Anterior Knee Pain and Bone Defects in ACL Reconstruction
Abstract & Commentary
Synopsis: Bone grafting to refill patellar and tibial defects from graft harvest did not affect the incidence of anterior knee pain following ACL reconstruction.
Source: Boszotta H, Prunner K. Refilling of removal defects: Impact on extensor mechanism complaints after use of a bone-tendon-bone graft for anterior cruciate ligament reconstruction. Arthroscopy 2000;16:160-164.
Although patella tendon autografts are commonly used for anterior cruciate ligament (ACL) reconstructions, patients not infrequently experience donor site morbidity. While bone grafting the patella defect has been shown to reduce fracture risk, it is not known whether bone grafting can reduce extensor mechanism complaints after reconstruction. Boszotta and Prunner addressed this with a prospective study involving 132 patients. From 1992 to 1995, patients underwent ACL reconstruction by one of two surgeons using similar techniques, except one surgeon used coring reamers for the tunnels and placed the bone in the tibial and patellar defects, while the other surgeon left the defects empty. The tendon defect was closed in both groups. There were 70 patients in the grafted group and 62 patients in the empty defect group.
At an average of 31 months for the grafted group and 37 months for the nongrafted group, all patients were evaluated radiographically and clinically. There were no major differences in complications between the two groups, and no patella fractures or patella tendon ruptures were seen. There were no significant differences between the two groups for stability as measured by physical examination or KT-1000 arthrometry, or for clinical outcome as measured by IKDC scores.
Roughly half of all patients complained of mild or moderate symptoms involving the extensor mechanism. In fact, the mean visual analog scale (VAS) scores for all patients (0 = no pain, 10 = severe pain) were nearly 6 for kneeling and 4 for squatting. There were no significant differences between the two groups by VAS for kneeling, squatting, stair climbing, crepitation, or anterior knee pain. Pain complaints correlated most closely with time since surgery, with few problems noted after two years. Also, pain related to the extensor mechanism showed a statistically significant correlation with loss of motion, including both flexion and extension deficits.
COMMENT BY DAVID R. DIDUCH, MS, MD
Extensor mechanism and anterior knee pain complaints can be seen with any graft choice for ACL reconstruction, but have been most commonly associated with patella tendon bone-tendon-bone autografts. In some instances, these complaints can drive graft selection, especially when patients are known to have pre-existing patellofemoral chondromalacia changes and pain. Although the ideal graft choice for ACL reconstruction is controversial and surgeon- and patient-dependent, patellar tendon removal does not appear to be the exclusive reason for patellofemoral complaints.
Boszotta and Prunner have effectively demonstrated that filling the defects with bone graft does not appear to affect extensor mechanism pain or complaints. No significant differences were seen between the two groups. They did this with a thorough, prospective study with adequate follow-up. Ideally, a single surgeon would have done both types of procedures to avoid influencing the results by subtle differences in technique. However, the fact that no differences were seen between the groups suggests that a step as small as grafting the defects during the procedure does not matter.
It probably does matter, however, to help reduce the risk of patella fracture. Because the risk of fracture following graft harvest has been shown to be approximately 1%, the sample size in this study was too small to determine any benefit in this regard. Boszotta and Prunner conclude that they now routinely fill the defects, but their results could just as easily have been interpreted the opposite way since no differences were noted. Given that fracture risk is diminished and cosmesis improved, filling the patella defect with bone graft remains a reasonable option.
With regards to anterior knee pain, this study confirms others in the literature that time since surgery and range of motion, especially extension, are most important. Loss of motion is not unique to patella tendon autografts. Good tunnel placement that avoids notch impingement, followed by appropriate rehabilitation to achieve full motion, would appear more important than the question of refilling bone defects to help avoid extensor mechanism pain.
Which of the following variables was shown to correlate significantly with anterior knee pain after ACL reconstruction?
a. Bone grafting the patella defect
b. Bone grafting the tibial defect
c. Closing the tendon defect
d. Loss of extension
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