Mia J. Katzel

Hop Distance Symmetry Does Not Indicate Normal Landing Biomechanics in Adolescent Athletes With Recent Anterior Cruciate Ligament Reconstruction

BACKGROUND: Return‐to‐sport protocols after anterior cruciate ligament reconstruction (ACLR) often include assessment of hop distance symmetry. However, it is unclear whether movement deficits are present, regardless of hop symmetry. OBJECTIVES: To assess biomechanics and symmetry of adolescent athletes following ACLR during a single‐leg hop for distance. METHODS: Forty‐six patients with ACLR (5–12 months post surgery; 27 female; mean ± SD age, 15.6 ± 1.7 years) were classified as asymmetric (operative‐limb hop distance less than 90% that of nonoperative limb [n = 17]) or symmetric (n = 29) in this retrospective cohort. Lower extremity biomechanics were compared among operative and contralateral limbs and 24 symmetric controls (12 female; mean ± SD age, 14.7 ± 1.5 years) using analysis of variance. RESULTS: Compared to controls, asymmetric patients hopped a shorter distance on their operative limb (P<.001), while symmetric patients hopped an intermediate distance on both sides (P≥.12). During landing, the operative limb, regardless of hop distance, exhibited lower knee flexion moments compared to controls and the contralateral side (P≤.04), with lower knee energy absorption than the contralateral side (P≤.006). During takeoff, both symmetric and asymmetric patients had less hip extension and smaller ankle range of motion on the operative side compared with controls (P≤.05). Asymmetric patients also had lower hip range of motion on the operative, compared with the contralateral, side (P = .001). CONCLUSION: Both symmetric and asymmetric patients offloaded the operative knee; symmetric patients achieved symmetry, in part, by hopping a shorter distance on the contralateral side. Therefore, hop distance symmetry may not be an adequate test of single‐limb function and return‐to‐sport readiness.

Improvements in landing biomechanics following anterior cruciate ligament reconstruction in adolescent athletes

ABSTRACT Motion analysis offers objective insight into biomechanics, rehabilitation progress and return to sport readiness. This study examined changes in three-dimensional movement patterns during drop jump landing between early and late stages of rehabilitation in adolescent athletes following anterior cruciate ligament reconstruction (ACLR). Twenty-four athletes (58% female; mean age 15.4 years, SD 1.2) with unilateral ACLR underwent motion analysis testing 3–6 months and again 6–10 months post-operatively. Kinematics and kinetics were compared between visits and between limbs using repeated measures ANOVA. The operative side exhibited lower vertical ground reaction force, less energy absorption and lower sagittal external moments at the knee and ankle, and lower peak dorsiflexion angles compared with the non-operative side regardless of visit. Between visits, hip and knee flexion increased bilaterally, as well as hip flexion moments and energy absorption. During early rehabilitation following ACLR, adolescent athletes reduced flexion and loading of the knee and ankle on their operative limb. Motion and loading increased over time, particularly at the hip, but remained reduced at the knee and ankle 6–10 months post-operatively.

Comparison of drop jump landing biomechanics and asymmetry among adolescents with hamstring, patellar and quadriceps tendon autografts for anterior cruciate ligament reconstruction

BACKGROUND Adolescent anterior cruciate ligament reconstruction (ACLR) commonly utilizes hamstring (HT), patellar (PT) or quadriceps (QT) tendon autografts, but consensus is lacking regarding optimal graft choice. This study compared landing biomechanics and asymmetries among ACLR patients with HT, PT and QT grafts and uninjured controls. METHODS This retrospective study included 61 adolescents with unilateral ACLR (27 HT, 20 PT, 14 QT; four to 12 months post-surgery, mean 6.4; age 15.4, SD 1.4 years) and 27 controls (14.6, SD 0.9 years) who were evaluated during drop jump landings. Lower extremity 3D biomechanics and asymmetries were compared. RESULTS Compared to controls, all operative limbs exhibited 1) greater hip flexion and lower dorsiflexion angles; 2) higher hip and lower knee and ankle flexion moments; 3) higher energy absorption at the hip (HT and QT only) and lower at the knee and ankle; and 4) higher knee abduction moments. Asymmetries observed in all ACLR groups included 1) lower knee and ankle flexion angles; 2) lower knee and ankle flexion moments; 3) lower energy absorption at the knee and ankle; and 4) higher hip and knee abduction moments on the operative side. The PT and QT groups demonstrated greater asymmetry in hip and knee flexion moments compared to HT. CONCLUSIONS While adolescent ACLR limbs offloaded the knee and ankle, patients with PT or QT grafts demonstrated greater deficiencies during rehabilitation than those reconstructed with HT. Graft choice in ACLR should remain patient-specific and aim to optimize biomechanics with the ultimate goal of minimizing graft re-tear and donor site morbidity.

