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Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surgical technique and preliminary results
THEKNE-02340; No of Pages 9 The Knee xxx (2016) xxx–xxx
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The Knee
Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surgical technique and preliminary results Marco Bigoni, Diego Gaddi, Massimo Gorla, Daniele Munegato, Marco Pungitore, Massimiliano Piatti, Marco Turati ⁎ Orthopedic Department, San Gerardo Hospital, Via Pergolesi 33, 20900 Monza, Italy
a r t i c l e
i n f o
Article history: Received 3 November 2015 Received in revised form 14 September 2016 Accepted 16 September 2016 Available online xxxx Keywords: Anterior cruciate ligament Arthroscopic fixation Open physes Pediatric Sport injury
a b s t r a c t Background: Anterior cruciate ligament (ACL) tears in children are increasingly common and present difficult treatment decisions due to the risk of growth disturbance. Although open primary ACL repair was abandoned in the historical literature, recent studies have suggested that there is a role for arthroscopic primary repair in patients with proximal tears. Methods: This is a retrospective review of five consecutive patients aged 9.2 years (range 8 to 10) who underwent suture anchor ACL reinsertion. Patients were included if they were Tanner stages 1–2 and proximal ACL tears with adequate tissue quality confirmed arthroscopically. The time frame was 81 days. Arthroscopic ACL reinsertion was performed with bioabsorbable suture anchor. Clinical evaluation, KT-1000™, and MRI were re-evaluated. Clinical outcomes were measured using International Knee Documentation Committee (IKDC), Lysholm and Tegner activity score. Results: At a mean follow-up of 43.4 months (range 25 to 56), no re-injury and leg length discrepancies were observed. Four patients had negative Lachman tests. The remainder had a grade 1 Lachman test. The mean side-to-side difference was 3 (2–4 mm). In MRI obtained at the last follow-up, no articular lesions or growth arrest were observed and the reinserted ACL was recognized in every exam. All patients returned to previous level of activity and presented normal and nearly normal IKDC score. The mean Lysholm score was 93.6. Conclusion: Arthroscopic ACL repair can achieve good short-term results with joint stability and recovery of sport activity in skeletally immature patients, with proximal ACL avulsion tear. © 2016 Elsevier B.V. All rights reserved.
1. Introduction Anterior cruciate ligament (ACL) tears are increasingly more common among children and adolescents [1]. To illustrate, ACL tears comprise 6.7% of all injuries and 30.8% of all knee injuries in pediatric and adolescent soccer players aged five to 18 [2]. The history of ACL rupture treatment in skeletally immature individuals is controversial. Non-surgical (conservative) management is associated with increased occurrence of new meniscal or cartilage injuries, reduced stability, and lower physical activity levels in comparison with surgical treatment [3–6]. Surgical management, on the other hand, restores knee stability and offers the
⁎ Corresponding author. E-mail address: [email protected] (M. Turati).
http://dx.doi.org/10.1016/j.knee.2016.09.017 0968-0160/© 2016 Elsevier B.V. All rights reserved.
Please cite this article as: Bigoni M, et al, Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surg..., Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.017
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possibility of maintaining comparable activity levels. This intervention is advantageous in younger patients who are noncompliant with bracing, and are intolerant of reduced physical activity [3,7,8]. However, a historical analysis of ACL open repair revealed an unacceptable failure rate [9–11]; thus, enthusiasm for this procedure waned. In order to parse-out factors contributing to this failure rate, Sherman et al. conducted an extensive subgroup analysis which included ACL tear type and tissue quality. They revealed better results in patients with proximal ACL avulsion tear and good tissue quality [12]. Genelin et al. subsequently employed this technique principally in proximal avulsion injury of ACL, and observed good mid-term results [13]. Nonetheless, both groups conducted open repairs and implemented long post-operative immobilization (six to eight weeks of long leg cast). In this context, a recent review of the literature showed that in a selected subset of patients, considering only proximal ACL tears, primary ACL repair could be reconsidered as an effective treatment [14]. However, it is the specific nature of surgical treatment in the skeletally immature, which can lead to growth disturbances with serious consequences such as angular deviation or leg shortening in up to 11% of cases [15,16]. These risks are especially apparent in patients in Tanner stages 1 and 2, who have higher growth potential and consequently have a higher risk of major limb growth disturbance compared with patients with closed physes [17]. In response to this confounding problem, novel surgical interventions have been attempted in order to mitigate physeal growth disruption. First, a novel minimally invasive arthroscopic ACL repair with suture anchor achieved short-term clinical success in a carefully selected adult population with proximal ACL avulsion and excellent tissue quality of the stump [18]. Secondly, Steadman et al. performed arthroscopic holes in the femoral ACL footprint to induce a “healing response” in selected skeletally immature patients. Although “healing response” should not be considered a repair technique, the good clinical outcomes in these pediatric patients with a proximal ACL tear lead us to consider children as the ideal candidates for arthroscopic suture anchor ACL repair [19]. The aim of this study is to describe a variation in the previously described suture anchor repair [24] to treat proximal ACL tears in the skeletally immature patients, and to evaluate the clinical and subjective results in the short-term follow-up.
2. Materials and methods This is a retrospective review and early follow-up of five consecutive skeletally immature patients (four boys and one girl) with proximal ACL tears that underwent arthroscopic ACL femoral reinsertion with a bioabsorbable anchor by the senior surgeon (M.B.) in our center between 2007 and 2010 (Figure 1). Children with a clinical ACL deficiency underwent knee radiographs and magnetic resonance imaging (MRI) to exclude spine avulsion and fracture and to recognize a proximal ACL avulsion (Figure 2). Indications for primary repair of the ACL included: (i) a primary proximal ACL lesion confirmed clinically and identified on MRI, (ii) any patient with open growth plates with a Tanner stage 1 or stage 2, (iii) informed consent signed by both parents, and (iv) an arthroscopic intraoperative confirmation of the adequate tissue quality and quantity of the ACL stump to perform the ACL reinsertion. In the presence of inadequate tissue, ACL reinsertion was converted to ACL reconstruction or conservative treatment according to parental consent. Exclusion criteria included any indications of: (i) ACL mid-substance or distal ruptures, (ii) spine avulsion, (iii) intra-epiphyseal growth disturbances, (iv) multi-ligament injury patterns (≥3 ligaments involved), and (v) any previous surgical interventions on the limb under consideration for treatment.
Figure 1. Principle of the ACL femoral reinsertion with a bioabsorbable anchor.
Please cite this article as: Bigoni M, et al, Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surg..., Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.017
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Figure 2. T1-weighted sagittal MRI of a left knee with a proximal avulsion ACL tear in an eight-year old patient.
