Patient-oriented and performance-based outcomes after knee autologous chondrocyte implantation: a timeline for the first year of recovery

Abstract

Context: It is well established that autologous chondrocyte implantation (ACI) can require extended recovery postoperatively; however, little information exists to provide clinicians and patients with a timeline for anticipated function during the first year after ACI.

Objective: To document the recovery of functional performance of activities of daily living after ACI.

Patients: ACI patients (n = 48, 29 male; 35.1 ± 8.0 y).

Intervention: All patients completed functional tests (weight-bearing squat, walk-across, sit-to-stand, step-up/over, and forward lunge) using the NeuroCom long force plate (Clackamas, OR) and completed patient-reported outcome measures (International Knee Documentation Committee Subjective Knee Evaluation Form, Lysholm, Western Ontario and McMaster Osteoarthritis Index [WOMAC], and 36-Item Short-Form Health Survey) preoperatively and 3, 6, and 12 mo postoperatively.

Main outcome measures: A covariance pattern model was used to compare performance and self-reported outcome across time and provide a timeline for functional recovery after ACI.

Results: Participants demonstrated significant improvement in walk-across stride length from baseline (42.0% ± 8.9% height) at 6 (46.8% ± 8.1%) and 12 mo (46.6% ± 7.6%). Weight bearing on the involved limb during squatting at 30°, 60°, and 90° was significantly less at 3 mo than presurgery. Step-up/over time was significantly slower at 3 mo (1.67 ± 0.69 s) than at baseline (1.49 ± 0.33 s), 6 mo (1.51 ± 0.36 s), and 12 mo (1.40 ± 0.26 s). Step-up/over lift-up index was increased from baseline (41.0% ± 11.3% body weight [BW]) at 3 (45.0% ± 11.7% BW), 6 (47.0% ± 11.3% BW), and 12 mo (47.3% ± 11.6% BW). Forward-lunge time was decreased at 3 mo (1.51 ± 0.44 s) compared with baseline (1.39 ± 0.43 s), 6 mo (1.32 ± 0.05 s), and 12 mo (1.27 ± 0.06). Similarly, forward-lunge impact force was decreased at 3 mo (22.2% ± 1.4% BW) compared with baseline (25.4% ± 1.5% BW). The WOMAC demonstrated significant improvements at 3 mo. All patient-reported outcomes were improved from baseline at 6 and 12 mo postsurgery.

Conclusions: Patients' perceptions of improvements may outpace physical changes in function. Decreased function for at least the first 3 mo after ACI should be anticipated, and improvement in performance of tasks requiring weight-bearing knee flexion, such as squatting, going down stairs, or lunging, may not occur for a year or more after surgery.

Figure 1

Walk-across. Outcome variables included stride width, stride length, and speed.

Figure 2

Weight-bearing squat. Percentage of body weight on the involved limb was evaluated at 0° (not pictured), 30°, 60°, and 90° of knee flexion.

Figure 3

Sit-to-stand. Beginning from a sitting position, participants were instructed, on receiving a visual and audio cue, to rise from sitting as quickly as possible without using hands to push off the box. Outcome measures included weight-transfer time, rising index, and weight symmetry.

Figure 4

Step-up/over. Beginning with both feet behind the box (not pictured), participants were instructed to step up and over the box and return to stationary standing as quickly as they could do so while still maintaining control. Outcome variables were lift-up index, impact index, and movement time.

Figure 5

Patient-reported outcome scores. Abbreviations: IKDC, International Knee Documentation Committee Subjective Knee Evaluation Form; SF-35 PCS, 36-Item Short-Form Health Survey Physical Component Scales; WOMAC, Western Ontario and McMaster Osteoarthritis Index. IKDC and Lysholm are scored from 0 to 100, with 100 representing an ideal score. SF-36 PCS uses a norm-based scoring system where 50 represents a mean score with a standard deviation of 10 and higher scores represent higher levels of function. The WOMAC is scored from 96 to 0, with 0 representing no disability. Error bars represent standard deviations. *P ≤ .05 compared with preoperative time point.

Figure 6

Timeline of functional recovery after autologous chondrocyte implantation.