Abstract
Background
There is some evidence that functional performance and validated outcome scores differ according to the gender, age, and sport participation status of a patient after anterior cruciate ligament (ACL) reconstruction. However, the impact of these three factors, and interaction among them, has not been studied across a large relatively homogeneous group of patients to better elucidate their impact.
Questions/purposes
We reviewed a large cohort of patients who had undergone ACL reconstruction to determine if ROM, knee laxity, objective performance measures, and validated outcome scores differed according to (1) gender; (2) age; and (3) sport participation status.
Methods
This was a retrospective analysis of prospectively collected data. Between 2007 and 2016, we performed 3452 single-bundle ACL reconstructions in patients who participated in sport before ACL injury. Of those, complete followup (including preoperative scores and scores at 1 year after surgery; mean, 14 months; range, 12–20 months) was available on 2672 (77%) of patients. Those lost to followup and those accounted for were not different in terms of age, gender, and sports participation at baseline. The study group consisted of 1726 (65%) men and 946 (35%) women with a mean ± SD age of 28 ± 10 years. For these patients, the following measures were obtained: knee ROM (flexion and extension deficit), instrumented knee laxity, single and triple hop for distance limb symmetry index (LSI), International Knee Documentation Committee (IKDC) subjective evaluation, and Single Assessment Numeric Evaluation score. Mean scores and measures of variability were calculated for each outcome measure. Comparisons were made among gender, age, and sport status.
Results
Men had less knee laxity after reconstruction (men 1.1 ± 2.2 mm, women 1.3 ± 2.4 mm; mean difference 0.2 mm [0.1–0.4], p < 0.001), greater limb symmetry (single limb hop men: 94% ± 12%, women 91% ± 13%, mean difference 3% [2%–4%], p < 0.001), and higher IKDC scores than did women (men 84 ± 12, women 82 ± 12, mean difference 2 [1–3], p < 0.001). With the exception of instrumented laxity, all outcome measures showed reduced deficits and higher scores in younger patients. This was most marked for LSI scores between the youngest and oldest aged patient groups (crossover hop: < 16 years 99% ± 10%, > 45 years 90% ± 16%, mean difference: 9 [5–11], p < 0.001). Patients who had returned to their preinjury sport also scored higher and had smaller deficits for all outcomes except ROM compared with patients who had not returned to sport at the time of followup (IKDC subjective: returned 90 ± 9, no sport 79 ± 12, mean difference 11 points [9–12], p < 0.001; single limb hop: returned 97 ± 10, no sport 91 ± 14, mean difference 6% [5%–7%], p < 0.001).
Conclusions
This study showed that some of the most commonly used functional performance and validated clinical scores for ACL reconstruction are superior for patients who are younger, male, and have returned to preinjury sport. Reference to these data allows clinicians to more effectively evaluate a patient based on their age, gender, and sport status when making return to sport and rehabilitation decisions.
Level of Evidence
Level III, therapeutic study.
Introduction
The incidence of anterior cruciate ligament (ACL) reconstruction is steadily rising [9] and it is well known that female gender is a risk factor for sustaining an ACL injury [6, 14, 15, 18]. With the number of females having ACL reconstruction also increasing, there is growing evidence that the outcome of ACL reconstruction may differ between men and women [1, 19]. Data from the Swedish Knee Ligament Registry have shown that women report worse scores on the Knee Injury and Osteoarthritis Outcome Score (KOOS) both before surgery and 1 and 2 years after ACL reconstruction [1]. A recent systematic review [19], which summarized a range of outcome measures, reported that women had inferior outcomes for instrumented knee laxity, Lysholm and Tegner activity scores, and a higher incidence of not returning to sports. There has also been a steady rise in the incidence of ACL reconstruction in younger patients [4], and recent age-related differences have been reported with younger patients returning to sports more frequently and sustaining a greater number of second ACL injuries [10, 13, 20, 21]. The level of sport participation after ACL reconstruction has also been shown to be related to patient outcomes with patients who return to sport shown to have better objective and subjective scores as measured by the International Knee Documentation Committee (IKDC) and superior functional limb symmetry [2].
Given these findings and the potential influence of gender, age, and sport participation on both performance measures and validated ACL reconstruction outcome scores, it would seem relevant to report such data according to these three aspects. In previous studies, these factors have typically been investigated separately rather than in combination. This is relevant because there are some data to suggest that gender differences are influenced by age. In one study, older females had lower KOOS sports and recreational activities subscale scores compared with older males, whereas there were no gender differences among younger patients [1].
In this study we therefore used a large cohort of patients who had undergone ACL reconstruction to determine if objective clinical and functional measures as well as validated outcome scores differed according to (1) gender; (2) age; and (3) sport participation status.
