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INTRODUCTION: Adjunctive suture augmentation of patellar plate fixation has yet to be investigated. Our biomechanical study sought to evaluate whether suture augmentation improves dorsal patellar locking plate fixation. Our hypothesis was that suture augmentation would improve fixation of this construct. METHODS: A transverse patella fracture in six matched cadaveric pairs was stabilized using a patellar locking plate with or without suture augmentation. Specimens were tested at 60° knee flexion with load placed through quadriceps. Cyclic loading followed by load to failure was done. Stiffness, deformation at peak, and nonrecoverable deformation were calculated. RESULTS: During cyclic loading, suture augmentation demonstrated a higher average stiffness throughout all loads. At the final cycle, deformation was markedly higher without suture augmentation. Average load to failure was higher with suture augmentation. Maximum load to failure occurred at 2500 N in both groups. CONCLUSION: Suture augmentation in a transverse patellar fracture model improved dorsal plate fixation, leading to less fracture displacement at the final load. Although suture augmentation demonstrated higher stiffness and lower deformation, these trends were not statistically significant. In both groups, plate fixation sustained very high loads, which reflects the fixation strength of the dorsal locking plate and screw construct in this fracture model.

Patellar failure in total knee arthroplasty is a major source of complications postoperatively. Previous patellar failure reports commonly cited dissociations of modular and metal-backed patellar implants. However, mechanical breakage of monoblock all-polyethylene patellar implants is very rare. We present a case of an early shear failure of a 3-peg modified dome all-polyethylene patellar implant at 16 months. The patient underwent a revision procedure and at 1-year follow-up, the patients patella and knee remained stable with no reported issues. Shear failure of polyethylene pegs requires excess cyclic shear stress imparted at the prosthetic-bone interface. Patellar implants with a cone design are more constrained and, if misaligned relative to the metallic trochlea, may impart excess shear force to the patella during flexion.

BACKGROUND: The polyarticular nature of Osteoarthritis (OA) tends to manifest in multi-joints. Associations between cartilage health in connected joints can help identify early degeneration and offer the potential for biomechanical intervention. Such associations between hip and knee cartilages remain understudied. PURPOSE: To investigate T1p associations between hip-femoral and acetabular-cartilage subregions with Intra-limb and Inter-limb patellar cartilage; whole and deep-medial (DM), deep-lateral (DL), superficial-medial (SM), superficial-lateral (SL) subregions. STUDY TYPE: Prospective. SUBJECTS: Twenty-eight subjects (age 55.1 ± 12.8 years, 15 females) with none-to-moderate hip-OA while no radiographic knee-OA. FIELD STRENGTH/SEQUENCE: 3-T, bilateral hip, and knee: 3D-proton-density-fat-saturated (PDFS) Cube and Magnetization-Prepared-Angle-Modulated-Partitioned-k-Space-Spoiled-Gradient-Echo-Snapshots (MAPSS). ASSESSMENT: Ages of subjects were categorized into Group-1 (≤40), Group-2 (41-50), Group-3 (51-60), Group-4 (61-70), Group-5 (71-80), and Group-6 (≥81). Hip T1p maps, co-registered to Cube, underwent an atlas-based algorithm to quantify femoral and acetabular subregional (R2-R7) cartilage T1p. For knee Cube, a combination of V-Net architectures was used to segment the patellar cartilage and subregions (DM, DL, SM, SL). T1p values were computed from co-registered MAPSS. STATISTICAL TESTS: For Intra-and-Inter-limb, 5 optimum predictors out of 13 (Hip subregional T1p, age group, gender) were selected by univariate linear-regression, to predict outcome (patellar T1p). The top five predictors were stepwise added to six linear mixed-effect (LME) models. In all LME models, we assume the data come from the same subject sharing the same random effect. The best-performing models (LME-modelbest) selected via ANOVA, were tested with DM, SM, SL, and DL subregional-mean T1p. LME assumptions were verified (normality of residuals, random-effects, and posterior-predictive-checks). RESULTS: LME-modelbest (Intra-limb) had significant negative and positive fixed-effects of femoral-R5 and acetabular-R2 T1p, respectively (conditional-R2 = 0.581). LME-modelbest (Inter-limb) had significant positive fixed-effects of femoral-R3 T1p (conditional-R2 = 0.26). DATA CONCLUSION: Significant positive and negative T1p associations were identified between load-bearing hip cartilage-subregions vs. ipsilateral and contralateral patellar cartilages respectively. The effects were localized on medial subregions of Inter-limb, in particular. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 1.

ObjectiveCartilage degeneration involves structural, compositional, and biomechanical alterations that may be detected non-invasively using quantitative MRI. The goal of this study was to determine if topographical variation in T1rho values correlates with indentation stiffness and biochemical contents of human patellar cartilage.DesignCadaveric patellae from unilateral knees of 5 donors with moderate degeneration were imaged at 3-Telsa with spiral chopped magnetization preparation T1rho sequence. Indentation testing was performed, followed by biochemical analyses to determine water and sulfated glycosaminoglycan contents. T1rho values were compared to indentation stiffness, using semi-circular regions of interest (ROIs) of varying sizes at each indentation site. ROIs matching the resected tissues were analyzed, and univariate and multivariate regression analyses were performed to compare T1rho values to biochemical contents.ResultsGrossly, superficial degenerative change of the cartilage (i.e., roughened texture and erosion) corresponded with regions of high T1rho values. High T1rho values correlated with low indentation stiffness, and the strength of correlation varied slightly with the ROI size. Spatial variations in T1rho values correlated positively with that of the water content (R2 = 0.10, p

OBJECTIVE: To explain the relationship between cartilage erosion and medial patellar luxation (MPL) and to identify risk factors in dogs. METHODS: A retrospective review was conducted on 90 dogs (103 stifles) surgically treated for MPL between January 2006 and March 2024. Data collected included signalment, side of operated stifle, patellar luxation grade, symptom duration, and lameness score. Cartilage erosion was evaluated for extent and location on the patella and femoral trochlea. Statistical analyses were conducted to identify risk factors. RESULTS: The prevalence of cartilage erosion of the patella and femoral trochlea was 47.6% (49/103) and 54.4% (56/103), respectively, increasing with a higher grade of patellar luxation. Lesions were most prevalent in the distolateral patella and proximomedial trochlea, with generalized lesions more prevalent in grade IV. The extent of both lesions was significantly associated with age, patellar luxation grade, and symptom duration, while body weight significantly correlated only with the cartilage erosion of the patella. No significant correlation was observed with sex, side of operated stifle, or lameness score. CONCLUSIONS: Many patients with MPL exhibited cartilage erosion in the patellofemoral joint, likely due to biomechanical mechanisms. Surgery can be indicated for patients with MPL, as it may prevent cartilage erosion while improving patellofemoral alignment and gait. When selecting surgical candidates, it is important to consider risk factors, such as patellar luxation grade, body weight, age, and symptom duration. CLINICAL RELEVANCE: Early surgical treatment is recommended, especially for dogs with higher body weight and higher grade of MPL, to prevent cartilage erosion and secondary osteoarthritis. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of our study is to describe a magnetic resonance imaging quantitative parameter to assess the morphology of the trochlea that could be measurable from normal to high‐grade trochlear dysplasia while evaluating the most proximal slice with trochlear cartilage. Methods: Two groups of patients have been compared: patients with no patellofemoral pain, no previous trauma and undergoing surgery for a suspected isolated meniscal tears (group A) and patients with objective patellar instability (group B). The cranial trochlear orientation (CTO) angle is defined as the angle between the posterior bicondylar line and the most lateral and most medial points on the subchondral bone covered by cartilage digitised on the first and most cranial image with the trochlear cartilage clearly visible. Results: The final cohort included 253 patients (109 in group A and 144 in group B). CTO was significantly higher in group B (−2.5 ± 8.4 vs. −10.8 ± 5,1; p <.001). Moreover, 75% of knees in group B had a CTO > −7°, while 75% of knees in group A had a CTO < −7°. CTO was measurable in all 253 knees, whereas the lateral trochlear inclination and the sulcus angle were measurable in only 202 knees. The entire cohort was also divided into knees with CTO ≤ 0° and CTO > 0°. All knees with a CTO > 0 were in group B, and 49% of knees with CTO < 0 were in group B. CTO was positively correlated with lateral patellar tilt. Conclusions: CTO is the only parameter that can be measured on the most cranial slice, in every patient, even in high‐grade trochlear dysplasia. According to this new system, the axial trochlear shape may be divided into two types: a positive CTO and a negative CTO, with the trochlea serving, respectively, as a medial and lateral barrier. Level of Evidence: Level III. [ABSTRACT FROM AUTHOR]

