Irreducible Posterolateral Knee Dislocation Associated with Interposition of the Vastus Medialis

Abstract

Posterolateral rotary knee dislocations are irreducible due to soft tissue incarceration within the joint. [3][4][5][6]8,11,13 Most commonly, the injury traps the free end of the torn medial collateral ligament (MCL) in the intercondylar notch. We present a previously unreported finding of vastus medialis interposition. The MRI, intraoperative findings, and clinical course unique to this case are described as well as the findings most common to posterolateral knee dislocations. CASE REPORTA 17-year-old male injured his right knee falling from the hood of a moving vehicle. The patient received initial care at an outside institution. A dislocation was recognized, but 2 attempts at closed reduction failed. The patient arrived at our institution 24 hours after the injury for definitive treatment.Physical examination revealed the right knee fixed at 30° of flexion with lateral subluxation of the patella and a prominent medial femoral condyle. A large skin pucker ( Figure 1) was noted over the medial joint line. The medial skin furrow was recognized as a sign of irreducibility, and no closed reduction was attempted. The limb was neurovascularly intact and the skin viable. Despite a palpable pulse in the foot, the concern for an occult vessel injury prompted further investigation. An arteriogram was normal.Plain radiographs showed widening of the medial compartment (Figure 2) of the knee joint. The patella was subluxated laterally. No evidence of bony ligamentous avulsion was found.The MRI demonstrated a soft tissue signal consistent with muscle within the notch and medial compartment.The torn posterior cruciate ligament (PCL) rested on the superior portion of this mass (Figure 3). The anterior cruciate ligament (ACL) was torn from its origin and was less clearly defined. The MCL and capsule did not appear on the cross sections and were obscured by the large muscle mass. The menisci, bone, and cartilage surfaces were unremarkable.A gentle examination under anesthesia accentuated the medial skin furrow, confirming the irreducibility of the injury. An open reduction was done 36 hours following the injury. The delay was secondary to failed attempts at closed reduction at an outside institution followed by a transfer to our institution. The medial femoral condyle rested deep to the subcutaneous tissue through a rent in the vastus musculature. The muscle belly was removed from the notch and medial compartment of the joint to expose the incarcerated MCL and capsule. A congruent reduction was achieved following removal of these structures. The PCL was repaired to its avulsed insertion site through a posteroanterior bony tunnel and tied over a post on the anterior cortex of the tibia (Figure 4). The MCL was Figure 1. The arrow indicates the pathognomonic sign of irreducibility, the medial skin furrow.

One-Stage Arthroscopic Reduction Combined with Multiligament Reconstruction or Repair for Irreducible Posterolateral Knee Dislocation: A Retrospective Case Series with Minimum 2-Year Follow-Up

“…[1][2][3] This injury typically occurs when a valgus force is applied to a flexed knee with external rotation of the tibia. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] The medial femoral condyle button-holes through the torn medial capsuloligament complex as a flexed knee is forced into severe valgus. As the deforming force dissipates, the knee partially reduces.…”

Irreducible lateral knee dislocation with incarceration of the lateral femoral condyle in the posterolateral capsuloligamentary structures: a case report and literature review

“…Entrapment of the capsuloligamentary elements in the intercondylar notch, with or without dislocation of the patella, is the specific causal mechanism for irreducible dislocation [7][8][9] . Up until now, incarcerated patellar tendon 10 , vastus medialis [11][12][13][14] , anteromedial capsule and retinaculum 3 , and the major part-the medial capsuloligamentary structures such as the medial capsule, the medial retinacular structures and the medial collateral ligament [1][2][3][4]6,8,11,[15][16][17][18][19][20] , have been emphasized as the principle factors which prevent closed manipulation.…”

A Chronic Posterolateral Knee and Patella Dislocation: Case Report

“…18,19 Once an irreducible posterolateral dislocation is recognized, it must be urgently reduced in order to preserve knee function. 2,4,[6][7][8][9][10]12,13,15,20 In our case, the delay in recognition ultimately affected the available treatment options and potentially the eventual outcome. 21 If a posterolateral dislocation is addressed immediately, an arthroscopic 9,6,22 and an open approach for reduction have been described.…”

“…This requires either an urgent open or an arthroscopic reduction. [4][5][6][7][8][9][10][11][12][13][14][15] However, an unrecognized or unreduced dislocation can lead to a significant increase in the complexity of definitive operative management with extensive scar tissue and decreased mobility of injured structures. Patient disability may also be severely influenced through permanently limited range of motion.…”