Meniscal allografts: indications and outcomes

Use of contralateral lateral meniscus for medial meniscal allograft transplantation: a cadaveric study

PURPOSE

Meniscal allografts are a preferred alternative to menisectomy in cases of irrepairable meniscal tears in young patients. Biological meniscal allograft transplantation requires a cadaveric donor, limiting its availability for transplantation. We are exploring the possibility of using contralateral lateral meniscus for medial meniscal allograft transplantation, as it can be easily procured from proximal tibial cuts from total knee replacement.

METHODS

Ten paired knees from five formalin-fixed Indian male cadavers were dissected. Outer and inner circumferences of the medial and meniscus, area of the articular surface of the medial tibial plateau covered by the native medial meniscus and transplanted lateral meniscus were noted. Measurements were taken using software ImageJ (National Institute of Health). The mean of the recordings from two independent observers was taken as the final value. Inter-observer and intra-observer reliability were also calculated.

RESULTS

The mean inner circumference of the medial meniscus was significantly larger than the lateral meniscus (p < 0.0001). However, outer circumferences were not significantly different from each other (p = 0.1). Area of the tibial plateau covered by the native medial meniscus was smaller than the area covered by the transplanted lateral meniscus, though the difference was not statistically significant. Inter-observer reliability and intra-observer reliability were good (ICC 0.904 and 0.927, respectively).

CONCLUSION

Based on measurements of the outer circumference of medial and lateral menisci, lateral meniscal allograft can be matched for transplantation on the contralateral medial side from the donor with same dimensions of the tibial plateau. Further clinical studies are necessary to prove the clinical significance of this cadaveric study.

LEVEL OF EVIDENCE

Diagnostic study.

Meniscal Allograft Transplantation

Meniscal allograft transplantation provides treatment options for patients with a meniscus-deficient knee with lifestyle-limiting symptoms in the absence of advanced degenerative changes. Meniscal transplantation helps to restore the native biomechanics of the involved knee, which may provide chondroprotective effects and restoring additional knee stability. Improvements in pain, function, and activity level have been seen in appropriately selected patients undergoing transplantation. Although various surgical implantation options exist, the majority focus on reproducing native attachments of the meniscal roots to allow near normal mechanics. Although meniscal transplantation may serve as a salvage procedure for symptomatic patients with a meniscus-deficient knee, it may prevent or delay the necessity of a more invasive arthroplasty procedure.

Does Age Itself Have an Adverse Effect on Survivorship of Meniscal Allograft Transplantation? A Cartilage Status and Time From Previous Meniscectomy-Matched Cohort Study

BACKGROUND

The aging process is accompanied by several conditions that could affect the outcome of meniscal allograft transplantation (MAT). These conditions have made it difficult for clinicians to determine the effect of chronologic age on survivorship after MAT.

HYPOTHESIS

Advanced age does not have an adverse effect on survivorship of MAT when controlling for age-related factors, such as cartilage status and time from previous meniscectomy.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

The records of 264 consecutive patients who underwent primary medial or lateral MAT were reviewed. To check whether there was a difference in MAT survivorship according to age, a cutoff value was calculated from a time-dependent receiver operating characteristic curve. Survival rates, as well as clinical improvement as determined using the Lysholm score, were compared between groups divided by the cutoff value. Patients were matched for cartilage status and elapsed time from previous meniscectomy. Differences in survivorship and clinical outcomes were assessed between the matched groups.

RESULTS

A time-dependent receiver operating characteristic curve showed that the difference in MAT survivorship was maximized with a cutoff age of 43 years. Kaplan-Meier analysis showed a significant difference in MAT survivorship between the older and younger groups (log-rank test, P = .01). However, after matching for cartilage status and time from previous meniscectomy, which left 56 patients per group, there was no significant difference in MAT survivorship (log-rank test, P = .10) between the groups. Regarding clinical outcomes, the mean Lysholm scores were not significantly different between the older and younger groups (P = .19, before matching; P = .39, after matching).

CONCLUSION

MAT survivorship was more affected by age-related prognostic factors, such as cartilage status and time from previous meniscectomy, than age itself. Clinical outcomes did not show differences according to age, either.

