Recurrent Patellar Instability Research Articles

MPFL Reconstruction in Skeletally Immature Patients: Comparison Between Anatomic and Non-Anatomic Femoral Fixation—Systematic Review

Background: MPFL reconstruction in children with open physis may be challenging, as a major concern during the surgery is to preserve the distal femoral physis. The purpose of this study was to compare the complication rate and the patient-reported outcomes in skeletally immature patients who underwent MPFL reconstruction using an anatomic (A) or non- anatomic (NA) surgical technique. Methods: For this systematic review, the authors adhered to the PRISMA guidelines. The literature search was conducted from inception to 31 May 2024. Three databases were used: Pubmed, Scopus and Cochrane library. We included skeletally immature patients who underwent MPFL reconstruction for chronic or recurrent patellar instability. The included studies should describe the surgical technique, report clinical outcomes and complications. Patients with closed physis, prior ipsilateral knee surgery, concomitant surgical procedures except for lateral retinacular release, multiligament knee injury, congenital or acute patellofemoral instability, hyperlaxity or less than 12 months follow up were excluded. Risk of bias was assessed using ROBINS-I, MINORS and MCMS scores. Results: Data from 304 procedures were collected, of which 208 were performed using an anatomic technique and 96 using a non-anatomic technique. Patient age at the time of surgery ranged from 8 to 17 years. The follow-up time ranged between 12 and 116.4 months. Postoperative Kujala (−0.73, p = 0.55) and Tegner (−0.70, p = 0.80) scores were better in the anatomic group compared to the non-anatomic one. Higher rates of recurrent instability (OR 0.91; 95%CI 0.44–1.86, p = 0.85), redislocation (OR 1.21; 95%CI 0.42–3.51, p = 0.8), subluxation (OR 0.73; 95%CI 0.29–1.83, p = 0.62), a positive apprehension test (OR 0.92; 95%CI 0.27–3.13, p = 0.89), stiffness (decreased ROM) (OR 1.63; 95%CI 0.33–1.72, p = 0.54) and reoperation (OR 1.16; 95%CI 0.35–3.80, p = 0.8) were reported in papers using the anatomic technique. Conclusions: The findings of this systematic review reveal that there is no significant difference between anatomic and non-anatomic MPFL reconstruction techniques in terms of patient-reported outcomes and complications. Thus, the choice of surgical technique might be left up to surgeon’s preference. Further high-quality, pediatric-oriented studies with long-term follow–up are needed to better guide clinical decision-making.

Clinical and Radiological Outcomes After Isolated Double-Bundle Medial Patellofemoral Ligament Reconstruction: A 5-Year Analysis.

There are few studies that have examined clinical and radiological outcomes at 5 years after isolated medial patellofemoral ligament (MPFL) reconstruction. To date, midterm outcomes after isolated double-bundle (DB) MPFL reconstruction are not well known. Isolated DB MPFL reconstruction using a patellar suture anchor technique would lead to improved functional scores and radiological findings, and these improvements would remain stable over the 5-year postoperative period. Case series; Level of evidence, 4. Isolated MPFL reconstruction was performed in patients with recurrent patellar instability between March 2013 and February 2017. Clinical and functional evaluations were performed via an interview using the Kujala, Lysholm, and Tegner scores preoperatively and at 6, 12, 24, and 60 months postoperatively. Radiographs were taken preoperatively, immediately postoperatively, and at 24 and 60 months after surgery. Radiographic assessments included measuring the modified Insall-Salvati ratio, congruence angle, and lateral patellofemoral angle. A total of 31 patients (31 knees) underwent isolated MPFL reconstruction; 4 patients did not complete 5-year follow-up, and thus, 27 patients (27 knees) were enrolled in the study. The mean age at the time of surgery was 22.0 ± 6.4 years (range, 14-32 years). All clinical and functional scores significantly improved in the first 2 years (P < .001), with the mean Kujala, Lysholm, and Tegner scores improving from 52.7 to 90.7, 49.6 to 92.7, and 2.9 to 5.1, respectively. There was no significant difference in scores between 2- and 5-year follow-up. All radiographic parameters significantly improved between preoperatively and immediately postoperatively (P < .001), with mean values for the modified Insall-Salvati ratio, congruence angle, and lateral patellofemoral angle improving from 1.7° to 1.6°, 5.7° to -6.6°, and 3.0° to 5.9°, respectively. No significant differences were observed in radiographic measurements between the postoperative time points. No patients experienced a patellar redislocation or fracture. The prospective analysis of isolated DB MPFL reconstruction at 5-year follow-up showed that clinical and radiological outcomes significantly improved postoperatively and were maintained to 5 years. These midterm results suggest that isolated DB MPFL reconstruction is an effective treatment option for patients with patellar instability.

Medial Patellofemoral Ligament Reconstruction Improves Patella Alta.

