Normal values of the axial patellotrochlear overlap on MRI: Good correlation with patellotrochlear index in patients with no patellofemoral pathology

BACKGROUND

There are several imaging-based measurements for patellofemoral height, which are obtained from sagittal images. However, these methods can be misleading with sagittal oblique slices and when the patella is tilted and/or chronically subluxated. This study aimed to describe a simple method of measuring patellar height using axial patellotrochlear overlap (APTO) on MRI.

METHODS

A retrospective observational study of 97 knees from 251 patients, excluding those with fractures, massive effusion, or patellofemoral conditions. APTO was measured as follows: (1) patellar length (P) - expressed as the number of axial images showing patellar articular cartilage; (2) trochlear overlap (T) - the number of axial images showing the overlap between patellar articular cartilage and articular cartilage of the lateral trochlea. APTO is the ratio T/P. All measurements were performed independently by six raters on two separate occasions. The raters were two orthopaedic consultants, one knee surgery fellow, two consultant musculoskeletal radiologists, and one radiology fellow. The conventional patellotrochlear index (PTI) was measured as a control for all patients by a senior musculoskeletal radiologist.

RESULTS

The mean APTO value was 36.7% (range 14.2-66.6; standard deviation 11.4). There was a positive correlation with the PTI, Pearson correlation coefficient: 0.76, P < 0.001. Intra-observer reliability was good (intraclass correlation coefficient(ICC): 0.66, 95% confidence interval (CI) 0.54, 0.76, P < 0.001). Inter-observer reliability was fair (ICC: 0.51, 95% CI 0.41, 0.6, P < 0.001).

CONCLUSIONS

APTO was shown to be a reliable measurement of patellar height and correlated with existing PTI for patellar height. Measurement of APTO on MRI could be a reliable alternative for the evaluation of patellar height. However, further studies are required to assess its validity in patients with patellofemoral pathology.

Proximal bone block with distal screw trajectory improves mechanical stability during distalization tibial tubercle osteotomy

PURPOSE

The purpose of this study was to quantify differences in mechanical stability of a wedge-shaped distalization tibial tubercle osteotomy (TTO) with a standard technique, versus a modified technique with use of a proximal bone block and distally angled screw trajectory.

METHODS

Ten fresh-frozen cadaver lower extremity specimens (five matched pairs) were utilized. Within each specimen pair, one specimen was randomly assigned to undergo a standard distalization osteotomy fixed with two bicortical 4.5-mm screws oriented perpendicular to the long axis of the tibia, and the other to undergo a distalization osteotomy with modified fixation utilizing a proximal bone block and distally angled screw trajectory. Each specimen's patella and tibia were mounted on a servo-hydraulic load frame using custom fixtures (MTS Instron). The patellar tendon was dynamically loaded to 400 N at a rate of 200 N/second for 500 cycles. Following the cyclic loading, loading to failure was done at 25 mm/min.

RESULTS

The modified distalization TTO technique demonstrated significantly higher average load to failure compared to the standard distalization TTO technique (1339 N vs. 844.1 N, p < 0.001). Average maximum tibial tubercle displacement during cyclic loading was significantly smaller in the modified TTO technique group compared to the standard TTO technique (1.1 mm vs. 4.7 mm, p < 0.001).

CONCLUSION

This study demonstrates that distalization TTO utilizing a modified technique with a proximal bone block and distally aimed screws is biomechanically superior to standard distalization TTO without proximal bone block and screw trajectory perpendicular to the long axis of the tibia. This increased stability may aid in reducing the reported higher complication rates (including loss of fixation, delayed union and nonunion) following distalization TTO, although future clinical outcome studies are warranted.

Patella alta and increased TT-TG distance do not adversely affect patient-reported outcomes following isolated MPFL reconstruction: A systematic review

OBJECTIVES

To analyze the effect of patellofemoral anatomical variations (patella alta, increased tibial tubercle-trochlear groove [TT-TG] distance, and trochlear dysplasia) on clinical outcomes after isolated medial patellofemoral ligament (MPFL) reconstruction.

METHODS

A comprehensive search from PubMed, Embase, and the Cochrane Library databases was conducted to identify studies that compared outcomes based on the presence or absence of patella alta, elevated tibial tubercle-trochlear groove (TT-TG) distance, and/or trochlear dysplasia. Exclusion criteria included reviews and meta-analyses, studies that included patients who underwent associated bony procedures, and those reporting outcomes after isolated MPFL reconstruction with no comparison between varying anatomical groups.

RESULTS

After application of selection criteria, 19 studies were included. Patella alta was not predictive of failure or poorer outcomes among 13 studies; however, 2 studies demonstrated poorer patient-reported outcome scores and/or higher failure rates with increasing patellar height. Increasing TT-TG distance demonstrated a statistically significant correlation with poorer outcomes in only one study, whereas 12 other studies showed no association. Trochlear dysplasia resulted in worse outcomes and greater failure rates in 6 studies, while 10 studies showed no statistically significant correlation between trochlear dysplasia and postoperative outcomes.

CONCLUSION

Patella alta and increased TT-TG distance did not adversely affect outcomes following isolated MPFL reconstruction in the preponderance of reviewed studies. Data are mixed regarding the impact of trochlear dysplasia on the outcomes of isolated MPFL reconstruction.

LEVEL OF EVIDENCE

IV.

Increased lower limb length ratio in patients with patellar instability

PURPOSE

Patellar height is a risk factor for patellar instability, correlated with the tibia length/femur length (T/F) ratio. This study aimed to explore the changes in the T/F ratio in patients with patella instability and the potential correlation with the morphology of the patellofemoral joint and extensor moment arm.

METHOD

A retrospective analysis was performed to assess the ratio of lower limb length morphological characteristics of the patellofemoral by full weight-bearing long-leg standing radiographs, magnetic resonance imaging, and computed tomography in 75 patients with patellar instability and 75 participants from a randomly selected control group from January 2020 to September 2021. A total of eight parts were measured, including mechanical tibia length/femur length (mT/F) ratio, anatomical tibia length/femur length (aT/F) ratio, hip-knee-ankle angle, femoral neck-shaft angle, femoral valgus cut angle, patellar height, Dejour classification, sulcus angle, trochlear angle, medial trochlear inclination, lateral trochlear inclination, patella tilt angle and patellar tendon moment arm to evaluate the difference of morphology between patient group and control groups.

RESULTS

The mT/F (0.840 ± 0.031 vs. 0.812 ± 0.026, p < 0.001) and aT/F (0.841 ± 0.033 vs. 0.808 ± 0.028, p < 0.001) ratios in the patient group were significantly greater than that in the control group. There was a significant correlation between patellar height and increased mT/F and aT/F ratios (p < 0.05).

CONCLUSION

Patients with patellar instability had a larger lower limb length ratio, and the change in lower limb length ratio was correlated with patellar height.

LEVEL OF EVIDENCE IV

The use of a 30-degree radiolucent triangle during surgery in distal avulsion fractures of the patella

BACKGROUND

Avoiding patella baja or alta after the Krackow suture technique for distal avulsion fractures of the patella can be challenging. We aim to introduce a simple and reproducible technique using a 30-degree radiolucent triangle involving the contralateral knee to ensure the correct positioning of the patella intraoperatively.

METHOD

The radiolucent triangle is positioned under the contralateral knee before operating the injured knee. A strict lateral view is obtained using fluoroscopy as a reference before a Krackow technique is performed on the avulsion fracture of the patella.

RESULTS

The triangle technique is straightforward and easily reproducible by surgeons of all levels. It allows the surgeon to correctly position the patella intraoperatively in avulsion fracture repair and modify tension on the patellar tendon.

CONCLUSION

This method avoids millimetric mispositioning of the operated patella, thus improving the management intraoperatively and could decrease postoperative complications.

Isolated medial patellofemoral ligament reconstruction is valid to stabilize patellofemoral joint but uncertain to reduce patellar height in setting of lateral patellar dislocation and patella alta

INTRODUCTION

Medial patellofemoral ligament reconstruction (MPFLR) is the most commonly used surgical treatment for patients with lateral patellar dislocation (LPD). It is still poorly understood whether or not MPFLR has a contributory effect on decreasing patellar height.

MATERIALS AND METHODS

Forty-five patients who underwent isolated MPFLR for LPD and patella alta were evaluated with a mean follow-up period of 24 months (22-25 months). Knee joint functions were evaluated by Banff patellofemoral instability instrument (BPII) 2.0 scores and Kujala scores. Patellofemoral engagement and stability were assessed by the patella tilt angle (PTA) and patellar congruence angle (PCA) measured by CT scans, and the patellar-glide test. Patellar height was calculated on lateral radiographs according to three methods: Caton-Deschamps ratios (CDR), Insall-Salvati ratios (ISR), and Blackburne-Peel ratios (BPR). A threshold value of p < 0.05 denoted a statistically significant difference.

RESULTS

Significant improvements were found in both BPII 2.0 scores, which increased from 41.7 to 77.8 (p < 0.001) and Kujala scores, which increased from 49.2 to 85.5 (p < 0.001). Post-operative PTAs and PCA decreased from 19.6 ± 8.8 to - 3.4 ± 6.2, and from 24.6 ± 7.3 to 13.1 ± 3.8 degrees respectively (p < 0.001). No patients showed lateral translation more than grade II in the patellar-glide test. Regarding patellar height, a tiny reduction (Δ = 0.02, Δ _max = 0.09) was discovered in using CDR (p = 0.027), rather than ISR or BPR. All measurements of radiographic indices had an excellent intra- and inter-rater reliability (ICC > 0.75).

CONCLUSIONS

Isolated anatomic MPFLR is sufficient to achieve good clinical outcomes, as well as patellofemoral stability and high rates of return-to-sport. However, it is unclear if the reconstructed MPFL has a contributory effect on reducing patellar height.

