"Custom-fit" versus "off-the-shelf" ACL functional braces

Many sports medicine practitioners believe "custom-fit" functional braces are superior in performance to "off-the-shelf" braces for anterior cruciate ligament (ACL)-deficient knees. However, this is not well substantiated. This study compares a Donjoy custom-fit ACL brace (CE 2000), Donjoy off-the-shelf brace (Goldpoint), and an athletic taping technique to determine their role in our clinical practice. Five patients (3 men and 2 women) with isolated, unilateral, chronic ACL tears with an average age of 27 years (range: 19-35 years) were used to evaluate these three restraint systems. Anterior tibial laxity, quadriceps and hamstrings strength, endurance, standing long jump, brace migration with exercise, and pattern of muscle response to forced anterior tibial displacement were studied. Each patient was tested without a brace and then in each of the three test conditions (custom brace, off-the-shelf brace, and tape), with the order of testing randomized. The Donjoy custom-fit ACL functional brace did not reduce anterior laxity or improve standing long jump, muscle strength, endurance, or muscle response times significantly more than the off-the-shelf ACL brace. Both braces improved anterior stability over knee taping when the knee muscles were contracted under the low forces used in this study. After 1 hour of exercise, brace migration was significantly greater (P=.03) for the CE-2000 custom brace (18.6 mm) than for the Goldpoint off-the-shelf brace (4.5 mm). There appears to be no advantage to the more expensive custom-fit knee brace over the off-the-shelf brace.     

A biomechanical evaluation of the Lenox Hill knee brace

This study was conducted to determine the effectiveness of the Lenox Hill knee brace in limiting anterior translation and external rotation of the tibia in reference to the femur in normal and ligament-deficient knees. Four fresh cadaver knees were fitted with Lenox Hill knee braces according to the manufacturer's guidelines. A computer-assisted testing apparatus was constructed that allowed each knee to be tested as a function of knee flexion angle, joint load, and soft tissue integrity. Each knee served as its own control. While 45 kg of anterior force was applied to the tibia of the anterior cruciate ligament deficient knees, the Lenox Hill knee brace was able to decrease anterior translation from an average of 10 mm, to 5.7 mm, at 30 degrees of flexion when no vertical load was present. This limiting effect was lost when the medial collateral ligament was sectioned in addition to the anterior cruciate ligament or when both the medial and the lateral collateral ligaments were sectioned along with the anterior cruciate ligament. When 20 Newton-meters (Nm) of torque was applied to the femurs at 30 degrees of flexion without vertical load, the Lenox Hill knee brace limited external rotation of the tibia in all tested categories. For intact knees at 30 degrees of flexion and no vertical load, the Lenox Hill knee brace decreased external rotation from 18 degrees to 10 degrees. In the anterior cruciate ligament-sectioned knees, external rotation was decreased from an average of 20.2 degrees to 16.1 degrees. In the knees with sectioned anterior cruciate and medial collateral ligaments, the average reduction was from 21.2 degrees to 15.4 degrees.(ABSTRACT TRUNCATED AT 250 WORDS)     

To brace or not to brace? How effective are knee braces in rehabilitation?

Since the clinical benefit of knee braces has yet to be defined, discussion about braces after reconstructive surgery of the anterior cruciate ligament remains controversial. The use of prophylactic braces in sport did not prove to be effective. In ACL insufficient knee joints, the operative treatment is preferred over the use of functional knee braces. Therefore, the postoperative rehabilitation presents the main application of braces. Modern operative techniques with an initial strong fixation of the ACL graft make a functional postoperative treatment without external fixation possible. In the presented meta-analysis of the literature about knee braces, results from clinical and experimental studies are compared. No published clinical data have shown that braces have any effect on postoperative outcome after ACL-reconstruction. Also, no evidence of a significant bracing effect could be demonstrated in the experimental in vivo or in vitro studies, except a limited stabilizing function for lower shear stress below the physiological loads. Consequently, the systematic use of braces in the rehabilitation after ACL reconstruction cannot be recommended.     

A viscoelastic knee brace for anterior cruciate ligament deficient patients

A biomechanical review of the anterior cruciate ligament deficient knee shows that the unbraced knee undergoes instability once its angular velocity exceeds normal cadence rate. It also shows that various braces that utilize extension limits for purposes of preventing subluxation and tibial rotation introduce abnormal gait and posture responses, which may impose on the patient's activities. A speed-regulated, viscoelastic knee brace has been designed, fabricated, and tested on two patients. The brace allows full range of knee motion and reduces the angular velocity of the tibia from near-full extension to neutral at normal, non-unstabilizing walking speeds. Capability is incorporated for adjusting the terminal angular velocity for each individual patient as well as for the same patient during the recovery period.     

