Arthroscopy of the Elbow in Clinically Normal Dog Using the Caudal Portals
The technique of arthroscopy of the elbow joint using the caudal portals is described. It was developed on six cadavers and six experimental dogs and allows a direct visualization of the olecranon fossa, caudo-lateral, caudo-medial and cranial compartments of the elbow joint. Arthroscopy of the caudal aspect of the elbow joint appears safe and reliable. None of anatomical structures are at risk on the caudal aspect of the elbow joint.
Since the first description of diagnostic arthroscopy of the elbow in dogs in 1993 (1), the procedure has been used for both diagnostic and therapeutic purposes (2-7). In small animal surgery, the most common approach to the elbow has been from the medial portal (1, 2, 4, 6). This medial approach has been used to expose and excise the fragmented medial coronoid process and cartilage flaps that result from osteochondritis (4, 6). However, the excision of loose fragments and the percutaneous treatment of non-dis-placed medial condylar fractures of the humerus requires adequate visualization of the cranial compartment of the elbow joint (2-4). A thorough examination of the elbow joint requires the exploration of its three compartments: medial, cranial and caudal humero-radial-ulnar joint spaces. The goal of this paper is to describe normal arthroscopic anatomy of the elbow in dogs using caudal portals for elbow arthroscopy (2).
Material and Methods
The instrument used consisted of a 2.7 mm 30° fore-oblique arthroscope with a 3.5 mm diameter arthroscopic sleeve. Light was supplied with a Xenon light source. The arthroscopic procedure was captured by a camera that was mounted on the scope and visualized on a monitor. The joint was distended and irrigated with Lactate Ringer solution. This procedure was documented by printed colour photographs and recorded on videotape.
Arthroscopy of the elbow requires a complete understanding of the regional anatomy. A thorough knowledge of both superficial and intra-articular structures is mandatory. Therefore, the bony, capsular, ligamentous, muscular, and tendinous structures of the elbow joint were identified in six cadavers (8) (Figs. 1-4). It is important to note that there are no any neurovascular structures on the caudal and caudo-lateral aspect of the elbow joint. This allows a risk free approach for arthroscopic procedures.
An experimental study on the arthroscopic anatomy of the elbow was performed in order to locate appropriate puncture sites. The study was per-formed in six normal canine patients weighing 30-40 kg. Each dog was anaesthetised and positioned in sternal recumbency with the elbow placed on the edge of the surgical table (Fig. 5). The front limb was prepared aseptically and draped allowing full mobility. The elbow was punctured (4) with a 19 gauge needle at the caudo-dorso-lateral portal (2). The puncture site was located medial to the lateral epicondylar ridge and cranial to the olecranon tuberosity pointing toward the olecranon fossa (Fig. 3). Lactate Ringer's solution (10-15 nil) was injected into the joint. After confirming that the joint capsule was dis-tended, the needle was replaced by the 3 mm egress cannula (8).
The caudo-lateral portal was located next by placing a 19 gauge needle halfway between the lateral epicondyle and cranial edge of the olecranon tuberosity (Fig. 1). These bony structures were identified by deep palpation (Table 1). The ideal location was above the dorsal aspect of the lateral epicondylar ridge and lateral to the olecranon process (Fig. 1). This portal allowed direct visualisation of the olecranon fossa, as well as the lateral compartment of the elbow joint. After incising the skin and joint capsule with a #11 scalpel blade, the arthroscopic sleeve was inserted into the joint and directed toward the olecranon fossa using a blunt trocar (Fig. 6). Upon penetration of the joint, the blunt trocar was replaced by the arthroscope. Systematic examination of the caudal olecranon fossa and caudo-lateral compartment of the elbow joint was then performed starting with: the olecranon, the olecranon fossa, the medial and lateral epicondylar ridge, the caudo-lateral recess and the lateral compartment of the elbow (Table 1).
