The use of modalities or physical agents as an intervention for the treatment of sports-related injuries has been a staple since the beginning of sports themselves. These procedure-based treatments have played a significant role in the management of a variety of sports-related injuries and postoperative rehabilitation programs. The earliest practices of using modalities to manage athletic injuries focused on treating acute inflammatory conditions and modulating pain symptoms. As the field of sports medicine has evolved, a plethora of physical agents have emerged and been introduced into clinical practice. The purpose of this chapter is to review commonly used modalities available to today’s sports medicine rehabilitation specialist, present relevant literature to support the use of these modalities, and describe our clinical experiences with each modality. This chapter focuses on the following physical agents:
Transdermal drug delivery: iontophoresis
The use of electrical currents has been incorporated into the practice of rehabilitation for thousands of years. The concept of using electrical currents can be traced as far back as the ancient Olympic Games in Greece, when the earliest predecessors of the sports medicine specialist used electric eels to treat athletes’ injuries. Today the clinical pathways for electrotherapy in athlete injury management take many forms, and electrotherapy is used in the clinical management of a wide range of sports-related pathologies and postoperative treatment protocols.
The electrical currents used to treat athletes and their injuries have evolved to a complex and varied mix of devices and applications. In the literature, electrical currents have been described as performing multiple functions, including pain management, facilitation of muscle contraction, functional retraining of a limb or body segment (as with patients who have experienced a cerebrovascular accident or spinal cord injury), promotion of soft tissue healing (including open wounds), encouragement of bone healing, and edema control in both acute and chronic conditions (through the movement of fluid stasis, including in periphetal vascular disease). Literature support for these claims is not always supported at the highest level of evidence (i.e., with randomized controlled trials), but rather support can be extrapolated from bench research and the theory of cellular response to the application of electrical currents. Many of the clinical applications of electrical currents in sports medicine are based on clinical experience and the preference of the clinician.
The development of most electrical current applications in sports medicine is designed to address three primary goals in the overall management of the injured athlete: to control postinjury or postsurgical inflammation, modulate pain, and restore normal muscle function through stimulation of the neuromuscular unit. In the past 30 years, over the course of clinical practice for the authors, the use of electrical currents for the aforementioned purposes has evolved through the development of various waveforms, wavelengths, and frequencies used for varying therapeutic benefits. This section focuses on the following relevant clinical applications of electrical currents used to treat athletic injuries:
Management of soft tissue swelling
Restoration of muscle function after injury or surgery
Although transcutaneous electrical nerve stimulation (TENS) technically refers to any electrical current delivered through the skin to stimulate the sensory branch of the motor nerve, the term “TENS” has been adapted in clinical practice to refer to stimulation of sensory nerves for the purpose of pain control (electroanalgesia) using a small portable or home unit. In sports medicine, the use of TENS (via use of small home units) for the management of pain has been less frequently described than in other areas of physical rehabilitation. However, TENS can be an effective treatment intervention and may facilitate an athlete’s early return to competition. The use of TENS for the management of chronic pain conditions such as osteoarthritis is widely accepted in clinical practice, but little agreement is found in the literature on the effectiveness of TENS.
In sports medicine, electroanalgesia is most frequently accomplished through use of larger clinical stimulation units that use premodulated or interferential currents. A premodulated current is a continuous sinusoidal waveform and sequentially increasing and decreasing current amplitude modulation effect that is preset to create an effect similar to the bust mode of a traditional TENS unit. Interferential stimulation is accomplished by crossing two medium-frequency premodulated currents, which produces envelopes or pulses of current that have altered properties from the original two currents. Interferential current is theorized to be more comfortable for the patient because it allows greater amplitude to be delivered through the skin by adjusting the sweep (modulation of the new frequency) and scan (modulation of one or both of the original currents).
Several theories support the effect of electrical currents that results in pain modulation, including the gate theory and the endorphin theory. The gate theory is based on stimulation of the larger “A” fibers with electrical current that inhibits synaptic transmission along the smaller “C” fibers. Prolonged electrical stimulation (40 to 60 minutes) of small afferent fibers is thought to trigger the release of beta-endorphin. Pain control is most likely a combination of both of these theories. Multiple studies have described the benefit of TENS for pain management in surgical and nonsurgical patients.