Meniscal transplantation: state of the art

Meniscal resection is the most common surgical procedure in orthopaedics. When a large meniscal loss becomes clinically relevant, meniscal allograft transplantation (MAT) is a feasible option. However, although this technique has evolved since the ‘80s, there are still several controversial issues related to MAT. Most importantly, its chondroprotective effect is still not completely proven. Its relatively high complication and reoperation rate is another reason for this procedure not yet being universally accepted. Despite its controversial chondroprotective effect, nevertheless, MAT has become a successful treatment for pain localised in a previously meniscectomised knee, in terms of pain relief and knee function. We conducted a careful review of the literature, highlighting the most relevant studies in various aspects of this procedure. Precise indications, how it behaves biomechanically, surgical techniques, return to sport and future perspectives are among the most relevant topics that have been included in this state-of-the-art review.

Meniscal Preservation is Important for the Knee Joint

Native joint preservation has gained importance in recent years. This is mostly to find solutions for limitations of arthroplasty. In the knee joint, the menisci perform critical functions, adding stability during range of motion and efficiently transferring load across the tibiofemoral articulation while protecting the cartilage. The menisci are the most common injury seen by orthopedicians, especially in the younger active patients. Advances in technology and our knowledge on functioning of the knee joint have made meniscus repair an important mode of treatment. This review summarizes the various techniques of meniscus tear repair and also describes biological enhancements of healing.

Enhanced cellular infiltration of human adipose-derived stem cells in allograft menisci using a needle-punch method

Background

The meniscus plays a crucial role in knee joint stability, load transmission, and stress distribution. Meniscal tears are the most common reported knee injuries, and the current standard treatment for meniscal deficiency is meniscal allograft transplantation. A major limitation of this approach is that meniscal allografts do not have the capacity to remodel and maintain tissue homeostasis due to a lack of cellular infiltration. The purpose of this study was to provide a new method for enhanced cellular infiltration in meniscal allografts.

Methods

Twenty medial menisci were collected from cadaveric human sources and split into five experimental groups: (1) control native menisci, (2) decellularized menisci, (3) decellularized menisci seeded with human adipose-derived stem cells (hASC), (4) decellularized needle-punched menisci, and (5) decellularized needle-punched menisci seeded with hASC. All experimental allografts were decellularized using a combined method with trypsin EDTA and peracetic acid. Needle punching (1-mm spacing, 28 G microneedle) was utilized to improve porosity of the allograft. Samples were recellularized with hASC at a density of 250 k/g of tissue. After 28 days of in vitro culture, menisci were analyzed for mechanical, biochemical, and histological characteristics.

Results

Menisci maintained structural integrity and material properties (compressive equilibrium and dynamic moduli) throughout preparations. Increased DNA content was observed in the needle-punched menisci but not in the samples without needle punching. Histology confirmed these results, showing enhanced cellular infiltration in needle-punched samples.

Conclusions

The enhanced infiltration achieved in this study could help meniscal allografts better remodel post-surgery. The integration of autologous adipose-derived stem cells could improve long-term efficacy of meniscal transplantation procedures by helping to maintain the meniscus in vivo.

Articular Cartilage Degenerates After Subtotal/Total Lateral Meniscectomy but Radiographic Arthrosis Progression Is Reduced After Meniscal Transplantation

BACKGROUND

Little is known about the degree of articular cartilage degeneration after subtotal/total lateral meniscectomy in patients who later undergo isolated lateral meniscal allograft transplantation (LMAT). It has not yet been studied whether arthritic changes as shown on radiographs were lower during the posttransplantation period than during the meniscus-deficient period.

HYPOTHESIS

Articular cartilage will significantly degenerate during the meniscus-deficient period, but the progression in radiographic arthrosis is reduced after LMAT.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

This study retrospectively reviewed 49 patients who underwent subtotal/total lateral meniscectomy before isolated LMAT performed over 1 year later by the same surgeon. International Cartilage Repair Society (ICRS) grades of the femorotibial joint at the time of subtotal/total meniscectomy and at LMAT were compared. Radiographic evaluation was performed at the time of initial meniscectomy, LMAT, and the latest follow-up in 38 patients (after 11 patients whose radiographs showed incomplete ossification at the time of meniscectomy were excluded). Arthrosis, based on Kellgren-Lawrence (K-L) grades, was determined on standing anteroposterior views. Joint space width (JSW) was measured on weightbearing flexion posteroanterior views.

RESULTS

Over a mean meniscus-deficient period of 4.5 years (range, 1-13 years), articular cartilage significantly degenerated on the femoral and tibial sides (P < .001). Grade ≥3 degeneration on the lateral tibial plateau was observed in 13 patients (27%) at the time of initial meniscectomy; this incidence doubled to 28 patients (57%) by the time of LMAT. The K-L grades worsened (P < .001) and JSWs narrowed significantly (-0.65 ± 1.09 mm; P = .001) during the mean meniscus-deficient period of 3.1 years. At radiographic assessment, however, the K-L grades (P = .097) and JSWs (4.06 ± 1.19 vs 3.92 ± 1.21 mm; mean difference, -0.14 ± 0.68 mm; P = .213) did not significantly change during the mean posttransplantation period of 3.8 years. The changes in ICRS grade and JSW during the meniscus-deficient period were not associated with age, body mass index, mechanical axis deviation, or Tegner activity level (P > .05 for all relationships).

