Meniscal allograft transplantation: undersizing grafts can lead to increased rates of clinical and mechanical failure

Current advances in engineering meniscal tissues: insights into 3D printing, injectable hydrogels and physical stimulation based strategies

The knee meniscus is the cushioning fibro-cartilage tissue present in between the femoral condyles and tibial plateau of the knee joint. It is largely avascular in nature and suffers from a wide range of tears and injuries caused by accidents, trauma, active lifestyle of the populace and old age of individuals. Healing of the meniscus is especially difficult due to its avascularity and hence requires invasive arthroscopic approaches such as surgical resection, suturing or implantation. Though various tissue engineering approaches are proposed for the treatment of meniscus tears, three-dimensional (3D) printing/bioprinting, injectable hydrogels and physical stimulation involving modalities are gaining forefront in the past decade. A plethora of new printing approaches such as direct light photopolymerization and volumetric printing, injectable biomaterials loaded with growth factors and physical stimulation such as low-intensity ultrasound approaches are being added to the treatment portfolio along with the contemporary tear mitigation measures. This review discusses on the necessary design considerations, approaches for 3D modeling and design practices for meniscal tear treatments within the scope of tissue engineering and regeneration. Also, the suitable materials, cell sources, growth factors, fixation and lubrication strategies, mechanical stimulation approaches, 3D printing strategies and injectable hydrogels for meniscal tear management have been elaborated. We have also summarized potential technologies and the potential framework that could be the herald of the future of meniscus tissue engineering and repair approaches.

Risk Factors for Graft Failure After Meniscal Allograft Transplantation: A Systematic Review and Meta-analysis

Background

Graft failure after meniscal allograft transplantation (MAT) may necessitate revision surgery or conversion to arthroplasty. A comprehensive understanding of the risk factors for failure after MAT of the knee may facilitate more informed shared decision-making discussions before surgery and help determine whether MAT should be performed based on patient risk.

Purpose

To perform a systematic review and meta-analysis of risk factors associated with graft failure after MAT of the knee.

Study Design

Systematic review; Level of evidence, 4.

Methods

The PubMed, OVID/Medline, and Cochrane databases were queried in October 2021. Data pertaining to study characteristics and risk factors associated with failure after MAT were recorded. DerSimonian-Laird binary random-effects models were constructed to quantitatively evaluate the association between risk factors and MAT graft failure by generating effect estimates in the form of odds ratios (ORs) with 95% CIs. Qualitative analysis was performed to describe risk factors that were variably reported.

Results

In total, 17 studies including 2184 patients were included. The overall pooled prevalence of failure at the latest follow-up was 17.8% (range, 3.3%-81.0%). In 10 studies reporting 5-year failure rates, the pooled prevalence of failure was 10.9% (range, 4.7%-23%). In 4 studies reporting 10-year failure rates, the pooled prevalence was 22.7% (range, 8.1%-55.0%). A total of 39 risk factors were identified, although raw data presented in a manner amenable to meta-analysis only allowed for 3 to be explored quantitatively. There was strong evidence to support that an International Cartilage Regeneration & Joint Preservation Society grade >3a (OR, 5.32; 95% CI, 2.75-10.31; P < .001) was a significant risk factor for failure after MAT. There was no statistically significant evidence to incontrovertibly support that patient sex (OR, 2.16; 95% CI, 0.83-5.64; P = .12) or MAT laterality (OR, 1.11; 95% CI, 0.38-3.28; P = .85) was associated with increased risk of failure after MAT.

Conclusion

Based on the studies reviewed, there was strong evidence to suggest that degree of cartilage damage at the time of MAT is associated with graft failure; however, the evidence was inconclusive on whether laterality or patient sex is associated with graft failure.

Meniscus Size Differs Between Patient and Donor Populations for Meniscus Allograft Transplantation

Purpose

To determine the extent of variability in meniscus size and anthropometric data between donors (supply) and patients (demand), to evaluate potential factors that may contribute to size discrepancies, and to determine whether the discrepancies lead to longer patient wait times.

Methods

Lateral and medial meniscal measurements, anthropometric data, and time to match a donor graft were extracted from a tissue supplier database. The frequency and distribution of meniscus size were analyzed. Body mass index (BMI), relative meniscus area, body mass to meniscus area index, and height to meniscus area index were compared between patient and donor pools via χ² tests and independent samples t-test. The effect of size on time to match was analyzed using analysis of variance and post-hoc Tukey test.

Results

The lateral meniscus patient population showed a greater frequency of larger size requirements compared to the donor population (P < .001) and the medial meniscus patient population showed a higher frequency of smaller meniscus size requirements (P < .001). The medial meniscus analysis showed significantly smaller meniscus areas (P < .001) in the patient population contributing to the observed trend of an increased body mass to meniscus area index and height to meniscus area index. The time to match a donor meniscus was affected by the patient meniscus size.

Conclusions

This analysis demonstrates variations in frequency of meniscus sizes between donor and patient populations. This variation is attributed to differences in anthropometric data between patient and donor populations. This work identifies a mismatch between demand and supply for certain patient sizes contributing to longer times to match.

Clinical Relevance

This work associated donor and patient mismatches with longer wait times. This can be useful for patient counseling as well as provide a framework to determine whether there are solutions within the current meniscus donor pool that can be used to meet this clinical need.

