Patellar Height Ratios Research Articles

Reliability and modality analysis of patellar height measurement in pediatric knee.

Various measurement methods and imaging technique are in use to measure patellar height in pediatric patients. However, there is no gold standard as to which measurement method and modality are the most reliable for pediatric patients. Therefore, the aim of this study was to determine the inter-observer reliability, intra-observer reliability, and applicability of various patellar height measurement methods in pediatric knee. Additionaly, we analyzed the reliability across different imaging modalities. Total 450 pediatric patients (age: 5-18 years) were evaluated using lateral knee radiographs and magnetic resonance imaging (MRI). The patellar height ratios were measured using five methods. Five methods were Insall-Salvati (IS), Koshino-Sugimoto (KS), Blackburne-Peel (BP), modified Insall-Salvati (MIS), and Caton-Deschamps (CD). The patients were categorized into two age groups: P (ages 5-13) and Q (ages 14-18). Each measurement was conducted twice by two raters. The intra-observer reliability, inter-observer reliability and inter-modality reliability were calculated. In addition, applicability was defined as the possibility to apply each measurement method to each age group. The KS method showed the highest inter-observer reliability and intra-observer reliability when using MRI for both age groups. The inter-observer reliability and intra-observer reliability of the IS for lateral knee radiographs was highest among all observers for group Q. The CD method showed the highest inter-observer reliability in group P, while the KS showed the highest intra-observer reliability in group P using lateral radiographs. The KS method showed the highest inter-modality reliability in group P, while the IS showed the highest inter-modality reliability in group Q. The KS method was applicable to all patients when using lateral knee radiography, and the IS method was applicable to all patients when using MRI. Our results show that the reliability of various measurement method and imaging technique differed based on pediatric knee age group when measuring patellar height. Therefore, in the case of pediatric patients, reliability measurement methods and imaging techniques according to the patient's age should be applied.

Effects of alendronate on cartilage lesions and micro-architecture deterioration of subchondral bone in patellofemoral osteoarthritic ovariectomized rats with patella-baja

BackgroundPatellofemoral osteoarthritis (PFJOA) is a subtype of knee OA, which is one of the main causes of anterior knee pain. The current study found an increased prevalence of OA in postmenopausal women, called postmenopausal OA. Therefore, we designed the ovariectomized rat model of patella baja-induced PFJOA. Alendronate (ALN) inhibits osteoclast-mediated bone loss, and has been reported the favorable result of a potential intervention option of OA treatment. However, the potential effects of ALN treatment on PFJOA in the ovariectomized rat model are unknown and need further investigation prior to exploration in the clinical research setting. In this study, the effects of ALN on articular cartilage degradation and subchondral bone microstructure were assessed in the ovariectomized PFJOA rat model for 10 weeks.MethodsPatella baja and estrogen withdrawal were induced by patellar ligament shortening (PLS) and bilateral ovariectmomy surgeries in 3-month-old female Sprague–Dawley rats, respectively. Rats were randomly divided into five groups (n = 8): Sham + V; OVX + V, Sham + PLS + V, OVX + PLS + V, OVX + PLS + ALN (ALN: 70 μg/kg/week). Radiography was performed to evaluate patellar height ratios, and the progression of PFJOA was assessed by macroscopic and microscopic analyses, immunohistochemistry and micro-computed tomography (micro-CT).ResultsOur results found that the patella baja model prepared by PLS can successfully cause degeneration of articular cartilage and subchondral bone, resulting in changes of PFJOA. OVX caused a decrease in estrogen levels in rats, which aggravated the joint degeneration caused by PFJOA. Early application of ALN can delay the degenerative changes of articular cartilage and subchondral bone microstructure in castrated PFJOA rat to a certain extent, improve and maintain the micrometabolism and structural changes of cartilage and subchondral bone.ConclusionThe early application of ALN can delay the destruction of articular cartilage and subchondral bone microstructure in castrated PFJOA rat to a certain extent.

