Tendon neuroplastic training for lateral elbow tendinopathy: 2 case reports

Abstract

Objective

To report 2 cases of lateral elbow tendinopathy treated with a novel adaptation of tendon neuroplastic training (TNT).

Clinical features

Patient 1

A 61-year-old male machine operator presented with one year of bilateral lateral elbow pain related to his occupation of using torque wrenches.

Patient 2

A 37-year-old male electrician presented with two months of recurrent left lateral elbow pain related to repetitive motions of gripping and pulling at work.

Intervention and outcome

Both patients underwent 8 weeks of a novel rehabilitation program, including TNT, which involved pacing their resistance exercises to a metronome. Both patients experienced clinically meaningful improvements in pain and functional outcome scores that were sustained at the 3-month follow-up.

Summary

Recent evidence suggests that the central nervous system may play a role in chronic tendinopathies. It is possible that TNT may address the central nervous system component of chronic/recurrent tendinopathy that is not addressed by traditional passive therapies. However, further research is needed.

Introduction

Lateral elbow tendinopathy, often referred to as “tennis elbow”, is a common condition in athletes and the general population.^1,2 Risk factors for this condition include repetitive and forceful movements, smoking, and obesity.² Many conservative treatment options are available including rest, bracing, cryotherapy, manual therapy, instrument-assisted soft-tissue mobilization, eccentric exercise, acupuncture, and extracorporeal shockwave therapy as well as injection of various agents.^3–10 Despite the multitude of treatment options available, up to 10% of cases continue to experience long-term pain and disability¹¹, with 89% of patients taking up to one year to recover³.

Anatomically, pathologic tendons experience an increase in tenocyte cell size and number, disorganization of collagen, increased proteoglycan and water content, and neovascularization.¹² In addition to structural, functional, and biochemical changes seen in tendinopathy^13,14, recent evidence has also demonstrated alterations to the motor cortex in patients with this condition^15–17. This includes measureable changes in corticospinal excitability and short-interval cortical inhibition.^18,19 Traditional passive treatments may not address these motor control issues and therefore might lead to less than desirable outcomes or chronicity of symptoms. In 2015, Rio et al.²⁰ introduced a tendon rehabilitation protocol aimed at addressing these motor control deficits seen in patients with tendinopathy. Tendon neuroplastic training (TNT) combines isometric or isotonic strength training with an externally-paced audio or visual cue. Patients perform a strength training task that loads the affected tendon, such as a single leg squat to load the patellar tendon. Rather than a self-paced eccentric-concentric maneuver, the patient matches the speed of the exercise to the audio and/or visual cue provided by a metronome. This type of externally-paced exercise has been shown to improve motor control in an acute strength training session¹⁹ as well as in patients with patellar tendinopathy²⁰. To our knowledge, TNT has not been applied for upper extremity tendinopathies.

The purpose of this manuscript is to describe the rehabilitation of two cases with a clinical diagnosis of lateral elbow tendinopathy using a novel TNT protocol.

Case Presentations

Two patients were seen in a private multi-disciplinary clinic for lateral elbow pain, and both provided written, informed consent to publish their data.

Patient 1 was a 61-year-old machine operator with a one year duration of bilateral elbow pain caused by repetitive torque wrench use. The pain was worse in his left elbow at the time of examination. He described the pain as achy, sharp when aggravated, and reported relief with rest. Previous treatment included ultrasound, laser, and a cortisone injection six months prior with only temporary relief. He also used an elbow brace, which provided some mild relief. The patient reported the pain as 7/10 on the visual analog scale (VAS) when aggravated. Plain radiographs were unremarkable for pathology. The patient’s medical history included essential tremor (i.e. a nerve disorder causing uncontrollable shaking), lumbar discectomy, and high cholesterol. The patient took medications including a statin, beta-blocker, and low dose aspirin daily. He did not report experiencing any other tendon pain.

Patient 2 was a 37-year-old electrician with a two month duration of left elbow pain, which was re-exacerbated following an original onset one year prior. At present the pain was aggravated with performing his daily duties as an electrician, such as pulling electrical cord and using hand tools. He rated the pain 6/10 on the VAS and reported rest as the only relieving factor. For this current episode, the pain was not improving and was affecting his ability to perform his job. His medical history was unremarkable.

A thorough global and regional examination including observation, range-of-motion (ROM), neurological, and orthopedic testing (Cozen’s, Mill’s, Maudsley’s)^21,22 was performed on each patient by the same chiropractor, with notable findings presented in Table 1. Based on history and physical examination findings, both patients fit the typical diagnostic criteria for tendinopathy including pain on palpation, pain with tendon loading, and the reduction of pain during activity, also known as the “warm-up phenomenon.” ¹⁴ As such, both patients were diagnosed with lateral elbow tendinopathy.

