PURPOSE: To evaluate factors that could impact bone healing following a tibial tubercle osteotomy distalization (dTTO) and the healing of the osteotomized tibial bone (OTB), focusing on its distal extent, where it contacts the anterior tibial shaft (ATS). Secondary aims: to document the average healing time at the dTTO interface, to evaluate frequency of postoperative bone absorption at the distal osteotomy interface, and whether the gap is related to complications of tibia fractures/delayed unions.
METHODS: Consecutive distal TTO patients were retrospectively reviewed including demographic data and distal gap measurements on intraoperative/postoperative sagittal knee radiographs. 'Gap resorption' was defined as >2 mm increase in the gap between intraoperative and follow-up radiographs.
RESULTS: A total of 101 knees underwent dTTO (2009-2015), 73 females/28 males; mean age(range): age 21 years old (13-45). 88% had x-rays that allowed assessment within 4 months. 62% had radiographic healing at the distal OTB-ATS. The initial gap was (mean [range]): 1.48 mm (0-8.4). All but two patients had initial gaps <3.3 mm. Eleven per cent had an increase in their distal bony gap >2 mm (range 2-7.8 mm) without radiographic evidence of motion at point of screw fixation. The mean thickness of the OTB as a % of total tibial width was 31% (range 22%-37%). There were 4 tibial fractures, none statistically related to initial gap distance, mm of distalization or %thickness of the osteotomy segment. Seven patients had gap resorption >2 mm, 2 with tibia fracture. Fracture time from surgery was 18-201 days.
CONCLUSION: Of the factors reviewed in this cohort, no factors were identified directly relating to risk of tibia fracture or bone healing except gap resorption >2 mm at OTB-ATS interface. At 4 months complete radiographic healing was present in 62%. Bone resorption at the distal OTB-ATS interface is recognised postoperatively (11%). Though not statistically correlated with timely healing, it may be a risk factor for tibial shaft fracture.
LEVEL OF EVIDENCE: Level III, retrospective comparative study.