The KineSpring load absorber implant: rationale, design and biomechanical characterization

Improved 2-Year Freedom from Arthroplasty in Patients with High-Risk SIFK Scores and Medial Knee Osteoarthritis Treated with an Implantable Shock Absorber versus Non-Operative Care

OBJECTIVE

Subchondral insufficiency fracture of the knee (SIFK) is associated with high rates of osteoarthritis (OA) and arthroplasty. The implantable shock absorber (ISA) is an extra-capsular implant that unloads the medial knee compartment. This study compared the 2-year freedom from arthroplasty rates in subjects with medial knee OA and SIFK when treated with an ISA versus a matched cohort of patients treated non-surgically.

DESIGN

This retrospective case-control study compared 2-year conversion rates to arthroplasty in SIFK score-, age-, and body mass index (BMI)-matched control subjects without prior surgical history with ISA-implanted subjects from an ongoing prospective study. Baseline and final radiographs, and MRIs were reviewed for evaluation of meniscus or ligament injuries, insufficiency fractures, and subchondral edema. Kaplan-Meier analysis assessed survival.

RESULTS

Forty-two patients (21 Control: 21 ISA), mean age = 52.3 ± 8.7 years, BMI = 29.5 ± 3.9 kg/m2, 40% female were evaluated. Both ISA and Control arms had the same numbers of low (n = 4), medium (n = 11), and high-risk (n = 6) SIFK scores. One- and 2-year freedom-from-arthroplasty rates were both 100% for ISA subjects, and 76% and 55%, respectively, for Controls (P = 0.001 for cross-group comparison). Control knees with low, medium, and high-risk SIFK scores had respective 1- and 2-year survival rates of 100% and 100%, 90% and 68% (P = 0.07 vs. ISA), and 33% and 0% (P = 0.002 vs. ISA).

CONCLUSIONS

ISA intervention was strongly associated with avoidance of arthroplasty at a minimum 2 years, especially in patients with high-risk SIFK scores. SIFK severity scoring predicted relative risk of conversion to arthroplasty through at least 2 years in non-surgically treated subjects.

Two-year clinical results of a novel load redistribution device for the treatment of medial knee OA

PURPOSE

A potential method to relieve the pain from medial osteoarthritis of the knee is to offload the medial compartment. The Latella^™ Knee Implant is a novel device designed to offload the medial compartment. The objective of the Cotera-1 study was to evaluate the preliminary safety and feasibility of the Latella implant to treat patients with medial OA of the knee, by a 2-year follow-up of a prospective multicenter feasibility study (Cotera-1) performed in the Netherlands and UK METHODS: In this first-in-man study, 11 participants received the Latella implant and were followed for 2 years, documenting physician assessment, Patient-Reported Outcome (PRO) scoring (KOOS, IKDC, Kujala, SF-36); Patient Global Assessment (PGA), radiographic analysis and MRI analysis, complications, reoperation rate and hip-knee-ankle axis.

RESULTS

The Latella Knee Implant system proved to be well tolerated and demonstrated a low-risk safety profile up to 24 months post-treatment. A responder analysis was performed of the subjects who still had the Latella implanted at 24-month time point (n = 9). Based on a MCID of eight for KOOS pain sub-scale, 78% of the subjects at the 24 month time point would be considered as responders. Similarly, based on improvement in the medial knee pain compared to baseline using the NRS scale of 1-10, 89% of the subjects at the 24-month time point would be considered as responders. Two patients were revised during follow-up: one for arthrofibrosis and one converted to TKA for progression of OA.

CONCLUSIONS

The early clinical experience with the Latella Knee Implant in this pilot feasibility study has been encouraging. It appears to be a safe implant with possible effect on medial OA. Additional studies need to be performed to assess the safety and efficacy of the procedure in a larger patient population.

LEVEL OF EVIDENCE

II.

Two-Year Results of the PHANTOM High Flex Trial: A Single-Arm Study on the Atlas Unicompartmental Knee System Load Absorber in Patients With Medial Compartment Osteoarthritis of the Knee

The Atlas Knee System was designed to fill the gap between no longer effective conservative treatments and more invasive surgery for young patients with medial knee osteoarthritis (OA). This article reports on the 2-year results of a single-arm study of 26 subjects who previously reported favorable clinical outcomes 1 year post implantation. Western Ontario and McMaster Universities Osteoarthritis Index pain and function scores improved by a clinically meaningful amount relative to baseline, and subjects had a return to normal range of motion. This study confirmed that the benefit of a joint unloading device in the management of young patients with medial knee OA is maintained over 2 years. This trial was registered with ClinicalTrials.gov (NCT02711254).

