The effect of lesion size on clinical outcomes after microfracture: a 2 to 8 year follow-up study

Abstract

Purpose: Microfracture is often the first choice treatment for chondral defects in the knee, but some studies have suggested outcomes are influenced by lesion size at the time of the index surgery. Some authors have suggested that microfracture is suitable only for lesions up to 200 mm2, and other authors have placed an upper size limit of 400 mm2 for microfracture. The purpose of this study was to determine if there was a relationship between the size of the cartilage lesion treated with the appropriate microfracture surgical technique and rehabilitation protocols and patient-centered outcomes. We hypothesized that at a minimum of two years after microfracture patient-reported function, activity level, and satisfaction with outcomes would be similar regardless of the chondral lesion size at the time of index surgery. Methods: An ethics board-approved clinical data registry was queried for knees with contained focal chondral lesions and treated with microfracture by a single surgeon. Six hundred ninety-two (692) knees met the inclusion criteria. The lesions were on the femoral condyles, the tibial plateaus, or in the patellofemoral joint. The size of the chondral lesion was carefully measured and documented at the index surgery. Patients were assigned to one of four groups based on lesion size: Group I <100 mm2, Group II 100-300 mm2, Group III 301-400 mm2, and Group IV >400mm2. Previously published microfracture technique and rehabilitation protocols were used. Average follow-up was four (4) years with a range of 2 to 8 years. The patient-centered outcomes measures used for this study were the Lysholm function score, the Tegner activity level scale, and patient satisfaction with outcomes where 0 = totally dissatisfied and 10 = totally satisfied. Results: At the latest follow-up, data were available as follows: Group I contained 123 patients, Group II had 138, Group III included 161, and Group IV contained 138 patients. Preoperatively, Groups I-III had an average Lysholm score of 62, and Group IV had an average Lysholm score of 50. At an average 4 years after the index microfracture procedure (range, 2 to 8 years) with 80% (560 of 692) follow-up, there were no significant differences between groups for Lysholm, Tegner, or patient satisfaction values (Table I). These findings were the same regardless of lesion location (femur, tibia, or patellofemoral joint). Conclusions: In this large group of patients with an average 4-year follow-up, lesion size at the time of index microfracture had no effect on the patient-reported function (Lysholm), activity level (Tegner) or patient satisfaction with outcomes. These results were consistent regardless of lesion location. These findings confirm our hypothesis that patient-centered outcomes are the same for a contained chondral lesion of the knee regardless of lesion size. With the proper surgical technique and rehabilitation protocols, size of the lesion should not be a limitation for the use of microfracture.Tabled 1Outcomes by Defect SizeLesion Size (mm2)Group I <100Group II 100 to 300Group III 301 to 400Group IV >400N123138161138Lysholm86.987.186.587.5Tegner4.64.84.85.0Patietn Satisfaction7.98.18.08.2 Open table in a new tab