Purpose: We aimed to establish patient‐reported outcome measure (PROM) reference data for a cohort of patients with prior patellar dislocation without previous knee surgery. Methods: All inhabitants of the Faroe Islands aged 15–19 years were sent an online survey via secure email to establish a national cohort. They were asked to answer questions regarding demographics, whether they had prior patellar dislocation and to complete the PROMs: the Banff Patella Instability Instrument (BPII), Kujala, Marx activity and EQ‐5D‐5L questionnaires. Participants who had undergone knee surgery were excluded. Participants who had prior patellar dislocation underwent radiographic examinations to diagnose trochlear dysplasia. The study included three cohorts: the general population, prior patellar dislocation and prior patellar dislocation and trochlear dysplasia cohorts. Results: Of the 3749 individuals contacted, 1119 completed the survey and responded to at least one PROM. Of these, 102 reported a history of patellar dislocation and 57 of them had trochlear dysplasia. All PROMs, except the Marx score, reflected a worse quality of life and function after patellar dislocation than in the general population cohort; this was most pronounced in the BPII. The percentage of people experiencing problems in EQ‐5D‐5L dimensions was higher in the patellar dislocation and trochlear dysplasia cohorts than in the general population cohort in all EQ‐5D‐5L domains, except anxiety/depression. Conclusion: Adolescents who had patellar dislocation reported reduced quality of life and function according to the BPII, Kujala and EQ‐5D‐5L index values, as well as all EQ‐5D‐5L domains, except for anxiety/depression. However, their activity levels remained high. Level of Evidence: Level III. [ABSTRACT FROM AUTHOR]

A new species Scorpiops tangae sp. n. is described from Laos, fully illustrated with color photos showing its morphology and habitus. Scorpiops tangae sp. n. is the only species of the genus with a combination of the following five characters: chelal trichobothrium Eb3 located in distal half of manus between trichobothria Dt and Est; patella of pedipalp with 11 ventral and 17 external trichobothria; fingers of pedipalps undulate in male; pedipalp movable finger with ca. 45 IAD; and chela length to width ratio 3.7 in male. In addition to morphology and hemispermatophore, we also present the information about the karyotype of S. tangae sp. n. (2n=105). [ABSTRACT FROM AUTHOR]

Background: This study aimed to evaluate the effectiveness of circumferential patellar denervation in reducing anterior knee pain (AKP) and improving clinical outcomes after total knee arthroplasty (TKA) without patellar resurfacing. Materials and methods: This prospective, non-randomized, observational study included patients who underwent primary TKA at our institution between August 2023 and January 2024. Patients were divided into two groups: those who received patellar denervation (PD group) and those who did not (NPD group). The primary outcome was the reduction in anterior knee pain (AKP), measured by the Visual Analog Scale (VAS). Secondary outcomes included the Kujala Knee Score, Western Ontario and McMaster Universities Arthritis Index (WOMAC), and range of motion (ROM). Assessments were conducted preoperatively and at 3 and 6 months postoperatively. Results: Four patients in the PD group and five in the NPD group were excluded from the study due to failure to complete follow-up. Thus, 74 female and 16 male patients with a mean age of 67.4 ± 4.2 years were included in the final analysis. There were no significant differences between the two groups with respect to age, sex, side of surgery, height, weight, BMI, grade of patellofemoral osteoarthritis, preoperative ROM, VAS score, Kujala score, and WOMAC score (p: n.s. for all variables). No significant differences were found between the groups for VAS, Kujala, and WOMAC scores at any time point (p: n.s.). Significant improvements in these scores over time were indicated by repeated measures ANOVA (p = 0.001 for both groups). Pairwise comparisons showed significant improvements from preoperative to postoperative months three and six and from postoperative months three to six (p = 0.001 for all comparisons). Both groups experienced decreased knee ROM at third month, which returned to preoperative values at sixth month with no significant differences. No complications were observed during the study. Conclusions: Circumferential patellar denervation does not provide additional benefit in reducing anterior knee pain or improving functional outcomes compared to the non-denervation approach in TKA without patellar resurfacing. Level of evidence: Level III, Prospective comparative study. [ABSTRACT FROM AUTHOR]

ABSTRACT Objective Methods Results Conclusions The risk factors for the degeneration of the patellofemoral joint (PFJ) have not been adequately and thoroughly studied. This study aimed to analyze the population distribution characteristics of patients with patellofemoral osteoarthritis (PFOA) and assess the correlation between PFOA and radiological parameters, including patella morphology, PFJ congruity, and patellar alignment. Moreover, the risk factors across various demographic groups were further analyzed.A retrospective analysis was conducted to examine the population distribution characteristics of PFOA patients from September 2020 to September 2023. Radiological parameters of the PFJ were measured from the anteroposterior and lateral views of knee joint as well as axial view of patella using X‐ray imaging and the PACS imaging system at the First Affiliated Hospital of Kunming Medical University. These parameters included patella morphology (patella type, width, thickness, and Wiberg index), PFJ congruity (patella height, Wiberg angle, sulcus angle, and lateral patella angle), and patellofemoral alignment (patella tilt angle, displacement, and lateral patellofemoral angle). PFOA severity was classified according to the Iwano PFJ radiological classification, and its correlation with the aforementioned parameters was examined. Additionally, risk factors for PFOA across different populations were further evaluated.The study included 1080 patients according to the inclusion and exclusion criteria. Age, female gender, overweight or obesity, and manual workers were significantly associated with PFOA. Moreover, type III patella (OR = 3.03, p < 0.05), greater patella width (OR = 1.12, p = 0.01), sulcus angle (OR = 1.04, p < 0.01), patella tilt angle (OR = 1.13, p < 0.01), and patella displacement (OR = 1.22, p < 0.01) as well as smaller patella thickness (OR = 0.87, p < 0.01), Insall–Salvati index (OR = 0.24, p = 0.04), and lateral patellofemoral angle (OR = 0.93, p = 0.02) were identified as risk factors for PFOA. Furthermore, greater patella thickness (OR = 1.17, p < 0.05) and smaller patella displacement (OR = 0.79, p < 0.01) correlated with higher Kujala patellofemoral scores. Discrepancies in risk factors across different populations were also observed.Older age, female gender, obesity, manual workers, and specific aberrations in patellofemoral parameters are predictive factors for PFOA. Additionally, greater patella thickness and smaller patella displacement were associated with increased severity of clinical symptoms. Thus, more attention should be paid to the discrepancies that exist in different populations. [ABSTRACT FROM AUTHOR]

Background: Controversy exists regarding the origin of femoral torsion, and specific treatment rules regarding the optimal position of femoral osteotomy in patients with recurrent patellar subluxation and excessive femoral torsion are scarce. Purpose: To establish a novel classification system for such patients, and to compare clinical and radiological outcomes after distal derotational femoral osteotomy (DDFO) between femoral torsion at proximal (neck and shaft) and distal levels. Methods: Between January 2014 and June 2019, patients who underwent DDFO were retrospectively reviewed. The segmental torsion analysis was performed to establish a novel classification system, and classify included patients into two groups: 35 patients in proximal torsion group and 38 patients in distal torsion group. These patients were followed-up for at least 3 years. Clinical evaluations included functional outcomes, physical examinations, quality of life, activity level, satisfaction, and complications. Radiological outcomes included patellofemoral osteoarthritis, congruence, and alignment. Results: Type I was defined as the proximal torsion. Type II was defined as the distal torsion. Proximal torsion group had lower postoperative femoral torsion (12.6 ± 2.6° vs. 14.8 ± 3.6°; P =.004) and higher surgical correction angle (21.6 ± 5.0° vs. 19.1 ± 3.0°; P =.009). All clinical and radiological outcomes improved significantly in both groups, but proximal torsion group had significantly higher quality of life (EQ-5D-5L: 0.96 ± 0.06 vs. 0.91 ± 0.07; P =.003. EQ-VAS: 92.0 ± 6.0 vs. 88.7 ± 5.8; P =.021) and Tegner activity score (5.2 ± 1.5 vs. 4.5 ± 1.4; P =.040), and fewer patellofemoral osteoarthritis (8.6% vs. 26.3%; P =.048). Two patients in the distal torsion group had subjective patellar instability. The percentage of patients with anterior knee pain was higher in the distal torsion group. Conclusion: A novel classification system for patients with recurrent patellar subluxation and excessive femoral torsion based on segmental femoral torsion analysis was established. DDFO was more appropriate for patients with proximal torsion, yielding higher surgical correction angle, and better clinical and radiological outcomes. Study design: Cohort study; Level of evidence, 3. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to investigate the effect of patellar denervation (PD) on pain, function and ability to kneel after unicompartmental knee arthroplasty (UKA). Methods: Patients with medial knee osteoarthritis who underwent UKA were prospectively selected. Patients were randomly divided into PD and non-PD groups based on whether patellar denervation was performed. Clinical assessment was performed using the Hospital for Special Surgery (HSS) knee score, Kujiala score, visual analogue scale (VAS) and forgotten joint score (FJS-12), as well as postoperative complications were recorded. The patients' postoperative self-perception and actual ability to perform different kneeling positions were assessed in the two groups. Results: UKA patients treated with PD achieved better Kujiala scores and FJS-12 scores, reduced anterior knee pain and improved kneeling ability postoperatively, validating the effectiveness of PD in UKA. Perception and actual performance of kneeling remained mismatched in PD patients, but performance during different kneeling activities was generally better than in non-PD patients. Trial registration: Clinical Trial Registration: ChiCTR1900025669. Conclusion: Patellar denervation can safely and effectively improve patellofemoral joint function, pain and kneeling ability in the early postoperative period after UKA. [ABSTRACT FROM AUTHOR]

