Introduction

Management of Vancouver type B1 and C periprosthetic fractures in elderly patients requires fixation and an aim for early mobilisation but many techniques restrict weightbearing due to re-fracture risk. We present the clinical and radiographic outcomes of our technique of total femoral plating (TFP) to allow early weightbearing whilst reducing risk of re-fracture.

Trauma and elective orthopaedic demands in New Zealand are increasing. In this study, prospective and retrospective data has been collected at Nelson Hospital and across New Zealand to identify the percentage of elective theatre time lost due to cancellation for acute patient care. Data has been collected from theatre management systems, hospital data systems and logged against secretarial case bookings, to calculate a percentage of elective theatre time lost to acute operating or insufficient bed capacity.

Data was collected over a five-month period at Nelson Hospital, with a total of 215 elective and 226 acute orthopaedic procedures completed. A total of 95 primary hip or knee arthroplasties were completed during this trial while 53 were cancelled. The total number of elective operative sessions (one session is the equivalent of a half day operating theatre time) lost to acute workload was 47.9. Thirty-three percent of allocated elective theatre time was cancelled - an equivalent of approximately one-full day elective operating per week.

Over a five-week period data was collected across all provincial hospitals in New Zealand, with an average of 18% of elective operating time per week lost due to acute workload. Elective cancellations were due to acute operating 40% of the time and bed shortages 60% of the time. The worst effected centre was Palmerston North which had an average of 33% of elective operating cancelled per week to accommodate acute surgery or due to bed shortages.

New Zealand's provincial orthopaedic surgeons are under immense pressure from acute operating that impedes provision of elective surgery. The New Zealand government definition of an ‘acute case’ does not reflect the nature of today's orthopaedic burden. Increasing and aging populations along with staff and infrastructure shortages have financial and societal impacts beyond medicine and require better definitions, further research, and funding from governance.

Objectives

Pulsed electromagnetic field (PEMF) stimulation was evaluated after anterior cervical discectomy and fusion (ACDF) procedures in a randomized, controlled clinical study performed for United States Food and Drug Administration (FDA) approval. PEMF significantly increased fusion rates at six months, but 12-month fusion outcomes for subjects at elevated risk for pseudoarthrosis were not thoroughly reported. The objective of the current study was to evaluate the effect of PEMF treatment on subjects at increased risk for pseudoarthrosis after ACDF procedures.

Aims

To investigate whether the duration of pain has an influence on the clinical outcomes of patients with low back pain (LBP) managed through the North East of England Regional Back Pain and Radicular Pain Pathway (NERBPP).

Trauma ward rounds (TWR) are usually preceded by trauma meetings where previous day admissions are discussed and management decisions made. Therefore, one would expect TWR to be relatively quick and efficient. We measured the distance walked during TWR over a one week period and examined effects of number of patients and their location on distance walked.

We used a pedometer (after calibration) to measure the distance walked by a single consultant orthopaedic surgeon during his trauma week. The consultant conducted a daily TWR after the trauma meeting where previous day admissions and postoperative patients were reviewed. We initially measured the distance required to visit five wards where trauma patients could be found (trial distance) and used that for comparison. We recorded number of patients reviewed and wards visited daily.

The distance walked daily during TWR was 1.37–2.4 times longer than trial distance. There was no correlation between number of patients reviewed or number of wards visited and distance walked. Despite the larger number of patients towards the end of the week (33 patients on 3 wards on last TWR), the distance walked remained shorter than on the first TWR (11 patients on 3 wards). The distance walked during the whole week was 30.8 miles!

We found no correlation between number of patients reviewed or their location and distance walked during TWR. The relatively shorter distances walked towards the end of the week could be explained by more familiarity and therefore, better organisation by the team as the week progressed.

Frequently, radiological data is transferred verbally between ED/GP/LMO to the Orthopaedic registrar. Given the different medical backgrounds and presentation skills there is often a limit to the verbal description of the radiographs. The aim of this study is to determine the feasibility and benefits of concurrently using picture messaging of X-rays to enhance communication between ED and Orthopaedic Registrars to optimise patient care. The X-rays of 40 patients referred to orthopaedics OPD or admitted from the ED were photographed and retrospectively reviewed on a mobile phone screen (240 × 320) by an orthopaedic registrar along with a printout of the patient history and verbal description of the x-ray as interpreted by the ED staff. No further information was provided to the registrar. A questionnaire was completed to subjectively and objectively evaluate the therapeutic benefit of the image review. Patient(tm)s management was compared to management plans after image review and differences were attributed to the visual inspection of the x-rays on the mobile phone.

