Quadriceps tendon autograft: A larger intraoperative diameter for primary anterior cruciate ligament reconstruction in Asian patients

INTRODUCTION

The optimal graft choice for anterior cruciate ligament reconstruction (ACLR) remains controversial. The ideal graft is one that is easy to harvest, offers optimal graft size options, and has low donor site morbidity and good graft incorporation.^[1] There are a few autograft options available for surgeons in ACLR, with hamstring (HS) tendon autografts being one of the more common options.^[2] HS autografts are easy to harvest and have shown good clinical outcomes, hence their popularity.^[3] However, the disadvantages of HS autografts include reduced knee flexion strength and slower graft incorporation compared to bone-patellar tendon-bone autograft.^[4,5] Moreover, the HS tendon thickness is often unpredictable, which could yield smaller than ideal HS autograft diameters intraoperatively.^[6]

In recent years, the quadriceps tendon (QT) autograft has become an increasingly popular choice for ACLR. The QT autograft has shown good biomechanical performance, low donor site morbidity, reduced post-operative pain, and preserves the integrity of the HSs.^[7-9] Furthermore, for any given individual, the QT autograft may provide consistently larger graft sizes compared to HS autograft.^[10] These characteristics have made QT autografts a viable potential alternative in ACLR.

While there is an abundance of literature on ACLR that analyzes the clinical outcomes of QT and HS autografts,^[11,12] there is a paucity of studies that account for patients’ height and weight when comparing the autograft diameters of QT and HS autografts, particularly within the Asian population. To the best of our knowledge, this is the first study to compare the intraoperative autograft diameters between QT and HS autografts in primary ACLR.

The primary aim of this study was to determine if final harvested QT autografts yielded larger autograft diameters intraoperatively compared to HS autografts after adjusting for height and weight in the Asian population. The secondary aims of this study were to provide recommendations for autograft choice in primary ACLR in the Asian population and to analyze mean autograft diameters obtained between genders. It was hypothesized that final harvested QT autografts provide significantly larger intraoperative autograft diameters compared to HS autografts after adjusting for height and weight.

MATERIALS AND METHODS

RESULTS

A total of 151 patients were included, comprising 40 patients who had QT autografts and 111 who had HS autografts [Table 1]. The mean ages of both groups were 27 years. There were 11 females in QT group and 24 females in HS group. The mean height in QT group was 169.8 cm and 172.5 cm in HS group. There was a significant difference in height between QT and HS groups (P = 0.046), but this difference in height would later be adjusted for in subsequent analysis between both the groups. The mean weight in QT group was 72.1 kg and 75.75 kg in HS group (P = 0.134). Laterality of ACLR and presence of concomitant injuries are presented in Table 1. The HS group had significantly more concomitant meniscal injuries than QT group (P = 0.009). There were no significant differences in age, gender, laterality of ACLR, and presence of other concomitant ligamentous injuries between the two groups. Within the HS group, 4-strand autograft was used in 55 patients, 42 patients used 5-strand autograft, 11 patients had 6-strand autograft, while 3 patients used 8-strand autograft.

The mean intraoperative QT autograft diameter was 9.14 mm ± 0.61 mm, and that of HS autograft was 8.15 mm ± 0.60 mm [Table 2]. After adjusting for age, gender, height, and weight, the QT autograft was significantly larger in diameter than HS autograft by 0.99 mm (P = <0.001). To obtain an HS autograft diameter of at least 8 mm, the patient’s height should ideally be >167 cm or weight >65 kg [Figures 1 and 2]. QT autograft diameters of 9 mm could be harvested in patients whose height is ≤167 cm or whose weight is ≤65 kg.

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Figure 1:

Multiple regression analysis models analyzing the effect of height on autograft diameter. To obtain a hamstring autograft diameter of at least 8 mm, the patient’s height should ideally be >167 cm. Quadriceps tendon autograft diameters of 9 mm could be harvested in patients whose height is ≤167 cm. The shaded area around the graph lines show the standard deviation range.