CONCLUSION

Patients who underwent isolated LMAT showed substantial articular cartilage degeneration at the time of initial subtotal/total lateral meniscectomy, and this degeneration progressed thereafter. Further progression of radiographic arthrosis was delayed after LMAT.

Graft Extrusion Related to the Position of Allograft in Lateral Meniscal Allograft Transplantation: Biomechanical Comparison Between Parapatellar and Transpatellar Approaches Using Finite Element Analysis

PURPOSE

To compare the relation of extrusion of the graft with the position of the allograft between the parapatellar and transpatellar approaches and to show the primary importance of an anatomically correct position by comparing the chondroprotective effects after lateral meniscal allograft transplantation (MAT) with those of normal healthy knees.

METHODS

Geometrical data from patients who underwent magnetic resonance imaging evaluation after lateral MAT were used as baseline input data for 3-dimensional and finite element analysis. The inclusion criteria were patients with symptomatic knees that had undergone meniscectomy who underwent lateral MAT with a minimum follow-up of 2 years. Patients with generalized arthritis, lower limb malalignment with greater than 5° valgus or varus, or uncorrected joint instability caused by ligament structure deficiency were excluded from this study. Patients were divided into the parapatellar group (25 patients) and transpatellar group (20 patients) according to surgical approach.

RESULTS

The mean width of the extruded meniscus was 4.32 ± 0.58 mm in the parapatellar group and 3.00 ± 0.61 mm in the transpatellar group (P < .0001). The mean relative percentage of extrusion was 42.48% ± 7.82% in the parapatellar group and 28.21% ± 4.49% in the transpatellar group (P < .0001). The mean angle between the bony bridge and the center of the tibial plateau was significantly greater in the parapatellar group (16.69° ± 2.68°) than in the transpatellar group (5.29° ± 1.55°, P < .0001). The mean distance from the entry point of the bony bridge to the center of the tibial plateau was also greater in the parapatellar group (16.68 ± 2.56 mm) than in the transpatellar group (10.81 ± 1.37 mm, P < .0001). The distance from the entry point of the bony bridge to the center of the tibial plateau significantly influenced the obliquity of the bony bridge in the parapatellar group (P = .002). On finite element analysis, the transpatellar approach was more similar to the intact knee model in terms of the contact area and stress of the lateral meniscus and medial meniscus as well as the maximum compressive and maximum shear stresses. Compared with the parapatellar approach, the transpatellar approach had lower maximum contact stress on the menisci and lower maximum compressive stress and maximum shear stress on the femoral and tibial articular surfaces.

CONCLUSIONS

The transpatellar approach led to a more anatomically correct positioning of the grafted meniscus with less meniscal extrusion than did the parapatellar approach in lateral MAT. Furthermore, the transpatellar model had lower maximum contact stress on the menisci than did the parapatellar model, and it also had lower maximum compressive stress and maximum shear stress on the femoral and tibial articular surfaces.

CLINICAL RELEVANCE

The transpatellar approach is likely to have a more anatomic placement of graft with a subsequent greater chondroprotective effect; thereby, it may reduce the overall risk of degenerative osteoarthritis after lateral MAT.

Meniscus transplantation

Understanding the structure and function of the meniscus is critical to understanding its role in overall knee joint function. Injury to, or removal of, meniscal tissue may be associated with articular cartilage wear, knee instability, and, ultimately, the progression of osteoarthritis. While every effort is made for preserving and/or repairing damaged meniscal tissue, in some cases, the meniscus is not amenable to repair after injury. For appropriately indicated patients with symptomatic meniscal deficiency, meniscus allograft transplantation is an excellent surgical solution aimed at reducing pain and improving function. Indications for meniscus allograft transplantation are limited, and concomitant procedures such as osteotomy for malalignment, ligamentous, and/or articular cartilage restoration may be necessary in order to ensure an optimal result following meniscus allograft transplantation. Surgical techniques for meniscus allograft transplantation are variable and include soft-tissue fixation versus bone plug fixation versus bone bridge fixation. Outcomes following meniscus allograft transplantation are generally good to excellent, though reoperation rates are relatively high. The purpose of this article is to provide a concise review of recently published data on meniscus allograft transplantation, with a focus on recent outcomes studies.

