More than just a bump: cam-type femoroacetabular impingement and the evolution of the femoral neck

Arthroscopic and Radiographic Features Distinguish Femoral Head Deformity from Idiopathic Cam, Slipped Capital Femoral Epiphysis, and Recurrent Cam After Slipped Epiphysis

Introduction

Hip impingement from slipped epiphysis and idiopathic cam is well known but not fully differentiated. Idiopathic cam can be a result of an undiagnosed slip. The mechanism of remodeling of slipped epiphysis deformity has also been controversial. The causes of recurrent femoral head deformity and new impingement beyond progression of the slip have not been studied.

Materials and Methods

A consecutive series of hips treated by arthroscopic femoral neck osteoplasty for impingement from slipped epiphysis were compared with a series of hips treated for idiopathic cam impingement. Demographics and clinical, radiographic, and arthroscopic features were retrospectively retrieved. The same parameters were studied in another consecutive series of hips treated for slipped epiphysis and developed recurrent pain from impingement. The deformity was analyzed to understand the causes of recurrence in these hips. The medial most point where the femoral head sphericity ended was called the Alpha point and the tissue covering the bone at the Alpha point was identified.

Results

Children with idiopathic cam were older, had less pain and limp, and less clinical deformity compared to those with slipped epiphysis. The damage pattern was chondrolabral separation and acetabular cartilage debonding from the subchondral bone by an articular cartilage covered bump in idiopathic cam impingement, while it was labral crushing and labral and cartilage abrasion by metaphyseal bone in slip impingement. Recurrent cam deformities after initial slips were from epiphyseal extension similar to the idiopathic cam deformity in 7 out of 9 hips.

Discussion

Slipped epiphysis and idiopathic cam seem to be distinct entities at the time of presentation. They were different in all findings except for having pain with flexion and internal rotation in both groups. Remodeling of slip deformity seems to occur by wear of the metaphyseal prominence on the acetabulum. Recurrence or worsening of cam deformity in slips occurred by growth of the epiphysis on to the neck anteriorly which can appear as a decrease in the posterior slip. The relationship of the Alpha point to the physeal scar and the tissue covering the femoral head at the Alpha point help differentiate between epiphyseal and metaphyseal cam deformities.

Level of Evidence

Level 3 retrospective comparative study.

The natural history of alpha angle in the last seventeen centuries

INTRODUCTION

Hip osteoarthritis is one of the most important and debilitating diseases affecting thousands of people all over the world. On the other hand, femoroacetabular impingement (FAI) is one of the known important causes of hip osteoarthritis. Cam deformity frequently presents in FAI showing an increased alpha angle. Increased alpha angle has been observed among young patients involved in demanding physical activities such as in sports (40-60%), whereas among the non-athletic population, increased alpha angle was observed in 15-20%. Although femoroacetabular pathology has been described over the recent years, it is not possible to determine when the angle increase actually begins prior to diagnosis. The aim of our study is to evaluate the femoral alpha angle in different human femurs in different civilization eras in West Mediterranean area.

MATERIALS AND METHODS

Available ancient femurs were selected from the Collection Center belonging to the archeological archives (ancient necropolis) from the fourth, fourteenth and eighteenth centuries. A comparison of the alpha angle was made of the measurements from the different groups accompanied by a sample of present-day femurs from the radiology database of CT scans. Data from 243 femoral bones were collected, 50 of which from the fourth century, 26 from the fourteenth century, 68 from the eighteenth century, and 99 femurs from the 20/twenty-first century.

RESULTS

Alpha angles in all historical samples showed pathological values (> 55º) up to a maximum of 11.5% of the cases. Meanwhile, the actual series showed pathological alpha angle in 60.1% of the cases with statistical significant differences.

CONCLUSION

The studied femurs of the western Mediterranean region from the fourth, fourteenth and eighteenth centuries showed pathological alpha angles in a smaller proportion than the actual sample.

LEVEL OF EVIDENCE

Level III, retrospective studies.

Extent of Cam Resection Relative to Epiphyseal Line and Its Association With Clinical Outcomes After Arthroscopic Treatment for Femoroacetabular Syndrome

Background:

Inadequate resection of cam lesions can cause inferior outcomes after hip arthroscopy and result in revision surgery for femoroacetabular impingement syndrome (FAIS).

