A painful squat test provides limited diagnostic utility in CAM-type femoroacetabular impingement

Purpose

The purpose of this study is to determine the relationship between a symptomatic maximal squat and the presence of radiographic CAM-type femoroacetabular impingement (FAI) on magnetic resonance imaging (MRI) and to determine the sensitivity and specificity of a maximal squat test for the presence of radiographic CAM-type femoral deformity in an adult population.

Methods

In this pilot study, 76 consecutive patients were recruited from an outpatient clinic at McMaster University. All patients presented with pre-arthritic hip pain and were asked to perform a maximal squat. The results of this test were compared to magnetic resonance imaging and magnetic resonance angiographic (MRI and MRA) findings evaluating and characterizing CAM-type FAI deformity.

Results

The sensitivity and specificity of the maximal squat test were 75 % (56.6–88.5 %) and 41 % (27.0–56.8 %), respectively, for CAM-type FAI deformity. The positive and negative likelihood ratios were modest at 1.3 (0.9–1.7) and 0.6 (0.3–1.2), respectively. This means that a 30 % pre-test probability is improved to 36 % following a positive squat test and reduced to 20 % with a negative squat test.

Conclusion

The maximal squat test was found to have marginal incremental diagnostic ability for CAM-type FAI. Its utility in the diagnostic evaluation of FAI remains limited. This survey elucidates areas of research for future studies relevant to the clinical diagnosis of FAI.

Level of evidence

III.     

Radiographic prevalence of CAM-type femoroacetabular impingement after open reduction and internal fixation of femoral neck fractures

Purpose

The purpose of this study was to estimate the radiographic prevalence of CAM-type femoroacetabular impingement (FAI) in elderly patients (≥50 years) who have undergone internal fixation for femoral neck fracture.

Methods

A total of 187 frog-leg lateral radiographs of elderly patients who underwent internal fixation for a femoral neck fracture were reviewed by two independent reviewers. The alpha angle, beta angle, and femoral head–neck offset ratio were calculated. The presence of two abnormal radiographic parameters was deemed to be diagnostic of radiographic CAM-type impingement.

Results

Radiographic CAM-type FAI was identified in 157 out of 187 (84 %) patients who underwent internal fixation for fractures of the femoral neck. Moderate-to-good inter-observer reliability was achieved in the measurement of radiographic parameters. With reference to fracture subtypes and prevalence of radiographic features of CAM-type morphology, 97 (72 %) out of 134 patients were positive for CAM in Garden subtypes I and II, whereas 49 (85.9 %) out of 57 patients had radiographic CAM in Garden III and IV subtypes.

Conclusion

There was a high prevalence of CAM-type FAI in patients that underwent surgical fixation of femoral neck fractures. This is significantly higher than the reported prevalence in non-fracture patient populations. The high prevalence of CAM morphology could be related to several factors, including age, fracture morphology, quality of reduction, type of fixation, and fracture healing.

Level of evidence

IV.     

Lack of correlation between ulnar variance and carpal bone angles on lateral radiographs in normal wrists.

It has been proposed that negative ulnar variance is a predisposing factor to development of posttraumatic carpal ligamentous instability. However, this implies that no correlation exists between ulnar variance and carpal bone angles in the normal wrist. Carpal bone angles on lateral wrist radiographs and ulnar variance were measured in a series of 75 normal wrists. The mean ulnar variance was -0.03 mm (SD 1.56, range -5 to 5). The correlation coefficients were 0.06, -0.11, and -0.05 between the ulnar variance, and radiolunate, radioscaphoid, and scapholunate angles, respectively. A correlation between the carpal angles on lateral wrist radiographs, and ulnar variance in normal wrists could not be demonstrated, suggesting that the presence of negative ulnar variance may serve as an impartial clue to the presence of ligamentous instability.     

Correlations between the alpha angle and femoral head asphericity: Implications and recommendations for the diagnosis of cam femoroacetabular impingement

Objective

To determine the strength of common radiographic and radial CT views for measuring true femoral head asphericity.

Patients and methods

In 15 patients with cam femoroacetabular impingement (FAI) and 15 controls, alpha angles were measured by two observers using radial CT (0°, 30°, 60°, 90°) and digitally reconstructed radiographs (DRRs) for the: anterior–posterior (AP), standing frog-leg lateral, 45° Dunn with neutral rotation, 45° Dunn with 40° external rotation, and cross-table lateral views. A DRR validation study was performed. Alpha angles were compared between groups. Maximum deviation from a sphere of each subject was obtained from a previous study. Alpha angles from each view were correlated with maximum deviation.