Background: Many adolescents experience knee pain, and only some undergo detailed imaging. In this population, the prevalence of abnormalities and normal variants on magnetic resonance imaging (MRI) scans is unknown. Purpose: To investigate the prevalence of abnormalities and normal variants of the knee on MRI scans and their relationship with participant characteristics in the general young adolescent population. Study Design: Cross-sectional study; Level of evidence, 3. Methods: This study was part of an open population-based cohort study that focuses on health, growth, and development from fetal life until adulthood. Between 2017 and 2020, adolescents aged 12 to 15 years underwent MRI of both knees. These MRI scans were assessed in a standardized way for abnormalities and normal variants to determine their prevalence. Logistic regression was used to analyze the presence of abnormalities and normal variants in relation to sex, height, weight, body mass index–standard deviation (BMI-SD), and ethnicity. Results: A total of 1910 participants (median age, 13.5 years; interquartile range, 13.4-13.7 years; 52% girls) were included in this study. Of them, 370 (19.4%) participants had at least 1 abnormality or normal variant. Bone marrow edema around the knee was the most prevalent finding, affecting 140 (7.3%) participants. In 107 (5.6%) participants, nonossifying fibromas were found. A total of 43 (2.3%) participants had characteristics of Osgood-Schlatter disease, 16 (0.8%) showed characteristics of Sinding-Larsen-Johansson syndrome, and osteochondritis dissecans was found in 13 (0.7%) participants. Variants such as discoid menisci were found in 40 (2.1%) participants and a bipartite patella in 21 (1.1%) participants. There were multiple associations between abnormalities or variants and participant characteristics, including bone marrow edema being more often present in boys (odds ratio [OR], 2.44; 95% CI, 1.69-3.52) and those with a lower BMI-SD (OR, 0.85; 95% CI, 0.73-0.98). Osgood-Schlatter and osteochondritis dissecans were more often present in boys (OR, 4.21 [95% CI, 2.01-8.85] and OR, 13.18 [95% CI, 1.71-101.58], respectively). Discoid menisci were associated with a non-Western ethnicity (OR, 2.06; 95% CI, 1.07-3.96) and higher BMI-SD (OR, 2.34; 95% CI, 1.76-3.11). Conclusion: Abnormalities and normal variants on MRI scans of the knees are common in adolescents. Physicians who are involved in the treatment of adolescents with knee pain need to be aware of this prevalence so that these children will not be overtreated or misdiagnosed. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study is to analyse the efficacy of using a combined infiltration between a popliteal artery and knee cap (IPACK) anaesthetic block and a selective saphenous nerve block compared to local infiltration with anaesthetic in knee replacement surgery. Methods: A retrospective observational study was conducted. A total of 312 patients who underwent primary total knee arthroplasty in our hospital between January 2019 and December 2022 were reviewed. Local intra-articular anaesthesia was used in 207 patients and combined nerve block in 105 patients (IPACK group). The mean age in the LIA group was 72.9 years and 70.4 years in the IPACK group. There were 44% men in the LIA group and 53.3% in the IPACK group. The primary outcome was the presence of poorly controlled pain requiring rescue opioid analgesia in the postoperative period. Secondary outcomes included pain scores, range of motion and length of hospital stay. Results: There were no significant differences in the age or gender distribution of patients between the two groups. One patient treated with anaesthetic blocks required rescue analgesia with opioids, while in the LIA group this occurred in 28.5% of cases. There were statistically significant higher VAS scores in the LIA group (p < 0.001). Range of motion was slightly greater in the block group (4.6°, p < 0.05). There were significant differences in hospital stay (2.4 days in the blocks group and 2.8 days in the LIA group (p < 0.05). Conclusions: In our series, patients treated with anaesthetic blocks showed better results with similar postoperative pain control. However, further studies are needed. [ABSTRACT FROM AUTHOR]

Purpose: To examine the frequency of patellofemoral joint (PFJ) osteoarthritis (OA) and its symptoms in the long-term course of open-wedge high tibial osteotomy (OWHTO). Methods: We analyzed 113 joints of 91 patients. OA and osteonecrosis (ON) developed in 91 and 22 joints, after an average postoperative period of 127.5 ± 19.5 months. For X-ray evaluation, the standing femorotibial angle (FTA), % mechanical axis (%MA), Caton–Deschamps index (CDI), patellar tilt angle (TA), lateral patellar shift (LPS), and PFJ space width (medial [MJS] and lateral [LJS]) were analyzed. PFJ-associated symptoms were evaluated using the hospital for special surgery patellar score (HSS-PS) and knee injury and osteoarthritis outcome score patellofemoral subscale (KOOS-PF). Statistical analysis was performed with paired and unpaired t tests, and a risk rate of less than 1% was significantly judged. Results: Preoperative FTA and CDI decreased from 180.8° to 170.0° and 0.88 to 0.70 at the final follow-up. Preoperative %MA lateralized from 20.8 to 66.0 at the final follow-up. TA and LPS values decreased significantly compared with before surgery until plate removal. The MJS and LJS significantly decreased, and OA with a joint space < 3 mm occurred in 14 cases. However, HSS-PS and KOOS-PF scores were not significantly different between the groups with and without OA. Conclusion: PFJ OA occurred in 12.4% cases in the long-term postoperative course of OWHTO; however, no symptomatic difference was found in the group with or without OA. [ABSTRACT FROM AUTHOR]

In the setting of total knee arthroplasty (TKA), prior patellectomy historically prompted the use of increased constraint implants, specifically posterior-stabilized (PS) designs. However, modern case series have reported similar outcomes utilizing cruciate-retaining (CR) implants. The primary outcome of this study was to compare implant retention rates between these 2 implant designs in prior patellectomy patients. Secondary outcomes included a comparison of patient-reported outcome scores and cause for revision. A comprehensive systematic review was performed using Web of Science, PubMed, and Scopus databases per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Boolean operator search terms included "patellectomy AND (arthroplasty) OR (replacement)." Case reports, review articles, < 2 years of follow-up, and studies in which the implant design could not be ascertained were excluded. An initial screening of titles and abstracts for inclusion was performed, followed by a full manuscript review of eligible articles. Single-data extraction was performed, followed by subsequent statistical analysis. A total of 9 studies (209 knees) met the inclusion criteria. The average time from patellectomy to TKA was 16.1 years. While all patients had significant improvement in functional outcomes, CR implants displayed proportionally greater improvement in Knee Society Scores compared to PS implants (+108 versus +98%, P ≤.001). However, there was a significantly greater rate of revision in the CR cohort compared to PS (18.6 versus 2.6%, P =.002). Prior patellectomy patients undergoing TKA have significant improvements in patient-reported functional outcomes and high midterm retention rates. While CR implant designs portend a potentially greater improvement in functional outcomes, they also have a greater risk for revision than their PS implant counterparts. However, contemporary implant designs and operative techniques likely render revision rates equivocal between CR and PS implants in postpatellectomy patients. [ABSTRACT FROM AUTHOR]

In mammals, the patella is the biggest sesamoid bone of the skeleton and is of crucial importance in posture and locomotion, ensuring the role of a pulley for leg extensors while protecting and stabilizing the knee joint. Despite its central biomechanical role, the relation between the shape of the patella and functional factors, such as body mass or locomotor habit, in the light of evolutionary legacy are poorly known. Here, we propose a morphofunctional investigation of the shape variation of the patella among modern rhinoceroses and more generally among perissodactyls, this order of ungulates displaying a broad range of body plan, body mass and locomotor habits, to understand how the shape of this sesamoid bone varies between species and relatively to these functional factors. Our investigation, relying on three dimensional geometric morphometrics and comparative analyses, reveals that, within Rhinocerotidae and between the three perissodactyl families, the shape of the patella strongly follows the phylogenetic affinities rather than variations in body mass. The patellar shape is more conservative than initially expected both within and between rhinoceroses, equids and tapirs. The development of a medial angle, engendering a strong mediolateral asymmetry of the patella, appears convergent in rhinoceroses and equids, while tapirs retain a symmetric bone close to the plesiomorphic condition of the order. This asymmetric patella is likely associated with the presence of a "knee locking" mechanism in both equids and rhinos. The emergence of this condition may be related to a shared locomotor habit (transverse gallop) in both groups. Our investigation underlines unexcepted evolutionary constraints on the shape of a sesamoid bone usually considered as mostly driven by functional factors. [ABSTRACT FROM AUTHOR]

Background: 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. Hypothesis: 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. Study Design: Case series; Level of evidence, 4. Methods: 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. Results: 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. Conclusion: 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. [ABSTRACT FROM AUTHOR]

