Accolade 2

The Anatomic Dual Mobility Restoration acetabular system (Stryker, Warsaw, Mazovia, Poland) with a mobile liner made of X3 highly cross-linked PE (Stryker, Warsaw, Mazovia, Poland) and a ceramic size 28-mm femoral head was used in both the phantom and the patient. The hip stems were a Bi-Metric size 7 (Biomet, Warsaw, IN, USA) in the phantom and Accolade II (Stryker, Warsaw, Mazovia, Poland) size 4 in the patient. Cup/liner 56-mm size was used in the phantom and 50-mm size was used in the patient. An experienced hip surgeon inserted the components into the Sawbone hip (No 1301-165-1, Sawbones, WA, USA) and also the patient by use of a posterolateral approach.

Cementless total hip arthroplasty was performed by a single orthopedic surgeon using an anterolateral Hardinge approach. The procedure involved implantation of a parallel‐sided femoral component11, 37 (Accolade II, Stryker Orthopaedics, Mahwah, NJ, USA), with a metallic head and a porous‐coated acetabular cup with polyethylene liner. The patients were mobilized with use of standard physiotherapy, and unrestricted weight‐bearing was encouraged with the aid of crutches.
A computerized method (Rhinoceros software, version 3.0SR5b, Robert McNeel & Associates, Seattle, WA, USA) was applied to measure femoral offset,38 canal flare index,39 cortical index,40 and stem‐to‐canal fill ratio41 from the anteroposterior hip radiographs. Fill ratio was defined as the percentage of endosteal space occupied by the implant.42 The ratio of the stem width over the femoral canal width was measured 10 mm above the lesser trochanter (proximal stem) and 60 mm below the lesser trochanter (middle stem).

All subjects underwent standardized cementless THA with implantation of a tapered parallel‐sided single‐wedge femoral stem (Accolade II, Stryker Orthopedics, Mahwah, NJ, USA)⁽²⁴⁾ using the recommended broach‐only technique.⁽²⁵⁾ The stem is the most frequently used femoral component of cementless THA in the United States.⁽¹⁾ The investigated stem type requires adequate bone stock and unaltered femoral anatomy.⁽²⁵⁾ During surgery, multiple tantalum RSA beads (1 mm in diameter) were inserted into the trochanteric bone (Fig. 1). Patients were mobilized postoperatively under the supervision of physiotherapists, and unrestricted weight bearing was allowed with the aid of crutches.

The enhanced workflow was used in all cases providing intra-operative feedback regarding broach and stem version, combined anteversion and guiding neck resection. Robotic arm assistance was used to perform reaming in the desired plane with the utilisation of stereotactic boundaries. The acetabular cup was also positioned with the assistance of the robotic arm and the haptic tunnel that maintains the planned orientation during implantation. In this prospective cohort study, all patients received a cementless femoral stem (Accolade II; Stryker, Mahwah, NJ, USA) and a peripheral self-locking porous acetabular shell (Trident PSL shell; Stryker).

The consecutive patients who underwent bilateral DAA-THAs simultaneously between May 2016 and November 2018 in our institute were retrospectively reviewed. Inclusion criterion: 1. bilateral THAs were performed through DAA simultaneously; 2. bilateral THAs were completed by one surgeon with the cementless acetabular cup (Pinnacle, Depuy, New Jersey, USA) and tapered femoral stem (Accolade II, Stryker, Mahwah, USA); 3. bilateral hips had the same stage of the same etiology (Crowe classification and Ficat classification) and bilateral acetabulum had similar bone mass [10 (link), 11 (link)]; 4. neither hip had the deformity caused by previous surgery and trauma. Exclusion criterion: 1. periprosthetic joint infection (PJI) or periprosthetic fractures in the postoperative follow-up period; 2. the follow-up period was shorter than 1 year. A total of 115 patients met the inclusion criterion and 102 patients were enrolled in this study finally (Fig. 1). The surgeon in this study has performed about 500 cases of DAA-THA and been defined as right-hander by the Edinburgh Handedness Inventory [12 (link)]. Institutional Review Board approval for this study was obtained (S2019–029-01).
Fig. 1

Flow chart of patient enrollment in this study

All operations were performed via the direct anterior approach, with the patient in the supine position on a standard table with fluoroscopic control [19 (link)]. A cementless stem was used in all cases, including the Accolade TMZF or Accolade II (Stryker Orthopaedics, Mahwah, NJ, USA) in 153 hips, Taperloc Complete Microplasty system (Zimmer Biomet, Warsaw, IN, USA) in five, meta-diaphyseal anchoring calcar-guided short-stemmed Optimys (Mathys Ltd., Bettlach, Switzerland) in eight, TwinSys femoral stem (Mathys Ltd.) in two, and Modulus System (Lima Corporate San Daniele Del Friuli, Udine, Italy) in two. A cementless cup was used in 166 patients; the Trident cup (Stryker Orthopaedics) was used in 157 hips (modular dual mobility cup in 54 hips), G7 cup and G7 dual mobility system (Zimmer Biomet) were used in five, and a Kerboull-type acetabular reinforcement device with X3 Rim Fit (Stryker Orthopaedics) was used in four. Postoperatively, all patients followed the same rehabilitation protocol and walking exercise with full weight-bearing began on postoperative day 1.