Anterior Femoroacetabular Impingement Research Articles

Large Hip Impingement Area and Subspine Hip Impingement in Patients With Absolute Femoral Retroversion or Decreased Combined Version.

It remains unclear if femoral retroversion is a contraindication for hip arthroscopy in patients with femoroacetabular impingement (FAI). To compare the area and location of hip impingement at maximal flexion and during the FADIR test (flexion, adduction, internal rotation) in FAI hips with femoral retroversion, hips with decreased combined version, and asymptomatic controls. Cross-sectional study; Level of evidence, 3. Twenty-four symptomatic patients (37 hips) with anterior FAI were evaluated. All patients had femoral version (FV) <5° according to the Murphy method. Two subgroups were analyzed: 13 hips with absolute femoral retroversion (FV <0°) and 29 hips with decreased combined version (McKibbin index <20°). All patients were symptomatic and had anterior groin pain and a positive anterior impingement test ; all had undergone pelvic computed tomography (CT) scans to measure FV. The asymptomatic control group consisted of 26 hips. Dynamic impingement simulation of maximal flexion and FADIR test at 90° of flexion was performed with patient-specific CT-based 3-dimensional models. Extra- or intra-articular hip impingement area and location were compared between the subgroups and with control hips using nonparametric tests. Impingement area was significantly larger for hips with decreased combined version (<20°) versus combined version (≥20°) (mean ± SD; 171 ± 140 vs 78 ± 55 mm2; P = .012) and was significantly larger for hips with FV <0° (absolute femoral retroversion) vs FV >0° (P = .025). Hips with absolute femoral retroversion had a significantly higher frequency of extra-articular subspine impingement versus controls (92% vs 0%; P < .001), compared to 84% of patients with decreased combined version. Intra-articular femoral impingement location was most often (95%) anterosuperior and anterior (2-3 o'clock). Anteroinferior femoral impingement location was significantly different at maximal flexion (anteroinferior [4-5 o'clock]) versus the FADIR test (anterosuperior and anterior [2-3 o'clock]) (P < .001). Patients with absolute femoral retroversion (FV <0°) had a larger hip impingement area, and most exhibited extra-articular subspine impingement. Preoperative FV assessment with advanced imaging (CT/magnetic resonance imaging) could help to identify these patients (without 3-dimensional modeling). Femoral impingement was located anteroinferiorly at maximal flexion and anterosuperiorly and anteriorly during the FADIR test.

Hip Impingement Location in Maximal Hip Flexion in Patients With Femoroacetabular Impingement With and Without Femoral Retroversion

Background: Symptomatic patients with femoroacetabular impingement (FAI) have limitations in daily activities and sports and report the exacerbation of hip pain in deep flexion. Yet, the exact impingement location in deep flexion and the effect of femoral version (FV) are unclear. Purpose: To investigate the acetabular and femoral locations of intra- or extra-articular hip impingement in flexion in patients with FAI with and without femoral retroversion. Study Design: Cross-sectional study; Level of evidence, 3. Methods: An institutional review board–approved retrospective study involving 84 hips (68 participants) was performed. Of these, symptomatic patients (37 hips) with anterior FAI and femoral retroversion (FV <5°) were compared with symptomatic patients (21 hips) with anterior FAI (normal FV) and with a control group (26 asymptomatic hips without FAI and normal FV). All patients were symptomatic, had anterior hip pain, and had positive anterior impingement test findings. Most of the patients had hip/groin pain in maximal flexion or deep flexion or during sports. All 84 hips underwent pelvic computed tomography (CT) to measure FV as well as validated dynamic impingement simulation with patient-specific CT-based 3-dimensional models using the equidistant method. Results: In maximal hip flexion, femoral impingement was located anterior-inferior at 4 o’clock (57%) and 5 o’clock (32%) in patients with femoral retroversion and mostly at 5 o’clock in patients without femoral retroversion (69%) and in asymptomatic controls (76%). Acetabular intra-articular impingement was located anterior-superior (2 o’clock) in all 3 groups. In 125° of flexion, patients with femoral retroversion had a significantly (P < .001) higher prevalence of anterior extra-articular subspine impingement (54%) and anterior intra-articular impingement (89%) compared with the control group (29% and 62%, respectively). Conclusion: Knowing the exact location of hip impingement in deep flexion has implications for surgical treatment, sports, and physical therapy and confirms previous recommendations: Deep flexion (eg, during squats/lunges) should be avoided in patients with FAI and even more in patients with femoral retroversion. Patients with femoral retroversion may benefit and have less pain when avoiding deep flexion. For these patients, the femoral location of the impingement conflict in flexion was different (anterior-inferior) and distal to the cam deformity compared with the location during the anterior impingement test (anterior-superior). This could be important for preoperative planning and bone resection (cam resection or acetabular rim trimming) during hip arthroscopy or open hip preservation surgery to ensure that the region of impingement is appropriately identified before treatment.

