Introduction. Spinal aBMD only explains 50–80% of vertebral strength, and the application of aBMD measurements in isolation cannot accurately identify individuals who are likely to eventually experience bone fracture, due to the low sensitivity of the test. For appropriate treatment intervention, a more sensitive test of bone strength is needed. Such a test should include not only bone mineral density, but also bone quality. Quantitative computed tomography-based finite element methods (QCT/FEM) may allow structural analyses taking these factors into consideration to accurately predict bone strength (PBS). To date, however, basic data have not been reported regarding the prediction of bone strength by QCT/FEM with reference to age in a normal population. The purpose of this study was thus to create a database on PBS in a normal population as a preliminary trial. With these data, parameters that affect PBS were also analyzed. Methods. Participants in this study comprised individuals who participated in a health checkup program with CT at our hospital in 2009. Participants included 217 men and 120 women (age range, 40–89 years). Exclusion criteria were provided. Scan data of the second lumber vertebra (L2) were isolated and taken from overall CT data for each participant obtained with simultaneous scans of a calibration phantom containing hydroxyapatite rods. A FE model was constructed from the isolated data using Mechanical Finder software. For each of the FE models, A uniaxial compressive load with a uniform distribution and uniform load increment was applied. For each participant, height and weight were measured, BMI was calculated. Simple linear regression analysis was used to estimate correlations between age and PBS as analyzed by QCT/FEM. Changes in PBS with age were also evaluated by grouping participants into 5-year age brackets. One-way analysis of variance was used to compare average PBS for participants in each age range. Mean PBS in the 40–44 year age range was taken as the young adult mean (YAM). The ratio of mean PBS in each age group to YAM was calculated as a percentage. A multivariate statistical technique was used to determine how PBS was affected by age, height, weight, and BMI. Result/Discussion. Mean PBS was lower in women than in men for all age ranges. PBS in men and women significantly decreased with age. Simple linear regression between age and PBS showed the annual rate of decline in PBS was 55 N/year in men and 164 N/year in women. Mean PBS in the 75–79 year age range was 77% of YAM in men and in women, that in the 70–79 year age range was 47% of YAM. PBS was strongly dependent on age, while physical status had less effect

Aims. Although absorbable sutures for the repair of acute Achilles tendon rupture (ATR) have been attracting attention, the rationale for their use remains insufficient. This study prospectively compared the outcomes of absorbable and nonabsorbable sutures for the repair of acute ATR. Methods. A total of 40 patients were randomly assigned to either braided absorbable polyglactin suture or braided nonabsorbable polyethylene terephthalate suture groups. ATR was then repaired using the Krackow suture method. At three and six months after surgery, the isokinetic muscle strength of ankle plantar flexion was measured using a computer-based Cybex dynamometer. At six and 12 months after surgery, patient-reported outcomes were measured using the Achilles tendon Total Rupture Score (ATRS), visual analogue scale for pain (VAS pain), and EuroQoL five-dimension health questionnaire (EQ-5D). Results. Overall, 37 patients completed 12 months of follow-up. No difference was observed between the two groups in terms of isokinetic plantar flexion strength, ATRS, VAS pain, or EQ-5D. No re-rupture was observed in either group. Conclusion. The use of absorbable sutures for the repair of acute ATR was not inferior to that of nonabsorbable sutures. This finding suggests that absorbable sutures can be considered for the repair of acute ATRs. Cite this article: Bone Joint J 2022;104-B(8):938–945

