This study sought to record the PROMs of patients who had undergone MAT, and to investigate whether there were differences reported in those patients with ‘surgical failure’ or ‘clinical failure’ versus those categorised as being ‘successful’.
For the whole sample, PROM scores showed generally good outcomes, with median KOOS, IKDC and Lysholm scores being 80, 55.8 and 81. Further investigation showed that there was a trend towards PROMs being lower in those patients with surgical failure, although this was not statistically significant. This was possibly due to the small sample of surgical failures (n=4). Patients classified as clinical failures did have significantly lower KOOS and IKDC scores, and lower post-operative Tegner values. In the present study, 74% of patients said that they would undergo MAT again. The median post-operative Lysholm, KOOS and IKDC scores in this sub-group were 88, 82, and 62.1 - scores consistent with good outcomes following MAT. However, there were no significant differences in PROMs between those who stated that they would undergo the procedure again compared to those who stated that they would not and those who were not sure.
The results for Lysholm, KOOS and Tegner scores compared favourably or similarly to other reported series in the published literature (14–16), although our IKDC scores were lower (15). Naimark et al. reported similar outcomes in patients who underwent arthroscopic partial meniscectomy (29). The Tegner scores were significantly reduced following surgery, probably due to the specific post-operative restrictions that were recommended by the operating surgeon.
It should be noted that there are other techniques to replace menisci, such as the Actifit and the Collagen Meniscal Implant. Interestingly, the studies evaluating the effect of these treatments also do not have a consensus on accepted definitions of failures (30). However, these implants are only suitable specifically for the treatment of partial meniscal loss where the is still continuity of the peripheral meniscal rim, as they require a meniscal rim for attachment (31). This therefore makes comparison to MAT difficult. De Coninck et al. reported more favourable outcomes in IKDC with the Actifit compared to our study, but our study showed higher results in KOOS and Lysholm scores (32). The two studies had comparable mean ages, but De Coninck excluded patients who had severe cartilage damage, whilst in our study 44% had an Outerbridge Grade III or IV, and this may explain the higher IKDC scores in their study. Furthermore, the KOOS and IKDC scores both contain questions regarding activities such as jumping, twisting and pivoting; activities which our participants were advised not to undertake, and so may bias results, as other studies also report higher scores in these questionnaires (33,34).
While the number of patients undergoing MAT remains small, finding the right tool to evaluate patients is problematic. New scoring systems may provide improved evaluation of MAT.
The Western Ontario Meniscal Evaluation Tool (WOMET) may be appropriate. It is a specific questionnaire aimed to detect the impact of meniscal tears on health-related quality of life (35). When first designing this present study, it was decided not to include WOMET as there were doubts at that time with regard to WOMET’s reliability, construct validity and responsiveness (36). It would also have caused questionnaire fatigue by adding a raft of further questions which may have reduced questionnaire completion rates. Whilst Sgroi et al. reported superior measurement of knee function and quality-of-life impairment using WOMET compared to the KOOS in patients treated for meniscal tears (37), to the authors’ knowledge, it had not been used in studies purely investigating MAT. Whether WOMET is indeed a more useful tool for the evaluation of patients who have undergone MAT, however, is a topic in itself for further research. Until the most appropriate and validated scoring system is established for the evaluation of patients who have undergone MAT, this present study suggests that success cannot be adequately defined.
The surgical failure rate of 9% was similar to that reported in other comparable studies, which have reported a failure rate of 10.4% (13). The clinical failure rate of 21% was greater than that reported by Lee et al. (16) (8.5%) and Zaffagnini et al. (14), (11%). The complication rate was 21%; similar to the 21.3% rate reported in the meta-analysis by El Attar et al. (7). A consensus regarding the current definition of clinical and surgical failure is required, since two (50%) patients with surgical failures and six (66.7%) with clinical failures said that they would undergo the MAT procedure again or were unsure. It is concerning that previous authors have solely used these endpoints to report the efficacy of MAT.
This study, therefore, suggests that the term ‘patient satisfaction’ may define success better than ‘surgical failure’ or ‘clinical failure’. Patient satisfaction, in terms of activity levels and current symptoms, do not in this study correlate with surgical outcomes. Patient satisfaction may be best incorporated into a questionnaire using the WOMET score, but again, this requires further research and discussion with specific patient focus groups.
