**4. Clinical outcomes**

Early results showed meniscus transplant could be a viable procedure; however, the initial results were mixed and raised concerns of long-term durability. It the first series of isolated meniscal allografts, Milakowski et al. demonstrated that graft processing methods were vital to the success of the procedure [9]. He reported the use of lyophilized grafts lead to inferior results compared to fresh frozen grafts. In the first American published series, Garrett et al. reported success in 35 of 43 patients (81%) at 2 to 7-year follow-up [26]. However, 6 of the 11 patients with grade IV chondromalacia failed, leading to the conclusion that while beneficial, grafts should not be placed in knees with advanced arthritis.

In the early experience of Noyes et al. they reported a high failure rate [27]. They evaluated 38 patients with 40 grafts, with a follow-up at an average of 40 months (24–62 months). While clinically the patients did significantly better, on MRI 30% of grafts demonstrated "altered characteristics" with another 28% demonstrating gross failure. Patients with no pre-operative arthritis demonstrated 10 abnormal MRIs out of 22, while the arthritic group showed abnormalities in 13 of 18, again demonstrating the folly of allograft implantation in arthritic knees.

#### *The Meniscus Deficient Knee: Options for Repair and Reconstruction DOI: http://dx.doi.org/10.5772/intechopen.99592*

Over time, graft processing methods, patient selection parameters, and surgical techniques were refined. With these improvements, meniscus allograft transplant ceased being seen as experimental (**Table 1**) [28].

Numerous short and mid-term studies reported that the vast majority of the grafts did not require reoperation, and a significant number of patients had decreased pain and improved function [29–32]. In a large series, Verdonk et al. reported a survivorship of 79% in the first 100 patients at a mean of 7.2 years [33].

Kim et al. published the most optimistic longer-term data on meniscal allograft transplantation, with 2 failures in 49 knees after a minimum follow-up of 8 years. The 10-year survival rate was 98.0% and the 15-year survival rate was 93.3% according to their Kaplan–Meier analysis [34].

Carter et al. demonstrated 10-year results in 40 of his original 46 patients [35]. Thirty-two (80%) stated they had improvement in symptoms from the preoperative level. The 10 year mean IKDC score improved from the pre-op mean 50.6 (range 32.2–68.9) to 70.1 (range 39.1–93.1). Seven patients required partial meniscectomies, for a 10-year graft survivorship of 83%. Of thirty-four patients with plain radiographs available at the time of implantation and at 10 years for comparison, fourteen had no change, 15 had mild osteoarthritis, and 5 moderate to advanced progression.

Noyes et al. in his later series, 58/72 patients had follow-up at a mean of 11.9 years ± 3.2 years [36]. Twenty-six underwent reoperation for a total graft survival rate of 55.2%. While demonstrating lower survivorship, their study group had greater chondral abnormalities and malalignment at baseline. Twenty patients underwent OATS procedures, and fourteen underwent an osteotomy in conjunction with the meniscal allograft at the time of implantation.

Van der Wal et al. reported on 63 meniscal allografts transplanted in 57 patients evaluated at 13.8 ± 2.8 years. Nineteen patients had grade IV chondromalacia at baseline, and their grafts were not secured with bone [37]. Their failure rate was 29% (18 grafts) and twelve patients (21%) were converted to a TKR at a mean follow-up of 10.8 years (range 4.3–13.7). They acknowledged that the degree of chondromalacia, ACL deficiency, and graft fixation contributed to failures, with these results confirming that strict patient selection is vital for long term success.


#### **Table 1.**

*Selected meniscal transplant studies survivorship rates.*

#### *Arthroscopy*

Systematic reviews have emerged providing data with compiled results at ten-plus years after meniscal transplant implantation. Novaretti et al. combined 11 studies with 688 meniscal allograft transplants and found a 10-year survivorship of 73.5%, and a 15-year survivorship of 60.3% [18]. Bin et al. evaluated the long-term survivorship of medial versus lateral meniscal transplants at greater than ten years in a meta-analysis of 9 studies totaling 694 grafts, and found that 52.6% of medial and 56.6% of lateral grafts were intact [19].

