The Prevalence of Cam Morphology: A Cross-Sectional Evaluation of 3,558 Cadaveric Femora

Alpha angle and anterior femoral neck offset identify different cohorts of cam morphology: an osteologic study

PURPOSE

The purpose of this study was to explore differences in cam morphology defined by alpha angle and anterior femoral neck offset, in the context of other anthropometric parameters in an osteologic collection to further elucidate whether each measurement tool is identifying the same underlying pathology.

METHODS

Anthropometric measurements of 992 cadaveric hips from the Hamann-Todd Osteological Collection were analyzed. Femurs with cam morphology were identified by AA >55° or AFNO <7mm. Anthropometric parameters stratified by cam morphology were assessed with Wilcoxon rank-sum and Pearson's chi-squared tests. Multivariate logistic regressions were performed on significant variables in univariate analysis to examine the predictive ability of anthropometric variables to cam morphology.

RESULTS

Cam morphology was identified in 242 hips via AA, 344 hips via AFNO, and 123 hips via both measures. Multivariate logarithmic regression analysis demonstrated that sex negatively predicted AA (females with less pathology, β= -0.14, p= 0.04), race negatively predicted AA (blacks with less pathology, β= -0.21, p<0.01), and proximal femoral osteoarthritis was positively associated with AA (β= 0.16, p= 0.02), while none of these were associated with AFNO. On the other hand, right side specimens were associated with AA (β= 0.15, p= 0.02) and AFNO (β= 0.25, p= <0.01), whereas combined version was unassociated with both measures.

CONCLUSION

In conclusion, cam morphology was identified in a modest percentage of osteological specimens by both AA and AFNO in our study. Further, associations of multiple demographic, anthropometric and anatomical parameters to alpha angle and anterior femoral neck offset suggest they may identify different subsets of cam morphology.

Predicting Outcomes in Hip Arthroscopy for Femoroacetabular Impingement Syndrome

PURPOSE OF REVIEW

Arthroscopic treatment of femoroacetabular impingement syndrome (FAIS) continues to rise in incidence, and thus there is an increased focus on factors that predict patient outcomes. The factors that impact the outcomes of arthroscopic FAIS treatment are complex. The purpose of this review is to outline the current literature concerning predictors of patient outcomes for arthroscopic treatment of FAIS.

RECENT FINDINGS

Multiple studies have shown that various patient demographics, joint parameters, and surgical techniques are all correlated with postoperative outcomes after arthroscopic FAIS surgery, as measured by both validated patient-reported outcome (PRO) scores and rates of revision surgery including hip arthroplasty. To accurately predict patient outcomes for arthroscopic FAIS surgery, consideration should be directed toward preoperative patient-specific factors and intraoperative technical factors. The future of accurately selecting patient predictors for outcomes will only improve with increased data, improved techniques, and technological advancement.

The quest for optimal femoral torsion angle measurements: a comparative advanced 3D study defining the femoral neck axis

PURPOSE

There is high variability in femoral torsion, measured on two-dimensional (2D) computed tomography (CT) scans. The aim of this study was to find a reliable three-dimensional (3D) femoral torsion measurement method, assess the influence of CAM deformity on femoral torsion measurement, and to promote awareness for the used measurement method.

METHODS

3D models of 102 dry femur specimens were divided into a CAM and non-CAM group. Femoral torsion was measured by one 2D-CT method described by Murphy et al. (method 0) and five 3D methods. The 3D methods differed in strategies to define the femoral neck axis. Method 1 is based on an elliptical least-square fit at the middle of the femoral neck. Methods 2 and 3 defined the centre of mass of the entire femoral neck and of the most cylindrical part, respectively. Methods 4 and 5 were based on the intersection of the femoral neck with a 25% and 40% enlarged best fit sphere of the femoral head.

