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The prevalence and clinical significance of sonographic tendon abnormalities in asymptomatic ballet dancers: a 24-month longitudinal study
  1. Jules Comin1,
  2. Jill L Cook2,
  3. Peter Malliaras1,
  4. Moira McCormack3,
  5. Michelle Calleja4,
  6. Andrew Clarke4,
  7. David Connell5
  1. 1Imaging @ Olympic Park, Melbourne, Victoria, Australia
  2. 2Primary Health Care, Monash University, Melbourne, Victoria, Australia
  3. 3Royal National Ballet, London, UK
  4. 4Department of Radiology, Royal National Orthopaedic Hospital, London, UK
  5. 5Department of Medical Imaging, Monash University, Melbourne, Victoria, Australia
  1. Correspondence to Dr Jules Comin, Imaging @ Olympic Park, 60 Olympic Boulevard, Melbourne 3002, Australia 3002; julescomin{at}gmail.com

Abstract

Introduction Sonographic abnormalities of the achilles and patellar tendons are common findings in athletes, and tendinopathy is a common cause of pain and disability in athletes. However, it is unclear whether the sonographic changes are pathological or adaptive, or if they predict future injury.

We undertook a cohort study to determine what sonographic features of the achilles and patellar tendons are consistent with changes as a result of ballet training, and which may be predictive of future development of disabling tendon symptoms.

Methods The achilles and patellar tendons of 79 (35 male, 44 female) professional ballet dancers (members of the English Royal Ballet) were examined with ultrasound, measuring proximal and distal tendon diameters and assessing for the presence of hypoechoic change, intratendon defects, calcification and neovascularity. All subjects were followed for 24 months for the development of patellar tendon or achilles-related pain or injury severe enough to require time off from dancing.

Results Sonographic abnormalities were common among dancers, both male and female, and in both achilles and patellar tendons. Disabling tendon-related symptoms developed in 10 dancers and 14 tendons: 7 achilles (3 right, 4 left) and 7 patellar (2 right, 5 left). The presence of moderate or severe hypoechoic defects was weakly predictive for the development of future disabling tendon symptoms (p=0.0381); there was no correlation between any of the other sonographic abnormalities and the development of symptoms.

There was no relationship between achilles or patellar tendons’ diameter, either proximal or distal, with an increased likelihood of developing tendon-related disability.

Conclusion The presence of sonographic abnormalities is common in ballet dancers, but only the presence of focal hypoechoic changes predicts the development of future tendon-related disability. This suggests that screening of asymptomatic individuals may be of use in identifying those who are at higher risk of developing tendon-related disability, which may in turn allow targeted modifications of training or other preventative regimens.

  • Achilles tendon
  • Ankle injuries
  • Measurement
  • Tendons
  • Ultrasound
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Introduction

The achilles and patellar tendons are subjected to considerable stress during many athletic endeavours. Pain and injuries involving these tendons are therefore very common among athletes, and particularly in ballet dancers, due to the unique demands of their art.1 ,2

Ultrasound is commonly used to interrogate these tendons when symptoms develop around the knee or ankle. Tendinosis symptomatology has been shown to correlate with various sonographic abnormalities.3–7 However, the ‘normal’ sonographic appearance of these tendons in high-demand athletes is not well established; a number of abnormalities have been reported to be common, even in asymptomatic individuals.8–11

It is not clear whether the presence of these sonographic features in asymptomatic athletes can predict the development of future symptoms/disability. Furthermore, tendon injuries often have a poor prognosis, even with treatment.12 ,13

If one were to identify what these sonographic features are, one may be able to screen presymptomatic athletes and introduce modifications to their training regimen, such as stretching and eccentric exercise,14 or even prophylactic interventions, such as protein-rich plasma or stem cell injection,15 ,16 in order to avert disability.

This study set out to define the baseline sonographic appearance of achilles and patellar tendons in a group of elite asymptomatic ballet dancers. This group was then followed for 24 months for the development of disabling tendon-related symptoms, in an attempt to distinguish sonographic features which might predict future disability, from those which are ‘benign features’ of heavy tendon use.

