Keywords

These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

1 Indications and Contraindications

1.1 Indications

According to current recommendations, meniscal allograft transplantation is indicated in three specific clinical settings:

  1. 1.

    Young patients with a history of meniscectomy who have pain localized to the meniscus-deficient compartment, a stable knee joint, no malalignment, and articular cartilage with only minor evidence of osteochondral degenerative changes [no more than grade 3 according to the International Cartilage Repair Society (ICRS) classification system (Table 5.1)], are considered ideal candidates for this procedure. Some studies [1–6] have shown that meniscal allografts can survive in an osteoarthritic joint (Outerbridge grade 3–4), with significant improvement in pain and function. Because of the more rapid deterioration in the lateral compartment [7], a relatively common indication for meniscal transplantation would be a symptomatic, meniscus-deficient, lateral compartment.

    Table 5.1 International cartilage repair society cartilage lesion evaluation system
    Full size table
  2. 2.

    Anterior cruciate ligament (ACL)-deficient patients who have had previous medial meniscectomy with concomitant ACL reconstruction and who might benefit from the increased stability afforded by a functional medial meniscus. It is the authors’ conviction, that an ACL graft is significantly protected by the meniscus allograft as much as the meniscus is protected by an ACL graft.

  3. 3.

    In an effort to avert early joint degeneration, some also consider young, athletic patients who have had total meniscectomy, as candidates for meniscal transplantation prior to symptom onset [8]. However, the results obtained so far still preclude a return to high-impact sports.

1.2 Contraindications

Advanced chondral degeneration is considered a contraindication to meniscal allograft transplantation, although some studies suggest that cartilage degeneration is not a significant risk factor for failure [9]. In general, greater than grade 3 articular cartilage lesions according to the ICRS classification system should be of limited surface area and localized. Localized chondral defects may be treated concomitantly, as meniscus transplantation and cartilage repair or restoration may benefit each other in terms of healing and outcome [10]. Chondrocyte transplantation or osteochondral grafting procedures should be performed after completion of the meniscal transplantation in order to prevent accidental damage to the patch or graft during meniscal allograft insertion [11]. Radiographic evidence of significant osteophyte formation or femoral condyle flattening is associated with inferior postoperative results because these structural modifications alter the morphology of the femoral condyle [12]. Generally, patients over age 50 have excessive cartilage lesions and are suboptimal candidates.

Axial malalignment tends to exert abnormal pressure on the allograft leading to loosening, degeneration, and failure of the graft [12]. A corrective osteotomy should be considered in patients with more than two degrees of deviation toward the involved compartment, as compared with the mechanical axis of the contralateral limb. Varus or valgus deformity may be managed with either staged or concomitant high tibial or distal femoral osteotomy [11]. However, as in any situation in which procedures are combined, it is unclear which aspect of the procedure is implicated in symptom resolution, such as relief of pain [12].

Other contraindications to meniscal transplantation are obesity, skeletal immaturity, instability of the knee joint (which may be addressed in conjunction with transplantation), synovial disease, inflammatory arthritis and previous joint infection, and obvious squaring of the femoral condyle.

2 Results

It is difficult to perform a meta-analysis of all the published results, because of the small populations studied and the differences (Table 5.2) in indications, contraindications, preservation techniques, preoperative Outerbridge grade, fixation techniques, surgical techniques, concomitant procedures, evaluation tools and rehabilitation protocols.

Table 5.2 The difficulty realizing a meta analysis of all the published results, because of the small populations studied and the differences in indications, contraindications, preservation techniques, preoperative outerbridge grade, fixation techniques, surgical techniques, concomitant procedures, evaluation tools and rehabilitation protocols
Full size table

In this chapter, we will try to present outcome data based on a review of the literature. A total of 39 studies have been included, representing 1,226 meniscus allografts (626 medial vs. 446 lateral, 154 not specified) in 1,145 patients. The mean age at the time of surgery was 34.4 years. The mean follow-up was 5.5 years. Overall, 340 isolated allograft transplantations were analysed, 427 were associated with ACL reconstruction, 107 with a corrective osteotomy and 215 with other procedures. It was not specified whether the remaining 137 allografts were associated with other procedures. Concerning the surgical fixation technique, 631 allografts were fixed using bone blocks and 488 using a soft-tissue fixation technique. For 107 allografts the fixation method was not specified. In the next paragraphs, the outcome is reported independently of the aforementioned parameters.

Methods to evaluate the success or failure of meniscal transplantation range from subjective pain scale measurements and patient perceptions of function to objective measurements such as physical and radiological examinations, magnetic resonance imaging (MRI), and second-look arthroscopy.

2.1 Subjective Assessment

All studies showed significant subjective improvement in pain scales and functional activity questionnaires. The data from most studies are summarized in Table 5.3. In general, isolated procedures and combined procedures tended to have similar outcomes. No differences were observed based on tissue preservation technique or fixation method. About 75–90 % of patients experienced fair to excellent results.

Table 5.3 Summary of subjective assessment
Full size table

2.2 Objective Clinical Scoring

2.2.1 Physical Examination

Almost all studies reported equal or improved physical examination findings at follow-up with regard to range of motion, pain, effusion, stability, function tests or IKDC score. The data from most studies are summarized in Table 5.4.