Open MRI assessment of anterior femoroacetabular clearance in active and passive impingement-provoking postures.

AimsCam and pincer morphologies are potential precursors to hip osteoarthritis and important contributors to non-arthritic hip pain. However, only some hips with these pathomorphologies develop symptoms and joint degeneration, and it is not clear why. Anterior impingement between the femoral head-neck contour and acetabular rim in positions of hip flexion combined with rotation is a proposed pathomechanism in these hips, but this has not been studied in active postures. Our aim was to assess the anterior impingement pathomechanism in both active and passive postures with high hip flexion that are thought to provoke impingement.MethodsWe recruited nine participants with cam and/or pincer morphologies and with pain, 13 participants with cam and/or pincer morphologies and without pain, and 11 controls from a population-based cohort. We scanned hips in active squatting and passive sitting flexion, adduction, and internal rotation using open MRI and quantified anterior femoroacetabular clearance using the β angle.ResultsIn squatting, we found significantly decreased anterior femoroacetabular clearance in painful hips with cam and/or pincer morphologies (mean -11.3° (SD 19.2°)) compared to pain-free hips with cam and/or pincer morphologies (mean 8.5° (SD 14.6°); p = 0.022) and controls (mean 18.6° (SD 8.5°); p < 0.001). In sitting flexion, adduction, and internal rotation, we found significantly decreased anterior clearance in both painful (mean -15.2° (SD 15.3°); p = 0.002) and painfree hips (mean -4.7° (SD 13°); p = 0.010) with cam and/pincer morphologies compared to the controls (mean 7.1° (SD 5.9°)).ConclusionOur results support the anterior femoroacetabular impingement pathomechanism in hips with cam and/or pincer morphologies and highlight the effect of posture on this pathomechanism.Cite this article: Bone Jt Open 2021;2(11):988–996.

Biochemical MRI With dGEMRIC Corresponds to 3D-CT Based Impingement Location for Detection of Acetabular Cartilage Damage in FAI Patients.

Background:Anterior femoroacetabular impingement (FAI) is associated with labral tears and acetabular cartilage damage in athletic and young patients. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) is an imaging method for detecting early damage to cartilage.Purpose:We evaluated the following questions: (1) What is the sensitivity and specificity of morphological magnetic resonance imaging (MRI) and dGEMRIC for detecting cartilage damage? Do the mean acetabular and femoral dGEMRIC indices differ between (2) superior acetabular clock positions with and without impingement and (3) between cam- and pincer-type FAI?Study Design:Cohort study (diagnosis); Level of evidence, 2.Methods:This was a retrospective comparative study of 21 hips (20 patients with symptomatic anterior FAI) without osteoarthritis on anteroposterior radiographs. Morphological MRI and dGEMRIC (3.0-T, 3-dimensional [3D] T1 maps, dual–flip angle technique) of the same hip joint were compared. Intraoperative acetabular cartilage damage was assessed in patients who underwent surgical treatment. Computed tomography (CT)–based 3D bone models of the same hip joint were used as the gold standard for the detection of impingement, and dGEMRIC indices and zones of morphologic damage were compared with the CT-based impingement zones.Results:Of the 21 hips, 10 had cam-type FAI and 8 had pincer-type FAI according to radiographs. The mean age was 30 ± 9 years (range, 17-48 years), 71% were female, and surgical treatment was performed in 52%. We found a significantly higher sensitivity (69%) for dGEMRIC compared with morphological MRI (42%) in the detection of cartilage damage (P < .001). The specificity of dGEMRIC was 83% and accuracy was 78%. The mean peripheral acetabular and femoral dGEMRIC indices for clock positions with impingement (485 ± 141 and 440 ± 121 ms) were significantly lower compared with clock positions without impingement (596 ± 183 and 534 ± 129 ms) (P < .001). Hips with cam-type FAI had significantly lower acetabular dGEMRIC indices compared with hips with pincer-type FAI on the anterosuperior clock positions (1 to 3 o’clock) (P = .018).Conclusion:MRI with dGEMRIC was more sensitive than morphological MRI, and lower dGEMRIC values were found for clock positions with impingement as detected on 3D-CT. This could aid in patient-specific diagnosis of FAI, preoperative patient selection, and surgical decision making to identify patients with cartilage damage who are at risk for inferior outcomes after hip arthroscopy.

