Humeral Stem Research Articles

Radiographic Study of Humeral Stem in Shoulder Arthroplasty After Lesser Tuberosity Osteotomy or Subscapularis Tenotomy.

Lesser tuberosity osteotomy (LTO) and subscapularis tenotomy (ST) are used for takedown of the subscapularis during shoulder arthroplasty. LTO offers the theoretical but unproven benefit of improved healing and function of the subscapularis. However, humeral stem subsidence and loosening may be greater when osteotomy is performed, which may compromise functional outcomes. Our hypothesis is that no difference in proximal collar press-fit humeral stem subsidence or loosening exists, with no impairment of functional outcomes using the LTO technique. Radiographs of 39 shoulders from 35 patients who underwent shoulder arthroplasty with a minimum of 1 year of radiographic follow-up were included in the study cohort. All patients received the same press-fit implant (Bigliani-Flatow; Zimmer Biomet). We collected data including demographic information; radiographic measurements, including humeral-acromial distance (HAD); subsidence; subluxation index; the presence of lucent lines >2 mm; and functional outcome scores using the Western Ontario Osteoarthritis of the Shoulder Index, the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire, and the Constant score. Subsidence was 2.8 ± 3.1 mm for LTO vs 2.5 ± 3.1 mm for ST (P = .72). HAD did not differ between the LTO and ST groups preoperatively (9.5 ± 2.4 mm vs 10.9 ± 2.7 mm, P = .11). The first postoperative and final follow-up films for HAD for the LTO and ST groups showed a statistically significant difference (first postoperative film, 11.9 ± 3.7 mm vs 15.9 ± 4.5 mm, P = .005; final follow-up film, 11.8 ± 3.2 mm vs 14.5 ± 3.9 mm, P = .03). We identified no differences in subsidence, lucent lines >2 mm, posterior subluxation, and Constant, and DASH functional outcome scores for patients undergoing total shoulder arthroplasty via the LTO vs ST techniques with the same proximal collar press-fit humeral stem at short-term follow-up.

Mid-term results of anatomical total shoulder arthroplasty for primary osteoarthritis using a short-stemmed cementless humeral component.

The aim of this study was to evaluate the clinical and radiological outcome of using an anatomical short-stem shoulder prosthesis to treat primary osteoarthritis of the glenohumeral joint. A total of 66 patients (67 shoulders) with a mean age of 76 years (63 to 92) were available for clinical and radiological follow-up at two different timepoints (T1, mean 2.6 years, sd 0.5; T2, mean 5.3 years, sd 0.7). Postoperative radiographs were analyzed for stem angle, cortical contact, and filling ratio of the stem. Follow-up radiographs were analyzed for timing and location of bone adaptation (cortical bone narrowing, osteopenia, spot welds, and condensation lines). The bone adaptation was classified as low (between zero and three features of bone remodelling around the humeral stem) or high (four or more features). The mean Constant score improved significantly from 28.5 (sd 11.6) preoperatively to 75.5 (sd 8.5) at T1 (p < 0.001) and remained stable over time (T2: 76.6, sd 10.2). No stem loosening was seen. High bone adaptation was present in 42% of shoulders at T1, with a slight decrease to 37% at T2. Cortical bone narrowing and osteopenia in the region of the calcar decreased from 76% to 66% between T1 and T2. Patients with high bone adaptation had a significantly higher mean filling ratio of the stem at the metaphysis (0.60, sd 0.05 vs 0.55, sd 0.06; p = 0.003) and at the diaphysis (0.65 sd 0.05 vs 0.60 sd 0.05; p = 0.007). Cortical contact of the stem was also associated with high bone adaptation (14/25 shoulders, p = 0.001). The clinical outcome was not influenced by the radiological changes. Total shoulder arthroplasty using a short-stem humeral component resulted in good clinical outcomes with no evidence of loosening. However, approximately 40% of the shoulders developed substantial bone loss in the proximal humerus at between four and seven years of follow-up. Cite this article: Bone Joint J 2018;100-B:603-9.

Humeral Stem Loosening Following Reverse Shoulder Arthroplasty: A Systematic Review and Meta-Analysis.

