COMPARATIVE STUDY OF SINGLE BUNDLE ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION USING THE PERONEUS LONGUS TENDON AUTOGRAFT VERSUS HAMSTRING TENDON AUTOGRAFT

Introduction: Arthroscopic anterior cruciate ligament (ACL) reconstruction can be performed using autograft from various sources namely bone patellar tendon bone graft, hamstring graft, or peroneus longus tendon. Purpose of this study was to compare the clinical outcome and donor site morbidity of ACL reconstruction with peroneus longus tendon versus hamstring tendon autograft in patients with an isolated ACL injury. Methods: Patients who undervent isolated single bundle ACL reconstruction were allocated in peroneus and hamstring groups and observed prospectively. Functional score (IKDC, & Modified Cincinnati score) was recorded preoperatively and 1 year post-operatively. Graft diameter was measured intra-operatively. Donor site morbidity were assessed with thigh circumference measurments and ankle scoring by MRC grading and FADI Score. Results: 56 patients (28-Hamstring and 28-peroneus group) met the inclusion criteria. The average Peroneus longus graft diameter (8.8±0.8) was significantly larger than the Hamstring graft diameter (8.1±0.9). In terms of 1-year postoperative outcomes statistically there is very little comparable difference between both these grafts when used for arthroscopic ACL


Introduction
Biomechanics is one major key to the function, stability and aging process of joints. The knee is a major and complex joint. Its stability and motion are basically controlled by ligaments such as the anterior cruciate ligament (ACL). The main functional role of the ACL is to provide stability against anterior tibial translation and internal rotation. Anterior cruciate ligament (ACL) injuries are common in athletes, incapacitating for certain sports activities and predispose towards meniscal and cartilage lesions and if left untreated may evolve to arthrosis. The typical mechanism of injury is deceleration with twisting, pivoting, or a change of direction. It was estimated by Wilk et al. (1999) that at least 60% of all ACL injuries sustained by athletes are due to a non-contact mechanism of injury. Perhaps the most common mechanism for sustaining an ACL injury is a valgus stress with tibial external rotation at the knee joint with the knee flexed (Ebstrup & Bojsen-Möller 2000, Natri 1996). This mechanism of ACL injury is especially common when the athlete lands from a jump (Wilk et al. 1999). essentially a hinged joint that is held together by the medial collateral, lateral collateral, anterior cruciate, and posterior cruciate ligaments. The ACL runs diagonally in the middle of the knee, preventing the tibia from sliding out in front of the femur, as well as rotational stability to the knee. ACL injury reconstruction has been done using silver wire, fascia lata, and Iliotibial band. Till present so many various techniques have been described for anterior cruciate ligament reconstruction from open procedure to arthroscopic procedure. In 1954, the development of successful arthroscope has led to new possibilities to the field of knee surgery. Since 1982, the Anterior Cruciate ligament reconstruction is performed arthroscopically often. Arthroscopic reconstruction of ACL has several advantages such as it is minimally invasive, it has higher accuracy of placement of the graft, less disturbance of normal surrounding tissue leading to faster recovery and rehabilitation, less stay in the hospital and minimum infections in the post-operative phase. ACL reconstruction improves knee stability and function with many graft types, either autografts or allografts (1,2) . An ideal graft donor should have acceptable strength, and of adequate size, and can be easily and safely harvested. Among these grafts, bone patellar tendon bone (BPTB) and four strand hamstring autografts are most common autografts used for ACL reconstruction and each has its advantages and disadvantages. BPTB have a merit that bone to bone healing which permits the effective incorporation of tunnel and graft leading to a faster return to function and sports activity. Risk of patellar fracture, large incision, fixed length, and weaker than native ACL makes it less suitable for ACL reconstruction (3,4,5) . A hamstring autograft is easy to harvest with minimal donor site morbidity and strength that is comparable to native ACL. On the other hand, it has unpredictable graft size and potential decrease in hamstring power, which is crucial for some athlete who need dominant hamstring power (6) . Some orthopaedic surgeons are therefore attempting to use the peroneus longus tendon as a graft of choice. Peroneus longus tendon autografts are commonly used in some orthopaedic procedures, including, Deltoid ligament Reconstruction (7) , spring ligament Reconstruction (8) , and medial patellofemoral ligament reconstruction (9) .There is synergistic action of peroneus longus and peroneus brevis for everting the ankle. Some studies have even found that the peroneus brevis Is a more effective evertor of the ankle, justifying the harvest of Peroneus longus tendon (10) . Some previous case series reported using the peroneus longus tendon as the first choice for an autograft in ACL reconstruction, with good clinical outcome and minimal donor site morbidity (11,12) , while other studies did not agree, due to donor site morbidity (13) .
There is high risk of graft failure and revision surgery if we uses a less graft diameter. Decreased hamstring autograft size and decreased patient age are predictors of early graft revision. Use of hamstring autografts 8 mm in diameter or less in patients aged under 20 years is associated with higher revision rates (14,15,16) . Some previous case series reported using the peroneus longus tendon as the first choice for an autograft in ACL reconstruction, with good clinical outcome and minimal donor site morbidity (11,12) , while other studies did not agree, due to donor site morbidity (13) . There is high risk of graft failure and revision surgery if we uses a less graft diameter. Decreased hamstring autograft size and decreased patient age are predictors of early graft revision. Use of hamstring autografts 8 mm in diameter or less in patients aged under 20 years is associated with higher revision rates (14,15,16) . Autograft shows moderate superiority compared with allograft, Allograft shows higher failure rate and higher risk of infection. (17) With the same cross-sectional surface area, there is no significant difference in tensile strength between the peroneus longus (446.1 ± 233.2) and a fourstrand hamstring (405.8 ± 202.9). Other biomechanical studies reported that the ultimate tensile strength of the peroneus longus tendon was 2500 N, while the ultimate tensile strength of the native ACL was 1725 N (18) . The amount of initial ligament damage is a statistically significant predictive factor of evolution into a complete tear. In a study by Bak et al., (19) only 30% of patients with partial ACL tears were able to return to the pre-injury level of sporting activity at 5 years follow-up, whereas Buckley et al. (20) in their study have reported 44% return to preinjury level of sports in 18 months. Use of peroneus longus tendon autograft is a recent development in the field of ACL reconstruction. The advantages are its strength and mean thickness is nearly same as that of native ACL and is very easy to harvest. Removing of PLT has no effect on stability of ankle. Zhao and Huangfu found that the anterior half of peroneus longus tendon has appropriate length and appropriate strength to be of use in reconstruction of ACL. Results after two years of followup when using the anterior half of the peroneus longus tendon have been found satisfactory, however there doesn't seem to be any direct comparison of the functional outcomes between anterior half of the peroneus longus tendon and hamstring tendon. Studying the biomechanical and kinematic aspects of removing the entire peroneus longus tendon has revealed no effect on gait or stability of the ankle.

