[Impingement of the hip]

[Femoroacetabular impingement in adolescents]

Femoroacetabular impingement syndrome (FAIS) is caused by a repetitive mechanical conflict between the acetabulum and the proximal femur, occurring in flexion and internal rotation. In cam impingement, bony prominences of the femoral head-neck junction induce chondrolabral damage. The acetabular type of FAIS, termed pincer FAIS, may be either due to focal or global retroversion and/or acetabular overcoverage. Combinations of cam and pincer morphology are common. Pathological femoral torsion may aggravate or decrease the mechanical conflict in FAI but can also occur in isolation. Of note, a high percentage of adolescents with FAI-like shape changes remain asymptomatic. The diagnosis of FAIS is therefore made clinically, whereas imaging reveals the underlying morphology. X‑rays in two planes remain the primary imaging modality, the exact evaluation of the osseous deformities of the femur and chondrolabral damage is assessed by magnetic resonance imaging (MRI). Acetabular coverage and version are primarily assessed on radiographs. Evaluation of the entire circumference of the proximal femur warrants MRI which is further used in the assessment of chondrolabral lesions, and also bone marrow and adjacent soft tissue abnormalities. The MRI protocol should routinely include measurements of femoral torsion. Fluid-sensitive sequences should be acquired to rule out degenerative or inflammatory extra-articular changes.

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.

[Imaging in joint-preserving hip surgery]

Instabilität und Impingement stellen die Hauptpathomechanismen dar, die bereits bei jungen Patienten durch erhöhten mechanischen Stress zu chondrolabralen Schäden, schmerzhafter Bewegungseinschränkung und frühzeitiger Coxarthrose führen können. Ziele der gelenkerhaltenden Chirurgie an der Hüfte sind die Korrektur der knöchernen Deformitäten und chondrolabraler Schäden sowie die Wiederherstellung der Gelenkfunktion. Voraussetzung dafür ist die Identifikation der ursächlichen Pathologien an der Hüfte, welche zudem in Kombination auftreten können. Die dezidierte Röntgen- und Magnetresonanzbildgebung der knöchernen Morphologie und der degenerativen Gelenkbinnenläsionen liefern einen essenziellen Beitrag für die Behandlungsindikation und die Behandlungsplanung. Der vorliegende Artikel soll einen kurzen Überblick über die Hüftdeformitäten mit deren Prävalenz, Pathomechanismus und indizierter Therapie sowie detaillierte Empfehlungen über die spezifische radiologische Abklärung geben.

Most of patients with femoral derotation osteotomy for posterior extraarticular hip impingement and high femoral version would do surgery again

AIMS

To assess (1) hip pain and function and ROM; (2) subsequent surgeries, complications; and (3) subjective satisfaction and PROMs in patients undergoing femoral derotation osteotomies.

METHODS

Femoral derotation subtrochanteric osteotomies to treat symptomatic posterior extraarticular ischiofemoral hip impingement were performed in 23 patients (25 hips) between 2013 and 2017. The mean age was 26 ± 8 years (96% female) with a minimum 2-year follow-up (mean follow-up of 4 ± 1 years). Surgical indication was a positive posterior impingement test and limited external rotation (mean 16° ± 8°) in extension in patients with abnormal high femoral version (mean 46° ± 9, measured on CT scans with the Murphy method) and high McKibbin instability index (mean 67°). Femoral osteotomies were combined with a surgical hip dislocation in 96% for cam resection and labrum or cartilage treatment. Preoperative MRI and 3D-CT with dynamic impingement simulation were evaluated.

RESULTS

(1) The posterior impingement test decreased significantly from preoperatively 100% to 4% (p < 0.001). External rotation in extension increased significantly (p < 0.001) from preoperative 16° ± 8 to 44° ± 16°. The MdA score increased significantly from 14 ± 1 to 16 ± 2 (p < 0.001) points.(2) At follow-up, all 25 hips were preserved. No conversion to THA and no revision osteosynthesis was performed. 64% underwent complete hardware removal.(3) 80% of the patients reported at follow-up that they would undergo surgery again. Subjective satisfaction (SHV) increased significantly (p < 0.001) from preoperatively 24% to 84% postoperatively.

