We hypothesised that a large acromial cover with an upwardly tilted glenoid fossa would be associated with degenerative rotator cuff tears (RCTs), and conversely, that a short acromion with an inferiorly inclined glenoid would be associated with glenohumeral osteoarthritis (OA). This hypothesis was tested using a new radiological parameter, the critical shoulder angle (CSA), which combines the measurements of inclination of the glenoid and the lateral extension of the acromion (the acromion index).

The CSA was measured on standardised radiographs of three groups: 1) a control group of 94 asymptomatic shoulders with normal rotator cuffs and no OA; 2) a group of 102 shoulders with MRI-documented full-thickness RCTs without OA; and 3) a group of 102 shoulders with primary OA and no RCTs noted during total shoulder replacement. The mean CSA was 33.1° (26.8° to 38.6°) in the control group, 38.0° (29.5° to 43.5°) in the RCT group and 28.1° (18.6° to 35.8°) in the OA group. Of patients with a CSA > 35°, 84% were in the RCT group and of those with a CSA < 30°, 93% were in the OA group.

We therefore concluded that primary glenohumeral OA is associated with significantly smaller degenerative RCTs with significantly larger CSAs than asymptomatic shoulders without these pathologies. These findings suggest that individual quantitative anatomy may imply biomechanics that are likely to induce specific types of degenerative joint disorders.

Cite this article: Bone Joint J 2013;95-B:935–41.

Objectives

Cadaveric models of the shoulder evaluate discrete motion segments using the glenohumeral joint in isolation over a defined trajectory. The aim of this study was to design, manufacture and validate a robotic system to accurately create three-dimensional movement of the upper body and capture it using high-speed motion cameras.

The glenohumeral joint is an important joint with large mobility of the human upper extremity. In shoulder arthroplasty patients often has an unsatisfactory outcome. In order to understand the biomechanical complexity of the shoulder, a novel computer controlled experimental shoulder simulator with an innovative muscle control were constructed. The main component of the simulator includes the active pneumatic muscles to replicate the deltoid and the rotator-cuff function and two springs as passive muscle. The aim of this study is to evaluate the impact of a variation of shoulder joint geometries on shoulder biomechanics in the basis of motion analysis. The radius of the glenoid cavity varied from 28–33mm with 2.5mm increment while the radius the humeral head are varied from 20.1–25.1 with 2.5mm increment. The “teach-in” function of the simulator allows an operator to assign the movement to the simulator where the lengths of the pneumatic muscles are recorded. Then the simulator repeats the assigned movement according to the recorded muscles length. The daily living activities includes abduction/adduction, internal/external rotation with adducted arm, and circumduction. The results show promising repeatability of the simulator with minor deviation. However, damage on the surface of the humeral head has been found which should be further studied for both shoulder behavior investigation and the shoulder simulator optimisation. Therefore, this study is a decent initial study toward the verification of the simulator and lead to a better understanding of shoulder biomechanical behavior to cope with the clinical problems in the future

The results of proximal humeral replacement following trauma are substantially worse than for osteoarthritis or rheumatoid arthritis. The stable reattachment of the lesser and greater tuberosity fragments to the rotator cuff and the restoration of shoulder biomechanics are difficult. In 1992 we developed a prosthesis designed to improve fixation of the tuberosity fragments in comminuted fractures of the proximal humerus. The implant enables fixation of the fragments to the shaft of the prosthesis and the diaphyseal fragment using screws, washers and a special toothed plate. Between 1992 and 2003 we used this technique in 50 of 76 patients referred to our institution for shoulder reconstruction after trauma. In the remaining 26, reconstruction with a prosthesis and nonabsorbable sutures was performed, as the tuberosity fragments were too small and too severely damaged to allow the use of screws and the toothed plate. The Constant score two years post-operatively was a mean of 12 points better in the acute trauma group and 11 points better in the late post-traumatic group than in the classical suture group. We recommend this technique in patients where the tuberosity fragments are large enough to allow fixation with screws, washers and a toothed plate

Purpose: We compared three fixation systems for proximal fractures of the humerus to elaborate a rigid extra-medullary implant: the basket plate. This novel implant allows fixation of the tubercles with a claw system associated or not with a central cephalic locking screw. The objectives of this study were: check the resistance of the prototype, evaluate the contributions of the claws, and the usefulness of locking. Material and methods: This was a prototype experimental study comparing a commonly used implant (Maconor2 plate) with the new implant using two series of static mechanical tests (Instrum). The tests were performed on 20 DMO-frozen anatomic specimens using the four-fragment fracture model. An implant was assigned to five groups of randomly selected specimens. The first tests (three groups) were axial compression tests mimicking abduction in the plane of the scaphoid. We analysed the overall mechanical behaviour of the implant and evaluated the locking system. The second tests (two groups) were traction tests. We analysed the behaviour of the fixed tuberosities. The mechanical resistance of the assemblies was noted as the limit load on the force: deformation curve and as the rigidity of the slope. Results: The first tests showed that the implant was improved by the locking system and had better overall mechanical characteristics than the compared implant, although the difference was not statistically significant. The better hold in the tubercles provided by the claws was expected after the first tests and confirmed by the second tests, but the difference was not significant. Discussion: The prototype improved with the locking system presented mechanical resistance equivalent to the compared model. The usefulness of locking could not be demonstrated but was considered to improve tolerance to loading by better force distribution. The contribution of the claws was not demonstrated statistically although the results are in line with early hopes. The present findings and data in the literature on shoulder biomechanics suggest that the tests should be conducted on a larger number of specimens to demonstrate a statistically significant difference. The tested series was too small. Conclusion: Comparison of mechanical resistance with theoretical data on forces applied to the proximal humerus show that the prototype is well adapted, allowing immediate postoperative motion. A prospective study is currently being conducted in our unit

