More than 200,000 anterior cruciate ligament (ACL) reconstructions are estimated to be performed annually in the United States. While ACL reconstruction has a very high rate of success and patient satisfaction, there is a subset of reconstructions that fail. Many failures are due to technical pitfalls and may be successfully addressed via revision ACL reconstruction. This article focuses on the evaluation of the patient with a failed reconstruction, the preoperative planning and technical execution of a revision ACL reconstruction, and the expected outcomes following this procedure.


The native ACL has a cross-sectional area of approximately 44mm, a stiffness of 242 N/mm, and an ultimate tensile load of 2160 N. It is composed of an anteromedial bundle and a posterolateral bundle, named after their respective attachments to the tibia. When the knee extends, the posterolateral bundle tightens; with the knee in flexion, the anteromedial bundle tightens. Single-bundle reconstruction is the mainstay of most surgical interventions, likely because of its relatively constant in situ force levels during knee flexion compared to the rather variable in situ force levels across the posterolateral bundle.3,4

Several anatomic landmarks have been described to define the tibial attachment of the ACL, including the anterior tibial spine, posterior border of the anterior horn of the lateral meniscus, and posterior cruciate ligament (PCL).5,7 The femoral attachment is at the posteromedial surface of the lateral femoral condyle within the intercondylar notch. The primary function of the ACL is to resist anterior translation of the tibia relative to the femur. However, its secondary role is to resist tibial rotation, as well as varus and valgus stresses about the knee.8,9 The knee also has several secondary restraints to anterior translation of the tibia, including the medial collateral ligament (MCL), the posterior horn of the medial meniscus, and the posterior joint capsule.10


Natural History of an ACL-Deficient Knee

The natural history of the ACL-deficient knee is not well understood. The combined effects of a great number of variables — such as patient activity, pre-injury level of competition, associated injuries, and a paucity of long-term follow up — can make the interpretation of studies challenging. Generally, it is thought that patients who continue to experience instability episodes are at greater risk of further articular cartilage and meniscal injury, and there is evidence to support this concept.

  • Recently, Frobell et al reported one of the few randomized, controlled clinical trials pertaining to this topic. The study consisted of 121 patients ranging from 18 to 35 years of age, 62 treated with rehabilitation plus early ACL reconstruction and 59 treated with rehabilitation and optional ACL reconstruction. Of the 59 patients treated with optional ACL reconstruction, 39% had chosen to undergo delayed ACL reconstruction over the 2-year follow-up period and; of those treated with a rehabilitation protocol alone, 36% had a symptomatic meniscal tear within this same 2-year follow-up period.11
  • Andersson et al also found a higher incidence of meniscal tears in patients with ACL insufficiency who did not undergo reconstruction. They reported a meniscus tear rate of 3% in the operative group versus 32% among patients treated non-operatively.12
  • In further support of this concept, Meuffels et al reported that multiple meniscectomy surgeries occurred in only 12% of their patients treated with ACL reconstruction, compared to 40% of their patients treated non-operatively at 10-year follow up among high level athletes.13
  • Nebelung and Wuschech reported a meniscectomy rate of 95% and grade IV cartilage lesions diagnosed during arthroscopy in 68% at 20-year follow up among patients in their series of elite ACL-deficient athletes.14
  • Furthermore, Lee et al noted a higher degree of cartilage damage during intra-operative assessments among ACL-deficient patients undergoing knee arthroplasty compared to patients with an intact ACL.15

As a result of these and similar reports, many surgeons recommend ACL reconstruction in young active patients and those with symptomatic instability. Revision ACL reconstruction is also recommended to restore knee stability in patients with recurrent symptomatic instability resulting from failed ACL reconstruction.

Recurrent Instability after ACL Reconstruction

Most patients who have undergone primary ACL reconstruction report good to excellent outcomes with regard to stability and return to pre-injury activity level.10,17,18 However, as with any procedure, not all patients experience successful recovery after surgery, whether assessed by objective or subjective outcome measures. Poor outcomes after primary ACL reconstruction can generally be classified into one or more of the following categories:10,19

  • Loss of motion
  • Persistent pain
  • Postoperative complications
  • Extensor mechanism dysfunction
  • Recurrent instability

Recurrent instability can be successfully managed with a revision ACL reconstruction, and the remainder of this discussion will focus on this clinical presentation and its treatment.

