@solstice
I believe that these are the studies to which Dr. Neustadt refers:

1. The Cockayne Meta-Analysis (2006): Published in the Archives of Internal Medicine, this systematic review of 13 randomized controlled trials found that Vitamin K2 (MK4) reduced hip fractures by 77%, vertebral fractures by 60%, and all non-vertebral fractures by 81%.

2. The Huang Meta-Analysis (2015): This study, published in Osteoporosis International, evaluated 19 randomized controlled trials and confirmed that MK4 significantly improves lumbar spine bone mineral density and reduces fracture incidence in postmenopausal women.

3, The Ma Meta-Analysis (2022): Published in Frontiers in Public Health, this more recent review included dozens of studies and over 6,000 participants, reinforcing that MK4 effectively maintains bone strength and decreases fracture risk.

Interestingly, mk4 is used in prescription form in Japan as a treatment for osteoporosis.
The problem is that mk4 must be taken frequently while mk7 stays in the system longer and thus can be taken less often. But....there are no large scale tests that say that mk7 protects as well as mk4 in terms of fracture prevention.

Here is an educational article with some information and discussion involving Dr. Neustadt: https://www.nbihealth.com/mk4-or-mk7-which-is-better-for-bones/

His own specialized bone health supplements, such as NBI Osteo-K, are designed for this frequent schedule needed with mk4, with 2 capsules taken three times a day to reach the full 45 mg dose needed for mk4.

I know a well known strontium citrate user who has said that if for any reason she could not take strontium citrate that she would switch to using MK4. Mk4 and mk7 are easily found as supplements.

Posting which I have on this topic:
https://www.inspire.com/m/Kathleen1314/journal/7c2651-mk4-and-mk7-research-and-studies-affecting-bone-health-vitamin-k/