Purpose. The importance of femoral head-neck morphology in the development of early hip osteoarthritis is recognized in femeroacetabular impingement (FAI), however no studies have examined FAI morphology in the developing hip, i.e. pre-closure of the proximal femoral physis. We developed a pilot project to study prevalence of CAM-type FAI hip morphology in both the pre- and post-closure proximal femoral physes of asymptomatic children using MR-imaging. We also examined biologic markers possibly related to FAI etiology, including Vitamin D metabolites, BMI, family history, and activity levels. Method. Recruitment included volunteers with asymptomatic lower extremities, and either pre- or post-closure of the proximal femoral physis. Males were 10–12 years (pre-closure) or 15–18 years (post-closure); females were 8–10 years or 14 18 years. Phlebotomy and urine sampling were used to assess metabolic markers. MRI of bilateral hips and a clinical exam including hip impingement tests were conducted. MR imaging assessment was independent and blinded and recorded using established parameters including alpha angles measured at both the 3:00 (anterior head-neck junction) and 1:30 (antero-superior head-neck junction) radial image positions. Results. Fifty-two volunteers were recruited (32 boys, 20 girls), of whom 44 had bilateral hips imaged (88 hips). Radiographic analysis showed no CAM-type morphology in pre-closure hips and 14% in post-closure hips, using established criteria (alpha > 50.5). The difference between alpha angle measurements at 3:00 and 1:30 positions (5.16) appears significant in developing hips. Conclusion. Results confirm our ability to recruit a cohort of asymptomatic children for the proposed methodology. Collected data found FAI in 14% of the closed-physes group and 0 % in the open physes group suggesting possible physeal closure importance. The difference between 3:00 and 1:30 alpha angle measurements was significantly less than in published adult figures, further suggesting a developmental role in CAM-Type FAI. This is the first published attempt to assess CAM-type FAI morphology in the developing hip. Preliminary data suggests the period just prior to physeal closure may have significant etiological implications. New parameters for imaging angles are suggested. The study results will guide future cohort study designs

To determine the effect that preoperative use of 3D printed models has on the outcomes for femoroacetabular impingement (FAI) surgery. Ninety patients that underwent FAI surgeries by the same surgeon were retrospectively analyzed. Patients were age- and sex-matched for two groups - those who had pre-operative 3D printed hip models (n=45) and those with conventional planning using X-rays and/or CT scan (n=45) were identified. Radiographic parameters on pre- and post-operative radiographs that include the alpha angle (45 Dunn view), center edge angle (CEA) (weight bearing AP pelvis), and head-neck offset ratio (cross-table lateral) were obtained. Clinical outcomes were assessed by analyzing iHOT and HOS scores pre- and post-operatively. Ninety patients (3D printed group 45, Conventional group 45) with a mean age of 36 years were evaluated. Mean follow-up time was 28 months. For all of the radiological variables (CEA and alpha angle), there was a significant improvement seen for both groups (p=0.001). However, the 3D printed group showed significantly better resection of bone to a normal alpha angle (< 5 5) than did the Conventional group. Additionally, head-neck offset was significantly better in the 3D printed group (p=0.001). Statistically significant improvements were seen in both groups on the HOS and iHOT-33 (p=0.001). Planning FAI surgery using 3D hip models helps in achieving better resection, especially in CAM-type FAI