Posterior femoroacetabular impact in patients with suspected anterior femoroacetabular impingement evaluated with a 3-dimensional dynamic study

BackgroundRecently, posterior femoroacetabular impact (PFAI) is considered as a cause of hip pain. The purpose of this study was to estimate the frequency of PFAI in patients with suspected symptomatic Anterior femoroacetabular impingement (AFAI) through 3D dynamic study. MethodsWe performed a retrospective observational study of patients with suspected of symptomatic AFAI evaluated by computed tomography (CT) from February 2015 to December 2017. PFAI was identified through a 3-dimensional (3D) dynamic study with Clinical Graphics software (Move Forward™, Zimmer Biomet, Inc. Miami, USA). Acetabular anteversion, femoral anteversion, neck-shaft angle, lateral central-edge (LCE) angle, alpha angle and range-of-motion were collected. ResultsThe study included 181 hips in 131 patients with a median age of 48 (Interquartile range-IQR: 38–59) years; 61.1% (80) were women. PFAI was found in 18.8% (34/181) of hips [95% confidence interval: 13.8%–25.1%]. Among hips with PFAI, 15 had AFAI. External rotation (PFAI: 40; IQR:40–45, AFAI: 45; IQR: 40–60) and neck-shaft angel were lower in the PFAI group (PFAI: 128.4 ± 4.3, AFAI: 133.7 ± 5.4). ConclusionThe impact between the acetabulum and femoral neck on the posterior-superior zone is a frequent finding in patients with symptomatic AFAI through a 3D dynamic study. Level of evidencelevel IV, Case-series

The association between anterior femoroacetabular impingement and femoral neck fractures: An observational study.

The impact between acetabulum and femoral neck is another possible mechanism of femoral neck fracture.Direct trauma of the greater trochanter may not be able to fully explain the mechanism underlying femoral neck fracture. In this study, we sought to investigate whether anterior femoroacetabular impingement are associated with femoral neck fractures.A total of 36 patients with femoral neck fracture who had undergone total hip arthroplasty or hemiarthroplasty were included in this study. These patients were divided into 2 groups: labrum tear group and normal labrum group. Patients’ age, gender, body mass index, muscle injury, injury pattern, trauma severity, femoral head-neck offset, femoral head-neck ratio, Cam deformity alpha angle, acetabular anteversion, femoral head diameter, acetabular index, cortical index, hip axis length, and neck stem angle were recorded and analyzed. SPSS 18.0 software was used for statistical analyses.According to intraoperative findings, 22 patients exhibited a labrum tear. Magnetic resonance imaging examination revealed bone contusion on the anterolateral margin of the acetabulum with muscle damage surrounding the hip. Among 14 cases without a labrum tear, no bone contusion and obvious muscle injury were found on the anterolateral margin of the acetabulum. Notably, muscle injury, injury pattern, trauma severity and femoral head-neck offset differed significantly (P < .05) between labrum tear and normal labrum groups.Previous studies have focused more on direct lateral trauma. In this study, the impact between acetabulum and femoral neck is another possible mechanism besides lateral impact. Specifically, the abnormal anatomy of the hip, such as femoral head-neck offset, may promote the fracturing process.

A Simple Percutaneous Technique to Reduce Valgus-Impacted Femoral Neck Fractures.

The mainstream surgery for valgus-impacted femoral neck fractures (FNFs) is closed reduction and internal fixation under fluoroscopy. However, femoral neck shortening and anterior femoroacetabular impingement are common complications in healed valgus-impacted FNFs after in situ fixation. Some methods have been reported to prevent complications, but these techniques require the use of a transfixing guide wire that passes through the femoral head, which may cause articular cartilage damage. We introduce a simple reduction technique using one Steinmann pin (S-pin) for valgus-impacted FNFs without any interference of the femur head. A S-pin was placed percutaneously at the inferomedial margin of the fracture, and reduction was achieved by applying manual valgus force along the fracture line. By restoring the anatomical alignment, we confirmed the maximum contact area of the fracture and connection of the medial cortical buttress, so the risk of nonunion was also minimized.

