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Abstract

Introduction:

Anterior cruciate ligament (ACL) tears are common knee injuries, especially among sportsmen and sportswomen. The aim of this study is to better understand the epidemiology of surgically managed ACL tears sustained in our institution.

Methods:

All patients who underwent arthroscopic ACL reconstruction by the senior author of this article in Singapore from 2008 to 2013 were studied. Patients who were diagnosed clinically and/or radiologically to have a complete tear of the ACL and subsequently underwent arthroscopic ACL reconstruction were included. Patients who suffered from traumatic knee dislocation were excluded. Two hundred and ninety-two patients were available for analysis. All patients were operated on by the senior author.

Results:

83.9% of patients were male. 60.5, 23.0, 8.46, and 8.11% were of Chinese, Malay, Indian and other origins, respectively. 69.6 and 28.7% were in white-collared and blue-collared jobs, respectively, while 1.69% were unemployed. Mean age at operation was 29.4 years. Mean body mass index was 25.3 kg/m². 82.4 and 17.6% of ACL tears were sports (contact—27.5%; non-contact—72.5%) and non-sports injuries (activities of daily living—94.2%, road traffic accidents—5.77%), respectively. The top four sporting activities causing ACL tears were soccer, basketball, racquet games and volleyball. 56.2% of ACL tears presented with concomitant knee injuries (medial meniscus—63.4%; lateral meniscus—31.1%; posterior cruciate ligament—5.49%). 84.5% were primary tears.

Conclusions:

In this epidemiological review of ACL injuries, we found that ACL injuries tend to cluster within certain population subgroups. Patterns of mechanisms of injuries have been observed. These findings may lead to better preventive and treatment strategies in the management of ACL tears.

Keywords

anterior cruciate ligament epidemiology Singapore sports

Introduction

Tears of the anterior cruciate ligament (ACL) are one of the most common knee injuries.¹ In the United States, knee injuries account for approximately 60% of high-school sports injuries, which are eventually surgically managed.^2,3 ACL tears account for more than 50% of knee injuries.⁴ It has plagued numerous sportsmen and sportswomen, contributing to as many as 80% of all sports injuries.^5,6 This potentially causes further recurrent knee injuries,^7,8 resulting in many not being able to return back to preinjury levels.⁹ For individuals not involved in sports, an ACL tear may contribute to premature osteoarthritis.^10,11 For patients who undergo surgical management of their ACL tear, the risk of early-onset osteoarthritis remains.¹² In the United States, US$1 billion is spent on ACL reconstruction.¹³ The injury itself is painful and disabling,¹⁴ causing lost time from both sports and work. As ACL tears also result in instability and deficits in neuromuscular control, they potentially result in decrease in balance capabilities.¹⁵

With recent improvements in ACL imaging via magnetic resonance imaging and arthroscopy, as well as developments in ACL reconstruction techniques, from the single-bundle ACL reconstruction, to double-bundle, anatomic techniques, and even triple-bundle ACL reconstruction, the current goals of ACL reconstruction remain as maintaining long-term knee health, reestablishing premorbid function and preventing future knee injuries. In all, with recent developments in technology, the ACL tear is no more “the beginning of the end for the knee,” as stated by Allman.¹⁶ Instead, proper ACL reconstruction and rehabilitation regimes have allowed numerous professional sportsmen and sportswomen to return back to intense sports participation. Numerous individuals with ACL tears, including non-sports professionals, have thus opted for ACL reconstruction, aware of the disadvantages of the ACL-deficient knee and benefits of surgery.

While there have been numerous studies on the epidemiology of ACL injuries in Western populations, there has been no study to date on the epidemiology of ACL injuries in Singapore. The objective of this study was hence to study our patients who underwent ACL reconstruction and potentially identify epidemiological patterns in the distribution of ACL tears within certain demographic groups for future scientific research.

Methods

Between 2008 and 2013, 296 consecutive patients with ACL tears were included. All patients who had a clinical history suggestive of an ACL tear and/or radiological diagnosis of ACL tear and underwent arthroscopic ACL reconstruction were included in this study. Patients who suffered an ACL tear as a result of a traumatic knee dislocation as well as patients with insufficient data obtained were excluded from this study. All patients were operated on by the senior author of the study, in a large academic hospital in Singapore.

