The effect of varus and valgus osteotomies on femoral version

Alpha Angle and Anterior Femoral Neck Offset Identify Different Cohorts of Cam Morphology: An Osteologic Study

PURPOSE

To explore differences in cam morphology defined by alpha angle (AA) and anterior femoral neck offset (AFNO) in the context of other anthropometric parameters in an osteologic collection to further elucidate whether each measurement tool is identifying the same underlying pathology.

METHODS

Anthropometric measurements of 992 cadaveric hips from the Hamann-Todd Osteological Collection were analyzed. Femurs with cam morphology were identified by AA >55° or AFNO <7 mm. Anthropometric parameters stratified by cam morphology were assessed with Wilcoxon rank-sum and Pearson χ2 tests. Multivariate logistic regressions were performed on significant variables in univariate analysis to examine the predictive ability of anthropometric variables to cam morphology.

RESULTS

Cam 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 = .04), race negatively predicted AA (Blacks with less pathology, β = -0.21, P < .01), and proximal femoral osteoarthritis was positively associated with AA (β = 0.16, P = .02), while none of these were associated with AFNO. On the other hand, right-side specimens were associated with AA (β = 0.15, P = .02) and AFNO (β = 0.25, P < .01), whereas the combined version was unassociated with both measures.

CONCLUSIONS

In conclusion, cam morphology was identified in a modest percentage of osteologic specimens by both AA and AFNO in our study. Further, associations of multiple demographic, anthropometric, and anatomical parameters to AA and AFNO suggest they may identify different subsets of cam morphology.

CLINICAL RELEVANCE

Cam morphology identified by AA versus AFNO may represent 2 different pathologic entities. Future studies should assess differences between these measures in a clinical cohort and determine whether these 2 definitions of cam morphology identify different clinical populations.

Establishment of an Accurate and Precise Alternative Intraoperative Technique for Determination of Femoral Version

BACKGROUND

Accurate assessment of the femoral version can be challenging in the operating room. We evaluated if an observer can reliably and accurately determine when a femoral neck is parallel to the floor with a modified C-arm technique. We compared this technique to the previously reported modified Ogata-Goldsand technique for determining the intraoperative femoral version.

METHODS

To evaluate if an observer can determine when the femoral neck is level to the ground, 72 cadaveric femurs were photographed laterally at the proximal femur with the bone rotated to simulate a version ranging from -20 degrees to +20 degrees in 5-degree increments. These were arranged in a grid layout and validated through 3-fold randomization and blinding. Five investigators selected the orientation they believed to be closest to the neutral (0 degrees) femoral version. Then, 4 full-size cadavers were examined in a surgical suite. The femoral version of each full-size femoral cadaver was estimated utilizing the modified C-arm technique versus the modified Ogata-Goldsand technique, with the Kingsley and Olmsted technique used as the widely accepted standard to measure the femoral version.

RESULTS

In determining the neutral femoral neck position, observers were able to determine 0 degrees of version accurately, with the average deviation being 4.4 ± 2.4 degrees. The modified C-arm technique produced an average measurement deviating 3.2 ± 4.2 degrees from the true value. The modified Ogata-Goldsand technique had an average measurement deviation of 2.3 ± 2.6 degrees from the true angle. The modified C-arm technique had an intraclass correlation coefficient of 0.82 for different observers and 0.81 when compared to the Kingsley and Olmsted method as the standard, versus 0.72 and 0.90 for the modified Ogata-Goldsand technique.

CONCLUSIONS

Observers can accurately perceive when a femoral neck is parallel to a virtual floor, supporting the inclusion of this parameter in the modified C-arm technique. Utilization of the modified C-arm technique is comparable to the modified Ogata-Goldsand technique.

CLINICAL RELEVANCE

The relative simplicity of the modified C-arm technique versus the modified Ogata-Goldsand technique makes the modified C-arm technique a reasonable additional option for measuring intraoperative femoral version.

Effects of femoral de-rotation on lower limb alignment using patient-specific guides with reliance on EOS scan, a retrospective study

The aim of this study is to evaluate the effects of midshaft femoral derotation surgery on the alignment of the lower limbs in the coronal and sagittal planes, as well as its impact on pelvic parameters in patients with significant femoral anteversion or retroversion.A retrospective review was conducted on patients who underwent femoral derotation procedures using a minimally invasive patient-specific external guide system from January 2014 to January 2022 at Macquarie University Hospital. The surgery was done using preoperative 3D modeling and patient-specific external guides. Inclusion criteria comprised patients presenting with hip, knee, or patellofemoral symptoms due to high femoral anteversion who had complete EOS scans performed preoperatively and postoperatively. The EOS imaging system was utilized for accurate assessment and comparative analysis of alignment changes following the femoral derotation.There were 22 limbs from 15 patients with an average age at operation of 30.41 ± 10.14 years (range 16.77-47.50). The average preoperative 3D EOS measurement of the femoral version in anteversion and retroversion groups were 32.84 ± 7.53° and - 22.67 ± 13.32°, respectively. The postoperative femoral version in anteversion and retroversion groups were 13.39 ± 12.90° and 3.67 ± 9.29° having p < 0.001 and p < 0.014, respectively. Paired t-test was employed to calculate statistical values. Other parameters, including Hip-knee-shaft (HKS) angle, knee angle, pelvic tilt, pelvic incidence, mechanical lateral distal femoral angle (mLDFA), and coronal plane alignment of the knee, were not statistically significant differences.This study provides evidence that femoral midshaft derotation surgery using patient-specific instrumentation (PSI) guides is an effective approach for correcting femoral anteversion and retroversion with no significant impact on coronal and sagittal lower limb alignment except femoral neck offset.

Association of Idiopathic Cam Morphology With Femoral and Acetabular Version: Analysis of 986 Cadaveric Hips

Background

Studies have correlated symptomatic femoroacetabular impingement (FAI) with femoral retroversion and cam lesions.

Purpose

To investigate any association between femoral and acetabular versions with cam deformity in a largely asymptomatic population.

Study Design

Descriptive laboratory study.

Methods

A total of 986 cadaveric hips were selected from a historical osteologic collection. Each hip was assessed to determine the femoral and acetabular versions, anterior offset, and alpha angle. Cam morphology was defined as an alpha angle >60°. Multiple regression analysis was performed to determine the relationship between age, femoral version, acetabular version, and either alpha angle or anterior femoral offset.

Results

The mean alpha angle and anterior offset for the sample population were 48.1°± 10.4° and 0.77 ± 0.17 cm, respectively, with cam morphology in 149 of the 986 (15.1%) specimens. No significant difference was observed between hips with and without cam morphology with respect to the femoral (10.8°± 10° vs 10.3°± 9.6°; P = .58) or acetabular versions (17.4°± 6° vs 18.2°± 6.3°; P = .14). Multiple regression analysis did not demonstrate an association between the femoral or acetabular versions and the alpha angle, and it showed a small association between the increasing femoral and acetabular versions and a decreased anterior femoral offset (both P < .01).

Conclusion

In a large random sample of cadaveric hips, cam morphology was not associated with femoral or acetabular retroversion. Combined with the existing literature, these findings suggest that retroversion is not associated with cam development.

Clinical Relevance

This study provides insight into the development of cam morphology, which may eventually aid in the evaluation and treatment of FAI.

Virtual 3D femur model to assess femoral version: comparison to the 2D axial slice approach

BACKGROUND

Quantifying femoral version is crucial in diagnosing femoral version abnormalities and for accurate pre-surgical planning. There are numerous methods for measuring femoral version, however, reliability studies for most of these methods excluded children with hip deformities.

OBJECTIVE

To propose a method of measuring femoral version based on a virtual 3D femur model, and systematically compare its reliability to the widely used Murphy's 2D axial slice technique.

MATERIALS AND METHODS

We searched our imaging database to identify hip/femur CTs performed on children (<18 years old) with a clinical indication of femoral version measurement (September 2021-August 2022). Exclusion criteria were prior hip surgery, and inadequate image quality or field-of-view. Two blinded radiologists independently measured femoral version using the virtual 3D femur model and Murphy's 2D axial slice method. To assess intrareader variability, we randomly selected 20% of the study sample for re-measurements by the two radiologists >2 weeks later. We analyzed the reliability and correlation of these techniques via intraclass correlation coefficient (ICC), Bland-Altman analysis, and deformity subgroup analysis.

