Tilt and Rotation Correction of Acetabular Version on Pelvic Radiographs

Background Pelvic tilt can affect the presence of the ischial spine sign and crossover sign. Numerous studies of pelvic tilt on radiographic measurements of pincer impingement have shown that increasing anterior tilt is associated with more radiographic signs of pincer impingement. However, to our knowledge, no study has directly compared supine and standing plain radiographs in patients with respect to lateral center-edge (LCE) angle, acetabular inclination, crossover sign, and ischial spine sign. Questions/purposes The purpose of this study was to evaluate the differences in supine and standing AP pelvis radiographs as they relate to the radiographic parameters of pincer impingement in an adult population evaluated for femoroacetabular impingement, specifically intrapelvic distances (sacrococcygeal to symphysis [SC-S] and coccyx tip to symphysis [T-S]), crossover sign (presence and percentage), LCE angle, inclination, and ischial spine sign.Methods Between August 2013 and June 2014, we obtained supine and standing radiographs for all new patients younger than 60 years who were evaluated for hip pain, when the diagnosis of fracture was not being considered; these formed the basis of this retrospective study. Patients were excluded if they had arthritis (Tönnis grade C 2), lumbar fusion, previous hip surgery, or malrotated films. Forty-six hips, symptomatic side, met the inclusion criteria (age of patients, 33 ± 14 years; 13 males, 33 females). Radiographic data that were collected included SC-S distance, T-S distance, LCE angle, acetabular inclination, presence and percentage of crossover sign, and presence of ischial spine sign. A paired t-test was used to compare continuous variables and chi-square test was used for categorical variables. Two independent readers performed measurements.Results From supine to standing films, the T-S distance decreased from 19 ± 18 mm to 6 ± 19 mm (p \ 0.001), and SC-S distance decreased from 47 ± 19 mm to 32 ± 20 mm (p \ 0.001), indicating less pelvic tilt in the standing position. The number of hips that had crossover signs decreased from supine (n = 18, 39%) to standing (n = 9, 20%) (p = 0.039). The amount of crossover decreased from 23% ± 10% to 11% ±13% (p \ 0.001). LCE angle did not change (27°± 7°to 27°± 8°) (p = 0.64) and inclination angle increased by a small amount (4.2°± 5°to 5.3°± 5°) (p = 0.002). The ischial spine sign decreased from supine (n = 20, 43%) to standing (n = 7, 15%) position (p = 0.003). Conclusions There is a decrease in the amount of pelvic tilt on standing AP pelvis radiographs resulting in a decrease in the incidence and amount of crossover sign and ischial spine sign, and a small increase in inclination. Standing radiographs should be the standard in evaluation of nonarthritic hip pain, specifically pincer femoroacetabular impingement. Surgeons should use caution in

Section: Methodsmentioning

confidence: 99%

Supine and Standing AP Pelvis Radiographs in the Evaluation of Pincer Femoroacetabular Impingement

Jackson¹,

Estess²,

Adamson³

2016

“…Mixed-type FAI had features of both cam-and pincer-type of FAI on conventional radiographs (Table 1). A contraindication for surgical treatment during the time of this study was advanced OA, defined as a Tönnis grade [45] of III. Preoperative clinical evaluation was performed by different observers and included the patient history, anterior impingement test [44], and full goniometric ROM.…”

Section: Methodsmentioning

confidence: 99%

Surgical Hip Dislocation for Treatment of Femoroacetabular Impingement: Factors Predicting 5-year Survivorship

