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Unilateral surgical treatment for patients with midportion Achilles tendinopathy may result in bilateral recovery
  1. Håkan Alfredson1,
  2. Christoph Spang2,
  3. Sture Forsgren2
  1. 1Department of Surgical and Perioperative Sciences, Sports Medicine, Umeå University, Umeå, Sweden
  2. 2Department of Integrative Medical Biology, Section for Anatomy, Umeå University, Umeå, Sweden
  1. Correspondence to Dr Sture Forsgren, Department of Integrative Medical Biology, Section for Anatomy, Umeå University, Umeå SE 901 87, Sweden; Sture.Forsgren{at}Anatomy.Umu.Se


Background Bilateral midportion Achilles tendinopathy/tendinosis is not unusual, and treatment of both sides is often carried out. Experiments in animals suggest of the potential involvement of central neuronal mechanisms in Achilles tendinosis.

Objectives To evaluate the outcome of surgery for Achilles tendinopathy.

Methods This observational study included 13 patients (7 men and 6 women, mean age 53 years) with a long duration (6–120 months) of chronic painful bilateral midportion Achilles tendinopathy. The most painful side at the time for investigation was selected to be operated on first. Treatment was ultrasound-guided and Doppler-guided scraping procedure outside the ventral part of the tendon under local anaesthetic. The patients started walking on the first day after surgery. Follow-ups were conducted and the primary outcome was pain by visual analogue scale. In an additional part of the study, specimens from Achilles and plantaris tendons in three patients with bilateral Achilles tendinosis were examined.

Results Short-term follow-ups showed postoperative improvement on the non-operated side as well as the operated side in 11 of 13 patients. Final follow-up after 37 (mean) months showed significant pain relief and patient satisfaction on both sides for these 11 patients. In 2 of 13 patients operation on the other, initially non-operated side, was instituted due to persisting pain. Morphologically, it was found that there were similar morphological effects, and immunohistochemical patterns of enzyme involved in signal substance production, bilaterally.

Conclusion Unilateral treatment with a scraping operation can have benefits contralaterally; the clinical implication is that unilateral surgery may be a logical first treatment in cases of bilateral Achilles tendinopathy.

  • Achilles tendon
  • Tendons
  • Lower extremity injuries

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Chronic pain in the midportion of the Achilles tendon, tendinopathy, is common. It accounts for 55–65% of Achilles tendon injuries.1 ,2 When the chronic pain is accompanied by structural changes, the condition may be referred to as Achilles tendinosis.3 Tendon overload, which is the most commonly accepted extrinsic risk factor for tendinopathy,4–6 cannot explain all cases of midportion Achilles tendinopathy/tendinosis; Achilles tendinopathy also occurs in inactive individuals.7 ,8 Many patients present with bilateral Achilles tendinopathy/tendinosis.9 In an 8-year longitudinal study on individuals initially presenting with unilateral Achilles tendinopathy, 41% also developed symptoms on the contralateral side.10

In a rabbit tendinopathy model, using a combined set-up of excessive exercise and electrical stimulation affecting the triceps surae muscle, the Achilles tendon on the experimental side exhibited characteristics of human Achilles tendinosis, including the presence of greater tenocyte numbers and increased tendon vascularity.11 Interestingly, in this rabbit model, the non-experimental control Achilles tendon also clearly exhibited these tendinosis characteristics. This raised questions about potential involvement of central neuronal mechanisms.11

Therefore, in the present observational study on a group of patients with bilateral Achilles tendinopathy/tendinosis, the primary clinical intention was to operate on the more symptomatic side and to review the results of that procedure prior to considering surgery on the contralateral Achilles. The surgical treatment (ultrasound (US)- guided and Doppler-guided scraping) was followed by early full weight-bearing loading. The most painful side at the time of investigation was operated on. Furthermore, specimens from both Achilles and plantaris tendons were evaluated microscopically in patients with bilateral Achilles tendinosis.

Materials and methods

Evaluation after unilateral treatment


Altogether 13 patients, 7 men and 6 women, mean age 53 years (range 34–70) with painful bilateral midportion Achilles tendinosis were included. The patients were primarily referred from general practitioners in the northern part of Sweden to the Sports Medicine Unit in Umeå due to chronic painful Achilles tendinopathy (6–120 months duration of symptoms). For some patients, the symptoms had started at approximately the same time point for both tendons, for others the symptoms had started on one side and later presented on the other side. The symptoms often alternated between the two tendons. All patients had tried rest from heavy Achilles tendon-loading activities (>3 months) without any effect. Most of the patients stated that they had tried eccentric exercise without effect, and a few of the patients could not undertake eccentric exercise because of comorbidities. Therefore, the surgical scraping method (c.f. below) was chosen. Clinical examination showed a tender thickening in the midportion of both Achilles tendons; there was a varying degree of tenderness between the two tendons. Ankle range of motion was normal bilaterally.