OBJECTIVE
The purpose of this study is to compare the functional outcome between the peroneus longus and hamstring tendon autograft in ACL reconstruction. If a peroneus longus autograft does in fact show a comparable functional outcome with less donor site morbidity compared with hamstring tendon, its use as the graft of choice in single bundle ACL reconstruction can be encouraged in clinical practice, especially in the group of patients in whom dominant hamstring power is needed or the group of patients who frequently kneel as part of their daily religious activity, where any anterior kneeling pain could not be tolerated.

MATERIAL AND METHODS
This study is a prospective observational study of a consecutive study series of ACL reconstruction patients. The diagnosis of ACL rupture was established and the patients gave their informed consent to be included in this study. Sample size was calculated 28 cases in each of two group at α error0.05 and power 80%. Expecting minimum difference of mean to be detected in graft diameter after peroneus longus autograft and hamstring autograft 0.6 mm with SD 0.8. Total fifty-six patients underwent singlebundle ACL reconstruction from November 2018 to October 2020. Patients who attend Department of Orthopaedics in SMS Hospital, Jaipur and attached hospitals with ACL tear were allocated in hamstring and peroneus group randomly according to simple chit box method.

INCLUSION CRITERIA
Patients between age group of 18 to 45 years presenting with complaint of knee joint pain, swelling, and joint instability having previous history of knee joint trauma during walking or other sport activity. 1. Willingness to participate in an investigational technique and follow-up with written consent. 2. Willingness to forgo any other concomitant conservative treatment modality; NSAIDS and orthotic devices during the study period. EXCLUSION CRITERIA 1. Previous surgery for knee joint or around knee joint fracture/pathology. 2. Patients having any peripheral vascular disease of lower limb. 3. ACL tear associated with other knee joint ligament, menisci or tendon injury. 4. Any knee joint anatomical or pathological abnormality other than ACL tear. 5. Patient having ankle joint, foot or hip joint abnormality. A detailed clinical history of the patient regarding mode of injury, time of injury, presenting complaints, past medical and surgical history and personal history was taken and documented. A knee effusion usually develops over the next 24 hours. A complete general physical examination including gait analysis was done. Clinical evaluation of patients was done on an outpatient clinic first and reassessment was done under anaesthesia prior to surgery.

