Hale, Rena F.

Background: Radiography is the initial imaging modality used to evaluate femoroacetabular impingement (FAI), and diagnostic radiographic findings are well-established. However, the prevalence of these radiographic findings in patients with hip pain is unknown. Purpose: The purpose was 3-fold: (1) to determine the overall prevalence of radiographic FAI deformities in young patients presenting with hip pain, (2) to identify the most common radiographic findings in patients with cam-type FAI, and (3) to identify the most common radiographic findings in patients with pincer-type FAI. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A geographic database was used to identify patients aged 14 to 50 years with hip pain between the years 2000 to 2016. The following were evaluated on radiographs: cam type: typical pistol grip deformity, alpha angle >55°; pincer type: crossover sign (COS), coxa profunda or protrusio acetabuli, lateral center edge angle (LCEA) ≥40°, Tönnis angle <0°; and mixed type: both cam- and pincer-type features. Posterior wall sign (PWS) and ischial spine sign (ISS) were also evaluated. The prevalence of each was determined. Descriptive statistics were performed on all radiographic variables. Results: There were 1893 patients evaluated, and 1145 patients (60.5%; 1371 hips; 374 male and 771 female; mean age, 28.8 ± 8.4 years) had radiographic findings consistent with FAI. Of these hips, 139 (10.1%) had cam type, 245 (17.9%) had pincer type, and 987 (72.0%) had mixed type. The prevalence of a pistol grip deformity and an alpha angle >55° was 577 (42.1%) and 1069 (78.0%), respectively. The mean alpha angle was 66.9°± 10.5°. The prevalence of pincer-type radiographic findings was the following: COS, 1062 (77.5%); coxa profunda, 844 (61.6%); ISS, 765 (55.8%); PWS, 764 (55.7%); Tönnis angle <0°, 312 (22.8%); LCEA ≥40°, 170 (12.4%); and protrusio acetabuli, 7 (0.5%). Conclusion: The overall prevalence of radiographic findings consistent with FAI in young patients with hip pain was 60.5%. Radiographic findings for mixed-type FAI were the most prevalent. The most common radiographic finding for cam-type FAI was an alpha angle >55°. The most common radiographic finding for pincer-type FAI was the COS.

Objectives: Following ACL reconstruction, objective measurements of functional testing are often incorporated into the decision-making process with regard to clearance for return to sport (RTS), in order to reduce the risk of second ACL injury. However, there is limited data to assess the predictive value of functional testing to risk of second ACL injury. Therefore, the purpose of this study was to determine whether performance on functional testing following primary ACL reconstruction can predict second ACL injuries. Methods: Patient records were retrospectively analyzed for individuals who presented with an ACL injury at a single institution from 1990-2010. A total of 335 patients who underwent primary ACL reconstruction, had functional testing at the six month ± one month time point postoperatively, and had a minimum of two year post-operative follow-up were included in this study. Functional testing included vertical jump, single leg hop, and triple leg hop. Functional testing is represented as a measure of limb symmetry and was calculated as the involved limb divided by the uninvolved limb providing a percentage relative to the uninvolved limb. Statistical analysis was performed to determine the significance of functional test limb symmetries between those with and without a secondary tear by sex, then by age. Unpaired T-tests with an alpha level less than 0.05 was performed with JMP 13 (SAS Institute Inc., Cary, NC). Group distributions as well as effect sizes were calculated. Results: 335 patients with a mean age of 25 (SD 9.76) at an average time of 9.05 years (SD 3.54) of follow-up after ACL reconstruction met inclusion criteria and underwent statistical analysis (females= 150, male= 185). Of the cohort, 53 patients (18%) experienced second tears (female= 26, male= 27) at an average time of 44.19 months (6.03- 168.4) following ACL reconstruction with 34 occurring on the contralateral side and 19 on the ipsilateral side. Results at six month post ACL reconstruction indicate a significant difference between those who experienced a second ACL injury and those who didn’t with respect to single hop limb symmetry (95% ±7% vs.90% ± 12%, P<0.01). Triple hop limb symmetry was also significantly different between those who suffered a second ACL tear and those who did not (94% ± 6% vs. 90% ±11%, P<0.01). No significant differences were found in limb symmetry of vertical jump. When data was analyzed by sex, significant differences were found in females in the single hop limb symmetry (96% ± 8%, vs. 89% ± 14%, P<0.05) as well as triple hop limb symmetry (95% ± 5% vs. 90% ± 12%, P< 0.05). No significant differences were found in vertical jump for neither females nor males. No significant differences were found when data was categorized by age or sex and age. Conclusion: Overall, at an average of 9.05 years follow-up, 18% of a young and active population of primary ACL reconstructions had a second ACL injury. Contralateral ACL injuries were observed at an increased frequency relative to subsequent ipsilateral ACL tears. Patients with greater limb symmetry on single hop or triple hop functional testing at 6 months are at an increased risk for second ACL tears. When functional testing is used for return-to-sport decisions, physicians should caution patients about the risk of subsequent ACL injury for high performing patients.

Advancements in computational musculoskeletal biomechanics are constrained by a lack of experimental measurement under real-time physiological loading conditions. This paper presents the design, configuration, capabilities, accuracy, and repeatability of The University of Texas at El Paso Joint Load Simulator (UTJLS) by testing four cadaver knee specimens with 47 real-time tests including heel and toe squat maneuvers with and without musculotendon forces. The UTJLS is a musculoskeletal simulator consisting of two robotic manipulators and eight musculotendon actuators. Sensors include eight tension load cells, two force/torque systems, nine absolute encoders, and eight incremental encoders. A custom control system determines command output for position, force, and hybrid control and collects data at 2000 Hz. Controller configuration performed forward-dynamic control for all knee degrees-of-freedom (DOFs) except knee flexion. Actuator placement and specimen potting techniques uniquely replicate muscle paths. Accuracy and repeatability standard deviations across specimen during squat simulations were equal or less than 8 N and 5 N for musculotendon actuators, 30 N and 13 N for ground reaction forces (GRFs), and 4.4 N·m and 1.9 N·m for ground reaction moments. The UTJLS is the first of its design type. Controller flexibility and physical design support axis constraints to match traditional testing rigs, absolute motion, and synchronous real-time simulation of multiplanar kinematics, GRFs, and musculotendon forces. System DOFs, range of motion, and speed support future testing of faster maneuvers, various joints, and kinetic chains of two connected joints.