Purpose:

To evaluate the association between postoperative cam lesions measured using the proximal boundaries of resection area (PBRE) relative to the epiphyseal line and 2-year outcomes after hip arthroscopy.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Included were patients with FAIS who had undergone primary hip arthroscopy between 2016 and 2018. The PBRE was calculated by measuring the linear distance from the PBRE to the epiphyseal line, dividing it by the diameter of the femoral head, and multiplying by 100; PBRE measurements were made at the 12-, 1-, and 2-o’clock positions on postoperative hip computed tomography. Within each clockface position, patients were divided into subgroups depending on whether their postoperative PBRE was greater than a half standard deviation above the mean (adequate resection) or less than or equal to a half standard deviation above the mean (inadequate resection). Patient-reported outcomes (PROs; Hip Outcome Score–Activities of Daily Living [HOS-ADL], International Hip Outcome Tool–Short Form [iHOT-12], modified Harris Hip Score [mHHS], and pain visual analog scale [VAS]) and rates of achieving the minimal clinically important difference (MCID) and patient-acceptable symptomatic state (PASS) were compared among the subgroups.

Results:

Included were 80 pairs of hips at 12 o’clock, 81 pairs of hips at 1 o’clock, and 80 pairs of hips at 2 o’clock. All subgroups demonstrated significant improvements in PRO scores at a minimum 2-year follow-up compared with preoperatively. At the 12-o’clock position, the subgroup with adequate resection had significantly superior HOS-ADL ( P = .004), iHOT-12 ( P < .001), and mHHS ( P < .001) scores and were more likely to achieve the MCID for the iHOT-12 score ( P = .035) and the PASS for the HOS-ADL ( P = .003), iHOT-12 ( P = .007), and mHHS ( P < .001) scores compared with the matched subgroup. There were no significant differences in PRO scores or rates of MCID and PASS for the 1- or 2-o’clock groups.

Conclusion:

The epiphyseal line may be a useful and reproducible landmark measurement for cam-type deformity. Patients considered to have inadequate resection at 12 o’clock had lower outcome scores at a minimum 2-year follow-up.

Prevalence of femoroacetabular impingement in elite baseball players

CAM-type femoroacetabular impingement continues to be an underrecognized cause of hip pain in elite athletes. Properties inherent to baseball such as throwing mechanics and hitting may enhance the risk of developing a cam deformity. Our goal is to gain an appreciation of the radiographic prevalence of cam deformities in elite baseball players. Prospective evaluation and radiographs of 80 elite baseball players were obtained during the 2016 preseason entrance examination. A sports medicine fellowship-trained orthopedic surgeon with experience treating hip disorders used standard radiographic measurements to assess for the radiographic presence of cam impingement. Radiographs with an alpha angle &gt;55° on modified Dunn views were defined as cam positive. Of the 122 elite baseball players included in our analysis, 80 completed radiographic evaluation. Only 7.3% (9/122) of players reported hip pain and 1.6% (4/244) had a positive anterior impingement test. The prevalence of cam deformities in right and left hips were 54/80 (67.5%) and 40/80 (50.0%), respectively. The mean alpha angle for cam-positive right and left hips were 64.7 ± 6.9° and 64.9 ± 5.8°, respectively. Outfielders had the highest risk of right-sided cam morphology (Relative Risk (RR) = 1.6). Right hip cam deformities were significantly higher in right-handed pitchers compared with left-handed pitchers (P = 0.02); however, there was no significant difference in left hip cam deformities between left- and right-handed pitchers (P = 0.307). Our data suggest that elite baseball players have a significantly higher prevalence of radiographic cam impingement than the general population.

Hip Preservation Surgery in Osteoarthritis Prevention: Potential Benefits of the Radiographic Angular Correction

