Patellofemoral dysbalance and genua valga: outcome after femoral varisation osteotomies

Tibial tuberosity-trochlear groove distance is significantly decreased by medial closing wedge distal femoral osteotomy

PURPOSE

While medial closing wedge distal femoral osteotomy (MCWDFO) has been used to address patella instability combined with valgus malalignment, its impact on patellofemoral parameters remains uncharted. Hence, this study seeks to establish a three-dimensional (3D) planning of MCWDFO and measure its effect on the tibial tubercle - trochlear groove distance (TTTG) through simulation and calculation.

METHODS

MCWDFO with a stepwise increment of one-degree varisation (1°-15°) was performed on 3D surface models of 14 lower extremities with valgus malalignment and 24 lower extremities with neutral alignment of the lower limb, resulting in a total of 608 simulations. Anatomic landmarks were employed to measure hip-knee-ankle angle (HKA), TTTG, and femoral torsion for each simulation. A mathematical formula was adopted to calculate TTTG changes following MCWDFO, and subsequently the mean simulated and calculated TTTG values were compared. Following a standardised protocol, MCWDFO was performed without rotational changes.

RESULTS

MCWDFO exhibited an almost linear reduction in TTTG, at a rate of approximately -1.05 ± 0.13 mm per 1° of varisation, demonstrating a strong negative correlation (R = -0.83; p < 0.001). Limb alignment did not exert an influence on TTTG change; however, it correlated with tibial plateau width. The mean difference between the simulated and calculated TTTG values amounted to 0.03 ± 0.03 mm per 1° varisation (p < 0.001).

CONCLUSION

The TTTG distance is linearly reduced by 1.05 mm for every 1° of varisation within the varus correction range of 0°-15° during MCWDFO. Patients with combined valgus and patellar instability may benefit from MCWDFO due to frequently pathological TTTG.

LEVEL OF EVIDENCE

Level III, descriptive laboratory study.

Additional Plate Fixation of Hinge Fractures After Varisation Distal Femoral Osteotomies Provides Favorable Torsional Stability: A Biomechanical Study

BACKGROUND

Hinge fractures are considered risk factors for delayed or nonunion of the osteotomy gap in distal femoral osteotomies (DFOs). Limited evidence exists regarding the treatment of hinge fractures after DFO, which could improve stability and thus bone healing.

PURPOSE

To (1) examine the effect of hinge fractures on the biomechanical properties of the bone-implant construct, (2) evaluate the biomechanical advantages of an additional fixation of a hinge fracture, and (3) test the biomechanical properties of different types of varisation DFOs.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 32 fresh-frozen human distal femora equally underwent medial closing wedge DFO or lateral opening wedge DFO using a unilateral locking compression plate. The following conditions were serially tested: (1) preserved hinge; (2) hinge fracture along the osteotomy plane; (3) screw fixation of the hinge fracture; and (4) locking T-plate fixation of the hinge fracture. Using a servo-hydraulic materials testing machine, we subjected each construct to 15 cycles of axial compression (400 N; 20 N/s) and internal and external rotational loads (10 N·m; 0.5 N·m/s) to evaluate the stiffness. The axial and torsional hinge displacement was recorded using a 3-dimensional optical measuring system. Repeated-measures 1-way analysis of variance and post hoc Bonferroni correction were used for multiple comparisons. Statistical significance was set at P < .05.

RESULTS

Independent from the type of osteotomy, a fractured hinge significantly (P < .001) increased rotational displacement and reduced stiffness of the bone-implant construct, resulting in ≥1.92 mm increased displacement and ≥70% reduced stiffness in each rotational direction, while the axial stiffness remained unchanged. For both procedures, neither a screw nor a plate could restore intact rotational stiffness (P < .01), while only the plate was able to restore intact rotational displacement. However, the plate always performed better compared with the screw, with significantly higher and lower values for stiffness (+38% to +53%; P < .05) and displacement (-55% to -72%; P < .01), respectively, in ≥1 rotational direction. At the same time, the type of osteotomy did not significantly affect axial and torsional stability.

CONCLUSION

Hinge fractures after medial closing wedge DFO and lateral opening wedge DFO caused decreased bone-implant construct rotational stiffness and increased fracture-site displacement. In contrast, the axial stiffness remained unchanged in the cadaveric model.

CLINICAL RELEVANCE

When considering an osteosynthesis of a hinge fracture in a DFO, an additional plate fixation was the construct with the highest stiffness and least displacement, which could restore intact hinge rotational displacement.

Distal femoral torsion is correlated with higher-grade trochlear dysplasia and shorter anterior condyles in patients with patellar dislocation and increased femoral torsion

PURPOSE

To describe the characteristics of femoral torsion in patients with different segmental torsion types and to evaluate the correlations between segmental torsion and the morphology of the femoral condyles and trochlea in patients with patellar dislocation and increased femoral torsion.

METHODS

Between January 2021 and March 2023, 69 patients were included and classified into two groups according to the femoral segment contributing the most to total torsion: 32 patients in Group A (femoral neck and shaft torsion) and 37 patients in Group B (distal torsion). Trochlear dysplasia was evaluated using Dejour's classification and sulcus angle. The morphology of the femoral condyles was evaluated using the lengths and ratios of the medial and lateral condyles. Correlations between femoral torsion and morphology were evaluated.

RESULTS

Total torsion was significantly correlated with femoral neck and shaft torsion (r = 0.882, P < 0.001) and distal torsion (r  = 0.262, P = 0.030). Femoral neck and shaft torsion was significantly increased with increasing total torsion. The trochlear sulcus was flatter and more dysplastic, and the anterior condyles were shorter in Group B. Distal torsion was significantly correlated with the lengths of the medial and lateral anterior condyles (r  = - 0.567, P < 0.001; r = -0.701, P < 0.001), sulcus angle (r  = 0.611, P < 0.001) and Dejour trochlea type (r  = 0.512, P = 0.001), while femoral neck and shaft torsion showed no correlations.