Background: Osteochondral defects (OCDs) in the knee joint have significant clinical implications, particularly regarding contact pressures and pressure distribution. Understanding how these factors are influenced by defect size and location is crucial for developing effective therapeutic strategies. Purpose/Hypothesis: The purpose of this study was to investigate the impact of defect size and location on contact pressures and pressure distribution in the knee joint. It was hypothesized that an increase in defect size would result in elevated contact pressures and alterations in pressure distribution, with specific variations related to defect location. Study Design: Descriptive laboratory study. Methods: The study utilized 6 cadaveric knees, including the patella and fibula, subjected to controlled compressive loading for measuring contact pressures. Simultaneously, computed tomography-based models were created for finite-element analysis (FEA) to investigate the impact of varying defect sizes and locations on contact pressures and pressure distribution in the knee joint, excluding the patellofemoral joint. The study employed analysis of variance to assess contact pressure and defect size association. Comparison between medial and lateral femoral condyles at full extension and 30° flexion angle was performed, followed by post hoc testing. Fisher exact test analyzed peak pressure point location and defect size, categorizing them into medial and lateral. Results: An increase in defect size corresponded with heightened contact pressures on both medial and lateral femoral condyles at full extension (P =.013 for medial and P =.024 for lateral). However, this correlation did not yield significant differences at 30° of flexion (P =.674 for medial and P =.333 for lateral). During mechanical testing, the highest pressures occurred near 5 mm defect dimensions. FEAs showed a significant increase in pressure and circumferential-edge stress with 7-mm defects. Peak contact pressure points shifted laterally with more significant defects. Conclusion: Our study demonstrated the impact of defect size, location, and alignment on knee joint contact pressures. Intervening promptly with defects exceeding 3 mm is crucial, as significant stress levels manifest beyond this threshold. Significant increases in contact pressures were noted with larger defect sizes, particularly between 3 and 10 mm at full extension. Peak pressure points shifted with defect size increments, and alignment variations showed minimal stress variation at 30° compared with 0°. FEA validated increasing contact pressures up to 7 mm defect size, beyond which pressures stabilized or slightly decreased. A concentrated pressure distribution on the medial side was observed. These findings inform our understanding of the biomechanical implications of OCDs. Clinical Relevance: In the field of sports medicine, this research offers valuable insights to clinicians and researchers, elucidating key factors influencing knee joint health and the potential consequences of OCDs. [ABSTRACT FROM AUTHOR]

Background: Available conventional tibial tubercle lateralization (TTL) parameters fail to account for individual patient size or anatomy. Purposes: To evaluate the predictive ability of individualized TTL parameters and clarify the best predictor of patellar dislocation (PD) and to determine the relationship of the best predictor with other risk factors of PD with quadriceps isotonic contraction. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: A total of 15 patients with PD (28 knees) and 14 controls (28 knees) underwent 4-dimensional computed tomography, and the image with the knee fully extended and quadriceps isotonically contracted was selected for evaluation. The following TTL parameters were measured on the images: tibial tubercle–trochlear groove (TT-TG) distance, tibial tubercle–Roman arch distance, and tibial tubercle–posterior cruciate ligament distance, as well as their ratios to femoral condylar width and patellar width (PW). In addition, the following parameters were measured: Insall-Salvati ratio, Blackburne-Peel ratio, Caton-Deschamps ratio, modified Insall-Salvati ratio, bisect offset index, congruence angle, lateral patellar tilt, lateral trochlear inclination, sulcus depth, sulcus angle, trochlear groove medialization, patella–patellar tendon angle, patellofemoral axis angle (P-FAA), patellar articular facet–patellar tendon angle, patellar articular facet–femoral axis angle (PA-FAA), and patellar shape according to Wiberg type. The area under the receiver operating characteristic curve (AUC) was calculated to access the diagnostic accuracy of the TTL parameters for PD, and the TTL parameters with high diagnostic ability were evaluated for correlation with the remaining parameters. Results: The TT-TG/PW ratio had the best diagnostic ability for PD (AUC = 0.890). The TT-TG/PW ratio was positively correlated with bisect offset index, congruence angle, lateral patellar tilt, P-FAA and PA-FAA (r = 0.610, 0.465, 0.635, 0.553 and 0.418, respectively; P ≤.027 for all), and TT-TG/PW ratio was greater in knees with type II versus type III patella (P =.017). Conclusion: With the knee fully extended and quadriceps isotonically contracted, the TT-TG/PW ratio was found to be the best predictor of PD and reflected individualized TTL, which helps with clinical preoperative planning. [ABSTRACT FROM AUTHOR]

Background: Patellar dislocation is a common knee injury and up to 35% of those who dislocate the patella can develop recurrent patellar instability. In the setting of recurrent instability, medial patellofemoral ligament (MPFL) reconstruction is often performed to restore knee stability. There has been recent interest in patient and surgical factors that influence outcomes of MPFL reconstruction. Much of the previous work has focused on influences of anatomic measures; however, patients and injury characteristics may also impact surgical outcomes. Hypothesis: Patients who experience >2 patellar dislocations before MPFL reconstruction would demonstrate poorer patient-reported outcomes (PROs) compared with those with ≤2 previous dislocations. Study design: Cohort study; Level of evidence, 3. Methods: Records were reviewed to identify patients who underwent MPFL reconstruction at a single institution between 2008 and 2016. Patients who underwent concomitant tibial tubercle osteotomy or fixation of an osteochondral fracture were excluded. Patient demographics (age, sex, body mass index [BMI]), number of previous patellar dislocations, and patient anatomic measures (Caton-Deschamps index (CDI), tibial tubercle-trochlear groove (TT-TG) distance, and trochlear sulcus angle) were collected. PROs were assessed with Norwich Patellar Instability score, Knee injury and Osteoarthritis Outcome Score (KOOS), and Marx activity score. Outcomes of patients with >2 patellar dislocations were compared with those with ≤2 dislocations using multiple linear regression analysis. Results: Medical record review revealed 160 patients who underwent isolated MPFL reconstruction (71 with ≥2 dislocations and 89 with >2 dislocations); 95 patients (59%) completed PROs at a median follow-up of 4.6 years postoperation (range, 1.0-12.6 years). Patients with ≥2 dislocations were younger (≥2 dislocations: 20.7 ± 7.3 years, >2 dislocations: 28.5 ± 10.0 years; P <.001), although there were no other differences in demographics or radiographic anatomic measures between groups. Adjusting for age, sex, BMI, CDI, TT-TG distance, and trochlear sulcus angle, patients with >2 dislocations had 13.7 points lower KOOS-Pain (P =.003), 8.3 points lower KOOS-Activities of Daily Living (P =.025), 18.2 points lower KOOS-Sports and Recreation (P =.009), and 19.8 points lower KOOS-Knee-Related Quality of Life (P =.008) subscale scores than patients with ≤2 dislocations. No significant differences in KOOS symptoms subscale, Norwich Patellar Instability, or Marx score were noted between groups. Conclusion: Patients with >2 patellar dislocations before MPFL reconstruction exhibited poorer PROs at a median of 4.8 years postoperation compared with those who had ≤2 dislocations before surgery, when adjusting for age, sex, BMI, CDI, TT-TG distance, and trochlear sulcus angle. [ABSTRACT FROM AUTHOR]

Background: Medial patellofemoral ligament (MPFL) reconstruction is a commonly employed surgical approach for recurrent patellar dislocation. However, the impact of elevated body mass index (BMI) on postoperative complication rates remains controversial. Purpose: To compare the clinical, radiographic, and functional outcomes of patients with normal BMI (18.5-24.9 kg/m2) and those with elevated BMI (≥25 kg/m2) who underwent MPFL reconstruction for recurrent acquired lateral traumatic patellar dislocation. Study Design: Cohort Study; Level of evidence, 3. Methods: A total of 70 patients who underwent MPFL reconstruction for recurrent patellar dislocation were included in this study. Patients with recurrent patellar dislocation were categorized into 2 groups based on their BMI: the normal BMI group and the elevated BMI group. Functional scores (Lysholm, International Knee Documentation Committee [IKDC], Tegner, and Kujala scores) and radiological measurements (patellar tilt angle, patellofemoral trochlear congruence, lateral patellofemoral angle, and lateral patellar displacement) were evaluated both preoperatively and at the last follow-up. The occurrence of postoperative complications at the last follow-up was also recorded. Differences in functional scores and radiological parameters before and after surgery were analyzed with paired-samples t tests or Wilcoxon signed-rank tests. Comparisons between groups were conducted using independent-samples t tests or the Kolmogorov-Smirnov test. Results: In the normal BMI group, there were 13 male patients and 27 female patients, with a mean follow-up duration of 26.15 ± 13.16 months. The mean age in this group was 21.93 ± 7.94 years. The elevated BMI group consisted of 12 male patients and 18 female patients, with a mean follow-up duration of 27.50 ± 15.79 months and a mean age of 23.30 ± 8.43 years. At the final follow-up, the incidence of surgical failure (patellar redislocation or subluxation and necessitating secondary surgery) was significantly higher in the elevated BMI group (6 out of 30 patients; 20.0%) compared with the normal BMI group (1 out of 40 patients; 2.5%) (P <.05). Both groups demonstrated significant improvement in postoperative Lysholm, IKDC, Tegner, and Kujala scores compared with the preoperative period (P <.05). Notably, the normal BMI group had significantly higher preoperative Lysholm and Tegner scores compared with the elevated BMI group (P <.05). Furthermore, the elevated BMI group exhibited less improvement in Tegner and Kujala scores compared with the normal BMI group (P <.05). Postoperative radiological parameters in both groups returned to the normal range (P <.05). There were no statistically significant differences between the 2 groups in terms of radiological parameters and their corresponding differences. Conclusion: Our study demonstrated statistically significant increases in postoperative clinical scores for both groups, although the intergroup differences varied. Specifically, patients with elevated BMI demonstrated poorer preoperative Lysholm and Tegner scores. The postoperative improvement in radiological parameters was equally good between the 2 groups. [ABSTRACT FROM AUTHOR]

