PURPOSE In total knee arthroplasty (TKA), it is important to obtain an appropriate flexion-extension gap. The extension gap is expanded by posteromedial vertical capsulotomy (PMVC). This study aimed to evaluate the increase in the extension gap by PMVC using a navigation system. METHODS In posterior stabilized (PS)-type TKA, PMVC was performed in 37 knees. The medial extension gap at 0° and flexion gap at 90° flexion of the knee joint using the navigation system before and after PMVC were measured. RESULTS The extension gap before the PMVC was 5.3 ± 2.9 mm. After PMVC, the extension gap had significantly increased to 8.0 ± 2.8 mm (p < 0.001). In addition, the flexion gap was 8.1 ± 2.7 mm before the PMVC, but it was 8.7 ± 2.8 mm after the PMVC, and the flexion gap was not enlarged (n.s.). CONCLUSION In PS-type TKA, it is possible to obtain selective expansion of about 2.7 mm of the extension gap by PMVC. Therefore, gap balance can be acquired by soft-tissue treatment while preserving the bone. The PMVC was a useful method for acquiring gap balance and preserving the bone stock. LEVEL OF EVIDENCE IV.

中文翻译：

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后内侧垂直囊切开术选择性地增加了后稳定全膝关节置换术中的延伸间隙。

目的在全膝关节置换术（TKA）中，重要的是要获得适当的屈伸间隙。通过后内侧垂直囊切开术（PMVC）扩大了延伸间隙。这项研究旨在评估使用导航系统的PMVC对延伸间隙的增加。方法在后稳定（PS）型TKA中，在37膝中进行PMVC。在PMVC之前和之后，使用导航系统测量了膝关节在0°时的内侧延伸间隙和在90°时屈曲的90度屈曲间隙。结果PMVC前的延伸间隙为5.3±2.9 mm。PMVC后，延伸间隙已明显增加到8.0±2.8 mm（p <0.001）。另外，屈曲间隙在PMVC之前为8.1±2.7 mm，但在PMVC曲折之后为8.7±2.8 mm，屈曲间隙没有扩大（ns）。结论在PS型TKA中，通过PMVC可以获得约2.7毫米的延伸间隙选择性膨胀。因此，可以在保留骨骼的同时通过软组织治疗获得间隙平衡。PMVC是获得间隙平衡和保留骨储备的有用方法。证据级别IV。