Grafted tendon healing in femoral and tibial tunnels after anterior cruciate ligament reconstruction

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1 Journal of Orthopaedic Surgery 2014;22(1):65-9 Grafted tendon healing in femoral and tibial tunnels after anterior cruciate ligament reconstruction Junsuke Nakase, 1 Katsuhiko Kitaoka, 2 Tatsuhiro Toratani, 1 Masahiro Kosaka, 1 Yoshinori Ohashi, 1 Hiroyuki Tsuchiya 1 1 Department of Orthopaedic Surgery, School of Medicine, Kanazawa University, Kanazawa, Japan 2 Department of Orthopaedic Surgery, Kijima Hospital, Japan ABSTRACT Purpose. To evaluate tendon-to-bone healing after anterior cruciate ligament (ACL) reconstruction in the fibrous interzone (FIZ) of the femoral and tibial tunnels using magnetic resonance imaging (MRI). Methods. Five men and 5 women (mean age, 29 years) underwent arthroscopic ACL reconstruction by a single surgeon, using the semitendinosus and gracilis tendon. The tendon-to-bone healing in the FIZ was evaluated using sagittal and coronal MRI at 1, 3, 6, 9, 12, and 24 weeks, with the knee flexed at 60º and the tendon graft straight in both images. The signal intensity of the FIZ was visually assessed by comparing it with anatomic landmarks in the same patient s knee, and classified into 4 grades. It was grade 3 when similar to that of the patellar tendon, grade 2 when similar to that of skeletal muscle, grade 1 when greater than that of muscle but less than that of joint fluid, and grade 0 when similar to that of joint fluid. At 24 weeks, subjective and objective functional outcomes were evaluated using the Lysholm score and the International Knee Documentation Committee score. Results. At 24 weeks, no patient had knee laxity. All patients had an International Knee Documentation Committee score of A, and their mean Lysholm score was In the femoral tunnel, the FIZ did not change during the first 9 weeks (in particular the anterior part), but healing occurred rapidly thereafter. In the tibial tunnel, the FIZ healed over time in all locations, and healing was complete in the lateral and posterior parts at 12 weeks, and in all locations at 24 weeks. The mean signal intensity grade was significantly higher in the tibial than femoral FIZ at 3 to 12 weeks (p<0.01). Conclusion. After ACL reconstruction, the tendonto-bone healing in the FIZ of the tibial tunnel was faster than that of the femoral tunnel. Key words: anterior cruciate ligament reconstruction; magnetic resonance imaging INTRODUCTION Anterior cruciate ligament (ACL) reconstruction using Address correspondence and reprint requests to: Dr Junsuke Nakase, 13-1 Takaramachi, Kanazawa , Japan. nakase1007@yahoo.co.jp

2 66 J Nakase et al. Journal of Orthopaedic Surgery the hamstring tendon is a valid form of treatment. 1 However, it is often associated with bone tunnel enlargement, 2 and takes a long time for the graft to heal within the bone tunnels and achieve sufficient mechanical strength. 3,4 Tendon-to-bone healing is slower than bone-to-bone healing. 5,6 Bone-patellar tendon-bone grafting results in greater donor-site morbidity. Autologous hamstring tendon grafting results in less donor-site morbidity, but tendon-tobone healing is slower. After ACL reconstruction, a cell- and vessel-rich fibrous interzone (FIZ) forms between the tendon graft and the bone tunnel wall and affects the strength of fixation. 7 Approaches that can accelerate and improve tendon-to-bone healing may reduce the risk of graft failure and enable early aggressive rehabilitation. Different approaches to enhance tendon-to-bone healing include mechanical stimulation, 8 tendon wrapping with periosteum, 9 and interface filling with growth factors, 10,11 bone marrow stromal cells, 12 and mesenchymal stem cells. 