Purpose
This study aimed to identify independent predictive factors for return to sports (RTS) after anterior cruciate ligament (ACL) reconstruction in competitive-level athletes and to determine ...optimal cut-off values for these factors at 6 months after surgery.
Methods
A total of 124 competitive athletes (50 males and 74 females; mean age, 17.0 years; preinjury Tegner activity scale > 7) who underwent primary ACL reconstruction were enrolled. Assessments at 6 months after surgery consisted of knee functional tests quadriceps index, hamstrings index, and single-leg hop for distance (SLH) and 2 self-report questionnaires IKDC subjective score and ACL-Return to Sport after Injury scale (ACL-RSI). At 1 year after surgery, athletes were classified into the RTS group (
n
= 101) or non-RTS group (
n
= 23) based on self-reported sports activities. After screening possible predictive factors of RTS, multivariate logistic regression and receiver operating characteristic curve analyses were performed to identify independent factors.
Results
Multivariate logistic regression analysis identified SLH (odds ratio, 2.861 per 10 unit increase;
P
< 0.001) and ACL-RSI (odds ratio, 1.810 per 10 unit increase;
P
= 0.001) at 6 months as independent predictors of RTS at 1 year after surgery. Optimal cut-off values of SLH and ACL-RSI were 81.3% (sensitivity = 0.891; specificity = 0.609) and 55 points (sensitivity = 0.693; specificity = 0.826), respectively.
Conclusion
In competitive athletes, SLH < 81% and ACL-RSI < 55 points at 6 months after surgery were associated with a greater risk of unsuccessful RTS at 1 year after surgery. SLH and ACL-RSI at 6 months could serve as screening tools to identify athletes who have difficulties with returning to sports after ACL reconstruction.
Level of evidence
III.
To determine whether preoperative quadriceps strength predicts the likelihood of return to sports (RTS) following anterior cruciate ligament reconstruction (ACLR) in competitive athletes.
...Case-control study.
Single-center.
A total of 221 competitive athletes who underwent primary ACLR were followed and divided into RTS (n = 177) and non-RTS (n = 44) groups based on self-reported sports activities at one year postoperatively.
Isokinetic quadriceps strength tests were performed preoperatively and at six months and one year postoperatively, and the quadriceps index (QI) was calculated. Functional performance was evaluated by the single-leg hop (SLH) test at six months postoperatively.
Preoperative QI significantly predicted the likelihood of RTS (odds ratio, 1.68 per 10-unit increase; P < 0.001), with a preoperative QI cut-off of 66% (AUC: 0.74; sensitivity: 68.9%; specificity: 77.3%). Subjects with a preoperative QI < 66% had a significantly lower postoperative QI, SLH, and rates of RTS compared to those with a higher preoperative QI (P < 0.01).
Preoperative quadriceps strength could predict the likelihood of RTS following ACLR, and a preoperative QI < 66% was associated with a greater risk of unsuccessful RTS at one year postoperatively. Preoperative QI should be evaluated as a predictor of RTS.
•RTS is an important consideration among athletes who underwent ACLR.•Preoperative QI could predict the likelihood of RTS, with a cut-off of 66%.•Athletes with low preoperative QI had significantly low postoperative knee function.•Preoperative QI should be evaluated as a predictor of RTS.
The ammonium polyphosphate composites of NH4PO3/(NH4)2MP4O13 (M=Ti and Si) were synthesized, and the correlation between electrochemical and structural properties were investigated at intermediate ...temperatures. In these composites, the compound of (NH4)2MP4O13 serves as a supporting matrix. Although both composites showed similar thermal behaviors in dry Ar and ambient air, electrochemical and structural properties were quite different from each other. NH4PO3/(NH4)2TiP4O13 composite exhibited the structural change of the supporting matrix into TiP2O7 regardless of atmosphere, and its conductivity was independent of the humidity. The apparent activation energy was evaluated to be ca. 0.4eV in both atmospheres. On the other hand, in the case of NH4PO3/(NH4)2SiP4O13 composite, the supporting matrix was stable in dry Ar whereas which was changed into SiP2O7 in air. In response to this phenomenon, the conductivity improved significantly in air with lower activation energy of ca. 0.2eV. These results indicated the existence of different proton conduction mechanism.
The ammonium polyphosphate composites of NH
4PO
3/(NH
4)
2MP
4O
13 (M
=
Ti and Si) were synthesized, and the correlation between electrochemical and structural properties were investigated at ...intermediate temperatures. In these composites, the compound of (NH
4)
2MP
4O
13 serves as a supporting matrix. Although both composites showed similar thermal behaviors in dry Ar and ambient air, electrochemical and structural properties were quite different from each other. NH
4PO
3/(NH
4)
2TiP
4O
13 composite exhibited the structural change of the supporting matrix into TiP
2O
7 regardless of atmosphere, and its conductivity was independent of the humidity. The apparent activation energy was evaluated to be
ca. 0.4 eV in both atmospheres. On the other hand, in the case of NH
4PO
3/(NH
4)
2SiP
4O
13 composite, the supporting matrix was stable in dry Ar whereas which was changed into SiP
2O
7 in air. In response to this phenomenon, the conductivity improved significantly in air with lower activation energy of
ca. 0.2 eV. These results indicated the existence of different proton conduction mechanism.
A new proton-conductive electrolyte of (NH
4)
2TiP
4O
13 was synthesized for intermediate temperature fuel cells. Structure of the resultant electrolyte was studied by X-ray diffraction and its ionic ...conductivities was obtained from AC impedance spectroscopy. Partial decomposition of (NH
4)
2TiP
4O
13 occurred by annealing at 300 °C under a dry argon atmosphere, resulting in the formation of TiP
2O
7, and after annealing its proton conductivity was evaluated to be about 5 mS cm
−1 at 300 °C under the same dry argon atmosphere. Electrolyte of (NH
4)
2SiP
4O
13 was prepared for comparison. In contrast to (NH
4)
2TiP
4O
13, it is stable under a dry Ar atmosphere at 300 °C, and its proton conductivity was 0.6 mS cm
−1. These results indicate that partial decomposition of (NH
4)
2TiP
4O
13 to TiP
2O
7 should be responsible for high proton conductivity.
