Jeremy J. Gebhart

Correlation of Pelvic Incidence With Cam and Pincer Lesions

Background: The sacropelvic parameter of pelvic incidence (PI) is a position-independent anatomic parameter that regulates lumbar lordosis and pelvic orientation. While it has been extensively studied in relation to spine pathology, only a single study has correlated PI with femoroacetabular impingement (FAI). Hypothesis: Decreased PI would be associated with an increased prevalence of cam and pincer lesions. Study Design: Controlled laboratory study. Methods: Measurements of the acetabulum, proximal femur, and sacropelvis were made bilaterally on 40 cadaveric specimens, for a total of 80 hips. Twenty specimens had the presence of bilateral cam deformities (alpha angle >55°), and 20 age- and sex-matched specimens had bilateral normal hips. Pincer lesions were defined as an anteversion <15°. Pelvic incidence and acetabular version were measured using standardized lateral photographs and a goniometer, respectively. Independent-samples t tests were performed to evaluate for differences in measured parameters between groups. Results: The mean PI was 43.1° ± 8.6° for hips with a cam lesion and 47.7° ± 9.3° for normal hips, demonstrating a significant association between decreased PI and the presence of a cam lesion (P = .02). The mean version of acetabula with pincer lesions (n = 28) was 11.4° ± 2.5°, and the mean version of normal acetabula (n = 52) was 20.1° ± 3.8°. The mean PI of hips with pincer lesions was 42.5° ± 8.5°, significantly less than that of normal hips, 47.0° ± 9.2° (P = .04). Conclusion: This study supports a recent study that suggested patients with pincer impingement have a smaller PI than the healthy population, and it is the first to demonstrate a significant association between decreased PI and cam-type femoral deformity. Based on results of this study, further clinical study of the effects of pelvic geometry on FAI is warranted. Clinical Relevance: While the study results do not prove a causal relationship, it is theorized that the restriction of range of motion and biomechanical adaptations of the pelvis around the hip joints resulting from a smaller PI may affect hip development and FAI. The influence of mechanical factors beyond the hip joint in the development of FAI should be considered by clinicians.

Are the Left and Right Proximal Femurs Symmetric

BackgroundThe 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/purposeWe therefore defined the degree of asymmetry between left and right proximal femurs and determined whether it was affected by demographics and proximal femoral anatomy.MethodsWe 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.ResultsAll 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.ConclusionsOur 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.

Pelvic Incidence and Acetabular Version in Slipped Capital Femoral Epiphysis.

Background: The etiology of slipped capital femoral epiphysis (SCFE) is multifactorial, but the role of sagittal balance of the pelvis as a contributing factor to its development has not been well studied. Our primary purpose was to determine whether a smaller pelvic incidence (PI), a position-independent anatomic parameter that regulates pelvic orientation, could be a factor that increases shear stress in the epiphyseal growth plate and potentially contributes to the development of SCFE. We also set out to determine whether acetabular retroversion was associated with SCFE. Methods: We obtained 14 cadaveric pelvi from the Hamann-Todd Osteological Collection whose femurs showed evidence of post-SCFE deformity. Two hundred age-matched, sex-matched, and race-matched pelvi were used as controls. PI and acetabular version were measured using standardized lateral photographs and goniometers, respectively. T tests were performed to evaluate for differences in measured parameters between groups. Results: The mean PI was 40.6±6.1 degrees for SCFE specimens and 47.4±9.9 degrees for normal specimens (P=0.01). The mean version of SCFE and normal acetabula was 15±7 and 17±6 degrees, respectively (P=0.39). There was also no significant difference in version between SCFE acetabula and the contralateral, uninvolved acetabular of the same specimen (15±7 vs. 17±8 degrees, P=0.33). Conclusions: Specimens with SCFE deformity demonstrated a smaller PI than a large cohort of normal control specimens. We found no significant difference between acetabular version of specimens with and without SCFE deformity. Contralateral or unaffected acetabuli of SCFE specimens were not more retroverted than the affected side of the same specimen. Clinical Relevance: Sagittal balance of the pelvis, and particularly decreased PI, may play an important role in the development of SCFE. The influence of mechanical factors beyond the hip joint in the development of SCFE should be considered by clinicians.