Aseptic stem loosening following reverse shoulder arthroplasty (RSA) is an uncommon complication. The timing and the factors contributing to aseptic stem loosening remain poorly understood. We performed a systematic review that identified 75 articles; 65 of the included articles were case series (Level-IV evidence), 8 were cohort studies (7 Level III, 1 Level II), and 2 were prospective randomized controlled trials (Level I). A meta-analysis of 1,660 cemented and 805 uncemented RSA stems was performed. We compared the rates of aseptic stem loosening, humeral radiolucent lines, and revision for stem loosening (1) between cemented and uncemented stems in cohorts with short and long mean follow-up periods (<5 and ≥5 years) as well as in all cohorts combined, and (2) among different etiological subgroups. Aseptic stem loosening occurred more commonly in the cohort with long compared with short follow-up time (2% versus 0.8%, p = 0.01). When comparing cemented with uncemented stems, there was no significant difference in the rates of aseptic stem loosening or revision for stem loosening in either the short or long-term follow-up groups. Humeral radiolucent lines were more common with cemented compared with uncemented stems (15.9% versus 9.5%, p = 0.002). Analyzed by etiology, the highest rate of aseptic stem loosening occurred in the tumor subgroup (10.8%), followed by RSA as a revision procedure after a failed arthroplasty (3.7%). No stems in the acute fracture or fracture sequelae subgroups developed aseptic stem loosening. Aseptic stem loosening occurred more commonly in cohorts with longer follow-up. There were no differences in the rates of aseptic stem loosening or revision for stem loosening between cemented and uncemented stems. Patients treated with RSA following excision of proximal humeral tumors and RSA as a revision procedure after a failed arthroplasty were at greater risk of aseptic stem loosening. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Effects of cemented versus press-fit primary humeral stem fixation in the setting of revision shoulder arthroplasty

The influence of primary humeral stem fixation method (cemented or press fit) on intraoperative or postoperative outcomes in the setting of revision shoulder arthroplasty is unknown. A retrospective analysis of a prospectively collected cohort of revision shoulder arthroplasty patients from a single tertiary center was performed. Demographic variables, intraoperative data, and 90-day complication rates were compared between cemented and press-fit primary stem fixation cohorts. Follow-up radiographs were graded and compared using a modified Gruen system for humeral lucencies. Eighty-six primary shoulder replacements (34 hemiarthroplasties, 39 anatomic total shoulder arthroplasties, 13 reverse total shoulder arthroplasties) underwent revision arthroplasty with humeral stem removal between 2004 and 2017. Forty-five patients had cemented primary humeral fixation and 41 had press-fit fixation. The cemented cohort was older than the cementless cohort (66.6 vs. 61.4 years; P = .03) but otherwise demonstrated no difference in gender, body mass index, type of primary prosthesis (hemi, total, or reverse), or time between primary and revision operations. The cemented and cementless cohorts showed similar rates of humeral osteotomy (28.9% vs. 29.3%; P = .97), operative time (133.5 vs. 121.3 minutes; P = .16), and 90-day complication rates (13.3% vs. 9.8%; P = .61). Cemented vs. press-fit primary stems also had similar rates of humeral lucencies seen on follow-up radiographs after revision (77.1% vs. 60.6%; P = .14). Humeral stem fixation with or without cement during primary shoulder arthroplasty demonstrated similar operative time, need for intraoperative humeral osteotomy, and postoperative complication rates in the setting of revision arthroplasty.

What is the best glenoid configuration in onlay reverse shoulder arthroplasty?

The purpose of this study was to analyze the effect of different glenoid configurations on arm position and range of motion (ROM) following reverse shoulder arthroplasty (RSA). The hypothesis was that different glenoid configurations would lead to changes in humeral offset, acromio-humeral distance (AHD), ROM, and rotator cuff muscle length. Using a three-dimensional (3D) computer model, implantation of an RSA was simulated with a 145° onlay humeral stem combined with five different glenoid configurations which varied in diameter and centre of rotation. Glenoid offset, the AHD, ROM, and muscle length were evaluated for each configuration. Changing glenoid design led to up to a 10mm change in offset and a 3mm change in the AHD. There was 7° of improvement in abduction and flexion between the different glenoid designs. Two of the configurations, the 36mm centered and the BIO-RSA, had an adduction deficit. In extension and external rotation arm with the arm at side, the eccentric 36mm glenosphere was the best configuration while the centered 36mm glenosphere was the worst configuration. The 42mm glenosphere limited external rotation at 90° of abduction. Varying the glenosphere configurations leads to ROM and muscle length changes following RSA. With a 145° onlay humeral stem, a 36 eccentric glenosphere theoretically optimizes ROM while limiting scapular notching.