Functional testing of braces for anterior cruciate ligament-deficient knees

Previous studies into the efficacy of bracing anterior cruciate ligament (ACL)-deficient knees have lacked objective functional testing. In this study of function the authors compare the effectiveness of three custom-made and three off-the-shelf braces in stabilizing symptomatic, unilateral, chronic, non-reconstructed, ACL-deficient knees. Ten subjects randomly performed six functional tests with each of the six test braces. Knee function was evaluated both objectively and subjectively. Two customized functional braces (Generation II Polyaxial Knee Cage and Lenox Hill Derotation Brace) provided the most objective improvement during ACL-dependent activities and also the most subjective stability. Laterally hinged braces were as effective as the more commonly used double-hinged models. Based on this study, the authors recommend the use of laterally hinged customized functional braces in the nonoperative treatment of the symptomatic ACL-deficient knee.     

Determination of a zero strain reference for the anteromedial band of the anterior cruciate ligament

The objective of this study was to verify a method previously used to determine a reference length for calculations of anterior cruciate ligament strain. In nine knee specimens, an arthroscopic force probe and a Hall effect transducer were placed in the anteromedial band of the ligament. Anteroposterior-directed shear loads then were applied to the knee joint with the knee flexed to 30°. From the sigmoidal curve for shear load versus displacement of the anterior cruciate ligament midsubstance, the length of the transducer at the inflection point was determined graphically by two independent examiners. Previous studies suggested that the inflection point corresponds to the slack-taut transition of the anteromedial band. The force probe was used to determine the actual length of the transducer when the anteromedial band became load bearing. No significant differences were found between the reference lengths determined by the inflection point method and the force probe. The force probe demonstrated that the anterior cruciate ligament became load bearing when an anterior shear load of 8.8 N was applied to the tibia with the knee at 30° of flexion. Furthermore, multiple cycles of anteroposterior shear loading did not influence these values. The force probe verified that the inflection method provides a reasonable estimate of the absolute strain reference (within 0.7% strain).     

Sense and nonsense of knee orthosis

The trend for early mobility after surgical treatment of knee joint ligament injuries has led to the production of a large number of different braces in recent years. To allow an approximation of the very complex motion of the human knee, the use of braces with so-called physiological hinges has been recommended in the last few years. The authors report on a group of 50 patients who had sustained injuries to the cruciate ligament and had received IOWA knee braces following surgical treatment, the fit being subsequently checked by X-ray. These checks clearly demonstrated that the hinge of the brace hardly coincides with the knee axes and that there were deviations ranging from 1 to 4 cm. The authors therefore come to the conclusion that brace-fit must be checked by X-ray in all cases and that incorrectly fitted braces should be corrected before use. There is so far no evidence that so-called physiological hinges are really superior to braces with single axes. The current trends and developments cannot really be justified as long as there is no guarantee that the axes of brace and human knee coincide both in motion and during weight-bearing.     

Biomechanics of the tibiofemoral joint and knee braces

We investigated whether the kinematics of modern knee braces reflect the natural movement of the knee, especially with regard to the roll-glide ratio. Seven commercially available modern knee braces were analyzed in a new measuring unit with a 6-D positional registration system, which had been developed for this study. The results were compared to the theoretically postulated joint movements.All knee braces produced a roll-glide ratio different from the natural movement of the knee. Only the Townsend brace protected the anterior cruciate ligament at the beginning of the movement.Biomechanically, none of the knee braces tested provided efficient protection for the knee movement. We propose a new functional external joint, which allows restoration of the natural roll-glide mechanism of the articulating surfaces.     

Custom-fit versus premanufactured braces

Custom-made and off-the-shelf functional knee orthoses from four manufacturers were evaluated. Anterior tibial translation testing was performed using a pneumatic mechanical surrogated knee. The mechanical surrogate was interfaced with a servohydraulic materials testing system, which applied all anterior/posterior displacements to an ultimate anterior load of 400 N. Comparison of the individual custom versus premanufactured braces showed that the custom braces demonstrated a statistically significant difference for restraining anterior displacement (P=.0001 to P=.0005). Pooled data from all tests showed that the custom brace measurements as a group restrained anterior displacement better than the premanufactured brace group by a mean difference of 0.84 mm (P=.0001). The authors question whether such small, sub-millimeter findings between custom and off-the-shelf functional derotation braces represent any clinically significant differences.     