Local examination
The opposite, normal extremity was examined initially to gain the patient's confidence and to establish a baseline of the patient's normal ligamentous tightness. The results of Lachman, anterior drawer and pivot shift tests were noted by surgeons independently. The patients with equivocal findings clinically at the outpatient clinic. Imaging Subsequently patients were subjected to MRI examination. A group of radiologists, who were unaware of clinical details, analyzed the status of ACL on MRI and reached a report in consensus.

Preparation for Surgery
Once the diagnosis of ACL tear was suspected by clinical and radiological findings, informed consent was taken to be a part of study and patient was counseled and advised to undergo surgery for ACL reconstruction. Routine pre operative blood investigations like hemogram, renal and liver function tests, serum electrolytes, random blood sugar, chest radiograph and an electrocardiograph were ordered and the patient reviewed with the anaesthetist along with reports for pre anesthetic check up. Pre-operative Modified cincinnati score and IKDC Score The patient was given the schedule of our study and an informed consent was taken for their willingness to participate in our study and agreement to come for follow up. The questionnaire for IKDC, and Modified cincinnati scoring were initially handed over to the patient to fill up. On most occasions, patients were not able to understand English and the terms mentioned therein, so we helped them fill the form by translating it into Hindi or their regional language. The patient was planned for surgery. The postoperative evaluation was performed 1 year after the surgery to give the patient enough time to complete the rehabilitation protocol and return to sports activity, as well as being likely to obtain peak function after an ACL injury.

ARTHROSCOPIC TECHNIQUE
A single senior knee surgeon performed all the procedures. The patients lay in a supine position under regional anaesthesia and a tourniquet was applied to the thigh and inflated after elevation and exsanguination. Standard anterolateral and anteromedial portals were used. Diagnostic arthroscopy for ACL rupture was performed, followed by graft harvesting of either the ipsilateral peroneus longus or the hamstring tendon. Hamstring graft harvesting; After the tendons have been positively identified, semitendinosus tendon is released from its tibial insertion. Release the tendon proximally by controlled tension on the tendon, while advancing the stripper proximally, followed by graft preparation. Peroneus graft harvesting; For the peroneus tendon, the location of the skin incision was marked, 2-3 cm above and 1 cm behind the lateral malleolus. The incision was made through the skin, subcutaneous tissue and superficial fascia. The peroneus longus and peroneus brevis tendons were identified. The location of the tendon division was marked, 2-3 cm above the level of the lateral malleolus. The distal part of the peroneus longus tendon to the peroneus brevis tendon was sutured with end-to-side sutures. The peroneus longus tendon was stripped proximally with a tendon stripper to about 4-5 cm from the fibular head to prevent peroneal nerve injury. Tibial and femoral tunnel preparation; The intercondylar notch was then cleared of fibrous tissue to ease visualisation during preparation of the tunnels, but some remaining ACL fibres were preserved as a reference for tunnel placement. The femoral tunnel and the tibial tunnel were then prepared independently. After drilling the tunnels, we proceeded with the implantation of the tendon with graft fixation on the femoral side with a button and graft fixation on the tibial side with a bioabsorbable screw after appropriate tensioning by cycling maneaurve.

Statistical analysis
A sample size calculation was performed using the Lemeshow method, as shown below. n = (z/Δ) 2 p(1-p). The proportion of patients with an ACL rupture (p) was found to be around 8% in our study population. With 95% CI and a precision level of 10%, the calculation was (1.96)2 × 0.08 × (0.92)/(0.1)2 = 28. At least 28 patients were needed in each group to be included in this study. The outcomes of continuous measurements (IKDC, modified Cincinnati and Lysholm scores) were compared between the two groups using the Mann-Whitney U test. Statistical significance was accepted at p < 0.05.

