Updated treatment guidelines for patellar instability: "un menu à la carte"

Promising results following derotational femoral osteotomy in patellofemoral instability with increased femoral anteversion: A systematic review on current indications, outcomes and complication rate

Purpose

Patellofemoral joint instability (PFJI) can surgically be treated with a multitude of approaches, depending on the underlying pathology. In the presence of increased femoral anteversion, some authors have reported good results with a derotational distal femoral osteotomy (DeDFO). The purpose of the study was to investigate the indications, outcomes and complication rate of DeDFO for PFJI.

Methods

A systematic review was performed according to the PRISMA guidelines (Preferred Reporting Items for Systematic Reviews and Meta-analyses) by searching Medline, Embase, Web of Science and Cochrane Library databases through 1 December 2023. Included were levels 1-4 clinical studies of skeletally mature patients undergoing a DeDFO for PFJI irrespective of concomitant procedures. Study characteristics, indications, radiological and clinical outcomes, surgical technique and concomitant procedures, re-dislocation and complication rate were all analysed, as was methodological quality.

Results

A total of 12 studies including 310 patients (325 knees) were included. Three studies were cohort studies, all others were case series. The mean patient age across the studies was 22 years, and the mean follow-up was 29.4 months. Femoral anteversion cut-off was between 20° and 30°. Every study included at least one concurrent soft tissue, bony or combined procedure. Across all studies, one case of re-dislocation was reported (0.3%) and four implant or osteotomy-related complications (1.2%) were reported. All studies reported a statistically significant increase in clinical scores.

Conclusion

This systematic review of DeDFO for patellofemoral instability in the presence of increased femoral anteversion demonstrates promising clinical results and an extremely low dislocation and complication rate. The heterogeneity of the cut-off in anteversion and concomitant procedures, especially tibial tubercle osteotomy with seemingly identical results, indicates the need for high-quality evidence for treating patellofemoral instability. Based upon this systematic review, we strongly recommend that DeDFO be added to the 'menu à la carte' of PFJI.

Level of Evidence

Level III Systematic Review.

The role of the most cranial trochlear orientation in patellar maltracking to better characterise trochlear morphology

PURPOSE

The purpose of our study is to describe a magnetic resonance imaging quantitative parameter to assess the morphology of the trochlea that could be measurable from normal to high-grade trochlear dysplasia while evaluating the most proximal slice with trochlear cartilage.

METHODS

Two groups of patients have been compared: patients with no patellofemoral pain, no previous trauma and undergoing surgery for a suspected isolated meniscal tears (group A) and patients with objective patellar instability (group B). The cranial trochlear orientation (CTO) angle is defined as the angle between the posterior bicondylar line and the most lateral and most medial points on the subchondral bone covered by cartilage digitised on the first and most cranial image with the trochlear cartilage clearly visible.

RESULTS

The final cohort included 253 patients (109 in group A and 144 in group B). CTO was significantly higher in group B (-2.5 ± 8.4 vs. -10.8 ± 5,1; p < .001). Moreover, 75% of knees in group B had a CTO > -7°, while 75% of knees in group A had a CTO < -7°. CTO was measurable in all 253 knees, whereas the lateral trochlear inclination and the sulcus angle were measurable in only 202 knees. The entire cohort was also divided into knees with CTO ≤ 0° and CTO > 0°. All knees with a CTO > 0 were in group B, and 49% of knees with CTO < 0 were in group B. CTO was positively correlated with lateral patellar tilt.

CONCLUSIONS

CTO is the only parameter that can be measured on the most cranial slice, in every patient, even in high-grade trochlear dysplasia. According to this new system, the axial trochlear shape may be divided into two types: a positive CTO and a negative CTO, with the trochlea serving, respectively, as a medial and lateral barrier.

LEVEL OF EVIDENCE

Level III.

Three different patellar fixation techniques yield similar clinical and radiological outcomes in recurrent patellar dislocation undergoing medial patellofemoral ligament reconstruction

PURPOSE

The purpose of this study was to evaluate and compare the clinical and radiological outcomes of three different patellar fixation techniques on medial patellofemoral ligament reconstruction (MPFLR) in the treatment of patellar dislocation (PD).

