A Case of Anatomic Reconstruction of an ACL Tear
A 26-year-old female patient presents with a non-contact valgus injury to her left knee, which she sustained while playing soccer. She felt a pop, with immediate pain and swelling, which have persisted. The authors diagnosed a tear of the anterior cruciate ligament, a common injury in athletes.
Nirav K. Patel, MD, MS, FRCS, and Christopher C. Dodson, MD
Anterior cruciate ligament (ACL) injuries affect athletes of all ages, with a female preponderance. [1,2] The most common mechanism of injury is a non-contact pivoting injury, although there may be direct contact and sometimes associated meniscal and collateral ligament injuries. In addition, the injury may cause instability, but some patients are able to tolerate the injury – although the minority of patients do not develop functional instability (instability with daily function or “copers”),  more than 90% of patients experience knee instability during cutting and pivoting maneuvers  and, in the long-term, develop secondary injury such as chondral damage and meniscal tears.
Typical presentation is the sensation of a “pop,” deep knee pain, and immediate swelling due to hemarthrosis. Athletes usually cannot complete the game, and clinical examination reveals an effusion, with positive Lachman’s and Pivot Shift tests. Magnetic resonance imaging (MRI) usually leads to an early diagnosis.
Treatment depends on the age, health, and, importantly, the activity level of the patient. Non-operative treatment with activity modification is appropriate in older, low-demand patients. Operative treatment includes ACL repair, which has high failure rates, or the current standard of care, ACL reconstruction, which aims to restore knee function and stability and facilitate a return to sport. 
Operative treatment is generally indicated for:
- Children (younger than age 16)
- Younger patients (ages 16 to 39)
- Older patients (over age 40) who are active
- Failure of a previous ACL reconstruction
Surgical techniques for ACL reconstruction center around:
- Location of femoral and tibial tunnels: anatomic versus non-anatomic
- Method of drilling the femoral tunnel: transtibial versus independent tunnel drilling
- Graft choice: bone-patellar-bone (BTB), hamstrings, or quadriceps; autograft versus allograft
- Flexible versus non-flexible reamers
Each technique and graft option has its pros and cons, with overall excellent clinical outcomes and normal to near-normal return of knee function in 85% to 90% of ACL reconstructions within 6 months of surgery. Return to sport rates vary between 50% and 92% postoperatively. Thus, the technique and graft of choice is usually based on surgeon preference and patient characteristics.
In the following case – a classic presentation of an ACL tear – we will describe anatomic ACL reconstruction with placement of the tibial and femoral tunnels in the footprints via an accessory anteromedial portal using flexible reamers and a BTB autograft.
A healthy 26-year-old female patient presented to our office with a non-contact valgus injury to her left knee, which she sustained while playing soccer. She felt a pop, with immediate pain and swelling and was unable to complete the game. Pain, swelling, and disability have persisted.
- Swelling of the left knee, with no skin changes
- No joint line or bony tenderness on palpation
- Range of motion: 0° to 100°, with an intact extensor mechanism
- Lachman’s test: 2+, with a soft end point
- Stable collaterals at 0° and 30° of flexion
- Soft calf; neurovascularly intact distally
- ACL tear
- Chondral defect of the knee
- No acute bony abnormality apart from an effusion and some lateral patellar tilt (Figure 1)
Figure 1. Plain radiographs of the left knee (A: anteroposterior, B: lateral, and C: sunrise views) showing an effusionon the lateral view (single arrow) and lateral patellar tilt on the sunrise view (double arrow).
Magnetic Resonance Imaging
- Pivot shift injury pattern, with osseous contusions at the posterolateral tibial plateau and sulcus terminalis of the lateral femoral condyle (Figure 2)
- Complete ACL tear
- Large, tense knee joint effusion
- Intact menisci and collateral ligaments
- Intact posterior cruciate ligament (PCL) and posterolateral corner
Figure 2. Magnetic resonance imaging – A: sagittal T1, B: sagittal T2 fat suppressed, C: coronal T2 fat suppressed, D: axial T2 fat suppressed. Single arrow: ACL tear; double arrows: bone contusions; triple arrows: effusion.
- ACL tear of the left knee
On initial presentation, 60 mL of bloody fluid was aspirated from the patient’s knee via a superolateral approach. A compression bandage was applied, and the patient was advised to apply ice and undergo “prehabilitation” (regain full range of motion) with a physical therapist to reduce swelling and improve range of motion.