CONCLUSION

Femoral torsion is a complex of femoral neck and shaft torsion and distal torsion, especially femoral neck and shaft torsion. Distal torsion was significantly correlated with a flatter trochlear sulcus, higher-grade trochlear dysplasia, and shorter anterior condyles. The new findings highlighted the importance of the segmental evaluation of femoral torsion, which would facilitate understanding of the anatomical characteristics of femoral torsion in patients with patellar dislocation and increased femoral torsion and may lead to improvement in the surgical options regarding femoral torsion.

LEVEL OF EVIDENCE

Level III.

[Periarticular knee osteotomies for pre-arthritic deformities in the frontal plane : Indications and surgical techniques]

BACKGROUND

Currently, periarticular knee joint osteotomies are an integral part of the treatment of early arthritic deformities in the knee joint.

DIAGNOSTICS

Analysis of the deformity is performed with a standardized full-leg standing x‑ray of both legs, as well as a lateral x‑ray of the knee joint that includes 2/3 of the proximal tibial shaft. An MRI examination of the knee joint is obtained to assess the articular cartilage, the ligaments and menisci. Torsion angle measurements with the CT/MRT supplement the diagnostics if necessary. Knowledge of normal physiological values and their standard deviations of the mechanical leg axis and the joint angles around the knee is obligatory.

THERAPY

The osteotomy is performed as close as possible to the femoral and/or tibial deformity. Postsurgical deformities including pathological patella position or a significant difference in leg length must be prevented. A description of proximal tibia opening or closing wedge osteotomies based on the nomenclature of the joint angles by Paley is presented. The indications for the various osteotomy techniques in the coronary plane are discussed in detail.

Finite element analysis of medial closing and lateral opening wedge osteotomies of the distal femur in relation to hinge fractures

PURPOSE

Intraoperative hinge fractures in distal femur osteotomies represent a risk factor for loss of alignment and non-union. Using finite element analysis, the goal of this study was to investigate the influence of different hinge widths and osteotomy corrections on hinge fractures in medial closed-wedge and lateral open-wedge distal femur osteotomies.

METHODS

The hinge was located at the proximal margin of adductor tubercle for biplanar lateral open-wedge and at the upper border of the lateral femoral condyle for biplanar medial closed-wedge distal femur osteotomies, corresponding to optimal hinge positions described in literature. Different hinge widths (5, 7.5, 10 mm) were created and the osteotomy correction was opened/closed by 5, 7.5 and 10 mm. Tensile and compressive strain of the hinge was determined in a finite element analysis and compared to the ultimate strain of cortical bone to assess the hinge fracture risk.

RESULTS

Doubling the correction from 5 to 10 mm increased mean tensile and compressive strain by 50% for lateral open-wedge and 48% for medial closed-wedge osteotomies. A hinge width of 10 mm versus 5 mm showed increased strain in the hinge region of 61% for lateral open-wedge and 32% for medial closed-wedge osteotomies. Medial closed-wedge recorded a higher fracture risk compared to lateral open-wedge osteotomies due to a larger hinge cross-section area (60-67%) for all tested configurations. In case of a 5 mm hinge, medial closed-wedge recorded 71% higher strain in the hinge region compared to lateral open-wedge osteotomies.

CONCLUSION

Due to morphological features of the medial femoral condyle, finite element analysis suggests that lateral-open wedge osteotomies are the preferable option if larger corrections are intended, as a thicker hinge can remain without an increased hinge fracture risk.

The Impact of Anatomical Predisposition and Mechanism of Trauma on Dislocation of the Patella: A Retrospective Analysis of 104 Cases

BACKGROUND

The aim of this study was to determine whether traumatic dislocation of the patella is provoked by the presence of predisposing factors and examine the role of the mechanism of injury.

METHODS

Cases diagnosed with dislocation of the patella and covered by the workers' compensation program were identified and classified as traumatic based on insurance regulations. We examined predisposing factors (e.g., frontal axis, torsional deviation, trochlear dysplasia, patella alta) in case groups based on age at dislocation and trauma mechanism. Retrospective cohort study, level of evidence III.

RESULTS

Our sample size comprised 104 cases, consisting of 54 children and 50 adults. The most common mechanism of injury in children and adults was rotational trauma. Only 20% of the children and 21% of the adults exhibited no relevant predisposing factors. Group specifically, falls accounted for the highest number of cases exhibiting none of the defined anatomical predisposing factors. Children are more frequently affected by predisposition-related dislocations than adults.

CONCLUSION

The proportion of predispositions is high. A fall, direct impact, or rotational trauma can be viewed as an adequate mechanism of trauma. For successful treatment, it is paramount to analyze the exact mechanism of the trauma and address any underlying predispositions.

The Influence of Surgical Realignment Procedures on Dynamic Patellar Tracking: A Dynamic Magnetic Resonance Imaging-Controlled Feasibility Study

Persisting patellar maltracking following surgical realignment often remains unseen. The aim of this study was to analyze the effects of realignment procedures on patellofemoral kinematics in patients with patellofemoral instability (PFI) and patellofemoral maltracking (PM) by using dynamic magnetic resonance imaging (MRI). Patients planned for surgical patellar realignment due to PFI and a clinically and radiologically apparent PM between December 2019 and May 2022 were included. Patients without PM, limited range of motion, joint effusion, or concomitant injuries were excluded. Dynamic mediolateral translation (dMPT) and patella tilt (dPT) were measured preoperatively and three months postoperatively. In 24 patients (7 men, 17 women; mean age 23.0 years), 10 tibial tubercle transfers, 5 soft tissue patella tendon transfers, 6 trochleoplasties, 3 lateral lengthenings, 1 varizating distal femoral osteotomy (DFO), and 1 torsional DFO were performed. At final follow-up, dMPT (from 10.95 ± 5.93 mm to 4.89 ± 0.40 mm, p < 0.001) and dPT (from 14.50° ± 10.33° to 8.44° ± 7.46°, p = 0.026) were significantly improved. All static radiological parameters were corrected to physiological values. Surgical patellar realignment contributed to the significant improvement of patellofemoral kinematics, with an approximation to normal values. The postoperative application of dynamic MRI allowed for a quantification of the performed correction, allowing for a postoperative control of success.

