The Patellar Instability Probability Calculator: A Multivariate-Based Model to Predict the Individual Risk of Recurrent Lateral Patellar Dislocation.

BACKGROUND: Predicting the risk of recurrence is of great interest when counseling patients after primary lateral patellar dislocation (LPD). PURPOSE: To investigate a multivariate model to predict the individual risk of recurrent LPD. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: The study population included patients with primary LPD, knee imaging, and a minimum 2-year follow-up after nonoperative treatment. Data including patient characteristics and anatomic patellar instability risk factors were collected retrospectively from 7 national study centers. Bivariate and multivariate regression analyses were carried out to identify risk factors for recurrent LPD and to generate an accuracy-optimized model for out-of-sample prediction. RESULTS: In total, 115 of 201 patients (57%) experienced recurrent LPD within 2 years after primary LPD. Age ≤16 years at primary LPD (odds ratio [OR], 5.0), history of contralateral instability (OR, 2.4), and trochlear dysplasia (Dejour type B-D: OR, 2.5; lateral trochlear inclination ≤12°: OR, 2.7) were significant risk factors for recurrent LPD (P < .05). The prediction accuracy including these 3 risk factors was 79%. Patella alta, an increased tibial tubercle to trochlear groove distance, and patellar tilt had neither an association with increased recurrence rates nor an influence on prediction accuracy of recurrent LPD. CONCLUSION: Young age and trochlear dysplasia are major risk factors for early recurrent LPD. A multivariate model including age at primary LPD, lateral trochlear inclination, and history of contralateral LPD achieved the highest prediction accuracy. Based on these findings, the patellar instability probability calculator is proposed to estimate the individual risk of early recurrence when counseling patients after primary LPD.

Transpatellar bone tunnels perforating the lateral or anterior cortex increase the risk of patellar fracture in MPFL reconstruction: a finite element analysis and survey of the International Patellofemoral Study Group.

PURPOSE: (1) To determine applied patellar drilling techniques for medial patellofemoral ligament (MPFL) reconstruction among members of the International Patellofemoral Study Group (IPSG) and (2) to evaluate the risk of patellar fracture for various patellar bone tunnel locations based on a finite element analysis (FEA) model. METHODS: In the first part of the study, an online survey on current MPFL reconstruction techniques was conducted among members of the IPSG. In the second part of the study, a three-dimensional FEA model of a healthy knee joint was created using a computed tomography scan. Patient-specific bone density was integrated into the patella, and cartilage of 3 mm thickness was modeled for the patellofemoral joint. According to the survey's results, two different types of patellar bone tunnels (bone socket and transpatellar bone tunnel) were simulated. The risk of patellar fracture was evaluated based on the fracture risk volume (FRV) obtained from the FEA. RESULTS: Finite element analysis revealed that subchondral bone socket tunnel placement is associated with the lowest FRV but increased with an anterior offset (1-5 mm). Transpatellar bone tunnels violating the lateral or anterior cortex showed a higher FRV compared to bone socket, with the highest values observed when the anterior cortex was penetrated. CONCLUSION: Violation of the anterior or lateral patellar cortex using transpatellar bone tunnels increased FRV compared to a subchondral patellar bone socket tunnel. In MPFL reconstruction, subchondral patellar bone socket tunnels should be considered for patellar graft fixation to avoid the risk of postoperative patellar fracture. LEVEL OF EVIDENCE: Survey; Descriptive laboratory study/Level V.

Operative Treatment Options for Patellofemoral Arthritis: An Expert Recommendation of the AGA Patellofemoral Committee.