RESULTS

Our study sample consisted of 142 femurs from 71 patients (10.6±4.4 years, male=31). Intra- and inter-reader correlations for both techniques were excellent (ICC≥0.91). However, Bland-Altman analysis revealed that the standard deviation (SD) of the absolute difference between the two radiologists for the Murphy method (mean 13.7°) was larger than that of the 3D femur model technique (mean 4.8°), indicating higher reader variability. In femurs with hip flexion deformity, the SD of the absolute difference for the Murphy technique was 17°, compared to 6.5° for the 3D femur model technique. In femurs with apparent coxa valga deformity, the SD of the absolute difference for the Murphy technique was 10.4°, compared to 5.2° for the 3D femur model technique.

CONCLUSION

The 3D femur model technique is more reliable than the Murphy's 2D axial slice technique in measuring femoral version, especially in children with hip flexion and apparent coxa valga deformities.

Imaging of Anatomical Variants Around the Hip

Considering the current widespread use of imaging as an integral part of managing hip pain, variable hip geometries and anatomical variants are increasingly being detected. These variants are commonly found in the acetabulum and proximal femur, as well as the surrounding capsule-labral tissues. The morphology of specific anatomical spaces confined by the proximal femur and the bony pelvis may also vary significantly among individuals. Familiarity with the spectrum of imaging appearances of the hip is necessary to identify variant hip morphologies with or without potential clinical relevance and reduce an unnecessary work-up and overdiagnosis. We describe anatomical variations and variable morphologies of the bony structures comprising the hip joint and the soft tissues, around the hip. The potential clinical significance of these findings is further analyzed in conjunction with the patient's profile.

Coxa valga and antetorta increases differences among different femoral version measurements

Aims

To evaluate how abnormal proximal femoral anatomy affects different femoral version measurements in young patients with hip pain.

Methods

First, femoral version was measured in 50 hips of symptomatic consecutively selected patients with hip pain (mean age 20 years (SD 6), 60% (n = 25) females) on preoperative CT scans using different measurement methods: Lee et al, Reikerås et al, Tomczak et al, and Murphy et al. Neck-shaft angle (NSA) and α angle were measured on coronal and radial CT images. Second, CT scans from three patients with femoral retroversion, normal femoral version, and anteversion were used to create 3D femur models, which were manipulated to generate models with different NSAs and different cam lesions, resulting in eight models per patient. Femoral version measurements were repeated on manipulated femora.

Results

Comparing the different measurement methods for femoral version resulted in a maximum mean difference of 18° (95% CI 16 to 20) between the most proximal (Lee et al) and most distal (Murphy et al) methods. Higher differences in proximal and distal femoral version measurement techniques were seen in femora with greater femoral version (r > 0.46; p < 0.001) and greater NSA (r > 0.37; p = 0.008) between all measurement methods. In the parametric 3D manipulation analysis, differences in femoral version increased 11° and 9° in patients with high and normal femoral version, respectively, with increasing NSA (110° to 150°).

Conclusion

Measurement of femoral version angles differ depending on the method used to almost 20°, which is in the range of the aimed surgical correction in derotational femoral osteotomy and thus can be considered clinically relevant. Differences between proximal and distal measurement methods further increase by increasing femoral version and NSA. Measurement methods that take the entire proximal femur into account by using distal landmarks may produce more sensitive measurements of these differences.

Cite this article: Bone Jt Open 2022;3(10):759–766.

The association between femoral neck shaft angle and degenerative disease of the hip in a cadaveric model

BACKGROUND

While the influences of acetabular dysplasia and overcoverage on hip arthritis have been studied, the impact of femoral neck-shaft angle on hip arthritis is much more poorly understood. The purpose of this study is to determine if a relationship exists between neck shaft angle and the development of osteoarthritis, a better understanding of which would be useful to surgeons planning osteotomies about the hip.

METHODS

533 cadaveric femora and acetabulae (1066 total) from the Hamann-Todd Osteological Collection (Cleveland, OH) were acquired. We measured true neck shaft angle using an AP photograph with the femoral neck parallel to the table. Femoral head volume to acetabular volume ratio, representing femoral head coverage, as well as femoral version were utilised. Correlation between neck shaft angle, femoral version, femoral head coverage and osteoarthritis were evaluated with multiple regression analysis.

RESULTS

The mean age and standard deviation was 56 ± 10 years. There were 64 females (12%) and 469 males. There were 380 Caucasians (71%) and 153 African-Americans. Mean femoral version was 11° ± 12° and mean true neck shaft angle was 127.7° ± 5.9° There was a strong correlation between age and arthritis (standardised beta 0.488, p < 0.001). There was a significant correlation between increasing true neck shaft angle and decreasing hip arthritis (standardised beta -0.024, p = 0.038). In the femoral head overcoverage subset, increasing true neck shaft angle was still significantly associated with decreasing hip arthritis (standardised beta -0.088, p = 0.018), although this relationship was not significant with femoral head undercoverage subset.

CONCLUSIONS

With sufficient acetabular coverage, a relative increase in femoral neck shaft angle within the physiologic range is associated with decreased hip osteoarthritis.

CLINICAL RELEVANCE

An understanding of the relationship between femoral neck shaft angle and hip osteoarthritis could be useful for surgeons planning pelvic or proximal femur osteotomies in children.

The distal femur trochlear groove appears to compensate for tibial deformity but not femoral deformity in an investigation of five-hundred and seventy-nine cadaveric skeletons

BACKGROUND

The etiology of patellofemoral disorders is multifactorial. Preoperative patellofemoral anatomy evaluation is of great importance in patients undergoing surgery for patellofemoral disorders. Although anatomical risk factors of patellofemoral disorders have been thoroughly investigated in clinical and radiological studies, there are sparse data regarding the association between trochlear dysplasia with other anatomical parameters. This study sought to explore those associations using a large osteological collection.

METHODS

Five-hundred and seventy-nine cadaveric skeletons were obtained from the Hamann-Todd osteological collection. Mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), femoral version, tibial torsion, lateral position of the tibial tubercle, and femoral length were modeled as predictors of medial and lateral flange height of the distal femur trochlea at various degrees of knee flexion.

RESULTS

The average age and standard deviation for the 1158 lower extremities analyzed was 55.9 ± 10.2 years. There were 500 males (86%) and 79 females. Increasing MPTA or tibial valgus predicted increasing lateral femoral flange height at 0, 30, and 50 degrees of knee flexion [(standardized beta 0.111, p = 0.01), (standardized beta 0.129, p < 0.001), and (standardized beta 0.186, p < 0.001), respectively]. Increasing internal tibial torsion predicted increased medial flange height at 30 and 50° [(standardized beta - 0.114, p = 0.006), (standardized beta - 0.108, p = 0.006), respectively]. Increased femoral retroversion predicted increasing lateral flange height at 0 and 30 degrees [(standardized beta - 0.105, p = 0.005), (standardized beta - 0.098, p = 0.004), respectively].

CONCLUSIONS

To maintain the equilibrium necessary for effective patellar tracking, the depth of trochlear groove appears to effectively compensate for some of the anatomical parameters of the proximal tibia associated with patellofemoral disorders, and appears to be less influenced by femoral alignment. The clinical relevance of these findings warrants further investigation, and emphasizes the importance of carefully assessing the lower limb alignment in the management of patellofemoral disorders.

Femoral neck shaft angle is not correlated with femoral version: A retrospective study of computed tomography scans

BACKGROUND

An understanding of femoral anteversion and neck-shaft angle (NSA) is essential to deliver optimal orthopaedic surgical care. Despite the importance, there is little research examining the relationship between femoral anteversion and the NSA in an adult population. This study sought to determine if there is a correlation between femoral neck shaft angle and version in skeletally mature adults using computed tomography (CT) scanograms.

METHODS

Between January 2010 and June 2017, all skeletally mature patients who had received a CT scanogram of the lower extremity were reviewed. Exclusion criteria included: (1) radiographic evidence of osteoarthritis, (2) history of hip, femur, or knee surgery or trauma, (3) and anatomic abnormalities of the proximal femur including prior slipped capital femoral epiphysis or Legg-Calvé-Perthes disease. Both femoral version and NSA were measured by a musculoskeletal fellowship trained radiologist using CT scanograms. Correlation between femoral version and NSA was determined using coefficient of determination (R²) and Pearson correlation coefficient (r) for the group as a whole and for each sex.

