Surgical predictors of clinical outcome six years following revision ACL reconstruction

Orthopedic surgeons know that knee surgeries that require revisions have inferior outcomes compared with primary surgeries but until now, the reason for this was unknown. Today a team of orthopedic physicians reports that opting for a transtibial surgical approach and choosing an inference screw for femoral and tibial fixation will improve the patient's odds of having a significantly better six-year clinical outcome.

The research was presented today at the American Orthopedic Society of Sports Medicine- Arthroscopy Association of North America Combined 2021 Annual Meeting by Rick Wright MD, Vanderbilt University Medical Center, Nashville, TN.

A team of orthopedic physicians and researchers from Washington University, St. Louis, MO., and Vanderbilt University Medical Center in Nashville, Tenn., designed a study to determine if surgical factors performed at the time of revision anterior cruciate ligament reconstruction have the ability to influence a patient's outcome at six-year follow-up.

Anterior cruciate ligament injury, which usually comprises a complete rupture or tear of the ligament, is one of the most common knee injuries. Surgery comprises ACL reconstruction, where the damaged ACL is replaced by either an autograft (tissue, such as part of the patellar tendon or hamstring tendons, extracted from the person's own body) or an allograft (a specially treated tendon or ligament extracted from a human cadaver) under arthroscopic control.

The researchers enrolled 1,234 revision ACL reconstruction patients (58 % male and 42 % female) between 2006 and 2011. Data collected included baseline demographics, surgical technique and pathology, and a series of validated patient-reported outcome instruments (IKDC, KOOS, WOMAC, and Marx activity rating score). Patients were followed up for 6 years and asked to complete the identical set of outcome instruments.

At six years, follow-up was obtained on 77% (949/1234) of the patients. The researchers found three significant drivers of poor outcomes among these patients, including that surgical variables driving outcome in revision patients were related to femoral and tibial fixation.

Using an interference screw for femoral fixation compared with a cross-pin resulted in significantly better outcomes in six-year IKDC scores (OR=2.2; 95% CI=1.2, 3.8; p=0.008), KOOS sports/rec and KOOS QOL subscales (OR range = 2.2-2.7; 95% CI=1.2, 3.8; p<0.001). Using an interference screw compared with a cross-pin also resulted in 2.6 times less likely to have a subsequent surgery within the six years.

Using an interference screw for tibial fixation compared to any combination of tibial fixation techniques also resulted in significantly improved IKDC (OR=2.0; 95% CI=1.3, 2.9; p=0.001), KOOS pain, ADL, sports/rec (OR range=1.5-1.6; 95% CI=1.0, 2.4; p<0.05) and WOMAC pain and stiffness subscales (OR range=1.5-1.8; 95% CI=1.0, 2.9; p<0.05).

Using a transtibial surgical approach compared to an anteromedial portal approach resulted in significantly improved KOOS pain and QOL subscales at six years (OR=1.5; 95% CI=1.02, 2.2; p<0.04).

Regarding tunnel position at the time of the revision surgery, surgeons who noted that the tibial tunnel aperture position was in the 'optimum position' fared significantly worse in six-year IKDC scores (OR=0.6; 95% CI=0.4, 0.8; p=0.003), Marx activity levels (OR=0.20; 95% CI=0.07, 0.6; p=0.005), KOOS symptoms, pain, sports/rec, and QOL subscales (OR range=0.56-0.68; 95% CI=0.38, 0.47; p<0.05), compared with surgeons who opted for either a blended new tunnel or noted that the previous tunnel had the same tunnel aperture, but 'compromised position'.

The research team also noted other factors that affected outcomes, including: lower baseline outcome scores, lower baseline activity level, being a smoker at the time of the revision, higher BMI, female gender, shorter time since the patient's last ACL reconstruction, and having a previous ACL reconstruction on the contralateral side all significantly increased the odds of reporting poorer clinical outcomes at 6 years.

"There are surgical variables that the physician can control at the time of an ACL revision which have the ability to modify clinical outcomes," said Dr. Rick Wright, "Based on outcomes at 6 years, opting for a transtibial surgical approach and choosing an inference screw for femoral and tibial fixation, will improve the patient's odds of having a significantly better 6-year clinical outcome."