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© 1996 The Journal of Bone and Joint Surgery, Inc. Release of the Flexor Hallucis Longus Tendon in Ballet Dancers*   , BOSTON, MASSACHUSETTSInvestigation performed at Children's Hospital, Boston
Thirteen female ballet dancers had an operative release of the flexor hallucis longus tendon because of isolated stenosing tenosynovitis, and the results were reviewed after a mean duration of follow-up of six years and six months (range, two to ten years). All of the patients danced at the advanced or professional level, and all had failed to respond to non-operative management. The mean age of the patients at the time of the operation was twenty years (range, thirteen to twenty-six years). Symptoms, which included pain and tenderness over the medial aspect of the subtalar joint, had been present for a mean of six months (range, two to twelve months) preoperatively and were exacerbated by jumping and by attempts to perform en pointe work. Crepitus was present in six patients, and triggering was present in three. No patient had evidence of a symptomatic os trigonum. Postoperatively, all patients participated in a formal physical-therapy program for a mean of nine weeks (range, four to thirteen weeks). All patients returned to dancing, within a mean of five months (range, two to nine months), and eleven reached a level of full participation in dancing without restriction. At the time of the most recent follow-up, all patients noted improvement compared with the preoperative condition. Eight patients were professional ballet dancers, four were students at advanced ballet schools, and one had stopped performing ballet for reasons unrelated to the tenosynovitis of the flexor hallucis longus. In addition, two of the students had decided not to pursue careers in dancing because of persistent, but greatly diminished, symptoms. No complications were noted in this series. We concluded that an operative release of the flexor hallucis longus is effective for the treatment of isolated stenosing tenosynovitis in female ballet dancers who place high demands on the foot and ankle and for whom non-operative treatment has failed.
Stenosing tenosynovitis of the flexor hallucis longus at the level of the sustentaculum tali is a rare entity that primarily affects female ballet dancers8,16,18,32. As reported by Hamilton, the condition is characterized by pain in the posteromedial part of the ankle that is exacerbated by en pointe work, often is relieved by rest, and tends to be chronic10,11. Stenosing tenosynovitis of the flexor hallucis longus apparently first was described in 1940 by Lewin, who successfully treated triggering of the great toe in a female ballet dancer with non-operative means21. Non-operative treatment of this disorder also was described by Lipscomb22 in 1944 and by Burman2 in 1953. Operative treatment of this condition apparently first was described in 1950 by Lapidus and Seidenstein; in that study, a male patient was able to return to athletic activities after the release of a triggering tendon19. Subsequently, most authors who have described the successful operative treatment of this condition have reported on female ballet dancers1,3,5,6,12,20,24,25,35,41. Isolated stenosing tenosynovitis of the flexor hallucis longus rarely is encountered in the general population; this may account for the relatively high prevalence of missed or delayed diagnoses when the condition occurs in dancers. Although the effectiveness of operative treatment was suggested by the authors of the previously mentioned case reports, we are aware of no study in which a series of patients who had this condition were managed operatively by the same surgeon. The senior one of us (L. J. M.) has been actively involved in the treatment of stenosing tenosynovitis of the flexor hallucis longus in ballet dancers for more than thirteen years. We retrospectively reviewed the records of thirteen patients to determine the clinical outcome after operative treatment of this condition. The operative technique is described in detail.
Thirteen patients who had isolated stenosing tenosynovitis of the flexor hallucis longus at the level of the ankle were managed with an operative release after the symptoms had failed to respond to non-operative treatment. The operations were performed between 1983 and 1991 under the direction of one surgeon (L. J. M.). The charts of the patients were reviewed, the patients were contacted, and information regarding preoperative and postoperative symptoms, function, signs, treatment, rehabilitation, time to full participation in dancing, and ongoing therapy was obtained. The mean duration of follow-up was six years and six months (range, two to ten years). All of the patients were female. The mean age at the time of the operation was twenty years (range, thirteen to twenty-six years). The left ankle was involved in nine patients and the right, in four. Seven patients were professional ballet dancers, and six were students at advanced ballet schools. The patients had been dancing for a mean of twelve years (range, six to nineteen years) and had been performing en pointe work for a mean of seven years (range, two to fourteen years). The patients had had pain and tenderness over the medial aspect of the subtalar joint for a mean of six months (range, two to twelve months) before the operation. The symptoms were exacerbated by jumping and by attempts to perform en pointe work. All patients had lost the ability to stand en pointe. Crepitus was present in six patients, and triggering was present in three. No patient had pain or tenderness in the posterolateral aspect of the ankle with forced passive plantar flexion, which would have suggested the involvement of an os trigonum. Radiographs were made for all patients and demonstrated an os trigonum in one. No clinically important degenerative changes or osseous abnormalities were noted in any patient. All patients were managed non-operatively for a mean of four months (range, two to six months). Non-operative treatment included restriction of activity, changes in dance technique, physical therapy, administration of non-steroidal anti-inflammatory medications, ice and contrast baths, use of a whirlpool, and ultrasound. Two patients had one injection of corticosteroids each. Non-operative therapy was considered to have failed when the disabling symptoms persisted or progressed.