RESULTS

There was no statistical correlation between femoral version and NSA for either the entire cohort or for each sex. For the entire cohort, R² = 0.0016 and r was 0.04 (p=0.45), for females, R² = 0.0005 and r was 0.0224 (p=0.72), and for males, R² = 0.0342 and r was 0.185 (p=0.07).

CONCLUSION

There was no correlation between femoral version and NSA. This finding is beneficial for surgeons to understand the proximal femoral anatomy. Patients with an increased femoral NSA should not be assumed to have increased femoral anteversion.

LEVEL OF EVIDENCE

Level III, Retrospective Cohort Study.

Femoral Neck Shaft Angle and Management of Proximal Femur Fractures: Is the Contralateral Femur a Reliable Template?

OBJECTIVES

To (1) assess interrater reliability of a novel technique for measurement of neck shaft angle (NSA); (2) use pelvic anteroposterior (AP) radiographs of unaffected hips to assess variability of NSA; and (3) evaluate the side-to-side variability of NSA to determine reliability of using the contralateral hip as a template.

DESIGN

Retrospective cohort study.

SETTING

Academic Level 1 regional trauma center.

PATIENTS/PARTICIPANTS

Four hundred six femora (203 patients) with standing AP pelvis radiographs were selected. Exclusions included lack of acceptable imaging, congenital abnormalities, or prior hip surgery.

INTERVENTION

An AP pelvis radiograph in the standing position.

MAIN OUTCOME MEASUREMENTS

Bilateral NSA measurements obtained in a blinded fashion between 2 reviewers. Pearson coefficients and coefficient of determination assessed correlations and variability between left and right NSA. Concordance correlation coefficients assessed the interrater reliability between measurements performed by the 2 reviewers.

RESULTS

Two hundred three patients (406 femora) were assessed. Male patients had a lower overall NSA mean of 131.56 degrees ± 4.74 than females with 133.61 degrees ± 5.17. There was no significant difference in NSA side-to-side in females (P = 0.18), 0.3 degrees [95% confidence interval (-0.15 to 0.75)], or males (P = 0.68), 0.19 degrees [95% confidence interval (-0.74 to 1.12)]. There was a strong linear relationship between left and right femora (r2 = 0.70). Forty-one percent of patients fell within the 131-135 degrees range bilaterally. Eighty-eight percent of patients had <5 degrees difference in NSA bilaterally and 0% had >10 degrees difference.

CONCLUSIONS

There is no significant variability between bilateral femora in males and females. Use of this measurement method and contralateral NSA for proximal femur fracture planning is supported.

Comparison of canine femoral torsion measurements using the axial and biplanar methods on three-dimensional volumetric reconstructions of computed tomography images

OBJECTIVE

To compare the results of the measurement of femoral torsion using the axial measurement method on three-dimensional (3D) volumetric reconstructions of computed tomography images AMM(CT), the biplanar measurement method on 3D volumetric reconstructions of computed tomography images BMM(CT) and a reference standard using the axial measurement method on stereolithographic bone models AMM (SBM).

STUDY DESIGN

Ex vivo study.

SAMPLE POPULATIONS

Three-dimensional volumetric reconstructions of computed tomography images and stereolithographic bone models from 23 femurs of 14 dogs with hind limb lameness presented for orthopedic evaluation.

METHODS

Three-dimensional volumetric reconstructions of computed tomography images and stereolithographic bone models of each femur were created from computed tomography data. Femoral torsion was measured using the AMM (CT) and the BMM (CT) and compared with a reference standard, the AMM (SBM).

RESULTS

No differences were noted among the measurement methods (P = .0863). Median measurement of femoral torsion using the AMM (CT) was 34.2°, the BMM (CT) was 36.7°, and the AMM (SBM) was 32.3°.

CONCLUSION

No differences existed among the AMM (CT), the BMM (CT), and the AMM (SBM).

CLINICAL SIGNIFICANCE

Both AMM (CT) and BMM (CT) can be used to measure femoral torsion in dogs with orthopedic disease.

Ischiofemoral Impingement Syndrome: Effect of Morphological Variations on the Diagnosis

OBJECTIVE

The purpose of this study is to clarify which morphologic variations of the hip on MRI are associated with the development of ischiofemoral impingement.

METHODS

Hip MRIs of patients who have been referred to our department between 2016-2017 were retrospectively reviewed and assessed for pathological signal changes in the quadratus femoris muscle and ipsilateral hip or buttock pain. After assessment, ischial angle, inclination angle, ischiofemoral space, quadratus femoris space, intertuberous distances and femur neck angle, femoral torsion angle and knee angle were measured and compared in 37 hips of 20 patients and 56 hips of 28 age-gender matched control subjects.

RESULTS

There were statistically significant differences between the patient and control groups in all MRI parameters except for intertuberous distances (p<0.05). Quadratus femoris space (p<0.001) and ischiofemoral space (p<0.001) were significantly lower and femoral torsion angle (p=0.02), femur neck angle (p=0.001), ischial angle (p=0.01) and inclination angle (p=0.03) values were significantly higher in patients compared with the control group.

CONCLUSION

Decreased ischiofemoral space and quadratus femoris space, increased femoral torsion angle, femur neck angle, ischial angle and inclination angle are found to be associated with IFI on MRI. These pelvic anatomical variations may predispose to ischiofemoral impingement and should be kept in mind for patients with hip pain.

Normative Values for Capital Femoral Epiphyseal Extension of the Developing Hip Based on Age, Sex, and Oxford Bone Age

BACKGROUND

Recent evidence suggests that increasing capital femoral epiphyseal extension may be an adaptive response that underlies the development of most cam morphology, whereas slipped capital femoral epiphysis is associated with its deficiency. However, there is an absence of rigorous data on the normal development of epiphyseal extension in the hip joint in modern adolescents. The aim of this study was to establish normative values for anterior and superior epiphyseal extension in a normal adolescent control population.

METHODS

A total of 210 pediatric subjects (420 hips) between the ages of 8 and 17 years old at the time of presentation who received pelvic radiographs were retrospectively reviewed. Basic demographic data were collected. All subjects with underlying hip pathology were excluded. Epiphyseal extension ratio (EER) was measured, defined as the ratio of extension of the capital femoral epiphysis down the femoral neck relative to the diameter of the femoral head. Superior EER was measured on the anterioposterior view and anterior EER on the frog-leg lateral view bilaterally. Skeletal maturity was graded based on Oxford bone age (OBA) at the proximal femur.

RESULTS

The superior EER increased from 0.63±0.05 at age 8 to 0.80±0.05 at age 17. The anterior EER similarly increased from 0.56±0.06 at age 8 to 0.74±0.05 at age 17. The superior and anterior EERs increased with age in a linear fashion for males (r=0.80 and 0.75, respectively) and females (r=0.67 and 0.65) through physeal closure. When subjects were standardized by the OBA stage of the femoral head, females and males showed no statistical difference at OBA stages 6, 7 or 8.

CONCLUSIONS

Superior and anterior EER increased throughout adolescent development until physeal closure. When controlling for skeletal maturity, there were no significant differences between sexes. This normative data may help guide future management and research of slipped capital femoral epiphysis and cam morphology.

LEVEL OF EVIDENCE

Level II, Diagnostic.

Proof of concept: hip joint damage occurs at the zone of femoroacetabular impingement (FAI) in an experimental FAI sheep model

OBJECTIVE

In ovine hips chondrolabral damage as seen in cam-type femoroacetabular impingement (FAI) can be induced via an intertrochanteric varus osteotomy. However, it is yet to proven whether the observed cartilage damage is caused by a dynamic cam type impingement. Thus we asked, (1) whether actual cartilage damage observed after FAI induction in ovine hips occurs at the predicted, computed zone of FAI; (2) whether the extent of cartilage damage increases with ambulation time in this animal model?

DESIGN

In this experimental, controlled, comparative study 20 sheep underwent unilateral FAI induction through an intertrochanteric varus osteotomy. Preoperatively sheep underwent computed tomography to generate three-dimensional models of the osseous pelvis and femur. The models were used to predict impingement zones before and after simulated varus osteotomy using range of motion (ROM) analysis. Sheep were sacrificed after 14-40 weeks of ambulation. At sacrifice cartilage was inspected and (1) location of actual damage and computed impingement zones were compared; (2) Cartilage damage was compared between short- and long ambulation groups.

