Posteromedial vertical capsulotomy selectively increases the extension gap in posterior stabilized total knee arthroplasty

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.

The development of the endothelin-1-induced gastric ulcer: time sequence analysis of morphologic changes

We have recently reported that the submucosal injection of endothelin-1 induces gastric ulcers in rats. In the present study, we have examined the time sequence of the macroscopic, histologic and ultramicroscopic features of the formation and development of the gastric ulcer induced by endothelin-1 (100 pmol submucosally). In rats, we examined the effect of endothelin-1 on the gastric mucosa macroscopically, on the gastric mucosal cells and vessels by light microscopy and on the ultra-structure of the gastric mucosal surface and of the gastric glands by electron microscopy. Gastric mucosal changes were evaluated 1, 4, 30 minutes, 1, 4, 8, 16, 20, 24 hours and 2, 4, 7, 14, 21 days after teh submucosal injection of endothelin-1. Application of endothelin-1 was immediately followed by arterial vasoconstriction and venous dilatation, 5 minutes later by interstitial haemorrhage and 30 minutes later by demise of epithelial cells. Electron microscopy showed almost complete exfoliation of the inter-pit cells 30 minutes after the injection. By 1 hour, superficial redness, apoptosis of superficial cells and loss of the intra-pit cells was detected. By 8 hours, there was mucosal haemorrhage and complete loss of intra-pit cells from the basal part of the gastric glands. Forty-eight hours later, there was a deep gastric ulcer with penetration of the muscularis mucosae. By 4 days, the ulcers had entered the chronic phase and by 1 week abnormal glands were covering the area of damage with no mucous production. By 3 weeks the damaged area was still structurally abnormal. The results of this study suggest that injury to the microvasculature may initiate the degenerative and structural changes of the gastric mucosa that lead to the production of this novel type of experimental gastric ulcer in rats.