Remnant-preserving anterior cruciate ligament reconstruction enhances proprioceptive recovery and functional outcomes: A retrospective analysis

INTRODUCTION

Anterior cruciate ligament (ACL) injuries are a common cause of long-term functional limitations, especially in physically active young individuals. While surgical reconstruction techniques have evolved to restore mechanical joint stability effectively, many patients continue to struggle with proprioceptive impairments that interfere with their ability to resume athletic activities and contribute to an increased risk of re-injury. Interestingly, individuals with similar ACL injuries often experience varying levels of functional disability, which has been linked by Dhillon et al.^[1,2] to differences in retained proprioceptive function.

The ACL plays a crucial role in the sensorimotor system of the knee joint,^[3] as it is richly supplied with mechanoreceptors such as Ruffini endings, Pacinian corpuscles, and Golgi tendon organ-like structures.^[4,5] These mechanoreceptors are responsible for detecting joint position and movement, thereby supporting both anticipatory (feedforward) and adaptive (feedback) motor control mechanisms essential for coordinated movement and stability.^[6] Conventional ACL reconstruction (ACLR) methods often result in the removal or disruption of these sensory structures. Conversely, remnant-preserving ACLR techniques aim to retain the native ligament tissue, thereby preserving the embedded mechanoreceptors and promoting better proprioceptive reinnervation and recovery.

This study aims to investigate proprioceptive and functional outcomes following remnant-preserving ACLR. Assessment was carried out using objective joint position sense (JPS) tests, along with validated scoring systems such as the Tegner-Lysholm knee score and the International Knee Documentation Committee (IKDC) subjective knee evaluation form.

PROCEDURE

This retrospective study was conducted on 62 patients who underwent remnant-preserving ACLR between May 2023 and April 2025 at a tertiary orthopedic center in Kolkata, West Bengal. Institutional ethical clearance was obtained prior to commencement. Patients included in the study were aged between 18 and 40 years, had isolated ACL tears confirmed by both magnetic resonance imaging (MRI) and arthroscopic evaluation, and underwent arthroscopic single-bundle ACLR using a four-fold hamstring autograft. A minimum follow-up duration of 12 months was required for inclusion. Patients were excluded if they had multiligamentous knee injuries, underwent revision ACLR, had a history of previous injuries or surgeries on the contralateral knee, or demonstrated radiological evidence of knee osteoarthrosis.

Surgical procedure

Arthroscopic single-bundle ACLR using a 4-fold hamstring autograft was planned. The femoral side was fixed using suspensory fixation (adjustable loop Endobutton) and the tibial side with a bioabsorbable interference screw. An accessory anteromedial portal was used to create an anatomically correct femoral tunnel. To establish the femoral bone tunnel, we carefully resect the necessary femoral fibers of the torn parts of the ACL to visualize the femoral insertion site. Then, we create an adequate low anteromedial portal to establish the femoral bone tunnel. After using the 4.5 mm drill, the final diameter of the femoral bone tunnel is usually achieved by using a reamer of the appropriate size, depending on the diameter of the hamstring graft, to avoid damaging the ACL footprints on the femoral side. On the tibial side, the ACL stump is usually kept intact. The ACL jig is placed at the medial drop point located posterior and medial to the anterior horn of the lateral meniscus [Figure 1]. The tunnel is positioned centrally and posterior to the ACL remnant. Fixation on the tibial side is performed with a bioabsorbable screw. The remnant is positioned to cover the ACL graft completely, ensuring that no portion of it lies in front of the tibial spine [Figure 2]. Finally, to prevent notch impingement or future cyclops lesion formation, we debride any remnants in front of the intercondylar notch.

Close

Figure 1:

The anterior cruciate ligament jig is placed at the medial drop point located posterior and medial to the anterior horn of the lateral meniscus.

Export to PPT

Close

Figure 2:

The remnant is positioned to cover the anterior cruciate ligament graft completely, ensuring that no portion of it lies in front of the tibial spine.

Export to PPT

RESULTS

A total of 62 patients (mean age: 26.8 ± 5.4 years; 45 males and 17 females) underwent remnant-preserving ACLR. The mean interval from injury to surgery was 3.2 ± 1.1 months [Table 1].

Significant improvements were observed in functional outcome scores over the follow-up period. The Lysholm score improved from a pre-operative mean of 54.1 ± 6.8–90.6 ± 4.2 at 12 months, while the IKDC score increased from 45.3 ± 7.2 to 87.4 ± 4.8 during the same period (P < 0.001) [Table 2]. Proprioceptive function, measured by JPS error at 20°, 50°, and 70° of knee flexion, showed significant recovery [Table 3]. A strong inverse correlation was found between JPS error and functional outcome, indicating that improved proprioception was linked to better functional recovery [Figure 3 and Table 4].

Close

Figure 3:

Inverse correlation between JPS error and functional outcome scores (Lysholm, IKDC- International knee documentation committee) at 12 months.

Export to PPT

Minor complications were reported, including arthrofibrosis (1.6%), superficial infection (1.6%), traumatic re-injury (3.2%), and cyclops lesion (3.2%) [Table 5]. One patient with a cyclops lesion required arthroscopic debridement, while the other patients improved through aggressive physiotherapy.

