Scheuermann's kyphosis

Overview

• 1^st described by Holger Scheuermann in 1921, a Danish physician
• Structural deformity characterized by anterior wedging of ³5° of three adjacent thoracic vertebrae (Sorensen, 1964); ³50° thoracic kyphosis abnormal
• Secondary radiographic findings of Schmorl's nodes, endplate narrowing, irregular endplates
• Adolescents typically present secondary to cosmetic deformity; adults secondary to pain
• Etiology unclear, indications for treatment debatable

Normal Thoracic Kyphosis

• Curvature extends from T2-T12 w/ T7 most dorsal vertebrae
• Anterior elements of spinal column resist compressive forces, posterior ligamentous structures resist tensile forces
• Kyphotic deformity may occur if anterior column unable to withstand compression, causing shortening of anterior column

• Typically increases throughout life; sagittal alignment of the thoracic spine displays a range of normal that is dynamic
• Scoliosis Research Society:
  1. Normal range thoracic kyphosis for growing adolescent 20-40°
  2. Any kyphosis at thoracolumbar or lumbar area abnormal

Epidemiology

• Prevalence of 0.4 to 8.3% (Sorensen, 1964)
• Two studies that Sorensen cited in 1951, 1955 reported prevalence of 0.4% - may have contained inherent bias as included only men rejected for military service
• Prevalence of 7.4% in subsequent review of 1,384 cadavers (Scoles, 1991)
• Prevalence approximately equal in males and females
• Radiographic findings c/w Scheuermann's not visible until age 12-13 (puberty); Hence, adolescent girls typically evidence findings 1^st 

Pathogenesis

• Many theories proposed but has yet to be elucidated
• Scheuermann hypothesized that AVN of ring apophysis (ring of cartilage about developing vertebral body) leads to premature cessation of growth anteriorly à vertebral body wedging
• Schmorl postulated that herniations of disk material through vertebral endplates lead to loss of disk height and anterior wedging
• Underlying genetic factor suggested (Halal, 1978; Skogland, 1985)
• Correlation with height and increased levels of growth hormone (Ascani, 1990)
• Gross anatomic findings: thickened ALL, narrowed vertebral disks, wedged vertebral bodies
• Histologic abnormality: decreased collagen to proteoglycan ratio in matrix of endplate à ?alteration in ossification and thus altered vertical growth
• Early osteoporosis may be an etiologic factor
• Mechanical factors: Scheuermann found high incidence in industrial workers

Clinical Evaluation

• Indications for treatment can be grouped into five categories: pain, progression of deformity, neurologic compromise, cardiopulmonary compromise, cosmesis
• Pain 50% (Sorensen, 1964)- Adolescents often p/w cosmetic or postural complaints; adults - pain
  - Usually paraspinal, just distal to apex of deformity
  - Often activity-related, relieved by rest; sometimes simply early fatigue

• Progression of deformity- Pay attention to h/o curve; delays in Dx possible if ignored, thought to be just poor posture

• Neurologic compromise- Cord compression mandates surgical treatment (rare)
  - Ranges from acute onset unilateral radiculopathy to insidious onset spastic paraplegia
  - 54° (Ryan and Taylor, 1982) to 95° (Lonstein, 1980)
  - Extradural cysts and thoracic disk herniations may contribute

• Cardiopulmonary compromise      - Extremely rare on initial presentation
          - Sorensen reported no negative effects
          - Murray reported restrictive pulmonary disease in curves >100° w/ apex in upper thoracic region

• Cosmesis      - Address w/ patient

• Physical Exam      - Sagittal deformity fairly rigid in hyperextension; in postural kyphosis, more correctable
          - Have patient bend forward, view deformity from side ("A-frame")
          - Typically increased cervical and lumbar lordosis
          - Shoulder girdles often rotated anteriorly
          - Evaluate for hamstring tightness, lower extremity neurologic function

Radiologic Evaluation

• Routine studies: AP & lateral (standing) XR of entire spine on long films and hyperextension lateral of thoracic spine
• Lateral XR: Schmorl's nodes, disk space narrowing, irregular endplates, vertebral wedging ³5° of three adjacent bodies (use Cobb technique)
• Lateral XR: r/o lumbar hyperlordosis, spondylolysis (30-50%), degenerative
• AP XR: r/o scoliosis (1/3 Scheuermann's kyphosis)
• Lateral XR in hyperextension: to assess flexibility of kyphosis; r/o postural kyphosis (as much as 60° deformity correctable) - Schmorl's nodes, etc. absent
• Presence of anterior bar à congenital kyphosis       

