RICKETS IN AN ADOPTED CHILD

RICHARD B. ISLINGER, M.D., Orthopaedic Resident

WILLIAM G. MACKENZIE, M.D., Attending Pediatric Orthopaedic Surgeon

July 15,1996

CLINICAL CASE PRESENTATION

ORTHOPAEDIC DEPARTMENT

THE ALFRED I. DUPONT INSTITUTE

WILMINGTON, DELAWARE

CASE HISTORY:

This patient was first seen here at the age of 2 and 1/2 years. She was referred here with the diagnosis of nutritional rickets.

Significant past medical history included the following:

She was adopted from Russia and according the Russian medical documents was born to a mother who suffered from alcohol abuse. She was born prematurely (gestational age not available) at 2000gms, 44cm, with an apgar of 5/6. Furthermore, she had previously been diagnosed with encephalopathy, anemia, fetal alcohol syndrome and rickets. - Since arriving here in the U.S., the adopted mother had her on vitamin supplements for 7 weeks. The mother states that the child began walking at the age of 27 months.

She was seen by both orthopaedics and pediatrics and her physical exam was as follows:

- She was well below the 5th percentile for both height and weight

- There was delayed psycho-motor and speech development

- Multiple rachitic deformities of the skeleton to include severe bowing of the tibias bilaterally (45 degrees), pigeon chest (pectus carinatum), thickened/widened wrists bilaterally and a trendelenberg gait on the left side.

INITIAL LAB STUDIES:

Ca: 9.7 - nl

PO₄: 6.2 - mildly increased

Alk Phos: 401 - mildly increased

UA: WNL

Vit D 1-25: 92 - mildly increased

X-RAY STUDIES:

- "cupping" of the distal radius and distal femur

- widening of the physis

- angular deformities

She was diagnosed with nutritional rickets and was treated with Calciferol 1200ug\day. Her first follow-up was 5 weeks later where she was noted to have a decreased Trendelenburg lurch and a decrease in her wrist thickening. 10 months later on follow-up she had a noticeable decrease in her tibial bowing along with almost complete resolution of the growth plate abnormalities. At her last follow-up on March 4th 1996 (she was 4 + 4yo) she had mild anterior lateral bowing of her tibia bilaterally with a normal thigh-foot angle and a mechanical axis that crossed the midline of her knee.

RICKETS:

Background:

• Earliest description of the disease - 1650
• Numerous etiological pathways but all involve a relative decrease in Ca and/or PO₄ which interferes with epiphyseal growth and normal mineralization of the skeleton in the growing child.
• Despite the many possible causes, the clinical presentation, histology, radiographic changes are virtually identical.

Clinical:

• Rachitic children are apathetic, irritable, with a height and weight below the 3rd percentile
• Dentition is delayed, often they have severe caries and defective enamel
• Spine often has long, smooth dorsal kyphosis (rachitic catback) and the chest shows enlargement of the costal cartilages (rachitic rosary)
• The extremities are most profoundly affected. Long bones are shortened and deformed, ligamentous laxity is common, and fractures are common.

Histology:

• Thin cortices with thin and irregular trabeculae
• Widened osteoid seams (unmineralized segments of bone)
• Relatively normal resting and proliferative zone, with a grossly abnormal zone of hypertrophy
• Zone of hypertrophy is widened 5-15 times normal
• Primary spongiosa show only limited bone formation

Radiographic:

• Osteopenia with thin cortices
• Physis is widened with irregular cupping
• Looser lines-transverse radiolucent lines on concave side of bone, usually not extending to far cortex(most commonly found in renal osteodystrophy and adult osteomalacia)

CAUSES:

• Deficiency- vitamin D intake is inadequate which causes diminished absorption of Ca from the gut.
• Gastrointestinal- interference with bile salt production which interferes with absorption of the fat soluble vitamin D. Ingested Ca forms an insoluble soap with free fatty acids and is lost in the feces.
• Vitamin D-Resistant Rickets- four main types.
1. Phosphate diabetes- vit D and Ca are normal but are hypophosphatemic and cannot mineralize skeleton.
2. Decrease in 1,25-dihydroxyvitamin D production- cannot convert 25-hydroxyvitamin D to 1,25 form and thus cannot absorb Ca.
3. End-organ insensitivity- gut cell is insensitve to 1,25 vit D
4. Renal tubular acidosis- excretes excessive amounts of Ca
• Renal Osteodystrophy- Damage to the glomerulus causes retention of PO₄ while tubular injury reduces the production of 1,25 vit D. Hyperphosphatemia further suppresses the production of 1,25 vit D andinhibits renal reabsorption and GI absorption of Ca.. Renal osteodystrophy is characterized by rickets, osteitis fibrosa (severe lysis of the skeleton due to secondary hyperparathyroidism), osteosclerosis (20%),and ectopic calcification.

