Background. The long-term impact of dividing Piriformis when performing a standard posterior approach to the hip has not been assessed. A less invasive approach in which the tendon is preserved has been described (the Piriformis-sparing minimally invasive [PSMI] approach). With advances in MRI technology it is now possible to image structures in close proximity to metal without artifact. The aim of the study was to compare the MRI features (muscle grade and bulk) of the divided and repaired Piriformis tendon group (by the standard posterior approach) with the preserved tendon group (by the PSMI approach). Methods. As part of an on-going randomized controlled trial comparing the PSMI approach with the standard posterior approach for total hip replacement, a subgroup of 20 consecutive patients who fulfilled the inclusion criteria were recruited. Patients received preoperative and 3 months and 2 year postoperative MRI scans. Patients and evaluators were blinded to allocation. Outcomes assessed included grade, volume and integrity of Piriformis. Results. There was significantly less deterioration in muscle grade (p = 0.002) and bulk (p = 0.013) in the preserved Piriformis tendon group in comparison to the divided and repaired Piriformis group. There was equal deterioration in muscle grade and bulk of all divided tendons (Obturator Internus and Piriformis by the standard approach and Obturator Internus by the PSMI approach). The majority (10/11) of the Piriformis tendons by the PSMI approach were intact post-operatively. Conclusions. The PSMI approach, in which the Piriformis tendon is preserved, is successful in maintaining the integrity of the tendon as well as preventing deterioration in grade and bulk of the muscle belly

The principle function of the “short external rotator” muscle group is primarily as an abductor and extensor of the flexed hip and is better referred to as the “Quadriceps Coxa” (QC). The QC has a profound influenced on weight bearing rising and propulsive motions. The SPAIRE technique preserves Obturator Internus (OI) and Piriformis (P) resulting in improved stability of the hip and potentially improved recovery and function in patients undergoing hip arthroplasty. Short term outcomes of the first 42 consecutive SPAIRE cases are compared with 86 consecutive cases using the traditional posterior approach that immediately preceded introduction of the technique. The purpose was to document the learning curve and confirm the safety of introducing SPAIRE into routine clinical practice. The two groups were comparable and there was no statistically significant difference in length of stay, blood loss, intra-or post-operative complications nor radiological measurements relating to the femoral or acetabular components. Statistically significant differences were found for component usage (more uncemented acetabula for SPAIRE), length of operation (8 mins longer with SPAIRE); patient satisfaction was higher at 6 weeks and measured leg length discrepancy less in the SPAIRE group. SPAIRE has been used routinely for all routine arthroplasties for over two years. RCTs are ongoing to document the effect of SPAIRE on recovery, long term function and activity level. If the potential benefits are confirmed SPAIRE may become the default technique for hip arthroplasty operations through a posterior approach for elective and hip fracture cases

Introduction: The piriformis syndrome is known as an entrapment of the sciatic nerve, in which the pain is felt over the upper part of the buttock and radiates down the leg. However, the pain in the buttock may also be located in the area of the ischial tuberosity, accompanied by referred pain to the back of the thigh and this is called the hamstring syndrome. The reason for the piriformis syndrome is quite often hypertrophy or inßammation of the muscle and that condition can be caused by sport or other strain even straight injury to the piriformis muscle. The hamstring syndrome is very often a disease of athletes, especially of sprinters, but may also occur in non-athletes. The pain begins mostly without trauma. The symptoms of the hamstring syndrome are caused by the tense tendinous structures of the hamstring muscles. This tendinous structure presses the sciatic nerve when sitting or exercising. The treatment of these syndromes is always at þrst conservative but if the pain lasts long enough you must consider the operative treatment. Patients and methods: There were 75 patients in the years 1975–95 who were operated because of piriformis or hamstring syndrome (40 hamstring and 35 piriformis). We sent the questionnaire to the operated patients and 45 patients answered (23 hamstring and 22 piriformis). Our retrospective study group consists of 45 patients. There were 13 female and 9 male in the piri-formis group and 6 female and 17 male in the hamstring group. The average age was 45 years (ranged 28–66 y) in the piriformis group and 28 years (ranged 15–43) in the hamstring group. Results: The mean follow-up was 8 years (ranged 2–18 y). The most common symptoms before operation were radiating pain in thigh 20 in the piriformis and 18 in the hamstring sdr, pain in the buttock 17 and 21, pain in sitting 15 and 21. Typically many of the hamstring patients complained pain when stretching the leg. The patients had suffered the symptoms 5,6 years in the piriformis sdr and 1,6 years in the hamstring sdr average. The result of the operation was excellent or good according to patientsñ opinion in the18 (82%) piriformis and in the 18 (87%) hamstring syndromes. The common þndings in the operation in the piriformis sdr were tight and tendinous structure in piriformis muscle, n. ischiadicus and piri-formis muscle adhered to each other and thick piriformis muscle. In the hamstring sdr the þndings were one or more distinct tense tendinous structure like a violin string, n. ischiadicus adhered to m. biceps and adhesions to n. ischiadicus. Conclusions: We prefer conservative treatment at þrst, but if symptoms are difþcult and last many months so operative treatment is a good choice. The results were better in the hamstring sdr. A modiþed Kocher incision was mostly used. Of course the preoperative diagnosis must be correct and you must use all modern possibilities for good diagnosis for example MRI.

