Arthroscopy: The Journal of Arthroscopic and Related Surgery 6(2):10&103 Published by Raven Press, Ltd. 8 1990 Arthroscopy Association of North America
Intraarticular Pressure and Capacity of the Elbow Shawn W. O’Driscoll,
M.D., Ph.D., F.R.C.S.(C), Bernard F. Morrey, M.D., and Kai-Nan An, Ph.D.
Summary: The compliance, capacity, and the position of minimum intraarticular pressure were measured in 13 thawed, fresh-frozen human elbows. The capacity of the joint capsule was 23 + 4 ml. The intraarticular pressure was the lowest at 80” of flexion. Capsular rupture occurred at relatively low intraarticular pressures-80 L 42 mm Hg. Knowledge of the capacity of the normal elbow joint combined with the fact that this joint capsule tends to rupture or permit extravasation of fluid into the periarticular soft tissues should be considered when infusing fluids during arthroscopy. Finally, the “resting position” of 80” of flexion minimizes capsular tension and therefore might contribute to the development of joint contracture associated with prolonged immobilization in this position. This would be consistent with the observation that patients with posttraumatic elbow stiffness have an average arc of flexion of 60-90”. Key Words: Elbow joint-Intraarticular pressure-Capsule compliante-Arthrography-Contracture.
Variation in joint position (flexion angle) in the presence of an effusion has been shown to pro-
bow joint capsule, (b) the position of minimum intraarticular pressure, and (c) the pressure at which capsular rupture occurs.
foundly affect intraarticular pressure in several joints in humans as well as in experimental animals (l-3). However, such data are not available for the human elbow, yet they might influence patient management after elbow injuries or surgery. Raised intraarticular pressure produces pain, thereby inhibiting rehabilitation and perhaps promoting joint stiffness (4). It would therefore be helpful to know what position offers maximum compliance and/or minimum intraarticular pressure. Furthermore, with the increasing value of elbow arthroscopy, it would be useful to have information regarding the capacity of this joint and the pressures that result in fluid extravasation or capsular rupture. The present investigation was conducted to determine (a) the compliance and capacity of the el-
MATERIALS AND METHODS Thirteen fresh-frozen upper extremities from 11 cadavers were thawed to room temperature. There were seven right and six left elbows, six were from men and seven from women. The ages of the patients at the time of death were not available. There was no physical evidence of elbow pathology; this was confirmed by arthrotomy at the end of each experiment. Each specimen was amputated through the midshaft of the humerus and disarticulated at the radiocarpal joint, leaving the remaining skin and soft tissues present. Intraarticular pressures were recorded using a modification of a previously published technique (3). Spectramed DTX disposable pressure transducer (Spectramed Inc., Oxnard, California, U.S.A.), connected to a strain gauge amplifier and meter display device fabricated by the section of engineering at the Mayo Clinic, was calibrated using a mercury column from 0 to
From the Orthopaedic Biomechanics Laboratory, Department of Orthopaedic Surgery, Mayo Clinic and Mayo Foundation, Rochester, Minnesota. Address correspondence to Dr. S. W. O’Driscoll at 55 Queen Street East, Suite 800, Toronto, MSC lR6, Canada.
