After surgery to repair a bunion deformity of the foot, X-rays taken immediately after the procedure can predict the risk that the bunion will return over time.
Bunions — also known by the medical name hallux valgus — are a bony deformity of the joint at the base of the big toe. They appear as a bump on the side of the foot, caused by misalignment of the big toe and the long bone (first metatarsal bone) connecting it to the ankle. When bunions cause significant pain and discomfort or interfere with walking, surgery can be performed to realign the bones.
However, for many patients, bunions gradually return after surgery. Previous studies have suggests recurrence rates of up to 25%.
South Korean investigators Dr Chul Hyun Park, of Yeungnam University Medical Center, and Dr Woo-Chun Lee, of Injie University Seoul Paik Hospital, wanted to find out whether measurements made on routine non-weight-bearing X-rays after surgery could predict the risk of recurrence in the months after the procedure.
The study included 93 patients who had bunion surgery on a total of 117 feet.
The researchers analysed changes in the hallux valgus angle, the intermetatarsal angle and sesamoid position over time. From this, they determined the relative risks of recurrence.
At an average follow-up of two years, the bunion recurrence rate was 17%. Recurrence was defined as a hallux valgus angle (HVA) — the angle formed by the toe bone and first metatarsal bone — of 20 degrees or more.
Results showed that patients with larger preoperative and postoperative HVAs were at higher risk of recurrence. Bunions were 28 times more likely to recur when the postoperative HVA was eight degrees or larger than when the HVA was less than eight degrees. The HVA continued to widen over time in patients with recurrent bunions, but stabilised at six months in those without recurrence.
Other factors associated with increased recurrence risk included severe bunions with a preoperative HVA of 40 degrees or larger and the position of a pair of small bones (sesamoids) under the joint on postoperative X-rays.
If future studies confirm their results, the researchers believe that X-rays taken during surgery might help develop guidelines for “satisfactory correction” of bunions — in particular, ensuring that surgery corrects the HVA to eight degrees or less.
The findings have been published in the Journal of Bone & Joint Surgery.