Aims. A revision for periprosthetic joint infection (PJI) in total hip arthroplasty (THA) has a major effect on the patient’s quality of life, including walking capacity. The objective of this case control study was to investigate the histological and ultrastructural changes to the gluteus medius tendon (GMED) in patients revised due to a PJI, and to compare it with revision THAs without infection performed using the same lateral approach. Methods. A group of eight patients revised due to a PJI with a previous lateral approach was compared with a group of 21 revised THAs without infection, performed using the same approach. The primary variables of the study were the fibril diameter, as seen in transmission electron microscopy (TEM), and the total degeneration score (TDS), as seen under the light microscope. An analysis of bacteriology, classification of infection, and antibiotic treatment was also performed. Results. Biopsy samples from the GMED from infected patients revealed a larger fibril diameter than control patients, as seen in the TEM (p < 0.001). Uninfected patients were slightly older and had their revisions performed significantly later than the infected patients. Histologically, samples from infected patients revealed significantly more vascularity (p < 0.001), the presence of glycosaminoglycans (p < 0.001), and a higher TDS (p = 0.003) than the control patients. The majority of patients had staphylococcal infections of various species. Conclusion. More histological degeneration in the GMED was found in patients undergoing THA revision surgery due to PJI than in patients undergoing THA revision surgery due to other reasons. Cite this article: Bone Jt Open 2023;4(8):628–635

Aims. Dislocation of the hip remains a major complication after periacetabular tumour resection and endoprosthetic reconstruction. The position of the acetabular component is an important modifiable factor for surgeons in determining the risk of postoperative dislocation. We investigated the significance of horizontal, vertical, and sagittal displacement of the hip centre of rotation (COR) on postoperative dislocation using a CT-based 3D model, as well as other potential risk factors for dislocation. Methods. A total of 122 patients who underwent reconstruction following resection of periacetabular tumour between January 2011 and January 2020 were studied. The risk factors for dislocation were investigated with univariate and multivariate logistic regression analysis on patient-specific, resection-specific, and reconstruction-specific variables. Results. The dislocation rate was 13.9% (n = 17). The hip COR was found to be significantly shifted anteriorly and inferiorly in most patients in the dislocation group compared with the non-dislocation group. Three independent risk factors were found to be related to dislocation: resection of gluteus medius (odds ratio (OR) 3.68 (95% confidence interval (CI) 1.24 to 19.70); p = 0.039), vertical shift of COR > 18 mm (OR 24.8 (95% CI 6.23 to 128.00); p = 0.001), and sagittal shift of COR > 20 mm (OR 6.22 (95% CI 1.33 to 32.2); p = 0.026). Conclusion. Among the 17 patients who dislocated, 70.3% (n = 12) were anterior dislocations. Three independent risk factors were identified, suggesting the importance of proper restoration of the COR and the role of the gluteus medius in maintaining hip joint stability. Cite this article: Bone Joint J 2022;104-B(10):1180–1188

Aims. The primary objective of this study was to develop a validated classification system for assessing iatrogenic bone trauma and soft-tissue injury during total hip arthroplasty (THA). The secondary objective was to compare macroscopic bone trauma and soft-tissues injury in conventional THA (CO THA) versus robotic arm-assisted THA (RO THA) using this classification system. Methods. This study included 30 CO THAs versus 30 RO THAs performed by a single surgeon. Intraoperative photographs of the osseous acetabulum and periacetabular soft-tissues were obtained prior to implantation of the acetabular component, which were used to develop the proposed classification system. Interobserver and intraobserver variabilities of the proposed classification system were assessed. Results. The BOne trauma and Soft-Tissue Injury classification system in total Hip arthroplasty (BOSTI Hip) grades osseous acetabular trauma and periarticular muscle damage during THA. The classification system has an interclass correlation coefficient of 0.90 (95% CI 0.86 to 0.93) for interobserver agreement and 0.89 (95% CI 0.84 to 0.93) for intraobserver agreement. RO THA was associated with improved BOSTI Hip scores (p = 0.002) and more pristine osseous surfaces in the anterior superior (p = 0.001) and posterior superior (p < 0.001) acetabular quadrants compared with CO THA. There were no differences between the groups in relation to injury to the gluteus medius (p = 0.084), obturator internus (p = 0.241), piriformis (p = 0.081), superior gamellus (p = 0.116), inferior gamellus (p = 0.132), quadratus femoris (p = 0.208), and vastus lateralis (p = 0.135), but overall combined muscle injury was reduced in RO THA compared with CO THA (p = 0.023). Discussion. The proposed BOSTI Hip classification provides a reproducible grading system for stratifying iatrogenic bone trauma and soft-tissue injury during THA. RO THA was associated with improved BOSTI Hip scores, more pristine osseous acetabular surfaces, and reduced combined periarticular muscle injury compared with CO THA. Further research is required to understand if these intraoperative findings translate to differences in clinical outcomes between the treatment groups. Cite this article: Bone Joint J 2024;106-B(9):898–906