Patellofemoral instability (PFI) is a common problem with various anatomic risk factors identified, including patella alta as one of the most powerful predictors. Given that the medial patellofemoral ligament (MPFL) is the primary soft tissue stabilizer of the patella, a common procedure to treat recurrent patellar instability is MPFL reconstruction. The aim of this study is to examine the relationship between MPFL reconstruction and patellar height. We hypothesize that after reconstruction, patellar instability patients would have demonstrable reduction in patella height and patella alta correction. Patient records were queried for patients who underwent MPFL reconstruction for recurrent patellar instability. Patient and operative demographics were collected. We measured Insall-Salvati ratio (ISR), Caton Deschamps index (CDI), and Blackburne-Peel ratio (BPR) in all patients at various time points. The height indices were compared across the preoperative, immediately postoperative, and 6-month time points in a pairwise fashion using paired-sample t-tests. Further subgroup analysis of patients (n=27) with elevated preoperative Caton Deschamps Index (defined as >1.3) was completed. The final cohort was 103 patients. There was a significant difference between pre- and postoperative ISR (P<0.001) and at 6-month follow up (P<0.001), between preoperative CDI and the 6-month follow-up (P<0.0010), and between the postoperative and preoperative CDI (P<0.001). There was also a difference between preoperative and postoperative BPR (P<0.001), as well as between the preoperative and 6-month follow-up BPR (P=0.002). Twenty-seven patients had an initial CDI greater than 1.3. Differences were observed between pre- and postoperative mean CDI (P=0.001) and at 6-month follow-up (P=0.006), between both postoperative and 6-month ISR (both P<0.001), and preoperative mean BPR and the postoperative (P=0.004) and 6-month mean BPR (P=0.027). Patients with pre-existing patella alta and recurrent patella dislocations who undergo isolated MPFL reconstruction have decreased patella alta at their 6-month follow-up as measured by ISR, CDI, and BPR. Patients without patella alta do not demonstrate statistically significant differences after their MPFL reconstruction. III (retrospective comparative study).

Implications for Femoral Tunnel Placement in Medial Patellofemoral Ligament Reconstruction Considering the Sagittal Trochlear Groove Curvature in Severe Trochlear Dysplasia Before and After Deepening Trochleoplasty

Background: Medial patellofemoral ligament reconstruction (MPFL-R) aims to restore proper ligament function with minimal changes in length during range of motion, yet the ideal area for femoral fixation of the graft remains controversial. Purpose: To determine the region where the isometric circular path of a simulated MPFL graft (best-fit circle) follows the sagittal radius curvature of the trochlea in normal (nontrochlear dysplastic) knees and to evaluate the best-fit circle coverage of different femoral fixation points in knees with severe trochlear dysplasia (TD) and after deepening trochleoplasty. Study Design: Controlled laboratory study. Methods: Twelve patients (4 male, 8 female; mean age, 24 ± 8 years) who underwent surgical treatment for recurrent lateral patellar instability due to severe TD were prospectively enrolled in this study. Four previously defined reference points for the femoral MPFL-R (Schöttle, Fujino, Stephen, and Oka) were identified, and the best-fit circle was drawn along the sagittal trochlear groove curvature. The divergence between each best-fit circle and the trochlear groove was calculated, with negative values indicating relative slackening and positive values indicating relative tightening of the simulated MPFL graft. Measurements were made on true-lateral fluoroscopic images before and after deepening trochleoplasty and compared with those of a sex-matched control group. Results: The best-fit circle of the Schöttle point followed the sagittal curvature of the trochlea most closely in both the control and trochlear dysplastic knees, followed by the Fujino, Stephen, and Oka points. As the radius of the trochlear groove curvature increased, the divergence of all best-fit circles to the trochlear groove became negative (all P < .05). This effect was most pronounced at the Stephen and Oka points, followed by the Fujino and Schöttle points (all P < .05). After deepening trochleoplasty, the divergence of the Schöttle point changed toward positive values (11.6% at 40°; P < .001). Concurrently, the best-fit circle divergence of all other reference points improved toward baseline (all P < .05). Conclusion: The isometric circle of the Schöttle point provides the best congruence with the sagittal trochlear groove curvature in both the normal trochlea and the dysplastic trochlea. After trochleoplasty, the best-fit circles of more distal femoral fixation points resulted in better congruence with the deepened trochlear groove, whereas the best-fit circle of Schöttle indicated graft tension during flexion. Clinical Relevance: According to the present study, different femoral fixation points should be considered depending on whether the TD is corrected.

Thick-shell sulcus-deepening trochleoplasty for recurrent patellar dislocation leads to clinically meaningful improvements and high patient satisfaction in adolescents with open physes

ObjectivesTo evaluate clinical and radiological outcomes of thick-shell, sulcus-deepening trochleoplasty in patients with open distal femoral physes and less than two years of growth remaining. We hypothesized that patients would have clinical and radiographic improvements in addition to high patient-reported outcomes following thick-shell, sulcus-deepening trochleoplasty. MethodsBone age was determined on preoperative magnetic resonance imaging (MRI) using the Pennock Knee Bone Age Atlas. Pre- and postoperative radiographs were used to measure the anatomic lateral distal femoral angle (aLDFA) and Blumensaat angle. International Knee Documentation Committee (IKDC), Kujala, and numerical patient satisfaction scores were assessed. Pre- and postoperative aLDFA and Blumensaat angles as well as patient-reported outcomes were analyzed via the Wilcoxon signed-rank test. ResultsSeventeen adolescents (21 knees) with DeJour Types B and D trochlear dysplasia and open distal femoral physes underwent Dejour thick-shell, sulcus-deepening trochleoplasty at a single institution. In twelve females (16 knees, 76.2%) the median chronological and bone ages at the time of operation were 14.9 and 14.3 years, respectively. In 5 males (5 knees, 27.7%), the median chronological and bone ages at the time of operation were 15.7 and 15.2 years, respectively. Mean follow-up time was 64 months postoperatively. Physes were closed in all knees at the time of final clinical and radiographic follow-up. The mean change in aLDFA and Blumensaat Angle was 0.73 (p ​= ​0.1074, 95% CI -0.09–1.57) and 0.88° (p ​= ​0.0477, 95% CI 0.10–1.88), respectively. Median IKDC scores improved from 57.3 preoperatively to 90.9 postoperatively, for a mean difference of 26.1 (p ​= ​0.00064, 95% CI 18.0–34.2). Median Kujala scores improved from 55.0 preoperatively to 95.0 postoperatively, for a mean change of 30.2 (p ​= ​0.0008, 95% CI 19.6–40.8). Overall mean numerical patient satisfaction was high (mean 9.26/10). One of 21 knees (4.8%) underwent additional surgery to address recurrent patellar instability. ConclusionThick-shell sulcus-deepening trochleoplasty for addressing recurrent lateral patellar instability in patients with open distal femoral physes and less than two years of growth remaining is safe and provides clinically meaningful improvements in addition to high patient satisfaction when combined with other patellar stabilization procedures. Level of evidenceIV, Retrospective Case Series.

