The Importance of Medial Patellar Shape as a Risk Factor for Recurrent Patellar Dislocation in Adults

BACKGROUND

Research on the cause of lateral patellar dislocation (LPD) has focused on trochlear morphologic parameters, joint alignment, and patellofemoral soft tissue forces. A paucity of information is available regarding how patellar morphologic parameters influence the risk for LPD.

PURPOSE/HYPOTHESIS

The purpose was to assess whether patellar morphology is a risk factor for recurrent LPD. It was hypothesized that (1) patients with recurrent LPD would have decreased patellar width and volume and (2) patellar morphologic parameters would accurately discriminate patients with recurrent LPD from controls.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 3.

METHODS

A total of 21 adults with recurrent LPD (age, 29.7 ± 11.1 years; height, 170.8 ± 9.9 cm; weight, 76.1 ± 17.5 kg; 57% female) were compared with 21 sex- and height-matched controls (age, 27.2 ± 6.7 years; height, 172.0 ± 10.6 cm; weight, 71.1 ± 12.8 kg; 57% female). Three-dimensional axial fat-saturated magnetic resonance imaging scans were used to measure patellar medial, lateral, and total width; patellar volume; patellar medial and lateral facet length; the Wiberg index; and previously validated knee joint alignment and femoral shape measurements (eg, tibial tuberosity to trochlear groove distance, trochlear dysplasia).

RESULTS

The LPD group demonstrated reduced medial patellar width (Δ = -3.6 mm; P < .001) and medial facet length (Δ = -3.7 mm; P < .001) but no change in lateral width or facet length. This resulted in decreased total patellar width (Δ = -3.2 mm; P = .009), decreased patellar volume (Δ = -0.3 cm3; P = .025), and an increased Wiberg index (Δ = 0.05; P < .001). No significant differences were found for all other patellar shape measures between cohorts. Medial patellar width was the strongest single discriminator (83.3% accuracy) for recurrent LPD. Combining medial patellar width, patellofemoral tilt, and trochlear groove length increased the discrimination to 92.9%.

CONCLUSION

The medial patellar width was significantly smaller in patients with recurrent LPD and was the single most accurate discriminator for recurrent LPD, even compared with traditional trochlear shape and joint alignment measures (eg, trochlear dysplasia, patella alta). Therefore, medial patellar morphology should be assessed in patients with LPD as a risk factor for recurrence and a potential means to improve treatment.

Patellar Lateralization, Absence of Joint Hypermobility, and the Mechanism of Injury Are Associated With Osteochondral Fracture After First-time Acute Lateral Patellar Dislocation in Adolescents: An MRI-based Evaluation

BACKGROUND

Although the risk factors for patellofemoral dislocation are clearly defined, risk factors for osteochondral fracture (OCF) after patellar dislocation are not as well defined. The aim of this study was to investigate the risk factors for OCF by evaluating patients with and without OCF after first-time acute patellar dislocation.

METHODS

This multicenter study was conducted as a retrospective examination of the radiologic measurements on the magnetic resonance imaging of 306 patients. The patients were divided into the OCF group and non-OCF group, and OCFs were grouped according to whether the fracture was in the patella or femur. Patellar height, patellar lateralization, trochlear morphology, patellofemoral matching, and patella types were evaluated on patient magnetic resonance imaging. The presence of joint hypermobility in the patients was determined according to the Beighton scale score. The injury mechanisms of the patients were grouped as sports-related injuries, injuries resulting from simple falls, and injuries during daily activities.

RESULTS

A total of 120 OCFs were detected in 108 (35.2%) patients, of which 96 (80%) were in the patella and 24 (20%) in the femur. The rate of OCF after sports-related injuries was found to be significantly higher than in other injury mechanisms ( P =0.001). More joint hypermobility was detected in patients without OCF ( P =0.041). The measurements of tibial tubercle-trochlear groove, tibial tubercle-posterior cruciate ligament distance and lateral patellar displacement were statistically higher in cases with OCF ( P =0.001). In patients with normal joint mobility, the rate of OCF localization in the patella was significantly higher ( P =0.035). No correlation was found between any other parameters and OCF ( P >0.05). The absence of joint hypermobility and the measurements of tibial tubercle-trochlear groove distance, tibial tubercle-posterior cruciate ligament distance, and lateral patellar displacement were independent risk factors for the incidence of OCF according to the logistic regression analysis.

CONCLUSIONS

The absence of joint hypermobility and patellar lateralization are independent risk factors for the occurrence of OCF after first-time patellar dislocation. Sports-related injury is a nonindependent risk factor for the presence of OCF. In patients with normal joint mobility, the incidence of OCF in the patella is higher than in the femur. These important factors should be considered when evaluating patients and starting their treatment.

LEVEL OF EVIDENCE

Level III-retrospective cohort study.

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

PURPOSE

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.

MATERIAL AND METHODS

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.

RESULTS

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.

CONCLUSION

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.

Measurement of TT-TG can change with sequential MRIs due to variations in tibiofemoral rotation in patellofemoral instability patients

PURPOSE

There are various anatomic risk factors for patellofemoral instability (PFI) that help guide surgical treatment, including the tibial tubercle to trochlear groove (TT-TG) distance. However, no study has analysed the temporal changes in TT-TG prior to surgical intervention. This study sought to understand the variations in TT-TG over time for pediatric patients suffering from PFI prior to surgical intervention. The authors hypothesised that the TT-TG would substantially change between time points.

METHODS

Patients undergoing medial patellofemoral ligament (MPFL) reconstruction between 2014 and 2019 by one of two fellowship-trained orthopaedic surgeons were identified. Patients were included if they had two preoperative magnetic resonance imaging (MRI) performed on the same knee within 7.5 months of each other prior to any surgical intervention and had an initial TT-TG greater than 10 mm.

RESULTS

After considering 251 patients for inclusion, 21 patients met the final inclusion criteria. The mean age was 14.5 ± 2.5 years and 61.9% were female. TT-TG was initially noted to be 15.1 ± 1.8 mm. At mean time after sequential MRIs of 5.0 ± 1.9 months, TT-TG was noted to be 16.7 ± 3.2 mm. The differences between initial and subsequent TT-TG ranged from a 21.2% decrease to a 61.1% increase, with a mean difference of an 11.3% increase. Comparison between initial and subsequent TT-TG values demonstrated a significant difference (p = 0.017). Change in tibiofemoral rotation ranged from -9.2° to 7.5°. When comparing the change in TT-TG to change in tibiofemoral rotation, a significant correlation was found (p = 0.019).

CONCLUSION

Despite only a mean time between MRIs of 5 months, variations in TT-TG ranged from a decrease of 21.2% to an increase of 61.1%. The significant relationship between the changes in TT-TG and changes in tibiofemoral rotation between MRIs suggest that TT-TG measurements may vary due to variations in tibiofemoral rotation at the time of individual MRIs.

LEVEL OF EVIDENCE

Level IV.

Patellofemoral joint geometry and osteoarthritis features 3-10 years after knee injury compared with uninjured knees

In this cross-sectional study, we compared patellofemoral geometry in individuals with a youth-sport-related intra-articular knee injury to uninjured individuals, and the association between patellofemoral geometry and magnetic resonance imaging (MRI)-defined osteoarthritis (OA) features. In the Youth Prevention of Early OA (PrE-OA) cohort, we assessed 10 patellofemoral geometry measures in individuals 3-10 years following injury compared with uninjured individuals of similar age, sex, and sport, using mixed effects linear regression. We also dichotomized geometry to identify extreme (>1.96 standard deviations) features and assessed likelihood of having extreme values using Poisson regression. Finally, we evaluated the associations between patellofemoral geometry with MRI-defined OA features using restricted cubic spline regression. Mean patellofemoral geometry did not differ substantially between groups. However, compared with uninjured individuals, injured individuals were more likely to have extremely large sulcus angle (prevalence ratio [PR] 3.9 [95% confidence interval, CI: 2.3, 6.6]), and shallow lateral trochlear inclination (PR 4.3 (1.1, 17.9)) and trochlear depth (PR 5.3 (1.6, 17.4)). In both groups, high bisect offset (PR 1.7 [1.3, 2.1]) and sulcus angle (PR 4.0 [2.3, 7.0]) were associated with cartilage lesion, and most geometry measures were associated with at least one structural feature, especially cartilage lesions and osteophytes. We observed no interaction between geometry and injury. Certain patellofemoral geometry features are correlated with higher prevalence of structural lesions compared with injury alone, 3-10 years following knee injury. Hypotheses generated in this study, once further evaluated, could contribute to identifying higher-risk individuals who may benefit from targeted treatment aimed at preventing posttraumatic OA.

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

OBJECTIVE

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.

DESIGN

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).

RESULTS

One knee from 1083 participants (age 56.7 ± 6.6 years; body mass index 28.0 ± 4.9 kg/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.

CONCLUSION

Frequent AKP at baseline was associated with worsening cartilage damage in the lateral PF joint over 2 years.

Patellar Tilt and Patellar Tendon-Trochlear Groove Angle Present the Optimum Magnetic Resonance Imaging Diagnostic Reliability for Patients With Patellar Instability

PURPOSE

To describe, in controls and in a population with patellar instability, magnetic resonance imaging values of measurements representing major associated factors for patellar instability (patellar height, trochlear dysplasia, and extensor mechanism alignment), as well as their cutoff values.

METHODS

In total, 323 knee magnetic resonance imaging scans, 142 with patellar instability and 181 controls without patellofemoral complaints (anterior cruciate, medial collateral ligament, meniscus ruptures or normal) were evaluated. Means, normality values in the control population, ideal cutoff values through receiver operating characteristic curves analysis, and interobserver reliability (intraclass correlation coefficient) were described for a series of measurements.

RESULTS

All measurements were statistically different in control and instability patients, except for the patellotrochlear index and tibial tuberosity to posterior cruciate ligament distance. The interobserver intraclass correlation coefficient was good or excellent (above 0.75) only for the patellotrochlear index, patellar tendon-trochlear groove (PTTG) angle, and patellar tilt. The optimal cutoff value for each measurement was: PTTG angle ≥25.3o with sensitivity (S) of 70% and specificity (E) of 89%, patellar tilt ≥16o (S: 69% and E: 84%), trochlear sulcus angle ≥153o (S: 75% and E: 76%), Carrillon ≤12.8o (S: 62% and E: 87%), PTTG distance ≥11mm (S: 71% and E: 78%), Caton-Deschamps index ≥1.23 (S: 72% and E: 76%) and trochlear bump ≥3.95 mm (S: 76% and E: 65%).

