Excessive Acetabular Coverage Research Articles

CORR Insights®: Does the Rule of Thirds Adequately Detect Deficient and Excessive Acetabular Coverage?

CORR Insights®: Does the Rule of Thirds Adequately Detect Deficient and Excessive Acetabular Coverage?

Does the Rule of Thirds Adequately Detect Deficient and Excessive Acetabular Coverage?

Assessment of AP acetabular coverage is crucial for choosing the right surgery indication and for obtaining a good outcome after hip-preserving surgery. The quantification of anterior and posterior coverage is challenging and requires either other conventional projections, CT, MRI, or special measurement software, which is cumbersome, not widely available and implies additional radiation. We introduce the "rule of thirds" as a promising alternative to provide a more applicable and easy method to detect an excessive or deficient AP coverage. This method attributes the intersection point of the anterior (posterior) wall to thirds of the femoral head radius (diameter), the medial third suggesting deficient and the lateral third excessive coverage. What is the validity (area under the curve [AUC], sensitivity, specificity, positive/negative likelihood ratios [LR(+)/LR(-)], positive/negative predictive values [PPV, NPV]) for the rule of thirds to detect (1) excessive and (2) deficient anterior and posterior coverages compared with previously established radiographic values of under-/overcoverage using Hip2Norm as the gold standard? We retrospectively evaluated all consecutive patients between 2003 and 2015 from our institutional database who were referred to our hospital for hip pain and were potentially eligible for joint-preserving hip surgery. We divided the study group into six specific subgroups based on the respective acetabular pathomorphology to cover the entire range of anterior and posterior femoral coverage (dysplasia, overcoverage, severe overcoverage, excessive acetabular anteversion, acetabular retroversion, total acetabular retroversion). From this patient cohort, 161 hips were randomly selected for analysis. Anterior and posterior coverage was determined with Hip2Norm, a validated computer software program for evaluating acetabular morphology. The anterior and posterior wall indices were measured on standardized AP pelvis radiographs, and the rule of thirds was applied by one observer. The detection of excessive anterior and posterior acetabular wall using the rule of thirds revealed an AUC of 0.945 and 0.933, respectively. Also the detection of a deficient anterior and posterior acetabular wall by applying the rule of thirds revealed an AUC of 0.962 and 0.876, respectively. For both excessive and deficient anterior and posterior acetabular coverage, we found high specificities and PPVs but low sensitivities and NPVs. We found a high probability for an excessive (deficient) acetabular wall when this intersection point lies in the lateral (medial) third, which would qualify for surgical correction. On the other hand, if this point is not in the lateral (medial) third, an excessive (deficient) acetabular wall cannot be categorically excluded. Thus, the rule of thirds is very specific but not as sensitive as we had expected. Level II, diagnostic study.

Impingement-free Hip Range of Motion in Asymptomatic Young Adult Females

Background: Femoroacetabular impingement is a recognized cause of early hip osteoarthritis. This is attributed to either a cam impingement caused by a non-spherical head or a pincer impingement caused by excessive acetabular coverage. Although many surgical techniques aim to improve hip range of motion, little normative data exist on dynamic impingement-free hip range of motion (ROM) in asymptomatic individuals. Hip ultrasound can effectively …

Reliability of a new hip lateral view to quantify alpha angle in femoroacetabular impingement

