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Ischial Tuberosity Avulsion Fracture in a Young Female Ballet Dancer.

Avulsion fracture of the ischial tuberosity is under-recognized in adolescents. (1) This fracture is more common in males, and occurs most often between the development of a secondary ossification center and its fusion during adolescence. (1),(2) It results from the overwhelming strength of tendons and muscles relative to bone during a strong contraction of the hamstrings. (2) The most common occasion for an eccentric load to the proximal hamstrings is during soccer, sprinting, football, and dance. (1) It is essential to diagnose hamstring rupture and avulsion injuries appropriately, as they are frequently misdiagnosed as a minor "hamstring pull." This can lead to chronic pain and disability secondary to inadequate management. (3) The following case report discusses a pediatric dancer who presented to a sport and dance medicine clinic with an avulsion fracture of the left ischial tuberosity sustained during eccentric loading of the hamstrings. This was accompanied by high-grade partial thickness tearing of adductor magnus and obturator internus muscles.

Case Presentation

A 14-year-old female ballet dancer (height: 168.4 cm; weight: 52.3 kg; BMI: 18.4 kg/[m.sup.2]) presented to a pediatric sport and dance medicine clinic describing a popping sensation isolated to the left buttock region. This dancer was training 12 to 13 hours per week in ballet, modern, tap, and contemporary. She was premenarchal, with maternal menarche at 18 years. She had no symptoms of the Female Athlete Triad. This injury was sustained during ballet training 1 day prior to presentation while weightbearing on the left leg. The dancer was performing a penche, with forward flexion of the torso and extension of the right leg at the hip. Initially she continued dancing, but subsequently, when leaping, she felt an additional popping sensation in the same region and excruciating pain. At this stage she was unable to weight bear and described tingling in the posterior thigh that did not extend beyond the knee. The patient was taken by ambulance to an urgent care center where x-rays (Fig. 1) were obtained and interpreted as a possible growth plate injury by the medical staff (according to the patient's mother). The patient was re-evaluated in a sport and dance medicine clinic 1 day later, and management was commenced involving pain relief with oxycodone twice daily, naproxen and paracetamol as required, and use of crutches.

Physical Examination

Examination of the left thigh revealed no ecchymosis or erythema posteriorly. Significant pain, tenderness, and swelling were present on inspection and palpation of the proximal left posterior hamstring and buttock region. There was tenderness along the proximal hamstrings at the insertion onto the ischial tuberosity. The knee and hamstrings could not be tested due to extreme pain. The patient could not perform a straight leg raise and could not weight bear without crutches. Range of motion was restricted by pain at 45[degrees] of hip flexion isolated to the left ischial tuberosity and radiating medially. Neurovascular structures were intact.

Diagnostic Evaluation

After close review, the x-rays were re-interpreted by the specialist as abnormal at the level of the ischial tuberosity bilaterally, with evidence of chronic avulsion and tug lesions. There was no significant displacement of a bony fragment on the affected side. Given the amount of pain and disability of the patient, there was clinical concern for extensive soft tissue injury, including full rupture at the insertion of the hamstring tendons to the ischial tuberosity. A pelvic MRI was ordered to evaluate for hamstring rupture at the level of the conjoined tendon or an acute bony avulsion. The musculoskeletal radiology team initially interpreted the MRI as a soft tissue proximal hamstring avulsion. Additionally, there was severe edema involving the left hip adductor muscles (quadratus femoris, obturator externus, and obturator internus), high-grade partial thickness tearing of the adductor magnus muscle at its femoral attachment, and highgrade partial thickness tearing of the obturator internus muscle at its iliac attachment. There was also soft tissue and deep fascial edema extending into the left perineum and left hemi-pelvis, which was likely reactive to the extensive muscle injuries (Fig. 2).

