Recurrent Patellofemoral Instability Research Articles

Comparable postoperative outcomes in patients treated with either open or arthroscopic trochleoplasty for patella dysplasia

BackgroundThe aim of this study was to compare the clinical and radiologic results of the arthroscopic and the open trochleoplasty techniques.MethodsA total of 83 trochleoplasties in 83 patients were performed between 2014 and 2021 in one institution. Surgical indications for trochleoplasty were recurrent patellofemoral instability and a lateral trochlear inclination angle (LTI) ≤ 11˚ and a trochlear depth ≤ 6 mm. Of the trochleoplasties, 40 were done by open technique (OT) and 43 by arthroscopic technique (AT). In every case an additional medial patellofemoral ligament (MPFL) reconstruction was performed. Additional tuberosity tibia transfer and/or de-rotation of the femur were done when indicated. Pre- and postoperative magnetic resonance imaging (MRI) were analyzed in respect to LTI, trochlear depth, and lateralization of the patella. Postoperative subjective clinical assessment was done using the Kujala Score, Banff II Score, Tegner Score, and Marx Score.ResultsOf the patients, 15 with OT and 20 with AT were available for follow-up. The mean follow-up was 29.9 months in the OT group and 12.7 months in the AT group. No re-dislocation was observed in either groups. A significant reduction of LTI, increase of trochlear depth, and a reduction of lateralization of the patella was observed between the pre- and postoperative MRI scans in both groups. No significant difference in the observed MRI parameters was found between the two groups. Neither was there a difference in the postoperative Kujala Score, Banff II Score, Tegner Score, and Marx Score between the two groups. Length of stay was on average 6.2 days in the AT group and 8.1 days in the OT group. The surgical time was on average 141 min in the OT group and 160 min in the AT group.ConclusionWe found that patients undergoing an arthroscopic trochleoplasty had a comparable outcome with respect to clinical and radiological parameters compared with patients treated by open trochleoplasty.

The Influence of Kinesiophobia and Pain Catastrophizing on Disease-Specific Quality of Life in Patients With Recurrent Patellofemoral Instability

Background: The Banff Patellofemoral Instability Instrument 2.0 (BPII 2.0) is a disease-specific, quality of life patient-reported outcome measure (PROM) that is valid and reliable in patients with recurrent lateral patellofemoral instability (LPI). Quality of life encompasses the physical, emotional, and psychological aspects of patient functioning and recovery. Purposes: To concurrently validate the BPII 2.0 to the Tampa Scale for Kinesiophobia (TSK-11), the Pain Catastrophizing Scale (PCS), and the Anterior Cruciate Ligament–Return to Sport after Injury Scale (ACL-RSI) in patients presenting with recurrent LPI and to assess baseline values for the PROMs in patients with LPI. Study Design: Cohort study (Diagnosis); Level of evidence, 2. Methods: A total of 107 consecutive patients with recurrent LPI were assessed between January and October 2021. Patients completed the BPII 2.0, TSK-11, PCS, and ACL-RSI. A Pearson r correlation coefficient was employed to examine relationships between the PROMs. Baseline values, as well as floor and ceiling effects and Cronbach alpha, were assessed for all PROMs. Results: All 107 patients completed the 4 PROMs. Patients included 28 men (26.2%) and 79 women (73.8%), with a mean (SD) age of 25.7 (9.8) years. The mean (SD) age at first dislocation was 14.8 (6.3) years. The TSK-11, PCS, and ACL-RSI were all statistically significantly correlated with the BPII 2.0 (P < .01; 2-tailed), with moderate correlations (r = -0.361-0.628) The R2 values indicated an overlap of the constructs measured by the PROMs. Conclusion: A statistically significant correlation was evident between the BPII 2.0 and the other PROMs. The BPII 2.0 does not explicitly measure kinesiophobia or pain catastrophizing; however, the significant statistical relationship of the TSK-11 and PCS to the BPII 2.0 suggests that this information is being captured and reflected.

Comparison of a Single Assessment Numeric Evaluation Method and the Banff Patella Instability Instrument 2.0 for Patients With Patellofemoral Instability.