RESULTS

(1) The average location and the extent of peripheral and central cartilage lesions did not differ with the computed impingement zones (all P > 0.05). (2) Grades of central, posterior cartilage damage were more severe in the long-compared to the short ambulation group (2.2 ± 1.8 vs 0.4 ± 0.5; P = 0.030).

CONCLUSIONS

In this experimental ovine FAI model the surgical induction of an osseous impingement conflict between the femur and acetabulum causes cartilage damage at the zone of simulated FAI.

Hip morphology predicts posterior hip impingement in a cadaveric model

INTRODUCTION

Posterior hip impingement is a recently-identified cause of hip pain. The purpose of this study is to characterise posterior femoroacetabular and ischiofemoral impingement and identify its predisposing morphologic traits.

METHODS

Two hundred and six cadaveric hips were randomly selected and taken through controlled motion in two pure axes associated with posterior hip impingement: external rotation (through the mechanical axis) and adduction (coronal plane). The range of motion and location of impingement was noted for each specimen. Morphologic traits including femoral/acetabular version, and true neck-shaft angle (TNSA) were also measured.

RESULTS

External rotation impingement occurred between the femoral neck and acetabulum in 83.0% of hips, and between the lesser trochanter and ischial tuberosity in 17.0%. Adduction impingement occurred between the lesser trochanter and ischial tuberosity in 78.6% of hips, and between the femoral neck and acetabulum in 21.4%. Multiple regression revealed that increased femoral/acetabular version predicted earlier external rotation and adduction impingement. Unstandardised betas ranging from -0.39 to -0.64 reflect that each degree of increased femoral/acetabular version individually accounts for a loss of external rotation or adduction of approximately half a degree before impingement ( p < 0.001 for each). Increased TNSA was associated with earlier adduction impingement only (unstandardised beta -0.35, p = 0.005).

DISCUSSION

Relative femoral/acetabular anteversion was associated with earlier posterior hip impingement. Coxa valga was associated with earlier adduction impingement, but protective against external rotation impingement. These findings highlight the importance of monitoring correction during femoral/acetabular osteotomies, as overcorrection of retroversion may predispose to earlier posterior impingement.

Changes in Proximal Femoral Shape During Fetal Development

BACKGROUND

Walker and Goldsmith's classic article on fetal hip joint development reported that neck/shaft angle did not change from 12 weeks of gestational age through term while version increased from 0 to 40 degrees. This suggests no change in coronal alignment during development, a conclusion we dispute. By re-examining their data, we found that the true neck/shaft angle (tNSA) decreased by 7.5 degrees as version increased by 40 degrees from 12 weeks of gestational age to term.

METHODS

Four investigators measured both femoral version and neck-shaft angle from photographs published by the authors of femurs at multiple stages of maturation from 12 weeks of gestational age to term. The tNSAs and inclination angles were calculated for each femur illustrated using previously validated formula. Changes in the morphology of the femur over time were analyzed using a Student t test. Interobserver and intraobserver reliability were also determined by the Pearson R coefficient.

RESULTS

As reported by Walker and Goldsmith, apparent neck/shaft angle (aNSA) did not significantly change during maturation, whereas version increased by 40 degrees. However, tNSA decreased by 7.5 degrees during maturation, while the inclination increased by 32 degrees over the same period. This paper demonstrates angular changes in both the coronal and transverse planes with a 4:1 ratio of angular change in the transverse and coronal planes respectively. Interobserver Pearson coefficient R=0.98 and an intraobserver Pearson coefficient R=0.99.

CONCLUSIONS

Although Walker and Goldsmith reported angular changes only in the transverse plane, we conclude that they identified angular changes in both the coronal and transverse planes. Here we show it is mathematically necessary for tNSA to decrease, if aNSA remains constant as version increases.

CLINICAL RELEVANCE

A reader who is not well versed in the difference between aNSA and tNSA or version and inclination cannot appreciate what Walker and Goldsmith presented. Surgeons operating on the proximal femur also benefit from understanding these distinctions.

An Anatomic Study on Whether Femoral Version Originates in the Neck or the Shaft

BACKGROUND

Femoral anteversion is generally asymptomatic but can result in lower extremity issues like patellofemoral instability and pain. Surgical correction of anteversion can be performed proximal, mid shaft or distal. A better understanding of the specific location of the rotational deformity can help guide the optimal location of the osteotomy. In this study we examine the contribution of the femoral neck and shaft to total femoral version.

METHODS

We studied 590 pairs of well-preserved cadaveric femurs. Total femoral version was defined as the axial plane angle between the femoral neck and posterior femoral condyles. Femoral shaft torsion was defined as the axial plane angle between the lesser trochanter and posterior femoral condyles. Neck version was the mathematical difference between total femoral version and shaft version.

RESULTS

Neck version (right femur R=0.582; left femur R=0.632) contributed slightly more than shaft version (right femur R=0.505; left femur R=0.480) to overall femoral version, but both were substantial and neither completely predicted overall femoral version. Age was not found to contribute to femoral version, and sex and race had statistically significant but small contributions.

CONCLUSIONS

Our data show that both the femoral neck and femoral shaft substantially contribute to femoral version, and to our knowledge is the first to statistically demonstrate that neither level can be used to predict total femoral version. This suggests that one cannot generalize a single optimal site for correction or prediction of femoral version from an osteological perspective, and that individualized assessment may be beneficial.

CLINICAL RELEVANCE

This study suggests that methodologies for determining the level of femoral version might be important as the level in any given patient can vary.

Comparison of Intraoperative Fluoroscopic Dunn View With Magnetic Resonance Imaging to Determine Femoral Version

PURPOSE

To compare femoral version measured with a fluoroscopic Dunn view taken at the time of hip arthroscopy with values derived from axial magnetic resonance imaging (MRI) scans.

METHODS

Of 159 hip arthroscopies performed from January 2014 through March 2015, 50 patients had magnetic resonance imaging (MRI) scans with a protocol that incorporates femoral version analysis. Dunn views are performed as a routine part of the preoperative fluoroscopic examination at the time of arthroscopy. Femoral version was measured from the fluoroscopic views and compared with values calculated from axial MRI images. The measurements were compared with a paired t test for difference in means, the intraclass correlation coefficient (ICC) for reliability, and the limits of agreement method of Bland and Altman.

RESULTS

There was a very small but statistically significant difference between the measurement on fluoroscopic Dunn view and the value on axial MRI (mean difference, 1.4°, P = .03). The ICC was 0.809 (P < .0001), indicating substantial agreement. By the Bland and Altman method, the 95% limits of agreement for fluoroscopic versus MRI measurement were -7.6 to 10.4, with no significant difference in variance by Pitman test (P = .526).

CONCLUSIONS

With careful attention to technique, the fluoroscopically simulated Dunn view can be used to measure femoral version with acceptable accuracy and obviates the need for repeat 3-dimensional imaging for patients who already have an MRI scan without version analysis.

LEVEL OF EVIDENCE

Level II, testing of previously developed diagnostic criteria with a gold standard.

Femoral Version and Tibial Torsion are Not Associated With Hip or Knee Arthritis in a Large Osteological Collection

BACKGROUND

Tibial torsion and femoral anteversion are common rotational abnormalities in children, and their courses are most often benign and self-resolving. Although neither usually requires surgical treatment, the decision to perform a derotational osteotomy is usually based on the degree of functional impairment. Neither condition is thought to influence the development of osteoarthritis of the hip or knee; however, to date there have been no large scale studies confirming this.

METHODS

Tibial torsion and femoral version in 1158 cadaveric tibiae and femora were measured using a camera setup based on previously described radiographic landmarks. Any specimens with obvious traumatic, rheumatic, or metabolic abnormalities were excluded. Degenerative joint disease of the hip and knee were each graded from 0 to 6. Correlations between tibial torsion, femoral version, age, race, and sex with osteoarthritis of the hip and knee joints were evaluated with multiple regression analysis.

RESULTS

The mean and SDs of tibial torsion and femoral anteversion were 7.9±8.8 and 11.4±12.0 degrees, respectively. African Americans had significantly increased tibial torsion (5.1±8.7 vs. 9.2±8.5 degrees, P<0.0005) and greater femoral anteversion (14.1±11.9 vs. 10.2±11.8 degrees, P<0.0005) compared with whites. The average grades for hip and knee osteoarthritis were 3.1±1.4 and 2.7±1.4. Using multiple regression analysis neither tibial torsion nor femoral version were independent predictors of hip or knee arthritis (P>0.05 for all).