As the field of hip arthroscopy continues to develop, functional measures and testing become increasingly important in patient selection, managing patient expectations prior to surgery, and physical readiness for return to athletic participation. The Hip Sport Test (HST) was developed to assess strength, coordination, agility, and range of motion prior to and following hip arthroscopy as a functional assessment. However, the relationship between HST and hip strength, range of motion, and hip-specific patient reported outcome (PRO) measures have not been investigated. The purpose of this study was to evaluate the correlation between the HST scores and measurements of hip strength and range of motion prior to undergoing hip arthroscopy. Between September 2009 and January 2017, patients aged 18-40 who underwent primary hip arthroscopy for the treatment of femoroacetabular impingement with available pre-operative HST, dynamometry, range of motion, and functional scores (mHHS, WOMAC, HOS-SSS) were identified. Patients were excluded if they were 40 years old, had a Tegner activity score < 7, or did not have HST and dynamometry evaluations within one week of each other. Muscle strength scores were compared between affected and unaffected side to establish a percent difference with a positive score indicating a weaker affected limb and a negative score indicating a stronger affected limb. Correlations were made between HST and strength testing, range of motion, and PROs. A total of 350 patients met inclusion criteria. The average age was 26.9 ± 6.5 years, with 34% females and 36% professional athletes. Total and component HST scores were significantly associated with measure of strength most strongly for flexion (rs = −0.20, p < 0 .001), extension (rs = −0.24, p<.001) and external rotation (rs = −0.20, p < 0 .001). Lateral and diagonal agility, components of HST, were also significantly associated with muscle strength imbalances between internal rotation versus external rotation (rs = −0.18, p=0.01) and flexion versus extension (rs = 0.12, p=0.03). In terms of range of motion, a significant correlation was detected between HST and internal rotation (rs = −0.19, p < 0 .001). Both the total and component HST scores were positively correlated with pre-operative mHHS, WOMAC, and HOS-SSS (p<.001 for all rs). The Hip Sport Test correlates with strength, range of motion, and PROs in the preoperative setting of hip arthroscopy. This test alone and in combination with other diagnostic examinations can provide valuable information about initial hip function and patient prognosis

While controversy remains as to the relative benefit of operative (OM) versus non-operative management (NOM) of Achilles tendon ruptures (ATR), few studies have examined the effect on high impact maneuvers such as jumping and hopping. The purpose of this study is to compare functional performance and musculotendinous morphology in patients following OM or NOM for acute ATR. Eligible patients were aged 18-65 years old with an ATR who underwent OM or NOM within three weeks of injury and were at least one-year post injury. Gastrocnemius muscle thickness and Achilles tendon length and thickness were assessed with ultrasound. Functional performance was examined with single-leg hop tests and isokinetic plantar strength at 60o/s and 120o/s. 24 participants completed testing (12/ group). Medial (OM: 2.2 ± 0.4 cm vs 1.9 ± 0.3 cm, NOM 2.15 ± 0.5 cm vs 1.7 ± 0.5 cm; p = 0.002) and lateral (OM 1.8 ± 0.3 cm vs 1.5 ± 0.4 cm, NOM 1.6 ± 0.4 cm vs 1.3 ± 0.5 cm; p = 0.008) gastrocnemius thickness were reduced on the affected limb. The Achilles tendon was longer (OM: 19.9 ± 2.2 cm vs 21.9 ± 1.6 cm; NOM: 19.0 ± 3.7 cm vs 21.4 ± 2.9 cm; p = 0.009) and thicker (OM: 0.48 ± 0.16 cm vs 1.24 ± 0.20 cm; NOM: 0.54 ± 0.08 cm vs 1.13 ± 0.23 cm; p < 0.001) on the affected limb with no differences between groups. Affected limb plantar flexion torque at 20o plantar flexion was reduced at 60o/s (OM: 55.6 ± 20.2 nm vs 47.8 ± 18.3 nm; NOM: 59.5 ± 27.5 nm vs 44.7 ± 21.0 nm; p = 0.06) and 120o/s (OM: 44.6 ± 17.9 nm vs 36.6 ± 15.0 nm; NOM: 48.6 ± 16.9 nm vs 35.8 ± 10.7 nm; p = 0.028) with no group effect. There was no difference in single leg hop performance. Achilles tendon length explained 31.6% (p = 0.003) and 18.0% (p = 0.025) of the variance in plantar flexion peak torque limb symmetry index (LSI) at 60o/s and 120o/s respectively. Tendon length explained 28.6% (p=0.006) and 9.5% (p = 0.087) of LSI when torque was measured at 20o plantar flexion at 60o/s and 120o/s respectively. Conversely, tendon length did not predict affected limb plantar flexion peak torque (nm), angle-specific torque at 20o plantar flexion (nm) and affected limb single leg hop distance (cm) or LSI (%). There was no difference in tendon length between treatment groups and deficits in gastrocnemius thickness and strength are persistent. Deficits in the plantar flexion strength LSI are partially explained by increased tendon length following Achilles tendon rupture, regardless of treatment strategy. Hop test performance is maintained and may be the result of compensatory movements at other joints despite persistent plantarflexion weakness