Aims. The aims of this study were to assess the exposure and preservation of the abductor mechanism during primary total hip arthroplasty (THA) using the posterior approach, and to evaluate gluteus maximus transfer to restore abductor function of chronically avulsed gluteus medius and minimus. Patients and Methods. A total of 519 patients (525 hips) underwent primary THA using the posterior approach, between 2009 and 2013. The patients were reviewed preoperatively and at two and five years postoperatively. Three patients had mild acute laceration of the gluteus medius caused by retraction. A total of 54 patients had mild chronic damage to the tendon (not caused by exposure), which was repaired with sutures through drill holes in the greater trochanter. A total of 41 patients had severe damage with major avulsion of the gluteus medius and minimus muscles, which was repaired with sutures through bone and a gluteus maximus flap transfer to the greater trochanter. Results. Abductor strength was maintained in the normal hips, but lateral hip pain progressed significantly, five years postoperatively (p < 0.0001). In the 54 patients with mild abductor tendon damage treated with simple repair, lateral hip pain also increased significantly during follow-up (p = 0.002). In the 35 patients with severe avulsion but good muscle repaired using a gluteus maximus flap transfer, abductor function was restored. The six patients with complete avulsion and poor muscle did not regain strong abductor power, but lateral hip pain decreased. Conclusion. The posterior approach offered excellent exposure and preservation of the abductor mechanism during primary THA. Augmentation of the repair with a gluteus maximus flap provided stable reconstruction of the abductor muscles and seemed to restore function in the hips with functioning muscles. Cite this article: Bone Joint J 2019;101-B(6 Supple B):116–122

We investigated the detailed anatomy of the gluteus maximus, gluteus medius and gluteus minimus and their neurovascular supply in 22 hips in 11 embalmed adult Caucasian human cadavers. This led to the development of a surgical technique for an extended posterior approach to the hip and pelvis that exposes the supra-acetabular ilium and preserves the glutei during revision hip surgery. Proximal to distal mobilisation of the gluteus medius from the posterior gluteal line permits exposure and mobilisation of the superior gluteal neurovascular bundle between the sciatic notch and the entrance to the gluteus medius, enabling a wider exposure of the supra-acetabular ilium. This technique was subsequently used in nine patients undergoing revision total hip replacement involving the reconstruction of nine Paprosky 3B acetabular defects, five of which had pelvic discontinuity. Intra-operative electromyography showed that the innervation of the gluteal muscles was not affected by surgery. Clinical follow-up demonstrated good hip abduction function in all patients. These results were compared with those of a matched cohort treated through a Kocher–Langenbeck approach. Our modified approach maximises the exposure of the ilium above the sciatic notch while protecting the gluteal muscles and their neurovascular bundle. Cite this article: Bone Joint J 2014;96-B:48–53

We dissected 20 cadaver hips in order to investigate the anatomy and excursion of the trochanteric muscles in relation to the posterior approach for total hip replacement. String models of each muscle were created and their excursion measured while the femur was moved between its anatomical position and the dislocated position. The position of the hip was determined by computer navigation. In contrast to previous studies which showed a separate insertion of piriformis and obturator internus, our findings indicated that piriformis inserted onto the superior and anterior margins of the greater trochanter through a conjoint tendon with obturator internus, and had connections to gluteus medius posteriorly. Division of these connections allowed lateral mobilisation of gluteus medius with minimal retraction. Analysis of the excursion of these muscles revealed that positioning the thigh for preparation of the femur through this approach elongated piriformis to a maximum of 182%, obturator internus to 185% and obturator externus to 220% of their resting lengths, which are above the thresholds for rupture of these muscles. Our findings suggested that gluteus medius may be protected from overstretching by release of its connection with the conjoint tendon. In addition, failure to detach piriformis or the obturators during a posterior approach for total hip replacement could potentially produce damage to these muscles because of over-stretching, obturator externus being the most vulnerable