BACKGROUND: The operative therapy of patellofemoral arthritis requires an individual approach depending on the underlying injury. However, the literature lacks recommendations for its course of action. PURPOSE: To generate an expert recommendation of therapy for different patellofemoral abnormalities in patients suffering from isolated patellofemoral arthritis. STUDY DESIGN: Consensus statement. METHODS: To generate recommendations, the AGA Patellofemoral Committee performed a consensus process using the Delphi method based on the available literature on isolated patellofemoral arthritis. RESULTS: In most statements and recommendations, a high percentage of consensus could be found. However, also in the expert group of the AGA Patellofemoral Committee, some controversies on the treatment of patellofemoral arthritis exist. CONCLUSION: The operative therapy of isolated patellofemoral arthritis is a challenging topic that leads to controversial discussions, even in an expert group. With this consensus statement of the AGA Patellofemoral Committee, recommendations on different operative treatment options were able to be generated, which should be considered in clinical practice.

Osgood-Schlatter disease: a 2020 update of a common knee condition in children.

PURPOSE OF REVIEW: Osgood-Schlatter disease (OSD) is one of the most common causes for anterior knee pain in children and adolescents resulting from a traction apophysitis of the tibial tubercle. While a peak in boys aged 12-15 years old was well documented, there seems to be no difference in sex distribution nowadays. This may result from increased participation of young females in high-impact sports. This review provides an up-to-date account on contemporary prophylaxis as well as diagnostic and therapeutic approaches. RECENT FINDINGS: Numerous studies have examined risk factors for OSD. These include body weight, muscle tightness, muscle weakness during knee extension and flexibility of hamstring muscles. In particular, shortening of the rectus femoris may substantially alter biomechanical functions of the knee. Conservative management remains successful in over 90% of patients. However, if disabling symptoms and pain persistent after physeal closure, operative treatment may be necessary. SUMMARY: OSD is a mostly self-limiting apophysitis of the tibial tubercle and the adjacent patella tendon in young active patients with open physis. Prevention strategies include quadriceps and hamstring stretching and therefore should be implemented in everyday practice routines for children who partake in regular sports activities.

Segmental torsion assessment is a reliable method for in-depth analysis of femoral alignment in Computer Tomography.

PURPOSE: De-rotational osteotomies are indicated in patients with pathologic femoral torsion. However, there is disagreement whether an osteotomy should be performed proximally or distally. Conventionally only the total torsion is measured, which does not allow differentiation between a torsional deformity located in the proximal or distal metaphysis or the diaphysis. The aim of this study is to validate a new multi-level measurement protocol for evaluation of the magnitude of torsion of the respective femoral segments in CT. PATIENTS AND METHODS: The torsional profile of 30 femora was evaluated in CT scans. For separate measurements of the torsion of the metaphysis and the diaphysis, four axes where determined: one through the femoral neck, a second determined by the midpoint of the femoral shaft and the lesser trochanter, a third determined by a tangent dorsal to the popliteal surface, and a fourth axis posterior to the condyles. The total femoral torsion was measured between the first and the fourth axis, proximal torsion between the first and the second, mid torsion between the second and the third, and distal torsion between the third and the fourth axis. Four investigators performed all measurements independently and intra-class correlation coefficients (ICC) were calculated to evaluate intra- and inter-rater reliability. RESULTS: Average total femoral torsion was 22.6 ± 8.7°, proximal torsion 47.7 ± 10.6°, mid torsion -33.4 ± 9.9°, and distal torsion 8.3 ± 3.2°. Intra-rater ICC ranged between 0.504 and 0.957 and inter-rater ICC between 0.643 and 0.992. The majority of the ICC were graded as "almost perfect" and some as "substantial" agreement. CONCLUSION: Evaluation of the segmental torsion of the femur allows in-depth analysis of femoral alignment. High reliability was shown for this measuring method in computed tomography, which can be deployed when studying interdependencies between joint pathologies and torsional deformities or when planning the site for an osteotomy. LEVEL OF EVIDENCE: Level III.

Successful adaption of the Banff Patella Instability Instrument (BPII) 2.0 into German.