Outcomes of lesser tuberosity osteotomy in revision anatomic shoulder arthroplasty

Lesser tuberosity osteotomy (LTO) is a common surgical approach during anatomic shoulder arthroplasty. Outcomes of LTO have been shown to be similar to subscapularis tenotomy and peel techniques, but little is known about the outcomes of LTO during revision arthroplasty. This retrospective case series included 10 consecutive patients who underwent LTO during revision shoulder arthroplasty at a single institution from 2012 to 2016. Patients underwent a preoperative computed tomography scan to evaluate the lesser tuberosity bone stock. Demographic information, radiographic evidence of LTO healing, outcomes of range of motion, subscapularis strength, and visual analog scale pain scores were analyzed. Revision total shoulder arthroplasty with LTO was performed for glenoid arthritis after hemiarthroplasty in 10 patients. Average age at surgery was 59.8 years, and no humeral stems were revised. Eight of 10 patients had prior subscapularis tenotomy. Average follow-up after revision surgery was 9.2 months. LTO union was documented in 80% and nondisplaced nonunion in 20%. At follow-up, 50% reported mild pain. Subscapularis strength testing was graded normal in 80% and weak in 20%. Average visual analog scale pain improved from 9.4 prerevision to 4.8 postrevision (P < .05). On average, range of motion improved in active forward elevation from 123° to 141° and remained unchanged in active external rotation from 42° to 42°. Patients undergoing LTO during revision anatomic shoulder arthroplasty demonstrate successful LTO bony healing, improvement in pain, and improved forward elevation. In select patients not requiring humeral stem revision, LTO is a safe and effective surgical approach to subscapularis management during revision anatomic shoulder arthroplasty.

Long-term humeral complications after Grammont-style reverse shoulder arthroplasty

Recent experiences with Grammont reverse shoulder arthroplasty (RSA) have revealed some problems related to the biomechanical changes of the shoulder and humeral stem complications. We analyzed humeral complications in a long-term follow-up of a large series of RSAs, searching for correlations between these and the initial etiology, the follow-up duration, and the clinical outcomes. Preoperative and postoperative clinical and radiologic assessments of 1035 RSAs with a minimum 5-year follow-up (implanted in 7 specialized shoulder centers between 1993 and 2010) were retrospectively collected. Postoperative humeral complications, managed conservatively or surgically, were radiographically documented. Overall, a 3.3% rate of postoperative humeral complications was found in our database. We identified 17 cases (1.6%) with postoperative humeral fractures, 15 cases (1.4%) with aseptic humeral loosening, and 3 cases (0.3%) with humeral stem disassembly. The humeral complications were more frequent in RSAs implanted for tumors, fracture sequelae, and revision for failed arthroplasty. Humeral complications after RSA are not rare, increase with longer follow-up, and have a negative impact on functional outcomes. Postoperative humeral fractures are more frequent in elderly patients, operated on through a superior approach, and after cemented stem implantation. In the absence of associated humeral loosening, conservative treatment should be preferred. Proximal humeral bone loss (due to revisions and tumors) is the most significant risk factor for humeral loosening. Implant unscrewing was initially related to a technological problem, which has been solved, and this complication has disappeared.

Grammont humeral design versus onlay curved-stem reverse shoulder arthroplasty: comparison of clinical and radiographic outcomes with minimum 2-year follow-up

There are few investigations comparing lateralized and medialized reverse total shoulder arthroplasty (RTSA) in patients with cuff tear arthropathy. This study assessed the outcomes of 2 RTSA designs. Sixty-eight consecutive cuff tear arthropathy patients (74 shoulders) with a follow-up of at least 24 months received a Grammont or an onlay curved short-stem humeral component, with or without glenoid lateralization; a cementless humeral stem was implanted in >90%. Clinical outcome measures included active range of motion (anterior and lateral elevation, external and internal rotation), pain, and the Constant-Murley score. Radiologic outcomes included radiolucency, condensation lines, cortical thinning, spot weld, loosening and subsidence, and tuberosity resorption for the humeral component and radiolucency, scapular notching, formation of scapular bone spurs, ossifications, and loosening for the glenoid component. Both prostheses provided significant differences between preoperative and postoperative scores and showed a similar complication rate. Scapular fractures were found only in the patients who received the curved short-stem implant. Glenoid bone grafting did not significantly affect clinical scores. Both implants provided similar postoperative shoulder mobility, even though the lateralized curved stem was associated with higher delta scores for external rotation (P = .002) and lower rates of scapular notching (P = .0003), glenoid radiolucency (P = .016), and humeral bone remodeling (P = .004 and P = .030 for cortical thinning and spot weld, respectively). Medialized and short-stem lateralized RTSA implants provided similar midterm clinical outcomes and range of motion. The curved short stem was associated with higher delta scores for external rotation and a lower rate of radiographic risk factors.