Non-Operative Management

Not all patients with residual ACL laxity are candidates for revision ACL reconstruction. A chief complaint of persistent pain after a failed ACL reconstruction without an anatomic explanation can be exacerbated by additional surgery, and addressing instability episodes with a revision ACL reconstruction is not likely to address underlying pain symptoms. Alternatives to operative intervention include non-operative treatment modalities, such as activity modification (avoiding pivoting and cutting sports), strengthening the dynamic knee stabilizers (hamstrings), and bracing.

Preoperative Planning

Patient History

A detailed history, including a patient’s age, activity level prior to the index procedure, inciting trauma, operative technique, and postoperative course, is needed to effectively treat recurrent instability. It is essential to identify whether the patient is primarily experiencing symptoms of stiffness, pain, or true instability, as well as which activities cause these symptoms. It is also important to gain an understanding of a patient’s postoperative therapy program and course of progression, including any traumatic incidents.

Recurrent instability after primary ACL reconstruction has an incidence of 3% to 10%.17,20,21 One of the most common etiologies of recurrent instability is graft failure.22,23 Although it can be difficult to isolate one distinct mechanism of graft failure, three different categories have been described:

  • Failure of incorporation
  • Suboptimal surgical technique
  • Traumatic re-injury

The most common cause of failed primary ACL reconstruction is a combination of factors, with trauma being the dominant etiology.24 The timing of recurrent instability gives clues to these possible etiologies.

  • If primary ACL reconstruction fails within 6 months of surgery, it is usually associated with an error in surgical technique, such as improper tunnel position, failure of fixation or improper tensioning.
  • Late recurrent instability, ie, greater than 6 months to 1 year postoperatively, is typically associated with traumatic re-rupture, or failure of graft incorporation.10,19,21,25,26

Another reason for recurrent instability is unrecognized malalignment or patholaxity during the initial evaluation and management. This may be the result of concomitant varus deformity, posterolateral laxity, MCL laxity, or loss of a secondary restraint such as medial meniscectomy at the time of initial surgery.10,21,27 In Laprade’s series of knee injuries presenting with hemarthrosis, 5% of patients had a combined ACL-PLC injury.28 It is essential to recognize this pathology and address it at the time of revision surgery if indicated.

When possible, obtain the operative report from the prior primary ACL reconstruction. Information about the type of graft used, implanted hardware, double- versus single-bundle reconstruction, anteromedial versus transtibial drilling of femoral tunnel, and associated intra-articular and extra-articular pathology, as well as its treatment and any complications experienced during the procedure, is extremely useful in guiding future interventions.

Physical Examination

A thorough physical examination is needed to identify objective findings to explain the patient’s symptomatology and treatment course. A clinical malalignment may be the first clue to recurrent instability. A varus thrust during gait suggests lateral or posterolateral instability. Buckling of the knee, particularly in the initial phase of gait, may indicate quadriceps weakness and result in perceived instability by the patient.

A neurovascular exam can be helpful in identifying a vascular injury, indicating possible initial knee dislocation. Although large effusions are common in a ruptured native ACL, rupture of an ACL graft may not lead to a significant effusion as a result of the decreased vascularity of the graft compared to native ACL. Prior skin incisions should be assessed for healing and positioning. The range of motion should be documented, as should hamstrings and quadriceps strength. These values should be compared to the contralateral extremity.

Anterior and posterior drawer tests are helpful in evaluating the competency of the ACL and PCL. Lachman’s testing has been noted to be a very sensitive test for ACL deficiency, especially when the contralateral knee has an intact native ACL. Varus and valgus stress testing at 30 degrees of flexion is used to evaluate the competency of collateral ligaments and opening with these stresses applied in full extension, usually suggests injury to collateral ligaments as well as other structures, such as the cruciate ligaments or joint capsule. The presence of a pivot shift is a highly sensitive test for detecting ACL deficiency. However, its utility is limited by the patient’s ability to relax and is often most useful when the patient is anesthesized.

Assessment of tibial external rotation (dial test) can be used to detect PCL or posterolateral corner (PLC) injuries. With the patient prone, more than than 10 degrees of asymmetry with external rotation through the tibia at 30 degrees knee flexion indicates injury to the PLC; asymmetry at 30 degrees and 90 degrees of knee flexion indicates injury to the PCL and the PLC. Varus recurvatum testing, demonstrating varus angulation, hyperextension, and external rotation of the tibia, suggests posterolateral rotary instability.

