Three-dimensional-printed custom-made patellar endoprosthesis for recurrent giant cell tumor of the patella:A case report and review of the literature

BACKGROUND Giant cell tumor(GCT)is a benign lesion and rarely involves the patella.This disease is characterized by a relatively high recurrence rate after primary treatment.En bloc resection has been a predominant option for recurrent GCT.However,total patellectomy can lead to disruption of the knee.Therefore,exploration of functional reconstruction of the extensor mechanism is worthwhile.CASE SUMMARY A 54-year-old woman presented with right knee pain and swelling,and was diagnosed as having a GCT in the patella following curettage and autograft.Medical imaging revealed a lytic and expanded lesion involving the whole patella with focal cortical breaches and pathological fracture.Based on the combination of histological,radiological,and clinical features,a diagnosis of recurrent GCT in the patella was made(Campanacci grade III).After a multidisciplinary team discussion,three-dimensional(3D)-printed custom-made patellar endoprosthesis was performed following en bloc resection for reconstructing the extensor mechanism.The patient was followed for 35 mo postoperatively.No evidence of local recurrence,pulmonary metastasis,or osteoarthritis of the right knee was observed.The active flexion arc was 0°-120°,and no extension lag was detected.A favorable patellar tracking and height(Insall-Salvati ratio 0.93)were detected by radiography.CONCLUSION We depict a case of a GCT at the right patella,which was successfully treated by patellectomy and 3D-printed custom-made endoprosthetic replacement.The patella normal reconstruction,the precise-fit articular design,and gastrocnemius flap augmentation could lead to satisfactory knee function and a low rate of complications in the short-term follow-up.

Eliminating impingement optimizes patellar biomechanics in high knee flexion

Background We investigated the impact of eliminating the impingement between extensor mechanism and tibial insert on patellar tracking and patellar ligament tension in high knee flexion.Methods Six cadaveric specimens were tested on an Oxford-type testing rig.The Genesis Ⅱ knee system was implanted into each specimen knee with the traditional tibial insert and high-flex insert successively.Compared to traditional insert, the high-flex insert was characterized with a chamfered anterior post and a chamfered anterior lip which eliminates patella-post and patellar ligament-anterior lip impingements.The patella was tracked with an NDI Optotrak Certus system.The patellar ligament tension was measured using a NKB S-type tension transducer.Results There was a decrease of resultant patellar translation relative to the femur with statistically significant （P 〈0.05）at 90° to 150° of knee flexion and a decrease of patellar ligament tension with statistical significance （P 〈0.05） at 100°,120°, 130°, and 140° of flexion using high-flex insert compared to traditional insert.Conclusions Eliminating the impingement between extensor mechanism and implant in high knee flexion altered patellar tracking and reduced patellar ligament tension, which would facilitate high knee flexion.