Mobile-bearing insert used with total knee arthroplasty does not rotate on the tibial tray during a squatting activity: a cross-sectional study.

BACKGROUND: Total knee arthroplasty (TKA) is commonly performed around the world. Implant designs include fixed-bearing and mobile-bearing. Mobile-bearing design was developed as a rotating platform that allows axial rotation of the insert around the longitudinal axis. This phenomenon may limit full exploitation of the characteristics of the mobile-bearing insert, which may cause wearing and reduce longevity. However, there is limited knowledge on rotational behavior of the polyethylene mobile-bearing insert under weight-bearing conditions. We aimed at determining the rotational motion of each component at full extension and flexed positions during a squatting activity after TKA. METHODS: This study was a cross-sectional study (level 4) involving patients with severe knee osteoarthritis scheduled to receive TKA. We examined 13 knees of 11 patients after mobile-bearing TKA (NexGen LPS-Flex, Zimmer Inc.) at 10 weeks and 1 year postoperatively. Four identical metallic beads were embedded into the insert. Wide-base squatting was chosen for analyses. Three-dimensional in vivo poses of the prostheses were created using a 3D-to-2D registration technique. During flexion, rotation of the femoral component relative to the insert (FEM/INS) and tibial component (FEM/TIB) as well as insert rotation relative to the tibial component (INS/TIB) were computed. Repeated measure 2-way ANOVA and post hoc test was used. RESULTS: In the fully extended position, FEM/INS was significantly smaller than INS/TIB both at 10 weeks (- 0.3° vs. 6.3°, p = .013) and 1 year (- 0.8° vs. 4.9°, p = .011), respectively. During the squatting activity, rotation motions of FEM/TIB, FEM/INS, INS/TIB were 5.7°, 5.9°, and 1.8° at 10 weeks and 6.3°, 5.5°, and 1.6° at 1 year, respectively. Rotation motion of FEM/INS was significantly greater than that of INS/TIB at both 10 weeks (p < .001) and 1 year (p < .001). CONCLUSIONS: The mobile-bearing insert enhances the compatibility of FEM/INS in extension; the amount of INS/TIB rotation is significantly smaller than that of FEM/INS during a squatting activity. This information will inform surgeons to take caution to perform TKA with a fixed insert in which 6.3° of rotational offset would be added to the rotational alignment at FEM/INS at full extension. TRIAL REGISTRATION: UMIN-CTR, UMIN000024196. Retrospectively registered on 9 September 2016.

Transtrochanteric rotational osteotomy for various hip disorders.

BACKGROUND: Joint-preserving procedures should be considered as much as possible for hip disorders in pediatric and young patients. However, in patients with extensive osteonecrosis (ON) of the femoral head combined with severe collapse and advanced secondary osteoarthritis (OA), the optimal procedure has not been elucidated. This retrospective study aimed to investigate the postoperative outcomes of 11 patients who underwent transtrochanteric rotational osteotomy (TRO) alone or with a combination treatment for various hip disorders in young patients and to evaluate the usefulness of TRO. METHODS: Eleven patients (11 hips) with a mean age at operation of 22 years were included. The mean follow-up duration was 9.4 years. Preoperative diagnosis was secondary OA in 6 patients (pigmented villonodular synovitis, 2; after rotational acetabular osteotomy, 1; pyogenic arthritis, 1; femoroacetabular impingement, 1; acetabular dysplasia, 1) and ON in 5 patients (slipped capital femoral epiphysis, 4; femoral neck fracture, 1). Combination treatment was performed in 2 patients with distraction arthroplasty and in 6 patients with intra-articular procedures (mosaicplasty, 1; drilling, 1; microfracture, 4; cam resection, 1). Clinical evaluation was performed by using the Merle d'Aubigne and Postel score (MDPS). Joint congruency and progression of osteoarthritic change in all cases, and progression of collapse in the ON patients were evaluated radiographically. RESULTS: The mean MDPS improved from 10.3 to 14.2 in the OA patients and from 9.4 to 14.8 in the ON patients. The OA grade was maintained or improved in 10 hips (91%). Progressive collapse was prevented in all ON patients, and good remodeling was demonstrated. CONCLUSION: Even in the highly degenerative cases, TRO enabled repair and prevention of the progression of OA. This procedure might be a useful salvage operation for treating secondary OA and ON of the hip even if the clinical condition is advanced, especially in young patients.

Rotational Acetabular Osteotomy.

Hip dysplasia is the most common cause of secondary osteoarthritis (OA). To prevent the early onset of secondary OA, Nishio's transposition osteotomy, Steel's triple osteotomy, Eppright's dial osteotomy, Wagner's spherical acetabular osteotomy, Tagawa's rotational acetabular osteotomy (RAO), and Ganz' periacetabular osteotomy (PAO) have been proposed. PAO and RAO are now commonly used in surgical treatment of symptomatic acetabular dysplasia in Europe, North America, and Asia. The aim of this paper is to present the followings: the patient selection criteria for RAO; the surgical technique of RAO; the long-term outcome of RAO; and the future perspectives.

Wear debris stimulates bone-resorbing factor expression in the fibroblasts and osteoblasts.

Wear debris is believed to cause periprosthetic osteolysis and loosening of total joint arthroplasties. We investigated the wear debris-mediated osteolysis in wild-type mice and macrophage-deficient Csf1op/Csf1op (op/op) mice using high density polyethylene (HDP) particles transplanted on the parietal bone surface. Four weeks after surgery, phagocytosis of the HDP particles by F4/80-positive macrophages and tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts was observed in the normal mice, but not in the macrophage-deficient op/op mice. These results suggest that macrophages are implicated in wear debris-dependent osteoclast formation. However, HDP particles were phagocytosed not only by macrophages but also by F4/80-negative cells in both genotypes of mice. Electron microscopic observation identified these cells as fibroblasts. Cell culture studies demonstrated that fibroblasts cultured with HDP-particles showed upregulation of interleukin-6 (IL-6) expression compared with non-treated fibroblasts. When we examined the gene expression of osteoblasts that belong to the mesenchymal cell lineage as fibroblasts, we found that the expression of not only IL-6 but also interleukin-1 beta (IL-1ß), tumor necrosis factor-alpha (TNF-α) and cyclooxygenase2 (Cox2) were up-regulated by HDP particle-stimulation. These findings suggest the possibility that fibroblasts and osteoblasts are involved in wear debris-mediated osteolysis within the tissue surrounding artificial joints through the production of bone resorbing factors IL-6, IL-1ß, TNF-α, and Cox2.