Concurrent to the retrospective review, the ED is currently trialling this with a Sony-Erickson K750i. After hours orthopaedic cases are sent via MMS to the registrar prior to consultation. In the emergency department, 10% of patients who presented with a fracture were reviewed in person by an orthopaedics registrar and none were admitted straight from ED whilst two were admitted following review at the OPD. X-rays of 40 patients were reviewed in this study. Twenty-seven patients presented with a fracture and four with islocations.

When the clinical data was reviewed alongside images of x-rays by an orthopaedic registrar, a difference in management plans were observed in 25% of cases and 7.5% where surgical intervention would yield a better result. Twenty-six of the twenty-seven fractures and four dislocations were successfully visualised on the MMS. In 18 cases, picture messaging provided additional information compared to verbal report alone. The limiting factor in picture messaging was the resolution and size of the radiograph. Ease of operation and portability was found to be satisfactory by both ED and Orthopaedic staff. Equipping the ED with the phone has enhanced communication with the orthopaedics department and increased the potential for optimising patient care. This will be formally assessed through questionnaires after 12 months trial of the phone.

Picture messaging is an inexpensive way of utilising technical advancements to improve patient care. Consistent with current literature, the quality of images was not sufficient as a diagnostic tool but rather a screening tool. Picture messaging is valuable practically and educationally and enhances the consultation and teaching process whilst encompassing medical staff who have limited skills in radiological description.

Objectives: Evaluating the efficacy of the Ilizarov fine-wire distraction/compression technique in the treatment of scaphoid nonunion (SNU), without the use of bone graft.

Design: A retrospective review of 15 consecutive patients in one centre.

Patients and Methods: 15 patients; 14 males, with a mean SNU duration of 13.9 months. Following frame application the treatment consisted of three stages: stage one – the frame was distracted 1mm per day until radiographs showed a 2–3mm opening at the SNU site (mean 10 days); the SNU site was then compressed for 5 days, until the fragments were in contact., the third stage involved immobilization with the Ilizarov fixator for 6 weeks.

Results: Radiographic and clinical bony union was achieved in all 15 patients after a mean of 89 days (70–130 days). Mean modified Mayo wrist scores improved from 21 to 86 at a mean follow-up of 37 months (24 –72 months), with good/excellent results in 12 patients. All patients returned to their pre-injury occupations and levels of activity at a mean of 117 days. Three patients suffered superficial K-wire infections, which resolved with oral antibiotics.

Conclusions: In these study group with this technique we achieved bony union without the need to open the SNU site and without the use of bone graft.

Closure with interrupted mattress sutures is useful where careful skin apposition is required following hindfoot surgery. However, suture removal can be technically difficult and painful. Modification with an additional suture loop creates a “traction loop suture”. We hypothesise this technique makes suture removal quicker and reduced tension placed on sutures during their removal reduces pain.

37 patients undergoing elective hindfoot surgery took part in a prospective clinical trial comparing traditional interrupted sutures with traction loop sutures. Each patient underwent half of each wound sutured with both types. Sutures were removed at 2 weeks and pain levels were determined during removal using the 10 cm visual analogue pain scale. Duration of time taken for each type of suture removal was measured. Wound complications were recorded at 2 and 6 weeks post-operative.

Results demonstrated traction loop sutures were 43% less painful to remove per wound than normal interrupted sutures (mean difference 1.06; standard deviation 1.56; 95% confidence interval 0.50 to 1.62; p-value 0.001). Traction loop sutures were also 31% quicker to remove per wound (mean difference 15.72 seconds; standard deviation 19.98; confidence interval 8.51 to 22.93; p-value < 0.001). At 2 weeks, 1 normally sutured wound suffered dehiscence. At 6 weeks, no complications were noted in either group.

Our results demonstrate that traction loop sutures provide a quick and simple means of reducing patients’ pain and time during suture removal. Traction loop suturing technique could be applied to other surgical specialities where interrupted suture closure is indicated.

