Saris, Daniël B.F.

Purpose To assess the reliability, predictability, and discriminative capacity of 3 anatomic measurements, tibial tubercle‐trochlear groove (TT‐TG), tibial tubercle‐posterior cruciate ligament, and patellar tendon‐lateral trochlear ridge (PT‐LTR), where PT‐LTR may offer a complementary approach to assessing recurrent patellofemoral instability (PFI) risk. Methods Patients diagnosed with PFI before primary patellofemoral stabilization surgery at a single institution between 2022 and 2024 were included. A control group without PFI was propensity matched 1:1 for age, sex, and laterality. Magnetic resonance images were evaluated to measure TT‐TG, tibial tubercle‐posterior cruciate ligament, and PT‐LTR. A priori power analysis determined the cohort size. Statistical analyses compared differences between the PFI and control groups with Student t‐tests, receiver operating characteristic analyses, and area under the curve with resultant sensitivity, specificity, and an optimal cutoff. Results Patients included 50 knees with PFI (28 women, 22 men; mean age 18 ± 5 years). The control group included 50 knees (27 women, 23 men; mean age 18 ± 4 years). Excellent inter‐ and intra‐rater reliability (intraclass correlation coefficient > 0.7) was shown for TT‐TG and PT‐LTR in the PFI and control groups. The distances for TT‐TG, tibial tubercle‐posterior cruciate ligament, and PT‐LTR were significant predictors ( P ≤ .025) of PFI. The average PT‐LTR distance difference for the PFI and control groups was 7.0 mm ( P < .001). PT‐LTR showed an area under the curve of 0.80 and, when ≥4.6 mm, was 66% sensitive and 92% specific for PFI. Conclusions The PT‐LTR distance is a reliable and discriminative metric for identifying PFI in both pediatric and adult populations. A PT‐LTR cutoff value of 4.6 mm showed diagnostic discrimination and substantially high specificity for recurrent PFI, indicating strong ability to identify patients with instability. Level of Evidence Level III, retrospective case control study.

Purpose To evaluate implantation rates, time to implantation, and predictors of implantation following matrix‐induced autologous chondrocyte implantation (MACI) biopsy for knee chondral defects. Methods Patients undergoing MACI biopsy or implantation for symptomatic knee chondral defects from 2017 to 2024 at a single institution were reviewed. At a minimum 1‐year follow‐up, the decision to proceed with implantation, recurrent symptoms, complications, and reoperations were assessed. Kaplan‐Meier analysis estimated time to implantation, and multivariable logistic regression identified predictors of MACI implantation. Results A total of 208 knees in 202 patients (mean age 28.0 ± 10.9 years, range 11‐59) underwent MACI biopsy for 243 chondral defects (patella [38%], femoral condyle [34%], and trochlea [26%]). At a mean follow‐up of 4.3 years (range 1.0‐8.3), 64 knees (31%) proceeded to second‐stage MACI implantation. Among 144 knees not implanted, 87 (60%) reported symptom improvement, and 26 (18%) had persistent symptoms. The remaining 22% did not undergo implantation due to another cartilage procedure, insurance denial, or pending scheduling. Patients who underwent biopsy at the home institution had a shorter time from biopsy to implantation compared with those biopsied at outside institutions (6.1 vs 13.1 months, P = .001). Median time to implantation was 9.4 months (95% confidence level: 7.2‐12.2) for home biopsies. Lower body mass index was associated with progression to implantation after adjusting for covariates (odds ratios 0.92, P = .019). Patients implanted within 4 months had larger chondral defects (4.0 vs 3.0 cm 2 , P = .045). At a mean 4.1‐year follow‐up, 6 patients (8%) experienced postoperative complications, including 3 (4%) who required revision chondroplasty. Conclusions MACI biopsy for knee chondral defects resulted in approximately one‐third of patients proceeding to MACI implantation, at a median of 9.4 months after biopsy. Lower body mass index was associated with higher likelihood of progression to implantation, larger chondral defects with earlier implantation, and among patients who did not proceed to implantation, approximately 60% reported symptom improvement following concomitant chondroplasty at the time of biopsy. Level of Evidence Level IV, retrospective case series.

