Relationship Between Offset Angle Alpha and Hip Chondral Injury in Femoroacetabular Impingement

doi:10.1016/j.arthro.2008.01.010

Arthroscopy: The Journal of Arthroscopic & Related Surgery

Volume 24, Issue 6, June 2008, Pages 669-675

https://doi.org/10.1016/j.arthro.2008.01.010 Get rights and content

Purpose: The purpose of this study was to examine the relationship between the size of cam lesions and the presence of cartilage damage, labral damage, or changes in range of motion in the hips with signs and symptoms of femoroacetabular impingement (FAI). Methods: Cross-table lateral radiographs were available for 102 consecutive patients presenting with signs and symptoms of FAI. Radiographs with excessive external rotation, dysplasia, severe arthritis, avascular necrosis, or Legg-Calvé-Perthes syndrome were excluded, leaving 82 patients available for analysis (47 men, 35 women; average age, 25 yr [range, 12 to 55 yr]). Offset angle alpha was measured from the films with a digital goniometer. Patients subsequently underwent hip arthroscopy and the surgical findings and hip range of motion were prospectively recorded. Results: Higher offset angle alpha was associated with the presence of acetabular rim chondral defects (P = .044) and full-thickness delamination of the acetabular cartilage (P = .034). Patients with detachment of the base of the labrum had a higher offset angle alpha (P = .016). Higher offset angle alpha was related to male sex (P = .001) and decreased range of motion (P < .05), but not to age. Conclusions: Cam-type FAI, as measured by an increased offset angle alpha, was correlated with increased chondral damage, labral injury, and decreased range of motion. Level of Evidence: Level II, development of diagnostic criteria on basis of consecutive patients with universally applied gold standard.

Section snippets

Methods

From March 2005 to December 2005, a consecutive series of 102 amateur and professional athletes demonstrating signs and symptoms consistent with FAI underwent arthroscopic hip surgery by the senior author (M.J.P.). Patients typically complained of hip and groin pain that limited activity, had a positive anterior impingement test, and showed classic radiographic evidence for FAI in the form of a cam or pincer lesion.⁵ The cohort therefore included patients with persistent hip pain despite

Results

Of the 102 patients with available radiographs, 82 patients (47 men, 35 women), with an average age of 25 years (range, 12 to 55), met the study criteria. The intraobserver reliability of the offset angle alpha measurements showed substantial agreement (ICC = 0.776), while the interobserver reliability had moderate agreement (ICC = 0.523; Table 1). The average offset angle alpha for the entire cohort was 53.9° (range, 29° to 80°). Men had higher offset angle (57° [range, 38° to 79°]) compared

Discussion

The main findings of this study were that larger cam lesions, as measured by the offset angle alpha, were associated with larger areas of acetabular cartilage damage, acetabular delamination, and labral base detachment. These findings are consistent with the pathogenesis proposed by Ganz et al.⁶ Furthermore, our findings confirm our hypothesis that patients with a higher offset angle alpha had greater cartilage damage, labral injury, and decreased range of motion.

The cartilage and labral damage

Conclusions

Cam-type FAI, as measured by an increased offset angle alpha, is associated with increasing chondral damage, labral injury, and decreased range of motion. Offset angle alpha is a useful measurement when performed on the cross-table lateral radiograph that reliably detects differences in cam lesion size from one patient to the next.

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Cited by (242)

