Unloader Brace Research Articles

Valgus Unloader Bracing Reduces Knee Adduction Moment during Gait in Normally-Aligned Healthy Subjects

Valgus Unloader Bracing Reduces Knee Adduction Moment during Gait in Normally-Aligned Healthy Subjects

A Mechanical Theory for the Effectiveness of Bracing for Medial Compartment Osteoarthritis of the Knee

Evidence that knee braces used for the treatment of osteoarthritis mediate pain relief and improve function by unloading the joint (increasing the joint separation) remains inconclusive. Alternatively, valgus-producing braces may mediate pain relief by mechanically stabilizing the joint and reducing muscle cocontractions and joint compression. In this study, therefore, we sought to examine the degree to which so-called unloader braces control knee instability and influence muscle cocontractions during gait. Sixteen subjects with radiographic evidence of knee malalignment and medial compartment osteoarthritis were recruited and fitted with a custom Generation II Unloader brace. Gait analysis was performed without use of the brace and with the brace in neutral alignment and in 4 degrees of valgus alignment. A two-week washout period separated the brace conditions. Muscle cocontraction indices were derived for agonist and antagonist muscle pairings. Pain, instability, and functional status were obtained with use of self-reported questionnaires, and the results were compared. The scores for pain, function, and stability were worst when the knee was unsupported (the baseline and washout conditions). At baseline, nine of the sixteen patients reported knee instability and five of the nine complained that it affected their activities of daily living. Poor knee stability was found to be correlated with low ratings for the activities of daily living, quality of life, and global knee function and with increased pain and symptoms. Knee function and stability scored best with the brace in the neutral setting compared with the brace in the valgus setting. The cocontraction of the vastus lateralis-lateral hamstrings was significantly reduced from baseline in both the neutral (p = 0.014) and valgus conditions (p = 0.023), and the cocontraction of the vastus medialis-medial hamstrings was significantly reduced with the valgus setting (p = 0.068), as a result of bracing. Patients with greater varus alignment had greater decreases in vastus lateralis-lateral hamstring muscle cocontraction. When knees with medial compartment osteoarthritis are braced, neutral alignment performs as well as or better than valgus alignment in reducing pain, disability, muscle cocontraction, and knee adduction excursions. Pain relief may result from diminished muscle cocontractions rather than from so-called medial compartment unloading.

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° compared with baseline (p = 0.001) and by 1.3° 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. Level of Evidence: Therapeutic Level II. See Instructions to Authors for a complete description of levels of evidence.

The Effectiveness of Self-Adjustable Custom and Off-the-Shelf Bracing in the Treatment of Varus Gonarthrosis

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. 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. 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. 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.

Management of Osteochondritis Dissecans of the Knee

Osteochondritis dissecans of the knee is being seen with increased frequency in pediatric and young adult athletes and is thought to be, in part, owing to earlier and increasingly competitive sports participation. Despite much speculation, the cause of both juvenile and adult osteochondritis dissecans remains unclear. Early recognition is essential. Whereas adult osteochondritis dissecans lesions have a greater propensity to instability, juvenile osteochondritis dissecans lesions are typically stable, and those with an intact articular surface have a potential to heal with nonoperative treatment through cessation of repetitive impact loading. The value of adjunctive immobilization, protected weightbearing, and unloader bracing has not been established. Skeletally immature patients with stable lesions that have not healed with nonoperative treatment should have consideration given to arthroscopic drilling to promote healing before the lesion progresses and requires more involved treatment with a less optimistic prognosis. Magnetic resonance imaging may allow early prediction of lesion healing potential. The majority of adult osteochondritis dissecans cases as well as those skeletally immature patients with unstable lesions and secondary loose bodies require fixation and possible bone grafting. Many unstable lesions will heal after stabilization, but long-term prognosis is not clear. Chronic loose fragments can be difficult to fix and have poor healing potential. Results of excision of large lesions from weightbearing zones are poor. Chondral resurfacing techniques have limited long-term data for cases of osteochondritis dissecans in skeletally immature patients.

Quantitative Electromyography Analysis of Disc Unloader Brace

The purpose of this study was to determine if the Disc Unloader brace was effective in reducing intradiscal pressure. There is a strong correlation between lumbar paraspinal activity and intradiscal pressure. We used ten healthy volunteers to measure lumbar paraspinal activity at L5 using a quantitative EMG system. After doing reliability and reproducibility testing which showed margin of error of 7%, ten volunteers were measured for quantitative EMG activity at the L5 paraspinal level in full lumbar flexion without the Disc Unloader brace three times and averaged. The same quantitative EMG testing was done in full flexion with the Disc Unloader brace on at the L5 paraspinal level three times and averaged. For five of the ten patients, we performed the test first with the Disc Unloader brace on whereas for the rest of the five, the test was performed first without the brace on. There were 7 females and 3 males with average age of 39 (range 26-46). The average area under the curve score was 173 +/- 27.1 microvolts at the L5 paraspinal for the ten healthy subjects without the Disc Unloader brace on. The average area under the curve score was 102 +/- 19.6 microvolts at the L5 paraspinal for ten healthy subjects with the Disc Unloader brace on. There was a statistically significant (p<0.05) reduction in quantitative paraspinal activity of 41% with the Disc Unloader brace on. We conclude that the Disc Unloader brace is effective in reducing quantitative EMG lumbar paraspinal myoelectric activity and therefore intradiscal pressures.

Poster 154: Quantitative electromyographic analysis of disk unloader brace.

Objective: To determine if the Disk Unloader brace is effective in reducing intradiskal pressure because there is a strong correlation between lumbar paraspinal activity and intradiskal pressure. Design: Descriptive crossover study. Setting: Academic-affiliated private physiatry practice. Participants: 10 healthy volunteers (7 women; 3 men; avg age, 39y; range, 26–46y). Interventions: We used 10 healthy volunteers to measure lumbar paraspinal activity at L5 using a Cadwell quantitative electromyography system. After completing reliability and reproducibility testing, which showed a margin of error of 7%, 10 volunteers were measure for quantitative electromyographic activity at the L5 paraspinal level in full lumbar flexion without the Disk Unloader brace 3 times and the results were averaged. The same quantitative electromyographic testing was done in full flexion with the Disk Unloader brace on at the L5 paraspinal level 3 times and the results were also averaged. For 5 of the 10 patients, we performed the test first with the Disk Unloader brace on whereas for the rest, the test was performed first without the brace. Main Outcome Measure: Quantitative electromyographic activity at the L5 paraspinal level in full lumbar flexion. Results: The average area under the curve (AUC) score was 173±27.1mV at the L5 paraspinal for the 10 healthy subjects without the Disk Unloader brace. The average AUC score was 102±19.6mV at the L5 paraspinal for 10 healthy subjects with the Disk Unloader brace. There was a statistically significant ( P<.05) reduction in quantitative paraspinal activity of 41% with the Disk Unloader brace on. Conclusions: We conclude that the Disk Unloader brace is effective in reducing quantitative electromyographic lumbar paraspinal activity and therefore intradiskal pressures.