***TASK***
the task is to simplify the input abstract of a biomedical literature

***INPUT***
the input is the abstract of a biomedical literature

***OUTPUT***
the output is the simplified abstract for the input abstract of a biomedical literature

***DOCUMENTATION***

***EXAMPLES***

Input: For this update of the review, we identified one new trial, bringing the total to 17 trials (1034 participants) - all of which were generally at moderate or high risk of bias. In 12 trials participants also received compression bandaging. Eleven trials compared a graft with standard care in which no graft was used. Two of these trials (102 participants) compared a dressing with an autograft; three trials (80 participants) compared frozen allografts with dressings, and two trials (45 participants) compared fresh allografts with dressings. Two trials (345 participants) compared tissue-engineered skin (bilayer artificial skin) with a dressing. In two trials (97 participants) a single-layer dermal replacement was compared with standard care. Six trials compared alternative skin grafting techniques. The first trial (92 participants) compared autografts with frozen allograft, a second (51 participants) compared a pinch graft (autograft) with porcine dermis (xenograft), the third (110 participants) compared growth-arrested human keratinocytes and fibroblasts with placebo, the fourth (10 participants) compared an autograft delivered on porcine pads with an autograft delivered on porcine gelatin microbeads, the fifth trial (92 participants) compared a meshed graft with a cultured keratinocyte autograft, and the sixth trial (50 participants) compared a frozen keratinocyte allograft with a lyophilised (freeze-dried) keratinocyte allografts. Significantly more ulcers healed when treated with bilayer artificial skin than with dressings. There was insufficient evidence from the other trials to determine whether other types of skin grafting increased the healing of venous ulcers. Bilayer artificial skin, used in conjunction with compression bandaging, increases venous ulcer healing compared with a simple dressing plus compression. Further research is needed to assess whether other forms of skin grafts increase ulcer healing.
Output:

Approximately 1% of people in industrialised countries have a leg ulcer at some time, mainly caused by poor blood flow back from the legs towards the heart. Skin grafts, either using the patient's own skin, artificial skin or donor skin/cells, have been evaluated to see whether they improve the healing of ulcers. The review of trials found evidence that tissue-engineered skin composed of two layers increases the chance of healing. There was not enough evidence to recommend any other type of graft, and further research is required.