Functional Brain Plasticity Associated with ACL Injury: A Scoping Review of Current Evidence

Table 3

Summary of included TMS studies (effect size is presented for between or within-group comparisons).

Study	Level of evidence	Group (, sex, mean age)	Type of surgery; time from injury/surgery	Outcomes	Task	Results	Effect size, Cohen’s
Pietrosimone et al. [35]	Case-control 3b	ACLR (, 9M, 19F, ); Healthy (, 9M, 20F, )	14 hamstrings, 12 patellar tendons, 2 allografts; months from surgery	AMT	Vastus medialis contraction at 5% MVIC	AMT was significantly higher in the ACLR limb () compared to the uninvolved limb ()—; AMT was significantly higher in the ACLR limb () compared to healthy controls ()—	ACLR vs. uninvolved limb,; ACLR vs. healthy,
Pietrosimone et al. [44]	Case series 4	ACLR (, 4 M, 11F, )	Unknown; months from surgery	AMT	Vastus medialis contraction at 5% MVIC	The ACLR limb presented average AMT values of T	Unable to determine
Lepley et al. [54]	Case-control 3b	ACLR (, 9M, 20F, ); Healthy (, 9M, 20F, )	Unknown; months from surgery	AMT	Vastus medialis and lateralis contraction at 5% MVIC	The ACLR group showed higher values of AMT (2T) compared to healthy controls (T), but the significance level of this difference is unknown	ACLR vs. healthy,
Lepley et al. [33]	Case-control, 3b	ACLR (, 9M, 11F, ); Healthy (, 9M, 11F, )	Nine hamstrings, 11 patellar tendons; Measurements taken at 3 points: (a) days after injury; (b) days after surgery; (c) weeks after surgery	AMT, MEP	Vastus medialis contraction at 5% MVIC	Both at presurgery and 2 weeks after surgery, there were no differences between groups in the AMT values; At 6 months postsurgery, both the ACLR limb (T) and the uninvolved limb (T) showed significantly higher AMT compared to the healthy group (T); No differences were found for MEP in any time point	For AMT: ACLR vs. uninvolved, -0.4; ACLR vs. healthy, -1.0
Ward et al. [53]	Case-series, 4	ACLD (, 7M, 21F, )	Unknown; months from injury	AMT	Vastus medialis contraction at 5% MVIC	There were no significant differences between the ACLD limb (T) and the uninvolved limb (T)—	ACLD vs. uninvolved,
Kuenze et al. [48]	Case-control, 3b	ACLR (, 12M, 10F, ); Healthy (, 12M, 12F, )	12 hamstrings, 10 patellar tendons; (hamstring) and (PT) months from surgery	AMT	Vastus medialis contraction at 5% MVIC	The ACLR limb showed a significantly higher AMT (T) compared to the uninvolved limb (T), but not when compared to the healthy group (T)	ACLR vs. uninvolved,; ACLR vs. healthy,
Luc-Harkey et al. [55]	Case-series, 4	ACLR (, 7M, 20F, )	18 patellar tendons (remaining unknown); months from surgery	AMT, ICF, SICI, MEP	Vastus medialis contraction at 5% MVIC	No significant differences in AMT were observed between the ACLR (T) and the uninvolved limb (T). No significant differences were observed for the remaining outcomes	For AMT: ACLR vs. uninvolved,
Norte et al. [51]	Case-control, 3b	ACLR (, 32M, 40F, ); Healthy (, 12 M, 18F, )	34 hamstrings, 29 patellar tendons, 9 allografts; months from surgery	AMT	Vastus medialis contraction at 5% MVIC	AMT values between the ACLR limb (T) and the uninvolved limb (T) were not significant; however, significant differences were found in the healthy group (T)	ACLR vs. uninvolved,; ACLR vs. healthy,
Norte et al. [50]	Case-control, 3b	ACLRearly (, 20M, 14F, ); ACLRlate (, 10M, 20F, ); ACLROA (, 2M, 6F, ); Healthy (, 12M, 18F, )	29 hamstrings, 26 patellar tendons, 23 allografts; , , months from surgery	AMT	Vastus medialis contraction at 5% MVIC	No significant differences in AMT were found between the ACLR limb and the uninvolved limb, both at early (T vs. T) and late ( vs. ) stages—; Both limbs of people with ACLR showed significant differences in AMT compared to the healthy controls (T)—	All ACLR groups vs. uninvolved limb; d = 0.05-0.09; All ACLR groups vs. healthy, -1.1
Zarzycki et al. [52]	Case-control, 3b	ACLR (, 8M, 10F, ); Healthy (, 8M, 10F, )	Eight hamstrings, 5 patellar tendons, 3 allografts; days after surgery	ICF, MEP, SICI, and RMT	Participant seated in dynamometer and relaxed	No significant differences were found in RMT between the ACLR limb (T) and the uninvolved limb (T)—; The ACLR limb showed significantly higher RMT compared to healthy controls (T)—; ACLR group showed higher MEP in both limbs compared to both healthy-matched limbs. ACLR group showed between-limb differences in SICI. No differences were observed in ICF	For RMT: ACLR vs. uninvolved,; ACLR vs. healthy,
Ward et al. [59]	Case-control, 3b	ACLR (, 12M, 6F, ); Healthy (, 12M, 6F, )	Unspecified; days after surgery	AMT, CSP, ICF, LICI, MEP, and SICI	Rectus femoris contraction at 10% MVIC	Differences in AMT between the ACLR limb (T), the uninvolved limb (T), and healthy controls (T) were not significant; The ACLR limb showed longer CSP compared to the uninvolved limb and healthy controls. No differences were observed for MEP, LICI, and SICI	For AMT: ACLR vs. uninvolved,; ACLR vs. healthy,
Héroux and Tremblay [58]	Case-control, 3b	ACLD (, 4M, 6F, ); Healthy (, 4F, )	22 (range 4-108) months from injury	RMT and MEP	Quadriceps contraction for MEP recordings (details unspecified)	RMT values from the ACLD limb were significantly lower () compared to the uninvolved limb. No comparisons were made to the healthy group; No differences were observed for MEP	Unable to determine

%T = percentage of 2.0 tesla; ACLD = anterior cruciate ligament deficiency; ACLR = anterior cruciate ligament reconstruction; AMT = active motor threshold; CSP = cortical silent period; ES = effect size; F = females; ICF = intracortical facilitation; LICI = long-interval intracortical inhibition; M = males; MEP = motor-evoked potential; MVIC = maximal voluntary isometric contraction; RMT = resting motor threshold; SICI = short-interval intracortical inhibition.