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Anterior cruciate ligament repair with internal brace augmentation: A systematic review

Open AccessPublished:March 30, 2022DOI:https://doi.org/10.1016/j.knee.2022.03.009

      Highlights

      • Proximal ACL tears have the most potential for healing after primary repair.
      • ACL repair with internal bracing has satisfactory outcomes in individual cohort studies with short to medium term follow-up.
      • ACL repair with internal bracing is a safe technique for treatment of proximal ruptures, with a failure rate of 10.4% at mean 2.7 years.
      • Subjective outcome scores and clinical laxity testing showed satisfactory results in meta-analysis across a total of 347 patients.

      Abstract

      Background

      Primary repair of anterior cruciate ligament (ACL) ruptures has re-emerged as a treatment option for proximal tears, with internal brace augmentation often utilised. The aim of this study is to provide an overview of the current evidence presenting outcomes of ACL repair with internal bracing to assess the safety and efficacy of this technique.

      Methods

      All studies reporting outcomes of arthroscopic primary repair of proximal ACL tears, augmented with internal bracing from 2014-2021 were included. Primary outcome was failure rate and secondary outcomes were subjective patient reported outcome measures (PROMs) and objective assessment of anteroposterior knee laxity.

      Results

      Nine studies were included, consisting of 347 patients, mean age 32.5 years, mean minimum follow up 2 years. There were 36 failures (10.4%, CI 7.4% - 14.1%). PROMs reporting was variable across studies. KOOS, Lysholm and IKDC scores were most frequently used with mean scores > 87%. The mean Tegner and Marx scores at follow-up were 6.1 and 7.8 respectively. The mean side to side difference measured for anteroposterior knee laxity was 1.2mm.

      Conclusions

      This systematic review with meta-analysis shows that ACL repair with internal bracing is a safe technique for treatment of proximal ruptures, with a failure rate of 10.4%. Subjective scores and clinical laxity testing also revealed satisfactory results. This suggests that ACL repair with internal bracing should be considered as an alternative to ACL reconstruction for acute proximal tears, with the potential benefits of retained native tissue and proprioception, as well as negating the need for graft harvest.

      Keywords

      1. Introduction

      Anterior cruciate ligament (ACL) reconstruction is currently the gold standard surgical treatment for ACL tears but has variable success rates in term of patient satisfaction and revision rates of around 10-15% [

      Samitier G, Marcano AI, Alentorn-Geli E, Cugat R, Farmer KW, Moser MW. Failure of anterior cruciate ligament reconstruction. Arch Bone Joint Surg 2015;3(4):220–40. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4628627/.

      ,
      • Sandon A.
      • Engström B.
      • Forssblad M.
      High risk of further ACL injury in a 10-year follow-up study of ACL-reconstructed soccer players in the Swedish national knee ligament registry.
      ,

      George MS, Dunn WR, Spindler KP. Current concepts review: revision anterior cruciate ligament reconstruction. Am J Sports Med 2006;34(12):2026–37. doi: 10.1177/0363546506295026.

      ]. Realisation of the limitations associated with ACL reconstruction has prompted renewed interest into other techniques which could improve outcomes after ACL rupture. Modern arthroscopic surgical instrumentation has made repair of ACL tissue easier and advancements in functional tissue engineering and regenerative medicine have resulted in a revival of ACL repair [
      • Kiapour A.M.
      • Murray M.M.
      Basic science of anterior cruciate ligament injury and repair.
      ,
      • Steadman J.
      • Matheny L.
      • Briggs K.
      • Rodkey W.
      • Carreira D.
      Outcomes following healing response in older, active patients: a primary anterior cruciate ligament repair technique.
      ]. Theoretically, this technique could restore normal patient anatomy, retaining proprioceptive fibres, whilst not causing donor site morbidity [
      • Webster K.E.
      • Wittwer J.E.
      • O'Brien J.
      • Feller J.A.
      Gait patterns after anterior cruciate ligament reconstruction are related to graft type.
      ].
      Outcomes following early ACL repair surgeries in the 1970s may have been confounded by the surgical technique used, which included both a large arthrotomy and extensive postoperative cast immobilisation, both of which are the opposite of the fundamental principles of modern ACL surgery, which focuses on early range of motion and accelerated rehabilitation [
      • van Eck C.F.
      • Limpisvasti O.
      • ElAttrache N.S.
      Is there a role for internal bracing and repair of the anterior cruciate ligament? A systematic literature review.
      ,
      • Shelbourne K.D.
      • Nitz P.
      Accelerated rehabilitation after anterior cruciate ligament reconstruction.
      ].
      The arterial blood supply to the ACL is from a web-like network within the synovial membrane, with the greatest density proximally and relatively poor vascularity in the middle and distal third of the ligament [
      • Toy B.J.
      • Yeasting R.A.
      • Morse D.E.
      • McCann P.
      Arterial supply to the human anterior cruciate ligament.
      ]. Furthermore, a recent study [
      • Takeuchi S.
      • Rothrauff B.B.
      • Kanto R.
      • Onishi K.
      • Fu F.H.
      Superb microvascular imaging (SMI) detects increased vascularity of the torn anterior cruciate ligament.
      ] found that the vascularity was significantly increased in a torn ACL compared to intact ligaments, adding evidence to support the potential for ACL healing. Sherman highlighted a subgroup of patients from his early ACL repair cohort who had acute, proximal ACL tears with excellent tissue quality who did well following ACL repair [
      • Sherman M.F.
      • Lieber L.
      • Bonamo J.R.
      • Podesta L.
      • Reiter I.
      The long-term followup of primary anterior cruciate ligament repair.
      ]. DiFelice and colleagues have proposed in several of their studies that proximal based tears of the ACL should be the focus when selecting patients for primary repair [
      • DiFelice G.S.
      • Villegas C.
      • Taylor S.
      Anterior cruciate ligament preservation: early results of a novel arthroscopic technique for suture anchor primary anterior cruciate ligament repair.
      ,
      • DiFelice G.S.
      • van der List J.P.
      Arthroscopic primary repair of proximal anterior cruciate ligament tears.
      ,

      van der List JP, Mintz DN, DiFelice GS. The location of anterior cruciate ligament tears: a prevalence study using magnetic resonance imaging. Orthop J Sports Med 2017;5(6):2325967117709966-. doi: 10.1177/2325967117709966.

      ,
      • Daniels S.P.
      • van der List J.P.
      • Kazam J.J.
      • DiFelice G.S.
      Arthroscopic primary repair of the anterior cruciate ligament: what the radiologist needs to know.
      ,
      • van der List J.P.
      • Mintz D.N.
      • DiFelice G.S.
      The locations of anterior cruciate ligament tears in pediatric and adolescent patients.
      ,
      • van der List J.P.
      • DiFelice G.S.
      Role of tear location on outcomes of open primary repair of the anterior cruciate ligament: a systematic review of historical studies.
      ,
      • van der List J.P.
      • DiFelice G.S.
      Primary repair of the anterior cruciate ligament: a paradigm shift.
      ,
      • van der List J.P.
      • DiFelice G.S.
      Preoperative magnetic resonance imaging predicts eligibility for arthroscopic primary anterior cruciate ligament repair.
      ,
      • DiFelice G.S.
      • van der List J.P.
      Clinical outcomes of arthroscopic primary repair of proximal anterior cruciate ligament tears are maintained at mid-term follow-up.
      ,
      • van der List J.P.
      • Jonkergouw A.
      • van Noort A.
      • Kerkhoffs G.
      • DiFelice G.S.
      Identifying candidates for arthroscopic primary repair of the anterior cruciate ligament: a case-control study.
      ].
      Murray et al [
      • Murray M.M.
      Current status and potential of primary ACL repair.
      ] have postulated that ACL healing can occur as long as mechanical homeostasis can be achieved to allow a stable fibrin-platelet scaffold to form at the injury site. This can be achieved using an additional scaffold such as a mechanical augment. Three main ACL repair techniques have been developed aiming to improve the mechanical environment, namely, Bridge Enhanced ACL Repair (BEAR) [

      Murray MM, Flutie BM, Kalish LA, Ecklund K, Fleming BC, Proffen BL, et al. The bridge-enhanced anterior cruciate ligament repair (BEAR) procedure: an early feasibility cohort study. Orthop J Sports Med 2016;4(11):2325967116672176. doi: 10.1177/2325967116672176.

