The Morphologic Patella Entry Point Into the Proximal Trochlea Is More Lateral in Recurrent Dislocators Than Controls as Measured by Entry Point-Trochlear Groove Angle.

PURPOSE: To create a metric for evaluating the degree of laterality of the patella's entry into the trochlea, the entry point-trochlear groove (EP-TG) angle, and to evaluate if this laterality is associated with recurrent patella instability. METHODS: The time frame of the study was January 2020 to February 2023. The inclusion criteria were patients treated by the senior author (J.P.F.) (with the exception of 2 patients who were treated by another provider at the institution who was aware of the study) who have been diagnosed with recurrent atraumatic patellar dislocations. Controls without knee pathology were selected from the New Mexico Decedent Imaging Database (NMDID). Simpleware ScanIP was used to create 3-dimensional (3D) models of the distal femurs from computed tomography scans. Anteroposterior images of these 3D models were uploaded to a custom EP-TG angle measuring tool. Three measurers used the tool to measure the EP-TG angle of the distal femurs. RESULTS: Twenty-eight patients were included for the recurrent dislocator group. Twenty-four decedents from the NMDID were selected for the control group, each with a left or right knee chosen randomly for measurement. A 1-sided Mann-Whitney U test, used to evaluate whether the recurrent dislocators had higher EP-TG angle values, yielded a P value <.001, demonstrating a high level of significance. A Bayesian mixed-effect model, used to determine how different the EP-TG angles are between the 2 groups, gave a posterior predictive interval of [11.93°, 19.12°] for the EP-TG angle shift of dislocators. The intraclass correlation coefficient was 0.648. CONCLUSIONS: The morphologic entry point of the patella into the proximal trochlea is more lateral in recurrent patella dislocators than in controls. This increased laterality can be measured by the EP-TG angle, which may be useful information for optimizing treatment of recurrent patella instability. LEVEL OF EVIDENCE: Level III, case control study.

Three-Dimensional Imaging of the Patellofemoral Joint Improves Understanding of Trochlear Anatomy and Pathology and Planning of Realignment.

Three-dimensional (3D) modeling using digital or printed models provides a unique perspective that caters to cognitive spatial ability in a way that can add to our understanding and mental representations of human anatomy. This is particularly useful in the setting of trochlear dysplasia, where the morphology of the groove can exhibit substantial variability and complexity. Using 3D reformatted images and models, a pragmatic understanding of how morphology influences patellofemoral pathology can be gleaned. Further, this perspective facilitates cognition of what patellar tracking may look like after realignment procedures. Using 3D modeling, concepts such as patella alta, trochlear depth, lateralization of the patellar entry point, trochlear curvature, and the presence of a proximal trochlear spur can help afford a better understanding of how trochlear anatomy may influence tracking while also providing insight as to the ideal tracking path. The use of 3D has recently emerged as a useful tool in multiple surgical subspecialties, particularly in situations involving surgical planning or complex anatomy. Given the complexity and variation in trochlear morphology in patients with trochlear dysplasia who develop either patellar instability or focal overloading, 3D modeling is well-suited to provide a perspective that can add to our understanding of trochlear dysplasia, and potentially even how we diagnose and treat it. LEVEL OF EVIDENCE: Level V, expert opinion.

A modified Delphi consensus statement on patellar instability: part I.

Aims: The aim of this study was to establish consensus statements on the diagnosis, nonoperative management, and indications, if any, for medial patellofemoral complex (MPFC) repair in patients with patellar instability, using the modified Delphi approach. Methods: A total of 60 surgeons from 11 countries were invited to develop consensus statements based on their expertise in this area. They were assigned to one of seven working groups defined by subtopics of interest within patellar instability. Consensus was defined as achieving between 80% and 89% agreement, strong consensus was defined as between 90% and 99% agreement, and 100% agreement was considered to be unanimous. Results: Of 27 questions and statements on patellar instability, three achieved unanimous consensus, 14 achieved strong consensus, five achieved consensus, and five did not achieve consensus. Conclusion: The statements that reached unanimous consensus were that an assessment of physeal status is critical for paediatric patients with patellar instability. There was also unanimous consensus on early mobilization and resistance training following nonoperative management once there is no apprehension. The statements that did not achieve consensus were on the importance of immobilization of the knee, the use of orthobiologics in nonoperative management, the indications for MPFC repair, and whether a vastus medialis oblique advancement should be performed.