Patients and Methods
This was a retrospective analysis of prospectively collected data. Between March 2007 and October 2016, 3452 single-bundle ACL reconstructions were performed in patients who participated in sport before ACL injury. Most patients had an arthroscopically assisted four-strand hamstring tendon graft using semitendinosus and gracilis tendons. Suspensory proximal fixation was used on the femoral side and interference screw fixation on the tibial side. Apart from graft harvest, a similar surgical technique was used for patients receiving a patellar tendon graft. For patients receiving a synthetic graft, the femoral tunnel was drilled from outside to in and both ends of the graft were fixed with an interference screw. Complete followup (including preoperative scores and scores at least 1 year after surgery; mean, 14 months; range, 12–20 months) was available on 2672 (77%) of patients. Those lost to followup and those accounted for were not different in terms of age, gender, and sports participation before their ACL injury. The average age of the full eligible cohort was 28.9 (SD 10) years, which was similar to the age of the group who was reviewed (average age 28.1 [SD 10] years). Of the full eligible cohort, 66% (n = 2265) were male and 34% female (n = 1187) compared with 65% (n = 1726) of males being followed up and 35% (n = 946) of females. One of our eligibility criteria was participation in sport before ACL injury. Thus, all those who were potentially eligible, and therefore those who were reviewed, participated in sport before injury. In the full eligible cohort, 94% of patients participated in Level I or II sports compared with 93% of those with full followup. Patients with bilateral ACL injuries were not included (N = 284) because many of the reported outcomes rely on comparison with a normal contralateral knee. A cohort of 368 patients who received a double-bundle reconstruction between 2007 and 2010 were not included. A small group of patients (N = 82) who did not participate in any form of sport (neither before nor after their ACL injury) were also excluded. Of the 2672 patients who participated, 102 underwent further surgery within the first 12 months after their ACL reconstruction procedure and were therefore excluded, leaving a sample of 2570 patients.
Postoperatively all participants underwent the same rehabilitation protocol. This protocol encouraged immediate full knee extension and the restoration of quadriceps function as soon as possible. Particular emphasis was placed on the restoration of vastus medialis function. Weightbearing was allowed on an as-tolerated basis from the first postoperative day. No braces or splints were used. Progression was guided by the presence and degree of pain and swelling.
Evaluation
Passive knee flexion of both knees was recorded with a goniometer with the patient in the lateral decubitus position. For comparative purposes, the deficit (in degrees) of the operated limb was used. Extension deficits were recorded with the method described by Sachs et al. [16] where the patient is positioned prone. The difference in heel height is converted to an extension deficit in degrees by a formula based on the difference in heel height and the patient’s height. This method records the deficit relative to the normal hyperextension of the contralateral limb rather than relative to an arbitrary 0.
Measurements of side-to-side differences in anterior tibial displacement were made with a KT-1000 arthrometer (MEDmetric Corp, San Diego, CA, USA) at 134 N. Three measures were taken from both knees and the average displacement in millimeters recorded. The side-to-side difference was recorded as the operated knee score minus the contralateral knee score.
Patients completed both a single hop for distance and a triple crossover hop for distance. Patients were instructed that they must hop as far as possible but control their landing. A familiarization trial was permitted and any trial where the landing was not controlled (i.e., touch down with the opposite foot) was excluded. Two successful trials from both limbs were recorded and the average of the two used to calculate a limb symmetry index (operated side score divided by contralateral side score × 100%) [12]. A limb symmetry index of < 100 indicates a deficit in the operated limb.
All patients completed a self-administered questionnaire that included the IKDC subjective knee evaluation score [7] and the Single Assessment Numeric Evaluation (SANE) score [22, 23]. For the IKDC subjective measure, scores range from 0 to 100 with higher scores indicating fewer symptoms and better function. For the SANE score, patients answered the following question: How would you rate your knee on a scale from 1 to 100 with 100 being normal? Patients were also asked whether they had returned to their preinjury sport with responses coded as not at all, training only, or returned to preinjury sport.
Any further surgical procedures to the ACL-reconstructed knee within the first 12 months were noted. Assessments were completed by a number of trained clinical assessors (PS, AR, TH, CW, HK, TP). Data were missing from the following number of patients for the included measures: five flexion, 12 extension, 13 instrumented laxity, 78 single hop, 105 crossover hop, 128 SANE score, and 173 IKDC subjective score. There were also 156 patients for whom we did not have sport participation status. In this study, we chose to focus on postoperative measures collected when the patient returned for their 1-year review. We did not include the level of preoperative function because this varies considerably, primarily because of the highly variable time from injury to surgery. This timeframe is typically short and therefore does not allow the patient to develop symptoms of instability, the principal symptom of chronic ACL insufficiency. Most patients in this setting actually restrict their activity, so using this level of function as a baseline could have artificially made the results of ACL reconstruction better than they really are.
Data Analysis
Mean scores and measures of variability were calculated for each outcome measure. Scores were also calculated according to gender, age, and sport participation level (“had not resumed sport,” “had resumed training,” or “had resumed competition at the preinjury level”). Comparisons among gender, age, and sport participation status were made with t-tests and one-way analysis of variance. All data were analyzed using IBM SPSS statistics (Version 23; IBM Corp, Armonk, NY, USA) software with significance set at p < 0.05.
Results
Men had less knee laxity after reconstruction, greater limb symmetry, and higher IKDC scores than did women. There was no difference in ROM measures between men and women (flexion deficit: men 3.6 ± 5; women 3.6 ± 5, mean difference 0° [−0.4 to 0.5], p > 0.05; extension deficit: men 0.6 ± 2; women 0.6 ± 2, mean difference 0 [−0.1 to 0.2], p > 0.05); Table 1). Knee laxity was less for men, but the overall magnitude of the difference was small (men 1.1 ± 2.2; women 1.3 ± 2.4; mean difference 0.2 mm [0–0.4], p < 0.001). Limb symmetry scores were greater for men than women (crossover hop: men 97 ± 12; women 94 ± 13, mean difference 3 [3–5], p < 0.001; Table 1). SANE scores were similar between men and women (men 86 ± 12; women 85 ± 11; mean difference 1 point [−0.5 to 1], p = 0.3). IKDC subjective scores were higher for men, but the magnitude of the difference was relatively small (men 84 ± 12, women 82 ± 12, mean difference 2 points [1–3], p < 0.001; Table 1).
