Femoroacetabular Impingement Is Associated With Sports-Related Posterior Hip Instability in Adolescents: A Matched-Cohort Study

Acetabular retroversion and cam morphology are contributing risk factors for posterior hip dislocation independent of the trauma mechanism

INTRODUCTION

A high-energy trauma impact is generally considered the crucial factor causing native hip dislocation. However, femoroacetabular variations are assumed to contribute to low-energy posterior hip dislocations, especially in adolescent athletes. The study aimed to analyze the femoroacetabular morphology of adults who sustained traumatic posterior hip dislocations, comparing high-energy, sports-related, and low-energy trauma mechanisms.

MATERIALS AND METHODS

One hundred forty-one patients with traumatic posterior hip dislocations were analyzed and matched to a control group of 141 patients with high-energy trauma mechanisms without hip or pelvic injury, matched for age, gender, and Body Mass Index (BMI). The trauma mechanism was analyzed, and the femoroacetabular morphology and concomitant femoral head or posterior acetabular wall fractures were assessed using computed tomography (CT) scans. Acetabular version, coverage, and pincer morphology were evaluated by measuring the lateral center-edge angle, acetabular index, acetabular depth/width ratio, cranial and central acetabular version angles, and the anterior and posterior acetabular sector angles (AASA, PASA). The caput-collum-diaphyseal (CCD) angle and coronal and axial alpha angles were measured to detect cam morphology.

RESULTS

A high-energy trauma caused posterior hip dislocations in 79.4%, sports-related mechanisms in 7.8%, and a low-energy impact in 12.8%. Patients with high-energy and sports-related dislocations exhibited a higher disposition for acetabular retroversion (p < 0.001). However, the acetabular version in low-energy mechanisms did not differ from the control group (p ≥ 0.05). Acetabular retroversion was associated with isolated dislocation, while acetabular overcoverage correlated with concomitant posterior acetabular wall fractures (p < 0.05). Alpha angles were significantly increased in patients with hip dislocations, independent of the trauma mechanism (p < 0.001).

CONCLUSION

Acetabular retroversion contributes to posterior hip dislocation in high-energy and sports-related trauma mechanisms and decreases the likelihood of sustaining concomitant fractures. Acetabular morphology was subordinate to causing hip dislocation following a low-energy impact. Increased alpha angles were identified as a risk factor contributing to posterior hip dislocations, regardless of the trauma mechanism.

Femoroacetabular Variations Are Predisposing Factors for Traumatic Posterior Hip Dislocation

BACKGROUND

Although high-energy trauma mechanisms are generally considered to cause traumatic posterior hip dislocations, femoroacetabular variations are assumed to contribute to low-impact hip dislocations. Thus, the present study aimed to identify morphologic femoral and acetabular risk factors that may also contribute to posterior hip dislocations in high-energy trauma mechanisms.

METHODS

The acetabular and femoral morphology of 83 hips with a traumatic posterior dislocation following a high-energy trauma mechanism were analyzed and matched to a control group of 83 patients who sustained high-energy trauma without a hip injury. The lateral center-edge angle, acetabular index, acetabular depth/width ratio, cranial and central acetabular version angles, and the anterior and posterior acetabular sector angles were measured on computed tomography to quantify femoroacetabular impingement (FAI) morphology, acetabular version, and coverage. The caput-collum-diaphyseal angle and the alpha angles in the coronal and axial planes were measured to detect cam-type FAI deformity. A receiver operating characteristic curve was utilized to determine threshold values for an increased risk of hip dislocation.

RESULTS

Acetabular retroversion and posterior acetabular undercoverage were significantly increased in patients with hip dislocations compared with controls (p < 0.001). The central acetabular version angle and posterior acetabular sector angle that indicated an increased risk of hip dislocation were ≤9° and ≤90°, respectively. Cam-type FAI deformity and coxa valga were significantly increased in the dislocation group (p < 0.001). The anterolateral alpha angle that indicated an increased dislocation risk was ≥47°.

