Update on Rehabilitation Protocol Following ACL Reconstruction

Anterior cruciate ligament lessions represent one of the most frequently met injuries of the knee, determining pain and instability and having a decisive impact over the patients functional level and quality of life. Regardless whether or not the decision of surgical intervention is made, patients with ACL tear are at higher risk of developing osteoarthritis, long term disability and an increased risk of additional meniscus tear. Literature data, although it offers a suffi cient amount of information on the subject, still presents debates on the advantages of one rehabilitation program over another. Achieving maximal range of motion as soon as possible is a main objective in ACL injuries, restrictions of mobility leading to prolonged rehabilitation periods. The are also discussions on the benefi ts of using open versus closed kinetic chain exercises, and also to what extend can the rehabititation program be accelerated in order to return the knee to the pre-injury state. The rehabilitation program must contain a multimodal approach composed of not only adapted kinetotherapy programs, but also associated modalities such as cryotherapy, neuromuscular stimulation, use of braces or hydrokinetotherapy in order to reduce pain and effusion and increase range of motion. The purpose of the present material is to analysis the existing data on the subject, and to evaluate the therapeutic benefi t of the rehabilitation modalities used in ACL injuries.


RESULTS AND DISCUSSIONS
Although literature data off ers suffi cient information on the subject, we could not observ a developed consensus or a uniformed designed protocol regarding rehabilitation of ACL injuries.Numerous randomized controlled studies were found, but in some cases the methodological design of the studies was mixed, presenting bias information or incomplete data on the experimental design [18][19][20] .
Th e fi rst issue that generates debate in the literature regards the use open vs. closed kinetic chain exercises following ACL reconstruction, both techniques presenting advantages and disadvantages.Th e general tendency is to prefer the CKCE due to the fact that they are predominantly focused on increasing muscle strengh on the quadriceps, and improving coordination.Th erefor CKCE are considered to be safer because they do not increase the tensile strain on the ACL and so, reduce the risk of tibial displacement, while using open chain kinetic exercises for ACL rehabilitation might increase the anterior shear of the knee 21,22

BACKGROUND
Anterior cruciate ligament lessions represent one of the most frequently met injuries of the knee, with an increasing incidence depending on the statistics, most of them occuring in athletes or young adults [1][2][3][4][5] .Th e reconstruction of the anterior cruciate ligament can be obtained by using diff erent surgical procedures and varies according to the graft material that is used.Th e outcomes after ACL reconstruction is depended on both surgical and rehabilitation factors 6,7 .Th e decision of reconstruction is dictated by the patient's symptomatology, as well as the the patients functional level, and the degree of participation in diff erent activities.Regarless whether or not the decision of surgical intervention is made, patients with ACL tear are at a higher risk of developing osteoarthritis, long term disability and an increased risk of additional meniscus tear 8 .Injury of the ACL occurs mostly during dynamic activities, therfor any alteration in the biomechanics or muscular control of the knee increases the risk of an ACL injury 9 .
According to some authors, ACL lessions have a four to six times higher incidence in female compare to male athletes 10 .Additionally it is estimated that a large percent of the patients with an ACL reconstruction will suff er a reintervention or additional meniscus tear 11 .Th e role of the rehabilitation is decisive.Numerous authors have suggested the association of diff erent rehabilitation techniques in order to outline the necessity of a structured rehabilitation protocol [12][13][14] .Various protocols express the idea of early motion, due to the fact that prolonged immobilization can generate a number of complications after surgery and lenghten the rehabilitation period.Th e type of exercises must be adapted in order to off er the protection required by the graft.Although most of the attention is dedicated to strentghtening the quadriceps muscle, the rehabilitation program should take into consideration all the muscle involved, particularly the hamstring muscles 15,16 .Th e clinical evaluation has be focused also on the patient related factors, that might infl uence the postoperative evolution and the time needed for rehabilitation.In order for those objective to be obtained, a preoperative rehabilitation program must be initiated in order to further assess the patients clinical particularities and to better estimate the further outcomes of the postsurgical period 17 .Th e rehabilitation program must contain a multimodal approach composed of not only adapted kinetotherapy programs, but also associated modalities such as cryotherapy, neuromuscular stimulation, use of one of the main arguments for prefering closed kinetic chain exercises compared to OKCE 24 .
