- Email: [email protected]
Musculoskeletal Concerns in the Young Athlete with Down Syndrome
Musculoskeletal Concerns in the Young Athlete with Down Syndrome Peter D. Pizzutillo, MD, and Martin J. Herman, MD Children and adolescents with Down syndrome frequently are involved in athletic pursuits. In addition to well-known associated medical conditions, such as hypothyroidism and cardiac anomalies, these individuals also are susceptible to musculoskeletal problems. Patellar instability, hip joint instability, slipped capital femoral epiphysis, bunions, and cervical spine instability have been reported with a significant incidence in this population. Early diagnosis of musculoskeletal problems allows for more effective interventions that preserve function and allow safe participation in sports activities. Oper Tech Sports Med 14:135-140 © 2006 Elsevier Inc. All rights reserved. KEYWORDS Down syndrome, young athletes, knee, hip, foot and cervical spine problems
D
own syndrome remains the most common human malformation, with an incidence of 1 in 600 live births.1 Although the early development of young children with Down syndrome is characterized by psychomotor delay, many of these children will demonstrate progressive improvement in motor skills with the ability to participate in advanced athletic activities. The Special Olympics organization has created a venue in which athletes with Down syndrome can experience the excitement and satisfaction that result from competition in a variety of sports. Through the sustained interest of members of the Special Olympics governing body and the experience garnered by clinicians from decades of screening and treatment of young athletes with Down syndrome, the public has been educated in regards potential medical and musculoskeletal problems in these individuals.2 Significant medical conditions that could affect the young individual with Down syndrome include cardiac anomalies (the most common is complete atrioventricular septal defect), hypothyroidism, hyperthyroidism, obstructive sleep apnea, and obesity.3,4 In the adult with Down syndrome, hearing and visual disorders, arthritis, coronary artery disease, diabetes, and dementia may develop.5 The medical management of these conditions in the Down population has evolved and resulted in marked improvements in sustaining function and quality of life. Department of Orthopaedic Surgery and Pediatrics, Drexel University College of Medicine, and Orthopaedic Surgery, St. Christopher’s Hospital for Children, Philadelphia, PA. Address reprint requests to Peter D. Pizzutillo, MD, St. Christopher’s Hospital for Children, E Erie Ave & N Front St, Philadelphia, PA 19134. E-mail: [email protected]
1060-1872/06/$-see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1053/j.otsm.2006.06.002
Ligamentous laxity and hypotonia frequently are observed in the active young athlete with Down syndrome and may increase the risk of injury. In addition to acute musculoskeletal injuries, patellar instability, hip instability, slipped capital femoral epiphysis, bunions, and cervical spine instability may develop without an identifiable proximate cause.
Patellar Instability Sudden and unexpected giving way of the knee may be experienced as atraumatic subluxation or dislocation of the patella and is more commonly observed in teenagers or adults rather than in the child with Down syndrome.6 Although spontaneous reduction of the patella is the rule, the patient may experience low-grade discomfort and a tendency for recurrent patellar instability. Hemarthrosis or significant effusion of the knee, acute disruption of the medial retinaculum, and intra-articular fractures of the knee frequently are associated with acute patellar instability in the non-Down population but are not usually observed in the Down population. Nonsurgical interventions consisting of strengthening of the quadriceps mechanism and the use of patellar restraining braces frequently are effective in controlling instability. When instability persists despite these interventions, surgical treatment is indicated.7 Soft-tissue stabilization of the patellofemoral complex may require both distal and proximal procedures to balance forces about the patella. Imbrication of the medial retinaculum and advancement of the vastus medialis obliquus also may require medial reinforcement with the semitendinosis tendon. Bony procedures involving reorientation of the tibial tubercle are not commonly needed in this 135
136
Figure 1 (A) Anteroposterior (AP) radiograph of hips and pelvis reveal mild subluxation of hips. (B) AP radiograph reveals progressive degenerative hip disease of both hips.
P.D. Pizzutillo and M.J. Herman of the femoral head and of the acetabulum and to dynamically analyze the direction of instability. Severe capsular and ligamentous laxity of the hip make clinical estimation of femoral torsion unreliable; computed tomography (CT) scan or magnetic resonance imaging (MRI) evaluation of the femur will more precisely determine the degree of existing anteversion or retroversion. Because the femoral head is frequently displaced posteriorly in this population, MRI or arthrography of the hip joint may provide information in regards the competence of the acetabulum, especially dysplasia of the posterior acetabular rim.10 Capsulorrhaphy of the hip joint, as an isolated procedure, is insufficient to maintain hip joint stability. Surgical correction of anteversion or retroversion of the femur and restoration of a competent acetabular rim have increased the success of hip stabilization. Despite a variety of surgical approaches to this problem, recurrent instability following surgical treatment is not uncommon and parents must be informed of this potential complication. In the mature individual, low-grade instability frequently leads to progressive, severe degenerative joint disease with resultant limited joint motion, pain with ambulation, and loss of function (Fig. 1).11 Maintenance of ambulatory function is important because it contributes to a better quality of life for the individual and eases the daily demands on the individual’s caretaker. Surgical intervention includes Chiari osteotomy of the ilium, arthrodesis of the hip joint, and total hip replacement. There are no clear guidelines for total hip replacement in the adult Down patient with advanced hip joint disease. Complications may include infection, dislocation of the joint components, and loosening of the femoral or acetabular components.
population because soft-tissue laxity is the prime factor in patellar instability.
