Introduction. Aseptic loosening is the main reason for total knee arthroplasty (TKA) failure, responsible for more than 25% of the revision procedures, with most of the problems occurring with the tibial component. While early loosening can be attributed to failure of primary fixation, late implant loosening is associated with loss of fixation secondary to bone resorption due to altered physiological load transfer to the tibial bone. Several attempts have been made to investigate these changes in bone load transfer in biomechanical simulations and bone remodeling analyses, which can be useful to provide information on the effect of patient, surgery, or design-related factors. On the other hand, these factors have also been investigated in clinical studies of radiographic changes of bone density following TKA. In this study we made an overview of the knowledge obtained from these clinical studies, which can be used to inform clinical decision making and implant design choices. Methods. A literature search was performed to identify clinical follow-up studies that monitored peri-prosthetic bone changes following TKA. Within these studies, effects of the following parameters on bone density changes were investigated: post-operative time, region of interest, alignment, body weight, systemic osteoporosis, implant design and cementation. Moreover, we investigated the effect of bone density loss on implant survival. Results. A total of 19 studies was included in this overview, with a number of included patients ranging from 12 to 7,760. Most studies used DEXA (n=16), while a few studies performed analyses on calibrated digital radiographs (n=2), or computed tomography (n=1). Postoperative follow-up varied from 9 months to 10 years. Studies consistently report the largest bone density reduction within the first postoperative year. Bone loss is mainly seen in the medial region. This has been attributed to the change in alignment following surgery, during which often the pre-operative varus knee is corrected to a more physiological alignment, resulting in a load shift towards the lateral compartment. Measurements in unoperated contralateral legs were performed in 3 cases, and two studies performed standardized DEXA measurements to provide information on systemic osteoporosis. While on the short term no changes were observed, significant negative correlations have been found between severity of osteoporosis and peri-prosthetic bone density. No clear effects of bodyweight and cementation on bone loss have been identified. Although some studies do find differences between implant types, the variation in the data makes it difficult to draw general conclusions from these findings. Several studies reported no effect of bone loss on implant migration. In another study, a medial collapse was associated with a medial increase in density, suggesting that altered loading and increased stresses are responsible for both bone formation and the overload leading to collapse. Discussion. There are important lessons to be learned from these clinical studies, although generally the large spread in the DEXA data restricts strong conclusions. There is a large variation in used ROI definitions, complicating direct comparisons. Finally, most studies report density changes of well-functioning reconstructions, since only very large studies are able to gather enough failed cases

The demand for revision total knee arthroplasty (TKA) has grown significantly in recent years. The two major fixation methods for stems in revision TKA include cemented and ‘hybrid’ fixation. We explore the optimal fixation method using data from recent, well-designed comparative studies.

We performed a systematic review of comparative studies published within the last 10 years with a minimum follow-up of 24 months. To allow for missing data, a random-effects meta-analysis of all available cases was performed. The odds ratio (OR) for the relevant outcome was calculated with 95% confidence intervals. The effects of small studies were analyzed using a funnel plot, and asymmetry was assessed using Egger's test. The primary outcome measure was all-cause failure. Secondary outcome measures included all-cause revision, aseptic revision and radiographic failure.

There was a significantly lower failure rate for hybrid stems when compared to cemented stems (p = 0.006) (OR 0.61, 95% CI 0.42-0.87). Heterogeneity was 4.3% and insignificant (p = 0.39). There was a trend toward superior hybrid performance for all other outcome measures including all-cause re-revision, aseptic re-revision and radiographic failure.

Recent evidence suggests a significantly lower failure rate for hybrid stems in revision TKA. There is also a trend favoring the use of hybrid stems for all outcome variables assessed in this study. This is the first time a significant difference in outcome has been demonstrated through systematic review of these two modes of stem fixation. We therefore recommend the use, where possible, of hybrid stems in revision TKA.

The purpose of this study was to develop a quality appraisal tool for the assessment of laboratory basic science biomechanical studies.

Materials andScore development comprised of the following phases: item identification/development, item reduction, content/face/criterion validity, weighting, test-retest reliability and internal consistency. For item identification/development, the panel was asked to independently list criteria and factors they considered important for cadaver study and generate items that should be used to appraise cadaver study quality. For content validity, the content validity ratio (CVR) was calculated. The minimum accepted content validity index (CVI) was set to 0.85. For weighting, equal weight for each item was 6.7% [15 items]. Based on these figures the panel was asked to either upscale or downscale the weight for each item ensuring that the final sum for all items was 100%. Face validity was assessed by each panel member using a Likert scale from 1–7. Strong face validity was defined as a mean score of >5. Test-retest reliability was assessed using 10 randomly selected studies. Criterion validity was assessed using the QUACS scale as standard. Internal consistency was assessed using Cronbach's alpha.

