8452 8453 The physis connects the proximal femoral epiphysis (the femoral 8454 head) to the metaphysis (femoral neck). In certain physiological 8455 or pathological conditions a ‘stress fracture’ through the physis 8456 allows the epiphysis to displace as it would with an intracap- 8457 sular femoral neck fracture, so the leg lies short and externally 8458 8459 8460 8461 *TABLE 44.7 A guide to some of the surgical options available for the management of Perthes’ disease.* 8462 8463 8464

Timing	Type of procedure	Comments	Aim
Early	Femoral osteotomy	Varus and derotation Consider an opening wedge osteotomy to maintain length	To cover ('contain') the vulnerable femoral head
	Innominate osteotomy
	Shelf acetabuloplasty
Intermediate	Arthrodiasasis	Hinged distraction to allow movement, primarily flexion/extension	To reduce deforming pressures on the femoral head
Late	Femoral osteotomy	Valgus With extension to undo a fixed flexion deformity or flexion to remove the anterior bump from impinging on the acetabulum	To improve joint congruity and hence function; to improve joint mechanics
	Arthrotomy	To remove osteochondral fragments
	Head–neck osteoplasty	After physeal closure	To improve head shape by reducing femoroacetabular impingement and increasing head/neck offset
	Trochanteric epiphysiodesis or distal transfer	Epiphysiodesis not effective after age 7–8 years	To improve lever arm function
Contralateral limb	Distal femoral epiphysiodesis		To reduce leg length discrepancy and effects on hip joint mechanics

8465 8466 rotated. There is painful limitation of hip movement. Hilton's 8467 law, which states that a joint is supplied by the same nerves as 8468 the muscles that move the joint, explains why many children 8469 present with knee pain although the pathology is in the hip. 8470 8471 8472 ## Incidence and aetiology 8473 8474 SCFE is rare, with an incidence of approximately 5 per 8475 100 000 population. Boys are affected most commonly. The 8476 peak incidence is related to the start of puberty and hence is 8477 earlier in girls. As a result of hormonally stimulated growth, 8478 the strength of the physis, its resistance to shear and its orien- 8479 tation are reduced. The hip is therefore ‘at risk’ and normal 8480 forces, exacerbated by obesity and repetitive minor trauma, 8481 precipitate a slip. Other conditions such as hypothyroidism, 8482 renal failure and previous radiotherapy treatment (local or to 8483 the pituitary) also increase the risk. 8484 8485 8486 ## Diagnosis 8487 8488 The diagnosis is suggested by the history and examination and 8489 confirmed on plain radiographs (Figure 44.22). Displacement 8490 is often more obvious on a lateral view and the diagnosis can 8491 [... Output truncated due to length. 935 tokens/3145 characters removed ...]