Volleyball is one of the most popular sports played in the world, with nearly 200 million participants.1,2 Athletic skills, such as diving and rolling, may increase risk because of the repeated trauma to the pelvis and torso. However, significant hip injuries in volleyball are relatively rare. Most injuries to the hip in volleyball are often classified as muscle strains.3 However, less common injuries, such as heterotopic ossification (HO), are a potential risk in traumatic sports. Heterotopic ossification is characterized by the abnormal growth of bone in soft tissue.4–10 The incidence of HO, specifically in cases of repetitive microtrauma, has not been well documented; however, prevalence of HO related to other injuries has been previously documented in spinal cord injuries (20% to 30%) and closed head injuries (10% to 20%).8–10 In addition, HO injuries have been identified concomitantly with hip arthroplasty (.06% to 90%) and distal humeral fractures (10% to 90%).8–10
Heterotopic ossification has two primary etiologies: acquired and neurogenic.9 Because of a neurogenic etiology, HO occurs due to spinal cord or central nervous system injury. However, acquired HO typically occurs due to trauma such as fracture, surgery, or direct muscular trauma. Acquired HO is more common in athletes,9 usually due to one traumatic incident, specifically surgery or direct blunt force.4–22 Bony areas, such as the cervical spine, elbow, and greater trochanter, are most commonly affected by HO.4–22 The current case depicts an acquired HO at the ilium due to repetitive trauma in a skeletally immature volleyball player.
Evaluation of acute blunt trauma injury typically includes physical examination and diagnostic imaging, such as radiograph and bone scan,9,23 yet lower impact repetitive trauma may not yield advanced imaging during the acute stages of injury. Radiographic evidence of HO may appear as early as 3 weeks or as late at 12 weeks from the initial trauma and can lead to several differential diagnoses, mostly related to soft tissue structures.9,24,25 The following case highlights acquired HO following a fracture of the anterior superior iliac spine (ASIS) fracture resulting from repeated microtrauma to the pelvis. Although HO is described thoroughly in the literature,4–22 the etiology and pathogenesis of this case provides a unique perspective for athletic health care practitioners to consider in their clinical practice.
A 17-year-old male high school volleyball player reported he repetitively “dove for balls” during in-season practices, which caused landing on his left hip. The athlete’s complaint at initial injury was persistent left hip and back pain. An athletic trainer revealed pain upon palpation of the left ilium and sacroiliac joint (SI), and the athlete complained of a persistent 6/10 pain level during the day with weight-bearing activity. The athlete characterized a decrease in pain during the night, reporting a 4/10 dull pain. Signs included mild swelling and point tenderness over the ilium, with no superficial discoloration or obvious deformities. Active and passive ranges of motion were within normal limits, with no deficits for trunk and hip strength. Initial clinical diagnostic tests of SI joint compression and distraction for possible SI joint pathology and pelvic fracture were negative. Additional assessment revealed no radicular pain or obvious deformities.
The suggested mechanism of injury indicated that repetitive trauma to the ASIS due to recurring exposure of the pelvis to the hard floor may have constituted a contusion or hip pointer at the time of initial evaluation. The athlete’s initial clinical diagnosis by the athletic trainer was documented as left hip contusion with low back pain from repetitive exposure to blunt trauma to the left ASIS.
The athlete ceased in-season volleyball practice for 2 weeks due to discomfort. During the 2-week absence from practice, the athlete received treatment that included passive hip and low back stretching, followed by ice application for 15 minutes occurring 3 times each week. After a total of 6 treatment sessions in 2 weeks, no noticeable physical abnormalities to the area were documented and the diagnosis was not altered. At that point, the athlete sought personal care through his chiropractor. Evaluation by the chiropractor substantiated the athletic trainer’s clinical diagnosis of left hip contusion and associated low back pain and an up-slipped left ilium. Mobilization, heat, and stretching were initiated by the chiropractor to address the up-slip of the left ilium.
