At least three of the following four fluoroscopically positioned, postoperative AP radiographs were analyzed: immediate postoperative, between the 3rd and 6th postoperative months, at one year postoperative and at two years postoperative. The immediate and the two year radiograph were required for study inclusion. The radiolucent line score (RLLS) was calculated using the technique of Molé, involving the summation of radiolucencies in each of six specified zones. The RLLS was compared between the two groups.
Group 1: 37 shoulders operated on between 1991 and 1995 with flat back, polyethylene glenoid implants cemented after curettage of the keel slot. Group 2: 35 shoulders operated on between 1997 and 1999 with the same glenoid implants cemented after cancellous bone compaction of the keel slot. At least 3 of the following 4 fluoroscopically positioned, postoperative AP radiographs were analyzed: immediate postoperative, between the 3rd and 6th months, at one year and at two years postoperative. The immediate and the two year radiograph were required for study inclusion. The radiolucent line score (RLLS) was calculated using the technique of Molé, involving the summation of radiolucencies in each of six specified zones. The RLLS was compared between the two groups.
Mean values remained unchanged for the three test times for the healthy knees. We therefore chose the preoperative values obtained for the healthy knee as the paired reference value for each patient. The values obtained for the operated knees were compared with these control values using two-way analysis of variance for paired variables.
Discussion Residual laxity was strongly correlated with clinical outcome: residual differential laxity less than 6 mm (threshold value) ensured a negative pivot test and 94% good results. We did not find any correlation between tunnel width and residual laxity. An overly anterior femoral position and medial meniscectomy significantly increased residual laxity. The femoral bore hole should be sufficiently posterior, 60 to 70% of the anteroposterior condylar width. Use of a synthetic reinforcement did not improve clinical or laximetric outcome in the reinforcement group; a natural plasty without synthetic reinforcement would be preferable.