CONCLUSIONS

Femoral derotation subtrochanteric osteotomies for the treatment of posterior extraarticular ischiofemoral hip impingement are safe and improve posterior hip pain and function and external rotation in mostly female patients with high femoral version and a high McKibbin instability index.

Prävalenz, Biomechanik und Diagnostik femoraler Achs- und Torsionsfehler

Abweichungen der Anatomie des proximalen Femurs (Torsionspathologien, Coxa valga/vara) führen zu Veränderungen der Biomechanik des Hüftgelenks. Dies kann sich in einem femoroazetabulären Impingement (FAI), einer Mehrbelastung durch erhöhten intraartikulären Druck oder einer Fehl- oder Überbelastung der Hüftgelenkabduktoren manifestieren. Die Morphologie des Beckens, insbesondere die Version und Überdachung des Azetabulums, kann einen kompensatorischen oder verstärkenden Effekt haben und muss in die globale Beurteilung des Hüftgelenks miteinbezogen werden. Eine ausführliche klinische und radiologische Evaluation ist für eine korrekte Diagnosestellung von entscheidender Bedeutung. Die Patienten berichten meist von inguinalen, z. T. aber auch von glutealen Schmerzen. Diese sind häufig von mechanischem Charakter und können durch bestimmte Bewegungen provoziert werden. Der Bewegungsumfang der Hüfte ist beim FAI vermindert, und es zeigt sich ein positiver vorderer und/oder hinterer Impingement-Test. Torsionspathologien führen häufig zu einem veränderten Gangbild. So präsentieren sich Patienten mit erhöhter femoraler Torsion oft mit einem innenrotierten, bei verminderter Torsion mit einem außenrotierten Gangbild. Zudem zeigt sich häufig eine Abduktoreninsuffizienz. Während zur Bestimmung des Collum-Diaphysen-Winkels (CCD-Winkel) eine zentrierte Beckenübersichtsröntgenaufnahme im a.-p.-Strahlengang verwendet werden kann, sollte die Bestimmung der Torsion anhand einer Computertomographie (CT) oder Magnetresonanztomographie (MRT) von Knien und Hüftgelenk erfolgen. Von entscheidender Bedeutung ist die Angabe der verwendeten Messmethode der femoralen Torsion, da große systematische Unterschiede der Torsionswerte zwischen den verschiedenen Messmethoden bestehen.

Three-Dimensional Magnetic Resonance Imaging Bone Models of the Hip Joint Using Deep Learning: Dynamic Simulation of Hip Impingement for Diagnosis of Intra- and Extra-articular Hip Impingement

Background:

Dynamic 3-dimensional (3D) simulation of hip impingement enables better understanding of complex hip deformities in young adult patients with femoroacetabular impingement (FAI). Deep learning algorithms may improve magnetic resonance imaging (MRI) segmentation.

Purpose:

(1) To evaluate the accuracy of 3D models created using convolutional neural networks (CNNs) for fully automatic MRI bone segmentation of the hip joint, (2) to correlate hip range of motion (ROM) between manual and automatic segmentation, and (3) to compare location of hip impingement in 3D models created using automatic bone segmentation in patients with FAI.

Study Design:

Cohort study (diagnosis); Level of evidence, 3.

Methods:

The authors retrospectively reviewed 31 hip MRI scans from 26 symptomatic patients (mean age, 27 years) with hip pain due to FAI. All patients had matched computed tomography (CT) and MRI scans of the pelvis and the knee. CT- and MRI-based osseous 3D models of the hip joint of the same patients were compared (MRI: T1 volumetric interpolated breath-hold examination high-resolution sequence; 0.8 mm³ isovoxel). CNNs were used to develop fully automatic bone segmentation of the hip joint, and the 3D models created using this method were compared with manual segmentation of CT- and MRI-based 3D models. Impingement-free ROM and location of hip impingement were calculated using previously validated collision detection software.