Operative Technique
The subcutaneous tissue is approximated with absorbable vertical mattress sutures, and the skin is closed with a running intracuticular suture. Steri-Strips (3M, St. Paul, Minnesota), a compressive dressing, and a posterior splint are applied. The patient usually is discharged on the day after the operation and remains non-weight-bearing until the initial follow-up visit, four to seven days after the operation. The splint then is removed, and formal physical therapy (including progressive weight-bearing and range-of-motion exercises) is begun. Strengthening exercises and a gradual return to barre activities and centre work (repetitive motions without the hand-held support of the barre and without jumping) are added as healing permits.
The intraoperative findings included thickening and stenosis of the tendon sheath (thirteen patients), synovial hypertrophy (ten patients), adhesions (nine patients), mucoid degeneration (eight patients), nodules (three patients), partial tears of the flexor hallucis longus tendon (three patients), and muscle fibers of the flexor hallucis longus in the stenotic sheath (two patients). A flexor digitorum accessorius longus was not encountered in any patient. The mean duration of formal postoperative physical therapy was nine weeks (range, four to thirteen weeks). All patients returned to dancing, within a mean of five months (range, two to nine months), and eleven reached a level of full participation in dancing without restriction. At the time of the most recent follow-up, eight patients were professional ballet dancers and four were students at advanced ballet schools. Two of the students had decided not to pursue professional dancing careers because of persistent, but greatly diminished, symptoms. The remaining patient had stopped performing ballet for reasons unrelated to the tenosynovitis. Of the ten patients who intended to remain fully active ballet dancers, three continued to have intermittent mild pain that did not interfere with their ability to perform, three continued to use non-steroidal anti-inflammatory medication for symptoms on occasion, and two continued to perform specific physical-therapy exercises for the ankles in addition to their normal routine. No complications were noted in the present series.
Professional dance places considerable stress on the body, particularly the lower extremities. Washington, in a review of 1662 dance-related injuries in theatrical dancers, reported that the lower extremity was the most common site of injury42. Ballet dancers, in particular, have a high prevalence of injuries, with the greatest percentage occurring in the foot and ankle. Solomon et al., in a review of 171 injuries in dancers, reported seventy-seven injuries of the foot and ankle, twenty-six injuries of the back, and twenty injuries of the knee39. Most patients have minor injuries that resolve over time3,33. Dancing en pointe is a distinctive feature of the routine of the female ballet dancer. This technique appears to be associated with an increased risk of injuries of the foot and ankle and to lead to tendinitis of the flexor hallucis longus in particular14,17,27,31. As noted in the present report, most dancers who need an operative release are female and perform en pointe work. The ability to dance en pointe is the result of many years of training and requires excessive plantar flexion of the ankle as well as physical strength, balance, and coordination38. When the dancer assumes the en pointe position, the flexor hallucis longus tendon may be stretched beyond its physiological limits. Factors such as decreased ligamentous laxity, poor en pointe positioning, pronation of the foot, and poor turn-out at the hips accentuate the demands on the flexor hallucis longus tendon12. These repetitive stresses, coupled with the anatomical situation at the tunnel beneath the sustentaculum tali, where the direction of the tendon changes acutely, predispose the flexor hallucis longus tendon to injury at this site. The structures at the posteromedial aspect of the ankle joint include (from medial to lateral) the tibialis posterior tendon, the flexor digitorum longus tendon, the posterior tibial vessels, the tibial nerve, and the flexor hallucis longus tendon9,15. A flexor digitorum accessorius longus also may be present in the form of fleshy fibers in the immediate vicinity of the neurovascular bundle and the flexor hallucis longus tendon; Nathan et al. noted such a structure in twelve of 100 cadavera29. All of these structures are deflected from a straight course as they cross the subtalar joint and are held in place by a localized thickening of deep fascia known as the flexor retinaculum9,15. The flexor hallucis longus tendon passes posterior to the medial malleolus and deep to the flexor retinaculum, occupying the groove between the medial and lateral tubercles of the posterior portion of the talus, and then passes plantar to the groove on the plantar surface of the sustentaculum tali. The fibro-osseous tunnel that is formed by these grooves and the flexor retinaculum is lined with a synovial sheath. The synovial sheath begins one centimeter proximal to the subtalar joint and encircles the flexor hallucis longus tendon distally to the area of the naviculocuneiform joints passing on the plantar aspect of the tibialis posterior tendon sheath9,11,15,37. This synovial tissue-lined fibro-osseous tunnel is the site of impingement in patients who have stenosing tenosynovitis of the flexor hallucis longus7. A spectrum of pathological lesions has been associated with stenosing tenosynovitis of the flexor hallucis longus. These lesions have included thickening and stenosis of the tendon sheath, tenosynovial hypertrophy, and adhesions6,12,13,34. Occasionally, an abnormally distal insertion of the muscle allows muscle fibers to be pulled into the sheath with extreme dorsiflexion of the great toe7,12,28,40. The tendon itself may demonstrate fusiform thickening or