The Concept of Femoroacetabular Impingement: Current Status and Future Perspectives

Femoroacetabular impingement (FAI) is a recently proposed mechanism causing abnormal contact stresses and potential joint damage around the hip. In the majority of cases, a bony deformity or spatial malorientation of the femoral head or head/neck junction, acetabulum, or both cause FAI. Supraphysiologic motion or high impact might cause FAI even with very mild bony alterations. FAI became of interest to the medical field when (1) evidence began to emerge suggesting that FAI may initiate osteoarthritis of the hip and when (2) adolescents and active adults with groin pain and imaging evidence of FAI were successfully treated addressing the causes of FAI. With an increased recognition and acceptance of FAI as a damage mechanism of the hip, defined standards of assessment and treatment need to be developed and established to provide high accuracy and precision in diagnosis. Early recognition of FAI followed by subsequent behavioral modification (profession, sports, etc) or even surgery may reduce the rate of OA due to FA

MAXIMAL DEPTH SQUATING IN ASYMPTOMATIC UNILATERAL CAM FAI

Femoracetabular impingement (FAI) is a condition that causes hip joint pain and has been found to result in decreased range of motion. However it is not known whether biomechanical deficiencies are associated with the mechanical impingement or further underlying issues associated with pain. This study consisted of comparing the squat biomechanics of two FAI groups to a matched control group. It was found that the asymptomatic group had squat performance very similar to the control group. Both the control and asymptomatic groups were able to squat to a deeper depth, had greater pelvic range of motion and a larger maximum hip flexion angle. These findings suggest that the bone deformity might not be directly related to restricting motion for the squat, and an issue of soft tissue damage and muscle problems may be the root cause, and should be the next avenue of study

DOES SYMMETRY OF LOWER LIMB KINETICS EXIST IN SITTING AND STANDING TASKS?

This study compared sit-to-stand and stand-to-sit symmetry for total hip arthroplasty patients (n=40) and a control group (n=19). 3D kinematics and kinetics were recorded. A symmetry index was calculated for kinetics. T-tests were significant for hip and knee moments and powers, and extension sum of moments for sit-to-stand, and for hip extension moment and power for stand-to-sit. THA patients mainly rely on their nonoperated limb to perform the sit-to-stand task. There was less asymmetry during the stand-to-sit tasks, were found significant. This study underlines the presence of asymmetrical kinetics in THA patient for these tasks, and demonstrated that sit-to-stand is more sensitive to asymmetry. These results should be considered in rehabilitation programs, and consequently allow these patients to return to a more active lifestyle

MUSCULAR CO-ACTIVATION IN SUBJECTS AFFECTED BY FEMOROACETABULAR IMPINGEMENT

Femoroacetabular Impingement (FAI) is a hip deformity that causes hip and groin pain. Previous research showed that FAI patients have altered hip kinetics and kinematics and pelvic kinematics. Whether or not this is due to different muscular strategies is still unclear. The purpose of this study was to investigate the muscular co-activation in FAI patients. Electromyographic signals were recorded from 16 hip muscles. The coactivation index was calculated for FAI symptomatic, asymptomatic and control groups. Even if not statistically significant, the co-activation measurements showed a trend similar to the findings for osteoarthritic (OA) patients. Additional investigations are warranted to confirm this analogy that could further relate FAI and OA development, and to confirm the hypothesis that FAI anomalies are also due to altered muscular strategies

IS PRINCIPAL COMPONENT ANALYSIS MORE EFFICIENT TO DETECT DIFFERENCES ON BIOMECHANICAL VARIABLES BETWEEN GROUPS?

The biomechanical analysis investigates variables such as angles, inter-segmental forces and moments at the joints. When the relevant parameters (e.g., range of motion, peak values) are selected a priori from these variables, they could not perfectly represent the information content of the original dataset. Therefore, in this study we want to validate the efficacy of the Principal Component Analysis (PCA) in overcoming the limitations of the a priori selection of the parameters. An application study is reported; the lower-limb joint mechanics between patients operated with two different surgical techniques for a total hip arthroplasty are analyzed with both the traditional analysis and the PCA. The findings from the two methods converged, but the PCA identified new sources of variability not previously detected

Leveraging machine learning and prescriptive analytics to improve operating room throughput

Successful days are defined as days when four cases were completed before 3:45pm, and overtime hours are defined as time spent after 3:45pm. Based on these definitions and the 460 unsuccessful days isolated from the dataset, 465 hours, 22 minutes, and 30 seconds total overtime hours were calculated. To reduce the increasing wait lists for hip and knee surgeries, we aim to verify whether it is possible to add a 5th surgery, to the typical 4 arthroplasty surgery per day schedule, without adding extra overtime hours and cost at our clinical institution. To predict 5th cases, 301 successful days were isolated and used to fit linear regression models for each individual day. After using the models' predictions, it was determined that increasing performance to a 77% success rate can lead to approximately 35 extra cases per year, while performing optimally at a 100% success rate can translate to 56 extra cases per year at no extra cost. Overall, this shows the extent of resources wasted by overtime costs, and the potential for their use in reducing long wait times. Future work can explore optimal staffing procedures to account for these extra cases

