Abstract: Acetabular version influences joint mechanics and the risk of impingement. Cross-sectional studies have reported an increase in acetabular version during adolescence; however, to our knowledge no longitudinal study has assessed version or how the change in version occurs. Knowing this would be important because characterizing the normal developmental process of the acetabulum would allow for easier recognition of a morphologic abnormality. Questions/purposes To determine (1) how acetabular version changes during adolescence, (2) calculate how acetabular coverage of the femoral head changed during this period, and (3) to identify whether demographic factors or hip ROM are associated with acetabular development. Methods This retrospective analysis of data from a longitudinal study included 17 volunteers (34 hips) with a mean (± SD) age of 11 ± 2 years; seven were male and 10 were female. The participants underwent a clinical examination of BMI and ROM and MRIs of both hips at recruitment and at follow-up (6 ± 2 years). MR images were assessed to determine maturation of the triradiate cartilage complex, acetabular version, and degree of the anterior, posterior, and superior acetabular sector angles (reflecting degree of femoral head coverage provided by the acetabulum anteriorly, posteriorly and superiorly respectively). An orthopaedic fellow (GG) and a senior orthopaedic resident (PJ) performed all readings in consensus; 20 scans were re-analyzed for intraobserver reliability. Thereafter, a musculoskeletal radiologist (KR) repeated measurements in 10 scans to test interobserver reliability. The intra- and interobserver interclass correlation coefficients for absolute agreement were 0.85 (95% CI 0.76 to 0.91; p 〈 0.001) and 0.77 (95% CI 0.70 to 0.84), respectively. All volunteers underwent a clinical examination by a senior orthopaedic resident (PJ) to assess their range of internal rotation (in 90° of flexion) in the supine and prone positions using a goniometer. We tested investigated whether the change in anteversion and sector angles differed between genders and whether the changes were correlated with BMI or ROM using Pearson’s coefficient. The triradiate cartilage complex was open (Grade I) at baseline and closed (Grade III) at follow-up in all hips. Results The acetabular anteversion increased, moving caudally further away from the roof at both timepoints. The mean (range) anteversion angle increased from 7° ± 4° (0 to 18) at baseline to 12° ± 4° (5 to 22) at the follow-up examination (p 〈 0.001). The mean (range) anterior sector angle decreased from 72° ± 8° (57 to 87) at baseline to 65° ± 8° (50 to 81) at the final follow-up (p = 0.002). The mean (range) posterior (98° ± 5° [86 to 111] versus 97° ± 5° [89 to 109] ; p = 0.8) and superior (121° ± 4° [114 to 129] to 124° ± 5° [111 to 134] ; p = 0.07) sector angles remained unchanged. The change in the anterior sector angle correlated with the change in version (rho = 0.5; p = 0.02). The change in version was not associated with any of the tested patient factors (BMI, ROM). Conclusions With skeletal maturity, acetabular version increases, especially rostrally. This increase is associated with, and is likely a result of, a reduced anterior acetabular sector angle (that is, less coverage anteriorly, while the degree of coverage posteriorly remained the same). Thus, in patients were the normal developmental process is disturbed, a rim-trim might be an appropriate surgical solution, since the degree of posterior coverage is sufficient and no reorientation osteotomy would be necessary. However, further study on patients with retroversion (of various degrees) is necessary to characterize these observations further. The changes in version were not associated with any of the tested patient factors; however, further study with greater power is needed. Level of Evidence Level II, prognostic study.

