As our techniques for anterior cruciate ligament reconstruction have
evolved, our focus has drifted from anatomy. We believe that it is important
to hearken back to anatomy and to fully understand normal anatomy so that we
can try to restore it with anterior cruciate ligament reconstruction surgery.
The results associated with current anterior cruciate ligament reconstruction
techniques are adequate but not exceptional. A recent meta-analysis of the
outcomes of anterior cruciate ligament reconstruction indicated that only 33%
of patients who had reconstruction with hamstring tendon graft and 41% of
those who had reconstruction with bone-patellar tendon-bone graft had normal
outcomes according to the final International Knee Documentation Committee
score1. There is
clearly room for improvement, and we think that the keys to improvement will
be based on anatomical anterior cruciate ligament reconstruction.
In their paper entitled "Morphology of the Femoral Intercondylar
Notch," Farrow et al. evaluate the anatomy of the lateral intercondylar
notch in 200 cadaveric specimens. The authors' goal—namely, to perform a
detailed study of the area where the anterior cruciate ligament attaches in
order to provide more reliable guidance for femoral tunnel placement—is
admirable. The authors note that the osseous ridge that Dr. Clancy termed the
"resident's ridge" was present in 194 of the 200 specimens. They
suggest renaming it the "lateral intercondylar ridge" on the basis
of its anatomic location. In their discussion, Farrow et al. state that
"it is likely that the lateral intercondylar ridge represents the
anterior border of the femoral attachment of the anterior cruciate
ligament," concurring with Hutchinson and Ash, who performed an earlier
study of the lateral intercondylar wall
anatomy2. Farrow et
al. also describe an osseous ridge along the medial aspect of the
intercondylar notch, which marks the posterior aspect of the posterior
cruciate ligament attachment.
We applaud the authors for the clinical relevance of their paper. Improper
femoral tunnel placement is a common error in anterior cruciate ligament
surgery, and the identification of consistent anatomic landmarks to assist in
more accurate tunnel placement is critical. The authors draw attention to the
clinically relevant point that most surgeons usually remove the "lateral
intercondylar ridge" during notchplasty prior to placing the femoral
tunnel. Unfortunately, notchplasty has become a routine step in anterior
cruciate ligament surgery, obliterating the osseous and soft-tissue landmarks
that outline the femoral attachment of the anterior cruciate ligament. We have
found that placing the arthroscope in the anteromedial portal allows full
visualization of the anterior cruciate ligament attachment site and makes
notchplasty unnecessary in about 95% of cases. If, after identification of the
soft-tissue and osseous landmarks of the insertion site and tunnel-marking,
visualization is still limited by a narrow notch, notchplasty can then be
performed. Initially, however, notchplasty should be avoided to allow
preservation of these important landmarks that guide accurate tunnel
placement.
In our center, we have also performed detailed anatomic studies of the
lateral intercondylar notch over the past two years. In addition to cadaveric
dissection and fetal histologic analysis, we performed sixty arthroscopic
dissections at the time of anterior cruciate ligament reconstruction to
identify the osseous ridges and soft-tissue attachments of the anterior
cruciate ligament bundles. Our findings support Farrow et al.'s conclusion
that the "lateral intercondylar ridge" consistently marks the
border of the anterior cruciate ligament attachment (the anterior border with
the knee in extension and the superior border with the knee in 90° of
flexion). We also discovered the existence of another ridge, the
"lateral bifurcate ridge," which separates the anteromedial and
posterolateral bundles of the anterior cruciate ligament at the femoral
attachment. This ridge is prominent in many knees undergoing anterior cruciate
ligament reconstruction, and we now use it as an anatomic landmark to guide
the placement of individual anteromedial and posterolateral bundles during
anterior cruciate ligament reconstruction. In addition to our cadaveric and
arthroscopic dissections, we performed three-dimensional laser digitization of
our specimens to study the topography of the anterior cruciate ligament
attachment. We found that the topography is different when the anteromedial
bundle attachment is compared with the posterolateral bundle attachment and
that the two ridges described above are easily visible
(Fig. 1). We also studied the
anatomy of the medial aspect of the intercondylar notch and found the
consistent presence of a ridge marking the posterior border of the posterior
cruciate ligament attachment, which Farrow et al. also described. These ridges
and changes in osseous topography may prove to be useful during
navigation-assisted ligament reconstruction.
We have even observed the presence of prominent osseous ridges along the
lateral intercondylar notch of the femur in many animals. For both humans and
animals, we suspect that the ridges and variation in slope of the anterior
cruciate ligament attachment exist because of osseous remodeling in response
to stress from the ligament fibers, in accordance with Wolff's law.
In summary, we congratulate Farrow et al. on the tremendous clinical
relevance of their anatomic study. Our studies in Pittsburgh confirm the
importance of the lateral intercondylar ridge as a landmark to guide accurate
femoral tunnel placement during anterior cruciate ligament reconstruction.
When treating fractures, reduction must come before fixation. Similarly, with
anterior cruciate ligament reconstruction surgery, we believe that it is most
important to restore the anatomy first and to consider graft choice and
fixation methods later. ?