review-the role of knee braces after acl lesion

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Page 1: Review-THE ROLE OF KNEE BRACES AFTER ACL LESION

[email protected] Motion is Life: www.bauerfeind.com

2009-12-17 | plage 1

ANTERIOR CRUCIATE LIGAMENT LESIONS: WHEN AND WHY TO USE KNEE BRACES

Introduction

KNEE STABILITY

Static Components

Dynamic Components

KNEE BRACES

Performance Variables Before

Application Surgery After Prophylactic Benefit

Conclusions

Page 2: Review-THE ROLE OF KNEE BRACES AFTER ACL LESION

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Introduction A first classification of knee braces was proposed in 1984 by the A.A.O.S. dividing them into prophylactic, functional and rehabilitative categories. (http://www.aaos.org/about/papers/position/1124.asp). Unfortunately this classification proved inconsistent since the same brace could fulfill more than one function. Other classifications, based on different criteria, followed but exhibited similar limits since they failed to set standardization criteria necessary to manufacture and /or choose knee braces. This is the reason why after almost 40 years from their first** appearance, the application of knee braces remains controversial. Is it possible to standardize the application of knee braces (= prescription + adaptation)? Are the results predictable?

Answering these questions means answering also the questions: when and why knee braces are useful. This paper, after reviewing the principle of knee brace performances and the variables affecting these results, concludes that selection of the suitable patient is the main standardization problem. The need of guidelines allowing the screening of the right brace for the right patient is emphasized since the potential contribution of knee braces in the conservative treatment of ACL lesions, though subjective, can be significant. However, in cases of ACL lesion occurring at tibial insertion levels, braces allow cicatrisation and their socio-economical contribution becomes easier to predict.

**In the early 70’s, Nicholas and Castiglia of Lenox Hill Hospital developed the derotation knee brace for professional football player Joe Namath.

KNEE STABILITY Stability of the knee joint is the result of a sophisticated balance involving the interaction and the integrity of mechanical neuromuscular and metabolic functions. This process is achieved through a complementary relationship between static and dynamic components[1] . The significance of proprioception on postural stabilization as assessed by ischemia - Brain Res 296, 103109 Diener, H., Dichgans, J., Guschlbauer, B., & Mau, H. -1984).

Static / Passive Components Ligaments, joint capsule, cartilage, friction, and the bony geometry within the articulation comprise the static (passive) components. Work by Hsieh and Walker on the loaded and unloaded knee joint has defined the contribution of each passive knee components, between 0 and 30° , in the control of knee rotatory and antero-posterior laxity[2]. (Stabilizing mechanism of the loaded and unloaded knee joint – Hsieh HH; Walker PS; - Am. J Bone Joint Surg 1976; 58:87-93.) At 30 degree of flexion there was an increase of 2,3 mm antero-posterior laxity, but after cutting both cruciate ligaments the laxity increased a further 9,5 mm. Under the load of body weight, there was an increase in laxity after cutting both the cruciates but much less than in the noload condition. Dejour and Bonin compared anterior tibial translation using a radiologic Lachman test and the lateral monopodal stance test in 281 patients with unilateral anterior cruciate ligament rupture[3]. (Tibial translation after anterior cruciate ligament rupture – Dejour H; Bonin M.- J Bone joint Surg [Br]. 1994; 76-B:745-9). In normal and in ACL-ruptured knees, the monopodal stance test showed that every 10 degrees increase in posterior inclination of the tibial plateau was associated with a 6 mm increase in anterior tibial translation; the radiological Lachman test showed a 3 mm increase for every 10 degrees increase in tibial slope.(p=0,0001). The bony geometry of the knee joint strongly affects tibial translation of the ACL-deficient knee but also the effectiveness of the hamstring muscle in compensation for ACL deficiency[4]. (Influence of Anthropometric and Mechanical Variations on Functional Instability in the ACL-Deficient Knee - WEN LIU and MURRAY E. MAITLAND -Annals of Biomedical Engineering, Vol. 31, pp. 1153–1161, 2003). Integrity of static stabilizers is measured through clinical joint stress testing (ligamentous laxity testing) and arthrometry, giving rise to the frequently used term clinical stability.

