Assessment of Return to Sport After ACL Reconstruction With Soft Tissue Autograft in Adolescent Athletes: Quadriceps Versus Hamstring Tendon

Abstract

Background:

Quadriceps tendon soft tissue autograft represents an increasingly popular graft option for anterior cruciate ligament reconstruction (ACLR), particularly for adolescents, some of whom have an open physis, precluding use of graft options with bone plugs.

Purpose/Hypothesis:

The purpose of this study was to quantify return-to-sport performance assessments in adolescents at 6 months after ACLR with all–soft tissue quadriceps tendon autograft (ACLR-Q) versus hamstring tendon autograft (ACLR-HS). It was hypothesized that ACLR-Q would be associated with improved hamstring strength and hamstring-to-quadriceps (HS:Q) ratios compared with ACLR-HS, albeit with decreased quadriceps strength.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Included were patients aged 12 to 19 years who underwent primary ACLR by a single surgeon and who completed a return-to-sport performance assessment between 5 and 9 months postoperatively. The performance assessment included manual muscle strength tests (hamstring, quadriceps, hip abductor and adductor), dynamic balance test (Y-balance), and functional hop tests (single hop, triple hop, crossover hop, 6-m timed hop). Data were converted to limb symmetry indices, and limb symmetry index deficits were compared between the ACLR-Q and ACLR-HS cohorts using the Student t test or Wilcoxon-Mann-Whitney test.

Results:

An initial cohort of 90 ACLR-Q patients was compared with 54 ACLR-HS patients, with no significant differences in patient characteristics. Differences in meniscal repair rates, however, prompted use of propensity score matching on age, sex, body mass index, meniscectomy, and meniscal repair to produce comparable subcohorts. The matching resulted in 67 ACLR-Q and 52 ACLR-HS patients. Hamstring strength deficits were significantly greater in ACLR-HS versus ACLR-Q patients (−40.5% vs −5.7%; P < .001). Quadriceps strength deficits were significantly greater in ACLR-Q versus ACLR-HS patients (−12.8% vs −0.4%; P < .001). ACLR-Q patients had a significantly greater HS:Q ratio on the operative knee (P < .001) and significantly higher Y-balance composite score deficits (−2.9% vs −0.4%; P = .01) than ACLR-HS patients. There were no significant differences in hop test performance between groups.

Conclusion:

Adolescent athletes who underwent ACLR-Q showed significantly greater quadriceps strength deficits but significantly smaller hamstring strength deficits than those who underwent ACLR-HS, leading to more favorable HS:Q ratios in ACLR-Q patients at 6 months postoperatively.

Keywords

anterior cruciate ligament ACL reconstruction quadriceps tendon autograft complications surgical learning curve

Anterior cruciate ligament (ACL) injury is an increasingly common injury in the pediatric and adolescent age groups,⁴⁹ owing in part to increasing competitive sport participation by younger athletes.¹⁵ Currently, ACL reconstruction (ACLR) is recommended as the treatment of choice, as ACL deficiency is associated with secondary chondral and meniscal injuries.^28,31 Although adolescents generally demonstrate good clinical results after ACLR with a high rate of return to sport (RTS),³⁰ subsequent graft rupture rates between 10% and 20% have been reported in the literature.^25,54 Graft type,²⁵ timing of RTS,¹² hamstring strength, and hamstring-to-quadriceps (HS:Q) ratio have been shown to be risk factors for ACL graft failure.^33,41

The 2 traditional graft choices for ACLR are hamstring and bone–patellar tendon–bone (BTB) autograft,^2,6 with the quadriceps tendon autograft growing in popularity as an alternative soft tissue graft choice, particularly in the adolescent population.¹⁷ However, soft tissue autografts may be preferable to autografts that involve harvesting of bone plugs. Grafts with bone plugs often cause greater donor-site morbidity, such as anterior knee pain and kneeling pain,³⁷ introduce risk of patellar fracture, and may not be a safe option in the adolescent population with open physes and significant growth remaining.¹⁴ The quadriceps tendon soft tissue autograft has the benefit of minimal risk of growth disturbance using transphyseal or physeal-respecting techniques,¹⁰ while providing advantages over hamstring tendon autografts, which may include larger, more consistent graft dimensions¹¹ and improved knee flexor strength postoperatively.³⁴ Clinically, ACLR with quadriceps tendon autograft (ACLR-Q) has been shown to have equivalent or better functional outcomes in comparison with ACLR with hamstring tendon autograft (ACLR-HS).^8,34 In the adolescent population specifically, ACLR-Q has demonstrated strong functional outcomes with lower rates of graft failure compared with hamstring tendon autografts.^17,42

Most patients expect to continue their athletic careers at their preinjury level after ACLR.⁵³ Therefore, graft choice may be influenced by patients’ likelihood of returning to sport. RTS performance assessments help to determine where a patient is in one’s rehabilitation and whether one is ready to RTS or not. These RTS assessments often include quadriceps and hamstring strength, functional assessments including hop tests, and measures involving quality of movement.⁵² Postoperative hamstring and quadriceps strength is often compared with the opposite limb using a limb symmetry index (LSI), which is expressed as a percentage and calculated as ([involved limb/uninvolved limb] − 1) × 100%.^9,18 Commonly cited benchmarks used to determine readiness to RTS include hamstring and quadriceps LSIs within −10% before RTS, while LSIs within −20% are recommended before return to running.^{1,26,35,38,50} Quantitative data of the RTS performance assessments have not been well studied in youth athletes, specifically with respect to the quadriceps tendon autograft.

