Effect of positioning error on the Hilgenreiner epiphyseal angle and the head-shaft angle compared to the femoral neck-shaft angle in children with cerebral palsy.

Children with cerebral palsy (CP) often have changes in proximal femoral geometry. Neck-shaft angle (NSA), Hilgenreiner epiphyseal angle (HEA) and head-shaft angle (HSA) are used to measure these changes. The impact of femoral rotation on HEA/HSA and of ab/adduction on HEA/HSA/NSA is not well known. This study aimed to determine and compare the effect of rotation, ab/adduction and flexion/extension on HEA/HSA/NSA. Radiographic measurements from 384 patients with Gross Motor Function Classification System (GMFCS) levels I-V were utilized. NSA/HSA for affected hips were used with femoral anteversion averages to create three-dimensional models of 694 hips in children with CP. Each hip was rotated, ab/adducted and flexed/extended to simulate malpositioning. HEA/HSA/NSA of each model were measured in each joint position, and differences from correct positioning were determined. Mean HEA error at 20° of internal/external rotations were -0.60°/3.17°, respectively, with the NSA error of -6.56°/9.94° and the HSA error of -3.69°/1.21°. Each degree of ab/adduction added 1° of the HEA error, with no NSA/HSA error. NSA was most sensitive to flexion. Error for all measures increased with increasing GMFCS level. HEA/HSA were minimally impacted by rotation. NSA error was much higher than HEA/HSA in internal rotation and flexion whereas HEA was sensitive to changes in ab/adduction. Given abduction is more easily detectable on imaging than rotation, HEA may be less affected by positioning errors that are common with children with CP than NSA. HSA was least affected by position changes. HEA/HSA could be robust, complementary measures of hip deformities in children with CP.

T1ρ and T2 MRI show hip cartilage damage in adolescents with healed Legg-Calvé-Perthes disease.

Legg-Calvé-Perthes disease (LCPD) is a juvenile hip disorder associated with residual femoral head deformity, cartilage degeneration and a high risk of early onset hip osteoarthritis. Assessing management of LCPD in the healed phase requires an understanding of when and where hip cartilage damage happens. While it has been shown that cartilage is degenerated in healed LCPD hips in adults, it is not clear when this degeneration begins. Our research question was: Are the MR markers of cartilage degeneration T1ρ and T2 increased in healed LCPD hips in adolescents? Twelve adolescents [10-17 years old (mean 14); 3 female 9 male] with healed LCPD (Stulberg 2-5; 8 unilateral and 4 bilateral) and 15 age- and sex-matched controls were imaged in a 3T MRI using a T1ρ and a T2 sequence. We applied a mixed-effects model adjusted for age and nested by subject to determine the effect of Stulberg grade on overall and regional mean T1ρ and T2 values. T1ρ was significantly higher overall and in the medial region of Stulberg ≥3 hips, and in the medial region of Stulberg 2 hips than in the control group. T2 was significantly higher in the medial region of Stulberg ≥3 hips than in the control group. Our results suggest that cartilage damage in LCPD has begun by adolescence and that T1ρ can detect early changes in cartilage associated with LCPD.

Relationships Between Severity of Deformity and Impingement in Slipped Capital Femoral Epiphysis.

BACKGROUND: In situ pinning, a low-risk treatment for slipped capital femoral epiphysis (SCFE), leaves the slipped femoral head in place and may reduce range of motion (ROM) and cause impingement. It is unclear when a more complex surgery should be considered, because the relationships between severity, slip stability, remodeling, impingement, and ROM are unknown. RESEARCH QUESTIONS: (1) Do more severe acute SCFE deformities (no bony remodeling) result in a greater loss of flexion ROM?(2) Does the presence or location of impingement on the pelvis vary with severity of acute SCFE deformity? METHODS: We developed a 3D geometric model of acute SCFE deformity from 1 computed tomography scan of a normal adolescent hip. Ethics board approval was obtained from our institution. Bone models were created from the segmented pelvis, epiphysis, and subphyseal femur.In total, 3721 SCFE deformities were simulated by combining posterior and inferior slips in the axial and coronal planes, respectively. Southwick angles were estimated from a frog-leg lateral projection. Deformities were divided into mild (0 to 30 degrees), moderate (30 to 60 degrees), and severe (≥60 degrees) Southwick groups. Each joint was flexed in combination with internal/external rotation until contact occurred. A total of 121 ROM trials, with different degrees of internal/external rotation (0 to 90 degrees at 1.5-degree steps) were performed for each deformity. RESULTS: In total, 3355 simulated SCFE deformities (363 could not be rotated out of impingement) were analyzed.Increasing slip severity reduced flexion ROM across the range of internal/external rotation. Contact occurred for most mild deformities, and for all moderate and severe deformities in at least 1 ROM trial. Impingement was observed mainly on the anterosuperior aspect of the acetabulum. CONCLUSIONS: Increasing slip severity in acute SCFE reduced flexion and increased incidence of impingement, primarily occurring on the anterosuperior aspect of the acetabulum. The impingement patterns observed are consistent with damaged cartilage locations seen in clinical literature. CLINICAL RELEVANCE: In this experimental model, moderate and severe acute slips in SCFE lead to reduced ROM and impingement with the acetabulum. This suggests that in situ pinning may result in impingement of moderate and severe acute SCFE slips.

