Patellofemoral Research Articles

Poster 267: Relationship Between Sagittal Tibial Tubercle-Trochlear Groove Distance and Outcomes Following Cartilage Restoration for Patellofemoral Articular Cartilage Lesions

Objectives: Increased contact force in the patellofemoral (PF) joint is a known contributor to cartilage damage and pain. A tibial tubercle that is posterior to the trochlear groove may lead to aberrant loading and cartilage wear. The sagittal tibial-tubercle trochlear groove distance (sTT-TG), defined as the distance between the nadir of the trochlear groove and the most anterior aspect of the tibial tubercle, aids in quantifying the degree of risk of acquiring new lesions. However, the relationship between sTT-TG and patient-reported outcomes following surgery has not been assessed. Therefore, the purpose of this study is to assess the association between sTT-TG and post-operative outcomes in patients undergoing cartilage restoration procedures for PF articular cartilage lesions. Methods: A retrospective review of patients who underwent osteochondral allograft (OCA) transplantation or autologous chondrocyte implantation (ACI) at a single academic institution from 2010 to 2020 was conducted. Patients were included they underwent OCA or ACI for a high-grade (Outerbridge 3 or 4) articular cartilage lesion located in the patellofemoral joint (unipolar or bipolar), if they were between 18 and 50 years of age at the time of surgery, had magnetic resonance imaging (MRI) available, and had a minimum 2-year clinical follow-up. Demographic data such as age, sex, body mass index (BMI), as well as defect characteristics including size, number, and grade were collected. Before surgery, sTT-TG distance was measured independently on axial T2-weighted MRI sequences by two raters (Rater A and Rater B). Both raters measured the sTT-TG for the entire cohort at two different time points with a two-week time interval between each rater’s initial and follow-up measurements. The Interclass Coefficient (ICC) using a single measure, absolute agreement, two-way mixed effects model was used to test the intra-rater reliability of Rater A and Rater B; mean measures were used to assess the inter-rater reliability for the combined mean of the two rater’s measurements. Patients were surveyed to assess pain and satisfaction on a Visual Analog Scale (VAS) from 0 to 100. Functional outcomes were collected using the Knee Injury and Osteoarthritis Outcome Score (KOOS). The rate of return to sports, complications, and graft failure were also recorded [JT1]. An independent samples t-test was used to compare lesion size between the OCA and ACI group. Linear and logistic regression models accounting for age, sex, BMI, and sTT-TG distance were used to assess the relationship between sTT-TG and PROs. Results: A total of 76 patients, mostly female (61.8%), with a mean age of 31.9 ± 8.3 years, BMI of 26.8, and 60.6 ± 23.6-month follow-up were included. There were 37 (48.7%) patients that underwent OCA transplantation and 39 (51.3%) that underwent ACI. A total of 98 lesions were identified, with the majority (n = 93, 94.9%) being Grade 4. Overall, 54 patients had unipolar lesions and 22 had bipolar lesions. The mean defect size was 2.9 ± 1.4 cm2 and 3.5 ± 2.9 cm2 for the OCA and ACI groups (p = 0.459), respectively, with an overall mean lesion area of 3.2 ± 2.3 cm2. Intra-rater reliability for sTT-TG measurements at each time point was excellent for Rater A (ICC of 0.99 [0.986-0.994] p<0.001) and Rater B (ICC of 0.99 [0.985-0.994]). Inter-rater reliability was excellent (ICC of 0.97 [0.955-.982] p<0.001), with an overall mean sTT-TG of -4.98 ± 4.93 mm (range: -18.9, 5.7). On average, 48.7% (n = 37) of patients returned to sport and of those, 22.4% (n=17) returned to a similar or higher level of sport activity. Mean pain and satisfaction were 26.7 ± 25.1 and 73.8 ± 27.7, respectively. Collectively, the mean KOOS subscores were - KOOS symptoms: 71.4 ± 2.3, KOOS pain: 79.5 ± 2.0, KOOS sport: 60.2 ± 2.8, and KOOS QoL: 52.0 ± 2.6. When controlling for age, sex, BMI, and follow-up, sTT-TG was not predictive of RTS (p=0.706), pain (p=0.698), satisfaction (0.757), or any KOOS subscore (p>0.05). Although, older age was associated with worse satisfaction (-0.819, 95% CI [-1.608,-0.03] and inferior KOOS pain (-0.606, 95% CI [-1.096,-0.116]), KOOS sport (-0.739, 95% CI [-1.445,-0.032]), and KOOS QoL (-0.786, 95% CI [-1.455,-0.117] p<0.05). Conclusions: In this cohort of patients that underwent an OCA or ACI for PF cartilage lesions, sTT-TG was not predictive of post-operative patient reported functional outcomes or complications. These findings suggest that while a more posterior tibial tubercle (negative sTT-TG) may contribute to a higher incidence of cartilage pathology, patients can have favorable short-term outcomes following cartilage restoration with OCA or ACI.