CONCLUSIONS

Caton-Deschamps index (≥1.23), trochlear sulcus angle (≥153o), ventral prominence of the trochlea (≥3.95 mm), PTTG distance (≥11 mm), PTTG angle (≥25.3o), Carrillon angle (≤12.8o), and patellar tilt (≥16o) presented better diagnostic performance for patellar instability. Patellotrochlear index and tibial tuberosity to posterior cruciate ligament distance were not related to patellar instability. The interobserver reliability of the factors related to patellar instability was excellent only for the PTTG angle and lateral patellar tilt.

LEVEL OF EVIDENCE

Level III, retrospective case-control study.

Editorial Commentary: Evaluation of Patellofemoral Instability Is Complex and Multifactorial

The work-up of patellofemoral instability is complex and multifactorial. Patient factors (i.e., age, activity demand, goals/expectations), clinical presentation (pain, instability, or both), and physical examination (i.e., J-sign, apprehension into flexion), must be correlated with imaging findings (radiographs, magnetic resonance imaging, computed tomography) and anatomic risk factors, including patella alta, trochlear dysplasia, patellar tilt, lateralized force vector, valgus, femoral anteversion, and tibial torsion. Thus, developing a standard battery of reliable and reproducible radiographic measures of patellofemoral instability is a challenge. Imaging cut-offs provide insight into relative risk of recurrent instability. We still fall short in using imaging parameters to predict when to operate, what procedure(s) to perform, and how the patient might do. Future directions include the use of artificial intelligence and 3-dimensional measurements to help simplify a complex problem.

Editorial Commentary: When Properly Indicated, Combined Tibial Tubercle Osteotomy Reduces Risk of Recurrent Patellofemoral Instability More Than Does Isolated Medial Patellofemoral Ligament Reconstruction

Clinical recognition and surgical treatment of patellofemoral instability has evolved dramatically over the past 3 decades. However, few patellofemoral patients present with an isolated medial patellofemoral ligament (MPFL) tear. Rather, patients often demonstrate patella alta, increased tibial tubercle to trochlear groove (TT-TG) distance, dysplasia, coronal malalignment, or combinations thereof. Given this, concomitant procedures such as tibial tubercle osteotomy (TTO) have become increasingly popularized, given their ability to anteriorize, medialize, and even distalize the patella to correct tracking. It is generally recommended that concurrent TTO be considered with primary medial patellofemoral ligament reconstruction (MPFLR) in patients with closed physes whose TT-TG distance is larger than 17 to 20 mm. MPFLR + TTO is generally safe and may decrease risk of revision surgery when compared with isolated MPFLR in properly indicated patients. However, it important to measure both knee rotation angle and tibial tubercle lateralization on magnetic resonance imaging, as both factors influence TT-TG. In patients in whom abnormal knee rotation angle is felt to be the primary driver of TT-TG, surgeons should proceed with caution when considering concomitant TTO. The pen may be mightier than the sword, but the osteotome may be mightier yet than the scalpel.

Patellofemoral joint loading and early osteoarthritis after ACL reconstruction

Patellofemoral joint (PFJ) osteoarthritis is common following anterior cruciate ligament reconstruction (ACLR) and may be linked with altered joint loading. However, little is known about the cross-sectional and longitudinal relationship between PFJ loading and osteoarthritis post-ACLR. This study tested if altered PFJ loading is associated with prevalent and worsening early PFJ osteoarthritis post-ACLR. Forty-six participants (mean ± 1 SD age 26 ± 5 years) approximately 1-year post-ACLR underwent magnetic resonance imaging (MRI) and biomechanical assessment of their reconstructed knee. Trunk and lower-limb kinematics plus ground reaction forces were recorded during the landing phase of a standardized forward hop. These data were input into a musculoskeletal model to calculate the PFJ contact force. Follow-up MRI was completed on 32 participants at 5-years post-ACLR. Generalized linear models (Poisson regression) assessed the relationship between PFJ loading and prevalent early PFJ osteoarthritis (i.e., presence of a PFJ cartilage lesion at 1-year post-ACLR) and worsening PFJ osteoarthritis (i.e., incident/progressive PFJ cartilage lesion between 1- and 5-years post-ACLR). A lower peak PFJ contact force was associated with prevalent early PFJ osteoarthritis at 1-year post-ACLR (n = 14 [30.4%]; prevalence ratio: 1.37; 95% confidence interval [CI]: 1.02-1.85) and a higher risk of worsening PFJ osteoarthritis between 1- and 5-years post-ACLR (n = 9 [28.1%]; risk ratio: 1.55, 95% CI: 1.13-2.11). Young adults post-ACLR who exhibited lower PFJ loading during hopping were more likely to have early PFJ osteoarthritis at 1-year and worsening PFJ osteoarthritis between 1- and 5-years. Clinical interventions aimed at mitigating osteoarthritis progression may be beneficial for those with signs of lower PFJ loading post-ACLR.

Assessments of early patellofemoral joint osteoarthritis features after anterior cruciate ligament reconstruction: a cross-sectional study

BACKGROUND

Persistent anterior knee pain and subsequent patellofemoral joint (PFJ) osteoarthritis (OA) are common symptoms after anterior cruciate ligament reconstruction (ACLR). Quadriceps weakness and atrophy is also common after ACLR. This can be contributed by arthrogenic muscle inhibition and disuse, caused by joint swelling, pain, and inflammation after surgery. With quadriceps atrophy and weakness are associated with PFJ pain, this can cause further disuse exacerbating muscle atrophy. Herein, this study aims to identify early changes in musculoskeletal, functional and quality of health parameters for knee OA after 5 years of ACLR.

METHODS

Patients treated with arthroscopically assisted single-bundle ACLR using hamstrings graft for more than 5 years were identified and recruited from our clinic registry. Those with persistent anterior knee pain were invited back for our follow-up study. For all participants, basic clinical demography and standard knee X-ray were taken. Likewise, clinical history, symptomatology, and physical examination were performed to confirm isolated PFJ pain. Outcome measures including leg quadriceps quality using ultrasound, functional performance using pressure mat and pain using self-reported questionnaires (KOOS, Kujala and IKDC) were assessed. Interobserver reproducibility was assessed by two reviewers.

RESULTS

A total of 19 patients with unilateral injury who had undergone ACLR 5-years ago with persistent anterior knee pain participated in this present study. Toward the muscle quality, thinner vastus medialis and more stiffness in vastus lateralis were found in post-ACLR knees (p < 0.05). Functionally, patients with more anterior knee pain tended to shift more of their body weight towards the non-injured limb with increasing knee flexion. In accordance, rectus femoris muscle stiffness in the ACLR knee was significantly correlated with pain (p < 0.05).

CONCLUSION

In this study, it was found that patients having higher degree of anterior knee pain were associated with higher vastus medialis muscle stiffness and thinner vastus lateralis muscle thickness. Similarly, patients with more anterior knee pain tended to shift more of their body weight towards the non-injured limb leading to an abnormal PFJ loading. Taken together, this current study helped to indicate that persistent quadriceps muscle weakness is potential contributing factor to the early development of PFJ pain.

3D patellar shape is associated with radiological and clinical signs of patellofemoral osteoarthritis

OBJECTIVE

To examine the association between 3D patellar shape and 1) isolated magnetic resonance imaging (MRI)-based patellofemoral osteoarthritis (PFOA), 2) the morphological features of PFOA, and 3) the clinical symptoms of PFOA.

DESIGN

MRI data from 66 women with isolated MRI-based PFOA and 66 age- and BMI-matched healthy women were selected from a cohort study. The patellae were manually segmented from MRI scans and used to create a 3D statistical shape model (SSM) of the patella. Structural abnormalities were semi-standardized scored on MRI using MRI osteoarthritis knee score (MOAKS). Regression analyses were applied to determine the associations between the shape parameters retrieved from the SSM, group status, clinical symptoms, and structural abnormalities.

RESULTS

Four shape variants showed a statistically significant (<0.05) association with the group status. The mode responsible for most of the shape variations showed participants with PFOA possess a relatively thicker dorsal bump on the articular part of the patella, compared to patellae of control participants. Three of these variants showed an association with the presence of osteophytes and cartilage loss on the patella. Multiple associations were found between patellar shape and the clinical symptoms of PFOA.

CONCLUSIONS

Patellar shape is associated with the prevalence of MRI-based PFOA in women. Some shape variants were also associated with clinical symptoms. Interestingly, one particular shape variant associated with the presence of MRI-based PFOA was earlier shown to be associated with structural abnormalities associated with OA in a population aged under 40. This may suggest that patellar shape may be an early detectable risk factor for PFOA.

Association of patella alignment with cartilage relaxation times and self-reported symptoms in individuals with patellofemoral degeneration

To determine the cross-sectional and longitudinal associations of patella alignment with cartilage relaxation and patients' self-reported symptoms. Thirty participants with isolated patellofemoral joint (PFJ) degeneration (six males, 53.7 ± 9.3 years) and 24 controls (12 males, 47.6 ± 10.7 years) were included. Magnetic resonance assessment was performed to provide grading of structural abnormalities, cartilage relaxation times, and patella alignment. Self-reported symptoms were assessed using the self-administrated knee injury and osteoarthritis outcome score (KOOS). All participants were examined at baseline and 3 years. Statistical parametric mapping and Pearson partial correlation were used to evaluate the associations between patella alignment with cartilage relaxation times and self-reported symptoms, respectively. The analyses were performed between baseline (cross-sectional) as well as the baseline against 3 years (longitudinal). Results indicated that patella height and patella flexion were associated with T1ρ and T2 relaxation times at baseline (percentages of voxels showing significant correlation [PSV] = 10.1%-24.8%; mean correlations [R] = 0.34-0.36; mean p = 0.015-0.026). Furthermore, greater patella lateral alignment, lateral tilt, and lateral spin were associated with longer T2 times at 3 years (PSV = 11.0%-14.4%, R = 0.39-0.44, p = 0.017-0.028). Last, a higher patella was associated with a lower KOOS at baseline and at 3 years (R = -0.33 to -0.35). The study suggests that patella malalignment is a risk factor for worsening cartilage health, informing clinicians of a better rehabilitation program that targets PFJ degeneration.

