The Direct Anterior Approach to Hip Reconstruction

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SECTION III Intermediate Direct Anterior Approach Topics

FIGURE 14.10 An example of the use of a “stitched” AP pelvis fluoroscopic image with Radlink software to evaluate cup position and resto ration of limb length and hip offset.

lateral decubitus position. 12,13 The first study used a nar row safe zone acetabular position defined at 30° to 45° of inclination and 5° to 25° of anteversion and found that both criteria were accomplished in only 47% of the cases. 12 The second study, when using the same target safe zone criteria, demonstrated that only 38% of ace tabular components met both criteria. 13 The surgeons in these studies used traditional anatomic landmarks for component placement, and these cases were again per formed with patients in the lateral decubitus position. In a separate study, a single center compared its experience with and without fluoroscopy for component positioning in THA performed in the lateral decubitus position. They found significant improvement in acetabular component

positioning within their safe zone when fluoroscopy was used in the lateral position (57% vs 44%). 14 When fluoroscopy is applied to the supine DAA, one study found decreased variability of acetabular compo nent positioning compared with THA performed without radiographic guidance through a posterior approach. 15 This benefit has even been demonstrated in the obese patient population in which precision of the acetabular cup position has been found to be poor in traditional approaches. 16,17 A study including 1599 patients showed no significant difference when comparing nonobese, obese, and morbidly obese patients’ acetabular cup posi tion using fluoroscopy through a DAA approach, with over 91% being placed in the “safe zone” for inclination and version. 18 When evaluating the effectiveness of the aforemen tioned additive fluoroscopic technologies, there is a rel ative paucity of literature to date. One group performed a prospective randomized trial comparing acetabular component positioning in DAA THA performed with fluoroscopy alone with fluoroscopy with the addition of Radlink. 19 They found a slight improvement in the abduction angle using Radlink (mean: 40.4° vs 42.3°, P < .001) with the cost of about two extra minutes of time needed for cup placement. A retrospective study from a single center compared acetabular component position and restoration of hip offset and limb length with the use of fluoroscopy alone with fluoroscopy with the OrthoGrid. 20 Improvement in hip offset and leg length equalization have been found with the addition of OrthoGrid during DAA THA without preoperative templating. 21

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FIGURE 14.11 An example of a virtual digital fluoroscopic overlay using JointPoint software.