan pressure sensor and translation will be tested in three orthogonal directions using a tensile testing machine. Four different knot anchor configurations (nice knot, surgical knot in two different configurations, Nicky's knot) will be tested for compression. The strongest knot anchor configuration will then be compared side to side with a transosseous configuration for translation. RESULTS: The nice knot in combination with bone anchors provides the strongest compression. In the side to side comparison of a nice knot anchor configuration versus a transosseous nice knot configuration, the transosseous technique shows more resistance to translation. DISCUSSION: An in situ repair by a combination of the nice knot with an anchor or a transosseous nice knot configuration can theoretically be used as a repair technique for an acromioclavicular dislocation. In comparison with existing techniques, this model shows favorable results for translation. LEVEL OF EVIDENCE: III, controlled laboratory study.

The relationship of the acromion to the distal clavicle in normal and symptomatic degenerated acromioclavicular joints.

INTRODUCTION: Although degenerative osteoarthritis of the acromioclavicular joint is a common finding on technical investigations, not every patient experiences pain or function loss. The difference between symptomatic and asymptomatic patients is currently not elucidated. Therefore, we want to investigate the acromioclavicular relationship in normal, asymptomatic, and symptomatic degenerated ACJ. MATERIALS AND METHODS: 84 normal ACJ, 39 asymptomatic degenerated ACJ, and 30 symptomatic degenerated ACJ were 3D reconstructed. The morphological dimensions and the relationship of the acromion and distal clavicle were measured using computational software. The reproducibility of this technique was evaluated using inter- and intra-observer reliability. RESULTS: The mean anteroposterior and superoinferior distance of both the clavicle and acromion was significantly larger in asymptomatic and symptomatic degenerative ACJ compared to the normal ACJ (p < 0.001). In symptomatic osteoarthritic ACJ, both the anterior and posterior borders of the acromion were significantly more anterior to the borders of the clavicle than in the normal group and asymptomatic group (p < 0.001). Subsequent ROC curve analysis resulted in a sensitivity of 86.7% and a specificity of 88.6% for anterior subluxation of the ACJ. This technique showed an excellent inter- and intra-observer reliability. CONCLUSIONS: In patients with degenerative ACJ, both the distal clavicle and acromion are enlarged. In asymptomatic patients, the AC relationship is the same as in normal patients, in contrast, in patients with symptomatic degenerative ACJ, the acromion is subluxated anteriorly compared to the clavicle.

A review of metallic and non-metallic cerclage in orthopaedic surgery: Is there still a place for metallic cerclage?

Cerclage techniques are simple, yet effective techniques to treat certain fractures and are known as one of the first operative techniques in orthopaedic surgery. The days when a twisted metal wire was the only available cerclage technique nonetheless have passed and today there are many different materials and techniques available. This review evaluates the differences between metallic and non-metallic cerclage techniques, thereby looking at biomechanical, technical and biological aspects. It also provides an overview of clinical applications for non-metallic cerclages. The use of metallic versus non-metallic cerclage might differ depending on indication, location and involved tissues. Currently metallic cerclage is mostly used to repair fractures because of its believed higher absolute strength. More recently though, non-metallic cerclage has been proven to withstand the same loads, while having a lower complication rate. This review suggests that mainly in the upper limb a non-metallic cerclage technique might become the golden standard, while in the lower limb both metallic and non-metallic cerclage techniques are complementary and dependent on indication.

Multiple nocardial abscesses of the brainstem and spinal cord diagnosed after an open biopsy through a cervical partial central corpectomy: case report.

Nocardiosis of the central nervous system is a challenging and difficult diagnosis for the clinician. The combination of infections of the brain and spinal cord is even more rare. The authors report on a patient with multiple lesions in the brainstem and cervical spinal cord. This 81-year-old immunocompetent woman presented with symptoms of progressive walking difficulty and ataxia. The results of an extensive workup with laboratory investigation, MRI, lumbar puncture, positron emission tomography (PET), and bone marrow biopsy remained inconclusive. Only after an open biopsy of a cervical lesion by an anterior approach through a partial central corpectomy of the cervical spine, was the diagnosis of nocardiosis made, allowing for specific antibiotic treatment.

