Increased Tibial Slope Raises Risk of Meniscal Allograft Failure

Anatomical Predictors of Meniscal Allograft Survivorship

Meniscal allograft transplantation (MAT) has become a standard surgical option for symptomatic patients with meniscal deficiency, aiming to restore knee mechanics and delay the onset of secondary osteoarthritis [1, 2]. While the procedure frequently yields significant improvements in functional status, long-term durability remains a challenge; a systematic review of 188 patients reported failure rates between 13% and 22.9%, often defined as conversion to arthroplasty or graft removal [3, 4, 5]. Clinicians must navigate several perioperative variables that influence these outcomes, including the degree of existing cartilage damage and the specific graft fixation technique employed [6, 7]. For instance, a meta-analysis of 11,413 patients found that bone-bridge fixation for medial MAT predicted a higher risk of nonfailure reoperation (any procedure to improve function without removing the graft) compared with bone-plug fixation (P <.001) [6]. Biomechanical evidence suggests that the sagittal plane geometry of the tibia, specifically the posterior tibial slope (the posterior downward inclination of the tibial plateau relative to the longitudinal axis of the bone), significantly alters knee kinematics and increases the forces transmitted through both native and reconstructed intra-articular structures [8]. A new study now examines how these anatomical variations specifically impact the clinical longevity and reoperation risks for patients undergoing meniscal replacement.

Long-Term Outcomes in a Young Surgical Cohort

To evaluate the impact of sagittal plane geometry on surgical longevity, the researchers conducted a retrospective review of a prospectively maintained database of patients who underwent meniscal allograft transplantation between 2003 and 2021. This longitudinal analysis focused on a relatively young and active patient population, with a mean age of 27.4 (standard deviation [SD], 9.1) years at the time of surgery. The study included a total of 175 knees in 174 patients, all of whom met the inclusion criteria of a minimum 2-year follow-up. The durability of the grafts was tracked over an extensive period, with a mean follow-up duration of 8.3 (SD, 3.8) years, providing a robust window into the long-term clinical course of these biological reconstructions. This extended follow-up is particularly relevant for practicing clinicians, as it captures the transition from early postoperative recovery to the late-stage mechanical failures that often occur in younger, more active individuals.

The primary endpoints of the study were categorized into two distinct clinical outcomes: reoperation and graft failure. Reoperation was defined as any subsequent surgical procedure performed on the index knee, while failure was strictly defined as the need for a revision meniscal allograft transplantation or conversion to total knee arthroplasty. The data revealed that reoperation occurred in 60 cases (34.3%) at a mean of 2.5 (SD, 2.8) years postoperatively. In contrast, the rate of definitive failure occurred in 8 cases (4.6%), with these events manifesting much later at a mean of 8.9 (SD, 2.9) years. These findings suggest that while more than one-third of patients may require secondary interventions relatively early (such as debridement or hardware removal), the actual loss of the graft or progression to joint replacement is a less frequent, late-stage event in this young cohort.

Quantifying the Impact of Slope on Graft Longevity

The researchers utilized multivariable regression (a statistical method that isolates the effect of one variable, like bone slope, while controlling for other factors like age or weight) to identify a clear correlation between sagittal plane anatomy and the durability of the reconstruction. Specifically, higher radiographic posterior tibial slope was associated with greater odds of reoperation (odds ratio [OR], 1.126; P = .024) and failure (OR, 1.654; P = .001). When evaluating the knee compartments individually via magnetic resonance imaging, the researchers found that higher medial posterior tibial slope was associated with greater odds of reoperation (OR, 1.166; P = .013) and failure (OR, 1.712; P < .001). Lateral anatomy also played a role in long-term survivorship, as higher lateral posterior tibial slope on magnetic resonance imaging was associated with greater odds of failure (OR, 1.279; P = .018). These findings suggest that steeper posterior inclinations increase the mechanical shear forces acting on the allograft, potentially accelerating tissue degradation or leading to secondary complications that require surgical intervention.

