The effect of dynamic femoroacetabular impingement on pubic symphysis motion: a cadaveric study

BACKGROUND

A link between femoroacetabular impingement and athletic pubalgia has been reported clinically. One proposed origin of athletic pubalgia is secondary to repetitive loading of the pubic symphysis, leading to instability and parasymphyseal tendon and ligament injury. Hypothesis/

PURPOSE

The purpose of this study was to investigate the effect of simulated femoral-based femoroacetabular impingement on rotational motion at the pubic symphysis. The authors hypothesize that the presence of a cam lesion leads to increased relative symphyseal motion.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twelve hips from 6 fresh-frozen human cadaveric pelvises were used to simulate cam-type femoroacetabular impingement. The hips were held in a custom jig and maximally internally rotated at 90° of flexion and neutral adduction. Three-dimensional motion of the pubic symphysis was measured by a motion-tracking system for 2 states: native and simulated cam. Load-displacement plots were generated between the internal rotational torque applied to the hip and the responding motion in 3 anatomic planes of the pubic symphysis.

RESULTS

As the hip was internally rotated, the motion at the pubic symphysis increased proportionally with the degrees of the rotation as well as the applied torque measured at the distal femur for both states. The primary rotation of the symphysis was in the transverse plane and on average accounted for more than 60% of the total rotation. This primary motion caused the anterior aspect of the symphyseal joint to open or widen, whereas the posterior aspect narrowed. At the torque level of 18.0 N·m, the mean transverse rotation in degrees was 0.89° ± 0.35° for the native state and 1.20° ± 0.41° for cam state. The difference between cam and the native groups was statistically significant (P < .03).

CONCLUSION

Dynamic femoroacetabular impingement as caused by the presence of a cam lesion causes increased rotational motion at the pubic symphysis.

CLINICAL RELEVANCE

Repetitive loading of the symphysis by cam impingement is thought to lead to increased symphyseal motion, which is one possible precursor to athletic pubalgia.

A classification-system improves the intra- and interobserver reliability of radiographic diagnosis of "pistol-grip-deformity"

Early detection of pistol-grip-deformity may be beneficial in optimising the outcome and the cost effectiveness of surgery. It is important to identify reliable radiographic parameters in assessing femoro-acetabular impingement (FAI) to develop a treatment algorithm. Radiographs of 47 patients ranging from "pistol grip deformity" to a normal head-neck-junction were measured for alpha angle and head ratio, and then classified by two different observers. The Bland-Altman plot was used for inter- and intraobserver agreement of alpha angle and head ratio. Inter- and intraobserver agreement for classification of "pistol grip deformity" was determined using weighted Cohen's kappa coefficient. Observer I achieved a kappa coefficient of 0.97. Observer II achieved a kappa coefficient of 0.92. An interobserver kappa coefficient between 0.87 and 0.92 was achieved by using a classification system. By testing for interobserver agreement, a bias of -0.004 with an upper limit of 0.461 and a lower limit of -0.47 was seen for the ratio and a bias of -3.7 with an upper limit of 17.2 and a lower limit of -24.6 for the alpha angle. Therefore, poor results were seen for intra- and interobserver reliability by using only a single plane for classification of "pistol grip deformity". The strength of agreement could be improved by using a classification system (based on two planes).

Impact of arthroscopy of the hip for femoroacetabular impingement on quality of life at a mean follow-up of 3.2 years