Results:

The difference between the CT- and MRI-based 3D models was <1 mm, and the difference between fully automatic and manual segmentation of MRI-based 3D models was <1 mm. The correlation of automatic and manual MRI-based 3D models was excellent and significant for impingement-free ROM (r = 0.995; P < .001), flexion (r = 0.953; P < .001), and internal rotation at 90° of flexion (r = 0.982; P < .001). The correlation for impingement-free flexion between automatic MRI-based 3D models and CT-based 3D models was 0.953 (P < .001). The location of impingement was not significantly different between manual and automatic segmentation of MRI-based 3D models, and the location of extra-articular hip impingement was not different between CT- and MRI-based 3D models.

Conclusion:

CNN can potentially be used in clinical practice to provide rapid and accurate 3D MRI hip joint models for young patients. The created models can be used for simulation of impingement during diagnosis of intra- and extra-articular hip impingement to enable radiation-free and patient-specific surgical planning for hip arthroscopy and open hip preservation surgery.

Lower pelvic tilt, lower pelvic incidence, and increased external rotation of the iliac wing in patients with femoroacetabular impingement due to acetabular retroversion compared to hip dysplasia

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?

METHODS

A retrospective, review board-approved, controlled study was performed including 120 hips in 86 consecutive patients with symptomatic FAI or hip dysplasia. Pelvic CT scans were reviewed to calculate parameters for sagittal balance (pelvic incidence (PI), PT, and sacral slope), anterior pelvic plane angle, pelvic inclination, and external rotation of the iliac wing and were compared to a control group (48 hips). The 120 hips were allocated to the following groups: AR (41 hips), hip dysplasia (47 hips) and cam FAI with normal acetabular morphology (32 hips). Subgroups of total AR (15 hips) and high acetabular anteversion (20 hips) were analyzed. Statistical analysis was performed using analysis of variance with Bonferroni correction.

RESULTS

PI and PT were significantly decreased comparing AR (PI 42° (SD 10°), PT 4° (SD 5°)) with dysplastic hips (PI 55° (SD 12°), PT 10° (SD 6°)) and with the control group (PI 51° (SD 9°) and PT 13° (SD 7°)) (p < 0.001). External rotation of the iliac wing was significantly increased comparing AR (29° (SD 4°)) with dysplastic hips (20°(SD 5°)) and with the control group (25° (SD 5°)) (p < 0.001). Correlation between external rotation of the iliac wing and acetabular version was significant and strong (r = 0.81; p < 0.001). Correlation between PT and acetabular version was significant and moderate (r = 0.58; p < 0.001).

CONCLUSION

These findings could contribute to a better understanding of hip pain in a sitting position and extra-articular subspine FAI of patients with AR. These patients have increased iliac external rotation, a rotational abnormality of the iliac wing. This has implications for surgical therapy with hip arthroscopy and acetabular rim trimming or anteverting periacetabular osteotomy (PAO). Cite this article: Bone Jt Open 2021;2(10):813-824.

Posterior Extra-articular Ischiofemoral Impingement Can Be Caused by the Lesser and Greater Trochanter in Patients With Increased Femoral Version: Dynamic 3D CT-Based Hip Impingement Simulation of a Modified FABER Test

Background:

Posterior extra-articular hip impingement has been described for valgus hips with increased femoral version (FV). These patients can present clinically with lack of external rotation (ER) and extension and with a positive posterior impingement test. But we do not know the effect of the combination of deformities, and the impingement location in early flexion is unknown.

Purpose:

To evaluate patient-specific 3-dimensional computed tomography (3D CT) scans of hips with increased FV and control hips for differences in range of motion, location and prevalence of osseous posterior intra- and extra-articular hip impingement.