Aims. To develop an early implant instability murine model and explore the use of intermittent parathyroid hormone (iPTH) treatment for initially unstable implants. Methods. 3D-printed titanium implants were inserted into an oversized drill-hole in the tibiae of C57Bl/6 mice (n = 54). After implantation, the mice were randomly divided into three treatment groups (phosphate buffered saline (PBS)-control, iPTH, and delayed iPTH). Radiological analysis, micro-CT (µCT), and biomechanical pull-out testing were performed to assess implant loosening, bone formation, and osseointegration. Peri-implant tissue formation and cellular composition were evaluated by histology. Results. iPTH reduced radiological signs of loosening and led to an increase in peri-implant bone formation over the course of four weeks (timepoints: one week, two weeks, and four weeks). Observational histological analysis shows that iPTH prohibits the progression of fibrosis. Delaying iPTH treatment until after onset of peri-implant fibrosis still resulted in enhanced osseointegration and implant stability. Despite initial instability, iPTH increased the mean pull-out strength of the implant from 8.41 N (SD 8.15) in the PBS-control group to 21.49 N (SD 10.45) and 23.68 N (SD 8.99) in the immediate and delayed iPTH groups, respectively. Immediate and delayed iPTH increased mean peri-implant bone volume fraction (BV/TV) to 0.46 (SD 0.07) and 0.34 (SD 0.10), respectively, compared to PBS-control mean BV/TV of 0.23 (SD 0.03) (PBS-control vs immediate iPTH, p < 0.001; PBS-control vs delayed iPTH, p = 0.048; immediate iPTH vs delayed iPTH, p = 0.111). Conclusion. iPTH treatment mediated successful osseointegration and increased bone mechanical strength, despite initial implant instability. Clinically, this suggests that initially unstable implants may be osseointegrated with iPTH treatment. Cite this article: Bone Joint Res 2022;11(5):260–269

Introduction. There is a lack of evidence-based treatments for patients with chronic pain after total knee arthroplasty (TKA). It is well-established that knee extensor and flexor muscle strength are markedly impaired following TKA, but no studies have examined muscle strength and power in patients with chronic pain after TKA. Therefore, the aim was to investigate if neuromuscular exercises and pain neuroscience education (PNE) were superior to PNE alone for improvement of muscle strength and power in patients with chronic pain after TKA. Method. This report presents the exploratory analysis of a randomized controlled trial (NCT03886259). Participants with chronic moderate-to-severe average daily pain intensity and no signs of prosthesis failure at least one year after primary TKA were included. Participants were randomized to receive either supervised neuromuscular exercise and PNE or the same PNE sessions alone. The outcomes were changes from baseline to 12-months for peak leg extension power and maximum muscle strength, measured during maximal voluntary isometric contractions, for the knee extensors and flexors. Result. Sixty-nine participants (age 62.2±7.2, 40 females) were included. No between-group differences were observed for peak leg extension power (difference 13.6 Watts, 95% CI -22.2 to 49.3), maximum knee extensor muscle strength (difference -20.9 Newtons, 95% CI -65.8 to 24.0) or maximum knee flexor muscle strength (difference 8.6 Newtons, 95% CI -11.9 to 29.1). Peak leg extension power (26.3 Watts, 95% CI 4.3 to 48.3) and maximum knee flexor muscle strength (19.7 Newtons, 95% CI 7.6 to 31.9) improved significantly in the neuromuscular exercise and PNE group with no significant improvements observed in the PNE alone group. Conclusion. Neuromuscular exercise and PNE did not improve muscle strength and power compared to PNE alone in patients with chronic pain after TKA. Acknowledgements. This study was funded by the Danish Rheumatism Association, the Svend Andersen Foundation and Lions Club Denmark