DISCUSSION

This study confirmed previously reported differences in the rotational profiles between races and sexes. However, neither tibial torsion nor femoral anteversion had a significant influence on the development of arthritis of the hip or knee.

CLINICAL RELEVANCE

These results support the practice of treating tibial torsion and femoral anteversion based on the symptomatology of the patient. Parents of asymptomatic children can be reassured that long-term consequences are unlikely.

The effect of valgus and varus femoral osteotomies on measures of anteversion in the dog

OBJECTIVE

To determine whether femoral osteotomies that change frontal plane alignment without affecting torsion influence anteversion and inclination.

METHODS

Femurs without deformity were scanned to create three-dimensional reconstructions. The femoral head-neck axis was identified by placement of a virtual intramedullary pin. A proximal osteotomy was simulated to create three conditions while keeping torsion constant: Normal, Coxa Valga (neck-shaft angle increased by 12°), and Coxa Vara (neck-shaft angle decreased by 12°). Femoral anteversion was measured from an axial image in all three conditions. Femoral inclination was calculated for all conditions using the neck-shaft and anteversion angles. Changes in anteversion and inclination were calculated and compared using a one-way repeated measures analysis of variance. Distal femoral osteotomies were then simulated with the native femurs, inducing 18° of distal varus with no change to torsion. Changes in anteversion and inclination for the Normal and Distal Varus conditions were calculated and compared by a paired t-test.

RESULTS

Version changed by a mean of 13.9° (± 1.5; p <0.0001) from the Coxa Valga to Coxa Vara conditions while inclination changed by a mean of 1.3° (± 0.39; p <0.01). Version changed by a mean of 6.6° (± 0.7; p <0.0001) between the Distal Varus and Normal conditions while inclination changed by a mean of -3.8° (± 0.75; p <0.001).

CLINICAL SIGNIFICANCE

Femoral version changes with changing frontal plane alignment even when torsion is constant. This should be considered when correcting femoral deformities.

An Anatomic Study of the Greater Trochanter Starting Point for Intramedullary Nailing in the Skeletally Immature

BACKGROUND

Trochanteric entry femoral nails have been increasing in popularity in the pediatric population for stabilization in fractures and osteotomies. The proper position for entry point in the coronal plane has been well studied; however, the sagittal plane in the pediatric population has not yet been well characterized.

METHODS

Eighty-eight cadaveric femora aged 8 to 20 years were studied in an apparent neck-shaft angle (ANSA) position, with distal condyles flat on the surface, and a true neck-shaft angle (TNSA) position, with internal rotation to neutralize femoral anteversion. Anterior and lateral offset were measured on lateral and anteroposterior photographs, respectively, as the perpendicular distance from the greater trochanter apex to the center of the intramedullary canal. The effect of rotational position (ANSA vs. TNSA) of the proximal femur was compared using the intraclass correlation coefficient for anterior and lateral offset. Correlations between age, demographics, anteversion, and greater trochanter morphology with anterior and lateral offset were evaluated with multiple regression analysis.

RESULTS

The mean age was 15.8±3.8 years. The mean anterior displacement of the trochanteric apex was 4.8±3.0 and 4.6±3.2 mm in the ANSA and TNSA positions, respectively. The mean lateral displacement was 10.6±4.2 and 9.7±4.0 mm in the ANSA and TNSA positions, respectively. The intraclass coefficient for anterior offset in the ANSA versus TNSA position was 0.704 and 0.900 for lateral offset. Change was minimal for anterior offset in the ANSA and TNSA positions versus age (standardized beta values 0.240, 0.241, respectively). There was a significant correlation with increasing lateral offset in the ANSA and TNSA positions with increasing age (standardized beta values 0.500, 0.385 respectively).

CONCLUSIONS

In the pediatric population, the tip of the greater trochanter is consistently anterior by approximately 5 mm. The mean lateral displacement was approximately 10 mm and increased with increasing age.

CLINICAL RELEVANCE

Nail entry at the pediatric greater trochanter apex would likely result in anterior placement. We recommend inserting the guidewire 5 mm posterior to the apex of the trochanter and confirming coronal and sagittal position with fluoroscopy.

Validity and Clinical Consequences of a Rotational Mechanism for Slipped Capital Femoral Epiphysis

BACKGROUND

Recent anatomic data supports a mechanism for slipped capital femoral epiphysis (SCFE) where the metaphysis rotates on the epiphysis through the eccentrically located epiphyseal tubercle as a pivot. The validity of such a mechanism and its clinical consequences have not been well investigated.

METHODS

This cadaveric study defined the normal location of the calcar ridge line in 100 paired femora and compared them with 11 SCFE specimens, and with 25 immature femora where the metaphysis was rotated 30, 60, and 90 degrees on the epiphysis to model progressive SCFE. Coronal, sagittal, and axial plane deformity were measured on the rotational model to define the characteristic deformity caused by rotation, and lateral epiphyseal foramina stretch was measured to quantify the protective effect of an eccentric pivot.

RESULTS

The posterior displacement of the fovea with respect to the calcar ridge line was 1±5 mm for the controls, versus 23±10 mm for the SCFE specimens (P<0.0005), and posterior displacement increased with incremental rotation in the rotational model (P<0.0005). The rotational model found minimal varus deformity, but substantial extension and retroversion, with deformities of 0±5, -16±12, and -38±9 degrees, respectively, at 90 degrees of rotation. The eccentric pivot mitigated lateral epiphyseal vessel stretch by 55% to 70%.

CONCLUSIONS

This study provides strong anatomic support for a rotational mechanism for stable SCFE. When the metaphysis is rotated on the epiphysis acutely, minimal varus deformity is created, while substantial retroversion occurs. As this rotation occurs the eccentric pivot protects the lateral epiphyseal vessels, and likely accounts for the low rate of avascular necrosis observed in stable SCFE.

CLINICAL RELEVANCE

If SCFE is treated in an open manner then the presence of a chronic rotational deformity should be considered. When planning osteotomies for deformity after a stable SCFE, any suspected varus component should be carefully investigated as it may represent retroversion deformity brought into view by external rotation posturing of the leg.

Decreasing pelvic incidence is associated with greater risk of cam morphology

OBJECTIVES

The spinopelvic relationship (including pelvic incidence) has been shown to influence pelvic orientation, but its potential association with femoroacetabular impingement has not been thoroughly explored. The purpose of this study was to prove the hypothesis that decreasing pelvic incidence is associated with increased risk of cam morphology.

METHODS

Two matching cohorts were created from a collection of cadaveric specimens with known pelvic incidences: 50 subjects with the highest pelvic incidence (all subjects > 60°) and 50 subjects with the lowest pelvic incidence (all subjects < 35°). Femoral version, acetabular version, and alpha angles were directly measured from each specimen bilaterally. Cam morphology was defined as alpha angle > 55°. Differences between the two cohorts were analysed with a Student's t-test and the difference in incidence of cam morphology was assessed using a chi-squared test. The significance level for all tests was set at p < 0.05.

RESULTS

Cam morphology was identified in 47/100 (47%) femurs in the cohort with pelvic incidence < 35° and in only 25/100 (25%) femurs in the cohort with pelvic incidence > 60° (p = 0.002). The mean alpha angle was also greater in the cohort with pelvic incidence < 35° (mean 53.7°, sd 10.7° versus mean 49.7°, sd 10.6°; p = 0.008).

CONCLUSIONS

Decreased pelvic incidence is associated with development of cam morphology. We propose a novel theory wherein subjects with decreased pelvic incidence compensate during gait (to maintain optimal sagittal balance) through anterior pelvic tilt, creating artificial anterior acetabular overcoverage and recurrent impingement that increases risk for cam morphology.Cite this article: W. Z. Morris, C. A. Fowers, R. T. Yuh, J. J. Gebhart, M. J. Salata, R. W. Liu. Decreasing pelvic incidence is associated with greater risk of cam morphology. Bone Joint Res 2016;5:387-392. DOI: 10.1302/2046-3758.59.BJR-2016-0028.R1.

A cadaveric investigation into the demographic and bony alignment properties associated with osteoarthritis of the patellofemoral joint

BACKGROUND

Patellofemoral joint osteoarthritis is common, although circumstances dictating its evolution and pathogenesis remain unclear. Advances in surgical technique have improved the ability to modify long-bone alignment in the coronal, sagittal, and axial planes. However, to our knowledge, there is no significant long-term data available in regard to the relationship between anatomic alignment parameters most amenable to surgical modification and patellofemoral joint osteoarthritis.