METHODS

Between 2015 and 2020, 130 patients with recurrent PD who underwent surgical reconstruction were eligible for this retrospective study: 48 patients were treated with the semi-tunnel bone bridge fixation technique (Group A), 42 patients were treated with the suture anchor fixation technique (Group B) and 40 patients were treated with the transpatellar tunnel fixation technique (Group C). Clinical outcomes included functional outcomes (Kujala, Lysholm and International Knee Documentation Committee scores), activity levels (Tegner activity score and return to sports), physical examinations, patellar re-dislocation rate and complications. Radiological outcomes included patellar congruence angle, patellar tilt angle, lateral patellar translation and lateral patellar angle.

RESULTS

All clinical and radiological outcomes improved significantly in all groups, without any significant difference among these three groups. At the final follow-up, no re-dislocation occurred, and all groups achieved a successful return to sports. However, the semi-tunnel bone bridge and suture anchor fixation techniques showed statistically higher Tegner activity scores (p = 0.004) and shorter time from surgery to return to sports (p = 0.007) than the transpatellar tunnel fixation technique.

CONCLUSION

The three MPFLR patellar fixation techniques achieved favourable and comparable clinical and radiological outcomes in the treatment of PD. Compared with the transpatellar tunnel fixation technique, the semi-tunnel bone bridge and suture anchor fixation techniques may be more effective with higher activity levels.

LEVEL OF EVIDENCE

Level III.

Patellar Instability: Imaging Findings

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

Specific considerations in female patients with patellar instability: current concepts

Prior literature suggests that patellofemoral instability (PFI) is significantly more prevalent in women than in men. This higher prevalence is commonly attributed to anatomical differences between sexes, particularly with patellofemoral alignment. These differences encompass a higher rate of trochlear dysplasia (TD), patella alta, an increased Q angle, and soft tissue imbalances. In recent years, worse outcomes have been reported in female patients after patellofemoral stabilization surgery using medial patellofemoral ligament reconstruction (MPFLr) alone or in combination with a tibial tubercle osteotomy (TTO), for this reason an "à la carte" plan (addressing the individuals anatomical risk factors) could be more appropriate for female patients.

Derotational distal femur osteotomy with medial patellofemoral ligament reconstruction can get good outcomes in the treatment of recurrent patellar dislocation with excessive TT-TG and increased femoral anteversion

Background

Surgery is the main treatment for recurrent patellar dislocation (PD). However, due to the complexity of anatomical factors, there is still a lack of consensus on the choice of combined surgical methods. This study aimed to compare the clinical and radiological outcomes of medial patellofemoral ligament reconstruction combined with derotational distal femur osteotomies (MPFLR + DDFO) and combined with tibial tubercle osteotomies (MPFLR + TTO) for recurrent PD with increased femoral anteversion angles (FAA) and excessive tibial tubercle-trochlear groove (TT-TG) distance.

Methods

In this retrospective analysis, MPFLR + DDFO and MPFLR + TTO patients from 2015 to 2020 were included. Group A (MPFLR + DDFO, n = 42) and B (MPFLR + TTO, n = 46) were formed. Clinical outcomes included physical examinations, functional outcomes (Kujala, Lysholm, International Knee Documentation Committee (IKDC), visual analog scale (VAS) and intermittent and persistent osteoarthritis pain scale (ICOAP), Tegner scores), and complications. The Caton-Deschamps index (CD-I), patellar title angle, patellar congruence angle, patella-trochlear groove distance, TT-TG distance, and FAA were used to assess radiological outcomes.

Results

All clinical outcomes improved significantly in both groups, but Group A had significantly better postoperative scores than Group B (Kujala: 89.8 ± 6.4 vs. 82.9 ± 7.4, P < 0.01; Lysholm: 90.9 ± 5.1 vs. 81.3 ± 6.3, P = 0.02; IKDC: 87.3 ± 9.0 vs. 82.7 ± 8.0, P < 0.01; Tegner: 6.0 (5.0, 9.0) vs. 5.0 (4.0, 8.0), P = 0.01). However, there was no significant difference in the VAS and ICOAP scores between the two groups. No dislocation recurrences occurred. Radiological outcomes improved significantly in both groups, but Group A had better outcomes. After surgery, the patellar height of 88.5% (23/26) patients in Group A and 82.8% (24/29) patients in Group B was restored to normal (the Caton-Deschamps index <1.2).