Good 5-year results and a low redislocation rate using an á la carte treatment algorithm for patellofemoral instability in patients with severe trochlea dysplasia.

Trochlear dysplasia is a major risk factor for recurrent patellar instability, reduced quality of lifeand osteoarthritis of the patellofemoral joint. Patellar instability in patients with trochlear dysplasia can be treated by trochleoplasty, usually in combination with medial patellofemoral ligament reconstruction (MPFL-R). An á la carte treatment algorithm, which also addresses patella alta, lateralisation of the tibial tuberosityand valgus or torsional malalignment when present has been standard in one clinic for treatment of patellar instability patients since 2009, based on the hypothesis that it results in optimal subjective and clinical outcome, normalisation of the lateral trochlea inclination (LTI) angle and a low rate of patellar redislocation. This prospective study reports the 5-year results for consecutive patients with high-grade trochlea dysplasia operated according to the algorithm 2010-2017, evaluated preoperatively and 1, 2and 5 years postoperatively. Clinical information on previous surgery and postoperative patellar stability, range-of-motion (ROM)and subsequent surgery were registered. Subjective outcome was evaluated by four patient-reported outcome measures (PROMs): Kujala, Lysholm, International Knee Documentation Committee and Knee injury and Osteoarthritis Outcome Score. The LTI angle was measured pre- and postoperatively on magnetic resonance imaging scans. There were 131 patients (87 females) with a median age of 22 years (range: 14-38). All had a trochleoplasty and an MPFL-R. Additional procedures (tibial tuberosity medialisation/distalisation and/or femoral/tibial osteotomy) were performed in 52%. All PROM scores improved from preoperatively to 1-year follow-up with further improvement at 2 and 5 years after surgery (p < 0.05). Three patients (2%) had a traumatic patellar dislocation 9, 12and 24 months postoperativelyand 38% underwent subsequent surgery (hardware removal, arthroscopically assisted brisement force, knee arthroscopy). A normalisation of the LTI angle (≥11°) was achieved in 76%. Treatment according to the à la carte algorithm for patients with patellar instability and high-grade trochlear dysplasia resulted in significant clinical and subjective improvement in all PROM scores and a very low redislocation rate (2%) 5years after surgery. Level II.

Poster 283: Revision Patellofemoral Surgery: A Retrospective Cohort Analysis

Objectives: To report demographic and radiologic data, and clinical outcomes of patients undergoing revision surgery for patellar instability Methods: This is a retrospective cohort study. We included patients undergoing revision surgery for patellar instability between January 2010 and January 2022 in our institution. Exclusion criteria included patients with missing information regarding their primary surgery, patients with congenital disorders and patients with a history of distal femoral or proximal tibial osteotomy. Statistical analysis was performed using SPSS v. 20. Results: Ninety-six patients underwent revision surgery for patellofemoral instability. Eight patients were excluded based on exclusion criteria (Figure 1). Of the 88 patients included in final analysis, 44 (50%) had their primary surgery in our institution and revision rate in our institution was 3.8%. Primary surgeries included lateral retinacular release (LRR):18, medial patellofemoral ligament (MPFL) reefing: 19, MPFL reconstruction (MPFLR): 33, Tibial tubercle osteotomy (TTO): 24 (Table 1). Revision surgeries included: Lateral patellofemoral ligament reconstruction for iatrogenic medial instability: 6, MPFL release for persistent pain: 3, MPFLR: 36, MPFLR with Patellar tendon shortening: 5, MPFLR with Trochleoplasty: 4, Revision of femoral screw: 1, TTO: 19, TTO+MPFLR: 10, TTO+Trochleoplasty: 1, TTO+MPFLR+Trochleoplasty: 3 (Table 2). Patients having LRR as primary surgery had more female patients and higher patellar tilt, MPFLR patients had higher incidence of trochlear dysplasia, MPFL reefing patients were younger (Table 1). In our cohort of patients undergoing revision surgery for patellar instability, the mean tibial tubercle-trochlear groove (TT-TG) distance was 17.2 mm and the mean Caton-Deschamps Index (CDI) was 1.42. The incidences of trochlear dysplasia and skeletally immature patients were 61% and 68.2%, respectively (Table 1). The Median follow up period after revision surgery was 81 months. The overall complication rate after revision surgery was 12.5% (11/88) and occurred at a median of 31.5 months. Ten patients had recurrent patellar instability and one patient had tibial tubercle fracture (Table 3). Conclusions: The overall incidence of revision surgery was 3.8 after a primary surgery for patellar instability at a median of 31.5 months. Complications occur in 12.5% of patients after the revision surgery with the majority (10/11) being recurrent patellar instability. In our cohort, CDI and the incidences of trochlear dysplasia and skeletally immature patients were increased while the mean TT-TG distance was not.

