Cervical spine (neck) pain is the fourth leading contributor to disability and up to 70% of individuals will experience cervical spine pain during their lifetime (13,30). Women are more likely to develop these symptoms than men, and at any given point in time, 5% of individuals will report symptoms (13,30). Cervical spine pain can affect an individual's quality of life in a multitude of ways ranging from occupational to sport and leisure impairments. Of the various conditions implicated in the etiology of neck pain, intervertebral disc disorders (herniation) seem to be reasonably common. Intervertebral disc herniations of the cervical spine may be a leading cause of radiculopathy, resulting in pain, paresthesias (numbness and tingling), diminished reflexes, sensory loss, and weakness (53). The annual incidence of cervical radiculopathy is approximately 83.2 per 100,000 in the general population and 1.79 per 1000 in military personnel (46,53). From an economic (cost) perspective, intervertebral disc disorders of the cervical spine impose a considerable financial burden, as the per capita expenditure for this condition is the highest as compared with other spinal disorders (37).
Pain associated with cervical spine disc herniations can be recurrent (returns after an initial episode), persistent, or progressive (gradually worsens) in nature. Specifically, evidence suggests that within 1 year of symptom onset, 36.6% of individuals will experience complete resolution of their symptoms. However, despite a good natural history, 22.8% of individuals will experience a recurrence of their cervical spine pain within 1 year (14). Although many will seek formal rehabilitation, the impairments and functional limitations that occur may persist well beyond the discharge from formal care (rehabilitation). Moreover, formal rehabilitation may fall short of returning a patient to premorbid recreational activities such as sports or fitness endeavors.
Thus, it is likely that strength and conditioning (S&C) specialists will encounter clients who have sustained a cervical spine disc herniation in the past and possibly many who are in the process of or who have completed formal rehabilitation. In some instances, individuals may seek the advice of a qualified S&C professional as a means of continuing to improve their function and returning to premorbid activity levels. Hence, it is important for the S&C specialists involved in the care of these individuals to have a clear understanding of the condition, ensuing impairments, precautions, appropriate exercise prescription, and modifications to properly carry out post-rehabilitative programming. In addition, it is important for S&C specialists to understand the signs of worsening symptoms to recognize the need for prompt referral to a qualified healthcare professional (physician).
The purpose of this article is to provide an overview of discogenic pathology and the continuum of care. Emphasis is placed on post-rehabilitation management strategies including exercise programming, precautions, and interdisciplinary communication. Long-term management strategies are discussed within the context of conservative post-rehabilitative care.
Although a detailed anatomical review of the cervical spine is beyond the purpose of this article, a brief review is necessary to understand recommendations and risk factors presented. The cervical spinal column (neck) generally consists of 7 articulating vertebrae and 6 intervertebral discs with the most distal disc presenting between the seventh cervical and the first thoracic vertebrae. Each intervertebral disc is comprised of a fibrous cartilaginous outer covering (annulus fibrosus) with a gel-like material (nucleus pulposus) located in the center of the disc (Figure 1A) (1). The main function of the intervertebral disc is to provide cushioning, movement, and stability to the spinal column (31,49). The disc provides cushioning by allowing the nucleus pulposus (NP) to migrate across the internal confinement of the annulus. In mature adults, the NP contains water (75% by weight) and hydrophilic (water imbibing) molecules called proteoglycan aggrecans (20% of the dry weight) (49). The high water content of a normal NP assists with the distribution of compressive loads evenly across the disc (31).
The cervical spine movements generally reside within 3 planes with 6-directional movements. The movements include flexion (moving chin toward the chest), extension (looking upward), rotation (turning head to either side), and lateral flexion (moving ear toward either shoulders). Although the intervertebral disc allows movement, it is also responsible for maintaining stability. The lack of spinal stability can be clearly seen in the presence of disc degeneration. With degeneration, the proteoglycan material and water composition decreases (49). This dehydration (desiccation) of the disc leads to instability (excessive motion) between the vertebrae, which could result in painful compression or stretching of spinal connective tissue such as ligaments or nerves (31). Independent of disc degeneration, cervical herniations may occur in both degenerated and nondegenerated discs as a result of abnormal loading, which is inclusive of activity as well as postures.