The purpose of this study was to quantify postoperative RTS performance assessments in adolescents 6 months after ACLR-Q versus those with ACLR-HS. Our hypothesis was that ACLR-Q would be associated with improved hamstring strength and HS:Q ratios compared with ACLR-HS, albeit with decreased postoperative quadriceps strength at 6 months.

Methods

Study Design

The institutional review board of the study institution approved the current study protocol, and all included participants or their parent/guardian provided written informed consent. Adolescent patients who underwent primary ACLR using either quadriceps or hamstring tendon autograft routinely underwent RTS strength performance assessments as part of standard postoperative care to assess rehabilitation progress and potential performance deficits 6 months after ACLR. The postoperative rehabilitation protocol for all patients consisted of that published by the Multicenter Orthopaedic Outcomes Network group.⁵⁶ The demographic data (age, height, and weight) were obtained from a review of the patient’s electronic medical record. The status and treatment of any meniscal tears, as well as the duration from ACLR to testing, were documented and included in the analysis.

Patient Selection

Included in the study were adolescent athletes who were 12 to 19 years of age, sustained ACL injuries and underwent primary ACLR between 2017 and 2019 with either all–soft tissue ACLR-Q or ACLR-HS by a single surgeon (B.E.H.) at a pediatric tertiary-care hospital. The choice of the all–soft tissue graft that was used (ACLR-Q vs ACLR-HS) was based on patient/family preference after a discussion with the surgical team regarding potential risks and benefits of both graft types including donor-site morbidity. Patients also needed to have completed an RTS performance assessment between 5 and 9 months postoperatively. Exclusion criteria were athletes ≥20 years of age, prior ipsilateral or contralateral knee surgery, use of allograft for the ACLR, and concomitant procedures other than meniscal repair or meniscectomy.

RTS Performance Assessments and Follow-up

The RTS performance assessments were completed by health care practitioners (board-certified athletic trainers) as part of the standard rehabilitation care at approximately 6 months postoperatively (between 5 and 9 months). The RTS performance assessments included strength testing (hip abductor, hip adductor, quadriceps, hamstring), HS:Q ratios, balance testing (Y-balance composite score), and functional hop testing (single hop, triple hop, crossover hop, 6-m timed hop).

Muscle Strength Tests

Quadriceps strength was assessed with patients seated at the edge of the treatment table with their knees at 90° of flexion. A handheld dynamometer (Hoggan Scientific LLC) was then applied to the anterior aspect of the distal tibia above the dome of the talus, and patients were asked to extend their knees with maximum effort. For hamstrings strength, patients were in a prone position with 90° of knee flexion, and a handheld dynamometer was applied at the posterior side (Achilles tendon side) of the distal tibia. Patients were then asked to further flex their knees toward the hip with maximum effort. For hip abductor strength testing, patients lay on their side; a handheld dynamometer was applied above the lateral malleolus, and patients were asked to move their legs toward the ceiling with maximum effort (direction of hip abduction).^46-48

Dynamic Balance Test

Dynamic balance was measured using a commercially available Y-balance assessment system (Functional Movement System). Participants were allowed to practice several times after instructions were provided then were asked to stand at the center of the equipment and push a plastic piece to anterior, posteromedial, and posterolateral directions, respectively.⁴⁵ This was performed 3 times in each direction for both limbs. The mean distance for each direction was used for the analysis with the composite score calculated by taking the sum of the 3 distances and dividing by 3 times the limb length, multiplied by 100.^19,45

Functional Hop Tests

Four types of hop tests were performed: the single hop, triple hop, crossover hop, and 6-m timed hop. Instructions were given before each hop test, and participants practiced each hop task several times. During the single-hop test, participants hopped 1 time with a single leg and were asked to maintain balance in landing for approximately 3 seconds. For the triple-hop test, participants hopped 3 times consecutively with a single leg and were asked to maintain balance in landing for 3 seconds on the final landing. In the crossover hop, participants hopped 3 times with zigzag figures (medial, lateral, and medial sequences) using a single leg. Participants were asked to maintain balance for 3 seconds at the landing of the final hop. For single hop and crossover hop, if participants could not maintain their balance for 3 seconds, a retest was performed. For the 6-m timed hop, participants were asked to hop a 6-m distance as fast as possible. Tape measures and stopwatches were used to perform the test.⁴⁵

Strength and functional deficits were reported as LSIs of the ACLR limb compared with the uninvolved limb, subtracting 100% from the scores.

Statistical Analysis

Patient characteristics, meniscal treatment, and RTS performance assessment outcomes were summarized for both the ACLR-Q and the ACLR-HS groups. Continuous variables were summarized using means and standard deviations, with median and interquartile range (IQR) values used where appropriate. Counts and percentages were used for categorical variables. LSI deficits were compared between the ACLR-Q group and the ACLR-HS group using the Student t test or the Wilcoxon-Mann-Whitney test depending on normality of the data. Propensity score matching was conducted to create matched subcohorts and remove meniscal repair rates as a confounder. The IBM SPSS statistical software (Version 21; SPSS Inc) was used for all analyses, and P < .05 was used as the threshold for statistical significance.