Despite significant improvements of survival in patients with localized osteosarcoma, about 30–40% of the patients still die on tumor progression or relapse. In order to improve therapeutic outcome we postulate the need for individualized intervention schemes based on biological characteristics of the tumor. Identification of molecular changes important for pathogenesis and tumor progression is complicated by the complex karyotype of the tumor with numerous structural and numerical alterations. Here we describe the use of Affymetrix single nucleotide polymorphism arrays in a genome wide high-resolution approach to assay both loss of heterozygosity and variations in DNA copy numbers in 46 osteosarcoma biopsy samples. We combined established histological response parameters with our genetic findings to predict prognosis.

We found that overall chromosomal changes in osteosarcoma are good predictors of response to chemotherapy and outcome. Analyzing the minimal recurrent regions harbouring chromosomal alterations we expanded our investigations towards identification of gains and losses of chromosomal material and found candidate genes as potential prognostic parameters and therapeutic targets. Identified genomic regions and genes were validated by mRNA-expression studies and correlated with proteom analysis by MALDI Imaging.

Thus, structural chromosomal alterations detected by SNP analysis may serve as a simple but robust parameter to predict response to chemotherapy. The results also indicate that we are able to identify several genomic loci with high potential to predict the outcome of the disease. Furthermore new potential target genes were identified by this genome wide screen.

The project is part of the Translational Sarcoma Research Network (TransSaRNet).

Squeaking in ceramic total hip joint replacements has become a controversial topic. This study aims to document the incidence of squeaking and other noise generation in a single surgeon series for ceramic on ceramic total hip joint replacements. Possible aetiological for squeaking causes are explored.

All patients from public and private who received ceramic on ceramic total hip joint replacements (Stryker trident-accolade) from 2002 to 2007 were identified via the New Zealand Joint registry. Following ethics approval all patients were contacted for a phone interview to question as to whether they had noted any noise generation. Patients who demonstrated noise generation were reviewed in clinic for full history and examination. Data including age, sex, weight, primary diagnosis, head size and cup size were obtained from clinical notes. Post operative x-rays were reviewed to analyse cup abduction and version.

Forty one ceramic total hip joint replacements in a total of thirty seven patients were reviewed via telephone interviews. Three patients complained of squeaking in the ceramic bearing while one patient complained of a grinding and one other of clicking. Two of the three who had recognised the squeaking were both able to reproduce the squeaking in the clinic room. The third patient was noted to have crepitus from anterior patello-femoral osteoarthritis. There was no statistical difference in age, weight, primary diagnosis or head size. In terms of abduction and version of the acetabular cups that squeaked, one had twenty seven degrees of ante-version and forty seven degrees of abduction and the other fifteen degrees of anteversion and thirty degrees of anteversion. Four cups lay outside the recommended fifteen-thirty five degrees of anteversion and thirty five-fifty five degrees of abduction yet showed no squeaking. Neither patient is troubled by the squeaking and neither would seek revision surgery. The incidence of squeaking in ceramic on ceramic total hip joint replacements appears to be around five percent with a similar number of patients experiencing other noises. The position of the acetabular cup does not appear to be the sole contributor to the noise and other aetiological causes need to be further investigated.

Purpose: To determine differences in muscle activity of superfical multifidus (SM) and iliocostalis lumborum (IL) between healthy subjects (H) and those with a past history of low back pain (HB) during unsupported sitting.

Background: Sitting has been implicated in the incidence of low back pain. However conflcting evidence is reported on the effect of sitting on the erector spinae with some studies noting an increase, others a decrease and others no difference in activity (Callaghan and McGill 2001, Jackson et al 2001, Dankaerts et al 2006). Most studies focus on subjects with current low back pain. It is known that following an episode of back pain deficits in muscle activty may persist (Hides et al 2001).

Methods: 20 subjects gave informed consent, 10 in each of the H and HB groups. Surface electromyography data was recorded from M and IL bilaterally over 4 time points over 15 minutes of unsupported ‘usual’ sitting. This data was normalised using MVCs and compared for differences using repeated measures ANOVA.

Results: Descriptive data for iliocostalis lumborum and superficial multifidus are presented respectively.

No significant difference was detected between groups or time points for either muscle (p> 0.05).

Conclusion: This preliminary study suggests that subjects with a history of low back pain and healthy subjects have no difference in muscle activity of SM and IL in unsupported sitting. This suggests that HB subjects have no residual muscular weakness and implies no further muscular rehabilitation is required. Further research with larger samples should be undertaken.

