Summary Statement. Incorrect pedicle screw placement can lead to neurological complications. Practice outside the operating room on realistic bone models, with force feedback, could improve safety. Pedicle forces in cadaveric specimens are reported, to support development of a training tool for residents. Introduction. Inserting screws into the vertebral pedicles is a challenging step in spinal fusion and scoliosis surgeries. Errors in placement can lead to neurological complications and poor mechanical fixation. The more experienced the surgeon, the better the accuracy of the screw placement. A physical training system would provide orthopaedic residents with the feel of performing pedicle cannulation before operating on a patient. The proposed system consists of realistic bone models mimicking the geometry and material properties of typical patients, coupled with a force feedback probe. The purpose of the present study was to determine the forces encountered during pedicle probing to aid in the development of this training system. Methods. We performed two separate investigations. In the first study, 15 participants (9 expert surgeons, 3 fellows, 3 residents) were asked to press a standard pedicle awl three times onto a mechanical scale, blinded to the force, demonstrating what force they would apply during safe pedicle cannulation and during unsafe cortical breach. In the second study, three experienced surgeons used a standard pedicle awl fitted with a one-degree of freedom load cell to probe selected thoracolumbar vertebrae of eight cadaveric specimens to measure the forces required during pedicle cannulation and deliberate breaching, in randomised order. A total of 42 pedicles were tested. Results. Both studies had wide variations in the results, but were in general agreement. Cannulation (safe) forces averaged approximately 90 N (20 lb) whereas breach (unsafe) forces averaged approximately 135–155 N (30–35 lb). The lowest average forces in the cadaveric study were for pedicle cannulation, averaging 86 N (range, 23–125 N), which was significantly lower (p<0.001) than for anterior breach (135 N; range, 80–195 N); medial breach (149 N; range, 98–186 N) and lateral breach (157 N; range, 114–228 N). There were no significant differences among the breach forces (p>0.1). Cannulation forces were on average 59% of the breach forces (range, 19–84%) or conversely, breach forces were 70% higher than cannulation forces. Discussion. To our knowledge, axial force data have not previously been reported for pedicle cannulation and breaching. A large range of forces was measured, as is experienced clinically. Additional testing is planned with a six-degree-of-freedom load cell to determine all of the forces and moments involved in cannulation and breaching throughout the thoracolumbar spine. These results will inform the development of a realistic bone model as well as a breach prediction algorithm for a physical training system for spine surgery. The opportunity to learn and practice outside of the operating room, including learning from deliberate mistakes, should increase the confidence and comprehension of residents performing the procedure, enhance patient safety, reduce surgical time, and allow faster progression of learning inside the operating room

To quantify bone-nail fit in response to varying nail placements by entry point translation in straight antegrade humeral nailing using three-dimensional (3D) computational analysis. CT scans of ten cadaveric humeri were processed in 3D Slicer to obtain 3D models of the cortical and cancellous bone. The bone was divided into individual slices each consisting of 2% humeral length (L) with the centroid of each slice determined. To represent straight antegrade humeral nail, a rod consisting of two cylinders with diameters of 9.5mm and 8.5mm and length of 0.22L mm and 0.44L mm respectively joined at one end was modelled. The humeral head apex (surgical entry point) was translated by 1mm in both anterior-posterior and medio-lateral directions to generate eight entry points. Total nail protrusion surface area, maximum nail protrusion distance into cortical shell and top, middle, bottom deviation between nail and intramedullary cavity centre were investigated. Statistical analysis between the apex and translated entry points was conducted using paired t-test. A posterior-lateral translation was considered as the optimal entry point with minimum protrusion in comparison to the anterior-medial translation experiencing twice the level of protrusion. Statistically significant differences in cortical protrusion were found in anterior-medial and posterior-lateral directions producing increased and decreased level of protrusion respectively compared to the apex. The bottom anterior-posterior deviation distance appeared to be a key predictor of cortical breach with the distal nail being more susceptible. Furthermore, nails with anterior translation generated higher anterior-posterior deviation (>4mm) compared to posterior translation (<3mm). Aside from slight posterolateral translation of the entry point from the apex, inclusion of a distal posterior-lateral bend into current straight nail design could improve nail fitting within the curved humeral bone, potentially improving distal working length within the flat and narrow medullary canal of the distal humeral shaft