DISCUSSION

There is strong evidence confirming the presence of mechanoreceptors in an intact ACL.^[7-11] Furthermore, mechanoreceptors have also been identified in the residual ACL tissue following injury, although their numbers appear to decline over time.^[12,13] This attrition may be slowed if the remaining fibers remain connected to the posterior cruciate ligament. These observations have prompted the development of several techniques – including remnant-preserving, remnant tensioning, and ACL augmentation procedures – designed to enhance the proprioceptive potential of the reconstructed ligament by conserving the original ACL remnant.

The findings from the present study suggest that preserving the ACL remnant during reconstruction significantly contributes to proprioceptive recovery. This is reflected in the observed decrease in JPS errors and corresponding improvements in functional outcome scores. These results reinforce the hypothesis that retaining viable remnants of the native ACL helps maintain mechanoreceptor presence, which likely promotes reinnervation and better neuromuscular control postoperatively.

Several authors have reported favorable clinical outcomes following remnant-preserving ACLR, often noting improvements in proprioceptive function. For example, Lee et al.,^[14] in a study involving 16 subjects, demonstrated a statistically significant correlation between tibial remnant preservation and better clinical and proprioceptive results. Similarly, Muneta et al.,^[15] in a larger cohort of 88 patients, noted a weak association between the volume of preserved remnant and postoperative stability and outcomes.

Despite encouraging outcomes, remnant-preserving techniques are not without challenges. Ahn et al.^[16] evaluated 53 patients who underwent ACLR using a femoral tensioning method in conjunction with remnant preservation. While they observed favorable clinical results without issues related to tunnel misplacement, MRI scans at 2-year follow-up revealed cyclops-like lesions in 12 patients, though notably, none experienced extension loss. Jung et al.^[17] conducted a comparative analysis of remnant-preserving tensioning versus remnant preservation alone and found no significant advantage of tensioning with respect to function or stability. In contrast, Hong et al.,^[18] through a prospective randomized controlled trial of 90 patients, concluded that remnant preservation offered no significant benefit over standard reconstruction. Second-look arthroscopy in their study showed comparable synovial coverage in both the remnant-preserving and conventional groups. Similarly, Park et al.,^[19] in a prospective study of 100 patients, did not observe significant differences in clinical outcomes when comparing remnant-preserving procedures to double-bundle ACLR.

The current study’s findings, demonstrating significantly reduced JPS errors and improved functional scores postoperatively, affirm the benefits of remnant preservation. This proprioceptive enhancement likely results from improved reinnervation of preserved mechanoreceptors. Notably, these outcomes are aligned with the broader shift in arthroscopic trends that favors tissue-preserving strategies. As emphasized by Rao and Pardiwala in their review of recent advances, modern knee arthroscopy is increasingly oriented toward biologic preservation, individualization of ACLR, and synovial coverage optimization to support proprioceptive recovery.^[20]

From an anatomical perspective, the individualized reconstruction of ACL tibial footprints, as highlighted by Mishra et al.^[21] in a pilot study on Indian patients, showed that anthropometric parameters such as height and gender may not reliably predict ACL insertional morphology. This underscores the need for arthroscopic personalization and careful remnant handling, rather than reliance on generalized graft positioning metrics.

In support of our findings, Lee et al.^[14] demonstrated improved proprioceptive function in subjects who underwent ACLR with tibial remnant preservation. Similarly, Muneta et al.^[15] observed that greater remnant volume correlated with improved postoperative outcomes. Ahn et al.^[16] employed a femoral tensioning technique and found MRI evidence of cyclops-like lesions, though functional outcomes remained unaffected. Likewise, Jung et al.^[17] noted, no added advantage of remnant tensioning over simple preservation. Contrastingly, both Hong et al.^[18] and Park et al.^[19] found no significant benefit of remnant-preserving approaches in randomized trials, though these studies emphasized stability and synovial coverage more than proprioception per se.

Our findings also support the broader “minimally invasive revolution” in arthroscopic surgery. As noted by Vaishya,^[22] the future of arthroscopy is likely to emphasize tissue preservation, biologic enhancement, and neurosensory conservation. These principles dovetail with our proprioceptive-focused results, reinforcing the paradigm shift away from resection-based approaches and toward strategies that promote functional restoration through biologically favorable means.

That said, remnant-preserving techniques present technical challenges, including tunnel visualization, risk of cyclops lesions, and individual variation in remnant quality. Our cohort experienced a 3.2% rate of symptomatic cyclops lesions, one requiring surgical debridement. In addition, the retrospective design and absence of a control group limit the generalizability of our conclusions.

Despite these contrasting reports, our study supports findings from recent literature that suggest remnant-preserving ACLR can accelerate synovialization, improve vascular supply, and enhance proprioceptive function. The demonstrated inverse relationship between JPS error and subjective scoring further highlights the importance of neurosensory preservation in postoperative recovery.

Nonetheless, this study is not without limitations. The retrospective design, lack of a randomized control group, and limited follow-up duration restrict the generalizability of the findings. Therefore, larger prospective randomized studies are warranted to confirm these results and establish clearer clinical guidelines.

CONCLUSION

Remnant-preserving ACLR appears to offer superior proprioceptive and functional outcomes compared to standard techniques. It reduces the operative time and provides early return to activity. Incorporating this approach in routine ACLR may aid in optimizing long-term joint function and rehabilitation outcomes. However, judicious preservation of the amount of ACL fibers is required posterior to the intermeniscal line to prevent postoperative loss of extension and cyclops lesion.