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Background: In patients with a degenerative tear of the medial meniscus, recent meta-analyses and systematic reviews have shown no treatment benefit of arthroscopic partial meniscectomy (APM) over conservative treatment or placebo surgery. Yet, advocates of APM still argue that APM is cost effective. Giving advocates of APM their due, we note that there is evidence from the treatment of other musculoskeletal complaints to suggest that a treatment may prove cost effective even in the absence of improvements in efficacy outcomes, as it may lead to other benefits, such as diminished productivity loss and reduced costs, and so the question of cost effectiveness needs to be answered for APM., Questions/purposes: (1) Does APM result in lower postoperative costs compared with placebo surgery? (2) Is APM cost-effective compared with placebo surgery?, Methods: One hundred forty-six adults aged 35 to 65 years with knee symptoms consistent with a degenerative medial meniscus tear and no knee osteoarthritis according to the American College of Rheumatology clinical criteria were randomized to APM (n = 70) or placebo surgery (n = 76). In the APM and placebo surgery groups, mean age was 52 ± 7 years and 52 ± 7 years, and 60% (42 of 70) and 62% (47 of 76) of participants were men, respectively. There were no between-group differences in baseline characteristics. In both groups, a standard diagnostic arthroscopy was first performed. Thereafter, in the APM group, the torn meniscus was trimmed to solid meniscus tissue, whereas in the placebo surgery group, APM was carefully mimicked but no resection of meniscal tissue was performed; as such, surgical costs were the same in both arms and were not included in the analyses. All patients received identical postoperative care including a graduated home-based exercise program. At the 2-year follow-up, two patients were lost to follow-up, both in the placebo surgery group. Cost effectiveness over the 2-year trial period was computed as incremental net monetary benefit (INMB) for improvements in quality-adjusted life years (QALY), using both the societal (primary) and healthcare system (secondary) perspectives. To be able to consider APM cost effective, the CEA analysis should yield a positive INMB value. Nonparametric bootstrapping was used to assess uncertainty. Several one-way sensitivity analyses were also performed., Results: APM did not deliver lower postoperative costs, nor did it convincingly improve quality of life scores when compared with placebo surgery. From a societal perspective, APM was associated with € 971 (95% CI -2013 to 4017) higher costs and 0.015 (95% CI -0.011 to 0.041) improved QALYs over 2-year follow-up compared with placebo surgery. Both differences were statistically inconclusive (a wide 95% CI that crossed the line of no difference). Using the conventional willingness to pay (WTP) threshold of € 35,000 per QALY, APM resulted in a negative INMB of € -460 (95% CI -3757 to 2698). In our analysis, APM would result in a positive INMB only when the WTP threshold rises to about € 65,000 per QALY. The wide 95% CIs suggests uncertain cost effectiveness irrespective of chosen WTP threshold., Conclusion: The results of this study lend further support to clinical practice guidelines recommending against the use of APM in patients with a degenerative meniscus tear. Given the robustness of existing evidence demonstrating no benefit or cost effectiveness of APM over nonsurgical treatment or placebo surgery, future research is unlikely to alter this conclusion.Level of Evidence Level III, economic analysis., Competing Interests: Each author certifies that there are no funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article related to the author or any immediate family members. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research ® editors and board members are on file with the publication and can be viewed on request., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the Association of Bone and Joint Surgeons.)

Competing Interests: The author certifies that there are no funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article related to the author or any immediate family members. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request.

Background: Previous studies have investigated the impact of social determinants of health, such as the type of healthcare insurance and household income, on children and adolescents with ACL tears. However, despite the increasing incidence of ACL injury in young patients and a substantial proportion of families who may prefer languages other than English, the relationship between language and clinical care remains unclear., Questions/purposes: To investigate the relationship between language and the care of children and adolescents with ACL tears, we asked: (1) Is a preferred language other than English (PLOE) associated with a delay between ACL injury and surgery? (2) Is a PLOE associated with a greater odds of a patient experiencing a meniscal tear and undergoing a meniscectomy than in those who prefer English?, Methods: We treated 591 patients surgically for ACL injuries between 2011 and 2021. Of those, we considered patients aged 18 years or younger who underwent primary ACL reconstruction for this retrospective, comparative study. Five percent (31 of 591) of patients were excluded because the date of injury was not clearly documented, 2% (11 of 591) were revision reconstructions, and 1% (6 of 591) underwent procedures that were intentionally delayed or staged, leaving 92% (543 of 591) for analysis. The mean age was 16 ± 2 years, and 51% (276 of 543) of patients were boys. The family's preferred language was noted, as were demographic data, time between injury and surgery, and intraoperative findings. A language other than English was preferred by 21% (113 of 543) of patients. Of these, 94% (106 of 113) preferred Spanish. In a univariate analysis, we used independent-samples t-tests, Mann-Whitney U-tests, and Fisher exact tests, as appropriate. Purposeful-entry multivariable regression analyses were used to determine whether PLOE was associated with increased time to surgery, concomitant meniscus injury, or performance of meniscectomy while adjusting for confounding variables. Variables were included in multivariable models if they met the threshold for statistical significance in univariate testing (p < 0.05)., Results: The median time between injury and ACL reconstruction was shorter in families who preferred English compared with those with a PLOE (69 days [IQR 80] versus 103 days [IQR 107)]; p < 0.001). After controlling for potentially confounding variables like insurance and age, we found that patients whose families had a PLOE had greater odds of undergoing surgery more than 60 days after injury (OR 2.2 [95% CI 1.3 to 3.8]; p = 0.005) and more than 90 days after injury (OR 1.8 [95% CI 1.1 to 2.8]; p = 0.02). After controlling for insurance, age, and other factors, PLOE was not associated with surgical delay beyond 180 days, concomitant meniscal tears, or performance of meniscectomy., Conclusion: In this study of children and adolescents undergoing primary ACL reconstruction, patients whose families prefer a language other than English experienced a longer delay between injury and surgery. In areas with a large proportion of families with a PLOE, partnerships with primary care clinicians, emergency departments, schools, athletic teams, and community organizations may improve efficiency in the care of children with ACL injuries. Clinicians proficient in other languages, reliable interpreter services, and translated references and resources may also be impactful. Our results suggest a need for further research on the experiences, needs, and long-term outcomes of these patients, as well as the association of preferred language with results after surgery., Level of Evidence: Level III, therapeutic study., Competing Interests: Each author certifies that there are no funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article related to the author or any immediate family members. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request., (Copyright © 2022 by the Association of Bone and Joint Surgeons.)

Competing Interests: The author certifies that there are no funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article related to the author or any immediate family members. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research ® editors and board members are on file with the publication and can be viewed on request.