Assessment of average femoral component rotation for balancing functionally aligned total knee replacement in varus deformity: Robotic image guidance study

Introduction and purposeEnsuring proper femoral component alignment post-Total Knee Arthroplasty (TKA) is crucial for normal patellofemoral (PF) kinematics. However, the customary 3° external rotation relative to the Posterior Condylar Axis (PC Axis) may not universally apply, and the expected final femoral component rotation remains unclear in functionally aligned knees. This study examines the relation between the Transepicondylar Axis (TEA) and PC axis, known as Posterior Condylar Angle (PCA) in Indian patients along with factors influencing PCA, and the feasibility of reproducing patient-specific PCA using image-guided Cuvis joint robot. MethodsForty patients (52 Knees) with primary osteoarthritis and varus deformity were prospectively evaluated. Native PCA was determined using CT-based J planner. Pre-operative patellar shape, PF tilt, PF shift, final femoral component rotation (representing post-operative PCA), final patellar tracking, and post-operative functional and radiological assessment at 3 months were recorded. ResultsStudy participants averaged 64.3 years of age, with a female-to-male ratio of 23 to 17. Varus deformities varied, with IA2 being most prevalent, and sagittal plane deformities included fixed flexion (34.6 %) and hyperextension (44.2 %). The average PCA was 1.9° (range: 0°–7.3°), with most knees (41 out of 52) below 3°. The majority had Wiberg type 1 patellae, with pre-operative patellar tilt averaging 5.63°, reducing post-operatively to 4.43°. Most patients (37 out of 40) achieved excellent Knee Society functional scores at the 3-month mark. Complications included one case of delayed wound healing and one femoral array pin breakage. Notably, our study revealed a significant deviation in PCA from the commonly reported 3° in Western literature, underscoring the need for region-specific considerations in TKA planning. ConclusionPCA of our population is statistically different from customary 3° followed with jig system. Image guided Robotics helps to identify patients specific PCA and reproducing the same was more commonly possible in patients with reducible Varus deformity.

Patellofemoral stabilization with and without cartilage restoration

Introduction/ObjectivesCartilage restoration as an adjunct to patellofemoral (PF) soft tissue and/or bony stabilization in patients with symptomatic PF instability remains controversial. Our purpose was to evaluate patients undergoing surgical stabilization for PF instability with or without concomitant cartilage restoration. MethodsRetrospective review of prospectively collected data identified patients undergoing surgical stabilization for recurrent patella instability, with or without concomitant cartilage restoration. Presurgical and postsurgical patient-reported outcomes were collected. Complications requiring reoperation were recorded. Statistically significant difference was set at P < .05. ResultsOne hundred thirty patients (144 knees) were included. One hundred thirteen knees in the isolated stabilization (STAB) and 31 knees in the Stabilization-Cartilage Restoration (STAB-CART) group. The average age was 20.64 and 25.03 in the STAB and STAB-CART groups (P = .034), respectively. STAB-CART group had significantly lower preoperative Knee injury and Osteoarthritis Outcomes Score (57.24 ± 17.45 vs 46.11 ± 14.74, P = .019) and Single Assessment Numeric Evaluation scores (43.15 ± 19.05 vs 26.85 ± 13.74, P = .002). Both groups statistically improved in all Knee injury and Osteoarthritis Outcomes Score, International Knee Documentation Committee, and Single Assessment Numeric Evaluation domains with no statistically significant differences at final follow-up between groups. Thirteen knees (11.5%) in the STAB and 6 knees (19.4%) in the STAB-CART group had complications requiring reoperation, including 6 and 3 revision stabilizations, respectively. There were no statistically significant differences in total major complications (P = .246) or medial PF ligament revision (P = .405). ConclusionsThe addition of cartilage restoration in patients undergoing soft tissue and/or bony PF stabilization appears to be safe and effective. Despite lower baseline scores, patients undergoing PF stabilization with cartilage restoration had similar final subjective outcome scores compared to the group without.

Exploring osteochondral damage patterns in acute patellar dislocation: insights into morphological associations and risk factors

Osteochondral damage (OD) is a significant outcome following acute patellar dislocation (APD), yet the factors contributing to its susceptibility remain unclear. The primary objective of this study was to assess the association between demographic characteristics, patellofemoral (PF) joint morphology, and the occurrence of OD. A retrospective analysis identified 74 patients with APD who underwent treatment in our unit between 2019 and 2022. All patients received MRI within a week of injury to assess OD, subsequently categorized according to the injury pattern. The Caton-Deschamps index (CDI), tibial tuberosity-trochlear groove distance (TT-TG), lateral trochlear inclination (LTI), sulcus angle (SA), patellar width (PW), patellar thickness (PT), and femoral condyle geometry were calculated from the MRI scans and compared between groups. The findings revealed that OD predominantly manifested in the lateral femoral condyle (LFC) region and the medial patella (MP) region. In our patient cohort, this study identified a significant association between sulcus angle and the incidence of OD in both MP and LFC regions. Additionally, a significant correlation was discerned between skeletal maturity and the incidence of OD in the LFC region within demographic characteristics.

Development of patellofemoral osteoarthritis with knee joint malalignment and lateral patellar dislocation after hindlimb suspension in growing rats.