Conclusions

Both MPFLR + TTO and MPFLR + DDFO obtained satisfactory clinical and radiological outcomes in the treatment of recurrent PD with increased FAA and excessive TT-TG. However, the outcomes of MPFLR + DDFO were better and should be considered a priority. MPFLR + TTO may be not necessary for such patients.

Medial Closing-Wedge Patellar Osteotomy in Patients With Patellofemoral Instability

Trochlear dysplasia is the main anatomical risk factor for objective patellar instability. Surgical correction of trochlea dysplasia via a trochleoplasty has been described with good clinical results reported. Concerns remain for who have abnormal patellofemoral tracking post a trochleoplasty due to incongruence between the two articulating surfaces. We described a medial closing wedge patellar osteotomy to improve congruency of the patellofemoral joint post-trochleoplasty.

Patello-femoral arthroplasty- indications and contraindications

Patellofemoral arthroplasty (PFA) is emerging as an attractive alternative to total knee arthroplasty (TKA) for isolated patellofemoral-osteoarthritis (PF-OA) for selected patients. The success of PFA is highly dependent on patient selection. This intervention is still burdened with a higher rate of revisions and a lower survival rate than TKA when the indications or the surgical technique are not optimal. We highlight the indications and contraindications of PFA to obtain satisfying functional outcomes and survivorship. Preoperative clinical and radiological assessment is critical to determine the presence of PFA indications, the absence of contraindications and the necessity of any associated procedures, particularly for the tibial tubercle. The typical indications are patients with isolated symptomatic PF-OA, with trochlear dysplasia, when bone-on-bone Iwano 4 osteoarthritis is observed, without significant malalignment and with the absence of risk factors for developing progressive tibiofemoral-OA. The three main causes of isolated PF-OA are primary OA, trochlear dysplasia and posttraumatic OA following patellar fracture. Trochlear dysplasia is the preferred indication for PFA. Lack of experience with arthroplasty or realignment of the extensor mechanism is a relative contraindication to performing PFA.

Editorial Commentary: Don't Neglect the Medial Side of the Knee in Patients With Anterior Cruciate Ligament Injury

The medial collateral ligament (MCL) of the knee, as well as the posteromedial complex (including the posterior oblique ligament [POL] and ramp lesions of the meniscus) is often considered the "neglected" ligament or corner because of the belief that these anatomic structures have enormous regenerative potential and therefore hardly ever need surgical treatment. In patients with anterior ligament cruciate (ACL) tears, the overall combined prevalence of MCL (superficial [sMCL] and deep [dMCL]) and isolated dMCL injuries is high (16.5% + 24.8% = 41.3%). In terms of the POL, with a restraint to both internal tibial rotation and valgus rotation during extension, I have some doubts regarding its role in anteromedial instability (AMRI). In fact, AMRI of the knee is caused mainly by injury to both the ACL and the MCLs, resulting in coupled anterior tibial translation and external rotation, causing the medial tibial plateau to subluxate anteriorly. The sMCL provides the most substantial restraint, and the dMCL and POL play more minor roles. Finally, in ACL-deficient knees, ramp lesions are prevalent (9.3%-24.0%), and failing to identify and treat these lesions results in knee instability. In my experience, all unstable ramp lesions should be repaired. In ACL-deficient knees in patients with a tibial slope >5°, an occult ramp lesion should be strongly suspected. In summary, the medial compartment of the knee is complex and encompasses many structures (MCL, POL, ramp, tibial slope), and I believe that we will increasingly move toward individualized treatment.

Anatomic Risk Factors for Patellofemoral Joint Instability: An Infographic as a Visual Learning Tool

Patellofemoral instability is a complex pathology with multiple risk factors, which affects mostly young females and may avert them from both activities of daily living and sports participation. Risk factors for instability include patella alta, trochlea dysplasia, abnormal lateral patellar tilt, and increased tibial tuberosity-trochlea groove distance. The knowledge of these anatomical abnormalities is the key to identifying the problem and succeeding in treating the patients.