In addition to these ligamentous examination maneuvers, a thorough meniscal and cartilage examination should be performed including, McMurray’s test and evaluation of joint line tenderness.

Patient Counseling

Preoperative planning should include counseling the patient about their expectations of postoperative function and outcome. Overall, revision surgery has been associated with worse outcomes compared to primary ACL reconstruction.16,24,29,30 The goal of revision surgery is to prevent further instability episodes associated with activity. Patients with limb malalignment, posterolateral rotational instability, arthrofibrosis, or significant bone deficits should be made aware that multiple surgeries in a staged fashion may be required.

A thorough discussion of the graft source should be done preoperatively. Prior autograft harvesting and patient concerns guide recommendations; however, graft selection is a broad topic and the relevant issues are discussed more thoroughly elsewhere.31 The largest series of patients undergoing revision ACL reconstructions reports a slightly increased rate of allograft use over autograft tissues.24

Allograft tissues commonly used to reconstruct the ACL include:

  • Bone-patellar tendon-bone
  • Achilles tendon
  • Tibialis tendon
  • Quadriceps tendon, with or without a patellar bone block
  • Hamstring tendons

Autograft options include:

  • Patella tendon
  • Hamstring tendon
  • Quadriceps tendon
Imaging and Instruments

Plain radiographs of the knees, including weight-bearing anteroposterior and lateral views, allow for assessment of:

  • Tunnel placement
  • Graft impingement
  • Tunnel osteolysis
  • Patellofemoral pathology
  • Retained hardware

Forty five-degree posteroanterior flexion weight-bearing radiographs provide a view of the femoral condylar notch and are also sensitive for joint space narrowing. A common cause of graft failure related to surgical technique is anterior placement of the femoral tunnel, and this is often detected on lateral radiograph (Figure 1). An anteriorly placed femoral tunnel can lead to tightening of the grafts in knee flexion, resulting in irreversible graft stretching or loss of knee flexion. Full-length alignment films are critical in patients with varus deformity or chronic posterolateral rotatory instability.

Figure 1. Lateral radiograph of the knee demonstrating excessive anterior position of the femoral tunnel. Anterior femoral tunnel position can lead to excessive graft tension and resulting laxity or failure.

CT scan is considered for a more extensive evaluation of bone loss and a more precise evaluation of tunnel morphology. MRI is also useful to further characterize tunnel size, as well as a thorough evaluation of ligamentous structures and concomitant intra-articular pathology. Specifically, the extensor mechanism, PLC structures, MCL, and PCL should be identified. Loose bodies, meniscal injury, cartilage injuries, and osteochondral injuries are also assessed. The utility of MRI images can be impaired in patients with retained metallic implants, which can create significant imaging artifacts.

The prior operative report and imaging studies are used to determine the necessary instruments to remove existing hardware. In addition to implant-specific extraction tools, commercially available ACL revision trays, which include coring reamers and other instruments for screw removal, can prove quite useful in these situations and should be available in the operating room at the time of surgery (Figure 2).10 Additional instruments to address any unexpected meniscal tears or cartilage lesions should also be made available.

Figure 2. A commercially available revision ACL tray contains invaluable tools including screw removal instruments and coring reamers.


Our preferred positioning for ACL reconstructive surgery is with the patient in the supine position using a lateral post and a thigh tourniquet. The lateral post should be placed proximal enough to allow for the surgeon’s hand to drill the tibial tunnel without hitting the table when the patient’s knee is flexed over the edge of the table.


Standard ACL reconstruction approaches are also used in revisions, with the caveat that formerly harvested autograft structures are no longer candidates for reconstruction donor sites (Figure 3).

Figure 3. A sterile marker is used to mark out portions of the previous incision that are able to be used for the revision procedure, noting that previous autograft harvesting limits available autograft donor sites


After administration of appropriate anesthesia, a thorough examination of the operative and contralateral knee is performed, with special attention paid to evaluating posterolateral, varus, and valgus instability, as these will not be addressed arthroscopically.