After the 2 weeks of volleyball cessation with conservative treatments and care from an athletic trainer and a chiropractor, the athlete received rehabilitation from an athletic trainer daily for 4 additional weeks and then a follow-up evaluation. The athlete engaged in a core stability program between weeks 2 through 6 following the injury. These exercises included fundamental volleyball movements of squatting, lunging, push presses, and Swiss ball techniques emphasizing transverse abdominal and gluteal activation and control. Progression of the obvious deformity was not observed at the sixth week from the initial evaluation. The athlete continuously complained of pain level 3/10 with exercise. However, 6 weeks after the initial evaluation, the athlete returned to volleyball activities without restrictions and completed the remainder of the season.
Six months after the initial evaluation, the athlete reported to the athletic trainer with a large mass on his left hip (Figure 1). The athlete had not received treatment from the athletic trainer for 4 months. No mass was present from the initial evaluation to the end of volleyball season; therefore, quantitative measurement was not available for comparison. The mass became more prominent when the athlete laterally flexed to his right. The patient was referred to his primary care physician (PCP) for further evaluation. The PCP ordered radiographs, which depicted a large ossification over the patient’s left ilium, specifically the ASIS (Figures 2 and 3). The PCP diagnosed a healed bone fracture and concluding occurrence of a hip microfracture at the iliac apophysis due to repetitive activity; over the course of the athlete’s recovery, the PCP definitively diagnosed the injury as an HO.
Figure 1. Left iliac crest mass upon visual inspection.
Figure 2. Radiographic imaging of the coronal and sagittal left iliac large bone mass.
Figure 3. Radiographic and visual comparison of the left iliac bone lesion.
At this point (6 months after the initial evaluation), the PCP prescribed rest and the athlete ceased all activity that caused pain. In addition, the PCP discussed the potential for elective surgery to remove the HO. Esthetically, the bone mass was an obvious deformity, but no further complications were noted. The patient declined the surgical option and decided to cease volleyball participation until pain fully subsided. Two months after volleyball cessation (8 months after initial evaluation), the athlete’s pain subsided and he resumed sport competition without activity restrictions. The athletic trainer provided a protective pad for volleyball activity. At the time of return, the athlete reported that he was continuing home exercises on a weekly basis, which included core strengthening. After returning to full in-season activity 8 months after the initial evaluation, the athlete continued to be pain free with no limitations or restriction in his activity. The bony mass was still visually present but asymptomatic.
Abnormally large bone growth of the ASIS, especially that which protrudes into the surrounding musculature, is rare in athletes and can be considered the salient feature of this report.9,26 The mechanism of injury was likely the result of repetitive trauma to bone, yet a complete understanding of the etiology and magnitude of growth remains elusive.9,26 Repeated trauma to the ASIS can result in avulsion injuries, contusions, myositis ossificans, fractures, hip pointer, or strains of the sartorius and tensor fascia lata. At the time of initial assessment, indications of a muscle strain and fracture were eliminated based on clinical evidence to the contrary. Muscle weakness or possible avulsion fracture were not diagnosed at the time of initial evaluation. The fracture that precipitated the HO may not have occurred from an isolated impact, but rather due to continued repetitive trauma through practice and competition for 2 months after the initial evaluation. The decision not to seek radiographs during the initial evaluation was based on the athletic trainer’s clinical findings,7,10,11 which, due to the rarity of HO in repetitive trauma and that HO is not typically visible on radiograph for 3 to 12 weeks, was congruent with current treatment regimens.5,9
Signs of HO include a loss of joint function and symptoms of peripheral nerve entrapment. Accurate diagnosis in the initial stage is challenging because HO may not present with signs and symptoms of fever, swelling, erythema, and decreased joint mobility.11,27 Therefore, the initial symptoms may mimic cellulitis, thrombophlebitis, osteomyelitis, tumor, strains, sprains, and varying infections.9,23,28–30 Initial symptoms of HO may be elusive given that heterotopic bone formation may initially occur distant from the site of trauma travelling to the site of injury to calcify over time.31 In addition, the literature suggests that the typical size of the HO varies and cannot be predicted from the magnitude of the original bony injury.9,31 The current literature suggests that bony injury may be a requisite for HO much like the current case presentation.9,31 Therefore, injuries with signs and symptoms of increased swelling and night pain with a mechanism of repetitive blunt trauma may warrant further reassessment, along with possible diagnostic testing. Because HO and other complications to contusion can arise days or weeks after the initial injury, continual reassessment is suggested. Clinicians should consider reevaluating typical hip pointers or ASIS contusions within the first 3 weeks of healing; in addition, when signs and symptoms persist, diagnostic imaging is warranted.
