Prevalence and Site of Medial Patellofemoral Ligament Injuries in Patients With Acute Lateral Patellar Dislocations: A Systematic Review and Meta-analysis

Comparison of five different fluoroscopic methods for identifying the MPFL femoral footprint

PURPOSE

The success of medial patellofemoral ligament (MPFL) reconstruction is closely linked to the precise positioning of the femoral tunnel. Intraoperative fluoroscopy is commonly utilized to identify the MPFL footprint. This study aimed to ascertain the most accurate fluoroscopic method among the five previously described methods used to determine the MPFL femoral footprint.

MATERIALS AND METHODS

Using 44 well-preserved dry femur bones, the MPFL femoral insertion site was demarcated using anatomical bony landmarks, namely the center of the saddle sulcus between the medial epicondyle, adductor tubercle and gastrocnemius tubercle. Fluoroscopic true lateral knee images were acquired and measurements taken, referencing established methods by Schottle et al., Redfern et al., Wijdicks et al., Barnett et al., and Kaipel et al. The distance between anatomic and fluoroscopic MPFL footprints was then measured on digital fluoroscopic images. The accuracy of the locations was compared using a margin of error of 5 and 7 mm.

RESULTS

The Schottle method consistently emerged superior, showcasing the smallest mean distance (3.2 ± 1.2 mm) between the anatomic and radiographic MPFL footprints and a high in-point detection rate of 90.9% under 5 mm criteria. While the Redfern method displayed perfect accuracy (100%) within the 7 mm criteria, the Schottle method also performed 97.7% accuracy.

CONCLUSIONS

For intraoperative identification of the MPFL footprint using fluoroscopy, the Schottle method is the most consistent and accurate among the assessed methods. Thus, its accuracy in detecting the MPFL footprint makes it recommended for MPFLR to ensure optimal outcomes.

LEVEL OF EVIDENCE

Level IV, cadaveric study.

[Radiological diagnostics of patellofemoral instability and patellar dislocation]

Patellofemoral instability (PFI) describes a (sub)luxation of the patella in the patellofemoral joint. Pathophysiologically, PFI is usually due to a nonphysiological movement of the patella, so-called maltracking, either due to acute trauma with injury to the supporting ligamentous apparatus or due to the presence of anatomical risk factors. Radiologically assessable risk factors for maltracking include trochlear dysplasia, patella alta, patellar tilt, lateralization of the tibial tuberosity, torsional deformity and genu valgum. This article presents the most commonly used and best validated measurement techniques. In addition, the characteristic injury pattern after lateral patellar dislocation is shown.

Acute patellar dislocation: how skeletal maturity affects patterns of injury

OBJECTIVE

The main objective of this study was to understand the role of skeletal maturity in the different patterns of osteochondral and ligamentous injuries after an acute lateral patellar dislocation.

MATERIALS AND METHODS

Two radiologists independently reviewed MRIs of 212 knees performed after an acute lateral patellar dislocation to evaluate the presence of high-grade patellar osteochondral injury, femoral osteochondral injury, and medial patellofemoral ligament injury. The association of skeletal maturity (indicated by a closed distal femoral physis), age, sex, and first-time versus recurrent dislocation with each of these various lesions was analyzed using Chi-square or T test, and multivariable logistic regression with estimation of odds ratios (OR).

RESULTS

Skeletal maturity was significantly associated with high-grade patellar osteochondral injury [OR=2.72 (95% CI 1.00, 7.36); p=0.049] and femoral-side MPFL tear [OR=2.34 (95% CI 1.05, 5.25); p=0.039]. Skeletal immaturity was significantly associated with patellar-side MPFL tear [OR=0.35 (95% CI 0.14, 0.90); p=0.029].

CONCLUSION

Patterns of injury to the patella and medial patellofemoral ligament vary notably between the skeletally immature and mature, and these variations may be explained by the inherent weakness of the patellar secondary physis.