Knee malalignment is a risk factor for patellar instability and patellofemoral osteoarthritis (PFOA), but etiologies remain unknown. We investigated the potential effects of decreased weight loading during growth on knee alignments and patellofemoral (PF) joint pathology. Hindlimb suspension (HS) was performed in 4-week-old female rats for 2, 4, and 8 weeks (HS groups). Age-matched rats were used as controls. Three-dimensional reconstructed images of the knee were obtained using X-ray computed tomography. Tibial tubercle-trochlear groove (TT-TG) distance, patellar tilt angle, and bisect offset were measured as indices of knee alignment. Histological analysis was also performed to evaluate the changes in cartilage and synovium in the PF joints. At Week 8, TT-TG distance, patella tilt angle, and bisect offset were significantly larger in the HS group than in the control group, respectively, indicating tibial external rotation, outward patellar tilt, and external displacement of the patella. Lateral patellar dislocation was frequently found in the HS group at Week 8 (five of eight knee joints, p < 0.05). Degenerative changes in the cartilage of the trochlear groove were observed at Week 8, and synovial changes such as hypertrophy and synovitis were observed at Weeks 4 and 8. Correlation analyses revealed significant relationships between the Mankin score and bisect offset, and between the OARSI synovitis score and all knee alignments indices. These results suggest that decreased weight loading on the lower extremities in growing rats resulted in knee malalignments characterized by external rotation of tibia and high incidence of lateral patellar dislocation with concomitant PFOA.

Magnetic Resonance Image Findings and Potential Anatomic Risk Factors for Chodromalacia in Children and Adolescents Suffering from Non-Overload Atraumatic Knee Pain in the Ambulant Setting.

To evaluate magnetic resonance image (MRI) findings in children and adolescents suffering from knee pain without traumatic or physical overload history and to identify potential anatomic risk factors. A total of 507 MRIs of 6- to 20-year-old patients (251 males; 256 females) were evaluated with regard to detectable pathologies of the knee. The results were compared to a control group without pain (n = 73; 34 males; 39 females). A binary logistic regression model and t-tests for paired and unpaired samples were used to identify possible risk factors and significant anatomic differences of the study population. In 348 patients (68.6%), at least one pathology was detected. The most commonly detected finding was chondromalacia of the patellofemoral (PF) joint (n = 205; 40.4%). Chondral lesions of the PF joint occurred significantly more often in knee pain patients than in the control group (40% vs. 11.0%; p = 0.001), especially in cases of a patella tilt angle > 5° (p ≤ 0.001), a bony sulcus angle > 150° (p = 0.002), a cartilaginous sulcus angle > 150° (p = 0.012), a lateral trochlear inclination < 11° (p ≤ 0.001), a lateralised patella (p = 0.023) and a Wiberg type II or III patella shape (p = 0.019). Moreover, a larger patella tilt angle (p = 0.021), a greater bony sulcus angle (p = 0.042), a larger cartilaginous sulcus angle (p = 0.038) and a lower value of the lateral trochlear inclination (p = 0.014) were detected in knee pain patients compared to the reference group. Chondromalacia of the PF joint is frequently observed in children and adolescents suffering from non-overload atraumatic knee pain, whereby a patella tilt angle > 5°, a bony sulcus angle > 150°, a cartilaginous sulcus angle > 150°, a lateral trochlear inclination < 11°, a lateralised patella and a Wiberg type II or III patella shape seem to represent anatomic risk factors.

Radiographic Incidence of Knee Osteoarthritis After Isolated ACL Reconstruction Versus Combined ACL and ALL Reconstruction: A Prospective Matched Study from the SANTI Study Group

Objectives: The aim of this study was to evaluate the incidence of OA with isolated ACLR in comparison with ACLR with ALLR at medium-term follow-up. We hypothesized that there would be no differences between the groups. Methods: Patients who underwent ACLR 1 ALLR with hamstring tendon autograft between January 2011 and March 2012 were propensity matched to patients who underwent isolated ACLR with bone–patellar tendon–bone (BPTB) or hamstring tendon autograft in the same period. Medium-term radiographic evaluation was performed using the International Knee Documentation Committee (IKDC) radiographic OA grading scale, modified Kellgren-Lawrence grade, and the surface fit method to assess percentage of joint space narrowing. Clinical outcomes were assessed with the following measures: IKDC, Knee injury and Osteoarthritis Outcome Score (KOOS), Lysholm, Tegner, and ACL Return to Sport after Injury. Results: A total of 80 patients (42 ACLR 1 ALLR and 38 isolated ACLR) were analyzed with a mean follow-up of 104 months. There was no significant difference between groups for joint space narrowing in the medial or lateral tibiofemoral or lateral patellofemoral (PF) compartment. However, 36.8% in the isolated ACLR group versus 11.9% in the ACLR 1 ALLR group had narrowing of the medial PF compartment (P = .0118). A lateral meniscal tear increased the risk of lateral tibiofemoral narrowing by nearly 5 times (odds ratio, 4.9; 95% CI, 1.547-19.367; P = .0123). The risk of medial PF narrowing was .4-fold with an isolated ACLR (odds ratio, 4.8; 95% CI, 1.44-19.05; P = .0179). Between the isolated ACLR group and the ACLR 1 ALLR group, the secondary meniscectomy rate was 13.2% versus 11.9% (not significantly different). There was no difference between groups in KOOS, Tegner, or IKDC scores. There was also no difference between groups for grades of osteoarthritic change for any classification system. Patients who received a BPTB graft had medial PF joint narrowing in 66.7% of cases as compared with 11.9% in those who received ACLR 1 ALLR (P = 0.118). Conclusions: ACLR 1 ALLR did not increase the risk of OA in the lateral tibiofemoral compartment when compared with an isolated] ACLR at medium-term follow-up. Isolated ACLR using BPTB was associated with a significantly increased risk of medial PF joint space narrowing.

