Study Guide

Down's Syndrome

Key Points:

Description:

Down syndrome (trisomy 21) is one of the most common chromosomal abnormalities to occur in humans. It presents with a characteristic phenotype and multiple associated medical conditions. General features include short stature, distinctive facies, and a variable degree of cognitive impairment. Common orthopaedic manifestations include ligamentous laxity, joint hypermobility, and hypotonia.

Epidemiology:

Down syndrome occurs in 1 in 660 live births. The risk of Down syndrome increases with maternal age. (Alman, 2014)

Clinical Findings:

Common physical features of Down syndrome include short stature, characteristic facies (epicanthal folds, flat nasal bridge, upward-slanting palpebral fissures, small mouth), hand abnormalities, flared iliac wings, ligamentous laxity, joint hypermobility, and hypotonia. Associated medical conditions can include abnormalities of the cardiac, ophthalmologic, otolaryngologic, gastrointestinal, neurological, and endocrine systems. Congenital heart disease and early onset Alzheimer’s disease may significantly impact patients. Patients are also at higher risk of certain cancers, such as leukemia and testicular cancer. (Caird, 2006; Alman, 2014)

Musculoskeletal manifestations are largely related to overall ligamentous laxity and joint hypermobility. These can include cervical spine instability (atlanto-axial or occipito-cervical), hip instability, patellar instability, and foot deformities. Other associated orthopaedic conditions include slipped capital femoral epiphysis (SCFE) and scoliosis. Patients can also develop a rare polyarticular arthropathy similar to juvenile idiopathic arthritis. (Caird, 2006; Alman, 2014)

Imaging Studies:

Radiographs can be helpful in diagnosing cervical spine instability, scoliosis, and hip dysplasia due to chronic instability, SCFE, and foot deformities. Routine screening for cervical instability is controversial; however, evaluation is required prior to patients receiving anesthesia for surgical procedures. Preoperative assessment should include lateral flexion-extension cervical radiographs. (Caird, 2006) If abnormalities are detected, MRI imaging may be warranted. In hip instability cases, advanced imaging (such as CT and MRI) should be considered for planning purposes prior to surgical reconstruction. (Alman, 2014; Sankar, 2012)

Treatment:

Most of the orthopaedic manifestations of Down syndrome can at least initially be managed nonoperatively. Treatment should be based on functional performance rather than radiographic findings. (Alman, 2014)  If planning surgical treatment, preoperative evaluation should include cardiac and cervical spine assessment. (Caird, 2006)

Patients with asymptomatic cervical spine instability can be monitored with periodic neurological and radiographic evaluation. The parents should be advised that certain activities, such as gymnastics or contact sports, may put their child at higher risk of cervical spine injuries. Symptomatic instability is an indication for a stabilization surgery. Cervical spine fusion has been recommended for patients with neurologic symptoms, ≤14 mm of space available for the cord on radiographs, and MRI or CT evidence of cord compression. (Ferguson, 1997) 

Treatment of scoliosis in Down syndrome patients is similar to that of idiopathic scoliosis. Skeletally immature patients with curves less than 30º can be managed with bracing and close follow-up, while surgery is reserved for more severe cases (Cobb angles >50º). (Caird, 2006)

Hip instability is driven both by bony abnormalities and hypermobility. (Shaw, 1992) Congenital hip dislocation is rare. Patients typically have stable hips prior to ambulating and subsequently may develop progressive instability with chronic subluxation or dislocation, which can result in acetabular dysplasia and damage to the femoral head. Treatment is centered around preventing early degenerative changes. Nonoperative management involving closed reduction and prolonged immobilization up to 1 year has been shown to be successful in children younger than 6 years. (Greene, 1998) If this fails or if the severity of the bony abnormalities involved preclude a trial of nonoperative treatment, surgical options include capsular plication and femoral and/or acetabular osteotomies. (Knight, 2011) Total hip arthroplasty can provide pain relief and improved function for patients with painful fixed dislocation and arthritis in adulthood. (Gross, 2013)

Down syndrome patients who present with SCFE are more likely to present with unstable and high-grade slips and demonstrate a higher rate of osteonecrosis. (Dietz, 2004) As in the general pediatric population, SCFE in children with Down syndrome is treated with in situ screw fixation. Thyroid function tests should be obtained as well due to the possibility of an underlying endocrine abnormality. (Alman, 2014)