Quadriceps muscle contraction causes medial patellofemoral ligament elongation by intermeshed fibers of vastus medialis oblique muscle

The first aim of this study was to compare the medial patellofemoral length between contracted and relaxed quadriceps muscle and second to assess the importance of the intermeshed vastus medialis oblique fibers. After a priori power analysis (α = 0.05, power [1-β] = 0.95), 35 healthy males aged 18-30 were prospectively examined with a 3.0-T magnetic resonance imaging (MRI) scanner in 10-15° of knee flexion. Two axial MRI sequences (25 s each) were made with relaxed and contracted quadriceps. Two blinded, independent raters measured twice medial patellofemoral ligament length (curved line) and attachment-to-attachment length (straight line). Mean medial patellofemoral ligament length and attachment-to-attachment length with relaxed quadriceps was: 65.5 mm (SD = 3.7), 59.7 mm (SD = 3.6), and after contraction, it increased to 68.7 mm (SD = 5.3), 61.2 mm (SD = 4.7); p < 0.01 and <0.001, respectively. Intraclass correlation coefficients for intra- and inter-rater reliabilities ranged from 0.55 (moderate) to 0.97 (excellent). Mean medial patellofemoral ligament length elongation after quadriceps contraction was significantly greater (3.2 mm, SD = 3.9) than mean attachment-to-attachment length elongation (1.6 mm, SD = 2.8); p < 0.001. Contraction of quadriceps muscle causes elongation of the medial patellofemoral ligament to the extent greater than the elongation of distance between its attachments. This confirms that medial patellofemoral ligament elongation after quadriceps contraction results not only from movement of its patellar attachment but also directly from intermeshed vastus medialis oblique fibers pulling medial patellofemoral ligament in a different direction creating a bow-like construct in agreement with the "pull-and-guide mechanism" proposed in the literature.

Physiotherapy Rehabilitation Post Patellar Dislocation (PRePPeD)-protocol for an external pilot randomised controlled trial and qualitative study comparing supervised versus self-managed rehabilitation for people after acute patellar dislocation

BACKGROUND

Patellar dislocations mainly affect adolescents and young adults. After this injury, patients are usually referred to physiotherapy for exercise-based rehabilitation. Currently, limited high-quality evidence exists to guide rehabilitation practice and treatment outcomes vary. A full-scale trial comparing different rehabilitation approaches would provide high-quality evidence to inform rehabilitation practice. Whether this full-scale trial is feasible is uncertain: the only previous trial that compared exercise-based programmes in this patient population had high loss to follow-up. This study aims to assess the feasibility of conducting a future full-scale trial comparing the clinical and cost-effectiveness of two different rehabilitation approaches for people with an acute patellar dislocation.

METHODS

Two-arm parallel external pilot randomised controlled trial and qualitative study. We aim to recruit at least 50 participants aged ≥ 14 years with an acute first-time or recurrent patellar dislocation from at least three English National Health Service hospitals. Participants will be randomised 1:1 to supervised rehabilitation (four to six, one-to-one, physiotherapy sessions of advice and prescription of tailored progressive home exercise over a maximum of 6 months) or self-managed rehabilitation (one physiotherapy session of self-management advice, exercise, and provision of self-management materials). Pilot objectives are (1) willingness to be randomised, (2) recruitment rate, (3) retention, (4) intervention adherence, and (5) intervention and follow-up method acceptability to participants assessed through one-to-one semi-structured interviews (maximum 20 participants). Follow-up data will be collected 3, 6, and 9 months after randomisation. Quantitative pilot and clinical outcomes will be numerically summarised, with 95% confidence intervals generated for the pilot outcomes using Wilson's and exact Poisson methods as appropriate.

DISCUSSION

This study will assess the feasibility of conducting a full-scale trial comparing supervised versus self-managed rehabilitation for people after acute first-time or recurrent patellar dislocation. This full-scale trial's results would provide high-quality evidence to guide rehabilitation provision for patients with this injury.

TRIAL REGISTRATION

ISRCTN registry ISRCTN14235231 . Registered on 09 August 2022.

The Top 50 Most Cited Articles on the Medial Patellofemoral Ligament (MPFL): A Bibliometric Analysis

Objectives

To determine which original articles on the topic of the medial patellofemoral ligament (MPFL) have been cited the most in the literature utilizing a bibliometric approach. Secondarily, to determine temporal trends between article types.

