What a great year it has been, some excellent tendinopathy research. Thanks to all the blog readers and subscribers and I wish you all the best for 2014
Some interesting studies to sink your skeptical and analytical minds into this month. Enjoy
Fessel et al. 2013 – Collagen fibrils are short so load must be transferred laterally between fibrils – collagen cross links function in this way. It is suggested that ground substance ‘crosslinks’ with may have a similar role, but this study shows no change in elastic modulus (stretch resistance) in ground substance deficient rat tail tendon fascicles.
Lohrer et al. found increased retrocalcaneal bursa pressure with insertional versus midportion Achilles pain using invasive techniques at surgery. Confirms pressure/compression involved at the insertion.
El Khoury et al. report further evidence of genetic risk factors for tendinopathy. TIMP2 (tissue inhibitor of metalloproteinase) DNA sequence variation is a risk factor for Achilles tendon pathology
Gardin et al. use contrast enhanced MRI (shows tissue vascularity, perfusion and capillary permeability) in Achilles patients pre and post 12 weeks of eccentrics. There was contrast enhancement in the fat ventral to the Achilles that disappeared after treatment. Contrast MRI in the tendon did not change pre-post 12 weeks of eccentrics, even though pain and function improved. Contrast enhancement in the fat pad did reduce post treatment – suggests peritendon tissues related to pain.
Garala et al. interesting study on psoas tendinopathy – defined irritation of the tendon at the iliopectineal ridge that is associated with anterior hip pain and a snapping sensation in the hip. Main MRI finding seems to be enlarged bursa rather than tendon pathology. 70% of their cohort were not helped by steroid injection and had a tenotomy, which seems high. Key = fix the underlying mechanics to minimize dynamic tendo-bursa compression.
Boesen et al. – growth hormone + rehab vs placebo +rehab among elderly males with healthy tendons. As expected, they found greater increases in patellar tendon CSA and stiffness in the growth hormone group. As with this groups study in last months blog, raises questions regarding therapeutic use.
Wilson et al. interesting retrospective follow up study of 47 greater trochanteric pain syndrome (GTPS) patients treated largely with steroid injection. Report prior failure of exercise, hydrotherapy, weight loss, orthotics, but details of treatment are not given. Huge issue with the study is diagnostic criteria for GTPS, ie they did not just include people with localized greater trochanteric pain. This probably explains why ultrasound was normal on many of the subset that was imaged with this modality. 87% of patients had between 1-6 steroid injections. Main finding = better response after 3 injections and unguided injections. Response to first injection predicted final outcome. Although follow up was up to 3 years, I worry about long term outcome of multiple steroid injections – we know its not good in the elbow (see Coombes et al. 2013, J Am Med Ass).
Stecco et al. performed histological (n=10 cadavers) and imaging study (n=60). Achilles MRI was performed on 30 cases with Achilles tendinopathy and 30 controls. Groups were matched for age and gender, but no mention of activity between groups. The Achilles, fascia crura and paratenon were thicker in cases compared with controls. Paratenon was more vascularized and innervated. Authors suggest these data support the idea that paratenon inflammation leads to tendon degeneration, although there is no prospective element to this study. Tendon thickening without clear paratenon changes are common clinically, and it is conceivable that a thick tendon subsequently leads to paratenon thickening – perhaps both temporal scenarios are possible.
Stecco et al. have performed a radiological, anatomical and histological study of the plantar fascia. Some great data – highlights include: 1) plantar fascia is richly innervated where it joins the fasciae of abductor hallucis and abductor digiti minimi – may explain pain more medial and lateral to the medial calcaneal tubercle; 2) there are Pacini and Ruffini corpuscles suggesting a proprioceptive function; 3) plantar fascia contains lots of hyoluronan (ground substance) – authors suggest that injecting hyoluronan may help plantar fascia patients by reducing ‘stress and friction between collagen fibres’. Can’t get my head around how adding more ground substance will help when there is lots there already!