A Superolateral Cam Lesion Location Increases Odds of Total Hip Arthroplasty 5 Years After Hip Arthroscopy
2024, Arthroscopy - Journal of Arthroscopic and Related Surgery
To determine if radiographic cam location is associated with hip survivorship and postoperative patient-reported outcomes (PROs) at 5-year follow-up.
We conducted a review of prospectively collected data of patients with cam lesions who underwent hip arthroscopy for femoroacetabular impingement syndrome. Cam lesions were categorized into 3 locations: superolateral, anterolateral, or anterior. Conversion to total hip arthroplasty (THA), revision rates, and reoperation rates were assessed. Patient-reported outcome measures, including modified Harris Hip Scores (mHHS) and Non-Arthritic Hip Scores (NAHS), were collected preoperatively and at 5-year follow-up.
Of the 156-patients, 125 met the final criteria (80.1%). Mean age was 41.1 ± 12.7 years. Seventy-one patients (56.8%) had superolateral cam lesions, 41 (32.8%) had anterolateral lesions, and 13 (10.4%) had anterior lesions. Revision rates within 5 years were 7.7% for anterior, 24.4% for anterolateral, and 14.1% for superolateral lesions; conversions to THAs were 15.4% for anterior), 7.3% for anterolateral, and 8.5% for superolateral. Reoperations were 23.1% for anterior, 29.3% for anterolateral, and 21.1% for superolateral. The superolateral cohort was younger than the anterior and anterolateral cohorts (anterior, 46.6 ± 12.2 years; anterolateral, 44.7 ± 12.2 years; superolateral, 38.1 ± 12.3 years; P = .006). Multivariable analysis showed the anterolateral group was significantly predictive of lower odds of undergoing THA compared to the superolateral group (odds ratio, 0.01; 95% CI, <0.01-0.72; P = .03). There were no differences in the 5-year improvement in mHHS (anterior, 32.4; anterolateral, 36.8; superolateral, 33.0; P = .29) or NAHS (anterior, 34.8; anterolateral, 39.0; superolateral, 37.3; P = .65).
A superolateral cam lesion increases the odds of conversion to THA within 5 years of hip arthroscopy compared to those with anterolateral lesions on multivariable analysis. Those with superolateral lesions were significantly younger compared to those with anterior or anterolateral lesions. Cam lesion location did not affect improvement in PROs at 5-year follow-up.
Level III, retrospective comparative prognostic trial.
Femoroacetabular Impingement Measurements Obtained From Two-Dimensional Radiographs Versus Three-Dimensional–Reconstructed Computed Tomography Images Result in Different Values
2024, Arthroscopy, Sports Medicine, and Rehabilitation
To compare the reliability and accuracy of radiographic measurements obtained from 2-dimensional (2D) radiographs and 3-dimensional (3D)-reconstructed computed tomography (CT) images in the assessment of femoroacetabular impingement syndrome (FAIS).
Consecutive patients with FAIS from January 2018 to December 2020 were identified and included in this study. Two fellowship-trained surgeons and 2 fellows performed blinded radiographic measurements. Lateral center-edge angle (LCEA) and Tönnis angles were measured on anteroposterior pelvic radiographs, and alpha angles were measured on frog lateral radiographs. Reliability coefficients for individual measurement accuracy were performed using the Cronbach alpha and intra- and inter-rater intraclass correlation coefficients (ICCs). Composite measurements for LCEA, Tönnis angle, and alpha angle were compared with the corresponding 3D value using paired sample t-tests.
Fifty-three patients with FAIS with standardized 2D radiographic and 3D-reconstructed CT imaging were included. All reliability metrics met thresholds for internal reliability. Inter-rater ICCs for LCEA, Tönnis angle, and alpha angle were (0.928, 0.888, 0.857, all P < .001). When we compared 2D radiographic measurements with 3D-reconstructed CT values, there was a significant difference in the LCEA for 2 authors: surgeon 1 (mean [M] = –9.14, standard deviation [SD] = 5.7); t(52) = –11.6, P < .001, and surgeon 2 (M = –5.9°, SD = 4.7); t(52) = –9.2, P < .001. Significant differences were seen for Tönnis angle for 2 authors: fellow 2 (M = 3.9°, SD = 5.6); t(52) = 5.1, P < .001, and surgeon 2 (M = –2.6°, SD = 4.1); t(52) = –4.6, P < .001. Alpha angle measurements compared to the 3D-reconstructed alpha angle at 2 o’clock was significantly different for 3 authors: fellow 1 (M = 11.9°, SD = 16.2); t(52) = 5.3, P < .001; fellow 2 (M = 10.4°, SD = 18.6); t(52) = 4.1, P = .002; and surgeon 2 (M = –6.5°, SD = 16.2); t(52) = –2.9, P = .005. Positive mean values indicate 2D radiographic measurements overestimated 3D reconstruction values and negative mean values indicate underestimation.
The use of 2D radiographs alone for preoperative planning of FAIS may lead to inaccuracies in radiographic measurements.
Level, III retrospective cohort study.