Methods

Articles on the topic of the MPFL were identified by utilizing the Web of Science Database. The search yielded 1596 results and the top 50 cited original articles were collected for further analysis. The following information was gathered for all included articles: title, first author's name, journal name, year of publication, impact factor of the journal in 2021, total number of citations of the article, average citations per year (ACY), geographic origin, institutions, research theme, and keywords. Articles were then grouped into one of three categories: cadaveric/anatomic, clinical, and radiologic.

Results

The total number of citations was 10,393. Most were published between the years 2000-2009 (66%) and in the journal, American Journal of Sports Medicine (34%). The mean ACY was 11.73 ± standard deviation 5.86 and the Kawasaki Municipal Hospital was the institution with the most articles included in the top 50 (n = 6, 12%). The top-cited articles focused on 3 themes: cadaveric/anatomic (n = 18, 36%), clinical (n = 25, 50%), and radiologic (n = 7, 14%). Cadaveric/anatomic articles had the highest average number of citations at 271.4 ± 153.9, followed by radiologic (173.3 ± 53.0) and clinical articles (171.8 ± 102.4). Over time, clinical articles were more likely to be included in the top 50 list, compared to cadaveric/anatomic/radiologic articles.

Conclusion

The most impactful MPFL articles relate to cadaveric/anatomic articles; however, over time, clinical articles became more prevalent.

Older Age, Female Sex, Anxiety, Substance Use Disorder, Osteoarthritis, Tibial Tubercle Osteotomy, and Opioid Familiarity Are Risk Factors for Prolonged Opioid Use Following Medial Patellofemoral Ligament Reconstruction

Purpose

To determine which preoperative factors are associated with prolonged opioid use after medial patellofemoral ligament reconstruction (MPFLR).

Methods

The M151Ortho PearlDiver database was queried for patients who underwent MPFLR between 2010 and 2020. Inclusion criteria included patients who underwent MPFLR using Current Procedural Terminology codes 27420, 27422, and 27427 and had a patellar instability diagnosis. Prolonged opioid use was defined as opioid use greater than 1 month after surgery. Postoperative opioid use from 1 month to 6 months was assessed. Multivariable logistic regression was used to evaluate the association between patient-related risk factors (age, sex, Charlson Comorbidity Index, anxiety, depression, substance use disorder, osteoarthritis, tibial tubercle osteotomy [TTO], and previous opioid use within 3 months to 1 week of surgery) with prolonged postoperative opioid use. Odds ratios (OR) and their associated 95% confidence intervals (CI) were calculated for each risk factor.

Results

A total of 23,249 patients were included. There was a higher proportion of female patients compared to male patients (67.8% vs 32.2%) in our cohort, as well as a large proportion of patients who had preoperative opioid use (23.9%). In total, 14.3% of patients had a concomitant TTO. Three months post-MPFLR, male patients were at a decreased risk of opioid usage (OR 0.75; CI 0.67-0.83; P ≤ .001). Older age (OR 1.01, CI 1.00-1.01; P ≤ .001), patients with pre-existing anxiety (OR 1.30, CI 1.15-1.47; P ≤ .001), substance use disorder (OR 2.04, CI 1.80-2.31; P ≤ .001), knee osteoarthritis (OR 1.70, CI 1.49-1.94; P ≤ .001), concomitant TTO (OR 1.91, CI 1.67-2.17; P ≤ .001), and opioid familiarity (OR 7.68, CI 6.93-8.52; P ≤ .001) were at a significantly increased risk of postoperative opioid usage.

Conclusions

Older age, female sex, anxiety, substance use disorder, osteoarthritis, tibial tubercle osteotomy, and opioid familiarity are risk factors for prolonged opioid use following MPFLR.

Level of Evidence

Level III, retrospective cohort study.

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.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

LEVEL OF EVIDENCE

IV; Systematic Review of Level I-IV studies.