Table 1.
All outcomes for the whole patient group for primary ACL reconstruction, males and females
| Patients | Descriptive statistics | Flexion deficit (degrees) | Extension deficit (degrees) | KT-1000 side-to-side difference (mm) | Single hop symmetry (%) | Crossover hop symmetry (%) | SANE score (points) | IKDC subjective (points) |
|---|---|---|---|---|---|---|---|---|
| All patients (N = 2570) | Mean (SD) | 3.6 (5) | 0.6 (2) | 1.2 (2) | 94 (13) | 96 (12) | 85 (11) | 83 (12) |
| Range | −15 to 35 | −8 to 15 | −6 to 10 | 25–140 | 30–140 | 5–100 | 11–100 | |
| Number of patients | 2565 | 2558 | 2557 | 2492 | 2465 | 2412 | 2397 | |
| Males (N = 1662) | Mean (SD) | 3.6 (5) | 0.6 (2) | 1.1 (2) | 94 (12) | 97 (12) | 86 (12) | 84 (12) |
| Range | −15 to 25 | −7 to 14 | −6 to 10 | 29–138 | 37–140 | 5–100 | 23–100 | |
| Number of patients | 1658 | 1653 | 1654 | 1606 | 1590 | 1566 | 1552 | |
| Females (N = 908) |
Mean (SD) | 3.6 (5) | 0.6 (2) | 1.3 (2) | 91 (13) | 94 (13) | 85 (11) | 82 (12) |
| Range | −15 to 35 | −8 to 15 | −5 to 10 | 25–140 | 37–140 | 9–100 | 11–100 | |
| Number of patients | 907 | 905 | 903 | 886 | 875 | 846 | 845 | |
| Mean difference [95% CI] | 0 [−0.4 to 0.5] | 0 [−0.1 to 0.2] | 0.2 [0–0.4]* | 3 [2–4]† | 3 [3–5]† | 1 [−0.5 to 1.4] | 2 [1.3–3.3]† | |
| ES | 0 | 0 | 0.1 | 0.24 | 0.24 | 0.1 | 0.2 |
Mean differences are absolute values; *p < 0.05; †p < 0.001 male versus female; ACL = anterior cruciate ligament; SANE = Single Assessment Numeric Evaluation; IKDC = International Knee Documentation Committee; CI = confidence interval; ES = effect size.
Younger patients had greater side-to-side differences in knee laxity but less ROM deficits and greater limb symmetry. The greatest side-to-side difference in knee laxity was seen in the younger than 16-year-old girls (Table 2) (< 16 years: 1.5 ± 3; > 45 years: 0.8 ± 3: mean difference 0.7 [0–2], p = 0.05). Limb symmetry scores (Table 3) decreased with increasing age with the greatest difference seen between the youngest and oldest patient groups (crossover hop: < 16 years 99 ± 10; > 45 years 90 ± 17 mean difference: 9 [5–11], p < 0.001). Both SANE and IKDC subjective scores decreased with increasing age with the greatest difference again being between the youngest to oldest patient groups (Table 4) (SANE: < 16 years 90 ± 10; > 45 years 82 ± 14, mean difference 8 points [5–11], p < 0.001; IKDC: < 16 years 88 ± 11, > 45 years 79 ± 14, mean difference 9 points [6–11], p < 0.001).
Table 2.