In order to properly visualize the caudal compartment of the elbow joint a caudo-dorso-lateral portal was created 1 to 1.5 cm dorsal and 1 to 1.5 cm medial to the caudo-lateral portal (Table 1). This portal was located over the olecranon fossa and allowed direct penetration through the olecranon foramen into the cranial recess. In order to view the caudo-medial recess of the elbow either a central portal through the triceps tendon (Fig. 3) or a caudo-medial portal was required (Table 1). The straight caudo-lateral portal was more ventrally located in the soft spot that was identified by digital palpation, in the center of the triangle made of the later epicondyle, radial head and olecranon tuberosity (Fig. 3) (Table 1). Evaluation of the lateral humeroradio-ulnar compartment was best visualized with the light source of the arthroscope at the "7 o'clock position" for the left elbow and "5 o'clock position" for the right elbow. Other accessory portals may be used as instrumental portals (Fig. 4) (Table 1). In all of the joints, the following structure could be identified by moving the tip of the arthroscope from the caudo-lateral portal into the olecranon fossa: the dorsal aspect of the anconeal process (Fig. 6, 7), olecranon fossa (Fig. 6. 7), the medial and lateral epicondylar ridges (Fig. 6, 7), the humeral trochlea (Fig. 7) and the caudo-lateral recess (Fig. 9). If the scope was moved hack and ventrally, one could then identify the caudal edge of the lateral epicondylar ridge (Fig. 9), and the lateral compartment of the elbow which includes the lateral humeral condyle, lateral coronoid process and radial head (Fig. 10). The lateral humero-radio-ulnar compartment was best visualized by the straight lateral portal (Fig. 10).
The caudo-dorsolateral or the caudo-central portals were the best for penetrating through the olecranon foramen and visualizing the cranial recess of the elbow, radial head, annular ligament, and the cranial humeral condyle (Fig. 1). The medial recess was best seen through the caudo-medial portal (Table 1, Fig. 12). Technical problems such as haemorrhage, obstruction of the view by synovial villi, and insufficient exposure of the articular cartilage were not observed (Fig. 11). None of the dogs showed any signs of pain during the post-operative physical examinations.
Since the first description of elbow arthroscopy in clinically normal dogs (1), the medial portal gained popularity for the diagnosis and treatment of fragmented coronoid process and osteochondritis dissecans lesions of the medial condyle (3, 5, 6). It allows excellent visualization of the medial compartment of the elbow joint (1) but the cranial, caudal olecranon and caudo-lateral compartment cannot be explored. Iatrogenic damage of the articular cartilage surface of the medial humeral condyle and of the medial coronoid process is possible, even in the hands of the best trained surgeon. Because of the potential danger (1, 3, 15) in human medicine it is improper to have the approach made in between two articular cartilage surfaces. In one study of 148 elbow joint arthroscopies, 14 joints showed signs of degenerative joint disease without a fragmented medial coronoid process (5) justifying the development of the cranial and caudal portals to look for other causes of joint degeneration. The cranio-lateral and cranio-medial portals were subsequently developed to explore the cranial compartment of the elbow joint (2). These portals have been used to: remove fragmented medial coronoid processes (3) or loose bodies (3), reduce medial condylar humeral fractures (4), excise large osteophytes of the radial head in severe degenerative joint disease (7), and excise multiple mice associated with synovial chondromatosis (9). Thorough examination of the elbow joint also requires the exploration of the caudal and caudo-lateral compartments. Further indications for caudal portals include the removal, or fixation, of ununited anconeal process, excision of osteophytes of the olecranon fossa and anconeal process, removal of loose bodies, per of synovial biopsies, treatment of septic arthritis and evaluation of pain of unknown origin (8) (Table 1). One of the benefits of the caudo-lateral portals over the caudo-medial portal is that major neurovascular structures are not at risk. The ulnar nerve on the caudo-medial surface of the elbow does increase the risk of iatrogenic nerve trauma. Therefore, since the medial compartment of the elbow maybe explored using the medial portal it is wise to avoid using the caudo-medial portal altogether. The caudo-central portals require an incision of the tendon of the triceps muscle. The author prefers the caudo-dorso-lateral portal when the triceps is displaced medially and protected from iatrogenic damage. The caudo-lateral portal allows the exploration of both the olecranon fossa and caudo-lateral recess of the elbow. The accessory caudo-lateral (1 cm above the caudo-lateral of the caudo-dorso-lateral portals) is preferred to excise the osteophytes of the anconeal process and fossa and for the removal or fixation of the olecranon process. During these procedures, the probe may he used as a retractor through the dorso-medial portal elevating the triceps tendon and improving the field of vision. Since the first description of diagnostic arthroscopy of the elbow joint in dogs (1), many indications have been developed both for diagnostic and therapeutic uses: removal of fragmented coronoid processes, excision of loose cartilage fragments, excision or fixation of the ununited anconeal process, treatment of severe invalidating degenerative joint disease of the elbow joint, treatment of septic arthritis, evaluation of chronic elbow instability and performance of synovial biopsies. The elbow may be safely explored entirely using several portals. A dog's elbow joint is a complex hinge joint that requires multiple portals for proper exploration. All compartments of the elbow should be thoroughly examined, as it is done in human arthroscopy. Our patients will benefit from the experience gained in human medicine (13-15).
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