History Of Patellar Dislocation Research Articles

The accuracy of multiple regression models for predicting the individual risk of recurrent lateral patellar dislocation

BackgroundRecurrent lateral patellar dislocation (RLPD) poses a significant threat to patients’ quality of life due to knee pain, patellofemoral cartilage damage, and potential traumatic arthritis. Predictive scoring systems have been developed to assess the risk of RLPD; however, their relative accuracy remains uncertain.PurposeTo investigate the accuracy of the multiple regression models to predict the individual risk of recurrent LPD.MethodsThe Patellar Instability probability calculator (PIP), Recurrent Instability of the Patella Score (RIP), and Patellar Instability Severity Score (PIS) scoring rules were measured in 171 patients with a history of patellar dislocation and 171 healthy individuals. Three prediction models were calculated based on the data to predict the risk of recurrent lateral patellar dislocation. The inter-observer and intra-observer reliability of each measurement parameter was evaluated. The predictive capacity of the three-prediction model was investigated using the receiver operating characteristic curve.ResultsIn the case group of 171 patients, PIS accurately predicted recurrent lateral Patella dislocation in 143 patients. RIP was 96, and PIP was 83. The positive predictive values were 92.9%, 64%, and 68% respectively. In the control group of 171 patients, the PIS was validated in 160 patients who would not experience dislocations. RIP was 117, and PIP was 50. The negative predictive values were 85.1%, 60.9%, and 36.2%, respectively. The area under the curve score for the PIS was 0.866, and the RIP was 0.673. the PIP was 0.678.ConclusionRIP and PIP did not work to predict LPD. PIS can accurately predict recurrent lateral patellar dislocation. It can aid doctors in making treatment decisions.Level of evidenceLevel III, retrospective comparative study.

Patellar Tendon–Trochlear Groove Angle Measured on a Single Computed Tomography Slice of the Distal Femoral Trochlear Groove Is a Reliable Measurement for the Evaluation of Patellar Instability

To verify the reliability of patellar tendon-trochlear groove angle (PTTG-A) measured by computed tomography (CT) and the clinical significance in evaluation of patellar instability. A retrospective study of hospitalized patients with knee pain or injury and had knee CT from January 2017 to June 2021 was performed. PTTG-A and tibial tuberosity-trochlear groove (TT-TG) distance were measured on CT. Spearman correlation analysis was analyzed between the 2 measurements. The intraclass correlation coefficient was determined for inter- and intraobserver reproducibility. The capacity of PTTG-A and TT-TG to predict patellar instability was evaluated by the receiver operating characteristic curve. Data from the control group were used to determine the pathologic thresholds and logistic regression analysis. Included were 113 patients. There were 60 patients with the history of at least 2 episodes of patellar dislocation (study group) and 53 patients without a history of patellar dislocation (control group). The respective PTTG-A and TT-TG distances in the study group (35.2 ± 8.4° and 19.6 ± 4.6 mm) were significantly greater than those of the controls (20.8 ± 5.8° and 13.3 ± 4.5 mm) (P < .001). The correlation between the 2 measurements was strong (r= 0.730, P < .001). The inter- and intraobserver reliability of the PTTG-A were better than TT-TG distance in both groups. The AUC of PTTG-A was greater than that of the TT-TG distance (0.895 vs 0.769, respectively). With the cutoff value of PTTG-A and TT-TG being 26.3° and 16.3 mm, the value of the pathologic threshold of PTTG-A was 30.0°, with a dominance ratio of 16.88 (95% confidence interval 2.88-98.89, P= .002). The PTTG-A measured on a single CT slice of the distal femoral trochlear groove is a more reliable measurement than TT-TG distance for the prediction of patellar instability. III; A retrospective cohort study.

The Tibial Tuberosity–Rotational Angle as a Novel Predisposing Parameter for Patellar Dislocation