Five items reached a CVI of 1 and 10 items a CVI of 0.875. For weighting five items reached a final weight of 10% and ten items 5%. The mean score for face validity was 5.6. Test-retest reliability ranged from 0.78–1.00 with 9 items reaching a perfect score. Criterion validity was 0.76 and considered to be strong. Cronbach's alpha was calculated to be 0.71 indicating acceptable internal consistency.

The new proposed quality score for basic science studies consists of 15 items and has been shown to be reliable, valid and of acceptable internal consistency. It is suggested that this score should be utilised when assessing basic science studies.

This Outcome Studies Software suite has been designed and carried out by Surgeons for Surgeons in order to provide the Orthopaedic Community with a valuable tool devoted to the computerized clinical follow-up of Joint Arthroplasty, named OrthoWave(tm). The development of the OrthoWave(tm) suite, since 1996, has got involved clinical studies coordinators, software engineers, orthopaedic surgeons, and statisticians. One underlying theme regarding Health Care has and always will be constant: the need to understand if our treatments actually work. Providing answers makes not only scientific sense but pragmatic and economic sense as well. In such a way, Evaluation in Joint Arthroplasty has become a master word in the realm of Orthopaedic Surgery, which thus gets many actors involved, be they Surgeons, Scientific Societies, Health Department Authorities, Journal Editors, and Orthopaedic Devices Manufacturer. While bearing in mind that more than a million of Hip and Knee replacements are worldly performed annually and there are thousands of devices and device combinations in use to achieve arthroplasties, these replacement procedures have to be properly evaluated as a very challenging procedure. An outcomes study software needs to allow for easy and user friendly collection of clinical data and related images, while preserving privacy of patients and their personal data. This software must then provide consistent statistical and survivorship analyzes in the very long run. The OrthoWave(tm) software has been widely used worldly, and currently features the on-line Version 6, now available as a web-based secured “cloud computing” computer system. The so called “regular databases” can be linked to additional “scientific databases” and “monitored databases” able to set up together a very consistent and efficient global system. Roughly speaking, OrthoWave addresses (1) data collection of Surgeons themselves, able to self evaluate their surgeries while owning their own data, (2) Local Registries, involving groups of Surgeons, to analyze, report and publish clinical series in the Literature, (3) Brand Registries, for tracking upon large multicenter studies at an early stage any problem that might occur with any given implant, (4) Clinical Affairs Departments in Industry, (5) and finally enables potential automatic links to National and International Joint Registries. This OrthoWave software has thus permitted a “fine tuning” of clinical results, radiographic findings, survival rates and real assessment of quality of life, helping to determine in large databases studies if implant composition or joint replacement features can be associated with decreased need for repeat surgery, and to outline best methodological approaches to the assessment of failures in arthroplasty, in terms of functioning, quality of life and long-term disability. All along these 14 years of continuous use of this OrthoWave software suite, we have tried to help it to be more and more efficient and user friendly. The current on-line web-based version now meets our expectation, and is flexible enough to adapt itself to future needs and better treatments for patients

Aim

To conduct a systematic review of non-rodent animal models (rabbit, pig, dog, goat and sheep) of bone infection. In the future, anti-infective technologies aiming to fight bone infections are depending on evaluation in reliable animal models. Therefore, it is highly relevant to evaluate the scientific quality of existing bone infection models.

Introduction

Achilles Tendon Rupture (ATR) is a prevalent injury in Western society. Much of the recent research has focused on measuring surgical methods and strength regained, rather than practical measures such as Return to Sport (RTS). A large systematic review was published in 2016 setting a benchmark RTS as 80%. The aim of this systematic review was to provide an up-to-date RTS following ATR.

Introduction

Innovations in surgical robotics and navigation have significantly improved implant placement accuracy in total knee arthroplasty (TKA). However, many comparative studies have not been shown to substantially improve revision rates or other clinical outcome scores. We conducted a simulation study based on the reported distribution of patient-specific characteristics and estimated potential effect of coronal plane alignment (CPA) on risk of revision to evaluate the hypothesis that most published study designs in this area have been too underpowered to detect improvements in revision rates.