Signal intensity of lateral meniscal allografts deteriorates over time: a longitudinal MRI analysis during a minimum follow-up of 8 years

PURPOSE

To evaluate the serial change of magnetic resonance imaging (MRI) signal intensity (SI) of lateral meniscal allografts in a long-term period of > 8 years and to determine whether the SI change adversely affected clinical outcomes.

METHODS

Thirty-three lateral meniscal allograft transplantation (LMAT) patients with MRI taken > 8 years after surgery were included. The allograft was assessed using MRI at five serial time points (1, 2-4, 4-6, 6-8, and > 8 years after surgery), based on the following grading system: grade 1, globular increased SI not adjacent to the articular surface; grade 2, linear SI within the meniscus; and grade 3, increased SI extended to the articular surface. MRI evaluation was performed for three locations of the allograft (anterior horn, mid-body, and posterior horn), and the serial changes of allograft SI at each location were analyzed using the generalized estimating equation (GEE) with cumulative logit link function. The patients were classified according to SI change at each location (stationary group and deterioration group), and the two groups were compared in terms of clinical outcomes using the Lysholm score.

RESULTS

The mean follow-up duration was 9.2 ± 1.2 years. During that period, SI of the allograft deteriorated over time, regardless of the location (anterior horn, p = 0.034; mid-body, p = 0.002; posterior horn, p < 0.001). The amount of SI deterioration at each location of the graft differed with a borderline significance (p = 0.050, GEE), and the proportion of grade 3 SI was higher at the posterior horn (36.4%) than at the other locations at the last follow-up (p < 0.001, chi-square test). However, no significant differences in the Lysholm scores were found between the stationary group and the deterioration group at all locations.

CONCLUSION

SI of the meniscal allograft deteriorated over time at all locations during the long-term follow-up. Deterioration of the graft was more prominent at the posterior horn than at the other locations. SI deterioration did not adversely affect the clinical outcomes, which should be interpreted with caution, considering the small sample size of this study. In the prognosis of lateral MAT, SI deterioration at the posterior horn is a more determining factor than that at the other part of the allograft. Therefore, SI at the posterior horn needs to be examined with special concern.

LEVEL OF EVIDENCE

III.

Autologous semitendinosus meniscus graft significantly improves knee joint kinematics and the tibiofemoral contact after complete lateral meniscectomy

PURPOSE

The purpose of this study was to investigate the potential of a doubled semitendinosus (ST) and a single gracilis tendon (GT) lateral meniscus autograft to restore the knee joint kinematics and tibiofemoral contact after total lateral meniscectomy (LMM).

METHODS

Fourteen human knee joints were tested intact, after LMM and after ST and GT meniscus autograft treatment under an axial load of 200 N during full range of motion (0°-120°) and four randomised loading situations: without external moments, external rotation, valgus stress and a combination of external rotation and valgus stress using a knee joint simulator. Non-parametric statistical analyses were performed on joint kinematics and on the tibiofemoral contact mechanics.

RESULTS

LMM led to significant rotational instability of the knee joints (p < 0.02), which was significantly improved after ST autograft application (p < 0.04), except for knee joint flexions > 60°. The GT autograft failed to restore the joint kinematics. LMM significantly increased the tibiofemoral contact pressure (p < 0.03), while decreasing the contact area (p < 0.05). The ST autograft was able to restore the contact mechanics after LMM (p < 0.02), while the GT replacement displayed only an improvement trend.

CONCLUSION

The doubled ST lateral meniscus autograft improved the knee joint kinematics significantly and restored the tibiofemoral contact mechanics almost comparable to the native situation. Thus, from a biomechanical point of view, ST meniscus autografts might be a potential treatment alternative for patients who are indicated for meniscus allograft transplantation.

High-grade preoperative osteoarthritis of the index compartment is a major predictor of meniscal allograft failure

INTRODUCTION

Preoperatively available predictors of meniscal allograft failure would help in patient counseling and surgical indication for meniscal allograft transplantation (MAT). It was hypothesized that young patient age, high posterior tibial slope (PTS), and high-grade osteoarthritis (OA) are predictors of meniscal allograft failure.

MATERIALS AND METHODS

Patients undergoing MAT with a minimum follow-up of 2 years were included in this retrospective study. Demographic and surgical data, and causes of meniscal allograft failure were collected. PTS and degree of OA (low-grade: Kellgren-Lawrence 0, 1, and 2; high-grade: Kellgren-Lawrence 3 and 4) of the index and opposite tibiofemoral compartments were determined on preoperative radiographs.

RESULTS

This study included 77 patients with a mean age of 25.7 ± 10.1 years at the time of MAT. After a mean follow-up of 7.6 ± 5.6 years, meniscal allograft failure was observed in 26 patients (34%). The median time from MAT to meniscal allograft failure was 1.3 years (inter-quartile range, 2.5 years). Meniscal allograft tears (88%) were the primary cause of graft failure, followed by high-grade OA (12%). Patients experiencing meniscal allograft failure were an average of 2.7 years (95% CI [2.2, 7.5], p = 0.202) older at the time of MAT than patients without failure. PTS was not found to be a predictor of meniscal allograft failure (odds ratio, 0.884 (95% CI [0.727, 1.073], p = 0.212)). Patients with high-grade preoperative OA of the index compartment had 28 times higher odds of experiencing meniscal allograft failure than patients with low-grade preoperative OA (p = 0.008).

