The anterior cruciate ligament (ACL) is a band of tough fibrous tissue located deep within the knee joint, connecting the thigh bone (femur) to the shin bone (tibia). This ligament plays a role in stabilizing the knee, preventing the tibia from sliding too far forward and controlling rotational movements. An ACL injury is common, especially in athletes participating in sports involving sudden stops, changes in direction, jumping, or pivoting. Recovery from an ACL injury involves specialized medical devices, used during surgery and rehabilitation. These devices support healing, restore function, and help individuals return to activity.
Surgical Fixation Devices
During ACL reconstruction surgery, specialized hardware anchors the new graft within bone tunnels created in the femur and tibia. Interference screws are a common approach, placed alongside the graft within the bone tunnels. Made from materials such as titanium, polyether ether ketone (PEEK), or bioabsorbable polymers, these screws hold the graft in place by radial compression. This reduces graft-tunnel motion and promotes direct healing between the graft and bone.
Another method of graft fixation is suspensory fixation, which positions the graft at a distance from the joint line. This technique uses devices such as cortical buttons, which are small plates or buttons with sutures. The sutures pass through the graft and a bone tunnel, securing the graft by engaging cortical bone. Suspensory fixation provides initial stability and is favored for soft tissue grafts, with adjustable loop designs allowing for precise tensioning. These devices provide stability for graft integration, facilitating early rehabilitation.
Graft Materials as Implants
The graft acts as a biological implant, replacing the torn ACL. Surgeons use two main types: autografts and allografts. An autograft is tissue harvested from the patient’s own body, reducing disease transmission and immune rejection. Autograft sites include the patellar tendon, hamstring tendons (semitendinosus and gracilis), and quadriceps tendon.
The bone-patellar tendon-bone (BPTB) autograft includes a segment of the patellar tendon with small bone blocks from the patella and tibia. These bone blocks allow for bone-to-bone healing within drilled tunnels, allowing for strong graft integration. Hamstring tendon autografts use portions of the semitendinosus and gracilis tendons, often quadrupled for strength. The quadriceps tendon autograft, which can include a bone block from the patella or be all-soft tissue, is an alternative. Allografts are tissues from a deceased donor. Allografts avoid a second surgical site but may have a higher reported failure rate in younger, active individuals. The choice between graft types is a shared decision, influenced by age, activity level, and donor site morbidity.
Post-Operative Bracing
Following ACL surgery, external knee braces are used to protect the healing graft and control knee motion. Immediately after the procedure, a rehabilitative brace is prescribed. These rigid braces feature adjustable hinges that allow the surgeon to set limits on the knee’s range of motion, often locked in extension initially. This brace shields the reconstructed ligament from forces that could compromise healing.
As rehabilitation progresses and the graft heals, patients transition to a functional brace. This brace is sleeker, providing dynamic support and stability with controlled range of motion. Functional braces are recommended for individuals returning to sports or high-demand activities, preventing re-injury by limiting unwanted rotation or excessive extension. Bracing protocols vary, but these devices support the knee as the knee regains strength and stability.
Rehabilitative Technology
Beyond surgical interventions and bracing, technologies aid in the physical therapy phase of ACL recovery. Continuous Passive Motion (CPM) machines are used in the early post-operative period to move the knee joint through a controlled range of motion without patient effort. This passive movement maintains joint flexibility, reduces stiffness, and may prevent scar tissue formation.
Cryotherapy units, also known as ice machines or cryopneumatic compression devices, manage post-operative pain and swelling. These devices circulate chilled water through a wrap around the knee, sometimes with intermittent compression. Controlled cold temperatures reduce blood flow, decreasing inflammation and alleviating discomfort, which can minimize narcotic pain medication. Neuromuscular Electrical Stimulation (NMES) devices deliver electrical impulses to muscles, especially the quadriceps. This stimulation re-educates and activates muscles weakened or inhibited after surgery, promoting strength recovery and improving muscle control.