13 Most such studies involve experiments on animals. A few have used humans and examined changes in bone tunnels over time, using sagittal or horizontal magnetic resonance imaging (MRI) with the knees in flexion. We evaluated the tendon-to-bone healing process after ACL reconstruction in the FIZ, using sagittal and coronal MRI at 1, 3, 6, 9, 12, and 24 weeks. Figure 1 Arthroscopic anterior cruciate ligament reconstruction using the semitendinosus and gracilis tendon graft, with bone grafting in the bone tunnels (arrows). MATERIALS AND METHODS This study was approved by the ethics committee of our hospital, and written informed consent was obtained from each patient. Between June and August 2010, 5 men and 5 women (mean age, 29 years) underwent arthroscopic ACL reconstruction by a single surgeon, using the semitendinosus and gracilis tendons (Fig. 1). 14 The tendons were harvested through an oblique anteromedial tibial incision at the pes anserinus. Soft tissue from the tendons was removed. The graft was double-folded and fixed by cross pins (bone mulch screws) on the femoral side and by a washer plate and screw (WasherLoc) on the tibial side. Bone grafting was performed in the proximal femoral bone tunnel and the anteromedial tibial bone tunnel. Postoperatively, bracing was not used. Weightbearing ambulation and range-of-motion training was started. Patients were allowed to resume sports after 6 months if there was no knee joint swelling, limited range of motion, or instability, and the strength of the knee extensor and flexor muscles was >80% of that on the unaffected side. Figure 2 The knee joint is flexed at 60º, and the tendon graft is straight in both the sagittal and coronal images.

3 Vol. 22 No. 1, April 2014 Grafted tendon healing in femoral and tibial tunnels 67 The tendon-to-bone healing in the FIZ was evaluated using sagittal and coronal T2-weighted fast spin echo MRI (slice thickness, 2.5 mm) at 1, 3, 6, 9, 12, and 24 weeks, with the knee flexed at 60º and the tendon graft straight in both images (Fig. 2). The signal intensity of the FIZ was visually assessed by comparing it with anatomic landmarks (patellar tendon, skeletal muscle, joint fluid, and synovial membrane) in the same patient s knee. 15 The medial and lateral sections in the coronal plane and anterior and posterior sections in the sagittal plane were evaluated. The evaluation became independent in the slices in which the femoral and tibial diameters were maximal (Fig. 3). The FIZ signal intensity was classified into 4 grades by another orthopaedic surgeon who was blinded to the clinical assessment. It was grade 3 when similar to that of the patellar tendon, grade 2 when similar to that of skeletal muscle, grade 1 when greater than that of muscle but less than that of joint fluid, and grade 0 when similar to that of joint fluid. At 24 weeks, subjective and objective functional outcomes were evaluated using the Lysholm score and the International Knee Documentation Committee score by the operating surgeon, who was blinded to the MRI findings. Comparisons were made using the paired Student s t-test. A p value of <0.05 was considered statistically significant. results Lateral Medial Anterior Posterior At 24 weeks, no patient had knee laxity according to the Lachman test and the Pivot-shift test. All patients had an International Knee Documentation Committee score of A, and their mean Lysholm score was In the femoral tunnel, the FIZ did not change during the first 9 weeks (in particular the anterior part), but healing occurred rapidly thereafter. In the tibial tunnel, the FIZ healed over time in all locations, and healing was complete in the lateral and posterior parts at 12 weeks, and in all locations at 24 weeks. The mean signal intensity grade was significantly higher in the tibial than femoral FIZ at 3 to 12 weeks (p<0.01, Table). Figure 3 (a) Coronal and (b) sagittal magnetic resonance imaging of the fibrous interzone (arrows) of the femoral and tibial tunnels. DISCUSSION MRI is useful in the evaluation of the tendon-bone Table Comparison of tendon-to-bone healing in the fibrous interzones in the femoral and tibial tunnels Bone tunnel Mean±SD tendon-to-bone healing in the fibrous interzone (signal intensity, grades 0 3) Week 1 Week 3 Week 6 Week 9 Week 12 Week 24 Femoral tunnel Anterior 1.0±0 0.7± ± ± ± ±1.4 Posterior 0.9± ± ± ± ± ±1.1 Medial 1.1± ± ± ± ± ±0.4 Lateral 0.9± ± ± ± ± ±0 Mean Tibial tunnel Anterior 0.9± ± ± ± ± ±0.4 Posterior 1.4± ± ± ± ± ±0 Medial 0.9± ± ±0 2.4± ± ±0.4 Lateral 1.6± ± ± ± ±0 3.0±0 Mean

