Patellar instability

MRI analysis of the physiological patellofemoral joint morphology of adult knees

OBJECTIVE

The aim of the present study was to determine physiological reference values for the morphology of the patella and to analyse these parameters according to patella position in healthy knee joints.

MATERIAL AND METHODS

Healthy knee joints of 409 patients (mean age, 52.3 years [± 16.8]) were analysed retrospectively on MRI images for Insall-Salvati index (ISI), sagittal patella thickness (PTS) and patella length (PLS) as well as axial patella thickness (PTA) and patella width (PWA). Differences between patellar diameters were analysed depending on ISI, side, age and gender.

RESULTS

Mean PTS was 20.1 mm (± 2.4), PLS 44.0 mm (± 4.4), PTA 21.8 mm (± 2.4) and PWA 44.5 mm (± 4.7). Depending on the vertical patellar position (ISI), all patellar parameters (p < 0.01) showed significant differences between patients with a patella alta, norma and baja. In general, a smaller ISI showed higher measured values for the patellar parameters. There were no significant differences for the laterality. Only PTS showed a significant age difference (p = 0.031). All parameters were significantly larger in male compared to female knees (p < 0.001).

CONCLUSION

Reference parameters for the patella morphology are reported. Concluding from the results, a relationship between vertical patellar position and patellar morphology seems to exist. This finding should be taken into account in diagnostics and therapy of patella disorders.

Patellofemoral Disorders in Soccer Players

Patellofemoral disorders are common in the world of soccer and impact players across all levels and ages of the sport. Patellofemoral disorders encompass a spectrum of conditions, from anterior knee pain to patellar instability, and are often influenced by complex biomechanical factors and anatomic variations that can predispose to these conditions. In recent years, there has been a growing emphasis on injury prevention strategies and data-driven approaches, championed by organizations like the Union of European Football Associations and individual professional clubs. Conservative management remains the initial approach for many players, including physical therapy and supportive devices. However, surgical intervention, particularly in cases of recurrent patellar dislocations, is often necessary. The understanding of patellofemoral biomechanics in soccer continues to evolve and offers opportunities for more effective injury prevention and tailored treatment strategies. Despite the challenges, a comprehensive approach to patellofemoral disorders in soccer is essential to preserve player health, enhance performance, and sustain the sport's vitality.

Patellar Instability: Imaging Findings

Patellofemoral instability results from impaired engagement of the patella in the trochlear groove at the start of flexion and may lead to pain and lateral patellar dislocation. It occurs most frequently in adolescents and young adults during sporting activities. Trochlear dysplasia, patella alta, and excessive lateralization of the tibial tuberosity are the most common risk factors for patellar instability. The main role of imaging is to depict and assess these anatomical factors and highlight features indicating previous lateral dislocation of the patella.

Femoral internal torsion greater than twenty-five degrees and/or external tibial torsion greater than thirty degrees as measured by computed tomography are threshold values for axial alignment correction in patellofemoral instability

OBJECTIVES

Patellofemoral instability (PFI) has multiple predisposing anatomic factors, including ligamentous hyperlaxity, coronal and axial malalignment, patella alta, trochlea dysplasia, excessive lateral patellar tilt, and excessive lateral Q vector. Yet, few studies have analyzed surgical thresholds for performing axial alignment corrective osteotomies in the treatment of PFI and patella maltracking. The objective of this systematic literature review was to determine if there is a threshold for axial plane alignment that triggers surgical correction for the treatment of patellar instability in the published literature.

METHODS

Using a predetermined search strategy, a systematic literature search of 10 major databases and gray literature resources was completed. Only studies reporting on patellar instability and outcomes were included. Radiologic indications, additional procedures, outcomes, and complications were reported. Titles and abstracts were screened, and full-text manuscripts were then selected and extracted. Variables related to radiographic and clinical parameters, patient demographics, surgery performed, surgical correction, complications, and reoperations were recorded preoperatively and postoperatively.

RESULTS

A total of 1132 abstracts and titles were screened by two reviewers, yielding 15 eligible studies. The reported threshold identified in our study for axial plane alignment that triggers surgical correction in most of the published literature when discussing PFI was either tibial torsion greater than 30° and/or femoral anteversion greater than 25°. Following rotational osteotomy of one or both long bones, one study (7%) reported improvements in tubercle-sulcus angle, two studies (13%) reported improvements in femoral-tibial angle, and four studies (27%) reported decreases in tibial torsion. For patient-reported outcomes, seven studies (47%) reported improvement in the Kujala score, five studies (33%) reported postoperative improvement in Lysholm, and four studies (27%) reported improvement in the International Knee Documentation Committee (IKDC) score. Nine studies (60%) reported preoperative femoral anteversion; however, only two studies compared pre- and post-operative values (one study reported a decrease in anteversion and another study reported an increase in anteversion).

CONCLUSION

When treating PFI, the reported threshold for axial plane alignment that triggers surgical correction in most of the published literature was tibial torsion greater than 30° and/or femoral anteversion greater than 25° as measured by CT. However, there is no consensus on the axial alignment measurement technique.

LEVEL OF EVIDENCE

III.

Association of Systemic Hormonal Contraceptives With Reconstruction Procedures for Patellar Instability

Background

Previous research suggests that estrogen plays a role in increased ligamentous laxity observed within the female population. Whereas many studies have sought to evaluate the impact of exogenous estrogen on anterior cruciate ligament injuries, research has not yet explored its impact on the medial patellofemoral ligament. Furthermore, less is known about the role of exogenous progesterone on ligamentous structures.

Purpose

To determine whether women prescribed systemic estrogen (ethinyl estradiol) or progesterone (norgestimate or etonogestrel) hormonal contraceptives had an increased risk of undergoing reconstruction surgery for patellar instability compared with women without a prescription for systemic hormonal contraceptives.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

The TriNetX Research Network database was queried using International Classification of Disease and Common Procedural Terminology codes for women aged 15 to 26 years who underwent reconstruction procedures for patellar instability between 2012 and 2022. Women were grouped according to whether they had a coded prescription for a systemic hormonal contraceptive containing either ethinyl estradiol or etonogestrel; controls were matched by age, sex, race, and ethnicity. The relative risk (RR) of undergoing reconstruction for patellar instability was determined for each contraceptive.

Results

After 1-to-1 propensity score matching, 0.054% (525/980,878) of women prescribed a systemic contraceptive containing ethinyl estradiol underwent reconstruction procedures for patellar instability compared with 0.043% (417/980,878) of controls (RR, 1.3; 95% CI, 1.1-1.4; P = .0004). Likewise, 0.058% (67/116,260) of women prescribed a form of systemic contraceptive containing only etonogestrel underwent reconstruction procedures for patellar instability compared with 0.026% (30/116,260) of controls (RR, 2.2; 95% CI, 1.5-3.4; P = .0002).

Conclusion

Female patients prescribed systemic contraceptives containing estrogen or progesterone had an increased rate of reconstruction procedures for patellar instability.