Notarnicola et al. – prospective randomized study of High Energy Laser Therapy vs ESWT in insertional Achilles tendinopathy. Both groups performed stretching (?!) and eccentric theraband exercises (?!). Both groups were better at 2 and 6 months – better pain but not functional outcomes in laser group at 6 months. Issues: 1) laser group received 10 sessions vs 3 in ESWT, so greater placebo, 2) stretching – although they still got better, so goes to show that stretching is not the antichrist in insertional tendinopathy, as it is sometimes in portrayed – whether it does any good is another question. 3) Soft functional outcomes. My take is that laser and ESWT may offer something in progressing patients through their loading and functional restoration journey – I would question some of the tissue ‘healing‘ effects proposed.
De Almeida et al. discuss the potential anti-inflammatory and mechanotransductive effects of acupuncture. Discuss evidence that positive effects of acupuncture include down regulation of TNF?, IL-1? and IL-6. However, can we assume decrease in some of these cytokines is positive in the degenerative tendon? (eg IL6 is associated with increased collagen synthesis – See Kjaer et al 2013, j App Physiol) Also suggest another mechanisms of acupuncture – increased collagen synthesis via direct stimulation of matrix cytoskeleton. It is hard to imagine how needle stimulation of tenocytes could induce similar mechanotransductive effects to loading, as is suggested in this paper. Great that people are discussing mechanisms of ESWT, laser and acupuncture, we definitely need more answers in this area.
Maas et al. – review of tendon adaptations to running – cross sectional studies show Achilles tendon is thicker in runners. Only 1 prospective study shows no increase in Achilles cross sectional area after a 32 week running intervention – maybe not long or intense enough (only ran mean 1.5hrs/week)? Limited statistical power (5-7% increase in tendon stiffness, n=11)? Sprinters have been shown to have greater Achilles stiffness than runners, but runners stiffness does not differ from controls – authors argue that sprinting involves more strain and therefore tendon adaptation – could also be that people with stiff tendons self select for sprinting. Overall, this review highlights potential for tendon adaptation from intense stretch-shorten cycle loading
Fascinating study by Farcy et al. – they measure calf-Achilles muscle/aponeurosis and tendon shortening during a ‘quick release’ movement. Ie the dynamometer is turned off whilst participants are strapped in and performing a maximal voluntary isometric contraction, so they experience a quick dorsiflexion. As expected, tendon shortening was 4xgreater than muscle and aponeurosis during this dynamic activity that can be likened to the eccentric to concentric turnaround in stretch shorten cycle movement. Clearly shows that under these active conditions the tendon is the key energy storage unit, not muscle/aponeurosis.
Stevens et al. performed an RCT comparing standard Alfredson eccentrics (180/day) and ‘do-as-tolerated’ program – ie do as many as they could tolerate rather than full 6×15. The ‘do-as-tolerated’ group performed significantly less repetitions on average per day, and there was a trend towards superior outcomes in this group at 3 weeks, and no difference between the groups at 6 weeks for VAS pain and VISA. Demonstrates well that ‘less is more’ in early phases, although study is limited by short term follow up of 6 weeks
McMillan et al. investigate Doppler in the plantar fascia. Plantar fascia patients had significantly thicker plantar fascias and greater power Doppler signal than controls on a 4 point ordinal scale, but most had only mild signal presence. There was no correlation with symptom duration and pain intensity. 2 plantar fascias with no pain had Doppler signal, which is consistent with the current view that Doppler is not diagnostic of pain. Mild Doppler signal is in contrast to other tendon, eg Achilles, patellar, but consistent with other largely compressive tendons, eg supraspinatus.
Nielsen et al. local insulin-like growth factor 1 (IGF-1) injections into young and older men’s patellar tendons stimulated a similar increase in collagen synthesis across both age group cohorts. So lower levels of circulating IGF-1 rather than reduced anabolic response to IGF-1 may be a factor in age related tendinopathy – ie virtually all tendinopathies have been associated with age, except for the patellar tendon !
Fletcher et al. report a negative relationship between energy cost of running and Achilles stiffness in women. No similar relationship in men, maybe due to limited power? (n=11). Lichtwark et al. 2008 (J Theor Biol) report a non linear relationship (ie optimal range) between Achilles stiffness and walking and running efficiency. Key is muscle fibre length and tendon stiffness need to be ‘tuned’ for optimal efficiency. eg a stiff tendon needs longer fibres and vice versa. Lichtwark also found greater compliance is better for walking efficiency – makes sense given walking is a lower load activity than running.