Comparison of clinical outcomes between ligament augmentation reconstruction system and conventional repair for acute Achilles tendon rupture: a retrospective cohort study

Abstract

Background

Achilles tendon rupture (ATR) often limits early rehabilitation following conventional repair. The ligament augmentation reconstruction system (LARS) offers immediate mechanical stability and enables early mobilization. However, few studies have directly compared LARS with conventional suture techniques in ATR.

Purpose

To compare the efficacy and safety of the LARS versus the conventional Kessler suture technique for managing acute closed ATR.

Study design

Retrospective Cohort Study.

Methods

A retrospective analysis was conducted on 91 patients who underwent surgical repair for ATR. The cohort was divided into two groups: 59 patients were treated with the LARS and 32 with the conventional Kessler suture technique. Functional outcomes were assessed using the Achilles tendon Total Rupture Score (ATRS) and American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot score at 3, 6, and 12 months postoperatively. Complications and re-rupture rates were systematically documented and compared between the groups.

Results

At the 3-month follow-up, the LARS group demonstrated significantly superior functional outcomes, with markedly higher ATRS (78.00 ± 15.01 vs. 55.00 ± 16.30, P < 0.001) and AOFAS scores (87.03 ± 5.44 vs. 82.03 ± 3.92, P < 0.001) compared to the conventional repair group. This superiority was maintained at the 6-month assessment for both the ATRS (88.00 ± 12.18 vs. 76.00 ± 13.23; P < 0.001) and AOFAS scores (94.78 ± 4.90 vs. 89.06 ± 4.54; P < 0.001). However, by 12 months postoperatively, the differences in both ATRS and AOFAS scores between the two groups were no longer statistically significant (P > 0.05). The LARS group reported one case of gastrocnemius weakness, while the conventional group experienced two cases of delayed wound healing and one superficial infection.

Conclusion

LARS repair enables a faster functional recovery in the short term compared to conventional Kessler repair, without increasing complication rates. While both techniques yield comparable excellent results by one year, the accelerated recovery pathway provided by LARS establishes it as a safe and effective treatment option, especially valuable for patients requiring an early return to activity.

Background

Achilles tendon rupture (ATR) is a common tendon injury [1], the incidence of which has been increasing [2, 3], especially among athletes and active individuals [4, 5]. This injury often leads to prolonged functional deficits, including loss of strength, limited range of motion, compensatory gait changes and even sciatica, significantly impairing the quality of life [6, 7]. Current treatment options for acute ATR include non-surgical management, conventional surgical repair, and a combination of surgical repair with early functional rehabilitation [8–10]. Thus, successful surgical repair is critical to restore tendon continuity, ensure biomechanical stability, and facilitate early rehabilitation [11].

While conventional surgical techniques for ATR, such as end-to-end suturing (e.g. Kessler technique) and autograft reinforcement, are well-established and yield acceptable outcomes, they are associated with several drawbacks. The initial tensile strength of the repair is often suboptimal, precluding early aggressive mobilization and necessitating prolonged immobilization, which in turn increases the risk of joint stiffness and muscle atrophy [12, 13]. Furthermore, the use of autografts, while providing reinforcement, is associated with donor-site morbidity and prolongs operative time [14]. Of particular concern, conventional methods remain associated with a non-negligible risk of rerupture [15].

In recent years, the ligament augmentation reconstruction system (LARS) has emerged as a synthetic augmentation device in orthopedic surgery. Engineered for high tensile strength and excellent biocompatibility, the LARS implant provides immediate mechanical stability to the tendon repair site [16]. By serving as an internal brace, it effectively distributes mechanical stress away from the primary suture line. This protective scaffolding helps minimize gap formation and reduce the risk of repair failure, thereby permitting a more accelerated rehabilitation protocol.

