The first fact shown is that in fractures of the scaphoid the fragments are not to any extent deprived of a properly nourishing blood supply. In no instance was any but the very slightest amount of bone necrosis to be seen, and only such as occurs in any fracture or after trauma. The excellent injection of the vessels with ink shows a profuse and most adequate vascular network reaching all parts of the bone, despite either fracture line or drill hole. Injection also shows in the later stage of the repair reaction a much less striking hyperemia in the scaphoid than in the radius. The hyperemia in the scaphoid is limited to a rather narrow zone just adjacent to the fracture line or drill defect, with the main body of the cancellous bone exhibiting only a mild degree of increase in vascularity.
There is, of course, no periosteal callus and the cartilaginous surface heals by fibrous tissue formation which usually forms depressed line across the smooth surface but which may be excessive and spread as a pannus across the surface. Where the cortex is covered by ligamentous attachments the fibrous tissue reaction is more pronounced and there is a fibrous overgrowth. The drill defect being made through the ligamentous, rather than cartilaginous, surface shows a very marked fibrous reaction at the surface which, however, is umbilicated as a rule.
As for the repair response in the cancellous body of the scaphoid this reaction appears quite as early as in the long bones, being noticed even in the animal sacrificed in two days. The response in the scaphoid, however, is not widespread but is confined to a very small region adjacent to the traumatized area; nor is the response as active as in the long bones. Leaving out of consideration for the moment all the subperiosteal repair, the medullary response in the long bone is more active and productive than in the cancellous bone of the scaphoid, and the medullary callous tissue so formed has reached a more advanced stage of development, either into osteoid or osseous tissue, than the corresponding cancellous callus in the scaphoid. There is, however, no noticeable difference in the mode of callous formation, the cancellous callus seeming to be entirely similar in form and method of formation as in the medulla of the long bones, passing through the routine phases of blood-clot, beginning organization by invasion of thin-walled vessels, proliferation of undifferentiated fibrous tissue, proliferation of osteoblastic elements, graduate transition of fibrous into osteoid tissue, and lastly, true bony masses formed. The presence of cartilage islands in the cancellous repair is relatively common, while it is not seen in the medullary type of callus. In no case is there any evidence of synovial fluid in the fracture line or defect, and no support at all could be found for the theory of the lytic effect of the joint fluid on bone repair. In all cases approximation of the fragments of the scaphoid is so exact and close that there is little cause to believe that undue mobility of the fragments prevents or delays union. There is reason for further study to investigate the effect of separation of the fragments to see if any extensive gap could be healed, though the very complete filling up of the rather large drill defect would point to the possibility of the cancellous callus gluing up a fairly large gap.
The fact that the zone of bony repair is so limited in the scaphoid would suggest that the skeletal function of the bone is perhaps of secondary importance to its hematopoietic function and that the real tissue of importance is the marrow which the cancelli shelter, while in the shafts of the long bones the reverse is true and skeletal repair is preeminent and, therefore more active.
(C) 1927 All Rights Reserved.The Journal of Bone and Joint Surgery, Inc.