Prospectively identified deficits in sagittal plane hip–ankle coordination in female athletes who sustain a second anterior cruciate ligament injury after anterior cruciate ligament reconstruction and return to sport☆
Introduction
An estimated 100,000–200,000 anterior cruciate ligament (ACL) injuries occur annually in the United States with the majority of patients electing to undergo ACL reconstruction (Kim et al., 2011) (ACLR). Athletes who attempt to return to sport (RTS) after ACLR are as much as 15 times more likely to sustain a second ACL injury to either knee in the first year after they return to sport (Paterno et al., 2012). Despite high second injury rates in ACLR, there is a lack of consensus regarding the underlying mechanism placing these athletes at increased risk for future injury. The current published literature has reported the relationship of various factors to second ACL injury rates, including demographic variables (Brophy et al., 2012), graft type (Kaeding et al., 2011), and biomechanical, neuromuscular, and proprioceptive factors (Paterno et al., 2010). Furthermore, other impairments in strength (Mattacola et al., 2002), balance (Mattacola et al., 2002, Paterno et al., 2013), proprioception (Mattacola et al., 2002), and limb symmetry with dynamic tasks (Paterno et al., 2007, Paterno et al., 2011) may extend for over 2 years after RTS from ACLR. Despite this extensive research, the effect of ACL injury and ACLR on postural coordination remains unknown.
Postural coordination has been defined as the coordination between various body parts that underlies the integration of the maintenance of upright stance (Bardy et al., 2002). The absence of joint position awareness at the knee joint may result in impairments to postural coordination due to altered muscle recruitment with dynamic movements, deficits in joint stability, and decreased ability to control normal movement (Chiu and Chou, 2013, Hamill et al., 1999, Kiefer et al., 2013a). Coordinated movements of the hip and ankle are critical to optimally position the knee joint in the absence of normal knee proprioception during dynamic athletic movements. Failure to coordinate the movements of the joints proximal and distal to the knee has the potential to place the knee joint in high-risk positions during dynamic movements. The failure to optimally position the knee may make the passive structures susceptible to pathologic stresses that increase the risk of subsequent ligament or graft failure following ACLR.
Abnormal sagittal plane joint coupling patterns between the hip and ankle in patients following ACLR have been identified in the literature when compared to healthy control subjects (Kiefer et al., 2013b). Coupling refers to the synergistic movement of multiple segments to coordinate a gross movement. Despite identification of this difference between ACLR patients and controls, current research has yet to identify whether unique patterns of abnormal postural coordination and joint coupling are residual impairments associated with a high risk for future ACL injury.
The purpose of this prospective study was to determine if there are altered sagittal plane postural coordination patterns in female athletes who subsequently go on to suffer a second ACL injury to either limb after ACLR and RTS. The hypothesis tested was that athletes who subsequently sustained a second ACL injury would demonstrate altered sagittal plane, hip–ankle postural coordination patterns indicative of persistent sensorimotor deficits leading to abnormal joint coupling patterns at the time of RTS compared to female athletes who would not subsequently sustain a second ACL injury.
Section snippets
Participants
Sixty-one female pivoting and cutting athletes with a primary, unilateral ACLR were prospectively tested and then tracked for 12 months following RTS to identify those who went on to a second ACL injury. Testing occurred when the subject was medically cleared to return to pivoting and cutting sports after ACLR by their physician and rehabilitation specialist. All subjects returned to a Level I/II pivoting or cutting sport (Daniel et al., 1994). Within 12 months of RTS, 14 subjects (11 soccer
Summary measure of variability
A main effect of group was observed for SDankle, F(1,26) = 4.235, P = .05, η2 = 0.14, which indicated that the ACL2 group exhibited a decreased amount of variability, or more rigid posture, in overall ankle movement [0.001 (0.0001°)] compared to the ACL1 group [0.002 (0.0005°)] (Table 2). The interactions were not significant (P > .05). No significant differences were found for SDhip (P > .05).
CRP features
Fig. 4 shows sample CRPs for an ACL1 athlete (left) and an ACL2 athlete (right). There are notable visual
Discussion
The results of this investigation support the stated hypothesis that female athletes who subsequently sustained a second ACL injury after ACLR and RTS would present with altered patterns of postural coordination at the time of RTS following initial ACLR. Specifically, females who subsequently sustained a second ACL injury demonstrated a more rigid posture (decreased variability of movement) at the ankle, less coordinated movements, and weaker coupling of movements between the hip and ankle
Conclusion
This study indicates that female patients who suffer a second ACL injury after ACLR and return to a pivoting and cutting sport present with altered hip–ankle coordination when compared to similar patients who did not suffer a second ACL injury. Failure to appropriately coordinate lower extremity movement between the adjoining proximal and distal hip and ankle in the absence of normal knee proprioception may place the knee in a high-risk position and increase the likelihood of a second ACL
Acknowledgements
The study was supported by the National Football League Charities and the National Institutes of Health/National Institute of Arthritis and Musculoskeletal and Skin Diseases grants R01-AR049735, R01-AR05563, R01-AR056259, and F32-AR055844.
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The Cincinnati Children's Hospital Medical Center Institutional Review Board approved this study.