THE USE OF ACETIC ACID IONTOPHORESIS IN THE MANAGEMENT OF A SOFT TISSUE INJURY

Abstract

Background:

Contusions are common injuries that occur in athletics. If repeated, complications like myositis ossificans can occur. This case describes the examination and treatment of an athlete with an acute soft tissue injury.

Objective:

To describe the treatment approach used with a hockey player who sustained a soft tissue injury in his upper extremity.

Case Description:

A 19 year old male sustained a soft tissue injury to his upper arm while playing hockey. The athlete complained of pain rated a 2-3 out of 10. He had a well circumscribed, firm, 8 by 5 centimeter palpable mass present along the lateral arm, and was able to passively flex his elbow from 56° to 135°, demonstrating a 56° loss of elbow extension. Functionally, he was able to perform most activities of daily living, but he was unable to play hockey. Over 29 days, the athlete was treated one time with pulsed ultrasound and ice and nine times with iontophoresis using a 2% acetic acid solution. Additionally, the athlete performed pain-free active range of motion exercises for the elbow.

Outcome:

Following treatment, the athlete's pain resolved, the palpable mass disappeared, and his passive range of motion at the elbow was 0° to 135°. Most importantly, the athlete was able to resume playing hockey.

Discussion:

Acetic acid iontophoresis may be a successful intervention for soft tissue injuries of the upper extremity. In this case, it appeared helpful in decreasing the athlete's impairments and contributed to quicker resumption of all functional activities in less time than previously reported in the literature using traditional treatment interventions.

INTRODUCTION

In intercollegiate contact athletics, muscle contusions are a common injury. In ice hockey, contusions represent the fourth most common injury sustained and account for 6.2% of all injuries in that sport¹.

A contusion is caused by the application of an external force to the surface of the body.^2–5 This force can be the result of a fall, collision between athletes, or contact with an opponent's equipment or other object in the playing area, all of which are common occurrences in competitive sports. The force damages the underlying muscle tissue and causes intramuscular bleeding.^{2, 6} This bleeding can be associated with pain, swelling, and loss of range of motion (ROM).^3–5

Contusions can vary considerably in severity and often are graded as mild, moderate or severe⁴ or in grades or degrees ranging from one to three.⁵ Generally, mild or grade one contusions need very little treatment and cause no, or very short periods of disability while a severe or grade three contusion requires more extensive treatment.⁴ Since the most common location for contusions is in the quadriceps, most of the grading systems refer to that area and use criteria specifically related to weight bearing activities. Table 1 shows one such grading system. For the purposes of this report, mild, moderate, or severe will be used to distinguish between different types of contusions.

Table 1.

An example of a classification system used for lower extremity contusions.¹ Since contusions are more prevalent in the lower extremity, most scales reference that area.

Classification	Characteristics
Mild	Localized tenderness in the quadriceps, knee motion of 90 degrees or more and no alteration of gait. The athlete is able to do a deep knee bend
Moderate	Swollen, tender muscle mass, less than 90 degrees of knee motion, and an antalgic gait. The athlete is unable to do a deep knee bend, to climb stairs, or to arise from a chair without considerable pain
Severe	The thigh is markedly tender and swollen and the contour of the muscle cannot be defined by palpation. Knee motion is less than 45 degrees and there is a sever limp. The athlete with this lesion prefers to walk with crutches and frequently has an effusion in the ipsilateral knee

The most common initial treatments used for contusions include cryotherapy, elevation, and immobilization to control the intramuscular bleeding. As the athlete's symptoms resolve, gentle ROM and strengthening exercises are initiated and progressed as tolerated. Return to athletics is allowed as the athlete regains normal flexibility and strength in the tissues that were injured. Often the athlete will wear protective padding over the area of the injury to minimize the risk of re-injury.^3,5

A potential complication of a muscle contusion is traumatic myositis ossificans. Although not fully understood, traumatic myositis ossificans involves the formation of heterotrophic bone within a contused muscle (Figure 1). This condition is most common in athletic individuals between the ages of 15-30 years^7–8 and often occurs in the quadriceps, adductors of the thigh, deltoid, and brachialis muscles.⁹

Figure 1.

Radiographic example of myositis ossificans in the upper extremity. The arrow points to the region of ossification.

Individuals who present with traumatic myositis ossificans report many of the same symptoms and have similar examination findings to individuals with contusions. They typically complain of pain, limited ROM and functional limitations. Upon examination, the injured area appears edematous and is warm and tender to the touch.^6–13 Individuals with myositis ossificans, however, will report repeated trauma to the affected area and, on exam, a firm, palpable mass is usually present.^8–11 Although ossification is present in this condition, it is unclear when radiographic examination is helpful in the overall diagnosis. It is estimated that radiographs of the injured area will demonstrate ossification anywhere between 2 to 6 weeks^5–6,14 after the initial injury.