      ], Dynamic Intraligamentary Stabilisation (DIS) [
      • Eggli S.
      • Kohlhof H.
      • Zumstein M.
      • Henle P.
      • Hartel M.
      • Evangelopoulos D.S.
      • et al.
      Dynamic intraligamentary stabilization: novel technique for preserving the ruptured ACL.
      ] and internal brace ligament augmentation (IBLA) [
      • MacKay G.M.
      • Blyth M.J.
      • Anthony I.
      • Hopper G.P.
      • Ribbans W.J.
      A review of ligament augmentation with the InternalBrace: the surgical principle is described for the lateral ankle ligament and ACL repair in particular, and a comprehensive review of other surgical applications and techniques is presented.
      ,
      • Wilson W.T.
      • Hopper G.P.
      • Byrne P.A.
      • MacKay G.M.
      Anterior cruciate ligament repair with internal brace ligament augmentation.
      ]. BEAR is a biologically enhanced scaffold used to treat midsubstance tears. DIS has been used with increasing prevalence in Europe but results have shown high re-operation rates particularly due to hardware irritation [
      • Osti M.
      • El Attal R.
      • Doskar W.
      • Hock P.
      • Smekal V.
      High complication rate following dynamic intraligamentary stabilization for primary repair of the anterior cruciate ligament.
      ,
      • Meister M.
      • Koch J.
      • Amsler F.
      • Arnold M.P.
      • Hirschmann M.T.
      ACL suturing using dynamic intraligamentary stabilisation showing good clinical outcome but a high reoperation rate: a retrospective independent study.
      ,
      • Kösters C.
      • Glasbrenner J.
      • Spickermann L.
      • Kittl C.
      • Domnick C.
      • Herbort M.
      • et al.
      Repair with dynamic intraligamentary stabilization versus primary reconstruction of acute anterior cruciate ligament tears: 2-year results from a prospective randomized study.
      ]. Internal bracing is the augmentation of a ligament repair with high strength suture tape, which reinforces the ligament and acts as a secondary stabiliser [
      • MacKay G.M.
      • Blyth M.J.
      • Anthony I.
      • Hopper G.P.
      • Ribbans W.J.
      A review of ligament augmentation with the InternalBrace: the surgical principle is described for the lateral ankle ligament and ACL repair in particular, and a comprehensive review of other surgical applications and techniques is presented.
      ]. This promotes natural healing of the repaired proximal ACL tear by protecting it from excessive elongation during the early healing stages. The results from the only cohort of patients treated with ACL repair and internal bracing, with outcomes reported at five years, was recently published [
      • Hopper G.P.
      • Aithie J.M.S.
      • Jenkins J.M.
      • Wilson W.T.
      • Mackay G.M.
      Satisfactory patient-reported outcomes at 5 years following primary repair with suture tape augmentation for proximal anterior cruciate ligament tears.
      ]. There have been several other authors reporting their outcomes in recent years, but to date no systematic review or meta-analysis specifically focusing on the technique of ACL repair with internal bracing. This systematic review with meta-analysis was therefore performed to assess the safety and efficacy of this technique. The aim is to provide an overview of the current evidence presenting outcomes of ACL repair with internal bracing.

      2. Methods

      2.1 Literature search

      A literature search was performed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines and the study was registered on PROSPERO (CRD42021267659). The search was conducted across the online databases, PubMed (Medline), Embase, and the Cochrane library. The search contained the keywords [“Anterior Cruciate Ligament” OR “ACL” AND “repair” AND “Internal Brace” OR “suture tape” OR “suture augmentation”]. Only English language articles were included and those published between 1st January 2014, and 1st July 2021. The start date was used as this is the time around which modern ACL repair methods began to be reported, with studies reporting on ACL repair prior to this generally using the open method rather than arthroscopic. Titles and abstracts of all identified records were reviewed, and the full text was reviewed for relevant articles by two authors, WW & GH. The reference lists of these articles were also reviewed, and any further potentially eligible studies were identified. As well as this, the ‘related articles’ function of PubMed was used to identify any further relevant publications. All studies reporting clinical outcomes of proximal ACL tears treated with primary arthroscopic repair and internal brace augmentation were included. Animal studies, cadaver studies, those reporting outcomes of case reports and those with less than one year follow-up were excluded.

      2.2 Quality of studies

      Level of evidence was assessed using the adjusted Oxford Centre for Evidence-Based Medicine 2011 Levels of Evidence [
      • Wright J.G.
      • Swiontkowski M.F.
      • Heckman J.D.
      Introducing levels of evidence to the journal.
      ]. The methodological quality of the studies was estimated using the Methodological Index for Non-Randomised Studies (MINORS) instrument [
      • Slim K.
      • Nini E.
      • Forestier D.
      • Kwiatkowski F.
      • Panis Y.
      • Chipponi J.
      Methodological index for non-randomized studies (minors): development and validation of a new instrument.
      ], utilising the first eight questions, specifically designed for assessing non-comparative studies.

      2.3 Data extraction

      Data were extracted from each study and collated in Excel 2017 (Microsoft Corp., Redmond, WA, USA). Information recorded included journal and year of publication, authors, number of patients, mean patient age, gender, length of follow-up (minimum and mean), delay from injury to surgery and baseline patient activity level (Tegner score). The primary outcome collected was the failure rate, defined by re-rupture or revision for symptomatic instability. Secondary outcomes were subjective patient reported outcomes measures (PROMs) and objective clinical assessment of knee laxity. The most reported PROMs that were considered in the analysis were the Knee Injury and Osteoarthritis Outcome Score (KOOS) [
      • Roos E.M.
      • Roos H.P.
      • Lohmander L.S.
      • Ekdahl C.
      • Beynnon B.D.
      Knee injury and osteoarthritis outcome score (KOOS)—development of a self-administered outcome measure.
      ], Lysholm score [
      • Lysholm J.
      • Gillquist J.
      Evaluation of knee ligament surgery results with special emphasis on use of a scoring scale.
      ] and International Knee Documentation Committee (IKDC) subjective score [
      • Hefti F.
      • Müller W.
      • Jakob R.P.
      • Stäubli H.U.
      Evaluation of knee ligament injuries with the IKDC form.
      ]. The activity level of patients at follow-up was assessed using the Tegner activity scale [

      Tegner Y, Lysholm J. Rating systems in the evaluation of knee ligament injuries. Clin Orthop Relat Res 1985(198):43–9. Available from: http://europepmc.org/abstract/MED/4028566.

      ] or Marx activity rating scale [
      • Marx R.G.
      • Stump T.J.
      • Jones E.C.
      • Wickiewicz T.L.
      • Warren R.F.
      Development and evaluation of an activity rating scale for disorders of the knee.
      ]. Objective laxity assessment was included if anteroposterior knee laxity was quantified using an instrumented method for Lachmann test.

