The biomechanical aspects of reconstruction for segmental defects of the mandible: a finite element study to assess the optimisation of plate and screw factors.

A bone plate is required to restore the load-bearing capacity of the mandible following a segmental resection. A good understanding of the underlying principles is crucial for developing a reliable reconstruction. A finite element analysis (FEA) technique has been developed to study the biomechanics of the clinical scenarios managed after surgical resection of a tumour or severe trauma to assist in choosing the optimal hardware elements. A computer aided design (CAD) model of an edentulous human mandible was created. Then 4 common segmental defects were simulated. A single reconstruction plate was designed to span the defects. The hardware variations studied were: monocortical or bicortical screw fixation and non-locking or locking plate design. A standardized load was applied to mimic the human bite. The von Mises stress and strain, spatial changes at the screw-bone interfaces were analysed. In general, the locking plate and monocortical screw fixation systems were most effective. Non-locking plating systems produced larger screw "pull-out" displacements, especially at the hemimandible (up to 5% strain). Three screws on either side of the defect were adequate for all scenarios except extensive unilateral defects when additional screws and an increased screw diameter are recommended. The simplification of screw geometry may underestimate stress levels and factors such as poor adaptation of the plate or reduced bone quality are likely to be indications for bicortical locking screw fixation. The current model provides a good basis for understanding the complex biomechanics and developing future refinements in plate or scaffold design.

Indications and outcomes for 100 patients managed with a pectoralis major flap within a UK maxillofacial unit.

There are few studies reporting the role of the pedicled pectoralis major (PPM) flap in modern maxillofacial practice. The outcomes of 100 patients (102 flaps) managed between 1996 and 2012 in a UK maxillofacial unit that preferentially practices free tissue reconstruction are reported. The majority (88.2%) of PPM flaps were for oral squamous cell carcinoma (SCC), stage IV (75.6%) disease, and there was substantial co-morbidity (47.0% American Society of Anesthesiologists 3 or 4). The PPM flap was the preferred reconstruction on 80.4% of occasions; 19.6% followed free flap failure. Over half of the patients (57%) had previously undergone major surgery and/or chemoradiotherapy. Ischaemic heart disease (P=0.028), diabetes mellitus (P=0.040), and methicillin-resistant Staphylococcus aureus (MRSA) infection (P=0.013) were independently associated with flap loss (any degree). Free flap failure was independently associated with total (2.0%) and major (6.9%) partial flap loss (P=0.044). Cancer-specific 5-year survival for stage IV primary SCC and salvage surgery improved in the second half (2005-2012) of the study period (22.2% vs. 79.8%, P=0.002, and 0% vs. 55.7%, P=0.064, respectively). There were also declines in recurrent disease (P=0.008), MRSA (P<0.001), and duration of admission (P=0.014). The PPM flap retains a valuable role in the management of advanced disease combined with substantial co-morbidity, and following free flap failure.

A finite element analysis of bone plates available for prophylactic internal fixation of the radial osteocutaneous donor site using the sheep tibia model.

INTRODUCTION: The strengthening effect of prophylactic internal fixation (PIF) with a bone plate at the radial osteocutaneous flap donor site has previously been demonstrated using the sheep tibia model of the human radius. This study investigated whether a finite element (FE) model could accurately represent this biomechanical model and whether stress or strain based failure criteria are most appropriate. METHODS: An FE model of an osteotomised sheep tibia bone was strengthened using 4 types of plates with unilocking or bicortical screw fixation. Torsion and 4-point bending simulations were performed. The maximum von Mises stresses and strain failure criteria were studied. RESULTS: The strengthening effects when applying stress failure criteria [factor 1.76-4.57 bending and 1.33-1.80 torsion] were comparable to the sheep biomechanical model [factor 1.73-2.43 bending and 1.54-2.63 torsion]. The strongest construct was the straight 3.5mm stainless steel unilocking plate. Applying strain criteria the strongest construct was the straight 3.5mm stainless DCP plate with bicortical screw fixation. CONCLUSIONS: The FE model was validated by comparison with the sheep tibia model. The complex biomechanics at the bone-screw interface require further investigation. This FE modelling technique may be applied to a model of the human radius and other sites.