Trochlea dysplasia, increased TT-TG distance and patella alta are risk factors for developing first-time and recurrent patella dislocation: a systematic review

PURPOSE

The aim of the study was to perform a systematic review and best knowledge synthesis of the present literature concerning biomechanical risk factors for developing first-time and recurrent patella dislocation.

METHODS

The study was performed as a systematic review following PRISMA guidelines. PubMed and EMBASE were systematically searched. Studies investigating participants with risk factors for first-time as well as recurrent patella dislocation were included. The records were screened, and data extracted independently by two researchers supervised by a third independent assessor. The study was registered in PROSPERO.

RESULTS

A total of 6233 records were screened, and 50 studies met the inclusion criteria. The biomechanical risk factors: trochlear dysplasia, increased tibial tuberosity-trochlear groove distance (TT-TG), and patella alta were found to be statistically significantly associated with patella dislocation in several publications and were thus recognized as risk factors for patella dislocation. The soft-tissue stabilizers: longer and thinner MPFL ligament, increased number of type 2C and decreased number of type 1 muscle fibers, and joint laxity were found to be statistically significantly associated with patella dislocation in a few publications, but due to limited evidence, no conclusion was made on this matter.

CONCLUSION

There is strong evidence in the literature that abnormalities of bony stabilizers, trochlear dysplasia, increased TT-TG distance, and patella alta are risk factors for patella dislocation. There is less evidence that soft-tissue stabilizers are risk factors. The study emphasizes the importance of a thorough investigation of bony stabilizers in clinical decision-making.

LEVEL OF EVIDENCE

Level 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

Distal femur varus-producing osteotomy: An updated review of patellofemoral implications and clinical outcomes

Background: Recent evidence seems to suggest the effectiveness of distal femur varus osteotomy in the management of patellofemoral instability in the setting of genu valgum. However, literature on this subject remains scarce and consists mostly of small case series. Hypothesis: This study aims to systematically review the literature on varus-producing distal femur osteotomy and critically analyze its implications on patellofemoral kinematics and stability. Results: The statistical analysis revealed that this surgery is able to restore a mechanical angle (mean hip–knee–ankle (HKA): 0.22°) and to improve the main clinical outcomes (Kujala score, Knee injury and Osteoarthritis Outcome Score, visual analog scale) after a mean follow up of 2.5 years. An objective of the present review was to investigate the mechanical implications of femoral osteotomy on the patellofemoral biomechanics. Indeed, the statistical analysis demonstrated changes after surgery in the main patella-femoral radiological angles (modified Insall–Salvati index, Caton–Deschamps index, Blackburne–Peel index). Interestingly the overcorrection of the mechanical axis (HKA), resulting in varus, had similar outcomes compared to studies that obtained a mechanical axis. Level of Evidence: Level II study.

Patellofemoral Instability Part I: Evaluation and Nonsurgical Treatment

Patellofemoral instability (PFI) is a prevalent cause of knee pain and disability. It affects mostly young females with an incidence reported as high as 1 in 1,000. Risk factors for instability include trochlear dysplasia, patella alta, increased tibial tubercle-to-trochlear groove distance, abnormal patella lateral tilt, and coronal and torsional malalignment. Nonsurgical and surgical options for PFI can treat the underlying causes with varied success rates. The goal of this review series was to synthesize the current best practices into a concise, algorithmic approach. This article is the first in a two-part review on PFI, which focuses on the clinical and radiological evaluation, followed by nonsurgical management. The orthopaedic surgeon should be aware of the latest diagnostic protocol for PFI and its nonsurgical treatment options, their indications, and outcomes.

Modified Langenskiöld procedure for congenital patella dislocations in pediatric patients

Background

Great difficulty and more failures were the descriptions of the treatment of congenital patella dislocation in pediatric patients. This study aims to evaluate the outcomes of patients with congenital patellar dislocations treated with the modified Langenskiöld procedure.

Methods

The medical records of 16 knees in 11 patients with a diagnosis of congenital patella dislocation were collected from September 2016 to March 2019. They were treated with the modified Langenskiöld procedure. The mean follow-up period was 37.8 months. The outcome measures were the Lysholm score, Kujala score, patellar stability, and knee range of motion.

Results

Eleven patients, namely, eight girls and three boys, with 16 knees were enrolled. The mean age at the time of operation was 3.1 years. The post-operative mean Lysholm score was 94.8 (SD 5.1; 87–100), whereas the Kujala score was 95 (SD 5.9; 86–100). There were no recurrent dislocations, and all patients had full extension postoperatively.

Conclusion

The modified Langenskiöld procedure is a promising solution for the treatment of congenital patella dislocations.

Level of evidence

Level IV; Case Series; Treatment Study.

Medial patellofemoral ligament reconstruction: A review

INTRODUCTION

Reconstruction of the medial patellofemoral ligament (MPFL) is an effective surgical method for the treatment of lateral patellar instability. At present, there is not much controversies regarding the femoral attachment, however, the controversies regarding patellar attachment versus attachment, number of graft strands, tension, isometry and so on. The following electronic databases will be searched: PubMed, the Cochrane Library, Embase, Web of Science, Medline. We will consider articles published between database initiation and March 2021. MPFL in the subject heading will be included in the study. Language is limited to English. Research selection, data extraction, and research quality assessment were independently completed by 2 researchers.

CONCLUSIONS

MPFL reconstruction is a reliable technique for the treatment of patellofemoral instability. The Schöttle point is still the mainstream method for locating the femoral attachment, the patellar attachment for single-bundle is located at the junction of the proximal one third and the distal two third of the longitudinal axis of the patella. For double-bundles, one is located in the proximal one third of the medial patellar edge and another is in the center of the patellar edge. Meanwhile, the adjustment of graft tension during operation is very important.

Good clinical outcomes after patellar cartilage repair with no evidence for inferior results in complex cases with the need for additional patellofemoral realignment procedures: a systematic review

PURPOSE

Focal, patellar cartilage defects are a challenging problem as most cases have an underlying multifactorial pathogenesis. This systematic review of current literature analysed clinical results after regenerative cartilage repair of the patella with a special focus on the assessment and treatment of existing patellofemoral malalignment.

METHODS

A systematic review was conducted to identify articles reporting clinical results after cartilage regenerative surgeries of the patella using the PubMed and Scopus database. The extracted data included patient-reported outcome measures (PROMS) and whether cartilage repair was performed alone or in combination with concomitant surgeries of underlying patellofemoral co-pathologies. In cases of isolated cartilage repair, specific exclusion criteria regarding underlying co-pathologies were screened. In cases of concomitant surgeries, the type of surgeries and their specific indications were extracted.

RESULTS

A total of 35 original articles were included out of which 27 (77%) were cohort studies with level IV evidence. The most frequently used technique for cartilage restoration of the patella was autologous chondrocyte implantation (ACI). Results after isolated cartilage repair alone were reported by 15 (43%) studies. Of those studies, 9 (60%) excluded patients with underlying patellofemoral malalignment a priori and 6 (40%) did not analyse underlying co-pathologies at all. Among the studies including combined surgeries, the most frequently reported concomitant procedures were release of the lateral retinaculum, reconstruction of the medial patellofemoral ligament (MPFL), and osteotomy of the tibial tubercle. In summary, these studies showed lower preoperative PROMS but similar final PROMS in comparison with the studies reporting on isolated cartilage repair. The most frequently used PROMS were the IKDC-, Lysholm- and the Modified Cincinnati Score.

