Arthroscopic Herbert screw fixation of patellar osteochondritis dissecans.

Osteochondritis dissecans of the patella is a rare cause of anterior knee pain. The lesion is thought to arise from chronic shear stress across the patella articular surface, producing a fragment of cartilage and subchondral bone that may remain in situ or become detached. When attempts at conservative treatment fail to provide satisfactory results, operative intervention is indicated. We present the case of a symptomatic lesion of the patella treated successfully with arthroscopic internal fixation using a retrogradely directed Herbert screw. The literature is reviewed with an emphasis on pathophysiology, diagnosis, and surgical treatment.

Alterations in the in vivo torque-velocity relationship after Achilles tendon rupture. Further evidence of speed-specific impairment.

The torque-velocity relationship of the ankle plantar flexors was determined in 31 patients recovering from Achilles tendon rupture. Isokinetic torque measurements were made at speeds of 0 to 240 degrees.s-1 at 24 degrees.s-1 intervals. Measurements of instantaneous torque were made at joint angles corresponding to neutral and 10 degrees plantar flexion. In 17 patients treated surgically, there was little difference between the injured and the uninjured leg. In contrast, patients who were treated by casting exhibited major differences between the injured and uninjured legs. This difference became amplified when torque values at 10 degrees plantar flexion were compared. Additionally, the differences between the injured and uninjured legs were not uniform. The differences in torque were greatest at slow test speeds and least at fast test speeds. Comparisons of the injured surgical and injured nonsurgical legs demonstrated that the surgical group had significantly greater torque. This difference was also speed specific. These findings demonstrate that both groups exhibited speed-specific impairment with the loss of muscle strength being greatest at slow speeds. Also, the degree of impairment was dependent on the ankle position at which torque was measured. Surgical treatment provides better functional results as observed by the torque-velocity relationship.

Histochemical properties of muscle allografts enhanced via cyclosporine.

Until recently, the transplantation of skeletal muscle across a major histocompatibility barrier has proved difficult. However, with the advent of cyclosporine (CsA), it has become possible to achieve extended survival across such histocompatibility barriers. To date, very little is known about the histochemical, biochemical, immunological or contractile properties of long-term-surviving muscle allografts. Consequently, it was the focus of this study to histochemically examine muscle allografts prolonged with CsA and determine the cross-sectional area of fast glycolytic muscle fibers. Measurements of cross-sectional area were made because they are an important correlate to the amount of tension a muscle can generate. Animals were assigned randomly to one of three groups: control (normal) (n = 5), syngeneic (n = 4), and allogeneic (n = 4). Muscle allografts were performed by transplanting the gastrocnemius of an ACI rat (RT1a) hindlimb into the hindlimb of a Lewis rat (LEW;RT1(1]. The syngeneic model consisted of an ACI-to-ACI transplant. Animals in the allograft group were given CsA (8 mg/kg/day) until the time of sacrifice. At approximately 100 days following transplantation, both syngeneic and allogeneic muscles were removed from the recipient, and quickly frozen in isopentane cooled by liquid nitrogen. Muscle fibers were classified as slow-oxidative (SO), fast-oxidative-glycolytic (FOG), or fast-glycolytic (FG) based upon their staining for myofibrillar ATPase and NADH-dehydrogenase. From each muscle, the cross-sectional area of approximately 175 FG muscle fibers was determined. The fast-glycolytic muscle fibers of both the syngeneic and allogeneic grafts demonstrated a substantial decrease in cross-sectional area. The mean value (+/- SD) for the fibers of the allografted muscle was 1165 +/- 533 microns 2. The mean (+/- SD) fiber cross-sectional area for the fibers of the syngeneic muscle was 973 +/- 421 microns 2. These values contrast with a mean (+/- SD) value of 3552 +/- 601 microns 2 for fibers from age-matched control animals. The differences between the syngeneic and allogeneic muscles were not significant (P greater than 0.05). However, both exhibited significant (P less than 0.01) atrophy compared with the control muscle.