Table 1.

Patient examination findings.

	Patient 1	Patient 2
Inspection: Elbow, Forearm, Wrist regions	Unremarkable	Unremarkable
Cervical Spine Screen: ROM testing	Full and pain-free	Full and pain-free
Upper Extremity Neurological Screen: Reflex, Motor, Sensory testing	DTRs 1+ Bilateral C5–7 Motor 5/5 Bilateral C5–T1 Sensory Bilaterally intact C5–T1	DTRs 1+ Bilateral C5–7 Motor 5/5 Bilateral C5–T1 Sensory Bilaterally intact C5–T1
Elbow ROM: Active and Passive	Full and pain-free	Full and pain-free
Location of Symptoms	Bilateral common extensor tendon	Left common extensor tendon
Strength	Wrist extension: 5/5 with pain	Wrist extension: 5/5 with pain
Orthopedic Tests	+ Cozen’s + Maudsley’s + Mill’s	+ Cozen’s + Mill’s
Palpatory Findings	Recreate chief complaint with palpation of common extensor tendon	Recreate chief complaint with palpation of common extensor tendon
QuickDASH Disability/Symptom Score	45.5	36.4

DASH = Disabilities of the Arm, Shoulder and Hand; DTR = deep tendon reflex; ROM = range of motion

Self-reported outcome measures included the QuickDASH disability/symptom score and numeric pain-rating scale (NPRS). The QuickDASH disability/symptom score is a valid and reliable instrument used to measure disability and symptomatology in patients with shoulder, arm, and hand pain.²³ The minimal clinically important difference has been reported to be 19 points with minimal detectable change being 11 points.²⁴

Intervention and Outcomes

Both patients performed a novel, eight week TNT protocol (Table 2) for the elbow without modifying any of their ongoing self-care strategies (i.e. bracing, rest), and they continued to perform their regular duties at work. In addition to the TNT protocol, Patient 1 received low-frequency electro-acupuncture in the elbow (LI10–11, supinator; 8 minutes; 2.5Hz) each week to help reduce his pain so that he could perform his rehabilitation protocol. He chose to have the left side treated only, as it was more symptomatic, and to use the right side as a control. Due to scheduling issues, Patient 2 performed the TNT protocol in isolation, only on the symptomatic side.

Table 2.

8-week tendon neuroplastic training protocol for lateral elbow tendinopathy.

WEEK	SETS	REPS	TEMPO	WEIGHT (LBS)
1	4	8	3sec up - 3sec down*	3
2	4	8	3sec up - 3sec down*	3
3	4	8	3sec up - 3sec down*	3
4	4	8	3sec up - 3sec down*	3
5	4	8	3sec up - 3sec down*	5
6	4	8	3sec up - 3sec down*	5
7	4	8	3sec up - 3sec down*	5
8	4	8	3sec up - 3sec down*	5

sec = seconds

^*Externally-paced with an audio/visual metronome (ProMetronome; http://eumlab.com/pro-metronome/). 2-minute rest between sets

The TNT protocol was to be performed on three non-consecutive days per week for eight consecutive weeks. The exercise involved isolated wrist extension and flexion with a dumbbell (Figure 1 & Supplementary Video online), paced to an external audio/visual cue on the patients’ smartphone (ProMetronome; http://eumlab.com/pro-metronome/). The patients were to listen to the sound and track the movement of the metronome with their eyes, as pacing to these types of external cues has been shown to modulate corticospinal excitability.^18,19,25 The pace of the metronome was set to 20 beats per minute such that each beat was three seconds apart. This allowed a three second concentric and three second eccentric phase. Four sets of eight repetitions were to be completed with a two minute rest in between each set. These parameters were adapted from previous supplementary data by Rio et al.²⁰ The patients were instructed to begin with a three to five pound weight and to ensure that this did not cause pain to exceed a severity of 5/10 during exercise. Gradual progression of weights was attempted at four week intervals, within tolerance.

Figure 1.

Wrist extension exercise paced to an audiovisual metronome (see supplementary video).

(ProMetronome; http://eumlab.com/pro-metronome/)

Outcomes for each patient can be seen in Table 3. The same chiropractor who performed the initial evaluations also oversaw each treatment session and performed final evaluations and discharge. Following the novel TNT protocol, both patients had clinically meaningful improvements in pain and function. Both patients self-reported higher than 90% compliance with the TNT protocol.

Table 3.

Outcome measures at pre- and post-intervention.

