Factors influencing femoral neck fracture healing after internal fixation with dynamic locking plate.

Introduction: The purpose of this study was to determine factors that affect the early failure of femoral neck fracture healing after internal fixation with a dynamic locking plate implant.
Patients and Methods: Retrospective analysis of all cases of femoral neck fracture (FNF) primarily treated with dynamic locking plate implant from 04/2014 to 04/2017 with a minimum of 6 month follow-up. For the purpose of the study age, sex and time from admission to surgery were retrieved from the hospital medical database. Patient's pre- and postoperative hip radiographs were reviewed by the authors. Radiographically detected fracture healing failure (non-union and screw cut-out) was recorded.
Results: For the period of the study, there were 77 consecutive FNF (76 patients) treated with the dynamic locking plate implant. Eight (10%) patients were lost to follow-up, 13 (17%) patients died within 6 months after surgery. Healing failure was identified in 23 (41%) of remaining 56 cases. Three of four (75% failure rate) failures were observed in cases with fair-quality reduction and two of two (100% failure rate) failures were noticed in the case of none telescoping screw located within subchondral bone. Multiple logistic regression showed an increased risk of fracture failure in cases with at least one completely collapsed telescoping screw (OR = 73.2; 95% CI 9.4-568.5, p < 0.01), while telescoping screws' location around centre of the femoral head reduces the risk of failure (OR = 14.7; 95% CI 1.6-135.1, p = 0.02).
Conclusion: In our group of patients, fracture healing failure of the FNF treated with dynamic locking plate reached 41%. This high failure rate was associated with poor fracture reduction, not subchondrally and centrally placed telescoping screws and in the case of complete collapse on at least one of the telescoping screws.