Alpha Angle Research Articles

IDENTIFYING RISK FACTORS FOR DISEASE PROGRESSION IN DEVELOPMENTAL DYSPLASIA OF THE HIP USING A CONTRALATERAL HIP MODEL

Developmental dysplasia of the hip can cause pain and premature osteoarthritis. However, the risk factors and timing for disease progression in young adults are not fully defined. This study identified the incidence and risk factors for contralateral hip pain and surgery after periacetabular osteotomy (PAO) on an index dysplastic hip.Patients followed for 2+ years after unilateral PAO were grouped by eventual contralateral pain or no-pain, based on modified Harris Hip Score, and surgery or no-surgery. Univariate analysis tested group differences in demographics, radiographic measures, and range-of-motion. Kaplan-Meier survival analysis assessed pain development and contralateral hip surgery over time. Multivariate regression identified pain and surgery risk factors. Pain and surgery predictors were further analyzed in Dysplastic, Borderline, and Non-dysplastic subcategories, and in five-degree increments of lateral center edge angle (LCEA) and acetabular inclination (AI).184 patients were followed for 4.6±1.6 years, during which 51% (93/184) reported hip pain and 33% (60/184) underwent contralateral surgery. Kaplan-Meier analysis predicted 5-year survivorship of 49% for pain development and 66% for contralateral surgery. Painful hips exhibited more severe dysplasia than no-pain hips (LCEA 16.5º vs 20.3º, p<0.001; AI 13.2º vs 10.0º p<0.001). AI was the sole predictor of pain, with every 1° AI increase raising the risk by 11%. Surgical hips also had more severe dysplasia (LCEA 14.9º vs 20.0º, p<0.001; AI 14.7º vs 10.2º p<0.001) and were younger (21.6 vs 24.1 years, p=0.022). AI and a maximum alpha angle ≥55° predicted contralateral surgery.5 years after index hip PAO, 51% of contralateral hips experience pain and 34% percent are expected to need surgery. More severe dysplasia, based on LCEA and AI, increases the risk of contralateral hip pain and surgery, with AI being a predictor of both outcomes. Knowing these risks can inform patient counseling and treatment planning.

Three-dimensional analysis of age and sex differences in femoral head asphericity in asymptomatic hips in the United States.

The sphericity of the femoral head is a metric used to evaluate hip pathologies and is associated with the development of osteoarthritis and femoral-acetabular impingement. To analyze the three-dimensional asphericity of the femoral head of asymptomatic pediatric hips. We hypothesized that femoral head asphericity will vary significantly between male and female pediatric hips and increase with age in both sexes. Computed tomography scans were obtained on 158 children and adolescents from a single institution in the United States (8-18 years; 50% male) without hip pain. Proximal femoral measurements including the femoral head diameter, femoral head volume, residual volume, asphericity index, and local diameter difference were used to evaluate femoral head sphericity. In both sexes, the residual volume increased by age (P < 0.05). Despite significantly smaller femoral head size in older ages (> 13 years) in females, there were no sex-differences in residual volume and aspherity index. There were no age-related changes in mean diameter difference in both sexes (P = 0.07) with no significant sex-differences across different age groups (P = 0.06). In contrast, there were significant increases in local aspherity (maximum diameter difference) across whole surface of the femoral head and all quadrants except the inferior regions in males (P = 0.03). There were no sex-differences in maximum diameter difference at any regions and age group (P > 0.05). Increased alpha angle was only correlated to increased mean diameter difference across overall surface of the femoral head (P = 0.024). There is a substantial localized asphericity in asymptomatic hips which increases with age in. While 2D measured alpha angle can capture overall asphericity of the femoral head, it may not be sensitive enough to represent regional asphericity patterns.

The Feasibility of Prenatal Ultrasonic Screening for Developmental Dysplasia of the Hip.

developmental dysplasia of the hip (DDH) is a condition characterized by abnormal hip development in infancy. Early diagnosis allows for effective treatment, while late presentation often necessitates complex surgical interventions. Current recommendations advise screening between the 6th and 8th week postnatal using an ultrasound, typically employing the Graf method. However, there is no universal consensus on whether ultrasound screening significantly increases treatment likelihood compared to clinical examination-guided ultrasound. This study aims to explore the feasibility of prenatal ultrasound for the early identification of DDH risk. This prospective observational study involved 100 pregnant women undergoing fetal hip ultrasounds during the second and third trimesters. Using the modified Graf method, alpha and beta angles were calculated on the fetus. Postnatally, alpha and beta angles were compared with the prenatal values. Prenatal ultrasound at the 24th week showed inconclusive results because of the difficulty in identification of Graf landmarks, while ultrasound at the 34th week proved to be a reliable and safe method for the quantitative determination of alpha and beta angles. Significant correlations were found between prenatal and postnatal alpha and beta angles. Moreover, significant differences in prenatal alpha and beta values were observed in patients developing mature/immature hips postnatally. Prenatal diagnostics show promise for predicting infant hip development. Further research is warranted to validate correlation strength and clinical applicability.