The benefit of arthroscopy of the hip in the treatment of femoroacetabular impingement (FAI) in terms of quality of life (QoL) has not been reported. We prospectively collected data on 612 patients (257 women (42%) and 355 men (58%)) with a mean age at the time of surgery of 36.7 years (14 to 75) who underwent arthroscopy of the hip for FAI under the care of a single surgeon. The minimum follow-up was one year (mean 3.2 years (1 to 7)). The responses to the modified Harris hip score were translated using the Rosser Index Matrix in order to provide a QoL score. The mean QoL score increased from 0.946 (-1.486 to 0.995) to 0.974 (0.7 to 1) at one year after surgery (p < 0.001). The mean QoL score in men was significantly higher than in women, both before and one year after surgery (both p < 0.001). However, the mean change in the QoL score was not statistically different between men and women (0.02 (-0.21 to 0.27) and 0.04 (-0.16 to 0.87), respectively; p = 0.12). Linear regression analysis revealed that the significant predictors of a change in QoL score were pre-operative QoL score (p < 0.001) and gender (p = 0.04). The lower the pre-operative score, the higher the gain in QoL post-operatively (ρ = -0.66; p < 0.001). One year after surgery the QoL scores in the 612 patients had improved in 469 (76.6%), remained unchanged in 88 (14.4%) and had deteriorated in 55 (9.0%).

Clinical diagnosis and arthroscopic treatment of acetabular labral tears

OBJECTIVE

To investigate the clinical diagnosis and arthroscopic treatment of acetabular labral tears.

METHODS

Twenty-one patients with unilateral acetabular labral tears hospitalized from November 2008 to December 2009 were included in this retrospective study. A definitive diagnosis was made preoperatively on the basis of physical examination, plain radiography and magnetic resonance arthrography (MRA). All cases were treated with arthroscopic surgeries: labral debridement (14 cases), labral debridement plus femoral osteoplasty (5 cases), and labral repair plus osteoplasty (2 cases). All patients were followed-up and the results evaluated using the visual analogue scale (VAS) and Harris hip score.

RESULTS

A positive flexion, abduction and internal rotation (FADIR) impingement sign was found in all 21 affected hips, a positive flexion, abduction and external rotation (FABER) impingement sign in 15, and a positive McCarthy test in 9. Plain radiography showed 11 cases had cam type impingement, in 6 of whom it was combined with pincer type impingement; and 2 cases had acetabular retroversion alone. Labral tears were observed on MRA in all cases and were all confirmed by arthroscopy. All patients were followed up for an average of 11.6 months (range, 6 to 19 months). The VAS decreased from (5.3 ± 1.3) preoperatively to (1.4 ± 0.9) 6 months postoperatively. The mean Harris hip score improved from (63 ± 9) preoperatively to (84 ± 10) 6 months postoperatively. All these differences were statistically significant.

CONCLUSIONS

Acetabular labral injury is closely correlated with femoro-acetabular impingement. Impingement tests and MRA have high sensitivity and accuracy in clinical diagnosis of labral tears. Arthroscopic debridement, repair and osteoplasty for labral tears results in a good early outcome.

The cam-type deformity of the proximal femur arises in childhood in response to vigorous sporting activity

BACKGROUND

The prevalence of a cam-type deformity in athletes and its association with vigorous sports activities during and after the growth period is unknown.

QUESTIONS/PURPOSES

We therefore compared the prevalence and occurrence of a cam-type deformity by MRI in athletes during childhood and adolescence with an age-matched control group.

PATIENTS AND METHODS

We retrospectively reviewed 72 hips in 37 male basketball players with a mean age of 17.6 years (range, 9-25 years) and 76 asymptomatic hips of 38 age-matched volunteers who had not participated in sporting activities at a high level.

RESULTS

Eleven (15%) of the 72 hips in the athletes were painful and had positive anterior impingement tests on physical examination. Internal rotation of the hip averaged 30.1° (range, 15°-45°) in the control group compared with only 18.9° (range, 0°-45°) in the athletes. The maximum value of the alpha angle throughout the anterosuperior head segment was larger in the athletes (average, 60.5° ± 9°), compared with the control group (47.4° ± 4°). These differences became more pronounced after closure of the capital growth plate. Overall, the athletes had a 10-fold increased likelihood of having an alpha angle greater than 55° at least at one measurement position.