Blood tests and bone scans should be used collectively if HO is suspected.9 In patients with HO, the blood tests will reveal increased serum alkaline phosphatase 2 weeks after the initial injury15,25 and can reach up to 3.5 times more than the normal value 10 weeks after the initial trauma.9,25 Alkaline phosphate values alone are not indicators of HO because values may also be normal or may remain elevated for years after injury.9,25
A 3-phase bone scan is the most accurate image technique for early detection as early as 3 weeks after the initial injury.15,25 Radiography images will not depict a positive HO until at least 3 to 12 weeks after the initial injury and therefore may not be sensitive enough for early diagnosis of HO.9,25 Bone scans have been used to monitor metabolic activity much like the soft-tissue computed tomography (CT) scan.32
In addition, the skeletally immature structure of an adolescent must be considered during diagnostic testing. The iliac crest apophysis begins to fuse around age 15 years but may continue until age 25 years. The open physis is the most prone area to injury; however, aphophysitis in adolescents is rare, which made this case difficult to diagnose.26 Sonography,26 magnetic resonance imaging,33 and CT34 have all been used to assess aphophysitis in adolescents. The key feature of diagnostic imaging for HO in adolescents is mild physeal widening of 3–5 mm and bone marrow edema.26
Treatment for HO may include activity modification, nonsteroidal anti-inflammatory drugs (NSAIDs), and rehabilitation.26,35–39 No consensus exists as to which medication, diphosphonates, or NSAIDs are most efficacious. However, several studies suggest starting diphosphonates as soon as elevated alkaline phosphatase is noted or when diagnostic imaging confirms the presence of HO.9,15,25 Radiation therapy and surgical removal of the HO have also resulted in positive patient outcomes.9,40–42 Although this patient was not prescribed medications, elected against surgery, and chose a more conservative approach, he returned to activity pain free.
Because HO can vary in presentation and pathogenesis, referral can be difficult in the acute stages (Table). However, for efficient and successful patient outcomes, athletic trainers should initiate referral within 3 weeks of the initial injury if and when symptoms persist. Furthermore, other factors may contribute to earlier referral (ie, age, trauma, obvious deformity). In this case, the athlete’s high pain tolerance and the etiology of the HO made the ilium fracture elusive and altered the timeline for care. Regardless, radiography would have likely yielded inconclusive results and advanced diagnostic imaging would have been necessary to reveal the presence of the HO. The absence of day-to-day contact after the end of the volleyball season may also have led to a delayed diagnosis. Bone remodeling can lead to excess growth and obvious deformity, particularly in athletes or patients with an open physis. Practitioners can provide patient education so patients can monitor abnormal occurrences once released from care.
Table: Differential Diagnosis of Acute Hip Injuries
Bone scans and CT scans are effective at identifying bony anomalies but are at the physician’s discretion. Furthermore, diagnostic imaging is sensitive to bone healing and may yield inconclusive findings if not performed in the necessary time frame. Diagnostic images will likely fail to produce an HO diagnosis during the acute stages of injury. In this particular case, the nature of the fracture is unknown (one traumatic incident or microtrauma); thus, immediate referral for diagnostic tests may or may not have revealed the fracture. Practitioners should have educated the athlete about the potential signs of HO after the initial diagnosis so the athlete understood the need to return to the practitioner for additional care. Athletes should understand that signs of palpable deformity, increased or continued point tenderness, and pain during sport participation or activities of daily living warrant additional consultation from their practitioner.
Adolescents with pelvic fractures similar to what has been described in this case study have typically returned to participation within 6 weeks.43 In addition to educating the patient on possible developing symptoms, this case review also highlights the need for initial plain radiographs to evaluate for possible stress of apophyseal avulsion injury specifically in adolescent populations that are skeletally immature.
