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Double-Tunnel Technique Was Similar to Single-Tunnel Technique in Clinical, Imaging and Functional Outcomes for Medial Patellofemoral Ligament Reconstruction: A Randomized Clinical Trial

  • Author Footnotes
    ∗ Y.Q., J.X., and Z.Y. contributed equally to this article.
    Yi Qiao
    Footnotes
    ∗ Y.Q., J.X., and Z.Y. contributed equally to this article.
    Affiliations
    Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China
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  • Author Footnotes
    ∗ Y.Q., J.X., and Z.Y. contributed equally to this article.
    Junjie Xu
    Footnotes
    ∗ Y.Q., J.X., and Z.Y. contributed equally to this article.
    Affiliations
    Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China
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  • Author Footnotes
    ∗ Y.Q., J.X., and Z.Y. contributed equally to this article.
    Zipeng Ye
    Footnotes
    ∗ Y.Q., J.X., and Z.Y. contributed equally to this article.
    Affiliations
    Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China
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  • Jiebo Chen
    Affiliations
    Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China
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  • Xiuyuan Zhang
    Affiliations
    Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China
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  • Song Zhao
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    Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China
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  • Caiqi Xu
    Correspondence
    and Caiqi Xu, M.D., Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, 600 Yishan Road, Shanghai, 200233, China.
    Affiliations
    Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China
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  • Jinzhong Zhao
    Correspondence
    Address correspondence to Jinzhong Zhao, M.D., Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, 600 Yishan Road, Shanghai, 200233, China.
    Affiliations
    Department of Sports Medicine, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China
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  • Author Footnotes
    ∗ Y.Q., J.X., and Z.Y. contributed equally to this article.

      Purpose

      This study aimed to compare the clinical, functional, and imaging outcomes of single-tunnel (ST) and double-tunnel (DT) techniques for medial patellofemoral ligament (MPFL) reconstruction.

      Methods

      Ninety-four patients with recurrent patellar instability were randomly divided into 2 groups, receiving either ST or DT MPFL reconstruction. Lateral reticulum release (LRR) and tibial tuberosity (TT) transfer were performed as combined procedures when necessary. Preoperative and postoperative clinical characteristics (symptoms and episodes of redislocation), functional outcomes (Kujala, Lysholm, Tegner, IKDC, and KOOS score), and radiological measurements (congruence angle, patellar tilt angle, lateral patellar angle, and lateral patellar translation) were analyzed.

      Results

      The analysis included data from 90 patients with 48 patients in the ST group and 42 patients in the DT group. Patients were followed up for a mean period of 37.8 (range: 27-50) months in the ST group and 38.6 (range: 25-53) months in the DT group. Forty-three patients in the ST group and 40 patients in the DT group received combined TT transfer, and all patients underwent LRR. At the latest follow-up, 1 patient in ST group experienced redislocation, while no patient in the DT group sustained clinical failure (P = .347). Imaging measurements decreased significantly to the normal range postoperatively. No significant difference was noted between the postoperative radiological results of the 2 groups. All clinical scores significantly improved postoperatively, and no significant difference was observed between the 2 groups except for the higher Lysholm score (P = .031), KOOS symptoms score (P = .021) and KOOS knee-related quality of life score (P = .043) in the DT group.

      Conclusion

      Both techniques could equally mitigate the patellar lateral translation or redislocation. Our results demonstrate several significant differences in functional outcomes that favored DT MPFL reconstruction but no difference in clinical failure rates and radiological results between ST and DT MPFL reconstruction.

      Level of Evidence

      Level I, randomized clinical trial.

      Introduction

      Recurrent patellar dislocation is a relatively common knee disorder associated with various pathological factors, such as patella alta, genu valgum and trochlear dysplasia.
      • Frings J.
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      Conservative versus surgical treatment for primary patellar dislocation.
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      Factors associated with an increased risk of recurrence after a first-time patellar dislocation: A systematic review and meta-analysis.
      • Nha K.W.
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      Surgical treatment with closing wedge distal femoral osteotomy for recurrent patellar dislocation with genu valgum.
      • Purushothaman B.
      • Agarwal A.
      • Dawson M.
      Posttraumatic chronic patellar dislocation treated by distal femoral osteotomy and medial patellofemoral ligament reconstruction.
      Among all the predisposing etiologies, medial patellofemoral ligament (MPFL) injury or laxity plays a crucial role since MPFL is the major passive restraint preventing lateral patella translation. With the absence or loosening of MPFL, patellar tracking is remarkably affected by the lateral force. Therefore, MPFL reconstruction (MPFLR) has been proven as an effective procedure
      • Lee J.I.
      • Jaffar M.S.A.
      • Choi H.G.
      • Kim T.W.
      • Lee Y.S.
      Effect of isolated medial patellofemoral ligament reconstruction in patellofemoral instability regardless of predisposing factors.
      that offers excellent subjective and functional outcomes with a low incidence of patellar redislocation.
      • Schneider D.K.
      • Grawe B.
      • Magnussen R.A.
      • et al.
      Outcomes after isolated medial patellofemoral ligament reconstruction for the treatment of recurrent lateral patellar dislocations: A systematic review and meta-analysis.
      As a sail-like structure routing from patella to femur, the patellar insertion point of MPFL is more flexible than the femoral insertion point, and functioned as a fan-shaped attachment over an extremely wide range.
      • Placella G.
      • Tei M.M.
      • Sebastiani E.
      • et al.
      Shape and size of the medial patellofemoral ligament for the best surgical reconstruction: A human cadaveric study.
      Although numerous techniques for MPFL reconstruction have been described in the literature, there is still insufficient evidence to support the superiority of one technique over another.
      • Wilkens O.E.
      • Hannink G.
      • van de Groes S.A.W.
      Recurrent patellofemoral instability rates after MPFL reconstruction techniques are in the range of instability rates after other soft tissue realignment techniques.
      • Panagopoulos A.
      • van Niekerk L.
      • Triantafillopoulos I.K.
      MPFL reconstruction for recurrent patella dislocation: A new surgical technique and review of the literature.
      • Ferrua P.
      • Kruckeberg B.M.
      • Pasqualotto S.
      • Berruto M.
      • Randelli P.
      • Arendt E.A.
      Proximal medial patellar restraints and their surgical reconstruction.
      With the increased understanding of the biomechanics and anatomy of the MPFL, tunnel reconstruction is favored due to its better outcomes than other techniques.
      • Desai V.S.
      • Tagliero A.J.
      • Parkes C.W.
      • et al.
      Systematic review of medial patellofemoral ligament reconstruction techniques: Comparison of patellar bone socket and cortical surface fixation techniques.
      However, the existing literature comparing the single-tunnel (ST) and double-tunnel (DT) techniques for MPFL reconstruction is relatively sparse.
      • Migliorini F.
      • Trivellas A.
      • Colarossi G.
      • Eschweiler J.
      • Tingart M.
      • Rath B.
      Single- versus double-bundle patellar graft insertion for isolated MPFL reconstruction in patients with patellofemoral instability: A systematic review of the literature.
      This study aimed to compare the clinical, functional, and imaging outcomes of ST and DT techniques for MPFL reconstruction. It was hypothesized that MPFLR with DT would result in superior clinical and functional outcomes, but equivalent radiological examination.

