Abstract
Background:
Meniscal allograft transplantation (MAT) was developed as a means of treating the symptoms of compartmental overload after meniscectomy. Despite more than 20 years of research in this field, many controversies still exist regarding meniscal transplantation.
Purpose:
The aims of this study were to assess (1) the quality of the published studies on MAT; (2) the indications for this type of surgery; (3) the methods used for preservation, sizing, and fixation of the allograft; and (4) the clinical and radiographic outcomes of this procedure and its role in preventing osteoarthritis.
Study Design:
Systematic review.
Methods:
Inclusion criteria for the articles were (1) English language, (2) peer-reviewed clinical studies with evidence levels 1 to 4, (3) reported clinical and/or radiological outcomes of MAT isolated or combined with other procedures, (4) minimum 12-month follow-up, (5) case series of at least 10 patients, and (6) a follow-up rate of at least 80% (no more than 20% of patients lost to follow-up).
Results:
A total of 55 studies matched the inclusion criteria (2 level 2, 7 level 3, and 46 level 4). The average Coleman methodology score was 49.73 ± 12.41 (range, 24-81). There was agreement in the literature regarding the indications for MAT: joint line pain and tenderness correlated with previous meniscectomy, young patients, without diffuse Outerbridge grade III and no grade IV cartilage damage, and a stable and well-aligned knee. Different graft types have been used: viable, fresh frozen, cryopreserved, and lyophilized. The most common method for graft sizing was plain radiography. Different fixation techniques have been described, with only a few studies comparing the clinical results of the different techniques and with no proven superiority of one method over the other. All the studies showed clinical improvement at last follow-up visit compared with preoperatively. The chondroprotective effect of MAT is still unclear.
Conclusion:
Meniscal allograft transplantation seems to provide good clinical results at short-term and midterm follow-up, with improvement in knee function as well as acceptable complication and failure rates. Higher quality studies are necessary to better assess the potential chondroprotective effect of MAT and to identify differences in terms of outcomes between different surgical techniques.
The meniscus is an important structure in load distribution, shock absorption, joint lubrication, stability, and proprioception.41,49,50 Unfortunately, total or subtotal meniscectomy, very common in the past, is still required nowadays in some patients. In 1998, Roos et al 69 evaluated 107 of 123 patients 21 years after open meniscectomy because of an isolated meniscal tear. The authors found that these patients had a 14-fold increase in the risk of radiographic osteoarthritis and a significantly higher incidence of knee pain compared with healthy matched controls. This evolving awareness about the importance of the meniscus and the dramatic consequences of total meniscectomy, together with advances in the surgical techniques, resulted in a significant increase in meniscus preservation/repair procedures.17,55,57 Irreparable or degenerative tears are not uncommon, making total or subtotal meniscectomy sometimes inevitable. To prevent the adverse effects of meniscectomy, meniscal allograft transplantation (MAT) was developed and subsequently proven to be effective in animal trials. 11 In 1989, Milachowski et al 56 reported experimental and short-term results of this technique. Since then, different laboratory studies have been performed to assess the potential benefits of MAT1,6,16 and to evaluate different types of allograft preservation.19,34 Subsequently, early clinical studies were published reporting on indications for transplantation, methods of graft preservation, surgical technique, and relevance of associated chondral and ligamentous damage.10,24,66,67 Yet, despite many articles published for over 20 years, many controversies still exist regarding different aspects of MAT. Unfortunately, the majority of the literature regarding MAT consists of uncontrolled and retrospective case series, with a lack of high-level studies.
The aims of this systematic review were to (1) assess the quality of the published studies on MAT; (2) identify the indications and contraindications for this type of surgery; (3) evaluate the methods used for preservation, sizing, and fixation of the allograft; and (4) evaluate the clinical and radiographic outcomes of this procedure and its possible role in preventing osteoarthritis. In addition, differences between lateral and medial MATs, MAT isolated and combined with other procedures, as well as bone versus suture-only fixation techniques were evaluated.
