[Efficiency of a postoperative treatment after rotator cuff repair with a continuous passive motion device (CPM)]

AIM

The main objective of this study was to prove that a postoperative combined continuous passive motion (CPM) and physiotherapy treatment protocol (CPM group) can achieve 90 degrees active abduction in the shoulder joint earlier than physiotherapy alone (PT group). The indication was a complete tear of the rotator cuff.

METHOD

The study was conducted under in-patient and out-patient conditions. 55 patients were included in this study. The prospective, randomized multicenter study design complies with DIN EN 540. The primary endpoint was the time span until 90 degrees active abduction was achieved by the patients.

RESULTS

Patients in the CPM group reached the primary endpoint on average 12 days earlier than the control group. This difference was statistically significant (p = 0.0292). Analyzing the secondary endpoints, e. g., pain and disablement, the results in the CPM group showed again advantages of the combined treatment protocol (CPM + physiotherapy).

CONCLUSION

The postoperative treatment of a total tear of the rotator cuff with a combined continuous passive motion and physiotherapy protocol provided a significantly earlier range of motion in the shoulder joint than physiotherapy alone. There was no report of CPM-related adverse effects.

Intramuskuläre Längenänderungen und Bewegungsausmaße nach lokalen Sehnentransfers zur Deckung eines retrahierten Supraspinatussehnendefektes

BACKGROUND

The current cadaver study was performed to evaluate and compare infraspinatus (ISP) vs. subscapularis (SSC) tendon transfer used for the repair of a large supraspinatus (SSP) rotator cuff defect. The main outcome measures were the range of motion and intramuscular length changes during motion.

METHODS

Thirteen fresh-frozen cadaver shoulders were used in the study. A supraspinatus defect extending to the apex of the humeral head (Patte size II) was created. Transosseous repair was then attempted with the ISP and with the SSC in all cases; intramuscular length changes were measured by Hall effect transducers during motion of the arm in steps of 30 degrees.

RESULTS

Repair was successful in all cases when the ISP was used, while use of the SSC resulted in a successful repair in only 8 of the 13 (61.5%). Passive range of motion did not differ between ISP and SSC. ISP was shortened during flexion and abduction in contrast to the SSC that was lengthened during flexion (p<0.05) and shortened to a lesser degree (p<0.05). Length changes during rotation were not significantly different.

CONCLUSIONS

In this cadaver model the ISP proved more favorable than the SSC for covering a Patte size II SSP defect if the assumption is true that lengthening of a muscle is less favorable than shortening because of the vascularization of the tendon.

Die Dezentrierung des Schultergelenkes als Spätfolge nach hemi- und totalendoprothetischem Gelenkersatz

BACKGROUND

Migration after shoulder arthroplasty can induce muscular dysbalance and instability of the shoulder joint. The aim of this study was to analyse the frequency, causes and consequences of secondary migration after shoulder arthroplasty.

METHODS

107 shoulder arthroplasties in patients with primary osteoarthritis (OA, n = 83) or avascular necrosis of the humeral head (AVN, n = 24), were followed clinically and radiographically over a period of 1 to 10 years.

RESULTS

17 Patients (16 %) developed secondary migration of the prosthesis. These were determined after a mean period of 33 months after shoulder arthroplasty. Patients with secondary migration of the prosthesis showed a worse function with a mean Constant score (CS) of 52.3 points in comparison to the patient group without migrated shoulder arthroplasties (62 points) (p = 0.038). In patients with total shoulder arthroplasty (TSA, n = 75), migration was observed in 13 % of cases during follow-up. Lucent lines at the glenoid were found in radiographs in 55 % of migrated shoulders and in 52 % of non-migrated shoulders (p = 0.633). The Constant score showed no significant difference between the groups (non-migrated shoulders 63 points, migrated shoulders 61 points, p > 0.5). Migration was seen in 22 % (7/32 patients) after hemiarthroplasty, however, no significant difference could be found between the respective Constant scores for migrated (47.7 points) or non-migrated (55.1 points) shoulders (p = 0.447). In patients with OA there was no significant difference in Constant score between migrated and non-migrated shoulders (p = 0.331), whereas patients with AVN showed significantly worse function after migrated shoulder arthroplasty (p = 0.007).

