Joseph M. Schwab

Prevalence of Cam-Type Deformity and Hip Pain in Elite Ice Hockey Players Before and After the End of Growth

Background: Elite-level sports activities have been associated with hip osteoarthritis and cam-type deformity. Purpose: To analyze the appearance and prevalence of an abnormal cam-type deformity of the proximal femur and its potential association to hip pain in adolescent and young adult athletes. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 77 elite-level male ice hockey players were evaluated with a questionnaire, clinical examination, and magnetic resonance imaging. The questionnaire and clinical examination were used to determine whether the hip being evaluated was symptomatic and what the internal rotation of the hip was. Magnetic resonance imaging was used to determine physeal status (open/closed) and α angle of the cranial half of the proximal femur using a standard clockface system. Results: The mean age of the patients was 16.5 years (range, 9-36 years); 15 of 77 (19.5%) athletes had a history of hip pain and a positive impingement test finding. The α angles were higher in athletes with closed physes versus open physes (58° vs 49°, respectively; P < .001). Symptomatic athletes had higher α angles compared with asymptomatic athletes at the 12-o’clock (52° vs 46°, respectively; P = .022), 1-o’clock (62° vs 52°, respectively; P < .001), and 2-o’clock (59° vs 50°, respectively; P < .001) positions. Internal rotation was significantly decreased in symptomatic compared with asymptomatic athletes (17° vs 23°, respectively). Higher α angles in the anterosuperior quadrant were significantly associated with decreased internal rotation. Conclusion: The data suggest that playing ice hockey at an elite level during childhood is associated with an increased risk for cam-type deformity and hip pain after physeal closure.

Valgus Hip With High Antetorsion Causes Pain Through Posterior Extraarticular FAI

BackgroundValgus hips with increased antetorsion present with lack of external rotation and posterior hip pain that is aggravated with hip extension and external rotation. This may be the result of posterior femoroacetabular impingement (FAI).Questions/purposesWe asked whether (1) the range of motion (ROM); (2) the location of anterior and posterior bony collision zones; and (3) the prevalence of extraarticular impingement differ between valgus hips with increased antetorsion compared with normal hips and hips with idiopathic FAI.MethodsSurface models based on CT scan reconstructions of 13 valgus hips with increased antetorsion, 22 hips with FAI, and 27 normal hips were included. Validated three-dimensional collision detection software was used to quantify the simulated hip ROM and the location of impingement on the acetabular and the femoral sides.ResultsHips with coxa valga and antetorsion showed decreased extension, external rotation, and adduction, whereas internal rotation in 90° of flexion was increased. Impingement zones were more anteroinferior on the femur and posteroinferior on the acetabular (pelvic) side; and the zones were more frequently extraarticular, posterior, or to a lesser degree anterior against the inferior iliac spine. We found a higher prevalence of extraarticular impingement for valgus hips with increased antetorsion.ConclusionsValgus hips with increased antetorsion predispose to posterior extraarticular FAI and to a lesser degree anteroinferior spine impingement.Level of EvidenceLevel II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Arthroscopic Versus Open Cam Resection in the Treatment of Femoroacetabular Impingement

PURPOSE The purpose of this study was to evaluate if osseous correction of the femoral neck achieved arthroscopically is comparable to that achieved by surgical dislocation. METHODS We retrospectively analyzed all patients who were treated with hip arthroscopy or surgical dislocation for cam or mixed type femoroacetabular impingement (FAI) in our institution between 2006 and 2009. Inclusion criteria were complete clinical and radiologic documentation with standardized radiographs. Group 1 consisted of 66 patients (49 female patients, mean age 33.8 years) treated with hip arthroscopy. Group 2 consisted of 135 patients (91 male patients, mean age 31.2 years) treated with surgical hip dislocation. We compared the preoperative and postoperative alpha and gamma angles, as well as the triangular index. Mean follow-up was 16.7 months (range, 2 to 79 months). RESULTS In group 1, the mean alpha angle improved from 60.7° preoperatively to 47.8° postoperatively (P < .001) and the mean gamma angle improved from 47.3° to 44.5° (P < .001). Over time, the preoperative mean alpha angle increased from 56.3° in 2006 to 67.5° in 2009, whereas the postoperative mean alpha angle decreased from 51.2° in 2006 to 47.5° in 2009. In group 2, the mean alpha angle improved from 75.3° preoperatively to 44.8° postoperatively (P < .001), and the mean gamma angle improved from 65.1° to 52.2° (P < .001). Arthroscopic revision of intra-articular adhesions was performed in 4 patients (6.1%) in group 1 and 16 patients (12%) in group 2. Three patients (2.2%) in group 2 underwent revision for nonunion of the greater trochanter. CONCLUSIONS Osseous correction of cam-type FAI with hip arthroscopy is comparable to the correction achieved by surgical hip dislocation. There is a significant learning curve for hip arthroscopy, with postoperative osseous correction showing improved results with increasing surgical experience. LEVEL OF EVIDENCE Level III, retrospective comparative study.