Cartilage Defects Are Negatively Associated With Long-Term Hip Survivorship Following Contemporary Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Propensity-Matched Analysis at Minimum 10-Year Follow-Up
2024, Arthroscopy - Journal of Arthroscopic and Related Surgery
To identify the timing and risk factors associated with secondary surgery following primary hip arthroscopy for femoroacetabular impingement syndrome (FAIS) at 10-year minimum follow-up.
A prospectively collected clinical repository was evaluated for cases of primary hip arthroscopy for FAIS between January 2012 and February 2013 with minimum 10-year follow-up. Patients who underwent secondary surgery were propensity matched 1:4 to patients who did not undergo secondary surgery, controlling for age, sex, and body mass index (BMI). The groups were compared on demographics, radiographs, intraoperative findings, operative procedures, and patient-reported outcomes. A Kaplan-Meier survivorship curve was generated. Among the reoperation-free survivors, minimal clinically important difference (MCID) and patient acceptable symptom state (PASS) achievement were recorded for Hip Outcome Score–Activities of Daily Living (HOS-ADL), Hip Outcome Score–Sports Specific (HOS-SS) subscales, modified Harris Hip Score (mHHS), 12-item international Hip Outcome Tool (iHOT-12), and Visual Analog Scale for Pain (VAS Pain).
Twenty-four reoperation patients (67% female; age 40.1 ± 14.3 years; BMI 27.2 ± 5.5) were matched to 96 reoperation-free patients (62% female; age 37.0 ± 10.8 years; BMI 25.2 ± 4.7, P ≥ .111). Mean follow-up was 10.3 ± 0.2 years. No preoperative demographic differences were found between groups. The reoperation group showed more high-grade cartilage defects on the acetabulum and femoral head (33% vs 8%, P = .004; 29% vs 7%, P = .007). A bimodal distribution of time to reoperation was evidenced independent of the secondary surgery performed. Among the reoperation-free survivors, MCID and PASS achievement was as follows: HOS-ADL (69.1%, 62.1%), HOS-SS (69.9%, 74.4%), mHHS (73.3%, 58.1%), iHOT-12 (n/a, 63.8%), and VAS-Pain (80.2%, 62.6%).
Patients requiring reoperation following primary hip arthroscopy for FAIS demonstrated more severe cartilage defects and a bimodal distribution of time to reoperation.
Level III, retrospective comparative case series.
Arthroscopic labral repair for femoroacetabular impingement: A systematic review
2022, Surgeon
The present systematic review investigated return to sport, patient reported outcome measures (PROMs), complications and subsequent progression to total hip arthroplasty (THA) in patients undergoing arthroscopic labral repair for FAI.
Following the PRISMA statement, the literature search was performed in February 2021. The outcomes of interest were: rate of return to sport, modified Harris Hip Score (mHHS), the subscales Activities of Daily Living and Sport-Specific Subscale of the Hip Outcome Score (HOS-ADL and HOS-SSS, respectively). Complications, revision surgeries and progression to total hip arthroplasty were recorded.
Data from 210 procedures were retrieved. The mean follow-up was 34.0 (24.0–42.5) months. The mean age of the patients was 32.0 (20.0–47.0) years, while the mean BMI was 20.9 (20.1–21.7) kg/m². 52.8% (111 of 210 patients) were women. At 24-month follow-up, 100% of the patients had returned to sport. At a mean of 34 months follow-up, the mean mHHS increased by 25.5% (P = 0.02), the mean HOS-ADL by 23.0% (P = 0.03), the mean HOS-SSS by 32.8% (P = 0.001). No complications were observed. The rate of revision was 4.3% (9 of 210 procedures). At a mean of 37.9 ± 7.5 months, 1.9% of patients (4/210) underwent THA.
Arthroscopic labral refixation for FAI yields reliably positive clinical outcomes, with a low rate of revision and conversion to THA.
Preoperative Alpha Angles Can Predict Severity of Acetabular Rim Chondral Damage in Symptomatic Cam-Type Femoroacetabular Impingement: A Prospective Observatory Study
2022, Arthroscopy - Journal of Arthroscopic and Related Surgery
Citation Excerpt :
However, it should be noted that patient characteristics between the present and the aforementioned studies were different. All of the aforementioned studies not only included patients of cam-type FAI but also included patients who received hip arthroscopy for mixed type FAI, pincer-type FAI, borderline dysplasia or intra-articular pathologies.3,4,16-18 The current study only included patients with the diagnosis of symptomatic cam-type FAI with/without focal pincer-type FAI, and the LCEA of the involved hip was between 25° and 39°.
To identify the relationship between the alpha angle and the severity of chondrolabral separation as well as acetabular rim chondral damage in symptomatic cam-type femoroacetabular impingement (FAI) with or without focal pincer-type FAI.