Objective: The aim of the study is to describe the morphology associated with the development of osteoarthritis (OA) in three different age groups. These data will contribute to defining the morphology associated with early and late hip OA. Methods: We studied 400 hips in 377 patients who had undergone primary THA due to idiopathic OA. Three groups were compared: group 1 (n = 147), younger patients, aged up to 60 years; group 2 (n = 155), patients aged between 61 and 74 years; and group 3 (n = 98), aged 75 or over. Five independent researchers measured the hip angles and the mean values were used to build a database. Results: No differences between groups in sex distribution and BMI were detected. Less coverage of the head (extrusion index), higher Tönnis angle, lower Wiberg and alpha angles characterized early OA hips. These differences increased with age, being greater between group 2 and group 3 (p < 0.01). However, significant differences were still present in the comparison between group 1 and group 2 (p < 0.01)). No differences were detected between group 2 and group 3. Conclusion: Elevated acetabular angle, head extrusion and decreased Wiberg angle characterize hip osteoarthritis at younger ages and should be the focus of hip preservation surgery in terms of osteoarthritis prevention. Pincer-type FAI (higher Wiberg and lower Tönnis angle) and higher alpha angle (CAM) are correlated with the development of later OA. These results shed doubt on applying the hip preservation surgery concept in terms of osteoarthritis prevention in FAI, especially in Pincer-type FAI patients.

Prognostic Factors for Conversion to Arthroplasty after Hip Arthroscopy. Review of the Literature

Arthroscopic techniques in the treatment of femoroacetabular impingement have experienced an exponential increase over recent years for both diagnosis and treatment. The main risks with treatment are poor clinical outcomes and the conversion to prosthesis. Better knowledge and understanding of the various risk factors leading to prosthesis will improve patient selection for arthroscopic treatments rendering better results. The published papers that have been selected are related to series of hip arthroscopies with risk factors that lead to total hip arthroplasty (THA), in the PubMed database, without a time limit, number of patients, or follow-up time. We selected over 302 papers, 19 papers that show risk factors for conversion to THA. The main risk factors found were femoral chondropathy grade III/IV (relative risk 58.1-12 times increased), acetabular (20-2.96 times), an articular space <2 mm (39-4.26 times), age (14.6-1.06 times), Tönnis 2 in radiographic studies (7.73-3.1 times), obesity (5.6-2.3 times), and osteoarthritis (4.6-2.4 times). There are several risk factors which in an isolated way, highly increase the risk of THA. Some of them have a clear relationship (chondropathy, reduced joint space, Tönnis 2, and osteoarthritis). Based on the review we observed that the elements that are most associated with a conversion to THA after a hip arthroscopy are a high degree of femoral and acetabular chondropathy, a reduced joint space below 2 mm, older age, Tönnis 2, obesity, and hip osteoarthritis.

Preoperative risk factors in hip arthroscopy

PURPOSE

Arthroscopic surgery is a usual technique to repair hip femoroacetabular impingement. Correlation exists among surgical indication, postoperative evolution, the final result, and the necessity of prosthesis in the near future. The assessment of specific parameters allowing us to evaluate the prognosis becomes vital to improve the results. The objective of this study is to check the variables found in patients with femoroacetabular impingement (FAI) treated with hip arthroscopy, and determine which of these variables would serve as key indicators in predicting the need for subsequent arthroplasty.

METHODS

Data from FAI surgical indications (age, weight, height, BMI, gender, side, radiographic Tönnis degree, cartilage lesion degree by Acetabular Labrum Articular Disruption (ALAD) degree, VAS value, HOS, mHHS and WOMAC) were collected from cases which should have had a minimum monitoring period of 2 years from 2007 to 2017. The results of the group which needed prosthesis were compared to the results of the ones who did not.

RESULTS

Among 452 patients who were monitored for an average of 5.8 years, 82 (18.1%) required conversion to prosthesis. The variables that indicated relatively high risk were fourth-degree acetabular labrum articular disruption (ALAD) chondral injury, preoperative radiographic Grade 2 Tönnis classification, age of over 55 years, WOMAC over 45 points, and HOS-ADL under 50 points. There were no significant differences between side, gender, VAS level, nor HOS.

CONCLUSIONS

The presence of chondral injuries such as acetabular labrum articular disruption (ALAD) 4, radiographic Grade 2 Tönnis classification, higher age, higher BMI, and worse WOMAC, along with mHHS and HOS-ADL preoperative results, are factors which lead to a poor prognosis following FAI hip arthroscopic surgery, increasing the risk of prosthetic conversion in the short or medium term.

LEVEL OF EVIDENCE

Level IV.

Characterizing cam-type hip impingement in professional women's ice hockey players

OBJECTIVE

There is a high prevalence of femoroacetabular impingement (FAI) amongst elite men's ice hockey players, yet little is known about the hips of players in the National Women's Hockey League (NWHL). The primary purpose of this study was to determine the prevalence of radiographic cam-type FAI in women's professional ice hockey players. The secondary purpose was to analyze the relationship between the cam deformity and both menarchal age and hip range-of-motion (ROM).