Patients were evaluated post-surgically by clinical evaluation of limb alignment and length, ligament stability, and bilateral instrumented ligament examination using the KT-1000™ knee arthrometer, applying 134-N of force (MEDmetric® Corporation, San Diego, California). Ligament stability was measured by Lachman test, anterior drawer, and pivot-shift test. Lachman grades of laxity were as follows: grade 0 (anterior tibial translation b 3 mm), grade 1 (three to five millimeters), grade 2 (five to 10 mm) and grade 3 (N 10 mm) [20]. Pivot-shift test was graded as negative (grade 0), glide (1), clunk (2), or gross (3) according to the International Knee Documentation Committee (IKDC) classification. One-leg hop test was used for functional assessment. All patients were revaluated after a follow-up period of at least two years with a Knee MRI. Clinical outcomes were measured using IKDC score, Lysholm score and Tegner activity scale [21–23]. Post-operative evaluations were performed by an independent examiner. All patients' parents provided a written informed consent in agreement with the protocol approved by the local ethics committee and conforming to the principles outlined in the World Medical Association Declaration of Helsinki. All data are expressed as mean ± standard deviation.
3. Surgical technique The patient, under general anesthesia, was placed in a supine position and a three-portal diagnostic arthroscopy was performed. We confirmed proximal ACL lesion and determined suitability of the ACL stump for reinsertion. A preparation of the femoral footprint with minimal debridement of soft tissue was performed to allow adequate visualization of the original isometric femoral insertion and obtain a bleeding bony bed. An accessory medial or transpatellar tendon access was performed to facilitate management and ligament repair. A spinal needle (18 gauge, 3.50 in.) was inserted through the anteromedial portal, and residual ACL tissue was transfixed in the proximal extremity of the stump (Figure 3). Great care was taken for the needle transfixion to pass through the center of the ACL diameter. A polydioxanone (PDS) 2–0 (Ethicon, Sommerville, NJ, USA) was then passed through the needle. Once the PDS was captured from the transpatellar tendon access, the surgeon with the probe put the ACL under tension towards the original femoral footprint, testing the reliability of correct and isometric reinsertion with the knee at 90° of flexion. Panaloc (3.5 mm, DePuyMitek, MA, USA) was then inserted into the joint through the anteromedial portal and fixed on the lateral femoral condyle in the femoral ACL footprint after appropriate drilling with the knee flexed at 90° (Figure 4). At this time, the posterior Panacril 2–0 was passed through the ACL using the PDS 2–0 previously prepared as a shuttle relay. The ACL was then re-approximated to the original position, tightened, and fixed with the knee at 90°. We used at first, a unique sliding knot with a self-looking loop as previously described (Samsung Medical Centre (SMC) knot) and secured it with two simple knots (Figure 5) [24]. To facilitate suture passage, we used a threaded clear cannula with obturator (DePuyMitek, MA, USA) in the anteromedial portal. After cutting the Panacril extremities, the joint's full range of motion and the absence of visual gap between the ACL stump and femoral footprint were verified. The tension and stiffness of the repaired ACL were confirmed with a probe and an intraoperative Lachman test was performed. Post-operatively, a fulltime long leg splint was applied for four weeks. Then, after the splint removal, weight bearing was allowed using a hinged knee brace for eight weeks with a gradual increase of range of motion. Rehabilitation protocol begins four weeks after surgery and includes knee motion exercises, isometric quadriceps activation, reinforcement training of the hamstrings, closed chain exercises, pool therapy, and proprioception exercises under physiotherapist guidance. After three to four Please cite this article as: Bigoni M, et al, Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surg..., Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.017
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Figure 3. Arthroscopic view of proximal ACL avulsion type lesion during transfixion with the spinal needle.
months from surgery, the patients start straight-line jogging, open chain and plyometric exercises. Cutting sports are allowed after six to seven months after surgery.
4. Results We evaluated 46 Tanner stages 1–2 patients with ACL deficiency between 2007 and 2010, for potential inclusion in this study. Forty-one patients were excluded based on inclusion and exclusion criteria. We included only those patients in the study with clinical, X-rays, MRI and arthroscopy confirmed proximal ACL tears. Eight patients underwent surgery, three of whom were excluded from the study on the basis of the quality of their ACL tissue (two partial ACL tears and one inadequate ACL tissue quality). These patients were treated conservatively. Figure 6 shows the flowchart of our series. The five patients who met the inclusion and exclusion criteria (four boys and one girl) had an age of 9.2 (range: eight to 10 years). Three patients had injuries in their right knee and two in their left knee. All patients sustained an identified sport-related knee injury (Table 1). All X-rays showed tibial and femoral open growth plates without intra-epiphyseal growth disturbances. The MRI showed isolated proximal ACL tears with no associated injuries. The time for surgery was less than four months for all patients with a mean time to surgery of 81 days (range 15 to 123 days).
Figure 4. Arthroscopic view of the lateral femoral condyle after the insertion of the anchor.
Please cite this article as: Bigoni M, et al, Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surg..., Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.017
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Figure 5. Arthroscopic view of the reinsertion of the ACL in anatomic position before the cutting of the knot.
Proximal ACL lesion with an adequate quality of the ACL stump was confirmed by arthroscopy; no meniscal or cartilage lesions were recorded. Suture anchor ACL repair was performed without intraoperative complications in all patients. Patients were followed up at 43.4 ± 14.82 months after surgery and none of them had suffered re-injury. The minimum and maximum follow-up time was 25 and 56 months respectively. At the follow-up, physical examination showed full range of passive and active motion of the knee compared to contralateral in all the patients. No growth plate disturbance with leg length in equality, malalignment or other post-operative complications were observed. Knee stability was evaluated using Lachman, anterior drawer, and pivot-shift tests and KT-1000™. A grade 1 Lachman test, positive anterior drawer test and grade 1 pivot-shift test were observed in one patient; other patients showed negative Lachman and anterior drawer test with a nearly normal pivot-shift test (grade 1, glide) compared with the contralateral knee. KT-1000™ testing revealed a mean manual maximum side-to-side difference of 3 mm ± 0.7 (range two to four millimeters) (Table 2), and the mean score from one-leg hop tests was 94.8% (range 86.5 to 102.0%). On MRIs obtained at last follow-up (minimum 25 months), all patients showed ACL ligaments anatomically reinserted to the femoral footprint with normal signal intensity. All patients showed open symmetric tibial physis without any chondral or meniscal lesions (Figure 7). During these assessments, all the patients described their knees as normal. The results of the subjective IKDC questionnaire was 93.3% (range 67.81 to 95.0%). The mean Lysholm score at the time of follow-up was 93.6 of 100 (range 68 to 100). Considering Tegner Activity scores, four patients have returned to their pre-injury level of daily activity and athletic participation; in only
46 patients Tanner 1-2 with ACL deficency (2007-2010)
Did not meet inclusion criteria: -Tibial eminence fracture (8) - Not proximal ACL tears (19) -Associated femoral or tibial Salter Harris fracture (3) - Refused surgery (5) - Multilementous lesions (3)
- Partial ACL tears (2) -Inadeguate ACL tissue quality (1)
Patients included (5)
Figure 6. Flow chart with inclusion and exclusion of Tanner stages 1–2 patients with ACL deficiency.
