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 Table of Contents  
CASE REPORT
Year : 2021  |  Volume : 41  |  Issue : 6  |  Page : 315-318

A rare case of symptomatic nonunion of avulsion fracture of the posterior medial meniscus root with concomitant posterior cruciate ligament injury


Department of Orthopedics, School of Medicine, College of Medicine, Taipei Medical University; Department of Orthopedics, Taipei Medical University Hospital, Taipei, Taiwan

Date of Submission12-Oct-2020
Date of Decision04-Jan-2021
Date of Acceptance19-Feb-2021
Date of Web Publication24-May-2021

Correspondence Address:
Dr. Jia-Lin Wu
250 Wuxing Street, Xinyi District, Taipei City
Taiwan
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jmedsci.jmedsci_329_20

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  Abstract 


The menisci are the essential structures of the knee joint because they disperse body weight and reduce friction during the movement. An avulsion fracture of the posterior medial meniscus root, also known as meniscal ossicles, can lead to meniscal extrusion. Consequently, the medial meniscus loses its ability to absorb hoop stress. One patient presented with nonunion posterior root avulsion fracture of the medial meniscus concomitant with posterior cruciate ligament (PCL) injury. The patient underwent arthroscopic suture repair through the placement of a tibial tunnel 1 year after injury. The fracture united well, and complete recovery was achieved at the 2-year follow-up. To the best of our knowledge, this is the first report describing a posterior root avulsion fracture of the medial meniscus with concomitant PCL avulsion fracture.

Keywords: Arthroscopy, medial meniscus root, posterior cruciate ligament injury


How to cite this article:
Wu SH, Lee SH, Lee CH, Wu JL. A rare case of symptomatic nonunion of avulsion fracture of the posterior medial meniscus root with concomitant posterior cruciate ligament injury. J Med Sci 2021;41:315-8

How to cite this URL:
Wu SH, Lee SH, Lee CH, Wu JL. A rare case of symptomatic nonunion of avulsion fracture of the posterior medial meniscus root with concomitant posterior cruciate ligament injury. J Med Sci [serial online] 2021 [cited 2021 Nov 27];41:315-8. Available from: https://www.jmedscindmc.com/text.asp?2021/41/6/315/316671




  Introduction Top


A meniscus root tear is defined as a radial tear within 1 cm of the meniscus insertion or an avulsion at the insertion of the meniscus.[1] Medial meniscus root tears lead to the significant changes in joint arthrokinematics, with increased lateral tibial translation and greater demand on the medial compartment. Therefore, the meniscus cannot convert axial loads into transverse hoop stress,[1],[2],[3] leading to accelerated cartilage degeneration, which results in a consequent injury comparable to total meniscectomy.[1] Meniscus root tears may be acute or chronic. Posterolateral meniscus root tears are typically associated with anterior cruciate ligament (ACL) tears,[4],[5] whereas posterior medial meniscus root tears (PMMRTs) are because of chronic degenerative meniscal disease that are mostly experienced by middle-aged women.[6],[7] Traumatic PMMRTs are less common, as are avulsion fractures of the meniscus root.[8],[9] To the best of our knowledge, only 13 such cases are reported in the literature thus far.[10],[11],[12],[13],[14],[15],[16],[17],[18],[19] We report the first case of an avulsion fracture of the posterior medial meniscus root with concomitant posterior cruciate ligament (PCL) injury.


  Case Report Top


A 38-year-old male fell from a bike and twisted his left knee. Therefore, he only received nonoperative treatment with oral pain management form a local clinic. However, he experienced progressive left knee swelling and pain 1 year later; thus, he was referred to our hospital. Upon initial clinical examination, we observed knee effusion, severe posterior knee pain, and tenderness over the posteromedial joint line; however, the posterior drawer test was Grade I positive, as it resulted in a hard endpoint. Collateral ligaments were stable, and the McMurray test was positive. Plain radiographs revealed a diagnosis of an avulsion fracture of the PCL along with a medial tibial plateau fracture near the intercondylar eminence [Figure 1]a and [Figure 1]b. Magnetic resonance imaging (MRI) showed a healed PCL avulsion fracture and a 0.6-cm avulsed osseous nodule at the medial meniscus root. A Grade-1 ACL sprain with edema at the medial femoral and tibial condyles was also noted [Figure 2]a and [Figure 2]b. Based on the clinical and radiographic findings, he was diagnosed with an avulsion fracture of the posterior medial meniscus root with a healed PCL avulsion fracture, and he accepted surgical treatment.
Figure 1: Preoperative radiographic images. (a) Anteroposterior view. (b) Lateral view (arrows indicate the avulsed bony fragment)

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Figure 2: Preoperative T1-weighted magnetic resonance images. (a) Coronal view. (b) Sagittal view (arrows indicate the avulsed root and posterior cruciate ligament bony fragment)

