Aims

The survival of humeral hemiarthroplasties in patients with relatively intact glenoid cartilage could theoretically be extended by minimizing the associated postoperative glenoid erosion. Ceramic has gained attention as an alternative to metal as a material for hemiarthroplasties because of its superior tribological properties. The aim of this study was to assess the in vitro wear performance of ceramic and metal humeral hemiarthroplasties on natural glenoids.

In shoulder arthroplasty, humeral resurfacing or short stem devices rely on the proximal humeral bone for fixation and load transfer. For resurfacing designs, the fixation takes place above the anatomical neck, whilst for short stem designs the resection is made at the anatomical neck and fixation is achieved in the bone distal to that resection. The aim of the study is to investigate the bone density in these proximal areas to provide information for implant design and guidance on appropriate positions to place implant fixation entities.

CT scans of healthy humeri were used to map bone density distribution in the humeral head. CT scans were manually segmented and a solid model of the proximal humerus was discretised into 1mm tetrahedral elements. Each element centroid was then assigned an apparent bone density based on CT scan Grey values. Matlab was used to sort data in spatial groups according to element centroid position to map bone density distribution. The humeral head was divided into twenty 2mm thick slices parallel to the humeral neck starting from the most proximal region of the humeral head to distal regions beneath epiphyseal plate (Fig 1a). Each slice was then radially divided into 30 concentric circles and each circle was angularly divided into 12 regions (Fig 1b). The bone density for each of these regions was calculated by averaging density values of element centroid residing in each region.

Average bone density in each slice indicates that bone density decreases from proximal region to distal regions below the epiphyseal plate and higher bone density was measured proximal to the anatomical neck of the humerus (Fig2). Figure 3 shows that, both above and below the anatomical neck, bone density increases from central to peripheral regions where eventually cortical bone occupies the space. This trend is more pronounced in regions below the anatomical neck and above the epiphyseal plate. In distal slices below the anatomical neck, a higher bone density distribution in inferior (calcar) regions was also observed.

Current generation short stem designs require a resection at the anatomical neck of the humerus and a cruciform keel to fix the implant in the distal bone. In the example in Figure 3, the anatomical neck resection corresponds to the 18 mm slice, with the central cruciform keel engaging between slices 18 mm and 27 mm. The data indicates that this keel should make use of the denser bone by the calcar for fixation, suggesting a crucifix orientation as highlighted in Figure 3. The current generation of proximally fixed humeral components are less invasive than conventional long-stemmed designs, but the disadvantage is that they must achieve fixation over a smaller surface area and with a less advantageous lever arm down the shaft of the humerus. By presenting a spatial density map of the proximal humerus, the current study may help improve fixation of proximally fixed designs, with a simple modification of implant rotational orientation to make use of the denser bone in the calcar region for fixation and load transfer.

Background

Total Shoulder Arthroplasty (TSA) has been shown to improve the function and pain of patients with severe degeneration. Recently, TSA has been of interest for younger patients with higher post-operative expectations; however, they are treated using traditional surgical approaches and techniques, which, although amenable to the elderly population, may not achieve acceptable results with this new demographic. Specifically, to achieve sufficient visualization, traditional TSA uses the highly invasive deltopectoral approach that detaches the subscapularis, which can significantly limit post-operative healing and function. To address these concerns, we have developed a novel surgical approach, and guidance and instrumentation system (for short-stemmed/stemless TSA) that minimize muscle disruption and aim to optimize implantation accuracy.

Introduction

Optimal orthopaedic implant placement is a major contributing factor to the long term success of all common joint arthroplasty procedures. Devices such as 3D printed bespoke guides and orthopaedic robots are extensively described in the literature and have been shown to enhance prosthesis placement accuracy. These technologies have significant drawbacks such as logistical and temporal inefficiency, high cost, cumbersome nature and difficult theatre integration. A radically new disruptive technology for the rapid intraoperative production of patient specific instrumentation that obviates all disadvantages of current technologies is presented.