The effectiveness of self-adjustable custom and off-the-shelf bracing in the treatment of varus gonarthrosis

BACKGROUND: A recent development in valgus-producing knee braces has been the adjustable "unloader" brace. The purpose of this study was to compare the effectiveness of off-the-shelf and custom-made patient-adjustable, valgus-producing knee unloader braces in relieving pain, reducing stiffness, and improving function and in reducing varus angulation and the peak adduction moments about the knee during gait and stair-stepping in patients with painful varus gonarthrosis of the knee. METHODS: Ten adult patients served as their own controls for the measurement of baseline values and then wore each of the two braces, one after the other, for four to five weeks in a random order. Pain, stiffness, and function were assessed with the Western Ontario and McMaster Universities Osteoarthritis Index. Gait and stair-stepping were evaluated with a three-dimensional motion analysis system and multicomponent force platform. Full-length (hip, knee, and ankle) standing anteroposterior radiographs were used to determine alignment of the knee. RESULTS: Both braces significantly reduced pain and stiffness (p<0.05), with the custom brace reducing stiffness significantly more than the off-the-shelf brace (p=0.030). The custom brace significantly improved function (p=0.010) and reduced the peak knee adduction moments during gait (p=0.033) and stair-stepping (p=0.002) compared with baseline values and compared with the off-the-shelf brace (p=0.029 and p=0.027, respectively). The custom brace significantly reduced varus angulation of the knee by 1.5 degrees compared with baseline (p=0.001) and by 1.3 degrees compared with the off-the-shelf brace (p=0.009). The off-the-shelf brace did not significantly reduce the varus angle. CONCLUSIONS: We investigated only the short-term effects of custom and off-the-shelf patient-adjustable valgus-producing knee "unloader" braces and found that patients with varus gonarthrosis of the knee may benefit significantly with respect to pain relief and reduced stiffness from use of either brace. However, such patients may experience additional significant benefit in improved function and reduced stiffness, varus angulation, and medial compartment loading of the knee from use of the custom-made patient-adjustable brace.     

Brace effects on the unstable knee in 21 cases. A roentgen stereophotogrammetric comparison of three designs

Three designs of knee braces were investigated in 21 knees with arthroscopically verified old tears of the anterior cruciate ligament. Anterior-posterior and rotatory instability with and without anterior traction were recorded with roentgen stereophotogrammetric analysis. Two of the designs examined reduced the anterior-posterior instability (ECKO, modified Lenox Hill), but not to normal levels. At 20 degree of flexion, none of the braces decreased the internal rotatory instability, whereas one type (modified Lenox Hill) reduced the external rotatory instability.     

Brace effects on the unstable knee in 21 cases: A roentgen stereophotogrammetric comparison of three designs

Three designs of knee braces were investigated in 21 knees with arthroscopically verified old tears of the anterior cruciate ligament. Anterior-posterior and rotatory instability with and without anterior traction were recorded with roentgen stereophotogrammetric analysis. Two of the designs examined reduced the anterior-posterior instability (ECKO, modified Lenox Hill), but not to normal levels. At 20° of flexion, none of the braces decreased the internal rotatory instability, whereas one type (modified Lenox Hill) reduced the external rotatory instability.     

Clinical application of biomechanic and functional anatomical findings of the knee joint]

In order to study the functional anatomy of the knee joint, careful anatomical dissections were conducted on over 130 fresh-frozen cadaveric knee specimens. We found no evidence to support the two-bundle and three-bundle theories of cruciate ligament fiber patterns. The longest fibers in the anterior cruciate ligaments (ACL) measured 37 mm, and the longest in the posterior cruciate ligament (PCL), 41 mm. Cruciate ligament insertions follow a transition line on tibia and femur. Usually not all the fibers of the cruciate ligaments are taut at the same time. They are progressively recruited according to the biomechanical demands placed on them. Fibre recruitment in the ACL is from knee flexion to extension and in the PCL from extension to flexion. The concept of fiber recruitment was recently evaluated mathematically. As a working hypothesis, the knee joint can be looked upon as a biological realization of the crossed four-bar linkage, even in three dimensions. In vitro measurements have shown that correct graft placement in cruciate reconstructions is critical for knee biomechanics. Incorrect placement of grafts may lead to decreased range of motion and/or increased laxity. Distance changes of 3 mm between femoral origin and tibial insertion of a graft may lead to a 400% increase of graft preload and will thus easily reach published pull-out forces for some of the graft fixation methods (button = 248 N). Precise drill guides and isometers may be helpful in any operative technique (open, arthroscopic). Using the IKDC evaluation form and the KT-1000 arthrometer, our studies on 25 patients demonstrated a direct correlation between intraoperative graft tracking and the clinical outcome 2 years after operation. Biomechanical studies to investigate in vivo strain patterns of the anterior cruciate ligament and in vitro strain patterns of isometrically placed cruciate graft reconstructions showed that they did not reach critical fixation failure or graft rupture loads. The highest values were measured in Lachman and anterior drawer testing. In the 20-kg Lachman test the maximum load was 96 +/- 6 N. This was twice the maximum loads of any of the quadriceps exercises (40-50 N). With an isometrically placed graft, full active range of motion postoperatively and exercises with isolated or combined contractions of quadriceps and hamstring muscles will result in small graft loads. Postoperative immobilization with plaster and/or protection with braces may therefore become obsolete.     

