Anatomic Analysis of Site-Specific Femoral Version and Cam Deformity in 1058 Cadaveric Hips

Abstract

Background:

Femoral version (FV) is an anatomic parameter that has recently received increased attention in its role in multiple hip pathologies, including femoroacetabular impingement (FAI) and cam lesion development.

Purpose:

To evaluate site-specific femoral version and assess the relationship with the size and location of cam deformity in cadaveric specimens.

Study Design:

Descriptive laboratory study.

Methods:

A total of 1058 cadaveric femurs were selected from a historical osteologic collection. Each femur was assessed to determine the α angle, total FV, neck-based FV, and shaft-based FV. Cam morphology was defined as an α angle >60°. Pearson correlation and multiple regression analysis were performed to determine the relationship between site-specific FV location and α angle.

Results:

Of the cadaveric femurs, the mean ± SD α angle was 54°± 11°. There were 354 (33%) cam deformities. The mean ± SD was 11°± 12° for total FV among all specimens, 24°± 10° for the femoral shaft version, and −13°± 19° for the femoral neck version. On multivariate analysis, sex, race, femoral neck version, and femoral shaft version were independent predictors for α angle (P < .05). Each degree increase predicted an increase in α angle of 0.09° (P = .006) for the femoral neck version and 0.14° (P = .02) for the femoral shaft version.

Conclusion:

Our study reveals an anatomic relationship between site-specific FV and cam deformity; an increase in shaft FV and neck FV predicted an increased α angle. While the observed absolute value of this relationship is small, site-specific FV remains a previously unrecognized area of interest that could help explain differences previously reported in the literature regarding the multifactorial symptomology in FAI.

Clinical Relevance:

FV is classically reported as one value combining the femoral neck version and torsion of the femoral shaft. In addition to the identified relationship between site-specific FV and cam deformity, this study encourages clinicians to consider both contributing anatomic components of femoral version, especially when identifying the level of deformity before corrective femoral osteotomy in patients with FAI.

Keywords

femoroacetabular impingement cam deformity femoral version α angle hip arthroscopy

Femoroacetabular impingement (FAI), a disorder of the hip joint caused by abnormal bony contact between the femoral head-neck junction and acetabulum, is found in 10% to 15% of the general adult population.¹⁸ The cause of FAI is multifactorial but often is the result of a cam deformity of the proximal femur, which causes both loss of femoral head sphericity and normal head-neck offset. While often idiopathic in nature, multiple secondary causes leading to cam deformities have been identified, including slipped capital femoral epiphysis, congenital hypoplasia of the femur, Legg-Calvé-Perthes disease, posttraumatic malunion, and protrusio acetabuli.⁷ Additionally, previous studies have shown that vigorous exercise during adolescence may trigger high skeletal stress along the lateral head-neck junction, causing pathologic skeletal overgrowth and ultimately a cam deformity.^26,27 However, notably, the presence of a cam does not directly lead to symptomatic FAI, with several reports finding rates of patients with asymptomatic cams to be 14% to 43%.^11,12 Ultimately, the development of a cam deformity is a dynamic process with an unclear cause and a variable clinical presentation.

Femoral version (FV) is a well-described anatomic parameter that has recently received a resurgence of attention in its role in multiple hip pathologies, including FAI and cam development. While previous work has shown that the presence of a cam lesion is mainly responsible for the reduction in hip flexion range of motion in FAI, it is FV that has a larger effect on the passive hip internal rotation range of motion.^16,19 Arshad et al⁴ identified that up to 51% of patients with symptomatic FAI had an abnormal FV. Thus, evaluating version abnormalities may help better understand the underlying pathology and symptomatology of patients with FAI, which could lead to implications for procedures to correct the underlying version deformity. This underscores the importance of understanding the interplay between cam and FV in the presentation and treatment of FAI.

Within our study, we sought to deepen the current understanding of the association between FV and cam deformity. In clinical practice, FV measurements are often described as a singular value. However, a more accurate account of the total FV includes the version attributable to both the femoral neck and femoral shaft. Archibald et al³ isolated each component of the FV and showed that both femoral neck and femoral shaft versions contribute to overall FV but cannot independently predict the amount of total FV. Therefore, although previous works have suggested that total femoral and acetabular version are not associated with cam morphology, each component has not been evaluated individually.²⁹ Given the unique interplay between FV and cam deformity as they relate to FAI, identifying the relationship between cam and location-specific FV is important. Therefore, the purpose of the study was to investigate site-specific FV and assess the relationship with cam deformity in cadaveric specimens. We hypothesize that although previous studies have not identified a correlation between total FV and cam deformity, site-specific analysis may demonstrate a novel relationship.