Please cite this article as: Bigoni M, et al, Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surg..., Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.017
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Table 1 Table 1 shows age, sex, injured site, injury mechanism, time to surgery from injury, and associated lesion to ACL injury. Patient
Age
Sex
Injured side
Injury mechanism
Time to surgery (days)
Follow-up time (months)
Intra-articular associated injury
1 2 3 4 5
10 10 9 9 8
M M M F M
Right Left Right Right Left
With-contact With-contact Without-contact Without-contact Without-contact
78 119 70 123 15
56 50 35 25 56
None None None None None
one patient had the Tegner activity score decreased from six pre-injury to four after surgery. Our youngest patient, who underwent ACL reinsertion at the age of eight, displayed the best clinical and subjective results at five-years of follow-up. 5. Discussion Anterior cruciate ligament (ACL) tears in children, which are increasingly common, present difficult treatment decisions due to the risk of long-bone growth disturbance associated with varied reconstructive techniques. Moreover, prompt implementation of restorative intervention is especially important as delaying surgical reconstruction until skeletal maturity requires unrealistically stringent activity restrictions in an attempt to prevent giving-way episodes and resultant meniscal or chondral damage [25,26]. Consequently, a more effective and reliable surgical technique is needed to restore function accompanied by minimal risk of growth disruption. In response, we currently present the technique of arthroscopic ACL femoral reinsertion with a bioabsorbable anchor as a viable restorative treatment in skeletally immature individuals (Tanner stages 1 and 2) with proximal avulsion tears with adequate stump tissue. Patients in our study showed mean side-to-side difference of three millimeters. As well as in other reports, all patients in this study returned to pre-injury levels of sport activity and showed good to excellent results in the Lysholm, IKDC and one-leg hop tests [18,27]. None of the patients in the study developed any axial deviation or leg length discrepancies. Long-standing ACL reconstructive techniques provide good, but variable, results and are accompanied by disadvantages including angular deviation, leg length discrepancy, and non-anatomical reconstruction [15,16]. More recent techniques that use soft tissue grafts and drill smaller holes have reduced major growth complications in the last decade, but there is no consensus on the surgical technique to be used in the case of patients in Tanner stages 1 and 2 with ACL-deficient knees [27,28]. There have been numerous studies describing physeal-sparing techniques in ACL reconstruction. Preservation of femoral physes have been previously regarded as an over the top technique [29,30] as have techniques using physeal-sparing tunnels [16,31]. Furthermore, in the preservation of tibial physes, ACL reconstruction could be performed with the transplant placed either over the front position under the intermeniscal ligament or through an epiphyseal tibial tunnel without perforating the growth plate [30,32]. A recent meta-analysis by Frosch et al. evaluates the clinical outcomes and risks of ACL surgery in skeletally immature patients. Oddly, according to their analysis, physeal-sparing techniques are associated with a higher risk of postoperative leg length differences or axis deviations than surgical approaches violating the growth plate. They confirmed also that ACL suturing does not result in any growth disturbance [33]. Anatomical physeal-sparing techniques utilize different sources of transplants; however, graft tissues can be stretched and may not follow knee growth, especially in younger patients who have significant growth potential [34]. One of the earliest techniques to treat ACL tears without reconstruction is ACL suture repair, described for the first time by Robson in 1903 [35]. ACL repair was used particularly in the 1970s and 1980s, with different techniques characterized by arthrotomy, drill holes for suture repair, and long post-operative cast immobilization [9]. Long-term clinical follow-up reported a high failure rate in patients treated with open primary repair. Poor results in approximately 30% of patients, a side-to-side difference with KT-1000 N5 mm in 21% of patients, and high rates of ACL revision surgery (13% to 24%) led to primary ACL repair being considered an unacceptable technique, and this technique was put aside for ACL reconstruction [9,11,36–38]. DeLee and Curtis evaluated the cases of three patients younger than 14 years with mid-substance tears of the ACL; all three of them were treated by primary surgical repair without augmentation procedures. During follow-up examinations they showed moderate degrees of clinical ACL laxity. The authors suggested that mid-substance ACL injuries in children have no better healing potential than in adults [39]. Likewise Engebretsen et al. performed a non-arthroscopic Palmer or Marshall suture technique in eight Table 2 Table 2 summarizes KT-1000™ side-to-side difference, knee evaluation, One-leg hop test at medical examination time. Patient
KT-1000™ (mm)
Pivot shift
Leg alignment/length discrepancy
One-leg hop test
ROM
1
3
Glide +
≥90% (ACL 150 cm/normal 146 cm)
0–130
2 3 4 5
4 2 3 3
Glide + Glide + Glide + Glide +
Valgus bilateral, recurvatum 10° bilateral, no length discrepancy Normal alignment no length discrepancy Normal alignment, no length discrepancy Normal alignment, recurvatum 10°, no length discrepancy Valgus bilateral, bilateral, no length discrepancy
≥90% (ACL 139 cm/normal 140 cm) 89% ≥ × ≥ 76% (ACL 109 cm/normal 126 cm) 0,86 ≥90% (ACL 81 cm/normal 89 cm) 0,91 ≥90% (ACL 134 cm/normal 139 cm) 0,96
0–130 0–130 0–130 0–130
Please cite this article as: Bigoni M, et al, Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surg..., Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.017
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Figure 7. Sagittal T1-weighted (A), sagittal T2-weighted (B) and coronal T2-weighted (C) MRI show open physes and a continuous ACL after the ACL femoral reinsertion.