CONCLUSION

Migration after total shoulder arthroplasty leads in the medium term neither to an increased frequency of lucent lines at the glenoid nor to a worsening of the functional score in comparison to non-migrated prosthesis. In patients with AVN, migration is accompanied by a worsening of the functional score and can consequently be regarded as a negative prognostic factor.

[Recommendations for expert assessment of tendon injuries]

Expert assessment of tendon injuries depends on differences between private and public insurance providers in the way preexisting conditions have to be taken into account. In most cases degenerative and injury-dependent factors have to be balanced. Common tendon injuries such as Achilles and biceps tendon ruptures as well as rotator cuff tears are discussed.

Posttraumatische Schulterinstabilit�t im Wachstumsalter

BACKGROUND

Post-traumatic shoulder instability in adolescence represents a very rare condition. However, most of these patients develop recurrent shoulder dislocations over time.

METHODS

We report about a retrospective study, which included 32 patients younger than 16 years of age. The mean follow-up was 5 years. Our evaluation focussed on patients' age at the time of first shoulder dislocation, type of injury, and the results after conservative and operative treatment.

RESULTS

After the first dislocation, all shoulders were immobilized for 3 weeks and were treated with physiotherapy afterwards. Of these 32 patients, 30 (94%) developed recurrent shoulder dislocations. Eight patients remained in a conservative regimen (age <15 years) and 21 patients were operated for persistent shoulder instability (age >15 years). The recurrence rate was 8 of 21 patients (36.5%) in the operative group and 4 of 8 patients in the conservative group. At the time of follow-up, 4 of 8 conservatively treated patients had returned to their former sports activities and 15 of 21 (71%) in the operated group.

CONCLUSIONS

Our results on post-traumatic shoulder instability in adolescence show high recurrence rates in both conservative and operative groups. After adolescence, including ossification of the glenoid, operative treatment is able to decrease the recurrence rate and to increase the sports ability of these young patients.

[Primary strength of conventional and alternative suture techniques of the rotator cuff. A biomechanical study]

The aim of this biomechanical study was to evaluate rotator cuff repair strength using different suture anchor techniques compared to conventional repair, taking into consideration the native strength of the supraspinatus tendon. Therefore, a defined defect of the supraspinatus was created in 50 freshly frozen cadaver specimen (group size n = 10; median age at death: 56 years). Five methods were employed for cuff repair: standard transosseous suture, modified transosseous suture with patch augmentation and three suture anchors (Acufex Wedge TAG, Acufex Rod TAG und Mitek GII). The maximum tensile load of the five techniques was: standard transosseous suture, 410 N; modified transosseous suture, 552 N; Wedge TAG, 207 N; Rod TAG, 217 N; Mitek GII, 186 N. The difference between the suture anchor and standard techniques were highly significant (P < 0.001). In this series, the Mitek Gll anchor showed the lowest anchor dislocation rate at 3% (n = 1). The Wedge TAG system had a dislocation rate of 27% (n = 8) and the Rod TAG system 43% (n = 13). Suture anchor techniques revealed about 20%, the standard technique 34% and its modification 60% of the hypothetically calculated native tendon strength. Compared to conventional transosseous suture techniques, the use of the suture anchors tested in this series does not significantly increase the primary fixation strength of rotator cuff repair. The metallic implant with two barbs (Mitek GII) seems to be superior to the polyacetal anchors when inserted into the spongiform bone of the greater tubercle. The considerably weaker repair strength needs to be taken into consideration in postoperative patient rehabilitation, especially after the use of suture anchors.

Fusion proteins for combined analysis of autoantibodies to the 65-kDa isoform of glutamic acid decarboxylase and islet antigen-2 in insulin-dependent diabetes mellitus

BACKGROUND

Prediction, risk assessment, and diagnosis of autoimmune diseases often rely on detection of autoantibodies directed to multiple target antigens, such as the 65-kDa isoform of glutamic acid decarboxylase (GAD65-abs) and the tyrosine phosphatase-like protein islet antigen-2 (IA2-abs), the two major subspecificities of islet cell antibodies (ICAs) associated with insulin-dependent diabetes mellitus. We hypothesized that a combination of autoantigens in a fusion protein unifying the important immunodominant epitopes could provide an efficient target for cost-effective, one-step screening of sera.