Background: Lesions of the posterior segment of the medial meniscus are the most common intraarticular lesions associated with ACL injuries. Ramp lesions are tears in the peripheral attachment of the posterior horn of the medial meniscus. Such injuries are difficult to detect on preoperative MRI. Arthroscopically, the prevalence of these lesions can reach 24%. Anatomical descriptions of the posterior horn of the medial meniscus are becoming clearer, however, histological descriptions are lacking, especially with regard to the presence or absence of capillaries., Questions/purposes: The present qualitative histologic study focused on the posterior segment of the medial meniscus and the meniscocapsular and meniscotibial junctions. Specifically, the objective of this study was to analyze the posterior segment of the medial meniscus and the meniscosynovial junction and to determine whether the meniscus tibial ligament exists., Methods: We dissected 10 unpaired cadaveric knees (five male, five female, age range 55 to 66 years), five left and five right, from the French "Don du corps" body donation program via a posterior approach to the posteromedial capsule. We excluded specimens with intra-articular abnormalities (ACL rupture, meniscal tear, arthrosis) preceding dissection by arthrotomy. We thus accessed the posterior segment of the medial meniscus and the meniscosynovial junction. The proximal capsule, posterior segment of the medial meniscus, entire meniscal capsular-tibial junction, and a fragment of the tibia were removed en bloc. For each knee, three sagittal spaced sections of the posterior segment of the medial meniscus (Zone 4 as defined by Śmigielski) were performed. Two experienced pathologists performed qualitative histological analysis on the 30 samples after Hematoxylin and eosin staining, and Safranin O staining., Results: Macroscopically, the meniscotibial attachments were pellucid and homogeneous, as were the meniscocapsular attachments; however, the meniscocapsular attachments appeared to be denser in both the anterior and posterior regions of the capsule. Microscopy of the meniscosynovial junction revealed loose collagen fibers that were partially oriented but not parallel, a cellular network featuring a few fibroblasts and adipocytes, and several capillaries. No between-attachment histologic differences were apparent; both tissues shared a site of attachment to the posterior horn of the medial meniscus. We did not detect the meniscotibial ligament, macroscopically or microscopically., Conclusions: A ramp lesion may not be a ligamentous injury because the meniscotibial ligament was not detected. Rather, it appears that a ramp lesion is a tear in the common attachment point between the posterior horn of the medial meniscus and meniscocapsular and meniscotibial junctions. This structure is vascularized, and contains nonoriented low cellularity collagen of moderate density., Clinical Relevance: Based on our results, a better rationale for the recommendation of surgical repair of a ramp appears to be needed, given the absence of a meniscotibial ligament, and the presence of capillaries in the meniscocapsular and meniscotibial attachments.

Background: Appropriate postoperative lower limb alignment is one important element of a successful unicompartmental knee arthroplasty (UKA). To predict postoperative alignment, it is important to investigate the association between preoperative imaging evaluations and lower limb alignment after medial UKA., Questions/purposes: (1) Do preoperative valgus stress radiographic and MRI measurements (% mechanical axis, hip-knee-ankle angle, medial meniscal extrusion distance, and osteophyte area at the medial femur and tibia) correlate with postoperative lower limb alignment after UKA; and (2) Can useful cutoffs be calculated in advance of surgery for those findings that were associated with coronal-plane overcorrection?, Methods: We retrospectively analyzed 125 patients with medial knee pain who underwent UKA from January 2012 to October 2018. Valgus stress radiography and MRI were performed routinely to assess the knee. Valgus stress radiography was obtained with the patient supine with the knee in full extension and a firm manual valgus force applied to the knee. Full-length weightbearing radiography was performed 3 months after surgery. There were 12% (15) of patients who did not undergo MRI, and 4% (five) of patients who did not receive the postoperative full-length weightbearing radiograph and they were excluded, leaving 84% (105) of patients available for analysis. There were 27 men and 78 women with a mean (range) age of 77 years ± 6 years (60 to 87). The preoperative diagnosis was medial osteoarthritis in 99 patients and osteonecrosis of the medial femoral condyle in six. To investigate the associations, we routinely measured % mechanical axis using radiography, and also measured the medial meniscal extrusion distance and osteophyte area at the medial femur and tibia using MRI after surgery. Medial meniscus extrusion distance was defined as the distance from the outermost edge of the medial meniscus to a line connecting the femoral and tibial cortices. From these parameters, postoperative alignment was estimated using regression and receiver operating characteristic curve analyses. Variables with p < 0.05 were included., Results: The % mechanical axis on the valgus stress radiograph and medial meniscal extrusion distance were correlated with postoperative lower limb alignment after UKA (adjusted correlation coefficient 0.72; p < 0.001, adjusted correlation coefficient 0.2; p = 0.003, respectively). The estimated % mechanical axis on the postoperative weightbearing radiograph was equal to -0.27 + 0.86% (% mechanical axis on valgus stress radiograph) + 1.14 mm (medial meniscal extrusion distance). Using a cutoff point of 36%, the % mechanical axis on valgus stress radiograph was associated with overcorrection after UKA (area under the curve: 0.89; odds ratio 14 [95% CI 0.75 to 0.95]; p < 0.001, sensitivity 77.8%, specificity 80.9%)., Conclusions: The overcorrection of a varus knee on a valgus stress radiograph before UKA and the increased extrusion of the medial meniscus on preoperative MRI was associated with a greater likelihood of overcorrected alignment after UKA. Future studies should conduct long-term follow-up of malalignment patients to assess the possible complications., Level of Evidence: Level III, diagnostic study.

Background: Partial meniscectomy is one of the most commonly performed orthopaedic procedures for a meniscus tear. Decreased contact area and increased contact pressure have been seen in partial meniscectomies from treatment of various types of meniscal tears; however, the biomechanical effect of a horizontal cleavage tear in the lateral meniscus and subsequent treatment are unknown., Questions/purposes: This study asked whether a horizontal cleavage tear of the lateral meniscus, resecting the inferior leaf, and further resecting the superior leaf would (1) decrease contact area and (2) increase peak contact pressure., Methods: Eleven fresh-frozen human cadaveric knees were evaluated under five conditions of intact meniscus, horizontal cleavage tear, inferior leaf resection, and resection of the inferior and superior leaves of the lateral meniscus. Tibiofemoral contact area and pressure were measured at 0° and 60° knee flexion under an 800-N load, normalized to that at the intact condition of the corresponding knee flexion, and compared across the five previously described conditions., Results: At 0° knee flexion, normalized contact area with inferior leaf resection (65.4% ± 14.1%) was smaller than that at the intact condition (100% ± 0.0%, p < 0.001); smaller than horizontal cleavage tear (94.1% ± 5.8%, p = 0.001) contact area; and smaller than repaired horizontal tear (92.8% ± 8.2%, p = 0.001) contact area. Normalized contact area with further superior leaf resection (50.5% ± 7.3%) was smaller than that at the intact condition (100% ± 0.0%, p < 0.001); smaller than horizontal cleavage tear (94.1% ± 5.8%, p < 0.001) contact area; and smaller than repaired horizontal tear (92.8% ± 8.2%, p < 0.001) contact area. At 60° flexion, normalized contact area with inferior leaf resection (76.1% ± 14.8%) was smaller than that at the intact condition (100% ± 0.0%, p = 0.004); smaller than horizontal cleavage tear (101.8% ± 7.2%, p = 0.006) contact area; and smaller than repaired horizontal tear (104.0% ± 13.3%, p < 0.001) contact area. Normalized contact area with further superior leaf resection (52.1% ± 16.7%) was smaller than that at the intact condition (100% ± 0.0%, p < 0.001); smaller than horizontal cleavage tear (101.8% ± 7.2%, p < 0.001) contact area; and smaller than repaired horizontal tear (104.0% ± 13.3%, p < 0.001) contact area. At 60° flexion, contact area with both leaf resection (52.1% ± 16.7%) was smaller than that with inferior leaf resection (76.1% ± 14.8%, p = 0.039). At 0° knee flexion, peak pressure increased to 127.0% ± 22.1% with inferior leaf resection (p = 0.026) and to 138.6% ± 24.3% with further superior leaf resection (p = 0.002) compared with that at the intact condition (100% ± 0.0%). At 60° flexion, compared with that at the intact condition (100% ± 0.0%), peak pressure increased to 139% ± 33.6% with inferior leaf resection (p = 0.035) and to 155.5% ± 34.7% (p = 0.004) with further superior leaf resection., Conclusions: Resection of the inferior leaf or both leaves of the lateral meniscus after a horizontal cleavage tear resulted in decreased contact area and increased peak contact pressure at 0° and 60° knee flexion., Clinical Relevance: In vitro resection of one or both leaves of a horizontal cleavage tear of the lateral meniscus causes increases in peak pressure, consistent with other types of partial meniscectomies associated in a clinical setting with excessive loading and damage to knee cartilage. Clinical outcomes in patients undergoing partial leaf meniscectomy could confirm this theory. Avoidance of resection may be relatively beneficial for long-term function. The findings of this in vitro study lend biomechanical support for nonoperative management.

