Biochemical characterization of a high affinity phosphate transporter (PiPT) from root endophyte fungus Piriformospora indica.

We have functionally characterized the high-affinity phosphate transporter (PiPT) from the root endophyte fungus Piriformospora indica. PiPT belongs to the major facilitator superfamily (MFS). PiPT protein was purified by affinity chromatography (Ni-NTA) and Size Exclusion Chromatography (SEC). The functionality of solubilized PiPT was determined in detergent-solubilized state by fluorescence quenching and in proteoliposomes. In the fluorescence quenching assay, PiPT exhibited a saturation concentration of approximately 2 µM, at a pH of 4.5. Proteoliposomes of size 121.6 nm radius, showed transportation of radioactive phosphate. Vmax was measured to be 232.2 ± 11 pmol/min/mg protein. We have found Km to be 45.8 ± 6.2 µM suggesting high affinity towards phosphate.

Radiological outcomes following open versus percutaneous fixation versus arthroscopically assisted percutaneous fixation of calcaneal fractures: a ten-year retrospective observational study.

BACKGROUND: Calcaneal fractures are often major injuries associated with considerable morbidity. The optimal surgical management of displaced calcaneal fractures remains contentious with open, percutaneous and arthroscopically assisted percutaneous approaches all offering potential benefits for patients. The aim of this study was to assess which of these three separate surgical approaches to the management of displaced calcaneal fractures provides the best radiographic deformity correction. METHODS: This is a retrospective observational study of all calcaneal fractures undergoing operative fixation at a single major trauma centre in the UK. The primary outcome was pre- and post-operative assessment of the deformity correction using radiographic parameters (angle of Gissane and Bohler's angle). Secondary outcomes included fracture configuration, complications and re-operation rate. RESULTS: Between 01/01/2009 and 31/12/2019, 152 calcaneal fractures in 134 patients underwent operative management via either an open or percutaneous approach. One-way ANOVA testing of the pre- and post-operative radiographic parameters demonstrated that an open approach offered superior post-operative correction of Bohler's angle when compared to percutaneous alone (p < 0.05); however, there was no difference in post-operative angle of Gissane (p > 0.05). The mean follow-up for complication and re-operation data was 3.5 years (range 0.1-12.4). Overall complication rate following all surgical fixation was 7.2% with a further 32.2% requiring further long-term surgical intervention for subtalar arthritis or removal of metalwork. CONCLUSION: Arthroscopically assisted percutaneous fixation does not offer superior radiographic deformity correction compared to percutaneous technique alone. Open fixation yielded improved correction of Bohler's angle when compared to percutaneous alone; however, there was no difference in post-operative angle of Gissane. LEVEL OF EVIDENCE: III.

The Use of Hindfoot Nails for Elderly Complex Distal Tibial and Ankle Fractures.

Elderly patients who sustain complex ankle or distal tibial fractures are often frail and comorbid and need surgery to contain the talus underneath the tibia in order to protect the soft tissue envelope and allow early unrestricted weightbearing. We performed a retrospective observational review of patients >65 years old who underwent a hindfoot nail fixation of an ankle or distal tibial fracture in our institution. Data collected included: injury sustained, open or closed injury, ASA grade, age at time of surgery, length of stay, postoperative mortality, complications, and further treatment. The primary outcome was reoperation. Secondary outcomes were infection and 1 year mortality. Seventy hind foot nailing procedures were undertaken. Sixty-three out of 70 patients were female. The average age of those who died within 1 year of surgery was 84 years. Forty-five out of 70 were open injuries. Eleven out of 70 patients died with 1 year of surgery (range 1-358 days postsurgery). Five out of 70 (7%) patients developed an infection. Four out of 5 of these injuries were open. Three out of 5 underwent removal of the nail due to infection. Two out of 5 had the infection suppressed with antibiotics. Ten out of 70 (14%) patients underwent locking bolt removal due to it backing out or being prominent and causing wound healing issues. Two out of 70 (3%) patients went on to have below knee amputations. Both were due to ongoing wound problems following open fractures. The hindfoot nail is an important implant when treating complex ankle and distal tibial fractures in an elderly population. It facilitates early mobilization to avoid deconditioning and other medical complications.

Crystal structure of a eukaryotic phosphate transporter.

Phosphate is crucial for structural and metabolic needs, including nucleotide and lipid synthesis, signalling and chemical energy storage. Proton-coupled transporters of the major facilitator superfamily (MFS) are essential for phosphate uptake in plants and fungi, and also have a function in sensing external phosphate levels as transceptors. Here we report the 2.9 Å structure of a fungal (Piriformospora indica) high-affinity phosphate transporter, PiPT, in an inward-facing occluded state, with bound phosphate visible in the membrane-buried binding site. The structure indicates both proton and phosphate exit pathways and suggests a modified asymmetrical 'rocker-switch' mechanism of phosphate transport. PiPT is related to several human transporter families, most notably the organic cation and anion transporters of the solute carrier family (SLC22), which are implicated in cancer-drug resistance. We modelled representative cation and anion SLC22 transporters based on the PiPT structure to surmise the structural basis for substrate binding and charge selectivity in this important family. The PiPT structure demonstrates and expands on principles of substrate transport by the MFS transporters and illuminates principles of phosphate uptake in particular.

