I found Ms. Curran’s observations to be very insightful. Below I have addressed some of the thought-provoking issues she raised.
Regarding Ms. Curran’s concern about the use of the pelvic thrust maneuver, I am aware of its inherent limitations. However, this maneuver was used to screen out any potential anatomical leg-length discrepancies from this study. I am aware that I might have also inadvertently screened out a few functional leg-length discrepancies (ie, false positives), but I did not see this as a problem. The intent was to include only functional leg-length discrepancies in this study.
Ms. Curran’s comment that in determining hip position, the posterosuperior iliac spine would be difficult to palpate or identify in obese patients is correct. This is why these patients were excluded from the study. The technique of palpating the posterosuperior iliac spine is not easy to master. However, I have used this technique for more than 30 years and feel very comfortable with the accuracy of the visual measurement. On each patient, I performed this test three times to make sure my findings were consistent. If the three iterations did not yield the same results, the patient was excluded from the study.
Concerning the absence of measurement reliability reports in the article, my research and practice is limited to postural mechanics. My experience in evaluating pronation patterns has spanned more than 30 years, and I have used the Foot Posture Index for several years on many patients and research subjects. I did not report the reliability of this technique because Redmond et al [
1] had already done so.
Ms. Curran notes that the stance position seemed unnatural. This modified stance position was adopted because it is my opinion that most abnormal foot pronation patterns are driven by structural lesions in the forefoot [
2]. Specifically, in 2002, I described a previously unreported embryologic foot type, which I termed
primus metatarsus supinatus, that I suggested was responsible for many of the abnormal pronation patterns we see clinically. Ms. Curran is correct in saying that the modified stance position does, in most cases, increase the abnormal pronation pattern. This occurs because forefoot mechanics drive the rearfoot, as I have stated above. I have written about the primus metatarsus supinatus foot type in other published papers and did not feel it was relevant to repeat this discussion in this article.
Regarding further investigation of the mechanical linking between the foot and innominate bone, Ms. Curran made some excellent suggestions pertaining to the use of three-dimensional kinematics or magnetic resonance imaging studies to confirm this linking. I agree that these studies should be done; however, they are beyond the scope of this article.
Regarding the incidence of functional leg-length discrepancy in various populations, the epidemiology of this condition was not included in my article and was in fact, beyond its scope.
Ms. Curran states: “In his ‘Discussion,’ the author refers to a study by Keeling,18 noting the small population size. This same statement can also be applied to Dr. Rothbart’s current study.” This is true, and I did acknowledge this at the end of my article.
I believe I may be the first author to publish on this proposed link between 1) the most pronated foot, 2) the most anteriorly rotated innominate bone, and 3) the resulting short leg. I agree with Ms. Curran: The results of this study should be viewed with caution until other studies can either confirm or refute them. It should be noted that the earlier (unpublished) study by Keeling is consistent with my findings.