      2.4 Statistical analysis

      Statistical analysis was performed using SPSS Statistics version 27.0 (SPSS Inc., Armonk, NY, USA). For each study the failure rate was calculated as the reported number of failures out of the total patient number in the study. These values were used to calculate 95% confidence intervals for each study. The overall failure rate was calculated as the harmonic mean; the total failures as a proportion of the total study population. Continuous variables were expressed as means ± standard deviations. In the analysis, pooled outcomes were assessed by calculating weighted means by the sample size of each study as a proportion of the overall total patient number reporting that outcome.

      3. Results

      In total the search revealed 285 articles which were screened and full text reviews conducted for 50 following exclusions (Fig. 1). Eleven studies met the inclusion criteria, but two of these were reporting on the same group of patients as other included studies, at different time points [
      • Heusdens C.H.W.
      • Hopper G.P.
      • Dossche L.
      • Roelant E.
      • Mackay G.M.
      Anterior cruciate ligament repair with Independent Suture Tape Reinforcement: a case series with 2-year follow-up.
      ,
      • Jonkergouw A.
      • van der List J.P.
      • DiFelice G.S.
      Arthroscopic primary repair of proximal anterior cruciate ligament tears: outcomes of the first 56 consecutive patients and the role of additional internal bracing.
      ]. Consequently, these two studies were excluded, and the two with longer follow-up retained, leaving nine overall which were included in the review [
      • Hopper G.P.
      • Aithie J.M.S.
      • Jenkins J.M.
      • Wilson W.T.
      • Mackay G.M.
      Satisfactory patient-reported outcomes at 5 years following primary repair with suture tape augmentation for proximal anterior cruciate ligament tears.
      ,
      • Gagliardi A.G.
      • Carry P.M.
      • Parikh H.B.
      • Traver J.L.
      • Howell D.R.
      • Albright J.C.
      ACL repair with suture ligament augmentation is associated with a high failure rate among adolescent patients.
      ,
      • Dabis J.
      • Yasen S.K.
      • Foster A.J.
      • Pace J.L.
      • Wilson A.J.
      Paediatric proximal ACL tears managed with direct ACL repair is safe, effective and has excellent short-term outcomes.
      ,
      • Douoguih W.A.
      • Zade R.T.
      • Bodendorfer B.M.
      • Siddiqui Y.
      • Lincoln A.E.
      Anterior cruciate ligament repair with suture augmentation for proximal avulsion injuries.
      ,
      • Schneider K.N.
      • Schliemann B.
      • Gosheger G.
      • Theil C.
      • Weller J.
      • Buddhdev P.K.
      • et al.
      Good to excellent functional short-term outcome and low revision rates following primary anterior cruciate ligament repair using suture augmentation.
      ,
      • Burton D.A.
      • Schaefer E.J.
      • Shu H.T.
      • Bodendorfer B.M.
      • Argintar E.H.
      Primary anterior cruciate ligament repair using suture tape augmentation: a case series of 29 patients with minimum 2-year follow-up.
      ,
      • Heusdens C.H.W.
      • Blockhuys K.
      • Roelant E.
      • Dossche L.
      • Van Glabbeek F.
      • Van Dyck P.
      Suture tape augmentation ACL repair, stable knee, and favorable PROMs, but a re-rupture rate of 11% within 2 years.
      ,
      • Ortmaier R.
      • Fink C.
      • Schobersberger W.
      • Kindermann H.
      • Leister I.
      • Runer A.
      • et al.
      Return to sports after anterior cruciate ligament injury: a matched-pair analysis of repair with internal brace and reconstruction using hamstring or quadriceps tendons.
      ,
      • Vermeijden H.D.
      • Yang X.A.
      • van der List J.P.
      • DiFelice G.S.
      Role of age on success of arthroscopic primary repair of proximal anterior cruciate ligament tears.
      ].
      Figure thumbnail gr1
      Fig. 1Prisma Flowchart illustrating inclusion and exclusion of studies for review
      There were no level one or two studies, three studies were level three [
      • Gagliardi A.G.
      • Carry P.M.
      • Parikh H.B.
      • Traver J.L.
      • Howell D.R.
      • Albright J.C.
      ACL repair with suture ligament augmentation is associated with a high failure rate among adolescent patients.
      ,
      • Ortmaier R.
      • Fink C.
      • Schobersberger W.
      • Kindermann H.
      • Leister I.
      • Runer A.
      • et al.
      Return to sports after anterior cruciate ligament injury: a matched-pair analysis of repair with internal brace and reconstruction using hamstring or quadriceps tendons.
      ,
      • Vermeijden H.D.
      • Yang X.A.
      • van der List J.P.
      • DiFelice G.S.
      Role of age on success of arthroscopic primary repair of proximal anterior cruciate ligament tears.
      ], while the remainder (67%) were level four studies. The methodological quality of studies was assessed using the MINORS criteria, and the mean score was 10 out of 16 points (Table 1). No studies included blinding and two included comparisons with ACL reconstruction patients [
      • Gagliardi A.G.
      • Carry P.M.
      • Parikh H.B.
      • Traver J.L.
      • Howell D.R.
      • Albright J.C.
      ACL repair with suture ligament augmentation is associated with a high failure rate among adolescent patients.
      ,
      • Ortmaier R.
      • Fink C.
      • Schobersberger W.
      • Kindermann H.
      • Leister I.
      • Runer A.
      • et al.
      Return to sports after anterior cruciate ligament injury: a matched-pair analysis of repair with internal brace and reconstruction using hamstring or quadriceps tendons.
      ].
      Table 1Summary of included studies with quality assessment of using the Methodological Index for Non-Randomized Studies (MINORS) criteria
      PublicationJournalEvidence LevelMINORS Score (16)
      Gagliardi et al. 2019
      • Gagliardi A.G.
      • Carry P.M.
      • Parikh H.B.
      • Traver J.L.
      • Howell D.R.
      • Albright J.C.
      ACL repair with suture ligament augmentation is associated with a high failure rate among adolescent patients.
      Am J Sports Med312
      Ortmaier et al. 2020
      • Ortmaier R.
      • Fink C.
      • Schobersberger W.
      • Kindermann H.
      • Leister I.
      • Runer A.
      • et al.
      Return to sports after anterior cruciate ligament injury: a matched-pair analysis of repair with internal brace and reconstruction using hamstring or quadriceps tendons.
      Sportverletz.-Sportschaden39
      Douoguih et al. 2020
      • Douoguih W.A.
      • Zade R.T.
      • Bodendorfer B.M.
      • Siddiqui Y.
      • Lincoln A.E.
      Anterior cruciate ligament repair with suture augmentation for proximal avulsion injuries.
      ASMAR49
      Schneider et al. 2020
      • Schneider K.N.
      • Schliemann B.
      • Gosheger G.
      • Theil C.
      • Weller J.
      • Buddhdev P.K.
      • et al.
      Good to excellent functional short-term outcome and low revision rates following primary anterior cruciate ligament repair using suture augmentation.
      J Clin Med49
      Dabis et al. 2020
      • Dabis J.
      • Yasen S.K.
      • Foster A.J.
      • Pace J.L.
      • Wilson A.J.
      Paediatric proximal ACL tears managed with direct ACL repair is safe, effective and has excellent short-term outcomes.
      KSSTA410
      Heusdens et al. 2020
      • Heusdens C.H.W.
      • Blockhuys K.