Methods

Asymptomatic members of the Royal Ballet (N=91) were invited to participate in a preseason screening programme of their patellar and achilles tendons. In total, 79 dancers (35 males and 44 females) agreed to participate (87% of the company). All the participants gave informed consent and screening took place with the consent of company management. Two ultrasound machines were hired for this purpose: a Philips iU22 and a Philips cx50 (Amsterdam, Netherlands). Three experienced radiologists participated in pretraining for operator reliability. Heights and weights were measured and recorded. All the dancers were scanned on the same day. Bilateral achilles and patella tendons were scanned sequentially with thickness measured at 1 cm from both origin and insertion. Hypoechoic change was noted and recorded as being either absent or mild, or moderate or severe. Tendon clefts, tears and neovascularisations were also identified. Intratendinous calcifications were noted as being present or absent. Additional anomalies were recorded and commented upon.

The dancers were followed clinically by the company physiotherapist (MM) for a period of 24 months. Any injuries or symptoms requiring time off from training or performing were recorded, and the nature of these injuries (diagnosed clinically or by imaging) was noted.

Mean values, with ranges and SDs, were calculated for anthropometric data and tendon thicknesses. The incidence of the presence of sonographic abnormalities was calculated. Unpaired t tests were used to analyse the continuous data (the association between tendon thickness and the development of symptoms). Fisher's exact test was used to analyse the categorical data (the association between abnormal appearances and the development of symptoms). All statistical analyses were performed using the SPSS V.17.0 software package (SPSS Inc, Chicago, Illinois, USA).

Results

Cross-sectional data have been tabulated (tables 1 and 2). Hypoechoic changes were the most common abnormality in both patellar and achilles tendons (prevalence of 12% in both locations).

Table 1

Demographic information and baseline tendon measurements comparison

Table 2

Baseline sonographic abnormalities present

Disabling tendon-related symptoms developed in 10 dancers and 14 tendons: 7 achilles (3 right, 4 left) and 7 patellar (2 right, 5 left) (table 3).

Table 3

Presence of disabling pain/symptoms during the follow-up period

There was a weak association between the presence of moderate-to-severe hypoechoic defects at baseline screening, and an increased incidence of disabling tendon-related symptoms for both achilles and patellar tendons (p=0.0381 for both).

There was no significant association between any of the other sonographic abnormalities and an increased incidence of disabling tendon-related disability (tables 4 and 5).

Table 4

Baseline ultrasound findings among dancers who remained asymptomatic and among dancers who developed symptoms (patellar tendons)

Table 5

Baseline ultrasound findings among dancers who remained asymptomatic and among dancers who developed symptoms (achilles tendons)

Increased thickness did not correlate with an increased incidence of tendon-related disability (tables 6 and 7).

Table 6

Achilles (TA) values in injured and uninjured dancers

Table 7

Patellar (PT) values in injured and uninjured dancers

Discussion

Our results showing a high incidence of sonographic abnormalities, including diffuse thickening, increased vascularity and focal abnormalities, in high-demand professional dancers is in concordance with other studies of athletes from various different sports.6 ,17–19

One current paradigm of tendinopathy is a continuum of pathological changes, with diffuse thickening thought to represent a ‘prepathological’ reactive state of ground substance deposition, and focal changes thought to represent a consequent degenerative state of tissue apoptosis and deterioration.20 This has been based on work that has shown that changes in the sonographic appearance of tendons follow a predictable sequence, with diffuse thickening preceding both the development of focal hypoechoic areas in previously normal tendons, and a return to normal appearance in previously focally hypoechoic tendons.21

Our results show that increased thickness was not correlated with an increased incidence of tendon-related disability: this lends further credence to the idea of tendon thickening as a prepathological and benign state.