Diagnostic Arthroscopy and Notchplasty

Standard portals are used for diagnostic arthroscopy, including a superolateral outflow portal, an anteromedial portal, and an anterolateral portal. Portal placement should be assessed independent of prior portal scars, as portal location should not be compromised for the sole purpose of reusing the previous incisions. A complete diagnostic arthroscopic evaluation of the knee should be performed, followed by treatment of other co-morbid conditions prior to the revision ACL reconstruction.

After the arthroscopic evaluation is complete and any other intra-articular pathology has been treated, the tourniquet is inflated. A bump is placed under the distal thigh and the knee is flexed to 90 degrees with the popliteal space free, allowing the neurovascular structures to fall posteriorly away from the posterior capsule. The previous graft is removed with a shaver. The shaver also is used to remove:

  • Any fat pad obstructing the view
  • Periosteum from the lateral wall of the notch
  • Any scar tissue present in the notch

In revision ACL reconstruction, the notch is often overgrown and narrow. A motorized burr is used to perform a notchplasty, starting at the anterior opening of the notch and carried back to the posterior wall as needed, with attention paid to the previous femoral tunnel placement. The posterior notch is inspected with a small, curved curette. A thin white strip of periosteum usually identifies the posterior wall. Definitive localization of the posterior wall is critical, especially in revision surgery because the borders of the notch are often irregular due to the previous surgery and altered anatomy.

Placement of the femoral tunnel too far anteriorly is the primary cause of recurrent laxity for ACL reconstructions and as a result, there is often enough room to place a second femoral tunnel in the appropriate position without interference or compromise from the previous tunnel (Figures 4a-b). In this case, the previous interference screw can be left in place or removed. A curved curette is used to remove a small area of bone to localize the desired position of the new femoral tunnel. If the previous femoral tunnel was well placed, it can be difficult to create a new tunnel that does not overlap with the old tunnel.

Figures 4a-b. The femoral tunnel of this failed ACL reconstruction is both vertical and anterior (4a, top), which allows for a revision femoral tunnel to be placed in an appropriate position, low on the femoral wall and immediately adjacent to the posterior cortex. The revision tunnel was reamed via a transtibial approach (4b, bottom).

In this situation, we have found that femoral tunnels placed with transtibial drilling often can be revised by drilling the revision tunnel through the anteromedial portal. The anteromedial portal can be drilled via a straight reamer with the knee in hyperflexion (>120 degrees) or via a commercially available flexible reamer with the knee in 90-100 degrees of flexion. This results in divergent tunnels, with only the intra-articular outlets overlapping.

If this strategy is unlikely to result in anatomic femoral tunnel placement with sufficient bone stock, it may be necessary to bone graft the bone defects and postpone ACL reconstruction. However, this is more commonly needed in the presence of revision tibial tunnel bone defects.

Graft Preparation

Graft preparation is performed after the tunnels are drilled to ensure that bone plugs on the graft are not undersized, in the unlikely event that the new tunnel and old tunnel substantially overlap and create a bony defect that is considerably larger than the standard tunnel size.

Graft selection is discussed preoperatively and a variety of options are available, as previously indicated. We commonly use bone-patellar tendon-bone allograft and do not re-harvest previously harvested tendons. Distal and proximal bone plugs are cut to a length of 25 mm, with a height of 10 mm and a width of 10 mm, using a micro-oscillating saw. A small rongeur is used to contour the bone plugs to fit through a 10-mm tunnel (Figure 5). Two-millimeter drill holes are placed between the proximal two thirds and the distal one third of the patellar bone plug; a single drill hole is placed in the tibial bone plug. The patellar bone plug drill holes are placed at a 90-degrees angle to each other, and No. 5 braided polyester sutures, loaded on Keith needles, are then passed through each hole.

Figure 5. A non-irradiated bone-patellar tendon-bone graft is utilized for revision ACL reconstruction. The bone plugs measure 10 mm x 10 mm x 25 mm.

A 10-mm sizer is used to confirm that the graft slides easily while still having contact with the sides of the sizer. The tendinous portion is then measured from bone plug to bone plug and the graft is protected with a saline-soaked gauze.

Tunnel Placement

The femoral and tibial tunnel placement should not be compromised based on the location of the previous tunnels, and the option of utilizing a two-incision technique (discussed below) or staged bone grafting followed by ACL reconstruction should be evaluated.