Background: Increased contact stresses after meniscectomy have led to an increased focus on meniscal preservation strategies to prevent articular cartilage degeneration. Platelet-rich plasma (PRP) has received attention as a promising strategy to help induce healing and has been shown to do so both in vitro and in vivo. Although PRP has been used in clinical practice for some time, to date, few clinical studies support its use in meniscal repair., Questions/purposes: We sought to (1) evaluate whether PRP augmentation at the time of index meniscal repair decreases the likelihood that subsequent meniscectomy will be performed; (2) determine if PRP augmentation in arthroscopic meniscus repair influenced functional outcome measures; and (3) examine whether PRP augmentation altered clinical and patient-reported outcomes., Methods: Between 2008 and 2011, three surgeons performed 35 isolated arthroscopic meniscus repairs. Of those, 15 (43%) were augmented with PRP, and 20 (57%) were performed without PRP augmentation. During the study period, PRP was used for patients with meniscus tears in the setting of no ACL reconstruction. Complete followup at a minimum of 2 years (mean, 4 years; range, 2-6 years) was available on 11 (73%) of the PRP-augmented knees and 15 (75%) of the nonaugmented knees. Clinical outcome measures including the International Knee Documentation Committee (IKDC) score, Tegner Lysholm Knee Scoring Scale, and return to work and sports/activities survey tools were completed in person, over the phone, or through the mail. Range of motion data were collected from electronic patient charts in chart review. With the numbers available, a post hoc power calculation demonstrated that we would have expected to be able to discern a difference using IKDC if we treated 153 patients with PRP and 219 without PRP assuming an alpha rate of 5% and power exceeding 80%. Using the Lysholm score as an outcome measure, post hoc power estimate was 0.523 and effect size was -1.1 (-2.1 to -0.05) requiring 12 patients treated with PRP and 17 without to find statistically significant differences at p = 0.05 and power = 80%., Results: There was no difference in the proportion of patients who underwent reoperation in the PRP group (27% [four of 15]) compared with the non-PRP group (25% [five of 20]; p = 0.89). Functional outcome measures were not different between the two groups based on the measures used (mean IKDC score, 69; SD, 26 with PRP and 76; SD, 17 without PRP; p = 0.288; mean, Tegner Lysholm Knee Scoring Scale, 66, SD, 32 with PRP and 89; SD, 10 without PRP; p = 0.065). With the numbers available there was no difference in the proportion of patients who returned to work in the PRP group (100% [six of six]) compared with the non-PRP group (100% [nine of nine]) or in the patients who returned to their regular sports/activities in the PRP group (71% [five of seven]) compared with the non-PRP group (78% [seven of nine]; p = 0.75)., Conclusions: Patients who sustain meniscus injuries should be counseled at the time of injury about the outcomes after meniscus repair. With our limited study group, outcomes after meniscus repair with and without PRP appear similar in terms of reoperation rate. However, given the lack of power and nature of the study, modest size differences in outcome may not have been detected. Future larger prospective studies are needed to definitively determine whether PRP should be used with meniscal repair. Additionally, studies are needed to determine if PRP and other biologics may benefit complex tear types., Level of Evidence: Level III, therapeutic study.

Background: Knee muscle weakness and a greater external knee adduction moment are suggested risk factors for medial tibiofemoral knee osteoarthritis. Knee muscle weakness and a greater knee adduction moment may be related to each other, are potentially modifiable, and have been observed after arthroscopic partial meniscectomy., Questions/purposes: The aim of this exploratory study was to determine if knee muscle weakness 3 months after arthroscopic partial meniscectomy (baseline) is associated with an increase in external knee adduction parameters during the subsequent 2 years., Methods: Eighty-two participants undergoing medial arthroscopic partial meniscectomy were assessed at baseline, and 66 participants who were reassessed 2 years later were included in our study. Isokinetic muscle strength and external adduction moment parameters (peak and impulse) during normal and fast walking were measured at baseline and followup. Multiple linear regression models were used to examine the association between baseline muscle strength and 2-year change in adduction moment parameters. A post hoc power calculation showed we had 80% power to detect a correlation of 0.31 between baseline muscle strength and change in the external knee adduction, with an alpha error of 0.05 and two-sided significance., Results: Maximal isokinetic muscle strength 3 months after arthroscopic partial meniscectomy was not associated with change in adduction moment parameters (p value range from 0.12 to 0.96)., Conclusions: No evidence was found to suggest that improving maximal knee muscle strength after a recent arthroscopic partial meniscectomy would reduce change in knee adduction moment observed during the subsequent 2 years. As muscle function is modifiable, future investigation of other aspects of muscle function that may relate to change in knee adduction moment is warranted.

Background: Although relatively uncommon, spontaneous healing from a meniscus injury has been observed even within the avascular area. This may be the result of the existence of mesenchymal stem cells in synovial fluid., Questions/purposes: The purpose of this study was to investigate whether mesenchymal stem cells existed in the synovial fluid of the knee after meniscus injury., Methods: Synovial fluid was obtained from the knees of 22 patients with meniscus injury just before meniscus surgery and from 8 volunteers who had no history of knee injury. The cellular fraction of the synovial fluid was cultured for 14 days followed by analysis for multilineage potential and presentation of surface antigens characteristic of mesenchymal stem cells. Colony-forming efficiency and proliferation potential were also compared between the two groups., Results: Cells with characteristics of mesenchymal stem cells were observed in the synovial fluid of injured knees to a much greater degree than in uninjured knees. The colony-forming cells derived from the synovial fluid of the knee with meniscus injury had multipotentiality and surface epitopes identical to mesenchymal stem cells. The average number of colony formation, obtained from 1 mL of synovial fluid, in meniscus-injured knees was 250, higher than that from healthy volunteers, which was 0.5 (p < 0.001). Total colony number per synovial fluid volume was positively correlated with the postinjury period (r = 0.77, p < 0.001)., Conclusions: Mesenchymal stem cells were found to exist in synovial fluid from knees after meniscus injury. Mesenchymal stem cells were present in higher numbers in synovial fluid with meniscus injury than in normal knees. Total colony number per synovial fluid volume was positively correlated with the postinjury period., Clinical Relevance: Our current human study and previous animal studies suggest the possibility that mesenchymal stem cells in synovial fluid increase after meniscus injury contributing to spontaneous meniscus healing.

