The surgical anatomy of the piriformis tendon, with particular reference to total hip replacement

Superior Transverse Atraumatic Reconstruction (STAR) approach provides a better-compared outcome to standard Direct Superior Approach (DSA): a matched, prospective comparative single-surgeon study

INTRODUCTION

The Direct Superior Approach (DSA) is a muscle-sparing hip approach that does not protect the piriformis and the other short external rotators. We present a DSA modification we named STAR (Superior Transverse Atraumatic Reconstruction), which has DSA advantages but always preserves piriformis. Our study compared the early postoperative, radiological, and functional results of patients undergoing primary total hip arthroplasty (THA) through the STAR approach with a matched DSA group performed by a senior surgeon.

METHODS

Each group, DSA, and STAR included 200 elective primary unilateral THAs performed by the surgeon between 2016-2017 and 2020-2021, respectively. Patients were included in both groups using the same inclusion criteria. Both groups were matched for age and sex. The same postoperative pain management, chemoprophylaxis, and physiotherapy protocols were followed in both groups. Two independent orthopaedic surgeons performed the clinical and radiological follow-up.

RESULTS

The STAR group had significantly lower mean incision length (p = 0.042) and hospital stay (p = 0.002) than the DSA group. The mean intraoperative blood loss (p = 0.085) and the need for blood transfusion (p = 0.228) were less for the STAR than the DSA group. The mean postoperative functional scores improvement was significantly higher for the STAR than the DSA group at the end of the first and third postoperative months.

CONCLUSIONS

The STAR approach offers earlier functional improvement, shorter hospital stay and less transfusion need than DSA for patients undergoing primary THA. Both approaches showed a limited complication risk and an outstanding acetabular and femoral access enabling the procedure.

Total hip arthroplasty with a superior approach and in situ preparation of the femoral stem: technique and feasibility in a prospective series of 80 cases

We report on the feasibility of a technique for total hip replacement with in situ preparation of the femoral stem through a superior approach and with the use of standard instruments. From December 2017 to august 2018, 100 patients were recruited for total hip replacement. 80 patients underwent THA through a superior approach with femoral broaching before femoral neck cut. We evaluated feasibility, complications and early functional outcome. There were no major complications. Postoperative leg length discrepancy was on average +0.6mm and offset -0.5mm. The mean acetabular cup inclination was 42.0° and the mean anteversion was 14.5°. The mean WOMAC score was 46 before, 76 at 1 month and 86 at 3 months after surgery. Functional scores (OARSI) were significantly improved at 3 months. Superior in situ total hip replacement is a reliable and reproducible technique with an excellent clinical outcome. It is an iteration to the posterior approach, hence the learning curve is steep and if needed, conversion to a standard posterior approach is possible.

Deep hip external rotator muscle size in ballet dancers compared to non-dancing athletes, and associations to pain

OBJECTIVES

To compare the deep hip external rotator (DHER) muscle (piriformis, gemelli, quadratus femoris (QF)) cross-sectional area (CSA) in dancers and athletes and evaluate the relationship between DHER size and hip pain.

STUDY DESIGN

Cross-sectional study.

SETTING

Elite ballet and sport.

PARTICIPANTS

33 professional ballet dancers and 33 age and sex-matched athletes.

MAIN OUTCOME MEASURES

CSAs of piriformis, gemelli and QF on magnetic resonance imaging (MRI). Hip pain scored with the Copenhagen Hip and Groin Outcome Score (HAGOS): Hip pain was categorised as 'yes' if HAGOS pain score was <100, 'no' if HAGOS pain was = 100.

RESULTS

Estimated marginal mean CSA of piriformis, gemelli and QF muscles was similar in athletes and dancers (p > 0.05), and CSAs were not associated with hip pain. Male and female dancers had similar sized DHER muscles. In athletes, CSA of piriformis was 55% (p = 0.02, Cohen's d(95%CI) = 0.98 (0.26,1.71)) and the gemelli were 34% (p = 0.03, Cohen's d(95%CI) = 0.98 (0.26,1.70)) larger in men than women; QF was 36% larger (p = 0.08, Cohen's d(95%CI) = 0.77 (0.06,1.48)).

CONCLUSION

Although ballet dancers perform in external rotation, their DHER are no larger than athletes and muscle size was not associated with hip pain.

Minimally invasive posterolateral hip approach with SPARTAQUUS (Spare the Piriformis And Respect The Active QUadratus femoris and gluteus mediUS) technique

Interest in the different surgical approaches to total hip arthroplasty remains high, but without any real consensus on which approach is the most beneficial. Several recent technical innovations have made it possible to reduce the risk of dislocation, therefore improving the efficacy of the posterolateral approach. Since 2003, we have been using a modified minimally invasive posterolateral approach called SPARTAQUUS (Spare the Piriformis And Respect The Active QUadratus femoris and gluteus mediUS), which spares the piriformis tendon, the quadratus femoris muscle and the gluteus medius muscle, and involves direct capsular repair. The "active posterosuperior hammock" effect of the piriformis tendon is therefore coupled with the "passive posterosuperior hammock" effect of the capsular repair, thus limiting the risks of posterior dislocation of the prosthetic hip joint.