Extended plantar limb (modified) chevron osteotomy versus scarf osteotomy for hallux valgus correction: A randomised controlled trial.

BACKGROUND: The purpose of this RCT was to compare the extended plantar limb (modified) chevron osteotomy with the scarf osteotomy in correcting hallux valgus deformity and improving functional scores and patient satisfaction. METHODS: Patients were randomly assigned and kept blind to surgical allocation. Cases requiring additional procedures including the Akin osteotomy were excluded. Outcomes were measured at 1 year following surgery. RESULTS: 84 patients (109 feet) were analysed (60 modified chevron; 49 Scarf). The mean age was 50.7 years (75F: 9M). Post-operative intermetatarsal angle (IMA) was significantly lower in the modified chevron group (5.8° versus 6.9°, p=0.045). Hallux valgus angle and distal metatarsal articular angle were similar. The magnitude of IMA correction with the modified chevron was also significantly greater (9.1° versus 7.1°, p=0.007). Both osteotomies produced comparable MOxFQ scores and satisfaction ratings. CONCLUSION: The modified chevron was superior to the scarf osteotomy in correcting IMA in hallux valgus deformity.

Chance fracture of the talus and calcaneum.

Combined talus and calcaneum fractures are rare in themselves. We report the case of an unusual fracture pattern of the talus and calcaneum in an otherwise, healthy 17-year-old male. Plain radiographic images of the foot revealed a fracture through the neck of the talus. Additional computed tomography imaging showed the fracture line extending through the talus and entire calcaneum. The fracture was open and associated with rupture of the tibialis anterior and extensor hallucis longus tendons. The patient underwent debridement with open reduction and internal fixation of the talar component of the fracture using 2 screws. The calcaneal component was treated conservatively. The soft tissue injuries to the 2 tendons were also repaired. The patient made good progress with this management.

Crystal structure of human aquaporin 4 at 1.8 A and its mechanism of conductance.

Aquaporin (AQP) 4 is the predominant water channel in the mammalian brain, abundantly expressed in the blood-brain and brain-cerebrospinal fluid interfaces of glial cells. Its function in cerebral water balance has implications in neuropathological disorders, including brain edema, stroke, and head injuries. The 1.8-A crystal structure reveals the molecular basis for the water selectivity of the channel. Unlike the case in the structures of water-selective AQPs AqpZ and AQP1, the asparagines of the 2 Asn-Pro-Ala motifs do not hydrogen bond to the same water molecule; instead, they bond to 2 different water molecules in the center of the channel. Molecular dynamics simulations were performed to ask how this observation bears on the proposed mechanisms for how AQPs remain totally insulating to any proton conductance while maintaining a single file of hydrogen bonded water molecules throughout the channel.

Ground Reaction Force Calcaneal Offset: A new measurement of hindfoot alignment.

BACKGROUND: The tibio-calcaneal angle (TCA) does not measure individual forefoot contributions to the overall foot balance. Using standard radiographs we calculated the ideal hindfoot alignment based on ground reaction force (GRF), independently from the tibial axis. METHODS: Thirty-six patients (40ft.) were included. Mean age was 56. Weight bearing radiographs were taken. Calcaneal offsets were measured using tibio-calcaneal angles and GRF algorithms. Measurements were compared using the Bland-Altman method. FINDINGS: Both methods agreed (p>0.05) but individual discrepancies were found. Mean measured offsets were -11.5mm (SD: 10.2) using TCA and -8mm (SD: 9.3) using GRF. Mean bias between the methods was -0.88mm. INTERPRETATION: The GRF algorithm successfully measured hindfoot alignment. The absence of a previous gold standard and radiographic variability are a limit. The TCA underestimated calcaneal offset. Discrepancies showed that forefoot position data provided increased accuracy. This could be of particular relevance for surgical planning.

Tibiotalocalcaneal arthrodesis with a curved, interlocking, intramedullary nail.

