OBJECTIVE: The objective of the study was to compare two methods (Ranawat's and Pierchon's) used to determine the centre of rotation of the hip and establish which method calculates a position nearer to the real centre of rotation. PATIENTS AND DESIGN: We selected 24 patients with unilateral osteoarthritis of the hip. The centre of rotation of the healthy hip was determined in two consecutive radiographic studies by superimposing a template of circles and using two axes as the reference lines (X-axis=teardrop line; Y-axis=a line perpendicular to the X-axis, drawn from the intersection of the ilio-ischiatic line and the teardrop line). After ensuring the stability of these references, both methods were applied to the same radiograph to determine which one established a centre of rotation nearer to the anatomical centre identified by the template of circles. RESULTS: When the values for the healthy hip are compared with those obtained using Ranawat's method, highly significant differences are observed for both X (P<0.0001) and Y (P<0.0001). When the results for the healthy hip are compared with the values obtained using Pierchon's method, neither the X (P=0.722 ) nor the Y values (P=0.112) show any significant differences. It would be advisable to use Pierchon's method to determine the centre of rotation during the preoperative planning for a total hip arthroplasty when the anatomical alteration is bilateral.
OBJECTIVE: The objective of the study was to compare two methods (Ranawat's and Pierchon's) used to determine the centre of rotation of the hip and establish which method calculates a position nearer to the real centre of rotation. PATIENTS AND DESIGN: We selected 24 patients with unilateral osteoarthritis of the hip. The centre of rotation of the healthy hip was determined in two consecutive radiographic studies by superimposing a template of circles and using two axes as the reference lines (X-axis=teardrop line; Y-axis=a line perpendicular to the X-axis, drawn from the intersection of the ilio-ischiatic line and the teardrop line). After ensuring the stability of these references, both methods were applied to the same radiograph to determine which one established a centre of rotation nearer to the anatomical centre identified by the template of circles. RESULTS: When the values for the healthy hip are compared with those obtained using Ranawat's method, highly significant differences are observed for both X (P<0.0001) and Y (P<0.0001). When the results for the healthy hip are compared with the values obtained using Pierchon's method, neither the X (P=0.722 ) nor the Y values (P=0.112) show any significant differences. It would be advisable to use Pierchon's method to determine the centre of rotation during the preoperative planning for a total hip arthroplasty when the anatomical alteration is bilateral.
Authors: Hasan Bombaci; Bestami Simsek; Mehmet Soyarslan; Mustafa Murat Yildirim Journal: Acta Orthop Traumatol Turc Date: 2017-10-10 Impact factor: 1.511