adolescents with proximal or mid-substance ACL tears; they were followed three to eight years after surgery and five of them were found unstable. They concluded that the Palmer–Marshall technique should not be used in children and adolescents [40]. Moreover Pressman et al. analyzed 42 children between the ages of six and 17 years, subdivided among three subgroups (conservative, primary repair, reconstruction). Six of them were treated by primary repair with a follow-up of 5.3 years (two to 13 years). Comparison between primary-suture and intra-articular reconstructions showed a trend that indicated better results in the reconstructive group. A concern of the authors was that they have not generated sufficient statistical-power with this study to determine optimal treatment [41]. Another study was conducted by Arnd et al. describing 76 children up to age 16 with knee injuries; a group of 13 intra-ligamentous ACL-ruptures were treated with suture (eight patients) and with patellar ligaments plasty (five patients). They showed poor clinical and objective outcomes during 6.3 years of follow-up after the surgery (three to 10 years). This group was not homogeneous regarding age, type of ACL tears or repair techniques. Cast immobilization was used for six to eight weeks, and as a consequence, the authors concluded that pain and immobilization caused a marked malfunction of the sensorimotor system, only partially remediated with intensive physiotherapy [42]. Attmanspacher et al., between 1994 and 2000, surgically-treated 45 patients with open physes and ACL deficiency. Of 45 patients, seven with intra-ligamentous rupture underwent ACL suture with a Marshall technique; in this subgroup of patients, the authors found poor clinical and functional outcomes and for these reasons they could no longer recommend it and identified it as obsolete. They did not discriminate intra-ligamentous proximal tears from mid-substance ACL tears, and acute-from chronictears (three days to two years) thereby confounding any further conclusions [43]. Nevertheless it has to be considered that some of these works were conducted more than 25 years ago [39–41]. Since then, there has been a revolution in (i) available diagnostic technologies, (ii) surgical techniques, and (iii) rehabilitative treatments whose implementation may substantially improve ACL repair outcomes [18,30,44,45]. Steadman et al. developed the concept of ACL “healing response” and showed very good clinical outcomes in skeletally immature patients with a proximal ACL tear [19]. A critical technological development assisting precise anatomical diagnoses in humans has been the advent of high quality MRI which permits identification of this type of lesion. This improvement in imaging, combined with improvements in arthroscopic surgical techniques, has resulted in improved outcomes for primary ACL repair in proximal tears and has led us to reconsider primary ACL repair as a clinical choice, especially if it is performed in skeletally immature patients with a strong biological healing response [12,46]. A more recent systematic review showed that a subclass of patients achieved acceptable to good long-term results, stressing the importance of considering: (i) a concomitant knee injury, (ii) the age of the patient, and most importantly, (iii) ACL tear pattern and location [14]. Sherman et al. correlated poor post-operative outcomes with mid-substance ACL tears treated with primary repair, and observed that ACL proximal lesions presented improved outcomes [12]. Moreover, Genelin et al. reported a side-toside difference of three millimeters with KT-1000 in 81% patients with isolated proximal ACL lesion treated with acute open proximal ACL reinsertion at a five to seven years of follow-up [13]. Gaulrapp and Haus reported good clinical results without growth defects in five skeletally immature patients with proximal ACL avulsion tears treated with open suture ACL repair [47]. It is now acknowledged that primary ACL repair in selected patient groups is an effective treatment, and novel techniques have been proposed [14,48–50]. Nguyen et al. analyzed the histological features of the spontaneous reattachment of the remnant of the human ACL to the posterior cruciate ligament and concluded that the proximal ACL presents high intrinsic healing response [51]. Notably, DiFelice et al. presented a new arthroscopic suture anchor primary ACL repair in a selected subgroup of patients with proximal avulsion ACL tear that maintains excellent tissue quality. They presented very good short-term results with seven of eight patients showing a side-to-side difference of less than three millimeters on KT-1000 maximum manual testing [18]. According to DiFelice our good short-term clinical results may be dependent on the strict selection of the study population and ACL lesion pattern. We considered this technique a valid option in skeletally immature patients not only to decrease surgery-related physeal growth plate damage, but also for the high ACL cellular activity in this population [52]. ACL healing in skeletally immature animal models occurs at a higher frequency than in adolescent and adult animals, due to the presence of a greater cell density and cellular migration potential in the ACL wound site of immature animals [53,54]. In an ACL transection model, Murray et al. observed that juvenile pigs presented a more productive repair response to ACL lesion than older animals [55]. The ACL repair tissue of juvenile animals presented a higher maximum load and stiffness with greater cellular density than the adults. The high repair Please cite this article as: Bigoni M, et al, Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surg..., Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.017
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capacity of intrinsic ACL cells in these populations may be a key to the success of the ACL suture repair of proximal ACL lesions. Nevertheless more studies about biochemical environment in pediatric traumatic knee lesions are required [56,57]. Recently Smith et al. described the interesting cases of three pediatric patients, in which two showed a femoral peel-off tear treated arthroscopically with a repair and a temporary internal bracing. The internal brace consisted of non-absorbable braided tape loaded onto a suspensory cortical fixation device; a bioabsorbable suture anchor screw was used to secure the distal end of the internal brace within the tibial metaphysis. The internal bracing was electively removed after three months. The authors documented good short-term clinical outcomes with excellent arthroscopical reports at three months [45]. By extension, the ACL femoral reinsertion with a bioabsorbable anchor as we describe herein should be considered an attractive solution; it has the advantage of being a simple and reproducible technique, and there is no second surgery needed to remove any device. We need more studies about the mechano-biological and pathophysiological proprieties of the proximal ACL treated with anchor reinsertion in skeletally immature models in comparison to bio-enhanced repair and other techniques in order to understand its potential in primary ACL. The functional ACL healing of skeletally immature animals leads us to consider Tanner stages 1 and 2 patients as the ideal population for this type of treatment. However, future studies should be conducted to understand the influence of age in proximal ACL reinsertions. Primary repair using bioabsorbable anchor respects the physes and the biology of the tissue necessary to repair an ACL interruption. Indeed, reinsertion permits the preservation of the native biology of the ligament and ACL cell populations without the interruption of blood supply and proprioceptive nerve endings. Various studies show that the tibial insertion of ACL includes the most mechanoreceptors and proprioceptive nerve fibers [58,59]. We believe that all ACL reconstruction techniques are more aggressive to these structures than preservation. Femoral reinsertion does not involve these anatomical structures and so, it could positively influence the balance and biomechanics of the knee, increasing the protection to the joint. This is a key point that has been considered in young active populations with ACL deficiency. Some limitations of our study should be noted. This is a retrospective study with a small cohort of patients and there is no comparison with patients treated in an alternative way although there may be ethical barriers to withholding potentially more effective treatment paradigms. Notwithstanding, our present aim is to describe preliminary results in a strictly selected group of patients. Lastly, patients were followed up in the short-term. In the face of potentially discouraging clinical results at midterm and long-term of open primary ACL repair, a longer follow-up is required. We suggest prospective studies with a larger cohort of patients and mid-term to long-term follow-up to consider this technique the recommendable treatment for this subgroup of immature patients with ACL tear. 6. Conclusion Arthroscopic ACL femoral reinsertion with a bioabsorbable anchor in Tanner stages 1 and 2 patients with proximal avulsion tears with adequate stump tissues showed good short-term results without physeal growth disturbances and maintaining the native ACL tissue. Acknowledgments The authors thank Dr. Robert J. Omeljaniuk for his assistance with the manuscript review. The authors declare that they have no conflict of interest or funding. 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Please cite this article as: Bigoni M, et al, Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surg..., Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.017