Antegrade femoral nailing through the greater trochanter, using nails designed for piriformis entry, is associated with varus and iatrogenic comminution. Nails designed for greater trochanter insertion theoretically reduce these complications, but clinical outcomes comparing these to piriformis entry remain unknown. We compared femoral shaft fracture repair with a nail designed for trochanteric entry to an identical nail without a trochanteric bend inserted through the piriformis fossa.

The trochanteric nail was easier to insert with decreased operative and fluoroscopy time. It resulted in equally high union rates, low complication rates, and functional results similar to conventional nailing through the piriformis fossa.

Trochanteric antegrade nailing of the femur is thought to be advantageous over conventional antegrade nailing due to improved ease of insertion, but is unproven. This study compares results of femoral shaft fracture treatment using a nail designed specifically for trochanteric entry, Trigen TAN, to results using an identical nail without a trochanteric bend inserted through the piriformis fossa, Trigen FAN.

A femoral nail specially designed for trochanteric insertion resulted in equally high union rates, equally low complication rates, and functional results similar to conventional antegrade femoral nailing through the piriformis fossa. As a result of increased ease of insertion, decreased operative time and decreased fluoroscopy time, the greater trochanter entry portal, coupled with an appropriately designed nail, represents a rational alternative for antegrade femoral nailing.

Insertion of a specially designed femoral nail though the trochanter is faster, easier, and requires less fluoroscopy time than conventional antegrade nailing through the piriformis fossa.

Overall, there was < 10° malalignment and no iatrogenic fracture comminution. The average operative time was 21% greater using the FAN nail than using the TAN nail, (p=.08). The average fluoroscopy time was 61% greater for the FAN group than for the TAN group, (p< .05). Trends in functional outcome (Lower Extremity Measure) were similar for both groups.

One hundred and eight patients treated for a femoral shaft fracture were included in this study. Ninety-eight patients were treated with either a Trigen TAN nail (n=38) or Trigen FAN nail (n=53); seventeen patients with insufficient follow-up were excluded from analysis.

Funding:Smith & Nephew, Memphis TN

Purpose

Femoral shaft fractures are routinely treated using antegrade intramedullary nailing under fluoroscopic guidance. Malreduction is common and can be due to multiple factors. Correct entry point identification can help minimize malreduction and the risk of iatrogenic fracture. This study aims to compare landmark identification used to guide nail entry, the piriformis fossa (PF) and the trochanteric tip (T), via computer navigation and conventional fluoroscopy.

The piriformis muscle is an important landmark in the surgical anatomy of the hip, particularly the posterior approach for total hip replacement (THR). Standard orthopaedic teaching dictates that the tendon must be cut in to allow adequate access to the superior part of the acetabulum and the femoral medullary canal. However, in our experience a routine THR can be performed through a posterior approach without sacrificing this tendon.

We dissected the proximal femora of 15 cadavers in order to clarify the morphological anatomy of the piriformis tendon. We confirmed that the tendon attaches on the crest of the greater trochanter, in a position superior to the trochanteric fossa, away from the entry point for broaching the intramedullary canal during THR. The tendon attachment site encompassed the summit and medial aspect of the greater trochanter as well as a variable attachment to the fibrous capsule of the hip joint. In addition we dissected seven cadavers resecting all posterior attachments except the piriformis muscle and tendon in order to study their relations to the hip joint, as the joint was flexed. At flexion of 90° the piriformis muscle lay directly posterior to the hip joint.