Other opinions on open vs closed kinetic chain exercises refer to the fact that closed kinetic chain exercises work mostly on the vasti muscles, while open kinetic chain exercises have a demanding eff ect on the rectus femoralis, and therfor allow more specifi c muscle strengthening due to an isolated muscle activity.On the other side, prolonged exercise will generate fatigue, which will put a destabilising risk for the ACL due to an isolated muscle strenghtening 25,26 .Closed kinetic chain exercises however, being mostly focused on the agonist muscles can not off er specifi c muscle strengthening, but can provide safer conditions for the ACL in case of fatigue.
Th e diff erences between the two remain to be discussed, especially because many of the daily activities can not be defi ned as open or closed chained, activities such as walking or stair climbing involving a combination of the two 27,28 .
Achieving maximal range of motion as soon as possible is a main objective in ACL injuries, restrictions of mobility leading to prolonged rehabilitation periods.Th ere are also separated opinions on the development of the rehabilitation program, some authors suggesting a prolonged immobilization in order to protect the graft and knee, while weight bearing should be avoided in order to prevent instability, other points of view implying early mobilisation and an accelerated rehabilitation that should start from the fi rst day postoperative in order to rapidly obtain full extension 29,30 .
Continuous passive motion following ACL reconstruction has been put into debate, whether it off er short or long term eff ects to the rehabilitation program.Most protocols propose the initialising of CPM early following surgery and continue upon four weeks postoperative, in order to protect the integrity of the repair and also to prevent de consequences of prolonged immobilization [31][32][33] .According to some authors initiating CPM immediatly after surgery reduces blood and oedema from the joint and the periarticular tissue, and so reduces the risk of post surgical joint stiff ness.However, in a review that included 7 randomized controlled studies and 465505 cases, 2 studies found no statistically signifi cant diff erences regarding joint laxity compared to the control group, while only 1 study found a signifi cantly greater active and passive knee fl exion in CPM patients.Th ere were no signifi cant diff erences between groups regarding pain, but 2 studies evidenced significant analgesy in the immediate postsurgery period for the CPM group.Th ere were no statistically signifi cant diff erences concerning swelling, joint position , blood drainage and complication between the two groups 34 .
Another matter of debate involves the aspect of restoring the operated knee to the pre-injury state, this leading to the idea of regaining bilateral knee symmetry.In order to obtain this, the evaluation of the patient and the rehabilitation program should begin pre-operatively and continue until complete knee symmetry is obtained post-surgery 35 .However, this results in the necessity of a close follow-up of the patient in order to evaluate long term eff ects of the surgical procedure.Pre interventional rehabilitation will initially start with reduction of pain, infl ammation and swelling of the involved limb, and continue with obtaining complete passive range of motion which is a key element to the entire rehabilitation protocol 36 .Once ROM and infl ammation are reduced, the rehabilitation program can continue with neuromuscular retraining.Also, an emphasis should be made on patient and family education regarding the purpose of the rehabilitation program, in order to gain a better adherence to the proposed objectives, and also to understand the postsurgical precautions regarding the state of the graft.Adherence to the rehabilitation programs is also important in gaining full functional level and reducing the reinjury rates 37,38 .Postoperative, ROM exercises should begin early in the fi rst phase after surgery in order to facilitate fl exion, which should be met at 120 degres after a maximum of 4 weeks, followed by a full symmetrical fl exion by the end of the 12 week 39 .
Another discussion involves weight-bearing, its progression being dictated depending on the surgical procedure and graft selection.Early weight bearing has been accepted to be benefi cial in reducing patellofemoral pain, and it also avoids the appearence of later complications such as arthrofi brosis.By most authors, weight bearing in the fi rst stage should be partial, with the use of crutches and subsequently progress according to the patients level of tolerance, allowing the joint to acclimate with increased loads 40 .
