Review Question - QID 218064

This patient presents with radiographs demonstrating a rotating hinged device, for which one of the absolute indications is hyperextension instability (Answer 1).

Hinged implants are the most constrained knee replacement prosthesis. Hinged implants feature a connecting rod between femoral and tibial components. Currently, the majority of hinged implants feature a rotating platform at the articular surface to attempt to decrease stress at the prosthesis-bone interface and better replicate normal knee kinematics. Rotating hinged implants provide stability in coronal and sagittal planes, while allowing free rotation in the axial plane. Modern rotating hinged devices have a built-in extension block which will prevent recurvatum deformities. The indications for hinged implants are wide and somewhat controversial. Hinged implants are most often indicated in the revision setting for complete collateral ligament instability, posterior capsular insufficiency resulting in hyperextension instability (ex. Polio), irreconcilable flexion-extension gap mismatch, or multiply revised implants with large bone defects. Despite the varying data on indications, surgeons should remember that increased constraint will cause increased stress on the prosthesis-bone interface and less constrained devices should be employed when possible.

Cottino et al. performed a retrospective review of 408 total knee arthroplasties (TKAs) performed with rotating hinge components to evaluate patient outcomes and survivorship. The study was performed from 2002 to 2012, using contemporary rotating hinge components in nononcological patients for primary and revision TKAs. The authors found a significant improvement in all outcome scores and a revision rate of 9.7% at 2 years and 22.5% at 10 years. The authors also noted a trend in lower risk of revision with the implementation of metaphyseal cones for more severe bone defects. The authors concluded that rotating hinge prosthesis can significantly improve patient outcomes and has excellent survivorship.

Kouk et al. performed a systematic review of literature reporting outcomes and/or complications of rotating hinge devices. The authors included 10 studies in the final criteria and found that 10-year survivorship ranged from 51% to 92.5% and complication rates ranged from 9.2% to 63%. The most common complications were infection and aseptic loosening. The study excluded primary and oncological cases and found that the most common indications were infection, aseptic loosening, instability, and bone loss. The authors concluded that good outcomes and survivorship can be expected although a high complication and revision rate profile exists with rotating hinged devices.

Figure A is an AP and lateral radiograph of a rotating hinge TKA implant.
Illustration A is a table of the Anderson Orthopaedic Research Institute (AORI) classification of bone defects around a TKA.

Incorrect Answers:
Answer 2: While complete collateral ligament deficiency often indicates rotating hinged implants, a laxed or attenuated collateral ligament is not. A constrained, nonhinged device with a large central post can be used to substitute for collateral attenuation with less of a stress-inducing implant.
Answer 3: Extensor mechanism deficiency is not an absolute indication for a hinged implant. Some authors argue that an absent extensor mechanism can result in laxity in flexion, risking dislocation in less constrained devices. Other authors argue that devices without the sagittal block will produce increased stress on the extensor mechanism, leading to failure. However, advances in techniques and biomaterials allow repair or reconstruction of the extensor mechanism to be reliably performed without the need to resort to a maximum constraint device.
Answer 4: Posterior Cruciate Ligament (PCL) deficiency is not an indication for a rotating hinged prosthesis. A less-constrained posterior cruciate stabilizing implant can be used in this scenario with fewer complications than a rotating hinged prosthesis.
Answer 5: A large, contained condylar defect is not an absolute indication for a hinged device. Revision TKA bone loss is commonly classified according to the Anderson Orthopaedic Research Institute (AORI) classification (Illustration A). Larger defects in a single femoral condyle would be classified as a Type 2A defect. Although the indications are expanding, rotating hinges are commonly reserved for larger defects (Type 2B or 3).