Purpose: The J-sign is a clinical evaluation tool that assesses for patellar maltracking and is considered positive if lateral translation of the patella in extension, in the pattern of an inverted J is observed. This study aims to determine the association of clinical J-sign with imaging features noted on dynamic kinematic computed tomography (DKCT). Methods: A retrospective review was conducted by reviewing the clinical records of all patients aged 18 years or younger who had a CT patellar tracking scan done between 1 January 2005 to 31 December 2016 in a single institution. Patients who had the presence or absence of a 'J-sign' evaluated clinically were included. Radiographic parameters evaluated using the axial cuts include the patellar tilt angle, congruence angle, Dejour's classification, femoral sulcus angle, trochlear groove depth, and Wiberg's classification. Patients were then divided into two groups based on the presence or absence of J-sign on clinical examination. The radiographic measurements were then analyzed for association with the presence or absence of J-sign on clinical examination. Results: Patients with a positive J-sign had an increased patellar tilt of 23.3° ± 14.2° and an increased congruence angle of 47.1° ± 28.5° when measured in extension as compared to a patellar tilt of 18.3° ± 10.8° and a congruence angle of 32.1° ± 20.8° in patients with a negative J-sign (p = 0.024 and 0.004, respectively). Comparisons of the change in congruence angles with the knee in full extension and at 20° flexion also yielded significantly higher change of 28.0° ± 20.4° in patients with a positive J-sign as compared to 11.9° ± 17.5° in patients with a negative J-sign. Patients with a positive J-sign also had an increased TT-TG distance of 17.6 ± 5.6 mm as compared to a TT-TG distance of 14.7 ± 6.9 mm in patients with a negative J-sign (p = 0.01). Conclusion: Patients with a positive J-sign had an increased patellar tilt and an increased congruence angle when measured in extension. Increased TT-TG distance was also significantly associated with positive J-sign. Patients with a positive J-sign also had a greater change in their congruence angle when measured with the knee in full extension and at 20° of flexion. [ABSTRACT FROM AUTHOR]

Hypermobility describes the movement of joints beyond normal limits. Whether hypermobility predisposes to patellar instability is yet to be established. We aimed to determine if joint hypermobility leads to an increased risk of patellar instability, and to evaluate outcomes of treatment for patellar instability in those who exhibit hypermobility. Published and unpublished literature databases were searched to September 7, 2023. Studies comparing prevalence of patellar dislocation/differences in treatment outcomes in patients with and without hypermobility were included. We identified 18 eligible studies (4,391 patients). The evidence was low in quality. A case series on 82 patients found that there was a relationship between generalised joint laxity and patellar instability. This was corroborated by a study comparing 104 patients with patellar dislocation to 110 patients without. Prevalence of generalised joint laxity was six time higher in the former (64.4% vs 10.9%, p < 0.001). Five studies found surgical intervention aimed at correcting patellar dislocation in patients with idiopathic hypermobility led to satisfactory outcomes. There was conflicting evidence regarding if hypermobile patients have worse outcomes than non-hypermobile patients following medial patellofemoral ligament reconstruction (MPFLR) in two studies. In addition, this procedure had a 19.1% failure rate in patients with Ehlers Danlos Syndrome (EDS), with hypermobility associated with a higher failure rate (p = 0.03). One study showed the type of graft used made no difference in outcome scores or re-dislocation rates (p > 0.5). Another study had 7/31 (22.6%) autografts which failed, compared to 2/16 allografts (12.5%) (p = 0.69). Joint hypermobility is a risk factor for patellar instability. Identification of at-risk groups may aid prevention of dislocations and allow for appropriate treatment. Patients with EDS experience poor outcomes following patellar stabilization surgery, with post-operative monitoring required. [ABSTRACT FROM AUTHOR]

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Purpose Methods Results Conclusion Level of Evidence Different cartilage repair techniques are widely used to regenerate cartilage, such as autologous chondrocyte implantation (ACI), osteochondral autograft transfer, microfracturing and minced cartilage. Defect size is a key parameter for selecting the best procedure to repair cartilage. However, the defect's size is not related to the patient's total cartilage surface. This is because assessing the femoral cartilage surface area is time‐consuming and therefore unsuitable in the daily clinical routine. It has been proposed that the femur's total cartilage area correlates positively with the transepicondylar distance (TEA).The knees of 40 subjects were analysed. Their average age was 30.1 ± 8.6 years. Twenty‐four female and 16 male subjects were examined. Their mean body height was 176.2 ± 8.8 cm. MRI scans were performed via 3‐Tesla MRI. These data were postprocessed and quantified using the browser‐based, customizable SATORI platform (Fraunhofer MEVIS). This software computed the femoral cartilage surface area (FeCA), the patella cartilage surface area (PCA), the TEA and the patella length.Body height reveals a good correlation (r = 0.722, p < 0.001) with the distal femur's cartilage area surface. However, regression analysis shows only moderate dependence (R2: 0.514). A very good correlation (r = 0.830, p < 0.001) was observed between the TEA distance and the total cartilage surface area of the distal femur. The regression analysis yields a good value (R2: 0.684). The cranio‐caudal length of the patella was chosen as a suitably measurable two‐dimensional parameter for correlation analysis with the patella's total cartilage surface area. Those results yield a poor correlation (r = 0.577, p < 0.001) between the two parameters, and regression analysis reveals a low value (R2: 0.384).The TEA is a reliable parameter for estimating the femur's cartilage area using MRI. A simple determination of this parameter allows the estimation of the femur's total cartilage area as well as the surface‐corrected defect size (SCDS) in daily routine.Level II [ABSTRACT FROM AUTHOR]

Purpose Methods Results Conclusion Level of Evidence The quadriceps tendon (QT) has recently gained increasing interest as an anterior cruciate ligament reconstruction (ACLR) graft due to minimally invasive harvesting techniques and low donor site morbidity. QT grafts can be used both with a patella bone block and as complete soft tissue grafts. However, it is unknown whether the QT graft type affects clinical outcomes. This study used data from the Danish Knee Ligament Reconstruction Registry (DKRR) to compare revision rates, knee stability and subjective clinical outcomes in patients who underwent ACLR with QT graft with bone block (QT‐B) or soft tissue only (QT‐S).Patients who underwent primary ACL reconstruction with QT autografts documented in the DKRR were included and divided into the QT‐B (n = 925) and QT‐S (n = 659) groups. The clinical outcome was evaluated using objective‐instrumented knee stability, pivot shift test, knee injury osteoarthritis outcome score (KOOS) and Tegner activity scores for the two cohorts performed at the 1‐year follow‐up. The overall revision rates were determined as well.Revision rates at 2 years were equally low in both graft groups at 2.8%. Similarly, post‐operative knee laxity was equal at 1.5 (1.4) and 1.6 (1.4) mm side‐to‐side laxity, respectively. However, QT‐B exhibited a reduced post‐operative positive pivot shift of 22% compared with 31% for QT‐S. Although the subjective outcomes were equal for the KOOS and Tegner activity scale scores at the 1‐year follow‐up, reduced improvements in KOOS were observed for QT‐B compared to QT‐S.ACL with a QT autograft harvested either with a bone block or as a soft tissue graft exhibited comparable revision rates and sagittal knee stability. Furthermore, ACL reconstruction using a QT graft with a bone block achieved better rotational stability with less pivot shift than ACL reconstruction using complete soft tissue QT grafts.Level III. [ABSTRACT FROM AUTHOR]

Background: Patellar instability is a well-known pathology in which kinematics can be investigated using metrics such as tibial tuberosity tracheal groove (TTTG), the bisect offset (BO), and the lateral patellar tilt (LPT). We used dynamic computed tomography (CT) to investigate the patellar motion of healthy subjects in weight-bearing conditions to provide normative values for TTTG, BO, and LPT, as well as to define whether BO and LPT are affected by the morphology of the trochlear groove. Methods: Dynamic scanning was used to acquire images during weight-bearing in 21 adult healthy volunteers. TTTG, BO, and LPT metrics were computed between 0° and 30° of knee flexion. Sulcus angle, sulcus depth, and lateral trochlear inclination were calculated and used with the TTTG for simple linear regression models. Results: All metrics gradually decreased during eccentric movement (TTTG, -6.9 mm; BO, -12.6%; LPT, -4.3°). No significant differences were observed between eccentric and concentric phases at any flexion angle for all metrics. Linear regression between kinematic metrics towards full extension showed a moderate fit between BO and TTTG (R2 0.60, β 1.75) and BO and LPT (R2 0.59, β 1.49), and a low fit between TTTG and LPT (R2 0.38, β 0.53). A high impact of the TTTG distance over BO was shown in male participants (R2 0.71, β 1.89) and patella alta individuals (R2 0.55, β 1.91). Conclusion: We provided preliminary normative values of three common metrics during weight-bearing dynamic CT and showed the substantial impact of lateralisation of the patella tendon over patella displacement. Relevance statement: These normative values can be used by clinicians when evaluating knee patients using TTTG, BO, and LPT metrics. The lateralisation of the patellar tendon in subjects with patella alta or in males significantly impacts the lateral displacement of the patella. Key Points: Trochlear groove morphology had no substantial impact on motion prediction. The lateralisation of the patellar tendon seems a strong predictor of lateral displacement of the patella in male participants. Participants with patella alta displayed a strong fit between the patellar lateral displacement and tilt. TTTG, BO, and LPT decreased during concentric movement. Concentric and eccentric phases did not show differences for all metrics. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to investigate whether the vastus medialis oblique (VMO) muscle compensates in patellar dislocation (PD) patients with the increased femoral anteversion angle (FAA). Methods: Between 2021 and 2024, we included 60 patients with recurrent PD (RPD group). Inclusion criteria were at least two episodes of PD, as well as complete CT scans of the knee and hip. Exclusion criteria included traumatic or habitual dislocation, previous knee surgery, etc. Of these patients, 30 with excessive FAA (≥ 30°) were assigned to the A group, and 30 without excessive FAA (< 30°) to the B group. A control group of 120 patients without patellofemoral disorders was also included (C group). The cross-sectional areas of the VMO and vastus lateralis muscle (VLM) were measured 20 mm above the patella on CT scans, and the VMO/VLM area ratio was calculated. The correlation between FAA and the VMO/VLM ratio was analyzed. Results: The RPD group had a significantly larger FAA (15.0 ± 1.9° vs. 30.1 ± 9.6°, P = 0.040) and a smaller VMO/VLM ratio (4.2 ± 1.5 vs. 3.5 ± 1.0, P = 0.014) compared to the C group. Within the RPD group, the A group had a higher VMO/VLM ratio than the B group (4.0 ± 1.1 vs. 3.0 ± 0.7, P = 0.029). The B group's VMO/VLM ratio was lower than that of the C group (3.0 ± 0.7 vs. 4.2 ± 1.5, P = 0.004). However, there was no significant difference in the VMO/VLM ratio between the A group and the C group. The VMO/VLM ratio showed a moderate positive correlation with FAA in the RPD group, with a correlation coefficient of r = 0.4 (P = 0.012), indicating a statistically significant relationship between the two. Conclusion: Patients with recurrent PD showed a smaller VMO/VLM ratio compared to controls. Increased FAA was correlated with compensatory thickening of the VMO and a higher VMO/VLM ratio in PD patients. This suggests that increased FAA may drive biomechanical adaptations in the quadriceps, stabilizing the patella. Clinicians should consider changes in FAA when assessing and treating PD. Level of evidence: Level III. [ABSTRACT FROM AUTHOR]

