The Effect of Extension Constraint Knee Bracing on Dynamic Balance, Gait Mechanics, and Joint Alignment

Evaluation of spring-loaded cane ground reaction forces during walking using time and frequency domain analysis

This study examined the effect of a spring-loaded cane stiffness reduction on upper and lower extremity ground reaction forces in time and frequency domain during cane-aided walking. Twenty-nine participants walked five times over two force plates with a spring-loaded cane set at four different stiffnesses and T-scope knee brace set at 30° of knee flexion to simulate a foot injury. Time-frequency domain analyses revealed an increase in ground reaction forces at the simulated injured foot and a decrease in ground reaction forces at the hand via the shaft of the cane for each spring loaded-cane stiffness reduction during walking. The results build on existing literature and highlight the use of spring-loaded canes, braking and propulsive ground reaction force measures, and frequency domain analysis to more accurately assess and monitor the rehabilitation and prevention of upper and lower extremity injuries during cane-aided walking.

Walking with an induced unilateral knee extension restriction affects lower but not upper body biomechanics in healthy adults

BACKGROUND

Unilateral knee flexion contractures (KFC) are frequently seen in orthopedic rehabilitation and often interfere with the normal gait pattern, resulting in passive and/or active secondary deviations. In order to prevent KFC-related complications such as patellofemoral pain or the knee spine syndrome, a comprehensive understanding of such deviations is necessary.

RESEARCH QUESTION

How does an artificially induced unilateral KFC affect whole body biomechanics in young healthy adults during gait?

METHODS

Twenty-four healthy young adults (females/males: 13/11; mean age: 27.3 ± 3.8 years) were included in this cross-sectional study. Using an 8-camera optical motion capture system and two embedded force plates, three-dimensional lower extremity, pelvis and trunk kinematics as well as lower extremity joint moments were derived during normal walking and walking with unilateral KFCs by means of a lightweight knee brace locked at 30° and 60° of flexion. Data were analyzed using one-dimensional statistical parametric mapping, allowing explorative group comparisons of continuous data rather than pre-defined discrete parameters.

RESULTS

On the braced side, increased hip flexion (p < 0.001, 1-100 % of gait cycle [%GC]), knee flexion (p < 0.001, 1-72 and 82-100 %GC) and ankle dorsiflexion angles (p < 0.001, 1-100 %GC) as well as external knee flexion moments (p < 0.001, 1-98 % of stance phase [%StPh]) and decreased ankle dorsiflexion (p < 0.001, 74-94 %StPh), hip flexion and hip adduction moments (p < 0.001, 1-32 %StPh and p < 0.001, 71-92 %StPh, respectively) were observed. The unbraced side showed similar but less pronounced deviations. Pelvis and upper body kinematics were not altered, suggesting that the lower limbs fully compensate for KFCs of less than 30°.

SIGNIFICANCE

Asymmetric limb loading and considerable increases in external knee flexion moments might increase the risk for adverse effects of lower extremity joints in the long-term. It seems therefore important to treat KFCs as early as possible and to implement preventive strategies to avoid possible complications.

Functional Brace in ACL Surgery: Force Quantification in an In Vivo Study

Background:

A need exists for a functional anterior cruciate ligament (ACL) brace that dynamically supports the knee joint to match the angle-dependent forces of a native ACL, especially in the early postoperative period.

Purpose/Hypothesis:

The purpose of this study was to quantify the posteriorly directed external forces applied to the anterior proximal tibia by both a static and a dynamic force ACL brace. The proximal strap forces applied by the static force brace were hypothesized to remain relatively constant regardless of knee flexion angle compared with those of the dynamic force brace.

Study Design:

Controlled laboratory study.

Methods:

Seven healthy adult males (mean age, 27.4 ± 3.4 years; mean height, 1.8 ± 0.1 m; mean body mass, 84.1 ± 11.3 kg) were fitted with both a static and a dynamic force ACL brace. Participants completed 3 functional activities: unloaded extension, sit-to-stand, and stair ascent. Kinematic data were collected using traditional motion-capture techniques while posteriorly directed forces applied to the anterior aspect of both the proximal and distal tibia were simultaneously collected using a customized pressure-mapping technique.

Results:

The mean posteriorly directed forces applied to the proximal tibia at 30° of flexion by the dynamic force brace during unloaded extension (80.2 N), sit-to-stand (57.5 N), and stair ascent (56.3 N) activities were significantly larger, regardless of force setting, than those applied by the static force brace (10.1 N, 9.5 N, and 11.9 N, respectively; P < .001).

Conclusion:

The dynamic force ACL brace, compared with the static force brace, applied significantly larger posteriorly directed forces to the anterior proximal tibia in extension, where the ACL is known to experience larger in vivo forces. Further studies are required to determine whether the physiological behavior of the brace will reduce anterior knee laxity and improve long-term patient outcomes.

Clinical Relevance:

ACL braces that dynamically restrain the proximal tibia in a manner similar to physiological ACL function may improve pre- and postoperative treatment.