A Diagnosis of Vitamin D Deficiency Is Associated With Increased Rates of Primary Patellar Instability and Need for Recurrent Surgical Stabilization

BACKGROUND

Vitamin D has been proven experimentally to affect musculoskeletal health. The purpose of this study was to identify the relationship between vitamin D deficiency and patellar instability.

HYPOTHESIS

Vitamin D deficiency is associated with an increased risk of experiencing primary patellar instability and recurrent patellar dislocation after primary surgical stabilization.

STUDY DESIGN

Retrospective comparative study.

LEVEL OF EVIDENCE

Level 3.

METHODS

A 1:1 matched retrospective study of 328,011 patients diagnosed with vitamin D deficiency was performed using the PearlDiver database. Incidence of primary patellar instability was calculated according to sex and age. Rates of primary patellar instability and surgical stabilization for recurrent dislocation were calculated with sex- and age-specific stratifications. Multivariable logistic regression was used to compare the rates of primary injury and recurrent stabilization while controlling for demographics and medical comorbidities.

RESULTS

A total of 656,022 patients were analyzed. The overall 1-year incidence rate of patellar instability in patients with vitamin D deficiency was 82.6 per 100,000 person-years (95% CI, 73.2-92.9), compared with 48.5 (95% CI, 41.4-56.5) in the matched control. Women were significantly more likely to experience primary patellar instability within 1 (adjusted odds ratio [aOR] = 1.45; 95% CI, 1.12-1.88) and 2 years (aOR, 1.31; 95% CI, 1.07-1.59) of hypovitaminosis D diagnosis. Patients aged 10 to 25 years with hypovitaminosis D were at greater risk of requiring recurrent patellar stabilization for both men (aOR, 2.48; 95% CI, 1.06-5.80) and women (aOR, 1.77; 95% CI, 1.04-3.02).

CONCLUSION

Patients diagnosed with vitamin D deficiency experienced higher rates of primary patellar instability and have greater risk of requiring recurrent surgical stabilization for subsequent dislocations.

CLINICAL RELEVANCE

These results suggest that monitoring and proactively treating vitamin D deficiency in the physically active patient may lower the risk of suffering primary patellar instability or recurrence after surgical stabilization.

Exploring osteochondral damage patterns in acute patellar dislocation: insights into morphological associations and risk factors

Osteochondral damage (OD) is a significant outcome following acute patellar dislocation (APD), yet the factors contributing to its susceptibility remain unclear. The primary objective of this study was to assess the association between demographic characteristics, patellofemoral (PF) joint morphology, and the occurrence of OD. A retrospective analysis identified 74 patients with APD who underwent treatment in our unit between 2019 and 2022. All patients received MRI within a week of injury to assess OD, subsequently categorized according to the injury pattern. The Caton-Deschamps index (CDI), tibial tuberosity-trochlear groove distance (TT-TG), lateral trochlear inclination (LTI), sulcus angle (SA), patellar width (PW), patellar thickness (PT), and femoral condyle geometry were calculated from the MRI scans and compared between groups. The findings revealed that OD predominantly manifested in the lateral femoral condyle (LFC) region and the medial patella (MP) region. In our patient cohort, this study identified a significant association between sulcus angle and the incidence of OD in both MP and LFC regions. Additionally, a significant correlation was discerned between skeletal maturity and the incidence of OD in the LFC region within demographic characteristics.

Epidemiology of patellar dislocations in the United States from 2001 to 2020: results of a national emergency department database

OBJECTIVES

Recent studies have shown an increasing incidence of patellar dislocations among children and adolescents. Updated, population-based studies of all patellar dislocations in the United States (US), however, are lacking. This study investigated recent trends in injury rates and demographics among patients sustaining patellar dislocations in the US from 2001 to 2020.