Anatomical Components Associated With Increased Tibial Tuberosity-Trochlear Groove Distance

Background:

Increased tibial tuberosity–trochlear groove (TT-TG) distance is an important indicator of medial tibial tubercle transfer in the surgical management of lateral patellar dislocation (LPD). Changes to TT-TG distance are determined by a combination of several anatomical factors.

Purpose:

To (1) determine the anatomical components related to increased TT-TG distance and (2) quantify the contribution of each to identify the most prominent component.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

Included were 80 patients with recurrent LPD and 80 age- and body mass index–matched controls. The 2 groups were compared in TT-TG distance and its related anatomical components: tibial tubercle lateralization (TTL), trochlear groove medialization, femoral anteversion, tibiofemoral rotation (TFR), tibial torsion, and mechanical axis deviation (MAD). The Pearson correlation coefficient (r) was calculated to evaluate the association between increased TT-TG distance and its anatomical parameters, and factors that met the inclusion criteria of P < .05 and r ≥ 0.30 were analyzed via stepwise multivariable linear regression analysis to predict TT-TG distance.

Results:

The LPD and control groups differed significantly in TT-TG distance, TTL, TFR, and MAD (P < .001 for all). Increased TT-TG distance was significantly positively correlated with TTL (r = 0.376; P < .001), femoral anteversion (r = 0.166; P = .036), TFR (r = 0.574; P < .001), and MAD (r = 0.415; P < .001), and it was signficantly negatively correlated with trochlear groove medialization (r = −0.178; P = .024). The stepwise multivariable analysis revealed that higher TTL, excessive knee external rotation, and excessive knee valgus were statistically significant predictors of greater TT-TG distance (P < .001 for all). The standardized estimates that were used for evaluating the predictive values were larger for TFR compared with those for TTL and MAD.

Conclusion:

TTL, TFR, and MAD were the main independent anatomical components associated with increased TT-TG distance, with the most prominent component being TFR. The association of TT-TG distance to each component analyzed in our study may help guide surgical planning.

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

INTRODUCTION

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

[Osteotomy in patellofemoral malalignment]

Anterior knee pain and patellofemoral instability are the two major symptoms of patellofemoral dysbalance. Various pathologies can cause these symptoms. In recent years, axis deviations have been increasingly discussed as a cause of patellofemoral dysbalance. In the frontal axis, valgus deformities are a major risk factor, but torsional deformities may be a cause as well. Increased femoral internal rotation or increased tibial external rotation are the key pathologies. Osteotomy is the treatment of choice. Valgus deformities require varisation osteotomy, which is either performed on the femur or tibia depending on the location of the deformity. Torsional deformities are treated by external femoral or internal tibial torsional osteotomy. Femoral osteotomies are located above the femoral condyles, tibial osteotomies above the tibial tuberosity. Tibial internal torsional correction must not exceed 15° because this would jeopardise structures such as the peroneal nerve. Rehabilitation includes partial weight-bearing for four to six weeks. Hardware removal can be performed half a year after osteotomy. The relevance of axis deviations and treatment by osteotomy in patellofemoral dysbalance has been highlighted in recent reviews. Several publications report promising results after osteotomy, including significant pain relief and achievement of patellofemoral stability.

Medial patellofemoral ligament reconstruction combined with biplanar supracondylar femoral derotation osteotomy in recurrent patellar dislocation with increased femoral internal torsion and genu valgum: a retrospective pilot study

Background

The purpose of this study was to evaluate the clinical and radiographic outcomes after medial patellofemoral ligament (MPFL) reconstruction combined with supracondylar biplanar femoral derotation osteotomy (FDO) in recurrent patellar dislocation (RPD) with increased femoral anteversion angle (FAA) and genu valgum.

Methods

Between January 2017 to December 2020, a total of 13 consecutive patients (13 knees, 4 males and 9 females, mean age 18.7 (range, 15–29 years) with RPD with increased FAA (FAA > 25°) and genu valgum (mechanical axis deformity of ≥5°) who underwent supracondylar biplanar FDO using a Tomofix-locking plate combined with MPFL reconstruction in our institution were included. Preoperative full-leg standing radiographs, lateral views, and hip-knee-ankle computed tomography (CT) scans were used to evaluate the mechanical lateral distal femoral angle (mLDFA), anatomical femorotibial angle (aFTA), mechanical axis, patellar height, tibial tubercle-trochlear groove (TT-TG) distance, and torsional angle of the tibial and femoral in the axial plane. Patient reported outcomes were evaluated using the International Knee Documentation Committee (IKDC) score, Kujala score, Lysholm score, visual analog scale (VAS), and Tegner score preoperatively and postoperatively. Postoperative CT scans were used to evaluate the changes of FAA and TT-TG, and full-leg standing radiographs was used to evaluate the changes of mLDFA, aFTA, and mechanical axis.

Results

A total of 13 patients (13 knees) were included with an average follow-up period of 26.7 months (range 24–33). No cases developed wound infection, soft tissue irritation, and recurrent patellar dislocation during the follow-up period after surgery. Bone healing at the osteotomy site was achieved in all cases, and all patients regained full extension and flexion. Clinical outcomes (VAS, Kujala, IKDC, Lysholom, and Tegner scores) improved significantly at the final follow-up after surgery (p < 0.05). The mean mLDFA, aFTA, mechanical axis, and TT-TG distance showed statistically significant improvement following the combined surgery (p < 0.05), while the CDI did not change significantly after surgery (p>0.05).

Conclusion

MPFL reconstruction combined with supracondylar biplanar FDO showed satisfactory clinical outcomes and radiographic results in the short-term follow-up period.