Nonetheless, comparative clinical evidence on the use of LARS versus conventional suture repair for acute ATR remains scarce. The existing focus has been on the use of LARS in other ligaments (e.g. anterior cruciate ligament) or chronic tendon reconstructions, rather than acute Achilles ruptures. To fill this knowledge gap, this study aimed to directly compare the safety and clinical outcomes of LARS-augmented repair with conventional Kessler suture repair in patients with acute closed ATR.

Methods

This study was designed as a retrospective cohort study.

Study subjects

This study included consecutive patients with acute closed ATR who underwent surgical treatment at the First Affiliated Hospital of Xiamen University from August 2021 to August 2024. The diagnosis was corroborated by clinical physical examination and imaging (ultrasound or MRI).

Inclusion criteria: (1) Age 18–60 years; (2) First episode of acute closed ATR with injury-to-surgery time ≤ 2 weeks; (3) No previous history of Achilles tendon injury or surgery; (4) Agreed to undergo postoperative follow-up; (5) Complete clinical and imaging data.

Exclusion criteria: (1) Open ATR or chronic rupture (injury > 2 weeks); (2) Re-rupture of the Achilles tendon or requiring revision surgery; (3) Presence of severe systemic diseases (such as uncontrolled diabetes, peripheral vascular disease, severe cardiopulmonary dysfunction, etc.) that may affect healing; (4) Long-term use of corticosteroids or fluoroquinolone antibiotics [17]; (5) Incomplete clinical data or loss to follow-up.

Grouping

Based on the surgical technique employed, the patients were categorized into two groups: the LARS group, which underwent augmentation repair using the LARS, and the conventional repair group, which received the modified Kessler end-to-end suture technique as the control.

The choice of surgical technique was determined by the treating surgeon based on routine clinical judgment and patient-specific factors, rather than preoperative functional status or predicted prognosis. To minimize potential selection bias, all consecutive patients who met the predefined inclusion and exclusion criteria during the study period were included.

Surgical methods

LARS group

All procedures were performed with the patient under general anesthesia in the prone position, with the affected limb elevated. Following routine disinfection and draping, a tourniquet was routinely applied to the proximal thigh to provide a bloodless surgical field during the procedure. A longitudinal incision was made at the rupture site to expose the tendon ends. After debridement of necrotic tissue, the end-to-end repair was performed using a modified Kessler suture technique with No. 2 nonabsorbable polyester sutures (Ethibond) (Fig. 1A, E). Subsequently, a transverse tunnel was created at approximately 0.5 cm above the Achilles tendon insertion. The tunnel diameter was selected to match the diameter of the LARS ligament, allowing smooth passage of the ligament without excessive looseness. The LARS (L130605D) was inserted through the tunnel (Fig. 1B, F). The ligament was passed through the tendon body in a crisscross manner 2–3 times, then directed longitudinally across the tendon rupture ends, and again crossed through the tendon body 2–3 times (Fig. 1C, G). The same procedure was repeated in reverse to return to the tendon insertion (Fig. 1D, H). Finaly, after adjusting the tendon tension to an appropriate level, both ends of the artificial ligament were tied and fixed, and the incision was closed layer by layer. Tendon tension was adjusted intraoperatively to achieve appropriate physiological tension, with the ankle positioned in slight plantarflexion and reference made to the contralateral side to avoid overtightening or elongation.

Fig. 1.

Schematic illustration of LARS-augmented Achilles tendon repair. In the schematic diagrams (A–D), the blue lines represent the No. 2 nonabsorbable polyester sutures (Ethibond) used for the end-to-end Achilles tendon repair following the modified Kessler technique. The yellow and purple lines represent the ligament augmentation reconstruction system (LARS), which is used for augmentation and reinforcement of the primary tendon repair. A, E Modified Kessler suture technique for end-to-end repair of the ruptured Achilles tendon. B, F A transverse tunnel was created approximately 0.5 cm above the Achilles tendon insertion, and the LARS was passed through it. C, G The LARS was obliquely passed through the tendon body 2–3 times, then longitudinally across the repair site, followed by another 2–3 oblique passes. D, H The LARS was returned to the tendon insertion site, and both ends were tied and secured after proper tension adjustment

Conventional repair group

Through the same incision, the tendon ends were exposed and necrotic tissue was debrided. End-to-end repair was performed using a modified Kessler suture technique, ensuring consistent tendon tension during suturing. The incision was then closed layer by layer after completion.

