BLOUNT'S DISEASE

STEVEN R. BOYEA, M.D., Resident, Orthopaedic Surgery

J. RICHARD BOWEN, M.D., Chief, Orthopaedic Surgery

June 10, 1996

CLINICAL CASE PRESENTATION

ORTHOPAEDIC DEPARTMENT

THE ALFRED I. DUPONT INSTITUTE

WILMINGTON, DELAWARE

CASE HISTORY:

History: The patient is a 14 + 6 year old black male with a one year history of progressively worsening left knee pain. He states that the pain began in both knees and was intermittent, Tylenol helped alleviate the pain. Over the past 6 months the pain is more isolated to the left knee and has become constant in nature. Within the last 2 weeks the constant pain has become bad enough to limit his activities. He is unable to attend school or walk more than several hundred feet because of the pain. The pain is now affecting his sleep. He does get some relief with rest and elevation of the knee. The pain also limits his motion in that knee. He denies any trauma to the knee and has no other medical problems. He is not taking any medications. There is no family history of leg deformities.

Physical Exam: The adolescent is a morbidly obese 14 + 6 year old black male. His extremity exam reveals an asymmetric pelvis with the right being elevated. There is a leg length inequality with the left leg being about 3.5 cm shorter than the right. He also demonstrates a significant proximal tibia vara of about 35^o. There was tenderness to palpation over the medial proximal metaphysis with some mild medial joint line tenderness. The knee demonstrated mild medial laxity on valgus stress. He does not demonstrate any anterior or posterior laxity or instability. There is knee flexion from 0-120^o with some tenderness. Hip and ankle show full range of motion and hi is neurovascularly intact. Strength is 5/5 in all muscle groups.

Radiographs: AP/Lateral of left knee from September of 1995 demonstrate a mild varus deformity with an estimated metaphyseal/diaphyseal angle of 8^o. There is also evidence of widening of the medial 1/3 of the proximal tibial physis . The AP of the left knee in May of 1996 shows worsening of the varus deformity with a metaphyseal/diaphyseal angle of 14^o. There is increased widening of the medial proximal tibial physis with evidence of sclerosis. The scanogram demonstrated a 4 cm leg length discrepancy, with the left shorter than the right . There is no abnormality in the hip or femur.

Assessment:

• Adolescent Tibia Vara (Blount's Disease) of the left leg
• Morbid Obesity

Treatment:

• Left proximal tibia osteotomy
• Placement of external fixator (Ilizarov) for straightening and possible lengthening

TIBIA VARA

Background:

1. First described by Erlander in 1922.
2. Blount presented 13 cases and reviewed the literature of another 15 cases in 1937 delineating between the different types, adolescent vs. infantile.
3. Langenskiold classified the six progressive radiographic stages in 1952.
4. Definition: Growth disorder of the medial aspect of the proximal tibial physis, with abrupt medial angulation of the proximal tibia distal to the epiphysis, leading to varus angulation of the proximal tibia and medial rotation of the tibia.

Epidemiology:

1. Risk factors
• obesity
• female gender
• afro-american lineage
• walking at an early age
• family history (?), 9-43% have an affected family member
2. Differential diagnosis
• physiologic bow legs, metaphyseal/diaphyseal varus angle less than 11^o
• rickets
• osteomyelitis
• trauma
• Ollier's disease
• metaphyseal chondrodysplasia
• focal fibrocartlaginous dysplasia

Classification:

1. Infantile: (Early onset)
• onset between 1-3 years
• bilateral
• usually symmetric
• occasional resolution
• etiology is abnormal compression on medial proximal tibial physis
2. Juvenile: (Late onset)
• onset between 4-10 years
• unilateral
• associated with a physeal bridge
3. Adolescent: (Late onset)
• onset over 11 years
• same as juvenile

Clinical Features:

1. Infantile:
• non-tender bony prominence or "beak" may be palpable over the medial tibial condyle
• excessive medial tibial torsion
• pronated feet
• shortening of the involved leg
2. Juvenile/Adolescent:
• pain and tenderness over the medial prominence of the proximal tibia
• mild medial knee ligamentous laxity
• obesity
• shortening of involved leg up to 3-4 cm

Radiographic Features:

1. Infantile:
• abrupt medial angulation "beaking" of the medial cortical wall of the proximal tibial metaphysis
• straight lateral wall of proximal tibial metaphysis
• metaphyseal/diaphyseal angle greater than 11^o
• tibial/femoral angle greater than 15^o
2. Juvenile/Adolescent:
• abrupt medial angulation of the medial cortical wall of the proximal tibial metaphysis
• metaphyseal/diaphyseal angle greater then 11^o
• tibial/femoral angle greater than 15^o
• middle part of the medial half of the epiphyseal plate is narrowed
• bony epiphyses are normal in shape with no step-off in the epiphyseal line

Histologic Features:

1. Islands of densely packed hypertrophied cartilage cells, not in the usual columnar organization
2. Acellular fibrous cartilage
3. Abnormal groups of capillary vessels

Staging: (Langenskiold, JBJS, 1964)

1. I: irregular metaphyseal ossification combined with medial and distal protrusion of the metaphysis
2. II, III, IV: evolves from a mild depression of the medial metaphysis to a step-off of the medial metaphysis
3. V: increased slope of medial articular surface and a cleft separating the medial and lateral epicondyle
4. VI: bony bridge across the physis

Management:

1. Non-operative
• observation, if within the first 2 years of life
• orthotics
• age 2-3 years
• metaphyseal/diaphyseal angle > 11^o
• tibial/femoral angle > 15^o
• KAFO is designed to provide rotational support, 23 hrs/day
• 50% progress
• takes 1 year to determine effectiveness
• ineffective in adolescents
2. Operative
• Infantile:
• absolute indications
• depression of the tibial plateau
• impending closure of the medial physis of proximal tibia
• ligamentous laxity of the knee
• relative indications
• metaphyseal/diaphyseal angle > 30^o
• tibial/femoral angle > 15^o
• method
• tibial osteotomy
• tibia rotated outward and angled laterally to give 6-10^o of valgus
• osteotomy of fibula through separate incision
• fixation with external fixator or internal fixation or cast
• Adolescent:
• same indications
• method
• same as above
• +/- epiphysiodesis based on age and leg length discrepancy

REFERENCES

1. Blount, W.P. Tibia vara. J Bone Joint Surg 19(1): 1-29, 1937.
2. Greene, W.B. Infantile tibia vara: Instructional course lecture. J Bone Joint Surg 75A(1): 130-142, 1993.
3. Henderson, R.C. Adolescent tibia vara: Alternatives for operative treatment. J Bone Joint Surg 74A(3): 342-350, 1992.
4. Hoffman, A. Blount's disease after skeletal maturity. J Bone Joint Surg 64A(7): 1004-1009, 1982.
5. Langenskiold, M.D. Tibia vara, osteochondrosis deformans tibiae. J Bone Joint Surg 46A(7): 1405-1420, 1964.
6. Loder, R.T. Infantile tibia vara. J Ped Orthop 7: 639-646, 1987.
7. Schoenecker, P.L. Blount's disease: A retrospective review and recommendations for treatment. J Ped Orthop 5: 181-186, 1985