9 RELATIONSHIP BETWEEN ARTHROSCOPIC FINDINGS AT THE TIME OF ACL RECONSTRUCTION AND TIBIOFEMORAL JOINT SPACE WIDTH

Abstract

Purpose: Little is known about the initial onset and early progression of post-traumatic OA (PTOA) following severe knee trauma such as that associated with anterior cruciate ligament (ACL) disruption. The purpose of this investigation was to study subjects following ACL injury with and without associated injuries to the cartilages (meniscal and articular cartilages) and determine the relationship between these concomitant injuries and tibiofemoral joint space width (JSW) compared to healthy, matched controls at 3–4 year follow-up. Methods: This investigation was designed as a prospective cohort study with a nested case-control analysis. Thirty-eight ACL-injured (20 women) and 32 healthy control subjects (18 women) matched for age, sex, race, BMI, and activity level were evaluated and followed over 3–4 years. Entry criteria for ACL-R subjects included: Age 14–55 yrs; BMI = 18.5–30, Tegner activity score >4; no relevant knee pathologies other than what was produced by the index injury; normal anatomic alignment; less than 2/3 menisectomy; and Gr IIIa articular cartilage lesions or less. All reconstructions occurred within 6 months of injury, and all subjects participated in a standardized rehabilitation program. Similar entry criteria were utilized for controls, with the exception of: no history of knee pain or dysfunction; no abnormal findings with clinical knee examination; and no abnormal findings on baseline MRI. Articular cartilage and meniscus lesions were identified via arthroscopic visualization at the time of ACL-R and graded by an experienced orthopedic surgeon. This information was recorded on the 2000 International Knee Documentation Committee (IKDC) Surgical Documentation Form, and included characterization of meniscus and articular cartilage lesion location, size, and severity. Bilateral, weight bearing tibiofemoral radiographs were obtained at baseline and 3–4 year follow-up intervals and JSW assessed using previously validated techniques. Subjects were considered to have significant JSW differences of their injured knee if the injured minus normal (contralateral) knee difference fell outside the calculated 95% confidence interval (CI) of bilateral differences measured in controls. Logistic regression (controlled for subject age, sex, BMI, and time between injury and ACL-R) was used for group comparisons and calculation of corresponding odds ratios. Results: Statistical analyses revealed two distinct groupings of JSW differences for the ACL-R subjects. Those with a grade IIb articular cartilage lesion or less and “intact” menisci in both the medial and lateral compartments (the “low-risk” group); or those with grade IIIa femoral articular cartilage lesions and/or menisectomy in either compartment (“high-risk” group). The low risk group was comprised of 25 subjects, and 72% (18/25) of these individuals had JSW values that fell within the normal 95% CI of control values. The high-risk group was comprised of 13 subjects, with only 38% (5/13) having normal JSW at follow-up. Subjects in the high risk group were significantly more likely to have JSW difference values that fell outside the 95% CI of controls in comparison to those in the low risk group (OR: 4.11; 95% CI: 1.01 to 39.55; p = 0.05). Conclusions: Suffering ACL injury in combination with either a grade IIIa articular cartilage lesion, or meniscus injury requiring surgical resection resulted in ACL-R subjects that were more than 4 times more likely to display abnormal JSW changes in comparison to ACL-R subjects without these concomitant injuries at 3–4 year follow-up. These dramatic changes occurred over a relatively short time interval following the injury and reconstruction in subjects with normal knee function and no symptoms of OA and this demonstrates the importance of these articular structures on what appears to be some of earliest changes associated with the initial onset of PTOA.