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Please cite this article as: Bigoni M, et al, Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surg..., Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.017
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The Knee
Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surgical technique and preliminary results Marco Bigoni, Diego Gaddi, Massimo Gorla, Daniele Munegato, Marco Pungitore, Massimiliano Piatti, Marco Turati ⁎ Orthopedic Department, San Gerardo Hospital, Via Pergolesi 33, 20900 Monza, Italy
a r t i c l e
i n f o
Article history: Received 3 November 2015 Received in revised form 14 September 2016 Accepted 16 September 2016 Available online xxxx Keywords: Anterior cruciate ligament Arthroscopic fixation Open physes Pediatric Sport injury
a b s t r a c t Background: Anterior cruciate ligament (ACL) tears in children are increasingly common and present difficult treatment decisions due to the risk of growth disturbance. Although open primary ACL repair was abandoned in the historical literature, recent studies have suggested that there is a role for arthroscopic primary repair in patients with proximal tears. Methods: This is a retrospective review of five consecutive patients aged 9.2 years (range 8 to 10) who underwent suture anchor ACL reinsertion. Patients were included if they were Tanner stages 1–2 and proximal ACL tears with adequate tissue quality confirmed arthroscopically. The time frame was 81 days. Arthroscopic ACL reinsertion was performed with bioabsorbable suture anchor. Clinical evaluation, KT-1000™, and MRI were re-evaluated. Clinical outcomes were measured using International Knee Documentation Committee (IKDC), Lysholm and Tegner activity score. Results: At a mean follow-up of 43.4 months (range 25 to 56), no re-injury and leg length discrepancies were observed. Four patients had negative Lachman tests. The remainder had a grade 1 Lachman test. The mean side-to-side difference was 3 (2–4 mm). In MRI obtained at the last follow-up, no articular lesions or growth arrest were observed and the reinserted ACL was recognized in every exam. All patients returned to previous level of activity and presented normal and nearly normal IKDC score. The mean Lysholm score was 93.6. Conclusion: Arthroscopic ACL repair can achieve good short-term results with joint stability and recovery of sport activity in skeletally immature patients, with proximal ACL avulsion tear. © 2016 Elsevier B.V. All rights reserved.
1. Introduction Anterior cruciate ligament (ACL) tears are increasingly more common among children and adolescents [1]. To illustrate, ACL tears comprise 6.7% of all injuries and 30.8% of all knee injuries in pediatric and adolescent soccer players aged five to 18 [2]. The history of ACL rupture treatment in skeletally immature individuals is controversial. Non-surgical (conservative) management is associated with increased occurrence of new meniscal or cartilage injuries, reduced stability, and lower physical activity levels in comparison with surgical treatment [3–6]. Surgical management, on the other hand, restores knee stability and offers the
⁎ Corresponding author. E-mail address: [email protected] (M. Turati).
http://dx.doi.org/10.1016/j.knee.2016.09.017 0968-0160/© 2016 Elsevier B.V. All rights reserved.
Please cite this article as: Bigoni M, et al, Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surg..., Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.017
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possibility of maintaining comparable activity levels. This intervention is advantageous in younger patients who are noncompliant with bracing, and are intolerant of reduced physical activity [3,7,8]. However, a historical analysis of ACL open repair revealed an unacceptable failure rate [9–11]; thus, enthusiasm for this procedure waned. In order to parse-out factors contributing to this failure rate, Sherman et al. conducted an extensive subgroup analysis which included ACL tear type and tissue quality. They revealed better results in patients with proximal ACL avulsion tear and good tissue quality [12]. Genelin et al. subsequently employed this technique principally in proximal avulsion injury of ACL, and observed good mid-term results [13]. Nonetheless, both groups conducted open repairs and implemented long post-operative immobilization (six to eight weeks of long leg cast). In this context, a recent review of the literature showed that in a selected subset of patients, considering only proximal ACL tears, primary ACL repair could be reconsidered as an effective treatment [14]. However, it is the specific nature of surgical treatment in the skeletally immature, which can lead to growth disturbances with serious consequences such as angular deviation or leg shortening in up to 11% of cases [15,16]. These risks are especially apparent in patients in Tanner stages 1 and 2, who have higher growth potential and consequently have a higher risk of major limb growth disturbance compared with patients with closed physes [17]. In response to this confounding problem, novel surgical interventions have been attempted in order to mitigate physeal growth disruption. First, a novel minimally invasive arthroscopic ACL repair with suture anchor achieved short-term clinical success in a carefully selected adult population with proximal ACL avulsion and excellent tissue quality of the stump [18]. Secondly, Steadman et al. performed arthroscopic holes in the femoral ACL footprint to induce a “healing response” in selected skeletally immature patients. Although “healing response” should not be considered a repair technique, the good clinical outcomes in these pediatric patients with a proximal ACL tear lead us to consider children as the ideal candidates for arthroscopic suture anchor ACL repair [19]. The aim of this study is to describe a variation in the previously described suture anchor repair [24] to treat proximal ACL tears in the skeletally immature patients, and to evaluate the clinical and subjective results in the short-term follow-up.
2. Materials and methods This is a retrospective review and early follow-up of five consecutive skeletally immature patients (four boys and one girl) with proximal ACL tears that underwent arthroscopic ACL femoral reinsertion with a bioabsorbable anchor by the senior surgeon (M.B.) in our center between 2007 and 2010 (Figure 1). Children with a clinical ACL deficiency underwent knee radiographs and magnetic resonance imaging (MRI) to exclude spine avulsion and fracture and to recognize a proximal ACL avulsion (Figure 2). Indications for primary repair of the ACL included: (i) a primary proximal ACL lesion confirmed clinically and identified on MRI, (ii) any patient with open growth plates with a Tanner stage 1 or stage 2, (iii) informed consent signed by both parents, and (iv) an arthroscopic intraoperative confirmation of the adequate tissue quality and quantity of the ACL stump to perform the ACL reinsertion. In the presence of inadequate tissue, ACL reinsertion was converted to ACL reconstruction or conservative treatment according to parental consent. Exclusion criteria included any indications of: (i) ACL mid-substance or distal ruptures, (ii) spine avulsion, (iii) intra-epiphyseal growth disturbances, (iv) multi-ligament injury patterns (≥3 ligaments involved), and (v) any previous surgical interventions on the limb under consideration for treatment.
Figure 1. Principle of the ACL femoral reinsertion with a bioabsorbable anchor.
Please cite this article as: Bigoni M, et al, Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surg..., Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.017
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Figure 2. T1-weighted sagittal MRI of a left knee with a proximal avulsion ACL tear in an eight-year old patient.