CONCLUSION

This comprehensive literature review demonstrated good clinical outcomes after patellar cartilage repair with no evidence of minor results even in complex cases with the need for additional patellofemoral realignment procedures. However, a meaningful statistical comparison between isolated patellar cartilage repair and combined co-procedures is not possible due to very heterogeneous patient cohorts and a lack of analysis of specific subgroups in recent literature.

LEVEL OF EVIDENCE

Level IV.

Relationship between Anatomical Risk Factors, Articular Cartilage Lesions, and Patient Outcomes Following Medial Patellofemoral Ligament Reconstruction

OBJECTIVE

The purpose of this study was (1) to determine which risk factors for patellar instability were associated with the presence of patellofemoral cartilage lesions and (2) to determine how cartilage lesion presence, size, and grade affect postoperative disease-specific quality of life.

DESIGN

Preoperative, intraoperative, and postoperative demographic, anthropometric (body mass index, Beighton score, hip rotation), radiographic (crossover sign, trochlear bump), cartilage lesion morphology (presence, size, location, grade), and outcomes data (Banff Patella Instability Instrument 2.0 [BPII 2.0]) were prospectively collected from patients undergoing isolated medial patellofemoral ligament reconstruction. For all knees (n = 264), single and multivariable logistic regression was used to determine if any patellar instability risk factors affected the odds of having a cartilage lesion. In patients with unilateral symptoms (n = 121), single variable linear regression was used to determine if the presence, size, or ICRS (International Cartilage Regeneration & Joint Preservation Society) grade of cartilage lesions could predict the 12 or 24+ month postoperative BPII 2.0 score.

RESULTS

A total of 84.5% of knees had patellofemoral cartilage lesions (88.3% involved the distal-medial patella). Trochlear dysplasia (high grade: odds ratio = 15.7, P < 0.001; low grade: odds ratio = 2.9, P = 0.015) was associated with the presence of a cartilage lesion. The presence, size, and grade of cartilage lesions were not associated with 12 or 24+ month postoperative BPII 2.0 scores.

CONCLUSIONS

Trochlear dysplasia was a risk factor for the development of patellofemoral cartilage lesions in this patient population. Cartilage lesions most commonly involve the distal-medial patella. There was no significant relationship between patellofemoral cartilage lesion presence, size, or grade and postoperative BPII 2.0 scores in short-term follow-up.

Hip and Knee Weakness and Ankle Dorsiflexion Restriction in Individuals Following Lateral Patellar Dislocation: A Case-Control Study

OBJECTIVE

To explore the relationship between ankle dorsiflexion range of motion (ROM) and hip and knee muscle strength between patients with a history of patellar dislocation (PD) to healthy controls.

DESIGN

Case-control study.

SETTING

Orthopedical specialty outpatient clinic at a tertiary hospital.

PARTICIPANTS

Eighty-eight individuals were recruited; 44 individuals aged 16 years or older, of both sexes, with a history of at least one episode of atraumatic unilateral or bilateral PD requiring emergency care (14 men; 30 women; mean age 20 years) and 44 healthy (control) individuals (11 men; 33 women; mean age 21 years) matched for age, weight, and height to PD cases.

INTERVENTION

Assessment of hip and knee strength and ankle dorsiflexion ROM.

OUTCOME MEASURES

Ankle dorsiflexion ROM was assessed through the lunge test with a goniometer. Hip and knee muscle strength was evaluated through isometric hand-held dynamometry. Differences between healthy and control individuals were assessed using Student t Tests and Mann-Whitney U Test.

RESULTS

Patellar dislocation individuals presented with a reduced ankle dorsiflexion ROM [mean difference (MD): 9 degrees; effect size (ES): 1.39; P < 0.001] and generalized hip and knee weakness (MD range: 4.74 kgf to 31.4 kgf; ES range: 0.52-2.35; P < 0.05) compared with healthy subjects.

CONCLUSION

Individuals with a history of PD have reduced ankle dorsiflexion ROM and hip and knee muscle strength compared with healthy controls.

Analysis of cartilage injury patterns and risk factors for knee joint damage in patients with primary lateral patella dislocations

BACKGROUND

Lateral patellar dislocation (LPD) frequently causes damage to the knee. Injury patterns and risk factors contributing to such injuries have not yet been examined in detail.

METHODS

We retrospectively analyzed 50 consecutive patients with primary LPD. Two reviewers evaluated the MRI images regarding risk factors for LPD (Dejours classification; Caton-Deschamps Index, CDI; distance from the tibial tuberosity to trochlear groove, TT-TG; trochlear depth, TD) as well as joint damages according to the Whole-Organ Magnetic Resonance Imaging Score (WORMS).

RESULTS

33 male and 17 female patients with a mean age of 23.2 (±9.6) years were included in this study. 52% were classified Dejours ≥ B, 34% had a CDI ≥ 1.3, 22% a TT-TG ≥ 20mm and 52% a TD < 3mm. 49 out of 50 patients (98%) showed abnormalities according to WORMS. The most frequently observed abnormalities were synovitis/effusion (49/50, 98%), bone marrow oedema (44/50, 88%) and cartilage damage (42/50, 84%). Most frequently affected subregions were medial (41/50, 82%) and lateral (31/50, 62%) patella as well as the anterior (43/50, 86%), central (42/50, 84%) and posterior (11/50, 22%) portion of the lateral femoral condyle. There was no significant correlation between any of the examined risk factors and joint damages according to WORMS. Male patients had higher scores regarding total cartilage damage (5.11 vs. 2.56, p = 0.029), total score for the lateral femorotibial joint (3.15 vs. 1.65, p = 0.026) and overall total WORMS score (12.15 vs. 8.29, p = 0.038).

CONCLUSION

Risk factors for LPD do not influence the risk of damages to the knee joint after primary LPD. Although LPD is generally known to affect more female than male patients, male patients suffered more severe injuries after primary LPD, particularly of the lateral femorotibial joint. Overall, our results underline the importance of MRI imaging after primary LPD.

[Management of objective patellar instabilities at the University Hospital Center Sylvanus Olympio of Lome, Togo]

Introduction

patellar instability is a rare multifactorial condition whose treatment is complex. The purpose of this study was to describe cases of patellar instabilities and then to assess treatment outcomes in low-income countries.

Methods

the study was conducted from March 2013 to February 2018. Eight patients aged >15 years and who had undergone surgery for objective patellar instability were enrolled. Before and after surgery knee function was assessed using IKDC score.

Results

the average age at surgery was 28.5 years and female sex was predominant (6 cases). Trochlear dysplasia was the main etiological factor (7 patients). In four cases dysplasia was related to patellar height (mean Caton index: 1.4). In five cases, section of lateral patellar retinaculum associated with TTA transposition and Insall's plasty was performed. Functional outcome was satisfactory, with a mean IKDC score of 91.3%.