RESULTS
During the study period, 61 patients underwent an isolated single-bundle ACL reconstruction. Five patients were excluded because of the presence of a concomitant injury to the meniscus/cartilage or refusal to participate in this study. 56 patients met the inclusion criteria, 28 patients in the hamstring group and 28 patients in the peroneus longus group. The demographic data of the study population are shown in Table 1&2. The mean age in PL graft people is 28.86 years and in STG graft is 26.6 years. Majority were males 51, and 5 were females. There is significant difference between duration of injury and procedure done. A duration of <3 month between injury and procedure done was found in 40 patients, while 16 out of 56 patients were having a history of >3 months. Right side was affected in 33 patients and left side was involved in 23 patients. There was wide variation in mechanism of injury causing ACL tear among patients,most common being Activity of daily living accounting for 29 cases, sports 21 cases and Road traffic accident 6 cases.

Graft diameter
Intraoperatively, the diameter of the graft was measured and recorded and the result shows that the mean diameter of the peroneus longus graft (8.8 ± 0.8 mm, range 8-10 mm) was significantly larger than that of the hamstring tendon (8.1 ± 0.9 mm, range 7-9 mm) (p = 0.011), with a mean difference of 0.7 mm, as shown in Table 3.     Manual Lachman and anterior drawer's tests were used for stability testings. On Lachmann's translation majority of patients were showing good knee stability and autograft strength in term of displacement 0-2 mm in 26 cases of PL group and 25 cases of STG group, while 3-5 mm translation was noted in 2 cases of PL group and 3 cases of STG group. At one year post-operatively knee effusion was complained by 1 case from both groups after a long time walking or sport activity which was resolved by rest and knee cap support.

Donor site morbidity of hamstring autografts
In the peroneus longus tendon group, no patients had thigh hypotrophy of more than 20 mm, only one patient had thigh hypotrophy of 20 mm and four patients had thigh hypotrophy of 10 mm. Thigh hypotrophy was significantly greater in the hamstring tendon group 1 year after the surgery (p = 0.002). The hamstring group showed a mean decrease in donor thigh circumference of 11.4 ± 3.6 mm, compared with the peroneus longus group, with a mean thigh circumference difference of 2.5 ± 0.5 mm.
Apart from the thigh circumference, an evaluation of the other potential donor site morbidities was also performed and it found that six patients (21.4%) complained of anterior kneeling pain.

Donor site morbidity of peroneus longus autografts
For the evaluation of donor site morbidity for peroneus longus tendon autografts, assessments of the functional score for the ankle using FADI scores was performed and the mean FADI score was 98 ± 3.4 (85.6-100).

