Objective: Knee distraction treatment for end-stage osteoarthritis successfully postpones arthroplasty for years. Studies performed thus far used general intended use, patient-personalised or custom-made devices. In this study, for the first time, a device specifically designed for knee distraction is evaluated.

Design: 65 patients (≤65 years) with end-stage knee osteoarthritis indicated for arthroplasty received knee distraction. Before, 1-year and 2-year post-treatment, questionnaires were filled out and knee radiographs made. Adverse events and self-reported pain medication were registered.

Results: Forty-nine patients completed 2-year follow-up: one patient did not complete treatment, three patients received arthroplasty in the first and four patients in the second year follow-up. Eight patients were lost to follow-up in the second year. The total Western Ontario and McMaster Universities Osteoarthritis Index score showed a clinically relevant improvement at 1 and 2 years (+26 and +24 points), as did all subscales (all p<0.001). The minimum radiographic joint space width improved over 1 (+0.5 mm; p<0.001) and 2 (+0.4 mm; p=0.015) years, as did the physical Short-Form 36 (+10 points; p<0.001). The most common adverse event was pin tract infection, experienced by 66% of patients, in 88% successfully treated with oral antibiotics. In two cases, hospitalisation and/or intravenous antibiotics were needed. Eight patients experienced device-related complications. None of the complications influenced 2-year outcomes. Before treatment, 42% of patients used pain medication, which had nearly been halved 1 (23%; p=0.02) and 2 years (29%; p=0.27) post-treatment.

Conclusions: Patients treated with a general applicable, for knee distraction purpose-built device showed, despite adverse events, significant clinical and structural improvement over 2 years.

Objective: Both, knee joint distraction (KJD) and high tibial osteotomy (HTO) are joint-preserving surgeries that postpone total knee arthroplasty (TKA) in younger osteoarthritis (OA) patients. Here we evaluate the 2-year follow-up of KJD versus TKA and KJD versus HTO in 2 noninferiority studies.

Design: Knee OA patients indicated for TKA were randomized to KJD (n = 20; KJD_TKA) or TKA (n = 40). Medial compartmental knee OA patients considered for HTO were randomized to KJD (n = 23; KJD_HTO) or HTO (n = 46). Patient-reported outcome measures were assessed over 2 years of follow-up. The radiographic joint space width (JSW) was measured yearly. In the KJD groups, serum-PIIANP and urinary-CTXII levels were measured as collagen type-II synthesis and breakdown markers. It was hypothesized that there was no clinically important difference in the primary outcome, the total WOMAC, when comparing KJD with HTO and with TKA.

Results: Both trials were completed, with 114 patients (19 KJD_TKA; 34 TKA; 20 KJD_HTO; 41 HTO) available for 2-year analyses. At 2 years, the total WOMAC score (KJDTKA: +30.4 [95% CI 23.0-37.9] points; TKA: +42.4 [95% CI 38.1-46.8]; KJDHTO: +21.6 [95% CI 13.8-29.4]; HTO: +29.2 [95% CI 23.6-34.8]; all: P < 0.05) and radiographic minimum JSW (KJDTKA: +0.9 [95% CI 0.2-1.6] mm; KJDHTO: +0.9 [95% CI 0.5-1.4]; HTO: +0.6 [95% CI 0.3-0.9]; all: P < 0.05) were still increased for all groups. The net collagen type-II synthesis 2 years after KJD was increased (P < 0.05). Half of KJD patients experienced pin tract infections, successfully treated with oral antibiotics.

Conclusions: Sustained improvement of clinical benefit and (hyaline) cartilage thickness increase after KJD is demonstrated. KJD was clinically noninferior to HTO and TKA in the primary outcome.

Introduction: Knee joint distraction (KJD) is a surgical technique for treatment of severe knee osteoarthritis at a relatively young age. In the absence of devices intended for KJD, this procedure has only been performed with devices with another intended use. In collaboration with patients, clinicians and medical device experts, a dedicated distraction (DD) device intended for KJD was developed.

Objectives: To compare user-friendliness between the new DD device and a previously used concept distraction (CD) device.

Methods: Patients were treated with either of the devices (n = 22 versus n = 22). The intervention duration and treatment complications were registered. After treatment, patients filled out a questionnaire about user-friendliness of the device during treatment, containing questions on difficulties performing activities regarding clothing, sleeping, pin care, daily activities, mobility, and complications. Results were compared between the 2 groups.