Poster 257: Assessing the Likelihood of Symptomatic Patellar Instability via the Two-Image Lateral Trochlear Inclination Angle as a Measurement of Trochlear Dysplasia

Objectives: Trochlear dysplasia is the most common anatomic risk factor for patellar instability (PI) and it is present in roughly 90% of patients with recurrent PI. Qualitative descriptions/categorizations of dysplasia include the Dejour and Oswestry-Bristol classifications. Quantitative measurements include the sulcus angle and the lateral trochlear inclination angle (LTI). The LTI has shown utility given that it is a numeric representation of dysplasia at the most proximal aspect of the trochlea where dysplasia is most severe. Recently, the two-image LTI has been described as a more accurate and reliable method to quantitate dysplasia compared to the original one-image LTI with high inter and intrarater reliability. However, since the advent of the two-image LTI, no analysis has been done to determine the likelihood of developing (PI) once the LTI reaches a certain value. A prior analysis of the single image LTI showed a value of 11° as a threshold value between patients with and without PI. The purpose of this study is to determine a two-image LTI threshold value at or below which a patient is likely to develop recurrent PI. Methods: Ninety-nine patients with PI and 91 age and sex matched control patients were identified. All patients had available magnetic resonance imaging (MRI) and any patients with unreadable imaging, questionable diagnosis or neuromuscular or arthritic conditions were excluded. Trochlear dysplasia was measured via the two-image LTI (Figure 1). In the study group, any negative LTI values (patients with dysplasia so severe that the trochlea is convex), were excluded from analysis. This left 64 study patients. Means and standard deviations were calculated, and an independent t-test determined significant differences between groups. A receiver-operating characteristic (ROC) curve was plotted to determine the area under the curve (AUC) and a threshold value was determined to best discriminate between study and control patients. Results: The mean two-image LTI in the study group was 9.4 ± 5.2 and 17.3 ± 6.77 in the control group (p &lt; 0.001). Intrarater reliability of 15 randomly selected study patients and 15 randomly selected control patients was excellent (Intraclass Correlation Coefficient: 0.963, 0.924-0.982). ROC AUC was 0.825 (95% CI: 0.758-0.891) as depicted in Figure 2. A threshold value of 14.5° (Table 1) was chosen as the best demarcating value between controls and PI patients with a sensitivity of 0.828 (53/64), specificity of .769 (70/91), and an accuracy of .793 (123/155). Conclusions: In comparison to the single image LTI, the two image LTI had a higher threshold value in discriminating between patients with and without PI (11° vs 14.5°). This is very likely due to the difference in measurement techniques. This information is valuable for risk stratification of patients with PI as one would expect patients with an LTI below 14.5° to have recurrent PI and those patients with a single dislocation with an LTI higher than 14.5° to be more likely to stabilize with conservative management. Given the reliability and representative nature of the two image LTI in assessing trochlear dysplasia, symptomatic trochlear dysplasia (that which results in patellar instability) can be defined for most people as dysplasia with a two image LTI £ 14.5°. [Figure: see text]

Isolated Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Instability Regardless of Tibial Tubercle–Trochlear Groove Distance and Patellar Height: Minimum 5-Year Outcomes

Background: It remains unclear which subset of patients with recurrent patellofemoral instability would benefit from a concomitant bony realignment procedure in addition to a medial patellofemoral ligament (MPFL) reconstruction. Purpose: To provide midterm results for patients who underwent an isolated MPFL reconstruction as part of an ongoing prospective trial. Study Design: Case series; Level of evidence, 4. Methods: Patients with recurrent patellar instability were prospectively enrolled in an institutional registry beginning in March 2014. Exclusion criteria included history of a previous surgery for patellar instability, an off-loadable (inferior/lateral) chondral defect, anterior knee pain ≥50% of their chief complaint, and a “jumping J” sign. All patients underwent primary, unilateral, isolated MPFL reconstruction regardless of their bony anatomic characteristics. Patient-reported outcome measures (PROMs), episodes of recurrent instability, and ability to return to sport were obtained annually. Radiographic measurements of baseline radiographs and MRI were obtained at baseline. Results: A total of 138 patients underwent isolated MPFL reconstruction between March 2014 and December 2019. The mean radiographic measurements were tibial tubercle–trochlear groove, 15.1 ± 4.9 mm; Caton-Deschamps index, 1.14 ± 0.16; patellar trochlear index, 46.9% ± 15.1%; trochlear depth index, 2.5 ± 1.2 mm; tibial tubercle to lateral trochlear ridge, −8.4 ± 5.7 mm; and patellar tendon to lateral trochlear ridge, 5.7 ± 6.2 mm. Trochlear dysplasia, defined as a trochlear depth index <3 mm, was present in 79/125 (63%) patients. A total of 50 patients reached ≥5 years, of whom 40 (80%) completed follow-up PROMs. A total of 119 patients reached ≥2 years, of whom 89 (75%) completed follow-up PROMs. Six patients (5%) reported recurrent instability with a mean time of 2.97 years after surgery. All PROMs improved over time except for the Pediatric Functional Activity Brief Scale (Pedi-FABS), which had no change. At 2 years, the mean changes from baseline for Knee injury and Osteoarthritis Outcome Score (KOOS) Quality of Life subscale (QOL), Pedi-FABS, International Knee Documentation Committee (IKDC) score, KOOS Physical Function Short Form (PS), and Kujala score were 42.1, 0.6, 35.1, –23.5, and 32.3, respectively. All changes had P values <.001 except for Pedi-FABS, which showed no change and had P > .999. At 5 years, the mean changes from baseline for KOOS-QOL, Pedi-FABS, IKDC, KOOS-PS, and Kujala score were 42.6, –2.8, 32.6, –21.5, and 31.6, respectively. All changes had P values <.001 except for Pedi-FABS, which showed no change and had P > .453. In total, 89% of patients returned to sport with a mean of 9.1 months. Conclusion: Midterm outcomes for patients who underwent isolated MPFL reconstruction were favorable and were maintained at 5 years. Outcomes for the expanded cohort of patients with a minimum 2-year follow-up support previously published results.

