Rehabilitation and functional outcomes in internally braced and standard ACL reconstructions

Abstract

Purpose

The purpose of this study was to compare surgical outcomes in patients who underwent ACL reconstruction, with and without internal bracing, at 1–3, 4–7, and 8–12 months of postoperative physical therapy. Previous studies show that ACL reconstruction with internal bracing allows earlier and more aggressive rehabilitation. Therefore, it was hypothesized that patients with internal bracing would display superior surgical recovery compared to ACL reconstruction alone after adjusting for length of physical therapy.1, 2, 3

Methods

Patients who underwent ACL reconstruction and had a minimum two-year follow-up were included. Demographics including age, gender, use of internal bracing, and pre-operative level of activity were collected. Patient-reported outcomes were assessed using KOOS scores.

Results

46 patients underwent ACL reconstruction between January 2013 and December 2015. The mean age was 31.53 ± 8.37 years. Patients who received ACL reconstruction with internal bracing reported similar improvement in KOOS scores (mean = 42.82 ± 15.44; median = 46.39 [34.52–51.80]) compared to ACL reconstruction alone (mean = 38.18 ± 19.91; median = 40.17 [29.49–53.90]) (p = 0.475). Patients who received ACL reconstruction with internal bracing reported comparable improvement to ACL reconstruction alone at 0–3 months (Internal bracing: mean = 35.39 ± 15.26, median = 40.45 [26.49–47.73]; No internal bracing: mean = 42.51 ± 12.33, median = 39.32 [35.69–52.94], p = 0.4113), 4–7 months (Internal bracing: 41.96 ± 14.49, 45.55 [33.94–52.68]; No internal bracing: 30.64 ± 32.29, 41.65 [26.17–46.12], p = 0.7491) and 8+ months groups (Internal bracing: 63.36 ± 13.06, 63.36 [58.74–67.98]; No internal bracing: 47.05 ± 10.14, 47.05 [43.46–50.63]) (p = 0.6985).

Conclusion

This study demonstrates no statistical difference in functional outcome scores when comparing patients with internally braced ACL reconstruction compared to standard reconstruction. Therefore, the increased structural support provided by use of internal bracing in ACL reconstruction does not afford to quicker improvement in patient-reported recovery.

1. Introduction

The anterior cruciate ligament (ACL) is the most commonly injured ligament in athletes, with data showing that the USA performs approximately 3,000,000 ACL reconstructions every year.^4,5 The current gold standard for treating ACL ruptures is ACL reconstruction.⁵ The goal of ACL reconstruction is to provide an anatomic substitution for the torn native ACL. ACL reconstruction is effective in replicating ACL mechanical function, requiring compliance with rehabilitation to restore optimal knee function.

Internal bracing is a novel surgical innovation that is theorized to provide an extra scaffolding support to the maturing ACL graft. The purpose of this study was to examine and compare surgical outcomes in patients who underwent ACL reconstruction, with and without internal bracing, alongside varying durations of postoperative physical therapy. Since an internal brace could, theoretically, provide stability to the graft to allow earlier and more aggressive rehabilitation, it is hypothesized that patients with internal bracing will maintain good surgical outcomes regardless of duration of physical therapy.

2. Methods

2.1. Study population

Following Institutional Review Board approval for this study, the authors (PMS, NEA, CVG) retrospectively reviewed all ACL reconstructions performed by a single fellowship-trained and board-certified sports medicine senior orthopedic surgeon (EHA) between January 2013 to December 2015 at a single Level I trauma center. Electronic medical records were accessed and patient information was recorded from a secure hospital computer or network. Patient information was de-identified and stored on an encrypted server. Operative reports of ACL reconstruction cases were reviewed for the use of internal bracing. Inclusion criteria were patients who underwent ACL reconstruction with a minimum follow-up of twelve months. 46 patients were eligible for inclusion. Patient demographics including age, gender, use of internal bracing, and pre-operative level of activity were collected.