Slipped Capital Femoral Epiphysis
Hip Joint Instability
Slipped capital femoral epiphysis (SCFE) has been reported with a greater incidence in the Down population than in the general population (Fig. 2).12,13 This can be explained in part by the increased incidence of obesity and of thyroid dysfunction in Down syndrome. Both of these factors have had a positive correlation with the development of SCFE in the
Instability of the hip joint may be observed in individuals with Down syndrome from the time of infancy to adulthood.8 Although ligamentous instability and hypotonia have been considered important factors in the development of hip instability in this population, we are not yet fully aware of all contributing factors. Hip subluxation and dislocation usually are noted in the first decade of life and present insidiously without a history of trauma or pain. Typically, a sudden, palpable displacement about the hip joint is noted during diapering or perineal care and medical advice is sought on an urgent basis. Physical examination will not detect evidence of trauma or neurologic loss but will reveal painless dislocation and relocation of the hip with abduction and adduction maneuvers. The very young child with hip instability may be treated with cast immobilization followed by abduction bracing.9 The success of this intervention is unpredictable but will provide prolonged hip stability in a proportion of patients. When immobilization has been used for 6 to 12 months and has failed to stabilize the hip joint, surgical intervention becomes more appropriate. It is critical to evaluate the anatomy
Figure 2 AP radiograph reveals unilateral SCFE.
Musculoskeletal concerns in the young athlete with Down syndrome general population. When compared with patients with SCFE in the general population, affected individuals with Down syndrome have a higher incidence of complications, including progressive degenerative changes of the hip and avascular necrosis of the femoral head. Although there is an expectation that the more secure fixation of SCFE provided by large cannulated screws may improve the ultimate results of surgical intervention, continued research is needed to improve our understanding of pathologic factors and to design more effective modes of treatment.
Bunions The development of bunions is common in individuals with Down syndrome and is likely related to hyperpronation of the flexible flatfoot in this population. It is fortunate that the majority of affected individuals will remain asymptomatic without impairment of ambulatory function. Surgical intervention is infrequently indicated since shoe modifications are usually effective in providing comfort.
Cervical Instability In 1961, Spitzer and coworkers14 reported atlantoaxial instability in mongolism, now called Down syndrome. This observation has been supported by multiple subsequent publications that have also documented the complications of spinal cord compromise and death.15-21 Despite decades of clinical observations and radiographic studies of the cervical spine in Down syndrome, we do not yet fully comprehend the integral factors that contribute to the development of cervical instability nor the natural history of abnormalities noted on radiographs. We do know that lateral flexion and extension radiographs of the cervical spine in Down syndrome may demonstrate significant differences when compared with those of the general population. Although increased intersegmental mobility of cervical spine segments may be objectively documented in Down syndrome, we are not certain of the clinical significance of these measurements because most affected individuals will remain asymptomatic throughout their life. We also know that sudden catastrophic neurologic impairment and death have been reported in this population as a result of cervical spinal instability.20 The challenge in this condition is to identify radiographic variations that correlate with true risk for neurologic injury and to distinguish them from variations that have no clinical significance. With this information, clinicians could avoid undertreatment or neglect of the at-risk individual and overtreatment, including unnecessary exclusion from sports activity, for the remainder of the Down population. Public awareness of instability of the cervical spine in individuals with Down syndrome has been heightened through the efforts of the Special Olympics organization. Although recommendations for screening of those involved in Special Olympic competition vary significantly throughout the nation, parental concern regarding potential neurologic injury of their children has prompted a variety of recommendations. Preparticipation screening of athletes is not standardized.