Results

There were no significant differences between alpha angles measured on radiographs and the corresponding DRRs (p = 0.72). Alpha angles were significantly greater in patients for all views (p ≤ 0.002). Alpha angles from the 45° Dunn with 40° external rotation, cross-table lateral, and 60° radial views had the strongest correlations with maximum deviation (r = 0.831; r = 0.823; r = 0.808, respectively). The AP view had the weakest correlation (r = 0.358).

Conclusion

DRRs were a validated means to simulate hip radiographs. The 45° Dunn with 40° external rotation, cross-table lateral, and 60° radial views best visualized femoral asphericity. Although commonly used, the AP view did not visualize cam deformities well. Overall, the magnitude of the alpha angle may not be indicative of the size of the deformity. Thus, 3D reconstructions and measurements of asphericity could improve the diagnosis of cam FAI.     

Arthroscopy for the treatment of femoroacetabular impingement in the athlete

Femoroacetabular impingement (FAI) has been recently recognized as a cause of hip pain, labral and chondral pathology, early osteoarthritis, and decreased athletic performance. Historically, treatment for FAI consisted of an open approach with surgical dislocation. It has been suggested that the operative trauma sustained during the open procedure may make it difficult for high-level athletes to return to play. As a result, an arthroscopic approach to treat FAI has been developed. The purpose of this article is to describe the arthroscopic technique for the treatment of cam and pincer-type hip impingement.     

A new reference line in diagnosing a high-riding patella on routine digital lateral radiographs of the knee

Objective

To propose a new reference line in diagnosing a high-riding patella (patella alta) on routine digital lateral radiographs of the knee.

Materials and methods

On 64 routine digital lateral radiographs of adult knees with no bone pathology or surgery and over the range of knee flexion between 1.6° and 79.1° (34.4°± 16.6°), the long axis of the superimposed egg-shaped femoral condyles was drawn and moved upward to pass through the point where the posterior contours of the femoral diaphysis and the femoral condyles meet—the posterior reference point—to become a new reference line. Any part of the patella crossing the new reference line indicated a high-riding patella. The new reference line was compared with the four most common patellar height ratios (Insall–Salvati, Grelsamer–Meadows or the modified Insall–Salvati, Caton Deschamps, and Blackburne–Peel) for the drawing time, accuracy, and reproducibility (intra- and interobserver agreement).

Results

The new reference line required approximately one-third to one-half of the drawing time compared to the most common patellar height ratios, with equal accuracy and complete reproducibility. On the contrary, the reproducibility of the most common patellar height ratios ranged from poor to moderate, with the best results for the Insall–Salvati ratio.

Conclusions

The new reference line proved to be a very simple, accurate, and reproducible tool in diagnosing a high-riding patella. We believe that our preliminary results are an encouraging impetus to more complex research.     

Ultrasound for the evaluation of femoroacetabular impingement of the cam type. Diagnostic performance of qualitative criteria and alpha angle measurements

Objective  

To develop and assess a technique to evaluate cam type femoroacetabular impingement (FAI) using ultrasound (US).     

超声诊断cam型股骨髋臼撞击综合征的定性诊断标准和α角测量

目的创建cam型股骨髋臼撞击(FAI)综合征的超声(US)诊断技术并对其进行评价。方法 50例病人(女24例,男26例)纳入研究(年龄16～59岁,平均39.1岁)。获取     

Effects of a hip brace on biomechanics and pain in people with femoroacetabular impingement

Objectives

This study evaluates whether hip bracing in patients with femoroacetabular impingement (FAI) (a) immediately reduces range of hip internal rotation, flexion, adduction, and pain during functional tasks; and (b) improves patient-reported outcomes when worn daily over 4 weeks.

Relationship between stress ankle radiographs and injured ligaments on MRI

Objective

This study was performed to investigate the relationship between the injured lateral ankle ligaments on MRI and stress ankle radiographs.

Materials and methods

Two hundred and twenty-nine consecutive patients (mean age 35.5 years, SD 14.6 years; 136 males and 93 females) that underwent ankle stress radiographs and MRI for lateral ankle instability were included. Tibiotalar tilt angle and anterior translation of talus were measured on stress ankle radiographs. Degree of lateral ligaments (anterior talofibular, calcaneofibular, and posterior talofibular) and deltoid ligament injuries were evaluated and scored as intact (0), partial injury (1), and complete injury (2) on MR images. Effusion of ankle joint was also recorded. The effects of gender, age, injuries of ligaments, and ankle joint effusion on stress radiographs were statistically analyzed.