The Influence of Tibial Tubercle–Sparing Slope-Reducing Osteotomy on Patellar Height in Patients Undergoing Revision ACL Reconstruction

Background: A posterior tibial slope (PTS) >12° is an independent risk factor for anterior cruciate ligament (ACL) graft rupture, and a high tibial osteotomy (HTO) for slope correction can help avoid it. Management of patellar height is of major concern when performing HTO. Purpose: To evaluate the effect of tibial tubercle–sparing anterior closing-wedge osteotomy on patellar height in revision ACL reconstruction (ACLR). Study Design: Case series; Level of evidence, 4. Methods: Patients who underwent arthroscopic revision ACLR combined with retro–tibial tubercle anterior closing-wedge HTO (ACW-HTO) between January 1, 2016, and March 31, 2021, were assessed for eligibility. Patellar height was measured on full weightbearing lateral radiographs according to the Insall-Salvati index (ISI) and Caton-Deschamps index (CDI) or frontal radiographs using the femoral patellar height index. The PTS was evaluated using the proximal anatomic axis of the tibia on standard short lateral radiographs. The delta (postoperative – preoperative) and the ratio (preoperative/postoperative) of the 3 patellar height indices and PTS were calculated. Preoperative and postoperative patellar heights were compared using independent t tests for each index. Also investigated was whether patients changed patellar height category (baja, normal, or alta) after slope osteotomy. Results: Among 475 revision ACLRs, 47 tibial tubercle–sparing ACW-HTOs were retained for analysis. No significant difference in patellar height was found between pre- and postoperative radiographs regardless of the index (preoperative – postoperative) (ISI: 1.0 ± 0.2 – 0.9 ± 0.2, P = .1729; CDI: 1.0 ± 0.2 – 1.0 ± 0.2, P = .4034; femoral patellar height index: 1.5 ± 0.2 – 1.5 ± 0.2; P = .5130). Fifteen patients (31.9%) exhibited a postoperative change in their patellar height category when measured by the ISI (6 moved up a category, 9 moved down one), and 18 patients (38.3%) changed category according to the CDI (10 moved up a category, 8 moved down one). No significant difference was found between pre- and postoperative patellar height among these patients (ISI: P = .2418; CDI: P = .3005). Conclusion: Changes in patellar height ratio are common after tibial tubercle–sparing ACW-HTO in patients undergoing revision ACLR. The clinical effect of these changes is unknown, and further study is needed to investigate whether they may result in patellofemoral symptoms.

The Onset and Development of Patella Alta in Children With Patellar Instability.

Patella alta is an anatomic risk factor for patellar instability in adolescents that is also linked to the risk factor of trochlear dysplasia. This study aims to determine the age of onset and age-related incidence of patella alta in a pediatric population of patients with patellar instability. We hypothesized that patellar height ratios would not increase with age, suggesting a congenital rather than the developmental origin of patella alta. A retrospective cross-sectional cohort of patients was collected with the following inclusion criteria: patients aged 5 to 18 who had a knee magnetic resonance imaging performed from 2000 to 2022 and the International Classification of Diseases code for patellar dislocation. Demographic information and details of the patellar instability episode(s) were collected with a chart review. Sagittal magnetic resonance imaging was used to measure Caton-Deschamps Index (CDI) and the Insall-Salvati Ratio (ISR) by 2 observers. Data were analyzed to assess for associations between patellar height ratios and age of the first dislocation and to assess if the proportion of patients categorized as having patella alta changed with age. The 140 knees included in the cohort had an average age of 13.9 years (SD=2.40; range: 8-18) and were 55% female. Patella alta was present in 78 knees (55.7%) using CDI>=1.2 and in 59 knees (42.1%) using ISR>=1.3. The earliest age patella alta was observed was at age 8 using CDI>=1.2 and age 10 using ISR>=1.3. There were no statistically significant associations between CDI and age without adjustment ( P =0.14) nor after adjustment for sex and body mass index ( P =0.17). The proportion of knees above the CDI threshold for patella alta to the knees below the cutoff did not show a significant change with age ( P =0.09). Patella alta, as defined by CDI, is seen in patients as young as 8 years old. Patellar height ratios do not change with age in patients with patellar dislocation, suggesting that patella alta is established at a young age rather than developing during the adolescent years. Level III-diagnostic, cross-sectional.