Introduction

The reliability of currently available proximal humeral fracture classi?cation systems has been shown to be poor, giving rise to the question whether a more objective measure entails improved predictability of surgical outcome. This study aims to apply a novel software system to predict the functional range of motion of the glenohumeral joint after proximal humeral fracture.

Background

Surgical simulators allow learner-focussed skills training, in controllable and reproducible environments suitable for assessment.

Background

Tears of the rotator cuff are a common pathology and poorly understood. Achieving a good functional outcome for patients may be difficult, and the degree of fat infiltration into the muscle is known to be a major determining factor to surgical repair and post operative function. It is the hypothesis of this study that the degree of retraction of the common central tendon as seen on MRI corresponds to the amount of fat infiltration classified according to the Goutallier grading System.

Objective: There is no non-invasive gold standard for measuring gap formation following rotator cuff repair; re-tears are reported both on MRI and Ultrasound. We present a novel RSA technique using a combination of 1mm tantalum beads and metal sutures to allow monitoring of gap formation following rotator cuff repair.

Methodology: We carried out ten open rotator cuff repairs with using trans-osseous sutures on patients with moderate to massive tears. During surgery RSA markers were inserted into the shoulder to allow postoperative monitoring of the repair. These markers took the form of 1mm RSA tantalum beads in the greater tuberosity, distal to the repair site, and three metal sutures in tendon, proximal to the repair site. Direct measurements of the distance between the markers each side of the repair were taken intra-operatively (T=O). RSA images were taken of the repair immediately postoperatively (T=1–2 hours), day 3, 2 weeks, 3 months and 1 year post-operatively. Ultrasound imaging was performed at the same intervals by consultant musculo-skeletal radiologists blinded to the RSA data.

Results: At the 3 month stage post-operatively RSA data shows an increase in the average gap between the 2 sets of markers, with considerable variation between patients (5mm to 19mm).

Conclusion: The results are highly suggestive of gap formation in the repair. The greatest increase in gap formation has been seen between 2 weeks and 3 months. During this time patients come out of their abduction arm sling and commence physiotherapy. It may be that due to excessive loading on the repair before it has fully healed has causes failure in some cases.

There is no non-invasive gold standard for measuring gap formation following rotator cuff repair; re-tears are reported both on MRI and Ultrasound. Roentgen Stereophotogrammetric Analysis (RSA) has previously been used to monitor microscopic migration of markers in rigid bodies. We present a novel RSA technique using a combination of 1mm tantalum beads and metal sutures to allow accurate monitoring of gap formation following rotator cuff repair. The RSA system combines a commercially made calibration cage with software developed at Imperial College. We verified the RSA system by analysing a movable glass phantom and comparing the data with precise physical measurements of the same object: it identified a 2mm distraction of the phantom to within 0.05mm. In vitro work involved cadaveric human shoulders. We placed three 1mm RSA tantalum beads in the greater tuberosity and three metal sutures in supraspinatus tendon. We then created a tear in supraspinatus at its insertion into the greater tuberosity. We were able to show that RSA images taken before and after the tear correlated closely with direct measurements. The processed data demonstrated movement associated with gap formation. We have performed two open rotator cuff repairs using trans-osseous sutures. During surgery RSA markers were inserted into the shoulder to allow post-operative monitoring of the repair (guided by the in vitro work). Direct measurements of the distance between markers each side of the repair were taken intra-operatively (T=O). RSA images were taken immediately post-operatively (T=1 hours), day 3, day 14, and day 84. The RSA data suggests gapping of typically 3mm may have occurred at the repair sites in both patients. Ultrasound imaging was performed at the same intervals by consultant musculoskeletal radiologists blinded to the RSA data. Preliminary results correlating the two modalities suggest that ultrasound can visualise gap formation accurately even immediately post-operatively.