ROM and knee laxity data according to patient age and gender
| Age group (years) | Flexion deficit (degrees) | Extension deficit (degrees) | KT-1000 side-to-side difference (mm) | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| All | Male | Female | All | Male | Female | All | Male | Female | ||
| < 16 (N = 132) | Mean (SD) | 3.4 (5) | 3.9 (5) | 3.0 (5) | 0.2 (2) | 0.1 (2) | 0.3 (2) | 1.3 (2) | 1.1 (2) | 1.5 (3) |
| Range | −10 to 20 | −8 to 20 | −10 to 20 | −8 to 6 | −5 to 6 | −8 to 5 | −5 to 10 | −5 to 5 | −2 to 10 | |
| Number of patients | 131 | 63 | 68 | 132 | 64 | 68 | 131 | 63 | 68 | |
| 16–25 (N = 1146) | Mean (SD) | 3.3 (5) | 3.3 (4) | 3.3 (5) | 0.6 (2) | 0.7 (2) | 0.5 (2) | 1.2 (2) | 1.1 (2) | 1.4 (2) |
| Range | −10 to 26 | −10 to 20 | −10 to 26 | −8 to 15 | −8 to 15 | −7 to 13 | −8 to 10 | −8 to 10 | −8 to 9 | |
| Mean difference [95% CI] | 0.1 [−0.7 to 0.9] | 0.6 [−0.6 to 2] | 0.3 [−1 to 2] | 0.4 [−0.1 to 0.8] | 0.6 [0–1.2]* | 0.2 [0–1] | 0.1 [–0.3 to 0.5] | 0 [–0.5 to 0.5] | 0.1 [0–1] | |
| ES | 0 | 0.2 | 0.1 | 0.2 | 0.3 | 0.1 | 0.1 | 0 | 0.1 | |
| Number of patients | 1142 | 770 | 372 | 1142 | 770 | 372 | 1138 | 768 | 370 | |
| 26–35 (N = 770) | Mean (SD) | 3.5 (5) | 3.4 (5) | 3.7 (6) | 0.7 (2) | 0.6 (2) | 0.7 (2) | 1.1 (2) | 1.0 (2) | 1.4 (2) |
| Range Mean difference [95% CI] |
−10 to 35 0.1 [−0.8 to 1.1] |
−10 to 20 0.5 [−1 to 2] |
−10 to 35 0.7 [−1 to 3] |
−8 to 15 0.5 [0.1–0.9]* |
−8 to 15 0.5 [0–1]* |
−6 to 9 0.4 [0–1] |
−5 to 10 0.2 [−0.2 to 0.6] |
−5 to 9 [−0.5 to 1] |
−4 to 10 0.1 [−1 to 1] |
|
| ES | 0 | 0.1 | 0.1 | 0.3 | 0.3 | 0.2 | 0.1 | 0.1 | 0 | |
| Number of patients | 770 | 538 | 232 | 764 | 533 | 231 | 767 | 536 | 231 | |
| 36–45 (N = 347) | Mean (SD) | 4.2 (5) | 4.5 (6) | 3.8 (5) | 0.8 (2) | 0.8 (2) | 0.8 (2) | 1.2 (2) | 1.2 (2) | 1.2 (2) |
| Range Mean difference [95% CI] |
−10 to 35 0.8 [0.3–1.9] |
−10 to 26 0.6 [−1 to 2] |
−10 to 35 0.8 [−1 to 2] |
−8 to 15 0.6 [0.3–1.1]† |
−5 to 15 0.8 [0–1]* |
−6 to 10 0.5 [−1 to 2]* |
−5 to 10 0.1[−0.3 to 0.6] |
−3 to 5 0.1 [−0.5 to 1] |
−6 to 10 0.3 [0–0.4] |
|
| ES | 0.2 | 0.1 | 0.2 | 0.3 | 0.4 | 0.3 | 0.1 | 0.1 | 0.1 | |
| Number of patients | 346 | 195 | 151 | 344 | 194 | 150 | 345 | 195 | 150 | |
| > 45 (N = 175) | Mean (SD) | 4.8 (6) | 4.5 (6) | 5.1 (6) | 0.7 (2) | 0.6 (2) | 0.7 (2) | 0.9 (2) | 1.0 (2) | 0.8 (3) |
| Range | −10 to 45 | −10 to 45 | −4 to 30 | −5 to 10 | −5 to 10 | −5 to 8 | −5 to 10 | −5 to 5 | −5 to 10 | |
| Mean difference [95% CI] | 1.4 [1.3–2.7]* | 0.6 [−1 to 3] | 2.1 [0–4]* | 0.5 [0–1]* | 0.5 [0.1–1] | 0.4 [0–1] | 0.4 [0.1–0.9] | 0.1 [−0.5 to1] | 0.7 [0–2] | |
| ES | 0.3 | 0.1 | 0.4 | 0.3 | 0.3 | 0.2 | 0.2 | 0.1 | 0.2 | |
| Number of patients | 175 | 92 | 83 | 175 | 92 | 83 | 175 | 92 | 83 | |
All statistical comparisons use < 16-year age group as the reference category; mean differences are absolute values; *p < 0.05; †p < 0.01; CI = confidence interval; ES = effect size.
Table 3.
Limb symmetry scores according to patient age and gender
| Age group (years) | Single hop limb symmetry (%) | Crossover hop limb symmetry (%) | |||||
|---|---|---|---|---|---|---|---|
| All | Male | Female | All | Male | Female | ||
| < 16 (N = 132) | Mean (SD) | 97 (11) | 99 (12) | 96 (10) | 99 (10) | 99 (9) | 99 (11) |
| Range | 57–138 | 57–138 | 65–116 | 76–126 | 78–121 | 76–126 | |
| Number of patients | 131 | 63 | 68 | 130 | 62 | 68 | |
| 16–25 (N = 1146) | Mean (SD) | 95 (11) | 97 (10) | 93 (11) | 98 (11) | 99 (10) | 96 (12) |
| Range | 37–140 | 37–140 | 40–140 | 38–140 | 42–140 | 38–140 | |
| Mean difference [95% CI] ES Number of patients |
2 [−1 to 4] 0.2 1123 |
2 [−1 to 4] 0.2 756 |
3 [0–6]*
0.3 367 |
1 [−1 to 3] 0.1 1120 |
0 [−2 to 3] 0 753 |
3 [0–5] 0.3 367 |
|
| 26–35 (N = 770) | Mean (SD) | 92 (14) | 93 (13) | 89 (14) | 96 (12) | 97 (12) | 93 (13) |
| Range | 29–138 | 29–138 | 40–131 | 37–140 | 37–140 | 50–139 | |
| Mean difference [95% CI] ES Number of patients |
5 [3–8]‡
0.4 742 |
6 [2–9]†
0.5 517 |
7 [3–11]‡
0.5 225 |
3 [1–6]†
0.3 732 |
2 [−1 to 6] 0.2 511 |
6 [3–9]‡
0.5 221 |
|
| 36–45 (N = 347) | Mean (SD) | 89 (15) | 90 (15) | 87 (16) | 91 (15) | 93 (14) | 88 (15) |
| Range | 31–126 | 34–126 | 31–126 | 39–130 | 48–130 | 39–120 | |
| Mean difference [95% CI] ES Number of patients |
8 [6–11]‡
0.6 330 |
9 [4–12]‡
0.6 183 |
9 [5–13]‡
0.6 147 |
8 [6–11]‡
0.6 323 |
6 [3–10]†
0.5 180 |
11 [7–15]‡
0.8 143 |
|
| > 45 (N = 175) | Mean (SD) | 89 (16) | 87 (16) | 90 (16) | 90 (16) | 91 (15) | 91 (18) |
| Range | 25–130 | 39–130 | 25–122 | 31–125 | 39–125 | 31–125 | |
| Mean difference [95% CI] ES Number of patients |
9 [5–12]‡
0.6 165 |
12 [7–16]‡
0.8 87 |
6 [2–10]†
0.4 78 |
9 [5–11]‡
0.6 159 |
8 [4–13]‡
0.6 84 |
8 [3–13]†
0.5 75 |
|
All statistical comparisons use < 16-year age group as the reference category; mean differences are absolute values; *p < 0.05; †p < 0.01; ‡p < 0.001; CI = confidence interval; ES = effect size.
