Report on a case series investigating a neurostimulation device for the treatment of pain and improvement of mobility and function following elbow surgery

P. Berger, J. Jacks
Pain Management Physiotherapy, Rochester Place, 173 Rivonia Road, Morningside, Johannesburg, South Africa

Introduction

Patients undergoing epicondylitis surgery whether medial or lateral have had chronic elbow pain for a prolonged period often of many months to a year in some cases that has been unresponsive to conservative measures.

Although epicondylitis is a common condition in the arm due to physical overload, the prevalence of definitive lateral epicondylitis was 1.3% and that of medial epicondylitis was 0.4% according to a study in Finland (between 2000 and 2001). The prevalence did not differ between men and women and was highest in subjects aged 45–54 years [1,5]. Prior to surgery these patients have usually had non-surgical treatment and conservative care that includes decreased activity, ice, non-steroidal anti-inflammatory medications, muscle strengthening [2] and these modalities usually help most people. Recalcitrant cases may require cortisone injections that demonstrate the best conservative treatment for lateral epicondylitis [3] but provides only short-term benefits in medial epicondylitis [4]. Lateral epicondylitis, also known as “tennis elbow,” is an overuse syndrome of the common extensor tendon, predominantly affecting the extensor carpi radialis brevis. Patients complain of poorly defined pain located over the lateral elbow that is typically exacerbated by activities requiring wrist extension and/or wrist supination against resistance. There will often be pain in the morning as well as after any period of time that the elbow has been held in a flexed position [5]. Medial epicondylitis is a clinical entity characterized by pain in the medial aspect of the elbow and dysfunction induced by degenerative changes in the origin of the flexor–pronator muscle mass.The accumulated pathological evidence suggests that the process is associated with fibrillary degeneration of collagen and angiofibroblastic hyperplasia at the origin of the flexor pronator muscle mass, microfragmentation or tears of the tendon, accumulation of vascular granulation tissue and tendinous necrosis, all of which are also accompanied by a secondary inflammatory reaction [6]. Non-operative treatment has been deemed highly successful,yet the few prospective reports available suggest that symptoms frequently persist or recur. Operative treatment is indicated for debilitating pain that is diagnosed after the exclusion of other pathologic causes for pain and that persists in spite of a well-managed non-operative regimen spanning a minimum of 6 months. The surgical technique involves excision of the pathologic portion of the tendon, repair of the resulting defect, and reattachment of the origin to the lateral or medial epicondyle.

Surgical treatment results in a high degree of subjective relief, although objective strength deficits may persist [7]. During the last decade, increased attention has been paid to persistent pain complaints after almost any surgical operation with reported incidences ranging between 5% and 50% [8]. The International Association for the Study of Pain defines post-surgical pain as persistent pain after surgery of greater than three months duration[9]. Persistent post-surgical pain syndromes (PPSP) have been considered neuropathic [8] and a strong association is reported between PPSP and sensory abnormalities [10]; however, there is evidence that mechanisms other than nerve injury such as inflammation, central sensitization or a combination of these may play a role. It is important to elucidate whether persistent pain is due to surgical injury of the nerves, ongoing inflammatory processes,injury to the somatic or visceral structures or other causes [11]. Most of those patients that elected to have the surgery for the elbow in these case reports had chronic pain before surgery with or without neuropathic symptoms. It was thought that treating the acute post-operative pain aggressively early by blocking pain,improving wound healing and improving strength may have some impact on post-surgical pain.

Methods

Seven patients who had elbow surgery either for golfers or tennis elbow were sent for neurostimulation within a day post-surgery. The University of the Witwatersrand Human Ethics Committee approval was received for the study. An information and consent form was presented to patients and duly signed.

The treatment protocol was divided into two sections.

The first three treatments with non-invasive pulsed radio frequency:

• 20 min in total
• brachial plexus region for 10 min superior to the clavicle
• brachial plexus region for 10 min inferior to the clavicle

This treatment was given on alternate days over 1 week before the splint was removed and the aim was to reduce pain immediately and to have a possible influence on post-operative pain syndromes that may occur, to prime the nerve supply to the elbow to increase mobility and to improve muscle strength (this could be visualized by fasciculation of the muscles under the splint) to enable better function after the splint was removed.

Once the splint was removed all measures and evaluations were taken before the second section of treatment was implemented.

Results

In the patient study group there were four females and three males and the ages ranged from 38 to 60 years. Only one patient had a golfers elbow repair the remainder had a tennis elbow repair. Five patients recovered well and two patients had to have the surgery redone due in the first patient to a complication within the arm due to a previous knife wound and a more extensive approach being required than as in the initial surgery and in the other patient re-operation was required after a fall that had occurred during the recovery period damaging the original site of the surgery.

There was significant pain post-surgery but the movements of flexion and extension were already quite advanced immediately after the splint was removed and this may have been expedited by the electrical stimulation. There were only two movements such as making a fist and washing the face that were evaluated on the fourth treatment as all others were not attainable and there were 12 movements that were attainable and evaluated from the sixth to ninth treatment.

Patient 107 had a good range of movement of flexion and patient 102 had a good range of extension before the 4th treatment.

On the last treatment, pain levels were greatly reduced except for the patient that had to be re-operated. Range of movements and activities were achieved or almost full.