BackgroundRadiographic measurement of the alpha angle (AA) in femoroacetabular impingement (FAI) is not well codified and invasive techniques such as MR- or CT-arthrography remain the gold standard. Excessive acetabular coverage described in pincer-type FAI can be seen on plain radiographs but has never been quantified and anterior center edge (ACE) angle, described on the false-profile view (FP) to measure anterior acetabular coverage has never been evaluated in FAI. HypothesisIn this study we wanted to determine if a plain radiograph could efficiently measure AA compared to CT-arthrography and if ACE could quantify the acetabular coverage in FAI. Materials and methodsWe developed a hip view combining a lateral view and a FP, called profile view in impingement position (PIP). Twenty-six patients operated for FAI had CT-arthrography, PIP and FP. Nineteen control subjects had the PIP. AA were measured twice by three raters and ACE once. We compared AA measured on patients between CT and PIP, on PIP between patients and controls, ACE measured on patients between PIP and FP, and did a reproducibility analysis. Means were compared by paired or unpaired t-tests; reproducibility was measured by intraclass correlation coefficient (ICC). ResultsMean AA was 65.8° (range, 48–85°) on CT-arthrography and 63.9° (range, 50–87°) on PIP (P>0.05). ICC for PIP measures were 0.8–0.9 for intra-rater and 0.6–0.9 for inter-rater reliability. Mean AA on PIP in patients was 63.3° (range, 52–87°) and 44.9° (range, 34–67°) in controls (P<0.001). Mean ACE was 26.8° (range, 14–41°) on PIP and 32.8° (range, 18–56°) on the FP (P=0.015). DiscussionThe PIP is a reliable view to measure the AA in FAI as measures on PIP and CT-arthrography were not significantly different with a good reproducibility. All of the painful hips and 2 controls had an AA>50°. PIP was not efficient to measure ACE. Level of evidenceLevel III, case-control study.

Circumferential Reconstruction of Severe Acetabular Labral Damage Using Hamstring Allograft: Surgical Technique and Case Series

With excessive acetabular coverage, such as coxa profunda or protrusio, contact between the femoral neck and acetabular rim cause direct damage to the labrochondral junction, and indirect edge loading from a levering effect which may result in hip arthrosis. Arthrosis may be delayed or avoided by addressing the overcoverage and restoring mechanical function of the labrum. We describe four cases of adjunctive complete acetabular labral replacement for circumferential, irreparable labral injury using fresh frozen semitendinous allografts through surgical hip dislocation. Over a two-year period four patients (age range: 20 to 47 years) underwent surgical hip dislocation to address femoroacetabular impingement with rim trimming, femoral osteochondroplasty, and labral reconstruction. Pre- and postoperative patient reported outcomes were assessed by Oxford Hip Score (OHS), Hip Outcome Score (HOS), and Global Treatment Outcome (GTO) score. Disease progression was graded using AP pelvic radiographs and arthroMR. The average LCE correction was 18º (range 7-25º), achieving an average LCE of 33º (range 32-35) postoperatively. Using protected weight bearing all trochanteric osteotomies healed within six weeks after surgery. OA did not progress in any hips. Mean OHS and HOS scores improved 6.3 and 19.8 at one-year follow up. All four patients reported good results according to the GTO. There were two adverse events that resolved and did not affect outcome. Despite complex deformities and preexisting cartilage and labrum wear in this young cohort, three of four patients reported significant functional improvement after treatment of this rare condition. Preliminary experience with circumferential labral reconstruction using hamstring allografts is promising, although long-term data needs to be established.

Prévalence des anomalies acétabulaires associées à une déformation en crosse de pistolet dans la coxarthrose

Acetabular retroversion, excessive acetabular coverage and abnormal head-neck-junction with a so-called “pistol-grip-deformity” were added to the classical description of hip dysplasia to describe pathological hip morphology. The aim of the current study was the detection of pathological acetabular geometry in patients with an abnormal head-neck-junction. Femoro-acetabular impingement and hip dysplasia features are frequent in patients with end-stage osteoarthritis before 60 years of age. We analysed our data bank retrospectively for all patients who received a Total Hip Arthroplasty (THA) due to end-stage osteoarthritis before the age of 60 years. The pelvic-views and the Dunn-view of these patients were screened for an abnormal head-neck-junction by measuring the head-ratio and the alpha-angle. An orthopaedic surgeon and a radiologist did this independently. These radiographies were measured for signs of acetabular dysplasia, excessive acetabular coverage and crossing sign. A consecutive series of 135 total hip arthroplasties were performed in patients aged less or equal to 60 years because of end-stage osteoarthritis. From these, 81 patients were classified as having an abnormal head-neck-junction. The mean head-ratio in these 81 patients was 1.52 ± 0.35, the mean alpha-angle was 62.5° ± 9.3°. The mean CE-angle of these 81 patients was 35.8° ± 10.4°, the mean CA-angle was 36.7° ± 5.7°, the mean depth-width-ratio was 49.1 ± 10, the mean extrusion-index was 19.1 ± 9.2 and the mean CCD-angle was 131.7° ± 7.3°. Of these 81 hips, 14 had isolated pistol grip deformity, while 11 hips had associated dysplasia, 38 had excessive acetabular coverage, and 14 had crossing sign. In addition, a crossing sign was identified in four of the 11 dysplastic hips and 19 of the 38 of the hips having excessive acetabular coverage. There was no statistically significant difference in regard to the age between the four groups ( P = 0.087). In contrast, the hips that had excessive acetabular coverage had increased CE angle (44.6° ± 7.2°) and decreased extrusion index (12.6 ± 6.5) ( P < 0.001), while dysplastic hips had increased roof obliquity (17.5° ± 4.5°) and increased extrusion index (29.6 ± 9.1) as well as decreased CE-angle (20.7° ± 3.0°) ( P < 0.001). There is a high coincidence of radiographic findings associated with an abnormal head-neck-junction consisting in excessive acetabular coverage and retroversion as well as hip dysplasia. These results advocate for restoring of the normal anatomy at the early stage to prevent end-stage osteoarthritis. Level IV retrospective historical study.

