Free nerve endings in the ligamentum capitis femoris

The characteristics of the mechanoreceptors of the hip with arthrosis

Mechanoreceptors have been extensively studied in different joints and distinct signals that convey proprioceptive information to the cortex. Several clinical reports have established a link between the number of mechanoreceptors and a deficient proprioceptive system; however, little or no literature suggest concentration of mechanoreceptors might be affected by hip arthrosis. The purpose of this study is first to determine the existence of mechanoreceptors and free nerve endings in the hip joint and to distinguish between their conditions: those with arthrosis and without arthrosis. Samples of 45 male hips were analyzed: 30 taken from patients with arthrosis that were submitted to total arthroplasty and 15 taken from male cadavers without arthrosis. The patients' ages ranged from 38 to75 years (average 56.5) and the cadavers' ages ranged from 21 to 50 years (average 35.5). The capsule, labrum, and femoral head ligament tissues were obtained during the arthroplasty procedure from 30 patients with arthrosis and from 15 male cadavers. The tissue was cut into fragments of around 3 mm. Each fragment was then immediately stained with gold chloride 1% solution and divided into sections of 6 μm thickness. The Mann-Whitney test was used for two groups and the ANOVA, Friedman and Kruskal-Wallis tests for more than two groups. Results show the mechanoreceptors (Pacini, Ruffini and Golgi corpuscles) and free nerve endings are present in the capsule, femoral head ligament, and labrum of the hip joint. When all the densities of the nerve endings were examined with regard to those with arthrosis and those without arthrosis, the mechanoreceptors of cadavers without arthrosis were found to be more pronounced and an increase in free nerve endings could be observed (p = 0.0082). Further studies, especially electrophysiological studies, need to be carried out to clarify the functions of the mechanoreceptors in the joints.

Hip joint pain in spastic dislocation: aetiological aspects

AIM

Children with severe forms of cerebral palsy (CP) are at high risk of hip joint displacement. Various studies have found that the pain from affected joints occurs in 40 to 84% of studied individuals. The purpose of this study was to establish a correlation between the density of nociceptors localized in selected areas of the spastic dislocated hip joint and clinical evidence of hip joint pain in children with CP.

METHOD

Nineteen samples of articular capsule and 19 samples of teres ligaments, collected during open hip joint reduction from 19 non-ambulatory children with spastic CP (Gross Motor Function Classification System level V; mean age 9y 6mo; 10 males, nine females), were studied. Pain was assessed using the numeric rating scale completed by caregivers. The density of nociceptive fibres was compared between the children with painful and children with painless hip joints, using S-100 and substance P monoclonal antibodies.

RESULTS

The presence of S-100 protein and substance P were significantly increased (p=0.024 and p=0.02 respectively) in the children with painful hip joints. There were significantly positive correlations between the intensity of pain and the density of nerve fibres with S-100 protein (teres ligament, p=0.001; joint capsule, p=0.032) as well as substance P (teres ligament, p=0.001).

INTERPRETATION

Direct and indirect inflammatory factors, present in dislocated hip joints with cartilage damage in children with spastic CP, lead to hip joint sensitization.

The epidemiology and demographics of hip dysplasia

The etiology of developmental dysplasia of the hip (DDH) is unknown. There are many insights, however, from epidemiologic/demographic information. A systematic medical literature review regarding DDH was performed. There is a predominance of left-sided (64.0%) and unilateral disease (63.4%). The incidence per 1000 live births ranges from 0.06 in Africans in Africa to 76.1 in Native Americans. There is significant variability in incidence within each racial group by geographic location. The incidence of clinical neonatal hip instability at birth ranges from 0.4 in Africans to 61.7 in Polish Caucasians. Predictors of DDH are breech presentation, positive family history, and gender (female). Children born premature, with low birth weights, or to multifetal pregnancies are somewhat protected from DDH. Certain HLA A, B, and D types demonstrate an increase in DDH. Chromosome 17q21 is strongly associated with DDH. Ligamentous laxity and abnormalities in collagen metabolism, estrogen metabolism, and pregnancy-associated pelvic instability are well-described associations with DDH. Many studies demonstrate an increase of DDH in the winter, both in the northern and southern hemispheres. Swaddling is strongly associated with DDH. Amniocentesis, premature labor, and massive radiation exposure may increase the risk of DDH. Associated conditions are congenital muscular torticollis and congenital foot deformities. The opposite hip is frequently abnormal when using rigorous radiographic assessments. The role of acetabular dysplasia and adult hip osteoarthritis is complex. Archeological studies demonstrate that the epidemiology of DDH may be changing.

