Objective To investigate effectiveness of a improved technique for perforation of patella combined with suture anchor and non-tourniquet for repairing acute rupture of the bone tendon junction of quadriceps tendon. Methods Between June 2010 and June 2016, 15 patients with acute rupture of the bone tendon junction of quadriceps tendon were treated with the improved technique for perforation of patella combined with suture anchor and non-tourniquet. Of them, 14 were male and 1 was female, aged from 19 to 74 years (mean, 44 years). Seven cases were sports injuries, 5 cases were caused by slipping, and 3 cases were caused by violent trauma. The duration of quadriceps tendon rupture ranged from 3 hours to 3 days (median, 2 days). The right side was involved in 9 cases, and the left side in 6 cases. All of the cases were closed injuries. The patients had no sequelae of limb dysfunction and no limb joint surgery in the past. All the patients received anteroposterior and lateral X-ray films of the knee joint and patella axial films during follow-up. Knee function of the patients after operation was evaluated by Lysholm scoring system and Kujala scoring system. Results The operation time was 50-60 minutes (mean, 55 minutes). The intraoperative blood loss was 50-150 mL, with an average of 87 mL. Primary healing of incision was obtained in all patients without complications. All patients were followed up 12-24 months (mean, 18 months). At 1 year after operation, the knee joint function of all patients recovered well; the knee Lysholm score was 92-96, with an average of 94 and the patellofemoral joint Kujala score was 90-95, with an average of 93. There was no re-rupture of quadriceps tendon or loosening of internal fixation during follow-up. According to the lateral and axial X-ray films at 1 year after operation, the patella depth index, femur trochlea depth, sulcus angle, and Insall-Salvati index were 3.62-4.09 (mean, 3.84), 4.45-6.50 (mean, 5.56), 137-145° (mean, 142°), and 0.90-1.18 (mean, 1.06). The lateral patellofemoral angle increased, and the patellar tilt angle and the patella lateral shift distance reduced, all showing significant differences when compared with preoperative ones (P<0.05). Conclusion The improved technique for perforation of patella combined with suture anchor and non-tourniquet for repairing acute rupture of the bone tendon junction of quadriceps tendon can reconstruct a stable patellofemoral joint, increase the strength of fixing, disperse stress effectively and evenly, and increase the area for tendon-bone healing.
ObjectiveTo investigate biomechanical effects of pseudo-patella baja on stress of patellofemoral joint after total knee arthroplasty (TKA) by using finite element analysis (FEA).MethodsA series of CT and MRI of the left knee joint of two healthy volunteers and three-dimensional (3D) scanned data of TKA prosthesis were taken, and the 3D models of knee before and after TKA were established. The finite element model of pseudo-patella baja, normal patella, and alta patella after TKA were constructed by Insall-Salvafi (IS) ratio and Blackburne-Peel (BP) ratio. The load was applied along the direction of quadriceps femoris. After testing the validity of the finite element model, the high contact stress of patellofemoral joint was measured on the von Mise stress nephogram of pseudo-patella baja, normal patella, and alta patella after TKA when the knee flexion was 30°, 60°, and 90°. The average contact area was calculated according to two volunteers’ data.ResultsOn the finite element model of the normal patella after TKA with knee flexion 30°, 475 N pressure was applied along the direction of quadriceps femoris. The contact stress of patellofemoral joint was (1.29±0.41) MPa, which was similar to the results reported previously. The finite element model was valid. The von Mise stress nephogram showed that the stress mainly focused on the medial patellofemoral articular surface during knee flexion, and the contact point gradually moved up with the knee flexion deepened. The stress on the medial and lateral patellofemoral articular surface increased with the knee flexion deepened but decreased with the increase of patellar height. The effects of patellar height and knee flexion on the high contact stress of patellofemoral joint were similar among the finite element models after TKA based on the data of two volunteers. The high contact stress of patellofemoral joint increased with the knee flexion deepened in the same patellar height models (P<0.05), but decreased with the increase of patellar height in the same knee flexion models (P<0.05). The high contact stress of patellofemoral joint of pseudo-patella baja model was significantly higher than normal and alta patella models (P<0.05). The average contact area of patellofemoral joint of pseudo-patella baja was bigger than normal and alta patella models with the knee flexion deepened.ConclusionThe pseudo-patella baja after TKA has an important effect on the biomechanics of patellofemoral joint. Reserving the joint line and avoiding the occurrence of pseudo-patella baja can decrease the risk of anterior knee pain, patellar arthritis, and other complications caused by the increasing of contact stress of patellofemoral joint.