Discrete mineralisation of the acetabular labrum: a novel marker of femoroacetabular impingement?

Three-Dimensional Reconstruction of Computed Tomography Imaging Is Not Reliable in Assessing Acetabular Rim Osteophytes or Acetabular Rim Pathology in Patients With Femoroacetabular Impingement

Purpose

To determine the reliability of 3-dimensional (3D) reconstruction of computed tomography (CT) imaging in evaluating acetabular rim morphology or acetabular rim osteophyte (ARO) existence and to group patients with femoroacetabular impingement (FAI) by ARO extent on coronal sections of CT and further compare clinical differences among groups.

Methods

Patients who underwent primary hip arthroscopy for FAI by the same surgeon between August 2016 and December 2018 with minimum 2-year follow-up were enrolled. The ARO was evaluated both on the acetabular gross anatomy (AGA) and coronal sections of CT, for its position, width (unit: mm), area (unit: mm2), and CT value (unit: HU). Patients were divided into 4 groups based on the extent of ARO on coronal CT: group A (ARO anterior to 12 o'clock), group P (ARO posterior to 12 o'clock), group AP (ARO across 12 o'clock), and group N (no ARO). Inter- and intraobserver correlation was analyzed. Demographic data, FAI deformity indicators on imaging, quantitative measurements of ARO, and pre- and postoperative patient-reported outcomes were compared among groups.

Results

There were 229 patients (229 hips) enrolled in total, 122 male (53.3%) and 107 female (46.7%), with a mean age of 37.2 ± 10.2 years. The correlation between 2 observers for grouping ARO using AGA was positive but poor (Kendall Tau-b coefficient = 0.157, P = .008). Moderate correlation was found between grouping based on AGA and coronal CT by the same observer (Kendall Tau-b coefficient = 0.482, P = .000). The patients were divided into 4 groups: 84 patients (36.7%) in group N, 2 patients (0.9%) in group A, 69 patients (30.1%) in group P, and 74 patients (32.3%) in group AP. Group N was younger in age (35.4 ± 10.7 years) than group P (39.6 ± 10.2 years) (P = 0.012) and had a larger proportion of women (57.1%) than group AP (36.5%) (χ2 = 6.869, P = .032). There was a greater proportion of positive posterior wall sign in group P (52.2%) than 48.6% for group AP and 33.3% for group N (χ2 = 6.397, P = .041). Group N had 61 (72.6%) Tönnis grade 0 hips compared with 37 (50%) in group AP (P = .014). No statistical significance was found among groups in pre- and postoperative α angle, lateral center-edge angle, and patient-reported outcomes. The widths of ARO in group AP for the 3 marked points from anterior to posterior were 3.88 ± 1.86, 4.84 ± 2.72, and 6.66 ± 3.18, separately (P＜.001); 15.73 ± 21.46, 19.22 ± 18.86, and 29.96 ± 17.05 for area (P＜.01); and 652.67 ± 214.12, 677.10 ± 274.81, and 728.84 ± 232.39 for CT value (P＜.05). For the ARO posterior to 12 o'clock, the group AP showed a larger width (6.66 ± 3.18), area (29.96 ± 17.05), and CT value (728.84 ± 232.39) than group P of (4.70 ± 2.25), (20.15 ± 12.91), and (641.84 ± 183.33) (P＜.001).

Conclusions

The evaluation of ARO on AGA is poor consistent with definite double-rim sign on coronal CT. There is a tendency of size-enlarging and density-increasing for ARO from anterior to posterior along the acetabular rim. Younger age, female gender, lower Tönnis grade, and negative posterior wall sign showed lower rate of ARO development.

Level of Evidence

Level IV, diagnostic case series.

Clinical outcomes after arthroscopic treatment of calcification with surrounding inflammation in the hip labrum

PURPOSE

The purpose of this study was to investigate the surgical methods and clinical outcomes of arthroscopic treatment of a special type of calcification with surrounding inflammation in the acetabular labrum of the hip, which was temporarily named "calcifying labrumitis".

METHODS

From April 2015 to November 2019, a total of seven patients with calcifying labrumitis of the hip who underwent arthroscopic excision of calcified lesions and suture or partial resection of the labrum were included in this study. Radiographs were retrospectively evaluated for morphologic characteristics of calcifying labrumitis. Each patient was assessed by the visual analogue scale (VAS), modified Harris hip score (mHHS), nonarthritic hip score (NAHS) and satisfaction rate before surgery and at the final follow-up evaluation.