137 The screening process may include clinical history and physical examination alone or combined with lateral flexion and extension radiographs of the cervical spine. This evaluation may occur as a one-time event or be serially repeated at variable intervals of time. Recommendations in regards the appropriate levels of competition for young athletes with Down syndrome vary from no limitations to total prohibition of involvement in any sports activity. The lack of uniformity may foster confusion for all involved and may have impact on the young athlete’s health, happiness and general well-being as well as create parental anxiety. We do know that individuals with early myelopathy will complain of decreased physical endurance before the onset of neurologic deficits, pathologic reflexes, or sphincter dysfunction. Therefore, it is extremely important to educate athletes and their caretakers about early warning signs of myelopathy, such as significant decrease in ability to walk a given distance that had been easily achievable in the recent past. Associated comorbidities, such as cardiac or thyroid dysfunction, may be responsible for the observed diminished physical activity; however, cervical spine instability has the potential for irreversible and profound spinal cord damage and must be ruled out by dynamic radiographic evaluation of the cervical spine. In the absence of radiographic cervical spine instability, medical evaluation is indicated. Obtaining radiographs of the cervical spine that are technically adequate can be a challenge with the individual with Down syndrome. When the young athlete is apprehensive and will not cooperate with positioning for neutral lateral radiographs of the cervical spine, images may be generated that portray spurious findings. Tilting of the head, rotation of the neck to one side, and incomplete effort in full flexion or extension of the neck result in poor images of the cervical spine and impede the evaluation of intersegmental instability. When neutral lateral radiographs cannot be obtained by routine methods, cineradiography can be helpful in aligning the head and neck in a neutral position for both flexion and extension views. The author recommends that the athlete’s treating physician be present during cineradiographic study to assist in successful imaging of the cervical spine. The clinician can allay the patient’s fear of the unknown, aid in positioning and directly observe the patient’s cooperation and effort in fully flexing and extending the neck. Neutral lateral flexion and extension radiographs of the cervical spine will allow accurate evaluation of the anatomy and stability of the occipitoatlantal junction, the atlantoaxial junction and each of the subaxial segments of the cervical spine (Fig. 3). If standard parameters of radiographic instability of the cervical spine that have been derived from the general population are applied to radiographs of individuals with Down syndrome, a significant percentage of studies will be interpreted as abnormal. On the basis of standards derived from observation of the general population, 20% of those with Down syndrome will demonstrate atlantoaxial instability and a greater number will demonstrate occipitoatlantal instability15 When followed into adulthood, 33% of individuals will exhibit radiographic abnormalities of the cervical spine, yet only 3% will develop neurologic problems.22
138
Figure 3 Lateral flexion and extension radiographs of the cervical spine in neutral allow accurate assessment of atlantoaxial integrity.
The lack of correlation of radiographic abnormalities of the cervical spine with clinical findings in the Down population has resulted in the author’s substitution of the term hypermobility for instability. Hypermobility connotes increased intersegmental motion with preserved spinal column integrity to protect the spinal cord, whereas instability implies a severe degree of intersegmental motion that threatens integrity of neural tissues. Confirmation of this concept will require the critical evaluation of a large sample of technically correct radiographs of the cervical spine in individuals with Down syndrome who are serially evaluated by clinical examination and by imaging of the cervical spine into adulthood. Only then can the natural history and clinical significance of radiographic changes of the cervical spine in Down syndrome be determined. Increased excursion of the cervical spine has been observed on lateral flexion and extension radiographs in Down syndrome at the occipitoatlantal junction and at the atlantoaxial junction. Occipitoatlantal instability in the general population is most commonly the result of severe trauma, such as vehicular injury. In the Down population, Tredwell documented posterior subluxation of the occipitocervical junction in 43 of 64 children with no reported neurologic deficits.15
P.D. Pizzutillo and M.J. Herman Other investigators have noted anterior occitipoatlantal hypermobility in children and adolescents with Down syndrome. Although occipitoatlantal hypermobility usually is not associated with neurologic risk, significant neurologic impairment has been reported in individuals with Down syndrome. This is more likely when hypermobility at the occipitoatlantal junction coexists with bony anomalies of the base of the skull, such as basilar invagination, with bony anomalies of the upper cervical spine, such as os odontoideum and atlantal arch hypoplasia, or in the presence of atlantoaxial instability.23,24 Measurement of occipitoatlantal instability on lateral radiographs is difficult with low interobserver reliability.25 Sagittal CT scan reconstructions in flexion and extension can provide more precise anatomic landmarks to facilitate evaluation. The author’s preferred technique for evaluation of motion of the occipitoatlantal junction is with the use of cineradiography to directly position the head and neck in neutral and to avoid rotational malalignment. If hypermobility of the occipitoatlantal junction is observed, it is important to review the athlete’s function history and to repeat a detailed physical examination, including a neurologic evaluation. If there is suggestion of cord compromise, MRI of the brainstem and cervical spinal cord and somatosensory-evoked potentials will help in determining the clinical significance of alterations noted on radiographs or CT scan. If these studies confirm cord compromise, posterior stabilization of occiput to C2 or to C3 is indicated to protect the cord from increasing injury and to allow healing of neural tissues. When cord injury is not confirmed, the individual and caretakers should be informed of the presence of occipitoatlantal hypermobility and advised that the young athlete should avoid high-risk activity, such as tumbling, gymnastics, football, ice hockey, wresting, and rugby, but may participate in noncontact sports. The authors recommend an annual history and physical examination of active individuals with occipitoatlantal hypermobility with serial radiographic evaluation of the cervical spine at a frequency dictated by the individual’s clinical status. There have been multiple reports of atlantoaxial instability in Down syndrome with an incidence of 10% to 30% of studied individuals. Lateral flexion and extension radiographs of the cervical spine allow measurement of the atlantodens interval (ADI) or the distance between the inferior border of the anterior arch of the atlas and the anterior border of the odontoid process (Fig. 4). In the general population, ADI up to 4.5 mm in children and 3 mm in adults is considered normal. In the Down population, ADI up to 10 mm has been observed in asymptomatic individuals. The neurologically normal individual with Down syndrome with ADI greater than 4.5 mm but less than 10 mm may participate in sports activity but should avoid high-risk activities, as noted previously. If an individual exhibits an ADI greater than 4.5 mm and has neurologic impairment, MRI of the cervical spinal cord aids in assessment of cord injury and, when present, posterior fusion of the atlantoaxial junction is indicated. In individuals with long-standing displacement of the atlas on the axis, laminectomy of the posterior arch of the
Musculoskeletal concerns in the young athlete with Down syndrome
139
Figure 4 Lateral radiograph of cervical spine in flexion reveals increased ADI.