Oblique Dorsiflexion Osteotomy of the Distal Tibia for Fixed Ankle Equinus: Surgical Technique.

There are significant challenges in the treatment of a severe rigid ankle equinus caused by a flat-topped talus, arthrogryposis, burn sequelae, or extensive scarring. Conventional approaches, such as soft tissue releases, often fail due to joint incongruence or compromised soft tissues, thereby necessitating supramalleolar osteotomies. The classic transverse supramalleolar osteotomy (TSO) of the distal tibia can lead to secondary anterior translation of the centre of rotation of the ankle and alters mechanical and anatomical axes. An alternative technique involves an oblique closing wedge osteotomy of the distal tibia, with a fulcrum near the ankle joint. This technical note delineates the planning parameters and procedural steps for the oblique dorsiflexion osteotomy of the distal tibia (ODODT). Using an anterior approach to the distal tibia, the "alpha angle," which determines the size of the closing wedge required for the foot to be plantigrade, is resected with a fulcrum at the most posterior part of the ankle joint, ensuring that the posterior cortex remains intact. The inclination of this resected wedge is planned preoperatively and is referred to as the "beta angle." This aims to equalise the lengths on both sides of the osteotomy. For osteotomy fixation, 2 or 3 cannulated screws in lag mode are employed. Postoperatively, a short cast boot is used for 6 weeks. The ODODT is a salvage solution for severe rigid ankle equinus when first-line foot and ankle procedures are impractical due to tibiotalar incongruence or poor soft tissues. Advantages include minimal translation of the centre of rotation of the ankle, excellent stability when the posterior cortex remains intact, avoidance of large internal fixation devices, and cost-effectiveness, making it suitable for low-resource settings. Olleac R, Farfan F, Acosta L, et al. Oblique Dorsiflexion Osteotomy of the Distal Tibia for Fixed Ankle Equinus: Surgical Technique. Strategies Trauma Limb Reconstr 2024;19(2):104-110.

High incidence of femoroacetabular impingement deformity in bi-column acetabular fractures.

Dynamic interaction of cam and pincer deformities can result in pathological contact forces in femoroacetabular impingement (FAI) syndrome. Similar deformities were noted during acetabular fracture reconstruction. We hypothesise that the prevalence of FAI deformity is higher in patients sustaining acetabular fractures than in a control group. This retrospective radiographic study compared the parameters that define FAI deformity in 100 patients consecutively admitted to a trauma unit with an acetabular fracture and a control group of 100 patients with lateral compression pelvic fracture without acetabular injury. Both underwent identical clinical imaging. Centre-edge angles (CEA) and alpha angles were used to define patients with pincer, cam, or mixed FAI deformity. There were significantly more patients with FAI deformity in the acetabular fracture group than in the control group (71% vs. 18%, p < 0.0001). There were considerably more fractures involving both anterior and posterior acetabular columns in patients with 'pincer' sockets (p = 0.02, OR = 2.95, 95% CI, 1.12-7.78). There is a high prevalence of cam and pincer deformities in patients with acetabular fractures, particularly bi-column fractures.

Association Between Alpha Angle and Acetabular Index in Screening for Developmental Dysplasia of the Hip.

Developmental dysplasia of the hip (DDH) is a critical orthopedic condition ranging from minor hip joint instability to complete dislocations, demanding early intervention to avoid severe complications, especially in children. In Mexico, stringent regulations under the Norma Oficial Mexicana (NOM) mandate hip screening for pediatric patients. The primary objective of this study is to investigate the relationship between alpha angles and the acetabular index in patients at six months of age, aiming to determine whether an increase in the alpha angle correlates with a better acetabular index. We included 120 patients who were screened for hip issues with Graf's methodology in June 2023 and September 2023 at the General Hospital of Mexico "Dr. Eduardo Liceaga" in Mexico City before three months of age and attended their follow-up appointment at six months of age, where acetabular index measurement was performed using the Carestream platform on institutional X-rays. In our statistical analysis, we obtained a statistically significant relationship between an increase in the left hip alpha angle and a decrease in the left hip acetabular index (p=0.015)although it was not significant for an acetabular index of less than 25° (p=0.055). A significant relationship was observed between the right hip acetabular index and the right hip alpha angle (p=0.017) but not significant for an acetabular index less than 25° (p=0.10). Universal hip screening is crucial for the early detection of DDH. Our study emphasizes using alpha-angle measurements (>70°) as reliable indicators of normal hip health.