Table 4.
Single Assessment Numerical Evaluation (SANE) and IKDC subjective knee score according to patient age and gender
| Age group (years) | SANE score | IKDC subjective score | |||||
|---|---|---|---|---|---|---|---|
| All | Male | Female | All | Male | Female | ||
| < 16 (N = 132) | Mean (SD) | 90 (10) | 92 (11) | 88 (9) | 88 (11) | 90 (10) | 85 (11) |
| Range | 45–100 | 45–100 | 50–100 | 40–100 | 51–100 | 40–100 | |
| Number of patients | 127 | 62 | 65 | 126 | 61 | 65 | |
| 16–25 (N = 1146) | Mean (SD) | 87 (10) | 88 (10) | 86 (10) | 86 (10) | 87 (10) | 83 (11) |
| Range | 10–100 | 10–100 | 40–100 | 38–100 | 38–100 | 40–100 | |
| Mean difference [95% CI] ES Number of patients |
3 [1–5] 0.3 1063 |
4 [2–7]†
0.4 718 |
2 [0–5] 0.2 345 |
2 [0–4]*
0.2 1060 |
3 [1–6]†
0.3 714 |
2 [−1 to 5] 0.2 346 |
|
| 26–35 (N = 770) | Mean (SD) | 84 (12) | 84 (13) | 84 (11) | 82 (12) | 82 (12) | 81 (13) |
| Range | 10–100 | 10–100 | 40–100 | 30–100 | 30–100 | 48–100 | |
| Mean difference [95% CI] ES Number of patients |
6 [4–9]‡
0.5 723 |
8 [6–12]‡
0.6 512 |
4 [1–7]‡
0.4 211 |
6 [4–8]‡
0.5 716 |
8 [5–11]‡
0.7 504 |
4 [1–8]†
0.3 212 |
|
| 36–45 (N = 347) | Mean (SD) | 83 (12) | 83 (13) | 84 (11) | 80 (13) | 80 (13) | 80 (13) |
| Range | 20–100 | 20–100 | 50–100 | 11–100 | 23–100 | 11–100 | |
| Mean difference [95% CI] ES Number of patients |
7 [5–9]‡
0.6 334 |
9 [6–13]‡
0.7 187 |
4 [1–7]†
0.4 147 |
8 [5–10]‡
0.6 331 |
10 [7–14]‡
0.8 186 |
5 [1–9]†
0.4 145 |
|
| > 45 (N = 175) | Mean (SD) | 82 (14) | 81 (13) | 83 (15) | 79 (14) | 78 (14) | 80 (13) |
| Range | 5–100 | 40–100 | 5–100 | 23–99 | 28–98 | 23–99 | |
| Mean difference [95% CI] ES Number of patients |
8 [5–11]‡
0.6 164 |
11 [7–15]‡
0.9 87 |
5 [1–10]*
0.4 77 |
9 [6–11]‡
0.7 163 |
12 [9–17]‡
1.0 87 |
5 [1–9]*
0.4 76 |
|
All statistical comparisons use < 16-year age group as the reference category; mean differences are absolute values; *p < 0.05; †p < 0.01; ‡p < 0.001; IKDC = International Knee Documentation Committee; CI = confidence interval; ES = effect size.
Patients who had returned to their preinjury sport had higher limb symmetry scores and better patient-reported outcomes. Both IKDC and SANE scores were higher in patients who had returned to their preinjury sport compared with those who had not (Table 5) (IKDC: returned 90 ± 9, no sport 79 ± 12, mean difference 11 points [9–12], p < 0.001; SANE: returned 90 ± 8, no sport 82 ± 13, mean difference 8 points [7–10], p < 0.001). Patients who had returned also had higher limb symmetry scores (single limb hop: returned 97 ± 10, no sport 91 ± 14, mean difference 6 [5–7], p < 0.001; crossover hop: returned 99 ± 10, no sport 94 ± 14, mean difference 5 [4–6], p < 0.001). Patients who had returned to their preinjury sport were also younger than those who had not (mean difference 5 years [3–6], p < 0.001).