Determination of Standard Values for Knee Version in a Healthy Population

BACKGROUND

Different measures are used to describe relevant anatomic variations that can result in patellofemoral instability and disorders. Knee version, the relative rotational alignment between the femur and tibia in the axial plane at the level of the knee, may have a decisive effect on the kinematics of the patellofemoral joint. However, data regarding the values of knee version are currently lacking.

PURPOSE

This study aimed to determine standard values for knee version in a healthy population.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 100 healthy volunteers (50 male and 50 female) without patellofemoral disorders or lower extremity malalignment were included in this study and underwent knee magnetic resonance imaging. The torsion values of the femur and tibia were independently measured using the Waidelich and Strecker method. Knee version, defined as static rotation of the tibia with respect to the femur in full extension, was determined by measuring the angle between the tangent lines to the dorsal femoral condyle (DFC) and the dorsal tibial head (DTH; defined by the posterior point of the proximal tibial plateau). Supplementary measurements were obtained as follows: (1) femoral epicondylar line (FEL), (2) tibial ellipse center line (TECL), (3) tibial tuberosity-trochlear groove (TT-TG) distance, and (4) tibial tuberosity-posterior cruciate ligament (TT-PCL) distance.

RESULTS

In 200 analyzed legs of 100 volunteers (mean age, 26.5 ± 5.8 years [range, 18 to 40 years]), we identified a mean internal femoral torsion of -23.8°± 9.7° (range, -46.2° to 1.6°), external tibial torsion of 33.2°± 7.4° (range, 16.4° to 50.3°), and external knee version (DFC to DTH) of 1.3°± 3.9° (range, -8.7° to 11.7°). Other measurements were as follows: FEL to TECL, -0.9°± 4.9° (range, -16.8° to 12.1°); FEL to DTH, -3.6°± 4.0° (range, -12.6° to 6.8°); and DFC to TECL, 4.0°± 4.9° (range, -12.7° to 14.7°). The mean TT-TG distance was 13.4 ± 3.7 mm (range, 5.3-23.5 mm), and the mean TT-PCL distance was 11.5 ± 3.5 mm (range, 6.0-20.9 mm). Female participants had significantly greater external knee version than male participants.

CONCLUSION

Coronal- and sagittal-plane alignments of the knee have a well-known effect on the biomechanics of this joint. Additional information about the axial plane may result in new decision-making algorithms for managing knee disorders. This study is the first to report standard values of knee version in a healthy population. As a subsequent step building on this work, we advocate for the measurement of knee version in patients with patellofemoral disorders, as this parameter may assist with new treatment guidelines in the future.

Is running good or bad for your knees? A systematic review and meta-analysis of cartilage morphology and composition changes in the tibiofemoral and patellofemoral joints

BACKGROUND

The general health benefits of running are well-established, yet concern exists regarding the development and progression of osteoarthritis.

AIM

To systematically review the immediate (within 20 min) and delayed (20 min-48 h) effect of running on hip and knee cartilage, as assessed using magnetic resonance imaging (MRI).

METHOD

Studies using MRI to measure change in hip or knee cartilage within 48 h pre- and post-running were identified. Risk of bias was assessed using a modified Newcastle-Ottawa Scale. Percentage change in cartilage outcomes were estimated using random-effects meta-analysis. Certainty of evidence was evaluated with the Grading of Recommendations Assessment, Development and Evaluation tool.

RESULTS

Twenty-four studies were included, evaluating 446 knees only. One third of studies were low risk of bias. Knee cartilage thickness and volume decreased immediately after running, with declines ranging from 3.3% (95% confidence interval [CI]: 2.6%, 4.1%) for weight-bearing femoral cartilage volume to 4.9% (95% CI: 4.43.6%, 6.2%) for patellar cartilage volume. T1ρ and T2 relaxation times were also reduced immediately after running, with the largest decline being 13.1% (95% CI: -14.4%, -11.7%) in femoral trochlear cartilage. Tibiofemoral cartilage T2 relaxation times recovered to baseline levels within 91 min. Existing cartilage defects were unchanged within 48 h post-run.

CONCLUSIONS

There is very low certainty evidence that running immediately decreases the thickness, volume, and relaxation times of patellofemoral and tibiofemoral cartilage. Hip cartilage changes are unknown, but knee changes are small and appear transient suggesting that a single bout of running is not detrimental to knee cartilage.

Versorgungsrealität patellastabilisierender Operationen

Hintergrund

Die patellofemorale Instabilität zählt zu den häufigsten Pathologien des Kniegelenks. Die Planung und Durchführung patellastabilisierender Operationen ist sehr variabel. Bezüglich der operativen Maßnahmen kommt der präoperativen Planung, gerade im Hinblick auf die häufig hohe Komplexität der zugrundeliegenden Pathologien, eine entscheidende Bedeutung zu.

Fragestellung

Ziel dieser Studie war es, die aktuelle Versorgungsrealität in Bezug auf Planung und Durchführung patellastabilisierender Operationen unter Mitgliedern der Deutschen Gesellschaft für Orthopädie und Unfallchirurgie (DGOU) abzubilden. Des Weiteren sollte erhoben werden, ob ggf. automatisierte Analysen der zugrundeliegenden Anatomie die Planung und Durchführung patellastabilisierender Operationen (im Primär- und Revisionsfall) beeinflussen würden.

Material und Methoden

Unter allen aktiven Mitgliedern der DGOU wurde per Mail eine anonymisierte Online-Umfrage mit 16 Fragen erhoben. 7974 Mitglieder wurden angeschrieben, 393 Rückmeldungen konnten anschließend analysiert werden.

Ergebnisse

Die MPFL-Plastik (89,8 %) ist die am häufigsten durchgeführte Operation zur Patellastabilisierung. Dahinter folgen Tuberositasversatzoperationen (64,9 %), Korrekturosteotomien (51,2 %) und Trochleaplastiken (19,9 %). Die Wahl bezüglich des operativen Vorgehens fällt überwiegend auf Grundlage einer Kombination aus klinischen und radiologischen Befunden (90,3 %). Für die Entscheidung zur Operation werden hauptsächlich MRT-Bildgebung (81,2 %), Standard-Röntgenbilder (77,4 %) und Beinganzaufnahmen (76,6 %) herangezogen. Insgesamt würden 59,3 % der Befragten eine automatisierte Analyse für eine vereinfachte präoperative Planung und die Detektion von entscheidenden radiologischen Parametern (59,0 %) in Anspruch nehmen, sofern diese zur Verfügung stünden.

Diskussion

Die Erhebungen dieser Umfrage unter Mitgliedern der DGOU weisen die MPFL-Plastik als zentralen Ansatzpunkt zur operativen Behandlung patellofemoraler Instabilitäten aus, diagnostisch ist die MRT-Bildgebung essenziell. Durch eine zukünftige Etablierung automatisierter Software-gestützter Analysemethoden könnte bei einer Vielzahl von Operateuren eine Erweiterung der radiologisch berücksichtigten Parameter in der Planung patellastabilisierender Operationen erreicht werden.

Patellar dislocation is associated with increased tibial but not femoral rotational asymmetry

PURPOSE

Patellar dislocation is associated with a range of anatomical abnormalities affecting the trochlea, extensor mechanism and the tibia. The relationship between patellofemoral instability and rotational abnormalities of the posterior condyles, trochlear groove and proximal tibia has not been adequately determined. This study aimed to identify the frequency and severity of anatomical risk factors to determine their relative contribution to patellofemoral instability.

METHODS

A retrospective morphological study was undertaken comparing multiple anatomical measurements with magnetic resonance imaging of 50 patients with patellofemoral instability to an age- and gender-matched Control group (n = 50). Several techniques were assessed measuring both femoral and tibial axial asymmetry. A new measurement, tibial rotational asymmetry, comparing a line between the midpoints of the collateral ligaments to the axis between the patellar tendon and posterior cruciate ligament, was assessed for its association with patellofemoral instability.

RESULTS

Compared to the controls, the patellofemoral instability group demonstrated a significant difference in tibial rotational asymmetry, with a mean of 2.9° (SD 3.2°) externally rotated vs - 1.6° (SD 2.2°) in the control group. Significant differences were also demonstrated regarding the sulcus angle, tibial tubercle-trochlear groove distance, tibial tubercle-posterior cruciate ligament distance, patellar size and the Insall-Salvati ratio. There were no differences between groups regarding the lengths of the posterior condyles, the heights of the trochlear ridges or lateralisation of the trochlear groove. Further analysis of the patellofemoral instability group revealed a subgroup of males with normal anatomy (7/50) and a subgroup of females with isolated patella alta (7/50).

CONCLUSION

Patellofemoral instability is associated with tibial rotational asymmetry due to lateralisation of the tibial tubercle. It is also associated with patella alta and reduced trochlear groove depth. The femoral axial shape is otherwise unchanged.

LEVEL OF EVIDENCE

III.

Tibial Tubercle-Trochlear Groove/Trochlear Width Is the Optimal Indicator for Diagnosing a Lateralized Tibial Tubercle in Recurrent Patellar Dislocation Requiring Surgical Stabilization

PURPOSE

To identify the individualized method of quantifying lateralization of the tibial tubercle with the best diagnostic effectiveness, as evaluated by measurement repeatability using the intraclass correlation coefficient (ICC), the size of the difference between the case group and the control group, and receiver operating characteristic (ROC) curve analysis.

METHODS

Patients who had undergone surgery for recurrent patellar dislocation (the case group) and patients who had no history of patellar dislocation (the control group) from January 2014 to December 2019 were included in the study. Six indices that describe lateralization of the tibial tubercle were calculated using either computed tomography (CT) or magnetic resonance imaging (MRI): tibial tubercle lateralization (TTL), tibial tubercle-trochlear groove (TT-TG) ratio, tibial tubercle-posterior cruciate ligament (TT-PCL) ratio, TT-TG index, (TT-TG)/patellar width (PW), and (TT-TG)/trochlear width (TW). Diagnostic effectiveness was evaluated by 1) intra-rater reliability (measurements on two occasions) and inter-rater reliability (measurements by two assessors) using the ICC, 2) the size of the difference between the case group and the control group, and 3) ROC curve analysis, measuring the area under the ROC curve (AUC) and the post hoc power.