Page 3: Review-THE ROLE OF KNEE BRACES AFTER ACL LESION

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Dynamic / Active Components Dynamic contributions to joint stability arise from feed-forward and feed-back neuromotor control over the skeletal muscles crossing the joint[5].

The importance of somatosensory information in triggering and scaling automatic postural responses in humans Exp Brain Res 101, 159164 - Inglis, J.T., Horak, F.B., Shupert, C.L., & Jones-Rycewicz, C. -1994.).

The contraction of quadriceps, hamstring and gastrocnemius generate stiffness and resistance to knee motion. Researchers have demonstrated that joint stiffness is the most important factor protecting the static components of the knee. Markolf reported a ten fold increase in joint stiffness when well-conditioned lower extremity muscles are contracted[6]. (In vivo knee stability. A quantitative assessment using an instrument clinical testing apparatus. Markolf KL, Graff- Radford A; Amstutz H. J Bone Joint Surg 60A:664-674; 1978.) Besides relieving strain on the static stabilizers of the knee, muscles are also capable of dissipating impact forces transmitted through knee joints[7]

. (Farley CT, Gonzalez O: Leg stiffness and stride frequency in human running. J Biomech 29:181 –186,1990).

This is an extremely important parameter in athletes, considering the force transfer through the lower extremity. Work by Skelly and DeVita has suggested that in vivo forces can exceed 20 times BW during jumping, turning,

and twisting sports[8]. (Compressive and shear forces on the tibia and knee during landing. Skelly WA, DeVita PL - Proceedings of 6th Biannual Conference of the Canadian Society for Biomechanics. Quebec, August1990 , pp59 –60 ).

These studies also underline the importance of timely muscle activation and hint at the importance of muscle reaction time and the time needed to reach peak muscle torque in injury situations.

When the capacity of the dynamic protection system is surpassed, passive (static) stabilizers can be strained excessively and injury can result. Understanding the co-ordination of muscle load sharing is therefore very important for preventing or predicting knee joint injury or stability. Unfortunately neuromuscular function is complex and our understanding of the many efferent pathways controlling dynamic muscle synergies and knee stability is limited. The infinite number of different combinations of muscle, ligaments and intra-articular contact forces (that can be applied to maintain a particular posture or produce a given movement) exceed the number of available equilibrium equations[9].

(The redundant nature of locomotor optimization laws - Collins et al. -J. Biomechanics, Vol.28, No.3, pp.251-267, 1995) This situation represents the main problem in motor-control research. The redundant nature of locomotor optimisation lows explains one of the most common features of human movements: motor variability [10].

(Motor Control Strategies Revealed in the Structure of Motor Variability -Mark L. Latash, John P. Scholz, and Gregor Schöner.Exercise and Sport Sciences Reviews - 2002 by the American College of Sports Medicine)

Variability increases in multi-joint limbs and allows a more flexible response to unpredictable events. As a consequence, many different possibilities exist for the activation of muscles in order to produce the necessary knee torque during different tasks.

KNEE BRACES

Performance Variables Braces can stabilize the knee by fixing frames of variable design and/or stiffness which follow and guide the knee kinematic depending on the congruence of their (specific) hinges with the tibio-femoral axes. The main (measurable and significant) parameter defining the performance of knee braces is the amount of joint laxity control. The mechanical variables (interfering in braces’ performances) are mainly related to patients’ specific anthropometric features. The body weight, as demonstrated by work of Hsieh and Walker -, reduces consistently total laxity from 8mm to 3 mm without and with body weight respectively. With double the load of body-weight, laxity can further be reduced to 2,3mm in patient with intact ACL.

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The bony geometry of the knee joint strongly affect tibial translation with and without ACL-deficiency, as mentioned before. The most important factor in reducing joint laxity however is not the tibial slope but the conformity of condylar surfaces. The brace-limb interface changes with muscle contraction sequence, strap tension and brace design and/or structure. Compliance and interaction with soft tissues plays a very important role particularly when considering the differences between genders[11].

