Reconstruction of patellar tendon following implantation of proximal tibia megaprosthesis for the treatment of post-traumatic septic bone defects.

INTRODUCTION: Latest advances made in joint replacement implants allows reconstruction of entire limbs. These special prostheses or megaprostheses were originally designed for the treatment of severe oncological bone loss. Nowadays, however, the indications and applications of these devices are expanding to other orthopaedic and trauma clinical conditions. Since 2008 we have implanted 152 megaprostheses in non-oncological conditions: 87 were implanted for post-traumatic failures aseptic/septic (represented by complex non-unions and critical size bone defects); 26 total femur, 52 distal femur and 9 proximal tibia. In this group of patients bone and soft tissues conditions are completely different compared to patients with oncological back ground. The presence of infection and previous surgeries can lead to adhesion, scar interference, muscular and tendon impairment and skin problems that lead to reduced function and severe joint stiffness. The purpose of this study is to evaluate the results of treatment of reconstruction of patellar tendon during implantation of proximal tibia megaprosthesis for the treatment of septic post traumatic critical bone defects.

PATIENTS AND METHODS: In this retrospective study, we evaluated 9 patients treated with proximal tibia megaprosthesis who underwent patellar tendon reconstruction. All patients presented a complete patellar tendon disruption at the time of prosthesis implantation. Procedures of reconstruction included a tendon-plasty of quadriceps and/or patellar tendons, a pie crusting of quadriceps fascia, a reinforcement of the apparatus with synthetic tendon graft substitutes (LARS) and a medial gastrocnemius muscular flap to reconstruct the extensor mechanism and obtain skin coverage when needed. The average follow up was 18 months (9-36). For each of the cases, we analysed the complications occurred regarding septic recurrence, patellar fracture, quadriceps and patellar tendon rupture and number of reinterventions. The clinical outcome was assessed by the WOMAC Score.

RESULTS: In all cases there was no infection recurrence or skin related problems. None of the patients require prosthesis revision due to loosening or device failure. No patellar fracture or quadriceps tendon failure was recorded. One patient presented a rupture of the reconstructed patellar tendon due to a trauma incident 18 months after the implantation and he required revision surgery. From a clinical point of view the average WOMAC score was 62.4 at 1 month rising to 72.6 at 3 months, 78.2 at 6 months, 76.4 at 1 year and 74.8 at 18 months.

CONCLUSION: When proximal tibia megaprosthesis is implanted and there are soft tissue and patellar tendon deficiency, soft tissue reconstruction can be achieved by appropriate lengthening of the tendon and a gastrocnemius flap reinforced by LARS. Such an approach allows restoration of the extensor mechanism and coverage of the prosthesis in an area where skin problems are frequently very common.