Conclusion

patellar instabilities are rare. Management is delayed in our developing countries, but outcomes are good when protocols are adapted.

Assessment and Trends of the Methodological Quality of the Top 50 Most Cited Articles on Patellar Instability

Background

Studies with a low level of evidence (LOE) have dominated the top cited research in many areas of orthopaedics. The wide range of treatment options for patellar instability necessitates an investigation to determine the types of studies that drive clinical practice.

Purpose

To determine (1) the top 50 most cited articles on patellar instability and (2) the correlation between the number of citations and LOE or methodological quality.

Study Design

Cross-sectional study.

Methods

The Scopus and Web of Science databases were assessed to determine the top 50 most cited articles on patellar instability between 1985 and 2019. Bibliographic information, number of citations, and LOE were collected. Methodological quality was calculated using the Modified Coleman Methodology Score (MCMS) and the Methodological Index for Non-Randomized Studies (MINORS). Mean citations and mean citation density (citations per year) were correlated with LOE, MCMS, and MINORS scores.

Results

Most studies were cadaveric (n = 10; 20.0%), published in the American Journal of Sports Medicine (n = 13; 26.0%), published between 2000 and 2009 (n = 41; 82.0%), and conducted in the United States (n = 17; 34.0%). The mean number of citations and the citation density were 158.61 ± 59.53 (range, 95.5-400.5) and 12.74 ± 5.12, respectively. The mean MCMS and MINORS scores were 59.62 ± 12.58 and 16.24 ± 3.72, respectively. No correlation was seen between mean number of citations or citation density versus LOE. A significant difference was found in the mean LOE of articles published between 1990 and 1999 (5.0 ± 0) versus those published between 2000 and 2009 (3.12 ± 1.38; P = .03) and between 2010 and 2019 (3.00 ± 1.10; P = .01).

Conclusion

There was a shift in research from anatomy toward outcomes in patellar instability; however, these articles demonstrated low LOE and methodological quality. Higher quality studies are necessary to establish informed standards of management of patellar instability.

Update on Patellar Instability

Patellar instability is a multifactorial clinical condition that affects a significant number of patients and occurs due to morphological variations of the joint and patellofemoral alignment. The present literature review study aimed to identify and summarize current concepts on patellar instability, in relation to associated risk factors, diagnostic criteria, and the benefits and risks of conservative and surgical treatments. For this purpose, a search was conducted in the following electronic databases: MEDLINE (via Pubmed), LILACS and Cochrane Library. It is concluded that the accurate diagnosis depends on the detailed clinical evaluation, including the history and possible individual risk factors, as well as imaging exams. The initial treatment of patellar instability is still controversial, and requires the combination of conservative and surgical interventions, taking into consideration both soft tissues and bone structures, the latter being the most common reason for choosing surgical treatment, especially lateral patellar instability.

A proposed safety angle for dual bundle MPFL reconstruction: an observational magnetic resonance imaging study

INTRODUCTION

The anatomical dual bundle medial patellofemoral ligament (MPFL) reconstruction technique is one of the surgical techniques used to treat lateral patellar instability. This commonly involves the creation of two patella bone tunnels through which the limbs of the grafts are inserted. The surgical risks include patellar fracture and penetration of patellofemoral articular surface. Thus, an easily reproducible intra-operative guiding parameter is useful to reduce such complications.

PURPOSE

The aim of this study is to demarcate a safe working zone in the axial plane for the patella tunnels.

METHODS

In this pilot study, we projected patella bone tunnels on the MRI knee images of 201 male patients with intact MPFLs. Two tunnel projections, superior and inferior, are made from the medial to the lateral sides of the patella. The projection of each superior and inferior tunnel is subdivided into three different angles in the axial plane. The tunnel length, thickness of the bone anterior to each tunnel and safety angle are measured. The safety angle refers to the angle between the longitudinal axis of each tunnel and the horizontal plane of the patella.

RESULTS

Our current study population consisted of 201 male patients (104 Wiberg type 1, 97 Wiberg type 2, no type 3 or 4). For the superior tunnels, the tunnel lengths are 14.8 mm, 24.3 mm and 27.2 mm. The respective safety angles are 24.9 degrees, 24.5 degrees and 8.8 degrees. The thickness of the bone anterior to the tunnels are 5.9 mm, 2.5 mm and 6.2 mm. For the inferior tunnels, the tunnel lengths are 18.4 mm, 21.9 mm and 34.9 mm. The respective safety angles are 23.5 degrees, 22.5 degrees and 8.5 degrees. The thickness of the bone anterior to the respective tunnels are 5.9 mm, 3.1 mm and 6.0 mm.

CONCLUSION

The proposed safety angle of 8.8 degree for the superior tunnel, and 8.5 degrees for the inferior tunnel is a potentially useful intra-operative guide for the surgeon and can potentially reduce the risks of fracture and articular cartilage injury in patellae with Wiberg 1 and 2 morphologies.

LEVEL OF EVIDENCE

Level II, retrospective study.

Gait deviations and muscle strength deficits in subjects with patellar instability

BACKGROUND

Abnormal tracking of the patella is a hallmark sign of patellar instability (PI). Gait deviations and strength deficits may exacerbate abnormal tracking. The identification of modifiable gait deviations and strength deficits can aid in developing more effective management strategies for individuals with PI. The purpose of this study was to identify modifiable gait and strength deficits in subjects with PI.

METHODS

32 subjects (16 PI, 16 controls, 3 males/13 females in each group, 21.1 years old, 23.5 BMI), performed an instrumented gait analysis while walking at 1.5 m per second. Subjects' peak hip adduction angles, external rotation angles, hip abduction moments, knee flexion angles, knee adduction angles, and knee extensor moments were measured during walking. Hip abduction, hip external rotation, and knee extension strength were assessed with a handheld dynamometer.

RESULTS

Individuals with PI displayed significantly lower peak knee adduction angles (1.8 ± 2.8° PI, 5.5 ± 4.5° control, p < .01) and peak hip abduction moments (0.2 ± 0.1 Nm/kg*m PI, 0.4 ± 0.1 Nm/kg*m control, p < .01). Subjects with PI were weaker in knee extension strength (14.5 ± 4.1 kg/m PI, 23.8 ± 7.2 kg/m control, p < .01), hip abduction strength (12.1 ± 2.0 kg/m PI, 17.8 ± 4.0 kg/m control, p < .01), and hip external rotation strength (5.5 ± 1.9 kg/m PI, 7.1 ± 1.3 kg/m control, p = .01).

CONCLUSION

Subjects with patellar instability have smaller joint moments and a more valgus knee position while walking. Coupled with deficits in muscle strength, this likely contributes to subjective reports of chronic patellar instability.

LEVEL OF EVIDENCE

III.

The relationship between patellar lateralization diagnostic imaging markers and non-contact internal knee derangements

BACKGROUND

To investigate differences in the tibial tubercle-trochlear groove (TT-TG) and patellar tendon-posterior cruciate ligament (PT-PCL) distances in symptomatic patients with non-contact internal knee derangements (IKD) and symptomatic patients with internally intact knees (control).

