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Orthop J Sports MedOrthop J Sports MedOJSspojsOrthopaedic Journal of Sports Medicine2325-9671SAGE Publications Sage CA: Los Angeles, CA 10.1177/2325967118S0013610.1177_2325967118S00136ArticleContralateral Lateral Femoral Condyle Allografts Provide an
Acceptable Surface Match for Simulated Classic Osteochondritis Dissecans Lesions
of the Medial Femoral Condyle Salka Nabeel MSE1Grant John A. MD, PhD, FRCSC21 University of Michigan Medical School,
Ann Arbor, MI, USA2 MedSport, Dept. of Orthopaedic Surgery,
University of Michigan, Ann Arbor, MI, USA27 7 2018 7 2018 6 7 suppl4 2018 AOSSM Annual Meeting Abstracts2325967118S00136© The Author(s) 20182018SAGE PublicationsThis open-access article is published and distributed under the
Creative Commons Attribution - NonCommercial - No Derivatives License
(http://creativecommons.org/licenses/by-nc-nd/4.0/), which
permits the noncommercial use, distribution, and reproduction of the article
in any medium, provided the original author and source are credited. You may
not alter, transform, or build upon this article without the permission of
the Author(s). For article reuse guidelines, please visit SAGE’s website at
http://www.sagepub.com/journals-permissions.Objectives:
The purpose of this study was to determine whether contralateral lateral
femoral condyle (LFC) allografts can provide an acceptable surface
topography match for classic osteochondritis dessicans (OCD) lesions of the
medial femoral condyle (MFC). Achievement of an acceptable donor-recipient
articular surface match (1 mm deviation) has been associated with
physiological joint stresses and predictably positive clinical outcomes. It
was hypothesized that LFC and MFC allografts would show no differences in
step-off height or surface deviation in all four quadrants of the graft.

Methods:
ample size calculation suggested ten groups of fresh frozen size-matched
human condyles, each group consisting of a donor MFC, donor LFC, and
recipient MFC. A 20 mm circular osteochondral “defect” simulating a
“classic” OCD lesion was created in the recipient MFC. Its most anterior
position was 1 cm posterior and 1 cm medial to the roof of the intercondylar
notch. A randomly selected donor MFC or LFC plug was then harvested and
transplanted using standard procedure (Fig 1A). The
transplanted condyle was scanned with nano-CT, reconstructed (Fig
1B), registered to an initial scan of the recipient MFC, and
processed with a custom MATLAB program to determine the surface root mean
squared deviation (dRMS) between the native and donor surfaces
(Fig 1C), percent area unacceptably proud (>1 mm;
%Aproud) and sunken (<-1 mm; %Asunk). Scans
were uploaded into DragonFly software where step-off height
(hRMS), percent circumference unacceptably proud (>1 mm;
%Cproud) and sunken (< -1 mm; %Csunk) were
measured (Fig 1D). The process was then repeated for the other
allograft plug. Two-way mixed ANOVAs with Sidak corrections for multiple
comparisons (α=0.05) were used. Exempt status was obtained from the
University’s IRB.

Results:
Both MFC and LFC plugs showed acceptable step-off heights in all four
quadrants. Neither allograft type nor location within the defect had a main
effect on step-off height (hRMS). In general, plugs were more
unacceptably sunken than proud, though no differences in %Csunk
were seen between allograft types or locations within the defect. In LFC
plugs, %Cproud was significantly greater laterally (by the
intercondylar notch) compared to all other locations around the plug
(p<0.0001), while no differences were seen based on location in MFC
plugs. The cartilage surface deviationn (dRMS),
%Aproud, and %Asunk were not significantly
affected by allograft type or location (Table 1).

Conclusion:
Previous studies demonstrated that contralateral LFCs provide acceptable
surface topography matches for centrally located defects of the MFC. In
evaluating the utility of LFC allografts for more laterally
located lesions characteristic of OCD, it was found that, similarly,
allograft type does not have an effect on surface deviation or step-off
height. With comparable surface deviations, both MFC and LFC allografts can
be expected to present similar stresses on the knee joint and achieve
predictably positive clinical outcomes, thus improving donor availability
and reducing surgical wait times for matches. LFC plugs did not differ from
MFC plugs in overall %Aproud, %Asunk,
%Cproud, or %Csunk suggesting that well placed LFC
plugs, like MFC plugs, may result in few post-surgical complications. Higher
step-off heights of LFC plugs near the intercondylar notch may contribute to
higher joint stresses and may serve as an area of focus in future
studies.

Figure 1. (A) en-face view of transplanted osteochondral allograft adjacent to
the intercondylar notch. (B) 3D reconstruction of nano-CT image
showing the four regional quadrants of the allograft considered in
this study. (C) Example color map of surface deviation of
transplanted condyle relative to native condyle (scale: in mm). (D)
Example of a sunken plug: hRMS measured between plug and
native cartilage surfaces (white arrow)

Table 1: Step-off height and surface deviation measurements for anterior,
posterior, medial, and lateral quadrants of the medial (MFC) and
lateral (LFC) allgrafts. (*) is significantly different from
(t) when comparing locations in a particular
allograft type (p<0.05). Data presented as mean ± standard
deviation.

 	
MFC
	
LFC
	
 	
Anterior
	
Medial
	
Posterior
	
Lateral
	
Overall
	
Anterior
	
Medial
	
Posterior
	
Lateral
	
Overall
	

hRMS (mm)
	0.62 ± 0.33	0.59 ± 0.33	0.58 ± 0.20	0.64 ± 0.42	0.63 ± 0.24	0.76 ± 0.36	0.53 ± 0.18	0.64 ± 0.45	0.94 ± 0.40	0.74 ± .12	

%Cproud
	0.00 ± 0.00	0.00 ± 0.00	1.67 ± 5.3	11.3 ± 27.0	2.42 ± 7.64	2.00 ± 5.26t
	1.33 ± 4.22t
	0.00 ± 0.00t
	28.0 ± 26.1*	8.08 ± 6.89	

%Csunk
	18.0 ± 27.9	17.7 ± 31.9	7.00 ± 15.3	11.0 ± 24.7	13.4 ± 17.9	26.0 ± 33.1	3.67 ± 7.77	16.7 ± 36.0	4.67 ± 7.06	13.2 ± 14.5	

 
	 	 	 	 	 	 	 	 	 	 	

dRMS(mm)
	0.49 ± 0.30	0.45 ± 0.21	0.47 ± 0.27	0.55 ± 0.26	0.51 ± 0.22	0.53 ± 0.38	0.61 ± 0.31	0.49 ± 0.31	0.53 ± 0.28	0.57 ± 0.25	

%Aproud
	4.38 ± 132	0.00 ± 0.00	0.00 ± 0.00	7.12 ± 11.8	3.16 ± 5.28	2.21 ± 4.52	15.1 ± 23.1	3.88 ± 11.7	5.06 ± 15.2	6.12 ± 10.6	

%Asunk
	2.42 ± 7.25	2.20 ± 5.96	9.41 ± 28.2	1.32 ± 3.97	3.63 ± 7.94	9.48 ± 28.1	2.11 ± 4.82	10.1 ± 30.2	5.18 ± 10.5	6.08 ± 12.1	
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