3D printing of an extremely tough hydrogel

A super tough hydrogel with tunable mechanical properties was 3D printed.

Lateral meniscus allograft transplantation: an arthroscopically-assisted single-incision technique using all-inside sutures with a suture hook

We present an arthroscopically-assisted single-incision technique using all-inside sutures with a suture hook in the lateral meniscus allograft transplantation. Although this technique is technically demanding, it provides vertically oriented and secure sutures with good tissue approximation without the accessory skin incision.

Revision of meniscal transplants: long-term clinical follow-up

PURPOSE

The primary aim is to document objective and subjective clinical outcome after knee arthroplasty for failed meniscal allograft transplantation; secondly, to investigate the influence of previous meniscal allograft surgery on the clinical outcome after a knee arthroplasty procedure; thirdly, to identify possible prognostic factors for the failure of meniscal allograft, such as potential number of concomitant procedures or pre-transplantation HSS-scores. The study population was compared to a control group of primary total knee arthroplasties.

METHODS

The pre-operative phase, prior to meniscal allograft transplantation, was evaluated by the HSS questionnaire. At final follow-up, the clinical outcome was evaluated by the HSS, KOOS and SF-36 questionnaires. The mean follow-up was 16 years and 2 months. The control group, matched for age and sex, comprised patients with primary total knee arthroplasty.

RESULTS

Statistical analysis showed that for the HSS-scores, there was no significant difference between the study population and the control group. KOOS data showed that the control group scored better overall. There was no significant difference between the HSS-scores after the transplantation and after the knee prosthesis. However, both showed a significant improvement regarding the clinical condition before meniscal transplantation.

CONCLUSIONS

The clinical results after revised meniscal transplantation by means of knee prosthesis are highly variable with a tendency to have a lower score than patients with a primary knee prosthesis. Patients who underwent a revision of their meniscal allograft transplantation by means of a knee arthroplasty still had a significant better clinical outcome than prior to the meniscal allograft transplantation. There were no prognostic factors found by which one can determine whether a meniscal allograft will have a good survival or not.

Transplantation of Achilles tendon treated with bone morphogenetic protein 7 promotes meniscus regeneration in a rat model of massive meniscal defect

Objective

This study was undertaken to examine whether bone morphogenetic protein 7 (BMP-7) induces ectopic cartilage formation in the rat tendon, and whether transplantation of tendon treated with BMP-7 promotes meniscal regeneration. Additionally, we analyzed the relative contributions of host and donor cells on the healing process after tendon transplantation in a rat model.

Methods

BMP-7 was injected in situ into the Achilles tendon of rats, and the histologic findings and gene profile were evaluated. Achilles tendon injected with 1 μg of BMP-7 was transplanted into a meniscal defect in rats. The regenerated meniscus and articular cartilage were evaluated at 4, 8, and 12 weeks. Achilles tendon from LacZ-transgenic rats was transplanted into the meniscal defect in wild-type rats, and vice versa.

Results

Injection of BMP-7 into the rat Achilles tendon induced the fibrochondrocyte differentiation of tendon cells and changed the collagen gene profile of tendon tissue to more closely approximate meniscal tissue. Transplantation of the rat Achilles tendon into a meniscal defect increased meniscal size. The rats that received the tendon treated with BMP-7 had a meniscus matrix that exhibited increased Safranin O and type II collagen staining, and showed a delay in articular cartilage degradation. Using LacZ-transgenic rats, we determined that the regeneration of the meniscus resulted from contribution from both donor and host cells.

Conclusion

Our findings indicate that BMP-7 induces ectopic cartilage formation in rat tendons. Transplantation of Achilles tendon treated with BMP-7 promotes meniscus regeneration and prevents cartilage degeneration in a rat model of massive meniscal defect. Native cells in the rat Achilles tendon contribute to meniscal regeneration.

A new arthroscopic technique for lateral meniscal allograft transplantation: cadaver feasibility study

INTRODUCTION

The three prerequisites for a successful meniscal allograft are fixation, graft sizing and precise positioning. The goal of this study was to demonstrate that lateral meniscal allografts can be reliably positioned using a fully arthroscopic technique.

HYPOTHESIS

This surgical technique is feasible and results in good positioning of the meniscal graft.