Pelvic Morphology Differs in Rotation and Obliquity Between Developmental Dysplasia of the Hip and Retroversion

BackgroundDevelopmental dysplasia of the hip (DDH) and acetabular retroversion represent distinct acetabular pathomorphologies. Both are associated with alterations in pelvic morphology. In cases where direct radiographic assessment of the acetabulum is difficult or impossible or in mixed cases of DDH and retroversion, additional indirect pelvimetric parameters would help identify the major underlying structural abnormality.Questions/PurposesWe asked: How does DDH and retroversion differ with respect to rotation and coronal obliquity as measured by the pelvic width index, anterior inferior iliac spine (AIIS) sign, ilioischial angle, and obturator index? And what is the predictive value of each variable in detecting acetabular retroversion?MethodsWe reviewed AP pelvis radiographs for 51 dysplastic and 51 retroverted hips. Dysplasia was diagnosed based on a lateral center-edge angle of less than 20° and an acetabular index of greater than 14°. Retroversion was diagnosed based on a lateral center-edge angle of greater than 25° and concomitant presence of the crossover/ischial spine/posterior wall signs. We calculated sensitivity, specificity, and area under the receiver operating characteristic (ROC) curve for each variable used to diagnose acetabular retroversion.ResultsWe found a lower pelvic width index, higher prevalence of the AIIS sign, higher ilioischial angle, and lower obturator index in acetabular retroversion. The entire innominate bone is internally rotated in DDH and externally rotated in retroversion. The areas under the ROC curve were 0.969 (pelvic width index), 0.776 (AIIS sign), 0.971 (ilioischial angle), and 0.925 (obturator index).ConclusionsPelvic morphology is associated with acetabular pathomorphology. Our measurements, except the AIIS sign, are indirect indicators of acetabular retroversion. The data suggest they can be used when the acetabular rim is not clearly visible and retroversion is not obvious.Level of EvidenceLevel III, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

The Acetabular Wall Index for Assessing Anteroposterior Femoral Head Coverage in Symptomatic Patients

BackgroundUnderstanding acetabular pathomorphology is necessary to correctly treat patients with hip complaints. Existing radiographic parameters classify acetabular coverage as deficient, normal, or excessive but fail to quantify contributions of anterior and posterior wall coverage. A simple, reproducible, and valid measurement of anterior and posterior wall coverage in patients with hip pain would be a clinically useful tool.Questions/PurposesWe (1) introduce the anterior wall index (AWI) and posterior wall index (PWI), (2) report the intra- and interobserver reliability of these measurements, and (3) validate these measurements against an established computer model.MethodsWe retrospectively reviewed 87 hips (63 patients) with symptomatic hip disease. A validated computer model was used to determine total anterior and posterior acetabular coverage (TAC and TPC) on an AP pelvis radiograph. Two independent observers measured the AWI and PWI on each film, and the intraclass correlation coefficient (ICC) was calculated. Pearson correlation was used to determine the strength of linear dependence between our measurements and the computer model.ResultsIntra- and interobserver ICCs were 0.94 and 0.99 for the AWI and 0.81 and 0.97 for the PWI. For validation against the computer model, Pearson r values were 0.837 (AWI versus TAC) and 0.895 (PWI versus TPC). Mean AWI and PWI were 0.28 and 0.81 for dysplastic hips, 0.41 and 0.91 for normal hips, 0.61 and 1.15 for hips with a deep acetabulum.ConclusionsOur data suggest these measures will be helpful in evaluating anterior and posterior coverage before and after surgery but need to be evaluated in asymptomatic individuals without hip abnormalities to establish normal ranges.Level of EvidenceLevel III, diagnostic study. See Instructions for Authors for a complete description of levels of evidence.

