Tendon modification with percutaneous Ultrasound-Guided Tenotomy using TENEX®: A histological and macroscopic analysis of a bovine cadaveric model

Abstract

Background: Chronic tendinopathy treatment remains elusive; however, percutaneous Ultrasound-Guided Tenotomy using TENEX® (PUTT) has demonstrated promising clinical outcomes, but the mechanism of action is not clearly defined. This study aims to describe potential mechanisms using an ex-vivo animal model. The objective of the study is to examine the histological effects of PUTT on the bovine soleus tendon across varying treatment durations.

Methods: Twelve bovine soleus tendons were allocated to four cohorts to undergo PUTT for 1, 3, 5, and 7 min. Each specimen was treated on one side, the opposite side serving as a control. Macroscopic and microscopic analyses were conducted to assess tendon sheath, fascicle, and perineural disruption. Fascicle penetration was measured using ImageJ software. Statistical analyses were performed using Analysis of Variance (ANOVA), with significance levels set at p < 0.05.

Results: Macroscopic and microscopic examination revealed progressive separation of the paratenon, peritendinous nerves, and fascicles, correlating with increased treatment duration. Fascicle penetration depths were 0.1 mm, 2.57 mm, 2.61 mm, and 3.93 mm at 1, 3, 5, and 7 min, respectively. ANOVA confirmed significant differences among groups (F (3, 8) = 620.898, p < 0.001), with a large effect size (η² = 0.996. Tukey's Honest Significant Difference (HSD) test revealed significant differences between most groups (p < 0.001), except between the 3-min and 5-min treatments, which showed no significant difference (p = 0.969).

Conclusion: PUTT induces significant structural changes in the paratenon and fascicle layer with longer treatment duration, resulting in more pronounced modifications.

Keywords: Chronic; Future; Nociceptors; Pain; Paratenon; Tendinopathy.

Fig. 1

A. Application of the PUTT needle on the treated surface of the tendon. B. Markings on each tendon to indicate the treatment (T) and control (C) surfaces.

Fig. 2

Progressive Levels of Paratenon Separation — This figure displays progressive levels of paratenon separation, providing detailed microscopic views that align with macroscopic observations. These images illustrate a time-dependent increase in the extent of separation, visually capturing the loosening of the peritendinous tissue and correlating each stage with the duration of PUTT. Arrows indicate areas of fiber misalignment and altered spacing between the peritendinous tissue and tendon fibrous structure.

Fig. 3

Comparison of Tendon Fibrous Tissue Modification — This image shows the structural differences in a tendon, highlighting tracts of modified fibrous tissue on the treated side compared to the untreated side after 5 min of treatment. (H&E, Longitudinal section, 2X).

Fig. 4

Paratenon Separation Following PUTT — This microscopic image illustrates the structural differences between the PUTT-treated and non-treated sides of a tendon. Black arrows highlight the paratenon layer, delineating notable separation from the tendon's fibrous layer in the treated region. (H&E, Cross Section, 2X).

Fig. 5

Vascular and Neural Presence in the Paratendinous Layer — This image reveals the presence of small vessels and nerve fibers within the paratendinous layer at the treated area. (H&E, Cross Section, 10X).

Fig. 6

Mean penetration depth by treatment duration — This line graph displays the mean depth of tissue penetration (in millimeters) across four treatment durations (1, 3, 5, and 7 min). It illustrates a progressive increase in penetration depth with extended treatment durations, emphasizing the dose-dependent effect of PUTT on tissue modification.