METHODS

A retrospective review of MRI studies was completed by comparing 78 patients with meniscal and ligamentous derangements of the knee to 63 internally intact knees (age range, 13 to 50 years). MRI findings were reviewed independently by two board-certified radiologists to assess for agreement. TT-TG and PT-PCL distances were measured on proton density-weighted axial images by two independent observers blinded to the MRI and arthroscopic findings. Independent t tests were used to determine differences in TT-TG distance between the internal derangement and control groups. Chi-square tests were used to compare categorical variables for distributional equality between study groups.

RESULTS

The mean TT-TG distance averaged across the two raters in the IKD group was 11.5 mm (95% confidence interval [CI], 10.6-12.4), compared to 8.3 mm (95% CI, 7.6-9.0) in the control group (p < 0.001). The mean PT-PCL distance similarly averaged across both raters was 20.6 mm (95% CI, 19.7-21.5) for the IKD group compared to 18.2 mm (95% CI, 17.2-19.2) for the control group (p < 0.001). Among the IKD group, there were 51 meniscal tears, 12 cruciate ligament tears, and 15 tears with a combination of meniscal and cruciate findings. IKD was significantly correlated with greater TT-TG distance (p < 0.001) and greater PT-PCL distance (p < 0.003) when compared with control.

CONCLUSIONS

Increased TT-TG distances and PT-PCL distances are associated with both cartilaginous and ligamentous internal knee injuries in the present study, with TT-TG distances greater than the 12 mm representing a new threshold for concern.

Familial patellar dislocation associated with t(15;20) (q24;q13.1)

Patellar instability is a common debilitating injury affecting young active individuals. It accounts for approximately 3% of all knee injuries. We report a family, of which five members across three generations, who suffered from autosomal dominant familial recurrent patellar dislocation as well as short stature. All of them have recurrent patellar dislocations before the age of 15. The affected patients in all three generations have been genetically screened. Genotypical evaluation revealed a balanced translocation of chromosomes 15 and 20.

[Arthroscopic medial patellofemoral ligament reconstruction combined with tibial tuberosity transfer for recurrent patellar dislocation]

OBJECTIVE

To investigate the effectiveness of arthroscopic medial patellofemoral ligament (MPFL) reconstruction combined with tibial tuberosity transfer for recurrent patellar dislocation.

METHODS

Between February 2012 and December 2013, 24 patients (24 knees) with recurrent patellar dislocation were treated with arthroscopic MPFL reconstruction combined with tibial tuberosity transfer. There were 7 males and 17 females, with a mean age of 23.2 years (range, 18-37 years). One patient had recurrence dislocation after operation in the other hospital, and the others were the first operation. The disease duration ranged from 6 months to 20 years (mean, 5.6 years). The patellar apprehension tests were positive. The preoperative Lysholm score was 49.79±11.67 and the Kujala score was 49.63±6.28. X-ray films showed that 13 patients had dysplasia of the patella and femoral trochlea; 8 patients had high tibia (Caton-Deschamps index>1.2); the congruence angle was (23.96±5.54)°. CT examination showed that the tibial tuberosity-trochlear groove distance (TT-TG) value was (23.71±2.35) mm.

RESULTS

All incisions healed by first intention. Twenty-two patients were followed up 59-81 months, with an average of 66.8 months. No dislocation occurred during the follow-up period. The patellar apprehension tests were negative. At 1 week after operation, the results of X-ray films and CT showed that the congruence angle angle was (-1.96±4.65)°, and the TT-TG value was (13.75±1.89) mm, which were significantly lower than those before operation ( P<0.05). At 6 months, 1 year, and last follow-up, Lysholm scores were 81.13±17.76, 91.35±3.60, and 92.23±2.71, respectively; and Kujala scores were 84.04±3.98, 91.48±3.64, and 91.45±3.29, respectively. The Lysholm and Kujala scores were significantly increased after operation when compared with the preoperative scores ( P<0.05). At last follow-up, the effectiveness was excellent in 11 cases, good in 8 cases, and fair in 3 cases, with an excellent and good rate of 86%.

CONCLUSION

Arthroscopic MPFL reconstruction combined with tibial tuberosity transfer for recurrent patellar dislocation can effectively improve the patellofemoral joint matching relationship and has a satisfactory short- and medium-term effectiveness.

Is femoral trochlear dysplasia related to global joint hypermobility?

BACKGROUND

Hypermobility is a known risk factor for patellar instability. In this study, we hypothesized that a significant relationship exists between global joint hypermobility and trochlear dysplasia.

METHODS

Follow-up patients from the shoulder department of our institution with global joint hypermobility (Group 1, n = 42) and healthy volunteers (Group 2, n = 42) without known knee complaints were included in our study. All participants underwent knee magnetic resonance imaging (MRI) for the evaluation of possible trochlear dysplasia, and the measurements included lateral trochlear inclination; trochlear facet asymmetry; the depth of the trochlear groove; condylar asymmetry; lateralization of the patella; sulcus angle; and the lateral, medial and central trochlear height. The Dejour classification was also assessed.

RESULTS

The age and gender distributions of the groups were similar (p > 0.05). The radiological evaluations revealed that the lateral trochlear inclination (p < 0.001), trochlear facet asymmetry (p < 0.001), depth of the trochlear groove (p < 0.001), lateralization of the patella (p < 0.001), sulcus angle (p < 0.001), and central trochlear height (p < 0.001) were significantly different between the two groups. The condylar asymmetry and lateral and femoral condylar height parameters were similar between the groups (p = 0.297, p = 0.890 and p = 0.521, respectively). According to the Dejour classification, 39 patients had dysplasia in Group 1, whereas dysplasia was detected in only 4 of the participants in Group 2.

CONCLUSIONS

Our study revealed that most of the trochlear dysplasia criteria were met in patients with global joint hypermobility. In addition to a clinical patellofemoral examination, the precise radiological evaluation of the joint is beneficial in patellofemoral instability patients with concomitant hypermobility. Patient cohort of this study was consist of patients underwent shoulder surgery.

Double-Bundle Medial Patellofemoral Ligament Reconstruction With Allograft

Medial patellofemoral ligament (MPFL) reconstruction is the treatment of choice for recurrent patellofemoral instability. Although attention to MPFL reconstruction in the orthopaedic literature has increased dramatically in recent years, there is no clear consensus on surgical technique, graft option, or method of fixation. Nevertheless, most studies have shown improved pain scores and low rates of recurrent dislocation in patients after surgery. Despite the early success of MPFL reconstruction, complications may occur more frequently than previously appreciated and include patellar fracture, postoperative instability, and loss of flexion. This article describes our technique for double-bundle MPFL reconstruction with an allograft while highlighting certain aspects of the procedure that are critical for achieving favorable outcomes. The main advantages of the technique include strong patellar fixation with suture anchors and anatomic graft placement at the origin and insertion of the native MPFL. In our experience, this method of reconstruction has been safe, reproducible, and effective in the treatment of patients with patellar instability.

[Combined operation involving tibial tubercle distalization for recurrent patellar dislocation with patella alta]

Objective

To explore the clinical effects of combined operation involving tibial tubercle distalization for the recurrent patellar dislocation with patella alta.

