Determining the Optimal Intramedullary Screw Canal Fill Ratio in Length Unstable Metacarpal Fractures: A Biomechanical Investigation.

PURPOSE: Intramedullary (IM) screw fixation is gaining popularity in the treatment of metacarpal fractures. Despite its rapid adoption, there is a paucity of evidence regarding parameters to optimize effectiveness. This study aimed to quantify the relationship between stability, IM screw size, and canal fill using a cadaveric model. METHODS: Thirty cadaveric metacarpals (14 index, 13 middle, and three ring fingers; mean age: 58.3 years, range: 48-70) were selected to allow for canal fill ratios of 0.7-1.1 for screws sized 3.0, 3.5, and 4.5 mm. Metacarpals underwent a 45° volar-dorsal osteotomy at the midpoint before fixation with an IM screw. Specimens were subjected to 100 cycles of loading at 10 N, 20 N, and 30 N before load-to-failure testing. Correlation coefficients for angular displacement on the final cycle at each load, peak load to failure, and average stiffness were assessed. RESULTS: Correlation coefficients for the angular displacement on the 100th cycle were as follows: 10 N, R = 0.62, 20 N, R = 0.57, and 30N, R = 0.58. Correlation values for peak load to failure as a function of canal fit were as follows: 3.0 mm, R = 0.5, 3.5 mm, R = 0.17, and 4.5 mm, R = 0.44. The canal fill ratio that intersected the line-of-best fit at an angular deformity of 10° was 0.74. Average peak forces for 3.0-, 3.5-, and 4.5-mm screws were 79.5, 136.5, and 179.6 N, respectively. Average stiffness for each caliber was 14.8, 33.4, and 52.3 N/mm. CONCLUSIONS: Increasing screw diameter and IM fill resulted in more stable fixation, but marginal gains were seen in ratios >0.9. A minimum fill ratio of 0.74 was sufficient to withstand forces of early active motion with angular deformity <10°. CLINICAL RELEVANCE: An understanding of the relationship of IM fill ratio of metacarpal screws to fracture stability may provide a framework for clinicians to optimally size these implants.

Transitional care programs for trauma patients: A scoping review.

BACKGROUND: Transitional care programs establish comprehensive outpatient care after hospitalization. This scoping review aimed to define participant characteristics and structure of transitional care programs for injured adults as well as associated readmission rates, cost of care, and follow-up adherence. METHODS: We conducted a scoping review in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews standard. Information sources searched were Medline, the Cochrane Library, CINAHL, and Scopus Plus with Full Text. Eligibility criteria were systematic reviews, clinical trials, and observational studies of transitional care programs for injured adults in the United States, published in English since 2000. Two independent reviewers screened all full texts. A data charting process extracted patient characteristics, program structure, readmission rates, cost of care, and follow-up adherence for each study. RESULTS: A total of 10 studies described 9 transitional care programs. Most programs (60%) were nurse/social-worker-led post-discharge phone call programs that provided follow-up reminders and inquired regarding patient concerns. The remaining 40% of programs were comprehensive interdisciplinary case-coordination transitional care programs. Readmissions were reduced by 5% and emergency department visits by 13% among participants of both types of programs compared to historic data. Both programs improved follow-up adherence by 75% compared to historic data. CONCLUSION: Transitional care programs targeted at injured patients vary in structure and may reduce overall health care use.

"The Feasibility of Targeted Muscle Reinnervation for the Management of Morton's Neuroma".

BACKGROUND: Despite multiple surgical modalities available for the management of Morton's neuroma, complications remain common. Targeted muscle reinnervation (TMR) has yet to be explored as an option for the prevention of recurrence of Morton's neuroma. The purpose of the present investigation was to determine the consistency of the relevant foot neurovascular and muscle anatomy and to demonstrate the feasibility of TMR as an option for Morton's neuroma. METHODS: The anatomy of 5 fresh-tissue donor cadaver feet was studied, including the course and location of the medial and lateral plantar nerves (MPNs and LPNs), motor branches to abductor hallucis (AH) and flexor digitorum brevis (FDB), as well as the course of sensory plantar digital nerves. Measurements for the locations of the muscular and sensory branches were taken relative to landmarks including the navicular tuberosity (NT), AH, FDB, and the third metatarsophalangeal joint (third MTPJ). RESULTS: The mean number of nerve branches to FDB identified was 2. These branch points occurred at an average of 8.6 cm down the MPN or LPN, 9.0 cm from the third MTPJ, 3.0 cm distal to AH distal edge, and 4.8 cm from the NT. The mean number of nerves to AH was 2.2. These branch points occurred at an average of 6.3 cm down the MPN, 11.9 cm from the third MTPJ, 0.8 cm from the AH distal edge, and 3.8 cm from the NT. CONCLUSIONS: Recurrent interdigital neuroma, painful scar, and neuropathic pain are common complications of operative management for Morton's neuroma. Targeted muscle reinnervation is a technique that has demonstrated efficacy for the prevention and treatment of neuroma, neuropathic pain, and phantom limb pain in amputees. Herein, we have described the neuromuscular anatomy for the application of TMR for the management of Morton's neuroma. Target muscles, including the AH and FDB, have consistent innervation patterns in the foot, and consequently, TMR represents a viable option to consider for the management of recalcitrant Morton's neuroma. LEVELS OF EVIDENCE: V.

