Reliability of measures used in radiographic evaluation of the adult hip

Evaluating pelvic tilt using the pelvic antero-posterior radiographs: A novel method

Pelvic tilt (PT) is an important parameter for orthopedic surgeries involving hip and spine, typically determined from sagittal pelvic radiographs. However, various challenges can compromise the feasibility of measurement from sagittal imaging, including obscured landmarks, anatomical variations, hardware interference, and limited medical resources. Addressing these challenges and with the aim of reducing radiation exposure to patients, our study developed a novel method to estimate PT from antero-posterior (AP) radiographs, using vertical distances from the pelvic outlet and obturator foramen. We correlated these measurements with PT, defined both anatomically (anterior pelvic plane, PTa) and mechanically (centers of femoral heads and sacral plate, PTm). The study explored creating linear, exponential, and multivariate regression models based on twelve 3D CT-derived pelvic models (six men, six women), simulating AP radiograph projections with controlled PTs. We then validated these models against 105 pairs of patient stereoradiographs. Statistical analysis revealed that combined exponential-linear models yielded the most accurate results, with Pearson correlation coefficients of 0.75 for PTa and 0.77 for PTm, and mean absolute errors of 3.7° ± 2.6° for PTa and 4.5° ± 3.4° for PTm, showing excellent measurement reliability (all ICCs > 0.9) without significant gender discrepancies. In conclusion, this study presents a validated, simple, and accessible method for estimating PT using AP radiograph parameters, supported by the Supporting Information S1: Excel Tool, showing great potential for clinical application in hip and spine procedures.

Variation in pelvic radiography practice: Why can we not standardise image acquisition techniques?

INTRODUCTION

Pelvic radiographs remain an essential investigation in orthopaedic practice. Although it is recognised that acquisition techniques can affect image appearances and measurement accuracy, it remains unclear what variation in practice exists and what impact this could have on decision making.

METHOD

This was a cross sectional survey of UK radiology departments utilising an electronic tool. An introductory letter and link was distributed. Responses were received from 69 unique hospital sites within the specified timeframe, a response rate of 37.9%.

RESULTS

There was no consistent technique for the positioning of patients for pelvic radiographs. The distance varied between 90 and 115 cm and 10 different centering points were described. In relation to leg position, the feet are usually internally rotated (65 of 69 [94.2%]). Only 1 teaching hospital (1 of 69 [1.4%]) uses a weight-bearing position as standard. Orthopaedic calibration devices were not in routine use, with only 21 using on pelvic x-rays (30.4%). Further, the type of device and application criteria were inconsistent.

CONCLUSIONS

To our knowledge this is the first study to directly compare radiographic positioning across hospital sites. Our data demonstrated marked variation in technique for pelvis radiographs with associated implications for clinical decision making. Research is required to determine the standard technique and quality outcome measures to provide confidence in diagnostic interpretation particularly for serial radiographs.

Restoration of the centre of rotation in primary total hip arthroplasty: the influence of acetabular floor depth and reaming technique

AIMS

One goal of total hip arthroplasty is to restore normal hip anatomy. The aim of this study was to compare displacement of the centre of rotation (COR) using a standard reaming technique with a technique in which the acetabulum was reamed immediately peripherally and referenced off the rim.

PATIENTS AND METHODS

In the first cohort the acetabulum was reamed to the floor followed by sequentially larger reamers. In the second cohort the acetabulum was only reamed peripherally, starting with a reamer the same size as the native femoral head. Anteroposterior pelvic radiographs were analysed for acetabular floor depth and vertical and horizontal position of the COR.

RESULTS

Horizontally, the mean medial displacement of the COR was 0.8 mm (standard deviation (sd) 1.4) in the peripheral remaing group and 5.0 mm (sd 3.30) in the standard reaming group (p < 0.001). Vertically, the mean superior displacement of the COR was 0.7 mm (sd 1.3) in the peripheral reaming group and 3.7 mm (sd 2.6) in the standard reaming group (p < 0.001). In the standard reaming group, there was a strong correlation between the pre-operative acetabular floor depth and displacement of the COR (p < 0.001).

CONCLUSION

Reaming the acetabulum to the floor can lead to significant displacement of the COR medially and superiorly. This displacement is related to the pre-operative acetabular floor depth and cannot always be compensated by using a high offset stem. Cite this article: Bone Joint J 2016;98-B:1597-603.

Changes of center of rotation and femoral offset in total hip arthroplasty

BACKGROUND

It is a challenge to reconstruct the center of rotation (COR) and femoroacetabular offset anatomically in total hip arthroplasty (THA). We addressed the controversy how we manage to preserve the COR and femoroacetabular offset with an uncemented total hip prosthesis implanted with free hand technique.

METHODS

We analyzed a prospective series of 73 patients who underwent primary THA. The series was composed of 40 females and 33 males, mean age 64 years (range, 35-90 years). The reasons for THA were primary osteoarthritis (n=63) and developmental dysplasia of the hip (n=10). Pre- and postoperative X-rays were done in a standardized format for anterior-posterior (AP) radiographs of the pelvis, and digitalized measurements were done using SectraTM. We compared preoperative measurements with the final outcome to determine changes in COR and femoral offset.

RESULTS

We found that 40 patients had their COR and 34 patients had their femoral offset preserved within preoperative 5.0 mm limits. Twenty-three patients had both their values of COR and femoral offset preserved within 5.0 mm limits. While a significant correlation was found between changes of femoral and global offset (r=0.786, P<0.001), there were no correlation between changes of acetabular and femoral offset (r=-0.027, P=0.822).

CONCLUSIONS

Using an uncemented THA and free hand technique, there is a fair reproducibility of anatomy. The variations were mostly minor, but our results indicate a potential for better restoring the location of COR and femoral offset when planning and implanting an uncemented THA.