BACKGROUND: Tibiotalocalcaneal fusion with a straight rod has a risk of damaging the lateral plantar neurovascular structures and may interfere with maintaining normal heel valgus position.We report the results of a prospective study of tibiotalocalcaneal (TTC) arthrodesis with a short, anatomically curved interlocking, intramedullary nail. MATERIAL AND METHODS: Forty-five arthrodesis in 42 patients, performed between Jan 2003 and Oct 2008, were prospectively followed. The mean followup was 48 (range, 10 to 74) months. The main indications for the procedure were failed ankle arthrodesis with progressive subtalar arthritis, failed ankle arthroplasty and complex hindfoot deformity. The outcome was measured by a combination of pre and postoperative clinical examination, AOFAS hindfoot scores, SF-12 scores and radiological assessment. RESULTS: Union rate was 89% (40/45). Eighty-two percent (37/45) reported improvement in pain and 73% (33/45) had improved foot function. Satisfactory hindfoot alignment was achieved in 84% (38/45). Postoperatively there was a mean improvement in the AOFAS score of 37. Complications included a below knee amputation for persistent deep infection, five nonunions, and three delayed unions. Four nails, six proximal and six distal locking screws were removed for various causes. Other complications included two perioperative fractures, four superficial wound infections and one case of lateral plantar nerve irritation. CONCLUSION: With a short, anatomically curved intramedullary nail, we had a high rate of tibiotalocalcaneal fusion with minimal plantar neurovascular complications. We believe a short, curved intramedullary nail, with its more lateral entry point, helped maintain hindfoot alignment.

2007 annual progress report synopsis of the Center for Structures of Membrane Proteins.

A synopsis of the 2007 annual progress report for the Center for Structures of Membrane Proteins, a specialized center of the Protein Structure Initiative.

Glycerol facilitator GlpF and the associated aquaporin family of channels.

The aqua (glycero) porins conduct water (and glycerol) across cell membranes. The structure of these channels reveals a tripathic channel that supports a hydrophobic surface and, opposite to this, a line of eight hydrogen-bond acceptors and four hydrogen-bond donors. The eight carbonyls act as acceptors for water (or glycerol OH) molecules. The central water molecule in the channel is oriented to polarize hydrogen atoms outward from the center. This arrangement suggests how the structure prevents the potentially lethal conduction of protons across the membrane. The structure also suggests the mechanism behind the selectivity of aquaglyceroporins for glycerol, the basis for enantioselectivity among alditols, and the basis for the prevention of any leakage of the electrochemical gradient.

Minimally invasive surgery (MIS) for total knee replacement; medium term results with minimum five year follow-up.

BACKGROUND: MIS TKA has been shown to offer a reduced in-patient stay, but no clinical difference at two years. Whilst there may be a benefit from earlier discharge, we need to ensure that there are no detrimental effects in the medium and long-term following MIS-TKA. To report the mid-term result from a prospective randomised controlled trial (RCT) comparing MIS-TKA with standard approach for TKA. METHODS: Using knee score questionnaires, we collected patient reported outcome measures (PROMs) regarding pain and function. Sixty-six patients (from an eligible cohort of 83 patients) completed the mid-term postal follow-up. RESULTS: There was no significant difference between groups for change in score from pre-operative to final follow-up in all three PROMs. Mean MIS and standard group improvement was: AKSS 53 and 51 (p=0.7644), OKS 15 and 16 (p=0.2341) or WOMAC 15 and 15 (p=0.9900) respectively. Both groups showed improvement in pain and function with no significant difference between groups. There was no difference between groups for revision due to malalignment at a mean six year follow-up. CONCLUSIONS: In addition to the early benefits regarding hospital stay and complications, we have found that at a mean of six years there was no increase in malalignment, pain or function with MIS techniques.

Selectivity and conductance among the glycerol and water conducting aquaporin family of channels.

The atomic structures of a transmembrane water plus glycerol conducting channel (GlpF), and now of aquaporin Z (AqpZ) from the same species, Escherichia coli, bring the total to three atomic resolution structures in the aquaporin (AQP) family. Members of the AQP family each assemble as tetramers of four channels. Common helical axes support a wider channel in the glycerol plus water channel paradigm, GlpF. Water molecules form a single hydrogen bonded file throughout the 28 A long channel in AqpZ. The basis for absolute exclusion of proton or hydronium ion conductance through the line of water is explored using simulations.

Minimally invasive total knee arthroplasty; a pragmatic randomised controlled trial reporting outcomes up to 2 year follow up.

