Abstract
In primary TKA, non- or semi-constrained TKA implants might have their limitations in the absence of collateral ligaments, severe deformity, large osseous defects and gross flexion-extension instability.
Although most primary TKA indications can be solved with modular, non-hinged implants, an adequate balancing might require a relevant soft tissue release. This consequently adds complexity and operative time with less predictable results in the elderly patient. The current literature reporting on short- to mid-term results of rotating hinged implants in primary osteoarthritis shows some quite diverse results and consequently different interpretations of this implant type in primary knee arthroplasty. Although some authors were able to show good and excellent clinical results in 91% of patients and consequent survival rates of a rotating hinge implant after 15 years up to 96% in primary indications, others found high complication rates of up to 25% of all operated patients, which remains unclear for us and is inconsistent with our clinical results in primary and revision TKA in over 30 years of experience with the ENDO-Model rotating hinge implant.
Our potential indications in the elderly for a rotating or pure hinged implant in primary TKA include: Complete MCL instability; Severe varus or valgus deformity (>20 degrees) with necessary relevant soft tissue release; Relevant bone loss including insertions of collaterals; Gross flexion-extension gap imbalance; Ankylosis; One staged implantation with specific antibiotics after PJI.
Due to general limited soft tissues or hyperlaxity, patients with neuropathic joints, or lack of extensor mechanism should be considered for a complete hinged implant. The ENDO-model hinge has only been minimally adapted since its development in the 70´s, including fully cemented long stems, in modular and non-modular versions. We strictly reserve a rotational hinge in primary indications for patients >70 years with a combined varus alignment, whereas in severe valgus deformities, a complete hinged implant version should be used for our implant design.