The tibial tuberosity (TT) in the axial plane is located on a curved line along the anterior cortex of the proximal tibia. Therefore, the linear measurement of TT position may not fully reflect TT malposition. To introduce TT-rotational angle (TT-RA) as a new anatomical parameter, which means the rotation of the TT relative to the dorsal condylar line of the tibia, and to validate its predictive value for patellar dislocation. Cross-sectional study; Level of evidence, 3. Included were 46 patients with a history of patellar dislocation and 46 age- and sex-matched controls who underwent axial magnetic resonance imaging. Seven radiological parameters were measured and compared between the 2 groups, including TT-trochlear groove (TT-TG) distance, tibial tubercle-posterior cruciate ligament (TT-PCL) distance, TT-PCL ratio, TT lateralization (TTL), trochlear groove medialization (TGM), TT-RA, trochlear groove-posterior condylar axis angle (TG-PCA), and knee rotation. The predictive values of parameters for patellar dislocation were assessed using multiple logistic regression analysis. The intra- and interobserver correlation coefficients for measuring the radiographic parameters showed good to excellent values., respectively. There were significant differences in the TT-TG distance (13.9 vs 6.8 mm; P < .001), TT-RA (16.0° vs 9.1°; P < .001), TG-PCA (93.7° vs 95.4°; P = .017), and knee rotation (0.9° vs 5.3°; P < .001) between the 2 groups. However, there was no significant difference in TT-PCL distance (20.7 vs 19.4 mm; P = .075), TT-PCL ratio (28.0% vs 26.6%; P = .136), TTL (65.7% vs 64.9%; P = .270), or TGM (54.9% vs 55.0%; P = .923). Multivariable analysis showed that 3 parameters were significantly associated with patellar dislocation: TT-RA (OR, 1.57; P < .001), TT-TG distance (OR, 1.52; P = .002), and knee rotation (OR, 0.75; P = .022). The TT-RA was a reliable predisposing parameter of patellar instability. It can be an alternative method of measurement when the TT-TG distance is not clearly defined.

Reliability of the Tibial Tubercle-Roman Arch Distance for Evaluating Tibial Tubercle Malposition and Predicting Patellar Dislocation via Magnetic Resonance Imaging.

Background:The tibial tubercle (TT)–trochlear groove (TT-TG) distance has low reproducibility in patients with a dysplastic trochlea, whereas the clinical value of the TT–posterior cruciate ligament (TT-PCL) distance remains controversial.Purposes:To establish a method to assess the position of the TT on magnetic resonance imaging (MRI) scans using the TT–Roman arch (TT-RA) distance, compare this method with the TT-TG and TT-PCL distance, and provide the pathological threshold value of the TT-RA distance in patients with patellar dislocation.Study Design:Cross-sectional study; Level of evidence, 3.Methods:The TT-RA distance, TT-TG distance, and TT-PCL distance were measured on MRI scans in 70 patients with a history of patellar dislocation and 70 healthy individuals. Inter- and intraobserver reliability of each measurement parameter were evaluated. The discriminatory capacity and the interrelationship of the 3 measurement parameters were investigated using Pearson correlation and the receiver operating characteristic curve. The pathological threshold values of these measurements were calculated according to the data of healthy individuals. Finally, logistic regression analysis was performed using these values.Results:Patients with patellar dislocation had a greater TT-RA distance compared with healthy individuals (18.05 ± 4.16 vs 13.86 ± 2.90 mm; P < .001). The TT-RA distance had a stronger diagnostic capacity, with an area under the curve of 0.802 compared with 0.625 for TT-PCL distance. Excellent reproducibility was seen for TT-RA distance measurement at any degree of trochlear dysplasia (all intraclass correlation coefficients [ICCs] >0.90). The inter- and intraobserver ICCs of the TT-TG distance measurements were extremely low for Dejour type D dysplasia (ICC, 0.509 and 0.616, respectively). The pathological TT-RA distance threshold was calculated as 19.5 mm. Logistic regression showed that patients with a TT-RA distance >19.5 mm were 11.7 times more likely to sustain patellar dislocation than were those with TT-RA distance less than this value.Conclusion:The TT-RA distance was a more reliable parameter with which to evaluate TT position than was TT-TG distance in patients with trochlear dysplasia. The TT-PCL distance was the least reliable among the 3 parameters studied.

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

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. 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. 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. 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 III, diagnostic study, retrospective cohort study.

