180° rotatory dislocation of the rotating platform of a posterior-stabilized mobile-bearing knee prosthesis; possible complication after closed reduction of a posterior dislocation--a case report

Anterior tibiofemoral dislocation after total knee arthroplasty: A case report and literature review

Anterior tibiofemoral dislocation after total knee arthroplasty is an extremely rare and serious event. Amongst English-published papers, we found only 15 relevant cases, 3 of which presented vascular complications. This manuscript aims to present a 77-year-old woman with a TC-Plus (Smith & Nephew) cruciate-retaining type in first time of knee prosthesis, who suffered an anterior tibiofemoral dislocation and were admitted to our hospital. The clinical management and outcome were evaluated. Furthermore, a review of literature was performed. We concluded that early detection and surgical intervention of vascular injury is the key in the survival of the limbs. If there is still knee instability after acute recovery, it seems that revision surgery with constrained total knee arthroplasty can bring about good clinical and functional results.

Functional Flexion Instability After Rotating-Platform Total Knee Arthroplasty

BACKGROUND

We sought to define "at risk" loading conditions associated with rotating-platform total knee arthroplasty (TKA-RP) implants that predispose to insert subluxation and spinout and to quantify tolerances for flexion-extension gap asymmetry and laxity in order to prevent these adverse events.

METHODS

Biomechanical testing was performed on 6 fresh-frozen cadaveric limbs with a TKA-RP implant with use of a gap-balancing technique, followed by sequential femoral component revision with variable-thickness polyethylene inserts to systematically represent 5 flexion-extension mismatch and asymmetry conditions. Each configuration was subjected to mechanical loading at 0°, 30°, and 60°. Rotational displacement of the insert on the tibial baseplate, lateral compartment separation, and insert concavity depth were measured with use of a digital caliper. Yield torque, a surrogate for ease of insert rotation and escape of the femoral component, was calculated with use of custom MATLAB code.

RESULTS

Design-intended insert rotation decreased with increasing knee flexion angles in each loading configuration. Likewise, yield torque increased with increasing joint flexion and decreased with increasing joint laxity in all testing configurations. Insert instability and femoral condyle displacement were reproduced in positions of increasing knee flexion and asymmetrical flexion gap laxity. The depth of lateral polyethylene insert concavity determined femoral condylar capture and defined a narrow tolerance of <2 mm in the smallest implant sizes for flexion gap asymmetry leading to rotational insert instability.

CONCLUSIONS

Decreased femoral-tibial articular surface conformity with increasing knee flexion and asymmetrical flexion gap laxity enable paradoxical motion of the femoral component on the upper insert surface rather than the undersurface, as designed.

CLINICAL RELEVANCE

Mobile-bearing TKA-RP is a technically demanding procedure requiring a snug symmetrical flexion gap. As little as 2 mm of asymmetrical lateral flexion laxity can result in decreased conformity, condyle liftoff, and insert subluxation. Flexion beyond 30° decreases bearing surface contact area and predisposes to reduced insert rotation and mechanical malfunction.

Complete 180-Degree Dislocation of a Rotating Platform after Closed Reduction for Mobile Bearing Spinout

Rotating-platform total knee arthroplasty was designed to help decrease backside polyethylene wear and allow maximal conformity between the femoral and tibial components, but there have been multiple reports of dislocation and spinout of these implants. There are 4 case reports in the literature of knee dislocations with 180° rotation of the platform, 3 of which occurred during relocation attempts. This is only the second case in a posterior-stabilized mobile-bearing device. We present a case of complete 180° dislocation of a rotating platform after closed reduction in a posterior-stabilized total knee arthroplasty, with subsequent conversion to hinge knee arthroplasty.

Spontaneous 180-Degree Rotatory Dislocation of Rotating-Platform Total Knee Arthroplasty

Rotating-bearing total knee arthroplasty has been theorized to have some advantages in the kinematics and wear characteristics of total knee arthroplasty. A rare complication of rotating-bearing total knee arthroplasty is rotary dislocation, spinout, of the polyethylene component. When these dislocations occur, they typically result in a 90-degree dislocation in respect to the axial axis of the knee. This case is unique in that it presents a complete 180-degree polyethylene dislocation without trauma.

