“…Following review nine of these papers were discarded for the following reasons: three were duplicates [3,8,13], two were editorials, one looked at the effect of physician owned hospitals on general competing hospitals, one looked at rural hospitals, one was a letter to the editor and one paper focused on Medicaid status. This left 21 papers of which nine were related to the knee [16][17][18][19][20][21][22][23][24], often as a more general assessment of the effect of volume on lower limb arthroplasty, and 12 looking at other aspects of orthopaedic practice [25][26][27][28][29][30][31][32][33][34][35][36]. An additional two papers [37,38] were also identified through a review of the bibliographies of identified papers.…”