RESULTS

Seven patients, one male and six females aged 29-48 years, were included in the study; of these patients, three had calcifying labrumitis on the left side and four had calcifying labrumitis on the right side. All patients had hip pain and limited range of motion for a mean of 7.5 ± 3.1 months (range, 3-12 months). The mean follow-up period was 34.9 ± 19.5 months (range, 12-66 months). The lateral central-edge angle (LCEA) was 31.7 ± 3.9° (range, 28.8-36.4°), and the α angle was 41.4 ± 5.3° (range, 33.6-48.2°). None of the patients had cam or pincer lesions. After complete removal of calcified lesions, five patients underwent repair of the labrum with a suture anchor, and two patients underwent partial resection of the labrum. The symptoms of all patients improved significantly at the last follow-up. Mean scores improved from 5.8 ± 1.5 to 1.1 ± 0.3 (p < 0.01) for the VAS, from 57.3 ± 10.6 to 90.8 ± 13.4 for the mHHS and from 62.5 ± 10.7 to 84.3 ± 9.6 for the NAHS. The satisfaction rate was 100%.

CONCLUSION

Calcifying labrumitis of the hip is a special kind of rare disease that is different from calcifications accompanying FAI and os acetabuli. Arthroscopic treatment of calcification with suture or partial resection of the labrum is an effective, safe and minimally invasive method, significantly relieving pain and improving hip joint function.

LEVEL OF EVIDENCE

Level IV.

Primary cam morphology; bump, burden or bog-standard? A concept analysis

BACKGROUND

Cam morphology, a distinct bony morphology of the hip, is prevalent in many athletes, and a risk factor for hip-related pain and osteoarthritis. Secondary cam morphology, due to existing or previous hip disease (eg, Legg-Calve-Perthes disease), is well-described. Cam morphology not clearly associated with a disease is a challenging concept for clinicians, scientists and patients. We propose this morphology, which likely develops during skeletal maturation as a physiological response to load, should be referred to as primary cam morphology. The aim of this study was to introduce and clarify the concept of primary cam morphology.

DESIGN

We conducted a concept analysis of primary cam morphology using articles that reported risk factors associated with primary cam morphology; we excluded articles on secondary cam morphology. The concept analysis method is a rigorous eight-step process designed to clarify complex 'concepts'; the end product is a precise definition that supports the theoretical basis of the chosen concept.

RESULTS

We propose five defining attributes of primary cam morphology-tissue type, size, site, shape and ownership-in a new conceptual and operational definition. Primary cam morphology is a cartilage or bony prominence (bump) of varying size at the femoral head-neck junction, which changes the shape of the femoral head from spherical to aspherical. It often occurs in asymptomatic male athletes in both hips. The cartilage or bone alpha angle (calculated from radiographs, CT or MRI) is the most common method to measure cam morphology. We found inconsistent reporting of primary cam morphology taxonomy, terminology, and how the morphology is operationalised.

CONCLUSION

We introduce and clarify primary cam morphology, and propose a new conceptual and operational definition. Several elements of the concept of primary cam morphology remain unclear and contested. Experts need to agree on the new taxonomy, terminology and definition that better reflect the primary cam morphology landscape-a bog-standard bump in most athletic hips, and a possible hip disease burden in a selected few.

Ossification of the acetabular rim: a highly prevalent finding in asymptomatic non-osteoarthritic hips of all ages

Objective

To estimate the prevalence of acetabular rim ossifications in the adult population with asymptomatic, morphologically normal hips at CT and to determine whether the presence of these ossifications is associated with patient- or hip-related parameters.

Methods

We prospectively included all patients undergoing thoracoabdominal CT over a 3-month period. After exclusion of patients with a clinical history of hip pathology and/or with signs of osteoarthritis on CT, we included a total of 150 hips from 75 patients. We analyzed the presence and the size of ossifications around the acetabular rim. The relationships between the size of acetabular rim ossifications and patient-related (sex, age, BMI) or hip-related parameters (joint space width, and cam- and pincer-type femoroacetabular impingement morphology) were tested using multiple regression analysis.

Results

The prevalence of acetabular rim ossifications in this population of asymptomatic, non-osteoarthritic hips was 96% (95% CI = [80.1; 100.0]). The presence of ossifications and their size were correlated between the right and left hips (Spearman coefficient = 0.64 (95% CI = [0.46;0.79]), p < 0.05)). The size of acetabular rim ossifications was significantly associated with age (p < 0.0001) but not with BMI (p = 0.35), gender (p = 0.05), joint space width (p ≥ 0.53 for all locations), or any of the qualitative or quantitative parameters associated with femoroacetabular morphology (p ≥ 0.34).

Conclusion

Acetabular rim ossifications are highly prevalent in asymptomatic, non-osteoarthritic adult hips at all ages. Their size is not correlated with any patient- or hip-related parameters except for age. These findings suggest that ossifications at the acetabular rim, when present in isolation, should not be considered a sign of osteoarthritis or femoroacetabular impingement morphology.