Relationship between DXA measured systemic bone mineral density and subchondral bone cysts in postmenopausal female patients with knee osteoarthritis: a cross-sectional study

BackgroundIndividuals with high systemic bone mineral density (BMD) may have an increased risk of incident knee osteoarthritis (OA). Besides that, radiographic osteophytes are strongly associated with BMD. Because of these reasons, the aim of the study was to investigate the possible association between radiological subchondral bone cyst (SBC) grade and systemic BMD and vitamin D status in the postmenopausal female patients with knee OA in a crosss-sectional study.MethodsThis study included of 48 osteoporosis treatment-free postmenopausal patients diagnosed with symptomatic medial compartment knee OA. BMD analysis was performed using dual-energy X-ray absorptiometry (DXA) and serum vitamin D levels were measured after recording patients’ findings. Each knee was scanned using computed tomography (CT), and categorical SBC scores were graded for the medial and lateral tibiofemoral (TF) and patellofemoral (PF) compartments and further calculated as compartmental total, total TF and grand total of both TF compartments. SBC scores were analysed with correlation analysis.ResultsThe patient population was characterized by radiographic joint space narrowing, obesity and low vitamin D status. Median medial total and grand total TF SBC scores were significantly different between the patient groups according to the Kellgren-Lawrence (KL) radiographic grading (p = 0.006 and p = 0.007, respectively). There were no correlations between femoral BMD values and SBC scores. However, positive correlations were detected significantly between L1 − 4 DXA values and TF SBC scores, but not with PF SBC scores (p = 0.005 for the correlation between L1 − 4 BMD and medial compartments total TF SBC score, p = 0.021 for the correlation between L1 − 4 BMD and grand total TF SBC score). No significant correlations were found with Vitamin D levels.ConclusionsDevelopment of TF OA high-grade SBCs may be linked to systemic bone mass as represented by trabecular bone-rich lumbar vertebrae. The relationship might point to the importance of bone stiffness as an acting factor in knee OA possibly with mechanical energy transfer to the joint.

Simultaneous Evaluation of Tibiofemoral and Patellofemoral Mechanics in Total Knee Arthroplasty: A Combined Experimental and Computational Approach.

Contemporary total knee arthroplasty (TKA) has not fully restored natural patellofemoral (P-F) mechanics across the patient population. Previous experimental simulations have been limited in their ability to create dynamic, unconstrained, muscle-driven P-F articulation while simultaneously controlling tibiofemoral (T-F) contact mechanics. The purpose of this study was to develop a novel experimental simulation and validate a corresponding finite element model to evaluate T-F and P-F mechanics. A commercially available wear simulator was retrofitted with custom fixturing to evaluate whole-knee TKA mechanics with varying patella heights during a simulated deep knee bend. A corresponding dynamic finite element model was developed to validate kinematic and kinetic predictions against experimental measurements. Patella alta reduced P-F reaction forces in early and midflexion, corresponding with an increase in T-F forces that indicated an increase in extensor mechanism efficiency. Due to reduced wrapping of the extensor mechanism in deeper flexion for the alta condition, peak P-F forces in flexion increased from 101% to 135% of the applied quadriceps load for the baja and alta conditions, respectively. Strong agreement was observed between the experiment and model predictions with root-mean-square errors (RMSE) for P-F kinematics ranging from 0.8 deg to 3.3 deg and 0.7 mm to 1.4 mm. RMSE for P-F forces ranged from 7.4 N to 53.6 N. By simultaneously controlling dynamic, physiological loading of the T-F and P-F joint, this novel experimental simulation and validated model will be a valuable tool for investigation of future TKA designs and surgical techniques.

Morphological analysis of three-dimensional MR images of patellofemoral joints in asymptomatic subjects

The existing methods for analyzing patellofemoral (PF) osteoarthritis (OA) are limited. Our purpose was to clarify the frequency, localization, and morphological progression of PFOA by observing three-dimensional (3D) magnetic resonance (MR) images from a cohort population. The subjects were 561 patients aged 30–79 years from the Kanagawa Knee Study who had not visited a hospital for more than three consecutive months for knee symptoms. MR images of the PF joints, separated into the medial and lateral types, were presented in order of the highest to lowest patella cartilage area ratios. Cartilage defects in the patella were detected in 37 subjects (6.6%). Medial lesions (4.6%) were significantly more frequent than lateral lesions (2.0%) (p < 0.01). For both medial and lateral lesions, the patellar cartilage defects were divided into confined and unconfined types. The 3D MR images of the PF joint showed that the patellar cartilage defect occurred along each ridge of the femoral trochlea. The 3D MR images revealed a 6.6% prevalence of patellar cartilage defects, higher in the medial than lateral regions. The 3D MR images can easily determine PF morphology and cartilage defect location, making them useful in understanding the pathophysiology and etiology of PFOA.

