Abstract
Introduction
In our institution, we started to perform THA with SuperPATH approach, including preservation of soft tissue around the hip (James Chow et al. Musculoskelet Med 2011) since July 2014, aiming for fast recovery and prevention of hip dislocation. For minimally-invasive approaches, however, there have been a few reports on malalignment of the implants related to shortage of operative field. The purpose of this study is to examine the short-term results of THA using SuperPATH, especially implant alignment.
Materials and methods
We performed a study of 45 patients (45 hips) with osteoarthritis of the hip joint who had a THA with SuperPATH approach. There were 8 men and 37 women with an average age of 73 years, which were minimally 24 months followed. Dynasty Bioform cup and Profemur Z stem (Microport Orthopaedics) were used for all cases. Patients were clinically assessed with Merle d'Aubigne score and complications. Implant alignment and stability were radiologically evaluated by annual X-ray and CT acquired two months after surgery.
Results
Merle d'Aubigne score was 10.2 (pain:2.8, mobility:4.4 walking ability:3.0) preoperatively and 16.6(pain:5.8, mobility:5.8, walking ability:5.0) at the latest follow-up. There were no dislocation and infection, but intraoperative proximal femoral fracture was found for two cases, which was managed to treat with additional circulating wire intraoperatively.
Latest follow-up X-ray image showed 95% of the stem A-P alignment to be within 2 degrees and 5% to be more than 2 degrees and less than 5 degrees, while 44% of the stem lateral alignment to be within 2 degrees, 47% to be more than 2 degrees and less than 5 degrees, and 8% to be more than 5 degrees. From CT images averaged cup position found to be 40±5 degrees for inclination, and 19±5 degrees for anatomic anteversion, averaged stem anteversion to be 33±9 degrees. Annual X-ray evaluation showed no radiolucent line and less than Grade 2 stress-shielding (Engh classification) around the implants for all cases. One case had more than 5mm subsidence of the stem in early postoperative period, but not progressively subsided. No loosening of components was evident.
Discussion and Conclusion
Many minimally-invasive approaches have developed, there have been many reports on fast recovery and low incidence of postoperative hip dislocation, however, the risk of complications or malalignment related to shortage of operative field has been pointed out. In this study, intraoperative proximal femoral fracture occurred for two cases. Also, though there were no loosening and the components position seemed excellent but lateral view of the X-ray showed 8% to be more than 5 degrees tilting alignment, resulting from femoral broaching required before femoral neck resection.
SuperPATH approach, including pass way from between the Gluteus Medius and the piriformis tendon, can preserve the whole short external rotators and capsule of the hip joint, leading to fast recovery and low incidence of postoperative dislocation. Moreover, this approach may be friendly to the surgeons familiar with the posterior approach because of easily conversion to the conventional posterior approach.