Hamstrings cocontraction reduces internal rotation, anterior translation, and anterior cruciate ligament load in weight-bearing flexion.

Strengthening of the hamstrings is often recommended following injury and reconstruction of the anterior cruciate ligament. It has been suggested that hamstrings activity stabilizes the knee and reduces anterior cruciate ligament load during weight-bearing flexion; however, the effects of hamstrings cocontraction on the kinematics and mechanics of the normal knee have not been assessed at physiological load levels. The aim of this study was to determine whether the addition of hamstrings force affects knee rotations, translations, and joint and quadriceps force during flexion with loads at physiological levels applied to the muscles and joints. Eight cadaveric knee specimens were tested with a servohydraulic mechanism capable of applying controlled dynamic loads to simulate quadriceps and hamstrings muscle forces throughout a physiological range of motion. A constant vertical load of physiologic magnitude was applied to the hip, and quadriceps force was varied to maintain equilibrium throughout flexion. Two conditions were tested: no hamstrings force and a constant hamstrings force equivalent to the vertical load. Hamstrings force significantly reduced internal rotation (p<0.0001) and anterior translation (p<0.0001), increased quadriceps force (p<0.0001) and normal resultant force on the tibia (p<0.0001), and reversed the direction of the shear force on the tibia (p<0.0001). These results suggest that hamstrings strengthening following anterior cruciate ligament injury may benefit anterior cruciate ligament-deficient and reconstructed knees by reducing the load in the ligament; however, they also imply that this comes at the expense of efficiency and higher patellofemoral and joint forces.     

The use of functional knee braces in the control of pathologic anterior knee laxity

Four designs of knee braces, Don-Joy 4 Point, RKS, Lenox Hill, and CTi, were evaluated in 42 patients with a unilateral knee brace. Brace migration was the predominant complaint, as noted in patient questionnaires. All braces tested reduced giving-way episodes (34 of 42 patients reported no giving way during brace usage). All four brands of braces reduced the grade of pivot shift (mean reduction = 0.8 grade). Instrumented laxity testing with the KT-1000 arthrometer was performed with an 89-N passive anterior displacement, high load passive anterior displacement, and a quadriceps contraction active displacement. Brace use decreased the measured pathologic anterior displacement on all tests. During functional testing with one-legged hop and 40-yard shuttle run, the mean values were not significantly changed by brace usage.     

Time-dependent increases in type-III collagen gene expression in medical collateral ligament fibroblasts under cyclic strains.

Numerous studies have demonstrated the capacity of mechanical strains to modulate cell behavior through several different signaling pathways. Understanding the response of ligament fibroblasts to mechanically induced strains may provide useful knowledge for treating ligament injury and improving rehabilitation regimens. Biomechanical studies that quantify strains in the anterior cruciate and medial collateral ligaments have shown that these ligaments are subjected to 4-5% strains during normal activities and can be strained to 7.7% during external application of loads to the knee joint. The objective of this study was to characterize the expression of types I and III collagen in fibroblast monolayers of anterior cruciate and medial collateral ligaments subjected to equibiaxial strains on flexible growth surfaces (0.05 and 0.075 strains) by quantifying levels of mRNA encoding these two proteins. Both cyclic strain magnitudes were studied under a frequency of 1 Hz. The results indicated marked differences in responses to strain regimens not only between types I and III collagen mRNA expression within each cell type but also in patterns of expression between anterior cruciate and medial collateral ligament cells. Whereas anterior cruciate ligament fibroblasts responded to cyclic strains by expression of higher levels of type-I collagen message with almost no significant increases in type-III collagen, medial collateral ligament fibroblasts exhibited statistically significant increases in type-III collagen mRNA at all time points after initiation of strain with almost no significant increases in type-I collagen. Furthermore, differences in responses by fibroblasts from the two ligaments were detected between the two strain magnitudes. In particular, 0.075 strains induced a time-dependent increase in type-III collagen mRNA levels in medial collateral ligament fibroblasts whereas 0.05 strains did not. The strain-induced changes in gene expression of these two collagens may have implications for the healing processes in ligament tissue. The differences may explain, in part, the healing differential between the anterior cruciate and medial collateral ligaments in vivo.     