Plyometric exercises have been recommanted as part of rehabilitation protocol, with some reservations being present because of the high load on the lower extremity that could predjudice knee articular cartilage.No diff erences were observed between low and high intensity plyometric exercises by some authors, (Chmielewski  et al. 2016), both type of exercises inducing favorable eff ects on knee function and psychosocial factor 41 .Stationary bike could begin after 4 weeks with gradual rapy combined with dynamic intermitent compression which has been proposed as an alternative to permanent static compression, that could provide better tissue oxygenation, and better facilitate soft tissue exchanges, on the same time decreasing the risk of skin necrosis associated with static cryotherapy 48 .Despite the widespread use of cryotherapy, there are still diff erences of opinion in the literature concerning the eff ectiveness of its various application methods and the quantifi cation of variables such as frequency, duration and best time for use.Th e cryotherapy application time ranges between 10 and 20 minutes, from two to four times a day.In the systemic review concerning the application of ice, few studies evaluated the eff ectiveness of ice after injuries to the soft tissues and there was no evidence of the best method and duration of the treatment 46,49 .
A meta-analisis on the eff ectiveness of cryotherapy in ACL reconstruction included seven randomized controlled trials and 553 participants, in which pain levels were signifi cant reduced in two studies in favor of cryotherapy group, while the rest of the studies repoarted dicrete improvements.Only one study expressed a signifi cant reduction of drainage in favour of cryotherapy group, while minimal improvements were observed for range of motion.Due to the experimental design of the mentioned studies and the risk of bias which was observed, further studies need to be conducted in order create a better a unifi ed protocol and also to determine which parameter is better for increasing the eff ective use of cryotherapy 50 .
Aquatic therapy has been suggested as part of rehabilitation protocol for ACL reconstructions, yet only few studies have been developed in this direction.Hydrokinetotherapy could facilitate movement and improve circulation due to the hydrostatic eff ect based on Archimedes law.Some studies observed that patients with hydrokinetotherapy in the rehabilitation program were able to walk a greater distance in 6 min compared to patients with conventional rehabilitation protocol at 1 month follow-up.Th is can be attributed to the fact that with water immersion, the gravitational forces can be partially or totally compensated, allowing only specifi c forces to act on the reconstructed knee.Water ambulation, such as using an underwater treadmill can be introduced in the rehabilitation program in order to gradually apply an increased load to the joint and contribute to the development of a normal gait pattern.Also, it has been suggested that hydrokinetotherapy programs associated with conventional programs could faciliate loading of the joint to a greater degree, and co-progression according to endurance.Th is will allow the patient to increase the muscle activity without putting the ligament graft to higher strain values 39 .Accelerated rehabilitation versus normal rehabilitation programs have been evaluated in randomized trials, but without any signifi cant results in shortening the rehabilitation period below 6 month.Th ere is very little scientifi c data on returning to sport activities earlier than 4 month, additional research being necessary in order express whether shorter rehabilitation periods are safer for the graft, articular cartilage and general outcome 42 .
Th ere is also low quality evidence on the benefi ts of surgical treatment of ACL followed by rehabilitation program compared to structured rehabilitation program only.In a study that tried to compare these diff erences, Monk et al. ( 2016), followed 141 patients with ACL injury that were divided into two groups -ACL reconstruction followed by particularised rehabilitation program and a second group composed of patients with conservative treatment reprezented by rehabilitation programs only.Th e authors express no signifi cant changes of the KOOS score for both groups at baseline or at fi ve years follow-up.Th ere were however low quality evidence on diferences between SF36 questionary components at follow up and also incomplete data on subsequent surgical treatment in the studied group 43 .
Return to more demanding activities and sports is still controversial.According to some authors 44 , one out of four patients with an ACL intervention will suff er a second tear within the next 10 years, while Paterno et al. 45 suggest the reaccurance of an injury within two years after returning to sport activities.According to Brosnan et al., progression to exercises such as vertical and horizontal jumping from double to single and progressive running should begin 4 month after the ACL reconstruction.In case of revisions for ACL reconstruction, the rehabilitation protocol remanins mainly the same until 12 weeks, progression to functional and sport activities beginning after 5 to 6 month 39,40 .