Postoperative rehabilitation protocol

The postoperative rehabilitation protocol was a standardized program developed and routinely implemented by the rehabilitation team at our institution.

All patients received structured physiotherapy guidance during hospitalization and standardized instructions for outpatient rehabilitation. Compliance with physiotherapy was routinely monitored during scheduled follow-up visits, and no major noncompliance requiring protocol modification was recorded in either group.

Importantly, patients in both groups completed their postoperative rehabilitation at the same rehabilitation center within our institution, under the supervision of the same rehabilitation team, thereby minimizing potential bias related to differences in rehabilitation facilities or therapist expertise.

LARS group

No plaster or brace immobilization was used postoperatively. From the first postoperative day, patients began toe flexion and gripping exercises, quadriceps and gluteal muscle strengthening, and ankle range-of-motion training. At 2 weeks, partial weight-bearing and greater ankle motion were gradually introduced. By 4 weeks, patients transitioned to full weight-bearing while strengthening the gastrocnemius and soleus muscles. Daily activities were generally resumed after 6–8 weeks, and running or jumping exercises were gradually reintroduced after 3 months.

Conventional repair group

Postoperative immobilization consisted of a long-leg plaster cast for 4 weeks followed by a short-leg cast for another 4 weeks, with the ankle maintained in plantarflexion to protect the repair site. During immobilization, patients mainly performed quadriceps and hip exercises, without active dorsiflexion or plantarflexion of the ankle. After cast removal, ankle range-of-motion exercises were initiated, followed by partial weight-bearing walking at 8 weeks and full weight-bearing at 12–14 weeks. Daily activities were typically resumed at around 4 months, while running and jumping were gradually reintroduced after 6 months.

Follow-up schedule and evaluation indicators

All patients were followed up in the outpatient clinic according to a standardized protocol at 3, 6, and 12 months postoperatively. The main evaluation indicators were as follows: Achilles Tendon Total Rupture Score (ATRS, total 100 points) [18]: to assess Achilles tendon functional recovery; American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot score (total 100 points) [19]: to quantify pain, function, and alignment; Re-rupture rate: to record any recurrence of rupture during follow-up; Complications: including poor wound healing, infection, tunnel osteolysis, gastrocnemius weakness, and sural nerve injury.

Statistical analysis

Missing data

As this was a retrospective study, some variables were incompletely recorded. Given that the proportion of missing data for key variables was low (< 5%), missing data were handled using a complete-case (available-case) approach, whereby patients with missing values were excluded only from the corresponding analysis.

Statistical analysis

Continuous variables are presented as mean (SD) and were compared between groups using the independent-samples t test. Categorical variables are expressed as number (%) and were compared using the chi-square test. All statistical analyses were performed using R software (version 4.3.2). P value < 0.05 was considered statistically significant.

Results

Comparison of baseline data

A total of 59 patients were included in the LARS group and 32 in the conventional repair group. Demographic and injury characteristics, including sex, age, time from injury to surgery, and the affected side, were well-balanced between the two groups, with no statistically significant differences (all P > 0.05), ensuring baseline comparability for subsequent outcome analysis (Table 1).

Table 1.