      Methods

      Study Design

      This was a randomized controlled clinical trial. Institutional review board approval was obtained from the Ethics Committee of Shanghai Sixth People’s Hospital (approval number 2017-008-[1]) and was registered in the Chinese Clinical Trial Registry (ChiCTR-IOR17010738) in February 2017. Patients were approached if they had 1) closed epiphysis, 2) more than 2 episodes of dislocation or 1 episode of dislocation plus multiple episodes of instability (lateral excursion of the patella), 3) unilateral symptoms, and 4) active level before injury. The exclusion criteria were as follows: 1) concomitant ligament injuries (except MPFL), 2) previous knee surgeries, 3) patella alta (Insall-Salvati index >1.2), 4) femoral trochlear dysplasia requiring trochleoplasty (type D by Dejour’s classification with a supratrochlear spur more than 5 mm
      • Dejour D.H.
      • Deroche É.
      Trochleoplasty: Indications in patellar dislocation with high-grade dysplasia. Surgical technique.
      ), 5) associated with cardiovascular or other systemic diseases, 6) drug or alcohol abuse, 7) pregnant or breastfeeding female, and 8) lower limb malalignment (>5° varus or valgus deformities). From March 2017 to November 2019, after screening the eligibility of 142 subjects, 94 patients were enrolled and randomly assigned to undergo double-tunnel or single-tunnel MPFL reconstruction via randomized number processed by Excel (Microsoft). The patients were followed up at 1.5, 3, 6, 12, and 24 months after operation. After 2 years, there was no fixed time point for further consultation. The minimum follow-up for inclusion was 2 years. Ninety patients completed the final follow-up, while 4 patients lost to follow-up due to broken contact. All patients provided written informed consent, and baseline demographic data were collected. The flowchart of patient selection is demonstrated in Fig 1.
      Figure thumbnail gr1
      Fig 1CONSORT (Consolidated Standards of Reporting Trials) flow diagram. DT, double-tunnel; LRR, lateral reticulum release; MPFLR, medial patellofemoral ligament reconstruction; ST, single-tunnel; TT, tibial tuberosity.

      Surgical Techniques

      A single experienced surgeon (J.Z.) in our institution conducted the surgical procedures from March 2017 to November 2019. All procedures were performed under general anesthesia in the supine position.

      Single-Tunnel MPFL Reconstruction

      The anterior half of the peroneus longus tendon (AHPLT) was harvested and braided with nonabsorbable sutures.
      • Tang J.
      • Zhao J.
      Wide patellar insertion medial patellofemoral ligament reconstruction with internal bracing.
      The level of the junction of the middle and proximal one third of the patella, which usually corresponds to the widest part of the patella, was identified. The point on the medial edge of the patella at this level was defined as middle-proximal junction (MPJ). A 1-cm longitudinal, medial incision was made over the MPJ. A single tunnel was drilled from the medial edge of the patella to the midline of the anterior surface of the patella, at the level of the MPJ.
      To determine the femoral tunnel, a 2-3-cm longitudinal medial incision was made to define the medial femoral epicondyle, the adductor tubercle and the gastrocnemius tubercle.
      • Chen J.
      • Han K.
      • Jiang J.
      • et al.
      Radiographic reference points do not ensure anatomic femoral fixation sites in medial patellofemoral ligament reconstruction: A quantified anatomic localization method based on the saddle sulcus.
      ,
      • Zhang X.
      • Xie G.
      • Zhang C.
      • Fang Z.
      • Zhao J.
      • Huangfu X.
      Comparation and evaluation of the accuracy of the sulcus localization method to establish the medial patellofemoral ligament femoral tunnel: a cadaveric and clinical study.
      The femoral tunnel was created at the midpoint among these three tubercles medially in a slight proximal and anterior deviation across the lateral cortex of the femur. The graft tendon was passed through the patellar tunnel and pulled back over the anterior surface of the patella. The arthroscope was placed in through the anteromedial portal, and the radiofrequency probe is placed in through the anterolateral portal with the knee in full extension. Lateral retinaculum release (LRR) was performed with tissue scissors by pulling the patella medially with the graft in the space between the vastus lateralis and the iliotibial band from the level of the anterolateral portal to the tendon-muscle junction of the vastus lateralis.
      • Tang J.
      • Zhao J.
      Wide patellar insertion medial patellofemoral ligament reconstruction with internal bracing.
      ,
      • Xu C.
      • Zhao J.
      • Xie G.
      Medial patella-femoral ligament reconstruction using the anterior half of the peroneus longus tendon as a combined procedure for recurrent patellar instability.
      A cortical suspensory fixation device with an adjustable loop (Arthrex, Naples, FL) was used to introduce the graft into the femoral tunnel. Both graft ends were tied to the adjustable loop, and the cortical fixation device was pulled through the femoral tunnel till the graft ends were pulled into the tunnel with the knee in 90° of flexion. The adjustable loop was tightened until the flipping button was pulled back against the lateral orifice of the femoral tunnel (Fig 2A ). An interference screw was used on the medial femoral side. Graft tension and patellar tracking with flexion-extension movements were checked during the procedure.
      Figure thumbnail gr2
      Fig 2Diagrams of surgical procedures from the frontal view (right knee). (A) Single-tunnel MPFL reconstruction: the tunnel was drilled from the medial edge of the patella to the midline of the anterior surface of the patella, at level of the MPJ. (B) Double-tunnel MPFL reconstruction: two tunnels were drilled from the medial edge of the patella to the midline of the anterior surface of the patella, at levels respectively 5 mm proximal and distal to the MPJ. A cortical suspensory fixation device was used in both techniques to fix at the femoral side. (C) Tibial tuberosity osteotomy. MPJ, middle-proximal junction; MPFLR, medial patellofemoral ligament reconstruction.

