Radiological signs of femoroacetabular impingement are linked to pelvic version in asymptomatic subjects.

INTRODUCTION: With the recent interest in hip-spine relationship, the link between femoroacetabular impingement (FAI) and the lumbar-pelvic-femoral complex (LPFC) appears decisive. The objectives of this study were (1) to compare the pelvic version, as well as (2) all the parameters of the LPFC between two populations of healthy subjects, comparing those with radiological signs of FAI to those without and finally, (3) to evaluate the LPFC parameters according to the type of FAI. HYPOTHESIS: Asymptomatic subjects with radiological signs of FAI had superior pelvic anteversion. MATERIALS AND METHOD: This retrospective study was based on a prospective cohort of 118 voluntary asymptomatic patients including 62 men (52.5%) with a mean age of 25.6 years±4.4 (19-39). The following parameters: pelvic version (PV), pelvic incidence (PI), lumbar lordosis (LL), sacral slope (SS), hip flexion, intrinsic (IER) and extrinsic (EER) extension reserve were measured using EOS imaging™ in the reference standing position and the lunge position. The radiological signs of FAI (cam, pincer, mixed) were identified on these acquisitions then separated into 2 groups. The first was the group presenting with one or more images of FAI (FAI+) and the second group with no images of FAI (FAI-). RESULTS: There were 143 hips in the FAI+ group compared to 93 hips in the FAI- group. There were 36.4% cams and 45% pincers. With an average of 9.08°±7.81 (-11.0; 27.0) versus 12.33°±8.94 (-5.0; 55.0), the PV was significantly lower (p=0.022) in the FAI+ group compared to the FAI- group. A post-hoc power analysis on the primary outcome (PV) confirmed sufficient power (1-ß=0.809). Compared to the FAI- group, the cam group presented a significantly lower IER and EER (respectively p=0.014 and p=0.047). The comparative analysis between the FAI- and pincer groups found a significant difference in PI (p=0.001), PV (p<0.001), IER (p=0.017) and hip flexion (p<0.001), SS in lunge position (p=0.031) and EER (p=0.039). CONCLUSION: Asymptomatic subjects with radiographic signs of FAI present with weak pelvic version when standing. This pelvic hyper-anteversion is mainly found in the event of a radiological pincer sign. LEVEL OF EVIDENCE: III, retrospective comparative study.

The influence of the sacral slope on pelvic kinematics and clinical manifestations in femoroacetabular impingement.

INTRODUCTION: The radiological study of the sagittal alignment of the spine in static and dynamic positions has allowed a better understanding of the clinical results of total hip prostheses. According to the Roussouly classification, the sacral slope in a standing position characterizes the patient with a stiff spine (less than 35̊) or a flexible spine (greater than 35̊). The objectives of this study were to compare, in a population of patients operated on for femoroacetabular impingement (FAI), firstly, the kinematics of the lumbar-pelvic-femoral complex and secondly, the clinical presentation depending on whether the spine is stiff or flexible. HYPOTHESIS: Patients with stiff spines (SS<35̊) were "hip users" and had less ability to compensate for their hip pathology. MATERIAL AND METHOD: This prospective and comparative multicenter study was conducted with patients operated on arthroscopically for FAI between 2020 and 2021. All patients included received preoperative EOS imaging of the lower limbs and spine, in standing and seated positions. The following parameters were measured: pelvic tilt (PT), pelvic incidence (PI), lumbar lordosis (LL), and sacral slope (SS), as well as dynamic parameters (intrinsic mobility of the hip: delta standing/sitting femoral sacral angle, and of the pelvis: delta standing/sitting sacral slope). The functional result was evaluated at 1 year. RESULTS: In the stiff spine group, 62 patients were included versus 138 in the flexible spine group. The mean follow-up was 15.1±3.3 months (9.2-24.3). Nineteen patients were lost to follow-up and there were 2 revisions for iterative arthroscopy. Intrinsic pelvic mobility and intrinsic hip mobility were 16̊±13.5 (-12; 44) and 44.5̊±28.5 (-9; 99) respectively in the stiff spine group. In the flexible spine group, these same measurements were 22̊±11.5 (-30; 45) and 29.7̊±22.7 (-33; 82) respectively. In the stiff spine group, the symptoms occurred at a significantly younger age: 28.3 years±9.5 (18-51) versus 31 years±8 (18-54) (p=0.017). DISCUSSION: The sacral slope is a determining factor in the kinematics of impingement and the appearance of symptoms. The sacral slope helps define the concept of a "hip user" in symptomatic FAI. LEVEL OF EVIDENCE: IV.