Genu Valgum Correction and Biplanar Osteotomies

Valgus malalignment is an important risk factor in recurrent patella instability. This article explores the role of corrective osteotomy and discusses the various described methods both on the femoral and tibial sides of the joint. A detailed operative technique of medial closing wedge distal femoral osteotomy is included.

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

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

[Assessment of patellar dislocations in childhood and adolescence : Accident-related or predisposition-related?]

BACKGROUND

Numerous predisposing factors are known for patellar dislocations but the extent to which these or the trauma cause the dislocation is often unclear.

AIM

This study investigated whether the analysis of the accident mechanism and anatomical predisposition in juvenile patellar dislocations enables a conclusion as to the causality.

MATERIAL AND METHODS

Retrospective cohort study, evidence level III. In-house employers' liability insurance association (BG) cases with the diagnosis of patella dislocation in patients under 18 years were descriptively evaluated with respect to demographic and predisposing aspects as well as regarding accident information. The accident mechanisms were sorted into subgroups: direct impact, trivial trauma, fall, torsional trauma.

RESULTS

A total of 54 patellar dislocations were identified with a patient age of 14 years (range 9-18 years). A mild valgus configuration was found in 39% of the cases, on average normal torsion, a tibial tuberosity-trochlea groove (TTTG) distance of 17 mm (range 8-24mm), with 41% a high proportion of patella alta and a trochlear deformity in 57%. Only 20% of the children had no relevant predispositions. The trivial traumas showed the highest proportion of recurrent dislocations with 50% and in the other accident categories the proportion of first dislocations was >75%. In the fall cohort the rate of children without relevant predisposition was highest.

CONCLUSION

The predisposition rate in infantile patellar dislocations is high; however, falls are always significant accident events as well as medial direct impact. Torsional trauma is also a significant causative factor, unless high-grade trochlear dysplasia is present, whereas trivial traumas are not.

Closing-wedge distal femoral osteotomy combined with medial patellofemoral ligament reconstruction for recurrent patellar dislocation with genu valgum

BACKGROUND

Medial patellofemoral ligament reconstruction (MPFLR) is a well-established procedure for addressing recurrent patellar dislocation (RPD) in young patients. However, despite being a promising procedure for RPD with genu valgum, there is a scarcity of reports on simultaneous MPFLR and closing-wedge distal femoral osteotomy (CWDFO). The purpose of the present study was to observe and analyse the clinical and imaging findings of CWDFO combined with MPFLR for RPD with genu valgum.

METHODS

From May 2015 to April 2018, 25 patients with RPD and genu valgum were surgically treated in our department. Anteroposterior long-leg, weight-bearing, lower-extremity radiographs, lateral radiographs and computed tomography (CT) scans of the patellofemoral joint were obtained, and the anatomical femorotibial angle (aFTA), mechanical lateral distal femoral angle (mLDFA), weight-bearing line rate (WBLR), patellar height, patellar lateral shift (PLS) and tibial tubercle-trochlear groove (TT-TG) distance were analysed. Validated knee scores, such as the Kujala, Lysholm, visual analogue scale (VAS) scores and Tegner socres, were evaluated preoperatively and 2 years postoperatively.

RESULTS

25 patients, with an average age of 19.8 years (14-27), were evaluated. During the 2-year follow-up period, all patients were able to achieve a better sports level without any problems, with no recurrence of patellar instability. Compared with preoperation, the aFTA, mLDFA, WBLR and PLS showed statistically significant improvement following the procedure (p < 0.001). Meanwhile, no significant differences in the Insall index and TT-TG distance were found. The mean Kujala score, average Lysholm score, VAS score and Tegner socres showed significant postoperative improvement.

CONCLUSIONS

CWDFO combined with MPFLR is a suitable treatment for RPD with genu valgum, and can lead to significant improvement in the clinical and imaging findings of the knee in the short term.

Prognostic factors for isolated medial patellofemoral ligament reconstruction: A systematic review

BACKGROUND

Evidence concerning the influence gender, age, and the time elapsed from the first dislocation to surgery in the outcomes of Medial Patella Femoral Ligament (MPFL) reconstruction are lacking. This systematic review was conducted to investigate whether patient characteristics have an influence in the clinical outcomes of MPFL reconstruction for patients with patellofemoral instability.

MATERIAL AND METHODS

This study followed the PRISMA guidelines. The main databases were accessed in February 2021. All the studies reporting outcomes of primary MPFL reconstruction in patients with recurrent patellofemoral instability were considered for inclusion. A multivariate analysis diagnostic tool was used to analyse the association between age, gender and time from injury to surgery and the surgical outcomes at last follow-up.

RESULTS

A total of 50 articles (2037 procedures) were included. The mean follow-up was 40.90 ± 24.8 months. The mean age was 23.6 ± 3.9 years. 64.3% (1309 of 2037 patients) were female. The mean time from injury to surgery was 64.5 ± 48.9 months. Women showed no statistically significant association with the Kujala score or complications. Older patients had a reduced risk to incur re-dislocations (P = 0.01) and revisions (P = 0.01). Longer time from injury to surgery was associated with greater risk to incur re-dislocations (P = 0.01), and with lower Kujala score (P < 0.0001). No other statistically significant association was evidenced.

CONCLUSION

The time span from the first patellar dislocation to the surgical reconstruction was a negative prognostic factor, while sex had no influence on surgical outcomes. The role of patients age on surgical outcomes remains unclear.

A hinge position distal to the adductor tubercle minimizes the risk of hinge fractures in lateral open wedge distal femoral osteotomy

PURPOSE

To evaluate the incidence and morphology of medial cortical hinge fractures in lateral open wedge distal femoral osteotomy (LOW-DFO) and to determine a safe zone for the position of the osteotomy hinge to minimize the risk of hinge fractures.

METHODS

Consecutive patients who underwent LOW-DFO for symptomatic valgus malalignment were screened for eligibility for this retrospective observational cohort study. Demographical and surgical data were collected. The incidence and morphology of medial cortical hinge fractures were evaluated on standard postoperative anterior-posterior knee radiographs. Comprehensive measurements evaluating the osteotomy gap and the position of the osteotomy hinge were taken. Additionally, each osteotomy hinge was assigned to a corresponding sector of a proposed five-sector grid of the distal medial femur.