Methods

Between April 2010 and May 2016, 14 cases of recurrent patellar dislocation with patella alta were treated with combined operation involving tibial tubercle distalization. There were 5 males and 9 females with an average age of 18.5 years (range, 13-26 years). The left knee was involved in 9 cases and the right knee in 5 cases. The patella had dislocated 3.3 times on average (range, 2-5 times). The interval between the first dislocation and admission was 19.7 months on average (range, 4-60 months), and the main symptoms were knee pain and limited knee movement. Preoperative X-ray films, CT, and MRI examinations of knee joint showed that the epiphyseal plate closed in all patients. Of all patients, 3 patients had avulsion fracture of the inner edge of patella, and 2 patients had free body in articular cavity. The tibial tuberosity-trochlear groove (TT-TG) distance, patellar-trochlear-groove distance, Caton-Deschamps index, knee range of motion (ROM), Lysholm score, International Knee Documentation Committee (IKDC) score, Kujala score, and Tegner score were compared pre- and post-operation.

Results

All patients had primary wound healing. All patients were followed up 24-72 months with an average of 34.6 months. X-ray film and CT examination showed that the patellar dislocation was corrected and the osteotomy of the tibial tubercle healed with an average healing time of 3.8 months (range, 3-5 month). At 1 day and 1 year after operation, the TT-TG distance, patellar-trochlear-groove distance, and Caton-Deschamps index showed significant differences when compared with preoperative values ( P<0.05), but there was no significant difference between 1 day and 1 year after operation ( P>0.05). At the 1 year and 2 years after operation, the knee ROM, Lysholm score, IKDC score, Kujala score, and Tegner score showed significant differences when compared with preoperative values ( P<0.05), and there was no significant difference between the 1 year and 2 years after operation ( P>0.05).

Conclusion

Combined operation involving tibial tubercle distalization is a safe and reliable method, which has satisfactory short-term effectiveness for the recurrent patellar dislocation with patella alta.

Nonoperative Treatment of Patellar Instability

The treatment of patellar instability is challenging and typically begins with nonoperative methods. Clinical decisions are made on an individual basis and may vary according to a number of factors. First-time patellar dislocations most commonly occur during sports participation. Initial evaluation, including patient history, physical examination, and appropriate imaging, determines care. Although nonoperative treatment consists primarily of regressive immobilization and physical therapy, there is little evidence to support particular protocols for either. Factors that may contraindicate nonoperative treatment include osteochondral lesions and recurrent instability. In these cases, surgery is considered. Reported recurrence rates after nonoperative treatment of acute patellar dislocation are 15% to 44%. Well-designed studies are needed to determine not only the outcomes of nonoperative versus surgical treatment of patellar instability but also the risk factors that may predict poor outcomes in either group.

High incidence of acute and recurrent patellar dislocations: a retrospective nationwide epidemiological study involving 24.154 primary dislocations

PURPOSE

The purpose of this study was to investigate the Danish population as a whole from 1994 to 2013 to find the incidence of acute and recurrent patellar dislocation.

METHODS

The study was performed as a descriptive epidemiological study. The Danish National Patient Registry was retrospectively searched from 1994 to 2013 to find the number of acute and recurrent patellar dislocation. National population data were collected from Statistics Denmark.

RESULTS

The period 1994-2013 saw a total registration of 24,154 primary patellar dislocations. A mean incidence of 42 (95% CI 37-47) per 100,000 person-years at risk was found, and young females aged 10-17 had the highest incidence of 108 (95% CI 101-116). In a 10-year follow-up, patients were at an overall risk of 22.7% (95% CI 22.2-23.2) of suffering a recurrent dislocation, with young girls aged 10-17 experiencing the highest risk, namely 36.8% (95% CI 35.5-38.0). The overall risk of suffering a patellar dislocation in the contralateral knee was 5.8% (95% CI 5.5-6.1) and 11.1% (95% CI 10.4-11.7) for patients aged 10-17.

CONCLUSION

A high incidence rate of primary patellar dislocation was found both as a mean in the population (42/100,000), and particularly in patients aged 10-17 (108/100,000). The risk of recurrent dislocation in the affected knee (22.7%) and the contralateral knee (5.8%) was high, which could indicate the influence of an underlying pathomorphology. This is relevant knowledge to the clinician, as he/she should be aware of the high risk of recurrent dislocation when deciding on treatment, especially in young patients.

LEVEL OF EVIDENCE

IV.

Anatomic patellar instability risk factors in primary lateral patellar dislocations do not predict injury patterns: an MRI-based study

PURPOSE

The primary goal was to describe the injury patterns in a population of primary (first time) lateral patellar dislocators (LPD) to lend clarity to commonly held notions about injury patterns in this population.

METHODS

A prospective study identifying patients presenting with LPD between 2008 and 2012. Inclusion criteria were a history and physical exam consistent with primary LPD, and an MRI consistent with the diagnosis without other significant ligamentous injury. On MRI, location of cartilage, medial patellofemoral ligament (MPFL) injury, and bone bruising were noted. Severity was categorized as partial or complete for MPFL and cartilage lesions. Anatomic patellar instability risk factors (patella alta, trochlear dysplasia, increased TT-TG, and lateral patella tilt) were recorded and compared to the injury patterns.

RESULTS

This study involved 157 patients; 107 patients were skeletally mature. Of the 157 patients, 26 had surgery for this injury due to clinician-perceived need for cartilage debridement. MPFL injury severity was complete rupture (N = 69, 44%), partial (N = 67, 43%), and none (N = 19, 13%). MPFL injury location was isolated femoral (N = 16, 10%), isolated patella (N = 26, 17%), isolated mid-substance (0%), multiple locations (N = 95, 61%), and none (N = 20, 13%). Chondral injury location was patella (N = 67, 43%), lateral femoral condyle (N = 11, 7%), multiple locations (N = 53, 34%), and none (N = 26, 17%). A majority (61%) of patellar chondral lesions were at its inferomedial aspect; all medial patellar retinacular partial injuries involved the inferomedial aspect of the patella, consistent with the insertion of the medial patellotibial ligament (MPTL). Skeletally immature patients had a greater risk of isolated patellar MPFL and chondral injury. No clear relationship was found between/across the location and/or severity of bone bruising, MPFL, or chondral injury.

CLINICAL RELEVANCE

Underlying anatomic patellar instability risk factors defined by MRI, do not predict injury patterns. MPFL and chondral injury, as well as bone bruising, are common following LPD. The medial patellotibial ligament is torn in patellar-based medial retinacular injuries, based on MRI injury location. Skeletal immaturity plays a role in the location of the injury pattern with isolated patellar-based MPFL/chondral injury being more common in the skeletally immature patient. Sex does not appear to be a factor in injury patterns after primary LPD. Knowledge of these injury trends will help focus the clinician in injury evaluation when managing primary patellar dislocations.

LEVEL OF EVIDENCE

Case series, Level IV.