Materials and Methods
In March 2014, a literature search to identify all English-language studies evaluating the clinical or radiological outcomes of MAT was performed on Medline, PubMed, EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL). The keywords used for this search included “meniscal,” “meniscus,” “allograft,” “transplantation,” “transplant,” “clinical outcome,” and “rehabilitation” alone and in various combinations using the Boolean operator “AND.” The initial research identified 2930 articles; all these titles were accurately screened by 2 authors (F.R. and S.B.) to exclude articles not related to this topic, leaving a total of 281 articles.
Inclusion criteria for this systematic review were the following: peer-reviewed level 1 to 4 studies, published in English, studies involving human participants, and description of the clinical and/or radiological outcomes of combined and/or isolated MAT in the knee. Only studies with a minimum 12-month follow-up were included, with no less than 10 patients and a follow-up rate of at least 80% (no more than 20% of patients lost to follow-up). All 281 abstracts were reviewed following these criteria by 2 different authors, and when necessary, controversies were addressed by reading and discussing the study. This screening left 55 articles for the present review. These articles were read entirely and the reference lists checked for missing relevant articles, with no additional studies found. Figure 1 shows this selection process. Of 55 studies included, only 37 were used for demographic data collection; data from studies that evaluated the same case series at different follow-up periods or with different goals were grouped. In this case, only the demographic and clinical outcome data from the most recent or complete article were analyzed, but if relevant, some data from the other articles were included. In case of unclear data, the corresponding authors were contacted to obtain more information. The level of evidence was assessed according to the method described by Wright et al. 94 In addition, the Coleman methodology score was calculated for each study by an independent reviewer to evaluate the methodological quality. 15
Diagram showing the selection process.
All articles were read, and data were extracted and collected on an Excel (Microsoft, Redmond, Washington, USA) worksheet. Data regarding the studies included authors, year, journal, and level of evidence. Demographic data included the number of patients and allografts (both performed and reviewed), age and sex of the patients, involved meniscus (medial or lateral) and knee (right or left), time from the initial injury or first meniscectomy, average follow-up, and the follow-up rate. The authors also collected patient-specific factors such as the degree of chondral degeneration, limb alignment, knee stability, and number of previous surgeries. Graft-specific factors recorded were the method of preservation, type of secondary sterilization, and method of graft sizing. Surgical technique factors included imaging used in preoperative planning, technique for graft insertion into the joint, meniscal fixation technique, and concomitant surgical procedures. Regarding the postoperative care, the authors recorded the weightbearing status, the timing of the range of motion (ROM), the use of a brace, the use of continuous passive motion (CPM), and the time to return to daily and sport activities. All the clinical outcomes reported in each study, including subjective scores, clinical assessments, patient satisfaction, radiological evaluations, and comparisons between different groups of patients (medial vs lateral, isolated vs combined MAT, and bone vs suture fixation), were also recorded. Finally, all the data regarding complications, the failure rate, and the overall success rate were included. For the statistical analysis, weighted averages were used with relative ranges.
Results
Description of Studies
Considering all 55 articles included in the review, none of the studies could be classified as level 1, according to the system described by Wright et al. 94 Two studies could be classified as level 22,3 and 7 as level 3,13,36,44,46,48,87,93 leaving 46 level 4 articles. # The Coleman methodology score 15 was also calculated for all the studies included in this review, with an average total score of 49.73 ± 12.41 (range, 24-81).
Data from 37 studies were included in the demographic and statistical analysis, for a total of 1666 MATs in 1623 patients. There were 1012 male (66.4%) and 511 female (33.6%) patients, and in 100 patients, the sex was not specified.4,21,73 The weighted average age at the time of surgery was 34.5 years (range, 19.3-46.9 years). The transplanted meniscus was medial in 49.2% and lateral in 50.8%. Sixteen studies reported the average time between meniscectomy and MAT, with an overall weighted average of 15.16 years (range, 1.1-35.8 years).** The weighted average follow-up was 53.61 months (range, 12-168 months), and the average follow-up rate was 94.02% (range, 80.6%-100.0%). Table 1 shows in detail the demographic data of the studies included; data from studies that evaluated the same patients at different follow-up periods or with different goals were grouped together. As a result, in Table 1, 55 studies are listed, but only data from 37 of them are reported.