atlas with atlantoaxial fusion may be required but surgical reduction of the atlas on the axis has frequently resulted in catastrophic neurologic complications and should be avoided. With increases in the ADI, there is a concomitant decrease in the space-available-for the cord (SAC; Fig. 5). When the ADI is 10 mm or greater, the odontoid process is impinging on the cord with the likelihood of subsequent myelopathy. Under these conditions, there is significant risk of neurologic damage with sudden flexion and extension movement of the neck and it is recommended that posterior fusion of the atlantoaxial junction be performed, even in the neurologically normal individual. The subaxial cervical spine usually is not affected in the child and adolescent but will exhibit degenerative changes of
Figure 5 Line drawing illustrates space-available-for cord (SAC).
Figure 6 Lateral radiograph of cervical spine in neutral alignment reveals multiple levels of degenerative disc disease.
the disc and apophyseal joints in adulthood (Fig. 6).26,27 There is little risk of neurologic compromise with these findings. Discomfort caused by degenerative changes usually is managed well with symptomatic treatments.
Conclusion The young athlete with Down syndrome is able to participate in sports activity and enjoy the same sense of camaraderie, accomplishment and pride that other young athletes experience. Annual evaluation of the athlete by physical examination and history is important for the early detection of extremity and spinal problems. Patellar instability, hip pathology and bunions are reported with increased frequency in this population and need to be appropriately treated for maintenance of function and the ability to participate in sports. Baseline lateral flexion and extension radiographs of the cervical spine must not be evaluated with standard criteria for instability derived from the non-Down population. Hypermobility at the occipitoatlantal junction and at the atlantoaxial junction are frequently observed and may never result in neurologic compromise. When hypermobility is documented, sports participation may include noncontact sports but should avoid sports that are at high risk for neck injury. When true instability and neurologic deficits are noted, surgical stabilization of the cervical spine is indicated.
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References 1. Bittles AH, Glasson EJ: Clinical, social and ethical implications of life expectancy in Down syndrome. Dev Med and Child Neuro 46:282286, 2004 2. Special Olympics bulletin. Participation by Individuals with Down Syndrome Who Suffer From Atlantoaxial Dislocation Condition. Washington, DC: Special Olympics, March 31, 1983 3. Ng DK, Chan C: Obesity is an important risk factor for sleep disordered breathing in children with Down syndrome. Sleep 27:1023-1024, 2004 4. Murph J, Hoey HMCV, Philip M, et al: Guidelines for the medical management of Irish children and adolescents with Down syndrome. Irish Med J 98:48-52, 2005 5. Van Allen MI, Fung J, Jurenka SB: Health care concerns and guidelines for adults with Down syndrome. Am J Med Genet 89:100-110, 1999 6. Dugdale TW, Renshaw TS: Instability of the patellofemoral joint in Down syndrome. J Bone Joint Surg 68:405-413, 1986 7. Mendez AA, Keret D, MacEwen GD: Treatment of patellofemoral instability in Down syndrome. Clin Orthop 234:148-158, 1988 8. Bennett GC, Rang M, Roye DP, et al: Dislocation of the hip in trisomy 21. J Bone Joint Surg 64B:289-294, 1982 9. Kirkos JM, Papavasilou KA, Kyrkos MJ, et al: Multidirectional habitual bilateral hip dislocation in a patient with Down syndrome. Clin Orthop 435:263-265, 2005 10. Katz DA, Kim YJ, Millis MBL: Periacetabular osteotomy in patients with Down syndrome. J Bone Joint Surg 87B:544-547, 2005 11. Hresko MT, McCarthy JC, Goldberg MJ: Hip disease in adults with Down syndrome. J Bone Joint Surg 75B:604-607, 1993 12. Bosch P, Johnston CE, Karol L: Slipped capital femoral epiphysis in patients with Down syndrome. J Pediatr Orthop 24:271-277, 2004 13. Dietz FR, Albanese SA, Katz DA, et al: Slipped capital femoral epiphysis in Down syndrome. J Pediatr Orthop 24:508-513, 2004 14. Spitzer R, Rabinowich JY, Wybar KC: A study of abnormalities of the skull, teeth and lenses in mongolism. J Can Med Assoc 84:567-572, 1961