PURPOSE: The aim of this study was to adapt, translate, and validate the Banff Patella Instability Instrument (BPII) 2.0 into German, enabling its use by German-speaking professionals for the evaluation of patients who present with patellofemoral instability. METHODS: Forward and backward translation was performed according to international recommendations. The final German version of the BPII 2.0 was investigated in patients with confirmed diagnoses of recurrent patellofemoral instability in Germany, Austria, and Switzerland. All patients received two packages of questionnaires, each containing the BPII 2.0, Kujala scoring questionnaire, Norwich Patella Instability scoring questionnaire, Short Form-36 (SF-36), and a visual analogue scale (VAS)-scale for pain and disability. The first and second packages of questionnaires were to be completed 7 days apart. The following parameters were assessed: internal consistency, test-retest reliability, floor and ceiling effects, and construct validity. RESULTS: The study population consisted of 64 patients (24 males and 40 females). The average age of the patients was 22 ± 6 years. The internal consistency (Cronbach's alpha) was excellent at both time points (0.93 and 0.95), and the test-retest reliability (ICC) was good (0.89). There were no floor or ceiling effects. There were statistically significant correlations between the BPII 2.0 and all other outcome measures apart from SF-36 mental health. CONCLUSION: The BPII 2.0 was successfully adapted into German. It is a reliable and valid instrument for evaluation of German-speaking patients who present with patellofemoral instability. LEVEL OF EVIDENCE: III.

What is the chance that a patella dislocation will happen a second time: update on the natural history of a first time patella dislocation in the adolescent.

PURPOSE OF REVIEW: Patellar instability occurs mainly in young patients and shows a high incidence of concomitant cartilage injuries. Recently there has been a strong attempt to identify risk factors and enhance imaging techniques to detect patients with an increased risk for recurrent patella dislocation.We describe current findings on factors associated with recurrent patella dislocation in the adolescent. RECENT FINDINGS: Trochlear dysplasia, patellar height, patellar tilt, tibial tuberosity-trochlear groove distance, skeletal maturity, and history of contralateral patellar dislocation are well known significant risk factors for recurrence in adolescent patients. Predictive models to calculate risk of recurrence have been reported recently. The Patellar Instability Severity Score was the first to include demographic and anatomic factors, which is of major value when counseling patients and relatives. SUMMARY: Several classification systems to predict the rate of recurrence after primary patella dislocation have been presented over the last years. Anatomic risk factors such as skeletal immaturity, trochlear morphology, patellar height, patellar tilt, and elevated tibial tuberosity-trochlear groove distance have been investigated. However, there is still a lack of knowledge as to how single risk factors or their interaction with each other may contribute.

Acquired femoral flexion deformity due to physeal injury during medial patellofemoral ligament reconstruction.

BACKGROUND: Reconstruction of the medial patellofemoral ligament (MPFL) is the most frequent surgical procedure performed in patients with patellar instability. Recently, concerns regarding physeal injury during femoral tunnel placement for anatomical MPFL reconstruction in children have been discussed. METHODS: This is the first case to report partial posterior physeal growth arrest and subsequent flexion deformity of the distal femur after MPFL reconstruction in a skeletally immature patient. The cause and treatment are discussed. RESULTS: Postoperative knee extension deficit and recurrent patellar instability were successfully treated with revision surgery including, distal femoral extension osteotomy, medialization of the tibial tuberosity, trochleoplasty and MPFL graft tensioning. CONCLUSION: This case highlights that care should be taken during femoral tunnel placement for anatomic graft fixation to avoid physeal injuries in skeletally immature patients.

A 1-Year Prospective Analysis of Ice Climbing Injuries.

