Electromyographic and Cinematographic

Size: px

Start display at page:

Download "Electromyographic and Cinematographic"

Beryl Collins
5 years ago
Views:

1 Electromyographic and Cinematographic Analysis of Elbow Function in Tennis Players with Lateral Epicondylitis John D. Kelley, MD, Stephen J. Lombardo, MD, Marilyn Pink,* MS, PT, Jacquelin Perry, MD, and Charles E. Giangarra, MD From the Centinela Hospital Medical Center, Biomechanics Laboratory, Inglewood, California ABSTRACT Lateral epicondylitis occurs frequently in tennis players and appears to be caused by tears in the extensor aponeurosis. The purpose of this study was to compare the electromyographic activities of 5 muscles in players with lateral epicondylitis with those of injury-free players during the single-handed backhand tennis stroke. Finewire electrodes were placed into the extensor digitorum communis, extensor carpi radialis longus and brevis, pronator teres, and flexor carpi radialis muscles in competitive tennis players; 8 players had lateral epicondylitis and 14 had normal upper extremities. The backhand stroke then was recorded on high-speed film and synchronized with the electromyographic signal. The injured players had significantly greater activity for the wrist extensors and pronator teres muscles during ball impact and early follow-through. This activity increase may have been caused by the abnormal mechanics evident on film, including a "leading elbow," wrist extension and an open racquet face near the time of ball impact, and ball contact in the lower half of the strings. These mechanics not only result in a lower level of play but also leave the wrist extensors and the pronator teres muscles vulnerable to injury. This is the first study that documents increased activity in muscles that have been previously injured. Up to 50% of all tennis players experience elbow pain. 2,13,17,19,20 Lateral epicondylitis is by far the most com - mon disorder, with estimates ranging from 75% to 80% of * Address correspondence and reprint requests to: Marilyn Pink, MS, PT, Centinela Hospital Medical Center, Biomechanics Laboratory, 555 East Hardy Street, Inglewood, CA No author or related institution has received any financial benefit from research in this study. the elbow problems that start in this area.5,14,16,20 Most authors believe the etiology involves an overuse syndrome that results in microscopic or macroscopic tears in the extensor aponeurosis, most frequently at the origin of the extensor carpi radialis brevis muscle. 6-8,14,16 Overload also may be caused by muscle contracture or inadequate forearm flexibility, or by a combination of both.&dquo; Treatment is generally conservative, consisting of rest, antiinflammatory medications, strengthening exercises, local steroid injections, and stroke modifications. Surgery is required for elbows that are resistant to nonoperative management.14, IS, 19 Prior electromyographic analyses of the elbow using surface electrodes have confirmed significant activity of the wrist extensors during backhand and forehand strokes.l,4,12 Morris et a1.15 used indwelling electrodes and high-speed photography to analyze the activity of specific elbow muscles. They demonstrated statistically significant increased activity of the extensor muscles in the backhand acceleration phase compared with the other phases. When comparing muscles, they found the greatest activities recorded in the extensor carpi radialis brevis (ECRB) and extensor digitorum communis muscles (EDC). More recently, Giangarra et al.9 used similar techniques and showed increased activity in the extensor carpi radialis longus (ECRL) and ECRB muscles during the acceleration phase of both the one-handed and two-handed backhand strokes. In these two studies of normal subjects, the muscles were used to stabilize the arm and wrist as an extension of the racquet. The purpose of this study was to record indwelling EMG patterns and amplitudes during the one-handed backhand stroke to compare tennis players who had lateral epicondylitis with tennis players who had never experienced lateral epicondylitis. This information will assist the physician and the coach in the management of players with lateral epicondylitis by providing a basis for rehabilitation, as well as by preventing injury through effective training and coaching programs. 359

360 MATERIALS AND METHODS Eight tennis players with lateral epicondylitis volunteered for this study at the Biomechanics Laboratory of Centinela Hospital, Inglewood, California.

