Surgery for patellar dislocation has evolved towards anatomical reconstructions with assessment and treatment of anatomical risk factors

Decreased Association Between Patellar Axial Malalignment and Patellar Height and Increased Association Between Patellar Axial Malalignment and Tibial Tubercle-Trochlear Groove During Weightbearing

BACKGROUND

Nonweightbearing preoperative assessments avoid quadriceps contraction that tends to affect patellar motion and appear to be inaccurate in quantifying anatomic factors, which can lead to incorrect corrections and postoperative complications.

QUESTIONS/PURPOSES

(1) Does the relationship of patellar axial malalignment and other anatomic factors change during weightbearing? (2) What anatomic factor was most strongly correlated with recurrent patellar dislocation during weightbearing?

METHODS

This prospective, comparative, observational study recruited participants at our institution between January 2023 and September 2023. During this time, all patients with recurrent patellar dislocations received both weightbearing and nonweightbearing CT scans; control patients who received unilateral CT scans because of injuries or benign tumors received both weightbearing and nonweightbearing CT scans. Between January 2023 and September 2023, 52 patients were treated at our institution for patellar dislocation. We included those who had experienced at least two dislocations. The exclusion criteria were as follows: (1) traumatic dislocation, (2) prior knee surgery, (3) osteoarthritis (≥ Kellgren-Lawrence Grade 3), and (4) abnormal walking and standing postures confirmed by the orthopaedic surgeon and an inability to complete weightbearing CT with their body in a neutral position (meaning their body weight was evenly placed on both knees) because of severe pain. After applying prespecified exclusions, 63% (33 patients) of the original number were included, and data for 33 patients (65 knees) with weightbearing CT data and 28 patients (52 knees) with nonweightbearing CT data were obtained. Because of ethical requirements, the control group included patients who underwent unilateral CT scanning (for an injury or a benign tumor), and weightbearing CT and nonweightbearing CT covered both knees. Control knees were confirmed to have normal patellofemoral function by physical examination by an orthopaedic surgeon involved with the study. The control group consisted of the normal knees (52 knees underwent both weightbearing CT and nonweightbearing CT) and the affected but uninvolved knees (47 knees underwent weightbearing CT and 6 knees underwent nonweightbearing CT), and a total of 52 patients (99 knees) with weightbearing CT data and 31 patients (58 knees) with nonweightbearing CT data were included. There were no differences between the recurrent patellar dislocation and control groups in terms of gender, side, and BMI. Although the patients in the control group were older than those in the study group, most patients in both groups were at or at least near skeletal maturity. Patellofemoral measurements were evaluated with the Insall-Salvati ratioextension, Blackburne-Peel ratioextension, Caton-Deschamps ratioextension, bisect offset index, lateral patellar tilt angle, tibial tubercle-trochlear groove, lateral trochlear inclination, sulcus depth, and sulcus angle. Intraclass correlation coefficients (ICCs) for all these measurements were greater than or equal to 0.70 and so were considered adequate for reliability. The correlations between patellar axial malalignment and other anatomic factors during weightbearing and nonweightbearing were compared, and anatomic factors between weightbearing and nonweightbearing were compared to investigate the relationship of patellar axial malalignment and anatomic factors during weightbearing. The correlation between anatomic factors and recurrent patellar dislocation and the diagnostic performance of each factor for recurrent patellar dislocation were reported to find the anatomic factor that most strongly correlated with recurrent patellar dislocation during weightbearing.

RESULTS

We observed several changes in axial malalignment measurements that occurred with weightbearing. The correlation between bisect offset index and Blackburne-Peel ratioextension decreased with weightbearing compared with the nonweightbearing state (r = 0.12 [95% confidence interval (CI) -0.12 to 0.35] with weightbearing versus r = 0.58 [95% CI 0.36 to 0.75]; p = 0.003). The correlation between bisect offset index and Caton-Deschamps ratioextension decreased with weightbearing compared with the nonweightbearing state (r = 0.25 [95% CI 0.03 to 0.47] versus r = 0.68 [95% CI 0.49 to 0.82]; p = 0.002). The correlation between bisect offset index and tibial tubercle-trochlear groove distance increased with weightbearing compared with the nonweightbearing state (r = 0.63 [95% CI 0.43 to 0.78] versus r = 0.38 [95% CI 0.05 to 0.62]; p = 0.04). The correlation between lateral patellar tilt angle and Blackburne-Peel ratioextension decreased with weightbearing compared with the nonweightbearing state (r = 0.05 [95% CI -0.17 to 0.28] versus r = 0.44 [95% CI 0.21 to 0.63]; p = 0.02). The correlation between the lateral patellar tilt angle and Caton-Deschamps ratioextension decreased with the weightbearing compared with the nonweightbearing state (r = 0.16 [95% CI -0.09 to 0.40] versus r = 0.46 [95% CI 0.19 to 0.66]; p = 0.04). The correlation between lateral patellar tilt angle and tibial tubercle-trochlear groove distance increased with weightbearing compared with the nonweightbearing state (r = 0.64 [95% CI 0.48 to 0.76] versus r = 0.41 [95% CI 0.13 to 0.64]; p = 0.048). Several parameters changed with weightbearing. In both recurrent patellar dislocation and control groups, the Insall-Salvati ratioextension and the tibial tubercle-trochlear groove distance were lower with weightbearing compared with nonweightbearing (recurrent patellar dislocation/control: p = 0.001/p < 0.001 versus p = 0.006/p < 0.001); bisect offset index was higher with weightbearing compared with nonweightbearing (recurrent patellar dislocation/control: p < 0.001/p < 0.001). In the control group, the Blackburne-Peel ratioextension and the Caton-Deschamps ratioextension were lower with weightbearing compared with nonweightbearing (p = 0.01, p = 0.007). The anatomic factor most strongly correlated with recurrent patellar dislocation during weightbearing was the bisect offset index (r = 0.73 [95% CI 0.65 to 0.79]; p < 0.001). The anatomic factor most strongly correlated with recurrent patellar dislocation during nonweightbearing was the sulcus depth (r = -0.70 [95% CI -0.78 to -0.59]; p < 0.001). The ROC analysis showed that during weightbearing, the bisect offset index had the best diagnostic ability for recurrent patellar dislocation (area under the curve [AUC] 0.93 [95% CI 0.89 to 0.97]), whereas when the patient was nonweightbearing, sulcus depth was the best predictor (AUC 0.91 [95% CI 0.85 to 0.96]).