Quality Improvement: Effect of Standardized Plastic Surgery Consultation Note Templates on Charge Capture.

BACKGROUND: Effective medical record documentation is imperative for both patient care and reimbursement for care provided. The purpose of this study was to compare coding/billing patterns for plastic surgery consultations before and after implementation of a standardized documentation protocol. METHODS: Standardized hand, facial trauma, and general plastic surgery consult note templates were created. Following institutional approval, records were reviewed for all plastic surgery consultations from January to October 2019. Template notes were universally implemented in July 2019. Medical coding was performed by a certified professional coder using the 1995 Evaluation and Management Review Worksheet. Coding/billing patterns between groups were compared with and without standardized documentation using univariate analysis. RESULTS: Seventy-five consecutive preimplementation consult notes and 75 consecutive postimplementation consult notes were selected for review. Each group included 25 hand, 25 facial trauma, and 25 general plastic surgery consultation notes. The history and physical examination components of the visit code were more frequently coded as "comprehensive"postimplementation (P = 0.000). There was no significant difference in coding for medical decision making between the two groups (P = 0.340). The final visit code was significantly higher in the postimplementation group (45.3% 99254/99284 versus 2.7%, P = 0.000), and the charges were significantly higher post implementation-average charge per consult $250 versus $203 (P = 0.000) with a 22.8% increase in total charges generated. CONCLUSION: Utilization of standardized consultation note templates increases the accuracy of coding and associated billing of inpatient and emergency department plastic surgery consultations through documentation and reflection of level of service provided.

Outcomes and Complications of Tendon Transfers to Address Pinch and Grasp Weakness: A Systematic Review of the Operative Management of Ulnar Nerve Paralysis.

BACKGROUND: Patients with ulnar nerve paralysis note difficulties performing activities of daily living because of weakness of pinch and altered grasp mechanism. This review investigates outcomes of tendon transfers for ulnar nerve paralysis to assist in shared decision-making with patients during preoperative counseling and to inform operative choices. METHODS: A systematic review was conducted to identify studies reporting outcomes following tendon transfer for ulnar nerve palsy. Studies were screened according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, and inclusion and exclusion criteria were applied. Primary outcome measures included postoperative pinch strength and mechanism of grasp. RESULTS: A total of 26 studies (687 patients) met criteria for inclusion. After pooled analysis, the flexor digitorum superficialis lasso procedure yielded the highest rate of complete correction of claw deformity (60.6 percent), followed by flexor digitorum superficialis four-tail operation (31.4 percent). The extensor carpi radialis longus four-tail operation yielded the greatest improvement in grip strength (3.8 kg). The extensor carpi radialis brevis four-tail operation resulted in the best open hand assessment and mechanism of closing scores; however, these studies did not objectively evaluate grip strength. The greatest increase in pinch strength was following tendon transfer to adductor pollicis alone. CONCLUSIONS: Despite the heterogeneous data, if the primary goal is improvement in the appearance of claw deformity, the evidence supports flexor digitorum superficialis lasso transfer. However, if the primary concern is grip strength, the data favor extensor carpi radialis longus four-tail transfer. When pinch strength is functionally limiting, adductorplasty alone is most effective. These data will assist providers in appropriately informing patients of common risks and complications and setting realistic expectations following tendon transfer procedures.

Evolution of Surgical Management of Sagittal Synostosis.