The one study to discuss 20-year follow-up was Carter et al. where 48/56 (86.7%) of patients were able to be contacted, and of those, had 21 required surgical treatment of the graft. Thirteen patients had an isolated partial meniscectomy. Eight patients had knee arthroplasty with 1 having prior partial graft removal and one also had a high tibial osteotomy (HTO). The average time to arthroplasty was 12.7 years. The graft survivorship was therefore 56.2% [13].

The take-away points from the usage of meniscal transplants involve proper patient selection, use of a properly prepared graft, and implantation in an appropriate knee. When an average-weight patient without varus or valgus knee abnormalities has a fresh meniscal allograft placed in a stable knee without moderate or severe arthritis or chondral loss, the graft survival can potentially be greater than twenty years.

The data supporting meniscal scaffold implantation does not go back nearly as long as meniscal transplant but is also robust. Clinical studies report outcomes for CMI ranging up to 12 years, while the longest study on Actifit reports up to 8 years, both demonstrating improvements in all knee clinical outcome scales (**Table 2**).

For the CMI implant, Monllau et al. demonstrated 83% good and excellent results at 10-year follow-up for 22 patients [38]. In a randomized trial comparing the long-term results of patients with ACL rupture and partial medial meniscus defects treated with ACL reconstruction and partial medial meniscectomy versus medial CMI implant, Bulgheroni et al. demonstrated significant improvement of all clinical scores at an average of 9.6 years [39]. Also, Zaffagnini et al. showed prospective study results between medial CMI implantation and partial medial meniscectomy [40]. The CMI group showed significantly lower VAS for pain, higher objective IKDC, and Tegner scores at 10-year follow-up.

The Actifit results are similarly impressive. Schuttler et al. demonstrated significant improvement in VAS from 5 preoperatively to 1 at 4 years of follow-up in a group of 18 Actifit patients [41]. Leroy et al. also showed, with a minimal followup of 5 years, 15 patients improved from 5.3 and 50 preoperative VAS and subjective IKDC scores respectively to 2.9 and 79 [42]. Finally, a meta-analysis of 613 Actifit patients demonstrated both VAS and Tegner scores improving significantly remaining higher up to 72 months [43]. Overall, there has been degeneration of the


#### **Table 2.**

*Selected meniscal scaffold studies survivorship rates.*

#### *The Meniscus Deficient Knee: Options for Repair and Reconstruction DOI: http://dx.doi.org/10.5772/intechopen.99592*

scaffold over time with some resulting increase in osteoarthritis, with a reported rate of 9.9% at a mean follow-up of 40 months and 6.7% at a mean follow-up of 44 months, for the Actifit and CMI patients, respectively [43].

The vast majority of meniscal scaffold literature has been published on medial implants, with a recent systematic review including 396 CMI with only 10% of them were implanted in the lateral compartment [44]. Zaffagnini et al. investigated 43 patients at 24± 1.9 months after lateral CMI implant. Their Lysholm score improved from 64.3 ± 18.4 preoperatively to 93.2 ± 7.2 at final follow-up, with pain experienced during strenuous activity and at rest was significantly reduced. At 2 years of followup, roughly 60% of patients reported activity levels similar to their preinjury values with a satisfaction rate of 95%. The presence of a higher BMI, the need for concomitant procedures, and a chronic injury pattern resulted in reduced outcomes [45].

Finally, Hirschmann et al. demonstrated the results of a series of 67 patients undergoing medial or lateral CMI implantation associated with ACL reconstruction (45%), high tibial osteotomy (7.5%) or microfracture (4.5%). At one year the cohort demonstrated a marked decrease in pain with a subsequent improvement in the Tegner, IKDC and Lysholm scores, with comparable results of the medial and the lateral groups [46].

And so, for the meniscal scaffolds, the useage and survivorship appear to be similar to those of the transplants; however, these implants are placed into patients with contained meniscal defects as opposed to the full meniscal loss which necessitates the use of a meniscus transplant. When an average-weight patient without varus or valgus knee abnormalities has a meniscal scaffold placed in a partially debreided meniscus in an otherwise stable knee without moderate or severe arthritis or chondral loss, the graft survival can potentially be greater than ten years based on current data.
