Aims. The frequency of severe femoral retroversion is unclear in patients with femoroacetabular impingement (FAI). This study aimed to investigate mean femoral version (FV), the frequency of absolute femoral retroversion, and the combination of decreased FV and acetabular retroversion (AR) in symptomatic patients with FAI subtypes. Methods. A retrospective institutional review board-approved observational study was performed with 333 symptomatic patients (384 hips) with hip pain due to FAI evaluated for hip preservation surgery. Overall, 142 patients (165 hips) had cam-type FAI, while 118 patients (137 hips) had mixed-type FAI. The allocation to each subgroup was based on reference values calculated on anteroposterior radiographs. CT/MRI-based measurement of FV (Murphy method) and AV were retrospectively compared among five FAI subgroups. Frequency of decreased FV < 10°, severely decreased FV < 5°, and absolute femoral retroversion (FV < 0°) was analyzed. Results. A significantly (p < 0.001) lower mean FV was found in patients with cam-type FAI (15° (SD 10°)), and in patients with mixed-type FAI (17° (SD 11°)) compared to severe over-coverage (20° (SD 12°). Frequency of decreased FV < 10° was significantly (p < 0.001) higher in patients with cam-type FAI (28%, 46 hips) and in patients with over-coverage (29%, 11 hips) compared to severe over-coverage (12%, 5 hips). Absolute femoral retroversion (FV < 0°) was found in 13% (5 hips) of patients with over-coverage, 6% (10 hips) of patients with cam-type FAI, and 5% (7 hips) of patients with mixed-type FAI. The frequency of decreased FV< 10° combined with acetabular retroversion (AV < 10°) was 6% (8 hips) in patients with mixed-type FAI and 5% (20 hips) in all FAI patients. Of patients with over-coverage, 11% (4 hips) had decreased FV < 10° combined with acetabular retroversion (AV < 10°). Conclusion. Patients with cam-type FAI had a considerable proportion (28%) of decreased FV < 10° and 6% had absolute femoral retroversion (FV < 0°), even more for patients with pincer-type FAI due to over-coverage (29% and 13%). This could be important for patients evaluated for open hip preservation surgery or hip arthroscopy, and each patient requires careful personalized evaluation. Cite this article: Bone Jt Open 2022;3(7):557–565

Aims

The effect of pelvic tilt (PT) and sagittal balance in hips with pincer-type femoroacetabular impingement (FAI) with acetabular retroversion (AR) is controversial. It is unclear if patients with AR have a rotational abnormality of the iliac wing. Therefore, we asked: are parameters for sagittal balance, and is rotation of the iliac wing, different in patients with AR compared to a control group?; and is there a correlation between iliac rotation and acetabular version?

Aims. Femoroacetabular impingement (FAI) patients report exacerbation of hip pain in deep flexion. However, the exact impingement location in deep flexion is unknown. The aim was to investigate impingement-free maximal flexion, impingement location, and if cam deformity causes hip impingement in flexion in FAI patients. Methods. A retrospective study involving 24 patients (37 hips) with FAI and femoral retroversion (femoral version (FV) < 5° per Murphy method) was performed. All patients were symptomatic (mean age 28 years (SD 9)) and had anterior hip/groin pain and a positive anterior impingement test. Cam- and pincer-type subgroups were analyzed. Patients were compared to an asymptomatic control group (26 hips). All patients underwent pelvic CT scans to generate personalized CT-based 3D models and validated software for patient-specific impingement simulation (equidistant method). Results. Mean impingement-free flexion of patients with mixed-type FAI (110° (SD 8°)) and patients with pincer-type FAI (112° (SD 8°)) was significantly (p < 0.001) lower compared to the control group (125° (SD 13°)). The frequency of extra-articular subspine impingement was significantly (p < 0.001) increased in patients with pincer-type FAI (57%) compared to cam-type FAI (22%) in 125° flexion. Bony impingement in maximal flexion was located anterior-inferior at femoral four and five o’clock position in patients with cam-type FAI (63% (10 of 16 hips) and 37% (6 of 10 hips)), and did not involve the cam deformity. The cam deformity did not cause impingement in maximal flexion. Conclusion. Femoral impingement in maximal flexion was located anterior-inferior distal to the cam deformity. This differs to previous studies, a finding which could be important for FAI patients in order to avoid exacerbation of hip pain in deep flexion (e.g. during squats) and for hip arthroscopy (hip-preservation surgery) for planning of bone resection. Hip impingement in flexion has implications for daily activities (e.g. putting on shoes), sports, and sex. Cite this article: Bone Joint Res 2023;12(1):22–32