Patellofemoral instability: Current status and future perspectives

The patellofemoral joint is complex, and the management of the first patellar dislocation is not well decoded. The progression to recurrent instability is common. Bony anatomy, muscle tone, and soft tissues are essential stabilizers to preserve the physiological patellar tracking, and they should be carefully evaluated when facing patients with instability.

Evaluation of modified and newly applied patella height indices in primary total knee arthroplasty

OBJECTIVE

The aim of this radiological study was to compare several relevant modified and newly applied patella height indices (PHI) in navigated primary total knee arthroplasty (TKA) to determine intra- and interobserver reliability in order to give a recommendation for clinical application in measuring patella height (PH) in primary TKA.

MATERIALS AND METHODS

A retrospective data analysis assessing different PHI (modified Insall-Salvati index (mISI), Caton-Deschamps index (mCDI), Blackburne-Peel index (mBPI), Plateau-Patella Angle (mPPA); Miura-Kawaramura index (MKI), Knee-Triangular index (KTI)) on lateral knee radiographs was performed by two blinded observers using the same software three months pre- and postoperatively. Concordance correlation coefficient and Pearson's correlation respectively were determined for intra- and interobserver rating as well as a categorization according to Landis and Koch and Cohen.

RESULTS

A total of 337/291 patients of a 5-year period could be analyzed pre-/postoperatively. Excellent postoperative interrater results according to the categorization of Landis and Koch were achieved for the mBPI (Pearson 0.98) > mPPA (0.90) > KTI (0.86), good results for the MKI (0.79) and the mCDI (0.69), and moderate results for the mISI (0.52) with a predominantly strong Cohen correlation in almost all cases. Preoperatively, the mBPI and the KTI were the best interrated PHI. No PH changes could be found postoperatively for the mISI, KTI, MKI, and mPPA.

CONCLUSION

The mBPI, the mPPA, and the KTI can be recommended for PH assessment in TKA. The mPPA might be the easiest one to use in a daily clinical set-up.

High incidence of complication following tibial tubercle surgery

OBJECTIVES

Tibial tubercle osteotomy (TTO) is a common procedure that is frequently used in the treatment of recurrent patellar instability and/or patellar chondrosis. Current estimates of TTO complications in the literature vary widely, with complication rates reaching 59 percent. This variability is due, in part, to inconsistent definitions of complication between studies. The purpose of this study was to identify our complication rate following TTO procedures, with sub-analysis of whether the complication rate was affected by: 1. An intra-articular component defined as an additional procedure that altered post-operative rehabilitation and 2. A distalization of the tubercle translation.

METHODS

All patients between May 2009 and May 2015 who underwent a TTO were retrospectively identified. Complications were defined as major (fracture of the tibia, deep infection, non-union, delayed union, arthrofibrosis, deep vein thrombosis (DVT) and loss of screw fixation) versus minor (superficial wound infection, disturbance of cutaneous sensation and delay in wound healing). Subgroup analysis of distalization versus no distalization and intra-versus extra-articular concomitant procedures were also analysed.

RESULTS

One hundred and sixty-three TTOs in 150 patients were included in the final cohort with a mean follow-up of 21.3 months. The overall complication rate was 35 major complications (21.5%) and 13 minor complications (8.0%), with a total complication rate of 29.5 percent. TTO distalization did not increase the rate of complications. DVT was only seen in the intra-articular procedure cohort (n = 3/1.8%). Arthrofibrosis was the most common complication, occurring in 17 knees.

CONCLUSION

The overall complication rate of TTOs was 29.5%, with arthrofibrosis (10.4%) as the largest complication. DVT increased with concomitant intra-articular procedure. Distalization of the tubercle compared to no distalization had no significant effect on complications.

LEVEL OF EVIDENCE

Retrospective Cohort study, level III.

Low re-dislocation rate following Bereiter trochleoplasty for recurrent patellar instability with severe trochlear dysplasia

PURPOSE

Trochlear dysplasia is an independent risk factor for recurrent patellar instability with evidence demonstrating its presence in up to 85% of patients with patellar instability. Severe trochlear dysplasia can be treated with trochleoplasty to improve engagement of the patella in the trochlear groove and prevent future dislocations. The aim of this study was to determine the clinical outcome of Bereiter trochleoplasty in patients with recurrent patellar instability and severe trochlear dysplasia.

METHODS

This was a retrospective case series of all trochleoplasties performed in our institution from 2008-2019. All clinical records and pre-operative MRI scans were reviewed to assess for trochlear dysplasia, tibial tuberosity to trochlear groove distance (TTTG) and patella height using patella trochlear index (PTI). Trochlear dysplasia was classified using Dejour classification. Incidence of re-dislocation, infection, arthrofibrosis, chondral necrosis and re-operation were recorded. All patients were invited to complete a post-operative visual analog score for pain (VAS-P) and Banff Patella Instability Instrument (BPII).

RESULTS

Fifty-eight trochleoplasties were performed in fifty patients during this period. All trochleoplasties were combined with additional procedures. 93% had concomitant medial patellofemoral ligament (MPFL) reconstructions and 47% had tibial tuberosity transfer. The mean follow-up period was 36.8 months. The rate of dislocation and arthrofibrosis were 5% each. There were no chondral necrosis or nonunion. The mean post-operative BPII was 58.4 and VAS-P was 30.4.

CONCLUSIONS

Bereiter trochleoplasty, often combined with MPFL reconstruction and/or tibial tuberosity transfer results in low re-dislocation and complication rate.

LEVEL OF EVIDENCE

IV.

Three-dimensional transfer of tibial tuberosity for patellar instability with patella alta preserves patellar position and clinical outcomes: A minimum 3-year follow-up study

BACKGROUND

The three-dimensional (3D) transfer of tibial tuberosity has been reported to improve patellofemoral congruity and showed good clinical outcomes during the short follow-up, however, little is known about whether the patellar position and clinical outcomes are preserved at longer follow-ups and the risk factors for poor clinical outcomes.

HYPOTHESIS

We hypothesized that patellar position and clinical outcomes would be preserved and the predisposing factors were associated with poor clinical outcomes after the 3D transfer of tibial tuberosity.

PATIENTS AND METHODS

Thirty-nine patients, with a mean age of 27.9 (15-52) years, who underwent the 3D transfer of the tibial tuberosity were enrolled. Patellar position was evaluated using the Caton-Deschamps index and patellar tilt. Clinical outcomes were evaluated with Lysholm and Kujala scores pre- and postoperatively. Age, body mass index (BMI), radiographic measurements, and range of motion (ROM) were compared between the poor group (defined as <80 points on Kujala score) and the good group (≥80 points). The mean follow-up period was 54.1 (36-100) months.

RESULTS

Patellar position decreased from 1.32 (1.21-1.53) preoperatively to 0.99 (0.84-1.07) at the final follow-up, according to the Caton-Deschamps index (p < 0.01). The mean patellar tilt decreased from 26.0° (21-40°) to 15.1° (5-28°) (p < 0.01). Kujala and Lysholm scales improved from 59.1 to 54.2 to 90.1 and 91.8 at final follow-up, respectively (p < 0.01). Increased BMI, lower femorotibial angle, limited ROM, and poor preoperative clinical outcomes were the predicting factors for poor postoperative clinical outcomes (p < 0.05).

CONCLUSION

The 3D transfer for patellar instability with patella alta preserved the patellar position and clinical outcomes for at least 3 years. Predisposing factors that may potentially affect postoperative clinical outcomes of the 3D transfer of tibial tuberosity include an increased BMI, valgus knee, limited ROM, and poor preoperative clinical outcomes.

Combined distal femoral osteotomy and tibial tuberosity distalization is effective in patients presenting with patellar instability and patellofemoral pain due to patella alta and femoral malalignment

INTRODUCTION

Patellar malalignment has been considered one of the major pathomechanical causes of patellofemoral instability and pain. The results have been reported after femoral varization/torsional osteotomy and tibial tuberosity distalization osteotomy (TTD-O). However, the combination of a femoral deformity (genu valgum/increased femur antetorsion) and patella alta remains underreported. Therefore, the aim of this study was to investigate the clinical outcomes of patients simultaneously treated by distal femoral osteotomy and TTD-O. The hypothesis was that restoration of patellofemoral (PF) alignment via the abovementioned osteotomies would achieve good patient-reported outcome measures.

MATERIALS AND METHODS

Between 2016 and 2019, a series of 25 knees in 20 patients were treated by a distal femoral osteotomy combined with a TTD-O aiming to correct patellofemoral malalignment consisting of genu valgum and/or increased femur antetorsion and patella alta. Six patients were lost to follow-up, and one patient refused to participate. Thus, 17 knees in 13 patients (male/female 1/12; age 27.4 ± 5.4 years) were included and comprised the study group for this investigation. Patients were evaluated after a mean of 3.1 ± 0.9 years postoperatively. The Kujala anterior knee pain scale and the PF-subscale of the Knee Osteoarthritis and Outcome score (KOOS-PF) were used to assess patients' reported outcome measures from pre- to postoperatively.

RESULTS

The mean amount of torsional correction, valgus correction, and tibial tuberosity distalization averaged 14° (10°-18°), 5.2° (3.8°-8°), and 9 mm (6°-15 mm), respectively. The Kujala score increased by an average of 24.18 points from a mean of 66.6 ± 18.3 points (34-93 points) preoperatively to 90.8 ± 14.2 points (44-100 points) postoperatively (95% CI - 33.0 to - 15.3; p < 0.0001). The KOOS-PF score increased by an average of 33.7 points from a mean of 49.5 ± 24.5 points (9.1-88.6 points) preoperatively to 83.2 ± 21.6 points (15.9 -100 points) postoperatively (95% CI - 47.5 to - 19.9; p < 0.0001).