Hip morphological characteristics and range of internal rotation in femoroacetabular impingement.

BACKGROUND: Radiographic features specifically related to the occurrence of femoroacetabular impingement (FAI) appear to be highly prevalent in the asymptomatic population. It remains unclear, however, how these incidental findings should be interpreted clinically and which other variables might differentiate between true incidental findings and preclinical patients. PURPOSE: To study the association between cam and overall hip morphological characteristics and range of motion in impingement patients, asymptomatic patients (healthy patients with radiographic features specific to FAI), and healthy controls. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Morphological parameters describing cam and overall hip anatomy were obtained from 30 patients (10 per subgroup) with use of 3-dimensional computational methods. In addition, the range of internal rotation in high flexion activities was evaluated, and its relation to hip morphological variables was analyzed in a multivariate regression model. RESULTS: Size of the cam lesion and range of motion significantly differed between groups (P < .05). The range of internal rotation on impingement testing was found to average 27.9° in the healthy control group compared with 21.1° in the asymptomatic control group with radiographic features specific to FAI (P < .001) and 12.3° in the patient group (P < .001). Cam size, acetabular coverage, and femoral version appeared to be predictive variables for the range of internal rotation. Seventy-five percent of variance between patients could be attributed to the combined effect of these 3 variables (R = .86). The range of motion was decreased in cam patients and asymptomatic patients, and early femoroacetabular conflict was not restricted to the area of the cam lesion but involved the entire anterior femoral head-neck junction. CONCLUSION: Decreased range of motion, as found in FAI, is not solely dependent on the size or even the occurrence of a cam lesion but should be interpreted by taking into account the overall hip anatomy, specifically femoral version and acetabular coverage. Decreased femoral anteversion and increased acetabular coverage add to the risk of early femoroacetabular collision during sports and activities of daily living and therefore appear to be additional predictive variables, besides the finding of a cam lesion, for the risk of clinical hip impingement development. In addition, the findings suggest that surgical osteochondroplasty to restore a normal range of motion may necessitate more excessive bone resection than what simply appears to be a bump on imaging.

Can we predict the natural course of femoroacetabular impingement?

We conducted a multivariate regression analysis (including both radiographic and activity related variables) in patients with osteoarthritis of the hip and structural changes related with femoroacetabular impingement. The purpose of this study was to investigate whether the age at which total hip arthroplasty may have to be performed, can be predicted in patients with femoroacetabular impingement (FAI). In 121 patients with FAI-related osteoarthritis, radiographic variables describing FAI-related parameters were obtained and the patients were questioned about their activity during early adulthood by means of the validated Baecke et al questionnaire. None of the variables significantly correlated with the final outcome parameter : age at surgery. As expected, based on the low correlation ratios of the different parameters investigated, a multiple-regression model was not accurate enough to allow any prediction on the natural course of FAI. We found that it is difficult to accurately predict the age at which a patient with FAI will develop early osteoarthritis. From our findings it appears that a hip with FAI is not always prone to early end-stage osteoarthritic degeneration, not even in patients with a high level of physical activity. Hence, considering the high prevalence of FAI-related radiographic findings, we conclude that not every radiographic abnormality requires treatment.

Pain-induced changes in the activity of the cervical extensor muscles evaluated by muscle functional magnetic resonance imaging.

