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At a glance

Genetically transmitted skeletal malformation characterized by hypoplasia or aplasia of the patella, epiphyseal, and hip/pelvic girdle anomalies.

Synonyms

Coxopodo Patellar Syndrome; Small Patella Syndrome; SPS; Scott-Taor Syndrome.

History

Ischiopatellar dysplasia is sometimes referred to the Scott-Taor Syndrome after researchers who first described ischiopatellar dysplasia recognized in 1979 that it was a clinically more benign disorder (Small Patella Syndrome) that is separate from the more severe Nail-Patella Syndrome.

Genetic inheritance

Autosomal dominant with variable penetrance (majority of patients); sporadic dominant mutation (rare).

Pathophysiology

Small Patella Syndrome (SPS) is a bone dysplasia affecting predominantly the pelvis, knees, and feet. The patellae are either small or absent; when present they may be laterally placed, resulting in recurrent dislocation of the patella.

Diagnosis and clinical aspects

Based on morphologic and radiologic appearances: increased space between the first and second toes, shortening and clinodactyly of the fourth and fifth toes, and flat feet are the findings in some patients. Absent or hypoplastic patellae (laterally placed or dislocated) are typical. Most patients have pelvic abnormalities: absent ischial ossification at the ischiopubic synchondrosis, infraacetabular axe-cut notch, high iliac angles, large femoral heads with narrowed femoral necks, coxa valga or vara, and hypoplastic lesser trochanters. Patients may complain of Femoropatellar Pain Syndrome, but symptoms referable to the pelvic girdle are very rare. Two sporadic cases of SPS associated with facial dysmorphic features have been reported: one patient had a flattened nose with prominent forehead, and the other had micrognathia, high-arched palate, and subglottic stenosis with generalized tracheomalacia; she also had bilateral talipes equinovarus (clubfeet). These facial and airway abnormalities likely are not part of the SPS itself. The differential diagnosis of SPS is either an isolated finding of displaced patellae or the “Nail-Patella Syndrome” (iliac horns, elbow abnormalities, nail dystrophy).

Precautions before anesthesia

No specific precautions with this medical condition.

Anesthetic considerations

Obtain a “skeletal survey”: SPS affects mainly pelvis, knees, and feet, but other parts of the skeleton may be abnormal. One case of minor spine involvement (mild thoracic scoliosis with normal pulmonary function, and lumbar hyperlordosis) reported. These findings should not affect anesthetic management unless scoliosis becomes significant enough to compromise breathing (pulmonary function tests are required). No anesthetic considerations specific to SPS.

Pharmacological implications

No specific pharmacological considerations.

Other conditions to be considered

  • Familial Recurrent Dislocation of the Patella (Congenital Dislocation of the Patella): Lateral displacement of the patella as a result of pull of the quadriceps muscle while the tibial tubercle abnormally lies lateral to the long axis of the femur. When the knee is flexed, the patella slides distally and ...

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