The Postoperative Meniscus

© 2006 Elsevier Inc. All rights reserved.

sportsmed.theclinics.com of preserving as much meniscal tissue as possible. Persisting symptoms following meniscal surgery may be from a recurrent tear at the site of previous surgery, the presence of a new tear at a site remote from the previous intervention, or extrameniscal pathology.

Accuracy of MRI in assessment of meniscal tears in nonoperated ''virgin'' menisci is well established [5-7]. The MRI criteria for diagnosing meniscal tears in such cases include regions of increased signal intensity on short echo time pulse sequences, which unequivocally extend onto an articular surface (grade 3 signal), alteration of meniscal morphology such as blunting and truncation of the meniscus, and identification of displaced meniscal fragments. Early studies of postoperative menisci quickly demonstrated the difficulties associated with using these criteria following meniscal surgery [8-10]. In particular it was established that grade 3 signal on T1 or intermediate-weighted sequences did not reliably predict a recurrent tear [8,9,11], demonstrating 100% sensitivity but a specificity of only 22% to 29% following meniscal repair [9,12,13]. Meniscal healing occurs with development of fibrovascular tissue, which exhibits increased signal intensity on short echo sequences indistinguishable from the original tear (Fig. 1). Furthermore, this signal abnormality may persist for many years following repair [14]. Signal conversion is also a potential pitfall mimicking a recurrent tear following partial meniscectomy. Signal conversion refers to the situation in which intrasubstance degenerative signal (grade 1 or 2), or the central healed margin of a prior meniscal tear cleft, extends to the neo-articular surface of the postoperative meniscus following resection of unstable components of a tear. Such resultant signal change within a stable postoperative meniscus may mimic the appearance of grade 3 intrame-niscal signal in the setting of a tear of a nonoperative meniscus. [15,16].

Consequently, revised criteria have been proposed for diagnosis of tears following meniscal surgery. These include grade 3 signal, which also exhibits fluid signal intensity on T2-weighted or other fluid-sensitive sequences (Fig. 2), identification of a displaced meniscal fragment (Fig. 3), or meniscal fragmentation [9]. Conventional criteria may still be used at locations other than the site of partial meniscectomy or repair and details of the prior surgical procedure or preoperative MRI is therefore useful.

In relation to meniscal repairs, application of the criterion consisting of fluid signal within the meniscus results in a higher specificity (88% to 92%) but lower sensitivity (60% to 69%) in comparison with grade 3 signal on short echo sequences [9,15,17].

Normal postoperative appearances of stable menisci following partial meniscectomy include blunting of the meniscal apex at the site of surgery (Fig. 4). Morphologic changes beyond those expected with partial meniscectomy have an accuracy rate of only 67% to 68% [15,18] when used alone in the assessment of a possible recurrent or residual meniscal tear (Fig. 5). Complexities in evaluation of menisci following partial meniscectomy appear to be partially related to the amount of meniscus resected at the time of surgery. Conventional MRI is most accurate in diagnosis of recurrent tears in patients with less than 25% of

Mri Post Operative MeniscusMeniscus Tear Pitfall Fibrovascular

Fig. 1. Sagittal FSE proton density (repetition time msec/echo time msec TR/TE, 2200/25) (A) and fat-suppressed T2-weighted (TR/TE, 3500/70) (B) MR images of a healing meniscal tear following meniscal repair. On the proton density image there is a persistent peripheral vertical linear intermediate intensity line contacting the articular surface within the posterior horn of the medial meniscus (black arrow), which would be consistent with a residual tear under conventional criteria. On the fat-suppressed T2-weighted image, however, there is no imbibition of fluid into the apparent tear cleft (white arrow), consistent with a healing meniscal repair.

the meniscus resected with an overall accuracy of 89% to 100% with arthroscopic correlation using the standard criteria of abnormal signal intensity that communicates with an articular surface on proton-density or Tl-weighted images [18-20]. When there has been a more extensive resection (resection > 25% meniscus), there is a reduction in accuracy to 84% [18] even when the criterion of fluid signal intensity on fluid-sensitive imaging is used. The fluid signal intensity is thought to represent fluid extending into a tear cleft but interestingly the presence of an effusion appears to produce either a small incremental increase [18] or an overall reduction in accuracy [20]. Other investigators have not found a significant difference between groups of patients with less than or more than 25% resection [15]. Given the reliance on identification of fluid signal within a tear, acquisition of fluid-sensitive (T2-weighted) MRI sequences in both the coronal and sagittal planes is thought to be optimal, and addition of fat suppression may additionally assist in increasing the conspicuity of a possible recurrent/residual tear. In our practice T2-weighted imaging with fat suppression is routinely employed, although proton-density images with fat suppression have also demonstrated similar diagnostic capabilities [15,21].

Given the complexities of postoperative meniscal imaging, the use of MR ar-thrography has been examined [18-20,22,23]. Direct MR arthrography with in-tra-articular injection of gadolinium in a dilution of 1:100 to 1:250 has the benefit of obtaining joint distension, increasing intra-articular pressure and reducing viscosity of synovial fluid, thereby facilitating imbibition of fluid into

Mri Partial Meniscectomy

Fig. 2. Sagittal FSE proton density (TR/TE, 2200/15) (A) and fat-suppressed T2-weighted (TR/TE, 3500/70) (B) MR images of a recurrent meniscal tear following partial meniscectomy. The proton density MR image demonstrates a poorly defined posterior horn of the medial meniscus following partial meniscectomy (black arrow). The fat-suppressed T2-weighted image demonstrates multiple fluid signal intensity areas within the meniscus consistent with a complex recurrent tear (white arrow).