Relationship between pelvic incidence and osteoarthritis of the hip

Objectives Sagittal alignment of the lumbosacral spine, and specifically pelvic incidence (PI), has been implicated in the development of spine pathology, but generally ignored with regards to diseases of the hip. We aimed to determine if increased PI is correlated with higher rates of hip osteoarthritis (HOA). The effect of PI on the development of knee osteoarthritis (KOA) was used as a negative control. Methods We studied 400 well-preserved cadaveric skeletons ranging from 50 to 79 years of age at death. Each specimen’s OA of the hip and knee were graded using a previously described method. PI was measured from standardised lateral photographs of reconstructed pelvises. Multiple regression analysis was performed to determine the relationship between age and PI with HOA and KOA. Results The mean age was 60.2 years (standard deviation (sd) 8.1), and the mean PI was 46.7° (sd 10.7°). Multiple regression analysis demonstrated a significant correlation between increased PI and HOA (standardised beta = 0.103, p = 0.017). There was no correlation between PI and KOA (standardised beta = 0.003, p = 0.912). Conclusion Higher PI in the younger individual may contribute to the development of HOA in later life. Cite this article: Dr J. J. Gebhart. Relationship between pelvic incidence and osteoarthritis of the hip. Bone Joint Res 2016;5:66–72. DOI: 10.1302/2046-3758.52.2000552.

Predictive anthropometric measurements for humeral head curvature.

BACKGROUND Estimation of size, shape, and curvature of the humeral head is important for shoulder replacement procedures and allograft transplantation, especially as we try to recreate normal anatomy. The purpose of this study was to investigate the value of various anthropometric measurements for predicting humeral head curvature. MATERIALS AND METHODS Cadaveric humeri were scanned with a 3-dimensional laser scanner. Length of the humerus, epicondylar breadth, and humeral head curvature were determined using data from the scans. A linear regression was performed for the length of the humerus, epicondylar breadth, gender, age, height, and weight. A stepwise linear regression with forward and backward substitution (α = 0.15) was performed for the most predictive variables from the initial linear regression. An equation for the prediction of humeral head radius of curvature was generated using this data. RESULTS The most predictive factors (R(2) > 0.5) were epicondylar breadth, height, sex, and humeral length. These 4 factors were included in a forward and backward stepwise regression. The resulting equation had an R(2) value of 0.812. CONCLUSION Of the predicted measurements evaluated, patient height, maximum humeral length, epicondylar breadth, and gender were most correlated with humeral head curvature. Including these 4 factors in a linear regression model increased the R(2) value to 0.812. If only a single measurement can be used to size the humeral head curvature, patient height will give the same accuracy as epicondylar breadth and can more easily be obtained. A patients height can help accurately predict the patients humeral head anatomy.

Differences in Medial and Lateral Posterior Tibial Slope An Osteological Review of 1090 Tibiae Comparing Age, Sex, and Race

Background: Injuries to the anterior cruciate ligament (ACL) are common, and a number of knee morphological variables have been identified as risk factors for an ACL injury, including the posterior tibial slope (TS). However, limited data exist regarding innate population differences in the TS. Purpose: To (1) establish normative values for the medial and lateral posterior TS; (2) determine what differences exist between ages, sexes, and races; and (3) determine how internal or external tibial rotation (as occurs during sagittal knee motion) influences the stereotactic perception of the TS. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 545 cadaveric specimens (1090 tibiae) were obtained from the Hamann-Todd osteological collection. Specimens were leveled in the coronal, sagittal, and axial planes using a digital laser. Virtual representations of each bone were created with a 3-dimensional digitizer apparatus. The TS of the medial and lateral tibial plateaus were measured using techniques adapted from previous radiographic protocols. Medial and lateral TS were then again measured on 200 tibiae that were internally and externally rotated by 10° (axially). Results: The mean (±SD) medial TS was 6.9° ± 3.7° posterior, which was greater than the mean lateral TS of 4.7° ± 3.6° posterior (P < .001). Neither the medial nor lateral TS changed with age. Women had a greater mean TS compared with men on both the medial (7.5° ± 3.8° vs 6.8° ± 3.7°, respectively; P = .03) and lateral (5.2° ± 3.5° vs 4.6° ± 3.5°, respectively; P = .04) sides. Black specimens had a greater mean medial TS (8.7° ± 3.6° vs 5.8° ± 3.3°, respectively; P < .001) and lateral TS (5.9° ± 3.3° vs 3.8° ± 3.5°, respectively; P < .001) compared with white specimens. Axial rotation was shown to increase the perception of the medial and lateral TS (P < .001). Conclusion: The medial TS was shown to be greater than the lateral TS. Important sex- and race-based differences exist in the TS. This study also highlights the role of axial rotation in measuring the TS.