2.2. Surgical technique

All patients were positioned supine. A proximal thigh tourniquet was placed, and the lower extremity was prepped and draped using standard sterile technique. For the autograft, the semitendinosus tendon was palpated and a transverse incision in the popliteal crease was made. The semitendinosus was identified, then harvested proximally utilizing an open stripper alongside distal excision using a closed stripper. The semitendinosus tendon was processed utilizing a standard Arthrex GraftLink (Naples, Florida) technique into a quadruple tendon. An anterolateral arthroscopic portal was made followed by an arthroscopic guide into the inferomedial portal. Upon identifying the ACL, it was removed in entirety using a combination of a sucker shaver and cautery. At the origin of the ACL, a femoral tunnel was created, using an Arthrex FlipCutter (Naples, Florida), and suture was shuttled across. At the site of insertion of the ACL, anterior to the PCL and medial to the anterior horn of the lateral meniscus, a tibial tunnel was drilled, and suture was passed through. The graft was then shuttled through the medial portal using an Arthrex TightRope (Naples, Florida). Tensioning was finalized on the tibia with an Arthrex ABS Button (Naples, Florida).

For patients undergoing internal bracing, a FiberTape was placed through the proximal loop of the TightRope construct. The internal brace was first tensioned distally. With a SwiveLock placed with the leg in 30-degree flexion and a posterior drawer force, the native ACL was then tensioned with the ABS button. Incisions were closed with 2-0 Vicryl, 3-0 nylon posteriorly, 2-0 nylon, and 3-0 Monocryl.

2.3. Postoperative rehabilitation

Postoperatively, patients were made weightbearing as tolerated in a hinged knee brace. A standard physical therapy protocol for ACL reconstruction was initiated following the initial postoperative visit in both cohorts identically at 2 weeks after surgery.⁶ At each subsequent visit, surgical recovery was evaluated and measured using the Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire. Physical therapy compliance was established based on the duration, in months, that the patient participated in physical therapy (level 1 = 1–3 months, level 2 = 4–7 months, level 3 = 8+ months).

2.4. Statistical analysis

The primary outcome for this study was functional outcomes in patients following ACL reconstruction with or without internal bracing and varying durations of postoperative physical therapy. Data collected from the forty-six patients who received ACL reconstruction included demographics (age, gender), whether internal bracing was used, physical therapy compliance, and preoperative and postoperative KOOS scores. The functional outcome measured was the change in pre- and postoperative KOOS scores.

Data normality was assessed using the Shapiro-Wilk test. Data characteristics were summarized by frequency and percentage for categorical variables; and mean, standard deviation (SD), median, and interquartile range (IQR) for continuous variables.

Two sample t-test was used to compare surgical outcomes between ACL reconstruction with and without internal bracing, and one-way ANOVA was used to compare each surgical outcome among compliance groups. Mann Whitney U testing was used to compare outcomes for internal bracing/compliance combination analysis.

All tests were two-sided at a significant level of 0.05. All analyses were performed using statistical software RStudio (Version 0.99.902). Post hoc power analysis was conducted to evaluate nonsignificant results.

3. Results

A total of 46 patients (23 male, 23 female) underwent ACL reconstruction between January 2013 and December 2015. The mean age of the sample was 31.53 ± 8.37 years. 23 patients underwent ACL reconstruction with internal bracing, and 23 patients underwent standard ACL reconstruction without internal bracing. Patient demographics are summarized in Table 1.

Table 1.

Patient Demographics. A total of 46 patients (23 male, 23 female) underwent ACL reconstruction between January 2013 and December 2015. The mean age of the sample was 31.53 ± 8.37 years. 23 patients underwent ACL reconstruction with internal bracing, and 23 patients underwent standard ACL reconstruction without internal bracing.

Patient Demographics	n (%)
Sex
Male	23 (50.0)
Female	23 (50.0)
Age (mean [SD], median [IQR])	31.53 [8.37], 30.50 [25.81–36.06]
Internal Bracing	23 (50.0)
Compliance
Level 1 (1–3 months)	14 (43.8)
Level 2 (4–7 months)	13 (40.6)
Level 3 (8–12 months)	5 (15.6)
IB and Compliance
Level 1, with IB	7 (21.9)
Level 2, with IB	8 (25.0)
Level 3, with IB	2 (6.2)
Level 1, without IB	7 (21.9)
Level 2, without IB	5 (15.6)
Level 3, without IB	3 (9.4)

Preoperative KOOS scores were available for 33 of the 46 patients, with a mean score of 49.31 ± 16.99 and median score of 48.21 [39.29–58.33]. Postoperative KOOS scores were available for 45 patients (97.83%), with a mean score of 89.35 ± 11.25 and median score of 92.90 [86.30–97.00]. The average change in KOOS score (ΔKOOS) for the 33 patients (71.74%) with pre- and postoperative KOOS scores was 40.85 ± 17.34, median was 41.05 [34.50–53.56]. Compliance data was available for 32 patients, all of which had pre- and postoperative KOOS scores as well (69.57%).