Background: Total knee arthroplasty (TKA) is the treatment of choice for end-stage knee osteoarthritis in many patients. In younger patients with predominantly medial compartment disease, high tibial osteotomy (HTO) is performed as a joint-preserving treatment. However, concerns remain regarding potentially compromised outcomes of TKA after previous HTO given the axial deviation, osteotomy site, secondary surgery, previous hardware, and instrumentation. Therefore, this study compared long-term implant survival, revision, and infection rates, and patient-reported outcomes between patients undergoing TKA after HTO and matched TKA-only controls. Methods: Postoperative complications and revision surgeries were prospectively recorded in patients who underwent TKA from 2000 to 2023 at a single academic center. Patients with previous ipsilateral HTO formed the study group and were propensity matched 1:2 to TKA-only patients without a previous osteotomy based on age, sex, and body mass index. Knee Society Scores (KSS) were collected prospectively. Implant survivorship was analyzed using Kaplan-Meier survival curves and Cox proportional hazards models. Results: The study included 134 HTO-TKA and 268 matched TKA-only patients, with a mean follow-up of 10.5 ± 6.4 years (range: 0-24 years) after TKA. Both groups showed significant postoperative improvements in KSS (p < 0.02) with comparable clinical outcomes (HTO-TKA: 79.0 (6.0), TKA-only: 79.0 (11.8)). Revision arthroplasty rates were 5.2% for HTO-TKA and 4.5% for TKA-only (p = 0.69); the mean time to revision was 8.1 ± 8.7 years vs. 4.4 ± 3.5 years, respectively (p = 0.30). Infection rates were 2.2% and 1.1%, respectively (p = 0.74). Conclusions: Revision and infection rates were comparable between HTO-TKA and matched TKA-only patients, with no statistically significant differences. Our findings demonstrate comparable patient-reported outcomes in both groups. These findings indicate that a previous HTO does not adversely affect TKA implant longevity or clinical outcomes when compared with matched primary TKA patients within the US population. Level of Evidence: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Cartilage defects remain a prevalent and challenging clinical problem, especially in young, active individuals. Existing treatments such as microfracture or autologous chondrocyte implantation either lack durability or require multiple surgeries and extensive cell culture. To address these limitations, we developed RECLAIM—a one-stage, two-cell-type procedure combining allogeneic mesenchymal stromal cells and autologous chondrons. RECLAIM harnesses the trophic and immunomodulatory properties of MSCs to stimulate autologous chondron-driven tissue repair, minimizing invasiveness while optimizing biologic regeneration. This article reviews the preclinical discovery, clinical translation, trial results, and platform potential of RECLAIM, which was recognized with the 2025 Arnold I. Caplan Award for Distinguished Research in OrthoBiologics. Our work builds on Professor Caplan's pioneering conceptualization of MSCs as “medicinal signaling cells” and establishes a model for academic, investigator-driven translation of regenerative science into clinical practice.

Background: Treatment decisions in patients with anterior cruciate ligament (ACL) injuries are influenced by multiple factors, such as the desire to return to sports or symptomatic instability. Identifying the differential treatment effect of ACL reconstruction (ACLR) compared with nonoperative management on a patient-specific level can inform surgical decision-making. Hypothesis: Unsupervised machine learning can identify distinct patient subgroups based on outcome achievement after ACL injury, and ACLR will exert a protective effect on the development of posttraumatic osteoarthritis (PTOA) over nonoperative management. Study Design: Cohort study; Level of evidence, 3. Methods: A longitudinal populational registry identified patients with ACL injuries from 1990 to 2016 with a minimum 7.5-year follow-up. An unsupervised random forest algorithm was utilized to develop and validate patient subgroups. Treatment effects of ACLR on outcomes were analyzed using a machine learning causal inference estimator. Patient subgroup membership was incorporated into a multivariable logistic regression to identify factors predictive of optimal outcomes. Results: A total of 923 patients (785 primary ACLR, 138 nonoperative) were included. The random forest algorithm arrived at an optimal partition of 2 subgroups, with 653 patients in the optimal outcome subgroup (368 male [56.4%]; mean age, 26.0 ± 10.2 years; mean body mass index [BMI], 26.5 ± 4.30) and 270 patients in the suboptimal outcome subgroup (152 male [56.3%]; mean age, 35.0 ± 10.1 years; mean BMI, 30.5 ± 5.54). The latter group demonstrated significantly increased rates of secondary meniscal injury, development of symptomatic PTOA, and progression to total knee arthroplasty (TKA) at the final follow-up (all P < .01). In the optimal outcome subgroup, ACLR had significantly protective treatment effects on the risk of secondary meniscal injury (average treatment effect [ATE], 61%), contralateral ACL injury (ATE, 8%), symptomatic PTOA (ATE, 16%), and progression to TKA (ATE, 6%) (all P < .01). Conversely, in the suboptimal outcome subgroup, ACLR only protected against symptomatic PTOA (ATE, 11%) and progression to TKA (ATE, 8%) (both P < .01). Conclusion: Two clinically meaningful subgroups were identified from retrospectively collected data and found to experience differential treatment responses after ACL injuries. ACLR decreased the rate of development of PTOA and TKA in both subgroups but was not as effective in preventing secondary meniscal injuries or contralateral ACL injuries in patients who were older, heavier, or had concomitant medial meniscus injuries.