2 360 MATERIALS AND METHODS Eight tennis players with lateral epicondylitis volunteered for this study at the Biomechanics Laboratory of Centinela Hospital, Inglewood, California. The subjects were four male and four female players with an average age of 47 (range, 35 to 61). All subjects played club-level tennis at local tennis clubs; three players were at the &dquo;b&dquo; level and five at the &dquo;c&dquo; level. The subjects had the classic symptoms associated with lateral epicondylitis, including pain in the area of the extensor origin, and examination findings of localized tenderness at the extensor origin and reproduction of symptoms with resisted wrist and middle-finger extension. Each subject played or practiced at least twice per week for a minimum of 1 year. All subjects consistently used a single-handed backhand technique. Each had been forced to stop playing for a minimum of 1 month within the previous year because of the lateral epicondyhtis. At the time of the study, they were able to play tennis at the same frequency as before their injuries, although because of the above-listed symptoms they also reported the inability to play as effectively as they had before their injuries. The subjects were free of any other disorders of the upper extremity or cervical spine. No subject had a history of surgery on the involved extremity, nor had any subject had successful stroke modification before participation in the study. The Basmajian single-needle technique3 was used to place the fine-wire electrodes. After proper skin preparation and isolation of the particular muscle, dual 50-micron insulated wires with 2- to 3-mm bared tips were inserted into the EDC, ECRL, ECRB, pronator teres (PT), and flexor carpi radialis (FCR) muscles using a 25-gauge needle as a cannula. The wires then were attached to leads that were insulated from ground plates and were taped to the subject s body. The signals from the leads were transmitted using an FM-FM telemetry system (model 4200-A, Bio- Sentry Telemetry, Torrance, CA) that was capable of transmitting data from all five muscles simultaneously. Correct wire electrode placement was confirmed by electrical stimulation of the muscle through the inserted wire and by a manual muscle test (MMT) specific to the inserted muscle while the telemetry signal was monitored on an oscilloscope. Each subject wore a battery-operated FM transmitter belt pack that was oriented to prevent restrictions in body movement. The EMG information was bandpassfiltered at 100 to 1000 Hz and was recorded on a multichannel instrumentation recorder for later retrieval. Two 16-mm high-speed cameras operating at 200 frames per second were positioned for lateral and overhead views to record each subject s performance. Without the use of adaptive equipment, each subject was allowed to warm up and then proceed to three trials of the single-handed backhand stroke. Marks were electronically placed on the film and the EMG data while the subject performed the backhand stroke to allow synchronization. The single-handed backhand tennis stroke was divided into the following phases (Fig. 1). Phase I, racquet preparation, began with the first motion Figure 1. The six phases of the single-handed backhand tennis stroke. of the backswing and ended with the first forward motion of the racquet. Phase II, acceleration, was split into an early phase and a late phase. The early acceleration phase began with the forward motion of the racquet (the first 34% of the acceleration phase). The late acceleration phase (the last 66% of the acceleration phase) ended with ball contact. Phase III, ball impact zone, consisted of the frame closest to ball contact and the frame immediately before and after ball impact. Phase IV, follow-through, began with ball contact and ended with completion of the swing. This was further subdivided into early follow-through (the first 25%) and late follow-through (the last 75%). The EMG data were converted from analog to digital signals by computer at a sampling rate of 2500 Hz and were quantitated by computer integration. After excluding the noise identified by the resting recording, the peak 1-second EMG signal during an MMT was selected as a normalizing value (100%). Activity patterns were assessed every 20 msec and expressed as a percentage of the MMT, which was the normalization base. These activity patterns were synchronized with film to obtain the percentage of muscle activity values at separate phases of the subject s motions. The data were then processed and checked for normality. Means and standard deviations were calculated for each phase. The data were then compared, using an independent t-test, with data obtained in this laboratory by Giangarra et a1.9 on the normal population who used a singlehanded backhand stroke (P < 0.05). In addition, each film was reviewed to assess the mechanics and techniques used in the stroke. RESULTS Electromyography Extensor carpi radialis brevis muscle. The ECRB muscle in the injured population demonstrated activity below 30%

361 TABLE 1 Means and standard deviations (in percent) for each muscle tested in normal and injured subjects MMT for the preparation and early acceleration phases.