In our experience in sports medicine, the most frequent use of electroanalgesia is for control of acute injury or postsurgical pain. An electrical stimulation protocol of interferential current with carrier frequencies of 3000 Hz and 3500 Hz, an 80 to 150 beat frequency, and a 20- to 30-minute cycle at a “strong but comfortable” intensity up to six treatment cycles per day is used in the region surrounding the injury or surgical incision. This protocol was adapted from Jarit et al. to address the goals of reducing pain and restoring early range of motion to a joint. This electroanalgesia treatment is often performed concurrently with cryotherapy to enhance the analgesic effects, facilitate a vasoconstrictive effect, and affect inflammatory exudates. Figure 38-1 demonstrates the use of stimulation for electroanalgesia in a football player who sustained an acute brachial plexus injury. The pad placement is in the region of the upper trapezius to control residual pain and spasm. Figure 38-2 demonstrates positions commonly used with patients after shoulder and knee surgery. In clinical work involving postoperative rotator cuff repairs and shoulder stabilization procedures, electroanalgesia with a TENS unit was effective when initiated within the first 24 hours after surgery and used for 7 to 21 days after the surgical procedure. In this study, the clinicians reported a reduction in the use of oral narcotics in the period of 5 days after surgery with utilization of TENS.
Acute soft tissue injury with a resultant inflammatory response is the most common limiting factor to early return-to-sport participation after injury to muscles, tendons, ligaments, and a joint capsule. The ability to limit the magnitude of an inflammatory response and facilitate the dissipation of accumulated swelling is a critical component of the rehabilitation process. Reduction of acute swelling can have an effect on other impairments, including range of motion, muscle performance, and proprioception. The use of electrical currents to address soft tissue trauma clinically is supported by two different theories: contractile and noncontractile effect.
The noncontractile effect theory is based on ion movement to increase lymphatic drainage. Ion movement is facilitated by a twin peak monophasic current, clinically known as high-volt pulsed galvanic stimulation or high-volt pulsed current (HVPC). The clinical utilization of HVPC has been supported since 1966 and has been described as effective for management of joint swelling and soft tissue inflammation. The protocol we use clinically implements the use of HVPC treatment in the acute phase of injury as part of a comprehensive treatment program that also includes medication, active therapeutic exercise, manual techniques, neuromuscular reeducation, and cryotherapy. Based on the type of injury, the duration of treatment for high-volt galvanic stimulation can be in 30-minute cycles or continuous for 24-hour cycles. With the standard of care in athlete management today, the need for aggressive treatment interventions to help the athlete return to activity expediently is essential. Figure 38-3 demonstrates the use of clinical and portable units for the delivery of high-voltage current.
The contractile theory is based on a muscle-pumping contraction that attempts to reproduce proper circulatory action. This influence of the electrical current on the skeletal muscle contractile pattern results in a pumping action to encourage fluid movement toward the heart and away from the extremity being treated. In addition to skeletal muscle contraction, smooth muscle tone in the lymphatic and venous system can also be influenced by the drainage pattern.
Muscle contraction is generated with an interrupted alternating current such as variable muscle stimulator (VMS), premodulated, or Russian currents, the same currents used for strengthening or functional electrical stimulation. A brief 1 : 1 ratio of contraction to relaxation between 5 and 10 seconds each can be used without risk of muscle fatigue due to submaximal contraction and is recommended. The recommended treatment time is 20 to 30 minutes multiple times per day with postsurgical patients. We recommend a minimum of six cycles per day.
Restoration of Muscle Function
The number one use of electrical currents in sports injury management today is to provide neuromuscular reeducation, which plays a critical role in our clinical postsurgical pathway. The use of electrical currents to stimulate the motor end plate or large efferent nerves to reeducate muscle volitional contractile control has gained wide popularity in the past 20 years. The type of electrical current is an alternating, symmetrical, or asymmetrical biphasic pulsed current or a medium-frequency burst current with an on/off duty cycle. Examples include Russian, VMS, and VMS burst currents. The advancement of these units in the past 5 years has made the use of electrical currents a standard of care when muscle shutdown has occurred. Many published rehabilitation protocols advocate the use of such currents to facilitate neuromuscular reeducation, which is beneficial in the acute phase of postsurgical rehabilitation.
Noyes and colleagues reported the use of neuromuscular stimulation in the initial phase of knee postsurgical rehabilitation protocols to avoid motion complications after anterior cruciate ligament reconstruction. The basis for the use of stimulation after knee surgery had its foundation in neurologic adaptation of the mechanoreceptor system in joints that are negatively influenced by joint pressure resulting from surgery. Kennedy et al. reported an inhibitory effect of knee joint receptors on the quadriceps muscle. Direct stimulation to the motor end plate may have the ability to bypass this inhibitory influence. Figure 38-4 demonstrates the setup for a study that produced an artificially induced joint effusion in the knee. This study supported the influence of joint effusion on muscle performance.