Associations between anterior knee pain and 2-year patellofemoral cartilage worsening: The MOST study

Anterior knee pain (AKP) is associated with patellofemoral osteoarthritis (PFOA), but longitudinal studies are lacking. If AKP precedes PFOA, it may create an opportunity to identify and intervene earlier in the disease process. The purpose of this study was to examine the longitudinal relation of AKP to worsening patellofemoral (PF) cartilage over two years. Participants were recruited from the Multicenter Osteoarthritis Study, a longitudinal study of individuals with or at risk for knee osteoarthritis (OA). Exclusion criteria included bilateral knee replacements, arthritis other than OA, and radiographic PFOA. At baseline, participants completed a knee pain map questionnaire and underwent knee magnetic resonance imaging (MRI). Imaging was repeated at 2-year follow-up. Exposure was presence of frequent AKP. Outcome was worsening cartilage damage in the PF joint defined as increase in MRI Osteoarthritis Knee Score from baseline to 2 years. Log-binomial models were used to calculate risk ratios (RR). One knee from 1083 participants (age 56.7±6.6 years; body mass index 28.0±4.9kg/m2) was included. Frequent AKP and frequent isolated AKP were present at baseline in 14.5% and 3.6%, respectively. Frequent AKP was associated with an increased risk (RR: 1.78, 95% confidence interval: 1.21, 2.62) of 2-year worsening cartilage damage in the lateral PF compartment. No association was found between frequent AKP and worsening in the medial PF joint. Frequent AKP at baseline was associated with worsening cartilage damage in the lateral PF joint over 2 years.

Three-Dimensional Printing of Models of Patellofemoral Joint Articular Cartilage in Patients With Patella Instability for Observing Joint Congruity

Three-dimensional (3D) modeling and printing are increasingly used in the field of orthopaedic surgery for both research and patient care. One area where they are particularly helpful is in improving our understanding of the patellofemoral (PF) joint. Heretofore, morphological studies that use 3D models of the PF joint have primarily been based on computed tomography imaging data and thus do not incorporate articular cartilage. Here, we describe a method for creating 3D models of the articular surfaces of the PF joint based on magnetic resonance imaging. Models created using this technique can be used to improve our understanding of the morphology of the articular surfaces of the PF joint and its relationship to joint pathologies. Of particular interest is our finding of articular congruity in printed articular cartilage surfaces of dysplastic PF joints of recurrent patella dislocators.

The Influence of Patello-Femoral Overstuffing After Modular Unlinked Bicompartmental Knee Arthroplasty (BiKA) for Medial Tibio-Femoral and Patello-Femoral Osteoarthritis of the Knee

BackgroundThe factors affecting results after bicompartmental knee arthroplasty (BiKA) have not been fully elucidated. This major ligament-preserving procedure may be more susceptible to overstuffing of the patello-femoral (PF) joint than the major ligament-sacrificing total knee arthroplasty. Currently, we investigated the effect of PF overstuffing after BiKA on its clinical outcome. MethodsThere were 71 patients (74 knees) who underwent modular unlinked BiKA at our clinic who had a follow-up of 5 to 9 years. Final follow-up results were assessed by evaluating knee range of motion, the 2011 Knee Society Score (2011KSS), Japanese Knee Osteoarthritis Measure, and radiological findings. The degree of postoperative PF overstuffing was evaluated by computed tomography and magnetic resonance images for 55 knees, and the correlation between the degree of overstuffing and postoperative clinical results were examined. ResultsOverall clinical results improved significantly after surgery without any revision cases. The X-ray measurements showed the improved coronal alignments and the appropriate implant installation angles. Higher degree of postoperative PF overstuffing caused by insufficient amount of osteotomy on the anterior surface of the femur correlated with worse postoperative total 2011KSS at 2 years after surgery (Spearman's rank correlation coefficient (rs) = −0.387, P = .004), as opposed to no correlation at the time of the final follow-up (Spearman's rank correlation coefficient = 0.068, P = .623). ConclusionModular unlinked BiKA provided patients with a high level of satisfaction and functional improvement over 5 to 9 years postoperatively. However, because PF overstuffing affects initial patient satisfaction, the amount of osteotomy should be determined carefully during the surgery.

Retro-tubercular Biplanar Medial Opening-Wedge High Tibial Osteotomy Results in Superior Patellofemoral Alignment Versus Supra-tubercular Osteotomy

