A mismatch of planning and achieved tibial plateau angle in cranial closing wedge surgery: An in silico and clinical evaluation of 100 cases

Objective(1) To determine whether Oxley's modified cranial closing wedge osteotomy (CCWO) results in a tibial plateau angle (TPA) of 5 & DEG; in silico, (2) compare in silico to clinical postoperative TPA and (3) determine the impact of ostectomy distalization in silico. Study designCross-sectional retrospective radiographic in silico study. Sample populationA total of 100 stifle radiographs; 90 dogs (small & LE;25 kg = 84; large >25 kg = 16). MethodsTibial plateau angles were measured preoperatively (TPA(Pre)), after in silico planning (TPA(Plan)), and postoperatively (TPA(Post)). Virtual ostectomies were evaluated for plate fit. Postoperative ostectomy position was measured. Virtual ostectomies were performed 5/7.5/10/15 mm from the patellar tendon insertion in 10 dogs from each preoperative TPA category (& LE;20 & DEG;/21-25 & DEG;/ 26-30 & DEG;/31-35 & DEG;/>35 & DEG;). Comparisons for TPA(Pre), TPA(Post), and TPA(Plan) were made between small and large dogs, and the outcome to the target 5 & DEG; between TPA categories and ostectomy positions. ResultsMean & PLUSMN; SD TPA(Pre) was 28.6 & PLUSMN; 6.2 & DEG; and higher in small than large dogs. Mean TPA(Plan) was 7.6 & PLUSMN; 2.7 & DEG;. Plate fit was appropriate in all. In silico, TPAs were greater than 5 & DEG; except for cases with TPA(Pre) > 35 & DEG;. Median TPA(Post) was 5.5 & DEG; (-4-21) and was higher in small (7 & DEG;) than large (4.5 & DEG;) dogs. Postoperative ostectomy position was more distal than Oxley's guidelines. When distalized >7.5 mm in silico, the magnitude of under-correction increased. ConclusionsOxley's modified CCWO did not result in TPA of 5 & DEG; in most cases. Ostectomy distalization exacerbated under-correction. Clinical impactCurrent guidelines should be modified to achieve 5 & DEG; TPA postoperatively.