Subtle Slipped Capital Femoral Epiphysis Is not Associated With Idiopathic Cam Morphology.

BACKGROUND: The etiology of idiopathic cam morphology remains unclear. One theory suggests that subtle slipped capital femoral epiphysis (SCFE) leads to proximal femoral changes resulting in cam morphology. The purpose of this study was to evaluate the association between subtle SCFE and cam morphology in a large osteological collection. METHODS: We examined 962 cadaveric hips to measure 2 markers of cam morphology, alpha angle and anterior femoral head-neck offset (AHNO), and a validated, objective marker of subtle SCFE deformity (calcar ridge line offset). When the femur is viewed medially, the calcar ridge line extends from the lesser trochanter proximally along the postero-inferior femoral neck and points toward the fovea. In SCFE-like deformity, the fovea deviates posteriorly from this projected line. Pearson correlations were performed to evaluate for possible association of calcar ridge line offset with alpha angle and AHNO. In addition, a multiple regression analysis was performed to determine the influence of age, alpha angle, and AHNO on calcar ridge line offset. RESULTS: There was no clinically relevant association between the calcar ridge line offset and alpha angle (r=-0.02, P=0.58) or AHNO (r=0.08, P=0.012). Furthermore, specimens whose calcar ridge line deviated 1 SD above the mean (more SCFE-like deformity) had a smaller alpha angle (46.6±9.1 vs. 48.3±10.6, P=0.046) and greater AHNO (0.83±0.19 vs. 0.77±0.16, P<0.001), both reflecting less cam-like morphology. On regression analysis, increasing age and increasing AHNO (decreased cam morphology) predicted increased calcar ridge line offset, though the model accounted for only 1.2% of the variance. CONCLUSIONS: Subtle SCFE-like deformity, as objectively measured from the calcar ridge line, was not predictive of more cam-like morphology, and in fact mild opposite associations were found. Further study is needed to identify other potential etiologies of idiopathic cam morphology. CLINICAL RELEVANCE: We present evidence from a large, well-documented osteological collection indicating that subtle SCFE is not associated with idiopathic cam morphology.

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.

Lower thoracic pedicle morphometry: male, taller, and heavier specimens have bigger pedicles.

STUDY DESIGN: An anatomic study of pedicle dimensions was performed for lower thoracic vertebrae from American human subjects. OBJECTIVE: To quantify the dimensions of the lower thoracic pedicles and to better define the demographic factors that could ultimately govern the caliber selection of pedicle screws. SUMMARY OF BACKGROUND DATA: Transpedicular screw fixation allows for segmental instrumentation into multiple vertebrae across multilevel fusion area, offering considerable biomechanical advantage over the conventional hook and lateral mass fixation. Large variations in morphology from previous studies may be related to differences in demographics, sample size, and methodology. METHODS: For this study, T7-T12 vertebrae from 503 American human cadavers were directly measured with a digital caliper. Examiner measured each vertebra to determine medial-lateral pedicle width and cranial-caudal pedicle height. Demographic information regarding age, sex, and race, as well as body height and weight, was available for all 503 subjects. RESULTS: Both pedicle height and pedicle width generally increased in size caudally down the lower thoracic spine. The highest pedicle height was at the T12 level with a mean of 17.08 mm. The widest pedicle width was at the T11 level with a mean of 9.31 mm. Males have larger pedicles than females for all upper thoracic levels. The tallest and heaviest groups had larger pedicles than the shorter and lighter groups, respectively. Age and race did not consistently affect pedicle dimension in a statistically significant manner. CONCLUSION: Our large-scale study of American specimens characterized the relationship between pedicle dimensions and a variety of demographic factors such as age, sex, body height and weight. With substantial statistical power, this study showed that male, taller, and heavier individuals had larger pedicles. LEVEL OF EVIDENCE: N/A.

Pedicle Morphometry of Lumbar Vertebrae: Male, Taller, and Heavier Specimens Have Bigger Pedicles.

STUDY DESIGN: An anatomic study of pedicle dimensions was performed for lumbar vertebrae from American subjects. OBJECTIVE: To quantify the dimensions of the lumbar pedicles and to better define the demographic factors that could ultimately govern the caliber selection of pedicle screws. SUMMARY OF BACKGROUND DATA: Transpedicular screw fixation allows for segmental instrumentation into multiple vertebrae across multilevel fusion area, offering considerable biomechanical advantage over the conventional hook and lateral mass fixation. Large variations in morphology from previous studies may be related to differences in demographics, sample size, and methodology. METHODS: For this study, L1-L5 vertebrae from 503 American human cadavers were directly measured with a digital caliper. Examiner measured each vertebra to determine medial-lateral pedicle width (PW) and cranial-caudal pedicle height (PH). Demographic information regarding age, sex, and race, as well as body height and weight, was available for all 503 subjects. RESULTS: PH decreased in size caudally down the lumbar spine, but PW increased in size. The largest PH was at the L1 level with a mean of 15.75 mm. The widest PW was at the L5 level with a mean of 18.33 mm. Males have larger pedicles than females for all lumbar levels. The tallest and heaviest groups generally had larger pedicles than the shorter and lighter groups, respectively. Age and race did not consistently affect pedicle dimension in a statistically significant manner. CONCLUSION: Our large-scale study of American specimens characterized the relationship between pedicle dimensions and a variety of demographic factors such as age, sex, body height, and weight. With substantial statistical power, the current study showed that male, taller, and heavier individuals had larger lumbar pedicles. LEVEL OF EVIDENCE: 3.