RESULTS

100 knees in 88 patients who had undergone surgery for recurrent patellar dislocation and 55 knees in 53 patients who had no history of patellar dislocation were analyzed. The ICC for all the methods were higher than .75. The mean differences between the case group and the control group for TTL, TT-TG ratio, TT-PCL ratio, TT-TG index, (TT-TG)/PW, and (TT-TG)/TW were 2%, 8%, 2%, 12%, 24% and 56%, respectively. The mean differences between the case group and the control group for (TT-TG)/TW was significantly greater than those for the other methods (P < .0001, unpaired t-test). AUC of TTL, TT-TG ratio, TT-PCL ratio, TT-TG index, (TT-TG)/PW, and (TT-TG)/TW were .708, .880, .630, .814, .882, and .905. AUC of (TT-TG)/TW was significantly greater than those of TTL and TT-PCL ratio (P < .0001). The post hoc power for TT-PCL ratio, TT-TG index, (TT-TG)/PW, TT-TG ratio, (TT-TG)/TW, and TTL were 78%, 81%, 88%, 88%, 91%, and 71%, respectively.

CONCLUSION

Of the six indices evaluated in this study, (TT-TG)/TW showed the greatest mean difference between the two groups, had the greatest diagnostic utility (as measured by AUC values) and had excellent inter-rater and intra-rater reliability (as measured by ICCs). Thus, it may be the best individualized index for diagnosing a lateralized tibial tubercle in patients with recurrent patellar dislocation requiring surgical stabilization compared to patients with no history of patellar dislocation.

LEVEL OF EVIDENCE

Level III, diagnostic study, retrospective cohort study.

Increased femoral antetorsion correlates with higher degrees of lateral retropatellar cartilage degeneration, further accentuated in genu valgum

PURPOSE

The role of increased femoral antetorsion (femAT) as a contributor to patellofemoral (PF) osteoarthritis (OA) is unknown. The purpose of this study was to investigate whether increased femAT was associated with advanced cartilage degeneration in the lateral PF joint.

METHODS

Patients who underwent complete radiographic workup for surgical intervention due to OA in any knee joint compartment were included. Cartilage morphology according to the International Cartilage Repair Society (ICRS) cartilage lesion classification system in the PF joint, femoral and tibial torsion, frontal leg axis, and tibial tuberosity-trochlear groove (TT-TG) distance were assessed. Increased femAT was defined as  > 20° according to previous reports.

RESULTS

A total of 144 patients were included. Ninety-seven patients had a femAT of  < 20° and 45 of  > 20°. A significant odds ratio (OR) was found for lateral retropatellar (OR 3.5; p = 0.02) ICRS grade 3 and 4 cartilage degeneration and increased femAT  ≥ 20°. In the medial PF compartment, increased femAT had an inverse effect (OR 0.16; p = 0.01). No significant ORs were found for TT-TG distance, tibial torsion, or leg axis. The lateral retropatellar ICRS grade showed a linear correlation to increased femAT values. In valgus knees, isolated lateral PF OA had an even more pronounced correlation to increased femAT (p = 0.004).

CONCLUSION

Increased femAT showed higher grades of lateral retropatellar cartilage degeneration, which was even more pronounced in valgus knees.

LEVEL OF EVIDENCE

Cohort study: Level III.

Efficacy and mid/long-term survivorship of mobile-bearing unicompartmental knee arthroplasty for medial compartment knee osteoarthritis combined patellofemoral joint arthritis: a prospective cohort study protocol

INTRODUCTION

Unicompartmental knee arthroplasty (UKA) is one of the most effective surgical procedures for treating isolated medial compartment knee osteoarthritis. However, previous studies have regarded patellofemoral osteoarthritis as a contraindication for UKA. In contrast, most current research shows that damage to the articular cartilage of the patellofemoral joint, even to the extent of full-thickness cartilage loss, has no influence on the outcome of UKA.

METHODS AND ANALYSIS

Study settings: This study is a prospective cohort study that will compare the Forgotten Joint Score and Lonner patellofemoral joint score of patients who have undergone UKA; the patients will be divided into two groups (with and without patellofemoral joint osteoarthritis (PFJOA)).

PRIMARY OBJECTIVE

Long-term follow-up will be used to evaluate the effect of the operation on the above-mentioned scores in both the groups.

SECONDARY OBJECTIVE

We will divide the patients from the with PFJOA group into three subgroups according to the localisation of patellofemoral cartilage lesions (medial zone, lateral zone and central zone). We aim to compare knee joint scores among these groups and clarify the impact of different wear sites on clinical efficacy. We will use CT to explore the potential mechanism through which UKA affects patellofemoral joint-related parameters (lateral patellar tilt, lateral patellar shift and tibia tuberosity-trochlear groove distance). We will also record mid-term/long-term post-surgery complications.

ETHICS AND DISSEMINATION

This study's protocol is in accordance with the Declaration of Helsinki. This study was approved by the Ethics Committee of Xuanwu Hospital. The results of this study will be disseminated in international peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ChiCTR2000030310.

Relation of Patellofemoral Joint Alignment, Morphology, and Radiographic Osteoarthritis to Frequent Anterior Knee Pain: Data from the Multicenter Osteoarthritis Study

OBJECTIVE

Patellofemoral (PF) alignment and trochlear morphology are associated with PF osteoarthritis (OA) and knee pain, but whether they are associated with localized anterior knee pain is unknown, which is believed to be a symptom specific to PF joint pathology. We therefore aimed to evaluate the relation of PF alignment and morphology, as well as PFOA and tibiofemoral OA, to anterior knee pain.

METHODS

The Multicenter Osteoarthritis Study is a cohort study of individuals with, or at risk for, knee OA. We evaluated cross-sectional associations of PF alignment, trochlear morphology, and PF and tibiofemoral radiographic OA, with localized anterior knee pain (defined with a pain map). We used 2 approaches: a within-person knee-matched evaluation of participants with unilateral anterior knee pain (conditional logistic regression), and a cohort approach comparing those with anterior knee pain to those without (binomial regression).

RESULTS

With the within-person knee-matched approach (n = 110; 64% women, mean age 70 years, body mass index [BMI] 30.9), PF alignment, morphology, and tibiofemoral OA were not associated with unilateral anterior knee pain. Radiographic PFOA was associated with pain, odds ratio 5.3 (95% confidence interval [95% CI] 1.6-18.3). Using the cohort approach (n = 1,818; 7% of knees with anterior knee pain, 59% women, mean age 68 years, BMI 30.4), results were similar: only PFOA was associated with pain, with a prevalence ratio of 2.2 (95% CI 1.4-3.4).

CONCLUSION

PF alignment and trochlear morphology were not associated with anterior knee pain in individuals with, or at risk for, knee OA. Radiographic PFOA, however, was associated with pain, suggesting that features of OA, more so than mechanical features, may contribute to localized symptoms.

Increased femoral anteversion is associated with inferior clinical outcomes after MPFL reconstruction and combined tibial tubercle osteotomy for the treatment of recurrent patellar instability

PURPOSE

This study aimed at investigating the influence of an increased femoral anteversion angle on clinical outcomes after medial patellofemoral ligament reconstruction and combined tibial tubercle osteotomy for the treatment of recurrent patellar instability. It was hypothesized that an increased femoral anteversion is associated with inferior clinical outcomes.

METHODS

From 2014 to 2016, a total of 144 consecutive patients with recurrent patellar instability were treated with medial patellofemoral ligament reconstruction and combined tibial tubercle osteotomy. The femoral anteversion angle was measured using three-dimensional computed tomography scans. Patients were allocated into group A (femoral anteversion < 20°), group B (femoral anteversion 20°-30°) and group C (femoral anteversion > 30°) based on the value of the femoral anteversion angle. Routine radiography and CT examinations were performed to evaluate the patellar height, trochlear dysplasia, genu valgum, and tibial tuberosity-trochlear groove (TT-TG) distance. The patellar lateral shift distance assessed with stress radiography was used pre- and postoperatively to quantify medial patellofemoral ligament residual laxity under anaesthesia. Patient-reported outcomes (Kujala, IKDC, and Lysholm scores) and patellar maltracking ("J-sign") were evaluated pre- and postoperatively. Finally, subgroup analysis was performed to investigate the influence of an increased femoral anteversion angle on the clinical and radiological outcomes.

RESULTS

A total of 66 patients (70 knees) were included with a median follow-up time of 28 months (range 24-32). After a minimum of 2 years of follow-up, all patient-reported outcomes (Kujala, Lysholm, and IKDC scores) improved significantly, and subgroup analysis showed that group C had significantly lower Kujala scores (75 ± 8 vs. 84 ± 8, P₁₃ = 0.003; 75 ± 8 vs. 82 ± 8, P₂₃ = 0.030), Lysholm scores (81 ± 9 vs. 87 ± 7, P₁₃ = 0.021) and IKDC scores (78 ± 6 vs. 85 ± 7, P₁₃ = 0.001; 78 ± 6 vs. 84 ± 6, P₂₃ = 0.005) than group A and group B. Twelve patients had a postoperative residual J-sign (17.1%), and significant differences were found between group C and group A regarding the rate of residual J-sign (32.1% vs. 4.8%, P₁₃ = 0.003). Postoperatively, group C had a greater patellar lateral shift distance than group A (10 ± 4 vs. 6 ± 4 mm, P₁₃ = 0.006) and group B (10 ± 4 vs. 6 ± 3 mm, P₂₃ = 0.008). Additionally, patients with a residual J-sign demonstrated greater medial patellofemoral ligament laxity than patients without a residual J-sign (12 ± 4 vs. 9 ± 3 mm, P = 0.009).

CONCLUSION

Patients with an increased femoral anteversion angle (> 30°) had inferior postoperative clinical outcomes, including greater patellar laxity, a higher rate of residual J-sign and lower patient-reported outcomes after medial patellofemoral ligament reconstruction and combined tibial tubercle osteotomy for the treatment of recurrent patellar instability.

LEVEL OF EVIDENCE

III, retrospective cohort study.