100 mm Hg. A three-way 100
stopcock
was connected
INTRAARTICULAR
CAPACITY
to a saline-filled syringe, the pressure transducer, and an arterial extension tube with a 25-gauge needle at the end. A fine needle was used to minimize leakage of fluid around the needle (3,5). The system was purged to eliminate air bubbles and the needle was inserted into the elbow joint through the posterolateral portal (triangle formed by the radial head, lateral epicondyle, and ulna) (6). The flow mechanics of this technique have previously been demonstrated to be adequately sensitive and responsive (3). A preliminary study demonstrated that less leakage occurred if the needle was inserted through the posterior aspect of the lateral collateral ligament. Compliance and capacity of the elbow joint capsule Capsular compliance was measured with the elbow in 90” of flexion. The intraarticular pressure was recorded after each slow incremental injection of 2 ml of saline into the joint. All pressure measurements were obtained 30 s after injection to standardize for the effects of capsular viscoelasticity and fluid flow across the synovium (2,3). The capacity of the joint was defined as that volume of injection at which capsular rupture or fluid leakage occurred (see Pressure Required for Capsular Rupture below). The elastance or “stiffness” of the joint capsule, which is defined as the unit increase in pressure per unit increase in volume (i.e., the slope of the pressure/volume curve), is the reciprocal of compliance. Position of minimum intraarticular pressure Once the capacity of the elbow joint had been reached, the position of minimum intraarticular pressure of the distended joint was determined by allowing the elbow unconstrained flexion/extension and pronation/supination with the effects of gravity eliminated. That the position assumed by the elbow corresponded to that of the minimum intraarticular pressure was confirmed by the observation that small deviations (2 or 3”) of flexion and extension from that position produced increases in the intraartitular pressure in every specimen. The effects of pronation and supination were also recorded, but these were negligible and probably within the range of experimental error. All joint flexion angles reported herein have been rounded off to the nearest 5”, which is compatible with the experimental accuracy. Pressure required for capsular rupture The pressure at which capsular leakage or rupture occurred with the elbow at 90” of flexion was
OF THE ELBOW
101
recorded. Capsular rupture was diagnosed by the loss of intraarticular pressure (i.e., intraarticular pressure was less after a further 2-ml injection). Fluid extravasation into the periarticular tissues was confirmed by dissection at the end of each experiment. Methylene blue was used in several of the specimens to determine the site of capsular leakage. RESULTS Capacity and stiffness of the elbow joint capsule Asymptotic decreases in intraarticular pressure were observed after each incremental fluid injection, as previously described. These can be explained by “relaxation” due to viscoelastic stretching at higher pressures (2,3). The lack of dye leakage into the soft tissues suggested that the pressure decreases were not due to fluid leakage. In general, the capsules were palpably distended after injection of -15-20 ml of fluid into the joints. The capacity of the capsule was 23 + 4 (mean + 1 SD) ml and ranged from 16 to 30 ml. The 95% confidence interval was from 20 to 25 ml. The data for the stiffness (pressure/volume relationship) of the elbow joint capsule are summarized in Table 1 and are depicted graphically in Fig. 1. It demonstrated the typical bilinear characteristics of soft tissue, where at low injected volumes a “toe” region was observed (2,3). The stiffness increased as the volume injected increased. It also fit a second-order polynomial curve pattern. Position of minimum intraarticular pressure The position (mean r 1 SD) of minimum intraartitular pressure was 80 + 8” and ranged from 65 to 90” (Table 1). The 95% confidence interval was from 75 to 85”. TABLE 1. Capacity and position of minimun pressure
of elbow joint capsule
Capacity (ml) na Mean SD 95% Confidence interval Minimum Maximum
12 23 4 2CL25 16 30
IAP at rupture (mm IQ) 12 80 42 54-108 32 170
Position of minimum IAP (degrees of flexion) 13 80 8 75-85 65 90
IAP, intraarticular pressure. (1n is different for the three tests due to technical problems with one specimen.