Distribution of angle alpha and angle kappa offsets among adult candidates for cataract surgery.

The current study aimed to describe the distribution of angle alpha and angle kappa offsets as well as their associated ocular biometric parameters in a large population of candidates for cataract surgery. This cross-sectional retrospective study included 8,119 eyes of 4,781 candidates for cataract surgery (mean age 70.7 ± 12.9 years). There were 49.9% right eyes, and 53.0% patients were females. The angles offset and ocular biometric parameters were measured by the IOLMaster 700 (Carl Zeiss Meditec, AG, Germany). Patient's age and gender, and most of their ocular biometric measurements were similar for the right and left eyes except for pupil diameter (4.01 ± 1.18 vs. 3.92 ± 1.14 mm, respectively, P< 0.001). The angle alpha offset magnitude was similar for the right and left eyes (0.50 ± 0.20 and 0.51 ± 0.21 mm, P= 0.08), whereas the angle kappa offset magnitude was greater in the right eyes (0.37 ± 0.21 vs. 0.33 ± 0.20 mm, P< 0.001). The angle kappa offset magnitudes were greater in the right eyes compared to the left eyes for both males (0.36 ± 0.21 vs. 0.33 ± 0.21 mm, respectively, P< 0.001) and females (0.37 ± 0.20 vs. 0.34 ± 0.20 mm, respectively, P< 0.001). The offset magnitudes of both angles varied significantly according to gender, eye laterality, angle location, and biometric parameters (e.g., axial length). The offset magnitudes of both angles were positively correlated in both right and left eyes. The offset magnitudes of both the angle alpha and angle kappa present significant variations according to gender, eye laterality, angle location, and biometric parameters, such as AL. These values are also population-specific.

Are hip joint imaging findings associated with symptoms and early hip osteoarthritis features in elite male Australian Football League draftees?

ABSTRACT 1) describe intra-articular features (prevalence and severity) and bony hip morphology (prevalence and size) in elite male Australia Football League (AFL) draftees; 2) examine the relationship between bony hip morphology (cam and pincer morphology) and intra-articular features (cartilage defects and labral tears); and 3) examine the relationship between intra-articular features, bony hip morphology, and the Copenhagen Hip and Groin Outcome Score (HAGOS). Cross-sectional study. 58 male AFL draftees underwent 3-tesla hip MRI. Alpha angle determined cam morphology and acetabular depth defined pincer morphology. For each hip, intra-articular features were scored semi-quantitatively. All players completed the HAGOS to determine hip/groin symptoms and sports function. Logistic regression determined whether bony hip morphology was associated with labral tears and cartilage defects. Mann-Whitney U tests evaluated the difference in HAGOS subscale scores between football players with and without intra-articular features and bony hip morphology. Cam and pincer morphology were evident in 20% and 19% of hips, respectively. Nearly half of hips (41%) had a labral tear, with only 14% having a cartilage defect. Greater alpha angle was associated with the presence of labral tears (OR 1.14, 95%CI 1.07 to 1.21, p < 0.001) but not cartilage defects. Hip imaging findings were not associated with lower (worse) HAGOS scores. Hip joint imaging findings were common in elite male AFL draftees but not associated with worse pain, symptoms, or sport function. Cam morphology may contribute to the development of labral tears in male AFL draftees.

Outcomes of the Modified Dunn Procedure Versus Delayed Imhauser Osteotomy for Moderate to Severe Stable Slipped Capital Femoral Epiphysis.

