Markus S. Hanke

What Are the Radiographic Reference Values for Acetabular Under- and Overcoverage?

BackgroundBoth acetabular undercoverage (hip dysplasia) and overcoverage (pincer-type femoroacetabular impingement) can result in hip osteoarthritis. In contrast to undercoverage, there is a lack of information on radiographic reference values for excessive acetabular coverage.Questions/purposes(1) How do common radiographic hip parameters differ in hips with a deficient or an excessive acetabulum in relation to a control group; and (2) what are the reference values determined from these data for acetabular under- and overcoverage?MethodsWe retrospectively compared 11 radiographic parameters describing the radiographic acetabular anatomy among hip dysplasia (26 hips undergoing periacetabular osteotomy), control hips (21 hips, requiring no rim trimming during surgical hip dislocation), hips with overcoverage (14 hips, requiring rim trimming during surgical hip dislocation), and hips with severe overcoverage (25 hips, defined as having acetabular protrusio). The hips were selected from a patient cohort of a total of 593 hips. Radiographic parameters were assessed with computerized methods on anteroposterior pelvic radiographs and corrected for neutral pelvic orientation with the help of a true lateral radiograph.ResultsAll parameters except the crossover sign differed among the four study groups. From dysplasia through control and overcoverage, the lateral center-edge angle, acetabular arc, and anteroposterior/craniocaudal coverage increased. In contrast, the medial center-edge angle, extrusion/acetabular index, Sharp angle, and prevalence of the posterior wall sign decreased. The following reference values were found: lateral center-edge angle 23° to 33°, medial center-edge angle 35° to 44°, acetabular arc 61° to 65°, extrusion index 17% to 27%, acetabular index 3° to 13°, Sharp angle 38° to 42°, negative crossover sign, positive posterior wall sign, anterior femoral head coverage 15% to 26%, posterior femoral head coverage 36% to 47%, and craniocaudal coverage 70% to 83%.ConclusionsThese acetabular reference values define excessive and deficient coverage. They may be used for radiographic evaluation of symptomatic hips, may offer possible predictors for surgical outcomes, and serve to guide clinical decision-making.Level of EvidenceLevel III, diagnostic study.

LCPD: Reduced Range of Motion Resulting From Extra- and Intraarticular Impingement

BackgroundLegg-Calvé-Perthes disease (LCPD) often results in a deformity that can be considered as a complex form of femoroacetabular impingement (FAI). Improved preoperative characterization of the FAI problem based on a noninvasive three-dimensional computer analysis may help to plan the appropriate operative treatment.Questions/purposesWe asked whether the location of impingement zones, the presence of additional extraarticular impingement, and the resulting ROM differ between hips with LCPD and normal hips or hips with FAI.MethodsWe used a CT-based virtual dynamic motion analysis based on a motion algorithm to simulate the individual motion for 13 hips with LCPD, 22 hips with FAI, and 27 normal hips. We then determined the motion and impingement pattern of each hip for the anterior (flexion, adduction, internal rotation) and the posterior impingement tests (extension, adduction, external rotation).ResultsThe location of impingement zones in hips with LCPD differed compared with the FAI/normal groups. Intra- and extraarticular impingement was more frequent in LCPD (79% and 86%, respectively) compared with normal (15%, 15%) and FAI hips (36%, 14%). Hips with LCPD had decreased amplitude for all hip motions (flexion, extension, abduction, adduction, internal and external rotation) compared with FAI or normal.ConclusionsHips with LCPD show a decreased ROM as a result of a higher prevalence of intra- and extraarticular FAI. Noninvasive assessment of impingement characteristics in hips with LCPD may be helpful in the future for establishment of a surgical plan.

Surgical hip dislocation does not result in atrophy or fatty infiltration of periarticular hip muscles

Surgical hip dislocation is the gold standard for treatment of femoroacetabular impingement (FAI). It utilizes an intermuscular and internervous approach to the hip. Concerns have been expressed that this approach causes soft tissue trauma resulting in post-operative muscle weakness of patients undergoing this procedure. We therefore asked whether surgical hip dislocation leads to (i) atrophy (decreased muscle diameter or cross-sectional area [CSA]) and (ii) degeneration (fatty infiltration) of 18 evaluated periarticular hip muscles. We retrospectively evaluated 32 patients (34 hips) following surgical hip dislocation for the treatment of FAI using pre and post-operative magnetic resonance (MR) arthrography of the hip. We evaluated muscle diameter, CSA and degree of fatty infiltration according to Goutallier for 18 periarticular hip muscles on axial and sagittal views. The mean interval between pre and post-operative MR was 1.9 ± 1.5 years (range, 0.4–6.1 years). Pre and post-operative muscle diameter and CSA of all 18 evaluated hip muscles did not differ. There was no post-operative change in the Goutallier classification for any of the evaluated 18 muscles. No muscle had post-operative degeneration higher than Grade 1 according to Goutallier. No atrophy or degeneration of periarticular hip muscles could be found following surgical hip dislocation for treatment of FAI. Any raised concerns about the invasiveness and potential muscle trauma for this type of surgery are unfounded. Level III, retrospective comparative study. See guidelines for authors for a complete description of levels of evidence.