Abstract: The understanding of the underlying mechanisms leading to FAI continues to evolve; it is evident that both the femoral (cam, retroversion) and acetabular (pincer, retroversion) anatomy may contribute to its development. Several studies have demonstrated the development of cam morphology during the growing years of the skeleton and its association with increased activity during the adolescence years. However, considerably less is known about the development of the acetabulum and what changes occur during the adolescent years, which appear to be the key developmental stage. Retrospective cross-sectional studies derived from CT-data (hence missing cartilaginous portions of the growing skeleton) noted that acetabular version increased with skeletal maturity – the authors noted that the posterior rim increased however recognised that this may have to do with the inability to detect the cartilage posteriorly. A recent MRI-based study, with MRIs performed at the 1-year interval of various developmental stages, showed that the acetabular version increases around adolescence, but did not identify how this may occur. Furthermore, none of the above studies accounted for the individual demographic data, the individual’s physical activity, or the femoral-sided anatomy. The aims of this prospective longitudinal study were to determine how 1. Acetabular version and 2. Coverage to the femoral head the acetabulum provides change during the adolescent years. Furthermore, we aimed to determine whether patient factors (BMI, activity levels) or the femoral-sided anatomy contribute to any of the changes observed. METHODS: 19 volunteers (38 hips) were recruited. The mean age of the cohort was 10.5±1.3 years old and 10 patients were female (52%). The volunteers underwent clinical examination (BMI, range of movement assessment) and a MRI scan of both hips. All participants presented for further clinical examination of both hips and a second MRI scan at an interval of 6 ± 2 years. The mean age at follow-up was 16.6 ±1.3. At the follow-up visit, volunteers were also asked to fill in the HSS Pediatric Functional Activity Brief Scale (Pedi-FABS) questionnaire, which reflects the level of physical activity of each volunteer. Assessments of MRI included the status of the tri-radiate cartilage complex (TCC) (Oxford Classification I – III: open – closed), the acetabular anteversion angle at various levels in the axial plane [5 mm below the roof (top), at the middle of the femoral head (middle) and 3 equidistant slices in-between top and middle] . We measured three acetabular sector angles (anteriorly, posteriorly and superiorly) at the middle of the femoral head, reflecting degree of femoral head coverage by the acetabulum. Alpha angles anteriorly and antero-laterally were determined for each hip for each time-point. Outcome measures included how the anteversion changed at each of the five levels and the mean change overall. We also determined how the sector angles changed over time anteriorly, posteriorly and superiorly. Change in anteversion and sector angles were influenced by the BMI, range of movement measurements, the Pedi-FABS or the alpha angle measurements. RESULTS: At the baseline MRI, all hips had a Grade I (open) TCC; the TCC was Grade III (closed) by follow-up MRI in all of the hips. The acetabular anteversion increased moving, caudally, further away from the roof for both time-points (Figure 1). The mean anteversion increased from a mean of 7.4°±3.8 (initial) to 12.2°±4 (follow-up) (p 〈 0.001). The increase in anteversion was 4.7° (range: 0 – 9). The increase in version occurred along all slices, but was greater at the rostral ¼ of the acetabulum (slices 1 and 2); 8/38 the hips had retroversion of the rostral ¼ of the acetabulum at the initial scan, whilst none of the hips had retroversion at follow-up. Females had greater anteversion than males (13.2° Vs 10.6°, p=0.04), however the change that occurred between scans was the same (4.6° Vs 5.0°; p=0.9). The anterior sector angle reduced from 72°±8 to 65°±8 (p=0.002); the posterior sector angle remained unchanged (98°±5° Vs. 97°±5) (p=0.8), whilst the superior sector angle slightly increased from 121°±4 to 124°±5° (p=0.007). The change in the anterior sector angle correlated with the change in version (rho=0.5, p=0.02). The change in version did not correlate with BMI, ROM, Pedi-FABS score or the measured alpha angles of the hip (p=0.1 – 0.6). DISCUSSION: The native acetabulum orientation changes around adolescence, with the version significantly increasing. The version increases as a result of a reduction of the femoral head coverage anteriorly (rather than an increase in posterior femoral head coverage). Therefore, if the normal developmental change did not occur, the associated retroversion would be related to anterior wall over-coverage rather than posterior deficiency. We identified no patient factors (BMI, activity level, range of movement) or proximal femoral anatomical factors (alpha angles) that were associated with this change. The increase in acetabular version may be related with the reduction in femoral version that occurs over the same period and hence further study is necessary.

Abstract: This article reviews a body of work performed by the investigators over 9 years that has addressed the significance of cam morphology in the development of hip osteoarthritis (OA). Early hip joint degeneration is a common clinical presentation and preexisting abnormal joint morphology is a risk factor for its development. Interrogating Hill's criteria, we tested whether cam‐type femoroacetabular impingement leads to hip OA. Strength of associatio n was identified between cam morphology, reduced range‐of‐movement, hip pain, and cartilage degeneration. By studying a pediatric population, we were able to characterize the temporality between cam morphology (occurring 1st) and joint degeneration. Using in silico (finite element) and in vivo (imaging biomarkers) studies, we demonstrated the biological plausibility of how a cam deformity can lead to joint degeneration. Furthermore, we were able to show a biological gradient between degree of cam deformity and extent of articular damage. However, not all patients develop joint degeneration and we were able to characterize which factors contribute to this ( specificity ). Lastly, we were able to show that by removing the cam morphology, one could positively influence the degenerative process ( experiment ). The findings of this body of work show consistency and coherence with the literature. Furthermore, they illustrate how cam morphology can lead to early joint degeneration analogous to SCFE, dysplasia, and joint mal‐reduction post‐injury. The findings of this study open new avenues on the association between cam morphology and OA including recommendations for the study, screening, follow‐up, and assessment (patient‐specific) of individuals with cam morphology in order to prevent early joint degeneration. Statement of significance: By satisfying Hill's criteria , one can deduct that in some individuals, cam morphology is a cause of OA. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3125–3135, 2018.

Abstract: » There is increasing evidence in the literature regarding the important health impact of and risk factors for injury in youth sport. » Increasing pediatric and adolescent activity intensity, such as is seen in earlier single-sport focus and specialization, may be associated with morphological changes in the growing skeleton. » Chronic subacute injury to the developing physes in the active child can lead to stress on the growth plate and surrounding tissues that induces developmental morphological changes in the joint. » There is evidence to suggest that frequent participation in sports that place particular stress across the physes of the proximal humerus, the proximal femur, and the distal radius can be associated with an increased risk of inducing developmental and morphological changes that could lead to future joint dysfunction and premature degeneration. » Additional research is necessary to better define the pathoetiology of activity-mediated morphological changes, as well as to create and validate parameters for safe involvement in competitive physical activities.