Integrating the Combined Sagittal Index Reduces the Risk of Dislocation Following Total Hip Replacement

Background: The aims of this matched cohort study were to (1) assess differences in spinopelvic characteristics between patients who sustained a dislocation after total hip arthroplasty (THA) and a control group without a dislocation, (2) identify spinopelvic characteristics associated with the risk of dislocation, and (3) propose an algorithm including individual spinopelvic characteristics to define an optimized cup orientation target to minimize dislocation risk.Methods: Fifty patients with a history of THA dislocation (29 posterior and 21 anterior dislocations) were matched for age, sex, body mass index (BMI), index diagnosis, surgical approach, and femoral head size with 200 controls. All patients underwent detailed quasi-static radiographic evaluations of the coronal (offset, center of rotation, and cup inclination/anteversion) and sagittal (pelvic tilt [PT], sacral slope [SS], pelvic incidence [PI], lumbar lordosis [LL], pelvic-femoral angle [PFA], and cup anteinclination [AI]) reconstructions. The spinopelvic balance (PI - LL), combined sagittal index (CSI = PFA + cup AI), and Hip-User Index were determined. Parameters were compared between the control and dislocation groups (2-group analysis) and between the controls and 2 dislocation groups identified according to the direction of the dislocation (3-group analysis). Important thresholds were determined from receiver operating characteristic (ROC) curve analyses and the mean values of the control group; thresholds were expanded incrementally in conjunction with running-hypothesis tests.Results: There were no coronal differences, other than cup anteversion, between groups. However, most sagittal parameters (LL, PT, CSI, PI - LL, and Hip-User Index) differed significantly. The 3 strongest predictors of instability were PI - LL &gt; 10° (sensitivity of 70% and specificity of 65% for instability regardless of direction), CSI standingof &lt; 216° (posterior instability), and CSI standingof &gt; 244° (anterior instability). A CSI that was not between 205° and 245° on the standing radiograph (CSI standing) was associated with a significantly increased dislocation risk (odds ratio [OR]: 4.2; 95% confidence interval [CI]: 2.2 to 8.2; p &lt; 0.001). In patients with an unbalanced and/or rigid lumbar spine, a CSI standingthat was not 215° to 235° was associated with a significantly increased dislocation risk (OR: 5.1; 95% CI: 1.8 to 14.9; p = 0.001).Conclusions: Spinopelvic imbalance (PI - LL &gt; 10° ) determined from a preoperative standing lateral spinopelvic radiograph can be a useful screening tool, alerting surgeons that a patient is at increased dislocation risk. Measurement of the PFA preoperatively provides valuable information to determine the optimum cup orientation to aim for a CSI standingof 205° to 245° , which is associated with a reduced dislocation risk. For patients at increased dislocation risk due to spinopelvic imbalance (PI - LL &gt; 10° ), the range for the optimum CSI is narrower.Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.</p

Sex differences in clinical outcomes following surgical treatment of femoroacetabular impingement

BACKGROUND: Sex-based differences in clinical outcomes following surgical treatment of femoroacetabular impingement remain largely uncharacterized; this prospective, multicenter study evaluated these differences both directly and adjusted for covariates. METHODS: Hips undergoing surgical treatment of symptomatic femoroacetabular impingement were prospectively enrolled in a multicenter cohort. Patient demographics, radiographic parameters, intraoperatively assessed disease severity, and history of surgical procedures, as well as patient-reported outcome measures, were collected preoperatively and at a mean follow-up of 4.3 years. A total of 621 (81.6%) of 761 enrolled hips met the minimum 1 year of follow-up and were included in the analysis; 56.7% of analyzed hips were female. Univariate and multivariable statistics were utilized to assess the direct and adjusted differences in outcomes, respectively. RESULTS: Male hips had greater body mass index and larger α angles. Female hips had significantly lower preoperative and postoperative scores across most patient-reported outcome measures, but also had greater improvement from preoperatively to postoperatively. The preoperative differences between sexes exceeded the threshold for the minimal clinically important difference of the modified Harris hip score (mHHS) and all Hip disability and Osteoarthritis Outcome Score (HOOS) domains except quality of life. Preoperative sex differences in mHHS, all HOOS domains, and Short Form-12 Health Survey physical function component score were greater than the postoperative differences. A greater proportion of female hips achieved the minimal clinically important difference for the mHHS, but male hips were more likely to meet the patient acceptable symptom state for this outcome. After adjusting for relevant covariates with use of multiple regression analysis, sex was not identified as an independent predictor of any outcome. Preoperative patient-reported outcome scores were a strong and highly significant predictor of all outcomes. CONCLUSIONS: Significant differences in clinical outcomes were observed between sexes in a large cohort of hips undergoing surgical treatment of femoroacetabular impingement. Despite female hips exhibiting lower baseline scores, sex was not an independent predictor of outcome or reoperation. LEVEL OF EVIDENCE: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence