Screw fixation compared to H-locking plate fixation for first metatarsocuneiform arthrodesis: a biomechanical study

Arthrodesis of the first metatarsocuneiform joint: a comparative cadaveric study of external and internal fixation

Arthrodesis of the first metatarsocuneiform joint for the treatment of severe hallux abductovalgus with or without hypermobility of the first ray has gained popularity in recent years. The purpose of the current study was to compare the strength of external fixation to internal fixation for arthrodesis of the first metatarsocuneiform joint in a cadaveric model. Ten pairs of fresh frozen lower extremity cadaver specimens were used, and randomly assigned to fixation at the first metatarsocuneiform joint with crossed cannulated screws or a monorail uniplanar external fixator. Test specimens were then loaded to failure, which was defined as 3 mm or more of displacement at the arthrodesis site. Because of complications encountered during testing, 4 pairs of specimens were excluded from the final results. In the remaining 12 specimens (6 pairs of cadaver limbs), the mean maximal load to failure was 2300.02 +/- 711.86 N for the external fixator and 1666.38 +/- 1072.75 N for the internal fixation construct, and although this difference was not statistically significant (P = .2557), it was likely to have been clinically significant since approximately 27.55% more force was required to disrupt the external fixation construct in comparison with the internal fixation construct. Given these findings, further research into the mechanical and clinical properties of internal and external fixation for first metatarsocuneiform joint arthrodesis is warranted.

LEVEL OF CLINICAL EVIDENCE

5.

Crossed screws versus dorsomedial locking plate with compression screw for first metatarsocuneiform arthrodesis: a cadaver study

BACKGROUND

We hypothesized that a dorsomedial locking plate with adjunct screw compression would provide superior rigidity compared to crossed screws for first metatarsocuneiform (MTC) arthrodesis.

MATERIALS AND METHODS

In ten matched lower extremity pairs, specimens in each pair were randomly assigned to receive screw fixation or plate with screw fixation. Bone mineral density (BMD) was measured. For the crossed-screw construct, two 4.0-mm cannulated screws were used. One screw was inserted dorsal to plantar beginning from the first metatarsal 10 to 15 mm distal to the joint, and the second was inserted from the cuneiform 8 to10 mm proximal to the joint, medial to the first screw, into the first metatarsal. For the plate construct, a 4.0-mm cannulated compression screw was inserted from the dorsal cortex of the first metatarsal to the plantar aspect of the medial cuneiform. A locking plate was inserted dorsomedially across the MTC joint. Specimens were loaded in four-point bend configuration (displacement rate, 5 mm/min) until failure of the fixation or 3-mm deformation. An extensometer was used to measure deformation.

RESULTS

There was no difference in load to failure or stiffness between the two groups. BMD was positively correlated with load to failure in the screw (r = 0.893, p = 0.001) and the plate (r = 0.858, p = 0.001) construct.

CONCLUSION

The plate construct with compression screw did not show different rigidity as compared with the screw construct with the numbers available.

CLINICAL RELEVANCE

Further investigation of a dorsomedial plate with adjunct screw compression may be warranted for first MTC arthrodesis.

Bunion surgery using locking-plate fixation of proximal metatarsal chevron osteotomies

BACKGROUND

Symptomatic large hallux valgus deformities commonly require surgical intervention with a proximal metatarsal osteotomy. A number of fixation methods have been described for proximal chevron osteotomies; one of the most recent is locking plates.

METHODS

We retrospectively reviewed the records of 16 consecutive patients (20 feet) with severe bunion deformities who had locking-plate fixation of proximal chevron osteotomies. Clinical evaluation focused on osteotomy healing, transfer lesions, and hardware-related complications. Preoperative and postoperative radiographic evaluation included the hallux valgus angle (HVA), 1-2 intermetatarsal angle (IMA), medial 1-2 intermetatarsal distance (MIMD; the amount of narrowing of the foot), sesamoid position, first metatarsal elevation, and metatarsal length change. A postoperative American Orthopaedic Foot and Ankle Society (AOFAS) score was obtained in all patients.

RESULTS

The average radiographic improvements were HVA, 16.0 degrees, IMA, 7.6 degrees, and MIMD, 9.0 mm. Sesamoid position improved in 16 of 20 feet. First metatarsal elevation averaged 0.8 degrees, and the average metatarsal shortening was less than 1 mm. The AOFAS score averaged 94.1 points. Two complications were unrelated to plate fixation.

CONCLUSIONS

The locking plate held alignment and position of the first ray after chevron osteotomy without clinical evidence of transfer lesions or hardware-related symptoms. Locking plates may improve stability of the proximal metatarsal after a chevron osteotomy for correction of hallux valgus.