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Orthopaedic Proceedings

Vol. 100-B, Issue SUPP_13 | Pages 41 - 41

1 Oct 2018

THE ARGUMENT FOR MURRAY “ANATOMIC CRITERIA” FOR MEASURING ACETABULAR CUP POSITION RATHER THAN THE COMMONLY USED “RADIOGRAPHIC CRITERIA”

Tatka J Brady AW Matta JM

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Introduction

Accurate acetabular position is an important goal during THA. It is also well known that accurate acetabular positioning is very frequently not achieved, even by experienced, high volume surgeons. Problems associated with cup malposition are: dislocation, accelerated poly wear, impingement, ceramic squeaking, metalosis. Murray et al described 3 methods of measurement and assessment of acetabular inclination and anteversion (I&A): anatomic, radiographic and operative. It is the hypothesis of the authors, that the differences and details of these 3 methods are poorly understood by many surgeons and this is contributory to inconsistent cup positioning. Additionally, the radiographic method, which is most commonly used for post op assessment and academic studies, contributes to misunderstanding and error. Modern computer guidance and software assessment of radiographs allows us to easily measure anatomic I&A which should be thought of as “true” I&A.

Methods

The mathematical criteria for radiographic measurement of anatomic I&A are defined as well as the mathematical relationships and discrepancies between anatomic and radiographic I&A for any given cup.

$\begin{matrix} A = A n g l e o f a n t e v e r s i o n o f c u p \\ I = A n g l e o f i n c l i n a t i o n o f c u p \end{matrix}$

E = Angle of ellipse major diameter to horizontal

E = Radiographic inclination

$\begin{array}{l} Sin A = \frac{H o r i z o n t a l w i d t h o f e l l i p s e}{L e n g t h o f e l l i p s e m a j o r d i a m e t e r} \\ Sin I = \frac{V e r t i c a l h e i g h t o f e l l i p s e}{L e n g t h o f e l l i p s e m a j o r d i a m e t e r} \end{array}$

Tan I = Tan E / Cos A

Tan E = (Tan I) x (Cos A)

Orthopaedic Proceedings

Vol. 84-B, Issue SUPP_I | Pages 67 - 67

1 Mar 2002

LETOURNEL CLASSIFICATION FOR ACETABULAR FRACTURES: EVALUATION OF INTER- AND INTRA-OBSERVER REPRODUCIBILITY

Beaulé PE Dory F Matta JM

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Purpose: A classification system for fractures is an important communication tool for surgeons allowing the development of management schemes as well as an estimation of the prognosis. The purpose of our work was to evaluate the inter- and intra-observer reproducibility of the Letournel classification system for acetabular fractures.

Material methods and results: Sixty-five x-rays (AP and Judet views) and computed tomography (CT) series were chosen at random from a data base containing 800 fractures. The distribution of the fracture types followed data in the literature. Three groups of observers were formed, each composed of three orthopaedic surgeons. Group 1 included surgeons who had studied with Letournel, group 2 surgeons specialised in acetabular fractures, and group 3 surgeons qualified for general traumatology surgery. The kappa coefficient was determined to assess agreement between observers. Each observer read the images twice without knowledge of the treatment. The observers first classed the fractures using the x-rays alone then with the x-rays in combination with the CT. Two sessions were organised, two months apart to avoid any possible memorisation. Reproducibility without then with CT for the first session were: group 1: 0.07 and 0.74; group 2: 0.71 and 0.69; group 3: 0.51 and 0.512. Results were similar in the second session. Intra-observer reproducibility without then with CT was: group 1: 0.80 and 0.83; group 2 0.80 and 0.80; group 3: 0.64 and 0.69. Among the six more experimented observers (groups 1 and 2), 100% agreement was found for 66% of the x-rays compared with 22% for the new observers.

Discussion and conclusion: The Letournel classification system using x-rays in combination or not with CT is reliable (kappa > 7) for properly trained surgeons with regular experience in treating acetabular fractures. The value of the CT in the assessment of acetabular fractures is well established for identifying detached elements and joint crush. Conversely, CT does not appear to be essential to class ace-tabular fractures. The Letournel classification can be used as a reliable tool for the description of acetabular fractures and taught to surgeons desiring to undertake regular treatment of these fractures.

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