Abstract. Purpose. The aim of this study was to assess how biomechanical gait parameters (kinematics, kinetics, and muscle force estimations) differ between patients with camtype FAI and healthy controls, through a systematic search. Methods. A systematic review of the literature from PubMed, Scopus, and Medline and EMBASE via OVID SP was undertaken from inception to April 2020 using PRISMA guidelines. Studies that described kinematics, kinetics, and/or estimated muscle forces in cam-type FAI were identified and reviewed. Results. The search strategy identified 404 articles for evaluation. Removal of duplicates and screening of titles and abstracts resulted in full-text review of 37 articles with 12 meeting inclusion criteria. The 12 studies reported biomechanical data on a total of 173 cam-FAI (151 cam specific, 22 mixed type) patients and 177 healthy age, sex and BMI matched controls. Cam FAI patients had reduced hip sagittal plane ROM (Mean difference −3.00 0 [−4.10, −1.90], p<0.001), reduced hip peak extension angles (Mean Difference −2.05 0[−3.58, −0.53], p=0.008), reduced abduction angles in the terminal phase of stance, and reduced iliacus and psoas muscle force production in the terminal phase of stance compared to the control groups. Cam FAI cohorts walked at a slower speed compared to controls. Conclusions. In conclusion, patients with cam-type FAI exhibit altered sagittal and frontal plane kinematics as well as altered muscle force production during level gait compared to controls. These findings will help guide future research into gait alterations in FAI and how such alterations may contribute to pathological progression and furthermore, how such alterations can be modified for therapeutic benefit

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

Introduction. Femoroacetabular impingement (FAI) is a morphological hip joint deformity associated with pain and early degenerative changes. Cam-type FAI is prevalent in young male athletes. While biomechanical deficiencies (decreased hip muscle strength and range of motion (ROM)) have been associated with symptomatic cam-type FAI (sFAI), results have been conflicting and little is known about biomechanical characteristics during dynamic tasks. Objectives. (1) Compare coronal-plane hip muscle strength, activation and joint rotation during movement tasks in sFAI hips against healthy controls. (2) Investigate the effect of hip internal rotation ROM (IR-ROM) on these outcomes. Methods. 11 sFAI and 24 well-matched healthy control hips from 18 young adult male athletes were recruited (Table.1). Passive hip IR-ROM was measured with goniometry. Weight-normalised hip abductor and adductor isometric maximal voluntary contraction torques were quantified with handheld dynamometry. Gluteus medius and adductor longus activation and hip coronal-plane kinematics were collected with surface electromyography (EMG) and motion-capture during time-defined phases of sit-to-stand (Fig.1) and single-leg-squat (Fig.2) tasks. Effect of sFAI with hip IR-ROM as a separate independent variable was calculated with 1-way MANCOVA. Results. sFAI had significantly less IR-ROM (19.25°±5.94) than controls (28.83°±7.24) (p<0.001). During the sit-to-stand ascent phase, significantly more hip abduction (F=4.93, p=0.03) was observed in sFAI (13.06°±3.16) compared to controls (10.16°±3.72). With IR-ROM differences controlled for, significantly higher gluteus medius:adductor longus EMG activation ratio (F=4.32, p=0.046) was observed in the same phase in sFAI (0.16±0.34) compared to controls (−0.11±0.31). No other significant results were found. Conclusion. sFAI hips demonstrate altered muscle activation and movement patterns when ascending from seated positions compared to controls, with reduced hip IR-ROM in sFAI hips influencing findings. Abductor and adductor function imbalance may explain why sFAI increases risk of early degenerative changes. Despite study limitations (no imaging for sFAI diagnosis), these findings should be considered when optimising rehabilitation in this population. For any figures and tables, please contact the authors directly