Results

Of 181 possible patients, 144 patients (90 ACLR-Q and 54 ACLR-HS patients) were initially identified as meeting the inclusion criteria for the study. There were no significant differences in demographic characteristics between the 2 groups. Differences in meniscal repair rates, however, prompted use of propensity score matching on age, sex, body mass index, meniscectomy, and meniscal repair to produce comparable subcohorts. After the propensity score matching, 119 patients were included in the study (67 ACLR-Q and 52 ACLR-HS patients) (Figure 1). The mean age of these patients was 15.7 ± 1.68 years, and 61% were female. The characteristics of the final study participants are shown in Table 1.

Figure 1.

Flow diagram depicting the ACLR patients included in the study along with reasons for exclusion at each stage. ACLR, anterior cruciate ligament reconstruction; ACLR-HS, ACLR with hamstring tendon autograft; ACLR-Q, ACLR with quadriceps tendon autograft; BMI, body mass index; RTS, return to sport.

Table 1

Characteristics of the Matched Cohort Overall and by Autograft Type^a

Characteristic	All Patients (N = 119)	ACLR-Q (n = 67)	ACLR-HS (n = 52)	P
Age at surgery, y	15.7 ± 1.68	15.7 ± 1.82	15.7 ± 1.49	.91
Female sex, %	72 (61)	43 (64)	29 (56)	.35
Height, m	1.7 ± 0.08	1.7 ± 0.09	1.7 ± 0.07	.84
Weight, kg	66.5 ± 13.59	66.9 ± 13.81	66.0 ± 13.42	.74
Body mass index, kg/m²	23.3 ± 4.05	23.4 ± 4.13	23.1 ± 4.00	.77

Data are reported as mean ± SD or n (%). ACLR-Q, anterior cruciate ligament reconstruction with quadriceps tendon autograft; ACLR-HS, anterior cruciate ligament reconstruction with hamstring tendon autograft.

Within the ACLR-Q group, the median time to RTS performance assessment was 6.3 months (IQR, 5.98-6.70 months), and it was 6.1 months (IQR, 6.0-6.47 months) within the ACLR-HS group. Concomitant meniscal pathology was addressed with meniscectomy in 30% of patients and with meniscal repair in 43% within the ACLR-Q group. In the ACLR-HS group, 33% underwent meniscectomy and 52% underwent a meniscal repair.

When comparing the ACLR-Q and ACLR-HS groups, there was no significant difference in mean hip abductor strength LSI (2.8% ± 22.68% vs 4.7% ± 20.04%; P = .62) or adductor strength LSI (−0.4% ± 12.14% vs −1.3% ± 13.00%; P = .71). However, mean hamstring strength LSI deficits were significantly greater in ACLR-HS patients than ACLR-Q patients (−40.5% vs −5.7%; P < .001). Conversely, mean quadriceps strength LSI deficits were significantly greater in ACLR-Q patients versus ACLR-HS patients, who did not on average demonstrate deficits (−12.8% vs −0.4%; P < .001). ACLR-Q patients had a significantly greater mean HS:Q ratio for the operative knee (0.6 ± 0.19 vs 0.3 ± 0.10; P < .001).

There was no significant difference in mean single-leg hop LSI deficits (−10.1% ± 14.07% vs −9.1% ± 15.13%; P = .76), mean crossover-hop LSI deficits (−8.1% ± 11.30% vs −2.0% ± 17.66%; P = .09), or mean 6-m timed hop LSI, in which there was not a deficit in either group (6.0% ± 10.66% vs 4.1% ± 11.71%; P = .43). ACLR-Q patients demonstrated significantly larger Y-balance mean composite score deficits than ACLR-HS patients (−2.9% vs −0.4%; P = .01) (Table 2).

Table 2

RTS Performance by Matched-Patient Autograft Type^a

Performance Measure	ACLR-Q (n = 67)	ACLR-HS (n = 52)	P
Time to RTS testing, mo	6.3 [5.98-6.70]	6.1 [6.0-6.47]	.11
Meniscectomy	20 (30)	17 (33)	.74
Meniscal repair	29 (43)	27 (52)	.35
Hip abductor strength LSI, %	2.8 ± 22.68	4.7 ± 20.04	.62
Hip adductor strength LSI, %	−0.4 ± 12.14	−1.3 ± 13.00	.71
Hamstring strength LSI, %	−5.7 ± 11.93	−40.5 ± 15.88	<.001
Quadriceps strength LSI, %	−12.8 ± 17.01	−0.4 ± 14.52	<.001
HS:Q ratio	0.6 ± 0.19	0.3 ± 0.10	<.001
Y-balance composite score LSI, % (n = 116)^b	−2.9 ± 5.25	−0.4 ± 5.04	.01
Single hop LSI, % (n = 97)^b	−10.1 ± 14.07	−9.1 ± 15.13	.76
Crossover hop LSI, % (n = 83)^b	−8.1 ± 11.30	−2.0 ± 17.66	.09
6-m timed hop LSI, % (n = 90)^b	6.0 ± 10.66	4.1 ± 11.71	.43

Data are reported as median [IQR], mean ± SD, or n (%). Boldface P values indicate statistically significant difference between groups (P < .05). ACLR-HS, anterior cruciate ligament reconstruction with hamstring tendon autograft; ACLR-Q, anterior cruciate ligament reconstruction with quadriceps tendon autograft; HS:Q, hamstring-to-quadriceps; LSI, limb symmetry index; RTS, return to sport.