CONCLUSION

The findings of this study indicate that the combination of a distal femoral osteotomy and a tibial tuberosity distalization osteotomy is effective in patients presenting with patellar instability and patellofemoral pain due to patella alta and femoral malalignment.

Inter- and intra-observer reliability of patellar height measurements in patients with and without patellar instability on plain radiographs and magnetic resonance imaging

INTRODUCTION

Many patella height indices exist in the literature. There is no single universally accepted radiological assessment for measuring patella height. The aims of this study were to determine which of the commonly used indices can most reliably measure patella height and compare the findings on both plain X-ray and magnetic resonance imaging (MRI) of the knee.

METHODS

This case-controlled study compared patients with recurrent patella instability (patella group) to a control group. Two observers measured six validated patella height indices on X-ray and MRI of both groups at two separate time periods. Between-group and within-group statistical analysis was undertaken of the data. The inter- and intra-observer reliability was assessed using the intraclass correlation coefficient (ICC) and the kappa measure of agreement (k).

RESULTS

Forty-four patients comprised the patella group and 50 patients the control group. There was a significant difference of most indices between the two groups (p < 0.05). There was a significant difference of most indices between the two imaging modalities (p < 0.05). The Insall-Salvati ratio had the greatest inter-observer reliability for both X-ray and MRI (ICC = 0.79 to 0.97; p < 0.001) (k = 0.50 to 1.00; p < 0.001).

CONCLUSION

Patella height indices significantly differ when measured on X-ray as compared to MRI. This may infer that a different set of normative values are required for each radiological modality, which we have proposed in this study. Overall, the Insall-Salvati ratio performed best and shows a high degree of intra- and inter-observer reliability on both X-ray and MRI.

Radiological evaluation of patellofemoral instability and possible causes of assessment errors

Patellofemoral instability (PI) is the disruption of the patella’s relationship with the trochlear groove as a result of abnormal movement of the patella. To identify the presence of PI, conventional radiographs (anteroposterior, lateral, and axial or skyline views), magnetic resonance imaging, and computed tomography are used. In this study, we examined four main instability factors: Trochlear dysplasia, patella alta, tibial tuberosity–trochlear groove distance, and patellar tilt. We also briefly review some of the other assessment methods used in the quantitative and qualitative assessment of the patellofemoral joint, such as patellar size and shape, lateral trochlear inclination, trochlear depth, trochlear angle, and sulcus angle, in cases of PI. In addition, we reviewed the evaluation of coronal alignment, femoral anteversion, and tibial torsion. Possible causes of error that can be made when evaluating these factors are examined. PI is a multi-factorial problem. Many problems affecting bone structure and muscles morphologically and functionally can cause this condition. It is necessary to understand normal anatomy and biomechanics to make more accurate radiological measurements and to identify causes. Knowing the possible causes of measurement errors that may occur during radiological measurements and avoiding these pitfalls can provide a more reliable road map for treatment. This determines whether the disease will be treated medically and with rehabilitation or surgery without causing further complications.

A comparison of sagittal MRI and lateral radiography in determining the Insall-Salvati ratio and diagnosing patella alta in the pediatric knee

BACKGROUND

The Insall-Salvati ratio is a technique for determining patellar height that relies on bony landmarks. Magnetic resonance imaging (MRI) and plain radiography are used interchangeably to assess the Insall-Salvati ratio in the pediatric population despite the lack of validity in the literature.

OBJECTIVE

The purpose of this study was to investigate if the Insall-Salvati ratio and patella alta as determined on MRI are comparable to those determined on radiography in pediatric patients.

MATERIALS AND METHODS

We conducted a retrospective review of 49 pediatric patients (age range: 7.5-17.0 years) with unfused growth plates who underwent both knee MRI and lateral knee radiography. Measurements for calculating the Insall-Salvati ratio (the ratio of patella tendon length to patella length) were obtained by three observers. Data were analyzed using paired t-tests and Pearson's correlation. A reliability assessment and inter-method agreements were performed. Patella alta was defined as an Insall-Salvati ratio > 1.2. Additional cutoffs of Insall-Salvati ratios > 1.3 and > 1.4 were also analyzed.

RESULTS

There was no statistically significant difference between Insall-Salvati ratio as determined on MRI (mean: 1.20) and radiographs (mean: 1.25; P > 0.05). There was a strong correlation between Insall-Salvati ratio as determined on MRI and radiographs (Pearson's r = 0.6) with moderate consistency (Cronbach's alpha = 0.78). There was a good level of agreement between the diagnosis of patella alta on MRI and radiographs when defined as an Insall-Salvati ratio greater than 1.2 and 1.3 (Cohen's kappa = 0.61).

CONCLUSION

The results demonstrate a strong association between Insall-Salvati ratio and patella alta derived from MRI and radiographs in children ages 7.5 years and older.

Influence of patella height after patella fracture on clinical outcome: a 13-year period

INTRODUCTION

The incidence of patella fracture is statistically low (0.5-1.5%) compared to other fractures of the extremities [Patella fractures 76(10):987-997, 2005]. In the latter research, patella fractures if treated surgically present an overall inferior functional outcome. Little is known about the influence of the postoperative patella height on the clinical outcome. Therefore, the aim of our study was to analyse the influence of the patella height on the patients' functional outcome after surgery.

METHODS

In this retrospective study the in-house trauma register of our level I University trauma center was screened for patients suffering patella fractures treated surgically. Patella height of the same patients was evaluated on lateral X-rays using the Insall-Salvati Ratio (ISR). The patients' X-rays were analyzed at two time points for the ISR, whereas group A presents ISR data right after surgery and group B data at the latest follow up (minimum 6 weeks). The change of mean ISR at both time points was tested for significance. The functional outcome was measured by the "Munich Knee Questionaire" (MKQ). These MKQ results of different patella heights and fracture types were compared.

RESULTS

The screening of our in-house trauma register revealed 375 patients between the years 2003 and 2016. Out of these 54 patients (34f, 20 m) were enrolled. In detail the follow-up time for ISR between group A and B accounted for a mean of 503.8 ± 655.7 days. The MKQ was assessed at a mean of 1367.0 ± 1042.8 days after surgery. According to the AO-classification 10% AO.34 type B and 90% AO.34 type C fractures were found. Group A showed in 9.1% a patella baja and in 27.3% a patella alta compared to group B presenting 20.0% patella baja and 14.5% patella alta. There was no significant difference in functional outcome referring to the MKQ in patella alta (MKQ 69.0% ± 18.2) or baja (MKQ 67.1% ± 17.9) (p = 0.9). No significant functional difference between AO34.type B (MKQ 74.5% ± 11.0) and AO34.type C fractures (MKQ 64.0% ± 15.0) resulted (p = 0.1).

CONCLUSION

Our results demonstrate that different postoperative patella heights apparently do not influence the functional outcome in the short follow-up.

Patella Alta: When to Correct and Impact on Other Anatomic Risk Factors for Patellofemoral Instability

Patella alta is described as abnormally high-riding patella in relation to the femur, the trochlear groove, or the tibia with decreased bony stability. Patella alta represents an important predisposing factor for patellofemoral instability. Different measurement methods are used to define patella alta. Despite the clinical importance of patella alta, there is only limited consensus on cutoff values, indications for treatment, and ideal correction. In addition, the impact of patella alta on other risk factors for lateral patellar instability is significant. This must be considered when assessing clinical complaints and choosing the best individual treatment. Combined surgical interventions may be necessary.

The reliability of the patellotrochlear index on magnetic resonance imaging for measuring patellofemoral height

BACKGROUND

The purpose of this study was to determine the inter- and intra-observer reliability of the patellotrochlear index (PTI) on magnetic resonance images (MRI) in patients with patellofemoral pain. The correlation between the PTI measured on MRI and the modified Insall-Salvati (MIS) ratio measured on radiographs was also assessed.

METHODS

The PTI was assessed on MRI images and the MIS ratio on radiographs of 66 knees of 62 patients. Assessment was performed by two orthopaedic surgeons, one orthopaedic surgery registrar, two radiologists and one radiology registrar. Correlation coefficients, standard errors of measurement and limits of agreement were calculated for the PTI. To assess the association between the PTI and the MIS ratio, the Pearson's correlation coefficient was calculated.

RESULTS

The PTI showed good interobserver reliability (intraclass correlation coefficient (ICC) 0.79; 95% confidence interval (CI) 0.73-0.85) and excellent intra-observer reliability (ICC 0.90; 95% CI 0.89-0.91). The standard error of measurement was 0.05 and limits of agreement with the mean ± 0.09. A very weak and not significant correlation was found between the PTI and the MIS (r = 0.02; P = 0.77).

CONCLUSIONS

The PTI showed good interobserver reliability and excellent intra-observer reliability. In order to conclude which measurement method of assessing patellar height is truly the most reliable, future studies should investigate agreement parameters (standard error of measurement, limits of agreement) besides solely correlation coefficients. We found a very weak correlation between the PTI and the MIS which suggests that at least one index has poor validity. Future validity studies on indices to assess patellar height are necessary.

Sagittal patellar flexion angle measurement determines greater incidence of patella alta in patellar tendinopathy patients

PURPOSE

The objective of this study was to compare patellar height and patella alta between a control cohort and patients with patellar tendinopathy by the sagittal patellar flexion angle (SPFA) measurement.

METHODS

Magnetic resonance imaging (MRI) scans of the knee were obtained from a sports imaging facility and screened to select patients with anterior knee pain. This symptomatic group was divided into two patient cohorts: those with and without MRI features of patellar tendinopathy. Lateral knee radiographs were reviewed and SPFA, knee flexion angle and Insall-Salvati ratio (IS) were measured from the radiographs by two independent reviewers.

