Using the transverse acetabular ligament as a landmark for acetabular anteversion: an intra-operative measurement

Morphological Characteristics of the Vietnamese Adult Human Acetabulum Using Multiplanar Reconstruction Computed Tomography in Total Hip Replacement Surgery

Background

The anatomical parameters of the acetabulum vary among races and geographical regions. Multislice Computed Tomography (CT) has proven to be a practical approach to assess morphological parameters of the acetabulum. The purpose of this study was to explore morphological characteristics of the acetabulum measured by CT scans in Vietnamese adults.

Methods

Thirty-five consecutive patients aged 18 years and older received indications and eligibility for total hip replacement surgery. Sixty-three acetabulum were examined with multislice computed tomographic system (CT) with multiplanar reconstruction (MPR). Measured morphometric parameters of acetabulum included acetabular inclination angle (AIA), acetabular anteversion angle (AAA), acetabular angle of sharp (AAS), sagittal acetabular angle (SAA), acetabular horizontal offset (AHO), transverse acetabular ligament anteversion (TALA), transverse acetabular ligament inclination (TALI), acetabular depth (ADe), acetabular depth ratio (ADr) and acetabular diameter (ADi).

Results

The mean values of acetabular diameter, femoral head diameter, AIA, AAA, AAS, SAA, TALA, TALI, AHO, ADe, ADr were 50.22±3.56 mm, 43.54±3.68 mm, 40.27±5.09 mm, 13.30±5.54 mm, 39.46±5.41 mm, 26.38±9.01 mm, 9.49±3.92 mm, 47.70±6.73 mm, 3.06±0.37 mm, 18.62±2.95 mm and 309.60±41.87 mm.

Conclusion

Our initial data has showed morphological characteristics of the acetabulum in Vietnamese adults, different from the populations from other parts of world. Also, significant correlation between the orientation of the acetabulum and the transverse acetabular ligament was documented.

Anatomical and Simulation Studies Based on Three-Dimensional-Computed Tomography Image Reconstruction of Femoral Offset

Although the hip joint morphology varies by race, few studies have investigated the associations between two-dimensional (2D) and three-dimensional (3D) morphologies. This study aimed to use computed tomography simulation data and radiographic (2D) data to clarify the 3D length of offset, 3D changes in the hip center of rotation, and femoral offset as well as investigate the anatomical parameters associated with the 3D length and changes. Sixty-six Japanese patients with a normal femoral head shape on the contralateral side were selected. In addition to radiographic femoral, acetabular, and global offsets, 3D femoral and cup offsets were investigated using commercial software. Our findings revealed that the mean 3D femoral and cup offsets were 40.0 mm and 45.5 mm, respectively; both were distributed around the mean values. The difference between the 3D femoral and cup offsets (i.e., 5 mm) was associated with the 2D acetabular offset. The 3D femoral offset was associated with the body length. In conclusion, these findings can be applied to the design of better ethnic-specific stem designs and can help physicians achieve more accurate preoperative diagnoses.

USE OF COMPUTER NAVIGATION IN TOTAL HIP ARTHROPLASTY (LITERATURE REVIEW)

OBJECTIVE

The aim: Analyze the accuracy and ease of use of various computer navigations in total hip arthroplasty.

PATIENTS AND METHODS

Materials and methods: Data from about 50 literature sources for the last two decades have been analysed.

CONCLUSION

Conclusions: Analyzing the accuracy and ease of use of various computer navigations in total hip arthroplasty, we offer two the most promising for further study and improvement systems: a semi-active navigation system and augmented reality system in total hip arthroplasty.

Orientation of Transverse Acetabular Ligament With Reference to Anterior Pelvic Plane

Background

Transverse acetabular ligament (TAL) is a 3-dimensional structure which cannot be defined by a single plane. Therefore, we aimed at describing the orientation of different parts of TAL with respect to anterior pelvic plane (APP) and correlate it with gender, body mass index (BMI), and Lewinnek’s safe zone.

Methods

A total of 109 consecutive patients undergoing imageless navigated THA were prospectively studied. Computer navigation was used as the measurement tool. APP was registered for navigation. After excision of osteophytes, a trial component matching the size of unreamed acetabular cavity was aligned with acetabular rim, outer and inner margins, and middle of TAL to record cup orientation with computer tracker.