Conventional amputation prostheses rely on the attachment of the socket to the stump, which may lead to soft-tissue complications. Intraosseous transcutaneous amputation prostheses (ITAPs) allow direct loading of the skeleton, but their success is limited by infection resulting from breaching of the skin at the interface with the implant. Keratinocytes provide the skin’s primary barrier function, while hemidesmosomes mediate their attachment to natural ITAP analogues. Keratinocytes must attach directly to the surface of the implant. We have assessed the proliferation, morphology and attachment of keratinocytes to four titaniumalloy surfaces in order to determine the optimal topography in vitro. We used immunolocalisation of adhesion complex components, scanning electron microscopy and transmission electron microscopy to assess cell parameters. We have shown that the proliferation, morphology and attachment of keratinocytes are affected by the surface topography of the biomaterials used to support their growth. Smoother surfaces improved adhesion. We postulate that a smooth topography at the point of epithelium-ITAP contact could increase attachment in vivo, producing an effective barrier of infection

Pedicle screw fixation is an effective and reliable method for achieving stabilization in lumbar degenerative disease. The procedure carries a risk of violating the spinal and neural canal which can lead to nerve injury. This audit examines the accuracy of screw placement using intra-operative image guidance. Retrospective audit of patients undergoing lumbar pedicle screw fixation using image guidance systems over an 18-month period. Case records were reviewed to identify complications related to screw placement and post-operative CT scans reviewed to study the accuracy of screw position. Of the 98 pedicle screws placed in 25 patients, pedicle violation occurred in 4 screw placements (4.1%). Medial or inferior breach of the pedicle cortex was seen in 2 screws (2%). Nerve root injury as a consequence of this violation was seen in one patient resulting in irreversible partial nerve root dysfunction. Mean set up time for the guidance system was 42 minutes. The mean operative time was 192 minutes. Violation of either the medial or inferior pedicle cortex during placement of fixation screws is a rare, but potentially serious complication bearing lasting consequences. Image-guided placement can be helpful and possibly improve accuracy; particularly in patients with distorted spinal anatomy

This project began as an audit of performance against the 18-week referral to treatment time (RTT) target but became an interesting development in clinical training. The electronic documents and PACS images for 50 consecutive routine GP referrals to an orthopaedic clinic were traced using the UCPN (Unique Care Pathway Number). The average time from referral to 1. st. clinic appointment was 57 days (range 29–117). 16 were discharged at 1. st. visit. 26 were listed for surgery: 20 at the 1. st. clinic, 3 at the 2. nd. clinic, 2 at the 3. rd. clinic, 1 after test results without clinic review. Average time from referral to listing was 68 days (range 28–177). For 25 patients who had surgery, average RTT was 164 days (61–394). 14 patients breached the target. The UCPN allows an overview of the diagnostic work-up for the whole care pathway. Time constraints and less opportunity for continuity of care have hampered effective training in the outpatient clinic. Using the UCPN in this way allows detailed case-based discussions to develop the non-technical surgical skills (NOTSS) of situation awareness and decision-making. In a system where 57 days are typically wasted waiting for a new clinic appointment, clinical reasoning skills must be scalpel sharp to meet the 18-week RTT target. This study hints that better characterising the third of patients discharged and the third directly listed for surgery at the first visit might help with demand management. Better characterising the third of patients needing further tests might allow those test results to be available by the first visit. The next step is to test if, indeed, the UCPN is an effective tool to hone mental dissection

Troponin I is a widespread used blood test to confirm myocardial damage, usually attributable to myocardial infarction. Troponin tests require to be taken 12 hours after the initial event, and thus may be a potential cause for delay. SIGN and Hip Fracture Audit guidelines recommend 98% of patients obtaining surgery within 24hrs of admission. A population of 347 neck of femur patients presenting to Glasgow Royal Infirmary were assessed over a one year period. 44 (13%) Patients were identified as having a pre-operative Troponin I test. Retrospective case note review of this patient cohort who had pre operative troponin testing was undertaken to identify timing of TnI testing, admission, surgery and medical comorbidies. Time to theatre was compared with the 24hr guideline. From the cohort, 32 Patients had case notes which were located, of which 4 had no filed notes from the admission giving a 28 patient sample population. 18 (64%) had a Troponin of ‘negative’ value (<0.04 μg/l) of which the mean delay to theatre from admission was 46.4 hrs (median 44.5hrs). All 18 breached the 24hr target, 5 were delayed >48hrs. Of the 10 ‘postive’ patients, mean TnI was 0.4 and time to theatre was 85hrs (median 69hrs) with one excluded as treated conservatively. Only one patient was treated within the 24hr target (3.7% of sample group treated operatively) p=<0.001. Scottish Hip Fracture Audit shows GRI to have an overall 98.6% compliance with the 24hr target. The data presented shows significant (near complete) failure to meet the 24hr target in patients tested preoperatively for Troponin I. Almost three-quarters of these patients have normal TnI, but delay may be attributable to additional comorbidities