Study Design:

Case series; Level of evidence, 4.

Methods:

Osseous 3D models based on segmentation of 3D CT scans were analyzed for 52 hips (38 symptomatic patients) with positive posterior impingement test and increased FV (>35°). There were 26 hips with an increased McKibbin instability index >70 (unstable hips). Patients were mainly female (96%), with an age range of 18 to 45 years. Of them, 21 hips had isolated increased FV (>35°); 22 hips had increased FV and increased acetabular version (AV; >25°); and 9 valgus hips (caput-collum-diaphyseal angle >139°) had increased FV and increased AV. The control group consisted of 20 hips with normal FV, normal AV, and no valgus (caput-collum-diaphyseal angle <139°). Validated 3D CT–based collision detection software for impingement simulation was used to calculate impingement-free range of motion and location of hip impingement. Surgical treatment was performed after the 3D CT–based impingement simulation in 27 hips (52%).

Results:

Hips with increased FV had significantly (P < .001) decreased extension and ER at 90° of flexion as compared with the control group. Posterior impingement was extra-articular (92%) in hips with increased FV. Valgus hips with increased FV and AV had combined intra- and extra-articular impingement. Posterior hip impingement occurred between the ischium and the lesser trochanter at 20° of extension and 20° of ER. Impingement was located between the ischium and the greater trochanter or intertrochanteric area at 20° of flexion and 40° of ER, with a modification of the flexion-abduction-ER (FABER) test.

Conclusion:

Posterior extra-articular ischiofemoral hip impingement can be caused by the lesser and greater trochanter or the intertrochanteric region. We recommend performing the modified FABER test during clinical examination in addition to the posterior impingement test for female patients with high FV. In addition, 3D CT can help for surgical planning, such as femoral derotation osteotomy and/or hip arthroscopy or resection of the lesser trochanter.

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.

Prevalence of combined abnormalities of tibial and femoral torsion in patients with symptomatic hip dysplasia and femoroacetabular impingement

AIMS

The prevalence of combined abnormalities of femoral torsion (FT) and tibial torsion (TT) is unknown in patients with femoroacetabular impingement (FAI) and hip dysplasia. This study aimed to determine the prevalence of combined abnormalities of FT and TT, and which subgroups are associated with combined abnormalities of FT and TT.

METHODS

We retrospectively evaluated symptomatic patients with FAI or hip dysplasia with CT scans performed between September 2011 and September 2016. A total of 261 hips (174 patients) had a measurement of FT and TT. Their mean age was 31 years (SD 9), and 63% were female (165 hips). Patients were compared to an asymptomatic control group (48 hips, 27 patients) who had CT scans including femur and tibia available for analysis, which had been acquired for nonorthopaedic reasons. Comparisons were conducted using analysis of variance with Bonferroni correction.

RESULTS

In the overall study group, abnormal FT was present in 62% (163 hips). Abnormal TT was present in 42% (109 hips). Normal FT combined with normal TT was present in 21% (55 hips). The most frequent abnormal combination was increased FT combined with normal TT of 32% (84 hips). In the hip dysplasia group, 21% (11 hips) had increased FT combined with increased TT. The prevalence of abnormal FT varied significantly among the subgroups (p < 0.001). We found a significantly higher mean FT for hip dysplasia (31°; SD 15)° and valgus hips (42° (SD 12°)) compared with the control group (22° (SD 8°)). We found a significantly higher mean TT for hips with cam-type-FAI (34° (SD 6°)) and hip dysplasia (35° (SD 9°)) compared with the control group (28° (SD 8°)) (p < 0.001).

CONCLUSION

Patients with FAI had a high prevalence of combined abnormalities of FT and TT. For hip dysplasia, we found a significantly higher mean FT and TT, while 21% of patients (11 hips) had combined increased TT and increased FT (combined torsional malalignment). This is important when planning hip preserving surgery such as periacetabular osteomy and femoral derotation osteotomy. Cite this article: Bone Joint J 2020;102-B(12):1636-1645.