Tibial guidewire placement is identical to that of primary ACL reconstruction, using a commercially available variable angle tibial guide either “point-to-elbow” or “point-to-point.” The tibial guide angle is determined using the N+7 rule, with N being the length of the tendinous portion of the graft.32 The guide is placed in the joint through the anteromedial portal, and a 1.5-cm skin incision is placed just medial to the tibial tubercle, in line with the anteromedial portal for placement of the guidewire. The tip of the guide is placed intra-articularly so that the guidewire penetrates the joint 6 to 7 mm anterior to the PCL and in a line that intersects the posterior aspect of the anterior horn insertion of the lateral meniscus. If transtibial femoral drilling is planned, attention is given to the guide pin trajectory, allowing for a femoral tunnel position of 1:00 to 1:30 position (left knee) or the 10:30 to 11:00 position (right knee).

If a metallic implant was used in the previous surgery, it is often in a location that necessitates its removal. After localizing the retained hardware, all overgrown soft tissue and bone are carefully removed, followed by extraction of the implant through the use of the appropriate instruments based on the previously obtained primary ACL reconstruction operative report. Next, the length of the planned tibial tunnel is determined with a calibrated tibial drill guide by advancing the bullet down to the tibia. The measurement on the bullet should be just longer than the tendinous portion of the graft (N+2 rule).33 The guidewire is then advanced, and after correct placement is confirmed, the tibial tunnel is created with a drill.

The arthroscope is placed into the tibial tunnel to inspect the tunnel for wall compromise from the previous tunnel. Next a curette is used to place a small mark in the femoral notch 6 mm (for a 10-mm graft) anterior to the posterior wall in the 1:00 to 1:30 position (left knee) or the 10:30 to 11:00 position (right knee). A Beath pin is advanced across the joint to this previously marked site on the femur. A 10-mm reamer is advanced by hand through the joint, using care not to damage the PCL. After the reamer is advanced to a depth of 10 mm, it is then brought back into the notch and the posterior wall of the new tunnel, as well as any convergence with the old tunnel, is inspected (Figure 6). With confirmation that the posterior wall of the femoral tunnel is intact, the reamer is advanced to a depth of 30 mm.

Figure 6. The adequacy of the posterior wall is confirmed via direct inspection, and the tunnel is reamed to 30 mm of depth.

Anteromedial Portal Drilling of Femoral Tunnel

After the tibial tunnel has been fully prepared and assessed for bone stock and alignment, the previous femoral tunnel can be inspected. If the femoral tunnel used for primary ACL reconstruction was established via a transtibial drilling technique with reasonable anatomic positioning, then anteromedial drilling of a new femoral tunnel can be helpful in order maximize the available bone stock and create a divergent tunnel. Anteromedial drilling with straight reamers is performed with the knee in hyperflexion (approximately 120 degrees); we find it helpful to have an assistant maintain this position.

Using a small curette, place a mark in the notch 6 mm from the back wall of the femur in the desired position. A 70-degree arthroscope can be placed in the anterolateral portal or a standard 30-degree arthroscope can be briefly switched to the anteromedial portal to confirm the position of the mark in the notch prior to drilling. Once the position of the new tunnel is properly marked and appropriate position confirmed (1:00 to 1:30 position in a left knee or the 10:30 to 11:00 position in a right knee), the knee is hyperflexed again to 120 degrees or greater and the Beath pin is introduced through the accessory anteromedial portal. It is advanced into the femur at the previously marked site until it exits the lateral thigh.

The reamer is advanced over the Beath pin under direct vision while passing by the medial femoral condyle. To aid in this step, low-profile offset reamers or an arthroscopic skid can be used. As with transtibial reaming, the reamer is advanced approximately 10 mm and the tunnel is checked for sufficient bone integrity and position. If the tunnel is appears adequate, it is drilled to 30 mm. Interference fixation is placed as described previously, with the notching and guidewire placed via the anteromedial portal.

As an alternative to straight femoral reamers, commercially available flexible reamer systems present several advantages with regard to lower positioning of the femoral tunnel, prevention of iatrogenic cartilage injury, utilization of over-the-top guide, and improved tunnel length. Anteromedial reaming can be accomplished with flexible reamers with the knee in approximately 100 to 110 degrees of flexion, rather the than 120 to 140 degrees needed for straight reamers, improving visualization during this step. An accessory medial portal is rarely needed to obtain an anatomic femoral tunnel.