BACKGROUND: We present a prospective, randomised, multi-surgeon, controlled trial comparing minimally invasive (MIS) and standard approach total knee arthroplasty (TKA). METHODS: Participants underwent unilateral TKA. Patients were randomised to Bristol, quadriceps sparing MIS or standard medial parapatellar approaches. Length of stay with secondary outcome measures including knee range of movement, Oxford Knee Score (OKS), Western Ontario and McMaster Universities Arthritis Index (WOMAC) and American Knee Society Score (KSS) up to 2 years. Radiographic and post operative assessment was blinded. RESULTS: 86 patients (92 knees) participated in the study. Mean operative time between MIS and control groups was 95.5 (95% CI 90.0-101.0) and 94.8 (95% CI 88.2-101.4) minutes respectively. Mean readiness for discharge was shorter in the MIS group 4.5±1.5 (95% CI, 4.1-4.9) days versus 5.9±2.7 (95% CI, 5.1-6.7) days amongst controls (p=0.004). Patients in the MIS group had fewer complications (p=0.003). One patient developed a deep vein thrombosis (DVT) and one required revision surgery, both in the control group. 83 patients completed follow up to 2 years (40 MIS, 43 controls). Range of movement and other outcome measures improved up to 1 year post-operatively with no statistically significant differences between MIS and controls. We found no evidence of radiographic loosening in either group at the 2 year follow up. CONCLUSIONS: MIS offers reduced length of stay and fewer complications for patients following TKR without evidence of component mal-alignment. Our findings of fewer systemic complications in MIS TKR patients warrant further future study. LEVEL OF EVIDENCE: Level 1.

Biceps femoris tendon injuries sustained while playing hockey.

A 42-year-old female nurse presented in March 2008 with a left proximal hamstring tendon injury sustained while playing hockey. At surgery, the proximal biceps femoris tendon and semitendonosus were found to be ruptured and were repaired. The patient made a good recovery but sustained a further hockey injury in January 2010 involving a complete tear and rupture of the biceps femoris tendon distally. This was managed conservatively and the patient was able to return to playing hockey 10 months later. Biceps femoris tendon injuries have been reported in sport but this is the first documented case of the injury occurring while playing hockey and is also the first reported case of a biceps tendon rupture proximally (hamstring tendon) followed by distal biceps femoris rupture at the knee in the same leg.

Isolated partial tear and partial avulsion of the medial head of gastrocnemius tendon presenting as posterior medial knee pain.

We present a case of medial head of gastrocnemius tendon tear. The type of injury widely reported in the literature is tear of the medial head of gastrocnemius muscle or 'tennis leg'. We previously reported an isolated partial tear and longitudinal split of the tendon to the medial head of gastrocnemius at its musculotendinous junction. The case we now present has notable differences; the tear was interstitial and at the proximal (femoral attachment) part of the tendon, the patient's symptoms and clinical examination suggested a medial meniscus tear, and magnetic resonance imaging demonstrated bone oedema at the tendon insertion site indicating a traction injury. Both cases suggest that isolated tear of the medial head of the gastrocnemius tendon may have a variety of presentations and appearances and should be considered in the differential diagnosis of tennis leg as well as medial meniscus tear.

A comparison of the long gamma nail with the sliding hip screw for the treatment of AO/OTA 31-A2 fractures of the proximal part of the femur: a prospective randomized trial.

BACKGROUND: Controversy exists with regard to whether to treat AO/OTA 31-A2 fractures of the proximal part of the femur with an intramedullary device or an extramedullary device. A prospective, randomized, controlled trial was performed to compare the outcome of treatment of these unstable fractures of the proximal part of the femur with either a sliding hip screw or a long gamma nail. METHODS: Two hundred and ten patients presenting with an AO/OTA 31-A2 fracture of the proximal part of the femur were randomized, at the time of admission, to fixation with use of either a long gamma nail or a sliding hip screw. The primary outcome measure was reoperation within the first postoperative year. Secondary measures included mortality, length of hospital stay, transfusion rate, change in mobility and residence, and quality of life as measured with the EuroQol 5D outcome score. RESULTS: There was no significant difference between the reoperation rates for the two groups. In total, five patients (three from the long-gamma-nail group and two from the sliding-hip-screw group) underwent revision surgery because of cut-out. Tip-apex distance was found to correlate with the implant cut-out rate. There was no significant difference between the two groups in terms of the EuroQol 5D outcome scores, the mortality rates after correction for the mini-mental score, or any of the secondary outcome measures. CONCLUSIONS: When compared with the long gamma nail, the sliding hip screw should remain the gold standard for the treatment of AO/OTA 31-A2 fractures of the proximal part of the femur because it is associated with similar outcomes with less expense.

Isolated tear of the tendon to the medial head of gastrocnemius presenting as a painless lump in the calf.

We report on a case of isolated tear of the medial head of gastrocnemius tendon. The patient presented with a painless lump in the right calf and denied any prior history of trauma or strain to the leg. A longitudinal split of the tendon was demonstrated at ultrasound and magnetic resonance imaging (MRI). There were no other abnormalities and the gastrocnemius muscle was normal. There are no reports in the literature of isolated gastrocnemius tendon tear. To date the calf muscle complex injury described in this area is tearing of the medial head of gastrocnemius muscle, sometimes referred to as "tennis leg". We conclude that an isolated tear of the tendon to the medial head of gastrocnemius should be considered in the differential diagnosis of a lump or swelling in the upper medial area of the calf and we recommend ultrasound or MRI as the investigations of choice.