Ashley L. Kapron

Radiographic prevalence of femoroacetabular impingement in collegiate football players: AAOS Exhibit Selection.

BACKGROUND The prevalence of femoroacetabular impingement may be greater in athletes than in the general population because of increased loading of the hip during sports. This study evaluated the radiographs of collegiate football players in order to quantify the prevalence of femoroacetabular impingement in asymptomatic athletes. METHODS Sixty-seven male collegiate football players (age, 21 ± 1.9 years) participated in this prospective study. Both hips (n = 134) were evaluated independently by two orthopaedic surgeons for radiographic signs of femoroacetabular impingement. The alpha angle and femoral head-neck offset were measured on frog-leg lateral radiographs. The lateral center-edge angle, acetabular index, crossover sign, and alpha angle were measured on anteroposterior radiographs. Data for continuous variables were averaged between observers prior to assessing prevalence. Cam femoroacetabular impingement was considered to be present if the femoral head-neck offset was <8 mm and/or the alpha angle was >50° on either radiograph. Pincer femoroacetabular impingement was considered to be present if the lateral center-edge angle was >40°, the acetabular index was <0°, and/or a positive crossover sign was detected by both observers. RESULTS Ninety-five percent of the 134 hips had at least one sign of cam or pincer impingement, and 77% had more than one sign. Twenty-one percent had only one sign of cam femoroacetabular impingement and 57% had both signs. Fifty-two percent had only one sign of pincer femoroacetabular impingement, 10% had two, and 4% had all three signs. Specifically, 72% had an abnormal alpha angle, 64% had a decreased femoral head-neck offset, 61% had a positive crossover sign, 16% had a decreased acetabular index, and 7% had an increased lateral center-edge angle. Fifty percent of all hips had at least one sign of pincer femoroacetabular impingement and at least one sign of cam impingement. Interobserver and intraobserver repeatability was moderate or better for each measure (range, 0.59 to 0.85). CONCLUSIONS Morphologic abnormalities associated with cam and pincer femoroacetabular impingement were common in these collegiate football players. The prevalence of cam and pincer femoroacetabular impingement was substantially higher than the previously reported prevalence in the general population.

The Scandinavian total ankle replacement: long-term, eleven to fifteen-year, survivorship analysis of the prosthesis in seventy-two consecutive patients.

BACKGROUND The objective of this study was to determine the long-term survivorship and clinical and radiographic results of the Scandinavian Total Ankle Replacement (STAR). METHODS From February 1996 to March 2000, seventy-seven ankles in seventy-two patients (thirty-seven female and thirty-five male patients, with an average age of fifty-six years) underwent total ankle replacement using the STAR prosthesis with a single coating of hydroxyapatite. Two patients were lost to follow-up, and twelve patients with thirteen ankle replacements died. The average duration of follow-up for the patients without revision was 12.4 years (range, 10.8 to 14.9 years). Sixty-two of the seventy-seven ankles were available for final follow-up. RESULTS Twenty-nine (38%) of the seventy-seven ankles had a revision of at least one of the metallic components. The probability of implant survival was 70.7% at ten years and 45.6% at fourteen years. The main reasons for revision were aseptic loosening, subsidence of the talar component, and progressive cyst formation. Polyethylene insert fractures were observed in eleven ankles. CONCLUSIONS While the midterm to short-term results for patients managed with the STAR prosthesis have been encouraging at 3.7 years, the long-term survivorship of the same cohort was considerably inferior. The subjective and clinical results of the patients with retained prostheses are generally good and comparable with results reported in the current literature.

The Effect of NSAID Prophylaxis and Operative Variables on Heterotopic Ossification After Hip Arthroscopy