The in vivo force-velocity relationship of the knee flexors and extensors.

Previous studies have compared the torque production of the knee flexors and extensors and developed a "hamstring-quadricep" ratio. Collectively, these studies indicate that the ratio of strength between the knee flexors and extensors is a function of test speed, with the ratio increasing at the faster test speeds. Unfortunately, these studies have employed the peak torque isokinetic method for making measurements. This technique suffers from a number of problems that are biomechanical and physiological in nature. Consequently, in this study, we employed comparison of the in vivo force-velocity relationship using an angle-specific method and a gravitational correction factor to more accurately determine flexor-extensor ratios and to better describe any variations occurring as a function of test speed. Nine male subjects volunteered to participate in this study. Each of the subjects participated in two test sessions. Subjects were tested at six angular velocities of 0, 48, 96, 144, 192, 240 deg/sec. At these respective test speeds, the mean flexor torques were 95.0, 94.8, 84.1, 66.2, 56.2, and 49.2 Nm, respectively. The corresponding values for the knee extensors were 252.2, 246.5, 220.7, 184.5, 161.9, and 146.4 Nm. Normalization of these torque-velocity relationships demonstrated that the in vivo force-velocity relationships of the two muscle groups are similar at slow speeds, but become disparate at higher velocities. When examining flexor-extensor torque ratios at the various test speeds, it was found that there were significant differences (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of high-intensity exercise on the VE-VCO2 relationship.

The intrinsic relationship between ventilation (VE) and carbon dioxide output (VCO2) is described by the modified alveolar ventilation equation VE = VCO2 k/PaCO2(1-VD/VT) where PaCO2 is the partial pressure of CO2 in the arterial blood and VD/VT is the dead space fraction of the tidal volume. Previous investigators have reported that high-intensity exercise uncouples VE from VCO2; however, they did not measure the PaCO2 and VD/VT components of the overall relationship. In an attempt to provide a more complete analysis of the effects of high-intensity exercise on the VE-VCO2 relationship, we undertook an investigation where five subjects volunteered to perform three steady-state tests (SS1, SS2, SS3) at 60 W. One week after SS1 each subject was required to perform repeated 1-min bouts of exercise corresponding to a work rate of approximately 140% of maximal oxygen uptake (VO2max). Two and 24 h later the subjects performed SS2 and SS3, respectively. This exercise intervention caused PaCO2 during SS2 and SS3 to be regulated (P less than 0.01) approximately 4 Torr below the control (SS1) value of 38.8 Torr. Additionally, significant alterations were noted for VCO2 with corresponding values of 1.15 (SS1), 1.10 (SS2), and 1.04 (SS3) l/min. No changes were noted in either VD/VT or VE. In summary, it seems reasonable to suggest that the disproportionate increase in VE with respect to VCO2 noted in earlier work does not reflect an uncoupling. Rather the slope of the VE-VCO2 relationship is increased in a predictable manner as described by the modified alveolar ventilation equation.

Skeletal muscle profiles in elite springboard and platform divers.

This investigation determined the vastus lateralis muscle fiber composition, as well as leg power and strength, in a group of 10 world class divers. Male divers had a low mean percentage of Type I fibers (36%), which was consistent with the functional demands of their sport, whereas females had a mean value of 61%. The ratio of Type I/Type II cross-sectional fiber area was 0.95 in females and 0.82 in males. Angle-specific torque-velocity relationships, derived from Cybex testing of the knee extensors, revealed high torque values in males but not in females. The observed male-female differences have no clear explanation, unless muscle fiber composition has greater importance in the more difficult dives executed by men.

Achilles tendon rupture. A review of the literature comparing surgical versus nonsurgical treatment.