RESULTS

3D methods resulted in higher femoral torsion measures than the 2D method; the mean torsion for method 0 was 8.12° ± 7.30°, compared to 9.93° ± 8.24° (p < 0.001), 13.21° ± 8.60° (p < 0.001), 8.21° ± 7.64° (p = 1.00), 9.53° ± 7.87° (p < 0.001) and 10.46° ± 7.83° (p < 0.001) for methods 1 to 5 respectively. In the presence of a CAM, torsion measured with method 4 is consistently smaller than measured with method 5.

CONCLUSION

2D measurement might underestimate true femoral torsion and there is a difference up to 5°. There is a tendency for a higher mean torsion in hips with a CAM deformity. Methods 4 and 5 are the most robust techniques. However, method 4 might underestimate femoral torsion if a CAM deformity is present. Since method 5 is independent of a CAM deformity, it is the preferred technique to define expected values of torsion.

Results of Arthroscopic Treatment for Femoroacetabular Impingement

Background. Femoroacetabular impingement (FAI) is one of the most frequent causes of hip pain and limited hip mobility in young and middle-aged patients. It is a result of repeated injury of hip structures, that leads to degenerative changes in hip labrum, cartilage and subchondral bone and provokes progressive development of hip osteoarthritis. Aim of study to analyze own experience of treating patients with femoroacetabular impingement and identify factors affecting its outcomes. Methods. Retrospective, uncontrolled, single-center clinical study included 128 patients with FAI which had 150 surgeries on 149 joints in in the period from 2013 to 2021. All patients underwent physical examination and X-ray diagnostics, their FAI type was identified. The alpha angle of external part of femoral head in anterior-posterior position and in the modified Dunn 45 position, as well as Tonnis angle, lateral central-marginal angle in Ogata modification and the height of articular gap along the lateral (LS) and medial edges (MS) of sclerosed acetabulum part were calculated. The i-HOT-33 and HOS scales were used to assess preoperative status and postoperative results. Results. The average follow-up period was 3.9 years (SD 1.71; min 1.05 and max 8.16). The study included 55 (43.0%) women and 73 (57.0%) men which underwent 64 (42.7%) and 86 (57.3%) surgeries respectively. The most common types of FAI, according to our data, were mixed type (53% of joints) and сam type (27.5% of joints). Insufficient coverage of the femoral head by the acetabulum (borderline dysplasia) in combination with the сam deformity of the femoral head was observed in 18.1%. Pincer-type FAI was observed in 1.4% of joints. We obtained the worst results with a combination of сam deformity and borderline dysplasia in comparison with cam- and mix-type FAI according to the i-HOT-33 and HOS scales. Patients age, deep cartilage damage, irreparable labrum damage and height decrease of the lateral part of the articular gap determined negative effect on treatment results according to the i-HOT-33 and HOS scales. Conclusion. Hip arthroscopy showed good short- and midterm outcomes in patients with FAI. Pain syndrome is most often manifested in patients with pathology of hip soft tissue structures concomitant to FAI. The combination of сam deformity and insufficient femoral head coverage, deep cartilage damage and a height decrease of the articular gap are important predictors of poor treatment results.

High bone mass and cam morphology are independently related to hip osteoarthritis: findings from the High Bone Mass cohort

BACKGROUND

High bone mass (HBM, BMD Z-score ≥  + 3.2) and cam morphology (bulging of lateral femoral head) are associated with greater odds of prevalent radiographic hip osteoarthritis (rHOA). As cam morphology is itself a manifestation of increased bone deposition around the femoral head, it is conceivable that cam morphology may mediate the relationship between HBM and rHOA. We therefore aimed to determine if individuals with HBM have increased odds of prevalent cam morphology. In addition, we investigated whether the relationship between cam and prevalent and incident osteoarthritis was preserved in a HBM population.

METHODS

In the HBM study, a UK based cohort of adults with unexplained HBM and their relatives and spouses (controls), we determined the presence of cam morphology using semi-automatic methods of alpha angle derivation from pelvic radiographs. Associations between HBM status and presence of cam morphology, and between cam morphology and presence of rHOA (or its subphenotypes: osteophytes, joint space narrowing, cysts, and subchondral sclerosis) were determined using multivariable logistic regression, adjusting for age, sex, height, weight, and adolescent physical activity levels. The association between cam at baseline and incidence of rHOA after an average of 8 years was determined. Generalised estimating equations accounted for individual-level clustering.