Controlling anterior tibial displacement under static load: a comparison of two braces

This article presents data comparing the restraining effect of the Lenox Hill and the CTi brace to static loading using the KT-1000 Knee Ligament Arthrometer. Testing was performed at 25 degrees and 90 degrees in 15 patients with documented single ligament injuries involving the anterior cruciate. The opposite knee was determined to be normal by subjective and objective testing and was used as the control. Results showed that the anterior drawer tests, both the Lenox Hill and the CTi brace improved the ACL deficient knee significantly. With 15 lb of passive loading, both the Lenox Hill and the CTi brace improved the drawer to within normal limits. However, only the CTi brace was able to return the drawer to within the normal range at the 20 lb force level. Neither brace improved the drawer to normal when subjected to the higher loads created by an active drawer test. At 90 degrees, 15 lb of passive loading could not discriminate between the braced and the unbraced knee or between the normal and ACL deficient knee. When 20 lb of force was applied, only the CTi brace improved the drawer significantly, which placed the drawer into the normal range. Under static testing condition, the CTi brace proved to be better than the Lenox Hill in controlling the anterior drawer in flexion and at 20 lb of passive loads; however, when higher loading forces were used in the active anterior drawer test, neither brace was effective in controlling anterior tibial translation.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of upper-limb motion on lower-limb muscle synchrony. Implications for anterior cruciate ligament injury

BACKGROUND: A high prevalence of rupture of the anterior cruciate ligament is associated with activities that incorporate both abrupt deceleration and catching a ball. In the present study, we examined whether the upper-limb motion involved in catching a ball affected the synchrony of the lower-limb muscles during tasks known to stress the anterior cruciate ligament-namely, abrupt decelerative landings. METHODS: Seven male and eleven female subjects decelerated abruptly to land in single-limb stance after catching a chest-height pass and after no catching. Ground-reaction force and electromyographic data for six lower-limb muscles were sampled while the subjects' landing technique was filmed. The joint-reaction forces and the sagittal planar net moments for the knee then were calculated to derive the tibiofemoral shear forces. The muscle onsets and peak muscle activities were temporally analyzed with respect to the time of initial foot-ground contact, the peak resultant ground-reaction force, and the peak tibiofemoral shear force. RESULTS: When catching a pass, the subjects demonstrated significantly (p < 0.05) earlier rectus femoris onset relative to the timing of the initial foot-ground contact and of the peak tibiofemoral shear force, and they showed delayed biceps femoris onset relative to the timing of the peak tibiofemoral shear force compared with the findings in the trials without catching. CONCLUSIONS: We concluded that catching a ball during an abrupt landing could increase the potential for an anterior cruciate ligament injury by limiting the time available for the hamstring muscles to generate posterior tibial-drawer force before the onset of the quadriceps-induced anterior tibial translation. Clinical Relevance: The integrity of the anterior cruciate ligament during landing relies on the proper coordination of the lower-limb muscles, particularly the quadriceps and the hamstrings. The present study demonstrated that motion of the upper-limbs may interfere with recruitment of these muscles, thereby predisposing the anterior cruciate ligament to injury.     

Knee braces

The preceding discussion has profiled the three different types of knee braces which are available on today's market. It also has attempted to discuss the controversies surrounding these braces and to analyze the scientific data presented to date. Prophylactic braces have been shown to be ineffective in preventing knee injuries in its present day design. Evidence also has shown that their use may even lead to increased knee injuries. Rehabilitative braces, on the other hand, do serve a useful purpose in regard to the operative and non-operative treatment of ligamentous knee injuries. With their ease of application and control of joint motion, they are an important addition to the surgeon's armamentarium. One must keep in mind, however, that these braces provide little static anterior/posterior control and the hinge settings may not actually affect true joint motion. Functional knee braces may play a role in the treatment of patients with pathological laxity due to an injury of the anterior cruciate ligament. Combined with an adequate rehabilitation program and activity modification, these braces do limit excessive anterior tibial translation under low loading conditions. However, under conditions of high loading these braces provide little or no resistance to anterior translation. Therefore, in most sporting activities, their efficacy is questionable. Knee bracing continues to be a complex and controversial topic in the field of orthopedic surgery.(ABSTRACT TRUNCATED AT 250 WORDS)