The position of the NP within the annulus during cervical movements can reasonably be predicted from an understanding of normal biomechanics as well as in vivo-based and in vitro-based laboratory studies. Research has shown that during cervical flexion, the NP tends to migrate posteriorly (owing to compression anteriorly), whereas during cervical extension, the NP migrates anteriorly (Figures 1B and 1C) (5,52). This biomechanical disc behavior becomes important when managing and preventing cervical disc herniation. Prolonged cervical flexion has been shown to promote and exacerbate nerve root compression via compression and loading of the disc that forces the NP posteriorly (18,52,56). The hydrostatic pressure created by the NP could lead to annular fissures (cracks) that can give the NP an exit (56). The protruded NP can either mechanically compress or irritate the nerve root, leading to neck pain and radiculopathy (1). These findings suggest that positions or repetitive movements that require overzealous cervical flexion should be avoided or minimized among patients with herniated discs. Specific neutral postures should be encouraged to maintain the natural lordotic curve of the neck. The normal cervical lordosis is an anterior curvature that results from the wedge shape of the intervertebral discs, with the anterior portion being thicker than the posterior portion (55). Maintaining the natural lordosis during exercises minimizes asymmetrical or anterior-based loading of the disc, which may lead to intervertebral disc herniation.
Individuals with symptomatic cervical disc herniation often present with complaints of either somatic pain (pain originating from intervertebral disc, capsules, ligaments, or muscles) or, in cases of nerve compression, radicular pain (pain originating from the nerve and dorsal root ganglions) (39). Somatic pain is usually described as a vague, deep, and aching pain that refers to the head, neck, shoulder, scapulae (shoulder blade), or chest wall (39). On the contrary, radicular pain is described as a sharp, burning, and shooting pain down the upper extremity (38). Patients with herniated discs can also experience neurological deficits (impairments) including altered deep tendon reflexes, weakness of the affected nerve, and loss of skin sensation that usually follows the affected nerve distribution (10).
Individuals with cervical disc herniations typically maintain prolonged sitting positions, which often lend to cervical flexion. Extended reading, writing, and computer use contribute to this posture as well. A study by Hagberg and Wegman (23) determined that occupations which require forward flexed postures of the spine tended to have an increased incidence of neck and arm pain. Additionally, a study by Ariens et al. (3) found a strong correlation between sitting, cervical flexion, and neck pain. From a biomechanical perspective, prolonged or repetitive cervical flexion would seemingly cause the NP to migrate posteriorly leading to neck pain.
Patients with neck and upper extremity pain often demonstrate postural deviations including forward head, protracted (rounded) shoulders, and an increased thoracic kyphosis (excessive rounding of the thoracic spine). Typically, these deviations present with tightness of the upper trapezius, levator scapular, pectoralis minor, and sternocleidomastoid musculature, as well as weakness of the lower trapezius, serratus anterior, and deep neck flexors (32). Research has demonstrated a strong association between forward head posture and neck pain (14,21,31). In the authors' experience, these impairments are common among a majority of individuals with neck pain, which is inclusive of those with disc herniations.
Magnetic resonance imaging (MRI) is the noninvasive study of choice for diagnosing cervical spine intervertebral disc pathology (40,44). Conventional radiographs (x-rays) are of limited value when diagnosing acute discogenic pathology since their sensitivity for detecting soft tissue is poor. Poor sensitivity generally equates to a test having excessive false negatives (missing the condition of interest). As the injury becomes chronic and degenerative changes occur, radiographs can be used to evaluate for intervertebral disc space narrowing or desiccation, which may indicate degenerative disc pathology. MRI has also demonstrated an excellent correlation with surgical findings for the diagnosis of cervical radiculopathy (27). From an S&C perspective, the role of diagnosis is not relevant; however, what can be gleaned from the aforementioned information is that many clients with a history of intervertebral disc herniation will likely communicate being diagnosed by MRI.
Electrodiagnostic testing, specifically needle electromyography (EMG), is an important evaluative tool for individuals with cervical spine pain with concomitant upper extremity radicular symptoms (pain, paresthesias, sensory changes, motor weakness, and diminished tendon reflexes). Electrodiagnostic tools, including EMG, nerve conduction tests, somatosensory evoked potentials, and late responses, provide objective evidence of nerve dysfunction. Needle EMG studies have a high utility for diagnosing cervical radiculopathy inasmuch as the test can localize the injury to a specific nerve root level and provide information on the acuity of the condition (24). From the S&C perspective, knowledge of this test being performed may provide insight into a neurological cause of weakness. Individuals with weakness from a nerve compression, for example, will take longer to respond to muscle performance exercises than those with weakness simply due to disuse.
