Original Research

Functional Knee Outcomes in Infrapatellar and Suprapatellar Tibial Nailing: Does Approach Matter?

Am J Orthop. 2015 December;44(12):E513-E516

References

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Mean OKS (maximum, 48 points) was 40.1 (range, 11-48) for the infrapatellar group and 36.7 (range, 2-48) for the suprapatellar group (P = .293). Table 2 summarizes the data. Radiographic reduction in the sagittal plane was improved (P = .044) in the suprapatellar group (2.90°) compared with the infrapatellar group (4.58°). There was no difference in rotational malreduction (0.31 vs 0.25 cortical width; P = .599) or in reduction in the coronal plane (2.52° vs 3.17°; P = .280). All patients in both groups maintained radiographic reduction within 5° in any plane throughout follow-up. There was no difference (P = .654) in radiographic follow-up between the infrapatellar group (11 mo) and the suprapatellar group (12 mo). The 1 nonunion in the suprapatellar group required return to the operating room for exchange intramedullary nailing. The suprapatellar approach required less (P = .003) operative fluoroscopy time (80.8 s; range, 46-180 s) than the standard infrapatellar approach (122.1 s; range, 71-240 s). Two patients in the suprapatellar group and 8 in the infrapatellar group did not have their fluoroscopy time recorded in the operative report.

Discussion

We have described the first retrospective cohort-comparison study of functional knee scores associated with traditional infrapatellar nailing and suprapatellar nailing. Although much has been written about the incidence of anterior knee pain with use of a patellar splitting or parapatellar approach, the clinical effects of knee pain after use of suprapatellar nails are yet to be addressed. In a cadaveric study, Gelbke and colleagues¹⁴ found higher mean patellofemoral pressures and higher peak contact pressures with a suprapatellar approach. These numbers, however, were still far below the threshold for chondrocyte damage, and that study is yet to be clinically validated. Our data showed no difference in OKS between the 2 groups. Despite being intra-articular, approach-specific instrumentation may protect the trochlea and patellar cartilage.

Although the OKS questionnaire was originally developed and widely validated to describe clinical outcomes of total knee arthroplasty,^15,16it has also been evaluated for other interventions, including viscosupplementation injections¹⁷ and high tibial osteotomy.¹⁸ We used the OKS questionnaire in our study because it is simple to administer by telephone and is not as cumbersome as the Knee Society Score or the Western Ontario and McMaster Universities Osteoarthritis Index. It is also more specific to the knee than generalized outcome measures used in trauma, such as the Short Form 36 (SF-36). Sanders and colleagues¹⁹ reported excellent tibial alignment, radiographic union, and knee range of motion using semi-extended tibial nailing with a suprapatellar approach. For outcome measures, they used the Lysholm Knee Score and the SF-36. Our clinical and radiographic results confirmed their finding—that the semi-extended suprapatellar approach is an option for tibial nailing.

OKS results by question (Table 3) showed that the infrapatellar group had less pain walking down stairs. This result approached statistical significance (P = .063). As surgeons at our institution began using the suprapatellar approach only during the final 2 years of the study period, mean follow-up was significantly (P < .001) less than for the infrapatellar group (12 vs 25 mo). Although there was no statistically significant difference in reduction quality on anteroposterior radiographs, the suprapatellar approach had improved (P = .044) reduction on lateral radiographs (2.90° vs 4.58°).

Although operative time did not differ between our 2 groups, significantly (P = .003) less fluoroscopy time was required for suprapatellar nails (80.8 s) than for infrapatellar nails (122.1 s). Positioning the knee in the semi-extended position offers easier access for fluoroscopy and less radiation exposure for the patient. Placing the nail in extension also helps eliminate the deforming forces that cause malreduction of proximal tibial shaft or segmental fractures. However, our study was limited in that only 2 surgeons at our institution used the suprapatellar approach, and both were fellowship-trained in orthopedic traumatology. This situation could have introduced bias into the interpretation of fluoroscopy data, as these surgeons may have been more comfortable with the procedure and less likely to use fluoroscopy. Both surgeons also performed infrapatellar nailing during the study period, and there was no statistical difference in fracture patterns between the groups, thus minimizing bias.

This study was retrospective but had several strengths. Sample size met the prestudy power analysis to determine a minimally clinically important difference in OKS results. The investigator who administered the telephone survey was blinded to surgical approach. This study was also the first clinical study to compare outcomes of infrapatellar and suprapatellar nailing. However, the study’s follow-up rate was a weakness. The patient population at our academic, urban, level I trauma center is transient. We lost 36 patients (45%) to follow-up; their telephone numbers in the hospital records likely changed since surgery, and we could not contact these patients.