A Small Amount of Retraction Force Results in Inadvertent Piriformis Muscle Damage During a Piriformis-Sparing Approach to the Hip

BACKGROUND

Piriformis-sparing approaches to the hip allow surgeons to avoid releasing the piriformis tendon during total hip arthroplasty; however, the consequences of retracting an intact piriformis tendon during such an approach remain ill-defined. The present study aimed to determine the upper limit of force that can be applied during retraction of the piriformis tendon to expose the hip, and to quantify the resultant damage to the piriformis musculotendinous complex.

METHODS

A patent-pending instrumented retractor was designed to record the applied force, duration, and angle of retraction during a piriformis-sparing posterior approach to the hip. In addition to the data collected with use of the instrumented retractor, damage to the piriformis muscle and tendon was quantified by a blinded observer.

RESULTS

There was no damage to the piriformis tendon in 22 (96%) of 23 hips during piriformis retraction for visualization of the hip capsule; however, there was complete or partial damage to the piriformis muscle at the sacral origin, belly, or musculotendinous junction (i.e., outside the surgical field) noted in 21 (91%) of 23 hips. The mean peak force to failure of the piriformis muscle was exceedingly small (29.0 ± 9.4 N; range, 10.1 to 44.9 N).

CONCLUSIONS

The mean peak force applied to the piriformis retractor is much less than the force required for several common daily activities, such as opening a door or crushing an empty aluminum can. Soft-tissue damage that occurs outside the surgical field during the retraction of unreleased muscles, like the piriformis muscle, is common and remains an uncontrolled surgical variable. This inadvertent soft-tissue damage is not routinely accounted for when accessing the invasiveness of a procedure. Hence, it is no longer adequate to define a minimally invasive surgical procedure simply as an approach that involves the limited release of anatomical structures.

CLINICAL RELEVANCE

The use of instrumented retractors may redefine surgical invasiveness by providing data that could alter our understanding of the soft-tissue damage caused by retraction and open the possibility of robot-assisted or damage-limiting retractor systems.

Prospective Evaluation of the Posterior Tissue Envelope and Anterior Capsule After Anterior Total Hip Arthroplasty

BACKGROUND

Femoral exposure for direct anterior approach (DAA) total hip arthroplasty (THA) invariably requires posterior soft tissue releases. Released posterior structures cannot be repaired. The purpose of this study is to describe the frequency and anatomic consequences of DAA THA posterior soft tissue releases and to compare the appearance of the anterior capsule between a group of patients who had capsulotomy and repair versus capsulectomy.

METHODS

Thirty-two DAA THA patients underwent metal artifact reduction sequence magnetic resonance imaging at discharge and 1-year follow-up. Seventeen had underwent capsulotomy and repair and 15 capsulectomy. A radiologist blinded to intraoperative data scored each metal artifact reduction sequence magnetic resonance imaging. Anterior capsular integrity, status of the piriformis and conjoint tendons, and muscle atrophy were graded. Descriptive statistics were performed to analyze results.

RESULTS

Immediately postoperatively, 75% of piriformis tendons were intact and 38% of conjoined tendons were intact. At 1 year, 97% had an intact piriformis and conjoined tendon, although many were in continuity through scar with the capsule. The posterior capsule directly contacted bone in all patients. At 1 year, none of the patients who underwent capsulotomy with repair had persistent anterior capsule defects, while 27% in the capsulectomy group had persistent defects.

CONCLUSION

Posterior capsule and conjoined tendon releases were commonly performed during DAA THA, yet continuity with bone was frequently achieved at 1 year. In this study, capsulotomy with repair resulted in no anterior capsular defects when compared with capsulectomy. These results may support improved THA stability observed after DAA with capsular repair despite posterior soft tissue releases.

LEVEL OF EVIDENCE

Level III, prospective cohort study.

A Rare Anatomical Variant of Unilateral Piriformis Muscle Agenesis: A Case Report

Anatomical variation of neuromuscular structures of the gluteal region is common. The piriformis muscle, in particular, has an important relationship with the sciatic nerve and may be associated with distinct clinical conditions. We report an incidental finding of unilateral piriformis muscle agenesis diagnosed on computed tomography and magnetic resonance imaging, a rare anatomical variant of the gluteal region.

Piriformis-Sparing Minimally Invasive Versus the Standard Posterior Approach for Total Hip Arthroplasty: A 10-Year Follow-Up of a Randomized Control Trial

BACKGROUND

Despite the popularity of minimally invasive approaches in total hip arthroplasty, studies regarding their impact on soft tissues and long-term benefits are lacking. This study aims to compare the 10-year functional outcome of the piriformis-sparing minimally invasive approach to the standard posterior approach for total hip arthroplasty surgery.