CERVICAL DISC HERNIATION INTERVENTIONS
Cervical disc herniations can be treated by nonoperative interventions (conservative) or surgery. Nonoperative treatment typically consists of rest, collar use, physical therapy, and pharmacological management (10). At times, patients with symptomatic herniated discs are recommended to rest and wear a hard collar. A study by Saal et al. (51) found that cervical disc herniations could be successfully treated by the application of a hard collar for 2 weeks, followed by an active, nonsurgical treatment approach, including physical therapy. Physical therapy consists of therapeutic exercises (often based on avoiding movements that worsen symptoms), manual therapy, traction, and postural training. Therapeutic exercises usually involve extension-oriented exercises, cervical and scapulae strengthening, and soft-tissue stretching, whereas manual therapy includes cervical and thoracic spine mobilization and manipulation. Postural training consisting of patient education on upright positioning and proper cervical control during limb movement is often incorporated into treatment. The evidence on the aforementioned interventions is limited; however, studies demonstrate that physical therapy treatment involving cervical and thoracic mobilization, neural stretching, and cervical-scapular strengthening significantly improves symptoms and function (47).
Cervical traction is another approach used during rehabilitation for the treatment of discogenic pain and radiculopathy. Individuals who benefit from this stretching and distraction of the cervical spine during physical therapy may be issued a portable unit for home use. It is important to note that current evidence does not support or deny the benefits of cervical traction for the treatment of disc herniations when compared with any other nonsurgical treatment approach (22). However, a multimodal treatment approach consisting of exercise, manual therapy, and traction has been shown to be effective in reducing pain and improving function in patients with neck and radicular pain (12). Based on a systematic review of the available evidence, the Orthopedic Section of the American Physical Therapy Association recommends cervical spine mobilization/manipulation, coordination, strengthening and endurance exercises, patient education, and counseling to best manage cervical spine pain (11). These recommendations are based on strong evidence from studies deemed to be of high quality based on research method and design. Thoracic spine mobilization/manipulation, stretching, repeated movements, nerve mobilizations, and traction were not consistently supported in the research and should be considered as adjuncts during rehabilitation for cervical spine pain (11). The value in recognizing interventions performed in physical therapy highlights the course of care a patient has received and should theoretically help the S&C professional appreciate the path of recovery. Moreover, the aforementioned material does serve to highlight the importance of physical activity which would seemingly be the overarching function of the S&C professional. Cervical disc disorders can be treated conservatively with oral medications including nonsteroidal anti-inflammatory drugs (NSAIDs), analgesics, muscle relaxants, and corticosteroids. Opioid analgesics can be used if all other medication is unsuccessful. Epidural steroid injection is a more invasive procedure; however, it is a viable option with documented results. Interventions where corticosteroid derivatives and analgesics are injected into the epidural space (inside the outer layer of the nerve root and spinal cord) have been shown to be beneficial for individuals with upper extremity pain originating from the cervical spine. Bush and Hillier (9) determined that periradicular or epidural injections resulted in satisfactory rehabilitation in all patients who were surgical candidates. Heckmann et al. (26) determined that 100% of individuals with cervical intervertebral disc herniations who were treated with conservative treatment (physical therapy, pharmacology) reported resolution or improvement in upper extremity symptoms. Ninety-seven percent demonstrated abolishment or marked decrease in sensory dysfunction and 94% demonstrated improvement in muscle weakness. Saal et al. (51) corroborated these findings when 87% of patients with cervical radiculopathy secondary to disc herniations achieved good or excellent outcomes with conservative treatment. This evidence demonstrates the potential benefits of conservative treatment; however, if nonoperative treatment is unsuccessful, there are multiple surgical interventions available to aide in relieving symptoms associated with cervical disc disorders. Having a baseline understanding of medications that an individual is taking has direct relevance to the S&C professional. Individuals with persistent pain may be taking pain medications, which could interfere with pain perception and possibly lead to injury with training. S&C professionals should consider deferring a training session when encountering a client who is taking muscle relaxers or opioid pain medications. Although NSAIDs and certain analgesics do not pose an immediate risk for injury, the S&C professional should recognize that clients who are taking these medications are not asymptomatic and may not respond well to an overzealous training program. Moreover, the importance of receiving physician clearance cannot be underemphasized.