Rupture of the Achilles tendon is being reported more frequently. Results published in the literature in the past 25 years were reviewed to determine the overall outcome comparing surgical with nonsurgical treatment and to identify areas needing further study. The rerupture rate for surgically treated patients was 12/777 or 1.54%, while that for nonsurgically treated patients was 40/226 or 17.7%. The complication rate for surgical treatment was 155/775 or 20.0%, while the nonsurgical rate was 2/20 or 10%. Most complications did not affect the eventual outcome. Time lost from work averaged 13 weeks for surgically treated patients and nine weeks for nonsurgically treated patients. Results of tests for functional recovery after treatment were slightly better for surgically treated patients and were worse for patients with reruptures treated nonsurgically. No study tested strength at a specified joint angle; this constitutes a major flaw in strength-testing studies, because strength is related to the functional joint position. The difference in cost between surgical and nonsurgical treatment, including the cost of rerupture treatment, may not be significant.

Skeletal muscle profiles among elite long, middle, and short distance swimmers.

Skeletal muscle profiles of fiber composition and leg power and strength were obtained in 30 national caliber swimmers (20 males, 10 females). Subjects were classified into three groups based upon the distance of their primary events [long distance (LDS), middle distance (MDS), and short distance (SDS) swimmers]. Intergroup analyses showed that the LDS group had the highest values of percent Type I muscle fiber composition (percent Type I and percent Type I area), and the lowest values of leg power and strength values (vertical jump and torque-velocity relationships). In addition, when grouped by Type I fiber composition, subjects having greater than or equal to 50% Type I fibers had significantly lower vertical jump and torque values than those having less than 50% Type I fibers. Overall, the compositional and functional measurements were consistent with the specific metabolic and contractile demands of the different swim groups.

Contractile properties of slow and fast muscle following tourniquet ischemia.

Tourniquet application is commonly used during surgery on an extremity to create a bloodless field. Investigations have focused on the ultrastructural, histochemical, and biochemical effects of tourniquet ischemia on muscle. Few studies, however, have examined the influence of tourniquet ischemia on the contractile properties of muscle. The purpose of this study was not only to examine this latter consideration, but also to determine whether slow and fast muscles exhibit a differential response. In adult male guinea pigs, the plantaris and soleus muscles of control (N = 5) and experimental legs (N = 5) were tested for time-peak-tension (TPT), one-half relaxation time (1/2RT), maximal twitch tension (Pt), and maximal tetanic tension (Po). The experimental leg was subjected to a 2 hour tourniquet which was placed around the thigh. Muscles of this leg were tested following a 2 hour recovery period. In three of the five animals, no response could be elicited from either the plantaris or soleus muscles of the experimental leg. In those instances where the experimental muscles were capable of generating force, the plantaris was clearly more effected. While tension production in the soleus was reduced by approximately 55%, the plantaris exhibited approximately a 90% decrease in tension output. Furthermore, both TPT and 1/2RT demonstrated consistent changes. These results indicate that the contractile properties of both the soleus and plantaris are dramatically effected by a 2 hour tourniquet. They further suggest that there may be a differential response based upon fiber type.

Does the gas exchange anaerobic threshold occur at a fixed blood lactate concentration of 2 or 4 mM?

The anaerobic threshold (theta an) is defined as the VO2 at which blood lactate concentration [lactate] begins to systematically increase (lactate "break point") during incremental exercise. Numerous studies have shown that gas exchange break points at the anaerobic threshold correlate highly (r congruent to 0.90) with the lactate break point. Recently, it has been suggested that the anaerobic threshold occurs at a fixed [lactate] of 2 mM or 4 mM. We therefore compared the gas exchange theta an to the three lactate criteria (break point, 2 mM, and 4 mM) for theta an estimation. Fourteen subjects performed an incremental cycle ergometer test. Ventilation and gas exchange were computed every 30 s. During the same 30-s intervals, venous blood was sampled for [lactate]. Four criteria were used for theta an determination: (1) systematic increase in VE/VO2, without a concomitant increase in VE/VCO2; (2) lactate break point; (3) 2 mM [lactate]; and (4) 4 mM [lactate]. Relative to the gas exchange criterion (i.e., #1), theta an was higher by 44, 280, and 1028 ml X min-1 for the three lactate criteria, respectively; the last two being significantly different (P less than 0.05). Thus, the anaerobic threshold discerned from gas exchange or the lactate break point does not correspond with a fixed, absolute [lactate] of 2 mM or 4 mM.