Arthroscopy,
Vol. 6, No. 2, 1990
102
S. W. O’DRISCOLL
Pressure required for capsular rupture Capsular rupture occurred at variable but relatively low pressures, ranging from 32-170 mm Hg. The mean + 1 SD pressure was 80 ? 42, and the 95% confidence interval was from 54 to 108 mm Hg (Table 1). It was not always possible to determine exactly where the capsules had ruptured. Fluid was frequently seen in the triceps and in the anterior forearm. DISCUSSION The capacity of the normal elbow joint has been estimated to be 10-15 ml based on experience with arthrography (5,6). From empirical observations, it has also been described as being greater (up to 20 ml) in cases of chronic instability and decreased in the presence of joint contractures (5). However, definitive data have not been available. The present investigation suggests that the capacity of the normal elbow is just over 20 ml which is less than that recommended for capsular distension for elbow arthroscopy (7,8). The capsules ruptured or leaked at relatively low intraarticular pressures. This should be considered whenever fluid is infused into the elbow joint, such as during arthroscopy. Furthermore, its lower tolerance for raised intraarticular pressure might indicate that the use of pressure irrigation or distension is more likely to lead to periarticular swelling during arthroscopic procedures on the elbow than on the knee. This could raise the risk of postarthroscopic joint stiffness. Inlra-Articular
Pressure/Volume
Relalionship
180 160 140 B *
120
E
60
2
IAP = 3
3 0.4 (WI) + 0.16 (WI)-
ET AL.
The position of maximum compliance (minimum intraarticular pressure) was found to be 80”. This differs somewhat from the position of 60” that has been previously suggested (45). This may be clinically relevant in two respects. First, these data enable the clinician to predict the position of greatest comfort in the presence of an effusion or hemarthrosis. It also explains why patients typically hold their elbows in approximately this position after injuries such as radial head fractures that cause hemarthroses. To move the elbow from this position would produce a painful increase in the intraarticular pressure. A second consideration is that these data might be interpreted as defining the “resting position” of the elbow. This position of 80” is very close to the electromyographic “resting position” of 70” in which there is minimal electromyographic activity in any of the major muscles about the elbow (9). Finally, the presence or absence of capsular distension or lack of it might play a role in posttraumatic elbow joint capsule contracture. If the elbow is immobilized for a prolonged period in the position of greatest comfort with its capsule lax, it would be more likely to contract than if it were extended or stretched somewhat. This would be analogous to the behavior of the collateral ligaments of the metacarpal-phalangeal and interphalangeal joints of the hand. Thus, the “resting position” might not be the “safe position” for immobilization with respect to the risk of contracture. If this is true, diminished capacities should be expected to be observed in elbows with contracture. Support for this observation is the finding that the average arc of motion of patients undergoing surgery for posttraumatic stiff elbows is 60-90” (10).
100
60 40 20 0 -201. 0
, 5
.,
., 10
., 15
., 20
.I
25
30
Volume Injected (ml)
FIG. 1. Elbow joint capsule stiffness. Intraarticular pressures (IAP) versus volume injected at flexion angle of 90” for individual specimens. Note that the IAPs are relatively low until 15-20 ml of fluid has been injected. After that, the IAP rises more sharply with each incremental injection. This “bilinear” pattern is typical of soft tissues, and capsular stiffness in particular. The dotted line represents the second-order poynomial regression equation that fits these data. The stiffness of the capsule is equal to the derivative of this equation or the slope of the pressure/volume curve [stiffness = 0.4 + 0.16 (vol)]. Note that it increases with increasing volume injected.
Arthroscopy,
Vol. 6, No. 2, 1990
Limitations of the present investigation This experiment was performed on thawed, previously fresh-frozen cadavers. It is possible that the soft tissues of these specimens, most of which were quite old, have different characteristics than those in the clinical setting. The patterns and general ranges of values are probably valid. The resting pressures were negative in some of the specimens, even though the elbows were resting horizontally. It was difficult to be certain of the patency of the needle until a small amount of fluid was injected. The reliability of these resting data is therefore uncertain. Data for the elbows flexed to 90” only is presented. In the pilot studies, an attempt was made to
INTRAARTICULAR
CAPACITY
record pressures at several positions of flexion, but this was not feasible. Significant flexion or extension of the elbows from 90” resulted in either softtissue stretching or fluid leakage, as the intraarticular pressures at 90” always fell below those recorded before moving the elbow. This position represents the commonly encountered and used position clinically and therefore still yields useful information. CONCLUSIONS We conclude the following: (a) The capacity of the elbow joint capsule is -20 ml. (b) The position of minimum intraarticular pressure is 80” of flexion. (c) The capsule ruptures at relatively low intraarticular pressures. (d) These data explain the position of comfort and the position of stiffness after elbow injury. Acknowledgment: The authors are grateful Emiko Horii for her assistance in the preparation imens for this study. This study was supported tional Institutes of Health grant AR26287 and McLaughlin Foundation of Canada.
