How to Radiographically Localize the Entheses of the Equine Stifle Joint

1. Introduction

Radiography of the equine stifle is an important diagnostic tool for visualization of bony changes. Unfortunately, there is limited information describing the precise radiographic location of the soft tissue attachments (entheses) within the joint.^1–3 We describe the anatomical location of most entheses of the equine stifle using four radiographic projections: caudocranial, lateromedial, caudolateralcraniomedial, and caudomedial-craniolateral.

2. Materials and Methods

The entheses corresponding to the cranial and caudal cruciate, meniscal, and collateral ligaments and the popliteal, common digital extensor, and peroneus tertius tendons were consistently localized on dissection of six equine stifle joints. A bone specimen of the equine stifle was assembled, using harvested menisci from a different horse for adequate positioning of the femoral condyles in relation with the tibial condyles. A string was used in a loop fashion across the femoral and tibial condyles to provide further stability to the joint. The patella was fixed, mimicking the normal weight-bearing location, using Play-Doh.

This bone specimen was then radiographed using four projections (caudocranial, lateromedial, caudolateral-craniomedial oblique, and caudomedialcraniolateral oblique) with barium paste on the precise location of every enthesis or pair of entheses (origin and insertion) corresponding to each structure mentioned above. Each structure was marked and radiographed individually. The radiographic projections were evaluated, and key osseous landmarks for the entheses were determined on the basis of radiographic localization and comparison with a dissected plastinated specimen.

3. Results

A total of 40 radiographic projections of the stifle specimen were obtained. Each enthesis was successfully localized, based on the barium marking on the bone specimen. Distinct radiographic landmarks were identified for all entheses. Figures 1 through 7 are representative radiographs that demonstrate the location of different entheses.
 

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