Risk factors for non union 1st MTPJ fusion with the use of a Dorsal Plate A. Kaye, G. Williams, A.P. Mollloy, C. Butcher, L.W. Mason University Hospital Aintree Liverpool

Introduction Common problem Common operation Typical union rates around 90%+ Minimal literature defining risk factors for non-union AIM: retrospective analysis of risk factors for delayed / non-union 1 in 40 over the age of 50 years

Methods Operations between April 2014 to April 2016 At least 6 months post-operative follow up Union = bridging bone on two radiographic views with no movement or pain on examination. Any doubt  CT confirmed Operations performed / supervised by three senior foot surgeons Dorsal approach using the Stryker Anchorage CP plate with dorsal to plantar compression screw through plate

Operative technique

Methods & Demographic 71 1st MTPJ attempted fusions in 62 patients Average follow-up 13 months (range, 6-30 months) Mean age of 61 years (range, 29-81 years) 9 male and 62 females Analysis of any risk factors associated with delayed union

Results Non union in 7 patients (combined 9.9%) All smokers united (n = 17) 100% union rate in patients with preoperative HVA <25 degrees 78% union rate if preoperative HVA >25 degrees 33% union rate if postoperative HVA >25 degrees Age, gender, diabetes, COPD and rheumatoid arthritis did not show significant associations with non-union

Standard OA united

Rheumatoid non-union with post op >25

Mal reduction >25deg 67% 14 <0.001* RISK FACTOR Nonunion % Relative Risk p value Mal reduction >25deg 67% 14 <0.001* Pre op HVA >25deg 21.9% 1.29 0.003* Diabetes 25% 0.32 0.175 Rheumatoid 29.6% 0.27 0.138 Hypothyroid 40% 0.19 0.073 Plate breakage 50% 0.15 0.046* Smoking 0 0 0.187 *Fishers exact test

Discussion Overall 10% non-union rate is expected from literature Pre operative hallux valgus or mal reduction causing non union Fixation method doesn’t address the tension side in transverse plane deformities We now use a dorsal plate with medial to lateral screw in hallux valgus deformities greater than 25 degrees pre-operative HVA

New method of medial to lateral screw

Conclusion Non union 7 patients (combined 9.9%) Union rate 100% if preoperative hallux valgus <25 degrees Preoperative moderate-severe hallux valgus and under corrected deformity are the most significant risk factors. This construct does not neutralise transverse plane deformities and supplemental fixation techniques may be needed in severe deformities. for non-union of 1st MTPJ arthrodesis using dorsal plate fixation.

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Conflicts of interest: Yes Mr A Molloy is a consultant for Stryker