Aims. Anchorage of pedicle screw rod instrumentation in the elderly spine with poor bone quality remains challenging. Our study aims to evaluate how the screw bone anchorage is affected by screw design, bone quality, loading conditions, and cementing techniques. Methods. Micro-finite element (µFE) models were created from micro-CT (μCT) scans of vertebrae implanted with two types of pedicle screws (L: Ennovate and R: S. 4. ). Simulations were conducted for a 10 mm radius region of interest (ROI) around each screw and for a full vertebra (FV) where different cementing scenarios were simulated around the screw tips. Stiffness was calculated in pull-out and anterior bending loads. Results. Experimental pull-out strengths were excellently correlated to the µFE pull-out stiffness of the ROI (R. 2. > 0.87) and FV (R. 2. > 0.84) models. No significant difference due to screw design was observed. Cement augmentation increased pull-out stiffness by up to 94% and 48% for L and R screws, respectively, but only increased bending stiffness by up to 6.9% and 1.5%, respectively. Cementing involving only one screw tip resulted in lower stiffness increases in all tested screw designs and loading cases. The stiffening effect of cement augmentation on pull-out and bending stiffness was strongly and negatively correlated to local bone density around the screw (correlation coefficient (R) = -0.95). Conclusion. This combined experimental, µCT and µFE study showed that regional analyses may be sufficient to predict fixation strength in pull-out and that full analyses could show that cement augmentation around pedicle screws increased fixation stiffness in both pull-out and bending, especially for low-density bone. Cite this article: Bone Joint Res 2021;10(12):797–806

Purpose of study and background. Spinal muscle area (SMA) is often employed to assess muscle functionality and is important for understanding the risk individuals may have of developing back pain or the risk of postural instability and falls.. However, handgrip strength (HGS) has also been utilized as a measure of general muscle capacity. This study aimed to examine the relationship between SMA and HGS to assess whether the latter could be used as an accurate indicator of the former. Methods. 150 participants (75 males and 75 females, aged 47–70 years) were selected from the UK Biobank dataset. Handgrip strength values were extracted and averaged over left and right values. Abdominal MRI images were examined and cross-sectional area of the erector spinae and multifidus determined at the L3/4 level and summed to provide a total muscle area. Results. HGS and SMA (mean±sd) were 39.6 ± 7.4 kg and 4664 ± 868 mm. 2. for males and 24.7 ± 5.9 kg, and 3822 ± 579 mm. 2. for females. Pearson correlation between HGS and SMA was r = 0.41 for males (p = <0.001), r = 0.40 for females (p = <0.001), and r = 0.61 for the combined groups (p<0.001). Conclusion. Significant correlations were found between HGS and SMA for individual sexes and combined groups. However, although HGS may be a useful measure for predicting modifications in group responses in spinal muscle function, for example, following an intervention, it does not have the power to confidently predict muscle values at an individual participant level. Conflicts of interest: No conflicts of interest. Sources of funding: Prince Sattam University, KSA, provided a PhD scholarship for Salman Alharthi

Aims. To draw a comparison of the pullout strengths of buttress thread, barb thread, and reverse buttress thread bone screws. Methods. Buttress thread, barb thread, and reverse buttress thread bone screws were inserted into synthetic cancellous bone blocks. Five screw-block constructs per group were tested to failure in an axial pullout test. The pullout strengths were calculated and compared. A finite element analysis (FEA) was performed to explore the underlying failure mechanisms. FEA models of the three different screw-bone constructs were developed. A pullout force of 250 N was applied to the screw head with a fixed bone model. The compressive and tensile strain contours of the midsagittal plane of the three bone models were plotted and compared. Results. The barb thread demonstrated the lowest pullout strength (mean 176.16 N (SD 3.10)) among the three thread types. It formed a considerably larger region with high tensile strains and a slightly smaller region with high compressive strains within the surrounding bone structure. The reverse buttress thread demonstrated the highest pullout strength (mean 254.69 N (SD 4.15)) among the three types of thread. It formed a considerably larger region with high compressive strains and a slightly smaller region with high tensile strains within the surrounding bone structure. Conclusion. Bone screws with a reverse buttress thread design will significantly increase the pullout strength. Cite this article: Bone Joint Res 2021;10(2):105–112