Surgical interventions for symptomatic mild to moderate knee osteoarthritis

BACKGROUND

Osteoarthritis affecting the knee is common and represents a continuum of disease from early cartilage thinning to full-thickness cartilage loss, bony erosion, and deformity. Many studies do not stratify their results based on the severity of the disease at baseline or recruitment.

OBJECTIVES

To assess the benefits and harms of surgical intervention for the management of symptomatic mild to moderate knee osteoarthritis defined as knee pain and radiographic evidence of non-end stage osteoarthritis (Kellgren-Lawrence grade 1, 2, 3 or equivalent on MRI/arthroscopy). Outcomes of interest included pain, function, radiographic progression, quality of life, short-term serious adverse events, re-operation rates and withdrawals due to adverse events.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and Embase up to May 2018. We also conducted searches of ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform for ongoing trials. Authors of trials were contacted if some but not all their participants appeared to fit our inclusion criteria.

SELECTION CRITERIA

We included randomised controlled trials that compared surgery to non-surgical interventions (including sham and placebo control groups, exercise or physiotherapy, and analgesic or other medication), injectable therapies, and trials that compared one type of surgical intervention to another surgical intervention in people with symptomatic mild to moderate knee osteoarthritis.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials and extracted data using standardised forms. We analysed the quality of evidence using the GRADE (Grades of Recommendation, Assessment, Development and Evaluation) approach.

MAIN RESULTS

A total of five studies involving 566 participants were identified as eligible for this review. Single studies compared arthroscopic partial meniscectomy to physical therapy (320 participants), arthroscopic surgery (debridement ± synovectomy ± chondroplasty) to closed needle joint lavage with saline (32 participants) and high tibial osteotomy surgery to knee joint distraction surgery (62 participants). Two studies (152 participants) compared arthroscopic surgery (washout ± debridement; debridement) to a hyaluronic acid injection. Only one study was at low risk of selection bias, and due to the difficulty of blinding participants to their treatment, all studies were at risk of performance and detection bias.Reporting of results in this summary has been restricted to the primary comparison: surgical intervention versus non-surgical intervention.A single study, included 320 participants with symptoms consistent with meniscal tear. All subjects had the meniscal tear confirmed on knee MRI and radiographic evidence of mild to moderate osteoarthritis (osteophytes, cartilage defect or joint space narrowing). Patients with severe osteoarthritis (KL grade 4) were excluded. The study compared arthroscopic partial meniscectomy and physical therapy to physical therapy alone (a six-week individualised progressive home exercise program). This study was at low risk of selection bias and outcome reporting biases, but was susceptible to performance and detection biases. A high rate of cross-over (30.2%) occurred from the physical therapy group to the arthroscopic group.Low-quality evidence suggests there may be little difference in pain and function at 12 months follow-up in people who have arthroscopic partial meniscectomy and those who have physical therapy. Evidence was downgraded to low quality due to risk of bias and imprecision.Mean pain was 19.3 points on a 0 to 100 point KOOS pain scale with physical therapy at 12 months follow-up and was 0.2 points better with surgery (95% confidence interval (CI) 4.05 better to 3.65 points worse with surgery, an absolute improvement of 0.2% (95% CI 4% better to 4% worse) and relative improvement 0.4% (95% CI 9% better to 8% worse) (low quality evidence). Mean function was 14.5 on a 0 to 100 point KOOS function scale with physical therapy at 12 months follow-up and 0.8 points better with surgery (95% CI 4.3 better to 2.7 worse); 0.8% absolute improvement (95% CI 4% better to 3% worse) and 2.1% relative improvement (95% CI 11% better to 7% worse) (low quality evidence).Radiographic structural osteoarthritis progression and quality of life outcomes were not reported.Due to very low quality evidence, we are uncertain if surgery is associated with an increased risk of serious adverse events, incidence of total knee replacement or withdrawal rates. Evidence was downgraded twice due to very low event rates, and once for risk of bias.At 12 months, the surgery group had a total of three serious adverse events including fatal pulmonary embolism, myocardial infarction and hypoxaemia. The physical therapy alone group had two serious adverse events including sudden death and stroke (Peto OR 1.58, 95% CI 0.27 to 9.21); 1% more events with surgery (95% CI 2% less to 3% more) and 58% relative change (95% CI 73% less to 821% more). One participant in each group withdrew due to adverse events.Two of 164 participants (1.2%) in the physical therapy group and three of 156 in the surgery group underwent conversion to total knee replacement within 12 months (Peto OR 1.76, 95% CI 0.43 to 7.13); 1% more events with surgery (95% CI 2% less to 5% more); 76% relative change (95% CI 57% less to 613% more).