CONCLUSION

Evaluations based on nonweightbearing examinations underestimated the interaction between the tibial tubercle-trochlear groove and patellar axial alignment, thus surgeons could consider weightbearing preoperative assessments for tibial tuberosity osteotomy to avoid failing to restore normal patellar axial alignment. Bisect offset index was an important indicator to improve detecting possible recurrent patellar dislocation in the state of functional activation of soft tissues and can estimate patellar tilt to simplify the preoperative evaluation procedure. For patients who are at high risk but who have not yet developed a patellar dislocation, assessing the risk of recurrent patellar dislocation with the bisect offset index during weightbearing can inform them about the intensity and manner of their daily exercise.

LEVEL OF EVIDENCE

Level III, prognostic study.

Heterogeneity in the use of osseous risk factors and limited use of relevant patient-reported outcome measurements in studies investigating treatment of patellar dislocation: A scoping review

PURPOSE

The treatment of patellar dislocation is tailored based on the presence or absence of osseous risk factors. The purpose of this scoping review was to investigate whether existing research addresses patient differences by mapping the use of osseous risk factors and patient-reported outcome measures (PROMs) in studies investigating the treatment of patellar dislocation.

METHODS

This study was a scoping review conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analysis extension for Scoping Reviews. Studies published between 1 January 2013 and 3 April 2023 were included if they investigated the treatment of patellar dislocation and registered osseous risk factor(s). Case series with fewer than 10 patients, reviews and meta-analyses were excluded.

RESULTS

A total of 8923 records were identified, of which 1007 articles underwent full-text screening, and 300 met the inclusion criteria. A twofold increase in articles investigating patellar dislocation treatment was observed between the years 2013 and 2022. This review identified 176 osseous risk factors and 56 PROMs. Among the included articles, 131 (44%) utilized osseous risk factors as in- or exclusion criteria, and 26 (9%) employed a PROM specifically developed for patellar instability evaluation. The most frequently investigated treatment was medial patellofemoral ligament reconstruction (231 articles, 77%), followed by tibial tubercle osteotomies (87 articles, 29%).

CONCLUSION

There is considerable heterogeneity among studies investigating the treatment of patellar dislocation. Less than half of studies define the patient population according to osseous risk factors, and only 1 in 10 studies use a PROM designed for patellar dislocation. This complicates the evaluation of treatment effects in relation to osseous risk factors.

LEVEL OF EVIDENCE

Level III.

Predictors and Early Treatment of Knee Arthrofibrosis After Arthroscopic Knee Ligament Reconstruction Surgery in Adolescent Patients

Background

Postoperative knee arthrofibrosis after arthroscopic ligament reconstruction is a serious complication. Among adolescents, risk factors for postoperative arthrofibrosis are not well characterized and the effectiveness of early manipulation under anesthesia (MUA) is not well established.

Purposes

To identify risk factors for arthrofibrosis after arthroscopic knee ligament reconstruction in adolescent patients and to evaluate the safety and effectiveness of early MUA.

Study Design

Case-control study; Level of evidence, 3.

Methods

The charts of all adolescent patients (<19 years of age) who underwent early MUA (<3 months) for knee stiffness after anterior cruciate ligament (ACL) or medial patellofemoral ligament (MPFL) reconstructions between 2008 and 2021 were retrospectively reviewed. Patients were matched 2:1 with patients without MUA from the same study period. The primary outcome was the final range of motion (ROM) after MUA. Logistic regression analysis was performed to identify predictors of MUA.

Results

A total of 25 patients (10 with ACL reconstruction and 15 with MPFL reconstruction) with a mean age of 14.8 ± 2.6 years were included for analysis. Overall, 44% were skeletally immature. Patients underwent MUA at a mean of 63.3 ± 19.5 days after the index surgery. The mean ROM improved significantly from 96.3°± 20.5° to 135°± 9.7° after MUA after a median follow-up of 8.1 months (interquartile range, 5.4-15.0 months). There were no complications associated with MUA, but 2 patients (8.0%) had MUA treatment failure. There were no differences in body mass index, type and frequency of associated procedures, or patellar height on lateral radiographs between the cohorts. The MUA cohort had statistically significant increased operative time, decreased preoperative motion, decreased ROM at 6 weeks postoperatively, and increased pain at 6 weeks postoperatively when compared with the non-MUA cohort. Regression analysis demonstrated that ROM at 6 weeks (OR: 0.83, 95% CI, 0.69-0.98, p = .034) was significantly associated with the need for MUA.

Conclusion

The findings of this study suggest that early (<3 months) MUA is safe and effective in treating knee arthrofibrosis in adolescent patients. MUA is a treatment alternative for patients with restricted ROM at 6 weeks that may help them recover full ROM.