P.D. Pizzutillo and M.J. Herman 15. Tredwell SJ, Newman DE, Lockith G: Instability of the upper cervical spine in Down syndrome. J Pediatr Orthop 10:602-606, 1990 16. Hungerford GD, Akkaraju V, Rawe SE, et al: Atlantooccipital and atlantoaxial dislocation with spinal cord compression in Down syndrome: a case report and review of the literature. Br J Radiol 54:758-761, 1981 17. Davidson RG: Atlantoaxial instability in individuals with Down syndrome: a fresh look at the evidence. Pediatrics 81:857-864, 1988 18. Pueschel SM, Herndon JH, Gelch MM: Symptomatic atlantoaxial subluxation in persons with Down syndrome. J Pediatr Orthop 4:682-688, 1984 19. Ferguson RL, Putney ME, Allen BL Jr.: Comparison of neurologic deficits with atlantodens intervals in patients with Down syndrome. J Spinal Disord 10:246-252, 1997 20. Nader-Sepahi A, Casey ATH, Hayward R, et al: Symptomatic atlantoaxial instability in Down syndrome. J Neurosurg (Pediatrics) 103:231237, 2005 21. Pueschel SM, Findley TW, Furia J, et al: Atlantoaxial instability in Down syndrome: roentgenographic, neurologic and somatosensory evoked potential studies, Pediatrics 110:515-521, 1987 22. Cristofaro RL, Donovan R, Cristofaro J: Orthopaedic abnormalities in an adult population with Down syndrome. Orthop Trans 10:442-443, 1986 23. Braakhekke JP, Gabreels FJ, Renier WO, et al: Cranio-vertebral pathology in Down syndrome. Clin Neurol Neurosurg 87:173-179, 1985 24. Crockard HA, Stevens JM: Craniovertebral junction anomalies in inherited disorders: part of the syndrome or caused by the disorder? Eur J Pediatr 154:504-512, 1995 25. Karol LA, Sheffield EG, Crawford D, et al: Reproducibility in the measurement of atlanto-occipital instability in children with Down syndrome. Spine 21:2463-2467, 1996 26. Frost M, Huffer WE, Sze CI, et al: Cervical spine abnormalities in Down syndrome. Clin Neuropathol 18:250-259, 1999 27. Olive PM, Whitecloud TS III, Bennett JT: Lower cervical spondylosis and myelopathy in adults with Down syndrome. Spine 13:781-784, 1988
D
own syndrome remains the most common human malformation, with an incidence of 1 in 600 live births.1 Although the early development of young children with Down syndrome is characterized by psychomotor delay, many of these children will demonstrate progressive improvement in motor skills with the ability to participate in advanced athletic activities. The Special Olympics organization has created a venue in which athletes with Down syndrome can experience the excitement and satisfaction that result from competition in a variety of sports. Through the sustained interest of members of the Special Olympics governing body and the experience garnered by clinicians from decades of screening and treatment of young athletes with Down syndrome, the public has been educated in regards potential medical and musculoskeletal problems in these individuals.2 Significant medical conditions that could affect the young individual with Down syndrome include cardiac anomalies (the most common is complete atrioventricular septal defect), hypothyroidism, hyperthyroidism, obstructive sleep apnea, and obesity.3,4 In the adult with Down syndrome, hearing and visual disorders, arthritis, coronary artery disease, diabetes, and dementia may develop.5 The medical management of these conditions in the Down population has evolved and resulted in marked improvements in sustaining function and quality of life. Department of Orthopaedic Surgery and Pediatrics, Drexel University College of Medicine, and Orthopaedic Surgery, St. Christopher’s Hospital for Children, Philadelphia, PA. Address reprint requests to Peter D. Pizzutillo, MD, St. Christopher’s Hospital for Children, E Erie Ave & N Front St, Philadelphia, PA 19134. E-mail: [email protected]
1060-1872/06/$-see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1053/j.otsm.2006.06.002
Ligamentous laxity and hypotonia frequently are observed in the active young athlete with Down syndrome and may increase the risk of injury. In addition to acute musculoskeletal injuries, patellar instability, hip instability, slipped capital femoral epiphysis, bunions, and cervical spine instability may develop without an identifiable proximate cause.
