Mid-term clinical results of primary total knee arthroplasty using metal block augmentation and stem extension in patients with rheumatoid arthritis.

BACKGROUND: Despite recent advancements in rheumatoid arthritis (RA) pharmacotherapy, surgeons still encounter severely damaged knees. The purpose of the present study was to analyze the mid-term clinical results of total knee arthroplasty (TKA) with metal block augmentation and stem extension. METHODS: A total of 26 knees in 21 patients who underwent primary TKA with metal block augmentation and stem extension were retrospectively reviewed. All patients with a mean age of 63 years had RA for a mean duration of 15 years. Functional and radiographic results as well as complications were evaluated at the mean follow-up period of 6 years after TKA. Eight knees were lost follow-up after the two-year evaluation. RESULTS: Tibial bone defects with average depth of 19 mm were preoperatively recognized in all 26 knees. The postoperative joint line was reconstructed on average 11 mm above the fibular head using average thickness of 11 mm tibial inserts and 9 mm metal blocks with stem extension. Significant improvements (p < 0.05 for all comparisons) were observed postoperatively in maximum extension angle from -10° to -1°, range of motion from 101 ° to 115 °, and Knee Society Score (knee score/function score) from 35/18 to 90/64. Non-progressive radiolucent lines beneath the metal block and osteosclerotic changes around the medullary stem were found in 16 knees (62%) and 14 knees (54%), respectively. There was two failures (8%): fragile supracondylar femur fractures and knee instability. No knees showed any radiographic implant loosening, dislocation, polyethylene insert breakage, peroneal palsy, or infection. CONCLUSIONS: Primary TKA with metal block augmentation and stem extension could effectively restore function in RA patients with advanced forms of knee joint destruction, and be reliable and durable for a mean postoperative period of 6 years. Further study is needed to determine the long-term results of TKA using metal block augmentation and stem extension.

Effects of FGF-2 on metaphyseal fracture repair in rabbit tibiae.

Fibroblast growth factor-2 (FGF-2) has been found to have stimulatory effects on fracture repair at diaphysis, while its effect on metaphyseal fracture repair, where spongiosal bone is dominant, has not been studied. This study was conducted to investigate the effect of FGF-2 on metaphyseal fracture healing in a rabbit proximal tibial metaphyseal model. The proximal tibial metaphysis of 6-month-old Japanese white rabbits was osteotomized bilaterally. Then 400 microg of FGF-2, mixed with gelatin hydrogel, and gelatin hydrogel alone (the control) were injected to each osteotomy site of the rabbit proximal tibiae, and the osteotomies were fixed with staples. One and 2 weeks after surgery, the osteoid area in the repairing spongiosal bone at the fracture site was significantly larger in the FGF-2 group than in the control group ( P < 0.05). On immunohistochemistry, proliferating-cell nuclear antigen-positive cells had a tendency to show greater numbers in the FGF-2 group. After 4 and 8 weeks, values for bone mineral density and the cancellous bone area in the healing region of the fracture site were significantly larger in the FGF-2 group ( P < 0.05). These data suggest that local application of FGF-2 may have an accelerating effect on the repair of metaphyseal fractures. Exogenous recombinant human rhFGF-2 may have potential clinical applications in metaphyseal fracture treatment.

Intramuscular bone induction by the simultaneous administration of recombinant human bone morphogenetic protein 2 and bisphosphonate for autobone graft.

An ideal substitute for bone graft is autobone tissue, of which there is an ample supply of the required form and with vascularity. Our strategy is to generate intramuscular autogenous bone by administering recombinant human bone morphogenetic protein 2 (rhBMP-2) with beta-tricalcium phosphate (beta-TCP) as a carrier, and to transplant this bone as a muscle-pedicled autograft. However, in a previous study (Jingushi et al., J. Orthop. Sci. 7, 490, 2002), bone resorption occurred early after bone induction. This study was conducted to determine whether rhBMP-2-induced bone tissue could be maintained by simultaneous administration of bisphosphonate, and to investigate whether the induced bone could be used for bone grafting. In this study, we first applied rhBMP-2 alone to a beta-TCP disk and inoculated it into rat quadriceps muscle. Bone area and the number of tartrate-resistant acid phosphatase (TRAP)-positive cells in the induced bone disk peaked at 2 weeks, and induced bone resorption occurred later. Bisphosphonate and rhBMP-2 were then simultaneously applied to a beta-TCP disk and inoculated as in the first experiment. The addition of bisphosphonate decreased the number of TRAP-positive cells and increased the bone area and compression strength at 4 weeks. In the last experiment, a rhBMP-2 applied beta-TCP disk treated with or without bisphosphonate was free-grafted to parietal bone 4 weeks after inoculation. Both bone disks united similarly. We concluded that the concurrent use of bisphosphonate prevented bone absorption attributed to osteoclast activity after bone induction by rhBMP-2. The bisphosphonate application did not disturb the union of induced bone to host bone.