3 361 TABLE 1 Means and standard deviations (in percent) for each muscle tested in normal and injured subjects MMT for the preparation and early acceleration phases. The activity jumped to 78% during late acceleration and increased to 94% MMT for ball impact. The electrical activity then diminished to 67% for early follow-through and dropped below 30% MMT for late follow-through (Table 1). When comparing the injured population with the uninjured population, significantly lower activity was seen during early acceleration (28% compared with 62% MMT) and significantly higher activity during ball impact (94% compared with 40% MMT) and early follow-through (67% compared with 43% MMT, Fig. 2). Extensor carpi radialis longus muscle. The ECRL muscle in the injured population revealed increasing activity from the time of preparation (28% MMT) to the time of ball impact (89% MMT). The action then diminished during early follow-through (62% MMT) and dropped to below 30% MMT for late follow-through (Table 1). The injured population exhibited significantly higher activity during the preparation phase (28% compared with 13% MMT) and during ball impact (89% compared with 43% MMT) than the uninjured group (Fig. 3). Extensor digitorum communis muscle. The EDC muscle in the injured group demonstrated increasing activity from the time of preparation (13% MMT) to late acceleration Figure 2. The EMG activity for extensor carpi radialis brevis Figure 3. The EMG activity for extensor carpi radialis longus (81% MMT). Ball impact and early follow-through dropped to moderate levels (42% and 45% MMT), followed by late follow-through that was below 30% MMT (Table 1). None of the injured group EDC muscle values were statistically different from those of the uninjured group (Fig. 4). Pronator teres muscle. The PT muscle in the injured population revealed activity below 30% MMT for the preparation, early acceleration, and late acceleration phases. Activity then increased during ball impact (60% MMT) and early follow-through (61% MMT). Late follow-through dropped to below 30% MMT (Table 1). The activity for the injured subjects was significantly higher than the activity for the uninjured subjects in the ball impact (60% compared with 26% MMT) and early follow-through (61% compared with 32% MMT) phases (Fig. 5). Flexor carpi radialis muscle. In the injured group, activity in the FCR muscle was below 30% MMT for the preparation and early acceleration phases. The action jumped to 53% MMT in late acceleration and increased to 70% MMT during ball impact. Early follow-through dropped to 53% MMT, and late follow-through was below 30% MMT (Table 1). Early acceleration and late followthrough activity were statistically higher than in the uninjured group (19% compared with 14% MMT, and 23% compared with 11% MMT, respectively (Fig. 6).

362 2. Wrist flexion in the early phases with an abrupt change to extension at ball impact and into early followthrough (six of eight subjects). 3.

4 Wrist flexion in the early phases with an abrupt change to extension at ball impact and into early followthrough (six of eight subjects). 3. Exaggerated wrist pronation that produced an &dquo;upward tilting&dquo; racquet face at ball impact (five of eight subjects). 4. Ball impact in the lower portion of the racquet string area (five of eight subjects). DISCUSSION Figure 4. The EMG activity for extensor digitorum communis Figure 5. The EMG activity for pronator teres muscle in normal and injured subjects. Wrist extensors The dominance of the wrist extensors (ECRB and ECRL muscles) during the backhand stroke paralleled that noted in uninjured populations.9, 15 In the injured group, statistically greater activity was found in four of the six phases. The greatest differences occurred at the time of ball impact. This correlates well with the fact that most players with lateral epicondylitis complain of symptoms at the time of ball impact. 14 It also supports the theory of overuse leading to tears in the extensor area. 6-8,14,16 This muscle activity increase at ball impact as well as the increase demonstrated at early follow-through can be explained by the poor stroke mechanics. The leading elbow and wrist moving into extension, as seen in the injured subjects, leave the forearm and wrist in an unstable position to resist the forces at ball impact. In the uninjured group, the elbow faced the ground, was not flexed at impact, and the wrist was in a neutral position. The statistically lower activity in the ECRB muscle in early acceleration can be traced to a flexed position of the wrist, as shown by statistically greater activity in the FCR muscle at the same time. The statistically greater ECRL muscle activity noted in the preparation phase parallels the trend for this higher activity in the FCR muscle during this phase. Extensor digitorum communis muscle Figure 6. The EMG activity for flexor carpi radialis muscle in normal and injured subjects. Cinematography All injured subjects exhibited at least two offour deviations from proper stroke mechanics (&dquo;proper&dquo; as demonstrated by the uninjured subjects9 and confirmed by review with a professional tennis instructor); six injured subjects exhibited three or four deviations. The deviations were as follows. 1. &dquo;leading elbow,&dquo;4 with the olecranon pointing at the net and the shoulder elevated and in internal rotation (six of eight subjects). The EDC muscle showed no statistically significant differences in the injured group compared with the uninjured group because the EDC muscle is largely a finger extensor, and the stroke deviations in the injured subjects did not significantly affect the finger extensors EMG activity. However, there was a large numerical difference at ball impact with the uninjured group having a 30% higher MMT than did the injured group. This may be because of the bimodal distribution in the uninjured group, with five subjects near 100% and six subjects at or below 45% MMT (injured group 42%). This may represent a trend in the group of uninjured subjects with low EMG activity that could lead to future problems. A prospective study of these six subjects would be of interest. Pronator teres muscle The PT muscle consistently demonstrated activity levels below 33% MMT in both groups with two exceptions. The two exceptions were in the injured population during ball