Introduction. Alpha angles have been used to identify the precise area on the femoral head/neck junction that causes cam-type FAI. Now, computer programs are available to calculate the precise motion pattern of a hip joint and identify areas of FAI, dysplasia and other morphological abnormalities. We hypothesise that one cannot rely on the alpha angle alone to predict the precise area of resection required to remove cam impingement. Methods. We used Clinical Graphics software to analyse a cohort of 142 hips. We recorded the alpha angle at 12, 1, 2 and 3 o'clock and whether resection was recommended by the software at these points. We then removed the patients with acetabular influences on potential FAI (pure cam group). Results. At the points recommended for resection alpha angles were found to be significantly higher than those where resection was not advised (52.88° v 49.29°, p=0.0001). However, of the alpha angles greater than 50°, resection was recommended in only 49%. Of the alpha angles less than 50°, resection was still recommended in 36%. In the pure cam-type FAI patients we found no statistically significant association between alpha angle and whether resection was or wasn't indicated (p=0.0536). We further analysed each point on the femoral head/neck. Alpha angles were highest at the 1 and 2 o'clock position which would fit with the anatomical variation that most surgeons would associate with the area of impingement. However, the most common recommended area for resection was between 3 and 5 o'clock. Conclusion. Alpha angle is a poor predictor of cam resection to remove FAI. The suggested location of osteochondroplasty required to remove impingement appears to be further anterior and inferior on the femoral neck than many surgeons might predict. Motional analysis software is a valuable tool in assisting surgeons to understand the morphological abnormalities that may affect the hip

There is a known association between femoroacetabular impingement (FAI) and osteoarthritis of the hip. What is not known is whether arthroscopic excision of an impingement lesion can significantly improve a patient’s symptoms. This study compares the one-year results of hip arthroscopy for cam-type FAI in two groups of patients. The study (osteoplasty) group comprised 24 patients (24 hips) with cam-type FAI who underwent arthroscopic debridement with excision of their impingement lesion. The control (no osteoplasty) group comprised 47 patients (47 hips) who underwent arthroscopic debridement without excision of their impingement lesion. In both groups, the presence of FAI was confirmed on pre-operative plain radiographs. The modified Harris hip score (MHHS) was used for evaluation pre-operatively and at one year’s follow-up. Non-parametric tests were used for statistical analysis. A tendency towards higher median post-operative MHHS scores was observed in the study than in the control group (83 vs. 77, p = 0.11). This was supported by a significantly higher portion of patients in the osteoplasty group with excellent/good results (83% vs. 60%, p = 0.043). It appears that even further symptomatic improvement may be obtained after hip arthroscopy for FAI by means of the femoral osteoplasty. When treating cam impingement arthroscopically, both central and peripheral compartments of the hip should always be accessed

Introduction and Aims: There is a known association between femoroacetabular impingement (FAI) and osteoarthritis of the hip. What is not known is whether arthroscopic excision of an impingement lesion can significantly improve a patient’s symptoms. Materials and Methods: This study compares the one-year results of hip arthroscopy for cam-type FAI in two groups of patients. The study (osteoplasty) group comprised 24 patients (24 hips) with cam-type FAI who underwent arthroscopic debridement with excision of their impingement lesion. The control (no osteoplasty) group comprised 47 patients (47 hips) who underwent arthroscopic debridement without excision of their impingement lesion. In both groups, the presence of FAI was confirmed on pre-operative plain radiographs. The modified Harris hip score (MHHS) was used for evaluation pre-operatively and at one year’s follow-up. Non-parametric tests were used for statistical analysis. Results: A tendency towards higher median post-operative MHHS scores was observed in the study than in the control group (83 vs. 77, p = 0.11). This was supported by a significantly higher portion of patients in the osteoplasty group with excellent/good results (83% vs. 60%, p = 0.043). Conclusions: It appears that even further symptomatic improvement may be obtained after hip arthroscopy for FAI by means of the femoral osteoplasty. When treating cam impingement arthroscopically, both central and peripheral compartments of the hip should always be accessed