Transhumeral loading during advanced upper extremity activities of daily living.

Percutaneous osseointegrated (OI) implants for direct skeletal attachment of upper extremity prosthetics represent an alternative to traditional socket suspension that may yield improved patient function and satisfaction. This is especially true in high-level, transhumeral amputees where prosthetic fitting is challenging and abandonment rates remain high. However, maintaining mechanical integrity of the bone-implant interface is crucial for safe clinical introduction of this technology. The collection of population data on the transhumeral loading environment will aid in the design of compliance and overload protection devices that mitigate the risk of periprosthetic fracture. We collected marker-based upper extremity kinematic data from non-amputee volunteers during advanced activities of daily living (AADLs) that applied dynamic loading to the humerus. Inverse dynamic analysis was applied to calculate the axial force, bending and torsional moments at three virtual amputation levels representing 25, 50, and 75% residual humeral length. The influences of amputation level, elbow flexion constraint, gender and anthropometric scaling were assessed. Results indicate that the proximal (25%) amputation level experienced significantly higher axial forces and bending moments across all subjects when compared to distal amputation levels (p≤0.030). Constraining elbow flexion had a limited influence on peak transhumeral loads. Male subjects experienced higher axial forces during all evaluated activities (p≤0.023). Peak axial force for all activities occurred during jumping jacks (174.5N). Peak bending (57.6Nm) and torsional (57.2Nm) moments occurred during jumping jacks and rapid internal humeral rotation, respectively. Calculated loads fall within the range of implant fixation failure loads reported in cadaveric investigations of humeral stem fixation; indicating that periprosthetic fracture may occur during non-contact AADLs. These kinematic data, collected over a range of AADLs, will aid in the development of overload protection devices and appropriate post-operative rehabilitation protocols that balance return to an active lifestyle with patient safety.

Stemless Prosthesis for Total Shoulder Arthroplasty.

The fourth generation of humeral components currently are being used in anatomic shoulder arthroplasty. Anatomic shoulder arthroplasty implants have evolved to better re-create anatomy, improve fixation, preserve bone, and facilitate revision surgery. Most of the design changes for shoulder arthroplasty implants have centered on the humeral stem, with a transition to shorter, metaphyseal humeral stems. Many of these humeral component design changes may be beneficial; however, long-term studies are necessary to determine if the results of anatomic shoulder arthroplasty with the use of newer humeral components can match those of anatomic shoulder arthroplasty with the use of older humeral components.

A New Stem Guide and a Tuberosity Anchoring "Lasso" System for Shoulder Hemiarthroplasty in the Treatment of Complex Proximal Humerus Fractures.

Hemiarthroplasty implantation for proximal humerus fracture is challenging. In case of young demanding patients with functional rotator cuff, humeral head replacement is an option if open reduction internal fixation is not a viable solution. The criteria for success in terms of clinical outcomes and longevity are anatomic healing of the tuberosities and stem positioning (restoring correct height, version, and axis). The purpose of this article is to describe a technique including a new stem guide and a tuberosity anchor "lasso" system for the implantation of hemiarthroplasty in complex proximal humerus fractures. A standard delto-pectoral approach is performed. After humeral head removal and tuberosity mobilization and debridement, a stem-positioning system guarantees correct height and version of the humeral stem, established after anatomic reduction of the greater tuberosity. A centering device is added on the humeral stem to prevent any varus or valgus. Fixation of the tuberosities is achieved with 6 nonabsorbable sutures fixed on a polyester "lasso" anchoring system circling the humerus, respecting the direction of rotator cuff tendons and adding double circumferential tightening. After reduction of the implant, stability, and passive range of motion are assessed intraoperatively and fluoroscopic control of the prosthesis is performed. The patient is maintained in a sling in neutral rotation and passive motion is started after 4 weeks; active motion is allowed after 2 months. We believe this surgical technique could help limit complications and prevent revision of the humeral stem in case of further conversion to reverse shoulder arthroplasty.

