Features of adjacent joint structures remodeling after prosthetic application of a tibial calcium-phosphate coated implant

Introduction Studying the reorganization of adjacent joint components due to prosthesis application and identifying predictors of arthrosis are key factors to successful functional restoration of a prosthetic limb.

The aim of this study was to evaluate the structural reorganization of the basic joint components after prosthetic application of a calcium phosphate-coated implant at long term.

Materials and Methods The study was conducted on five intact and six experimental mongrel male dogs, aged 1.8 ± 0.5 years and weighing 19.0 ± 1.2 kg. A tibial stump was modeled at the level of the upper third of the diaphysis. A Ti6Al4V calcium-phosphate coated implant was used 2.5 months later. The study was conducted at six and 12 months after prosthesis application. Histomorphometry of the synovial membrane and osteochondral component of the tibial plateau was performed on semithin and paraffin sections using an AxioScope.A1 microscope with Zenblue software (CarlZeissMicroImagingGmbH, Germany).

Results Mild synovitis detected at six months (hyperplasia of the integumentary layer, predominance of macrophage-like synoviocytes, plasma cells, and mast cells) was reversible in 70 % of cases at 12 months. Signs of impaired synovial blood supply were recorded. Articular cartilage changes according to the OARSI scale corresponded to grades 0–1 at six months and grades 1–2 at 12 months (in one case, synovial pannus). Basophilic line abnormalities were noted: vessel density (number of vessels per unit of visual field analyzed) was (0.35 ± 0.02) at six months and (0.30 ± 0.02) at 12 months. Differences between time points were statistically insignificant, p = 0.736. Subchondral bone plate thickness was significantly (p = 0.0105) lower than in the control. At 12 months, the median subchondral bone plate thickness was 33 % higher than the one in the control animals, and the bone index was 31 % higher; differences were statistically significant. Active osteoblasts that were lining bone trabeculae were noted at all stages; fuchsinophilic structures predominated in the bone matrix when stained with Masson's method.

Discussion The histological signs of inflammation and impaired blood supply to the synovial membrane, thinning of the articular cartilage, and invasion of the synovial pannus into the superficial zone and vessels into the deep cartilage zone were prognostic markers of osteoarthritis.

Conclusion Structural changes in the osteochondral component of the tibial plateau one year after application of a tibial calcium phosphate-coated implant were consistent with the initial stage of osteoarthritis. Mild non-infectious synovitis was reversible. The use of calcium phosphate-coated implants promoted the activation of reparative osteogenesis and mineralization of the bone matrix in the subchondral zone.

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