METHODS

Five-hundred and seventy-one cadaveric skeletons were obtained from the Hamann-Todd osteological collection. Mechanical lateral distal femoral angle, medial proximal tibial angle, tibial slope, femoral version, tibial torsion, the position of the tibial tubercle relative to the width of the tibial plateau, trochlear depth, and patellar size were measured using validated techniques. A previously published grading system for patellofemoral joint arthritis was used to quantify macroscopic signs of degenerative joint disease.

RESULTS

Increasing age (standardized beta 0.532, p<0.001), female gender (standardized beta 0.201, p=0.002), and decreasing mechanical lateral distal femoral angle (standardized beta -0.128, p=0.025) were independent correlates of increased patellofemoral joint osteoarthritis. A relatively more laterally positioned tibial tubercle trended towards predicting patellofemoral joint osteoarthritis (standardized beta 0.080, p=0.089).

CONCLUSIONS

These findings confirm that patellofemoral joint osteoarthritis is strongly associated with increasing age and female gender. Valgus alignment of the distal femur, a relatively more lateral location of the tibial tubercle, and a shallower trochlear grove appear to have modest effects on the development of patellofemoral joint osteoarthritis.

Capital Femoral Growth Plate Extension Predicts Cam Morphology in a Longitudinal Radiographic Study

BACKGROUND

Recent evidence has suggested that cam morphology may be related to alterations in the capital femoral growth plate during adolescence. The purpose of this study was to evaluate the relationship between capital femoral growth plate extension and cam morphology in a longitudinal radiographic study.

METHODS

We used a historical, longitudinal radiographic collection to identify 96 healthy adolescents (54 boys and 42 girls) with at least 5 consecutive annual radiographs of the left hip including closure of the capital femoral physis. We reviewed 554 anteroposterior radiographs of the left hip to measure the anteroposterior modification of the alpha angle of Nötzli and of the superior epiphyseal extension ratio (EER), measured as the ratio of extension of the capital femoral epiphysis down the femoral neck relative to the diameter of the femoral head. Measurements were made at 3 points in femoral head maturation corresponding to the Oxford bone age (OBA) femoral head stages 5, 6, and 7/8.

RESULTS

There was a mean increase in the anteroposterior alpha angle (10.7° ± 14.0°) and EER (0.12 ± 0.08) between OBA stages 5 and 7/8, corresponding to maturation and closure of the capital femoral physis. There was a positive correlation between the final anteroposterior alpha angle and both the final EER (r = 0.60) and the change in the EER (r = 0.58). A receiver operating characteristic curve generated to predict an anteroposterior alpha angle of ≥78° through the EER demonstrated an area under the curve of 0.93, indicating that an increasing EER had excellent diagnostic accuracy for predicting concurrent cam morphology.

CONCLUSIONS AND CLINICAL RELEVANCE

Superior epiphyseal extension was directly and temporally associated with an increase in anteroposterior alpha angle and more cam-like morphology. This alteration in the capital femoral epiphysis occurred immediately before physeal closure (OBA stage 7/8). Given the association of epiphyseal extension with activities that increase shear forces across the physis, we proposed that epiphyseal extension may be an adaptive mechanism to stabilize the physis and prevent slipped capital femoral epiphysis.

A Modified Ogata-Goldsand Technique for Simplified Intraoperative Measurement of Femoral Version

BACKGROUND

Femoral anteversion can be difficult to determine intraoperatively, particularly in cases with complicated deformity. Although biplanar methodology exists for measuring femoral anteversion, the measurements are generally based on the proximal femur, without consideration for the femoral bow.

METHODS

We directly measured femoral version in 70 mature cadaveric femora. Using the standard Ogata-Goldsand approach, femoral version was geometrically calculated after measuring apparent neck-shaft angle and the β-angle, which is the angle between the femoral neck and proximal femoral shaft on a direct lateral view. We then used a modified β-angle, measured between the femoral neck and a line representing the entire femur.

RESULTS

Mean anatomic femoral anteversion was 20±11 degrees. Mean calculated femoral version using the standard Ogata-Goldsand technique was 32±13 degrees, whereas mean calculated femoral version using the modified Ogata-Goldsand technique was 22±12 degrees. Repeated measures ANOVA analysis found an overall statistically significant difference between the 3 groups (P<0.0001). Pairwise comparisons revealed a significant difference between directly measured version and the standard Ogata-Goldsand technique (P<0.0001) but not between directly measured version and the modified Ogata-Goldsand technique (P=0.76).

CONCLUSIONS

Standard biplanar imaging techniques do not account for the femoral bow and can significantly overestimate femoral anteversion. If a line is drawn from the posterior femoral condyles to the posterior aspect of the greater trochanter, femoral anteversion is better approximated. Intraoperatively, we obtain this line by positioning a marker over the skin under fluoroscopy. Clinically, if one aims for a modified β-angle of 5 degrees, a postosteotomy anteroposterior radiograph is no longer necessary, given the knowledge that with apparent neck-shaft angles ranging from 115 to 155 degrees, version will lie within a generally accepted range between 2 and 11 degrees.

CLINICAL RELEVANCE

In complex operative cases where imaging is desired to measure intraoperative femoral version, we recommend a modified and simplified lateral view measurement technique, which improves accuracy by accounting for the femoral bow.

Assessment of Femoral Antetorsion With MRI: Comparison of Oblique Measurements to Standard Transverse Measurements

OBJECTIVE

Abnormal femoral antetorsion is associated with the development of femoroacetabular impingement (FAI). Anatomically correct antetorsion measurements are performed on transverse MR images over the proximal and distal femur, but some authors use alternative measurements on oblique images parallel to the femoral neck axis. We set out to assess the relationship between these two measurement methods and to obtain reference values for oblique measurements in patients with FAI and healthy control subjects. We also evaluated whether the oblique measurements could be used to predict the standard transverse measurements.

SUBJECTS AND METHODS

MRI data of 126 individuals, 63 asymptomatic volunteers and 63 patients with FAI (age 20-50 years), were included in this prospective study. Two readers independently assessed antetorsion with oblique measurements and standard transverse measurements. Differences between subgroups were compared with the unpaired t test. Trigonometric calculations were used to predict standard antetorsion measurements on the basis of oblique measurements. Interobserver agreement and Bland-Altman plots were calculated.

RESULTS

Reference values for assessing femoral antetorsion with the oblique method were established, with mean (± SD) values of 9.4° ± 7.9° (reader 1) and 9.8° ± 8.4° (reader 2) for patients and 9.2° ± 8.4° (reader 1) and 9.6° ± 9.1° (reader 2) for asymptomatic volunteers. The oblique method generated smaller antetorsion values than the standard transverse method (p < 0.001), with an average difference of 3.5° ± 3.2° for reader 1 and 3.6° ± 3.5° for reader 2. Differences between predicted antetorsion values based on oblique measurements and standard measurements were minimal: 0.1° ± 2.9° (p = 0.62) for reader 1 and 0.3° ± 3.3° (p = 0.29) for reader 2. Interobserver agreement was high for all antetorsion measurements (intra-class correlation coefficient, 0.945-0.977).

CONCLUSION

Oblique measurements of femoral antetorsion were smaller than standard transverse measurements, but they can be used to accurately predict standard measurements.

The Antiquity of the Cam Deformity: A Comparison of Proximal Femoral Morphology Between Early and Modern Humans

BACKGROUND

The precise etiology of cam impingement continues to be incompletely understood. The prevailing hypothesis posits that the deformity arises as a developmental injury prior to skeletal maturation. There is a possible evolutionary role, with an aspherical femoral head affording upright humans better stability. We set out to identify the antiquity of the cam deformity to better understand the comparative roles of modern behavior and evolution in its development.

METHODS

We used 249 physical specimens of femora from the Libben osteological collection, a set of bones from an ancient population who lived between the eighth and the eleventh century. These femora were photographed in four different orientations, and six specific proximal femoral angles were measured. The values were also compared with those from modern human femora using the Student t test, with a two-tailed p value of 0.05 denoting significance.