Harvest of All-Soft Tissue Quadriceps Tendon Autograft for Anterior Cruciate Ligament Reconstruction With or Without Closure of Resulting Defect Has No Effect on Patellar Height

To evaluate the radiographic effect of quadriceps tendon harvest on patellar height and to determine whether closure of a quadriceps graft harvest defect resulted in a significant change in patellar height compared to nonclosure. We conducted a retrospective review of prospectively enrolled patients. The institutional database was queried and all patients who underwent quadriceps autograft anterior cruciate ligament reconstruction between 2015 and March 2020 were included. Graft harvest length in millimeters and final graft diameter after preparation for implantation were obtained from the operative record and demographic data were obtained from the medical record. Radiographic analysis was performed of eligible patients using standard ratios of patellar height: Insall-Salvati (IS), Blackburn-Peele (BP), and Caton-Deschamps (CD). Measurements were performed using digital calipers on a digital imaging system by 2 postgraduate fellow surgeons. Preoperative and postoperative radiographs were performed at 0° according to a standard protocol. Postoperative radiographs were performed 6 weeks postoperatively in all cases. Preoperative patellar height ratios were compared with postoperative patellar height ratios for all patients using t-tests. Subanalysis was then performed to compare the effect of closure of with nonclosure on patellar height ratios using repeated-measures analysis of variance. Interrater reliability between the 2 reviewers was assessed using an intraclass correlation coefficient calculation. In total, 70 patients met final inclusion criteria. There were no statistically significant changes from pre- to postoperative values for either reviewer for IS (reviewer 1, P= .47; reviewer 2, P= .353), BP (reviewer 1, P= .98; reviewer 2, P= .907), or CD (reviewer 1, P= .107; reviewer, 2 P= .188). The closure and nonclosure groups were adequately powered and no statistically significant demographic differences between the closure and nonclosure groups was identified for sex (P= .066), age (P= .343), weight (P= .881), height (P= .42), laterality (P= 1), meniscal repair (P= .332), graft diameter (P= .068), or graft length (P= .183). According to the repeated measures analysis of variance, closure of the quadriceps defect had no significant impact on any of the knee ratios. However, reviewer identity had a significant influence on the CD ratio. Intraclass correlation coefficient analysis revealed excellent agreement between reviewers for the IS (0.982) and BP (0.954) ratios, but only moderate-to-good agreement for the CD (0.751) ratio. Harvest of quadriceps tendon graft does not result in radiographic changes in patellar height. Furthermore, closure of the quadriceps defect does not appear to result in radiographic changes in patellar height. III, retrospective comparative trial.

Comparison of tibial anatomical-mechanical axis angles and patellar positions between tibial plateau levelling osteotomy (TPLO) and modified cranial closing wedge osteotomy (AMA-based CCWO) for the treatment of cranial cruciate ligament disease in large dogs with tibial plateau slopes greater than 30\xb0 and clinically normal Labradors retrievers

BackgroundThe objective of this study was to evaluate tibial anatomical-mechanical axis angles (AMA-angles) and proximodistal and craniocaudal patellar positions following tibial plateau levelling osteotomy (TPLO) and AMA-based modified cranial closing wedge osteotomy (CCWO) in large dogs with tibial plateau angle (TPA) > 30°, to compare these postoperative positions with those of a control group of healthy normal dogs, and to assess which procedure yields postoperative morphology of the tibiae and stifles that is most consistent with that of the unaffected group. This study also investigated whether the occurrence of patellar ligament thickening (PLT), which is commonly observed 2 months postoperatively after TPLO, is associated with misplacement of the osteotomy. A total of 120 dogs weighing more than 20 kg, 40 of which were control animals, were enrolled in this retrospective study. Stifles were radiographically evaluated preoperatively and postoperatively on the side with CCLR and on the healthy contralateral side and compared with clinically normal stifles. PLT was reassessed after 2 months.ResultsSignificant decreases in median patellar height ratio were found after both procedures (TPLO 0.24 (0.05–0.8); CCWO 0.22 (0.05–0.4)). The postoperative craniocaudal patellar position and the median AMA angle differed significantly among the groups (P = 0.000) (TPLO 87.5% caudal to the AA and 3.12° (0.76–6.98°); CCWO 100% cranial to the AA and 0° (− 1.34–0.65°); control group 5% caudal to the AA and 0.99° (0–3.39°)).At 8 weeks, PLT grade differed significantly in the two operated groups (P = 0.000) (TPLO 40% 0–2, 20% 2–4, 40% > 4; CCWO 98.8% 0).ConclusionsTPLO and AMA-based CCWO are associated with significant decreases in patellar height; however, the PLT results 2 months postoperatively differed between the two groups; the decrease in patellar height and PLT were independent of osteotomy position in the TPLO group. Compared to TPLO, CCWO results in reduced postoperative AMA angles and craniocaudal patellar positions that more closely resemble those of unaffected dogs, suggesting that the CCWO procedure allows us to better correct the caudal bowing of the proximal tibia that is often associated with deficient stifles in large dogs with TPA > 30°.