to Dr. of specby Naby the
OF THE ELBOW
103
REFERENCES 1. Jayson MIV, Dixon ASJ. Intra-articular pressure in rheumatoid arthritis of the knee. III. Pressure changes during joint use. Ann Rheum Dis 1970;29:266-8. 2. Levick JR. The influence of hydrostatic pressure on transsynovial fluid movement and on capsular expansion in the rabbit knee. .l Physiol 1979;289:69-82. 3. O’Driscoll SW, Kumar A, Salter RB. The effect of the volume of effusion, joint position and continuous passive motion on intra-articular pressure in the rabbit knee. J Rheumatol 1983;10:360-3. 4. Morrey BF. Anatomy of the elbow joint. Philadelphia: WB Saunders, 1985:18, 66, 105, 107. 5. Johansson 0. Capsular and ligament injuries of the elbow joint. A clinical and arthrographic study. Acta Chir &and 1962;suppl 287:1-159. 6. Hudson TM. Elbow arthrography. Orthop Clin North Am 1981;19:227-41. 7. Guhl JF. Arthroscopy and arthroscopic bow. Orthopedics 1985 ;8: 1290-6.
surgery of the el-
8. Lynch GJ, Meyers JF, Whipple TL, Caspari RB. Neurovas-
cular anatomy and elbow arthroscopy. throscopy
Inherent risks. Ar-
1986;2: 191-7.
9. Pertuzon E, Lestienne
S. Determination dynamique delatosition d’equilibre d’une articulation. Int Z Angew Physiol 1973;31:315-25.
10. Morrey BF. Post-traumatic stiffness of the elbow: treatment by distraction arthroplasty. J Bone Joint Surg [Am] (in press).
Arthroscopy. Vol. 6, No. 2, 1990
Intraarticular Pressure and Capacity of the Elbow Shawn W. O’Driscoll,
M.D., Ph.D., F.R.C.S.(C), Bernard F. Morrey, M.D., and Kai-Nan An, Ph.D.
Summary: The compliance, capacity, and the position of minimum intraarticular pressure were measured in 13 thawed, fresh-frozen human elbows. The capacity of the joint capsule was 23 + 4 ml. The intraarticular pressure was the lowest at 80” of flexion. Capsular rupture occurred at relatively low intraarticular pressures-80 L 42 mm Hg. Knowledge of the capacity of the normal elbow joint combined with the fact that this joint capsule tends to rupture or permit extravasation of fluid into the periarticular soft tissues should be considered when infusing fluids during arthroscopy. Finally, the “resting position” of 80” of flexion minimizes capsular tension and therefore might contribute to the development of joint contracture associated with prolonged immobilization in this position. This would be consistent with the observation that patients with posttraumatic elbow stiffness have an average arc of flexion of 60-90”. Key Words: Elbow joint-Intraarticular pressure-Capsule compliante-Arthrography-Contracture.
Variation in joint position (flexion angle) in the presence of an effusion has been shown to pro-
bow joint capsule, (b) the position of minimum intraarticular pressure, and (c) the pressure at which capsular rupture occurs.
