Secondary Causes of SUFE

Apply the modified Klein's line to BOTH hips, look for the metaphyseal blanch of Steel and physeal widening, and confirm on a frog-lateral. Then ask explicitly whether the epiphysis has gone posteroinferior or superolateral.

If the physes are widened symmetrically with intact Klein's lines bilaterally you are looking at metabolic bone disease rather than a slip — but that same disease is why a slip will follow. Do not stop at Klein's line: atypical slips are significantly more often VALGUS, in which the epiphysis displaces superolaterally and Klein's line stays intact. Rotation on the AP is the commonest false positive, so never diagnose a slip on a single AP.

Plot height and weight on the growth chart before ordering anything, and note the sex as a datum rather than an assumption.

Age 10-16 with height at or above the 50th centile and obesity supports idiopathic. Under 10, over 16, or height below the 10th centile mandates an endocrine and renal workup — atypical children in Chung's series averaged 132 cm and 36 kg against 149 cm and 57 kg. Loder's split is sharper still: only hypothyroid and growth-hormone-deficient patients slipped under 10, while every other endocrinopathy at an atypical age presented over 16. And the sex ratio inverts: 73 per cent of non-endocrine slips are male but 53 per cent of endocrine-associated slips are female.

Look at the contralateral hip on every film and record whether the slips were simultaneous or metachronous.

Bilateral simultaneous slip strongly favours a secondary cause — hypothyroidism, renal osteodystrophy or growth hormone therapy. Sequential slip occurs in idiopathic disease too, but a metachronous slip in a child under 10 remains secondary until proven otherwise. Bilaterality was 61 per cent in Loder's endocrine series and 9 of 11 in Oppenheim's renal series, against roughly a fifth to a quarter in idiopathic disease.

Ask directly about growth hormone, thyroid replacement, chemotherapy, and radiotherapy fields — and about dialysis.

In Chung's tertiary series 19 of 22 atypical children were childhood cancer survivors: 16 chemotherapy-associated and 9 radiotherapy-associated, against only 4 primary endocrine. Radiation slips follow fields for Wilms tumour, neuroblastoma or pelvic sarcoma, typically 2 to 5 years later. Growth hormone deficiency carries an SCFE incidence of 583.8 per 100,000, and 92 per cent of Loder's growth-hormone-deficient patients slipped during or after supplementation.

Scan the whole pelvis and any incidentally included bone, then request a left hand and wrist radiograph.

Subperiosteal resorption and a rugger-jersey spine point to renal osteodystrophy. Frayed cupped metaphyses point to rickets. Fragmented stippled epiphyses point to hypothyroidism. Asymmetric hypoplasia with growth arrest lines points to radiotherapy. Symmetrical multi-joint epiphyseal irregularity points to a dysplasia. On bone age, a delay of two years or more supports hypothyroidism, panhypopituitarism or chronic disease — Loder's endocrine patients averaged a bone age of 11.6 against a chronological age of 16.5. Bone age also grades remaining growth and therefore contralateral slip risk.

Send TSH and free T4, urea and electrolytes with creatinine, calcium, phosphate, alkaline phosphatase, parathyroid hormone and vitamin D; add IGF-1, cortisol and gonadotrophins if pituitary disease is suspected. Refer to paediatric endocrinology or nephrology in parallel with fixation, and agree who will keep asking about the other hip.

Hypothyroidism is usually diagnosed AT the slip — the orthopaedic team finds it — whereas growth hormone deficiency is usually already known. Risk rises with the number of deficient hormones. In renal osteodystrophy the metabolic control is part of the treatment: the single fixation failure in Oppenheim's series occurred with inadequately controlled renal disease and was salvaged by subtotal parathyroidectomy, not by revising the metalwork. And surveillance must be long: Hwang found a median 3.6 years from endocrine diagnosis to slip, with 27 per cent occurring beyond five years.