When choosing a racket, choose one with slightly more flex, such as one made from composite materials, eg. fibreglass and graphite combo. This will be more forgiving of any miss hits and lessen the strain on your arm. The type of string used in the racket is as important as the racket itself.

Natural gut has a high degree of elasticity which gives it its 'lively' feel, and hold its tension relatively well. Unfortunately it also tends to be more expensive and sensitive to weather. Synthetic strings are more durable and generally less expensive but don¹t tend to have the elasticity of natural gut. Modern manufacturing techniques are constantly improving and have however, brought the play characteristics of synthetics more in-line with natural gut.

As yet there's no clear scientific evidence showing that using a vibration dampener will prevent tennis elbow, and there's no evidence that the vibrations alone, transmitted to the arm from striking a ball, will cause tennis elbow. The pain experienced by tennis elbow sufferers is primarily due to inflammation of tendons on the lateral side of the elbow. This is generally an overuse injury of the forearm muscles resulting from accumulated microtrauma in the tendons.

As a result it's more common in the over 30's or those using a single-handed backhand technique. For those who already have tennis elbow symptoms, using a vibration dampener would no doubt make hitting more comfortable. What research has shown us, however, is that there are a lot of other things you can do to reduce the amount of shock and vibration transmitted to the arm.

These include checking your technique, improving your skill level (take some lessons), becoming stronger, gripping the handle firmly but not too tight, avoid holding too high or too low on the racket handle, checking your using the correct grip size for your hand, trying to hit the ball using the 'sweetspot' on the strings, increasing the size of your racket head, using rackets of standard length only, loosening your string tension, using good quality strings, preferably natural gut, and using a cushioned overgrip on the handle.

with thanks to Andy Ireland, LTA Physiotherapist offers tips on how to prevent 'Tennis Elbow'.

Extract from Wikipedia:
Cortisone injections
In four clinical trials comparing corticosteroid injection to placebo (lidocaine) injection that show no effect of the steroids. Complications from repeated steroid injections include skin problems such as hypopigmentation and fat atrophy leading to indentation of the skin around the injection site.

Exercises and stretches
There are several recommendations regarding prevention, treatment, and avoidance of recurrence that are largely speculative including:

1.Stretches and progressive strengthening exercises to prevent re-irritation of the tendon;[18]
2.Progressive strengthening involving use of weights or elastic theraband to increase pain free grip strength and forearm strength;
3.Racquet sport players also are commonly advised to strengthen their shoulder rotator cuff, scapulothoracic and abdominal muscles by Physiotherapists to help reduce any overcompensation in the wrist extensors during gross shoulder and arm movements;
4.Soft tissue release or simply massage can help reduce the muscular tightness and reduce the tension on the tendons; and
5.Strapping of the forearm can help realign the muscle fibers and redistribute the load.
6.Use of a racket designed to dampen the effect of ball striking.

There is little evidence to support the value of these interventions for prevention, treatment, or avoidance of recurrence of lateral epicondylosis.