The association of frontal plane alignment to MRI-defined worsening of patellofemoral osteoarthritis: the MOST study

OBJECTIVE

To determine the sex-specific relation of frontal plane alignment (FPA) to magnetic resonance imaging (MRI)-defined features of patellofemoral osteoarthritis, and also to tibiofemoral osteoarthritis and knee pain.

METHOD

The Multicenter Osteoarthritis Study is cohort study comprised of individuals with or at risk of knee osteoarthritis. We determined the sex-specific dose-response relation of baseline FPA to MRI-defined patellofemoral and tibiofemoral structural worsening, and incident knee pain, over 7 years.

RESULTS

In women only, greater varus alignment was associated with medial patellofemoral osteophytes (risk ratio [RR] 1.7 [95% CI 1.2, 2.6]) and valgus with lateral patellofemoral osteophytes (RR 1.9 [1.0, 3.6]). In men, greater varus increased risk for medial tibiofemoral cartilage worsening (RR 1.7 [1.1, 2.6]), and valgus for lateral tibiofemoral cartilage worsening (RR 1.8 [1.6, 2.2]). In women, findings were similar for tibiofemoral cartilage, but varus also increased risk for medial bone marrow lesions [BMLs] (RR 2.2 [1.6, 3.1]) and medial osteophytes (RR 1.8 [1.3, 2.5]), and valgus for lateral BMLs (RR 3.3 [2.2, 4.5]) and osteophytes (RR 2.0 [1.2, 3.2]). Varus increased risk of incident pain in men (RR 1.7 [1.4, 2.2]) and women (RR 1.3 [1.0, 1.6]), valgus did so in men only (RR 1.5 [1.1, 1.9]).

CONCLUSION

FPA was associated with patellofemoral osteophyte worsening in women, though overall was more strongly associated with tibiofemoral than patellofemoral osteoarthritis feature worsening. FPA in women was more consistently associated with structural worsening, yet men had higher associations with incident pain.

The Patello-Femoral Joint Degeneration and the Shape of the Patella in the Population Needing an Arthroscopic Procedure

Background: the main goal of the study was to investigate the prevalence of the articular cartilage defects (ACD) in the patellofemoral (PF) region of the knee joint based on the anatomical shapes of patella and its impact on the level of physical activity in the population needing arthroscopic procedures for all types of pathologies in the knee. Methods: The articular cartilage status of the PF region was obtained from 1098 arthroscopic procedures of the knee joint. The ACD were correlated to Wiberg’s shape of the patella and classified according to the degree, size and depth of the ACD in the PF region using the ICRS (International Cartilage Repair Society) system: group I consisting of patients with Wiberg type I shape (W1), group II—patients with Wiberg type II shape (W2) and group III—patients with Wiberg type III shape (W3). The Tegner physical activity scale was used to evaluate the physical activity of the patients. Results: The mean of ACD size (PF region) in the W3 group was 3.10 ± 0.99 cm², which was a statistically significantly larger area in comparison with the W1 (1.90 ± 0.63 cm²; p < 0.0000) and W2 (1.95 ± 0.71 cm²; p < 0.0000). The patients from the W3 group (mean 3.10 ± 0.99) were less physically active (<4 Tegner) compared to the W2 group (mean of 4.48 ± 0.88; p = 0.004) and W1 group (mean of 4.55 ± 0.72; p = 0.002). Conclusions: The patients with the Wiberg type III patella shape had a higher incidence and larger size of ACD in the PF of the knee compared to the groups of Wiberg type I and II. Wiberg III patients with a lower level of physical activity had a larger size of ACD in the PF joint.

Analysis and multiclass classification of pathological knee joints using vibroarthrographic signals

BACKGROUND AND OBJECTIVE

Vibroarthrography (VAG) is a method developed for sensitive and objective assessment of articular function. Although the VAG method is still in development, it shows high accuracy, sensitivity and specificity when comparing results obtained from controls and the non-specific, knee-related disorder group. However, the multiclass classification remains practically unknown. Therefore the aim of this study was to extend the VAG method classification to 5 classes, according to different disorders of the patellofemoral joint.

METHODS

We assessed 121 knees of patients (95 knees with grade I-III chondromalacia patellae, 26 with osteoarthritis) and 66 knees from 33 healthy controls. The vibroarthrographic signals were collected during knee flexion/extension motion using an acceleration sensor. The genetic search algorithm was chosen to select the most relevant features of the VAG signal for classification. Four different algorithms were used for classification of selected features: logistic regression with automatic attribute selection (SimpleLogistic in Weka), multilayer perceptron with sigmoid activation function (MultilayerPerceptron), John Platt's sequential minimal optimization algorithm implementation of support vector classifier (SMO) and random forest tree (RandomForest). The generalization error of classification algorithms was evaluated by stratified 10-fold cross-validation.

RESULTS

We obtained levels of accuracy and AUC metrics over 90%, more than 93% sensitivity and more than 84% specificity for the logistic regression-based method (SimpleLogistic) for a 2-class classification. For the 5-class method, we obtained 69% and 90% accuracy and AUC respectively, and sensitivity and specificity over 91% and 69%.

CONCLUSIONS

The results of this study confirm the high usefulness of quantitative analysis of VAG signals based on classification techniques into normal and pathological knees and as a promising tool in classifying signals of various knee joint disorders and their stages.

Patellofemoral arthritis treated with resurfacing implant: Clinical outcome and complications at a minimum two-year follow-up

BACKGROUND

This study evaluated the clinical and radiographic outcomes of a series of patients treated with an anatomic inlay resurfacing implant, with a minimum two-year follow-up.

METHODS

Fifteen patients underwent patellofemoral-resurfacing procedures using a HemiCAP Wave Patellofemoral Inlay Resurfacing implant from 2010 to 2013. Clinical outcomes included: Visual Analog Scale (VAS), Lysholm score, Knee Society Score (KSS), and evaluation of Kujala, and Hospital for Special Surgery Patellofemoral score (HSS-PF). The postoperative complications were analyzed.

RESULTS

Nineteen knees were evaluated; the average follow-up was 35.2months. Fourteen were women, with an average age of 54years. The pre-operative/postoperative clinical results presented a significant improvement: VAS 8/2.5, Lysholm 31.9/85.8, KSS 39.8/82.5, Kujala 32.1/79.3 and Hospital for Special Surgery Patellofemoral score (HSS-PF) 15.9/90.6. A total of 87% of patients were either satisfied or very satisfied with the overall outcome. There were no radiographic signs of loosening. Seven postoperative complications were recorded: two presented ongoing knee pain, one postoperative stiffness, one patellar bounce due to maltracking, two ilio-tibial band syndrome, and one tibial anterior tuberosity osteotomy nonunion. Two patients underwent a total knee arthroplasty conversion and were considered a failure. None of these complications were implant related.

CONCLUSIONS

Patellofemoral inlay resurfacing for isolated patellofemoral arthritis was an effective and safe procedure with high levels of patient satisfaction. No mechanical implant failure was seen at a minimum two-year follow-up. This implant design appeared to be an alternative to the traditional patellofemoral prostheses. Concomitant osteochondral lesions, patellofemoral dysplasia or patellar maltracking might be poor prognostic factors for this type of implant.

Objective quantification of trochlear dysplasia: Assessment of the difference in morphology between control and chronic patellofemoral instability patients

BACKGROUND

Trochlear dysplasia is an important risk factor associated with patellofemoral instability, but it remains difficult to classify with consistency. Currently there is no objective way to quantify the dysplasia. The purpose of this study is to define and quantify objectively the trochlear morphology by volume and length via computed tomography (CT).

METHODS

One-hundred control patients (136 knees) were retrospectively reviewed and compared to 36 consecutive patients (72 knees) who were treated surgically for recurrent patellar instability and known trochlear dysplasia based on a lateral radiograph. Trochlear morphology was analyzed from a pre-operative CT and data presented as trochlear sulcus volume trochlear length. To determine where along the trochlear length dysplasia is most variable, the trochlear length was radiographically divided into thirds, volume was quantified along that section and compared to control trochlear.

RESULTS

A significant difference in trochlear morphology exists between cohorts, volume (1.98 vs 3.77cm³) and length (31.97 vs 34.66mm) (p<0.05). However, there appears to be a gender based difference in trochlea morphology. The trochlea volumetric analysis between the female cohorts (L: 2.02cm³ vs. 2.94cm³, R: 1.95cm³ vs. 2.93cm³) demonstrated significantly less volume in instability patients (p<0.001). The proximal third of the trochlear contributed the majority of dysplasia difference determined by comparing mean trochlear volume, 95% of the difference. This difference decreased in distal sections, 53% and 32% respectively.

CONCLUSION

This reproducible technique can be used to quantify the trochlea morphology, in order to describe the severity of a dysplasia.

Patellofemoral morphology and alignment: reference values and dose-response patterns for the relation to MRI features of patellofemoral osteoarthritis

OBJECTIVE

We aimed to (1) determine reference values for trochlear morphology and patellofemoral (PF) alignment in adults without magnetic resonance imaging (MRI)-defined PF full thickness cartilage damage or knee pain; and (2) evaluate dose-response patterns for these measures with prevalent MRI-defined PF structural damage and/or knee pain.

DESIGN

The Framingham Community Cohort is a population-based sample of ambulatory adults aged ≥50 years. We evaluated six morphology and alignment measures using MRI (n = 985), and reported reference values (mean ± 2SD) in a subsample without MRI-defined PF full thickness cartilage damage or knee pain (n = 563). With restricted cubic spline Poisson regression, we evaluated dose-response patterns of each of the six measures with prevalent MRI-defined PF structural damage or joint pain. Our primary outcome was full thickness cartilage damage.

RESULTS

For dose-response curves, prevalence ratios (PR) increased monotonically for all measures except patellar tilt, which rose with both lateral and medial tilt. Associations were generally strongest in the lateral PF compartment. PR for the strongest predictors of full thickness cartilage damage reached clinical relevance (PR > 1.5) at sulcus angle (SA) ≥135.0°; patellar tilt angle at ≤1.0° and ≥15.0°; and bisect offset ≥57.0%. Lateral trochlear inclination (LTI) achieved PR > 1.5 at ≤23.0° for full thickness cartilage damage with pain.

CONCLUSIONS

SA, patellar tilt, and bisect offset were most strongly associated with full thickness cartilage damage. LTI, patellar tilt and bisect offset had stronger associations with the addition of pain. These findings contribute to better identifying a subset of patients who may benefit from mechanically based interventions.