Three-Dimensional Printing of Models of Patellofemoral Joint Articular Cartilage in Patients With Patella Instability for Observing Joint Congruity.

Three-dimensional (3D) modeling and printing are increasingly used in the field of orthopaedic surgery for both research and patient care. One area where they are particularly helpful is in improving our understanding of the patellofemoral (PF) joint. Heretofore, morphological studies that use 3D models of the PF joint have primarily been based on computed tomography imaging data and thus do not incorporate articular cartilage. Here, we describe a method for creating 3D models of the articular surfaces of the PF joint based on magnetic resonance imaging. Models created using this technique can be used to improve our understanding of the morphology of the articular surfaces of the PF joint and its relationship to joint pathologies. Of particular interest is our finding of articular congruity in printed articular cartilage surfaces of dysplastic PF joints of recurrent patella dislocators.

A modified Delphi consensus statement on patellar instability: part II.

Aims: The aim of this study was to establish consensus statements on medial patellofemoral ligament (MPFL) reconstruction, anteromedialization tibial tubercle osteotomy, trochleoplasty, and rehabilitation and return to sporting activity in patients with patellar instability, using the modified Delphi process. Methods: This was the second part of a study dealing with these aspects of management in these patients. As in part I, a total of 60 surgeons from 11 countries contributed to the development of consensus statements based on their expertise in this area. They were assigned to one of seven working groups defined by subtopics of interest. Consensus was defined as achieving between 80% and 89% agreement, strong consensus was defined as between 90% and 99% agreement, and 100% agreement was considered unanimous. Results: Of 41 questions and statements on patellar instability, none achieved unanimous consensus, 19 achieved strong consensus, 15 achieved consensus, and seven did not achieve consensus. Conclusion: Most statements reached some degree of consensus, without any achieving unanimous consensus. There was no consensus on the use of anchors in MPFL reconstruction, and the order of fixation of the graft (patella first versus femur first). There was also no consensus on the indications for trochleoplasty or its effect on the viability of the cartilage after elevation of the osteochondral flap. There was also no consensus on postoperative immobilization or weightbearing, or whether paediatric patients should avoid an early return to sport.

Three-Dimensional Reproductions for Surgical Decision-Making in the Treatment of Recurrent Patella Dislocation.

Patellofemoral instability may be attributed to a variety of soft tissue and osseous factors, of which dysplasia of the femoral trochlea significantly predisposes patients to recurrent instability events. Surgical planning and decision-making remain wholly predicated upon two-dimensional imaging-derived measurements and classification systems, although aberrant patellar tracking in the setting of trochlea dysplasia is a three-dimensional (3-D) complexity. 3-D reconstructions of the patellofemoral joint (PFJ) may be considered to better comprehend the complex anatomy of patients with recurrent patella dislocation and/or trochlea dysplasia. We describe a classification and integrated interpretation system by which these 3-D reproductions of the PFJ may be analyzed to enhance surgical decision making in the treatment of this condition to achieve optimal joint stability and long-term preservation.

Incidence of Early Adverse Events After Tibial Tubercle Osteotomy.