      • Roelant E.
      • Dossche L.
      • Van Glabbeek F.
      • Van Dyck P.
      Suture tape augmentation ACL repair, stable knee, and favorable PROMs, but a re-rupture rate of 11% within 2 years.
      KSSTA411
      Burton et al. 2021
      • Burton D.A.
      • Schaefer E.J.
      • Shu H.T.
      • Bodendorfer B.M.
      • Argintar E.H.
      Primary anterior cruciate ligament repair using suture tape augmentation: a case series of 29 patients with minimum 2-year follow-up.
      Arthroscopy49
      Vermeijden et al. 2021
      • Vermeijden H.D.
      • Yang X.A.
      • van der List J.P.
      • DiFelice G.S.
      Role of age on success of arthroscopic primary repair of proximal anterior cruciate ligament tears.
      Arthroscopy310
      Hopper et al. 2021
      • Hopper G.P.
      • Aithie J.M.S.
      • Jenkins J.M.
      • Wilson W.T.
      • Mackay G.M.
      Satisfactory patient-reported outcomes at 5 years following primary repair with suture tape augmentation for proximal anterior cruciate ligament tears.
      KSSTA411
      The meta-analysis consisted of 347 patients of which 161 (46%) were male. The mean age was 32.5 years, with a pre-injury Tegner activity score mean of 6.3. The mean minimum follow up was 2 years (range 1 – 5 years). There were a total of 36 failures out of 347 patients (10.4%, CI 7.4% - 14.1%, Table 2).
      Table 2Summary of patient characteristics in each of included studies and reported failure rates following ACL repair with internal bracing. (Overall shows totals and weighted means/standard deviations for meta-analysis)
      PublicationSample Size (n)Male (n)Delay to surgery (days)Tegner score pre-injuryMean Age (Years)Follow up mean (Years)Follow up minimum (Years)Failures (n)Failure rate (%)Failure 95% CI LowFailure 95% CI High
      Gagliardi et al. 2019
      • Gagliardi A.G.
      • Carry P.M.
      • Parikh H.B.
      • Traver J.L.
      • Howell D.R.
      • Albright J.C.
      ACL repair with suture ligament augmentation is associated with a high failure rate among adolescent patients.
      22123413.93.22.2940.920.763.7
      Ortmaier et al. 2020
      • Ortmaier R.
      • Fink C.
      • Schobersberger W.
      • Kindermann H.
      • Leister I.
      • Runer A.
      • et al.
      Return to sports after anterior cruciate ligament injury: a matched-pair analysis of repair with internal brace and reconstruction using hamstring or quadriceps tendons.
      2485.734.01.000014.3
      Douoguih et al. 2020
      • Douoguih W.A.
      • Zade R.T.
      • Bodendorfer B.M.
      • Siddiqui Y.
      • Lincoln A.E.
      Anterior cruciate ligament repair with suture augmentation for proximal avulsion injuries.
      271827.42.82.0414.80.924.3
      Schneider et al. 2020
      • Schneider K.N.
      • Schliemann B.
      • Gosheger G.
      • Theil C.
      • Weller J.
      • Buddhdev P.K.
      • et al.
      Good to excellent functional short-term outcome and low revision rates following primary anterior cruciate ligament repair using suture augmentation.
      932626.042.01.81.033.20.79.1
      Dabis et al. 2020
      • Dabis J.
      • Yasen S.K.
      • Foster A.J.
      • Pace J.L.
      • Wilson A.J.
      Paediatric proximal ACL tears managed with direct ACL repair is safe, effective and has excellent short-term outcomes.
      2084512.92.72.400011.9
      Heusdens et al. 2020
      • Heusdens C.H.W.
      • Blockhuys K.
      • Roelant E.
      • Dossche L.
      • Van Glabbeek F.
      • Van Dyck P.
      Suture tape augmentation ACL repair, stable knee, and favorable PROMs, but a re-rupture rate of 11% within 2 years.
      35176.032.82.0411.43.226.7
      Burton et al. 2021
      • Burton D.A.
      • Schaefer E.J.
      • Shu H.T.
      • Bodendorfer B.M.
      • Argintar E.H.
      Primary anterior cruciate ligament repair using suture tape augmentation: a case series of 29 patients with minimum 2-year follow-up.
      292132.22.82.026.90.822.8
      Vermeijden et al. 2021
      • Vermeijden H.D.
      • Yang X.A.
      • van der List J.P.
      • DiFelice G.S.
      Role of age on success of arthroscopic primary repair of proximal anterior cruciate ligament tears.
      6033387.129.42.22.0813.35.924.6
      Hopper et al. 2021
      • Hopper G.P.
      • Aithie J.M.S.
      • Jenkins J.M.
      • Wilson W.T.
      • Mackay G.M.
      Satisfactory patient-reported outcomes at 5 years following primary repair with suture tape augmentation for proximal anterior cruciate ligament tears.
      371837.85.75.0616.26.232
      Overall [n or mean (SD)]34716121 (18)6.3 (0.5)32.5 (8.7)2.7 (1.2)2.0 (1.1)3610.4 (9.7)3.6 (5.0)22.3 (13.4)
      Postoperative complications that did not involve ACL re-rupture were only reported in one study [
      • Vermeijden H.D.
      • Yang X.A.
      • van der List J.P.
      • DiFelice G.S.
      Role of age on success of arthroscopic primary repair of proximal anterior cruciate ligament tears.
      ]. Rates of re-operation, which was generally indicated for hardware irritation or subsequent meniscal injury were no different than in the reconstruction group considered in that study [
      • Vermeijden H.D.
      • Yang X.A.
      • van der List J.P.
      • DiFelice G.S.
      Role of age on success of arthroscopic primary repair of proximal anterior cruciate ligament tears.
      ]. In the paediatric cohort presented by Dabis et al. [
      • Dabis J.
      • Yasen S.K.
      • Foster A.J.
      • Pace J.L.
      • Wilson A.J.
      Paediatric proximal ACL tears managed with direct ACL repair is safe, effective and has excellent short-term outcomes.
      ], re-operation was considered standard care in all skeletally immature patients to release the internal brace at three months postoperatively.
      Subjective PROMs reporting at final follow up was variable across studies with KOOS, Lysholm and IKDC scores the most frequently reported (Table 3). Lysholm score was utilised in five studies [
      • Gagliardi A.G.
      • Carry P.M.
      • Parikh H.B.
      • Traver J.L.
      • Howell D.R.
      • Albright J.C.
      ACL repair with suture ligament augmentation is associated with a high failure rate among adolescent patients.
      ,
      • Dabis J.
      • Yasen S.K.
      • Foster A.J.
      • Pace J.L.
      • Wilson A.J.
      Paediatric proximal ACL tears managed with direct ACL repair is safe, effective and has excellent short-term outcomes.
      ,
      • Schneider K.N.
      • Schliemann B.
      • Gosheger G.
      • Theil C.
      • Weller J.
      • Buddhdev P.K.
      • et al.
      Good to excellent functional short-term outcome and low revision rates following primary anterior cruciate ligament repair using suture augmentation.
      ,
      • Heusdens C.H.W.
      • Blockhuys K.
      • Roelant E.
      • Dossche L.
      • Van Glabbeek F.
      • Van Dyck P.
      Suture tape augmentation ACL repair, stable knee, and favorable PROMs, but a re-rupture rate of 11% within 2 years.
      ,
      • Vermeijden H.D.
      • Yang X.A.
      • van der List J.P.
      • DiFelice G.S.
      Role of age on success of arthroscopic primary repair of proximal anterior cruciate ligament tears.
      ], KOOS in four studies [
      • Hopper G.P.
      • Aithie J.M.S.
      • Jenkins J.M.
      • Wilson W.T.
      • Mackay G.M.
      Satisfactory patient-reported outcomes at 5 years following primary repair with suture tape augmentation for proximal anterior cruciate ligament tears.
      ,
      • Dabis J.