Background: Failed ACL reconstruction frequently is accompanied by irreparable medial meniscal tear and/or visible osteoarthritis (OA) in the medial tibiofemoral joint. Thus, assessment for the presence of varus malalignment is important in caring for patients in whom revision ACL reconstruction is considered., Questions/purposes: We determined whether patients undergoing revision ACL reconstruction (1) have more frequent varus malalignment coupled with more severe degrees of medial meniscal injury and/or medial tibiofemoral OA, and (2) would meet potential indications for high tibial osteotomy more frequently than patients undergoing primary ACL reconstruction., Methods: We compared 58 patients undergoing revision ACL reconstruction and 116 patients undergoing primary ACL reconstruction. The mechanical tibiofemoral angle and the weight loading line (%) of the knee were measured. Additionally, radiographic degrees of OA in the tibiofemoral joints, and meniscal conditions were assessed. Then, proportions of potential candidates for high tibial osteotomy between the two groups were compared based on the following indications: (1) weight loading line less than 5%, (2) weight loading line less than 25% and medial tibiofemoral OA Kellgren-Lawrence Grade 3 or greater, or (3) weight loading line less than 25% and Kellgren-Lawrence Grade 2 medial tibiofemoral OA plus subtotal or total medial meniscectomy status., Results: The revision ACL reconstruction group had more frequent varus malalignment in terms of proportion of knees with more varus mechanical tibiofemoral angle than varus 5° (19% versus 8%, p = 0.029) and knees with weight loading line less than 25% (22% versus 9%, p = 0.011). This group also had more frequent high-grade injury of the medial meniscus (34% versus 16%, p = 0.007) and tended to have more frequent higher-grade radiographic OA at the medial tibiofemoral joint (19% versus 9%, p = 0.076). The percentage of patients meeting potential indications for high tibial osteotomy was greater in this group (14% versus 2%, p = 0.003)., Conclusions: We found that many patients undergoing revision ACL surgery may be reasonable candidates for concurrent high tibial osteotomy to address concomitant alignment and OA issues in the medial compartment. However, whether that additional intervention is offset by added risk and morbidity should be the focus of a future study, as it cannot be answered by a study of this design.

Arthroscopic partial meniscectomy can be complicated by excessive resection, damage to articular cartilage, neurovascular injury, persistent drainage from portals, and infection; the procedure can be rendered more difficult, and the outcome less certain, if the surgeon fails to recognize concomitant injuries, malpositions the portals, or misidentifies the components of a meniscus tear. We review the problems that can occur as a result of errors made before, during, and after surgery.

Background: Wide variation in procedure utilization suggests that surgical indications might not be rigorously defined. An alternative explanation is that surgical outcomes are valued differently across groups. When a patient, using the information provided by the surgeon, places high value on successful results or is indifferent to the costs of ineffective treatment, the treatment threshold is lower and more surgery will be chosen., Questions/purposes: Is there a high variation in patients' preferences and, therefore, high variation in treatment thresholds? Do people poorly estimate their own treatment thresholds?, Methods: I presented a hypothetical scenario describing a diagnostically uncertain meniscus injury to 100 college students, asking them to rate the value of the four end points based on treatment choice (arthroscopy chosen/declined) and post hoc knowledge of the true diagnosis (tear present/absent). From those data, I calculated treatment thresholds. Subjects also estimated their treatment threshold directly., Results: The calculated treatment thresholds ranged from 4% to 88%. A discrepancy of at least 20% between the calculated and subject-estimated thresholds was present in 61 subjects., Conclusions: There is great variance in the treatment threshold reported; additionally, many subjects poorly predicted their own calculated treatment thresholds., Clinical Relevance: Variability in patient preferences for outcome is an important, but perhaps underestimated, clinical parameter. Meaningful assessment of patient preferences when recommending treatment or creating clinical practice guidelines will lead to better shared decision making.

Background: To prevent further degeneration, it is desirable to fill a meniscal defect with a supportive scaffold that mimics the mechanics of native tissue. Degradable porous scaffolds have been used, but it is unclear whether the tissue that fills the site of implantation is mechanically adequate, particularly with respect to frictional performance., Questions/purposes: We therefore determined the frictional behavior of native and engineered meniscal replacement tissue from in vivo implantation over time., Methods: We evaluated boundary and mixed-mode friction coefficients of tissue generated in porous polyurethane scaffolds used to augment the repair of the meniscus of 13 skeletally mature sheep after partial meniscectomy. Implants were removed for evaluation at 3, 6, and 12 months. The friction coefficient, aggregate modulus, and hydraulic permeability were evaluated for tissue harvested from native meniscus adjacent to the implants, native meniscus from the intact contralateral knee, and repair tissue from the site of the scaffold implantation. The equilibrium friction coefficient (μ(eq)) was measured in the presence of a lubricant bath of either phosphate-buffered saline (PBS) or equine synovial fluid (ESF)., Results: Boundary μ(eq) in PBS of engineered meniscus improved with time and was similar to native tissue after 6 months. ESF enhanced lubrication for all samples at nearly all time points demonstrating the efficacy of ESF as a joint lubricant for repair tissue as well as native meniscus. Modulus increased and permeability decreased with implantation, likely as a result of tissue ingrowth., Conclusions: Promoting tissue ingrowth into porous scaffolds is a potential strategy for improving friction performance in meniscal repair.

Background: Many factors affect recovery from arthroscopic partial meniscectomy, including patient sex. However, sex differences in time to maximal recovery of knee function and factors influencing differential rates of recovery are unknown., Questions/purposes: We determined (1) preoperative sex differences, (2) sex differences in rate and extent of recovery through 1 year postoperatively, and (3) clinical and fitness variables that could explain potential sex differences in recovery from partial meniscectomy., Patients and Methods: The study sample consisted of 180 patients undergoing arthroscopic partial meniscectomy. Sex, age, body mass index, history of prior injury, length of time between knee injury/impairment and surgical evaluation, weekly exercise frequency, and self-reported fitness were assessed preoperatively, and extent of osteoarthritis was recorded postoperatively. We used the Tegner-Lysholm scale to assess knee function preoperatively and postoperatively at weeks 1, 3, 8, 16, 24, and 48 followups., Results: Females had worse knee function and delayed maximal recovery, requiring 1 year, compared with males, who required only 4 months. History of prior knee injury and lower self-reported fitness were associated with slower recovery in females but not in males. Osteoarthritis was associated with slower recovery but not related to sex. Body mass index, length of time between injury/impairment and surgical evaluation, and weekly exercise frequency did not influence rate of recovery., Conclusions: Females have delayed recovery after arthroscopic partial meniscectomy. Prior knee injury and self-reported low fitness are associated with delayed recovery for females but not for males.

