Effect of collateral ligament presence on results in rotating hinge prosthesis

Rotating Hinged Knee (RHK) arthroplasty is a value treatment option as a salvage procedure for revision knee arthroplasty and complex primary knee arthroplasty in which the joint stability can't be sustained with less constrained implants. There are various studies with significant different outcomes on functional outcomes and implant survival of this prostethis. The aim of this study is to evaluate the functional results of patients who have undergone this procedure and compare the integrity of their collateral knee ligaments postoperatively, regardless of their preoperative collateral knee ligament injuries. Material and Methods Patients who fit the inclusion criteria and whom have been operated with a rotating hinged knee implant between the years 2011-2021 were included in this study. Then patients were seperated into three groups by a radiologist who is an expert on musculoskeletal imaging according to their collateral knee ligament integrity using a Mavric MRI sequence for metal artifact reduction obtained at least one year postoperatively. Radiographic evaluation was made using the knee society total knee arthroplasty roentgenographic evaluation and scoring system on antero-posterior and lateral views of the operated knee. Lower extremity anatomic axis on coronal plane was determined on orthoroentgenograms. Then patients were evaluated on their latest outpaitent clinic visits with The Visual Analogue Scale (VAS), Knee Society Score (KSS), Knee Society Function Score (KSS-F), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and their range of motion. Results The mean age of the patients were 66,2 years and the mean follow-up time were 54,6 months. Indications for this procedure were aseptic loosening, septic loosening, pain without a known cause after primary total knee arthroplasty and complex primarytotal knee arthroplasty cases such as post-traumatic arthrosis. On Mavric sequence MR images, both collateral ligaments were intact in 53 patients, only MCL (medial collateral ligament) were injured in 14 patients, both collateral ligaments were injured in 12 patients. Lower extremity axis was calculated 4,1° in valgus. 8 patients had radiolucency in radiographs which was interpreted as loosening yet none of them had any related symptoms. Three groups based on the integrity of the collateral ligaments had no statistically significant difference according to The Visual Analogue Scale (VAS), Knee Society Score (KSS), Knee Society Function Score (KSS-F), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and range of motion .Patients who have undergone rotating hinged arthroplasty surgery for complex primary knee osteoarthritis had sigificantly better outcomes in KSS, KSS-F and WOMAC scores. Conclusion The most important finding of this study is; there are no significant clinical, radiologic or functional differences between three patient groups. The functional outcomes are better when RHK arthroplasty is performed on complex primary cases rather than revision surgeries. There is a need of more extensive randomized controlled trials to measure the effects of collateral ligament integrity on the long-term outcomes of RHK arthroplasty. Key Words: Collateral Ligaments, MAVRIC-SL, Metal Artefact, Rotating-hinge Total Knee Arthroplasty, Total Knee Arthroplasty