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Abstract
Background Achilles tendinopathy is a serious and frequently occurring problem, especially in elite athletes. Recent research has suggested a role for the plantaris tendon in non-insertional Achilles tendinopathy.
Aim To assess whether excising the plantaris tendon improved the symptoms of Achilles tendinopathy in elite athletes.
Methods This prospective consecutive case series study investigated 32 elite athletes who underwent plantaris tendon excision using a mini-incision technique to treat medially located pain associated with non-insertional Achilles tendinopathy. Preoperative and postoperative visual analogue scores (VAS) for pain and the foot and ankle outcome score (FAOS) as well as time to return to sport and satisfaction scores were assessed.
Results At a mean follow-up of 22.4 months (12–48), 29/32 (90%) of athletes were satisfied with the results. Thirty of the 32 athletes (94%) returned to sport at a mean of 10.3 weeks (5–27). The mean VAS score improved from 5.8 to 0.8 (p<0.01) and the mean FAOS improved in all domains (p<0.01). Few complications were seen, four athletes experienced short-term stiffness and one had a superficial wound infection.
Conclusions The plantaris tendon may be responsible for symptoms in some athletes with non-insertional Achilles tendinopathy. Excision carries a low risk of complications and may provide significant improvement in symptoms enabling an early return to elite-level sports.
- Tendinosis
- Calf / calves
- Eccentric
- Effectiveness
- Elite performance
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Introduction
Mid-substance Achilles tendinopathy is debilitating condition frequently encountered in elite athletes and it may be a career-ending condition in up to 5% of professional athletes.1 Pain in the Achilles may be due to intrinsic tendon pathology but it may also be secondary to degeneration or inflammation of the surrounding structures (paratendinopathy).2
The most effective rehabilitation for Achilles tendinopathy is appropriate loading of the tendon. This can be achieved by modifying elastic tendon activities and prescription of strengthening exercises.3 If conservative measures fail then surgery may be indicated and many different methods have been described. Open Achilles surgery may be successful in 75–100%4–8 of patients but debridement with excision of areas of tendinosis weakens the tendon and return to sport may be delayed for up to 18 months.9 Treatments addressing the peritendinous structures may decompress the paratenon, remove adhesions between the tendon and paratenon and fat pad, or denervate the tendon by scraping the ventral aspect while removing areas of neovascularistion.4 These procedures avoid violating the tendon itself and therefore a quicker return to sport may be possible. Minimally invasive procedures such as paratenonectomy and tendinoscopy with plantaris release can achieve good results.10 ,11
Recent studies have proposed a role of the plantaris tendon in the development of focal medial Achilles tendinopathy and medially located Achilles tendon pain.12 The plantaris arises from the lateral aspect of the supracondylar line of the femur and inserts into the medial aspect of the calcaneus passing deep to the medial gastrocnemius but superficial to soleus. Anatomical studies show that in some cases there is a direct attachment of the plantaris to the medial Achilles tendon.2 It acts as an inverter and plantar-flexor at the ankle and as a weak flexor at the knee. At the level of the Achilles the plantaris lies within the Achilles paratenon along the medial or ventromedial aspect of the Achilles tendon.4 ,13
As plantaris crosses the knee and ankle joints there is a differential movement between it and the Achilles at the medial border of the Achilles tendon. It is also stiffer and stronger than the Achilles tendon and it has been suggested that these factors lead to friction, inflammation and adhesions between the plantaris and the Achilles tendons.14 Reports of isolated plantaris rupture15–17 and the finding of an intact plantaris with Achilles rupture would support this, as tendons with identical kinetics would be expected to rupture simultaneously.
Recent studies have reported encouraging results with release of adhesions surrounding the Achilles and sectioning of the plantaris tendon.10 ,18 ,19 However, these are small studies and whether this approach provides long-term symptomatic relief of pain without compromising athletic ability in the highest demanding athletic patients has not yet been demonstrated.
The purpose of this study was to evaluate the clinical results and time of return to sports following mini-incision Achilles tendon release and plantaris excision in a consecutive series of elite athletes with focal medially located Achilles tendon pain.