ABSTRACTPurposeDouble‐level osteotomies (DLOs) have shown promising results for knee joint preservation, however, most ultimately progress in terms of degenerative disease resulting in conversion to total knee arthroplasty (TKA). Therefore, the purpose of this study was to examine the time to TKA conversion, long‐term clinical outcomes and revision rates of patients who have undergone TKA after prior ipsilateral DLO.MethodsPatients who underwent simultaneous or staged DLO and subsequently underwent conversion to TKA at a single academic institution from 1997 to 2022 were evaluated. The type of osteotomy performed (opening‐ vs. closing‐wedge), osteotomy hardware fixation, when and if osteotomy hardware was removed, implanted TKA components and revision rates were recorded. Postoperative outcomes, including Forgotten Joint Score‐12 (FJS‐12), Tegner Activity Scale score and subjective knee preference were also obtained.ResultsA total of 22 patients (24 knees) underwent TKA following DLO and were followed for an average of 26.1 ± 7.7 years. The average time from DLO to TKA conversion was 14.1 ± 6.5 years, with 70.8% of knees converting to TKA more than 10 years after DLO. The mean follow‐up after conversion to TKA was 12.0 ± 7.7 years. Only 12.5% of patients received a varus‐valgus or hinged‐constrained TKA. At the final follow‐up, the mean FJS‐12 was 75.8 ± 23.1, while the mean Tegner Activity Scale score was 2.5 ± 1.1. Seventy‐seven percent of patients had no subjective knee preference or preferred their DLO‐TKA knee. Only two knees (7.4%) underwent subsequent revision after index arthroplasty at a mean of 9.3 years postoperatively.ConclusionsA majority of DLOs (70.8%) converted to TKA after more than a decade. Subsequent TKA function was favorable as most patients had either no subjective knee preference or preferred their DLO‐TKA knee. This study demonstrates both long‐term joint preservation and uncompromised TKA function after prior DLO.Level of EvidenceLevel IV.

AimsDistal femoral osteotomies (DFOs) are commonly used for the correction of valgus deformities and lateral compartment osteoarthritis. However, the impact of a DFO on subsequent total knee arthroplasty (TKA) function remains a subject of debate. Therefore, the purpose of this study was to determine the effect of a unilateral DFO on subsequent TKA function in patients with bilateral TKAs, using the contralateral knee as a self-matched control group.MethodsThe inclusion criteria consisted of patients who underwent simultaneous or staged bilateral TKA after prior unilateral DFO between 1972 and 2023. The type of osteotomy performed, osteotomy hardware fixation, implanted TKA components, and revision rates were recorded. Postoperative outcomes including the Forgotten Joint Score-12 (FJS-12), Tegner Activity Scale score, and subjective knee preference were also obtained at final follow-up.ResultsA total of 21 patients underwent bilateral TKA following unilateral DFO and were followed for a mean of 31.5 years (SD 11.1; 20.2 to 74.2) after DFO. The mean time from DFO to TKA conversion was 13.1 years (SD 9.7) with 13 (61.9%) of DFO knees converting to TKA more than ten years after DFO. There was no difference in arthroplasty implant systems employed in both the DFO-TKA and TKA-only knees (p > 0.999). At final follow-up, the mean FJS-12 of the DFO-TKA knee was 62.7 (SD 36.6), while for the TKA-only knee it was 65.6 (SD 34.7) (p = 0.328). In all, 80% of patients had no subjective knee preference or preferred their DFO-TKA knee. Three DFO-TKA knees and two TKA-only knees underwent subsequent revision following index arthroplasty at a mean of 12.8 years (SD 6.9) and 8.5 years (SD 3.8), respectively (p > 0.999).ConclusionIn this self-matched study, DFOs did not affect subsequent TKA function as clinical outcomes, subjective knee preference, and revision rates were similar in both the DFO-TKA and TKA-only knees at mean 32-year follow-up.Cite this article: Bone Jt Open 2024;5(11):1013–1019.