ABSTRACT: Numerous methods for surgical correction of sagittal synostosis have been described in the literature, yielding similar outcomes. At the authors' institution, surgical approaches to correct this condition have evolved over the past few decades, including Π, H-type craniectomies (Renier), endoscopic suturectomy, and our current technique, the FLAG procedure. Our aim is to review the evolution of these surgical techniques at our institution and compare patient outcomes. A retrospective review was performed on consecutive patients undergoing correction for craniosynostosis from 2008 to 2018. All patients with a diagnosis of nonsyndromic isolated sagittal craniosynostosis were included and classified into one of 4 groups by the type of surgical correction performed (H-type, FLAG, endoscopic, other). The authors identified 166 consecutive patients with a mean age at time of surgery of 6.7 ± 4.0 months. 91 (54.8%) carried a diagnosis of nonsyndromic sagittal synostosis. 63 patients underwent H-type procedures, 9 underwent FLAG procedures, 5 underwent endoscopic procedures, and 14 were classified as other (distraction or other implant). Perioperatively, the FLAG group had the shortest ICU stay (1.3 days, P < 0.05), postoperative transfusion requirement (42cc pRBC, P < 0.001), and complication rate (0.0%). The endoscopic group had the shortest surgical time at 2.00 hours (p < 0.001). No statistically significant difference in cranial index or revision procedures between the four groups was identified. Overall, the mean length of follow-up was 25.3 months. All procedures had similar results for cranial index with decreased surgical time, transfusion volume, and hospital stay seen in FLAG and endoscopic groups.

Improving Use of a Hospital Transitional Care Clinic.

BACKGROUND: In response to Medicare readmission penalties, some hospitals have introduced transitional care clinics (TCCs) to meet the care needs of patients recently discharged from the emergency room or inpatient setting. This study was undertaken to increase the proportion of low-income, medically complex patients using a TCC at a large academic medical center, Northwestern Medical Group Transitional Care Clinic (NMG-TC). METHODS: This quality improvement study combined interviews and quantitative data analysis to determine how to increase use of NMG-TC. Physicians and patients were interviewed and surveyed to identify opportunities to expand clinic use. Logistic regression analysis of electronic health record (EHR) data was used to identify sociodemographic and clinical conditions influencing the TCC appointment show rate. RESULTS: Provider surveys and interviews suggested that referrals would likely increase via automation of referral guidelines and enhanced transitional care education. Patient interviews indicated that better communication of NMG-TC purpose, emphasizing nonmedical offerings, and warm handoffs could increase engagement. EHR analyses revealed that patients least likely to attend appointments were male, uninsured, non-Hispanic black, or homeless; had documented substance use; or lived > 50 miles from the clinic. Conversely, patients with heart failure, anxiety, or malignancy were more likely to attend appointments. CONCLUSION: TCC show rates could be improved with better communication of NMG-TC benefits to both patients and referring providers, as well as warm appointment handoffs, particularly for patients least likely to attend scheduled visits.

Granulocytic Sarcoma: A Rare Cause of Wrist Pain.

Septic, inflammatory, or crystal-induced arthritis are common etiologies of wrist pain without antecedent trauma associated with pain, loss of motion, swelling, redness, and warmth. In this report, we detail the case of granulocytic sarcoma of the wrist that presented as acute wrist pain, swelling, and limitation in motion. Granulocytic sarcoma is an exceedingly rare extramedullary tumor associated with acute myeloblastic leukemia. It may be found in any part of the body; however, upper extremity involvement is uncommon. To our knowledge, this is the first description of granulocytic sarcoma occurring in the wrist joint.

Injectable Microannealed Porous Scaffold for Articular Cartilage Regeneration.

BACKGROUND: The purpose of this study is to assess the feasibility of a novel microporous annealed particle (MAP) scaffolding hydrogel to enable both articular cartilage and subchondral bone biointegration and chondrocyte regeneration in a rat knee osteochondral defect model. METHODS: An injectable, microporous scaffold was engineered and modified to match the mechanical properties of articular cartilage. Two experimental groups were utilized-negative saline control and MAP gel treatment group. Saline and MAP gel were injected into osteochondral defects created in the knees of Sprague-Dawley rats. Photo-annealing of the MAP gel was performed. Qualitative histologic and immunohistochemical analysis was performed of the treated defects at 2, 4, and 8 weeks postsurgery. RESULTS: The injectable MAP gel successfully annealed and was sustained within the osteochondral defect at each timepoint. Treatment with MAP gel resulted in maintained size of the osteochondral defect with evidence of tissue ingrowth and increased glycosaminoglycan production, whereas the control defects presented with evidence of disorganized scar tissue. Additionally, there was no significant inflammatory response to the MAP gel noted on histology. CONCLUSIONS: We have demonstrated the successful delivery of an injectable, flowable MAP gel scaffold into a rat knee osteochondral defect with subsequent annealing and stable integration into the healing wound. The flowable nature of this scaffold allows for minimally invasive application, for example, via an arthroscopic approach for management of wrist arthritis. The MAP gel was noted to fill the osteochondral defect and maintain the defect dimensions and provide a continuous and smooth surface for cartilage regeneration, suggesting its ability to provide a stable scaffold for tissue ingrowth. Future chemical, mechanical, and biological gel modifications may improve objective evidence of cartilage regeneration.

