Hamstring origin-anatomy, angle of origin and its possible clinical implications

INTRODUCTION

The posterior compartment of the thigh is composed of three major muscles collectively known as the hamstring muscles. These consist of the biceps femoris short and long head, semimembranosus and semitendinosus. Excluding the short head of biceps femoris, the hamstrings contribute to the movement of the hip and the knee joints as they span across both joints. Our hypothesis is that the nature of the conjoint tendon -ischial angle predisposes to an increased risk of tearing in this hamstring component. We therefore aim to look at the anatomy of the hamstring origin at the ischial tuberosity and spatial relationship between the long head of biceps, semitendinosus and semimembranosus in the form of vector angles.

MATERIAL AND METHODS

100 consecutive pelvic MRIs in patients under the age of 40 years were reviewed by musculoskeletal radiology fellow and a consultant musculoskeletal radiologist with more than 10 years' experience in musculoskeletal radiology and measured the angle of origin of conjoined tendon and semimembranosus at its ischial origin. P value using a paired t-test was less than 0.0001 confirming that the difference in the vector angle of the different hamstring components was statistically significant.

RESULTS

The median angle of origin of conjoined tendon was 12° and for semimembranosus was 6°. Applying the concept of Newton's second law to the angles calculated we demonstrated that an increase of 9% force applied to the conjoint tendon origin when compared to the semimembranosus tendon.

CONCLUSION

We hypothesis that the difference in the angle of origin of the components of hamstrings might be one of the reasons for the difference in the incidence and patterns of the injuries of the various muscles of the hamstrings.

The effect of conjoint tendon release on gait after direct anterior total hip arthroplasty

INTRODUCTION

There has been considerable interest in the direct anterior (DA) approach to total hip arthroplasty (THA) recently. To facilitate exposure of the proximal femur it is sometimes necessary to release the conjoint tendon.

AIM

To prospectively investigate whether release of the conjoint tendon has an impact on gait in the early postoperative period.

METHODS

We measured gait velocity, stride length, single-limb support and single-limb support symmetry preoperatively, at discharge from the hospital, and 2, 6 and 12 weeks and postoperatively. Participants also completed the Timed Up and Go and a series of questionnaires (WOMAC, SF-12, Harris Hip Score, and pain VAS) at each visit.

RESULTS

36 participants undergoing a DA THA with a single surgeon were enrolled in this study. 22 participants had a release of the conjoint tendon during their surgery. We found no differences between the groups for any gait, patient-reported or surgical outcomes (p < 0.05). There was a total of 3 complications reported in the release group, and 1 complication in the group that did not have a release.

CONCLUSION

Although the conjoint tendon has an important role in the biomechanics of the hip, we found release of the conjoint tendon during the DA approach for THA to have no impact on gait or patient reported outcomes within 12 weeks post-surgery. Therefore, if the exposure of the proximal femur is limited, a low threshold for release of the conjoint tendon is recommended to improve visualisation.

The stabilization effect of the conjoint tendon in reverse total shoulder arthroplasty

BACKGROUND

Numerous factors determine stability of reverse total shoulder arthroplasty. The effect of the conjoint tendon in relation to stability remains unknown. In this biomechanical study, we evaluated the influence of the conjoint tendon on the anterior stability of reverse total shoulder arthroplasty with a hemispherical glenosphere and a glenosphere with 9 mm lateralisation.

METHODS

A reverse total shoulder arthroplasty was implanted in 6 human cadaveric shoulders. The anterior stability was evaluated using a shoulder simulator. Two conditions, intact and dissected conjoint tendon, and 2 component configurations, a hemispherical glenosphere and a glenosphere with 9 mm lateralisation, were tested in each specimen. Testing of anterior stability was performed in 30° and 60° of abduction, with 0° and 30° of external rotation in the glenohumeral joint.

FINDINGS

The conjoint tendon showed a significant influence on the anterior stability with a hemispherical glenosphere in 30° and 60° with neutral rotation (p = 0.028) as well as 30° abduction with 30° (p = 0.028) external rotation. The 9 mm lateralised glenosphere stabilized significantly reverse total shoulder arthroplasty with resected conjoint tendon compared to the hemispherical glenosphere with resected conjoint tendon (p = 0.028).

INTERPRETATION

In a biomechanical setting the conjoint tendon has a stabilizing influence on the anterior stability of the reverse total shoulder arthroplasty with a hemispherical glenosphere in an abducted arm position, but this stabilizing effect was not seen with the lateralised glenosphere. The single influence of the lateralisation of the glenosphere on anterior stability was shown in cases of resected conjoint tendon.

