Changes in Infrapatellar Fat Pad Volume 6 to 12 Months After Anterior Cruciate Ligament Reconstruction and Associations With Patient-Reported Knee Function.

CONTEXT: Hypertrophy of the infrapatellar fat pad (IFP) in idiopathic knee osteoarthritis has been linked to deleterious synovial changes and joint pain related to mechanical tissue impingement. Yet little is known regarding the IFP's volumetric changes after anterior cruciate ligament reconstruction (ACLR). OBJECTIVES: To examine changes in IFP volume between 6 and 12 months after ACLR and determine associations between patient-reported outcomes and IFP volume at each time point as well as the volume change over time. In a subset of individuals, we examined interlimb IFP volume differences 12 months post-ACLR. STUDY DESIGN: Prospective cohort study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: We studied 26 participants (13 women, 13 men, age = 21.88 ± 3.58 years, body mass index = 23.82 ± 2.21 kg/m2) for our primary aims and 13 of those participants (8 women, 5 men, age = 21.15 ± 3.85 years, body mass index = 23.01 ± 2.01 kg/m2) for our exploratory aim. MAIN OUTCOME MEASURE(S): Using magnetic resonance imaging, we evaluated the IFP volume change between 6 and 12 months post-ACLR in the ACLR limb and between-limbs differences at 12 months in a subset of participants. International Knee Documentation Committee subjective knee evaluation (IKDC) scores were collected at 6-month and 12-month follow-ups, and associations between IFP volume and patient-reported outcomes were determined. RESULTS: The IFP volume in the ACLR limb increased from 6 months (19.67 ± 6.30 cm3) to 12 months (21.26 ± 6.91 cm3) post-ACLR. Greater increases of IFP volume between 6 and 12 months were significantly associated with better 6-month IKDC scores (r = .44, P = .03). The IFP volume was greater in the uninjured limb (22.71 ± 7.87 cm3) than in the ACLR limb (20.75 ± 9.03 cm3) 12 months post-ACLR. CONCLUSIONS: The IFP volume increased between 6 and 12 months post-ACLR; however, the IFP volume of the ACLR limb remained smaller than that of the uninjured limb at 12 months. In addition, those with better knee function 6 months post-ACLR demonstrated greater increases in IFP volume between 6 and 12 months post-ACLR. This suggests that greater IFP volumes may play a role in long-term joint health after ACLR.

Gait Biomechanics in Individuals Meeting Sufficient Quadriceps Strength Cutoffs After Anterior Cruciate Ligament Reconstruction.

CONTEXT: Quadriceps weakness is associated with disability and aberrant gait biomechanics after anterior cruciate ligament reconstruction (ACLR). Strength-sufficiency cutoff scores, which normalize quadriceps strength to the mass of an individual, can predict who will report better function after ACLR. However, whether gait biomechanics differ between individuals who meet a strength-sufficiency cutoff (strong) and those who do not (weak) remains unknown. OBJECTIVE: To determine whether vertical ground reaction force, knee-flexion angle, and internal knee-extension moment differ throughout the stance phase of walking between individuals with strong and those with weak quadriceps after ACLR. DESIGN: Case-control study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Individuals who underwent unilateral ACLR >12 months before testing were dichotomized into strong (n = 31) and weak (n = 116) groups. MAIN OUTCOME MEASURES: Maximal isometric quadriceps strength was measured at 90° of knee flexion using an isokinetic dynamometer and normalized to body mass. Individuals who demonstrated maximal isometric quadriceps strength ≥3.0 N·m·kg-1 were considered strong. Three-dimensional gait biomechanics were collected at a self-selected walking speed. Biomechanical data were time normalized to 100% of stance phase. Vertical ground reaction force was normalized to body weight (BW), and knee-extension moment was normalized to BW × height. Pairwise comparison functions were calculated for each outcome to identify between-groups differences for each percentile of stance. RESULTS: Vertical ground reaction force was greater in the weak group for the first 22% of stance (peak mean difference [MD] = 6.2% BW) and less in the weak group between 36% and 43% of stance (MD = 1.4% BW). Knee-flexion angle was greater (ie, more flexion) in the strong group between 6% and 52% of stance (MD = 2.3°) and smaller (ie, less flexion) between 68% and 79% of stance (MD = 1.0°). Knee-extension moment was greater in the strong group between 7% and 62% of stance (MD = 0.007 BW × height). CONCLUSIONS: Individuals with ACLR who generated knee-extension torque ≥3.0 N·m·kg-1 exhibited different biomechanical gait profiles than those who could not. More strength may allow for better energy attenuation after ACLR.

Walking gait asymmetries 6 months following anterior cruciate ligament reconstruction predict 12-month patient-reported outcomes.