Baseline characteristics of patients

Characteristics	LARS (n = 59)	Kessler (n = 32)	Overall (n = 91)	P value
Age (year)	38.69 (11.57)	39.19 (14.01)	38.87 (12.41)	0.858
Gender				1.000
Female	7 (11.9%)	4 (12.5%)	11 (12.1%)
Male	52 (88.1%)	28 (87.5%)	80 (87.9%)
Affected side				0.091
Right	43 (72.9%)	22 (68.8%)	65 (71.4%)
Left	16 (27.1%)	10 (31.2%)	26 (28.6%)
Time from injury to surgery (days)	6.85 (3.58)	6.97 (3.45)	6.89 (3.52)	0.876
AOFAS score	24.05 (6.43)	25.50 (10.63)	24.56 (8.13)	0.420
ATR score	15.56 (6.05)	15.09 (6.43)	15.40 (6.15)	0.732

AOFAS score, American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot score; ATR score, Achilles tendon Total Rupture Score; Continuous variables were presented as mean (SD) and categorical variables as number (%)

Functional score results

At the 3-month follow-up, the LARS group demonstrated significantly superior outcomes in both ATRS (78.00 ± 15.01 vs. 55.00 ± 16.30; P < 0.001) and AOFAS scores (87.03 ± 5.44 vs. 82.03 ± 3.92; P < 0.001) compared to the conventional repair group. This significant advantage was maintained at 6 months for both the ATRS (88.00 ± 12.18 vs. 76.00 ± 13.23; P < 0.001) and AOFAS scores (94.78 ± 4.90 vs. 89.06 ± 4.54; P < 0.001), indicating a more rapid functional recovery in the early to mid-term postoperatively. However, by 12 months, the differences between the two groups had converged, with no statistically significant differences observed in either the ATRS (98.00 ± 4.34 vs. 98.00 ± 4.68; P = 0.976) or AOFAS scores (97.15 ± 4.12 vs. 97.12 ± 4.14; P = 1.000), suggesting comparable long-term functional outcomes (Table 2).

Table 2.

Comparison of postoperative functional scores between LARS and Conventional groups at 3, 6, and 12 months

Timepoint	Scale	LARS, mean (SD)	Kessler, mean (SD)	P value
3 months	ATRS	78.00 (15.01)	55.00 (16.30)	< 0.001
	AOFAS	87.03 (5.44)	82.03 (3.92)	< 0.001
6 months	ATRS	88.00 (12.18)	76.00 (13.23)	< 0.001
	AOFAS	94.78 (4.90)	89.06 (4.54)	< 0.001
12 months	ATRS	98.00 (4.34)	98.00 (4.68)	0.976
	AOFAS	97.15 (4.12)	97.12 (4.14)	1.000

AOFAS, American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot score; ATRS, Achilles tendon Total Rupture Score; Continuous variables were presented as mean (SD)

Complications

The overall complication rate was low and comparable between the two groups (P > 0.05). Specifically, the LARS group had one case of gastrocnemius weakness. Clinical evaluation revealed no evidence of rerupture, nerve injury, or implant-related complications. The weakness was considered likely related to temporary muscle inhibition during early rehabilitation and was managed conservatively with targeted physiotherapy, with gradual improvement observed during follow-up. The conventional repair group experienced two cases of delayed wound healing and one superficial infection. All complications resolved with appropriate management, and no re-ruptures were recorded in either group.

Discussion

The results of this study showed that the LARS repair group had better early postoperative functional recovery compared with the conventional end-to-end Kessler suture repair group. At 3 months postoperatively, the ATRS, and AOFAS scores in the LARS group were significantly higher than those in the conventional group, suggesting better early functional recovery and patient satisfaction. This result is closely related to the rehabilitation protocol of the LARS group, which did not require plaster immobilization and allowed early mobilization after surgery. In contrast, patients in the conventional repair group underwent plaster immobilization for 8 weeks postoperatively, which restricted early joint activity and delayed functional recovery. It is noteworthy that at the 12-month follow-up, there was no significant difference in functional recovery between the two groups, indicating that the primary advantage of LARS lies in the early postoperative period, whereas long-term outcomes were comparable between the two groups. In terms of complications, both groups had low incidence rates with no statistically significant difference, suggesting that the safety of LARS is not inferior to that of conventional repair.

