PCL Landmark Studies

FRCS Level

What the Question Was

The PCL literature asks a narrower set of questions than the ACL's, because the injury is less common and the ligament is harder to reach.

What restrains posterior translation and how much of it is the PCL. What happens when the posterolateral structures are cut as well. What does an isolated PCL injury do to the knee over time. And can a reconstruction restore posterior stability.

The second question is the one that made the literature matter, because it produced a finding that changed how combined injury is recognised. 3.8.1 covers the function.

What Was Done

Girgis and colleagues described both cruciates in the same cadaveric work, including the PCL's bundle arrangement and its reciprocal tension pattern through flexion.

Gollehon, Torzilli and Warren ran the sectioning study in the 1980s that cut the PCL and the posterolateral structures in sequence and in combination, measuring posterior translation and external rotation at a range of flexion angles.

Grood and colleagues ran related sectioning work that separated posterior translation from rotation and showed that the two behave differently depending on which structure has gone.

Harner quantified the PCL's cross sectional area and compared the bundles mechanically, which is the anatomical argument behind double bundle reconstruction.

Race and Amis tested PCL bundle function and reconstruction constructs in the 1990s, including the question of whether a single graft can reproduce the reciprocal pattern.

What It Showed

The PCL is the primary restraint to posterior translation, and it supplies most of that restraint at higher flexion angles rather than uniformly.

Isolated PCL sectioning increases posterior translation and does not produce a large increase in external rotation. Cutting the posterolateral structures as well does.

That dissociation is the mechanical basis of the dial test: rotation at thirty degrees and at ninety degrees separates an isolated posterolateral injury from a combined one. 3.10.7 covers it.

The bundles are unequal in size and in behaviour, and the larger anterolateral bundle carries most of the load in flexion. 3.8.3 covers bundle function.

No reconstruction tested in these studies restored normal posterior translation across the flexion range, which is a consistent finding rather than a single result.

What It Changed

Recognition of combined injury. The posterolateral corner became a structure examined deliberately rather than an afterthought, and that change is traceable to the sectioning work.

The dial test entered examination teaching as a test with a mechanical rationale rather than as a manoeuvre with a name.

Double bundle PCL reconstruction was designed from the bundle comparison work, which is a clear case of a laboratory finding generating an operation.

The consistent failure to restore normal translation changed the stated aim of PCL surgery in much of the literature, from restoration to improvement.

Fellowship Level

What Was Done

The whole chapter rests on sequential sectioning, so its strengths and its limits are the chapter's strengths and limits.

Sequence order matters more here than in the ACL work, because the structures being cut share function. A study that cuts the PCL first and a study that cuts the corner first can produce different attributions from the same specimens.

Flexion angle matters as much as structure. A posterior drawer measured only at ninety degrees misses the pattern that makes the finding useful.

Specimen number is small throughout. These are studies of ten or so knees, and the variability between specimens is large relative to the effects being measured.

What It Showed

Where the literature is strong: the restraint hierarchy and the translation and rotation dissociation. Both have been reproduced in several laboratories.

Where it is weak: what an isolated PCL injury does over years. The natural history literature is observational, small, and drawn from patients who presented, which selects for the ones doing badly.

Where it is contested: whether double bundle reconstruction outperforms single bundle in patients. The laboratory case is clear and the clinical case is not. 3.8.9 covers it.

The gait literature adds something the sectioning studies cannot: a PCL deficient knee adapts, and the adaptation is visible in walking long before it is symptomatic. 3.8.7 covers the pattern.

What to Read Now

Read a sectioning study's cutting order before its conclusion, because the order constrains what can be attributed.

Read posterior translation figures with their flexion angle attached, and discard any quoted without one.

Treat the double bundle question as open and read new work for whether its comparator is a well done single bundle procedure.

Read the gait work alongside the cadaveric work, since it is the only evidence here about a knee that is alive and loaded.

Consultant Perspective

What It Changed

The decision this literature informs is whether to operate on a PCL injury at all, and the evidence supports a balance rather than a position.

Arguing for surgery: the sectioning work shows real and measurable instability, the contact mechanics work shows altered loading that plausibly leads to degeneration, and the gait work shows adaptation that the patient does not choose.

Arguing against: no construct in this literature restored normal translation, the natural history evidence is too weak to say who will deteriorate, and a procedure that improves a measurement without changing the trajectory has bought little.

Take the patient's age and physiology into account, because the degeneration argument has decades to act in a young patient and may not in an older one. Take their comorbidities into account, since this is a long and demanding rehabilitation. Take the demands on their knee into account, because posterior instability declares itself on stairs and descending slopes rather than in a straight line. Take their psychological state into account, since a knee that feels unreliable produces guarding that outlasts the ligament. And ask for their own ideas, concerns and expectations, because many patients with an isolated PCL injury are functioning well and have come for reassurance rather than for an operation.

Record the balance and what tipped it, since the literature will not tip it.

What to Read Now

What a trainee should take from this chapter is that a strong mechanical finding and a weak clinical one can sit in the same subject, and that the PCL is the clearest example in the knee.

Read the combined injury literature first, because recognising the corner changes management more than any decision about the PCL itself.

Be explicit when teaching that the stated aim of PCL reconstruction in most of this literature is improvement rather than restoration, and that the difference is not a matter of surgical skill.