L’ostéotomie tibiale antérieure de déflection avec préservation de la TTA ne modifie pas la hauteur rotulienne

Anterior-closing wedge high tibial osteotomy (ACW-HTO) in ACL reconstruction (ACLR) can prevent graft rupture in patients with posterior tibial slope (PTS) > 12°. Management of patellar height is of concern when performing HTO. The objective was to evaluate the effect of tibial tubercle-sparing ACW-HTO on patellar height in revision ACLR. A retrospective analysis of prospectively collected data from 2 centers was performed. All patients who underwent tibial tubercle-sparing ACW-HTO in revision ACLR were identified and included. Data regarding age, gender and body mass index were collected. Patellar height was measured on full weightbearing pre- and postoperative x-rays. The tibial-referenced indexes of Insall–Salvati (ISI), Caton–Deschamps (CDI) and Blackburne–Peel (BPI) were assessed on lateral x-rays. The Femoral Patellar Height Index (FPHI), femur-referenced, was calculated on frontal x-rays. Pre- and postoperative PTS were assessed using the proximal anatomic axis of the tibia and the tangent line to the medial tibial plateau. All radiological measurements were performed by two trained sports medicine physicians, twice at three-month intervals. Mean values were retained for statistical analysis. Inter- and intra-observer reliability were assessed for each parameter. Forty-seven tibial tubercule-sparing ACW-HTO were retained for analysis. Most patients were male (n = 32, 68.1%) with a mean age of 28.9 ± 9.2 years old (range 17–58). Good to excellent intra- and inter-observer reliability were reported for all parameters. The mean decrease in PTS was 8.60° ± 2.95 (range 3–13.6). No significant difference in patellar height was found between pre- and postoperative x-rays regardless of the index (P > .05). Linear regression investigated the influence of change in slope (delta PTS) on change in patellar height (delta and ratio). No influence of delta PTS was found on all parameters except on the CDI ratio (ratio = preoperative/postoperative, P = .0088). Multivariate analysis showed a significant influence of delta PTS on the CDI ratio (P = .0335), but none on the ISI (P = .7037), BPI (P = .6324), and FPHI (P = 5709) ratios. A change in PTS appeared to influence the Caton–Deschamps Index, but this tibial plateau-referenced method may be biased after HTO. No change in patellar height was observed with others index after tibial tubercle-sparing ACW-HTO.

MRI evaluation of predisposing factors in patellar instability

Objectives: In this study, we have attempted to evaluate the predisposing factors of patellar instability on magnetic resonance imaging (MRI) and to compare the significance of measurement at the level of trochlear bone versus cartilage for trochlear dysplasia. Material and Methods: Thirty patients of patellar instability were assessed on MRI for risk factors of patellar instability including trochlear dysplasia, tibial tuberosity to trochlear groove (TT-TG) distance, and patellar height ratio. Results: Twenty-one (70%) and 27 (90%) cases were positive for decreased trochlear depth when measured at the level of trochlear bone and cartilage, respectively. Eighteen (60%) and 25 (83.33%) cases were positive for trochlear facet asymmetry when measured at trochlear bone and cartilage, respectively. Twelve cases (40 %) were positive for patella alta. Ten cases (33.33%) were positive for decreased lateral trochlear inclination. Seven cases (23.3%) had increased TT to TG distance. Twenty-four cases (80%) were of age equal to or <25 years. Conclusion: According to our study, trochlear dysplasia is the most common predisposing factor of patellar instability (100%) followed by patella alta (40%) and TT-TG distance (23.3%). Trochlear depth and facet asymmetry produce better results as a predisposing factor for instability of patella when measured at the level of trochlear cartilage as compared to trochlear bone with P = 0.001.

Patella Baja in Total Knee Arthroplasty.

Patella baja in total knee arthroplasty can result in impingement, pain, and decreased range of motion. Etiology can range from previous knee surgeries such as anterior cruciate ligament reconstruction, retrograde femoral nail, infrapatellar fat pad resection, and previous total knee arthroplasty. Diagnosis can be confirmed by one of a number of measurements of patellar height including Insall-Salvati and Blackburne-Peel ratios. It is important to differentiate between true patella baja and pseudopatella baja by patellar height ratio. Treatment includes correct identification of the underlying etiology and appropriate management. Surgical management strategies include tibial tubercle osteotomy, distal femoral augment and revision, proximalization of the patellar component, modification of the anterior tibial component, and/or Z-plasty of the patellar tendon. We review the outcomes for each of these procedures.

