Something Wrong With This Picture

To the Editor:

The case report by Christopher M. Rancont, DO,¹ in the September 2007 issue of JAOA—The Journal of the American Osteopathic Association describes the use of standing postural radiographs of the pelvic region and hips to identify the absence of leg length discrepancy in a patient who had undergone hip arthroplasty.

As many of us know, having regularly used this radiographic technique as developed by Willman,² the existence of a hip arthroplasty prosthetic device in a patient presents a special challenge.

I have two issues of concern regarding Dr Rancont's case report.¹ First, the radiographs presented in the article as Figure 1 and Figure 3 do not include vertical plumb lines. Yet, the vertical plumb line is key to the application of Dr Willman's technique.² Without the plumb line, there is no accurate reference to the horizon and, therefore, measurements are subject to error. Even the measurement line superimposed on Figure 3 was obviously added after the radiograph was taken. The lack of a plumb line is important because there is considerable wobble to the film—depending on how it is placed into the cassette—as anyone who has had the experience of loading radiographic film in a darkroom can attest. Also, whether using conventional film or a digital process, one cannot rely on the assumption that the upright Bucky support column is level to the floor. Therefore, one cannot reliably use the edges of the film as a reference.

The second issue of concern is raised by the presence of the prosthetic device in the patient's right hip.¹ With such a device, it is not clear where to draw the reference lines to evaluate the femoral head height bilaterally. My experience has been that the reference line for the femoral head on the left should be across the top of the natural femoral head, intersecting the plumb line. On the right side, the reference line should intersect the top of the artificial femoral head, not the top of the appliance at the acetabular rim.

In the radiographs shown in Figure 1 and Figure 3 of Dr Rancont's article,¹ it appears—even without a plumb line—that there is a significant difference in femoral head height between the left and right sides. In Figure 3, the femoral head height of the natural bone appears to be more superior than the femoral head height of the prosthesis. Furthermore, the author's discussion of the measurements in “Radiographic Findings” describes a difference in femoral head height of 2 mm.¹ Later in this section, there is the statement, “Sacral base unleveling was minimal at 4.4 mm toward the right.”¹ If this statement is correct, that measurement is double the amount of the femoral head height difference—and certainly, in my opinion, it would represent a significant sacral tilt. Indeed, when I look at the angle of the sacral tilt in Figure 3, there appears to be a significant tilt warranting consideration of a heel lift for leveling the sacral base. Consideration might be given to gradual leveling of the sacral base with monthly incremental increases in heel-lift height, coupled with osteopathic manipulative treatment for preventing chronic psoas spasm.

In conclusion, I believe that the case report by Dr Rancont¹ is an excellent reminder of the importance of the mechanics of leg length difference and sacral base unleveling. However, the case report is deficient in its description of the standing postural radiographic technique used—particularly considering the presence of an arthroplasty prosthesis on one side. In addition, it is difficult to make accurate diagnostic conclusions without the use of a steel plumb line passing through the Bucky device in front of the film. This modification to the standard radiographic setup is essential for the proper administration of the technique described by Willman et al,³ which was based on the original work of Willman.² Let's not forget how effective osteopathic manipulative treatment can be in conjunction with heel lifts to level the sacrum. A small change in structure can lead to a big change in function.