foundly affect intraarticular pressure in several joints in humans as well as in experimental animals (l-3). However, such data are not available for the human elbow, yet they might influence patient management after elbow injuries or surgery. Raised intraarticular pressure produces pain, thereby inhibiting rehabilitation and perhaps promoting joint stiffness (4). It would therefore be helpful to know what position offers maximum compliance and/or minimum intraarticular pressure. Furthermore, with the increasing value of elbow arthroscopy, it would be useful to have information regarding the capacity of this joint and the pressures that result in fluid extravasation or capsular rupture. The present investigation was conducted to determine (a) the compliance and capacity of the el-
MATERIALS AND METHODS Thirteen fresh-frozen upper extremities from 11 cadavers were thawed to room temperature. There were seven right and six left elbows, six were from men and seven from women. The ages of the patients at the time of death were not available. There was no physical evidence of elbow pathology; this was confirmed by arthrotomy at the end of each experiment. Each specimen was amputated through the midshaft of the humerus and disarticulated at the radiocarpal joint, leaving the remaining skin and soft tissues present. Intraarticular pressures were recorded using a modification of a previously published technique (3). Spectramed DTX disposable pressure transducer (Spectramed Inc., Oxnard, California, U.S.A.), connected to a strain gauge amplifier and meter display device fabricated by the section of engineering at the Mayo Clinic, was calibrated using a mercury column from 0 to
From the Orthopaedic Biomechanics Laboratory, Department of Orthopaedic Surgery, Mayo Clinic and Mayo Foundation, Rochester, Minnesota. Address correspondence to Dr. S. W. O’Driscoll at 55 Queen Street East, Suite 800, Toronto, MSC lR6, Canada.
100 mm Hg. A three-way 100
stopcock
was connected
INTRAARTICULAR
CAPACITY
to a saline-filled syringe, the pressure transducer, and an arterial extension tube with a 25-gauge needle at the end. A fine needle was used to minimize leakage of fluid around the needle (3,5). The system was purged to eliminate air bubbles and the needle was inserted into the elbow joint through the posterolateral portal (triangle formed by the radial head, lateral epicondyle, and ulna) (6). The flow mechanics of this technique have previously been demonstrated to be adequately sensitive and responsive (3). A preliminary study demonstrated that less leakage occurred if the needle was inserted through the posterior aspect of the lateral collateral ligament. Compliance and capacity of the elbow joint capsule Capsular compliance was measured with the elbow in 90” of flexion. The intraarticular pressure was recorded after each slow incremental injection of 2 ml of saline into the joint. All pressure measurements were obtained 30 s after injection to standardize for the effects of capsular viscoelasticity and fluid flow across the synovium (2,3). The capacity of the joint was defined as that volume of injection at which capsular rupture or fluid leakage occurred (see Pressure Required for Capsular Rupture below). The elastance or “stiffness” of the joint capsule, which is defined as the unit increase in pressure per unit increase in volume (i.e., the slope of the pressure/volume curve), is the reciprocal of compliance. Position of minimum intraarticular pressure Once the capacity of the elbow joint had been reached, the position of minimum intraarticular pressure of the distended joint was determined by allowing the elbow unconstrained flexion/extension and pronation/supination with the effects of gravity eliminated. That the position assumed by the elbow corresponded to that of the minimum intraarticular pressure was confirmed by the observation that small deviations (2 or 3”) of flexion and extension from that position produced increases in the intraartitular pressure in every specimen. The effects of pronation and supination were also recorded, but these were negligible and probably within the range of experimental error. All joint flexion angles reported herein have been rounded off to the nearest 5”, which is compatible with the experimental accuracy. Pressure required for capsular rupture The pressure at which capsular leakage or rupture occurred with the elbow at 90” of flexion was
OF THE ELBOW
101
recorded. Capsular rupture was diagnosed by the loss of intraarticular pressure (i.e., intraarticular pressure was less after a further 2-ml injection). Fluid extravasation into the periarticular tissues was confirmed by dissection at the end of each experiment. Methylene blue was used in several of the specimens to determine the site of capsular leakage. RESULTS Capacity and stiffness of the elbow joint capsule Asymptotic decreases in intraarticular pressure were observed after each incremental fluid injection, as previously described. These can be explained by “relaxation” due to viscoelastic stretching at higher pressures (2,3). The lack of dye leakage into the soft tissues suggested that the pressure decreases were not due to fluid leakage. In general, the capsules were palpably distended after injection of -15-20 ml of fluid into the joints. The capacity of the capsule was 23 + 4 (mean + 1 SD) ml and ranged from 16 to 30 ml. The 95% confidence interval was from 20 to 25 ml. The data for the stiffness (pressure/volume relationship) of the elbow joint capsule are summarized in Table 1 and are depicted graphically in Fig. 1. It demonstrated the typical bilinear characteristics of soft tissue, where at low injected volumes a “toe” region was observed (2,3). The stiffness increased as the volume injected increased. It also fit a second-order polynomial curve pattern. Position of minimum intraarticular pressure The position (mean r 1 SD) of minimum intraartitular pressure was 80 + 8” and ranged from 65 to 90” (Table 1). The 95% confidence interval was from 75 to 85”. TABLE 1. Capacity and position of minimun pressure
of elbow joint capsule
Capacity (ml) na Mean SD 95% Confidence interval Minimum Maximum
12 23 4 2CL25 16 30
IAP at rupture (mm IQ) 12 80 42 54-108 32 170
Position of minimum IAP (degrees of flexion) 13 80 8 75-85 65 90
IAP, intraarticular pressure. (1n is different for the three tests due to technical problems with one specimen.