Patella alta is reduced following MPFL reconstruction but has no effect on quality-of-life outcomes in patients with patellofemoral instability.

The primary purpose of this study was to determine if isolated medial patellofemoral ligament (MPFL) reconstruction for lateral patellofemoral instability altered the patellar height ratio. Secondary purposes were to use disease-specific quality-of-life scores to determine if MPFL reconstruction is as successful in patients with patella alta, compared to those without; and whether the change in the patellar height ratio after MPFL reconstruction is influenced by demographic and clinical factors. Demographic and clinical data were collected pre-operatively on 283 patients with recurrent patellofemoral instability. Pre-operative and 6-month post-operative true-lateral radiographs were assessed to determine the patellar height ratio using the Caton-Deschamps index. A Caton-Deschamps index ≥ 1.2 was defined as patella alta. Paired t tests evaluated the effect of MPFL reconstruction on the Caton-Deschamps index. Using a two-sample t test, pre- and 24-month post-operative Banff Patellofemoral Instability Instrument (BPII) scores were assessed for differences in clinical outcomes between patients with and without patella alta. Pearson (for continuous variables) and Spearman rank correlations (for binary/ordinal variables) were calculated to determine the relationship between the patellar height ratio, demographic and pathoanatomic risk factors, and pre- and post-operative BPII scores. Pre- and post-operative true-lateral radiographs were admissible for 229/283 patients (81%) following isolated MPFL reconstruction. A statistically significant difference in the Caton-Deschamps index was evident from pre- to post-operative for the entire cohort (p < 0.001). The mean decrease in ratio was 0.03, and the effect size was 0.27, classified as small. Pre-operatively 52/229 patients (22.7%) demonstrated a Caton-Deschamps index ≥ 1.2, mean = 1.27 (SD = 0.08); post-operatively 21/229 patients (9.2%) demonstrated patella alta, mean = 1.18, (SD = 0.10), p < 0.001 (two-tailed). The mean decrease in the Caton-Deschamps index for patients with pre-operative patella alta was 0.10; the effect size was 0.82, classified as large. Pearson r correlation of patella alta to the pre- and post-operative BPII scores demonstrated no statistically significant relationship. This study has demonstrated that treatment of lateral patellofemoral instability with an isolated MPFL reconstruction results in a statistically significant decrease in patellar height ratio, with the effect size being greatest in patients with higher pre-operative Caton-Deschamps indices. In patients that presented with patella alta, normalization of the patellar height ratio occurred in 31/52 (59.6%) of the cases. Pre-operative patella alta was not associated with a statistically significant difference in disease-specific BPII outcome scores at any time point. Given these findings, the utility and results of tibial tubercle distalization in patients with patella alta should be a focus of further research. Level of evidence IV.

Patellofemoral Pain in Adolescents: Understanding Patellofemoral Morphology and Its Relationship to Maltracking

Background: Developing bone is highly adaptable and, as such, is susceptible to pathological shape deformation. Thus, it is imperative to quantify if changes in patellofemoral morphology are associated with adolescent-onset patellofemoral pain, as a pathway to improve our understanding of this pain’s etiology. Purpose: To quantify and compare patellofemoral morphology in adolescent patients with patellofemoral pain with matched healthy adolescent controls and determine if a relationship exists between patellofemoral shape and kinematics (measured during active flexion-extension). Study Design: Cross-sectional study; Level of evidence, 3. Methods: Using 3-dimensional static magnetic resonance images acquired during a previous study, we measured patellar, trochlear, and lateral patellar width; trochlear and patellar depth; Wiberg index; patellar-height ratio; lateral trochlear inclination; cartilage length; and lateral femoral shaft length. Student t test was used to compare shape parameters between adolescents with patellofemoral pain and controls. Pearson correlations and stepwise linear regression models were used to explore the relationship among morphology, kinematics (medial-lateral shift/tilt), and pain. Results: Relative to controls, adolescents with patellofemoral pain had larger sulci (mean ± SD, 6.6 ± 0.7 vs 6.0 ± 1.1 mm; 95% CI, 0.6 mm; P = .043; d = 0.66), lateral patellar width (23.1 ± 2.4 vs 21.4 ± 2.6 mm; 95% CI, 1.6 mm; P = .033; d = 0.70), and patella-trochlear width ratio (1.2 ± 0.1 vs 1.1 ± 0.1; 95% CI, 0.1; P < .001; d = 1.26). Shape correlated with kinematics in both cohorts and in the entire population. In the patellofemoral pain group, lateral shaft length (r = 0.518; P = .019), Wiberg index (r = 0.477; P = .033), and patellar-height ratio (r = −0.582; P = .007) were correlated with medial shift. A moderate correlation existed between patellar-height ratio and lateral patellar tilt (r = 0.527; P = .017). Half of the variation in patellar shift in the patellofemoral pain cohort was explained by the patellar-height ratio and Wiberg index (R2 = 0.487; P = .003). Linear correlations with pain were not found. Conclusion: This study provides direct evidence that patellofemoral morphology is altered and influences maltracking in adolescents with patellofemoral pain, highlighting the multifactorial etiology of this pain. Neither morphology nor kinematics (measured during active flexion-extension) correlated with pain. Both increases and decreases in these parameters likely lead to pain, negating a direct linear correlation.