RESULTS

A total of 99 patients consisting of 48 patellar tendinopathy patients and 51 control patients were included. There was a significantly higher mean patellar height (p = 0.002, d = 0.639) and a greater patella alta incidence in the patellar tendinopathy cohort (25.0%) compared to the controls (3.9%) (p = 0.022, d = 0.312). Insall-Salvati ratio measurements showed no difference in patella alta incidence between tendinopathy and control cohorts. There was excellent inter- and intra-observer reliability of SPFA measurements (ICC 0.99).

CONCLUSION

This is the first study to demonstrate a greater incidence of patella alta in patellar tendinopathy patients compared to controls. A greater patella alta incidence amongst patellar tendinopathy patients as defined by SPFA was found to be clinically relevant, as it suggests these patients may comprise the recalcitrant patient subgroup who do not improve with current surgical intervention and may therefore benefit from a biomechanical surgical solution.

LEVEL OF EVIDENCE

III.

Ipsilateral patellofemoral morphological abnormalities are more severe than those of contralateral joints in patients with unilateral patellar dislocation

PURPOSE

To determine the differences in anatomic parameters between ipsilateral dislocated knees and contralateral non-dislocated knees in patients with unilateral patellar dislocation and to identify any variations in ipsilateral knees contributing to contralateral anatomic abnormalities.

METHODS

A total of 82 patients with unilateral patellar dislocation from 2016 to 2019 were retrospectively evaluated. Bilateral anatomic factors, including the tibial tubercle to trochlear groove (TT-TG) distance, lower limb rotational deformities, trochlear dysplasia, patella tilt, and patellar height, were assessed by CT.

RESULTS

The study included 46 patients (32 females and 14 males, mean age ± SD 20.5 ± 6.8). The interobserver reliability of each parameter showed excellent agreement. The ipsilateral TT-TG distance (P = 0.004), patella tilt (P = 0.001), and patellar height (P = 0.01) were greater in the ipsilateral knees than in the contralateral knees. The lateral trochlea inclination (LTI) in the contralateral knees was larger than that in the ipsilateral knees (P = 0.022). There was a significant difference in the distribution of trochlear dysplasia of Dejour between the ipsilateral knees (dislocated side) and the contralateral knees (P = 0.036). However, bilateral femoral and/or tibial torsion, and bilateral knee joint rotation did not differ significantly. Binary logistic regression showed that only ipsilateral LTI revealed significant ORs of 8.83 (P = 0.016) and 7.64 (P = 0.018) with regard to contralateral abnormal tibial torsion and LTI, respectively.

CONCLUSION

In patients with unilateral patellar dislocation, the ipsilateral TT-TG distance, patella tilt, and patellar height values were larger in the ipsilateral knees than in the contralateral knees, and trochlear dysplasia was more severe in the ipsilateral joints. The risks of contralateral pathological tibial torsion and LTI were 8.8- and 7.6-fold higher, respectively, in patients with abnormal ipsilateral LTI.

LEVEL OF EVIDENCE

Level IV.

Influence of tibial tuberosity position and trochlear depth on patellar tracking in patellar instability: Variations with Patella Alta

BACKGROUND

Patella alta reduces articular constraints acting on the patella from the trochlear groove with the knee extended. The current study was performed to address how patella alta alters the influence of tibial tuberosity position and trochlear depth on patellar tracking in patients being treated for patellar instability.

METHODS

Fifteen subjects with recurrent patellar instability participated in knee extension within a dynamic CT scanner. Computational models were reconstructed from the motions to characterize patellar lateral shift, patellar tilt, patellar height, trochlear depth and lateral position of the tibial tuberosity at 0° and 30° of knee flexion. Linear regressions were used to correlate patellar tracking with anatomy for an alta group (7 knees, Caton-Deschamps index > 1.2) and a non-alta group.

FINDINGS

For the alta group, lateral patellar shift and tilt increased with increasing lateral position of the tibial tuberosity at 0° (r² > 0.8, P < 0.005). For the non-alta group, lateral patellar shift and tilt increased as depth of the groove decreased at 0° (r² > 0.8, P = 0.001). Lateral patellar tilt also increased with increasing lateral position of the tibial tuberosity at 30° for the non-alta group (r² = 0.55, P = 0.04).

INTERPRETATION

For patients with patellar instability, lateral patellar maltracking with the knee extended can be largely attributed to either a shallow trochlear groove or a combination of patella alta and a lateral position of the tibial tuberosity. These relationships should be considered in both conservative and surgical treatment planning.

Outcomes of MPFL reconstruction with tibial tubercle transfer for recurrent patellar instability with high grade trochlear dysplasia in Indian population

BACKGROUND

Patellar instability is a painful condition which affects the quality of life and mobility of young individuals. The aim of this study is to observe the results of medial patello-femoral ligament reconstruction with hamstring autograft along with a modified Fulkerson osteotomy, for recurrent instability of patella with high-grade trochlear dysplasia in Indian population.

MATERIALS & METHODS

We conducted a prospective observational study of 26 knees (21 patients) who attended our outpatient department from June 2014 to February 2019, with recurrent instability of the patella and high-grade trochlear dysplasia. All knees were treated with MPFL reconstruction with hamstring autograft and modified Fulkerson osteotomy.

RESULTS

The mean follow-up period was 30 months (range: 24-50). The mean Lysholm scores improved from 49.9 (range: 30-63) preoperatively to 82.5 (range: 51-100) (p < 0.05), Kujala scores from 55.5 (36-67) to 85.9 (55-100) and International Knee Documentation Committee (IKDC) scores from 50.2 (31.6-62.3) to 82.9 (54.7-98.3) (p < 0.05) at 2 years follow-up. TT-TG distance decreased from 21.2 mm (18-25) to 11.6 mm (10-13) (p < 0.05) and patellar tilt angle decreased from 24.2° (18°-35°) to 7.2° (5°-10°) (p < 0.05). One knee had superficial skin infection in immediate post-operative period. Three knees had postoperative stiffness, which improved on manipulation under anesthesia. Six knees had implant irritation from the osteotomy screws which were removed after bony union was achieved. Functional scores were low in two knees due to patello-femoral pain, but they did not have recurrent instability.

CONCLUSION

MPFL reconstruction with tibial tubercle transfer gives good functional outcomes in 92.3% patients with recurrent patellar instability, associated with high-grade trochlear dysplasia in Indian population.

Prevalence of lateral patellofemoral maltracking and associated complications in patients with Osgood Schlatter disease

OBJECTIVE

To evaluate adults with history of Osgood Schlatter disease (OSD) for imaging features of lateral patellofemoral maltracking.

METHODS

In a span of four years, 10,181 unique non-contrast knee MRIs were performed on patients aged 20-50. Patients with acute trauma, prior surgery, and synovial pathologies were excluded. 171 exams had imaging findings of OSD, and an age-matched control group of 342 patients without OSD was randomly selected. Two radiologists retrospectively reviewed MRIs for features of lateral patellofemoral maltracking. Maltracking was defined as edema in superolateral Hoffa's fat or a tibial tuberosity-trochlear groove (TT-TG) distance ≥20 mm with either patellar tilt/translation. Binomial logistic regression identified predictors of maltracking in OSD. Optimal TT-TG distance to indicate maltracking was determined by receiver operating characteristic curve.

RESULTS

59% (101/171) of the knees with OSD showed findings of maltracking, with patella alta, trochlear dysplasia, and quadriceps tendinosis as significant predictors of maltracking (p < 0.001). Patellofemoral chondrosis was present in 63% (107/171), with maltracking contributing to higher grade chondrosis more so than increasing age (OR 8.4 versus 1.07). 13 mm was the optimal cut-off TT-TG distance to indicate maltracking (sensitivity 83%, specificity 80%). The prevalence of maltracking in the control group was 15% (p < 0.001 compared with the OSD group).

CONCLUSION

Adults with sequelae of OSD are at high risk of maltracking and are likely to develop patellofemoral chondrosis. A lower threshold for identifying maltracking patients, including a lower cut-off TT-TG distance can help identify those at risk. Radiologists should maintain a high index of suspicion for maltracking in adults with OSD to guide clinical intervention.

MPFL reconstruction corrects patella alta: a cohort study

PURPOSE

Patella alta is an established risk factor for recurrent lateral patella dislocations. Medial patellofemoral ligament (MPFL) reconstruction has been shown to reduce patella height. Our hypothesis is that isolated MPFL reconstruction corrects patella alta, thereby reducing the risk of recurrent patella dislocation.

METHODS

A prospective cohort study of 33 knees which underwent MPFL reconstruction for recurrent patella dislocation. The pre-operative and post-operative patella height and Kujala knee outcome scores, as well as tibial tuberosity-trochlear groove (TT-TG) distance, and the grade of trochlear dysplasia were recorded.

RESULTS

The mean age was 21.5 years (16-34 years). There was significant reduction in patella height in all patients (p < 0.001), a 67% normalisation of patella alta (CD ≥ 1.2) (p < 0.004), and improvement in the Kujala scores 57.1 (pre-operatively) to 94.8 (post-operatively, p < 0.0001). The recurrent dislocation rate was 3%.

CONCLUSION

MPFL reconstruction alone results in correction in patella alta and improvement in clinical outcomes.

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

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Why compromise the patella? Five-year follow-up results of medial patellofemoral ligament reconstruction with soft tissue patellar fixation

PURPOSE

This study investigates the redislocation rate and functional outcome at a minimum follow-up of five years after medial patellofemoral ligament (MPFL) reconstruction with soft tissue patellar fixation for patella instability.

METHODS

Patients were retrospectively identified and knees were evaluated for trochlea dysplasia according to Dejour, for presence of patella alta and for presence of cartilage lesion at surgery. At a minimum follow-up of five years, information about an incident of redislocation was obtained. Kujala, Lysholm, and Tegner questionnaires as well as range of motion were used to measure functional outcome.