      Double-Tunnel MPFL Reconstruction

      As in the reconstruction with a ST, the same single incision and approach were used
      • Tang J.
      • Zhao J.
      Wide patellar insertion medial patellofemoral ligament reconstruction with internal bracing.
      (Fig 2B). Two tunnels were created from the medial edge of the patella to the midline of the anterior surface of the patella, at levels 5 mm proximal and distal, respectively, to the MPJ. The graft was passed through the double tunnel in a looped fashion. LRR was performed. The fixation on the femoral side was the same way as in ST reconstruction. Graft tension and patellar tracking with flexion-extension movements were checked in the same fashion of single-tunnel MPFLR.

      Combined Procedure

      Eighty-three patients received tibial tubercle medialization, as tibial tubercle-trochlear groove (TT-TG) was greater than 15 mm. The procedure of TT transfer
      • Zhao J.
      • Huangfu X.
      • He Y.
      The role of medial retinaculum plication versus medial patellofemoral ligament reconstruction in combined procedures for recurrent patellar instability in adults.
      is a modification of Fulkerson’s osteotomy (Fig 2C). Briefly, a 4-cm longitudinal incision was made along the lateral edge of the tibial tuberosity. Through this movable skin window, tibial tubercle osteotomy was performed along a plane from the medial edge of the tibial tubercle and the posterolateral ridge of the proximal tibia, creating a 6-8-cm bone fragment with a tapering distal end. The proximal part of the bone fragment was transferred anteromedially, with the distal tapering end left in place or, in some cases, rotated laterally along the osteotomy surface. The magnitude of the medialization of the proximal end of the tibial tubercle was measured and adjusted as needed. The purpose was to mitigate the TT-TG distance to 5-10 mm. The transferred tibial tubercle was fixed with K-wires in the desired position.

      Rehabilitation Protocol

      Patients were allowed to bear weight and walk with a brace locked in extension immediately after operation. Calf raise training were started on the first day after surgery. Range-of-motion exercises began immediately, but the knee flexion angle was restricted to 45°, 90°, and 120° in the 1st, 2nd, and 3rd 2-week periods following the operation, respectively. The brace was removed at 6 weeks after surgery. Proprioception training began 6 weeks following the operation; running and agility training started 3 months after operation. All sports were gradually resumed after 6 months.

      Outcome Measurements

      Primary Outcome

      Clinical failure of MPFLR,
      • Zhao J.
      • Huangfu X.
      • He Y.
      The role of medial retinaculum plication versus medial patellofemoral ligament reconstruction in combined procedures for recurrent patellar instability in adults.
      as primary outcome, was determined by patellar redislocation or multiple episodes of patellar instability. The physical examination of patients was conducted by two sports medicine fellowship-trained orthopedic surgeons independent of the surgical team in a blind fashion.