All tendons were examined with high-resolution grey scale-US and Colour Doppler (CD), Acuson Segoia (Siemens), at inclusion. A linear multifrequency (8–13 MHz) probe was used to study tendon structure and thickness. CD was used to diagnose regions with high blood flow, and to locate where the blood flow entered the tendon. Both Achilles tendons were examined. The tendons of all included patients (both sides) showed typical findings of tendinosis, with midportion thickening, irregular tendon structure and high blood flow from the ventral soft tissues into the ventral tendon. Nevertheless, for some patients, there were varying degrees of thickness between the two tendons. In principle, the level of CD-detected blood flow was the highest for the most painful tendon.

Mini-open surgery-scraping

The US and Doppler findings guided the surgical procedure. We operated on the most painful tendon with the intention of operating on the other tendon later. The operation was done under local anaesthetic (xylocaine+adrenaline). A longitudinal skin incision (1–2 cm) was made on the medial side of the Achilles midportion, and the medio-ventral side of the tendon was carefully identified. In the region with structural changes and high blood flow (marked by skin markers), the tendon was completely released from the ventral soft tissue by sharp dissection with a knife, staying close to the ventral tendon. This was followed by haemostasis, using diathermy. The skin was closed with non-resorbable sutures.

Postoperative rehabilitation

Day 1: rest, foot kept elevated. Day 2: range of motion exercises (flexion/extension in ankle joint), light stretching and start of short walks without crutches. Days 3–7: gradually increased walking distances. Days 8–14: addition of light cycling. After 2 weeks: sutures removed. Gradually increasing tendon-loading activities up to full participation in heavy Achilles tendon-loading recreational and sports activities after 4–5 weeks.

Follow-up: Focus was devoted to the pain. A majority of the patients were followed up clinically up to 6 months postoperatively and for a short period by US and CD: for long-distance patients, further follow-ups were done telephonically. Final follow-up was for all patients done by telephone (see below). Apart from evaluating pain, overall patient satisfaction was also evaluated.

Outcome measures

a. Before surgery and at 6 month follow-up (for the operated side):

Pain during Achilles tendon-loading activity: The patients recorded tendon pain during their regular activity (walking, recreational sport level, etc), before and after treatment, on a 100 mm-long visual analogue scale (VAS), where no pain was recorded as 0 and severe pain as 100.

Patient satisfaction with the result of the treatment: This was also recorded by the patients on a 100 mm-long VAS, where not satisfied at all was recorded as 0 (% satisfaction) and fully satisfied was recorded as 100 (% satisfaction).

b. At the final follow-up (evaluation concerning the recovery for both tendons):

Telephone interview was performed. Pain during Achilles tendon-loading activity was evaluated. The patients were asked about the occurrence of tendon pain in both Achilles tendons during their usual activity (including walking for some, recreational sport for others).

Patient satisfaction was also evaluated at final follow-up. The patients were asked about satisfaction with the result of the treatment (satisfied or not satisfied).

Examination of tendon structure and immunoreaction pattern


Specimens from three patients who were suffering from bilateral Achilles tendinosis were evaluated. These included two men (35 and 50 years) and one woman (57 years). The tendinosis diagnosis was verified clinically and by US+CD as described above.


The surgical procedure was the same as described above, except that in two patients the plantaris tendon was contiguous with the medial Achilles tendon and in these patients that tendon was excised bilaterally. Biopsies (1–2×3–4 mm) from the ventromedial Achilles, and also biopsies from the excised plantaris tendons, were taken for analysis. In total, from these three patients, we obtained biopsies from the Achilles tendons of two individuals and plantaris tendons of two individuals.

Sectioning and fixation

After the surgical procedure, the specimens were immediately fixed by immersion overnight at 4°C, in a solution of 4% formaldehyde in 0.1 M phosphate buffer, pH 7.0. They were then thoroughly washed in Tyrode's solution, containing 10% sucrose, at 4°C overnight, mounted on thin cardboard in OCT embedding medium (Miles Laboratories, Naperville, Illinois, USA) and frozen at −80°C until sectioning. Series of 7 µm thick sections were cut using a cryostat. The sections were mounted on slides precoated with crome-alum gelatine and were then dried. Sections from all the samples were processed for demonstration of tissue morphology (staining with H&E) and for a demonstration of immunoreaction for tyrosine hydroxylase (TH). Tenocytes in tendinosis tendons, much more so than tenocytes of normal tendons, show immunoreactions for TH.12 ,13