Abstract. Objectives. Acute compartment syndrome (ACS) is a progressive form of muscle ischaemia that is a surgical emergency and can have detrimental outcomes for patients if not treated optimally. The current problem is that there is no clear diagnostic threshold for ACS or guidance as to when fasciotomies should be performed. A new diagnostic method(s) is necessary to provide real-time information about the extent of muscle ischaemia in ACS. Given that lactic acid is produced by cells through anaerobic respiration, it may be possible to measure H+ ion concentration and to use this as a measure of ischaemia within muscle. Although we are familiar with the key biochemical metabolites involved in ischaemia; and the use of viability dyes in cell culture to distinguish between living or dead cells is well recognised; research has not been undertaken to correlate the biochemical and histological findings of ischaemia in skeletal muscle biopsies. Our primary aim was to investigate the potential for viability dyes to be used on live skeletal muscle biopsies (explants). Our secondary aim was to correlate the intramuscular pH readings with muscle biopsy viability. Methods. Nine euthanised Wistar rats were used. A pH catheter was inserted into one exposed gluteus medius muscles to record real-time pH levels and muscle biopsies were taken from the contralateral gluteus medius at the start of experiment and subsequently at every 0.1 of pH unit drop. Prior to muscle biopsy, the surface of the gluteus medius was painted with a layer of 50µmol/l Brilliant blue FCF solution to facilitate biopsy orientation. A 4mm punch biopsy tool was used to take biopsies. Each muscle biopsy was placed in a base mould filled with 4% ultra-low melting point agarose. The agarose embedded tissue block was sectioned to generate 400 micron thick tissue slices with a vibratome. The tissue slices were then placed in the staining solution with Hoechst 33342, Ethidium homodimer-1 and Calcein am. The tissue slices were imaged with Zeiss LSM880 confocal microscope's Z stack function. A dead muscle control was created by adding TritonX-100 to other tissue slices. For quantitative analyses, the images were analysed in Image J using the selection tool. This permitted individual cells to be identified and the mean grey value of each channel to be defined. Using the dead control, we were able to identify the threshold value for living cells using the Calcein AM channel. Results. Viability dyes, used primarily for cell cultures, can be used with skeletal muscle explants. Our study also showed that despite a significant reduction in tissue pH concentration over time, that almost 100% of muscle cells were still viable at pH 6.0, suggesting that skeletal muscle cells are robust to hypoxic insult in the absence of reperfusion. Conclusions. Viability dyes can be used on skeletal muscle biopsies. Further research investigating the likely associations between direct measured pH using a pH catheter, the concentrations of key cellular metabolic markers, and muscle tissue histology using vitality dyes in response to ischaemia, rather than hypoxia, is warranted. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Intact abductors of the hip play a crucial role in preventing limping and are known to be damaged through the direct lateral approach. The extent of trauma to the abductors after revision total hip replacement (THR) is unknown. The aim of this prospective study was to compare the pre- and post-operative status of the gluteus medius muscle after revision THR. We prospectively compared changes in the muscle and limping in 30 patients who were awaiting aseptic revision THR and 15 patients undergoing primary THR. The direct lateral approach as described by Hardinge was used for all patients. MRI scans of the gluteus medius and functional analyses were recorded pre-operatively and six months post-operatively. The overall mean fatty degeneration of the gluteus medius increased from 35.8% (1.1 to 98.8) pre-operatively to 41% (1.5 to 99.8) after multiple revision THRs (p = 0.03). There was a similar pattern after primary THR, but with considerably less muscle damage (p = 0.001), indicating progressive muscle damage. Despite an increased incidence of a positive Trendelenburg sign following revision surgery (p = 0.03) there was no relationship between the cumulative fatty degeneration in the gluteus medius and a positive Trendelenburg sign (p = 0.26). The changes associated with other surgical approaches to the hip warrant investigation. Cite this article: Bone Joint J 2014;96-B:1618–22