Early Functional Outcomes After Prepectoral Breast Reconstruction: A Case-Matched Cohort Study.

INTRODUCTION: Staged, tissue expander-based implant reconstruction continues to be the most common mode of breast reconstruction after mastectomy and has evolved significantly for the past 60 years. Prepectoral acellular dermal matrix (ADM)-assisted breast reconstruction is gaining popularity with complication rates similar to total submuscular and ADM-assisted partially submuscular reconstruction. Ours is among the first reports comparing postoperative pain and early functional outcomes between 2-stage ADM-assisted prepectoral and partial submuscular breast reconstruction. METHODS: Patients reconstructed with a 2-stage, ADM-assisted prepectoral approach were case matched with patients who had undergone ADM-assisted, partial submuscular reconstruction. Demographics and complication rates were compared. Primary outcomes included postoperative pain, number of days until full active shoulder range of motion was achieved, and postoperative days until drain removal. RESULTS: Forty-five breasts among 24 patients were reconstructed with ADM-assisted prepectoral tissue expanders after mastectomy and 90 breasts among 48 patients were reconstructed with ADM-assisted partial submuscular placement. There was a similarly acceptable complication profile between the 2 groups. The prepectoral group had significantly lower inpatient pain scores, required significantly less intravenous opioids and less oral opioids as outpatients. The prepectoral group saw a return to full active range of shoulder motion in half the number days of the partial submuscular group. Drain duration was similar between groups. CONCLUSIONS: Prepectoral ADM-assisted breast reconstruction can be performed safely and with significantly less pain and earlier return to function than partial submuscular expander placement. Expander placement exclusively in the prepectoral pocket did not result in increased drain duration while affording patients the benefits of avoiding surgical elevation of the pectoralis muscle.

Reducing Infection Rates in Implant-Based Breast Reconstruction: Impact of an Evidence-based Protocol.

BACKGROUND: Infection is the most significant complication in implant-based breast reconstruction, potentially leading to reconstructive failure. We hypothesized that implementation of an evidence-based protocol marked by preoperative decolonization and sterility optimization would result in a decline in postoperative infection rates. METHODS: Informed by a literature review, we developed an evidence-based, perioperative infection prevention protocol implemented in 2015. Surgical outcomes were compared between patients who had undergone implant-based breast reconstruction before and after protocol implementation. A Fisher exact test was used to compare infection rates before and after protocol implementation. A logistic regression analysis was modeled to evaluate the impact of the protocol on infection rate while controlling for nonmodifiable risk factors. RESULTS: Three hundred fifty-eight breasts underwent reconstruction before protocol implementation and 135 afterward. Patients were similar in terms of demographics and surgical characteristics. There was a significantly reduced incidence of clinically relevant infection after protocol implementation (9.5%-2.9%, P = 0.013). Logistic regression analysis confirmed that the protocol was independently associated with a decrease in infection risk (odds ratio, 0.244; P = 0.021). After protocol implementation, no gram-positive bacteria were isolated among cultures obtained from infected periprosthetic fluid. Radiation and drain duration greater than 21 days were independently associated with greater risk for infection. CONCLUSIONS: Our evidence-based protocol was associated with a significant decline in infection rates among implant-based breast reconstruction patients and was particularly effective for gram-positive infections. We will continue to use this protocol in our practice and will consider future directions for addressing gram-negative infections as well.

Using hospital use trends to improve transitional care.

