The anterior cruciate ligament (ACL) stands as a pivotal structure within the knee joint, pivotal for maintaining its stability. Roughly half of major knee injuries trace back to ACL tears, making them a significant concern. ¹

When faced with ACL insufficiency, ACL reconstruction emerges as the go-to surgical remedy. This procedure has undergone significant evolution over the years, refining techniques and graft selection. Patients undergoing ACL reconstruction with the Hamstring tendon (HST) as an autograft experience expedited recovery of quadriceps strength, enhanced graft integration, superior tensile strength, and reduced joint stiffness, leading to commendable patient compliance. ² However, this method isn't without its limitations, including unpredictable graft size, potential diminishment of knee joint flexion power, and risks such as infection due to inadequate closure of the sartorius fascia, along with saphenous nerve injury during harvesting.³

In recent years, the Peroneus longus tendon (PL) has emerged as an alternative to HST grafts.^4,5 Studies have shown that the tensile strength of four-strand hamstrings and double-strand peroneus longus surpasses that of a native ACL, suggesting the viability of utilizing peroneus longus for ACL reconstruction.⁶ The PL boasts advantages in terms of both diameter and length over hamstrings autografts. Remarkably, even the anterior half of the PL tendon exhibits sufficient length and strength for effective ACL reconstruction, with biomechanical and kinematic studies confirming that harvesting the entire PL does not compromise ankle stability or gait. ^7,8

Assessing donor site morbidity, muscle strength emerges as a crucial factor affecting physical performance, daily activities, and sports involvement post-surgery. Therefore, evaluating knee and ankle joint motor power becomes imperative following ACL reconstruction with either HST or PL grafts.

The objective of this study lies in comparing the functional outcomes of knee and ankle joints using Lysholm score, and IKDC Score, while also assessing donor site morbidity through measurements of knee flexion and extension strength and ankle eversion and plantar flexion strength via handheld dynamometry (HHD) post-ACL reconstruction using hamstrings and peroneus longus autografts. These outcomes were meticulously evaluated preoperatively, at 6 months, and at 1 year postoperatively for both groups and subjected to thorough analysis.

The study design is prospective study to analyse comparative functional outcome between hamstring vs peroneus longus auto graft in patients undergoing ACL reconstruction. Proper consent for participation in the study was sought and study was approved by institutional ethics committee. Diagnosis of ACL tear was made via clinical evaluation and MRI imaging. A total of 53 eligible patients were selected and preoperative data were collected in terms of demography, anterior knee translation through lachman test, thigh circumference, ankle ROM and questionnaires such as, International Knee Documentation Committee (IKDC) score and Lysholm Knee score.

Inclusion criteria

1. Age 18-45 years
2. Patient willing to participate in the study
3. Isolated ACL tear

Exclusion criteria

1. Patient not willing to participate in the study
2. Other associated ligaments or meniscus injury
3. Professional atheletics.

All the eligible patients were operated in a tertiary care centre hospital in TRIHMS Naharlagun for ACL Reconstruction (ACLR) during the time period of March 2021 to April 2023. Intraoperative graft sizes and anterior knee translation post graft fixation were measured, and records were maintained.

Eligible patients were operated with either autologous ipsilateral hamstring or peroneus longus graft which were randomised based on simple chit box randomisation. A single senior surgeon operated all the cases.

Graft Harvesting:

In PL (Peroneus Longus) group, incision was made 2 cm proximally and 1 cm posterior to lateral malleolus. Subcutaneous tissue and fascia were dissected in line with the skin incision. The Peroneus longus and Peroneus Brevis were palpated and identified. Peroneus longus was harvested using a standard tendon stripper.

In Hamstring group, a 2-3 cm incision was made in line with pes anserinus midway between tibial tuberosity and posteromedial border of tibia. After subcutaneous dissection in line with skin incision, sartorial fascia was identified with blunt dissection. The tendon of gracilis and semitendinosus were palpated and identified. The tendon of gracilis was identified superior to Semitendinousus, while semitendinosus tendon was thicker in diameter in comparison with the gracilis tendon. with inverted L shaped incision sartorial fascia was dissected and gracilis and semitendinosus tendon separated.

In both groups adequate length and thickness of graft was prepared. Minimum graft thickness of 8.5mm was prepared as demonstrated by Brett et al. The graft was double/quadruple folded accordingly.

Following graft preparation in both groups, using trans portal technique femoral and tibial tunnels were drilled and the prepared graft was passed using ethibond sutures and secured using endobutton and bioscrew. Closure was done.

Post operatively patient was started on physiotherapy immediately aiming at 90 degree knee flexion by 3 weeks post-operative. Follow up were done at 6 months and 1 year post operatively and proper records of the data were maintained in terms of anterior knee translation through lachman test, thigh circumference,  International Knee Documentation Committee (IKDC) score, and Lysholm Knee score.