CONCLUSIONS

Acetabular retroversion, posterior acetabular undercoverage, and cam-type FAI morphology may be risk factors contributing to traumatic posterior hip dislocation in high-energy trauma mechanisms.

LEVEL OF EVIDENCE

Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Patients With Simple Posterior Hip Dislocations Have Higher Rates of Hip Dysplasia and Borderline Dysplasia

OBJECTIVES

To determine if patients suffering simple, posterior hip dislocations are more likely to display dysplastic characteristics of their acetabulum as compared with those suffering fracture dislocations.

DESIGN

Retrospective cohort study.

SETTING

Level 1 trauma center.

PATIENTS/PARTICIPANTS

Eighty-six patients suffering posterior, native hip dislocations over a 5-year period.

MAIN OUTCOME MEASUREMENT

The primary outcome was measurement of the lateral center edge angle (LCEA), acetabular index (AI), acetabular version, and femoro-epiphyseal acetabular roof (FEAR) index.

RESULTS

Eighteen patients (20.9%) sustained simple dislocations, whereas 68 patients (79.1%) suffered fracture dislocations. Patients with simple dislocations had decreased LCEA (25.7 vs. 34.3; P < 0.001), increased AI (7.4 vs. 5.8; P = 0.019), and decreased acetabular anteversion (14.02 vs. 18.45; P = 0.011). Additionally, patients with simple dislocations had higher rates of dysplasia and borderline dysplasia (61.1% vs. 7.3%; P < 0.001). Patients with fracture dislocations had higher rates of concomitant injuries (60.9% vs. 29.4%; P = 0.039) and higher injury severity scores (8.1 vs. 12.3; P = 0.022).

CONCLUSION

Patients who sustain simple hip dislocations are more likely to have undercoverage of the femoral head by the acetabulum as compared with patients suffering fracture dislocations. In addition, the simple dislocation group had a lower ISS and fewer concomitant injuries, which likely relates to a lower energy required for dislocation in the setting of lesser bony constraint. Surgeons treating these complicated injuries should consider measurements of LCE and AI when counseling patients on treatment strategies.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Hip Dislocation and Subluxation in Athletes: A Systematic Review

BACKGROUND

Hip dislocation is a rare occurrence during sports but carries serious implications for athletes.

PURPOSE

To systematically review treatment strategies and outcomes for hip dislocation in athletes, with the ultimate goal of providing sports medicine physicians with the information necessary to appropriately treat and counsel patients sustaining this injury.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

PubMed, MEDLINE, and Embase were searched for studies relating to hip instability and athletics from January 1, 1989 to October 1, 2019. Abstracts and articles were evaluated on the basis of predefined inclusion and exclusion criteria. Inclusion criteria were the following: (1) data from ≥1 patients, (2) native hip dislocation or subluxation occurring during sports, (3) patients aged at least 10 years, and (4) written in English. Exclusion criteria were (1) patients younger than 10 years; (2) nonnative or postoperative hip dislocation or subluxation; (3) a native hip injury without dislocation or subluxation; (4) patients with dislocation or subluxation secondary to neuromuscular, developmental, or syndromic causes; (5) dislocation or subluxation not occurring during sports; (6) patients with physeal fractures; or (7) review articles or meta-analyses. Data were recorded on patient demographics, injury mechanism, treatment strategies, and clinical and radiographic outcomes. Where possible, pooled analysis was performed. Studies were grouped based on reported outcomes. Meta-analysis was then performed on these pooled subsets.