To compare the changes in patellofemoral (PF) joint alignment, focusing on multiple planes, between two different types of biplanar medial opening-wedge high tibial osteotomy (OWHTO). Patients who underwent biplanar OWHTO between July 2017 and May 2021 were retrospectively evaluated. They were allocated to either the supra-tubercular (ST)- or retro-tubercular (RT)-OWHTO group. The following radiologic parameters were compared between the two groups: 1) weight-bearing line ratio (WBLR), 2) patellar height, 3) posterior tibial slope (PTS), 4) tibial tubercle-trochlear groove (TT-TG) distance, 5) TT-TG angle, and 6) femoral shaft-patellar tendon (FS-PT) angle. Clinical outcomes and the minimal clinically important difference (MCID) were also evaluated. In total, 104 knees that underwent ST-OWHTO and 105 knees that underwent RT-OWHTO were evaluated. The patellar height significantly decreased only after ST-OWHTO (P < .001). The TT-TG distance and FS-PT angle significantly increased, more after ST-OWHTO than RT-OWHTO (mean change value: 5.72 mm vs 1.91 mm; P < .001 for TT-TG distance; and 4.72° vs 1.80°; P < .001 for FS-PT angle). The TT-TG angle increased significantly after ST-OWHTO (mean change value: 7.62°; P < .001) but decreased after RT-OWHTO mean change value:-4.30°; P < .001). The PTS more increased after RT-OWHTO than after ST-OWHTO (mean change value: 0.91° vs 1.69°; P= .003). Clinical outcomes in both groups improved postoperatively, and no significant differences were observed between the groups. RT-OWHTO resulted in lesser changes in multiplane PF joint alignment than ST-OWHTO. However, no difference was observed in clinical outcomes between both groups, and PTS increased after RT-OWHTO. Therefore, these aspects of RT-OWHTO should also be considered. Level III, retrospective cohort study.

Surgical treatment of knee osteoarthritis focusing on the patellofemoral joint

Background: Surgical management of the osteoarthritic knee joint consists of osteotomies such as a high tibial osteotomy (HTO), uni-compartmental knee arthroplasty (UKA), and total knee arthroplasty (TKA). These surgeries mainly treat the tibiofemoral joint but can also have an impact on the patellofemoral (PF) joint. These changes in PF joint can affect the surgical outcome.Current Concepts: PF joint problems are relative contraindications in UKA. However, recent studies have reported that these problems do not markedly affect the result of UKA. During HTO, the patella height and tracking can change, affecting the PF joint problem. The effect of the PF joint can be minimized through various methods of closing wedge HTO or modified opening wedge (OW) HTO, such as retro-tubercular biplanar OWHTO. However, this method is controversial regarding its impact on clinical outcomes. In TKA, pain caused by PF joint problems can be reduced using techniques such as patella resurfacing, patelloplasty, and denervation; however, there is no clear consensus.Discussion and Conclusion: The surgical treatment of degenerative knee osteoarthritis has an impact on the PF joint, which can affect the outcome of surgery and vice versa. However, these impacts only occasionally cause clinical difference. Conclusively, these surgeries should be done by considering the PF joint because changes in the joint can affect the surgical outcome.

Identifying multivariate disease trajectories and potential phenotypes of early knee osteoarthritis in the CHECK cohort.

To gain better understanding of osteoarthritis (OA) heterogeneity and its predictors for distinguishing OA phenotypes. This could provide the opportunity to tailor prevention and treatment strategies and thus improve care. Ten year follow-up data from CHECK (1002 early-OA subjects with first general practitioner visit for complaints ≤6 months before inclusion) was used. Data were collected on WOMAC (pain, function, stiffness), quantitative radiographic tibiofemoral (TF) OA characteristics, and semi-quantitative radiographic patellofemoral (PF) OA characteristics. Using functional data analysis, distinctive sets of trajectories were identified for WOMAC, TF and PF characteristics, based on model fit and clinical interpretation. The probabilities of knee membership to each trajectory were used in hierarchical cluster analyses to derive knee OA phenotypes. The number and composition of potential phenotypes was selected again based on model fit (silhouette score) and clinical interpretation. Five trajectories representing different constant levels or changing WOMAC scores were identified. For TF and PF OA, eight and six trajectories respectively were identified based on (changes in) joint space narrowing, osteophytes and sclerosis. Combining the probabilities of knees belonging to these different trajectories resulted in six clusters ('phenotypes') of knees with different degrees of functional (WOMAC) and radiographic (PF) parameters; TF parameters were found not to significantly contribute to clustering. Including baseline characteristics as well resulted in eight clusters of knees, dominated by sex, menopausal status and WOMAC scores, with only limited contribution of PF features. Several stable and progressive trajectories of OA symptoms and radiographic features were identified, resulting in phenotypes with relatively independent symptomatic and radiographic features. Sex and menopausal status may be especially important when phenotyping knee OA patients, while radiographic features contributed less. Possible phenotypes were identified that, after validation, could aid personalized treatments and patients selection.

Is quadriceps strength associated with patellofemoral joint loading after anterior cruciate ligament reconstruction?

ObjectiveTo test whether quadriceps strength is associated with measures of patellofemoral (PF) joint loading during running and hopping in people after an anterior cruciate ligament reconstruction (ACLR). DesignCross-sectional study. SettingBiomechanics laboratory. ParticipantsSixty-five participants (24 women; 41 men) 1–2 years post-ACLR. Main outcome measuresPeak isometric quadriceps strength for the surgical limb was measured using a dynamometer. Motion analysis and ground reaction force data were combined with musculoskeletal modelling to measure PF joint loading variables for the reconstructed knee (peak knee flexion angle; peak/impulse of the PF joint contact force; time to peak PF joint contact force) during the stance phase of running and during the landing phase of a standardised forward hop. Linear regression analysis (adjusting for age and sex) assessed the association between quadriceps strength and PF joint loading variables. ResultsTwo significant, albeit modest, associations were revealed. Quadriceps strength was associated with the time to peak PF joint contact force during running (β = −0.001; 95%CI -0.002 to −0.000; R2 = 0.179) and the impulse of the PF joint contact force during hopping (β = 0.014; 95%CI 0.003 to 0.024; R2 = 0.159). ConclusionsA strong link between quadriceps strength and PF joint loading was not evident in people 1–2 years post-ACLR.

