We retrospectively compared two matched groups of patients with LCP disease initially classified as Herring B or C [3
], a group treated nonoperatively and a group treated operatively with FVO. Between 1977 and 1997, we saw 280 patients with LCP disease. Of these, 28 with unilateral disease, initially classified as Herring B or C and operated on using FVO, were available for clinical and radiographic reviews at maturity and had radiographs available from the initial consultation. We recommended surgery for inadequate coverage of the femoral head in the fragmentation phase. Inadequate coverage does not directly relate to the Herring classification at a given time as a patient classified as having Herring Class B disease subsequently may have either adequate or inadequate coverage of the femoral head. We used Heyman’s index [4
] as a quantification of the coverage of the femoral head. A Heyman’s index greater than 120% was considered inadequate coverage. We created a comparison group of 28 patients treated nonoperatively from the same time interval (1977–1997). All patients had unilateral LCP disease, initially classified as Herring B or C.
In the operative group, the mean age of onset was 7.1 years (range, 4.7–11.4 years); there were 26 classified as having Herring B and two classified as having Herring C disease. The mean age of the patients at surgery was 7.8 years (range, 5.8–11.8 years). The minimum followup was 3.9 years (mean, 9.4 years; range, 3.9–12.7 years). In the nonoperative group, the mean age of onset was 5.8 years (range, 1.8–12.5 years); there were 24 patients classified as having Herring B and four classified as having Herring C disease. Age at onset distribution between the two groups was similar (p = 0.068), as was the distribution of Herring classes (p = 0.34). The minimum followup was 3.3 years (mean, 10.7 years; range, 3.3–15.6 years).
Osteotomy involved a transverse subtrochanteric osteotomy performed through a lateral incision. The proximal fragment was placed in varus and impacted into the distal fragment. The osteotomy was fixed using either an S-shaped plate or a straight plate on the lateral surface of the femur (Fig. ).
The osteotomy was fixed using either (A) a straight plate or (B) an S-shaped plate (right) on the lateral surface of the femur.
Anteroposterior (AP) and frog lateral radiographs of the pelvis were obtained at presentation in both groups. We (MJ, MK) classified the initial radiographs according to the classification of Herring et al. [3
] and final radiographs using the system of Stulberg et al. [10
] (Fig. ).
The Stulberg classification is shown for patients who were treated operatively and nonoperatively.
At last followup, both groups had AP radiographs of the pelvis and long-leg views in the standing position to assess limb alignment. We (MJ, MK) determined limb alignment as follows: the mechanical axis was taken from the center of the femoral head to the midpoint of the surface of the talar dome [7
]. When it was not possible to locate the center of the femoral head, the axis was taken from the center of a circle obtained by tracing the shape of the acetabulum (ie, the theoretical center of the femoral head if this were a normal joint). The MAD then was determined by measuring the distance between the lateral-most part of the tibial plateau and the mechanical axis expressing this as a percentage of the width of the tibial plateau. Thus, a value less than 50% was indicative of lateral MAD or valgus and greater than 50% was indicative of medial MAD or varus [7
] (Fig. ). Patients with a difference between the diseased side and the normal side with respect to lower limb alignment were defined as having altered alignment. Among patients with altered alignment, patients with valgus alignment on the diseased side compared with the opposite side were identified and referred to as having valgus alignment. In the same way, patients with varus alignment on the diseased side compared with the opposite side were identified and referred to as having varus alignment.
Measurement of the MAD of the lower limb is shown.
Limb length discrepancy (LLD) at maturity between the diseased side and the opposite side was assessed radiographically. LLD was defined as the difference in height (expressed in millimeters) and measured on scaled long-leg views between the two highest parts of the ossified femoral heads. As a convention, negative values indicated shortening of the diseased side. The mean LLD at maturity in the operative group was compared with the mean LLD at maturity in the nonoperative group using analysis of variance.
We assessed how much varus was performed at the time of surgery and how much was remodeled with time up to skeletal maturity. The preoperative neck shaft angle (NSA) of the diseased upper femur, the immediate postoperative NSA, and the NSA at final followup were assessed radiographically. Two different paired-sample t tests were used to look for a major difference between preoperative NSA and postoperative NSA and postoperative NSA and NSA at final followup. The two groups were checked for similarity with respect to age at onset (analysis of variance) and Herring classification (chi square test). To determine the distribution of patients with valgus alignment among operative and nonoperative patients, we used a chi square test. The statistical analysis was performed using SPSS® software (SPSS Inc, Chicago, IL).