Functional Imaging of the Knee-A Comprehensive Review

Knee pain is a common presenting problem in the general population. Radiographs and magnetic resonance imaging (MRI) are the cornerstones of imaging in current clinical practice. With advancements in technology, there has been increasing utilization of other modalities to evaluate knee disorders. Dynamic assessment utilizing computed tomography and portable ultrasounds have demonstrated the capacity to accurately assess and reproducibly quantify kinematics of knee disorders. Cartilage physiology can be evaluated with MRI. Emerging research has even demonstrated novel musculoskeletal applications of positron emission tomography to evaluate anterior cruciate ligament graft metabolic activity following reconstruction. As technology continues to evolve and traditional ways are improved upon, future comparative studies will elucidate the distinct advantages of the various modalities. Although radiology is still primarily an anatomic specialty, there is immense potential for functional imaging to be the standard of care. This review focuses on the most common musculoskeletal applications of functional imaging as well as future utilization.

Inconsistent repeatability of the Dejour classification of trochlear dysplasia due to the variability of imaging modalities: a systematic review

PURPOSE

The purpose of this systematic review was to critically assess the quality of papers that report on the intra- and inter-observer repeatability of the Dejour classification for trochlear dysplasia, and to identify the possible causes for poor repeatability.

METHODS

Two authors independently conducted an electronic search (four databases) on 8 February 2023 for studies (English or French) that assessed trochlear dysplasia classifications on imaging of skeletally mature participants. Exclusion criteria were reviews of clinical studies, conference proceedings, or editorials. After title, abstract, and full-text screening, characteristics of eligible studies were tabulated (author, year, journal, study design, cohort characteristics, and intra- and/or inter-observer agreement coefficients). The methodological quality of studies was assessed using the Joanna Briggs Institute (JBI) checklist for analytical cross-sectional studies. Authors analysed three components of the included studies: (1) classifications based on true lateral radiographs and slice imaging; (2) dysplasia graded into Type A vs B vs C vs D and 3) coefficients of intra- and/or inter-observer agreement.

RESULTS

The electronic search returned 3,178 references, and after removal of duplicates and irrelevant studies, ten were eligible for data extraction. A second search (31 July 2023) yielded one additional study. Eight studies did not include lateral radiographs, two studies did not explicitly state if radiographs were true lateral views, and one used true lateral radiographs in isolation. Classification of trochlear dysplasia into A vs B vs C vs D using different imaging modalities resulted in moderate to near-perfect intra-observer agreement, and slight to near-perfect inter-observer agreement. Studies distinguished between moderate and severe dysplasia using a variety of combinations: A vs B/C/D, A/B vs C/D and A/C vs B/D.

CONCLUSION

This systematic review revealed that the Dejour classification remains the most widely used to assess trochlear dysplasia and that the majority of studies that assessed the reliability of the Dejour classification, reported moderate to near-perfect inter-observer agreement; however, pooling of results for comparison among the included studies was inappropriate due to substantial variation in imaging protocols and non-standardised criteria to distinguish severe from moderate dysplasia.

LEVEL OF EVIDENCE

Level IV.

TRIAL REGISTRY

The PROSPERO registration number is CRD42023386731.

Length Changes of the Medial Patellofemoral Ligament During In Vivo Knee Motion: An Evaluation Using Dynamic Computed Tomography

BACKGROUND

Medial patellofemoral ligament (MPFL) reconstruction is associated with high complication rates because of graft overloading from incorrect graft positioning. To improve clinical outcomes, it is crucial to gain a better understanding of MPFL elongation patterns.

PURPOSE

To assess MPFL length changes in healthy knees from 0° to 90° of dynamic flexion and their relationship with anatomic parameters of the patellofemoral joint.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Dynamic computed tomography scans of an active flexion-extension-flexion movement in 115 knees from 63 healthy participants were evaluated to construct knee joint models. Using these models, the MPFL length was measured as the shortest wrapping path from the Schöttle point on the femur to 3 insertion points on the superomedial border of the patella (proximal, central, and distal). MPFL length changes (%) relative to the length in full extension were calculated, and their correlations with the tibial tuberosity-trochlear groove distance, Caton-Deschamps index, and lateral trochlear inclination were analyzed.

RESULTS

The proximal fiber was the longest in full extension and progressively decreased to a median length of -6.0% at 90° of flexion. The central fiber exhibited the most isometric pattern during knee flexion, showing a median maximal decrease of 2.8% relative to the full extension length and no evident elongation. The distal fiber first slightly decreased in length but increased at deeper flexion angles. The median overall length changes were 4.6, 4.7, and 5.7 mm for the proximal, central, and distal patellar insertion, respectively. These values were either not or very weakly correlated with the tibial tuberosity-trochlear groove distance, Caton-Deschamps index, and lateral trochlear inclination when the anatomic parameters were within the healthy range.

