We greatly appreciate the interest in our article, “Staged Surgical Dislocation and Redirectional Periacetabular Osteotomy. A Report of Five Cases”.

We are, of course, familiar with Professor Klaue’s great contribution describing the concept of the acetabular rim syndrome as a clinical presentation of dysplasia of the hip. Professor Klaue correctly points out that, in patients with more classic forms of acetabular dysplasia, the acetabular rim is subject to axial overload with resultant fatigue failure of the acetabular labrum and its bony attachment.

We also agree with Professor Klaue’s statement that, in the dysplastic hip condition, rim alterations may heal spontaneously provided there is adequate correction of the abnormal acetabular coverage. In the original description of the acetabular rim syndrome, all of the patients reported had evidence of classic acetabular dysplasia with a profound lack of lateral acetabular coverage (a lateral center edge angle of less than twenty degrees). This is in contrast to our series, in which four of the five patients had initial center edge angles of greater than twenty degrees. Also, contrary to Professor Klaue’s statement, this information was clearly provided in Table 1 of our manuscript.

Additionally, we believe that there are hips, such as those reported in our case series, which suffer from combinations of impingement and instability or dysplasia. These hips may have a combination of acetabular rim pathology from static axial overload and a characteristic chondral injury (usually hyaline cartilage delamination in the 12-3 o'clock position of the acetabulum resulting from dynamic shear injury with repetitive flexion and internal rotation of the hip). This pattern of injury has now been widely recognized and is associated with femoroacetabular impingement. This injury pattern was decidedly not part of the original description of the acetabular rim syndrome because the underlying pathomorphology of the hip was different.

In hips with impingement or combined impingement and dysplasia, once a chondral delamination injury occurs, there is no scientific basis to support spontaneous healing of such an injury regardless of morphology correction on either side of the joint. Current strategies utilized to treat such chondral injuries include resection of the lesion together with the underlying subchondral bone, resection of the damaged cartilage with microfracture, and gluing of the hyaline cartilage flap to the underlying subchondral bone. To date, it is unclear which of these methods is superior.

Although we do agree with Professor Klaue that the operations reported in our series could perhaps be performed simultaneously, albeit with separate surgical procedures on both the acetabular and femoral sides, these hips were treated early in our experience and we were concerned about the magnitude of such surgery. With more precise preoperative imaging and more years of surgical experience, we would now favor surgical correction at a single sitting provided that the dual goals of morphology correction and chondrolabral treatment could be met.

To the Editor:

I read with interest the article, "Staged Surgical Dislocation and Redirectional Periacetabular Osteotomy. A Report of Five Cases" (1). The authors admit that performing two major open operations for treating a morphological abnormality of the hip joint may seem overly aggressive. Clinical data suggest that morphological alterations at the acetabular rim in hip dysplasia heal spontaneously as soon as the morphology and orientation (in french: coxométrie) of the joint is corrected. These alterations include limbus tears, ganglia and bony rim fragments which consolidate without other treatment (2). The authors based their pre-operative assessment on localized lesions shown by magnetic resonance imaging. Unfortunately, there is no mention of precise coverage assessment, while this aspect has been suggested to be of primary importance (3). Under this aspect and based on our series, impingement can be treated exclusively by re-orienting the acetabular cup (4) and eventually the femur, or remodeling the femur in one session. There is no scientific reason to advocate removal of altered parts of the acetabular roof (which obviously might add new pathology) and performing a secondary re-orientation of the whole acetabulum. The key to success (with one operation) lies probably in a precise pre-operative assessment of the coverage of the femoral head for planning a specific re-orientation of the acetabulum in 1 to 3 planes.

The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated.

References

1. Anderson LA, Crofoot CD, Erickson JA, Peters CL. Staged surgical dislocation and redirectional periacetabular osteotomy: a report of five cases. J Bone Joint Surg Am. 2009;91:2469-76.

2. Klaue K, Durnin CW, Ganz R. The acetabular rim syndrome. A clinical presentation of dysplasia of the hip. J Bone Joint Surg Br. 1991;73:423-9.

3. Klaue K, Wallin A, Ganz R. CT evaluation of coverage and congruency of the hip prior to osteotomy. Clin Orthop Relat Res. 1988;232:15-25.

4. Reynolds D, Lucas J, Klaue K. Retroversion of the acetabulum. A cause of hip pain. J Bone Joint Surg Br. 1999;81:281-8.