METHODS

This descriptive epidemiologic study retrospectively analyzed the National Electronic Injury Surveillance System (NEISS) database to identify cases of acute patellar dislocations presenting to US Emergency Departments (EDs) from 2001 to 2020. Annual, overall, and age-adjusted incidence rates (IRs, expressed per 100,000 at-risk person-years) and additional patient/injury characteristics were analyzed. Average annual percent change (AAPC) estimates are presented to indicate the magnitude/direction of trends in annual injury rates.

RESULTS

An estimated total of 159,529 patellar dislocations occurred over the study period for an overall IR of 2.58 (95% CI = 2.04-3.12). Accounting for population growth, the overall annual incidence increased significantly from 2.61 in 2001 to 3.0 in 2020 (AAPC = 2.8, p < 0.0001). When considering sex and age, statistically significant increases in annual IRs were observed among males aged 10-19 years (AAPC = 3.8, p < 0.0001), females aged 10-19 years (AAPC = 5.3, p < 0.0001), and females aged 20-29 years (AAPC = 3.5, p = 0.0152), while no significant changes were observed in any other age groups. Two-thirds of patellar dislocations involved sports-related injury mechanisms. The annual incidence of both sports-related and non-sports-related injuries increased significantly over the study period (sports-related: AAPC = 2.6, p = 0.0001; non-sports-related: AAPC = 3.4, p = 0.0001). Athletic patellar dislocations occurred most commonly in basketball and dance.

CONCLUSION

The number of patients sustaining patellar dislocations is increasing in the US. Similar increasing trends were observed in both males and females aged 10-19 years, whereas injury rates increased in the third decade only among females. A large percentage of injuries occur during athletic activity, but both sports- and non-sports-related patellar dislocations are on the rise.

Epidemiology of Lateral Patellar Dislocation Including Bone Bruise Incidence: Five Years of Data from a Trauma Center

OBJECTIVE

Systematic summary of the epidemiology of patellar dislocation is rare. This study aims to investigate sex-, age-, type-, injury causing events-, incidence of bone bruise and time from last injury (TFLI)-specific characteristics, and detail the epidemiological characteristics of patellar dislocation.

METHOD

In this descriptive epidemiological study, a total of 743 patients who have a history of lateral patellar dislocation with either first-time patellar dislocation (FPD) or recurrent patellar dislocation (RPD) between August 2017 and June 2022 at our institution met the inclusion criteria and were selected in this study. Patient characteristics including the type, gender, age, events leading to patellar dislocation, incidence of patellar bone bruise, and the time from last injury (TFLI) of patellar dislocation were retrospectively obtained and described. Magnetic resonance imaging scans (MRI) of the knee were reviewed for insuring bone bruise.

RESULTS

Among the 743 patients with patellar dislocation who required surgical reconstruction of the medial retinaculum, 418 (56.2%) had RPD and 325 (43.8%) had FPD. There were more females (65.0%) than males (35.0%) in patellar dislocation patients. Among the female patients, those aged <18 years had higher incidence (31.4%) of patellar dislocation. Among the male patients, those aged <18 and 19-28 years had higher incidence (16.8%) of patellar dislocation. Of all age groups, the prevalence rate of patellar dislocation was high in juvenile population and females, but with no statistical significance. The most common patellar dislocation-causing event was sport accidents (40.1%), followed by life accidents (23.2%). The incidence of left-knee patellar dislocation was slightly higher than that of right-knee patellar dislocation. The incidence of patellar bone bruise of RPD (63.2%) was significantly lower (p < 0.05) than that of FPD (82.2%). Patellar dislocation patients with bone bruise had shorter time from last injury (TFLI) than those without patellar bone bruise (p < 0.05).

CONCLUSIONS

The incidence of bone bruise of RPD was lower than that of FPD, and patients with patellar bone bruise may have a shorter time from last injury than those without bone bruise.