The concept of Single Assessment Numeric Evaluation (SANE) has been introduced for several clinical entities; however, a validated SANE focusing on patients with patellofemoral instability has not been described. The purpose of this study was to investigate the expressiveness of SANE questions (SQs) for the assessment of patients experiencing patellofemoral instability. It was hypothesized that the complexity of patellofemoral instability cannot be demonstrated by a single question. Cohort study (diagnosis); Level of evidence, 2. Between October 2022 and March 2023, 120 consecutive patients (male/female, 50/70; mean age, 23.9 ± 8.0 years; mean body mass index, 25.3 ± 5.1 kg/m2) with patellofemoral instability were assessed with the Banff Patella Instability Instrument 2.0 (BPII 2.0). Patients were randomized into 3 groups (40 patients each) and asked to answer 1 of 3 SQs: "How do you rate your knee joint if a completely stable kneecap means 100%?" (SQ 1), "How do you rate your knee joint if complete satisfaction means 100%?" (SQ 2), and "How do you rate your knee joint if complete normal function means 100%?" (SQ 3). Means ± standard deviations were compared using 1-way analysis of variance, the correlation between BPII 2.0 and each SQ was assessed by Pearson correlation, and Bland-Altmann analysis was performed to investigate biases of each SQ in comparison with BPII 2.0. The mean BPII 2.0 score was 40.5 ± 16.8 points, and the mean results of SQ 1, SQ 2, and SQ 3 were 44.2% ± 26.0%, 42.6% ± 25.4%, and 44.2% ± 18.9%, respectively, without significant differences between the groups (all P > .05). The correlations between BPII 2.0 and SQ 1, SQ 2, and SQ 3 were high (r = 0.75; 95% CI, 0.58 to 0.86; P < .0001), low (r = 0.35; 95% CI, -0.05 to 0.6; P = .02), and low (r = 0.31; 95% CI, -0.002 to 0.56; P = .051), respectively. Bland-Altman analysis between BPII 2.0 and SQ 1, SQ 2, and SQ 3 revealed biases of -0.12 (SD, 17.1), -1.45 (SD, 24.4), and -8.0 (SD, 19.4), respectively. The SQ "How do you rate your knee joint if a completely stable kneecap means 100%?" demonstrated concurrent validity with the BPII 2.0 and may serve as a helpful tool to quickly assess patients with recurrent patellofemoral instability in a preoperative setting.

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.

Paper 37: Outcomes of Medial Patellofemoral Ligament Reconstruction Patients Over 30 Years of Age

Objectives: Medial patellofemoral ligament reconstruction (MPFLR) is a common procedure to treat recurrent patellofemoral instability, typically in a younger, active patient population. While many patients treated with MPFLR fall into this age group, patellar instability is encountered in older patients as well. Outcomes in older patient populations have been less frequently reported in the literature. We hypothesize that patients over 30 at the time of surgery will have poorer postoperative patient reported outcome measures (PROMs) following MPFLR than patients under age 30. Methods: Retrospective review was undertaken to identify patients who underwent isolated MPFLR between 2008 and 2020. Chart review was utilized to obtain patient demographic, anatomical, and surgical factors. Patients were contacted via mail and/or phone and patient-reported outcomes were recorded. PROMs included the knee injury and osteoarthritis injury outcome score (KOOS), Norwich patellar instability score, and Marx activity score. Differences between groups were evaluated by Mann-Whitney and Fisher-exact tests. KOOS and Norwich scores were also evaluated using a multivariable linear regression adjusting for the following variables selected a priori: sex, body mass index, Caton-Deschamps index, TT-TG distance, sulcus angle, and the presence or absence of ≥ Grade 2 cartilage damage. Results: A total of 228 patients underwent isolated MPFL reconstruction in the study period. 177 patients (78%) had data on repeat patellar dislocations at least 1 year postoperatively, with a median follow-up interval of 40.8 months (3.4 years) postoperative. Of these 177, 140 were under age 30 at time of surgery, 7 (5%) of whom had a repeat dislocation; of 37 patients at or over age 30 at time of surgery, 2 (6.6%) had a repeat dislocation. 147 patients further completed KOOS, Norwich, and Marx activity score surveys with a median follow-up of 45.3 months (3.8 years) post-operative. Patients ≥ 30 years old at surgery (n=31) had lower KOOS pain (82.1 vs 91.7; p=0.03), KOOS activities of daily living (94.1 vs 97.1; p=0.04), and Marx activity scores (1 vs 7; p&lt;0.001) compared to the patients under age 30 (n=116) (Table 1). After adjusting for covariates, multivariable regression models for KOOS and Norwich scores showed only KOOS pain subscores were lower for patients ≥ 30 years (β= -4.2; 95% CI -8.3, -0.2; p=0.04). Conclusions: Patients over age 30 at the time of MPFLR demonstrated similar recurrence risk but lower KOOS pain and Marx activity scores at 3.8 years postoperative than patients under age 30 at the time of MPFLR. [Figure: see text]

Combined Medial Quadriceps Tendon-Femoral Ligament and Medial Patellofemoral Ligament Reconstruction for Revision Patellofemoral Soft-Tissue Stabilization