The piriform fossa is a term used by orthopaedic surgeons to refer the trochanteric fossa and normally has no relation to the attachment site of the piriformis tendon. In hip flexion the piriformis lies directly behind the hip joint and might reasonably be considered to contribute to the stability of the joint.

We conclude that the anatomy of the piriformis muscle is often inaccurately described in the current surgical literature and terms are used and interchanged inappropriately.

Cite this article: Bone Joint J 2013;95-B:764–9.

The aim of this review is to evaluate the current available literature evidencing on peri-articular hip endoscopy (the third compartment). A comprehensive approach has been set on reports dealing with endoscopic surgery for recalcitrant trochanteric bursitis, snapping hip (or coxa-saltans; external and internal), gluteus medius and minimus tears and endoscopy (or arthroscopy) after total hip arthroplasty. This information can be used to trigger further research, innovation and education in extra-articular hip endoscopy.

We undertook a randomised controlled trial to compare the piriformis-sparing approach with the standard posterior approach used for total hip replacement (THR). We recruited 100 patients awaiting THR and randomly allocated them to either the piriformis-sparing approach or the standard posterior approach. Pre- and post-operative care programmes and rehabilitation regimes were identical for both groups. Observers were blinded to the allocation throughout; patients were blinded until the two-week assessment. Follow-up was at six weeks, three months, one year and two years. In all 11 patients died or were lost to follow-up.

There was no significant difference between groups for any of the functional outcomes. However, for patients in the piriformis-sparing group there was a trend towards a better six-minute walk test at two weeks and greater patient satisfaction at six weeks. The acetabular components were less anteverted (p = 0.005) and had a lower mean inclination angle (p = 0.02) in the piriformis-sparing group. However, in both groups the mean component positions were within Lewinnek’s safe zone. Surgeons perceived the piriformis-sparing approach to be significantly more difficult than the standard approach (p = 0.03), particularly in obese patients.

In conclusion, performing THR through a shorter incision involving sparing piriformis is more difficult and only provides short-term benefits compared with the standard posterior approach.

The SPAIRE technique (Spare Piriformis And Internus, Repair Externus) involves a muscle sparing mini-posterior approach to the hip. Evidence will be prevented that the principle function of the “short external rotator” muscle group is primarily as an abductor and extensor of the flexed hip and has a profound influenced on weight bearing rising and propulsive motions; also that details of the insertions of the piriformis tendon and conjoint insertion of obturator internus and the gemelli (the Quadriceps Coxa) have previously been poorly appreciated. We have developed a surgical technique (SPAIRE) during which the only tendon released, and subsequently repaired, is obturator externus. The author has carried out the SPAIRE technique for all routine hip arthroplasties for the last 18 months. This cohort has been compared with a matched control group for a comprehensive array of outcome measures. Results show no disadvantage of using the technique. On-table stability is so impressive that when the SPAIRE technique has been used no postoperative restrictions whatsoever are placed on the patient who is immediately encouraged to exercise the hip through a full excursion of movement. Fewer tendons are damaged using the SPAIRE technique than any other approach to the hip including Direct Anterior and Direct Superior approaches. Randomised prospective studies are on-going using objective measurements of Gait and muscle power as well as functional and patient reported outcomes to prove benefit of the SPAIRE technique. For hemiarthroplasty cases a separate RCT is being undertaken comparing the SPAIRE technique with a direct lateral approach. It is believed that this technique may become the default technique for hemi- and total- hip arthroplasty through a posterior approach and for all hip fracture arthroplasty cases