Erratum to: What MRI Findings Predict Failure 10 Years After Surgery for Femoroacetabular Impingement?

In the study, ‘‘What MRI Findings Predict Failure 10 Years After Surgery for Femoroacetabular Impingement?’’ the overview of the study population in Fig. 1 is incorrect as published. A total of 20 hips underwent MRA at another institution, not eight hips. Additionally, 10 hips had been operated on the contralateral side with a similar appearance, not 22 hips. The corrected Fig. 1 is shown in this erratum. We apologize for the error. Surgical Treatment for Symptomatic FAI July 2001 – March 2003 n = 146

ArtiFacts: Femoroacetabular Impingement—A New Pathology?

I n ArtiFacts, we tend to explore what the material culture in orthopaedics tells us about the evolving practice of orthopaedic medicine. In this month’s guest column, we are taking a slightly different tack. Rather than looking at a medical device, we will examine a pathological specimen that challenges a contemporary assumption. Using modern methods of examination, Moritz Tannast MD and his clinical research team in collaboration with the Anthropological Institute in Zürich, Switzerland, analyzed the bones of an approximately 5000-yearold specimen and discovered clear macroscopic features of a cam-type femoroacetabular impingement deformity—a condition typically found in high-level athletes of the 20 and 21 centuries. Indeed, the science in this column is intriguing. But the presentation, which includes a number of images and a supplemental video, truly makes this a fascinating story for the reader.

Imaging of femoroacetabular impingement-current concepts

Following the recognition of femoroacetabular impingement (FAI) as a clinical entity, diagnostic tools have continuously evolved. While the diagnosis of FAI is primarily made based on the patients’ history and clinical examination, imaging of FAI is indispensable. Routine diagnostic work-up consists of a set of plain radiographs, magnetic resonance imaging (MRI) and MR-arthrography. Recent advances in MRI technology include biochemically sensitive sequences bearing the potential to detect degenerative changes of the hip joint at an early stage prior to their appearance on conventional imaging modalities. Computed tomography may serve as an adjunct. Advantages of CT include superior bone to soft tissue contrast, making CT applicable for image-guiding software tools that allow evaluation of the underlying dynamic mechanisms causing FAI. This article provides a summary of current concepts of imaging in FAI and a review of the literature on recent advances, and their application to clinical practice.

The Reversed Less Invasive Stabilisation System-Distal Femur Technique: Application in an Adult Patient with Osteogenesis Imperfecta Sustaining a Femoral Fracture.

Introduction: The aim of this study was to report the surgical management and to discuss the options for fracture fixation in an adult patient with osteogenesis imperfecta (OI) who sustained a trochanteric femoral fracture after a simple fall from standing position. Case Report: As a result of multiple fractures during childhood, this adult patient with OI presented with a short stature. The radiographs revealed a displaced, intertrochanteric fracture with subtrochanteric extension of the left femur. The intramedullary canal was narrow, the femur presented with a severe bowing deformity, and the bone quality was poor. The implant of choice was plating using the reversed less invasive stabilisation system-distal femur (LISS-DF) technique. This technique was introduced for the management of subtrochanteric fractures in the elderly with poor bone stock. In addition, a locking plate attached to the LISS-DF allowed for additional screw placement at the apex of the curvature of the femur although the plate was not in line with the femur at this site. Cerclages were used for metaphyseal reduction and fixation. 4-month postoperatively, the patient was ambulatory without any assistance with full weight bearing. At the latest follow-up 1-year postoperatively, the patient was still free of complaints and at her preinjury activity level. Conclusion: The presented technique was successful as a salvage procedure in a rare case of adult OI presenting with a femoral fracture with characteristics influencing the decision-making in treatment options.