Patients with recurrent patellofemoral instability in whom prior medial patellofemoral ligament (MPFL) reconstruction fails present unique challenges for revision soft-tissue stabilization owing to scar tissue formation, limited patellar bone stock for anchor placement, and increased risk of patellar fracture. We describe a technique for revision patellofemoral soft-tissue stabilization that combines MPFL and medial quadriceps tendon–femoral ligament reconstruction techniques through combined fixation to the patella with 1 suture anchor and soft-tissue fixation to the quadriceps tendon. The proposed technique maximizes restoration of resistance to lateral translation by attempting to re-create the native MPFL attachment and minimizes patellar fracture risk in the setting of poor bone stock through the use of a single 1.8-mm all-suture suture anchor rather than bone tunnels or multiple anchor placement for bony fixation.

Simultaneous MPFL reconstruction and guided growth resultin low rates of recurrent patellofemoral instability.

Implant-mediated guided growth (IMGG) is used to address coronal plane deformity in skeletally immature patients. Few studies have reported on IMGG and simultaneous medial patellofemoral ligament (MPFL) reconstruction for paediatric patients with concurrent genu valgum and patellofemoral instability (PFI). This study aimed to report on the outcomes of these simultaneous procedures. This was a retrospective review of paediatric patients undergoing simultaneous MPFL reconstruction and IMGG between 2016 and 2023. Mechanical lateral distal femoral angle (mLDFA), hip-knee-ankle angle (HKA)and mechanical axis deviation (MAD) were measured on full-length hip-to-ankle plain radiographs. Measurements were taken preoperatively, prior to implant removal and/or at final follow-up with minimum 1-year clinical follow-up. A total of 25 extremities in 22 patients (10 female) underwent simultaneous IMGG and MPFL reconstruction. The mean age at surgery was 12.6 ± 1.7 years. The mean duration of implant retention was 18.6 ± 11.3 months. Nineteen extremities (76%) underwent implant removal by final follow-up. Preoperative HKA corrected from a mean of 5.8 ± 2.3° to -0.8 ± 4.5° at implant removal or final follow-up (p < 0.001), with mLDFA and MAD similarly improving (both p < 0.001). HKA corrected a mean of 0.7 ± 0.9° per month, while mLDFA and MAD corrected a mean of 0.5 ± 0.6°/month and 2 ± 3 mm/month, respectively. At the time of implant removal or final follow-up, 88% of patients demonstrated alignment within 5°of neutral. Only one extremity experienced subsequent PFI (4%). For 14 patients who underwent implant removal with further imaging at a mean of 7.8 ± 4.9 months, only one patient (7%) had a valgus rebound to an HKA > 5°. Simultaneous MPFL reconstruction and IMGG provided successful correction of lower extremity malalignment with only one recurrence of PFI. This approach is a reliable surgical option for skeletally immature patients with genu valgum and PFI. Level 4 case series.

Combination of tibial tubercle transfer, medial patellofemoral ligament reconstruction, trochleoplasty and lateral release for patellofemoral instability provides good middle- to long-term outcomes in adolescents.

There are limited studies that have reported the middle- to long-term outcomes of combined procedures consisting of more than two procedures for patellofemoral instability. The current study aims to investigate and report the middle- to long-term outcomes of a combination procedure of tibial tubercle transfer, medial patellofemoral ligament reconstruction, trochleoplasty and lateral release for patellofemoral instability in patients aged 18 years and below. In the cohort study, all patients aged 18 years old or younger who underwent a combination procedure of tibial tubercle transfer, medial patellofemoral ligament reconstruction, trochleoplasty and lateral release for recurrent patellofemoral instability were included. A total of 21 patients were included in the study. All patients had no further patellofemoral dislocation, pain and apprehension following the 4-in-1 surgery (p < 0.01). There was a significant improvement in the Kujala score from 36.1 (SD 12.9) pre-operatively to 93.1 (SD 3.6) post-operatively (p < 0.001). The patients also had a statistically significant improvement in their radiological factors, including the patellar tilt angle (p < 0.001), sulcus angle (p = 0.001), trochlear groove depth (p = 0.041), tibial tubercle-trochlear groove distance (p < 0.001) and Caton-Deschamps index (p = 0.001). A combination procedure of tibial tubercle transfer, medial patellofemoral ligament reconstruction, trochleoplasty and lateral release leads to good middle- to long-term subjective, functional and radiographic outcomes for patients with recurrent patellofemoral instability and underlying predisposing factors of increased TT-TG distance of more than 20mm, Dejour B or D trochlear dysplasia and medial patellofemoral ligament rupture. IV.

