Deep gluteal syndrome is an increasingly recognized disease entity, caused by compression of the sciatic or pudendal nerve due to non-discogenic pelvic lesions. It includes the piriformis syndrome, the gemelli-obturator internus syndrome, the ischiofemoral impingement syndrome, and the proximal hamstring syndrome. The concept of the deep gluteal syndrome extends our understanding of posterior hip pain due to nerve entrapment beyond the traditional model of the piriformis syndrome. Nevertheless, there has been terminological confusion and the deep gluteal syndrome has often been undiagnosed or mistaken for other conditions. Careful history-taking, a physical examination including provocation tests, an electrodiagnostic study, and imaging are necessary for an accurate diagnosis.

After excluding spinal lesions, MRI scans of the pelvis are helpful in diagnosing deep gluteal syndrome and identifying pathological conditions entrapping the nerves. It can be conservatively treated with multidisciplinary treatment including rest, the avoidance of provoking activities, medication, injections, and physiotherapy.

Endoscopic or open surgical decompression is recommended in patients with persistent or recurrent symptoms after conservative treatment or in those who may have masses compressing the sciatic nerve.

Many physicians remain unfamiliar with this syndrome and there is a lack of relevant literature. This comprehensive review aims to provide the latest information about the epidemiology, aetiology, pathology, clinical features, diagnosis, and treatment.

Cite this article: Bone Joint J 2020;102-B(5):556–567.

Simvastatin is a 3-Hydroxy-3-methylglutaryl Co-enzyme inhibitor, widely used to reduce lipid levels. Recent studies have demonstrated pleiotropic beneficial effects the skeleton. We aim to demonstrate the effect of Simvastatin on the osteogenic differentiation and proliferation of murine embryonic stem cells.

Tg2a cells were cultured in maintenance medium until confluence and passaged twice into tissue culture flasks. They were then seeded into 6 well and 24 well plates at a density of 10.000 cells/cm2 and cultured for 3 days in maintenance medium mixed at 1:1 with HepG2 conditioned medium. The culture then continued using osteogenic medium with different concentrations of simvastatin for another 16 days. Measurements included Alizarin Red quantification for calcified matrix, ALP assay, RT-PCR for genes expressed during osteogenic differentiation (osteocalcin, Runx2, osterix, Col1a1).

Simvastatin has dose dependent effect on mineralized matrix formation. Alizarin Red quantification assays demonstrated that simvastatin (all dose groups) induced a statistically significant increase in calcified matrix formation on day 11 (P< 0.05) and 16 (P< 0.01) compared to the control group. ALP activity was significantly higher on day 8 in the groups that had a simvastatin concentration of 1nM, 10nM and 100nM (P< 0.05). RT-PCR has demonstrated that simvastatin caused increased expression of all genes measured on differentiation. Statins can induce bone formation when combined with embryonic stem cells.

In a previous study, we found that pre-TKA patients were severely disabled in high-flexion activities but perceived these disabilities as being no more important than pain relief and the restoration of daily routine activities. This study was conducted to investigate functional disabilities and patient satisfaction in Korean patients after TKA.

Of 387 patients who had undergone TKA with a follow-up longer than 12 months, 270 (69.7%) completed a questionnaire designed to evaluate functional disabilities, perceived importance and patient satisfaction.

The top 5 severe functional disabilities were difficulties in kneeling, squatting, sitting with legs crossed, sexual activity, and recreational activities. The top 5 in order of perceived importance were difficulties in walking, using a bathtub, working, climbing stairs, and recreation activities. Severities of functional disabilities were not found to be correlated with perceived importance. The patients (8.5%) dissatisfied with their replaced knees had more severe functional disabilities than the satisfied for most activities. The dissatisfied patients tended to perceive functional disabilities in high-flexion activities to be more important than the satisfied.