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Diagnostic arthroscopy through a standard anterolateral portal confirmed the diagnosis. An avulsed small bony fragment was noted at the posterior medial meniscus root [Figure 3]a. Probing revealed that the fragment was unstable, although the PCL seemed stable and the PCL avulsion fracture had healed. The ACL and the bodies of both menisci were intact. The fibrous scar lesion of tibial avulsion site was curetted, and the subchondral bone was exposed.
Figure 3: Diagnostic arthroscopy of the left knee through the anterolateral portal showing the avulsion fracture (star) of the posterior medial meniscus root. (a) A suture hook was inserted and the posterior medial meniscus root was sutured with one polydioxanone suture loop. (b and c) The polydioxanone suture was shifted to the ethibond suture. (d) The fragment was reduced anatomically

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The root avulsion fracture was reattached using a transtibial pullout suture technique. One number 2-0 polydioxanone suture (PDS) was passed between the junction of the posterior root of the medial meniscus and the avulsed bony fragment using a suture hook in a simple suture configuration [Figure 3]b and [Figure 3]c. Using an ACL tibial drill guide, a 4.5-mm bone tunnel was reamed from the anterolateral tibial cortex to the bone bed of the posterior root of the medial meniscus. The sutures of the meniscus were then pulled out through the tibial tunnel using a wire loop. Then, the PDS suture was shifted to the number 2 ethibond polyester suture, and its free ends were pulled to reduce the avulsed posterior medial meniscus root appropriately [Figure 3]d. We subsequently tied them on the anterolateral surface of the tibia with the knee flexed at 45°.

Postoperatively, his knee was maintained in a brace, and partial weight bearing was allowed. Knee flexion was restricted to 0° for the first 2 weeks followed by a gradual increment of 10° weekly. Six-month postoperative radiographs and MRI showed the attachment of the avulsed fragment to the tibial eminence with no displacement [Figure 4] and [Figure 5]. A year after surgery, he regained normal knee function and recovered completely, Lysholm scores increased from 59 preoperatively to 90 postoperatively.
Figure 4: Postoperative radiographic images. (a) Anteroposterior view. (b) Lateral view (arrows indicate well-healed bony fragment)

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Figure 5: Postoperative T1-weighted magnetic resonance images. (a) Coronal view. (b) Sagittal view (arrows indicate well-healed bony fragment)

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  Discussion Top


Avulsion fractures of the meniscus root, also referred to as meniscal ossicles,[10] are rare injuries, with limited case reports. To the best of our knowledge, only 13 such cases have been reported in the literature thus far.[10],[11],[12],[13],[14],[15],[16],[17],[18],[19]

With regard to the pathomechanism of our case, concomitant avulsion fractures of the posterior medial meniscus root and PCL suggest a direct blow to the proximal tibia of a flexed knee, which represents a typical injury mechanism of the PCL. At the time of PCL avulsion from the tibia, the medial tibial plateau can subluxate posteriorly over the femur, which places high stress on the posterior root of the medial meniscus.

A recent report showed a prevalence rate of 0.15% for meniscal ossicles in 1287 consecutive MRI examinations.[20] Moreover, our hospital revealed a 0.44% (2 of 456 cases) prevalence rate of meniscal ossicles among the patients with meniscus root tears. Our case highlights a previous debate regarding the etiology of meniscal ossicles. Posttraumatic theory states that the formation of ossicles is the result of metaplasia and heterotopic ossification within the meniscus because of either a single traumatic event or recurrent microtrauma.[21],[22],[23],[24] Conversely, phylogenetic theory states that the ossicle is a vestigial remnant structure of congenital origin, as meniscal ossicles are commonly seen in primates, cats, and dogs.[25],[26],[27] However, meniscal ossicles developed in our patient because of delayed treatment. Therefore, this case favors posttraumatic theory over phylogenetic theory.

Meniscal ossicles are either treated conservatively, or limited meniscal resection of the ossicle is performed.[21],[22],[25],[28] Refixation of root tears is the method of choice for restoring the biomechanical function of the meniscus.[29],[30],[31],[32] In one study, mean Lysholm scores increased from 55 preoperatively to 86 postoperatively after transtibial repair for root avulsion fractures of the medial meniscus.[32] Our patient still had mechanical symptoms and pain after conservative treatment despite no significant laxity, and the root avulsion seemed to be the cause of symptoms. Therefore, we performed transtibial pullout suture repair of the avulsion fracture and treated the PCL avulsion fracture conservatively. From our experience, we recommend surgical reattachment and not meniscectomy for avulsion fractures of the posterior root of the medial meniscus.


  Conclusion Top


This is the first report describing a posterior medial meniscus root with concomitant PCL injury. Based on the findings of the literature, root avulsion fractures are rare, but surgeons must be aware of this injury pattern, especially in young males presenting after an acute traumatic event of the knee joint.

Declaration of patient consent

The authors certify that they had obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]



 

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