Key Points

• Acetabular rim ossifications are extremely common in asymptomatic, non-osteoarthritic adult hips.

• Acetabular rim ossifications are present independently from other signs of osteoarthritis in adult hips at all ages and should not be interpreted as a pathological finding.

• The diagnosis of osteoarthritis or femoroacetabular impingement morphology should not be made based on the sole presence of ossifications at the acetabular rim.

Acetabular Ossicles: Epidemiology and Correlation With Femoroacetabular Impingement

PURPOSE

To investigate (1) the prevalence, size, and location of acetabular ossicles in general population; (2) differentiation between the characteristic types of acetabular ossicles: unfused ossification centers (true os acetabuli), rim fractures, labral calcifications and loose bodies; and (3) correlation between acetabular ossicles, and femoroacetabular impingement (FAI) with symptoms.

METHODS

Patients aged 16 to 60 years who underwent abdominal and pelvic computed tomography (CT) with non-orthopaedic indications in 2016 and patients who underwent hip arthroscopy surgery from 2010 to 2016 in our institution were included for asymptomatic and symptomatic groups, respectively. Two investigators evaluated CT images to find the prevalence, size, location of acetabular ossicles, and relationship with symptoms and FAI. We correlated them with types of ossicles.

RESULTS

This study included 5684 patients with 11368 hips (2790 male and 2894 female; mean age, 44.3 years) for asymptomatic group, and 264 patients with 289 hips (171 male and 93 female; mean age, 34.4 years) for symptomatic group. The prevalence of ossicles in symptomatic and asymptomatic groups was 8.65% (25/289) and 3.33% (378/11,368), respectively. The distribution of ossicles types in general population were labral calcifications (55.09%), rim fractures (35.73%), unfused ossification center (1.24%), and loose bodies (7.94%). Labral calcification had the smallest size and mostly was asymptomatic. Rim fracture was correlated with FAI in general (83.33%; P < .001) but not with any types of FAI. Size of ossicles was related with symptom (895.28 vs 103.64 mm³; P < .001).

CONCLUSIONS

The prevalence of acetabular ossicles in general population are 3.46%, with significantly higher prevalence of acetabular ossicles were found in symptomatic group (8.65% vs 3.33%). Size of acetabular ossicles was significantly associated with hip pain. Labral calcification was the most common type of acetabular ossicles. Significant relationship was found between rim fracture and FAI but not with any specific types of FAI.

LEVEL OF EVIDENCE

Level III, Retrospective comparative study.

How Many Radiographs Does It Take to Screen for Femoral Cam Morphology?: A Noninferiority Study

PURPOSE

To compare a 2-view radiograph series (AP of the pelvis and 45° Dunn of the hip) with a 5-view radiograph series for sensitivity in identifying femoral cam morphology.

MATERIALS AND METHODS

This is a retrospective review of consecutive patients with a 5-view radiograph series (AP pelvis and AP, 45° Dunn, frog lateral, and false profile of the affected hip) from 2016 to 2017. Three fellowship trained radiologists blindly and independently evaluated 2 views (AP pelvis and Dunn) for a femoral cam lesion, acetabular rim calcification, Tonnis grade, and important incidental findings. Two weeks later, the same assessment was made on all 5 views. A noninferiority test of the 2-view series vs the 5-view series for sensitivity in identifying femoral cam morphology was conducted. Individual reader sensitivity calculations were performed and agreement was determined with the kappa statistic.

RESULTS

The 2-view series was noninferior to the 5-view series for cam identification (P value = 0.010). In comparing the 2-view vs 5-view series for individual readers, there was no difference in the sensitivities (84%-100% vs 85%-98%, P = 0.85-1.0) or specificities (11%-56% vs 7%-56%, P = 0.58-1.0) for cam identification. There was fair to excellent 2-view intrareader agreement (k = 0.38-0.93) and similar inter-reader agreement between the 2-view and 5-view (k = 0.33 vs 0.37).

CONCLUSIONS

A 2-view radiograph series (AP pelvis and Dunn hip) is noninferior to a 5-view radiograph series for sensitivity in identifying femoral cam morphology.

Calcification of the acetabular labrum of the hip: prevalence in the general population and relation to hip articular cartilage and fibrocartilage degeneration

Background

Meniscal calcification is considered to play a relevant role in the pathogenesis of osteoarthritis of the knee. Little is known about the biology of acetabular labral disease and its importance in hip pathology. Here, we analyze for the first time the calcification of the acetabular labrum of the hip (ALH) and its relation to hip cartilage degeneration.