Clinical Course

The patient was evaluated 2 days after initial presentation, by which time the tingling in the posterior thigh had dissipated. Her pain levels had slightly decreased to a 5/10, but she was still unable to weight bear and had difficulty moving her leg. The patient was referred for surgical consultation because of the concern for full rupture of the proximal hamstrings at the insertion site of the ischial tuberosity. She was also advised to continue symptomatic management with cool compresses, combination hydrocodone/paracetamol, and paracetamol for pain relief, and the assistance of a wheelchair and crutches to avoid weightbearing. Examination at this stage revealed swelling in the buttock and proximal thigh and loss of contour of the proximal hamstrings with decreased tone. There was no palpable defect, ecchymosis, or erythema in the buttock or posterior thigh. There was tenderness over the lateral ischium but not in the distal thigh. There was also mild swelling in the ankle and foot, but dorsiflexion and plantar flexion of the foot and extension of the great toe were intact. The patient was unable to flex the knee actively against gravity, and passive range of motion allowed 90[degrees] of knee flexion. Extending from this position induced pain. Sensation was intact.

Upon re-review of the MRI by the radiology team and chief surgeon for dance medicine at the sport and dance medicine institution, it was felt that the injury to the proximal hamstrings was a bony avulsion with minimal displacement, as opposed to strictly a soft tissue avulsion. A clinical decision was therefore made to treat the young dancer non-operatively with rest, weaning off anti-inflammatories, and compression stockings and shorts.

After 2 weeks of rest, the patient had reduced pain and was weaned off pain relief except for paracetamol, although she remained tender over the proximal hamstrings. She could flex her knee against some resistance in a seated position but experienced pain at 45[degrees] during a straight leg raise. She remained non-weightbearing on crutches and was recommended to begin touchdown weightbearing. She was referred for extensive rehabilitation with a dance physical therapist.

Review 6.5 weeks after injury showed continuing improvement with conservative treatment and physical therapy. The patient was able to ambulate in a pool without pain. On examination, she continued to demonstrate tenderness at the tuberosity and superior to the external rotators. She experienced pain with resisted external hip rotation and resisted knee flexion while prone. Atrophy of the left quadriceps was evident when supine. She could actively straight leg raise to 45[degrees] with an extended knee. With knee flexion, she could passively flex the hip to 90[degrees]. Straight leg raises were recommended to prevent further atrophy of the quadriceps. She was continued on paracetamol three times daily to relieve pain, which had significantly diminished.

Final review 5 months after injury showed full return of strength and no pain. She had returned to dance, but would take an additional 4 to 8 weeks off jumps and splits before full return to all dance styles (6 months from date of injury).

Discussion

This case study presents a young dancer with sudden onset severe pain and popping sensation in the left buttock. Although avulsion fractures of the ischial tuberosity are considered uncommon, this diagnosis should be seriously considered in adolescent dancers, and excluded via imaging. In the pediatric population, avulsion injuries are more prevalent than in adults due to inherent weakness across the open apophyses. (4) There is increasing incidence in 14 to 17 year olds, which has been associated with enhanced participation in competitive sport. (4) Rossi and Dragoni (5) investigated the prevalence of avulsion fractures in young athletes; in 1,238 radiographs of athletes aged 11 to 35 years taken for focal traumatic symptoms they found 109 cases of ischial tuberosity avulsion fracture (8.8%). In that study, gymnasts were most affected by ischial tuberosity avulsion fractures (41% of total fractures), followed by soccer players (34% of total fractures). Other sports had a lower prevalence.

Dancers are unique in their pattern of muscle strength and range of motion. Ballet requires an unusual emphasis on hip abduction and external rotation compared to hip adduction and internal rotation. (6),(7) Studies have found reduced passive hip adduction and internal rotation ranges in ballet dancers compared to controls, (7) which contributes to the common finding of tight iliotibial bands (ITB) in this populaton. (8) Additionally, dancers have exhibited larger angle-specific hip external rotation strength and inner hip external rotation range of motion than controls. (9) Despite the rigorous strength required to execute long holds in various ballet positions, studies have repeatedly found dancers to have lower torque values compared to other athletes, with only 77% of weight-predicted strength norms. (10),(11) This is likely influenced by the low body weight seen in dancers and the low proportion of skeletal muscle consisting predominantly of slow twitch fibers.12 This is important because decreased thigh strength is associated with greater injury rates. (13) Muscle fatigue also contributes to the risk of injury, with hamstring avulsion from the ischial tuberosity common in dancers and other athletes who place stress on stretched hamstrings. (14)