      Secondary Outcomes

      Secondary outcomes consisted of patient-reported outcome measures (PROM), including the Kujala score,
      • Kujala U.M.
      • Jaakkola L.H.
      • Koskinen S.K.
      • Taimela S.
      • Hurme M.
      • Nelimarkka O.
      Scoring of patellofemoral disorders.
      Knee Injury and Osteoarthritis Outcome (KOOS) score,
      • 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.
      Tegner Score,
      • Tegner Y.
      • Lysholm J.
      Rating systems in the evaluation of knee ligament injuries.
      International Knee Documentation Committee (IKDC) subjective score,
      • Irrgang J.J.
      • Anderson A.F.
      • Boland A.L.
      • et al.
      Development and validation of the international knee documentation committee subjective knee form.
      ,
      • Rossi M.J.
      • Lubowitz J.H.
      • Guttmann D.
      Development and validation of the International Knee Documentation Committee Subjective Knee Form.
      and Lysholm score.
      • Lysholm J.
      • Gillquist J.
      Evaluation of knee ligament surgery results with special emphasis on use of a scoring scale.
      As a statistically significant outcome may not be clinically relevant,
      • Harris J.D.
      • Brand J.C.
      • Cote M.P.
      • Faucett S.C.
      • Dhawan A.
      Research pearls: The significance of statistics and perils of pooling. Part 1: Clinical versus statistical significance.
      frequencies of patients with overall change scores exceeding minimal clinically important difference (MCID) or similar threshold as minimal detectable change (MDC) were calculated to determine clinical relevance and improvement. MCID in Kujala score of 12 points,
      • Agarwalla A.
      • Liu J.N.
      • Wu H.H.
      • Kalbian I.L.
      • Garcia G.H.
      • Shubin Stein B.E.
      Return to work following tibial tubercle osteotomy for patellofemoral osteoarthritis and pain.
      KOOS of 10 points,
      • Roos E.M.
      • Lohmander L.S.
      The Knee injury and Osteoarthritis Outcome Score (KOOS): From joint injury to osteoarthritis.
      IKDC of 11.5 points,
      • Grevnerts H.T.
      • Terwee C.B.
      • Kvist J.
      The measurement properties of the IKDC-subjective knee form.
      and MDC in Lysholm score of 8.9 points,
      • Harris J.D.
      • Brand J.C.
      • Cote M.P.
      • Faucett S.C.
      • Dhawan A.
      Research pearls: The significance of statistics and perils of pooling. Part 1: Clinical versus statistical significance.
      Tegner of 1 point,
      • Harris J.D.
      • Brand J.C.
      • Cote M.P.
      • Faucett S.C.
      • Dhawan A.
      Research pearls: The significance of statistics and perils of pooling. Part 1: Clinical versus statistical significance.
      were used. In addition, computed tomography scans (CT) were taken for radiological outcome measurements. Lateral patellar angle (LPA), congruence angle (CA), patellar tilt angle (PTA), lateral patellar translation (LPT) and TT-TG distance were assessed on CT, according to the previous methods.
      • Zhao J.
      • Huangfu X.
      • He Y.
      The role of medial retinaculum plication versus medial patellofemoral ligament reconstruction in combined procedures for recurrent patellar instability in adults.
      ,
      • Zhao J.
      • Huangfu X.
      • He Y.
      • Liu W.
      Recurrent patellar dislocation in adolescents: medial retinaculum plication versus vastus medialis plasty.
      All imaging parameters were measured by two sports medicine fellowship-trained orthopedic surgeons independent of the surgical team in a blind fashion. Intra-class correlation coefficients (ICC) were calculated for inter-rater reliabilities of the measurements.

      Adverse Events and Complications

      All possible adverse events and complications related to the surgical procedures were recorded, such as poor wound healing, nonunion of the osteotomy area, knee joint dysfunction (anterior knee pain and stiffness), and patellar fracture.

      Sample Size Calculation and Power Analysis

      The estimated sample size was calculated with a priori power test on G power software (version 3.1). A clinical failure rate of 4.54% and 26.9% in previous research,
      • Wang C.H.
      • Ma L.F.
      • Zhou J.W.
      • et al.
      Double-bundle anatomical versus single-bundle isometric medial patellofemoral ligament reconstruction for patellar dislocation.
      and an α of 0.05 and power of 0.80 was employed, resulting in a minimum 32 patients in each group. Assuming a dropout rate of 10%, the minimal sample size was set to 36 in each group.

      Statistical Analysis

      Analyses of the data obtained in the study were performed with SPSS (26.0; IBM). After testing the distribution of data for normality, the independent-sample t-test was employed to compare variables with a normal distribution, otherwise the Mann-Whitney U-test was used. The chi-square test was used to compare nominal variables. Statistical significance was set to P < .05.

      Results

      General Demographics

      Total 94 patients (49 patients in ST group and 45 patients in DT group) were included in this study, and 90 patients completed the final follow-up, while 4 patients were lost to follow-up due to broken contact (Fig 1). The overall mean follow-up duration was 37.8 (range: 27-50) and 38.6 (range: 25-53) months for the ST and DT groups, respectively. Forty-three patients in ST group and 40 patients in DT group received combined TT transfer, and all patients received LRR. The baseline demographic characteristics of the patients are provided in Table 1.
      Table 1Baseline Demographic of the 2 Groups
      CharacteristicST Group (n = 48)DT Group (n = 42)P Value
      Male/Female16 / 3215 / 27.813
      Age (years)23.8 (15-39)21.4 (14-41).063
      Body mass index (kg/m2)22.4(17.7-38.8)23.3(15.5-34.6).402
      Left/Right side26 / 2220 / 22.535
      Patella height0.9 ± 0.20.9 ± 0.2.665
      Articular cartilage status (Lesion/Normal)15 / 3314 / 28.833
      Number of dislocations4.3 (1-17)4.7 (1-15).484
      Duration of symptoms (month)24.7 (1-108)20.3 (1-48).581
      Follow-up period (month)37.8 (27-50)38.6 (25-53).194
      Data are presented as n or means ± standard deviation, mean (range). The independent-sample t-test was employed to compare continuous variables and the chi-square test was used to compare nominal variables.

      Primary Outcome

      Clinical Failure

      The rate of clinical failure was 2.1% (1 of 48) in the ST group, while no patient in the DT group experienced clinical failure. There was no significant difference between the two groups (P = .347). The patient with patellar redislocation in the ST group was successfully managed with a revision surgery for MPFLR.