Defining the role of TT-TG and TT-PCL in the diagnosis of lateralization of the Tibial tubercle in recurrent patellar dislocation

BackgroundThe radiological indicators can help doctors determine whether to make tibial tubercle transfer. But which indicator is better is still in question.Methods117 knees in 103 patients who had undergone patellar surgery and 60 knees in 58 patients who had no history of patellar dislocation from 2014 to 2019 were analyzed. Significant differences of tibial tubercle–trochlear groove (TT-TG) on CT and tibial tubercle–posterior cruciate ligament (TT-PCL) on MRI between the case group and the control group were estimated by an unpaired t test. Significant differences between TT-TG on CT and TT-TG on MRI were estimated by a paired t test. The correlation between TT-PCL on MRI and tibial width was estimated by Pearson test. Receiver operating characteristic (ROC) curves and the area under the ROC curve (AUC) were measured to assess the diagnostic accuracy of TT-TG and TT-PCL on MRI.ResultsThe intraclass correlation coefficient (ICC) for TT-TG between CT and MRI evaluated by two raters was were 0.566. When comparing TT-TG on CT with that on MRI, the mean difference was 2.5 mm (p< 0.001). The mean TT-TG difference on CT between the case group and the control group was 5.3 mm, which was significantly bigger than the mean TT-PCL difference on MRI of 1.2 mm(p< 0.001). AUC of TT-TG on CT and TT-PCL were 0.838 and 0.580 (P< 0.001). TT-PCL correlated with tibial width (r=0.450, P< 0.001).ConclusionA statistically significance and a fair ICC proved that TT-TG could not be used interchangeably. The bigger mean difference between the case group and the control group and better AUC proved that TT-TG on CT might be an indicator more suitable for measuring the lateralization of the tibial tubercle. And TT-PCL should be considered as an individual parameter because of the significant correlation between TT-PCL and tibial width.

Comparison of muscle activation levels and knee valgus between individuals with medial patellofemoral ligament reconstruction and healthy individuals during fatiguing step down task

BackgroundMedial patellofemoral ligament reconstruction becomes first-choice surgical procedure for patients with a history of lateral patellar dislocations but there is limited knowledge about neuromuscular activation patterns of individuals with a history of patellar dislocation who underwent medial patellofemoral ligament reconstruction. ObjectiveThe aim of this study was to compare muscle activation levels and knee valgus during step down performance test between individuals with a history of medial patellofemoral ligament reconstruction and healthy individuals. MethodsFifteen individuals with medial patellofemoral ligament reconstruction and 15 healthy individuals were included. Vastus medialis obliquus, vastus lateralis and gluteus medius muscle activation levels and knee valgus were measured during 60-s- step down performance test. Two-way repeated-measures of analysis of covariance was used for statistical analysis. FindingsCompared to the healthy individuals, individuals with medial patellofemoral ligament reconstruction showed lower vastus medialis obliquus (p = .04) and gluteus medius (p = .005) activation levels, and higher knee valgus (p = .002) in last period of the step down performance test. InterpretationSince the significant results were only observed in the fatiguing section of the test, endurance tests may provide more information about neuromuscular control of the individuals with history of medial patellofemoral ligament reconstruction. Future studies should investigate whether endurance exercises that target to improve vastus medialis obliquus and gluteus medius activity result in better clinical outcomes than conventional programs for individuals with medial patellofemoral ligament reconstruction.

Lateralization of the Tibial Tubercle in Recurrent Patellar Dislocation: Verification Using Multiple Methods to Evaluate the Tibial Tubercle.

The tibial tubercle deviation associated with recurrent patellar dislocation (RPD) has not been studied sufficiently. New methods of evaluation were used to verify the extent of tubercle deviation in a group with patellar dislocation compared with that in a control group, the frequency of patients who demonstrated a cutoff value indicating that tubercle transfer was warranted on the basis of the control group distribution, and the validity of these methods of evaluation for diagnosing RPD. Sixty-six patients with a history of patellar dislocation (single in 19 [SPD group] and recurrent in 47 [RPD group]) and 66 age and sex-matched controls were analyzed with the use of computed tomography (CT). The tibial tubercle-posterior cruciate ligament (TT-PCL) distance, TT-PCL ratio, and tibial tubercle lateralization (TTL) in the SPD and RPD groups were compared with those in the control group. Cutoff values to warrant 10 mm of transfer were based on either the minimum or -2SD (2 standard deviations below the mean) value in the control group, and the prevalences of patients in the RPD group with measurements above these cutoff values were calculated. The area under the curve (AUC) in receiver operating characteristic (ROC) curve analysis was used to assess the effectiveness of the measurements as predictors of RPD. The mean TT-PCL distance, TT-PCL ratio, and TTL were all significantly greater in the RPD group than in the control group. The numbers of patients in the RPD group who satisfied the cutoff criteria when they were based on the minimum TT-PCL distance, TT-PCL ratio, and TTL in the control group were 11 (23%), 7 (15%), and 6 (13%), respectively. When the cutoff values were based on the -2SD values in the control group, the numbers of patients were 8 (17%), 6 (13%), and 0, respectively. The AUC of the ROC curve for TT-PCL distance, TT-PCL ratio, and TTL was 0.66, 0.72, and 0.72, respectively. The extent of TTL in the RPD group was not substantial, and the percentages of patients for whom 10 mm of medial transfer was indicated were small. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Lateral Release for Anterior Knee Pain Without Instability. Outcome Evaluation at Long Term Follow Up