Assessment of demographic and pathoanatomic risk factors in recurrent patellofemoral instability

PURPOSE

The WARPS/STAID classification employs clinical assessment of presenting features and anatomic characteristics to identify two distinct subsets of patients within the patellofemoral instability population. The purpose of this study was to further define the specific demographics and the prevalence of risky pathoanatomies in patients classified as either WARPS or STAID presenting with recurrent patellofemoral instability. A secondary purpose was to further validate the WARPS/STAID classification with the Banff Patella Instability Instrument (BPII), the Marx activity scale and the Patellar Instability Severity Score (ISS).

METHODS

A convenience sample of 50 patients with recurrent patellofemoral instability, including 25 WARPS and 25 STAID subtype patients, were assessed. Clinical data were collected including assessment of demographic risk factors (sex, BMI, bilaterality of symptoms, affected limb side and age at first dislocation) and pathoanatomic risk factors (TT-TG distance, patella height, patellar tilt, grade of trochlear dysplasia, Beighton score and rotational abnormalities of the tibia or femur). Patients completed the BPII and the Marx activity scale. The ISS was calculated from the clinical assessment data. Patients were stratified into the WARPS or STAID subtypes for comparative analysis. An independent t test was used to compare demographics, the pathoanatomic risk factors and subjective measures between the groups. Convergent validity was tested with a Pearson r correlation coefficient between the WARPS/STAID and ISS scores.

RESULTS

Demographic risk factors statistically associated with a WARPS subtype included female sex, age at first dislocation and bilaterality. Pathoanatomic risk factors statistically associated with a WARPS subtype included trochlear dysplasia, TT-TG distance, generalized ligamentous laxity, patellar tilt and rotational abnormalities. The independent t test revealed a significant difference between the ISS scores: WARPS subtype (M = 4.4, SD = 1.1) and STAID subtype (M = 2.5, SD = 1.5); t(48) = 5.2, p < 0.001. The relationship between the WARPS/STAID and the ISS scores, measured using a Pearson r correlation coefficient, demonstrated a strong relationship: r = -0.61, n = 50, p < 0.001.

CONCLUSIONS

This study has demonstrated statistically significant evidence that certain demographics and pathoanatomies are more prevalent in each of the WARPS and STAID patellofemoral instability subtypes. There was no difference in quality-of-life or activity level between the subtypes. The WARPS/STAID score demonstrated convergent validity to the ISS and divergent validity to the BPII score and the Marx activity scale. This study has further validated both the WARPS/STAID classification and the ISS of patients that present with recurrent patellofemoral instability.

LEVEL OF EVIDENCE

III.

Treatment of Primary Acute Patellar Dislocation: Systematic Review and Quantitative Synthesis of the Literature

PURPOSE

The aim of this study was to evaluate clinical outcomes, rate of redislocation, and complications after conservative or surgical procedures used to treat primary acute patellar dislocation.

METHODS

A comprehensive search of PubMed, Medline, CINAHL, Cochrane, Embase, and Google Scholar databases using various combinations of the keywords "patella," "dislocation," "treatment," "acute," "primary" was performed. The following data were extracted: demographics, chondral defects and soft tissue lesions, outcome measurements, type of management, recurrence of instability, and complications.

RESULTS

A total of 2134 knees in 2086 patients were included, with an average age at dislocation of 20.3 years. The average Kujula score was 75.6 for patients treated conservatively and 88.7 for patients undergoing surgical treatment in the short-medium follow-up (less than 5 years); the average Kujula score was 87.5 for patients treated conservatively and 86.6 for patients undergoing surgical treatment in the long-term follow-up (more than 5 years). The rate of recurrence was significantly lower in the surgical group (25%) than in the conservative group (36.4%). The overall complication rate was 6.5% (29 of 441 knees) in the surgical management group. No complications were reported for patients treated conservatively.

CONCLUSIONS

Surgical treatment of primary acute patellar dislocation leads to significantly lower rate of redislocation and provides better short-medium clinical outcomes, whereas in the long-term follow-up, results of patients treated conservatively were as good as those of surgical patients. Further randomized controlled trials, describing anatomical abnormalities and soft-tissue integrity that may influence the choice of treatment, are needed.

LEVEL OF EVIDENCE

Systematic review, level IV.

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.

Increased Magnetic Resonance Imaging Signal of the Lateral Patellar Facet Cartilage: A Functional Marker for Patellar Instability?

BACKGROUND

In the knee joint, predisposition for patellar instability can be assessed by an abnormal Insall-Salvati index, tibial tuberosity-trochlear groove (TTTG) distance, and abnormal shape of patella and trochlea. Given the complex anatomic features of the knee joint with varying positions of the patella during motion, the presence of a single or even a combination of these factors does not inevitably result in patellar instability. After trocheoplasty in patients with trochlear dysplasia, assessment of trochlear cartilage and subchondral bone is limited due to postoperative artifacts. Identification of presence of edema in the patellar cartilage may be helpful to identify patellar instability before and after surgery in these patients.

PURPOSE

To determine whether increased signal intensity of the lateral patellar facet cartilage or measurements of abnormal patellofemoral articulation are associated with patellar instability before and after trochleoplasty.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Twenty-two patients with clinical diagnosis of patellar instability who underwent trochleoplasty, with magnetic resonance imaging (MRI) of the knee before and after surgery, were identified. The following observations and measurements were obtained in preoperative imaging: Insall-Salvati ratio, tibial tuberosity-trochlear groove (TTTG) distance, patellar shape (Wiberg), trochlear shape (Hepp), and edema in the lateral patellar facet cartilage. At 3 to 12 months after surgery, the presence or absence of edema in the cartilage of the lateral facet of the patella, the trochlear shape, and TTTG distance were reassessed. Wilcoxon matched-pairs signed rank test and Student t test were used. Interreader agreement was calculated as the Cohen κ or paired Student t test.

RESULTS

Increased cartilage signal was present in 20 patients before trochleoplasty and in 4 after trochleoplasty. Insall-Salvati ratio was greater than 1.20 in 20 patients. Patellar shape was greater than type 2 in 18 patients. Trochlear shape was greater than type 2 in 21 patients before and 7 after trochleoplasty. Mean TTTG distance was 14 mm before and 10 mm after surgery. When results before and after surgery were compared, a significant difference was found for cartilage signal, TTTG distance, and trochlear shape. Agreement for observations was moderate to substantial, and no significant differences were found for interreader agreement ( P > .05).

CONCLUSION

Patellar cartilage at the lateral facet of the patella can be assessed after trochleoplasty despite postoperative artifacts in the trochlea. A decrease of patellar edema seems to be associated with improved femoropatellar articulation. Moreover, patellar edema may be used as a functional criterion of patellofemoral instability. This would provide additional information compared to morphologic criteria which just describe predisposing factors for femoropatellar instability.

Partial quadriceps tendon transfer for revision medial patellofemoral ligament reconstruction: A new surgical technique

Medial patellofemoral ligament (MPFL) reconstruction for patellofemoral instability is a common procedure. Although MPFL reconstruction is a successful procedure in terms of return to normal life or sports, revision cases are challenging due to previous holes into the patella or implants placed in the anatomical femoral insertion site. In this technical note, the use of a partial quadriceps tendon transfer to the adductor magnus tendon is presented as a good solution for revision cases to avoid the use of implants, bone drilling, use of allografts, or two-stage surgical procedures. In addition, this procedure could be also used as a primary procedure in skeletally immature patients.