MATERIAL AND METHODS

Twelve fresh cadavers were used in the study. The meniscal graft implantation procedure was performed entirely by arthroscopy. The meniscal horns were fixed with screw-in suture anchors and the meniscal border was fixed to the capsule by arthroscopic meniscus-capsule sutures. The main outcome measure of good implant positioning was based on the distance between the implanted location of the posterior horn of the lateral meniscus (PHLM) and its original location. To accomplish this, aerial photographs of the tibial plateau were used to compare the insertion zones and to calculate the distance between them. These measurements were performed by two surgeons and then compared.

RESULTS

Eleven of the 12 procedures (92%) were performed successfully. The posterior horn of the lateral meniscus was positioned an average of 4.3mm in the medial-lateral axis and 1.7 mm in the anterior-posterior axis away from its original location. Thus the position of the implanted PHLM was on average 4.6mm away from its original location.

DISCUSSION

This fully arthroscopic technique is feasible. It offers the advantages associated with minimally-invasive surgery and results in good positioning of the posterior horn of the allograft. Two limitations of this study are that the size of the implant was not matched and the chosen fixation method was not subjected to biomechanical evaluation. The lack of a tibial tunnel will make it easier to combine this procedure with ACL reconstruction. In these conditions, the clinical application of this technique seems to be timely.

LEVEL OF PROOF

IV - Controlled experimental study.

Total meniscectomy in adolescents: a 40-year follow-up

We continued a prospective longitudinal follow-up study of 53 remaining patients who underwent open total meniscectomy as adolescents and who at that time had no other intra-articular pathology of the knee. Their clinical, radiological and patient-reported outcomes are described at a mean follow-up of 40 years (33 to 50). The cohort of patients who had undergone radiological evaluation previously after 30 years were invited for clinical examination, radiological evaluation and review using two patient-reported outcome measures. A total of seven patients (13.2%) had already undergone total knee replacement at the time of follow-up. A significant difference was observed between the operated and non-operated knee in terms of range of movement and osteoarthritis of the tibiofemoral joint, indicating a greater than fourfold relative risk of osteoarthritis at 40 years post-operatively. All patients were symptomatic as defined by the Knee Injury and Osteoarthritis Outcome Score. This study represents the longest follow-up to date and it can be concluded that meniscectomy leads to symptomatic osteoarthritis of the knee later in life, with a resultant 132-fold increase in the rate of total knee replacement in comparison to their geographical and age-matched peers.

Comparison of medial and lateral meniscal transplantation with regard to extrusion of the allograft, and its correlation with clinical outcome

We compared extrusion of the allograft after medial and lateral meniscal allograft transplantation and examined the correlation between the extent of extrusion and the clinical outcome. A total of 73 lateral and 26 medial meniscus allografts were evaluated by MRI at a mean of 32 months (24 to 59) in 99 patients (67 men, 32 women) with a mean age of 35 years (21 to 52). The absolute values and the proportional widths of extruded menisci as a percentage were measured in coronal images that showed maximum extrusion. Functional assessments were performed using Lysholm scores. The mean extrusion was 4.7 mm (1.8 to 7.7) for lateral menisci and 2.9 mm (1.2 to 6.5) for medial menisci (p < 0.001), and the mean percentage extrusions were 52.0% (23.8% to 81.8%) and 31.2% (11.6% to 63.4%), respectively (p < 0.001). Mean Lysholm scores increased significantly from 49.0 (10 to 83) pre-operatively to 86.6 (33 to 99) at final follow-up for lateral menisci (p = 0.001) and from 50.9 (15 to 88) to 88.3 (32 to 100) for medial menisci (p < 0.001). The final mean Lysholm scores were similar in the two groups (p = 0.312). Furthermore, Lysholm scores were not found to be correlated with degree of extrusion (p = 0.242).

Thus, transplanted lateral menisci extrude more significantly than transplanted medial menisci. However, the clinical outcome after meniscal transplantation was not found to be adversely affected by extrusion of the allograft.

Lyophilised medial meniscus transplantations in ACL-deficient knees: a 19-year follow-up

PURPOSE

The treatment of meniscal tears has changed since the early 1980s. Meniscus transplantation emerged as a treatment option during that period. This study aims to present the long-term results of the first lyophilised meniscus allograft transplants in Turkey.

METHODS

Between 1990 and 1992, four transplants of the medial meniscus combined with anterior cruciate ligament (ACL) reconstruction were performed on patients with a history of medial meniscectomy and anterior knee instability at our institution. For all patients who underwent meniscus lyophilised allograft transplantation and revision ACL reconstruction, clinical outcomes were evaluated over a mean period of 19 years of postoperative follow-up by clinical assessment, Tegner score, Lysholm score, Knee Society Score, radiography and magnetic resonance imaging (MRI).