Femoroacetabular Impingement Patients With Decreased Femoral Version Have Different Impingement Locations and Intra- and Extraarticular Anterior Subspine FAI on 3D-CT–Based Impingement Simulation: Implications for Hip Arthroscopy

Background: It remains unclear whether decreased femoral version (FV) causes anterior intra- or extra-articular femoroacetabular impingement (FAI). Therefore, we evaluated symptomatic hips with decreased FV, with and without cam and pincer FAI, by using computed tomography (CT)–based virtual 3-dimensional (3D) impingement simulation and compared this group with patients with normal FV and with asymptomatic hips. Purpose: To investigate (1) the osseous range of motion, (2) the osseous femoral and acetabular impingement zones, and (3) whether hip impingement is extra- or intra-articular in symptomatic hips with FAI. Study Design: Cross-sectional study; Level of evidence, 3. Methods: An institutional review board–approved, retrospective comparative analysis was performed on a total of 84 hips in 68 participants. Of these, 37 hips in 24 symptomatic patients with FAI had decreased FV. These hips were compared with 21 hips of 18 symptomatic patients with anterior FAI with normal FV (10°-25°) and 26 asymptomatic hips with no FAI and normal FV. All patients with FAI were symptomatic and had anterior hip pain and a positive anterior impingement test. They underwent pelvic CT scans to measure FV. Decreased FV was defined as FV less than 5°. The 37 hips with decreased FV presented both with and without cam and pincer FAI. All 84 hips were evaluated by use of CT-based 3D models and a validated 3D range of motion and impingement simulation. Asymptomatic hips were contralateral normal hips imaged in patients undergoing total hip arthroplasty. Results: Hips with FAI combined with decreased FV had a significantly (P < .001) lower mean flexion (114°± 8° vs 125°± 13°) and internal rotation (IR) at 90° of flexion (18°± 6° vs 32°± 9°, P < .001) compared with the asymptomatic control group. Symptomatic patients with FAI and normal FV had flexion of 120°± 16° and IR at 90° of flexion of 23°± 15°. In a subgroup analysis, we found a significantly (P < .001) lower IR in 90° of flexion in hips with FV less than 5° combined with mixed-type FAI compared with hips with FV less than 5° without a cam- or pincer-type deformity. The maximal acetabular impingement zone for hips with decreased FV was located at the 2-o’clock position and ranged from 1 to 3 o’clock. In hips with decreased FV, most of the impingement locations were intra-articular but 32% of hips had combined intra- and extra-articular FAI in internal rotation in 90° of flexion. During the flexion-adduction-IR test performed in 10° and 20° of adduction, extra-articular subspine FAI had significantly (P < .001) higher prevalence (68% and 84%) in hips with decreased FV compared with normal hips. Conclusion: Hips with FAI and decreased FV had less flexion and internal rotation in 90° of flexion compared with the asymptomatic control group. The majority of hip impingement due to low FV was intra-articular, but one-third of samples had combined intra- and extra-articular subspine FAI. Anterior extra- and intra-articular hip impingement can be present in patients who have FAI with decreased FV. This could be important for patients undergoing hip arthroscopy.

Modified head-neck offset for diagnosing anterior femoro-acetabular impingement.

The head-neck offset described by Eijer et al. (eHNO), which is used to diagnose anterior femoro-acetabular impingement (FAI), can be difficult to measure. The aim of this study was to verify if a modified head-neck offset (mHNO) provides more accurate and reproducible values than those of the eHNO. The eHNO, mHNO, cephalic radius and alpha angle were measured on frog-leg radiographs of a group of patients with FAI and a control group (T); three independent reviewers measured the 50 hips in each group twice. The comparison of the two HNOs focused on reproducibility (intraclass correlation coefficient), validity (correlation with alpha angle), practical utility (difference between means in the FAI and control groups) and accuracy of the diagnostic thresholds. The mHNO had better reproducibility (p < 0.05) within and between observers in all study subjects than that of the eHNO (0.938 and 0.979 vs 0.881 and 0.904). The correlation with the alpha angle was also better (p < 0.05) for the mHNO than that for the eHNO. The diagnostic performances of the mHNO and mAOR thresholds were higher than those of the eHNO, eAOR and alpha angle. The new HNO is easier to measure, more reproducible and more accurate. A modified HNO <5 mm and a modified AOR <0.100 on the frog-leg view argued in favour of a pathological cam-type head-neck junction.