The clinical impact of these anatomical variations was particularly pronounced in the medial compartment. In patients who underwent medial meniscal allograft transplantation specifically, the medial posterior tibial slope was associated with higher odds of both reoperation and failure. This localized risk highlights the importance of compartment-specific anatomical assessment during preoperative planning. Despite these significant associations with surgical longevity, the study revealed a notable disconnect between joint mechanics and patient perception. There was no association between posterior tibial slope and postoperative patient-reported outcomes, which are standardized questionnaires used to quantify a patient's subjective pain and function. This lack of correlation indicates that while patients with steeper slopes may report high levels of satisfaction and functional improvement in the short term, their underlying anatomy still predisposes them to a significantly higher risk of graft failure and the need for subsequent procedures.

Discrepancies Between Radiographic and MRI Measurements

The researchers utilized two primary imaging modalities to quantify the sagittal orientation of the tibial plateau, revealing significant differences in how each tool represents the joint's anatomy. Posterior tibial slope (PTS) was measured on lateral knee radiographs, providing a global assessment of the bony inclination. To achieve compartment-specific detail, medial posterior tibial slope (MPTS) and lateral posterior tibial slope (LPTS) were measured on magnetic resonance imaging (MRI). The study reported a mean radiographic PTS of 8.8° ± 3.2°. When evaluating the individual compartments via MRI, the mean MPTS was 5.1° ± 2.7° and the mean LPTS was 5.8° ± 3.3°. These measurements are critical for clinicians to consider, as the steepness of these slopes directly influences the shear forces acting upon a meniscal allograft during weight-bearing activities.

A significant finding for surgical planning is the systematic difference between these imaging techniques. The data showed that MRI measurements significantly underestimated radiographic measurements by an average of 3.3° ± 2.9°. This discrepancy suggests that clinicians relying solely on MRI for preoperative planning may be working with a lower perceived slope than what is present on lateral radiographs. Despite this offset, both modalities demonstrated high consistency in their execution. The intraclass correlation coefficients (a statistical measure of how consistently different measurements or observers agree) for intrarater reliability ranged from 0.920 to 0.931. Furthermore, the intraclass correlation coefficients for interrater reliability ranged from 0.855 to 0.952, indicating excellent reproducibility between different clinicians and across repeated assessments. Surgeons must account for this 3.3-degree variance when interpreting MRI-based anatomical assessments to ensure accurate risk stratification for graft failure.

References

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2. Kodra JD, Serkan S, Lee MS, et al. Long-term Outcomes and Survivorship of Meniscal Allograft Transplantation: A Systematic Review With Minimum 10-Year Follow-up.. The American journal of sports medicine. 2026. doi:10.1177/03635465251405494

3. Carpenter ML, Cotter EJ, Villarreal-Espinosa JB, et al. Osteochondral Allograft Transplantation With Concomitant Meniscal Allograft Transplantation Improves Clinical Outcomes and Yields High Patient Satisfaction: A Systematic Review.. Arthroscopy : the journal of arthroscopic & related surgery : official publication of the Arthroscopy Association of North America and the International Arthroscopy Association. 2025. doi:10.1016/j.arthro.2025.01.040

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5. Yong C, Morrison L, Brunet T, Rondinelli A, Palet R, McCullen G. Defining Failure of Meniscus Allograft Transplants: A Narrative Review for Establishing Standardized Guidelines. 2025. doi:10.70709/mtjh6bobe1il

6. Haider AA, Fulkerson DE, Boghosian T, et al. Predictive Factors for Change in Patient-Reported Outcome Measures and Nonfailure Reoperations After Meniscal Allograft Transplantation: A Systematic Review and Meta-analysis.. The American journal of sports medicine. 2026. doi:10.1177/03635465251383058

7. Kunze KN, Davie RA, Ramkumar PN, Chahla J, Nwachukwu BU, Williams RJ. Risk Factors for Graft Failure After Meniscal Allograft Transplantation: A Systematic Review and Meta-analysis. Orthopaedic Journal of Sports Medicine. 2023. doi:10.1177/23259671231160296

8. Wal WAVD, Meijer DT, Hoogeslag RA, LaPrade RF. Meniscal Tears, Posterolateral and Posteromedial Corner Injuries, Increased Coronal Plane, and Increased Sagittal Plane Tibial Slope All Influence Anterior Cruciate Ligament–Related Knee Kinematics and Increase Forces on the Native and Reconstructed Anterior Cruciate Ligament: A Systematic Review of Cadaveric Studies. Arthroscopy The Journal of Arthroscopic and Related Surgery. 2021. doi:10.1016/j.arthro.2021.11.044