RESULTS

A total of 100 patients (60% female) with a mean age of 31 ± 13 years were included. The overall incidence of medial cortical hinge fractures was 46% and three distinct fracture types were identified. The most frequently observed fracture type was extension of the osteotomy gap (76%), followed by a proximal (20%) and distal (4%) course of the fracture line in relation to the hinge. Group comparison (hinge fracture vs. no hinge fracture) showed statistically significant higher values for the height of the osteotomy gap (p = 0.001), the wedge angle (p = 0.036), and the vertical distance between the hinge and the proximal margin of the adductor tubercle (AT; p = 0.002) in the hinge fracture group. Furthermore, a significantly lower horizontal distance between the hinge and the medial cortical bone (p = 0.036) was observed in the hinge fracture group. A statistically significant higher incidence of medial cortical hinge fractures was observed when the position of the osteotomy hinge was proximal compared to distal to the proximal margin of the AT (53% vs. 27%; p = 0.023).

CONCLUSION

Medial cortical hinge fractures in LOW-DFO are a common finding with three distinct fracture types. To minimize the risk of medial cortical hinge fractures, it is recommended to aim for a position of the osteotomy hinge at the level of or distal to the proximal margin of the adductor tubercle.

LEVEL OF EVIDENCE

Prognostic study; Level III.

Increased external tibial torsion is an infratuberositary deformity and is not correlated with a lateralized position of the tibial tuberosity

PURPOSE

To perform a segmental analysis of tibial torsion in patients, with normal and increased external tibial torsion, suffering from chronic patellofemoral instability (PFI) and to investigate a possible correlation between tibial torsion and the position of the tibial tuberosity.

METHODS

Patients with chronic PFI who underwent torsional analysis of the lower limb using a standardized hip-knee-ankle MRI between 2016 and 2018 were included. For segmental analysis of tibial torsion, three axial levels were defined which divided the tibia into two segments: a distal, infratuberositary segment and a proximal, supratuberositary segment. Torsion was measured for the entire tibia (total tibial torsion, TTT), the proximal segment (proximal tibial torsion, PTT), and the distal segment (distal tibial torsion, DTT). Based on TTT, patients were assigned to one of two groups: Normal TTT (< 35°) or increased external TTT (> 35°). Position of the tibial tuberosity was assessed on conventional MRI scans by measuring the tibial tuberosity-trochlea groove (TT-TG) and the tibial tuberosity-posterior cruciate ligament (TT-PCL) distances.

RESULTS

Ninety-one patients (24 ± 6 years; 78% female) were included. Mean external TTT was 29.6° ± 9.1° and 24 patients (26%) had increased external TTT. Compared to patients with normal TTT, patients with increased external TTT demonstrated significantly higher values for DTT (38° ± 8° vs. 52° ± 9°; p < 0.001), whereas no difference was found for PTT ( - 13° ± 6° vs.  - 12° ± 6°; n.s.). Furthermore, a significant correlation was found between TTT and DTT (p < 0.001), whereas no correlation was found between TTT and PTT (n.s). With regard to TT-TG and TT-PCL distances, no significant differences were observed between the two groups (TT-TG: 15 ± 6 vs. 14 ± 4 mm, n.s.; TT-PCL: 22 ± 4 vs. 21 ± 5 mm, n.s.) and no correlation was found with TTT, DTT, or PTT (n.s.).

CONCLUSION

In patients with chronic PFI, increased external TTT of greater than 35° is an infratuberositary deformity and does not correlate with a lateralized position of the tibial tuberosity.

LEVEL OF EVIDENCE

Level III.

Lateral Trochlear Inclination Angle: Measurement via a 2-Image Technique to Reliably Characterize and Quantify Trochlear Dysplasia

Background:

Trochlear dysplasia (TD) is a risk factor for patellar instability (PI). The Dejour classification categorizes TD but has suboptimal reliability. Lateral trochlear inclination (LTI) is a quantitative measurement of trochlear dysplasia on a single axial magnetic resonance imaging (MRI) scan.

Hypothesis:

A modified LTI measurement technique using 2 different axial MRI scans that reference the most proximal aspect of the trochlear cartilage on 1 image and the fully formed posterior condyles on the second image would be as reliable as and significantly different from the single-image measurement technique for LTI. Further, the 2-image LTI would adequately represent overall proximal trochlear morphologic characteristics.

Study Design:

Cohort study (diagnosis); Level of evidence, 2.

Methods:

Patients aged 9 to 18 years treated for PI between 2014 and 2017 were identified. The Dejour classification was radiographically determined. Single-image LTI was measured on a single axial MRI scan at the most proximal aspect of visible trochlear cartilage. A 2-image LTI was measured from 2 separate MRI scans: 1 at the most proximal aspect of trochlear cartilage and the second at the fully formed posterior condyles. This 2-image LTI was repeated at 3 subsequent levels (the first measurement is referred to as LTI-1; repeated measurements are LTI-2, LTI-3, and LTI-4, moving distally). In total, 65 patients met the inclusion criteria, and 30 were randomly selected for reliability analysis.

Results:

Inter- and intrarater reliability trended toward more variability for single-image LTI (intraclass correlation coefficient [ICC], 0.86 and 0.88, respectively) than for 2-image LTI (ICC, 0.97 and 0.96, respectively). The Dejour classification had lower intra- and interrater reliability (ICC, 0.31 and 0.73, respectively). Average single-image LTI (9.2° ± 12.6°) was greater than average 2-image LTI-1 (4.2° SD ± 11.9°) (P = .0125). Single-image LTI classified 60% of patients with PI as having TD, whereas the 2-image LTI classified 71% as having TD. The 2-image LTI was able to capture 91% of overall proximal trochlear morphologic characteristics.