METHODS

Data were collected for NWHL players during pre-participation physicals. Alpha angles were measured on 45° Dunn radiographs, with alpha angles >55° defined as cam-positive. Pearson correlation coefficients (ρ) were performed to analyze the relationship between alpha angle and both ROM measurements and menarchal age, with statistical significance set at p < 0.05.

RESULTS

Twenty-six athletes were included. Twenty-four (92%) had alpha angles >55°; 20 players (77%) had bilateral cam deformity. Average menarchal age was 13.8 ± 1.7 years. There was a significant association between age of menarche and alpha angle (ρ = 0.36, p < 0.02). There was no significant association between alpha angle and hip ROM (p > 0.05).

CONCLUSION

Elite women's ice hockey players have a higher prevalence of cam-type morphology than the general population. The positive association between alpha angle and menarchal age lends additional support to the etiological hypothesis of the cam lesion resulting from activity-related stress at the proximal femoral physis during skeletal development. Professional women's ice hockey players have a high risk of developing cam-type morphology, although each player's menarchal age may mediate her individual risk for cam development.

The clinical presentation, diagnosis and pathogenesis of symptomatic sports-related femoroacetabular impingement (SRFAI) in a consecutive series of 1021 athletic hips

AIM

To examine the pathogenesis and clinical presentation of sports-related femoroacetabular impingement (SRFAI) in a large consecutive series of symptomatic athletes.

METHODS

Between January 2009 and February 2017 prospectively collected data from competitive athletes within the Gaelic Athletic Association (GAA), and who subsequently underwent arthroscopic treatment for symptomatic FAI, were analysed. Data was collected using internationally validated health questionnaires (Harris Hip Score, UCLA, SF-36, WOMAC) and recognised clinical (ROM, symptom presentation, provocation tests) and radiological (AP pelvis, Dunn, False profile) indicators/measures of FAI.

RESULTS

A total of 1021 consecutive cases (mean 26.6 ± 6.2 years) were included. In every case, conservative treatment failed to resolve symptoms with athletes attending an average of 2.4 ± 1.1 health care professionals prior to referral. Symptoms developed gradually (78%) and consisted primarily of groin pain (76.1%) and hip stiffness (76.5%) following activity. An acetabular rim deformity (pincer) was present in all cases; a cam deformity in 72.1%. The prevalence and degree of cam deformity increased with progressing age groups (p < 0.001); mean lateral centre-edge angle remained static (p = 0.456). Increasing CEA, alpha angle and presence of rim fracture was associated with a reduction in all ranges of hip movement (p < 0.001).

CONCLUSION

Symptomatic SRFAI presented in this large series of GAA athletes failed to resolve with non-operative treatment. Increasing hip deformity resulted in poorer ROM. Abnormal acetabular morphology remains static with increasing athletic age while cam deformity is progressive and most likely a secondary pathology.

Reported Prevalence of Radiographic Cam Deformity Based on Sport: A Systematic Review of the Current Literature

Background

Repetitive loading and shear stress across the proximal femur account for the high prevalence of cam deformity in athletes.

Purpose

To systematically review the literature to identify the reported number, age, mean alpha angle measurements, and differences between male and female athletes with radiographic cam deformity based on sport.

Study Design

Systematic review; Level of evidence, 4.

Methods

A systematic review was conducted of studies in the literature between January 1990 and March 2018 that reported on athletes with radiographic cam deformity based on sport. PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines were followed, and PubMed, Biosis Previews, SPORTDiscus, PEDro, and EMBASE databases were used. Inclusion criteria included studies documenting radiographic cam deformity based on alpha angle measurements categorized according to the athlete's primary sport and according to sex. Exclusion criteria were (1) studies not documenting primary sport, (2) studies not reporting total number of athletes with radiographic cam deformity, and (3) studies not separating cam deformity based on sex or using alpha angle measurements. Statistical analysis was used to compare mean reported age and alpha angle measurements between males and females.

Results

A total of 28 studies consisting of 1160 male and 53 female athletes with radiographic cam deformity were identified. Cam lesions were most commonly reported in soccer athletes among both males and females, followed by hockey and American football. Male athletes had significantly higher mean alpha angle measurements (59.9° ± 5.5°) compared with female athletes (48.3° ± 6.9°) (P = .001). No significant difference in age was appreciated between males (21.1 ± 4.0 years) and females (21.7 ± 3.0 years) (P = .62).

