gms | German Medical Science

Objectives: Dynamic intraligamentary stabilization (DIS) of anterior cruciate ligament (ACL)ruptures has gained recent popularity. In theory the polyethylene suture attached to a spring reinforces the ruptured ACL. This should cause regeneration of the ACL in time. However, it is known that the ACL has a limited capacity to regenerate.

The objective of this study is to identify through MRI the amount of regeneration of ACL fibers in DIS patients compared to patients treated non-operatively for ACL rupture. Furthermore, subjective clinical outcome between the two treatment groups were analyzed.

Methods: A prospective cohort of patients suffering an ACL rupture treated by DIS within 3 weeks after trauma were compared to a prospective cohort of non-operatively treated patients suffering an ACL rupture. Patients were matched for age, sex, body mass index and pre-trauma Tegner score. On baseline and one-year follow-up, the following ACL MRI features were assessed: Fiber continuity, signal intensity, slope, distance between Blumensaat line-ACL, tension, thickness, clear boundaries, tissue outside original insertions and presence of a tibial and femoral remnant. Furthermore, the Lysholm questionnaire was assessed one year after injury. To compare the treatment groups Mann-Whitney U test was used for non-normally distributed variables in the statistical analyses. Pearson-Chi Square test was used for comparing the MRI features. P<.05 was considered statistically significant.

Results and conclusion: Thirty-one DIS and 31 non-operatively treated patients were included. The mean age was 32.3 (SD 8.5) years, 47 % was female and median pre-trauma Tegner score was 7 (interquartile range (IQR) 6-8). The following MRI features were significantly different at one-year follow-up; the non-operatively treated group had more fiber continuity: (20% vs. 0%, p=0.042). The DIS treated group showed better tensioning and slope of the ACL (43% vs. 13%, p<0.0001). The DIS treated group showed slightly higher Lysholm scores (median score 100 (IR 95-100) vs. median score 95 (IR 84-99), p<0.0001), though this was not a clinically relevant difference. The median Tegner score at one-year follow-up was in the DIS group 7 (IQR 6-8) and in the non-operatively treated group 4 (IQR 4-7), p<0.0001.

The MRI features of the DIS treated patients showed better slope and tension of the ACL, this might be due to the direct reinforcement through the polyethylene suture. However, the DIS group showed less fiber continuity and thus less regeneration. This might be the result of the diminished mechanical stimulation of the ACL fibers after reinforcement, a stress shielding effect. Thus, our data show that a DIS procedure will not cause regeneration of the ACL fibers but it might cause less bowing of the ACL after rupture. Both groups showed high subjective outcome scores at one-year follow-up.