Hip Arthroscopy: Where We Are, and Where We Are Going.

Hip Arthroscopy: Where We Are, and Where We Are Going.

45°-45°-30°Frog-leg radiograph for diagnosing cam-type anterior femoroacetabular impingement: Reproducibility and thresholds

BackgroundThe many radiographic views suggested for evaluating anterior femoroacetabular impingement (FAI), due to a cam effect, are not specific for this condition and have not been proven of diagnostic value in studies, including control groups. Using a new and specific radiographic view, we evaluated the reproducibility of the main radiographic criteria for FAI, determined normal values for these criteria in a control group, and established diagnostic threshold values. HypothesisThis specific view offers good reproducibility and effectively detects abnormal values of criteria for FAI. Materials and methodsInter-observer and intra-observer reproducibility of specific radiographic criteria (αangle and modified head-neck offset [HNO]) were computed from preoperative and postoperative radiographs of 96 hips (75 patients, 61 males and 14 females) using the specific 45°-45°-30° frog-leg view (F45 view). Values in the group with FAI were compared to those in a control group of asymptomatic volunteers (100 hips, 27 males and 23 females). ResultsInter-observer and intra-observer reproducibility was very good, with intra-class correlation coefficients of 0.955and 0.987, respectively, for the α angle and of 0.895 and 0.984, respectively, for the HNO. Mean values of both parameters differed significantly between the FAI and control groups: 73.9° (53° to 96°) vs. 49.3° (35° to 69°) for the αangle, respectively; and 2.5mm (–4.6 to 9.4) vs. 7.6mm (1.7 to 11.8) for HNO, respectively. The normal values defined as the boundary of the 95% reference interval in the control group were<60.2° for the α angle, and>4.6mm for the HNO. DiscussionThe45°-45°-30° frog-leg view is useful for diagnosing FAI due to a cam effect. This view is easy to perform, and the thresholds determined in our study assist in its interpretation: α angle values>58° in females and>63° in males indicate cam-type femoral geometry. In both genders, HNO values<5mm support a diagnosis of anterior FAI. Level of evidenceLevel III, case-control study.

Letter to the Editor

To the Editor: Boykin et al. [2] presented a review of 18 rowers (21 hips) with MRI-confirmed labral tears in the anterior half of the acetabulum treated from 2003 to 2010. The most common presentations were groin pain (15 of 21 hips) and positive anterior femoroacetabular impingement (FAI) sign (17 of 21 hips). Fifteen of 21 hips had radiographic FAI (10 pure cam lesions and five mixed cam/pincer). Mechanism of labral injury was proposed to be repeated hip hyperflexion. It was stated that rowers’ hips go from extreme flexion to extension during the stroke. Among the hips that were treated with arthroscopic surgery (18 of 21), femoral head/neck osteochondroplasty was performed in six cases. Among these 18 patients, 10 returned to rowing, six did not, and two had missing data at a mean of 8 months (range, 3 to 25 months) after surgery. The unfavorable return to sport in this series was contrasted with an epidemiologic study showing a low percentage of rowing injuries resulted in an inability to train for more than 1 month [9]. Regarding mechanism of injury, rowers’ hips do not enter anatomical extension during rowing (approximately 20° of hip flexion remains in the finish position) [3, 8]. Hyperflexion implies joint flexion beyond normal limits [5]. Normal passive ROM at the hip joint is 135° flexion and 30° extension [4]. Kinematic analysis reveals that the ROM of the hip falls within normal ROM during rowing, and is not hyperflexed [3]. Therefore, it is likely that the high incidence of FAI in this series precipitated the tears and symptoms among majority of the rowers. Importantly, femoral alpha angle measurement of Magnetic Resonance Arthrography shows considerable variability, and clinical impingement tests remain the most reliable predictor of the presence of FAI [6]. With regards to the main goal of the paper — determining “the likelihood that a rower with labral injury, treated arthroscopically, will return to sport,” — is it possible that the low postoperative return rate was a consequence of performing femoral head/neck osteochondroplasty in only six of 15 hips with cam lesions, therefore, not directly addressing the joint impairment? Additionally, the three patients with bilateral hip pathology were only surgically treated unilaterally. How did the three untreated hips impact return to rowing? Furthermore, it is known that symptom duration longer than 3 years is associated with poor outcome after hip arthroscopy [1], however, no preoperative symptom duration was presented [2]. Finally, as return to rowing was assessed as early as 3 months postoperatively, what was the rehabilitation protocol? Return to sport after hip arthroscopy should be advanced slowly to prevent continued irritation or reinjury [7]. In the cited retrospective study regarding musculoskeletal injury present in elite-level rowers competing at the Junior World Rowing Championships, [9] the authors emphasized that study design may have resulted in under-reporting of severe rowing injury, as severely injured rowers may not have recovered to compete at the World Rowing Championships. Additionally, without presenting return to sport data in context of number of rowers who wanted to return to rowing but could not due to reoccurring symptoms, this aspect of analysis by Boykin et al. is limited in its utility [2].