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Figure 2:

Multiple regression analysis models analyzing the effect of weight on autograft diameter. To obtain a hamstring autograft diameter of at least 8 mm, the patient’s weight should ideally be >65 kg. Quadriceps tendon autograft diameters of 9 mm could be harvested in patients whose weight is ≤65 kg. The shaded area around the graph lines show the standard deviation range.

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Subgroup analysis of autograft diameters among males and females was performed [Table 3]. The mean intraoperative autograft diameters for QT group remained significantly larger than HS group among both males (9.19 mm ± 0.62 mm vs. 8.25 mm ± 0.56 mm, P = 0.001) and females (9.00 mm ± 0.59 mm vs. 7.81 mm ± 0.62 mm, P = 0.000). There was no significant difference in mean intraoperative autograft diameters between males and females within the QT group (9.19 mm ± 0.62 mm vs. 9.00 mm ± 0.59 mm, P = 0.387). The mean intraoperative diameter of HS autografts was significantly smaller in females when compared to males (7.81 mm ± 0.62 mm vs. 8.25 mm ± 0.56 mm, P = 0.001).

Additional subgroup analysis was conducted to compare the autograft diameter between patients in HS groups that had 5 or more strands of HS autografts [Table 4]. The mean intraoperative autograft diameter for HS (≥5-strand) was 8.35 mm ± 0.56 mm. The QT autograft remained significantly larger in diameter than this subgroup by 0.79 mm (P = <0.001). Further regression analysis was conducted within the QT group alone to determine the marginal effect of height and weight on QT autograft diameter [Table 5]. The regression model showed that changes in height (P = 0.618) and weight (P = 0.625) did not have a significant effect on QT autograft diameter.

DISCUSSION

This study demonstrates that intraoperative QT autografts utilized are significantly larger in diameter than HS autografts in the Asian population, after adjusting for height and weight. There have been numerous studies that similarly showed good anatomical and biomechanical characteristics of the QT autograft and that QT autografts are larger in size than HS autografts. The differences between QT and HS autografts are described in Table 6.^[5,14]

Brinkman et al. shared similar findings of significantly larger autograft size in QT group compared to HS group (9.64 mm vs. 7.90 mm).^[15] However, their study focused on the Western population, and patients’ physical parameters were not factored into the analysis. Variation in terms of HS size and hence autograft diameter is expected in the population. It was shown that a difference in knee anthropometry may exist between the Western and Asian populations, where Asians may yield smaller HS autograft diameters.^[16] Thus, achieving an optimal autograft diameter remains a topic of concern for the Asian population. Moreover, harvesting the QT is advantageous due to its significantly larger volume, allowing for customization of autograft thickness to be harvested while still preserving the integrity of the remaining QT.^[17] Contrastingly, the HS autografts are often limited by the size of the original HSs.^[18]

Autograft diameter has been theorized to be an important predictor of long-term outcome.^[19] A larger autograft has been shown to have lower failure rates with a lower likelihood of revision surgery.^[20,21] Park et al. found high revision rates in HS autograft diameter of <8 mm (5.2%) compared to autograft diameter of ≥8 mm (0%).^[19] Similarly, Magnussen et al.^[22] and Mariscalco et al.^[23] concluded that autografts of diameter ≤8 mm had noticeably higher revision rates compared to autografts of >8 mm in diameter. This study found that to obtain a HS autograft diameter of at least 8 mm, the patient’s height should ideally be >167 cm or weight >65 kg. According to the literature, Tuman et al.^[24] observed that a height <147 cm would likely have an autograft diameter of <7 mm, while Treme et al.^[25] found that height <140 cm and weight <50 kg were at highest risk of autograft diameter <7 mm. Within the Asian population, harvesting the QT autograft should be strongly considered in patients of height ≤167 cm or weight ≤65 kg to obtain an autograft diameter of 8 mm.