OBJECTIVE: To describe rates, patterns, and causes of acute injuries in an increasingly popular outdoor sport. DESIGN: Prospective cohort study. SETTING: One winter season ranging from November 2011 to March 2011. PARTICIPANTS: Seventy ice climbers from 13 different countries and various performance levels. MAIN OUTCOME MEASURES: Participants were asked to complete a monthly Internet-based survey regarding their completed hours of training and competitions and eventual sustained injuries. RESULTS: During 4275 hours of ice climbing, 42 injuries occurred, of which 81.0% were defined as mild, 16.6% as moderate, and 2.4% as severe. The calculated injury rate was 9.8 injuries per 1000 hours of sports exposure. Intermediate ice climbers had a significantly higher injury risk compared with advanced ice climbers (odds ratio, 2.55; 95% confidence intervals, 1.17-5.54; P = 0.018). About 73.8% of all injuries occurred on a frozen waterfall, icicles, or icefalls, whereas 4.8% occurred on artificial ice walls. The head was the most injured body part (47.6%), followed by the knee (14.3%) and the shoulder (11.9%). The most common types of injuries were abrasions (38.1%), contusions (35.7%), and joint sprains (7.1%). Falling ice was the main circumstance leading to injury (59.5%). All athletes with a head injury wore a helmet; however, only 35.0% mentioned they used protective goggles. CONCLUSION: Ice climbing is a sport with moderate risk for injury with most of the reported injuries being of minor severity. However, severe and fatal injuries, although less common, also occur. Advanced ice climbers with greater experience and skill level have a lower overall injury risk.

Short to mid-term results of stemless reverse shoulder arthroplasty in a selected patient population compared to a matched control group with stem.

PURPOSE: Little scientific evidence on the clinical and radiological outcome after stemless reverse shoulder arthroplasty (RSA) exists. The hypothesis of this study was that stemless RSA has an inferior outcome compared to RSA with stem. METHODS: All cases of cuff-arthropathy fullfilling strict selection criteria (selection rate 18.4 %) were treated with stemless RSA between 2009 and 2013. Twenty nine of 37 cases (78.4 %) were clinically and radiologically examined by an independent observer. Twenty four of the 29 cases could be matched with 24 patients that underwent conventional stemmed RSA at a different institution based on the following criteria: indication (cuff-arthropathy), age (within 5 years), gender, and time of follow-up (within 2 years). Clincial and radiological outcomes of both groups were compared. RESULTS: After mean follow-up of 35 months (range 24-75) no significant difference regarding constant score, ASES, subjective shoulder value, pain score, patient satisfaction, strength, and range of motion was detected. One case of traumatic dislocation was observed in the stemless RSA group. Scapular notching grade 1 was detected in two cases of the stemless group while in the stemmed group five cases with grade 1 and four cases with grade 2 notching were observed. Average post-operative humeral component inclination (neck-shaft angle) in the stemless RSA group (134.4°) was significantly steeper than in the stemmed RSA group (155°) (p < 0.001). No loosening of the humeral component was observed in both groups. CONCLUSION: At short to mid-term follow-up, stemless RSA does not feature inferior clinical or radiological outcomes in a strictly selected patient population.

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

The Contribution of Different Femur Segments to Overall Femoral Torsion.

BACKGROUND: Femoral torsion is a critical parameter in hip and knee disorders. The unproven assumption is that the femoral neck exclusively contributes to the overall torsion of the femur. PURPOSE/HYPOTHESIS: The aim of this study was to measure femoral torsion at different levels in patients with abnormally high or low femoral torsion and to compare the results with healthy volunteers. Our hypothesis was that the pattern of torsion distribution among the different femoral levels varies between patients with abnormal torsion and healthy volunteers. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Magnetic resonance images of patients with a history of patellar instability and torsion of the femur ≥25° (11 patients, 16 femurs) and ≤0° (14 patients, 22 femurs) were analyzed. Our controls were 30 healthy volunteers (60 femurs). To assess femoral torsion, 4 lines were drawn: a first line through the center of the femoral head and neck, a second line through the center of the femur at the top of the lesser trochanter, a third line tangent to the posterior aspect of the distal femur just above the attachment of the gastrocnemius, and a fourth line tangent to the posterior condyles. Three investigators performed the measurements; 1 performed the measurements twice. RESULTS: All femur segments showed significantly different torsion among the high-torsion, low-torsion, and control groups. Regarding the pattern of torsion distribution, on average, all levels contributed to the torsion. The ratio between the average neck and shaft torsion shifted toward a higher value in the high-torsion group, mostly because of a lack of external torsion in the shaft, and toward a lower value in the low-torsion group, owing to both a lack of internal torsion of the neck and increased external torsion in the shaft. CONCLUSION: We established a difference between neck, mid, and distal femoral torsion with reproducible measurements. Our data suggest that all 3 levels of the femur contribute to the total femoral torsion, with a different pattern among patients with high torsion and patellar instability.