Background: Tibial tubercle osteotomy (TTO) is a commonly utilized surgical procedure for the treatment of patellofemoral instability. Although midterm and long-term outcomes are known, perioperative complications have not been consistently reported. Purpose: To identify the incidence and predictors of adverse events in the first 90-day perioperative period after TTO. Study Design: Case series; Level of evidence, 4. Methods: Patients undergoing primary TTO between January 1, 2010, and December 31, 2019, were included. Readmissions in the first 90 days after surgery were collected, and data were collected for the following variables: age, sex, smoking status, body mass index, laterality, preoperative diagnosis, presence of trochlear dysplasia, tourniquet use, TTO procedure, tibial tubercle distalization, trochleoplasty, chondral procedure, number of screws, and use of an epidural catheter. Predictors of readmission for any reason were identified using multivariable logistic regression analysis. Results: A total of 345 TTO procedures were included in the final analysis. The incidence of readmissions for any reason was 20.6% (71/345). The most common reason for readmission was postoperative pain (26/345 [7.5%]), followed by wound complications (19/345 [5.5%]) and epidural catheter-related complications (overall: 16/345 [4.6%]; specific: 16/167 [9.6%]. The incidence of major complications was 2.0% (7/345). The number of patients with each major complication was as follows: 1 for deep vein thrombosis, 2 for pulmonary embolism, 1 for septic arthritis, 1 for tibial tubercle fracture, and 2 for loss of fixation. Female sex and smoking were associated with readmission for pain. Conclusion: The incidence of major complications after TTO was very low (2.0%), but 20.6% of cases required readmission, primarily for an indwelling epidural catheter (3.5%) and postoperative pain (7.5%). Concomitant soft tissue procedures and the number of screws were associated with readmission after TTO. Utilizing individualized postoperative pain management and preoperative discussions about expected pain may help to avoid readmission for pain after TTO.

Three-Dimensional Printing of the Patellofemoral Joints of Patellar Instability Patients.

Three-dimensional (3D) modeling and printing comprise an important tool for orthopaedic surgeons. One area in which 3D modeling has the potential to dramatically improve our understanding of biomechanical kinematics is pathologies of the patellofemoral joint, in particular trochlear dysplasia. We describe a method for creating 3D printed models of the patellofemoral joint, including computed tomography image acquisition, image segmentation, model creation, and 3D printing. The models created can help surgeons understand and plan surgery for recurrent patellar dislocations.

Localization of the Adductor Tubercle in the Skeletally Immature: A Computed Tomography Study With Patellofemoral Surgical Implications.

BACKGROUND: The adductor tubercle of the distal femur is utilized by surgeons as an anatomic landmark to identify graft anchor placement during medial patellofemoral ligament (MPFL) and medial quadriceps tendon femoral ligament (MQTFL) reconstruction for patellofemoral instability. In the skeletally immature population, its location relative to the physis has not been well defined. PURPOSE: To identify the location of the adductor tubercle relative to the distal femoral physis in skeletally immature individuals and gain insight regarding optimal graft anchor placement for pediatric patients undergoing MPFL and MQTFL reconstruction. STUDY DESIGN: Descriptive laboratory study. METHODS: Thin-cut computed tomography scans of 37 male cadaveric specimens (age, 4-16 years) were obtained from the New Mexico Decedent Image Database. A measurement protocol to identify the adductor tubercle was created with guidance from a fellowship-trained musculoskeletal radiologist. By utilizing axial, coronal, and sagittal views of knee computed tomography scans, the adductor magnus tendon was identified and followed distally to its insertion (adductor tubercle) on the distal femur. Distance from the midpoint of the adductor magnus tendon insertion relative to the physis in the proximal-distal orientation was measured. The anterior-posterior distance of the midpoint tendon insertion relative to the posterior femoral cortex line was also evaluated. RESULTS: The midpoint of the adductor magnus tendon was at the physis in 30 specimens. One 8-year-old cadaveric specimen had an insertion 1.1 mm distal to the physis. In all specimens ≥15 years old (n = 6), the adductor magnus tendon insertion was distal to the physis with a mean distance of 2.73 mm. The location of the adductor tubercle was always posterior (mean, 5.1 mm) with respect to the posterior femoral cortex line. CONCLUSION: The location of the adductor tubercle in male pediatric patients is likely at or distal to the physis. Thus, the findings of this study directly conflict with previous studies that suggested a more proximal location. CLINICAL RELEVANCE: Optimal graft anchor placement during MPFL and MQTFL reconstruction in the skeletally immature patient can be challenging because of the variability reported in previous studies of the medial patellofemoral complex origin relative to the physis. This study suggests that distal-rather than proximal-graft anchor placement might better help restore patellofemoral isometry.