Poster 312: Graft harvest for ACL reconstruction from the contralateral knee does not increase patellofemoral arthritis rates versus a normal knee

Objectives: Previous outcome studies after anterior cruciate ligament (ACL) reconstruction have suggested a link between patella tendon (PT) graft harvest and increased incidence of patellofemoral (PF) degenerative changes. However, with the graft harvest on the same knee as the ACL reconstruction, it is difficult to specifically elucidate whether this association is directly from the graft harvest itself as opposed to other factors. Knowledge of the incidence of PF osteoarthritis (OA) after graft harvest from the contralateral knee may provide insight into this relationship. The purpose of this study was to compare PF OA rates between contralateral versus ipsilateral graft harvest for ACL reconstruction. Methods: A database of long-term follow up of ACL reconstruction patients done by a single surgeon was queried to find surgeries done between minimum 15 years and maximum 25 years ago. Patients were included if they had long term radiographs within this window for evaluation of PF OA. Exclusion criteria included revision ACL reconstruction, bilateral ACL involvement, subsequent graft retear, contralateral ACL tear, PF chondral wear seen at the time of surgery, preoperative or subsequent surgeries to either knee, or the presence of preoperative PF OA. Once patients met inclusion criteria, they were separated into groups based on ipsilateral or contralateral PT graft harvest. Standard Merchant’s radiographs were taken by the same technicians with the assistance of a Merchant’s board. Radiographs were graded by the physical therapist that saw the patient back for their long term research visit, each individually trained to grade the images based on the set criteria. Radiographs were graded as none, mild, moderate, or severe PF OA based on joint space narrowing of none, &lt;50%, &gt;50% but &lt;100%, and complete, respectively. Patellofemoral OA rates were then statistically compared utilizing chi-squared analysis or Fisher’s exact test. These criteria produced an ipsilateral group with 95 patients and a contralateral group with 98 patients. Mean ages at time of surgery, height, weight, and sex distribution were not statistically different between groups. The ipsilateral group had a slightly, but statistically significantly, longer mean follow up interval (20.0 vs. 17.4 years, p&lt;.001). Results: In the ipsilateral graft group, PF OA of any grade was present in 20.0% of the involved ACL reconstructed knees and 9.5% of the uninvolved normal knees, which was a statistically significant difference ( p=.041, OR 2.4). In the contralateral graft group, PF OA was present in 10.2% of the ACL reconstructed knees and 13.3% of the contralateral graft donor knees ( p=.506). Patellofemoral OA of any grade was present in 14.7% of all knees in the ipsilateral group and 11.7% of all knees in the contralateral group ( p=.348). When comparing the uninvolved normal knee from the ipsilateral group to the contralateral graft donor knee of the contralateral group, there was no statistical difference in PF OA rates of any grade (9.5% vs. 13.3% p=.407). The ACL reconstructed knee in the ipsilateral group exhibited PF OA in 20.0% and 10.2% in the contralateral group ( p=.057). With regard to moderate or severe PF OA in either knee, the rates were not statistically significant between the ipsilateral and contralateral groups. When comparing the ipsilateral group normal knee to the contralateral group donor knee, the rates of moderate or severe PF OA were 1.1% and 2.0% respectively, which was not statistically significantly different. Conclusions: Previous studies suggest that patella tendon grafts are associated with higher rates of PF OA after ACL reconstruction. Our study reveals that PF OA rates are not statistically increased when a patella tendon graft alone is taken from the knee, when compared to a normal control knee. However, when ACL reconstruction and PT graft are combined in the same knee, there is a statistically significant increase in PF OA versus the uninvolved normal knee, with the ACL reconstructed knee with ipsilateral graft being 2.4 times more likely to experience PF OA than the uninvolved knee. Furthermore, harvesting the ACL graft from the contralateral knee trends toward decreased PF OA rates in the ACL reconstructed knee, though this is not statistically significant. We conclude that the PT graft itself does not increase PF OA rates and that contralateral PT graft harvest may provide advantages to ipsilateral graft harvest with regard to PF OA.