Methods

The study used dry cadaveric samples from the Hamann-Todd Osteological Collection (Cleveland, Ohio). The collection contains disarticulated skeletons of over 3000 individuals from between 1912 and 1938.¹⁴ The collection includes demographic information associated with each cadaveric specimen, including age, sex, and race. Any specimen with evidence of deformity or pathology, such as slipped capital femoral epiphysis, posttraumatic injury changes, or Legg-Calvé-Perthes disease, was excluded from the study. After exclusion, 1058 cadaveric specimens had been included. For each specimen, total FV, femoral shaft version, femoral neck version, and α angle were all previously measured and taken from our existing database.

Total FV was measured using the described Kinglsey-Olmsted method.¹⁵ The femur was positioned on wooden blocks with the posterior femoral condyles and greater trochanter as the points of contact. In this position, the plane of the full length of the femur was parallel to the laboratory table, and the elevation on blocks ensured that the femoral head did not contact a surface, thereby maintaining the bone's position. A photograph was taken from a craniocaudal view of the femur. Using ImageJ (National Institutes of Health), total FV was measured using the plane of the wooden blocks on which the posterior condyles were positioned and the axis of the femoral neck (Figure 1A). Based on current practices, specimens with an FV under 5° were classified as retroverted, specimens with an FV between 5° and 20° were considered normal, and specimens with an FV over 20° were classified as excessively anteverted. Although there is no widely accepted definition of normal femoral anteversion, we chose the definition most commonly used in current literature.^8,13,17

Figure 1.

(A) Total femoral version measured using the plane of the wooden blocks on which the posterior condyles were positioned and the axis of the femoral neck. (B) Femoral shaft version defined as the angle between the lesser trochanter and the posterior femoral condyles, with a dotted reference line establishing the lesser trochanter axial axis. (C) The α angle measured as the angle between the line representing the femoral neck axis and a line from the center of the best-fit circle to the point where the anterior cortical surface of the femoral head-neck junction first exits the best-fit circle.

Next, based on the method described by Archibald et al,³ shaft version was defined as the angle between the lesser trochanter and the posterior femoral condyles. To measure this, the femur was placed in the anatomic position on a plexiglass surface. The plane of the femur was rotated until the lesser trochanter was parallel to the table surface. Using an axial photo, the angle between the plexiglass and laboratory table was measured (Figure 1B). Lastly, neck version was calculated by subtracting the measured shaft version from the total FV.

The α angle was measured using a method modified from that described by Nötzli et al.²⁵ With the femur positioned as described for measuring FV, standardized photos were taken from the inclination view, an oblique craniocaudal view angled perpendicular to the femoral neck that approximates the femoral neck orientation used for radial magnetic resonance imaging. A best-fit circle was placed over the femoral head. The α angle was measured as the angle between the line representing the femoral neck axis and a line from the center of the best-fit circle to the point where the anterior cortical surface of the femoral head-neck junction first exits the best-fit circle (Figure 1C). Specimens were documented as having a cam deformity when the α angle measured over 60°.¹ Measurements were obtained by 2 orthopaedic surgery residents trained by the senior author (R.W.L.). Intraclass correlation values were determined based on sample measurements from 25 specimens.

All statistical analysis was performed using SPSS (SPSS, Inc). The study population was characterized using descriptive statistics as well as correlations and chi-square. Multiple regression analysis was performed to analyze the relationship between the α angle and the measured variables. The α level was set at .05.

Results

In total, 1058 cadaveric femurs were included in the study. There were 726 (69%) femurs from White specimens and 330 (31%) from Black specimens. Of the 1058 analyzed femurs, 146 (14%) were from women, and 912 (86%) were from men. The mean ± SD age was 56 ± 10 years.

Of the 1058 cadaveric femurs, the mean ± SD α angle was 54°± 11°. There were 354 (33%) cam deformities, with a mean ± SD α angle of 67°± 6°. The mean ± SD amount of total FV among all specimens was 11°± 12°, while the amount of total FV among specimens with cam deformities was 11°± 12°. Across all specimens, there were 277 retroverted femurs, 533 femurs with normal FV, and 248 femurs with excessive femoral anteversion with regard to total FV. For the measured specimens, the mean ± SD amount was 24°± 10° for the femoral shaft version and −13°± 19° for the femoral neck version. For the measured specimens with a cam deformity, the mean ± SD amount was 24°± 10° for the femoral shaft version and −12°± 19° for the femoral neck version (Table 1). Therefore, the femoral shaft–based version was anteverted on average compared with the femoral neck–based version, which was retroverted on average. In most cases, the orientation of version was in opposing directions between the site-specific locations. The intraclass correlation coefficients for measurements were as follows: total FV, 0.94; femoral shaft version, 0.86; and α angle, 0.86.