The prevalence of acetabular anomalies associated with pistol-grip-deformity in osteoarthritic hips

Acetabular retroversion, excessive acetabular coverage and abnormal head-neck-junction with a so-called "pistol-grip-deformity" were added to the classical description of hip dysplasia to describe pathological hip morphology. The aim of the current study was the detection of pathological acetabular geometry in patients with an abnormal head-neck-junction. Femoroacetabular impingement and hip dysplasia features are frequent in patients with end-stage osteoarthritis before 60 years of age. We analysed our data bank retrospectively for all patients who received a Total Hip Arthroplasty (THA) due to end-stage osteoarthritis before the age of 60 years. The pelvic-views and the Dunn-view of these patients were screened for an abnormal head-neck-junction by measuring the head-ratio and the alpha-angle. An orthopaedic surgeon and a radiologist did this independently. These radiographies were measured for signs of acetabular dysplasia, excessive acetabular coverage and crossing sign. A consecutive series of 135 total hip arthroplasties were performed in patients aged less or equal to 60 years because of end-stage osteoarthritis. From these, 81 patients were classified as having an abnormal head-neck-junction. The mean head-ratio in these 81 patients was 1.52±0.35, the mean alpha-angle was 62.5°±9.3°. The mean CE-angle of these 81 patients was 35.8°±10.4°, the mean CA-angle was 36.7°±5.7°, the mean depth-width ratio was 49.1±10, the mean extrusion index was 19.1±9.2 and the mean CCD-angle was 131.7°±7.3°. Of these 81hips, 14 had isolated pistol-grip-deformity, while 11 hips had associated dysplasia, 38 had excessive acetabular coverage, and 14 had crossing sign. In addition, a crossing sign was identified in four of the 11 dysplastic hips and 19 of the 38 of the hips having excessive acetabular coverage. There was no statistically significant difference in regard to the age between the four groups (P=0.087). In contrast, the hips that had excessive acetabular coverage had increased CE-angle (44.6°±7.2°) and decreased extrusion index (12.6±6.5) (P<0.001), while dysplastic hips had increased roof obliquity (17.5°±4.5°) and increased extrusion index (29.6±9.1), as well as decreased CE-angle (20.7°±3.0°) (P<0.001). There is a high coincidence of radiographic findings associated with an abnormal head-neck-junction consisting in excessive acetabular coverage and retroversion as well as hip dysplasia. These results advocate for restoring of the normal anatomy at the early stage to prevent end-stage osteoarthritis. Level IV retrospective historical study.

Prevalence of Radiographic Findings Thought to Be Associated with Femoroacetabular Impingement in a Population-based Cohort of 2081 Healthy Young Adults