DISCUSSION
Rupture of the ACL impairs the stability of the knee, resulting in difficulty with athletic performance, increases risk of subsequent meniscal injury, and increased risk of early degenerative joint disease. ACL rupture more commonly occurs during sports injuries, or during road traffic accidents . Forceful valgus-external Rotation is the most common mechanism of injury. ACL injury is more common in males and younger age Autograft choice is one of the most important considerations during ACL reconstruction surgery of the knee. Bone-patellar tendonbone complex, hamstring tendon autografts, and peroneus longus autograft are commonly used as the graft sources.
The BPTB graft is considered as a gold standard for ACL reconstruction because of its strength, consistency of the size of the graft, ease of harvesting and most importantly because of bone-to-bone healing within the tibial and femoral tunnel.
Complications of bone patella tendon bone graft include patellar tendon rupture, patellar/tibial fracture, quadriceps weakness, loss of full extension, anterior knee pain, difficulty in kneeling. Hence it is to be avoided in patients whose occupation or lifestyle requires frequent kneeling.
The hamstring tendon grafts have greater mechanical strength than a bone-patellar tendon-bone graft. Patients treated with hamstring tendon grafts are less likely to suffer patella-femoral pain and extension loss. Using the hamstring tendon can cause a significant change in hamstring muscle strength. Cases of Hamstring group also had a thigh muscle hypotrophy of 10 mm or more while it was not found in peroneus group.
Peroneus longus can be used as an alternative to hamstring autograft as biomechanically PLT is strong as native ACL. It is easy to harvest as it is superficially located, the peroneus longus tendon can be exposed quickly as to the semitendinosus tendons. Also, there aren`t many complications related to the structures around the peroneus longus tendon as compared to the hamstring tendons which makes it easier for one to harvest the graft.
There is no effect on ankle eversion power as peroneus brevis tendon is left in-situ which is strong evertor of ankle in comparison to peroneus longus (21). Furthermore we tenodessed peroneus longus stump with peroneus brevis tendon. In the operated ankle, MRC grading of flexion /extension, inversion/ eversion, and rotation of ankle were grade 5. In this study we found that the ankle functions were grossly preserved in almost all the patients which was elucidated by grading the power of the muscles of the foot particularly the eversion movement on a scale of five and comparing it with the normal ankle.
We found that there was a significant difference in graft diameter between the hamstring and peroneus longus tendons, with a mean difference of 0.6 mm in favour of group (25-35 year). Most of ACL injury were reported due to activity of daily living, knee twisting injury by slip and fall, jogging, running, sports activity and road traffic accidents. Patients met with road traffic accidents had multiple associated injuries. Difference in age specific incidence trends in male and female patients may potentially reflect difference in sports participation and probability of more prevalence of road traffic accidents and outdoor activity among males Irrespective of mode of trauma most of patients reported and operated within 3 months of injury. On 1 year follow up we foud that these patients were having less complain and good knee functions as compare to patients who delayed surgery for more than 3 months. MRI study of the knee joint of patients who reported late showed higher incidence of cartilage erosion and meniscal tear. This indicate that a longer duration of torn ACL produces strain over other structures of knee causing meniscal tear, cartilage erosions and evolve to arthrosis.
Manual Lachman and anterior drawer's tests were used for stability testings. Patients operated with peroneus graft showed excellent knee stability intra-op, and 6 months postoperatively. On 6 months follow-up only 2 cases out of 28 cases of peroneus group reported 3-5 mm translation on Lachman`s test. There was only a minor difference in the number and the distribution of grading of instability in both groups.
Knee stiffness in term of lack of extension and lack of flexon were also comparable in both groups. An extension loss of 3-5 degree or more was seen only in 1 case of PL and 2 cases of STG group. Flexon loss of 6-15 deg or more was seen only in 1 case of PL group and 2 case of STG group.
Hypoasthesia in infrapatellar area is a complication of knee arthroscopy which is caused by injury to infra patellar branch of saphenous nerve (IPBSN) during hamstring graft harvesting or tibial tunnel drilling. The infrapatellar branch of saphenous nerve emerged as fibers of the womb of the sartorius muscle, than it divide in one superior and one inferior branch, which present great variability in their path. Donor site morbidity in one patient using hamstring grafts as hypoesthesia caused by injury to the infrapatellar branch of the saphenous nerve was noted. The superior IBSN is at risk for iatrogenic injury with an accessory medial portal placed at 60º of knee flexon. Iatrogenic injury to this nerve can be avoided by doing arthrotomy for accessory medial portal placement at 110º knee flexon. (22) We used IKDC score for post-op subjective assessment of knee stability and functioning. An IKDC score 86-95 is considered as excellent outcome. Mean IKDC score was 92.3±6.2 in PL group and 90.1±9.2 in STG group 1 year post-operatively.
With the result of this study, the use of the peroneus longus as the graft of choice in single-bundle ACL reconstruction can be encouraged in clinical practice, because it shows comparable functional scores compared the peroneus graft. Previous studies have concluded that a graft diameter of 8.5 mm had a 1.7% revision rate. Furthermore, the risk of a patient needing a revision ACL reconstruction was 0.82 times lower with every 0.5 mm increase in graft diameter between graft thicknesses of 7 mm and 9 mm (16) . Study found a significant positive correlation between a 1 mm increase in graft diameter, with a higher KOOS score and IKDC score, and a higher revision rate with graft sizes of less than 8 mm (12,14) . Rudy ME, Phatama KY (2017) reported that the ultimate tensile strength of the peroneus longus tendon was 2500 N, while the ultimate tensile strength of the native ACL was 1725 N (18) .
with the hamstring tendon with less donor site morbidity, especially in groups of patients who frequently kneel in their daily activities, as they do in our country. Results of our study clearly showed that both Peroneus longus and hamstring tendon grafts could effectively improve knee stability and functions after anterior cruciate ligament reconstruction. The peroneus longus autograft showed a better functional score at the 1-year follow up compared with the hamstring autograft.

CONCLUSION
In this Hospital based prospective comparative randomized interventional study for Single-bundle ACL reconstruction, Peroneus longus tendon autografts found superior to Hamstring autografts in term of excellent functional outcome (IKDC & Modified Cincinnati Scores, Single leg functional Hop test ), more strong and thicker graft, knee stability (Lachmann's & Anterior Drawer test ) and showed good results to the four-strand hamstring tendon , with no donor site morbidity.