Return-to-sport outcomes and donor-site impact assessment following anterior cruciate ligament reconstruction: A randomized trial comparing peroneus longus and hamstring autografts

INTRODUCTION

As sports participation increases, so do injury rates, especially anterior cruciate ligament (ACL) tears, which often damage menisci, cartilage, or ligaments.^[1] The ACL is crucial for joint stability, preventing forward movement of the tibia and controlling rotation, with approximately 85% of resistance to forward movement. Injury mechanisms are often non-contact, involving deceleration, rapid changes in direction, or awkward landings.^[2] A torn ACL hampers activity, causes knee instability, meniscal damage, and can lead to early osteoarthritis. Surgical reconstruction is preferred, especially for athletes and active people, to restore stability and range of motion (ROM) and prevent long-term joint deterioration.^[3]

Conventionally, ACL reconstruction relies on autografts, such as bone-patellar tendon-bone (BPTB) and hamstring tendons (HTs). BPTB facilitates quick healing and a faster return to activity, but may lead to donor site issues such as knee pain, patellar fractures, and quadriceps weakness.^[4]Hamstring grafts are less invasive, with lower complication risks, but can have inconsistent sizes, hamstring weakness, and concerns about graft elongation. Recently, the peroneus longus tendon (PLT) has garnered interest as a promising autograft due to its structural strength, larger graft diameter, and minimal functional deficit, which is attributed to its synergy with the peroneus brevis. Research indicates that its tensile strength is comparable to that of native ACL and hamstring grafts.^[5] Early results suggest that PLT grafts might improve outcomes, reduce donor-site complications, and preserve good knee and ankle function.

Although the HT is frequently used for ACL reconstruction, it has limitations, such as inconsistent graft size, donor-site morbidity, and post-surgical muscle weakness, which can be particularly challenging for athletes. The PLT may be a better alternative due to its biomechanical similarity and reduced donor-site complications. However, existing research lacks comprehensive, prospective studies that compare functional outcomes and donor site effects specifically in high-demand athletes. This study seeks to address that gap by systematically evaluating the differences between peroneus longus and hamstring grafts in terms of knee stability, functional recovery, and complications, ultimately providing evidence-based guidance for graft selection in ACL reconstruction.

MATERIALS AND METHODS

This randomized, prospective study was conducted at a tertiary care teaching hospital. Patients were recruited from both outpatient and inpatient services after meeting the inclusion and exclusion criteria. The study focused on athletes aged 16–45 years presenting with isolated ACL injuries, with or without meniscal damage. Exclusion criteria included patients younger than 15 or older than 45, those who declined informed consent, individuals with osteoarthritis or significant cartilage damage, multiligament knee injuries, previous ACL surgeries, or psychiatric conditions or any foot or ankle condition affecting donor-site function, including cavus foot, flatfoot, ankle instability, previous ankle surgery, or neuromuscular deformity that renders the site unsuitable for PLT harvest.

Participants were randomly allocated to the PLT group or the HT group through computer-generated randomization. Allocation was concealed by an independent coordinator who managed the randomization sequence and revealed group allocation only after patient enrolment and consent, keeping investigators blinded. Surgeon blinding was unfeasible, but the outcome assessment was fully blinded, with an independent evaluator conducting post-operative evaluations without knowing the graft type. This evaluator, uninvolved in recruitment, randomization, or surgery, ensured objective measurement. Potential confounders were controlled through strict randomization, concealed allocation, standard protocols, blinded assessment, and explicit inclusion and exclusion criteria, ensuring group comparability and reducing bias.

Each patient had arthroscopic single-bundle ACL reconstruction. One group received a PLT autograft, and the other received an HT autograft. Graft sizes were measured during surgery. All participants provided written informed consent to participate in the study, in accordance with the ethical guidelines set by the institutional committee on human experimentation and the revised Declaration of Helsinki (2000).

Based on Rhatomy et al.’s findings, a mean graft diameter difference of 0.6 mm with a pooled standard deviation of 0.8 mm was used for sample size calculation.^[5] With a significance level (α) of 0.05 and 80% power (1–β), and accounting for a 20% potential loss to follow-up, the sample size was increased to 57/group. To ensure robustness, 60 patients were recruited per group, for a total of 120 patients [Figure 1].