Background: The thrust of meniscal surgery has now moved toward meniscal preservation. Repair is particularly indicated on the lateral side where the sequelae of resection are severe even in an older patient population., Questions/purposes: The aim of this study was to analyze the success of all-inside meniscus repairs in a carefully selected patient population., Methods: Three hundred twelve repairs were performed in 288 patients with a mean age of 32 years (range, 17-46 years). One hundred seventy-one lateral menisci and 141 medial menisci were repaired. The minimum followup was 12 months (mean, 18 months; range, 12-55 months). Medicolegal cases, major trauma, and knee dislocations were excluded. Failure was defined as persistent meniscal symptoms beyond 16 weeks, an MRI diagnosis of a nonhealed meniscal tear beyond 52 weeks, reoperation for the meniscal tear, and failure to return to the patient's previous functional level., Results: There were three painful capsular sutures that required removal, two cases of complex regional pain syndrome, and two deep venous thromboses. The repair failed in 6% of cases with associated ACL reconstruction and 14.1% of cases without ACL reconstruction. Repeat surgery was typically performed at a mean of 16 months (range, 1-44 months)., Conclusions: At short-term followup, all-inside meniscus repairs have good outcomes in the majority of highly selected cases, although this was a very selected cohort with a large number of associated ACL reconstructions., Level of Evidence: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Background: Quadriceps muscle strength, which is essential for the function and stability of the knee, has been found to be impaired even years after arthroscopic partial meniscectomy. However, the neuromuscular alterations that could account for such muscle weakness remain unclear., Questions/purposes: We investigated (1) the side-to-side asymmetries in quadriceps muscle strength 6 months after arthroscopic partial meniscectomy, (2) the physiologic mechanisms (neural versus muscular) underlying muscle weakness, and (3) the impact of quadriceps weakness on muscle control at submaximal force levels., Patients and Methods: We tested 14 volunteers (10 men, four women) with an average age of 44 +/- 9 years (range, 24-59 years) at 6 +/- 1 months after unilateral medial arthroscopic partial meniscectomy. We measured maximal voluntary strength and muscle activation during isometric, concentric, and eccentric contractions using isokinetic dynamometry and surface EMG, respectively. We assessed vastus lateralis muscle size and architecture using ultrasonography. We measured muscle control at submaximal force levels with a repositioning test (knee proprioception) and a low-force target-tracking task (steadiness, accuracy)., Results: Isometric and concentric quadriceps strength and vastus lateralis EMG activity were lower on the involved than on the uninvolved side. Muscle architecture and muscle control did not differ between the involved and uninvolved sides., Conclusions: Our results showed quadriceps weakness exists 6 months after arthroscopic partial meniscectomy. As suggested by the EMG results, this is likely attributable to neural impairments (activation failure) that affect muscle control at maximal but not submaximal force outputs., Level of Evidence: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Unlabelled: Curettage is the most attractive procedure for surgically treating a giant cell tumor because it preserves joint function. However, since many giant cell tumors compromise subchondral bone this technique can jeopardize the articular surface with subsequent fractures or collapse. We asked whether intralesional curettage of a giant cell tumor close to the knee that combined morselized bone and cortical structural allograft would preserve joint function. We retrospectively reviewed 22 patients treated with that approach. The minimum followup was 2 years (average, 48 months; range, 24-80 months). The distal femur was involved in 12 patients and proximal tibia in 10. Complications and failures were recorded and functional results evaluated with Musculoskeletal Tumor Society score. We determined survivorship using the Kaplan-Meier technique using removal of the implant as the endpoint. The survival was 85% and the average functional score 28 points. Three of the 22 patients had a local tumor recurrence and one had a partial subchondral collapse not requiring further treatment. Among the remaining patients, none had fracture, infection, or knee instability. The combination of fragmented and cortical allograft allows reconstructing the bone defect and ligaments created after extensive curettage of a knee giant cell tumor obtaining normal joint function and a high survival rate with minimal complications in a high percentage of the patients., Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Unlabelled: Local attempts to repair a cartilage lesion could cause increased levels of anabolic and catabolic factors in the synovial fluid. After repair with regenerated cartilage, the homeostasis of the cartilage ideally would return to normal. In this pilot study, we first hypothesized levels of synovial fluid markers would be higher in patients with cartilage lesions than in patients with no cartilage lesions, and then we hypothesized the levels of synovial fluid markers would decrease after cartilage repair. We collected synovial fluid samples from 10 patients before autologous chondrocyte transplantation of the knee. One year later, a second set of samples was collected and arthroscopic evaluation of the repair site was performed. Fifteen patients undergoing knee arthroscopy for various symptoms but with no apparent cartilage lesions served as control subjects. We measured synovial fluid matrix metalloproteinase-3 (MMP-3) and insulinlike growth factor-I (IGF-I) concentrations with specific activity and enzyme-linked immunosorbent assays, respectively. The levels of MMP-3 and IGF-I were higher in patients having cartilage lesions than in control subjects with no cartilage lesions. One year after cartilage repair, the lesions were filled with repair tissue, but the levels of MMP-3 and IGF-I remained elevated, indicating either graft remodeling or early degeneration., Level of Evidence: Level III, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

This study presents the survivorship data of a consecutive series of primary meniscal-bearing total knee replacements at one institution at 8 to 15 years followup. We reviewed 125 meniscal-bearing knee replacements in 93 patients at a minimum followup of 96 months (mean, 130 months; range, 96-191 months). The tibial and femoral components were cemented in 71 knees; uncemented femurs and tibias were used in 48 knees; and cemented tibias and uncemented femurs were used in six knees. One patient was lost to followup. Seventeen knees failed, three as a result of infection. Five knees were revised for loose tibial components and one for a loose femoral component. A second femoral component was identified as radiographically loose. All the loose components were uncemented. Five knees had reoperation for fractured bearings and one for a dislocated bearing. This knee was later rerevised for a loose uncemented tibia. One knee was revised for instability and a second knee was identified as grossly unstable but not revised. Kaplan-Meier survival analysis showed survivorship of approximately 90% at 9 years, which decreased to 71% at 15 years. Uncemented components had an increased aseptic loosening rate compared with cemented components. Meniscal-bearing replacements with cement fixation appeared successful, although bearing fracture seems to be a predominant failure mode at long-term followup.

When treating a horizontal meniscus tear, the surgeon must decide whether to resect one or both leaves of the tear. We asked whether there is a biomechanical advantage to sparing one leaf when performing a partial meniscectomy for horizontal meniscus tear. We used pressure-sensitive film to measure the contact area, mean pressure, and peak pressure on the lateral tibial plateau of cadaveric sheep knees loaded to 2x body weight. For tears restricted to the posterior third, single-leaf resection decreased contact area by 40% compared with the intact case. Sparing one leaf was beneficial because resection of the second leaf reduced contact area an additional 15%. Similarly, mean pressure was increased 24% for single-leaf resection and an additional 27% for double-leaf resection. Peak pressure showed no differences with single- and double-leaf resections. For tears that span the entire meniscus, single-leaf resection reduced contact area by 59%, increased mean pressure by 55%, and increased peak pressure by 19%. Double-leaf resection in this situation did not change these values substantially, suggesting sparing one leaf offers no benefit over resecting both leaves with extensive horizontal meniscus tears.