Fig. 2. Sagittal FSE proton density (TR/TE, 2200/15) (A) and fat-suppressed T2-weighted (TR/TE, 3500/70) (B) MR images of a recurrent meniscal tear following partial meniscectomy. The proton density MR image demonstrates a poorly defined posterior horn of the medial meniscus following partial meniscectomy (black arrow). The fat-suppressed T2-weighted image demonstrates multiple fluid signal intensity areas within the meniscus consistent with a complex recurrent tear (white arrow).

a potential meniscal tear cleft [17,24]. Gentle exercise following the injection may further assist in forcing gadolinium into a recurrent or residual meniscal tear cleft. T1-weighted acquisitions on which dilute gadolinium contrast material illustrates increased (bright) signal intensity, additionally affords a higher

Meniscus Tear Exercises
Fig. 3. Coronal FSE intermediate-weighted image (TR/TE, 3600/35) in a patient with a prior partial meniscectomy displaying a recurrent tear as illustrated by a displaced meniscal fragment in the meniscocapsular recess superior to the body of the medial meniscus (arrow).
Coronary Recess
Fig. 4. Coronal FSE intermediate weighted image (TR/TE, 3500/35) illustrating the normal postoperative blunting of apical free margin of the body of the lateral meniscus following partial meniscectomy (black arrow).

signal-to-noise ratio than T2-weighted imaging. The drawbacks of the technique include its invasive nature and the additional time required for the injection. On MR arthrographic studies, tears are diagnosed by demonstrating areas of similar signal intensity to the intra-articular gadolinium extending from the joint space into the substance of the meniscal remnant (Fig. 6). Improved accuracy of 87% to 93% has been illustrated using MR arthrography over conventional MRI in mixed groups of patients having undergone previous repair or partial meniscectomy [18,22,23]. These results were not always statistically significant, although this may be a result of the study design and the number of patients recruited [12,23]. In the subset of patients with a meniscal resection of less than 25%, direct MR arthrography does not appear to exhibit a diagnostic advantage over conventional MR imaging.

Intravenous injection of gadolinium followed by delayed imaging results in diffusion of contrast into articulations with an indirect arthrographic effect and has been advocated as an alternative to direct MR arthrography. Although this technique avoids the need for an intra-articular injection it lacks the potential advantage of joint distension achieved by direct MR arthrography. However, similar accuracies to direct MR arthrography have been demonstrated in the few investigations studying the utility of indirect MR arthrography in the diagnosis of postoperative recurrent or residual meniscal tears. Studies with intravenous injection of gadolinium have also been used to evaluate the enhancement of fibrovascular granulation tissue to assess the healing process following meniscal repair with gradual reduction in the intensity of enhancement with time [25]. These authors have also suggested that there is gradual reduction in tear size on serial examinations, while distraction of meniscal

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Fig. 5. Coronal intermediate-weighted (TR/TE, 3700/35) (A) and T2-weighted fat-suppressed (TR/TE, 3500/70) (B) MR images demonstrating irregularity of the body of the lateral meniscus following partial meniscectomy (arrows). There is no imbibition of fluid on T2-weighted images and no tear was identified at repeat arthroscopy.

Fig. 5. Coronal intermediate-weighted (TR/TE, 3700/35) (A) and T2-weighted fat-suppressed (TR/TE, 3500/70) (B) MR images demonstrating irregularity of the body of the lateral meniscus following partial meniscectomy (arrows). There is no imbibition of fluid on T2-weighted images and no tear was identified at repeat arthroscopy.

fragments by more than 1 mm has been proposed as a potential sign of a recurrent tear [26].

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  • tarquinia
    Are all grade 2 siginal within the lateral meniscus degeneration?
    8 years ago
  • niklas
    What is apical blunting of the medial meniscus?
    7 years ago
  • jennifer
    Can you get get stress fracture after meniscus surgery?
    5 years ago
  • lorenza
    What is post meniscectomy syndrome stress fracture?
    5 years ago
  • t
    How do stress fractures occur after meniscal surgery?
    4 years ago
  • gabriele
    How to avoid stress fracture after meniscus surgery?
    3 years ago
  • stephen
    How to repair stress fracture after menicus repair?
    3 years ago
  • Venerando
    What is a stress fracture in the knee after meniscus surgery?
    2 years ago
  • fredrik
    What is a stress fracture after menicus repair surgery burni g?
    2 years ago
  • Selene Greece
    What is a stress fracture after meniscus repair surgery burning?
    2 years ago
  • ELIAS
    Can I get a stress fracture after a minisectomy?
    8 months ago
  • yusef
    Can i get a stress fracture after having part of my miniscus removed?
    8 months ago
  • Adaldrida
    Can you get a stress knee fracture after orthoscopic knee surgery?
    6 months ago
  • Mario
    Did meniscus repair cause tibia fracture?
    1 month ago
  • neftalem
    When are you out of the woods for getting a stress fracture after miniscus surgtery?
    1 month ago
  • Riikka
    Are knee stress fractures common after miniscus surgery?
    26 days ago

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