Despite the vast quantities of published artificial intelligence (AI) algorithms that target trauma and orthopaedic applications, very few progress to inform clinical practice. One key reason for this is the lack of a clear pathway from development to deployment. In order to assist with this process, we have developed the Clinical Practice Integration of Artificial Intelligence (CPI-AI) framework – a five-stage approach to the clinical practice adoption of AI in the setting of trauma and orthopaedics, based on the IDEAL principles ( Cite this article:
The Te Whatu Ora Southern catchment area covers the largest geographical region in New Zealand (over 62,000 km2) creating logistical challenges in providing timely access to emergency neck of femur (NOF) fracture surgery. Current Australian and New Zealand guidelines recommend that NoF surgery be performed within 48 hours of presentation. The purpose of this study was to compare the outcomes for patients with NoF fractures who present directly to a referral hospital (Southland Hospital) compared to those are transferred from rural peripheral centres. A retrospective cohort study identified 79 patients with NoF who were transferred from rural peripheral centres to a referral hospital for operative management between January 2011 to December 2020. This cohort was matched 1:1 by age and sex to patients with NoF who presently directly to the referral hospital over the same period. The primary outcome was to compare time to surgery between the groups and secondary outcomes were to compare length of hospital stay, complication rates and mortality rates at 30-days and 1-year.Introduction
Methods
Treatment of posterior malleolar (PM) ankle fractures remain controversial. Despite increasing recommendation for small PM fragment fixation, high quality evidence demonstrating improved clinical outcomes over the unfixated PM is limited. We describe the medium-to-long term clinical and radiographical outcomes in younger adult patients with PM ankle fractures managed without PM fragment fixation. A retrospective cohort study of patients aged 18–55 years old admitted under our orthopaedic unit between 1st of April 2009 and 31st of October 2013 with PM ankle fractures was performed. Inclusion criteria were that all patients must mobilise independently pre-trauma, have no pre-existing ankle pathologies, and had satisfactory bimalleolar and syndesmotic stabilisation. Open fractures, talar fractures, calcaneal fractures, pilon fractures, subsequent re-injury and major complications were excluded. All PM fragments were unfixated. Clinical outcomes were evaluated using Foot and Ankle Ability Measure (FAAM) with activities of daily living (ADL) and sports subscale, visual analogue scale (VAS) and patient satisfaction ratings. Osteoarthrosis was assessed using modified Kellgren-Lawrence scale on updated weightbearing ankle radiographs. 61 participants were included. Mean follow-up was 10.26 years. Average PM size was 16.19±7.39%. All participants were evaluated for clinical outcomes, demonstrating good functional outcomes (FAAM-ADL 95.48±7.13; FAAM-Sports 86.39±15.52) and patient satisfaction (86.16±14.42%), with minimal pain (VAS 1.13±1.65). Radiographical outcomes were evaluated in 52 participants, showing no-to-minimal osteoarthrosis in 36/52 (69.23%), mild osteoarthrosis in 14/52 (26.92%) and moderate osteoarthrosis in 2/52 (3.85%). Clinical outcomes were not associated with PM fragment size, post-reduction step-off, dislocation, malleoli fractured or syndesmotic injury. PM step-off and dislocation were associated with worse radiographical osteoarthrosis. Other published medium-to-long term studies reported overall good outcomes, with no differences after small fragment fixation. The unfixated smaller posterior malleolus fragment demonstrated overall satisfactory clinical and radiographical outcomes at 10-year follow-up and may be considered a valid treatment strategy.