Functional outcomes were assessed using the Lysholm score and IKDC score. Muscle strength surrounding the knee and ankle joints was evaluated before surgery, encompassing both normal and ACL-deficient knees. Muscle strength measurements were quantified in pounds (lb) using a handheld dynamometer, with the normal side serving as the control. Postoperatively, muscle strength on the operated side was assessed at 6 months and 1 year using the MAKE method with an HHD. During this assessment, the HHD was held statically while the patient exerted full force, and the average of three readings was recorded.^9,10,11

In the assessment of knee flexion strength, the prone position was utilized, maintaining the knee at a 90-degree angle. Employing a dynamometer, positioned approximately 10cm above the lateral malleoli on the posterior aspect of the leg, with due stabilization of both thigh and leg, facilitated the measurement process. The evaluation of knee extension strength occurred in a sitting position, where the knee joint rested at a 90-degree angle, suspended freely at the table's edge. Placing the handheld dynamometer approximately 10cm above the lateral malleoli on the anterior aspect of the leg, with proper stabilization of the thigh and leg, ensured accurate measurement.

For the assessment of ankle plantar flexion strength, the patient assumed a supine position with extended hip and knee, while the ankle maintained a neutral alignment. The dynamometer was positioned proximal to the arch of the metatarsal heads on the plantar surface of the foot, with meticulous knee stabilization.In evaluating ankle eversion strength, the patient reclined in a lateral position, with both hip and knee extended and the ankle neutrally positioned. Placing the dynamometer over the lateral border of the foot at the midpoint of the 5th metatarsal, while ensuring leg stability with both medial malleoli in contact, facilitated precise measurement.

To mitigate study bias, all measurements were conducted by a single individual. The placement of the handheld dynamometer and the procedure for measuring muscle strength at the knee and ankle, along with the patient's positioning, are depicted in Figures 2 and 3. The handheld dynamometer was strategically positioned over the limb to ensure the person taking measurements had the greatest mechanical advantage possible. The patients were allowed to return to sports in an average of 6 months post-operatively.

Statistical analysis was done utilizing the SPSS 21.0 version for Windows. Significance was determined at P < 0.05. Comparative analyses of two or more independent proportions were executed using the Chi-square test or Fisher exact test. Inferential statistics were employed, utilizing the chi-square test, independent t-test, and Mann-Whitney test. Mean comparisons between independent groups or mutually exclusive groups were conducted via the independent t-test.

In this study, out of 53 selected eligible patients 7 were lost to follow up.  A total of 20 hamstring group and 26 peroneus longus group completed the study. Randomisation was done using simple chit technique to assign patients to individual group. Among the study group 39 were males while 14 were females (Table 1). The predominant causes of injury were road traffic accidents (19), self-falls (18), and sports-related incidents(16), as detailed in Table 1. Notably, the HST group exhibited a higher rate of surgical site infection (3 patients) compared to the PL group (1 patient). However, following wound debridement and resuturing, gradual wound healing was observed. Additionally, 6 patients in the HST group reported kneeling pain, while no patients experienced ankle pain, numbness around the knee or ankle joints, or limitations in ankle joint movement.

Key findings of this investigation revealed that PL autografts led to enhanced Lysholm and IKDC functional scores (Table 2). Moreover, the PL group exhibited superior improvement in knee flexion strength after one year compared to the HST autograft group(Table 3).

Functional outcomes assessed at the one-year mark indicated substantial improvements in IKDC scores for both HST and PL groups, with particularly significant results in the PL group (p-value 0.003). Lysholm’s score similarly improved in both groups.

Comparison of donor site morbidity between the HST and PL groups revealed improved knee flexion strength in both cohorts at six months and one year of follow-up. Significantly, the PL group exhibited greater enhancement (p-value 0.02), likely attributable to the preservation of the hamstring tendon in this group, thereby preventing early loss of knee flexion strength and range of motion. Analysis of knee extension strength showed notable improvement at both follow-up points, with the HST group demonstrating superiority. However, no significant differences were observed when comparing both groups (p-value 0.5). Regarding ankle function, both plantar flexion and eversion strength decreased in the PL group at six months but later improved, albeit not reaching the strength of the unaffected side (Table 4).

Preoperatively, anterior drawer, Lachman’s, and pivot shift tests were conducted to confirm diagnoses and assess knee joint translation. Postoperatively, these tests were repeated at the one-year follow-up to evaluate anterior translation (Tables 5–7).

Table 1: Distribution of DEMOGRAPHY

Table 2: Distribution of FUNCTIONAL SCORES

Table 3: Distribution of pre-and post-operative donor site morbidity of knee flexion and knee extension between HTS and PL group after 6 months and 1 year.

Table 4: Distribution of Pre and post operative donor site morbidity of ankle plantar flexion and eversion in PL group after 6 months and 1 year.