Table 5.
All outcomes according to sport participation status and patient with further surgery
| Sport group | Descriptive statistics | Age† | Flexion deficit | Extension deficit | KT-1000 side-to-side difference | Single hop symmetry | Crossover hop symmetry | SANE score | IKDC subjective |
|---|---|---|---|---|---|---|---|---|---|
| No sport (N = 990) | Mean (SD) | 30 (10) | 4 (5) | 1 (2) | 1.2 (2) | 91 (14) | 94 (14) | 82 (13) | 79 (12) |
| Range | 12–66 | −20 to 40 | −6 to 15 | −6 to 10 | 28–130 | 36–130 | 5–100 | 12–100 | |
| Mean difference [95% CI] ES Number of patients |
0.5 [0–1] 0.1 990 |
0 [0–0.3] 0 985 |
0.3 [0.1–0.5]†
0.2 984 |
6 [5–7]‡
0.5 955 |
5 [4–6]‡
0.4 944 |
8 [7–10]‡
0.7 989 |
11 [9–12]‡
1.0 984 |
||
| Training (N = 815) | Mean (SD) | 28 (10) | 3.5 (5) | 1 (2) | 1.3 (3) | 93 (13) | 96 (12) | 86 (10 | 84 (11) |
| Range | 12–63 | −12 to 25 | −8 to 13 | −8 to 10 | 25–138 | 31–140 | 20–100 | 11–100 | |
| Mean difference [95% CI] ES Number of patients |
0 [−0.5 to 0.5] 0 812 |
0 [−0.2 to 0.2] 0 810 |
0.4 [0.1–0.6]*
0.2 811 |
4 [2–5]‡
0.34 799 |
3 [2–4]‡
0.3 788 |
4 [3–5]‡
0.4 814 |
6 [4–7]‡
0.6 809 |
||
| Returned to preinjury level of competition (N = 609) | Mean (SD) | 26 (9) | 3.5 (4.4) | 1 (2) | 0.9 (2) | 97 (10) | 99 (10) | 90 (8) | 90 (9) |
| Range | 12–60 | −15 to 22 | −7 to 14 | −5 to 9 | 40–140 | 51–134 | 20–100 | 45–100 | |
| Number of patients | 608 | 608 | 607 | 584 | 582 | 607 | 602 |
All statistical comparisons use the “returned to preinjury level of competition” group as the reference category; mean differences are absolute values; *p < 0.05; †p < 0.01; ‡p < 0.001between sport participation groups; SANE = Single Assessment Numeric Evaluation; IKDC = International Knee Documentation Committee; CI = confidence interval; ES = effect size.
Discussion
Although female gender is a well-established risk factor for primary ACL injury, second ACL injury rates have been reported to be high in both younger men and women [13, 20, 21]. Although many factors may potentially influence the outcomes of ACL reconstruction, there is emerging evidence that both functional performance and validated outcome scores differ according to a patient’s gender, age, and sport participation status [1, 19]. However, most of these data has come from quite heterogeneous patient groups and there has been limited attempts to investigate the gender and age differences in the same population of patients despite some data that show that gender differences might be associated with age [1]. This study sought to determine if a range of measures including laxity, ROM, objective performance measures, and validated outcomes after ACL reconstruction differed according to gender, age, and sport participation status. The results showed that men had less knee laxity and better limb symmetry and IKDC subjective knee scores than women. Younger patients had more favorable outcomes for all measures other than knee laxity, which was greater in younger patients. Patients who had returned to their preinjury sport scored higher for objective functional measures as well as validated outcomes scores (IKDC, SANE score) than patients who had not returned to sport.
The most salient limitation of the current study is that outcome measures were collected at one time point, approximately 12 months postsurgery. Although it is recognized that patients may continue to improve, this time point was chosen because it reflects when patients in our clinic have their final review. This time point is also clinically relevant because patients have typically recently recommenced sport participation or are making decisions about whether to do so. We did not include all possible outcome measures and tools such as the KOOS and EQ-5D have also been shown to have utility in this patient group. The SANE score was chosen because single-item assessments have been advocated to relieve the burden of clinician and patient time and resources for self-reported data [17]. There are three other potential sources of bias in a study such as ours. Transfer bias relates to the loss to followup, and in the current study, this loss was 23%. It is therefore possible that those patients who were not included were in some way systematically different from those who were included. Although there may still be subtle differences, we were able to confirm that there were no differences between the patients who were and were not included in terms of gender, age, or sport participation status (the three main factors investigated in the current study). Another source of bias is assessment bias. In this study, a number of assessors was used but each was trained, supervised, and monitored according to our standardized assessment protocols. Although the analysis for this study was performed retrospectively, the data were collected prospectively, which helps to minimize assessment bias. Finally, selection bias should be considered. In this study, all patients received a single-bundle ACL reconstruction except for a small cohort who received a double-bundle graft between 2007 and 2010 and the latter patients were not included in this study.
