Introduction: The number of hinged total knee arthroplasty (HTKA) procedures is constantly increasing. There are two hinge types: central (CHTKA) and posterior (PHTKA). The primary purpose of the study was to compare implant survival in patients with CHTKA versus PHTKA. The secondary purpose was to analyse the radiological and clinical results of the implants.
Hypothesis: There is no difference between the two groups.
Materials and methods: This study involved 53 patients who received a HTKA for either primary, trauma or revision surgery, of these 32 were in the CHTKA group and 21 in the PHTKA group, with a mean age of 69 years (38-89). The exclusion criteria were: etiology of sepsis, incomplete records and refusal to use data. The revision rate, with the replacement of prosthetic components, was the primary endpoint. The secondary outcomes were: mobility, complications, VAS, IKS, Devane, Charnley and Oxford knee scores, and radiological progression.
Results: The mean follow-up was 51 months (1-139). At 60 months, overall survival rate of the HTKA was 81%, with a confidence interval (CI) of 95% (71-93.2), and there was no difference between CHTKA and PHTKA, 77.7% (95% CI, 63.3-95.4) versus 85.7% (95% CI, 72-100), p=0.625, respectively. Flexion was 101°±15 (80-140) for CHTKA versus 98°±12 (30-130) for PHTKA, p=0.006. VAS was 0.5±16 (0-6) for CHTKA versus 1.6±14 (0-4) for PHTKA, p=0.000008. The IKS was 103±39 (15-180) for CHTKA versus 81±51 (9-200) for PHTKA, p=0.03. There were no differences in either radiological progression, complications or other functional scores.
Discussion: No significant difference was observed between the survival of CHTKA and PHTKA. CHTKA had better flexion, reduced VAS and increased IKS. Surgeons should be aware of these findings and apply careful consideration to their choice of hinge.
Level of evidence: IV; retrospective single-centre study.
Keywords: Central or posterior; Hinge; Survival; Total knee arthroplasty.
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