A comparison of gas exchange indices used to detect the anaerobic threshold.

This study was undertaken to determine which of four commonly used ventilatory or gas exchange indices provides the most accurate and reliable detection of the anaerobic threshold (AT). Sixteen subjects performed two cycle ergometer tests to volitional fatigue. After 4 min of unloaded cycling, the work rate was increased 20 W/min. Ventilatory and gas exchange measurements were made every 30 s throughout each test. During one of the two tests (randomly assigned), venous blood was also sampled every 30 s for subsequent determinations of blood lactate (HLa) concentration. Four ventilatory and gas exchange indices (VE, VCO2, R, VE/VO2) were used separately to detect the AT. The AT determined from systematic increases in HLa concentration was used as the criterion measure. AT values (means +/- SE) (VO2, l/min) using VE, VCO2, R, VE/VO2, and HLa were 1.79 +/- 0.11, 1.74 +/- 0.11, 1.58 +/- 0.06, 1.84 +/- 0.11, and 1.85 +/- 0.11 l/min, respectively. The highest correlation between a ventilatory or gas exchange AT and ATHLa (i.e., criterion measure) was found for VE/VO2 (r=0.93, P less than 0.001). The VE/VO2 also provided the highest test-retest correlation for detection of the AT (r = 0.93, P less than 0.001). Multiple correlational analyses did not significantly enhance detection of the AT. These results favor the use of VE/VO2 for noninvasive detection of the AT because it proved to be the most sensitive and reliable ventilatory or gas exchange index studied.

Supracondylar fractures of the humerus. A comparative study of Dunlop's traction versus percutaneous pinning.

A retrospective comparative study was done of two groups of patients with displaced supracondylar fractures of the humerus. The patients in the first group were treated with Dunlop's traction, while those in the second group were treated by percutaneous pin fixation. There were thirty-six patients in the group treated with Dunlop's traction, of whom twenty-seven were seen in follow-up with an average time of 2.7 years. Twenty-eight patients were in the group treated with pin fixation, of whom twenty were seen in follow-up with an average time of 2.9 years. In each case the chart and roentgenograms were reviewed and the patient was examined. The results showed a 33 per cent incidence of cubitus varus (so-called gunstock deformity) in the patients treated with Dunlop's traction as compared with 5 per cent in those pinned percutaneously. The range of elbow motion was also slightly better in the group treated with pin fixation. Furthermore, the costs and hospital stays were significantly less in those treated by pinning. Complications in both groups were few.

Primary coccidioidal synovitis of the knee: a report of four cases and review of the literature.

Primary coccidioidal synovitis of the knee is a rare disorder and controversy exists in the literature over the efficacy of treatment with synovectomy and Amphotericin B therapy. Four cases are presented illustrating features of the natural history, diagnosis, and treatment of the disease.

Anaerobic infection after total hip replacement. Report of three cases.

In a series of 387 consecutive total hip replacements there were nine infections (2.3% infection rate). Three of the infections were caused by an anaerobic gram positive cocci, Peptococcus. This is an increased incidence of infection for this previously rare pathogen. The anaerobic infections occurred despite prophylactic antibiotic coverage with Keflin. No causative factors such as hospital, operating time, operating personnel, medical disease, or blood loss could be associated with the observed anaerobic infections. Two of the anaerobic infections appeared late. This is consistent with other reports of anaerobic infections in implants. Drainage after total hip arthroplasty operation must be cultured for anaerobes as well as aerobes, especially late infections in patients on prophylactic antibiotics. Drainage which is sterile to aerobic culture should alert the physician to a possible anaerobic infection.