LARS has the advantages of high tensile strength, good biocompatibility, and the ability to provide immediate mechanical stability, enabling patients to begin rehabilitation training early after surgery and reducing risks such as muscle atrophy, joint stiffness, and deep vein thrombosis caused by prolonged immobilization [20–23]. In addition, compared with autografts techniques, LARS repair avoids tendon harvesting and donor-site preparation, which may simplify the surgical workflow.

However, several potential concerns regarding LARS implantation remain. First, synthetic ligament materials may undergo wear or rupture over long-term implantation [24, 25]. Although current follow-up studies have not reported significant implant-related complications, the long-term safety of LARS in Achilles tendon reconstruction requires further evaluation. Second, late complication such as foreign body reaction continue to attract clinical attention. For instance, a case report described the development of foreign body granuloma 10 years after Achilles tendon reconstruction with LARS, necessitating graft removal and tendon transfer revision [26]. Moreover, some studies have suggested possible bone resorption within the bone tunnel [27, 28]. Although no such events were observed in the present study, these long-term risks cannot be entirely excluded. Finally, the relatively high cost of LARS materials may impose an additional financial burden on patients.

From a clinical perspective, LARS repair provides a safe, effective, and short rehabilitation option for the treatment of acute closed ATR, especially for young or athletic patients with high demands for early functional recovery. Its advantages include avoiding plaster immobilization, allowing early mobilization, and significantly improving postoperative satisfaction. However, this study also has limitations. First, the sample size of this study was relatively small, and the follow-up time was 12 months, which is insufficient to evaluate the long-term efficacy and complications of LARS. Second, this study did not adopt a multicenter randomized controlled design, which may introduce selection bias. Third, the gap size between the ruptured tendon ends was not routinely measured or documented in this retrospective study, which precluded further analysis of its potential influence on surgical outcomes. Fouth, detailed patient characteristics such as profession, level of sports participation, body mass index, and specific mode of injury were not systematically collected in this retrospective cohort, which limited further adjustment for activity-related and anthropometric confounders. Finally, functional evaluation was mainly based on subjective scales, lacking objective imaging or biomechanical evaluation indicators. Future studies should include large-sample, multicenter, long-term prospective studies to further validate the long-term safety and stability of LARS in Achilles tendon repair.

Conclusion

In conclusion, LARS repair for acute closed ATR confers a clear early advantage, facilitating accelerated functional recovery and rehabilitation while maintaining a low complication profile. Although the long-term outcomes converge with those of conventional repair, the LARS technique establishes itself as a viable and valuable alternative, particularly for patients seeking an expedited return to activity. Further studies are warranted to validate its long-term efficacy and safety.

Author contributions

Conceptualization: Z.Q., F.L. and Y.Y.; Methodology: Z.Q. and Y.Y.; Software: Z.Q.; Validation: F.L.; Formal analysis: Z.Q. and F.L.; Investigation: Y.Y.; Resources: Y.G.; Data curation: Z.Q.; Writing-original draft preparation: Z.Q., F.L. and Y.Y.; Writing-review and editing: Z.C.; Visualization: Z.Q.; Supervision: Z.C., Y.G. and C.M.; Project administration: Z.C., Y.G. and C.M.; Funding acquisition: Y.G. All authors reviewed the manuscript.

Funding

This project was supported by the Xiamen Municipal Science and Technology Bureau’s medical-engineering integrated guidance project (3502Z20244ZD2008).

Data availability

Please contact the corresponding authors if data is required.

Declarations

Ethics approval and consent to participate

This study was conducted in accordance with the Declaration of Helsinki and all participants provided written informed consent prior to their inclusion in the study.

Consent for publication

At our institution, the standard surgical informed consent form routinely includes consent for the use of anonymized clinical data for research purposes. Therefore, written informed consent for both surgical treatment and participation in clinical research was obtained from all patients at the time of care.

Competing interests

The authors declare no competing interests.