Medial Patellofemoral Ligament Reconstruction is Preferred to Repair or Reefing for First-Time Patellar Dislocation: A Systematic Review and Meta-analysis

Purpose

The purpose of this systematic review aimed to investigate the clinical outcome of medial patellofemoral ligament (MPFL) reconstruction, MPFL repair and medial reefing for patients with first-time patellar dislocation.

Methods

Databases of PubMed, EMBASE, Cochrane Library and Web of Science were searched up to May 8, 2022. Only articles treating first-time patellar dislocation with MPFL reconstruction, MPFL repair and medial reefing were included in the analysis. Eligible identification, data extraction, quality assessment and statistical analysis were performed by two independent reviewers. The primary outcome measures were the incidences of postoperatively redislocation and reoperation. The second outcomes were the Kujala functional score and complications (including infection, osteoarthritis, and loss of range of motion).

Results

Twenty-two studies involving 668 patients met the inclusion criteria. Of which, four studies involving 126 patients were in MPFL reconstruction group, ten studies involving 220 patients in MPFL repair group and 9 studies involving 322 patients in medial reefing group. Our results showed that the MPFL reconstruction (1.8%, 95% CI - 0.5 to 4.0%) had a significantly lower rate of postoperative redislocation and reoperation rate than the MPFL repair (15.4%, 95% CI 5.2-25.7%) and medial reefing (18.0%, 95% CI 9.3-26.7%). Besides, no significant differences were found in the Kujala score and complication rate among the three treatments.

Conclusion

The available evidence demonstrated that MPFL reconstruction could achieve significantly lower redislocation rate and reoperation rate than MPFL repair and medial reefing after first-time patella dislocation. Furthermore, there was not enough evidence to reveal that MPFL reconstruction provided better functional outcome compared with MPFL repair and medial reefing. MPFL reconstruction is a preferred surgical treatment for patients with first-time patellar dislocation.

Level of Evidence

Level IV, systematic review of Level I-IV.

Soft-tissue fixation is not inferior to suture-anchor fixation in reconstruction of the medial patellofemoral ligament using a nonresorbable suture tape

PURPOSE

Reconstruction of the medial patellofemoral ligament (MPFL-R) with nonresorbable suture tape (FiberTape^®, FT) is becoming popular. Patella-side fixation of the FT can be performed with suture anchors or via soft-tissue fixation. The aim of this study was to investigate whether patella-side soft-tissue fixation can achieve equivalent primary stability compared to suture-anchor fixation.

METHODS

In ten human, fresh-frozen knee joint specimens (m/f 6/4; age 74 ± 9 a), the MPFL was identified and dissected near the femoral insertion site. In five knee joints, the MPFL-R using FT was performed with soft-tissue fixation at the patella (study group; SG), and in five knee joints, the FT was fixed via suture anchors (control group, CG). All reconstructions were evaluated until load to failure of the patella-side fixation with a displacement rate of 200 mm/min.

RESULTS

The mean maximum load to failure in the SG was 395.3 ± 57.9 N. All reconstructions failed by complete tearing off the medial patellar retinaculum from its medial patellar margin, but fixation of the FT remained stable. In the CG, the mean maximum load to failure was 239.4 ± 54.5 N and was significantly different compared to the SG (p = 0.04). All reconstructions failed via pullout of the suture anchors. Stiffness and elongation did not differ between the groups, and no failure of the FT was observed in any of the specimens.

CONCLUSION

Primary stability of soft-tissue MPFL-R using FT was superior to suture-anchor fixation. Both fixation techniques provided sufficient primary stability, superior to previously reported native MPFL tensile strengths. MPFL-R with FT could be a possible alternative procedure for MPFL-R, eliminating potential complications due to autologous tendon graft harvesting.

MPFL repair after acute first-time patellar dislocation results in lower redislocation rates and less knee pain compared to rehabilitation: a systematic review and meta-analysis

PURPOSE

This study aimed to explore the efficacy of medial patellofemoral ligament (MPFL) repair versus nonoperative rehabilitation treatment on the rate of patellar redislocation and functional outcomes in skeletally mature patients with traumatic, first-time patellar dislocations.