Demographic Data of the Studies a
Studies that evaluated the same patients at different follow-up periods or from different perspectives are grouped. NP, not provided.
Data refer to total number of patients, not patients followed by the authors.
Indications and Contraindications
The indications for MAT were not reported in 5 studies.42,54,63,72,93 In the other studies, MAT was performed to relieve joint line pain after (sub)total meniscectomy. Garrett and Stevenson 24 were the first to correlate a higher risk of MAT failure with lower limb malalignment and/or ligamentous instability. Six articles42,63,72,75,76,93 (225 MATs) did not report on the assessment of limb alignment, and 3 studies42,63,76 (151 MATs) did not mention ligamentous instability. Diffuse Outerbridge grade III or grade IV degeneration, joint space narrowing >2 to 3 mm, and >grade II degeneration according to the Fairbank classification are described as contraindications for MAT in all studies reporting on preoperative chondral status, except for 3 articles.10,20,77 Fifteen studies †† reported the number of previous surgeries, with a weighted average of 1.94 (range, 0.2-3.5).
Graft Preservation, Sterilization, and Sizing
Five studies4,25,35,72,73 did not describe in detail the type of graft preservation. In 468 cases (31.4%), a cryopreserved allograft was used, while in 901 knees (60.6%), a fresh-frozen graft was preferred. In 1 study, 93 the results of 17 lyophilized allografts were reported, while another study 87 evaluated the results of 100 viable grafts. In 3 studies,10,93,96 gamma sterilization (102 MATs) was described, and in 16 studies, ‡‡ a nonirradiated one (725 MATs) was described. The remaining studies did not describe the sterilization method. Twenty-three studies used the radiographic method §§ of Pollard et al 62 (843 MATs) to size the graft. Other authors also used sex, weight, and height in allograft sizing54,78,85; in 4 studies2,12,52,77 (227 MATs), these anthropometric measures were associated with radiographs for meniscal sizing. Also, magnetic resonance imaging (MRI) was shown to be a reliable tool in allograft sizing 64 and was used together with radiographs in 1 study 65 (22 cases). Also, computed tomography alone and in combination with radiographs 53 was used to size the allograft in 2 studies (53 cases).42,96 Appendix Table A1 (available online at http://ajsm.sagepub.com/supplemental) shows these data in detail.
Surgical Techniques
In 1989, Milachowski et al 56 was the first to evaluate a series of MATs; in this series, transplantation was performed using medial or lateral arthrotomy with collateral ligament detachment or splitting. Later, the application of joint distractors was proposed to preserve the collateral ligaments. 10 However, the arthroscopically assisted MAT technique is now the most commonly used technique. Four studies10,25,84,88 (235 MATs) described open techniques, 24 studies ∥∥ (1045 MATs) described arthroscopically assisted techniques, and 7 studies2,13,26,35,42,70,77 (302 MATs) reported all arthroscopic techniques. In 4 studies,30,72,88,93 collateral ligament detachment was described, and in 1 study, 10 a joint distractor was used. Bone fixation was described in 1107 MATs and the suture-only technique in 459 procedures; 1 study 13 did not describe the type of fixation. On the medial side, 493 MATs were performed with bone fixation, while in the lateral compartment, bone fixation was used in 614 MATs. The graft should be secured to the capsule through a meniscal repair technique if it is accepted that peripheral fixation is a prerequisite for healing and vascularization of the graft. Twelve studies ¶¶ did not describe the type of capsular fixation. In the other studies, different techniques were reported for capsular fixation: an all-inside technique was performed in 154 MATs, an inside-out technique was performed in 703 MATs, and a mixed technique was used in the remaining cases. Five studies4,42,45,70,73 reported on isolated MAT, while in 31 studies, ## associated procedures were performed; in the remaining study, 59 it was unclear whether associated procedures were performed. A total of 873 associated procedures were performed (52.4% of all MATs): 321 anterior cruciate ligament reconstructions (ACLRs), 112 osteotomies, 13 combined ACLRs and osteotomies, and 440 other procedures (mostly cartilage procedures). Appendix Table A1 (available online) describes these data in detail.