Conclusion:

LTI has higher reliability when performed using a 2-image measurement technique compared with single-image LTI and Dejour classification. The strong correlation between 2-image LTI and average LTI shows that 91% of TD is represented on the most proximal axial image. Because the single-image measurement appears to underestimate dysplasia, previously described thresholds should be reexamined using this 2-image technique to appropriately characterize TD.

High failure rate 10.8 years after vastus medialis transfer and lateral release (Green's quadricepsplasty) for recurrent dislocation of the patella

PURPOSE

In adolescent patients with recurrent patellar dislocation, the Green's quadricepsplasty stabilizes the patella in a combination of a lateral release, a transfer of the medial head of the quadriceps onto the lateral part of the patella and an imbrication of the medial patellar retinaculum and joint capsule. This study aimed to evaluate the long-term performance, considering re-dislocations and functional outcomes. We hypothesized a high failure rate in the long term.

METHODS

In this single surgeon and single center study 26 knees in 23 patients (mean age 14.2 years; 4-22 years, 18 females) with recurrent patellofemoral dislocation underwent a vastus medialis transfer, medial reefing and lateral release as it was described by Green in 1965 with a mean follow-up 10.8 years (6-24 years). Clinical assessment was carried out with an IKDC-score (international knee documentation committee) and a self-assessment for each knee separately. The radiologic evaluation included measurement of the patella height, the grade of trochlear dysplasia and the sulcus angle.

RESULTS

In 12 of 26 cases (46.2%) the patella did not re-dislocate after vastus medialis transfer and lateral release. In 11 of 26 cases (42.3%), the patients described the function of their knees as normal or nearly normal according to IKDC after the surgical treatment without any re-dislocation. In 14 of 26 cases (53.8%), the patella re-dislocated. 7 of these 14 cases underwent a revision operation. Re-dislocations occurred after a mean interval of 21 months after the index procedure. In only 2 of 26 cases (7.7%) the patients returned to sports.

CONCLUSION

Green's procedure to stabilize patellofemoral instabilities results in a high failure rate on the long-term and low subjective assessments. We do not recommend performing vastus medialis transfer, medial imbrication and lateral release as a standalone technique.

LEVEL OF EVIDENCE

IV.

Failure Analysis in Patients With Patellar Redislocation After Primary Isolated Medial Patellofemoral Ligament Reconstruction

Background:

Reconstruction of the medial patellofemoral ligament (MPFL) has become a popular surgical procedure to address patellofemoral instability. As a consequence of the growing number of MPFL reconstructions performed, a higher rate of failures and revision procedures has been seen.

Purpose:

To perform a failure analysis in patients with patellar redislocation after primary isolated MPFL reconstruction.

Study Design:

Case series; Level of evidence, 4.

Methods:

Patients undergoing revision surgery for reinstability after primary isolated MPFL reconstruction were included. Clinical notes were reviewed to collect demographic data, information on the primary surgery, and the mechanism of patellar redislocation (traumatic vs nontraumatic). Preoperative imaging was analyzed regarding femoral tunnel position and the prevalence of anatomic risk factors (ARFs) associated with patellofemoral instability: trochlear dysplasia (types B through D), patella alta (Caton-Deschamps index >1.2, patellotrochlear index <0.28), lateralization of the tibial tuberosity (tibial tuberosity–trochlear groove distance >20 mm, tibial tuberosity–posterior cruciate ligament [TT-PCL] distance >24 mm), valgus malalignment (mechanical valgus axis >5°), and torsional deformity (internal femoral torsion >25°, external tibial torsion >35°). The prevalence of ARF was compared between patients with traumatic and nontraumatic redislocations and between patients with anatomic and nonanatomic femoral tunnel position.

Results:

A total of 26 patients (69% female) with a mean age of 25 ± 7 years were included. The cause of redislocation was traumatic in 31% and nontraumatic in 69%. Position of the femoral tunnel was considered nonanatomic in 50% of patients. Trochlear dysplasia was the most common ARF with a prevalence of 50%, followed by elevated TT-PCL distance (36%) and valgus malalignment (35%). The median number of ARFs per patient was 3 (range, 0-6), and 65% of patients had 2 or more ARFs. Patients with nontraumatic redislocations showed significantly more ARFs per patient, and the presence of 2 or more ARFs was significantly more common in this group. No significant difference was observed between patients with anatomic versus nonanatomic femoral tunnel position.

Conclusion:

Multiple anatomic risk factors and femoral tunnel malposition are commonly observed in patients with reinstability after primary MPFL reconstruction. Before revision surgery, a focused clinical examination and adequate imaging including radiographs, magnetic resonance imaging (MRI), standing full-leg radiographs, and torsional measurement with computed tomography or MRI are recommended to assess all relevant anatomic parameters to understand an individual patient’s risk profile. During revision surgery, care must be taken to ensure anatomic placement of the femoral tunnel through use of anatomic and/or radiographic landmarks.

The complexity of bony malalignment in patellofemoral disorders: femoral and tibial torsion, trochlear dysplasia, TT-TG distance, and frontal mechanical axis correlate with each other

PURPOSE

Several anatomic risk factors associated with patellofemoral disorders have been described. The purpose of this study was to analyze the relationship between bony parameters commonly used to analyze and define patellofemoral malalignment.

METHODS

Patients with patellofemoral disorders presenting between 2016 and 2018 who underwent a standardized radiographic workup including conventional radiographs, weight bearing full-leg radiographs, magnetic resonance imaging (MRI) of the knee, and torsional analysis using hip-knee-ankle MRI were initially included. Patients with a history of lower extremity fracture and a history of surgical procedures affecting bony alignment or partial/total arthroplasty were subsequently excluded. Radiographs and MRI of all included patients were analyzed by four independent observers. Parameters of interest were: femoral torsion, tibial torsion, trochlear dysplasia, tibial tuberosity-trochlear groove (TT-TG) distance, and frontal mechanical axis. All parameters were compared between patients with low grade and high grade trochlear dysplasia as well as between female and male patients. Correlation of continuous variables was assessed with the Pearson correlation coefficient. A binary logistic regression model was used for the calculation of odds ratio between different parameters. Interclass correlation coefficients (ICC) were calculated to determine the interobserver reproducibility.