Poster 306: Establishing the Minimum Clinically Important Difference Two Years Following Medial Patellofemoral Ligament Reconstruction

Objectives: Medial patellofemoral ligament (MPFL) reconstruction is used to address cases of recurrent patellar instability. Minimal clinically important difference (MCID) is an important marker that relays the smallest clinical improvement in which patients feel a significant change after surgery. MCID has been previously established for MPFL reconstruction after 6 months and 1 year. To date, no study has established MCID for patient reported outcomes 2 years after MPFL reconstruction. The purpose of this study is to define the MCID for the Kujala, International Knee Documentation Committee (IKDC), and Knee Injury and Osteoarthritis Outcome Score for Joint Reconstruction (KOOS JR) at minimum two-year follow-ups after isolated MPFL reconstruction. Methods: All patients undergoing isolated MPFL reconstruction for recurrent patellar instability at a single institution between December 2015-June 2021 were included. Patients with concomitant osseous procedures beyond chondroplasty and any ligamentous procedure were excluded. A distribution-based approach was used to calculate the MCID. This was performed by determining the standard deviation (SD) of the delta two-year patient reported outcome scores (PROS) and then multiplying the SD by 0.5. The number of patients achieving MCID were then presented as a percentage. Results: Eighty-six of 117 patients who underwent isolated MPFL reconstruction completed preoperative and a two-year follow-up PRO survey (59 female, 27 male; age 21.1 ± 8.7 years). For Kujala, the preoperative mean was 59.3 ± 17.1, two-year follow-up mean was 87.6 ± 13.6, and MCID was 9.2 with 88% of the cohort achieving MCID. For IKDC, preoperative mean was 50.2 ± 17.2, two-year mean was 80.5 ± 18.6, and MCID was 12.4 with 80% of patients achieving MCID. KOOS JR had a preoperative man of 66.0 ± 14.6, two-year follow-up mean of 88.8 ± 11.9, and MCID of 8.5 with 72% of patients meeting this MCID (Figure 1). Conclusions: At two years following MPFL reconstruction, the MCID’s for clinically relevant subjective PROS were 9.2 (Kujala), 12.5 (IKDC), and 8.5 (KOOS JR). MCID’s for MPFL reconstruction are already established for 6-month and 1-year time points, and this was the first presentation of two-year MCID values. Establishing the 2-year MCID for MPFL reconstruction gives surgeons another tool to use in the diagnoses of patellar instability patients who may be struggling post-operatively.

Poster 254: Improvements in Kujala at Minimum Two-Years Following Medial Patellofemoral Ligament Reconstruction are Correlated with Intraoperative Instability Measurements: A Multivariate Analysis of Risk Factors

Objectives: Isolated medial patellofemoral ligament reconstruction (MPFLR) is an effective treatment for those suffering from patellofemoral instability. Currently, many concomitant procedures are associated with MPFLR that address underlying pathologic anatomy. The indication and need for such procedures are currently not well understood and often involve the use of more invasive techniques. We aim to identify patients who may be more vulnerable to worse outcomes. The purpose of this study is to correlate demographic, anatomical, and clinical risk factors to minimum two-year outcomes following isolated MPFLR. Methods: A retrospective review of patients undergoing isolated MPFLR for recurrent patellar instability at a single institution between December 2015-June 2021 was performed. Patients with concomitant osseous procedures beyond chondroplasty and any ligamentous procedure were excluded. Included patients completed patient reported outcome (PRO) surveys preoperatively then at a minimum of 2 years postoperatively. Demographic, radiographic, surgical, and clinical data was collected. Univariate correlations to minimum 2-year delta-PRO scores were calculated, then those reaching significance were included in a multivariable linear regression analysis. Results: One hundred and thirteen MPFLR patients were included (77 female, 36 male; age: 21.6 ± 9.1 years). Final Kujala score was 88.44 ± 14.12 at 2.97 ± 1.11 years postoperatively. On univariate testing, final Kujala score was significantly correlated with age at time of surgery ( P=0.035; r=0.218), body mass index (P=0.035; r=-0.204), and the degree of knee flexion at which the patella can no longer be manually dislocated laterally during an examination under anesthesia (Instability Resolution Angle — IRA; P=0.010; r=-0.318). The delta final Kujala score (mean score 30.72 ± 19.68) was significantly correlated with age at time of surgery (P=0.032; r=-0.207), age at time of first patellar instability event (P=0.001; r=0.364), Caton-Deschamps Index (CDI; P=0.026; r=-0.235), trochlear width (P=0.016; r=0.251), the percentage of trochlear-patellar overlap on sagittal MRI (P=0.031; r=0.227), and the depth of the central trochlear trough from the lateral trochlear peak (P=0.035; r=0.221)(Table 1). On multivariable linear regression analysis, a larger IRA remained significantly correlated with worse final Kujala scores ( P= 0.018) and delta final Kujala ( P= 0.04). Conclusions: A larger IRA on examination under anesthesia is independently correlated with worse final and delta final Kujala scores at a minimum of two-years after isolated MPFLR. This finding can help guide surgeons in their decision to do an isolated MPFLR or add in larger, more invasive procedures that address underlying anatomic pathologies.

