Experimental Joint Contracture Correction with Low Torque-Long Duration Repeated Stretching

Abstract

Tension is necessary to maintain and restore the mechanical properties of soft connective tissues. Conversely, reduced tension states such as produced by immobilization weaken mechanical properties and facilitate joint contracture. We assessed the effect of low torque-long duration stretching to increase the range of motion (ROM) and to restore the mechanical properties of contracted joints in 66 rat knees immobilized for 40 days. After remobilization, we randomly divided the contracted knees into four treatment groups treated with repeated stretches of diverse torques and duration: stretching with low-torque and long-duration, high-torque and short-duration, high-torque and long-duration, low-torque and short duration. We included control and natural recovery groups. Phase lag in all treatment groups recovered to the same range as in the normal controls. Dynamic stiffness, which was not altered by joint immobilization, increased in all treatment groups. Deformation and load to failure improved substantially only in the low-torque and long-duration stretching group. Low-torque and long-duration repeated stretching leads to a greater restoration of ROM with more normal mechanical properties compared to high-torque and short duration stretching.

Amount of Torque and Duration of Stretching Affects Correction of Knee Contracture in a Rat Model of Spinal Cord Injury

“…The use of stretching to prevent and treat contractures after immobilization is supported by numerous animal studies [3,8,12,30,32,39,40]. Ample evidence from these animal studies suggests that contracture management can be achieved through repeated or sustained stretching in the case of contractures not attributable to injury to the central nervous system [3,8,10,39,40].…”

“…The direction of the stretch was set toward extension with traction applied to the whole lower extremity for consistent torque as established by Usuba et al [39]. The hightorque condition was an applied force of 0.045 Nm; this results in maximal stretching in the rat knee.…”

“…The hightorque condition was an applied force of 0.045 Nm; this results in maximal stretching in the rat knee. The low-torque condition was an applied force of 0.02 Nm; this results in moderate stretching [39]. The static stretching time for one treatment was set at 30 minutes for long duration and 15 minutes for short duration.…”

“…Ample evidence from these animal studies suggests that contracture management can be achieved through repeated or sustained stretching in the case of contractures not attributable to injury to the central nervous system [3,8,10,39,40]. In contrast, contractures after central nervous system injuries are the result of neural and nonneural factors, including paralysis and structural changes in soft tissues [15,19] .…”

“…However, it remains unclear whether the effects observed in these trials are clinically worthwhile, and the therapeutic effect of stretching on the pathophysiology of contractures has received little attention. In addition, the magnitude and duration of the stretching force applied have been guided mainly by subjective clinical impressions and the patient's subjective feedback [39].…”