Translate this page into:
Patellar dislocation after total knee Arthroplasty: Stabilization technique using medial flap and suture anchors
, Luis Camacho Tercerosd, Ezequiel Beckere, Florencia Garbinid, Eduardo J. Bochateya,c,f, Fernando A. Lopreitea,c,g
⁎Corresponding author: Walter F. Martínez. wfm5252@gmail.com
-
Received: ,
Accepted: ,
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.
Abstract
Abstract
Patellar dislocation following total knee arthroplasty (TKA) is an uncommon but functionally significant complication. Its management requires careful evaluation of prosthetic alignment, patellofemoral mechanics, and soft tissue integrity. The aim of this study was to describe a surgical stabilization technique using a medial retinacular flap fixed to the patella with suture anchors, combined with controlled lateral retinacular release, and to analyze its clinical and functional outcomes.
We conducted a retrospective case series between 2011 and 2023 in two specialized orthopedic centers. Fourteen patients with patellar dislocation after primary TKA—without prosthetic loosening or significant malrotation—were included. Clinical evaluation included pain (VAS), function (Lysholm score), satisfaction (Likert scale), and return to daily activities. Mean follow-up was 8.3 years.
All patients achieved a functional range of motion (≥0°–100°) without recurrence or instability. Lysholm scores improved significantly from 46.4 ± 3.05 to 83.8 ± 5.85 (p < 0.0001), and VAS pain scores decreased from 6.0 ± 0.71 to 1.2 ± 0.84 (p = 0.0012). No infections, hematomas, or reoperations were recorded. Overall satisfaction was high, with 85.7 % of patients reporting being satisfied or very satisfied.
The medial flap technique with suture anchor fixation is effective, reproducible, and low in morbidity. It represents a safe and less invasive alternative for the treatment of patellar dislocation following TKA in patients without mechanical failure.
IV. Case series.
Abstract
Highlights
•Novel surgical technique: First description of medial retinacular flap fixation with anchors after TKA dislocation.•Excellent outcomes: Significant functional gain (Lysholm 46.4→83.8, p<0.0001) with 0% recurrence at 8.3 years.•Low-morbidityalternative: Simple, low-morbidity option for elderly or high-risk patients without prosthetic malalignment.
Keywords
Patellar dislocation
TKA
Medial retinaculum repair
Suture anchors
Soft tissue stabilization
1 Introduction
Patellar instability is an uncommon but clinically significant complication following total knee arthroplasty (TKA), with an estimated incidence ranging from 1 % to 15 % in primary procedures and even higher rates in revision surgeries.1–3 Its etiology is multifactorial, involving both patient-related and technical factors.
Patient-related risk factors include preoperative valgus alignment, quadriceps weakness—particularly of the vastus medialis obliquus—patellofemoral dysplasia, previous episodes of patellar subluxation, and preexisting lateral patellar displacement.4–7 Technical causes include residual valgus malalignment of the limb, excessive internal rotation of the femoral and/or tibial components, asymmetric patellar resection, lateralized positioning or excessive thickness of the patellar button, soft tissue imbalance, and insufficient lateral release (8–10 = . Moreover, implant design plays a role: femoral components with shallow, symmetrical trochlear grooves are associated with increased risk of patellar dislocation.11
Among the spectrum of patellofemoral instability, frank dislocation represents one of the most challenging entities, with significant functional compromise and a high risk of prosthetic failure if left untreated.4
Management requires surgical intervention. When significant component malposition is identified, revision arthroplasty is indicated. However, in patients with proper prosthetic alignment and soft tissue imbalance, alternative procedures such as medial patellofemoral ligament (MPFL) reconstruction or medial retinacular repair combined with lateral release have shown favorable outcomes in selected cases. 12–14
This study presents a surgical technique for patellar stabilization using a medial retinacular flap fixed to the patella with suture anchors, without the need for augmentations or ligament reconstructions, combined with controlled lateral retinacular release. The aim is to describe the technique and analyze the clinical and functional outcomes in a series of patients with patellar dislocation following TKA.
2 Materials and methods
2.1 Study design
A retrospective case series study was conducted between December 2011 and June 2023 in two national referral centers for knee surgery. The objective was to evaluate the clinical and functional outcomes of a surgical stabilization technique in patients with patellar dislocation following total knee arthroplasty (TKA).