ARE THERE SIDE-TO-SIDE DIFFERENCES IN KNEE MORPHOLOGY IN PATIENTS WITH BILATERAL PATELLAR INSTABILITY

Introduction It is not known if there are side-to-side differences in knee morphology in patients with bilateral patellar instability (BPI). Such knowledge would help to answer the question whether similar treatment and prognosis could be expected for both knees in patients with BPI. The purpose of our study was to evaluate and compare anatomic / morphologic risk factors between knees in patients with BPI. Materials and Methods Of 294 patients who underwent surgical stabilization for patellar instability (2008-2017), 32 patients were identified who underwent staged or simultaneous bilateral surgery. This formed the study cohort. Demographic data, mechanism of initial injury and first knee side to be symptomatic were recorded. Radiographs and MRI of these 64 knees were evaluated for trochlear dysplasia (trochlear depth), patellar height (Caton-Deschamps index, Insall-Salvati ratio), patellar tilt, TT-TG distance, sulcus angle (cartilaginous and bony) and trochlear bump (cartilaginous and bony). The number and percentage of knees with pathologic values for measured risk factors were analyzed. For each risk factor, 15% side-to-side differences were considered significant. Statistical correlation was calculated between the time of presentation (first symptomatic knee) and magnitude of risk factors. All measurements were repeated after a 3-week interval and ICC was calculated to determine intraobserver reliability. Results The mean age of 32 patients was 14.6 years. 17/32 patients were females. 29 patients had staged surgery with mean interval of 21 months between surgeries; 3 patients had simultaneous surgery on each knee. Patients with BPI had multiple risk factors. 22/32 patients (69%) had the same Dejour type of trochlear dysplasia. For each measured risk factor, the number and percentage of patients with 15% or more side-to-side differences is shown (Table 1). There were significant side-to-side differences in patellar height ratios, TT-TG distance, and trochlear bump. The timing of presentation did not correlate with increased risk factors, i.e, the knee that presented earlier did not have increased risk factors compared to contralateral knee. ICC showed excellent intraobserver reliability. Conclusion There were significant side-to-side differences between knees in patients with BPI. Treatment and prognosis should be based on anatomic risk factors for each knee in patients with BPI. [Table: see text]

Patellar Height Assessment Methods: An Update.

* Direct and indirect radiographic methods have been proposed for patellar height assessment. Direct methods relate the position of the patella to the femur, and indirect methods relate the position of the patella to the tibia.* Various knee flexion angles have been used for practicality or because obtaining a true lateral knee radiograph is difficult. Knee flexion angles and quadriceps contraction modify patellar height measurements because of proximal patellar displacement and influence patellar height ratios.* Over time, progression from a simple radiographic measurement to modern biomechanical and imaging technologies has added complexity to the techniques devised to measure patellar height. Currently, the definition of patellar height and its causal relationship to the conditions commonly associated with anterior knee pain remain controversial.

Static patellofemoral alignment in anterior cruciate ligament deficient knees; a retrospective analysis with magnetic resonance imaging

Static patellofemoral alignment in anterior cruciate ligament deficient knees; a retrospective analysis with magnetic resonance imaging

Incidence of Patella Alta in Anterior Knee Pain- Assessment with Patellar Height Ratio's

Altered patellar alignment is associated with anterior knee pain and multitude of conditions that affect the patellofemoral joint. The study aim was to report the incidence of patella altaand patella baja in indian population with anterior knee pain and to investigate whether the normal limits of the patellar height ratios are applicable in indian population.