Traditional management of moderate to severe stable slipped capital femoral epiphysis (SCFE) has been in situ fixation followed by reconstructive surgery if symptoms arise. This delayed approach may lead to irreversible intra-articular damage of the hip over time. The purpose of this study was to compare radiographic and clinical outcomes of the modified Dunn procedure (MDP) versus in situ fixation followed by delayed Imhauser osteotomy (DIO). This was a retrospective study from a single institution between 2001 and 2021. Among 250 patients diagnosed with SCFE, a total of 18 (18 hips) treated with MDP and 16 (18 hips) treated with DIO for moderate to severe stable SCFE were included. Most patients who underwent DIO either had concomitant (11/18 hips) or subsequent (2/18 hips) open osteochondroplasty. Mean follow up was 4.7 years (range: 1 to 12.8y). Radiographs were reviewed to measure Southwick angle, anteroposterior and lateral alpha (α) angles, and femoral head-neck offset ratio preoperatively and at latest follow up. Charts were reviewed for demographics, subsequent surgeries, complications, and Heyman-Herndon clinical outcomes. The amount of deformity correction was greater in the MDP than DIO group based on anteroposterior α angles (mean: 22.3 vs. 11.9 degrees, P =0.046) and femoral head-neck offset ratios (mean: 0.26 vs. 0.12, P =0.001). There was no significant difference in Heyman-Herndon scores (both 16/18, 88.9% good to excellent outcomes, P >0.999). Less reoperations were performed in the MDP than DIO group (2/18, 11.1% vs. 9/18, 50%; P =0.004). AVN occurred in 2/18 hips (11.1%) in the MDP group with both surgeries performed early in the series and underwent prior in situ screw fixation compared with 0/18 hips (0%) in the DIO group ( P =0.486). One patient in the DIO group was later diagnosed with osteoarthritis. MDP resulted in more anatomic coronal and sagittal plane deformity correction, less reoperations, and similar Heyman-Herndon clinical outcomes compared with DIO. AVN occurred in the MDP group whereas osteoarthritis occurred in the DIO group. These complications must be weighed against improved long-term clinical results for patients who would otherwise be at risk for premature degenerative joint disease due to residual proximal femoral deformity. Level III-retrospective comparative study.

The different subtypes of cam morphology as defined by statistical shape modeling and their relationship with the development of hip osteoarthritis: A nationwide prospective cohort study (CHECK) with 10 years follow-up

ObjectiveTo determine if subtypes of cam morphology on anteroposterior (AP) radiographs exist using statistical shape modelling (SSM), and to assess their association with incident radiographic hip osteoarthritis (RHOA) within 10 years. DesignThe nationwide prospective Cohort Hip and Cohort Knee (CHECK) study included 1,002 participants aged 45-65 years with 10-year follow-up. Subtypes of cam morphology were defined as SSM-based shape variations of femoral head-neck junction that are associated with baseline cam morphology (alpha angle ≥60°). The association between each subtype in hips free of osteoarthritis at baseline (Kellgren & Lawrence (KL) grade <2) and incident RHOA (KL grade≥2, or a total hip replacement) was estimated using logistic regression at 10-year follow-up and stratified by sex. ResultsIn sex-combined group, but also for males and females separately, cam morphology subtypes were captured in modes 1, 3, 4, and 5 with odds ratios (ORs) ranging from 0.39(0.27-0.58) to 2.25(1.64-3.10). For sex-combined group, only mode 3, a flattened head-neck junction, was associated with incident RHOA (OR:1.14, 1.02-1.27). Males’ modes 1 and 3 and females’ modes 3 and 4 were associated with RHOA. Notably, the female mode 4, a slightly flattened neck but with subtle curvature, was significantly protective for RHOA (OR:0.88, 0.80-0.98). ConclusionsWe identified four distinct morphological subtypes of cam morphology defined by alpha angle. Only some subtypes were found acting as risk factors for RHOA at 10-year follow-up, which differed between males and females. This highlights the need to study cam morphology beyond the alpha angle alone.

Borderline Developmental Dysplasia of the Hip With Osseous Impingement as Distinct From Femoroacetabular Impingement and Developmental Dysplasia of the Hip.

Borderline developmental dysplasia of the hip (BDDH) accompanied by cam deformity and subspinous impingement has been found to benefit from arthroscopic surgery. However, the research comparing BDDH combined with osseous impingement to femoroacetabular impingement (FAI) without borderline dysplasia remains limited. To compare the clinical symptoms, intraoperative findings, and outcomes of hip arthroscopy in patients with BDDH and osseous impingement versus cam-type FAI. It was hypothesized that BDDH with osseous impingement could be classified as a distinct entity between FAI and developmental dysplasia of the hip (DDH). Cohort study; Level of evidence, 3. Data were collected from patients 18 to 50 years old who underwent primary hip arthroscopy between September 2016 and October 2020. Patients were divided based on preoperative lateral center-edge angle (LCEA) into 2 groups: (1) BDDH group (LCEA 18°-25°; n = 67); and (2) cam-type FAI group without BDDH (FAI group; LCEA 25°-40° and alpha angle >55°; n = 145). Disparities in symptoms, preoperative examination, intraoperative findings and procedures, and patient-reported outcome (PRO) scores were compared. Follow-up was available for 61 (91.0%) patients in the BDDH group and 125 (86.2%) patients in the FAI group. The incidence of cam deformity in BDDH patients was 91.8%. The preoperative characteristics and intraoperative findings were similar between the groups; however, preoperative internal and external hip rotation, Tönnis angle, femoroepiphyseal acetabular roof index, labral size, capsule thickness, and percentage of ligamentum teres tear were significantly higher in the BDDH group than the FAI group, and the percentage of pain aggravating factor, cam deformity, and anterior inferior iliac spine types 2 and 3 were also significantly different between groups (P < .05 for all). The percentage of intraoperative minimal acetabuloplasty, subspinous decompression, labral repair, ligamentum teres debridement, and capsular closure was significantly higher in the BDDH group than the FAI group, while the percentage of femoroplasty was higher in the FAI group (P < .05). Pre- to postoperative improvement on PRO scores was seen in both groups. Given the differences in etiology and surgical procedures between the 2 conditions, it is suggested that BDDH with osseous impingement be classified as an entity distinct from FAI and DDH (and separate from BDDH without impingement) while excluding joint instability.