(Gender difference in active musculoskeletal stiffness: quantification in controller measurement of knee joint dynamics Part I + II -Granata KP, Wilson SE, Padua DA.- J Electromyogr Kinesiol. 2002 Apr;12(2):119-26.-)

Levels of muscle contraction. Results show that braces can decrease anterior tibial translation between 28.8% and 39.1% without the stabilizing contractions of the hamstring, quadriceps, and gastrocnemius muscles. With lower extremity muscle activation and bracing, anterior tibial translation was decreased between 69.8% and 84.9%[12]. (Anterior cruciate ligament functional brace use in sports - Wojtys EM, Kothari SU, Huston L J.-

Am J Sports Med. 1996 Jul-Aug;24(4):539-46.). In order to limit mechanical laxity, braces must interact in the balance between the mechanical, neuromuscular and – even to a certain extent the metabolic - functions of the knee. The final balance (they interfere with) will not only depend on the mechanical variables mentioned above but also on the neuromuscular impairment following the ACL-deficiency. In fact, patients with ACL – deficient knee display quite different muscle recruitment patterns leading to different efficiency of anterior tibial translation control. Some individuals can stabilize their knees following anterior cruciate ligament rupture even during activities involving cutting and pivoting (copers), others have instability with daily activities (non-copers) [13].

(Dynamic stability in the anterior cruciate ligament deficient knee. 2001; 9(2):62-71.) . Rudolph KS, Axe MJ, Buchanan TS, Scholz JP, Snyder-Mackler L- Knee Surg Sports Traumatol Arthrosc.

Non-copers utilize a stabilization strategy which stiffens the knee joint which, not only is unsuccessful but, may lead to excessive joint contact forces which have the potential to damage articular structures[14]. (Movement patterns after anterior cruciate ligament injury: a comparison of patients who compensate well for the injury and those who require operative stabilization. Rudolph KS, Eastlack ME, Axe MJ, Snyder-Mackler L-J Electromyogr Kinesiology, 1998 Dec;8(6):349-62.) However, humans learn to stabilize unstable dynamics using the skilful and energy-efficient strategy of selective control of impedance geometry. With practice, subjects can produce smooth movements in the context of various loads. This ability has been demonstrated both for external loads (force fields) that vary with limb velocity [16] (Lackner and DiZio 1994; Conditt et al. 1997; Gandolfo et al. 1996;Goodbody and Wolpert 1998; Shadmehr and Mussa-Ivaldi 1994) and intrinsic loads such as joint interaction torques in multi-joint movements. [17; 18] (Almeida et al. 1995; Sainburg et al. 1995, 1999; Cooke and Virji-Babul 1995; Virji-Babul and Cooke 1995; Gribble and Ostry 1999).

The contribution of knee braces in the achievement of (dynamic) joint stability is not just the effect of the external passive brace stiffness but much more the result of the sensory integration in the new feedback control of the knee joint-brace complex[15].

(Gait adaptations before and after anterior cruciate ligament reconstruction surgery. - Devita P, Hortobagyi T, Barrier J, Torry M, Glover KL, Speroni DL, Money J, Mahar MT. -Med Sci Sports Exerc. 1997 Jul; 29(7):853-9.)

This is necessarily the result of a learning process similar to that experienced by users of prosthetic devices after amputation. They will learn how to use mechanical impendence in order to generate forces which resist destabilizing motion [19].

(The central nervous system stabilizes unstable dynamics by learning optimal impedance.- Burdet E, Osu R, Franklin DW, Milner TE; Kawato M. -Nature. 2001 Nov 22;414(6862):446-9.)

Application Noyes demonstrated that one third of ACL-deficient patients who underwent rehabilitation with braces were able to fully compete in athletics, one third had to modify their sport activity, one third continued to have problems of instability, needing either subsequent meniscal surgery or ACL reconstruction. Daniel et al. in a prospective outcome study demonstrated that activity modification must be required of all patients who are considering non-surgical treatment. (Am J Sport Med 1994; 22:632-644)- Older patients may be more willing to modify their activities and only 8% to 10% of patients over 35 years of age underwent ACL-reconstruction.

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Non-surgical treatment of 62 patients, with different activity levels, has been reported by Tramond & Benquet (1997). They found both excellent and unsatisfactory ACL cicatrisation results, using orthotic treatment in 76% and 24% of cases, respectively (http://www.anmsr.asso.fr/anmsr00/51tramond.htm). Though all patients exhibited the same ACL-lesion at tibial insertion level these results were surprising since, until that moment, spontaneous cicatrisation of torn ACL was considered impossible (Marshal- Holfen and Hefti-Kleiner). These results confirmed the findings of Hiara et al. (J Computer Assisted Tomography 20(2):317-321 March-April 1996). The pictures below report the evolution of the cicatrisation process from zero to four and eight months using a brace for six – eight weeks after injury followed by a standard re-education protocol. Other than with middle-ACL-lesions, cicatrisation and lesion occurs here in the same place without implication of PCL.