All patients underwent arthroscopic reconstruction of the ACL through a standard two-portal arthroscopic procedure with ipsilateral semitendinosus and gracilis autograft. A longitudinal incision was used for the harvest. The harvested grafts were fixed in a four-strand, single-bundle fashion with transverse corticocancellous femoral fixation with the Transfix® (Arthrex) device and secured on the tibial side with a biointerference screw. The graft was fixed through a transtibial technique. All patients underwent standard post-reconstruction rehabilitation protocol and physician follow-up. Patients were put on an ACL brace postoperatively. The use of a brace was emphasized strictly for the first 6 weeks postoperatively. Patients started ambulation without the brace at 6 weeks and were gradually rehabilitated to treadmill running at approximately 12 weeks postoperatively. Patients were told not to return to sports earlier than 6 months postoperatively.

After ethical approval was obtained via the Singhealth Centralized Institutional Review Board, an anonymized data set of all demographic data and information regarding concomitant injuries was extracted from the hospital database (Table 1). They were subsequently statistically analyzed.

Table 1.

Demographic data of study population.

Characteristics	Subgroups	Proportion of population (%)/mean (range, SD)
Gender	Males	248/296 (83.9)
	Females	48/296 (16.2)
Race	Chinese	179/296 (60.5)
	Malay	68/296 (23.0)
	Indian	25/296 (8.46)
	Others	24/296 (8.11)
Age (years)	29.4 (14.8–60.1; 8.69)
Height (cm)	171 (151–197; 7.63)
Weight (kg)	74.4 (46–125; 13.8)
BMI (kg/m ² )	25.3 (18.0–49.9; 4.25)
Mechanism of ACL tear	Sports	244/296 (83.4)
	Non-sports	52/296 (17.6)

BMI: body mass index; ACL: anterior cruciate ligament.

Results

Our study revealed that 83.9% (248/296) and 16.2% (48/296) of patients with ACL tears were males and females, respectively. Racially, 60.5% (179/296) were Chinese, 23.0% (68/296) were Malay, 8.46% (25/296) were Indian, and 8.11% (24/296) were of other origins.

The mean age at operation was 29.4 years (range 14.8–60.1, SD 8.69). Mean height was 171 cm (range 151–197 cm, SD 7.63). Mean weight was 74.4 kg (range 46–125 kg, SD 13.8). Mean body mass index (BMI) was 25.3 kg/m² (range 18.0–49.9 kg/m², SD 4.25).

Sports-related ACL tears (83.4% (244/296); 95% confidence interval (CI) = 79.2–87.6%) were more prevalent than non-sports–related ACL tears (17.6% (52/296); 95% CI = 13.3–21.9%). The prevalence of ACL tears that took place in a sports setting was similar at 87.1% for males and 87.5% for females. The top four sporting activities of patients sustaining sports ACL tears were soccer, basketball, racquet games (badminton, squash, and tennis), and volleyball. Of the sporting injuries, 72.5% (177/244) were due to non-contact mechanism of injuries, such as pivoting and cutting. Only 27.5% (67/244) were a result of contact mechanisms, such as collisions and tackles. Among non-sports–related ACL tears, 94.2% (49/52) occurred during activities of daily living, such as slipping, tripping, and falling down the staircase, while 5.77% (3/52) were due to road traffic accidents.

56.1% (166/296; 95% CI = 50.5–61.9%) of our study population presented with concomitant knee injuries. Of that, medial meniscal (MM) tears were the most prevalent concomitant injury upon diagnostic arthroscopy at 62.7% (104/166; 95% CI = 54.9–69.7%) of all concomitant knee injuries. 31.9% (53/166; 95% CI = 24.8–39.0%) of patients sustained a concomitant lateral meniscal (LM) tear. 5.42% (9/166; 95% CI = 2.00–8.90%) of patients sustained a posterior cruciate ligament tear. The proportion of males and females with concomitant knee injuries noted upon diagnostic arthroscopy was similar at 56.0% (139/248; 95% CI = 48.0–64.0%) and 56.3% (27/48; 95% CI = 42.3–70.3%), respectively. The prevalence of MM injuries were 64.7% (90/139) and 51.9% (14/27) (p value = 0.205; 95% CI = 55.3–70.0%) of all concomitant knee injuries in males and females, respectively. However, LM tears seemed to be more prevalent in females than males, at 48.1% (13/27) and 28.8% (40/139) (p value = 0.0482; 95% CI = 24.8–39.0%) of all concomitant knee injuries, respectively.

