Methods

We examined 12 patients (19 knees) implanted with a low contact stress (LCS) mobile-bearing TKA system using a two- to three-dimensional registration technique as previously reported [1]. All 12 patients were diagnosed with medial knee osteoarthritis. The in vivo kinematics of dynamic deep knee flexion under WB and non-WB (NWB) conditions were compared. We evaluated the knee range of motion, femoral axial rotation relative to the tibial component, anteroposterior translation, and kinematic pathway of the femorotibial contact point for both the medial and lateral sides.

Patients & Methods

We reviewed the medical records and radiographs of the studied subjects after approval of this study by the institutional review board committee. Experiment 1: Between October 2011 and May 2012, 60 consecutive primary THAs were performed with the mini-trochanteric approach, which involved reattaching the osteotomised fragment using UHMWPE tape (Nesplon; Alfresa Pharma, Osaka, Japan). [Fig.1] By splitting the anterior one-fourth of the gluteus medius, the minitrochanteric osteotomy, a half-ellipsoid body about 15 mm long, 10 mm wide, and 5 mm deep, is performed using a curved chisel. After implanting of the prosthesis, the osteotomised fragment is reattached by using two 3-mm wide Nesplon tapes. Using 2.4 mm Kirshner wire, two sets of drill holes are created below the trochanteric bed of the femur. Nesplon tapes are passed through each drill hole and penetrated over the trochanteric fragment. Nesplon tape is tied using a double-loop sliding knot in conjunction with a special tightening gun tensioner up to 20 kgf. [Fig.2] The radiographic results were retrospectively analyzed to determine the incidence of nonunion and complications related to trochanteric site. Hip functional results were rated according to the Japanese Orthopedic Association (JOA) hip score. Experiment 2: Between July 2011 and May 2012, 5-mm wide Nesplon tapes were used for restoration of intraoperative femoral fractures in 4 primary THAs. For the repair of intraoperative proximal femoral fractures, 5-mm wide Nesplon tape is tightened with cerclage wiring technique using the gun tensioner up to 30 kgf. [Fig.3] The postoperative radiographic changes were analyzed.

Methods

We retrospectively reviewed 6 hips (6 patients) that had undergone femoral revisions with a circumferential metal mesh, impacted bone allografts, and a cemented stem. The mean follow-up period was 2.9 years (range, 1.4–3.8 years). Hip joint function was evaluated with the Japanese Orthopaedic Association hip score, and radiographic changes were determined from radiographs. The initial resistance of cemented stem complexes to axial and rotational force was measured in a composite bone model with various segmental losses of the proximal femur.

Case

The patient was a 64 old woman and complained of chronic mild pain around her left groin region. X-ray examination revealed that osteolysis had been expanding around the screws and extended proximally. The revision surgery was performed for the massive osteolysis through Hardinge antero-lateral approach. The retrieved implants included a cementless cup made of titanium alloy (QPOC cup, Japan Medical Materirals Inc.(JMM) Osaka, Japan), the outer surface of which was plasma-sprayed with titanium for porous formation and coated with AWGC in the deep layer. It was found that the polyethylene liner was destructed partially in the supero-lateral portion, but the cup was well fixed to the bone. The bone-attached area was found to be dispersed over the porous surface of the hemispherical cup. Histological examination revealed that matured bony tissue intruded into the porous surface of the cup, and contacted to bone directly, which was also demonstrated in the back-scattered electron image. It was also demonstrated that there were residual silicon (Si) rich regions on the porous surface by the SEM-EDX analysis, which indicated that constituents of AWGC still remained on the surface. On the other hand, the results of elementary analyses in the Si rich regions varied among the sections, which probably indicated that the extent of degradation and absorption of AWGC varied among the sections.

AWGC was one of the bioactive ceramics and reported to have an ability to bond to bone earlier than hydroxyapatite (HA). In the present case, though massive osteolysis occurred with aggressive wear, it did not expand on the porous surface, and rather progressed along the smooth surface of the screws. Considering that there are many clinical studies reporting poor clinical results of HA-coated smooth cups, bioactive ceramic coating may function well and bring superior clinical results when combined with porous coated substrate. In our study, though the cause of massive polyethylene wear and intrapelvic giant osteolysis could not be revealed, the porous cup with AW-GC bottom coating was well fixed and gained bone-ingrowth at the porous surface under osteolytic conditions, which may demonstrate the long-term durability of this surface treatment.