The effects of the sagittal plane malpositioning of the patella and concomitant quadriceps hypotrophy on the patellofemoral joint: a finite element analysis.

PURPOSE: Anterior knee pain is a common symptom after intramedullary nailing in tibia shaft fracture. Moreover, patellofemoral malalignment is also known to be a major reason for anterior knee pain. Patellofemoral malalignment predisposes to increased loading in patellar cartilage. In the previous study, we have demonstrated the quadriceps atrophy and patellofemoral malalignment after intramedullary nailing due to tibia shaft fracture. In this study, our aim was to clarify the effects of quadriceps atrophy and patellofemoral malalignment with the pathologic loading on the joint cartilage. METHODS: Mesh models of patellofemoral joint were constructed with CT images and integrated with soft tissue components such as menisci and ligaments. Physiological and sagittal tilt models during extension and flexion at 15°, 30° and 60° were created generating eight models. All the models were applied with 137 N force to present the effects of normal loading and 115.7 N force for the simulation of quadriceps atrophy. Different degrees of loading were applied to evaluate the joint contact area and pressure value with the finite element analysis. RESULTS: There was increased patellofemoral contact area in patellar tilt models with respect to normal models. The similar loading patterns were diagnosed in all models at 0° and 15° knee flexion when 137 N force was applied. Higher loading values were obtained at 30° and 60° knee flexions in sagittal tilt models. Furthermore, in the sagittal tilt models, in which the quadriceps atrophy was simulated, the loadings at 30° and 60° knee flexion were higher than in the physiological ones. CONCLUSIONS: Sagittal malalignment of the patellofemoral joint is a new concept that results in different loading patterns in the patellofemoral joint biomechanics. This malalignment in sagittal plane leads to increased loading values on the patellofemoral joint at 30° and 60° of the knee flexions. This new concept should be kept in mind during the course of diagnosis and treatment in patients with anterior knee pain. Definition of the exact biomechanical effects of the sagittal tilting will lead to the development of new treatment modalities.

[Cementless total hip replacement in patients with high total dislocation: the results of femoral shortening by subtrochanteric segmental resection]. / Yüksek kalça çikikli hastalarda çimentosuz total kalça artroplastisi: Subtrokanterik segmental rezeksiyon ile femoral kisaltma sonuçlari.

OBJECTIVES: We evaluated the results of femoral shortening by subtrochanteric segmental resection in patients who underwent total hip replacement (THR) for high total dislocation of the hip. METHODS: We performed THR in 19 hips of 16 patients (15 females, 1 male; mean age 41 years; range 22 to 55 years) with high total dislocation of the hip. All the patients had severe hip pain. In all cases, femoral shortening by subtrochanteric segmental resection and an anatomical reconstruction of the acetabulum were performed with the use of cementless femoral components and cementless acetabular components with screws, respectively. The Harris hip scoring system was used for functional assessments. Radiologic assessments were based on the DeLee and Charnley criteria for the acetabular component, and on the Gruen zones and the Engh criteria for the femoral component. The mean follow-up period was 44 months (range 22 to 79 months). RESULTS: Union was achieved in all cases in a mean of 14 weeks (range 11 to 15 weeks). The mean leg length discrepancy decreased from 4 cm to 1.5 cm postoperatively. A positive Trendelenburg sign was found in 13 patients and four patients before and after surgery, respectively. The mean Harris hip score improved from 37 to 83 postoperatively. None of the patients developed deep infection, dislocation, sciatic nerve palsy, or nonunion at the osteotomy site. No clinical and radiologic signs of loosening were observed and no revisions were required. CONCLUSION: Femoral shortening with subtrochanteric segmental resection in THR is a safe technique in patients with high total dislocation of the hip, leading to satisfactory functional results.