RESULTS

The study included 352 individuals, of whom 235 (66.7%) were female and 234 (66.5%) had HBM. Included individuals contributed 694 hips, of which 143 had a cam deformity (20.6%). There was no evidence of an association between HBM and cam morphology (OR = 0.97 [95% CI: 0.63-1.51], p = 0.90) but a strong relationship was observed between cam morphology and rHOA (OR = 3.96 [2.63-5.98], p = 5.46 × 10-11) and rHOA subphenotypes joint space narrowing (OR = 3.70 [2.48-5.54], p = 1.76 × 10-10), subchondral sclerosis (OR = 3.28 [1.60-6.60], p = 9.57 × 10-4) and osteophytes (OR = 3.01 [1.87-4.87], p = 6.37 × 10-6). Cam morphology was not associated with incident osteoarthritis (OR = 0.76 [0.16-3.49], p = 0.72).

CONCLUSIONS

The relationship between cam morphology and rHOA seen in other studies is preserved in a HBM population. This study suggests that the risk of OA conferred by high BMD and by cam morphology are mediated via distinct pathways.

3D MRI of the Hip Joint: Technical Considerations, Advantages, Applications, and Current Perspectives

Magnetic resonance imaging (MRI) is a common choice among various imaging modalities for the evaluation of hip conditions. Conventional MRI with two-dimensional acquisitions requires a significant amount of time and is limited by partial-volume artifacts and suboptimal fluid-to-cartilage contrast. Recent hardware and software advances have resulted in development of novel isotropic three-dimensional (3D) single-acquisition protocols that cover the volume of the entire hip and can be reconstructed in arbitrary planes for submillimeter assessment of bony and labro-cartilaginous structures in their planes of orientation. This technique facilitates superior identification of small labral tears and other hip lesions with better correlations with arthroscopy. In this review, we discuss technical details related to 3D MRI of the hip, its advantages, and its role in commonly encountered painful conditions that can be evaluated with great precision using this technology. The entities described are femoroacetabular impingement with acetabular labral tears, acetabular dysplasia, avascular necrosis, regional tendinopathies and tendon tears, bursitis, and other conditions.

Less hip range of motion is associated with a greater alpha angle in people with longstanding hip and groin pain

PURPOSE

A higher alpha angle has been proposed to correlate with lower hip range of motion, but the association in people with longstanding hip and groin pain is currently unclear. The aims were to: (1) assess the association between range of motion and alpha angle in patients with longstanding hip and groin pain; (2) examine if a cut-off value in range of motion variables could identify patients with an alpha angle above or below 60°.

METHODS

Seventy-two participants were consecutively recruited from an orthopaedic department after referral for hip- and groin-related pain. Passive hip range of motion was measured in flexion, internal rotation with 90° hip flexion, internal rotation in neutral hip position, external rotation with 90° hip flexion, and abduction. The alpha angle was calculated from a frog-leg lateral radiograph. Linear regression examined the association between range of motion and alpha angle, and an ROC-curve analysis was performed to identify the sensitivity and specificity of range of motion cut-offs.

RESULTS

Lower range of motion in internal rotation in flexion, external rotation, and abduction were associated with higher alpha angle. Internal rotation of 27° or less displayed good sensitivity (81%) and specificity (85%) to detect an alpha angle above 60°, while a cut-off of 41° in external rotation and 27° in abduction showed a sensitivity of 72% and specificity of 50% and 60%, respectively.

CONCLUSION

Less internal rotation in flexion, external rotation, and abduction are associated with a greater alpha angle in a cohort of people with longstanding hip and groin pain. A cut-off of 27° in internal rotation has good sensitivity and specificity to identify people with an alpha angle above or below 60° and have the potential to be used in the clinical setting to identify patients that require further imaging, or that are unlikely to have cam morphology.

LEVEL OF EVIDENCE

II.