Deficits in Sagittal and Frontal Plane Mechanics during Drop Jump in Young Athletes with Recent Anterior Cruciate Ligament Reconstruction

Objectives: While the vertical drop jump (VDJ) is an established predictor of ACL injury risk, most studies have focused on frontal and transverse plane assessment in young adult athletes. This study assessed sagittal as well as frontal plane biomechanics during VDJ in adolescent athletes following recent anterior cruciate ligament reconstruction (ACLR). Methods: 29 limbs with unilateral ACLR (69% female, mean age 15.8 ± 1.6 years, 5 to 12 months post-surgery), 29 contralateral non-operative limbs, and 19 control limbs (53% female, mean age of 15.5 ± 1.8 years) were evaluated during VDJ. Lower extremity three-dimensional kinematic and kinetic data from initial contact to peak knee flexion were compared among groups using analysis of variance with Bonferroni post-hoc tests. Results: The operative limbs had significantly lower peak ground reaction forces (GRF) than both control and contralateral limbs (ACLR: 1.7 body weights (BW), Contralateral: 2.1 BW, Control: 2.1 BW; p≤0.01) along with lower average external knee flexion moments (ACLR: 0.7Nm/kg, Contralateral: 0.9Nm/kg, Control: 1.1Nm/kg; p≤0.05) and reduced power absorption at the knee (ACLR: 0.9Nm/kg, Contralateral: 1.5Nm/kg, Control: 1.2Nm/kg; p≤0.01). Operative limbs had lower peak knee flexion (ACLR: 96.8°; Contralateral: 100.7°; p=0.001) and knee flexion excursion (ACLR: 75.0°, Contralateral: 82.5°; p=0.003) than contralateral limbs, but did not differ from controls in these measures. Both operative and non-operative limbs had greater peak hip flexion (ACLR: 98.9°, Contralateral: 99.8°, Control: 83.5°; p≤0.006), hip flexion excursion (ACLR: 60.8°, Contralateral: 65.6°, Control: 49.6°; p=), and power absorption at the hip (ACLR: 1.0Nm/kg, Contralateral: 1.2Nm/kg, Control: 0.7Nm/kg; p<0.03) compared with controls. In the coronal plane, both the operative and non-operative limbs demonstrated higher peak knee valgus moments compared to controls (ACLR: 0.5Nm/kg, Contralateral: 0.4Nm/kg, Control: 0.2Nm/kg; p≤0.02) and utilized less hip ab/adduction range (ACLR: 1.7°, Contralateral: 1.9°, Control: 6.1°; p≤0.003) though there were no differences in knee valgus angles (p≥0.31) or excursion (p≥0.52). Conclusion: Lower GRF and less energy absorbed at the knee during VDJ suggests a landing strategy that shifts loading from the post-surgical knee to the hip and contralateral limb. The frontal plane knee deficits in both the operative and non-operative limbs may place the limb at an elevated risk for future injury or re-injury. Avoidance of loading the reconstructed knee and residual deficits in frontal plane hip and knee control on either limb may indicate lack of readiness to return to full activity after recent ACLR.

Effect of ACL Graft Type on Side-Step Cutting in Young Athletes

Objectives: Due to the slightly higher re-tear rate for ACL reconstruction (ACLR) with hamstring (HT) versus patellar tendon (PT), differences in movement strategies were assessed during side-step cutting in young athletes with recent ACLR to determine if graft type affected post-operative motion. Methods: Dominant limbs from 21 athletes without lower extremity injury or previous surgery (age 14.9 ± 2.0 years) and 26 limbs with recent (5.1-8.0 months post-operative) unilateral ACLR were included, 18 with HT grafts (age 16.6 ± 3.7 years) and 8 with PT (age 16.7 ± 1.2 years). Lower extremity 3-dimensional data was recorded during the deceleration phase (initial contact to maximum knee flexion) of a 45° cut. Group differences were assessed using analysis of variance with Bonferroni post-hoc tests. Results: The HT group had a slower approach velocity than controls (2.9 vs. 3.5 m/s; p=0.006) with intermediate velocity in the PT group (3.2 m/s). Both the HT and PT groups had lower peak ground reaction force (GRF) compared to controls (HT: 2.0 body weights, PT: 2.2 BW, Control: 2.8 BW; p≤0.02), along with lower peak knee flexion moments (HT: 1.4 Nm/kg, PT: 1.3 Nm/kg, Control: 2.2 Nm/kg; p=0.002). The PT group had less power absorption at the knee than controls (0.3 vs. 0.7 Nm/kg; p=0.07), while the HT group had more at the hip (0.4 vs. 0.1 Nm/kg; p=0.04). The HT group also had higher peak hip flexion (HT: 65.8°, PT: 53.9°, Control: 55.1°; p≤0.06) and hip sagittal plane excursion (HT: 9.4°, PT: 3.6°, Control: 2.8°; p≤0.05) than the PT and control groups. The HT group had lower peak knee valgus moments than controls (0.05 vs. 1.2 Nm/kg; p=0.01) as well as a greater range of frontal plane pelvic (8.2° vs. 3.4°; p=0.03) and hip (7.6° vs. 3.0°; p=0.05) motion. The PT group had intermediate values for valgus moment (0.8 Nm/kg) and pelvic (4.9°) and hip (3.3°) excursion. Conclusion: While both ACLR groups showed reduced GRFs and knee flexion moments compared with controls, the HT group demonstrated greater adaptations proximally with increased hip flexion and frontal plane pelvic and hip excursion. The lower frontal and sagittal plane hip motion in the PT group may be due to anterior knee pain associated with PT grafts. Since the HT group exhibited movement adaptations, but no observable pathologic movement patterns, such as increased knee valgus moment, other factors likely account for the observed higher re-tear rate in HT vs. PT ACLR.