Chronic Patellar Dislocation Treated With Extensive Lateral Release and Vastus Medialis Obliquus Advancement: A Case Report

The following case report demonstrates a case of a chronic irreducible patellar dislocation, age-indeterminate associated with a large medial patellar avulsion fracture that was treated with a vastus medialis obliquus advancement following an extensive lateral release. This case is the only known report of this kind in the literature. The patient is a 41-year-old Caucasian female who presented to the clinic with an age-indeterminate, chronically dislocated patella. She has a past medical history of hypertension and ischemic stroke 1 year prior to presentation, leading to expressive aphasia and lower extremity weakness in addition to patellar instability dating back to age 13. An unsuccessful patellofemoral reduction was performed at an outside clinic, and she was placed in a knee immobilizer and referred to our office. Clinically, the patient had limited knee range of motion with a fixed lateral patellar dislocation that was confirmed on imaging. This case report demonstrates a surgical reduction technique that can be utilized by orthopedic surgeons for chronic patellar dislocations that are not amenable to routine patellar instability surgeries due to the contraction of surrounding soft tissue, chronic bone abnormalities, and position of the chronic dislocation. An extensive lateral release followed by vastus medialis obliquus advancement was performed to center the patella within the trochlear groove and to allow for stable articulation throughout range of motion. The patient was able to regain painless, full range of motion of her knee postoperatively with patellar stability noted on both physical exam and radiographic imaging.

All-Suture Anchor Onlay Fixation for Medial Patellofemoral Ligament Reconstruction: A Biomechanical Comparison of Fixation Constructs

Background

The use of all-suture anchors (ASAs) for onlay patellar and femoral fixation of medial patellofemoral ligament (MPFL) grafts may provide clinical benefit, particularly in the small or pediatric knee; however, biomechanical data supporting the use of ASAs are lacking.

Purpose/Hypothesis

The purpose of this study was to compare ASAs to larger interference implants for MPFL reconstruction in a time-zero biomechanical model. It was hypothesized that ASAs would have comparable cyclic elongation to interference fixation and would exceed published biomechanical values for the native human MPFL.

Study Design

Controlled laboratory study.

Methods

Eighteen fresh-frozen porcine patellas and femurs were divided into equal groups (n = 9 per group) for MPFL reconstructions. Patellar fixation utilized two 3.9-mm interference suture anchors (ISAs) or two 2.6-mm ASAs, while femoral fixation utilized one 6×20-mm interference screw (IS) or one 2.6-mm ASA. Human gracilis tendon grafts were used. Specimens were dynamically loaded for 100 cycles each in sequential 5- to 30-N (phase 1) and 5- to 50-N (phase 2) blocks at 1 Hz followed by load-to-failure testing at 305 mm/min.

Results

No differences were found in cyclic elongation after phase 1 and phase 2 loading between ASA and interference implants on either the femoral or patellar side. On the femur, IS had significantly greater ultimate stiffness (54.2 vs 46.1 N/mm; P < .001) and ultimate load (366 vs 278 N; P = .019) compared to ASA. On the patella, ISAs had significantly greater ultimate stiffness (70.5 vs 53.1 N/mm; P < .001) but a significantly lower ultimate load (244 vs 307 N; P = .014) compared to ASAs. All groups significantly exceeded the published physiological values for native human MPFL stiffness and failure load.

Conclusion

ASA onlay fixation had comparable cyclic elongation to that of interference fixation for femoral and patellar MPFL reconstruction. Although differences in ultimate stiffness and ultimate load were noted between implants, all of the values exceeded published values for the human MPFL.

Clinical Relevance

This biomechanical study presents ASA cortical onlay fixation as a viable option for MPFL reconstruction. ASAs require less bone removal, potentially reducing the risk of patellar fracture and minimizing fixation complexity in the setting of open femoral growth plates. Future clinical studies will provide insight into successful tendon-to-bone healing, failure rates, and near- and long-term patient-reported outcomes.

The Benefits of a Rehabilitation Program Following Medial Patellofemoral Ligament Reconstruction

The medial patellofemoral ligament (MPFL) is critical for patellar stability. This study investigates the efficacy of a one-year physical therapy rehabilitation program following MPFL reconstruction using Synthetic Graft (SG) and Quadriceps Tendon Autograft (QTA). Thirty-five patients aged 18-38 underwent MPFL reconstruction (20 SG, 15 QTA). They participated in a structured rehabilitation program to improve their range of motion (ROM), muscle strength, pain management, and overall quality of life (QoL). The program included physiotherapy and MLS laser, Game Ready Therapy, EMS, TENS, TECAR, and lymphatic drainage. Before and after the program, assessments included knee flexion and extension using goniometry, muscle strength via the Medical Research Council (MRC) scale, knee circumference, pain intensity on the Visual Analogue Scale (VAS), and QoL with the EQ-5D instrument. Significant improvements were observed in knee flexion (37.57° vs. 114.71°, p < 0.001), muscle strength (MRC scale 1-4 points vs. 4-5 points, p < 0.001), and pain reduction (VAS 6.66 vs. 0.46, p < 0.001). The functional coefficient of mobility and QoL scores also markedly increased. Patients with QTA improved some parameters better than those with SG. These findings support the effectiveness of a comprehensive rehabilitation program in enhancing knee functionality, reducing pain, and improving QoL post-MPFL reconstruction. Personalized rehabilitation protocols are recommended to optimize recovery outcomes.

Decreased femoral trochlea axial orientation corrected by derotational distal femur osteotomy in patients with patellar dislocation yields satisfactory outcomes

PURPOSE

The femoral trochlea axial orientation has been shown to be a better predictor of patellar dislocation than the femoral anteversion angle. However, no study has investigated the importance of the femoral trochlea axial orientation in the surgical treatment of patellar dislocation. It is aimed to explore the pathological threshold of the femoral trochlea axial orientation and its guiding implications for surgical interventions in the study.

METHODS

Sixty-four patients with patellar dislocation and 64 controls were included for measurement of the femoral trochlea axial orientation. The ability to predict the patellar dislocation and the pathologic threshold of the femoral trochlea axial orientation were evaluated using the receiver operating characteristic curve. One hundred patients with medial patellofemoral ligament reconstruction and 25 patients with derotational distal femur osteotomy were divided into two groups based on the femoral trochlea axial orientation cut-off value and their postoperative knee functions, and patellar tilt angles were compared.