The number in parentheses represents the number of patients with available data for the given characteristic.

Discussion

The current study demonstrated that adolescent athletes who underwent ACLR-HS showed significantly greater mean hamstring strength deficits of 40.5% compared with those who underwent ACLR-Q. Furthermore, ACLR-HS patients demonstrated a significantly reduced mean HS:Q ratio, thus supporting the study hypothesis. Given that the hamstring muscles and other knee flexor muscle groups may be considered the most important functional or dynamic knee stabilizers,^5,33,41 the sequelae of such severe weakness may be considered clinically significant deficits, particularly as they relate to risk of ACL retear and graft rupture. Notably, patients who underwent ACLR-Q had significantly greater mean quadriceps strength deficits—12.8% at 6 months postoperatively—compared with patients who underwent ACLR-HS. However, these differences did not seem to have a substantial functional influence, as there was no significant difference in functional hop test performances between the 2 groups. While the difference in Y-balance composite score deficit between the ACLR-Q (−2.9%) and the ACLR-HS groups (−0.4%) also met the threshold for statistical significance, there may be minimal clinical significance to such a difference, as both deficits were quite small and well within the commonly accepted threshold of 10% deficit,^{1,26,35,38,50} or a more strict 6% deficit,^7,36,43 that may be used to gauge what is safe or reasonable for clearing patients to RTS.

The magnitude of quadriceps weakness at 6 months after ACLR-Q (mean LSI: −12.8%) in this study is somewhat expected, based on results from previous studies after ACLR with both quadriceps or BTB autograft harvest,^22,27,47 both of which represent disruptions to the normal function or integrity of the extensor mechanism, simply at different points along the length of the entire muscle-tendon unit. A recent study assessing muscle strength in adolescents 6 to 9 months post-ACLR using BTB autografts reported a mean 12.2% deficit in quadriceps strength.⁴⁷ Similarly, Hunnicutt et al²⁷ assessed 30 patients undergoing ACLR with either quadriceps tendon or BTB autograft and found similar quadriceps strength LSIs between the 2 groups at a mean of 8 months postoperatively. Additionally, Han et al²² studied 144 patients and found no significant difference in quadriceps isokinetic strength after ACLR with either quadriceps tendon autograft or BTB autograft at 1 year postoperatively. While Hughes et al²⁶ found that patients who had undergone ACLR with quadriceps tendon autografts had significantly greater quadriceps isokinetic strength deficits compared to those with BTB autografts at 5 to 8 months postoperatively, there was no significant difference between the groups at the 9- to 15-month follow-up.

The adolescent athletes in this study with ACLR-HS demonstrated severe hamstring deficits with mean LSI values of −40.5%, as well as a significantly reduced HS:Q ratio of 0.3. Commonly cited benchmarks used to determine readiness to RTS include hamstring and quadriceps LSIs within −10% before RTS, while LSIs within −20% are recommended before return to running.^{1,26,35,38,50} Fischer et al¹⁶ compared mostly adult patients who had undergone ACLR with either hamstring or quadriceps tendon autograft and similarly found that the hamstring tendon autograft group had significantly reduced HS:Q ratios at both 5.5 and 7.6 months postoperatively. Higher HS:Q ratios may be clinically important, as a study by Kyritsis et al³³ in professional athletes found that hamstring strength deficits were associated with an increased risk of graft failure. Specifically, the study found that for each 10% decrease in HS:Q ratio there was a >10-fold increase in risk of graft failure. Furthermore, Palmieri-Smith et al⁴¹ found that in patients who previously had ACLR, those who did not sustain reinjury had higher levels of hamstring activity before landing, further substantiating the importance of hamstring strength in preventing reinjury. In 2 previous studies, the magnitude of the hamstring deficit was not as severe, with mean LSIs of −20.5% at 5 to 8 months²⁶ and −13.7% at 5.5 months,¹⁶ respectively. However, the patients in these studies were not exclusively adolescents. In a previous study of adolescent patients ≤21 years of age, a mean hamstring strength deficit of 31.7% was reported when hamstring tendon autografts were used.⁴⁷ Given that only patients ≤19 years of age were included in the current study, the magnitude and, in kind, the clinical impact of hamstring deficits after ACLR-HS may be higher in younger populations.

