scholarly journals Factors Contributing to Graft Matching in a Patellar Osteochondral Allograft Selection Model (211)

2021 ◽  
Vol 9 (10_suppl5) ◽  
pp. 2325967121S0032
Author(s):  
Hailey Huddleston ◽  
Theodore Wolfson ◽  
David Christian ◽  
Nozomu Inoue ◽  
Adam Yanke
Keyword(s):  
Articular Cartilage ◽  
Subchondral Bone ◽  
Point Cloud ◽  
Articular Surface ◽  
Osteochondral Allograft ◽  
Least Mean Square ◽  
Bone Surface ◽  
Cartilage Surface ◽  
Articular Cartilage Surface ◽  
Surface Models

Objectives: Patellar osteochondral allograft (OA) transplantation has been shown to be a successful treatment in patients with isolated patellar cartilage injury. Currently, there is minimal guidance in anatomic and sizing factors that portend similar patellar surface topography. The most commonly utilized patellar sizing criteria to match the donor and recipient is radiographic tibial width. Our hypothesis is that specific patella anatomic factors will better predict surface topography matching. To our knowledge, no prior study has investigated the topography of the patella and what intrinsic factors of the graft and the recipient affect matching of the chondral and osseous layers between the graft and defect. Methods: Computed tomography (CT) images of the specimens were acquired and three-dimensional (3D) CT models of the patella were then created and exported into point-cloud models using a 3D reconstruction software program. Circular articular cartilage and subchondral bone defect models were created in each point-cloud model of the recipient patella with a diameter of 18 mm and 22.5 mm at 3 locations: the medial, central, and lateral portions of the patellar surface. Circular articular cartilage and subchondral bone graft models were created on all possible locations on the articular cartilage surface models of the donor patellae (Figure 1). The graft models were virtually placed on the surface of the defect model. Orientation of the graft model was adjusted so that its axis matched that of the defect site. Least distances between the graft and the defect articular surface models were calculated and were defined as the shortest distance from the point in question to the corresponding point in space. A mean value of the least distances was calculated for each position of the graft model. The mean least distance of subchondral bone surface in each point was calculated simultaneously. The graft model was then rotated 360° around the axis perpendicular to the articular cartilage surface in 1° increments, and the least distance of articular cartilage surface and the resulting least distance of subchondral bone surface were calculated at each rotating angle. This procedure was repeated for all points in the articular surface model of the donor patella. Step-off was then calculated as the least mean square difference between the defect and graft along the periphery. Stepwise linear regression was used for each defect location to analyze which variables predict degree of mismatch in millimeters. Results: A total of 16 patella were utilized in analysis. Comparison of cartilage least mean square distances between locations demonstrated that the lateral location had significantly less surface incongruity compared to the other two locations (vs medial: p = .0038, vs central: p = .0046). In addition, significant differences in subchondral bone distances were observed between the locations (lateral vs medial: p = .0007, lateral vs central: p < .0001, medial vs central: p < .0001) (Table 1). The associations of six anatomic and morphologic variables with cartilage mismatch, bone mismatch, and step-off for 18 mm and 22.5 mm defects are presented in Tables 2 and Table 3. All variables were analyzed as the difference in value between the recipient and donor. For both lesion sizes, cartilage step-off was the most susceptible to variable differences. Compared to the 18 mm defect group, the 22.5 mm defects were more affected (higher coefficients) by the same differences in variables. Differences in tibial width were associated mismatch for central lesions (eg. 22.5mm defect coefficient: -0.026, p < .001), while cartilage width was associated with mismatch for lateral lesions. (eg. 22.5 mm defect coefficient: -0.034, p < .023). Conclusions: Multiple clinically relevant factors were found to affect graft and defect chondral mismatch and to a lesser extent osseous mismatch. For all three locations at both defect sizes, step-off was the most susceptible to differences in patellar morphology between the donor and recipient. In addition, differences in tibial width, a commonly used metric for patellar graft matching, did not significantly predict chondral mismatch for lateral and medial sized lesions. These findings should be considered when selecting and preparing the graft in a patella osteochondral allograft procedure.

scholarly journals Factors contributing to graft matching in a patellar osteochondral allograft selection model