Introduction. Most of patients with unilateral hip disease shows muscle volume atrophy of pelvis and thigh in the affected side because of pain and disuse, resulting in reduced muscle weakness and limping. However, it is unclear how the muscle atrophy correlated with muscle strength in the patient with hip disorders. A previous study have demonstrated that the volume of the gluteus medius correlated with the muscle strength by volumetric measurement using 3 dimensional computed tomography (3D-CT) data, however, muscles influence each other during motions and there is no reports focusing on the relationship between some major muscles of pelvis and thigh including gluteus maximus, gluteus medius, iliopsoas and quadriceps and muscle strength in several hip and knee motions. Therefore, the purpose of the present study is to evaluate the relationship between muscle volumetric atrophy of major muscles of pelvis and thigh and muscle strength in flexion, extension and abduction of hip joints and extension of knee joint before surgery in patients with unilateral hip disease. Material and Methods. The subjects were 38 patients with unilateral hip osteoarthritis, who underwent hip joint surgery. They all underwent preoperative computed tomography (CT) for preoperative planning. There were 6 males and 32 females with average age 59.5 years old. Before surgery, isometric muscle strength in hip flexion, hip extension, hip abduction and knee extension were measured using a hand held dynamometer (µTas F-1, ANIMA Japan). Major muscles including gluteus maximus, gluteus medius, iliopsoas and quadriceps were automatically extracted from the preoperative CT using convolutional neural networks (CNN) and were corrected manually by the experienced surgeon. The muscle volumetric atrophy ratio was defined as the ratio of muscle volume of the affected side to that of the unaffected side. The muscle weakness ratio was defined as the ratio of muscle strength of the affected side to that of the unaffected side. The correlation coefficient between the muscle atrophy ratio and the muscle weakness ratio of each muscle were calculated. Results. The average muscle atrophy ratio was 84.5% (63.5%–108.2%) in gluteus maximus, 86.6% (65.5%–112.1%) in gluteus medius, 81.0% (22.1%–130.8%) in psoas major, and 91.0% (63.8%–127.0%) in quadriceps. The average muscle strength ratio was 71.5% (0%–137.5%) in hip flexion, 88.1% (18.8%–169.6%) in hip abduction, 78.6% (21.9%–130.1%) in hip extension and 84.3% (13.1%–122.8%) in knee extension. The correlation coefficient between the muscle atrophy and the ratio of each muscle strength between the affected and unaffected side were shown in Table 1. Conclusion. In conclusion, the muscle atrophy of gluteus medius muscle, psoas major muscle and quadriceps muscle significantly correlated with the muscle weakness in hip flexion. The muscle atrophy of psoas major muscle and quadriceps muscle also significantly correlated with the muscle weakness in knee extension. There were no significant correlation between the muscle atrophy and the muscle weakness in hip extension and abduction

Complete or nearly complete disruption of the attachment of the gluteus is seen in 10–20% of cases at the time of THA. Special attention is needed to identify the lesion at the time of surgery because the avulsion often is visible only after a thickened hypertrophic trochanteric bursa is removed. From 1/1/09 to 12/31/13, 525 primary hip replacements were performed by a single surgeon. After all total hip components were implanted, the greater trochanteric bursa was removed, and the gluteus medius and minimus attachments to the greater trochanter were visualised and palpated. Ninety-five hips (95 patients) were found to have damage to the muscle attachments to bone. Fifty-four hips had mild damage consisting of splits in the tendon, but no frank avulsion of abductor tendon from their bone attachments. None of these cases had severe atrophy of the abductor muscles, but all had partial fatty infiltration. All hips with this mild lesion had repair of the tendons with #5 Ticron sutures to repair the tendon bundles together, and drill holes through bone to anchor the repair to the greater trochanter. Forty-one hips had severe damage with complete or nearly complete avulsion of the gluteus medius and minimus muscles from their attachments to the greater trochanter. Thirty-five of these hips had partial fatty infiltration of the abductor muscles, but all responded to electrical stimulation. The surface of the greater trochanter was denuded of soft tissue with a rongeur, the muscles were repaired with five-seven #5 Ticron mattress sutures passed through drill holes in the greater trochanter, and a gluteus maximus flap was transferred to the posterior third of the greater trochanter and sutured under the vastus lateralis. Six hips had complete detachment of the gluteus medius and minimus muscles, severe atrophy of the muscles, and poor response of the muscles to electrical stimulation. The gluteus medius and minimus muscles were sutured to the greater trochanter, and gluteus maximus flap was transferred as in the group with functioning gluteus medius and minimus muscles. Postoperatively, patients were instructed to protect the hip for 8 weeks, then abductor exercises were started. The normal hips all had negative Trendelenburg tests at 2 and 5 years postoperative with mild lateral hip pain reported by 11 patients at 2 years, and 12 patients at 5 years. In the group of 54 with mild abductor tendon damage that were treated with simple repair, positive Trendelenburg test was found in 5 hips at 2 years and in 8 hips at 5 years. Lateral hip pain was reported in 7 hips at 2 years, and in 22 at 5 years. In the group of 35 hips with severe avulsion but good muscle tissue, who underwent repair with gluteus maximus flap transfer, all had good abduction against gravity and negative Trendelenburg tests at 2 and 5 years postoperative, and none had lateral hip pain. Of the 6 hips with complete avulsion and poor muscle who underwent abductor muscle repair and gluteus maximus flap transfer, all had weak abduction against gravity, mildly positive Trendelenburg sign, and mild lateral hip pain at 2 and 5 years postoperative. Abductor avulsion is uncommon but not rare, and is detected during THA only by direct examination of the tendon and removal of the trochanteric bursa. Simple repair of mild abductor tendon damage did not prevent progressive abductor weakness in some hips; and the increase in number of patients with lateral hip pain from 2 to 5 years suggests progressive deterioration. Augmentation of the repair with a gluteus maximus flap appears to provide a stable reconstruction of the abductor muscles, and seemed to restore abductor function in the hips with functioning muscles