Importantly, the adolescent athletes in the ACLR-Q group in the current study underwent RTS performance assessments at a median of 6.3 months postoperatively. Considering the commonly used benchmark of 10% deficits in LSIs,^{1,26,35,38,50} the only RTS performance assessment for which these patients, on average, did not meet the benchmark was the quadriceps strength LSI (mean: −12.8%). However, a 10% quadriceps deficit may not be as important as a definitive threshold for RTS, as Novaretti et al³⁹ found that there was no significant difference in the rate of return to preinjury level of sport at 6 months using either a 10% or a 20% quadriceps strength deficit threshold. In other words, a 6-month time frame may be too early to use for RTS criteria, given that 9-month testing may show adequate RTS performance for the quadriceps autograft group. A recent study evaluating RTS assessments in adolescents after ACLR-Q found a similar quadriceps LSI deficit of 15% at 6 months.⁴⁴ However, the authors found that at 9 months there was significant improvement in the quadriceps strength LSI deficits, to a magnitude of 7.5%.⁴⁴

Although the current study demonstrated a statistically significant difference in Y-balance composite scores between the ACLR-Q (−2.9%) and ACLR-HS (−0.4%) groups, this difference does not likely represent a clinically important difference. In previous studies examining the relationship between the Y-balance test in athletes and risk of future lower extremity injuries, a threshold of 6% deficit on the composite test has been reported to represent a clinically important value.^7,36,43

Finally, there was no significant difference in functional hop test performance between the ACLR-Q and ACLR-HS groups in the current study. Moreover, the magnitude of LSI deficits for each of the functional hop tests was either close to, or met the established criteria of, <10% deficit for safely returning to sport, which has been previously established.^21,33 Quadriceps strength and function have been shown to play a vital role in functional performance and hop tests.^23,40,57 Therefore, the functional hop test results from the current study suggest that the patients in this study may have a promising ability to achieve quadriceps recovery among adolescent ACLR-Q patients. However, it is interesting to note that crossover/ 6-m timed hop test and Y-balance deficits were <10% for both groups despite a mean quadriceps deficit of 12.8% and a mean hamstring deficit of 40.5%. Several previous studies have similarly found a lack of association between strength deficits and hop test performance after ACLR.^3,24,29 Some have suggested that this lack of correlation relates to patients’ ability to compensate for strength deficits with strong hip or trunk muscles.^3,24,29 While it has been previously reported that quadriceps deficit at 6 months postoperatively does not affect the probability of returning to sport,³² others have found that quadriceps strength deficits increase the risk of ACL reinjury.²⁰ Future studies assessing the longer term impacts of strength deficits, functional hop test results, and Y-balance composite scores on patient-reported outcomes, functional outcomes, and rerupture rates will help to better discern the clinical implications of the deficits identified in the present study. A better understanding of the future clinical implications of the 6-month strength deficits identified in the present study may help us understand whether consideration of changes to the postoperative rehabilitation protocol for these patients might be important.

Limitations

Limitations of this investigation include the study design, which was a retrospective rather than prospective cohort study or randomized controlled trial. However, in order to mitigate effects from confounding variables, propensity-matched scoring was used to create comparable subgroups. We also did not collect race- and ethnicity-related information. Several recent studies have suggested that racial and ethnic parameters influence the care and outcomes of ACLR patients, and the absence of these variables may have affected the results of the current study.^4,13 Furthermore, the RTS testing was performed at a median of 6.2 months from surgery. Repeat RTS performance assessments at a later time point may have further demonstrated the readiness of the adolescent athletes to RTS after ACLR with either of the soft tissue autograft options. The contralateral limb was used for comparison to determine the strength and functional deficits of the operative limb. Because patients can experience detraining and possibly atrophy of the uninvolved limb after ACLR, these LSI values could overestimate the strength and function of the operative limb compared with the true preinjury capacity level.⁵⁵ Conversely, the contralateral limb could experience gains in strength throughout rehabilitation, which can cause LSI values to underestimate the absolute strength of the operative limb relative to baseline.

Furthermore, isometric measures were used to quantify strength in this study. Isokinetic strength measures might have provided more reliable measures of strength. Preoperative testing was not performed in this study and may have served as a useful comparison, particularly of the uninvolved limb. In addition, we did not assess whether the adolescent athletes included were ultimately able to RTS or if they were able to do so at their preinjury level. Although a proper assessment of other RTS outcomes would not have been possible given the timeline of the study, it remains an important consideration for future investigation. Moreover, it is important to note that there are a number of other important factors that play a role in the ability to RTS, rather than simple performance benchmarks, such as an adolescent’s psychological readiness.⁵¹ Therefore, the results of this study should be taken in context of the larger RTS considerations that include an athlete’s mental and physical readiness as well as the level and type of sport participation.

Conclusion

Adolescent athletes who underwent ACLR-Q showed significantly greater quadriceps strength deficits (mean LSI: −12.8%), but significantly smaller hamstring strength deficits, than those who underwent ACLR-HS (mean LSI: −40.5%), leading to more favorable HS:Q ratios in ACLR-Q patients 6 months postoperatively. While Y-balance composite score deficits were smaller in ACLR-HS patients than ACLR-Q patients, no differences were detected in hop test performance. The degree to which these performance metrics influence eventual athletic performance and ACL graft-tear risk remains a critical area of continued investigation.

Footnotes

Final revision submitted April 18, 2023; accepted May 19, 2023.

One or more of the authors has declared the following potential conflict of interest or source of funding: B.E.H. has received nonconsulting fees from Arthrex; education payments from Arthrex, Kairos Surgical, and Pylant Medical; consulting fees from Imagen Technologies; and royalties from Springer Science & Business Media; B.E.H. also has stock/stock options in Imagen Technologies. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Ethical approval for this study was obtained from Boston Children’s Hospital (reference No. IRB-P00032638).