Treatment of patellofemoral pain syndrome with lateral retinaculum release. In a subset of patients with anterior knee pain (AKP) no predisposing factors can be identified, apart from a vague imbalance of the extensor mechanism arising from weakness of vastus medialis obliquus or overcostraint from lateral retinaculum. In those rare cases, after failure of nonsurgical therapy, current treatment consists of surgical transection of the lateral retinaculum release (LR) with an open or arthroscopic technique. Historically LR was performed alone to treat pathologies like patellar instability that needed a different approach like a transposition. Moreover, literature suggests that results obtained by the LR in the short term decrease after few years of follow-up, advising its use as a corollary act during other procedures. Aim of the present paper was to analyze at a long-term follow-up a cohort of patients suffering from AKP and treated with LR, in terms of subjective scores, pain reduction, return to activities, and patello-femoral alignment, trying to describe indications for this procedure. A retrospective review of patient with AKP that performed a Lyonnese CT scan and underwent LR was performed. Exclusion criteria were: missing information, history of patellar dislocation, diagnosed pathologies different from a patellofemoral disorder, associated pathologies, traumatic injuries, and disorders affecting the collagenous tissue. 54 agreed to undergo a follow-up examination, and signed the informed consent for the participation in this study. Demographic, clinical, radiological data were analyzed, along with NRS, Tegner, and Kujala scores. Mean follow up was 74 month; patients were divided in two groups according to the presence of subjective instability. Instability group was made of 21 patients, while stability group was made of 33 patients. At follow up the benefit of LR was statistically significant for all the scores with a p<0,0001 in both groups. The parameters used for radiological evaluation of the joint alignment were not affected by the surgery, showing a non statistically significant difference for both groups. Comparing the two groups revealed no statistical difference in terms of NRS score and Tegner level, respectively with a p<0,151 and p<0,543. An interesting correlation was found, instead, when comparing the Kujala scores between the groups, with a p<0,00145 in favor of the stability group. The main finding of this paper is that LR appears to be effective in treating patello-femoral pain, in those patients without malalignment and without subjective sensation of instability. This paper also depicts worst results with LR as the only treatment for a patellofemoral pain with instability. In conclusion, the paper demonstrates an actual efficacy of LR able to obtain a good outcome and patient satisfaction even on the long term. It should not be indicated for the treatment of instability because the results are worse and tend to decrease over time, and for this pathology should only be a secondary concomitant procedure. More well-designed studies with clearly de?ned inclusion criteria, standardized methods of assessment, and adequate follow-up are certainly needed, in order to understand the missing aspects, and to uniform the scientific community in regards of the effectiveness of LR.