Reliability and agreement of manual and automated morphological radiographic hip measurements

ObjectiveTo determine the reliability and agreement of manual and automated morphological measurements, and agreement in morphological diagnoses. MethodsThirty pelvic radiographs were randomly selected from the World COACH consortium. Manual and automated measurements of acetabular depth-width ratio (ADR), modified acetabular index (mAI), alpha angle (AA), Wiberg center edge angle (WCEA), lateral center edge angle (LCEA), extrusion index (EI), neck-shaft angle (NSA), and triangular index ratio (TIR) were performed. Bland-Altman plots and intraclass correlation coefficients (ICCs) were used to test reliability. Agreement in diagnosing acetabular dysplasia, pincer and cam morphology by manual and automated measurements was assessed using percentage agreement. Visualizations of all measurements were scored by a radiologist. ResultsThe Bland-Altman plots showed no to small mean differences between automated and manual measurements for all measurements except for ADR. Intraobserver ICCs of manual measurements ranged from 0.26 (95%-CI 0–0.57) for TIR to 0.95 (95%-CI 0.87–0.98) for LCEA. Interobserver ICCs of manual measurements ranged from 0.43 (95%-CI 0.10–0.68) for AA to 0.95 (95%-CI 0.86–0.98) for LCEA. Intermethod ICCs ranged from 0.46 (95%-CI 0.12–0.70) for AA to 0.89 (95%-CI 0.78–0.94) for LCEA. Radiographic diagnostic agreement ranged from 47% to 100% for the manual observers and 63%–96% for the automated method as assessed by the radiologist. ConclusionThe automated algorithm performed equally well compared to manual measurement by trained observers, attesting to its reliability and efficiency in rapidly computing morphological measurements. This validated method can aid clinical practice and accelerate hip osteoarthritis research.

The Association Between the Development of Cam Morphology During Skeletal Growth in High-Impact Athletes and the Presence of Cartilage Loss and Labral Damage in Adulthood: A Prospective Cohort Study With a 12-Year Follow-up

Background: Cam morphology develops during skeletal growth, but its influence on cartilage and the labrum in high-impact athletes later in life is unknown. Purpose: To (1) explore the association between the presence and duration of cam morphology during adolescence and the cartilage and labral status 7 to 12 years later and (2) report the prevalence of cartilage loss and labral damage in a population of young male athletes (<32 years old) who played professional soccer during skeletal growth. Study Design: Cohort study (Prognosis); Level of evidence, 2. Methods: A total of 89 healthy male academy soccer players from the Dutch soccer club Feyenoord (aged 12-19 years) were included at baseline. At baseline and 2.5- and 5-year follow-ups, standardized supine anteroposterior pelvis and frog-leg lateral radiographs of each hip were obtained. At 12-year follow-up, magnetic resonance imaging of both hips was performed. Cam morphology was defined by a validated alpha angle ≥60° on radiographs at baseline or 2.5- or 5-year follow-up when the growth plates were closed. Hips with the presence of cam morphology at baseline or at 2.5-year follow-up were classified as having a “longer duration” of cam morphology. Hips with cam morphology only present since 5-year follow-up were classified as having a “shorter duration” of cam morphology. At 12-year follow-up, cartilage loss and labral abnormalities were assessed semiquantitatively. Associations were estimated using logistic regression, adjusted for age and body mass index. Results: Overall, 35 patients (70 hips) with a mean age of 28.0 ± 2.0 years and mean body mass index of 24.1 ± 1.8 participated at 12-year follow-up. Cam morphology was present in 56 of 70 hips (80%). The prevalence of cartilage loss was 52% in hips with cam morphology and 21% in hips without cam morphology (adjusted odds ratio, 4.52 [95% CI, 1.16-17.61]; P = .03). A labral abnormality was present in 77% of hips with cam morphology and in 64% of hips without cam morphology (adjusted odds ratio, 1.99 [95% CI, 0.59-6.73]; P = .27). The duration of cam morphology did not influence these associations. Conclusion: The development of cam morphology during skeletal growth was associated with future magnetic resonance imaging findings consistent with cartilage loss in young adults but not with labral abnormalities.