References

Adams

Logerstedt

Hunter-Giordano

Axe

Snyder-Mackler

. Current concepts for anterior cruciate ligament reconstruction: a criterion-based rehabilitation progression. J Orthop Sports Phys Ther. 2012;42(7):601-614. doi:10.2519/jospt.2012.3871

Arnold

Calcei

Vogel

, et al. ACL Study Group survey reveals the evolution of anterior cruciate ligament reconstruction graft choice over the past three decades. Knee Surg Sports Traumatol Arthrosc. 2021;29(11):3871-3876. doi:10.1007/s00167-021-06443-9

Barfod

Feller

Hartwig

Devitt

Webster

. Knee extensor strength and hop test performance following anterior cruciate ligament reconstruction. Knee. 2019;26(1):149-154. doi:10.1016/j.knee.2018.11.004

Bram

Talathi

Patel

DeFrancesco

Striano

Ganley

. How do race and insurance status affect the care of pediatric anterior cruciate ligament injuries? Clin J Sport Med. 2020;30(6):e201-e206. doi:10.1097/JSM.0000000000000706

Bryant

Creaby

Newton

Steele

. Dynamic restraint capacity of the hamstring muscles has important functional implications after anterior cruciate ligament injury and anterior cruciate ligament reconstruction. Arch Phys Med Rehabil. 2008;89(12):2324-2331. doi:10.1016/j.apmr.2008.04.027

Buller

Best

Baraga

Kaplan

. Trends in anterior cruciate ligament reconstruction in the United States. Orthop J Sports Med. 2015;3(1):2325967114563664. doi:10.1177/2325967114563664

Butler

Southers

Gorman

Kiesel

Plisky

. Differences in soccer players’ dynamic balance across levels of competition. J Athl Train. 2012;47(6):616-620. doi:10.4085/1062-6050-47.5.14

Cavaignac

Coulin

Tscholl

Nik Mohd Fatmy

Duthon

Menetrey

. Is quadriceps tendon autograft a better choice than hamstring autograft for anterior cruciate ligament reconstruction? A comparative study with a mean follow-up of 3.6 years. Am J Sports Med. 2017;45(6):1326-1332. doi:10.1177/0363546516688665

Clagg

Paterno

Hewett

Schmitt

. Performance on the modified Star Excursion Balance Test at the time of return to sport following anterior cruciate ligament reconstruction. J Orthop Sports Phys Ther. 2015;45(6):444-452. doi:10.2519/jospt.2015.5040

10.

Crum

Kay

Lesniak

Getgood

Musahl

de Sa

. Bone versus all soft tissue quadriceps tendon autografts for anterior cruciate ligament reconstruction: a systematic review. Arthroscopy. 2021;37(3):1040-1052. doi:10.1016/j.arthro.2020.10.018

11.

DeAngelis

Fulkerson

. Quadriceps tendon—a reliable alternative for reconstruction of the anterior cruciate ligament. Clin Sports Med. 2007;26(4):587-596. doi:10.1016/j.csm.2007.06.005

12.

Dekker

Godin

Dale

Garrett

Taylor

Riboh

. Return to sport after pediatric anterior cruciate ligament reconstruction and its effect on subsequent anterior cruciate ligament injury. J Bone Joint Surg Am. 2017;99(11):897-904. doi:10.2106/JBJS.16.00758

13.

Devana

Solorzano

Nwachukwu

Jones

. Disparities in ACL reconstruction: the influence of gender and race on incidence, treatment, and outcomes. Curr Rev Musculoskelet Med. 2022;15(1):1-9. doi:10.1007/s12178-021-09736-1

14.

Fabricant

Kocher

. Management of ACL injuries in children and adolescents. J Bone Joint Surg Am. 2017;99(7):600-612. doi:10.2106/JBJS.16.00953

15.

Fabricant

Lakomkin

Sugimoto

Tepolt

Stracciolini

Kocher

. Youth sports specialization and musculoskeletal injury: a systematic review of the literature. Phys Sportsmed. 2016;44(3):257-262. doi:10.1080/00913847.2016.1177476

16.

Fischer

Fink

Herbst

, et al. Higher hamstring-to-quadriceps isokinetic strength ratio during the first post-operative months in patients with quadriceps tendon compared to hamstring tendon graft following ACL reconstruction. Knee Surg Sports Traumatol Arthrosc. 2018;26(2):418-425. doi:10.1007/s00167-017-4522-x

17.

Gagliardi

Carry

Parikh

Albright

. Outcomes of quadriceps tendon with patellar bone block anterior cruciate ligament reconstruction in adolescent patients with a minimum 2-year follow-up. Am J Sports Med. 2020;48(1):93-98. doi:10.1177/0363546519885371

18.

Greenberg

Ganley

Lawrence

JTR

. Strength and functional performance recovery after anterior cruciate ligament reconstruction in preadolescent athletes. Sports Health. 2014;6(4):309-312. doi:10.1177/1941738114537594

19.

Gribble

Hertel

. Considerations for normalizing measures of the Star Excursion Balance Test. Meas Phys Educ Exerc Sci. 2003;7(2):89-100. doi:10.1207/S15327841MPEE0702_3

20.

Grindem

Snyder-Mackler

Moksnes

Engebretsen

Risberg

. Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: the Delaware-Oslo ACL cohort study. Br J Sports Med. 2016;50(13):804-808. doi:10.1136/bjsports-2016-096031

21.