Patellofemoral instability is more common than hip instability in Down syndrome patients, estimated to occur in 10% to 20% of patients. Many patients are asymptomatic and do not require treatment. Nonoperative management (physical therapy and orthotics) has been shown to maintain or improve ambulation in patients who are ambulatory at baseline. Patients with severe or functionally disabling instability may benefit from surgery. (Bettuzzi, 2009) Surgical treatment involves soft-tissue balancing and bony realignment of the patellar tendon insertion. Degenerative arthritis may still develop regardless of treatment method. (Mendez, 1988)

Foot deformities seen in Down syndrome include pes planovalgus, metatarsus primus varus, and hallux valgus. Mild symptomatic cases can be treated with modified shoe wear, orthotics, and stretching programs. Surgical realignment procedures are generally reserved for patients with intractable pain or inability to ambulate. (Caird, 2006) 

Complications:

There have been many reports of complications following surgical management of the orthopaedic manifestations of Down syndrome. In cases of cervical instability, complications associated with arthrodesis include infection, wound dehiscence, junctional instability, nonunion, bone graft resorption, and neurologic deterioration. (Mik, 2008) Surgical management of hip instability similarly can have a high complication rate, including infection, redislocation or subluxation, nonunion, wound hematoma, and proximal femur fracture. (Bennet, 1982; Katz, 2005) Given the risks associated with surgery, nonoperative management of the musculoskeletal problems of Down syndrome is often recommended initially. When surgery is undertaken, it is imperative that the patient and parents are educated of the higher complication rates.

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References:

  1. Alman BA, Goldberg, MJ. Syndromes of Orthopaedic Importance. In: Weinstein SL, Flynn JM, eds. Lovell and Winter’s Pediatric Orthopaedics, Seventh Edition. Philadelphia, PA: Lippincott; 2014: Chapter 8. 
  2. Bennet GC, Rang M, Roye DP, Aprin H. Dislocation of the hip in trisomy 21. J Bone Joint Surg Br. 1982;64:289-294.
  3. Bettuzzi C, Lampasi M, Magnani M, et al. Surgical treatment of patellar dislocation in children with Down syndrome. Knee Surg Sports Traumatol Arthrosc. 2009;17:334-340.
  4. Caird MS, Wills BP, Dormans JP. Down Syndrome in children: the role of the orthopaedic surgeon. J Am Acad Orthop Surg. 2006;14:610-619.
  5. Dietz FR, Albanese SA, Katz DA. Slipped capital femoral epiphysis in Down syndrome. J Pediatr Orthop. 2004;24:271-277.
  6. Ferguson RL, Putney ME, Allen BL Jr. Comparison of neurologic deficits with atlanto-dens intervals in patients with Down syndrome. J Spinal Disord. 1997;10:246-252.
  7. Green WB. Closed treatment of hip dislocation in Down syndrome. J Pediatr Orthop. 1998;18:643-647.
  8. Gross AE, Callaghan JJ, Zywiel MG, Greiner JJ, Kosashvili Y, Johnson AJ, Clohisy JC, Backstein D, Mont MA.  Total hip arthroplasty in Down syndrome patients: an improvement in quality of life: replacement arthroplasty in Down syndrome (RADS) study group.  J Arthroplasty 2013;28(4):701-706. 
  9. Katz DA, Kim YJ, Millis MB. Periacetabular osteotomy in patients with Down’s syndrome. J Bone Joint Surg Br. 2005;87:544-547.
  10. Knight DM, Alves C, Wedge JH.  Femoral varus derotation osteotomy for the treatment of habitual subluxation and dislocation of the pediatric hip in trisomy 21: a 10-year experience.  J Pediatr Orthop. 2011;31(6):638-643. 
  11. Mendez AA, Keret D, MacEwen GD. Treatment of patellofemoral instability in Down’s syndrome. Clin Orthop Relat Res. 1988;234:148-158.
  12. Mik G, Gholve PA, Scher DM, Widman RF, Green DW. Down syndrome: orthopedic issues. Curr Opin Pediatr. 2008;20:30-36.
  13. Sankar WN, Schoenecker JG, Mayfield ME, Kim YJ, Millis MB.  Acetabular retroversion in Down syndrome.  J Pediatr Orthop 2012;32(3):277-281.
  14. Shaw ED, Beals RK. The hip joint in Down’s syndrome. A study of its structure and associated disease. Clin Orthop Relat Res 1992;278:101-107. 

Top Contributors:

Christine Bowman MD
Karen Bovid MD