RESULTS

A total of 602 articles were initially identified, and after screening by 2 reviewers, 27 articles reporting on 145 patients were included in the final review. There were 2 studies that identified morphological differences between patients with posterior dislocation and controls, including decreased acetabular anteversion (P = .015 and .068, respectively), increased prevalence of a cam deformity (P < .0035), higher alpha angles (P≤ .0213), and decreased posterior acetabular coverage (P < .001). No differences were identified for the lateral center edge angle or Tonnis angle. Protected postreduction weightbearing was most commonly prescribed for 2 to 6 weeks, with 65% of reporting authors recommending touchdown, toe-touch, or crutch-assisted weightbearing. Recurrence was reported in 3% of cases. Overall, 4 studies reported on findings at hip arthroscopic surgery, including a 100% incidence of labral tears (n = 27; 4 studies), 92% incidence of chondral injuries, 20% incidence of capsular tears, and 84% incidence of ligamentum teres tears (n = 25; 2 studies). At final follow-up, 86% of patients reported no pain (n = 14; 12 studies), 87% reported a successful return to play (n = 39; 10 studies), and 11% had radiographic evidence of osteonecrosis (n = 38; 10 studies).

CONCLUSION

Various treatment strategies have been described in the literature, and multiple methods have yielded promising clinical and radiographic outcomes in patients with native hip dislocation sustained during sporting activity. Data support nonoperative treatment with protected weightbearing for hips with concentric reduction and without significant fractures and an operative intervention to obtain concentric reduction if unachievable by closed means alone. Imaging for osteonecrosis is recommended, with evidence suggesting 4- to 6-week magnetic resonance imaging and follow-up at 3 months for those with suspicious findings in the femoral head.

Interrater Reliability of the Prone Apprehension Relocation Test

Background:

The Prone Apprehension Relocation Test (PART) augments existing radiographic measures and clinical provocative maneuvers in diagnosing hip instability. One measure of the potential clinical utility of the PART depends on the reproducibility of test results by evaluating providers including physicians, licensed athletic trainers, and physical therapists.

Purpose:

To determine the interrater reliability of the PART among health care providers.

Study Design:

Cohort study (diagnosis); Level of evidence, 3.

Methods:

We retrospectively identified patients in our institution’s hip preservation registry who presented between September 2017 and June 2019 for evaluation of hip pain. Patients included in the study had the PART performed by a single physician as well as 1 of 12 physician extenders (a licensed athletic trainer or a physical therapist). The providers were blinded to the findings of the other examining professional. Interrater reliability was assessed using the Cohen κ (≥0.75 was considered excellent; between 0.75 and 0.40, moderate; and ≤0.40, poor).

Results:

A total of 96 patients (190 hips) were included in this study (61 women and 35 men, average age 32 ± 12.1 years). A total of 23 hips had a positive PART from both examiners. Interrater reliability was excellent between health care professionals for the PART when evaluating the right hip (κ = 0.80), left hip (κ = 0.82), and when combining the results for left and right (κ = 0.81). A subanalysis of patients with a positive PART from both raters demonstrated that 19 of the 23 hips had a lateral center-edge angle >25°.

Conclusion:

Our study demonstrated excellent interrater reliability of the PART, supporting its use in the physical evaluation of painful hips.

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.

Hip Instability in the Athlete: Anatomy, Etiology, and Management

In this review, the recent literature evaluating the anatomic considerations, etiology, and management options for athletes with hip instability are investigated. Studies on the osseous, chondrolabral capsuloligamentous, and dynamic muscular contributions to hip stability are highlighted. Microinstability, iatrogenic instability, and femoroacetabular impingement-induced instability are discussed with a focus on demographic and outcomes research in athletes. Surgical techniques including both open and arthroscopic approaches are additionally evaluated.

Cam Osteochondroplasty for Femoroacetabular Impingement Increases Microinstability in Deep Flexion: A Cadaveric Study

PURPOSE

The purpose of this in vitro cadaveric study was to examine the contributions of each surgical stage during cam femoroacetabular impingement (FAI) surgery (i.e., intact-cam hip, T-capsulotomy, cam resection, and capsular repair) toward hip range of motion, translation, and microinstability.