Gustavsson

Neeter

Thomeé

, et al. A test battery for evaluating hop performance in patients with an ACL injury and patients who have undergone ACL reconstruction. Knee Surg Sport Traumatol Arthrosc. 2006;14(8):778-788. doi:10.1007/s00167-006-0045-6

22.

Han

Seong

Lee

. Anterior cruciate ligament reconstruction. Clin Orthop Relat Res. 2008;466(1):198-204. doi:10.1007/s11999-007-0015-4

23.

Hashemi

Breighner

Jang

Chandrashekar

Ekwaro-Osire

Slauterbeck

. Increasing pre-activation of the quadriceps muscle protects the anterior cruciate ligament during the landing phase of a jump: an in vitro simulation. Knee. 2010;17(3):235-241. doi:10.1016/j.knee.2009.09.010

24.

Herrington

Ghulam

Comfort

. Quadriceps strength and functional performance after anterior cruciate ligament reconstruction in professional soccer players at time of return to sport. J Strength Cond Res. 2021;35(3):769-775. doi:10.1519/JSC.0000000000002749

25.

Edmonds

Chambers

Bastrom

Pennock

. Risk factors for early ACL reconstruction failure in pediatric and adolescent patients: a review of 561 cases. J Pediatr Orthop. 2018;38(7):388-392. doi:10.1097/BPO.0000000000000831

26.

Hughes

Burnham

Hirsh

, et al. Comparison of short-term Biodex results after anatomic anterior cruciate ligament reconstruction among 3 autografts. Orthop J Sports Med. 2019;7(5):2325967119847630. doi:10.1177/2325967119847630

27.

Hunnicutt

Gregory

McLeod

Woolf

Chapin

Slone

. Quadriceps recovery after anterior cruciate ligament reconstruction with quadriceps tendon versus patellar tendon autografts. Orthop J Sports Med. 2019;7(4):2325967119839786. doi:10.1177/2325967119839786

28.

James

Dawkins

Schachne

, et al. Early operative versus delayed operative versus nonoperative treatment of pediatric and adolescent anterior cruciate ligament injuries: a systematic review and meta-analysis. Am J Sports Med. 2021;49(14):4008-4017. doi:10.1177/0363546521990817

29.

Johnston

Feller

McClelland

Webster

. Strength deficits and flexion range of motion following primary anterior cruciate ligament reconstruction differ between quadriceps and hamstring autografts. J ISAKOS. 2021;6(2):88-93. doi:10.1136/jisakos-2020-000481

30.

Kay

Memon

Marx

Peterson

Simunovic

Ayeni

. Over 90% of children and adolescents return to sport after anterior cruciate ligament reconstruction: a systematic review and meta-analysis. Knee Surg Sports Traumatol Arthrosc. 2018;26(4):1019-1036. doi:10.1007/s00167-018-4830-9

31.

Kay

Memon

Shah

, et al. Earlier anterior cruciate ligament reconstruction is associated with a decreased risk of medial meniscal and articular cartilage damage in children and adolescents: a systematic review and meta-analysis. Knee Surg Sports Traumatol Arthrosc. 2018;26(12):3738-3753. doi:10.1007/s00167-018-5012-5

32.

Krych

Arutyunyan

Kuzma

Levy

Dahm

Stuart

. Adverse effect of femoral nerve blockade on quadriceps strength and function after ACL reconstruction. J Knee Surg. 2014;28(01):83-88. doi:10.1055/s-0034-1371769

33.

Kyritsis

Bahr

Landreau

Miladi

Witvrouw

. Likelihood of ACL graft rupture: not meeting six clinical discharge criteria before return to sport is associated with a four times greater risk of rupture. Br J Sports Med. 2016;50(15):946-951. doi:10.1136/bjsports-2015-095908

34.

Lee

. Outcomes of anatomic anterior cruciate ligament reconstruction: bone-quadriceps tendon graft versus double-bundle hamstring tendon graft. Am J Sports Med. 2016;44(9):2323-2329. doi:10.1177/0363546516650666

35.

Lynch

Logerstedt

Grindem

, et al. Consensus criteria for defining “successful outcome” after ACL injury and reconstruction: a Delaware-Oslo ACL cohort investigation. Br J Sports Med. 2015;49(5):335-342. doi:10.1136/bjsports-2013-092299

36.

Mayer

Queen

Taylor

, et al. Functional testing differences in anterior cruciate ligament reconstruction patients released versus not released to return to sport. Am J Sports Med. 2015;43(7):1648-1655. doi:10.1177/0363546515578249

37.

Mouarbes

Menetrey

Marot

Courtot

Berard

Cavaignac

. Anterior cruciate ligament reconstruction: a systematic review and meta-analysis of outcomes for quadriceps tendon autograft versus bone–patellar tendon–bone and hamstring-tendon autografts. Am J Sports Med. 2019;47(14):3531-3540. doi:10.1177/0363546518825340

38.

Nawasreh

Logerstedt

Cummer

Axe

Risberg

Snyder-Mackler

. Do patients failing return-to-activity criteria at 6 months after anterior cruciate ligament reconstruction continue demonstrating deficits at 2 years? Am J Sports Med. 2017;45(5):1037-1048. doi:10.1177/0363546516680619

39.