Hip resurfacing in patients under thirty years old: an attractive option for young and active patients.

PURPOSE: Metal-on-metal hip resurfacing is offered as an alternative to traditional hip arthroplasty for young, active adults with advanced osteoarthritis. The concept of hip resurfacing is considered very attractive for this specific population (hard-on-hard bearing component with a large femoral head limiting the risk of dislocation, and allowing femoral bone stock preservation). METHODS: A prospective clinical trial was designed to investigate the outcome of hip resurfacing in young patients (under 30 years old). We studied 24 hips in 22 patients. Mean age at operation was 24.9 years (range 17.1-29.9). No patient was lost to follow-up. RESULTS: There was no revision at average follow-up of 50.6 months (44-59). Mean UCLA activity score improved from 5.5 (1-9) pre-operatively to 7.6 (1-10) postoperatively (p < 0.001). Mean Harris hip score increased from 43.9 (19-67) to 89.3 (55-100) (p < 0.001). Radiological analysis discerned no osteolysis and no implant migration. CONCLUSION: The absence of short-term complications, such as mechanical failure or dislocation, is encouraging and leads us to think that mid-term results will be satisfactory. Moreover, the specific advantages of hip resurfacing (bone stock preservation, excellent stability, low risk of dislocation, large-diameter head) make the procedure a very attractive option for young subjects.

Cementless metal-on-metal versus ceramic-on-polyethylene hip arthroplasty in patients less than fifty years of age: a comparative study with twelve to fourteen-year follow-up.

BACKGROUND: We previously reported the outcomes of a case-control study, at a minimum of five years of follow-up, comparing metal-on-metal and ceramic-on-polyethylene bearings for cementless primary hip arthroplasty in active patients below the age of fifty years. This report is an update on these groups after a minimum duration of follow-up of twelve years. METHODS: Thirty-nine metal-on-metal cementless hip replacements with a 28-mm-diameter Metasul articulation were compared with a control group that included thirty-nine cementless ceramic-on-polyethylene hip replacements performed with a 28-mm-diameter head. The Metasul group included thirty patients with a mean age of forty years (range, twenty-three to forty-nine years), and the control group included thirty-two patients with a mean age of forty-one years (range, fifteen to forty-nine years). The groups were matched for age, activity level, preoperative Harris hip score, acetabular cup diameter, and indication for hip arthroplasty. All patients had a high level of activity, with 82% rated as grade IV or V according to the Devane scale. RESULTS: After a mean duration of follow-up of thirteen years (twelve to fourteen years), only one hip (3%) had asymptomatic acetabular osteolysis and no hip (0%) had been revised in the metal-on-metal group, whereas eighteen hips (46%) had osteolysis and eleven hips (28%) had been revised because of wear or osteolysis in the ceramic-on-polyethylene group (p < 0.003). In the metal-on-metal group, the median Co concentration in the whole blood was 0.95 µg/L (0.4 to 4.8 µg/L) and the median Cr concentration was 1.2 µg/L (0.1 to 5.6 µg/L). The twelve-year survival rate (with reoperation for any reason as the end point) was 100% in the metal-on-metal group and 70% (95% confidence interval, 63% to 77%) in the ceramic-on-polyethylene group (p = 0.003). CONCLUSIONS: After twelve to fourteen years of follow-up, metal-on-metal implants demonstrated better radiographic and survival results than ceramic-on-polyethylene implants in young, very active patients. Current wrought metal-on-metal implants with a 28-mm-diameter head and high carbide concentration did not produce the high rates of osteolysis and allergic reactions that may be observed with cast low-carbide metal-on-metal bearings after a shorter duration of follow-up.