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"Nutcracker fracture" in a ballet dancer performing in the nutcracker.

Mid-foot injuries are rare but potentially debilitating in professional dancers. Fracture of the tarsal cuboid bone is commonly referred to as the "nutcracker fracture," owing to its mechanism of injury: an acute compression of the cuboid between the anterior process of the calcaneus and the base of the fourth and fifth metatarsals, "cracking" the cuboid as a nutcracker would a nut. (1) We present a unique case of a cuboid fracture in a dancer who ironically sustained it while dancing in the holiday classic The Nutcracker.

Case Report

A 26-year-old female professional ballet dancer presented to the covering sports medicine provider, a physician assistant in orthopaedic surgery, during a performance of The Nutcracker after inverting her left foot and ankle in the second act. While jumping, she landed en pointe with impact on the lateral forefoot and subsequently inverted her ankle. She did not fall to the floor, and though she felt significant pain on the lateral side of her foot and ankle, she finished the performance with modification to further jumps. On examination, significant swelling had developed immediately on the lateral aspect of the ankle and mid-foot, followed by ecchymosis of the mid foot. She exhibited a positive squeeze test for distal tibiofibular pain and was exquisitely tender over the lateral mid-foot, lateral ankle ligaments, and distal fibula. Instability testing was difficult to perform due to the dancer's significant pain, guarding, and swelling. She was given an Aircast[R] boot and crutches for protected weightbearing, and an urgent appointment in the sports medicine clinic was arranged.

The dancer was formally evaluated in the sports medicine clinic by the company's orthopaedic surgeon. Clinically, she was found to be 5'-10" (177.5 cm) in height, 135 lbs. (61.6 kg) in weight, with a BMI of 19.6 kg/[m.sup.2]. She had onset of menses at 16, with consistent monthly cycles. She denied any past medical or surgical issues, including injury to the left foot or ankle and any family history of osteopenia or osteoporosis. Nutritionally, she reported no food allergies or intolerance, restrictive, bingeing, or purging behavior, and no history of irritable bowel syndrome or inflammatory bowel disease. Her diet included meat and dairy, and she took no supplements. She had never been on oral steroids, anti-epileptics, or proton pump inhibitors.

Radiographs of the left foot and ankle showed a minimally displaced but comminuted fracture of the cuboid and swelling of the ankle consistent with an acute ligamentous injury. This prompted both CT scan of the foot and MRI of the foot and ankle to better define the injury from both bony and soft tissue perspectives. CT clearly demonstrated a minimally displaced, comminuted cuboid fracture with articular extension into both the calcaneocuboid joint posteriorly and the cuboid-metatarsal joints anteriorly, with little to no articular incongruity (Fig. 1). There was limited shortening of the cuboid and lateral column of the foot. MRI showed complete avulsion injury of the anterior talofibular ligament (ATFL) and the calcaneofibular ligament (CFL) and partial tears of the posterior talofibular ligament, the anterior tibiofibular ligament, and tearing of the interosseous membrane. The medial column of the foot was intact on CT and MRI (Fig. 2).

The fracture was treated non-operatively, given the limited intraarticular incongruity, the minimally displaced nature of the comminution, and the maintained lateral column length. However, due to the additional significant soft tissue injuries involving the syndesmosis and lateral ankle ligaments and the articular extension of the cuboid fracture, she was made non-weightbearing in a short leg cast for 6 weeks. A bone stimulator was administered. At the 6-week mark, plain film radiographs showed signs of healing (Fig. 3). Clinically, the dancer had a significant decrease in swelling, pain, and both bony and soft tissue tenderness. She was then transitioned to an Aircast[R] boot; however, she was still advised to practice protected weightbearing due to the complex nature of the cuboid fracture and the injury to her lateral ligaments and syndesmosis. She was allowed to begin early range-of-motion exercises.