Methods

In this cross-sectional post-mortem study of an unselected sample of the general population, 170 ALH specimens and 170 femoral heads from 85 donors (38 female, 47 male; mean age 62.1 years) were analyzed by high-resolution digital contact radiography (DCR) and histological degeneration grade. The medial menisci (MM) from the same 85 donors served as an intra-individual reference for cartilage calcification (CC). Scanning electron microscopy (SEM), energy dispersive analysis (ED) and Raman spectroscopy were performed for characterization of ALH CC.

Results

The prevalence of CC in the ALH was 100% and that in the articular cartilage of the hip (ACH) was 96.5%. Quantitative analysis revealed that the amount of ALH CC was higher than that in the ACH (factor 3.0, p < 0.001) and in the MM (factor 1.3, p < 0.001). There was significant correlation between the amount of CC in the fibrocartilage of the left and right ALH (r = 0.70, p < 0.001). Independent of age, the amount of ALH CC correlated with histological degeneration of the ALH (Krenn score) (r = 0.55; p < 0.001) and the ACH (Osteoarthritis Research Society International (OARSI), r = 0.69; p < 0.001). Calcification of the ALH was characterized as calcium pyrophosphate dihydrate deposition.

Conclusion

The finding that ALH fibrocartilage is a strongly calcifying tissue is unexpected and novel. The fact that ALH calcification correlates with cartilage degeneration independent of age is suggestive of an important role of ALH calcification in osteoarthritis of the hip and renders it a potential target for the prevention and treatment of hip joint degeneration.

Labral calcification in end-stage osteoarthritis of the hip correlates with pain and clinical function

The acetabular labrum of the hip (ALH) is recognized as a clinically important structure, but knowledge about the pathophysiology of this fibrocartilage is scarce. In this prospective study we determined the prevalence of ALH calcification in patients with end-stage osteoarthritis (OA) and analyzed the relationship of cartilage calcification (CC) with hip pain and clinical function. Cohort of 80 patients (70.2 ± 7.6years) with primary OA scheduled for total hip replacement. Harris Hip Score (HHS) was recorded preoperatively. Total ALH and femoral head (FH) were sampled intraoperatively. CC of the ALH and FH was analyzed by high-resolution digital contact radiography. Histological degeneration of the ALH (Krenn-Score) and FH (OARSI-Score) was determined. Multivariate linear regression model and partial correlation analyses were performed. The prevalence of cartilage calcification both in the ALH and FH was 100%, while the amount of CC in the ALH was 1.55 times higher than in the FH (p < 0.001). There was a significant inverse regression between the amount of calcification of both the ALH and the FH and preoperative HHS (β_ALH  = -2.1, p = 0.04), (β_FH  = -2.9, p = 0.005), but pain was influenced only by ALH calcification (β_ALH  = -2.7, p = 0.008). Age-adjusted, there was a significant correlation between cartilage calcification and histological degeneration (ALH:r_s  = 0.53, p < 0.001/FH: r_s  = 0.30, p = 0.007). Fibrocartilage and articular cartilage calcification are inseparable pathological findings in end-stage osteoarthritis of the hip. Fibrocartilage calcification is associated with poor and painful hip function.

CLINICAL SIGNIFICANCE

ALH fibrocartilage appears to be particularly prone to calcification, which may explain higher pain levels in individuals with a high degree of ALH calcification independent of age and histological degeneration. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1248-1255, 2018.

Clinical outcomes of patients with symptomatic acetabular rim fractures after arthroscopic FAI treatment

This study aims to investigate the influence of the acetabular rim fractures on outcomes of hip arthroscopy at minimum 2-year follow-up. Between January 2009 and August 2012, data were prospectively collected on all patients undergoing hip arthroscopy. Anatomic findings, including presence of rim fractures, were recorded intraoperatively. Patients were assessed preoperatively and at 3 months, 1 year and minimum 2 years postoperatively with four patient-reported outcome measures: modified Harris Hip Score, Non-Arthritic Hip Score, Hip Outcome Score-Activities of Daily Living and Hip Outcome Score-Sport Specific Subscales. Pain was estimated using a visual analog scale. Satisfaction was measured on a scale from 0 to 10. Patients with rim fractures were identified and retrospectively matched to a control group based on gender, BMI category, and age at surgery within 3 years and compared in terms of demographic factors, intraoperative findings, procedures and outcomes. Twenty-one patients with rim fractures were matched to a control group of 21 patients with symptomatic femoroacetabular impingement without rim fractures. No significant differences were detected with respect to demographic characteristics, surgical procedures (besides the removal of rim fractures), or in terms of preoperative, postoperative, or improvement in patient-reported outcome scores and satisfaction. The presence or absence of an acetabular rim fracture does not significantly influence clinical outcomes at minimum 2-year follow-up after hip arthroscopy. Case-control study design is used in this study.