Prevalence of Cam Morphology in Females with Femoroacetabular Impingement

Femurs in patients with hip dysplasia have fundamental shape differences compared with cam femoroacetabular impingement

Femoral deformities are common in developmental dysplasia of the hip (DDH), but decisions about how to treat them are not standardized. Of interest are deformities that may be akin to cam femoroacetabular impingement (FAI). We used three-dimensional and two-dimensional measures to clarify the similarities and differences in proximal femur shape variation among female patients with DDH (n = 68) or cam FAI (n = 60). Three-dimensional measures included femoral head asphericity, as well as shape variation using statistical shape modeling and principal component analysis (PCA). Two-dimensional measures included the α-angle, head-neck offset (HNO) and the neck-shaft angle (NSA). Significant shape variations were captured in the first five PCA modes, with the greatest shared variation between groups being the length from the lesser trochanter to the femoral head and greater trochanter height. Variations unique to DDH were irregularities at different areas of the femoral head, but not at the lateral femoral head-neck junction where variation was strong in FAI. The FAI group also had unique variations in greater trochanter shape. DDH femoral heads were less spherical, as indicated by larger sphere-fitting errors (P < 0.001). Radiographically, the DDH group had significantly smaller α-angles (P < 0.001), larger head-neck offsets (P = 0.02) and larger NSAs (P < 0.001). Both the articular and extra-articular regions of the proximal femur have distinct shape features in DDH and cam FAI that can uniquely affect the biomechanics of each disorder. Accordingly, approaches to addressing each disorder should be unique.

Ligamentum Teres Lesions Are Associated With Poorer Patient Outcomes in a Large Primary Hip Arthroscopy Cohort of 1,935 Patients

Purpose

To retrospectively evaluate the prevalence and characteristics of ligamentum teres (LT) lesions identified in a single-surgeon hip arthroscopy cohort and to compare surgical outcomes of those with, and without, identified LT lesions.

Methods

Patients who underwent primary hip arthroscopy between 2005 and 2018 in one surgeon’s clinic were identified. Those with a history involving extra-articular scoping or any previous surgery on the ipsilateral hip were excluded. Patient-reported outcome measures completed before and after surgery included the Hip Disability and Osteoarthritis Outcome Score, Nonarthritic Hip Score, and 12-item International Hip Outcome Tool. Conversion to hip joint replacement was ascertained through a national register.

Results

A total of 1,935 primary hip arthroscopies (from 1,607 different patients) were included in this study. In total, 323 LT lesions were identified. Those with LT lesions were older than those without (40.3 ± 11.3 years compared with 33.9 ± 12.1 years; P < .001), and more frequently female (58.2% vs 41.8%; P = .001). Hips with lesions had a smaller lateral center-edge angle than other hips (33.0 ± 6.8° vs 34.1 ± 6.0°; P = .004). All patient-reported outcome measures improved significantly (P < .001) from pre- to post-surgery for patients with and without LT lesions. However, patients with LT lesions reported less improvement in the 12-item International Hip Outcome Tool (difference –5.60; P = .004) and in Hip Disability and Osteoarthritis Outcome Score symptoms (–4.41; P = .004), sports (–7.81; P < .001), and quality of life subscales (–8.85; P < .001) than those without lesions. Hips with LT lesions also had a 6.2% 2-year rate of subsequent hip replacement (20/323 hips) compared with those without lesions (0.9%; 14/1612 hips; P < .001).

Conclusions

In this single-surgeon hip arthroscopy cohort, identification of LT lesions was associated with poorer patient-reported outcomes and increased likelihood of conversion to arthroplasty within 2 years. These findings suggest a poorer prognosis for patients with LT injury compared with those without.

Level of Evidence

Level III, retrospective cohort study.

Nonarthritic Hip Pathology Patterns According to Sex, Femoroacetabular Impingement Morphology, and Generalized Ligamentous Laxity

BACKGROUND

Sex differences are frequently encountered when diagnosing orthopaedic problems. Current literature suggests specific sex differences, such as a higher prevalence of cam-type femoroacetabular impingement syndrome in male patients and features of hip instability in female patients.

PURPOSE

To identify hip pathology patterns according to sex, alpha angle deformity, and generalized ligamentous laxity (GLL) in a nonarthritic patient population that underwent primary hip arthroscopy in the setting of femoroacetabular impingement syndrome and labral tears.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Patients who underwent primary hip arthroscopy between February 2008 and February 2017 were included and separated into male and female groups for initial analysis. Patients were excluded if they had Tönnis osteoarthritis grade >1, previous ipsilateral hip surgery, or previous hip conditions. The demographics, radiographic findings, intraoperative findings, and surgical procedures were then analyzed and compared. Subanalyses were performed for both groups. A threshold of 1 SD above the mean alpha angle in the male group was used to create 2 subgroups. For female patients, GLL based on a Beighton score ≥4 was used to divide the group. Intraoperative findings were compared for both subanalyses.

RESULTS

A total of 2701 hips met all inclusion and exclusion criteria. Of those, 994 hips were in the male group and 1707 in the female group. The mean ± SD age was 36.6 ± 13.8 and 37.1 ± 15.0 years for the male and female groups, respectively(P = .6288). The average body mass index was significantly higher in the male group (P < .0001). GLL was more common in women (38.6%) than men (13.6%) (P < .001). The male group had a higher proportion of acetabular Outerbridge grade 3 (21.8%) and 4 (19.2%) lesions when compared with the female group (9.3% and 6.3%, respectively) (P < .0001). Men in the subgroup with an alpha angle ≥78° reported higher rates of acetabular Outerbridge grade 4 damage than men with an alpha angle <78° (P < .001). Mean lateral center-edge angle was lower in the female subgroup with Beighton score ≥4 vs <4 (23.7°± 4.2° vs 31.3°± 5.8°; P < .0001).