Purpose Methods Results Conclusions Level of Evidence During kinematically aligned (KA) total knee arthroplasty (TKA), the surgeon may need to rectify an over‐resection of the medial, lateral or posterior tibia. This study tested the hypothesis that a bone graft taken from the tibial resection or patella and impacted beneath a tibial baseplate would heal, regardless of whether the tibial component and knee were in outlier ranges according to mechanical alignment (MA) criteria. The study also tested the hypothesis that the Oxford Knee Score (OKS) and Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS JR) would improve beyond the substantial clinical benefit and that the source and thickness of the bone graft would not influence their improvement.This retrospective study radiographically assessed the healing of a bone graft from the tibial resection (n = 19) or patella (n = 10) in 29 KA TKAs (18 females, mean age 65 years). The tibial component and knee alignment were categorized as in‐range or outliers based on reported MA criteria for bone graft healing and implant survival. The one‐sample t test identified differences in the improvement of the OKS and KOOS JR from their reported substantial clinical benefit of 16 and 20 points, respectively.At an average follow‐up of 37 months, all bone grafts healed even though ≥55% of tibial components and 34% of knees were varus outliers according to MA criteria for bone healing and implant survival. Amongst the 29 patients, the mean OKS and KOOS JR improvements of 25 ± 11 and 47 ± 21 points, respectively, surpassed the threshold of their respective substantial clinical benefit (p < 0.01) and were not influenced by the bone graft's source and thickness (p ≥ 0.51).During cemented KA TKA, the surgeon can use a bone graft from the tibial resection or patella to rectify a tibial over‐resection. This technique led to consistent bone healing and improved outcome scores.Level IV. [ABSTRACT FROM AUTHOR]

We consider the setting where (1) an internal study builds a linear regression model for prediction based on individual-level data, (2) some external studies have fitted similar linear regression models that use only subsets of the covariates and provide coefficient estimates for the reduced models without individual-level data, and (3) there is heterogeneity across these study populations. The goal is to integrate the external model summary information into fitting the internal model to improve prediction accuracy. We adapt the James–Stein shrinkage method to propose estimators that are no worse and are oftentimes better in the prediction mean squared error after information integration, regardless of the degree of study population heterogeneity. We conduct comprehensive simulation studies to investigate the numerical performance of the proposed estimators. We also apply the method to enhance a prediction model for patella bone lead level in terms of blood lead level and other covariates by integrating summary information from published literature. [ABSTRACT FROM AUTHOR]

A male, Division II collegiate football player presented with an extracondylar lateral patellar dislocation with inversion of the patella on its vertical axis following impact with the ground on the medial side. The patient was sedated for closed patellar reduction. He returned to full participation after 6 weeks of a progressive strength program. Extracondylar patellar inversion is not often associated with severe force or a direct blow, but the case described occurred after a high-impact tackle to the ground. This is also the only published case of a collegiate athlete returning to collision sport after sustaining an inverted extracondylar patellar dislocation. Despite the deformity and emergent nature of an inverted patellar dislocation, having patients complete early mobilization activities, including range of motion, and aggressive strengthening and functional progressions may facilitate a quick and safe return to highly intensive and competitive physical activity. [ABSTRACT FROM AUTHOR]

Background: Amongst primary patella tumor Campanacci grade 3 tumor of Giant cell tumor of bone (GCTB) and malignant tumors requires patellectomy. We had a patient with huge recurrent GCTB of patella with involvement of skin. We reconstructed extensor mechanism of Knee with long iliotibial band (ITB) tendon graft. Material and Methods: After patellectomy, we harvested long ITB graft (length 22 cm; width proximally 6 cm, distally 1.5 cm) through patellectomy wound and small "L" shaped incision proximally. We passed ITB graft from patella tendon and quadriceps tendon in figure of 8 manner and sutured it back to itself and host tendon with fiber Wire and closed both the wounds primarily. We started ROM and quadriceps strengthening in graded manner. We measured functional outcome with Musculoskeletal Tumour Society (MSTS) scoring system. Results: There were no post-operative complications. At 10 weeks follow up, patient had no extension lag and knee ROM was 90°. At final follow up of 7 months patient regained pre-operative functional status without knee instability. Her MSTS score was 30 and she was disease free. Conclusion: Reconstruction of extensor mechanism of knee with ITB graft doesn't have donor site morbidity and gives excellent function with graded physiotherapy protocol. [ABSTRACT FROM AUTHOR]

Purpose: The suprapatellar bursa is located in the proximal deep layer of the patella and is thought to reduce tissue friction by changing from a single-membrane structure to a double-membrane structure during knee joint motion. However, the dynamics of the suprapatellar bursa have only been inferred from positional relationships, and the actual dynamics have not been confirmed. Methods: Dynamics of the suprapatellar bursa during knee joint motion were observed in eight knees of four Thiel-fixed cadavers and the angle at which the bursa begins to show a double membrane was revealed. The flexion angles of knee joints were measured when the double-membrane structure of the suprapatellar bursa began to appear during knee joint extension. Results: The suprapatellar bursa changes from a single membrane to a double-membrane structure at 91 ± 4° of flexion, when the knee joint is moved from a flexed position to an extended position. Conclusion: The suprapatellar bursa may be involved in limitations to knee joint range of motion and pain at an angle of approximately 90°. Further studies are needed to verify whether the same dynamics are observed in living subjects. [ABSTRACT FROM AUTHOR]

BACKGROUND: Assessment of readability and reliability of online resources for orthopedic patients is an area of growing interest, but there is currently limited reporting on this topic for patellar instability (PI) and medial patellofemoral ligament reconstruction (MPFLR). METHODS: Utilizing the Searchresponse.io dataset, we analyzed inquiries related to PI and MPFLR. Readability and reliability were assessed using the Automated Reading Index, Flesch Reading Ease, and the JAMA benchmark criteria. RESULTS: Analysis of 363 frequently asked questions from 130 unique websites revealed a predominant interest in fact-based information. Readability assessments indicated that the average grade level of the resources was significantly higher than the 6th grade level and reliability varied between resources. CONCLUSION: Although the internet is an easily accessible resource, we demonstrate that PI and MPFLR resources are written at a significantly higher reading level than is recommended, and there is inconsistent reliability amongst resources with medical practice websites demonstrating the lowest reliability. [ABSTRACT FROM AUTHOR]

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Neofunctionalization of duplicated gene copies is thought to be an important process underlying the origin of evolutionary novelty and provides an elegant mechanism for the origin of new phenotypic traits. One putative case where a new gene copy has been linked to a novel morphological trait is the origin of the arachnid patella, a taxonomically restricted leg segment. In spiders, the origin of this segment has been linked to the origin of the paralog dachshund-2 , suggesting that a new gene facilitated the expression of a new trait. However, various arachnid groups that possess patellae do not have a copy of dachshund-2 , disfavoring the direct link between gene origin and trait origin. We investigated the developmental genetic basis for patellar patterning in the harvestman Phalangium opilio , which lacks dachshund-2. Here, we show that the harvestman patella is established by a novel expression domain of the transcription factor extradenticle. Leveraging this definition of patellar identity, we surveyed targeted groups across chelicerate phylogeny to assess when this trait evolved. We show that a patellar homolog is present in Pycnogonida (sea spiders) and various arachnid orders, suggesting a single origin of the patella in the ancestor of Chelicerata. A potential loss of the patella is observed in Ixodida. Our results suggest that the modification of an ancient gene, rather than the neofunctionalization of a new gene copy, underlies the origin of the patella. Broadly, this work underscores the value of comparative data and broad taxonomic sampling when testing hypotheses in evolutionary developmental biology. [ABSTRACT FROM AUTHOR]