CONCLUSION

The median MPFL length changed by approximately 5 mm between 0° and 90° of flexion. Proximally, the length continuously decreased, indicating slackening behavior. Distally, the length increased at deeper flexion angles, indicating tightening behavior.

CLINICAL RELEVANCE

In MPFL reconstruction techniques utilizing the Schöttle point to establish the femoral insertion, one should avoid distal patellar insertion, as it causes elongation of the ligament, which may increase the risk for complications due to overloading.

Intraoperative control by Schanz-screws is inaccurate to achieve the exact amount of correction in de-rotational osteotomies

PURPOSE

The accuracy of intraoperative control of correction commonly is achieved by K-wires or Schanz-screws in combination with goniometer in de-rotational osteotomies. The purpose of this study is to investigate the accuracy of intraoperative torsional control in de-rotational femoral and tibial osteotomies. It is hypothesized, that intraoperative control by Schanz-screws and goniometer in de-rotational osteotomies around the knee is a safe and well predictable method to control the surgical torsional correction intraoperatively.

METHODS

55 consecutive osteotomies around the knee joint were registered, 28 femoral and 27 tibial. The indication for osteotomy was femoral or tibial torsional deformity with the clinical occurrence of patellofemoral maltracking or PFI. Pre- and postoperative torsions were measured according to the method of Waidelich on computed tomography (CT) scan. The scheduled value of torsional correction was defined by the surgeon preoperatively. Intraoperative control of torsional correction was achieved by 5 mm-Schanz-screws and goniometer. The measured values of torsional CT scan were compared to the preoperative defined and intended values and deviation was calculated separately for femoral and tibial osteotomies.

RESULTS

The surgeon's intraoperative measured mean value of correction in all osteotomies was 15.2° (SD 4.6; range 10-27), whereas the postoperatively measured mean value on CT scan was 15.6 (6.8; 5.0-28.5). Intraoperatively the femoral mean value measured 17.9° (4.9; 10-27) and 12.4° (1.9; 10-15) for the tibia. Postoperatively the mean value for femoral correction was 19.8 (5.5; 9.0-28.5) and 11.3 (5.0; 5.0-26.0) for tibial correction. When considering a deviation of plus or minus 3° to be acceptable femorally 15 osteotomies (53.6%) and tibially 14 osteotomies (51.9%) fell within these limits. Nine femoral cases (32.1.%) were overcorrected, four cases undercorrected (14.3%). Four tibial cases of overcorrection (14.8%) and 9 tibial cases of undercorrection (33.3%) were observed. However, the observed difference between femur and tibia regarding the distribution of cases between the three groups did not reach significance. Moreover, there was no correlation between the extent of correction and the deviation from the intended result.

CONCLUSION

The use of Schanz-screws and goniometer in de-rotational osteotomies as an intraoperative control of correction is an inaccurate method. Every surgeon performing derotational osteotomies must consider this and include postoperative torsional measurement in his postoperative algorithm until new tools or devices are available to guarantee a better intraoperative accuracy of torsional correction.

STUDY DESIGN

Observational study.

LEVEL OF EVIDENCE

III.

Isolated Medial Patellofemoral Ligament Reconstruction in Patellar Instability: Does the Distance Between Tibial Tuberosity-Trochlear Groove Make a Difference?

Introduction

Medial patellofemoral ligament reconstruction (MPFLR) is used in most patellar instability surgeries, there is controversy on adding a tibial tuberosity osteotomy (TTO).

Objective

To describe the results of isolated MPFLR in patellar instability according to the Tibial Tuberosity-Trochlear Groove distance (TT-TG).

Methods

Retrospective study of patients with patellar instability with a mature skeleton in one center between 2016 and 2021, using isolated MPFLR. Patients with incomplete clinical and/or radiological records and less than one year follow-up were excluded. Pre-surgical demographic and radiological data (TT-TG, Caton-Deschamps (CD) index, patellar tilt, trochlear dysplasia) were recorded. Patients were divided into three groups according to TT-TG distance (Group 1: < 17 mm, Group 2: 17-19, Group 3: ≥ 20 mm). A pre and post-surgical Kujala score was performed. Local complications, satisfaction, recurrence and/or reintervention were recorded. Pre-surgical variables between groups, intra and inter-group Kujala differences were compared using Bartlett's test. Consent from the patients and approval from the local ethics committee were obtained.