METHODS

Twelve cadaveric cam hips were denuded to the capsule and mounted onto a robotic tester. The hips were positioned in several flexion positions-full extension, neutral (0°), 30° of flexion, and 90° of flexion-and performed internal-external rotations to 5 Nm of torque in each position. The hips underwent a series of surgical stages (T-capsulotomy, cam resection, and capsular repair) and were retested after each stage. Changes in range of motion, translation, and microinstability (overall translation normalized by femoral head radius) were measured after each stage.

RESULTS

Regarding range of motion, cam resection increased internal rotation at 90° of flexion (change in internal rotation = +6°, P = .001) but did not affect external rotation. Capsular repair restrained external rotation compared with the cam resection stage (change in external rotation = -8° to -4°, P ≤ .04). In terms of translation, the hip translated after cam resection at 90° of flexion in the medial-lateral plane (change in translation = +1.9 mm, P = .04) relative to the intact and capsulotomy stages. Regarding microinstability, capsulotomy increased microinstability in 30° of flexion (change in microinstability [Δ_M] = +0.05, P = .003), but microinstability did not further increase after cam resection. At 90° of flexion, microinstability did not increase after capsulotomy (Δ_M = +0.03, P = .2) but substantially increased after cam resection (Δ_M = +0.08, P = .03), accounting for a 31% change with respect to the intact stage.

CONCLUSIONS

Cam resection increased microinstability by 31% during deep hip flexion relative to the intact hip. This finding suggests that iatrogenic microinstability may be due to separation of the labral seal and resected contour of the femoral head.

CLINICAL RELEVANCE

Our in vitro study showed that, at time zero and prior to postoperative recovery, excessive motion after cam resection could disrupt the labral seal. Complete cam resection should be performed cautiously to avoid disruption of the labral seal and postoperative microinstability.

Microinstability of the hip: a systematic review of the imaging findings

OBJECTIVES

To undertake a systematic review of the morphologic features associated with hip microinstability and determine whether there are suggestive or diagnostic imaging findings.

METHODS

Four electronic databases were searched up to September 2019 to identify original research reporting morphologic features in individuals with either a clinical diagnosis of hip microinstability (instability without overt subluxation/dislocation) or those with symptomatic laxity demonstrated on imaging (increased femoral head translation/distraction or capsular volume). Studies focussing on individuals with pre-existing hip conditions (including definite dysplasia (lateral centre edge angle < 20°), significant trauma, previous dislocation or surgery were excluded. Methodological quality was assessed by the Quality Assessment of Diagnostic Accuracy Studies 2 tool.

RESULTS

Twenty-two studies met inclusion criteria (clinical diagnosis of microinstability n = 15 and demonstration of laxity n = 7). Imaging information gathered from the studies includes radiographs (n = 14), MRI (n = 6), MR arthrography (n = 4), CT (n = 1) and intraoperative examination. Most studies exhibited design features associated with an overall high or unclear risk of bias. Some dysplastic features are associated with microinstability or laxity reference measures; however, microinstability is frequently diagnosed in those with a lateral centre edge angle > 25°. Other associated imaging findings reported include impingement morphology, anterior labral tearing, femoral head chondral injury, ligamentum teres tears and capsular attenuation.

CONCLUSIONS

The current literature does not provide strong evidence for imaging features diagnostic of microinstability. In the appropriate clinical context, dysplastic morphology, anterior labral tears and ligamentum teres tears may be suggestive of this condition although further research is needed to confirm this.

PROSPERO REGISTRATION

CRD42019122406.

