Chevron osteotomy is a commonly performed procedure for the treatment of hallux valgus and results in AVN of the first metatarsal head in up to 20% of cases. This study aims to map out the arrangement of vascular supply to the first metatarsal head and its relationship to the limbs of the chevron cuts. Ten cadaveric lower limbs were injected with an Indian ink/latex mixture and the feet dissected to evaluate the blood supply to the first metatarsal. The dissection was carried out by tracing the branches of dorsalis pedis and posterior tibial vessels. A distal chevron osteotomy through the neck of the metatarsal was mapped and the relationship of the limbs of the osteotomy to the blood vessels was recorded. The first metatarsal head was found to be supplied by branches from the first dorsal metatarsal, first plantar metatarsal and medial plantar arteries of which the first one was the dominant vessel in 8 of the specimens studied. All the vessels formed a plexus at the plantar-lateral aspect of the metatarsal neck, just proximal to the capsular attachment with varying number of branches from the plexus then entering the metatarsal head. The plantar limb of the proposed chevron cuts exited through this plexus of vessels in all specimens. Contrary to the widely held view, only minor vascular branches could be found entering the dorsal aspect of the neck. The identification of the plantar-lateral corner of the metatarsal neck as the major site of vascular ingress into the first metatarsal head suggests that constructing the chevron osteotomy with a long and thick plantar arm exiting well proximal to the capsular attachment may decrease the incidence of AVN.
We studied five cadaver shoulders to determine the strength relationship of the four rotator cuff muscles. The mean fibre length and volume of each muscle were measured, from which the physiological cross-sectional area was calculated. This value was used to estimate the force which each muscle was capable of generating. The lever arm of each muscle about the humeral head was then measured and the moment exerted was calculated. The strength ratios between the muscles were more or less constant in the five specimens. Subscapularis was the most powerful muscle and contributed 53% of the cuff moment; supraspinatus contributed 14%, infraspinatus 22% and teres minor 10%. The force-generating capacity of the subscapularis was equal to that of the other three muscles combined.