Abstract Purpose The demographic and radiological risk factors of subchondral insufficiency fractures of the knee (SIFK) continue to be a subject of debate. The purpose of this study was to associate patient‐specific factors with SIFK in a large cohort of patients. Methods Inclusion criteria consisted of patients with SIFK as verified on magnetic resonance imaging (MRI). All radiographs and MRIs were reviewed to assess characteristics such as meniscus tear presence and type, subchondral oedema presence and location, location of SIFK, mechanical limb alignment, osteoarthritis as assessed by Kellgren–Lawrence grade and ligamentous injury. A total of 253 patients (253 knees) were included, with 171 being female. The average body mass index (BMI) was 32.1 ± 7.0 kg/m 2 . Results SIFK was more common in patients with medial meniscus tears (77.1%, 195/253) rather than tears of the lateral meniscus (14.6%, 37/253) ( p < 0.001). Medial meniscus root and radial tears of the posterior horn were present in 71.1% (180/253) of patients. Ninety‐one percent (164/180) of medial meniscus posterior root and radial tears had an extrusion ≥3.0 mm. Eighty‐one percent (119/147) of patients with SIFK on the medial femoral condyle and 86.8% (105/121) of patients with SIFK on the medial tibial plateau had a medial meniscus tear. Varus knees had a significantly increased rate of SIFK on the medial femoral condyle in comparison to valgus knees ( p = 0.016). Conclusion In this large cohort of patients with SIFK, there was a high association with medial meniscus root and radial tears of the posterior horn, meniscus extrusion ≥3.0 mm as well as higher age, female gender and higher BMI. Additionally, there was a particularly strong association of medial compartment SIFK with medial meniscus tears. As SIFK is frequently undiagnosed, identifying patient‐specific demographic and radiological risk factors will help achieve a prompt diagnosis. Level of Evidence Level IV.

