Method for setting total graft force and load sharing in augmented ACL grafts

Lew, William D.; Engebretsen, Lars; Lewis, Jack L.; Hunter, Robert E.; Kowalczyk, Curtis

doi:10.1002/jor.1100080512

Cited by 17 publications

(11 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the past, large stents, such as the carbon fiber graft or Ligament Augmentation Device (LAD), and even the middle third of the patellar tendon, have been used to protect repair of the ACL,14-16 however, these procedures all involved placement of a relatively large amount of material in the same space as the ACL, thus leaving less room for formation of a hypertrophic scar and also resulting in extensive disruption to the native ACL insertion sites. The technique proposed here could possibly provide a means to modulate load and protect the healing ACL, particularly during initial healing17,18, while still allowing preservation of the insertion sites and scar volume. An additional advantage with this technique is that the sutures could be selected or designed to support the repair for a specified period of time and then release or resorb, to minimize any potential complication of stress shielding by the suture-stent.…”

Section: Discussionmentioning

confidence: 99%

Can suture repair of ACL transection restore normal anteroposterior laxity of the knee? An ex vivo study

Fleming

Carey

Spindler

et al. 2008

Journal Orthopaedic Research

100

View full text Add to dashboard Cite

Recent work has suggested the transected anterior cruciate ligament (ACL) can heal and support reasonable loads if repaired with sutures and a bioactive scaffold; however, use of a traditional suture configuration results in knees with increased anterior-posterior (AP) laxity. The objective was to determine whether one of five different suture repair constructs when performed at two different joint positions would restore normal AP knee laxity. AP laxity of the porcine knee at 608 of flexion was evaluated for five suture repair techniques. Femoral fixation for all repair techniques utilized a suture anchor. Primary repair was to either the tibial stump, one of three bony locations in the ACL footprint, or a hybrid bony fixation. All five repairs were tied with the knee in first 308 and then 608 of flexion for a total of 10 repair constructs. Suture repair to bony fixation points within the anterior half of the normal ACL footprint resulted in knee laxity values within 0.5 mm of the ACL-intact joint when the sutures were tied with the knee at 608 flexion. Suture repair to the tibial stump, or with the knee at 308 of flexion, did not restore normal AP laxity of the knee. Three specific suture repair techniques for the transected porcine ACL restored the normal AP laxity of the knee at the time of surgery. Additional studies defining the changes in laxity with cyclic loading and in vivo healing are indicated. ß

show abstract

Section: Discussionmentioning

confidence: 99%

Can suture repair of ACL transection restore normal anteroposterior laxity of the knee? An ex vivo study

Fleming

Carey

Spindler

et al. 2008

Journal Orthopaedic Research

100

View full text Add to dashboard Cite

show abstract

“…The use of ligament augmentation and particularly the toad sharing in multiple component grafts has been studied using a pneumatic loading apparatus (PLA) together with a buckle transducer for ligament tension measurements in four studies [26,37,52,53]. This experimental setup has previously been described together with an error analysis [55].…”

Section: Human In Vitro Tension Studies Performed On Unloaded Jointsmentioning

confidence: 99%

“…Lew et al [52] used what they called the force-setting technique on a composite graft consisting of a bonepatella tendon-bone together with the LAD TM. They varied the ratio of load sharing (3:1, 1:1, 1:3) and kept the total graft force within the range of the normal ACL at 30 ~ of flexion in eight cadaver knees.…”

Section: Human In Vitro Tension Studies Performed On Unloaded Jointsmentioning

confidence: 99%

Review on tension in the natural and reconstructed anterior cruciate ligament

Andersen

Amis

1994

Knee Surg, Sports traumatol, Arthroscopy

View full text Add to dashboard Cite

This article reviews the methodology and results of published studies concerned with tension in the natural and reconstructed anterior cruciate ligament (ACL). This also includes studies of fiber length changes with knee motion and the relationships between graft tunnel placements and isometricity. Little work has been done in vivo: in humans, length changes of the anterior ACL fibers have been measured at operation, while animal longitudinal studies have been few and have given conflicting results. Work in vitro has used many methods to study ACL tension directly or indirectly, via length changes in fibers, but many authors have reported variable results, caused partly by inter-specimen differences and lack of control of forces or kinematics. It seems likely that different grafts require different peroperative tensions to restore normal stability when measured immediately after application at one knee position. But graft placement and the angle at which tensioning is performed also matter. Over-tensioning constrains knees under load cycling. Similarly, it is difficult to measure and therefore also to decide how tension should be distributed between an ACL graft and and augmentation to the graft. It was concluded that the published studies provide many guidelines for the effects of different graft placements or tensioning protocols but, overall, there is little firm evidence on which to recommend any particular ACL reconstruction protocol.

show abstract

“…Experiments on combined loading represent a new level of complexity for bench testing and bring us a step closer to identifying relative magnitudes of ligament forces under more relevant loading conditions. Buckle transducers have been used to measure forces in the anteromedial band of the anterior cruciate ligament (1,4) and in the entire ligament in conjunction with measurements of forces in autogenous graft substitutes augmented with the LAD synthetic ligament augmentation device (3M, Minneapolis, MN, U.S.A.) (2,5). With the buckle technique, the recorded forces reflect only that portion carried by the instrumented fiber; foreshortening and distortion of the instrumented cruciate fibers occur (3).…”

mentioning

confidence: 99%

Combined knee loading states that generate high anterior cruciate ligament forces

Markolf¹,

Burchfield

Shapiro³

et al. 1995

Journal Orthopaedic Research

800

794

View full text Add to dashboard Cite

Injuries to the anterior cruciate ligament frequently occur under combined mechanisms of knee loading. This in vitro study was designed to measure levels of ligament force under dual combinations of individual loading states and to determine which combinations generated high force. Resultant force was recorded as the knee was extended passively from 90 degrees of flexion to 5 degrees of hyperextension under constant tibial loadings. The individual loading states were 100 N of anterior tibial force, 10 Nm of varus and valgus moment, and 10 Nm of internal and external tibial torque. Straight anterior tibial force was the most direct loading mechanisms; the mean ligament force was approximately equal to applied anterior tibial force near 30 degrees of flexion and to 150% of applied tibial force at full extension. The addition of internal tibial torque to a knee loaded by anterior tibial force produced dramatic increases of force at full extension and hyperextension. This loading combination produced the highest ligament forces recorded in the study and is the most dangerous in terms of potential injury to the ligament. In direct contrast, the addition of external tibial torque to a knee loaded by anterior tibial force decreased the force dramatically for flexed positions of the knee; at close to 90 degrees of flexion, the anterior cruciate ligament became completely unloaded. The addition of varus moment to a knee loaded by anterior tibial force increased the force in extension and hyperextension, whereas the addition of valgus moment increased the force at flexed positions. These states of combined loading also could present an increased risk for injury. Internal tibial torque is an important loading mechanism of the anterior cruciate ligament for an extended knee. The overall risk of injury to the ligament from varus or valgus moment applied in combination with internal tibial torque is similar to the risk from internal tibial torque alone. External tibial torque was a relatively unimportant mechanism for generating anterior cruciate ligament force.

show abstract

Method for setting total graft force and load sharing in augmented ACL grafts

Cited by 17 publications

References 14 publications

Can suture repair of ACL transection restore normal anteroposterior laxity of the knee? An ex vivo study

Can suture repair of ACL transection restore normal anteroposterior laxity of the knee? An ex vivo study

Review on tension in the natural and reconstructed anterior cruciate ligament

Combined knee loading states that generate high anterior cruciate ligament forces

Contact Info

Product

Resources

About