Oral and maxillofacial surgery "presentation hot spots" in the United Kingdom over the last decade from the BAOMS annual meetings.

The annual scientific meeting of the British Association of Oral and Maxillofacial Surgeons (BAOMS) is primarily a national meeting with a minor international contribution (3%). In the 10 years between 2002 and 2011 there were 1639 oral and poster presentations, and there was a significant increase in the total number of presentations (93-313, p<0.001). There have also been substantial increases in the proportion of poster (36-80%, p=0.005) and clinical presentations (88-94%, p=0.02). The 10 most productive units contributed roughly half of all UK presentations, whilst the top 5 deaneries contributed 61%. The trends in output by the most productive units are noted and the total output of units and deaneries within the United Kingdom (UK) is shown on a colour map. The information will be of value to trainees when considering the merits of a training unit and region.

Refinements in osteotomy design to improve structural integrity: a finite element analysis study.

Osteotomy cuts are typically made using a saw, and the meeting point acts as a focus for the concentration of stress and failure. We have studied the impact of different designs of osteotomy cut. Cadaver sheep tibias were scanned by computed tomography (CT) and transformed into a computer-aided design (CAD) model. A standard marginal resection defect was created and then modified, and a finite element analysis made. The relative stress concentrations at the intersection of osteotomy cuts were recorded using principal stresses S1, S3, and von Mises stress, von Mises under both 4-point bending and torsion testing. The osteotomy designs studied were: right-angled and bevelled osteotomy end cuts, overcutting, and a stop drill hole. Peak stress values for 4-point bending and torsion were 24-30% greater at the right-angled osteotomy than the bevelled end cut. Overcutting dramatically increased peak stress values caused by bending and torsion by 48% and 71%, respectively. Substantially lower concentrations of stress were noted with a stop hole using both a 90° (bending 38% and torsion 56%), and a tangential (bending 58% and torsion 60%) cut. A bevelled osteotomy has substantially lower concentrations of stress than a right-angled osteotomy. It is important to avoid creating an overcut as this causes an appreciable increase in the concentration of stress, while a stop drill hole substantially reduces the stress. The creation of a stop hole and the use of judicious bevelling techniques are modifications in the design of an osteotomy that are readily applicable to surgical practice.

Comparison of sensory recovery at the subfascial and suprafascial donor sites of the free radial flap.

The radial flap may be raised using a subfascial or suprafascial approach. The latter donor site is associated with fewer healing complications. We retrospectively evaluated the quality of sensory recovery within two comparable groups of 30 patients with subfascial and suprafascial donor sites. When considering the two groups, two-point discrimination was the modality most commonly reduced, with 97% of patients in both groups having reduced sensation in at least one anatomical zone. Sensation of sharp touch was most often lost; 90% in the subfascial and 83% in the suprafascial groups lost sensation in at least one anatomical zone. Roughly half the patients had reduced perception of light touch (43% and 50%), whilst perception of heat (27% and 17%) and cold (33% and 27%) were lost least often. At least one modality in at least one anatomical zone was lost or reduced in all patients, and roughly two-thirds (73% and 63%) had a reduction in 3 or more. The only significant difference between the donor and non-donor arms was reduced perception of sharp touch in the anterior forearm in both groups (p<0.001). Perception at the two sites (including the anatomical snuff box) was similar except for superior thenar palmar light touch (p=0.015) in the suprafascial group, which may indicate injury to the thenar cutaneous sensory branches during subfascial dissection.

Serum testosterone levels in surgeons during major head and neck cancer surgery: a suppositional study.