Platform shoulder arthroplasty: a systematic review

Platform shoulder arthroplasty systems may allow conversion to a reverse total shoulder arthroplasty (RTSA) without removing a well-fixed, well-positioned humeral stem. We sought to evaluate the complications associated with humeral stem exchange versus retention in patients undergoing conversion shoulder arthroplasty with a platform shoulder arthroplasty system. PubMed, MEDLINE, CINAHL (Cumulative Index to Nursing and Allied Health Literature), and Embase were searched from database inception through October 9, 2016, for all articles comparing humeral stem retention versus exchange during conversion RTSA or that pertained to conversion RTSA with stem retention alone. All studies were screened in duplicate for eligibility. A methodologic quality assessment was completed for included studies. Pooled outcomes assessing complications, operative time, blood loss, and reoperations were determined. We included 7 studies (236 shoulders), including 1 level III and 6 level IV studies. Pooled analysis demonstrated significantly higher overall complications (odds ratio, 6.89; 95% confidence interval [CI], 2.48-19.13; P = .0002), fractures (odds ratio, 4.62; 95% CI, 1.14-18.67; P = .03), operative time (mean difference, 62.09 minutes; 95% CI, 51.17-73.01 minutes; P < .00001), and blood loss (mean difference, 260.06 mL; 95% CI, 165.30-354.83 mL; P < .00001) with humeral stem exchange. Stem exchange was also associated with increased risk of reoperation (P = .0437). Conversion arthroplasty with retention of the humeral stem is associated with lower overall complications, blood loss, operative time, and reoperations in comparison with stem exchange.

Radiographic changes differ between two different short press-fit humeral stem designs in total shoulder arthroplasty

The purpose of this study was to compare the radiographic changes of the humerus in the short term after total shoulder arthroplasty with two different short-stem humeral components. The hypothesis was that there would be no difference in radiographic changes or functional outcome based on component type. A retrospective review was conducted of primary total shoulder arthroplasties performed with a short press-fit humeral component. Group A included a collarless humeral stem with an oval geometry and curved stem (Ascend or Ascend Flex; Wright Medical, Memphis, TN, USA). Group B included a humeral stem with a metaphyseal collar, rectangular geometry, and straight stem (Apex; Arthrex, Inc., Naples, FL, USA). Radiographic changes and functional outcome were evaluated at a minimum of 2 years postoperatively. There were 42 patients in group A and 35 patients in group B available for analysis. There was no difference in functional outcome between the groups. In group A, the mean total radiographic change score of the humerus was 3.9, with changes classified as low in 38% and high in 62%. In group B, the mean total radiographic change score of the humerus was 2.5, with changes classified as low in 77% and high in 23% (P < .001). Medial calcar osteolysis was present in 71% of group A compared with 28.5% of group B (P < .001). At short-term follow-up, there is no difference in functional outcome or revision between 2 different humeral stem designs. However, bone adaptive changes and the rate of medial calcar osteolysis are significantly different.

The effect of implant linking and ligament integrity on humeral loading of a convertible total elbow arthroplasty.

Both unlinked and linked total elbow arthroplasty (TEA) implants have been employed with no consensus as to the optimal design. The present study aimed to evaluate the effect of collateral ligament integrity and implant linkage on wear-inducing loads in a convertible TEA. Eight fresh frozen upper extremities were tested in an elbow motion simulator. A convertible TEA with an instrumented humeral stem was inserted using computer navigation. Elbow kinematics and humeral loading were recorded with the TEA both linked and unlinked. The collateral ligaments were then sectioned and testing was repeated. In the dependent position, there was no effect of implant linkage or ligament sectioning on humeral loading. Humeral loading was significantly greater following sectioning of the collateral ligaments but not after linking the TEA with the arm in the valgus position. Humeral loading was significantly greater after linking the TEA but not after sectioning of the collateral ligaments and with the arm in the varus position. Collateral ligament integrity reduces wear-inducing loads for both an unlinked and linked TEA. Linkage of a convertible TEA increases humeral loading, which may have detrimental effects on implant longevity.