CONCLUSIONS

Our observations suggest a high intensity of sports activity during adolescence is associated with a substantial increase in the risk of cam-type impingement. These patients also may be at increased risk of subsequent development of secondary coxarthrosis.

LEVEL OF EVIDENCE

Level II, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Prevalence of joint-related pain in the extremities and spine in five groups of top athletes

PURPOSE

Joint-related pain conditions from the spine and extremities are common among top athletes. The frequency of back pain has, however, been studied in more detail, and the frequency of low-back pain in top athletes in different high-load sports has been reported to be as high as 85%. Sport-related pain from different joints in the extremities is, however, infrequently reported on in the literature.

METHODS

Seventy-five male athletes, i.e. divers, weight-lifters, wrestlers, orienteers and ice-hockey players and 12 non-athletes (control group) were included in the study. A specific self-assessed pain-oriented questionnaire related to the cervical, thoracic and lumbar spine, as well as the various joints, i.e. shoulders, elbows, wrists, hips, knees and ankles, was filled out by the athletes and the non-athletes.

RESULTS

The overall frequency of pain reported by the athletes during the last week/last year was as follows; cervical spine 35/55%; thoracic spine 22/33%; lumbar spine 50/68%; shoulder 10/21%; elbow 7/7%; wrist 7/8%; hip 15/23%; knee 22/44%; and ankle 11/25%. The corresponding values for non-athletes were cervical spine 9/36%; thoracic spine 17/33%; lumbar spine 36/50%; shoulder 0/9%; elbow 9/0%; wrist 0/0%; hip 9/16%; knee 10/9%; and ankle 0/0%. A higher percentage of athletes reported pain in almost all joint regions, but there were no statistically significant differences (n.s.), with the exception of the knees (P = 0.05). Over the last year, athletes reporting the highest pain frequency in the lumbar spine were ice-hockey players and, in the cervical spine, wrestlers and ice-hockey players. The highest levels of knee pain were found among wrestlers and ice-hockey players, whereas the highest levels for wrist pain were found among divers, hip pain among weight-lifters, orienteers and divers and ankle pain among orienteers. For the thoracic spine, shoulder and elbow regions, only minor differences were found.

CONCLUSION

There was no statistically significant difference in prevalence of pain in the neck, spine and joints between top athletes in different sports or between athletes and non-athletes. However, pain in one spinal region was correlated to reported pain in other regions of the spine. Moreover, pain in the spine was also correlated to pain in the shoulders, hips and knees.

"At-risk" positioning and hip biomechanics of the Peewee ice hockey sprint start

BACKGROUND

Femoroacetabular impingement (FAI) is becoming a prevalent overuse injury diagnosis among hockey players. In the adult ice hockey stride, the "at-risk" hip position, defined by internal rotation during flexion and external rotation during abduction, reportedly increases hip vulnerability to labral injury as a result of FAI.

HYPOTHESIS

Peewee youth ice hockey players display the kinematics for both described at-risk hip positions (internal rotation during flexion and external rotation during abduction) in the ice hockey sprint start.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Twelve healthy male Peewee ice hockey players (mean age, 10.8 ± 0.6 years) participated in this study. Thirty-five anatomic landmarks were used to analyze the 3-dimensional kinematic and kinetic variables of the hip associated with the ice hockey sprint start. Ten high-speed (120-Hz) infrared cameras recorded the trials, which were subsequently analyzed with Motion Monitor software. The sprint start was recorded over 4 defined periods of motion: start, push, swing, and even.

RESULTS

In the "push" period, 11.5° of external rotation was observed concurrently with 13.2° of abduction in the push leg, and 6.8° of internal rotation occurred with 33.8° of flexion in the lead leg. During the recovery phase of the "swing" period, maximum internal rotation was 5.6° with concurrent hip flexion of 44.2° in the push leg, while lead leg internal rotation reached a maximum of 10.8° with hip flexion of 35.1° during the "even" period.