	Patient 1	Patient 2
PRE NPRS score	7	6
POST NPRS score	3	1
NPRS change	4	5
PRE QuickDASH Disability/Symptom score	45.5	36.4
POST QuickDASH Disability/Symptom score	25.0	11.4
QuickDASH Disability/Symptom change	20.5	25.0

DASH = Disabilities of the Arm, Shoulder and Hand; NPRS = Numeric Pain Rating Scale

Patient 1 received eight electro-acupuncture treatments once per week over eight weeks. At the end of the trial of care, he reported significant reduction in the frequency and intensity of pain, with the occasional flare up if he had performed more strenuous activities at work. He also noted some improvement in the right elbow symptoms, which had not undergone treatment or rehabilitation. At three month follow-up, the patient’s symptoms had remained stable and he had begun performing the TNT protocol on the opposite arm.

Patient 2 did not receive any passive treatment and only performed the TNT protocol. At eight weeks the patient reported significant improvements in his ability to work with reduced pain and with increased strength. He continued the TNT protocol for an additional four weeks. At three month follow-up, he had ceased the rehabilitation protocol because he was able to perform all of his duties at work pain-free and no longer experienced any symptoms.

Both patients were able to perform the protocol and achieve significant recovery without reducing the frequency or intensity of their work duties.

Discussion

Tendinopathies are common in the general and athletic populations and many conservative treatments fail to resolve these injuries.^1,26–29 These cases were the first to describe a novel rehabilitation protocol for lateral elbow tendinopathy using TNT. Many structural and biomechanical pain generators have been identified for tendinopathy^13,14, however recent evidence also suggests that the central nervous system may play a role³⁰. This can be measured using transcranial magnetic stimulation (TMS), an electromagnetic method used to stimulate small regions of the cerebral cortex. Corticospinal excitability and short interval cortical inhibition, both quantitative measures of motor control, have been shown to be altered in tendinopathy.^16,20 A study by Heales et al.¹⁵ also found bilateral sensory and motor deficits on the unaffected side of patients with unilaterally identified tendinopathies in both the lower and upper extremity. In our two cases, these sensorimotor deficits may have contributed to their condition, however this type of quantitative measurement is not common in clinical practice and was not available.

Several methods have been proposed to address these deficits in motor control. It has been demonstrated that corticospinal excitability can be increased when skill training is externally-paced using a metronome.³¹ Furthermore, Leung et al.¹⁹ found that metronome-paced strength training can reduce short interval cortical inhibition and increase corticospinal excitability compared to self-paced training in healthy individuals. In our two cases, addressing these deficits through metronome-based training may have contributed to the successful outcome, as traditional self-paced strength training does not alter motor control.¹⁹ As TNT is proposed to address the central nervous system component of tendinopathy, it is plausible to also consider that our first case saw improvement in the untreated arm due to the crossover phenomenon.³² Due to several neuroanatomical connections between the left and right brain, it has been observed that strength training of one limb can lead to strength gains of the opposite limb.³² This may provide the opportunity for a clinician to recommend rehabilitation of the contralateral limb in a painful tendinopathy, when the condition is too painful to begin training on the affected side.

Our protocol was adapted from Rio et al.²⁰ and involves using an audiovisual metronome to pace the exercise. A weighted wrist extension was chosen to target the extensor carpi radialis brevis, as this accounts for 90% of lateral elbow tendinopathies.³ Compared to other conservative therapies, TNT addresses the motor control deficits present in tendinopathy. The mainstay of tendon rehabilitation is eccentric training, and there is more recent evidence to support the efficacy of heavy slow resistance training.³³ These training modalities address the tensile strength deficits present in tendinopathy through progressive loading, but fail to adequately address the deficits in the central nervous system. TNT is a combination of resistance exercise and metronome-based training; therefore, this technique may adequately address both the deficits in tendon strength and motor control seen in tendinopathy. However, further research in needed to validate this claim.

Limitations of these case reports are inherent in their study design. Due to the lack of a control group, we cannot rule out the possibility that the patients’ improvement was due to the treatment provided, the multimodal treatment (in the case of Patient 1), or some other unidentified confounding factor. Owing to the chronic/recurrent nature of the condition, it seems unlikely that natural history led to the resolution of the patients’ symptoms. Additional research is needed to demonstrate improvement in motor control in patients with tendinopathy, as current evidence has not studied these techniques in this population. Furthermore, randomized controlled trials are needed to determine the efficacy of TNT compared to other conventional treatment methods for tendinopathy.

Summary

Tendon neuroplastic training is a novel technique that aims to address the central nervous system involvement of tendinopathies. Combining resistance exercise with metronome-based training can potentially improve the tensile capacity of the tendon and reduce motor control deficits. This two-patient case series presents a new intervention for lateral elbow tendinopathy using TNT concepts. Both patients achieved clinically meaningful changes in the Quick Dash and the NPRS, without time lost from work, after performing the eight week rehabilitation program.