Ruptura irreparable del Manguito Rotador en Artroplastía de Hombro: Resolución “simple” de la complicación con Artroplastía Reversa

La lesión del manguito rotador en pacientes con una prótesis total de hombro anatómica es cada vez más frecuente. Ante esta situación surge el dilema de reparar la ruptura o efectuar una revisión hacia una artroplastia inversa. Se presenta el caso de un paciente que consulta por una ruptura masiva del manguito rotador del hombro derecho, de seis meses de evolución, luego de haber intentado levantar un objeto de 30 kg. Como antecedente se le había implantado una artroplastia total del hombro derecho modular y universal por artrosis glenohumeral primaria. Dada la irreparabilidad de la lesión y la adecuada integración biológica proximal del tallo humeral cementado y el platillo metálico glenoideo no cementado, se procedió a la reconversión a artroplastia inversa de hombro intercambiando solo los componentes modulares de la prótesis. La evolución posquirúrgica fue favorable, recuperó un rango de movilidad satisfactorio durante la rehabilitación. Las prótesis modulares universales ofrecen la posibilidad de la conversión “simple” de una artroplastia de hombro total a una inversa, sin necesidad de revisar el tallo humeral ni el platillo glenoideo, y así disminuir la morbilidad del procedimiento.

Revision of failed shoulder hemiarthroplasty to reverse total arthroplasty: analysis of 157 revision implants

There remains a paucity of studies examining the conversion of failed hemiarthroplasty (HA) to reverse total shoulder arthroplasty (RTSA). Therefore, the purpose of this study was to examine a large series of revision HA to RTSA. A population of 157 patients who underwent conversion of a failed HA to a revision RTSA from 2006 through 2014 were included. The mean follow-up was 49 months (range, 24-121 months). The indications for revision surgery included instability with rotator cuff insufficiency (n = 127) and glenoid wear (n = 30); instability and glenoid wear were associated in 38 cases. Eight patients with infection underwent 2-stage reimplantation. Patients experienced significant improvements in their preoperative to postoperative pain and shoulder range of motion (P < .0001), with median American Shoulder and Elbow Surgeons and Simple Shoulder Test scores of 60 and 6 points, respectively. There were 11 (7%) repeated revision surgeries, secondary to glenoid component loosening (n = 3), instability (n = 3), humeral component disassembly (n = 2), humeral stem loosening (n = 1), and infection (n = 2). Implant survivorship was 95.5% at 2 years and 93.3% at 5 years. There were 4 reoperations including axillary nerve neurolysis (n = 2), heterotopic ossification removal (n = 1), and hardware removal for rupture of the metal cerclage for an acromial fracture (n = 1). At final follow-up, there were 5 "at-risk" glenoid components. Patients experience satisfactory pain relief and recovery of reasonable shoulder function after revision RTSA from a failed HA. There was a relatively low revision rate, with glenoid loosening and instability being the most common causes.

Polyethylene dissociation from humeral stem status after reverse total shoulder arthroplasty

Reverse shoulder arthroplasty (RSA) is an important treatment option for 4-part proximal humerus fractures in the elderly and arthrosis of the glenohumeral joint with incompetence of the rotator cuff. Unique complications do occur with use of this type of prosthesis. We present 4 cases of polyethylene dissociation after RSA. In a series of 549 patients who underwent RSA, the incidence of polyethylene dissociation was found to be 0.7%. Polyethylene dissociation is a rare complication after RSA. Surgeons should be aware of this possibility if a closed reduction of an RSA dislocation is not possible.

Humeral bone resorption after anatomic shoulder arthroplasty using an uncemented stem

Bone resorption around the femoral stem after total hip arthroplasty is a well-known phenomenon. However, only a few studies have evaluated bone resorption after shoulder arthroplasty. This study investigated the prevalence of humeral bone resorption after different shoulder arthroplasty procedures. The study included 147 shoulders that underwent total shoulder arthroplasty (TSA) or humeral head replacement (HHR) with an uncemented humeral stem from November 2008 to May 2015 and were monitored for more than 1 year. The prevalence of humeral bone resorption and risk factors were investigated. The most advanced grade of bone resorption, grade 0, occurred in 21 shoulders (14.3%). Grade 1 bone resorption occurred in 10 (6.8%), grade 2 in 28 (19.0%), grade 3 in 61 (41.5%), and grade 4 in 27 (18.4%). High occurrence of bone absorption was observed in zones 1, 2, and 7. Grade 4 bone resorption did not occur in zones 3 and 5. HHR, on-growth type stem coating, and occupation ratio were significant independent risk factors for grade ≥3 bone resorption, whereas female sex and HHR were significant independent risk factors for grade 4. Bone resorption was observed in 126 shoulders (85.7%), and full-thickness cortical bone resorption occurred in 27 shoulders (18.4%). Bone resorption was frequently observed at the greater tuberosity, lateral diaphysis, and calcar region (zones 1, 2, and 7). Significant risk factors included female sex, HHR with rotator cuff reconstruction, on-growth type stem coating, and high occupation ratio of the implant.

