Determination of the intermetatarsal angle reduction following metatarsal head osteotomies

Preliminary Experience With a Minimally Invasive Technique for Hallux Valgus Correction With No Fixation

BACKGROUND

Percutaneous operative techniques for hallux valgus (HV) correction are less damaging to soft tissues and the first metatarsophalangeal joint, and they carry a lower risk of wound complications. We report our preliminary results using a percutaneous technique that allowed correction of the deformity without internal fixation.

METHODS

One hundred ninety-five consecutive patients with isolated symptomatic HV were surgically treated using a percutaneous technique without any form of internal fixation, with a mean follow-up of 34.6 months. The American Orthopaedic Foot & Ankle Society (AOFAS) hallux-metatarsophalangeal-interphalangeal scale score was used for clinical assessment. Radiographic evaluation included pre- and postoperative assessment of the hallux valgus angle (HVA), intermetatarsal angle (IMA), distal metatarsal articular angle (DMAA), and sesamoid position in weightbearing radiographs.

RESULTS

According to the AOFAS score, the patients improved from a preoperative median of 54.7 to 89.6 at 2 years' follow-up (P = .002). Patients were satisfied or very satisfied in 94% of cases at the latest follow-up. A mean radiographic correction of the HVA of 15.5 degrees, of the IMA of 5.4 degrees, and of the DMAA of 5.4 degrees was achieved. The AOFAS global score and every individual parameter improved significantly between pretreatment and latest follow-up (P > .01). A total of 19 (9.7%) complications were reported.

CONCLUSION

This percutaneous technique, which did not use any form of internal fixation described, produced durable results for the correction of HV, reliably correcting the deformity and resulting in significant improvement in function and decrease of pain.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Mathematical model for pre-operative planning of linear and closing-wedge metatarsal osteotomies for the correction of hallux valgus

First-metatarsal osteotomy is performed for an abnormal intermetatarsal angle and severe hallux valgus deformity. The metatarsal head is slid along the osteotomy and fixed with a Kirschner wire to achieve angular and linear realignment with respect to the other metatarsals. When reduction of joint subluxation is also sought, a bone wedge is removed. A mathematical model and a corresponding computer-based tool were developed for pre-operative planning of the optimum surgical solution. Standard intermetatarsal angle correction, head-to-sesamoids re-alignment, joint subluxation reduction and metatarsal length adjustment were all pursued. A standard pre-surgical dorso-plantar radiograph of the patient, with an additional metal ball for calculation of X-ray magnification, was necessary to analyse the original and final geometrical configurations. For the first time, expected bone loss and wire diameter were also considered. The angles of bone cuts and the amount of sliding along these cuts were calculated by the model according to the surgical goal. All the resulting geometrical parameters, both in the pre- and planned post- operative configuration, were provided in graphical and tabular form. In a change from former qualitative analysis of radiograms, the surgeon can now enter the operating theatre with a detailed plan of the goal to be achieved.

Mathematical analysis of first metatarsal osteotomies

The mathematical analysis of most first metatarsal osteotomy corrections for metatarsus primus varus is presented and interpreted with respect to metatarsal lengthening or shortening and changes in clinical reference angles (e.g., intermetatarsal or angle of declination). The critical parameters for each osteotomy such as location and angles of cuts and amount of displacement are defined and their theoretical effects on the final correction determined. Although exactitude in surgical methodology and an absolute prediction of final clinical results are impossible at the present time, even guidelines as to the potential effectiveness of various surgical techniques and quantitative methods for subsequent evaluation are lacking. This mathematical analysis can provide guidelines for prospective choices and a basis for retrospective interpretation as well as represent a critical component for biomechanical calculations.