RESULTS

There were significant differences in the femoral trochlea axial orientation (60.8 ± 7.9 vs. 67.8 ± 4.6, p < 0.05) between patients with patellar dislocation and the normal population. The sensitivity and specificity of the femoral trochlea axial orientation were 0.641 and 0.813, respectively, at the femoral trochlea axial orientation smaller than 63.8°. Amongst patients having had isolated medial patellofemoral ligament reconstruction with decreased femoral trochlea axial orientation, knee function was poorer after surgery. The prognosis of patients with the femoral trochlea axial orientation correction in derotational distal femur osteotomy was better than that for patients without correction.

CONCLUSIONS

The femoral trochlea axial orientation had good predictive efficiency for patellar dislocation. Isolated medial patellofemoral ligament reconstruction is not sufficiently effective for patients with patellar dislocation and decreased femoral trochlea axial orientation. Patients with a decreased femoral trochlea axial orientation can have better surgical outcomes after correction by derotational distal femur osteotomy.

LEVEL OF EVIDENCE

Level III.

Patellar Lateralization, Absence of Joint Hypermobility, and the Mechanism of Injury Are Associated With Osteochondral Fracture After First-time Acute Lateral Patellar Dislocation in Adolescents: An MRI-based Evaluation

BACKGROUND

Although the risk factors for patellofemoral dislocation are clearly defined, risk factors for osteochondral fracture (OCF) after patellar dislocation are not as well defined. The aim of this study was to investigate the risk factors for OCF by evaluating patients with and without OCF after first-time acute patellar dislocation.

METHODS

This multicenter study was conducted as a retrospective examination of the radiologic measurements on the magnetic resonance imaging of 306 patients. The patients were divided into the OCF group and non-OCF group, and OCFs were grouped according to whether the fracture was in the patella or femur. Patellar height, patellar lateralization, trochlear morphology, patellofemoral matching, and patella types were evaluated on patient magnetic resonance imaging. The presence of joint hypermobility in the patients was determined according to the Beighton scale score. The injury mechanisms of the patients were grouped as sports-related injuries, injuries resulting from simple falls, and injuries during daily activities.

RESULTS

A total of 120 OCFs were detected in 108 (35.2%) patients, of which 96 (80%) were in the patella and 24 (20%) in the femur. The rate of OCF after sports-related injuries was found to be significantly higher than in other injury mechanisms ( P =0.001). More joint hypermobility was detected in patients without OCF ( P =0.041). The measurements of tibial tubercle-trochlear groove, tibial tubercle-posterior cruciate ligament distance and lateral patellar displacement were statistically higher in cases with OCF ( P =0.001). In patients with normal joint mobility, the rate of OCF localization in the patella was significantly higher ( P =0.035). No correlation was found between any other parameters and OCF ( P >0.05). The absence of joint hypermobility and the measurements of tibial tubercle-trochlear groove distance, tibial tubercle-posterior cruciate ligament distance, and lateral patellar displacement were independent risk factors for the incidence of OCF according to the logistic regression analysis.

CONCLUSIONS

The absence of joint hypermobility and patellar lateralization are independent risk factors for the occurrence of OCF after first-time patellar dislocation. Sports-related injury is a nonindependent risk factor for the presence of OCF. In patients with normal joint mobility, the incidence of OCF in the patella is higher than in the femur. These important factors should be considered when evaluating patients and starting their treatment.

LEVEL OF EVIDENCE

Level III-retrospective cohort study.

Medial Patellofemoral Ligament Reconstruction: A Case Report for an Integrated Rehabilitation Approach

Medial patellofemoral ligament (MPFL) reconstruction is a surgical treatment, primarily indicated for patients grappling with recurrent patellar instability stemming from traumatic injury or underlying anatomical anomalies. This abstract aims to elucidate the indispensable role of physiotherapy in the post-operative rehabilitation trajectory for individuals subjected to MPFL reconstruction. Physiotherapy emerges as a linchpin in securing a triumphant outcome, fostering the healing of patellar stability, augmentation of range of motion (ROM), and bolstering muscular strength while concurrently mitigating potential complications. The abstract accentuates salient facets of a physiotherapeutic regimen, encompassing prompt post-operative mobilization, meticulously tailored exercise paradigms, adept utilization of manual therapy modalities, and comprehensive patient education. Notably, this collaborative endeavor between orthopedic surgeons and physiotherapists is pivotal in optimizing patient convalescence, restoring them to their pre-injury functional acumen. A paramount emphasis is placed on individualized rehabilitation strategies, gradual and systematic exercise protocols, and patient adherence, thereby underscoring how the harmonious synergy between surgical and physiotherapeutic interventions augments the prospects of achieving a successful MPFL reconstruction outcome.