RESULTS

Eighty-nine knees were included. Follow-up rate for redislocation was 79.8% and for functional outcome 58.4%. After a mean follow-up of 5.8 years, the redislocation rate was 5.6%. There was significant improvement of the Kujala score (68.8 to 88.2, p = 0.000) and of the Lysholm score (71.3 to 88.4, p = 0.000). Range of motion at follow-up was 149.0° (115-165). 77.5% of the knees had patella alta and 52.9% trochlear dysplasia types B, C, or D. Patellar cartilage legions were present in 54.2%. Redislocations occurred in knees with trochlear dysplasia type C in combination with patella alta.

CONCLUSION

MPFL reconstruction with soft tissue patellar fixation leads to significant improvement of knee function and low midterm redislocation rate. Patients with high-grade trochlear dysplasia should be considered for additional osseous correction.

Evaluation of infrapatellar tendon plication in spastic cerebral palsy with crouch gait pattern: a pilot study

OBJECTIVE

In order to substantially improve crouch pattern in cerebral palsy, the existent patella alta needs to be addressed. This pilot study evaluates the effectiveness of a previously described infrapatellar tendon plication for the treatment of patella alta in crouch gait pattern in skeletally immature spastic cerebral palsy patients.

METHODS

In 10 skeletally immature patients (20 knees) with spastic diplegia and crouch gait, the previously described technique by Joseph et al. for infrapatellar tendon plication was evaluated within the setting of single event multilevel surgery (SEMLS). Outcome measures included knee extension lag, Koshino's radiological index for patella alta, and the occurrence of complications. Patients were followed-up for a minimum of 12 months.

RESULTS

The extensor lag improved and was statistically significant in all cases of the study with no incidence of tibial apophyseal injury at the latest follow-up. Radiographic Koshino index normalized and was maintained all through the follow-up period except in one patient (5%) who was overcorrected. Two patients (4 knees, 20%) showed postoperative knee stiffness due to casting which resolved with physiotherapy within six weeks. One knee (5%) developed a superficial infection which also resolved uneventfully with repeated dressings.

CONCLUSION

The described infra-patellar plication technique in skeletally immature spastic diplegics appears effective, safe, and reproducible.

A pre-operative grade 3 J-sign adversely affects short-term clinical outcome and is more likely to yield MPFL residual graft laxity in recurrent patellar dislocation

PURPOSE

The purposes of this study were to investigate the anatomical risk factors of grade 3 J-sign and analyse the influence of J-sign grades on the short-term clinical outcomes of patients with recurrent patellar dislocation.

METHODS

From 2016 to 2018, a total of 168 patients with recurrent patellar dislocation (187 knees) underwent medial patellofemoral ligament reconstruction with or without tibial tuberosity medialization. Pre-operative J-sign severity was graded according to a previously described classification (grades 1-3). Potential anatomical risk factors of J-sign were explored. Comparisons were assessed between patients with different grades of J-sign using univariate and binary logistic regression analyses. The Kujala score was assessed and compared with pre-operative values, and stress fluoroscopy was performed to assess medial patellofemoral ligament residual graft laxity. Among the 130 included cases, 104 knees with at least 1-year follow-up were included in the clinical outcome analyses to explore the influence of several anatomical factors and J-sign grade on short-term clinical outcomes.

RESULTS

A total of 118 patients (130 knees) were included in the present study. The median age at surgery was 21 years (range 13-38), and 111 affected knees belonged to female patients (85%). Univariate and multivariate logistic regressions between the grade 3 group and the grade 1-2 groups showed that increased femoral anteversion, excessive external tibial torsion, and patella alta were three independent risk factors of grade 3 J-sign in patients with recurrent patellar dislocation. A total of 104 knees with at least a 1-year follow-up were included in the clinical outcome analyses. The median Kujala score improved from 54 (range, 38-72) pre-operatively to 86 (range, 70-100) post-operatively. Although no re-dislocation was reported during the follow-up, 6 out of 32 patients in the grade 3 group demonstrated "MPFL residual graft laxity" based on post-operative stress radiography (18.8%), which was significantly higher than in the grade 1-2 groups (0%, p < 0.001). Subgroup analysis showed that patients with grade 3 J-sign had significantly lower post-operative Kujala scores than those with grade 1-2 J-sign (p < 0.001). Moreover, increased femoral anteversion (≥ 30°) was correlated with an inferior post-operative Kujala score (p = 0.023).

CONCLUSION

The three independent anatomic risk factors of grade 3 J-sign in patients with recurrent patellar dislocation were increased femoral anteversion, excessive external tibial torsion, and patella alta. A pre-operative grade 3 J-sign was correlated with a lower post-operative Kujala score and more "MPFL residual graft laxity" in patients with recurrent patellar dislocation treated with MPFL reconstruction with or without tibial tuberosity medialization at a minimum 1-year follow-up.

LEVEL OF EVIDENCE

III.

A study of the possible effect of abnormal patella height on meniscal tears

Objective

Patellar height is key to knee biomechanics. Variations (alta/baja) have been associated with instability/dislocations, ACL ruptures etch. The effect of abnormal patella height and meniscal lesions is not clear yet; this is a first investigation of this relation.

Methods

100 patients with meniscal tears were X-Rayed to determine patellar height using the Insall-Salvati ratio and the Caton-Deschamps Index.

Results

20% had abnormal patellar height according to the Insall-Salvati ratio and 9% based on the Caton-Deschamps index.

Conclusion

This indicates that patella height could be a parameter in the occurrence of meniscal injuries worth investigating in larger populations; yet the mechanism remains unclear.

Sagittal patellar flexion angle: a novel clinically validated patellar height measurement reflecting patellofemoral kinematics useful throughout knee flexion

PURPOSE

Patellar height measurements on lateral radiographs are dependent on knee flexion which makes standardisation of measurements difficult. This study described a plain radiographic measurement of patellar sagittal height which reflects patellofemoral joint kinematics and can be used at all degrees of flexion.

METHODS

The study had two parts. Part one involved 44 normal subjects to define equations for expected patellar position based on the knee flexion angles for three new patellar height measurements. A mixed model regression with random effect for individual was used to define linear and polynomial equations for expected patellar position relating to three novel measurements of patella height: (1) patellar progression angle (trochlea), (2) patellar progression angle (condyle) and (3) sagittal patellar flexion. Part two was retrospective and involved applying these measurements to a surgical cohort to identify differences between expected and measured patellar position pre- and post-operatively.

RESULTS

All three measurements provided insight into patellofemoral kinematics. Sagittal patellar flexion was the most useful with the least residual error, was the most reliable, and demonstrated the greatest detection clinically.

CONCLUSIONS

Clinically applied radiographic measurements have been described for patellar height which reflect the sagittal motion of the patella and can be used regardless of the degree of flexion in which the radiograph was taken. The expected sagittal patellar flexion linear equation should be used to calculate expected patellar height.

LEVEL OF EVIDENCE

IV.

Combined quadriceps lengthening (using an external ring fixator) and patellar tendon reconstruction (using a tendoachilles allograft) in a case of chronic patellar tendon rupture: A case report

BACKGROUND

Patellar tendon rupture is an infrequent and debilitating condition, which if left untreated, is complicated by quadriceps contracture and patella alta. This results in reduced function of the knee extensor mechanism including extension lag, reduced range of motion (ROM), chronic knee pain, and frequent falls. Early primary repair has good results in most cases and is performed by opposing and suturing the tendon ends. However, when there is a delay between rupture and repair or in case of a re-rupture, primary repair techniques may not work due to retraction of the extensor mechanism. Several treatment modalities have been proposed in such cases, but there is no clear consensus.

METHODOLOGY

We present the case of a 39-year-old male with chronic rupture of patellar tendon that was reconstructed with a two-stage technique. In the first stage, a ring-fixator was applied to stretch the quadriceps muscle and the second stage consisted of reconstruction of the patellar tendon with a tendoachilles allograft. This procedure was performed in two stages five weeks apart and almost four years after the initial injury.

RESULTS

Results were excellent at three years' follow-up with the patient achieving full extension, a ROM of 0-110° and 85% quadriceps strength. There was significant improvement in his pain, mobility and quadriceps bulk.

CONCLUSION

To our knowledge, this treatment has not previously been described in the literature. We present this case as a proven treatment option for treatment of chronic patellar tendon injuries with extensor mechanism shortening.

Preoperative patellofemoral anatomy affects failure rate after isolated patellofemoral inlay arthroplasty

PURPOSE

To analyze whether preoperative patellofemoral anatomy is associated with clinical improvement and failure rate after isolated patellofemoral arthroplasty (PFA) using a modern inlay-type trochlear implant.

METHODS

Prospectively collected 24 months data of patients treated with isolated inlay PFA (HemiCAP^® Wave, Arthrosurface, Franklin, MA, USA) between 2009 and 2016, and available digitalized preoperative imaging (plain radiographs in three planes and MRI) were retrospectively analyzed. All patients were evaluated using the WOMAC score, Lysholm score, and VAS pain. Patients revised to TKA or not achieving the minimal clinically important difference (MCID) for the total WOMAC score or VAS pain were considered failures. Preoperative imaging was analyzed regarding the following aspects: Tibiofemoral OA, patellofemoral OA, trochlear dysplasia (Dejour classification), patellar height (Insall-Salvati index [ISI]; Patellotrochlear index [PTI]), and position of the tibial tuberosity (TT-TG and TT-PCL distance).

RESULTS

A total of 41 patients (61% female) with a mean age of 48 ± 13 years could be included. Fifteen patients (37%) were considered failures, with 5 patients (12%) revised to TKA and 10 patients (24%) not achieving MCID for WOMAC total or VAS pain. Failures had a significantly higher ISI, and a significantly lower PTI. Furthermore, the proportion of patients with a pathologic ISI (> 1.2), a pathologic PTI (< 0.28), and without trochlear dysplasia were significantly higher in failures. Significantly greater improvements in clinical outcome scores were observed in patients with a higher preoperative grade of patellofemoral OA, ISI ≤ 1.2, PTI ≥ 0.28, TT-PCL distance ≤ 21 mm, and a dysplastic trochlea.

