The role of tendon microcirculation in Achilles and patellar tendinopathy

Abstract

Tendinopathy is of distinct interest as it describes a painful tendon disease with local tenderness, swelling and pain associated with sonographic features such as hypoechogenic texture and diameter enlargement. Recent research elucidated microcirculatory changes in tendinopathy using laser Doppler flowmetry and spectrophotometry such as at the Achilles tendon, the patellar tendon as well as at the elbow and the wrist level. Tendon capillary blood flow is increased at the point of pain. Tendon oxygen saturation as well as tendon postcapillary venous filling pressures, determined non-invasively using combined Laser Doppler flowmetry and spectrophotometry, can quantify, in real-time, how tendon microcirculation changes over with pathology or in response to a given therapy. Tendon oxygen saturation can be increased by repetitive, intermittent short-term ice applications in Achilles tendons; this corresponds to 'ischemic preconditioning', a method used to train tissue to sustain ischemic damage. On the other hand, decreasing tendon oxygenation may reflect local acidosis and deteriorating tendon metabolism. Painful eccentric training, a common therapy for Achilles, patellar, supraspinatus and wrist tendinopathy decreases abnormal capillary tendon flow without compromising local tendon oxygenation. Combining an Achilles pneumatic wrap with eccentric training changes tendon microcirculation in a different way than does eccentric training alone; both approaches reduce pain in Achilles tendinopathy. The microcirculatory effects of measures such as extracorporeal shock wave therapy as well as topical nitroglycerine application are to be studied in tendinopathy as well as the critical question of dosage and maintenance. Interestingly it seems that injection therapy using color Doppler for targeting the area of neovascularisation yields to good clinical results with polidocanol sclerosing therapy, but also with a combination of epinephrine and lidocaine.

Figure 1

Oxygen-to-see probe, a combined laser Doppler and spectrophotometry system to determine Achilles microcirculation non-invasively.

Figure 2

Oxygen-to-see system combining Laser Doppler flowmetry and spectrophotometry non-invasively to determine tendon capillary blood flow, tendon oxygen saturation, and tendon postcapillary venous filling pressures.

Figure 3

Capillary tendon blood flow in mid-portion symptomatic Achilles tendinopathy (left tendon) vs. the corresponding asymptomatic contralateral Achilles tendon in 50 patients with Achilles mid-portion tendinopathy.

Figure 4

Superficial (upper numbers [rE as arbitrary unit]) and deep (lower numbers) capillary flow at the second postoperative day following minimal invasive percutaneous Achilles tendon repair at the left leg.

Figure 5

Myocardial oxygen saturation (SO2%) following 5 min (red), 15 min (yellow) and 30 min (green) of ischemia following clamping of the left descending coronary artery and reperfusion with decreased baseline myocardial oxygen saturation after 15 and 30 min of ischemia indicating an ischemia-induced damage to the myocardium (Knobloch K, unpublished data).

Figure 6

Myocardial oxygenation following preconditioning with 2 min of repetitive ischemia/reperfusion (I/R) following clamping of the left descending coronary artery in humans (Knobloch K, unpublished data)

Figure 7

Achilles tendon capillary blood flow at 2 mm depth before (left) and after (right) 12 weeks of daily painful eccentric training in chronic Achilles tendinopathy among 59 patients with symptomatic 64 tendons.

Figure 8

Achilles tendon oxygen saturation before (left) and after (right) 12 weeks of daily painful eccentric training in chronic Achilles tendinopathy in 59 patients with symptomatic 64 tendons.

Figure 9

Oxygen-to-see system to determine capillary blood flow, tendon oxygen saturation and tendon postcapillary venous filling pressures non-invasively using combined Laser Doppler flowmetry and spectrophotometry.

Figure 10

Proposed flow chart of tendon degeneration starting with the healthy Achilles tendon and extrinsic a nd/or intrinsic factors over asymptomatic states with increase in tendon diameter and detectable capillary blood flow and/or Power Doppler flow to symptomatic states and consecutive tendon rupture. Created by Knobloch with accomplishments to Richards et al. 2005, Maffuli et al. 2000, Kannus et Josza 1991.