Comparison of Contact Pressure Change Following Medial and Lateral Osteochondral Allograft Harvest
+1Schweizer, SK; 1Werner, FW; 1Sutton, LG; 1Taormina, JL; 1Scuderi, MG
+1SUNY Upstate Medical University, Syracuse, NY
Senior author: [email protected]
Introduction:
Given the limited healing potential of cartilage,
treatment of focal cartilaginous defects in the weight bearing portion of
the knee is a difficult problem for orthopedic surgeons. Both short and
mid-term studies have shown autologous osteochondral transfer (OATS)
to be a valid option, with good results, for the treatment of such
lesions.1,2 While OATS repair yields a desirable hyaline-like cartilage,
there continues to be concern over graft site morbidity. It has been
proposed that grafts harvested from sites that see significant contact
pressure are more likely to be associated with crepitous, pain, and
possibly early degeneration. Simonian et al3 and others4 have shown
that all harvest sites along the lateral condylar ridge and in the femoral
notch see significant contact pressure. However, they have failed to
report on contact pressures along the medial condylar ridge following
osteochondral harvest. Our hypothesis is that donor sites on the medial
femoral condyle will see decreased or zero contact pressure, and should
lead to a lower risk of graft site morbidity.
Methods: Six fresh frozen cadaver knees were dynamically tested in a
deep knee bend simulator5 from ten to 105 degrees while physiologic
tendon loads were applied to the quadriceps and hamstrings. Loading
was based on reported flexion moment data of Nagura et al.6 Testing
was done at 10% and 30% of maximum load, which resulted in a peak
quadriceps force of 535 N and 54 N for the hamstrings. Prior to testing,
excess soft tissue was removed and a rod was cemented into the femoral
bone canal for attachment of the knee to the simulator. The tibia was
potted with the tibial plateau horizontal and centered in the pot. A
parapatellar incision was made on either side of the patella and a
Tekscan pressure sensor was affixed to the medial and lateral portions of
the trochlear notch of the femur (fig 1). Data was collected in the intact
case (Case 1), after two medial and two lateral 6mm cartilage cores were
removed (Case 2), after a 4mm core removed from the lateral side
between the 6mm cores (Case 3) and following a 6mm core removed
from over the 4mm core (Case 4)(fig 2). The peak pressure and the
loaded contact area on each femoral condyle were determined. The
pressure data was integrated to determine the total force on each
condyle. The peak and average pressure in the region surrounding each
core, before and after coring, were also examined. Repeated measures
ANOVA and paired t tests were used, at p<.05 to compare the results.
Results: Contact area was statistically greater in the area of the lateral
donor sites than the medial beyond 41o in the intact knee and beyond 61o
in the fully cored knee (fig 3). Furthermore, ten of the 12 medial harvest
sites had no contact from the patella, while only three of 18 lateral sites
saw no contact. Additionally, the lateral condyle received statistically
greater force than the medial condyle beyond 57o in the intact knee and
beyond 81o after coring (fig 4). The peak contact pressure was greater
lateral only between 78 and 100o in the intact knee and between 88 and
96o in the fully cored knee (fig 5). There were no statistical differences
in the peak (table 1) or average pressure (table 2) surrounding each
cored hole before or after coring.
Discussion: Given that the medial coring sites are in fact nonarticulating in most cases, we conclude that harvesting from these sites
should lower the risk of graft site morbidity. This is additionally
supported by our results, which showed that the articulating areas of the
medial femoral condyle saw significantly less force than the lateral side.
References: 1. Hangody, JBJS 85:25-32, 2003. 2. Marcacci, AJSM
35(12):2014-2021, 2007. 3. Simonian, AJSM 26(4):491-494, 1998.
4. Guettler, Arthroscopy 21(6):715-720, 2005. 5. Werner, ORS (2008)
2010. 6. Nagura, J Bio 20:881-886, 2002.
Average Peak pressure in MPa surrounding cored holes (std dev)
Table 1
Before
Coring case Coring case Coring case
coring
1
2
3
Lat superior core 0.62 (0.33) 0.91 (1.03) 1.11 (1.69) 0.95 (1.17)
Lat mid core
1.20 (0.57) 1.37 (1.08) 1.23 (1.24) 1.22 (1.50)
Lat inferior core 1.98 (1.44) 1.75 (1.02) 1.74 (1.38) 1.57 (1.01)
Med superior core 0.59 (0.46) 0.85 (0.93) 0.57 (0.46) 0.46 (0.43)
Med inferior core 0.41 (0.58) 0.60 (0.93) 0.44 (0.60) 0.51 (0.63)
Average of average pressure in MPa surrounding cored holes (std dev)
Table 2
Before
Coring case Coring case Coring case
coring
1
2
3
Lat superior core 0.24 (0.23) 0.29 (0.35) 0.21 (0.18) 0.16 (0.14)
Lat mid core
0.44 (0.33) 0.49 (0.34) 0.45 (0.48) 0.23 (0.13)
Lat inferior core 0.80 (0.71) 0.66 (0.60) 0.56 (0.54) 0.47 (0.27)
Med superior core 0.12 (0.12) 0.12 (0.12) 0.09 (0.09) 0.07 (0.08)
Med inferior core 0.04 (0.07) 0.08 (0.17) 0.08 (0.18) 0.07 (0.13)
Poster No. 1101 • 55th Annual Meeting of the Orthopaedic Research Society