Introduction. Gluteus medius is disrupted during lateral approach total hip arthroplasty (THA) which may impact its function and ability to control the pelvis. The objective was to compare gluteus medius activation and joint mechanics associated with a Trendelenburg sign (pelvic drop, trunk lean) during gait and hip abductor strength between patients that underwent lateral or posterior THA approaches one year post-surgery and healthy adults. Methods. Participants that underwent primary THA for hip osteoarthritis using lateral (n=21) or posterior (n=21) approaches, and healthy adults (n=21) were recruited for this cross-sectional study. Participants completed five walking trials. Surface electromyography captured gluteus medius activation. A 3-dimensional optical motion capture system measured frontal plane pelvic obliquity and lateral trunk lean angles. Participants performed maximum voluntary isometric contractions (MVIC) on a dynamometer to measure hip abductor torque. Characteristics from gait waveforms were identified using principal component analysis, and participant waveforms were scored against these characteristics to produce principal component scores. One-way analysis of variance and effect sizes (d) compared gait principal component scores and isometric hip abductor torque between groups. Results. Lateral THA group had statistically significant higher gluteus medius PC-scores indicating higher overall amplitudes during gait (p<0.01, d=0.97) and prolonged midstance activation (p=0.01, d=0.95) compared to the healthy group (Figure). There were no statistically significant (p>0.05) differences in pelvis or trunk angles. Isometric hip abductor torque was significantly (p=0.03, d=0.74) lower in the lateral THA than healthy group. There were no statistically significant differences between THA groups (d=0.27–0.50). Conclusions. Although the lateral THA group had lower abductor torque, there were no Trendelenburg signs during gait. Elevated gluteus medius activation in this group was a compensation for the weakness, and the muscle produced sufficient force to control the pelvis. Also, 1 year post-THA there were no statistically significant gait differences between lateral and posterior approaches. For any tables or figures, please contact the authors directly

Few surgical techniques to reconstruct the abductor mechanism of the hip have been reported, with outcomes reported only from case reports and small case series from the centres that described the techniques. As in many of our revision THA patients the gluteus maximus was affected by previous repeat posterior approaches, we opted to reconstruct the abductor mechanism using a vastus lateralis to gluteus medius transfer. We report the results of such reconstructions in seven patients, mean age 66 (range, 53–77), five females, presenting with severe abductor deficiency (MRC grade 1–2). Five patients had previous revision THA, two with a proximal femoral replacement, one patient had a primary THA after a failed malunited trochanteric fracture, and one patient had a native hip with idiopathic fatty infiltration of glutei of >90%. All patients had instrumented gait analysis, and surface electromyography (EMG) of the glutei, TFL, and vastus muscles simultaneously before surgery and at each post-op follow-up. Postoperatively, patients were allowed to weight bear as tolerated and were requested to wear an abduction brace for the first six weeks after surgery to protect the transfer. All patients improved after surgery and reached an abductor power of 3 or more. All patients walked without support six months after surgery and were satisfied with the result. Abductor function continued to improve beyond one year of follow-up, and some patients reached an abductor power of 5. EMG demonstrated that the transferred vastus lateralis started firing synchronously with gluteus medius after three months post-surgery, suggesting adaptation to its new function. No knee extension weakness was recorded. One patient complained of lateral thigh numbness and was dissatisfied with the cosmetic look of her thigh after surgery. Our preliminary results are encouraging and comparable with those achieved by the originators of the technique

The direct lateral (or anterolateral) approaches to the hip for revision THA involve detachment of the anterior aspect of the gluteus medius from the trochanter along with a contiguous sleeve of the vastus lateralis. Anterior retraction of this flap of gluteus medius and vastus lateralis and simultaneous posterior retraction of the femur creates an interval for division of gluteus minimus and deeper capsular tissues and exposure of the joint. To enhance reattachment of this flap of the anterior portion of the gluteus medius and vastus lateralis back to the trochanter, an oblique wafer of bone can be elevated along with the muscle off of the anterolateral portion of the trochanter. This bony wafer prevents suture pull out when large nonabsorbable sutures are used around or through the fragment and passed into the bone of the trochanteric bed for reattachment during closure. To prevent excessive splitting proximally into the gluteus medius muscle (and resulting damage to the superior gluteal nerve), it is often helpful to extend the muscle split further distally down into the vastus lateralis. This combined with careful elevation of the gluteal muscles off of the ilium (instead of splitting them) helps provide excellent and safe exposure of the entire rim of the acetabulum and access to the supracetabular region for bone grafting, acetabular augment placement and even fixation of the flanges of a cage. A simple method for posterior column plating via the anterolateral approach involves contouring of the distal end of the plate around the base of the ischium at the inferior edge of the socket. When an extended osteotomy of the femur is needed to correct deformity, remove a well-fixed implant or cement, the “extensile” variation of this same surgical approach involves a Wagner style (lateral to medial) osteotomy of the greater trochanter and proximal femur. The anterior portion of the femur after it is osteotomised is elevated as a separate segment while maintaining the soft tissue attachments to the bone as much as possible to aid osteotomy healing. After implant or cement removal, this approach gives excellent direct access to the distal femur for placement of a long stem revision femoral component without bone-implant conflict proximally because of the bow of the femur. The anterolateral approach (and extensile variants detailed above) can be used routinely and safely in the full range of revision THA procedures, or it can be employed selectively, if desired, in cases at increased risk for dislocation

