Proximal pole fractures of the scaphoid have a high incidence of nonunion and avascular necrosis. Because of their poor prognosis, the treatment of these fractures remains controversial. Fracture preparation and bone grafting were kept to a minimum, in order to preserve as much bone stock as possible, and to avoid damage to the already compromised vascularity of the proximal fragment. No postoperative splinting was used and most patients were able to return to their normal work within a few weeks of surgery.
Union was often slow 3 to 36 months and appeared to be related to the vascularity of the bone fragments. However, even when bone union was incomplete, the fracture remained stable, with no loss of fixation. The ten patients with unsatisfactory results had all developed late avascular necrosis of the proximal pole, requiring salvage surgery.
Stable internal fixation of proximal pole nonunion leads to rapid symptomatic improvement in the majority of cases and sets the scene for revascularisation and healing.
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With more than twice the patients than the femoral flap group it gives greater statistical reliability but the large number of complications either compromises the outcome or increases the need for reoperations. Someone could say that this finding is expected. On the one hand, the far larger number of hand surgery teams that used this flap makes the results more reproducible.
Sometimes by experimenting on the various parameters, like the method of internal fixation or by extending the flap's range of indications, the results are not good. For example, Straw et al. The best ROM improvement calculated for the group of the various dorsal radius flaps. They concluded that the flap itself does not play a role in postoperative wrist motion. From these aforesaid factors, the first two are unpredictable and can depend on the surgical technique and the individual biological reactions to the trauma for each patient.
From the other two, immobilization time did not vary significantly among groups and postoperative rehabilitation was seldom described. Therefore, it is rather difficult to come up with a conclusion that a flap is superior over the others in respect to the ROM. Regarding the fate of the nonunion when a VBF is used on a smoker, there were very few articles that reported consolidation rate for the smokers individually. So, we could not produce a percentage of success for all types of flaps, and the results we found cannot export safe conclusions because of the small number of patients and the inability to reach statistical significance in the majority of them.
But when we compared the healing rate between smokers and nonsmokers the result was undoubtedly in favor of nonsmokers. This conclusion agrees with other publications that state the negative effect of smoking in the healing process, either of soft tissues or of fracture consolidation. From the calculations that have to do with collapse or instability of scaphoid and how the various flaps deal with this fact, we found some very interesting results. These results come in full accordance with the opinion expressed by many authors, that the dorsal radius flaps are not the best choice for correcting a humpback deformity of the scaphoid, independent of whether or not the proximal pole is avascular.
On the contrary, for waist nonunions especially with associated humpback deformity, they suggest either volar radius flaps or free VBFs, 8 because they are better shaped to fit volarly and manage to restore the structure as close to normal as possible. The reason for the inappropriateness of the dorsal flaps is that when one places them volarly, he risks kinking of the pedicle. Payatakes correctly attributes some failures of Chang et al.
Our analysis showed a positive correlation for the PQ and iliac flap but strangely not for the palmar radius and free femoral flap, something that would be totally anticipated according to the above. Despite the fact that one of the indications for the use of a VBF is the presence of scaphoid proximal pole AVN, we found in our computations that these flaps are not panacea for these patients in all cases. Additionally, a negative correlation was found between the union rate and presence of proximal pole AVN in the iliac, dorsal radius, and palmar radius flap groups.
That is also reported by other authors 44 - 46 who did not have the results that they had expected on their patients with PP AVN. From the correlation of the healing rate with various parameters like time up until operation and mean age, in Table 7 , we can derive few conclusions, and some results are difficult to interpret.
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About time passed between injury and operation, in almost all flaps it is clear that the more prolonged this parameter is, the lower the healing rate. The only type of flap that had a positive correlation between duration of nonunion before operative treatment and union rate was the iliac flap. We could say the same about the postoperative immobilization period, even though in palmar radius group we found a positive correlation. In a lot of articles, the immobilizing cast was removed when there was radiological evidence of union.
That fact would give a false, but strong positive correlation between these two parameters. That is the reason why we consider that this correlation is not reliable. Regarding the mean age of the patients in each group, we found that in four groups the older the patients the lower the success rate, but in two other groups the opposite is valid. That finding agrees with what Merell et al.
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For the rest of the correlations in Table 8 the results were variable and we could not reach firm conclusions. There was an inconsistency in reporting results throughout the literature. For example, we could not reach a statistical significant result analyzing the radiologic parameters because these variables were reported only in a minority of the articles.
Proximal Scaphoid Nonunion-Osteosynthesis
In some of the flap groups they were actually totally missing, so no comparison between them was feasible. Another reason was that in a number of articles these values were reported in absolute degrees and in others as a percentage of change, so not having the preoperative values, we could not make a comparison. That has also occurred with other variables. A prospective study with normalized groups of patients that would also scholarly report all the information regarding the scaphoid nonunion, would help clarify in a more appropriate way both the relevant supremacy of the VBFs from one another and possibly the advantage of each in particular indications.