Results: Intervention duration was on average 56 versus 44 minutes (P < .001) for CD and DD device, respectively. Pin tract infections were the most prevalent complication (73% of CD patients vs 55% of DD patients; P = .210). 34 patients filled out the questionnaire (16 CD device vs 18 DD device). User-friendliness was better for the DD device for 6/25 questions (all P < .05) and not different between devices for remaining questions (all P > .1).

Conclusions: The DD device intended for KJD reduces surgery time and improves user-friendliness compared to the CD device. As such, the DD device contributes to implementation of KJD treatment in regular care.

Objective: Knee joint distraction (KJD), a joint-preserving surgery for severe osteoarthritis (OA), provides clinical and structural improvement and postpones the need for total knee arthroplasty (TKA). This study evaluates 9-year treatment outcome and identifies characteristics predicting long-term treatment success.

Design: Patients with severe tibiofemoral OA (n = 20; age<60 years) indicated for TKA were treated with KJD. Questionnaires, radiographs, and magnetic resonance imaging (MRI) were used for evaluation. Survival after treatment was analyzed, where ‘failure’ was defined by TKA over time.

Results: 9-year survival was 48%, and 72% for men (compared to 14% for women; P = 0.035) and 73% for those with a first-year minimum joint space width (JSW) increase of >0.5 mm (compared to 0% for <0.05 mm; P = 0.002). Survivors still reported clinical improvement compared to baseline (ΔWOMAC +29.9 points (95%CI 16.9–42.9; P = 0.001), ΔVAS −46.8 mm (−31.6–61.9; P < 0.001)). Surprisingly, patients getting TKA years after KJD still reported clinical improvement although less pronounced (ΔWOMAC +20.5 points (−1.8—42.8; P = 0.067), ΔVAS −25.4 mm (−3.2–47.7; P = 0.030)). Survivors showed long-lasting minimum JSW increase (baseline 0.3 mm (IQR 1.9), follow-up 1.3 mm (2.5); P = 0.017) while ‘failures’ did not (baseline 0.4 mm (1.8), follow-up 0.2 mm (1.5); P = 0.161). First-year minimum JSW on radiographs and cartilage thickness increase on MRI predict 9-year survival (HR 0.05 and 0.12, respectively; both P < 0.026). Male gender was associated with survival (HR 0.24; P = 0.050).

Conclusions: KJD shows long-lasting clinical and structural improvement. In addition to a greater survival rate for males (>two out of three), the initial cartilage repair activity appears to be important for long-term clinical success.

Objective: In end-stage knee osteoarthritis, total knee arthroplasty (TKA) may finally become inevitable. At a relatively young age, this comes with the risk of future revision surgery. Therefore, in these cases, joint preserving surgery such as knee joint distraction (KJD) is preferred. Here we present 5-year follow-up data of KJD.

Design: Patients ( n = 20; age <60 years) with conservative therapy resistant tibiofemoral osteoarthritis considered for TKA were treated. Clinical evaluation was performed by questionnaires. Change in cartilage thickness was quantified on radiographs and magnetic resonance images (MRI). The 5-year changes after KJD were evaluated and compared with the natural progression of osteoarthritis using Osteoarthritis Initiative data.

Results: Five-years posttreatment, patients still reported clinical improvement from baseline: ΔWOMAC (Western Ontario and McMaster Universities Arthritis Index) +21.1 points (95% CI +8.9 to +33.3; P = 0.002), ΔVAS (visual analogue scale score) pain -27.6 mm (95%CI -13.3 to -42.0; P < 0.001), and minimum radiographic joint space width (JSW) of the most affected compartment (MAC) remained increased as well: Δ +0.43 mm (95% CI +0.02 to +0.84; P = 0.040). Improvement of mean JSW (x-ray) and mean cartilage thickness (MRI) of the MAC, were not statistically different from baseline anymore (Δ +0.26 mm; P = 0.370, and Δ +0.23 mm; P = 0.177). Multivariable linear regression analysis indicated that KJD treatment was associated with significantly less progression in mean and min JSW (x-ray) and mean cartilage thickness (MRI) compared with natural progression (all Ps <0.001).

Conclusions: KJD treatment results in prolonged clinical benefit, potentially explained by an initial boost of cartilaginous tissue repair that provides a long-term tissue structure benefit as compared to natural progression. Level of evidence, II.

