Cost Analysis of Conversion Total Knee Arthroplasty: A Multi-Institutional Database Study

Utilizing Evolved Extramedullary Techniques for Conventional Knee Arthroplasty in Post-traumatic Knee Arthritis With Retained Hardware: A Retrospective Analysis

Introduction For post-traumatic knee arthritis with retained implants, performing conventional primary total knee arthroplasty (TKA) can be challenging due to altered bony structures or mechanical obstructions. Without current computer-aided navigation, we can still perform conventional TKA by extramedullary means according to the parallelism and the reference to inherent anatomical landmarks. In this study, we aim to present a novel extramedullary method applied during conventional total knee arthroplasty (TKA) and the clinical outcomes observed in our series. Methods Between April 2014 and March 2021, patients with post-traumatic knee arthritis and retained hardware scheduled for TKAs at our institute were included. All the index procedures were performed with primary cemented TKA prostheses by the same surgeon. After the proximal tibial cut perpendicular to the tibial shaft, the following distal femur cut was executed according to the parallelism between these cuts. Certain interfering hardware located on the metaphyseal area, like screws or staples, were removed as needed. In addition, most of the conventional principles and techniques in traditional knee replacement were followed. Clinical outcomes, including perioperative blood loss, transfusion rate, inpatient stay, knee functional score, and radiographic evaluation, were recorded and reviewed. Results Within a period of eight years, there were 12 patients with a mean age of 67.8 years old enrolled. Overall, there was a good restoration of optimal mechanical alignment after surgery, and the mean hip-knee-ankle (HKA) angle was 180.2o compared to their preoperative deformity (HKA 174.0o ± 10.4o). Clinical assessments according to the Knee Society score showed good knee scores (87.1), functional scores (87.1), and motion arc (106.7o). No patient required allogenic blood transfusion or prolonged stays (range: five to eight days). In the last outpatient visit, no radiographic implant failure was found, and no surgical site-specific complications were reported after clinical follow-ups for at least two years. Conclusions Our results suggest that post-traumatic knee arthritis with remnant hardware can be safely and effectively treated with conversion TKAs according to the suggested extramedullary (EM) techniques in this study. With minimal removal of interfering hardware, reduced surgical trauma as well as operation time, helps to achieve short-term clinical benefits, including reduced blood loss, inpatient stay, faster recovery, and even restoration of optimal limb alignment.

Unexpected positive cultures in conversion hip and knee arthroplasty

PURPOSE

Total hip and knee arthroplasty in patients with previous history of periarticular surgery, such as osteosynthesis, can be surprisingly complex. This type of procedure is known as conversion arthroplasty (cTHA or cTKA) and has a higher risk of complications. The rates of unexpected positive cultures (UPC) and the risk of periprosthetic joint infection (PJI) compared to primary arthroplasty is unclear. The main purpose of this study was to evaluate rates of Unexpected Positive Cultures (UPC) in a series of conversion arthroplasty patients. The main questions to answer are: 1. Are the patients with conversion arthroplasties more susceptible to UPC than other causes of revision arthroplasties? 2. Are the conversion patients with UPC more susceptible to developing PJI?

METHODS

This was a retrospective review of patients submitted to cTHA and cTKA from January 2012 to September 2018. Patients with history of previous infection or with missing intraoperative cultures were excluded. The UPC was defined as a single positive culture obtained during a procedure previously considered aseptic and PJI was defined according to the 2018 ICM criteria. After excluding 141 cases, 205 patients were analyzed, 160 hips and 45 knees.

RESULTS

Nine (4.4%) UPC were identified, five (3.1%) in the hip group and four (8,9%) in the knee group. Staphylococcal species were the most common isolated bacteria (n = 7, 77.7%). During the study period, four (1,9%) patients were diagnosed with PJI. Only one case had an UPC and a different germ was identified during revision arthroplasty workup.

CONCLUSIONS

While UPC are more prevalent in conversion knee arthroplasties compared to conversion hip arthroplasties, the rates are similar to those observed in revision arthroplasty for other indications. Importantly, the presence of a UPC in conversion arthroplasty does not appear to elevate the risk of subsequent periprosthetic joint infection, provided a thorough PJI workup has been conducted preoperatively. Therefore, in such cases, UPCs may be safely disregarded.