Background: Heterotopic ossification (HO) is a known complication of hip arthroscopy. Little is known about the factors that lead to HO after hip arthroscopy. Purpose: The aim of this study was to evaluate the effect of nonsteroidal anti-inflammatory drugs (NSAIDs) and other operative variables on the development of HO. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 357 consecutive cases of hip arthroscopy were retrospectively reviewed over a 3-year period. Routine NSAID prophylaxis was not performed for the first 117 cases. Prophylaxis with naproxen for 3 weeks was then routinely prescribed for the remaining 240 cases. Complete follow-up was available for 288 of the original 357 cases. The presence of HO and its characteristics were recorded for each patient, along with baseline demographic and surgical variables. Odds ratios and logistic regression were used to identify causal factors for HO. Results: The incidence of HO in cases in which the patient did not receive NSAID prophylaxis was 25.0% (23/92) versus 5.6% (11/196) of cases in which the patient received NSAIDs. Patients who received no NSAID prophylaxis were 13.6 times more likely to develop HO postoperatively (95% confidence interval, 2.44-75.5; P = .003). Comparing just mixed-type femoroacetabular impingement resections, patients who received no NSAID prophylaxis were 16.6 times more likely to develop HO postoperatively (95% confidence interval, 2.2-126.0; P = .006). Multivariate logistic regression identified the performance of a mixed-type femoroacetabular impingement resection (P = .011) and the absence of NSAID prophylaxis (P = .003) as predictors of HO development. The majority of HO cases (29/34) occurred in patients with mixed-type femoroacetabular impingement who had both osteochondroplasty and acetabuloplasty. Complications of NSAID therapy in this study population included acute renal failure, hematochezia from acute colitis, and gastritis. Conclusion: Routine NSAID prophylaxis reduces but does not eliminate the incidence of HO in patients undergoing hip arthroscopy. Heterotopic ossification was more likely to develop in patients undergoing acetabuloplasty along with osteochondroplasty and in those who did not receive prophylactic postoperative NSAIDs. Side effects from the investigated NSAID regimen can be serious and should be weighed against the potential benefits in preventing the formation of HO.

Coxa Profunda: Is the Deep Acetabulum Overcovered?

BackgroundCoxa profunda, or a deep acetabular socket, is often used to diagnose pincer femoroacetabular impingement (FAI). Radiographically, coxa profunda is the finding of an acetabular fossa medial to the ilioischial line. However, the relative position of the acetabular fossa to the pelvis may not be indicative of acetabular coverage.Questions/purposesWe therefore determined the incidence of coxa profunda and evaluated associations between coxa profunda and other radiographic parameters of acetabular coverage commonly used to diagnose pincer FAI and acetabular dysplasia.MethodsWe evaluated the radiographs of three cohorts for coxa profunda, lateral center edge (LCE) angle, acetabular index, posterior wall sign, and crossover sign. Data from 67 collegiate football players were collected prospectively (Cohort 1). We identified two patient cohorts through retrospective review of all 179 hips undergoing hip preservation surgery from 2002 to 2008 (83 periacetabular osteotomies [Cohort 2] and 96 surgical dislocation and osteochondroplasties [Cohort 3]).ResultsIn all three cohorts, we detected no difference in the LCE angle or acetabular index between hips with and without coxa profunda. Coxa profunda existed in hips representing the spectrum of acetabular coverage measured by LCE angle (−18° to 60°) and acetabular orientation determined by the crossover sign.ConclusionsCoxa profunda was a common radiographic finding in both symptomatic patients and asymptomatic football players. Coxa profunda existed in hips representing the spectrum of acetabular coverage and was not associated with an overcovered acetabulum. We conclude coxa profunda is unrelated to overcoverage and suggest its use in diagnosis of pincer FAI be abandoned in favor of other determinants of focal or general overcoverage.Level of EvidenceLevel III, diagnostic study. See Instructions for Authors for a complete description of levels of evidence.

Hip Internal Rotation Is Correlated to Radiographic Findings of Cam Femoroacetabular Impingement in Collegiate Football Players

PURPOSE The objective of this study was to determine whether physical examinations (flexion-abduction-external rotation [FABER], impingement, range-of-motion profiles) could be used to detect the bony abnormalities of femoroacetabular impingement (FAI) in an athletic population. METHODS We performed a prospective study of 65 male collegiate football players. Both hips were evaluated by 2 orthopaedic surgeons for radiographic signs of FAI. The alpha angle and head-neck offset were measured on frog-leg lateral films. The center-edge angle, acetabular index, crossover sign, and alpha angle were measured on anteroposterior films. Measurements were averaged for both observers. Maximum hip range of motion in flexion (supine) and internal/external rotation (supine, sitting, and prone) was measured with a goniometer. Pain provoked by the impingement and FABER tests was also recorded. Examinations were completed at 2 of 4 stations (2 duplicates), each staffed by 2 clinicians (1 examined and 1 measured). The relation between each range-of-motion and radiographic measure was determined. Data from each station were assessed separately. Only those regressions significant (P < .05) for paired stations were considered clinically significant. RESULTS The alpha angle and head-neck offset measured on the frog-leg lateral films were significantly correlated (all P < .01) to supine, sitting, and prone internal rotation for all stations. Correlation coefficients ranged from -0.59 to -0.35 for alpha angle and 0.42 to 0.57 for head-neck offset. Although 95% of the hips had at least 1 radiographic sign of FAI, pain was reported in only 8.5% and 2.3% during the impingement and FABER tests, respectively. CONCLUSIONS Internal rotation correlates to radiographic measures of cam FAI in this cohort of collegiate football players. Football players with diminished internal rotation in whom hip pain develops should be evaluated for underlying cam FAI abnormalities. LEVEL OF EVIDENCE Level IV, therapeutic case series.