Reconceptualization of Trochlear Dysplasia in Patients With Recurrent Patellar Dislocation Using 3-Dimensional Models.

Background: Common classification schemes, measurements, and surgical planning for trochlear dysplasia are predicated on 2-dimensional imaging views. Purpose: To investigate patellofemoral joint osseous anatomy using 3-dimensional (3D) printed models to describe osseous anatomic trochlear variations in patients with recurrent patellar dislocation. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Computed tomography scans were obtained from 20 patients with recurrent patellar dislocation and 10 healthy control knees, and 3D prints generated from these computed tomography scans were studied with respect to mediolateral positioning of the proximal trochlear groove and groove obliquity as well as changes in the appearance, height, and orientation of the medial and lateral trochlear ridges. Each trochlea was centered with respect to a vertical line perpendicular to the distal femoral condyles and through the central intercondylar notch roof, with the 3D models resting on their posterior femoral condyles. A novel 3D measurement method was devised to assess groove obliquity, termed the entry point-transition point (EP-TP) angle. The EP was defined as the midpoint of the flattened region of the proximal trochlea where the lateral and medial ridges of the proximal trochlea meet, and the TP was the point along the trochlear groove at which the groove shape changes from an oblique orientation proximally to one more vertical distally. Measurements were obtained by 3 reviewers, and reliability analyses were performed. Results: With the dysplastic knees arranged according to flattening of the trochleas, increased obliquity of the trochlear grooves was observed, as reflected by increased EP-TP angles as well as more lateral patellar EPs into the proximal trochleas of these recurrent patellar dislocation knees when compared with the control knees. The degree of trochlear dysplasia (according to the Dejour classification and trochlear flatness in the frontal and axial planes) was associated with diminished prominence of the lateral trochlear convexity, increasingly lateralized proximal trochlear EPs, increased trochlear groove obliquity, lateral trochlear curvature, and progressive medial ridge deformity. Conclusion: The 3D reproductions enabled unique conceptualization of trochlear deformity associated with recurrent patellar dislocation.

Quadriceps Tendon Attachment Technique for Medial Quadriceps Tendon-Femoral Ligament (MQTFL) Reconstruction in the Surgical Treatment of Recurrent Patella Dislocation.

Medial quadriceps tendon-femoral ligament (MQTFL) reconstruction for prevention of recurrent patella dislocation is an alternative to medial patellofemoral ligament (MPFL) reconstruction. Because the reconstruction graft attaches to the quadriceps tendon, no patella drill hole is required, thereby eliminating iatrogenic fracture risk. The procedure remains anatomically accurate and early results are comparable to MPFL reconstruction for preventing patella dislocation. The MQTFL reconstruction graft is brought up under the vastus medialis obliquus distal to the patella apex, such that its orientation is directed toward the medial patellofemoral complex (MPFC) midpoint, also known as Tanaka's point. The graft is then secured by looping it around the vastus medialis and rectus femoris tendons, after which optimal graft length is easily established by cycling the knee, after which it is sutured securely into the deep quadriceps tendon precisely at the anatomic midpoint of the MPFC. Anatomic reconstruction of the MQTFL-in which graft orientation is crucial-confers reliable patellofemoral joint stability in the surgical treatment of patients with recurrent patella dislocations.

Coronal Malalignment-When and How to Perform a Tibial Tubercle Osteotomy.

