Promising medium-term results of anterior approach with an anatomical short stem in primary hip arthroplasty

Abstract

Background: In the last decade, the increase in the use of the direct anterior approach to the hip has contributed to the diffusion of the use of short stems in orthopedic surgery. The aim of the study is to verify the medium-term clinical and radiographic results of a cementless anatomic short stem in the anterior approach to the hip. We also want to verify whether the use of the standard operating room table or the leg positioner can affect the incidence of pre- and postoperative complications.

Materials and methods: All total hip arthroplasty patients with a 1-year minimum follow-up who were operated using the MiniMAX stem between January 2010 and December 2019 were included in this study. Clinical evaluation included the Harris Hip Score (HHS), Western Ontario and McMaster Universities Hip Outcome Assessment (WOMAC) Score, and Short Form-36 (SF-36) questionnaires. Bone resorption and remodeling, radiolucency, osteolysis, and cortical hypertrophy were analyzed in the postoperative radiograph and were related to the final follow-up radiographic results. Complications due to the use of the standard operating room table or the leg positioner were evaluated.

Results: A total of 227 patients (238 hips) were included in the study. Average age at time of surgery was 62 years (range 38-77 years). Mean follow-up time was 67.7 months (range 12-120 months). Kaplan-Meier survivorship analysis after 10 years revealed 98.2% survival rate with revision for loosening as endpoint. The mean preoperative and postoperative HHS were 38.35 and 94.2, respectively. The mean preoperative and postoperative WOMAC Scores were 82.4 and 16.8, respectively. SF-36 physical and mental scores averaged 36.8 and 42.4, respectively, before surgery and 72.4 and 76.2, respectively, at final follow-up. The radiographic change around the stem showed bone hypertrophy in 55 cases (23%) at zone 3. In total, 183 surgeries were performed via the direct anterior approach (DAA) on a standard operating room table, and 44 surgeries were performed on the AMIS mobile leg positioner. Comparison between the two patient groups did not reveal significant differences.

Conclusion: In conclusion, a short, anatomic, cementless femoral stem provided stable metaphyseal fixation in younger patients. Our clinical and radiographic results support the use of this short stem in the direct anterior approach.

Level of evidence: IV.

Keywords: Anatomic hip stem; Direct anterior approach; Leg positioner; Short hip stem; Standard table.

Fig. 1

Radiographic follow-up and definition of Gruen’s periprosthetic zones in anteroposterior view (a) and axial view (b)

Fig. 2

Bilateral avascular necrosis of femoral head in a 46-year-old patient (a). Five years radiographic follow-up: anteroposterior view (b) and axial view of right (c) and left (d) hips. Undisplaced fracture of calcar region treated with preventive cerclage on right hip

Fig. 3

Kaplan–Meier survivorship analysis after 10 years. Survival rate of 98.2% (95% CI, 94.1–96.1%) with revision for loosening as endpoint

Fig. 4

Radiographic change around stem in a 62-year-old patient: postoperative radiograph (left), 1 year follow-up radiograph showing bone cortical hypertrophy in zone 3 (central), 5 years follow-up radiograph with evidence of stabilization of cortical hypertrophy