Plateau-patella angle: An option for the evaluation of patellar height in patients with patellar instability

BACKGROUND

Patellar instability is a debilitating disease. An important factor related to recurrent dislocation is patellar height. A new method of patellar height measurement, the plateau-patella angle (PPA), was proposed in 2011. However, to date, there is no study evaluating the use of this method in patients with patellar instability. The aim of this study was to evaluate the PPA in patients with recurrent patellar dislocation.

METHODS

This was a retrospective evaluation of the radiographs of 78 knees with patellar instability. Patellar height was measured using the Insall-Salvati (I/S), Caton-Deschamps (C/D) and Blackburne-Peel (B/P) indices and the PPA. The qualitative and quantitative correlations between the various methods and between observers were calculated.

RESULTS

The PPA had a Pearson correlation of 0.76 (P<0.001) with the I/S index, 0.78 (P<0.001) with the C/D index and 0.90 (P<0.001) with the B/P index. In the qualitative correlation using the Spearman coefficient, the PPA had a correlation of 0.52 (P<0.001) with the I/S index, 0.72 (P<0.001) with the C/D index and 0.70 (P<0.001) with the B/P index. The correlations between the conventional methods were as follows: 0.57 (P<0.001) between the I/S and C/D indices; 0.61 (P<0.001) between the I/S and B/P indices; and 0.73 (P<0.001) between the C/D and B/P indices.

CONCLUSION

The determination of the PPA is a reproducible method that is consistent with the methods currently used to measure patellar height in patients with recurrent patellar dislocation.

High Femoral Anteversion Is Related to Femoral Trochlea Dysplasia

PURPOSE

To investigate the possible relation between femoral anteversion (AV) and trochlear morphology.

METHODS

Among 560 available lower-limb computed tomography (CT) scans, those with previous fracture, arthroplasty, or osteotomy were excluded and 40 cases were randomly selected. The following 4 lines were determined from the CT scans: 1 through the center of the femoral head and neck; 1 through the lesser trochanter and the center of the femoral shaft; 1 as a tangent to the dorsal part of the distal femur, just above the gastrocnemius insertion; and 1 as a tangent to the posterior condyles. Between the respective lines, the following parameters of femoral AV were determined: (1) total AV, (2) proximal AV, (3) diaphyseal AV, and (4) distal AV. Trochlea parameters were determined from 2 separate axial CT slices (proximal trochlea and 5 mm farther distally): trochlea height (medial, central, lateral), transverse trochlea shift, trochlea depth, sulcus angle, lateral trochlea slope, and Dejour trochlea type. To prove or disprove our study hypothesis, a correlation analysis was performed between the variables of AV and trochlear morphology.

RESULTS

The total AV was significantly correlated with the trochlea parameters trochlea depth (P = .032), sulcus angle (P = .05), and lateral trochlea slope (P = .001). The diaphyseal AV was significantly correlated with the sulcus angle (P = .009). The distal AV showed significant correlations with medial, central, and lateral trochlea height (.005 <P < .032) and with Dejour trochlea type (P = .043).

CONCLUSIONS

The morphology of the trochlea is significantly related to femoral AV. Increased AV is associated with a flatter, more dysplastic trochlea. This was particularly true for AV located at the distal femur.

LEVEL OF EVIDENCE

Level III, diagnostic study of nonconsecutive patients.

An Algorithmic Approach to the Management of Recurrent Lateral Patellar Dislocation

High-level evidence supports nonoperative treatment for first-time lateral acute patellar dislocations. Surgical intervention is often indicated for recurrent dislocations. Recurrent instability is often multifactorial and can be the result of a combination of coronal limb malalignment, patella alta, malrotation secondary to internal femoral or external tibial torsion, a dysplastic trochlea, or disrupted and weakened medial soft tissue, including the medial patellofemoral ligament (MPFL) and the vastus medialis obliquus. MPFL reconstruction requires precise graft placement for restoration of anatomy and minimal graft tension. MPFL reconstruction is safe to perform in skeletally immature patients and in revision surgical settings. Distal realignment procedures should be implemented in recurrent instability associated with patella alta, increased tibial tubercle-trochlear groove distances, and lateral and distal patellar chondrosis. Groove-deepening trochleoplasty for Dejour type-B and type-D dysplasia or a lateral elevation or proximal recession trochleoplasty for Dejour type-C dysplasia may be a component of the treatment algorithm; however, clinical outcome data are lacking. In addition, trochleoplasty is technically challenging and has a risk of substantial complications.

The Incidence of Complications of Tibial Tubercle Osteotomy: A Systematic Review

PURPOSE

The goal of this review was to quantify the risk of perioperative and early postoperative complications of tibial tubercle osteotomy (TTO) with different techniques.

METHODS

A systematic review of multiple databases was performed to identify studies that reported complications of TTO. Complications were defined as any adverse outcome, including osteotomy site nonunion, fracture, infection, wound complications, neurovascular complications, deep vein thrombosis (DVT), and pulmonary embolism (PE). Major complications were defined as nonunion, fracture, infections/wound complications requiring return to the operating room, and DVT or PE. The risk of subsequent hardware removal was also quantified.

RESULTS

The 19 identified studies included a total of 787 TTOs: 472 direct medialization procedures (Elmslie-Trillat technique), 193 anteromedialization procedures (Fulkerson technique), and 102 procedures in which the tibial tubercle was completely detached for medialization or distalization, or a combination. The overall complication risk was 4.6%. The risk of complications was higher when the tibial tubercle was completely detached (10.7%) than with Elmslie-Trillat (3.3%) or Fulkerson (3.7%) procedures (P = .004). The overall risk of major complications was 3.0%. Hardware removal was performed in 36.7% of osteotomies and was less frequent with the Elmslie-Trillat technique (26.8%) than with the Fulkerson technique (49.0%) or complete tubercle detachment (48.3%) (P < .001).

CONCLUSIONS

Tibial tubercle osteotomy is a complex surgical procedure with a significant risk of complications. Osteotomies that involve complete detachment of the tubercle have an increased risk of complications compared with those in which a distal cortical hinge is maintained.

LEVEL OF EVIDENCE

Level IV, systematic review of Level IV studies.

[Patellofemoral instability in trisomy 21: MPFL-Reconstruction as a single procedure]

BACKGROUND

Patellar instability is a common orthopaedic condition which is often seen in younger individuals. Biomechanical studies have shown that the medial patellofemoral ligament (MPFL) is the most important soft tissue that restrains lateral subluxation of the patella in the beginning of flexion of the knee joint.

METHODS

MPFL reconstruction is an effective procedure to treat recurrent patellar dislocation. Double-bundle and single-bundle procedures have been described. If double-bundle reconstruction is not possible, there are good postoperative outcomes with single-bundle procedure as well.

DISCUSSION

This is the first report of MPFL reconstruction as a single procedure to treat patellar instability in patients with down syndrome.