Similar to the knee, the influence of injury or surgery on the shoulder can result in muscular shutdown of the rotator cuff muscle group. Reported outcomes with use of neuromuscular stimulation at the shoulder in open rotator cuff repair and open capsular shifts demonstrated a reestablishment of normal range of motion in a shorter time frame when compared with a group of patients who did not undergo stimulation, although both groups eventually regained the same motion. The use of electrical stimulation for neuromuscular reeducation to the deltoid and rotator cuff musculature facilitated the ability to regain motion in a shorter period, which permitted initiation of an active strengthening program in an earlier phase of rehabilitation. The protocol outlined follows the same progression with a multistage sequence.
Regaining motor control of a joint after injury or surgery aids return of functional motion. The first level of training at the shoulder is the concept of coactivation of the cuff musculature with the deltoid muscle to promote normal timing of the muscular force couple. Figure 38-5, A , demonstrates pad placement for a patient 24 hours after labral repair to excite the deltoid and supraspinatus muscles. At the same time current is delivered , the patient is instructed to volitionally contract the total cuff structure by performing a cuff shrug (i.e., pulling the humeral head into the glenoid). The coactivation concept controls translation of the humeral head, reducing the risk of injury of repaired tissue. Parameters for stimulation are set at 10 seconds on/10 seconds off with a medium-frequency biphasic alternating current such as VMS or VMS burst. The ramp time is unit dependent, but our protocol suggests a minimal ramp time to simulate normal physiologic muscle firing capacity. This protocol uses a 10-minute treatment cycle to limit the potential for muscle fatigue during the treatment. This treatment protocol is repeated by the patient up to six cycles per day using a home stimulation unit with treatment parameter capabilities.
After control of the supraspinatus is obtained, the protocol switches focus to the external rotators. Figure 38-5, B , demonstrates the position used to isolate training of the external rotators. It is believed that the placement of the postsurgical shoulder into internal rotation causes the muscle spindles of the external rotators to be in a lengthened position, which causes a decrease in muscle contraction capability. The sequencing of training initially is to reestablish neutral position and then to gradually move into a 45-degree position over a 3- to 4-week period, depending on the procedure.
The third phase of the protocol is designed to incorporate closed chain exercises into the clinical pathway to facilitate the mechanoreceptors while also minimizing the forces on the rotator cuff and capsule. Figure 38-6 demonstrates positions for closed chain training. This sequence gradually takes the athlete from a nonfunctional to a functional position. Treatment timing is the same as previously discussed.
Literature support for clinical use of electrical stimulation is ample for rehabilitation of the knee after injury and surgery. Delitto et al. reported on the use of electrical stimulation to the quadriceps muscle after anterior cruciate ligament injury and its ability to hasten neuromuscular redevelopment of quadriceps motor control and produce increased strength gains. Petterson and Snyder-Mackler recently reported the influence of using electrical neuromuscular stimulation in persons with chronic quadriceps weakness; increased strength was achieved with electrical stimulation. Other investigators have reported similar findings, and although the long-term benefit with or without electrical stimulation may show no difference, the fact that it assists with an earlier return of motor control and motion makes it a clinical standard.
Initial neuromuscular training is to the quadriceps muscle with activation to regain control of extension range of motion and patella position. The concept of isolated training of one segment of the quadriceps muscle group has not been supported in the literature, and thus our pad placement is over the vastus medialis oblique and femoral nerve to stimulate the quadriceps in its entirety. The position then progresses from extension isometrics to active extension from 40 to 0 degrees and gradually to 90 to 0 degrees, with speed of progression based on pathology. Stimulation is applied with the same parameters as previously described for the shoulder; pad placement is demonstrated in Figure 38-7 for quadriceps reeducation.
The next phase in the progression of the protocol is advancement to a closed chain positioning technique to replicate the functional demands on the quadriceps during gait training, as well as other high-level functional positions. Ambulation requires high eccentric torque production from the quadriceps in the last 15 degrees of extension, and therefore training in this position serves to improve gait training mechanics. The eccentric requirement of the quadriceps peaks during loading response and remains high throughout mid stance, which is often the portion of the gait cycle where patients experience symptoms of “giving way” with knee pathologies. Figure 38-6, B , on postsurgical day 5, stresses active control of the terminal extension angle with use of active muscle contraction augmented with electrical stimulation for muscle contraction. At this point in the treatment program, treatment parameters similar to those described earlier are used; however, the duty cycle is modified to a 5 second on/5 second off cycle. As described previously, we recommend decreasing or eliminating the ramp time to more closely replicable normal firing patterns of the musculoskeletal unit.
The final phase of functional training with neuromuscular stimulation centers on the adaptation of angles that are highly stressed. The goal at this point is to retrain joint proprioceptive sensing, which is disrupted after injury or surgery. Common angles include 15- to 30-degree flexion/extension positions and the control of knee valgus moment, which has been found to have an influence on injury. Figure 38-8, A and B , demonstrates an eccentric and concentric activity to control knee position to avoid valgus angulations.