ROTATING HINGE REVISION TOTAL KNEE ARTHROPLASTY FOR SEVERE ARTHROFIBROSIS

Background: Stiffness following total knee arthroplasty is a challenging complication for both the patient and surgeon, with an incidence that ranges from 1% to 13%1. There are several correctable mechanical causes for stiffness including malposition, malalignment, overstuffing, aseptic loosening, patella baja, and heterotopic ossification(2). Idiopathic stiffness is often termed arthrofibrosis and is more difficult to treat(1). Once patients have exhausted nonoperative options, including physical therapy and manipulation under anesthesia, revision surgery may be considered. Rotating hinge revision total knee arthroplasty has been shown to be an effective surgical treatment for severe arthrofibrosis. Description: First, remove all soft-tissue and osseous sources of stiffness and adequately expose the knee, then remove all previous components. Create a stable and balanced extension gap, and, conversely, a relatively loose flexion gap, which allows for a substantial increase in range of motion. Then, in order to prevent instability in flexion, a rotating hinge prosthesis is utilized, which allows for appropriate kinematic motion despite gap imbalance. Additional steps to regain flexion include medial and lateral distal femoral partial condylectomies, as well as patellar component revision. Alternatives: The first line of treatment for stiffness following total knee arthroplasty is nonoperative and is mainly focused on physical therapy(3). Manipulation under anesthesia can also be performed within the first 12 weeks postoperatively(3). Surgical treatments can include arthroscopic debridement as well as open debridement with possible polyethylene liner exchange. If there is a mechanical cause for stiffness, then this should also be addressed surgically. For cases of arthrofibrosis without a clear mechanical etiology or for cases in which the above treatment has failed, complete revision of the femoral and tibial components should be considered(3). An alternative option to the technique proposed here is to utilize a varus-valgus constrained implant. Rationale: Revision with a hinged implant allows for a more aggressive approach to regaining motion, as compared with all other surgical alternatives. By revising all components, the surgeon is able to remove all sources of stiffness and reconstruct the knee until as much range of motion as possible is achieved. Unfortunately, even with balanced extension and flexion gaps, refractory stiffness is common. Asolution for this residual stiffness is to unbalance the gaps and create a loose flexion gap. By doing so, the surgeon is advised to switch to a hinged implant to create a kinematically balanced knee. Any other revision implant, such as a varus-valgus constrained implant, would risk flexion instability. Expected Outcomes: Several studies have examined the use of revision total knee arthroplasty with a hinged implant for arthrofibrosis and have showed substantial improvements in knee range of motion. Bingham et al. showed that the rotating hinge group had a 20 degrees improvement in range of motion (p=0.048)(1). Hermans et al. found a 35.8 degrees flexion gain in the hinge group compared with a 14.2 degrees flexion gain in the varus-valgus constrained group (p=0.0002)(4). van Rensch et al. found a median gain of 45 degrees of range of motion(5). Patients should be aware that this procedure involving the use of a hinged implant has similar risks to other revision total knee arthroplasty procedures; specifically, there is a risk of recurrent arthrofibrosis as well as mechanical complications(1,5).