Hip preservation

Classical indications for hip preserving surgery are: femoro-acetabular impingement (FAI) (intra- and extra-articular), hip dysplasia, slipped capital femoral epiphysis, residual deformities after Perthes disease, avascular necrosis of the femoral head.

Pre-operative evaluation of the pathomorphology is crucial for surgical planning including radiographs as the basic modality and magnetic resonance imaging (MRI) and/or computed tomography (CT) to evaluate further intra-articular lesions and osseous deformities.

Two main mechanisms of intra-articular impingement have been described:

(1) Inclusion type FAI (‘cam type’).

(2) Impaction type FAI (‘pincer type’).

Either arthroscopic or open treatment can be performed depending on the severity of deformity.

Slipped capital femoral epiphysis often results in a cam-like deformity of the hip. In acute cases a subcapital re-alignment (modified Dunn procedure) of the femoral epiphysis is an effective therapy.

Perthes disease can lead to complex femoro-acetabular deformity which predisposes to impingement with/without joint incongruency and requires a comprehensive diagnostic workup for surgical planning.

Developmental dysplasia of the hip results in a static overload of the acetabular rim and early osteoarthritis. Surgical correction by means of periacetabular osteotomy offers good long-term results.

Cite this article: EFORT Open Rev 2020;5:630-640. DOI: 10.1302/2058-5241.5.190074

Location of Intra- and Extra-articular Hip Impingement Is Different in Patients With Pincer-Type and Mixed-Type Femoroacetabular Impingement Due to Acetabular Retroversion or Protrusio Acetabuli on 3D CT-Based Impingement Simulation

BACKGROUND

Diagnosis and surgical treatment of hips with different types of pincer femoroacetabular impingement (FAI), such as protrusio acetabuli and acetabular retroversion, remain controversial because actual 3-dimensional (3D) acetabular coverage and location of impingement cannot be studied via standard 2-dimensional imaging. It remains unclear whether pincer hips exhibit intra- or extra-articular FAI.

PURPOSE

(1) To determine the 3D femoral head coverage in these subgroups of pincer FAI, (2) determine the impingement-free range of motion (ROM) through use of osseous models based on 3D-computed tomography (CT) scans, and (3) determine the osseous intra-and extra-articular 3D impingement zones by use of 3D impingement simulation.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

This is a retrospective, comparative, controlled study involving 70 hips in 50 patients. There were 24 patients (44 hips) with symptomatic pincer-type or mixed-type FAI and 26 patients (26 hips) with normal hips. Surface models based on 3D-CT scans were reconstructed and compared for hips with acetabular retroversion (30 hips), hips with protrusio acetabuli (14 hips), and normal asymptomatic hips (26 hips). Impingement-free ROM and location of impingement were determined for all hips through use of validated 3D collision detection software based on CT-based 3D models. No abnormal morphologic features of the anterior iliac inferior spine were detected.

RESULTS

(1) Mean total femoral head coverage was significantly (P < .001) increased in hips with protrusio acetabuli (92% ± 7%) and acetabular retroversion (71% ± 5%) compared with normal hips (66% ± 6%). (2) Mean flexion was significantly (P < .001) decreased in hips with protrusio acetabuli (104°± 9°) and acetabular retroversion (116°± 6°) compared with normal hips (125°± 13°). Mean internal rotation in 90° of flexion was significantly (P < .001) decreased in hips with protrusio acetabuli (16°± 12°) compared with normal hips (35°± 13°). (3) The prevalence of extra-articular subspine impingement was significantly (P < .001) higher in hips with acetabular retroversion (87%) compared with hips with protrusio acetabuli (14%) and normal hips (0%) and was combined with intra-articular impingement. The location of anterior impingement differed significantly (P < .001) between hips with protrusio acetabuli and normal hips.