Aims. Rotational acetabular osteotomy (RAO) is an effective joint-preserving surgical treatment for acetabular dysplasia. The purpose of this study was to investigate changes in muscle strength, gait speed, and clinical outcome in the operated hip after RAO over a one-year period using a standard protocol for rehabilitation. Patients and Methods. A total of 57 patients underwent RAO for acetabular dysplasia. Changes in muscle strength of the operated hip, 10 m gait speed, Japanese Orthopaedic Association (JOA) hip score, and factors correlated with hip muscle strength after RAO were retrospectively analyzed. Results. Three months postoperatively, the strength of the operated hip in flexion and abduction and gait speed had decreased from their preoperative levels. After six months, the strength of flexion and abduction had recovered to their preoperative level, as had gait speed. At one-year follow-up, significant improvements were seen in the strength of hip abduction and gait speed, but muscle strength in hip flexion remained at the preoperative level. The mean JOA score for hip function was 91.4 (51 to 100)) at one-year follow-up. Body mass index (BMI) showed a negative correlation with both strength of hip flexion (r = -0.4203) and abduction (r = -0.4589) one year after RAO. Although weak negative correlations were detected between strength of hip flexion one year after surgery and age (r = -0.2755) and centre-edge (CE) angle (r = -0.2989), no correlation was found between the strength of abduction and age and radiological evaluations of CE angle and acetabular roof obliquity (ARO). Conclusion. Hip muscle strength and gait speed had recovered to their preoperative levels six months after RAO. The clinical outcome at one year was excellent, although the strength of hip flexion did not improve to the same degree as that of hip abduction and gait speed. A higher BMI may result in poorer recovery of hip muscle strength after RAO. Radiologically, acetabular coverage did not affect the recovery of hip muscle strength at one year’s follow-up. A more intensive rehabilitation programme may improve this. Cite this article: Bone Joint J 2019;101-B:1459–1463

Recognized anatomic variations that lead to patella instability include patella alta and trochlea dysplasia. Lateralization of the extensor mechanism relative to the trochlea is often considered to be a contributing factor; however, controversy remains as to the degree this contributes to instability and how this should be measured. As the tibial tuberosity-trochlear groove (TT-TG) is one of most common imaging measurements to assess lateralization of the extensor mechanism, it is important to understand its strengths and weaknesses. Care needs to be taken while interpreting the TT-TG value as it is affected by many factors. Medializing tibial tubercle osteotomy is sometimes used to correct the TT-TG, but may not truly address the underlying anatomical problem. This review set out to determine whether the TT-TG distance sufficiently summarizes the pathoanatomy, and if this assists with planning of surgery in patellar instability. Cite this article: Bone Jt Open 2022;3(3):268–274

Sarcopenia is an age-related geriatric syndrome which is associated with subsequent disability and morbidity. Currently there is no promising therapy approved for the treatment of sarcopenia. The receptor activator of nuclear factor NF-κB ligand (RANKL) and its receptor (RANK) are expressed in bone and skeletal muscle. Activation of the NF-κB pathway mainly inhibits myogenic differentiation, which leads to skeletal muscle dysfunction and loss. LYVE1 and CD206 positive macrophage has been reported to be associated with progressive impairment of skeletal muscle function with aging. The study aims to investigate the effects of an anti-RANKL treatment on sarcopenic skeletal muscle and explore the related mechanisms on muscle inflammation and the polarization status of macrophages. Sarcopenic senescence-accelerated mouse P8 (SAMP8) mice at month 8 were treated intraperitoneally with 5mg/kg anti-RANKL (IK22/5) or isotype control (2A3; Bio X Cell) antibody every 4 weeks and harvested at month 10. Senescence accelerated mouse resistant-1 (SAMR1) were collected at month 10 as the age-matched non-sarcopenic group. Ex-vivo functional assessment, grip strength and immunostaining of C/EBPa, CD206, F4/80, LYVE1 and PAX7 were performed. Data analysis was done with one-way ANOVA, and the significant level was set at p≤0.05. At month 10, tetanic force/specific tetanic force, twitch force/specific twitch force in anti-RANKL group were significantly higher than control group (all p<0.01). The mice in the anti-RANKL treatment group also showed significantly higher grip strength than Con group (p<0.001). The SAMP8 mice at month 10 expressed significantly more C/EBPa, CD206 and LYVE1 positive area than in SAMR1, while anti-RANKL treatment significantly decreased C/EBPa, CD206 and LYVE1 positive area. The anti-RANKL treatment protected against skeletal muscle dysfunctions through suppressing muscle inflammation and modulating M2 macrophages, which may represent a novel therapeutic approach for sarcopenia. Acknowledgment: Collaborative Research Fund (CRF, Ref: C4032-21GF)

