Background: Total knee arthroplasty (TKA) for poliomyelitis patients is controversial due to its higher complication rate compared with that of TKA for osteoarthritis. In this study we evaluated the results, at a minimum of 10 years, of a consecutive series of third-generation rotating hinge total knee arthroplasties (RHKs) in patients affected by poliomyelitis. Methods: We conducted a retrospective analysis of 14 patients (15 TKA) performed between January 2000 and October 2021 that underwent a third-generation rotating hinge arthroplasty (Nex Gen RHK Zimmer). The clinical results using the American Knee Society Score (AKSS) were evaluated at an average follow-up of 154 months (min 120–max 216 months). Result: Of the 15 cases, 2 were lost at follow-up and 1 was excluded by the final evaluation due to infection. Of the remaining 12 cases at the final follow-up, the average AKKS clinical score improved from 30.08 points preoperatively, to 78.83 points postoperatively, while the average AKKS function score improved from 29.17 points to 56.25 points. We report only one intraoperative complication consisting of a femoral fracture at the tip of the stem, and a case of patellar fracture occurred 3 months after the index procedure. The presence of radiolucent lines was sporadic, while radiosclerotic lines were commonly visible around the stem extension, predominantly at the tip. Conclusions: The third generation of rotating hinge knee replacement has proved to be effective in polio patients, improving clinical and functional scores, and no cases of mechanical failure occurred.

INTRODUCTION The incidence of periprosthetic fractures (PFFs) is estimated to range from 0.1% to 4.1%1, due to the increasing prevalence of joint arthroplasties, coupled with an aging population. Numerous risk factors, including advanced age (>80 years), female gender, implant type, prior diagnoses of osteonecrosis and rheumatoid arthritis, revision surgery, aseptic stem mobilization, and the use of non-cemented stems, have been identified. Survivors of periprosthetic fractures often experience functional deterioration, facing a fourfold higher risk of hospitalization for postoperative complications compared to patients undergoing primary implantation, especially in the first postoperative year. MATERIALS AND METHODS Between 2018 and 2022, at the Maggiore Hospitals in Bologna and the San Matteo Policlinic in Pavia, we performed osteosynthesis on 84 patients with periprosthetic fractures of Vancouver type B1 or C. In 38 patients, we employed angular stable plates with the Zimmer Biomet NCB-PP® system. In 46 patients, we utilized INTRAUMA plates: DF distal femur and PFF proximal. Relevant postoperative follow-up outcomes considered included reintervention, infectious complications, radiographic healing, and functional recovery, with reference to changes in the Glasgow Outcome Scale (GOS) and the Harris Hip Score (HHS). All patients underwent clinical and radiographic evaluations during the follow-up period, averaging 28 months (range: 12-48 months), with a minimum follow-up duration of 12 months. RESULTS At the 4-month postoperative assessment, 71% of patients maintained their preoperative functional level, 19% experienced a 1-point GOS scale drop, and 10% died (GOS 5). The average HHS at 4 months was 80.2 points (range: 65-90). At the 6-month follow-up, 98.2% of patients achieved complete healing on radiographic examination. Only 1 patient (1.2%) developed a pseudoarthrosis site with synthesis device rupture. Only 1 patient (1.2%) required additional surgical treatment 2 years later due to the development of un aseptic perisynthetic fluid collection, while the remaining 5 patients (6%) who developed complications benefited from conservative treatment: 4 patients (3.6%) with infectious complications were treated with intravenous antibiotics. In the 2 patients (2.3%) with mobilization or rupture of synthesis devices, clinical and radiographic monitoring was opted for. 8 patients (10.7%) died: one 48 hours after the surgery, and the other 7 more than one month after the surgery. CONCLUSION Our clinical findings align with to existing scientific literature on periprosthetic fractures (B1 and C according to Vancouver classification). Moreover, good stability has been guaranteed at the radiological follow up by Zimmer Biomet NCB-PP® and INTRAUMA DF distal femur and PFF proximal plates. The locking construct allows for improved stability especially in osteoporotic bone.