The position of the tibia tubercle in 0°-90° flexion: comparing patients with patella dislocation to healthy volunteers.

PURPOSE: The aim of this study was to measure the tibia tubercle trochlea groove distance (TT-TG) as a function of knee flexion. Our hypothesis was that there is a different pattern in healthy volunteers and patients with patella instability (PFI). METHODS: Thirty-six knees of 30 patients with at least one dislocation of the patella and 30 knees of 30 healthy volunteers as control group were analysed with magnetic resonance imaging by three different observers. The TT-TG was measured in steps of 15° between 0° and 90° of knee flexion. Furthermore, the alignment of the leg (MA), the femur torsion (FTor) and the tibia torsion (TTor) was calculated. RESULTS: The TT-TG was higher in patients compared to volunteers and in extension compared to flexion. This difference was statistically significant (p<0.05). Most of the patients with a TT-TG above 20 mm in extension showed a high decrease in flexion to normal values. In some patients, this compensating mechanism fails. MA, FTor and TTor were not different in patients and control group (n.s.). CONCLUSION: The TT-TG distance is dynamic and decreased significantly during flexion in knees with PFI and healthy volunteers. However, there were a small number of patients in the PFI group where this compensation mechanism did not work. Therefore, the decision to perform a tibia tubercle osteotomy should not be based on one single measurement in extension or 30° of knee flexion. LEVEL OF EVIDENCE: II.

Tibial tubercle-posterior cruciate ligament distance: a new measurement to define the position of the tibial tubercle in patients with patellar dislocation.

BACKGROUND: In patients with patellar instability, a pathological tibial tubercle-trochlear groove (TT-TG) distance is a risk factor. However, the TT-TG distance gives no information about the location of the malformation. HYPOTHESIS: Not all patients with a pathological TT-TG distance (≥20 mm) had lateralization of the tibial tubercle. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 2. METHODS: Fifty-eight knees in 49 patients with 2 or more patellar dislocations and 60 knees in 30 volunteers with no history of dislocation were analyzed using magnetic resonance imaging (MRI). The tibial tubercle-posterior cruciate ligament (TT-PCL) distance was defined as the mediolateral distance between the tibial tubercle midpoint and the medial border of the posterior cruciate ligament. The distance was measured parallel to the dorsal aspect of the proximal tibia (dorsal tibia condylar line). Three observers performed the measurements. Significant differences in the TT-PCL distance between the patient and the control group were estimated using an unpaired t test. The inter- and intraobserver variability of the measurement was performed. RESULTS: The intraclass correlation coefficients for inter- and intraobserver variability of the TT-PCL distance were higher than 0.74 and 0.93, respectively. A statistically significant difference (P < .05) was found between the TT-PCL distance in the control group (mean [SD], 18.4 [3.35] mm) and in patients (21.9 [4.30] mm). The mean (SD) TT-TG was 18.9 (5.16) mm in the patient group and 11.9 (4.67) mm in the control group (P < .05). In the control group, 95% had a TT-PCL distance <24 mm. In the patient group, 22 of 58 knee joints (38%) had a TT-PCL distance ≥24 mm. Seventeen of 40 knee joints (43%) with a TT-TG distance ≥20 mm had a TT-PCL distance <24 mm. CONCLUSION: Only 57% of the patients with a pathological TT-TG distance (≥20 mm) had lateralization of the tibial tubercle in relation to the posterior cruciate ligament. The TT-PCL distance is an alternative method for determining the position of the tibial tubercle.