J. Spang

The relationship between trochlear dysplasia and medial patellofemoral ligament rupture location after patellar dislocation: An MRI evaluation

The medial patellofemoral ligament (MPFL) and the native trochlear geometry represent two of the most critical components of patellofemoral stability. We sought to define the relationship between trochlear dysplasia and MPFL rupture location in patients with documented patellar dislocations. We hypothesized that patients with lower grades of trochlear dysplasia would have patellar based MPFL ruptures, while patients with higher grade dysplasia would have femoral-sided ruptures. We reviewed post-injury MRIs of 59 patients with documented patella dislocation. Information gathered included: type of trochlear dysplasia in the axial plane MRI, location of MPFL rupture, patellar height ratio, tibial tuberosity to trochlear groove distance (TTTG), number of dislocations prior to MRI, and time between the latest patella dislocation and the MRI. Statistical calculations utilized the Chi-Square-Test. We classified 11 cases as a dysplasia type A, 35 as a type B, 11 as a type C, and 2 cases as a trochlear dysplasia type D. In 7 patients (12%) the MPFL rupture was patella based, in 18 patients (31%) intra-ligamentous, in 33 cases (56%) femoral sided and in one case no MPFL could be identified. In contrast to our original hypothesis, the type of trochlear dysplasia does not appear to be related to the rupture location of the MPFL after patellar dislocation. According to our results, it is not possible to presume the location of the MPFL rupture based on assessment of the trochlear morphology. Therefore, a MRI is mandatory for final indication of any surgery.

Biochemical markers of cartilage metabolism are associated with walking biomechanics 6-months following anterior cruciate ligament reconstruction: Biomechanics and Biomarkers Post ACLR

The purpose of our study was to determine the association between biomechanical outcomes of walking gait (peak vertical ground reaction force [vGRF], vGRF loading rate [vGRF‐LR], and knee adduction moment [KAM]) 6 months following anterior cruciate ligament reconstruction (ACLR) and biochemical markers of serum type‐II collagen turnover (collagen type‐II cleavage product to collagen type‐II C‐propeptide [C2C:CPII]), plasma degenerative enzymes (matrix metalloproteinase‐3 [MMP‐3]), and a pro‐inflammatory cytokine (interleukin‐6 [IL‐6]). Biochemical markers were evaluated within the first 2 weeks (6.5 ± 3.8 days) following ACL injury and again 6 months following ACLR in eighteen participants. All peak biomechanical outcomes were extracted from the first 50% of the stance phase of walking gait during a 6‐month follow‐up exam. Limb symmetry indices (LSI) were used to normalize the biomechanical outcomes in the ACLR limb to that of the contralateral limb (ACLR/contralateral). Bivariate correlations were used to assess associations between biomechanical and biochemical outcomes. Greater plasma MMP‐3 concentrations after ACL injury and at the 6‐month follow‐up exam were associated with lesser KAM LSI. Lesser KAM was associated with greater plasma IL‐6 at the 6‐month follow‐up exam. Similarly, lesser vGRF‐LR LSI was associated with greater plasma MMP‐3 concentrations at the 6‐month follow‐up exam. Lesser peak vGRF LSI was associated with higher C2C:CPII after ACL injury, yet this association was not significant after accounting for walking speed. Therefore, lesser biomechanical loading in the ACLR limb, compared to the contralateral limb, 6 months following ACLR may be related to deleterious joint tissue metabolism that could influence future cartilage breakdown.

Greater intracortical inhibition associates with lower quadriceps voluntary activation in individuals with ACL reconstruction

Decreased voluntary activation contributes to quadriceps weakness following anterior cruciate ligament reconstruction (ACLR). Alterations in neural excitability are likely responsible for reductions in quadriceps voluntary activation, and may be due to specific alterations in intracortical inhibition and facilitation. Therefore, we sought to determine if intracortical inhibition (SICI) and intracortical facilitation (ICF) associate with quadriceps voluntary activation in individuals with ACLR. Twenty-seven participants with a primary, unilateral ACLR were enrolled in this study. Bilateral central activation ratio (CAR) and paired-pulse transcranial magnetic stimulation were used to assess quadriceps voluntary activation, as well as SICI and ICF in the vastus medalis, respectively. Pearson Product Moment correlations were used to determine the association between CAR and (1) SICI, and (2) ICF in each limb. Lesser CAR associated with lesser SICI amplitude (r = 0.502, P = 0.008) in the ACLR limb. No associations in the contralateral limb were significant. Our results suggest greater intracortical inhibition associates with lesser voluntary activation in individuals with ACL. Implementing interventions that target intracortical inhibition may aid in restoring quadriceps voluntary activation following ACLR.

