To the best of our knowledge, our report is the first in which intramedullary screw fixation with routine bone autografting was performed during the primary surgery. Although the current gold standard for treatment is intramedullary screw fixation, delayed unions and refractures with this procedure are not uncommon [5, 7, 8, 11, 12]. Bone autografiting could solve the problem because it is osteoconductive, osteoinductive, and provides osteogenic cells [13, 14].
The intramedullary screw fixation without bone grafting had the advantage of early return-to-play. In the previous literature, mean time to return-to play was reported 7.5 to 8.5 weeks [4, 15, 16]. Although positive outcomes have been reported, considerable frequency of complications have been reported [5, 13]. Larson et al. reported 40 percent of failure rate in the procedure, and especially a higher proportion of elite athletes had high incidence of failure .
The poor blood supply to the metaphyseal region of the proximal fifth metatarsal is considered the factor to lead to a deficiency in fracture healing factors [17, 18]. This insufficiency in biology may be indirectly addressed by the application of bone autografting . Hunt and Anderson used bone grafts in combination with insertion of a screw with the greatest possible diameter in 15 revision surgeries and six primary surgeries of nonunion or refracture . They reported that all patients returned to competition, but the mean time of return-to-play was 12.3 weeks. The period of non weight-bearing and immobilization of the affected area tends to be longer than in other reports due to the bone autografting. However, we believe that bone autografting is an effective option to obtain the secure bone union in the surgical treatment of proximal fifth metatarsal metaphyseal-diaphyseal fracture.
Although several authors considered that routine bone autografting to the fracture site was not necessary, especially in acute fracture according to classification of Torg et al. [15, 20], we performed routine bone autografting for all fracture types. Glasgow et al. reported 11 patients with failure of surgically managed fractures, and six of 11 patients were acute fracture . Wright et al. analyzed six patients with treatment failure. In the study, all patients had acute fracture at the time of primary surgery . We considered that delayed unions and nonunions often occur in acute fracture according to classification of Torg et al. as well as delayed union or nonunion according to Torg’s classification. Thus, we consider that routine bone grafting for all fracture types is effective.
In the present study, while delayed unions or nonunions were not observed, some patients experienced stress fractures at the screw tips and thermal necrosis of skin due to reaming heat. In both patients developed a stress fracture at the screw tips, the screw tip was in contact with the dorsal bone cortex. In one patient, the dorsal convex curvature was large, and the screw tips inevitably contacted the dorsal bone cortex in order to ensure that the screw threads completely crossed the fracture site. In such situations, it is important to insert the screw so that aligns as closely as possible with the bone axis to avoid excessive stress on the dorsal bone cortex side. One solution is to place the screw insertion point at a sufficiently dorsal position, and to insert the screw toward the sole side. However, given that the screw head is positioned dorsally in this procedure, for a soccer player, pain may appear in the area when kicking. Hence, it is necessary to countersink the screw head sufficiently. Preoperative evaluation of the morphology of metatarsals is crucial. When stress fracture at screw tip occurs, replacing the screw contacting with cortex is a foundational rule of treatment. In the present study, however, the screw tip stress fracture unioned without screw replacing in one patient. If the patient could continue playing with shoe insole, we might treat stress fracture conservatively. But, in the case which patients feel pain, there must be no wavering of replacing screw because the stress fracture has the potential to develop complete fracture.
Pre-drilling is required when inserting the cancellous screw and this can lead to thermal necrosis. Heat generated when drilling hard sclerotic bone or from friction between the bent guide pin and the drill is a likely cause. We have been cooling the skin with cold water during drilling ever since this patient, and have not observed skin burns thereafter. Recently, we consider releasing the pneumatic tourniquet effective for preventing thermal necrosis, and routinely release the pneumatic tourniquet before reaming. Blood flow is poor for the skin around the metatarsals. Once a thermal necrosis occurs, it may require a prolonged healing period.
There were several limitations in this study. There is no comparison group and the study sample was relatively small. Another limitation is that the follow-up period is less than two years in two patients. Although most refractures were diagnosed within one year after surgery in previous studies [11, 21], refractures could occur at any time. The short follow-up period is an important limitation of this study. Finally, two different fracture locations were analyzed in combination. Although several authors reported the proximal diaphyseal fifth metatarasal fracture is more difficult to obtain satisfactory outcomes than Jones fracture [1, 22], the largest study in comparison between two fracture locations revealed no difference in clinical and radiographic outcomes . We also consider that the treatment of Jones fracture is challenging as well as proximal diaphyseal fifth metatarsal fracture. Acknowledging these weaknesses, we believe that this series contributes valuable information for surgical treatment of challenging proximal fifth metatarasal metaphyseal-diaphyseal fracture because of the encouraging outcome.
We have reported the outcomes of intramedullary screw fixation combined with bone autografting. Consistent with our aims, the results suggest that the procedure is useful for preventing delayed unions and refractures. However, caution is required as we have experienced other complications.