2.2 Inclusion and exclusion criteria
Included were patients who developed lateral patellar dislocation as a postoperative complication of primary TKA, without evidence of component loosening or active periprosthetic infection, and with confirmed rupture of the medial retinaculum.
Excluded were cases with medial patellar dislocation, severe combined femoral or tibial malrotation (>7° internal rotation), residual valgus alignment (>3°), loosened prostheses, or active infections.
2.3 Patient selection and data collection
Patients were selected retrospectively through review of surgical databases, electronic medical records, radiology reports, and intraoperative photographic documentation. Two researchers independently collected the data; discrepancies were resolved by consensus with a third reviewer. To minimize interpretative bias, functional scores were assessed by professionals not directly involved in the surgeries.
2.4 Ethical considerations
The study was approved by the ethics committees of the participating institutions. All patients signed informed consent for surgery and authorized the use of their clinical information for academic and scientific purposes, in accordance with the Declaration of Helsinki.
2.5 Study population
Fourteen patients (9 women, 5 men) were included, with a mean age of 74 years (range: 67–85). Mean follow-up was 8.3 years (range: 2–14) from the revision surgery. Patellar dislocation was clinically evident and radiographically confirmed in all cases. Eight patients had patellar replacement. Tibial and femoral component rotation was assessed using computed tomography following the methods described by Berger et al.15 and Huter et al. 16 respectively. Lower limb alignment was evaluated via scanogram to determine residual valgus. Three cases followed direct trauma to the operated knee, while eleven were caused by indirect mechanisms. The mean time from primary TKA to revision surgery was 98 days (range: 40–240).
2.6 Surgical technique
Under spinal anesthesia and in the supine position, the original anteromedial approach from the primary TKA was used. After confirming patellar dislocation, a medial flap was prepared from the remnant retinaculum and adjacent soft tissues (Fig. 1). A controlled lateral retinacular release was also performed, preserving the superior lateral genicular vessels, allowing patellar recentering over the trochlea using clamps to provisionally hold the flap (Fig. 2).
Once a free range of motion of at least 90° was confirmed, three 3,5 mm titanium or PEEK suture anchors were placed in the lateral border of the patella (Fig. 3). The medial flap was then advanced over the anterior surface of the patella and sutured using a U-shaped trajectory with the anchor threads: passing through the anterior surface, entering the medial border of the flap, and exiting laterally for knot tying. Reinforcing figure-of-eight stitches were added (Fig. 4). Patellar stability was assessed at 90° of flexion, and no augmentations or ligament reconstructions were required.
2.7 Postoperative rehabilitation
The protocol included immobilization with a full-leg brace for three weeks. From day ten, partial removal was allowed to initiate active flexion-extension exercises (0°–45°) without load. By the fourth week, the brace was fully removed, flexion was progressively increased to 90°, and quadriceps strengthening physiotherapy was initiated.
2.8 Outcome assessment
The following parameters were evaluated:•Pain: via visual analog scale (VAS) and Lysholm score.•Function and mobility: using the Lysholm score during follow-up visits.•Patient satisfaction: via five-point Likert scale.•Functional recovery: measured as time to return to daily activities.
3 Results
Fourteen patients with patellar dislocation after total knee arthroplasty (TKA) were treated using a medial flap and suture anchor fixation. All patients showed favorable outcomes, with no recurrence of dislocation or signs of patellar instability at final follow-up.
Final range of motion was functional in all cases (≥0°–100°). The mean time to return to daily or work activities was 12 weeks postoperatively. Patellar tracking correction was satisfactory in 100 % of cases, as confirmed by radiographic imaging (Fig. 5).
Postoperative follow-up revealed:•One patient experienced mild walking pain during the early weeks (VAS 2), which resolved by week 11.•Three patients reported functional pain when rising or climbing stairs. Two improved with rehabilitation, while one had persistent moderate discomfort that did not require reoperation.•One case of patellar tracking overcorrection was noted but managed non-surgically with quadriceps strengthening (Fig. 6
No complications such as infections, hematomas, patellar fractures, necrosis, wound dehiscence, or need for manipulation under anesthesia were observed.
