A fifteen-year-old male soccer player presented six weeks after sustaining a left knee injury while playing competitive soccer. There had been no previous injury to this knee. The patient reported that the knee had "given out" after coming into direct contact with the opposing goalkeeper. He was diagnosed as having a medial collateral ligament (MCL) injury by a pediatric sports medicine specialist at another facility, and the knee was then treated with application of a brace and physical therapy. The patient continued to have popping and catching with medial joint-line tenderness, and he was referred to our office for further evaluation.
Physical examination revealed medial joint-line tenderness as well as pain at the femoral origin of the MCL. The patient had a positive Lachman test and a negative McMurray maneuver, with good tone of the quadriceps and hamstrings bilaterally.
Radiographs of the left knee that were made on the first day after the injury revealed open physes at the distal end of the femur and the proximal end of the tibia and no evidence of acute fracture. A magnetic resonance imaging (MRI) study of the knee, acquired five weeks after the injury, demonstrated previous injury to the MCL and ACL with no evidence of a meniscal tear.
Operative Technique
For this type of injury, we routinely perform an anatomic single-bundle ACL reconstruction with use of an accessory medial portal and hamstring autograft. In this young patient, however, we had concerns about the interphyseal trajectory through the distal lateral femoral physis that would occur with this technique. Consequently, we obtained intraoperative fluoroscopic views of the knee after a Beath pin was advanced through the far medial portal to the anatomic center of the femoral footprint. The Beath pin was then advanced so that the blunt end was brought to the femoral footprint of the ACL, allowing the knee to be positioned in extension (Figs. 1-A and 1-B).
Intraoperative anterior (Fig. 1-A) and lateral (Fig. 1-B) fluoroscopic images showing a Beath pin in the trajectory of an anatomic femoral tunnel placed through the far medial portal. This trajectory intercepts the lateral physis and lateral perichondral ring.
The fluoroscopic images confirmed our suspicion that the horizontal trajectory of the anatomic femoral tunnel, when placed through the far medial portal, would appreciably increase the volume of physeal injury at the lateral distal femoral physis. After examining the fluoroscopic images, we abandoned our usual technique and proceeded with an all-epiphyseal two-incision femoral-tunnel technique to allow anatomic placement of the graft through the femur, as has previously been described10. A second incision was made laterally, and the tibial guide was used to place the guide pin with use of an outside-to-inside technique. An 8-mm reamer was advanced across the femur under fluoroscopic visualization (Fig. 2). The tibial tunnel was drilled with an 8-mm reamer with use of our traditional transphyseal technique. The remainder of the operation was completed without incident, and images were acquired as needed (Figs. 3-A through 4-B). At six months after the operation, the patient had full range of motion and negative Lachman and pivot-shift tests and had returned to competitive sports.
Intraoperative fluoroscopic image showing the 8-mm reamer being advanced in an outside-to-inside technique during an all-epiphyseal anatomic femoral tunnel procedure.
Intraoperative arthroscopic images showing minimal evidence of previous ACL tissue along the intercondylar wall (the so-called empty wall sign) (Fig. 3-A), the anatomic location for the femoral tunnel (Fig. 3-B), and the final result of the ACL reconstruction (Fig. 3-C).
Postoperative anteroposterior (Fig. 4-A) and lateral (Fig. 4-B) radiographs showing the location of both the femoral and tibial tunnels.
The focus of this case report is to make the surgeon aware of the potential increased risk of growth disturbance to the lateral femoral physis when reconstructing the ACL through the anatomic femoral footprint with use of an accessory medial portal. This technique has the potential to eccentrically traverse the lateral physis, creating a lateral zone of injury and causing damage to the lateral portion of the perichondral ring.
Kercher et al. performed an anatomic three-dimensional MRI study that estimated the physeal injury inflicted by a vertical, centrally located 8-mm transphyseal tunnel to be only 2.4% of the total distal femoral physis13. On the basis of our intraoperative fluoroscopic image, it is estimated that 10% to 15% of the physis would have been injured with an 8-mm reamer. This is well above the threshold of physeal injury and as much as three times the recommended maximum area of injury (4% to 7%)12,13. In addition to the potentially increased area of physeal injury with an anatomically placed femoral tunnel, the location of the physeal injury changes to a more lateral position. On the postoperative radiographs of our skeletally mature patients who have had ACL reconstruction, we have noted that the lateral exit point of the anatomic femoral tunnel is usually located at the physeal scar.
Injury to the lateral physis at the distal end of the femur and/or the perichondral ring increases the likelihood of an angular growth disturbance as compared with a centrally located physeal zone of injury. Placement of an anatomic femoral tunnel in this case would risk injury to the lateral perichondral ring. This potential for physeal injury can clearly be seen in the intraoperative fluoroscopic image, and the surgeon reconstructing the ACL in a young patient should be aware of this risk.
There is a relatively small risk for growth arrest as a result of ACL reconstruction in patients with open physes if certain precautions are followed: vertical tunnel placement, limiting graft diameter, utilizing soft-tissue grafts for reconstruction, avoiding fixation across the physis, and limiting tension of grafts across the physis1,4,7. The use of a traditional one-thirty to two o'clock femoral position through a transtibial approach has been associated with a good outcome, and no cases of growth disturbance or arrest have been reported when utilizing the aforementioned transtibial technique. We recognize that our patient has little bone growth remaining, and therefore his risk for a problematic growth disturbance is low, regardless of technique. However, the potential for growth disturbance in patients with growth remaining is concerning. We also recognized that there have been no reports of growth abnormalities when the previously mentioned precautions are utilized with transtibial femoral reaming at the traditional one o'clock to two o'clock position. Certainly, a trans-tibial approach for a nonanatomic ACL reconstruction in our patient would have been acceptable. However, we, like others, are concerned about residual rotational instability when utilizing the transtibial technique.
Alternative methods of ACL reconstruction have been described in the skeletally immature individual10. The all-epiphyseal two-incision technique allows for avoidance of the physis while still providing an anatomic location for the femoral ACL tunnel. If there are concerns about injury to the physis, other options, such as the over-the-top technique, retrograde reaming, and flexible reaming3,6,10,15 may be used. We strongly encourage the use of fluoroscopy during femoral tunnel placement in patients with open physes when reaming an anatomic femoral tunnel, especially when the tunnel is being placed through an accessory or far medial portal. If the trajectory of the tunnel will eccentrically traverse the lateral physis at the distal end of the femur and/or the perichondral ring, an all-epiphyseal or alternative technique should be utilized. To our knowledge, there are currently no reports of physeal growth arrest due to anatomic femoral tunnel placement during ACL reconstruction. Nevertheless, the orthopaedic surgeon should be aware of the pertinent anatomy and the potential for complication when utilizing an anatomically placed femoral tunnel for ACL reconstruction in the skeletally immature patient.