Particle-Induced Osteolysis Is Mediated by TIRAP/Mal in Vitro and in Vivo: Dependence on Adherent Pathogen-Associated Molecular Patterns.

BACKGROUND Proinflammatory signaling by toll-like receptors (TLRs) likely contributes to biologic responses to wear particles causing aseptic loosening. We recently reported associations with aseptic loosening in patients with polymorphisms in the locus encoding an adapter protein specific for TLR-2 and TLR-4 known as toll/interleukin-1 receptor domain-containing adapter protein/MyD88 adapter-like (TIRAP/Mal). To directly examine the contribution of TIRAP/Mal, we tested the hypothesis that TIRAP/Mal deficiency reduces the activity of wear particles. Signaling by TLR-2 and TLR-4 through TIRAP/Mal can be activated by bacterial pathogen-associated molecular patterns (PAMPs) such as lipopolysaccharide or endogenous alarmins. To distinguish between those possibilities, we tested the hypothesis that the effects of TIRAP/Mal depend on the adherence of bacterial PAMPs to the particles. METHODS In vitro mRNA levels and secretion of tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 were measured after incubating wild-type and TIRAP/Mal(-/-) macrophages in the presence or absence of titanium particles with adherent bacterial debris, so-called endotoxin-free particles, or particles with adherent lipopolysaccharide. In vivo osteolysis was measured after implanting titanium particles on the calvaria of wild-type and TIRAP/Mal(-/-) mice. RESULTS TIRAP/Mal deficiency significantly inhibited the activity of titanium particles with adherent bacterial debris to stimulate in vivo osteolysis and in vitro cytokine mRNAs and secretion. Those effects are dependent on adherent PAMPs because removal of >99% of the adherent bacterial debris from the particles significantly reduced their activity and the remaining activity was not dependent on TIRAP/Mal. Moreover, adherence of highly purified lipopolysaccharide to the endotoxin-free particles reconstituted the activity and the dependence on TIRAP/Mal. CONCLUSIONS TIRAP/Mal deficiency reduces inflammatory responses and osteolysis induced by particles with adherent PAMPs. CLINICAL RELEVANCE Our results, coupled with the genetic associations between aseptic loosening and polymorphisms within the TIRAP/Mal locus, support TLR signaling through TIRAP/Mal as one of the factors that enhances the activity of wear particles and further support the hypothesis that bacterial PAMPs likely contribute to aseptic loosening in a subset of patients.

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.

Important Differences Exist in Posterior Condylar Offsets in an Osteological Collection of 1,058 Femurs

Posterior condylar offset (PCO) has important implications in total knee arthroplasty (TKA) function and design. In an osteological study of 1,058 femurs, we measured PCO using two separate techniques with a 3D digitizer. Measurements were standardized for the size of the femur. The medial PCO was greater than lateral PCO (32.6mm vs. 31.2mm, P<0.0001). In 53% of individuals, the medial PCO differed between sides by more than 2mm. Age did not affect standardized medial or lateral PCO. Compared with African-Americans, Caucasians had a larger standardized medial (1.3mm vs. 1.2mm, P=0.006) and lateral (1.1mm vs. 1.0mm, P=0.004) PCOs. The standardized medial (1.2mm vs. 1.3mm, P=0.073), and lateral (1.1mm vs. 1.1mm, P=0.098), PCO did not differ between men and women, respectively.

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.