The effect of knee braces, following different treatment options of ACL-injuries, was investigated and reported in many studies during the last decades. Regarding their conclusion, the limits of our understanding are clearly identified by considering:

• the interferences of variability of muscle motor synergies pattern, (copers and nocopers), • the difference in human learning strategy exploiting mechanical impedance and • the individual anthropometric variables and their interference on braces performance.

Before (surgery?) There is no need of urgent surgery in patients with isolated ACL tears, unless for high level sportsmen. Isolated ACL tears, however is quite rare a condition since different peripheral structures are often involved in the traumatic ACL tears leading to different levels of impairment. The flexion end extension limitation provided by braces is necessary to protect the cicatrisation process of peripheral structures during early rehabilitation. Recovery and patient performances, after ACL tears, depend on both mechanical and neuromuscular deficits difficult to predict. Although potential copers (individuals who have the potential to compensate for the absence of an ACL without episodes of giving way after return to pre-injury activity) have developed some characteristics of a successful stabilization strategy, the presence of kinematic alterations indicates that they may benefit from training programs and from knee braces. Non-copers (those who have knee instability following ACL rupture with return to pre-injury activities), depending on the level of their deficit and / or mobility demand, may choose nonsurgical or surgical treatment. In the first case brace protection is advisable during risk activities. The conclusions of the following works by Switrum et al. and Smith et al. shows that lack of evidence and lack of benefits should not be confused[20; 21]. (The effects of a functional knee brace during early treatment of patients with nonoperated acute Anterior cruciate ligament tear: aprospective randomized study. Swirtun LR, Jansson A, Renström P. Clin J Sport Med. 2005 Sep; 15(5):299-304.)

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CONCLUSIONS: Nonoperated acute ACL-deficient patients experienced a positive effect of the brace regarding sense of instability and rehabilitation. However, these findings were not supported by objective outcomes.

(Effects of functional knee bracing on muscle-firing patterns about the chronic anterior cruciate ligament-deficient knee. Smith J, Malanga GA, Yu B, An KN.-Arch Phys Med Rehab. 2003 Nov; 84(11):1680-6)

CONCLUSIONS: Brace use in this population did not consistently result in more favourable muscle firing patterns during the single-leg hop manoeuvre. Interindividual responses to brace use indicate the need for further research to investigate the multiple strategies that may exist to stabilize the ACL-deficient knee. In the meantime, functional knee brace use among ACL-deficient patients remains empirical.

After surgery Can functional braces protect the ACL, or its replacement? Are braces needed after ACL reconstruction? Work of Fleming, Renstrom, Beynnon, Engstrom, and Peura AJSM 2000 demonstrated that braces do not harm the ACL “in vivo” and can protect ACL, or its replacement, both in non weight-bearing and in weight-bearing conditions. The magnitude of this strain shielding effect was considered insufficient (140 N) to effectively protect the knee under normal activities of daily living and sports dynamic conditions. The heterogeneity of patients’ physio-anatomical variables, of braces designs and of the surgical reconstruction techniques (and results) make this conclusion, obviously, quite relative. Certainly braces do not replace the ACL function (neither does it surgery). Nevertheless, partially limiting tibial / femoral motion and dampening the forces transmitted to the ACL replacement, braces can augment other protecting mechanisms such as neuromuscular response to impact forces on the tibia substantially, though subjectively. Braces are needed after surgery depending on graft source and reconstruction technique. Hamstring tendon autograft reconstruction needs a longer screw fixation time protection, with respect to middle-third-patellar tendon. The mean load to failure for the patellar tendon grafts is 1.784 ± 580 N, compared with 2.422 ± 538 N for the hamstring tendons. Braces cannot provide this level of shielding effect. After ACL-reconstruction with autogenous patellar tendon however, during the “ligamentizazion” phase (characterized by avascularisation and necrosis) the graft reaches its weakest resistance level while two third of the collagen mass may be resorbed. (Amiel et al. –J Ortop Res. 1986; 4(2):162-172), After 6 -8 weeks its tensile resistance decreases to 10% only of the original fresh allograft. The table below shows that, regardless of the source of the plastic, the shielding effect of braces become substantial under this circumstance.

