Comparison of 2-Dimensional and 3-Dimensional Metacarpal Fracture Plating Constructs Under Cyclic Loading.

PURPOSE: Metacarpal fractures are commonly treated by a variety of means including casting or open reduction internal fixation when unacceptable alignment is present following attempted closed reduction. Dorsal plating with either single-row 2-dimensional or double-row 3-dimensional plates has been proposed. This study's purpose was to determine if there are any differences in fixation construct stability under cyclic loading and subsequent load to failure between the lower profile 3-dimensional and the larger 2-dimensional plates in a metacarpal fracture gap sawbone model. METHODS: Thirty metacarpal cortico-cancellous synthetic bones were cut with a 1.75-mm gap between the 2 fragments simulating mid-diaphyseal fracture comminution. Half of the metacarpals were plated with 2.0-mm locking 2-dimensional plates and half with 1.5-mm locking 3-dimensional plates. The plated metacarpals were mounted into a materials testing apparatus and cyclically loaded under cantilever bending for 2,000 cycles at 70 N, then 2,000 cycles at 120 N, and finally monotonically loaded to failure. Throughout testing, fracture gap sizes were measured, failure modes were recorded, and construct strength and stiffness values were calculated. RESULTS: All 3-dimensional constructs survived both cyclic loading conditions. Ten (67%) 2-dimensional constructs survived both loading conditions, whereas 5 (33%) failed the 120-N loading at 1377 ± 363 cycles. When loaded to failure, the 3-dimensional constructs failed at 265 N ± 21 N, whereas the 2-dimensional constructs surviving cyclic loading failed at 190 N ± 17 N. CONCLUSIONS: The shorter, thinner 3-dimensional metacarpal plates demonstrated increased resistance to failure in a cyclic loading model and increased load to failure compared with the relatively longer, thicker 2-dimensional metacarpal plates. CLINICAL RELEVANCE: The lower-profile 3-dimensional metacarpal plate fixation demonstrated greater stability for early postoperative resistance than the thicker 2-dimensional fixation, whereas the smaller size and lower profile of the 3-dimensional plates potentially reduces soft tissue stripping, implant prominence, and risk of extensor tendon irritation.

A Computed Tomography Study of Gender Differences in Acetabular Version and Morphology: Implications for Femoroacetabular Impingement.

PURPOSE: To assess the prevalence of acetabular retroversion in a large population of patients with asymptomatic hips. Furthermore, we sought to identify gender differences in acetabular morphology to address the current thinking that retroversion and pincer-type femoroacetabular impingement (FAI) are more common in women. METHODS: We retrospectively reviewed morphologic features of acetabula from a consecutive series of trauma-protocol computed tomography scans of patients without pelvis injury. An automated algorithm determined the acetabular rim profile and center of the femoral head, normalized the frontal plane of the pelvis, and calculated version and coverage. We then compared male and female rim profiles, specifically focusing on version and acetabular wall coverage in the 1-o'clock (anterosuperior), 2-o'clock (central), and 3-o'clock (inferior) positions. RESULTS: Of 1,088 patients in the database, 878 had complete data (i.e., age, ethnicity, and body mass index) and were therefore included in the final analysis. Of these, 34.3% were women and 65.7% were men. Mean global acetabular version was 19.1° for men and 22.2° for women (P < .001). Mean acetabular version for men and women was 15.5° and 18.3°, respectively, in the 1-o'clock position; 21.5° and 24.0°, respectively, in the 2-o'clock position; and 20.2° and 24.3°, respectively, in the 3-o'clock position (P < .001 for all 3). True retroversion (<0°) was observed only in the 1-o'clock position. The prevalence of true acetabular retroversion in the 1-o'clock position for men and women was 4.3% and 3%, respectively (P = .36). CONCLUSIONS: Mean global and focal acetabular anteversion was greater in women, and the prevalence of focal cephalad retroversion in the 1-o'clock position was not significantly different compared with men. Acetabular retroversion and anterior overcoverage are not more prevalent in women in the anterosuperior acetabulum, where femoroacetabular impingement most commonly occurs. LEVEL OF EVIDENCE: Level III, diagnostic study.

Functional acetabular orientation varies between supine and standing radiographs: implications for treatment of femoroacetabular impingement.

BACKGROUND: Often, anteroposterior (AP) pelvic radiographs are performed with the patient positioned supine. However, this may not represent the functional position of the pelvis and the acetabulum, and so when assessing patients for conditions like femoroacetabular impingement (FAI), it is possible that standing radiographs better incorporate the dynamic influences of periarticular musculature and sagittal balance. However, this thesis remains largely untested. QUESTIONS/PURPOSES: The purpose of this study was to determine the effect of supine and standing pelvic orientation on (1) measurements of acetabular version and common radiographic signs of FAI as assessed on two- and three-dimensional (3-D) imaging; and (2) on terminal hip range of motion (ROM). METHODS: Preoperative pelvic CT scans of 50 patients (50 hips) who underwent arthroscopic surgery for the treatment of FAI between July 2013 and October 2014 were analyzed. The mean age of the study population was 29 ± 10 years (range, 15-50 years) and 70% were male. All patients had a standing AP pelvis radiograph, a reconstructed supine radiograph from the CT data, and a 3-D model created to allow manipulation of pelvic tilt and simulate ROM to osseous contact. Acetabular version was measured and the presence of the crossover sign, prominent ischial spine sign, and posterior wall sign were recorded on simulated plain radiographs. Measurements of ROM to bony impingement were made during (1) simulated hip flexion; (2) simulated internal rotation in 90° of flexion (IRF); and (3) simulated internal rotation in 90° of flexion and 15° adduction (FADIR), and the location of bony contact between the proximal femur and acetabular rim was defined. These measurements were calculated for supine and standing pelvic orientations. A paired Student's t-test was used for comparison of continuous variables, whereas chi square testing was used for categorical variables. A p value of < 0.05 was considered significant. RESULTS: When changing from supine to the standing radiographs, both mean cranial and central version increased by 2° ± 4° (95% confidence interval [CI], 1°-3°) and 2° ± 3° (95% CI, 1°-3°), respectively (both p < 0.001). However, with the numbers available, there were no changes in the proportion of positive crossover, posterior wall, and prominent ischial spine signs. Standing pelvic position tilt resulted in an increased hip flexion of 3° (95% CI, 2°-4°) as well as an increase in IRF of 2° (95% CI, 1°-3°) and FADIR of 3° (95% CI, 2°-4°) (all p < 0.001). CONCLUSIONS: The functional orientation of the acetabulum varies between supine and standing radiographs and must be considered when diagnosing and treating patients with symptomatic FAI. Standing pelvic orientation results in posterior pelvic tilt and later occurrence of FAI in the arc of motion. Although we cannot recommend standing radiographs on the current study alone, we do recommend larger studies to determine whether any significant differences truly exist.

