Introduction

• ACL injury occurs with an estimated incidence of one in 3000 among the general United States population.1 In the majority of these cases, ACL reconstruction has proven to be a reliable and durable procedure for restoring stability, and more than 100,000 of these procedures are performed annually.2

• Good to excellent results in terms of patient satisfaction, stability, and return to play are observed in between 75% and 90% of these cases.3 Clinical failure, however, remains a problem, with rates as high as 10% to 15% at short- and intermediate-term follow-up.4

• Despite improvements in graft fixation and a better understanding of ACL anatomy and biomechanics, this failure rate seems to be holding relatively constant, resulting in higher absolute numbers of clinical failure as the number of reconstructions performed annually continues to rise.5

• There are a number of complex scenarios surrounding ACL injury that require special consideration and can contribute to suboptimal clinical outcomes. Among these are revision of a failed reconstruction, ligament injury in the skeletally immature, treatment of ACL injury in the context of concomitant chondral injury, and treatment of the chronically ACL-deficient arthritic knee.

Figure 52-1 Flowchart summarizing potential causes of clinical failure following anterior cruciate ligament reconstruction.

monly encountered types of tunnel malposition, any combination of tibial and femoral tunnel may be observed. Types of tunnel malposition and their effects on knee motion are summarized in Table 52-1.

Failure to recognize and treat combined instability patterns represents another significant cause of graft failure, thought to account for as many as 15% of cases.7 Injury to secondary stabilizers of the knee such as the medial collateral ligament, pos-terolateral corner, and the posterior horn of the medial meniscus can occur during the initial trauma or can become damaged over time, placing additional stress on the graft and potentiating early failure. Posterolateral instability has been reported to accompany as many as 15% of chronic ACL injuries.3 Unrecognized angular malalignment conditions, such as the double varus and triple varus knee (explained later in this chapter) can also lead to excessive graft strain and early failure.8

Catastrophic failure of graft fixation is uncommon but has been reported.9 Certain technical errors are known to contribute to failure of fixation, including interference screw divergence and graft-tunnel mismatch.4,10 In cases of screw divergence, the path taken by the interference screw diverges with that of the graft, decreasing contact area between the screw and the graft and weakening fixation strength.4 This is more problematic with the dual-incision technique than the endoscopic technique,

Figure 52-2 Lateral radiograph demonstrating anterior malposition of the femoral tunnel.

although more common with the endoscopic technique. On the femoral side, with the endoscopic technique, screw divergence may still provide a "wedge" or "doorstop," despite suboptimal contact between the interference screw and bone block. This is not the case with femoral-side fixation using the dual-incision technique, as a result of placement of the interference screw from outside-in.

Figure 52-3 The shape of the distal femur results in a cam mechanism that puts excessive tension on grafts whose femoral point of fixation has been anteriorized. Graft A has a femoral tunnel in the desired posterior position and approximates isometry during flexion. Grafts B and C have progressively anteriorized femoral points of fixation and experience excessive strain with knee flexion as the posterior condyles engage.

Table 52-1 Tunnel Position

Anatomic Position

Tunnel Malposition

Cause

Effect on Graft

Patient Complaint

Femur Sagittal: 1-2mm anterior

Anterior

Failure to identify true

Excessive tension in

Loss of flexion; recurrent

to posterior femoral cortex

posterior margin of

flexion

instability with graft

in notch

notch; "resident's ridge"

attenuation

Coronal: 1 o'clock (left knee)

Central

Placement of graft

Inability to control

Persistent rotatory instability

or 11 o'clock (right knee)

(vertical)

centrally in the notch

rotatory forces

without elimination of pivot

position

shift

Posterior

Nonanatomic technique

Excessive tension in

Loss of extension; recurrent

with graft fixation in

extension

instability with graft

"over-the-top" position

attenuation

Tibia Sagittal: at point of

Anterior

Excessively large angle on

Excessive tension in

Loss of flexion; loss of

intersection between

tibial guide/tunnel;

flexion; notch

extension with notch

posterior aspect of anterior

failure to adequately

impingement in

impingement; morning

horn of lateral meniscus

débride ACL stump and

extension

stiffness; recurrent

and medial tibial spine;

identify tibial landmarks

instability with graft

1-2mm anterior to leading

attenuation

edge of PCL

Coronal: midpoint of upslope

Posterior

Excessively small angle

Impingement on PCL

Loss of extension; loss of

of medial tibial spine

on tibial guide/tunnel

in flexion

flexion; recurrent instability

with graft attenuation

Lateral

Failure to identify tibial

Impingement on

Loss of flexion; catching

footprint of ACL

lateral femoral

sensation

condyle in flexion

Medial

Failure to identify tibial

Impingement on PCL

Loss of flexion

footprint of ACL

in flexion

ACL, Anterior cruciate ligament; PCL, posterior cruciate ligament.

ACL, Anterior cruciate ligament; PCL, posterior cruciate ligament.

If the length of a bone-tendon-bone graft does not match the composite length of the recipient tibial tunnel + intra-articular + femoral tunnel lengths, then a graft-tunnel mismatch exists. The surface area of bone block in the tibial tunnel for interference screw fixation is therefore reduced, again weakening fixation strength.11 This may lead to micromotion and graft attenuation in the early postoperative period. Several strategies have been advocated for graft tunnel mismatches, including conversion to a dual-incision technique if recognized prior to femoral tunnel creation, recessing the femoral bone plug, rotating the graft 540 degrees to shorten the construct, or removing the bone block to create a free bone block modification. Traumatic tear of a well-functioning reconstruction is also a possible mode of failure, particularly within a population of high-level athletes.

Was this article helpful?

0 0
Cure Tennis Elbow Without Surgery

Cure Tennis Elbow Without Surgery

Everything you wanted to know about. How To Cure Tennis Elbow. Are you an athlete who suffers from tennis elbow? Contrary to popular opinion, most people who suffer from tennis elbow do not even play tennis. They get this condition, which is a torn tendon in the elbow, from the strain of using the same motions with the arm, repeatedly. If you have tennis elbow, you understand how the pain can disrupt your day.

Get My Free Ebook


Post a comment