Table 5: Distribution of Anterior drawer test analysis in HTS and PL group pre and post-operative follow-up after 1 year

Table 6: Lachman’s test analysis in HTS and PL group pre and post-operative follow up after 1 year

Table 7: Pivot shift test analysis in HTS and PL group

There has been many studies investigating ACL reconstruction for the efficacy of peroneus longus graft, with particular attention paid to functional outcomes and donor site morbidity. ^12-14 Our study contributes to this study by evaluating the performance of the peroneus longus (PL) tendon autograft compared to the hamstring tendon (HST) autograft, specifically focusing on functional outcomes and donor site morbidity at the one-year follow-up.

Previous research has highlighted favorable outcomes with PL tendon usage in ACL reconstruction, echoing our findings. Angthong's study raised concerns regarding donor site morbidities such as reduced peak torque eversion and inversion, as well as decreased ankle function¹². However, our study revealed no statistical differences in ankle eversion strength compared to the contralateral normal ankle, with no instances of ankle instability or reduced mobility in the PL group after one year.

Contrary to assertions regarding PL's negligible influence on foot arch maintenance¹³, our study found no instances of ankle instability or arch architecture loss among patients at the one-year mark. Additionally, while Adachi N's study suggested potential weaknesses in HST strength at deep flexion angles post-ACL reconstruction¹⁵, our observations indicated a reduction in knee flexion strength in the HST group compared to the contralateral knee after one year, whereas the PL group demonstrated improved knee flexion.

Rhatomy et al. in their studies examining plantar flexion and eversion strength following PL tendon usage have shown consistent findings of no significant differences compared to the normal contralateral side at the end of 6 months post operatively.¹¹ Similarly, our study revealed no statistical significance in plantar flexion and eversion strength between the donor ankle and the contralateral ankle after one year, reinforcing the viability of PL as a graft option.

The combination of PL tendon and peroneus brevis (PB) tends to distribute pressure over the forefoot, with no notable difference in isokinetic strength in first ray plantar flexion strength between donor and contralateral ankles observed in previous studies^11,16 and corroborated by our findings. The intact PB could likely contribute to this phenomenon. Otis et al. stated that PB remains a potent evertor at the ankle joint, retaining its efficacy even post-PL harvesting.¹⁷ This underscores the efficacy of PL as a graft option, with PB continuing to serve as an efficient evertor at the ankle joint post-harvesting.

In a study involving 25 patients, aimed at assessing functional outcomes post-ACL reconstruction utilizing a triple-layered PL graft, Khajotia noted notable improvements. The analysis revealed an enhancement in IKDC scores, with no reported instances of ankle dysfunction among patients. However, two individuals experienced pressure pain at the graft harvest site six months post-surgery¹⁸.

Jinshen et al. conducted a comprehensive systematic review and meta-analysis encompassing 925 patients to evaluate the functional outcomes post ACL reconstruction utilizing hamstrings and peroneus longus autografts. Their findings showcased superior improvements in Lysholm and IKDC scores among the peroneus longus group compared to the hamstrings group. Although no disparity was noted in FADI scores, a marginal reduction in AOFAS score was observed in the peroneus longus group. The study concluded that peroneus longus stands as an optimal graft choice, offering a potential solution to the challenge of quadriceps-hamstrings imbalance post hamstrings tendon harvesting.¹⁹

Wiradiputra et al. reported no restrictions in ankle eversion and first ray plantar flexion, coupled with robust ankle motor strength. Their analysis revealed a 100% AOFAS score at the end of one year, endorsing peroneus longus as a preferred option for ACL reconstruction.²⁰

Sholahuddin's two-year follow-up study on patients undergoing peroneus longus graft for ACL reconstruction demonstrated outstanding outcomes across various metrics including IKDC, MCS, Tegner-Lysholm score, AOFAS, and FADI scores. Additionally, favorable results were observed in graft diameter, thigh hypotrophy, ankle function, and serial hop tests.²¹

Kusumastutia conducted a retrospective observational analytical study involving 75 patients over one year. Significant enhancements were noted in mean IKDC, MCS, Tegner-Lysholm score, KSS (function), AOFAS, and FADI scores post-operatively. Notably, there were no significant differences in eversion and plantar flexion strength between the contralateral normal ankle and the donor site. However, three patients in the HST group experienced neuropraxia. The study affirmed peroneus longus as a promising graft option for ACL reconstruction.²²

Numerous studies have underscored the viability of peroneus longus grafts in ACL reconstruction, highlighting minimal or absent donor site morbidity compared to other graft options. Future investigations could delve into ankle stability and strength measurements, correlating them with functional scores post peroneus longus tendon harvesting.

Limitations of the study include manual ligament laxity assessment, which may introduce inter-observer bias. Employment of a KT1000 arthrometer and isokinetic dynamometer for muscle strength measurement could enhance accuracy in future research endeavors.

The peroneus longus tendon emerges as a promising autograft option for ACL reconstruction, boasting superior thickness, and length, coupled with minimal donor site morbidity and excellent knee functional outcomes. Its potential extends beyond ACL repair, presenting an advantageous choice in addressing simultaneous multi-ligament injuries in the knee joint.

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