Background. Cam-type femoro-acetabular impingement (FAI) is increasingly recognised as a cause of mechanical hip symptoms in young adults. It is likely that it is a cause of early hip degeneration. Ganz et al have developed a therapeutic procedure involving trochanteric flip osteotomy and dislocation of the hip, and have reported good results. We have developed an arthroscopic osteochondroplasty to reshape the proximal femur and relieve impingement. Methods. Fifty patients who presented with mechanical hip symptoms and had demonstrable cam-type FAI on radially-reconstructed MR arthrography, were treated by arthroscopic osteochondroplasty. Ten patients had a post-operative CT; from these images flexion and internal rotation range was tested in a virtual reality (VR) model to determine adequacy of resection. All patients were followed up for a minimum of one year, and post-operative Non-Arthritic Hip Scores (NAHS, maximum possible score 100) compared with pre-operative NAHS. Results. Mean operating time was 110 minutes. 31 patients were discharged on the day of surgery, the remainder on the following day. There were no complications. All patients were asked to be partially weight-bearing with crutches for four weeks but most returned to work within two weeks. The VR models showed satisfactory resection, although there was clear evidence of improved precision with practice. Symptoms improved in all but two patients, with mean NAHS improving from 54 pre-operatively to 87 at one year. The two patients who did not improve, were both found to have unexpectedly extensive acetabular articular cartilage damage. Conclusion. Arthroscopic femoral reshaping to relieve FAI is feasible, safe and reliable. However it is technically difficult and time-consuming. The results are comparable to open dislocation and debridement, but the arthroscopic procedure avoids the prolonged disability and the complications associated with trochanteric flip osteotomy

Introduction:. Femoro-acetabular impingement reduces the range of motion of the hip joint and is thought to contribute to hip osteoarthritis. Surgical treatments attempt to restore hip motion through resection of bone at the head-neck junction. Due to the broad range of morphologies of FAI, the methodology of osteochondroplasty has been difficult to standardize and often results in unexpected outcomes, ranging from minimal improvement in ROM to excessive head resection with loss of cartilage and even neck fracture. In this study we test whether a standardized surgical plan based on a pre-determined resection path can restore normal anatomy and ROM to the CAM-impinging hip. Methods:. Computer models of twelve femora with classic signs of cam-type FAI were reconstructed from CT scans. The femoral shaft and neck were defined with longitudinal axes and the femoral head by a sphere of best fit. Boundaries defining the maximum extent of anterior resection were constructed: (i) superiorly and inferiorly along the anterior femoral neck at 12:30 and 5:30 on the clock face, approximating the locations of the vascularized synovial folds; (ii) around the head-neck junction along the edge of the articular cartilage; and (iii) at the base of the neck, perpendicular to the neck axis, 20–30 mm lateral to the articular edge. All four boundaries were used to form 3 alternative resection surfaces that provided resection depths of 2 mm (small), 4 mm (medium), and 6 mm (large) at the location of the cam lesion. Solid models of each femur after virtual osteochondroplasty were created by Boolean subtraction of each of the resection surfaces from the original femoral model. For each depth of neck resection, we measured the following: (i) alpha angle, (ii) anterior offset of the head-neck junction, and (iii) volume of bone removed. Before and after each resection, we also measured the maximum internal rotation of the hip in 90° flexion and 0° abduction. Results:. The initial alpha angles of the twelve femora averaged 63.8°, with corresponding average anterior head-neck offset of 5.8 mm and average maximum internal rotation of 16.3°. Impingement prevented one specimen from attaining the initial position of 90° flexion and 0° abduction. Implementation of pre-operative plans demonstrated that normal alpha angles (<55°) could be achieved using resection depths of 2 mm, 4 mm, and 6 mm (small: 48.8°, medium: 40.8°, large: 35.3°). The corresponding changes in internal rotation were +7.7° (to 24.0°; p < 0.001), +11.8° (to 28.1°; p < 0.001), and +14.7° (to 31°; p < 0.001), with anterior offsets of 8.0 mm, 9.9 mm, and 11.2 mm, respectively. The corresponding volume of resected bone ranged from 0.57 cm. 3. to 3.20 cm. 3. . Conclusions:. Our study shows that a standardized method of pre-operative planning may enable surgeons to restore normal hip ROM, alpha angles, and anterior offsets through pre-determined bony resection. This method shows how osteochondroplasty can be customized to each deformity, thus removing only the necessary amount of bone to correct each abnormality. We believe implementation of our boundaries and method will enable surgeons to consistently and quantitatively reproduce and teach osteochondroplasty, and that this method is readily adaptable to computerized machining of the femur