Systematic Review and Prevalence Meta-Analysis of Quadriceps Femoris Morphology: Significance of the Quadriceps Tendon in Anterior Cruciate Ligament Reconstruction.

The quadriceps femoris (QF) muscle is traditionally described as a four-headed structure (QF4), yet recent anatomical studies have identified significant morphological variations, including accessory heads and complex quadriceps femoris tendon (QFT) layering. These anatomical differences are especially relevant when harvesting the QFT for anterior cruciate ligament (ACL) reconstruction, where graft quality and structure are critical to surgical success. This study aimed to systematically review and quantitatively synthesize available data on QF variants, with a focus on accessory heads and tendon architecture. This systematic review and meta-analysis followed PRISMA 2020 and Evidence-Based Anatomy Workgroup guidelines. Cadaveric studies reporting QF variants were identified through searches of multiple databases and anatomical journals. Pooled prevalence estimates and mean QFT lengths were calculated using random-effects models. Heterogeneity and publication bias were also assessed. Eighteen studies encompassing 1066 lower limbs met inclusion criteria. The five-headed QF (QF5) was the most common variant (54.11%), followed by the classical four-headed form (QF4) (40.74%). Rare morphologies with six to eight heads (QF6-QF8) were also documented. Among accessory heads, the vastus lateralis (VL) type was most prevalent (21.35%), while an independent tensor vastus intermedius (TVI) occurred in 13.54% of limbs. The QFT most frequently displayed a trilaminar structure (47.73%), with quadrilaminar architecture observed in 42.49%. The mean QFT length was 78.63 mm. This meta-analysis confirms that the QF often deviates from classical anatomical descriptions, frequently exhibiting supernumerary heads and multilayered tendon architecture. These findings highlight the importance of detailed preoperative imaging and personalized surgical planning to minimize complications and optimize graft selection in ACL reconstruction.