Failure of conservative management often results in the decision to proceed to surgery (33). The main purpose of surgery is to relieve cervical pain and nerve root compression (20). This is performed by anterior and posterior cervical discectomy, which consists of partial or full disc removal in the presence or absence of cervical fusion (29). Cervical discectomy could also be accompanied with an artificial disc replacement (21). Gebremariam et al. (20) conducted a systematic review on the effectiveness of different treatment methods for cervical disc herniation. The authors concluded that there is insufficient evidence regarding the effectiveness of operative over conservative management, as well as there is no clear advantage between surgical techniques. However, a recent systematic review compared the outcomes of disc replacement with anterior cervical discectomy, and the results showed better midterm to long-term functional outcomes and less complications for the disc replacement approach (48). It is important to note that patients deemed appropriate for surgery often have failed conservative management or had a severity level inappropriate for nonoperative management. S&C professionals encountering clients who have had surgery should seek to obtain clearance and specific guidelines or precautions from the surgeon. In many cases, due to privacy regulations, surgeons may not be open to discussing their patients' medical care. Medical offices have specific forms that must be signed by individual patients denoting who can be privy to their healthcare information.
In these instances, the S&C professional should request that their client serve as an intermediary to facilitate communication, which may include but is not limited to completion of paperwork authorizing information to be communicated, or help arrange for particular guidelines or precautions to be provided.
Individuals with cervical disc herniations may seek the advice of S&C specialists to establish and progress fitness programs upon completion of rehabilitation. For the S&C specialist with an understanding of cervical disc herniations, this may provide an opportunity for patients to continue progressing toward their goals. Of particular importance is the understanding that worsening not only involves increased neck pain but may also involve pain that travels further into the upper extremity. This change in symptom pattern (pain traveling further distal with regard to the upper extremity) is referred to as peripheralization. On the contrary, centralization is the term used to describe pain that retreats to a location closer to the spine, which suggests improvement. In such cases, clear communication between the S&C specialist and physician or rehabilitation provider is necessary to ensure the safety and appropriateness of routine. Moreover, it is recommended that any patient receiving post-rehabilitation interventions receive medical clearance from a qualified healthcare provider. A discussion with the client's healthcare provider should be inclusive of precautions, contraindications, and guidance toward appropriate activity levels and expectations. Weight training may be a component of the exercise program therefore it is important for S&C specialists to recognize that weight lifting has been associated with cervical disc herniations (41). Given this association, the S&C specialist should have a clear understanding of safe and appropriate exercises for these clients. For instance, the S&C specialist should be cognizant of the client's posture during exercise. Maintaining good posture not only ensures proper form but also minimizes the risk of injury. Clients with a history of herniated discs should avoid rounded shoulders and forward head postures. These postural dysfunctions tend to position the cervical spine in flexion, which often leads to loading of the disc and reproduction of the client's symptom. Clients should be encouraged to exercise in an upright posture, maintaining the natural lordotic curve (arch) of the lower back, keeping the shoulder blades (scapulae) retracted and depressed (back and down), and keeping the chin tucked with eyes level (not looking down).
CERVICAL MUSCULATURE RESISTANCE TRAINING
Training of the cervical spine musculature plays a pivotal role in the management and prevention of discogenic pain. S&C specialists should consider including exercises that target the deep cervical flexors (DCFs) as studies have shown that patients with neck pain often present with weakness of the longus coli and capitus which are the main contributors to deep neck flexion (17). Addressing DCF weakness can substantially decrease pain, improve upright posture, and potentially avoid future recurrence (16,45). Lifting the head with a chin tuck can effectively strengthen the DCFs. The head lift is usually performed by having the client lie face up on a flat table. The client is instructed to maximally tuck the chin in, and while maintaining the tuck, the head is lifted approximately 2–3 inches off the table (Figure 2). Special care must be taken not to exceed 2–3 inches, as this substantially increases the likelihood of loading the disc and reproduction of symptoms. The head lift should be held for at least 10 seconds for 12 repetitions. This exercise can be progressed with longer duration holds, shorter rest, and increased repetitions. If the client is unable to maintain the chin tuck for 10 seconds, the head lift can be regressed by positioning the client on an inclined table. Individuals with weakness of the deep neck flexors may demonstrate compensations during the exercise including protracting the head (gliding the jaw forward) or excessive neck flexion (bringing the chin toward the chest or lifting the head greater than 3 inches). Individuals seeking more detailed information of improving muscle performance of the DCF musculature should refer to Improving Muscle Performance of The Deep Neck flexors by Hanney and Kolber (25).