central necrosis12,31,41. In more severe instances of the condition, calcific nodules or partial degenerative tears in the tendon may lead to triggering35. A dancer who has stenosing tenosynovitis of the flexor hallucis longus typically has pain and swelling posterior to the medial malleolus. The symptoms occur in association with any use of the foot, particularly attempts to raise the arch of the foot, and are exacerbated by jumping and by attempts to assume the full en pointe position. When the condition is severe, crepitus as well as a triggering sensation may develop at the ankle in association with extension of the great toe3,6,12,33,35,41. When a nodule is trapped in the tunnel, the distal phalanx of the great toe remains in extension; thus, the dancer cannot assume the en pointe position as she is unable to maintain the interphalangeal joint in the neutral position3. A physical examination typically reveals local tenderness over the tendon sheath posterior and inferior to the medial malleolus, and nodules may be palpated at the site of tenderness. A passive range of motion of the great toe typically causes less pain than does a resisted active range of motion. Passive extension of the interphalangeal joint of the great toe may also trap a nodule in the fibro-osseous tunnel and produce a snapping or triggering sensation when the flexor hallucis longus contracts, pulling the nodule out of the tunnel3,6,12,20,24,31,34-36. Limited dorsiflexion of the great toe usually is noted when the knee is completely extended and the ankle is in full dorsiflexion; some authors have suggested that this finding is indicative of a functional contracture of the flexor hallucis longus tendon12,40. The evaluation also should include radiographs of the ankle and foot; a lateral radiograph made with the ankle in the full en pointe position will help to determine if an os trigonum is present. Although Lynch and Pupp stated that tomography is necessary to diagnose stenosis of the tendon sheath of the flexor hallucis longus24, we have not found this to be the case. The differential diagnosis of pain in the posterior aspect of the foot or ankle of a dancer includes other mechanical overuse injuries as well as systemic and inflammatory conditions, such as rheumatoid arthritis, gonorrhea, syphilis, tuberculosis, gout, Reiter syndrome, inflammatory bowel disease, and various neoplastic diseases1,22-24,30. A condition that merits special consideration in the differential diagnosis is os trigonum syndrome. This condition may often coexist or be confused with tendinitis of the flexor hallucis longus. An os trigonum is a separate portion of the lateral tubercle of the talus that can become symptomatic either through direct impingement during plantar flexion of the joint or through irritation of the contiguous flexor hallucis longus tendon, which passes between it and the medial tubercle of the talus. It is our impression that dancers have a relatively high prevalence of an os trigonum as well as an increased prevalence of symptoms due to the presence of such a structure and that this proclivity is related to the excessive plantar flexion of the ankle that is required in ballet. Hamilton12, in a review of problems of the foot and ankle in ballet dancers, reported seventeen instances in which a release of the flexor hallucis longus was combined with an excision of an os trigonum and noted difficulty in evaluating the results of the combined procedure. Exploration of an os trigonum that appears to be contributing to symptoms may be necessary at the time of the exploration of the flexor hallucis longus in a dancer who has pain with en pointe work4,12,13,26,43. Early treatment of isolated tenosynovitis of the flexor hallucis longus consists of rest, administration of non-steroidal anti-inflammatory medications, ice or contrast baths, gentle stretching, massage, water therapy (including barre exercises performed in a pool), and ultrasound. Training may continue without en pointe exercises, and turn-out should be reduced so that the weight of the body remains centered over the foot. In addition, the dancer should eliminate contributing factors such as the use of soft, worn-out shoes; gripping of the floor with the toes when jumping; so-called rolling in (pronation of the foot); dancing on hard floors; and landing on the heels when coming down from jumps3,11,12,31,33. If there is progression or recurrance of the symptoms, stronger non-steroidal anti-inflammatory medications or a brief period of immobilization (three to four weeks) may be tried, followed by physical therapy11-13. Injections of corticosteroids seldom are performed because of the risk of weakening or rupturing of the tendon. Operative release of the flexor hallucis longus tendon is recommended when disabling symptoms persist despite non-operative treatment. Potential complications of the procedure include infection, skin-sloughing, pain at the site of the scar, and damage to the neurovascular bundle. Stiffness or the recurrence of tenosynovitis of the flexor hallucis longus may result from postoperative scarring or inadequate release of the tendon sheath, or both. In addition, although such a situation has not yet been reported, some authors have suggested that complete release of the retinaculum that is part of the fibro-osseous tunnel may lead to subluxation of the tendon3,11,12. None of these problems were encountered in our small series. The results of the present study indicate that an operative release of the flexor hallucis longus is effective for the treatment of isolated stenosing tenosynovitis at the level of the ankle joint after non-operative therapy has failed. Thus, we recommend operative treatment of this career-threatening problem in female ballet dancers who place high demands on the ankle and foot and for whom non-operative measures have been unsuccessful.
*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.
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