Background: After Jules-Emile Pean and Neer, unconstrained prosthetic arthroplasty of the shoulder is widely used for glenohumeral osteoarthritis (OA), rheumatoid arthritis (RA) and trauma. While the debate continues over whether humeral head replacement (HHR) or total shoulder arthroplasty (TSR) is better for OA and RA, hemiarthroplasty is preferred in the trauma situation. Aims: A retrospective review (1993–2000) of 54 patients with the DePuy Global second generation modular shoulder hemiarthroplasty is presented. We highlight the various complications encountered in the longer term and attempt to use our experience to rationalize treatment choice. Methods: 49 shoulders in 41 patients were available for review. Case records and radiographs were reviewed and clinical assessment carried out. Functional assessment was done using the Constant (CM) and the American Shoulder and Elbow Society systems (ASES). Patients were also asked to complete a shoulder self assessment questionnaire (Insalata, Hospital for Special Surgery). Results: The pre-op diagnosis was 20 RA, 12 OA, 11 trauma. The mean age was 63.4Yrs. The mean follow up was 6.8Yrs (4–11 Yrs). The mean Constant scores for the 3 groups were 48.1 RA, 46.3 OA, and 56.6 trauma. The mean ASES functional scores were 39.6 RA, 37.5 OA and 32.9 trauma. Active elevation in the RA group was a mean of 83.5°, and 69.5° for OA and 79° for the trauma group. 65% of the RA group was completely pain free compared to 50% and 54% in the OA and trauma groups respectively. Patient satisfaction was high in the RA and OA groups but poor in the trauma group. 90% of RA patients had evidence of superior migration of the prosthesis (ASM), with the majority of them developing cuff dysfunction. 36% of trauma patients had tuberosity escape/nonunion. 100% of OA patients developed late glenoid erosion. Presence of secondary glenoid arthrosis and ASM co-related with poor function (r =0.5, p< 0.05). Discussion. Second generation prosthesis can prejudice the shoulder biomechanics. Over-tensioning the joint can lead to both glenoid wear and cuff rupture. In OA patients, satisfaction was highest, but function was poor. Patients with out cuff tear pre-operatively did not develop it later. They may thus benefit from a TSR compared to HHR. RA patients had the least pain, best function and high satisfaction. Most had evidence of either primary or secondary cuff dysfunction. In them patients HHR may be the preferred option. Trauma patients did poorly in all respects. More anatomical reconstruction and greater emphasis on salvage of the humeral head is required in this group

Objectives

The long head of the biceps (LHB) is often resected in shoulder surgery and could therefore serve as a cell source for tissue engineering approaches in the shoulder. However, whether it represents a suitable cell source for regenerative approaches, both in the inflamed and non-inflamed states, remains unclear. In the present study, inflamed and native human LHBs were comparatively characterized for features of regeneration.

Aims

In patients with a rotator cuff tear, tear pattern and tendon involvement are known risk factors for the development of pseudoparalysis of the shoulder. It remains unclear, however, why similar tears often have very different functional consequences. The present study hypothesizes that individual shoulder anatomy, specifically the moment arms (MAs) of the rotator cuff (RC) and the deltoid muscle, as well as their relative recruitment during shoulder abduction, plays a central role in pseudoparalysis.

The August 2015 Trauma Roundup³⁶⁰ looks at: Thromboprophylaxis not required in lower limb fractures; Subclinical thyroid dysfunction and fracture risk: moving the boundaries in fracture; Posterior wall fractures refined; Neurological injury and acetabular fracture surgery; Posterior tibial plateau fixation; Tibial plateau fractures in the longer term; Comprehensive orthogeriatric care and hip fracture; Compartment syndrome: in the eye of the beholder?

In the UK we have many surgeon inventors – surgeons who innovate and create new ways of doing things, who invent operations, who design new instruments to facilitate surgery or design new implants for using in patients. However truly successful surgeon inventors are a rare breed and they need to develop additional knowledge and skills during their career in order to push forward their devices and innovations. This article reviews my own experiences as a surgeon inventor and the highs and lows over the whole of my surgical career.