Ease of reamer passage around the medial femoral condyle can be improved with the specialized flexible guide pin and reamer system, reducing the likelihood of iatrogenic injury. Flexible reaming allows for the use of a cannulated 6- or 7-mm over-the-top guide specially designed for anteromedial portal drilling. This prevents the guide pin from disengaging the curette mark within the lateral notch as the guide pin is inserted and engaged into the femur. The improved trajectory of the flexible guide pin and reamers also allows for increased femoral tunnel depth and decreases the propensity for posterior wall blow out.

As with the straight reamers, direct arthroscopic visualization is used to pass the flexible reamer around the medial femoral condyle. The femoral tunnel drilling and graft fixation is performed as described above, with notching of the aperture and screw guide pin insertion through the anteromedial portal with the knee at 90 to 100 degrees of flexion.

Graft Passage and Tensioning

Once appropriate tunnels have been drilled, suture attached to the bone plug of the graft is inserted through a Beath pin and the pin is advanced through the lateral thigh. Careful visualization of the bone plug advancing into the femoral tunnel ensures the graft does not rotate. The bone plug is then positioned at the anterior aspect of the tunnel. With the knee in approximately 80 degrees of flexion and the femoral bone plug adequately positioned, inspection at the tibial tunnel distally provides an opportunity to assess for any construct mismatch. If no mismatch is observed, the knee is then flexed to 120 degrees and gentle tension is applied to the graft as the interference screw is placed over a guide wire.

Again, careful visualization is used to ensure that the screw threads do not lacerate the graft and that the final position of the screw is recessed 1 to 2 mm within the femoral tunnel. Next the knee is taken through an arc of motion while palpating the tibial bone plug, carefully noting the appropriate isometry of the graft. While manually tensioning the graft, the knee is held near extension and the tibial interference screw is placed.

If necessary, the tibial bone plug can be reinforced by tying the previously placed sutures through the bone plug over a post created with a screw and washer just distal to the tibial tunnel. A final range-of-motion check is performed, including an assessment of graft impingement on the femoral notch in full extension. A gentle Lachman test is also performed to ensure that stability has been restored.

Two-Incision Technique

A two-incision technique can be used when the previous femoral tunnel was placed in the optimal anatomic position or osteolysis around the previous tunnel significantly limits placement of the new, more anatomic tunnel. The fundamental difference of this technique is fixation of the graft at the lateral cortex of the distal femur.

This approach uses the same tunnel aperture, but at a different angle and is typically not affected by previous ACL reconstruction. However, in cases in which the primary ACL reconstruction was performed with a two-incision technique, our standard endoscopic technique for femoral tunnel placement usually can be utilized without difficulty.

Tunnel Placement in Two-Incision Technique

As with the single-incision technique, the femoral and tibial tunnel placement should not be compromised based on the location of the previous tunnels, and the option of staged bone grafting followed by delayed ACL reconstruction should be evaluated. The tibia is drilled as described above.

However, if, after the tibial tunnel is drilled, assessment of the femoral tunnel location within the notch is less than satisfactory, then a commercially available rear-entry drill guide can be used if the patient has an intact lateral femoral cortex. A laterally based longitudinal incision is made over the distal femoral metaphysis and the tip of the rear-entry drill guide is placed at the posterior aspect of the lateral wall of the notch in the 1:30 position (left knee) or 10:30 position (right knee). The sliding bullet is then advanced to bone, and the guide wire is advanced into the notch. The PCL is protected with a large curette as a 10-mm reamer is used to create the femoral tunnel from the lateral cortex into the notch. After carefully visualized passage of the graft as before, an interference screw is placed at the lateral cortex and advanced until it is flush with the bone plug. The remainder of the reconstruction is performed as described previously.

Bone Grafting of the Tibial Tunnel

Bone grafting may be necessary if there is significant bone loss at the previous tibial tunnel or femoral site that would compromise either positioning or fixation of the graft; staged revision ACL reconstruction follows. This issue can be observed in patients treated with previous synthetic graft reconstructions or with previous bioscrews, both of which can result in an intense inflammatory reaction that causes graft failure and bone loss. However, it has also been suggested that tunnel osteolysis can occur with hamstring grafts due to the proposed “windshield wiper” effect of the graft with non-aperture fixation (Figures 7a-b).16,34

Figures 7a-b. Non-aperture fixation has resulted in tunnel widening of both the femoral and tibial tunnels in this failed ACL reconstruction.

