The best treatment of LCPD remains unknown, although in two recent prospective studies, surgery in certain subgroups yielded a higher likelihood of a spherical head than nonoperative treatment [18
]. The goals of our meta-analysis were to determine whether (1) either a FVO or SIO results in better radiographic head sphericity at the end of the disease process as compared with nonoperative treatment modalities; and (2) age of onset of LCPD or stage of disease at the time of treatment affected the risk of having an aspherical head.
Limitations of this meta-analysis are severalfold. First, only English language papers were used and the search was limited to the Cochrane databases, Medline, and EMBASE. Although some recommend including other databases, a recent publication [45
] examining meta-analyses in orthopaedics suggests that searching the Cochrane databases, Medline, and EMBASE provides a 97% recall rate and that expansion to Web of Science or Cumulative Index to Nursing and Allied Health Literature does not improve the recall rate. Second, the analysis is based solely on nonrandomized studies. This is a major limitation but as a result of the relatively low incidence of LCPD, such trials become extremely difficult. Third, it is difficult to take into account the various effect modifiers and confounders such as age at onset, age at treatment, preoperative ROM, stage of the disease process at the time of treatment, extent of head involvement, extent of head collapse at the time of treatment, sex, femoral head extrusion, and subluxation on the effect of the treatment type. The ideal situation would include having deidentified raw data sets available such that more extensive subgroup analyses would be feasible. Despite the lack of such data sets, a subgroup analysis on the effect of age, one of the greatest effect modifiers for femoral head sphericity in LCPD, was possible and is presented in this review. Fourth, nonblinded retrospective data can often contain bias information skewing the findings of such an analysis. The creation of the “a” type study is an attempt to minimize different forms of bias including selection bias, confounding by severity, and confounding by indication. This could also account for the moderate to high amount of heterogeneity seen in the analyses. The heterogeneity is low when the “a” type studies were analyzed alone perhaps indicating that the results of the final subgroup analysis (Level II and IIIa only) may be most relevant. Fifth, only published data were used for this analysis and as such, such stratification by age or stage of disease at the time of surgery was not possible in all of the studies. As a result of this, the subgroup analyses involve a limited number of patients. For this reason also, we were unable to assess the effect of surgery on head sphericity in patients older than 8 years. The 6- to 8-year age range appears to be a gray zone and additional data may have provided a more suiting conclusion on the effect of surgery on femoral head sphericity in this age range. Furthermore, multiple comparisons were not adjusted for; however, we believe the questions asked were relevant and the conclusions of this study are in keeping with current thoughts on LCPD [17
]. Also, this study uses femoral head sphericity as a surrogate for long-term health of the hip. Although Stulberg et al. [46
] and McElwain et al. [37
] demonstrated a clear correlation between femoral head sphericity and radiographic and functional outcomes, long-term functional outcome studies comparing operative and nonoperative treatments would yield a more direct answer to this question. Finally, head involvement, whether by the Catterall [6
] or the modified lateral pillar [19
] classification, was not incorporated into this study. Although it is possible that they have substantial bearing on femoral head sphericity, it was not possible to perform a subgroup analysis based on this factor.
Although the overall pooled ORs when all studies are included show that surgery increases the likelihood of femoral head sphericity, the subgroup analyses performed based on age yields more relevant findings with patients older than age 6 years showing a higher likelihood of femoral head sphericity when treated surgically and those aged 6 to 8 years showing only a trend toward improved femoral head sphericity. Based on the lack of an effect size in those younger than 6 years as well as those between 6 and 8 years, it would seem that children older than 8 years would have the largest effect size on femoral head sphericity from surgery. Age appears to be an important factor in terms of altering the natural history of LCPD. Long-term radiographic outcome studies have stressed the importance of age at onset as an important prognostic factor [5
] and multiple therapeutic studies [8
] have alluded to the importance of age at onset and treatment. It would appear that the older children (older than 6–8 years) are less likely to have a spherical femoral head [7
] and it is this same cohort that appears to benefit from surgery. Wiig et al. [50
] showed that surgery in the form of a proximal FVO was better than physiotherapy or bracing in patients 6 years of age or older with greater than 50% head involvement, whereas children younger than 6 years with greater than 50% head involvement did not appear to benefit from the surgery. Meanwhile, Herring et al. [18
] reported improved femoral head sphericity by FVO or SIO in patients older than 8 years of age who were classified with a lateral pillar B or B/C border hip in comparison to those treated by bracing, ROM, or no treatment.
The Level IIa and IIIa studies revealed patients undergoing FVO or SIO during or before the fragmentation phase have better femoral head sphericity at the end stage of LCPD than those undergoing nonoperative treatment (OR, 1.46; p = 0.02; 95% CI, 1.06–2.01). The primary analyses (all Level II and III studies and all patients despite stage at treatment) revealed similar results (OR, 1.29; p = 0.02; 95% CI, 1.05–1.60). Interestingly, when analyzing all Level II and III studies treated during or before fragmentation, the beneficial effect of surgery was lost (OR, 1.29; p = 0.06; 95% CI, 0.99–1.68). This would imply that the stage at treatment is not an important prognostic factor. Axer et al. [2
] reported on 70 patients undergoing varus osteotomy and showed that of patients who had surgery in the early/necrotic phase, only 9% had poor femoral head sphericity as per the Mose methods, whereas 14% of those during the intermediate/fragmentation phase had poor sphericity and 56% of those treated in the late/reossification/regeneration phase had poor sphericity. Jani and Dick [23
] reported a better Catterall [6
] outcome distribution in patients treated immediately with a varus derotation osteotomy (VDRO) as opposed to waiting for risk factors to appear. Joseph et al. [26
] reported a multivariate logistic regression analysis on 97 patients undergoing a VDRO. They found that if surgery was performed during or after late fragmentation, the OR of femoral head asphericity was 16.58 (p < 0.01; 95% CI, 2.6–103.13) as compared with surgery performed during or before early fragmentation. These and multiple other studies [2
] have found better femoral head sphericity when surgery has been performed at an earlier stage. Despite our findings, we also believe stage at treatment is crucial in terms of altering the natural history of the disease. One possible explanation for why the inclusion of all Level II and III studies resulted in a loss of effect is that the “b”-type studies incorporated some level of confounding by indication or confounding by severity in that the surgically treated patients were older [5
] or had more severe disease [12
], both of which are factors associated with aspherical femoral heads.
The data from this meta-analysis suggest a FVO or SIO improves femoral head sphericity in children older than 8 years. Although surgery does not appear to alter the natural history of the disease in those younger than 6 years, children aged 6 to 8 years remain in a gray zone in which the role for surgery is less obvious. Herring et al. [18
] included a skeletal age analysis that revealed a cutoff of skeletal age of 6 years for improvement by surgery. It is quite possible that skeletal age rather than chronological age is a more important or consistent prognostic factor for improved radiographic outcomes. Further studies should incorporate skeletal age correlations with their findings. Furthermore, it is important that future studies include skeletal age at presentation and at surgery, pertinent active radiographic classification systems that can differentiate disease stage (modified Elizabethtown and modified lateral pillar), quantification of head involvement (modified Catterall or Salter-Thompson), end-stage radiographic classification systems that can be correlated to long-term outcomes (Mose and Stulberg), and validated functional outcome scores to better understand the physical impact or effects of our interventions.