Background

Aseptic loosening is the leading cause of total knee arthroplasty (TKA) failure in the long term, of which osteolysis from polyethylene wear debris remains a problem that can limit the lifetime of TKA past the second decade. To help speed up design innovations, our goal was to develop a computational framework that could efficiently predict the effect of many sources of variability on TKA wear—including design, surgical, and patient variability.

Use of “CPR” distance has proven clinical utility in stratifying risks of “steep cups” in MOM failures.[1, 4] The CPR indice has been defined as distance between point of intersection of the hip reaction force (Fig. 1: vector-R in contact patch) and closest point on the inner cup rim.[4] However, the CPR indice has limitations. It assumes that, (1) the hip load-vector (R) will be angled 10°-medial in all patients, (2) the contact patch will be same size in all patients, and (3) the contact patch will be invariant with increasing MOM diameter. In contrast it is known from retrieval studies that larger MOM bearings created much larger wear patches.[3] Furthermore, the size of cup wear-patches in MOM bearings can now be estimated with some certainty using simulator wear data.[2] Our objective was to develop an algorithm that would predict (i) contact-patch size for all cup designs and diameters, (ii) determine actual margin of safety (Fig. 1: MOS) for different laterally-inclined cups, and (iii) predict critical test angles for “steep” cup studies in hip simulators.

The ‘CPR-distance’ (Fig. 1) is subtended by the CPA angle, but the true margin of safety is the distance from edge of wear patch to cup rim, indicated here by MOS angle. In this algorithm the wear-patch size (CAP angle) is a key parameter, as derived from MOM wear data (Fig. 2). The CAP angles decrease with increasing MOM diameter, as defined by strong linear trend (R=0.998). The key 2nd parameter is cup inclination angle that juxtaposes the wear-pattern to the cup rim (CCI). For hemispherical cups the critical inclination is given by CCI = 90 – CAP/2, where articulation angle ABA = 180o. The cup bearing-surface is typically reduced < 180o(sub-hemispherical profile, instrumentation groove, rim bevel, etc). These effects are grouped under ‘rim-detail’, as defined by RD = (180-ABA)/2 (Fig. 1). Thus critical inclination any cup is given by CCI = 90o – (CAP/2) – RD = (ABA – CAP)/2. The margin-of-safety (Fig. 1) is then represented by the equation MOS = 100 – (CIA + CAP/2 + RD).

Applicability of the new algorithm can be visualized with a 48mm MOM (cup ABA=160o) run in a standard simulator test (Fig. 3). The algorithm predicts that with cup at 40o inclination there is good margin of safety (11.8o), representing a 5mm distance. This would become much reduced at CIA = 50o, while true edge-wear appears at the 60o test inclination (Fig. 3. EW = −8.2o). For clinical comparison with ‘CPR-distances’, the algorithm shows that positioning the wear patch 10o-medial (Figs. 1, 3) has margin of safety averaging 11.5 mm (MOS) less than was predicted by the CPR indice. While CPR has shown clinical utility, it is believed that compensating for actual size of cup wear-patterns provides a more realistic risk assessment for different MOM diameters in different cup positions. Thus the new algorithm permits accurate depiction of cup wear-patterns for use in both clinical and simulator studies.

Introduction

In vitro studies have shown that low clearance metal-on-metal hip joints have the potential of reducing wear during the running-in phase [1]. However, cementless acetabular cup relies on press fitting into the acetabulum, which can generate non-uniform compressive stresses and non-uniform in vivo cup deformation [2, 3]. This could then lead to equatorial contact, resulting in higher wear and friction for a MoM bearing with low clearance. To benefit from low wear generated by low clearance and at the same time to avoid the potential of head seizure and high frictional torque caused by cup deformation, a deflection compensation acetabular cup (DefCom) has been developed based on the Birmingham Hip Resurfacing (BHR) device. The articulating sphere of the DefCom cup provides a low clearance bearing area, whilst the non-articulating sphere maintains the standard BHR clearance. The aim of this study was to evaluate the wear performance of the novel DefCom hip joint using a hip wear simulator.

Introduction

Many journals require outcome data at 2 years post-operative for the assessment of operative procedures in spinal surgery. This study seeks to clarify the timescale of improvement after surgery to see if a shorter period of assessment will indicate the final outcome.

Our aim was to compare the biomechanical strength modified side-to-side repair with modified pulvertaft technique keeping overlap length, anchor points, type of suture, suture throw and amount of suture similar.

