Reply to the Letter to the Editor

To the editor,

We read the letter to the editor regarding our article [4] with great interest.

Lax-Perez and colleagues criticize that our analysis only describes the cam-type morphology as a potential contributor to traumatic posterior hip dislocation. In addition, they suggest other factors (retrotorsion of the femoral neck, retroversion of the acetabulum, decreased acetabular depth) as additional predisposing factors in their case report [2]. We were surprised to read this since it is contradictory to our published article. First, “retroversion of the femoral neck” was mentioned both in the Introduction and the Discussion section of our manuscript. The appropriate reference by Upadhyay et al. [6] from 1985 was cited several times in our paper. Second, “retroversion of the acetabulum” was even the second key study variable of our analysis. Third, “decreased acetabular depth” is proposed by Lax-Perez and colleagues as a potentially contributing factor for traumatic hip dislocation without profound scientific evidence. As mentioned in our article, there is only one case report of a traumatic hip dislocation [5] in a dysplastic hip. This is consistent with our findings where the dislocation (study) group had a mean lateral center edge angle of 32°.

Their case report [2] describes one single patient with a posterior hip dislocation related to a low energy trauma. The scientific data in that report are limited, without quantification of the decreased femoral head-neck junction, acetabular coverage/orientation, or femoral torsion. In addition, given the lack of an appropriate control group, their report does not offer scientific evidence to support their hypothesis. Reading the case report carefully, there is even a conceptual discrepancy between the suggested therapy in their report, and the surgical management of the patient. The treatment consisted of an open reduction and internal fixation of the posterior wall fracture through a standard Kocher-Langenbeck approach. This does not allow a direct visualization of the impingement conflict or a surgical correction of the underlying pathomorphology. In this case, a full surgical dislocation of the hip with an additional trochanteric osteotomy could have been beneficial for verification of the proposed mechanism, description of the intraarticular damage pattern, and concomitant treatment of any related acetabular and femoral pathomorphologies.

In conclusion, the data in our study matches the theory of the case report [2], and is concordant with other publications [1, 3]. The case report neither reports an original description of a pathomechanism, nor the necessary scientific data for its justification.