AUTHORS' CONCLUSIONS

The review found no placebo-or sham-controlled trials of surgery in participants with symptomatic mild to moderate knee osteoarthritis. There was low quality evidence that there may be no evidence of a difference between arthroscopic partial meniscectomy surgery and a home exercise program for the treatment of this condition. Similarly, low-quality evidence from a few small trials indicates there may not be any benefit of arthroscopic surgery over other non-surgical treatments including saline irrigation and hyaluronic acid injection, or one type of surgery over another. We are uncertain of the risk of adverse events or of progressing to total knee replacement due to very small event rates. Thus, there is uncertainty around the current evidence to support or oppose the use of surgery in mild to moderate knee osteoarthritis. As no benefit has been demonstrated from the low quality trials included in this review, it is possible that future higher quality trials for these surgical interventions may not contradict these results.

High tibial osteotomy increases patellofemoral pressure if adverted proximal, while open-wedge HTO with distal biplanar osteotomy discharges the patellofemoral joint: different open-wedge high tibial osteotomies compared to an extra-articular unloading device

PURPOSE

Valgus high tibial osteotomy (HTO) and a recently introduced extra-articular absorber have been shown to efficiently unload the medial compartment of the knee. However, only little is known about the influence of these treatment modalities on biomechanics of the patellofemoral joint. The purpose of this study was to investigate and compare the impact of different HTO techniques and implantation of an extra-articular absorber on patellofemoral contact forces.

METHODS

Fourteen fresh frozen cadaveric knees were tested in a specially designed knee simulator that allowed simulation of isokinetic flexion-extension motions under physiological loading. Mean contact pressure (ACP) and peak contact pressure (PCP) of the patellofemoral joint was measured continuously between 0° and 120° of knee flexion using a pressure sensitive film in the following conditions: native, after biplanar medial open-wedge HTO with 5° and 10° correction angle performing an ascending frontal osteotomy of the tibial tuberosity, and after implantation of an extra-articular absorber system (KineSpring®). Including a second testing cycle with a biplanar medial open-wedge HTO with 5° and 10° correction angle performing descending frontal osteotomy of the tibial tuberosity. Values after each procedure were compared to the corresponding values of the native knee.

RESULTS

Biplanar proximal osteotomy leaded to a significant increase of retropatellar compartment area contact pressure compared to the first untreated test cycle (Δ 0.04 ± 0.01 MPa, p = 0.04). Similar results were observed measuring peak contact pressure (Δ 1.41 ± 0.15 MPa, p = 0.03). With greater correction angle 5°, respectively, 10° peak and contact pressure increased accordingly. In contrast, the biplanar distal osteotomy group showed significant decrease of pressure values (p = 0.004). The extracapsular, extra-articular absorber had no significant influence on pressure levels in the patellofemoral joint.

CONCLUSION

HTO with a proximal biplanar osteotomy of the tuberositas tibia significantly increased patellofemoral pressure conditions depending on the correction angle. In contrast a distally directed biplanar osteotomy diminished these effects while implantation of an extracapsular, extra-articular absorber had no influence on the patellofemoral compartment at all. Consequently, patients with varus alignment with additional retropatellar chondropathia should be treated with a distally adverted osteotomy to avoid further undesirable pressure elevation in the patellofemoral joint.

A Case Report of the Successful Conversion of One of the Longest Standing KineSpring Joint Unloading Systems

Introduction

We present the case of a successful conversion of a KineSpring joint unloading system to a total knee replacement. This is, to the best of our knowledge, the so far longest surviving implant in Germany that has been successfully converted.