Background: Patellar tendinopathy is a multifactorial condition characterized by micro-degenerative changes in the patellar tendon. This results from repeated stress to the knee extensor mechanism from explosive movement, axial malalignment, and/or abnormal patellar height. Currently, there is no standard surgical procedure for the treatment of severe patellar tendinopathy. Indications: Patellar tendon reconstructions for patellar tendinopathy may be indicated when >50% of the tendon attachment is degenerative and detached from the distal patella and non-operative treatment, like physical therapy, bracing, and injections, have not relieved symptoms. Debridement may not offer long-term viability against augmentation of the patellar tendon with autografts, with a risk of recurrent breakdown of the patellar tendon attachment with resumption of previous activities that initially lead to overload. Technique Description: An anterior incision was made from the superior pole of the patella to the tibial tubercle. Then, dissection was performed medially to harvest the gracilis and semitendinosus tendons. Open harvesters were used, and the hamstring tendons were released proximally, keeping the tibial insertions attached. A horizontal pin was drilled across the tibial tubercle and reamed with a 4.5 mm reamer. A passing stitch was fed through the tunnel. The proximal and distal margins of the patella were localized with spinal needles and a pin was drilled across its midportion, 5 mm deep to the dorsal cortical margin, and then rearmed. Degenerative tissue at the patellar tendon was excised. The gracilis tendon was passed medial to lateral through the tibial tubercle, and a Q-Fix anchor anchored the grafts medially and laterally. The semitendinosus graft was passed medial to lateral through the patella followed by the gracilis tendon lateral to medial. Appropriate reconstruction graft tension was confirmed and grafts were whipstitched together. Results: Clinical outcomes for the debridement of severe patellar tendinopathy report 77% symptomatic relief. With many unable to return to activity, patellar tendon reconstruction can be indicated. Outcomes for reconstructions for severe patellar tendinopathy are not reported. Discussion: Patellar tendon reconstruction with hamstring autografts for the treatment of severe patellar tendinopathy can provide a strong reconstruction graft to allow for the resumption of high-level activities. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication. [ABSTRACT FROM AUTHOR]

Abstract Background Patellar instability is a well-known pathology in which kinematics can be investigated using metrics such as tibial tuberosity tracheal groove (TTTG), the bisect offset (BO), and the lateral patellar tilt (LPT). We used dynamic computed tomography (CT) to investigate the patellar motion of healthy subjects in weight-bearing conditions to provide normative values for TTTG, BO, and LPT, as well as to define whether BO and LPT are affected by the morphology of the trochlear groove. Methods Dynamic scanning was used to acquire images during weight-bearing in 21 adult healthy volunteers. TTTG, BO, and LPT metrics were computed between 0° and 30° of knee flexion. Sulcus angle, sulcus depth, and lateral trochlear inclination were calculated and used with the TTTG for simple linear regression models. Results All metrics gradually decreased during eccentric movement (TTTG, -6.9 mm; BO, -12.6%; LPT, -4.3°). No significant differences were observed between eccentric and concentric phases at any flexion angle for all metrics. Linear regression between kinematic metrics towards full extension showed a moderate fit between BO and TTTG (R 2 0.60, β 1.75) and BO and LPT (R 2 0.59, β 1.49), and a low fit between TTTG and LPT (R 2 0.38, β 0.53). A high impact of the TTTG distance over BO was shown in male participants (R 2 0.71, β 1.89) and patella alta individuals (R 2 0.55, β 1.91). Conclusion We provided preliminary normative values of three common metrics during weight-bearing dynamic CT and showed the substantial impact of lateralisation of the patella tendon over patella displacement. Relevance statement These normative values can be used by clinicians when evaluating knee patients using TTTG, BO, and LPT metrics. The lateralisation of the patellar tendon in subjects with patella alta or in males significantly impacts the lateral displacement of the patella. Key Points Trochlear groove morphology had no substantial impact on motion prediction. The lateralisation of the patellar tendon seems a strong predictor of lateral displacement of the patella in male participants. Participants with patella alta displayed a strong fit between the patellar lateral displacement and tilt. TTTG, BO, and LPT decreased during concentric movement. Concentric and eccentric phases did not show differences for all metrics. Graphical Abstract

Abstract Objective This study aims to quantitatively assess the relationship between the patella alignment and morphology and knee osteoarthritis (KOA), as well as the kinematics and kinetics of the knee, using gait analysis. Methods Eighty age-matched patients with KOA and control subjects were evaluated. Incident radiographic osteoarthritis (iROA) was identified using a Kellgren-Lawrence (KL) grade of ≥ 2. The modified Insall-Salvati ratio (Mod-ISR), patellar tilt angle (PTA), and patella index (PI) were utilized to evaluate the sagittal and transverse alignment of the patella and its morphology, respectively. Regression analyses were conducted to explore associations between patellar measurements and KOA, iROA, kinematics, and kinetics. Results Significant differences were observed between the control and KOA groups in terms of KL grade, patella alta, abduction angle, and reaction force to the ground (P 0.05, respectively). Conclusion This study provides further evidence that proper alignment and morphology of the patella might be associated with maintaining normal biomechanical function. In addition, intervention measures targeting relevant patellar parameters, such as Mod-ISR, PTA, and PI, may positively impact KOA treatment outcomes.

Aims: Patient dissatisfaction is not uncommon following primary total knee arthroplasty. One proposed method to alleviate this is by improving knee kinematics. Therefore, we aimed to answer the following research question: are there significant differences in knee kinematics based on the design of the tibial insert (cruciate-retaining (CR), ultra-congruent (UC), or medial congruent (MC))? Methods: Overall, 15 cadaveric knee joints were examined with a CR implant with three different tibial inserts (CR, UC, and MC) using an established knee joint simulator. The effects on coronal alignment, medial and lateral femoral roll back, femorotibial rotation, bony rotations (femur, tibia, and patella), and patellofemoral length ratios were determined. Results: No statistically significant differences were found regarding coronal alignment (p = 0.087 to p = 0.832). The medial congruent insert demonstrated restricted femoral roll back (mean medial 37.57 mm; lateral 36.34 mm), while the CR insert demonstrated the greatest roll back (medial 42.21 mm; lateral 37.88 mm; p < 0.001, respectively). Femorotibial rotation was greatest with the CR insert with 2.45° (SD 4.75°), then the UC insert with 1.31° (SD 4.15°; p < 0.001), and lowest with the medial congruent insert with 0.8° (SD 4.24°; p < 0.001). The most pronounced patella shift, but lowest patellar rotation, was noted with the CR insert. Conclusion: The MC insert demonstrated the highest level of constraint of these inserts. Femoral roll back, femorotibial rotation, and single bony rotations were lowest with the MC insert. The patella showed less shifting with the MC insert, but there was significantly increased rotation. While the medial congruent insert was found to have highest constraint, it remains uncertain if this implant recreates native knee kinematics or if this will result in improved patient satisfaction. Cite this article: Bone Jt Open 2024;5(7):592–600.

Abstract Hypothesis/purpose The prevalence of trochlear dysplasia is common in different populations. Background The prevalence of trochlear dysplasia in the general population, categorised by sex, race, age, and body mass index, has been sparse. This study aimed to define the prevalence of trochlear dysplasia based on the latter categories. Study design Cohort retrospective study. Methods 1162 skeletal mature healthy femora were obtained from a CT-scan-based modelling system (SOMA). Thin slice CT scans were acquired exclusively for medical indications such as polytrauma (20%), CT angiography (70%) and other reasons (i.e. Total Joint Replacement) (10%). Trochlear dysplasia was measured using Pfirmann’s method. Patient demographics such as age, race and sex were recorded. Results The overall prevalence of trochlear dysplasia is 4.5% and is far more common in Asian female patients compared to Caucasian, African and Middle Eastern knees. Conclusion Overall, the prevalence of dysplasia in the general population was determined to be 4.5%, with female patients being more likely to suffer from the condition. Patients of Asian and Caucasian race were more likely to have trochlear dysplasia, while Middle Eastern male patients displayed more dysplastic values than their female counterparts.

An osteoblastoma is a benign bone tumor characterized by osteoblast proliferation that is more commonly diagnosed in young men during adolescence and youth. The condition mainly occurs in the posterior regions of the spine and sacrum, but in rare cases, the patella as well. We present a case of patellar osteoblastoma successfully managed through intralesional curettage and grafting, highlighting the need for comprehensive imaging and pathological studies to ensure an accurate diagnosis. A 26-year-old male with a history of knee plica excision presented with persistent knee pain over 1 year. Radiographic and CT evaluations revealed an osteolytic lesion in the patella, further characterized by MRI. An incisional biopsy confirmed the diagnosis of osteoblastoma. Intralesional curettage and grafting were performed. Later, subsequent follow-up demonstrated complete pain relief, restoration of knee function, and optimal graft incorporation. As shown in this case, precise diagnosis and effective management are key to improving the quality of life of patients. Furthermore, it illustrates that intralesional curettage and grafting are effective treatments for patellar osteoblastomas. Given the rarity of this condition, further research and comprehensive case studies are imperative to establish standardized guidelines for improved healthcare and patient outcomes. In summary, while the clinical characteristics of patellar osteoblastoma resemble those of osteoblastomas in general, its unique presentation warrants specific attention. Individualized consideration of adjuvant measures, graft selection, and preventive fixation is vital to ensure optimal outcomes in patellar osteoblastoma management.