This study indicates that despite severe disabilities in high-flexion activities, most Korean patients after TKA would not consider high-flexion disability to be more important than other daily routine activities. Moreover, postoperative high-flexion disabilities would not adversely influence satisfaction for most patients. Nevertheless, such disabilities are likely to cause dissatisfaction among those that are not prepared to modify their traditional life-styles.

Despite the well-documented improvement in coronal alignment achieved by computer assisted navigation, varying results have been reported for sagittal alignment. Current navigation systems rely on a sagittal femoral mechanical axis identified by the navigation system, but little information is available on the relationship between the sagittal mechanical axis and anatomical axes for intra-operative or postoperative radiographic assessments. We asked whether deviations exist between sagittal femoral mechanical axis and anatomical axes and attempted to identify predictors of the deviations found.

In 100 consecutive patients (200 knees) undergoing TKA, angles between two anatomical axes (the anterior cortical line and mid-medullary line) and two sagittal mechanical axes identified by current navigation systems were measured as proxies of the deviations between them on true lateral radiographs of the whole femur. Correlation analyses and multivariate regression were carried out to identify predictors of deviations.

Significant deviations existed with wide ranges between the anatomical axes and the sagittal mechanical axes. Degree of femoral bowing and femoral length were found to be predictors of deviations between sagittal femoral mechanical axes and anatomical axes.

This study suggests that surgeons applying navigation technology to TKA need to consider deviations between the sagittal femoral mechanical axes and anatomical axes when they intend to place a femoral component at a target sagittal orientation with respect to an anatomical reference.

Application of computer assisted navigation (CAN) has been documented to improve the accuracy of limb alignment and implant positioning. However, a recent study reported that a great deal of disparities occurred between the radiographic and navigational measurements calling the basic argument for application of CAN to TKA into question. In the authors’ practice using CAN for TKA, we have observed consistent disparities between the preoperative radiographic assessments and intraoperative navigational assessments of limb alignment in the coronal plane. A large disparity between radiographic and navigational assessments of limb alignment would be presenting a challenging question whether or not the surgeon can rely on the information provided by the CAN system. We developed a novel method to measure the coronal limb alignment and have found that the radiographic measurements with the novel method remarkably reduce the disparities between the radiographic and navigational assessments of the coronal limb alignment. This study was conducted to document the existence of the disparities between the radiographic and navigational assessments of the limb alignment and the value of our novel method to perform preoperative radiographic measurements of limb alignment.

In 107 TKAs performed using a CAN system (Ortho-pilot: B. Braun-Aesculap, Tuttlingen, Germany), radiographic assessments of coronal limb alignment were assessed using preoperative and postoperative whole limb radiographs taken with weight bearing with two different methods: a standard method, angle between the femoral mechanical axis (the line connecting hip center and the top pint of the femoral intercondylar notch) and a tibial mechanical axis (the line connecting the mid-point between the medial and lateral tibial eminences and the mid-point of the talus dome) and a novel method, the angle between the weight loading line (the line connecting the hip center and the mid-point of the talus dome) and the tibial mechanical axis. A negative value was given to a varus alignment and a positive value to the valgus alignment. During surgery, the coronal limb alignment was measured by the navigation system two different time-points: after registration and after implantation of prostheses. The disparity between the radiographic and navigational assessments was calculated with subtracting the radiographic assessments by the navigational assessments.

The disparity between the radiographic and navigational assessments was significantly smaller with the novel method than with the standard method. The mean difference between the radiographic and navigational assessments of preoperative limb alignment was −6.5o (range: −19 ~ 1) with the standard method and −0.9o (range: −8o to 4o) with the novel method. The mean difference between the radiographic and navigational assessments of the postoperative limb alignment was −1.96 (range: −11 ~ 3) with the standard method and −1.3 (range: −6 ~3).

This study documents that a wide range of disparities occurs between the radiographic and navigational assessments of limb alignment and the amount of disparity occurs in preoperative assessments. Our findings indicate that our novel method to perform the radiographic assessments of limb alignment can be a useful tool to interpret the information intraoperatively given by the navigation system.