Natural History

• Wide variation in natural history; patients w/ mild deformities have few clinical sequelae but a subset of patients have refractory symptoms
• Back pain and fatigue in adolescent may improve w/ skeletal maturity
• Paajaanen et al(1989) reported 55% of disks in young adults w/ Scheuermann's w/ abnormal MRI changes (rate five times that in asymptomatic controls)
• The Natural History and Long-term Follow-up of Scheuermann Kyphosis (JBJS-A, Murray et al, 1993)      - 67 patients w/ mean kyphotic angle 71° for average 32 years (compared w/ age-            matched controls)
        - Back pain more intense and localized in thoracic spine
  - Had less demanding jobs, less extension of thoracic spine
  - Similar, however, overall quality of life; little preoccupation w/ appearance
        - Higher incidence of restrictive lung disease kyphotic curves >100°
  -           Bradford et al(1977) reported 50% incidence severe pain w/ increased incidence pain when kyphosis centered over upper lumbar spine
  -           Lowe et al(1987) reported severe deformity and back pain as common sequelae in adolescents who went untreated

Treatment

• Ranges from observation to anterior and posterior reconstructive surgery

Nonoperative

• Anti-inflammatory medications - useful short-term adjunct
• Exercise - extension or postural exercises will not improve or halt progression of fixed deformity, but thoracic extension program combined w/ aerobic exercise may improve physical conditioning and decrease pain
• Bracing -Typically reserved for patients w/ 1 yr or more of skeletal growth remaining (Risser's stage 3 or below)
  -can provide up to 50% correction of deformity but gradual loss of correction over time
        - 45° can be used as threshold (Sachs, 1987)
        - Milwaukee-style brace (neck ring and anterior and posterior uprights connected to pelvic girdle)
        - Obtain lateral radiograph to confirm proper fit w/ f/u in 3-4 wks for brace check, then every 4-6 mo
  - Sachs et al (1987): 1) 120 patients f/u >5 yrs after brace discontinued, 69% still had improvement 3° or more from initial radiograph  2) When deformity ³74°,         brace treatment failed
        - Role of bracing in skeletally mature patient less clear

Operative

• Adolescent w/ curve ³75° despite appropriate bracing may be candidate
• Goals of treatment: safely obtain solid arthrodesis throughout length of kyphosis w/ correction of deformity
• Posterior-only, anterior-only, or combined anterior-posterior approach
• Abnormal kyphosis corrected by surgically shortening posterior column or lengthening anterior column or both

Anterior-only approach

• Described by Kostuik (1988), less widely used
• Anterior diskectomy and interbody fusion and anterior instrumentation w/ Harrington distraction system augmented by postop bracing
• 36 patients - reduction of mean preop deformity of 75.5° to 60°

Posterior-only approach

• Advantages: decreased EBL and surgical time, no risks of thoracotomy
• Disadvantages: higher rate of pseudoarthrosis, less correction
• Recommended approach for flexible deformity that corrects on hyperextension to <50°; may add segmental fixation and posterior facetectomy for greater deformities

Anterior-Posterior approach

• For more rigid deformities (>75°) that does not correct to <50° on hyperextension lateral view*;* one sitting or staged
• Anterior approach open or thoracoscopically, right side to avoid great vessels
• Anterior release and interbody fusion performed on all levels that are wedged or have a narrowed disk space
• Posterior correction performed by compression technique or leverage technique
• Posterior fusion w/ dual rods segmentally attached to compression instrumentation is treatment of choice, preceded by anterior release and interbody fusion
• Harrington compression system vs. segmental posterior systems (Cotrel-Dubousset, Texas Scottish-Rite Hospital, Isola) that obviate need for postop brace
• Overall correction should not exceed 50% initial deformity or <40° - reduces risk of proximal and distal junctional kyphosis

Lumbar Scheuermann's disease

• Less common
• More often causes back pain on mechanical basis (more common in athletes and manual laborers)
• Pain often self-limited
• Same radiographic findings but NOT associated w/ vertebral wedging

References

• Scheuermann's Kyphosis in Adolescents and Adults: Diagnosis and Management.  Tribus, C.B.  JAAOS.  1998; 6:36-43
• Scheuermann's Disorder.  Koop, S.E.  OKU: Pediatrics 2.
• Review of Orthopaedics, 4^th ed.  Miller, M.D.
• Cambell's Operative Orthopaedics.