Results

67 patients met the selection criteria, mean age of 23 years, 70% were women. There were no pre surgical, radiological nor follow-up differences between the groups (average 27 months). Pre and post-surgical Kujala score, respectively: Group 1: 37-78, Group 2: 37-78, Group 3: 39-79. All groups had a significant improvement (p < 0.05), there were no significant differences in improvement between groups (p > 0.05). There were three patients with a redislocation episode, all in group 1. One patient had a mobilization under anesthesia due to an arthrofibrosis (Group 2). 97% of all cases reported being satisfied.

Conclusion

Isolated MPFLR in patellar instability presents a functional improvement, with a low rate of complications and failure, regardless of the pre surgical TT-TG.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43465-023-00906-6.

Patellar Tracking: An Old Problem with New Insights

Patellofemoral pain and instability are common indications for imaging that are encountered in everyday practice. The authors comprehensively review key aspects of patellofemoral instability pertinent to radiologists that can be seen before the onset of osteoarthritis, highlighting the anatomy, clinical evaluation, diagnostic imaging, and treatment. Regarding the anatomy, the medial patellofemoral ligament (MPFL) is the primary static soft-tissue restraint to lateral patellar displacement and is commonly reconstructed surgically in patients with MPFL dysfunction and patellar instability. Osteoarticular abnormalities that predispose individuals to patellar instability include patellar malalignment, trochlear dysplasia, and tibial tubercle lateralization. Clinically, patients with patellar instability may be divided into two broad groups with imaging findings that sometimes overlap: patients with a history of overt patellar instability after a traumatic event (eg, dislocation, subluxation) and patients without such a history. In terms of imaging, radiography is generally the initial examination of choice, and MRI is the most common cross-sectional examination performed preoperatively. For all imaging techniques, there has been a proliferation of published radiologic measurement methods. The authors summarize the most common validated measurements for patellar malalignment, trochlear dysplasia, and tibial tubercle lateralization. Given that static imaging is inherently limited in the evaluation of patellar motion, dynamic imaging with US, CT, or MRI may be requested by some surgeons. The primary treatment strategy for patellofemoral pain is conservative. Surgical treatment options include MPFL reconstruction with or without osseous corrections such as trochleoplasty and tibial tubercle osteotomy. Postoperative complications evaluated at imaging include patellar fracture, graft failure, graft malposition, and medial patellar subluxation. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Reconstruction of High-Grade Trochlea Dysplasia in a Young Female with Recurrent Patella Dislocation: A Case Report

The patellofemoral joint involves a combination of bony structures and soft tissues to maintain stability. Patella instability is a disabling condition, and the cause is multifactorial. The main risk factors include patella alta, trochlea dysplasia, excessive tibial tuberosity to trochlea grove (TT-TG) distance, and excessive lateral patella tilt. In this case report, we highlight the thinking process of diagnosis and method for selecting the optimal treatment in accordance with the guidelines by Dejour et al. when we are presented with a patient with patella instability. A 20-year-old Asian woman without underlying medical conditions, presented with recurrent (>3 episodes) right patella dislocation for 7 years. Investigations revealed a type D trochlea dysplasia, increased TT-TG distance, and excessive lateral tilt angle. She underwent trochlea sulcus deepening, sulcus lateralization and lateral facet elevation, lateral retinacular release, and medial quadriceps tendon-femoral ligament (MQTFL) reconstruction. Due to the complexity behind the anatomy and biomechanics of patella instability, an easy-to-follow treatment algorithm is essential for the treating surgeon to provide effective and efficient treatment. MQTFL reconstruction is recommended for recurrent patella dislocation due to satisfactory clinical and patient reported outcomes and a reduced risk of iatrogenic patella fracture. Controversies for surgical indication in lateral retinacular release, and whether the sulcus angle is an accurate parameter for diagnosis of trochlea dysplasia, remain, and further research is required.

The Femoral Sulcus Deepening Trochleoplasty of Lyon

The sulcus deepening trochleoplasty procedure has been described for the management of patellofemoral instability in patients with severe trochlear dysplasia. Here, we describe the updated Lyon sulcus deepening trochleoplasty technique. This technique with a stepwise approach allows one to prepare the trochlea, remove the subchondral bone, osteotomize the articular surface, and fix the facets with 3 anchors while minimizing the risk of complications.