Advances in algorithms developed with sensor data from smart phones demonstrates the capacity to passively collect qualitative gait metrics. The purpose of this feasibility study was to assess the recovery of these metrics following joint reconstruction. A secondary data analysis of an ethics approved global, multicenter, prospective longitudinal study evaluating gait quality data before and after primary total knee arthroplasty (TKA, n=476), partial knee arthroplasty (PKA, n=139), and total hip arthroplasty (THA, n=395). A minimum 24 week follow-up was required (mean 45±12, range 24 - 78). Gait bouts and gait quality metrics (walking speed, step length, timing asymmetry, and double support percentage) were collected from a standardized smartphone operating system. Pre- and post-operative values were compared using paired-samples t-tests (p<0.05). A total of 595 females and 415 males with a mean age of 61.9±9.3 years and mean BMI of 30.2±6.1 kg/m2 were reviewed. Walking speeds were lowest at post-operative week two (all, p<.001). Speeds exceeded pre-operative means consistently by week 21 (p=0.015) for PKA, and week 13 (p=0.007) for THA. The average weekly step length was lowest in post-operative week two (all, p<0.001). PKA and THA cases achieved pre-operative step lengths by week seven (p=0.064) and week 9 (p=0.081), respectively. The average weekly gait asymmetry peaked at week two post-operatively (all, p <0.001). Return to pre-operative baseline asymmetry was achieved by week 11 (p=0.371) for TKA, week six (p=0.541) for PKA, and week eight (p=.886) for THA. Double limb support percentages peaked at week two (all, p<0.001) and returned to pre-operative levels by week 24 (p=0.089) for TKA, week 12 (p=0.156) for PKA, and week 10 (p=0.143) for THA. Monitoring gait quality in real-world settings following joint reconstruction using smartphones is feasible, and may provide the advantage of removing the Hawthorne effect related to typical gait assessments and in-clinic observations.
Due to widespread cancellations in elective orthopaedic procedures, the number of patients on waiting list for surgery is rising. We aim to determine and quantify if disparities exist between inpatient and day-case orthopaedic waiting list numbers; we also aim to determine if there is a ‘hidden burden’ that already exists due to reductions in elective secondary care referrals. Retrospective data were collected between 1 April 2020 and 31 December 2020 and compared with the same nine-month period the previous year. Data collected included surgeries performed (day-case vs inpatient), number of patients currently on the orthopaedic waiting list (day-case vs inpatient), and number of new patient referrals from primary care and therapy services.Aims
Methods
The purpose of this study was to demonstrate the feasibility of passively collecting objective data from a commercially available smartphone-based care management platform (sbCMP) and robotic assisted total knee arthroplasty (raTKA). Secondary data analysis was performed using de-identified data from a commercial database that collected metrics from a sbCMP combined with intraoperative data collection from raTKA. Patients were included in this analysis if they underwent unilateral raTKA between July 2020 and February 2021, and were prescribed the sbCMP (n=131). The population consisted of 76 females and 55 males, with a mean age of 64 years (range, 43 – 81). Pre-operative through six-week post-operative data included step counts from the sbCMP, as well as administration of the KOOS JR. Intraoperative data included surgical times, the hip-knee-ankle angle (HKA), and medial and lateral laxity assessments from the robotic assessment. Data are presented using descriptive statistics. Comparisons were performed using a paired samples t-test, or Wilcoxon Signed-rank test, with significance assessed at p<0.05. A minimal detectable change (MDC) in the KOOS JR score was considered ½ standard deviation of the preoperative values.Introduction
Methods
The purpose of this study was to characterize the recovery of physical activity following knee arthroplasty by means of step counts and flight counts (flights of stairs) measured using a smartphone-based care platform. This is a secondary data analysis on the treatment cohort of a multicenter prospective trial evaluating the use of a smartphone-based care platform for primary total and unicondylar joint arthroplasty. Participants in the treatment arm that underwent primary total or unicondylar knee arthroplasty and had at least 3 months of follow-up were included (n=367). Participants were provided the app with an associated smart watch for measuring several different health measures including daily step and flight counts. These measures were monitored preoperatively, and the following postoperative intervals were selected for review: 2–4 days, 1 month, 1.5 month, 3 months and 6 months. The data are presented as mean, standard deviation, median, and interquartile range (IQR). Signed rank tests were used to assess the difference in average of daily step counts over time. As not all patients reported having multiple stairs at home, a separate analysis was also performed on average flights of stairs (n=214). A sub-study was performed to evaluate patients who returned to preoperative levels at 1.5 months (step count) and 3 months (flight count) using an independent samples T test or Fisher's Exact test was to compare demographics between patients that returned to preoperative levels and those that did not.Introduction
