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Lee et al	

Table 2.  Frequency of the Osteochondral Lesions in Each of
the 9 Zones (n = 16).
Tibial Zone
1
2
3
4
5
6
7
8
9

Figure 3.  Anatomic grid classification of distal tibia plafond
developed by Elias et al.10 Reprinted with permission from the
American Orthopaedic Foot & Ankle Society.10

the mean. Wilcoxon signed-rank test or a paired t test was
used to compare pre- and postoperative continuous or continuously ranked data, including VAS score and functional
scores (FAAM score and SF-12). Mann-Whitney test was
used to compare continuous or continuously ranked data,
including VAS score and functional scores (FAAM score
and SF-12 scores) between the 2 groups according to the
OCD lesion size. The chi-square test was performed to evaluate the preoperative and postoperative level of sports
activity. P values <.05 were considered statistically significant. In terms of sample size calculation, we performed a
post hoc calculation with G*Power software (version
3.1.9.2, Düsseldorf, Germany). The power of this study was
0.85 with N = 16, alpha level = 0.05, and effect size = 0.8.
This study was approved by our institutional review
board, and the need for submission of written informed consent was waived.

Results
Intraoperatively, 12 patients were found to have an isolated
osteochondral lesion of the tibial plafond, and 4 patients
were found to have bipolar lesions both in the talar dome
and the tibial plafond. The mean size of the osteochondral
lesion was 65.2 ± 43.2 mm2 (range, 16-150). The frequency
of the osteochondral lesions in each zone is provided in
Table 2. All anterior regions including anterolateral, anterocentral, and anteromedial region of the tibial plafond (zones
1, 2, and 3) were the most common locations in our study.
The mean preoperative VAS score improved significantly
from 8.3 ± 1.2 to 1.8 ± 1.2 at the final follow-up (P <
.001). The activity daily living subscale of the FAAM score
improved from 57.6 ± 21.2 to 84.3 ± 14.3 at the final

Frequency

%

3/16
3/16
3/16
1/16
2/16
0/16
2/16
2/16
0/16

18.75
18.75
18.75
6.25
12.5
0
12.5
12.5
0

follow-up (P < .001), and the sports subscale of the FAAM
score improved from 34.5 ± 26.0 to 65.2 ± 30.2 at the final
follow-up (P < .001). Likewise, the SF-12 PCS score
improved significantly from 36.3 ± 10.7 to 46.0 ± 10.3 at
the final follow-up (P = .004), and the SF-12 MCS also
improved significantly from 41.3 ± 18.1 to 52.6 ± 9.2 at
the final follow-up (P = .035) (Table 3). Preoperatively, all
of the patients (n = 16/16) participated in a sport activity
and all of them could return to the sports activity at the final
follow-up point, the level of sports activity was significantly lower than the previous level before the surgery (P =
.012) (Table 4). Additionally, we categorized patients into 2
groups according to OCD lesion size: size <100 mm2 (n =
10) vs size ≥100 mm2 (n = 6) and compared the functional
outcomes between the 2 groups. The final clinical outcomes
including the VAS score (P = .147), the FAAM activity
daily living subscale (P = .875), the FAAM sports subscale
(P = .792), the SF-12 PCS (P = .181), and the SF-12 MCS
(P = .368) did not have any significant differences between
the 2 groups. Functional outcomes including the FAAM and
the SF-12 have been shown to be sensitive to significant
changes over time. The assessment of responsiveness was
done at the individual level to determine a change in score;
it could be interpreted as the minimal clinically important
difference (MCID).20 Martin et al20 reported the MCID
were 8 and 9 points for the ADL subscale and Sports subscale of the FAAM score, respectively, in their study. The
MCID for the SF-12 PCS was reported as 4.3 points after
total knee arthroplasty.7 There was no complication such as
infection, wound dehiscence, or readmission related to the
surgery in this study.

Discussion
In this study, we highlight that arthroscopic microfracture
for osteochondral lesions of the tibial plafond could lead to
satisfactory clinical outcomes, and all functional scores
including VAS pain score, SF-12 score, and FAAM score
were significantly improved. Furthermore, we observed
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