Where Are We Now?
In the current study, Kessler and Cannamela  report the incidence of Legg-Calve-Perthes disease (LPCD), an idiopathic form of avascular necrosis of the femoral head, in a cohort of 800,000 children in Southern California insured through the Kaiser Permanente Health System. Of those, 10% of children in the cohort were covered by Medi-Cal/Medicaid. In 2016, 38% of US children received health insurance from Medicaid, as did and 41% of children in California . Thus, the insured patients in this study likely had a higher socioeconomic status than did U.S. children in general. The authors found that the incidence of LCPD in their cohort was approximately three in 100,000 children and was most commonly found in children aged 2 to 5, whites, males, and obese children.
Interestingly, the reported incidence of LCPD ranges from 0.2 to 19.1 per 100,000 children —a wide variation. That same meta-analysis found increased incidence of LCPD in boys, whites, and in Northern latitudes . Previous reports [2-4] also found increased rates of LCPD in smoking households, children exposed to prenatal maternal smoking, and children with low birth weight, all of which may be associated with lower socioeconomic status.
The wide variation of LPCD incidences also has implications for its treatment options. Indeed, LCPD continues to be a challenge to manage, and controversies remain about which approach may be most effective. Two prospective studies, for example, recommend surgical management—primarily proximal femoral varus osteotomy for children over age 6 to 8 years of age [7, 15]. However, when examining the number of patients needed to treat in order to achieve a better result in adulthood, nonoperative patients older than 8 years of age had 33% good results, and 67% fair/poor results, whereas femoral osteotomy patients had 62% good results and 38% fair/poor . But some centers report good results from aggressive nonoperative management with casting and A-frame bracing , which is far more restrictive than the nonoperative approaches used in the two prospective studies [7, 15]. Ultimately, LCPD is a rare cause of THA in adults, representing 0.6 to 1.3% of all total hip replacements [1, 5]. At 20-year followup, approximately 5% of patients with LCPD treated nonoperatively in childhood will undergo THA for degenerative arthritis , reflecting a good-to-intermediate prognosis for most patients, although more than one-third of patients at 20 years following diagnosis have daily or weekly hip pain .
Where Do We Need To Go?
Treatment advances for LCPD have come slowly, largely because its pathophysiology remains a mystery. Aside from an ischemic insult to the femoral head, the underlying etiology for LCPD is unknown, although hypercoagulability, hyperactivity, gymnastics, toxic synovitis, femoral retroversion, body weight, socioeconomic status, and smoke exposure all have been implicated [10, 13]. A first step in treating a disease is understanding the cause and precipitating risk factors. Improved knowledge regarding the populations at risk may help elucidate disease mechanisms. Thus, ongoing incidence studies are an important step in developing a cure, in addition to well-done prospective controlled studies to evaluate novel therapies.
How Do We Get There?
There is an urgent need for improved knowledge of the pathophysiology regarding LCPD to develop pharmacologic or other treatments for this condition. Femoral osteotomy and subsequent implant removal requires two surgical procedures, and, interestingly, the amount of varus angulation does not change the surgical results . This would imply that the biologic effects of surgery are more important than the mechanical ones.
In the modern era of stem cells and local delivery of pharmacologic agents, new translational approaches must be developed for LCPD based on the pathophysiology of the disease to decrease the morbidity and increase efficacy of current treatments. As we await local pharmacologic management, treatment with varus osteotomy, or nonoperative containment treatment may be reasonable approaches through review of evidence-based medicine and an honest shared-decision making process with families.
1. Baghdadi YM, Larson AN, Stans AA, Mabry TM. Total hip arthroplasty for the sequelae of Legg-Calvé-Perthes disease. Clin Orthop Relat Res. 2013;471:2980-2986.
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[Published online ahead of print]. DOI: 10.1097/CORR.0000000000000490
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