CONCLUSION

Using CT-based 3D hip models, we found that hips with pincer-type and mixed-type FAI have significantly larger femoral head coverage and different osseous ROM and location of impingement compared with normal hips. Additionally, intra- and extra-articular subspine impingement was detected predominantly in hips with acetabular retroversion. Acetabular rim trimming during hip arthroscopy or open surgical hip dislocation should be performed with caution for these hips. Patient-specific analysis of location of impingement using 3D-CT could theoretically improve diagnosis and planning of surgical treatment.

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.

Prevalence and diagnostic accuracy of in-toeing and out-toeing of the foot for patients with abnormal femoral torsion and femoroacetabular impingement: implications for hip arthroscopy and femoral derotation osteotomy

AIMS

Abnormal femoral torsion (FT) is increasingly recognized as an additional cause for femoroacetabular impingement (FAI). It is unknown if in-toeing of the foot is a specific diagnostic sign for increased FT in patients with symptomatic FAI. The aims of this study were to determine: 1) the prevalence and diagnostic accuracy of in-toeing to detect increased FT; 2) if foot progression angle (FPA) and tibial torsion (TT) are different among patients with abnormal FT; and 3) if FPA correlates with FT.

PATIENTS AND METHODS

A retrospective, institutional review board (IRB)-approved, controlled study of 85 symptomatic patients (148 hips) with FAI or hip dysplasia was performed in the gait laboratory. All patients had a measurement of FT (pelvic CT scan), TT (CT scan), and FPA (optical motion capture system). We allocated all patients to three groups with decreased FT (< 10°, 37 hips), increased FT (> 25°, 61 hips), and normal FT (10° to 25°, 50 hips). Cluster analysis was performed.

RESULTS

We found a specificity of 99%, positive predictive value (PPV) of 93%, and sensitivity of 23% for in-toeing (FPA < 0°) to detect increased FT > 25°. Most of the hips with normal or decreased FT had no in-toeing (false-positive rate of 1%). Patients with increased FT had significantly (p < 0.001) more in-toeing than patients with decreased FT. The majority of the patients (77%) with increased FT walk with a normal foot position. The correlation between FPA and FT was significant (r = 0.404, p < 0.001). Five cluster groups were identified.

CONCLUSION

In-toeing has a high specificity and high PPV to detect increased FT, but increased FT can be missed because of the low sensitivity and high false-negative rate. These results can be used for diagnosis of abnormal FT in patients with FAI or hip dysplasia undergoing hip arthroscopy or femoral derotation osteotomy. However, most of the patients with increased FT walk with a normal foot position. This can lead to underestimation or misdiagnosis of abnormal FT. We recommend measuring FT with CT/MRI scans in all patients with FAI. Cite this article: Bone Joint J 2019;101-B:1218-1229.

Patient-Specific 3-D Magnetic Resonance Imaging-Based Dynamic Simulation of Hip Impingement and Range of Motion Can Replace 3-D Computed Tomography-Based Simulation for Patients With Femoroacetabular Impingement: Implications for Planning Open Hip Preservation Surgery and Hip Arthroscopy

BACKGROUND

Femoroacetabular impingement (FAI) is a complex 3-dimensional (3D) hip abnormality that can cause hip pain and osteoarthritis in young and active patients of childbearing age. Imaging is static and based on 2-dimensional radiographs or computed tomography (CT) scans. Recently, CT-based 3D impingement simulation was introduced for patient-specific assessments of hip deformities, whereas magnetic resonance imaging (MRI) offers a radiation-free alternative for surgical planning before hip arthroscopic surgery.

PURPOSE

To (1) investigate the difference between 3D models of the hip, (2) correlate the location of hip impingement and range of motion (ROM), and (3) correlate diagnostic parameters while comparing CT- and MRI-based osseous 3D models of the hip in symptomatic patients with FAI.

STUDY DESIGN

Cohort study (Diagnosis); Level of evidence, 2.