Poster 305: Redislocation After Medial Patellofemoral Ligament Reconstruction is Correlated with Preoperative Measurements and Intraoperative Instability Measurements

Objectives: Medial patellofemoral ligament reconstruction is performed to address cases of patellar instability. Historically, this is a well-tolerated procedure though complications, including redislocation and recurrent instability can occur. While risk factors for redislocation following MPFLR have been proposed, there remains no agreed upon consensus. This is even more true in setting of isolated MPFL reconstruction, as concomitant procedures may naturally exclude certain anatomic risk factors. The purpose of this study was to correlate demographic, anatomical, and clinical risk factors to redislocation following isolated medial patellofemoral ligament reconstruction (MPFLR). Methods: A retrospective review of patients who underwent isolated MPFLR for recurrent patellar instability at a single institution between December 2015-June 2021 was performed. Included patients had a minimum of 2 years of follow-up data available. Demographic, pre-operative radiographic, surgical, and clinical data was compared between those who had a dislocation event after surgery and those who did not. Subluxation and subjective instability were not considered dislocation events. Independent samples T-test and univariate binary logistic regression was performed. Results: This study included 126 patients with a mean age of 21.74 ± 9.20 and a mean BMI of 25.93 ± 6.36. Of these, 67.5% were female and 61.9% of operations were on the left knee. In total, 8.7% (11/126) of patients experienced a redislocation event with a mean time to redislocation of 19.11 months after surgery (range 5 – 32 months). On preoperative magnetic resonance imaging (MRI), greater trochlear bump height measured to bone (p=0.032) and measured to cartilage (p=0.033) was associated with redislocation (Table 1). Additionally, patients who redislocated were found to have a wider sulcus angle (p=0.022). On examination under anesthesia, a greater flexion instability resolution angle – the angle of knee flexion at which the patella no longer dislocates – was found to be associated with redislocation (p=0.041) (Figure 1). These variables all retained significance during univariate regression. Conclusions: MPFLR is associated with a high level of success with a redislocation rate of 8.7% in this study. On pre-operative MRI, wide sulcus angle and increased bump height measured to bone and to cartilage were risk factors for redislocation. Additionally, redislocation was associated with a greater flexion instability resolution angle (IRA).

Poster 241: Comparison of Short-Term Clinical Outcomes of Medial Patellofemoral Ligament Reconstruction Using Superficial Quadriceps Tendon and Using Hamstring Tendon in Patella Instability

Objectives: Medial patellofemoral ligament reconstruction (MPFLR) is widely acknowledged as a therapeutic approach for patella instability. While hamstring autografts are widely used in MPFLR, there are concerns regarding complications associated with the patella bone tunnel and fixation hardware, such as the endobutton. As an alternative, the superficial quadriceps (SQ) tendon has also been used presently. To date, few studies have evaluated the comparison of clinical outcomes between the grafts. The purpose of the present study is to compare the short-term clinical outcomes of MPFLR using superficial quadriceps tendon and using hamstring tendon. Methods: All patients who had undergone MPFLR for patella instability between 2017 and 2020 and were able to follow up for &gt;2 years were retrospectively evaluated. For autograft of MPFLR, hamstring was inserted to the patellar bone tunnel formed at superomedial corner of the patella or through the whole patella (ST group), while the center third of the superficial layer of the quadriceps tendon graft was harvested and turned medially leaving its attachment to the patella intact (SQ group). Both grafts were fixed at Schottle’s point with an initial tension of 10-20 N and 30° of knee flexion. Preoperative assessment included the range of knee motion (ROM), and radiographic features such as tibial tubercle–trochlear groove (TT-TG) distance, patellar tilt, and sulcus angle. The Kujala score, Tegner activity score, Lysholm score, ROM, and patellar tilt were assessed at one year postoperatively. Failure was defined by a postoperative patellar dislocation, surgical revision for recurrent patellar instability or any complication. Paired t test and 2-way repeated measure analysis of variance followed by multiple comparison using the Bonferroni test was carried out for statistical analysis, and statistical differences were considered significant for values of p &lt; 0.05. Results: Among 70 MPFL reconstructions, 65 patients (92.9%, 24 males and 41 females) were able to follow-up. The mean follow-up period was 3.1 years (2 to 5 years). There were 22 patients in the ST group and 43 patients in the SQ group. There was no difference in preoperative TT-TG distance (ST group: 14.1 mm ± 4.6 mm, SQ group: 16.2 mm ± 3.1 mm) and sulcus angle (ST group: 143.1° ± 12.4°, SQ group: 139.6° ± 8.9°). Postoperatively, there was no significant difference in Tegner activity score (ST group: 5.5 points ± 2.2 points, SQ group: 5.8 points ± 2.2 points), but the SQ group showed significantly high score in Lysholm score (ST group: 88.7 points ± 12.5 points, SQ group: 95.9 points ± 5.9 points; p &lt; 0.01) and Kujala score (ST group: 91.8 points ± 4.1 points, SQ group: 94.9 points ± 5.1 points; p &lt; 0.01). ROM improved postoperatively, but there was no significance between the 2 groups. The Tilting angle (preoperative; ST group: 24.8° ± 12.0°, SQ group: 20.2° ± 8.3°) improved significantly (postoperatively; ST group: 10.9° ± 4.8°, SQ group: 11.5 ± 4.5°) (p &lt; 0.01). There were 3 failures (13.6%) in the ST group with 2 patellar fractures and 1 postoperative patellar dislocation requiring additional surgery. Conclusions: Both groups had good short-term results, but postoperative Lysholm score and Kujala score were higher in the SQ group. Postoperative improvement in tilting angle reveals that both grafts contribute to restoring MPFL function. However, concerning failures that occurred in the ST group, SQ autograft may be safe and considerable for MPFLR. [Figure: see text][Figure: see text]

Poster 248: Isolated Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Instability Regardless of Tibial Tubercle-Trochlear Groove Distance and Patellar Height: Differential Outcomes for Chondral Defects

Poster 248: Isolated Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Instability Regardless of Tibial Tubercle-Trochlear Groove Distance and Patellar Height: Differential Outcomes for Chondral Defects

Preoperative subjective assessment of disease-specific quality of life significantly influenced the likelihood of achieving the minimal clinically important difference after surgical stabilization for recurrent lateral patellar instability.