Rehabilitation Protocols
There is no agreement among the included studies regarding the rehabilitation protocol after MAT. In addition, the postoperative regimen significantly varied also when considering the concomitant procedures. Full weightbearing was allowed at the weighted average time of 6.2 ± 1.9 weeks and full ROM at the weighted average of 6.3 ± 2.9 weeks after surgery. In 24 studies, a a brace was used, while in 9 articles,13,25,40,73-75,84,93,96 the use of CPM was described.
Clinical Outcomes
Thirteen different scoring systems were described: the most commonly used were the Lysholm score, the Tegner 80 activity score, the International Knee Documentation Committee 32 (IKDC) subjective form, the visual analog scale (VAS) for pain and/or overall knee function, the Knee injury and Osteoarthritis Outcome Score 61 (KOOS), the IKDC objective form, 30 and the Short Form–12 (SF-12) or SF-36. 8 The other scores included the Noyes sports and symptoms score, 58 the modified Cincinnati score,9,60 the Fulkerson knee score, 23 the Hospital for Special Surgery score, 31 the Western Ontario and McMaster Universities Osteoarthritis Index 7 (WOMAC), the Knee Assessment Scoring System, and the Knee Outcome Survey. 33
The weighted average Lysholm score increased from 55.5 ± 2.1 preoperatively to 82.7 ± 2.7 at the last follow-up. Similarly, the weighted average overall VAS score for pain decreased from 6.4 ± 0.4 to 2.4 ± 0.4 at the last follow-up. Some authors described a worsening of the results over time. Figure 2 shows the different outcomes correlated with the average follow-up. Only 14 studies b reported on the overall satisfaction rate, with a weighted average of 81.6% ± 3.8%. Eighteen studies c compared the results of medial and lateral MATs; of these studies, only 220,82 reported differences in terms of clinical outcomes, with slightly shorter survival for medial MAT.
Different outcomes correlated with the average follow-up with a tendency to decrease over time. VAS, visual analog scale.
Thirteen studies d compared the clinical outcomes or survivorship of isolated MAT versus MAT combined with other procedures. No statistically significant differences were described. Few studies reported a comparison between bone plugs and suture-only fixation. In this review, 2 studies2,30 compared the 2 techniques with no differences in terms of clinical outcomes, although some authors 2 reported higher complication and failure rates with the suture-only technique. In the present review, radiological postoperative evaluations with radiographs were reported in 18 studies, for a total of 519 allografts. e Also, MRI was used by 16 authors f for the follow-up evaluation of 597 MATs. One of the most common parameters evaluated by the authors was graft extrusion, with a weighted average value of 3.8 ± 0.3 mm. There is some agreement in considering second-look arthroscopic surgery as the most precise evaluation method of MAT. Eleven studies g reported 140 second-look arthroscopic procedures, usually observing graft integrity, incorporation, vascularization, shrinkage, and extrusion but also changes in cartilage status from the time of surgery. Of the 140 grafts analyzed, 93 were reported as well healed. Appendix Table A1 (available online) reports in detail the clinical outcomes from the different studies.
Complications and Failures
There were 176 complications reported after MAT, with a weighted average complication rate of 10.6%. The most commonly reported complication was a tear of the allograft in 105 cases (59.6% of all the complications). Synovitis or effusion was detected in 54 cases, superficial infections in 11 cases, reduction in ROM in 5 cases, and deep infection in 1 case.
Among the studies included in this review, there was no agreement in the definition of allograft failure: MAT revision, conversion to total knee arthroplasty, poor clinical results, poor MRI findings, and in 1 study, subsequent meniscectomy. 21 Only 11 studies h reported on this topic: the total number of failed allografts was 145, with an overall weighted failure rate of 8.7%. Considering 2 different groups based on graft preservation (cryopreserved vs fresh frozen), and analyzing only studies in which the failure rate was reported, we found a higher failure rate in the cryopreserved group (18.2% vs 9.9%, respectively). We used the χ2 test, and the difference between the 2 groups was statistically significant (P = .0004). Twelve studies i did not report on the failure rate (see the Appendix, available online). Only 5 studies54,77,84,88,92 reported the Kaplan-Meier cumulative survival rate. Stone et al 77 reported an average overall survival time of the allograft of 9.9 ± 0.4 years, while in the study by Verdonk et al, 88 the average cumulative survival time was 11.6 years both for medial and lateral allografts, and van der Wal et al 84 reported a 52.5% survival rate at 16 years in 63 allografts.
