Research articleDoes patellar alignment or trochlear morphology predict worsening of patellofemoral disease within the first 5 years after anterior cruciate ligament reconstruction?
Introduction
Traumatic knee injury, such as anterior cruciate ligament (ACL) rupture, results in a 2–4 fold increased odds of developing knee osteoarthritis (OA) compared to non-injured knees [1,2]. Despite patient perspectives [3], the increased risk of developing knee OA following ACL injury is not mitigated by surgical reconstruction (ACLR) [[4], [5], [6]]. Although typically considered a disease of the tibiofemoral joint, OA following ACLR occurs frequently in the patellofemoral joint [5,[7], [8], [9]] with a median prevalence of nearly 50% 10–15 years post-ACLR [10]. Patellofemoral OA following ACLR is associated with pain [9]. Therefore, it is clinically important to identify risk factors for patellofemoral OA following ACLR that could serve as targets for physical therapy intervention, particularly in the early stages of disease where the potential for disease modification is most promising [11].
Aberrant biomechanics are believed to be a key causal mechanism for OA onset and progression in the general population and particularly in individuals following ACLR [12,13]. While ACLR is effective at restoring the tibiofemoral anteroposterior laxity typically present following ACL rupture, altered patellofemoral tracking is observed in ACL deficient knees and may persist despite ACLR [13,14]. Abnormal patellar alignment and trochlear morphology may lead to decreased joint contact area and increased joint stress [15,16]. Thus, irrespective of whether patellar malalignment or abnormal trochlear morphology exists prior to, or develops following, ACL injury or reconstruction, it may increase the risk of patellofemoral OA [17,18]. We recently reported that patellar alignment and trochlear morphology were cross-sectionally associated with prevalent patellofemoral OA features one year post-ACLR [18]. However, we were unable to infer causality. Moreover, healing of both the ligament graft as well as surrounding tissue (such as subchondral bone) continues for at least two years after ACLR towards baseline joint health and function [19]. Therefore, following a cohort beyond this early recovery period is important to better understand the longitudinal associations between alignment and morphology, and symptomatic and structural decline, in the patellofemoral joint.
The aims of our current longitudinal study were to: (i) describe patellofemoral alignment and trochlear morphology at one and five years post-ACLR, including evaluating change over time; (ii) determine whether alignment and morphology measured at one year increase the risk of worsening patellofemoral OA features at five years; and (iii) evaluate the associations between alignment and morphology at one year to self-reported pain and function at five years.
Section snippets
Study design
In this longitudinal observational study, we originally included 111 participants who had undergone ACLR approximately one year prior [7,18]. Participants were aged 18–50 years at the time of surgery. Briefly, exclusion criteria included: i) any injury to, or symptoms in, the ACLR knee prior to the index ACL injury; ii) ACLR > 15 months prior to enrolment; iii) injury or follow-up surgery within the first year following ACLR; and iv) any other condition that influenced daily function. In the
Results
Complete demographic and MRI data were available for 73 participants at both one and five years post-ACLR (Table 1, Table 2). Excluded participants did not complete the five-year assessment for the following reasons: pregnant (n = 1), lost to follow-up (n = 10), unable/declined to attend due to distance or time constraints (n = 16); removed from study by participating surgeon due to conflict with participation in another study (n = 4); more than five years between original injury and surgery
Discussion
This first longitudinal evaluation of patellofemoral alignment and morphology post-ACLR found abnormal alignment to be prevalent one year following ACLR (bisect offset 14%, lateral patellar tilt angle 53%); while abnormal morphology was less common. Change in alignment and morphology over time was also uncommon, though lateral patellar tilt angle exceeded MDC95 values in 34% of our sample, possibly indicating increased lateral tilt over time. Lateral displacement, lateral tilt, and morphology
Conclusions
We observed that more lateral displacement (bisect offset), more lateral patellar tilt, and a shallower trochlea one year post-ACLR was associated with lateral patellofemoral cartilage worsening from baseline to follow-up. In addition, a lower trochlear angle and higher medial trochlear inclination was associated with patellofemoral BML worsening, particularly in the lateral compartment. Malalignment in the axial plane was prevalent, while sagittal plane malalignment and abnormal morphology
Funding and conflicts of interest
This work was supported by Arthritis Australia (Grant in Aid), La Trobe University’s Sport, Exercise and Rehabilitation Research Focus Area (Project Grant), the Queensland Orthopaedic Physiotherapy Network (Project Grant), the University of Melbourne (Research Collaboration Grant), and the University of British Columbia’s Centre for Hip Health and Mobility (Society for Mobility and Health). E. Macri received funding support from the Australian Endeavour Award Research Fellowship and Vanier
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Present address: Department of General Practice, Erasmus MC, Rotterdam, NL.