To evaluate which factors exert a predictive value for not reaching the minimal clinically important difference (MCID) in patients who underwent a tailored operative treatment for recurrent lateral patellar dislocation(RLPD). A total of 237 patients (male/female 71/166; 22.4 ± 6.8 years) were included. The Banff Patellofemoral Instability Instrument 2.0 (BPII 2.0) and subjective rating of knee function and pain (numeric analogue scale [NAS]; 0-10) were used to evaluate patients' outcomes from pre- to postoperatively. Gender, age at the time of surgery, body mass index (BMI), nicotine abuse, psychiatric diseases, cartilage statusand pathoanatomic risk factors were evaluated as potential predictors for achieving the MCID using univariate logistic regression analysis. The MCID for the BPII 2.0was calculated at 9.5 points. Although the BPII 2.0 and NAS for knee function and pain improved significantly in the total cohort from pre- to postoperatively (all p < 0.001), 29 patients did not reach the MCID at the final follow-up. The analysis yielded that only the preoperative NAS for function and BPII 2.0 score values were significant predictors for reaching the MCID postoperatively. The optimal threshold was calculated at 7 (NAS function) and 65.2 points (BPII 2.0). Age at the time of surgery should be considered for patients with a preoperative BPII 2.0 score >62.5. The probability of reaching BPII 2.0 MCID postoperatively depends only on the preoperative BPII 2.0 value and subjective rating of knee function, as well as age at the time of surgery for patients undergoing surgical treatment of RLPD. Here, presented results can assist clinicians in advising and presenting patients with potential outcomes following treatment for this often complex and multifactorial pathology. Level III.

Double-Level Knee Derotational Osteotomy Yields Better Postoperative Outcomes Than Tibial Tubercle Transfer Combined With Medial Patellofemoral Ligament Reconstruction in Patients With Recurrent Patellar Instability and Severe Malrotation

PurposeTo assess the postoperative outcomes of double level knee derotational osteotomy (KDRO) combined with medial patellofemoral ligament reconstruction (MPFLR), and to compare it with tibial tuber transfer (TTT) and MPFLR without derotational osteotomy in patients with recurrent patellar instability (RPI) and a marked torsional deformity. MethodsFrom March 2020 to December 2021, patients with torsion deformity (combined femoral torsion and tibial torsion ≥ 30°) were retrospectively included. The minimum follow-up time was 18 months. Patients received KDRO and MPFLR were categorized into KDRO group and patients received a combined TTT and MPFLR were categorized into control group. Preoperative and postoperative clinical symptoms, patient-reported outcomes (PROs) (Kujala, visual analogue scale [VAS], Lysholm, International Knee Documentation Committee [IKDC], Tegner, and Knee Injury and Osteoarthritis Outcome [KOOS] scores) and imaging parameters (femoral torsion, tibial torsion, patellar height, femoral trochlear dysplasia, congruence angle, patellar tilt angle, lateral patellar angle, lateral patellar translation, and tibial tubercle–trochlear groove distance) were analyzed. ResultsIn all, 36 patients were included with 18 in KDRO group and 18 in control group. The mean follow-up time was 30 (range 21-39) months. At the latest follow-up, no patient experienced re-dislocation in either group. Except for the femoral torsion and tibial torsion in the control group, postoperative imaging parameters were significantly reduced to the normal range. KDRO group has a lower patellar tilt angle (P=.043, effect size 0.64). All clinical scores in both groups significantly improved postoperatively. KDRO group has better functional scores than control group except the KOOS daily living activities subscore and the KOOS sports and recreation subscore. More proportions of patients in KDRO group met the minimal clinically important difference (MCID) for most PROs than control group. Eight patients (44%) in the control group complained of postoperative anterior knee pain, compared with 1 patient (6%) in KDRO group (P=.018). ConclusionKDRO combined with MPFLR was associated with better postoperative outcomes than TTT combined with MPFLR in patients with RPI and a torsion deformity.

Shallow trochlear groove and narrow medial trochlear width at the proximal trochlea in patients with trochlear dysplasia: Athree-dimensional computed tomography analysis.

Although the Dejour classification is the primary classification system for evaluating trochlear dysplasia, concerns have been raised about its reliability owing to its qualitative criteria and challenges associated with obtaining accurate radiographs. This study aimed to quantify trochlear dysplasia using three-dimensional (3D) computed tomography (CT) reconstruction with novel parameters related to the transepicondylar axis (TEA). Sixty patients were enrolled, including 20 with trochlear dysplasia and 40 healthy controls. The 3D CT model was generated using the Materialise Interactive Medical Image Control System software. The following six parameters were measured in eight consecutive planes at 15° intervals (planes 0-105): the distance from the TEA to the most cortical point of the lateral condyle ('LP-TEA', where LP stands for lateral peak), medial condyle ('MP-TEA', MP for medial peak)and deepest point of the trochlea ('TG-TEA', TG for trochlear groove). The distances from the medial epicondyle (MEC) to the corresponding TEA points were measured ('LP-MEC', 'MP-MEC'and 'TG-MEC'). In the dysplasia group, TG-TEA (planes 0, 15and 30) and MP-MEC (planes 0, 15and 30) were significantly greater than those in the control group (all p < 0.05 for planes of TG-TEA and MP-MEC). For type A dysplasia, LP-MEC (plane 0) was greater than that in the control group. For type B dysplasia, the MP-MEC (planes 0 and 15) and TG-TEA (planes 0 and 15) were greater than those of the control group. For type D dysplasia, MP-MEC (planes 0, 15and 30) and TG-TEA (planes 0 and 15) were elevated. The 3D CT reconstruction analysis established a reproducible method for quantifying osseous trochlear morphology. Patients with trochlear dysplasia had a shallow TG and narrow medial trochlear width at tracking angles of 0°-30°. This finding corroborates the clinical manifestations of recurrent patellar instability that occur during early flexion. Level III.