All-inside meniscus repairs are becoming more common with the invention of meniscal arrows, darts, screws, staples, and other suture devices. With the rising popularity of these new all-inside meniscal repair devices, it is necessary to assess the effectiveness of various all-inside surgical interventions used in the treatment of meniscal tears. We performed an evidence based review of the outcomes of all-inside meniscus repair devices. Seventy-seven percent of identified studies were case series; 10% were retrospective comparative studies; 6.5% were prospective comparative studies; and 6.5% were prospective randomized studies. The failure rates ranged from 0 to 43.5%. We found no substantial differences in the failure rates among various meniscus devices. We also found no substantial differences in failure rates with length of followup. Given the paucity of randomized controlled studies comparing different all-inside meniscal repairs, no definite conclusions can be made regarding the difference in clinical outcomes of various all-inside meniscal repair devices.

Meniscal transplantation has become an accepted treatment option for selected symptomatic patients who have undergone a complete or near-complete meniscectomy. Basic and preliminary clinical studies suggest a meniscal allograft may replicate (though not completely) the shock-absorbing function of the normal meniscus to alleviate pain and provide measurable improvement in knee function. However, there is limited information on which to base crucial clinical decisions in treating the meniscectomized patient. I systematically explored available literature to address four general questions: Who is the ideal patient for a meniscal transplantation? What is the ideal method of graft sizing, preservation, and implantation? What is the accepted means of postoperative rehabilitation and timing of a return to athletic activities? And finally, what is the overall success rate of this procedure? This review of existing clinical trials revealed several crucial treatment principles for surgeons performing this procedure: (1) achieving or reestablishing normal knee alignment and stability; (2) implanting a size-matched, non-irradiated graft with secure fixation of the meniscal horns; and (3) ensuring patients return only to light sports activities to maximize the chances for graft survival. By following these principles, symptomatic improvement can be achieved in the majority of patients.

Unlabelled: The use of tissue engineering for cartilage repair has emerged as a potential therapeutic option and has led to the development of Hyalograft C, a tissue-engineered graft composed of autologous chondrocytes grown on a scaffold entirely made of HYAFF 11, an esterified derivative of hyaluronic acid. Here we present the results of an ongoing multicenter clinical study conducted with the primary objective to investigate the subjective symptomatic, functional and health-related quality of life outcomes of patients treated with Hyalograft C. Clinical results on the cohort of 141 patients with followup assessments ranging from 2 to 5 years (average followup time: 38 months), are reported. At followup 91.5% of patients improved according to the International Knee Documentation Committee subjective evaluation; 76% and 88% of patients had no pain and mobility problems respectively assessed by the EuroQol-EQ5D measure. Furthermore, 95.7% of the patients had their treated knee normal or nearly normal as assessed by the surgeon; cartilage repair was graded arthroscopically as normal or nearly normal in 96.4% of the scored knees; the majority of the second-look biopsies of the grafted site histologically were assessed as hyaline-like. Importantly, a very limited complication rate was recorded in this study. The positive clinical results obtained indicate that Hyalograft C is a safe and effective therapeutic option for the treatment of articular cartilage lesions., Level of Evidence: Therapeutic study, Level III-2 (retrospective cohort study). See the Guidelines for Authors for a complete description of levels of evidence.

Meniscal pathology causing loss of function is a common problem that requires treatment in a large number of individuals each year. A patient with a meniscal-deficient knee is doomed to the development of osteoarthritis, pain, and knee dysfunction. The amount, shape, and composition of meniscal tissue influence its function and, therefore, influence the health of the knee joint. When preservation of healthy meniscal tissue cannot be accomplished, methods for replacement or regeneration of meniscal tissue are necessary. This review article will discuss current methods of meniscal tissue replacement and regeneration and potential future modes of therapy.

Intra-articular knee injuries in children traditionally have been considered rarer than injuries in adults. Few studies establish the prevalence of knee injuries before skeletal maturity, but arthroscopic studies suggest an increased frequency of anterior cruciate ligament ruptures, meniscal tears, and osteochondral fractures. We report our experience with 15 anterior cruciate ligament injuries and 38 meniscus injuries treated between 1996 and 2001. The treatment of anterior cruciate ligament injuries is determined by Tanner's maturity criteria. In the three cases of Stage II injuries, surgery was delayed for up to 24 months in the 12 older patients, an immediate reconstruction was done using hamstring tendons in the three youngest patients, and patellar tendon treatment was done in the remaining cases. We had only one complication caused by the fracturing of the bone plug. The most frequent meniscus injuries were the traumatic tears (23 cases), 80% of which were peripheral and longitudinal. Whenever possible, the entire meniscus (suture in 4 cases) or the greater part of it (economic resection in 19 cases) should be conserved. Despite the satisfactory results, the average followup of the meniscal series (26.1 months) is too short a period to evaluate thoroughly the deterioration of the joint after a meniscectomy.

Lower body positive pressure allows unloading of the lower extremities during exercise in a pressurized treadmill chamber. This study assessed the preliminary feasibility of lower body positive pressure exercise as a rehabilitation technique by examining its effects on gait mechanics and pain, postoperatively. Fifteen patients who had arthroscopic meniscectomy or anterior cruciate ligament reconstruction participated in this study. Patients exercised for 5 minutes at 2.0 mph under three body weight conditions (normal body weight, 60% body weight, and 20% body weight) in random order. Bilateral ground reaction force, electromyographs, and dynamic knee range of motion were collected, and pain was assessed using a visual analog scale. Ground reaction forces for surgically treated and contralateral extremities were reduced 42% and 79% from normal body weight conditions when ambulating at 60% and 20% body weight, respectively. After meniscectomy, ambulatory knee range of motion decreased only at 20% body weight (37 degrees), compared with normal body weight conditions (49 degrees). Peak electromyographic activity of the biceps was maintained at all body weight conditions, whereas that of the vastus medialis was reduced at 20% body weight. Pain relief was significant with lower body positive pressure ambulation after anterior cruciate ligament reconstruction. This study showed that lower body positive pressure exercise is effective at reducing ground reaction forces, while safely facilitating gait postoperatively.

The current study aims to elucidate the midterm to long-term progression of arthroscopic meniscal repair which had been confirmed through a second-look arthroscopy at an average of 10 months after repair. Twenty-eight menisci of 28 patients were investigated at 8 to 14 years (mean, 10.2 +/- 1.8 years), eight after isolated meniscal repair (Isolated group) and 20 after concomitant anterior cruciate reconstruction (Anterior cruciate ligament group). All were rated excellent except four that rated good in the anterior cruciate ligament group as indicated by Lysholm's score at followup. None of the Isolated group, but 12 of the Anterior cruciate ligament group, had osteoarthritic changes seen on radiographs. Four and 19, respectively, had increased signal intensity on magnetic resonance imaging scans, 10 in the Anterior cruciate ligament group had changes of Grade 3 severity. However, no meniscal signs or symptoms were present and no significant relationship between findings of radiographs and magnetic resonance imaging scans was apparent. Anterior cruciate reconstructed knees that were changed to Grade 3 severity as seen on magnetic resonance imaging scans had higher sagittal instability seen on stress radiography than knees with Grade 2 or less severe changes. The anterior laxity of the knees influenced the severity of meniscal signal changes on the magnetic resonance imaging scans.