      Secondary Outcomes

      Functional Outcomes

      Results of the clinical scores (Kujala, Lysholm, Tegner, IKDC, and five KOOS subscales) for ST and DT groups are displayed in Table 2. No significant difference was detected between the two groups preoperatively. At the final follow-up, significant improvements were observed in both groups (all P < .05). When comparing clinical outcomes between two technique groups postoperatively, the DT group had a higher Lysholm score (83.7 ± 13.5 vs 89.5 ± 11.4; P = .031), KOOS symptoms score (74.7 ± 12.1 vs 81.2 ± 14.1; P = .021) and KOOS knee-related quality of life score (61.8 ± 22.2 vs 71.1 ± 20.3; P = .043). No significant difference was noted for other scores between the groups. As for clinically significant differences, MCIDs or MDCs for all PROMs were exceeded by mean overall improvement scores except IKDC score, KOOS pain and symptom scores in ST group, and KOOS activities of daily living score in DT group. A total of 40 patients (83%) in the ST group and 37 patients (88%) in the DT group had a clinically relevant improvement of Kujala score, 39 patients (81%) in the ST group and 35 patients (83%) in the DT group of Lysholm, 38 patients (79%) in the ST group and 35 patients (83%) in the DT group of IKDC, a median of 40 patients (83%) in the ST group and 35 patients (83%) in the DT group of KOOS, and 41 patients (85%) in the ST group and 36 patients (86%) in the DT group of Tegner. No significant difference was found between the percentage of two groups.
      Table 2Comparison of Functional Scores Between the 2 Groups
      ST GroupDT GroupP Value
      Kujala score
       Preoperative70.4 ± 20.268.7 ± 19.1.730
       Final follow-up84.5 ± 14.788.9 ± 14.4.156
      P = .002P < .001
      Lysholm score
       Preoperative64.9 ± 15.072.0 ± 15.4.074
       Final follow-up83.7 ± 13.589.5 ± 11.4.031
      P = .001P < .001
      Tegner score
       Preoperative2.52 ± 1.042.65 ± 1.03.671
       Final follow-up3.89 ± 1.184.32 ± 1.29.113
      P = .004P < .001
      IKDC score
       Preoperative65.7 ± 16.562.0 ± 17.1.366
       Final follow-up74.3 ± 12.577.3 ± 12.3.254
      P = .005P < .001
      KOOS Scores

       Pain
       Preoperative84.3 ± 12.584.6 ± 13.6.909
       Final follow-up92.7 ± 7.595.7 ± 7.2.057
      P = .002P < .001
       Symptoms
       Preoperative66.9 ± 14.069.6 ± 15.7.451
       Final follow-up74.7 ± 12.181.2 ± 14.1.021
      P = .003P = .001
       Function in daily living activities
       Preoperative85.5 ± 15.688.1 ± 13.1.454
       Final follow-up96.1 ± 5.397.5 ± 4.8.172
      P < .001P < .001
       Function in sports and recreation
       Preoperative56.9 ± 31.452.3 ± 28.8.542
       Final follow-up80.0 ± 18.584.3 ± 20.6.302
      P < .001P < .001
       Knee-related quality of life
       Preoperative47.0 ± 23.252.9 ± 24.5.312
       Final follow-up61.8 ± 22.271.1 ± 20.3.043
      P = .006P = .009
      Data are presented as means ± standard deviation. The independent-sample t-test was employed to compare the scores between the 2 groups and the matched t-test was used to compare the preoperative and postoperative scores. Significant P values for comparison between two groups at final follow-up are bolded. IKDC, International Knee Documentation Committee; KOOS, Knee Injury and Osteoarthritis Outcome Score.

      Radiological Outcomes

      Results of the measurements for TT-TG, CA, PTA, LPA, and LPT are provided in Table 3. The measured radiological parameters showed excellent agreement with ICCs > 0.85. Preoperative results were similar between the groups. At the final follow-up, the parameters in both groups returned to the normal ranges and were statistically significant (P < .001) compared with preoperative findings. No significant difference was detected between the groups postoperatively.
      Table 3Computed Tomography Assessment Comparison Between the 2 Groups
      ST GroupDT GroupP Value
      TT-TG distance
       Preoperative20.0 ± 4.120.4 ± 4.6.619
       Final follow-up10.2 ± 4.511.3 ± 4.0.233
      P = .020P = .005
      Congruence angle
       Preoperative44.6 ± 20.041.1 ± 23.1.445
       Final follow-up−23.2 ± 36.8−13.4 ± 39.5.230
      P < .001P < .001
      Patellar tilt angle
       Preoperative29.5 ± 9.031.6 ± 10.2.301
       Final follow-up7.6 ± 10.411.4 ± 8.6.062
      P < .001P < .001
      Lateral patellar angle
       Preoperative12.9 ± 9.613.4 ± 13.9.849
       Final follow-up−9.1 ± 10.0−6.1 ± 8.3.137
      P < .001P < .001
      Lateral patellar translation
       Preoperative13.4 ± 6.916.2 ± 13.5.200
       Final follow-up1.4 ± 4.82.3 ± 5.1.408
      P < .001P < .001
      Data are presented as means ± standard deviation. The independent-sample t-test was employed to compare the variables between the 2 groups and the matched t-test was used to compare the preoperative and postoperative variables. TT-TG, tibial tubercle-trochlear groove.

      Complications and Adverse Events

      Four patients (8.3%) in the ST group complained of mild anterior knee pain, compared with 2 patients (4.8%) in the DT group (P = .498). 5 patients (10.4%) in the ST group and 4 in the DT group (9.5%) experienced mild knee range-of-motion (ROM) limitation (could not flex beyond 110°), such as deep squat (P = .888). The mean postoperative ROM for ST group was 125 ± 8° with 127 ± 9° for DT group. No complications, including donor-site morbidity, patellar fracture, infection, or chronic effusion, have been reported. The overall rate of complications and adverse events showed no significant differences between the two groups.