Distal Femoral Valgus and Recurrent Traumatic Patellar Instability: Is an Isolated Varus Producing Distal Femoral Osteotomy a Treatment Option?

Genu valgum, a risk factor for recurrent patellofemoral instability, can be addressed with a varus producing distal femoral osteotomy (DFO). The purpose of this study is to report 3-year clinical and radiographic outcomes on a series of skeletally mature adolescents with traumatic patellofemoral instability and genu valgum who underwent a varus producing DFO. Consecutive patients (n=11) who underwent an isolated DFO for recurrent traumatic patellar instability over a 4-year study period (2009 to 2012) were reviewed. All patients were below 19 years of age, skeletally mature, had ≥2 patellar dislocations, genu valgum (≥ zone II mechanical axis) and failed nonoperative treatment. Exclusion criteria included less than three-year follow-up, congenital or habitual patellar instability, osteotomy indicated for pathology other than patellar instability, or biplanar osteotomies. Demographic, clinical, and radiographic data were retrospectively analyzed. Recurrence of instability and outcome measures (Kujala and Tegner Activity Scale) were collected at final followed-up prospectively. Ten of 11 patients (average age, 16 y; range, 14 to 18 y; 4 male individuals: 7 female individuals) with an average follow-up of 4.25 years (range, 3.2 to 6.0 y) met inclusion criteria. The average body mass index (BMI) of all patients was 31.3 (range, 19.7 to 46.8) with 91% considered overweight (BMI>25) and 55% obese (BMI>30). The average preoperative lateral distal femoral angle was 75.4 degrees with an average correction of 10.4 degrees (range, 7 to 12 degrees) (P<0.001). Mean patellar height ratios were reduced; with Caton-Deschamps Index significantly reduced to 1.08 (range, 0.86 to 1.30) (P<0.005). The average postoperative Kujala score was 83.6 (range, 49 to 99) with 7 subjects (70%) reporting good to excellent function (Kujala > 80) and 8 (80%) having no further episodes of instability. The mean postoperative Tegner activity score was 5.5 (range, 3 to 7). A distal femoral varus producing osteotomy may change radiographic parameters associated with patellar instability and improve clinical outcomes by reducing symptomatic patellofemoral instability in this patient population. Level IV.

Medial Patellofemoral Ligament Reconstruction Reduces Radiographic Measures of Patella Alta in Adults.

Background:Patellar height has long been considered a risk factor for patellofemoral instability. However, recent pediatric literature demonstrated a reduction in patellar height measurements following medial patellofemoral ligament (MPFL) reconstruction.Purpose:To assess the mean change in patellar height and the percentage of skeletally mature patients with patellar height ratios reduced to within-normal limits following MPFL reconstruction.Study Design:Case series; Level of evidence, 4.Methods:Adult patients undergoing primary MPFL reconstruction for recurrent lateral patellar instability between 2005 and 2013 were identified. Pre- and postoperative (within 1 year of surgery) lateral knee radiographs were assessed for patellar height indices, including Caton-Deschamps, Blackburne-Peel, and Insall-Salvati ratios. The change in patellar height and the number of patients reduced from abnormal to normal patellar height ratios following MPFL reconstruction were assessed.Results:Overall, 32 adult patients were included in the study, with a mean age of 25.7 years (range, 18-55 years). There were 21 women (66%) and 11 men (34%). Insall-Salvati, Blackburne-Peel, and Caton-Deschamps ratios all demonstrated significant reductions in patellar height between pre- and postoperative lateral knee radiographs (P < .001). All 3 indices showed a reduction in the number of patients meeting the criteria for patella alta following MPFL reconstruction. A total of 64% of patients had an abnormal preoperative Caton-Deschamps ratio reduced to within normal limits postoperatively.Conclusion:MPFL reconstruction provides a consistent reduction in patellar height measurements. The Caton-Deschamps ratio was reduced to the reference range following MPFL reconstruction in 64% of patients with preoperative patella alta. Surgeons treating patellofemoral instability should expect a reduction in patellar height after ligament reconstruction, which may affect the need for more invasive distalization procedures.

Patellar Height Measurements on Radiograph and Magnetic Resonance Imaging in Patellar Instability and Control Patients.

