Hinge Fractures Are Underestimated on Plain Radiographs After Open Wedge Proximal Tibial Osteotomy: Evaluation by Computed Tomography.

BACKGROUND: Lateral hinge fracture (LHF) after medial open wedge high tibial osteotomy (MOWHTO) may not be recognized on perioperative plain radiographs. Such cases may be identified at follow-up and misdiagnosed as delayed LHF. PURPOSE: This study aimed to investigate the extent of LHF misdiagnosis and to determine whether patients with LHFs have inferior clinical outcomes after MOWHTO. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Fifty-one knees in 50 patients (36 women, 14 men; mean age, 51.8 years; range, 24-64 years) who had undergone MOWHTO with locking plate fixation between October 2013 and April 2016 were retrospectively reviewed. LHFs identified on intraoperative fluoroscopy and immediate postoperative radiographs were compared with the actual incidence based on computed tomography (CT) scans performed within 2 days of surgery. Delayed LHFs, not visible on the CT scans but found on later follow-up radiographs, were also assessed. More frequent radiographic check-ups were recommended in patients with LHFs, and weightbearing was delayed until evident callus formation was seen on follow-up radiographs for type 2 or 3 fractures. The loss of correction, the time of union, and complication rate were compared between the knees with LHF and those without LHF. Clinical outcome was measured according to the Knee Society (KS) scores. RESULTS: Overall, 14 early LHFs (27.5%) were identified on CT scans. Of these, 7 LHFs (13.7%) were observed on perioperative radiographs, and the remaining 7 LHFs were identified on later radiographs. Delayed LHFs occurred in 2 cases (3.9%). In the 16 knees with LHF, minimal loss of correction was observed 1 month to 1 year postoperatively without statistical significance. No alignment changes were seen in the 35 knees without LHFs. In the LHF versus no LHF groups, no significant differences were seen regarding time of union (5.3 ± 1.7 months vs 5.4 ± 1.8 months, respectively; P = .898) and postoperative KS scores (knee score, 96.6 ± 2.5 vs 95.3 ± 6.4, P = .435; functional score, 94.4 ± 9.6 vs 89.1 ± 10.9, P = .107). No other complications occurred in either group. CONCLUSION: Most LHFs after MOWHTO occurred intraoperatively, but half (7/14) were not identified on postoperative radiographs. CT scans would enable detection of early LHFs that would otherwise have been mistaken for delayed LHF. However, clinical outcomes did not differ between patients with and without LHF.

Femoral Component Varus Malposition is Associated with Tibial Aseptic Loosening After TKA.

BACKGROUND: The notion that neutral alignment is mandatory to assure long-term durability after TKA has been based mostly on short-film studies. However, this is challenged by recent long-film studies. QUESTIONS/PURPOSES: We conducted this long-film study to know (1) whether the risk of aseptic revision for nontraumatic reasons was greater among knees with greater than 3° varus or valgus (defined as "outliers") than those that were aligned within 3° of neutral on long-standing mechanical axis (hip to knee) radiographs; and (2) what the failure mechanisms were and whether the malalignment was femoral or tibial in origin, or both, among those in the outlier group. METHODS: Between November 1998 and January 2009 we performed 1299 cemented, posterior cruciate ligament-substituting TKAs in 867 patients for primary osteoarthritis. We had inadequate long-standing radiographs to analyze postoperative alignment for 124 of those knees, and an additional 24 were excluded for prespecified reasons. Consequently, 1151 knees were enrolled in our study. Of these, 982 (85%) in 661 patients (620 women and 41 men) who had followup greater than 24 months were analyzed. The knees were divided according to whether the postoperative mechanical axis was neutral (0° ± 3°), varus (> 3°), or valgus (< -3°) alignment on long-standing radiographs. The survivorships free from aseptic revision for nontraumatic reasons were compared among groups. The mechanical femoral and the tibial component alignment (MFCA and MTCA, respectively) were investigated to know the origin of overall mechanical malalignment of the outlier knees. The mean duration of followup was 8 ± 4 years (range, 2-17 years). Thirty-five knees (4%) showed aseptic loosening at 7 ± 4 years (range, 0.1-14 years) and five (1%) showed polyethylene wear at 12 ± 1 years (range, 10-13 years). Tibial loosening (73%) was the most common reason for aseptic revision followed by femoral loosening (30%). Of this cohort, 687 (70%), 250 (25%), and 45 (5%) knees had overall mechanical neutral, varus, and valgus alignment, respectively. Factors associated with the risk of aseptic revision were identified by Cox regression. RESULTS: The varus outliers (but not the valgus outliers) failed more often than the neutral knees (10% [25 of 250] versus 2% [13 of 687]; odds ratio [OR], 5.8, 95% CI, 2.9-11.5; p < 0.001). Ten-year survivorship free from aseptic revision was lower among varus outliers than among knees with neutral alignment (87% [95% CI, 80%-93%] versus 98% [95% CI, 97%-99%]; p = 0.001). Femoral component varus malpositioning was the main origin of the varus outliers (MFCA = 4.2° ± 2.0°; MTCA = 0.9° ± 1.7°) and was a risk factor for aseptic revision compared with neutral femoral positioning (OR, 14.0; 95% CI, 1.9-105.6; p < 0.001). CONCLUSIONS: This long-film study corresponds to previous short-film studies for the notion that varus malalignment is associated with inferior long-term implant survivorship. Although aseptic loosening occurred most commonly on the tibial side, the primary origin of the overall varus malalignment was femoral component varus malpositioning. Aiming for neutral alignment in TKA still seems to be a reasonable strategy in clinical practice. LEVEL OF EVIDENCE: Level III, therapeutic study.