The direct anterior approach in total hip replacement anatomically offers the chance to minimise soft-tissue trauma because an intermuscular and internervous plane is explored. This motivated us to abandon our previously used transgluteal approach and to adopt the direct anterior approach for total hip replacement. Using MRI, we performed a retrospective comparative study of the direct anterior approach with the transgluteal approach. There were 25 patients in each group. At one year post-operatively all the patients underwent MRI of their replaced hips. A radiologist graded the changes in the soft-tissue signals in the abductor muscles. The groups were similar in terms of age, gender, body mass index, complexity of the reconstruction and absence of symptoms. Detachment of the abductor insertion, partial tears and tendonitis of gluteus medius and minimus, the presence of peri-trochanteric bursal fluid and fatty atrophy of gluteus medius and minimus were significantly less pronounced and less frequent when the direct anterior approach was used. There was no significant difference in the findings regarding tensor fascia lata between the two approaches. We conclude that use of the direct anterior approach results in a better soft-tissue response as assessed by MRI after total hip replacement. However, the impact on outcome needs to be evaluated further

Introduction: It was hypothesized that ipsilateral upper extremity loading will decrease hip abductor activity by decreasing the adductor moment and thus relieving the symptoms of patients with gluteus medius tendinitis. The aim of the study was to test the hypothesis with a electrophysiological and clinical study. Materials and Methods: Seven voluntary men with no hip complaint were included in the electrophysiological phase of the study. The motor unit activities of the gluteus medius were measured for each subject during the consecutive loading of the ipsilateral, contralateral and both upper extremities, with 2, 3, 5 and 7 kilograms. Seventeen patients (age range 34–67) with acute symptoms of gluteus medius tendinitis were included in the clinical phase of the study. Dynamic VAS scores were recorded for each patient during gait with consecutive loading of the ipsilateral, contralateral and both upper extremities, for each 2, 3, 5 and 7 kilograms. Wilcoxon and Mann-Whitney U tests were used in statistical analysis. The p values below 0.05 were considered significant. Results: In the electrophysiologic study the ipsilateral upper extremity loading with 7 kg in 4 patients, and with 5 and 7 kilograms in 2 patients resulted in a motor unit activities with moderate interference, while motor unit activities with full interference were recorded during all other loadings. The motor unit activity interference scores recorded during the ipsilateral upper extremity loading with 5 kilograms of above, were significantly less then all other loading combinations (p < 0.05). In the clinical study, the ipsilateral upper extremity loading with 3 kilograms and above resulted in significantly less VAS scores then the other loading combinations (p< 0.05). Conclusion: Ipsilateral upper extremity loading decrease the motor unit activity of the ipsilateral gluteus medius muscle and relieves the symptoms of the patients with gluteus medius tendinitis. Ipsilateral upper extremity loading can lead up to new strategies in the rehabilitation of gluteus medius tendinitis