      Discussion

      The most important finding of this study was that the DT MPFLR could result in more favorable functional outcomes but could also result in an equivalent clinical failure rate and radiological parameters to ST MPFLR.
      Of all MPFLR procedures, transpatellar tunnel technique became a more preferrable procedure due to its stronger fixation force than the suture anchor both biomechanically and clinically.
      • Ji G.
      • Wang H.
      • Su X.
      • Wang J.
      • Wang F.
      The modified semi-tunnel bone bridge technique achieved statistically better knee function than the suture anchor technique.
      • Mountney J.
      • Senavongse W.
      • Amis A.A.
      • Thomas N.P.
      Tensile strength of the medial patellofemoral ligament before and after repair or reconstruction.
      • Russo F.
      • Doan J.
      • Chase D.C.
      • Farnsworth C.L.
      • Pennock A.T.
      Medial patellofemoral ligament reconstruction: Fixation technique biomechanics.
      Furthermore, tunnel reconstruction allows for the similar strength of native MPFL
      • Mountney J.
      • Senavongse W.
      • Amis A.A.
      • Thomas N.P.
      Tensile strength of the medial patellofemoral ligament before and after repair or reconstruction.
      with no use of extra fixation devices
      • Ercan N.
      • Akmese R.
      • Ulusoy B.
      Single-tunnel and double-tunnel medial patellofemoral ligament reconstructions have similar clinical, radiological and functional results.
      and a favorable environment for bone-tendon healing, as there are no implants between the graft and bone.
      • Sarikaya B.
      • Bozkurt C.
      • Sipahioglu S.
      • Çetin B.V.
      • Altay M.A.
      Patellar fixation with suspensory fixation device in single-tunnel medial patellofemoral ligament reconstruction.
      So far, various drilling techniques have been developed.
      • Desai V.S.
      • Tagliero A.J.
      • Parkes C.W.
      • et al.
      Systematic review of medial patellofemoral ligament reconstruction techniques: Comparison of patellar bone socket and cortical surface fixation techniques.
      ,
      • Lenschow S.
      • Schliemann B.
      • Gestring J.
      • Herbort M.
      • Schulze M.
      • Kösters C.
      Medial patellofemoral ligament reconstruction: Fixation strength of 5 different techniques for graft fixation at the patella.
      However, the tunnel number or size remains controversial. As the major passive restraint preventing lateral patella translation, numerous research articles have elaborated on the anatomy of MPFL, from a sail-like,
      • Placella G.
      • Tei M.M.
      • Sebastiani E.
      • et al.
      Shape and size of the medial patellofemoral ligament for the best surgical reconstruction: A human cadaveric study.
      or complex polygon-shaped structure
      • Ge Y.
      • Chen S.
      • Kato T.
      • Zdanowicz U.
      • Smigielski R.
      A polygon-shaped complex appearance of medial patellofemoral ligament with dynamic functional insertion based on an outside-in and inside-out dissection technique.
      to the concept of functional bundles.
      • Kang H.J.
      • Cao J.H.
      • Pan S.
      • Wang X.J.
      • Yu D.H.
      • Zheng Z.M.
      The horizontal Y-shaped graft with respective graft tension angles in anatomical two-bundle medial patellofemoral ligament reconstruction.
      Nevertheless, the insertion point on the patellar side was rather flexible and covered an extremely wide range. Hence, double-bundle (DB) MPFL reconstruction, rather than single-bundle (SB), has been popular and has achieved good outcomes
      • Wang C.H.
      • Ma L.F.
      • Zhou J.W.
      • et al.
      Double-bundle anatomical versus single-bundle isometric medial patellofemoral ligament reconstruction for patellar dislocation.
      ,
      • Kang H.J.
      • Cao J.H.
      • Pan S.
      • Wang X.J.
      • Yu D.H.
      • Zheng Z.M.
      The horizontal Y-shaped graft with respective graft tension angles in anatomical two-bundle medial patellofemoral ligament reconstruction.
      ,
      • Kang H.
      • Cao J.
      • Yu D.
      • Zheng Z.
      • Wang F.
      Comparison of 2 different techniques for anatomic reconstruction of the medial patellofemoral ligament: A prospective randomized study.
      from an anatomic perspective. In addition, DB reconstruction has an angular synergy effect biomechanically, which grants a greater resistance to patellar dislocation at a smaller flexion angle.
      • Wang Q.
      • Huang W.
      • Cai D.
      • Huang H.
      Biomechanical comparison of single- and double-bundle medial patellofemoral ligament reconstruction.
      The DT technique, as a type of DB reconstruction, fixed the graft at the patellar side through two transpatellar tunnels. Hence, DT MPFL reconstruction, theoretically, is one procedure that combines the advantage of transpatellar tunnel technique and DB MPFL reconstruction, as the separate tunnels could simulate the MPFL wide footprint on the patella.
      In the present study, the DT MPFLR group had relatively better functional outcomes, but similar clinical failure rate compared with ST group. DT group has a higher Lysholm score, KOOS symptoms, and knee-related quality of life score than ST group, whereas other outcomes, such as Kujala score, were similar between the 2 groups. As for clinically significant differences, MCIDs or MDCs for all PROMs were exceeded by mean overall improvement scores except IKDC score, KOOS pain and symptom scores in ST group, and KOOS activities of daily living score in DT group. These findings are mostly consistent with previous research by Li et al.
      • Li J.
      • Li Z.
      • Wang K.
      • Liu C.
      • Wang Y.
      • Wang H.
      Medial patellofemoral ligament reconstruction: A comparison of single-bundle transpatellar tunnel and double-anchor anatomic techniques for the treatment of recurrent lateral patellar dislocation in adults.
      . Li et al.
      • Li J.
      • Li Z.
      • Wang K.
      • Liu C.
      • Wang Y.
      • Wang H.
      Medial patellofemoral ligament reconstruction: A comparison of single-bundle transpatellar tunnel and double-anchor anatomic techniques for the treatment of recurrent lateral patellar dislocation in adults.
      noted that the double-anchor group showed a higher functional outcome than the traditional ST group with no significant difference in patellar re-dislocation between the 2 groups. The main reason for better functional outcome in the DT group than in the ST group might be the same with DB over SB, that DT reconstruction could simulate the native MPFL wide footprint on the patella, and restore the anatomy of MPFL better as stated in biomechanical studies by Placella et al.