Patellar Dislocation: Workup and Decision-Making

Acute patellar dislocation (PD) is usually a problem of adolescents and young adults. In most cases, it is a sports-related injury. It is the result of an indirect force on the knee joint, which leads to valgus and external rotation of the tibia relative to the femur. PD is unlikely to occur on a knee with normal patellofemoral joint (PFJ) anatomy. Acute PD consists of an acute injury of the ligamentous medial patellar stabilizers in the background of factors predisposing to patellar instability. These factors are classified into three groups. The first group refers to the integrity of the ligamentous medial patellar restraints, particularly, the medial patellofemoral ligament (MPFL). The second group refers to an abnormal PFJ anatomy, which renders the patella inherently unstable inside the trochlea. The third group refers to the overall axial and torsional profile of the lower limb and to systemic factors, such as ligament laxity and neuromuscular coordination of movement. PD at a younger age is associated with an increased number and severity of patellar instability predisposing factors and lower stress to dislocate the patella. Acute primary PD is usually treated conservatively, while surgical treatment is reserved for recurrent PD. The aim of treatment is to restore the stability and function of the PFJ and to reduce the risk of patellar redislocation. Surgical procedures to treat patellar instability are classified into non-anatomic and anatomic procedures. Non-anatomic procedures are extensor mechanism realignment techniques that aim to center the patella into the trochlear groove. Anatomic procedures aim to restore the PFJ anatomy (ruptured ligaments, osteochondral fractures), which has been severed after the first incident of PD. Anatomic procedures, especially MPFL reconstruction, are more effective in preventing recurrent PD, compared with non-anatomic techniques. Theoretically, all factors that affect PFJ stability should be evaluated and, if possible, addressed. This is practically impossible. Considering that the MPFL ruptures in almost all PDs, MPFL reconstruction is the primary procedure, which is currently selected by most surgeons as a first-line treatment for patients with recurrent PD. Restoration of the axial and torsional alignment of the lower limbs is also increasingly implemented by surgeons. Non-anatomic surgical techniques, such as tibial-tuberosity osteotomy, are used as an adjunct to anatomic procedures. In the presence of multiple PFJ instability factors, acute MPFL reconstruction may be the treatment of choice for acute primary PD as well. Skeletal immaturity of the patient precludes osseous procedures to avoid premature physis closure and subsequent limb deformity. Unfortunately, restoration of the patient's previous activity level or participation in more strenuous sports is questionable and not easy to predict. In the case of competitive athletes, PD may prevent participation in elite levels of sports.

The influence of primary treatment approach on outcomes in patients with osteochondral fracture after patellar dislocation: a case series

BACKGROUND

We characterized the relation of primary treatment approaches to the need of later surgical interventions and the outcomes of patellar dislocation in patients with patellofemoral osteochondral fracture (OCF).

METHODS

Overall, 134 patients with OCF were categorized in two groups according to treatment approach: primary surgery (operation within 90 days from injury) and conservative treatment. Data on surgical procedures, OCF characteristics, and patellofemoral anatomy were retrospectively collected. To measure subjective outcomes, 54 patients completed the knee-specific patient-reported outcome measures (PROMs) Kujala score, Tegner activity scale, the knee injury and osteoarthritis outcome score (KOOS) quality of life (QoL) subscale, and visual analog scale pain items.

RESULTS

The mean follow-up time was 4.9 years [standard deviation (SD) 2.7 years]. The primary treatment approach was surgery in 73 patients (54%) and conservative in 61 patients (46%) of whim 18 (30%) needed late surgery. Of primary surgery patients, the OCF was reimplanted in 45 patients (62%) and removed in the rest. Of all patients, 31 needed surgery in the later phase after the primary treatment approach (either reoperation or surgery after insufficient outcome of conservative treatment). In conservatively treated patients, OCF was smaller and patellofemoral joint malformation was more severe than in surgery group. Among patients who completed the PROMs, the outcomes appeared generally acceptable in both groups.

CONCLUSIONS

Although a majority of the primary treatment approaches for OCF after patellar dislocation were definitive, one-fourth of patients required surgery in the later phase. PROMs did not indicate major differences between the study groups.

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.

Biomechanical Comparison of 3 Medial Patellofemoral Complex Reconstruction Techniques Shows Medial Overconstraint but No Significant Difference in Patella Lateralization and Contact Pressure

PURPOSE

The purpose of this study was to investigate biomechanical differences of medial patellofemoral ligament (MPFL) reconstruction, medial quadriceps tendon femoral ligament (MQTFL) reconstruction, and a combination of these techniques to restore lateral patellar constraint and contact pressures.

METHODS

Eight fresh frozen cadaver knees were mounted to a custom jig with physiological quadriceps tendon loading. Flexion angles and contact pressure (CP) were dynamically measured using Tekscan® pressure sensors and Polhemus® Liberty 6 degree of freedom (6DOF) positioning sensors in the following conditions: 1) intact 2) MPFL and MQTFL deficient, 3) MPFL reconstructed, 4) Combined MPFL + MQTFL reconstructed, and 5) MQTFL reconstructed. Lateral patellar translation was tested using horizontally directed 30 N force applied at 30° of knee flexion. The knees were flexed in dynamic fashion, and CP values were recorded for 10°, 20°, 30°, 50°, 70°, and 90° degrees of flexion. Group differences were assessed with ANOVA's followed by pairwise comparisons with Bonferroni correction.

RESULTS

MPFL (P = .002) and combined MPFL/MQTFL (P = .034) reconstruction significantly reduced patellar lateralization from +19.28% (9.78%, 28.78%) in the deficient condition to -17.57% (-27.84%, -7.29%) and -15.56% (-33.61%, 2.30%), respectively. MPFL reconstruction was most restrictive and MQTFL reconstruction the least -7.29% (-22.01%, 7.45%). No significant differences were found between the three reconstruction techniques. Differences in CP between the three reconstruction techniques were not significant (<.02 MPa) at all flexion angles.

CONCLUSION

The present study found no significant difference for patellar lateralization and patellofemoral CP between MPFL, combined MPFL/MQTFL, and MQTFL reconstruction. All 3 techniques resulted in stronger lateral patellar constraint compared to the native state, while the MQTFL reconstruction emulated the intact state the closest.

CLINICAL RELEVANCE

Various surgical techniques for medial patellofemoral complex reconstruction can restore patellar stability with similar patellofemoral articular pressures.

Complication Rates After Medial Patellofemoral Ligament Reconstruction Range From 0% to 32% With 0% to 11% Recurrent Instability: A Systematic Review

PURPOSE

To review the incidence of complications following primary medial patellofemoral ligament (MPFL) reconstruction for recurrent patellar instability.

METHODS

A literature search was conducted by querying PubMed and Scopus databases from database inception through August 2022 according to the 2020 Preferred Reporting Items for Systematic Review and Meta-analysis guidelines using the terms "Medial Patellofemoral Ligament," "MPFL," "reconstruction," "patellar," and "instability." Inclusion criteria included studies reporting complications following primary MPFL reconstruction for recurrent patellar instability. Exclusion criteria consisted of studies reporting on patients undergoing concurrent osteotomy procedures, revision reconstruction, and biomechanical or anatomic studies. The incidence of specific complications was aggregated from the included studies.