These studies have also served to highlight the variable relationship between sonographic appearance and pain; although tendon appearance does appear to follow a continuum from normal-to-diffuse thickening to focal hypoechoic change, with or without neovascularity, this does not appear to correlate exactly with symptoms. However, this is probably of comparatively little importance clinically, as once tendon-related pain has developed, management can be effectively guided by patient symptoms and activity tolerance without any necessary contribution from ultrasound.

What may be of more clinical utility is an understanding of the relationship between sonographic abnormalities and the likelihood of the development of symptoms in asymptomatic individuals, as this could allow ultrasound to be used as a screening tool to identify athletes at risk and guide prophylactic treatments or training modifications.

Several longitudinal studies have investigated whether sonographic tendon appearances in asymptomatic individuals are predictive for future symptomatic tendinopathy, with conflicting results.

Giombini et al8 examined the achilles, patellar and quadriceps tendons in 37 elite fencers and found that sonographic abnormalities predicted future symptoms only in the patellar tendon, and not the quadriceps or achilles.

Cook and Purdam22 examined only the patellar tendons in 23 asymptomatic basketball players, and found no association between sonographic abnormalities and future symptoms.

Hirschmuller et al23 examined the achilles tendons in 634 asymptomatic runners, and found that only neovascularity was a risk factor for symptom development.

Fredberg and Bolvig10 examined the achilles and patellar tendons in 54 asymptomatic elite soccer players, and found that the presence of hypoechoic regions was closely associated with the development of symptoms.

Gisslen et al24 ,25 examined the patellar tendons in volleyball players. No statistical analysis of the predictive value of sonographic changes in asymptomatic subjects was performed; one study demonstrated a higher incidence of future symptomatology in those with sonographic abnormalities than those without, but the other showed no increase.

The results of our study have demonstrated that of all the sonographic abnormalities assessed, only the presence of moderate or severe hypoechoic defects predicted future tendon disability, and that even this relationship was a weak one.

The conflicting results of these studies are probably a result of a number of factors. First, each was conducted among athletes from a different sport; these sports place very different demands on the tendons (loading, stretching and volume of activity) and have different incidences of tendon disorders. Second, what constitutes a hypoechoic area or significant neovascularity is not well defined in any of these papers, and is likely a highly subjective evaluation. Tendon thickness is a measure with greater interobserver reproducibility, but, as has been discussed, may only represent a prepathological state. Third, what constitutes significant symptoms is similarly subjective. Our paper only considered the tendon to be symptomatic if the dancer was forced to abandon training, whereas others used clinical tests and examination or questionnaire.

These points of difference also address the main weaknesses of this study. Most are difficult to be addressed, but future trials should include more subjects and multiple different types of athletes, and a more rigorous and standardised method for grading both sonographic abnormalities and symptomatology.

Our study demonstrates that the presence of focal hypoechoic changes may predict the future development of tendon-related disability.

This suggests that screening of asymptomatic individuals may be of use in identifying those who are at higher risk of developing tendon-related disability, which may in turn allow targeted modifications of training or other preventative regimens.

Further studies are needed to confirm predictive accuracy, and define exactly which features are the most important.

What are the new findings?

  • Sonographic abnormalities and tendon thickening are common in asymptomatic ballet dancers.

  • The presence of focal hypoechoic change, but not other sonographic abnormalities, predicts future development of disabling tendinopathy.

  • Increased tendon thickness on ultrasound does not predict the future development of disabling tendinopathy in asymptomatic athletes.

Implications for clinical practice?

  • The presence of focal hypoechoic change in tendons of asymptomatic athletes needs to be managed pre-emptively to avoid the development of future symptomatic tendinopathy, which can cause severe disability and be difficult to treat.

  • Tendon thickening and other sonographic abnormalities in the tendons of asymptomatic athletes probably do not require preventative treatment or modification of activities.

References

View Abstract

Footnotes

  • Contributors JC, JLC and PM wrote the manuscript, DC, MC and AC performed the sonography and MM undertook clinical follow-up.

  • Competing interests None.

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

  • ▸ References to this paper are available online at http://bjsm.bmjgroup.com

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