Growth arrest

Discussion:

- bone bridge obliterates growth-plate cartilage & prevents growth;

- peripheral bone bridges predispose patient to angular deformities;

- most common sites of growth arrest include the distal tibia, distal femoral and distal ulnar physis;

- much less common sites include distal radius and proximal humerus;

- Radiology:

- extent of bone bridge is demonstrated by CT scanning and tomograms;

- Indications for Bone Bridge Resection:

- resection is indicated if less than 1/3 to 1/2 of growth plate is involved;

- younger children tend to have a better prognosis w/ resection than older children;

- less than 2 years of remaining growth is a relative contra-indication for bone bridge resection;

- central bars are more amenable to resection than peripheral bars;

- ischemic or septic related bone bars have a poor prognosis w/ resection;

- Technical Pearls:

- interposition of fat is easiest and most commonly used agent to prevent bone bridge formation (alternatives include silastic, methyl methacrylate, or free epiphysis)

Infantile Blounts Disease: (pathologic tibia vara)

- differential diagnosis and examination (see genu varum)

- most common form of disease;

- growth disorder of medial portion of proximal tibial physis;

- characterized by medial angulation& internal rotation of proximal tibia;

- etiology is related to repetitive trauma to posteromedial proximal tibia physis from ambulating on a knee with varus alignment;

- infantile tibia vara is seen between 2-4 years of age;

- usually bilateral;

- associated with internal tibial torsion;

- children w/ tibia vara are usually in upper percentiles of weight (for age)& began walking early;

- this contrasts w/ dysplastic children who present w/ bow legs but who are in the lower percentiles for height and weight;

- gait is characterized by painless varus thrust in stance phase;

- developmental knee alignment:

- normal knee alignment progresses from 10-15 deg of varus at birth to max or peak valgus angulation of 10-15 deg at age of 3 to 3.5 yrs;

- neutral alignment:

- neutral femoral-tibial alignment is achieved when pts are 12-14 months old;

- Greene: neutral femoral-tibial alignment at 14 months old;

- Radiographs:

- show metaphyseal diaphyseal angle of >11 deg early (this angle is formed by lines between metaphyseal beaks& perpendicular

to the longitudinal axis of the tibia);

- radiographs show a localized deformity at proximal tibial level w/ a medial metaphyseal lesion;

- in contrast, the common physiologic bowlegs involves both the tibia &distal femur (during 2nd year);

- Orthotic Management

- includes long-leg, locked-knee braces w/ pelvic band to control rotation, worn while child is wt bearing;

- night time bracing doesn't address pathophysiology (ineffective)

- Surgical Indications:

- if deformity does not correct before age 4-5 yrs, surgery is indicated;

- osteotomy of proximal tibia and fibula should also include lateral rotation to produce a +10-degree thigh-foot angle;

- if surgery is delayed beyond ages of 6-8, recurrence is expected;

- consider tibial osteotomy when medial physeal slope is > 60 deg;

- w/ medial physeal slope of 50 to 60 degrees, orthotic treatment is consider if there are risk factors;

- obesity, female gender, and a poor social situation are poor prognostic signs for successful bracing;

- example of proximal tibial osteotomy:

- in the report by Chotigavanichaya C, et al (2002), the authors performed a retrospective

review of 74 tibial osteotomies performed for Blount disease;

- patients were divided into three groups based on age and treatment;

- group A (26 osteotomies), 4 years old or younger

- group B (34 osteotomies), older than 4 years, were treated the same with osteotomy and crossed pins;

- group C (14 osteotomies), older than 4 years, was treated with osteotomy and external fixator;

- at 6 years of follow-up, the recurrence of varus deformity was 46%, 94%, and 72% in groups A, B, and C, respectively;

- there was no correlation between recurrence of varus deformity and preoperative deformity angle or degree of surgical correction;

- fixation with crossed pins or external fixator was not a factor

- surgery at 4 years old or younger and correction of the postoperative deformity angle in valgus may obviate recurrence of varus

deformity in Blount disease at long-term follow-up

Ref: Recurrence of varus deformity after proximal tibial osteotomy in Blout disease: long-term follow-up

- Physeal Arrest:

- prior to development of a physeal arrest, treatment consists of proximal tibial osteotomy;

- once a medial physeal arrest occurs, treatment becomes more difficult;

- considerations for treatment would be tibial osteotomy w/ or w/o completion of fusion of the physeal plate;

- physeal bar resection & interposition is an unproven technique;

- if physeal bridge of bone is identified, then resection of osseous bar with interposition of fat, cement, or medical-grade elastomer should be considered;

- physeal bar resection in infantile tibia vara is difficult and results are unpredictable;

- osseous bridge > 50% of width of growth plate is usually listed as contraindication to physeal bar excision;

- references:

- Correction of Non-Blount's Angular Knee Deformity by Permanent Hemiepiphyseodesis.

- Guided Growth for Angular Correction: A Preliminary Series Using a Tension Band Plate.

- Hemiepiphysiodesis for the Correction of Angular Deformity About the Knee.

Instructional Course Lectures, The American Academy of Orthopaedic Surgeons. Infantile Tibia Vara.

Elevation of the medical plateau of the tibia in the treatment of Blount disease.

Normal limits of knee angle in white children--genu varum and genu valgum.

Use of the Metaphyseal-Diaphyseal Angle in the Evaluation of Bowed Legs.

Physiological bowing and tibia vara. The metaphyseal-diaphyseal angle in the measurement of bowleg deformities.

Blount disease: A review of the English literature.