Discussion

Sporting activity has been increasing over the years. The Singapore Sports Council revealed that the prevalence of individuals in Singapore who exercise at least once a week has increased from 24% in 1992 to 42% in 2011, while the prevalence of those who exercise at least three times a week has increased from 8% in 1992 to 20% in 2011.¹⁷ Such trends potentially result in an increased incidence of injuries, especially knee injuries.¹⁸ Kim et al. predicted a rise in knee arthroscopies by 49% from 1996 to 2006 in the United States. Instead, in their 2011 study, it was revealed that there was a 77% increase in the number of ACL reconstructions from 1996 to 2006.¹⁹ The objective of our study was to describe and analyze the demographic patterns of surgically managed ACL tears within a sample population in Asia. Singapore being a multiethnic society provides a suitable platform for a diverse study population. To the best of our knowledge, this is the first study in Singapore eliciting epidemiological patterns of ACL tears in our nation. Through this study, we noted several patterns worth discussing.

First, we noted that the mean BMI was within the overweight category at 25.3 kg/m². This corroborated with the findings noted by Evans et al. in military subjects.²⁰ At 25.6 kg/m² ± 3.6 and 24.4 kg/m² ± 2.9 for patients with and without ACL injuries, respectively, patients with ACL injuries had a statistically significant (p = 0.005) higher BMI as compared to the general population. Similarly, a study performed by Kluczynski et al. showed that 48.0% of their study population had a BMI of 25.0 or higher, with 13.2% having a BMI greater than 30.0.²¹ The ACL controls both anterior tibial translation and axial tibial rotation upon the knee. Basic science studies have shown that excessive strain, especially in flexion, does increase the risk of an ACL tear to the patient.^22
–24 A higher BMI thus possibly contributes to ACL tears due to the increased axial strain placed on the ACL.

In this study, the authors also noted that the mean age at ACL reconstruction was 29.4 years. This was consistent with findings from the current literature. Rahr-Wagner et al.²⁵ found from their study based on data from Danish registries that the median age for ACL reconstructed patients was 28.2 years (Inter-Quartile Range [IQR]: 20.5–38.5 years). A study conducted by Nordenvall et al.²⁶ in Sweden revealed that the mean age of their study population of ACL reconstruction patients was 32.3 years (SD: 13.3). A study performed in Canada by Leroux et al.²⁷ found that the median age for their study cohort on patients undergoing ACL reconstruction revisions was 30 years (IQR: 22–39 years), suggesting that the median age for their ACL reconstruction patients is even lower than 30 years.

We observed that the prevalence of females sustaining ACL tears (16.2%) was much lower than that of males. Although females have a higher risk of sustaining ACL tears due to various intrinsic risk factors, such as a smaller notch size, higher Q-angles, increased foot pronation and tibial internal rotation,²⁸ the prevalence of ACL tears among males was most likely due to the higher risk exposure among males. Data from the Singapore Sports Council¹⁷ shows that the proportion of males (47%) who regularly exercise is higher than females (38%). Furthermore, a higher proportion of males (19%) participate in sports of vigorous intensity as compared to females (10%). Other studies show corroborative results with regard to the higher prevalence of ACL tears among males. In relation to their study population, Leathers et al. observed a statistically significant male predominance of ACL reconstructions in their male-to-female incidence ratio of 2.03 (p < 0.001).²⁹ Similar results were also noted by Mall et al. in the United States, with incidence rates of ACL reconstructions in males and females of 25.42 per 100,000 person-years and 18.06 per 100,000 person-years, respectively.³⁰ A nationwide study performed by Nordenvall et al. in Sweden revealed that 58.6% of patients who underwent cruciate ligament reconstruction were male and that males had a higher risk of injury than female patients (relative risk (RR) = 1.44, 95% CI = 1.41–1.46).²⁶ A study in China by Mei et al. separated their analysis for athletes and nonathletes. They showed that although the aggregate prevalence of females with ACL tears was 29.3%, the prevalence of female athletes with ACL tears was significantly higher than female nonathletes with ACL tears (56.1% vs. 25.0%, p < 0.001).³¹ In a study conducted by Rosa et al.,³² the prevalence of ACL injuries among females was higher than compared to males in certain sports, such as Handball (16% vs. 4.61%), while such injuries were more prevalent among males than females in other sports, such as volleyball (12.5% vs. 9.09%). There are a very few studies that evaluate the unique risk factors for ACL injuries in males.^33
–35 A systematic review conducted by Alentorn-Geli et al.³⁶ revealed that this is due to anatomical risk factors, such as a high posterior tibial slope of the lateral tibial plateau.