At 3 months post-injury, a repeat CT scan was performed to allow for three-dimensional analysis of healing of the complex fracture and to ensure anatomic congruency (Fig. 4). The fracture showed excellent signs of healing without displacement and maintained congruity and length. Clinically, the dancer showed no significant laxity on anterior drawer or sub-talar tilt. She was allowed to progress to weightbearing activities with further physical therapy guided by the company's physical therapist. Given the stable nature of the fracture at 3 months, a further CT scan was deferred, and the fracture was followed by serial radiographs. Due to the prolonged immobilization, a gradual return to dance was employed under the guidance of the physical therapist. The patient reported no pain or instability at 5 months post-injury and exhibited full ankle range of motion, strength, excellent ligamentous stability, balance, and proprioception. Radiographs confirmed satisfactory bony healing (Fig. 5), and the patient was allowed to reintroduce dance over the ensuing month. Six months post-injury, she returned to dance at the professional level without pain, instability, or discomfort. She continues to dance without issue over 1 year out from injury.

Discussion

Fractures of the foot and ankle in dancers are common. (2) Their origin can be classified as acute or traumatic, chronic or stress, or a combination thereof. (3) Furthermore, all fractures should prompt consideration of the dancer's metabolic bone health. In dealing with an acute dance fracture, it is important to rule out underlying stress injury or, even more so, low bone mineral density, as they can have significant implications for treatment and rehabilitation. In a recent study, 23% of professional ballet dancers were found to have low bone density. (4) Factors that contribute to bone health are complex and multifactorial. The female athlete triad is a medical condition that influences bone health, and all dancers with (and without) fractures should be screened for it. It involves three inter-related components on a spectrum: low energy availability with or without disordered eating, menstrual dysfunction, and low bone mineral density. (5) The International Olympic Committee has rebranded and expanded the term female athlete triad to relative energy deficiency in sports (RED-S). This comprehensive term includes men and emphasizes a complex syndrome that affects metabolic rate, menstrual function, bone health, immunity, protein synthesis, and cardiovascular health. (6)

As mentioned earlier, fractures of the mid-foot are rare in dancers as they are typically associated with high energy trauma. However, the unique placement of a female dancer's foot on demi-pointe and pointe while executing jumps and pointe work may be considered a risk factor. Injury to the medial column of the mid-foot--i.e., Lisfranc joint--has been described as occurring through a missed jump landing (as in our case) or when a female dancer is pulled onto pointe and her foot catches a seam or irregularity in the floor. (7) Fracture of the cuboid through a "nutcracker" mechanism of acute compression of the cuboid between the anterior process of the calcaneus and the base of the fourth and fifth metatarsals is often accompanied by concomitant medial column injuries, so it is vital for the clinician to rule out medial side injury to the Lisfranc joint, the navicular, and the base of the first metatarsal. (8) Isolated injury to the cuboid is more common in the case of significant plantar flexion and inversion of the forefoot with relatively low energy. (9)

Cuboid fractures are important to recognize and to validate with appropriate imaging. The cuboid is integral to the lateral column of the foot, and there is limited tolerance for shortening before the foot falls into a planovalgus position. Indications for surgical reduction and fixation include shortening of the cuboid or a displaced intra-articular fracture that puts the patient at significant risk for post-traumatic osteoarthritis. Depending on comminution, fragment size and orientation, and other fracture and injury characteristics, surgery can involve open reduction and internal fixation, spanning external fixation, or in some circumstances a combination of the two. (10) Minimally displaced fractures can be treated nonoperatively with immobilization and protected weightbearing followed by progressive rehabilitation. Long-term outcomes of mid-foot fractures in the absence of medial column injury are generally positive. (11)

Fractures of the cuboid in dancers require appropriate identification and management. Imaging modalities may include plain film radiographs, CT scan to characterize the fracture, and MRI to evaluate for concomitant soft tissue injury. Surgery should be considered for significantly shortened and displaced fractures. Fortunately, our dancer exemplifies the possibility of a return to dance and full activity in the case of an isolated cuboid fracture and high-grade ankle sprain.

http://dx.doi.org/10.12678/1089-313X.19.3.124

Sasha Carsen, M.D., M.B.A., Bridget J. Quinn, M.D., Elizabeth Beck, P.A.-C., and Lyle J. Micheli, M.D., Division of Sports Medicine, Boston Children's Hospital, Boston, Massachusetts. Heather Southwick, M.S.P.T., Boston Ballet Company, Boston, Massachusetts.