In our study, we have used turkey tendons. Two investigators performed 34 repairs during one summer month. All mechanical testing was carried out using the tensile load testing machine. Variables measured were maximum load, load to first failure, modulus, load at break, mode of failure, site of failure, tensile strain, and tensile stress. The statistical comparison was carried by Levene's test and T test for means.

The mean maximum load tolerated by modified side-to-side repair was 50.3N(S.D13.7) and that by modified pulvertaft 46.96N(S.D: 16.4), overall it was 48.29 N (S.D: 14.57). The tensile stress at maximum load for modified pulvertaft and modified side-to-side repair was 4.2MPa(S.D: 3.1) and 4.7 MPa (S.D: 3.8) respectively {Overall 4.3MPa(S.D: 3.5)}. The tensile stress at yield was 4.01 MPa (S.D: 3.1) and 5.5 MPa (S.D: 3.7) respectively for modified pulvertaft and modified side-to-side repair {overall 4.44 MPa (S.D: 3.45)}. The tensile strain at maximum load respectively for side-to-side and modified pulvertaft repair was 7.87%(S.D: 33.3) and 7.84%(S.D: 34.02) respectively.

We found no statistical difference between 2 repairs in terms of strength, load to first failure, and maximum load to failure. The suture cut through was the commonest mode of failure.

Our study uniquely compares two techniques under standard conditions, and contrary to existing evidence found no difference.

Primary spinal cord injury is followed by secondary, biochemical, immunological, cellular changes in the injured cord

A review article written by Brian Kwon looking critically at the use of hypothermia for SCI. It shows that it is neuroprotective in some settings (i.e. cardiac arrest). However, there are 25 animal studies with mixed results and only eight human SCI studies. Importantly, they are all case series of local, not systemic hypothermia. And the last one published was in 1984.

Rho is a critical molecule in SCI. Rho ultimately inhibits axonal growth cone proliferation. Stopping RHO therefore will promote the growth cone. There are two drugs that ultimately targets rho. These are anti nogo antibodies and cethrin both of which ultimately inhibit rho.

President Obama lifted the ban on federal funding of stem cell research. This was a monumental occasion and was right around the time that the FDA approved the first trial of hESC for SCI.

The FDA trial of Geron is with Thoracic ASIA A SCI patients with transplantation of ESC directly into the cord at 7 to 14 days after injury. Geron has provided evidence to the FDA that there is no teratoma formation with transplantation of a human ESC to a rat or mouse. However, we do not know what will happen in a human to human transplant.

In conclusion, use of steroids in setting of SCI is diminishing. There is no clinical evidence to support use of systemic hypothermia. Current clinical trials of pharmacologic therapy include Minocycline and RILUTEK(r) (riluzole) for neuroprotection, Anti-Nogo Antibodies and Cethrin(r) for axonal growth by ultimately inhibiting Rho. There is only one small study supporting safety, not efficacy of OEC transplantation.

There is an apparent need for easily accessible research data on Periprosthetic hip joint infections (PJI)(1). Administrative discharge registers could be a valuable single-sources for this purpose, and studies originating from such registers have been published(2–4). However, the quality of routinely collected data for administrative purposes may be questionable for use in epidemiological research. The aim of this study was to estimate the positive predictive value of the International Classification of Disease 10th revision (ICD-10) periprosthetic hip joint infection diagnose code T84.5.

The study was performed as a cross-sectional study on data extracted from the Danish National Patient Register. Patients with a registration of performed surgical treatment for hip PJI were identified via the ICD-10 code T84.5 (Infection and inflammatory reaction due to internal joint prosthesis) in association with hip-joint associated surgical procedure codes. Medical records of the identified patients (n=283) were verified for the existence of a periprosthetic hip joint infection. Positive predictive values with 95% confidence intervals (95% CI) were calculated.

A T84.5 diagnosis code irrespective of the associated surgical procedure code had a positive predictive value of 85 % (95% CI: 80–89). Stratified to T84.5 in combination with an infection-specific surgical procedure code the positive predictive value increased to 86% (95% CI: 80–91), and in combination with a noninfection-specific surgical procedure code decreased to 82% (95% CI: 72–89).

This study is the first to evaluate the only discharge diagnose code of prosthesis-related infection in an administrative discharge register. It is apparent, that codes in administrative discharge registers are prone to misclassification on an administrative level, either by wrongful coding by the physician or administrative personal in the registration process. Misclassification must be expected and taken into consideration when using single-source administrative discharge registers for epidemiological research on periprosthetic hip joint infection. We believe that the periprosthetic hip joint infection diagnose code can be of use in single-source register based studies, but preferably should be used in combination with alternate data sources to ensure higher validity(5)

This study is funded in part by the Lundbeck foundation Centre for Fast-track Hip and Knee Surgery, Denmark.