Heterotopic ossification may be a condition exacerbated in the adolescent population due to open epiphysis, which promotes bone growth that may become extreme with trauma. A diagnosis of HO may be elusive in the first few weeks, initially presenting as a hip pointer, contusion, or muscle strain. Diagnosis is difficult because diagnostic tests are not effective in detecting HO until 3 weeks after the initial injury.
Although HO in athletes has not been identified in the literature previously, this case marks the need to consider a broad differential diagnosis in athletes who endure repetitive trauma to better ascertain the need for additional evaluation and diagnostic imaging.
Implications for Clinical Practice
Practitioners should make a concerted effort to monitor athletes who have incurred a similar injury and refer them for diagnostic testing after 3 weeks if symptoms remain stagnant or increase. Likewise, practitioners should educate patients to return for reevaluation when signs warrant. These actions, in addition to protective padding, may reduce extended time loss and inhibit the development of a large mass, such as the mass that developed in this case. Thus, the practitioner should follow-up with athletes experiencing injuries that may become HO, regardless of the typical season cycle, and include patient education and timely diagnostic testing as key components to conclusive diagnosis and treatment.
- Schafle MD, Requa RK, Patton WL, Garrick JG. Injuries in the 1987 National Amateur Volleyball Tournament. Am J Sports Med. 1990;18(6):624–631. doi:10.1177/036354659001800612 [CrossRef]
- Verhagen EA, Van der Beek AJ, Bouter LM, Bahr RM, Van Mechelen W. A one season prospective cohort study of volleyball injuries. Br J Sports Med. 2004;38(4):477–481. doi:10.1136/bjsm.2003.005785 [CrossRef]
- Agel J, Palmieri-Smith RM, Dick R, Wojtys EM, Marshall SW. Descriptive epidemiology of collegiate women’s volleyball injuries: National Collegiate Athletic Association Injury Surveillance System, 1988–1989 through 2003–2004. J Athl Train. 2007;42(2):295–302.
- Casavant AM, Hastings H II, . Heterotopic ossification about the elbow: A therapist’s guide to evaluation and management. J Hand Ther. 2006;19(2):255–266. doi:10.1197/j.jht.2006.02.009 [CrossRef]
- Hink SM. Heterotopic ossification: a review of symptoms and treatment. Rehabilitation Nursing. 1994;19(3):169–173.
- Hudson SJ, Brett SJ. Heterotopic ossification—a long-term consequence of prolonged immobility. Crit Care. 2006;10(6):174. doi:10.1186/cc5091 [CrossRef]
- Lane JE, Dean RJ, Foulkes GD, Chadler PW. Idiopathic heterotopic ossification in the intensive care setting. Postgraduate Medical Journal. 2002;78(922):494–495. doi:10.1136/pmj.78.922.494 [CrossRef]
- Pape HC, Lehmann U, van Griensven M, Gansslen A, von Glinski S, Krettek C. Heterotopic ossifications in patients after severe blunt trauma with and without head trauma: incidence and patterns of distribution. J Orthop Trauma. 2001;15(4):229–237. doi:10.1097/00005131-200105000-00001 [CrossRef]
- Shehab D, Elgazzar AH, Collier BD. Heterotopic ossification. J Nucl Med. 2002;43(3):346–353.
- Subbarao JV, Garrison SJ. Heterotopic ossification: diagnosis and management, current concepts and controversies. J Spinal Cord Med. 1999;22(4):273–283.
- Brooker AF, Bowerman JW, Robinson RA, Riley LH Jr, . Ectopic ossification following total hip replacement. Incidence and a method of classification. J Bone Joint Surg Am. 1973;55(8):1629–1632.