Case Report

The patient is a 75-year-old woman who presented to clinic with problems of her left knee. She had a KineSpring joint unloading system implanted in March 2011 for severe medial osteoarthritis of her left knee that was unresponsive to maximal conservative treatment. After nearly 7 pain-free years, we successfully converted the KineSpring joint unloading system into a total knee replacement (Vega, Aesculap, Germany).

Conclusion

The KineSpring joint unloading system is possible treatment option for younger patients with mild-to-moderate osteoarthritis of the knee reluctant to total knee replacement, without compromising further surgical options.

Comparison of the efficiency of an extra-articular absorber system and high tibial osteotomy for unloading the medial knee compartment: an in vitro study

PURPOSE

The unloading effect of an extra-articular absorber system on the knee joint medial compartment was compared with high tibial osteotomy (HTO) under physiological conditions in vitro.

METHODS

Seven fresh-frozen cadaveric knees were used to test isokinetic flexion-extension motions under physiological loading using a biomechanical knee simulator. Tibiofemoral area contact and peak contact pressures were measured using pressure-sensitive film in the untreated medial compartment. Pressures were measured after KineSpring System implantation and HTO (5° and 10° correction angles) performed with an angular-stable internal fixator (Tomofix).

RESULTS

Implantation of the unloading device resulted in significantly decreased medial compartment area contact pressure (Δ0.02 ± 0.01 MPa, p = 0.001) and peak contact pressure (Δ0.3 ± 0.1 MPa, p = 0.001) compared with the first test cycle results in the untreated knee. HTO significantly decreased the pressure (p = 0.001). Compared with the first test cycle, HTO (5° correction angle) decreased the mean contact pressure by Δ0.03 ± 0.01 MPa and peak contact pressure by Δ0.3 ± 0.01 MPa. With a 10° correction angle, HTO decreased contact pressure by Δ0.04 ± 0.02 MPa and peak contact pressure by Δ0.4 ± 0.1 MPa compared with that at the 5° correction angle.

CONCLUSION

Implantation of an extra-capsular unloading device resulted in a significant unloading effect on the medial compartment comparable to that achieved with HTO at 5° and 10° correction angles. Thus, implantation of an extra-articular, extra-capsular absorber could become the method of choice when treating patients with unicompartmental osteoarthritis that cannot be adequately treated by HTO because of their straight-leg axis.

Severe metallosis and elevated chromium in serum following implantation of the joint unloading implant system

In recent years, the minimally invasive joint-preserving implant system has been developed. The main goal of this device is to unload the medial knee compartment without affecting the lateral compartment. The current authors describe a severe metallosis and elevated chromium in serum following implantation of the joint unloading implant system of a 50-year-old male patient, presented to our hospital 3 years after implantation of a KineSpring System into his left knee due to unicompartmental medial osteoarthritis (OA) in an external hospital. Radiographs showed radiological signs for loosening of the screws in the tibia and a progressive OA on the medial and patellofemoral compartments. Revision surgery with removing of the unloading device was performed at our hospital. The intraoperative situs presented a severe metallosis around the device. Five days after revision surgery, the laboratory parameters revealed an elevated value for chromium in serum, while nickel and cobalt values in serum were normal. Reliable clinical data about the long-term results of the KineSpring System is desperately needed. Further studies are warranted to work out the effects of cobalt and chromium levels and further side effects following the implantation of the extra-articular absorber system.

Feasibility of the Atlas Unicompartmental Knee System Load Absorber in Improving Pain Relief and Function in Patients Needing Unloading of the Medial Compartment of the Knee: 1-Year Follow-Up of a Prospective, Multicenter, Single-Arm Pilot Study (PHANTOM High Flex Trial)

In young patients with medial knee osteoarthritis (OA), surgical intervention may not be desirable due to preferences to avoid bone cutting procedures, return to high activity levels, and prolong implant survival. The Atlas Knee System was designed to fill the gap between ineffective conservative treatments and invasive surgery. This single-arm study included 26 patients, aged 25 to 65 years, who completed 12 months of follow-up. All dimensions of the Knee injury and Osteoarthritis Outcome Score (KOOS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Knee Society Score significantly improved from baseline to 12 months. About 96.2% and 92.3% of patients experienced a ⩾20% improvement in their KOOS pain and WOMAC pain scores, respectively, at 12 months. This study highlights the potential benefit of a joint unloading device in the management of young patients with medial knee OA. The trial is still ongoing and another analysis is planned at 24 months.