Methods
Recent advances in algorithms developed with passively collected sensor data from smart phones and watches demonstrate new, objective, metrics with the capacity to show qualitative gait characteristics. The purpose of this feasibility study was to assess the recovery of gait quality following primary total hip and knee arthroplasty collected using a smartphone-based care platform. A secondary data analysis of an IRB approved multicenter prospective trial evaluating the use of a smartphone-based care platform for primary total knee arthroplasty (TKA, n=88), unicondylar knee arthroplasty (UKA, n=28), and total hip arthroplasty (THA, n=82). Subjects were followed from 6 weeks preoperative to 24 weeks postoperative. The group was comprised of 117 females and 81 males with a mean age of 61.4 and BMI of 30.7. Signals were collected from the participants' smartphones. These signals were used to estimate gait quality according to walking speed, step length, and timing asymmetry. Post-operative measures were compared to preoperative baseline levels using a Signed-Rank test (p<0.05).Introduction
Methods
Patients' perspective and experience is heavily modulated by their understanding of their pre-operative disability along with their overall coping strategy and life philosophy. Given that evidence-based practice is relying on patient-reported outcomes more and more, the orthopaedic community must be diligent in differentiating patients that may have the same objective outcome but vary widely on a patient-reported subjective basis. In clinical practice, patient selection is often a sensitive, experience-based decision process that screens for catastrophization, recognizing that certain patients will not benefit from a simple surgery. It is well appreciated that patient's catastrophization can affect their subjective outcome but there is little reported literature on this abstract concept. The study set out to determine if post-operative outcomes correlated with pre-operative catastrophization scales. This current study set out to look at a cohort of complex consecutive foot and ankle cases and describe the relationship between Patient Catastrophizing Score (PCS) and multiple functional outcomes that are used commonly in foot and ankle specifically (SF-12 & FAOS). The PCS has three subcategory rumination, helplessness and magnification. A single institution undertook recruitment in consecutive patients within three surgeon's practice. In the end, 46 patients were found to be eligible in the study with an average age of 54.72 ± 14.41 years-old, a majority female 30 / 46 (65.22%), a minority employed at the pre-operative visit 19/46 (41%) and with an average BMI of 26.2 ± 5.56. We found that the mental component of the SF12 had a statistically significant negative effect with the rumination score (r=−1.03) (p = 0.01) and the helplessness score (r=−1.05) (0.001). There was no statistically significant effect for the physical component of the SF-12. Looking at the FAOS Pain component, it correlated was significantly with the PCS rumination (Multivariate : r= −7.6 (p=0.002) Univariate: r=−2 (0.03)) and helplessness (Multivariate : r=−6.73 (p=0.01) Univariate: r=−1.5 (p=0.03)). Otherwise the FAOS ADL component showed correlation as well with the PCS rumination (Multivariate: r=−4.67 (p=0.02) Univariate : r=−1.85 (p=0.01)), helplessness (Multivariate r=−5.89 (p = 0.01) Univariate r=−1.81 (p = 0.001)) and total score (Multivariate : r=3.74 (p=0.02) Univariate r=−0.75 (p=0.01)). The FAOS Quality of life component was statistically significant for the rumination score (Univariate r=−11.59) (p < 0.05) and the helplessness score (Univariate r=−9.65) (p = 0.002) also the PCS total (Univariate r=8.54) (p = 0.0003). As layed out in our hypothesis, this study did show an association between an increase patient catastrophizing score pre-operatively and a worse outcome in the following scores: Mental component of SF12, FAOS Pain, FAOS ADL and FAOS Quality of life components. This is an association and no causality can be proven within the limits of this current pilot study, but remains alarming. In elective surgeries, catastrophization should be screened for using the PCS form and potentially modulated pre-operatively with the help of allied health therapist while a patient is on the waitlist.