2020 ◽  
Vol 8 (7_suppl6) ◽  
pp. 2325967120S0045
Author(s):  
Hailey Huddleston ◽  
Adam Yanke ◽  
Nozomu Inoue
Keyword(s):  
Articular Cartilage ◽  
Subchondral Bone ◽  
Osteochondral Allograft ◽  
Surface Model ◽  
Multivariate Linear Regression Analysis ◽  
Bone Surface ◽  
Cartilage Surface ◽  
Bone Width ◽  
Articular Cartilage Surface ◽  
Allograft Selection

Objectives: When performing a patellar osteochondral allograft, the patellar allograft is harvested from a similar anatomic location as the defect. This approach assumes that graft will have similar topography to the patellar defect. However, to our knowledge, no prior study has investigated the topography of the patella and what intrinsic factors of the graft and the recipient affect mismatch of the chondral and osseous layers between the graft and defect. Methods: Three-dimensional (3D) computed tomography (CT) models of the patella were created and exported into point-cloud models using a 3D reconstruction program (Mimics, Materialise Inc., Leuven, Belgium). Circular articular cartilage and subchondral bone defect models were created in each model of the recipient patella (diameter=18mm) at 3 locations: medial, distal, and lateral. Articular cartilage and subchondral bone graft models were created on all possible locations on the articular cartilage surface models of the donor patellae. 3D surface topographies of the articular cartilage surface and resulting subchondral bone surfaces were compared between graft and defect models. The graft models were virtually placed on the surface of the defect model. Least distances, defined as the shortest distance from the point in question to the corresponding point in space, where a perfect congruent match would equal a least distance of 0.00mm for given data points on the simulated articular cartilage surface, were calculated. A mean value of the least distances was calculated for each position of the graft model and for the subchondral bone surface, simultaneously. The graft model was then rotated 360° around the axis perpendicular to the articular cartilage surface in 1° increments, and the least distance of articular cartilage surface and least distance of subchondral bone surface were calculated at each rotating angle. This procedure was repeated for all points in the articular surface model of the donor patella. The 3D model creation and geometry matching were performed using a custom-written program coded by in Microsoft Visual C++ with Microsoft Foundation Class programming environment (Microsoft Corp., Redmond, WA). Multivariate linear regression analysis was conducted in SPSS (v26, IBM, Armonk, NY). Results: Chondral and osseous mismatch between the graft and defect were analyzed. ANOVA analysis on the multivariate linear regressions found significant predictors of cartilage mismatch for medial (p=0.002), lateral (p=0.022), and central (p=0.001) defects when testing 5 variables. However, no predicting variables were identified for osseous mismatch for medial (p=0.099), lateral (p=0.703), and central (p=0.641) defects. Differences in tibia width (p=0.005), bone width (p=0.004), and medial cartilage length (p=0.003) were predictive of mismatch in medial defects. When evaluating lateral defects, no variables were found to significantly effect mismatch, However, in this lateral defect group, the collinearity assumption of the regression was violated, as the VIF for bone width and lateral length were over 10. For the central group, difference in bone width (p=0.037), difference in percent of patella that was medial facet (p=0.001), and difference in tibial width (p=0.006) were predictive of mismatch. Conclusions: Differences between graft and recipient tibia width, bone width, and size of the medial or lateral facet are significant predictors of mismatch in patella allograft selection.

scholarly journals The Effect of Patellar Surface Morphology On Subchondral Bone Alignment When Matching Patellar Osteochondral Allografts (206)

2021 ◽  
Vol 9 (10_suppl5) ◽  
pp. 2325967121S0031
Author(s):  
Mithun Neral ◽  
Karan Patel ◽  
Michael Getty ◽  
Nabeel Salka ◽  
John Grant
Keyword(s):  
Surface Morphology ◽  
Subchondral Bone ◽  
Osteochondral Allograft ◽  
Force Distribution ◽  
Bone Surface ◽  
Cartilage Surface ◽  
Significant Difference ◽  
Surface Deviation ◽  
Osteochondral Allografts