5 363 impact and early follow-through, when significantly greater activity was recorded. This finding can be explained by the exaggerated pronation at ball impact as well as the fact that the ball contacted the strings in the lower half of the racquet (neither of these findings was consistently found in the uninjured group9). Both of these facts would tend to cause a supination force that would require increased pronator activity for stabilizing the racquet. Flexor carpi radialis muscle The injured population demonstrated significantly increased activity in the FCR muscle from the uninjured group during the early acceleration and late follow-through phases. The overall activity levels were both below 25% MMT; therefore, these values may not have a significant effect on injury other than the fact that they parallel imbalances seen in the wrist extensors as mentioned earlier. This is the first study to document increased activity in muscles that have been previously injured. Prior studies of presurgical and acutely symptomatic conditions have shown decreased activity in the involved muscles.1o,11,21 This decreased activity may have been the result of inhibition of the involved muscles secondary to pain. In the current study our subjects were in a subacute phase of injury. They were not in acute pain during the backhand stroke, and the increased activity reflected the mechanics that produced stress in the muscles of injury. Therefore, the subacute population may give us a clue as to cause, whereas the acute population may give us clues as to effect. More studies of factors such as grip size, string tension, and racquet head size may further delineate their roles in producing lateral elbow problems in tennis players. CONCLUSIONS 1. Increased wrist extensor activity was consistently demonstrated in the group with previous injuries. This correlates with the etiology of overactivity with tears in these muscles. 2. The abnormal EMG activities were in keeping with the abnormal stroke mechanics of leading elbow, wrist extension, exaggerated wrist pronation, and ball contact in the lower portion of the string area as evidenced by high-speed film. 3. The major differences between the injured group and the uninjured group in stroke mechanics were at the time of ball impact. This finding concurs with clinical evidence. 4. This is the first study to document increased activity in previously injured muscles. An increase in activity rather than a decrease in activity may have occurred because the subjects were in a subacute phase of injury. Therefore, faulty mechanics may lead to increased activity and to subsequent injury. REFERENCES 1. Adelsberg S: The tennis stroke: An EMG analysis of selected muscles with rackets of increasing grip size. Am J Sports Med 14: , Allman F, Nirschl R, Plagenhoef S, et al: Tennis elbow: Who s most likely to get it, and how. Physician Sportsmed 3: 43-58, Basmajian JV: Muscles Alive: Their Functions Revealed by Electromyography. Baltimore, Williams & Wilkins, Bernhang AM, Dehner W, Fogarty C: Tennis elbow: A biomechanical approach. Am J Sports Med 2: , Cabrera J, McCue F: Nonosseous athletic injuries of the elbow, forearm and hand. Clin Sports Med 5: , Coonrad R: Tennis elbow. Instr Course Lect 35: , Coonrad R, Hooper R: Tennis elbow: Its course, natural history, conservative and surgical management. J Bone Joint Surg 55A: , Gardner R: Tennis elbow: Diagnosis, pathology and treatment. Clin Orthop 72: , Giangarra CE, Conroy B, Jobe FW, et al: Electromyographic and cinematographic analysis of elbow function in tennis players using single- and double-handed backhand strokes. Am J Sports Med 21: , Glousman RE, Barron J, Jobe FW, et al: An electromyographic analysis of the elbow in normal and injured pitchers with medial collateral ligament insufficiency. Am J Sports Med 20: , Glousman RE, Jobe FW, Tibone JE, et al: Dynamic electromyographic analysis of the throwing shoulder with glenohumeral instability. J Bone Joint Surg 70A: , Groppel JL, Nirschl RP: A mechanical and electromyographical analysis of the effects of various joint counterforce braces on the tennis player. Am J Sports Med 14: , Gruchow HW, Pelletier D: An epidemiologic study of tennis elbow. Incidence, recurrence, and effectiveness of prevention strategies. Am J Sports Med 7: , Leach R, Miller J: Lateral and medial epicondylitis of the elbow. Clin Sports Med 6: , Morris M, Jobe FW, Perry J, et al: Electromyographic analysis of elbow function in tennis players. Am J Sports Med 17: , Nirschl R: Soft tissue injuries about the elbow. Clin Sports Med 5: , Nirschl R: Tennis elbow. Orthop Clin North Am 4: , Priest J: Tennis elbow. The syndrome and a study of average players. Minn Med 59: , Priest J, Braden V, Gerberich S: The elbow and tennis, Part I. Physician Sportsmed 8: 81-91, Priest J, Braden V, Gerberich S: The elbow and tennis, Part II. Physician Sportsmed 8: 77-85, Scovazzo ML, Browne A, Pink M, et al: The painful shoulder during freestyle swimming. An electromyographic cinematographic analysis of twelve muscles. Am J Sports Med 19: , 1991

PRPLE. Lateral Epicondylitis (Tennis Elbow)

PRPLE. Lateral Epicondylitis (Tennis Elbow) PRPLE Lateral Epicondylitis (Tennis Elbow) What is Tennis Elbow? Chronic lateral epicondylopathy (tennis elbow) is an overuse injury to the tendons/muscles on the outside (lateral) aspect of the elbow.