The Biomechanical Outcomes of Autologous Chondrocyte Implantation

Knee joint articular cartilage is a primary load-bearing surface that endures repetitive high impact loading during activities of daily living. Individuals of any age can injure the knee's articular cartilage. However, as cartilage has an innate limited capacity to regenerate, surgical interventions that adopt tissue engineering techniques are often necessary to repair cartilage and preserve the joint.

Autologous chondrocyte implantation (ACI) is a surgical procedure that is offered to some patients with focal cartilage injuries of the knee. The first pilot study on the use of ACI in humans was published by Brittberg and colleagues in 1994. By 2010 35,000 ACI procedures had been performed worldwide.

Patient-reported outcomes and survivorship of ACI have been well reported in current literature. However, objective biomechanical and functional outcomes of ACI patients are not well understood. This knowledge is essential for optimising treatment, because poor functional outcome is known to worsen quality of life. This is particularly true for patients of working age who wish to return to an active and independent lifestyle.

The applicant recently conducted and published a systematic review on the functional outcome of ACI. The review identified only 19 eligible articles of 20 ACI cohorts. The data showed that the average range of motion (ROM) improved with clinical (>5˚) and statistical significance (p < 0.05) postoperatively: 130.5± 14.8˚ to 136.1±10.2º, however only 7 studies reported both pre- and post-operative RoM. Knee strength significantly improved within the first two postoperative years but remained poorer than control groups at final follow-up (n=11). The review also found no statistical differences between ACI and control groups in their ability to perform functional activities like the 6-minute walk and hop tests post-operatively (n = 8). Only two papers had published on the kinematics of gait post-operatively. Both papers reported the outcomes of the same cohort, stating that there were no significant differences in spatio-temporal parameters between ACI patients and controls post-operatively. However, kinematic differences were observed during two specific phases of the gait cycle. Differences were also reported in peak knee adduction and peak knee extension moments.

The limited literature identified by this review highlighted the urgent need for research into the functional outcomes of joint preservation surgeries like ACI to optimise functional outcome.

Inclusion criteria

• Diagnosis of a chondral injury to the knee by a consultant orthopaedic surgeon Participants must have this diagnosis, else they are not eligible for ACI surgery.
• Listed for ACI for a chondral injury by a consultant orthopaedic surgeon Participants must be listed for ACI, as this is the treatment of interest in this research study
• Over 18 years old Participants must be legally capable of providing informed consent for the study.

Exclusion criteria

• Listed for any treatment other than ACI Participants must be listed for ACI, as this is the treatment of interest in this research study
• Under 18 years old. Participants must be legally capable of providing informed consent for the study.