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Figure 1: CONSORT flow chart of the study. PLT: Peroneus longus tendon, HT: Hamstring tendon

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All patients underwent a comprehensive clinical assessment, including the Lachman test, Anterior Drawer Test, and Pivot Shift Test, followed by magnetic resonance imaging (MRI) confirmation of ACL tear. Demographic data, mechanism of injury, and interval from injury to surgery were recorded. Patients were evaluated at baseline and postoperatively at 6 weeks, 3 months, and 6 months using International Knee Documentation Committee (IKDC) subjective knee evaluation score,^[6] Lysholm knee score,^[7] the American Orthopaedic Foot and Ankle Society (AOFAS) Score,^[8] thigh circumference (measured 15 cm above the patella) was recorded to assess muscle atrophy, and donor site morbidity was evaluated accordingly.

The post-operative protocol comprised several stages. In the initial phase (0–2 weeks), a knee immobilizer was used, ankle pump exercises were performed, and the knee was passively moved between 0° and 90°. During the early stage (2–6 weeks), knee flexion gradually increased to full range, and partial weight-bearing was initiated. The intermediate phase (6–12 weeks) concentrated on strengthening and balance training with full weight-bearing. The advanced phase (3–6 months) involved running and sport-specific drills. Ultimately, patients typically resumed sports after 6–9 months, once satisfactory functional testing confirmed readiness.

RESULTS

Demographic and baseline characteristics were comparable between groups, including age, gender, height, weight, body mass index (BMI), involved side, and sports distribution, with no significant differences [Table 1]. The peroneus group showed a similar pattern of contact and non-contact injuries compared to the hamstring group: 25% versus 35% for contact injuries and 75% versus 65% for non-contact injuries (P= 0.49). The median injury duration was 9 weeks for the peroneus group and 14.5 weeks for the hamstring group, with no significant difference (P = 0.807). Injury mechanisms included collision (15% vs. 25%), hit (5% vs. 10%), slip or fall (5% vs. 0%), and twisting (75% vs. 65%) (P = 0.666).

MRI findings showed comparable distributions: ACL tear Grade III (25% vs. 30%), ACL tear Grade III plus MM sprain (10% in both), ACL tear Grade III plus MMT (50% vs. 55%), ACL tear Grade III plus medial meniscus tear (MMT) plus lateral meniscus tear (LMT) (5% vs. 0%), and ACL tear high grade plus MMT (10% vs. 5%) (P = 1).

The peroneus longus graft demonstrated a significantly larger average diameter (9.1 ± 0.79 mm) than the hamstring graft (8.35 ± 0.49 mm), with median and range data also favoring the peroneus group. Therefore, harvesting the peroneus longus consistently yields a thicker graft. This difference was statistically significant (P = 0.0009). No complications were reported in either group.

Following surgery, knee stability assessments showed similar enhancements in both groups. Nearly all patients in each cohort tested negative for Lachman’s and Anterior Drawer tests during follow-up, with only a few Grade I laxity cases in the hamstring group. Pivot shift and McMurray tests yielded comparable post-operative results, with most patients testing negative by 6 weeks and no significant differences between groups. These findings suggest that both graft types effectively restore knee stability.

Early differences in functional outcomes were observed, with Lysholm scores showing greater initial improvements in the peroneus group at 6 weeks and 3 months. However, no significant difference was found at the final follow-up [Table 2]. IKDC scores exhibited a similar pattern, with the peroneus group demonstrating significantly better improvements at all 3 post-operative time points. By 6 months, however, the difference narrowed as both groups attained high functional scores. These early improvements in the peroneus group likely reflect initial patterns of knee strength recovery, yet both groups ultimately achieved comparable functional levels.

AOFAS scores showed differences only during the early post-operative period, with the peroneus group scoring significantly lower at 6 weeks, likely due to initial donor-site discomfort and temporary ankle weakness [Table 2]. By 3 months, these differences diminished, and at 6 months, both groups achieved similar results with no persistent issues. This trend suggests that early ankle problems caused by PLT harvest completely resolve with rehabilitation.

Thigh circumference trends revealed a notable benefit in the peroneus group at 3 and 6 months [Table 3]. Although both groups experienced early post-operative muscle atrophy, the peroneus group recovered more effectively, approaching pre-operative circumference by 6 months. Conversely, the hamstring group exhibited ongoing mild hypertrophy at 3 months, aligning with known effects of hamstring harvesting. The uninjured limb showed no significant differences between groups, indicating that the observed changes were due to graft harvest and post-operative recovery.