The traditional method of soft-tissue balancing during TKA is subjective in nature, and stiffness and instability are common indications for revision, suggesting that TKA balancing by subjective assessment is suboptimal. This study examines the intraoperative mediolateral loads measured with a nanosensor-enabled tibial insert trial and the sequential balancing steps used to achieve quantitative balance. Data obtained from a prospective multicenter study was assessed to determine the effect of targeted ligament release on intra-articular loading, and to understand which types of releases are necessary to achieve quantified ligament balance. A group of 129 patients received sensor-assisted TKA, as part of a prospective multicenter study. Medial and lateral loading data were collected pre-release, during any sequential releases, and post-release. All data were collected at 10, 45, and 90 degrees during range of motion testing. Ligament release type, release technique type, and resultant loading were collected.Introduction & Aims
Methods
Up to 60% of total hip arthroplasties (THA) in Asian populations arise from avascular necrosis (AVN), a bone disease that can lead to femoral head collapse. Current diagnostic methods to classify AVN have poor reproducibility and are not reliable in assessing the fracture risk. Femoral heads with an immediate fracture risk should be treated with a THA, conservative treatments are only successful in some cases and cause unnecessary patient suffering if used inappropriately. There is potential to improve the assessment of the fracture risk by using a combination of density-calibrated computed tomographic (QCT) imaging and engineering beam theory. The aim of this study was to validate the novel fracture prediction method against Six femoral heads from six subjects were tested, a subset (n=3) included a hole drilled into the subchondral area of the femoral head via the femoral neck (University of Leeds, ethical approval MEEC13-002). The simulated lesions provided a method to validate the fracture prediction model with respect of AVN. The femoral heads were then modelled by a beam loaded with a single joint contact load. Material properties were assigned to the beam model from QCT-scans by using a density-modulus relationship. The maximum joint loading at which each bone cross-section was likely to fracture was calculated using a strain based failure criterion. Based on the predicted fracture loads, all six femoral heads (validation set) were classified into two groups, high fracture risk and low fracture risk (Figure 1). Beam theory did not allow for an accurate fracture load to be found because of the geometry of the femoral head. Therefore the predicted fracture loads of each of the six femoral heads was compared to the mean fracture load from twelve previously analysed human femoral heads (reference set) without lesions. The six cemented femurs were compression tested until failure. The subjects with a higher fracture risk were identified using both the experimental and beam tool outputs.Introduction
Methods
Avascular necrosis (AVN) of the femoral head (FH) initiates from biological disruptions in the bone and may progress to mechanical failure of the hip. Mechanical and structural properties of AVN bone have not been widely reported, however such understanding is important when designing therapies for AVN. Brown et al.[1] assessed mechanical properties of different regions of AVN FH bone and reported 52% reduction in yield strength and 72% reduction in elastic modulus of necrotic regions when compared to non-necrotic bone. This study aimed to characterise structural and mechanical properties of FH bone with AVN and understand the relationship between lesion volume and associated mechanical properties. Twenty FH specimens from patients undergoing hip arthroplasty for AVN and six non-pathological cadaveric FH controls were collected. Samples were computed tomography scanned and images analysed for percentage lesion volume with respect to FH volume. Samples were further divided for structural and mechanical testing. The mechanical property group were further processed to remove 9mm cylindrical bone plugs from the load bearing and non-load-bearing regions of the FHs. FH and bone plug samples were tested in compression (1mm/min); elastic modulus and yield stress were calculated.INTRODUCTION
METHODS
This study aimed to evaluate the impact on length of hospital stay from dedicated infectious diseases input for orthopaedic infection patients compared to sporadic infection specialist input. We conducted an observational cohort study of 157 adults with orthopaedic infections at a teaching hospital in the UK. The orthopaedic infections included were: osteomyelitis, septic arthritis, infected metalwork and prosthetic joint infections, and adults were aged 18 years or more. Prior to August 2016, advice on orthopaedic infection patients was adhoc with input principally from the on-call infectious diseases registrar and phone calls to microbiology whereas after August 2016 these patients received regular input from dedicated infectious diseases doctor(s). The dedicated input involved bedside reviews, medical management, correct antimicrobial prescribing, managing adverse drug reactions, increased use of outpatient parenteral antimicrobial therapy (OPAT) services especially self-administration of intravenous antibiotics and shared decision-making for treatment failure, whilst remaining under orthopaedic team care. Orthopaedic patients operated on for management of their infection between 29/8/16 and 15/3/17 were prospectively identified and orthopaedic operation records were used to retrospectively identified patients between 29/8/15 and 15/3/16. The length of stay was compared between the 2 groups.Aim