Introduction. Total hip arthroplasty (THA) is a common operation. Different operative approaches have specific benefits and compromises. Soft tissue injury occurs in total hip arthroplasty. This prospective study objectively measured muscle volume changes after direct anterior and posterior approach surgeries. Methods. Patients undergoing Direct Anterior Approach (DAA) and Posterior Approach (PA) THA were prospectively evaluated. 3 orthopaedic surgeons performed all surgeries. Muscle volumes of all major muscles around the hip were objectively measured using preoperative and 2 different postoperative follow-up MRIs. 2 independent measurers performed all radiographic volume measurements. Repeated-measures ANOVA was used to compare mean muscle volume changes over time. Student's t-test was used to compare muscle volumes between groups at specific time intervals. Results. MRIs for 10 DAA and 9 PA patients were analyzed. No significant differences between groups were found in BMI or Age. Pre-operative muscle volume comparisons showed no significant differences. Average postoperative follow-up times were 9.6 and 24.3 weeks. First follow-up showed significant atrophy for the DAA in Gluteus Medius (−7.3%), Gluteus Minimus (−17.5%), and Obturator Internus (−37.3%) muscles. Final follow-up showed significant recovery in Gluteus Medius (+12%) and Minimus (+11.1%) muscles. In the PA, atrophy was significant at first follow-up for Gluteus Minimus (−11.8%), Obturator Internus (−46.8%) and Externus (−16%), Piriformis (−26.5%), and Quadratus Femoris (−30.4%) muscles. Recovery was not seen in any of the significantly atrophied muscles. Muscles with significant quantified fatty atrophy at final follow-up were Obturator Internus [+5.51% (DAA); +7.65% (PA)] and Obturator Externus [+5.55% (PA)]. 3/9 PA patients demonstrated abductor tendinosis, while no DAA patients demonstrated tendinosis. Discussion. Significant atrophy for each group was seen more commonly in the anatomic regions disturbed by each approach respectively. In both approaches, muscles surgically released from their insertion showed greater atrophy, and incomplete recovery

Introduction We believe minimally invasive surgery should be defined by the extent of soft tissue dissection rather than incision length. We describe a new technique that is truly soft-tissue sparing and report our early results. The surgical approach The landmarks for the incision are identified and an incision is made over the posterior aspect of the greater trochanter. Piriformis is preserved. A capsular repair is performed through drill holes into bone. There are no restrictions to mobility. No specialised instruments are required. Method The standard posterior approach (group 1) was compared with the PSMI approach (group 2) in a prospective cohort study of 200 consecutive patients over 60 years of age. Patients were scored pre-operatively and followed up prospectively, by a blinded observer. Results Mean operation time was about 1 hour in both groups. Mean incision length was 21.5 cm in group 1 and 8.4cm in group 2. Mean blood loss in group 1 was significantly higher than group 2 (P< 0.0001). Mean inpatient stay was significantly higher in group 2 (P< 0.0001). Minimum follow-up was 3 years in group 1 and 1.5 years in group 2. There were 3 dislocations in group 1, and none in group 2. There were 2 re-operations in both groups. The relative improvement in WOMAC scores was significantly greater in group 2 at 3 months and 1 year (P< 0.05). Conclusion: This is the first study to suggest the benefits of minimally invasive surgery may be prolonged. Cosmesis is a by-product rather than primary objective

Introduction We believe minimally invasive surgery should be defined by the extent of soft tissue dissection rather than incision length. We describe a new technique that is truly soft-tissue sparing and report our early results. The surgical approach The landmarks for the incision are identified and a 6–8cm oblique incision is made over the posterior aspect of the greater trochanter. Longer incisions are required in more difficult cases. Piriformis and the proximal insertion of gluteus maximus are preserved. After implant insertion, meticulous capsular repair is performed through drill holes into bone to reconstruct the posterior envelope. There are no restrictions to mobility. No specialised instruments are required. Method The standard posterior approach (group 1) was compared with the PSMI approach (group 2) in a prospective cohort study of 200 consecutive patients over 60 years of age. In the standard approach the external rrotators were dettached. The capsule was repaired to bone, and the piriformis tendon reattached to the Gluteus Medius tendon. Routine restrictions to mobility were imposed. Patients were scored pre-operatively and followed up prospectively, by a blinded observer. Results Demographics and functional scores were similar. Mean operation time was about 1 hour in both groups. Mean incision length was 21.5 cm (range 15 – 25) in group 1 and 8.4 cm (range 6 – 16) in group 2. Mean blood loss in group 1 was significantly higher than group 2 (P< 0.0001, 95%CI 191–547). Mean inpatient stay was 8.0 days in group 1, and 4.8 days in group 2 (P< 0.0001, 95%CI 3.4–6.0). Minimum follow-up was 3 years in group 1 and 1.5 years in group 2. There were 3 dislocations in group 1, and none in group 2. There were 2 re-operations in both groups. The relative improvement in WOMAC scores was significantly greater in group 2 at 3 months and 1 year (P< 0.05). Conclusion The PSMI approach to the hip is truly soft-tissue sparing. It is safe and relatively easy to perform. The stability and minimal morbidity allow early mobilisation. This is the first study to suggest the benefits of minimally invasive surgery may be prolonged. Cosmesis is a by-product rather than primary objective