Serum testosterone levels are known to have diurnal variation and to decrease by up to 2% per year after the age of 40. They can also be affected by stress and aggressive behaviour as well as various medical conditions. Although studies have investigated the role of mood and stress, none has specifically evaluated the effect of operative procedures on surgeons testosterone levels, particularly those in our own specialty, one that has historically been associated with perceived 'high testosterone' levels. We devised a suppositional study, particularly pertinent for publication at the beginning of April. This was a prospective randomised study of five male consultant maxillofacial surgeons (including two with male pattern baldness) and assayed serum testosterone levels at rest, during, and after a series of major ablative and reconstructive procedures. The resting testosterone levels were found to be similar in all surgeons (220 ± 120.9 mcg/ml). During major head and neck procedures, a statistically significant increase in serum testosterone was found (up to a maximum concentration of 1062.50 mcg/ml). Multivariate analysis revealed that the likely predictors of increasing serum testosterone were: size and extent of tumour and complexity, and type of microvascular reconstruction (all P<0.001). The long-term effects of chronically raised serum testosterone warrant further investigation but recent evidence has found that it may be cerebro-protective against conditions including Alzheimer's syndrome.

Biomechanical study of a unilocking T-plate system for prophylactic internal fixation of the radial osteocutaneous donor site using the sheep tibia model.

Prophylactic internal fixation (PIF), with a bone plate in either the anterior (over the section defect) or posterior (on intact cortex) position, has substantially reduced the incidence of fracture at the donor site of the radial osteocutaneous free flap. This study uses the sheep tibia model to compare the effectiveness of new T-shaped titanium plates utilising a unilocking screw system with a 3.5 mm steel plate and bicortical screw fixation system commonly applied for PIF. Forty matched pairs of adult sheep tibias were tested in torsion and 4-point bending. An osteotomised bone was significantly weaker (p<0.001) than an intact bone in both bending and torsion with a mean loss of 77% and 64% of strength respectively. The tibia withstood much greater bending loads. All of the constructs significantly strengthened an osteotomised bone by a factor of 1.73-2.43 times in bending and 1.54-2.63 in torsion. The 2.4 mm T-plate in an anterior position (section) was the baseline against which other plates in differing positions were compared. The 3.5 mm T-plate section, DCP section and DCP cortex constructs had 41%, 30% and 2% greater mean bending strengths respectively but only the 3.5 mm T-plate section result approached statistical significance (p=0.06). In torsion the DCP section, 3.5 mm T-plate section and DCP cortex constructs had 56% (p=0.01), 27% (p=0.06) and 25% greater mean strengths respectively. When compared to an intact bone the mean bending strength restored by the DCP section (84%) and 3.5 mm T-plate section (87%) constructs was greatest and effectively restored the strength to that of an intact bone (100%). In torsion the mean strength restored by the DCP section (62%), DCP cortex (44%), 3.5 mm T-plate section (40%) and 2.4 mm T-plate (36%) remained significantly less than an intact bone. All of the plate constructs significantly strengthened an osteotomised bone but overall the 3.5 mm T-plate section and DCP section were the strongest constructs and most suitable for PIF. The lighter 2.4 mm T-shaped titanium plate was least effective. The strongest reinforcement in bending and torsion was the 3.5 mm T-plate section and DCP section respectively. The 3.5 mm DCP section plate was significantly stronger (p=0.01) than the 3.5 mm T-plate in torsion and remains the most effective construct for resisting torsional stresses, which are probably the commonest cause of fracture in clinical practice.

The sternocleidomastoid perforator flap.

The conventional pedicled sternocleidomastoid (SCM) flap has a poor arc of rotation, limited volume and precarious vascularity. This report describes a new technique for raising a SCM flap based on the perforating vessels of the superior thyroid vascular pedicle. The upper and lower attachments of the sternocleidomastoid muscle are divided. Four medically and/or surgically compromised patients have successfully undergone reconstruction of hemiglossectomy (1), partial glossectomy (1) and rim of mandible (2) defects for malignancy. The arc of rotation of the SCM flap is greatly increased and the potential applications for the flap expanded.

Early detection of bone union with transcutaneous ultrasound in the management of non-union of the mandible.