      • Yasen S.K.
      • Foster A.J.
      • Pace J.L.
      • Wilson A.J.
      Paediatric proximal ACL tears managed with direct ACL repair is safe, effective and has excellent short-term outcomes.
      ,
      • Douoguih W.A.
      • Zade R.T.
      • Bodendorfer B.M.
      • Siddiqui Y.
      • Lincoln A.E.
      Anterior cruciate ligament repair with suture augmentation for proximal avulsion injuries.
      ,
      • Burton D.A.
      • Schaefer E.J.
      • Shu H.T.
      • Bodendorfer B.M.
      • Argintar E.H.
      Primary anterior cruciate ligament repair using suture tape augmentation: a case series of 29 patients with minimum 2-year follow-up.
      ] and IKDC subjective score in four studies [
      • Gagliardi A.G.
      • Carry P.M.
      • Parikh H.B.
      • Traver J.L.
      • Howell D.R.
      • Albright J.C.
      ACL repair with suture ligament augmentation is associated with a high failure rate among adolescent patients.
      ,
      • Schneider K.N.
      • Schliemann B.
      • Gosheger G.
      • Theil C.
      • Weller J.
      • Buddhdev P.K.
      • et al.
      Good to excellent functional short-term outcome and low revision rates following primary anterior cruciate ligament repair using suture augmentation.
      ,
      • Heusdens C.H.W.
      • Blockhuys K.
      • Roelant E.
      • Dossche L.
      • Van Glabbeek F.
      • Van Dyck P.
      Suture tape augmentation ACL repair, stable knee, and favorable PROMs, but a re-rupture rate of 11% within 2 years.
      ,
      • Vermeijden H.D.
      • Yang X.A.
      • van der List J.P.
      • DiFelice G.S.
      Role of age on success of arthroscopic primary repair of proximal anterior cruciate ligament tears.
      ]. Meta-analysis revealed mean scores greater than 87% of maximum for all three subjective PROMs. The mean Tegner and Marx scores at follow-up were 6.1 and 7.8 respectively. The mean pre-injury Tegner score for those reported was 6.3, demonstrating a small decrease in activity level from pre-injury to follow-up (p<0.001). Of the four studies that reported both pre-injury and follow-up Tegner scores, two [
      • Schneider K.N.
      • Schliemann B.
      • Gosheger G.
      • Theil C.
      • Weller J.
      • Buddhdev P.K.
      • et al.
      Good to excellent functional short-term outcome and low revision rates following primary anterior cruciate ligament repair using suture augmentation.
      ,
      • Heusdens C.H.W.
      • Blockhuys K.
      • Roelant E.
      • Dossche L.
      • Van Glabbeek F.
      • Van Dyck P.
      Suture tape augmentation ACL repair, stable knee, and favorable PROMs, but a re-rupture rate of 11% within 2 years.
      ] showed equivalent scores and two [
      • Ortmaier R.
      • Fink C.
      • Schobersberger W.
      • Kindermann H.
      • Leister I.
      • Runer A.
      • et al.
      Return to sports after anterior cruciate ligament injury: a matched-pair analysis of repair with internal brace and reconstruction using hamstring or quadriceps tendons.
      ,
      • Vermeijden H.D.
      • Yang X.A.
      • van der List J.P.
      • DiFelice G.S.
      Role of age on success of arthroscopic primary repair of proximal anterior cruciate ligament tears.
      ] showed a decrease of less than one point at follow-up.
      Anteroposterior (AP) knee laxity was quantified in four studies using KT-1000 [
      • Gagliardi A.G.
      • Carry P.M.
      • Parikh H.B.
      • Traver J.L.
      • Howell D.R.
      • Albright J.C.
      ACL repair with suture ligament augmentation is associated with a high failure rate among adolescent patients.
      ,
      • Schneider K.N.
      • Schliemann B.
      • Gosheger G.
      • Theil C.
      • Weller J.
      • Buddhdev P.K.
      • et al.
      Good to excellent functional short-term outcome and low revision rates following primary anterior cruciate ligament repair using suture augmentation.
      ], Rolimeter [
      • Heusdens C.H.W.
      • Blockhuys K.
      • Roelant E.
      • Dossche L.
      • Van Glabbeek F.
      • Van Dyck P.
      Suture tape augmentation ACL repair, stable knee, and favorable PROMs, but a re-rupture rate of 11% within 2 years.
      ] or KiRa triaxial accelerometer [
      • Dabis J.
      • Yasen S.K.
      • Foster A.J.
      • Pace J.L.
      • Wilson A.J.
      Paediatric proximal ACL tears managed with direct ACL repair is safe, effective and has excellent short-term outcomes.
      ]. The mean side to side difference in laxity for Lachmann test was 1.2mm .
      Table 3Secondary outcomes measures recorded in each study, including subjective PROMs and objective measurement of knee laxity. (Overall shows totals and weighted means/standard deviations for meta-analysis)
      PublicationSample Size (n)KOOSIKDCLysholmMarxTegnerLachmann Difference (mm)
      Gagliardi et al. 2019
      • Gagliardi A.G.
      • Carry P.M.
      • Parikh H.B.
      • Traver J.L.
      • Howell D.R.
      • Albright J.C.
      ACL repair with suture ligament augmentation is associated with a high failure rate among adolescent patients.
      2290.81002.0
      Ortmaier et al. 2020
      • Ortmaier R.
      • Fink C.
      • Schobersberger W.
      • Kindermann H.
      • Leister I.
      • Runer A.
      • et al.
      Return to sports after anterior cruciate ligament injury: a matched-pair analysis of repair with internal brace and reconstruction using hamstring or quadriceps tendons.
      245.3
      Douoguih et al. 2020
      • Douoguih W.A.
      • Zade R.T.
      • Bodendorfer B.M.
      • Siddiqui Y.
      • Lincoln A.E.
      Anterior cruciate ligament repair with suture augmentation for proximal avulsion injuries.
      2783.78.6
      Schneider et al. 2020
      • Schneider K.N.
      • Schliemann B.
      • Gosheger G.
      • Theil C.
      • Weller J.
      • Buddhdev P.K.
      • et al.
      Good to excellent functional short-term outcome and low revision rates following primary anterior cruciate ligament repair using suture augmentation.
      9387.492.661.0
      Dabis et al. 2020
      • Dabis J.
      • Yasen S.K.
      • Foster A.J.
      • Pace J.L.
      • Wilson A.J.
      Paediatric proximal ACL tears managed with direct ACL repair is safe, effective and has excellent short-term outcomes.
      2096.59571.2
      Heusdens et al. 2020
      • Heusdens C.H.W.
      • Blockhuys K.
      • Roelant E.
      • Dossche L.
      • Van Glabbeek F.
      • Van Dyck P.
      Suture tape augmentation ACL repair, stable knee, and favorable PROMs, but a re-rupture rate of 11% within 2 years.
      3585.38661.0
      Burton et al. 2021
      • Burton D.A.
      • Schaefer E.J.
      • Shu H.T.
      • Bodendorfer B.M.
      • Argintar E.H.
      Primary anterior cruciate ligament repair using suture tape augmentation: a case series of 29 patients with minimum 2-year follow-up.
      2984.3
      Vermeijden et al. 2021
      • Vermeijden H.D.
      • Yang X.A.
      • van der List J.P.
      • DiFelice G.S.
      Role of age on success of arthroscopic primary repair of proximal anterior cruciate ligament tears.
      6091.3926.2
      Hopper et al. 2021
      • Hopper G.P.
      • Aithie J.M.S.
      • Jenkins J.M.
      • Wilson W.T.
      • Mackay G.M.
      Satisfactory patient-reported outcomes at 5 years following primary repair with suture tape augmentation for proximal anterior cruciate ligament tears.
      3788.57.3
      Overall [n or mean (SD)]34787.7 (4.6)88.5 (2.2)92.4 (3.5)7.8 (0.6)6.1 (0.4)1.2 (0.3)