The Gibson and Moore postero-lateral approach is one of the most often used in hip replacement. The advantage of this approach is an easy execution but it's criticized because of its invasivity to muscle-tendinous tissues especially on extrarotators muscles and because of predisposition to posterior dislocation. Since June 2003 we executed total hip replacements using a modified postero-lateral approach which allows to preserve the piriformis and quadratus femoris muscles and to detach just the conjoint tendon (gemelli and obturator internus). Articular capsule is preserved and it will be anatomically sutured at the end of the procedure as well as the conjoint tendon with two transossesous sutures. Piriformis and quadratus femoris muscles result untouched by this approach. We have executed 500 surgeries with this modified approach. We have used different stems (straight, anatomical, modular and short) and press fit acetabular cup with polyethylene or ceramic insert and we have always used 36 mm femoral heads when allowed by the cup dimensions. We have used any size both of stems and cups without limitation due to the surgical approach. The mean age is 61.8 y.o., 324 females and 176 males. Obese patients, hip dysplasia Crowe 3 and 4 and post traumatic arthrosis are exclusion factors for the execution of this approach. If possible we have maintained the capsulo-tendinous less invasivity. The BMI is not an excluding factor because it's just the gluteus region that is an important factor to decide if to execute or not a less invasive approach. Analyzing our 500 cases we didn't have any case of malpositioning of the stem in varus or valgus (more than 5°) and considering acetabular cup we had the tendency to position it in valgus position (not more than 40°) in the first 20 cases. No leg discrepancy more than 1 cm were observed. Intra-operative blood loss have been reduced of about 30 % and 50% in the post-operative. All the patients were able to active hip mobilization within the first day after surgery with a mean range of motion of 0-70°. The patients were mobilized the first day after surgery and 80% of them were able to assisted walk within second day after surgery. The mean time of stay in hospital was 6.8 days. After 4 weeks 98% of the patients were able to walk without crutches. One case of deep infection were evaluated and then solved with surgical debridement; no wound dehiscence. We had 1 case of anterior hip dislocation in dysplastic arthrosis due to a technical mistake. In 1 case we had femoral nerve palsy, then solved, probably because of anterior retractor malpositioning. We had 5 cases of piriformis muscle contracture without sciatic nerve palsy, then solved. We think that for total hip replacement this conservative postero-lateral approach, thanks to capsule-tendinous modification we have adopted, could be considered an anatomical approach, which doesn't present more dislocation risks compared to other approaches to the hip also thanks to the introduction of 36 mm femoral head that gives more stability and proprioceptiveness. Besides this approach gives the possibility of a shorter rehabilitation as seen above and it could be consider optimal for total hip replacement

