This review, published in the American Journal of Sports Medicine this past month (Jan. 2013), is an updated review that focuses on prevention of secondary ACL tears following ACL reconstruction. It is very well done and should be read by anyone who is currently working on an athletic patient coming off ACL reconstruction. The authors discussed some of the current concepts from a wide range of articles, as well as their own research that they performed. Predictors of future injury and evidence based practices to correct these deficiencies are discussed.
Some of the key points to the review:
- Abnormal movement patterns after an ACL rupture are not isolated to the injured knee alone. There is mounting evidence of a bilateral neuromuscular response to an ACL injury that persists and
may even be exacerbated after reconstruction
- Specifically, peak knee angles, moments, and joint powers were higher in the uninvolved limb of athletes after ACLR when compared with controls and to their own unin- jured limb. Interestingly, these behaviors are not unlike those in athletes with acute ACL deficiency
- Compensatory strategies of the uninvolved hip were the primary predictor of risk in athletes who went on to a secondary ACL injury within 1 year of returning to sports activity.
- As 1 of 4 predictive factors in a highly specific and sensitive model for secondary ACL injury risk, the transverse-plane uninvolved hip net moment impulse early during landing independently predicted the risk of a secondary injury with 77% sensitivity and 81% specific-ity.
- Much like primary ACL injuries, the majority of secondary ACL injuries are caused by noncontact mechanisms,92 under- scoring altered intrinsic neuromuscular control as an impor- tant factor in injury risk.
- Similarly, in a group of 63 athletes cleared to return to sport after ACLR, 14 of the 42 (33%) female athletes went on to a contralateral ACL rupture within 1 year. Female athletes represented 88% of the documented contra- lateral limb ACL injuries
- While deficits in hamstring strength were unrelated to functional performance tasks in athletes 6 months after ACLR,41 the ratio of hamstring-to-quadriceps torque production appears to be a key variable in the primary ACL injury risk model.63 Strength symmetry of at least 85% is now advocated for ath- letes beginning reintegration into cutting, pivoting, and jumping sports.
- Performance on the single-limb hop test for distance on ACL-deficient patients predicted their self-reported func- tion 1 year after ACLR with 71% sensitivity and specific- ity.3
- The coordinated coactivation of the hamstrings and quadriceps may play a role in mitigating primary injury risk by way of reducing ligament strain29 and promoting normal landing mechanics.26 Balanced agonist and antago- nist coactivation may also protect the reconstructed knee against second ACL injury risk via similar protective mech- anisms. Deficits in the neuromuscular coordination of the hamstrings and quadriceps on the reconstructed limb may manifest as excessive landing contact noise during both double- and single-legged landing tasks
- Progressive single-limb landing activities, like anterior and lateral jumping progressions (Figure 2), may not only accentuate post-ACLR limb deficits69 but can also provide an excellent training tool to help athletes avoid quadriceps-dominant landing techniques56 and achieve the desired level of sports performance symmetry
- The cumulative data indicate that reduced hamstring strength and recruitment is related to initial and likely secondary injury risk, which supports the use of isoki- netic testing in return-to-sport decision making and guidance of interventions to reduce the risk of a second injury.
As the list above is not all inclusive, I found those points to be very beneficial. Some things we can take away: We must look at the uninvolved side quite closely throughout the rehabilitation process, we must consider hamstring strength relative to quadricep strength for ligament stability, neuromuscular control is a huge factor in predicting secondary ACL tears, and consistently retesting biomechanics of double and single leg exercises from all 3 planes is extremely important in both identifying deficiencies and prescribing rehabilitation exercises (maybe we should consistently videotape their biomechanics as they progress?- Food for thought).