Methods
A prospective consecutive case series of elite athletes (competing at national or international level) underwent surgical excision of the plantaris tendon and paratenon release. Athletes presenting to the Fortius Clinic or the Hampshire Clinic from January 2009 to January 2013 with symptoms consistent with non-insertional Achilles tendinopathy were included. All had focal, medially located Achilles tendon pain and swelling along the medial edge of the Achilles tendon approximately 4–7 cm from insertion into the Os calcis. Medial pain was distinguished from lateral pain by palpating each side of the tendon in turn and determining the side of maximal tenderness. All underwent MRI examination that confirmed paratendinitis as defined by a signal change in the paratenon or Kager’s fat pad (with or without a plantaris tendon adherent to, or invaginated into the ventromedial border of the Achilles tendon). Some also had signal change suggestive of mid-substance Achilles tendinosis. All athletes were initially treated conservatively with an ultrasound-guided paratenon stripping injection of 40 mL local anaesthetic (without steroid) between the Achilles and fat pad and the Achilles and plantaris tendon followed by a formal eccentric stretching exercise programme. Those that failed to improve after a minimum of 6 weeks were then considered for surgery or a further paratenon injection. Athletes with a good response to injection therapy were offered a repeat injection (not usually within 6 months) or surgery. All patients were consented for inclusion in the study which was approved by the institutions review board.
At surgery, a 2–3 cm incision was made along the medial edge of the Achilles tendon at the point of maximal tenderness/swelling. The paratenon was opened and adhesions between it and the Achilles tendon were released. Any connections along the ventral aspect of the Achilles tendon were released by sharp dissection. The plantaris tendon was identified, released from the medial aspect of the Achilles tendon and transected. It was then passed on a haemostat as proximally as possible (approximately 10–15 cm) within the paratenon where a stab incision was made and the plantaris tendon was delivered through the skin and sectioned proximally under tension at its musculotendinous junction. A firm compressive bandage was placed over the operative site and athletes were encouraged to elevate the leg for 10 days but allowed to mobilise with crutches weight bearing as able. Ankle range of motion exercises were encouraged from 48 h postoperatively after reduction of dressings to a double elastic bandage. Once wound healing had been ensured, an Achilles strengthening programme was introduced at 2 weeks, to encourage movement of the Achilles to reduce the chance of adhesions to the paratenon and ventral fat pad. Individual reconditioning programmes were tailored on a patient-specific basis by their local physiotherapy team. Return to sporting activity was dictated independently by the athletes’ local medical team.
All athletes were assessed with patient reported outcome measures. Preoperatively and postoperatively a visual analogue score (VAS) and the foot and ankle outcome score (FAOS) was used and post-treatment satisfaction and return to sport score was recorded. The point at which the athlete was able to return to full training was taken as the ‘return to sport’ end point. In bilateral cases all patients had returned to their pretreatment sporting level before developing symptoms in the other leg.
Statistical analysis
The results were analysed using a spreadsheet (Excel 2007, Microsoft; Seattle, Washington, USA). Data were normally distributed and Student t tests were used to compare between groups. A p value of <0.05 was considered significant.
A retrospective power analysis based on a 10% minimum clinically important difference for FAOS, two tails and 5% significance gave 100% power with a sample size of 32.
Results
There were 32 elite athletes (22 men) with a mean age 27.2 years (range 19–42). Fourteen cases involved the right side, 16 the left side and 2 were bilateral. There was no loss to follow-up but one athlete did not complete the postoperative FAOS score. Athletic activity is shown below (table 1); in addition, there was one triathlete, cricketer, golfer, netball and volleyball player.
Patient characteristics by sport
The mean follow-up was 22.1 months with a minimum follow-up of 12 months (range 12–48). The mean time to return to elite-level sport was 10.3 weeks (95% CI 8.6 to 12, range 5–27). There was a significant improvement in VAS scores for pain from 5.8 (95% CI 5.4 to 6.3) to 0.8 (0.3 to 1.3, p<0.001). There was also a significant improvement in FAOS scores from a mean of 333 (321 to 345) to 449 (431 to 468; table 2).
Change in FAOS scores following surgery
Following surgery 22/32 (69%) patients were very satisfied, 7/32 (22%) partially satisfied and 3/32 (9%) not satisfied. Two athletes had to retire from elite sport, four had stiffness symptoms and one had a superficial wound infection that settled with oral antibiotics.
Although all athletes had MRI evidence of change around the plantaris tendon with tethering to the Achilles tendon and surrounding Achilles paratendinitis, 11/32 (34%) had no signs of Achilles tendinosis on MRI (table 3).
Differences in improvement between tendinopathic and non-tendinopathic athletes (significant differences italicised)
Discussion
In our cohort of elite athletes we achieved high rates of patient satisfaction and significant improvements in VAS and FAOS scores. At a mean follow-up of 22.4 months, 90% of athletes were satisfied and 94% had returned to sport (at a mean of 10.3 weeks). The mean VAS score improved from 5.8 to 0.8 and the mean FAOS was significantly improved in all domains.