In addition to the muscular strength and range of motion patterns unique to dance, adolescent growth affects dancers and creates biomechanical imbalances. The rate of growth has been identified as a risk factor for lower extremity injury in elite adolescent ballet dancers. (15) The adolescent growth spurt typically occurs between ages 11 and 14. (16) Furthermore, the ischial tuberosity may not fuse until the third decade of life. (14) During the adolescent growth spurt, muscles grow slower than bones, and the faster growth rate of the legs compared to the torso often results in improper alignment of the pelvis; hence, anterior pelvic tilt and tight hip flexors are commonly seen in growing dancers. (16) The resulting lack of strength and flexibility can increase the risk of injury. (16) This is of fundamental importance to the current case study, as the combination of decreased flexibility due to growth while performing an extreme range of eccentric loading exercises, along with the relatively increased strength of tendons and muscles compared to the ischial tuberosity due to non-fused secondary ossification centers, ultimately caused this injury. (2) The presence of chronic hamstring tug on the ischial tuberosity in this case suggests that inflexible hamstrings and chronic traction had been an ongoing issue for this dancer and were not previously addressed. (17)

A complicating factor of this injury was the extensive soft tissue injury to the hamstrings, adductors, and external rotator musculature. The combination of injuries that occurred during this slow, routine ballet movement was extraordinary. This was likely influenced by the aforementioned consequences of growth in a young dancer. (16) Interestingly, a previous study of dancers found that 88% of acute hamstring injuries occurred during slow activities rather than powerful movements. (18) Thigh injuries in dance range from 5% to 16% of total injury incidence, with hamstring and ITB syndrome being the most common. (19) Adductor magnus injury is a frequent differential diagnosis for hamstring strain, given the mutual attachment to the ischial tuberosity and shared presentation of pain on palpation over the ischial tuberosity insertion. (14) In dancers, adductor injury occurs concurrently with hamstring injuries in 33% of cases. (19) While adductor longus injuries are quite common in athletes, the only adductor injuries reported in ballet dancers are adductor magnus strains in conjunction with hamstring injuries. (19) This was the mechanism of injury in the case reported here.

Prevention is essential to the avoid similar devastating injuries that can cost a year of rehabilitation before returning to dance. It has been recommended that ballet training during the growth spurt should include sub-maximal muscle loading as a means of increasing strength rather than maximal loading. (20) It has also been recommended that limits should be placed on sections of class that include impact jumps, pointe work on one leg, challenging lifts in partnering classes, and movements placing strain on the knees. (16) Prevention programs offered by some institutions are ideal because they address individual deficiencies in flexibility and strength in young dancers and structure exercise regimens for dance training accordingly. In addition, the importance of educating the student dance population cannot be underestimated. In retrospect, the dancer-patient in this study exhibited signs of chronic hamstring "tug" that she did not fully appreciate or understand until they culminated in the avulsion fracture.

In most cases that are diagnosed early, avulsions heal with conservative treatment that includes rest and relative immobilization. (21) Full recovery is likely with a graded physical therapy program following acute injury. (17) Surgery should be considered in a number of cases, including hamstring muscle insertion total rupture or dislocation of the avulsion by more than 2 cm. (21) However, delayed diagnosis can also lead to surgery to restore painful non-union or relieve symptoms in individuals who may not have otherwise required surgery. (1) Focus should be on correct diagnosis in young athletes presenting with bony pelvic pain, as ischial avulsion fractures are the most likely of all pelvic fractures to result in persistent disability and limitation of sporting activity if not treated correctly. (17) In some cases, an MRI is warranted to evaluate the extent of the soft tissue injury. A retrospective study of pediatric ischial avulsions found MRI to be effective in identifying an injury that was undetectable radiographically. (22) In the present case, the MRI was pivotal in that the bony avulsion was not readily seen on plain radiographs; the extensive injury to the deep external rotators of the hip that are so critical in dance was only detected on MRI. The advanced diagnostics in this case significantly helped to guide operative versus non-operative treatment and inform patient and family expectations with regard to the extent of the injury and need for a comprehensive and specialized dance rehabilitation program.