CONCLUSIONS

High-grade preoperative OA of the index compartment was found to be a significant and clinically relevant predictor of meniscal allograft failure. Surgeons should be aware of the impact of OA on meniscal allograft survival, which needs to be considered in patient counseling and surgical indication for MAT in patients.

Meniscal allograft transplantation in discoid meniscus patients achieves good clinical outcomes and superior chondroprotection compared to meniscectomy in the long term

PURPOSE

To compare the long-term clinical and radiological results of meniscal allograft transplantation (MAT) for discoid lateral meniscus (DLM) patients with MAT for non-discoid lateral meniscus patients and meniscectomy (ME) for DLM patients and, thus, to determine whether DLM patients are suitable candidates for MAT.

METHODS

Eight MAT cases in DLM patients were identified (discoid MAT group), six MAT cases in non-discoid lateral meniscus patients (non-discoid MAT group) and ten total meniscectomy cases in DLM patients (discoid ME group) were matched as controls. Subjective evaluations, postoperative radiography and magnetic resonance imaging (MRI) were conducted at 5 years and 10-14 years, respectively. Joint degeneration was evaluated by the Kellgren-Lawrance (KL) grade and joint space width (JSW). MRI with T2 mapping sequences was used to quantitatively evaluate degeneration of the joint cartilage and shrinkage of the allografts. Student's t test was used to compare quantitative variables and the Mann‒Whitney U test was used to compare categorical variables.

RESULTS

There was no difference in Lysholm, IKDC, Tegner or VAS scores amongst the discoid MAT, non-discoid MAT and discoid ME groups at the final follow-up. No revision surgery was performed in any MAT patient. The JSW narrowing in the discoid MAT group was better than that in the discoid ME group (0.8 ± 0.4 mm vs. 2.1 ± 1.3 mm, p = 0.012) and worse than that in the non-discoid MAT group (0.1 ± 0.1 mm, p = 0.003). The KL progression of the discoid MAT group was less than that of the discoid ME group (1.3 ± 0.7 vs. 2.3 ± 0.9, p = 0.034). The discoid ME group had worse cartilage lesion progression than the discoid MAT and non-discoid MAT groups. The allograft width of the DLM patients shrank more than that of the non-discoid patients at the meniscus midbody (3.6 ± 0.9 mm vs. 6.2 ± 1.9 mm, p = 0.015).

CONCLUSION

Compared to meniscectomy, MAT achieved similar long-term symptom relief and superior chondroprotection in discoid meniscus patients. Despite more graft shrinkage, the outcomes of MAT in discoid meniscus patients were comparable to those in non-discoid meniscus patients. Therefore, DLM patients may be suitable candidates for MAT procedures.

LEVEL OF EVIDENCE

Level III.

Securing Transplanted Meniscal Allografts Using Bone Plugs Results in Lower Risks of Graft Failure and Reoperations: A Meta-analysis

BACKGROUND

Meniscal allograft transplant (MAT) is an important treatment option for young patients with deficient menisci; however, there is a lack of consensus on the optimal method of allograft fixation.

HYPOTHESIS

The various methods of MAT fixation have measurable and significant differences in outcomes.

STUDY DESIGN

Meta-analysis; Level of evidence, 4.

METHODS

A single-arm meta-analysis of studies reporting graft failure, reoperations, and other clinical outcomes after MAT was performed. Studies were stratified by suture-only, bone plug, and bone bridge fixation methods. Proportionate rates of failure and reoperation for each fixation technique were pooled with a mixed-effects model, after which reconstruction of relative risks with confidence intervals was performed using the Katz logarithmic method.

RESULTS

A total of 2604 patients underwent MAT. Weighted mean follow-up was 4.3 years (95% CI, 3.2-5.6 years). During this follow-up period, graft failure rates were 6.2% (95% CI, 3.2%-11.6%) for bone plug fixation, 6.9% (95% CI, 4.5%-10.3%) for suture-only fixation, and 9.3% (95% CI, 6.2%-13.9%) for bone bridge fixation. Transplanted menisci secured using bone plugs displayed a lower risk of failure compared with menisci secured via bone bridges (RR = 0.97; 95% CI, 0.94-0.99; P = .02). Risks of failure were not significantly different when comparing suture fixation to bone bridge (RR = 1.02; 95% CI, 0.99-1.06; P = .12) and bone plugs (RR = 0.99; 95% CI, 0.96-1.02; P = .64). Allografts secured using bone plugs were at a lower risk of requiring reoperations compared with those secured using sutures (RR = 0.91; 95% CI, 0.87-0.95; P < .001), whereas allografts secured using bone bridges had a higher risk of reoperation when compared with those secured using either sutures (RR = 1.28; 95% CI, 1.19-1.38; P < .001) or bone plugs (RR = 1.41; 95% CI, 1.32-1.51; P < .001). Improvements in Lysholm and International Knee Documentation Committee scores were comparable among the different groups.

CONCLUSION

This meta-analysis demonstrates that bone plug fixation of transplanted meniscal allografts carries a lower risk of failure than the bone bridge method and has a lower risk of requiring subsequent operations than both suture-only and bone bridge methods of fixation. This suggests that the technique used in the fixation of a transplanted meniscal allograft is an important factor in the clinical outcomes of patients receiving MATs.