Conclusion

Radiographic cam deformity is most commonly reported in athletes participating in soccer and hockey. Males possessed significantly greater mean alpha angle measurements compared with females, whereas no significant difference in mean age at the time of diagnosis was appreciated between sexes.

Femoral cam deformity due to anterior capsular force: A theoretical model with MRI and cadaveric correlation

BACKGROUND

Cam deformity is associated with epiphyseal extension onto the anterosuperior femoral head-neck before physeal closure. A century ago, anatomists speculated that this femoral prominence acts as a pulley bar to withstand capsular compression in hip extension with pressure concentrated where the zona orbicularis (ZO) joins the iliofemoral ligament (IFL). An animal model has shown that growth plates deflect laterally and distally when exposed to forces perpendicular to growth. These observations raise the question of whether capsular pressure against the epiphysis can stimulate cam formation.

PURPOSE

The purposes are to measure: (1) the distance from the ZO/IFL confluence to the maximal epiphyseal extension (MEE) and cam apex; and (2) acetabular depth at this location, since less coverage increases capsular contact on the physis.

METHODS

MRI scans of 39 subjects (47 hips) were measured. Acetabular depth was compared between those with and without a cam deformity. Secondarily, anatomic findings were correlated on a cadaveric specimen.

RESULTS

The cam apex and MEE were adjacent to the ZO/IFL confluence in all subjects (mean, 6.3 mm). Controlling for sex, acetabular depth was less (12.5%, p = 0.012) in the group with cam deformity. Contact points were confirmed in the specimen.

CONCLUSIONS

The cam apex and MEE occur at the ZO/IFL confluence in the thickest region of the anterosuperior capsule and vary with acetabular depth. This supports a theoretical model postulating that capsular forces against an immature epiphysis may induce cam formation, particularly in individuals who repetitively tension the anterior capsule.

Prevalence of Cam-Type Morphology in Elite Ice Hockey Players

BACKGROUND

Femoroacetabular impingement (FAI) has been increasingly recognized as a cause of hip pain in athletes at all levels of competition, specifically ice hockey players.

PURPOSE/HYPOTHESIS

The purpose of this study was to define the prevalence of cam and pincer radiographic deformity in elite ice hockey players. The hypothesis was that elite hockey players will have a higher prevalence of radiographic hip abnormalities compared with the general population.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Anteroposterior and frog-leg lateral radiographs on 137 elite ice hockey players were prospectively obtained during the 2014-2015 preseason entrance examinations. Study participants included National Hockey League roster players as well as the respective farm team members. Demographic data were collected, including age, position, shooting side, and any history of hip pain or hip surgery. Patients with a history of hip surgery were excluded from the analysis. A single sports medicine fellowship-trained orthopaedic surgeon used standard radiographic measurements to assess for the radiographic presence of cam or pincer deformity. Radiographs with an alpha angle ≥55° on a frog-leg lateral view were defined as cam-positive. Each participant underwent a preseason physical examination with an assessment of hip range of motion and impingement testing.

RESULTS

A total of 130 elite ice hockey players were included in the analysis; 180 (69.4%) hips met radiographic criteria for cam-type deformity. The prevalence in right and left hips was 89 (69.5%) and 91 (70.0%), respectively; 70 (60.8%) players demonstrated bilateral involvement. Hips with cam deformity had a mean alpha angle of 67.7° ± 8.3° on the right and 68.9° ± 9.0° on the left. Of the patients with alpha angles ≥55°, 5.6% (5/89) had a positive anterior impingement test of the right hip, while 11% (10/91) had positive anterior impingement test of the left. Players with radiologic cam deformity had a statistically significant deficit in external rotation of the right hip, as well as in both internal and external rotation of the left hip, compared with those with normal alpha angles. When assessing for crossover sign, 64 of 107 (59.8%) had a positive radiographic finding. Forty-one players (38.3%) had evidence of a crossover sign of the right hip and 42 (39.3%) of the left. When comparing position players, goalies had the highest prevalence of cam-type deformity (93.8%) and the least acetabular coverage.

CONCLUSION

The study data suggest that elite ice hockey players have a significantly higher prevalence of radiographic cam deformity in comparison to what has been reported for the general population.