[Treatment of patellar instability]

First-time patellar luxation appears typically in teenagers and young adults below the age of 16 years, with a prevalence of 45/100,000/year. This luxation is treated with brief limited mobility in a bandage, and with a complementary physiotherapy if the mobility is influenced afterwards. Risk factors for patellar instability are patellofemoral dysplasia, hyperlaxity, patella alta and valgus malalignment in the knee joint. In case of repeated luxation the treatment is surgical, i.e. reconstruction of the medial patellofemoral ligament recreating the medial patella-stabilizing structures. If the dysplasia is severe, tuberositas tibiae-osteotomy and trochlea plastic can correct a lateral tracking of the knee joint. Generally, patella-stabilizing surgery is successful with a reluxation rate of only a few per cent.

Noninvasive surface damage assessment of bovine articular cartilage explants by reflected polarized light microscopy

Articular surface damage is a hallmark of cartilage degeneration. Noninvasive assessment of cartilage microstructural alterations has potential clinical value. In this study, we use bovine patellofemoral articular cartilage explants treated with mechanical scraping and collagenase to create cartilage surface disruption, and use polarized reflectance microscopy to quantify alterations to surface and sub-surface microstructure. Reflected polarized signal was sensitive to mild damage to the cartilage surface, and highlighted disruptive alterations. The results indicate the efficacy of reflected polarized light microscopy in assessing the microstructural status of superficial articular cartilage.

Association of baseline knee sagittal dynamic joint stiffness during gait and 2-year patellofemoral cartilage damage worsening in knee osteoarthritis

OBJECTIVE

Knee sagittal dynamic joint stiffness (DJS) describes the biomechanical interaction between change in external knee flexion moment and flexion angular excursion during gait. In theory, greater DJS may particularly stress the patellofemoral (PF) compartment and thereby contribute to PF osteoarthritis (OA) worsening. We hypothesized that greater baseline knee sagittal DJS is associated with PF cartilage damage worsening 2 years later.

METHODS

Participants all had OA in at least one knee. Knee kinematics and kinetics during gait were recorded using motion capture systems and force plates. Knee sagittal DJS was computed as the slope of the linear regression line for knee flexion moments vs angles during the loading response phase. Knee magnetic resonance imaging (MRI) scans were obtained at baseline and 2 years later. We assessed the association between baseline DJS and baseline-to-2-year PF cartilage damage worsening using logistic regression with generalized estimating equations (GEE).

RESULTS

Our sample had 391 knees (204 persons): mean age 64.2 years (SD 10.0); body mass index (BMI) 28.4 kg/m² (5.7); 76.5% women. Baseline knee sagittal DJS was associated with baseline-to-2-year cartilage damage worsening in the lateral (OR = 5.35, 95% CI: 2.37-12.05) and any PF (OR = 2.99, 95% CI: 1.27-7.04) compartment. Individual components of baseline DJS (i.e., change in knee moment or angle) were not associated with subsequent PF disease worsening.

CONCLUSION

Capturing the concomitant effect of knee kinetics and kinematics during gait, knee sagittal DJS is a potentially modifiable risk factor for PF disease worsening.

Are metric parameters sufficient alone in evaluation of the patellar instability? New angular measuring parameters

PURPOSES

When the evaluation of patellar instability is examined from the aspect of the conical-cylindrical anatomy of the tibia, metric measurement parameters such as the tuberositas tibia (TT)-trochlear groove (TG) and patellar tendon (PT) insertion-trochlear groove (TG) distances are not sufficient. We asked whether defined angular parameters reveal the rotational movement of the tuberositas tibia on the tibia shaft, additional to the metric parameters and there is a correlation between the metric and angular parameters.

METHODS

19 patients with patellar instability and 22 patients without patellar instability were evaluated. For all patients, two angle and three length parameters were evaluated on the slices taken. Evaluations were made of the TT-TG, the midpoint of the PT insertion-TG distances, the anatomic midpoint of the dome of the TT-TG, the TG-PT angle, and the TG-dome angle (DA). The Pearson correlation test was used for the statistical analysis of correlations between groups.

RESULTS

A statistically significant increase was determined in the patellar instability group in the TG-DA and TG-PT angle values compared to the group without patellar instability ( p < 0.05). In both groups, a positive and strong correlation was determined between the TT-TG and the TG-PT and dome of the TT-TG distances, but no statistically significant correlation was determined between the tuberositas TT-TG and TG-PT angle and TG-DA.

CONCLUSION

Metric parameters may not be sufficient alone in the evaluation of patellar instability. Metric parameters should be supported by additional angular parameters which reveal the rotational movement of the TT on the tibia shaft.

Aberrant Calreticulin Expression in Articular Cartilage of Dio2 Deficient Mice

OBJECTIVE

To identify intrinsic differences in cartilage gene expression profiles between wild-type- and Dio2-/--mice, as a mechanism to investigate factors that contribute to prolonged healthy tissue homeostasis.

METHODS

Previously generated microarray-data (Illumina MouseWG-6 v2) of knee cartilage of wild-type and Dio2 -/- -mice were re-analyzed to identify differential expressed genes independent of mechanical loading conditions by forced treadmill-running. RT-qPCR and western blot analyses of overexpression and knockdown of Calr in mouse chondro-progenitor cells (ATDC5) were applied to assess the direct effect of differential Calr expression on cartilage deposition.

RESULTS

Differential expression analyses of articular cartilage of Dio2-/- (N = 9) and wild-type-mice (N = 11) while applying a cutoff threshold (P < 0.05 (FDR) and FC > |1,5|) resulted in 1 probe located in Calreticulin (Calr) that was found significantly downregulated in Dio2-/- mice (FC = -1.731; P = 0.044). Furthermore, overexpression of Calr during early chondrogenesis in ATDC5 cells leads to decreased proteoglycan deposition and corresponding lower Aggrecan expression, whereas knocking down Calr expression does not lead to histological differences of matrix composition.

CONCLUSION

We here demonstrate that the beneficial homeostatic state of articular cartilage in Dio2-/- mice is accompanied with significant lower expression of Calr. Functional analyses further showed that upregulation of Calr expression could act as an initiator of cartilage destruction. The consistent association between Calr and Dio2 expression suggests that enhanced expression of these genes facilitate detrimental effects on cartilage integrity.

Infrapatellar fat pad syndrome: a review of anatomy, function, treatment and dynamics

The infrapatellar (Hoffa's) fatpad is an important structure within the knee, whose function and role are both poorly understood. This review explores the anatomy, neural innervation, vascularity, role in biomechanics, pathology, imaging (stressing the importance of dynamic ultrasound assessment) and treatment of disorders presenting within this structure.

Evaluation of anterior knee pain in a PS total knee arthroplasty: the role of patella-friendly femoral component and patellar size

BACKGROUND

Total knee arthroplasty gives excellent objective results. Nevertheless, the subjective findings do not match the normal knee perception: Often, it depends on patellar pain onset. In this study, we analyzed clinical and radiological items that can affect resurfaced patellar tracking, and role of a patella-friendly femoral component and patellar size on patellar pain onset.

MATERIALS AND METHODS

Thirty consecutive patients were implanted using the same-cemented posterior-stabilized TKA associated with patella resurfacing. Fifteen patients were implanted using a classical femoral component, while another 15 patients were implanted using a patella-friendly femoral component. The statistical analysis was set to detect a significant difference (p < 0.05) in clinical and radiological outcomes related to several surgical parameters. Clinical and functional outcomes were recorded using the Knee Society Scoring System (KSS) and patellar pain with the Burnett questionnaire.

RESULTS

Mean follow-up was 25 months. KSS results were excellent in both groups. Group 2 (patella-friendly femoral model) reached a higher percentage of 100 points in the clinical and functional KSS, but there was no statistical difference. Also, no statistical differences for Burnett Questionnaire results were recorded. We had one case of patellar clunk syndrome in the standard femoral component group and one poor result in the second group. Postoperative radiographic measurements evidenced no statistical differences in both groups. In group 1 (classical femoral component), better significant result (p < 0.05) war recorded at clinical evaluation according to the Knee Society Scoring System (KSS) in case of wider patellar component resurfaced.

CONCLUSIONS

The present study reveals no statistically significant difference in the incidence of anterior knee pain between classical and "patella-friendly" femoral components. With the particular type of implant design utilized in this study, when the classical femoral component is used, bigger patellar implant sizes (38 and 41 mm) showed superior clinical outcome.

Hidden osteophyte formation on plain X-ray is the predictive factor for development of knee osteoarthritis after 48 months--data from the Osteoarthritis Initiative

OBJECTIVE

To examine whether the detection of osteophytes anywhere in the knee could serve as a pre-radiographic biomarker for osteoarthritis (OA) development.

METHODS

Baseline magnetic resonance imaging (MRIs) of 132 participants in the Osteoarthritis Initiative (OAI) were studied. Based on radiographs, 66 knees were assessed as osteoarthritis-free (no-osteoarthritis [NOA], or Kellgren/Lawrence [K/L] severity grade 0/1 both at baseline and 48 months), and another 66 knees were assessed as having radiographic OA changes (pre-radiographic osteoarthritis [PROA], or with K/L grade 0/1 at baseline and grade ≥ 2 at 48 months). Using baseline MRI data, we examined eight sites of osteophyte formation: the medial and lateral femoral condyle (MFC and LFC, respectively); medial and lateral tibial plateau (MTP and LTP, respectively); medial and lateral facets of the patellofemoral joint (PM and PL, respectively); tibial spine (TS); and femoral intercondylar notch (IC). Knee joint osteophyte size was assessed via the 8-point marginal osteophytes item of the whole-organ magnetic resonance imaging score (WORMS). The frequencies and distributions of osteophytes were compared between groups.

RESULTS

Mild-size osteophytes (defined as score ≥ 2) were observed more frequently at the MFC (P = 0.00278), MTP (P = 0.0046), TS (P = 0.0146), PM (P < 0.0001), PL (P = 0.0012), and IC (P < 0.0001) in PROA knees than in NOA knees. Moderate-size osteophytes (defined as score ≥ 4) were more frequently observed in PROA knees than in NOA knees only at the IC (P < 0.0001).

CONCLUSION

Knees with osteophyte formation at the IC, even those of K/L severity grade 0/1, are at risk for the development of radiographic OA by 48 months.