BACKGROUND: This study evaluates the Northwestern Medicine Group Transitional Care clinic (NMG-TC), which transitions patients from an urban hospital to primary care at partner community clinics. We evaluate change over the 55 month study period in emergency department, observation or inpatient use within 90 days of an initial NMG-TC visit. METHODS: Electronic health records were used to determine patient demographic, insurance and clinical characteristics, including inflation-adjusted total hospital charges in the 90 days prior and the 90 days after an initial NMG-TC visit. Multiple logistic regression was used to estimate the likelihood of any 90-day post-NMG-TC visit hospital use, controlled for the simultaneous effects of patient characteristics and pre-visit hospital use level. RESULTS: There were 3318 patients with 90-day follow-up of whom 28.5% had 90 day post-visit hospital encounters. Patients with cancer, infectious disease or pain diagnoses at the time of a NMG-TC visit had the highest 90-day post-visit hospital use. The level of pre-NMG-TC visit hospital charges, the number of NMG-TC visit diagnostic categories and the number of NMG-TC visits all showed a sharply graded effect on subsequent hospital use. Patients with a first NMG-TC visit in the last nine months of the study (2015-2016) had a 38% lower likelihood of any 90-day hospital use (OR = 0.62, 95% CI = 0.45-0.84) as compared to patients seen in 2011-2012. CONCLUSION AND IMPLICATIONS: Reduced post-visit hospital use is likely related to increased clinic resources, Affordable Care Act insurance expansions, and improved clinical and community social service expertise. LEVEL OF EVIDENCE: Cohort study, Level 2.

Convergent Signaling Pathways Controlled by LRP1 (Receptor-related Protein 1) Cytoplasmic and Extracellular Domains Limit Cellular Cholesterol Accumulation.

The low density lipoprotein receptor-related protein 1 (LRP1) is a ubiquitously expressed cell surface receptor that protects from intracellular cholesterol accumulation. However, the underlying mechanisms are unknown. Here we show that the extracellular (α) chain of LRP1 mediates TGFß-induced enhancement of Wnt5a, which limits intracellular cholesterol accumulation by inhibiting cholesterol biosynthesis and by promoting cholesterol export. Moreover, we demonstrate that the cytoplasmic (ß) chain of LRP1 suffices to limit cholesterol accumulation in LRP1(-/-) cells. Through binding of Erk2 to the second of its carboxyl-terminal NPXY motifs, LRP1 ß-chain positively regulates the expression of ATP binding cassette transporter A1 (ABCA1) and of neutral cholesterol ester hydrolase (NCEH1). These results highlight the unexpected functions of LRP1 and the canonical Wnt5a pathway and new therapeutic potential in cholesterol-associated disorders including cardiovascular diseases.

The nuclear hormone receptor PPARγ counteracts vascular calcification by inhibiting Wnt5a signalling in vascular smooth muscle cells.

Vascular calcification is a hallmark of advanced atherosclerosis. Here we show that deletion of the nuclear receptor PPARγ in vascular smooth muscle cells of low density lipoprotein receptor (LDLr)-deficient mice fed an atherogenic diet high in cholesterol, accelerates vascular calcification with chondrogenic metaplasia within the lesions. Vascular calcification in the absence of PPARγ requires expression of the transmembrane receptor LDLr-related protein-1 in vascular smooth muscle cells. LDLr-related protein-1 promotes a previously unknown Wnt5a-dependent prochondrogenic pathway. We show that PPARγ protects against vascular calcification by inducing the expression of secreted frizzled-related protein-2, which functions as a Wnt5a antagonist. Targeting this signalling pathway may have clinical implications in the context of common complications of atherosclerosis, including coronary artery calcification and valvular sclerosis.

Cdc48 and Ufd3, new partners of the ubiquitin protease Ubp3, are required for ribophagy.

Ubiquitin-dependent processes can be antagonized by substrate-specific deubiquitination enzymes involved in many cellular functions. In this study, we show that the yeast Ubp3-Bre5 deubiquitination complex interacts with both the chaperone-like Cdc48, a major actor of the ubiquitin and proteasome system, and Ufd3, a ubiquitin-binding cofactor of Cdc48. We observed that these partners are required for the Ubp3-Bre5-dependent and starvation-induced selective degradation of yeast mature ribosomes, also called ribophagy. By contrast, proteasome-dependent degradation does not participate in this process. Our data favour the idea that these factors cooperate to recognize and deubiquitinate specific substrates of ribophagy before their vacuolar degradation.

Transglutaminase-3 enzyme: a putative actor in human hair shaft scaffolding?

