Introduction: Radial Tunnel Syndrome is characterised by pain over the anterolateral proximal forearm. It is thought to result from compression of the posterior interosseous nerve, and is estimated to be present in 5% of tennis elbow syndrome. This condition has been treated with surgical decompression with varying success. Other nerve compression syndromes are treated with steroid injections and these are reliable in giving relief, even if only temporary. Blind injections have been used as a diagnostic tool in Radial Tunnel Syndrome, but guided steroid injections have not yet been evaluated.

Methods: Patients attending one hospital over three years with unresolved lateral epicondylitis were clinically diagnosed with radial tunnel syndrome. They underwent injection of the radial tunnel guided by a nerve stimulator. The patients were evaluated prior to the injection with a brief pain inventory score produced by the British Pain Society. They were evaluated three months after the injection with a further brief pain inventory score. The scores were compared with Student’s t test.

Results: Ten patients were recruited over three years. The average pain score before and after injection was not significantly different ( P = 0.4386). An interference score reflecting impeding of function as a result of pain was also not significantly different ( P = 0.095).

Discussion: The results of guided injection are worse than a series of blind injections in the literature. We question why this has occurred when the opposite would have been expected. There are several possible explanations. There may have been a double hit phenomenon with the injection only affecting one of two pathological areas. The area of compression may be more proximal to the site of injection. The pathology of radial tunnel syndrome has not been definitively described and the pathology may not be one suitable for treatment with a steroid injection. Post mortem examination of the posterior interosseous nerve in patients with this syndrome may reveal the pathology of the syndrome.

Conclusion: Guided injections for radial tunnel syndrome are not effective. The pathology of this syndrome may be different to conventional nerve compression syndromes. We question indications for surgical decompression and suggest further work to investigate this syndrome.