Objective: In end-stage knee osteoarthritis the treatment of choice is total knee arthroplasty (TKA). An alternative treatment is knee joint distraction (KJD), suggested to postpone TKA. Several studies reported significant and prolonged clinical improvement of KJD. To make an appropriate decision regarding the position of this treatment, a cost-effectiveness and cost-utility analysis from healthcare perspective for different age and gender categories was performed.

Methods: A treatment strategy starting with TKA and a strategy starting with KJD for patients of different age and gender was simulated. To extrapolate outcomes to long-term health and economic outcomes a Markov (Health state) model was used. The number of surgeries, QALYs, and treatment costs per strategy were calculated. Costs-effectiveness is expressed using the cost-effectiveness plane and cost-effectiveness acceptability curves.

Results: Starting with KJD the number of knee replacing procedures could be reduced, most clearly in the younger age categories; especially revision surgery. This resulted in the KJD strategy being dominant (more effective with cost-savings) in about 80% of simulations (with only inferiority in about 1%) in these age categories when compared to TKA. At a willingness to pay of 20.000 Euro per QALY gained, the probability of starting with KJD to be cost-effective compared to starting with a TKA was already found to be over 75% for all age categories and over 90-95% for the younger age categories.

Conclusion: A treatment strategy starting with knee joint distraction for knee osteoarthritis has a large potential for being a cost-effective intervention, especially for the relatively young patient.

Objectives: Knee joint distraction (KJD) has been associated with clinical and structural improvement and SF marker changes. The current objective was to analyse radiographic changes after KJD using an automatic artificial intelligence-based measurement method and relate these to clinical outcome and SF markers.

Methods: Twenty knee osteoarthritis patients were treated with KJD in regular care. Radiographs and WOMAC were collected before and ∼1 year post-treatment. SF was aspirated before, during and after treatment; biomarker levels were assessed by immunoassay. Radiographs were analysed to obtain compartmental minimum and standardized joint space width (JSW), Kellgren-Lawrence (KL) grades, compartmental joint space narrowing (JSN) scores, and osteophytosis and sclerosis scores. Results were analysed for the most affected compartment (MAC) and least affected compartment. Radiographic changes were analysed using the Wilcoxon signed rank test for categorical and paired t-test for continuous variables. Linear regression was used to calculate associations between changes in JSW, WOMAC pain and SF markers.

Results: Sixteen patients could be evaluated. JSW, KL and JSN improved in around half of the patients, significant only for MAC JSW (P < 0.05). MAC JSW change was positively associated with WOMAC pain change (P < 0.04). Greater monocyte chemoattractant protein 1 (MCP-1) and lower TGFβ-1 increases were significantly associated with changes in MAC JSW (P < 0.05). MCP-1 changes were positively associated with WOMAC pain changes (P < 0.05).

Conclusion: Automatic radiographic measurements show improved joint structure in most patients after KJD in regular care. MAC JSW increased significantly and was associated with SF biomarker level changes and even with improvements in pain as experienced by these patients.

Objectives: Knee joint distraction (KJD) has been shown to result in long-term clinical improvement and short-term cartilage restoration in young OA patients. The objective of the current study was to evaluate MRI cartilage thickness up to 10 years after KJD treatment, using a 3D surface-based approach.

Methods: Twenty end-stage knee OA patients were treated with KJD. MRI scans (1.5 T) were performed before and at 1, 2, 5, 7, and 10 years after treatment. Tibia and femur cartilage segmentation and registration to a canonical surface were performed semi-automatically. Statistical parametric mapping with linear mixed models was used to analyse whole-joint changes. The influence of baseline patient characteristics was analysed with statistical parametric mapping using linear regression. Relevant weight-bearing parts of the femur were selected to obtain the average cartilage thickness in the femur and tibia of the most- (MAC) and least-affected compartment. These compartmental changes over time were analysed using repeated measures ANOVA; missing data was imputed. In all cases, P <0.05 was considered statistically significant.

Results: One and 2 years post-treatment, cartilage in the MAC weight-bearing region was significantly thicker than pre-treatment, gradually thinning after 5 years, but still increased at 10 years post-treatment. Long-term results showed that areas in the least-affected compartment were significantly thicker than pre-treatment. Male sex and more severe OA at baseline somewhat predicted shorter-term benefit (P >0.05). Compartmental analyses showed significant short- and long-term thickness increase in the tibia and femur MAC (all P <0.05).

Conclusion: KJD results in significant short- and long-term cartilage regeneration, up to 10 years post-treatment.