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

PurposeThe purpose of this work is 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. MethodsThe time frame of the study was January 2020 to February 2023. The inclusion criteria were patients treated by the senior author (JPF) (with the exception of two 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 three-dimensional (3D) models of the distal femurs from CT scans. AP 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. Results28 patients were included for the recurrent dislocator group. 24 decedents from NMDID were selected for the control group, each with a left or right knee chosen randomly for measurement. A one-sided Mann-Whitney U test, used to evaluate whether the recurrent dislocators had higher EP-TG angle values, yielded a p value <0.001, demonstrating a high level of significance. A Bayesian mixed effect model, used to determine how different the EP-TG angles are between the two groups, gave a posterior predictive interval (PPI) of [11.93, 19.12] degrees for the EP-TG angle shift of dislocators. The intraclass correlation coefficient was 0.648. ConclusionsThe morphological 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 EP-TG angle, which may be useful information for optimizing treatment of recurrent patella instability. Level of EvidenceLevel III Case Control Study

Patellofemoral stabilization with and without cartilage restoration

Introduction/ObjectivesCartilage restoration as an adjunct to patellofemoral (PF) soft tissue and/or bony stabilization in patients with symptomatic PF instability remains controversial. Our purpose was to evaluate patients undergoing surgical stabilization for PF instability with or without concomitant cartilage restoration. MethodsRetrospective review of prospectively collected data identified patients undergoing surgical stabilization for recurrent patella instability, with or without concomitant cartilage restoration. Presurgical and postsurgical patient-reported outcomes were collected. Complications requiring reoperation were recorded. Statistically significant difference was set at P < .05. ResultsOne hundred thirty patients (144 knees) were included. One hundred thirteen knees in the isolated stabilization (STAB) and 31 knees in the Stabilization-Cartilage Restoration (STAB-CART) group. The average age was 20.64 and 25.03 in the STAB and STAB-CART groups (P = .034), respectively. STAB-CART group had significantly lower preoperative Knee injury and Osteoarthritis Outcomes Score (57.24 ± 17.45 vs 46.11 ± 14.74, P = .019) and Single Assessment Numeric Evaluation scores (43.15 ± 19.05 vs 26.85 ± 13.74, P = .002). Both groups statistically improved in all Knee injury and Osteoarthritis Outcomes Score, International Knee Documentation Committee, and Single Assessment Numeric Evaluation domains with no statistically significant differences at final follow-up between groups. Thirteen knees (11.5%) in the STAB and 6 knees (19.4%) in the STAB-CART group had complications requiring reoperation, including 6 and 3 revision stabilizations, respectively. There were no statistically significant differences in total major complications (P = .246) or medial PF ligament revision (P = .405). ConclusionsThe addition of cartilage restoration in patients undergoing soft tissue and/or bony PF stabilization appears to be safe and effective. Despite lower baseline scores, patients undergoing PF stabilization with cartilage restoration had similar final subjective outcome scores compared to the group without.

Evaluation of the Results of Reconstruction of Medial Patellofemoral Ligament in the Treatment of Recurrent Patellar Instability Using Hamstring Autograft by Dual Patella Docking Technique

Abstract Background: Recurrent patellar instability can significantly affect a patient’s life quality. This study evaluated the results of medial patellofemoral ligament (MPFL) reconstruction in the recurrent patellar instability treatment using hamstring autograft by dual patellar docking technique. Materials and Methods: This prospective study was performed on 20 recurrent patellar instability patients. Magnetic resonance imaging and computed tomography scans were performed to confirm MPFL tear and assess the tibial tubercle-trochlear groove distance. Various clinical and radiographic evaluations were performed preoperatively. The surgical technique involved diagnostic arthroscopy, graft preparation, patellar preparation, graft passage, femoral tunnel preparation, and graft fixation. Results: Postoperatively, a substantial progression was observed in the International Knee Documentation Committee score, Kujala score, Cincinnati score, and Lysholm score compared to preoperative values (P &lt; 0.001). In addition, the postoperative measurements of patellar tilt angle and patellar congruence angle were significantly lower than their respective preoperative values (P &lt; 0.001). All 20 (100%) patients had negative findings in the postapprehension test, indicating improved stability. In the postcompression test, 3 (15%) patients showed positive results, whereas 17 (85%) patients had negative results. In terms of complications, 2 (10%) patients experienced patellofemoral pain, 1 (5%) patient had residual patellar translation without dislocation, 1 (5%) patient had limited flexion, and the majority of patients (16, 80%) had no complications. Conclusions: MPFL reconstruction with patellar docking yielded good results with Kujala and Lysholm, as well as adequate, satisfactory congruence angles for most patients. This procedure has exhibited a high success rate in addressing patellofemoral instability.