METHODS

Chimeric proteins composed of GAD65 and IA2 residues were constructed, analyzed for their immune reactivity with monoclonal antibodies and sera, and used in a diagnostic assay with (35)S-labeled protein as antigen.

RESULTS

Length and order of GAD65 and IA2 sequences were critical for conservation of the conformational epitopes in the fusion protein. Among four chimera tested, only IA2((606-979))/GAD65((1-585)) retained wild-type-like folding of GAD65 and IA2 domains and yielded a stable protein after baculovirus expression. Reactivity of GAD65 antibody- and IA2 antibody-positive sera from patients newly diagnosed with insulin-dependent diabetes mellitus, from ICA-positive prediabetics, and from ICA-positive first-degree relatives demonstrated conservation of the relevant autoreactive epitopes. The assay based on the in vitro translated fusion antigen had a sensitivity and specificity identical to those for detection of GAD65- and IA2-abs based on the two separate GAD65 and IA2 proteins.

CONCLUSIONS

Autoantigens such as GAD65 and IA2 can be combined successfully in a fusion protein of similar immune reactivity. This allows simultaneous detection of GAD65- and IA2-abs in a one-step screening assay and cost-effective identification of positive individuals at risk of diabetes or at onset of disease.

[Injury pattern in shoulder dislocation in the elderly patient]

PROBLEM

Recurrent shoulder dislocation is reported to be rare in older patients. While injuries of the glenoid labrum and the anterior capsule following primary dislocation in younger patients seem to determine the rate of instability, the pattern of damages in the elderly has rarely been studied.

METHODS

91 patients with an age older than 40 years with the diagnosis of primary (group A, n = 50) or recurrent (group B, n = 41) anterior shoulder dislocation were included in a prospective study. By analysis of the findings in x-rays, MRI, CT-scans and in 36 patients of diagnostic arthroscopy the pattern of intra- and periarticular pathology was evaluated.

RESULTS

While the incidence of bony Bankart- and Hill-Sachs lesions was constantly spread over the age groups the pattern of soft tissue damages was different. Up to the age of 60 years lesions of the glenoid labrum were leading while in older patients the prevalence of rotator cuff tears became about 70 percent.

CONCLUSIONS

The development of secondary osteoarthritis and persisting symptoms in older patients with rotator cuff tears after traumatic shoulder dislocation requires early diagnosis and appropriate treatment.

A growth and differentiation factor-5 (GDF-5)-coated suture stimulates tendon healing in an Achilles tendon model in rats

Growth and differentiation factor-5 (GDF-5) is essential for normal skeletal development and induces tendon-and ligament-like structures at ectopic sites. Therefore, we investigated the influence of a GDF-5-coated suture on the healing Achilles tendon in rats. The right Achilles tendon in 80 rats was transected and sutured with an absorbable polyglactin suture. Animals were randomized to an uncoated-suture control and a GDF-5-coated suture group. At 1, 2, 4 and 8 weeks after surgery the repair tissue was evaluated biomechanically and histologically. Biomechanical testing revealed significantly thicker tendons, which were stiffer at 1, 2, and 4 weeks, in the experimental group than in the control group. The maximum tensile strength was significantly increased at 2 weeks after surgery. Histologically we found cartilage-like cell nests 4 weeks after tendon repair, which were positive for type II collagen. In conclusion, local growth factor delivery by a coated suture material showed a promising beneficial effect on tendon repair. The appearance of cartilage-like structures may demonstrate the chondroinductive capacity of GDF-5, which in these circumstances, however, might be overcome by modifications of the GDF-5 dose and/or the suture material.

[Traumatic rupture of the rotator cuff in an adolescent--case report]

A traumatic rotator cuff tear is a very rare condition, especially in the adolescent. We report about a 14-year-old boy who fell onto the right arm while riding his bicycle. Immediately after the accident he described some kind of click in his right shoulder. he was referred to our institution 3 days after the trauma. The MRI showed a huge defect of the labrumligament complex including the rotator interval. Intraoperatively, we found a complete disruption of the subscapularis and supraspinatus tendons as well as of the anterior stabilizers. We performed a modified Bankart repair and a reconstruction of the ruptured rotator cuff. The patient returned to his former sports as cyclist 3 months after surgery. This case is of clinical relevance because of the traumatic disruption of an intact rotator cuff in a young patient. Not the bone but rather the tendons and ligaments were the weakest link in this situation. In cases of primary traumatic shoulder dislocation, we have to look for bony and soft-tissue damage including the rotator cuff. With the present high standards in ultrasound and MR imaging we have to keep these techniques in mind in order not to overlook this type of accompanying injury.