Arthroscopy,
Vol. 6, No. 2, 1990
102
S. W. O’DRISCOLL
Pressure required for capsular rupture Capsular rupture occurred at variable but relatively low pressures, ranging from 32-170 mm Hg. The mean + 1 SD pressure was 80 ? 42, and the 95% confidence interval was from 54 to 108 mm Hg (Table 1). It was not always possible to determine exactly where the capsules had ruptured. Fluid was frequently seen in the triceps and in the anterior forearm. DISCUSSION The capacity of the normal elbow joint has been estimated to be 10-15 ml based on experience with arthrography (5,6). From empirical observations, it has also been described as being greater (up to 20 ml) in cases of chronic instability and decreased in the presence of joint contractures (5). However, definitive data have not been available. The present investigation suggests that the capacity of the normal elbow is just over 20 ml which is less than that recommended for capsular distension for elbow arthroscopy (7,8). The capsules ruptured or leaked at relatively low intraarticular pressures. This should be considered whenever fluid is infused into the elbow joint, such as during arthroscopy. Furthermore, its lower tolerance for raised intraarticular pressure might indicate that the use of pressure irrigation or distension is more likely to lead to periarticular swelling during arthroscopic procedures on the elbow than on the knee. This could raise the risk of postarthroscopic joint stiffness. Inlra-Articular
Pressure/Volume
Relalionship
180 160 140 B *
120
E
60
2
IAP = 3
3 0.4 (WI) + 0.16 (WI)-
ET AL.
The position of maximum compliance (minimum intraarticular pressure) was found to be 80”. This differs somewhat from the position of 60” that has been previously suggested (45). This may be clinically relevant in two respects. First, these data enable the clinician to predict the position of greatest comfort in the presence of an effusion or hemarthrosis. It also explains why patients typically hold their elbows in approximately this position after injuries such as radial head fractures that cause hemarthroses. To move the elbow from this position would produce a painful increase in the intraarticular pressure. A second consideration is that these data might be interpreted as defining the “resting position” of the elbow. This position of 80” is very close to the electromyographic “resting position” of 70” in which there is minimal electromyographic activity in any of the major muscles about the elbow (9). Finally, the presence or absence of capsular distension or lack of it might play a role in posttraumatic elbow joint capsule contracture. If the elbow is immobilized for a prolonged period in the position of greatest comfort with its capsule lax, it would be more likely to contract than if it were extended or stretched somewhat. This would be analogous to the behavior of the collateral ligaments of the metacarpal-phalangeal and interphalangeal joints of the hand. Thus, the “resting position” might not be the “safe position” for immobilization with respect to the risk of contracture. If this is true, diminished capacities should be expected to be observed in elbows with contracture. Support for this observation is the finding that the average arc of motion of patients undergoing surgery for posttraumatic stiff elbows is 60-90” (10).