Conclusion

Avulsion fracture of the ischial tuberosity is a diagnosis that should be seriously considered in adolescent athletes, particularly dancers, presenting with hamstring pain. Early imaging and correct diagnosis can serve to guide clinical management, prevent unnecessary surgery, and avoid a longer duration of rehabilitation and time away from dance.

References

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(5.) Rossi F, Dragoni S. Acute avulsion fractures of the pelvis in adolescent competitive athletes: prevalence, location and sports distribution of 203 cases collected. Skeletal Radiol. 2001 Mar;30(3):127-31.

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(8.) Winston P, Awan R, Cassidy JD, Bleakney RK. Clinical examination and ultrasound of self-reported snapping hip syndrome in elite ballet dancers. Am J Sports Med. 2007 Jan;35(1):118-26.

(9.) Gupta A, Fernihough B, Bailey G, et al. An evaluation of differences in hip external rotation strength and range of motion between female dancers and non-dancers. Br J Sports Med. 2004 Dec;38(6):778-83.

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(13.) Koutedakis Y, Khaloula M, Pacy P, et al. Thigh peak torques and lower-body injuries in dancers. J Dance Med Sci. 1997 Mar;1(1):12-5.

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(15.) Bowerman E, Whatman C, Harris N, et al. Are maturation, growth and lower extremity alignment associated with overuse injury in elite adolescent ballet dancers? Phys Ther Sport. 2014 Nov;15(4):234-41.

(16.) The Education Committee of the International Association for Dance Medicine and Science. The challenge of the adolescent dancer. J Dance Educ. 2001;1(2):74-6.

(17.) Sundar M, Carty H. Avulsion fractures of the pelvis in children: a report of 32 fractures and their outcome. Skeletal Radiol. 1994 Feb;23(2):85-90.

(18.) Askling C, Lund H, Saartok T, Thorstensson A. Self-reported hamstring injuries in student-dancers. Scand J Med Sci Sports. 2002 Aug;12(4):230-5.

(19.) Deleget A. Overview of thigh injuries in dance. J Dance Med Sci. 2010 Sep;14(3):97-102.

(20.) Phillips C. Strength training of dancers during the adolescent growth spurt. J Dance Med Sci. 1999 Jun;3(2):66-72.

(21.) Kujala UM, Orava S. Ischial apophysis injuries in athletes. Sports Med. 1993 Oct;16(4):290-4.

(22.) Meyers AB, Laor T, Zbojniewicz AM, Anton CG. MRI of radio-graphically occult ischial apophyseal avulsions. Pediatr Radiol. 2012 Nov;42(11):1357-63.

Jessica Biernacki, MD, Dai Sugimoto, PhD, Pierre d'Hemecourt, MD, and Andrea Stracciolini, MD

Jessica Biernacki, MD, Melbourne Medical School, University of Melbourne, Parkville, Victoria, Australia. Dai Sugimoto, PhD, Pierre d'Hemecourt, MD, and Andrea Stracciolini, MD, The Micheli Center for Sports Injury Prevention, Waltham, Massachusetts; Division of Sports Medicine, Department of Orthopaedics, Boston Children's Hospital, Boston, Massachusetts; and Department of Orthopaedic Surgery, Harvard Medical School, Boston, Massachusetts.

Correspondence: Jessica Biernacki, MD, Melbourne Medical School, University of Melbourne, Victoria, Australia 3010; jessica.biernacki@rch.org.au.

Caption: Figure 1 Radiographs of the pelvis: A, anterior-posterior pelvis; B, anterior-posterior hip; and C, cross-table hip.

Caption: Figure 2 MRI images of the pelvis: A, avulsion fracture of the ischial tuberosity; B, extensive soft tissue injury of external rotators; and C, bony avulsion fracture.

Please Note: Illustration(s) are not available due to copyright restrictions.
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Author:Biernacki, Jessica; Sugimoto, Dai; d'Hemecourt, Pierre; Stracciolini, Andrea
Publication:Journal of Dance Medicine & Science
Article Type:Report
Date:Oct 1, 2018
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