Objectives: Recent research has shown that implanting a patellar osteochondral allograft with a non-matched surface morphology (i.e., Wiberg classification) does not create increased chondral surface deviation or circumferential step-off in the donor plug compared to the native patella. While much of the research on patellar osteochondral allografts has been focused on chondral surface matching, little has been done to determine if the subchondral bone alignment at the donor:native interface plays a role in graft healing, local force distribution, and long term success of the allograft transplant. Previous work in our lab demonstrated that even when the patellar cartilage surface was well matched, notable differences in subchondral bone alignment were observed. The purpose of this study was therefore to use surface contour mapping of subchondral bone to determine if differences in Wiberg classification play a role in the ability of donor patellar osteochondral allograft subchondral bone to align with the native patellar subchondral bone when treating osteochondral defects of the patellar apex. The hypothesis was that patellar surface morphology would have an effect on subchondral bone surface height deviation and circumferential step-off when performing osteochondral allograft transplants of the patellar apex. Methods: Sixty fresh frozen human patellae were acquired from a national donor procurement company. Twenty (10 Wiberg I and 10 Wiberg II/III) patellae were designated as the recipient and then nano-CT scanned. Each recipient was size-matched (within ±2mm tibial width) to both a Wiberg I and a Wiberg II/III patellar donor. A 16mm circular osteochondral “defect” centered on the central ridge of the patella was then created in the recipient patella. A randomly-ordered donor Wiberg I or Wiberg II/III plug was harvested from a homologous location and transplanted into the recipient. The recipient was then nano-CT scanner, digitally reconstructed, and superimposed on the initial nano-CT scan of the native recipient patella. After careful atraumatic removal of the first donor plug, the process was repeated using the other allograft plug. MATLAB was used to determine the root mean square (RMS) surface height deviation between the native and donor subchondral bone surfaces. Dragonfly 3D imaging software was used to measure the RMS subchondral bone step-off height at 3° increments around the circumference of the graft. Surface height deviation and circumferential step-off height were analyzed for the whole surface and by quadrant to determine if there were local differences. ANOVA was used to compare surface deviation and step-off heights between matched and unmatched grafts. Sidak’s multiple comparison test was used to complete sub-analysis between patellar graft quadrants. Comparisons were made between matched and unmatched grafts in terms of the RMS surface height deviation and step-off, as well as in the percentage of measurements that were more than 0.5mm, 1mm, and 2mm proud or sunken relative to the native surface. Results: There were no significant differences in RMS subchondral bone surface height deviation between matched and unmatched Wiberg plugs as a whole or by quadrant (RMS range = 0.69 to 0.97mm, p = 0.45 – 1.0). There was a significant difference in RMS circumferential step-off height between matched (1.14 ± 0.52mm) and unmatched (1.38 ± 0.49mm) Wiberg plugs ( p=0.015). The majority of these increased step-off measurements occurred in the lateral quadrant with lateral quadrant RMS step-off of 0.89 ± 0.43mm in matched grafts and 1.60 ± 0.78mm in unmatched grafts ( p=0.007). There was also a significant difference in the percent of step-off measurements greater than 2mm sunken in the lateral quadrant between matched and unmatched grafts (5.17 ± 20.87% matched, 24.5 ± 36.39% unmatched, p=0.028). There were no significant differences between matched and unmatched grafts for any other comparison using 0.5, 1, or 2mm cut-offs for circumferential step-off or surface height deviation. Combining all allografts, the respective proportion of surface deviation and circumferential step-off height measurements that were above the stated thresholds were as follows: 31% and 34% for a 0.5mm threshold, 15% and 21% for a 1mm threshold, and 2% and 8% for a 2mm threshold. Conclusions: While unmatched Wiberg patella osteochondral allograft implantation did not result in significantly different subchondral bone surface height deviations, there were significant differences in circumferential subchondral bone step-off heights. The majority of step-off height differences between Wiberg matched and unmatched osteochondral allografts occurred in the lateral quadrant. In comparison to previous data evaluating differences in the cartilage surface match in these patellar OCA transplants, the deviations and step-off heights in the subchondral bone identified in the current study were approximately 0.5mm greater than the differences in the cartilage surface. These findings therefore suggest there is greater variability in the alignment of the subchondral bone in these patellar osteochondral allografts than there is in the cartilage surface. Further investigation using finite element analysis modeling will help determine the implications of subchondral bone surface deviation and circumferential step-off on local cartilage:bone compression and shear force distribution. These studies may shed light on the mechanisms of failure in patellar osteochondral transplants and may help to better understand the contribution of subchondral bone alignment in OCA healing and long-term outcome.