OBJECTIVES: To investigate the effect of experimental neck muscle pain on the activation of the cervical extensor muscles during the performance of a cervical extension exercise by the use of muscle functional magnetic resonance imaging. METHODS: The activity of the multifidus, semispinalis cervicis, semispinalis capitis, and splenius capitis muscles was investigated bilaterally at 2 cervical levels (C2 to C3 and C7 to T1) in 15 healthy individuals. Measurements were taken at rest and after the performance of a cervical extension exercise without and with induced pain of the right upper trapezius (intramuscular injection of hypertonic saline). RESULTS: In the pain condition, the activity of the multifidus/semispinalis cervicis was reduced bilaterally at the C7 to T1 level (P=0.045). For the semispinalis capitis, there were no significant differences between both conditions. The splenius capitis showed a significantly higher T2 shift at the left side at the C2 to C3 level (P=0.008) and a lower T2 shift at the right side at the C7 to T1 level (P=0.023). DISCUSSION: This is the first study that has shown pain to immediately affect the activity of both deep and superficial cervical extensor muscle layers during a cervical extension exercise. The findings support recommendations for evaluation of cervical extensor muscle function early in the management of painful cervical spine injuries.

Use of muscle functional magnetic resonance imaging to compare cervical flexor activity between patients with whiplash-associated disorders and people who are healthy.

BACKGROUND: Chronic whiplash-associated disorders (WAD) have been shown to be associated with motor dysfunction. Increased electromyographic (EMG) activity in neck and shoulder girdle muscles has been demonstrated during different tasks in participants with persistent WAD. Muscle functional magnetic resonance imaging (mfMRI) is an innovative technique to evaluate muscle activity and differential recruitment of deep and superficial muscles following exercise. OBJECTIVE: The purpose of this study was to compare the recruitment pattern of deep and superficial neck flexors between patients with WAD and controls using mfMRI. DESIGN: A cross-sectional design was used. METHOD: The study was conducted in a physical and rehabilitation medicine department. The participants were 19 controls who were healthy (10 men, 9 women; mean [+/-SD] age=22.2+/-0.6 years) and 16 patients with WAD (5 men, 11 women; mean [+/-SD] age=32.9+/-12.7 years). The T2 values were calculated for the longus colli (Lco), longus capitis (Lca), and sternocleidomastoid (SCM) muscles at rest and following cranio-cervical flexion (CCF). RESULTS: In the overall statistical model for T2 shift, there was a significant main effect for muscle (F=3.906, P=.033) but not for group (F=2.855, P=.101). The muscle x group interaction effect was significant (F=3.618, P=.041). Although not significant, there was a strong trend for lesser Lco (P=.061) and Lca (P=.060) activity for the WAD group compared with the control group. Although the SCM showed higher T2 shifts, this difference was not significant (P=.291). LIMITATIONS: Although mfMRI is an innovative and useful technique for the evaluation of deep cervical muscles, consideration is required, as this method encompasses a postexercise evaluation and is limited to resistance types of exercises. CONCLUSIONS: Muscle functional magnetic resonance imaging demonstrated a difference in muscle recruitment between the Lco, Lca, and SCM during CCF in the control group, but failed to demonstrate a changed activity pattern in the WAD group compared with the control group. The mild symptoms in the WAD group and the wide variability in T2 values may explain the lack of significance.

The use of functional MRI to evaluate cervical flexor activity during different cervical flexion exercises.

The purpose of this study was to investigate the recruitment pattern of deep and superficial neck flexors evoked by three different cervical flexion exercises using muscle functional MRI. In 19 healthy participants, transverse relaxation time (T2) values were calculated for the longus colli (Lco), longus capitis (Lca), and sternocleidomastoid (SCM) at rest and following three exercises: conventional cervical flexion (CF), craniocervical flexion (CCF), and a combined craniocervical flexion and cervical flexion (CCF-CF). CCF-CF gave the highest T2 increase for all muscles. CCF displayed a significantly higher T2 increase for the Lca compared with the Lco and the SCM. When comparing the CCF and CF, no significant difference was found for the Lca, whereas the Lco and SCM displayed a higher T2 increase during CF compared with CCF. This study shows that muscle functional MRI can be used to characterize the specific activation levels and recruitment patterns of the superficial and deep neck flexors during different cervical flexion exercises. During CCF-CF, all synergists are maximally recruited, which makes this exercise useful for high-load training. CCF may provide a more specific method to assess and retrain Lca muscle performance compared with CF and CCF-CF. This study highlights the need to differentiate between the Lco and Lca when evaluating their function, since these results demonstrate a clear difference in activation of both muscles.