Coronal malalignment of the patellofemoral joint may contribute to both instability as well as pain and joint overload. The use of distal realignment procedures has evolved to include uniplanar and multiplanar osteotomies, which allows patient-specific treatment. With a careful understanding of the complex pathoanatomy, including osseous, soft tissue, and dynamic muscular factors, an appropriately designed tibial tubercle osteotomy (TTO) is an invaluable tool for the orthopedic surgeon to improve joint biomechanics and off-load articular injuries. Current techniques have improved TTO surgery to limit complications and produce reliably good results.

Current Concepts Regarding Patellofemoral Trochlear Dysplasia.

Optimal treatment of patients with patellofemoral trochlear dysplasia and recurrent patellar instability requires in-depth understanding of this complex structural anomaly. An extensive review of the literature suggests that dysplasia occurs as a result of aberrant forces applied to the patellofemoral joint in the majority of cases. Evidence supports surgical stabilization that reconstructs the medial patellofemoral and/or medial quadriceps tendon-femoral ligament without added trochleoplasty in the majority of patients with trochlear dysplasia and recurrent patellar instability. Adding tibial tubercle transfer distally, medially, or anteromedially in those who need it to treat specific deficits in alignment or articular cartilage can be beneficial in selected patients with trochlear dysplasia and recurrent patellar instability. Trochleoplasty may be appropriate in those few cases in which permanent stable patellofemoral tracking cannot be restored otherwise, but the indications are not yet clear, particularly as trochleoplasty adds risk to the articular cartilage. Improved understanding of imaging techniques and 3-dimensional reproductions of dysplastic patellofemoral joints are useful in surgical planning for patients with recurrent patellar instability and trochlear dysplasia.

Editorial Commentary: The Best Medial Patellofemoral Reconstruction May Include Components of Both Quadriceps and Patellar Attachments.

Given different functions of the medial quadriceps tendon-femoral ligament and medial patellofemoral ligament components of the proximal medial patellar restraints, reconstructions to the midpoint of the medial patellofemoral ligament and medial quadriceps tendon-femoral ligament are probably optimal, combining the benefits of both in surgical treatment of recurrent patella instability.

Medial Patellofemoral Ligament Reconstruction in Skeletally Immature Patients.

Patellofemoral instability is a common problem affecting children and adolescents, with recurrent instability often requiring surgical intervention. Medial patellofemoral ligament (MPFL) reconstruction has become a mainstay for the treatment of patellofemoral instability because of the biomechanical importance of the MPFL against lateral dislocation as well as the high frequency of MPFL injury following traumatic patellar dislocation. The concern in managing skeletally immature patients is the potential for injury to the distal femoral physis. Here, we highlight 2 techniques for MPFL reconstruction. The first technique utilizes a hamstring autograft. The steps include: Step 1: Harvest the semitendinosus graft from a 2-cm posteromedial incision with use of an open tendon harvester proximally and a closed tendon harvester distally. Step 2: Prepare the graft for double-bundle reconstruction, allowing for approximately 50 to 60 mm for the reconstructed MPFL and 15 to 20 mm for graft placement within the patella and femoral sockets. Step 3: Use a guidewire and reamer to create 2 patellar sockets approximately 15 mm long each. Step 4: Use a guidewire under fluoroscopy to position and create a femoral socket distal to the distal femoral physis approximately 15 mm long. Step 5: Fix the graft on the femur with use of a tenodesis screw, pass the graft through the soft-tissue space between the fascia and synovium to the superior half of the patella, then dock the free ends of the graft onto the 2 patellar sockets with "PEEK (polyetheretherketone) SwiveLocks (Arthrex)" while the knee is in 30° of flexion. We also review a second technique of docking the hamstring graft onto the adductor tubercle and suturing it proximally to the deep distal medial aspect of the quadriceps tendon. Although only a limited number of studies have reported the outcomes of MPFL reconstruction in skeletally immature patients, such studies have demonstrated a high return to preoperative level of sports activity and a reduced prevalence of recurrent patellar instability.