The lateral view head-neck index (LVHNI): A diagnostic tool for the sequelae of slipped capital femoral epiphysis

It is a well-known fact that slipped capital femoral epiphysis (SCFE) is one of the causes of premature hip osteoarthritis and anterior femoroacetabular impingement. But there are no reliable, published diagnostic methods to measure the residual deformity of slipped capital femoral epiphysis. We propose using the lateral view head-neck index (LVHNI) measurement on a specific lateral X-ray view of the hip for this purpose. The LVHNI can detect and quantify the posterior translation of the femoral head and this index can be measured reliably. A prospective radiography study was performed by three observers. The hip X-rays of patients who were being treated by arthroplasty for hip osteoarthritis (total hip replacement or hip resurfacing) between January 2010 and December 2011 were analyzed. The LVHNI, which quantifies the posterior translation of the femoral head, was measured on a lateral view of the hip in 45° flexion/45° abduction/30° external rotation. The presence of a pistol grip deformity on A/P X-rays was also assessed. The analysis was performed on 131 hips in 120 patients having an average age of 61 years (range 37-91). The chosen LVHNI threshold of 9% resulted in a sensitivity of 89.1% (95% CI: 78.8%-95.5%) and a specificity of 82.4% (95% CI: 71.2%-89.7%) for detecting the presence of a pistol grip deformity. Twenty percent of the hips with no visible deformity on A/P X-rays had a pathological index value. The inter-observer reproducibility was good for the LHNI [intraclass correlation coefficient (ICC): 0.61; 95% CI: 0.51-0.71] and for detecting a pistol grip deformity (ICC: 0.74; 95% CI: 0.62-0.85). The intra-observer reproducibility was excellent for the LHNI (ICC: 0.78; 95% CI: 0.57-0.88) and the pistol grip deformity (ICC: 0.85; 95% CI: 0.74-0.92). The LVHNI is a reliable and reproducible tool to identify deformities secondary to SCFE on specific lateral femoral neck X-rays. If the index value is greater than 9%, SCFE sequelae may be present. In addition, this study showed that 20% of hips with normal A/P X-rays had a pathological index. Level IV, prospective diagnostic study without control group.

Combined Hip Arthroscopy and Limited Open Osteochondroplasty for Anterior Femoroacetabular Impingement: Early Patient Reported Outcomes

Many surgical techniques have been described for femoroacetabular impingement (FAI) surgery to help with improvement of pain and function in symptomatic patients. The aim of this study was to evaluate early patient reported outcomes and complications using combined hip arthroscopy and limited open osteochondroplasty technique. We retrospectively analysed 27 hips in 26 patients. Outcomes were assessed using the nonarthritic hip score (NAHS), UCLA score and Visual analogue scale (VAS) pain score. The average age of patients was 31.3 years and they were followed up for an average of 22.3 months. Average improvement of NAHS score was 39.55 points (p<.0001), 18 patients (72%) had at least 30 points increase in NAHS. There was 3 points average improvement in UCLA score (p<.0001). 17 patients (68%) had UCLA activity level of 6 and above. The average improvement of VAS pain score was 27.5 points (p<.0001). Minor complications included neuropraxia of the lateral femoral cutaneous nerve in three patients who recovered at three months with no sequelae, while one patient developed asymptomatic heterotopic ossification Brooker grade I. One patient had neuropraxia of the sciatic nerve which recovered completely within six months. One patient had a conversion to THR at 12 months. This is an effective technique to treat FAI for reducing pain and improving function at short term follow-up and has a low complication rate without appearing to have a significant learning curve. The failure rate can be reduced if proper case selection is done.