Tears of the ligamentum teres: prevalence in hip arthroscopy using 2 classification systems

BACKGROUND

The ligamentum teres (LT) anatomy has been known for many years. While its functionality remains debatable, it is well recognized that the LT can be a source of pain in the hip joint. In 1997, a landmark publication by Gray and Villar established a classification for LT tears and increased the awareness of LT disorders. However, the incidence of LT tears and the various tear types is unknown.

PURPOSE

The authors report the prevalence of LT tears in a population of patients who underwent hip arthroscopy, using both the Gray and Villar classification and a new descriptive classification.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Between February 2008 and January 2011, 616 hip arthroscopies were performed by the senior author. After excluding revision surgeries, a total of 558 surgeries (502 patients) were included in the study. Data were collected regarding patients' demographics, mechanism of injury, range of motion, magnetic resonance results, and intraoperative findings. Preoperative hip-specific questionnaire scores and pain level were recorded as well. Ligamentum teres tears were classified according to Gray and Villar's classification, and were also categorized using a descriptive grading system as follows: 0, no tear; 1, <50% tear; 2, >50% tear; or 3, 100% tear.

RESULTS

A total of 284 (51%) of the 558 surgeries in this cohort revealed LT tears. According to the descriptive grading system, 22% were grade 1, 24% were grade 2, and 5% were grade 3. According to the Gray and Villar classification 3.7% had full rupture, 43% had a partial tear, and 4.5% had a degenerative tear. Patients with LT tears were significantly older and had worse preoperative functional scores; they did, however, have a greater range of motion. Intraoperatively, an association with larger labral tear size and acetabular chondral damage was found. Magnetic resonance arthrography was found to have low accuracy and sensitivity in detection of LT tears. No correlation to the pain level was found.

CONCLUSION

Ligamentum teres tears had a higher prevalence in this study than was published in the past, most probably attributable to a lower threshold used in defining a tear. The incidence is defined both using the Gray and Villar classification, as well as a new descriptive classification system that categorizes the LT according to amount of tearing.

Hip instability

Understanding of the etiology and pathology of hip instability has increased in recent years as new information has emerged regarding the disease processes of the hip. Hip instability, heretofore considered uncommon in clinical practice, is increasingly recognized as a pathologic entity. Instability may be classified as traumatic or atraumatic, and diagnosis is made based on patient history, physical examination, and imaging studies. Plain radiography, MRI, MRI arthrography, and hip instability tests (eg, posterior impingement, dial) can be used to confirm the presence of instability. Nonsurgical management options include physical therapy and protected weight bearing. Surgical intervention, whether arthroscopic or open, is required for large acetabular fractures and refractory instability. Knowledge of the etiology and evolving research of hip instability is essential to understand the spectrum of hip disease.

Healing of the ruptured ligamentum teres after hip dislocation--an arthroscopic finding

Following recent advances in arthroscopy of the hip, interest has increased in injuries to the ligamentum teres and treatment strategies for them. Following a traumatic dislocation of the hip joint it is thought that the ligamentum teres is likely to be ruptured and it is thought that healing cannot occur because of the continued movement of the joint. We report on two patients with a past history of an established traumatic dislocation of the hip joint who were seen at subsequent hip arthroscopy to have a soft-tissue connection between the femoral head and the cotyloid fossa of the acetabulum. This suggests that the ligamentum teres has the potential to heal.

The ligamentum teres of the adult hip

Advances in hip arthroscopy have renewed interest in the ligamentum teres. Considered by many to be a developmental vestige, it is now recognised as a significant potential source of pain and mechanical symptoms arising from the hip joint. Despite improvements in imaging, arthroscopy remains the optimum method of diagnosing lesions of the ligamentum teres. Several biological or mechanical roles have been proposed for the ligament. Unless these are disproved, the use of surgical procedures that sacrifice the ligamentum teres, as in surgical dislocation of the hip, should be carefully considered. This paper provides an update on the development, structure and function of the ligamentum teres, and discusses associated clinical implications.