RESULTS

A total of 151 patients could be included for detailed analysis. Group comparison revealed that patients with high grade trochlear dysplasia showed significantly higher values for femoral torsion (low grade: 9.8° ± 11.0°, high grade: 16.8° ± 11.5°; p < 0.001) and significantly higher values for TT-TG distance (low grade: 19.0 mm ± 5.0 mm, high grade: 21.9 mm ± 5.4 mm; p = 0.002). No significant difference was found for age, tibial torsion, and frontal mechanical axis. With regard to gender, female patients had higher values for femoral torsion (female: 15.6° ± 11.3°, male: 11.0° ± 12.7°; p = 0.044). The correlation analysis found significant correlation between femoral torsion and tibial torsion (r = 0.244, p = 0.003), femoral torsion and TT-TG distance (r = 0.328, p < 0.001), femoral torsion and frontal mechanical axis (r = 0.291, p < 0.001), and tibial torsion and TT-TG distance (r = 0.182, p = 0.026).

CONCLUSION

Bony malalignment in patients with patellofemoral disorder is a complex problem given the significant correlation between femoral and tibial torsion, trochlear dysplasia, TT-TG distance, and frontal mechanical axis. Advanced imaging to analyze rotational and frontal plane alignment is recommended in patients with trochlear dysplasia and/or increased TT-TG on standard radiographs and knee MRI. Understanding of the bony pathology in patellofemoral disorders is key to improve the therapeutic and surgical decision.

LEVEL OF EVIDENCE

III, retrospective cohort study.

Corrective osteotomies of femur and tibia: which factors influence bone healing?

INTRODUCTION

Corrective osteotomies of the lower limb are standard procedures in orthopedic surgery. Still, there is only limited research on factors affecting bone healing after osteotomies. We hypothesize that especially the location of the osteotomy, smoking status and BMI affect bone healing.

MATERIAL AND METHODS

The healing process of 547 patients who underwent osteotomies of the lower limb (259 female, 288 male; average 40.6 years, range 14-77) was evaluated. To assess bone healing, participants were divided into three groups by bone healing duration ( < 5/5-8/ > 8 months). Differences in healing duration related to the anatomic level of the osteotomy (diaphysis vs. metaphysis), age, gender, smoking status, BMI, and modus of the osteotomy (open vs. closed wedge) were tested for significance using an ordinal regression analysis.

RESULTS

A significant correlation between bone healing and the anatomical level of the osteotomy on femur and tibia and the patients' smoking status was found. The odds of the diaphysis considering bone healing was 0.187 (95% CI, 0.08-0.44) times that of the metaphysis (Wald χ²(1) = 14.597, p < 0.000). The odds ratio of smokers considering bone healing was 0.192 (95% CI, 0.11-0.33) times that of non-smokers (Wald χ²(1) = 35.420, p < 0.000). All other analyzed factors did not show a significant correlation with bone healing.

CONCLUSIONS

Smoking status and the localization of the osteotomy on femur and tibia (diaphysis vs. metaphysis) are significantly correlated with bone healing duration. In line with current literature emphasizing the detrimental effect of smoking on bone healing, our findings should encourage surgeons to think twice about the indication to perform osteotomies on smokers. Furthermore, if applicable, osteotomies should be performed in the metaphyseal areas of femur and tibia.

Surgical treatment is better than non-surgical treatment for primary patellar dislocation: a meta-analysis of randomized controlled trials

BACKGROUND

At present, the best treatment for primary patellar dislocation (PPD) has not been unified. Moreover, meta-analyses comparing the non-surgical and surgical treatments of PPD are lacking. Thus, we aimed to compare the clinical efficacy of surgical or non-surgical treatment of PPD.

METHODS

Randomized controlled studies of surgical and non-surgical treatments of PPD from 1966 to 2018 were retrieved from the following databases: PubMed, EMBASE, Cochrane Library, Wanfang Database, China Knowledge Network, Google Scholar, and Weipu Database. We screened for literature that met the inclusion criteria and extracted useful data for our meta-analysis.

RESULTS

Nine studies, involving 492 patients, met the inclusion criteria and were analyzed in this study. The recurrence rate of patellar dislocation in the surgical group was lower than that in the non-surgical group (P = 0.04]). Subgroup analysis according to the follow-up time showed that the Kujala score (P < 0.001) and lower recurrence rate of dislocation (P = 0.05) than the non-surgical group in the short term. Subgroup analysis according to surgical year showed that the surgical group get higher Kujala score (P < 0.001) and lower recurrence rate of dislocation (P = 0.01) than the non-surgical group in recent years.

CONCLUSION

Surgical treatment can provide better clinical results in a short period of time, and patients may achieve good results within 10 years owing to the advances in surgical techniques and instruments. Thus, we recommend surgical treatment as the preferred treatment for primary patellar dislocation.

Preoperative patellofemoral anatomy affects failure rate after isolated patellofemoral inlay arthroplasty

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

Level III, retrospective analysis of prospectively collected data.

Closed-wedge Patelloplasty for the Treatment of Distal Patellofemoral Maltracking and Instability due to Severe Patellar Dysplasia: Case Report and Surgical Technique

Background

Patellofemoral maltracking is caused by different anatomical factors. Most of them are associated with a proximal maltracking, which alters the patella's engagement into the trochlear groove and predisposes the patellofemoral joint for instability. Different surgical techniques have been described to realign patellar tracking, however, most of which address proximal patellar maltracking.

Aim

The aim of this article is to demonstrate the influence of patella-related deformities on patellar tracking and to present a novel surgical technique for the treatment of distal patellar maltracking, caused by a severe patellar dyplasia.

