In this report, we described a case of hardware failure after closing wedge DFO. In the analysis of the complication associated with closing and opening-wedge DFOs, both these procedures have similar major potential complications such as fracture, hematoma, and pulmonary embolism. Minor complications such as stiffness and postoperative pain also appeared in both groups. The common complications were plate prominence, discomfort, or irritation over the plate [5]. Nonunion or hardware failure is a generally a concern during opening wedge DFO due to the opened gap. However, in one systematic review, medial closing wedge DFO showed a higher incidence of hardware failure and loss of correction when compared to opening wedge DFO [6]. This implies that closing wedge DFO is not safe.
Outcome of DFO may be improved by the precise method of fixation. The DFO plate configuration is slightly anteriorly positioned, and distal fixation holes are limited when compared with conventional plates for distal femur fractures, which is curved posteriorly for fixation of the femoral condyle. This may affect fixation stability. Correct surgical indication and rehabilitation also influence the complication rate of DFO [7].
With regards to the failure mechanism in our patient, the intraoperative stability and postoperative management were similar to other patients who underwent DFO. However, this patient experienced an unexpected migration of a broken screw to the knee joint. There was recurrent painful swelling of the knee, and aspiration from the operated site revealed joint fluid.
In addition, there was atrophic nonunion with bony resorption occurring at the osteotomy site. These two occurrences do not bode well for hardware stability since hardware failure is related to mechanical instability, while bony resorption is a biological deficiency. Based on our assumption, the presence of joint fluid is an obstacle to bone union, leading to metal failure [8]. Therefore, preservation of the suprapatellar pouch during DFO is of paramount importance. In the present case, fixation was performed slightly anteriorly using a custom-made DFO plate, whereby the suprapatellar pouch might have been penetrated during the approach or during subsequent plate application [1]. This was confirmed during the revision surgery, and the broken screw was assumed to have migrated via this path.
The present study was aimed at providing a lesson to surgeons who might experience a similar situation. We assumed that the causes of the complication were as follows: Firstly, there might have been penetration of the joint during the index surgery. This could have caused regurgitation of joint fluid to the osteotomy site, impeding bone union. Secondly, metal failure was a result of nonunion, with subsequent migration of broken screw into the joint.
Postoperative knee swelling should be further investigated to ascertain the reason, as seen in this case whereby joint fluid aspirated from an extra articular operation site should raise the suspicion of an adverse cause. Finally, the most important message would be to preserve the suprapatellar pouch during DFO and to repair the capsule if breached.
DFO is performed at the adjacent area of the knee joint, and surgeons should preserve the suprapatellar pouch and knee joint to prevent such unusual complication as occurred in our case.