Although considered self-limiting, myositis ossificans can lead to short-term disability. Jackson and Feagin⁴ found that athletes at the United States Military Academy, West Point, averaged 73 days of disability from myositis ossificans of the anterior thigh. Likewise, Huss and Puhl⁷ described ten cases of myositis ossificans in which symptoms lasted an average of 3.95 months. For individuals participating in athletics, the development of myositis ossificans can be “season ending” as this condition may preclude the athlete from athletic participation until resolved.¹⁰

In some cases of myositis ossificans, the palpable mass never reabsorbs. Thorndike¹⁴ reported that in a series of 25 cases of traumatic myositis ossificans involving either the upper or lower extremity in a variety of different muscle groups, only 36% completely reabsorbed. Many times this residual mass can be the primary cause of continued disability. This is especially true if the ossification is at the origin or insertion of a muscle near a joint.¹⁴

The best treatment for myositis ossificans is somewhat unclear. Treatments reported in the literature have included restriction of activity, oral and injectable anti-inflammatory medications, aspiration of the original hematoma, range of motion exercises, a regimen of rest, ice, compression and elevation (RICE), pulsed ultrasound, electrical stimulation, and protective padding.^{4–6,8–11,13–14} In cases that do not resolve, surgical excision of the bony mass has been advocated.^{5,7–8,11,14}

Acetic acid iontophoresis has been used for the treatment of myositis ossificans.^15–16 Originally described by Le Duc in 1908 as ion transfer, iontophoresis uses direct current and the principle that an electric charge will repel a similarly charged ion to move substances across the skin.¹⁶ It is theorized that acetic acid delivered via iontophoresis is effective for ossifying conditions because the acetate ion combines with the insoluble calcium carbonate that is present with ossifying structures. This combination forms calcium acetate which is more soluble and, therefore, more readily absorbed by the body.¹⁵

To date, there have been no clinical research studies to substantiate the use of iontophoresis with acetic acid for treating myositis ossificans. There is, however, a case report by Wieder¹³ involving a male soccer player who had a 3 week old, 10 by 6 centimeter mass on the anterior thigh as a result of trauma. In this case, the mass was treated with a 2% solution of acetic acid delivered via iontophoresis, pulsed ultrasound, and passive range of motion three times per week for three weeks. Additionally, the athlete was instructed to limit his activity level. At the end of three weeks, the mass had reduced by 98.9% allowing the athlete to regain full ROM and resume playing soccer.

Although the outcome of Wieder's¹³ case report is impressive, it is unclear as to which treatment actually caused resolution of the mass, the iontophoresis or ultrasound alone or the combination of the two. Alternatively, time alone may have contributed to the resolution of the mass.

The purpose of this case report is to describe the use of iontophoresis with a 2% solution of acetic acid as a primary treatment intervention for a collegiate athlete with a soft tissue injury in his non dominant upper extremity.

CASE DESCRIPTION

The athlete was a left hand dominant, 19 year old college, club hockey player who was hit repeatedly across his right upper arm with a hockey stick over the course of ten days. The athlete originally attempted to manage his symptoms with cryotherapy and stretching into elbow extension. Because of persistent pain, swelling, and tenderness to palpation in the traumatized area, he consulted the team orthopaedist 12 days after the original injury. On clinical exam, the injured area was warm, edematous, tender to the touch, and a large, palpable mass was present. Radiographs were ordered and read as normal. Figure 1 presents an example radiograph (not from the patient in this case) showing myositis ossificans in the upper extremity. The athlete was diagnosed as having myositis and was referred for physical therapy.

Upon initial physical therapy examination, the athlete complained of an “aching” pain along the lateral aspect of his right arm rated 2 out of 10 at rest and 3 out of 10 at worst on a verbal rating scale. He also noted tenderness to palpation over the lateral aspect of the right arm and had a well circumscribed, 8 by 5 centimeter, firm, palpable mass that was located in the brachialis muscle. Additionally, the athlete was able to passively flex his elbow from 56° to 135°, demonstrating a 56° loss of elbow extension. No other ROM limitations in the right upper extremity were found. Functionally, he was able to perform most activities of daily living as the injury did not involve his dominant arm, but he was unable to play hockey. The athlete's past medical history was not significant for previous injury to the involved extremity.