Cross-relaxation imaging of human patellar cartilage in vivo at 3.0T

OBJECTIVE

To compare quantitative magnetization transfer (qMT) parameters of patellar cartilage measured using cross-relaxation imaging (CRI) in asymptomatic volunteers and patients with osteoarthritis.

DESIGN

The study was performed with Institutional Review Board approval and with all subjects signing informed consent. CRI of the knee joint was performed at 3.0T on 20 asymptomatic volunteers and 11 patients with osteoarthritis. The fraction of macromolecular bound protons (f), the exchange rate constant between macromolecular bound protons and free water protons (k), and the T2 relaxation time of macromolecular bound protons (T2(B)) of patellar cartilage were measured. Mann-Whitney-Wilcoxon rank-sum tests were used to compare qMT parameters between asymptomatic volunteers and patients with osteoarthritis.

RESULTS

Average f, k, and T2(B) of patellar cartilage was 12.46%, 7.22 s(-1), and 6.49 μs respectively for asymptomatic volunteers and 12.80%, 6.13 s(-1), and 6.80 μs respectively for patients with osteoarthritis. There were statistically significant differences between groups of subjects for k (P < 0.01) and T2(B) (P < 0.0001) but not f (P = 0.38) of patellar cartilage.

CONCLUSION

Patients with osteoarthritis had significantly lower k and significantly higher T2(B) of patellar cartilage than asymptomatic volunteers which suggests that qMT parameters can detect changes in the macromolecular matrix of degenerative cartilage.

Variation in tibial tubercle-trochlear groove measurement as a function of age, sex, size, and patellar instability

BACKGROUND

The tibial tubercle-trochlear groove (TT-TG) measurement was developed to quantify morphologic abnormalities about the knee associated with patellar instability and to help guide surgical decision making.

PURPOSE

To assess variations in TT-TG as a function of patient age and size in a population of patients with patellar instability compared with those with no instability.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

All patients younger than 20 years who underwent surgery for patellar instability from 2010 to 2012 were included in this retrospective study. A total of 180 patients with no history of patellar instability or patellofemoral complaints were used as a control group. The TT-TG was measured on magnetic resonance axial images using the centers of the tibial tubercle and the trochlear groove. Data were normalized based on patient height, weight, body mass index (BMI), and femur width. Alpha was set at P < .05 to declare significance.

RESULTS

The average age of the 45 patellar instability patients was 15.4 years (range, 10-18 years), their mean TT-TG was 16.3 mm (range, 6.5-26 mm), and 51% were male. By comparison, the mean age of the control group was 16 years (range, 10-19 years), the mean TT-TG was 11.7 mm (range, 3-22 mm), and 58% were male. The TT-TG and the normalized TT-TG for height, weight, BMI, and femur width were all greater in the patellar instability group compared with the control group (P ≤ .001). Thirty-one percent of patients had a TT-TG greater than 20 mm in the instability group compared with 3% in the control group (P < .05, specificity 97%, sensitivity 31%). The TT-TG was found to increase as a function of height in both groups (r = 0.14, P = .04) and decreased with age only in the instability group (r = -0.3, P = .04).

CONCLUSION

An elevated TT-TG is associated with patellar instability both in pediatric and adolescent patients. However, this measurement varies as a function of patient age and height, with each centimeter in height increasing the TT-TG by 0.12. Normalization of TT-TG to patient height may control for size variations and should be undertaken in the work-up and management of patients with patellar instability.

The effects of weight-bearing conditions on patellofemoral indices in individuals without and with patellofemoral pain syndrome

OBJECTIVE

The purpose of this study is to evaluate differences between the patellofemoral joint indices after supine, non-weight-bearing and standing position, and weight-bearing Merchant view radiographs in individuals without and with patellofemoral pain syndrome (PFPS).

MATERIALS AND METHODS

Radiographs of 44 knees without PFPS and 51 knees with PFPS were retrospectively evaluated. In both positions, the non-weight-bearing and weight-bearing Merchant views, patellar indices such as patellar tilt angle, lateral patellofemoral angle, lateral subluxation distance, lateral patellar displacement, and congruence angle were measured, respectively. The differences between the patellofemoral joint indices in knees with and without PFPS were analyzed using univariate and multivariate regression analysis, in regards to correlation factors.

RESULTS

The patellar tilt angle (p = 0.0002), lateral subluxation distance (p = 0.038), lateral patellar displacement (p = 0.0004), and congruence angle (p < 0.0001) on the weight-bearing Merchant view was significantly decreased in normal knees without PFPS. In pathologic knees with PFPS, the patellar tilt angle (p < 0.0001), lateral subluxation distance (p < 0.0001), lateral patella displacement (p < 0.0001), and congruence angle (p < 0.0001) on weight-bearing Merchant view was also significantly decreased. The difference between the patellofemoral indices was significantly more in knees specifically with PFPS (p < 0.05).

CONCLUSIONS

These results suggest that patellofemoral indices measured during non-weight-bearing supine position do not sufficiently represent the patellofemoral kinematics during normal weight-bearing activities. We conclude that this study establishes the clinical significance and relevance of assessing the patellofemoral kinematics by weight-bearing, standing Merchant view radiographs, when evaluating patients with patellofemoral problems.

The evaluation of the influence of selected patellofemoral joint geometry indicators observed in magnetic resonance imaging on the incidence of anterior knee pain in patients after anterior cruciate ligament reconstruction using hamstrings

BACKGROUND

Anterior knee pain (AKP) is a frequent serious clinical problem after anterior cruciate ligament (ACL) reconstruction, regardless of the graft material used. The author conducted prospective studies of the correlation between AKP and disturbed geometry of patello-femoral joint observed in magnetic resonance imaging (MRI), in patients with injured ACL reconstructed with the use of hamstrings.

MATERIAL AND METHODS

The study included 60 patients (34 males and 26 females), at the mean age of 31, who underwent ACL reconstruction with flexors. Only patients without clinical AKP symptoms or AKP factors after reconstruction were included in the study. Before surgery, in all patients MRI was performed in order to evaluate the patellar height, excessive patellar pressure (EPP) and patellar lateralization (PL). In the postoperative course, AKP and its correlation with the ratios mentioned above were observed.

RESULTS

In the group of patients included in the study, pathological patellar height was not observed, EPP was diagnosed in 15%, PL in 13.3% and EPP and PL jointly in 11.9% of the patients. AKP was observed in 8 out of 9 patients with abnormal lateral pressure, 7 patients with EPP and 7 patients with concomitant excessive lateral pressure and PL. The first symptoms of AKP appeared between the seventh and twelfth week after surgery and increased after 12 weeks.

CONCLUSIONS

The occurrence of excessive lateral pressure syndrom (EPP) and PL confirmed in MRI was very strongly correlated (89% and 100%, respectively) with the occurrence of AKP after ACL reconstruction. The evaluation of the patellofemoral joint geometry, taking into account the EPP and PL ratios in pre-operative magnetic resonance image (MRI) in patients with injured anterior cruciate ligament, may allow us to establish the AKP risk group and administer suitable preventive treatment (prophylaxis).

[Pre-operative assessment of the patellofemoral joint in unicompartmental knee replacement using Oxford Phase III and its influence on outcome]

OBJECTIVE

To determine whether anterior knee pain and/or radiological evidences of degeneration of the patellofemoral joint influence the outcome of unicompartmental knee arthroplasty (UKA).

METHODS

Between January 2006 and December 2010, 95 consecutive patients (100 knees) with unicompartmental knee osteoarthritis were treated with Oxford UKA, including 34 males and 61 females. The mean age was 68.2 years (range, 55-82 years). The average Body Mass Index was 26.3 kg/m(2)(range, 24-28 kg/m(2)). Pre-operative there were 43 knees (43.0%) with anterior knee pain and 57 knees (57.0%) without it. Pre-operative radiological status of the patellefemoral joint were defined using Ahlback and Altman systems. The pre- and post-operative results of Oxford Knee Score (OKS), American Knee Society Score (AKS) and Western Ontario and Macmaster (WOMAC) were compared using paired t-test, the results between different groups were compared using grouped t-test.

RESULTS

All cases were followed up for average 50 months (24-84 months). At the last follow-up, none had complications of infection, fat embolism, deep vein thrombosis, malposition of prosthesis, dislocation or loosing. The mean femoral component alignment was -0.7° ± 5.2° (valgus/varus), -0.8° ± 4.5°(flexion/extension); the mean tibial component alignment was -0.1° ± 2.2°(valgus/varus), -0.4° ± 2.4° (flexion/extension). The clinical outcomes were significantly improved compared with pre-operation regardless of presence (OKS: t = 19.04, P < 0.01; AKS knee:t = 38.56, P < 0.01;AKS function:t = 39.29, P < 0.01;WOMAC:t = 43.22, P < 0.01) or absence (OKS: t = 31.57, P < 0.01; AKS knee:t = 40.34, P < 0.01; AKS function:t = 43.62, P < 0.01; WOMAC: t = 47.06, P < 0.01) of anterior knee pain. The results were significantly improved compared with pre-operation (P < 0.01) regardless of whether degeneration of the patellofemoral joint. There was no statistically significant difference in outcome between patients with evidence of degeneration in the medial patellofemoral joint and those without (P > 0.05) . Patients with lateral patellofemoral degeneration had a worse score than those without, OKS (t = 2.56, P = 0.01) and WOMAC (t = 2.20, P = 0.03) by the Altman score, OKS (t = 2.29, P = 0.02) by the Ahlback score. For AKS measures there was no statistically significant difference in outcome (P > 0.05) .

CONCLUSIONS

Neither anterior knee pain nor radiological evidence of medial patellofemoral joint degeneration would influnence the outcome of UKA, lateral patellofemoral joint degeneration have an increased risk of a poor result.

Association of trochlear dysplasia with degenerative abnormalities in the knee: data from the Osteoarthritis Initiative

OBJECTIVE

To evaluate trochlear morphology as a potential risk factor for patellofemoral osteoarthritis, determined by morphological and quantitative measurements of cartilage degeneration using 3-T magnetic resonance imaging (MRI) of the knee.