High prevalence of patellar dislocation and trochlear dysplasia in a geographically and genetically isolated society: an observational national cohort study from the Faroese Knee Cohort

BACKGROUND AND PURPOSE

We aimed to calculate the prevalence of patellar dislocation (PD) and trochlear dysplasia (TD) in a national cohort aged 15-19 years in the Faroe Island.

PATIENTS AND METHODS

All inhabitants in the Faroe Islands aged 15-19 years were invited to answer an online survey, including demographics and questions regarding prior PD. Participants with prior PD were invited for radiographs and MRI of both knees to be taken. Trochlear dysplasia was defined as one of the following: Dejour type A-D on radiographs, lateral trochlear inclination angle (LTI) < 11°, or trochlear depth < 3 mm on MRI.

RESULTS

3,749 individuals were contacted, 41 were excluded, and 1,638 (44%) completed the survey. 146 reported a prior PD (the PD cohort) and 100 accepted to participate and have radiographs and MRI taken of both knees (the clinical PD cohort), 76 of whom were diagnosed with TD. The national prevalence of PD was 8.9%. The national prevalence of symptomatic TD was 6.8%. The prevalence of TD in the clinical PD cohort was 76%. TD was bilateral in 78% of TD patients, but only 27% of patients with bilateral TD had PD in both knees.

CONCLUSION

The prevalence of PD in the Faroe Islands is found to be very high. The national prevalence of TD and the prevalence of TD in participants with prior PD is high, indicating a potential genetic influence.

The larger patellar tilt angle and lower intercondylar notch angle might increase posterior cruciate ligament injury risk: a retrospective comparative study

BACKGROUND

Posterior cruciate ligament (PCL) injuries are common ligament injuries of the knee, and previous studies often focused on the associations between the morphology of the knee and PCL injuries. Studies on the correlation between PCL injuries and patellofemoral alignment are limited.

METHODS

This retrospective study included 92 patients with PCL injured and 92 patients with PCL intact. Measurement parameters were compared between the two groups, including patellar tilt angle, congruence angle, patellar height, hip-knee-ankle angle, lateral trochlear inclination, femoral condyle ratio, bicondylar width, intercondylar notch width and index, notch angle, trochlear facet asymmetry, and trochlear sulcus depth and angle. Independent risk factors associated with PCL injuries were identified by logistic regression analyses.

RESULTS

In the PCL injured group, the patellar tilt angle was significantly larger (13.19 ± 5.90° vs. 10.02 ± 4.95°, P = 0.04); the intercondylar notch angle was significantly lower (60.97 ± 7.83° vs. 67.01 ± 6.00°, P = 0.004); the medial and lateral femoral condyle ratio were significantly larger (0.63 ± 0.64 vs. 0.60 ± 0.56, P = 0.031; 0.65 ± 0.60 vs. 0.58 ± 0.53, P = 0.005) than in the PCL intact group. There were 11 patients with patellar dislocation in the PCL injured group, accounting for 12%. In these patients, the patellar height was higher (1.39 ± 0.17 vs. 1.09 ± 0.25, P = 0.009); the trochlear sulcus angle was larger (157.70 ± 8.7° vs. 141.80 ± 8.78°, P < 0.001); and the trochlear sulcus depth was shallower (3.10 ± 1.20mm vs. 5.11 ± 1.48mm, P = 0.003) than those in the patients without patellar dislocation. Multivariate analyses showed that patellar tilt angle (each increase 1 degree, OR = 1.14) and intercondylar notch angle (each increase 1 degree, OR = 0.90) were independent risk factors for PCL injuries.

CONCLUSION

The patients with PCL injuries had larger patellar tilt angles, lower intercondylar notch angles, and longer posterior femoral condyles than patients with PCL intact. The larger patellar tilt angle and lower intercondylar notch angle might be risk factors for PCL injuries.