The current data are consistent with data from the Swedish Knee Ligament Registry, which also showed differences in patient-reported outcomes between men and women [1]. In these registry data, females had worse outcomes than males for the KOOS score and the EQ-5D generic health status measure. The current data extend this finding to other commonly used patient-reported outcomes (IKDC subjective and SANE scores) as well as measures of functional limb symmetry and knee laxity. In the current study, women had greater laxity than men, which is consistent with findings from a recent systematic review [19]. However, unlike the current data, which showed higher subjective IKDC scores in women, the same review showed no differences between men and women for subjective IKDC scores with results from individual studies being mixed (two studies favoring females and one favoring males).
Most of the measurement outcomes included in this study varied according to the age of the patient group. This was notable for limb symmetry measures, which became increasingly less symmetric with increasing patient age. In the current study, limb symmetry was measured using single limb hop tests, because these tests are increasingly being used to inform return to sport decision-making [5, 11]. The finding that younger patients tend to score higher, and on this basis may be considered to be more ready to return to sport, should be considered in the context of the fact that younger patients have the highest rates of second ACL injury. It is also not necessarily implied that older patients have unsatisfactory surgical results, because overall both the objective functional and validated outcome scores were high for all age groups, showing that successful surgical results can be achieved in older patients. Again, this is consistent with findings from the Swedish ACL register, which showed similar KOOS results across a range of age groupings at 1, 2, and 5 years postsurgery [1]. It is nonetheless of interest that the best outcomes in terms of patient stability were seen in the older group who had the worst outcomes in terms of symptoms and function and return to sport.
Most patients who undergo ACL reconstruction aim to return to their preinjury sport. The current data support previous data, which show that outcomes are better for patients who have returned to their preinjury sport than those who have not [3, 8]. In the current study, patient-reported outcomes and limb symmetry scores were most noticeably different between those who had returned and those who had not. When interpreting these data, it is however relevant to note that patients who had returned to their preinjury sport were younger; therefore, some of the differences may be the result of age.
The findings from this study showed that some of the most commonly used functional performance and validated clinical scores for ACL reconstruction are higher for patients who are younger, male, and have returned to their preinjury sport. These are important data for clinicians who are making both rehabilitation and return to sport decisions. Such decisions and associated discussions with patients can be based specifically on the patient’s age, gender, and sport status rather than the “average” patient who has ACL reconstruction. The current data are robust for measures taken at approximately 1 year after ACL reconstruction, but further studies are required to determine whether the same differences are present at other time points.
Acknowledgments
We acknowledge the support of surgeons Dr Timothy Whitehead and Dr Cameron Norsworthy and the research staff at OrthoSport Victoria: Patricia Seccombe, Anneka Richmond, Taylor Hartwig, Clare Wheedon, Haydn Klemm, and Tabitha Porter.
Footnotes
Each author certifies that he or she has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.
All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request.
Clinical Orthopaedics and Related Research® neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDA-approval status, of any drug or device prior to clinical use.
Each author certifies that his or her institution approved the human protocol for this investigation, that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained.
This work was performed at La Trobe University and OrthoSport Victoria, Victoria, Australia.
References
- 1.Ageberg E, Forssblad M, Herbertsson P, Roos EM. Sex differences in patient-reported outcomes after anterior cruciate ligament reconstruction: data from the Swedish knee ligament register. Am J Sports Med. 2010;38:1334–1342. doi: 10.1177/0363546510361218. [DOI] [PubMed] [Google Scholar]
- 2.Ardern CL, Taylor NF, Feller JA, Webster KE. Fifty-five per cent return to competitive sport following anterior cruciate ligament reconstruction surgery: an updated systematic review and meta-analysis incluing aspects of physcial functioning and contextual factors. Br J Sports Med. 2014;48:1543–1552. doi: 10.1136/bjsports-2013-093398. [DOI] [PubMed] [Google Scholar]
- 3.Ardern CL, Webster KE, Taylor NF, Feller JA. Return to the preinjury level of competitive sport after anterior cruciate ligament reconstruction surgery: two-thirds of patients have not returned by 12 months after surgery. Am J Sports Med. 2011;39:538–543. doi: 10.1177/0363546510384798. [DOI] [PubMed] [Google Scholar]