The Gibson and Moore postero-lateral approach is one of the most often used in hip replacement. The advantage of this approach is an easy execution but it’s criticized because of its invasivity to muscletendinous tissues especially on extrarotators muscles and because of predisposition to posterior dislocation. Since June 2003 we executed total hip replacements using a modified postero-lateral approach which allows to preserve the piriformis and quadratus femoris muscles and to detach just the conjoint tendon (gemelli and obturator internus). Articular capsule is preserved and it will be anatomically sutured at the end of the procedure as well as the conjoint tendon with two transossesous sutures. Piriformis and quadratus femoris muscles result untouched by this approach. We have executed 500 surgeries with this modified approach. We have used different stems (straight, anatomical, modular and short) and press fit cetabular cup with polyethylene or ceramic insert and we have always used 36 mm femoral heads when allowed by the cup dimensions. We have used any size both of stems and cups without limitation due to the surgical approach. The mean age is 61.8 y.o., 324 females and 176 males. Obese patients, hip dysplasia Crowe 3 and 4 and post traumatic arthrosis are exclusion factors for the execution of this approach. If possible we have maintained the capsulo-tendinous less invasivity. The BMI is not an excluding factor because it’s just the gluteus region that is an important factor to decide if to execute or not a less invasive approach. Analyzing our 500 cases we didn’t have any case of malpositioning of the stem in varus or valgus (more than 5°) and considering acetabular cup we had the tendency to position it in valgus position (not more than 40°) in the first 20 cases. No leg discrepancies more than 1 cm were observed. Intra-operative blood loss have been reduced of about 30 % and 50% in the post-operative. All the patients were able to active hip mobilization within the first day after surgery with a mean range of motion of 0–70°. The patients were mobilized the first day after surgery and 80% of them were able to assisted walk within second day after surgery. The mean time of stay in hospital was 6.8 days. After 4 weeks 98% of the patients were able to walk without crutches. One case of deep infection were evaluated and then solved with surgical debridement; no wound dehiscence. We had 1 case of anterior hip dislocation in dysplastic arthrosis due to a technical mistake. In 1 case we had femoral nerve palsy, then solved, probably because of anterior retractor malpositioning. We had 5 cases of piriformis muscle contracture without sciatic nerve palsy, then solved. We think that for total hip replacement this conservative postero-lateral approach, thanks to capsuletendinous modification we have adopted, could be considered an anatomical approach, which doesn’t present more dislocation risks compared to other approaches to the hip also thanks to the introduction of 36 mm femoral head that gives more stability and proprioceptiveness. Besides this approach gives the possibility of a shorter rehabilitation as seen above and it could be consider optimal for total hip replacement

A prospective evaluation comparing functional results in conventional and percutaneous femoral nailing techniques was performed. 4 patients (8 nails) were operated on with a conventional IM nailing technique (CT), and 4 (8 nails) with the percutaneous technique (PT). Limited trochanteric approach was performed, allowing the setting up of the sighting device for the nail. Patient was positioned on the lateral side, hip at 60° flexion. A long k-wire was passed through the skin, along the axis of the medullary canal in the anterior-lateral part of the Piriformis fossa, into the medullary canal. A small skin incision was performed, and then a cannulated drill introduced over the k wire. The reamer guide was pushed down to the distal femoral metaphysis. Percutaneous flexible reaming was then performed in a conventional manner, taking care to introduce the reamer through the gluteus medius with no torque. Section was performed through the same incision with a modified intramedullary saw. The nail was inserted, fixed on a modified sighting device. The continuous passive machine was set up in the recovery room or in the intensive care unit. Physiotherapy was directed towards maintaining knee range of motion. Patients were evaluated for scar size, muscle function, leg raise and range of motion (ROM). Follow-up averaged 30 (CT) and 11 (PT) months. Gain averaged 61 mm (CT) and 79 mm (PT). Scar size for nail insertion ranged from 6 to 11 cm (CT) and 1.1 to 3 cm (PT). Total number of operations from nail insertion to removal, including GA for ratcheting (GAR) and GA for other complications (GAC) was: 18 (CT, all nails removed) 9 (PT, among them 3 removal operations on the waiting list). On postoperative day 1, all patients with PT returned to a subnormal ROM. At one week, Knee flexion averaged 93° (CT) and 131° (PT). For CT, it increased gradually, passing 100° at 8 weeks, and 130° at 20 weeks. In PT, the minimum obtained was 126° at 10 weeks, passing 130° at 13 weeks. In CT, the decreased knee flexion was 90° (5 knees) and 80° (1 knee), while in PT; only 2 knees went below 110° (85 and 95°). Trendelenburg sign was negative in all PT by 3 months. Percutaneous IM nailing, along with a good physiotherapy programme, seems to improve tremendously the outcome and decrease the complication rate, even in large limb lengthenings, which are considered as major surgery and often are associated with numerous complications

Aims

Although the short stem concept in hip arthroplasty procedure shows acceptable clinical performance, we sometimes get unexplainable radiological findings. The aim of this retrospective study was to evaluate changes of radiological findings up to three years postoperatively, and to assess any potential contributing factors on such radiological change in a Japanese population.

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.

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.

Aims

We wished to quantify the extent of soft-tissue damage sustained during minimally invasive total hip arthroplasty through the direct anterior (DA) and direct superior (DS) approaches.

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.