ALLOGRAFS ACCEPTED VALUES FOR ULTIMATE TENSILE LOAD AND STIFFNESS (J Bone Joint Surg [Br] 2001; 83-B: 625-34.)

Ultimate tensile load (N) Stiffness (N/mm) Native ACL (1) 2.160 242 Doubled semitendinosus/gracilis (2) 4.140 807 Bone-patellar tendon-bone (10 mm) (3) 2.977 455 Quadriceps (10 mm) 2.352 326 Bone-patellar tendon-bone allograft fresh frozen 2.552 633 Bone-patellar tendon-bone allograft 1.990 531 after 3 Mrad irradiation (1). Woo SL, Hollis JM, Adam DJ, Lyon RM, Takai S. Tensile properties of the human femur-anterior cruciate ligament-tibia complex. The effect of specimen age and orientation. Am J Sports Med-1991; 19:217-25.

(2). Hamner DL, Brown CH Jr, Steiner ME, Hecker AT, Hayes WC.Hamstring tendon grafts for reconstruction of the anterior cruciate ligament: biomechanical evaluation of the use of multiple strands and tensioning techniques. J Bone Joint Surg [Am] 1999; 81-A: 549-57.

(3). Cooper DE, Deng XH, Burstein AL, Warren RF. The strength of the central third patellar tendon graft. Am J Sports Med 1993; 21:818-23.

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After 2 years, the graft resistance and stiffness are reduced by 50%. The tendon grafts exhibit significantly higher stiffness than do normal ligaments and are thus at greater risk of loading, which may result in plastic or permanent deformation. The evolution of the four stages of the remodeling process of the ligament graft is substantially influenced by rehabilitation. Unfortunately rehabilitation protocols exhibit remarkable differences. Symptomatic ACL-deficient patients who have early degenerative joint diseases or who have had meniscectomy can predictably be stabilized by ACL reconstruction; however the patient should be counseled to protect the knee and voluntarily modifying activities. Subjective benefit using braces after surgery were confirmed by Risberg et al 1998. A prospective randomized study with a two years follow-up concluded that the patients who were rehabilitated with the use of a brace had less pain and a tendency towards fewer complications during the early post-operative period than the patients who were rehabilitated without the use of a brace. However, there were no differences in terms of function or knee laxity at the two-year follow-up[22].

(Is a knee brace advantageous after anterior cruciate ligament surgery? A prospective, randomised study with a two-year follow-up.- Brandsson S, Faxen E, Kartus J, Eriksson BI, Karlsson J.-)

Prophylactic Benefit There is a wide range of A-P laxity in normal knees and a knee with a ruptured ACL and tight MCL may have less anterior laxity than an intact knee with relatively lax primary (ACL) and secondary (MCL) restrains[23].

(An in vivo biomechanical evaluation of anterior-posterior motion of the knee: roentgenographic measurement technique, stress machine, and stable population. –Torzilli PA; Greenberg RL; Insall J; - J Bone Joint Surg [Am] 1981; 63-A: 960-8)

It is understandable that different studies about the need of braces for preventing injuries show conflicting results. A recent study concluded that data from existing research are inconsistent. Based on a Strength of Recommendation Taxonomy level of evidence of 2 with a grade B recommendation, the authors could not conclusively advocate or discourage the use of prophylactic knee braces in the prevention of knee injuries in collegiate football players[24].

(A systematic review of prophylactic braces in the prevention of knee ligament injuries in collegiate football players. Pietrosimone BG, Grindstaff TL, Linens SW, Uczekaj E, Hertel J. J Athl Train. 2008 Jul-Aug; 43(4):409-15. ).