Insall-Salvati (IS) ratio, modified IS ratio (mIS), Caton-Deschamps (CD) index, and Blackburne-Peel (BP) index are patellar height measurements commonly made on lateral radiographs (XRs) in patients with patellofemoral instability. More recently, magnetic resonance imaging (MRI) has been used as an additional imaging modality to measure patellar height. However, different imaging modalities have not been previously compared for all of these measurements. First, to compare the patellar height measurements of IS, mIS, CD, and BP on XR and MRI in first-time lateral patellar dislocation (LPD) patients and a control population and, second, to evaluate for the effect of sex and skeletal maturity. All first-time LPD patients with both MRI and XR of the knee within 6 weeks of injury from 2008 to 2012 were included in the LPD group (n = 112). Patients without patellofemoral instability who underwent both MRI and XR of the knee served as controls (n = 129). Two independent observers measured patellar height. Mean values were compared among the radiographic modalities, sex, and skeletal maturity status. Interobserver reliability was assessed using intraclass correlation coefficients (ICCs). Patellar height in the LPD group measured greater on MRI than on XR for all four patellar height ratios (IS: 0.11; mIS: 0.07; CD: 0.18; BP: 0.08). In controls, MRI also demonstrated higher readings than XR on two indices (CD: 0.17; BP: 0.16). Skeletally immature patients measured higher than skeletally mature patients in the majority of the measurements by 0.12 to 0.20 on MRI and XR; the majority of the measurements showed no sex differences. ICC was excellent for IS on both MRI (ICC = 0.830) and XR (ICC = 0.849) and for CD on XR (ICC = 0.786). Patellar height measured greater on MRI than XR by approximately 0.10 across four patellar height measurement indices. Skeletally immature patients measured higher than skeletally mature on both MRI and XR, but sex did not have an effect. This is a retrospective cohort study and its level of evidence is 3.

Patellofemoral instability: Quantitative evaluation of predisposing factors by MRI

Objective: To determine the contribution of MRI in evaluating patellofemoral instability (PFI) and to compare the underlying predisposing factors between the study and control groups. Materials and methods: We enrolled knee MRI scans of 38 patients with lateral patellar dislocation (LPD) and 38 control subjects. All MRI scans were examined for LPD and patellofemoral joint (PFJ) morphological abnormalities. The lateral trochlear inclination angle, sulcus angle and trochlear depth were the MR measures for trochlear dysplasia (TD), patellar height ratio was used for evaluation of patella alta, the patellar tilt angle, and the tibial tuberosity-trochlear groove (TT-TG) distance were also measured. Results: MRI confirmed PFI in 84.2% of study group and detected abnormal PFJ morphological factors in all cases. The prevalences and mean values of all MR parameters showed significant differences (p<0.001) between the study and control groups. MR parameters for TD had the highest sensitivity of 57.9%, while the TT-TG distance was the most specific 97.4% for PFI. The prevalence of combined PFJ abnormal morphological factors was 36.8% in the study group. Conclusion: MRI was useful in quantitative measuring of the predisposing factors contributing to PFI resulting in significant difference in all MR parameters between the study and control groups.

A knee brace alters patella position in patellofemoral osteoarthritis: a study using weight bearing magnetic resonance imaging

To assess using weight bearing magnetic resonance imaging (MRIs), whether a patellar brace altered patellar position and alignment in patellofemoral joint (PFJ) osteoarthritis (OA). Subjects age 40-70 years old with symptomatic and a radiographic Kellgren-Lawrence (K-L) evidence of PFJOA. Weight bearing knee MRIs with and without a patellar brace were obtained using an upright open 0.25T scanner (G-Scan, Easote Biomedica, Italy). Five aspects of patellar position were measured: mediolateral alignment by the bisect offset index, angulation by patellar tilt, patellar height by patellar height ratio (patellar length/patellar tendon length), lateral patellofemoral (PF) contact area and finally a measurement of PF bony separation of the lateral patellar facet and the adjacent surface on the femoral trochlea (Fig.1). Thirty participants were recruited (mean age 57 SD 27.8; body mass index (BMI) 27.8 SD 4.2); 17 were females. Four patients had non-usable data. Main analysis used paired t tests comparing within subject patellar position with and without brace. For bisect offset index, patellar tilt and patellar height ratio there were no significant differences between the brace and no brace conditions. However, the brace increased lateral facet contact area (P=.04) and decreased lateral PF separation (P=.03). A patellar brace alters patellar position and increases contact area between the patella and femoral trochlea. These changes would lower contact stress at the PFJ. Such changes in patella position in weight bearing provide a possible biomechanical explanation for the success of the PFJ brace in clinical trials on PFJOA.