MATERIALS AND METHODS

MEDLINE, PubMed and EMBASE were searched from database inception to May 2022 for studies examining the management options for acute first-time patellar dislocations. This study was conducted in accordance with PRISMA and R-AMSTAR guidelines. Data on redislocation rates, functional outcomes including the Kujala score for anterior knee pain, and complication rates were extracted. A meta-analysis was used to pool the mean postoperative Kujala score and calculate the proportion of patients sustaining redislocations using a random effects model. Quality assessment of included studies was performed for all included studies using the MINORS and Detsky scores.

RESULTS

This review included a total of 25 studies and 1,361 patients. The pooled mean redislocation rate in 15 studies comprising 798 patients in the rehabilitation group was 30% (95% CI 25-36%, I² = 65%). Moreover, the pooled mean redislocation rate in 10 studies comprising 170 patients undergoing MPFL repair was 7% (95% CI 3-12%, I² = 30%). The pooled mean postoperative Kujala score in 8 studies comprising 396 patients in the rehabilitation group was 82.5 (95% CI 78.3-86.8, I² = 91%), compared to a score of 88 (95% CI 87-90, I² = 76%) in 3 studies comprising 94 patients in the repair group. Range of motion deficits was reported in 3.8% of 893 patients in the rehabilitation group and 2.0% of 205 patients in the repair group.

CONCLUSION

MPFL repair resulted in a lower rate of redislocation, less knee pain, and noninferiority with respect to a range of motion deficits compared to nonoperative treatment for the management of acute first-time patellar dislocations.

LEVEL OF EVIDENCE

IV.

High Rates of Damage to the Medial Patellofemoral Ligament, Lateral Trochlea, and Patellar Crest After Acute Patellar Dislocation: Magnetic Resonance Imaging Analysis

PURPOSE

The primary outcome of interest of this study was to determine the frequency, location, and extent of chondral injuries and medial patellofemoral ligament (MPFL) tears, along with the rate of loose bodies, in the knee after acute primary patellar dislocation. The secondary outcome of interest was to conduct a multivariate analysis to investigate whether the presence of pathoanatomic abnormalities, including structural differences in the knees of the patients, is associated with the features of the lesions.

METHODS

Patients who underwent magnetic resonance imaging after primary acute patellar dislocation were identified from our institutional databases. We analyzed a total of 175 magnetic resonance imaging scans of patients aged between 14 and 25 years who were eligible for inclusion.

RESULTS

Chondral damage to the medial facet of the patella was present in 36 patients; patellar crest, 78 patients; and lateral patellar facet, 28 patients. One patient presented with chondral defects in the medial trochlear facet, whereas 118 patients showed chondral defects in the lateral trochlear facet. Loose bodies were present in 142 patients. A total of 161 patients (92%) showed MPFL damage. The patellar portion was affected in 119 patients. Of the patients, 28 showed a partially damaged MPFL (<50%), 42 showed MPFL damage greater than 50%, and 49 presented with a complete tear of the MPFL. MPFL lesions were observed on the femoral side in 42 patients. Fourteen patients presented with an avulsion fracture on the patellar side; 28 patients, on the femoral side.

CONCLUSIONS

The MPFL was injured in 92% of 175 patients after a first-time acute patellar dislocation. Chondral damage was most frequent at the patellar crest, followed by the lateral femoral epicondyle. No association was found between patella alta, the sulcus angle, the Q angle, the tibial tubercle-trochlear groove distance, trochlear and patellar dysplasia, and soft-tissue damage.

LEVEL OF EVIDENCE

Level IV, retrospective cohort study.

YouTube Videos Lack Efficacy as a Patient Education Tool for Rehabilitation and Return to Play Following Medial Patellofemoral Ligament Reconstruction

Purpose

To investigate the efficacy of YouTube videos as a patient education resource related to rehabilitation and return to play following medial patellofemoral ligament (MPFL) reconstruction.