Tibial Tubercle Osteotomy for Anterior Knee Pain

Objectives:The aim of this study was to evaluate the mid-term radiological and clinical outcomes of tibial tubercle osteotomy in patients affected by anterior knee pain. In addition, prognostic factors correlated with the outcomes were evaluated.Methods:The patients treated with tibial tubercle osteotomy (anteromedialization) for anterior knee pain between 2002 and 2014 were included. Exclusion criteria: 1) previous knee surgeries; 2) different procedures to treat anterior knee pain; 3) history of patellar dislocation, 4) Rheumatic conditions. Different variables were collected, as shown in. The patients were prospectively evaluated using the WOMAC short form and Kujala scores. An objective evaluation was performed looking for different potential risk factors and using part of the International Knee Documentation Committee (IKDC) score. Radiological evaluation was performed, including the congruence angle, the grade of osteoarthritis (Kellegren-Lawrence) and the patellar tilt angle. Three main outcomes were identified. The multiple logistic regression was used to analyze the correlation between the variables and a worse outcome.Results:72 cases were included in the study (9 bilateral). 72.2% of the cases were female, and the average age was 42,2 years (SD15,9). The average BMI was 24.4 kg/m2 (SD5,2). In 70.8% of patients a lateral release was associated to the tibial tubercle osteotomy. 77.8% of patients were evaluated clinically, the remaining, who were unable to come for the visits, were interviewed and the subjective scores were administered by phone. The average follow-up was 68.4 months (SD35.5).In 62.5% of cases a valgus lower limb alignment was detected, with 25% and 39.3% of patients having respectively an increased femoral antiversion and foot pronation. Post-operatively there was a statistical significant improvement in all the scores. No differences in the pre-operative and post-operative congruence angle or patellar tilt were detected (p>0.05). All the osteotomies were healed at the last follow-up. No major complications were detected. In 19 cases a further surgery was necessary, with 17 cases of hardware removal and one case of arthrofibrosis. In one case a major subsequent surgery was necessary (Total Knee Arthroplasty): the cumulative survivorship resulted equal to 92.3% (SD7.4%) at the final follow-up.At the multiple regression analysis, a lower WOMAC score was associated with increased age (> 45 years, OR=141.69), increased femoral antiversion (OR=69.94), poor post-operative muscular trophism (OR=127.61) and persistent post-operative pathologic Q angle (OR=18.84). Similarly, a lower Kujala score was associated with increased age (OR=8.36) and increased foot pronation (OR=5.10). Patients’ poor satisfaction was associated only to post-operative factors, such as presence of a positive Rabot test (OR=4.42) and poor muscolar trophism (OR=5.14). Fig.1 shows the results of regression analysisConclusion:In this study good clinical and radiological outcomes were obtained at mid-term follow-up using tibial tubercle osteotomy to treat anterior knee pain, with a cumulative survivorship of 92.3%. The procedure did not affect radiological angles such as the congruence one or the patellar tilt. Older age, increased femoral antiversion, poor post-operative muscolar trophism, increased foot pronation and persistent pathologic Q angle were significantly correlated with worse subjective outcomes.

What Components Comprise the Measurement of the Tibial Tuberosity-Trochlear Groove Distance in a Patellar Dislocation Population?

The tibial tuberosity-trochlear groove distance is used as an indicator for medial tibial tubercle transfer; however, to our knowledge, no studies have verified whether this distance is strongly affected by tubercle lateralization at the proximal part of the tibia. We hypothesized that the tibial tuberosity-trochlear groove distance is mainly affected by tibial tubercle lateralization at the proximal part of the tibia. Forty-four patients with a history of patellar dislocation and forty-four age and sex-matched controls were analyzed with use of computed tomography. The tibial tuberosity-trochlear groove distance, tibial tubercle lateralization, trochlear groove medialization, and knee rotation were measured and were compared between the patellar dislocation group and the control group. The association between the tibial tuberosity-trochlear groove distance and three other parameters was calculated with use of the Pearson correlation coefficient and partial correlation analysis. There were significant differences in the tibial tuberosity-trochlear groove distance (p < 0.001) and knee rotation (p < 0.001), but there was no difference in the tibial tubercle lateralization (p = 0.13) and trochlear groove medialization (p = 0.08) between the patellar dislocation group and the control group. The tibial tuberosity-trochlear groove distance had no linear correlation with tubercle lateralization (r = 0.21) or groove medialization (r = -0.15); however, knee rotation had a good positive correlation in the patellar dislocation group (r = 0.62). After adjusting for the remaining parameters, knee rotation strongly correlated with the tibial tuberosity-trochlear groove distance (r = 0.69, p < 0.001), whereas tubercle lateralization showed moderate significant correlations in the patellar dislocation group (r = 0.42; p = 0.005). Because the tibial tuberosity-trochlear groove distance is affected more by knee rotation than by tubercle malposition, its use as an indicator for tibial tubercle transfer may not be appropriate. Surgical decisions of tibial tubercle transfer should be made after the careful analysis of several underlying factors of patellar dislocation.

