RESUMEN
Background: Increased load bearing across the patellofemoral and tibiofemoral articulations has been associated with total knee arthroplasty (TKA) complications. Therefore, the purpose of this study was to quantify the biomechanical characteristics of the patellofemoral and tibiofemoral joints and simulate varying weight-bearing demands after posterior cruciate ligament-retaining (CR) and posterior-stabilized (PS) TKAs. Methods: Eight fresh-frozen cadaveric knees (average age, 68.4 years; range, 40-86 years) were tested using a custom knee system with muscle-loading capabilities. The TKA knees were tested with a CR and then a PS TKA implant and were loaded at 6 different flexion angles from 15° to 90° with progressively increasing loads. The independent variables were the implant types (CR and PS TKA), progressively increased loading, and knee flexion angle (KFA). The dependent variables were the patellofemoral and tibiofemoral kinematics and contact characteristics. Results: The results showed that at higher KFAs, the position of the femur translated significantly more posterior in CR implants than in PS implants (36.6 ± 5.2 mm and 32.5 ± 5.7 mm, respectively). The patellofemoral contact force and contact area were significantly greater in PS than in CR implants at higher KFAs and loads (102.4 ± 12.5 N and 88.1 ± 10.9 N, respectively). Lastly, the tibiofemoral contact force was significantly greater in the CR than the PS implant at flexion angles of 45°, 60°, 75°, and 90° KFA, the average at these flexion angles for all loads tested being 246.1 ± 42.1 N and 192.8 ± 54.8 N for CR and PS implants, respectively. Conclusions: In this biomechanical study, CR TKAs showed less patellofemoral contact force, but more tibiofemoral contact force than PS TKAs. For higher loads across the joint and at increased flexion angles, there was significantly more posterior femur translation in the CR design with a preserved posterior cruciate ligament and therefore significantly less patellofemoral contact area and force than in the PS design. The different effects of loading on implants are an important consideration for physicians as patients with higher load demands should consider the significantly greater patellofemoral contact force and area of the PS over the CR design.
Asunto(s)
Artroplastia de Reemplazo de Rodilla , Ligamento Cruzado Posterior , Soporte de Peso , Humanos , Anciano , Fenómenos Biomecánicos , Anciano de 80 o más Años , Soporte de Peso/fisiología , Persona de Mediana Edad , Ligamento Cruzado Posterior/cirugía , Adulto , Masculino , Femenino , Cadáver , Articulación de la Rodilla/cirugía , Articulación de la Rodilla/fisiología , Prótesis de la Rodilla , Articulación Patelofemoral/cirugía , Articulación Patelofemoral/fisiología , Rango del Movimiento ArticularRESUMEN
OBJECTIVES: This biomechanical study seeks to define the relative effectiveness of contemporary single and dual implant constructs for fixation of an extra-articular proximal tibia fracture model. METHODS: An extra-articular proximal tibia fracture model was created using synthetic tibias. Four constructs were tested. Constructs included (1) lateral locked plate (LLP), (2) intramedullary nail (IMN), (3) combined LLP and IMN (PN), and (4) LLP and medial locked plate. Specimens were axially loaded through the medial plateau to evaluate construct stiffness and the ability to resist varus collapse. RESULTS: Dual implant constructs were stiffer than single implant constructs in this model. Although DP and PN were stiffer than IMN at all loads tested, the difference was notable only for DP at higher loads. Isolated LLP provided insufficient stability to be tested at higher loads. CONCLUSION: Dual plate fixation provides the greatest resistance to varus collapse. In the clinical setting, consideration must be given to the fracture morphology, desired construct stiffness, and soft-tissue envelope in selecting the optimal construct to be used.
Asunto(s)
Fijación Intramedular de Fracturas , Fracturas de la Tibia , Fenómenos Biomecánicos , Placas Óseas , Fijación Interna de Fracturas , Humanos , Tibia/cirugía , Fracturas de la Tibia/cirugíaRESUMEN
PURPOSE: The purpose of this study was to compare glenohumeral stability following a Latarjet, a free bone block (FBB), and a FBB with remplissage for bipolar bone loss. METHODS: Nine matched pairs of fresh frozen cadavers were tested in a custom biomechanical apparatus with rotation and progressive translational loading. The free bone block group consisted of a distal tibial allograft with an all-suture tape construct. The Latarjet group was performed with the native coracoid and two partially threaded cannulated screws. A bipolar bone loss model was created with 20% glenoid bone loss and an off-track Hill-Sachs lesion. Testing conditions included the 1) native state, 2) bipolar bone loss model, 3) Latarjet, 4) FBB with distal tibial allograft secured with cerclage sutures, and 5) FBB with remplissage. Each condition was tested for translation, humeral head apex shift, stiffness, and dislocation force. RESULTS: There were no differences in translation, stiffness, or dislocation forced between the FBB alone and Latarjet groups. The FBB with remplissage group demonstrated the lowest anterior-inferior translation at 90° of ER, which was statistically significant compared to Latarjet 20N (P = .013) and compared to the FBB alone at 40N (P = .024) and 50N (P = .011). The FBB with remplissage group was significantly stiffer compared to FBB alone at 90° ER with approximately 60% change in stiffness (P = .028). The force required to dislocate the humeral head after treatment was highest in the FBB with remplissage group, which was statistically significant compared to the FBB alone (P = .003) and Latarjet groups (P = .018). CONCLUSION: The addition of remplissage to a FBB restores translation and stiffness closer to the intact state compared to a FBB alone or Latarjet in a bipolar bone loss model with an off-track Hill-Sachs lesion. In this model, dislocation force significantly increased with the addition of remplissage to the FBB. CLINICAL RELEVANCE: This biomechanical study provides evidence that Latarjet and FBB are both acceptable forms of treatment for bipolar bone loss, but stability can be enhanced with the addition of remplissage following glenoid reconstruction.