Fracture of the insert cone of a polyethylene liner in a failed posterior-stabilized, rotating-platform total knee arthroplasty

Failures unique to posterior cruciate-substituting total knee prostheses rarely include polyethylene post fractures but have been described. We report a case involving a fracture of the distal insert cone of a rotating-platform (RP) polyethylene liner in a primary total knee arthroplasty. This case highlights a 67-year-old male presenting with new-onset knee pain and recurrent effusions with osteolysis 11 years following placement of a posterior-stabilized, RP total knee arthroplasty. At the time of revision surgery, the polyethylene insert cone was found to be fractured just below the junction between cone and the body of the insert. Liner exchange, synovectomy, and osteolytic-defect curettage and cement packing were performed. One year following revision surgery, the patient is without pain and has returned to function without limitations. Clinicians must be aware of this possible failure with RP prostheses in the setting of pain with a stable knee, recurrent aseptic effusions, and osteolysis.

Spinout/Dislocation in Mobile-Bearing Total Knee Arthroplasty: A Report of 26 Cases

BACKGROUND

Excellent medium-term to long-term results for function and survivorship have been shown with mobile-bearing (MB) total knee arthroplasty (TKA). One of the key arguments against its use is the risk of "spinout" or dislocation of the MB. The aim of this study is to discuss the etiology, prevention, incidence, management, and outcome of spinout.

METHODS

Between October 1993 and February 2016, 8373 consecutive primary MB TKAs were performed irrespective of preoperative deformity. Before 2001, soft-tissue knee balancing was achieved by release of collateral ligaments and all spinouts were treated by open reduction. Thereafter, soft-tissue balancing was achieved without ligament release and with the use of a higher conformity MB and all spinouts were reduced closed, giving 2 comparative cohorts.

RESULTS

Twenty-six spinouts occurred in 8373 (0.31%) patients. In the first cohort up until May 2001, there were 14 spinouts of 2379 (0.58%) cases. There were 12 in cohort 2, in those patients having surgery after May 2001, thus giving an incidence of 12 of 5994 (0.2%), which was significantly lower than in cohort 1 (P < .01). Spinout was associated with the valgus knee (P < .01) and most (73%) occurred within the first 6 months. There was 1 arthrodesis in cohort 1 and 1 both-component revision in cohort 2.

CONCLUSION

The etiology of spinout is flexion gap instability. It can normally be reduced closed with recurrence being uncommon. Focus on soft-tissue balance necessary with an MB TKA can reduce the incidence of revision for instability as compared to a fixed-bearing TKA. Therefore, the risk of spinout should not be used as an argument against the MB TKA.

Pain After Total Knee Arthroplasty Due to Unrecognized 180° Rotation of the Mobile-Bearing Tibial Insert: A Case Report

CASE

A woman presented with continuously worsening right knee pain and stiffness six years after a total knee arthroplasty. During revision total knee arthroplasty, we discovered that the rotating-platform tibial component was rotated 180°. This likely occurred during a minor bedside fall on postoperative day one after the index procedure.

CONCLUSION

This case demonstrates that a 180° rotation of the rotating tibial insert can occur with minimal trauma, resulting in persistent pain and stiffness. This cause of pain should be added to the differential diagnosis of patients with pain after total knee arthroplasty with a rotating-platform tibial insert.

Acute, recurrent total knee dislocation: Polyethylene dislocation and malreduction

A 62-year-old man underwent total knee arthroplasty using a mobile-bearing prosthesis. Four days post-operatively the patient experienced the first of several acute knee dislocations. Closed reduction was performed at an outside hospital a total of three times prior to presentation at this institution. A two-stage exchange of the TKA was recommended due to the clinical suspicion for an infected prosthesis. Upon surgical exploration, it was discovered that the polyethylene insert had spun out completely to 180°. Closed reduction attempts of a posterior dislocation of a mobile-bearing knee prosthesis may contribute to complete 180° spinout of the polyethylene insert.

Case report: Total knee arthroplasty polyethylene liner disengagement identified by arthrography

We report a case of total knee arthroplasty polyethylene liner disengagement identified by plain film arthrography and CT arthrography.

[Spin out - an avoidable complication in total knee replacement]

Spin out of a rotating polyethylene (PE) platform after total knee replacement leads to rotation of the bearing compared to the fixed metal components of the prosthesis at the femur and tibia of approximately 90°. This complication occurs only in prosthesis designs which do not have a rotation limitation. Identification of this complication and its management are described exemplified by two cases. Strategies to avoid spin out are discussed. The most promising way is to avoid using prosthesis designs in which spin out can occur.