4 68 J Nakase et al. Journal of Orthopaedic Surgery junction after ACL reconstruction. Generally, the tendon-bone junction takes approximately 3 months to achieve biological fixation. There have been studies on enhancing biological fixation of the junction, 11,16 as well as MRI studies on evaluating changes in bone tunnels after ACL reconstruction. 17,18 In the present study, healing at the graft-bone junction was slower in the femur. This suggests that knee flexion and extension caused greater movement of the tendon graft anteroposteriorly than mediolaterally. Thus, healing progressed more in the lateral and medial aspects of the bone tunnel where the compressive force from the tendon graft to the bone tunnel was greater, compared to the anterior and posterior aspects. In the tibia, healing of the tendonbone junction was mostly in the posterior and lateral aspects, where a compressive force was exerted from the tendon graft to the bone tunnel during knee flexion and extension. In addition, bone grafting in the tibial anteromedial bone tunnel also exerted a compressive force and thus facilitated fixation at the tendon-bone junction. In an experiment with rabbits, grafted tendon healing in the tibial tunnel was inferior to that in the femoral tunnel, owing to the effects of bone quality. 19,20 In clinical practice, in some patients undergoing ACL reconstruction the femoral tunnel is not covered by the synovial membrane. 8 Healing at the tendon-bone junction is generally worse in the femoral than tibial tunnel, because during knee extension and flexion the grafted tendon is subjected to more movement in the femoral than tibial tunnel. The position of the knee joint differs in rabbits and humans. Rabbit knees are mostly in a flexed position. Our results may also have been affected by large amounts of residual tissue in the tibial tunnel after ACL injury. One of the limitations of this study was the small sample size. Moreover, tendon-bone junction healing was not adjusted for patient age or activity level. Evaluation of the FIZ in the femoral tunnel might have been incorrect owing to halation caused by metallic implants. REFERENCES 1. Aglietti P, Giron F, Buzzi R, Biddau F, Sasso F. Anterior cruciate ligament reconstruction: bone-patellar tendon-bone compared with double semitendinosus and gracilis tendon grafts. A prospective, randomized clinical trial. J Bone Joint Surg Am 2004;86: Wilson TC, Kantaras A, Atay A, Johnson DL. Tunnel enlargement after anterior cruciate ligament surgery. Am J Sports Med 2004;32: L Insalata JC, Klatt B, Fu FH, Harner CD. Tunnel expansion following anterior cruciate ligament reconstruction: a comparison of hamstring and patellar tendon autografts. Knee Surg Sports Traumatol Arthrosc 1997;5: Steiner ME, Hecker AT, Brown CH Jr, Hayes WC. Anterior cruciate ligament graft fixation. Comparison of hamstring and patellar tendon grafts. 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5 Vol. 22 No. 1, April 2014 Grafted tendon healing in femoral and tibial tunnels Radice F, Yanez R, Gutierrez V, Rosales J, Pinedo M, Coda S. Comparison of magnetic resonance imaging findings in anterior cruciate ligament grafts with and without autologous platelet-derived growth factors. Arthroscopy 2010;26: Uchio Y, Ochi M, Adachi N, Kawasaki K, Kuriwaka M. Determination of time of biologic fixation after anterior cruciate ligament reconstruction with hamstring tendons. Am J Sports Med 2003;31: Lui PP, Ho G, Shum WT, Lee YW, Ho PY, Lo WN, et al. Inferior tendon graft to bone tunnel healing at the tibia compared to that at the femur after anterior cruciate ligament reconstruction. J Orthop Sci 2010;15: Wen CY, Qin L, Lee KM, Wong MW, Chan KM. Grafted tendon healing in tibial tunnel is inferior to healing in femoral tunnel after anterior cruciate ligament reconstruction: a histomorphometric study in rabbits. Arthroscopy 2010;26:58 66.