Minimally Invasive Medial Patellofemoral Ligament Reconstruction With Patellar-Sided Tensioning Using All-Suture Anchors

Medial patellofemoral ligament (MPFL) reconstruction is a commonly performed procedure to reestablish the checkrein to the lateral patellar translation in patients with recurrent patellofemoral instability. Graft tensioning is one of the most critical aspects of the procedure. Most surgical methods for MPFL reconstruction involve tensioning and securing the graft on the femoral side. In this article, we describe a technique for patellar-sided tensioning of the graft using all-suture anchors, which provides the surgeon with the ability to finely control graft tension with two independent graft limbs, while preserving patellar bone stock.

Systematic Review: Pedicled Strip of Quadriceps Tendon Graft for Primary Medial Patellofemoral Ligament Reconstruction in Recurrent Patellofemoral Instability

Systematic Review: Pedicled Strip of Quadriceps Tendon Graft for Primary Medial Patellofemoral Ligament Reconstruction in Recurrent Patellofemoral Instability

Physeal Sparing Approaches for MPFL Reconstruction.

To update and concepts for pediatric physeal-sparing patellofemoral stabilization surgery. Recent studies have demonstrated positive results in patellofemoral stabilization in pediatric populations with physeal-sparing techniques that limit the potential for physeal damage. Comprehensive analysis remains limited by population and technique heterogeneity. Physeal-sparing patellofemoral stabilization, most significantly through physeal-sparing reconstruction of the medial patellofemoral ligament complex remains a viable option for pediatric patients with recurrent patellofemoral instability.

Does Tibial Tuberosity Osteotomy Improve Outcomes When Combined With Medial Patellofemoral Ligament Reconstruction in the Presence of Increased Tibial Tuberosity-Trochlear Groove Distance? A Systematic Review and Meta-analysis.

There has been recent debate regarding the optimal surgical management strategy for recurrent patellofemoral instability in the presence of an increased tibial tuberosity-trochlear groove (TT-TG) distance. In particular, performing a combined tibial tuberosity osteotomy (TTO) and medial patellofemoral ligament reconstruction (MPFLR) for patients with a TT-TG >20 mm has been questioned, with the hypothesis that an isolated MPFLR (iMPFLR) would be just as effective. To pool and compare outcomes after MPFLR+TTO versus iMPFLR in patients with a TT-TG >20 mm. Systematic review; Level of evidence, 4. PubMed-MEDLINE, Embase, Web of Science, and Cochrane Central were searched, and a systematic review was performed. Included were studies that reported postoperative redislocation rates and/or functional outcome scores for patients with recurrent patellar instability and a TT-TG >20 mm who underwent either MPFLR+TTO or iMPFLR and had minimum 2-year follow-up data. Methodologic quality was assessed using the modified Coleman Methodology Score (mCMS). A proportional meta-analysis comparing redislocation, subjective instability, and total complication rates was performed, and mean postoperative functional outcome scores were pooled using a random-effects model with a restricted maximum likelihood estimator. In total, 1548 studies were screened, from which 13 were included for analysis. Of the 386 included patients (406 knees), 276 underwent MPFLR+TTO and 110 underwent iMPFLR. The mean mCMS was 61.3 ± 10.5 (range, 48-77). The pooled postoperative redislocation rate was 1.22% (95% CI, 0.22%-7%), with no significant difference between the study groups (P = .9995). The pooled complication rate was 10.17% (95% CI, 6.2%-16.3%) with no difference between groups (P = .9275), although the MPFLR+TTO group had higher heterogeneity in complication rates (I2 = 79.4%) compared with iMPFLR (I2 = 0%). There was no group difference in the pooled postoperative Lysholm scores (P = .5177), but patients who underwent iMPFLR had significantly higher postoperative Kujala scores compared with those who underwent MPFLR+TTO (P = .0283). Even in the presence of previously indicative anatomic factors (TT-TG >20 mm), TTO combined with MPFLR does not seem to confer additional benefit compared with iMPFLR. This finding could be advantageous in minimizing the burden of additional surgery with its associated risks. The study findings should, however, be interpreted with caution given the heterogeneity of the studies.

Sulcus-Deepening Trochleoplasty for High-Grade Trochlear Dysplasia: Demystifying the Procedure-a Review of the Current Literature.