RESULTS

In total, 249 femora from 175 individuals were included in the final analysis. The ages of the individuals ranged between seventeen and fifty-five years. Interobserver and intraobserver correlation was good or excellent for all variables measured. Compared with modern populations, ancient human hips were significantly more anteverted (19.96° versus 12.85°; p < 0.001) and varus (true neck-shaft angle, 121.96° versus 129.23°; p < 0.001). The alpha angle was significantly lower in ancient humans (35.33° versus 45.61°; p < 0.001), and none of the ancient femora met the modern criteria for a cam deformity (an alpha angle of >50°).

CONCLUSIONS AND CLINICAL RELEVANCE

It appears that the cam deformity was nonexistent among ancient humans and is perhaps predominantly a product of modern-day stresses. Further clinical investigation into behavioral modifications in adolescence is warranted to potentially prevent the development of deformity and impingement.

An Anatomic Study on Whether the Patella is Centered in an Ideal Anteroposterior Radiograph of the Knee

BACKGROUND

Currently, an anteroposterior radiograph of the knee is judged based on a centered position of the patella between the femoral condyles. We are not aware of any anatomic literature supporting this recommendation.

QUESTIONS/PURPOSES

Orthogonal images are required for accurate assessment of knee deformity. Although an image with the patella centered at the distal femur is generally accepted as a true anteroposterior (AP) radiograph of the knee, there is minimal anatomic data to support that this view is orthogonal to a true lateral view of the knee where the condyles are overlapped. We designed an anatomical study to test the relationship between these two radiographic views.

METHODS

We studied 428 well-preserved cadaveric skeletons ranging from 40 to 79 years of age at death. Centering of the patella was calculated based on distal femoral and patellar widths. Multiple regression analysis was then performed to determine the relationship between patellar centering and age, gender, ethnicity, mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), femoral anteversion, and contralateral centering.

RESULTS

Average patellar centering was 0.13 ± 0.04, indicating that the average patella was laterally positioned in the distal femur. Only mLDFA and contralateral centering showed statistically significant independent correlations with patellar centering with modest standardized beta coefficients of 0.10 and 0.23, respectively.

CONCLUSIONS

In the average specimen, the patella is laterally deviated by 13% of the condylar width. Clinicians should be aware that a lateral view with the femoral condyles overlapped is not always orthogonal to a patella-centered AP view when planning and implementing deformity correction.

Three-dimensional Effect of the Single Plane Proximal Femur Osteotomy

Purpose

Three-dimensional (3D) effects of the single plane osteotomies of the proximal femur are compared and analyzed by the trigonometric method.

Materials and Methods

The shape of proximal femur was simplified as a bent line. The bent line is the continuation of the three points-the center of the femoral head, the center of femoral neck at the base, and the center of the femoral shaft. Then rotated the proximal femur at the junction of the neck and shaft with the each rotation axis of X, Y, Z, defined the frontal plane as a XY plane, sagittal plane as a YZ plane, and transverse plane as a XZ plane.

Results

The varus osteotomy of the proximal femur in the frontal plane with the rotation axis 'Z' that meant the increase of the X coordinate and the decrease of Y coordinate with constant Z coordinate (Δx>Δy, Δz=0) resulted in decreased anteversion in the transverse plane and increased flexion in the sagittal plane. The derotation osteotomy (Δx>Δz, Δy=0) resulted in varus in the frontal plane and extension in the sagittal plane. The flexion osteotomy (Δz>Δy, Δx=0) resulted in increased anteversion in the transverse plane and varus in the frontal plane.

Conclusion

Single plane osteotomy for the proximal femur results in the angular correction in all three planes and may have the similar 3D effect of the certain double or triple osteotomy. So single plane osteotomy could be enough to correct some complex deformities.

The effects of femoral external derotational osteotomy on frontal plane alignment

PURPOSE

Femoral osteotomies are the preferred treatment in significant torsional deformity of the femur. The influence of torsional osteotomies on frontal plane alignment is poorly understood. Therefore, the aim of the present study was to evaluate the effects of external derotational osteotomies on proximal, mid-shaft and distal levels onto frontal plane alignment.

METHODS

The effect of rotation around the anatomical axis of the femur on frontal plane alignment was determined with a 3D computer model, created from CT data of a right human cadaver femur. Virtual torsional osteotomies of 10°, 20° and 30° were performed at proximal, mid-shaft and distal levels under five antecurvatum angles of the femur. The change of the frontal plane alignment was expressed by the mechanical lateral femoral angle.

RESULTS

Proximal derotational osteotomies resulted in an increased mechanical lateral distal femoral angle (mLDFA) of 0.8°-2.6° for 10°, of 1.6°-5.1° for 20° and of 2.3-7.9° for 30° derotational osteotomy, indicating an increased varus angulation. Supracondylar derotational osteotomy resulted in a decreased mLDFA of -0.1° to -1.7° for 10°, of -0.2 to -3.7° for 20° and of -0.7 to -6.9° for 30° derotational osteotomy, indicating an increased valgus angulation. The effect increased with the amount of torsional correction and virtually increased antecurvatum angles. Mid-shaft torsional osteotomies had the smallest effect on frontal plane alignment.

CONCLUSION

This three-dimensional computer model study demonstrates the relationship between femoral torsional osteotomies and frontal plane alignment. Proximal external derotational osteotomies tend to result in an increased varus angulation, whilst distal external derotational osteotomies tend to result in an increased valgus angulation. As a clinical consequence, torsional osteotomies have an increased risk of unintentional implications on frontal plane alignment.

An anatomical study of the entry point in the greater trochanter for intramedullary nailing

Malpositioning of the trochanteric entry point during the introduction of an intramedullary nail may cause iatrogenic fracture or malreduction. Although the optimal point of insertion in the coronal plane has been well described, positioning in the sagittal plane is poorly defined. The paired femora from 374 cadavers were placed both in the anatomical position and in internal rotation to neutralise femoral anteversion. A marker was placed at the apparent apex of the greater trochanter, and the lateral and anterior offsets from the axis of the femoral shaft were measured on anteroposterior and lateral photographs. Greater trochanteric morphology and trochanteric overhang were graded. The mean anterior offset of the apex of the trochanter relative to the axis of the femoral shaft was 5.1 mm (sd 4.0) and 4.6 mm (sd 4.2) for the anatomical and neutralised positions, respectively. The mean lateral offset of the apex was 7.1 mm (sd 4.6) and 6.4 mm (sd 4.6), respectively. Placement of the entry position at the apex of the greater trochanter in the anteroposterior view does not reliably centre an intramedullary nail in the sagittal plane. Based on our findings, the site of insertion should be about 5 mm posterior to the apex of the trochanter to allow for its anterior offset.

A Comparison of the Accuracy of Three Intraoperative Techniques for Measuring Rotational Correction in Varus Derotational Osteotomies of the Femur

BACKGROUND

Based on the complexity of proximal femoral geometry, osteotomies in the coronal plane may change femoral version, while osteotomies in the plane of the femoral neck should not. Theoretically, this relationship can lead to a systematic error when measuring rotational correction in the proximal part of the femur.

METHODS

We developed a mathematical model to predict the error with three different techniques for rotational measurement: (1) a pin along the axis of the femoral neck and a lateral pin across the femoral condyles, (2) a proximal lateral pin perpendicular to the femur and a lateral pin across the femoral condyles, and (3) two anterior pins representing a score mark on the proximal part of the femur. Varus derotational osteotomies were performed on twenty-four Sawbone femora, and femoral anteversion and the angles between each set of pins were measured.

RESULTS

Our mathematical model predicted no error with the neck-pin technique regardless of the type of osteotomy performed. With the lateral pin technique, there was no predicted error with the neck plane osteotomy but a large error with the coronal plane osteotomy. The score-mark technique had a small amount of error with the neck plane osteotomy and a large error with the coronal plane osteotomy. Our Sawbones model measurements correlated well with the mathematical model, with intraclass correlation coefficients of 0.96, 0.89, and 0.91 for the neck-pin, lateral pin, and score-mark techniques, respectively.

CONCLUSIONS

This study describes and validates a model for predicting the error of three different techniques for measuring femoral rotation. It demonstrates that inadvertent systematic error can occur with lateral pin and score-mark techniques, particularly when the osteotomy is out of plane with the femoral neck.

CLINICAL RELEVANCE

Although the mathematics of this study are complex, the conclusions are clinically straightforward: rotational error is minimized by performing an osteotomy in the plane of the femoral neck or by using a pin in the femoral neck to judge rotation. If neither of these techniques is employed, then systematic error can be introduced and can be substantial.