Lateral Center-Edge Angle Is Not Predictive of Acetabular Articular Cartilage Surface Area: Anatomic Variation of the Lunate Fossa

2020 ◽  
Vol 48 (8) ◽  
pp. 1967-1973 ◽  
Author(s):  
Thai Q. Trinh ◽  
Michael Leunig ◽  
Christopher M. Larson ◽  
John Clohisy ◽  
Jeff Nepple ◽  
...  
Keyword(s):  
Articular Cartilage ◽  
Surface Area ◽  
Articular Surface ◽  
Cartilage Surface ◽  
Center Edge ◽  
Articular Cartilage Surface ◽  
Significant Difference ◽  
Lateral Center Edge Angle ◽  
Lunate Fossa ◽  
Center Edge Angle

Background: Surgical treatment of symptomatic femoroacetabular impingement (FAI) and dysplasia requires careful characterization of acetabular morphology. The lateral center-edge angle (LCEA) is often used to assess lateral acetabular anatomy. Previous work has questioned the LCEA as a surrogate for acetabular contact/articular cartilage surface area because of the variable morphology of the lunate fossa. Hypothesis: We hypothesized that weightbearing articular cartilage of the acetabulum would poorly correlate with LCEA secondary to significant variation in the size of the lunate fossa. Study Design: Cohort study (Diagnosis); Level of evidence, 3. Methods: Patients with 3D CT imaging undergoing either hip arthroscopy or periacetabular osteotomy for FAI or symptomatic hip instability were retrospectively identified. The LCEA and femoral head diameter were measured on an anteroposterior pelvis radiograph. Patients were grouped according to their lateral acetabular coverage as undercoverage (LCEA, <25°), normal coverage (LCEA, 25°-40°), or overcoverage (LCEA, >40°). Patients were randomly identified until each group contained 20 patients. The articular surface area was measured from preoperative 3D CT data. Linear regression analysis was performed to examine the relationship between articular surface area and LCEA. Continuous and categorical data were analyzed utilizing analysis of variance and chi-square analysis. Statistical significance was set at P < .05. Results: No difference in age ( P = .52), body mass index (BMI) ( P = .75), or femoral head diameter ( P = .66) was noted between groups. A significant difference in articular surface area was observed between patients with undercoverage and those with overcoverage (20.4 cm2 vs 24.5 cm2; P = .01). No significant difference was identified between the undercoverage and normal groups (20.4 cm2 vs 23.3 cm2; P = .09) or the normal and overcoverage groups (23.3 cm2 vs 24.5 cm2; P = .63). A moderate positive correlation was observed between LCEA and articular surface area across all patients ( r = 0.38; P = .002) but not when patients with undercoverage were excluded ( r = 0.02; P = .88). Significant variation in surface area was observed within each group such that no patient in any group was outside of 2 SDs of the means of the other groups. When patients were categorized into quartiles established by the articular surface area for the entire population, 40% of patients with overcoverage were observed in the first or second quartile (lower area). Conclusion: Lateral acetabular undercoverage based on the LCEA (<25°) correlates with decreased acetabular surface area. Normal or increased acetabular coverage (LCEA, >25°), however, is not predictive of increased, normal, or decreased acetabular surface area.