Results

Ninety-nine patients (41 males and 58 females, mean BMI of 28.8kg/m²) were studied after applying exclusion criteria. Mean acetabular inclination was 55.15°, 53.00°, 47.70°, and 42.60° respectively, for acetabular rim, outer, middle, and inner margins of the TAL. Corresponding mean acetabular anteversion was 6.63°, 7.41°, 11.23° and 14.90°respectively. Overall, 17.17%, 28.28%, 47.47% and 71.71% of cup orientation corresponding to acetabular rim, outer, middle, and inner margin of TAL respectively, were within Lewinnek’s safe zone. No association was established between BMI and acetabular orientation. Males had overall lesser anteversion than females.

Conclusion

We describe orientation of outer, middle, and inner margins of TAL, as reference planes for TAL, in relation to APP. The anteversion differs significantly with gender. A knowledge about these will assist surgeon in component placement during THA, with inner margin of TAL providing the best chance of orientation out of the studied landmarks.

Lewinnek Safe Zone References are Frequently Misquoted

BACKGROUND

Optimal acetabular component orientation in total hip arthroplasty (THA) is a necessity in achieving a stable implant. Although there has been considerable debate in the literature concerning the safe zone, to date, there has not been any review to determine if these references are consistent with the definition applied by Lewinnek et al. in 1978. Therefore, this article aims to examine the available literature in the PubMed database to determine how often a correct reference to the safe zone as defined by Lewinnek was applied to discussions regarding THA.

METHODS

A search for literature in the PubMed database was performed for articles from 1978 to 2019. Search criteria included terms 'Lewinnek,' 'safe zone,' and 'total hip arthroplasty.' Exclusions included abstract-only articles, non-English articles, articles unrelated to THA, and those lacking full content.

RESULTS

A review of literature yielded 147 articles for inclusion. Overall, only 11% (17) cited the Lewinnek article correctly. Forty-five percent (66) of articles referenced measurements in the supine position, 18% (26) referenced other positions, and 37% (55) did not specify. Nineteen percent (28) reported measurements of the acetabular cup orthogonal to the anterior pelvic plane, while 73% (108) did not, and 7% (11) did not specify. Twenty-three percent (34) measured from computed tomography scans instead of other methods.

CONCLUSIONS

In the discussion of the safe zone regarding THA, only 11% of articles listed are consistent with the definition established by Lewinnek. This warrants further investigation into a consistent application of the term and its implications for THA implant stability and dislocation rates.

"Channel Lines": A Simple Surgical Technique to Aid in Achieving Patient-specific Ante-version During Implantation of Uncemented Acetabular Cups

Accurate acetabular cup placement is a crucial step for a successful total hip replacement. Transverse acetabular ligament is an important and reliable landmark that helps in determining the version during the placement of acetabular cups. However, the visualization of transverse acetabular ligament may not be easy as the view may be blocked by the implants and the instruments. We have devised a simple technique to aid in achieving patient-specific ante-version during implantation of uncemented acetabular cups by using "channel lines."

Placement of the acetabular component

Ideal placement of the acetabular component remains elusive both in terms of defining and achieving a target. Our aim is to help restore original anatomy by using the transverse acetabular ligament (TAL) to control the height, depth and version of the component. In the normal hip the TAL and labrum extend beyond the equator of the femoral head and therefore, if the definitive acetabular component is positioned such that it is cradled by and just deep to the plane of the TAL and labrum and is no more than 4mm larger than the original femoral head, the centre of the hip should be restored. If the face of the component is positioned parallel to the TAL and psoas groove the patient specific version should be restored. We still use the TAL for controlling version in the dysplastic hip because we believe that the TAL and labrum compensate for any underlying bony abnormality. The TAL should not be used as an aid to inclination. Worldwide, > 75% of surgeons operate with the patient in the lateral decubitus position and we have shown that errors in post-operative radiographic inclination (RI) of > 50° are generally caused by errors in patient positioning. Consequently, great care needs to be taken when positioning the patient. We also recommend 35° of apparent operative inclination (AOI) during surgery, as opposed to the traditional 45°.