Methods

YouTube was queried using 6 predetermined search terms. Videos were included if they met the following criteria: (1) written in the English language; and (2) within the first 100 videos for each search term. Videos were excluded if they met any of the following criteria: (1) not written in the English language; (2) did not include medial patellofemoral ligament/MPFL in the title; (3) duplicate videos; (4) part of a multivideo series such a vlogs; (5) advertisements; and (6) videos <1 minute. The remaining videos were evaluated by 2 independent viewers and scored using 4 distinct scoring systems: Global Quality Scale, The Patient Education Materials Assessment Tool for Audiovisual Materials (PEMAT), MPFL Rehabilitation and Return to Play Score, and the Journal of the American Medical Association benchmark criteria. The data was analyzed with IBM SPSS Statistics, version 27). The Kruskal–Wallis test was used to compare quality scores and video analytics to their assigned categories. Results where P < .05 were considered statistically significant and pairwise comparison analysis was completed to determine the video categories with statistically significant differences. Correlation of categorical variables with video analytics (views, video power index, duration, and days since publication) and quality scores was determined using the Pearson Correlation coefficient.

Results

Of the initial 600 videos, 58 met inclusion criteria, which were subsequently reviewed and scored. Most videos scored on the low-end of the possible scoring ranges with a mean Global Quality Scale score of 1.61 (standard deviation [SD] 0.81), PEMAT Understandability score of 59.40 (SD 17.54), PEMAT Actionability score of 18.20 (SD 29.92), MPFL Rehabilitation and Return to Play Score of 1.64 (SD 2.13), and Journal of the American Medical Association benchmark score of 2.08 (SD 0.75).

Conclusions

The videos in YouTube’s library received low scores in quality, reliability, understandability and actionability. Therefore, YouTube is currently a poor source of information for patients regarding postoperative rehabilitation and return to play following MPFL reconstruction.

Clinical Relevance

Patients increasingly view medical information online. YouTube is second only to Google as the most used search engine. It is important to understand the quality of information patients receive on YouTube following MPFL reconstruction so orthopaedic surgeons know to guide patients to higher-quality alternatives.

Ability of Medial Patellofemoral Ligament Reconstruction to Overcome Lateral Patellar Motion in the Presence of Trochlear Flattening: A Cadaveric Biomechanical Study

BACKGROUND

Medial patellofemoral ligament (MPFL) reconstruction is an established operative procedure to restore medial restraining force in patients with patellar instability. In the setting of a shallow sulcus, it is unclear whether an isolated MPFL reconstruction is sufficient to restore patellofemoral stability.

HYPOTHESIS

Progressively increasing the sulcus angle would have an adverse effect on the ability of an MPFL reconstruction to restrain lateral patellar motion.

STUDY DESIGN

Controlled laboratory study.

METHODS

Seven fresh-frozen human cadaveric knees were harvested and prepared for experimentation. Each specimen was run through the following test conditions: native, lateral retinacular release, lateral retinacular repair, MPFL release, MPFL reconstruction, and MPFL reconstruction with trochlear flattening. Four 3-dimensional printed wedges (10°, 20°, 30°, and 40°) were created to insert beneath the native trochlea to raise the sulcus angle incrementally and simulate progressive trochlear flattening. For each test condition, the knee was positioned at 0°, 15°, 30°, and 45° of flexion, and the force required to displace the patella 1 cm laterally at 10 mm/s was measured. Group comparisons were made with repeated measures analysis of variance.

RESULTS

In the setting of an MPFL reconstruction, as the trochlear groove was incrementally flattened, the force required to laterally displace the patella progressively decreased. A 10° increase in the sulcus angle significantly reduced the force at 15° (P = .01) and 30° (P = .03) of knee flexion. The force required to laterally displace the patella was also significantly lower at all knee flexion angles after the addition of the 20°, 30°, and 40° wedges (P≤ .05). Specifically, a 20° increase in the sulcus angle reduced the force by 29% to 36%; a 30° increase, by 35% to 43%; and a 40° increase, by 40% to 47%.

CONCLUSION

Despite an MPFL reconstruction, the force required to laterally displace the patella decreased as the sulcus angle was increased in our cadaveric model.

CLINICAL RELEVANCE

An isolated MPFL reconstruction may not be sufficient to restore patellar stability in the setting of a shallow or flat trochlea. Patients with an abnormal sulcus angle may have recurrent instability postoperatively if treated with an isolated MPFL reconstruction.