RESULTS

Twenty-eight studies, consisting of 1,478 patients (n = 1521 knees), with a mean age of 23.3 years (mean range, 19-34.3 years) were identified. The overall incidence of complications ranged from 0% to 32.3% of knees. Failure ranged from 0% to 10.7% of knees, whereas patellar fractures occurred in 0% to 8.3% of knees, primarily in patients treated with full-length transverse tunnel or 2-tunnel techniques. All patellar fractures occurred in patients with patellar tunnels ranging from 4.5 to 6.0 mm in diameter. The incidence of postoperative knee stiffness/range of motion deficit ranged from 0% to 20%. Persistent anterior knee pain, ranged from 0% to 32.3%.

CONCLUSIONS

Complications following primary MPFL reconstruction ranged from 0% to 32.3% of knees, primarily consisting of residual anterior knee pain. Failure ranged from 0% to 10.7% of knees, whereas patellar fractures were reported in 0% to 8.3% of knees. Fractures primarily occurred with a full-length transverse tunnel or 2-tunnel techniques, whereas all fractures occurred with patellar tunnels ranging from 4.5 mm to 6.0 mm in diameter.

LEVEL OF EVIDENCE

IV; Systematic Review of Level I-IV studies.

Prediction of Subsequent Contralateral Patellar Dislocation after First-Time Dislocation Based on Patellofemoral Morphologies

The subsequent dislocation of a contralateral patellofemoral joint sometimes occurs after a first-time lateral patellar dislocation (LPD). However, the anatomic risk factors for subsequent contralateral LPD remain elusive. This study included 17 patients with contralateral LPD and 34 unilateral patellar dislocators. The anatomic parameters of the contralateral patellofemoral joints were measured using CT images and radiographs that were obtained at the time of the first dislocation. The Wilcoxon rank-sum test was performed, and a binary regression model was established to identify the risk factors. The receiver operating characteristic curves and the area under the curve (AUC) were analyzed. The tibial tubercle-Roman arch (TT-RA) distance was significantly different between patients with and without contralateral LPD (24.1 vs. 19.5 mm, p < 0.001). The hip−knee−ankle (HKA) angle, patellar tilt, congruence angle, and patellar displacement were greater in the study group than in the control group (p < 0.05). The TT-RA distance revealed an OR of 1.35 (95% CI (1.26−1.44]), p < 0.001) and an AUC of 0.727 for predicting contralateral LPD. The HKA angle revealed an OR of 1.74 (95% CI (1.51−2.00), p < 0.001) and an AUC of 0.797. The Patellar tilt, congruence angle, and patellar displacement had AUC values of 0.703, 0.725, and 0.817 for predicting contralateral LPD, respectively. In conclusion, the contralateral patellofemoral anatomic parameters were significantly different between patients with and without subsequent contralateral LPD. Increased TT-RA distance and excessive valgus deformity were risk factors and could serve as predictors for contralateral LPD. At first-time dislocation, the abnormal position of the patella relative to the trochlea may also be an important cause of subsequent LPD.

Outcomes following the operative treatment of intra-articular fracture combined with medial patellofemoral ligament reconstruction after patellar dislocation

Purpose

We examine the outcomes following operative treatment of intra-articular fracture combined with medial patellofemoral ligament (MPFL) reconstruction after patella dislocation.

Methods

Patients were retrospectively identified from medical records using diagnostic and surgical procedure codes. Radiological anatomical parameters and bony abnormalities of injured knees were assessed from magnetic resonance images (MRI). Inclusion criteria were traumatic patellar dislocation with chondral or osteochondral fracture and MPFL rupture, operative treatment of a chondral or osteochondral fracture combined with MPFL reconstruction, and minimum follow-up of 2 years. Outcomes were measured using the Kujala score, Tegner activity scale, and the Knee injury and Osteoarthritis Outcome Score Quality-of-Life subscale (KOOS-QLS).

Results

During 2012 and 2015, 322 patients were treated because of patellar dislocation. Thirty-three patients had chondral or osteochondral fracture. Eleven patients (five males and six females) with a mean [standard deviation (SD)] age of 17.0 (6.5) years at the time of surgery met the inclusion criteria and were included. Five of the 11 patients had a subchondral and six an osteochondral fracture. Eight patients had a fracture in the patella and three in the femur. All patients had bony abnormalities in the knee. Nine out of 11 patients scored over 90/100 points on the Kujala scale and had good results on the Tegner scale [before surgery 5.0 (2.7) points versus after surgery 5.3 (1.6) points] and the KOOS-QLS [4.1 (4.2) points] outcome measures.

Conclusion

The removal or fixation of the fracture fragment combined with MPFL reconstruction is a feasible option in the treatment of symptomatic osteochondral or subchondral fragment in traumatic patellar dislocation. The short-term outcomes are encouraging.

Level of evidence: Level IV, retrospective case series.

Axial orientation of the femoral trochlea is superior to femoral anteversion for predicting patellar instability

PURPOSE

The femoral anteversion angle is considered to be the same as femoral torsion; however, the femoral anteversion angle is strongly influenced by the femoral posterior condylar morphology. It remains unclear whether the femoral anteversion angle and axial orientation of the femoral trochlea can predict patellar instability. This study aimed to redefine the femoral inherent torsion, verify whether the femoral anteversion angle reflects the femoral inherent torsion, and compare the validity and calculate the cut-off values of the femoral anteversion angle and femoral trochlear axial orientation for predicting patellar instability.