The epidemiology of patellar luxation in an insured Swedish dog population

Patellar luxation (PL) is a common orthopaedic condition in dogs. This study aimed to evaluate the incidence and cause-specific mortality rate, age at diagnosis, and risk factors for medial PL (MPL), lateral PL (LPL), and bidirectional PL (BPL). Other diagnoses in dogs with PL were also explored. The study population included just over 600,000 dogs insured by Agria Pet Insurance in Sweden (2011-2016). There were 2726 dogs with PL. Medial patellar luxation affected 90 % of the dogs with PL, followed by LPL (5.9 %), BPL (2.4 %), and unspecified PL (1.6 %). The median age at first diagnosis during the study period was 2.8 years for MPL, 2.7 years for LPL, and 1.5 years for BPL. In total, 168 (6.2 %) of the dogs with PL had cruciate ligament rupture. There were substantial breed-specific differences in the risk of PL: almost all breeds at increased risk of MPL were small-sized, while several of the breeds at increased risk of LPL were large-sized. The breeds at high risk of BPL varied in size. Females had an increased risk of MPL (RR 1.2, 95 % CI: 1.1-1.3, p < 0.001) and a decreased risk of LPL (RR 0.72, 95 % CI: 0.51-1.0, p = 0.042) compared to males. In total, 116 dogs were euthanised due to PL and the breeds with the highest risk of PL-related euthanasia were the Pyrenean mountain dog, Dogue de Bordeaux, and German pinscher. The median age for PL-related euthanasia was 2.2 years.

Factors associated with an increased risk of osteochondral injuries after patellar dislocations: a systematic review

PURPOSE

The purpose of the study was to summarize the available evidence and identify risk factors for osteochondral injuries (OCIs) after patellar dislocations.

METHODS

A systematic literature review was conducted in PubMed, Embase, Web of Science, Cochrane Library, and China national knowledge infrastructure from inception to December 22, 2022, according to the preferred reporting items for systematic reviews and meta-analyses guidelines. Studies regarding risk factors for OCIs after patellar dislocations were included. Literature search, data extraction, and quality assessment were performed independently by two authors.

RESULTS

A total of 16 studies with 1945 patients were included. The risk factors for OCIs after patellar dislocation were categorized into four main categories, including demographic characteristics, patellar depth and position, femoral trochlear morphology, and other risk factors in this study. Five and three studies supported the idea that male sex and skeletal maturation may be risk factors, respectively. Normal femoral trochlea (two studies) and complete medial patellofemoral ligament (MPFL) injuries (two studies) may be associated with the development of OCIs. Three studies show that ligamentous laxity or joint hypermobility may prevent OCIs. Patellar depth and position (eight studies) may not be associated with the development of OCIs.

CONCLUSIONS

Based on the available evidence, an increased risk of OCIs following patellar dislocation may be associated with male sex and skeletal maturation. Furthermore, normal femoral trochlea and complete MPFL injuries may increase the risk of OCIs, while factors such as ligamentous laxity or joint hypermobility may reduce the risk.

LEVEL OF EVIDENCE

Level IV, systematic review of Level II and IV studies.

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.

Familial association and epidemilogical factors as risk factors for developing first time and recurrent patella dislocation: a systematic review and best knowledge synthesis of present literature

PURPOSE

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

METHODS

The study was conducted according to the PRISMA guidelines and registered in PROSPERO. EMBASE and PubMed were systematically searched on the 5th of May 2022. Studies investigating participants with genetic and epidemiological risk factors for the first time as well as recurrent patella dislocation were included. The records were screened, and data were extracted independently by two researchers supervised by a third independent assessor.

RESULTS

A total of 6,649 records were screened, and 67 studies were included. Familial association was described as a risk factor for patella dislocation in 17 studies. One study found that participants with a family history of patella dislocation had a 3.7 higher risk for patella dislocation in the contralateral asymptomatic knee, and another study found a family history of PD in 9% of 74 participants. Eleven studies found an accumulation of patella dislocation across generations in specific families. Additionally, a range of genetic syndromes was associated with patella dislocation. Young age is a well-investigated risk factor for patella dislocation, but the results are inconsistent. Only five and eight studies investigated skeletal immaturity and gender as risk factors for patella dislocation, respectively.