Discussion
An analysis of the literature on MAT is difficult because of the lack of high-level evidence and the variability of surgical techniques, concomitant procedures, and clinical scores. For these reasons, a meta-analysis of the data is not feasible.
The first aim of this review was to assess the quality of the published studies. In this review, the authors reported on 55 studies, with 46 level 4 case series. The Coleman methodology score 15 was calculated to assess the quality of these studies, with an average score of 49.73 ± 12.41 (range, 24-81), which is comparable with other studies. 18
The second aim of this review was to evaluate the indications and contraindications for this type of surgery. There is agreement in the literature regarding the indications for MAT: joint line pain associated or not with other symptoms correlated with previous meniscectomy, young patients, without diffuse Outerbridge grade III and no grade IV cartilage damage, and a stable and well-aligned knee. However, in some studies, the indications have been expanded. Stone et al 77 in 2010 reported the results of 119 primary MATs combined with articular cartilage repair in older patients (average age, 46.9 years; range, 14.1-73.2 years); in that study, 46.1% of the patients were older than 50 years. 77 The same research group also reported on 47 MATs performed in 45 patients with preoperative evidence of arthrosis and Outerbridge degeneration >grade II (81% grade IV), with an average time to failure of 4.4 years. 77
The third aim of the present review was to assess the methods used for preservation, sizing, and fixation of the allograft. A number of different graft types have been used: viable, fresh frozen, cryopreserved, and lyophilized. Most of the authors preferred a fresh-frozen (60.6% of MATs) or cryopreserved graft (31.4% of MATs), which showed similar results. 19 Wirth et al 93 were the only ones to report the results of 17 lyophilized allografts at 14 years of follow-up compared with deep-frozen grafts. The authors concluded that deep-frozen grafts generally performed better than the lyophilized transplants.
Meniscal allograft transplantation is associated with the potential transmission of bacterial, viral, or fungal pathogens. In the past, gamma irradiation was the most popular sterilization method of allografts. However, this technique was demonstrated to affect the biomechanical properties of the grafts. 86 In the studies included in this review, a nonirradiated sterilization technique was utilized for 525 MATs. Numerous methods for graft sizing were described, with the radiographic method of Pollard et al 62 being the most used (843 MATs). However, there are no clinical studies comparing the outcomes of the different sizing methods.
The surgical technique has significantly evolved over time, and currently, the arthroscopically assisted technique is the most commonly used (1045 MATs). One of the main controversies regarding MAT is the type of graft fixation. Some authors reported that anatomic and solid fixation of the graft with bone plugs restored normal contact mechanics in both medial and lateral MATs. 66 On the other hand, Rodeo et al 68 showed significantly higher histological scores for meniscal transplantation without bone plugs compared with suture-only fixation. A few studies compared the clinical results of the different fixation techniques. Abat et al 2 reported the results of 88 MATs: 33 fixed with the suture-only technique (group A) and 55 with bone plugs (group B). The authors found no significant differences in terms of clinical outcomes between the 2 groups. However, a significantly higher complication rate was found in group A compared with group B (33.3% vs 16.4%, respectively), together with a higher failure rate (9% vs 3.6%, respectively), although this difference was not significant. In addition, a higher percentage of extruded menisci was found in group A compared with group B (36.3% vs 28.13%, respectively; P = .001). Hommen et al 30 reported the results of 13 MATs fixed with the suture-only technique and 7 with bone-plug fixation, and no differences were described in terms of the Lysholm score (77 and 73 points, respectively; P = .3228). A total of 873 associated procedures (52.4% of MATs) were reported in this review. The most frequent associated procedures were ACLRs, osteotomies (mostly high tibial osteotomy [HTO]), and cartilage procedures. Some authors compared the clinical results of MAT alone and combined with other surgeries. None of these studies reported significant differences between the 2 groups. Verdonk et al 88 compared the cumulative survival rate of isolated medial MAT and MAT combined with HTO, with 72.4% and 83.3% survivorship at 10 years, respectively (difference not significant). Cole et al 14 reported the results of 21 isolated MATs and 19 MATs combined with other procedures. The authors concluded that there were no significant differences in all the clinical outcomes evaluated; 81% of patients in the isolated group and 74% in the combined group were satisfied with the procedure received.
