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緒言:外果骨折や内果骨折に対する治療法はほぼ統一した見解が定着している一方,後果骨折に対する手術方法に関しては議論の余地が多い.三果骨折は両果骨折に比べて外傷性関節症の発症率が高く,その治療成績は明らかに劣っている.従来の手術方法はリガメントタキシスによる間接的整復と前方からのスクリュー固定が汎用されている.これに対して,近年は解剖学的整復を追求した後方アプローチによる直接的整復と後方からのプレート固定が散見されるようになってきた.本研究の目的は後果骨折に対する後外側と前方アプローチの治療成績を比較検討することである.方法:対象は2007年4月から2018年6月までに後果骨折に対して整復内固定術を施行した33例(後方群16例,前方群17例)とした.調査項目は年齢,性別,受傷機転,AO分類,原口分類,後果関節面の骨片形態,外果骨折・内果骨折の有無,手術待機期間,後果・外果・内果・脛腓靱帯に対する固定方法,術者経験年数,手術時間,術中出血量,ターニケット使用時間,術後6ヵ月時におけるBurwell評価基準による治療成績,および術後合併症とした.結果:患者背景に関しては両群間に統計学的有意差を認めなかったが,手術待機期間は後方群において有意に長かった(後方群11±4.2日,前方群7±4.3日,オッズ比0.7,p=0.025).Burwell評価基準による解剖学的整復率は後方群において有意に高く(後方群87.5%,前方群52.9%,p=0.036),自覚症評価と他覚評価に関しても後方群において優れた傾向であった(後方群87.5%,前方群58.8%,p=0.071).術後合併症に関しては,後方群において腓腹神経障害1例,前方群において創部感染1例を認めた.結論:後果骨折に対する後外側アプローチ整復内固定術は,前方アプローチ整復内固定術と比べて解剖学的整復が得られやすく,良好な治療成績につながると考えられた.特に,後果骨片がdepression typeを呈する場合や手術待機期間が長くなる場合は後外側アプローチを適応すべきと考えられた.(著者抄録)Background & Objectives: While the treatment of lateral and medial malleolar fractures is well established, several controversies exist in the management of posterior malleolar fractures. The involvement of the posterior malleolus in fractures of the ankle adversely affects the functional outcome and may be associated with the development of post-traumatic osteoarthritis. Although anatomical reduction is one of the predictors of successful outcomes, the most common method of fixation of the posterior malleolus is by indirect reduction and anteroposterior screws via an anterior approach. The purpose of this study was to compare radiographic and functional outcomes of posterior malleolar fractures treated with direct reduction via a posterolateral approach versus indirect reduction via an anterior approach. Materials and Methods: We retrospectively analyzed 33 patients with posterior malleolar fractures who underwent open reduction and internal fixation using either posterolateral or anterior approaches between April 2007 and June 2018. Fixation of the posterior malleolus was made with buttress plate and/or posterior-to-anterior screws in 16 patients using the posterolateral approach, and anterior-to-posterior screws in 17 patients using the anterior approach. Demographic data, type of fracture, internal fixation method, surgeon experience, surgical time, blood loss, tourniquet time, postoperative complication, and Burwell criteria (including radiographic, subjective, and objective criteria) were used as the main outcome measurements, and results were evaluated at the 6-month follow-up visit. Results: Demographic data were similar between groups, but the waiting duration from injury to surgery in the posterolateral group was significantly longer than in the anterior group (11 ± 4.2days vs 7 ± 4.3days, odd ratio: 0.7, p=0.025). Despite this increase in the waiting period, the posterolateral group demonstrated a significantly superior reduction compared to the anterior group (87.5% vs 52.9%, p=0.036) and indicated trends toward improvement in the subjective outcome (87.5% vs 58.8%, p=0.071) and objective outcome (87.5% vs 58.8%, p=0.071). As a postoperative complication, one patient showed signs of sural nerve disorder in the posterolateral group but with no evidence of wound dehiscence. In contrast, one patient in the anterior group did present with surgical site infection. Conclusions: We concluded that the direct reduction technique via a posterolateral approach enables a better quality of reduction and better functional outcome in the management of the posterior malleolar fracture compared with the indirect technique via an anterior approach. Especially in cases of depressed fracture or late timing of surgery, the posterolateral approach should be adopted as an optimal treatment.