The study sought to determine the association between gait biomechanics (vertical ground reaction force [vGRF], vGRF loading rate [vGRF-LR]) collected 6 months following anterior cruciate ligament reconstruction (ACLR) with patient-reported outcomes at 12 months following ACLR. Walking gait biomechanics and all subsections of the Knee Injury and Osteoarthritis Outcomes Score (KOOS) were collected at 6 and 12 months following ACLR, respectively, in 25 individuals with a unilateral ACLR. Peak vGRF and peak instantaneous vGRF-LR were extracted from the first 50% of the stance phase. Limb symmetry indices (LSI) were used to normalize outcomes in the ACLR limb to that of the uninjured limb (ACLR/uninjured). Linear regression analyses were used to determine associations between biomechanical outcomes and KOOS while accounting for walking speed. Receiver operator characteristic curves were used to determine the accuracy of 6-month biomechanical outcomes for identifying individuals with acceptable patient-reported outcomes, using previously defined KOOS cut-off scores, 12 months post-ACLR. Individuals with lower peak vGRF LSI 6 months post-ACLR demonstrated worse patient-reported outcomes (KOOS Pain, Activities of Daily life, Sport and Recreation, Quality of Life) at the 12-month exam. A peak vGRF LSI ≥0.99 6 months following ACLR associated with 13.33× higher odds of reporting acceptable patient-reported outcomes 12 months post-ACLR. Lesser peak vGRF LSI during walking at 6-months post-ACLR may be a critical indicator of worse future patient-reported outcomes. Clinical significance achieving early symmetrical lower extremity loading and minimizing under-loading of the ACLR limb during walking may be a potential therapeutic target for improving patient-reported outcomes post-ACLR. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2932-2940, 2018.

Time between anterior cruciate ligament injury and reconstruction and cartilage metabolism six-months following reconstruction.

BACKGROUND: To determine the association between time from injury to ACL reconstruction (TimeInjury-ACLR) and biochemical markers of cartilage metabolism and inflammation six months following ACL reconstruction (ACLR). METHODS: Individuals with a unilateral ACL injury were enrolled at initial presentation in the orthopedic clinic; blood was collected six months following ACLR. Enzyme-linked immunosorbent assays were used to analyze the ratio of serum concentrations of type-II collagen breakdown (C2C) to synthesis (CPII), plasma matrix metalloproteinase-3 (MMP-3), interleukin-6 (IL-6), and serum aggrecan neoepitope (ARGS). We used separate linear regressions to assess associations between biochemical markers and TimeInjury-ACLR. RESULTS: Twenty-two participants (50% females, mean [SD], age 21.9 [4.5] years old; BMI 23.8 [2.6] kg/m2) completed the study. TimeInjury-ACLR ranged from nine to 67days (31.0 [14.4days]). Greater TimeInjury-ACLR predicted greater serum C2C:CPII ratios six months following ACLR (C2C:CPII=0.15 [0.02], R2=0.213, P=0.030). Males (R2=0.733, P=0.001) but not females (R2=0.030, P=0.609) demonstrated a significant association between greater C2C:CPII and TimeInjury-ACLR at the six-month follow-up exam. TimeInjury-ACLR did not associate with IL-6, MMP-3, or ARGS at six months. CONCLUSIONS: Greater time between injury and ACL reconstruction was associated with greater serum C2C:CPII six months following ACLR in males but not females, and IL-6, MMP-3, and ARGS levels were not associated with TimeInjury-ACLR in males or females. The time between ACL injury and ACLR may affect collagen metabolism in males and should be further investigated in a larger study along with other patient-relevant outcomes.

Associations between cartilage proteoglycan density and patient outcomes 12months following anterior cruciate ligament reconstruction.

BACKGROUND: Lower proteoglycan density (PGD) of the articular cartilage may be an early marker of osteoarthritis following anterior cruciate ligament (ACL) reconstruction (ACL-R). The purpose this study was to determine associations between the Knee Injury and Osteoarthritis Outcomes Score (KOOS) and PGD of the articular cartilage in the femur and tibia 12-months following ACL-R. METHODS: We evaluated KOOS pain, symptoms, function in activities of daily living (ADL), function in sport and recreation (Sport), and quality of life (QOL), as well as PGD using T1rho magnetic resonance imaging in 18 individuals 12.50±0.70months (these are all mean±standard deviation) following unilateral ACL-R (10 females, eight males; 22.39±4.19years; Marx Score=10.93±3.33). Medial and lateral load-bearing portions of the femoral and tibial condyles were sectioned into three (anterior, central and posterior) regions of interest (ROIs). T1rho relaxation times in the ACL-R knee were normalized to the same regions of interest in the non-surgical knees. Alpha levels were set at P≤0.05. RESULTS: Worse KOOS outcomes were significantly associated with greater T1rho relaxation time ratios in the posterior-lateral femoral condyle [pain (r=-0.54), ADL (r=-0.56), Sport (r=-0.62) and QOL (r=-0.59)] central-lateral femoral condyle [Sport (r=-0.48) and QOL (r=-0.42)], and the anterior-medial femoral condyle [Sport (r=-0.46) and QOL (r=-0.40)]. There were no significant associations between the KOOS and T1rho outcomes for tibial ROI. CONCLUSIONS: Lower PGD of the femoral cartilage in the ACL-R knees was associated with worse patient-reported outcomes.