When a flap has been used by few authors or worst only by one, then the results are possibly not reproducible. There is the possibility that in their hands the results with the graft were optimal but they are not reliable even if the number of treated patients is large. Statistically they are not equally reliable to other flapgroup's results with the same number of patients but presented by multiple authors. We tried to quantify some of the indications and conclusions that were made by other authors and to upset various fallacious deductions.
The initial quiver of VBFs was enriched throughout the years and now the hand surgeon has a wide range of choices. However, there are other flaps equally promising like the femoral flap, which proved to be the most potent, despite its complexity. In any case, further analysis should be conducted to determine the most suitable model of treatment for each patient with scaphoid nonunion. Konstantinos Ditsios and Professor Anastasios Christodoulou were responsible for the supervision of the entire study.
Especially Dr. Ditsios contributed with his knowledge and experience as a specialized hand surgeon. Ioannis Konstantinidis collected the data, analyzed them, and wrote the paper. That study reports about torque resistance of several screws in relation to each other, no considerations can be drawn on absolute torque values of ex or in vivo specimens.
This assessment in the lower torque range up to mNm Fig 6 is particularly necessary since no in vivo data on actual loads are available, and precise measurements in vivo do not appear technically solvable thus far. Recording implant-specific, torque-dependent clearance of the fragments in rotational twist-out direction with consideration of the number of early failures particularly reflects the screw-specific quality and reliability of the osteosynthesis.
In fact, it was possible to stress a large share of the osteosyntheses in the range of up to mNm torque with a low failure rate. However, loads of up to mNm then resulted in clearly visible differences in the stabilization capacity of the various screw types, wherein the BSS long. Due to its construction which is uncoupled from the rotating shaft, the screw base, which rotates freely apart from a small amount of residual friction, prevents rotational instability in the twist-out direction by enlargement of the osteotomy gap , therefore the scaphoid bone fragments consequently remain in contact and continue to maintain friction between the fragments.
Distancing of the fragments which is linked to displacement in the twist-out direction and therefore loosening of the screw-fragment connection is expected in all screw models wherein the screw body is rigid within itself. It is likely that this particularly affects the stabilization properties of the HCS screw, which, due to its uniform thread gradient, transforms twist-out movements into enlargements of the osteotomy gap. In contrast to screws with a single, rigid screw body and variable pitches, the compression force is almost solely determined by the construction attributes of the screw itself as well as the bone density.
The surgeon may influence the compression force only by the grade of initial fragment reduction and deeper insertion. Since a frictional connection is given only in the screw tip and head areas in central threadless shaft screws, screws with continuous thread were conceived, with the objective of a better development and consistency of the compression and pull out force within the bone [ 11 ].
The progressively changing gradient between the continuous threads causes the screw to clamp and dowel itself within the porous cancellous bone. If this clamping effect decreases due to rotation in the twist-out direction, the osteosynthesis promptly loses rotational stability. Certain properties which apply to all compression screw osteosyntheses, such as the time-dependent reduction of compression force and thereby the loss of interfragmentary friction adhesion in vitro human bone [ 11 , 19 ], as well as the inability of all conventional screws not to prevent rotational movement when friction adhesion is exceeded, led us to develop compression screws with additional construction elements to stabilize the scaphoid synthesis against torsion load.
Both BSS were developed in order to block both fragments against rotation by a second screw which protrudes from the cross-section of the compression screw without significantly enlarging the dimensions of the standard headless screws used in the test. In the BSS long. BSS obl. Plastic deformation of both screw elements of the BSS obl. The stability of the BSS long. We could not observe plastic deformation of the BSS long.
As the study is limited to in vitro manipulation measurements we cannot fully expect compatibility of the set-up to the in vivo situation. As no systemic reaction and healing processes can be mimicked, we can only to some extent rely on simulating the acute osteosynthesis condition and early biomechanical conditions. The scaphoid specimens are limited to aged bones, as cadaver bodies for anatomical research are usually not available from younger donors.
Apart from the rotational direction of scaphoid fragments in scaphoid non unions [ 26 ] no in vivo data on the extent of interfragment rotation and on acting forces in vivo situations are described in literature and those will be very difficult to obtain in relevant quality. Concerning acting torque along wrist movements we were forced to rely on published modeling data [ 9 ] for a rough estimate. There is no direct proof from clinical studies or even animal studies if and to what extent interfragmentary rotation influences bone healing or failure of bone healing [ 5 , 27 ].
Related proximal scaphoid nonunion-osteosynthesis
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