Background: Cam-type femoroacetabular impingement (FAI) is becoming more recognized. Cartilage lesions of the acetabulum and labral tears are frequently encountered. The goal of this study was to accurately describe and communicate these injuries and thus providing a standard for reporting injury, management, and outcome. Methods: We evaluated acetabular cartilage lesions and labral tears found during hip arthroscopy in 52 patients with radiological signs of cam-type FAI. They were graded according to the morphology and extent of the lesion. The labral tears were described according to the classification by Lage. Results: Eleven patients (21.2%) had normal cartilage, 14 (26.9%) had a grade 1, 17 (32.7%) a grade 2, 6 (11.5%) a grade 3, and 4 (7.7%) a grade 4 lesion. Labral tears were found in 31 patients (59.6%). There was a high correlation between age and the presence and extent of acetabular cartilage and labral lesions (r=0.70; p< 0.0001 and r=0.45; p< 0.001 respectively). There was also a high correlation between the extent of the acetabular cartilage lesion and the presence of labral lesions (r=0.62; p< 0.0001). Conclusion: In our study there was a high prevalence of associated injuries (86.5%) in cam-type FAI. Despite the recognized consequences of associated lesions on treatment and outcome, no classification system includes this aspect of FAI. Based on our findings, we developed a system to grade acetabular cartilage lesions according to their morphology and extent. This should provide the surgeon with a standardized tool to better describe the full extent of the injury and treat it accordingly

Abstract. Background. Femoroacetabular impingement (FAI) has been extensively investigated and is strongly associated with athletic participation. The aim of this systematic review is to assess: the prevalence of cam-type FAI across various sports, whether kinematic variation between sports influences hip morphology, and whether performance level, duration and frequency of participation or other factors influence hip morphology in a sporting population. Methods. A systematic search of Embase, PubMed and the Cochrane Library was undertaken following PRISMA guidelines. The study was registered on the PROSPERO database (CRD4202018001). Prospective and retrospective case series, case reports and review articles published after 1999 were screened and those which met the inclusion criteria decided a priori were included for analysis. Results. The literature search identified 58 relevant articles involving 5,683 participants. Forty-nine articles described a higher prevalence of FAI across various ‘hip-heavy’ sports, including soccer, basketball, baseball, ice hockey, skiing, golf and ballet. In studies including non-athlete controls, a greater prevalence of FAI was reported in 66.7% of studies (n=8/12). The highest alpha angle was identified at the 1 o'clock position (n=9/9) in football, skiing, golf, ice hockey and basketball. Maximal alpha angle was found to be located in a more lateral position in goalkeepers versus positional players in ice hockey (1 o'clock vs 1.45 o'clock). A positive correlation was also identified between the alpha angle and both age and activity level (n=5/8 and n=2/3, respectively) and also between prevalence of FAI and both age and activity level (n=2/2 and n=4/5), respectively. Conclusions. Hip-heavy sports show an increased prevalence of FAI, with specific sporting activities influencing hip morphology. Both a longer duration and increased level of training also resulted in an increased prevalence of FAI

Objective: To evaluate if the complete resection of the femoral bump, in cam-type FAI increases the postoperative flexion and internal rotation. Material and Method: We reviewed 24 consecutive pre-operative and postoperative hip CT scans in 24 patients with FAI (22 male and 2 female, mean age 36.9 years) who underwent arthroscopic hip surgery for the removal of a bony prominence on the femoral neck-head junction. We measured the alpha angle in two places: in the classical location, in the mid plane of the femoral neck axis and proximally, in the same plane but in first quarter of the femoral neck height. Then we compared these results with the presence of a residual prominence diagnosed in the 3 dimensionally reconstructed images of the postoperative CT scan and the virtual range of motion of the 3D models using impaction detection software. Results: We found 7 cases with a residual bony prominence at the femoral neck-head junction in the 3D model of the proximal femur after the surgery. In this group the mean mid femoral neck alpha angle was significantly improved from 69.7° before the surgery to 48.3° (p=0.028), however the proximal alpha angle was not significantly improved 71.1° preoperative versus 62.7 (p=0.176) after the surgery. In the 17 patients without a residual bump, both alpha angles were improved, the mid alpha angle from 64.9° before the surgery to 40.76° (p=0.000) after the surgery and the proximal alpha angle from 65.8° to 38.4° (p=0.000). The range of motion of hip in the impaction detection software was also significantly improved in both groups, from flexion of 103° to 116° (p=0.001) in the group without a residual bump and from 102 to 118 (p=0.046) in the group with a residual bony prominence after the surgery. The internal rotation at 90° of flexion was also improved in both groups with a statistically significant difference (p=0.001 versus p=0.028 respectively). Conclusion: The complete arthroscopic resection of the femoral bump improves significantly the ranges of flex-ion and internal rotation in patients with cam-type FAI