Morphological abnormalities of the hip in acetabular fractures

Poor prognosis factors in surgical treatment of acetabular fracture-dislocations have been well established but there is little information about how morphological abnormalities of the hip may affect the surgical outcome. Hip anatomy has a wide range of variations. Morphological abnormalities of the hip can also be observed in patients with acetabular fractures. We present a case of a complication in a patient with a complex acetabular fracture, acetabular retroversion and femoroacetabular impingement. A 31-year old male patient was transferred to our trauma center following a high speed road traffic accident. Trauma series CT revealed cerebral contusion, subdural hematoma, aortic dissection and a left transverse plus posterior wall acetabular fracture. The left hip was reduced and the acetabular fracture was treated with a Kocher Langenbeck approach in prone position. The pelvic X- ray evidenced an anatomic reduction and signs of acetabular retroversion with positive posterior wall sign and crossover sign. CT scan evidenced increased alpha angle in the femoral head neck junction. During the follow up, 2 months after the acetabular fixation, patient suffered a posterior left hip dislocation and a total cementless hip arthroplasty was performed. Patients with acetabular retroversion and femoroacetabular impingement (CAM lesion) may be at risk of posterior dislocation. The influence of acetabular version and impingement may be also closely involved in how challenging the determination of hip stability can be in patients with posterior wall acetabular fractures. Acetabular retroversion and FAI may be related to the dislocation of unstable patterns with small fragments (wall sizes less than 20%). In this case postoperative precautions were not enough. We believe capsular reattachment with anchors and bracing may be useful in these selected cases. As these patients are not candidates for retroPAO (the recommended treatment for acetabular retroversion) maybe arthroscopic anterior wall riming and CAM resection should be performed at an early stage to decrease or avoid fulcrum.

Etiology and Pathomechanics of Femoroacetabular Impingement

PURPOSE OF REVIEW

Femoroacetabular impingement is a common cause of hip pain in young patients and has been shown to progress to osteoarthritis. The purpose of this review is to better understand the development of femoroacetabular impingement.

RECENT FINDINGS

Recent literature shows little genetic transmission of FAI. However, molecular studies show strong similarities with the cartilage in osteoarthritis. The development of cam lesions has a strong association with sports participation, particularly at the time of physeal closure suggesting abnormal development. Lumbar, pelvis, and femoral biomechanics may also play an important role in dynamic impingement. In summary, femoroacetabular impingement is a dynamic process with many influences. Further research is needed to clarify the pathophysiology of FAI development in hopes of finding preventative options to reduce symptoms and progression to osteoarthritis.

Hip Radiograph Findings in Patients Aged 40 Years and Under with Posterior Pelvic Pain

BACKGROUND

Several sacroiliac joint (SIJ) provocative tests used to assess posterior pelvic pain involve moving and stressing the hip. It is unknown if there is a subgroup of patients with posterior pelvic pain who have underlying hip deformity that could potentially influence performance and interpretation of these tests.

OBJECTIVE

To describe the prevalence of radiographic hip deformity and hip osteoarthritis in a group of adults 40 years old and under who met the clinical diagnostic criteria for treatment of posterior pelvic pain with an image guided intra-articular SIJ injection.

DESIGN

Retrospective cohort study.

SETTING

Tertiary university orthopedic department PATIENTS (OR PARTICIPANTS): One hundred and forty-eight patients were evaluated (83% (123/148) female; mean age 31.3 ± 6.2 years). All had completed a trial of comprehensive noninvasive treatment for posterior pelvic pain and had a minimum of three positive SIJ provocative tests on physical examination.

METHODS

Retrospective review identified patients undergoing SIJ injection for pain recommended and performed by seven physiatrists between 2011 and 2017. Hip radiographs were read by a physician with expertise in hip measurements with previously demonstrated excellent intrarater reliability.

MAIN OUTCOME MEASUREMENTS

Percentage of patients with hip deformity findings.

RESULTS

No patients meeting the inclusion criteria had significant radiographic hip osteoarthritis (Tonnis ≥2 indicating moderate or greater radiographic hip osteoarthritis) and 4/148 (3%) were found to have mild radiographic hip osteoarthritis. Prearthritic hip disorders were identified in 123 (83%, 95% CI: 76, 89%) patients. For those patients with prearthritic hip disorders, measurements consistent with femoroacetabular impingement (FAI) were seen in 61 (41%) patients, acetabular dysplasia in 49 (33%) patients, and acetabular retroversion in 85 (57%) patients. Acetabular retroversion was identified in 43% (crossover sign) and 39% (prominent ischial spine) of patients.

