Allografts for anterior cruciate ligament reconstruction

Anterior cruciate ligament (ACL) reconstruction remains one of the most frequently performed orthopedic procedures, and graft selection remains one of the most crucial preoperative treatment decisions. The use of allograft tissue has increased in the past decade for both primary and revision ACL reconstruction, as these tissues can play a role in the treatment algorithm based on patient age, activity level, and overall treatment goals. Several recent investigations have demonstrated comparable clinical outcomes and failure rates in various patient populations with the use of non-irradiated allograft tissue when compared to autograft tissue. As such, there is an increasing importance placed on the surgeon’s understanding of allograft tissue options, collection and sterilization procedures, indications for use, and surgical techniques.

Potential advantages of using allograft tissue compared to autograft include the following:

• Decreased donor site morbidity with less risk of pain, namely anterior knee pain, quadriceps weakness, patellar fracture, patellar tendon rupture, saphenous nerve injury, and residual hamstring weakness

• Decreased operating room time

• Improved cosmesis with smaller incisions

• Larger graft sizes allowing utilization of adequately sized grafts, especially in a revision setting (bone loss, etc.)

Potential disadvantages of using allograft include the following:

• Higher cost

• Availability

• Reliability of vendors

• Slower graft incorporation, delaying rehabilitation

• Possibility of disease transmission and/or immunologic response

• Potentially increased risk of failure among younger athletes

In ACL reconstruction, graft selection should be performed on an individual basis; however, in certain populations of patients, allograft may be preferable over autograft, whereas in others the opposite may be true.

Patients for whom allograft may be preferred include the following:

• Patients aged 35–40 years of age and older

• Lower demand patients

• Skeletally immature athletes

• Patients with a history of patellofemoral pain or prior patellar surgery

• Laborers or athletes who frequently kneel

• Patients undergoing revision ACL reconstruction

• Patients undergoing multiligament reconstructive surgery

Allograft use is less desirable in the following situations:

• High-level athletes younger than 40 years old

• Elite-level athletes

• Sprinters or hurdlers who require full terminal flexion strength

• Patients with autoimmune diseases or immunocompromised patients

• Patient with inflammatory arthropathy

Patients should be allowed to make informed decisions on graft choice following a discussion of risks and benefits with the treating surgeon.

Always have informed consent from the patient to use an allograft.

Know your allograft supplier’s track record and tissue-processing techniques, including sterilization methods (especially the use of irradiation) and proprietary cleansing techniques.

Have a second allograft available if problems arise with the original graft (label error, tissue quality, technical error, contamination), or discuss use of autograft if something is wrong with the allograft.

Prepare anatomic tunnels using independent drilling techniques. Use of the described footprint method ensures an anatomic reconstruction that is not vulnerable to variable patient anatomy or errant referencing of other intra-articular landmarks. Nonanatomic ACL grafts are at increased risk for failure independent of autograft or allograft selection.

Oscillating saws and rongeurs are best for removal of excess bone and sizing of the bone plug.

Allografts may be reasonable options for ACL reconstruction on older and lower demand patients, particularly those with existing patellofemoral pain and/or extensor mechanism disorders.

Make sure to order the properly sized allograft, particularly in the case of bone–patellar tendon–bone (BTB) allograft. The patient’s height can be used as a guideline for length of the soft tissue component of the graft.

It is critical to recognize and treat any concomitant malalignment or ligamentous injuries, including medial collateral ligament (MCL), lateral collateral ligament (LCL), posterior cruciate ligament (PCL), and posterolateral corner (PLC) injury. Failure to recognize and treat these conditions will predispose the ACL reconstruction to failure regardless of graft type.

Both Achilles and BTB allografts require careful preparation of the bone plug to avoid fracture; bone crimpers should not be used, as they can fragment the bone.

With BTB allografts, length and graft-tunnel mismatch can be an issue; tibial tunnel length should be adjusted accordingly. Leaving the tibial bone plug as long as possible and trimming it after the graft is passed is a good way to avoid this.

Graft incorporation and biologic remodeling are slower in allografts when compared to autografts, necessitating avoidance of early, aggressive rehabilitation and delayed return to play in order to help minimize the risk of graft failure secondary to inadequate host incorporation.