MATERIALS AND METHODS

MRI of the right knees of 304 randomly selected subjects, aged 45-60 years, from the Osteoarthritis Initiative (OAI) progression cohort were screened for trochlear dysplasia, defined by an abnormal trochlear depth. Out of 304 subjects, n = 85 demonstrated a shallow trochlea (depth ≤3 mm; 28 %). In these, and also in a random sample of controls with normal trochlear depth (n = 50), the facet ratio and the sulcus angle were calculated and knee structural abnormalities were assessed by using a modified Whole Organ MR Imaging Score (WORMS). Cartilage segmentation was performed and T2 relaxation times and patellar cartilage volume were determined. ANOVA and multivariate regression models were used for statistical analysis of the association of MRI structural measures and trochlear morphology.

RESULTS

Knees with a shallow trochlea showed higher patellofemoral degeneration (WORMS mean ± standard deviation, 11.2 ± 0.5 versus 5.7 ± 0.6; multivariate regression, P < 0.001) and lower patellar cartilage volume than controls (900 ± 664 mm(3) versus 1,671 ± 671 mm(3); P < 0.001). Knees with an abnormal medial-to-lateral facet ratio (<0.4) showed increased patellofemoral WORMS scores (12.3 ± 0.9 versus 8.3 ± 0.5; P < 0.001). Knees with an abnormal sulcus angle (>170°) also showed increased WORMS scores (12.2 ± 1.1 versus 8.6 ± 0.6; P = 0.003). T2 values at the patella were significantly lower in the dysplasia group with a shallow trochlea. However, significance was lost after adjustment for cartilage volume (P = 0.673).

CONCLUSION

Trochlear dysplasia, defined by a shallow trochlea, was associated with higher WORMS scores and lower cartilage volume, indicating more advanced osteoarthritis at the patellofemoral joint.

Morphological analysis of the knee joint in patients with hip dysplasia

PURPOSE

The purpose of this study was to investigate the morphological changes of the knee in patients with untreated developmental dysplasia of the hip.

METHODS

Morphological analysis of 150 knee joints in 75 patients with developmental dysplasia of the hip was performed by examining computed tomographic (CT) images. Of these patients, 36 had unilateral developmental dysplasia of the hip and 39 had bilateral developmental dysplasia of the hip. Therefore, 36 hips were normal, and 114 hips were dislocated. CT images ranged from the iliac crest to 2 cm inferior to the tibial tuberosity.

RESULTS

Compared with the knees in patients with normal hips, the femoral condyles in patients with dislocated hips were smaller and exhibited greater medial and lateral condylar asymmetry. The anterior femoral condylar angle of the femur was increased, as was the groove angle, while the trochlear groove was shallower in patients with dislocated hips. Furthermore, the lateral patella shift was reduced and the patellar tilt angle was increased in patients with dislocated hips compared with patients with normal hips. The extent of changes in these variables differed with the degree of dislocation. However, the posterior condylar angle of the femur was not affected by the degree of dislocation.

CONCLUSION

These findings suggest that developmental dysplasia of the hip is associated with morphological changes in the knee joint. These changes should be considered during hip and knee surgery.

LEVEL OF EVIDENCE

Prospective study, level II.

CaReS (MACT) versus microfracture in treating symptomatic patellofemoral cartilage defects: a retrospective matched-pair analysis

BACKGROUND

Treating patellofemoral articular cartilage lesions remains a challenging task in orthopedic surgery. Whereas microfracture and autologous chondrocyte implantation yield good results on femoral condyles, the therapeutic state of the art for treating patellofemoral lesions is yet to be determined. In this study, we compared the CaReS technique, which is a matrix-associated autologous chondrocyte implantation technique, to microfracture for treating patellofemoral articular cartilage lesions.

METHODS

Between May 2003 and December 2005, 17 patients with an isolated patellofemoral cartilage defect (International Cartilage Repair Society III/IV) were treated with the CaReS technique at our department. After adjusting for inclusion and exclusion criteria, ten of these patients could be included in this study; ten patients treated with microfracture were chosen as a matched-pair group. Clinical outcome was evaluated 3 years after surgery by the 36-item Short Form Health Survey Questionnaire (SF-36), International Knee Documentation Committee (IKDC) subjective evaluation of the knee, Lysholm Score, and Cincinnati Modified Rating Scale scores.

RESULTS

Patients treated with CaReS had statistically significantly improved IKDC, Lysholm, and Cincinnati scores 36 months after surgery compared with preoperatively. When comparing outcome between groups 36 months after surgery, there was no statistically difference in IKDC, Lysholm, and Cincinnati scores.

CONCLUSIONS

This is the first trial comparing the CaReS technique and microfracture for treating patellofemoral articular cartilage lesions, and results show that CaReS(®) yields comparable results to microfracture. The small number of patients is a limiting factor of the study, leading to results without statistical significance. A multicentric prospective randomized study comparing the two procedures is desirable.

[Arthroscopic reconstruction of medial patellofemoral ligament with hamstring tendon autografts for treatment of recurrent patellar dislocation]

OBJECTIVE

To investigate the effectiveness of reconstructing medial patellofemoral ligament with hamstring tendon autografts for the treatment of recurrent patellar dislocation under arthroscopy.

METHODS

Between January 2005 and January 2010, 22 cases of recurrent patellar dislocation were treated by lateral retinacular release and reconstruction of the medial patellofemoral ligament with hamstring tendon autografts under arthroscopy. There were 5 males and 17 females, aged 15-19 years (mean, 17.3 years). The average number of dislocation was 4 (range, 3-8). The main clinical symptoms were pain and swelling of knee joint, weakness in the leg, and limited range of motion (ROM). The patellar tilt test, pressing pain of patellofemoral ligament insertion, and apprehension sign showed positive results. According to International Knee Documentation Committee (IKDC) scoring criteria, the subjective IKDC score was 36.7 +/- 4.7, and the Lysholm score was 69.3 +/- 3.8. X-ray films showed that the patella inclined outwards.

RESULTS

All incisions healed by first intention. Twenty-two cases were followed up 18-49 months (mean, 34 months). Pain and swelling of knee joint and weakness were improved obviously. No recurrence was found during follow-up. The ROM of knee in flexion and extension was improved when compared with preoperative ROM. The subjective IKDC score was 92.4 +/- 5.3 and the Lysholm knee score was 91.7 +/- 5.2, showing significant differences when compared with preoperative scores (P < 0.05).

CONCLUSION

Reconstruction of the medial patellofemoral ligament with hamstring tendon autografts under arthroscopy is an effective method to treat recurrent patellar dislocation.

Magnetic resonance imaging in patellar lateral femoral friction syndrome (PLFFS): prospective case-control study

OBJECTIVES

To describe morphologic abnormalities and signs of patellar lateral femoral friction syndrome (PLFFS) detected by magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Prospective study of 56 knees (21 patients and 30 controls) studied by 3Tesla MRI. Comparative analysis of clinical data, quantitative and qualitative imaging criteria in a population of patients with anterior knee pain associated with an abnormal MRI signal along the lateral alar folds of the infrapatellar fat pad, a characteristic sign of PLFFS, and a control population with no anterior knee pain or abnormal signal from the infrapatellar fat pad.

RESULTS

Patients with PLFFS have anterior and/or lateral knee pain. Their knee has anatomical predispositions for instability, primarily with patella alta (P<0.0001), patellar tilt more than 13.5° (P<0.0001), a patellar nose length less than 9 mm (P=0.0037), a patellar nose ratio less than 0.25 (P<0.0001), a TT-TG distance more than 10 mm (P<0.0001), and a trochlear prominence more than 4 mm (P=0.0056). In 35% of patients, patellar chondropathy is visible, and 48% of patients have patellar or trochlear subchondral abnormalities.

CONCLUSION

Anterior, lateral, and medial knee pain may be related to PLFFS. Anatomical predispositions contributing to instability are found in these patients. There may be associated chondropathies and osteochondropathies.

Current controversies in partial knee arthroplasty

Partial knee arthroplasty has enjoyed renewed interest during the past decade. It is helpful to be familiar with the classic and current indications, contraindications, and technical aspects of partial knee arthroplasty, including patellofemoral, medial unicompartmental, and lateral unicompartmental knee arthroplasty. Various implant choices for partial knee arthroplasty can be compared and evaluated based on patient characteristics, design qualities, and reported outcomes. It is also helpful to review the indications and techniques for performing medial or lateral unicompartmental knee arthroplasty in combination with arthroscopically assisted reconstruction of the anterior cruciate ligament.

[Treatment of patellar instability in children and adolescents]

To address recurrent patellar instability in children and young adolescents a variety of therapeutic options exist either as non-operative or operative treatment. Recent options, such as reconstruction of the medial patellofemoral ligament have evoked a new focus of attention on this topic. The intention of this article is to present diverse therapeutic options and to evaluate them by reference to the current literature.

The lateral compartment in knees with isolated medial and patellofemoral osteoarthritis: a histologic analysis of articular cartilage

The purpose of this study was to examine, at a histologic level, the articular cartilage of the radiographically normal lateral compartment in knees with isolated medial and possibly patellofemoral osteoarthritis. Twenty patients with radiographic evidence of medial compartment osteoarthritis and a radiographically osteoarthritis-free lateral compartment underwent a tricompartmental total knee arthroplasty. The resected lateral femoral condyle and lateral tibial plateau were evaluated by a fellowship-trained musculoskeletal pathologist for the presence, or lack thereof, of osteoarthritis at a microscopic level. Both the tibia and femur showed evidence of mild osteoarthritis at a microscopic level. This study shows that in patients with radiographic evidence of medial osteoarthritis and a radiographically normal lateral compartment, there is mild osteoarthritis in the lateral compartment.

Combined single photon emission computerised tomography and conventional computerised tomography (SPECT/CT) in patellofemoral disorders: a clinical review

Patellofemoral disorders are common conditions seen in a knee clinic but can present a great diagnostic challenge to the orthopaedic surgeon. Combined single photon emission computerised tomography with conventional computer tomography (SPECT/CT) provides the clinician with precise anatomical and physiological information of the patellofemoral joint. We present a clinical review that highlights the value of SPECT/CT in patients with patellofemoral disorders, where other modalities such as radiographs, MRI, and conventional CT did not provide sufficient information. SPECT/CT has proven to be helpful for establishing the diagnosis and guidance for further treatment. SPECT/CT should be recognised as a valuable diagnostic tool in orthopaedic patients.