Imaging evaluation of patellofemoral joint instability: a review

The multifactorial origin of anterior knee pain in patellofemoral joint disorders leads to a demanding diagnostic process. Patellofemoral misalignment is pointed out as one of the main causes of anterior knee pain. The main anatomical risk factors of patellofemoral instability addressed in the literature are trochlear dysplasia, abnormal patellar height, and excessive tibial tubercle-trochlear groove distance. Diagnostic imaging of the patellofemoral joint has a fundamental role in assessing these predisposing factors of instability. Extensive work is found in the literature regarding the assessment of patellofemoral instability, encompassing several metrics to quantify its severity. Nevertheless, this process is not well established and standardized, resulting in some variability and inconsistencies. The significant amount of scattered information regarding the patellofemoral indices to assess the instability has led to this issue. This review was conducted to collect all this information and describe the main insights of each patellofemoral index presented in the literature. Five distinct categories were created to organize the patellofemoral instability indices: trochlear dysplasia, patellar height, patellar lateralization, patellar tilt, and tibial tubercle lateralization.

Derotational distal femoral osteotomy for patients with recurrent patellar instability and increased femoral antetorsion improves knee function and adequately treats both torsional and valgus malalignment

PURPOSE

The aim of the study was to evaluate the functional and radiological outcome following derotational distal femoral osteotomy (D-DFO) in patients with high-grade patellofemoral instability (PFI) and an associated increased femoral antetorsion (FA). It was hypothesized that D-DFO would lead to a good functional and radiological outcome, and that both torsional and coronal malalignment could be normalized.

METHODS

Patients that underwent D-DFO between 06/2011 and 12/2018 for high-grade PFI with an increased FA (> 20°) were included. Patient-reported outcome measures (Visual Analog Scale [VAS] for pain, Kujala score, Lysholm score, International Knee Documentation Committee subjective knee form [IKDC], and Tegner Activity Scale [TAS]) were evaluated pre- and minimum 24 months postoperatively. Magnetic resonance imaging of the lower extremity and weight-bearing whole-leg anteroposterior radiographs were conducted pre- and postoperatively. The change in FA, coronal limb alignment, and PROMs were tested for statistical significance.

RESULTS

In total, 27 patients (30 knees) were included. The D-DFO aimed to only correct FA (Group 1) or to additionally perform a varization (Group 2) in 14 cases each. In the remaining two cases, double-level osteotomies were performed to correct additional tibial deformities. In 25 cases (83.3%), concomitant procedures also addressing patellofemoral instability were performed. At follow-up (38.0 months [25-75% interquartile range 31.8-52.5 months]), a significant reduction in pain (VAS for pain: 2.0 [1.0-5.0] vs. 0 [0-1.0], p < 0.05), significant improvement in knee function (Kujala Score: 55.6 ± SD 13.6 vs. 80.3 ± 16.7, p < 0.05; Lysholm Score: 58.6 ± 17.4 vs. 79.5 ± 16.6, p < 0.05; IKDC: 54.6 ± 18.7 vs. 74.1 ± 15.0, p < 0.05), and an increase in sporting activity (TAS: 3.0 [3.0-4.0] vs. 4.0 [3.0-5.0], p = n.s.) were reported. Femoral antetorsion was significantly reduced (28.2 ± 6.4° vs. 13.6 ± 5.2°, p < 0.05). A significant varization was observed in Group 2 (2.4 ± 1.2° valgus vs. 0.3 ± 2.4° valgus; p < 0.05). In one case, patellar redislocation occurred 70 months postoperatively.

CONCLUSION

In patients with PFI and an associated increased FA, D-DFO achieved a significant reduction in pain, an improvement of subjective knee function, as well as an adequate correction of torsional and coronal alignment.

LEVEL OF EVIDENCE

Retrospective case series, Level IV.

How to fix a tibial tubercle osteotomy with distalisation: A finite element analysis

BACKGROUND

Antero-medialisation osteotomy combined with a distalisation procedure may require a more stable fixation as the osteotomy fragment loses both proximal and distal support. This finite element analysis aimed to compare the mechanical behaviour of different fixation techniques in tibial tubercle antero-medialisation osteotomy combined with distalisation procedure.