Based on the athlete's mechanism of injury, and objective findings from the examination, a contusion of the underlying soft tissue and fracture of the humerus were both considered as possible differential diagnoses. A fracture seemed unlikely due to normal radiographs and a contusion/hematoma seemed more plausible. However, the presence of a large, firm mass in the area of trauma and the significant loss of ROM into elbow extension seemed to suggest the possibility of other pathology. Based upon prior experience and examination findings similar to previously reported cases in the literature,^4,7,13 the authors hypothesized that the athlete may have developed myositis ossificans. Although not present when his radiographs were read, it is possible that this condition developed between the time the diagnostic test was administered (12 days after injury) and the initial physical therapy examination (18 days after injury). Unfortunately, no additional radiographs were ever taken so radiographic confirmation of myositis ossificans was never achieved. Literature suggests that myositis ossificans should be considered in the differential diagnosis of any young athlete who presents with pain, a palpable mass and a flexion contracture in the upper arm.⁷

Iontophoresis, using a 2% solution of acetic acid, was chosen as an intervention for this athlete. This intervention was selected based on the authors' past success in applying this treatment to similar conditions and on Wieder's¹³ case report. Because the medication had to be ordered (Columbine Drug, Loveland, CO 80538 USA), the athlete's first treatment consisted of 1 MHz pulsed ultrasound with a 20% duty cycle at 1.2 W/cm² for 10 minutes directly over the mass. This was followed by an ice massage directly over the injury for 8 minutes. The pulsed ultrasound was utilized based on Wieder's case report¹³ and its proposed mechanical effects of microstreaming.^17–18 Although not fully understood, the introduction of ultrasound to biologic tissues has been shown to create microstreaming or small movements of the ions and fluids surrounding cells. It is thought that these movements may assist in cell membrane permeability and cellular activity. The authors thought that this might assist in healing of the injury. The ice massage was chosen to help reduce the inflammatory response that was present in the area.¹⁹ The athlete was instructed to perform gentle active range of motion (AROM) exercises into elbow extension. Additionally, he was told not to play hockey and to be careful to avoid contusing the injured area again during day-to-day activities.

Two days later, acetic acid iontophoresis was administered using a Phoresor II Auto model number PM850 (Iomed, Salt Lake City, Utah 84104 USA). As the acetate ion is a negatively charged ion (anion),¹⁵ the cathode was attached to the treatment electrode. This electrode (oval in shape, holding 2.5 cc of acetic acid) was placed directly over the mass while the 4 square inch reference electrode (anode) was secured on the posterior surface of the proximal forearm approximately 10 inches distal from the treatment electrode (Figure 2). Both areas were cleaned well with isopropyl alcohol prior to application of the electrodes. The treatment dose was 80 mA-minutes. Following the treatment, the athlete's skin was noted to be erythematous under the treatment electrode. The athlete was instructed to monitor the treatment area for any abnormal changes and continue to perform pain-free AROM into elbow extension as previously described.

Figure 2.

Iontophoresis set up. Note active electrode (negative electrode) containing 2.5 cc's of acetic acid located proximally over the upper arm in the region of the palpable firm mass and dispersive electrode (positive electrode) located distally on the forearm.

Three days later, when the athlete returned for his next treatment, the skin where the electrodes were attached appeared normal. The same treatment was applied, except after completion of the iontophoresis, the treatment electrode was secured in place by pre-wrap and athletic tape and the athlete was told to keep it in place until the following morning (approximately 15 hours). Although there is no evidence for this practice of maintaining the electrode in contact after cessation of current flow, the electrode was secured in place with the idea that further absorption may occur with additional exposure to the medication as has been suggested with other forms of transdermal medication delivery.²⁰ This treatment regimen was continued for an additional seven times over the course of 23 days for a total of nine iontophoresis treatments over 29 days.

OUTCOME

The results of this athlete's case are presented in Table 2. Thirteen days after the initiation of his treatment program, the athlete's right passive elbow ROM improved to 35° to 135°. During this time, one treatment of pulsed ultrasound and three iontophoresis treatments had been administered. Two days later, his passive elbow ROM had improved to 23° to 135° and five days later was 7° to 135°. Three days after that, a total of twenty-three days since the start of treatment, the athlete was cleared by the team orthopaedist to begin playing hockey with a protective pad over the area of injury. Iontophoresis treatments were continued for an additional two sessions as the mass was still palpable. Following those treatments, the athlete stopped coming for treatment.

Table 2.

Patient's improvement in elbow extension PROM with the provided treatment. The number of treatments is indicated in the column to the far right.

Treatments/Days since start of PT	Elbow PROM (degrees)	Total Change in PROM (degrees)	Cumulative Treatment
0/0	56–135	n/a
4/13	35–135	21	1 US; 3 ionto
5/15	23–135	33	1 US; 4 ionto
8/20	7–135	49	1 US; 7 ionto
8/23		Return to hockey
10/29	n/t	n/a	1 US; 9 ionto
10/83	0–135	56	1 US; 9 ionto

An e-mail sent by the athlete approximately five weeks after the last treatment reported that the arm “…is completely healed, full motion, no pain when straightening.” At a final follow-up appointment almost 12 weeks after the start of his treatment (a little over 14 weeks since the initial injury) the athlete demonstrated full passive ROM into elbow extension and no palpable mass was present. The athlete reported independence with all activities including hockey, reported no pain, and had 5/5 strength throughout the right upper extremity.