To report the prevalence of qualitative radiographic findings for femoroacetabular impingement (FAI) and associations among them and to characterize the inter- and intraobserver variability of these interpretations. This study is part of an institutional review board-approved population-based prospective follow-up of 2081 of 4006 (participation rate, 51.9%) young adults (874 [42.0%] male participants, 1207 [58.0%] female participants; mean age, 18.6 years) who took part in a randomized hip trial on developmental dysplasia of the hip. All participants gave informed consent. Two pelvic radiographs were obtained. Pistol-grip deformity, focal femoral neck prominence, and flattening of the lateral head, all suggestive of cam-type impingement, and the posterior wall sign, excessive acetabular coverage, and crossover sign, all suggestive of pincer-type impingement, were assessed subjectively by an experienced radiologist. To assess inter- and intraobserver agreement, images from 350 examinations were read independently twice by two observers. Cam-type deformities were seen in 868 male and 1192 female participants, respectively, as follows: pistol-grip deformity, 187 (21.5%) and 39 (3.3%); focal femoral neck prominence, 89 (10.3%) and 31 (2.6%); and flattening of the lateral femoral head, 125 (14.4%) and 74 (6.2%). Pincer-type deformities were seen in the same numbers of male and female participants, respectively, as follows: posterior wall sign, 203 (23.4%) and 131 (11.0%); and excessive acetabular coverage, 127 (14.6%) and 58 (4.9%) (all P < .001, according to sex distribution). The crossover sign was seen in 446 (51.4%) and 542 (45.5%) of the male and female participants, respectively (P = .004). There was a high degree of coexistence (odds ratio [OR] > 2) among most FAI findings. Interobserver agreement was good to very good (κ = 0.74-0.84) in rating cam- and pincer-type findings. Intraobserver agreement was moderate or good (κ = 0.49-0.80) for all findings for both observers. Overall, radiographic FAI findings are quite common in a population of healthy young adults, especially in males, with a high degree of coexistence among most findings (OR > 2).

The Iliocapsularis Muscle: An Important Stabilizer in the Dysplastic Hip

The iliocapsularis muscle is a little known muscle overlying the anterior hip capsule postulated to function as a stabilizer of dysplastic hips. Theoretically, this muscle would be hypertrophied in dysplastic hips and, conversely, atrophied in stable and well-constrained hips. However, these observations have not been confirmed and the true function of this muscle remains unknown. We quantified the anatomic dimensions and degree of fatty infiltration of the iliocapsularis muscle and compared the results for 45 hips with deficient acetabular coverage (Group I) with 40 hips with excessive acetabular coverage (Group II). We used MR arthrography to evaluate anatomic dimensions (thickness, width, circumference, cross-sectional area [CSA], and partial volume) and the amount of fatty infiltration. We observed increased thickness, width, circumference, CSA, and partial volume of the iliocapsularis muscle in Group I when compared with Group II. Additionally, hips in Group I had a lower prevalence of fatty infiltration compared with those in Group II. The iliocapsularis muscle typically was hypertrophied, and there was less fatty infiltration in dysplastic hips compared with hips with excessive acetabular coverage. These observations suggest the iliocapsularis muscle is important for stabilizing the femoral head in a deficient acetabulum. This muscle serves as an anatomic landmark when performing a periacetabular osteotomy. Additionally, preoperative evaluation of morphologic features of the muscle can be used as an adjunct for decision making when treating patients with borderline hip dysplasia or femoroacetabular impingement.

Femoral Morphology Differs Between Deficient and Excessive Acetabular Coverage

Structural deformities of the femoral head occurring during skeletal development (eg, Legg-Calvé-Perthes disease) are associated with individual shapes of the acetabulum but it is unclear whether differences in acetabular shape are associated with differences in proximal femoral shape. We questioned whether the amount of acetabular coverage influences femoral morphology. We retrospectively compared the proximal femoral anatomy of 50 selected patients (50 hips) with developmental dysplasia of the hip (lateral center-edge angle [LCE] < or = 25 degrees ; acetabular index > or = 14 degrees ) with 45 selected patients (50 hips) with a deep acetabulum (LCE > or = 39 degrees ). Using MRI arthrography we measured head sphericity, epiphyseal shape, epiphyseal extension, and femoral head-neck offset. A deep acetabulum was associated with a more spherical head shape, increased epiphyseal height with a pronounced extension of the epiphysis towards the femoral neck, and an increased offset. In contrast, dysplastic hips showed an elliptical femoral head, decreased epiphyseal height with a less pronounced extension of the epiphysis, and decreased head-neck offset. Hips with different acetabular coverage are associated with different proximal femoral anatomy. A nonspherical head in dysplastic hips could lead to joint incongruity after an acetabular reorientation procedure. Level IV, retrospective comparative study. See the Guidelines for Authors for a complete description of levels of evidence.