Patellar tendinopathy: histopathological examination and follow-up of surgical treatment

The aim of this study was to determine the exact localization of the histopathological process (bone, bone-tendon junction or tendon), and to determine whether the underlying pathologic process is predominantly of inflammatory or degenerative nature, then to evaluate the outcome of the surgical treatment of patellar tendinopathy.

A prospective cohort study was performed in order to analyze the outcome of surgical treatment of patellar tendinopathy, as well as to document histopathological changes in bone, bone-tendon junction, and in the patellar ligament in 34 professional athletes treated with patellar apicotomy. All the patients included in the study were classified as stage 3 according to Blazina and showed no improvement after at least 6 months of conservative treatment. The postoperative follow-up was from 1 to 8 years with a mean value of 4.7 years.

The postoperative results were analyzed using a semiquantitative scoring system where the functional outcome was classified as very good if the athlete returned to his sporting activity without any negative side effects, good if the athlete resumed his sporting activities with modest painful sensations present only at the maximum level of physical exertion, and poor if any reduction of athletic activity was present. In twenty patients a histopathological examination of resected bone and tendon tissue was performed. The specimens were stained with hematoxylin-eosin and examined under a light microscope using polarization. Special stains used were Alcian blue, to detect any increase in ground substance, and Prussian blue which enhances conspicuity of hyaline degeneration and enables detection of hemosiderin. Immunohistochemistry was performed in order to analyze presence of blood vessels, leukocytes and histiocytes.

Very good results were achieved in 20 of operated knees, good results were achieved in 12 of knees and poor results were achieved in 2 of operated knees. Pathological changes in the bone were found in 35% of analyzed specimens, abnormality at the bone-tendon junction were found in 75% of the specimens, and changes in the patellar tendon were found in all extracted specimens. The histopatholological nature of the lesions found within the tendon tissue in all of the analyzed specimens belongs to the group of degenerative changes.

Currently a consenus has been established that the expression tendinitis is "out", and the term tendinopathy should be used instead. No inflammatory cells and no increase in prostaglandins can be detected in the tendons. Histopathological studies of the tissue fibrils affected by tendinosis characteristically demonstrate hypercellularity, hypervascularity, lack of inflammatory infiltrates, and disorganization and loosening of collagen fibers.

The clinical results and histopathological examination in our series justified our operative method. In the chronic stage these lesions are irreversible and constitute permanent intratendinous lesions. It thus seems logical to excise these lesions from their origin at the apex of the patella and entry into the adjacent tendon. It is also recommended on the basis of our and other authors' research that the term patellar tendinopathy should be used instead of tendonitis/tendinitis.