Editorial Commentary: Restoring Native Meniscal Anatomy With Medial Meniscus Allograft Transplantation and Augmentation of the Meniscotibial Ligament May Decrease Meniscal Graft Extrusion

While studies have shown significant clinical improvement after medial meniscus allograft transplantation (MMAT) with good long-term graft survivorship, progression to osteoarthritis still occurs, even in the presence of intact grafts. Several factors can potentially explain the lack of chondroprotection despite graft survivorship, including meniscal degeneration, tearing, and remodeling after the initial procedure. A major factor contributing to progression of osteoarthritis is meniscal extrusion, which is seen in up to 60% of patients and seems to be more of an issue in medial meniscus transplantation compared to lateral and is present even immediately postoperatively. Grafts without extrusion provide protective effects similar to the native meniscus, while greater than 3 mm of extrusion leads to nearly complete loss of the protective effects. A reconstruction of the meniscotibial ligament, in addition to standard MMAT, may significantly decrease meniscal extrusion. Optimization of graft size, quality, and meniscal root positioning is best to prevent extrusion and restore native biomechanics.

Variations of cross-sectional meniscal morphology between similar-sized menisci: implications on donor selection for meniscal allograft transplantation

PURPOSE

This study aimed to investigate the morphological variations in the cross-sectional anatomy of the meniscus between similar-sized matched menisci.

MATERIALS AND METHODS

Knee MRI of 329 patients with intact menisci were retrospectively reviewed, and the meniscal length (ML), meniscal width (MW), and cross-sectional dimensions (meniscal height and width) of the anterior, posterior horns, and the corpus were measured. Patients with similar-sized menisci who had less than 1 mm difference in ML and MW were matched. 330 male-to-male medial menisci (MM), 623 male-to-male lateral menisci (LM), 82 female-to-female MM, 233 female-to-female LM, 176 cross-gender MM, and 265 cross-gender LM unique combination of ideally matched pairs (total: 1709) were generated. The disparity in the cross-sectional dimensions, absolute difference, and the paired percent differences was statistically analyzed.

RESULTS

The ML and MW in all groups were statistically similar, with a predefined absolute difference of 1 mm both for ML and MW (paired percent difference < 5%). The cross-sectional segmental meniscal dimensions were similar within all groups, but the paired percent differences showed high variations between a mean of 12.1-21.5% and up to 150.9%. The paired percent difference of MM in each segmental dimension was similar among different gender combinations. However, segmental paired percent differences of LM showed statistical differences in anterior horn width (AHW) (p: 0.001) and posterior horn width (PHW) (p: 0.001). In subgroup comparisons, the paired percent difference of AHW was higher in the female-to-female group compared to cross-gender (p: 0.023) and male-to-male groups (p: 0.001). The paired percent difference of PHW was smaller in the male-to-male group compared to female-to-female and cross-gender groups (p: 0.001 for both).

CONCLUSIONS

Segmental cross-sectional anatomy showed wide variations despite strict matching in ML and MW. These variations were present in all gender combinations. The meniscal 3D shape is unique, but acceptable limits of similarity need further research.

LEVEL OF EVIDENCE

Retrospective study, Level III.

Meniscus regeneration by 3D printing technologies: Current advances and future perspectives

Meniscal tears are a frequent orthopedic injury commonly managed by conservative strategies to avoid osteoarthritis development descending from altered biomechanics. Among cutting-edge approaches in tissue engineering, 3D printing technologies are extremely promising guaranteeing for complex biomimetic architectures mimicking native tissues. Considering the anisotropic characteristics of the menisci, and the ability of printing over structural control, it descends the intriguing potential of such vanguard techniques to meet individual joints’ requirements within personalized medicine. This literature review provides a state-of-the-art on 3D printing for meniscus reconstruction. Experiences in printing materials/technologies, scaffold types, augmentation strategies, cellular conditioning have been compared/discussed; outcomes of pre-clinical studies allowed for further considerations. To date, translation to clinic of 3D printed meniscal devices is still a challenge: meniscus reconstruction is once again clear expression of how the integration of different expertise (e.g., anatomy, engineering, biomaterials science, cell biology, and medicine) is required to successfully address native tissues complexities.

The Long-term Chondroprotective Effect of Meniscal Allograft Transplant: A 10- to 14-Year Follow-up Study

BACKGROUND

The long-term chondroprotective effect of meniscal allograft transplant (MAT) and its superiority over meniscectomy have rarely been reported.

HYPOTHESIS

MAT would reduce osteoarthritis (OA) progression when compared with the meniscus-deficient knee. Graft extrusion distance would strongly affect the chondroprotective effect of the MAT.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 17 knees receiving MAT were followed up as the MAT group. The MAT group was further divided into the nonextrusion subgroup (n = 9) and the extrusion subgroup (n = 8) according to 3-mm extrusion on the magnetic resonance imaging (MRI) coronal section. A further 26 consecutive patients receiving meniscectomy in the same period were followed up as the ME group. The healthy control group consisted of healthy contralateral legs chosen from the MAT and ME groups (n = 27). Joint space width (JSW) narrowing was measured on radiographs. Three-dimensional MRI with a T2 mapping sequence was used to quantitatively analyze cartilage degeneration and meniscal allograft extrusion in 5 directions (0°, 45°, 90°, 135°, and 180°). The cartilage degeneration index (CDI) was calculated according to the size and degree of the chondral lesions on MRI scans. The correlation between the CDI increase and the extrusion distance was analyzed.