CONCLUSION

Preoperative patellofemoral anatomy is significantly associated with clinical improvement and failure rate after isolated inlay PFA. Less improvement and a higher failure rate must be expected in patients with patella alta (ISI > 1.2 and PTI < 0.28), absence of trochlear dysplasia, and a lateralized position of the tibial tuberosity (TT-PCL distance > 21 mm). Concomitant procedures such as tibial tuberosity transfer may, therefore, be considered in such patients.

LEVEL OF EVIDENCE

Level III, retrospective analysis of prospectively collected data.

Reconstruction of Neglected Patellar Tendon Rupture using Tendoachilles' Allograft with Transosseous Tunnels: A Case Report

Introduction:

Neglected patellar tendon ruptures are uncommon. They are challenging due to the proximal migration of patella and soft-tissue contractures. They are usually managed with autografts or allografts with or without synthetic augmentation, and fixation is done using metallic implants.

Case Report:

A 59-year-old farmer presented with an inability to straighten his knee for 6 months after sustaining a cut lacerated wound with a sickle. He was diagnosed with a patellar tendon rupture. Tendoachilles’ allograft reconstruction was done by creating transosseous tunnels in the patella and tibial tuberosity with a figure of 8 con figurations of the final construct. Synthetic augmentation and metallic implants were not used. Excellent clinical and radiological results were achieved at 3 years’ follow-up.

Conclusion:

Chronic patellar tendon ruptures can be managed using allograft without the need for synthetic augmentation or fixation with implants. This gives excellent clinical and radiological results.

Reconstruction of the medial patellofemoral ligament and reinforcement of the medial patellotibial ligament is an effective treatment for patellofemoral instability with patella alta

PURPOSE

To evaluate the clinical outcome of the combined reconstruction of the medial patellofemoral ligament (MPFL) and medial patellotibial ligament (MPTL) for patellar instability with patella alta.

METHODS

A total of 108 patients underwent a combined reconstruction of the MPFL and MPTL, and 58 patients were included in this study. The clinical results were evaluated and compared using the International Knee Documentation Committee (IKDC) scores, Kujala scores, and visual analogue scale (VAS) scores. The tibial tuberosity-trochlear groove (TT-TG) distance, three indices of patellar height (Insall-Salvati ratio, modified Insall-Salvati ratio, and Caton-Deschamps index), and patellar shift and tilt were defined preoperatively and at the 12- and 24-month follow-up visits.

RESULTS

At the 12- and 24-month follow-up visits, 86.2% (50/58) and 87.9% (51/58) of the subjective outcomes were excellent, 5/58 (8.6%) and 4/58 (6.9%) were good, 1/58 (1.7%) and 2/58 (3.4%) were fair, and 2/58 (3.4%) and 1/58 (1.7%) were poor. There were significant improvements in the IKDC scores, from 51.9 ± 13.8 preoperatively to 80 ± 19.2 (P < 0.05) at 12 months and 85 ± 13.9 (P < 0.05) at 24 months; Kujala scores, from 55.1 ± 15.2 preoperatively to 82.6 ± 14.9 (P < 0.05) at 12 months and 89.5 ± 10.2 (P < 0.05) at 24 months; and VAS scores, from 58 ± 11 preoperatively to 12 ± 5 (P < 0.05) at 12 months and 11 ± 4 (P < 0.05) at 24 months. The patellar tilt, patellar shift, Insall-Salvati ratio, modified Insall-Salvati ratio, Caton-Deschamps index, and TT-TG distance all decreased significantly compared with the preoperative values, and there were no significant differences between the values at the 12- and 24-month follow-ups.

CONCLUSION

The results of this study show that a combined reconstruction of the MPFL and MPTL is an effective treatment for patellar instability with patella alta. This article emphasizes the combined effect of MPFL and MPTL instead of MPFL alone and provides an effective option for the treatment of recurrent patellar dislocation with patella alta.

LEVEL OF EVIDENCE

Case series, Level IV.

Patella alta and patellar subluxation might lead to early failure with inlay patello-femoral joint arthroplasty

PURPOSE

With the growing interest in resurfacing procedures, several new implants have been recently introduced for isolated patello-femoral joint arthroplasty (PFA). However, not much data are available for these new techniques or about the right indications for each type of implant.

METHODS

Out of a retrospective cohort of 20 inlay PFA, 11 PFA with an elevated Insall-Salvati index and an increased patello-femoral congruence angle showed an initial satisfactory result, but presented thereafter with recurrent pain and "clunk" phenomena. They were all revised after a median time of 25 months (range 8-28 months) into an onlay technique PFA and analyzed for their failure mode and revision technique.

RESULTS

Clinical symptoms such as clunking, as well as abraded areas craniolateral of the inlay implant found intraoperatively, were the main observations of this study. The modified Insall-Salvati index (mISI) was significantly higher in the revised knees compared to the unrevised (median 1.8 versus 1.6; p = 0.041). VAS and KSS significantly improved after revision (median VAS reduction in pain of 4.0 points, median KSS improvement of 20.0 points; p < 0.05).

CONCLUSION

Patients with high-normal patellar height index or patella alta, as well as a craniolateral type of arthritis with additional lateralization, should be considered contra-indicated for an inlay technique PFA. They could be considered for a PFA system reaching further proximal into the distal femur. An onlay PFA can be an option for early revision of failed inlay implants. The clinical relevance of this study is that patella alta and patellar subluxation are more difficult to adjust for with an inlay PFJ component.

LEVEL OF EVIDENCE

Level IV.

Reliability of patellotrochlear index in patellar height assessment on MRI-correction for variation due to change in knee flexion

OBJECTIVES

To assess the reliability of patellotrochlear Index (PTI) in patellar height assessment on successive MRI scans in asymptomatic patients.

MATERIALS AND METHODS

Sixty-four patients with two successive MRI scans (128 studies) of the same knee for non-patellofemoral joint symptoms were identified retrospectively. PTI and knee flexion angle were assessed independently by three observers to assess interobserver reliability. The effect of knee flexion on PTI was assessed by comparing the change in values of PTI in each patient correlated with change in knee flexion.

RESULTS

Sixty-four MRIs of patients (M:F) aged between 18 and 35 years (mean 24.6) years were assessed. The mean PTI for initial scan group was 0.33% (95% CI: 0.29-0.37; SD: 0.15) and consecutive scan group was 0.30% (CI: 0.27-0.33; SD: 0.3). The difference was not significant (p = 0.097 using a paired t test) with high inter-observer correlation (0.9) in both sets. Spearman's rho for knee flexion angle and PTI was found to be positive and statistically significant (0.41; p = 0.001). A linear regression model was derived using a scatter chart of change in PTI with change in knee flexion for each patient. The gradient of the linear regression line was used to estimate a cPTI (corrected PTI) value (corrected to 0 degrees of knee flexion), defined as cPTI = PTI - 1.3a (a = knee flexion angle).

CONCLUSIONS

This study demonstrates high inter-observer correlation of PTI on MRI and high test-retest reliability indicating unconscious quadriceps contraction does not change the index sufficiently. Knee flexion significantly alters PTI, increased patellotrochlear engagement with flexion increases the index. We propose use of the formula cPTI = PTI -1.3a to correct the index to 0 degree knee flexion in clinical practice.

Association of patella alta with worsening of patellofemoral osteoarthritis-related structural damage: data from the Osteoarthritis Initiative

OBJECTIVES

To determine the association between Insall-Salvati ratio (ISR), a measure of patella alta, and worsening of Magnetic Resonance Imaging (MRI)-based osteoarthritis (OA)-related patellofemoral joint structural damages over 24-month in participants of the Osteoarthritis Initiative (OAI).

DESIGN

Using weighted random sampling method, we selected a sample of 500 knees (from 1,677 knees with available baseline and 24-months MRI OA Knee Score (MOAKS) measurements), which is OAI-representative regarding knee OA-related factors (i.e., baseline age, sex, body mass index (BMI), and radiographic Kellgren-Lawrence grading). The ISR was measured in all enrolled knees using baseline sagittal 3T-MRI plane by three radiologists. Baseline and 24-month MOAKS variables for patellofemoral bone marrow lesions (BMLs), cartilage damages, and osteophytes were extracted, and the associations between ISR and 24-month worsening of these 3T-MRI features were evaluated using multivariable regression models. After computing receiver operating characteristic curves, the optimal cutoff point of ISR for indicating worsening of patellofemoral OA was determined. P-values were adjusted for multiple comparisons and false discovery rate (FDR) adjusted P-values were reported.

RESULTS

In this longitudinal analysis, 24-month worsening of BML (odds ratio [OR] (95% confidence interval [95% CI]):11.18 (3.35-39.6), adjusted-p-value:<0.001) and cartilage scores (OR:7.39 (1.62-34.71), adjusted-p-value:0.042) in lateral patella was associated with higher baseline ISR. However, higher ISR was not statistically associated with medial patellar or medial and lateral trochlear BML or cartilage scores worsening. We determined the optimal cutoff point of ISR≥1.14 (95% CI: 1.083-1.284) for predicting lateral patellofemoral OA-related structural damages worsening over 24-months (sensitivity:73.73%; specificity: 66.67%).

CONCLUSIONS

Given the uncertainly surrounding the results, our overall findings suggest that ISR could be considered as a predictor of lateral patellofemoral OA-related structural damages worsening with the optimal cutoff point of ≥1.14 using knee sagittal MRI measurements.