The most common and biomechanically influential pathoanatomic risk factor for recurrent patellofemoral instability is trochlear dysplasia. Sulcus-deepening trochleoplasty is a procedure developed to address high-grade trochlear dysplasia in the setting of patellofemoral instability. The purpose of this paper is to outline the current classification and surgical management of trochlear dysplasia as well as to review the current literature on the clinical outcomes and complications of sulcus-deepening trochleoplasty. This review outlines the most recent literature reporting evidence behind the decision-making to perform a trochleoplasty in the setting of patellofemoral instability and high-grade trochlear dysplasia. Critical parameters include grade of trochlear dysplasia, severity of symptoms, pertinent physical examination findings, surgical techniques, modifications for skeletally immature patients, and considerations for the revision setting. Historic studies have elicited concerns regarding high reported complication rates for trochleoplasty; however, recent studies consistently report good clinical outcomes and acceptable complication rates, similar to those of other patellar stabilizing procedures. The addition of a trochleoplasty in patients with high-grade dysplasia results in a lower re-dislocation rate, significant improvements in patient-reported outcome measures (PROMs) as well as high levels of patient satisfaction and return to sport. The use of sulcus-deepening trochleoplasty for the treatment of high-grade dysplasia and recurrent patellofemoral instability is a well-established technique with good outcomes and an acceptable complication profile. In patients with high-grade dysplasia, trochleoplasty results in lower re-dislocation rates, high patient satisfaction scores, and good clinical and functional outcomes. An understanding of trochleoplasty and its indications should be in the armamentarium of surgeons treating patellofemoral instability.

Different gait pattern in adolescence with patellofemoral instability

BackgroundPatellofemoral instability influences the gait pattern and activity level in adolescents. However, gait biomechanics to cope with recurrent patella instability and its relation to radiological findings has hardly been studied. MethodsWe retrospectively analyzed kinematic and kinetic gait analysis data, magnetic resonance images and X-ray of 32 adolescents with unilateral recurrent patellofemoral instability aged 12 to 18 years. Subjects were assigned to 3 groups based on their sagittal knee moment in the loading response and mid stance phase. Kinematic and kinetic differences among the groups were analyzed using a one-way ANOVA. A multinomial logistic regression model provided a further analysis of the relationship between gait biomechanics and MRI as well as X-ray parameters. FindingsAll three groups showed different characteristics of the knee kinematics during loading response and single stance: while the patella-norm-loading group showed a slightly reduced knee flexion (p 〈0,01), the patella-unloading group kept the knee nearly extended (p < 0,01) and patella-overloading group showed an increased knee flexion (p = 0,01) compared to the other groups. In single stance the patella-overloading group maintained increased knee flexion (p < 0,01) compared to patella-unloading group and patella-norm-loading group. None of the radiological parameters proved to be related to gait patterns. InterpretationThe paper describes different gait coping strategies and their clinical relevance in subjects with patellofemoral instability. However, we did not find any relation of gait biomechanics to skeletal morphology.

Poster 143: Patella Fixation Using All-Suture Versus Knotted and Knotless Solid Suture Anchors in Medial Patellofemoral Ligament Reconstruction: A Biomechanical Analysis