Abstract. Background. Progressive muscle ischaemia results in reduced aerobic respiration and increased anaerobic respiration, as cells attempt to survive in a hypoxic environment. Acute compartment syndrome (ACS) is a progressive form of muscle ischaemia that is a surgical emergency resulting in the production of Lactic acid by cells through anaerobic respiration. Our previous research has shown that it is possible to measure H+ ions concentration (pH) as a measure of progressive muscle ischaemia (in vivo) and hypoxia (in vitro). Our aim was to correlate intramuscular pH readings and cell viability techniques with the intramuscular concentration of key metabolic biomarkers [adenosine triphosphate (ATP), Phosphocreatine (PCr), lactate and pyruvate], to assess overall cell health in a hypoxic tissue model. Methods. Nine euthanised Wistar rats were used in a non-circulatory model. A pH catheter was used to measure real-time pH levels from one of the exposed gluteus medius muscles, while muscle biopsies were taken from the contralateral gluteus medius at the start of the experiment and subsequently at every 0.1 of a pH unit decline. The metabolic biomarkers were extracted from the snap frozen muscle biopsies and analyzed with standard fluorimetric method. Another set of biopsies were stained with Hoechst 33342, Ethidium homodimer-1 and Calcein am and imaged with a Zeiss LSM880 confocal microscope. Results. Our study shows that the direct pH electrode readings decrease with time and took an average of 69 minutes to drop to a pH of 6.0. The concentrations of ATP, pyruvate and PCr declined over time, and the concentration of lactate increased over time. At pH 6.0, both ATP and PCr concentrations had decreased by 20% and pyruvate has decreased by 50%, whereas lactate had increased 6-fold. The majority of cells were still viable at a pH of 6.0, suggesting that skeletal muscle cells are remarkably robust to hypoxic insult, although this was a hypoxic model where reperfusion was not possible. Conclusions. Our research suggests that histologically, skeletal muscle cells are remarkably robust to hypoxic insult despite the reduction in the total adenine nucleotide pool, but this may not reflect the full extent of cell injury and quite possibly irreversible injury. The timely restoration of blood flow in theory should halt the hypoxic insult, but late reperfusion results in cellular dysfunction and cell death due to localised free radical formation. Further research investigating the effects of reperfusion in vivo are warranted, as this may identify an optimal time for using pharmacological agents to limit reperfusion injury, around the time of fasciotomy to treat acute compartment syndrome. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Aims. The gluteus minimus (GMin) and gluteus medius (GMed) have unique structural and functional segments that may be affected to varying degrees, by end-stage osteoarthritis (OA) and normal ageing. We used data from patients with end-stage OA and matched healthy controls to 1) quantify the atrophy of the GMin and GMed in the two groups and 2) describe the distinct patterns of the fatty infiltration in the different segments of the GMin and GMed in the two groups. Methods. A total of 39 patients with end-stage OA and 12 age- and sex frequency-matched healthy controls were prospectively enrolled in the study. Fatty infiltration within the different segments of the GMin and the GMed was assessed on MRI according to the semiquantitative classification system of Goutallier and normalized cross-sectional areas were measured. Results. The GMin was smaller in the OA-group (p < 0.001) compared to the control group, but there was no group difference in the size of the GMed (p = 0.101). Higher levels of fatty infiltration were identified in the anterior segment of the GMin (p = 0.006) and the anterior (p = 0.006) and middle (p = 0.047) segments of the GMed in the OA group. All subjects in the control group had fatty infiltration of the anterior segment of the GMin, but all except one had no fatty infiltration in the entire GMed. Conclusion. End-stage OA was associated with significant atrophy of the GMin and higher levels of fatty infiltration, particularly in the anterior segments of the GMin and GMed. Minor fatty infiltration of the anterior segment of GMin appears to be a normal part of ageing. Our study has demonstrated different patterns of atrophy and fatty infiltration between patients with end-stage OA and healthy matched peers. Cite this article: Bone Jt Open 2021;2(1):40–47

Introduction. Complete or nearly complete disruption of the gluteus attachment is seen in 10–20% of cases at the time of total hip arthroplasty (THA). Special attention is needed to identify the lesion at the time of surgery because the avulsion often is visible only after a thickened hypertrophic trochanteric bursa is removed. The purpose of this study was to evaluate a technique designed to restore abductor function by transferring the gluteus maximus to compensate for the deficient medius and minimus muscles. Methods. From Jan 1 2009 to Dec 31 2013, 525 primary THAs were performed by the author. After the components were implanted, the greater trochanteric bursa was removed, and the gluteus medius and minimus attachments to the greater trochanter were visualized and palpated. Ninety-five hips (95 patients) were found to have damaged muscle attachments to bone. Fifty-four hips had mild damage consisting of splits in the tendon, but no frank avulsion of abductor tendon from the bone attachment. None had severe atrophy of the abductor muscles, but all had partial fatty infiltration. All hips with this mild lesion had repair of the tendons with #5 Ticron sutures to repair the tendon bundles together, anchored to the greater trochanter. Forty-one hips had severe damage with complete or nearly complete avulsion of the gluteus medius and minimus muscles from their attachments to the greater trochanter. Thirty-five of these hips had partial fatty infiltration of the abductor muscles, but all responded to electrical stimulation. The surface of the greater trochanter was denuded of soft tissue with a rongeur, the muscles were repaired with five-seven #5 Ticron mattress sutures passed through drill holes in the greater trochanter, and a gluteus maximus flap was transferred to the posterior third of the greater trochanter and sutured under the vastus lateralis. Six hips had complete detachment of the gluteus medius and minimus muscles, severe atrophy of the muscles, and poor response of the muscles to electrical stimulation. The gluteus medius and minimus muscles were sutured to the greater trochanter, and the gluteus maximus flap was transferred. Postoperatively, patients were instructed to protect the hip for 8 weeks, then abductor exercises were started. Results. The normal hips all had negative Trendelenburg tests at 2 and 5 years postoperative with mild lateral hip pain reported by 11 patients at 2 years, and 12 patients at 5 years. In the 54 with mild abductor tendon damage treated with simple repair, positive Trendelenburg test was found in 5 hips at 2 years and in 8 hips at 5 years. Lateral hip pain was reported in 7 hips at 2 years, and in 22 at 5 years. In the 35 hips with severe avulsion but good muscle tissue, who had repair with gluteus maximus flap transfer, all had good abduction against gravity and negative Trendelenburg tests at 2 and 5 years postoperative, and none had lateral hip pain. Of the 6 hips with complete avulsion and poor muscle who underwent abductor muscle repair and gluteus maximus flap transfer, all had weak abduction against gravity, mildly positive Trendelenburg sign, and mild lateral hip pain at 2 and 5 years postoperative. Conclusions. Abductor avulsion is uncommon but not rare, and is detected during THA only by direct examination of the tendon and removal of the trochanteric bursa. Simple repair of mild abductor tendon damage did not prevent progressive abductor weakness in some hips; and the increase in number of patients with lateral hip pain from 2 to 5 years suggests progressive deterioration. Augmentation of the repair with a gluteus maximus flap appears to provide stable reconstruction of the abductor muscles, and seemed to restore function in the hips with functioning muscles

