Anatomic Posterolateral Knee Reconstructions Require a Popliteofibular Ligament

Reconstruction Through a Tibial Tunnel 1McCarthy M A; 2Camarda L; 1Wijdicks, C A 3Johansen, S; 3Engebretsen, L; +1LaPrade, R F

+1University of Minnesota, Minneapolis, MN, 2University of Palermo, Palermo, Italy, 3University of Oslo, Oslo, Norway

Senior author lapra001@umn.edu

INTRODUCTION

The posterolateral knee houses some of the more complicated

musculoskeletal anatomy and, as a result, injuries to this region

represent challenging problems in diagnosis and treatment for clinicians.

Further, rehabilitation from these injuries is arduous for patients to

undertake. Thus, much research has been devoted to delineating

anatomic and radiographic features of posterolateral corner structures

and injury patterns [1,2]. Further, many different reconstructions have

been described. Our focus is on the applied functional anatomy and

reconstruction of the three main stabilizers of the posterolateral knee: 1)

the fibular collateral ligament, 2) the popliteus tendon and, 3) the

popliteofibular ligament. The popliteofibular ligament’s role in an

anatomic reconstruction of a Grade III posterolateral corner injury was

the focus of this study. To our knowledge, no study has validated the

importance of the popliteofibular ligament in an anatomic

reconstruction, as much debate has arisen in the literature regarding the

importance of its inclusion in the reconstruction. Some have described

the popliteofibular ligament as detrimental to the restoration of an intact

knee function, citing overconstraint in internal rotation and subsequent

limitation in external rotation [3,4]. Thus, the purpose of our study is to

assess two reconstructions, one with and one without the popliteofibular

ligament, in comparison to the intact state.

METHODS

Six paired, fresh-frozen cadaveric knee specimens were used in this

study, each without evidence of prior injury. The femur was sectioned

20 cm from the joint line and the tibia 13 cm from the joint line. The

specimens were then potted in polymethylmethacrylate (PMMA) to

ensure secure fixation. A customized knee testing apparatus, previously

described, was used to firmly hold the femur while allowing movement

of the tibia and biomechanical testing at various knee flexion states [5].

External forces were applied at 0⁰, 20⁰, 30⁰, 60⁰ and 90⁰ of knee

flexion. For each test state, applied forces used were 10 Nm

varus/valgus load, 5 Nm internal/external rotation torques and 88 N

anterior/posterior drawer loads. Load and motion data were recorded in

synchrony using the Motion Monitor software (Innovative Sport

Training, Chicago, IL).

Each knee in a matched pair underwent one of two anatomic

posterolateral knee reconstructions. Group 1 knees had all three major

posterolateral knee stabilizers reconstructed in a method previously

described [1]. The matched knee, in Group 2, was reconstructed in the

same way, except here the popliteofibular ligament was left out of the

reconstruction (Figure 1). Instead of reconstructing it through a tibial

tunnel, as in Group 1, the fibular collateral graft exiting the

posteromedial fibula was brought back proximally and sutured onto

itself. Each knee was tested in sequential order: intact knee, followed by

reconstruction, followed by testing of complete sectioning of these three

structures.

through the tibial tunnel. Instead, it is sutured on itself, leaving the

popliteofibular ligament not reconstructed.

RESULTS For an applied external rotation torque, we found significant changes

in comparing the sectioned to intact knees at all degrees of knee flexion

tested for both groups of knees (p < .05). In analyzing the data for the

two reconstruction techniques, we found no significant differences in

reconstructing the fibular collateral ligament, popliteus tendon and

popliteofibular ligament (group 1 reconstruction) or the modified

reconstruction (group 2) compared to the intact state for external

rotation.

We found significant increases in varus rotation when comparing the

sectioned to intact knees at all degrees of knee flexion tested for both

groups (p <.05). There were no significant differences between the intact

state and group 1 reconstructions at any flexion angle. There were

significant increases in varus gapping between the group 2

reconstructions and the intact knee at 0⁰ (p < .05), 20⁰ (p < .05) and 60⁰

(p < .05) degrees of knee flexion.

Figure 1: Posterior and lateral illustrations of the modification of an

anatomic reconstruction from one previously described.

Note the fibular collateral ligament graft does not become the

popliteofibular graft.

The sectioned state, when compared to the intact state, showed

significant increases in internal rotation at 60⁰ and 90⁰ (p < .05). We

found no difference between the intact and group 1 reconstruction knees

at all angles. The group 2 reconstruction, which did not reconstruct the

popliteofibular ligament, had a significant increase in internal rotation

compared to the intact state at 60⁰ and 90⁰ of knee flexion (p < .05).

We found significant increases in posterior translation when

comparing the sectioned to intact states. There was no significant

difference between the Group 1 reconstruction and intact knee state at all

degrees of knee flexion. The group 2 reconstruction was unable to

restore posterior translation to the level of the intact state at 0⁰ and 20⁰

(p < .05) of knee flexion.

Comparison of the intact to sectioned knee states revealed a

significant increase in anterior translation at 0⁰ (p < .05). The intact

state compared to the reconstructed state for both groups did not show

any significant changes at any degrees of flexion tested.

No significant changes were observed in comparing the intact versus

sectioned states for both reconstruction groups in valgus at all degrees of

knee flexion. Further, no significant changes from the intact state were

observed when compared to both reconstruction groups.

DISCUSSION

Our results show the importance of the popliteofibular ligament in

anatomic posterolateral knee reconstructions, because its inclusion more

closely reproduced intact knee biomechanics. Further, our data did not

show abnormal restriction of knee motion with the popliteofibular

ligament placed through a tibial tunnel. We recommend that

reconstructing the popliteofibular ligament through a tibial tunnel should

be included in anatomic reconstructions of the posterolateral knee.

REFERENCES

1. LaPrade RF, et al. Am J Sports Med 2004; 32: 1405-1414.

2. LaPrade RF, et al. Am J Sports Med 2000; 28: 191-199.

3. Markolf KL, et al.J Bone Joint Surg Am 2007; 89: 2351-2358.

4. Nau T, et al. Am J Sports Med 2005; 33: 1838-1845.

5. Griffith CJ, et al. Am J Sports Med 2009; 37: 140-148.

ACKNOWLEDGEMENTS

Project supported by the Sports Medicine Research Fund of the

Minnesota Medical Foundation.

Poster No. 1130 • 56th Annual Meeting of the Orthopaedic Research Society