3.1 Clinical and functional assessment
Functional evaluation showed statistically significant improvement:•Lysholm Score: improved from 46.4 ± 3.05 to 83.8 ± 5.85 (difference: 37.4; 95 % CI: ±3.07; p < 0.0001)•VAS (pain): decreased from 6.0 ± 0.71 to 1.2 ± 0.84 (difference: −4.8; 95 % CI: ±1.14; p = 0.0012)Table: Clinical and Functional OutcomesVariablePreoperative (Mean ± SD)Postoperative (Mean ± SD)Difference (95 % CI)p-valueLysholm46.40 ± 3.0583.80 ± 5.8537.40 (±3.07)<0.0001VAS6.00 ± 0.711.20 ± 0.84−4.80 (±1.14)0.0012
3.2 Categorical distribution
On the Lysholm scale, 6 patients were rated as “excellent”, 7 as “good”, and 1 as “fair”. No poor outcomes were reported.RESULTNUMBER OF CASESExcellent6Good7Fair1Poor0Total14
According to the Likert satisfaction scale:SATISFACTIÓNNUMBER OF CASESVery satisfied5Satisfied7Neutral1Dissatisfied1Very dissatisfied0Total14
No reoperations or mechanical failures of the medial flap were reported. Intraoperative assessment highlighted the importance of precise flap tensioning, as both excessive and insufficient tension may affect patellar tracking, as observed in the single case of overcorrection.
4 Discussion
Patellar dislocation following total knee arthroplasty (TKA) is an uncommon but clinically significant complication. Surgical management requires a comprehensive evaluation of patient history, prosthetic alignment, patellofemoral biomechanics, and soft tissue integrity.
In the absence of clear malalignment of components or limb axis, the initial approach should focus on soft tissue reconstruction strategies. In this context, the technique described here—based on a medial retinacular flap fixed to the patella with suture anchors, complemented by a controlled lateral release—offers an anatomic and functional solution without the need for grafts, augmentations, or complex ligamentous reconstructions.
Several authors have proposed similar approaches. Heller introduced a stepwise algorithm that prioritizes anatomic treatment in patients without mechanical failure, reserving prosthetic revision for cases of malrotation or loosening. Putman et al. suggested that combined internal rotation ≥7° may warrant component exchange, although no validated thresholds currently exist. However, multiple studies agree that a significant proportion of post-TKA patellofemoral instabilities are due to medial extensor mechanism insufficiency without prosthetic malposition.17–19
Matar et al. described a technique combining extensive lateral release, advancement of the vastus medialis obliquus, and reinforcement of the extensor mechanism20. Lakstein and others have reported good outcomes with lateral patellar facetectomy21–23. Whiteside, in a series of 31 patients, reported no recurrences following distal realignment procedures24.
Medial patellofemoral ligament (MPFL) reconstruction has also been extensively studied, with favorable outcomes in selected patients25–28. However, its use in the prosthetic setting presents technical and anatomical challenges: interference with metallic components, graft requirements, higher risk of overcorrection, and increased surgical invasiveness. In contrast, the medial flap with anchor fixation offers a simpler and more reproducible solution, particularly useful in elderly patients or those with poor bone quality.
Recent literature supports this conservative and anatomical approach. Van Gennip and Lamotte reported good results with MPFL reconstruction, though they acknowledged the associated technical difficulties4,12. Motsis et al. and Assiotis et al. in systematic reviews, emphasized the need to tailor the surgical strategy to the dislocation's underlying mechanism and noted that many instabilities can be resolved with medial reinforcement techniques without requiring prosthetic revision13,14.
Finally, anchor fixation provides additional advantages: it enables solid attachment to the medial patellar edge without bone tunnels, shortens surgical time, and avoids the need for additional metal implants.
Taken together, the results from this series support the use of this technique in patients with patellar dislocation after TKA without mechanical failure. Its low morbidity, reproducibility, and functional recovery position it as a valid and safe option within the orthopedic surgeon's therapeutic arsenal.