METHODS

Tibial tubercle osteotomy combined with distalisation was modelled based on computerised tomography data, which were acquired from a patient with patellar instability requiring this procedure. Six different fixation configurations with two 3.5-mm cortical screws (1), two 4.5-mm cortical screws (2), three 3.5-mm cortical screws (3), three 4.5-mm cortical screws (4), three 3.5-mm screws with 1/3 tubular plate (5), and four 3.5-mm screws with 1/3 tubular plate (6) were created. A total of 1654 N of force was applied to the patellar tendon footprint on the tibial tubercle. Sliding, gap formation, and total deformation between the osteotomy components were analyzed.

RESULTS

Maximum sliding (0.660 mm), gap formation (0.661 mm), and displacement (1.267 mm) were seen with two 3.5-mm screw fixation, followed by two 4.5-mm screws, three 3.5-mm screws, and three 4.5-mm screws, respectively, in the screw-only group. Overall, the minimum displacement was observed with the four 3.5-mm screws with 1/3 tubular plate fixation model.

CONCLUSIONS

Plate fixation might be recommended for tibial tubercle antero-medialisation osteotomy combined with distalisation procedure because it might allow early active range of motion exercises and weight-bearing.

Patellar medial closing-wedge osteotomy in patello-femoral instability: Indications and outcomes

Background

Patellofemoral (PF) instability is a syndrome involving several factors and conditions. Trochlear dysplasia (TD) has been shown to be the feature most frequently diagnosed in patients with OPI (Objective Patellar Instability). Even the patella might have an altered shape. Articulating during growth with an abnormal trochlea might lead the patellar posterior surface to modify accordingly, becoming congruent with the trochlear shape. A mismatch between the two articulating surfaces has a role in patellofemoral dislocations.Rarely and in case of a highly dysplastic patella, reshaping only the trochlear groove might lead subsequently to an incongruence between the two bones.When isolated sulcus-deepening trochleoplasty does not restore a congruent patellofemoral tracking tested perioperatively, further surgical procedures might be required.

Methods

A medial closing wedge patellar osteotomy (MCWPO) added to sulcus deepening trochleoplasty should be performed to create a congruent patellofemoral joint.Indications for this procedure are Wiberg type III or IV patella with an intraoperative abnormal patellar tracking after the sulcus deepening trochleoplasty procedure has been concluded.

Results

From January 2012 to August 2020, 21 (6 right and 15 left knees) sulcus deepening trochleoplasties with a concomitant medial closing wedge patellar osteotomy have been performed. The mean follow up was 35,25 months (ranging from 10 to 60 months). The average Kujala, IKDC and Lysholm score were respectively 70,14 ± 15,51; 55,75 ± 7,12 and 77,12 ± 14,80. No further patellar dislocation has been assessed in those patients during follow up.

Conclusion

This technique has shown good and promising clinical outcomes and should be considered when treating patients with a still unsatistactory patellofemoral tracking after the sulcus deepening trochleoplasty has been performed due to a patella-trochlea shape mismatch.

Patellar dislocation following distal femoral replacement after extra-articular knee resection for bone sarcoma: A case report

BACKGROUND

For the treatment of bone sarcoma in the distal femur, wide-margin resection and knee reconstruction with tumor endoprosthesis are standard therapies. Extra-articular knee resection is required in cases of tumor invasion of the knee joint; however, the incidence of complications, such as aseptic loosening, prosthesis infection, and implant failure, is higher than that following intra-articular knee resection. To the best of our knowledge, there are three reports of patellar dislocations after replacement of a tumor endoprosthesis.

CASE SUMMARY

A 36-year-old man with no significant past medical history was admitted to our institution with continuous pain in his left knee for 4 mo. An open biopsy was performed, and the patient was diagnosed with a left distal femoral malignant bone tumor. Extra-articular knee resection and knee reconstruction with a tumor endoprosthesis were performed. Although the alignment of the tumor prosthesis was acceptable, knee instability was noticed postoperatively. The axial radiographic view of the patellar and computed tomography showed lateral patellar dislocation at 4 wk postoperatively. The patient had to undergo a lateral release and proximal realignment. He could perform his daily activities at 9 mo postoperatively. Radiography revealed no patellar re-dislocation.

CONCLUSION

Proximal realignment may be considered during primary surgery if there is an imbalance in the forces controlling the patellar tracking.