The management of complicated non-union of free flap osteotomy sites is both challenging and time consuming. If external fixation has been applied it may be difficult to know when sufficient bone union has occurred for safe removal of the fixation device. The progression of bony healing is conventionally monitored with radiographs or occasionally computed tomography (CT). Transcutaneous ultrasound is a simple, safe, and readily available investigation that gives early objective evidence of bone healing, reassuring both the patient and the surgeon.

The use of the pectoralis major flap for advanced and recurrent head and neck malignancy in the medically compromised patient.

A retrospective review of seventy-one PPM flaps used between 1996 and 2010 primarily for oral and oropharyngeal squamous cell carcinoma presenting as either advanced stage IV primary disease (41/43), extensive recurrent (10) or metastatic (9) neck disease. The PPM flap was most commonly used following resection of the mandible (23) or the tongue/oropharynx (19). When the PPM flap was the preferred reconstruction option (54) the main indication, in addition to advanced disease, was significant medical co-morbidity (23). The majority of PPM flaps (75%) were used in the latter half of the series for an increasing number of patients in poor health with advanced disease. There was no evidence of an increase in age, ASA grade or extent of disease during this period. Approximately one quarter (17) of the flaps were used after failure of a free flap, most commonly a DCIA (7) or radial (6) flap. The 30day mortality in this group of compromised patients undergoing major surgery for advanced disease was 7% (5/71). The overwhelming majority had significant co-morbidity (94% grade 2 or higher with 63% ASA grade 3) and 90% had already undergone previous major surgery and/or radiotherapy. The 1-year, 3-year and 5-year overall survival rates were 65.5%, 39.1% and 11.0% respectively with cancer-specific survival rates of 82.0%, 65.5% and 65.5%. The majority died of disease related to the underlying co-morbidity. We recommend an aggressive approach to the surgical resection of advanced and recurrent disease but a pragmatic approach to reconstruction. The PPM major flap is reliable for reconstruction of defects of the mandible, tongue and oropharynx with a complete flap failure rate of 2.8%. Lateral defects of the mandible were managed without a plate and with an acceptable outcome in the context of limited life expectancy. This is the largest study of the use of the PPM flap for this type of patient group. The flap retains a major role in the management of advanced primary or recurrent disease, extensive metastatic neck disease and after failure of a free flap when in conjunction with significant co-morbidity.

The use of a T-shaped contoured unilocking titanium radial plate for prophylactic internal fixation of the radial osteocutaneous donor site.

The radial osteocutaneous flap retains a limited role in reconstructive maxillofacial surgery The application of prophylactic internal fixation, using straight 3.5 mm plates, has become established to substantially reduce the incidence of fracture at the radial donor site. New lower profile T-shaped 2.4 mm plates and anatomically contoured 3.5 mm plates are now available, both with unilocking screw fixation systems. These plates are easy to apply and allow the removal of up to 50% of the circumference of the radial bone, including the maximum amount of good quality bone from the distal radius. Although there have been no reports of complications as a result of a stress shielding effect with larger plates these refinements in plate design should lessen any remaining concerns.

Review of the radial free flap: still evolving or facing extinction? Part two: osteocutaneous radial free flap.

The osteocutaneous radial flap is robust, reliable, and relatively simple to harvest, which will ensure that it remains one of the established reconstructive options in most maxillofacial units. Evidence based on clinical observational studies and biomechanical studies supports the routine or selective use of prophylactic internal fixation to strengthen the radial osteocutaneous donor site. This allows safe harvesting of the maximum volume of available bone, up to half of the circumference, with minimal risk of fracture or long term complications. The incidence of fracture with the plate placed either anteriorly or posteriorly is equally low, but the anterior position is technically easier and probably less likely to cause additional morbidity. This approach probably produces the least morbidity that may currently be achieved when managing the inherent flaws of the radial hard tissue donor site. The introduction of prophylactic internal fixation consolidates the role of the osteocutaneous radial flap for repair of defects that require a relatively small volume of bone and an appreciable area of thin soft tissue, particularly when a long vascular pedicle is desirable. This includes low level defects of the maxilla, some defects of the mandible, and niche reconstructions, such as the orbital rim. It remains useful as a first choice of flap when there is appreciable peripheral vascular disease, when there are other serious coexisting medical conditions; if it is the preferred choice of the patient for functional reasons such as mobility of the lower limb or hip, and as a salvage flap when other reconstructive options have been exhausted.