This study aimed to quantify the relationship between passive tension of rotator cuff repair and arm position intraoperatively and to examine the effect of the passive tension on gap formation in cadaveric rotator cuff repairs.

Five patients undergoing open surgical reconstruction of the rotator cuff were recruited. The operations were performed by a single surgeon using a standardised technique, which was acromioplasty, minimal debridement, mobilisation of tissue, bone troughs and transosseous suture tunnels.

A Differential Variable Reluctance Transducer (DVRT) was placed at the apex of the debrided tendon. An in situ calibration was performed to relate the output from the DVRT to actual tension in the tendon. The tension generated was recorded as the supraspinatus tendon was advanced into a bone trough and secured.

The relationship between arm position and repair tension was measured, by simultaneously collecting data from the DVRT and a calibrated goniometer. Particular attention was paid to the three standard positions of post-operative immobilisation; full adduction with internal rotation, neutral rotation with a 30° abduction wedge and ninety degrees of abduction.

Five cadaveric shoulders were used for the creation of standardised rotator cuff tears which were then repaired using the technique described above. The difference in tension measured between full adduction and 30° abduction was statically applied for twenty four hours and the gap formation measured.

Repair tension increased with advancement of the supraspinatus tendon into the bone trough. Abduction reduced the repair load, this was observed mainly in the first 30° of abduction. The mean reduction in load by 30° of abduction was 34 N.

Twenty four hours of 34N static loading caused gap formation in each cadaveric rotator cuff repairs, the mean was 9.2 mm.

Rotator cuff repairs tension can be reduced by postoperative immobilisation in 30° abduction. The change in tension with full adduction was caused gap formation in cadaveric rotator cuff repairs.

The management of proximal humeral fractures is determined by fragment displacement. Intra-operative and radiological classification systems have been proposed, namely AO and the Neer classifications to assess therapeutic options.

This study evaluates the usefulness of these classification systems by the creation of physical 3D models using a rapid prototyping technique avoiding the problems associated with 3D illusions on a 2D screen.

Seven consecutive patients with complex fractures of the proximal humerus were investigated using the data from multi-sliced spiral CT scans. Fractures associated with dislocation were excluded. The data from these CTs was segmented to reveal the anatomy of interest and converted to a stereolithographic format from which the physical models could be made of the proximal humerus via a laser guided filament deposition process. Further manipulation with software allowed angulation and displacements of fragments to be measured.

Inter-observer agreement: All models were assessed by three surgeons. A consultant with a special interest in shoulder surgery, a fellowship trained surgeon and a senior house officer in basic surgical training. Independent assessment of the fractures from the models was made using the Neer and AO classifications. In only 1 incidence did all 3 observers agree on the classification, in 5 incidences only two observers agreed and on 8 occasions none of the observers agreed. Indeed there were 9 occasions that at least one observer thought the fracture pattern could not be applied to a classification.

Fracture Patterns: Observation of the individual models together with measurements of angulation and displacement by further software analysis, demonstrated major subtypes namely valgus and varus angulation with minimal displacement of the greater tuberosity. Appreciation of the integrity of the medial hinge and buckling could be made in relation to the different fracture patterns.

This study highlights concerns on the validity of current classification systems. It also questions whether the existing systems reflect the pathophysiological subtypes of these fractures allowing comparison of surgical results in order to evaluate treatment options.

INTRODUCTION: Regular review [1, 2] of cervical injuries occurring in rugby players is an important step toward maximising the safety of the players. It is hoped that the recognition of recurring patterns of injury would lead to appropriate rule modification by the regulatory bodies of the sport. Serious cervical injuries in rugby have been reported to occur by a range of mechanisms, including those involved with scrummaging, tackling, rucking and mauling.