This study has several limitations. Its retrospective nature introduces potential selection bias, and the small cohort, though representative of this uncommon complication, precludes subgroup analyses. The absence of a control group (e.g., MPFL reconstruction) limits comparative conclusions, and while follow-up was substantial (mean 8.3 years), longer-term data are needed to assess durability. Finally, all surgeries were performed by experienced arthroplasty surgeons, which may affect reproducibility in less specialized settings.
5 Conclusion
Patellar dislocation following total knee arthroplasty (TKA) is an uncommon but clinically significant surgical challenge. In patients without evident mechanical failure of prosthetic components, treatment with a medial retinacular flap fixed to the patella using suture anchors, combined with controlled lateral retinacular release, proved to be an effective, reproducible, and low-morbidity technique.
The results of this series demonstrated satisfactory functional recovery, a low complication rate, and high patient satisfaction, without the need for complex ligament reconstructions or reoperations. This approach may be particularly beneficial in elderly patients or those with increased surgical risk, and represents a safe alternative within the stepwise management of patellar instability following TKA.
Informed consent
Written informed consent was obtained from all participating patients prior to their inclusion in the study. Patients authorized the use of their clinical and imaging data for research and publication purposes, ensuring confidentiality and anonymity.
Credit author statement
All authors contributed to the interpretation of results, critically revised the manuscript for intellectual content, and approved the final version.
Statement on generative AI and AI-assisted technologies in the writing process
During the preparation of this manuscript, the author(s) used ChatGPT to improve readability and language. After using this tool, the author(s) reviewed and edited the content as needed and take full responsibility for the content of the publication.
Methods o Figure Legends: Schematic Fig. 2 y 4 were created using AI-assisted tools ChatGPT for illustrative purposes and were cross-validated by the surgical team against intraoperative findings.
Ethical considerations
The principles of the World Medical Association's Code of Ethics (Declaration of Helsinki) were upheld. All sensitive patient data were protected. Informed consent was obtained from all patients included in this study.
Ethical approval
This study was approved by the Ethics Committee of Instituto de Tratamiento y Rehabilitación Articular (ITRA), Ciudad Autónoma de Buenos Aires, Argentina, (Protocol No. 00000435678) in accordance with the World Medical Association's Declaration of Helsinki (2013 revision).
Data protection
All patient data were anonymized and stored securely in accordance with the General Data Protection Regulation and local privacy laws (Ley de Protección de Datos Personales de Argentina, Ley No. 25.326). Original records are kept in password-protected hospital databases accessible only to the research team.
AI-assisted technologies disclosure
As stated in the manuscript, ChatGPT was used solely to improve language readability. The authors reviewed and edited all content and assume full responsibility for the accuracy and integrity of the work.
Ethical principles
Beneficence: Surgical indications followed evidence-based guidelines to maximize patient outcomes.
Non-maleficence: Complications were actively monitored and managed.
Autonomy: Patients were informed of alternative treatments and risks.
Justice: Patient selection was unbiased, regardless of gender, age, or socioeconomic status.
Composite patient consent form
"We certify that all 14 patients provided written informed consent for:-Use of their anonymized clinical data-Publication of non-identifiable surgical images-Analysis of their cases in this study"
Credit author statement
Walter F. Martínez: Conceptualization, methodology, surgical technique design, original draft writing, critical revision.
Luis Camacho Terceros: Data collection, formal statistical analysis.
Ezequiel Becker: Visualization (figures), data collection.
Florencia Garbini: Data collection, formal statistical analysis.
Eduardo J. Bochatey: Data collection, formal statistical analysis, validation, visualization (figures/tables).
Fernando A. Lopreite: Supervision, project administration, manuscript review, final approval.
All authors contributed to the interpretation of results, critically revised the manuscript for intellectual content, and approved the final version.
Funding statement
This research received no specific grant from funding agencies in the public, commercial, or not-for-profit sectors. All study-related expenses (including surgical materials, data collection, and manuscript preparation) were personally funded by the authors.
No funding organization or sponsor was involved in:-Study design-Data collection/analysis-Manuscript writing-Decision to submit for publication
References
- Patellar complications after total knee arthroplasty. Orthop Traumatol Surg Res. 2019;105(1S):S43-S51.
- [Google Scholar]
- Patellar dislocation following total Knee replacement. J Bone Joint Surg Am. 1985;67:1321-1327.