Introduction: Closure with interrupted mattress sutures is useful where careful skin apposition is required following hindfoot surgery. However, suture removal around the hindfoot can be awkward and painful. Modification with an additional loop creates a “traction loop suture”. We hypothesise this technique makes removal easier and reduced tension placed on sutures during their removal reduces pain.

Materials: 17 patients undergoing elective hindfoot surgery were included. Nylon suture was used for all wound closures. Suturing and removal techniques were standardised. Ethical approval and patient consent was obtained.

Methods: Half of each wound length was sutured normally and the other with traction loop sutures (both interrupted mattress type). Follow-up was at 2 and 6 weeks. Comparison of time taken for suture removal and associated wound complications were noted for both. Pain scores during suture removal were recorded using a screen to “blind” the patient and a visual analogue pain score (VAPS) was obtained. Statistical analysis calculated p-values at the 5% significance level and 95% confidence intervals (CI).

Results: Traction loop sutures were 20% faster to remove than normal interrupted sutures (mean difference 19.3 seconds, CI 5.39 to 33.1 seconds, p-value 0.004). Traction loop sutures were also 20% less painful during removal (mean difference 1.05 on VAPS, CI 0.021 to 2.085, p-value 0.027. At 2 weeks, 1 normally sutured wound suffered complications. At 6 weeks, no complications were noted in either group.

Discussion: Traction loop sutures provide a statistically significant method of reducing pain and time during suture removal. The study method could be applied to comparisons of other skin closures where removal is required. The technique is novel and requires minimal change in suturing.

Conclusion: Pain levels and time taken for removal of interrupted mattress sutures are significantly reduced using the traction loop suture technique in hindfoot surgery. The study is continuing.

The aim of this study was to validate the use of three models of fracture fixation in the assessment of technical skills. We recruited 21 subjects (six experts, seven intermediates, and eight novices) to perform three procedures: application of a dynamic compression plate on a cadaver porcine model, insertion of an unreamed tibial intramedullary nail, and application of a forearm external fixator, both on synthetic bone models. The primary outcome measures were the Objective Structural Assessment of technical skills global rating scale on video recordings of the procedures which were scored by two independent expert observers, and the hand movements of the surgeons which were analysed using the Imperial College Surgical Assessment Device.

The video scores were significantly different for the three groups in all three procedures (p < 0.05), with excellent inter-rater reliability (α = 0.88). The novice and intermediate groups specifically were significantly different in their performance with dynamic compression plate and intramedullary nails (p < 0.05). Movement analysis distinguished between the three groups in the dynamic compression plate model, but a ceiling effect was demonstrated in the intramedullary nail and external fixator procedures, where intermediates and experts performed to comparable standards (p > 0.6). A total of 85% (18 of 21) of the subjects found the dynamic compression model and 57% (12 of 21) found all the models acceptable tools of assessment.

This study has validated a low-cost, high-fidelity porcine dynamic compression plate model using video rating scores for skills assessment and movement analysis. It has also demonstrated that Synbone models for the application of and intramedullary nail and an external fixator are less sensitive and should be improved for further assessment of surgical skills in trauma. The availability of valid objective tools of assessment of surgical skills allows further studies into improving methods of training.

To determine the effect of experience of the operator and the effect of type of anaesthesia used on re-manipulation rates of fracture distal radius manipulated in A& E, a retrospective review of distal radius fractures manipulated in A& E between January 2000 and January 2001. Operators were divided into two categories: junior (SHO grade) and senior (higher grade) doctor.

54 patients with fracture distal radius had manipulation in A& E. 15 male and 39 female patients with mean age of 61 years (52 for males and 63 for females) were included.

42 (78%) fractures were manipulated under haematoma block (18 by junior, 23 by senior doctor) and 12 (22%) fractures were manipulated under Bier block (1 by junior, 11 by senior doctor). Operator’s grade was not clearly mentioned in one case. 13 out of 54 patients (24%) needed fracture re-manipulation under general anaesthesia. 12 out of 42 fractures manipulated under haematoma block (30%) needed re-manipulation compared to only one out of 12 fractures (8%) manipulated under Bier block (p=0.25). 9 out of 19 fractures manipulated by junior doctors needed re-manipulation compared to only 4 out of 34 fractures manipulated by senior doctors (p=0.007). Haematoma block was used for 18 out of 19 cases by junior doctors and for 23 out of 34 cases by senior doctors (p=0.038). Average number of fracture clinic follow-ups was 4 (range 2 to 8).