Patients were evaluated post-surgically by clinical evaluation of limb alignment and length, ligament stability, and bilateral instrumented ligament examination using the KT-1000™ knee arthrometer, applying 134-N of force (MEDmetric® Corporation, San Diego, California). Ligament stability was measured by Lachman test, anterior drawer, and pivot-shift test. Lachman grades of laxity were as follows: grade 0 (anterior tibial translation b 3 mm), grade 1 (three to five millimeters), grade 2 (five to 10 mm) and grade 3 (N 10 mm) [20]. Pivot-shift test was graded as negative (grade 0), glide (1), clunk (2), or gross (3) according to the International Knee Documentation Committee (IKDC) classification. One-leg hop test was used for functional assessment. All patients were revaluated after a follow-up period of at least two years with a Knee MRI. Clinical outcomes were measured using IKDC score, Lysholm score and Tegner activity scale [21–23]. Post-operative evaluations were performed by an independent examiner. All patients' parents provided a written informed consent in agreement with the protocol approved by the local ethics committee and conforming to the principles outlined in the World Medical Association Declaration of Helsinki. All data are expressed as mean ± standard deviation.
3. Surgical technique The patient, under general anesthesia, was placed in a supine position and a three-portal diagnostic arthroscopy was performed. We confirmed proximal ACL lesion and determined suitability of the ACL stump for reinsertion. A preparation of the femoral footprint with minimal debridement of soft tissue was performed to allow adequate visualization of the original isometric femoral insertion and obtain a bleeding bony bed. An accessory medial or transpatellar tendon access was performed to facilitate management and ligament repair. A spinal needle (18 gauge, 3.50 in.) was inserted through the anteromedial portal, and residual ACL tissue was transfixed in the proximal extremity of the stump (Figure 3). Great care was taken for the needle transfixion to pass through the center of the ACL diameter. A polydioxanone (PDS) 2–0 (Ethicon, Sommerville, NJ, USA) was then passed through the needle. Once the PDS was captured from the transpatellar tendon access, the surgeon with the probe put the ACL under tension towards the original femoral footprint, testing the reliability of correct and isometric reinsertion with the knee at 90° of flexion. Panaloc (3.5 mm, DePuyMitek, MA, USA) was then inserted into the joint through the anteromedial portal and fixed on the lateral femoral condyle in the femoral ACL footprint after appropriate drilling with the knee flexed at 90° (Figure 4). At this time, the posterior Panacril 2–0 was passed through the ACL using the PDS 2–0 previously prepared as a shuttle relay. The ACL was then re-approximated to the original position, tightened, and fixed with the knee at 90°. We used at first, a unique sliding knot with a self-looking loop as previously described (Samsung Medical Centre (SMC) knot) and secured it with two simple knots (Figure 5) [24]. To facilitate suture passage, we used a threaded clear cannula with obturator (DePuyMitek, MA, USA) in the anteromedial portal. After cutting the Panacril extremities, the joint's full range of motion and the absence of visual gap between the ACL stump and femoral footprint were verified. The tension and stiffness of the repaired ACL were confirmed with a probe and an intraoperative Lachman test was performed. Post-operatively, a fulltime long leg splint was applied for four weeks. Then, after the splint removal, weight bearing was allowed using a hinged knee brace for eight weeks with a gradual increase of range of motion. Rehabilitation protocol begins four weeks after surgery and includes knee motion exercises, isometric quadriceps activation, reinforcement training of the hamstrings, closed chain exercises, pool therapy, and proprioception exercises under physiotherapist guidance. After three to four Please cite this article as: Bigoni M, et al, Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surg..., Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.017
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Figure 3. Arthroscopic view of proximal ACL avulsion type lesion during transfixion with the spinal needle.
months from surgery, the patients start straight-line jogging, open chain and plyometric exercises. Cutting sports are allowed after six to seven months after surgery.
4. Results We evaluated 46 Tanner stages 1–2 patients with ACL deficiency between 2007 and 2010, for potential inclusion in this study. Forty-one patients were excluded based on inclusion and exclusion criteria. We included only those patients in the study with clinical, X-rays, MRI and arthroscopy confirmed proximal ACL tears. Eight patients underwent surgery, three of whom were excluded from the study on the basis of the quality of their ACL tissue (two partial ACL tears and one inadequate ACL tissue quality). These patients were treated conservatively. Figure 6 shows the flowchart of our series. The five patients who met the inclusion and exclusion criteria (four boys and one girl) had an age of 9.2 (range: eight to 10 years). Three patients had injuries in their right knee and two in their left knee. All patients sustained an identified sport-related knee injury (Table 1). All X-rays showed tibial and femoral open growth plates without intra-epiphyseal growth disturbances. The MRI showed isolated proximal ACL tears with no associated injuries. The time for surgery was less than four months for all patients with a mean time to surgery of 81 days (range 15 to 123 days).
Figure 4. Arthroscopic view of the lateral femoral condyle after the insertion of the anchor.
Please cite this article as: Bigoni M, et al, Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surg..., Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.017
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Figure 5. Arthroscopic view of the reinsertion of the ACL in anatomic position before the cutting of the knot.
Proximal ACL lesion with an adequate quality of the ACL stump was confirmed by arthroscopy; no meniscal or cartilage lesions were recorded. Suture anchor ACL repair was performed without intraoperative complications in all patients. Patients were followed up at 43.4 ± 14.82 months after surgery and none of them had suffered re-injury. The minimum and maximum follow-up time was 25 and 56 months respectively. At the follow-up, physical examination showed full range of passive and active motion of the knee compared to contralateral in all the patients. No growth plate disturbance with leg length in equality, malalignment or other post-operative complications were observed. Knee stability was evaluated using Lachman, anterior drawer, and pivot-shift tests and KT-1000™. A grade 1 Lachman test, positive anterior drawer test and grade 1 pivot-shift test were observed in one patient; other patients showed negative Lachman and anterior drawer test with a nearly normal pivot-shift test (grade 1, glide) compared with the contralateral knee. KT-1000™ testing revealed a mean manual maximum side-to-side difference of 3 mm ± 0.7 (range two to four millimeters) (Table 2), and the mean score from one-leg hop tests was 94.8% (range 86.5 to 102.0%). On MRIs obtained at last follow-up (minimum 25 months), all patients showed ACL ligaments anatomically reinserted to the femoral footprint with normal signal intensity. All patients showed open symmetric tibial physis without any chondral or meniscal lesions (Figure 7). During these assessments, all the patients described their knees as normal. The results of the subjective IKDC questionnaire was 93.3% (range 67.81 to 95.0%). The mean Lysholm score at the time of follow-up was 93.6 of 100 (range 68 to 100). Considering Tegner Activity scores, four patients have returned to their pre-injury level of daily activity and athletic participation; in only
46 patients Tanner 1-2 with ACL deficency (2007-2010)
Did not meet inclusion criteria: -Tibial eminence fracture (8) - Not proximal ACL tears (19) -Associated femoral or tibial Salter Harris fracture (3) - Refused surgery (5) - Multilementous lesions (3)
- Partial ACL tears (2) -Inadeguate ACL tissue quality (1)
Patients included (5)
Figure 6. Flow chart with inclusion and exclusion of Tanner stages 1–2 patients with ACL deficiency.