Patient Preferences Regarding Surgical Interventions for Knee Osteoarthritis

Surgical interventions for knee osteoarthritis (OA) have markedly different procedure attributes and may have dramatic differences in patient desirability. A total of 323 patients with knee OA were included in a dual response, choice-based conjoint analysis to identify the relative preference of 9 different procedure attributes. A model was also developed to simulate how patients might respond if presented with the real-world knee OA procedures, based on conservative assumptions regarding their attributes. The “amount of cutting and removal of the existing bone” required for a procedure had the highest preference score, indicating that these patients considered it the most important attribute. More specifically, a procedure that requires the least amount of bone cutting or removal would be expected to be the most preferred surgical alternative. The model also suggested that patients who are younger and report the highest pain levels and greatest functional limitations would be more likely to opt for surgical intervention.

A Novel Implant System for Unloading the Medial Compartment of the Knee by Lateral Displacement of the Iliotibial Band

Background:

Medial knee osteoarthritis (OA) typically occurs with excessive mechanical load within the medial compartment, resulting in degeneration of the articular cartilage.

Purpose:

A novel extracapsular implant (Latella Knee Implant) has been developed to unload the medial compartment of the knee. The implant displaces the iliotibial band (ITB) over the lateral femoral condyle, thereby increasing its effective moment arm, resulting in a transfer of load from the medial compartment to the lateral compartment of the knee. A cadaveric study was performed to evaluate the effect of altering the moment arm of the ITB on knee biomechanics.

Study Design:

Controlled laboratory study.

Methods:

A 6-degrees-of-freedom robotic testing system was utilized to measure medial and lateral compartment loads in 8 fresh-frozen cadaveric knees at various ITB loads and knee flexion angles. Measurements were made with and without the implant in place. The system measured the compartment forces at flexion angles between 0° and 30° under 3 simulated loading conditions (300 N quadriceps, 100 N hamstrings, and [1] 0 N ITB, [2] 50 N ITB, [3] 100 N ITB).

Results:

Lateral displacement of the ITB between 15 and 20 mm resulted in medial compartment unloading between 34% and 65%.

Conclusion:

Unloading the medial compartment with this novel implant has the potential to address the treatment gap for patients with medial knee OA.

Clinical Relevance:

Currently, there exists a treatment gap for patients with medial compartment OA who have exhausted conservative management but whose disease and symptoms do not warrant more invasive surgical procedures. An extracapsular implant to unload the medial compartment could fill this treatment gap by providing patients and surgeons with a less invasive option for early to mid-stage OA. Unloading the medial compartment may alleviate pain and improve function, allowing patients with early-stage medial OA to remain active longer prior to considering more invasive options such as arthroplasty.

Device-length changes and implant function following surgical implantation of the KineSpring in cadaver knees

Introduction

The KineSpring implant system has been shown to provide load reductions at the medial compartment of the knee, and has demonstrated clinical success in reducing pain and increasing function in patients with medial knee osteoarthritis. These results depend on the ability of the KineSpring to rotate, lengthen, and shorten to accommodate knee motions, and in response to knee position and loading.

Purpose

The present study was undertaken to determine length changes of the implanted KineSpring in response to a range of knee positions, external knee loads, and placements by different orthopedic surgeons.

Materials and methods

KineSpring system components were implanted in ten cadaver leg specimens by ten orthopedic surgeons, and absorber-length changes were measured under combined loading and in different positions of the knee.

Results and conclusion

Spring compression consistent with knee-load reduction, and device lengthening and shortening to accommodate knee loads and motions were seen. These confirm the functionality of the KineSpring when implanted medially to the knee.

Joint unloading implant modifies subchondral bone trabecular structure in medial knee osteoarthritis: 2-year outcomes of a pilot study using fractal signature analysis

Background

Knee osteoarthritis (OA) is largely attributable to chronic excessive and aberrant joint loading. The purpose of this pilot study was to quantify radiographic changes in subchondral bone after treatment with a minimally invasive joint unloading implant (KineSpring^® Knee Implant System).

Methods

Nine patients with unilateral medial knee OA resistant to nonsurgical therapy were treated with the KineSpring System and followed for 2 years. Main outcomes included Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain, function, and stiffness subscores and independent core laboratory determinations of joint space width and fractal signature of the tibial cortex.