RESULTS

The median value of Tegner score was 3 before index surgery and 2.5 at year 19 postoperatively. The median value of Lysholm score was 60.5 before index surgery and 62.5 at year 19. All of the patients had Outerbridge grade IV osteoarthritis by X-ray examination at year 19.

CONCLUSION

Successful meniscus transplantation depends on many factors. This study examines the effect of allografts on these factors and describes experiences with lyophilised allografts in four male patients.

LEVEL OF EVIDENCE

IV.

Gene Therapy for Cartilage Repair

The concept of using gene transfer strategies for cartilage repair originates from the idea of transferring genes encoding therapeutic factors into the repair tissue, resulting in a temporarily and spatially defined delivery of therapeutic molecules to sites of cartilage damage. This review focuses on the potential benefits of using gene therapy approaches for the repair of articular cartilage and meniscal fibrocartilage, including articular cartilage defects resulting from acute trauma, osteochondritis dissecans, osteonecrosis, and osteoarthritis. Possible applications for meniscal repair comprise meniscal lesions, meniscal sutures, and meniscal transplantation. Recent studies in both small and large animal models have demonstrated the applicability of gene-based approaches for cartilage repair. Chondrogenic pathways were stimulated in the repair tissue and in osteoarthritic cartilage using genes for polypeptide growth factors and transcription factors. Although encouraging data have been generated, a successful translation of gene therapy for cartilage repair will require an ongoing combined effort of orthopedic surgeons and of basic scientists.

Arthroscopic meniscal allograft transplantation without bone plugs

Partial or total meniscectomy are common procedures performed at Orthopedic Surgery departments. Despite providing a great relief of pain, it has been related to early onset knee osteoarthritis. Meniscal allograft transplantation has been proposed as an alternative to meniscectomy. The purposes of this study were to describe an arthroscopic meniscal allograft transplantation without bone plugs technique and to report the preliminary results. All meniscal allograft transplantations performed between 2001 and 2006 were approached for eligibility, and a total of 35 patients (involving 37 menisci) were finally engaged in the study. Patients were excluded if they had ipsilateral knee ligament reconstruction or cartilage repair surgery before meniscal transplantation or other knee surgeries after the meniscal transplantation. Scores on Lysholm, Subjective IKDC Form, and Visual Analogue Scale (VAS) scale for pain were obtained at a mean follow-up of 38.6 months and compared to pre-operative data. Data on chondral lesions were obtained during the arthroscopic procedure and through imaging (radiographs and MRI) studies pre-operatively. Two graft failures out of 59 transplants (3.4%) were found. Daily life accidents were responsible for all graft failures. Significant improvements for Lysholm, Subjective IKDC Form, and VAS for pain scores following the meniscal allograft transplantation were found (P < 0.0001). Controlling for chondral lesion, there was no significant interactions for Lysholm (n.s.), Subjective IKDC Form (n.s.), and VAS for pain scores (n.s.). This study demonstrated that an arthroscopic meniscal allograft transplantation without bone plugs improved knee function and symptoms after a total meniscectomy. Improvements were observed independently of the degree of chondral lesion.

Transpatellar approach in lateral meniscal allograft transplantation using the keyhole method: can we prevent graft extrusion?

PURPOSE

technique for guide wire placement during meniscal allograft transplantation (MAT) is usually based on the parapatellar approach that is not in the anatomical direction of meniscal horn bony insertions. Here, we present a surgical technique to achieve the correct anatomical position of the meniscal graft using the transpatellar approach.

METHODS

a guide wire was introduced through the patellar tendon in the direction of the meniscal insertion sites passing the lateral tibial spine. The insertion plane of the guide wire was approximately at the medial aspect of the tibial tuberosity and slightly medial to the midplane of the patellar tendon. After confirmation with C-arm, the guide wire was cut at the level just beneath the patellar tendon. The knee was then brought to the extension position which lessened the tension of the patellar tendon and retracted it to the medial aspect to expose the end of the guide wire. Drilling and insertion of bone block was performed accordingly.

RESULTS

eleven consecutive patients with total or near-total meniscectomy of the knee underwent MAT with the described technique. The mean extrusion taken on 1-year postoperative non-weight-bearing MRI was 1.6 mm (range 0.5-2.9 mm). None of the patients presented with symptoms requiring a secondary surgery at the time of review.

CONCLUSION

the described technique focuses on achieving correct positioning of the tibia tunnel through the patellar tendon and tunnel reaming in the extended knee position via the mini-open parapatellar approach during lateral MAT. This "transpatellar approach" could be an effective method for anatomical placement of meniscal graft.