CONCLUSION

During the sprint start, youth ice hockey players externally rotate in abduction during the push-off phase and internally rotate through increasing hip flexion during the recovery phase, displaying the at-risk hip positions of the ice hockey skating stride.

CLINICAL RELEVANCE

During the sprint start, youth ice hockey players position their hips in a manner that can cause impingement of the femoral neck against the acetabulum and potentially lead to labral tears and/or articular cartilage damage. This knowledge could be applied to assist in the prevention of overuse injuries of the hip as youth hockey players mature and increase in skill level.

A pre-operative approach of range of motion simulation and verification for femoroacetabular impingement

BACKGROUND

Femoroacetabular impingement (FAI) is increasingly recognized as a potential cause of hip osteoarthritis. A system capable of pre-operatively simulating hip range of motion (ROM) by given surface models from either healthy or FAI diseased bone is desirable.

METHODS

An impingement detection system using bounding sphere hierarchies was first developed. Both precision and accuracy of the impingement detection system were verified by a custom-designed phantom to imitate ball-and-socket hip movement. The impingement detection system was then implemented into the hip ROM simulation system to simulate the ROM of (1) healthy pelvis and femur, and (2) healthy pelvis and pathologic femur. The ROM simulation system was also verified by manipulating sawbones under the navigation of an optical tracking system.

RESULTS

The impingement detection system achieved a distance error of 0.53 ± 0.06 mm and an angular error of 0.28 ± 0.03°. The impingement detection accuracies were 100%, 100%, and 96% in three different phantom orientations, respectively. The mean errors between simulated and verified ROM were 0.10 ± 1.39° for the 'healthy pelvis and femur' group, and - 2.38 ± 3.49° for the 'healthy pelvis and pathologic femur' group.

CONCLUSION

The present study demonstrates a pre-operative approach to virtually simulate and predict the functional hip ROM based on the given bone models. The impingement detection and ROM simulation systems developed may also be used for other orthopedic applications.

Intra- and interobserver variability of magnetic resonance imaging for quantitative assessment of abductor and external rotator muscle changes after total hip arthroplasty

PURPOSE

Magnetic resonance imaging (MRI) is one of the most widely used noninvasive diagnostic modalities for musculoskeletal evaluation. We conducted a retrospective study to determine whether MRI of the hip joint abductor and external rotator muscles yields reproducible findings in patients after total hip arthroplasty (THA).

MATERIALS AND METHODS

MR images were obtained 12 months after THA in 10 patients and were analyzed by two independent, blinded observers. The images were analyzed on workstations with three-dimensional analysis capabilities. The readers evaluated the gluteus medius, gluteus minimus, and obturator externus muscles on the nonoperated side (NOS) and the THA side. For each of the three muscles, the readers analyzed the cross-sectional area, cross-sectional signal intensity, intensity in a region of interest (ROI), and volume on both sides.

RESULTS

Unlike intraobserver variability, interobserver variability showed significant differences between the measurements for some abductor and external rotator muscles, especially for volume (p<0.001-0.02) and cross-sectional area (p<0.001-0.05) analysis of the gluteus medius and minimus muscles on the THA side but also on the NOS. There were no differences in signal intensity in the ROI (p=0.29-0.83). The coefficients of variation (CoV) of all 4 parameters quantified were lower on the NOS (average, 5.9%) than on the THA side (average, 7.3%). Analysis of the gluteus minimus muscle volume showed both higher intraobserver (18.8%) and interobserver (13.9%) variability on the THA side.

CONCLUSION

MRI is an accurate and reliable test for evaluation of soft tissue structures in patients who have undergone THA. MRI evaluation of abductor muscles yields reproducible results on the THA side and on the NOS. Prosthesis artifacts limit evaluation of the gluteus minimus muscle on the THA side and cannot be recommended. Since interobserver variability was always higher than intraobserver variability, follow-up examinations should ideally be performed by the same reader in order to obtain clinically meaningful results.