Micromotion measurement at the interfaces of cemented tibial endoprosthetic replacements: A new standardized in vitro model using open-cell rigid foam.

Early aseptic loosening following primary total knee arthroplasty related to several factors might appear at the interface implant-cement or cement-bone. A standardized in vitro model might provide information on the relevance of single variable parameter of cementation including technique and cement respectively bone structure on fixation strength. Micromotion measurement using different directions of load should detect the primary stability of the interfaces. An open-cell rigid foam model was used for cementation of PFC-Sigma tibial trays with Palacos®. Pins were applied to the model for continuous non-destructive measurement. Relative micromotions for rotation, valgus-varus and extension flexion stress were detected at the interfaces as well as cement penetration was measured. The reproducibility of the measurement could be shown for all interfaces in extension-flexion movements. For rotation a negative trend was shown for the interface cement-prosthesis and cement-bone concerning varus-valgus stress reflecting varying surgical cementation technique. More micromotion related to extension-flexion force might reflect the design of the implant. Measurement of relative micromotion and cement distribution appear accurate to detect small differences of movement at different interfaces of cemented tibial implants and the results are reproducible for most parameter. An increased number of specimens should achieve statistical relevance for all measurements.

Diagnosis Dilemma, Culture-Negative Periprosthetic Hip Infection Versus Acute Gouty Arthritis: A Case Report.

CASE: We report the case of acute gouty arthritis mimicking infection in a 59-year-old woman who had an extensive history of periprosthetic joint infection (PJI) and multiple revisions. Initial laboratory testing, examination, and recency bias suggested recurrent PJI, but aspiration revealed an acute gout attack without superimposed infection. The patient's examination and serological markers improved off antibiotics, and she subsequently avoided an unnecessary revision surgery. CONCLUSION: Although rare, acute gouty arthritis should be considered in every patient, and complete workup should be performed, regardless of infectious or rheumatologic history.

Effect of Fracture Type, Treatment, and Surgeon Training on Reoperation After Vancouver B Periprosthetic Femur Fractures.

BACKGROUND: The treatment of Vancouver B periprosthetic proximal femur fractures (PPFFs) is complex due to the overlap between arthroplasty and orthopedic trauma techniques. Our purpose was to assess the effects of fracture type, treatment difference, and surgeon training on the risk of reoperation in Vancouver B PPFF. METHODS: A collaborative research consortium of 11 centers retrospectively reviewed PPFFs from 2014 to 2019 to determine the effects of variations in surgeon expertise, fracture type, and treatment on surgical reoperation. Surgeons were classified as per fellowship training, fractures using the Vancouver classification, and treatment as open reduction internal fixation (ORIF) or revision total hip arthroplasty with or without ORIF. Regression analyses were performed with reoperation as the primary outcome. RESULTS: Fracture type (Vancouver B3 versus B1: odds ratio [OR]: 5.70) was an independent risk factor for reoperation. No differences were found in reoperation rates with treatment (ORIF versus revision: OR 0.92, P = .883). Treatment by a nonarthroplasty-trained surgeon versus an arthroplasty specialist led to higher odds of reoperation in all Vancouver B fracture (OR: 2.87, P = .023); however, no significant differences were seen in the Vancouver B2 group alone (OR: 2.61, P = .139). Age was a significant risk factor for reoperation in all Vancouver B fractures (OR: 0.97, P = .004) and in the B2 fractures alone (OR: 0.96, P = .007). CONCLUSION: Our study suggests that age and fracture type affect reoperation rates. Treatment type did not affect reoperation rates and the effect of surgeon training is unclear.