CONCLUSIONS

Approximately 57% of adult patients under the age of 40 years with the clinical symptom complex of SIJ pain were found to have radiographic acetabular retroversion. This is a higher percentage than the 5%-15% found in asymptomatic people in the current literature. Further study is needed to assess links between hip structure, hip motion, and links to pelvic pain including peri and intra-articular SIJ pain.

LEVEL OF EVIDENCE

III.

Acetabular Retroversion and Decreased Posterior Coverage Are Associated With Sports-related Posterior Hip Dislocation in Adolescents

BACKGROUND

Leverage of the femoral head against the acetabular rim may lead to posterior hip dislocation during sports activities in hips with femoroacetabular impingement (FAI) deformity. Abnormal concavity of the femoral head and neck junction has been well described in association with posterior hip dislocation. However, acetabular morphology variations are not fully understood.

QUESTIONS/PURPOSES

The purpose of this study was to compare the acetabular morphology in terms of acetabular version and coverage of the femoral head in adolescents who sustained a posterior hip dislocation during sports and recreational activities with a control group of patients without a history of hip disease matched by age and sex.

METHODS

In this case-control study, we identified 27 adolescents with posterior hip dislocation sustained during sports or recreational activities who underwent a CT scan of the hips (study group) and matched them to patients without a history of hip disease being evaluated with CT for possible appendicitis (control group). Between 2001 and 2017, we treated 71 adolescents (aged 10-19 years old) for posterior hip dislocations. During the period in question, we obtained CT scans or MR images after closed reduction of a posterior hip dislocation. One patient was excluded because of a diagnosis of Down syndrome. Twenty-one patients who were in motor vehicle-related accidents were also excluded. Twelve patients were excluded because MRI was obtained instead of CT. Finally, three patients with no imaging after reduction and seven patients with inadequate CT reformatting were excluded. Twenty-seven patients (38%) had CT scans of suitable quality for analysis, and these 27 patients constituted the study group. We compared those hips with 27 age- and sex-matched adolescents who had CT scans for appendicitis and who had no history of hip pain or symptoms (control group). One orthopaedic surgeon and one pediatric musculoskeletal radiologist, not invoved in the care of the patients included in the study, measured the lateral center-edge angle, acetabular index, acetabular depth/width ratio, acetabular anteversion angle (10 mm from the dome and at the level of the center of the femoral heads), and the anterior and posterior sector angles in the dislocated hip; the contralateral uninvolved hip of the patients with hip dislocations; and both hips in the matched control patients. Both the study and control groups had 25 (93%) males with a mean age of 13 (± 1.7) years. Inter- and intrarater reliability of measurements was assessed with intraclass correlation coefficient (ICC). There was excellent reliability (ICC > 0.90) for the acetabular anteversion angle measured at the center of the femoral head, the acetabular version 10 mm from the dome, and the posterior acetabular sector angle.

RESULTS

The mean acetabular anteversion angle (± SD) was lower in the study group at 10 mm from the acetabular dome (-0.4° ± 9° versus 4° ± 4°; mean difference -5°; 95% confidence interval [CI], -9 to -0.3; p = 0.015) and at the center of the femoral heads (10° ± 5° versus 14° ± 4°; mean difference -3°; 95% CI, -6 to -0.9; p = 0.003). A higher proportion of acetabula was severely retroverted in the study group (14 of 27 [52%]; 95% CI, 33%-71% versus four of 27 [15%]; 95% CI, 1%-28%; p = 0.006). The mean posterior acetabular sector angle was lower in the study group (82° ± 8° versus 90° ± 6°; mean difference -8°; 95% CI, -11 to -4; p < 0.001), whereas no difference was found for the anterior acetabular sector angle (65° ± 6° versus 65° ± 7°; mean difference 0.3°; 95% CI, -3 to 4; p = 0.944). There was no difference for the lateral center-edge angle (27° ± 6° versus 26° ± 5°; p = 0.299), acetabular index (5° ± 3° versus 6 ± 4°; p = 0.761), or acetabular depth/width ration (305 ± 30 versus 304 ± 31; p = 0.944) between groups. Acetabular anteversion angle at the center of the femoral heads (11° ± 4° versus 14° ± 4°; p = 0.006) and the posterior acetabular sector angle (86° ± 7 ° versus 91° ± 6°; p = 0.007) were lower in the contralateral uninvolved hips compared with control hips.

