Radiographic Assessment of the Knee after Patellar Tendon Reconstruction for Chronic Anterior Cruciate Ligament Deficiency

Background: The aim of this study was to evaluate the patellar height and degenerative changes of the knee by radiographic assessment after patellar tendon reconstruction for chronic anterior cruciate ligament deficiency. Methods: This series included 44 patients (44 knees) with an average age of 31 years and an average follow up of 58 months. The central one third of the patellar bone-tendon-bone was used to reconstruct the anterior cruciate ligament in all patients. Radiographic assessment of the patellar height was measured using the Insall-Salvati method, and the degenerative changes of the knee using the Ahlback classification. Results: After harvesting the mid-third of the patellar tendon, 28 of 44 cases (64%) showed a shortening with an average of 9.1%, whereas 12 cases (27%) showing a lengthening of the patellar tendon with an average of 9.4%. Four patients (9%) showed no change in patellar tendon length. Despite the changes in patellar tendon length, the pre- and post-operative patellar height changes were only marginally significant (p=0.061). Patella baja was noted in eight knees (18.2%) and patella alta in four (9.1%). Of the 12 knees with patella alta or baja, knee pain was observed in one patient (8.3%). The incidence of degenerative changes was 74% in knees with anterior cruciate ligament (ACL) reconstruction plus meniscectomy, versus 41% with ACL reconstruction without meniscectomy (p=0.031). Conclusion: Harvesting of the mid-third of the patellar tendon resulted in changes in the patellar tendon length, however, it only marginally affected the patellar height. Meniscectomy was associated with a higher rate of degenerative changes, however, ACL injury alone significantly contributed to the development of degenerative changes of the knee.