The patient underwent left knee arthroscopic anatomic ACL reconstruction 2 weeks post-injury, once her swelling was down and range of motion increased to 0° to 120°, with a BTB autograft.
- The procedure was performed under general anesthesia with the patient in the supine position and a popliteal crease at the break in the bed.
- The leg was placed in a leg holder to allow the application of valgus stress. A high thigh tourniquet was applied and inflated at 250 mmHg. The leg was then prepared and draped in a routine manner.
- The bone-patellar-bone graft was harvested via a small incision, just medial to the midline, with preservation of the paratenon. A 1-cm wide tendon portion was harvested from the central third of the tendon, with bone blocks at least 2 cm in length and 1 cm in depth.
- The inferomedial area of this incision was exposed and a vertical incision was made using the bovie at the tibial flare, midway between the crest and posteromedial edge of the tibia. The crossing veins were coagulated, as dissection was down to bone, before medial and lateral flaps were raised for tibial tunnel drilling.
- A standard anterolateral portal was made for the arthroscope (30°), and an anteromedial working portal was made just next to the patellar tendon, with adequate trajectory to the femoral notch using a spinal needle.
- With the foot of the table dropped down to 90°, a diagnostic arthroscopy was performed and revealed no abnormalities aside from the ACL tear. The stump was debrided (Figure 3).
- A tibia drilling tip aiming guide was inserted via the medial portal. The tip was held on the anatomic tibial footprint on the torn ACL stump, which is generally located in front of the posterior cruciate ligament/tibial spines and in line with the posterior edge of the anterior horn of the lateral meniscus. The bullet for the guide was held on the tibial flare.
- A guide wire was passed via the bullet, the position checked, and then an acorn reamer was used to create the tibial tunnel (Figure 4).
- A 70° arthroscope with shavers was then used via the anterolateral portal to clear debris and the notch so that the anatomic femoral footprint could be identified. A notchplasty was performed.
- The BTB autograft was prepared during the above step.
- Via the anteromedial portal, a curved guide was placed into the 2 o’clock position on the footprint, approximately 7mm from the posterior wall (Figure 5).
- A flexible guide pin was fired in with the leg hyperflexed to 110°. The position was checked and fired out of the femur.
- With the leg in neutral (90°), a flexible reamer was used to drill the femoral tunnel (Figure 6). The posterior wall was checked for integrity (Figure 7) and tunnel was then drilled to a 25-mm depth.
- A number 5 Ethibond suture was passed through the femur via the guide pin eyelet and out through the tibia, and then used to pass the graft under direct visualization (Figure 8).
- The femoral bone block was secured following notching of the tunnel superiorly (Figure 9) and insertion of a metal interference screw over a nitinol wire using a non-flexible screw driver (Figure 10). Screw/tunnel mismatch was minimized by ensuring that the screw driver was parallel to the tunnel.
- The knee was cycled to uncrimp tendon fibers and the tibial tunnel was tapped over a nitinol wire. The tibial bone block was secured with a biocomposite screw with the leg in extension. Although not used by the senior author, a posteriorly directed force can be applied to the proximal tibia. Screw/ tunnel mismatch was minimized by ensuring the tap and screwdriver were parallel to the tunnel.
- The arthroscope was utilized again to ensure the absence of notch impingement and intra-articular screw prominence (Figure 11).
- The tourniquet was released and hemostasis was achieved. Excess autograft bone was inserted into the patella and tibial graft sites, with demineralized bone matrix (Stimublast) to supplement. The wound was closed in layers as per routine. Specifically, the patella tendon was closed using interrupted absorbable braided suture (number 1 Vicryl) and the paratenon using a continuous absorbable braided suture (number 2-0 Vicryl).
Figure 3. Arthroscopic image of an ACL tear with empty lateral wall (A; single arrow) and ACL stump debridement (B; double arrow).
Figure 4. Arthroscopic image of the tibial tunnel (arrow).
Figure 5. Arthroscopic image of the femoral guide on the ACL footprint of the lateral femoral condyle.
Figure 6. Arthroscopic image of the flexible reamer on the ACL footprint of the lateral femoral condyle over a flexible guidewire.
Figure 7. Arthroscopic image of the posterior wall (single arrow) and flexible guidewire (double arrow) in the femoral tunnel.
Figure 8. Arthroscopic image (A) of the Ethibond suture used to pass the graft through the femur (single arrow) and tibia (double arrows); graft in position (B).
Figure 9. Arthroscopic image (A) showing notching of the femoral tunnel (single arrow) and placement of the guidewire (B) into the notch (single arrow) above the graft/ femoral bone block (double arrows).