CONCLUSION

There may be a familial association with patella dislocation, but further investigation is necessary to determine the strength and etiology of the association. There is weak evidence that epidemiological risk factors, such as age, skeletal immaturity, gender, and BMI are risk factors for patella dislocation.

LEVEL OF EVIDENCE

IV.

Incidence and concomitant chondral injuries in a consecutive cohort of primary traumatic patellar dislocations examined with sub-acute MRI

PURPOSE

To present age- and sex-specific cumulative annual incidences of primary traumatic lateral patellar dislocation (LPD) and to detail patient characteristics and concomitant chondral injuries including osteochondral fractures, as visualized on magnetic resonance imaging (MRI), in a large consecutive cohort of knee-injured individuals.

METHODS

Data on primary traumatic lateral patellar dislocations were collected from a large consecutive cohort of knee injuries examined with sub-acute MRI in a single centre with a well-defined catchment area. Annual incidences for different age-groups in relation to gender were calculated together with the risk of concomitant chondral and osteochondral injury, during sports and in general.

RESULTS

A total of 184 primary patellar dislocations were identified in the cohort of 1145 acute knee injuries (n=175) and surgical records (n=9). Knee MRI was performed within a median of six days of injury. Median age of patients with primary LPD was 16 years (interquartile range, 14-21; range, 9-47) and 41% were females. Males were significantly older than females at the time of injury (median age 17 vs. 15, P = 0.021) and sustained their primary LPD during sports more often than females (65 vs. 40%, P < 0.001). Primary LPD occurred most frequently at the age of 13 to 15 years where the annual incidence was 125 (95% CI, 96-160) per 100,000 persons. The overall annual incidence of primary LPD was 14 (95% CI, 12-16) per 100,000 persons, with a predominance of males versus females (17 vs. 11, P = 0.01). Concomitant lesions to joint surfaces were displayed on MRI or during surgery in 75 (43%) knees. Osteochondral fractures were seen in 32 knees (18%). We found no statistically significant difference in the risk of osteochondral fracture between those injured during sports or during leisure activity (14 vs. 24%, P = 0.08).

CONCLUSIONS

The annual incidence of first-time patellar dislocation was found to be 14 per 100,000 individuals with the highest incidence found among those aged 13-15 years. Primary LPD was more common among males and was sustained during sports activity in 55% of the cases. Associated injuries to the chondral surfaces should be expected in 43% of knees with primary LPD where 18% represent osteochondral fractures.

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.

Persistent morbidity after Medial Patellofemoral Ligament Reconstruction - A registry study with an eight-year follow-up on a nationwide cohort from 1996 to 2014

BACKGROUND

To evaluate the trends in treatment of patellar dislocation in the Danish population as a whole from 1996 to 2014 and evaluate the incidence of persistent morbidity after Medial Patellofemoral Ligament Reconstruction (MPFL-R).

METHODS

This epidemiological study was performed by retrospectively searching the Danish National Patients Registry from 1996 to 2014. The study investigated the trends in surgery performed on patients with patellar dislocations and the risk of persistent patellar morbidity (PPM) with an eight-year follow-up. PPM was defined as a new patella-related contact to the healthcare system more than a year after surgery.

RESULTS

From 1996 to 2014, a total of 1956 MPFL-R were performed in Denmark. In 2014, MPFL-R constituted 75% of all patella-stabilizing surgery and was performed on almost 10% of patients with patellar dislocation. The mean risk of PPM eight years after surgery was 20.9% (18.3-23.4%), and young patients aged 10-17 showed the highest risk of 28.9% (23.7-33.7%). The risk of PPM over time was significantly higher for other patella-stabilizing surgery (33.8%) and patients receiving conservative treatment (29.4%) compared to MPFL-R.