Please cite this article as: Bigoni M, et al, Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surg..., Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.017
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Table 1 Table 1 shows age, sex, injured site, injury mechanism, time to surgery from injury, and associated lesion to ACL injury. Patient
Age
Sex
Injured side
Injury mechanism
Time to surgery (days)
Follow-up time (months)
Intra-articular associated injury
1 2 3 4 5
10 10 9 9 8
M M M F M
Right Left Right Right Left
With-contact With-contact Without-contact Without-contact Without-contact
78 119 70 123 15
56 50 35 25 56
None None None None None
one patient had the Tegner activity score decreased from six pre-injury to four after surgery. Our youngest patient, who underwent ACL reinsertion at the age of eight, displayed the best clinical and subjective results at five-years of follow-up. 5. Discussion Anterior cruciate ligament (ACL) tears in children, which are increasingly common, present difficult treatment decisions due to the risk of long-bone growth disturbance associated with varied reconstructive techniques. Moreover, prompt implementation of restorative intervention is especially important as delaying surgical reconstruction until skeletal maturity requires unrealistically stringent activity restrictions in an attempt to prevent giving-way episodes and resultant meniscal or chondral damage [25,26]. Consequently, a more effective and reliable surgical technique is needed to restore function accompanied by minimal risk of growth disruption. In response, we currently present the technique of arthroscopic ACL femoral reinsertion with a bioabsorbable anchor as a viable restorative treatment in skeletally immature individuals (Tanner stages 1 and 2) with proximal avulsion tears with adequate stump tissue. Patients in our study showed mean side-to-side difference of three millimeters. As well as in other reports, all patients in this study returned to pre-injury levels of sport activity and showed good to excellent results in the Lysholm, IKDC and one-leg hop tests [18,27]. None of the patients in the study developed any axial deviation or leg length discrepancies. Long-standing ACL reconstructive techniques provide good, but variable, results and are accompanied by disadvantages including angular deviation, leg length discrepancy, and non-anatomical reconstruction [15,16]. More recent techniques that use soft tissue grafts and drill smaller holes have reduced major growth complications in the last decade, but there is no consensus on the surgical technique to be used in the case of patients in Tanner stages 1 and 2 with ACL-deficient knees [27,28]. There have been numerous studies describing physeal-sparing techniques in ACL reconstruction. Preservation of femoral physes have been previously regarded as an over the top technique [29,30] as have techniques using physeal-sparing tunnels [16,31]. Furthermore, in the preservation of tibial physes, ACL reconstruction could be performed with the transplant placed either over the front position under the intermeniscal ligament or through an epiphyseal tibial tunnel without perforating the growth plate [30,32]. A recent meta-analysis by Frosch et al. evaluates the clinical outcomes and risks of ACL surgery in skeletally immature patients. Oddly, according to their analysis, physeal-sparing techniques are associated with a higher risk of postoperative leg length differences or axis deviations than surgical approaches violating the growth plate. They confirmed also that ACL suturing does not result in any growth disturbance [33]. Anatomical physeal-sparing techniques utilize different sources of transplants; however, graft tissues can be stretched and may not follow knee growth, especially in younger patients who have significant growth potential [34]. One of the earliest techniques to treat ACL tears without reconstruction is ACL suture repair, described for the first time by Robson in 1903 [35]. ACL repair was used particularly in the 1970s and 1980s, with different techniques characterized by arthrotomy, drill holes for suture repair, and long post-operative cast immobilization [9]. Long-term clinical follow-up reported a high failure rate in patients treated with open primary repair. Poor results in approximately 30% of patients, a side-to-side difference with KT-1000 N5 mm in 21% of patients, and high rates of ACL revision surgery (13% to 24%) led to primary ACL repair being considered an unacceptable technique, and this technique was put aside for ACL reconstruction [9,11,36–38]. DeLee and Curtis evaluated the cases of three patients younger than 14 years with mid-substance tears of the ACL; all three of them were treated by primary surgical repair without augmentation procedures. During follow-up examinations they showed moderate degrees of clinical ACL laxity. The authors suggested that mid-substance ACL injuries in children have no better healing potential than in adults [39]. Likewise Engebretsen et al. performed a non-arthroscopic Palmer or Marshall suture technique in eight Table 2 Table 2 summarizes KT-1000™ side-to-side difference, knee evaluation, One-leg hop test at medical examination time. Patient
KT-1000™ (mm)
Pivot shift
Leg alignment/length discrepancy
One-leg hop test
ROM
1
3
Glide +
≥90% (ACL 150 cm/normal 146 cm)
0–130
2 3 4 5
4 2 3 3
Glide + Glide + Glide + Glide +
Valgus bilateral, recurvatum 10° bilateral, no length discrepancy Normal alignment no length discrepancy Normal alignment, no length discrepancy Normal alignment, recurvatum 10°, no length discrepancy Valgus bilateral, bilateral, no length discrepancy
≥90% (ACL 139 cm/normal 140 cm) 89% ≥ × ≥ 76% (ACL 109 cm/normal 126 cm) 0,86 ≥90% (ACL 81 cm/normal 89 cm) 0,91 ≥90% (ACL 134 cm/normal 139 cm) 0,96
0–130 0–130 0–130 0–130
Please cite this article as: Bigoni M, et al, Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surg..., Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.017
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Figure 7. Sagittal T1-weighted (A), sagittal T2-weighted (B) and coronal T2-weighted (C) MRI show open physes and a continuous ACL after the ACL femoral reinsertion.