RESULTS

The mean follow-up time was 11.3 years (range, 10-14 years). The MAT group had moderate superiority in chondral protection with less JSW narrowing (0.58 ± 0.66 mm) and CDI increase (1132 ± 1589) compared with the ME group (JSW narrowing: 1.26 ± 1.13 mm, P = .025; CDI increase: 2182 ± 1958, P = .079). The JSW narrowing (0.71 ± 0.80 mm; P = .186) and CDI increase (2004 ± 1965; P = .830) of the extrusion subgroup were close to those of the ME group, demonstrating that a 3-mm extrusion led to complete loss of the meniscal chondroprotective effect. The nonextrusion group had significantly less JSW narrowing (0.48 ± 0.48 mm; P = .042) and CDI increase (358 ± 249; P = .011) than the ME group. The JSW narrowing of the healthy control group was 0.22 ± 0.27 mm. The cartilage T2 values of the extrusion subgroup were similar to those of the ME group, with more OA features, whereas the T2 values of the nonextrusion subgroup were closer to those of the healthy control group. The extrusion distance in the 90° direction (P = .002) and the follow-up time (P = .019) significantly affected the CDI increase in the multivariate regression model. The average extrusion distance in the 45°, 90°, and 135° directions better predicted chondroprotection compared with the other individual directions.

CONCLUSION

MAT had moderate advantages in chondroprotection compared with meniscectomy in the long term. Graft extrusion distance strongly affected the chondroprotective effect of MAT. The chondroprotective effect of the nonextruded meniscal allograft was close to that of the native meniscus, whereas the allografts with an extrusion >3 mm completely lost their function after meniscectomy.

Autologous semitendinosus tendon graft could function as a meniscal transplant

PURPOSE

Meniscectomy results in poor knee function and increased risk for osteoarthritis. Meniscal allograft transplantation is not widely used due to costs and availability. The semitendinosus tendon (ST) has the potential to remodel and revascularize in an intraarticular environment, such as ACL reconstruction. The objective for this pilot study was to investigate whether the ST graft could function as a meniscal transplant.

METHODS

The ST was doubled and sutured with running sutures and pull-out sutures in each end. Bone tunnels were used for root anchorage and the graft was sutured with allinside, inside-out and outside-in technique. The pull-out sutures were fixed over a button. Partial weight bearing was allowed with limited range of motion in a brace for the first 6 weeks. Evaluation was assessed using clinical examination, radiology and patient reported outcome.

RESULTS

A total of seven patients have been included between January 2018 and June 2020. Six medial transplants and one lateral transplant were performed. Mean age was 29 years. Four patients had completed the 12-month follow-up. Improvements were noted for IKDC Global Score, KOOS pain subscale and Lysholm. MRI indicated that the transplant become more wedge-like with visible roots and minor protrusion.

CONCLUSIONS

Even though this is primarily a technical report the follow-up data indicate that the transplant survives and adapts in shape and capabilities to an original meniscus. There were no adverse events and the patients seem to improve in terms of pain and quality of life.

Association Between Meniscal Allograft Tears and Early Surgical Meniscal Allograft Failure

BACKGROUND

Meniscal allograft transplantation (MAT) has become a viable treatment option for patients with symptomatic meniscal deficiency. Some patients experience early surgical meniscal allograft failure attributed to causes that have not yet been sufficiently clarified.

PURPOSE

To evaluate the prevalence, types, and distribution of arthroscopically confirmed meniscal allograft tears and the associated effect on surgical meniscal allograft survival.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Patients undergoing MAT with a minimum 2-year follow-up were retrospectively reviewed. Descriptive and surgical data were collected. Type and location of arthroscopically confirmed meniscal allograft tears were recorded and compared between medial and lateral allografts and suture-only and bone block fixation. A survival analysis was conducted to evaluate the effect of meniscal allograft tears on surgical meniscal allograft survival.

RESULTS

This study included 142 patients (54% male; mean ± SD age, 29.6 ± 10.4 years) with a mean follow-up of 10.3 ± 7.5 years. The prevalence of meniscal allograft tears was 32%, observed at a median of 1.2 years (interquartile range, 2.8 years) after MAT. The posterior horns were most frequently affected, followed by the posterior roots, midbodies, anterior horns, and anterior roots. The most frequently observed tear types were root tears (43%), followed by longitudinal, horizontal, radial, complex, bucket-handle, and meniscocapsular separation tears. A statistically significant association was found between meniscal allograft tear types and fixation techniques (P = .027), with root tears predominant after suture-only as compared with bone block fixation (57% vs 22%). Patients with meniscal allograft root tears were a mean of 5.4 years (95% CI, 1.6-9.2 years; P = .007) younger than were patients without root tears. The 1-year surgical meniscal allograft survival rate was significantly lower for torn versus intact meniscal allografts (75% vs 99%; P < .001).

CONCLUSION

Meniscal allograft root tears were predominant, associated with younger patient age, and more often observed when using the suture-only fixation technique versus the bone block fixation technique. Torn meniscal allografts were associated with early surgical graft failure when compared with intact meniscal allografts, resulting in a significantly lower 1-year survival rate.

Prognostic Factors to Determine Survivorship of Meniscal Allograft Transplant: A Systematic Review

Background:

There is much room for improvement and optimization of meniscal allograft survivorship.

