Shares in Tissue Regenix jumped on Tuesday, after the producer of devices for regenerative medicine said it had taken a "critical step" towards securing approval for a new treatment.The UK's Medicines and Healthcare Products Regulatory Agency (MHRA) has given the green light to the first stage of clinical trials on the company's Orthopure XT, a decellularised tendon device for the reconstruction of a torn anterior cruciate ligament.If successful with the treatment's first trials, Tissue Regenix could then aim at obtaining clearance from the European Union, which would allow it to distribute the product throughout the continent.Anterior cruciate ligament (ACL) injuries are among the most common and serious injuries for professional athletes.However, while they are often placed in the hands of extremely skilful surgeons, some 900,000 people a year suffer from a similar injury and are unable to afford such expensive reconstructive surgery."An ACL tear is a very common sports injury, so we are delighted at the decision by the MHRA to allow Tissue Regenix to start the first clinical trial of the OrthoPure XT," said group chief executive Antony Odell."It is an important step in bringing this innovative device to market and is a positive step so soon after the news that the clinical trial for the OrthoPure XM (meniscus) product has commenced. "Tissue Regenix shares were up 10.61% to 18.25p at 14:33 on Tuesday.