Method
Total knee arthroplasty (TKA) is currently one of the most common elective surgical procedures in the United States. The increase in the proportion of younger patients in receipt of surgery, in concert with a dramatic rise in the incidence of obesity, has contributed to the on-going, exponential increase in the number of arthroplasties performed annually. Despite materials advances for implants, the U.S. revision burden has remained static for the last decade. According to the 2013 CMS MEDPAR file the typical CMS reimbursement falls far short of costs incurred by the hospital, resulting in an average net loss of revenue of $9,539; and over 90% of hospitals lose money for every revision case performed. Today, approximately 5% of all primaries performed will result in an early revision (< 3 years). In order to understand ways with which to mitigate the incidence of early revision due to mechanical complications, a multicentric group of sensor-assisted patients was follow-up out to 3 years. In this study, 278 sensor-assisted patients were followed out to 3 years. The intraoperative devices used in this study contain microsensors and a processing unit. Kinetic and center of load location data are projected, in real-time, to a screen. Because of the wireless nature of the intraoperative sensors, the patella can be reduced, and kinematic data can be evaluated through the range of motion. For each patient, the soft-tissue envelope was balanced to within a mediolateral differential of 15 lbf., through the ROM, as per the suggestion of previously reported literature. The average patient profile indicates: age = 69.7 years, BMI = 30.4, gender distribution = 36% male/64% female. Any adverse event within the 3-year follow-up interval was captured. By 3 years, 1 patient in this population has required revision surgeon due to mechanical complicatons. Overall adverse events included: pain in hip (3), pain in contralateral knee (2), wound drainage (3), DVT (1), death (1), stiffness in operative knee (2), infection (3), global pain (2), back pain (2). Based on the average reported number of early revisions that occur in the U.S. (5% of primaries), it was anticipated for this patient group to require approximately 13 revisions by the 3-year follow-up interval. Using 2013 CMS MEDPAR data, these 13 revisions would have resulted in $124,007 cost-to-hospital. However, only 1 revision (0.4%) was observered, therefore $114,468 in additional costs were spared for the aggregate of participating hospitals. This data suggests that the incorporation of kinetic sensors in TKA may assist the surgeon in achieving soft-tissue balance and thereby avoiding adverse mechanical complications that require surgical intervention.
Total knee arthroplasty (TKA) patients are consistently reported to be less satisfied than total hip arthroplasty (THA) patients. A patient's perception of success of his/her own total knee is dictated by their levels of post-operative pain and function, and many return to follow-up visits with inexplicable pain and stiffness that contradict favorable radiographic results. Several of these chief complaints that contribute to dissatisfaction are associated with soft-tissue imbalance. Therefore, in an effort to thoroughly understand the post-operative impact of soft-tissue balance on satisfaction, a multicenter study was conducted to evaluate the satisfaction outcomes of quantifiably balanced patients. In this study, 102 sensor-assisted patients were followed out to 3 years. The intraoperative devices used in this study project kinetic loading (lbf.) and center of load location data, in real-time, to a screen. Because of the wireless nature of the intraoperative sensors, the patella can be reduced, and kinematic data can be evaluated through the range of motion. The target balance window that was used in this study has been previously reported in literature and includes: 1) a mediolateral differential of 15 lbf., through the ROM, and 2) Sagittal plane stability as determined by a posterior drawer analysis. A robust, face-validated satisfaction survey was administered at 3-year follow-up and included 7 questions with answers on a 5-point Likert scale. At 3 years, post-operatively, 97.2% of this patient group reported being “satisfied” to “very satisfied” with their procedure, in comparison to the 81% average TKA satisfaction reported in literature (df = 11). The comparative literature included annual satisfaction intervals from 1 to 5 years (n = 33,775) which is comparable to the interval reported in this patient group. The sensor-assisted patient group exhibited a 16% increase in the proportion of satisfaction over what is currently reported in the comparative literature (p = 0.001). Despite the success rate of TKA, unfavorable patient-reported satisfaction continues to present a problem for operative recipients and surgeons. Because satisfaction is dependent upon several variables – including pain, function, and activity levels – the satisfaction survey used in this study represents a more accurate account of patient perception than many traditional surveys. It was shown that sensor-balanced TKA patients exhibited a 16% increase in the proportion of those reporting being “satisfied” to “very satisfied”, over the average satisfaction reported in literature. Allowing the surgeon to quantitatively balance the soft-tissue envelope, dynamically, has continued to a significant decrease in the proportion of dissatisfaction.