Soft tissue restrictors of femoral elevation in direct anterior approach-an anatomic study

Background

With the patient in a constant supine position, elevation of the femur in THA (DAA) provides a more intuitive and conducive location of the acetabulum for the correct placement of the acetabular prosthesis, but elevation of the femur for broaching becomes more challenging. The purpose of this study is to analyze the restriction of the ischiofemoral ligament and short external rotation muscles, and its effect on the elevation of the proximal femur in the DAA.

Methods

The study subjects comprised 5 freshly frozen cadavers with 10 normal hips. All of the anatomic dissections of all of the hips were performed through the DAA. The ischiofemoral ligament, piriformis, conjoint tendon, and external obturator were successively resected. All of the proximal femurs of the specimens were levered by a point tip curved retractor that was connected with a dynamometer. Through preliminary measurements, an applied force of 80 N was adopted and maintained on the curved retractor. The experiment was repeated to measure the displacement of the proximal femur being raised after the posterior structures of the hip joint had been resected in a stepwise fashion. The displacement of the retractor was recorded, and the data were then analyzed.

Results

The distance significantly increased after the ischiofemoral ligament was severed (P < 0.001). A prominent increase was demonstrated after the conjoint tendons were severed (P < 0.001). The distance insignificantly increased after the piriformis was severed (P > 0.05). After the obturator externus was cut off, the distance increased by an insignificant amount (P > 0.05).

Conclusion

In DAA, the ischiofemoral ligament contributed stability when the femur was being raised. The main contribution of restriction was provided by the conjoint tendon. The tendons of the obturator externus muscle and piriformis muscle did not provide any significant restriction when the femur was being raised.

Optimization of bone-block positioning in the Bristow-Latarjet procedure: a biomechanical study

BACKGROUND

In the Bristow-Latarjet procedure, optimal positioning of the coracoid bone-block on the anterior aspect of the glenoid (standing or lying on the glenoid rim) remains debated. A biomechanical study assessed the effect of the position of the bone-block with its attached conjoint tendon on anterior and inferior stabilization of the humeral head.

MATERIALS AND METHODS

The Bristow-Latarjet procedure was performed on 8 fresh cadaveric shoulders. The bone-block size was systematically at 2.5×1×1 cm. Anterior translation of the humeral head was stress induced under 30-N traction, in maximum external rotation at 0° and at 90° abduction: respectively, adduction and external rotation (ADER), and abduction and external rotation (ABER). Under radiological control, displacement of the center of the humeral head was compared with the glenoid surface at the 3, 4 and 5 o'clock (medial, antero-inferior and inferior) positions for the 2 bone-block positionings.

RESULTS

The lying position at 4 o'clock substantially decreased anterior and inferior displacement of the humeral head respectively in ADER and ABER; and in ABER it also tended to decrease anterior translation, but not significantly. The standing bone-block position did not affect translation.

CONCLUSIONS

Positioning the bone-block so that it lies on the anterior aspect of the glenoid in the middle of the antero-inferior quarter of the rim at 4 o'clock can decrease anterior displacement of the humeral head and inferior glenohumeral translation, especially in ADER for anterior displacement and in ABER for inferior displacement.

STUDY DESIGN

Laboratory study.

Testicular outcome following laparoscopic second stage Fowler-Stephens orchidopexy

OBJECTIVE

To assess outcome after laparoscopic second-stage Fowler-Stephens orchidopexy (L2(nd)FSO).

PATIENTS AND METHODS

Retrospective review of 94 children (aged 0.75-16 years, median 2.75 years), who underwent L2(nd)FSO for 113 intra-abdominal testes between January 2000 and May 2009: 75 unilateral, 19 bilateral (11 synchronous; 8 metachronous). Follow-up (range 3 months-10.9 years, median 2.1 years) was available for 88 children (102 testes: 71 unilateral, 31 bilateral).

RESULTS

Testicular atrophy occurred in 9 out of 102 (8.8%), including 8 out of 71 (11.3%) unilateral and 1 out of 31 (3.2%) bilateral intra-abdominal testes (multivariate analysis: p = 0.59). Testicular ascent ensued in 9 out of 102 (8.8%), comprising four (5.6%) unilateral and five (16.1%) bilateral testicles (multivariate analysis: p = 0.11). Of the 18 bilateral testes brought to the scrotum synchronously none atrophied and four (22.2%) ascended, compared to one (7.7%) atrophy and one (7.7%) ascent among the 13 testes brought to the scrotum on separate occasions (Fisher exact test: p = 0.42 and p = 0.37, respectively). Mobilization of the testis through the conjoint tendon tended towards less ascent (multivariate analysis p = 0.08) but similar atrophy (p = 0.56) compared to mobilization through the deep-ring/inguinal canal. Logistical regression analysis identified no other patient or surgical factors influencing outcome.

CONCLUSIONS

This is the largest series of L2(nd)FSO to date. A successful outcome is recorded in 85 out of 102 (83.3%) testicles. Atrophy occurred in 8.8% and ascent in 8.8%.