Quantitative Sensory Testing (QST) - Does assessing ... - TI Pharma

5. QST in patients with tendinopathy
4. Discussion
Although most quantitative sensory tests demonstrated similar results for the patient
group and the control group, we found several interesting differences. We found
significant differences in mechanical pain threshold and vibration disappearance
threshold in athletes with a chronic PT compared to healthy controls. In patients
with PT no signs of mechanical dynamic allodynia could be found. No psychological
differences between the two groups could be detected.
Mechanisms of peripheral and central sensitisation have been described in several
musculoskeletal disorders, such as chronic low back pain, fibromyalgia, whiplash,
myofascial pain syndrome and other pain syndromes such as irritable bowel syndrome,
chronic headache etc. (Nijs et al 2010; Winkelstein 2004; Yunus 2009). In sports injuries
the role of sensitisation or lowered pain thresholds i.e. hyperalgesia has been described
in patients with shoulder impingement (Hidalgo-Lozano et al 2010) and patellofemoral
pain syndrome (Jensen et al 2008). In our study injured athletes showed considerable
and significant aberrations of the mechanical pain threshold (MPT). This pinprick
allodynia reflects the involvement of central sensitisation upon the peripheral input
from the myelinated (Aδ-fibre) nociceptive input (Davis & Pope 2002; Keizer et al
2008). A reduced pain threshold of Aδ-fibre nociceptors is a plausible explanation why
pain occurs during or shortly after sports activities. Such phenomenon is described to
be very characteristic for (patellar) tendinopathy and is referred to in the classification
of PT (Blazina et al 1973). A reduction of mechanical pain thresholds can be an
explanation why sports activities that normally do not induce pain now become painful.
Sensitisation accounts for the presence of a mechanical or kinetic allodynia in PT and is
therefore a logical explanation for the occurrence of pain in the patellar tendon during
or after activities.
The vibration disappearance threshold (VDT) is a continuum measure, the differences
found in VDT means that patients feel the vibration for a longer (median 6.25) period
of time compared to the healthy subjects. This hyperesthesia could be regarded as a
sign of an increased sensitivity in somatosensory function. The clinical relevance of
this finding is difficult to interpret and has not been described previously. Further
evidence that sensitisation might play a role in PT is that mechanical pain sensitivity
was increased in patients.
Webborn (2008) indicated that the pain in tendinopathy can possibly be seen as
neuropathic pain (Webborn 2008). According to the IASP definition neuropathic pain
is related to lesions within the nervous system (diagnoses such as diabetes, herpes
zoster, poly-neuropathy or post surgery neuralgias) or as a dysfunction (low back pain,
fibromyalgia) (Merskey & Bogduk 2004). Treede et al. (2008) suggested replacing
the word ‘dysfunction’ with ‘disease’. Neuropathic pain should be demonstrated with