Review Question - QID 220021

The patient has Charcot arthropathy with significant valgus deformity and bone loss, best treated with a total knee arthroplasty using components with an increased level of constraint. Though this is the appropriate treatment, it is important to counsel the patient that the increased level of constraint increases the risk of loosening over time.

Total knee arthroplasty (TKA) can be performed using components that vary across a spectrum of constraint from cruciate-retaining (CR) or anterior-stabilized/ultra-congruent designs that maintain the PCL, to cruciate-substituting (PS) that sacrifice the PCL, and condylar-constrained or rotating-hinge designs that make up for absent collateral ligamentous support. In the case of neuropathic (Charcot) arthropathy, which results from progressive destruction of joint spaces through repeated subclinical microtrauma of an insensate joint, the collateral support structures of the knee (namely the MCL and/or LCL) are typically damaged or attenuated to a degree that CR and PS knees do not allow for sufficient restoration of knee stability post-operatively. Thus, in patients with Charcot arthropathy, selective use of constraint and enhanced fixation techniques using metaphyseal cones and long stems provides improvement in clinical function and survivorship. Despite this fact, it is important to counsel patients that increased constraint does increase the risk for loosening over time, under which circumstances conversion to a rotating-hinged design may be necessary.

Tibbo et al. reviewed the contemporary results of primary total knee arthroplasty in patients with neuropathic (Charcot) arthropathy. The authors retrospectively reviewed 27 patients undergoing 37 TKAs for Charcot arthropathy from 2000 to 2015 and found that 81% were treated with either a varus-valgus constrained or rotating-hinge device, 81% had supplemental stem fixation, and metaphyseal cones were utilized in 19% of cases. They concluded that primary TKA for Charcot arthropathy with selective use of increased constraint and enhanced metaphyseal component fixation led to significant improvement in pain and clinical outcomes when compared with older techniques; however, there was a high perioperative complication rate.

Bae et al. looked at long-term outcomes of total knee arthroplasty in the Charcot joint. The authors reviewed the results of 11 total knee arthroplasties using rotating hinge prostheses in 9 patients with a Charcot joint secondary to neurosyphilis at 11- and 22-year followup and found that complications were noted in 3 knees, including 2 dislocations of the knee and 1 deep infection. They concluded that the clinical results of total knee arthroplasty were satisfactory in most cases of Charcot joint, strongly recommending the use of rotating hinge prostheses in Charcot joints; However, they note that the procedure is technically demanding, and that there were considerable complications.

Figures A and B are AP and lateral radiographs of a Charcot knee demonstrating significant valgus deformity with destruction and collapse of the lateral femoral condyle and subluxation of the medial tibiofemoral compartment.

Incorrect Answers:
Answer 1: A short-stemmed CR implant design would not be appropriate for a patient with global instability in the setting of Charcot arthropathy.
Answers 2 and 5: Neither AS/UC nor PS designs would compensate for this patient's very clear MCL attenuation.
Answer 3: The patient would certainly qualify for a rotating-hinge design before a salvage procedure such as an arthrodesis nail was considered.