Tumors of the patella are uncommon. A 28-year-old male, who presented with intermittent knee pain of 9 months duration, with swelling and tenderness over the patella underwent a clinico-radiological evaluation which revealed fluid-fluid levels, suggestive of an aneurysmal bone cyst (ABC). Conventional treatment of ABCs usually consists of curettage and autologous bone grafting. However, in this case, a total patellectomy resulted in full functional restoration and resumption of activities, thereby ascertaining this method as a successful treatment option for primary ABC of the patella.

Background: There is no consensus on the frequency and timing of platelet-rich plasma (PRP) injection in tendon healing. We aimed to evaluate the effectiveness of single versus multiple PRP injections in the healing of patellar tendon defects in the experimental model, through histological and biomechanical investigation. Methods: Forty-four male skeletally mature Dutch rabbits were randomly divided into the five study groups (A, B,C, D,E). After creating a longitudinal acute patellar tendon defect on both knees (One-third the width of the patella tendon), the right legs of the rabbits were used as the intervention group and the left legs as the control groups. Animals in groups A, B, and C were euthanized on days 7, 14, and 28, respectively, after the first PRP injection. Animals in group D received the second PRP injection on day 10 and was euthanized on day 14. Animals in group D received the second and third PRP injections on days 10 and 20, respectively, and were euthanized on day 28. The outcomes were evaluated histologically (modification of Movin's Grading) and biomechanically. Results: The inflammatory condition was exaggerated in groups D and E. Load at failure was higher in the non-injected side of groups D and E, while there was no significant difference between the right and left legs of the three groups A, B and C. In other word, groups with a single PRP injection were more resistant to the increasing load compared to the groups with multiple PRP injections. Conclusions: PRP improves tendon healing if injected early after injury, while its injection after the initial phase of injury hampers tendon healing. In addition, a single PRP injection seems to be more effective than multiple PRP injection. Therefore, in cases where PRP injection is indicated for tendon repair, such as acute tendon injury, we recommend using a single PRP injection during tendon repair surgery. [ABSTRACT FROM AUTHOR]

Purpose Methods Results Conclusions Level of Evidence Donor site morbidity is the main drawback to using bone‐patellar tendon‐bone (BPTB) as a graft in anterior cruciate ligament (ACL) reconstruction. The objective of the study was to determine whether refilling the patellar bone defect after BPTB harvesting with autograft bone decreased kneeling pain to a greater degree when compared with a group in which bone defect is left unaddressed.This is a randomised single‐blinded controlled study. Forty patients were randomised into two groups; group 1: Patellar bone defect filled with autologous bone; group 2: Bone defect left undressed. Pain was measured by means of pressure algometry (PA). Functional outcomes were measured with the Kujala and Victorian Institute of Sport Assessment‐Patella (VISA‐P) score. Magnetic resonance imaging (MRI) was done to measure bone buildup between groups at the 1‐year follow‐up.No differences were observed in the different algometry measurements and the scores were assessed at 3, 6 and 12 months postoperatively. The ratio of void filled remained consistently higher (p = 0.003) in group 1 when compared to group 2.Although refilling the lower pole of the patella with autologous bone from the harvested BPTB autograft loads the bone defect, it does not reduce pain at the donor site 1 year after surgery.Therapeutic study level 1. [ABSTRACT FROM AUTHOR]

Background: Anterior knee pain due to patellar maltracking following total knee arthroplasty (TKA) reduces patients' satisfaction. This study aimed to determine the patellofemoral pressure (PFP) in patients with favorable patellar tracking (FT) and impaired patellar tracking (IT) following TKA, the factors causing patellar maltracking, and the effect of lateral retinacular release (LRR) on patients with IT. Methods: Forty-four patients with varus knee osteoarthritis undergoing cruciate-retaining TKA were enrolled. After component implantation, patients with a separation of ≥ 2 mm of the patellar medial facet from the medial femoral trochlea throughout knee range of motion were classified into the IT group; meanwhile, the others were classified into the FT group. PFP was measured intraoperatively in three phases: (1) with the resurfaced patella (RP); (2) with the resurfaced patella and knee (RPK); and (3) when LRR was performed in IT (post-LRR). The PFPs at 0°, 90°, 120°, and 135° knee flexion were compared between FT and IT using the Mann–Whitney U test. Pairwise comparison of the PFP in IT between RPK and post-LRR was performed using the Wilcoxon signed-rank test. Correlations between PFP and pre- and postoperative radiographic parameters, such as hip–knee–ankle angle, lateral distal femoral angle, medial proximal tibial angle, anterior femoral offset, Insall–Salvati ratio (ISR), patellar tilt, and patellar resection angle (PRA), were evaluated using Spearman's rank correlation coefficients. Results: High lateral PFP in the knee flexion position led to patellar maltracking. Patients with IT (n = 24) had higher lateral and lower medial PFP than did patients with FT (n = 20) at 90°, 120°, and 135° knee flexion in RP and RPK. LRR in IT reduced the lateral PFP in the knee flexion position. PRA and ISR were correlated with the lateral PFP at no less than 90° in RP and RPK. Conclusions: This study demonstrated that internal rotational patellar resection, which resulted in a thick medial patellar remnant and a thin lateral counterpart, and patella alta were the causative factors of high lateral PFP, which induced patellar maltracking after TKA. Surgeons should avoid internal rotational patellar resection to achieve FT and perform LRR in patients with patellar maltracking. [ABSTRACT FROM AUTHOR]

Background: Excessive posterior tibial slope (PTS) has been associated with a higher risk of graft failure after anterior cruciate ligament reconstruction (ACLR). Although anterior closing wedge osteotomy (ACWO) can reduce the PTS, it may also change the coronal alignment and patellar height. Purpose: To elucidate the radiological outcomes after infratubercle ACWO, specifically to evaluate its influence on perioperative changes in patellar height. Methods: Patients who underwent infratubercle ACWO with combined ACLR with a minimum follow-up of 3 months were included. Surgery was indicated when the PTS was greater than 12°. Radiological evaluation included measurements of the hip–knee–ankle angle (HKA), PTS, femoral patellar height index (FPHI), and Caton–Deschamps index (CDI) preoperatively and 3 months postoperatively. Patellar height was classified as patella baja, normal, or alta based on CDI values. Knee recurvatum was measured preoperatively and at final follow-up. Results: A total of 21 patients with a mean age of 21.6 ± 3.0 years were included. Although HKA did not significantly change, significant corrections were achieved in the PTS from 14.5° ± 1.6° to 5.7° ± 1.0° (p < 0.001). No significant change in FPHI was found (preoperative: 1.33 ± 0.11 vs postoperative: 1.30 ± 0.09). Patellar height categories showed no significant differences pre- and postoperatively, while three patients (14.3%) changed their patellar height category (all moved up one category). Knee recurvatum increased significantly from 4.9° ± 2.9° preoperatively to 7.8° ± 3.1° at the final follow-up (p < 0.001). Conclusions: Precise sagittal correction was achieved after infratubercle ACWO without altering the coronal alignment and patella height. Level of Evidence: IV, Case series. [ABSTRACT FROM AUTHOR]

Simple Summary: This case report describes the surgical technique and clinical outcome of reconstructing the quadriceps mechanism using a composite frozen calcaneal tendon–bone block allograft in a dog which had resorption of the tibial tuberosity following complications resultant from a tibial tuberosity transposition procedure. In this case, a dog exhibited chronic lameness due to the resorption of the tibial tuberosity following surgical correction of a medial patella luxation. To address these issues, a novel surgical procedure was employed using a composite calcaneal tendon–bone block allograft. The graft reconstructed the tibial tuberosity and facilitated reattachment of the patellar tendon. The surgery promptly restored the quadriceps extensor mechanism, enabling the dog to bear weight on the affected limb within 2 weeks. Twenty-nine months later, the dog had satisfactory limb function without recurrence of patella luxation. This case demonstrates the effectiveness of using a calcaneal tendon–bone allograft to restore the quadriceps extensor mechanism in dogs with irreparable tibial tuberosity fracture. A non-reducible tibial tuberosity fracture is a rare complication of tibial tuberosity transposition performed during correcting of medial patella luxation (MPL) in dogs. This condition severely disrupts the quadriceps extensor mechanism, leading to significant pelvic limb lameness. An 11-year-old, 1.8 kg spayed female Yorkshire Terrier sustained a comminuted left tibial tuberosity fracture during surgical correction of an MPL. Six months after surgery, the dog was markedly lame and unable to extend the left stifle. Radiographs revealed patella alta and resorption of the fragmented tibial tuberosity. A composite frozen allogeneic calcaneal tendon–bone block was utilized to reconstruct the tibial tuberosity and reattach the patellar ligament. Initial postoperative radiographs confirmed restoration of a normal patellar ligament to patella length ratio (1.42). Both the allogeneic bone used for tibial tuberosity reconstruction and the tendon used to reattach the patellar ligament were successfully integrated. The dog regained satisfactory limb function without recurrence of patella luxation, as reported by the owners 29 months postoperatively. The use of a calcaneal tendon–bone allograft effectively restored the functional integrity of the quadriceps extensor mechanism, providing a viable option for addressing quadriceps insufficiency resulting from the loss of the osseous tibial insertion. [ABSTRACT FROM AUTHOR]