Purpose. The Purpose of this study was to evaluate hamstring strength after autogenous hamstring anterior cruciate ligament(ACL) reconstruction with emphasis on deeper knee flexion angles. A comparison of hamstring strength between patients undergoing ACL reconstruction using semitendinosus(ST), and those with semitendinosus and Gracilis(STG) tendons was conducted. Method. Sixty patients were prospectively followed after undergoing ACL reconstruction surgery. Forty patients received a ST graft, and 20 patients had a STG graft. All patients had standard IKDC subjective knee evaluation completed, and had bilateral hamstring strengths tested using isokinetic testing with a Cybex Orthotron machine. In addition, a hand held Microfet dynamometer was used to measure hamstring strengths at deeper knee flexion angles at six, 12, and 24 months. Results. When comparing the surgical hamstring strength compared to the control side at deeper knee flexion angle, the STG and ST group had and average of 65.0% and 79.8% strength respectively at 6 months(p<0.05). While at one year the STG and ST group had 63.6%, and 78.3% of their hamstring strength(p<0.05). Conclusion. Hamstring strength at deeper flexion angles after ACL reconstruction using autogenous semitendinosus and gracilis tendons is significantly weaker than using semitendinosus alone. The use of single tendon ACL reconstruction should be advocated to decrease morbidity of this procedure

Aims. Loosening of the tibial component after total knee arthroplasty (TKA) is a common indication for revision. Increasing the strength of the initial tibial implant/cement interface is desirable. There is little information about the surgical techniques that lead to the highest strength. We investigated the effects of eight variables on the strength of the initial tibial baseplate/cement interface. Materials and Methods. A total of 48 tibial trays were cemented into acrylic holders using cement from two manufacturers, at three different times (early, normal, and late) using two techniques: cementing the tibial plateau or the plateau and the keel; and involving two conditions of contamination with marrow fat (at the metal/cement and cement/cement interfaces). Push-out tests were performed with load continuously recorded. Results. Compared with normal conditions, early cementing increased the mean strength of the interface when using the two cements, Simplex and Palacos, by 48% and 72%, respectively. Late cementing reduced the strength by 47% and 73%, respectively. Cementing the keel increased the mean strength by 153% and 147%, respectively, for the two cements. Contamination of the metal/cement interface with fat reduced the mean strength by 99% and 94% for the two cements but adding cement to the underside of the tibial tray prior to insertion resulted in the mean strength being lowered by only 65% and 43%, respectively. Conclusion. In order to maximize the strength of the tibial tray/cement interface, cement should be applied to the component soon after mixing, contamination of the interface should be avoided, and the keel and the plateau should be cemented

Recently, a new suture was designed to minimize laxity in order to preserve consistent tissue approximation while improving footprint compression after tendon repair. The aims of this study were: (1) to compare the biomechanical competence of two different high strength sutures in terms of slippage and failure load, (2) to investigate the influence of both knots number and different media (air, saline and fat) on the holding capacity of the knots. Alternating surgical knots of two different high-strength sutures (group1: FibreWire; group2: DynaCord; n = 105) were tied on two roller bearings with 50N tightening force. Biomechanical testing was performed in each medium applying ramped monotonic tension to failure defined in terms of either knot slippage or suture rupture. For each group and medium, seven specimens with either 3, 4, 5, 6, or 7 knots each were tested, evaluating their knot slippage and ultimate load to failure. The minimum number of knots preventing slippage failure and thus resulting in suture rupture was determined in each group and medium, and taken as a criterium for better performance when comparing the groups. In each group and medium failure occurred via suture rupture in all specimens for the following minimum knot numbers: group1: air – 7, saline – 7, fat – 7; group2: air – 6; saline – 4; fat – 5. The direct comparison between the groups when using 7 knots demonstrated significantly larger slippage in group1 (6.5 ± 2.2 mm) versus group2 (3.5 ± 0.4 mm) in saline (p < 0.01) but not in the other media (p ≥0.52). Ultimate load was comparable between the two groups for all three media (p ≥ 0.06). The lower number of required knots providing sufficient repair stability, smaller slippage levels and identical suture strength, combined with the known laxity alleviation effect demonstrate advantages of DynaCord versus FibreWire