Previous studies have documented how partial and complete meniscectomy affect articular contact pressure, but changes in load transfer through the complete osteochondral structure of the proximal tibia after partial and complete meniscectomy are not well known. The current study measured trabecular bone strain changes in the medial tibial plateau resulting from partial and complete medial meniscectomy. Midcoronal sections were prepared from knees from cadavers. High quality digital images, made from contact radiographs of loaded samples, were compared with digital images of unloaded samples using in-house software to measure trabecular bone strain. Measurements were made on specimens with an intact medial meniscus, after removal of the inner (2/3) of the meniscus, and after complete meniscectomy. Partial meniscectomy caused minimal increases in trabecular bone strain throughout the proximal tibia. However specimens with complete meniscectomy had significant trabecular bone strain increases. Many patients sustaining meniscus tears are young, therefore, it is important to understand mechanical changes associated with partial meniscectomy. The data suggest partial meniscectomy causes little change in load transfer through the proximal tibia, supporting partial meniscectomy as a good surgical option for patients with meniscus tears.

The meniscus plays an important role in the function of the knee. Preservation of the meniscus is preferred if possible when considering treatment of a meniscus tear. A thorough understanding of the anatomy of the meniscus, the structure, the mechanics, and other factors of meniscal healing are critical when evaluating the torn meniscus for a reparative procedure. Many options for meniscus repair exist for the orthopaedist. Options such as open repair or arthroscopically-assisted inside-out techniques have long-term favorable results. The all-inside techniques are attractive because of the decrease in operative time and ease of the technique. Short-term results are positive for the all-inside technique; however, good long-term data on these techniques are lacking. Few well-designed prospective studies exist on any of the meniscus repair techniques. Future directions include the potential use of growth factors and gene therapy to augment meniscus repair.

The purpose of the current study was to obtain additional information about the biomechanical behavior of different fixation techniques for meniscus repair using recently developed biodegradable implants and suture repair techniques. The posterior horns of human menisci were used to investigate the meniscus repair construct of the Arrow, Screw, Stinger, Fastener, T-fix, and horizontal and vertical mattress suture. A 20 mm-longitudinal incision was made in the meniscus, similar to a bucket handle lesion, 3 mm from the meniscosynovial rim and was repaired. One hundred cycles between 5 N and 15 N were done using a tension load machine with a loading rate of 10 N/second. The stiffness, displacement, and pullout strength were examined. The significantly highest stiffness was found for the vertical mattress suture (17.1 N/mm) and Stinger (15 N/mm) followed by the Arrow (13.7 N/mm), T-fix (10.5 N/mm), and horizontal mattress suture (10 N/mm). Superior load to failure was obtained for the suture repair in comparison with the biodegradable implants. Despite the lower pullout strength of biodegradable implants, similar stiffnesses were found for the Stinger and Arrow in comparison with the mattress suture technique. These techniques provide the most rigid fixation that is essential for tissue healing.

Normative preoperative Short Form-12 Health Survey components summary scores have not been reported for patients who have knee conditions treated with arthroscopy. During one calendar year, 269 consecutive patients with a knee injury (119 meniscus lesions, 73 anterior cruciate ligament ruptures, 54 articular cartilage lesions, and 23 with patellar instability) completed the Short Form-12 Health Survey before medical evaluation. Mental Component Scale and Physical Component Scale scores were computed. Scores were compared with previously published normative and age-specific data for several medical conditions and the United States general population. With the number of patients available, no significant differences were detected between knee conditions for the Mental Component Scale and Physical Component Scale scores. In general, Physical Component Scale scores among patients with knee conditions were similar to previously reported Physical Component Scale scores for patients with orthopaedic shoulder conditions and significantly lower than the United States population norms. These data can be used as historic control groups to represent patients with knee conditions requiring arthroscopy. Age-specific Mental Component Scale and Physical Component Scale scores are indicated when comparing groups with a limited age range.

An independent measurement of the quality of outcome of 31 consecutive Oxford medial unicompartmental knee replacements in 28 patients and 130 total knee replacements in 104 patients performed between 1993 and 1997 is reported. The indications for surgery were anteromedial osteoarthritis for unicompartmental replacement and more extensive osteoarthritis for total knee replacement. All patients were treated by one surgeon. As a validated outcome measure of knee function, the Oxford 12-item knee questionnaire showed identical outcome in both groups with a mean score of 36.5 (maximum possible, 48). Neither the pain nor the functional outcomes were significantly different, although patients receiving unicompartmental replacement were better able to descend stairs. Two patients needed revision surgery in the unicompartmental replacement group compared with only one patient in the total knee replacement group. The femoral component of two unicompartmental replacements showed radiologic signs of loosening. The tibial component of one total knee replacement appeared loose, but the patient had no symptoms. In comparison with total knee replacement, implantation of meniscal bearing unicompartmental replacement technically is demanding and unforgiving. However, revision of a failed Oxford unicompartmental replacement is easier than revision of a failed total knee replacement, and the authors recommend this device for younger patients in whom one could expect a total knee replacement to fail within their lifetime.

The purpose of this study was to determine functional and radiographic changes on long-term followup of knees with isolated meniscal tears. Sixty-seven patients were evaluated retrospectively with an average of 12.2 years' followup using the scale of Tapper and Hoover. The criteria for the radiographic results were the Fairbank's changes as the standard comparing the preoperative and the postoperative conditions of the affected knee with the contralateral knee. Seventy-nine percent of the patients had a satisfactory outcome in terms of function. The amount of meniscus removed and the Outerbridge classification of the articular cartilage at the time of the meniscectomy were determining factors for long-term functional results. Osteoarthritic deterioration was seen in 48% of patients after the surgery, but radiographic deterioration after arthroscopic partial meniscectomy was mild on long-term followup. Medial meniscectomy and the amount of meniscus removed were risk factors for postoperative radiographic change. Age, gender, and the degree of cartilage degeneration at the time of operation, in contrast, showed no significant association. Arthroscopic partial meniscectomy for isolated meniscal injury yields favorable functional results but leads to significantly increased osteoarthritic change in the long-term.

Damage to the meniscus after trauma or injury is associated with detrimental changes in joint function that can lead to pain, disability, and degenerative joint changes. Recently, tissue engineering strategies for meniscal repair have been suggested including using biocompatible grafts as a substrate for regeneration, and cellular supplementation to promote remodeling and healing. Little is known, however, about the contributions of these novel repair strategies to restoration of normal meniscal function. Biomechanical factors play a role in the design and synthesis of tissue engineered biomaterials and bioreactors, and also are important for evaluating the efficacy of these new strategies for restoring normal meniscal function. In this report, an overview is presented of biomechanical factors that are critical to meniscal function followed by a review of biomechanical considerations for the design and evaluation of tissue engineered strategies for meniscal repair. Recommendations for future study of biomechanical factors in tissue engineered meniscal repair also are provided.