3.1. Comparison between internal bracing and compliance

The internally braced group demonstrated mean ΔKOOS of 42.82 ± 15.44 and median of 46.39 [34.52–51.80], while the non-internally braced group that had a mean ΔKOOS of 38.18 ± 19.91 and median of 40.17 [29.49–53.90]. There was no statistically significant difference between the groups in terms of ΔKOOS(p = 0.475) (Fig. 1).

Fig.1.

Comparison of mean and median KOOS scores between internally braced ACL reconstruction and non-internally braced ACL reconstruction.

The groups that attended physical therapy for 1–3 months had a mean ΔKOOS of 38.63 ± 13.82 and median of 39.32 [30.96–48.18]. The groups that attended physical therapy for 4–7 months had a mean ΔKOOS of 37.43 ± 22.32 and median of 41.94 [33.79–52.68]. Patients that participated in physical therapy for 8+ months had a mean ΔKOOS of 55.20 ± 13.41 and median of 54.17 [50.56–58.81]. The ΔKOOS was not significantly different among the three compliance groups (p = 0.229) (Fig. 2).

Fig. 2.

Comparison of mean and median KOOS scores between varying levels of physical therapy compliance following ACL Reconstruction.

The internally braced group that attended physical therapy for 1–3 months had a mean ΔKOOS of 35.39 ± 15.26 and median of 40.45 [26.49–47.73]. The internally braced group that attended physical therapy for 4–7 months had a mean ΔKOOS of 41.96 ± 14.49 and median of 45.55 [33.94–52.68]. The internally braced group that attended physical therapy for 8+ months had a mean ΔKOOS of 63.36 ± 13.06 and median of 63.36 [58.74–67.98] (Fig. 3). The non-internally braced group that attended physical therapy for 1–3 months had a mean ΔKOOS of 42.51 ± 12.33 and median of 39.32 [35.69–52.94]. The non-internally braced group that attended physical therapy for 4–7 months had a mean ΔKOOS of 30.64 ± 32.29 and median of 41.65 [26.17–46.12]. The non-internally braced group that attended physical therapy for 8+ months had a mean ΔKOOS of 47.05 ± 10.14 and median of 47.05 [43.46–50.63] (Fig. 3). No statistically significant difference was found between groups in this subgroup analysis (1–3 months, p = 0.4113; 4–7 months, p = 0.7491; 8+ months, p = 0.6985).

Fig. 3.

Comparison of mean and median KOOS scores among internally braced and non-internally braced ACL Reconstruction groups with varying levels of physical therapy compliance.

4. Discussion

Graft healing occurs in three phases: 1) an early graft healing phase with central graft necrosis and hypocellularity, 2) a proliferation phase with the most intensive remodeling and revascularization, 3) ligamentization phase with continued remodeling to replicate the native ACL.7, 8, 9 During the proliferation phase, the graft undergoes its greatest degree of cellular activity alongside modifications in the extracellular matrix.7, 8, 9 As a result, the graft is structurally weak and most likely to fail.⁸ Internal bracing could, theoretically, provide stability during these critical phases of healing and rehabilitation, allowing for a faster recovery.

The internal brace is a braided ultra-high-molecular-weight-polyethylene suture or suture tape that is used to reinforce the strength of ligament graft and enhance the healing process. The goal of the internal brace is to serve as a scaffold for soft tissue repair and to strengthen the graft that will replace the ruptured ACL.1, 2, 3 Both of these properties, hypothetically, allow earlier and more aggressive mobilization and rehabilitation; thereby, improving healing and overall outcomes.1, 2, 3 Thus, an internal brace could provide stability to the graft and allow continued rehabilitation for a faster recovery.