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

PurposeThe 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. MethodsAnthropometric 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. ResultsCam 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. ConclusionIn 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.

Combined assessment of acetabular coverage and femoral head-neck shapes predicts osteoarthritis progression after periacetabular osteotomy.

Postoperative osteoarthritis (OA) progression is a major determinant of failure after curved periacetabular osteotomy (CPO). A large postoperative combination angle, i.e., the combination of computed tomography-based anterior center edge and alpha angles, is associated with femoroacetabular impingement after CPO, but its association with postoperative OA progression is unclear. We aimed to identify the anatomical parameters that can lead to OA progression after CPO and the impact of the combination angle on the same. We included 90 hips that were subjected to CPO at our center between March 2013 and March 2018. Seventeen hips showed OA progression with an increase in the Tönnis classification after surgery; 73 hips showed no progression. Radiographic anatomical parameters, including the lateral and anterior center edge angles, femoral and acetabular anteversion, and combination angle, and clinical outcomes, including modified Harris Hip Scores (mHHSs), postoperative anterior impingement, and range of motion, were compared between the two groups. Statistical significance was set at P < 0.05. Postoperative OA progression was significantly affected by preoperative OA evidence (P = 0.017), acetabular anteversion < 5.0° (P = 0.003), and a combination angle > 107.0° (P = 0.025). Patients with radiographic OA progression were associated with poor mHHSs (P = 0.017) and high frequencies of anterior impingement with a limited hip flexion and internal rotation angle. OA progression after CPO may be associated with preoperative evidence of OA and postoperative acetabular retroversion as well as a large combination angle. Surgeons should focus on the potential effects of preoperative OA grades, postoperative reduction in acetabular anteversion, and postoperative combination angle.

Poster 218: Localized Acetabular Bone Density Distributions Are Altered in Unilateral Femoral Acetabular Impingement

Objectives: Femoral acetabular impingement (FAI) can lead to bony and cartilage changes at the joint, and it has been suggested that changes in bone mineral density in the acetabulum may correlate with osteoarthritic degeneration of the hip. In this study, we aimed to use opportunistic quantitative computed tomography (QCT) to map density distributions across the acetabular region in patients with unilateral FAI and determine if there were differences between the affected and unaffected side. Furthermore, we assessed if these differences in density distributions were associated with radiographic measures of FAI. Methods: Twenty patients (age 31.9 (SD 9.2), 13 female) who underwent surgery for unilateral FAI and had an associated CT scan of both hips were included in this retrospective study. Both sides of the pelvis were segmented, and 3D models were created. Estimated bone density values were mapped across the bone models via QCT. A thin-spline semi-landmarking approach was used to allow density values at equivalent anatomical points to be compared within patients and across the group. With the contralateral side used as the control, differences in bone density between sides were calculated. A mixed effect linear regression model was used to determine if there were associations between the localized bone density and radiographic measures of Tonnis grade, alpha angle, lateral center edge angle (LCEA), and cross over sign, while controlling for age and sex. To visualize the data, density changes and statistical results were color-mapped to the bone models. Results: Overall, several regions of the acetabulum were found to have increased bone density in the affected side compared to the contralateral (Figure 1). Specifically, the anterior-superior parts of the acetabular rim appeared to be most affected, along with the posterosuperior region (Figure 2). Limited associations were found between localized density and the clinical variables, with the most notable finding being a region of the superior rim that was found to be associated with the alpha angle (Figure 3). Conclusions: FAI leads to distinct patterns of bone density changes around the acetabulum, although there is still variability at the level of the individual patient. It is unclear whether these changes in bone density may be related to the underlying condition, alterations in the patient’s mechanics due to pain, or a combination of these factors. Providing detailed density maps of the bony anatomy may also assist surgical providers in planning interventions. Further research may elucidate the relationship between bone density changes and long-term degeneration of the joint.