The etiology of osteoarthritis of the hip: an integrated mechanical concept

The etiology of osteoarthritis of the hip has long been considered secondary (eg, to congenital or developmental deformities) or primary (presuming some underlying abnormality of articular cartilage). Recent information supports a hypothesis that so-called primary osteoarthritis is also secondary to subtle developmental abnormalities and the mechanism in these cases is femoroacetabular impingement rather than excessive contact stress. The most frequent location for femoroacetabular impingement is the anterosuperior rim area and the most critical motion is internal rotation of the hip in 90 degrees flexion. Two types of femoroacetabular impingement have been identified. Cam-type femoroacetabular impingement, more prevalent in young male patients, is caused by an offset pathomorphology between head and neck and produces an outside-in delamination of the acetabulum. Pincer-type femoroacetabular impingement, more prevalent in middle-aged women, is produced by a more linear impact between a local (retroversion of the acetabulum) or general overcoverage (coxa profunda/protrusio) of the acetabulum. The damage pattern is more restricted to the rim and the process of joint degeneration is slower. Most hips, however, show a mixed femoroacetabular impingement pattern with cam predominance. Surgical attempts to restore normal anatomy to avoid femoroacetabular impingement should be performed in the early stage before major cartilage damage is present.

LEVEL OF EVIDENCE

Level V, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Free nerve endings and morphological features of the ligamentum capitis femoris in developmental dysplasia of the hip

A conflict exists on whether the ligamentum capitis femoris has the neuro-morphological structures required for nociception or proprioception of the hip joint. Therefore, we investigated the morphological features and the presence of mechanoreceptors in 24 ligamentum capitis femoris biopsies obtained at open reduction in patients with developmental dysplasia of the hip. Of these 24 hips, 16 were completely dislocated and eight were subluxated. The mean age was 33.8 months (range 13-52 months) at the time of surgery. En bloc ligamentum capitis femoris and pulvinar were taken for biopsy specimen. Ligamentum capitis femoris was dissected and the weight of each ligament was determined using a highly sensitive balance. Specimens were stained with hematoxylin and eosin and Masson trichrome for routine histolopathological evaluation and examined immunohistochemically using monoclonal antibody against S-100 protein. All specimens were graded on a four-grade system according to the amount of coarse-thick collagen bundles and hyalinization. The mean number and type of mechanoreceptors of each specimen were recorded. When the mean age, the patient's weight and the ligamentum capitis femoris weight of each group (completely dislocated vs. subluxated) were compared, there were no significant differences. In the ligamentum capitis femoris of the dislocated hips, the cells were irregularly distributed, had different shapes, and appeared to be in different stages of functional activity. The collagen fiber bundles were thicker than in the subluxated hips, distributed and of varied thickness. The elastic fibers of the dislocated hips were thicker and more numerous than those in the subluxated hips. We found a significant difference between the two groups with regard to the grade of collagen and hyalinization of ligamentum capitis femoris (P<0.004). We found type IVa, free nerve endings in 16 of 24 samples of ligamentum capitis femoris. The 66.6% presence of free nerve endings in the ligamentum capitis femoris suggests a role in nociception/proprioception of the hip in developmental dysplasia of the hip. Interestingly, the percentage and the mean numbers of free nerve endings containing ligamentum capitis femoris were similar in completely dislocated hip group and the subluxated group (62.5 vs. 75%, 12.13+/-9.07 vs. 9.37+/-9.24, respectively). We conclude that the morphological features of ligamentum capitis femoris are influenced by the severity of developmental dysplasia of the hip, whereas the distribution of free nerve endings are not influenced.

Operative treatment of primary synovial osteochondromatosis of the hip

BACKGROUND

Primary synovial osteochondromatosis of the hip, a rare benign condition characterized by multiple intra-articular osteochondral loose bodies and synovial hyperplasia, may result in mechanical symptoms and degenerative arthritis if untreated. The purpose of this study was to report the results of arthrotomy alone or combined with anterior dislocation of the hip to perform synovectomy and removal of loose bodies in patients with this condition.

METHODS

We retrospectively reviewed a consecutive series of twenty-one patients (twenty-one hips) with primary synovial osteochondromatosis of the hip treated with open surgical débridement. On the basis of the extent of extra-articular involvement as seen on preoperative magnetic resonance imaging, eight of the twenty-one patients underwent synovectomy and removal of loose bodies following anterior dislocation of the hip and thirteen underwent the same procedure with arthrotomy alone. At a mean of 4.4 years postoperatively, the patients were assessed clinically and radiographically with special attention to disease recurrence, osteoarthritis progression, and surgical complications.

