Bone grafting for reconstructive osteotomies of the foot

Mechanical Stress Redistribution in the First Metatarsal Bone After Autologous Bone Harvesting

BACKGROUND

The first metatarsal bone is a viable source for autologous bone grafting in foot and ankle surgery and may serve as another convenient graft site to correct a flail toe deformity. We aimed to determine how progressive bone removal from the first metatarsal affects the mechanical redistribution of the foot and whether this bone removal increases the risk of fracture.

METHODS

A three-dimensional finite element model developed from computed tomographic images obtained from a healthy man were used to evaluate traction stresses on the first metatarsal bone as a function of applied loads on the talus and Achilles tendon at two phases of the gait cycle (and according to the depth of bone removal).

RESULTS

Simulations indicated that when maximum load was applied to the Achilles tendon, tensile stress increased from 2.049 MPa in the intact foot to 5.941 MPa in the area of maximum bone harvest during the stance phase. Furthermore, as the volume of bone extracted from the first metatarsal increased, there was a redistribution of stress that differed significantly from that of the intact foot.

CONCLUSIONS

Although the maximum stress on the first metatarsal was not significantly affected by increasing the volume of bone harvested, the ankle should be splinted in plantarflexion during the postoperative period to eliminate the stance phase of gait and reduce the risk of metatarsal fracture.

What leads to failure of joint-preserving surgery for ankle osteoarthritis?: when this surgery fails, what next?

This article discusses the lack of scientific evidence regarding the treatment of failed joint-preserving surgery. Most of the concepts of treatment derive from treatment modalities in trauma and orthopedic surgery. The main question for the foot and ankle specialist is whether the joint can be salvaged. The definition of failure is difficult. Therefore pain reported by the patient is the main symptom that dictates the course of treatment. Whenever possible the joint should be maintained. However, if pain is associated with global radiographic osteoarthritis, total ankle replacement or fusions are the only means to solve the problem.

Case report: a modified 1-stage technique for the treatment of brachymetatarsia

Brachymetatarsia is an abnormal shortening of a metatarsal. It causes disruption of the normal metatarsal parabola, resulting in metatarsalgia, calluses and dislocation of the digits. Patients often express discontent with the appearance of their feet. Lengthening by distraction osteogenesis and 1-stage intercalary bone grafting procedures are the mainstays of operative treatment. We present a modified 1-stage technique, combining the use of a Chevron osteotomy of the fourth metatarsal with shortening osteotomies of the second and third metatarsals. Bone removed from the third metatarsal was used to lengthen the fourth. The Chevron segments provided mediolateral, dorsoplantar, and rotational stability. The technique was used on both feet of 1 patient. The mean increase in AOFAS score was 34.5 (right foot, 46; left foot, 23.) There were no complications. A 1-stage technique does not require an external fixator or postoperative manipulation and has a quicker healing time. Taking the bone graft from neighboring metatarsals decreases the discrepancy between metatarsal lengths. A smaller increase in the length of the fourth ray is then required, and the chance of neurovascular injury as a result of soft-tissue stretching is minimized. This technique allows restoration of the metatarsal parabola and provides good correction, immediate stability, and good integration.

LEVELS OF EVIDENCE

Therapeutic Level IV, Case Study.

Mechanical stress redistribution in the calcaneus after autologous bone harvesting

The calcaneus is a desirable site for harvesting autologous bone for use in foot surgery. However, fracture of the calcaneus is a serious complication associated with bone harvesting from this site. Currently it is unknown how much bone may be safely harvested from the calcaneus without inducing a fracture. The purpose of this study was to investigate the effect of progressive bone removal from the calcaneus onto the mechanical stress redistribution of the foot, and therefore on the increase in fracture risk. Different loads were applied on the talus to evaluate the calcaneus stress distribution at different situations. Because of the potential increase in mechanical stress in the calcaneus, secondary to contraction of the Achilles tendon, we also evaluated the mechanical behavior properties of the foot with increasing traction force in the Achilles tendon. A three-dimensional (3D) finite element (FE) model developed from CT images obtained from a healthy individual was used to compute displacement, tension and compression stresses in six situations, including intact foot, and five depth of the bone block removed, with a maximum depth of 7.5 mm. The results from these simulations indicated that when the maximum load was applied at the Achilles tendon, the tension stress increased from 42.16 MPa in the intact foot to 86.28 MPa with maximum bone harvesting. Furthermore, as the volume of bone extracted from the calcaneus increases, there is a redistribution of stresses that differs significantly from the intact foot. In fact, although the maximum stress was not significantly affected by increasing the volume of bone harvested-except when increasing the Achilles tendon force-, stresses did increase in areas of the calcaneus is vulnerable to injury, leading to an increase in fracture risk.

Tricortical calcaneal bone graft and management of the donor site

The clinical outcomes of 19 patients requiring autogenous grafts for foot surgery were followed up until healing at the donor site occurred. In all cases, tricortical bone was extracted from the calcaneus for use at another pedal site. The first cohort of 9 patients had the calcaneal deficit replaced with allogenic cubes. The second cohort received no tissue replacement. Patients were reviewed postoperatively with a questionnaire and clinical examination to evaluate the outcome of the operations. Radiographic outcomes were observed at the donor and recipient sites in both groups until healing was confirmed as bridging trabeculation. Incorporation of the graft at the donor site was also reviewed. Clinical outcomes, namely pain, local sensory function, and return to footwear, were satisfactory in all patients and were not significantly different between groups. One patient from each group sustained a heel fracture. The donated autogenous grafts at the recipient sites were all incorporated uneventfully at 6 months. In the first cohort, allogenic graft incorporation in the calcaneus was complete in only 2 patients at the 12-month stage. The remaining 7 cases showed reduction of the deficit by new bone formation arising from the calcaneus. Donor sites with allogenic bone replacement healed at a median of 18 months (interquartile range, 18-18 months). In the group without replacement, healing occurred at a median of 6 months (interquartile range, 6-12 months), a highly statistically significant difference (P < .001). In the second cohort without allogenic graft replacement, radiographic filling at the donor site was complete within a 12-month period. Tricortical bone can be successfully harvested from the calcaneus, but there may an associated risk of heel fracture. The role of replacement allogenic bone in assisting healing at the donor site is unclear.

The severe flexible flatfoot: a combined reconstructive procedure with rerouting of the tibialis anterior tendon

A combined procedure is described that addresses all the components at fault in the severely flexible flatfoot deformity in children. The Evans calcaneal distraction wedge osteotomy will lengthen the lateral column, correcting the heel valgus and forefoot abduction. A naviculo--first cuneiform wedge resection (medial and plantar) and fusion will shorten and reshape the collapsed medial arch. This is augmented by reconstruction and plication of the lengthened plantar ligaments, with plantar rerouting of the tibialis anterior tendon to act as a strong plantar ligament. In addition, shifting the tibialis anterior's pull proximally acts as a sling to the talar head. Z plasty of the tight tendo Achillis is always needed. Nineteen feet in 11 patients were the subject of this study. The period of follow-up ranged from 8 to 42 months. The results were assessed according to the relief of foot strain and calf pains, improvement in shoewear, general activity, and foot shape. To evaluate foot shape, reconstruction of the medial arch and heel posture were assessed. The children and parents were satisfied with the final results in 17 feet (89.5%). Improvement of the radiological measurements was evident and was statistically significant.