Modular Fluted Tapered Stems for Periprosthetic Femoral Fractures: Excellent Results in 171 Cases.

BACKGROUND: Modular fluted tapered (MFT) stems have advanced treatment of Vancouver B2 and B3 periprosthetic femoral fractures, but series to date have been limited with respect to cohort size and follow-up duration. The purpose of this study was to determine implant survivorship, radiographic results, complications, and clinical outcomes of Vancouver B2 and B3 periprosthetic femoral fractures treated with MFT stems in a large series of patients. METHODS: We identified 171 Vancouver B2 (109) and B3 (62) periprosthetic femoral fractures treated with an MFT stem between 2000 and 2018 using our institutional total joint registry. The mean age was 75 years, 50% were female, and the mean body mass index was 29 kg/m2. The median stem diameter was 18 mm and median stem length was 210 mm. The cumulative incidences of revision and reoperation with death as the competing risk were calculated, radiographs were reviewed, and clinical outcomes were evaluated using the Harris hip score (HHS). The mean follow-up was 5 years. RESULTS: The 10-year cumulative incidence of any revision was 10%. There were 17 revisions, of which only 3 were for the distal fluted portion of the MFT stem. Revision indications included periprosthetic joint infection (PJI) (n = 6) and dislocation (n = 11). The 10-year cumulative incidence of any reoperation was 15%. In addition to the above 17 revisions, there were 7 reoperations for superficial wound complications (n = 4), Vancouver B1 periprosthetic femoral fracture (n = 1), vascular occlusion (n = 1), and acetabular cartilage degeneration requiring an acetabular component (n = 1). Radiographically, there was 1 fracture nonunion. All unrevised MFT stems were radiographically well fixed. Subsidence of ≥5 mm occurred in 11%, but all implants were stable at the most recent follow-up. The mean HHS was 75 at 2 years (n = 71). CONCLUSIONS: In this large series of 171 Vancouver B2 and B3 periprosthetic femoral fractures treated with MFT stems, we found that such constructs were associated with a high rate of fracture healing and provided extremely reliable and durable implant fixation, with no revisions for aseptic loosening. Dislocation and PJI were the most common complications. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Human outgrowth knee fibroblasts from patients undergoing total knee arthroplasty exhibit a unique gene expression profile and undergo myofibroblastogenesis upon TGFß1 stimulation.

Arthrofibrosis is characterized by excessive extracellular matrix (ECM) deposition that results in restricted joint motion after total knee arthroplasties (TKAs). Currently, treatment options are limited. Therefore, an in vitro model of knee-related myofibroblastogenesis is valuable to facilitate investigation of the arthrofibrotic process, diagnostic and therapeutic options. In this study, we obtained intraoperative posterior capsule (PC), quadriceps tendon (QT), and suprapatellar pouch (SP) tissues from the knees of four patients undergoing primary TKAs for osteoarthritis. From these tissues, we isolated primary cells by the outgrowth method and subsequently characterized these cells in the absence and presence of the pro-myofibroblastic cytokine, transforming growth factor beta 1 (TGFß1). Light microscopy of knee outgrowth cells revealed spindle-shaped cells, and immunofluorescence (IF) analysis demonstrated staining for the fibroblast-specific markers TE-7 and vimentin (VIM). These knee outgrowth fibroblasts differentiated readily into myofibroblasts as reflected by enhanced α-smooth muscle actin (ACTA2) mRNA and protein expression and increased mRNA expression of collagen type 1 (COL1A1) and type 3 (COL3A1) with collagenous matrix deposition in the presence of TGFß1. Outgrowth knee fibroblasts were more sensitive to TGFß1-mediated myofibroblastogenesis than adipose-derived mesenchymal stromal/stem cells (MSCs). While outgrowth knee fibroblasts isolated from three anatomical regions in four patients exhibited similar gene expression, these cells are distinct from other fibroblastic cell types (i.e., Dupuytren's fibroblasts) as revealed by RNA-sequencing. In conclusion, our study provides an in vitro myofibroblastic model of outgrowth knee fibroblasts derived from patients undergoing primary TKA that can be utilized to study myofibroblastogenesis and assess therapeutic strategies for arthrofibrosis.