Results

WOMAC scores, on average, improved by 92% for pain, 91% for function, and 79% for stiffness over the 2-year follow-up period. Joint space width in the medial compartment of the treated knee significantly increased from 0.9 mm at baseline to 3.1 mm at 2 years; joint space width in the medial compartment of the untreated knee was unchanged. Fractal signatures of the vertically oriented trabeculae in the medial compartment decreased by 2.8% in the treated knee and increased by 2.1% in the untreated knee over 2 years. No statistically significant fractal signature changes were observed in the horizontally oriented trabeculae in the medial compartment or in the horizontal or vertical trabeculae of the lateral compartment in the treated knee.

Conclusion

Preliminary evidence suggests that the KineSpring System may modify knee OA disease progression by increasing joint space width and improving subchondral bone trabecular integrity, thereby reducing pain and improving joint function.

Post-traumatic knee osteoarthritis in the young patient: therapeutic dilemmas and emerging technologies

Traumatic knee injury is common in young adults and strongly contributes to premature development of knee osteoarthritis (OA). Post-traumatic knee OA poses a therapeutic dilemma to the physician, since no known therapy has an acceptable safety profile, effectively relieves joint pain, and enjoys reasonable patient acceptance. Consequently, these young patients will ultimately be faced with the decision to either undergo surgical intervention, despite prosthesis durability concerns, or to continue with ineffective nonsurgical treatment. Emerging therapies, such as biologics, disease-modifying drugs, partial joint resurfacings, and minimally invasive joint-unloading implants are currently being studied to fill this therapeutic void in the young patient with post-traumatic knee OA.

Early knee osteoarthritis management should first address mechanical joint overload

Early knee osteoarthritis poses a therapeutic dilemma to the musculoskeletal clinician. Despite the recent interest in arthroscopic and injectable regenerative therapies intended to repair or restore a focal target such as cartilage, meniscus, or subchondral bone, none have been shown to slow disease progression. A likely cause of these disappointing treatment outcomes is the failure to address chronic and excessive loading of the knee joint. A growing body of evidence suggests that first-line therapies for early knee osteoarthritis should emphasize unloading the knee joint since any potential therapeutic benefit of regenerative therapies will likely be attenuated by excessive mechanical demand at the knee joint. Minimally invasive medical devices such as patient-specific interpositional implants and extracapsular joint unloading implants are currently in development to address this clinical need.

Failed joint unloading implant system in the treatment of medial knee osteoarthritis

In the setting of end-stage osteoarthritis of the knee, total knee arthroplasty is the gold-standard treatment. Recently, a minimally invasive, joint preserving treatment option in the treatment of medial osteoarthritis of the knee has been developed. It is called the KineSpring(®) (Moximed(®) International GmbH, Zurich, Switzerland). The goal of this novel device is to reduce medial compartment loading without significantly affecting the loading of the lateral compartment. In this context, the current authors present a case of device failure using these new implants, which at 7 months post-op necessitated revision surgery with complete removal of the device.

Cost-effectiveness and economic impact of the KineSpring ® Knee Implant System in the treatment for knee osteoarthritis

PURPOSE

To investigate the cost-effectiveness and economic impact of the KineSpring System in the treatment for knee osteoarthritis in Germany.

METHODS

Functional outcome scores of the general German population and knee osteoarthritis (OA) patients under surgical treatments (HTO, UKA and TKA), conservative treatments and treatment with the KineSpring System were used to derive the utility scores for each group. Quality-adjusted life years (QALYs) of each group were estimated using the utility scores. Finally, cost-utility analysis was performed using cost and QALYs data. The economic impact of knee OA in Germany was assessed in terms of annual total direct cost and indirect cost, total diseased population and potential QALYs saved with the KineSpring System.

RESULTS

Assuming the durability of 10 years, the cost-utility ratio of the KineSpring System, surgical treatments and conservative treatments compared to no treatment in 2012 was euro>3,402/QALY, euro 4,899/QALY and euro 9,996/QALY, respectively. With even a lesser durability of 5 years, the cost-utility ratio of the KineSpring System maintained superiority over surgical treatments and conservative treatments (euro 7,327/QALY, euro 9,706/QALY and euro 10,467/QALY, respectively). The KineSpring System is a highly cost-effective alternative for knee osteoarthritis compared with the current accepted cost-effective threshold (willingness to pay) of $50,000 US/QALY gained. Our models suggest KineSpring System, if adapted widely could save up to 2.0 ± 0.07 million QALY assuming it has a 5-year durability and save up to 3.9 ± 0.1 million QALY assuming it has a 10-year durability.