Overlapping Allografts Provide Superior and More Reliable Surface Topography Matching Than Oblong Allografts: A Computer-Simulated Model Study

2021 ◽  
pp. 036354652110030
Author(s):  
Hailey P. Huddleston ◽  
Atsushi Urita ◽  
William M. Cregar ◽  
Theodore M. Wolfson ◽  
Brian J. Cole ◽  
...  
Keyword(s):  
Articular Cartilage ◽  
Surface Topography ◽  
Osteochondral Allograft ◽  
Cartilage Defects ◽  
Radius Of Curvature ◽  
Cartilage Surface ◽  
3 Dimensional ◽  
Cloud Models ◽  
And Cartilage ◽  
Osteochondral Allografts

Background: Osteochondral allograft transplantation is 1 treatment option for focal articular cartilage defects of the knee. Large irregular defects, which can be treated using an oblong allograft or multiple overlapping allografts, increase the procedure’s technical complexity and may provide suboptimal cartilage and subchondral surface matching between donor grafts and recipient sites. Purpose: To quantify and compare cartilage and subchondral surface topography mismatch and cartilage step-off for oblong and overlapping allografts using a 3-dimensional simulation model. Study Design: Controlled laboratory study. Methods: Human cadaveric medial femoral hemicondyles (n = 12) underwent computed tomography and were segmented into cartilage and bone components using 3-dimensional reconstruction and modeling software. Segments were then exported into point-cloud models. Modeled defect sizes of 17 × 30 mm were created on each recipient hemicondyle. There were 2 types of donor allografts from each condyle utilized: overlapping and oblong. Grafts were virtually harvested and implanted to optimally align with the defect to provide minimal cartilage surface topography mismatch. Least mean squares distances were used to measure cartilage and subchondral surface topography mismatch and cartilage step-off. Results: Cartilage and subchondral topography mismatch for the overlapping allograft group was 0.27 ± 0.02 mm and 0.80 ± 0.19 mm, respectively. In comparison, the oblong allograft group had significantly increased cartilage (0.62 ± 0.43 mm; P < .001) and subchondral (1.49 ± 1.10 mm; P < .001) mismatch. Cartilage step-off was also found to be significantly increased in the oblong group compared with the overlapping group ( P < .001). In addition, overlapping allografts more reliably provided a significantly higher percentage of clinically acceptable (0.5- and 1-mm thresholds) cartilage surface topography matching (overlapping: 100% for both 0.5 and 1 mm; oblong: 90% for 1 mm and 56% for 0.5 mm; P < .001) and cartilage step-off (overlapping: 100% for both 0.5 and 1 mm; oblong: 86% for 1 mm and 12% for 0.5 mm; P < .001). Conclusion: This computer simulation study demonstrated improved topography matching and decreased cartilage step-off with overlapping osteochondral allografts compared with oblong osteochondral allografts when using grafts from donors that were not matched to the recipient condyle by size or radius of curvature. These findings suggest that overlapping allografts may be superior in treating large, irregular osteochondral defects involving the femoral condyles with regard to technique. Clinical Relevance: This study suggests that overlapping allografts may provide superior articular cartilage surface topography matching compared with oblong allografts and do so in a more reliable fashion. Surgeons may consider overlapping allografts over oblong allografts because of the increased ease of topography matching during placement.

A Fibril Reinforced Poroelastic Model of Articular Cartilage Including Depth Dependent Material Properties

1999 ◽  
Author(s):  
L. P. Li ◽  
M. D. Buschmann ◽  
A. Shirazi-Adl
Keyword(s):  
Articular Cartilage ◽  
Regional Differences ◽  
Articular Surface ◽  
Collagen Fibrils ◽  
Superficial Zone ◽  
Cartilage Surface ◽  
Poroelastic Model ◽  
Oriented Parallel ◽  
Strain Dependent ◽  
Very High

Abstract Articular cartilage is a highly nonhomogeneous, anisotropic and multiphase biomaterial consisting of mainly collagen fibrils, proteoglycans and water. Noncalcified cartilage is morphologically divided into three zones along the depth, i.e. superficial, transitional and radial zones. The thickness, density and alignment of collagen fibrils vary from the superficial zone, where fibrils are oriented parallel to the articular surface, to the radial zone where fibrils are perpendicular to the boundary between bone, and cartilage. The concentration of proteoglycans increases with the depth from the cartilage surface. These regional differences have significant implications to the mechanical function of joints, which is to be explored theoretically in the present work by considering inhomogeneity along the cartilage depth. A nonlinear fibril reinforced poroelastic model is employed as per Li et al. (1999) in which the collagen fibrils were modeled as a distinct constituent whose tensile stiffness was taken to be very high and be strain dependent but whose compressive stiffness was neglected.

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