The S&C specialist should also incorporate exercises that address the deep cervical extensors (DCEs), which play an essential role in the stability of the cervical spine (8). Recent studies have shown that there is a significant association between weakness of the DCEs including the multifidi and semispinalis cervicis, and neck pain (15,19). Given this association, it is prudent for the S&C specialist to design an exercise program that involves DCE. The muscular performance of the DCE can be improved by having the client perform exercises involving cervical retraction. Cervical retractions should be started seated to ensure proper form and tolerance. To perform cervical retractions, the client glides the jaw fully toward the spine while avoiding flexion of the cervical spine (Figure 3A). Once the proper form is achieved, the prone cervical retractions can be performed by lying on the stomach with the chest positioned over the edge of a flat table, arms at the sides, and scapulae midway between fully squeezed and fully away from the spine (Figure 3B). Retraction is held in this position for 10 seconds, for a set of 12 repetitions. This exercise can be progressed by increasing the duration of the hold, greater repetitions, as well as performing the exercise seated with an elastic band. Individuals with weakness of the DCEs may demonstrate compensations including neck extension (looking up), trunk extension (arching the back), or leaning the trunk backward.
SCAPULAR MUSCULATURE RESISTANCE TRAINING
Resistance training plays an important role in return to premorbid activity level after rehabilitation from cervical disc herniation. Of note, the muscles supporting the scapula should be addressed, specifically the serratus anterior, middle trapezius, and lower trapezius. A delay in activation and decreased duration of firing of the serratus anterior has been noted in individuals with neck pain who demonstrate forward head and protracted shoulder postures (28,57). Individuals with cervical disc herniation often demonstrate these postural dysfunctions, and it would therefore be appropriate to include serratus anterior strengthening in a post-rehabilitation program. The serratus anterior is best recruited during the push-up plus exercise (2). Ludewig et al. (36) determined that the push-up plus significantly improved recruitment of the serratus anterior as compared with standard push-ups. The push-up plus is typically performed by having the client protract the shoulders (push scapulae as far as possible from the spine) at the top of the push-up position and maintain the position for at least 10 seconds for a set of 12 repetitions (Figure 4A). This exercise can be progressed by increasing the repetitions, sets, and elastic bands. If an individual does not possess enough strength to perform the aforementioned exercise, or if pain is a limiting factor, the push-up plus can be performed on hands and knees, or against the wall (Figure 4B). Individuals performing the push-up plus may demonstrate common technique errors that involve flaring the elbows out as well as pointing the hands inward. Maintaining the elbows and hands directly under the shoulder joint to encourage better scapulae position, maximize scapular muscle recruitment as well as minimize upper extremity undue stress can easily prevent these errors.
Neck pain should be suspected in the presence of protracted shoulder postures and poor scapular control. Protracted shoulders impair the ability of the musculature to efficiently stabilize the scapulae during static and dynamic movement, which may exacerbate neck pain (6). Protracted shoulder postures during sitting activities have been associated with impaired EMG activity of the trapezius muscle (54,58). Based on the muscular attachment, weakness of the lower and middle trapezius could result in excessive scapular elevation and excessive stress on the shoulder complex and the cervical spine. Thus, it is in the client's best interest to participate in an exercise program that includes strengthening of the lower and middle trapezius muscles. The middle and lower trapezius muscles are typically strengthened by lying on the stomach on a flat table with the chest over the edge and with the shoulders abducted to 90° (Figure 5A) and 130° (Figure 5B) while simultaneously retracting the cervical spine. These positions are held for 10 seconds for 12 repetitions eventually progressing to longer holds, higher repetitions, and loads. Individuals with weakness of the middle and lower trapezius muscles may demonstrate cervical extension (looking up), cervical protraction (gliding the jaw forward), or trunk extension (arching of the back) while performing this exercise.
