ObjectiveTo evaluate the mid-term effectiveness of rotating hinge knee prosthesis for severe knee deformity. MethodsA retrospective analysis was made on the clinical data of 24 patients (24 knees) who received rotating hinge knee prosthesis for total knee arthroplasty between January 2003 and June 2011. There were 14 males and 10 females, aged from 60 to 81 years (mean, 70 years). The disease causes included osteoarthritis in 5 cases, rheumatoid arthritis in 7 cases, traumatic arthritis in 9 cases, and Charcot's arthropathy in 3 cases. The disease duration ranged from 5 to 25 years (mean, 14.5 years). Of them, 13 cases had flexion deformity, 7 cases had valgus deformity, and 16 cases had varus deformity. The operation time, the amount of bleeding between operation and drainage-tubes removal, hospitalization time, incision healing, and complications were recorded. The results were evaluated according to Knee Society Score (KSS), visual analogue scale (VAS), and the range of motion (ROM) of knee. Short-form 36 health survey scale (SF-36) was used to evaluate the life quality of patients. The position of prosthesis was observed through X-ray examination. ResultsThe operation time ranged from 70 to 90 minutes (mean, 78 minutes). The amount of bleeding between operation and drainage-tubes removal ranged from 400 to 1 000 mL (mean, 650 mL). The hospitalization time ranged from 14 to 18 days (mean, 15.2 days). Patellar fracture occurred in 1 case (4.17%) during operation, swelling and effusion of incision in 1 case (4.17%), and periprosthetic infections in 2 cases (8.33%) after operation. All patients were followed up 2-10 years (mean, 5.5 years). The X-ray films showed no evidence of obvious radiolucent line, osteolysis, prosthesis subsidence, and limb alignment change. The results of KSS, VAS socres, and ROM of knee at 1 year postoperatively and last follow-up were significantly better than preoperative ones (P<0.05), but no significant difference was found between at 1 year postoperatively and last follow-up (P>0.05). The physiological function and body pain scores were significantly lower than the reference value of urban men over 60 years old from Sichuan province (t=2.42, P=0.02; t=5.26, P=0.00), but no significant difference was found in the other scores of the SF-36 when compared with the reference value (P>0.05). ConclusionThe mid-term effectiveness of total knee arthroplasty using rotating hinge knee for severe knee prosthesis deformity is satisfactory. But complications of postoperative infection should be emphasized.
Articular surface conformity is a critical factor influencing the biomechanics of knee prostheses, yet its impact on the biomechanics of rotation-hinged knee (RHK) prostheses and their tibial fixation remains unclear. In this study, a rotational platform tibial insert model of RHK prostheses with varying coronal and sagittal conformities is established. Finite element analysis was performed under ISO boundary conditions to investigate the effects of articular surface conformity on the biomechanics of the RHK prosthesis and tibial fixation. The study revealed that when the coronal conformity decreased from 0.83 to 0.33, the maximum Mises stress in the tibia and the maximum contact pressure in the insert increased by 10.78% and 52.62%, respectively, while the maximum shear stress in the bone cement decreased by 10.17%. When sagittal conformity decreased from 0.88 to 0.47, the maximum Mises stress in the tibia and maximum contact pressure in the insert increased by 5.62% and 14.31%, respectively, while Mises stress at the hinge-rotation axis and bone cement shear stress decreased by 62.53% and 29.46%, respectively. A reduction in conformity decreased the contact area. Sagittal conformity has a lesser impact on insert contact pressure compared to coronal conformity, but a more significant impact on bone cement shear stress, and reducing sagittal conformity could effectively reduce the Mises stress at the hinge-rotation axis. The coronal conformity of the RHK prosthesis on the rotational platform more effectively regulates contact mechanics, reducing sagittal conformity facilitates lowering hinge-rotation axis Mises stress and bone cement shear stress without significantly increasing contact pressure, thereby mitigating risks of prosthesis failure such as dislocation, fracture, and loosening.