Study finds suprapatellar approach to IMN insertion superior to infrapatellar approach
A study comparing two intramedullary nail (IMN) insertion techniques in the treatment of distal tibia fractures found that the suprapatellar approach yielded a significantly lower rate of malalignment (3.8 percent) than the infrapatellar approach (26.1 percent). Although use of a locked IMN in an infrapatellar technique "has been shown to enable a successful outcome," according to the authors, "obtaining correct alignment has historically been problematic." This is due to the difficulty in properly placing the IMN in the broadened region of the distal tibia.
The results were presented at the 2015 annual meeting of the Orthopaedic Trauma Association (OTA) by Frank R. Avilucea, MD, of the University of Cincinnati. The retrospective cohort study involved 266 skeletally mature patients with a distal tibia fracture treated with an IMN; the suprapatellar technique was used in 132 patients (49.6 percent).
The two treatment groups were evenly matched for age, sex, fracture grade, and presence of open fracture. Distal tibia fractures were graded according to the OTA classification scheme, based upon the initial injury radiographs. Patients with extra-articular fractures (OTA 43-A) and simple intra-articular fractures (OTA 43-B) that were within 5 cm of the tibial plafond, displaced and unstable, and treated with an IMN were included in the study. Those with an ipsilateral proximal tibia fracture, knee injury, preexisting ankle arthrodesis, and insufficient radiographic or chart data were excluded.
Either a patellar-tendon splitting approach or a parapatellar approach (medial or lateral) was used in patients treated with the infrapatellar IMN insertion technique. All surgeries were performed by fellowship-trained orthopaedic trauma surgeons. The insertion technique used was at the discretion of the surgeon as was the decision for open reduction–internal fixation of an associated distal fibula fracture.
Treatment of fibular fractures was similar in both groups, as was the rate of fibular fixation. Primary angular malalignment occurred in 35 patients with infrapatellar IMN insertion (26.1 percent), and in 5 patients who underwent suprapatellar IMN insertion (3.8 percent) (P < 0.0001). Additionally, statistically significant differences in alignment were seen in both the coronal and sagittal planes (P < 0.0001 for each).
Straighter leg = less manipulation
Dr. Avilucea explained that placing an IMN into a tibia has classically been performed with the knee bent (> 90 degrees). However, this position presents a challenge in maintaining fracture reduction, because "significant manipulation of the leg is required to obtain fluoroscopic images during placement of hardware."
Surgeons must carefully control the leg and the distal fracture segment to successfully ream the tibia and center the IMN in both the anteroposterior and lateral planes of the distal fragment. According to the authors, "Eccentric reaming or failure to control the distal segment may therefore lead to significant malalignment and deformity."
Among the deleterious effects of malunion of the distal tibia, Dr. Avilucea said, are increased tibiotalar contact pressures, which "can cause significant hindfoot and ankle stiffness."
In contrast, for the suprapatellar technique, the leg is in a semi-extended position, eliminating the need for manipulation to obtain images during the procedure. "Once fracture reduction is obtained, the reduction may be maintained during the reaming and nail passage portions of the case because the limb remains static, a factor that our study highlights as critical to ensure anatomic reduction," they wrote.
According to Dr. Avilucea, the results of the study confirmed the hypothesis that stationary positioning of the extremity during reduction, reaming, and implant placement would improve alignment of distal tibia fractures treated with the suprapatellar technique.
Limitations of the study he presented were its retrospective nature and the absence of clinical outcome data. "Our primary aim," he said, "was to assess postoperative alignment."
"The suprapatellar technique does make it easier and more likely for the surgeon to successfully obtain and maintain anatomic alignment when inserting an IMN for difficult fractures of the tibia," said senior author Hassan R. Mir, MD, MBA, FACS. "Proper technique must be used to protect the knee during portal creation and instrumentation."
Coauthors of "Suprapatellar Intramedullary Nail Technique Lowers Rate of Malalignment of Distal Tibia Fractures" with Dr. Avilucea and Dr. Mir are Kostas Triantafillou, MD; Paul S. Whiting, MD; and Edward A. Perez, MD. The authors' disclosure information can be accessed at www.aaos.org/disclosure
Terry Stanton is a senior science writer for AAOS Now. He can be reached at firstname.lastname@example.org
- Malunion can cause increased tibiotalar contact pressures and lead to degradation of articular tissue.
- The infrapatellar approach for IM nail insertion for distal tibia fractures is less invasive than ORIF, but has a malunion rate of approximately 25 percent.
- This study of 266 patients with distal tibia fractures recorded a malunion rate for the suprapatellar approach of just 3.8 percent.
- The better alignment results appear to be primarily related to the extended, stationary positioning of the leg during the procedure.
- Vallier HA, Cureton BA, Patterson BM: Randomized, prospective comparison of plate versus intramedullary nail fixation for distal tibia shaft fractures. J Ortho Trauma 2011;25(12):736-741.
- Im GI, Tae SK: Distal metaphyseal fractures of tibia: A prospective randomized trial of closed reduction and intramedullary nail versus open reduction and plate and screws fixation. J Trauma 2005;59(5):1219-1223; discussion 23.