CONCLUSIONS

A rapid rise in the use of MPFL-R was found from 2005 to 2014, constituting 75% of all patella-stabilizing surgery in 2014. The overall risk of persistent patellar morbidity within eight years after MPFL-R was 21%. MPFL-R was found to give a significantly lower risk of PPM over time as compared to other patella-stabilizing surgery and conservative treatment.

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.

High rate of recurrent patellar dislocation in skeletally immature patients: a long-term population-based study

PURPOSE

Patellar dislocation can occur in isolation or be associated with chronic instability. The goals of this study are to describe the rate and factors associated with additional patellar instability events (ipsilateral recurrence and contralateral dislocation), as well as the development of patellofemoral arthritis in patients who are skeletally immature at the time of first patellar dislocation.

METHODS

The study included a population-based cohort of 232 skeletally immature patients who experienced a first-time lateral patellar dislocation between 1990 and 2010. A chart review was performed to collect information related to the initial injury, treatment, and outcomes. Subjects were followed for a mean of 12.1 years to determine the rate of subsequent patellar dislocation (ipsilateral recurrence or contralateral dislocation) as well as clinically significant patellofemoral arthritis.

RESULTS

104 patients had ipsilateral recurrent patellar dislocation. The cumulative incidence of recurrent dislocation was 11% at 1 year, 21.1% at 2 years, 37.0% at 5 years, 45.1% at 10 years, 54.0% at 15 years, and 54.0% at 20 years. Patella alta (HR 10.6, 95% CI 3.6, 36.1), TT-TG ≥ 20 mm (HR 18.7, 95% CI 1.7, 228.2), and trochlear dysplasia (HR 23.7, 95% CI 1.0, 105.2) were associated with recurrence. Similarly, 18 patients (7.8%) had contralateral patellar dislocation. The cumulative incidence of patellofemoral arthritis was 0% at 2 years, 1.0% at 5 years, 2.0% at 10 years, 10.1% at 15 years, 17% at 20 years, and 39.0% at 25 years. Osteochondral injury was associated with arthritis (HR 25.7, 95% CI 6.2, 143.8). There was no association with trochler dysplasia (HR 1.2, 95% CI 0.2, 5.0), recurrent patellar instability (HR 1.2, 95% CI 0.2, 7.2), gender (HR 1.3, 95% CI 0.3, 5.6), or patellar-stabilizing surgery (HR 0.7, 95% CI 0.2, 3.5) and arthritis.

CONCLUSION

Skeletally immature patients had a high rate of recurrent patellar instability that was associated with structural abnormalities such as patella alta,TT-TG ≥ 20 mm, and trochlear dysplasia. Approximately 10% of patients experienced a contralateral dislocation and 20% of patients developed arthritis by 20 years following initial dislocation. Osteochondral injury was associated with arthritis.

LEVEL OF EVIDENCE

Retrospective case series, Level IV.

Valgus instability as a cause for recurrent lateral patellar dislocation: a new mechanism for patellofemoral instability?

An association between lateral patellar dislocation (LPD) and medial collateral ligament injury (MCL) has recently been demonstrated on MRI. The same valgus injury that disrupts the femoral MCL insertion can also cause a simultaneous MPFL tear at its femoral insertion, due to the close anatomical relationship of both ligamentous structures. Valgus laxity due to MCL-deficiency increases the Q-angle and further adversely affects patellar stability. A knee diagnosed with a severe MCL tear, should be evaluated for patellofemoral instability, as a temporary patella dislocation could have been caused by the same injury and an acute LPD indicating a tear of the MPFL can be associated with a concomitant injury of the MCL. In case of recurrent symptoms of patellofemoral instability in a MCL-deficient knee, both the MPFL and MCL should be managed operatively. An isolated MPFL reconstruction in this knee is likely to fail due to a persistent increase of the Q-angle.