Steppacher

Huemmer

Schwab

et al. 2014

Background Patients with femoroacetabular impingement (FAI) often develop pain, impaired function, and progression of osteoarthritis (OA); this is commonly treated using surgical hip dislocation, femoral neck and acetabular rim osteoplasty, and labral reattachment. However, results with these approaches, in particular risk factors for OA progression and conversion to THA, have varied. Questions/purposes We asked if patients undergoing surgical hip dislocation with labral reattachment to treat FAI experienced (1) improved hip pain and function; and (2) prevention of OA progression; we then determined (3) the survival of the hip at 5-year followup with the end points defined as the need for conversion to THA, progression of OA by at least one Tönnis grade, and/or a Merle d'Aubigné-Postel score less than 15; and calculated (4) factors predicting these end points. Methods Between July 2001 and March 2003, we performed 146 of these procedures in 121 patients. After excluding 35 patients (37 hips) who had prior open surgery and 11 patients (12 hips) who had a diagnosis of Perthes disease, this study evaluated the 75 patients (97 hips, 66% of the procedures we performed during that time) who had a mean followup of 6 years (range, 5-7 years). We used the anterior impingement test to assess pain, the Merle d'Aubigné-Postel score to assess function, and the Tönnis grade to assess OA. Survival and predictive factors were calculated using the method of Kaplan and Meier and Cox regression, respectively. Results The proportion of patients with anterior impingement decreased from 95% to 17% (p \ 0.001); the Merle d'Aubigné-Postel score improved from a mean of 15 to 17 (p \ 0.001). Seven hips (7%) showed progression of OA and another seven hips (7%) converted to THA Survival free from any end point (THA, progression of OA, or a Merle d'Aubigné-Postel \ 15) of well-functioning joints at 5 years was 91%; and excessive acetabular rim trimming, preoperative OA, increased age at operation, and weight were predictive factors for the end points. Conclusions At 5-year followup, 91% of patients with FAI treated with surgical hip dislocation, osteoplasty, and labral reattachment showed no THA, progression of OA, or an insufficient clinical result, but excessive acetabular trimming, OA, increased age, and weight were associated with early failure. To prevent early deterioration of the joint, excessive rim trimming or trimming of borderline dysplastic hips has to be avoided.

“…As such, their technique is unable to provide quantitative assessment of the actual amount of crossover. Other techniques do not provide accurate measurements of the length and width of crossover [3,4,23]. Our proposed technique provides consistent, quantitative measurement of the length and width of crossover, thereby defining the amount of overhanging acetabular rim.…”

Section: Discussionmentioning

confidence: 95%

“…We defined the inclination of the pelvis according to the method of Tannast et al [23]. For consistency, neutral position for each pelvis was defined at an angle of 60°between the sacral promontory and the pubic symphysis.…”

Section: Methodsmentioning

confidence: 99%

“…Furthermore, defining the anterior and posterior rims on AP radiographs can be difficult [12]. Several methods [3,17,23] have been proposed to eliminate the effect of pelvic tilt on the appearance of the crossover sign. Dandachli et al [4] showed the crossover sign has a high predictive value, although a low specificity, for depicting acetabular version when compared with 3-D CT data.…”

Section: Introductionmentioning

confidence: 99%

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A Quantitative Method to Assess Focal Acetabular Overcoverage Resulting From Pincer Deformity Using CT Data

Murphy

Subhawong

Chhabra

et al. 2011

Background Current assessment techniques for focal acetabular overcoverage are neither consistent nor quantitatively accurate. Questions/purposes We propose: (1) a method to precisely quantify the amount of focal acetabular overcoverage in a patient's pincer deformity based on CT data; (2) to evaluate the consistency of this method; and (3) to compare the method with conventional radiographic assessments.Methods We developed a method to assess focal acetabular overcoverage using points selected from CT scans along the acetabular rim after realigning the pelvis into a neutral position. Using four resampled and segmented pelvic CT scans of cadaveric specimens with virtually induced impingement, two observers independently tested the algorithm's consistency. Our algorithm assessed the amount of focal acetabular overcoverage using CT data and projected data from reconstructed radiographs. Results (1) We successfully showed the feasibility of the software to produce consistent, quantitative measurements. (2) Testing showed the average difference between observers in aligning the pelvis was 0.42°, indicative of a consistent approach. (3) Differences between measurements on three-dimensional (3-D) CT and simulated radiographs were significant. Conclusions The proposed method represents a new avenue in consistently quantifying focal acetabular overcoverage using CT models while correcting for pelvic tilt and rotation. Our analysis confirms AP hip radiograph simulations overestimate the amount of overhanging acetabular rim in a pincer deformity. Clinical Relevance This technique has potential to improve preoperative diagnostic accuracy and enhance surgical planning for correction of a pincer deformity resulting from focal acetabular overcoverage.