Cryotherapy is generally used after ACL reconstruction for the reduction of pain, infl ammation and oedema.Th e action mechanisms include local vasoconstriction which prevents fl uid extravasation and inhibition of aff erent nerve conduction that reduces muscle spasm and pain levels and also lowers local metabolism activity preventing cell death.Th ere have been many techniques proposed in order to achive those eff ects with points of view off ering benefi ts on one techique over another 46,47 .More recent techniques refer to cryothe-the review did not evidence a possible agravating eff ect when prescribing a brace, and also it was not observed an increase in pain or risk of injury 57,58 .

CONCLUSIONS
Literature data is abundent in terms of randomized controlled studies and meta-analysis regarding the benefi t of using one rehabilitation protocol compared to another.Th ere is a need for a structured rehabilitation program that should begin preoperative and continue with a rigurous follow-up period starting from the fi rst day post surgery and continue until 12 month after.Th ere is also a need for clinical outcome measures to be developed in an uniform way that should takes into consideration the physical, behavioral, and cognitive elements in an interdisciplinary context.Th e association of aquatic therapy off ers an improvement to the rehabilitation process, while additional techniques such NMES, cryotherapy and bracing are proving to be eff ective, yet more riguours data in needed to establish a consensus on ACL rehabilitation program.Th e authors declare that all the procedures and experiments of this study respect the ethical standards in the Helsinki Declaration of 1975, as revised in 2008(5), as well as the national law.Informed consent was obtained from all the patients included in the study.uld improve the rehabiltiation process in patients who do not tolerate land exercises because of diminished pain tolerance, age, or low activity level [51][52][53] .

Abbreviations
Neuromuscular electrical stimulation has been proven to be eff ective in increasing muscle strengh of the quadriceps muscle in the early phases of the rehabilitation process.Association of NMES with repeated sit-to-stand-to-sit exercises has been observed to be benefi cial in increasing muscle strength of the knee extensors, which conducted to lower pain perception and a better symmetry in lower extremity loading 54 .Also, it has been reported by some authors, a greater chance of achieving clinical criteria for advancing to agility training at 16 weeks, for patients that associated NMES to the usual rehabilitation program 55 .
Other modalities proposed as part of the rehabilitation program refer to trigger point dry needling of the quadriceps vastus medialis for treatment of trigger point miofascial syndrome that can be associated after ACL reconstructions.Th e technique is proposed in the last phase of the rehabilitation program.Velázquez-Saornil et al. (2016) in a randomized, single-blinded, clinical trial which included 44 subacute patients with surgical reconstruction after ACL rupture observed statistically signifi cant diff erence for both the group that received rehabilitation program and the group that received rehabilitation program associated with dry needling of the vastus medialis (eta2 coeffi cient from 0.962 to 0.980, p <0.01), for VAS and WOMAC scores, with higher scores for the dry needling group, although pain intensity was higher in the fi rst day of treatment for the dry needling group 56 .
Th e association of bracing as part of the rehabilitation program has been reviewed in multiple articles.Th e use of braces is particularly designed to limit the range of motion and also to prevent the knee from excessive varus and valgus stress.In a review by Wright et al. the authors evaluated the advantages of postoperative bracing, but all of the studies included contained biased data, including improper description of the randomization.Only one study observed an improvement regarding extension following locking the brace in full extension, at fi rst week post surgery.On the same time of the Hunt Valley II meeting, January 2005.Am J Sports Med.2006;34(9):1512-1532. 3. Lyman S, Koulouvaris P, Sherman S, Do H, Mandl LA, Marx RG.Epidemiology of anterior cruciate ligament reconstruction: trends, readmissions, and subsequent knee surgery.J Bone Joint Surg Am. 2009;91(10):2321-2328.1. Mall NA, Chalmers PN, Moric M, Tanaka MJ, Cole BJ, Bach BR Jr, Paletta GA Jr Incidence and trends of anterior cruciate ligament reconstruction in the United States.Am J Sports Med.2014 Oct;42(10):2363-70.2. Griffi n LY, Albohm MJ, Arendt EA, et al.Understanding and preventing noncontact anterior cruciate ligament injuries: a review