Cartilage lesions in patellofemoral dislocations: incidents/locations/when to treat

Patellofemoral (PF) dislocations are frequently associated with chondral injury. Chondral and osteochondral lesions are often associated with traumatic (high-energy) PF dislocations, whereas atraumatic (low-energy) PF dislocations in patients with significant PF risk factors have a much lower incidence of osteochondral damage. This article provides a historical overview and delineates the current state of radiographic and clinical outcomes of osteochondral lesions after PF dislocation. The importance of understanding risk factors of redislocation is emphasized, and the current treatment options for these cartilage lesions associated with PF dislocation are briefly summarized.

The prevalence of canine patellar luxation in three centres. Clinical features and radiographic evidence of limb deviation

The medical records of 155 dogs with patellar luxation (PL) from three different centres were analysed. Each case was classified according to the nature of its luxation and any concurrent orthopaedic conditions plus the age at diagnosis were also noted. Measurements relating to angle of inclination (AOI) of the femoral neck and medio-lateral bowing of the femur and tibia at the stifle were also recorded. The femoral and tibial data were compared to dogs with another orthopaedic condition in a case-control assessment. Labradors were most commonly affected (21%). Most luxations were medial (92%) and 54% of affected dogs were female. The mean AOI of the hip was 148.95 degrees . There was a statistically significant difference between the stifles of dogs with PL compared to a control population. This study concluded that PL in large breeds is increasing. Lateral luxation was uncommon and was not associated exclusively with large breeds. Females were more likely to have PL than males and being female was a risk factor associated with coxa valga. There are significant differences in medio-lateral stifle conformation between dogs with PL and control dogs.

Recurrent patellar dislocation: reappraising our approach to surgery

INTRODUCTION

The management of recurrent traumatic patellar dislocation includes surgical realignment. There is no clear distinction whether proximal soft tissue or distal procedures produce superior results. However, distal realignment procedures are commonly associated with greater morbidity. We advocate a distal procedure only for cases which are more severe, such as the presence of patellar maltracking.

MATERIALS AND METHODS

Between January 2002 and June 2007, all patients who had a history of traumatic patellar dislocation with recurrent symptoms and failed conservative management underwent surgical realignment. Patients who had evidence of lateral patellar subluxation on computed tomography (CT) scan were offered a distal realignment procedure using the Elmslie-Trillat or Roux Goldthwaite procedure. All other patients underwent proximal soft tissue medial patellofemoral ligament (MPFL) reconstruction. Pre and postoperative functional International Knee Documentation Committee (IKDC), Lysholm and Tegner score assessments were performed for a minimum follow-up period of 6 months. The mean scores for each group were analysed using the Wilcoxon Matched-Pairs Signed-Ranks test and the Mann-Whitney U test was used to evaluate the difference between the groups.

RESULTS

A total of 23 patients underwent surgery for patellar realignment. Of whom, 14 patients had a distal realignment procedure while 9 patients had a proximal procedure of MPFL reconstruction. There was greater morbidity reported with distal realignment procedures. Pre and postoperative IKDC, Lysholm and Tegner scores showed significant improvement for both treatment arms. However, there was no significant difference between the improvement scores for both groups.

CONCLUSION

Patients with significant patellar maltracking following traumatic patellar dislocation would benefit from distal realignment using the Elmslie-Trillat or Roux Goldthwaite procedure. Otherwise, a proximal soft tissue procedure involving MPFL reconstruction would be adequate. A management algorithm is proposed for clinical use.

Frequency and distribution of patellar luxation in dogs. 134 cases (2000 to 2005)

This study investigated the frequency and distribution of patellar luxation in the dogs presented to the Chonbuk National University Animal Medical Centre during January 2000 to September 2005. Patellar luxations were classified as medial or lateral, and unilateral or bilateral, were graded I to IV, and were subdivided according to age, sex and size of the dogs. The incidence of medial patellar luxation (MPL) was greater than the incidence of lateral patellar luxation (LPL) in both small and large dogs. Small-breed dogs were admitted almost exclusively with MPL. LPL was found uncommon; however it was observed more often in larger-breed dogs. Surgical correction was performed primarily in the dogs (165 stifles in 111 dogs) with grade II, III and IV patellar luxations following different surgical techniques. The combination of the surgical techniques was found to be more effective for the management of the disease. The prognosis was found to be favourable, because when the grade was low, the dog was younger, without cruciate ligament rupture, and as the surgical correction was performed with combination of more techniques.