Infection is the primary failure modality for transcutaneous implants because the skin breach provides a route for pathogens to enter the body. Intraosseous transcutaneous amputation prostheses (ITAP) are being developed to overcome this problem by creating a seal at the skin-implant interface to prevent bacterial invasion. Oral gingival epithelial cell adhesion creates an infection free seal around dental implants; however this has yet to be demonstrated outside the oral environment. All epithelial cells attach via hemidesmosomes (HD) and focal adhesions (FA) and their expression is an indicator of adhesion efficiency. The aim of this study was to compare epidermal keratinocyte with oral gingival epithelial cell adhesion on titanium alloy in vitro to determine whether these two cell types differ in their speed and strength of adhesion. It was hypothesised that oral gingival epithelial cells attach to titanium alloy earlier than epidermal keratinocytes; with greater expression of hemidesmosomes and focal adhesions. Human oral gingival epithelial cell (HGEP) and primary human epidermal keratinocyte (HPEK) adhesion to titanium alloy, was assessed at 4, 24, 48 and 72 hrs. Adhesion was measured by the number of FAs per unit cell area and expression of HDs using a semi-quantitative scale. At 4 and 24hrs, there was a significant increase in vinculin marker expression per unit cell area of 4.3 and 4.7 times in HGEP compared with HPEK (p=0.000). At 48 and 72hrs there were no significant differences. HD expression was significantly greater in HGEP at 4 and 24hrs (p=0.002) compared with HPEK. Up-regulation of HD expression in HPEK lagged that of HGEP until 48hrs, after which no significant differences were observed. This study has demonstrated that oral gingival cells up-regulate both focal adhesion and hemidesmosome expression at earlier time points compared with epidermal keratinocytes. Expression of hemidesmosomes lags that of focal adhesions, suggesting that focal adhesion formation is a prerequisite for hemidesmosome assembly. We postulate that early attachment of oral gingival epithelial cells to dental implant biomaterials may be responsible for the formation of an infection-free seal

Summary Statement. Pedicle screws provide robust fixation and rigid immobilization. There has been no attempt to correlate the anatomic dimensions of thoracic and lumbar pedicles with the accuracy of navigated insertion. This study demonstrates that comparable accuracy using this technique. Introduction. Pedicle screws provide robust mechanical fixation, which makes their use attractive; their use enables fixation of the three spinal columns. There remains concern about the potential both for misplacement; various investigators have studied the accuracy of pedicle screw insertions, comparing different techniques. What is not clear, however, is whether there is any relation between the variables of pedicles’ anatomic dimensions, screw dimensions and accuracy. This study aims to elucidate the relationship between these variables. Patients & Methods. We conducted a retrospective review of consecutive pedicle screws that were inserted in the thoracic and lumbar spine at our institution. Screws were inserted using the navigated method (Stealth Station® TREON™, Medtronic, Louisville, CO). The accuracy of the screw insertion was measured using the classification system developed by Gertzbein and Robbins; pedicle dimensions were measured from post-operative computed tomography scans. The corresponding pre-operative scans were then used to measure the pedicle dimensions at the other levels. The magnitude of a cortical breach in the pedicle was represented by a letter: A (no breach), B (<2mm), C (>2mm, <4mm), D (>4mm, <6mm) and E (>6mm). In addition, measurements were made of the anatomic dimensions of the pedicles. The combination of these two measures allowed for direct correlation to be made between the accuracy of screw insertion, screw dimensions and pedicle anatomy. We then computed the proportion of each pedicle (width) occupied by a screw. Results. A total of 765 screws were reviewed, 493 were in the thoracic spine and 272 in the lumbar spine. Of the screws in the thoracic spine, 472 (96%) were either fully in the pedicle or less than 2mm beyond the cortex (within the A+B classification); when considered separately, 323 (66%) were completely within the pedicle (A) and 149 (30%) were less than 2mm beyond the cortex. A total of 21 (4%) screws were beyond 2mm but within 6mm (C+D). In the lumbar spine, 270 (99%) were either completely within the cortex or less than 2mm exposed (classified as A or B). The nadir of pedicle width was at T4. From L1 to L5, measured pedicle width also rose. This pattern was followed, although it was less profound, when screw diameter was measured in the lumbar spine (and even less so in the thoracic vertebrae). The height of pedicles was noted to progressively increase, peaking at the thoraco-lumbar junction. The mid thoracic region was associated with screws occupying the greatest proportion of pedicle diameter. Discussion/Conclusion. The use of pedicle screws in the thoracic and lumbar spine remains relatively safe. The accuracy of navigated insertion was found to compare well to previous series’. Although there is some association between the anatomical dimensions of pedicles and the dimensions of screws, this doesn't seem to be a strong association. Based on the findings in this series, future studies that relate the long term outcome (e.g. failure or screw loosening) with proportion of pedicle diameter taken up by a screw may be warranted