[Achilles tendon rupture. A prospective study assessing various treatment possibilities]

The object of this study was to compare treatment of ruptured Achilles tendon by operative "end to end" surgery, percutaneous repair, or conservative therapy clinically; a subject of considerable controversy in the literature. These three methods were compared in 73 patients in a randomized trial between 1994 and 1996. After 2.5 years (11-41 months), the actual activities were assigned to the Hannover Achilles tendon score and the ability of doing work or sport activities was assessed. After this period, 59.3% of the patients showed good and excellent results on the Achilles tendon score, with over 79 points (open surgery 59.1%, percutaneous 60%, conservative treatment 58.3%). None of the patients reached the maximum score of 100 points. During the isometric strength tests, the patients with percutaneous repair had a lower weakening of the treated leg (8.9%) compared to the open-operated (12.7%) and non-operated patients (17.8%). Of the patients who had percutaneous surgery, 88% rated their treatment as good or excellent; those who had open surgery 77.3%, and those with conservative treatment 75%. The percutaneous group were able to resume work and sport much sooner than the other two groups. Bearing in mind the literature and these results, we have developed an algorithm for treating Achilles tendon rupture to assist decision making in daily routine. In this way, the use of percutaneous Achilles tendon repair can be carried out in most of cases.

[Recommendations for diagnosis and expert assessment of traumatic rotator cuff lesions]

Traumatic rotator cuff lesions are a very rare condition. However, this article represents a comprehensive survey according to current knowledge on anatomy, biomechanics, and pathogenesis of rotator cuff pathology. Because of the relatively high prevalence of degenerative changes with increasing age, including partial and complete rotator cuff tears, it may be difficult to demonstrate the causality of an acute traumatic rotator cuff tear. Therefore, a catalogue of potential adequate and inadequate trauma mechanisms is proposed. Emphasis is also placed on posttraumatic diagnostic steps following persistent rotator cuff deficient shoulder function (e.g., ultrasound, MRI). From a legal aspect (e.g., private accident insurance, workers compensation claim), different minor and major criteria are defined, which could help experts to judge the causality of posttraumatic rotator cuff deficiency. These criteria mainly refer to distinct details concerning patients' history, trauma mechanism, primary clinical appearance, and diagnostic findings.

The peaked audiometric configuration in Meniere's disease: disease related?

A retrospective analysis of audiograms was completed for persons from 3 different patient groups. These 3 groups were (1) persons with unilateral Meniere's disease, (2) persons with unilateral acoustic tumor, and (3) persons from the general clinical population of an audiology clinic in a major medical center. As Paparella, McDermott, Luiz, and de Sousa (1982) also report, the most common audiometric configuration in the Meniere's disease group was peaked, a condition in which poorer hearing is reported in the low and high frequencies, and an island of better hearing sensitivity occurs at either 1.0 or 2.0 kHz. Some of the peaked audiograms from persons in our Meniere's disease group could be a result of a low-frequency hearing loss caused by Meniere's disease combined with a high-frequency hearing loss due to aging or other environmental factors. However, 27% (13/48) of the peaked audiograms in ears with Meniere's disease were found in persons with no hearing loss in the high frequencies of their nondiseased ear. Thus, the peaked audiometric configuration is associated with Meniere's disease, as suggested by research results from animals with experimentally induced endolymphatic hydrops. Peaked audiometric configurations were also observed in roughly 9% of the general clinical population and in 12.5% of ears of persons with acoustic tumors. A rule--based on the audiometric configurations that maximized identification of patients with Meniere's disease--using the general clinical population as a control did not fare as well when the tumor group was used as a control. This finding provides further evidence that peaked audiograms, although common to Meniere's disease, are not pathognomonic of this disease. Furthermore, these results indicate that the diagnosis of Meniere's disease from audiometric profiles is risky, at best.