Atypical hip impingement

OBJECTIVE

This article summarizes how atypical forms of hip impingement can be assessed with radiographs, CT, and MRI.

CONCLUSION

Subspine impingement, ischiofemoral impingement, and iliopsoas impingement are atypical forms of hip impingement and are less common than classic femoroacetabular impingement. Additional forms of atypical impingement, such as abnormal femoral antetorsion, abnormal pelvic and acetabular tilt, and extreme hip motion, can occur combined with classic femoroacetabular impingement or as separate entities.

Two or more impingement and/or instability deformities are often present in patients with hip pain

BACKGROUND

Damage to the hip can occur due to impingement or instability caused by anatomic factors such as femoral and acetabular version, neck-shaft angle, alpha angle, and lateral center-edge angle (CEA). The associations between these anatomic factors and how often they occur in a painful hip are unclear but if unaddressed might explain failed hip preservation surgery.

QUESTIONS/PURPOSES

We determined (1) the influence of sex on the expression of impingement-related or instability-related factors, (2) the associations among these factors, and (3) how often both impingement and/or instability factors occur in the same hip.

METHODS

We retrospectively reviewed a cohort of 170 hips (145 patients) undergoing MR arthrography of the hip for any reason. We excluded 58 hips with high-grade dysplasia, Perthes' sequelae, previous surgery, or incomplete radiographic information, leaving 112 hips (96 patients). We measured femoral version and alpha angles on MR arthrograms. Acetabular anteversion, lateral CEA, and neck-shaft angle were measured on pelvic radiographs.

RESULTS

We observed a correlation between sex and alpha angle. Weak or no correlations were observed between the other five parameters. In 66% of hips, two or more (of five) impingement parameters, and in 51% of hips, two or more (of five) instability parameters were found.

CONCLUSIONS

Patients with hip pain frequently have several anatomic factors potentially contributing to chondrolabral damage. To address pathologic hip loading due to impingement and/or instability, all of the anatomic influences should be known. As we found no associations between anatomic factors, we recommend an individualized assessment of each painful hip.

Are the left and right proximal femurs symmetric?

BACKGROUND

The contralateral femur frequently is used for preoperative templating for THA or hemiarthroplasty when the proximal femur is deformed by degenerative changes or fracture. Although femoral symmetry is assumed in these situations, it is unclear to what degree the contralateral femur is symmetrical.

QUESTIONS/PURPOSE

We therefore defined the degree of asymmetry between left and right proximal femurs and determined whether it was affected by demographics and proximal femoral anatomy.

METHODS

We obtained 160 paired femurs from individuals (20-40 years old), evenly distributed for gender and ethnicity (African-American and Caucasian). The height and weight of the individuals were recorded. We measured the femoral head diameter, minimal femoral neck diameter in the AP and cephalocaudal (CC) planes, and the AP femoral diaphyseal diameter. The absolute and percent differences were determined.

RESULTS

All femoral measurements showed an absolute difference less than 2 mm and a percent asymmetry and difference less than 2% for the femoral head, less than 4% for the femoral neck, and less than 3.5% for the femoral shaft. We found no correlation or predictive value between absolute differences and asymmetry and age, ethnicity, gender, or weight. Height was negatively associated with femoral head differences and thus increased symmetry of the femoral head.

CONCLUSIONS

Our data support assumptions of substantial symmetry of the proximal femur and highlights that asymmetry is not affected by demographics or the size of the proximal femur. Asymmetry tends not to occur in isolated segments of the femur.

An anatomic study of the epiphyseal tubercle and its importance in the pathogenesis of slipped capital femoral epiphysis

BACKGROUND

It has been proposed that the epiphyseal tubercle on the inferior surface of the capital femoral epiphysis may be responsible for the clinical distinction between a stable and an unstable slipped capital femoral epiphysis (SCFE). The anatomy of the tubercle and its relationship to the lateral epiphyseal vessels have not previously been rigorously defined.

METHODS

Twenty-two cadaveric capital femoral epiphyses from donors who had been three to seventeen years of age were analyzed and then digitized with use of a high-resolution laser scanner. The height, location, and approximate surface area of the epiphyseal tubercle were measured and were normalized to the size of the entire capital femoral epiphysis.

RESULTS

In all specimens except that from the youngest donor, the foramina for the lateral epiphyseal vessels were visible and were located directly superior to the epiphyseal tubercle. The height of the epiphyseal tubercle was 4.4 ± 1.1 mm. When normalized to the overall size of the capital femoral epiphysis, the relative height (r = 0.71) and relative area (r = 0.56) of the epiphyseal tubercle decreased with increasing age. The epiphyseal tubercle was consistently located in the posterosuperior quadrant, with its position being more posterior and less superior in specimens from younger donors.

CONCLUSIONS

The epiphyseal tubercle appears to be a major stabilizer, or keystone, of the capital femoral epiphysis and the lateral epiphyseal vessels. Its relative decrease in height and surface area with increasing age may help explain the susceptibility of individuals to SCFE in adolescence: in a stable SCFE, the physis rotates on the tubercle; however, in an unstable SCFE, the tubercle dislodges, leading to more substantial displacement of the capital femoral epiphysis and the lateral epiphyseal vessels, risking osteonecrosis.

Femoral antetorsion: comparing asymptomatic volunteers and patients with femoroacetabular impingement

PURPOSE

To assess the range of femoral antetorsion with magnetic resonance (MR) imaging in asymptomatic volunteers and patients with different subtypes of femoroacetabular impingement (FAI) because abnormal femoral antetorsion might be a contributing factor in the development of FAI.

MATERIALS AND METHODS

This study was institutional review board approved; all individuals provided signed informed consent. Sixty-three asymptomatic volunteers and 63 patients with symptomatic FAI between age 20 and 50 years were matched for age and sex. They underwent standard MR imaging with two additional rapid transverse sequences over the proximal and distal femur for antetorsion measurement. Twenty volunteers underwent a second MR imaging examination in the same leg. Two readers independently measured femoral antetorsion. The time for the additional sequences was tabulated. Interobserver agreement was calculated; differences in antetorsion were assessed by using analysis of variance and the unpaired t test.

RESULTS

Femoral antetorsion can be assessed with MR imaging in about 80 seconds, with high interobserver agreement (intraclass correlation coefficient [ICC] = 0.967) and high agreement between different MR examinations (ICC = 0.966). Women had a significantly larger antetorsion than men (P < .001 for both readers), and antetorsion of the left femur was significantly larger than that of the right femur (P = .01 for reader 1, P = .02 for reader 2). Overall, antetorsion was similar in volunteers and in patients for reader 1 (12.7° ± 10.0 [standard deviation] vs 12.6° ± 9.8, respectively; P = .9) and reader 2 (12.8° ± 10.1 vs 13.5° ± 9.8, respectively; P = .7). Femoral antetorsion was significantly higher in patients with pincer-type FAI than in those with cam-type FAI for reader 1 (18.3° ± 9.8 vs 10.0° ± 9.1, P = .02) and reader 2 (18.7° ± 10.5 vs 11.6° ± 8.8, P = .04).

CONCLUSION

Femoral antetorsion can be measured rapidly and with good reproducibility with MR imaging. Patients with pincer-type FAI had a significantly larger femoral antetorsion than patients with cam-type FAI.

Evaluation of proximal femoral geometry using digital photographs

The morphologic features of the proximal femur are used in preoperative planning prior to total hip arthroplasty. Recent literature evaluating the anatomy of the proximal femur, as it relates to total hip arthroplasty, has relied heavily on radiographs or computed tomography. We used digital photographs to compare 200 cadaveric femora in individuals who died prior to 40 years of age: 25 African-American males, 25 African-American females, 25 Caucasian males, 25 Caucasian females. With our technique and definition, the actual angles and dimensions of the proximal femur that we normally rely on during total hip arthroplasty were measured. There were small, but statistically significant differences, between males and females in neck-shaft angle, neck inclination, and absolute horizontal and vertical offset. Females tended to have a lower neck-shaft angle and more neck inclination. When standardizing the offset distances with femoral head diameter, the horizontal offset ratio was higher in female specimens. There was no correlation between horizontal and vertical offset. Improved knowledge of the morphology of the proximal femora will assist the surgeon in restoring the geometry of the proximal femur during total hip arthroplasty. This information also supports the concept of modularity of the femoral neck in order to independently adjust neck-shaft angle, neck inclination, and horizontal offset.