Does patella alta lead to worse clinical outcome in patients who undergo isolated medial patellofemoral ligament reconstruction? A systematic review

INTRODUCTION

The aim of this systematic review is to determine the effect of patella height on clinical outcomes after isolated MPFL reconstruction for patella instability. Our primary hypothesis is that patients with patella alta report similar outcomes after isolated MPFL reconstruction compared to patients with normal patella height.

METHODS

A review of the literature was performed according to the PRISMA guidelines. PubMed, EMBASE, and the Cochrane Library were searched from inception to January 10th 2018. Studies were identified using synonyms for "medial patellofemoral ligament", "reconstruction" and "patella alta".

RESULTS

The search resulted in 467 reports on PubMed, 175 on EMBASE and 3 on the Cochrane Library. We included and analyzed in detail six studies describing outcomes after isolated medial patellofemoral ligament reconstruction with regard to patellar height. We found that both patients with patella alta and normal patella height reported satisfactory outcomes after isolated medial patellofemoral ligament reconstruction. However, because of applied exclusion criteria in the included studies the total number of patients with severe patella alta was small (13/74 patients with patella alta, 18%).

CONCLUSIONS

Based on the current literature we suggest that additional tibial tubercle distalisation is not mandatory in patients with mild patella alta (Caton-Deschamps Index 1.2-1.4). To assess the best indications for different surgical procedures for patients with patella instability future research is needed to develop a clear and uniform definition of relevant patella alta.

LEVEL OF EVIDENCE

III.

Medial patellofemoral ligament reconstruction fails to correct mild patella alta in cases of patellofemoral instability-a case-control study

PURPOSE

Medial patellofemoral ligament reconstruction (MPFL-R) is the gold standard in patella soft tissue surgery for patellofemoral instability. Although claimed, recent reports indicate that MPFL-R may fail to distalize the patella in mild cases of patella alta. The present study is a retrospective case-control study to compare radiographic patella height between MPFL-R and historical Insall's proximal realignment (IPR) pre- and post-operatively with respect to distalization and assess redislocation rates at a mid-term follow-up.

METHODS

Sixty-four patients were age/sex matched (1:1), yielding 32 patients for group 1 MPFL-R (cases) and 32 patients for group 2 IPR (controls). Insall-Salvati, Blackburne-Peel and Caton-Deschamps indices were analyzed for differences pre- and post-operatively. An additional inter-rater reliability analysis was performed by means of intra-class correlation (ICC). Redislocation rates were considered as treatment failures in this study.

RESULTS

ICC was excellent for all three patella indices. MPFL-R failed to show significant differences if compared to IPR with respect to distalization in mild stages of patella alta. Moreover, redislocation rates significantly favored MPFL-R (3.1%) over IPR (12.5%; p < 0.0001).

CONCLUSIONS

MPFL-R has become a popular option to restore native patellofemoral biomechanics after ligament rupture. However, the procedure's potential to correct concomitant patella alta should not be overestimated and indications considered carefully.

How does patellar tendon advancement alter the knee extensor mechanism in children treated for crouch gait?

BACKGROUND

The patellar tendon advancement (PTA) procedure, often coupled with a distal femoral extension osteotomy (DFEO), is increasingly used to treat persistent crouch gait. In this study, we investigated relationships between patella position, knee flexion, and the patellar tendon moment arm in children treated with the DFEO and PTA procedures.

METHODS

We retrospectively analyzed pre- and post-operative radiographs and gait metrics from 63 knees that underwent DFEO and PTA procedures at Gillette Children's Specialty Healthcare. A computational musculoskeletal model of the knee was used to simulate the PTA procedure and predict the effects on the patellar tendon moment arm.

RESULTS

Approximately 80% of the knees exhibited patella alta prior to surgery. Post-operatively, 86% of the knees exhibited patella baja. The surgically altered patella position produced a 13% increase in the patellar tendon moment arm in extended knee postures, which agreed well with model predictions. However, the computational model also suggests that baja may compromise patellar tendon moment arms in flexed knee postures. Crouch gait was significantly reduced postoperatively, with a 27 ± 18° reduction in average knee flexion in stance. There was considerable inter-subject variability in outcomes with nine knees not exhibiting a meaningful enhancement of knee extension (<15° change). The subjects who improved were significantly younger and exhibited greater enhancement of the patellar tendon moment arm after surgery.

CONCLUSIONS

This study shows that the PTA procedure enhances the lever arm of the knee extensor mechanism, and this factor may be important in resolving crouch gait.

MPFL in First-Time Dislocators

PURPOSE OF REVIEW

Historically, the standard of care for patients with an acute patella dislocation has been non-operative with the exception being those with a loose body or osteochondral fracture requiring fixation or removal.

RECENT FINDINGS

Recent literature has brought into question this standard of care approach and defined a higher risk subset of first-time dislocators who may benefit from early operative treatment. In addition, these studies suggest that operative treatment not only reduces the risk of recurrence but may improve outcomes overall and specifically in the pediatric population. Though the "high risk" population of first-time dislocators has been more clearly defined, how we treat them remains controversial. We continue to need more evidence-based guidelines to help us manage who we should be fixing and how we should be fixing them. We currently have several multi-center studies in progress, including one specifically looking at the question of medial patellofemoral ligament reconstruction in first-time pediatric and adolescent dislocators.

Patellofemoral reconstruction for patellar instability with patella alta in middle-aged patients: Clinical outcomes

INTRODUCTION

Although several surgical treatments for patellar instability with patella alta have been reported, the clinical outcomes and optimal surgical procedures for patellar instability with patella alta in middle-aged patients are still controversial. We hypothesized that optimal surgical procedures for patellar instability with patella alta in middle-aged patients may induce good clinical outcomes with better patellofemoral geometry.

MATERIALS AND METHODS

Twelve middle-aged patients with a mean age of 44 years (range: 40-55 years), who presented with patellar instability and patella alta, were treated with a combination of several surgeries, such as medial patellofemoral ligament (MPFL) reconstruction, trochleoplasty, lateral release, and three-dimensional transfer of the tibial tuberosity, based on a surgical algorithm. Patellar position and clinical outcomes were evaluated postoperatively. The mean follow-up time was 41.5 months (range: 24-72 months).

RESULTS

Patellar position altered from 1.31 (1.21-1.53) preoperatively to 0.88 (0.69-1.06) postoperatively on the Caton-Deschamps Index (p<0.01). The tibial tuberosity-trochlear groove (TT-TG) distance altered from 21.8mm (20.1-25.8mm) to 10.3mm (5.1-14.7mm), and patellar tilt ranged from 28.1° (21-40°) to 14.6° (5-28°), respectively (p<0.01). Clinical outcomes on the Lysholm and Kujala scales improved from 43.1 and 38.4 to 86.7 and 78.3, respectively, at final follow-up (p<0.01). Surgical treatment that included trochleoplasty resulted in better outcomes than other surgical combinations without trochleoplasty (p<0.05). Sulcus angle and postoperative patellar tilt improved more in those who underwent trochleoplasty than in those who did not (p<0.05).

DISCUSSION

Surgical treatment for patellar instability with patella alta in middle-aged patients resulted in improved clinical outcomes. In particular, a combination surgery including trochleoplasty resulted in the greatest improvement in case of severe trochlear dysplasia.

LEVEL OF EVIDENCE

IV. Retrospective case series study.

Medial patellofemoral ligament reconstruction in children: do osseous abnormalities matter?

PURPOSE

Management of post-traumatic patellar instability in children with osseous abnormalities is challenging because of the presence of an open physis. The aim of our study was to compare the rate of recurrence after isolated reconstruction of the medial patellofemoral ligament (MPFL) in children with or without osseous abnormalities.

METHODS

The medical records of 25 children (27 knees) with recurrent patellar dislocation were reviewed. Each child underwent an isolated reconstruction of the MPFL using a hamstring graft. At the last follow-up, a clinical and radiographic evaluation was performed, including assessment of functional outcomes based on the Kujala score. Patients were compared in terms of the occurrence of a pre-existing osseous abnormality.

RESULTS

The mean age at the time of the surgery was 13.8 years. Eleven patients had trochlear dysplasia (40%), three had a patella alta (11%) and seven had an increased TT-TG (26%). The recurrence rate was 3.7% (one patient), after a mean follow-up of 41.1 months. Recurrence was not more frequent in patients with preoperative anatomical predisposing factors. The mean Kujala score was 95. The mean time to return to practicing sports was 7.1 months.

CONCLUSIONS

Isolated MPFL reconstruction is an effective option for the management of post-traumatic patellofemoral instability in skeletally immature patients. The results of this technique seem to be independent on either proximal or distal misalignments such as trochlear dysplasia, patella alta, or increased TT-TG.

An analysis of knee anatomic imaging factors associated with primary lateral patellar dislocations

PURPOSE

Various knee anatomic imaging factors have been historically associated with lateral patellar dislocation. The characterization of these anatomic factors in a primary lateral patellar dislocation population has not been well described. Our purpose was to characterize the spectrum of anatomic factors from slice imaging measurements specific to a population of primary lateral patellar dislocation. A secondary purpose was to stratify these data by sex/skeletal maturity to better detail potential dimorphic characteristics.

METHODS

Patients with a history of primary lateral patellar dislocation between 2008 and 2012 were prospectively identified. Ten MRI measurements were analysed with results stratified by sex/skeletal maturity. A '4-factor' analysis was performed to detail the number of 'excessive' anatomic factors within a single individual.

RESULTS

This study involved 157 knees (79 M/78 F), and 107 patients were skeletally mature. The measurements demonstrate more anatomic risk factors in this population than historical controls. Patella height and trochlear measurements are the most common 'dysplastic' anatomic factors in this population. There were differences based on sex for some patellar height measurements and for TT-TG; there were no differences based on skeletal maturity.