METHODS

Seventy-three patients with patellar instability and 73 matched controls underwent computed tomography to measure the femoral anteversion angle, femoral inherent torsion, and femoral trochlear axial orientation. Pearson's product moment correlation coefficients and linear regression were calculated to determine correlations between measurements. Receiver operating characteristic curves and nomograms were plotted to evaluate the predictive validity of the femoral anteversion angle and femoral trochlear axial orientation for patellar instability.

RESULTS

All measurements showed excellent intra- and inter-observer reliability. Compared with the control group, the patellar instability group had a significantly larger femoral anteversion angle (25.4 ± 6.4° vs. 20.2 ± 4.5°) and femoral inherent torsion (18.3 ± 6.7° vs. 15.8 ± 3.4°), and significantly smaller femoral trochlear axial orientation (58.1 ± 7.3° vs. 66.9 ± 5.1°). The femoral anteversion angle and femoral trochlear axial orientation had area under the receiver operating characteristic curve values of 79 and 84%, respectively, and cut-off values of 24.5° and 62.7°, respectively. The calibration curve and decision curve analysis showed that the femoral trochlear axial orientation performed better than the femoral anteversion angle in predicting patellar instability. There was a strong correlation between the femoral anteversion angle and femoral inherent torsion (r > 0.8). Linear regression analysis of the femoral inherent torsion with the femoral anteversion angle as the prediction variate showed moderate goodness-of-fit (adjusted R² = 0.69).

CONCLUSION

The femoral anteversion angle moderately reflects the femoral inherent torsion. The femoral trochlear axial orientation is better than the femoral anteversion in predicting patellar instability in terms of predictive efficiency, consistency with reality, and net clinical benefit. These findings warn orthopaedists against overstating the role of the femoral anteversion angle in patellar instability, and suggest that the femoral trochlear axial orientation could aid in identifying at-risk patients and developing surgical strategies for patellar instability.

LEVEL OF EVIDENCE

III.

Age, body mass index, female gender, and patellofemoral cartilage degeneration predict worse patient outcome after patellofemoral instability surgery

PURPOSE

To evaluate predicting factors for patient-reported outcomes and revision interventions following surgical treatment of patients with patellofemoral instability.

METHODS

From a prospective database at the university Orthopedic Department, 138 knees from 116 patients who underwent patellofemoral instability surgery (2012-2019) were enrolled in a retrospective analysis: 34 cases of isolated MPFLrec; 92 cases of MPFLrec plus tibial tuberosity transfer; and 12 cases of MPFLrec plus trochleoplasty. Patient-reported outcome measures were recorded for knee-specific function (KOOS), general quality of life (EQ-5D), and activity level (Tegner scale). Post-operative revision interventions were also actively recorded. As potential predicting factors, patient demographic (gender, age, BMI) and radiographic (pre-operative: patellar height and tilt, tibial tuberosity-trochlear groove distance, trochlear dysplasia, knee osteoarthritis; post-operative: MPFL insertion point; intra-operative: isolated vs. combined procedures, chondropenia severity score) parameters were analyzed using multivariate linear regression models.

RESULTS

With median follow-up of 4.4 (1.0-8.9) years, all patient-reported outcome measures had significantly improved from pre-operative levels: KOOS cumulative, from 71 (15) to 78 (16); EQ-5D, from 0.68 (0.20) to 0.78 (0.21); and Tegner activity scale, from 3 (0-10) to 4 (0-10). No patellofemoral instability revision procedures were performed. One-fifth (27/138) of the operated knees required second surgical interventions, predominately due to hardware or arthrofibrosis. Patients who required post-operative knee manipulation under anesthesia or arthroscopic debridement showed lower post-operative improvement for KOOS cumulative and EQ-5D. Age, BMI, patellofemoral knee osteoarthritis, and shorter follow-up time revealed significant negative correlations to some of the post-operative KOOS subscales. Age was negatively correlated to post-operative EQ-5D, while post-operative Tegner activity scale was negatively correlated to female gender and patellofemoral chondropenia severity score. Femoral MPFL insertion point revealed no association with any outcome measures.

CONCLUSION

Patellofemoral instability surgery for isolated or combined MPFLrec is safe and substantially improves knee function and patient quality of life and activity levels. Serious adverse events are rare, with no recurrent patellofemoral instability. Patients who required post-operative knee manipulation or arthroscopic debridement showed less improvement in subjective measures of treatment outcomes. Older age, higher BMI, worse pre-operative patellofemoral cartilage status, and female gender had negative effects on outcome.

LEVEL OF EVIDENCE

III.

The tibial tubercle-posterior cruciate ligament (TT-PCL) distance does not truly reflect the lateralization of the tibial tubercle

PURPOSE

The role of the tibial tubercle-posterior cruciate ligament (TT-PCL) and tibial tubercle-trochlear groove (TT-TG) in recurrent patellar instability (RPI) remains unclear. This study aims to confirm the validity of the TT-TG and TT-PCL in predicting RPI and to verify whether the TT-PCL can truly reflect the lateralization of the tibial tubercle.

METHODS

A total of 50 patients with RPI and 50 controls were recruited and underwent magnetic resonance imaging examinations. The TT-TG, TT-PCL, and tibial tubercle lateralization (TTL) were measured independently by two authors in a blinded and randomized fashion. T-test was used for parametric variances and the Mann-Whitney U and Chi-square tests were used for non-parametric variances. Pearson's product moment correlation coefficients were calculated to determine correlations between the defined measurements. The intraclass correlation coefficient was used to assess the reliability of the measurements.

RESULTS

All defined measurements showed excellent intra- and inter-observer reliability. The TT-TG distance, TT-PCL distance, and TTL were significantly greater in the PI group than in the control group. The AUC was highest for the TT-TG distance compared with that for the TT-PCL distance, and TTL were 0.798, 0.764, and 0.769, with the calculated cut-off value of 12.5 mm, 16.5 mm, and 66.1 percentages. There was a moderate correlation (r = 0.595) between the TT-TG distance and TTL, and a weak correlation (r = 0.430) between the TT-PCL distance and TTL.