Paper 54: Long Term Clinical and Radiological Review of Matrix-Induced Autologous Chondrocyte Implantation

Objectives: Long-term outcomes following matrix-induced autologous chondrocyte implantation (MACI) are required to better demonstrate later-stage clinical outcomes, patient satisfaction and longevity of repair tissue. This prospective study sought to present the long-term (minimum 10 year) clinical and radiological outcomes of the largest prospectively assessed MACI dataset yet to be reported and compare outcomes in patients undergoing tibiofemoral (TF) versus patellofemoral (PF) MACI. Methods: Between September 2002 and December 2012, 204 patients that underwent MACI were prospectively registered into a research program and assessed pre-surgery and at 2, 5 and 10 years. Of these, 168 patients (182 grafts) were available for clinical review at a minimum 10 years (range 10 to 16 years), of which 151 also underwent MRI. Included in the 182 MACI grafts with minimum 10-year review were: 83 medial femoral condyle (MFC), 32 lateral femoral condyle (LFC), 35 trochlea and 32 patella. Clinically, patients were evaluated with the Knee Injury and Osteoarthritis Outcome Score (KOOS), the 36-item Short Form Health Surveys (SF-36), a visual analogue scale for pain frequency (VAS-F) and severity (VAS-S), satisfaction and peak isokinetic knee extensor and flexor strength. Limb symmetry indices (LSIs) were calculated for strength measures. Grafts were scored on MRI via the magnetic resonance observation of cartilage repair tissue (MOCART) system, with a focus on tissue infill and an overall MRI graft composite score. Results: All PROMs significantly improved (p&lt;0.0001) over the pre- and post-operative period to 2-years post-surgery (Figure 1), with no statistical change (p&gt;0.05) from 2-years to final 10-year follow-up. While the peak isokinetic knee extensor LSI improved significantly over time (p=0.016), at final follow up the mean LSI for peak isokinetic knee flexor and extensor strength was 99.1% and 92.8%, respectively. At final follow-up, 93% of patients were satisfied with MACI to provide knee pain relief, 77% were satisfied with their ability to participate in sports and 89% were satisfied overall. A statistically significant decline was observed from 5 years post-surgery to final follow-up in the MOCART variable of subchondral lamina (p=0.002), while a non-statistical decline was observed in tissue infill (p=0.066) and the overall MRI composite score (p=0.072) (Figure 2), with the MRI-based progression of one patient over the period demonstrated in Figure 3. Of the 151 grafts reviewed via MRI at 10 years or beyond, 14 (9.3%) had failed as defined by graft de-lamination or a graft bed devoid of any repair tissue. Furthermore, of the 36 patients (out of the prospectively recruited 204) that were not available for longer term review, 7 had already proceeded to total knee arthroplasty (TKA) and 1 patient had undergone secondary MACI at the same MFC site due to earlier graft failure. Therefore, a total of 22 patients (10.8%) had essentially failed at or before the final review time. At final follow-up, patients that underwent MACI in the TF (versus PF) joint reported significantly better KOOS sub-scale scores for Pain (p=0.013, TF mean 86.5, PF mean 80.1), Sport (p&lt;0.001, TF mean 71.5, PF mean 60.5) and Quality of Life (p=0.010, TF mean 65.8, PF mean 58.7), as well as a greater knee extensor strength LSI (p=0.002, TF mean 96.0%, PF mean 85.8%). While the TF group demonstrated better 10-year MOCART scores for tissue infill (p=0.027, TF mean 3.2, PF mean 2.9), there were no other differences in MRI-based scores including the overall MRI composite score (p=0.481, TF mean 3.0, PF mean 3.1). Conclusions: This study reports the largest prospective series of patients with long-term review, demonstrating good clinical scores, levels of patient satisfaction and graft survivorship beyond 10 years. Patients undergoing TF (versus PF) MACI reported better long-term clinical outcomes, despite largely similar MRI-based outcomes.

Morphological variations at the knee associated with osteoarthritis: a case-control study using data from the GOAL study

Aim: To identify constitutional morphological features at the knee that associate with knee osteoarthritis (OA, KOA). Methods: This was a case-control study using data from the Genetics of Osteoarthritis and Lifestyle (GOAL) study. Radiographic measurements at the knee were undertaken by a single trained observer. Measurement of 12 characteristics was undertaken in 815 controls with asymptomatic structurally normal knees to examine right-left symmetry and variation with gender and age. Measurements were then compared to “cases” (315 asymptomatic and structurally unaffected knees of people with radiographic and symptomatic OA in the contralateral knee) on the assumption that the morphology of the unaffected knee represented the morphology of the contralateral knee prior to the development of OA. Right-left symmetry of morphological measures in controls was examined using paired t test and minimal detectable change (MDC). Linear regression was used to examine the association between measurements and demographic characteristics. Association of morphological features and unilateral KOA [defined as OA in either patellofemoral (PF) or tibiofemoral (TF) joints], PFOA and TFOA were determined using binary logistic regression and odds ratio (OR) and 95% confidence interval (CI) calculated. Cumulative risk of measurements in determining OA was examined using receiver operating characteristic (ROC) curves. Results: Narrow sulcus and condylar angles, increasing distal femoral, proximal tibial tilt, and increasing varus alignment associated with KOA. ROC curves including all significant morphological features and age, gender, height, and weight predicted knee, PF joint (PFJ), and TF joint (TFJ) OA with area under the curve (AUC) of 0.91, 0.89, and 0.90 respectively. On the contrary, a model only containing age, gender, height, and weight predicted knee, PFJ, and TFJ OA with AUC of 0.59, 0.67, and 0.59 respectively. Conclusions: Five morphological features associated independently with KOA were identified. Together they explain a large proportion of risk for OA.