Femoroacetabular Impingement Predisposes to Traumatic Posterior Hip Dislocation

Traumatic posterior hip dislocation in adults is generally understood to be the result of a high-energy trauma. Aside from reduced femoral antetorsion, morphologic risk factors for dislocation are unknown. We previously noticed that some hips with traumatic posterior dislocations had evidence of morphologic features of femoroacetabular impingement (FAI), therefore, we sought to evaluate that possibility more formally. We asked whether hips with a traumatic posterior hip dislocation present with (1) a cam-type deformity and/or (2) a retroverted acetabulum. We retrospectively compared the morphologic features of 53 consecutive hips (53 patients) after traumatic posterior hip dislocation with 85 normal hips (44 patients) based on AP pelvic and crosstable axial radiographs. We measured the axial and the lateral alpha angle for detection of a cam deformity and the crossover sign, ischial spine sign, posterior wall sign, retroversion index, and ratio of anterior to posterior acetabular coverage to describe the acetabular orientation. Hips with traumatic posterior traumatic dislocation were more likely to have cam deformities than were normal hips, in that the hips with dislocation had increased axial and lateral alpha angles. Hips with posterior dislocation also were more likely to be retroverted; dislocated hips had a higher prevalence of a positive crossover sign, ischial spine sign, and posterior wall sign, and they had a higher retroversion index and increased ratio of anterior to posterior acetabular coverage. Hips with posterior traumatic dislocation typically present with morphologic features of anterior FAI, including a cam-type deformity and retroverted acetabulum. An explanation for these findings could be that the early interaction between the aspherical femoral head and the prominent acetabular rim acts as a fulcrum, perhaps making these hips more susceptible to traumatic dislocation.

Experimental study of an original radiographic view for diagnosis of cam-type anterior femoroacetabular impingement

Primary paraclinical investigation to look for femoral morphological abnormality consistent with cam-type anterior femoroacetabular impingement (FAI) must include specific radiographic projections of the hip from the following: cross-table, frog-leg or Dunn (90° and 45° flexion). We use a frog-leg type view with fixed angles as described by Chiron, obtained with the patient in a supine position, with the hip in 45° flexion-abduction and 30° external rotation. The X-ray beam is anteroposterior and centred on the femoral head. We evaluated this view by comparing it with other views in common use. In this experimental study, we created artificial radio-opaque morphological abnormalities secured onto normal femoral necks. The femurs were placed in relation to a fixed pelvis using orthogonal landmarks, in the positions of the various radiographic views. The digital radiographs were analysed by two observers. Nineteen femurs were included to reveal a difference of 5° between the alpha angle of Nötzli et al. [11] measured on the Dunn view and the frog-leg 45/45/30 view (Student's paired test). The highest mean values of the alpha angle of Nötzli were always obtained with the frog-leg 45/45/30 view (87.4°, 86.2°, 84.5°) and the lowest with the cross-table view. We found a mean difference of 8.95° with the 90° Dunn view (P = 0.00007), 3.44° with the 45° Dunn view (P = 0.004) and 13.47° with the cross-table view (P = 0.002). This experimental study confirmed the value of the frog-leg 45/45/30 view in assisting diagnosis of cam-type FAI.

Anterior femoroacetabular impingement: An update

Anterior femoroacetabular impingement can cause early hip osteoarthritis. The typical patient is an adult younger than 50 years of age, often with a history of sporting activities. The main symptom is intermittent pain triggered by static flexion (low seats) or dynamic flexion (during sporting or occupational activities that require repeated hip flexion). The characteristic physical finding is pain triggered by placing the hip in internal rotation and 70 to 110° of flexion. In additional to anteroposterior and false-profile radiographs, lateral Dunn or Ducroquet views should be obtained on both sides to visualize the anterior part of the head-neck junction. Instead of being concave, the head-neck junction is either flat or convex, causing a cam effect that damages the labrum and anterosuperior cartilage. Non-sphericity of the femoral head with an anterior ovoid bulge induces a similar cam effect. In pincer impingement, which is less common, over-coverage by the anterosuperior acetabular rim pinches the labrum between the rim and the femoral head-neck junction when the hip is flexed. Pincer impingement is related to acetabular retroversion or protrusion. Arthrography coupled with computed tomography or magnetic resonance imaging visualizes the morphological abnormalities (e.g., ovoid shape of the femoral head or retroversion of the acetabulum) and detects secondary lesions such as labral tears or separation or damage to the anterosuperior cartilage. Arthroscopy allows removal of the damaged labrum and correction of the morphological abnormalities via femoroplasty to restore the normal concave shape of the neck and/or acetabuloplasty to eliminate over-coverage. Short- or mid-term results are satisfactory in 75 to 80% of patients. However, the presence of degenerative lesions in about two-thirds of patients at the time of arthroplastic surgery limits the probability of achieving good long-term results.

