The modern humeral head resurfacing was developed by Stephen Copeland, M.D. and introduced in 1986 as an alternative to stemmed humeral implants. At the time, first and second generation monoblock and modular stems with non-offset humeral heads posed many challenges to the surgeon to recreate the pre-morbid humeral head anatomy during anatomic TSA. The consequences of non-anatomic humeral head replacement were poor range of motion, increased native glenoid or glenoid component wear and premature rotator cuff failure. Additionally, the early generation humeral stems were very difficult to extract when revision was needed. The original stemless devices were cup resurfacing implants that were designed based on the early hip experience. The Copeland resurfacing device offered the ability to better match native humeral head anatomy and was considered less invasive and easier to revise. Glenoid exposure required more extensive dissection but TSA could be successfully completed.

Clinical results for motion, function and outcome scores are similar to stemmed implants. The survivorship of the implants is also on par with other available implants and loosening has not been an issue. Stress shielding is not reported. Multiple manufacturers offered similar products all designed to try to predictably recreate the pre-morbid anatomy and to make insertion easier.

Critical review of resurfacing arthroplasty radiographs has raised concern about the challenges of placing the implant with proper sizing and position. Most surgeons have implanted resurfacing implants as hemiarthroplasties. The development of anatomic TSA implants has allowed surgeons to better recreate the normal pre-morbid anatomy of the humerus. Newer stem designs are convertible or easily removable. This counters many of the original design benefits of resurfacing. The primary reason for revision of resurfacing implants is malposition followed by glenoid arthrosis and rotator cuff failure. Revision surgery after resurfacing has had mixed results.

Stemless implants were introduced in Europe 13 years ago. Stemless devices share the benefits of resurfacing as minimally invasive and easier to revise. The added benefit of better glenoid access allows the surgeon to implant a glenoid. Most available implants have minimal follow-up. Mid-term follow-up of one design has demonstrated good fixation and loosening is uncommon. No studies are available that critically evaluate the surgeon's ability to recreate normal pre-morbid anatomy, whether revision arthroplasty is bone preserving and if results of revision will improve.

Infection prevention in shoulder arthroplasty is an evolving challenge as further understanding of the pathogens becomes available. Infection rates for reverse TSA is higher than anatomic TSA. Standard decolonization protocols from our hip and knee colleagues has decreased the acute post-operative infection risk to less than 1%. By identifying at risk populations anti-MRSA precautions including intranasal antibiotics and anti-bacterial soaps for pre-surgical skin preparation have reduced the incidence of staphylococcus infections. The emerging understanding of propionibacterium acnes (P. acnes) as a primary pathogen in late shoulder periprosthetic joint infection (PJI) has led to new recommendations including pre-operative skin cleansing with 5% benzoyl peroxide to reduce infection risk. Pre-operative IV antibiotic is recommended and chlorhexidine skin prep for surgery.

In the operating room, the concern is the surgeon's exposure to skin and sebaceous glands where P. acnes is prevalent. After skin incision the surgeon should use a new blade for deep incision. Application of vancomycin powder to the subcutaneous tissue may be beneficial after incision to treat potential contamination from the incision through skin. Glove change prior to handling implants and thorough irrigation before implantation is prudent. The role of antibiotic loaded bone cement for infection prevention remains unproven. Topical vancomycin powder at closure is a low cost option and has shown benefit in spine surgery but efficacy is unproven in the shoulder. Silver impregnated wound dressings may also prevent infection and are a convenient option for patient care with regards to bathing.

Preventing infections in shoulder arthroplasty, particularly P. acnes, remains a challenge. A significant number of revision TSAs are found to have positive cultures for P. acnes creating a significant burden for patients and surgeons.

Revision of the humeral component in shoulder arthroplasty is frequently necessary during revision surgery. Newer devices have been developed that allow for easy extraction or conversion at the time of revision preserving bone stock and simplifying the procedure. However, early generation anatomic and reverse humeral stems were frequently cemented into place. Monoblock or fixed collar stems make accessing the canal from above challenging. The cortex of the Humerus is far thinner than the femur and stress shielding has commonly led to osteopenia. Many stem designs have fins that project into the tuberosities putting them at risk for fracture on extraction.

Extraction starts with an extended deltopectoral incision from the clavicle to the deltoid insertion. The proximal humerus needs to be freed from adhesions of the deltoid and conjoined tendon. The deltopectoral interval is fully developed. Complete subscapularis and anterior capsular release to the level of the latissimus tendon permits full exposure of the humeral head. After head removal the stem can be assessed for loosening and signs of periprosthetic joint infection. The proximal bone around the fin of the implant should be removed from the canal. If possible, the manufacturer's extractor should be utilised. If not, then a blunt impactor can be placed from below against the collar of the stem to assist in extraction. With luck the stem can be extracted from the cement mantle. If there is no concern for infection, the cement-in-cement technique can be used for revision. Otherwise, attempts should be made to extract all the cement and cement restrictor, if present. The small cement removal tools from the hip set can be used and specialised shoulder tools are available. An ultrasound cement removal device can be very helpful. The surgeon must be particularly careful to avoid perforation of the humeral cortex. This is especially important when near the radial nerve as injury can occur

When a well-fixed stem is encountered, an osteotomy of the proximal humerus is necessary. The surgeon can utilise a linear cut with an oscillating saw along the bicipital groove for the length of the implant. An osteotome is used to crack the cement mantle allowing stem extraction. Alternatively, a window can be created to offer additional access to the cement mantle.

In the event the surgeon has required an osteotomy or window, cerclage wires, cables or suture will be needed and when the bone is potentially compromised, allograft bone graft struts (tibial shaft) are used for additional support. Care is needed when passing cerclage wires to avoid injury to the radial nerve which is adjacent to the deltoid insertion.

If infection is suspected or confirmed an ALBC spacer is placed. When single stage revision is planned both cemented and uncemented stem options are available. Cement placed around the humeral stem has been suggested to decrease infection incidence.

Revision of cemented humeral stems is a continued challenge in revision shoulder surgery. Newer systems and reverse total shoulder options have improved the surgeon's ability to achieve good outcomes when revising prior shoulder arthroplasty.

Introduction

Regular, repeated stretching increases joint range of movement (RoM), however the physiology underlying this is not well understood. The traditional view is that increased flexibility after stretching is due to an increase in muscle length or stiffness whereas recent research suggests that increased flexibility is due to modification of tolerance to stretching discomfort/pain. If the pain tolerance theory is correct the same degree of micro-damage to muscle fibres should be demonstrable at the end of RoM before and after a period of stretch training. We hypothesise that increased RoM following a 3 weeks hamstrings static stretching exercise programme may partly be due to adaptive changes in the muscle/tendon tissue.