Enhancing the radiological classification system from the distal femur to the proximal tibia

Introduction The inner diaphyseal diameter of the distal femur, at 20 cm from the lateral joint line, is the strongest risk factor for predicting aseptic loosening in total knee arthroplasty using rotating hinge prosthesis. In this context, the Citak classification has been introduced presenting three different types of the distal femur anatomy. The aim of the study is to develop a novel classification system for the proximal tibia. Materials and Methods Two-hundred patients with standard knee antero-posterior radiographs were included in this study. We measured the inner diameter of the tibia 16 cm distally from the tibial plateau and 3 cm distally from the tibial spine. The ratio between these two measurements was applied as the novel index ratio. Results According to the 25th and 75th percentiles, three groups can be clustered for each gender. A higher distribution of the type B pattern was found in female and male patients. However, type A with a narrow inner diaphyseal diameter was less common in female patients The median intra-observer reliability for rater 1 was 0.997. The inter-observer reliability was high (ICC 0.998). There was a moderate correlation between the AP diameter and height (r = 0,568); a low correlation between the AP diameter and weight (r = 0.376). The novel index shows no significant correlation between the index ratio and height (r = 0.082), weight (r = 0.014) or BMI (r= - 0.038). The novel index shows no statistically significant correlation between the index ratio and height (r = 0.082) or weight (r = 0.014) or BMI (r= - 0.038). Conclusion The novel classification presents three different types of tibia for each gender: type C has a wider inner diaphyseal diameter compared to type A with a narrow inner diaphyseal diameter. Type B has the widest distribution among the subjects.

A case of an atraumatic implant failure after primary rotating-hinge total knee arthroplasty

Rotating-hinge knee implants are fully constrained knee prostheses commonly used for revision total knee arthroplasty. Nevertheless, rotating-hinge devices have been increasingly utilized in primary setting. Complications are inevitable in orthopedic surgery, however, implant breakage after RHK arthroplasty has been rarely described in medical literature. We present a rare case of 70-year-old Caucasian, male patient who suffered an atraumatic femoral stem breakage in a primary NexGen ® Rotating Hinge Knee (Zimmer-Biomet ® , Warsaw, IN, USA).

Rotating Hinge Knee Arthroplasty for Revision Prosthetic-Knee Infection: Good Functional Outcomes but a Crucial Need for Superinfection Prevention

Introduction: Management of chronic infection following total knee arthroplasty (TKA) is challenging. Rotating hinged prostheses are often required in this setting due to severe bone loss, ligamentous insufficiency, or a combination of the two. The nature of the mechanical and septic complications occurring in this setting has not been well-described. The aim of this study was to evaluate patient outcomes using a hinge knee prosthesis for prosthetic knee infections and to investigate risk factors for implant removal.Methods: This was a retrospective cohort study that included all patients treated in our tertiary level referral center between January 2009 and December 2016 for prosthetic knee infection with a hinge knee prosthesis. Only patients with a minimum 2-year of follow-up were included. Functional evaluation was performed using international knee society (IKS) “Knee” and “Function” scores. Survival analysis comparing implant removal risks for mechanical and septic causes was performed using Cox univariate analysis and Kaplan-Meier curves. Risk factors for implant removal and septic failure were assessed.Results: Forty-six knees were eligible for inclusion. The majority of patients had satisfactory functional outcomes as determined by mean IKS scores (mean knee score: 70.53, mean function score: 46.53 points, and mean knee flexion: 88.75°). The 2-year implant survival rate was 89% but dropped to 65% at 7 years follow-up. The risk of failure (i.e., implant removal) was higher for septic etiology compared to mechanical causes. Patients with American society of anesthesiologists (ASA) score>1, immunosuppression, or with peripheral arterial diseases had a higher risk for septic failure. Patients with acute infection according to the Tsukayamaclassification had a higher risk of failure. Of the 46 patients included, 19 (41.3%) had atleast one infectious event on the surgical knee and most of these were superinfections (14/19) with new pathogens isolated. Among pathogens responsible for superinfections (i) cefazolin and gentamicin were both active in six of the cases but failed to prevent the superinfection; (ii) cefazolin and/or gentamicin were not active in eight patients, leading to alternative systemic and/or local antimicrobial prophylaxis consideration.Conclusions: Patients with chronic total knee arthroplasty (TKA) infection, requiring revision using rotating hinge implant, had good functional outcomes but experienced a high rate of septic failure, mostly due to bacterial superinfection. These patients may need optimal antimicrobial systemic prophylaxis and innovative approaches to reduce the rate of superinfection.

Ligament Balancing and Constraint in Revision Total Knee Arthroplasty

Ligament balancing in revision knee arthroplasty is crucial to the success of the procedure. The medial collateral ligament and lateral ligament complex are the primary ligamentous structures that provide stability. Revisions can be performed with nonconstrained cruciate-retaining, posterior cruciate substituting, or anterior-stabilized/ultracongruent inserts when there are symmetrical flexion/extension gaps and intact collateral ligaments. When the collateral ligaments are insufficient either due to attenuation or incompetence from bone loss, a more constrained knee system is needed. Constrained condylar knees provide increased stability to both varus/valgus and rotation forces with a nonlinked construct. This increased constraint, however, does lead to increased stress at the implant–bone interface which requires more robust metaphyseal fixation. In cases of significant soft tissue disruption, severe flexion/extension gap mismatch or extensor mechanism disruption, a rotating hinge knee is needed to restore stability. Advances in revision implant design have led to improved outcomes and longer survivorship then earlier iterations of these implants. Surgeons should always strive to use the least constraint needed to achieve stability but must have a low threshold to increase constraint when ligament integrity is compromised.

Total Knee Arthroplasty in Patients With Prior Ipsilateral Hip Fusion: A Surgical Technique

Background: In patients with severe osteoarthritis of the knee with prior ipsilateral hip fusion who require total knee arthroplasty (TKA), a controversial issue is whether to first convert the hip fusion to a total hip arthroplasty (THA) or to perform TKA without reconstruction of the hip. Also, immobility of the ipsilateral, fused hip adds significant technical challenge because the usual positioning of the leg requires modification in order to gain access needed for the TKA. Technique: In such cases, we position the patient with the knee suspended, similar to how we perform knee arthroscopy. In our experience, the ipsilateral knee has significant deformity and is best addressed with a constrained, hinged TKA. Results: In 3 patients with severe knee osteoarthritis with prior ipsilateral hip fusion—a 72-year-old man and a 79-year-old woman with hip arthrodesis due to posttraumatic arthritis and an 81-year-old woman with hip arthrodesis due to congenital dislocation of the hip—rotating-hinge knee prostheses were implanted due to severe knee instability. All 3 patients had satisfactory results, without complications, after follow-up of 1 to 5 years. Conclusions: We obtained satisfactory results in the short and medium term without previously converting the hip arthrodesis to THA by positioning patients with the knee suspended, in a way similar to when knee arthroscopy is performed, and implanting rotating hinge TKAs due to severe preoperative knee instability.