Table 5.4 Objective clinical scoring summary
Full size table

2.2.2 Radiological Examination

Joint space narrowing indicating cartilage degeneration was observed in a number of patients and tended to increase with a longer duration of follow-up. However, a significant number of patients showed no signs of progression. Based on these limited data, meniscus allograft transplantation is believed to have a chondroprotective effect in 30–40 % of patients. However, the majority of patients are on the ‘slippery slope of osteoarthritis’ and will further deteriorate over time. It is unknown whether allograft transplantation delays the natural course of osteoarthritis after meniscectomy. Future research is mandatory to determine the chondroprotective power of meniscus allograft transplantation (Table 5.5).

Table 5.5 Radiological evaluation
Full size table

2.2.3 MRI Analysis

Routine preoperative MRI may be useful for documentation of articular cartilage defects, subchondral bone status, and any remaining meniscus. Potter et al. [13] demonstrated that MRI provides accurate assessment of meniscal position, horn and capsular attachments, meniscal degeneration and adjacent articular cartilage. It correlates well with arthroscopic evaluation of the transplant and is noninvasive. The development of dynamic and weightbearing MRI shows promise for its use in meniscal transplant analysis (Table 5.6).

Table 5.6 MRI Analysis
Full size table

In order to overcome the observed discrepancy between clinical outcome and meniscal allograft status and to assess any progression of degenerative articular changes after this type of surgery, objective outcome measures such as MRI have to be included in outcome studies. Only limited literature data are available reporting that meniscal allografting halts or slows down further degeneration [14–17]. In one recent long-term study progression of cartilage degeneration according to MRI and radiological criteria was halted in 35 % of patients, indicating a potential chondroprotective effect [18]. A recent controlled large animal study also confirmed this chondroprotective effect [19]. These data could support the use of prophylactic meniscal transplantation in meniscectomized patients without clinical symptoms, thus potentially limiting secondary cartilage degeneration. Further prospective comparative studies are mandatory to test this hypothesis.

Using MRI, meniscal allograft extrusion has been described independent of the surgical fixation technique. In our experience, using soft-tissue fixation, extrusion is observed in the corpus and anterior horn of the lateral graft, while the posterior horn is most frequently within normal values [18]. This extrusion could reduce the functional surface of the graft and thus potentially also its biomechanical function. Biological reasons for the observed extrusion posttransplantation could include progressive stretch and failure of the circumferential collagen bundle due to insufficient repair potential or increased catabolism. Future research should focus on the biology involved in ongoing metabolic and cellular processes after transplantation.

Lyophilized allografts showed more shrinkage and degeneration, indicated by altered signal intensity, than did other grafts. Therefore, this preservation technique is no longer used. In the long term, all allograft types show some shrinkage. The exact meaning of the observed shrinkage has yet to be determined. Possible hypotheses are tissue loss due to mechanical wear or a biological process of contraction often observed in scar tissue formation and healing.

In general, healing of the allograft to the rim is observed in the vast majority of patients. The meniscus allograft signal is most frequently abnormal with a more greyish appearance. The authors believe that this change in signal reflects biological remodeling of the extracellular matrix of the allograft, rather than true degenerative changes.

2.2.4 Second-Look Arthroscopy

Some authors have demonstrated that clinical evaluation only based on symptoms and physical examination does not allow reliable assessment of the status of the meniscus. Arthroscopic evaluation, however, should not be used as a routine postoperative evaluation tool. Most frequently, it is performed upon clinical suspicion of an intra-articular problem. In some cases, arthroscopic evaluation can be performed in association with another procedure around the knee (Table 5.7).

Table 5.7 Evaluation by second-look arthroscopy
Full size table

In general, and in accordance with the MRI evaluation, good healing of the allograft to the rim is observed in the vast majority of patients. Tearing and shrinkage can be present. The status of the allograft, however, correlates poorly with the clinical outcome.

3 Failures and Survival Analysis

In the literature, no consensus exists on the criteria for failure or success. A number of authors use the clinical outcome, while others propose more objective outcome parameters such as MRI or second-look arthroscopy. In general, using objective parameters, the clinical success rate is higher than estimated. In the majority of studies, a clinical success rate of 70 % and higher has been reported at the final follow-up. Because the success rate has a tendency to decrease over time, it would be preferable to use survivorship analysis rather than failure rate to describe the success of such a procedure. A survivorship is much more powerful to describe the results irrespective of the duration of follow-up. We all are aware that nothing ruins good results more than a long-term follow-up… (Table 5.8).

Table 5.8 Failure criteria and failure rate
Full size table

Based on the available survivorship data, a clinical survivorship of 70 % at 10 years can be anticipated for both medial and lateral allografts. Ligament instability, axial malalignment and cartilage degeneration are considered by most authors to be associated with a higher failure rate and inferior results, although some authors have reported satisfactory results in degenerative knees.

4 Conclusion

In conclusion, ample evidence has been presented to support meniscus allograft transplantation in meniscectomized painful knees, with observance of the proper indications. Significant relief of pain and improvement in function have been achieved in a high percentage of patients. These improvements appear to be long-lasting in 70 % of patients. Based on plain radiology and MRI, a subset of patients does not show further cartilage degeneration, indicating a potential chondroprotective effect. The lack of a conservatively treated control group is considered a fundamental flaw in the reported studies, making it difficult to establish the true chondroprotective effect of this type of treatment.

Based on the presented results, meniscus allograft transplantation should no longer be considered experimental surgery for the meniscectomized painful knee.