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Biomechanical factors in planning of periacetabular osteotomy.

Niknafs N, Murphy RJ, Armiger RS, Lepistö J, Armand M - Front Bioeng Biotechnol (2013)

Bottom Line: For each combination of thickness distribution and compressive properties, the optimal alignment of the acetabulum was found; the resultant geometric and biomechanical characterization of the hip were compared among the optimal alignments.The optimal alignment increased the lateral coverage of the femoral head and decreased the obliqueness of the acetabular roof in all patients.However, in all groups the biomechanically predicted optimal alignment resulted in decreased joint contact pressure and improved acetabular coverage.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Johns Hopkins University , Baltimore, MD , USA.

ABSTRACT

Objective: This study addresses the effects of cartilage thickness distribution and compressive properties in the context of optimal alignment planning for periacetabular osteotomy (PAO).

Background: The Biomechanical Guidance System (BGS) is a computer-assisted surgical suite assisting surgeon's in determining the most beneficial new alignment of a patient's acetabulum. The BGS uses biomechanical analysis of the hip to find this optimal alignment. Articular cartilage is an essential component of this analysis and its physical properties can affect contact pressure outcomes.

Methods: Patient-specific hip joint models created from CT scans of a cohort of 29 dysplastic subjects were tested with four different cartilage thickness profiles (one uniform and three non-uniform) and two sets of compressive characteristics. For each combination of thickness distribution and compressive properties, the optimal alignment of the acetabulum was found; the resultant geometric and biomechanical characterization of the hip were compared among the optimal alignments.

Results: There was an average decrease of 49.2 ± 22.27% in peak contact pressure from the preoperative to the optimal alignment over all patients. We observed an average increase of 19 ± 7.7° in center-edge angle and an average decrease of 19.5 ± 8.4° in acetabular index angle from the preoperative case to the optimized plan. The optimal alignment increased the lateral coverage of the femoral head and decreased the obliqueness of the acetabular roof in all patients. These anatomical observations were independent of the choice for either cartilage thickness profile, or compressive properties.

Conclusion: While patient-specific acetabular morphology is essential for surgeons in planning PAO, the predicted optimal alignment of the acetabulum was not significantly sensitive to the choice of cartilage thickness distribution over the acetabulum. However, in all groups the biomechanically predicted optimal alignment resulted in decreased joint contact pressure and improved acetabular coverage.

No MeSH data available.


Related in: MedlinePlus

Pressure profile of a sample acetabulum loaded by the standing force (medial view). In this subject, the non-linear DEA-predicted higher stress levels over the acetabulum.
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Figure 7: Pressure profile of a sample acetabulum loaded by the standing force (medial view). In this subject, the non-linear DEA-predicted higher stress levels over the acetabulum.

Mentions: In almost all patients, the value of maximum contact pressure exhibited a decrease from the original to the optimal alignment (Table 2); however, two patients exhibited a slight increase in the value of maximum pressure (less than 3%) when optimal alignment was found using non-linear DEA with the population-based dysplastic cartilage distribution. On average, the CT-based cartilage thickness profile resulted in the largest decrease in peak contact pressures (59 ± 16%), followed by uniform (52 ± 21%) and population-based cartilage models (47 ± 22% for the normal population and 39 ± 24% for the dysplastic population); i.e., CT-based cartilage models predicted alignments corresponding to the largest predicted benefit in alleviation of contact pressures. A sample pressure profile is illustrated in Figure 7 and a sample realignment is presented in Figure 8.


Biomechanical factors in planning of periacetabular osteotomy.

Niknafs N, Murphy RJ, Armiger RS, Lepistö J, Armand M - Front Bioeng Biotechnol (2013)

Pressure profile of a sample acetabulum loaded by the standing force (medial view). In this subject, the non-linear DEA-predicted higher stress levels over the acetabulum.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126379&req=5

Figure 7: Pressure profile of a sample acetabulum loaded by the standing force (medial view). In this subject, the non-linear DEA-predicted higher stress levels over the acetabulum.
Mentions: In almost all patients, the value of maximum contact pressure exhibited a decrease from the original to the optimal alignment (Table 2); however, two patients exhibited a slight increase in the value of maximum pressure (less than 3%) when optimal alignment was found using non-linear DEA with the population-based dysplastic cartilage distribution. On average, the CT-based cartilage thickness profile resulted in the largest decrease in peak contact pressures (59 ± 16%), followed by uniform (52 ± 21%) and population-based cartilage models (47 ± 22% for the normal population and 39 ± 24% for the dysplastic population); i.e., CT-based cartilage models predicted alignments corresponding to the largest predicted benefit in alleviation of contact pressures. A sample pressure profile is illustrated in Figure 7 and a sample realignment is presented in Figure 8.

Bottom Line: For each combination of thickness distribution and compressive properties, the optimal alignment of the acetabulum was found; the resultant geometric and biomechanical characterization of the hip were compared among the optimal alignments.The optimal alignment increased the lateral coverage of the femoral head and decreased the obliqueness of the acetabular roof in all patients.However, in all groups the biomechanically predicted optimal alignment resulted in decreased joint contact pressure and improved acetabular coverage.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Johns Hopkins University , Baltimore, MD , USA.

ABSTRACT

Objective: This study addresses the effects of cartilage thickness distribution and compressive properties in the context of optimal alignment planning for periacetabular osteotomy (PAO).

Background: The Biomechanical Guidance System (BGS) is a computer-assisted surgical suite assisting surgeon's in determining the most beneficial new alignment of a patient's acetabulum. The BGS uses biomechanical analysis of the hip to find this optimal alignment. Articular cartilage is an essential component of this analysis and its physical properties can affect contact pressure outcomes.

Methods: Patient-specific hip joint models created from CT scans of a cohort of 29 dysplastic subjects were tested with four different cartilage thickness profiles (one uniform and three non-uniform) and two sets of compressive characteristics. For each combination of thickness distribution and compressive properties, the optimal alignment of the acetabulum was found; the resultant geometric and biomechanical characterization of the hip were compared among the optimal alignments.

Results: There was an average decrease of 49.2 ± 22.27% in peak contact pressure from the preoperative to the optimal alignment over all patients. We observed an average increase of 19 ± 7.7° in center-edge angle and an average decrease of 19.5 ± 8.4° in acetabular index angle from the preoperative case to the optimized plan. The optimal alignment increased the lateral coverage of the femoral head and decreased the obliqueness of the acetabular roof in all patients. These anatomical observations were independent of the choice for either cartilage thickness profile, or compressive properties.

Conclusion: While patient-specific acetabular morphology is essential for surgeons in planning PAO, the predicted optimal alignment of the acetabulum was not significantly sensitive to the choice of cartilage thickness distribution over the acetabulum. However, in all groups the biomechanically predicted optimal alignment resulted in decreased joint contact pressure and improved acetabular coverage.

No MeSH data available.


Related in: MedlinePlus