Clients with forward head and protracted shoulder postures have a tendency to have pectoralis minor tightness (32). Pectoralis minor tightness may excessively anteriorly tilt and internally rotate the scapulae. Abnormal positioning of the scapulae and altered scapular movement patterns can lead to neck and shoulder pathology, therefore the S&C specialist should incorporate pectoralis minor stretches into a post-rehabilitation program. The pectoralis minor can be stretched by lying face up on top of a foam roll with the shoulders abducted and elbows flexed to 90° (high-five position or 90/90) (Figure 6A). While maintaining this position, the client allows the arms to horizontally abduct as far as possible until a comfortable stretch is felt in front of the chest. The pectoralis minor can also be stretched with the client lying face up on top of a foam roll with the arms positioned at 150° of shoulder scaption (flexion in the scapular plane) (Figure 6B). Recent evidence has shown that positioning the shoulder in 150° of scaption lengthens the pectoralis minor more effectively than the 90/90 position (42). Furthermore, the stretch should be held for approximately 15–30 seconds for at least 2 repetitions, as research has shown to be appropriate for improving pectoralis minor length (59). Although, there is a lack of consensus on the frequency, the authors of this article recommend stretching to be performed daily if improvements are to be gained. It is important for S&C specialists to observe the client's form and posture while performing the aforementioned exercise and provide manual, verbal, and visual cuing as needed. This will maximize recruitment of the targeted muscles and minimize stress to the cervical intervertebral discs.
The following example (Table 1) is an exercise routine tailored for a client with a history of a herniated cervical disc. The described program is designed for the asymptomatic client in the post-rehabilitation phase of care, and as previously stated, medical clearance is recommended before participating in this proposed program. The program is to be performed 3 times per week with a least 1 day of rest between sessions to allow the injury prone tissue to sufficiently recover. The exercises chosen are designed to strengthen the cervical and scapular muscles as well as to improve the client's posture. The program emphasizes proper form as well as avoidance of flexion and forward head postures during the exercises (Figure 7, 8, 9). The resistance program will focus on muscular endurance training with higher repetitions, longer holds, lower loads, and shorter rest periods as most of the selected musculature are segmental stabilizers which are comprised of greater proportion of aerobic, limited force production type I fibers (4,7,35,43). When participating in this program, muscle soreness may be expected within 24–48 hours; however, symptoms such as dull, burning, or sharp neck or upper extremity pain should not be expected. Caution should be taken if the client is currently receiving pharmacological treatment. Taking NSAIDs, analgesics, and corticosteroids may raise pain tolerance, which in turn could predispose the client to injury by possibly disturbing the conscious control to tissue failure (34). Lastly, the exercise program should also be performed without holding the breath as the internal discal pressure could potentially increase and lead to reproduction of the client's previous neck and arm pain (50).
Given changes in healthcare cost as well as visit limitations, individuals are likely to discontinue formal rehabilitative care before achieving premorbid fitness and activity levels. Although the patient's condition is typically stable at the time of discharge, impairments may persist. When persistent impairments and functional limitations are present, S&C professionals may find themselves in an opportune position to guide the client in their pursuit of increased function; therefore, an understanding of appropriate post-rehabilitative care is necessary. Exercise programming should consist of advice for maintaining proper posture, improving muscle performance, and return to higher level fitness activities when appropriate. More importantly, it is essential that those S&C specialists involved in post-rehabilitative care recognize the onset of unexpected symptoms (pain persisting beyond a few days or traveling to the shoulder or extremity) to identify the need for prompt referral to a qualified healthcare practitioner. Lastly, the likelihood of neck pain recurrence is high, thus advancement should be gradual with close monitoring of the client's response to training. Communication with the client's healthcare professionals before designing a program would seem useful for understanding the long-term prognosis and relevant precautions. S&C specialists are in a position to potentially make a significant impact with their post-rehabilitative clients; however, this would seem dependent upon devising safe and effective exercise programs that foster the return to sport and fitness activities.
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