CONCLUSION

Both the TT-TG distance and TT-PCL distance can be measured with excellent reliability on magnetic resonance imaging. The TT-TG distance, rather than the TT-PCL distance, has a better performance in predicting RPI. Most interestingly, the TT-PCL distance cannot reflect the real lateralization of TT. This study provides new information to evaluate TTL in patients with RPI.

LEVEL OF EVIDENCE

III.

Increased tibial tubercle-trochlear groove and patellar height indicate a higher risk of recurrent patellar dislocation following medial reefing

PURPOSE

Identifying anatomical risk factors on recurrent dislocation after medial reefing is important for deciding surgical treatment. The present study aimed to retrospectively analyze the preoperative magnetic resonance imaging (MRI)-based parameters of patients treated with medial reefing and whether these parameters lead to a higher risk of recurrent dislocation.

METHODS

Fifty-five patients (18.6 ± 6.6 years) who underwent medial reefing after primary traumatic patellar dislocation (84% with medial patellofemoral ligament [MPFL] rupture) were included. Patients were followed up for at least 24 months postoperatively (3.8 ± 1.2 years) to assess the incidence of recurrent patellar dislocation. In patients without recurrent dislocation, the Kujala and subjective IKDC scores were assessed. Moreover, the tibial tubercle-trochlear groove (TT-TG), sulcus angle, patellar tilt, patellar shift, and lateral trochlea index (LTI) were measured. The patellar height was measured using the Caton-Dechamps (CDI), Blackburne-Peel (BPI), and Insall-Salvati index (ISI). The cohort was subclassified into two groups with and without recurrent dislocation. Differences between groups were analyzed with respect to the MRI parameters.

RESULTS

Forty percent had a pathological sulcus angle of > 145°, 7.2% had an LTI of < 11°, 47.3% had a patellar tilt of > 20°, and 36.4% had a TT-TG of ≥ 16 mm. Increased patellar height was observed in 34.5, 65.5, and 34.5% of the patients as per CDI, BPI, and ISI, respectively. Nineteen (34.5%) patients suffered from recurrent dislocation. Compared with patients without recurrent dislocation, those with recurrent dislocation had a significantly lower LTI (p = 0.0467). All other parameters were not significantly different between the groups. Risk factor analysis showed higher odds ratios (OR > 2), although not statistically significant, for MPFL rupture (OR 2.05 [95% confidence interval 0.38-11.03], LTI (6.6 [0.6-68.1]), TT-TG (2.9 [0.9-9.2]), and patellar height according to ISI (2.3 [0.7-7.5]) and CDI (2.3 [0.7-7.5])). Patients without recurrent dislocation had a Kujala score of 93.7 ± 12.1 (42-100) points and an IKDC score of 90.6 ± 11.7 (55.2-100) points.

CONCLUSION

Anatomical, MRI-based parameters should be considered before indicating medial reefing. A ruptured MPFL, an LTI < 11°, a TT-TG ≥ 16 mm, a patellar tilt > 20 mm, and an increased patellar height according to ISI and CDI were found to be associated, although not significantly, with a higher risk (OR > 2) of recurrent patellar dislocation after medial reefing. Thorough preoperative analysis is crucial to reduce the risk of recurrent dislocation in young patient cohorts.

LEVEL OF EVIDENCE

Level IV.

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.

Patients unable to return to play following medial patellofemoral ligament reconstructions demonstrate poor psychological readiness

PURPOSE

Medial patellofemoral ligament reconstruction (MPFLR) is often indicated in athletes with lateral patellar instability to prevent recurrence and allow for a successful return to play. In this patient population, the ability to return to play is one of the most important clinical outcomes. The purpose of the current study was to analyze the characteristics of patients who were unable return to play following MPFL reconstruction.

METHODS

A retrospective review of patients who underwent MPFL reconstruction and subsequently did not return to play after a minimum of 12-months of follow-up was performed. Patients were evaluated for their psychological readiness to return to sport using the MPFL-Return to Sport after Injury (MPFL-RSI) score, which is a modification of the ACL-RSI score. A MPFL-RSI score > 56 is considered a passing score for being psychologically ready to return to play. Additionally, reasons for not returning to play including Visual Analog Scale for pain (VAS), Kujala score, satisfaction, and recurrent instability (including dislocations and subluxations) were evaluated.

RESULTS

The study included a total of 35 patients who were unable to return to play out of a total cohort of 131 patients who underwent MPFL reconstruction as treatment for patellar instability. Overall, 60% were female with a mean age of 24.5, and a mean follow-up of 38 months. Nine patients (25.7%) passed the MPFL-RSI benchmark of 56 with a mean overall score of 44.2 ± 21.8. The most common primary reasons for not returning to play were 14 were afraid of re-injury, 9 cited other lifestyle factors, 5 did not return due to continued knee pain, 5 were not confident in their ability to perform, and 2 did not return due to a feeling of instability. The mean VAS score was 1.9 ± 2.3, the mean Kujala score was 82.5 ± 14.6, and the mean satisfaction was 76.9%. Three patients (8.7%) reported experiencing a patellar subluxation event post-operatively. No patient sustained a post-operative patellar dislocation.

CONCLUSION

Following MPFL reconstruction, patients that do not return to play exhibit poor psychological readiness with the most common reason being fear of re-injury.

LEVEL OF EVIDENCE

IV.

[A rare cause of an acutely locked knee joint: superior patellar dislocation]

The case of a 56-year-old male patient with locking of the knee in extension without trauma is presented. Patient history, clinical examination and radiographs confirmed a superior dislocation of the patella. Closed reduction led to full weight bearing with free range of motion without further complaints. Knowledge of this uncommon cause of a locked knee joint leads to immediate treatment avoiding complex imaging modalities, such as computed tomography (CT) or magnetic resonance imaging (MRI). No further treatment was necessary in the majority of the cases published in the literature.