Arthroscopic Evaluation of Patellofemoral Congruence With Rotation of the Knee Joint and Electrical Stimulation of the Quadriceps

The aim of this study was to investigate the pathoanatomic features of patellar instability by arthroscopically comparing patellofemoral congruence with rotation of the knee joint and/or electrical stimulation of the quadriceps (ESQ) between knees with and without patellar instability. We retrospectively examined 83 knee joints in 83 patients. The joints were classified into 2 groups: group 1 comprised those without a history of patellar dislocation and included 59 patients (25 male and 34 female patients), and group 2 comprised those with a history of patellar dislocation and included 24 patients (9 male and 15 female patients). Evaluation of patellofemoral congruence at 30° of flexion of the knee joint was conducted based on an axial radiograph and arthroscopic findings. The congruence angle was measured on the radiograph. The position of the patellar central ridge (PPCR) on the trochlear groove during arthroscopy was measured using still video frames of knee joints with rotational stress and/or ESQ. Statistical differences in the measurements between the 2 groups were assessed with the unpaired t test and the area under the receiver operating characteristic curve of each measurement. There were significant differences (P < .0001) between the 2 groups in the congruence angle on radiographs and PPCR in knee joints with rotational stress and/or ESQ on arthroscopy. External and internal rotation of the knee joint caused lateral and medial patellar shift, respectively, in both groups, but the shift was significantly larger in group 2. ESQ in addition to rotation caused further patellar shift in group 2 but reduced patellar shift in group 1. Measurement of PPCR with external rotation of the knee and ESQ was the only method to show an area under the receiver operating characteristic curve of 1. There were significant differences in the effects of rotation of the knee joint and/or ESQ on patellofemoral congruence at 30° of flexion of the knee joint on arthroscopy between knees with and without patellar instability. Level III, diagnostic study of nonconsecutive patients.

Magnetic Resonance Imaging Analysis of Rotational Alignment in Patients With Patellar Dislocations

Background: The role of anatomic risk factors in patellofemoral instability is not yet fully understood, as they have been observed in patients either alone or in combination and in different degrees of severity. Purpose: To prospectively analyze rotational limb alignment in patients with patellofemoral instability and in controls using magnetic resonance imaging (MRI). Study Design: Cross-sectional study; Level of evidence, 3. Methods: Thirty patients (mean age, 22.9 y; range, 12-41 y) with a history of patellar dislocation and 30 age- and sex-matched controls (mean age, 25.2 y; range, 16-37 y) were investigated. The patients underwent MRI of the leg at 1.5 T using a peripheral angiography coil and a T2-weighted half-Fourier acquisition single-shot turbo spin echo (HASTE) sequence for measuring femoral antetorsion, tibial torsion, knee rotation, and mechanical axis deviation (MAD). The mean values of these parameters were compared between patients and controls. In addition, the patients underwent an assessment to determine the influence of rotational limb alignment on lateral trochlear inclination, trochlear facet asymmetry, trochlear depth, Insall-Salvati index, and tibial tuberosity–trochlear groove distance. Results: Patients had 1.56-fold higher mean femoral antetorsion (20.3° ± 10.4° vs 13.0° ± 8.4°; P < .01) and 1.6-fold higher knee rotation (9.4° ± 5.0° vs 5.7° ± 4.3°; P < .01) compared with controls. Moreover, patients had 2.9 times higher MAD (0.81 ± 0.75 mm vs −0.28 ± 0.87 mm; P < .01). Differences in tibial torsion were not significant. Also, there were no significant correlations between parameters of rotational alignment and standard anatomic risk factors. Conclusion: Our results suggest that some patients with nontraumatic patellar instability have greater internal femoral rotation, greater knee rotation, and a tendency for genu valgum compared with healthy controls. Rotational malalignment may be a primary risk factor in patellar dislocation that has so far been underestimated.

An analysis of the medial patellofemoral ligament length change pattern using open-MRI

Recently, for a recurrent patellar dislocation, medial patellofemoral ligament (MPFL) reconstruction has come to be commonly performed, yet the precise in vivo MPFL biomechanics still remains to be clarified. The purpose of this study was to analyze the length change pattern of MPFL in vivo. The subjects were comprised of ten male and ten female healthy volunteers. The length of the MPFL was measured using an open-MRI both from a leg extended position and a highly knee-flexed position in order to analyze the length change pattern of the MPFL. The MPFL length for men and women resulted in an average of 52±3mm and 43±2mm at the knee extended position, respectively. The length change pattern of the MPFL presented a slight change at up to a flexion angle of 60° and a decrease at over 60°. In terms of morphology, the fiber bundle of the MPFL experienced linear tension at a knee flexion angle of 60°. We determined that the MPFL length in vivo exhibited a specific length change pattern. MPFL mainly contributes to the medial constraint of a patella with a knee flexion of 0° to 60°, wherein it is expected to have the strongest strain at 60°. However, more studies are needed to obtain a better understanding of cases with a history of patellar dislocation.