Objectives. Screw plugs have been reported to increase the fatigue strength of stainless steel locking plates. The objective of this study was to examine and compare this effect between stainless steel and titanium locking plates. Methods. Custom-designed locking plates with identical structures were fabricated from stainless steel and a titanium alloy. Three types of plates were compared: type I unplugged plates; type II plugged plates with a 4 Nm torque; and type III plugged plates with a 12 Nm torque. The stiffness, yield strength, and fatigue strength of the plates were investigated through a four-point bending test. Failure analyses were performed subsequently. Results. For stainless steel, type II and type III plates had significantly higher fatigue strength than type I plates. For titanium, there were no significant differences between the fatigue strengths of the three types of plates. Failure analyses showed local plastic deformations at the threads of screw plugs in type II and type III stainless steel plates but not in titanium plates. Conclusion. The screw plugs could increase the fatigue strength of stainless steel plates but not of titanium plates. Therefore, leaving screw holes open around fracture sites is recommended in titanium plates. Cite this article: L-W. Hung, C-K. Chao, J-R. Huang, J. Lin. Screw head plugs increase the fatigue strength of stainless steel, but not of titanium, locking plates. Bone Joint Res 2018;7:629–635. DOI: 10.1302/2046-3758.712.BJR-2018-0083.R1

Background. Revision total knee arthroplasties (rTKA) are performed with increasing frequency due to the increasing numbers of primary arthroplasties, but very little is known regarding the influence of muscle strength impairments on functional limitations in this population. Objectives. The aim of this study was to assess relationship between muscle strength and functional level in patient with rTKA. Design and Methods. Twenty-three patients (8 males, 15 females) were included in the study with mean age 68.4±10 years. Patients performed 3 performance tests (50-Step Walking Test, 10 Meter Walk Test, 30-Second Chair-Stand Test), and one self-report test (HSS) were preferred to assess patients. The maximum isometric muscle strength of quadriceps femoris and hamstring muscles of all the patients was measured using Hand-Held Dynamometer (HHD). Results. While moderate-to-strong significant correlations was found between quadriceps femoris muscle strength and 30- Second Chair-Stand Test (r=0.390, p=0.049), 50-Step Walking Test (r=−0.530, p=0.005), 10 Meter Walk Test (r=−0.587, p=0.002), there were not significant correlation between HSS knee score and all performance-based tests (p>0.05). Also there were not significant correlation between hamstring muscle strength and all other measurement tests (p>0.05). Conclusion. The moderate-to-strong statistical significant correlation between quadriceps femoris muscle strength and functional performance tests suggests that improved postoperative quadriceps strengthening could be important to enhance the potential benefits of rTKA

Objectives. Bisphosphonates (BP) are the first-line treatment for preventing fragility fractures. However, concern regarding their efficacy is growing because bisphosphonate is associated with over-suppression of remodelling and accumulation of microcracks. While dual-energy X-ray absorptiometry (DXA) scanning may show a gain in bone density, the impact of this class of drug on mechanical properties remains unclear. We therefore sought to quantify the mechanical strength of bone treated with BP (oral alendronate), and correlate data with the microarchitecture and density of microcracks in comparison with untreated controls. Methods. Trabecular bone from hip fracture patients treated with BP (n = 10) was compared with naïve fractured (n = 14) and non-fractured controls (n = 6). Trabecular cores were synchrotron scanned and micro-CT scanned for microstructural analysis, including quantification of bone volume fraction, microarchitecture and microcracks. The specimens were then mechanically tested in compression. Results. BP bone was 28% lower in strength than untreated hip fracture bone, and 48% lower in strength than non-fractured control bone (4.6 MPa vs 6.4 MPa vs 8.9 MPa). BP-treated bone had 24% more microcracks than naïve fractured bone and 51% more than non-fractured control (8.12/cm. 2. vs 6.55/cm. 2. vs 5.25/cm. 2. ). BP and naïve fracture bone exhibited similar trabecular microarchitecture, with significantly lower bone volume fraction and connectivity than non-fractured controls. Conclusion. BP therapy had no detectable mechanical benefit in the specimens examined. Instead, its use was associated with substantially reduced bone strength. This low strength may be due to the greater accumulation of microcracks and a lack of any discernible improvement in bone volume or microarchitecture. This preliminary study suggests that the clinical impact of BP-induced microcrack accumulation may be significant. Cite this article: A. Jin, J. Cobb, U. Hansen, R. Bhattacharya, C. Reinhard, N. Vo, R. Atwood, J. Li, A. Karunaratne, C. Wiles, R. Abel. The effect of long-term bisphosphonate therapy on trabecular bone strength and microcrack density. Bone Joint Res 2017;6:602–609. DOI: 10.1302/2046-3758.610.BJR-2016-0321.R1