CONCLUSION

Primary lateral patellar dislocation patients have MRI measurements of knee anatomic factors that are generally more dysplastic than the normal population; however, there is a broad spectrum of anatomic features with no pattern predominating. Characterizing knee anatomic imaging factors in the patient with a primary lateral patellar dislocation is a necessary first step in characterizing the (potential) differences between the primary and recurrent patellar dislocation patient.

LEVEL OF EVIDENCE

IV.

Does patella lowering improve crouch gait in cerebral palsy? Comparative retrospective study

BACKGROUND

Patella lowering aims to improve quadriceps function as a means of correcting crouch gait in patients with cerebral palsy. Few studies have assessed the effects of patella lowering as a component of multilevel surgery.

HYPOTHESIS

Including patella lowering into the components of multilevel surgery is beneficial in patients with crouch gait and patella alta.

MATERIAL AND METHODS

In 12 lower limbs with patella alta (Caton-Deschamps index>1.4) in 41 children with cerebral palsy, patella lowering was performed, without distal femoral extension osteotomy or hamstring release. Among limbs with similar surgical procedures (e.g., hamstring lengthening, rectus femoris transfer) except for patella lowering, controls were selected retrospectively by matching on a propensity score for patella lowering. The propensity score was computed based on preoperative knee flexion contracture, knee extension lag, and minimum knee flexion at mid-stance. Clinical and 3D kinematic data were compared between the two groups.

RESULTS

The improvement in minimum knee flexion at mid-stance was significantly greater in the group with patellar lowering (-24°±12°vs. -12°±7°). The Gait Deviation Index improved similarly in the two groups. Knee flexion contracture improved only in the group with patellar lowering. Extension lag did not improve in either group. Peak knee flexion during the swing phase remained unchanged in both groups.

DISCUSSION

Patellar lowering is effective in diminishing minimum knee flexion at mid-stance in patients with patella alta and crouch gait due to cerebral palsy. Patellar lowering has not adverse effects on gait. These findings cannot be assumed to apply to patients with normal patellar height.

LEVEL OF EVIDENCE

IV (retrospective study).

Influence of age on clinical outcomes of three-dimensional transfer of the tibial tuberosity for patellar instability with patella alta

PURPOSE

To evaluate the clinical outcomes of three-dimensional (3D) transfer of the tibial tuberosity for patellar instability with patella alta, with a focus on the influence of age at initial surgery.

METHODS

Three-dimensional surgery was performed on 28 knees with a mean follow-up of 46 months. Patients were separated into three groups based on the age at initial surgery: group A, 10 knees and an average age of 16.3 ± 1.8 (14-19) years; group B, 10 knees and an average age of 22.1 ± 2.5 (20-28) years; and group C, eight knees and an average age of 44.0 ± 2.2 (40-46) years. Patellofemoral geometry improvement focused on patella alta by determining the Insall-Salvati ratio and Caton-Deschamps index, rotational malalignment by measuring the tibial tubercle-trochlear groove (TT-TG) distance, and lateral patellar subluxation by measuring the patellar tilt. Clinical outcomes were evaluated by the Lysholm and Kujala scores, which were compared before and after surgery. Cartilage degeneration was evaluated by the International Cartilage Repair Society grading system at initial arthroscopy.

RESULTS

The patellar height, TT-TG, and patellar tilt significantly improved in all groups postoperatively (p < 0.05). The Lysholm and Kujala scores also significantly improved postoperatively; however, both scores were lower in group C than in the other groups (p < 0.05). Particularly, pain scores were more severe in group C than in the other groups, and the severity of cartilage degeneration correlated with the pain scores (p < 0.05). Cartilage damage differed significantly between the groups at initial arthroscopy; particularly, group C included grades III and IV cartilage degeneration (p < 0.05).

CONCLUSIONS

Age at initial surgery may be the predicting factor for poor clinical outcomes of 3D transfer surgery. The clinical outcome may depend on the age at surgery, which correlated with cartilage damage; thus, surgeons should be given this information when patients are considered undergoing patella surgery.

LEVEL OF EVIDENCE

Therapeutic case series, Level IV.

How is patella height modified after total knee arthroplasty?

INTRODUCTION

Since the first measurement method of patella height in 1929 (Janssen), more than 16 methods have been described. Most of these measures are not suitable to measure patella height after total knee arthroplasty (TKA). One of us (JC) modified the original Caton Deschamps (oCD), index with a new relative index called modified Caton Deschamps (mCD) index, by using new landmarks. The purpose of this study was to determine how patella height is modified after TKA.

MATERIAL AND METHOD

Sixty primary TKAs were consecutively prospectively enrolled. One type of implant was used (cementless postero-stabilized TKA, rotating plateau, cemented patella resurfacing). Patient's characteristics, functional and radiological outcomes were recorded pre-operatively and at one year follow-up. Pre-operative and post-operative outcomes were compared by paired t-test. Post-operative outcomes were compared between groups by one-way analysis of variance.

RESULTS

Average difference between pre and post-operative mCD was 0.19 in this series. In 81.7% of cases, patella was lowered. Patients were classified in three groups according to patella height lowering. Between these three groups, no significant statistical differences (IKS score knee and function, range of motion) could be identified.

DISCUSSION

In TKA, patella assessment in sagittal plane is as important as frontal or horizontal planes. True patella infera (TPI) is mostly due to patella tendon shortening measured by oCD. Pseudo patella infera (PPI) measured by mCD is mostly due to joint line elevation (over femoral cut with an over thickness of the tibial component). In this study a moderate patella lowering (minor than 15%) does not have a significant impact on the functional results (IKS, ROM) nevertheless in 80% patella is lowered. The next step will be to analyze precisely what factors are influencing this lowering and what prevention could be suggested in primary and revision TKA.

Determination of reference values and frequency of occurrence of patella alta in German shepherd dogs: a retrospective study

Background

Patella alta and patella baja are important conditions underlying a predisposition to many joint diseases, including patellar luxation and patellar chondromalacia of the articular cartilage. The frequencies of patella alta and patella baja have not yet been determined. The objectives of this study were to determine the frequency of patella alta and to determine reference values to the position of the vertical patella according to two modified techniques of the Insall–Salvati method in a group of 65 German shepherd dogs (115 stifle joints).

Results

The upper limits of reference values for the normal vertical position of the patella were 1.79 and 2.13, depending on the method of measurement. A high prevalence of patella alta was observed in the group of German shepherd dogs. A correlation was demonstrated between the classification of dogs’ joints in the patella alta group and the multiplied risk of canine hip dysplasia (CHD) through the estimation of odds ratios.

Conclusions

Dogs with patella alta were healthy dogs that did not exhibit orthopaedic problems in the stifle joints. The results revealed that the risk of CHD is twice as high in dogs with higher patellar ligament length to patella length ratio.

Predictors for anterior pelvic tilt following surgical correction of flexed knee gait including patellar tendon shortening in children with cerebral palsy

INTRODUCTION

Patellar tendon shortening procedure within single event multilevel surgeries was shown to improve crouch gait in Cerebral Palsy (CP) patients. However, one of the drawbacks associated to the correction of flexed knee gait may be increased pelvic anterior tilt with compensatory lumbar lordosis.

RESEARCH QUESTION

Which CP patients are at risk for excessive anterior pelvic tilt following correction of flexed knee gait including patellar tendon shortening?

METHODS

32 patients with CP between 8 and 18 years GMFCS I&II were included. They received patellar tendon shortenings within multilevel surgery. Patients with concomitant knee flexor lengthening were excluded. Gait analysis and clinical testing was performed pre- and 24.1 (SD=1.9) months postoperatively. Patients were subdivided into more/less than 5° increase in anterior pelvic tilt. Preoperative measures indicating m. rectus and m. psoas shortness, knee flexor over-length, hip extensor and abdominal muscle weakness and equinus gait were compared between groups. Stepwise multilinear regression of the response value increase in pelvic tilt during stance phase was performed from parameters that were significantly different between groups.

RESULTS

34% of patients showed more than 5° increased pelvic anterior tilt postoperatively. Best predictors for anterior pelvic tilt from preoperative measures were increased m. rectus tone and reduced hip extension during walking that explained together 39% of the variance in increase of anterior pelvic tilt.

DISCUSSION

Every third patient showed considerable increased pelvic tilt following surgery of flexed knee gait. In particular patients with preoperative higher muscle tone in m. rectus and lower hip extension during walking were at risk and both features need to be addressed in the therapy.

Comparative Study on Insall-Salvati Index by Radiological and Clinical Methods in a Tertiary Care Centre of North Bengal, India

INTRODUCTION

Patellar height is an important parameter of patellar stability. Its importance is evident from various attempts to measure it, by different scientists from time to time and many indices have been derived among which Insall-Salvati index (IS index) is the most simple, accurate and easy to measure. In this study a new clinical method has been tried to measure patellar height by applying the same principle of IS index.

AIM

To compare clinical method of measurement of IS index with the one derived radiologically and to establish the higher cut off value of the clinical method.

MATERIALS AND METHODS

In the present study 186 knee joints (93 subjects) were subjected to measurement of patellar height by both clinical and radiological methods. The IS index was measured bilaterally from lateral view of X-ray plates and it was measured clinically in every knee joint. Both the values were compared using students t-test and higher cut off values were set for normal knee joint for the clinical method.

RESULTS

Among 93 study participants majority were females (54.83%), age of the patients varied from 10-68 years with mean age of 28 years and Standard deviation (SD) of 16.4. It was found that, there was no statistically significant difference between the mean values obtained by clinical method of measurement, compared to conventional one (IS Index) for both the genders and age groups on both the sides. A cut off value of 0.98 cm by clinical method gives sensitivity of 80% and specificity of 36% with area under the ROC curve 0.596.

CONCLUSION

The subjects with patellar height of less than cut off value by clinical method can avoid radiological investigation as there was no statistically significant difference of IS index between radiological and clinical methods.