Prospective analysis of uncomplicated bone bruises in the pediatric knee

To determine the incidence of uncomplicated knee bone contusions in pediatric patients. MRI studies were obtained using either high-field (1.5 T) or mid-field strength magnets (0.2-0.3 T), identifying 48 pediatric patients suitable for study. Contusion location, size, and any ligamentous or meniscal injuries were recorded. Exclusionary criteria did not include plain film findings, the interval between injury to imaging, or history of patellar dislocation [Fulkerson (2002) 30:447-456]. Uncomplicated bone bruises were those occurring in the absence of other internal derangements of the knee, such as meniscal and ligament tears. Consensus imaging findings by two reviewing radiologists revealed a 25% incidence of uncomplicated bruises (12/48 patients). These bone bruises involved the lateral and medial knee compartments 56 and 44% of the time, respectively. Bruises of the lateral compartment were larger (2.4 cm) than those found in the medial compartment (1.8 cm). Given the high incidence of symptomatic but uncomplicated contusions identified in this study of a pediatric population, we suggest appropriate joint rest and follow-up without other intervention as a primary course of treatment.

Patellar tendon length — the factor in patellar instability?

Patellar tendon length has been compared in 42 knees with a history of patellar dislocation, and 51 control knees. A lateral X-ray and a magnetic resonance image (MRI) were taken of each knee. The mean radiological patellar tendon length was 46 mm in the controls and 53 mm in the dislocation group. From MRI images, the mean was 44 mm in controls and 52 mm in the dislocation group. This means that the patellar tendon is significantly ( P<0.0001) longer in patients with a history of patellar dislocation on both MRI and X-ray. There is no significant difference ( P=0.52) between X-ray and MRI measurements of tendon length. The distance between the tibial plateau and the point of tendon insertion was also measured and found to be 28 and 29 mm in the control and dislocation groups, respectively. There is no significant difference between these two measures ( P=0.19). In conclusion, patella alta is caused by a long patellar tendon rather than a low insertion into the tibia. Measuring the length of the patellar tendon using MRI is more specific and more sensitive than the Caton–Deschamps index for patellar instability.

Lateral retinacular release of the patella

From October 1977 through January 1984, 2,330 arthroscopic procedures of the knee were performed by one of the authors (G.J.S.). Among these procedures, 35 lateral retinacular releases were performed through minimal, lateral incisions. Twenty-two knees in 22 patients were available for follow-up evaluation, and these cases were reviewed retrospectively. The average age of the patients at the time of surgery was 22.6 years. The average follow-up period was 48 months. The patients were divided into three subgroups on the basis of their preoperative diagnosis. Group I (eight knees) had a history of patellar dislocations; group II (seven knees) had recurrent patellar subluxation, identified by history and physical and radiographic examinations; and group III (seven knees) had patellar pain without a history of dislocations or subluxation and with no symptoms of instability. All of these patients underwent diagnostic arthroscopy and lateral retinacular release, as well as arthroscopic treatment of associated pathology. Postoperatively and at the time of followup, all patients were evaluated for pain, function and patellar instability. In 15 patients with a history of patellar dislocation or subluxation, 67% were found to have had significant improvement in their symptoms, which was borne out by the findings during physical examination. None was worse following treatment. Among the seven patients with no history of patellar dislocation or subluxation, only one of the seven had a satisfactory result. Based upon the findings of this study, it was concluded that arthroscopic lateral retinacular release is a reasonable, initial step in the surgical treatment of patellar dislocation or subluxation, resistant to conservative treatment. Its efficacy in cases of recalcitrant patellar pain without a history of instability is doubtful.

Patellar pain and quadriceps rehabilitation. An EMG study.

Eighteen patients (26 knees) giving a history of patellar dislocation and/or subluxation and continued patellar symptoms underwent evaluation to determine the efficacy of their rehabilitation programs. Four-channel cine-electromyography was utilized to assess the relative muscular effort of the vastus medialis, vastus lateralis, vastus medialis obliquus, and rectus femoris in a series of exercises. Ten degrees of flexion of the knee reduced effective muscle effort in the vasti group to an average of 1/4 of the muscle effort demonstrated in full extension of the knee. No consistent pattern was noted by altering the rotation of the hip from neutral to external or internal rotation. The addition of weight (5 lb) to the ankle did not enhance the muscle effort with the knee in full extension. Quadsets and straight leg-raising exercises in full knee extension offer the best quadriceps rehabilitation program in the patient with a patellar malalignment syndrome and persistent symptoms.