- 4.Dodwell ER, Lamont LE, Green DW, Pan TJ, Marx RG, Lyman S. 20 years of pediatric anterior cruciate ligament reconstruction in New York State. Am J Sports Med. 2014;42:675–680. doi: 10.1177/0363546513518412. [DOI] [PubMed] [Google Scholar]
- 5.Grindem H, Snyder-Mackler L, Moksnes H, Engebretsen L, Risberg MA. Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: the Delaware-Oslo ACL cohort study. Br J Sports Med. 2016;50:804–808. doi: 10.1136/bjsports-2016-096031. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Hewett TE, Myer GD, Ford KR. Anterior cruciate ligament injuries in female athletes: Part 1, mechanisms and risk factors. Am J Sports Med. 2006;34:299–311. doi: 10.1177/0363546505284183. [DOI] [PubMed] [Google Scholar]
- 7.Irrgang JJ, Anderson AF, Boland AL, Harner CD, Kurosaka M, Neyret P, Richmond JC, Shelbourne KD. Development and validation of the International Knee Documentation Committee subjective knee form. Am J Sports Med. 2001;29:600–613. doi: 10.1177/03635465010290051301. [DOI] [PubMed] [Google Scholar]
- 8.Logerstedt D, S DS, Grindem H, Lynch A, Eitzen I, Engebretsen L, Risberg MA, Axe MJ, Snyder-Mackler L. Self-reported knee function can identify athletes who fail return-to-activity criteria up to 1 year after anterior cruciate ligament reconstruction: a delaware-oslo ACL cohort study. J Orthop Sports Phys Ther. 2014;44:914–923. [DOI] [PMC free article] [PubMed]
- 9.Mall NA, Chalmers PN, Moric M, Tanaka MJ, Cole BJ, Bach BRJ, Paletta GAJ. Incidence and trends of anterior cruciate ligament reconstruction in the United States. Am J Sports Med. 2014;42:2363–2370. doi: 10.1177/0363546514542796. [DOI] [PubMed] [Google Scholar]
- 10.Morgan MD, Salmon LJ, Waller A, Roe JP, Pinczewski LA. Fifteen-year survival of endoscopic anterior cruciate ligament reconstruction in patients aged 18 years and younger. Am J Sports Med. 2016;44:384–392. doi: 10.1177/0363546515623032. [DOI] [PubMed] [Google Scholar]
- 11.Nawasreh Z, Logerstedt D, Cummer K, Axe MJ, Risberg MA, Snyder-Mackler L. 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;45:1037–1048. doi: 10.1177/0363546516680619. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12.Noyes FR, Barber SD, Mangine RE. Abnormal lower limb symmetry determined by function hop tests after anterior cruciate ligament rupture. Am J Sports Med. 1991;19:513–518. doi: 10.1177/036354659101900518. [DOI] [PubMed] [Google Scholar]
- 13.Paterno MV, Rauh MJ, Schmitt LC, Ford KR, Hewett TE. Incidence of second ACL injuries 2 years after primary ACL reconstruction and return to sport. Am J Sports Med. 2014;42:1567–1573. doi: 10.1177/0363546514530088. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Prodromos CC, Han Y, Rogowski J, Joyce B, Shi K. A meta-analysis of the incidence of anterior cruciate ligament tears as a function of gender, sport, and a knee injury-reduction regimen. Arthroscopy. 2007;23:1320–1325. doi: 10.1016/j.arthro.2007.07.003. [DOI] [PubMed] [Google Scholar]
- 15.Renstrom P, Ljungqvist A, Arendt E, Beynnon B, Fukubayashi T, Garrett W, Georgoulis T, Hewett TE, Johnson R, Krosshaug T, Mandelbaum B, Micheli L, Myklebust G, Roos E, Roos H, Schamasch P, Shultz S, Werner S, Wojtys E, Engebretsen L. Non-contact ACL injuries in female athletes: an International Olympic Committee current concepts statement. Br J Sports Med. 2008;42:394–412. doi: 10.1136/bjsm.2008.048934. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Sachs RA, Daniel DM, Stone ML, Garfein RF. Patellofemoral problems after anterior cruciate ligament reconstruction. Am J Sports Med. 1989;17:760–765. doi: 10.1177/036354658901700606. [DOI] [PubMed] [Google Scholar]
- 17.Shelbourne KD, Barnes AF, Gray T. Correlation of a Single Assessment Numeric Evaluation (SANE) rating with modified Cincinnati knee rating system and IKDC subjective total scores for patients after ACL reconstruction or knee arthroscopy. Am J Sports Med. 2012;40:2487–2491. doi: 10.1177/0363546512458576. [DOI] [PubMed] [Google Scholar]
- 18.Sutton KM, Bullock JM. Anterior cruciate ligament rupture: differences between males and females. J Am Acad Orthop Surg. 2013;21:41–50. doi: 10.5435/JAAOS-21-01-41. [DOI] [PubMed] [Google Scholar]
- 19.Tan SH, Lau BP, Khin LW, Lingaraj K. The importance of patient sex in the outcomes of anterior cruciate ligament reconstructions: a systematic review and meta-analysis. Am J Sports Med. 2016; 44:242–54. [DOI] [PubMed]
- 20.Webster KE, Feller JA. Exploring the high reinjury rate in younger patients undergoing anterior cruciate ligament reconstruction. Am J Sports Med. 2016;44:2827–2832. doi: 10.1177/0363546516651845. [DOI] [PubMed] [Google Scholar]
- 21.Webster KE, Feller JA, Leigh WB, Richmond AK. Younger patients are at increased risk for graft rupture and contralateral injury after anterior cruciate ligament reconstruction. Am J Sports Med. 2014;42:641–647. doi: 10.1177/0363546513517540. [DOI] [PubMed] [Google Scholar]
- 22.Williams GN, Gangel TJ, Arciero RA, Uhorchak JM, Taylor DC. Comparison of the single assessment numeric evaluation method and two shoulder rating scales: outcomes measures after shoulder surgery. Am J Sports Med. 1999;27:214–221. doi: 10.1177/03635465990270021701. [DOI] [PubMed] [Google Scholar]
- 23.Williams GN, Taylor DC, Gangel TJ, Uhorchak JM, Arciero RA. Comparison of the single assessment numeric evaluation method and the Lysholm score. Clin Orthop Relat Res. 2000;373:184–192. doi: 10.1097/00003086-200004000-00022. [DOI] [PubMed] [Google Scholar]