Purpose:

To understand prognostic factors for survivorship using evidence-based selection criteria in order to identify patients who would best benefit from meniscal allograft transplant (MAT).

Study Design:

Systematic review; Level of evidence, 4.

Methods:

We conducted this systematic review to analyze prognostic factors for survivorship of MAT. The Cochrane Central Register, PubMed publisher, Embase.com, and Web of Science databases were searched through August 8, 2019. Included studies entailed patients of any age who received MAT with a reported association between prognostic factors and survivorship of the allograft. Two reviewers independently screened all titles and abstracts for eligibility, extracted the data, assessed the risk of bias using the Newcastle-Ottawa Scale, and performed a best-evidence synthesis.

Results:

The review included 18 studies with a total of 1920 patients. The mean follow-up time was 6.0 years (range, 2.1-11.2 years). A total of 20 prognostic factors were identified and shown to be associated with survivorship of MAT. Strong evidence was found that severe cartilage damage was associated with poor survivorship. Strong evidence was also found showing that sex, knee compartment, surgical side, concomitant anterior cruciate ligament (ACL) reconstruction, and concomitant osteotomy for malalignment had no effect on survivorship. Moderate evidence was found that body mass index (<36), tobacco use, and arthroscopic versus open procedure had no influence on survivorship. Conflicting evidence was found that older age and kissing cartilage lesions (lesions on both the femur and tibia vs on a single side) decreased survivorship.

Conclusion:

Severe cartilage damage decreases the survivorship of MAT. Concomitant ACL reconstruction and osteotomy showed no relationship to survivorship. Many determinants showed conflicting and limited evidence. Older age may be of interest and should be further studied.

Imaging of meniscal allograft transplantation: what the radiologist needs to know

Meniscal allograft transplantation is an emerging surgical option for younger patients with symptomatic meniscal deficiency, which aims to restore anatomic biomechanics and load distribution in the knee joint, and by so doing to potentially delay accelerated osteoarthritis. In this review article, we summarize the structure and biomechanics of the native meniscus, describe indications and procedure technique for meniscal allograft transplantation, and demonstrate the spectrum of expected postoperative imaging and role of imaging to identify potential complications.

Comparison of meniscal allograft transplantation techniques using a preclinical canine model

Meniscal allograft transplantation (MAT) can be a safe, effective treatment for meniscal deficiency resulting in knee dysfunction, leading to osteoarthritis (OA) without proper treatment with 5-year functional success rates (75%-90%). While different grafts and techniques have generally proven safe and effective, complications include shrinkage, extrusion, progression of joint pathology, and failure. The objective of this study was to assess the functional outcomes after MAT using three different clinically-relevant methods in a preclinical canine model. The study was designed to test the hypothesis that fresh meniscal-osteochondral allograft transplantation would be associated with significantly better function and joint health compared with fresh-viable or fresh-frozen meniscus-only allograft transplantations. Three months after meniscal release to induce meniscus-deficient medial compartment disease, research hounds (n = 12) underwent MAT using meniscus allografts harvested from matched dogs. Three MAT conditions (n = 4 each) were compared: frozen meniscus-fresh-frozen meniscal allograft with menisco-capsular suture repair; fresh meniscus-fresh viable meniscal allograft (Missouri Osteochondral Preservation System (MOPS)-preservation for 30 days) with menisco-tibial ligament repair; fresh menisco-tibial-fresh, viable meniscal-tibial-osteochondral allografts (MOPS-preservation for 30 days) with menisco-tibial ligament preservation and autogenous bone marrow aspirate concentrate on OCA bone. Assessment was performed up to 6 months after MAT. Pain, comfortable range of motion, imaging, and arthroscopic scores as well histological and cell viability findings were superior (P < .05) for the fresh menisco-tibial group compared with the two other groups. Novel meniscal preservation and implantation techniques with fresh, MOPS-preserved, viable meniscal-osteochondral allografts with menisco-tibial ligament preservation appears to be safe and effective for restoring knee function and joint health in this preclinical model. This has the potential to significantly improve outcomes after MAT.

Radiographic Methods Are as Accurate as Magnetic Resonance Imaging for Graft Sizing Before Lateral Meniscal Transplantation

BACKGROUND

Accurate allograft matching is deemed critical for meniscal transplantation; thus, precise measurements are essential to correctly calculate meniscal size. Several methods for meniscal sizing have been described, but there remains a discussion on which is the most accurate for the lateral meniscus.

PURPOSE

To compare the accuracy of radiographic, anthropometric, and magnetic resonance imaging (MRI) methods of determining width and length of the lateral meniscus with actual dimensions after anatomic dissection.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten fresh-frozen human cadaveric knees without any evidence of meniscal or ligamentous injury were primarily imaged using radiography and MRI and subsequently underwent dissection to assess the anatomic size of each meniscus. Four methods were used to predict the size of the lateral menisci: anthropometric, radiographic (Pollard and Yoon), and MRI. Absolute differences in length and width between actual and predicted sizes were determined.