Comparison of lateral shuffle and side-step cutting in young recreational athletes

This study compared three-dimensional (3-D) hip and knee kinematics and kinetics between lateral shuffle and side-step cutting movements to determine whether the simpler lateral shuffle movement can be used in place of cutting to assess knee injury risk. A total of 78 patients (52 female) and 34 controls (16 female) aged 8-19 years performed lateral shuffle and 45° side-step cutting movements. Hip and knee kinematics and kinetics between initial contact and peak knee flexion were calculated using the Plug-in-Gait model and compared between activities using Pearsons correlation and paired t-tests. Peak knee valgus angle correlated strongly (r=0.86, p<0.0001), while minimum (r=0.25, p=0.0001) and peak hip abduction (r=0.24, p=0.0003), and peak hip internal rotation (r=0.33, p<0.0001) correlated only weakly between the two activities. Peak external knee valgus moment (r=0.32, p<0.0001) and average external knee (r=0.42, p<0.0001) and hip (r=0.37, p<0.0001) flexion moments correlated weakly to moderately between activities. Subjects were more internally rotated (3.6°, p<0.0001) and less abducted (16.7° and 17.3° for minimum and maximum, p<0.0001) at the hip during cutting, with higher hip (0.12, p<0.0001) and lower knee (-0.02, p=0.0001) non-dimensional flexion moments. These results suggest that the lateral shuffle movement may be useful for evaluating knee valgus, particularly during initial visual assessment. However, the lateral shuffle may not be challenging enough to reveal poor neuromuscular control over hip ab/adduction and rotation, necessitating follow-up assessment of cutting, ideally using 3-D motion analysis.

Evaluation Of Three-Dimensional Motion During Side-step Cutting After Anterior Cruciate Ligament Reconstruction in Pediatric Athletes

Objectives: This study assessed three-dimensional kinematic and kinetic data during side-step cutting in young athletes following anterior cruciate ligament (ACL) reconstruction. Methods: The study included 28 pediatric athletes (mean age 15.6 ± 2.2 years) who underwent ACL reconstruction due to a non-contact injury. Lower extremity and trunk three-dimensional kinematic and kinetic data was collected during a side-step cut. Testing occurred within 12 months (mean time since surgery 5.3 ± 2.1 months) post-surgery. Outcomes were evaluated at initial foot contact and between initial foot contact and maximum knee flexion of the cutting limb. Differences between the operative limb and non-operative (contralateral) limb were investigated using paired t-tests. Results: The operative limb had higher peak adduction (-0.14° ± 7.3 vs. -6.1° ± 5.0, p=0.001) and higher peak pelvic obliquity (14.0° ±6.2 vs. 10.5° ±5.7, p=0.01) compared to the non-operative limb. While there was no significant difference in peak ground reaction force (23.2 N/kg ± 4.7 vs. 24.5 N/kg ± 4.5, p=0.15), the operative limb had lower peak knee flexion (53.3° ± 13.5 vs. 59.6° ±10.0, p=0.004), ankle dorsiflexion (14.5° ± 7.5 vs. 18.6° ± 6.5, p=0.007), and external knee flexor moment (1.4 Nm/kg ± 0.61 vs. 1.9 Nm/kg ± 0.62, p=0.002) leading to the operative limb having less power absorption at the knee (0.38 Ws/kg ± 0.31 vs. 0.58 Ws/kg ± 0.28, p=0.005). At initial contact the operative limb was more adducted (-5.0° ± 7.6 vs. -8.6° ± 3.9; p=0.02) and flexed (56.3° ± 11.4 vs. 52.5° ± 12.7; 0.06) at the hip and more flexed at the knee (21.5° ± 17.1 vs. 17.2° ± 13.6; p=0.06). The operative limb also had more pelvic elevation (8.1° ± 7.0 vs. 5.5° ± 3.8; p=0.04) and had more trunk rotation (rotation relative to the lab; -11.4° ±7.2 vs. -5.3° ±8.6; p=0.004). Eight of the 28 operative limbs had an asymmetry greater than 10% of the non-operative limb on one of the kinematic or kinetic variables; though all eight limb asymmetries occurred on different movement variables. Conclusion: Following ACL reconstruction pediatric athletes exhibit asymmetry several months post-surgery. The operative limb displayed deficits and asymmetry in hip control and shock absorption strategies after initial contact until maximum knee flexion which could increase the risk of future re-injury based on prior biomechanical studies. The contralateral limb also demonstrated deficits and asymmetries at initial contact. These asymmetrical movement patterns and deficits potentially put the non-operative limbs at an increased risk for injury and potentially lend insight into why patients who tear one ACL are at increased risk of contralateral ACL injury. If asymmetry is indicative of future injury risk, this should be considered during treatment, rehabilitation and return to sport decision-making.