Osteoarthritis (OA) is a debilitating disease characterised by degradation of articular cartilage and subchondral bone remodeling. Current therapies for early or midstage disease do not regenerate articular cartilage, or fail to integrate the repair tissue with host tissue, and therefore there is great interest in developing biological approaches to cartilage repair. We have shown previously that platelet-rich plasma (PRP) can enhance cartilage tissue formation. PRP is obtained from a patient's own blood, and is an autologous source of many growth factors and other molecules which may aid in healing. This raised the question as to whether PRP could enhance cartilage integration. We hypothesise that PRP will enhance integration of bioengineered cartilage with native cartilage. Chondrocytes were isolated from bovine metacarpal-phalangeal joints, seeded on a porous bone substitute (calcium polyphosphate) and grown in the presence of FBS to form an PRP soaked bioengineered implants, integrated with the host tissue in 73% of samples, whereas control bioengineered implants only integrated in 19% of samples based on macroscopic evaluation (p<0.05). The integration strength, as determined by the normalised maximum force to failure, was significantly increased in the PRP soaked implant group compared to controls (219 +/− 35.4 kPa and 72.0 +/− 28.5 kPa, respectively, p<0.05). This correlated with an increase in glycosaminoglycan and collagen accumulation in the region of integration in the PRP treated implant group, compared to untreated controls after 2 weeks (p<0.05). Immunohistochemical studies revealed that the integration zone was rich in collagen type II and aggrecan. The cells at the zone of integration in the PRP soaked group had a 2.5 fold increase in aggrecan gene expression (p=0.05) and a 3.5 fold increase in matrix metalloproteinase 13 expression (p<0.05) compared to controls. PRP soaked bio-engineered cartilage implants showed improved integration with native cartilage compared to non-treated implants, perhaps due to the increased matrix accumulation and remodeling at the interface. Further evaluation is required to determine if PRP improves integration
The rate of technological innovation in procedural total knee arthroplasty has left little time for critical evaluation of a new technology before the adoption of even newer modalities. With more drastic financial restrictions being placed on operating room spending, orthopaedic surgeons are now required to provide excellent results on a budget. It is integral that both clinical efficacy and cost-effectiveness of these intraoperative technologies be fully understood in order to provide patients with effectual, economically conscious care. The purpose of this qualitative analysis of literature was to evaluate clinical and economic efficacy of the three most prominent technologies currently used in TKA: computer navigation, patient-specific instrumentation, and kinetic sensors. Three hundred and ninety one publications were collected; 100 were included in final qualitative analysis. Criteria for inclusion in the analysis was defined only insofar as that each piece assessed one of the above listed aspects of the three technologies Literature included in the final evaluation contained background information on each respective technology, clinical outcomes, revision rates, and/or cost analyses. All comparisons were conducted in a strictly qualitative manner, and no attempts were made to conduct interstudy statistical analyses due to the high level of variability in methodology and data collected.Introduction
Methods
Instability after total knee arthroplasty (TKA) represents, in excess of, 7% of reasons for implant failure. This mode of failure is correlated with soft-tissue imbalance, and has continued to be problematic despite advances in implant technology. Thus, understanding the options available to execute safe and effective soft-tissue release is critical to mitigating future complications due to instability. This study aimed to use intraoperative sensors to evaluate a multiple needle puncturing technique (MNPT), in comparison with traditional transection-based release, to determine its biomechanical and clinical efficacy. Seventy-five consecutive, cruciate-retaining TKAs were performed, as part of an 8-site multicenter study. All procedures were performed with the use of an intraoperative sensor to ensure quantitative balance, as per previously reported literature. Of the 75-patient cohort, 50 patients were balanced with the MNPT; 20 patients were balanced with traditional transection. All patients were followed out to 1-year, and administered KSS, WOMAC, and satisfaction. Alignment and ROM was captured for all patients, pre-operatively and at the 1-year follow-up interval.Introduction
Methods
