Focal chondral and osteochondral defects of the knee are common injuries found in the patellofemoral joint and can significantly impair a patient’s quality of life and therefore, are an area of great interest to orthopedic surgeons and patients. Many surgical options for treating those patellofemoral cartilage lesions are available, however, with limited evidence comparing their results.
In this systematic review and meta-analysis, we compiled information from 59 articles on patellofemoral cartilage restoration. We included all reported techniques and grouped these based on principle of treatment for quantitative analysis. The groups were osteochondral allografts transplantation, osteochondral autografts transfer, chondrocyte cell-based therapy, bone marrow-based therapy, with or without orthobiologic augmentation and scaffolds.
We found some important information in regard to lesion characteristics and comorbidities. Patellar lesions were more frequent (65.7%), followed by trochlear lesions (23.8%) and bipolar lesions (10.5%). Overall, lesions tended to be large (mean 3.9 cm2), with chondrocyte cell-based being performed in larger lesions (mean 4.7 cm2), while scaffolds (mean 2.2 cm2) and OAT (mean 1.5 cm2) were performed in smaller lesions. Instability and anatomical risk factors were present in 11.9% and 32.1% of the cases, respectively.
In terms of treatment, chondrocyte cell-based therapy account for most of the procedures (65.7%), followed by bone marrow-based therapy (17.2%), osteochondral autografts transfer (8%), osteochondral allografts transplantation (6.6%) and scaffolds (2.2%). Concomitant procedures were common, especially tibial tuberosity osteotomy (TTO) to address underlying malalignment and/or unload the patellofemoral joint. As expected, the high prevalence of anatomical risk factors drives surgeons to perform TTOs in 27.7% of the cases; more so in chondrocyte cell-based (37%) and bone marrow-based (42.1%) techniques than in osteochondral graft techniques (allograft 8.4% and autograft 8.2%).
Clinical results were good, improvement was observed on at least one patient-reported outcome (PRO) in chondrocyte cell-based (83%), OAT (78%), OCA (71%) bone marrow-based (64%), and scaffolds (50%). Furthermore, on IKDC score and Lysholm scores, there were no differences between the groups. Also, no differences were found on minor (mean 7.6%) and major complication rates (mean 8.3%) between the groups. However, there was an increased failures incidence in the osteochondral allograft group (22.7%) compared to the other groups (6.8%).
As reported in previous studies, we found accurate reporting of lesion characteristics and concomitant procedures is highly variable and inadequate in many cases. Therefore, we could not properly evaluate the effect of age, sex, etiology, location of the lesion and TTO. Further details on the type or direction of the osteotomy, similarly, were not frequently reported. Therefore, although anteromedialization is believed to be the most frequently performed TTO in this setting, this could not be confirmed. It is important to point out, that moving forward, studies should ensure better reporting of those variables.
In summary, considering the number of procedures performed, the differences in variables and the clinical outcomes, we believe that, to date, there is more consistent evidence to support the use of chondrocyte cell-based therapy in large lesions and OAT in small lesions as a means to obtain reliable and successful long-term clinical improvement. Still, we acknowledge data may not be clearly reflective of OCA potential utility as a primary cartilage repair choice in the patellofemoral joint for appropriately selected lesions, especially with significant bone deficiency, as higher failure rates can be due to decrease rate of realignment procedures performed in the OCA population and/or may reflect its selective use in complex or salvage situations (uncontained lesions, cystic osteochondral defects, failure prior cell based or prior OCA).
Betina B. Hinckel, MD, PhD, is an assistant professor at Oakland University in Rochester, Michigan in the department of orthopedic surgery at William Beaumont Hospital in Royal Oak, Michigan.