Introduction

There is considerable interest in the orthopaedic community in understanding the multifactorial process of taper fretting corrosion in total hip arthroplasty (THA). Previous studies have identified some patient and device factors associated with taper damage, including length of implantation, stem flexural rigidity, and head offset. Due to the complexity of this phenomenon, we approached the topic by developing a series of matched cohort studies, each attempting to isolate a single implant design variable, while controlling for confounding factors to the extent possible. We also developed a validated method for measuring material loss in retrieved orthopaedic tapers, which contributed to the creation of a new international standard (ASTM F3129-16).

Testing potential therapeutics in the regeneration of the disc requires the use of model systems. Although several animal models have been developed to test intervertebral disc (IVD) regeneration, application becomes costly when used as a screening method. The bovine IVD organ culture system offers an inexpensive alternative, however, in the current paradigm, the bony vertebrae is removed to allow for nutrient diffusion to disc cells. This provides limitations on the conditions and strategies one can employ in investigating IVD regeneration and mechanisms in degenerative disc disease (i.e. complex loading). Although one method has been attempted to extend the survival of bovine vertebrae containing IVDs (vIVD) cell viability declined after two weeks in culture. Our goal was to develop and validate a long-term organ culture model with vertebral bone, which could be used subsequently for studying biological repair of disc degeneration and biomechanics.

Preparation of vIVDs: Bovine IVDs from the tails of 22–28-month-old steers were prepared for organ culture by parallel cuts through the adjacent vertebral bodies at 1cm from the endplates using an IsoMet®1000 Buehler precision sectioning saw. vIVDs were split into two groups: IVDs treated with PrimeGrowth Media kit (developed by Intervertech and licensed to Wisent Bioproducts) and IVDs with DMEM. The PrimeGrowth group was incubated for 1h in PrimeGrowth Isolation Medium (Cat# 319–511-EL) and the DMEM group for 1h in DMEM. After isolation, IVDs were washed in PrimeGrowth Neutralisation Medium (Cat# 319–512-CL) while the other IVDs were washed in DMEM. The discs isolated with PrimeGrowth and DMEM were cultured for up to 5 months in sterile vented 60 ml Leakbuster™ Specimen Containers in PrimeGrowth Culture Medium (Cat# 319–510-CL) and DMEM with no mechanical load applied. Live/Dead Assay: vIVDs cultured for 1 or 5 months were dissected and cell viability was assessed in different regions by confocal microscopy using Live/Dead® (Invitrogen) fluorescence assay. Glucose Diffusion: After one month of culture, vIVDs were incubated for 72h in diffusion medium containing PBS (1x), CaCl2 (1mM), MgCl2 (0.5mM), KCl2 (5mM), 0.1% BSA and 150µM 2-NDBG, a D-glucose fluorescent analogue. Discs were dissected and IVD tissues were incubated in guanidinium chloride extraction buffer. Extracts were measured for fluorescence.

After 5 months in culture, vIVDs prepared with PrimeGrowth kit demonstrated approximately 95% cell viability in all regions of the disc. However, dramatic reductions (∼90%) in vIVD viability were measured in DMEM group after 1 month. vIVD viability was related to the amount of 2-NDBG incorporated into the disc tissue.

We have developed a novel method for isolating IVDs with vertebral bone capable of long-term viability. This method may not only help in the discovery of novel therapeutics in disc regeneration, but could also advance our understanding on complex loading paradigms in disc degeneration.

STS are rare malignant tumours of mesenchymal origin giving a wide array of histological types and behaviour. Common sites of involvement include the extremities which are of most relevance to orthopaedic surgeons. Like almost all other malignancies, STS become more common with increasing age with median age of 65 years.

All patients aged 65 and over with STS of the extremities referred to the NZ Tumour Registry at Middlemore Hospital between 1967 and 2010 were included in the study. Data collected include baseline demographics (age, sex), diagnosis, site, time of referral, definitive treatment, adjuvant therapy, surgical margins (if applicable), local recurrence, survival, and cause of death. Each patient was staged according to AJCC (1997, 5th edition) and Enneking's staging systems. Primary outcomes were measured in terms of 5-year survival alongside with cause of death.