Paper 18: The Pendulum Has Swung: A 14-Year Analysis of Patients Presenting for Failed Hip Arthroscopy Shows Rising Incidence of Cam Over-Resection and Decreasing Incidence of Under-Resection

Background: There is a paucity of literature regarding prevalence of femoral resection in the setting of revision hip arthroscopy. Few studies have examined different types of resections and their presentation. Purpose: To describe the prevalence of femoral resection types in the setting of revision hip arthroscopy for residual femoroacetabular impingement syndrome (FAIS) symptomatology. Methods: A search of the institutional prospective registry was performed for patients who presented for evaluation of failed previous arthroscopy between February 2008 and June 2022, and subsequently underwent revision arthroscopy. AP and Dunn view radiographs were reviewed from our study population. On the basis of measurements on both radiographs, patients were divided into 3 categories: overresection (OR) in which the resection measured 5% or more of the femoral head diameter, underresection (UR) in which residual CAM morphology was found (alpha angle &gt;60°), and neutral resection, alpha angle less than 60° and no overresection. Both AP and Dunn radiographs were used to identify over- and under- resections. Results: A total of 622 hips were reviewed and measured on both AP and Dunn radiographs. Of the 622 hips, there were 373 right and 249 left hips. The average age was 33.7 ± 12.0, and the average body mass index (BMI) was 26.0 ± 5.2. Three hundred sixty-five hips were classified as UR and 265 hips as OR. The mean prevalence rates from 2008 to 2022 for neutral resection, over-resection and under-resection were 48.1%, 20.3%, and 31.6%, respectively. The prevalence rates of UR have decreased since 2008, while prevalence rates of OR have increased concomitantly. The steadily decreasing prevalence rates of UR was negatively correlated with the increasing OR ((R=-0.829, P&lt;.0001), as well as with neutral resections (R=-0.735, P=0.002). The ratio of UR to OR reversed entirely, from 4:1 in 2010, to 1: 2.3 ( P &lt; 0.00001) in 2020. Conclusions: Amongst patients presenting for failed hip arthroscopy over the last 14 years, the pendulum has swung from under-resection towards over-resection. Indeed, as of 2020, over-resections were more than twice as common as under-resections. This may be a result of heightened awareness in FAIS, and previous literature emphasizing the risks of under-resection. As we gain increased understanding of the risks of over-resection, the findings of this study highlight the importance of achieving an anatomical spherical resection.

Paper 46: Modern Hip Arthroscopy for FAIS Delays the Natural History of Osteoarthritis in a Fourth of Patients: A 12-Year Follow-Up Analysis

Objectives: Little is known about the impact of modern hip arthroscopy on the natural history of femoroacetabular impingement syndrome (FAIS) with respect to joint preservation. The purpose of this investigation was to (1) characterize the natural history of FAIS and (2) understand the impact of modern hip arthroscopy by radiographically comparing the hips of patients who underwent only unilateral primary hip arthroscopy with a minimum follow-up of ten years. Methods: Between 2010-2012, 619 consecutive patients were reviewed from the practice of a single fellowship-trained hip arthroscopist. Inclusion criteria were FAIS, primary unilateral hip arthroscopy (labral repair, femoroplasty, capsular closure), and minimum ten-year follow-up. The preoperative and minimum ten-year postoperative radiographs of patients were evaluated at each timepoint. Both operative and nonoperative hips were graded using the Tönnis classification or the presence of hip arthroplasty by two independent reviewers. Subgroup analyses were performed. Results: A total of 200 hips from 100 patients were available with 74% follow-up at a mean of 12.0 years were evaluated. The nonoperative hip advanced to a worse Tönnis grade in 48% (48/100) of cases compared to 28% (28/100) among operative hips (Table 1). At follow-up, Tönnis grades between hips were equal in 70% (70/100) of the cases, the operative hip had a better grade 25% (25/100) of the time, and the nonoperative hip had a better grade 5% (5/100) of the time (Table 2). Modern hip arthroscopy conferred a relative risk reduction of 42% in osteoarthritis progression. Borderline dysplasia, age, preoperative Tönnis grade, and alpha angle &gt; 65° were key risk factors in the radiographic progression of osteoarthritis. Conclusions: While the majority of patients (70%) undergoing hip arthroscopy for FAIS did not experience differences between operative and nonoperative hips in terms of the radiographic progression of osteoarthritis, the natural history was favorably altered in a quarter of patients after arthroscopic correction (Figure 1). Modern hip arthroscopy indications and techniques represent a valid joint preservation procedure conferring a relative risk reduction of 42% in the progression of osteoarthritis. Mixed patterns of impingement and instability that underwent arthroscopy were the fastest to degenerate.

Paper 17: Does Higher Quality CAM Resection Correlate with Better Patient-Reported Outcomes?