Spinal flexion is the commonest mechanism of injury and has been associated with scrum engagement, scrum collapse, rucking or mauling, and mistimed tackling. The second most common mechanism of cervical spinal injury is hyper-extension. This commonly occurs during tackling, particularly the ‘gang tackle’ involving several participants simultaneously, where sudden deceleration of a player’s head may lead to cervical hyperextension, focal spinal stenosis and potential damage to the spinal cord by a “pincer” mechanism.

The most commonly reported levels of injury are C5/6 and C4/5 [3].

METHODS: A retrospective review of neck injuries presenting to a major spinal injuries facility and resulting from all codes of football (rugby union, rugby league, soccer, indoor soccer and touch) was conducted and 38 cases identified.

RESULTS: Of the 38 patients, 14 were injured playing rugby union, 15 rugby league, three soccer, one indoor soccer, one touch football and four were playing an unidentified code. Six players were injured while scrummaging, five rugby union and one rugby league. 21 people were injured as tacklees, four as tacklers and two with unspecified involvement in a tackle. One person was injured whilst “heading” the ball, and three people were injured in a non-contact or unspecified action. At final follow-up, four people were found to be quadriplegic (ASIA A), 10 quadriparetic (ASIA B – 0 C –1 and D –9) and 24 recovered completely (ASIA E).

In vivo loading data for the rotator cuff would be of value to scientists and clinicians interested in the shoulder in the testing of surgical repairs, design of rehabilitation programs and for finite element models.

A technique for insertion and retrieval of the Arthroscopically Insertable Force Probe (AIFP - Microstrain Inc. Burlington, Vermont, USA) from the subscapularis is described was initially established in a cadaveric model. Ethical approval was obtained for AIFP insertion into the subscapularis tendon of volunteers during diagnostic shoulder arthroscopy. An in situ calibration was carried out using a modified arthroscopic grasper ( Smith and Nephew, Huntingdon, UK). After motor effects of interscalene block had worn off dynamic data relating to subscapularis tendon loading was collected. The AIFPs were removed through a port site by traction on an O (3.5 metric) nylon suture without complication.

Maximum loading of the subscapularis tendon was measured during internal rotation from neutral with the arm fully adducted. Forces measured exceeded 200N.

This paper describes a novel technique for the insertion, calibration and retrieval of AIFPs from the rotator cuff. In vivo tendon loading data was obtained. The techniques described may be applied to other structures of interest to orthopaedic surgeons.

Background: Greater tuberosity disuse osteoporosis is a consequence of rotator cuff tear. This is a significant problem as the tendon is implanted into a trough within the greater tuberosity during repair. Failure of the repair is a common complication (up to 50%). We hypothesise that failure in re-implantation is due to deficient bone cell response to mechanical stimulation in the tuberosity.

Methods: In order to establish whether these cells are capable of responding appropriately to mechanical stimuli, the response of bone cells derived from the tuberosity was compared with that of cells derived from the acromion. This was measured in terms of strain related increases in alkaline phosphatase (ALP) activity and nitric oxide (NO) production (which are recognised markers of osteoblast differentiation and their response to mechanical strain). Primary osteoblasts were cultured from samples of acromion and greater tuberosity taken during routine rotator cuff repair (n=10 pairs). The derived cells were:

Placed under cyclic strain at a physiological magnitude for 10 minutes at 1Hz using well established controls. Samples of media were analyzed for changes in NO and the cells were reacted for ALP activity, or:

Results: The results suggest that cells derived from the acromion exhibit significant strain related increases in cellular NO release and in ALP activity, whereas cells derived from the humeral greater tuberosity fail to exhibit any such increases. In marked contrast, cells derived from both sites exhibit increases in ALP activity in response to dexamethasone treatment.

Conclusions: Our results suggest that whilst cells derived from the tuberosity, after rotator cuff tear, respond appropriately to chemical and hormonal stimuli, they are compromised in their ability to respond to mechanical stimulation. Therefore, it is tempting to speculate that such relationships are also evident in vivo and that they underpin re-implantation failures.