Knee ROM improved consistently in both groups, with no significant differences between them at any follow-up point [Table 4]. Flexion and extension recovered effectively, with most patients achieving full or near-full motion by 6 months. These results are consistent with typical recovery timelines after ACL reconstruction and suggest that graft type did not influence knee ROM recovery.

Ankle ROM, assessed to quantify donor-site morbidity, showed early post-operative differences. Plantarflexion and dorsiflexion were significantly reduced in the peroneus group at 6 weeks and 3 months; however, values equalized by 6 months, as shown in Table 4.

The inversion and eversion patterns were similar, with early deficits fully resolving by the final follow-up. These results confirm that harvesting the PLT causes a predictable, temporary decrease in ankle motion that recovers with rehabilitation and does not result in long-term complications.

DISCUSSION

ACL Reconstruction restores function, with various graft options explored to optimize outcomes. The peroneus longus graft, an alternative to hamstring grafts, offers benefits such as reduced donor-site morbidity and comparable functional outcomes. This prospective study investigates whether the peroneus graft surpasses the hamstring graft in primary ACL reconstruction, noting the scarcity of research comparing these grafts in athletes.

The demographic characteristics in this study demonstrated adequate comparability between groups. The mean age of participants (22.3±3.2 years in the peroneus group and 22.2±4.1 years in the hamstring group) was similar, aligning with previous studies by Rhatomy et al.,^[9] Asif et al.,^[10] Vijay et al.,^[11] Agarwal et al,^[12] and Keyhani et al.^[13] The young average age reflects the athlete-focused cohort, differing from studies involving more general populations. Gender distribution was also not significantly different between groups, consistent with Dwidmuthe et al.,^[14] who found no gender-based differences in tendon graft outcomes.

Anthropometric variables such as height, weight, and BMI were similar across both groups, confirming that randomization effectively balanced potential confounders. Studies by Rhatomy et al.^[9] and Asif et al.^[10] also reported no significant differences in anthropometry affecting graft performance. Injury details, including laterality and mechanism, were well-balanced. Twisting injuries were most common, aligning with findings by Kobayashi et al.,^[15] Evans et al.,^[16] and Yu and Garrett,^[17] who identified pivoting and non-contact twisting as the leading causes of ACL tears in athletes. In our results, 70% of injuries were non-contact, similar to Zult et al.,^[18] highlighting the typical injury mechanism in athletic populations.

The PLT group has a significantly larger graft diameter (9.1 ± 0.79 mm) than the HT group (8.35 ± 0.49 mm), consistent with studies by Rhatomy et al.,^[9] Asif et al.,^[10] Dwidmuthe et al.,^[14] and Keyhani et al.^[13] Graft diameter is vital as smaller hamstring grafts tend to fail more often, making PLT beneficial for athletes needing strong grafts. Charan Teja et al.^[19] also reported long-term success with peroneus longus grafts, supporting its reliability as an alternative to hamstring grafts.

Post-operative knee stability tests yielded favorable outcomes in both groups, with few grade I laxity cases. These findings align with those of Hossain et al.,^[20] Asif et al.^[10] Vijay et al.,^[11] and Agarwal et al.,^[12] who found no significant differences in Lachman or Anterior Drawer tests between PLT and HT autografts. The absence of a positive Pivot Shift at final follow-up is consistent with previous studies, including Agarwal et al.^[12] and Hossain et al.^[20] These results suggest that PLT grafts restore stability similar to that of hamstring grafts. Arora and Shah^[21] also reported excellent short-term outcomes with peroneus longus autograft and lateral extra-articular tenodesis in revision ACL reconstruction, emphasizing its strength and versatility.

The functional outcomes demonstrated early post-operative gains in the PLT group. The Lysholm score rose faster at 6 weeks and 3 months, though by 6 months, scores were similar in all groups [Figure 2]. While previous studies— by Vijay et al.,^[11] Agarwal et al.,^[12] Keyhani et al.,^[13] and Dwidmuthe et al.^[14] found no significant differences in Lysholm scores, some research has noted higher average scores in the PLT group, aligning with our results. The quicker recovery in PLT patients may be due to reduced anterior knee pain and less post-operative discomfort during flexion, often linked to hamstring-harvest issues. Similar positive early functional trends were reported by Vijay et al.^[22] who observed comparable or better recovery patterns with peroneus longus grafts.