Junior doctors had significantly higher preference for haematoma block and significantly higher re-manipulation rate. Re-manipulation rates were higher with fractures manipulated under haematoma block compared to Bier block.

Adequate training and supervision should be provided for SHOs while performing such procedures in A& E. Use of Bier block as a regional anaesthesia for manipulation of distal radius fractures in A& E should be encouraged.

To measure for evidence of early subsidence of Accolade tapered uncemented femoral stems. To quantify any subsidence and to identify factors which may predispose to this.

A retrospective audit of patients who have received Accolade stem total hip joint replacement in Hawkes Bay Hospital from October 2003 to October 2004. Post operative and follow up x rays (within one year of surgery) were reviewed and position of femoral component in the femur was measured and adjusted for magnification and angulation.

Thirty-eight patients were identified. Patients age averaged 66 years old (44 – 82yo). Results show an mean subsidence of 2.8mm with a range of 0 – 13mm.

There is evidence of early subsidence of Accolade femoral stems. In cases of large subsidence under sizing of the femoral component was identified as the most significant contributing factor.

14 systems for anterior cervical stabilisation were evaluate under flexion-compression bending using test procedures conforming to Static and Fatigue Test Methods for Spinal Implant Assemblies using Corpectomy Models Part 2a [ISO/TC 150/SC5 N127C]

Plates of standardised active length were tested in an in-vitro model of a single corpectomy of the lower cervical spine using composite test blocks manufactured by Sawbones to have physical properties similar to cervical vertebrae.

Results reveal a wide range in final yield strengths with bi-cortical systems significantly stronger than uni-cortical ones. There was a fourfold difference in ultimate load between the stronger and weakest systems.

We found that mode of failure was influenced by plate thickness, screw length and screw placement.

Landmines continue to be a major cause of injury to both military and civilian personnel. This has lead to various strategies including the development of anti-landmine boots and vehicles. In an attempt to assess the efficacy of these strategies various physical and computer simulation models have been developed. International assessment technologies currently rely heavily on either live animal or human cadaver testing. Both these strategies are subject to wide individual variations and major practical and ethical problems. They are therefore not employed by the Australian Defence Organisation (ADO).

A multi-disciplinary team has been assembled by the ADO to develop both a “flesh and bone” human model and a computer simulation. The biomechanical human analogue is constructed from materials that have been developed to reflect the strength properties and performance of human tissues (biofidelity). The surrogates are also equipped with various sensory devices allowing analysis of the local and remote effects of load transmission throughout the body.

In the first stage of the program Frangible Synthetic Legs (FSL’s) were developed. These FSL’s have been blast tested in the presence of “protective” boots and vehicle platforms. These tests have yielded critical information on lower limb injury mechanisms and have highlighted the failings of some of these “protective” strategies.

These frangible surrogate humans can be reproduced with great consistency and, once sufficiently evolved, should remove the need for experimental assessment on either live animals or human cadavers. Whilst the Human Surrogate technology has application in the development of mine resistant boot technologies, it is also transferable to the various aeronautic and automotive crash test injury programs which are currently deficient in model biofidelity.

Introduction: Large numbers of women are taking hormone replacement therapy (HRT) or an oestrogen containing contraceptive pill. They are being advised that these medications can increase their risk of developing deep vein thrombosis (DVT) and there has been considerable recent publicity.

Aim: To determine the practice of New Zealand orthopaedic surgeons when women taking such medications present for major surgery.

Method: A postal survey was sent to all New Zealand orthopaedic surgeons. The current practice was compared with recently revised national guidelines and manufacturers advice.

Results: The response rate was 80% (118/148). There was wide variation in the beliefs surrounding the peri-operative use of both of these medications. Of the surgeons who replied, 44% indicated that they would routinely advise discontinuing the combined oral contraceptive pill peri-operatively for major surgery, 24% indicated that they would routinely advise discontinuing HRT peri-operatively. The mean duration that surgeons would discontinue the medication pre-operatively was 13 days for the contraceptive pill and nine days for HRT. The mean time for re-starting medication post-operatively was 18 days for the contraceptive pill and 13 days for HRT.