In this review, different rehabilitation protocols were reported. Most of the authors adopted partial weightbearing and restricted ROM, but there was no agreement in bracing and the use of CPM. However, Cole at al 14 allowed weightbearing as tolerated immediately after surgery, with good results, and Stollsteimer et al 76 allowed immediate full ROM, with good pain relief.
There is no agreement in the literature on the return to sport after MAT; Alentorn-Geli et al 4 reported the outcomes of 15 MATs preformed in soccer players, with a 85.7% rate of return to sport at an average of 7.6 months after surgery. Chalmers et al 12 reported on 13 high-level athletes with a 77% rate of return to the preinjury level of performance.
The last aim of this review was to evaluate the clinical and radiographic outcomes of MAT and its role in the possible prevention of osteoarthritis. The most commonly used measures were the Lysholm score, 51 Tegner score, 80 and VAS score for pain. In all studies, the clinical outcome scores improved from preoperatively to last follow-up. As shown in Figure 2, the clinical outcome scores tended to decrease over time. It is difficult to discern which factors significantly affect the outcomes. Some authors compared the results of medial and lateral MATs, but there was no agreement regarding the superiority of one group over the other. Verdonk et al 88 reported a 28% failure rate on the medial side and 16% on the lateral side. They also calculated the cumulative survival rate at 10 years, which was 74.2% for medial MAT and 69.8% for lateral MAT, with no significant differences in survival plots. van Arkel et al 83 reported the results of 63 patients (23 medial and 40 lateral MATs), with a cumulative success rate of 88% for the lateral meniscus and 63% for the medial meniscus. Hommen et al 30 showed that patients with lower preoperative Lysholm scores also had inferior postoperative results compared with the other patients. Stollsteimer et al 76 reported better results in patients with a body weight <225 lb, cumulative Outerbridge grade <V, and Outerbridge grade <II in each area.
The chondroprotective effect of MAT has been demonstrated in an animal model, 37 but it is still unclear in humans. This is partially because of the lack of standardized evaluation methods. Radiographically different grading scores (including Kellgren-Lawrence, Fairbank, Outerbridge, joint space narrowing) were used to evaluate joint changes. Some studies described an advancement of osteoarthritis after MAT, while other studies showed opposite findings. In particular, Hommen et al 30 described involved compartment degeneration in 10 of 15 patients, with joint line narrowing varying from an average of 5.15 mm preoperatively to 4 mm at the last follow-up. On the other hand, Roumazeille et al 70 reported on 22 patients with an average joint line of 3.7 ± 1.7 mm preoperatively and 3.6 ± 2.3 mm at the last follow-up.
Another controversy is whether meniscal extrusion is correlated with a specific type of fixation and with worse outcomes compared with nonextruded menisci. Some authors reported that suture-only fixation techniques are correlated with a higher rate of extruded menisci but without any correlation with the clinical outcomes. 21 In addition, Koh et al 42 studied MRI scans of 73 lateral and 26 medial MATs and found that the transplanted lateral meniscus has a significantly higher rate of extrusion than the medial one, with an average extrusion distance of 4.7 mm and 2.9 mm, respectively. Lee et al 45 found a positive correlation between trough obliquity and graft extrusion. Second-look arthroscopic procedures were described in different studies, with a total of 137 cases. However, arthroscopic surgeries were often performed in symptomatic patients, and few studies reported on systematic second-look surgery. Wirth et al 93 described the arthroscopic findings of second-look procedures in 19 of 23 patients who underwent MAT; they found that all 14 patients who received a lyophilized allograft showed a one-third to complete reduction in size of the graft. Potter et al 63 analyzed the results of 19 second-look arthroscopic procedures and 17 histological biopsy specimens from areas of increased MRI signal intensity. The authors confirmed the correlation between MRI results, arthroscopic findings, and histological results and did not find any immune reactions against the graft.