The family of transglutaminases (TGase) is known to be involved in terminal differentiation processes in the epidermis. These enzymes contribute also to the physical resistance and the preservation of the hair follicle structure. Our particular interest in hair fiber keratinization led us to focus on the TGase 3, exclusively expressed in the hair shaft. To date its function is still to be elucidated, thus we have developed a multidisciplinary approach in order to define the localization, activity, and substrates of TGase 3. The hair fiber is characterized by the expression of specific proteins essentially consisting of keratin intermediate filaments and keratin-associated proteins (KAPs), which are essential for the formation of a rigid hair shaft through their extensive disulfide cross-links. Gel electrophoresis combined with mass spectrometry experiments revealed an unexpected protein migration pattern, suggesting the existence of covalent interactions other than disulfide bonds. Western blot and amino-acid analysis revealed the presence of gamma-glutamyl-epsilon-lysine isopeptide linkages that could constitute this second covalent network. Our hypothesis is that TGase 3-driven specific isopeptide bonds between intermediate filaments and KAPs participate to the progressive scaffolding of the hair shaft.

The way forward, enhanced characterization of therapeutic antibody glycosylation: comparison of three level mass spectrometry-based strategies.

Glycosylation which plays a crucial role in the pharmacological properties of therapeutic monoclonal antibodies (MAbs) is influenced by several factors like production systems, selected clonal population and manufacturing processes. Efficient analytical methods are therefore required in order to characterize glycosylation at different stages of MAbs discovery and production. Three mass spectrometry (MS)-based strategies were compared to analyze N-glycosylation of MAbs either expressed in murine myeloma (NS0) or Chinese Hamster Ovary (CHO) cell lines, the two current main production systems used for therapeutic MAbs. First a top-down approach was used on intact and reduced MAbs by liquid chromatography coupled to an electrospray ionization-time of flight mass spectrometer (LC-ESI-TOF), which provided fast and accurate profiles of MAbs glycosylation patterns for routine controls. Secondly, after digestion of the antibody with the peptide N-glycosidase F (PNGase F) enzyme, released N-linked glycans were directly analyzed by electrospray ionization-tandem mass spectrometry (ESI-MS/MS) without any prior derivatization, which gave precise details on the structure of the most abundant glycoforms. Finally, a bottom-up approach on tryptic glycopeptides using a nanoLC-Chip-MS/MS ion trap (IT) system equipped with a graphitized carbon column was investigated. Data were compared to those obtained with a more classical C18 reversed phase column showing that this last method is well suited to detect low abundant glycoforms and to provide in one shot information regarding both the oligosaccharide structure and the amino acid sequence of its peptide moiety.

Tandem use of X-ray crystallography and mass spectrometry to obtain ab initio the complete and exact amino acids sequence of HPBP, a human 38-kDa apolipoprotein.

The Human Phosphate Binding Protein (HPBP) is a serendipitously discovered apolipoprotein from human plasma that binds phosphate. Amino acid sequence relates HPBP to an intriguing protein family that seems ubiquitous in eukaryotes. These proteins, named DING according to the sequence of their four conserved N-terminal residues, are systematically absent from eukaryotic genome databases. As a consequence, HPBP amino acids sequence had to be first assigned from the electronic density map. Then, an original approach combining X-ray crystallography and mass spectrometry provides the complete and a priori exact sequence of the 38-kDa HPBP. This first complete sequence of a eukaryotic DING protein will be helpful to study HPBP and the entire DING protein family.

Characterisation of a novel growth hormone variant comprising a thioether link between Cys182 and Cys189.

A novel variant of recombinant human growth hormone (r-hGH), isolated from biopharmaceutical preparations produced in E. coli, was identified and characterised. This variant contains a nonreducible thioether bridge near the C terminus between Cys182 and Cys189 and was characterised using various analytical techniques. As previous work by Cunningham and Wells (1993) highlighted the involvement of several residues in this part of the sequence in the binding and affinity of the molecule to its receptor, the presence of this modified intramolecular link may have important implications with regard to the biological behaviour of the molecule. Furthermore, as the conversion of a disulfide into a thioether was previously reported for a therapeutic monoclonal antibody (Tous et al., 2005), this may imply that disulfide bridges located in this part of the molecule have a generic susceptibility to thioether formation. This in turn is relevant to the biopharmaceutical industry for monitoring the integrity of disulfide bridges near the protein C terminus. The present study exhibits a state of the art physicochemical investigation for the unequivocal elucidation of a novel structure involving peptide mapping with mass spectrometry and de novo peptide sequencing. Changes in the higher order structure of the molecule were highlighted by near UV circular dichroism and molecular modelling.