Impingement of the hip

Femoroacetabular impingement (FAI) describes the repetitive painful contact between the acetabulum, the pelvis and the proximal femur. This bony abutment can lead to a characteristic pattern of chondrolabral damage and is one of the main etiological factors in the development of juvenile osteoarthritis of the hip joint. This article describes the current treatment concepts of FAI and the radiological assessment including an overview of standard measurement methods, coxometric parameters and cut-off values. Furthermore, the authors stress the importance of a profound understanding of the entire configuration of the pelvis and the dynamic interplay of its components.ZusammenfassungDas Konzept des femoroazetabulären Impingements (FAI) beschreibt den schmerzhaften repetitiven ossären Anschlag zwischen Azetabulum respektive Becken und proximalem Femur. Es kann zu einer charakteristischen Schädigung an den Gelenkbinnenstrukturen führen und stellt somit eine Hauptursache für die Entstehung der juvenilen Coxarthrose dar. Der vorliegende Artikel beinhaltet neben der Beschreibung des aktuellen Behandlungskonzepts beim FAI die entsprechende radiologische Abklärung inklusive einer Übersicht über Standardmessmethoden und coxometrische Grenzwerte und legt den Fokus auf das Verständnis der Gesamtmorphologie bei dieser komplexen Fragestellung.AbstractFemoroacetabular impingement (FAI) describes the repetitive painful contact between the acetabulum, the pelvis and the proximal femur. This bony abutment can lead to a characteristic pattern of chondrolabral damage and is one of the main etiological factors in the development of juvenile osteoarthritis of the hip joint. This article describes the current treatment concepts of FAI and the radiological assessment including an overview of standard measurement methods, coxometric parameters and cut-off values. Furthermore, the authors stress the importance of a profound understanding of the entire configuration of the pelvis and the dynamic interplay of its components.

Impingement der Hüfte

Femoroacetabular impingement (FAI) describes the repetitive painful contact between the acetabulum, the pelvis and the proximal femur. This bony abutment can lead to a characteristic pattern of chondrolabral damage and is one of the main etiological factors in the development of juvenile osteoarthritis of the hip joint. This article describes the current treatment concepts of FAI and the radiological assessment including an overview of standard measurement methods, coxometric parameters and cut-off values. Furthermore, the authors stress the importance of a profound understanding of the entire configuration of the pelvis and the dynamic interplay of its components.ZusammenfassungDas Konzept des femoroazetabulären Impingements (FAI) beschreibt den schmerzhaften repetitiven ossären Anschlag zwischen Azetabulum respektive Becken und proximalem Femur. Es kann zu einer charakteristischen Schädigung an den Gelenkbinnenstrukturen führen und stellt somit eine Hauptursache für die Entstehung der juvenilen Coxarthrose dar. Der vorliegende Artikel beinhaltet neben der Beschreibung des aktuellen Behandlungskonzepts beim FAI die entsprechende radiologische Abklärung inklusive einer Übersicht über Standardmessmethoden und coxometrische Grenzwerte und legt den Fokus auf das Verständnis der Gesamtmorphologie bei dieser komplexen Fragestellung.AbstractFemoroacetabular impingement (FAI) describes the repetitive painful contact between the acetabulum, the pelvis and the proximal femur. This bony abutment can lead to a characteristic pattern of chondrolabral damage and is one of the main etiological factors in the development of juvenile osteoarthritis of the hip joint. This article describes the current treatment concepts of FAI and the radiological assessment including an overview of standard measurement methods, coxometric parameters and cut-off values. Furthermore, the authors stress the importance of a profound understanding of the entire configuration of the pelvis and the dynamic interplay of its components.

Computer Assisted Diagnosis and Treatment Planning of Femoroacetabular Impingement (FAI)

Femoroacetabular impingement (FAI) is a dynamic conflict of the hip defined by a pathological, early abutment of the proximal femur onto the acetabulum or pelvis. In the past two decades, FAI has received increasing focus in both research and clinical practice as a cause of hip pain and prearthrotic deformity. Anatomical abnormalities such as an aspherical femoral head (cam-type FAI), a focal or general overgrowth of the acetabulum (pincer-type FAI), a high riding greater or lesser trochanter (extra-articular FAI), or abnormal torsion of the femur have been identified as underlying pathomorphologies. Open and arthroscopic treatment options are available to correct the deformity and to allow impingement-free range of motion. In routine practice, diagnosis and treatment planning of FAI is based on clinical examination and conventional imaging modalities such as standard radiography, magnetic resonance arthrography (MRA), and computed tomography (CT). Modern software tools allow three-dimensional analysis of the hip joint by extracting pelvic landmarks from two-dimensional antero-posterior pelvic radiographs. An object-oriented cross-platform program (Hip2Norm) has been developed and validated to standardize pelvic rotation and tilt on conventional AP pelvis radiographs. It has been shown that Hip2Norm is an accurate, consistent, reliable and reproducible tool for the correction of selected hip parameters on conventional radiographs. In contrast to conventional imaging modalities, which provide only static visualization, novel computer assisted tools have been developed to allow the dynamic analysis of FAI pathomechanics. In this context, a validated, CT-based software package (HipMotion) has been introduced. HipMotion is based on polygonal three-dimensional models of the patient’s pelvis and femur. The software includes simulation methods for range of motion, collision detection and accurate mapping of impingement areas. A preoperative treatment plan can be created by performing a virtual resection of any mapped impingement zones both on the femoral head-neck junction, as well as the acetabular rim using the same three-dimensional models. The following book chapter provides a summarized description of current computer-assisted tools for the diagnosis and treatment planning of FAI highlighting the possibility for both static and dynamic evaluation, reliability and reproducibility, and its applicability to routine clinical use.