Improper soft-tissue balancing can result in postoperative complications after total knee arthroplasty (TKA) and may lead to early revision. A single-use tibial insert trial with embedded sensor technology (VERASENSE from OrthoSensor Inc., Dania Beach, FL) was designed to provide feedback to the surgeon intraoperatively, with the goal to achieve a “well-balanced” knee throughout the range of motion (Roche et al. 2014). The purpose of this study was to quantify the effects of common soft-tissue releases as they related to sensor measured joint reactions and kinematics. Robotic testing was performed using four fresh-frozen cadaveric knee specimens implanted with appropriately sized instrumented trial implants (geometry based on a currently available TKA system). Sensor outputs included the locations and magnitudes of medial and lateral reaction forces. As a measure of tibiofemoral joint kinematics, medial and lateral reaction locations were resolved to femoral anterior-posterior displacement and internal-external tibial rotation (Fig 1.). Laxity style joint loading included discrete applications of ± 100 N A-P, ± 3 N/m I-E and ± 5 N/m varus-valgus (V-V) loads, each applied at 10, 45, and 90° of flexion. All tests included 20 N of compressive force. Laxity tests were performed before and after a specified series of soft-tissue releases, which included complete transection of the posterior cruciate ligament (PCL), superficial medial collateral ligament (sMCL), and the popliteus ligament (Table 1). Sensor outputs were recorded for each quasi-static test. Statistical results were quantified using regression formulas that related sensor outputs (reaction loads and kinematics) as a function of tissue release across all loading conditions. Significance was set for p-values ≤ 0.05.Introduction
Methods
Avascular necrosis of the femoral head (AVN) is associated with collapse of the femoral head and arthritic degeneration of the joint. The combination of an implant inserted into the femoral head that provides mechanical support and bone grafting to promote bone formation may offer a possible joint-preserving solution1. Seventeen such procedures were performed between November 2012 and March 2014 during an IRB approved clinical trial. Thirteen out of 18 patients remained unrevised at a minimum of 12 months; the results of radiographic and histological analysis of four revisions are presented. The investigational device (Figure 1) was developed as a joint preserving treatment for AVN with a clinical grade of IIC or less according to the ARCO grading system2. The device consisted of a braided spherical Nitinol cage with a Titanium / Nitinol orientation feature. It was implanted using fluoroscopic navigation into a spherical cavity cut into the femoral head via an 11mm diameter access tunnel. Once deployed, the implant was filled with a lightly impacted mixture of autologous bone graft and bone marrow soaked Conduit TCP (DePuy CMW, Blackpool, UK). The implant's purpose was to provide mechanical support to the weakened subchondral surface while the bone graft mixture re-integrated with the host bone. The retrieved femoral heads were trimmed to leave approximately 3mm of bone around the implant, dehydrated, embedded in methacrylate resin, sectioned and thinned into 50–70µm coronal slices for histological analysis. The following observations were made (Figure 2): Case 1 (Female, age 70, ARCO IIB, revised after 2 days): The patient was revised for spontaneous sub-trochanteric fracture secondary to osteoporosis. Contact between the native bone and bone graft was observed. Marrow elements and repair tissue were visible within the pores in the graft (Figure 2a). Case 2 (Male, age 67, ARCO IIIC, revised after 82 days): Two wires were broken but retained within the braided structure. A radiolucent gap caused by the presence of fibrous tissue between the graft mixture and native bone was evident suggesting that the implant was unable to prevent progression in this case. Case 3 (Female, age 70, ARCO IIC, revised after 482 days): The cavity penetrated the subchondral surface; at revision the implant was found to have breached the articular cartilage. There was partial separation of the proximal osteonecrotic fragment and no evidence of graft revascularisation or remodelling within the implant. Case 4 (Male, age 42, ARCO IIC, revised after 469 days): There was no indication of bone graft re-integration. Collapse of the necrotic bone and deformation of the implant was diagnosed from 1 year follow-up x-rays. This treatment has preserved the joints of fourteen patients. Of the four revised, two patients had clinical grades or bone quality contra-indicated for the device and three had lesions occupying more than 30% of the femoral head: Improved criteria for patient selection may be required. The device is only partially load-bearing and incapable of stabilising fractures: The radiolucent band associated with fibrous tissue formation may be an early indication of failure.Conclusion