Patellar Instability Sudden and unexpected giving way of the knee may be experienced as atraumatic subluxation or dislocation of the patella and is more commonly observed in teenagers or adults rather than in the child with Down syndrome.6 Although spontaneous reduction of the patella is the rule, the patient may experience low-grade discomfort and a tendency for recurrent patellar instability. Hemarthrosis or significant effusion of the knee, acute disruption of the medial retinaculum, and intra-articular fractures of the knee frequently are associated with acute patellar instability in the non-Down population but are not usually observed in the Down population. Nonsurgical interventions consisting of strengthening of the quadriceps mechanism and the use of patellar restraining braces frequently are effective in controlling instability. When instability persists despite these interventions, surgical treatment is indicated.7 Soft-tissue stabilization of the patellofemoral complex may require both distal and proximal procedures to balance forces about the patella. Imbrication of the medial retinaculum and advancement of the vastus medialis obliquus also may require medial reinforcement with the semitendinosis tendon. Bony procedures involving reorientation of the tibial tubercle are not commonly needed in this 135
136
Figure 1 (A) Anteroposterior (AP) radiograph of hips and pelvis reveal mild subluxation of hips. (B) AP radiograph reveals progressive degenerative hip disease of both hips.
P.D. Pizzutillo and M.J. Herman of the femoral head and of the acetabulum and to dynamically analyze the direction of instability. Severe capsular and ligamentous laxity of the hip make clinical estimation of femoral torsion unreliable; computed tomography (CT) scan or magnetic resonance imaging (MRI) evaluation of the femur will more precisely determine the degree of existing anteversion or retroversion. Because the femoral head is frequently displaced posteriorly in this population, MRI or arthrography of the hip joint may provide information in regards the competence of the acetabulum, especially dysplasia of the posterior acetabular rim.10 Capsulorrhaphy of the hip joint, as an isolated procedure, is insufficient to maintain hip joint stability. Surgical correction of anteversion or retroversion of the femur and restoration of a competent acetabular rim have increased the success of hip stabilization. Despite a variety of surgical approaches to this problem, recurrent instability following surgical treatment is not uncommon and parents must be informed of this potential complication. In the mature individual, low-grade instability frequently leads to progressive, severe degenerative joint disease with resultant limited joint motion, pain with ambulation, and loss of function (Fig. 1).11 Maintenance of ambulatory function is important because it contributes to a better quality of life for the individual and eases the daily demands on the individual’s caretaker. Surgical intervention includes Chiari osteotomy of the ilium, arthrodesis of the hip joint, and total hip replacement. There are no clear guidelines for total hip replacement in the adult Down patient with advanced hip joint disease. Complications may include infection, dislocation of the joint components, and loosening of the femoral or acetabular components.
population because soft-tissue laxity is the prime factor in patellar instability.
Slipped Capital Femoral Epiphysis
Hip Joint Instability
Slipped capital femoral epiphysis (SCFE) has been reported with a greater incidence in the Down population than in the general population (Fig. 2).12,13 This can be explained in part by the increased incidence of obesity and of thyroid dysfunction in Down syndrome. Both of these factors have had a positive correlation with the development of SCFE in the
Instability of the hip joint may be observed in individuals with Down syndrome from the time of infancy to adulthood.8 Although ligamentous instability and hypotonia have been considered important factors in the development of hip instability in this population, we are not yet fully aware of all contributing factors. Hip subluxation and dislocation usually are noted in the first decade of life and present insidiously without a history of trauma or pain. Typically, a sudden, palpable displacement about the hip joint is noted during diapering or perineal care and medical advice is sought on an urgent basis. Physical examination will not detect evidence of trauma or neurologic loss but will reveal painless dislocation and relocation of the hip with abduction and adduction maneuvers. The very young child with hip instability may be treated with cast immobilization followed by abduction bracing.9 The success of this intervention is unpredictable but will provide prolonged hip stability in a proportion of patients. When immobilization has been used for 6 to 12 months and has failed to stabilize the hip joint, surgical intervention becomes more appropriate. It is critical to evaluate the anatomy
Figure 2 AP radiograph reveals unilateral SCFE.
Musculoskeletal concerns in the young athlete with Down syndrome general population. When compared with patients with SCFE in the general population, affected individuals with Down syndrome have a higher incidence of complications, including progressive degenerative changes of the hip and avascular necrosis of the femoral head. Although there is an expectation that the more secure fixation of SCFE provided by large cannulated screws may improve the ultimate results of surgical intervention, continued research is needed to improve our understanding of pathologic factors and to design more effective modes of treatment.
Bunions The development of bunions is common in individuals with Down syndrome and is likely related to hyperpronation of the flexible flatfoot in this population. It is fortunate that the majority of affected individuals will remain asymptomatic without impairment of ambulatory function. Surgical intervention is infrequently indicated since shoe modifications are usually effective in providing comfort.