      4. Discussion

      This systematic review found that nine studies have reported outcomes of ACL repair with internal bracing in a total of 347 patients. The mean failure rate was 10.4% at mean follow-up of 2.7 years postoperatively. This would suggest that the technique is safe for use in acute proximal ACL tears. The results should however be interpreted with caution, as the level of evidence is low with most results coming from uncontrolled case series. In addition, the risk of bias is high with a significant proportion of the patients coming from the institutions of the innovators [
      • Hopper G.P.
      • Aithie J.M.S.
      • Jenkins J.M.
      • Wilson W.T.
      • Mackay G.M.
      Satisfactory patient-reported outcomes at 5 years following primary repair with suture tape augmentation for proximal anterior cruciate ligament tears.
      ,
      • Vermeijden H.D.
      • Yang X.A.
      • van der List J.P.
      • DiFelice G.S.
      Role of age on success of arthroscopic primary repair of proximal anterior cruciate ligament tears.
      ]. It is clear that the technique is worthy of consideration and that further well designed randomised controlled trials are required in order to explore the outcomes more thoroughly. Indeed, proposals for randomised trials have been registered with published protocols [
      • Van Der List J.P.
      • Vermeijden H.D.
      • Sierevelt I.N.
      • Rademakers M.V.
      • Falke M.L.M.
      • Helmerhorst G.T.T.
      • et al.
      Repair versus reconstruction for proximal anterior cruciate ligament tears: a study protocol for a prospective multicenter randomized controlled trial.
      ,
      • Heusdens C.H.W.
      • Zazulia K.
      • Roelant E.
      • Dossche L.
      • Van Tiggelen D.
      • Roeykens J.
      • et al.
      Study protocol: a single-blind, multi-center, randomized controlled trial comparing dynamic intraligamentary stabilization, internal brace ligament augmentation and reconstruction in individuals with an acute anterior cruciate ligament rupture: LIBRƎ stud.
      ].
      Animal and human biomechanical studies have shown that adding an internal brace to a construct is stronger and may be useful in resisting re-injury while the ACL is healing [
      • Massey P.
      • Parker D.
      • McClary K.
      • Robinson J.
      • Barton R.S.
      • Solitro G.F.
      Biomechanical comparison of anterior cruciate ligament repair with internal brace augmentation versus anterior cruciate ligament repair without augmentation.
      ,
      • Heitmann M.
      • Gerau M.
      • Hötzel J.
      • Giannakos A.
      • Frosch K.H.
      • Preiss A.
      Ligament bracing–augmented primary suture repair in multiligamentous knee injuries.
      ,
      • Seitz H.
      • Pichl W.
      • Matzi V.
      • Nau T.
      Biomechanical evaluation of augmented and nonaugmented primary repair of the anterior cruciate ligament: an in vivo animal study.
      ,
      • Bachmaier S.
      • Smith P.A.
      • Bley J.
      • Wijdicks C.A.
      Independent suture tape reinforcement of small and standard diameter grafts for anterior cruciate ligament reconstruction: a biomechanical full construct model.
      ,

      Bachmaier S, Difelice GS, Sonnery-Cottet B, Douoguih WA, Smith PA, Pace LJ, et al. Treatment of acute proximal anterior cruciate ligament tears—Part 2: the role of internal bracing on gap formation and stabilization of repair techniques. Orthop J Sports Med 2020;8(1):232596711989742. doi: 10.1177/2325967119897423.

      ]. Internal bracing has a crucial role in stabilising ACL repair at loads occurring during normal daily activity. The additional strength of the internal brace increases ultimate tensile strength and leads to reduced peak loads on the ACL repair construct, as well as restricting gap formation to below 3 mm at loads up to 350N [

      Bachmaier S, Difelice GS, Sonnery-Cottet B, Douoguih WA, Smith PA, Pace LJ, et al. Treatment of acute proximal anterior cruciate ligament tears—Part 2: the role of internal bracing on gap formation and stabilization of repair techniques. Orthop J Sports Med 2020;8(1):232596711989742. doi: 10.1177/2325967119897423.

      ].
      There have been several review articles on ACL repair published in the past few years [
      • van Eck C.F.
      • Limpisvasti O.
      • ElAttrache N.S.
      Is there a role for internal bracing and repair of the anterior cruciate ligament? A systematic literature review.
      ,
      • Kandhari V.
      • Vieira T.D.
      • Ouanezar H.
      • Praz C.
      • Rosenstiel N.
      • Pioger C.
      • et al.
      Clinical outcomes of arthroscopic primary anterior cruciate ligament repair: a systematic review from the scientific anterior cruciate ligament network international study group.
      ,
      • Ahmad S.S.
      • Schreiner A.J.
      • Hirschmann M.T.
      • Schroter S.
      • Dobele S.
      • Ahrend M.D.
      • et al.
      Dynamic intraligamentary stabilization for ACL repair: a systematic review.
      ,
      • DiFelice G.S.
      Anterior cruciate ligament injury: is ACL repair better than ACL reconstruction?.
      ,
      • Heusdens C.H.W.
      ACL repair: a game changer or will history repeat itself? A critical appraisal.
      ,

      Hoogeslag RAG, Brouwer RW, de Vries AJ, Boer BC, Huis In 't Veld R. Efficacy of nonaugmented, static augmented, and dynamic augmented suture repair of the ruptured anterior cruciate ligament: a systematic review of the literature. Am J Sports Med 2020;48(14):3626–37. doi: 10.1177/0363546520904690.

      ,
      • Hughes J.D.
      • Lawton C.D.
      • Nawabi D.H.
      • Pearle A.D.
      • Musahl V.
      Anterior cruciate ligament repair: the current status.
      ,

      Mahapatra P, Horriat S, Anand BS. Anterior cruciate ligament repair - past, present and future. J Exp Orthop 5;2018:20.