CONCLUSIONS

Decreased acetabular anteversion angle and posterior acetabular coverage of the femoral head were associated with posterior dislocation of the hip in adolescents with sports-related injury even in the absence of a high-energy mechanism. Further studies are necessary to clarify whether a causative effect exists between acetabular and femoral morphology and the dislocation of the hip in patients with sports-related injuries.

LEVEL OF EVIDENCE

Level III, prognostic study.

Femoroacetabular Impingement in Pediatric Patients

Subacute, nontraumatic hip pain is often a diagnostic challenge. Femoroacetabular impingement (FAI) is a common cause of atraumatic hip pain that is poorly understood. FAI is a result of abnormal morphologic changes in either the femoral head or the acetabulum. FAI is more prevalent in people who perform activities requiring repetitive hip flexion, but it remains common in the general population. Evaluation begins with physical examination maneuvers to rule out additional hip pathology and provocation tests to reproduce hip pain. Diagnosis is often made by radiography or magnetic resonance imaging. Initial treatment is generally more conservative, featuring activity modification and physical therapy, whereas more aggressive treatment requires operative management.

Computer-assisted anteverting eccentric rotational acetabular osteotomy for recurrent posterior dislocation associated with acetabular retroversion: a case report

Background

Acetabular retroversion is a rotatory abnormality of the entire hemipelvis that includes anterior over-coverage and posterior deficiency of the acetabulum, and is associated with pincer-type femoroacetabular impingement and posterior hip instability. Acetabular retroversion is thought to cause posterior dislocation of the hip in athletes due to both the pincer-type femoroacetabular impingement and posterior hip instability.

Case presentation

A 26-year-old Japanese man had acetabular retroversion that induced recurrent posterior dislocation of his hip due to excessive hip flexion while wakeboarding. We performed anteverting eccentric rotational acetabular osteotomy using preoperative three-dimensional planning and an intraoperative computerized navigation system. Our patient was able to return to sports activities 1 year postoperatively.

Conclusions

Both preoperative three-dimensional surgical planning software and an intraoperative navigation system can provide a highly accurate map for this complicated surgery that simultaneously improves the pincer-type femoroacetabular impingement and posterior deficiency of the acetabulum.

A Contemporary Definition of Hip Dysplasia and Structural Instability: Toward a Comprehensive Classification for Acetabular Dysplasia

Hip dysplasia has long been known to be a risk factor for pain and degenerative changes in the hip joint. The diagnosis of dysplasia has historically been based on assessments of acetabular anatomy on the anteroposterior pelvic radiograph, most commonly the lateral center-edge angle. Recent advances in imaging of the dysplastic hip with computerized tomography scans have demonstrated that hip dysplasia is in fact a 3-dimensional (D) deformity of the acetabulum and that multiple patterns of hip instability exist that may not be completely assessed on 2D imaging. A more thorough understanding of acetabular anatomy permits an evolution away from vague terms such as "borderline dysplasia." A 3D assessment of the acetabulum and the resultant patterns of instability may be more appropriate since this would allow more accurate treatment to correct the structural instability with acetabular reorientation. With this information, we propose a diagnostic framework that groups symptomatic dysplastic hips into one of 3 categories based on the primary direction of instability: (1) anterior, (2) posterior, and (3) global. This framework may aid the clinician in developing a differential diagnosis for the assessment of hip pain and suspected instability, and for planning an appropriate surgical management.