Evolution of lesions of the labrum-ligament complex in posttraumatic anterior shoulder instability: a prospective study

The aim of this study was to evaluate the evolution of intraarticular disease in posttraumatic shoulder instability. Ninety-one patients with posttraumatic shoulder instability were examined arthroscopically. The intraarticular disease was recorded on a special documentation sheet (containing 67 descriptive items). The patients were divided into 5 subgroups: first-time dislocation (n = 9); first or second recurrence (n = 12); 3 to 5 recurrences (n = 23); 6 or more recurrences (n = 32); and chronic subluxations (n = 15). All data were examined statistically. Each lesion was correlated with stage of evolution, age, and number of recurrences. The most frequent lesions were regrouped into "lesion families." The initial and most constant lesion was the periosteal disinsertion of the anteroinferior labrum (single lesion). The labral detachment was succeeded in a second stage by the disinsertion of the glenohumeral ligament complex (double lesion). With additional recurrences, stress mechanisms altered the detached structures through tissue damage (triple lesion). The fourth stage saw the extension of the degenerative process, which led to failure at the insertion site and destruction of the labrum-ligament complex (quadruple lesion). This study reveals that recurrences progressively damage stabilizing structures. A pathophysiological classification into 4 stages is proposed, however, that would permit a precise therapeutic strategy for arthroscopic shoulder stabilization.

[Tensile strength of the tendon of the supraspinatus muscle in the human. A biomechanical study]

The traumatic tear of the rotator cuff has been discussed very intensively for a long time despite the fact that there do not exist representative objective data about the native tensile strength of these tendons. The aim of this study was to evaluate the age related native strength of the supraspinatus tendon. 25 fresh frozen cadaver specimen (age: 23-94, 24 h post mortem, 18 male, 7 female) were tested using so called cryojaws for soft tissue fixation. The results showed the major part of the tensile forces to be transmitted through the anterior thicker part of the tendon (e.g. 14 bony avulsions in this area). We found significant correlations between age and maximum strength (p < 0.001), age and stiffness of the tendon (p < 0.005) and stiffness and maximum strength (p < 0.001). These results show that tensile strength and stiffness of the supraspinatus tendon decrease with age. However, a 65 year old specimen still demonstrates a weight bearing structure (about 900 N maximum tensile strength) and is not necessarily ruptured or degeneratively altered.

Ex vivo clonotype primer-directed gene amplification to identify malignant T cell repertoires

A novel strategy that utilizes input genomic DNA and overcomes limitations encountered with traditional RNA reverse transcription-polymerase chain reaction (PCR) amplification methodology is described to screen for T cell receptor (TCR) repertoires. The methodology has been developed to identify individual T cell clonotypes with regard to their unique receptor beta chain variable/diversity/joining (VDJ) region gene rearrangement. The technique avoids preselection for a given antigen specificity and is therefore independent of artificial bias introduced by in vitro cell population expansion. This technique was used to detect and identify genetically of malignant clones from heterogeneous mononuclear cell populations from an array of hemato-oncological disorders, including mycosis fungoides/Sézary Syndrome, adult T cell leukemia, and large granular lymphoproliferative disease. An initial primary PCR, directed by a TCR-J beta generic primer and a complement of family-specific TCR-V beta primers, defines predominant T cell receptor variable gene usage. Use of a TCR-J beta generic primer supplants the use of a constant region primer anchor and thus eliminates the need to target mRNA. The process of variable gene screening also expedites gene sequencing. By sequencing through the VDJ juxtaposed region, i.e., the third complementarity determinant region, clonotype-specific primers are developed and used in a secondary clonotype primer-directed PCR (CPD-PCR) to detect, with extreme sensitivity and specificity, unique T cell clonal repertoires. Analysis of the products of the CPD-PCR permits the detection of a single malignant cell among one million polyclonal cells and supercedes the constraints of prior studies that provide a limited evaluation of family variable gene repertoire usage. This strategy may be applied in the detection of minimal residual disease, in surveillance after induction of disease-free states, and in analyzing the effectiveness of purging autologous bone marrow of malignant clones.