Background: Osteochondral allograft transplantation (OCAT) is an accepted knee joint–preserving treatment strategy for focal osteochondral lesions that is often conducted in combination with meniscal allograft transplantation (MAT). Despite its frequent and simultaneous utilization, there remains a lack in the literature reporting on outcomes and failure rates after concomitant procedures. Purpose: To determine (1) the midterm clinical success rate after OCAT+MAT in comparison with a matched-pair cohort undergoing isolated OCAT, (2) whether patient-specific and procedural variables influence the risk of failure, and (3) patient-reported outcome measures over time. Study Design: Cohort study; Level of evidence, 3. Methods: A single-center matched-pair cohort study was conducted investigating outcomes in patients who underwent OCAT of the medial or lateral femoral condyle with and without MAT between 2004 and 2020. Patients were matched 1:1 by age (±5 years), sex (male or female), body mass index (±5), and grouped Kellgren and Lawrence grade (grades 0-1 or 2-4). The minimum follow-up time was 2 years. Radiographic variables (International Cartilage Regeneration & Joint Preservation Society [ICRS] grade and Kellgren and Lawrence grade) were assessed preoperatively and at follow-up. Subjective patient-reported outcome measures (Lysholm score, Knee injury and Osteoarthritis Outcome Score [KOOS] including subscores, International Knee Documentation Committee [IKDC] score, and visual analog scale score) were collected preoperatively and at follow-up. Clinical failure was defined as revision surgery for graft failure or conversion to total knee arthroplasty. Patient-reported, clinical, and radiographic outcomes were compared between groups. Results: In total, 66 patients (33 treated with isolated OCAT, 33 treated with OCAT+MAT; 57.6% male) with a mean age of 26.3 years (range, 18-62 years) were followed for a mean of 5.6 years (minimum, 2 years; range, 24-218 months). The 2 cohorts showed no difference in Kellgren and Lawrence grade postoperatively ( P = .59). There was a significantly higher ICRS grade detected at follow-up in the OCAT+MAT group (2.81 ± 1.10) compared with the OCAT group (2.04 ± 0.96) ( P < .05). There were no statistically significant differences between the groups regarding reoperation rate (OCAT: n = 6; OCAT+MAT: n = 13; P = .116), time to reoperation (OCAT: 46.67 ± 47.27 months vs OCAT+MAT: 28.08 ± 30.16 months; P = .061), and failure rate (OCAT: n = 4 [12.1%] vs OCAT+MAT: n = 5 [15.2%]; P = .66). In the OCAT+MAT group, an increase of tibial slope by 1° conferred a 1.65-fold increase in the hazard for failure over decreased slope (hazard ratio, 1.65; 95% CI, 1.10-2.50; P < .05). The overall survival rate was 86% at a mean follow-up of 5.6 years. Patient-reported outcome scores were significantly improved at the final follow-up compared with preoperative status. No significant differences were seen between groups with respect to subjective IKDC, Lysholm, Tegner, and KOOS results, except for the KOOS Symptoms subscale score, which was significantly higher in the OCAT+MAT group than in the OCAT group (mean difference, 14.6; P < .05) and did exceed the minimal clinically important difference threshold of 10.7. Conclusion: Midterm results after isolated OCAT and OCAT+MAT show high rates of healing and sustainable subjective improvement of knee function and quality of life. However, it should be noted that the difference in reoperation rate and time to reoperation between the groups is arguably clinically important and that lack of statistical significance may be because of low power. These results imply that isolated OCAT is an efficient joint-preserving treatment that can be combined with MAT in well-selected patients with meniscal insufficiency without negative influence on global clinical outcomes.

Purpose To compile and analyze structural and clinical outcomes after meniscus root tear treatment as currently described in the literature. Methods A review was conducted to identify studies published since 2011 on efficacy of repair, meniscectomy, and nonoperative management in the treatment of meniscus root tears. Patient cohorts were grouped into treatment categories, with medial and lateral root tears analyzed separately; data were collected on patient demographics, structural outcomes including joint space width, degree of medial meniscal extrusion, progression to total knee arthroplasty, and patient‐reported outcome measures. Risk of bias was assessed using the MINORS (methodological index for non‐randomized studies) criteria. Heterogeneity was measured using the I‐statistic, and outcomes were summarized using forest plots without pooled means. Results The 56 included studies comprised a total of 3,191 patients. Mean age among the included studies ranged from 24.6 to 65.6 years, whereas mean follow‐up ranged from 12 to 125.9 months. Heterogeneity analysis identified significant differences between studies. Change in joint space width ranged from –2.4 to –0.6 mm (i.e., decreased space) after meniscectomy (n = 186) and –0.9 to –0.1 mm after root repair (n = 209); change in medial meniscal extrusion ranged from –0.6 to 6.5 mm after root repair (n = 521) and 0.2 to 4.2 mm after meniscectomy (n = 66); and event rate for total knee arthroplasty ranged from 0.00 to 0.22 after root repair (n = 205), 0.35 to 0.60 after meniscectomy (n = 53), and 0.27 to 0.35 after nonoperative treatment (n = 93). Root repair produced the greatest numerical increase in International Knee Documentation Committee and Lysholm scores of the 3 treatment arms. In addition, root repair improvements in Knee Injury and Osteoarthritis Outcome Score Pain (range: 22‐32), Sports and Recreational Activities (range: 23‐36), Quality of Life (range: 22‐42), and Symptoms subscales (range: 10‐19), in studies with low risk of bias. Conclusions The literature reporting on the treatment of meniscus root tears is heterogenous and largely limited to Level III and IV studies. Current evidence suggests root repair may be the most effective treatment strategy in lessening joint space narrowing of the knee and producing improvements in patient‐reported outcomes. Level of Evidence Level IV, systematic review of Level II‐IV studies.