Objectives: Chronic anterior knee pain is a common complication after intramedullary nailing of a tibial shaft fracture. The source of pain is often not known, although it correlates with a simultaneous decrease in thigh muscle strength. No long-term follow-up study has assessed whether weakness of the thigh muscles is associated with anterior knee pain after the procedure in question.
Design: Prospective study.
Setting: University Hospital of Tampere, University of Tampere.
Patients: The muscular performance of 40 consecutive patients with a nailed tibial shaft fracture was tested isokinetically in a follow-up examination an average of 3.2 ± 0.4 (SD) years after the initial surgery. An 8-year follow-up was possible in 28 of these cases.
Main Outcome Measurements: Isokinetic muscle strength measurements were made in 28 patients at an average 8.1 ± 0.3 (SD) years after nail insertion and an average 6.6 ± 0.3 (SD) years after nail extraction. All nails were extracted at an average 1.6 ± 0.2 years after the nailing.
Results: Seven patients were painless initially and still were at final follow-up (never pain, or NP). In 13 patients, the previous symptom of anterior knee pain was no longer present at final follow-up [pain, no pain (PNP)], and the remaining 8 had anterior knee pain initially and at final follow-up [always pain group (AP)]. With reference to the hamstring muscles, the mean peak torque difference between the injured and uninjured limb was -2.2% ± 12% in the NP group, 1.6% ± 15% in the PNP group, and 10.3% ± 30% in the AP group at a speed of 60 degrees/second (Kruskal-Wallis test; χ2 = 1.0; P = 0.593). At a speed of 180 degrees/second, the corresponding differences were -2.9% ± 23% and 7.0% ± 19% and 4.4% ± 16% (Kruskal-Wallis test; χ2 = 1.7; P = 0.429). With reference to the quadriceps muscles, the mean peak torque difference was -2.8% ± 9% in the NP group, 5.9% ± 15% in the PNP group, and -13.0% ± 16% in the AP group at a speed of 60 degrees/second (Kruskal-Wallis test; χ2 = 7.9; P = 0.019). At 180 degrees/second, the corresponding differences were -9.4% ± 13% and 4.9% ± 16% and -1.9% ± 9%, respectively (Kruskal-Wallis test; χ2 = 4.8; P = 0.092).
Conclusion: Based on this prospective long-term follow-up study, it appears that the anterior knee pain symptoms that are present after intramedullary nailing of a tibial shaft fracture disappear in a number of patients 3 to 8 years after surgery. Quadriceps, but not hamstring weakness, and lower functional knee scores are associated with anterior knee pain at 8 years.