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

Femoroacetabular impingement (FAI) is a pathologic condition of the hip that leads to osteoarthrosis. The goal of the surgical hip dislocation is to correct the bony malformations to prevent the progression of osteoarthrosis. We investigated the topographical cartilage thickness variation in patients with FAI and early stage osteoarthrosis using an ultrasonic probe during surgical hip dislocation. We performed a prospective case-series of 38 patients (41 hips) that underwent surgical hip dislocation. The mean age at operation was 30.6 (range, 18–48) years. Indication for surgery was symptomatic FAI with 4 hips (10%) with pincer-type, 7 hips (17%) with cam-type, and 20 hips (73%) with mixed-type of FAI. Cartilage thickness was measured intraoperatively using an A-mode 22 MHz ultrasonic probe at 8 locations on the acetabular cartilage. The thickest acetabular cartilage was found in the weight bearing zone (range 2.8–3.5mm), whereas the thinnest cartilage was in the posterior acetabular horn (1.0–2.2 mm). In all hips, cartilage was thicker in the periphery area compared to the central area. In the anterior and posterior acetabular horn, the anterior area, and the superior area (central parts) a significantly decreased cartilage thickness in pincer-type compared to cam-type of FAI was found (p<0.05). Cartilage thickness shows topographical differences in all types of FAI with pincer-type of FAI having generally thinner cartilage than cam-type FAI. This is the first study measuring in vivo cartilage thickness in the human hip

Cam-type femoroacetabular impingement (cam-FAI) can be treated with femoral neck osteochondroplasty to increase the clearance between the femoral head/neck and the acetabular rim. Because femur-acetabulum contact is very difficult to assess directly in patients, it is not clear if this surgery achieves its objective of reducing femur-acetabulum contact, and it is not clear how much of the femoral head/neck region should be resected to allow clearance in all activities. Our research question was: “Does femoral neck osteochondroplasty increase femur-acetabulum clearance in an extreme hip posture in patients with cam FAI?”. We recruited 8 consecutive patients scheduled to undergo arthroscopic femoral neck osteochondroplasty to treat cam-type FAI. We assessed clearance between the acetabulum and the femoral neck before surgery and at 6 months post-op using an upright open MRI scanner that allowed the hip to be scanned in flexed postures. We scanned each subject in a supine hip flexion (90 degree), adduction and internal rotation (FADIR) posture. We measured the beta angle, which describes clearance between the acetabular rim and the femoral head/neck deformity. Osteochondroplasty increased clearance from a mean beta angle of −9.4 degrees (SD 19.3) to 4.4 degrees (SD 16.2°) (p<0.05). This finding suggests that femoral neck osteochondroplasty increases femur-acetabulum clearance substantially for a posture widely accepted to provoke symptoms in patients with cam-FAI

Posterior extraarticular ischiofemoral hip impingement can be caused by high femoral torsion and is typically located between the ischium and the lesser trochanter. We asked if patients undergoing derotational femoral osteotomies for posterior FAI have (1) decreased hip pain and improved function and evaluated (2) subsequent surgeries and complications?. Thirty-three hips undergoing derotational femoral osteotomies between 2005 and 2016 were evaluated retrospectively. Of them 15 hips underwent derotational femoral osteotomies and 18 hips underwent derotational femoral osteotomies combined with varisation (neck-shaft angle >139°). Indication for derotational osteotomies was a positive posterior impingement test in extension and external rotation, high femoral torsion (48° ± 9) on CT scans and limited external rotation. Offset improvement was performed to avoid intraarticular impingement in hips with a cam-type FAI. All patients were female and mean followup was 3 ± 2 (1 – 11) years. At latest followup the positive posterior and anterior impingement test decreased from preoperatively 100% to 5% (p< 0.001) and from preoperatively 85% to 30% (p< 0.001). The mean Merle d'Aubigné Postel score increased from 14 ± 1 (11 – 16) to 16 ± 1 (13 – 17) at latest followup (p< 0.001). At followup 32/33 hips had been preserved and one hip had been converted to a total hip arthroplasty (THA). In two hips (6%) revision osteosynthesis was performed for delayed healing of the femoral osteotomy. Derotational femoral osteotomies for the treatment of posterior extraarticular ischiofemoral impingement caused by high femoral torsion result in decreased hip pain and improved function at midterm followup but had 6% delayed healing rate requiring revision surgery