Novaretti

Franciozi

Forgas

Sasaki

Ingham

SJM

Abdalla

. Quadriceps strength deficit at 6 months after ACL reconstruction does not predict return to preinjury sports level. Sports Health. 2018;10(3):266-271. doi:10.1177/1941738118759911

40.

Palmieri-Smith

Lepley

. Quadriceps strength asymmetry after anterior cruciate ligament reconstruction alters knee joint biomechanics and functional performance at time of return to activity. Am J Sports Med. 2015;43(7):1662-1669. doi:10.1177/0363546515578252

41.

Palmieri-Smith

Strickland

Lepley

. Hamstring muscle activity after primary anterior cruciate ligament reconstruction—a protective mechanism in those who do not sustain a secondary injury? A preliminary study. Sports Health. 2019;11(4):316-323. doi:10.1177/1941738119852630

42.

Pennock

Johnson

Turk

, et al. Transphyseal anterior cruciate ligament reconstruction in the skeletally immature: quadriceps tendon autograft versus hamstring tendon autograft. Orthop J Sports Med. 2019;7(9):2325967119872450. doi:10.1177/2325967119872450

43.

Plisky

Rauh

Kaminski

Underwood

. Star Excursion Balance Test as a predictor of lower extremity injury in high school basketball players. J Orthop Sports Phys Ther. 2006;36(12):911-919. doi:10.2519/jospt.2006.2244

44.

Saper

Wong

Strauss

. Adolescent patients exhibit significant improvements in strength and functional performance from 6 to 9 months after ACL reconstruction with quadriceps autograft. Arthrosc Sports Med Rehabil. 2021;3(3):e837-e843. doi:10.1016/j.asmr.2021.01.026

45.

Sugimoto

Heyworth

Brodeur

Kramer

Kocher

Micheli

. Effect of graft type on balance and hop tests in adolescent males following anterior cruciate ligament reconstruction. J Sport Rehabil. 2019;28(5):468-475. doi:10.1123/jsr.2017-0244

46.

Sugimoto

Heyworth

Collins

Fallon

Kocher

Micheli

. Comparison of lower extremity recovery after anterior cruciate ligament reconstruction with transphyseal hamstring versus extraphyseal iliotibial band techniques in skeletally immature athletes. Orthop J Sports Med. 2018;6(4):2325967118768044. doi:10.1177/2325967118768044

47.

Sugimoto

Heyworth

Yates

Kramer

Kocher

Micheli

. Effect of graft type on thigh circumference, knee range of motion, and lower-extremity strength in pediatric and adolescent males following anterior cruciate ligament reconstruction. J Sport Rehabil. 2020;29(5):555-562. doi:10.1123/jsr.2018-0272

48.

Sugimoto

Howell

Tocci

Meehan

. Risk factors associated with self-reported injury history in female youth soccer players. Phys Sportsmed. 2018;46(3):312-318. doi:10.1080/00913847.2018.1462651

49.

Tepolt

Feldman

Kocher

. Trends in pediatric ACL reconstruction from the PHIS database. J Pediatr Orthop. 2018;38(9):e490-e494. doi:10.1097/BPO.0000000000001222

50.

Thomeé

Kaplan

Kvist

, et al. Muscle strength and hop performance criteria prior to return to sports after ACL reconstruction. Knee Surg Sports Traumatol Arthrosc. 2011;19(11):1798-1805. doi:10.1007/s00167-011-1669-8

51.

Truong

Mosewich

Holt

Miciak

Whittaker

. Psychological, social and contextual factors across recovery stages following a sport-related knee injury: a scoping review. Br J Sports Med. 2020;54(19):1149-1156. doi:10.1136/bjsports-2019-101206

52.

van Melick

van Cingel

REH

Brooijmans

, et al. Evidence-based clinical practice update: practice guidelines for anterior cruciate ligament rehabilitation based on a systematic review and multidisciplinary consensus. Br J Sports Med. 2016;50(24):1506-1515. doi:10.1136/bjsports-2015-095898

53.

Webster

Feller

. Expectations for return to preinjury sport before and after anterior cruciate ligament reconstruction. Am J Sports Med. 2019;47(3):578-583. doi:10.1177/0363546518819454

54.

Webster

Feller

. Exploring the high reinjury rate in younger patients undergoing anterior cruciate ligament reconstruction. Am J Sports Med. 2016;44(11):2827-2832. doi:10.1177/0363546516651845

55.

Wellsandt

Failla

Snyder-Mackler

. Limb symmetry indexes can overestimate knee function after anterior cruciate ligament injury. J Orthop Sport Phys Ther. 2017;47(5):334-338. doi:10.2519/jospt.2017.7285

56.

Wright

Haas

Anderson

, et al. Anterior cruciate ligament reconstruction rehabilitation. Sports Health. 2015;7(3):239-243. doi:10.1177/1941738113517855

57.

Xergia

Pappas

Zampeli

Georgiou

Georgoulis

. Asymmetries in functional hop tests, lower extremity kinematics, and isokinetic strength persist 6 to 9 months following anterior cruciate ligament reconstruction. J Orthop Sport Phys Ther. 2013;43(3):154-162. doi:10.2519/jospt.2013.3967