Objectives: Patients with recurrent patellofemoral instability are indicated for medial patellofemoral ligament (MPFL) reconstruction. Multiple different patellar graft fixation methods exist in MPFL reconstruction surgery, namely bone tunnels, interference screws, and suture anchors. Meta analysis has shown suture patellar fixation to have superior patient reported outcomes with no statistical difference in failure rates when compared to transpatellar tunnel fixation clinically. Amongst suture anchor designs, all-soft-suture anchors occupy a smaller volume than solid suture anchors, requiring a smaller diameter tunnel during placement and thus theoretically can reduce the risk of patella fracture and articular surface violation. However, there is concern that all-soft-suture anchors may be biomechanically inferior to their hard-bodied anchor counterparts. Additionally, there is a paucity of research comparing different anchor designs (knotted vs knotless) amongst hard-bodied anchors in the setting of MPFL reconstruction. The purpose of this study is to perform a biomechanical comparison of newer generation soft-bodied anchors and hard-bodied suture anchors with different fixation methods when performing an osseous-based MPFL reconstruction in a cadaveric model. Methods: Fourteen patellae were randomized into three groups: PEEK hard-body knotless (HB-knotless), PEEK hard-body knotted (HB-knotted), and soft-body knotless (SB-knotless) anchors placed at the anatomic MPFL insertions in the direct medial position and at the superomedial aspect of each patella. Prior to anchor placement, bone density at the sites of anatomic MPFL insertions was measured on standard radiographs. After anchor placement, patellae were potted, and anchors were tested in a materials test system in a cyclic regimen (10-30 N, 100 cycles) immediately followed by load-to-failure (6mm/sec). All testing was performed in line with the anchor alignment (Figure 1). Outcome measures included maximum load and cyclic creep, defined as the difference in segment length from the peak load of the first cycle to the peak load of the 100th cycle of testing. One-way ANOVA and Fisher exact tests were used to evaluate outcomes between groups. Statistical significance was set at p &lt; 0.05. Results: Analysis included 6 SB-knotless, 14 HB-knotted, and 8 HB-knotless anchors. The groups were equivalent in age (range 30 years – 70 years; p = 0.657) and bone density (p = 0.134) in a 4:3 male-to- female ratio. There was no significant difference in cyclic creep detected between SB-knotless (3.00 ± 0.79 mm), HB- knotless (2.80 ± 0.42 mm), and HB-knotted (3.25mm ± 0.70 mm) groups (p = 0.301). HB-knotted exhibited a lower maximum load (111.30 ± 43.71 N) than HB-knotless (180.01 ± 58.87 N) (p = 0.017), but no significant difference to SB-knotless (149.34 ± 61.38 N) (p = 0.310) (Figure 2). HB- knotless and SB-knotless did not have a significant difference in maximum load (p = 0.529). When evaluating the influence of patellar anchor site on performance, there was no significant difference in cyclic creep or maximum load between direct medial and superomedial anchor positioning in SB-Knotless (p = 0.800, p = 0.800), HB-Knotted (p = 0.719, p = 0.219), or HB-Knotless (p = 0.886, p = 0.057) groups, respectively. There were 6 SB-knotless, 12 HB-knotted, and 7 HB-knotless anchors that failed by anchor pull-out, with 2 HB-knotted and 1 HB-knotless which failed either by the suture breaking within the anchor or the knot failing (Figure 3). This difference between failure mechanisms was not significant. Conclusions: Hard-body knotless anchors provide superior load to failure than traditional hardbody knotted anchors. Additionally, all-soft-suture anchors performed as well as their counterparts in both load to failure and resistance to cyclic creep. This work suggests surgeons should be comfortable using either hard-body or all-soft-suture anchors when performing osseous-based MPFL reconstructions and may consider opting for a knotless mechanism when utilizing a PEEK hard-bodied anchor for this purpose. A clinical study should take place next to validate these cadaveric findings.

Poster 294: Patellar Tendon Insertion is Not Distalized following Tibial Tubercle Osteotomy with Distalization

Objectives: Patella alta is a common anatomic risk factor in patients with patellofemoral instability and/or patellofemoral cartilage lesions, occurring in nearly 25% of these patients. Distalization tibial tubercle osteotomy (TTO) is effective in patients with patella alta in association with patellofemoral instability and cartilage lesions. Prior studies have suggested that increased patellar tendon length itself is a risk factor for recurrent patellofemoral instability, and have proposed the addition of a patellar tendon tenodesis via placement of a suture anchor proximal to the distalization TTO. However, concerns regarding increased patellofemoral cartilage stresses with addition of patellar tendon tenodesis have limited its adoption. The purpose of this study was to evaluate patellar tendon length and alignment parameters on preoperative and postoperative MRI and to evaluate patient reported outcomes (PROs) following distalization tibial tubercle osteotomy (TTO) without patellar tendon tenodesis in patients with patella alta. Methods: We conducted a retrospective review of 20 adult patients who underwent distalization TTO for patellar alta at our institution (December 2014-August 2021). All patients underwent preoperative and postoperative magnetic resonance (MR) imaging of the affected knee. Distalization TTO utilized a wedge-shaped osteotomy measuring ˜5cm in length and was fixed with two 4.5mm bicortical fully threaded screws following TT transfer. Caton-Deschamps (CDI), axial and sagittal TT-TG indices1, patellar tendon length and distances from tibial plateau to patellar tendon insertion and tibial tubercle were assessed (Figure 1). PROs included IKDC Subjective Knee Evaluation, KOOS Quality of Life Form, Kujala Anterior Knee Pain From, and Veterans RAND 12 Item Mental (VR12-MH) and Physical Health (VR12-PH) Surveys. Clinical data, including demographics, complication and perioperative data, was obtained from preoperative and postoperative charts in our electronic medical record. Results: Average age at time of surgery was 27.4 years (range: 14 – 42 years) and all patients were female. Average BMI was 24.9 +/- 4.4 kg/m2. Eleven patients (55%) were diagnosed with isolated patellofemoral cartilage lesions, four patients (20%) were diagnosed with patellofemoral instability without associated cartilage lesions and five patients (25%) were diagnosed with both instability and cartilage lesions. At the time of TTO distalization, eleven patients (55%) underwent matrix-induced autologous chondrocyte implantation (MACI), nine patients (45%) underwent MPFL reconstruction, four patients (20%) underwent lateral release/lengthening, and three patients (15%) underwent osteochondral allograft (OCA) implantation. Fourteen patients (70%) underwent anteromedialization of the tibial tubercle in addition to distalization. Radiographic parameters demonstrated improved patellar height (CDI decreased from 1.36 to 1.11 (p &lt; 0.001), improved rotational alignment (axial TT-TG decreased from 14.3mm to 11.1mm (p = 0.018)) and anteriorization of the TT (sagittal TT-TG increased from -4.3mm to -1.4mm (p = 0.037)) following distalization TTO. Distance from the tibial plateau to the PT insertion decreased from 20.1mm preoperatively to 17.9mm postoperatively (p&lt; 0.020) and patellar tendon length decreased from 53.4mm preoperatively to 50.0mm postoperative (p &lt; 0.001). Average distalization was 6.4mm. IKDC scores increased from 37.1 to 60.5 (p = 0.011), KOOS QOL scores increased from 19.5 to 42.1 (p &lt; 0.001), Kujala scores increased from 50.9 to 70.6 (p = 0.018), VR12-MH scores increased from 52.7 to 59.2 (p = 0.024) and VR12-PH scores increased from 35.1 to 41.7 (p = 0.009). Of the patients with preoperative patellofemoral instability, there were no cases of recurrent instability postoperatively. Ten patients (50%) underwent elective removal of hardware of TTO screws at an average of 10.7 months. There were four (20%) complications in this cohort, with two cases (10%) of postoperative arthrofibrosis requiring manipulation under anesthesia, one case (5%) of postoperative MRSA infection of the MPFL graft and one case (5%) of tibial tubercle delayed union requiring bone grafting and revision fixation. Conclusions: Distalization TTO without patellar tendon tenodesis is an effective surgical technique for improving patellar height in patients with patella alta and patellofemoral instability and/or patellofemoral cartilage lesions, with improvements in radiographic parameters and PROs postoperatively. There were no cases of recurrent instability in this cohort. The patellar tendon insertion does not appear to be significantly distalized following distalization TTO, likely related to scarring of the patellar tendon just proximal to the osteotomy site postoperatively. Given the complexity of risk factors associated with patellofemoral instability and patellofemoral cartilage lesions, distalization TTO provides an additional tool for patient-specific surgical management, without the need for patellar tendon tenodesis.