Multi-echo GRE imaging of knee cartilage.

PURPOSE: To visualize healthy and abnormal articular cartilage, we investigated the potential of using the 3D multi-echo gradient echo (GRE) signal's magnitude and frequency and maps of T2* relaxation. MATERIALS AND METHODS: After optimizing imaging parameters in five healthy volunteers, 3D multi-echo GRE magnetic resonance (MR) images were acquired at 3T in four patients with chondral damage prior to their arthroscopic surgery. Average magnitude and frequency information was extracted from the GRE images, and T2* maps were generated. Cartilage abnormalities were confirmed after arthroscopy and were graded using the Outerbridge classification scheme. Regions of interest were identified on average magnitude GRE images and compared to arthroscopy. RESULTS: All four patients presented with regions of Outerbridge Grade I and II cartilage damage on arthroscopy. One patient had Grade III changes. Grade I, II, and III changes were detectable on average magnitude and T2* maps, while Grade II and higher changes were also observable on MR frequency maps. For average magnitude images of healthy volunteers, the signal-to-noise ratio of the magnitude image averaged over three echoes was 4.26 ± 0.32, 12.26 ± 1.09, 14.31 ± 1.93, and 13.36 ± 1.13 in bone, femoral, tibial, and patellar cartilage, respectively. CONCLUSION: This proof-of-principle study demonstrates the feasibility of using different imaging contrasts from the 3D multi-echo GRE scan to visualize abnormalities of the articular cartilage. © 2016 International Society for Magnetic Resonance in Medicine Level of Evidence: 1 J. MAGN. RESON. IMAGING 2017;45:1502-1513.

Cartilage health in high tibial osteotomy using dGEMRIC: Relationships with joint kinematics.

PURPOSE: The aims of this study are to determine how opening-wedge high tibial osteotomy (HTO) affects cartilage health in the tibiofemoral (TF) joint and patella, and to explore relationships between TF and patellofemoral (PF) joint kinematics and cartilage health in HTO. METHODS: 14 knees (13 subjects) with medial TF osteoarthritis (OA) were examined before HTO and 6 and 12 months after HTO using delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) to evaluate cartilage health at the TF joint and patella. They were also examined using a validated 3D MR knee kinematics measurement to obtain 11 rotations and translations at both TF and PF joints. RESULTS: No statistically significant differences in overall TF or patellar dGEMRIC score were found at 6 or 12 months after HTO. However three subjects had large decreases (mean 105 ms) in TF dGEMRIC at 6 months that recovered at 12 months. Kinematics for these subjects were compared to subjects who did not have decreases in TF dGEMRIC at 6 months (n=5). Differences were observed between groups with HTO in anterior and proximal tibial translation (mean differences 3.05 mm and 1.35 mm), and patellar flexion (mean difference 3.65°). These changes were consistent between 6 and 12 months, despite recovery of TF dGEMRIC values. CONCLUSIONS: We did not find significant differences in TF or patellar dGEMRIC before and after HTO with all subjects, however there were differences in kinematics between subjects who had a decrease in TF dGEMRIC at 6 months and those who did not. This suggests a link between joint kinematics and cartilage health in HTO. CLINICAL RELEVANCE: The effect of opening-wedge high tibial osteotomy on cartilage GAG concentration may be linked to specific changes in knee kinematics following surgery.