Repair of the medial patellofemoral ligament with suture tape augmentation leads to similar primary contact pressures and joint kinematics like reconstruction with a tendon graft: a biomechanical comparison.

PURPOSE: To compare suture tape-augmented MPFL repair with allograft MPFL reconstruction using patellofemoral contact pressure and joint kinematics to assess the risk of patellofemoral over-constrainment at point zero. METHODS: A total of ten fresh frozen cadaveric knee specimens were tested in four different conditions of the MPFL: (1) native, (2) cut, (3) reconstructed with tendon graft, and (4) augmented with suture tape. The patellofemoral mean pressure (MP), peak pressure (PP) and contact area (CA) were measured independently for the medial and lateral compartments using pressure-sensitive films. Patellar tilt (PT) and shift (PS) were measured using an optical 3D motion tracking system. Measurements were recorded at 0°, 10°, 20°, 30°, 60° and 90° of flexion. Both the tendon graft and the internal brace were preloaded with 2 N, 5 N, and 10 N. RESULTS: There was no significant differences found between surgical methods for medial MP, medial PP, medial CA, lateral MP and PS at any preload or flexion angle. Significant differences were seen for lateral PP at 20° knee flexion and 10 N preload (suture tape vs. reconstruction: 1045.9 ± 168.7 kPa vs. 1003.0 ± 151.9 kPa; p = 0.016), for lateral CA at 10° knee flexion and 10 N preload (101.4 ± 39.5 mm2 vs. 108.7 ± 36.6 mm2; p = 0.040), for PT at 10° knee flexion and 2 N preload (- 1.9 ± 2.5° vs. - 2.5 ± 2.3°; p = 0.033) and for PT at 0° knee flexion and 10 N preload (- 0.8 ± 2.5° vs. - 1.8 ± 3.1°; p = 0.040). A preload of 2 N on the suture tape was the closest in restoring the native joint kinematics. CONCLUSIONS: Suture tape augmentation of the MPFL resulted in similar primary contact pressures and joint kinematics in comparison with MPFL reconstruction using a tendon graft. A pretension of 2 N was found to restore the knee joint closest to normal patellofemoral kinematics.

Unilateral anterior knee pain is associated with increased patellar lateral position after stressed lateral translation.

PURPOSE: To objectively compare side-to-side patellar position and mobility in patients with idiopathic unilateral anterior knee pain (AKP) using a stress-testing device concomitantly with magnetic resonance imaging. It is hypothesized that the painful knees present greater patellar mobility than the contralateral non-painful knees. METHODS: From a total sample of 359 patients, 23 patients with idiopathic unilateral AKP (30.9 years, 23.4 kg/m2, 43% males) were included within the present study. Both knees of all the patients were examined by conventional imaging, including the measurement of trochlear sulcus angle, Caton-Deschamps index, tibial tuberosity to trochlear groove distance, patellar tilt angle and patellar subluxation (both at rest and upon quadriceps contraction). Additionally, the same patients underwent stress testing (Porto Patella Testing Device); these measurements were taken with the patella at rest, after lateral patellar translation and after lateral patellar tilt. Clinical and functional outcomes were obtained using physical examination and the Kujala and Lysholm scores. RESULTS: Painful knees showed statistically significant higher patellar lateral position after stressed lateral translation than non-painful knees (p = 0.028), 9.8 ± 3.6 mm and 7.1 ± 6.3 mm, respectively. The adjusted multivariate logistic model identified the patellar position after lateral displacement to be significantly associated with AKP (OR = 1.165) and the model (AUC = 0.807, p < 0.001) showed reasonable sensitivity (67%) and specificity (73%). CONCLUSION: Patients with idiopathic unilateral AKP with morphologically equivalent knees showed statistically significant increased patellar lateral position after stressed lateral displacement in their painful knee. The greater lateral patellar mobility quantified by the PPTD testing brings more objectivity to the diagnosis. LEVEL OF EVIDENCE: II.