Patients who received hip arthroscopy under the diagnosis of symptomatic cam-type FAI between January 2018 and August 2018 were identified in a prospectively collected database. Patients were excluded if preoperative lateral center-edge angle <25°, lateral center-edge angle ≥40°, Tönnis grade >1, with previous surgery on the affected hip, or with concomitant synovial disease. The chondrolabral junction was classified into intact chondrolabral junction, stable chondrolabral separation and unstable chondrolabral separation. The classification of acetabular rim chondral damage was modified from the MAHORN (Multicenter Arthroscopy of the Hip Outcomes Research Network) classification: normal/softening, bubble, pocket, flap, and exposed bone. The relationship between the hip morphology and severity of chondrolabral junction and acetabular rim chondral damage was assessed.
A total of 71 patients with the mean age of 33.2 ± 11.0 years were included. Preoperative alpha angles on anteroposterior (AP) or Lauenstein view positively correlated with the severity of acetabular rim chondral damage (P = .028 and P = .016, respectively). A significant increment of the alpha angle between 2 consecutive grades of acetabular rim chondral damage was 7.1° (P = .001) on AP view and 5.2° on Lauenstein view (P = .001). The cut-off values for predicting advanced acetabular rim chondral damage (pocket, flap or bony exposure) were an AP alpha angle of 70° (P = .025) and a Lauenstein alpha angle of 57° (P = .003). There was no significant association between the alpha angle and the severity of chondrolabral separation.
In patients with symptomatic cam-type FAI with or without focal pincer-type FAI, greater preoperative alpha angles on AP and Lauenstein views can predict more severe acetabular chondral damage.
Level III.
Combination of Anterior Acetabular Coverage and Femoral Head Shape Predicts Femoroacetabular Impingement After Periacetabular Osteotomy
2022, Journal of Arthroplasty
Femoroacetabular impingement (FAI) after periacetabular osteotomy (PAO) may be affected by both anterior acetabular coverage and femoral head shape. This study aimed to radiographically evaluate the relationship of the combination of acetabular coverage and femoral head shape with the occurrence of FAI after curved PAO.
In this study, 76 hip joints from patients with symptomatic developmental dysplasia of the hip underwent curved PAO. The relationship between the combined postoperative anterior center-edge and alpha angles (ie, the combination angle) and the occurrence of postoperative FAI was evaluated. Clinical factors and the preoperative and postoperative 3-dimensional center-edge angles, acetabular versions, femoral versions, radiographic alpha angles of the femoral head, and the combination angle were measured and compared to clinical outcomes.
The modified Harris Hip Scores, University of California, Los Angeles activity scores, and acetabular coverage angles were significantly improved following curved PAO. Receiver operator characteristic curve analysis demonstrated that the combination angle over 108° may be a predictive factor for the occurrence of FAI after curved PAO. Multivariate analysis demonstrated that an age <40 years (odds ratio 6.6, 95% confidence interval 1.2-36.4, P = .037) and a combination angle <108° (odds ratio 9.2, 95% confidence interval 1.7-50.0, P = .010) were significantly associated with modified Harris Hip Scores ≧90 points.
A combination angle >108° may be a predictive factor for the occurrence of FAI after curved PAO and impaired clinical outcomes. To avoid postoperative FAI, we propose that osteochondroplasty of the femoral head should be performed for patients with preoperative combination angles >90°.

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Original ArticleRelationship Between Offset Angle Alpha and Hip Chondral Injury in Femoroacetabular Impingement

Section snippets

Methods

Results

Discussion

Conclusions

J Orthop Sci

Patterns of osteoarthritis of the hip

J Bone Joint Surg Br

Femoroacetabular impingement: A cause for osteoarthritis of the hip

Clin Orthop Relat Res

Acetabular labral tears rarely occur in the absence of bony abnormalities

Clin Orthop Relat Res

Arthroscopic management of femoroacetabular impingement: Osteoplasty technique and literature review

Am J Sports Med

Anterior femoroacetabular impingement: Part ITechniques of joint preserving surgery

Clin Orthop Relat Res

Hip morphology influences the pattern of damage to the acetabular cartilage: Femoroacetabular impingement as a cause of early osteoarthritis of the hip

J Bone Joint Surg Br

The contour of the femoral head-neck junction as a predictor for the risk of anterior impingement

J Bone Joint Surg Br

Comparison of six radiographic projections to assess femoral head/neck asphericity

Clin Orthop Relat Res

Original Article
Relationship Between Offset Angle Alpha and Hip Chondral Injury in Femoroacetabular Impingement