DISCUSSION

Although it is impossible to make definitive conclusions based on a case report, the clinical scenario presented here provides some evidence that use of acetic acid iontophoresis was helpful in the treatment of what was hypothesized to be traumatic myositis ossificans. This intervention appeared to be successful in decreasing the athlete's pain, calor, and tenderness to palpation; increasing his ROM; assisting in the re-absorption of the palpable mass; and returning him to his previous activity levels.

Additionally, the interventions selected in this case may have been helpful in decreasing the period of disability reported in the literature using traditional treatment interventions following an injury of this type. In this case, the athlete was able to return to competitive hockey 23 days after the initiation of physical therapy treatment, or 41 days after his original injury with only minor restrictions into elbow extension and a small palpable mass. This result is 32 days sooner than the lower extremity cases reported by Jackson and Feagin⁴ and 75 days sooner than the upper extremity cases reported by Huss and Puhl.⁷

The period of disability reported in this case is comparable to the six weeks reported by Wieder¹³ who used similar interventions in a case of myositis ossificans in the quadriceps. Wieder's use of ultrasound in addition to acetic acid iontophoresis is the primary difference between the two cases. It is unknown whether more extensive use of ultrasound in this case would have been helpful.

Although the working diagnostic hypothesis in this case was of the presence of myositis ossificans, radiographic evidence did not support this. Because the cases described by Jackson and Feagin⁴ and Huss and Puhl⁷ demonstrated radiographic signs of myositis ossificans, the shorter period of disability described in this case, as compared to theirs, may have been because the athlete in this case report had a contusion/hematoma rather than myositis ossificans. However, even if the clinical condition that was being treated was a contusion, the athlete in this case report had a shorter period of disability when compared to previously reported cases with similar conditions treated with traditional means. The cases described by Jackson and Feagin,⁴ included five cadets who had moderate to severe contusions that never developed ossification (as determined by radiographs). These cadets suffered an average of 49 days of disability or 8 days more disability than the case described here. Although 8 days is a short period of time, it may be clinically significant if it allows an athlete to return at the end of the season, for playoffs, or in time to face a critical opponent.

It is possible that the period of disability for the athlete in this case study, as compared to the cases reported by other authors, may be different due to the location and/or size of the lesion. Thorndike¹⁴ reported that smaller ossifications and ossifications in the upper extremity tend to have a greater chance of re-absorption. The cases reported by Jackson and Feagin⁴ were all lower extremity cases which could account for the longer period of disability they reported. Huss and Puhl⁷ described upper extremity cases, but failed to indicate the size of the lesions. The case report by Wieder¹³ involved the lower extremity and the area of the lesion seemed to be bigger (10 by 6 centimeters versus 8 by 5 centimeters). Because she was able to achieve a similar period of disability with a larger lesion in the lower extremity, Wieder's chosen treatment interventions may have been overall more effective than the interventions used in this case.

If it is true that the clinical condition being treated in this case was a contusion rather than myositis ossificans, the therapeutic mechanism that has been proposed when using acetic acid iontophoresis on an ossified structure does not apply to this case. Although it is possible that acetic acid may have some effect on a hematoma, it seems more plausible that the direct current itself may have influenced the result in this case. It has been shown that the application of direct current at the levels used in this case report cause vasodilation.^21–22 Vasodilation, especially when used in the non-acute stage of an injury, may have enhanced the resolution of the contusion and be responsible for the results reported in this case.

Although other interventions, including daily AROM, one treatment using pulsed ultrasound, and one ice massage were included in this athlete's plan of care, those interventions are not considered influential in the overall outcome of this case report. The athlete's improvement in elbow ROM seemed to be more closely associated with decreasing the size of the mass rather than any tissue changes that the AROM exercises would have produced. Likewise, it seems unlikely that one treatment of ultrasound and ice massage had a significant impact on the correction of impairments, absorption of the mass, and resolution of the disability. However, it is unknown whether the period of disability would have been significantly shortened with consistent addition of pulsed ultrasound and/or cryotherapy to the treatment regimen.

This case report suggests that acetic acid iontophoresis may be a useful treatment for soft tissue injuries including contusions and possible traumatic myositis ossificans. Application of this treatment may be important for correcting the impairments associated with these conditions, and reducing the overall time of disability.

Clearly, large scale, controlled research studies are needed to investigate the influence of iontophoresis with acetic acid on impairments and functional outcomes for people with soft tissue injuries. Future investigations could also examine the efficacy of iontophoresis alone versus in combination with adjunctive therapies like ultrasound and cryotherapy. Likewise, the relationship between time of disability and involvement of the upper and lower extremity, and time of disability and the size of the ossification could more clearly be defined.