The height and weight of the patient have a significant correlation with the thickness of the QT or HS tendons.^[26-28] Gender also has a correlation with the size of autografts, where males had longer and wider HS autografts in contrast to age-matched females.^[27,28] Most studies showed that body mass index does not have a strong correlation with autograft size.^[28,29] Among these factors, height appears to have the strongest correlation with autograft diameter.^[19,28] This study factored in these anthropometric variables and gender when comparing between QT autograft and HS autograft groups, and is the first to compare QT and HS autografts among the Asian population.

Ho et al.^[28] found that females had a significantly smaller HS autograft size when compared to males. Height and weight also had a stronger correlation with HS autograft diameter in females than in males. This study showed similar results where the mean intraoperative HS autograft diameter was significantly smaller than in males. However, gender did not have a significant effect on the obtainable intraoperative diameter of QT autografts. Hence, the QT autograft harvest could yield a satisfactory intraoperative QT autograft diameter regardless of the patient’s gender.

Other studies have shown that ACLR using 5- or 6-strand HS autografts can provide an autograft diameter of more than 8 mm.^[30] Even when compared to this subgroup of patients who received ≥5-strand HS autografts, QT autografts remained significantly larger in size. Furthermore, this study’s regression analysis showed that the diameter of QT autografts was not significantly affected by height and weight.

Thwin et al.^[31] found that pre-operative MRI measurement of graft size was superior to anthropometric variables in predicting HS autograft diameter. The use of pre-operative MRI measurements of HS tendons could be considered in predicting HS autograft diameter. If the predicted HS autograft diameter is suboptimal, QT autograft harvest should then be strongly considered as an alternative.

Harvesting of the QT autograft must be balanced against the potential risks of harvesting one with an excessively large width or diameter. Traditional literature has demonstrated that there was no difference in extensor muscle strength for the QT autograft group when compared to HS autograft, but significantly reduced knee flexion strength was observed in HS group compared to QT group.^[32] However, a recent study concluded that QT autograft harvest can lead to possible knee extensor deficits and prolonged return to knee extension strength.^[26] There is also a theoretical risk of graft impingement of an excessively large autograft within the narrow femoral intercondylar notch. In addition to the benefits of a larger autograft, harvesting the QT is associated with reduced post-operative pain and analgesia usage in patients with QT autografts compared to patients with HS autografts. Runer et al.^[33] also found that patients with QT autografts have good patient-reported functional and clinical outcomes with low donor site morbidity after primary ACLR.

Some limitations apply to this current study. Being a retrospective analysis, patient allocation to groups and randomization were not prospectively performed. Although the sample size was limited, power calculation indicated adequacy. In addition, only the patient’s height and weight were recorded as part of their anthropometric measurements. Other parameters such as thigh length, leg length, and thigh circumference were not collected. These data may suggest a correlation with autograft diameter and would have helped to strengthen the findings of this study. The final QT autograft diameter harvested may be argued as partially dictated by the surgeon intraoperatively. However, as earlier described, the width harvested is a balance between harvesting an adequately sized autograft and the potential detriments of harvesting a QT autograft that is excessively large. The aim of the surgeon will not be to maximize the width of QT autograft harvested. It is also prudent to note that the width harvested does not translate to a similar diameter of the final QT autograft. Further studies should also be conducted to evaluate the functional outcomes of patients with QT autografts compared to HS autografts to provide us with greater in-depth knowledge with regard to graft selection in ACLR in the Asian population.

CONCLUSION

This study has demonstrated that the final harvested QT autograft is able to provide a significantly larger intraoperative autograft diameter compared to the HS autograft in the Asian population after adjusting for height and weight. Harvesting the QT autograft should be strongly considered in patients of height ≤167 cm or weight ≤65 kg to obtain an autograft diameter of 8 mm within the Asian population.