Management:

• Measurements of BUN, Creatinine, Ca, PO₄, alk phos, 1,25 and 25 vit D, PTH, and urine Ca and PO₄ to help establish the diagnosis and categorize the type.
• First step is ALWAYS treat the underlying metabolic abnormality first. Often after proper medical therapy the patient will go onto normal growth and lifestyle.
• The limb malalignment is often dependent upon when the metabolic abnormality occurred. If it is before two years old a varus deformity will occur, after two years old a valgus deformity is most likely.
• If malalignment fails to improve after the underlying metabolic abnormality is corrected, bracing and/or surgery may be indicated.

SELECTED LITERATURE REVIEW:

Normal development:

1. The tibiofemoral angle in the newborn and infant is in varus (15 degrees). At 18 to 24 months the tibiofemoral angle becomes more neutral. The tibiofemoral angle then changes to valgus and is at its maximum at age three to four (12 dgrees). It then corrects itself to that of the adult by age 7 (6 degrees in boys, 7 in girls).
2. Internal tibial torsion often accompanies physiologic genu varus and accentuates the "bowlegs"
3. Pes planus and external tibial torsion may accompany genu valgum- will accentuate "knock knees"

Rachitic pathology

• Pathologic genu varum- large differential. Metabolic bone disease results in bilateral pathology.
• Pathologic genu valgus- smaller differential. Renal Osteodystrophy is the most frequent cause of bilateral pathologic valgus deformity
• Earlier surgical treatment for lower extremity abnormalities concentrated on correcting the deformity by osteotomy and plating or multiple osteotomies and intramedullary nailing. Ferris et. al., described a surgical procedure in which he staged the osteotomies. The first stage consisted of multiple diaphyseal osteotomies with "kebabing" over an intramedullary nail, and this was performed at any age. They found correction of multidirectional deformities with wedge osteotomies and plating difficult. Thesecond stage consisted of a metaphyseal osteotomy which was helpful in correcting deformities around the knees and was most successful if performed toward the end of growth. Fixation was with a blade plate or staples
• Paley and Tetsworth performed corticotomies followed by placement of external ring fixators with hinges placed at the apex of the deformities for gradual correction. For multiapical deformities, they felt that meticulous preoperative planning was the key for successful realignment of the extremity. Their preoperative planning consisted of an elaborate method for elucidating the mechanical axis deviation (MAD) of the extremity and the subsequent amount of angular correction needed to realign themechanical axis
• Stanitski was successful treating rachitic limbs using the Ilizarov technique. She found that decreasing the correction rate from 1 mm/day down to 0.5mm/day in rachitic bone improved the quality of the regenerate bone and she had no nonunions. With the Ilizarov technique, her patients were allowed to weight bear as tolerated

When caring for rachitic deformities it is of paramount importance to correct the underlying metabolic abnormality first prior to any surgical intervention. If the metabolic abnormality is not corrected, surgical intervention will likely fail.

TREATMENT RECOMMENDATIONS:

• Continued medical therapy as indicated
• Continued orthopaedic observation
• No surgical intervention needed at this time since the patient's deformities continue to improve.

OUTCOME EXPECTATIONS:

• With the continued improvement seen in this child, we would expect an excellent outcome in this individual
• If after the patient has reached or is near skeletal maturity and there is limiting deformity still present, surgical intervention with expectations of a good result can be undertaken.

REFERENCES:

1. Ferris B, Walker C, Jackson A, Kirwan E.: The Orthopaedic Management of Hypophosphatemic Rickets. J Pediatr Orthop 11:367-373; 1991.
2. Kling TF Jr.: Angular Deformities of the Lower Limbs in Children. Orthop Clin North Am 18:513-527; 1987.
3. Paley D, Tetsworth K.: Mechanical Axis Deviation of the Lower Limbs. Clin Orthop 280:65-71; 1992.
4. Salenius P, Vankka E.: The Development of the Tibiofemoral Angle in Children. J Bone Joint Surg (Am) 57:259-261; 1975.
5. Stanitski DF.: Treatment of Deformity Secondary to Metabolic Bone Disease With the Ilizarov Technique. Clin Orthop 301:38-41; 1994.
6. Zaleske DJ. Metabolic and Endocrine Abnormalities. In: Lovell W, and Winter RB, 4th ed. Pediatric Orthopaedics. Philadelphia: Lippincott-Raven, 1996.