RESULTS

The mean Harris hip score for the entire series of patients improved from 58 points preoperatively to 91 points at the time of the latest follow-up. Eighteen of the twenty-one patients had a good or excellent clinical result, and seventeen patients were satisfied with the result of the surgery. The clinical scores, patient satisfaction scores, and radiographic grades of osteoarthritis at the time of the latest follow-up did not differ significantly between the group treated with dislocation and the group treated without dislocation. Symptomatic disease recurred in two of the thirteen hips treated with arthrotomy alone and in none of the hips that had undergone dislocation. However, the surgical complication rate was higher in the group treated with dislocation than it was in the group treated without dislocation (p = 0.042). While patients with some signs of mild osteoarthritis at the initial procedure had a higher rate of osteoarthritis progression, severe osteoarthritis requiring arthroplasty had developed in only one patient at the time of follow-up.

CONCLUSIONS

At a mean of 4.4 years postoperatively, we found that open synovectomy and removal of loose bodies for the treatment of primary synovial osteochondromatosis of the hip is a reliable procedure that can effectively relieve symptoms. Our results also indicated that synovial osteochondromatosis may recur in patients with extensive involvement who are treated with synovectomy alone without dislocation of the hip; however, surgical complications are more likely to occur in patients managed with anterior dislocation of the hip and synovectomy.

[Lig. capitis femoris. Arthroscopic diagnosis and treatment of degenerative and traumatic disorders]

The LT arises from the transverse acetabular ligament and the posterior inferior portion of the acetabular fossa and attaches to the femoral head at the fovea capitis. Lesions of the LT are accompanied by dislocation or subluxation of the hip as well as acetabular fractures. However, rupture may occur simply from a twisting injury in the absence of major trauma. Atraumatic degeneration associated with osteoarthritis and dysplasia as well as after Perthes' disease and slipped epiphysis capitis can occur. The symptoms of pain, popping, locking, and catching are nonspecific for a variety of intra-articular lesions. Most of the patients complain of deep anterior groin pain, but sometimes simply pain upon activity or loss of motion are described. No examination finding would distinguish injury to the ligament. The diagnosis of rupture of the LT remains elusive to various imaging techniques. Magnetic resonance arthrography is much more sensitive than magnetic resonance imaging at detecting various lesions but has a low sensitivity for ruptures of the LT. Lesions of the LT can be diagnosed using arthroscopy and respond remarkably well to arthroscopic débridement. Long-term results and potential consequences of treatment remain to be defined.

Mechanoreceptor evaluation of hip joint capsule and ligamentum capitis femoris in developmental hip dysplasia: a preliminary study

We aimed to determine if there are mechanoreceptors in the hip joint capsule and ligamentum capitis femoris (LCF) of patients with developmental dysplasia of the hip (DDH). We took capsule and LCF biopsies from 20 hips of 20 patients who were operated on because of DDH. The mean age was 10.2 months (range 6-20 months) at the time of surgery. There were 12 girls and eight boys. Teratologic and secondary hip dislocations were not included in this study. Full thickness, 0.5 x 0.5 cm anterior capsule and LCF portions were taken for biopsy specimen. Specimens were stained with hemotoxylin eosin and examined immunohistochemically using monoclonal antibody against S-100 protein. In both analyses no mechanoreceptor was found in any samples of capsule or LCF. In this preliminary study we could not find mechanoreceptors in the local anterior joint capsule and LCF of the hip in children with DDH. We think that additional studies are necessary in order to understand the mechanoreceptor characteristics of the hip joint in children not only with DDH but also in children with healthy hips.

MR imaging of sports-related hip disorders

Hip arthroscopy is being used increasingly for the diagnosis and treatment of hip disorders. MR imaging performed with appropriate technical considerations may aid not only in preoperative planning but in the appropriate selection of patients, which tends to lead to better postoperative results. Although the painful hip is imaged most commonly by radiography, MR imaging is considered the next imaging test of choice for evaluation of most common hip abnormalities in athletes, including labral injuries, ligament injuries, osteochondral injuries, fractures, bursitis, and musculotendinous injuries. MR arthrography can be a particularly useful technique for dedicated assessment of hip joint internal derangements.