Table 1

Demographics and Measurements Across Each Cohort Based on Cam Morphology ^a

Characteristic	Complete Cohort (N = 1058)		With Cam (n = 354)		Without Cam (n = 704)
Characteristic	Value	Range	Value	Range	Value	Range
Age	56 ± 10	40 to 79	55 ± 11	40 to 79	56 ± 10	40 to 79
Sex (male), No. (%)	912 (86)	—	321 (91)		591 (84)	—
Race (White), No. (%)	726 (69)	—	267 (75)		459 (65)	—
Total femoral version, deg	11 ± 12	−41 to 54	11 ± 12	−18 to 54	11 ± 12	−41 to 40
Neck femoral version, deg	−13 ± 19	−64 to 63	−12 ± 19	−61 to 63	−13 ± 19	−64 to 35
Shaft femoral version, deg	24 ± 10	−24 to 53	24 ± 10	−24 to 45	24 ± 10	−6 to 53
α Angle, deg	54 ± 11	26 to 94	67 ± 6	60 to 94	48 ± 7	26 to 60

Values are presented as mean ± SD unless otherwise indicated.

On univariate analysis, an increasing α angle was correlated with both male sex (r = −0.074, P = .02) and White race (r = −0.102, P < .001). Increasing total version was correlated with female sex (r = 0.07, P = .02), decreasing age (r = −0.062, P = .04), and White ethnicity (r = −0.16, P < .001). Femoral shaft version was positively correlated with female sex (r = 0.110, P < .001). Femoral neck version was positively correlated with Black race (r = 0.18, P < .001). There was no correlation between total FV and α angle (r = 0.054, P = .08). Additionally, both femoral shaft version and femoral neck version were not correlated to α angle independently (r = −0.001, P = .98; r = 0.035, P = .26) (Table 2).

Table 2

Correlations Between Demographics, Femoral Version, and α Angle ^a

Variable	α Angle	Total Version	Shaft Version	Neck Version
α Angle	1
Total version	0.54 (.78)	1
Shaft version	−0.001 (.98)	—	1
Neck version	0.035 (.26)	—	−0.817 (<.001)	1
Age	−0.005 (.87)	−0.062 (.042)	−0.002 (.95)	−0.039 (.207)
Sex	−0.074 (.02)	0.070 (.022)	0.110 (<.001)	−0.015 (.63)
Race	−0.102 (.001)	0.160 (<.001)	−0.027 (.38)	0.117 (<.001)

Correlations are presented as the Pearson correlation, with statistical significance in parentheses. Female sex was represented as “1” and Black race was represented as “1” for analysis.

On multivariate analysis, we found that sex, race, femoral neck version, and femoral shaft version were independent predictors for α angle (P < .05). Black race predicted a decrease in α angle of 2.8° (P < .001). Female sex predicted a decrease in α angle of 2.2° (P = .03). Each degree increase in femoral neck version predicted an increase in α angle of 0.09° (P = .006). Similarly, each degree increase in femoral shaft version predicted an increase in α angle of 0.14° (P = .02) (Table 3). Additionally, a multivariate regression was performed to identify if total FV predicted α angle while controlling for age, sex, and race. Each degree increase in total FV predicted an increase in α angle of 0.07° (P = .016).

Table 3

Multivariate Regression Analysis of Predictors of α Angle, Including the Origin of Femoral Version

Independent Variable	Standard β	Unstandardized β	Confidence Interval	P Value
Age	−0.032	−0.036	−0.10 to 0.03	.31
Race	−0.11	−2.78	−4.33 to −1.22	<.001
Sex	−0.068	−2.22	−4.24 to −0.20	.031
Femoral neck version	0.15	0.090	0.03 to 0.15	.006
Femoral shaft version	0.17	0.14	0.02 to 0.26	.020

Discussion

Abnormal FV is a common coexisting pathology in those with FAI and approaches an incidence of nearly 50%.^4,20 However, previous literature has been limited due to measuring FV as a singular parameter, when in reality, FV is more nuanced in terms of its precise anatomic location within the femur. Using data from a cadaveric collection where the separate components of FV could be measured, we identified that both femoral shaft and femoral neck version are independent predictors of α angle magnitude in multiple regression analysis. Each degree increase predicts an increase in α angle of 0.09° for femoral neck anteversion and 0.14° for femoral shaft anteversion. Additionally, our study demonstrated sex- and race-based differences in α angle and FV; Black men were more likely to have a smaller α angle, while younger White women were more likely to have a larger amount of femoral anteversion.

Two previous studies have examined the association between cam deformity and FV. Chadayammuri et al⁶ examined a cohort of 221 patients undergoing hip arthroscopy and found that patients with a cam lesion had a larger degree of femoral anteversion. Thus, if cam lesions are associated with femoral anteversion, in our study, femoral shaft version was on average anteverted compared with femoral neck version and, therefore, may explain the greater relationship between α angle and femoral shaft version. In contrast, a more recent study of 986 hips from our same cadaveric collection found no significant association between the 2 variables, although there was a trend that supported more FV with cam morphology.²⁹ Of note, due to the expansive nature of the osteologic collection, only 115 specimens with 230 femurs overlapped across the 2 studies, explaining the differences in cam incidence across the 2 study cohorts. We hypothesize that a better understanding of these 2 parameters may exist when examining version as both shaft and neck contributions.

