Microcirculatory effects of topical glyceryl trinitrate on the Achilles tendon microcirculation in patients with previous Achilles tendon rupture

Abstract

Topical glyceryl trinitrate treatment has demonstrated short- to mid-term efficacy in chronic noninsertional Achilles tendinopathy. However, the underlying mechanisms are far from being understood. We hypothetized that Achilles tendon capillary blood flow changes immediately after topical glyceryl trinitrate treatment. Fifteen patients (55 + or - 15 years, VAS 5.8 + or - 2.3) with current mid-portion Achilles tendon pain 36 months after open surgical Achilles tendon repair for tendon rupture were included. On the Achilles mid-portion, 1.2 mg topical glyceryl trinitrate was sprayed. Microcirculatory monitoring included capillary blood flow, tendon oxygen saturation and postcapillary venous filling pressures at the insertion and 2, 4 and 6 cm above the insertion using a combined laser Doppler and spectrophotometry system. Baseline capillary blood-flows of the painful versus the uninjured tendon were increased [108 + or - 46 vs. 81 + or - 20 (2 cm above the insertion), 104 + or - 40 vs. 76 + or - 20 (4 cm above the insertion), 111 + or - 53 vs. 90 + or - 21 (6 cm above the insertion, P < 0.05)]. However, topical glyceryl trinitrate did not change capillary blood-flow at 2 and 8-mm tissue depths at the painful Achilles tendon or the healthy tendon. Tendon oxygenation was not changed at the painful or the healthy Achilles tendon. Postcapillary venous filling pressure was reduced at 8 mm at the mid-portion in the painful Achilles tendon only (113 + or - 37 vs. 95 + or - 31, P = 0.030). Acute topical glyceryl trinitrate facilitates capillary venous outflow in painful Achilles tendons. However, capillary blood-flow and tendon oxygenation remain unchanged following acute topical glyceryl trinitrate application. Elevated capillary blood-flow at the entire mid-portion is encountered at baseline in previously ruptured painful Achilles tendons even 3 years after surgical repair of the Achilles tendon indicating an altered microcirculatory flow pattern.

Characteristics of Intratendinous Microcirculation Shortly After an Achilles Rupture and Subsequent Treatment Outcomes

“…The StO 2 values in the repaired Achilles tendons were only significantly greater than those in the noninjured tendons at 3 months after surgery (Table 2). Our findings regarding the THb levels support those of a previous study, which found greater capillary blood flows in the repaired tendon among subjects at an average time point of 3 years after surgery [5].…”

“…To the best of the authors' knowledge, only a single previous study has used near‐infrared spectroscopy to observe tendon microcirculation in repaired Achilles tendons in humans and found that capillary blood flows in repaired tendons were greater than those in uninjured tendons at an average of 3 years after surgery [5]. More studies in humans are required to prove these findings from the studies in animals mentioned previously.…”

Achilles Tendinopathy: Current Concepts about the Basic Science and Clinical Treatments

“…Acute GTN facilitates capillary venous outflow in painful Achilles tendons. However, in another study, capillary blood-flow and tendon oxygenation remain unchanged following GTN application [88]. A randomized double-blind placebo-controlled study demonstrated improvements in symptoms using GTN patches [89].…”

Achilles Tendinosis: Treatment Options

“… 16) It is believed that it increases collagen production by fibroblasts, cellular adhesion, and local vascularity. However, a study by Osadnik et al 17) concluded that a topical glyceryltrinitrate facilitates capillary venous outflow in painful Achilles tendons and that the capillary blood flow and tendon oxygenation remain unchanged. In a randomized double-blind placebo-controlled study by Hunte and Lloyd-Smith, 18) a topical glyceryltrinitrate patch was more effective than placebo for reducing pain from chronic non-insertional Achilles tendinosis in the first 12 and 24 weeks of use.…”