CONCLUSION

In this analysis of a large cohort of patients who underwent hip arthroscopy, 2 patterns of hip pathologies were related to sex. On average, male patients had larger alpha angles and increased acetabular chondral damage when compared with their female counterparts. Furthermore, a larger cam-type anatomy was associated with more severe acetabular chondral damage in men. In the female group, the incidence of features of hip instability such as GLL were significantly higher than in the male group.

Prevalence of femoro-acetabular impingement in non-arthritic patients with hip pain: a meta-analysis

PURPOSE

As the prevalence of femoro-acetabular impingement syndrome (FAIS) in symptomatic patients who lack evidence of hip osteoarthritis (OA) remains to be described, the purpose of this study was to calculate the prevalence of FAIS in this patient population.

METHODS

Libraries of PubMed, Embase, and Ovid were systematically reviewed for all studies between 2009 and 2019, investigating femoro-acetabular impingement and hip pain. Level I-IV studies delineating patients with hip pain who do not have OA (Tonnis or Outerbridge grades < three) were included. Demographics, outcomes, radiographic parameters, and criteria were entered into a meta-analysis to calculate the incidence of FAIS in non-arthritic symptomatic hips.

RESULTS

In total, 2264 patients (2758 hips) were included in the pooled analysis. Weighted mean age was 31 years. The incidence of FAIS in patients with no evidence of osteoarthritis but who complain of hip pain is 61% (47.3-74.4%). In total, 1483 hips were diagnosed with FAIS. Of the studies that described the rates of all three of the various subtypes of FAIS in their reports, 37% had a combined-type, 38% had a cam-type, and 25% had a pincer-type FAIS.

CONCLUSION

Femoroacetabular impingement should be suspected in 47 to 74% of patients with hip pain and without arthritis. Physicians must maintain a high index of suspicion for FAIS in young patients presenting with hip pain, as FAIS is a common and treatable condition that, if left alone, may lead to hip degeneration.

Relationship between crossover sign and anterior center-edge angle

Purpose

The aim of this study was to evaluate the relationship between the anterior center-edge angle (ACEA) and lateral center-edge angle (LCEA) and crossover ratio.

Methods

Consecutive patients presenting for evaluation of hip pain were reviewed. The following measurements were recorded and analyzed: Crossover ratio, LCEA, ACEA, and alpha-angle.

Results

68 patients met inclusion criteria. The only statistically significant radiographic measurement when stratified by gender was alpha angle (P < 0.001). There was moderate correlation between crossover ratio and ACEA and LCEA with coefficients of -0.48 and -0.48, respectively.

Conclusion

A correlation exists between crossover ratio and ACEA and LCEA.

Using a numerical method to precisely evaluate the alpha angle in a hip image

The alpha angle is a parameter extensively used to assess for cam-type femoroacetabular impingement (FAI) in a 2D image of the hip. As this angle requires estimation of the axis of the femoral neck, the drawing of this axis often results in measurement errors due to subjective judgment, influencing inter-rater and intra-rater agreements. In the present study, sampling points were captured from the edges of a femoral neck and head in the 2D image, and the best curves of the two were fitted respectively by using the curve fitting method. The morphology of the femoral neck was outlined by two polynomials, and the femoral head was represented by an equation of a circle. By means of the proposed method, the results reveal that the inter-rater ICCs in X-ray and MRI were respectively 0.905 and 0.969, and the intra-rater ICCs in X-ray and MRI were respectively 0.892 and 0.840. The Bland-Altman plot shows that the values obtained by the proposed method and the conventional method were not consistent; nevertheless, the linear regression analysis indicated the two measurement results had a significant association (p < 0.001). This study provides a repeatable and agreed α angle measuring method, which contributes to identifying normal and abnormal femoral head-neck morphologies. The proposed numerical method would contribute to diagnose early FAI.

The Influence of Squat Kinematics and Cam Morphology on Acetabular Stress

PURPOSE

To evaluate the effect of varying degrees of simulated cam morphology on acetabular stress magnitude and location using a finite element model with 1 subject that incorporates population-specific hip/pelvis kinematics during a squat task.

METHODS

A reference model of the hip joint was created from magnetic resonance images obtained from 1 asymptomatic 28-year-old man without femoroacetabular impingement (FAI) morphology or hip dysplasia (alpha angle 41.9°, lateral center edge angle 34.0°, neck-shaft angle 137°, and no visible articular cartilage lesions or bone marrow edema on magnetic resonance). The femoral head/neck geometry was manipulated to mimic different cam morphology severities as reported in a previous study (minimum, moderate, and large). Peak hip and pelvis squat kinematics from healthy individuals (hip flexion 112.6°, abduction 10.5°, internal rotation 14.8°) and persons with FAI (hip flexion 106.3°, abduction 10.5°, internal rotation 8.9°) were applied to the control and cam models. Relative acetabular joint stress values and location of contact were the variables of interest.

RESULTS

Average von Mises stress values for control, minimum, moderate, and large cam models were 9.64, 9.27, 11.36, and 28.43 MPa, respectively. Contact in the control and minimum cam models occurred within the acetabular cup. In the moderate and large cam models, contact shifted anterosuperiorly within the acetabular cup and to anterosuperior acetabular rim, respectively.

CONCLUSIONS

Despite simulating lower degrees of hip flexion and internal rotation, increased stress and a shift in contact location were observed in the simulated models of FAI. This finding suggests that decreased hip internal rotation in this population during functional tasks may be the result of bony abutment.

CLINICAL RELEVANCE

Clinicians should be cautious about prescribing deep squats for persons with cam morphology. Performing squat exercises with neutral or external hip rotation may limit bony abutment at high hip flexion angles.