Effect of Lower Extremity Torsion on Clinical Outcomes After Medial Patellofemoral Ligament Reconstruction and Tibial Tubercle Transfer for Recurrent Patellofemoral Instability

Background: Increased femoral torsion (FT) or tibial torsion (TT) has been suggested to be a potential risk factor for recurrent patellofemoral instability. However, the influence of increased FT or TT on the postoperative clinical outcomes of recurrent patellofemoral instability has rarely been investigated. Purpose: To assess the effect of increased FT or TT on postoperative results in patients with recurrent patellofemoral instability after combined medial patellofemoral ligament reconstruction (MPFLR) and tibial tubercle transfer, along with the influence of other risk factors. Study Design: Cohort study; Level of evidence, 3. Methods: Out of 91 patients, the study’s analyses included 86 patients with recurrent patellofemoral instability who were treated with MPFLR and tibial tubercle transfer and enrolled between April 2020 and January 2021. FT and TT were assessed using preoperative computed tomography images. According to the torsion value of FT or TT, patients were categorized into 3 groups for each of FT and TT: group A (<20°), group B (20°-30°), and group C (>30°). Patellar height, femoral trochlear dysplasia, and the tibial tuberosity–trochlear groove (TT-TG) distance were also assessed. Patient-reported outcome scores (Tegner, Kujala, International Knee Documentation Committee [IKDC], Lysholm, and Knee injury and Osteoarthritis Outcome Score [KOOS]) were evaluated pre- and postoperatively. Clinical failure of MPFLR was recorded. Subgroup analysis was conducted to evaluate the effect of increased FT or TT on the postoperative outcomes. Results: A total of 86 patients were enrolled with a median follow-up time of 25 months. At the final follow-up, all functional scores improved significantly. Patella alta, high-grade trochlear dysplasia, and increased TT-TG distance did not have any significant effect on the postoperative functional scores. Regarding FT, subgroup analysis indicated that all functional scores of group C were lower than those of groups A and B except the KOOS knee-related Quality of Life score. For TT, group C had lower scores than group A for all functional outcomes except Tegner and KOOS Quality of Life and lower scores than group B for Kujala, IKDC, KOOS (Symptoms and Sport and Recreation subscales), Tegner, and Lysholm scores. The comparison between group A and group B, whether for FT or TT, revealed no significant differences. Conclusion: For patients with recurrent patellofemoral instability, increased lower extremity torsion (FT or TT >30°) was associated with inferior postoperative clinical outcomes after combined MPFLR and tibial tubercle transfer.