Review of the radial free flap: is it still evolving, or is it facing extinction? Part one: soft-tissue radial flap.

The versatile fasciocutaneous radial flap is robust and reliable, straightforward to harvest, and often produces a satisfactory reconstruction with relatively little long-term morbidity at the donor site. Many surgeons prefer to use a limited number of trusted flaps, and these qualities will ensure that in the intermediate future most surgical trainees will continue to be shown the fasciocutaneous radial flap as both the basic training flap and the established option for reconstruction. Evidence from observational clinical studies and one randomised clinical trial indicates that there is increasing support for the use of the evolutionary technique of suprafascial dissection to minimise morbidity at the donor site. The suprafascial donor site may be repaired with either a meshed or unmeshed partial-thickness skin graft, or a fenestrated full-thickness skin graft, with good rates of successful healing. The application of a negative pressure dressing to the wound seems to facilitate the healing of all types of skin graft. The subfascial donor site, however, remains more prone to complications. It may be helpful to position the donor site of the flap more proximally, but this has not been proven. These refinements probably produce the best outcomes that can currently be achieved, given the inherent flaws of the radial donor site.

A randomized controlled trial on cross-infection control in maxillofacial trauma surgery: a comparison of intermaxillary fixation techniques.

Glove perforations and percutaneous injuries occur commonly during the treatment of facial fractures and reveal the need for safer techniques, especially in intermaxillary fixation. The Rapid IMF device does not use any wires and may provide better cross-infection control than wiring methods. The aim of this study was to test the hypothesis that Rapid IMF is associated with fewer glove perforations/ percutaneous injuries than traditional wiring techniques. The authors carried out a randomized controlled trial which included 120 patients with fractures of the mandible requiring open reduction and fixation. The participants were allocated either to the study group and treated with intraoperative Rapid IMF or to the control group and managed with intraoperative eyelet wire ties. Analysis of the results showed that the Rapid IMF group had significantly fewer glove perforations than the traditional method (0.67 per operation compared with 1.5), (P<0.0001). The incidence of skin-penetrating injuries was the same in both groups (rate 0.02/ procedure). The application of Rapid IMF was significantly faster than wiring (P<0.0001). Minor intraoperative complications were noted in both groups, but more in the Rapid IMF group. Most concerned loosening or fracture of the anchorage ties but the surgical outcome was not affected. Rapid IMF is a safer alternative to wiring methods with significant reduction in glove perforation rates and is quicker to apply than conventional wiring techniques.

'The interpreter' in the maxillofacial outpatient clinic.

The role of an interpreter is crucial in an ethnically diverse city such as Leicester. Four hundred and seventy-three patients attending the outpatient department were studied. The majority could speak English to some degree. Thirty-one (7%) patients required an interpreter. This was most frequently a family member (70%) or multilingual clinician (27%). The latter are a valuable resource in the health service.

Cancellation of elective oral and maxillofacial operations.

Our aim was to assess whether the Commission for Health Improvement Performance Indicator value of 0.5% of cancellations on the day of operation or less had been achieved. We reviewed 912 consecutive elective operations, both day case and inpatient over an 8-month period (January-August 2003). A total of 117 procedures (13%) were cancelled for non-clinical or logistical reasons, of which 39 (4%) were cancelled on the day of the operation. Only 3 of the 39 patients who wanted a new admission date within 28 days of cancellation could not be accommodated. The performance indicator value of 0.3% was below the target threshold. An additional 60 (7%) patients had their admissions cancelled the day before operation and 18 (2%) had their operations deferred for a day before they were cancelled. However, these patients have been specifically excluded from the performance indicator.