The contribution of braces however, in the prevention of injuries, will depend not only on the initial laxity but also on the exposure to risks. Risk increase is also related to the age-dependent tensile strength variations of the ACL complex. Between 20 and 90 years the tensile strength of ACL complex (including insertion) falls from 3.000 to 500kN [25].. (Tensile properties of the human femurus-anterior cruciate ligament-tibia complex. The effect of specimen age and orientation-Woo SLY.;Hollis JM et al.- Am J Sport Med –Vol.19 N.3-1991)

Mean value of the tensile strength (kN) of ACL complex related to age (years).-

20

30

40

50

60

70

80

90

100

05001.0001.5002.0002.5003.000

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Even after ACL-reconstruction the preventive role of braces was confirmed by a cohort study (Level of evidence, 3.) involving an anterior cruciate ligament–reconstructed group of 820 skiers who had had an anterior cruciate ligament reconstruction 2 years or earlier[26].. (Effect of functional bracing on knee injury in skiers with anterior cruciate ligament reconstruction: a prospective cohort study- American Journal of Sports Medicine 34:1581-1585 (2006) ©- William I. Sterett, MD*, Karen K. Briggs, MPH, Timothy Farley, MD and J. Richard Steadman, MD) Because of the increased risk of subsequent knee injury in nonbraced skiers, the authors recommend functional

bracing for skiers with anterior cruciate ligament reconstruction. Whether the protective effect of functional bracing can be extrapolated to other high-demand patients is yet to be determined.

Conclusions

Consistent with the variability of: muscular recruitment patterns, individual physio-anatomical features and ability to develop learning strategies of mechanical impedance, brace-users experience different benefits. The unpredictability of the functional results, after A.C.L injury, makes the use of functional knee braces, among physicians and patients, necessarily empirical. ACL surgery has made remarkable progresses and it is tempting to advocate its general application. Unfortunately, muscle function in most subjects does not return to pre-traumatic conditions after ACL reconstruction independently from the surgical technique. Wojtys reported that at 12 to 18 months postoperatively, when knee rehabilitation was terminated, significant deficiencies in muscle performance persisted in most patients[27]... (Longitudinal effects of anterior cruciate ligament injury and patellar tendon autograft reconstruction on neuromuscular performance. Edward M. Wojtys, MD* and Laura J. Huston, MS. The American Journal of Sports Medicine 28:336-344 (2000). ACL surgery has been often proposed in order to prevent the onset of osteoarthritis (regardless of patients’ age). Excessive laxity (in extension) is probably the mechanism that leads to osteoarthritis in ACL- ruptured knees. (Dejour et all.1987, 1988b) but reconstructing the ACL can hasten rather than delay the onset of osteoarthritis. (Feagin,Cabaut and Curl 1982; Barlett and Crow 1984; Johnsonet al.1984; Fried et al.1985; Zarins and Rowe 1988). ACL reconstruction cannot prevent tibial rotation even though anterior tibial translation is re-established. (Georgulis AD. Et al. Knee Surg Sport Traumatol. Arthrosc. 11(6):360-365 – 2003). After six-eight weeks from successful surgery, the use of functional knee braces is probably of limited benefit. Postoperatively however, the full value of a brace, is not fully known due to non-sensitive and limited outcome evaluations. With nonoperative treatment, a practical decision-making scheme for returning patients to activity after anterior cruciate ligament rupture is crucial. The contribution of knee braces on the improvement of feedback control can be assessed following and /or adapting i.e. the Fitzgerald and L. Snyder-Meckler experience[28]...

(A decision-making scheme for returning patients to activity with nonoperative treatment after anterior cruciate ligament rupture.- G. K. Fitzgerald , M. J. Axe , L. Snyder-Mackler- Exerc. Sport Sci. Rev. Vol.31, N°4 pp.195-200; 2003.).

This protocol, designed for returning patients to high-level activity with nonoperative treatment, included a screening examination consisting of four one-legged hop tests, the incidence of knee giving-way, a self-report functional survey, and a self-report global knee function rating. Following a similar protocol- modified according to age and /or levels of mobility demand- the possible improvement of feedback control of serial prefabricated braces could be tested screening patients according to their (improved) performances.

The socio-economical benefit of knee braces can only be assessed by exploiting their full potential. Consistent with the facts and remarks described before, the existing guide lines for ACL surgery, (suggested by the A.A.O.S. but similar in most countries), should reconsider the contribution of braces according to the following table.