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: Cam-type femoroacetabular impingement (FAI) is a pre-osteoarthritic condition causing premature joint degeneration. Cam-deformities are characterised by decreased cranial offset of the femoral head/neck junction and aspherity of the femoral head causing delamination of the acetabular cartilage and detachment of the acetabular labrum. To asses the epidemiological aspects of cam-type FAI we evaluated Nötzlis alpha angle and our own Triangular Index (TI) for use on plain AP pelvic radiographs. Materials and Methods: Cam malformation was assessed in 2.803 pelvic radiographs by the alpha (α) angle and the TI to define pathological cut off values. The α-angle and TI were assessed in AP and lateral hip radiographs of 164 patients scheduled for THR and the influence of varying rotation on the α-angle and TI was assessed in femoral specimens. The distribution of Cam-deformities was assessed in 3.712 standardized AP pelvic radiographs using the α-angle and TI. Results: Mean AP α-angle male/female was 55°/45°. The α-angle and TI was highly interrelated, OR 8.6–35 (p< 0.001). Almost all cam-malformations were identifiable in AP projections, sensitivity 88–94% compared to axial view. The TI proved robust for cam identification during rotation (± 20°) compared to the α-angle (−10° to +20°). The distribution of pathologic TI and α-angle (Right/Left) were 11.6/12.5% and 6.1/7.4% in males and 2.2/3.2% and 2.1/3.8% in females. We found a pronounced sexrelated difference in cam-deformity distribution, OR 2.0–6.3 (p< 0.001). Conclusion: The triangular index and the α-angle were found reliable for epidemiological purpose. Overall prevalence of definite cam-deformity was app. 10% in men and 2,5% in women

Introduction: Whereas in traumatic avascular necrosis of the femoral head (ANFH) loss of the femoral head’s blood supply is due to a mechanical event, in non-traumatic AFNH it is the result of a wide variety of etiologies (e.g. alcoholism, hypercortisonism, etc.), which have in common that they lead to an intravascular complication with subsequent malperfusion of the femoral head. Additionally, for part of non-traumatic ANFH no causative factors are known, why they are called idiopathic. A mechanical cause for nontraumatic ANFH – as e.g. a repetitive trauma of the femoral head supplying deep branch of the medial femoral circumflex artery and its terminal branches by abutment of the femur against the acetabulum as in femoroacetabular impingement (FAI) – has not been discussed so far. Methods: The anteroposterior and lateral radiographs of 118 hips in 77 patients, who were operated in our institution between January 1995 and December 2005 because of nontraumatic ANFH, were evaluated with respect to the configuration of the head-neck junction. In a qualitative analysis the head-neck contour of all femora was assigned to one of the following four groups: regular waisting, mildly reduced waisting, reduced to distinctly reduced waisting or completely lacking waisting. In a quantitative analysis, angle alpha according to Nötzli et al. (2002) was measured. Furthermore, the CCD angle was measured to assess the orientation of the femoral neck in the frontal plane as well as the LCE-angle according to Wiberg and the acetabular index of the weightbearing zone to rule out any acetabular anomalies. Results: In this retrospective analysis, for 44.1% of the hip joints hypercortisonism, for 40.7% alcoholism, for 12.7% hypercholesterinemia and for 11.0% no risk factors were found documented in the patients’ files. In AP and lateral radiographs a regular waisting was found in 60.2% and 9.3%, a mildly reduced waisting in 32.2% and 37.3%, a reduced waisting or distinctly reduced waisting in 7.6% and 35.6%, and a completely lacking waisting in 0% and 16.9%, respectively, and the mean angle alpha was 63° ± 18° and 67° ± 14°, respectively. On average, the (frontally projected) CCD angle was 133° ± 6°, the LCE angle 30° ± 7° and the acetabular index of the weightbearing zone 4° ± 5°. Conclusion: Nötzli et al. found an angle alpha of 42° ± 2° for healthy individuals. A markedly increased angle alpha in both radiographic planes of the 118 investigated hips with nontraumatic ANFH was found, demonstrating a reduced shape of their head-neck junction in the anterior and lateral aspect. Together with the fact that no gross pathological deviations for the orientation of the femoral neck and the acetabulum were found, this may hint at cam-type FAI to occur in this hips and thus potentially at a mechanical (co-) factor in developing non-traumatic ANFH

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