- Brouwer KM, Lindenhovius AL, de Witte PB, Jupiter JB, Ring D. Resection of heterotopic ossification of the elbow: a comparison of ankylosis and partial restriction. J Hand Surg Am. 2010;35(7):1115–1119. doi:10.1016/j.jhsa.2010.03.040 [CrossRef]
- Chen NC, Julka A. Hinged external fixation of the elbow. Hand Clin. 2010;26(3):423–433, vii. doi:10.1016/j.hcl.2010.04.004 [CrossRef]
- Clohisy JC, Zebala LP, Nepple JJ, Pashos G. Combined hip arthroscopy and limited open osteochondroplasty for anterior femoroacetabular impingement. J Bone Joint Surg Am. 2010;92(8):1697–1706. doi:10.2106/JBJS.I.00326 [CrossRef]
- Garland DE, Shimoyama ST, Lugo C, Barras D, Gilgoff I. Spinal cord insults and heterotopic ossification in the pediatric population. Clin Orthop. 1989;245(45):303–310.
- Puzas JE, Brand JS, Howare GA, Lio CC, Evarts CM. Heteroptic bone formation after operation: a quantitative histologic and biochemical study. Surg Forum. 1984;35:521–523.
- Rhee JM. Cervical arthroplasty: a success, failure, or both?Spine J. 2010;10(1):731–732. doi:10.1016/j.spinee.2010.06.002 [CrossRef]
- Roberts JA, Bennet GC, MacKenzie JR. Physeal widening in children with myelomeningocele. J Bone Joint Surg Br. 1989;71(1):30–32.
- Robinson CG, Polster JM, Reddy CA, et al. Postoperative single-fraction radiation for prevention of heterotopic ossification of the elbow. Int J Radiat Oncol Biol Phys. 2010;77(5):1493–1499. doi:10.1016/j.ijrobp.2009.06.072 [CrossRef]
- Schurch B, Capaul M, Vallotton MB, Rossier AB. Prostaglandin E2 measurements: their value in the early diagnosis of heterotopic ossification in spinal cord injury patients. Arch Phys Med Rehabil. 1997;78(7):687–691. doi:10.1016/S0003-9993(97)90074-5 [CrossRef]
- Teasell RW, Mehta S, Aubut JL, et al. A systematic review of the therapeutic interventions for heterotopic ossification after spinal cord injury. Spinal Cord. 2010;48(5):512–521. doi:10.1038/sc.2009.175 [CrossRef]
- Wyndaele JJ. Heterotopic ossification following spinal cord injury. Spinal Cord. 2010;48(7):511. doi:10.1038/sc.2010.75 [CrossRef]
- Chmelova J, Mrazkova D, Dzupa V, Baca V, Grill R, Pleva L. The role of plain radiography in pelvic trauma in the era of advanced computed tomography [Czech]. Acta Chir Orthop Traumatol Cech. 2006;73(6):394–399.
- Mysiw WJ, Tan J, Jackson RD. Heterotopic ossification. The utility of osteocalcin in diagnosis and management. Am J Phys Med Rehabil. 1993;72(4):184–187. doi:10.1097/00002060-199308000-00002 [CrossRef]
- Orzel JA, Rudd TG. Heterotopic bone formation: clinical, laboratory, and imaging correlation. J Nucl Med. 1985;26(2):125–132.
- Herbert KJ, Laor T, Divine JG, Emery KH, Wall EJ. MRI appearance of chronic stress injury of the iliac crest apophysis in adolescent athletes. Am J Rotengenology. 2008;190(6):1487–1491. doi:10.2214/AJR.07.3399 [CrossRef]
- Wharton GW, Morgan TH. Ankylosis in the paralyzed patient. J Bone Joint Surg Am. 1970;52(1):105–112.
- Goldberg MA, Schumacher HR. Heterotopic ossification mimicking acute arthritis after neurologic catastrophes. Arch Intern Med. 1977;137(5):619–621. doi:10.1001/archinte.1977.03630170043013 [CrossRef]
- Ragone DJ Jr, Kellerman WC, Bonner FJ Jr, . Heterotopic ossification masquerading as deep venous thrombosis in head-injured adult: Complications of anticoagulation. Arch Phys Med Rehabil. 1986;67(5):339–341.
- Singer BR. Heterotopic ossification. Br J Hosp Med. 1993;49(4):247–251, 254–245.
