Introduction

Arthroscopy is a minimally invasive surgical technique. Intra-articular structures can be visualised by inserting an arthroscope, a rigid fibreoptic endoscope, into the joint via a small stab incision ('key-hole' surgery). The elbow, shoulder and stifle are the joints most commonly evaluated with arthroscopy. Less commonly assessed joints include the carpus, tarsus and hip. The elbow, shoulder and stifle will be covered in this lecture.

Joint pathology which can be diagnosed or managed using arthroscopy includes:

 Elbow--medial coronoid disease/fragmented coronoid process; united anconeal process; osteochondritis dissecans (OCD) of the medial humeral condyle; joint incongruency; incomplete ossification of the humeral condyles

 Shoulder--OCD of the humeral head or caudal glenoid; biceps tendinopathy; glenohumeral ligament damage

 Stifle--cranial cruciate ligament rupture; meniscal injury; OCD of the femoral condyles

Arthroscopy can be used as a diagnostic tool to assess intra-articular structures or for the management of certain conditions by removing loose cartilage or osteochondral fragments, debridement of intra-articular structures or transecting tendons.

Arthroscopy has certain advantages over exploratory arthrotomy, such as: gaining an improved and magnified view of the intra-articular structures; fewer postoperative complications; decreased periarticular dissection and therefore, in theory, there is decreased morbidity and discomfort. Potential complications include fluid extravasation, iatrogenic cartilage damage and, with inexperience, failure to recognise lesions.

Arthroscopy Equipment

Arthroscopes

For small animal arthroscopy 1.9 mm, 2.4 mm and 2.7 mm diameter arthroscopes are used. The arthroscope has an eyepiece and objective lens at opposite ends. The objective lens can be flat (0 degrees), or oblique (30 degrees or 70 degrees) to increase the field of view. A 30-degree angle is most commonly used. The arthroscope is protected by an arthroscopic cannula. The cannula requires an obturator, blunt or pointed, to facilitate placement into the joint. The cannula has a channel to allow lavage solution to flow, which maintains intraoperative distension of the joint and improves visualisation.

Arthroscopic Camera

This attaches to the eyepiece and allows the image to be viewed on a monitor.

Arthroscopy Tower

This comprises:

 Monitor--the arthroscopy image is transmitted on to this screen.

 Light source--illuminates the joint via a fiberoptic cable. Xenon bulbs are recommended as they offer increased light intensity and superior colour, but they are more expensive than tungsten-halogen bulbs. Repeatedly switching the bulb 'on' and 'off' can cause it to burn out. Always have a spare in case the bulb fails during a procedure.

 Image capture unit--allows documentation of the procedure with stills and/or video.

 Irrigation system--gravity flow can be used but a fluid compression bag can provide increased pressure. Arthroscopic pumps offer precise control of fluid flow. Recommended pressure for smaller joints is 65-80 mmHg.

 Powered equipment--motorised shavers and radiofrequency/electrocautery units can be used for arthroscopic surgical procedures.

Hand Instruments

 Probes--a right-angled tip allows probing of the articular cartilage, menisci, OCD flaps and osteochondral fragments. Measurement markers allow more accurate sizing of lesions.

 Forceps--grasping forceps, with or without a locking handle, are used to remove unwanted tissue. Biopsy forceps are used to sample tissue for analysis.

 Arthroscopic knives--used to treat meniscal injuries, for tenodesis (transecting a tendon) or sectioning soft tissue attachments to bony fragments.

 Curettes--used to debride cartilage and/or bone.

 Hand burr--used to debride cartilage and/or bone.

Instrument Cannulae

These provide access to the joint; allow smoother changing of instruments; make finding the instrument portal easier; and decrease fluid extravasation. Switching sticks are used to introduce a cannula into the joint or to change cannulae during the procedure.

Instrument Care and Sterilisation

Hand instruments can be autoclaved similarly to other surgical equipment. Only certain arthroscopes are autoclavable. Autoclaving reduces the life expectancy of an arthroscope due to heat damage, so cold sterilisation is often preferred. This is performed by soaking the arthroscope in a glutaraldehyde solution for 20-30 minutes. Be sure to thoroughly clean the arthroscope after soaking, by rinsing with lavage solution, as the glutaraldehyde solution is cytotoxic and can cause significant tissue reaction.