Case Description

We report the case of a 23-year-old patient with a severe patellar dysplasia, presenting a distal patellar maltracking with recurring dislocations in deep flexion. Due to her instability, the patient was immobilised and dependent on the constant use of walking aids. Radiological images showed a concavely shaped patellar, which articulated exclusively with the lateral epicondyle and caused the patella to dislocate laterally, starting at a flexion angle of 60°. An anterior closing-wedge osteotomy was used to reshape and recenter the patella, which was complemented by a medial patellofemoral ligament reconstruction. At the 18-month follow-up, the patient presented pain free and fully remobilised, without the use of walking aids. Patellar tracking was reestablished, with a possible knee flexion until 140°. No redislocation of the patella had occurred.

Conclusion

Distal patellofemoral maltracking, caused by a severe patellar dysplasia, can successfully be treated with an anterior closed-wedge osteotomy of the patella. In combination with a medial patellofemoral ligament reconstruction, patellofemoral stability can be reestablished, to prevent further dislocations.

Clinical Significance

There are multiple factors, which may cause patellar maltracking. A thorough clinical and radiological preoperative analysis is mandatory, in order to clearly identify the underlying pathologies, as these may affect patellar tracking proximally or distally.

How to cite this article

Frings J, Freudenthaler F, Krause M, et al. Closed-wedge Patelloplasty for the Treatment of Distal Patellofemoral Maltracking and Instability due to Severe Patellar Dysplasia: Case Report and Surgical Technique. Strategies Trauma Limb Reconstr 2020;15(3):184-192.

Hemiepiphysiodesis is a potentially effective surgical management for skeletally immature patients with patellofemoral instability associated with isolated genu valgum

PURPOSE

Genu valgum is one of the well-known predisposing factors for patellofemoral instability. The study aims to investigate the outcomes of isolated hemiepiphysiodesis in the correction of genu valgum and in the management of recurrent patellofemoral instability. The hypothesis was that hemiepiphysiodesis alone would result in significant correction of genu valgum, thereby preventing recurrent patellofemoral instability.

METHODS

In the cohort study, all skeletally immature patients who underwent isolated hemiepiphysiodesis for recurrent patellofemoral instability were included. All patients included in the study had a minimum of 1-year follow-up duration prior to the conclusion of the study.

RESULTS

Sixteen of twenty knees had no further patellofemoral instability post-operatively. The change in the status of patellofemoral instability was statistically significant (p = 0.001), similar to the change in the tibiofemoral angle (p = 0.015) and patellar tilt angle (p = 0.002). Comparison between patients with and without patellofemoral instability post-operatively revealed that the pre-operative patellar tilt angle (p = 0.005) and tibiofemoral angle (p = 0.001), post-operative patellar tilt angle (p = 0.004) and tibiofemoral angle (p = 0.027) as well as the change in patellar tilt angle (p = 0.001) and tibiofemoral angle (p = 0.001) were all significant predictors of the outcomes of genu valgum.

CONCLUSION

Hemiepiphysiodesis is a potentially effective surgical management for skeletally immature patients with patellofemoral instability associated with isolated genu valgum. This is especially for patients who are skeletally immature and have sufficient remaining years for their genu valgum to be corrected using hemiepiphysiodesis. These patients also tended to have less severe genu valgum and patellar tilt angle, which could be corrected using hemiepiphysiodesis with the remaining years of growth.

LEVEL OF EVIDENCE

II.

Combined distal femoral osteotomy (DFO) in genu valgum leads to reliable patellar stabilization and an improvement in knee function

PURPOSE

Valgus deformities of the lower extremity influence patellofemoral joint kinematics. However, studies examining the clinical outcome after treatment of patellar instability and maltracking due to valgus deformity are rare in recent literature. This study's purpose is to analyze the clinical results after combined distal femoral osteotomy (DFO) for treatment of patellar instability.

METHODS

From 2010 to 2016, 406 cases of patellofemoral instability and maltracking were treated. Twenty cases of recurring (≥ 2) patellar dislocations with genu valgum and unsuccessful conservative treatment were included in the study. A radiological analysis was performed, and anteroposterior (AP), lateral and long leg standing radiographs were analyzed, and the leg axis was pre- and postoperatively measured. At least 12 months postoperatively, the clinical leg axis, range of motion (ROM), apprehension sign, Zohlen sign, and J-sign were physically examined. Pain level and knee function were objectified on a visual analogue scale (VAS). The Lysholm, Kujala, and Tegner scores, re-dislocation rate, and patient satisfaction were also examined.

RESULTS

20 combined DFOs on 18 patients with a median age of 23 years (15-55 years) were performed. The preoperative mechanical leg axis was 6.5° ± 2.0° valgus, and the mean tibial tuberosity to trochlear groove (TT-TG) distance was 19.1 ± 4.8 mm. All patients reported multiple dislocations. Intraoperatively, 71% presented III°-IV° cartilage lesions, located retropatellarly in 87% and correlating negatively with the postoperative Lysholm score (r = - 0.462, p = 0.040). The leg axis was corrected by 7.1° ± 2.6°, and in 17 cases, the tibial tubercle was additionally medialized by 10 ± 3.1 mm. All patellae were re-stabilized with medial patellofemoral ligament reconstruction. After a median period of 16 (12-64) months, the pain level decreased from 8.0 ± 1.4 to 2.3 ± 2.1 (VAS p ≤ 0.001) and knee function improved from 40.1 ± 17.9 to 78.5 ± 16.6 (Kujala p ≤ 0.001), 36.1 ± 19.5 to 81.6 ± 11.7 (Lysholm p ≤ 0.001), and 2.0 (1-5) to 4.0 (3-6) (median Tegner p ≤ 0.001). No re-dislocation was observed.

CONCLUSION

Combined DFO is a suitable treatment for patellar instability and maltracking due to genu valgum, as it leads to very low re-dislocation rates, a significant reduction of pain, and a significant increase of knee function with good-to-excellent results in the short-term follow-up. However, a high prevalence of substantial cartilage lesions is observed, causing postoperative limitations of knee function.

LEVEL OF EVIDENCE

IV, retrospective cohort study.