- Urist MR, Nakagawa M, Nakata N, Nogami H. Experimental myositis ossificans: cartilage and bone formation in muscle in response to a diffusible bone matrix-derived morphogen. Arch Pathol Lab Med. 1978;102(6):312–316.
- Bressler EL, Marn CS, Gore RM, Hendrix RW. Evaluation of ectopic bone by CT. Am J Roentgenol. 1987;148(5):931–935.
- Pisacano RM, Miller TT. Comparing sonography with MR imaging of apophyseal injuries of the pelvis in four boys. Am J Roentgenol. 2003;181(1):223–230.
- Aksoy B, Ozturk K, Ensenyel CZ, Kara AN. Avulsion of the iliac crest apophysis. Int J Sports Med. 1998;19(1):76–78. doi:10.1055/s-2007-971885 [CrossRef]
- Cella JP, Salvati EA, Sculco TP. Indomethacin for the prevention of heterotopic ossification following total hip arthroplasty. Effectiveness, contraindications, and adverse effects. J Arthroplasty. 1988;3(3):229–234. doi:10.1016/S0883-5403(88)80020-2 [CrossRef]
- Diehl JJ, Best TM, Kaeding CC. Classification and return-to-play considerations for stress fractures. Clin Sports Med. 2006;25(1):17–28, vii. doi:10.1016/j.csm.2005.08.012 [CrossRef]
- Freiberg AA, Cantor R, Freiberg RA. The use of aspirin to prevent heterotopic ossification after total hip arthroplasty. Clin Orthop. 1991Jun;(267):93–96.
- Kjaersgaard-Andersen P, Ritter MA. Short-term treatment with nonsteroidal antiinflammatory medications to prevent heterotopic bone formation after total hip arthroplasty. A preliminary report. Clin Orthop. 1992Jun;(279):157–162.
- Thomas BJ, Amstutz HC. Results of the administration of diphosphonate for the prevention of heterotopic ossification after total hip arthroplasty. J Bone Joint Surg Am. 1985;67(3):400–403.
- Coventry MB, Scanlon PW. The use of radiation to discourage ectopic bone. A nine-year study in surgery about the hip. J Bone Joint Surg Am. 1981;63(2):201–208.
- Healy WL, Lo TC, DeSimone AA, Rask B, Pfeifer BA. Single-dose irradiation for the prevention of heterotopic ossification after total hip arthroplasty. A comparison of doses of five hundred and fifty and seven hundred centigray. J Bone Joint Surg Am. 1995;77(4):590–595.
- Knelles D, Barthel T, Karrer A, Kraus U, Eulert J, Kolbl O. Prevention of heterotopic ossification after total hip replacement. A prospective, randomised study using acetylsalicylic acid, indomethacin and fractional or single-dose irradiation. J Bone Joint Surg Br. 1997;79(4):596–602. doi:10.1302/0301-620X.79B4.6829 [CrossRef]
- Tuzuner T, Ozturan KE, Karaca E, Ulgur M. Avulsion fracture of the anterior superior iliac spine in a volleyball player [Turkish]. Acta Orthop Traumatol Turc. 2003;37(4):340–343.
Differential Diagnosis of Acute Hip Injuries
|INJURY||SIGNS AND SYMPTOMS||SALIENT DIAGNOSTIC FACTOR|
|Oblique contusion||Possible pain, discoloration, lack of some rotatory ROM||Point tender location, lack of ROM in rotation and lateral side bending, known mechanism of injury|
|Hip pointer||Possible pain, discoloration, AROM NWNL, decreased hip flexion strength||Point tender location and known mechanism of injury|
|Hip flexor strain||Decreased hip ROM, painful ROM, possible lack of continuity in hip musculature, lack of full strength||Known mechanism of injury, manual muscle testing to specific hip musculoskeletal anatomy|
|ASIS fracture||Increased pain and point tender at fracture site, decreased hip flexion ROM, decreased hip flexor strength||Positive radiograph|
|Myositis ossificans (ectopic and heterotopic)||Increased pain in musculature where formation of extraskeleton bone growth is apparent||Illumination on radiograph|
|Exostosis||Increased pain with new formation of bone on top of bone||Illumination on radiograph|