Preparation for Surgery

Patient Preparation and Positioning

The patient is anaesthetised and perioperative analgesia and antibiosis administered. For elbow arthroscopy the patient is placed in lateral recumbency with the surgical limb most dependent. The elbow is placed at the edge of the table or over a sandbag. The upper limb is drawn caudally. The portals are created medially. If bilateral elbow arthroscopy is being performed, the patient may be in dorsal recumbency with both elbows abducted. Shoulder arthroscopy requires the patient to be in lateral recumbency with the surgical limb uppermost; the portals are created laterally or cranially. For stifle arthroscopy the patient is placed in dorsal recumbency; the portals are created craniomedially and craniolaterally.

The surgical site is clipped and surgically prepared as for routine surgery. For thoracic limb arthroscopy, the entire limb can be clipped and prepared for surgery and free-limb draping can be performed. This allows easier manipulation of the limb during the procedure. With elbow and shoulder arthroscopy, a clip extending ~10-15 cm from the intended portal sites may be adequate. With stifle arthroscopy the entire limb is clipped and prepared for surgery and free-limb draping is performed. Always check the required clip with the surgeon prior to surgery. Once in theatre, the patient is fully draped with the operative area exposed. An adhesive drape with a fluid collection pocket is applied to the skin.

Theatre Preparation

The arthroscopy tower should be close to the table and in full view of the surgeon. The surgeon, patient and monitor should be positioned in a straight line, which allows easier orientation during the procedure and prevents the surgeon from straining to see the monitor.

Once all the equipment is opened and the theatre trolley prepared, the theatre nurse should connect the fluid irrigation system to the lavage solution (lactated Ringers or 0.9% saline). The monitor, image capture unit and powered equipment (if required) are switched 'on'. The arthroscopic camera and cable are covered with a protective sterile sheath and the arthroscope is attached. The light cable is connected to the light source but not switched 'on' until the surgeon is ready. This prolongs the longevity of the bulb and prevents the light from burning the drapes and/or patient.

Surgery

Arthrocentesis is performed to ensure the needle is within the joint. The synovial fluid can be kept for analysis if required. The joint is distended with 5-15 ml of lavage solution. The arthrocentesis needle can remain in situ as an egress needle or a separate one can be placed later in the procedure. A needle is placed into the joint at the intended site for the arthroscope portal. A stab incision, alongside the needle, is created superficial to the joint capsule. The needle is removed and the arthroscopic cannula, with a blunt obturator, is inserted through the joint capsule into the joint. The obturator is removed and the arthroscope is placed inside the cannula and securely connected. The light cable and irrigation fluid tubing are connected. Fluid pressure and flow are established. This can be monitored and adjusted by the theatre nurse. Arthroscopic assessment of the joint is performed and images acquired as necessary. Placement of an instrument portal is performed using a needle under arthroscopic guidance (triangulation). A stab incision is created alongside the needle (as above) and a switching stick placed into the joint. An instrument cannula is slid over the switching stick and into the joint. Instruments can now be inserted and surgery/manipulations performed. Any further images are collected and saved, and the instruments are removed. Closure of the skin alone is adequate.

As a surgical assistant you will be required to help with positioning of the patient. Intraoperative flexion, extension, traction or pressure, to 'open-up' certain areas of the joint, can improve the visualisation of intra-articular structures. You may be required to pass instruments during the procedure; therefore familiarising yourself with the equipment prior to surgery is recommended.

After Surgery

Patient Care

An intra-articular injection of bupivacaine and/or morphine is administered for analgesia. Further opiate therapy is provided, as necessary for the next 24 hours. Non-steroidal anti-inflammatory drug therapy is administered postoperatively. A sterile adhesive dressing is placed over the surgical site. Patients are often discharged the day following arthroscopy, although the procedure is well tolerated and some cases can be managed as day patients.

Equipment Care

The surgical equipment should be rinsed as soon as the procedure is finished. The camera lens can be cleaned with surgical spirit. Enzymatic cleaners can be used to clean both the arthroscope and instruments. Hand instruments but not the arthroscope can be cleaned in an ultrasonic cleaner. The instruments are packed and autoclaved for the next procedure. The arthroscope is cleaned, dried, visually inspected for damaged areas, which show up as unclear/black spots, and placed in a padded box until the next usage. The light cable can be packed and autoclaved or stored for cold sterilisation before the next procedure.

References

1.  Beale BS, Hulse DA, et al. Small animal arthroscopy. Philadelphia: WB Saunders, 2003.