Characterization of symptomatic hip impingement in butterfly ice hockey goalies

PURPOSE

This study aimed to characterize the radiographic deformity observed in a consecutive series of butterfly goalies with symptomatic mechanical hip pain and to use computer-based software analysis to identify the location of impingement and terminal range of motion. We also compared these analyses to a matched group of positional hockey players with symptomatic femoroacetabular impingement (FAI).

METHODS

A consecutive series of 68 hips in 44 butterfly-style hockey goalies and a matched group of 34 hips in 26 positional hockey players who underwent arthroscopic correction for symptomatic FAI were retrospectively analyzed. Each patient underwent preoperative anteroposterior (AP) and modified Dunn lateral radiographs and computed tomography (CT) of the affected hips. Common FAI measurements were assessed on plain radiographs. Patient-specific, CT-based 3-dimensional (3D) models of the hip joint were developed, and the femoral version, alpha angles at each radial clock face position, and femoral head coverage were calculated. Maximum hip flexion, abduction, internal rotation in 90° flexion (IRF), flexion/adduction/internal rotation (FADIR), and butterfly position were determined, and the areas of bony collision were defined.

RESULTS

Butterfly goalies had an elevated mean alpha angle on both AP (61.3°) and lateral radiographs (63.4°) and a diminished beta angle (26.0°). The mean lateral center-edge angle (LCEA) measured 27.3° and acetabular inclination was 6.1°. A crossover sign was present in 59% of the hips. The maximum alpha angle on the radial reformatted computed tomographic scan was significantly higher among the butterfly goalies (80.9° v 68.6°; P < .0001) and was located in a more lateral position (1:00 o'clock v. 1:45 o'clock; P < .0001) compared with positional players.

CONCLUSIONS

Symptomatic butterfly hockey goalies have a high prevalence of FAI, characterized by a unique femoral cam-type deformity and noted by an elevated alpha angle and loss of offset, which is greater in magnitude and more lateral when compared with that in positional hockey players. Associated acetabular dysplasia is also common among hockey goalies.

LEVEL OF EVIDENCE

Level IV, prognostic case series.

Cam-type deformities: Concepts, criteria, and multidetector CT features

Interpreting imaging studies of a painful hip requires detailed knowledge of the regional anatomy. Some variants of the proximal femur, such as cam-type deformities, can course asymptomatically or cause femoroacetabular impingement. The principal numerical criterion for defining cam-type deformities, the alpha angle, has some limitations. In this article, we review the anatomic variants of the anterior aspect of the proximal femur, focusing on cam-type deformities. Using diagrams and multidetector CT images, we describe the parameters that are useful for characterizing these deformities in different imaging techniques. We also discuss the potential correspondence of imaging findings of cam-type deformities with the terms coined by anatomists and anthropologists to describe these phenomena.

Mechanical factors explain development of cam-type deformity

OBJECTIVE

A cam-type deformity drastically increases the risk of hip osteoarthritis (OA). Since this type of skeletal anomaly is more prevalent among young active adults, it is hypothesized that the loading conditions experienced during certain types of vigorous physical activities stimulates formation of cam-type deformity. We further hypothesize that the growth plate shape modulates the influence of mechanical factors on the development of cam-type deformity.

DESIGN

We used finite element (FE) models of the proximal femur with an open growth plate to study whether mechanical factors could explain the development of cam-type deformity in adolescents. Four different loading conditions (representing different types of physical activities) and three different levels of growth plate extension towards the femoral neck were considered. Mechanical stimuli at the tissue level were calculated by means of the osteogenic index (OI) for all loading conditions and growth plate shape variations.

RESULTS

Loading conditions and growth plate shape influence the distribution of OI in hips with an open growth plate, thereby driving the development of cam-type deformity. In particular, specific types of loads experienced during physical activities and a larger growth plate extension towards the femoral neck increase the chance of cam-type deformity.

CONCLUSIONS

Specific loading patterns seem to stimulate the development of cam-type deformity by modifying the distribution of the mechanical stimulus. This is in line with recent clinical studies and reveals mechanobiological mechanisms that trigger the development of cam-type deformity. Avoiding these loading patterns during skeletal growth might be a potential preventative strategy for future hip OA.