The Prevalence of Radiographic Findings of Structural Hip Deformities in Female Collegiate Athletes

Background: Structural deformities of the hip, including femoroacetabular impingement (FAI) and acetabular dysplasia, often limit athletic activity. Previous studies have reported an increased prevalence of radiographic cam FAI in male athletes, but data on the prevalence of structural hip deformities in female athletes are lacking. Purpose: (1) To quantify the prevalence of radiographic FAI deformities and acetabular dysplasia in female collegiate athletes from 3 sports: volleyball, soccer, and track and field. (2) To identify possible relationships between radiographic measures of hip morphologic characteristics and physical examination findings. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Anteroposterior (AP) pelvis and frog-leg lateral radiographs were obtained from 63 female athletes participating in Division I collegiate volleyball, soccer, and track and field. Lateral center edge angle (LCEA) and acetabular index were measured on AP films. Alpha angle and head-neck offset were measured on frog-leg lateral films. Pain during the supine impingement examination and hip rotation at 90° of flexion were recorded. Random-effects linear regression was used for group comparisons and correlation analyses to account for the lack of independence of observations made on left and right hips. Results: Radiographic cam deformity (alpha angle >50° and/or head-neck offset <8 mm) was found in 48% (61/126) of hips. Radiographic pincer deformity (LCEA >40°) was noted in only 1% (1/126) of hips. No hips had radiographic mixed FAI (at least 1 of the 2 cam criteria and LCEA >40°). Twenty-one percent (26/126) of hips had an LCEA <20°, indicative of acetabular dysplasia, and an additional 46% (58/126) of hips had borderline dysplasia (LCEA ≥20° and ≤25°). Track and field athletes had significantly increased alpha angles (48.2° ± 7.1°) compared with the soccer players (40.0° ± 6.8°; P < .001) and volleyball players (39.1° ± 5.9°; P < .001). There was no significant difference in the LCEA (all P > .914) or the prevalence of dysplasia (LCEA <20°) between teams (all P > .551). There were no significant correlations between the radiographic measures and internal rotation (all P > .077). There were no significant differences (all P > .089) in radiographic measures between hips that were painful (n = 26) during the impingement examination and those that were not. Conclusion: These female athletes had a lower prevalence of radiographic FAI deformities compared with previously reported values for male athletes and a higher prevalence of acetabular dysplasia than reported for women in previous studies.

Correlations between the alpha angle and femoral head asphericity: Implications and recommendations for the diagnosis of cam femoroacetabular impingement

OBJECTIVE To determine the strength of common radiographic and radial CT views for measuring true femoral head asphericity. PATIENTS AND METHODS In 15 patients with cam femoroacetabular impingement (FAI) and 15 controls, alpha angles were measured by two observers using radial CT (0°, 30°, 60°, 90°) and digitally reconstructed radiographs (DRRs) for the: anterior-posterior (AP), standing frog-leg lateral, 45° Dunn with neutral rotation, 45° Dunn with 40° external rotation, and cross-table lateral views. A DRR validation study was performed. Alpha angles were compared between groups. Maximum deviation from a sphere of each subject was obtained from a previous study. Alpha angles from each view were correlated with maximum deviation. RESULTS There were no significant differences between alpha angles measured on radiographs and the corresponding DRRs (p=0.72). Alpha angles were significantly greater in patients for all views (p≤0.002). Alpha angles from the 45° Dunn with 40° external rotation, cross-table lateral, and 60° radial views had the strongest correlations with maximum deviation (r=0.831; r=0.823; r=0.808, respectively). The AP view had the weakest correlation (r=0.358). CONCLUSION DRRs were a validated means to simulate hip radiographs. The 45° Dunn with 40° external rotation, cross-table lateral, and 60° radial views best visualized femoral asphericity. Although commonly used, the AP view did not visualize cam deformities well. Overall, the magnitude of the alpha angle may not be indicative of the size of the deformity. Thus, 3D reconstructions and measurements of asphericity could improve the diagnosis of cam FAI.