Arthroscopic Analysis of the Radiologic Abnormalities of the Hip Associated with Anterior Femoroacetabular Impingement

� Purpose: We wanted to arthroscopically analyze the femoral osseous abnormalities (bumps) in hips with anterior femoroacetabular impingement (FAI) and the other radiologic abnormalities of the hip joint associated with this. Materials and Methods: We retrospectively reviewed the radiographs of 45 patients (51 hips) who underwent arthroscopic treatment under the impression of FAI from January to August, 2008. The indications for surgery included persistent hip pain, the absence of advanced osteoarthritis, physical examination or MRA findings consistent with an acetabualr labral tear. Preoperative and postoperative plain radiographs (pelvis AP, frog-leg lateral, cross table lateral and the false profile view) were taken. As the occasion demanded, 3D-CT or MRA were performed. Results: For the radiologic findings, a decreased head-neck offset (<8 mm) was seen in 15 hips. Femoral bumps were seen in 26 hips and among them, 11 hips were associated with acetabular retroversion, 5 hips were associated with a prominent acetabular rim and 13 hips were located on the flattening of the neck due to a decreased offset. Pistol grip deformity was found in 21 hips and acetabular retroversion was done in 32 hips. Regarding the secondary changes, spurs on the acetabulum of the femur were found in 14 hips and femoral bony cysts were found in 23 hips. Arthroscopically, all the hips had acetabular degenerative labral tear and the acetabular cartilage was injured in 32 hips (62.7%). Among them, 25 hips underwent acetabular retroversion. Conclusion: Femoral osseous abnormalities are seen in various locations and these abnormalities have various shapes. A considerable number were associated with pincer impingement and they could produce a 'kissing lesion' between the acetabulum and femur. Identification of these abnormalities on radiographs aids confirming FAI in hips with symptomatic early osteoarthritis.

Imaging data in a prospective series of adult hip pain in under-50 year-olds

Two hundred and ninety-two patients under the age of 50 years, presenting with mechanical hip pain, were included in a prospective multicenter study. In 241 cases, imaging assessment included AP standing pelvic X-ray and Lequesne's false profile (LFP) and/or lateral neck (Ducroquet, Dunn or variant) hip X-ray. Cross-sectional arthroscan and/or arthro-MRI images were available in 81 cases. Exploration looked for acetabular and femoral head/neck dysplasia liable to induce cam or pincer anterior femoroacetabular impingement (AFAI), respectively. Labral and chondral lesions arise secondarily to hip osteoarthritis (HOA) and/or AFAI. Two-thirds of patients showed HOA. Only 6% showed a strictly normal aspect on imaging. More than half (52%) of cases had cam AFAI, half of these involving an osteophytic neck, associated in more than 90% of cases with large multifocal bone spurs of the head, neck and acetabula. These cases were considered ambiguous, due to the uncertainty as to the congenital nature of the cervico-cephalic dysmorphy; if they are excluded, only 23% of the series involved cam AFAI. Crossover sign on AP standing pelvic X-ray is the best assessment criterion for acetabular retroversion, the most frequent form of acetabular dysplasia underlying pincer AFAI, and should be explored for. Secondary neck lesions were visible only on lateral neck view in 42% of cases: this view should be included in standard radiologic work-up in under-50 year-olds. The alpha angle can be measured on this type of lateral view and on axial arthroscan and arthro-MR images; more than half of the cases in which it was pathological involved an osteophytic neck and thus a pseudo-cam effect.

JOSEPH C. MCCARTHY, MD, on “Combined Hip Arthroscopy and Limited Open Osteochondroplasty for Anterior Femoroacetabular Impingement” by John C. Clohisy, MD, et al.

The authors analyze thirty-five patients following arthroscopic and limited open femoral osteoplasty for symptomatic cam femoroacetabular impingement. Although the follow-up was short (less than three years), all patients were followed for at least two years after surgery. The fact that five additional patients were lost to follow-up prior to two years demonstrates the difficulty in locating young, mobile patients following nonprosthetic procedures. Given the importance of a complete data set, this study illustrates the potential benefits of a national registry that makes use of a unique HIPAA-protected patient identifier. The authors enumerated their clinical and radiographic …