Biomedical Engineering Reference
In-Depth Information
5.3.2.1 Debridement
Arthroscopic abrasion arthroplasty is a procedure where the cartilage defect is smoothed and re-
shaped. Burrs, diseased tissue, delaminated cartilage, and flaps can be removed to improve the gliding
motion and to provide temporary relief. Osteochondral defects can also be treated by removing the
dead bone or sclerotic lesions to result in fibrocartilage production. The fibrocartilage repair tissue
has been reported to last up to six years [
688
]. Reports have shown that, for chondromalacia patellae,
75% of the patients were satisfied with the procedure when followed up [
689
]. Even for athletes, the
procedure has shown quick success, with resumption of sports activities on an average of 10.8 weeks
following the procedure [
690
]. Cartilage debridement has been applied to various joints, including
the knee [
691
,
692
], elbow [
693
,
694
], ankle [
695
], and shoulder [
696
], oftentimes in combination
with other procedures.
5.3.2.2 Microfracture
As articular cartilage possesses little intrinsic healing response, the introduction of mesenchymal stem
cells and growth factors via microfracture from the subchondral bone has been widely employed for
isolated chondral defects of the knee [
697
,
698
], shoulder [
699
], and ankle [
700
]. The damaged
cartilage is first removed down to the calcified zone to expose healthy adjacent tissue. The calcified
cartilage is then removed, and evenly spaced microfractures into the subchondral bone are introduced.
Blood then fills the defect, resulting in a fibrin clot that initiates a healing response as described
in Chapter 2 The repair tissue is thus fibrocartilaginous in nature, with inferior material properties
as compared to healthy articular cartilage. Insufficient repair tissue (i.e., too thin) can also result in
altered biomechanics that lead to degeneration. To improve upon this, microfracture has been used
in combination with coverings, such as a periosteal flap [
699
] or natural (chitosan [
701
] and collagen
scaffolds [
702
,
703
]) and synthetic materials (e.g., PGA and hyaluronan [
704
]). Other improvements
to the technique include the addition of a BMP-4 carrier, which showed more rapid repair [
705
].
BMP-7 has been shown to increase the volume of repair tissue generated [
706
]. A recent systematic
review of 28 studies describing 3,122 patients has shown that the procedure is effective within the
first 24 months in improving knee function [
707
]. Subsequently, the effectiveness wears off, especially
for patients forty years and older [
707
,
708
], as the fibrocartilage formed can eventually degenerate,
resulting in recurred loss of function.
5.3.2.3 Autologous Implants
Though limited in source, autologous implants enjoy several advantages as transplant materials such
as not eliciting immune responses and having functionality close to the tissues they are replacing.
Taken from non-load bearing regions, autologous implants may be less stiff but contain live, autol-
ogous cells to potentially allow for continued remodeling. Unlike allogeneic tissue, the concern for
disease transmission is greatly mitigated in this case. However, the scarcity of source material, donor
site morbidity, differences in shape between the implant and the recipient site, and, significantly, the
need for multiple invasive surgeries (first to retrieve the implant, then to insert it), limit the use of
autologous implants. Chondral implants face the significant problem of integration, and autologous
implants typically fall into two forms, osteochondral plugs and autologous cells.