- [Google Scholar]
- Medial patellofemoral ligament reconstruction for patellar maltracking following total knee arthroplasty is effective. Knee Surg Sports Traumatol Arthrosc. 2014;22(10):2569-2573.
- [Google Scholar]
- Ursachen und Management der Patellainstabilitäten nach künstlichem Gelenkersatz: lateralisation, Subluxation und Luxation. Orthopade. 2016;45(5):399-406.
- [Google Scholar]
- Causes of instability after total knee arthroplasty. J Arthroplast. 2014;29:360-364.
- [Google Scholar]
- Preoperative radiological parameters predicting the need for lateral retinacular release in total knee arthroplasty. J Arthroplast. 2019;34:2925-2930.
- [Google Scholar]
- Radiographic features predictive of patellar maltracking during total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc Off J ESSKA. 2009;17:1217-1224.
- [Google Scholar]
- Factors affecting patellar tracking after total knee arthroplasty. J Arthroplast. 2002;17:942-947.
- [Google Scholar]
- Understanding the patellofemoral joint in total knee arthroplasty. Can J Surg J Can Chir. 2019;62:57-65.
- [Google Scholar]
- Early patellofemoral revision following total knee arthroplasty. J Arthroplast. 1995;10:287-291.
- [Google Scholar]
- Medial patellofemoral ligament reconstruction for patellar instability following total knee arthroplasty: a review of 6 cases. Orthop Traumatol Surg Res. 2016;102(5):607-610.
- [Google Scholar]
- Patellar instability after total knee arthroplasty. J Orthop Surg (Hong Kong). 2009;17(3):351-357.
- [Google Scholar]
- Patellar complications following total knee arthroplasty: a review of the current literature. Eur J Orthop Surg Traumatol. 2019;29(8):1605-1615.
- [Google Scholar]
- Malrotation causing patellofemoral complications after total knee arthroplasty. Clin Orthop Relat Res. 1998;356:144-153.
- [Google Scholar]
- Manejo del mal recorrido rotuliano tras una artroplastia total de rodilla: una revisión sistemática. Musculoskelet Surg. 2023;107:143-157.
- [Google Scholar]
- Patellar malalignment treatment in total knee arthroplasty. Joints. 2013 Jun 12;1(1):10-17.
- [Google Scholar]
- New treatment of patellar instability after total knee arthroplasty: a case report and review of literature. World J Clin Cases. 2020 Nov 6;8(21):5487-5493.
- [Google Scholar]
- Extensive proximal extensor mechanism realignment for chronic patella dislocations in revision knee arthroplasty: surgical technique. Knee. 2020 Dec;27(6):1821-1832.
- [Google Scholar]
- [The treatment of patellar dislocation: a systematic review] Z Orthop Unfall. 2011;149:630-645.
- [Google Scholar]
- Partial lateral patellar facetectomy as an alternative to lateral release in Total Knee Arthroplasty (TKA) J Arthroplast. 2014 Nov;29(11):2146-2149.
- [Google Scholar]
- Lateral facetectomy decreased patellofemoral contact pressure in total knee replacement: a cadaveric study. J Clin Orthop Trauma. 2017;8:82-84.
- [Google Scholar]
- Distal realignment of the patellar tendon to correct abnormal patellar tracking. Clin Orthop Relat Res. 1997 Nov;344:284-289.
- [Google Scholar]
- Medial patellofemoral ligament (MPFL) reconstruction for the treatment of patellofemoral instability. J Knee Surg. 2014;27:139-146.
- [Google Scholar]
- Medial patellofemoral ligament reconstruction for patellar dislocation due to rupture of the medial structures after total knee arthroplasty: a case report and review of the literature. J Med Investig. 2014;61:409-412.
- [Google Scholar]
- Medial patellofemoral ligament reconstruction for subluxating patellofemoral arthroplasty. Knee. 2011;18:130-132.
- [Google Scholar]
- Through-tunnel reconstruction with Ligament Augmentation and Reconstruction System (LARS) for managing post-arthroplasty patellofemoral instability. BMC Muscoskelet Disord. 2025 Jan 3;26(1):12.
- [Google Scholar]