Objectives: The relationships between CAM resection quality and patient-reported outcomes (PROs) are unknown in the literature. This study aimed to investigate the correlation of CAM resection quality with patient’s self-reported International Hip Outcome Tool (iHOT) scores collected annually post-surgery. Methods: A retrospective analysis was conducted including patients who underwent primary hip arthroscopy for femoroacetabular impingement (FAI) between 2012 and 2019. Inclusion criteria were pre-operative radiographic signs of CAM-type impingement (alpha angle &gt; 55 °) and post-operative plain radiographs. Exclusion criteria were radiographic signs of a pincer or mixed impingement, history of femoral neck or proximal femur fracture, and treatment of concomitant hip pathologies. The following data were collected: demographic information, radiographic findings, and iHOT scores. CAM resection quality data were categorized based on findings from three plain radiographs (anteroposterior (AP) pelvis, frog leg lateral, and 45° Dunn views). High quality resections were defined as those post-operative alpha angle &lt;55°. Results: This study included 148 participants who underwent CAM resection. From Frog leg views, 88% of patients had high-quality resections and presented superior post-operative iHOT scores compared to the 12% of patients with poor resection quality during the 1-year to 5-year follow-up period. Likewise, from Dunn views 82% of patients with a high-quality CAM resection displayed a similar trend in post-operative iHOT scores compared to 18% of patients with poor resection quality on Dunn views. However, this positive association between resection quality and post-operative iHOT scores was not evident in AP imaging. With AP views, 82% of patients with high-quality resections did not show a significant difference in iHOT scores compared to 18% of patients with poor resection quality. Conclusions: This study found that high quality CAM resection from arthroscopic surgery correlated with better iHOTs up to 5-years post-surgery from the Dunn and frog leg radiographic imaging views.

Poster 181: Hip Arthroscopy with Concomitant Periacetabular Osteotomy Demonstrates Excellent Outcomes and Survivorship at Minimum 10-Year Follow-Up

Objectives: Multiple studies have shown that hip arthroscopy with concomitant periacetabular osteotomy (PAO) is a safe and effective treatment option for patients presenting with Symptomatic acetabular dysplasia and intra-articular pathology. While excellent short- and mid-term outcomes have been previously reported, there exists a paucity of literature investigating long-term outcomes of hip arthroscopy with concomitant PAO. The purpose of this study was to report minimum 10-year follow-up results and survivorship of hip arthroscopy with concomitant PAO to treat acetabular dysplasia and intraarticular pathologies such as femoroacetabular impingement (FAI) and labral tears. Methods: Data from October 2010 to December 2012 was prospectively collected and retrospectively reviewed to identify patients undergoing hip arthroscopy with concomitant PAO. Patients were included in the present analysis if they had preoperative and minimum 10-year patient reported outcomes (PROs) documented for the modified Harris Hip Score (mHHS), Nonarthritic Hip Score (NAHS), Hip Outcome Scored Sports-Specific Subscale (HOS-SSS), and pain on a visual analog scale (VAS), as well as the International Hip Outcome Tool (iHOT-12) and patient satisfaction score on a 0-10 scale. Results: Fifteen patients were eligible for analysis and 12 had complete minimum 10-year follow-up (80.0%) at mean 10.2 years postoperation. There were 10 females (83.3%) and 2 males (16.7%) included in the study with a mean age and BMI of 24.4 years and 24.5 kg/m2, respectively. The mean lateral center-edge angle (LCEA) of all included hips in the analysis increased from 13.8° to 29.8° postoperatively ( P&lt;0.05) and the anterior center-edge angle (ACEA) increased from 14° to 28.8° postoperatively ( P&lt;0.05). Additionally, the Tönnis angle of acetabular inclination decreased from 17.9° to 7.3° postoperatively ( P&lt;0.05) and the alpha angle decreased from 56.5° to 52.1° postoperatively ( P&lt;0.05). There was significant improvement in all PROs from baseline to minimum 10-year follow-up (mHHS; NAHS; HOS-SSS, P&lt; 0.05). All patients achieved high rates of MCID for mHHS, NAHS, and HOS-SSS, as well as high rates of PASS for mHHS and VAS. The 10-year survivorship for all patients included in the analysis was 83.3% with 2 patients (16.7%) progressing to total hip arthroplasty (THA) at mean 58.0 months postoperatively. Additionally, 2 patients (16.7%) underwent subsequent ipsilateral revision hip arthroscopy at mean 79.5 months postoperatively. Conclusions: Patients with dysplasia and intra-articular pathology such as labral tears and FAI can be safely treated using hip arthroscopy with concomitant PAO. These patients can achieve excellent long-term outcomes and high rates of survivorship at minimum 10 years postoperation.