Significant improvements were observed within 2 months in all treatment arms. Elbow function and ROM improved independent of the treatment, indicating that MT is as effective as TENS and FB for EHR. However, the results of this study also reveal that MT had no additional effect when combined with TENS and FB.
According to Mohr et al.,20 the pain of EHR is not exclusively caused by structure-associated lesions, such as the bulging of extensor-sinews, edema, or other MRI findings. The presence of these lesions on MRI also does not correlate with subjective pain ratings.21 Manual therapy addresses not only the elbow bones but the functional chains in the musculoskeletal system that are associated with her as well. The functional chains may represent segmental dysfunctions in the cervical spine or TRP in the shoulder or the extensor muscles of the forearm. Physiotherapists were prompted to diagnose and treat functional chains and TRP, which may affect the therapeutic effect of MT observed in this study. The target structures for MT include joints (especially in the elbow and cervical spine), muscles (TRP within the shoulder belt), and the fascia of the upper extremity.
Cloward et al.22 described referred pain after irritation of the intervertebral discs of the cervical spine that resembled EHR, as it radiated into the arm and shoulder (the Cloward -zones) after irritation of the intervertebral discs between C4 and C6. The intensity of the structures on T1-weighted MRIs has been reported not to be correlated with the patient's subjective pain.21 These results support the hypothesis of the nociceptive supply of the intervertebral discs in the cervical spine, which may account for the pain radiating to the elbow. Yamashita et al.23 reported mechanosensitive afferent nerves of lumbar facet joints and the surrounding tissue in rabbits that included proprioceptors with low thresholds and high line velocity and nociceptors with high thresholds and low line velocity. MT on joints may alter proprioceptive inputs at the spinal cord, which may contribute to its therapeutic effect in patients with EHR.
TRP provide another promising mechanism for the treatment with MT. According to Simons et al.,24 TRP are defined as areas within the muscle that can produce referred pain. TRP differ from non-tensed muscles, as they have reduced distances to the endomysium, fragmented or worn-out muscle fibers, atrophy of type II fibers, and necrosis.25 TRP have been reported to have a higher pH and higher concentrations of bradykinin, substance P (SP), calcitonin gene-related peptide (CGRP), tumor necrosis factor-alpha, interleukins 1b, 6, and 8, norepinephrine, and other inflammatory mediators. Active TRP possessed the highest concentrations of these mediators,26 and taut-bands (tensed regions of muscle tissue) have been identified on magnetic resonance elastography.25 The manipulation of TRP during MT may alter nociception in these regions, which may contribute to its therapeutic effect.
Buchmann et al.27 measured the changes in tension within TRP before and during neuromuscular blockage (general anesthesia) and found that segmental interneuronal changes may play a role in the pathophysiology of TRP. Fernandez-Carnero et al.28 described both central and peripheral mechanisms of sensitization of TRP in the forearm for patients with EHR compared to those of healthy controls.
There are no studies specifically focusing on pain development in the elbow, as it relates to the fascia. Tesarz et al.29 reported that the thoracolumbar fascia (TLF) is important for deep back pain in a rat model, as the concentrations of SP and CGRP in the outer fascia and subcutis were elevated. The hyperexcitability of spinal neurons and deep structures of the back (muscles and TLF) generated new receptor fields after a second injection of nerve growth factor suggesting that the development of back pain is a complex interaction that involves the fascia.30 This type of interaction may also be present in EHR pain, and MT may alter the afferent input from these target tissues on a segmental neuronal level.
Generally, the results of previous studies do not support the theory of a single, local cause of EHR pain. On the contrary, the results indicate that spinal neuronal mechanisms of sensitization also contribute to EHR pain, suggesting that MT on target tissues may affect the segmental neuronal level of arousal and, therefore, contribute to the nociceptive turnover in the perception of pain.
The present study has some limitations. First, the PRTEE has not been validated for use in Germany and was translated for the purpose of this study. Due to its high reliability and international approval, the usefulness of the PRTEE was assumed in the study and was, therefore, administered to the participants. Second, MT was provided by different therapists, and no data is available regarding the experience of or specific methods used by the therapists. Third, although forearm braces are commonly used in Germany, there is no evidence from randomized controlled trials supporting their use. Finally, this study did not evaluate the use of concomitant medications, such as analgesics. Future research to further evaluate this subject area is necessary.