Meniscal allograft transplantation

PURPOSE

Meniscal allograft transplantation (MAT) has become an accepted treatment option for patients undergoing meniscectomy with recalcitrant pain in the corresponding compartment. Whether MAT can oppose cartilage degeneration is unclear. Our purpose was to perform a systematic review of available literature to answer the following: (1) Does MAT prevent advancing chondrosis? (2) Who is the ideal candidate for MAT? (3) What is the survival time for allograft in a stable knee? (4) Can MAT be successful when performed with concomitant procedures? (5) Is there an outcome difference between medial and lateral meniscal allograft transplants? (6) What is the expected function of a knee that has undergone MAT?

METHODS

Two authors performed a systematic review of the literature pertaining to MAT. Included in the review are studies with at least 2 years' follow-up, studies with validated outcome measures, and studies in which the allograft meniscal horns were secured with bony fixation.

RESULTS

We identified 14 clinical articles that satisfied our inclusion and exclusion criteria. Thirteen of the articles provided Level IV evidence, and one article provided Level III evidence.

CONCLUSIONS

MAT can result in alleviation of knee pain, improvement in knee function, and good patient satisfaction if performed in the optimal candidate. Improvements in both objective and subjective outcome measures were shown in relatively young patients without significant chondromalacia who underwent concomitant procedures for cartilage defects, limb malalignment, and/or knee instability. We detected no significant difference in outcomes when comparing medial and lateral meniscal allograft transplants. We detected no significant difference when comparing isolated MAT with MAT performed with concomitant procedures.

LEVEL OF EVIDENCE

Level IV, systematic review of Level III and IV studies.

An acellular, allograft-derived meniscus scaffold in an ovine model

PURPOSE

The purpose of this study was to develop a meniscus scaffold that has increased porosity and maintains the native meniscus extracellular matrix in an ovine model.

METHODS

The medial menisci of skeletally mature ovine (n = 16) were harvested; half were made into meniscus scaffolds (n = 8), and half remained intact (n = 8). Intact and scaffold meniscus tissues were compared by use of histology, DNA content analysis, in vitro cellular biocompatibility assays, and ultrastructural analysis. An additional 16 knees were used to investigate the biomechanics of the intact meniscus compared with the meniscus scaffold.

RESULTS

DNA content and histology showed a significant decrease in cellular and nuclear content in the meniscus scaffold (P < .003). Biocompatibility was supported through in vitro cellular assays. Scanning electron microscopy and micro-computed tomography showed a substantial increase in porosity and pore connectivity in the meniscus scaffold compared with the intact meniscus (P < .01). There was no statistical difference between the ultimate load or elastic modulus of the intact and meniscus scaffolds.

CONCLUSIONS

In this study a meniscus scaffold was evaluated for potential clinical application as a meniscus transplant construct in an ovine model. The data showed that a decellularized meniscus scaffold with increased porosity was comparable to the intact meniscus, with an absence of in vitro cellular toxicity. Although some compositional alterations of the extracellular matrix are to be expected during processing, it is evident that many of the essential structural components remained functional with maintenance of biomechanical properties.

CLINICAL RELEVANCE

This meniscus scaffold has potential for future clinical application as a meniscus transplant construct.

TNF, Pig CD86, and VCAM-1 Identified as Potential Targets for Intervention in Xenotransplantation of Pig Chondrocytes

Xenotransplantation of genetically engineered porcine chondrocytes may benefit many patients who suffer cartilage defects. In this work, we sought to elucidate the molecular bases of the cellular response to xenogeneic cartilage. To this end, we isolated pig costal chondrocytes (PCC) and conducted a series of functional studies. First, we determined by flow cytometry the cell surface expression of multiple immunoregulatory proteins in resting conditions or after treatment with human TNF-α, IL-1α, or IL-1β, which did not induce apoptosis. TNF-α and to a lesser extent IL-1α led to a marked upregulation of SLA I, VCAM-1, and ICAM-1 on PCC. SLA II and E-selectin remained undetectable in all the conditions assayed. Notably, CD86 was constitutively expressed at moderate levels, whereas CD80 and CD40 were barely detected. To assess their function, we next studied the interaction of PCC with human monoblastic U937 and Jurkat T cells. U937 cells adhered to resting and in a greater proportion to cytokine-stimulated PCC. Consistent with its expression pattern, pig VCAM-1 was key, mediating the increased adhesion after cytokine stimulation. We also conducted coculture experiments with U937 and PCC and measured the release of pig and human cytokines. Stimulated PCC secreted IL-6 and IL-8, whereas U937 secreted IL-8 in response to PCC. Finally, coculture of PCC with Jurkat in the presence of PHA led to a marked Jurkat activation as determined by the increase in IL-2 secretion. This process was dramatically reduced by blocking pig CD86. In summary, CD86 and VCAM-1 on pig chondrocytes may be important triggers of the xenogeneic cellular immune response. These molecules together with TNF could be considered potential targets for intervention in order to develop xenogeneic therapies for cartilage repair.