Immmunofluorescence processing

The processing for TH was performed in accordance with procedures that are previously described.12 As primary antibody, a rabbit TH-antibody (P40101) from Pel-Freez (Rogers, Arkansas, USA) was applied. It was used at a dilution of 1 : 100 and incubation proceeded for 60 min. As secondary antiserum, tetramethylrhodamine isothiocyanate-conjugated swine antirabbit IgG (Dakopatts, Glostrup, Denmark; dilution 1 : 40, incubation for 30 min at 37°C) was used. Examination was carried out in a Zeiss Axioskop 2 plus microscope, equipped with epifluorescence optics and an Olympus DP70 digital camera. Specificity of the TH antiserum has been evaluated previously.12


Pain and patient satisfaction during the initial 6 months postoperatively

Before the operation, the VAS for Achilles tendon pain during the habitual Achilles tendon-loading activity was 76 (mean) (range 55–98). After the operation, the VAS for Achilles tendon pain concerning the operated side and during habitual Achilles tendon-loading activity was significantly decreased to 7 (mean) (range 0–23).

11 of 13 patients were 97% (mean) (range 82–100) satisfied with the result of the operation. Of these 11 satisfied patients, 5 patients described full satisfaction at 6–8 weeks follow-up, 4 patients at 10–18 weeks follow-up and 2 patients at 26 weeks follow-up.

Pain and patient satisfaction at final follow-up

At telephone follow-up at a mean of 37 months (range 16–67) after treatment, 10 of 13 patients were completely pain free in both Achilles tendons during their habitual Achilles tendon-loading activity. In 1 of 13 patients, there was occasionally minor pain in the non-operated Achilles tendon during running, which did not prevent running.

Eleven (the 10 pain-free patients and the one with minor pain) of the 13 patients declared that they were satisfied bilaterally with the result of the treatment. Due to this, an operation for the contralateral non-operated side was not indicated. Two patients required surgery due to Achilles tendon pain in the initially non-operated tendon during tendon-loading activity.

Morphological and immunohistochemical evaluation

Specimens of Achilles/plantaris tendons from three patients with bilateral Achilles tendinosis and who were operated bilaterally were examined histologically (via staining with H&E) and immunohistochemically (via staining for a demonstration of TH). It was observed that the tendon tissue of both right and left sides showed typical tendinosis features including abundant tenocytes (figure 1). Tenocytes were seen to be lined up in rows. The morphological appearance within the tendon tissue was similar in the tendons of both sides. That was the case for the Achilles as well as the plantaris tendons examined. A large number of blood vessels were seen within the tendon tissue, as well as in the loose peritendinous connective tissue, for both tendons and on both sides (figure 2). For the Achilles (figure 3) as well as the plantaris (not illustrated) tendons, tenocytes exhibited TH immunoreactions on both sides.

Figure 1

Tendon tissue from the right-sided (A) and left-sided (B) Achilles tendons of a patient suffering from chronic tendon pain (tendinopathy) bilaterally. The sections were stained for H&E. There is an abnormally large number of tenocytes bilaterally. The tenocytes are partly lined up in rows.

Figure 2

Peritendinous loose connective tissue just outside tendon tissue proper of plantaris tendons. Tendon from the right side (A) and from the left side (B). Staining for H&E. There is a marked presence of fine blood vessels on both sides.

Figure 3

Sections of tendon tissue of Achilles tendons processed for the demonstration of TH. Tendon of right side (A) and tendon of left side (B). There is an expression of TH immunoreaction in tenocytes in both (A) and (B) (arrows).


The present study shows that 11 of 13 patients had bilateral pain relief and patient satisfaction in the long-term evaluation after unilateral Achilles tendon surgery. There was thus a bilateral recovery after unilateral surgery. Although this could be interpreted to be a result of ‘postoperative rest’ of the non-operated tendon, such reasoning has potential flaws. First, ‘rest’ is not one of the evidence-based treatments for tendinopathy in general, nor for Achilles tendinopathy specifically.14 ,15 Mechanotherapy is required to stimulate tendon tissue repair,16 as it is in other types of connective tissue. Second, the patients had previously undergone prolonged periods of ‘rest’ without symptom relief. Third, patients who undergo this specific type of mini-open surgery procedure are instructed to start walking without crutches on the first postoperative day. They then increase to full Achilles tendon-loading activities in recreation or high-level sports after 4–5 weeks. Thus, it could be argued that the non-operated side might be carrying ‘more load’ as the patient ‘protects’ the operated side. Recovery in that case would be consistent with mechanotherapy—increased loading—on the non-operated side. Nevertheless, for this group of patients, for whom the intention was to surgically treat both sides but to start with one side, there was recovery also on the non-operated side for the majority of patients and there was no need for surgery on that side in these cases. These findings have clinical implications for patients with bilateral symptoms.