Correspondence: Sasha Carsen, M.D., M.B.A., Division of Sports Medicine, Boston Children's Hospital, 319 Longwood Ave, Boston, Massachusetts, 02115; scarsen@hotmail.com.

References

(1.) Hermel MB, Gershon-Cohen J. The nutcracker fracture of the cuboid by indirect violence. Radiology. 1953 Jun;60(6):850-4.

(2.) Kadel NJ. Foot and ankle injuries in dance. Phys Med Rehabil Clin N Am. 2006 Nov;17(4):813-26, vii.

(3.) Goular M, O'Malley MJ, Hodgkins CW, Charlton TP. Foot and ankle fractures in dancers. Clin Sports Med. 2008 Apr;27(2):295-304.

(4.) Hoch AZ, Papanek P, Szabo A, et al. Association between the female athlete triad and endothelial dysfunction in dancers. Clin J Sport Med. 2011 Mar;21(2):119-25.

(5.) Joy E, De Souza MJ, Nattiv A, et al. 2014 female athlete triad consensus statement on treatment and return to play of the female athlete triad. Curr Sports Med Rep. 2014 Jul-Aug:13(4):219-32.

(6.) Mountjoy M, Sundgot-Borgen J, Burke J, et al. The IOC consensus statement: beyond the Female Athlete Triad--Relative Energy Deficiency in Sport (RED-S). Br J Sports Med. 2014 Apr;48(7):491-7.

(7.) Kadel N. Foot and ankle problems in dancers. Phys Med Rehabili Clin N Am. 2014 Nov:25(4):829-44.

(8.) Kou JX, Fortin PT. Commonly missed peritalar injuries. J Am Acad Orthop Surg. 2009 Dec;17(12):775-86.

(9.) Van Raaij TM, Duffy PJ, Buckley RE. Displaced isolated cuboid fractures: results of four cases with operative treatment. Foot Ankle Int. 2010 Mar;31(3):242-6.

(10.) Borelli J Jr, De S, VanPelt M. Fracture of the cuboid. J Am Acad Orthop Surg. 2012 Jul;20(7):472-7.

(11.) Brunet JA, Wiley JJ. The late results of tarsometatarsal joint injuries. J Bone Joint Surg Br. 1987 May;69(3):437-40.

Caption: Figure 1: A, CT sagittal plane of the foot showing fracture of the cuboid without significant shortening. B, CT coronal plane of the foot showing comminuted fracture of the cuboid with distraction of the fracture fragments and intra-articular extension. C, Axial plane of the foot, again, demonstrating comminuted cuboid fracture with distraction of fracture fragments.

Caption: Figure 2: A, T2-weighted MRI of the ankle in the coronal plane showing a tear of the anterior tibiofibular ligament. B, STIR weighted MRI of the foot in axial long axis plane showing intact Lisfranc joint. C, T1-weighted MRI of the foot in the axial long axis plane showing intact Lisfranc joint.

Caption: Figure 3: X-ray 6 weeks post-injury showing signs of healing.

Caption: Figure 4: CT scan 3 months post-injury showing signs of bony healing; A, sagittal plane; B, axial plane.

Caption: Figure 5: Five month follow-up plain film radiograph demonstrating excellent healing of the cuboid fracture.

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Article Details
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Title Annotation:Case Report
Author:Carsen, Sasha; Quinn, Bridget J.; Beck, Elizabeth; Southwick, Heather; Micheli, Lyle J.
Publication:Journal of Dance Medicine & Science
Article Type:Report
Date:Jul 1, 2015
Words:1945
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