Pros, cons, and future possibilities for use of computer navigation in hip arthroscopy.

The recent integration of computer-assisted surgery as a resource for preoperative planning and intraoperative assistance in hip arthroscopy has paved the way for more precise surgical planning and the potential for improved operative results. The aims of computer-assisted surgery are to better define the pathoanatomy underlying patient symptomatology in an effort to refine surgical techniques, decrease human error, and ultimately improve clinical outcomes. Multiple studies have been published describing various technologies. The majority of these systems create 3D dynamized computer models from 2D CT scans to allow for precise preoperative planning, and some offer real-time intraoperative capabilities. Although these technologies have shown potential for increasing surgical precision in treating femoroacetabular impingement, they are not without limitations, including an inability to factor in soft-tissue structures and an incompatibility with dysplastic and arthritic hips. Future studies must be conducted to determine whether these systems result in improved clinical outcomes.

An increase in cranial acetabular version with age: implications for femoroacetabular impingement.

This cadaveric study aimed to determine if acetabular retroversion demonstrates predictable changes with age that could inform understanding of factors that may contribute to the pathophysiology of femoroacetabular impingement. Two-hundred forty pelves were divided into young and old groups. Version was measured at the cranial (5mm below superior rim), central (transverse of acetabulum), and caudal (5mm above inferior rim) locations. The data showed a significant difference between young (10±10°) and old (13±9°) cranial version (P=.02). Cranial retroversion increases with age and may reflect a developmental component in the etiology of the focal rim impingement lesion or ossification of the damaged labrum. Global acetabular retroversion does not appear to change with age and may reflect a congenital etiology.

Characterization of Human Anterosuperior Acetabular Depression in Correlation With Labral Tears.

BACKGROUND: Labral tears often occur in the same quadrant of the acetabulum at a small depression previously referred to as the psoas valley. Understanding the anatomic variations of this depression could help us understand the etiology of labral tears. PURPOSE: To describe the location and dimensions of the depression located in the anterosuperior acetabular rim. The hypothesis was that the location of this depression would be consistent with the common location of acetabular labral tears described in the literature. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 240 pelvic specimens were divided into 2 groups (n = 120 for each) according to age (younger age group: 21.36 ± 3.12 years [range, 14-24 years]; older age group: 42.30 ± 10.27 years, [range, 25-60 years]).Specimens were also categorized based on sex (mean age: 31.93 ± 12.31 years [male]; 32.08 ± 13.66 years [female]) and race (mean age: 31.45 ± 13.16 years [black]; 32.57 ± 12.82 years [white]). The depth and width of the acetabular depression were measured using a digital caliper, and the location was measured using a goniometer. RESULTS: The psoas valley was observed in every specimen and was located in the anterosuperior quadrant of the acetabulum. Its depth was significantly greater (P < .001) in males (5.35 ± 1.60 mm) than in females (3.95 ± 1.31 mm). The width of the psoas valley was also greater (P < .001) in males (29.39 ± 3.98 mm) than in females (24.49 ± 4.80 mm). There were no differences in size or location of the depression between races or age groups. The psoas valley was located between 3.92 ± 0.42 o'clock anteriorly and 2.12 ± 0.77 o'clock posteriorly. CONCLUSION: The differences observed in the study data are believed to be a result of the different anatomic morphologies of the pelvis in males and females. This loss of bony support, caused by the depression, could be the underlying cause of weakening of the acetabular labrum as people age. CLINICAL RELEVANCE: The loss of bony support in the anterosuperior acetabular depression could contribute to the labral tears that commonly occur in this area. Understanding the normal anatomy of this area could be important in determining the risk of labral tears as well as treatment options.

Posterior shoulder instability in the contact athlete.

Historically, posterior shoulder instability has been a challenging problem for contact athletes and orthopedic surgeons alike. A complete understanding of the normal shoulder anatomy and biomechanics and the pathoanatomy responsible for the instability is necessary for a successful clinical outcome. In addition, the surgeon must be familiar with the diagnostic imaging and physical examination maneuvers required for the correct diagnosis without missing any other concurrent abnormalities. This understanding will allow orthopedists to plan and execute the appropriate management, whether this may involve conservative or surgical intervention. The goal should always be to correct the abnormality and have the patient return to play with full strength and no recurrent instability.