Cervical Instability In 1961, Spitzer and coworkers14 reported atlantoaxial instability in mongolism, now called Down syndrome. This observation has been supported by multiple subsequent publications that have also documented the complications of spinal cord compromise and death.15-21 Despite decades of clinical observations and radiographic studies of the cervical spine in Down syndrome, we do not yet fully comprehend the integral factors that contribute to the development of cervical instability nor the natural history of abnormalities noted on radiographs. We do know that lateral flexion and extension radiographs of the cervical spine in Down syndrome may demonstrate significant differences when compared with those of the general population. Although increased intersegmental mobility of cervical spine segments may be objectively documented in Down syndrome, we are not certain of the clinical significance of these measurements because most affected individuals will remain asymptomatic throughout their life. We also know that sudden catastrophic neurologic impairment and death have been reported in this population as a result of cervical spinal instability.20 The challenge in this condition is to identify radiographic variations that correlate with true risk for neurologic injury and to distinguish them from variations that have no clinical significance. With this information, clinicians could avoid undertreatment or neglect of the at-risk individual and overtreatment, including unnecessary exclusion from sports activity, for the remainder of the Down population. Public awareness of instability of the cervical spine in individuals with Down syndrome has been heightened through the efforts of the Special Olympics organization. Although recommendations for screening of those involved in Special Olympic competition vary significantly throughout the nation, parental concern regarding potential neurologic injury of their children has prompted a variety of recommendations. Preparticipation screening of athletes is not standardized.
137 The screening process may include clinical history and physical examination alone or combined with lateral flexion and extension radiographs of the cervical spine. This evaluation may occur as a one-time event or be serially repeated at variable intervals of time. Recommendations in regards the appropriate levels of competition for young athletes with Down syndrome vary from no limitations to total prohibition of involvement in any sports activity. The lack of uniformity may foster confusion for all involved and may have impact on the young athlete’s health, happiness and general well-being as well as create parental anxiety. We do know that individuals with early myelopathy will complain of decreased physical endurance before the onset of neurologic deficits, pathologic reflexes, or sphincter dysfunction. Therefore, it is extremely important to educate athletes and their caretakers about early warning signs of myelopathy, such as significant decrease in ability to walk a given distance that had been easily achievable in the recent past. Associated comorbidities, such as cardiac or thyroid dysfunction, may be responsible for the observed diminished physical activity; however, cervical spine instability has the potential for irreversible and profound spinal cord damage and must be ruled out by dynamic radiographic evaluation of the cervical spine. In the absence of radiographic cervical spine instability, medical evaluation is indicated. Obtaining radiographs of the cervical spine that are technically adequate can be a challenge with the individual with Down syndrome. When the young athlete is apprehensive and will not cooperate with positioning for neutral lateral radiographs of the cervical spine, images may be generated that portray spurious findings. Tilting of the head, rotation of the neck to one side, and incomplete effort in full flexion or extension of the neck result in poor images of the cervical spine and impede the evaluation of intersegmental instability. When neutral lateral radiographs cannot be obtained by routine methods, cineradiography can be helpful in aligning the head and neck in a neutral position for both flexion and extension views. The author recommends that the athlete’s treating physician be present during cineradiographic study to assist in successful imaging of the cervical spine. The clinician can allay the patient’s fear of the unknown, aid in positioning and directly observe the patient’s cooperation and effort in fully flexing and extending the neck. Neutral lateral flexion and extension radiographs of the cervical spine will allow accurate evaluation of the anatomy and stability of the occipitoatlantal junction, the atlantoaxial junction and each of the subaxial segments of the cervical spine (Fig. 3). If standard parameters of radiographic instability of the cervical spine that have been derived from the general population are applied to radiographs of individuals with Down syndrome, a significant percentage of studies will be interpreted as abnormal. On the basis of standards derived from observation of the general population, 20% of those with Down syndrome will demonstrate atlantoaxial instability and a greater number will demonstrate occipitoatlantal instability15 When followed into adulthood, 33% of individuals will exhibit radiographic abnormalities of the cervical spine, yet only 3% will develop neurologic problems.22
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Figure 3 Lateral flexion and extension radiographs of the cervical spine in neutral allow accurate assessment of atlantoaxial integrity.