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THE ROLE OF KNEE BRACES AFTER ANTERIOR CRUCIATE LEGAMENT LESIONS

BEFORE

SURGERY

WHEN

1. ACL rupture at tibial insertion level.

2. Non-isolated ACL lesions.

3. After screening procedure of patients exhibiting improved performances.

4. When exposed to (sport?) risk after conservative treatment

WHY

1. Full cicatrisation possible in 3 out of 4 patients.

2. Protection of peripheral structures by limitations of extension-flexion.

3. Different “quality and quantity” of neuromuscular deficit makes the effect of braces unpredictable.

4. The shielding effect of braces depends on mechanical variables but can be significant.

AFTER

SURGERY

1. One month protection (from week 4 to 8) after Patella Tendon / Kenneth-Jones ACL-reconstruction.

2. Three months protection after Semitendinosus / Macintosh ACL-reconstruction.

3. Neuromuscular deficit persisting after surgery and rehabilitation

1. Remodeling process.

2. Screw fixation time

3. Proprioceptive improvement

REFERENCE

1. The significance of proprioception on postural stabilization as assessed by ischemia - Brain Res 296, 103109 Diener, H., Dichgans, J., Guschlbauer, B., & Mau, H. -1984).

2. Stabilizing mechanism of the loaded and unloaded knee joint – Hsieh HH; Walker PS; - Am. J Bone Joint Surg 1976; 58:87-93.

3. Tibial translation after anterior cruciate ligament rupture – Dejour H; Bonin M.- J Bone joint Surg [Br]. 1994; 76-B:745-9.

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4. Influence of Anthropometric and Mechanical Variations on Functional Instability in the ACL-Deficient Knee - WEN LIU and MURRAY E. MAITLAND -Annals of Biomedical Engineering, Vol. 31, pp. 1153–1161, 2003.

5. The importance of somatosensory information in triggering and scaling automatic postural responses in humans Exp Brain Res

101, 159164 - Inglis, J.T., Horak, F.B., Shupert, C.L., & Jones-Rycewicz, C. -1994.).

6. In vivo knee stability. A quantitative assessment using an instrument clinical testing apparatus.- Markolf KL, Graff- Radford A; Amstutz H. J Bone Joint Surg 60A:664-674; 1978.):

7. Farley CT, Gonzalez O: Leg stiffness and stride frequency in human running. J Biomech 29:181 –186,1990:

8. Compressive and shear forces on the tibia and knee during landing. Skelly WA, DeVita PL - Proceedings of 6th Biannual

Conference of the Canadian Society for Biomechanics. Quebec, August1990 , pp59 –60)

9. The redundant nature of locomotor optimization laws - Collins et al. -J. Biomechanics, Vol.28, No.3, pp.251-267, 1995:

10. Motor Control Strategies Revealed in the Structure of Motor Variability -Mark L. Latash, John P. Scholz, and Gregor Schöner.Exercise and Sport Sciences Reviews - 2002 by the American College of Sports Medicine.

11. Gender difference in active musculoskeletal stiffness: quantification in controller measurement of knee joint dynamics Part I + II -

Granata KP, Wilson SE, Padua DA.- J Electromyogr Kinesiol. 2002 Apr;12(2):119-26.-

12. Anterior cruciate ligament functional brace use in sports - Wojtys EM, Kothari SU, Huston L J.- Am J Sports Med. 1996 Jul-Aug;24(4):539-46.).

13. Dynamic stability in the anterior cruciate ligament deficient knee. 2001; 9(2):62-71.) . Rudolph KS, Axe MJ, Buchanan TS, Scholz

JP, Snyder-Mackler L- Knee Surg Sports Traumatol Arthrosc.

14. Movement patterns after anterior cruciate ligament injury: a comparison of patients who compensate well for the injury and those who require operative stabilization. Rudolph KS, Eastlack ME, Axe MJ, Snyder-Mackler L-J Electromyogr Kinesiology, 1998 Dec;8(6):349-62.)

15. Gait adaptations before and after anterior cruciate ligament reconstruction surgery. - Devita P, Hortobagyi T 16. (Lackner and DiZio 1994; Conditt et al. 1997; Gandolfo et al. 1996;Goodbody and Wolpert 1998; Shadmehr and Mussa-Ivaldi 1994.

17. Almeida et al. 1995; Sainburg et al. 1995, 1999; Cooke and Virji-Babul 1995;

18. Virji-Babul and Cooke 1995; Gribble and Ostry 1999).

19. The central nervous system stabilizes unstable dynamics by learning optimal impedance.-

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