ACL Surgery Complications

Anterior cruciate ligament injuries are common in young athletes as well as middle-aged adults. While anterior cruciate ligament (ACL) injuries may be treated non-surgically, the majority of the patients opt for surgical management of the ACL tears.

The surgical management is usually done in the form of arthroscopic reconstruction. The arthroscopic ACL reconstruction is a very safe surgery but patients may have concerns regarding immediate and long-term complications of the surgery.

Intraoperative image showing knee arthroscopic ACL reconstruction.

During an ACL reconstruction surgery using an arthroscope, the surgeon harvests a graft from the patient or uses a cadaveric or synthetic graft to replace the torn ligament. The surgery involves the use of key-hole incisions. The surgeon introduces a small camera with a light source through the keyhole incision.

The minute instruments are inserted through another keyhole incision. The surgeon guides the instruments using the arthroscopic camera display on the outside screen. The graft is securely tightened and the knee is placed in a brace. An ACL rehabilitation is started to achieve optimum function and a return to normal activities/sports.

The complication of ACL reconstruction may be summarized as the ones due to pre-operative decisions, intraoperative causes, and postoperative causes.

Implant (screw) used for securing the graft.

Preoperative decisions

• ACL reconstruction is deferred until the swelling has subsided after an acute injury. Performing the surgery too early may lead to knee stiffness after the ACL reconstruction. Generally, ACL reconstruction surgery is deferred until the patient is able to bend (90 degrees) and straighten the injured knee fully.
• Missing of additional injures of the knee structures such as medial collateral ligament, posterior lateral corner injuries and meniscus may lead to instability of the ACL reconstruction and possible graft failure. The patient may complain of continued knee pain and instability after ACL reconstruction. The additional injuries may be recognized with careful physical examination and radiological studies.
• Not performing the ACL surgery when needed and waiting for too long may lead to damage to the articular knee cartilage and meniscus. The patient should be educated regarding the possible risks of non-operative treatment and should be advised to limit activities with continued bracing.

Intraoperative complications

• Kneecap (patella) fracture may occur during the surgery when a bone-patellar-tendon-bone (BPTB) graft is taken. The fracture of the kneecap may occur as a result of improper bone cuts during harvesting the graft.
• Improper harvest of the hamstring graft may either lead to a very small graft or may lead to knee bending weakness. Excessive harvest of the hamstring graft may weaken the hamstring muscle and may lead to knee flexion weakness.|
• There may be an inadvertent injury to the saphenous nerve during cutting of the skin and the tissues. The saphenous nerve injury may lead to numbness and tingling over the inner aspect of the knee joint.|
• There is a risk of damage to the major blood vessels and nerves behind the knee that may lead to amputation or paralysis of the foot.|
• ACL graft mismatch may occur as a result of a smaller, longer, wider, or narrower graft as compared to the graft tunnels. The mismatch may cause instability or stiffness of the knee joint.|
• Similarly improper placement of the graft tunnel may lead to instability, loss of knee flexion, loss of knee extension, knee pain, and graft rupture.

Instruments used to drill the tunnel in ACL reconstruction.

Postoperative complications

• Stiffness is a common post-ACL reconstruction complication that is defined as the incomplete range of motion of the knee following surgery. The complication may be a result of poor technique during surgery or due to poor adherence to post-operative rehabilitation protocol. Aggressive rehabilitation, manipulation under anesthesia, arthroscopic adhesiolysis may be used to relieve knee stiffness.
• Patella fracture after ACL reconstruction may result from graft harvesting. The patella fracture may require surgical management.
• Pain, swelling, redness, the rise of temperature, and stiffness may occur as a result of infection. Radiological and knee aspirate and cultures may be needed for diagnosis. The infection may be managed with thorough lavage, antibiotics, debridement, etc. The management may at times necessitate the removal of the graft.
• Pain in the front of the knee after the surgery is commonly associated with patellar tendon graft but may also occur in cases of allograft and quadriceps tendon graft. The pain may occur due to noncompliance with postoperative rehabilitation protocol.

ACL reconstruction is a safe surgery and the associated complications are rare. Compliance with postoperative rehabilitation protocol ensures a quick return to activities of daily living and sports.