Purpose: Medial opening wedge high tibial osteotomy (MOW-HTO) is a well-described operative method for the treatment of medial gonarthrosis in selected patients. One of the concerns with MOW-HTO is the potential delayed or nonunion across the medial gap. Traditionally, this gap was filled with autograft to facilitate union. Although alternative graft options, such as allograft, are available and have theoretical advantages over autograft, little is known about their efficacy relative to autograft in MOW-HTO. The purpose of our study was to perform a retrospective matched cohort study comparing union, re-operation and complication rates between autograft and morselized allograft as filler for the medial gap created in MOW-HTO.

Method: Forty patients who underwent MOW-HTO for sympathetic varus deformity with the use of autograft bone were matched for age, sex, body mass index, deformity and deformity correction with 40 patients who underwent the same procedure with the use of morselized bone allograft. The operative technique utilized, type of hardware fixation and rehabilitation program were similar for both groups. The primary outcome assessed was union rate as evaluated on radiographs by two independent blinded examiners. Re-operation and complication rates were assessed as secondary outcomes.

Results: A total of 73/80 patients in the study (91%) developed union, 4/80 (5%) developed nonunion, and 3/80 (4%) required early revision. The union rate was 95% and 88% in the autograft and allograft groups respectively. Three percent in the autograft and 8% in the allograft groups developed nonunion (p=0.64). Thirteen percent of the autograft patients required re-operation compared to 18% from the allograft patients (p=0.53). Complications were encountered in 28% of the autograft group and in 23% of the allograft group (p > 0.05). There was a 10% incidence of harvest site complications in the autograft group. The average operative time was 21 minutes shorter using allograft compared with using autograft (p< 0.01).

Conclusion: No statistical significant difference was demonstrated between the groups for union, re-operation rates and overall complication rates. However, the autograft group had a significant 10% incidence of harvest site complications and a statistically significant increased operative time. We conlcude that allograft is safe and efficacious to use in valgus producing MOW-HTO. Allograft avoids harvest site complications and is associated with decreased operative time when compared to autograft.