Tibial tunnel bone grafting is performed by removing retained hardware and extensively debriding all remaining soft tissues within the tunnel using a combination of shaver, curette, and rasp. If sclerotic bone is encountered, a 2-mm drill can be used to drill the wall of the tunnel. The resulting debrided tunnel is then filled with autograft iliac crest bone dowels or commonly available allograft bone dowels. The dowels are inserted using a press-fit technique, with the dowels measuring 1-mm larger in diameter than the diameter of the tunnel.

Revision ACL reconstruction must be staged to allow time for incorporation of the bone graft, which can be monitored on CT imaging. The rate of incorporation is variable, with recommendations ranging from 3 to 6 months; longer incorporation times are associated with prior synthetic ligament graft reconstruction.10,34

Pearls and Pitfalls

  • It is critical to determine whether the patient’s chief complaint is instability or pain.
  • For patients age 25 years and younger, a good reason is needed not to perform revision reconstruction of an ACL-deficient knee.
  • For patients age 45 years and older, a good reason is needed to consider revision reconstruction in an ACL-deficient knee.
  • Subjective and objective findings of instability should be present to support consideration of revision surgery. Some patients with objective instability are able to participate at a high level of competition in cutting sports without symptomatic instability.
  • Managing patient expectations through appropriate pre-operative counseling is paramount to successful rehabilitation, especially among revision surgery patients.
Interference Screws
  • In our experience, metallic screws allow easy identification of tunnel placement. We currently do not use “bioabsorbable” screws because we have found that they commonly do not absorb and can be difficult to drill across and difficult to remove during revision surgery.
Synthetic Grafts
  • Careful debridement of all synthetic material must be performed to prevent further immune reaction around the new graft.

Postoperative Care

Postoperatively, all patients are placed in a hinged knee brace locked in extension, with the patient permitted to be weight-bearing as tolerated in the brace. The brace can be removed when the patient is not ambulating, and range-of-motion (ROM) exercises are begun in the immediate postoperative period. The hinged knee brace can usually be discontinued within 1 week of surgery.

Formal outpatient physical therapy is initiated within a few days of surgery. Postoperative rehabilitation goals are outlined below:

  • Months 1-3: Focus on ROM and quadriceps strengthening
  • Months 3-4: Progress to eccentric quadriceps strengthening and running
  • Months 4-7: Continue strengthening
  • Months 7-8: Begin agility drills
  • Months 8-9: Begin sport-specific drills
  • No contact sports are permitted until 9 months postoperatively


As mentioned previously it is important to appropriately counsel patients preoperatively, as revision ACL reconstruction is associated with worse outcomes than primary ACL reconstruction.16,24,29,30 Battaglia et al, in their series of 63 patients with mean follow-up of 6 years, reported a rate of 71% good/excellent outcomes. However, only 59% of the patients in that study were able to return to playing sports, albeit at a decreased capacity, and there was an additional 25% revision rate. Furthermore, they demonstrated that duration to revision ACL reconstruction correlated with radiographic arthritic changes.16

Noyes et al reported a failure rate of 27% among autograft revision ACL reconstructions and 33% among the allograft group.35 Other reports on revision ACL reconstruction have also shown worse outcomes when compared to primary ACL reconstruction and have attributed these observations to tunnel malposition (29, 30). However, these reports include a rather small series of patients with varied pathology and no description of the exact technical errors; thus, they have contributed very little toward improving revision ACL reconstruction outcomes.

A large, multi-institutional, prospective, longitudinal cohort investigation has been established in an effort to improve our understanding of the relevant factors affecting outcomes among these patients.24 It is our hope such studies will allow physicians to maximize the treatment and functional level of revision ACL reconstruction patients.


Overall, revision ACL reconstruction is associated with a higher complication rate than primary surgery.16,19,20 The types of complications are identical to those associated with primary surgery; however there is a significantly higher rate of stiffness, cartilage injury and catastrophic failure (up to 25% in some series).

Numerous authors have noted a higher rate of cartilaginous damage at the time of revision ACL reconstruction. Although a causative relationship has never been established, this cartilage damage noted at revision surgery, as well as the duration to revision surgery, has been reported to correlate with the radiographic degenerative changes.


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