Introduction:

Since2007, we have used CT-based fluoroscopy-matching navigation system (Vector Vision Hip Ver.3.5.2, BrainLAB, Germany) in revision total hip arthroplasty. This system completes the registration procedure semi-automatically by matching the contours of fluoroscopic images and touching 3 adequate points to the contours of 3D bone model created in the computer. Registration procedure using fluoroscopic figures has finished before making surgical incision. It needs no elongation time during the operation. The objective of this study was to evaluate the accuracy of CT-based fluoroscopy-matching navigation system in revision THA.

Introduction

Since2007, we have used CT-based fluoroscopy-matching navigation system (Vector Vision Hip Ver.3.5.2, BrainLAB, Germany) in Total hip arthroplasty. This system completes the registration procedure semi-automatically by matching the contours of fluoroscopic images and touching 3 adequate points to the contours of 3D bone model created in the computer. Registration procedure using fluoroscopic figures has finished before making surgical incision. It needs no elongation time during the operation. The accuracy of navigation system depends on the techniques of registration used for the navigation and secure fixation of the dynamic reference markers. These could be affected by the different type of approaches. The objective of this study was to evaluate the accuracy of CT-based fluoroscopy-matching navigation system in THA and compare the cup position by anterolateral and posteolateral approaches.

Objectives: The direct anterior approach (DAA) is a distal portion of Smith-Peterson approach to the hip joint. Independent from the length of skin incision, no muscular dissection has to be done for total hip arthroplasty (THA). We have developed minimally invasive THA using DAA on the standard surgical table. The purpose of this study is to present the clinical results of 162 THAs with this approach and to know whether DAA can be safely performed on a standard surgical table.

Patients and Methods: Between August in 2004 and June in 2006, 189 primary THAs in 167 patients were performed through DAA in our hospital. We excluded patients with severe developmental dysplasia (12 hips) and with previous hip surgery (7 hips). The severity of dysplasia was graded according to the Crowe classification. We excluded Crowe type 3 or 4 osteoarthritis which requires a modified procedure to cope with the difficult anatomic situation and a different rehabilitation protocol, although it was possible to perform THA with DAA. In order to assess the recovery rate and safety of a rapid rehabilitation protocol after surgery, we also excluded patients with walking disability of uninvolved lower limb (8 hips). Thus, the results included 162 hips in 149 patients (125 women and 24 men). They were followed for at least 3 months postoperatively. The mean age was 62.6 years. The mean BMI was 23.1. The preoperative diagnosis was osteoarthritis in 142 hips, avascular necrosis of the femoral head in 11 hips, femoral neck fracture in 7 hips and rapid destructive cox-arthrosis in 2 hips. In patients with osteoarthritis, 136 hips (95.7%) are secondary to developmental dysplasia (Crowe 1: 112 hips, Crowe 2: 24 hips). Only 5 hips (5.4%) were primary osteoarthritis. The Bicontact total hip stem was used in 135 hips, the CentPilar system in 21 hips and others in 6 hips.

Results: Mean surgical time was 70.1 (range: 45 to 150) minutes. Mean operative blood loss was 368 (range: 73 to 1053) ml. Patients were able to walk over 50 meters with T-cane an average of 4.7 (1~30) days after surgery. Complications included one cup migration, one traumatic dislocation, one transient femoral nerve palsy, one heterotopic ossification and one asymptomatic stem subsidence (4 mm) in the early period postoperatively. The cup migration occurred 1 month after surgery and required re-surgery through the same incision. The radiographic analysis showed a mean cup inclination of 42.1 ± 7.1 degrees and a mean anteversion angle of 16.9 ± 4.3 degrees. The femoral component coronal alignment was within 3 degrees of neutral position in 159 hips. Varus alignment of more than 3 degrees was found in 3 hips.

Conclusion: We confirmed that the direct anterior approach was a safe and reproducible technique on the standard surgical table and allowed the prosthesis to implant correctly with no muscular dissection and no risk of denervation.