Meniscoligamentous band between the posterior horn of the lateral meniscus and the anterior cruciate ligament: arthroscopic, anatomical and histological observations

BACKGROUND

Following the example of the anterior cruciate ligament reconstruction, the success of meniscus allograft transplantation relies on good position of the graft and firm anchorage. The anatomy of the intercondylar region and the connections between the cruciate ligament and the meniscal horns have been the subject of many surveys. However, as far as we know, there is only one description of meniscoligamentous band between the posterior horn of the lateral meniscus (PHLM) and the anterior cruciate ligament (ACL) (Lahlaïdi in Rev Chir Orthop Reparatrice Appar Mot 57(8):593-600, 1971).

METHODS

Fourteen cadaveric knees have been dissected to study the presence and variations of the band between the PHLM and the ACL. In addition, we undertook a histological study to ensure its ligamentous nature.

RESULTS

This meniscoligamentous band was found 13 times amongst the 14 investigated knees, and its ligamentous intra-articular extra-synovial nature was proved.

CONCLUSIONS

This study helps us to better understand the biomechanics of the menisci that are both stable and mobile structures.

The ineffectiveness of fibrin glue and cyanoacrylate on fixation of meniscus transplants in rabbits

Our aim was to evaluate whether a fibrin glue and octyl-cyanoacrylate can promote fixation of meniscal allograft in rabbits. The medial menisci of 18 rabbits were frozen and stored at -73 degrees C (30 days) and then was allotransplantation and fixed by: GSu (n=6) soft tissue; GFi (n=6) fibrin glue; GCy (n=6) cyanoacrylate. They were evaluated by daily surgery recovery score (4 weeks), gross inspection and cells density on scaffold. A severe inflammatory response with caseous necrosis from the inside of the joint on through the approach incision led us to an early sacrifice (16th day) of all animals of GCy. The daily score of recovery was similar in both groups GSu and GFi, with a peak of 40% of mild suffering score in the 12th day. At the 4th week in all animals of GFi the menisci were loose into the joint and the density of cells of collagen matrix was significantly fewer (p<0.001) than the GSu. The octyl-cyanoacrylate adhesive was totally inadequate for use on fixation of an allograft implant due to the severe inflammatory response. The fibrin glue was inappropriate to promote the allograft fixation and subsequently impaired the cells spread into the collagen matrix of allograft implant.

Meniscal allograft size can be predicted by height, weight, and gender

PURPOSE

Our purpose was to determine if height, weight, and gender can be used to accurately predict proper meniscal allograft dimensions.

METHODS

Data were obtained from the Joint Restoration Foundation (AlloSource, Centennial, CO) regarding meniscal size and patient characteristics from meniscal donors. Donor height, weight, sex, age, and anatomic meniscal dimensions were recorded for 930 donor menisci in 664 patients. Multivariate regressions were completed using gender, height, and weight as independent variables and lateral meniscus length, lateral meniscus width, medial meniscus length, and medial meniscus width as dependent variables. The regression formulas were then reapplied to the data in order to produce estimated meniscus dimensions based on donor height, weight, and gender. A 90:10 split of the data was used to validate the regression models. Predicted meniscal size was then compared to actual meniscal size and the results compared to current measurement techniques.

RESULTS

Regression formulas showed the ability to predict meniscal size based on gender, height, and weight with standard deviations (SDs) equal to or less than current radiographic techniques (SD, 6.4% to 8.2%). Average differences between predicted size and actual size ranged from 5.2% to 6.5% for length and 5.2% to 6.0% for width. Patient height was found to be a much more powerful predictor of meniscal size than patient weight. Data from the 90:10 split of data validated the model on an independent sample. These validated outputs were then compared to contemporary techniques and found to have lower SDs and average error rates in the majority of cases.

CONCLUSIONS

We have proposed a validated regression model that uses height, weight, and gender variables to accurately predict required allograft meniscal size. We compared it against previously published data for radiographic and magnetic resonance imaging sizing techniques and found it to produce results that were, overall, slightly more accurate.

CLINICAL RELEVANCE

This model provides a novel method for sizing meniscal allografts.