RESULTS

The anatomic lateral meniscal width and length were 33.01 ± 4.25 mm (mean ± SD; range, 24.84-40.18 mm) and 31.41 ± 5.06 mm (range, 25.2-40.05 mm), respectively. Regarding width, the anthropometric method demonstrated an absolute difference from anatomic measurement significantly greater when compared with the Pollard technique and MRI (P = .002). Regarding length, the Pollard method presented an absolute difference significantly greater than all other techniques (P = .003). In terms of the ability to measure width and length, MRI accurately predicted meniscal size within 10% of the anatomic size in 65% of measurements, the Yoon method in 54%, and the Pollard method in 20% (P = .01). Radiographs tended to overestimate the true size of the lateral meniscus, while the anthropometric technique overestimated width in all specimens.

CONCLUSION

This study demonstrated that MRI and the Yoon radiographic method are comparable in terms of accuracy for graft sizing before lateral meniscal transplantation. While MRI is useful, a contralateral MRI is required, which makes the Yoon radiographic method recommended given the ease and cost advantage. The original Pollard technique and the anthropometric method are not recommended.

CLINICAL RELEVANCE

Over- and undersizing of meniscal transplants has been implicated in graft failure. Therefore, increasing the reliability of preoperative meniscal measurements is deemed important for the success of meniscal allograft transplantation.

Meniscal allograft transplantation: a review of indications, techniques, and outcomes

When compared to meniscectomy, meniscus allograft transplantation (MAT) may provide superior long-term benefits to young, active patient populations who have lost meniscal function because of irreparable damage, such as, an avascular tear, previous repair failure, and unsalvageable tear types. Positive outcomes are most likely to be achieved when meniscus allograft transplantation is performed in appropriately selected patients. Indications include patients younger than 50 years of age, with a history of subtotal or total meniscectomy without concomitant articular cartilage defects, uncorrectable joint malalignment, and/or knee instability. Outcomes for meniscal allograft transplantation are promising with studies reporting long-term graft survivorship as high as 89% at 10 years and significant improvements in multiple patient reported outcome measures. LEVEL OF EVIDENCE: Level V.

Risk of Subsequent Knee Arthroplasty After Sports Medicine Procedures

INTRODUCTION

Approximately 10% of men and 13% of women older than the age of 60 are affected by symptomatic osteoarthritis of the knee. Anatomic repair or reconstruction after knee injury has been a central tenet of surgical treatment to reduce the risk of osteoarthritis. The purpose of this study was to examine common sports medicine procedures of the knee and determine the proportion of patients who subsequently undergo total knee arthroplasty (TKA).

METHODS

The MarketScan database was queried from the period of January 2007 through December 2016. Patients were identified, who underwent a procedure of the knee, as defined by Current Procedural Terminology codes relating to nonarthroplasty procedures of the knee. Patients in whom laterality could not be confirmed or underwent another ipsilateral knee procedure before TKA were excluded from this study. The primary outcome of this study was the overall rate of TKA after index knee surgery. Time from index procedure to TKA was a secondary outcome. A multivariate regression analysis was used to control for covariates such as age, sex, and comorbidity status.

RESULTS

A total of 843,749 patients underwent one of the 13 common sports medicine procedures of the knee. The procedure with the highest unadjusted rate of subsequent TKA was arthroscopic osteochondral allograft (5.81%), whereas anterior cruciate ligament (ACL) reconstruction with meniscus repair demonstrated the lowest rate of subsequent TKA (0.01%). When adjusting for confounding factors, the regression analysis identified meniscal transplantation (odds ratio [OR] = 3.06, P < 0.0001) as having the highest risk of subsequent TKA, followed by osteochondral autograft (OR = 1.74, P = 0.0424) and arthroscopic osteochondral allograft (OR = 1.49, P < 0.0001). ACL reconstruction with meniscus repair (OR = 0.02, P < 0.0001), ACL reconstruction alone (OR = 0.17, P < 0.0001), ACL with meniscectomy (OR = 0.20, P < 0.0001), and meniscal repair (OR = 0.65, P < 0.0001) had the lowest rate of subsequent TKA. ACL reconstruction with meniscus repair had the longest period from index procedure to TKA at 2827 days.

CONCLUSION

ACL reconstruction and meniscus preservation demonstrated an extremely low rate of conversion to TKA when compared with patients who needed salvage interventions such as meniscus and cartilage transplantation. None of the salvage interventions delayed the need for a TKA. Meniscal transplantation had the highest risk of all procedures of going on to a TKA.

Meniscus sizing using three-dimensional models of the ipsilateral tibia plateau based on CT scans - an experimental study of a new sizing approach

Purpose

Selection of a meniscus allograft with a similar three-dimensional (3D) size is essential for good clinical results in meniscus allograft surgery. Direct meniscus sizing by MRI scan is not possible in total meniscectomy and indirect sizing by conventional radiography is often inaccurate. The purpose of this study was to develop a new indirect sizing method, based on the 3D shape of the ipsilateral tibia plateau, which is independent of the meniscus condition.

Methods

MRI and CT scans of fifty healthy knee joints were used to create 3D surface models of both menisci (MRI) and tibia plateau (CT). 3D bone models of the proximal 10 mm of the entire and half tibia plateau (with / without intercondylar area) were created in a standardized fashion. For each meniscus, the best fitting “allograft” couple out of all other 49 menisci were assessed by the surface distance of the 3D meniscus (best available allograft), of the 3D tibia plateau (3D-CT) and by the radiographic method of Pollard (2D-RX).

