Discussion
impingement, deformity, knee flexion, knee joints, TKA, calculus
POSTERIOR
The most important finding of this MRI study was the sexual dimorphism of the posterior condylar offset of the femur and the medial posterior slope of the tibia in non-arthritic knees of Egyptian adults. To the best of our knowledge, no prior studies have measured the two on the Middle Eastern cohort. The current research is, in fact, a continuation of previously published work on the MRI-based anthropometric measurement of the Egyptian non-arthritic knees [Irrespective of sex, the medial offset was larger than its counterpart, a finding supported by multitude of studies [Sexual dimorphism of the offset was formerly reported by many authors. Koh et al. [Some may argue a sex-specific femoral component might not be essential as the offset may be recreated using a posterior referencing system to perform a measured resection of the posterior condyles of the femur that will preserve any difference between them [The importance an offset restoration bears on postoperative range of flexion appears controversial and depends on the type of knee replacement. Some researchers advocate the postoperative decrease in the offset by more than 3 mm reduces the postoperative ROM in Cruciate–Retaining (CR) yet not in Posterior–Stabilized (PS) knee implants. It is, therefore, critical to preserve the offset in the CR rather than in PS knees to ensure optimal ROM after surgery [Weinberg et al. [On top of that, both slopes were significantly larger in Egyptians as opposed to Caucasians [The restoration of the slope has been shown to delay the tibiofemoral impingement and thus substantially improve the range of knee flexion [Our study has certain limitations. The cohort was a single ethnic group which makes the sexual dimorphism of the offset and the slope limited to our geographic area although it may provide a background for comparison with other similar studies elsewhere. We feel more ethnicity-based research is indispensable to begin with. In addition, the measurements were performed on MRIs of non-arthritic knees. This is not a usual stance while performing TKA on arthritic knees. We nonetheless think measurements on healthy knees should act as the foundation in designing new implants for specific populations. Knowing what healthy looks like is, in a nutshell, a mandatory first step to knowledge. Surgeons should, therefore, consider the issue of extra bony cuts in cases of severe deformity during the preoperative planning. Lastly, the absence of a musculoskeletal radiologist among the coauthors might be perceived as a justly limitation. Comparing our results with those formerly reported in other studies might be criticized for being unreliable due to differences in measurement methods, types of imaging, and diverse conditions of the knee joints. Our intent here, however, was not to perform a meta-analysis, but rather to corroborate our review of the current literature with a relatively meaningful statistical calculus. Our study does merit some advantages, of course, such as a large cohort measured by two raters on the MRI as well as favorable statistical power (≥ 90%). The MRI has demonstrated superb capabilities in measuring the offset as it can appraise the thickness of the articular cartilage of merely ≈ 2.75 mm [