Alfredson18 recently reported on 56 patients with long-standing Achilles tendinopathy comprising 73 tendons. At surgery 58 of the 73 tendons were found to have a thickened plantaris closely related to the tendinopathic Achilles. He excised the plantaris tendons in a combined procedure with scraping and ventral release of the Achilles.
Pearce et al10 showed good results by releasing the plantaris tendon endoscopically. In 11 patients who underwent the procedure the mean American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score improved significantly and the Ankle Osteoarthritis Scale (AOS) scores for pain and disability also improved. This followed an earlier report by van Sterkenburg et al19 who describe good results in three patients treated with a mini-open technique. All patients improved in VAS for pain and function and two of the three improved on the Victorian Institute of Sport Assessment questionnaire – Achilles score.
If the plantaris is the underlying pathology, eccentric exercises may not improve symptoms because of the differential in tendon stiffness and the development of adhesions and friction between the plantaris and Achilles tendons. It is thought that the early changes of inflammation may lead to a focal Achilles tendinosis.12 It is also conceivable that a compressive effect of thickened, inflamed tissue next to the Achilles tendon could induce tendinopathic changes with the Achilles tendon. A minimally invasive procedure to remove the adhesions, excise the plantaris tendon and debride neovascularisation along the ventral aspect of the Achilles tendon may offer significant advantages over procedures that violate the Achilles tendon itself by improving symptoms while allowing a rapid return to sporting activities.
We chose to excise a long segment of the plantaris tendon in order to avoid reattachment of tendon to the Achilles that could lead to the recurrence of symptoms more proximally. Almost all athletes were able to return to elite-level sporting activity suggesting that despite the fact that the plantaris is used in running and in particular sprinting, excising the plantaris does not compromise function even at the highest levels. Return to elite sporting activity was quicker than the 4–12 months20 that would be expected if the Achilles tendon had been debrided and areas of tendinosis excised.
One-third of athletes had no Achilles tendinosis on MRI despite showing abnormalities related to the plantaris. However they had similar mean baseline VAS scores to those athletes with Achilles tendinosis and their symptoms were significantly improved following surgery, yet not as much as those with tendinosis. This suggests that the plantaris has a role in the generation of pain.
Limitations
This study had no athletes who underwent isolated excision of the plantaris, and stripping of the peritendinous tissues alone could have produced the same results. It is also difficult to quantify the MRI changes seen in peritendinous structures. Also, the number of athletes who improve with conservative measures alone is unknown, although we attempted conservative treatment initially in all cases. It may be that our cohort placed a higher value on reducing time out of sport than would a non-elite athletic population thus reducing the time given to conservative measures.
Our study may also be affected by selection bias, limitations of the scoring systems and a lack of control group. Further studies, ideally a blinded randomised controlled trail, are needed to confirm the precise involvement of the plantaris tendon in Achilles tendinopathy and whether purely excising the plantaris in those patients without Achilles tendinosis produces a satisfactory result. The temporal relationship between plantaris pathology and the development of subsequent Achilles tendinopathy and the role of the plantaris in sporting activities also requires further exploration.
Conclusion
The plantaris tendon may be an important contributory factor in the underlying pathophysiology of medially located Achilles tendon pain and focal non-insertional Achilles tendinopathy. Excision of the plantaris tendon and debridement of the ventral aspect of the Achilles tendon appears to be a safe procedure and provides a significant improvement in symptoms with an early return to elite-level sports in a high percentage of athletes.
What are the new findings?
This study supports the concept that the plantaris tendon is a cause for some Achilles tendinopathy.
Excising the plantaris tendon in elite athletes with non-insertional Achilles tendinopathy significantly improves FAOs and visual analogue scores.
The procedure is safe and allows as early return to elite sport.
How might it impact on clinical practice in the near future?
The plantaris should be investigated as a possible source of Achilles pain.
This technique should be considered in patients with medial-sided non-insertional Achilles tendinopathy who fail conservative measures.
References
Footnotes
Contributors JDFC conceived the hypothesis, performed the surgery, collected some of the data and edited the manuscript. RF wrote the initial manuscript, performed the data analysis and contributed to the editing. NP was responsible for editing the manuscript.
Competing interests None.
Provenance and peer review Not commissioned; externally peer reviewed.