CONCLUSION

An economic advantage for using the KineSpring System over other surgical and conservative treatments in knee OA patients in Germany is suggested by our model. According to currently accepted cost-effectiveness guidelines, the KineSpring Knee Implant System for knee OA is a cost-effective strategy.

The KineSpring(®) Knee Implant System: an implantable joint-unloading prosthesis for treatment of medial knee osteoarthritis

Symptomatic medial compartment knee osteoarthritis (OA) is the leading cause of musculoskeletal pain and disability in adults. Therapies intended to unload the medial knee compartment have yielded unsatisfactory results due to low patient compliance with conservative treatments and high complication rates with surgical options. There is no widely available joint-unloading treatment for medial knee OA that offers clinically important symptom alleviation, low complication risk, and high patient acceptance. The KineSpring^® Knee Implant System (Moximed, Inc, Hayward, CA, USA) is a first-of-its-kind, implantable, extra-articular, extra-capsular prosthesis intended to alleviate knee OA-related symptoms by reducing medial knee compartment loading while overcoming the limitations of traditional joint-unloading therapies. Preclinical and clinical studies have demonstrated excellent prosthesis durability, substantial reductions in medial compartment and total joint loads, and clinically important improvements in OA-related pain and function. The purpose of this report is to describe the KineSpring System, including implant characteristics, principles of operation, indications for use, patient selection criteria, surgical technique, postoperative care, preclinical testing, and clinical experience. The KineSpring System has potential to bridge the gap between ineffective conservative treatments and irreversible surgical interventions for medial compartment knee OA.

Midterm Outcomes and Predictors of Clinical Success With the KineSpring Knee Implant System

The purpose of this study was to (1) evaluate joint pain and function in knee osteoarthritis (OA) patients treated with a joint-sparing, extracapsular implant and (2) identify patient characteristics that influenced clinical outcomes. This study included 99 patients with symptomatic medial knee OA refractory to conservative care who were treated with the KineSpring Knee Implant System and followed for a mean of 17 months (range, 1.5 to 48 months). All devices were successfully implanted and activated with no intraoperative complications. Statistically significant mean improvements of 56%, 50%, and 38% were observed for Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain, Function, and Stiffness scales, respectively (all P < 0.001). Regardless of gender, age group, body mass index classification, or disease severity, all WOMAC domain scores significantly improved during the postoperative follow-up period. WOMAC clinical success rates were 77.8% for Pain, 77.8% for Function, and 68.7% for Stiffness. Neither gender, age group, body mass index classification, nor disease severity predicted clinical success in any WOMAC domain. In conclusion, the KineSpring System yields clinically meaningful improvements in joint pain and function in patients with medial knee OA. Additionally, unlike joint-altering procedures such as knee arthroplasty or high tibial osteotomy, patient characteristics had little association with postoperative clinical outcomes.

Conservative management of symptomatic knee osteoarthritis: a flawed strategy?

Conservative management of medial compartment knee osteoarthritis (OA) is a misleading term used to describe the application of medical, orthotic, and/or rehabilitative therapies exclusive of surgical interventions. The implication of this nomenclature is that these therapies offer satisfactory symptom relief, alter disease progression, and have limited side effects. Unfortunately, conservative therapeutic options possesses few, if any, characteristics of an ideal treatment, namely one that significantly alleviates pain, improves knee function, and reduces medial compartmental loading without adverse side effects. As uncompensated mechanical loading is a primary culprit in the development and progression of knee OA, we propose that the therapeutic perspective of conservative treatment should shift from pharmacological treatments, which have no influence on joint loading, minimal potential to alter joint function, substantial associated risks, and significant financial costs, towards minimally invasive load absorbing therapeutic interventions. A safe and effective minimally invasive medical device specifically engineered for symptomatic relief of medial knee OA by limiting joint contact forces has the potential to reduce the clinical and economic knee OA burden. This review characterizes the current standard of care recommendations for conservative management of medial compartment knee OA with respect to treatment efficacy, risk profile, and economic burden.

