Paper 44: Greater valgus alignment predicts worse survivorship following lateral meniscal allograft transplantation

Objectives: Large pre-operative deviations in lower limb coronal alignment are thought to affect MAT survivorship by altering biomechanical load in the affected compartment. It has been theorized that increased load may impair graft re-vascularization, increasing the risk of subsequent failure.Patients who undergo MAT with significant deviations in coronal alignment are often indicated for concomitant realignment osteotomy to prevent graft failure. However, the influence of more subtle malalignment on MAT outcomes has not been described. Furthermore, the precise degree of malalignment at which an osteotomy should be considered has not been reported. The current study aims to assess the relationship between lower extremity coronal alignment and survivorship of lateral MAT in patients who did not undergo a concomitant realignment osteotomy. The hypothesis was that a greater degree of valgus alignment would be associated with an increased risk of lateral MAT failure.
Methods: Patients who underwent lateral MAT at a single institution (2011- 2024) were retrospectively reviewed. Patients were included if they had pre-operative standing long-leg radiographs and did not undergo concomitant realignment osteotomy. Hip-knee angle (HKA), percent mechanical axis deviation (PMAD), lateral distal femoral (LDFA), medial proximal tibial (MPTA), and joint line convergence (JLCA) angles were measured. More positive HKA and JLCA were defined as more valgus alignment. PMAD was determined by measuring the distance from the medial edge of the proximal tibia to the point where the mechanical axis intersected the tibial plateau and reported as a percentage of tibial plateau width, such that a larger PMAD corresponded to more valgus alignment. MAT failure was defined as any type of revision surgery on the same meniscus, unicompartmental knee arthroplasty of the same compartment, or total knee arthroplasty. Cox regression was used to obtain hazard ratios (HR) for each radiographic measure while controlling for age, sex, BMI, and graft fixation technique (suture-only, bone bridge, or bone plug). Receiver operating characteristic (ROC) analysis was performed to evaluate the ability of HKA and PMAD to discriminate between graft survival and failure. Youden's index was used to determine optimal cutoff values. Kaplan-Meier analysis and log-rank test were used to compare graft survivorship above and below ROC cutoffs. Significance was set at p < 0.05 for all analyses.
Results: A total of 52 patients (63.5% male) were included with mean age 26.0+-7.9, BMI 27.0+-5.7, and follow-up time 4.5+-3.8 years (Table 1). There were 8 failures (15.4%) with median time-to-failure of 1.7 years [IQR: 0.5 - 5.9]. Kaplan-Meier analysis yielded an estimated mean graft survival time of 9.9 years [95% CI: 8.5 - 11.2] and 2-, 5-, and 10-year graft survivorship estimates of 91.8%, 83.4%, and 73.6% respectively (Table 1) (Figure 1).Cox regression controlling for age, sex, BMI, and fixation technique demonstrated that a greater degree of valgus alignment, as measured by HKA (HR=2.065, p=0.018) and PMAD (HR=1.207, p=0.005), was positively associated with MAT failure. Conversely, increased LDFA (HR:0.539, p=0.028) was negatively associated with MAT failure. JLCA and MPTA showed no significant association with MAT failure (Table 2). ROC analysis suggested that HKA > 1.65° valgus (Area under curve [AUC]: 0.723, sensitivity: 62.5%, specificity: 79.5%) and PMAD > 6.8% lateral of center (AUC: 0.756, sensitivity: 62.5%, specificity: 84.1%) may be used as cutoffs for predicting MAT failure (Figure 3). Log-rank test confirmed worse Kaplan-Meier survivorship for patients with HKA > 1.65° valgus (64.3% vs. 84.6%; p = 0.012) and PMAD > 6.8% lateral of center (58.3% vs. 92.5%; p = 0.002) (Figure 2).
Conclusions: Even mildly increased pre-operative valgus alignment was associated with increased risk of failure following lateral MAT without concomitant realignment procedures. Specifically, every 1° increase in valgus alignment corresponded with a 106.5% increased risk of lateral MAT failure. Conversely, a more varus LDFA was found to be protective. Whereas significant valgus deformity is typically corrected with concomitant varus-producing distal femoral osteotomy (DFO), this study is the first to propose specific cutoff values for alignment with the ability to discriminate between graft survival and failure (HKA > 1.65° valgus and PMAD > 6.8% lateral of center). These findings suggest that concomitant realignment procedures may be beneficial even in patients with subtle valgus deformities who undergo lateral MAT.