Allografts for Medial Patellofemoral Ligament (MPFL) Reconstruction in Adolescent Patients with Recurrent Patellofemoral Instability: A Systematic Review.

This systematic review updates the currently available evidence on medial patella-femoral ligament (MPFL) reconstruction using allografts. The outcomes were measured with patient-reported outcome measures (PROMs), redislocation and complication rates. This study was performed according to the 2020 PRISMA guidelines using the PubMed, Scopus, Web of Science databases, accessed in February 2023. Studies examining the clinical outcomes of MPFL reconstruction with allografts in adolescents and children with recurrent patellofemoral instability (PFI) were included. Data from three trials, including 113 surgical procedures in 121 children, were retrieved. 40% (48/121) of the included patients were girls. The mean age of the patients was 14.7 ± 0.8 years, and the mean follow-up length was 38.1 ± 16.5 months. With MPFL allograft reconstruction, the Kujala score improved by 14.7% (p < 0.0001) and the IKDC by 38.8% (p < 0.0001). The rate of dislocations was 5% (6 of 121), reoperation for instability was 11% (13 of 121), and subluxation was 2% (1 of 47). Conclusion: These results encourage the use of allografts for MPFL reconstruction in adolescent patients with recurrent patellofemoral instability. Though patellofemoral instability is common in clinical practice, the current literature lacks clinical evidence on allograft MPFL reconstruction. Additional high-quality investigations are required to properly establish the long-term advantages of allograft MPFL and its complication rate.

Cross-cultural Validation of the Norwegian Version of the Banff Patellofemoral Instability Instrument 2.0.

The Banff Patellofemoral Instability Instrument (BPII) 2.0 is a disease-specific quality of life questionnaire for patients with patellofemoral instability. While good psychometric properties have been demonstrated, the data lack cross-cultural validity, construct validity, and an established measurement error. To (1) translate and cross-culturally adapt the BPII 2.0 to the Norwegian version (BPII 2.0-No) and (2) examine the psychometric properties of the Norwegian version. Cohort study (diagnosis); Level of evidence, 3. The BPII 2.0 was translated according to international guidelines. A cohort of 100 patients surgically treated for recurrent patellofemoral instability completed the BPII 2.0-No, related outcome measures (Norwich Patellar Instability Score, International Knee Documentation Committee Subjective Knee Form 2000, Knee injury and Osteoarthritis Outcome Score, and Tampa Scale of Kinesiophobia), and functional tests (Y-Balance Test-Lower Quarter, single-leg hop tests, and knee extension strength) before and/or 6 months after surgery. We evaluated the face and content validity, internal consistency (Cronbach α), test-retest reliability (intraclass correlation coefficient [ICC]), measurement error (SEM and smallest detectable change at the individual [SDCind] and group levels [SDCgroup]). Construct validity was assessed by testing 9 hypotheses on the correlation between the BPII 2.0-No and the outcome measures/functional tests (Pearson r). The BPII 2.0-No had good face and content validity. Internal consistency was excellent (α = .95), and no floor or ceiling effects were found. Test-retest reliability was high (ICC2,1 = 0.87; 95% CI, 0.77-0.93), and measurement error was low (SEM = 7.1). The SDCind was 19.7 points and the SDCgroup was 2.8 points. Eight of the 9 hypotheses regarding construct validity were confirmed. The BPII 2.0-No was found to be valid and reliable. This study adds further knowledge on the measurement properties of the BPII 2.0 that can be used internationally.

Hip Pain after Distal Femoral Derotational Osteotomy for a Patient with Patellar Instability: A Case Report

Increased torsional deformity of femur is one of the most important factors in recurrent patellofemoral instability. And distal femoral derotational osteotomy is an effective treatment option in patients with increased femoral torsional deformity. However, groin pain is a rare complication after femoral derotational osteotomy. The patient was a 23-year-old female suffering from anterior knee pain and patellar instability in her left leg. Continuous CT scans of the hip, knee, and ankle were performed and the femoral anteversion was 44.99°. Considering the significant enlargement of the femoral internal torsion which may contribute most for dislocation of patella, we did a derotational osteotomy of distal femur. The anterior knee pain and patellar instability were resolved after surgery. The femoral internal torsion angle was corrected to 21.47°. But she developed left hip pain in the groin area which she had never encountered before 1 year after the surgery. We believed that the hip pain was closely related to the surgery. And the imaging and follow-up partly confirmed this. The situation of the hip joint should be carefully evaluated before doing derotational osteotomy in recurrent patellofemoral instability and patient should be informed that derotational osteotomy may cause hip pain. Clinical studies are needed to further clarify the impact of derotational osteotomy on the hip.