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.

Sagittal patellar tilt and concomitant quadriceps hypotrophy after tibial nailing.

PURPOSE: The aim of the study was to analyse the patellofemoral alignment in the sagittal plane following tibial fracture surgery with intramedullary nailing and its relationship to parapatellar muscle status. METHODS: The patellofemoral MRI results of 27 patients (15 males and 12 females) treated with locked intramedullary nailing following tibia shaft fracture were reviewed. The mean age of the patients was 41.8 (±15) years. The patella-patellar tendon angle (P-PT) and the distance between the inferior patellar pole and the tibial tubercle (DP-TT) were evaluated for both the operated extremity and the contralateral normal side. MRI assessment of the infrapatellar fat pad, quadriceps, sartorius, gracilis, semi-membranosus muscles and biceps muscles was also carried out. The correlation between the changes in skeletal muscle mass, the volume of the infrapatellar fat pad and the alterations in the DP-TT distances and P-PT angles were analysed. RESULTS: The quadriceps muscle cross-sectional diameter had a mean of 157.2 mm(2) (115.6/319.5) in the operated extremity, and it was 193 mm(2) (77.6/282.2) in the non-operated normal side (p = 0.001). For the Gracilis muscle, the mean was 84.4 mm(2) (19.7/171) at the operated extremity and 75.7 mm(2) (26.9/238.2) on the normal side (p = 0.05). The cross-sectional areas of the semi-membranosus, sartorius and biceps muscles in the operated and non-operated extremity were not noticeably different (n.s). The P-PT angle was 153° (129.7/156.4) in the operated extremity and 145.7° (137.6/163.4) in the non-operated normal extremity (p < 0.05). While DP-TT distance was 11.4 mm (9.4/20.4) in the operated extremity, it was 14.1 mm (7.3/17.1) in the non-operated extremity (p = 0.001). The correlation analyses revealed that the quadriceps hypotrophy negatively correlated (r = -0.4, p = 0.02) with the P-PT angle but positively correlated with the increase in gracilis muscle volume (r = 0.4, p = 0.03). CONCLUSION: This study revealed that patellofemoral joint kinematics in the operated extremity was diminished in the sagittal plane correlating with the quadriceps muscle volume loss and gracilis muscle hypertrophy. The modalities focused on both preventing and treating the hypotrophy of the quadriceps muscle following the surgical treatment of tibial fracture, which may help to overcome this quite common pathology.

Quantitative gait characteristics of children who had successful unilateral clubfoot operation.

OBJECTIVES: In this study, we aimed to evaluate the functional results of patients operated for unilateral clubfoot who had good clinical outcome with gait analysis. We also investigated the deviation from the normal, and determined the compensation mechanisms by comparing this data with the unaffected feet and with the feet of healthy children. METHODS: Sixteen children [10 boys, 6 girls; mean age, 6.8 years (range 4-9 years)] with surgically treated unilateral clubfoot and 24 age-matched healthy children were included in the study. Foot length, calf circumference, ankle range of motion, and radiographic measurements were recorded. All time-distance (walking velocity, cadence, step time, step length, double support time), kinematic (joint rotation angles of pelvis, hip, knee, and ankle in sagittal, coronal and transverse planes), and kinetic (ground reaction forces, moments, and powers of hip, knee, and ankle) data were evaluated. RESULTS: Calf circumference and ankle range of motion of involved extremity were significantly less than the unaffected side (p<0.05). Quantitative gait data revealed that children with clubfoot had slower walking velocity (0.75±0.25 m/sec vs. 1.02±0.18 m/sec, p=0.01), shorter stride length (0.72±0.23 m vs. 0.91±0.05 m, p=0.01) than healthy children group. Affected foot of unilateral clubfoot patients had more toe-in than healthy children (-14.24±21.78° vs. 18.54±7.90°, p=0.001). Unaffected side showed increased pelvic excursions and medio-lateral ground reaction forces as well as decreased ankle and hip motion in sagittal plane. CONCLUSION: Even asymptomatic well-treated children with unilateral clubfoot may have gait deviations both in the affected and unaffected sides. These alterations may also be the result of the subclinical involvement of the so called healthy foot by disease (clubfoot) as well as the compensatory mechanisms.