      ,
      • Malahias M.A.
      • Chytas D.
      • Nakamura K.
      • Raoulis V.
      • Yokota M.
      • Nikolaou V.S.
      A narrative review of four different new techniques in primary anterior cruciate ligament repair: “Back to the Future” or another trend?.
      ,
      • Nwachukwu B.U.
      • Patel B.H.
      • Lu Y.
      • Allen A.A.
      • Williams R.J.
      Anterior cruciate ligament repair outcomes: an updated systematic review of recent literature.
      ,
      • Papalia R.
      • Torre G.
      • Papalia G.
      • Campi S.
      • Maffulli N.
      • Denaro V.
      Arthroscopic primary repair of the anterior cruciate ligament in adults: a systematic review.
      ,
      • van der List J.P.
      • Vermeijden H.D.
      • Sierevelt I.N.
      • DiFelice G.S.
      • van Noort A.
      • Kerkhoffs G.M.M.J.
      Arthroscopic primary repair of proximal anterior cruciate ligament tears seems safe but higher level of evidence is needed: a systematic review and meta-analysis of recent literature.
      ]. These have mainly consisted of patients treated with DIS, BEAR or primary repair without augmentation. The overall consensus in these reviews is in keeping with what we have found; that prospective studies comparing ACL repair with ACL reconstruction, with longer follow-up are needed. The majority of reviews highlight the promising results and suggest that from the current evidence ACL repair is a safe treatment option for acute ACL ruptures. None of the previous reviews have specifically focused on the treatment of proximal tears with repair and internal bracing. Nonetheless, the failure rate of 10.4% demonstrated in this study compares well with those previously published for ACL repair at mid term follow up, approximately 7-11% [
      • van der List J.P.
      • Vermeijden H.D.
      • Sierevelt I.N.
      • DiFelice G.S.
      • van Noort A.
      • Kerkhoffs G.M.M.J.
      Arthroscopic primary repair of proximal anterior cruciate ligament tears seems safe but higher level of evidence is needed: a systematic review and meta-analysis of recent literature.
      ]. Compared to ACL reconstruction these rates are slightly higher than those quoted from registries, however two recent meta-analyses showed an ipsilateral reinjury rate of 7% at 2 years, and up to 23% in patients who are younger than 25 years and returning to sport [
      • Wiggins A.J.
      • Grandhi R.K.
      • Schneider D.K.
      • Stanfield D.
      • Webster K.E.
      • Myer G.D.
      Risk of secondary injury in younger athletes after anterior cruciate ligament reconstruction.
      ,
      • Xie X.
      • Liu X.
      • Chen Z.
      • Yu Y.
      • Peng S.
      • Li Q.
      A meta-analysis of bone–patellar tendon–bone autograft versus four-strand hamstring tendon autograft for anterior cruciate ligament reconstruction.
      ].
      Fig. 2 shows the failure rates and confidence intervals for each study and all but one of the studies show similar results. Gagliardi et al. [
      • Gagliardi A.G.
      • Carry P.M.
      • Parikh H.B.
      • Traver J.L.
      • Howell D.R.
      • Albright J.C.
      ACL repair with suture ligament augmentation is associated with a high failure rate among adolescent patients.
      ] demonstrated a high failure rate in 22 patients, aged 7-18 years compared to 157 ACL reconstructions. This rate is concerningly high, and out of keeping with the other studies in this analysis. Examining the detail of that study, there were only 22 patients in the repair group, a much smaller sample size than the reconstruction comparator group and also one of the smallest cohorts in this review. Also, both the mean age and the percentage of skeletally mature patients were higher in the reconstruction group (15.7 years and 58%, respectively) compared to the repair group (13.9 years and 32%, respectively). It is well documented that younger patients are significantly more likely to sustain a further ACL injury, making this group higher risk [
      • Webster K.E.
      • Feller J.A.
      Exploring the high reinjury rate in younger patients undergoing anterior cruciate ligament reconstruction.
      ]. The 60% of this high risk population who underwent successful ACL repair, had no significant differences in return to sport rates, subjective PROMs or objective assessment compared to those who had reconstruction [
      • Gagliardi A.G.
      • Carry P.M.
      • Parikh H.B.
      • Traver J.L.
      • Howell D.R.
      • Albright J.C.
      ACL repair with suture ligament augmentation is associated with a high failure rate among adolescent patients.
      ]. In contrast to Gagliardi et al [
      • Gagliardi A.G.
      • Carry P.M.
      • Parikh H.B.
      • Traver J.L.
      • Howell D.R.
      • Albright J.C.
      ACL repair with suture ligament augmentation is associated with a high failure rate among adolescent patients.
      ], Dabis et al. [
      • Dabis J.
      • Yasen S.K.
      • Foster A.J.
      • Pace J.L.
      • Wilson A.J.
      Paediatric proximal ACL tears managed with direct ACL repair is safe, effective and has excellent short-term outcomes.
      ] reported no failures in their cohort of 20 young patients, mean age 12.9, treated with primary repair with internal bracing at two years follow-up. Paediatric patients had previously been reported to have good outcomes from ACL repair in a small case series [
      • Smith J.O.
      • Yasen S.K.
      • Palmer H.C.
      • Lord B.R.
      • Britton E.M.
      • Wilson A.J.
      Paediatric ACL repair reinforced with temporary internal bracing.
      ]. All patients demonstrated complete ACL healing at three months postoperatively, returned to activities at four months, and showed good objective outcomes at two years. Second look arthroscopy was carried out to remove the temporary internal brace to prevent growth arrest and confirmed healing in all cases [
      • Dabis J.
      • Yasen S.K.
      • Foster A.J.
      • Pace J.L.
      • Wilson A.J.
      Paediatric proximal ACL tears managed with direct ACL repair is safe, effective and has excellent short-term outcomes.
      ,
      • Smith J.O.
      • Yasen S.K.
      • Palmer H.C.
      • Lord B.R.
      • Britton E.M.
      • Wilson A.J.
      Paediatric ACL repair reinforced with temporary internal bracing.
      ]. Subsequent MRI confirmed a taut, healed and well-vascularised ACL in all patients [
      • Smith J.O.
      • Yasen S.K.
      • Palmer H.C.
      • Lord B.R.
      • Britton E.M.
      • Wilson A.J.
      Paediatric ACL repair reinforced with temporary internal bracing.
      ].
      Figure thumbnail gr2
      Fig. 2Graph showing the failure rate of ACL repair with internal bracing for each study, rate in percent and 95% confidence intervals
      The length of follow-up of the studies in this review was on average 2.7 years, with some only reporting one year follow-up. Only one study [
      • Hopper G.P.
      • Aithie J.M.S.
      • Jenkins J.M.
      • Wilson W.T.
      • Mackay G.M.
      Satisfactory patient-reported outcomes at 5 years following primary repair with suture tape augmentation for proximal anterior cruciate ligament tears.
      ] reported outcomes at minimum five years postoperatively and the failure rate was 16%. It is worth noting that historic attempts at ACL repair using the open technique had demonstrated satisfactory outcomes at two years, but subsequently showed poor longer term outcomes, with around half of patients requiring revision surgery by five years [
      • Kaplan N.
      • Wickiewicz T.L.
      • Warren R.F.
      Primary surgical treatment of anterior cruciate ligament ruptures. A long-term follow-up study.
      ,
      • Meunier A.
      • Odensten M.
      • Good L.
      Long-term results after primary repair or non-surgical treatment of anterior cruciate ligament rupture: a randomized study with a 15-year follow-up.
      ,
      • Sherman M.F.
      • Lieber L.
      • Bonamo J.R.
      • Podesta L.
      • Reiter I.
      The long-term followup of primary anterior cruciate ligament repair. Defining a rationale for augmentation.
      ,
      • Strand T.
      • Mølster A.
      • Hordvik M.
      • Krukhaug Y.
      Long-term follow-up after primary repair of the anterior cruciate ligament: clinical and radiological evaluation 15–23 years postoperatively.
      ,
      • Feagin J.A.
      • Curl W.W.
      Isolated tear of the anterior cruciate ligament: 5-year follow-up study.
      ]. It is encouraging that this trend has not been demonstrated in the five year outcomes that are available for this technique, but further longer term reports are awaited.
      Whilst the choice of subjective PROMs scores used across the studies was variable, the results were similar for all outcome measures, with mean scores in excess of 87% of maximum. These figures are greater than those quoted as being the required threshold for a ‘patient acceptable symptom state’ following ACL reconstruction [
      • Muller B.
      • Yabroudi M.A.
      • Lynch A.
      • Lai C.L.
      • van Dijk C.N.
      • Fu F.H.
      • et al.
      Defining thresholds for the patient acceptable symptom state for the IKDC subjective knee form and KOOS for patients who underwent ACL reconstruction.
      ].
      There was a small decrease in mean Tegner activity score from pre-injury levels. An overall decrease in the activity scores postoperatively has also been reported for patients undergoing ACL reconstruction [
      • Nwachukwu B.U.
      • Voleti P.B.
      • Chang B.
      • Berkanish P.
      • Mahony G.T.
      • Williams 3rd, R.J.
      • et al.
      Comparative influence of sport type on outcome after anterior cruciate ligament reconstruction at minimum 2-year follow-up.
      ,
      • Spindler K.P.
      • Huston L.J.
      • Wright R.W.
      • Kaeding C.C.
      • Marx R.G.
      • Amendola A.
      • et al.
      The prognosis and predictors of sports function and activity at minimum 6 years after anterior cruciate ligament reconstruction: a population cohort study.
      ].
      Return to sport following ACL repair with internal bracing was examined in one study [
      • Ortmaier R.
      • Fink C.
      • Schobersberger W.
      • Kindermann H.
      • Leister I.
      • Runer A.
      • et al.
      Return to sports after anterior cruciate ligament injury: a matched-pair analysis of repair with internal brace and reconstruction using hamstring or quadriceps tendons.
      ] where the authors matched 24 patients treated with ACL internal brace repair with
      25 hamstring and 20 quadriceps tendon ACL reconstruction patients. At a minimum of one year follow-up, the overall return to sports rate was 91% with no significant differences in return to sports rate or time between the groups. These figures are a potential improvement on the reported rates from ACL reconstruction [
      • Ardern C.L.
      • Webster K.E.
      • Taylor N.F.
      • Feller J.A.
      Return to sport following anterior cruciate ligament reconstruction surgery: a systematic review and meta-analysis of the state of play.
      ,
      • Ardern C.L.
      • Webster K.E.
      • Taylor N.F.
      • Feller J.A.
      Return to the preinjury level of competitive sport after anterior cruciate ligament reconstruction surgery.
      ,
      • Ardern C.L.
      • Taylor N.F.
      • Feller J.A.
      • Whitehead T.S.
      • Webster K.E.
      Sports participation 2 years after anterior cruciate ligament reconstruction in athletes who had not returned to sport at 1 year.
      ].
      In the four studies that did report objective quantified measures of knee laxity [
      • Gagliardi A.G.
      • Carry P.M.
      • Parikh H.B.
      • Traver J.L.
      • Howell D.R.
      • Albright J.C.
      ACL repair with suture ligament augmentation is associated with a high failure rate among adolescent patients.
      ,
      • Dabis J.
      • Yasen S.K.
      • Foster A.J.
      • Pace J.L.
      • Wilson A.J.
      Paediatric proximal ACL tears managed with direct ACL repair is safe, effective and has excellent short-term outcomes.
      ,
      • Schneider K.N.
      • Schliemann B.
      • Gosheger G.
      • Theil C.
      • Weller J.
      • Buddhdev P.K.
      • et al.
      Good to excellent functional short-term outcome and low revision rates following primary anterior cruciate ligament repair using suture augmentation.
      ,
      • Heusdens C.H.W.
      • Blockhuys K.
      • Roelant E.
      • Dossche L.
      • Van Glabbeek F.
      • Van Dyck P.
      Suture tape augmentation ACL repair, stable knee, and favorable PROMs, but a re-rupture rate of 11% within 2 years.
      ], this technique was successful in preventing excessive anterior tibial translation, with a mean side to side difference overall of 1.2mm. Whilst this static stability is encouraging, further detailed functional testing to assess dynamic knee stability and the effect on knee kinematics and kinetics during functional tasks is required.
      The results of this systematic review suggest that ACL repair with internal bracing is a safe treatment option as an alternative to ACL reconstruction in acute proximal tears, with acceptable failure rates and satisfactory outcomes. This would have the potential benefits of retained native anatomy with proprioceptive fibres and negating the risk of donor site morbidity during graft harvest. Furthermore, primary ACL reconstruction would be an option in the approximately 1 in 10 patients who do suffer failure of repair, and is a straightforward surgery in comparison to revision surgery for failed ACL reconstruction [
      • Fradin T.
      • Haidar I.M.
      • Rayes J.
      • Ngbilo C.
      • Vieira T.D.
      • Sonnery-Cottet B.
      Arthroscopic ACL reconstruction after failed ACL repair.
      ].
      We recognise however that ACL repair technique is not suitable for all patients and careful patient selection is fundamental to the process. The studies included in this review report the results of patients with proximal tears, with midsubstance or distal tears probably best treated with other techniques. However, recent studies suggest that around half of patients have tears that are amenable to primary repair [