Results

Gender (p?=?0.010), age (p?=?0.020), and anterior talofibular ligament (ATFL) injury (p?<?0.001) were the factors significantly affecting tibiotalar tilt angle. Posterior talofibular ligament (PTFL) injury (p?=?0.014) was found to be the only significant factor affecting the anterior translation on the anterior drawer radiographs.

Conclusions

ATFL injury and PTFL injury on MRI significantly affected tibiotalar tilt angle and anterior drawer on stress radiographs. Other factors, such as age and gender, need to be considered in evaluating radiographic lateral ankle instability.     

Conservative management of femoroacetabular impingement (FAI) in the long distance runner

Femoroacetabular impingement (FAI) is one cause of anterior hip pain that may occur in a long distance runner. By definition FAI is due to bony abutment of the femoral neck and the acetabulum. This occurs primarily with end-ranges of hip flexion and adduction. An understanding of running mechanics and performing a thorough examination will help the clinician provide an appropriate intervention for these athletes. A course of conservative treatment that includes patient education, manual therapy and strengthening should be tried prior to surgical management.     

Cam and pincer femoroacetabular impingement: characteristic MR arthrographic findings in 50 patients

PURPOSE: To retrospectively characterize magnetic resonance (MR) arthrographic findings in patients with cam femoroacetabular impingement (FAI) and in those with pincer FAI. MATERIALS AND METHODS: Institutional review board approval and informed consent were not required. MR arthrographic studies obtained in 50 consecutive patients (30 men, 20 women; mean age, 28.8 years) with FAI were analyzed for labral abnormalities, cartilage lesions, and osseous abnormalities of the acetabular rim. The nonspherical shape of the femoral head at the head-neck junction was measured in eight positions around the femoral head and neck and used to calculate the alpha angle. Acetabular depth was measured. Surgical diagnosis served as the reference standard. The Wilcoxon rank sum test was used for statistical analysis. RESULTS: At surgery, hips in 33 patients were classified as having cam FAI and hips in 17 patients were classified as having pincer FAI. In both groups, the mean age of patients was 28.8 years. There were significantly more men (n = 27) with cam FAI and more women (n = 14) with pincer FAI. The alpha angle was significantly larger in patients with cam FAI at the anterior and anterosuperior positions. The acetabulum was significantly deeper in patients with pincer FAI than in patients with cam FAI. Cartilage lesions at the anterosuperior and superior positions were significantly larger in patients with cam FAI than in patients with pincer FAI. Cartilage lesions at the posteroinferior position were significantly larger and labral lesions at the posterior and posteroinferior positions were more pronounced in patients with pincer FAI than in patients with cam FAI. Osseous abnormalities were not significantly different between the groups. Osseous bump formation at the femoral neck was significantly more common in patients with cam FAI than in patients with pincer FAI. CONCLUSION: Characteristic MR arthrographic findings of cam FAI include large alpha angles and cartilage lesions at the anterosuperior position and osseous bump formation at the femoral neck; characteristic findings of pincer FAI include a deep acetabulum and posteroinferior cartilage lesions.     

Femoral head-neck offset measurements in 339 subjects: distribution and implications for femoroacetabular impingement

Purpose

The α-angle is a frequently used measurement to quantify head-neck offset pathology in cam-type femoroacetabular impingement. However, diverging norm values and reference intervals have been described, especially in men.

Methods

The α-angle, the head-neck offset ratio and the triangular index were measured on anteroposterior and lateral radiographs of 339 (170 men and 169 women) subjects without evident underlying hip pathology.

Results

For male subjects, the mean α-angle was 49.4° (SD 10.5°) on anteroposterior and 49.1° (SD 10.6°) on lateral radiographs, whereas for female subjects, it was 45.0° (SD 8.0°) and 46.1° (SD 9.9°), respectively. Thus, calculated upper limits of reference intervals in the population screened were 70° for both radiographic projections in men and 61° (anteroposterior) and 66° (lateral) in women.

Conclusion

These data substantiate recent findings that the pathological threshold of the α-angle in male subjects may be lower than that previously assumed.

Level of evidence

Diagnostic, Level III.