Figure 10. Arthroscopic image of the femoral interference screw above the femoral bone block of the graft.
Figure 11. Arthroscopic image of the final ACL reconstruction of the knee in flexion (A) and extension (B).
- The patient was placed in a soft dressing and knee brace locked in extension and was allowed to bear weight as tolerated for 4 weeks.
- Cryotherapy was initiated immediately postoperatively.
- The brace was unlocked only for exercises, with emphasis on early full passive extension.
- The brace was then unlocked after the fourth week and the patient was allowed to wean off it over two weeks. This extended bracing period is the author’s preference to help minimize the risk of falls from quadriceps inhibition and, potentially, injuries such as patellar fracture.
- At 3 weeks postoperatively, physical therapy was initiated with closed chain (isometric and eccentric) hamstring and quadriceps strengthening, with active range of motion between 30° and 90°.
- Rehabilitation progressed as per routine, with return to sport at 9 months.
The patient presented at 9 months postoperatively having completed her rehabilitation program, including sport-specific training, without any complaints of pain, instability, stiffness, or swelling. Physical examination showed no effusion, full range of motion, negative Lachman test, and full quadriceps/hamstring power.
ACL rupture is a common injury in athletes who participate in pivoting and cutting sports; it is more common in females than in males. Patients classically present following a non-contact pivoting injury with effusion, stiffness, and instability with a positive Lachman’s test. There may also be associated meniscal and other ligamentous injuries.
Non-operative treatment with physical therapy and lifestyle modification can be offered to older and sedentary patients. There is, however, a risk of secondary injury to the menisci and chondral surfaces should instability persist. As such, surgical intervention is generally recommended for young and active patients, particularly if they will wish to return to sports involving pivoting and cutting maneuvers.
Surgical intervention with ACL repair has high failure rates and is not recommended. ACL reconstruction is more successful in restoring knee stability. Techniques vary regarding tunnel placement, method of femoral tunnel drilling, and graft choice.  In view of the generally good results with all options, surgeon preference and patient characteristics usually dictate which technique is employed.
The 70° arthroscope was used successfully to provide better visualization of the native anatomy, allowing for easier visualization and instrumentation of the notch. In addition, the anterolateral viewing portal uses fewer incisions and avoids the “sword-fighting phenomenon” of anteromedial portals.  Flexible guide wires and reamers have been introduced recently, and their use is described in this case of anatomic ACL reconstruction. [6, 7] The advantages include:
- Ease of tunnel positioning, recreating an anatomic femoral tunnel
- Achieve longer and more consistent tunnel length
- No need to hyperflex the leg, which can cause surgical field contamination, requires an assistant, and may reduce visualization
- Less iatrogenic damage to the medial femoral condyle from reamer passage
- May reduce posterior wall blow out
- May reduce peronal nerve injury by increasing guide pin exit distance
- Tunnel and screw mismatch
- Possible flexible guide pin bending and flexible reamer breakage
- Increased cost
- Lack of availability
Further studies are needed to determine outcomes of ACL reconstruction using flexible guide wires and reamers.
Complications of surgery are commonly due to tunnel malposition, accounting for 70% of all failures. Other causes include:
- Stiffness, such as less than full range of motion preoperatively, tunnel malposition, or cyclops lesion
- Graft fixation failure
- Missed concomitant injuries, such as injury to the posterolateral corner
- Overly aggressive rehabilitation
- Patient non-compliance with rehabilitation
ACL reconstruction has excellent functional outcomes, with good return-to-sport rates. Rehabilitation is key to this, with early postoperative interventions such as cryotherapy, maintaining full extension, and immediate weight bearing with or without a brace. Rehabilitation then progresses to range of motion and closed chain (hamstring and quadriceps) exercises, before gradually increasing the activity level with a physical therapist. Injury prevention programs for female patients and skiers also have a role.
In summary, anatomic ACL reconstruction using BTB autograft via an appropriate anteromedial portal and a 70° arthroscope has good results. The use of flexible reamers is new, with practical advantages that require further research.
Nirav K. Patel, MD MS FRCS, and Christopher C. Dodson, MD, are from The Rothman Institute at Thomas Jefferson University Hospital, Philadelphia, Pennsylvania. They specialize in sports-related injuries of the shoulder, elbow and knee.
Sports Medicine Section Editor, Rothman Institute Grand Rounds
The authors have no disclosures relevant to this article.
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