Partial humeral replacement for peri-prosthetic fractures of the humerus

IntroductionTreating peri-prosthetic fractures of the humerus can be very challenging, especially when there is poor bone stock and in the presence of adjacent joint prostheses. We discuss the option of a partial humeral replacement as a salvage procedure for such cases with some technical comments. MethodsThis paper presents a technique which utilises a custom- made cemented connector to incorporate the existing well functioning elbow or shoulder replacement with a commercially available partial humeral replacement (PHR) or to an existing prosthetic humeral stem. ResultsOur series involves 6 patients with severe rheumatoid arthritis, all female, with a mean age of 62.5 years. Their surgeries were performed over a span of 10 years, with an average follow up of 49 months. All had a well functioning implant at final follow-up, with a mean Mayo Elbow Performance score of 65. There were no cases of infection, nerve injury or dislocation in our patients. There were 2 deaths in our series, from unrelated medical causes at 2 and 4 years following their surgery. ConclusionAlthough a partial humeral replacement connected to a well functioning implant is a rare procedure for salvage of a humeral peri-prosthetic fracture, it can be a viable option in certain patient populations. Every attempt should be made to maintain the secondary shoulder stabilisers at the proximal humerus as a functioning unit.

Mechanics and complications of reverse shoulder arthroplasty: morse taper failure analysis and prospective rectification

Since Sir John Charnley began his monumental hip arthroplasty work in 1958, clinical researchers have been incrementally improving longevity and functionality of total joint systems, although implant failure occurs on occasion. The purpose of this study is to report the fracture of the humeral tray Morse taper of a reverse total shoulder system (RTSS), which to date has not been reported with metallurgic analysis for any RTSS. There was no reported antecedent fall, motor vehicle collision, or other traumatic event prior to implant fracture in this case. Analysis was performed on the retrieved failed implant by Scanning Electron Microscopy (SEM) and Electron Dispersion Spectroscopy (EDS) in an attempt to determine the failure method, as well as to offer improvements for future implants. At the time of revision surgery all explants were retained from the left shoulder of a 61-year old male who underwent a non-complicated RTSS 4 years prior. The explants, particularly the cracked humeral tray, were processed as required for SEM and EDS. Analysis was performed on the failure sites in order to determine the chemical composition of the different parts of the implant, discover the chemical composition of the filler metal used during the electron beam welding process, and to detect any foreign elements that could suggest corrosion or other evidence of failure etiology. Gross visual inspection of all explants revealed that implant failure was a result of dissociation of the taper from the humeral tray at the weld, leaving the Morse taper embedded in the humeral stem while the tray floated freely in the patient’s shoulder. SEM further confirmed the jagged edges noted grossly at the weld fracture site, both suggesting failure due to torsional forces. EDS detected elevated levels of carbon and oxygen at the fracture site on the taper only and not on the humeral tray. In order to determine the origin of the high levels of C and O, it was considered that in titanium alloys, C and O are used as stabilizers that help raise the temperature at which titanium can be cast. Since the presence of stabilizers reduces ductility and fatigue strength, all interstitial elements are removed after casting. Considering this, the presence of C and O suggests that not all of the interstitials were removed during the manufacturing process, resulting in decreased fatigue strength. Further destructive analytical testing would verify weld quality and failure mode. RTSSs are quite successful in select patients not amenable to traditional shoulder arthroplasty options. This case report highlights how an implant may function well for several years and then suddenly fail without warning. SEM and EDS analysis suggest that residual C and O in the taper lowered the metal implant’s integrity, leading to torsional cracking at the weld junction of the humeral tray and the taper. The elevated levels of C and O measured at fracture sites on both the tray and the taper suggest poor quality filler metal or failure to remove all interstitial elements after casting. In both cases, the results would be decreased fatigue strength and overall toughness, leading to mechanical failure. A manufacturer’s recall of all implants soon followed the reporting of this implant failure; subsequently, the metal materials were changed from Ti6Al4V to both titanium alloy and cobalt-chrome alloy (Co-Cr-Mo). Time will tell if the alterations were sufficient.