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Among several surgical interventions to
chondral lesions, microfracture technique is
presumably most widely performed procedure.
In this regard, the result of Level I RCT [10,
11], showing no significant difference in
clinical outcome or histological results between
ACI and microfracture might have considerable
clinical relevance. Conversely, recent Level I
RCT demonstrated that ACI using cultured
chondrocytes with higher chondrogenic
differentiation potentials resulted in better
structural repair by histomorphometry and
overall histologic evaluation at 12 months [12].
Knee injury and Osteoarthritis Outcome Score
(KOOS) at 12 to 18 months after characterized
ACI was comparable with microfracture,
however, their longer follow-up (3 year) results
demonstrated that ACI group showed better
KOOS thanmicrofracture group [13]. However,
such significance disappeared at 5 year followup
[14]. These series of reports of the RCT suggest
the importance of long term followup post ACI
and moreover of the accumulation of evidence
for the evaluation of this new therapy.
Also, recent prospective comparative study
revealed that arthroscopic second-generation
ACI using Hyalograft C showed significantly
better improvement of the International Knee
Documentation Committee objective and
subjective scores than microfracture at 5-year
follow-up [15]. These results suggest that the
progress in cell culture technique as well as the
optimization of scaffold development might
improve the clinical results of new generation
ACI. Additional RCTs of ACI with micro
fracture with more patient number and with
longer follow-up will be required to draw a
definitive conclusion.
There was one Level II RCT of matrix-guided
ACI versus collagen-covered ACI [16].
No significant difference was found between
the two interventions in terms of clinical score,
arthroscopic scoring or histological assessment.
Based on the results no advantage of using
collagen I/III based scaffold in ACI was
demonstrated. This study did not provide
enough information on blind participants or
outcome assessors, which should be taken into
consideration. Further high quality RCT will be
required.
There was one Level II RCT comparing
periosteum covered ACI (ACI-P) versus type I/
III collagen covered ACI (ACI-C) for the
osteochondral defect of the knee [17]. There was
no significant difference in the clinical outcome,
while significant number of patients who had the
periosteum-covered ACI required shaving of a
hypertrophied graft. Based on the results, the
authors concluded that there is no advantage in
using periosteum. However, there was difference
in the patients’ profile between these groups.
The osteochondral defects were located at patella
in 61% of ACI-P group and at femoral condyles
in 74% of ACI-C group. There was a report
showing that there was a difference in the clinical
result of ACI between the femoral condyle and
patella [18]. Therefore, regional difference might
influence the result and there might be caution
required to interpret the results.
In addition to the comparative studies with
respect to the treatment procedures, there was s
prospective comparative study to test the
influence of sports activity level and
postoperative rehabilitation program on the
outcome of ACI. The patients with high sports
activity level showed significantly better results
in the ICRS and Cincinnati scores than the
patients with lower activity level. The result
suggests physical training might contribute to
the improvement of long-term clinical results
[19]. Moreover, there was randomized
controlled study to test the influence of
accelerated rehabilitation on the outcome of
MACI.Accelerated postoperative rehabilitation
with 4 week-earlier full weight bearing than the
conventional program resulted in better pain
relief effect [20].
As comparedwithACI, the number of published
stem cell therapy is limited. There were only
two Level II prospective comparative studies
published using stem cell therapy approach.
One study reported the comparison of
mesenchymal stem cell implantation (MSCI)
plus high tibial osteotomy (HTO) with cell-free
scaffold transplantation plus HTO [21]. There
was no significant difference in clinical