The lack of correlation of radiographic abnormalities of the cervical spine with clinical findings in the Down population has resulted in the author’s substitution of the term hypermobility for instability. Hypermobility connotes increased intersegmental motion with preserved spinal column integrity to protect the spinal cord, whereas instability implies a severe degree of intersegmental motion that threatens integrity of neural tissues. Confirmation of this concept will require the critical evaluation of a large sample of technically correct radiographs of the cervical spine in individuals with Down syndrome who are serially evaluated by clinical examination and by imaging of the cervical spine into adulthood. Only then can the natural history and clinical significance of radiographic changes of the cervical spine in Down syndrome be determined. Increased excursion of the cervical spine has been observed on lateral flexion and extension radiographs in Down syndrome at the occipitoatlantal junction and at the atlantoaxial junction. Occipitoatlantal instability in the general population is most commonly the result of severe trauma, such as vehicular injury. In the Down population, Tredwell documented posterior subluxation of the occipitocervical junction in 43 of 64 children with no reported neurologic deficits.15
P.D. Pizzutillo and M.J. Herman Other investigators have noted anterior occitipoatlantal hypermobility in children and adolescents with Down syndrome. Although occipitoatlantal hypermobility usually is not associated with neurologic risk, significant neurologic impairment has been reported in individuals with Down syndrome. This is more likely when hypermobility at the occipitoatlantal junction coexists with bony anomalies of the base of the skull, such as basilar invagination, with bony anomalies of the upper cervical spine, such as os odontoideum and atlantal arch hypoplasia, or in the presence of atlantoaxial instability.23,24 Measurement of occipitoatlantal instability on lateral radiographs is difficult with low interobserver reliability.25 Sagittal CT scan reconstructions in flexion and extension can provide more precise anatomic landmarks to facilitate evaluation. The author’s preferred technique for evaluation of motion of the occipitoatlantal junction is with the use of cineradiography to directly position the head and neck in neutral and to avoid rotational malalignment. If hypermobility of the occipitoatlantal junction is observed, it is important to review the athlete’s function history and to repeat a detailed physical examination, including a neurologic evaluation. If there is suggestion of cord compromise, MRI of the brainstem and cervical spinal cord and somatosensory-evoked potentials will help in determining the clinical significance of alterations noted on radiographs or CT scan. If these studies confirm cord compromise, posterior stabilization of occiput to C2 or to C3 is indicated to protect the cord from increasing injury and to allow healing of neural tissues. When cord injury is not confirmed, the individual and caretakers should be informed of the presence of occipitoatlantal hypermobility and advised that the young athlete should avoid high-risk activity, such as tumbling, gymnastics, football, ice hockey, wresting, and rugby, but may participate in noncontact sports. The authors recommend an annual history and physical examination of active individuals with occipitoatlantal hypermobility with serial radiographic evaluation of the cervical spine at a frequency dictated by the individual’s clinical status. There have been multiple reports of atlantoaxial instability in Down syndrome with an incidence of 10% to 30% of studied individuals. Lateral flexion and extension radiographs of the cervical spine allow measurement of the atlantodens interval (ADI) or the distance between the inferior border of the anterior arch of the atlas and the anterior border of the odontoid process (Fig. 4). In the general population, ADI up to 4.5 mm in children and 3 mm in adults is considered normal. In the Down population, ADI up to 10 mm has been observed in asymptomatic individuals. The neurologically normal individual with Down syndrome with ADI greater than 4.5 mm but less than 10 mm may participate in sports activity but should avoid high-risk activities, as noted previously. If an individual exhibits an ADI greater than 4.5 mm and has neurologic impairment, MRI of the cervical spinal cord aids in assessment of cord injury and, when present, posterior fusion of the atlantoaxial junction is indicated. In individuals with long-standing displacement of the atlas on the axis, laminectomy of the posterior arch of the
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Figure 4 Lateral radiograph of cervical spine in flexion reveals increased ADI.
atlas with atlantoaxial fusion may be required but surgical reduction of the atlas on the axis has frequently resulted in catastrophic neurologic complications and should be avoided. With increases in the ADI, there is a concomitant decrease in the space-available-for the cord (SAC; Fig. 5). When the ADI is 10 mm or greater, the odontoid process is impinging on the cord with the likelihood of subsequent myelopathy. Under these conditions, there is significant risk of neurologic damage with sudden flexion and extension movement of the neck and it is recommended that posterior fusion of the atlantoaxial junction be performed, even in the neurologically normal individual. The subaxial cervical spine usually is not affected in the child and adolescent but will exhibit degenerative changes of
Figure 5 Line drawing illustrates space-available-for cord (SAC).
Figure 6 Lateral radiograph of cervical spine in neutral alignment reveals multiple levels of degenerative disc disease.
the disc and apophyseal joints in adulthood (Fig. 6).26,27 There is little risk of neurologic compromise with these findings. Discomfort caused by degenerative changes usually is managed well with symptomatic treatments.
Conclusion The young athlete with Down syndrome is able to participate in sports activity and enjoy the same sense of camaraderie, accomplishment and pride that other young athletes experience. Annual evaluation of the athlete by physical examination and history is important for the early detection of extremity and spinal problems. Patellar instability, hip pathology and bunions are reported with increased frequency in this population and need to be appropriately treated for maintenance of function and the ability to participate in sports. Baseline lateral flexion and extension radiographs of the cervical spine must not be evaluated with standard criteria for instability derived from the non-Down population. Hypermobility at the occipitoatlantal junction and at the atlantoaxial junction are frequently observed and may never result in neurologic compromise. When hypermobility is documented, sports participation may include noncontact sports but should avoid sports that are at high risk for neck injury. When true instability and neurologic deficits are noted, surgical stabilization of the cervical spine is indicated.
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