A laterally positioned concave trochlear groove prevents patellar dislocation

Patellofemoral instability is a disabling condition that occurs in adolescence. Recurrence after patellar dislocation has been reported in 2-50% of patients. We compared the distal femur in patients with patellofemoral instability with distal femura of a healthy cohort using mathematical quantification of two-dimensional shape variation at the same position in different knees. One hundred eight computed tomography scans from 54 patients with patellofemoral instability were compared with 197 computed tomography scans from 102 subjects with normal knees. We used principal components analysis to quantify variation in shape of the trochlear groove as it allows comparison of knees with patellofemoral instability to healthy knees. We found that subjects who had dislocated their patella had a flattened trochlear groove, whereas normal knees had a more concave groove. The position of the trochlear groove was more medial in patients with patellofemoral instability compared with normal knees. Groove position was more important than shape when predicting which patellae were likely to dislocate.

Lateral patella dislocation associated with an irreducible posterolateral knee dislocation: literature review

Posterolateral dislocations involve significant injury to the medial structures of the knee, therefore particular attention should be paid to repairing the medial patella stabilizers at the time of open reduction.

Epidemiology and natural history of acute patellar dislocation

BACKGROUND

The goals of this study were to (1) define the epidemiology of acute patellar dislocation, (2) determine the risk of subsequent patellar instability episodes (subluxation and/or redislocation) during the study period, and (3) identify risk factors for subsequent instability episodes.

STUDY DESIGN

Prospective cohort study.

METHODS

The authors prospectively followed 189 patients for a period of 2 to 5 years. Historical data, injury mechanisms, and physical and radiographic measurements were recorded to identify potential risk factors for poor outcomes.

RESULTS

Risk was highest among females 10 to 17 years old. Patients presenting with a prior history of instability were more likely to be female (P < .05) and were older than first-time dislocation patients (P < .05). Fewer first-time dislocators (17%) had episodes of instability during follow-up than patients with a previous history of instability (49%) (P < .01). After adjusting for demographics, patients with a prior history had 7 times higher odds of subsequent instability episodes during follow-up than first time dislocators (adjusted odds ratio = 6.6, P < .001).

CONCLUSIONS

Patellar dislocators who present with a history of patellofemoral instability are more likely to be female, are older, and have greater risk of subsequent patellar instability episodes than first-time patellar dislocators. Risk of recurrent patellar instability episodes in either knee is much higher in this group than in first-time dislocators.

Acute traumatic extension deficit of the knee

The purpose of this study was to evaluate the events leading to acute traumatic extension deficit of the knee and the arthroscopic findings in these patients. A total of 78 consecutive patients treated in the Turku university hospital during the years 1994-1996 were included. The mean annual incidence of acute traumatic extension deficits of the knee in our study was 1.1 per 10 000 inhabitants. The single most common (33%) event causing the extension deficit was non-sports related twisting of the knee. Various sports related activities accounted for 42% of the extension deficits, and soccer was the most common sport in this group. In conclusion, acute traumatic extension deficit of the knee is usually a sign of serious intra-articular damage, and the most likely finding (in 82% of the patients in our study) is either a meniscal rupture, an anterior cruciate ligament (ACL) rupture, a patellar dislocation, or a combination of these. The lesions in these knees require prompt evaluation by an orthopaedic surgeon mainly because of the high number of bucket-handle and menisco-capsular insertion ruptures of the menisci, which are possibly suitable for repair.