The BMLR analysis did not find any risk factors that were significantly associated with failure, although gender (surgical and clinical failure) and number of concomitant procedures (clinical failure) were nearly significant. However, given the heterogeneity of concomitant procedures, future studies could investigate the effect of these different procedures on the success of MAT. The odds ratios showed that except for lateral (vs medial) MAT in surgical failure, all risk factors increased the odds of surgical or clinical failure. However, many of these odds ratios were close to unity, reinforcing their lack of statistical significance.
This study’s analyses support the findings of Parkinson et al. (13) and Ahn et al. (38) that potential risk factors of age, gender and number of concomitant procedures were not related to surgical failure. However, our study disagrees with those studies, in that Outerbridge classification and lateral vs medial were not found to be significant factors in our analysis. Whilst some studies have found that articular cartilage damage at the time of surgery and medial (vs. lateral) allografts are associated with a higher risk of surgical failure (13), this study supports the findings of other papers that conclude that cartilage damage does not make a difference (38–40) and that medial allografts are not at a higher risk of surgical failure (40). Importantly, however, it should be noted that where articular cartilage damage was found in the relevant compartment of a patient’s knee at the time of MAT surgery, the articular cartilage pathology was also treated at the same time; with radiofrequency coblation chondroplasty for unstable or rough partial thickness chondral damage, with microfracture for small (<2cm2) full-thickness defects or with articular cartilage grafting (using Chondrotissue grafting) for larger (>2cm2) defects. Therefore, it could be surmised that appropriate concomitant treatment of articular cartilage lesions possibly lessens or even eliminates the otherwise increased risk of failure after MAT that might otherwise be associated with increasing severity of articular cartilage damage.
One reason for the lack of significance found in some of our analyses might be the small sample size in the present study, combined with the number of risk factors examined, which could have led to a lack of statistical power. The methods in the present study were better controlled compared to some previous research: only fresh-frozen meniscal allografts (which are biologically and mechanically superior to other forms of preservation (41)) were used, and these were all sourced from a single provider, and a single one-surgeon technique was used. Previous authors have either not reported their allograft sources (38,42) or have used multiple providers with different preservation techniques (13). Additionally, the generally good outcomes following MAT in the present study may be attributable to the surgical technique; suture fixation of the allograft to the capsule combined with trans-tibial bone tunnel suture fixation is the current preferred technique (14,43,44). Techniques using bone plug fixation risk articular cartilage damage and have been associated with a higher failure rate (45,46).
There was no difference in the SF-12 mental sub-scores in patients who said that they would undergo surgery again versus those who would not, although the physical sub-score was approaching significance. Saltzman et al. (47) and Rue et al. (48) also previously reported that the physical component improved significantly following MAT but that the mental score did not.
It was observed that following MAT, patients returned to fewer and lower levels of sport. Seventeen patients were satisfied with the level of sport achieved following MAT, but 17 others were dissatisfied. Nearly 80% of patients did expect there to be a difference in the level of physical activity that they could achieve after MAT, although there were no differences between the satisfaction levels between those who expected there to be a difference and those who did not. It is unclear whether the protective post-operative regime or the MAT procedure itself explains the dissatisfaction about not being able to return to sport.
The present study had a number of limitations. First, the sample size was smaller than some comparable studies (13,38) and so statistical power will have been weakened. However, this was offset by the tight control over materials and methods, and by the use of one surgeon, reducing variability in the procedures. Whilst this ensures homogeneity, longer-term studies are required to ensure a sample size is large enough for an adequately powered analysis for each failure sub-group analysis. MAT is a relatively new procedure in the UK and sample sizes are currently small.
Second, there were no pre-operative PROMs available, apart from the Tegner values. As this was a retrospective study, the collection of pre-operative scores was not feasible. However, this is not unusual, and other authors (13,38) have also used retrospective methods. As with all retrospective studies, there will be significant recall bias. It is still possible to draw useful conclusions from retrospective studies, but in future more prospective PROMs should be taken prior to MAT surgery.
As there was no continual follow-up, clinical failure may have occurred prior to the time at which the study was performed. It was also not possible in this study to review the potential risk factors of mechanical axis, instability or BMI, as not enough information was available for this within the patient records, and therefore a confounding effect in our results cannot be ruled out. However, in the senior author’s practice it is standard practice to correct any varus or valgus malignment greater than 5o with an appropriate realignment osteotomy either in advance of or at the same time as MAT.