Apart from the male–female prevalence statistics, we also noted that the majority of patients who sustained ACL tears in sports settings sustained their injuries during non-contact situations. ACL tears which occur in a non-contact setting typically take place when there is either rotation or valgus stress placed on the knee.^37

–40 In this study, the authors noted that this usually occurred when an individual pivots, cuts (rapidly decelerates and changes direction), or falls. This classically were observed in sports, such as soccer, basketball, racquet games, and volleyball. ACL tears occurring due to a contact mechanism take place when there is a direct blow to the knee causing an eventual hyperextension or valgus stress and positioning of the knee. In our study, this was especially present during collisions and tackles. Hence, such forms of injuries were more prevalent in contact sports, such as soccer and basketball.

Isolated ACL injuries are uncommon. Associated injuries to the menisci, other ligaments, joint cartilage, and subchondral or cancellous bone tend to occur when a patient sustains an ACL tear.⁴¹ Such patterns in concomitant knee injuries can be explained by the type of mechanism and force of trauma causing the ACL tears. Mall et al.³⁰ revealed that since 1994, the two most common concomitant knee injuries were MM and LM tears. In 2006, they identified that 44.3 and 17.4% of patients who underwent ACL reconstruction sustained the concomitant MM and LM tears, respectively. The greater prevalence of concomitant LM injuries in females compared to males (p value = 0.0482), as seen in this study, can possibly be explained by excessive valgus positioning of knees in females when they sustain their ACL tears. Video analysis by Krosshaug et al. shows that female players tend to flex their hip and knees more significantly when they land after a jump and consequently, had a 5.3 times higher RR of sustaining a valgus collapse than did male players.⁴² Myer et al. also suggest that non-contact mechanisms of injury for ACL tears should be higher in females than males as electromyography results revealed that females utilize neuromuscular activation strategies, which may contribute to “dynamic valgus” and ACL rupture when performing high-risk maneuvers.⁴³ Such increased valgus stress noted in females is bound to result in increased stress to the lateral meniscus and hence, a higher prevalence of LM tears in females with ACL tears. Other possible explanations include the higher pelvic width-to-femoral length ratios in females, which results in both an increased static and dynamic valgus of the knee,⁴⁴ as well as quadriceps dominant deceleration in females.^45

–49

The ethnic distribution of the patients in our study is similar to that in Singapore in general. The national census in Singapore revealed that the proportion of individuals of the Chinese, Malay, Indian, and other ethnicities were 74.3, 13.3, 9.1, and 3.3%, respectively.⁵⁰ It is the opinion of the study group that ethnicity is not associated with ACL tears.

Conclusion

In conclusion, the authors noted that in Singapore, ACL tears tended to be more prevalent in the male population. The average patient with an ACL tear was overweight. The majority of ACL tears presented with concomitant knee injuries. At the point of diagnostic arthroscopy, more than a third of all patients presented with a concomitant MM tear. Most ACL tears occurred in sports settings, with non-contact mechanisms being more prevalent. Lateral meniscus tears in patients with ACL tears were more prevalent in females. Further studies should thus look into the epidemiological patient profiles and mechanisms of injury for prevention strategies based on the results above.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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Epidemiology of surgically managed anterior cruciate ligament ruptures in a sports surgery practice

Abstract

Introduction:

Methods:

Results:

Conclusions:

Keywords

Introduction

Methods

Results

Discussion

Conclusion

Footnotes

Declaration of conflicting interests

Funding

References