A total of 116 patients. 21 upper extremities, 95 lower extremities. Average age of 74 with a 1.2:1 female to male ratio.

Stage 1 disease was uncommon, accounting for only 5 cases (4%). 3 patients died within 5 years (1 due to metastatic disease and 2 from non-sarcoma related disease). 2 patients were still alive in 2010 with 1 of them surviving >5yrs.

Stage 2 disease was found in 41 patients (35%). Common histologies included malignant fibrous histiocytoma (MFH), liposarcomas, or leiomyosarcomas (LMS). 44% (n=18) had greater than 5-year survival. 20% (n=8) died within 5 years succumbing to metastatic disease. 11 were under 5-yr follow up.

Stage 3 disease was found in 48 patients (41%). MFH was by far the most common diagnosis accounting for 63% of patients. 5-year survival 25% (n=12). 5-year mortality 56% (n=27) mainly from advanced disease and metastases. Rest (n=9) are still within 5-yr follow up. Distant metastases at presentation were seen in about 10% of all patients (12 cases) with the most common site of involvement being the lung. 9/13 died of metastatic disease within 5 yrs while others are still within the 5 yr follow up period.

STS are most commonly observed in the elderly and prognosis depends on several factors. Management should ideally be carried in a specialised centre with early referral and combined multidisciplinary approach to optimise patient outcome.

Aim. metagenomic next-generation sequencing (mNGS) has shown to be a useful method for pathogen detection in prosthetic joint infections (PJI). The technique promises to minimize the PJIs without the known causative agent. Our study aimed to compare diagnostic accuracies of cultures and mNGS. Method. In this study, a meta-analysis following PRISMA recommendations was performed. PubMed and OVID Medline databases were used for article search. The studies using mNGS whole-genome sequencing method and the ones where PJI diagnosis was based on one of the currently recognized criteria were included. Studies were excluded if they comprised less than twenty cases, the ones with insufficient data for the analyses (true positive, true negative, false positive and false negative values for both mNGS and culture results) and publications with strong duplication bias. Univariate metanalysis using a random-effect model has been performed in R studio with a “meta” package. Pooled sensitivity and pooled specificity were calculated. Results. Seven studies with a total of 822 cases were included in the meta-analysis, 476 cases defined as PJI and 346 controls. Two studies used IDSA (Infectious Diseases Society of America) diagnostic criteria and the Illumina HiSeq 2500 platform for sequencing and five studies used MSIS (MusculoSkeletal Infection society). Four of those used the BGISEQ-500 sequencing platform. For one study there was no data available. Studies were performed on prosthetic hip and knee joints. Through meta-analysis, it was observed that mNGS technique is more sensitive than cultures with 90% (CI 79%– 95%) and 74% (CI 68%-79%) respectively (p=0.006). The specificity between methods was similar, for mNGS reaching 94% (CI 89%-96%) and for cultures 97% (CI 90%-99%) (p=0.285). In the PJI group, 117 new possible pathogens that were not isolated by microbiological culture were detected by the mNGS, most frequently anaerobes and coagulase-negative staphylococci both in 20/117 (17.1%) cases. Fourteen new organisms were detected in the control group and were mostly regarded as contaminants. Conclusions. Metagenomic sequencing has shown to be more sensitive than microbiological cultures in pathogen detection and thus has a great potential to improve the diagnosis and treatment of PJI. More studies on different prosthetic joints and comparing different diagnostic criteria for PJI would be needed to better understand the true diagnostic power of this method

Abnormal patella height has been found to be one of the main reasons for abnormal contact between patella and trochlear groove leading to patellar instability in children. Many methods have been described to diagnose patellar instability but most of them are justified only in adults. The reason being incomplete ossification in the paediatric population. These methods have been divided into direct and indirect methods. We analysed the MRI scan of knee of 57 children between 12–14 years of age with no previous diagnosis of patellar instability. Patients with a diagnosis of patellar instability, previous surgery on the knee or trauma and poor MRI scan were excluded from the study. We used Insall -Salvati Index (ISI), Caton-Deschamp Index (CDI) and Patella-Trochlear Index (PTI) and compared the results. We found that 40% of measurements by CDI and 41% by ISI showed patella alta in patients with normal patella height. 10% of patients in PTI readings had value suggestive of abnormal patella height. We concluded that PTI is a more reliable index to be used in children as it uses the length of articular surface and does not rely on bony landmarks. Studies done show PTI is a more reliable and accurate method of measuring patella height