METHODS

The authors performed an institutional review board-approved comparative and retrospective study of 31 hips in 26 symptomatic patients with FAI. We compared CT- and MRI-based osseous 3D models of the hip in the same patients. 3D CT scans (slice thickness, 1 mm) of the entire pelvis and the distal femoral condyles were obtained. Preoperative MRI of the hip was performed including an axial-oblique T1 VIBE sequence (slice thickness, 1 mm) and 2 axial anisotropic (1.2 × 1.2 × 1 mm) T1 VIBE Dixon sequences of the entire pelvis and the distal femoral condyles. Threshold-based semiautomatic reconstruction of 3D models was performed using commercial software. CT- and MRI-based 3D models were compared with specifically developed software.

RESULTS

(1) The difference between MRI- and CT-based 3D models was less than 1 mm for the proximal femur and the acetabulum (median surface distance, 0.4 ± 0.1 mm and 0.4 ± 0.2 mm, respectively). (2) The correlation for ROM values was excellent (r = 0.99, P < .001) between CT and MRI. The mean absolute difference for flexion and extension was 1.9°± 1.5° and 2.6°± 1.9°, respectively. The location of impingement did not differ between CT- and MRI-based 3D ROM analysis in all 12 of 12 acetabular and 11 of 12 femoral clock-face positions. (3) The correlation for 6 diagnostic parameters was excellent (r = 0.98, P < .001) between CT and MRI. The mean absolute difference for inclination and anteversion was 2.0°± 1.8° and 1.0°± 0.8°, respectively.

CONCLUSION

Patient-specific and radiation-free MRI-based dynamic 3D simulation of hip impingement and ROM can replace CT-based 3D simulation for patients with FAI of childbearing age. On the basis of these excellent results, we intend to change our clinical practice, and we will use MRI-based 3D models for future clinical practice instead of CT-based 3D models. This allows radiation-free and patient-specific preoperative 3D impingement simulation for surgical planning and simulation of open hip preservation surgery and hip arthroscopic surgery.

What Is the Prevalence of Cam Deformity After Prophylactic Pinning of the Contralateral Asymptomatic Hip in Unilateral Slipped Capital Femoral Epiphysis? A 10-year Minimum Followup Study

BACKGROUND

Prophylactic pinning of the asymptomatic and normal-appearing contralateral hip in patients with unilateral slipped capital femoral epiphysis (SCFE) remains controversial. Understanding the minimal 10-year clinical, functional, and radiographic outcomes of the contralateral asymptomatic hip in unilateral SCFE may be helpful in the decision regarding whether the benefits associated with potentially preventing a SCFE are outweighed by the risk of additional surgery.

QUESTIONS/PURPOSES

Among patients with SCFE treated with prophylactic pinning of the asymptomatic and contralateral hip, we sought (1) to determine the complications and reoperations; (2) to evaluate the development of cam deformities and the frequency and severity of osteoarthritis progression; and (3) to characterize hip pain and function as measured by the Harris hip score (HHS) and the Hip Disability and Osteoarthritis Outcome Score (HOOS) at minimal 10-year followup.

METHODS

Between 1998 and 2005 all patients with SCFE seen at our institution were treated with the modified Dunn procedure and all were offered prophylactic pinning of the contralateral asymptomatic hip. Of the 41 patients who underwent the unilateral modified Dunn procedure and who had an asymptomatic contralateral hip, 37 patients (90%) underwent pinning of that contralateral hip. Of those, 33 patients (80%) were available for clinical and radiographic evaluation for this retrospective study at a minimum of 10 years (mean followup 12 ± 2 years) after surgery. Three patients of the 37 patients only had 10-year clinical followup, including questionnaires sent by mail and telephone, because they refused further radiographic followup and one patient was lost to followup. The group included 19 males and 17 females whose age at surgery was a mean of 13 ± 2 years. Medical charts were reviewed and patients were asked about complications and additional surgical procedures. Most recent postoperative radiographs were evaluated for measurement of the alpha angle, head-neck offset, epiphysis orientation, and osteoarthritis grading according to Tönnis classification and minimum joint space width. The presence of a cam deformity was defined by an alpha angle measurement > 60° on the AP radiograph and/or > 55° on the lateral radiograph. Hip function and pain were assessed by the HHS and HOOS outcome measures.