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Figure 2: Evaluation of Lysholm, the International Knee Documentation Committee (IKDC), and the American Orthopaedic Foot and Ankle Society (AOFAS) scores in the study group.

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Throughout follow-up, the IKDC scores consistently remained higher in the PLT group [Figure 2]. While earlier studies such as Rhatomy et al.,^[9] Agarwal et al.,^[12] and Dwidmuthe et al.^[14] did not find significant differences between graft types, a trend favoring PLT appears in athletic groups. This may be due to improved hamstring function and strength, which are crucial for performance and recovery. Reasons include quicker hamstring recovery, avoiding flexor weakness, and less anterior knee pain with PLT. Shah et al.^[23] also highlighted excellent outcomes with six-strand hamstring grafts, noting that graft configuration and strength may influence recovery as much as graft source.

Regarding donor-site morbidity, initial AOFAS ankle scores and ankle ROM tests [Figure 3] showed greater weakness in the PLT group early on, which resolved by 6 months. This recovery trend aligns with findings from studies by He et al.,^[24] Dwidmuthe et al.,^[14] Dharmayuda et al.,^[25] and Vijay et al.,^[11] which also found no long-term impairment of ankle function after PLT harvest. The temporary decline in plantarflexion, dorsiflexion, inversion, and eversion is expected, given the peroneus longus’ role in ankle stability. However, the peroneus brevis compensates, helping restore ankle biomechanics over time. The full recovery of ankle ROM and AOFAS scores at 6 months in our group underscores the safety of PLT harvest for athletes.

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Figure 3: Assessment of the range of motion at the knee and ankle (degrees) between the two groups. P: Plantarflexion, D: Dorsiflexion, I: Inversion, E: Eversion

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Knee ROM recovered similarly in both groups, aligning with Shelbourne et al.,^[26] who demonstrated that effective rehabilitation protocols are more influential for ROM recovery than graft type. Our results also concur with earlier studies that found no differences in ROM after PLT or HT harvest.

Thigh circumference recovery was significantly better in the PLT group at both the 3- and 6-month follow-ups [Figure 4]. Similar findings were reported by Gök et al.^[27] Punnoose et al.^[28] and Keyhani et al.^[13] who noted less muscle atrophy and increased thigh girth in PLT patients. Since hamstring harvest directly affects knee flexor strength and may cause early post-operative inhibition and slower muscle regrowth, PLT could promote better quadriceps-hamstring balance during rehabilitation. Athletes’ commitment to recovery and better baseline conditioning might further enhance these benefits.

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Figure 4: Comparative analysis of thigh circumference (injured and uninjured limbs) between two grafts.

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Overall, the present study emphasizes that PLT autograft produces results comparable to or even better than HT in various areas, while also providing benefits such as larger graft diameter, faster early recovery, and less thigh muscle atrophy. Notably, long-term functional data do not support concerns about ankle donor-site morbidity. These findings add valuable athlete-focused evidence to the expanding research endorsing PLT as a dependable graft option.

This study has notable strengths, including a relatively large sample size with balanced randomization, a standardized surgical technique, consistent rehabilitation, and blinded outcome assessment, all of which enhance the validity of the comparisons. In addition, by including only athletic individuals it provides valuable insights into graft performance under high-demand conditions. However, the study has limitations. The 6-month follow-up period, although sufficient to assess early recovery and donor-site morbidity, may not fully capture long-term graft durability, reinjury rates, or return-to-sport timing. Furthermore, the absence of double blinding introduces a potential risk of observer bias, although outcome assessors were blinded to graft type. Future research with extended follow-up periods and larger multicenter athletic cohorts is required to further confirm the biomechanical and clinical advantages of PLT grafts.

CONCLUSION

Both peroneus longus and HT autografts are effective graft choices for ACL reconstruction, offering comparable functional outcomes in terms of knee stability and patient-reported outcomes. However, the PLT graft tends to cause less donor site morbidity, reduces thigh muscle atrophy, and potentially allows for a quicker return to sports. These results suggest that the PLT may be a reliable alternative to the traditional hamstring graft, particularly when maintaining hamstring function is crucial.