Recently released New Zealand guidelines recommend that HRT should be stopped for at least 30 days prior to elective surgery and withheld for 90 days following surgery. Less than 3% of surgeons appeared to be routinely following this recommendation. Most manufacturers of combined oral contraceptive pills recommend stopping the medication for at least four weeks prior to elective surgery. Only 25% of surgeons routinely practice in accordance with these recommendations.

Discussion: This survey demonstrated substantial differences between actual clinical practice, recently revised national guidelines and manufacturers’ advice. These differences need to be brought to the attention of surgeons and guideline producers alike. A review of international literature and recommendations revealed that these guidelines are very conservative and that strong evidence for them is lacking. Issues to be considered include the practicalities of implementing such recommendations; the associated risks of discontinuing medication; the presence of other risk factors; the type of surgery; the use of thromboprophylaxis and not least the wishes of the patient. The possible medico-legal implications are uncertain and caution in this area is advised.

Over the centuries there has been a pattern of order developing from chaos in the behaviour of nations.

The 20th century has demonstrated major conflict between nations, and Defence Health has supported the core activity of the Australian Defence Force (ADF), which has been the aim of military medicine generally in all world defence forces. Preventative medicine and mass casualty treatment, as well as the maintenance of health and return to duty from minor injuries, has been a success for all traditional military medical structures.

It has been known that if the civilian population is supportive of the military effort, this is a significant advantage. The military medical assets directed in this manner to the local civilians builds bridges for lasting peace.

In 1989 the world changed, with the Cold War won and leaving the United States as the only super power. From that time, conflict has tended to be intrastate rather than between sovereign states, with a rise in communal or ethnic conflict. This situation is probably not going to change in the foreseeable future as there are no longer client states being controlled by super powers.

Since that time the Australian Defence Force has been involved in the treatment of indigenous Australian citizens, UN humanitarian missions and disaster relief. In fact the military medical assets of the ADF have been busier in the last 30 years in Military Operations Other Than War than in war itself.

The original concept of the Forward Surgical Teams developed in Adelaide was modular, encompassing a General surgeon, an Orthopaedic surgeon, an Intensive Care specialist and an Anaesthetist, and thus they were able to cover trauma sustained by most combat casualties. This module was man-liftable and able to be deployed by aircraft, by vehicle and also on board ship, augmenting existing medical facilities according to need.

This module in its varying forms has stood the Australian Forces well in Rwanda, Bougainville, East Timor, PNG, disaster relief and Aboriginal health missions.

It may be that further health modules can be developed, such as a Burns module, a Paediatric module and a Primary Care module, building on the increasing medical knowledge base, sub-specialisation and advancing technology. These building blocks can come together to form significant hospitals if necessary.

The ADF has provided first-world medicine and third-world medicine, producing a dichotomy in requirement for medical skills and technology, depending on circumstances. Being busy enhanced our logistical support systems and organisational skills. Medical experience was gained, and the foundation for lasting peace and building communities was established.

If war is considered the greatest social disease left then the pathology of war is in history. The diagnosis is easy but the treatment and prevention difficult.

Early in an emergency the military medical assets of any defence force are able to be deployed under difficult living conditions, and can provide health care for those who have survived the disaster whether it be man-made or natural.

Introduction: This is a report of a new anatomical feature in the knee. This finding to our knowledge has never been described before. The feature consists of a shallow oval impression in the synovium on the femoral surface of the floor of the suprapatellar pouch over the lateral side just before the trochlear entry to the lateral femoral condyle. Clinical correlation was considered to be a separate study and not part of this anatomic description.

Methods: During arthroscopy of the knee the presence or absence of the “entry feature” was noted, entered on a database consecutively and prospectively. All arthroscopies were carried out by the senior author. 21 cadaveric knees (formalin preserved) were dissected.

Results: Out of 457 consecutive knee arthroscopies carried out by the senior author the “entry feature” was present in 294 and not noticed in 163. Histology of the synovium in this region was normal. 21 formalin preserved cadaveric knees demonstrated the “entry feature” in 17 and absent in 4.

Conclusion: We propose the “entry feature” as a new anatomical landmark for the arthroscopic knee surgeon. It gives an initial impression of the patellar position on the synovial floor just before commencing its excursion towards the trochlear.