Comparison of Three-Dimensional Motion During Side-Step Cutting in Pediatric Athletes with Recent ACL Reconstruction and those with No ACL Surgical History

Objectives: This study assessed differences between pediatric athletes’ anterior cruciate ligament (ACL) reconstructed limb and non-reconstructed limb compared to limbs with no lower extremity surgical history during a side-step cut. Methods: 28 limbs with an ACL reconstruction within the 12 months prior to testing (operative limbs), 28 contralateral limbs (non-operative limbs) and 56 limbs with no lower extremity surgical history (control limbs; 28 individuals) were included. Lower extremity kinematic and kinetic 3-dimensional data was recorded during the deceleration phase of a side-step cut. Outcomes were evaluated at initial foot contact and between initial foot contact and maximum knee flexion of the cutting limb. Differences between operative and non-operative limbs and control limbs were assessed using analysis of variance with Bonferroni post-hoc tests. Results: Operative limbs had higher peak hip adduction (-0.14° ± 7.3 vs. -6.1° ± 5.0, =0.01) and higher average external knee valgus moments (0.16 Nm/kg ± 0.50 vs. -0.21Nm/kg ± 0.58, p=0.02) compared to control limbs. In terms of shock absorption, operative limbs had lower peak ground reaction forces (23.2 N/kg ± 4.7 vs. 28.3 N/kg ± 5.8, p<0.0001) and peak ankle dorsiflexion (14.5° ± 7.5 vs. 20.0° ± 6.4, p=0.002) compared to control limbs with lower peak external knee flexor moments (1.4 Nm/kg ± 0.61 vs. 2.0 Nm/kg ± 0.63, p<0.0001) and less power absorption at the knee (0.38 Ws/kg ± 0.31 vs. 0.55Ws/kg ± 0.34, p=0.05) and ankle (0.43 Ws/kg ± 0.21 vs. 0.65 Ws/kg ± 0.41, p=0.01). Though non-operative limbs had less knee valgus (-1.0° ± 3.5 vs. 1.1° ± 3.3, p=0.04) at initial contact, they had higher peak knee valgus (3.6° ± 5.7 vs. 0.58° ± 4.1, p=0.04) and higher average external knee valgus moments (0.09 Nm/kg ±0.59 vs. -0.21Nm/kg ±0.58, p=0.06) compared to control limbs. Non-operative limbs also had less pelvic obliquity compared to control limbs (10.4° ± 5.8 vs. 14.6° ± 7.7, p=0.04). Lower peak ground reaction forces (24.5 N/kg ± 4.5 vs. 28.3 N/kg ± 5.8, p=0.005), increased power absorption at the hip (0.43 Ws/kg ± 0.48 vs. 0.15 Ws/kg ± 0.23, p=0.005), and decreased power absorption at the ankle (0.49 Ws/kg ± 0.23 vs. 0.65 Ws/kg ± 0.41, p=0.09) were seen in non-operative compared to control limbs. Conclusion: Limbs with ACL reconstruction exhibited poorer hip stability compared to control limbs. ACL reconstructed limbs also had less energy absorption at the knee and lower peak vertical ground reaction forces, likely reflecting an avoidance strategy when performing a cut using an ACL reconstructed limb. The uninjured, contralateral limbs of ACL reconstructed patients also demonstrated reduced ground reaction forces and altered neuromuscular control. These changes may reflect overall tentativeness in performing a cut but also suggest baseline suboptimal neuromuscular control that possibly lends insight into the increased risk of contralateral ACL tear seen in patients who have sustained an index ACL tear. It is also possible that the biomechanical strategies present on the operative side could be putting the non-operative limb at risk for injury. These findings support the need for ongoing research into rehabilitation protocols and return to sport timing and also support to existing injury prevention programs.