Neutral to Slightly Undercorrected Mechanical Leg Alignment Provides Superior Long-Term Results in Patients Undergoing Matrix-Associated Autologous Chondrocyte Implantation

Neutral to Slightly Undercorrected Mechanical Leg Alignment Provides Superior Long-Term Results in Patients Undergoing Matrix-Associated Autologous Chondrocyte Implantation

Johannes Weishorn, MD, GERMANY Johanna Wiegand, MD, GERMANY Severin Zietzschmann, MD, GERMANY Raphael Trefzer, MD, GERMANY Kevin-Arno Koch, MD, GERMANY Tilman Walker, GERMANY

Heidelberg University Hospital, Heidelberg, Baden-Württemberg, GERMANY


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Anatomic Location

Anatomic Structure

Treatment / Technique


Summary: A differentiated approach to leg alignment with an individualized target range of 4° varus to -2.5° valgus for medial defects and -2° valgus to 0.5° varus for lateral defects results in a significantly higher likelihood of achieving a patient-acceptable symptomatic state.


Purpose

To evaluate the role of leg alignment on long-term clinical outcome after matrix-associated autologous chondrocyte implantation (M-ACI) and to define an individualized target range to optimize clinical outcome.

Methods

The present study examined patients who underwent M-ACI of the femoral condyle. The Knee Injury and Osteoarthritis Outcome Score (KOOS) and Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) was used to assess results. Clinical outcomes were related to Patient Acceptable Symptomatic State (PASS). For intra- and interobserver reliability of mTFA, mMPTA, and mLDFA, we calculated intraclass correlation coefficients (ICC) using a two-way mixed model with absolute agreement. A regression model and ROC curve were used to identify an individual range of alignment where a favorable clinical outcome could be expected in the long term.

Results

Additional osteotomy was performed in 50% of patients with similar clinical outcomes as physiologic aligned patients (p>0.05). The curve-fitting regression model identified a target range of -2.5° valgus to 4.5° varus for ideal postoperative alignment (R²=0.12, p=0.01). Patients within this range were more likely to achieve PASS (70% vs. 27%, p=0.001). In medially treated defects, a refined range of -2.5° valgus to 4° varus alignment was found (R²=0.15; p=0.01). These patients were more likely to achieve PASS (67% vs. 30%, p=0.01) and showed favorable postoperative KOOS and MOCART scores (p=0.02). Patients with lateral defects were more likely to achieve PASS within a range of -2° valgus and 0.5° varus (90% vs. 45%, p=0.03) and showed favorable postoperative KOOS and MOCART scores (p=n.s.).

Conclusions

An individual range of leg alignment - whether achieved by osteotomy or physiologic alignment - should be respected in M-ACI treatment. A neutral to slightly undercorrected alignment favors the postoperative outcome after M-ACI. When planning surgery for patients with focal cartilage defects of the femoral condyle, these ranges should be recognized as critical factors.