RESULTS

No complications with prophylactic in situ pinning were recorded. Four of 36 (11%) patients underwent subsequent surgical treatment for cam-type femoroacetabular impingement (FAI), and hardware removal was performed in four hips (11%). The mean alpha angle was 53° ± 8° on the AP radiograph and 49° ± 8° on the lateral view at followup. In total, 10 of 33 hips (30%) had a cam morphology at the femoral head-neck junction and four (12%) were symptomatic and underwent FAI surgery. Six of 33 patients (18%) developed an asymptomatic cam morphology at the femoral head-neck junction; in three of 33 hips (9%), the cam deformity instead of lesion were visible only on the lateral projection, and 9% were visible on both the AP and lateral projections. The preoperative offset of the femoral head-neck junction was 10 ± 3 mm on the AP view and 11 ± 4 mm on the lateral view. At followup, the AP offset was 7 ± 3 mm and the lateral offset was 6 ± 3 mm, and on the lateral view, the offset was < 10 mm in eight hips (22%). No patient had radiographic signs of hip osteoarthritis (Tönnis Grade 0). The mean minimum joint space width was 4 ± 0.4 mm. The mean HHS for the 32 patients who did not undergo subsequent surgery was 97 ± 5 at latest followup. The mean postoperative HOOS was 94 ± 8 for the 32 patients at latest followup.

CONCLUSIONS

At a minimum followup of 10 years after prophylactic pinning of a contralateral asymptomatic hip, most patients achieve excellent hip scores; however, a substantial proportion will develop a symptomatic cam deformity despite prophylactic pinning. No patient had signs of osteoarthritis at a minimum of 10 years, but almost one-third of the patients who underwent prophylactic pinning developed a cam deformity.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Patients with severe slipped capital femoral epiphysis treated by the modified Dunn procedure have low rates of avascular necrosis, good outcomes, and little osteoarthritis at long-term follow-up

AIMS

The modified Dunn procedure has the potential to restore the anatomy in hips with severe slipped capital femoral epiphyses (SCFE). However, there is a risk of developing avascular necrosis of the femoral head (AVN). In this paper, we report on clinical outcome, radiological outcome, AVN rate and complications, and the cumulative survivorship at long-term follow-up in patients undergoing the modified Dunn procedure for severe SCFE.

PATIENTS AND METHODS

We performed a retrospective analysis involving 46 hips in 46 patients treated with a modified Dunn procedure for severe SCFE (slip angle > 60°) between 1999 and 2016. At nine-year-follow-up, 40 hips were available for clinical and radiological examination. Mean preoperative age was 13 years, and 14 hips (30%) presented with unstable slips. Mean preoperative slip angle was 64°. Kaplan-Meier survivorship was calculated.

RESULTS

At the latest follow-up, the mean Merle d'Aubigné and Postel score was 17 points (14 to 18), mean modified Harris Hip Score was 94 points (66 to 100), and mean Hip Disability and Osteoarthritis Outcome Score was 91 points (67 to 100). Postoperative slip angle was 7° (1° to 16°). One hip (2%) had progression of osteoarthritis (OA). Two hips (5%) developed AVN of the femoral head and required further surgery. Three other hips (7%) underwent implant revision due to screw breakage or change of wires. Cumulative survivorship was 86% at ten-year follow-up.

CONCLUSION

The modified Dunn procedure for severe SCFE resulted in a low rate of AVN, low risk of progression to OA, and high functional scores at long-term follow-up. The slip deformities were mainly corrected but secondary impingement deformities can develop in some hips and may require further surgical treatment. Cite this article: Bone Joint J 2019;101-B:403-414.