Neural damage in 16 lateral retinacula excised at the time of Insall proximal realignments or isolated lateral retinacular releases performed in patients with symptomatic patellofemoral malalignment was evaluated by means of conventional histology and immunohistochemical and morphometric analyses. A relationship between clinical and histologic findings was found. An increase in the proportion of innervated tissue was correlated with anterior knee pain syndrome. We found a significant relationship between total neural area and pain. The group with moderate pain had the highest number of nerves and the highest neural area. In reference to total neural area and pain, there was a significant difference only between the patients with moderate pain and those with light pain, but not between patients with severe pain and those with moderate pain. The group with severe pain also showed a high neural area, although with a lower number of nerves. The severe-pain group had the largest nerves (24% of nerve fibers surpassing 25 microns diameter) in a zonal disposition, in which there were groups of nerve fibers in some fields and no nerve fibers in others. The group with moderate pain had an increase in medium and small nerve fibers (mean diameter, 18 microns), predominantly of tiny perivascular fibers. Moreover, we believe that instability in patients with patellofemoral malalignment can be explained in part because of loss of proprioception due to neural damage.

Four infants had soft, skin-colored nodules in the midline plantar region of the heels since birth. The lesions were asymptomatic, bilateral, and symmetric, and measured approximately 1 cm in diameter. Their size increased in proportion to the growth of the child. In three infants the lesions persisted at 1 year of age, while in the fourth they remained at age 12 years. The nodules were not associated with any other disease or abnormality. A review of the literature revealed only one Argentinean series comprising four cases, and two communications at international pediatric congresses by French and American authors who reported five and three cases, respectively. We describe four additional cases of precalcaneal congenital fibrolipomatous hamartoma and comment on their histopathologic and ultrastructural characteristics.

Patellar tendon donor defect (PTDD) healing after patellar tendon autograft (PTA), was evaluated in 12 lambs (24 knees), by means of conventional histology, immunohistochemistry and image analysis. The results of this study indicate that the PTDD is replaced by a tissue that does not assume the histological characteristics of a normal patellar tendon. Both the Hoffa fat pad (HFP) and the paratenon play an important role in the healing process, although qualitative and quantitative chronological differences were found, which supports the concept of a "two-time process". The HFP initiates the repair process, and is the main active proliferative tissue compartment during the first week. Once the process is established, the paratenon and, in particular, its synovial lining, starts proliferative activity and virtually substitutes that of the HFP, which rapidly loses activity in a few days. Moreover, donor-site morbidity after PTA could be the result of histological changes in the patellar tendon and environs in only a few cases. We have found inflammatory and neural changes in the refilled PTDD that could explain the anterior knee pain after PTA. Likewise, we have observed loss of Golgi corpuscles in the refilled PTDD, which could lead to proprioceptive loss after ACL reconstruction with PTA. Finally, we have observed shrinkage of the PTDD scar that could contribute to the etiopathogenia of a patella infera.

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