DnaA protein overproduction abolishes cell cycle specificity of DNA replication from oriC in Escherichia coli

Initiation of DNA replication from oriC in Escherichia coli takes place at a specific time in the cell division cycle, whether the origin is located on a chromosome or a minichromosome, and requires participation of the product of the dnaA gene. The effects of overproduction of DnaA protein on the cell cycle specificity of the initiation event were determined by using minichromosome replication as the assay system. DnaA protein was overproduced by inducing the expression of plasmid-encoded dnaA genes under control of either the ptac or lambda pL promoter. Induction of DnaA protein synthesis caused a burst of minichromosome replication in cells at all ages in the division cycle. The magnitude of the burst was consistent with the initiation of one round of replication per minichromosome in all cells. The replication burst was followed by a period of reduced minichromosome replication, with the reduction being greater at 30 than at 41 degrees C. The results support the idea that the DnaA protein participates in oriC replication at a stage that is limiting for initiation. Excess DnaA protein enabled all cells to achieve the state required for initiation of DNA polymerization by either effecting or overriding the normal limiting process.

Overexpression of the dnaA gene in Escherichia coli B/r: chromosome and minichromosome replication in the presence of rifampin

The replication of chromosomes and minichromosomes in Escherichia coli B/r was examined under conditions in which the dnaA gene product was overproduced. Increased levels of the DnaA protein were achieved by thermoinduction of the dnaA gene, under the control of the lambda pL promoter, or by cellular maintenance of multicopy plasmids carrying the dnaA gene under the control of its own promoters. Previous work has shown that overproduction of DnaA protein stimulates replication of the chromosomal origin, oriC, but that the newly initiated forks do not progress along the length of the chromosome (T. Atlung, K. V. Rasmussen, E. Clausen, and F. G. Hansen, p. 282-297, in M. Schaechter, F. C. Neidhardt, J. L. Ingraham, and N. O. Kjeldgaard, ed., The Molecular Biology of Bacterial Growth, 1985). In the present study, it was found that overproduction of DnaA protein caused both a two- to threefold increase in the amount of residual chromosome replication and an extended synthesis of minichromosome DNA in the presence of rifampin. The amount of residual chromosome replication was consistent with the appearance of functional replication forks on the majority of the chromosomes. Since the rate of DNA accumulation and the cellular DNA/mass ratios were not increased significantly by overexpression of the dnaA gene, we concluded that the addition of rifampin either enabled stalled replication forks to proceed beyond oriC or enabled new forks to initiate on both chromosomes and minichromosomes, or both.

Duplication of Escherichia coli during inhibition of net phospholipid synthesis

In Escherichia coli BB26-36, the inhibition of net phospholipid synthesis during glycerol starvation affected cell duplication in a manner that was similar in some respects to that observed during the inhibition of protein synthesis. Ongoing rounds of chromosome replication continued, and cells in the D period divided. The initiation of new rounds of chromosome replication and division of cells in the C period were inhibited. Unlike the inhibition of protein synthesis, however, the accumulation of initiation potential in dnaA and dnaC mutants at the nonpermissive temperature was not affected by the inhibition of phospholipid synthesis. Furthermore, proteins synthesized during the inhibition of phospholipid synthesis can be utilized later for division. The results are consistent with a dual requirement for protein and phospholipid synthesis for both the inauguration of new rounds of chromosome replication and the initiation of septum formation. Once initiated, both processes progress to completion independent of continuous phospholipid and protein synthesis.

Comparison among patterns of macromolecular synthesis in Escherichia coli B/r at growth rates of less and more than one doubling per hour at 37 degrees C

In Escherichia coli B/r, the relationship between the patterns of chromosome replication and of synthesis of envelope components differs at various growth rates. At growth rates greater than 1.0 doubling per h at 37 degrees C, the average mass and age at initiation of rounds of chromosome replication are similar to those at increase in incorporation of precursors into a major outer membrane protein and phosphatidylethanolamine. At growth rates less than 1.0 doubling per h at 37 degrees C the average mass and age at increase in the synthesis of these envelope components differ from those at initiation of chromosome replication. The average cell mass per chromosomal origin at initiation of rounds of chromosome replication is not a constant and varies between growth rates greater and less than 1.0 doubling per h.

Cell division of cycle of Bacillus subtilis: evidence of variability in period D

In Bacillus subtilis the deoxyribonucleic acid content and the extent of cell division during inhibition of chromosome replication increased as a function of the average cell mass, independent of the growth rate. At each growth rate, mass, deoxyribonucleic acid, and residual division varied in different cultures. The variation is consistent with a large variability in the D period. At growth rates higher than 1.5 doublings per h at 37 degrees C, the change in D accounts for the growth rate dependence of the mass and deoxyribonucleic acid content.