|
Address: Musculoskeletal Research Unit, School of
Clinical and Surgical Sciences, University of Edinburgh, Edinburgh,
U.K.
|
|
Key Words: Autologous osteochondral grafting, human cartilage,
chondrocyte, articular surgery, cell death.
|
|
Abstract: Although autologous osteochondral grafting
has been widely applied in humans, most in vitro work has
been on animal models. The aims of this study were to: (i)
elaborate a full thickness human femoral condylar model using
discard material from knee arthroplasty resections, and (ii)
use this model to assess chondrocyte viability in response
to surgical trauma.
Homogeneous regions of human lateral femoral condyle bone-cartilage
were procured from knee arthroplasty resections. These were
graded prospectively, firstly by visual inspection, and then
by confocal laser scanning microscopy (CLSM). Samples were
subjected to tests of tissue hydration, including analysis
of water content and swelling after excision from underlying
bone. Surgical cuts were made in explants that were macroscopically
and microscopically normal (i.e. Grade 0). Associated margins
of death were assessed from both transverse and surface perspectives.
Thirty-nine samples were obtained from anterior and distal
femoral cuts (16 knees from 13 patients) for (1) macroscopic
grading, (2) microscopic analysis, (3) analyses of water content
as cut and on re-equilibration after excision from bone. Thirteen
were Grade 0 on macroscopic viewing - however one showed fibrillation
on microscopy and was therefore reassigned Grade 1. Grade
0 tissue had a water content of 73.8±0.38%, in agreement
with control values from the literature. Tissues of Grades
2 and 3 were significantly (P=0.03, and P=0.004) more hydrated
(76.0±0.59%, 76.7±0.99%) than Grade 0 tissue.
Grade 0 tissue from the anterior cut did not swell significantly
following excision from subchondral bone. However Grade 0
tissue from the distal cut showed a small but statistically
significant (P=0.019) increase in water content (1.68±0.39%)
following excision. With increasing grade there was increased
tendency to swell off the bone (P<0.0001). Transverse imaging
showed that the Acufex MP surgical harvester caused a greater
margin of cell death (211±18.3µm) in the superficial
zone (SZ) than the mid-zone (50.5±13.6µm; P=0.022),
or SZ death from a scalpel cut (33.0±8.5µm; P=0.0009).
Similarly, in unfixed samples viewed from the surface perspective,
the margin of death for the surgical harvester (277±7.2µm)
was significantly (P<0.0001) greater than that for the
scalpel (38.8±7.2µm).
If macroscopically and microscopically non-degenerate, then
human lateral femoral condylar cartilage from the anterior
cut of knee resections has normal biophysical parameters (water
content and lack of swelling on excision). The surgical harvester
(Acufex), used in human osteochondral grafting, caused a substantial
margin of cell death at the periphery of the graft, and the
SZ appeared to be especially vulnerable. This effect may be
important in terms of limiting the reparative capacity of
the SZ. The harmful effect on viability is likely to impede
lateral repair which is fundamental to subsequent structural
and functional integrity.
|