Clinical presentation and disease characteristics of femoroacetabular impingement are sex-dependent

BACKGROUND

Cam-type femoroacetabular impingement (FAI) is generally described as being more common in males, with pincer-type FAI being more common in females. The purpose of this study was to determine the effect of sex on FAI subtype, clinical presentation, radiographic findings, and intraoperative findings in patients with symptomatic FAI.

METHODS

We compared cohorts of fifty consecutive male and fifty consecutive female patients who were undergoing surgery for symptomatic FAI. Detailed information regarding clinical presentation, radiographic findings, and intraoperative pathology was recorded prospectively and analyzed. FAI subtype was classified on the basis of clinical diagnosis and radiographic evaluation.

RESULTS

Female patients had significantly greater disability at presentation, as measured with use of the modified Harris hip score (mHHS), the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the Hip Disability and Osteoarthritis Outcome Score (HOOS), and the SF-12 (12-Item Short Form Health Survey) physical function subscore (all p ≤ 0.02), despite a significantly lower UCLA (University of California at Los Angeles) activity score (p = 0.03). Female patients had greater hip motion (flexion and internal rotation and external rotation in 90° of flexion; all p ≤ 0.003) and less severe cam-type morphologies (a mean maximum alpha angle of 57.6° compared with 70.8° for males; p < 0.001). Males were significantly more likely to have advanced acetabular cartilage lesions (56% of males compared with 24% of females; p = 0.001) and larger labral tears with more posterior extension of these abnormalities (p < 0.02). Males were more likely than females to have mixed-type FAI and thus a component of pincer-type FAI (combined-type FAI) (62% of males compared with 32% of females; p = 0.003).

CONCLUSIONS

We found distinct, sex-dependent disease patterns in patients with symptomatic FAI. Females had more profound symptomatology and milder morphologic abnormalities, while males had a higher activity level, larger morphologic abnormalities, more common combined-type FAI morphologies, and more extensive intra-articular disease.

LEVEL OF EVIDENCE

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

The Otto Aufranc Award. On the etiology of the cam deformity: a cross-sectional pediatric MRI study

BACKGROUND

Femoroacetabular impingement (FAI) has been recognized as a common cause of hip pain as well as a cause of hip arthritis, yet despite this, little is known about the etiology of the cam morphology or possible risk factors associated with its development.

QUESTIONS/PURPOSES

The purposes of our study were to determine when the cam morphology associated with FAI developed in a cross-sectional cohort study of pediatric patients pre- and postphyseal closure using MRI and whether increased activity level during the period of physeal closure is associated with an increased likelihood that the cam deformity will develop.

METHODS

Alpha angles were measured at the 3 o'clock (anterior head-neck junction) and 1:30 (anterosuperior head-neck junction) positions in both hips with a cam deformity defined as an alpha angle ≥ 50.5° at the 3 o'clock position. Forty-four volunteers (88 hips) were studied: 23 with open physes (12 females, mean age 9.7 years; 11 males, age 11.7 years) and 21 with closed physes (five females, age 15.2 years; 16 males, age 16.2 years). Daily activity level using the validated Habitual Activity Estimation Scale was compared for patients in whom cam morphology did and did not develop.

RESULTS

None of the 23 (0%) patients prephyseal closure had cam morphology, whereas three of 21 (14%, p = 0.02; all males) postclosure had at least one hip with cam morphology. Daily activity level was higher (p = 0.02) for patients with the cam morphology (7.1 hours versus 2.9 hours). Mean alpha angles at the 3 o'clock head-neck position were 38° (95% confidence interval [CI], 37.2°-39.1°) in the open physes group and 42° (95% CI, 40.16°-43.90°) in the closed physes group; at the 1:30 head-neck position, they were 45° (95% CI, 44.0°-46.4°) in the open physes group and 50° (47.9°-52.3°) in the closed physes group.

CONCLUSIONS

The fact that cam morphology was present exclusively in the closed physeal group strongly supports its development during the period of physeal closure with increased activity level as a possible risk factor.

Cam morphology in the human hip

A growing interest exists in the diagnosis and treatment of femoroacetabular impingement. Although cam morphology of the proximal femur may conceptually appear to be a relatively simple topographical aberrancy, it is actually positioned amid a complex developmental, kinematic, and biomechanical region of the human body. The authors introduce a new classification scheme and review the historical and anthropological considerations, biomechanics, and genetic factors involved in cam morphology.