Conclusion

Prior to this case series of patients undergoing epicondylitis surgery the author had evaluated a random group of eight patients from 2006 to 2011 from the patient records that had also had the above mentioned surgery and had been referred by their orthopaedic surgeons for pain control and improved mobility.
On evaluation of this group of patients there was consistency with other studies in the comparison of their ages, gender and type of surgery with lateral epicondylitis surgery performed more frequently that medial epicondylitis surgery [1,5]. Unfortunately there was limited information in VAS and wound status in some of the patients but there was evidence of some patients requiring treatment many weeks after surgery, 16 weeks in one patient with the minimum referral being 10 days after surgery. There were a minimum number of treatments provided in one patient of two treatments and a maximum number of 12 treatments in another patient, with varying numbers of treatments in the others. Some of the wounds were oedematous and inflamed, most of the patients had limitation of extension of the elbow and there was only 50% resolution of the condition in these elbows according to the notes scrutinized. The treatments that were offered to these patients were usually multiple modalities that included ultrasound, electro-acupuncture, infrared laser, functional electrical stimulation, stretching, mobilization of the joint and exercises depending on the condition. These treatments would extend for longer than 20 min duration.

Although the incidence of neuropathic pain and or PPSP in elbow surgery is minimal yet chronic pain may be more common than realized. The condition could elicit chronic pain that may be due to pathogenic mechanisms that can be ascribed to preoperative, intra-operative and post-operative factors and that may produce ongoing complications for the patient and even neuropathic symp-toms. It was then decided to use this example of post-operative elbow surgery for treatment with a neurostimulator (Stimpod) that is minimal, non-invasive, of short duration and cost-effective and may prevent PPSP and relieve neuropathic symptoms.

In the results achieved the patients in the pilot study had some relief of severe and uncomfortable pain before the splint was removed and they required less medication than prescribed as it was given on an as needed basis. After the splint was removed pain levels increased as mobility improved but the pain increase was due to stretching of injured tissues with active movements and did not produce chronic and or spontaneous pain.

The most surprising effect was the movement that was already available immediately after the splint was removed and that continued to improve to full range without the usual treatment requiring mobilization, stretching and strengthening during rehabilitation.

The wounds also demonstrated minimal oedema and inflamma-tion that is not usually expected with recent surgery and continued to improve in some cases to an imperceptible scar. Scarring and sen-sitivity in the wound may augur chronic pain conditions and it is imperative to block pain and improve wound healing to prevent persistent pain and dysfunction.

By the last treatment patients had significantly improved and at one month after the last treatment the patients had almost all attained their goals of pain relief, range of movement and strength in their functional activities.

Patients were generally content with their progress in pain, movement and the type of treatment that was offered as it was of short duration, with a limited number of treatments required to achieve these results with minimal discomfort.

The neurostimulation device stimulated the brachial plexus in the first three treatments that then activates the specific nerve sup-ply affected by the operation, e.g. radial nerve superior and inferior to the elbow if a lateral epicodylitis surgery was performed. Initially this stimulation produced minimal fasciculation in the nerve but as the nerve conduction improved then activity within the nerve sup-ply became more evident with strong fasciculations occurring. This current could also translate in the opposite direction to the dorsal root ganglion of the cervical nerve roots.

When the splint was removed and the wound was exposed the neurostimulation was then applied to the radial nerve (in lateral epicondylitis surgery) superior and inferior to the elbow and to either end of the wound. The effect of this was increased fasciculations in the radial nerve and this even occurred with stimulation on the wound. Again the current would translate in the opposite direction to the brachial plexus and the dorsal root ganglion of the nerve involved.

The neurostimulation device that has been used in this case series appears to have effects on nerve conduction e.g. found in Bell’s palsy patients and relieves neuropathic pain from different aetiologies in many clinical situations since 2009 [12,20].

This type of neurostimulation was originally developed from a nerve-mapping device used by anaesthetists (2003) to detect a nerve before injecting and creating a nerve block prior to surgery. It was thought that to apply a magnetic field of 133 kHz to the square wave component of the nerve mapping current, a treatment would be developed that may be similar to that used in conventional pulsed radiofrequency (PRF) and that also included nerve mapping detection. In effect the current can target the nerve supply to an injury or damaged region. It is possible that nerve stimulation of the affected nerve may become a seminal treatment for blocking pain, normalizing nerve conduction with improvement in strength and range of movements. This treatment would there-fore be non-invasive and of short duration to create these healing effects.

In conventional PRF there is no destruction of the tissue involved (this could be at the dorsal root ganglion, among others) and it is the presence of the high frequency (pulsed 500 kHz) that improves nerve pain and dysfunction, albeit during an invasive procedure. It is also known that pulsed and continuous radio frequency adjacent to the dorsal root ganglion in a rat model induces latent cellular activity [22]. Neuroscientists measure expression of c-fos as an indirect marker of neuronal activity as c-fos is often expressed when neurons fire action potentials. Up-regulation of c-fos mRNA in a neuron indicates recent activity [23].

The neurostimulation provided to these patients demonstrated a capacity to decrease acute post-surgical pain, improve mobility and wound healing with treatment of short duration and minimal intervention by the physiotherapist. There was no sign of neuropathic symptoms in these patients 6 months post-surgery and any pain that was experienced could be attributed to a normal post-operative healing process and improvement in strength with functional activities. All patients were able to resume their normal function and sporting activities.

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