Persistent Muscle Inhibition after ACL Reconstruction: Role of Reflex Excitability

PURPOSE Persistent voluntary quadriceps activation deficits are common after anterior cruciate ligament reconstruction (ACLR), but the direct causes are unclear. The primary purpose of this study was to determine whether spinal reflex excitability deficits are present in individuals with a history of ACLR, and secondarily to determine whether spinal reflex excitability predicts which individuals possess full voluntary quadriceps activation. METHODS One hundred and forty-seven individuals (74 healthy and 73 ACLR) participated in this cross-sectional case-control study. Quadriceps spinal reflex excitability was quantified using the Hoffmann reflex normalized to the maximal muscle response (H:M ratio). Voluntary quadriceps activation was evaluated with the burst superimposition technique and calculated via the central activation ratio (CAR). Separate 2 × 2 ANCOVA tests were used to compare between-limb and between-group differences for H:M ratio and CAR. A receiver operating characteristic curve was used to determine the accuracy of H:M ratio to predict if ACLR participants present with full voluntary activation (CAR ≥ 0.95). RESULTS The ACLR H:M ratio was not different between limbs or compared with the healthy group (P > 0.05). Although ACLR CAR was lower bilaterally compared with the healthy group (P < 0.001), it did not differ between limbs. The H:M ratio has poor accuracy for predicting which individuals exhibit full voluntary activation (receiver operating characteristic area under the curve = 0.52, 95% CI = 0.37,0.66; odds ratio = 2.2, 95% CI = 0.8, 5.9). CONCLUSIONS Spinal reflex excitability did not differ between limbs in individuals with ACLR or compared with healthy participants. The level of quadriceps spinal reflex excitability has poor accuracy at predicting which ACLR individuals would demonstrate full voluntary quadriceps activation.

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.

Walking gait asymmetries 6 months following anterior cruciate ligament reconstruction predict 12-month patient-reported outcomes: GAIT AND OUTCOMES POST-ACLR

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.

Quadriceps Rate of Torque Development and Disability in Persons With Tibiofemoral Osteoarthritis

• BACKGROUND: Declines in the ability to rapidly generate quadriceps muscle torque may underlie disability in individuals with tibiofemoral osteoarthritis. • OBJECTIVE: To determine whether quadriceps rate of torque development (RTD) predicts self‐reported disability and physical performance outcomes in individuals with tibiofemoral osteoarthritis. • METHODS: This controlled laboratory, cross‐sectional study assessed quadriceps strength and RTD in 76 individuals (55% female; mean ± SD age, 61.83 ± 7.11 years) with symptomatic and radiographic tibiofemoral osteoarthritis. Early (0‐50 milliseconds), late (100‐200 milliseconds), and overall peak RTDs were quantified in the symptomatic (involved) and contralateral limbs and used to calculate bilateral average values. Disability was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) function subscale and 3 physical performance tests, including the (1) 20‐m fast‐paced walk, (2) 30‐second chair stand, and (3) timed stair climb. Separate univariate regression models were used to determine the unique associations among measures of quadriceps RTD, WOMAC function score, and physical performance outcomes after accounting for quadriceps strength (change in R2). • RESULTS: Greater involved‐side late RTD and greater bilateral average early RTD were associated with faster walking (change in R2 = 0.05, P = .013 and change in R2 = 0.05, P = .043, respectively). Greater bilateral average late RTD was associated with faster walking (change in R2 = 0.20, P<.001) and faster stair climb (change in R2 = 0.11, P = .001). No quadriceps RTD variable was significantly associated with WOMAC function score (change in R2 range, <0.01‐0.017). • CONCLUSION: Involved‐limb quadriceps RTD was weakly associated with physical performance outcomes, but not self‐reported disability, in individuals with tibiofemoral osteoarthritis. Bilateral average quadriceps RTD was moderately associated with walking speed. • LEVEL OF EVIDENCE: Prognosis, level 2b. • KEY WORDS: chair stand, self‐reported function, stair climb, strength, walking speed

Gait biomechanics in individuals with patellar tendon and hamstring tendon anterior cruciate ligament reconstruction grafts

Anterior cruciate ligament reconstruction (ACLR) restores joint stability following ACL injury but does not attenuate the heightened risk of developing knee osteoarthritis. Additionally, patellar tendon (PT) grafts incur a greater risk of osteoarthritis compared to hamstring grafts (HT). Aberrant gait biomechanics, including greater loading rates (i.e. impulsive loading), are linked to the development of knee osteoarthritis. However, the role of graft selection on walking gait biomechanics linked to osteoarthritis is poorly understood, thus the purpose of this study was to compare walking gait biomechanics between individuals with HT and PT grafts. Ninety-eight (74 PT; 24 HT) subjects with a history of ACLR performed walking gait at a self-selected speed from which the peak vertical ground reaction force (vGRF) during the first 50% of the stance phase and its instantaneous loading rate, peak internal knee extension and valgus moments, and peak knee flexion and varus angles were obtained. When controlling for time since ACLR and quadriceps strength, there were no differences in any kinetic or kinematic variables between graft types. While not significant, 44% of the PT cohort were identified as impulsive loaders (displaying a heelstrike transient in the majority of walking trials) compared to only 25% of the HT cohort (odds ratio = 2.3). This more frequent observation of impulsive loading may contribute to the greater risk of osteoarthritis with PT grafts. Future research is necessary to determine if impulsive loading and small magnitude differences between graft types contribute to osteoarthritis risk when extrapolated over thousands of steps per day.