Disuse osteoporosis of the greater tuberosity is a consequence of rotator cuff tear. This is a significant problem as the tendon is implanted into a trough within the greater tuberosity during repair. Failure of the repair is a common complication (up to 50%). We hypothesized that failure in re-implantation is due to deficient bone cell response to mechanical stimulation in the tuberosity. In order to establish whether these cells are capable of responding appropriately to mechanical stimuli, the response of bone cells derived from the tuberosity was compared with that of cells derived from the acromion. This was measured in terms of strain related increases in alkaline phosphatase (ALP) activity, nitric oxide (NO) and prostaglandin (PG) production (which are recognised markers of osteoblast differentiation and their response to mechanical strain).

Primary osteoblasts were cultured from samples of acromion and greater tuberosity taken during routine rotator cuff repair (n=5 pairs). The derived cells were placed under cyclic strain at a physiological magnitude for 10 min at 1Hz using well established controls. Samples of media were analysed for changes in NO and PG production and the cells were reacted for ALP. Cells were stimulated with dexamethasone, ascorbic acid and beta-glycerophosphate (established mediators of osteoblast differentiation) then reacted for ALP.

Preliminary results suggest that cells derived from the acromion exhibit significant increases in cellular NO release and in ALP activity, whereas cells derived from the humeral greater tuberosity fail to exhibit any such increases. In marked contrast cells derived from both sites exhibit increases in ALP activity in response to dexamethasone, ascorbic acid and beta-glycerophosphate treatment.

The results suggest that whilst cells derived from the tuberosity after rotator cuff tear respond appropriately to chemical and hormonal stimuli, they are compromised in their ability to respond to mechanical stimulation. It is tempting to speculate that such relationships are also evident in vivo and that they underpin reimplantation failures.

To quantify the variation in strain between the deep and superficial layers of the supraspinatus tendon, ten cadaveric shoulders were tested on a purpose built rig. Differential Variable Reluctance Transducers (DVRTs) were inserted into the superficial and deep aspects of the tendon spanning the critical zone. DVRTs accurately measured linear displacement and from this strain was calculated.

The strain was measured for two aspects of supraspinatus action, abduction from 0 to 120 degrees with a tensile load (100 Newtons) and static load increases at zero abduction (20, 50, 100, 150 and 200 Newtons). After preconditioning, ten sets of results were recorded for each load/position.

The hypothesis, there is a statistically significant difference in strain between the superficial/deep supraspinatus tendon during abduction and with static loading, was tested using a one way ANOVA.

During abduction a statistically significant difference in strain was measured between the layers of the supraspinatus tendon at thirty degrees (p=0.000428) and this increased with further abduction.

Tensile loading increased tendon strain more in the deep layer of the tendon. This was statistically significant at loads greater than 150N (p= 0.007).

The variation in properties between the superficial and deep layers of the supraspinatus tendon has been proposed as a cause of differential strain (1). This study confirms statistically different strains between the superficial and deep tendon layers. It is proposed that the resulting shearing effect initiates intratendinous defects and ultimately tears.

This study was carried out to investigate the outcome of rotator cuff repair surgery in 14 centres in th UK in a randomised controlled trial. It also looked at a comparison of a long-acting absorbable suture (Panacyrl) and a non-absorbabable suture (Ethibond).

All patients were treated with open repair of their rotator cuff tear with modified Mason-Allen sutures used in 83% of cases. One hundred and fifty-nine patients were included in the analysis. patients had Constant scores carried out pre-operatively, six and 12 months as well as ultrasound real time dynamic scans at eight weeks, six and 12 months.

Constant pain scores, total constant scores and re-tear rates were measured. There was a significant improvement in the Constant score after rotator cuff repair surgery. However for large tears, the re-tear rate at six months is approximately 50%. Despite this high retear rate there was still a good benefit from surgery. Is the improvement in those cases with a re-tear a consequence of the sub-acromial decompression (SAD) and what would have been the outcome with an ASD alone?