      • Placella G.
      • Speziali A.
      • Sebastiani E.
      • Morello S.
      • Tei M.M.
      • Cerulli G.
      Biomechanical evaluation of medial patello-femoral ligament reconstruction: Comparison between a double-bundle converging tunnels technique versus a single-bundle technique.
      and Wang et al.
      • Wang Q.
      • Huang W.
      • Cai D.
      • Huang H.
      Biomechanical comparison of single- and double-bundle medial patellofemoral ligament reconstruction.
      Anatomical reconstruction of MPFL is important as demonstrated that incorrect graft placement could increase medial patellofemoral contact pressures by over 50% in biomechanical research.
      • Elias J.J.
      • Cosgarea A.J.
      Technical errors during medial patellofemoral ligament reconstruction could overload medial patellofemoral cartilage: A computational analysis.
      As for the primary outcome, there was no significant difference between two groups due to the possible reasons, as follows. First, no significant difference was indicated between the maximum load for the 2 techniques,
      • Placella G.
      • Speziali A.
      • Sebastiani E.
      • Morello S.
      • Tei M.M.
      • Cerulli G.
      Biomechanical evaluation of medial patello-femoral ligament reconstruction: Comparison between a double-bundle converging tunnels technique versus a single-bundle technique.
      and they could both provide the fixation force strong enough to effectively prevent the lateral translation of the patella. Second, in addition to MPFLR, most patients also received LRR and tibial tubercle transfer in the present study, thus resulting in better restoration of anatomy and malalignment correction of patellofemoral joint. These combined procedures could all help reduce the clinical failure rate. Additionally, the AHPLT was used as the graft for MPFLR in the present study. It locates superficially in the distal leg and permits easy harvesting in 5-10 minutes with strength similar to that of the semitendinosus tendon.
      • Zhao J.
      • Huangfu X.
      The biomechanical and clinical application of using the anterior half of the peroneus longus tendon as an autograft source.
      Furthermore, the selection of AHPLT could avoid multiple incisions or a long incision around the TT when TT transfer is required. Our results suggested that DT MPFLR with AHPLT was effective and safe. Moreover, it might have some advantages in functional outcomes over ST technique and could be considered in clinical practice.
      Regarding radiological outcomes, the measurements showed no significance between two groups postoperatively. Both techniques could effectively correct the patellar alignment and rotation. Li et al.
      • Li J.
      • Li Z.
      • Wang K.
      • Liu C.
      • Wang Y.
      • Wang H.
      Medial patellofemoral ligament reconstruction: A comparison of single-bundle transpatellar tunnel and double-anchor anatomic techniques for the treatment of recurrent lateral patellar dislocation in adults.
      demonstrated similar results in comparison between ST technique and double-anchor technique, except for the patellar tilt angle. The double-anchor group showed smaller patellar tilt angle. However, in line with our results, Ercan et al.
      • Ercan N.
      • Akmese R.
      • Ulusoy B.
      Single-tunnel and double-tunnel medial patellofemoral ligament reconstructions have similar clinical, radiological and functional results.
      demonstrated the similar outcomes in ST and DT group.
      In the present study, no significant difference was found in complications between the 2 techniques. One of the major complications with the transpatellar technique was patellar fracture.
      • Parikh S.N.
      • Wall E.J.
      Patellar fracture after medial patellofemoral ligament surgery: A report of five cases.
      • Schiphouwer L.
      • Rood A.
      • Tigchelaar S.
      • Koëter S.
      Complications of medial patellofemoral ligament reconstruction using two transverse patellar tunnels.
      • Bonazza N.A.
      • Lewis G.S.
      • Lukosius E.Z.
      • Roush E.P.
      • Black K.P.
      • Dhawan A.
      Effect of transosseous tunnels on patella fracture risk after medial patellofemoral ligament reconstruction: A cadaveric study.
      • Astur D.C.
      • Gouveia G.B.
      • Borges J.H.
      • et al.
      Medial patellofemoral ligament reconstruction: A longitudinal study comparison of 2 techniques with 2 and 5-years follow-up.
      The DT technique was considered to have a greater risk than ST technique due to the additional tunnel, but both the current study and Mohammed et al.’s
      • Mohammed R.
      • Hunt N.
      • Gibbon A.J.
      Patellar complications in single versus double tunnel medial patellofemoral ligament reconstruction.
      research noted no case of such complication in both groups. Additionally, Christiansen et al.
      • Christiansen S.E.
      • Jacobsen B.W.
      • Lund B.
      • Lind M.
      Reconstruction of the medial patellofemoral ligament with gracilis tendon autograft in transverse patellar drill holes.
      noted that the transverse holes violating the anterior patellar cortex was the main reason for patellar fracture in their study. Deasey et al.
      • Deasey M.J.
      • Moran T.E.
      • Lesevic M.
      • Burnett Z.R.
      • Diduch D.R.
      Small, short, oblique patellar tunnels for patellar fixation do not increase fracture risk or complications in MPFL reconstruction: A retrospective cohort study.
      indicated that oblique tunnels with an anterior patellar exit was a safe technique with only 1 out of 215 knees encountering a fracture. By using shorter tunnels with smaller diameters and maintaining a sufficient bone bridge in DT reconstruction, the risk of patellar fracture could be minimized. Previous studies by Deasey et al.
      • Deasey M.J.
      • Moran T.E.
      • Lesevic M.
      • Burnett Z.R.
      • Diduch D.R.
      Small, short, oblique patellar tunnels for patellar fixation do not increase fracture risk or complications in MPFL reconstruction: A retrospective cohort study.
      , Niu et al.
      • Niu J.
      • Qi Q.
      • Fu K.
      • Duan G.
      • Liu C.
      • Wang F.
      Medial patellofemoral ligament reconstruction with semi-patellar tunnel fixation: Surgical technique and mid-term follow-up.
      and Toritsuka et al.
      • Toritsuka Y.
      • Amano H.
      • Mae T.
      • et al.
      Dual tunnel medial patellofemoral ligament reconstruction for patients with patellar dislocation using a semitendinosus tendon autograft.