The cam-type deformity--what is it: SCFE, osteophyte, or a new disease?

Cam-type deformity of the proximal femur is a risk factor for the development of cam-type femoroacetabular impingement and a prearthrotic condition of the hip. The etiology of cam-type deformity remains unclear. There are a number of causes of cam-type deformity including sequellae of slipped capital femoral epiphysis, Legg-Calvé-Perthes disease or Perthes-like deformities, postinfectious, and traumatic. However, the majority of cam-type deformities arise without any apparent preexisting hip disease. These “idiopathic” cam-type deformities likely represent a majority of cases, and show clear racial and sex differences, as well as developmental and genetic influences. Idiopathic cam-type deformity also seems to be a distinct entity from residual or silent slipped capital femoral epiphysis, as well as osteoarthritis-induced osteophytes. In this paper we examine the different pathogenetic aspects of the proximal femur that contribute to cam-type deformity and/or symptomatic cam-type femoroacetabular impingement.

The use of cervical vertebrae plates for cortical substitution in posterior wall acetabular fractures.

We report a new technique for operative fixation of posterior wall acetabular fractures that require cortical substitution. This technique uses cervical vertebrae plates that are H-shaped as an alternative to the combination of standard locking or nonlocking pelvic reconstruction plates and cortical substitution plates, ie, spring plates. We believe this technique provides a more robust structural support with the plate acting as a cortical substitute in comminuted fracture patterns. Compared with pelvic reconstruction plates, cervical vertebrae plates are almost twice as wide. Additionally, the plate configuration allows more screws per unit length compared with pelvic reconstruction plates, potentially providing more points of fixation. Finally, cost comparison of the two plates shows the cervical vertebrae plates to be less expensive than standard pelvic reconstruction plates. Our series of 23 consecutive patients shows outcomes similar to the published literature for standard pelvic reconstruction plates, and initial results show no early hardware failure.

Biomechanics of the Hip

The hip joint plays a crucial role in daily living and athletic activities. The specific anatomy and biomechanics of the human hip joint is a consequence of the evolution of permanent bipedal gait. Acetabular and femoral anatomy ensure an inherently stable hip with a wide range of motion. Abnormal anatomy can lead to hip joint instability or impingement and is a risk factor for the development of arthritis of the joint. The forces acting upon the hip joint are mainly a function of gravitational force and strength of the muscles surrounding the hip and their respective lever arms. Depending on the activity, the hip may be subjected to a peak force of up to 8 times the bodys weight. Both conservative and surgical treatment of fractures of the proximal femur can result in a variety of anatomical changes that can affect the biomechanics of the hip. Recognizing the biomechanical principles of the hip joint is essential for understanding normal hip function and is the basis of treatment concepts for congenital, traumatic, or degenerative hip diseases.

Intra-articular Lesions: Imaging and Surgical Correlation.

The past 2 decades have seen a substantial increase in hip joint preserving procedures, primarily secondary to not only hip dysplasia, but the recognition and description of femoroacetabular impingement (FAI), and its association with chondral lesions, as a potentially pre-arthritic condition. Morphological magnetic resonance imaging (MRI) plays an essential role in the preoperative assessment of osseous deformities and in particular of the resulting joint degeneration. An accurate descriptive report of chondrolabral lesions is warranted describing the tear pattern, size, localization, and extension of the lesions. This is important because different damage patterns and localization of the lesions may determine the surgical approach. The current imaging standard is direct magnetic resonance arthrography (MRA) with a small field of view, with acquisition of radial images in addition to the classic coronal, sagittal, and axial-oblique images. Early cartilage damage detected on direct MRA obtained with or without traction can predict long-term failure after FAI surgery.

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.