100
60 40 20 0 -201. 0
, 5
.,
., 10
., 15
., 20
.I
25
30
Volume Injected (ml)
FIG. 1. Elbow joint capsule stiffness. Intraarticular pressures (IAP) versus volume injected at flexion angle of 90” for individual specimens. Note that the IAPs are relatively low until 15-20 ml of fluid has been injected. After that, the IAP rises more sharply with each incremental injection. This “bilinear” pattern is typical of soft tissues, and capsular stiffness in particular. The dotted line represents the second-order poynomial regression equation that fits these data. The stiffness of the capsule is equal to the derivative of this equation or the slope of the pressure/volume curve [stiffness = 0.4 + 0.16 (vol)]. Note that it increases with increasing volume injected.
Arthroscopy,
Vol. 6, No. 2, 1990
Limitations of the present investigation This experiment was performed on thawed, previously fresh-frozen cadavers. It is possible that the soft tissues of these specimens, most of which were quite old, have different characteristics than those in the clinical setting. The patterns and general ranges of values are probably valid. The resting pressures were negative in some of the specimens, even though the elbows were resting horizontally. It was difficult to be certain of the patency of the needle until a small amount of fluid was injected. The reliability of these resting data is therefore uncertain. Data for the elbows flexed to 90” only is presented. In the pilot studies, an attempt was made to
INTRAARTICULAR
CAPACITY
record pressures at several positions of flexion, but this was not feasible. Significant flexion or extension of the elbows from 90” resulted in either softtissue stretching or fluid leakage, as the intraarticular pressures at 90” always fell below those recorded before moving the elbow. This position represents the commonly encountered and used position clinically and therefore still yields useful information. CONCLUSIONS We conclude the following: (a) The capacity of the elbow joint capsule is -20 ml. (b) The position of minimum intraarticular pressure is 80” of flexion. (c) The capsule ruptures at relatively low intraarticular pressures. (d) These data explain the position of comfort and the position of stiffness after elbow injury. Acknowledgment: The authors are grateful Emiko Horii for her assistance in the preparation imens for this study. This study was supported tional Institutes of Health grant AR26287 and McLaughlin Foundation of Canada.
to Dr. of specby Naby the
OF THE ELBOW
103
REFERENCES 1. Jayson MIV, Dixon ASJ. Intra-articular pressure in rheumatoid arthritis of the knee. III. Pressure changes during joint use. Ann Rheum Dis 1970;29:266-8. 2. Levick JR. The influence of hydrostatic pressure on transsynovial fluid movement and on capsular expansion in the rabbit knee. .l Physiol 1979;289:69-82. 3. O’Driscoll SW, Kumar A, Salter RB. The effect of the volume of effusion, joint position and continuous passive motion on intra-articular pressure in the rabbit knee. J Rheumatol 1983;10:360-3. 4. Morrey BF. Anatomy of the elbow joint. Philadelphia: WB Saunders, 1985:18, 66, 105, 107. 5. Johansson 0. Capsular and ligament injuries of the elbow joint. A clinical and arthrographic study. Acta Chir &and 1962;suppl 287:1-159. 6. Hudson TM. Elbow arthrography. Orthop Clin North Am 1981;19:227-41. 7. Guhl JF. Arthroscopy and arthroscopic bow. Orthopedics 1985 ;8: 1290-6.
surgery of the el-
8. Lynch GJ, Meyers JF, Whipple TL, Caspari RB. Neurovas-
cular anatomy and elbow arthroscopy. throscopy
Inherent risks. Ar-
1986;2: 191-7.
9. Pertuzon E, Lestienne
S. Determination dynamique delatosition d’equilibre d’une articulation. Int Z Angew Physiol 1973;31:315-25.
10. Morrey BF. Post-traumatic stiffness of the elbow: treatment by distraction arthroplasty. J Bone Joint Surg [Am] (in press).
Arthroscopy. Vol. 6, No. 2, 1990