The overall complication rate was 12.2% when considering MAT isolated and combined with other procedures, while it was 3.6% when considering only isolated MAT. One of the potential risks of MAT includes histoincompatibility. A single case of acute rejection of a cryopreserved graft has been reported. 29 Noyes et al 59 described a case of MAT of a medial and lateral graft in the same knee that was removed after 8 weeks because of an inflammatory reaction, probably caused by an acute rejection or allergic response. However, human leukocyte antigen matching was performed in early MATs without any additional benefits and was therefore abandoned.5,91
There is no agreement in the literature regarding the definition of MAT failure; some authors described it as removal of the graft or subsequent knee replacement. Other authors defined MAT as failed in case of no improvement in the symptoms, no satisfaction of the patients, or according to different arthroscopic or MRI findings/parameters. Therefore, the evaluation of MAT failure is difficult because of this wide variability of definitions. However, in this review, a total of 145 MAT failures (8.7%) were identified.
We analyzed the failure rate difference between cryopreserved and fresh-frozen grafts in MAT, considering only the studies in which a failure rate was described and the relative MAT number. We found a lower failure rate in fresh-frozen compared with cryopreserved grafts in MAT (9.9% vs 18.2%, respectively), and the result was statistically significant (P = .0004).
This study has some limitations related to the articles included in the review. The authors attempted to remove any overlapping data sets (ie, same cases reported in more than 1 article), but in some studies, this was unclear. Of 55 studies, 10 had a potential overlap of the data: 3 articles by J.K. Sekiya,74,75,95 4 by B.J. Cole,14,54,71,73 and 3 by J.K. Ha.27,28,36 We contacted the authors for further verification of the accuracy of the data.
Conclusion
Since the first trial on MAT in 1989, 56 hundreds of such procedures have been performed and their results described in the literature. The small number of patients within the studies and preponderance of low-level evidence throughout the studies make an analysis of the data very difficult. However, this is mainly because of the narrow indications for MAT and ethical issues that do not allow for randomized controlled trials in the meniscal deficiency scenario. The data available suggest that MAT is indicated in young or middle-aged patients with joint line pain due to previous meniscectomy in a well-aligned and stable knee without diffuse arthrosis. Most of the authors implanted nonirradiated cryopreserved or fresh-frozen allografts. There is still no agreement regarding the most reliable sizing method and graft fixation technique.
In conclusion, MAT seems to provide good clinical results at the short and medium term, with improvement in knee function and acceptable complication/failure rates. High-quality studies are necessary to better study the potential chondroprotective effect of MAT and to identify significant differences between different surgical techniques.
Footnotes
One or more of the authors has declared the following potential conflict of interest or source of funding: A.A. receives royalties from Arthrex Inc and Arthrosurface and is a consultant for Arthrex Inc.
An online CME course associated with this article is available for 1 AMA PRA Category 1 Credit™ at 
. In accordance with the standards of the Accreditation Council for Continuing Medical Education (ACCME), it is the policy of The American Orthopaedic Society for Sports Medicine that authors, editors, and planners disclose to the learners all financial relationships during the past 12 months with any commercial interest (A ‘commercial interest’ is any entity producing, marketing, re-selling, or distributing health care goods or services consumed by, or used on, patients). Any and all disclosures are provided in the online journal CME area which is provided to all participants before they actually take the CME activity. In accordance with AOSSM policy, authors, editors, and planners’ participation in this educational activity will be predicated upon timely submission and review of AOSSM disclosure. Noncompliance will result in an author/editor or planner to be stricken from participating in this CME activity.
#
##
References
Supplementary Material
Please find the following supplemental material available below.
For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.
For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.