Successful two-stage revision of a KineSpring® joint unloading implant: a case study

Few nonsurgical treatment options are available to the patient with debilitating knee osteoarthritis (OA) that is refractory to conservative care. The KineSpring® System joint unloading implant is a unique device that reduces the load carried by the medial compartment of the knee joint by up to 13 kilograms during the stance phase of gait. We report a case of a male patient who underwent implant with the KineSpring System for symptomatic knee OA but subsequently required revision due to local infection. We performed a novel two-stage revision procedure where the absorber unit was removed in the first phase and a new absorber was placed 3 months later after the infection resolved. A key finding of this case was that knee OA pain resolved with the KineSpring System, returned following explant of the absorber unit, and resolved again following implant of the new absorber. Another important aspect of this case was that the femoral and tibial bases of the KineSpring System remained in situ, which simplified each phase of the revision procedure.

Knee Osteoarthritis Treatment with the KineSpring Knee Implant System: A Report of Two Cases

Osteoarthritis (OA) is a leading cause of disability in middle-aged and older adults with the prevalence expected to increase by 40% by 2025. This dramatic projected increase in OA reflects, in large part, the alarming obesity epidemic. Indeed, it is now well understood that abnormal loading across the knee joint due to malalignment and/or excessive weight gain is responsible for accelerating OA progression. Consequently, there is a therapeutic need for alternative knee OA treatments that directly address joint overload to fill the gap between ineffective conservative care and invasive joint-modifying surgical procedures. We describe two cases that presented with bilateral knee OA resistant to conservative treatments, each with one knee previously and unsuccessfully treated with high tibial osteotomy to improve alignment and the contralateral knee successfully treated with a joint-preserving, load-absorbing implant (KineSpring Knee Implant System).

Evaluation of the safety of a novel knee load-bypassing device in a sheep model

BACKGROUND

Unloading treatments for osteoarthritis of the knee, such as valgus braces, have been shown to reduce medial joint-loading and pain. The purpose of this preclinical study was to investigate the tissue response to an extracapsular implantable device (KineSpring System; Moximed, Hayward, California) that is designed to reduce loading across the medial compartment of the knee.

METHODS

Eleven sheep were implanted with the KineSpring System, consisting of bases secured to the medial femoral and tibial cortices with bone screws and also consisting of a joint-spanning load-absorber composed of a piston and spring assembly inside a polymeric sheath. In nine sheep, titanium alloy washers with either an uncoated or a plasma-sprayed titanium-hydroxyapatite (TPS-HA) coated undersurface were fixed with screws to the contralateral femur and tibia to investigate the effects of surface treatment on extracortical bone apposition. The functionality of the KineSpring System was assessed by fluoroscopy, tissue response was determined by gross and microscopic histology, and implant fixation was determined by radiography, microradiography, and histomorphometry at four, twelve, twenty-six, and fifty-two weeks.

RESULTS

The function of the KineSpring System was confirmed in all sheep. Seventeen of eighteen TPS-HA coated bases and thirty-six of thirty-six washers had stable bone fixation; one coated base was loose with evidence of infection. At four weeks, there was an early, expected inflammatory response, but this response resolved by twelve weeks and a pseudosynovial membrane formed around the sheath. Bone apposition increased over time for the TPS-HA coated bases and for uncoated washers (p &lt; 0.05). There was good apposition of the TPS-HA coated washers even at early time points, with no subsequent increase in apposition over time.

CONCLUSIONS

The KineSpring System demonstrated safety in a simulated use model for periods of up to fifty-two weeks. Screws result in stable implant fixation and TPS-HA coating allows for early and long-lasting cortical bone apposition and integration.

CLINICAL RELEVANCE

This implant warrants further investigation as a means of reducing medial compartment loading and pain in patients with osteoarthritis of the knee.

Unload it: the key to the treatment of knee osteoarthritis

Osteoarthritis (OA) of the knee is a major public health problem whose prevalence is expected to grow dramatically commensurate with the aging of the population and increasing rates of obesity. Unfortunately, little progress has been made therapeutically to avert this epidemic. We hypothesize that the lack of effective interventions is due, in large part, to an overemphasis on pharmacotherapy and direct chondral repair. Instead, we propose that research and development efforts be aimed at addressing the aberrant biomechanics that are the primary driver in the progression of knee OA. In particular, technologies that "unload" the joint may reverse the structural damage, which is the cardinal feature of this disease. Re-establishing a favorable local mechanical environment may not only delay the requirement for an invasive joint reconstruction procedure but obviate the need entirely.