Chondromalacia Patellae

¹ From the Nuffield Orthopaedic Centre, Oxford

The results in this series of similar patients with similar involvement of the patella by chondromalacia were better following patellectomy than following a shaving procedure. If the patient was female and below twenty years of age, and if the symptoms were severe, the prognosis was poor with the shaving procedure. The length of history, clinical signs, and occupation were not helpful guides to prognosis. At operation the greater the extent of the pathological changes seen in the patellar cartilage, the worse the result with the shaving procedure, but with patellectomy there was no difference. The presence of a mirror lesion did not influence the results in either group. Postoperative quadriceps wasting did not influence the quality of results in either group. Quadriceps power was variable in different patients. Following patellectomy patients with weak quadriceps were slightly worse symptomatically than those with normal power. Following the shaving procedure, poor results occurred often when there was normal quadriceps power. Appearance of the knee was no more of a problem after patellectomy than after shaving, since, in both cases, the patient had a scar. After patellectomy the defect in the quadriceps was filled with fibrous tissue and sometimes bone so that it was difficult to detect the defect in many patients.

Roentgenographic deterioration was slight in both groups. One-third of the patients had slight irregularity of the femoral condyles following patellectomy but there was no correlation with the quality of the functional results. Ossification in the quadriceps tendon following patellectomy was not associated with pain. There was no rapid degeneration of the knee joint cartilage following either procedure, suggesting that chondromalacia patellae does not necessarily lead to degenerative arthritis.

Shaving is an inexact way of removing all the diseased articular cartilage and it is likely that there is diseased cartilage remaining. If the area of cartilage affected is large, it is particularly unlikely that this will be removed adequately by shaving of the patella since it is difficult to distinguish between normal and abnormal cartilage macroscopically. This would explain why the poor results which occur with shaving occurred in those with the most extensive changes. By contrast excision of the whole patella removes the source of irritation and the symptoms subside.

This series demonstrates that, not only does patellectomy relieve symptoms reliably when performed for chondromalacia patellae, but also that the postoperative function of the knee is good. From the functional point of view, it appears important to maintain the quadriceps power postoperatively after patellectomy. There is little evidence, so far, from the literature and in this series to show that the morbidity of the procedure is great, and, in particular, that rapid degeneration of

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the cartilage of the femoral condyles occurs due to prolonged contact with the quadriceps tendon.

From the findings it appears doubtful that shaving of the patella should be performed unless the fissuring and fibrillation in the patella involves an area no more than 1.3 centimeters in diameter of the surface and does not involve the subchondral bone. In these circumstances, when the changes are slight, it may be better to excise the area of articular cartilage and the underlying subchondral bone plate in anticipation that the defect will be filled with fibrocartilage from the subchondral bone as occurs experimentally⁴.

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