Background. Trunk muscles play an important role in supporting the spinal column. A decline in trunk muscle mass, as measured by bioelectrical impedance analysis (TMM–BIA), is associated with low back pain and poor quality of life. Purpose. The purpose of this study was to determine whether TMM–BIA correlates with quantitative and functional assessments traditionally used for the trunk muscles. Methods. We included 380 participants (aged ≥ 65 years; 152 males, 228 females) from the Shiraniwa Elderly Cohort (Shiraniwa) study, for whom the following data were available: TMM–BIA, lumbar magnetic resonance imaging (MRI), and back muscle strength (BMS). We measured the cross-sectional area (CSA) and fat-free CSA of the paravertebral muscles (PVM), including the erector spinae (ES), multifidus (MF), and psoas major (PM), on an axial lumbar MRI at L3/4. The correlation between TMM–BIA and the CSA of PVM, fat-free CSA of PVM, and BMS was investigated. Results. TMMBIA correlated with the CSA of total PVM and each individual PVM. A stronger correlation between TMM–BIA and fat-free CSA of PVM was observed. The TMM–BIA also strongly correlated with BMS. Conclusion. TMM–BIA is an easy and reliable way to evaluate the trunk muscle mass in a clinical setting. Conflict of interest. None. Sources of funding. None

Introduction. During revision surgery, the active electrode of an electrocautery device may get close to the implant, potentially provoking a flashover. Incidents have been reported, where in situ retained hip stems failed after isolated cup revision. Different sizes of discoloured areas, probably induced by electrocautery contact, were found at the starting point of the fracture. The effect of the flashover on the implant material is yet not fully understood. The aim of this study was to investigate the fatigue strength reduction of Ti-6Al-4V titanium alloy after electrocautery contact. Material and Methods. 16 titanium rods (Ti-6Al-4V, extra low interstitial elements, according to DIN 17851, ⊘ 5 mm, 120 mm length) were stress-relief annealed (normal atmosphere, holding temperature 622 °C, holding time 2 h) and cooled in air. An implant specific surface roughness was achieved by chemical and electrolytic polishing (Ra = 0.307, Rz = 1.910). Dry (n = 6) and wet (n = 6, 5 µl phosphate buffered saline) flashovers were applied with a hand-held electrode of a high-frequency generator (Aesculap AG, GN 640, monopolar cut mode, output power 300 W, modelled patient resistance 500 Ω). The size of the generated discoloured area on the rod's surface - representative for the heat affected zone (HAZ) - was determined using laser microscopy (VK-150x, Keyence, Japan). Rods without flashover (n = 4) served as control. The fatigue strength of the rods was determined under dynamic (10 Hz, load ratio R = 0.1), force-controlled four-point bending (FGB Steinbach GmbH, Germany) with swelling load (numerical bending stress 852 MPa with a bending moment of 17.8 Nm) until failure of the rods. The applied bending stress was estimated using a finite-element-model of a hip stem during stumbling. Metallurgical cuts were made to analyse the microstructure. Results. The control rods failed at the pushers of the setup (median: 94,550, range: 194,000 cycles). The rods with flashover failed directly at the HAZ significantly earlier than the control rods (p = 0.018). The analysis of the microstructure showed a transformation of the equiaxed α+β microstructure to a bimodal state. The size of the HAZs were equal for the dry (median: 1.51 mm. 2. , range: 5.68 mm. 2. ) and wet flashovers (median: 0.92 mm. 2. , range: 2.50 mm. 2. , p = 0.792). The cycles to failure were smaller for the dry flashover (median: 22,650 cycles, range: 5,700) than the wet flashover but not reaching statistical significance (median: 32,200, range: 57,900; p = 0.052). No correlation between the dimension of the HAZs and the cycles to failure was found (dry: r. 2. = 0.019, p = 0.8; wet: r. 2. = 0.015, p = 0.721). Discussion. Flashovers induced by an electrocautery device reduce the fatigue strength of Ti-6Al-4V. Since no correlation between the size of the HAZs and the cycles to failure was found, every contact between electrocautery devices and metal implants should be avoided. For any figures or tables, please contact authors directly