An Updated Overview of the Anatomy and Function of the Proximal Medial Patellar Restraints (Medial Patellofemoral Ligament and the Medial Quadriceps Tendon Femoral Ligament).

The medial patellofemoral ligament (MPFL) has been widely accepted to function as "the primary static restraint to lateral patellar displacement." However, current growing evidence suggests that there is a complex of medial patellofemoral/tibial ligaments, both proximal [MPFL, and medial quadriceps tendon femoral ligament (MQTFL)], and distal (medial patellotibial ligament and the medial patellomeniscal ligament) which restrain lateral patellar translation at different degrees of knee flexion. Specifically, the MQTFL has gained popularity over the last decade because of pure soft tissue attachments into the extensor mechanism that allow for avoidance of drilling tunnels into the patella during reconstruction. The purpose of this article was to report on the current knowledge (anatomy, biomechanics, diagnosis, indications for surgery, and techniques) on the proximal medial patellar restraints, namely the MPFL and the MQTFL, collectively referred to as the proximal medial patellar restraints.

When and How I Add Trochleoplasty in the Treatment of Recurrent Patella Instability.

Long experience and recent evidence suggest that trochleoplasty is needed in very few patella stabilization surgeries. As trochleoplasty adds risk, this author recommends it only in patients with high degrees of dysplasia, prominent supratrochlear spurs, ligamentous laxity, and more dramatic J signs.

Fifteen-Year Minimum Follow-Up of Anteromedial Tibial Tubercle Transfer for Lateral and/or Distal Patellofemoral Arthrosis.

PURPOSE: To evaluate a minimum 15-year clinical and radiographic follow-up after anteromedial tibial tubercle transfer (anteromedialization [AMZ]) for lateral and/or distal patellar facet arthrosis. METHODS: Patients treated from 1996 to 2000 were contacted. The inclusion criteria were a minimum of 15 years' follow-up after AMZ for isolated persistent retropatellar pain related to lateral and/or distal patellar chondrosis. The exclusion criteria were clinical patellar instability, revision, and significant medial patellar facet or adjacent compartment chondrosis. The anatomic location(s) and severity of arthrosis, as well as the degree of lateral maltracking, were documented. Follow-up data included pain, activity level, and satisfaction. RESULTS: Of 23 patients, 15 met the inclusion criteria. All were women (17 knees) followed up for a mean of 17.1 years (range, 15.4-18.8 years). The mean age at surgery was 29.5 years. Satisfactory results were reported in 94% of knees (16 of 17), based simply on patients' subjective evaluation of the degree of success perceived. An important criterion of satisfaction was that these patients stated they would opt to undergo surgery again under the same circumstances. For 35% of knees, patients reported engaging in recreational activities, whereas for 18%, patients were minimally active. The average pain score (range, 0-10) for 75% was 2.1, and most of these patients showed grade I or II arthrosis. Post-AMZ symptomatic medial patellar subluxation was corrected successfully in 2 patients. Removal of hardware was performed in 59% of knees, and additional procedures were required in 41%. No cases of postoperative lateral patellar instability or conversion to knee arthroplasty occurred. CONCLUSIONS: Anteromedial tibial tubercle transfer without articular cartilage implantation is effective in patellofemoral joint preservation, ameliorating symptoms and facilitating active lifestyles for a minimum of 15 years to nearly 20 years in patients with lateral and/or distal patellofemoral arthrosis. For 94% of knees, patients would choose to undergo the procedure again under the same circumstances. Fifty-nine percent underwent screw removal, and 41% required additional procedures, mostly arthroscopic. No patients in this therapeutic case series underwent an arthroplasty procedure. LEVEL OF EVIDENCE: Level IV, therapeutic cases series.