Our current report found that both shaft-based FV and neck-based FV were independent predictors of α angle. However, while this correlation was statistically significant, the clinical significance of this observation remains unclear. When you apply the result to patients across the accepted range of femoral anteversion, a patient with 20° of shaft-based anteversion would have only a 2.1° larger predicted α angle compared with a patient with 5° of shaft-based anteversion. This might be implied by the findings in our study, which demonstrate that women have larger femoral anteversion, but men have increased α angles. Both findings are supported by previous literature.^6,9,31 Thus, while this study introduces a new concept of localizing FV, the clinical significance of these results with regard to α angle remains unclear and begs the question if the findings have a role in explaining FAI symptomatology.

The issue of cam deformity and subsequent FAI is complex, with a multifactorial cause and varied clinical presentation, including a large percentage of the population with an asymptomatic cam deformity. Currently described predictive parameters for FAI symptoms include α angle, femoral neck shaft angle, loss of offset, and pelvic range of motion.^23,24 Additionally, it has been shown that in those with symptomatic FAI, patients have larger cam lesions.²¹ However, the effect of FV in patients with symptomatic or asymptomatic FAI remains unclear. Moreover, variation in the magnitude and specific location of version could contribute differently to overall clinical presentation. In a study of 67 patients, Grammatopoulos et al¹⁰ showed that impingement symptoms caused by cam lesions were not explained by differences in FV, while Audenaert et al⁵ proposed that the combination of decreased femoral anteversion and increased acetabular coverage contributes to the risk of early femoroacetabular collision and is predictive of the risk of developing clinical hip impingement. Notably, these conflicting conclusions were not based on the analysis of site-specific FV. The results of our study highlight a statistically significant but comparatively small relationship between site-specific FV and the amount of cam deformity. However, it is important to note that this study included a relatively random population and still found an effect. Future study in populations with pathology may uncover larger findings, and it is possible that the localization of version may help explain previous contradictions in the literature concerning overall symptomology in FAI. As both previous studies used total FV, a future study differentiating between both femoral shaft and femoral neck version in the analysis of clinical symptoms is warranted.

FV is classically reported as a value that combines the version of the femoral neck and torsion of the femoral shaft. This study encourages clinicians to consider both contributing anatomic components of FV to identify the level of deformity. Following an attempt at nonoperative management, symptomatic cam morphology is often managed with hip arthroscopy via femoral osteoplasty, while femoral rotational osteotomies are reserved for cases with abnormal FV or failed previous surgical management.^2,22,30 A systematic review found that while clinical improvement can likely be achieved with hip arthroscopy despite the amount of FV, patients with excessive anteversion or retroversion had worse overall improvement.²⁸ Therefore, when planning to perform a corrective femoral osteotomy in patients with FAI, the surgeon should evaluate site-specific FV to adequately correct the underlying deformity.

There are several limitations to this study. As the study used a historical cadaveric collection, there is a theoretical possibility that skeletal differences exist between the historic specimens in our collection and the general population today. Previous reports have proposed that participation in high-demand sports during adolescence is a predisposing factor in the development of cam deformity. As we are unable to assess lifestyle, occupational, or nutritional differences in this study, we cannot evaluate these potential variables of interest or confounders. Second, although female sex and Black specimens were predictive of a smaller α angle, the sex- and race-related differences in α angle may be different from those reported in this study due to the significantly lower number of female and Black specimens, in addition to a lack of Asian or Native American specimens. Compared with a previous study from the same osteologic collection, we found a higher overall incidence of cam morphology in our population, introducing the possibility of a sampling bias. While it is worthwhile to report the overall incidence of cam morphology in this population, the main goal of the study was to investigate the underlying relationship between cam morphology and site-specific FV, which should be minimally affected by the sampling method. As with any cadaveric study, our results take into account only the osteological parameters and cannot account for the role of soft tissue and muscle connections that potentially impart some level of variation. Further, the specimens did not include the acetabulum, and thus we cannot determine the interplay with acetabular version, although previous cadaveric studies have not identified an association between cam morphology and acetabular version.²⁹ Lastly, we are unable to directly correlate osteologic parameters to predict symptomatology, as this is a cadaveric study.

Conclusion

Footnotes

Final revision submitted July 5, 2025; accepted July 26, 2025.

The authors have declared that there are no conflicts of interest in the authorship and publication of this contribution. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Ethical approval was not sought for the present study.

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