Postoperative rehabilitation/physical therapy is key to restoring biomechanical properties of the knee. Physical therapy is traditionally recommended to be started two weeks following uncomplicated ACL reconstruction. Proper rehabilitation is essential to initiate mobilization and increase knee strength that will improve tissue healing, collagen deposition and remodeling, and restore biomechanical and neuromuscular knee function.¹⁰ Exercises learned during postoperative rehabilitation can promote life-long healing and the comfort needed to return to physical activity.

The current study supports that ACL reconstruction with internal bracing results in similar patient reported functional outcomes. Patients who received ACL reconstruction with internal bracing reported an slight improvement in KOOS scores (mean = 42.82 ± 15.44; median = 46.39 [34.52–51.80]) compared to ACL reconstruction alone (mean = 38.18 ± 19.91; median = 40.17 [29.49–53.90]). However, this difference did not meet statistical significance (p = 0.475). This finding is consistent with the results of a retrospective study by Jonkergouw et al. that also failed to show a statistically significant difference with the addition of internal bracing.¹¹ The study had a comparable sample size to the current study, suggesting that higher power studies investigating the utility of internal bracing in ACL reconstruction is limited following review of the current literature.

When assessing the effect of physical therapy compliance on patient reported outcomes, mean and median ΔKOOS scores of internally braced reconstructions trended towards greater scores beginning in those with 4–8-months of physical therapy, shown by the internally braced mean and median (41.96 ± 14.49, 45.55 [33.94–52.68]) being greater than standard reconstruction (30.64 ± 32.29, 41.65 [26.17–46.12]). This relationship strengthened in the 8+ month group as the difference between the mean and median for internally braced (63.36 ± 13.06, 63.36 [58.74–67.98]) and traditionally reconstructed (47.05 ± 10.14, 47.05 [43.46–50.63]) ΔKOOS widened. However, these differences also lacked statistical significance, further necessitating the need for higher power studies to detect difference between groups.

Increased KOOS scores with physical therapy compliance when comparing reconstruction with internal bracing and controls may be explained with the structural integrity of the graft at different time points. From 4 to 12 weeks, the graft is undergoing “proliferative changes.” The integrity of the graft is at its weakest and decreases from an overall work of 150 N*M to 75 N*M.^8,12 Microscopically, the graft is undergoing massive degrees of cell migration, revascularization, and ECM remodeling.^8,12 This helps demonstrate the lack of significant difference found between the two subgroups from 1 to 3 months. The mean and median outcome scores widen in comparison at the 4–7 and 8+ interval. This is likely due to the increased scaffolding and structure of the ACL when anchored with the internal brace in the proliferative phase -- which hastens reconstruction and transition to the “Ligamentization Stage” at 13+ weeks.^8,12

4.1. Limitations

There are many limitations identified in this study, namely low power and inherent biases in data reporting. Power analysis when comparing functional outcomes following ACL reconstruction with or without internal bracing indicated that a sample size of 234 participants would be required to demonstrate a statistically significant difference between the two groups. Additionally, there exists the potential for recall bias as patients were self reporting length of physical therapy as well as KOOS scores through questionnaires. Since many of these surveys were done well after therapy or past the ACL reconstruction, there lies the possibility of error in reporting. Finally, duration of physical reported by patients is based on in person physical therapy and does not include duration of self-guided physical therapy exercises.

5. Conclusion

This study demonstrates similar mean and median functional outcome scores when comparing patients with internally braced ACL reconstruction compared to standard reconstruction. Patients with internally braced ACL reconstruction reported higher outcome scores alongside compliant physical therapy at 4–7 months and 8+ months compared to controls, although this did not meet statistical significance (p = 0.425). Future studies that demonstrate higher power are essential to investigate this theoretic benefit of internal brace protection, which may be more valuable during the time of recovery when the maturing graft is at its weakest.

Funding

No benefits in any form have been received or will be received related directly or indirectly to the subject of this article.

Author's contribution

Authors PMS, NEA, KMK, CVG, XG, and EHA made significant contributions to research design, data acquisition, and analysis and interpretation of data. Authors PMS, MDG, NEA, KMK, MDG, KWZ, and EHA participated in visualization, drafting and revising the manuscript. All authors have read and approved the final manuscript.

Declaration of competing interest

One of the authors has declared the following potential conflict of interest or source of funding: E.H.A. is a paid consultant for Arthrex Inc. and OrthAlign. No other authors have financial disclosures.