After THR, trochanteric soft tissue abnormalities may be associated with residual trochanteric pain and limping. However, normal MR appearance of the trochanteric region after THR is not known. The aim was to evaluate MR imagings in asymptomatic and symptomatic patients after THR through a transgluteal approach. Triplanar MR images of 25 asymptomatic (14 men, mean age 60.4 years, 11 women, mean age 60.2) and 49 symptomatic patients (19 men, mean age 62.7 years, 20 women, mean age 64.3) at least 1 year after THR were analyzed by two blinded radiologists. In 14 symptomatic patients MR imaging was correlated to surgical findings. Tendon defects were uncommon in asymptomatic and significantly more frequent in symptomatic patients (gluteus minimus 8% vs. 56%, p< 0.001; lateral gluteus medius 16% vs 62%, p< 0.001; posterior gluteus medius 0% vs18%, p< 0.025). Signal changes within tendons were very frequent in both groups except for the posterior gluteus medius tendon which demonstrated this finding more frequently in symptomatic patients (20% vs 59%, p=0.002). Changes in tendon diameter were very frequent in both groups but significantly (p=0.001–009) more frequent in symptomatic patients. Fatty atrophy was evident in the anterior two thirds of the gluteus minimus muscle in both asymptomatic and symptomatic patients. In the posterior superior third of the gluteus minimus muscle differences of fatty degeneration were significant. Fatty atrophy of the gluteus medius muscle was only present in symptomatic patients. Bursal fluid collections were more frequent in asymptomatic (32% vs 62%, p=0.021). MR diagnosis was confirmed in all 14 patients undergoing revision surgery. Although more frequent in symptomatic patients many MR findings are frequently found in asymptomatic patients. However, defects of the abductor tendons and fatty atrophy of the gluteus medius and the posterior part of the gluteus minimus muscle are rare in asymptomatic patients

No animal model currently exists for hip abductor tendon tears. We aimed to 1. Develop a large animal model of delayed abductor tendon repair and 2. To compare the results of acute and delayed tendon repair using this model. Fourteen adult Romney ewes underwent detachment of gluteus medius tendon using diathermy. The detached tendons were protected using silicone tubing. Relook was performed at six and 16 weeks following detachment, histological analysis of the muscle and tendon were performed. We then attempted repair of the tendon in six animals in the six weeks group and compared the results to four acute repairs (tendon detachment and repair performed at the same time). At 12 weeks, all animals were culled and the tendon–bone block taken for histological and mechanical analysis. Histology grading using the modified Movin score confirmed similar tendon degenerative changes at both six and 16 weeks following detachment. Biomechanical testing demonstrated inferior mechanical properties in both the 6 and 16 weeks groups compared to healthy controls. At 12 weeks post repair, the acute repair group had a lower Movin's score (6.9 vs 9.4, p=0.064), and better muscle coverage (79.4% of normal vs 59.8%). On mechanical testing, the acute group had a significantly improved Young's Modulus compared to the delayed repair model (57.5MPa vs 39.4MPa, p=0.032). A six week delay between detachment and repair is sufficient to produce significant degenerative changes in the gluteus medius tendon. There are significant histological and mechanical differences in the acute and delayed repair groups at 12 weeks post op, suggesting that a delayed repair model should be used to study the clinical problem