      also indicated that DT technique is a safe procedure of MPFLR without significantly increasing the risk of patellar fracture. Furthermore, compared with the ST technique, the DT technique still has several disadvantages due to the additional tunnel, including the risk of articular surface violation and the need for a longer graft.
      • Deasey M.J.
      • Moran T.E.
      • Lesevic M.
      • Burnett Z.R.
      • Diduch D.R.
      Small, short, oblique patellar tunnels for patellar fixation do not increase fracture risk or complications in MPFL reconstruction: A retrospective cohort study.
      ,
      • Makovicka J.L.
      • Hartigan D.E.
      • Patel K.A.
      • Tummala S.V.
      • Chhabra A.
      Medial patellofemoral ligament reconstruction using all-soft suture anchors for patellar fixation.
      The other frequently reported problems were knee stiffness and patellofemoral pain,
      • Parikh S.N.
      • Nathan S.T.
      • Wall E.J.
      • Eismann E.A.
      Complications of medial patellofemoral ligament reconstruction in young patients.
      ,
      • Burnham J.M.
      • Howard J.S.
      • Hayes C.B.
      • Lattermann C.
      Medial patellofemoral ligament reconstruction with concomitant tibial tubercle transfer: A systematic review of outcomes and complications.
      which also appeared in the present study. The loss of knee flexion was successfully managed with maneuver release and progressive physical therapy. The pain is usually associated with preoperative patellar or trochlear cartilage lesions, and thus occurs regardless of which technique is employed to reconstruct the MPFL.
      • Mohammed R.
      • Hunt N.
      • Gibbon A.J.
      Patellar complications in single versus double tunnel medial patellofemoral ligament reconstruction.
      ,
      • Kang H.
      • Zheng R.
      • Dai Y.
      • Lu J.
      • Wang F.
      Single- and double-bundle medial patellofemoral ligament reconstruction procedures result in similar recurrent dislocation rates and improvements in knee function: a systematic review.
      As for the complication rates, the overall mean rate (16.7%) was mainly within the range reported by Desai et al.
      • Desai V.S.
      • Tagliero A.J.
      • Parkes C.W.
      • et al.
      Systematic review of medial patellofemoral ligament reconstruction techniques: Comparison of patellar bone socket and cortical surface fixation techniques.
      (0%-28%) for bone socket technique. The rate of patellar fracture (0%) was the same with the most studies included in the research of Desai et al.,
      • Desai V.S.
      • Tagliero A.J.
      • Parkes C.W.
      • et al.
      Systematic review of medial patellofemoral ligament reconstruction techniques: Comparison of patellar bone socket and cortical surface fixation techniques.
      and the overall value was reported by Kang et al.
      • Kang H.
      • Zheng R.
      • Dai Y.
      • Lu J.
      • Wang F.
      Single- and double-bundle medial patellofemoral ligament reconstruction procedures result in similar recurrent dislocation rates and improvements in knee function: a systematic review.
      (0.1%).
      As for the surgical procedures, LRR and TT transfers were performed in addition to MPFLR. Whether TT transfer plays the major role in improving the outcomes remains unknown. TT transfer has been proven as an effective bony procedure to treat patients with patella alta.
      • Otsuki S.
      • Nakajima M.
      • Fujiwara K.
      • et al.
      Influence of age on clinical outcomes of three-dimensional transfer of the tibial tuberosity for patellar instability with patella alta.
      For patients with a normal patellar height, TT transfer was usually considered with MPFLR in case of a lateral positioned tuberosity (TT-TG > 15 or 20 mm), and usually provides a good outcome.
      • Burnham J.M.
      • Howard J.S.
      • Hayes C.B.
      • Lattermann C.
      Medial patellofemoral ligament reconstruction with concomitant tibial tubercle transfer: A systematic review of outcomes and complications.
      However, isolated MPFLR has also been reported to achieve a satisfactory result regardless of the TT-TG distance.
      • Sappey-Marinier E.
      • Sonnery-Cottet B.
      • O'Loughlin P.
      • et al.
      Clinical outcomes and predictive factors for failure with isolated MPFL reconstruction for recurrent patellar instability: A series of 211 reconstructions with a minimum follow-up of 3 years.
      ,
      • Erickson B.J.
      • Nguyen J.
      • Gasik K.
      • Gruber S.
      • Brady J.
      • Shubin Stein B.E.
      Isolated medial patellofemoral ligament reconstruction for patellar instability regardless of tibial tubercle-trochlear groove distance and patellar height: Outcomes at 1 and 2 years.
      Additionally, Kim et al.
      • Kim J.M.
      • Sim J.A.
      • Yang H.
      • Kim Y.M.
      • Wang J.H.
      • Seon J.K.
      Clinical comparison of medial patellofemoral ligament reconstruction with or without tibial tuberosity transfer for recurrent patellar instability.
      indicated that MPFLR with and without TT transfer yielded similar outcomes in patients with patellar instability with a TT-TG distance of 15 to 25 mm. The influence of TT transfer in the present study awaits investigation.

      Limitations

      Several limitations should be considered in the present study. First, the enrolled patients were mainly young and female. Despite its consistency with the population distribution of recurrent patellar dislocation, bias may still exist. Additionally, patients with certain abnormalities, such as patella alta, severe trochlear dysplasia, or lower limb malalignment were not included. Secondly, since LRR and TT transfers were performed in addition to MPFLR, which exact procedure had the greatest effect on improving clinical failure remains unknown. Furthermore, not all patients received a combined TT transfer, which could add heterogeneity. Third, the duration of follow-up was relatively short and potential degenerative changes, such as the development of patellofemoral osteoarthritis, were difficult to detect at 2-year follow-up, and they were not evaluated in the present study. Additionally, the present study might have been underpowered as the sample size calculation was based on a large effect size, and all the functional scores were higher for the DT group, suggesting that there might have been a beta error.

      Conclusion

      Both techniques could equally mitigate the patellar lateral translation or redislocation. Our results demonstrate several significant differences in functional outcomes that favored DT MPFL reconstruction but no difference in clinical failure rates and radiological results between ST and DT MPFL reconstruction.

      Supplementary Data

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