adolescents with proximal or mid-substance ACL tears; they were followed three to eight years after surgery and five of them were found unstable. They concluded that the Palmer–Marshall technique should not be used in children and adolescents [40]. Moreover Pressman et al. analyzed 42 children between the ages of six and 17 years, subdivided among three subgroups (conservative, primary repair, reconstruction). Six of them were treated by primary repair with a follow-up of 5.3 years (two to 13 years). Comparison between primary-suture and intra-articular reconstructions showed a trend that indicated better results in the reconstructive group. A concern of the authors was that they have not generated sufficient statistical-power with this study to determine optimal treatment [41]. Another study was conducted by Arnd et al. describing 76 children up to age 16 with knee injuries; a group of 13 intra-ligamentous ACL-ruptures were treated with suture (eight patients) and with patellar ligaments plasty (five patients). They showed poor clinical and objective outcomes during 6.3 years of follow-up after the surgery (three to 10 years). This group was not homogeneous regarding age, type of ACL tears or repair techniques. Cast immobilization was used for six to eight weeks, and as a consequence, the authors concluded that pain and immobilization caused a marked malfunction of the sensorimotor system, only partially remediated with intensive physiotherapy [42]. Attmanspacher et al., between 1994 and 2000, surgically-treated 45 patients with open physes and ACL deficiency. Of 45 patients, seven with intra-ligamentous rupture underwent ACL suture with a Marshall technique; in this subgroup of patients, the authors found poor clinical and functional outcomes and for these reasons they could no longer recommend it and identified it as obsolete. They did not discriminate intra-ligamentous proximal tears from mid-substance ACL tears, and acute-from chronictears (three days to two years) thereby confounding any further conclusions [43]. Nevertheless it has to be considered that some of these works were conducted more than 25 years ago [39–41]. Since then, there has been a revolution in (i) available diagnostic technologies, (ii) surgical techniques, and (iii) rehabilitative treatments whose implementation may substantially improve ACL repair outcomes [18,30,44,45]. Steadman et al. developed the concept of ACL “healing response” and showed very good clinical outcomes in skeletally immature patients with a proximal ACL tear [19]. A critical technological development assisting precise anatomical diagnoses in humans has been the advent of high quality MRI which permits identification of this type of lesion. This improvement in imaging, combined with improvements in arthroscopic surgical techniques, has resulted in improved outcomes for primary ACL repair in proximal tears and has led us to reconsider primary ACL repair as a clinical choice, especially if it is performed in skeletally immature patients with a strong biological healing response [12,46]. A more recent systematic review showed that a subclass of patients achieved acceptable to good long-term results, stressing the importance of considering: (i) a concomitant knee injury, (ii) the age of the patient, and most importantly, (iii) ACL tear pattern and location [14]. Sherman et al. correlated poor post-operative outcomes with mid-substance ACL tears treated with primary repair, and observed that ACL proximal lesions presented improved outcomes [12]. Moreover, Genelin et al. reported a side-toside difference of three millimeters with KT-1000 in 81% patients with isolated proximal ACL lesion treated with acute open proximal ACL reinsertion at a five to seven years of follow-up [13]. Gaulrapp and Haus reported good clinical results without growth defects in five skeletally immature patients with proximal ACL avulsion tears treated with open suture ACL repair [47]. It is now acknowledged that primary ACL repair in selected patient groups is an effective treatment, and novel techniques have been proposed [14,48–50]. Nguyen et al. analyzed the histological features of the spontaneous reattachment of the remnant of the human ACL to the posterior cruciate ligament and concluded that the proximal ACL presents high intrinsic healing response [51]. Notably, DiFelice et al. presented a new arthroscopic suture anchor primary ACL repair in a selected subgroup of patients with proximal avulsion ACL tear that maintains excellent tissue quality. They presented very good short-term results with seven of eight patients showing a side-to-side difference of less than three millimeters on KT-1000 maximum manual testing [18]. According to DiFelice our good short-term clinical results may be dependent on the strict selection of the study population and ACL lesion pattern. We considered this technique a valid option in skeletally immature patients not only to decrease surgery-related physeal growth plate damage, but also for the high ACL cellular activity in this population [52]. ACL healing in skeletally immature animal models occurs at a higher frequency than in adolescent and adult animals, due to the presence of a greater cell density and cellular migration potential in the ACL wound site of immature animals [53,54]. In an ACL transection model, Murray et al. observed that juvenile pigs presented a more productive repair response to ACL lesion than older animals [55]. The ACL repair tissue of juvenile animals presented a higher maximum load and stiffness with greater cellular density than the adults. The high repair Please cite this article as: Bigoni M, et al, Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surg..., Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.017
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capacity of intrinsic ACL cells in these populations may be a key to the success of the ACL suture repair of proximal ACL lesions. Nevertheless more studies about biochemical environment in pediatric traumatic knee lesions are required [56,57]. Recently Smith et al. described the interesting cases of three pediatric patients, in which two showed a femoral peel-off tear treated arthroscopically with a repair and a temporary internal bracing. The internal brace consisted of non-absorbable braided tape loaded onto a suspensory cortical fixation device; a bioabsorbable suture anchor screw was used to secure the distal end of the internal brace within the tibial metaphysis. The internal bracing was electively removed after three months. The authors documented good short-term clinical outcomes with excellent arthroscopical reports at three months [45]. By extension, the ACL femoral reinsertion with a bioabsorbable anchor as we describe herein should be considered an attractive solution; it has the advantage of being a simple and reproducible technique, and there is no second surgery needed to remove any device. We need more studies about the mechano-biological and pathophysiological proprieties of the proximal ACL treated with anchor reinsertion in skeletally immature models in comparison to bio-enhanced repair and other techniques in order to understand its potential in primary ACL. The functional ACL healing of skeletally immature animals leads us to consider Tanner stages 1 and 2 patients as the ideal population for this type of treatment. However, future studies should be conducted to understand the influence of age in proximal ACL reinsertions. Primary repair using bioabsorbable anchor respects the physes and the biology of the tissue necessary to repair an ACL interruption. Indeed, reinsertion permits the preservation of the native biology of the ligament and ACL cell populations without the interruption of blood supply and proprioceptive nerve endings. Various studies show that the tibial insertion of ACL includes the most mechanoreceptors and proprioceptive nerve fibers [58,59]. We believe that all ACL reconstruction techniques are more aggressive to these structures than preservation. Femoral reinsertion does not involve these anatomical structures and so, it could positively influence the balance and biomechanics of the knee, increasing the protection to the joint. This is a key point that has been considered in young active populations with ACL deficiency. Some limitations of our study should be noted. This is a retrospective study with a small cohort of patients and there is no comparison with patients treated in an alternative way although there may be ethical barriers to withholding potentially more effective treatment paradigms. Notwithstanding, our present aim is to describe preliminary results in a strictly selected group of patients. Lastly, patients were followed up in the short-term. In the face of potentially discouraging clinical results at midterm and long-term of open primary ACL repair, a longer follow-up is required. We suggest prospective studies with a larger cohort of patients and mid-term to long-term follow-up to consider this technique the recommendable treatment for this subgroup of immature patients with ACL tear. 6. Conclusion Arthroscopic ACL femoral reinsertion with a bioabsorbable anchor in Tanner stages 1 and 2 patients with proximal avulsion tears with adequate stump tissues showed good short-term results without physeal growth disturbances and maintaining the native ACL tissue. Acknowledgments The authors thank Dr. Robert J. Omeljaniuk for his assistance with the manuscript review. The authors declare that they have no conflict of interest or funding. 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Please cite this article as: Bigoni M, et al, Arthroscopic anterior cruciate ligament repair for proximal anterior cruciate ligament tears in skeletally immature patients: Surg..., Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.017