Possible mechanisms explaining pain relief after Achilles tendon surgery

Sensory innervation is responsible for the pain sensations in Achilles tendinosis. The scraping operation most likely influences the sensory innervation in the peritendinous tissue. The US-guided and Doppler-guided scraping operation has a high success rate with good clinical results and pain relief in a majority of patients on different Achilles tendon-loading activities (ranging from inactive individuals to professional athletes).17

How can then the pain relief, which in this study occurs also for the contralateral non-operated Achilles tendon, be explained? One hypothesis is that unilateral influences on the sensory innervation in the peritendinous tissue in response to the scraping procedure have secondary effects contralaterally, that is, an influence on the sensory innervation in the scraped side also has influences on the pain system on the other side. Supporting this suggestion, unilateral primary-afferent activation for extremities can be related to the occurrence of contralateral affections.18 Regarding arthritic joints, it is thought that a neurogenic component is responsible for the symmetrical joint involvements, and that this is related to primary-afferent activation on one side, secondarily leading to contralateral activation of homologous afferents.19 The fact that the contralateral responses seen upon experiments for limbs are topographically precise20 indeed suggests that the contralateral responses seen in these experiments imply a neurogenic mechanism rather than systemic effects. It has actually became clear that the contralateral responses are stimulus specific, that is, if the unilateral stimulus is pro-inflammatory, the contralateral response is also proinflammatory.21 It should be recalled that the central connections that can combine right and left sides at the spinal cord level may not only be overlapping terminals of sensory nerve fibres, but can also correspond to spinal interneurones and dendrites of motor neurons.22 Milligan and coworkers furthermore found that the unilateral neuritis that led to bilateral allodynia in their study was mediated by microglia, as well as proinflammatory cytokines.23

Histopathology in Achilles and plantaris tendons

Our biopsy samples revealed similar structural appearances in both Achilles midportions in patients with bilateral Achilles symptoms. There were typical tendinosis-like features in the Achilles tendons of both sides. These features included the presence of a very large number of tenocytes and the occurrence of lining-up of tenocytes24–30 as well as a large number of vessels within the tendon tissue and in the peritendinous connective tissue.27 ,28 ,31 Typical features of tendinosis tissue12 ,13 seen in the tendons in both sides, also included the occurrence of TH-immunoreactivity for the tendon cells.

Plantaris tendons from patients where the plantaris tendons were found in very close relation to the medial side of the Achilles midportion, a situation that often exists,32 ,33 were also evaluated, as well as the Achilles tendons. Tendinosis-like features were also noted bilaterally in this case. It has recently been observed that the plantaris tendons show similar histopathological appearances as the Achilles tendon itself in cases with Achilles tendinosis when the plantaris tendon is located very close to the Achilles tendon.34

When performing the scraping operation, the Achilles tendon is completely released from the ventral soft tissue in the regions that are identified by US to have structural changes (hypoechogenicity) and abnormally high blood flow (Doppler). We believe that the nerves located in the peritendinous tissue are affected. It is thus known that the region where the scraping is performed conforms to peritendinous tissue in which there is an occurrence of high blood flow17 and in which there is a marked presence of large blood vessels exhibiting a perivascular innervation and nerve fascicles containing sympathetic and sensory nerve fibres.31 The major part of the innervation of the Achilles tendon is actually to be found in the peritendinous region, only occasional nerve fibres being present within the tendon tissue proper.28

Clinical implications

The present study includes the results of surgery on a limited number of patients. In this series, patients with bilateral midportion Achilles tendinosis experienced a good result with pain relief bilaterally even though surgical scraping treatment was performed on only one of the Achilles tendons. Irrespective of the mechanism explaining this, it has clinical implications—it may save patients with bilateral symptoms from one operation.

What are the new findings?

  • Unilateral surgical treatment (scraping operation) for patients with bilateral midportion Achilles tendinopathy/tendinosis resulted in pain relief bilaterally, resulting in there being no need for surgery on the initially non-operated side in 11/13 patients.

How might the study have an impact on clinical practice in the near future?

  • In patients with chronic painful bilateral midportion Achilles tendinopathy/tendinosis, unilateral treatment with the ultrasound-guided and Doppler-guided surgical scraping technique may also derive benefits on the non-operated side. Thus, unilateral treatment with this method, followed by a wait-and-see period, seems appropriate.


The authors thank Ms Ulla Hedlund for excellent technical support.


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  • Contributors HA carried out the surgical operations and was responsible for the clinical evaluations. SF was responsible for the writing of the manuscript. HA and CS were also involved in the writing process. SF and CS were responsible for the morphological evaluations.

  • Funding Financial support has been obtained from the Swedish National Centre for Research in Sports (CIF) (P2012-0122, FO2012-0078) and the Faculty of Medicine, Umeå University.

  • Ethics approval Ethical approval was obtained from the Ethical Committee at the Medical Faculty of Umeå University and the Regional Ethical Review Board in Umeå (project nr. 04-157M).

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.