      van der List JP, Mintz DN, DiFelice GS. The location of anterior cruciate ligament tears: a prevalence study using magnetic resonance imaging. Orthop J Sports Med 2017;5(6):2325967117709966-. doi: 10.1177/2325967117709966.

      ]. In addition, the mean time interval from injury to surgery reported in the meta-analysis was just 21 days, and we recognise that such a fast turnaround time may not always be possible in some healthcare structures, without significant organisational change. The longest time interval reported is six weeks post-injury, which might still be challenging to achieve in some scenarios. There are however no reports of attempted repair after a longer delay, although it is generally accepted that tissue quality and therefore repairability deteriorates with time.
      Other factors which influence failure rate following ACL reconstruction are activity level and degree of laxity, in that high demand patients with gross pivot instability are higher risk. These patients have been found to benefit from an additional procedure to reconstruct or augment the anterolateral ligament (ALL) with a significant reduction in re-rupture rates [
      • Getgood A.M.J.
      • Bryant D.M.
      • Litchfield R.
      • Heard M.
      • McCormack R.G.
      • Rezansoff A.
      • et al.
      Lateral extra-articular tenodesis reduces failure of hamstring tendon autograft anterior cruciate ligament reconstruction: 2-year outcomes from the STABILITY study randomized clinical trial.
      ,

      Haidar I, Fradin T, Rayes J, Vieira T, Cédric N, Sonnery-Cottet B, et al. Isolated ACL reconstruction versus combined ACL and anterolateral ligament reconstruction: a matched case series with mean follow up of 9 years. Orthop J Sports Med 2021;9(7_suppl4):2325967121S0023. doi: 10.1177/2325967121s00237.

      ]. This concept has also been utilised successfully with ACL repair and internal bracing and has the potential to significantly lower re-rupture rates in high risk patients [

      Hopper GP, Aithie JMS, Jenkins JM, Wilson WT, Mackay GM. Combined anterior cruciate ligament repair and anterolateral ligament internal brace augmentation: minimum 2-year patient-reported outcome measures. Orthop J Sports Med 2020;8(12):232596712096855. doi: 10.1177/2325967120968557.

      ].

      5. Conclusion

      This systematic review with meta-analysis shows that ACL repair with internal bracing is a safe technique for treatment of proximal ruptures, with a failure rate of 10.4%. Subjective scores and clinical laxity testing also revealed satisfactory results. This suggests that ACL repair with internal bracing should be considered as an alternative to ACL reconstruction in suitable cases, with the potential benefits of retained proprioception, as well as negating the need for graft harvest.

      Declaration of Competing Interest

      The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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