CORRELATION BETWEEN ENDOBUTTON POSITION AND FUNCTIONAL OUTCOME AFTER ACL RECONSTRUCTION: PLAIN XRAY EVALUATION

The correct positioning of the femoral tunnel and endobutton position determine the success of ACL reconstruction (ACLR). Improper femoral tunnel placement most common errors in failed ACLR. However, plain post-operative imaging in the early state is not routinely performed. EndoButton position evaluation by XRay was made because this technique was cheap and reliable in Indonesia. There is no consensus on the ideal positioning of EndoButton in compare with functional outcome after ACLR. The study aimed to evaluate anatomic positions of tunnel and fixation devices, and also provide a baseline examination for future controls regarding tunnel placement and fixation devices, and also evaluation functional outcome after ACL procedure and also evaluation of functional outcome after ACLR with IKDC score. Between February 2019 to July 2019, 20 patients aged 17 to 59 years, with post ACL reconstruction were involved in this study. We are evaluating sex, age, affected the side of the knee, complication after an operation, related activity with injury, and evaluation postoperatively with femoral angle measurement Xray AP and lateral view. We also evaluated and correlate post ACRL and functional outcomes with the International Knee Documentation Committee (IKDC) score. The mean age of patients was 28,38 ± 9,3 years, (87,15% men and 12,5% women). There is no complication after the operation in all patients. Nine patients (56,3%) affected on the left side, and seven patients (43,8%) affected right-sided. All patients are performed single-bundle augmentation techniques for ACL reconstruction. Five (31,3%) patient has history fall and eleven (68,8%) patients caused by sports activity. All patient has Femoral angle measurement from knee AP view x-rays more than 17o, with minimum 39o and maximum 54o, with mean 46,63 ± 4,2. From lateral x rays, we interpreted nine patients (45%) interpreted as shallow and high, and 55% others interpreted as deep and low (optimal). The mean of IKDC score pre-op was 58,1±4,6 and means IKDC postoperatively 6 months was 84,68 ± 5,1. There was a significant difference in functional outcome between optimal endobutton and not optimal endobutton position group with p-value < 0,05. Early post-operative imaging (knee x-rays) provides useful information regarding tunnel placement and fixation devices. It also serves as a baseline examination for future reference. In this study, a single bundle ACL reconstruction shows a satisfying outcome.


INTRODUCTION
The anterior cruciate ligament (ACL) is the most frequently reported injured knee ligament that requires surgical reconstruction. 1 The annual incidence rates of an ACL injury are between 30 and 40 ruptures per 100,000 inhabitants depending on the population. 2 The ACL reconstruction makes two bone tunnels femur and tibia connected. The graft is fixed to the femur using the EndoButton. 2,3 Malpositioning of the EndoButton is considered as one of the most common technical errors in ACL reconstruction. 4 It is estimated that up to 80% of technical failures are based on improper tunnel placement. No study has been reported to evaluate EndoButton position and their correlation with the functional outcome with plain Xray. Xray was chosen because of its reach in the Indonesian population and cheap than Ct scan and MRI. 5 When used, radiographic measurements show reliable correlation with anatomic dissection measurements of ACL insertion sites and correlation with their functional outcome. 6,7 Correct endobutton positioning is essential for an optimum clinical outcome in all ACL patients. 7 The purpose of this paper is to enable the reader to accurately read postoperative radiographs after singlebundle ACL reconstruction, and also evaluation of functional outcome after ACL reconstruction with IKDC score.

RESEARCH METHODS
Between February 2019 to July 2019, 20 patients aged 17 to 59 years, with post ACL reconstruction was involved in this study. We are evaluating sex, age, affected side of knee, complication after operation, related activity with injury, and evaluation postoperatively with x-rays AP (femoral angle measurement) and lateral radiograph, evaluate functional outcome with IKDC (International Knee Documentation) score, we also evaluate the correlation between functional outcome and position of endobutton after ACL reconstruction.

RESULTS AND DISCUSSION
The mean age of patients was 28,38 ± 9,3 years, (87,15% men and 12,5% women). There is no complication after the operation in all patients. Eleven patients (56,3%) affected on the left side, and nine patients (43,8%) affected on the right side. All patients are performed single-bundle augmentation techniques for ACL reconstruction. Six (31,3%) patients have history fall and fourteen (68,8%) patients caused by sports activity. All patient has femoral angle measurement from knee AP view x-rays with minimum 39o and maximum 54o, with mean 46,63 ± 4,2.
From lateral x-rays, we interpreted nine patients (45%) interpreted as shallow and high, and 55% others interpreted as deep and low (optimal). The mean of IKDC preop was 58,1 4,6 and means op IKDC postoperatively 6 months was 84,68 ± 5,1. The group of optimal endobutton position was 11 patients and not an optimal patient was 9 patients, with means in each group was 86,9 ± 1,4 dan 82,3 ± 1,6; with p-value was 0,45(p < 0.05). There was a significant difference between 2 groups (optimal endobutton position and not optimal endobutton position with correlation with functional outcome.  Improper femoral tunnel position has been identified as one of the most frequent errors in failed ACLR. The femoral tunnel should be lateral to the midline of the knee, in the range of 50% to 65% from the lateral edge. In this study, we found 55% data interpreted in optimal (deep and low). Parker et al recommended term and direction describing femoral tunnel placement using a grid, divided in to deep and low and shallow and high. 2-4 This technique was simple to evaluate the femoral tunnel placement (endobutton position). Khalfayan et al emphasis that the femoral tunnel, in lateral view should be more than 60% along Blumensat's line from anterior to posterior. Evaluation with AP view we found mean of the femoral angle and endobutton position angle in 20 patients was 46,63 ± 4,2 with minimum 39 o and maximum 54o. [4][5][6] We evaluated the functional outcome period 6 months with IKDC score and found that significant differences between endobutton position and functional outcome. There is no previous study evaluated the correlation between functional outcome and endobutton position. In our study, we found a significant correlation between functional outcome and endobutton position (p<0,05). 7-10

CONCLUSIONS
Simple plain x rays evaluation after ACRL can be a modality as screening and determine the position of endobutton. The optimal position of endobutton correlates with good functional outcome after ACRL in this study.