METHODS

Hundred patients were randomized, 48 patients to the piriformis-sparing approach and 52 to the standard approach. Primary outcomes were hip function and piriformis muscle volume and grade on magnetic resonance imaging. Secondary outcomes were pain, satisfaction score, and complications. Evaluators were blinded to allocation. Participants were followed up to 10 years.

RESULTS

Ten years following surgery, both groups reported excellent pain relief, improved hip function, and high satisfaction. The significant differences were improvement in piriformis muscle volume (P = .001) and muscle grade (P = .007) in the piriformis-sparing group compared to the standard group. There were no significant differences in all other outcomes.

CONCLUSION

Aside from being less injurious to the piriformis muscle, the piriformis-sparing approach offered the same long-term functional benefits as the standard posterior approach at 10 years.

Injuries of the obturator muscles in professional soccer players

PURPOSE

Obturator externus and internus muscular tears are uncommon injuries. Only a few case reports exist, mainly in high-level athletes. Our aim is to describe a series of obturator externus and internus muscular tears in professional soccer players.

METHODS

Injury data from four teams from the First Division of the Spanish Soccer League were collected over a total of four seasons. Any soccer player who sustained an injury to either the obturator externus or internus identified on magnetic resonance (MRI) was included. All injured players were treated non-operatively with a goal of returning to play as fast as possible.

RESULTS

Sixteen players sustained injuries to the obturator externus and internus during matches or training sessions. The main complaint was anterior hip pain with a physical examination showing pain during internal rotation or external rotation of the flexed hip. The MRI documented 12 muscular tears of the obturator externus, and 4 muscular tears of the obturator internus. All injuries were treated conservatively based on physical therapy, analgesic medications, and underwent a symptoms-based rehabilitation protocol. Mean return to play was 11.5  ±  8.8 days.

CONCLUSION

Although uncommon, tears of the obturator externus and internus occur in professional soccer players. The MRI scan was essential to the location, classification, and evaluation of the injury size. The clinical relevance of our investigation is based on the relatively benign prognosis of these injuries.

LEVEL OF EVIDENCE

IV.

Deep gluteal space problems: piriformis syndrome, ischiofemoral impingement and sciatic nerve release

BACKGROUND

Deep gluteal syndrome (DGS) is an underdiagnosed entity characterized by pain and/or dysesthesias in the buttock area, hip or posterior thigh and/or radicular pain due to a non-discogenic sciatic nerve entrapment in the subgluteal space. Multiple pathologies have been incorporated in this all-included "piriformis syndrome", a term that has nothing to do with the presence of fibrous bands, obturator internus/gemellus syndrome, quadratus femoris/ischiofemoral pathology, hamstring conditions, gluteal disorders and orthopedic causes.

METHODS

This article describes the subgluteal space anatomy, reviews known and new etiologies of DGS, and assesses the role of the radiologist and orthopaedic surgeons in the diagnosis, treatment and postoperative evaluation of sciatic nerve entrapments.

CONCLUSION

DGS is an under-recognized and multifactorial pathology. The development of periarticular hip endoscopy has led to an understanding of the pathophysiological mechanisms underlying piriformis syndrome, which has supported its further classification. The whole sciatic nerve trajectory in the deep gluteal space can be addressed by an endoscopic surgical technique. Endoscopic decompression of the sciatic nerve appears useful in improving function and diminishing hip pain in sciatic nerve entrapments, but requires significant experience and familiarity with the gross and endoscopic anatomy.

LEVEL OF EVIDENCE

IV.

An appraisal of the short lateral rotators of the hip joint

The short lateral rotators (piriformis, obturator internus, superior and inferior gemelli, obturator internus, and quadratus femoris) are functionally important muscles, significantly contributing to hip joint stability. They act as "postural muscles", holding the femoral head in the acetabulum during hip movements, thus are frequently monitored in gait analysis and for muscle rehabilitation post-injury. Despite the need to precisely identify and repair these muscles for stability postoperatively, clinical complications have resulted from the inadequate and inconsistent understanding of their morphological and functional anatomy. Furthermore, the short lateral rotators have complex entheses (osteotendinous insertions on bone) and may be subject to overuse injury in sport. This study aims to review the reported morphology of the short lateral rotators in order to ascertain whether discrepancies exist in our understanding of these muscles, and if further investigation is required to aid in gait analysis, clinical management of hip pathologies, and prevention of overuse injuries. Following a literature search strategy, 59 primary references were retrieved from three databases, with additional 26 anatomical textbooks selected for critical evaluation. Numerous inaccuracies and inconsistencies in the anatomical descriptions of the attachments, patterns of innervation and actions exist, and often insufficiently supported by primary findings. There is also a paucity of information regarding the architectural pattern of the muscles, which would be useful in clarifying the function of these dynamic stabilizers of the hip joint. A better anatomical understanding of these muscles will better inform hip reconstruction and lead to improved surgical outcomes by reducing post-operative complications.