The meniscus performs critical functions within the knee, and its loss frequently leads to osteoarthritis and irreversible joint damage. Because prosthetic replacement of the meniscus has proven ineffective, the authors used tissue engineering techniques to develop a resorbable collagen scaffold (collagen meniscus implant) that supports ingrowth of new tissue and eventual regeneration of the lost meniscus. Eight patients underwent arthroscopic placement the collagen meniscus implant to reconstruct and restore the irreparably damaged medial meniscus of one knee. Seven patients had one or more prior meniscectomies, and one patient had an acute meniscus injury. Patients were observed with frequent clinical, serologic, radiographic, and magnetic resonance imaging examinations for at least 24 months (range, 24-32 months). All patients underwent relook arthroscopy and biopsy of the implant regenerated tissue at either 6 or 12 months after implantation. All patients improved clinically from preoperatively to 1 and 2 years postoperatively based on pain, Lysholm scores, Tegner activity scale, and self assessment. Relook arthroscopy revealed tissue regeneration in all patients with apparent preservation of the joint surfaces based on visual observations. Histologic analysis confirmed new fibrocartilage matrix formation. Radiographs confirmed no progression of degenerative joint disease. The collagen meniscus implant is implantable, biocompatible, resorbable, and supports new tissue regeneration as it is resorbed. This tissue seems to function similar to meniscus tissue by protecting the chondral surfaces.

Torn meniscal cartilages and the consequences of missing meniscus tissue represent the major indications for operative arthroscopy of the knee. After recognizing the importance of the meniscus, clinicians made the shift away from complete meniscectomy to partial meniscectomy aided by the development of arthroscopic instrumentation. Despite extensive basic science data showing the importance of a complete meniscus for normal force transference, meniscus repair occurs in less than 10% of all meniscal tears found at arthroscopy. This paper will discuss the reasons for the common clinical approach and compare that approach with an aggressive approach of salvaging and replacing meniscus tissue, and will offer speculations about future directions for meniscus repair, reconstruction, and replacement.

From July 1990 through June 1994, 106 knees (102 patients) were treated for discoid meniscus. Fifteen knees (15 patients) were associated with other intraarticular anatomic variants. There were eight knees (8 patients) with anomalous insertion of the anterior horn of the medial meniscus into the anterior cruciate ligament, and seven knees (7 patients) with anterior expansion of the anterior portion of the anterior cruciate ligament below the anterior tibial margin. Among the latter, one patient also had anterior transposition of the anterior insertion of the medial meniscus, while obliteration of the popliteal hiatus was seen in another patient. The discoid menisci were reshaped in 13 knees (13 patients), totally resected in one knee, and in one patient the discoid meniscus was treated with repair of a peripheral tear and reshaping. Followup ranged from 24 to 54 months (average, 37 months) after surgery. The results were excellent in eight knees, good in five knees, and fair in two knees as graded using the Ikeuchi scale. These anatomic variants, other than the discoid meniscus, did not seem to be related to the patient's symptoms.

In a rabbit model the healing process of the anterior attachment of the medical meniscus was observed during the first 12 weeks after sharp transection and refixation in a tibial bone channel. Evaluations of the healing tissue were histologic analysis, application of immunohistochemical methods to show collagen types and nerve regeneration, and mechanical load to failure tests. Secondary changes to knee joint cartilage, as signs of eventual dysfunction of the refixed meniscus, were evaluated by analysis of proteoglycan fragment concentration in joint fluid and histologic analysis of knee joint articular cartilage and synovium. The healing tissue between the refixed attachment and bone matured from highly cellular, nonspecific granulation tissue at 1 week, to bone, fibrocartilaginous, and fibrous tissues, which at some sites developed an insertion specific tissue arrangement within a 12-week period. However, the irregular interface between the fibrocartilaginous tissue and the underlying bone, which is typical for a normal insertion, was not reestablished. Labeling for collagen Types I and II in the newly formed insertion did not return to normal. In addition a few collagen fibers connected the refixed attachment tissue to bone. New bone formation turned the initially cancellous bone tunnel walls into more solid cortical bone. However, new bone formation did not fill the distal part of the channel. The refixed meniscal attachment underwent necrosis and was revitalized by cell ingrowth from the periphery. Nerve fibers were found in the newly formed insertion by 12 weeks. The failure load at tensile testing never reached more than 20% that of a normal attachment. Degeneration of articular cartilage and increased proteoglycan fragment in the joint fluid were common after this procedure. These data suggest that, despite the focal appearance of insertion specific tissues and healing of collagen fibers to bone, the tissue architecture of a normal meniscal insertion and a normal meniscal joint protective function were not reestablished.

Ten normal subjects and 10 patients with a posterior cruciate retaining mobile bearing total knee replacement performed successive deep knee bends under fluoroscopy to determine tibiofemoral contact positions. At full extension the average initial contact position for the normal and mobile total knee replacement was 6.2 mm (range, 4.8 to 12 mm) anterior, and -4.4 mm (range, 3.9 to 11 mm) posterior to the sagittal tibial midplane, respectively. At 60 degrees flexion, the normal knee rolled back to -5.8 mm (range, -2.5 to -13.2 mm), whereas the mobile bearing total knee replacement rolled back to -9.2 mm (range, -4 to -17 mm). From 60 degrees to 90 degrees, normal knees rolled back to -7.8 mm (range, -5.8 to -13.8 mm), but the mobile bearing total knee replacement slid anteriorly to -5 mm (range, 2 to -12 mm). All mobile bearing total knee replacements had some form of roll back, but some slid anterior more than others. Five of 10 mobile bearing total knee replacements had some movement of the bearings while the others remained fixed. Patellar kinematics was similar to normal but reflected tibiofemoral abnormalities.

Radial displacement of the medial meniscus in knees that have not undergone meniscectomy was measured using magnetic resonance imaging. In age matched subjects, the amount of displacement was compared with the presence or absence of radiographic signs described by Fairbank. A medial displacement index, defined as the ratio of meniscal overhang to meniscal width, was used to quantify meniscal displacement. The medial displacement indices for knees with and without radiographic signs were 0.45 +/- 0.22 and 0.08 +/- 0.10, respectively (mean +/- standard deviation). Differences were highly significant. The greatest meniscal displacements were seen in knees with radiographic Fairbank's signs; no knee with such signs had an undisplaced meniscus. It is concluded that radiographic signs of osteoarthritis known to follow meniscectomy can develop in knees that exhibit significant radial displacement of the medial meniscus. Radial displacement may be related to loss of meniscal function because the radiographic signs are similar to those that follow meniscectomy.

In a prospective study, magnetic resonance imaging was performed before arthroscopy for all patients (n = 121) with a meniscal tear (n = 125). Criteria of the study were stable cruciate and collateral ligaments, absence of pathologic radiographic findings, and absence of prior surgical interventions of the involved knee joint. In 43 knees (34%), the clinical diagnosis of a meniscal tear was discarded because of the results of the magnetic resonance imaging examination. Synovitis was diagnosed in 16 patients (13%), articular cartilage damage in 10 patients (8%), bone bruise injuries in 10 patients (8%), osteochondritis dissecans in 3 patients (2%), disruption of the inner layer of the medial collateral ligament in 3 patients (2%), and osteonecrosis in 1 patient. The use of magnetic resonance imaging in establishing diagnosis of disorders of the knee joint altered treatment in a significant proportion of patients. Magnetic resonance imaging should be done before arthroscopy of the knee in all cases in which the clinical diagnosis has been reduced to a suspected meniscus injury.