Results

3D-CT sizing was significantly better by using only the half tibia plateau without the intercondylar area (p < 0.001). But neither sizing by 3D-CT, nor by 2D-RX could select the best available allograft. Compared to 2D-RX, 3D-CT sizing was significantly better for the medial, but not for the lateral meniscus.

Conclusions

Automatized, indirect meniscus sizing using the 3D bone models of the tibia plateau is feasible and more precise than the previously described 2D-RX method.. However, further technical improvement is needed to select always the best available allograft.

Three-dimensional meniscus allograft sizing-a study of 280 healthy menisci

Background

Inaccurate meniscus allograft size is still an important problem of the currently used sizing methods. The purpose of this study was to evaluate a new three-dimensional (3D) meniscus-sizing method to increase the accuracy of the selected allografts.

Methods

3D triangular surface models were generated from 280 menisci based on 50 bilateral and 40 unilateral knee joint magnetic resonance imaging (MRI) scans. These models served as an imaginary meniscus allograft tissue bank. Meniscus sizing and allograft selection was simulated for all 50 bilateral knee joints by (1) the closest mean surface distance (MeSD) (3D-MRI sizing with contralateral meniscus), (2) the smallest meniscal width/length difference in MRI (2D-MRI sizing with contralateral meniscus), and (3) conventional radiography as proposed by Pollard (2D-radiograph (RX) sizing with ipsilateral tibia plateau). 3D shape and meniscal width, length, and height were compared between the original meniscus and the selected meniscus using the three sizing methods.

Results

Allograft selection by MeSD (3D MRI) was superior for all measurement parameters. In particular, the 3D shape was significantly improved (p < 0.001), while the mean differences in meniscal width, length, and height were only slightly better than the allograft selected by the other methods. Outliers were reduced by up to 55% (vs. 2D MRI) and 83% (vs. 2D RX) for the medial meniscus and 39% (vs. 2D MRI) and 56% (vs. 2D RX) for the lateral meniscus.

Conclusion

3D-MRI sizing by MeSD using the contralateral meniscus as a reconstruction template can significantly improve meniscus allograft selection. Sizing using conventional radiography should probably not be recommended.

Trial registration

Kantonale Ethikkommission Zürich had given the approval for the study (BASEC-No. 2018-00856).

Contralateral MRI scan can be used reliably for three-dimensional meniscus sizing - Retrospective analysis of 160 healthy menisci

BACKGROUND

Meniscus allograft transplantation is a valuable surgical option for post-meniscectomy syndrome. For best results, the selected allograft should be as similar as possible to the original meniscus. Three-dimensional meniscus sizing could be a new approach to improve the accuracy of meniscus matching. The contralateral anatomy might therefore be a suitable reconstruction template. The purpose of this study was to compare the three-dimensional shape of the right and left menisci by bi-planar segmentation of magnetic resonance imaging (MRI) scans.

METHODS

Three-dimensional surface models of healthy menisci were created based on 40 bilateral MRI scans. Manual segmentation was performed on the MRI data in sagittal and coronal planes. For side-to-side comparison, each left meniscus model was mirrored and then superimposed to its corresponding right meniscus model. Differences between the meniscus pairs were assessed by width, length, height and surface distances. Inter-reader reliability, as well as accuracy of bi-planar segmentation was assessed by two different readers.

RESULTS

The meniscus pairs were not significantly different in terms of width, length and height (P = at least 0.138). Side difference of mean surface distances was 0.76 mm (±0.13 standard deviation (SD)) for medial and 0.78 mm (±0.15 SD) for lateral menisci. Inter-reader reliability was good to excellent (0.828-0.987).

CONCLUSION

The three-dimensional shapes of the left and right menisci are very similar. Therefore, the contralateral meniscus can be used as a template for three-dimensional meniscus allograft sizing. Three-dimensional meniscus segmentation and sizing can be performed accurately by combination of sagittal and coronal planes.

Morphometric measurements to predict meniscal size in skeletally mature dogs for meniscal transplantation

OBJECTIVE

To determine a relationship between morphometric measurements (MM) and meniscal dimensions (MD) in the dog.

STUDY DESIGN

Cadaveric study.

ANIMALS

Eighteen mixed-breed canine cadavers (22.35 ± 4.06 kg); 36 each of medial and lateral menisci.

METHODS

The following MM were obtained in duplicate: height at scapula, withers, pelvis, rump, and greater trochanter; chest circumference; pelvic circumference; length from occiput to the base of the tail; hock to stifle length (HS); body weight; body condition score; and body fat percentage (BF%). Stifles were disarticulated, and digital photographs of in situ menisci were used to obtain meniscal measurements in duplicate. Morphometric parameters were compared with MD via Pearson correlation (r). A correlation of r ≥ 0.65 was considered strong.

RESULTS

The strongest correlation was noted between HS and MD, with r = 0.85 for lateral meniscal width, r = 0.77 for medial meniscal length, and r = 0.76 for medial meniscal width. Lateral meniscal length had the strongest correlation with height at rump (HRu) (r = 0.73). Body weight correlated strongly with meniscal width and fairly with meniscal length. Body condition score and BF% correlated weakly with MD.

CONCLUSION

Hock to stifle length was an easily obtainable variable and was proportional to MD.

CLINICAL SIGNIFICANCE

Hock to stifle length may be considered by tissue banks and veterinary surgeons as a quick and cost effective screening tool for appropriate meniscal sizing in dogs.