Objectives

All-suture anchors are increasingly used in rotator cuff repair procedures. Potential benefits include decreased bone damage. However, there is limited published evidence for the relative strength of fixation for all-suture anchors compared with traditional anchors.

We split 100 porcine flexor tendons into five groups of 20 tendons for repair. Three groups were repaired using the Pennington modified Kessler technique, the cruciate or the Savage technique, one using one new device per tendon and the other with two new devices per tendon. Half of the tendons received supplemental circumferential Silfverskiöld type B cross-stitch. The repairs were loaded to failure and a record made of their bulk, the force required to produce a 3 mm gap, the maximum force applied before failure and the stiffness. When only one device was used repairs were equivalent to the Pennington modified Kessler for all parameters except the force to produce a 3 mm gap when supplemented with a circumferential repair, which was equivalent to the cruciate.

When two devices were used the repair strength was equivalent to the cruciate repair, and when the two-device repair was supplemented with a circumferential suture the force to produce a 3 mm gap was equivalent to that of the Savage six-strand technique.

We used a goat model of a contaminated musculoskeletal defect to determine the effectiveness of rapidly-resorbing calcium-sulphate pellets containing amikacin to reduce the local bacterial count. Our findings showed that this treatment eradicated the bacteria quickly, performed as well as standard polymethylmethacrylate mixed with an antibiotic and had many advantages over the latter. The pellets were prepared before surgery and absorbed completely. They released all of the antibiotic and did not require a subsequent operation for their removal. Our study indicated that locally administered antibiotics reduced bacteria within the wound rapidly. This method of treatment may have an important role in decreasing the rate of infection in contaminated wounds.

Compartment syndrome of the foot requires urgent surgical treatment. Currently, there is still no agreement on the number and location of the myofascial compartments of the foot. The aim of this cadaver study was to provide an anatomical basis for surgical decompression in the event of compartment syndrome. We found that there were three tough vertical fascial septae that extended from the hindfoot to the midfoot on the plantar aspect of the foot. These septae separated the posterior half of the foot into three compartments. The medial compartment containing the abductor hallucis was surrounded medially by skin and subcutaneous fat and laterally by the medial septum. The intermediate compartment, containing the flexor digitorum brevis and the quadratus plantae more deeply, was surrounded by the medial septum medially, the intermediate septum laterally and the main plantar aponeurosis on its plantar aspect. The lateral compartment containing the abductor digiti minimi was surrounded medially by the intermediate septum, laterally by the lateral septum and on its plantar aspect by the lateral band of the main plantar aponeurosis. No distinct myofascial compartments exist in the forefoot.

Based on our findings, in theory, fasciotomy of the hindfoot compartments through a modified medial incision would be sufficient to decompress the foot.

In this study a combination of autologous chondrocyte implantation (ACI) and the osteochondral autograft transfer system (OATS) was used and evaluated as a treatment option for the repair of large areas of degenerative articular cartilage. We present the results at three years post-operatively. Osteochondral cores were used to restore the contour of articular cartilage in 13 patients with large lesions of the lateral femoral condyle (n = 5), medial femoral condyle (n = 7) and patella (n = 1). Autologous cultured chondrocytes were injected underneath a periosteal patch covering the cores. After one year, the patients had a significant improvement in their symptoms and after three years this level of improvement was maintained in ten of the 13 patients. Arthroscopic examination revealed that the osteochondral cores became well integrated with the surrounding cartilage. We conclude that the hybrid ACI/OATS technique provides a promising surgical approach for the treatment of patients with large degenerative osteochondral defects.