Accuracy and Feasibility of Dual Fluoroscopy and Model-Based Tracking to Quantify In Vivo Hip Kinematics During Clinical Exams

Accurate measurements of in-vivo hip kinematics may elucidate the mechanisms responsible for impaired function and chondrolabral damage in hips with femoroacetabular impingement (FAI). The objectives of this study were to quantify the accuracy and demonstrate the feasibility of using dual fluoroscopy to measure in-vivo hip kinematics during clinical exams used in the assessment of FAI. Steel beads were implanted into the pelvis and femur of two cadavers. Specimens were imaged under dual fluoroscopy during the impingement exam, FABER test, and rotational profile. Bead locations measured with model-based tracking were compared with those measured using dynamic radiostereometric analysis. Error was quantified by bias and precision, defined as the average and standard deviation of the differences between tracking methods, respectively. A normal male volunteer was also imaged during clinical exams. Bias and precision along a single axis did not exceed 0.17 and 0.21 mm, respectively. Comparing kinematics, positional error was less than 0.48 mm and rotational error was less than 0.58°. For the volunteer, kinematics were reported as joint angles and bone-bone distance. These results demonstrate that dual fluoroscopy and model-based tracking can accurately measure hip kinematics in living subjects during clinical exams of the hip.

Influence of Ankle Position and Radiographic Projection Angle on Measurement of Supramalleolar Alignment on the Anteroposterior and Hindfoot Alignment Views

Background: Using digitally reconstructed radiographs (DRRs), we determined how changes in the x-ray beam projection angle from the horizon, tibiotalar joint angle, and axial rotation of the foot influenced measurements of the medial distal tibial angle (MDTA) on the anteroposterior (AP) and hindfoot alignment views (HAV). Methods: Seven cadaver foot-ankle specimens were scanned by computed tomography (CT) at fixed tibiotalar joint positions, ranging from 15 degrees of dorsiflexion to 25 degrees of plantarflexion. DRRs were created from each CT scan to simulate alterations in the horizontal projection angle (0 to 25 degrees) and foot axial rotation (–30 to 30 degrees). The MDTA was measured on each DRR and compared with that quantified on the baseline HAV and AP view. Results: Altering the horizontal projection angle by ≥5 degrees and >10 degrees significantly altered the MDTA for the AP view and the HAV, respectively. Shifting dorsiflexion and plantarflexion caused minor changes in the MDTA that were only statistically significant for the HAV. Axial rotation significantly changed the MDTA on both views, but deviations were more pronounced for the HAV. Conclusions: Compared with the HAV, the MDTA on the AP view was less sensitive to changes in foot-ankle position. However, increasing the tilt of the x-ray beam from the horizon altered the MDTA on the AP view substantially. Clinical Relevance: To avoid misinterpretation of the MDTA, we recommend using the AP view to quantify supramalleolar alignment as it is less sensitive to changes in positioning of the foot-ankle. When acquiring an AP film, the x-ray beam should be directed along the horizon to ensure consistent assessment of the MDTA across patients.

Comparison of Cannulated Screws Versus Compression Staples for Subtalar Arthrodesis Fixation

Background: Different fixation techniques have been described in the literature for isolated subtalar arthrodesis (ISA). The purpose of this study was to compare the fusion rate and clinical outcome of ISA using cannulated compression screws or compression staples. Methods: Thirty-three patients (33 feet) underwent ISA using screw (17 feet) or staples (16 feet) fixation. Patients were followed for 42.7 ± 16.4 months (range, 24.5-84.3 months). The subtalar fusion was assessed radiographically and clinically. Clinical outcome measures included the visual analog scale (VAS) for pain and American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score. Results: The average pain score decreased significantly from 6.4 ± 1.1 (range, 5-9) to 0.8 ± 1.3 (range, 0-4) (P < .001). In the screws group, the average AOFAS hindfoot score increased significantly from 54.6 ± 8.8 (range, 37-67) preoperatively to 86.1 ± 7.1 (range, 71-91) postoperatively (P < .001). In the staples group, the average AOFAS hindfoot score increased significantly from 53.4 ± 11.1 (range, 33-69) preoperatively to 83.4 ± 6.9 (range, 71-91) postoperatively (P < .001). The AOFAS hindfoot score was comparable in both groups (P = .149). Only the AOFAS hindfoot score function subgroup in the screw fixation was significantly higher than in the staples fixation group (P = .005). There were 4 cases of nonunion at the site of subtalar arthrodesis (2 from screws group, 2 from staples group). The complication rate was comparable in both groups. Conclusion: The fusion rate was comparable in both groups, while the postoperative functional outcome was significantly better in the screw fixation group. Level of Evidence: Level III, retrospective comparative cohort study.