controlled environment treatment ernest m . burgess,;triction that could impede circulation within...

CONTROLLED ENVIRONMENT TREATMENTFOR LIMB SURGERY AND TRAUMA

(A PRELIMINARY REPO T) a

Ernest M . Burgess,

DirectorProsthetics Research Study

Eklind Flail, Room 4091102 Columbia Street

Seattle, Washington 98104

Clinical Professor of Orthopedic SurgeryUniversity of Washington

School of MedicineSeattle, Washington 98195

Larry R . Pedegana, M .D.

Clinical AssociateProsthetics Research Study

Eklind Hall, Room 4091102 Columbia Street

Seattle, Washington 98104

ABSTRACT

This paper demonstrates a new approach to postsurgical andpost-traumatic wound management in the lower limbs . Our ownresults of 20 below-knee amputations are documented. A lessdetailed report is then given of experience with an additional 20amputees : this second group includes experience not only here atSeattle but at five other centers in the United States . The samemethod for wound management and for control of edema was em-ployed in all cases.

The method, Controlled Environment Treatment (CET), usesered air as a dressing medium, with a control console to maintain

p ressure, const : tt or varying, according to a preset program.tre and h,axiidity are also controllable, as is gas composi-

tion. The limb, Thee- with its controlled environment, is con-tained within a p1.i, e, trartsparcnt, treatment bag, which permits

a This work was performed under Veterans Administration Contract No . V663P-784

16

Burgess and Pedegana : Controlled Environment Treatment

inspection and palpation of the wound site without disturbing thebacteriologically .sterile air within the chamber . A special sealreduces air leakage yet avoids constriction of the limb.

This CET system was originally developed by the Department ofHealth and Social Security, Biomechanical Research and Develop-ment Unit, Roehampton, England. Subsequent developments arealso noted of an improved Mark II CET Unit and of simpler, re-lated, management systems for conditions not requiring sterileenvironments .

BACKGROUND

Background on Wound Healing

Wound healing has been described as "the foundation of sur-gery . " Every traumatic and incisional injury initiates an orderlysequence of cellular and molecular events which serve to restorestructural continuity (11) . New operations, new techniques, andnew systems of surgical management must all rely on wound heal-ing for success.

The voluminous literature on the subject of wound healing inthe past has related to an understanding of the physiological re-sponse of injured tissue, as exhibited by the repair process (11,12,21,24) . Excluding burn care, little attention has been paid tothe physical treatment of the postoperative wound . Conventionalpostoperative management consists of application of a variety ofsterile dressings . The problems associated with these conventionaldressings are the lack of adequate control over pressure, humidity,temperature, immobilization, and sterility of the wound site.Investigations have shown that pressure under "pressure supportdressings " is variable, unpredictable, often poorly localized, andin limbs can frequently have a proximal tourniquet effect . Mois-ture, humidity, healing wound-surface environmental temperature,and sterility under conventional dressings, are difficult to monitorand control . The wound is invisible and can only be observed byperiodic removal and renewal of dressings . This process removesany blood and serum which have oozed from the wound, butdressing changes may be painful for the patient . Removal of apotential culture medium must be balanced against the risk of newcontamination. The pressure of the new dressing again is variable.Edema may increase while the wound is exposed.

Regarding pressure, until recently very little has been added toBlair 's classic treatise, "The Influence of Mechanical Pressure onWound Healing," published in 1924 (3) . As we come to understand

17

Bulletin of Prosthetics Research—Fall 1977

more fully the pressure relationships within injured tissue, and theeffects of externally applied pressure, one realizes how generallyhaphazard has been the use of pressure in post-surgical and post-traumatic wound management (1,15,16,17,23).

The argument is advanced that this area of treatment is not soimportant and that present techniques, though not precise, appearto be adequate . This attitude is not justified by current knowledgeof the physiology of wound healing . Cellular repair and regenera-tion are among the most basic and fascinating aspects of livingmatter . An increasing understanding of these life processes paral-lels the rapid accumulation of knowledge in genetics . The clinicianis committed to as much practical application of this knowledgeas is possible in support of the body and the healing process : amore complete understanding of the biomechanical, electrical,chemical, and genetic forces involved in the repair process accen-tuates the importance of presenting to the healing tissue the mostfavorable physical environment.

Background Leading to Development of Investigation

Our interest in the clinical investigation of the wound healingenvironment for the past 13 years has been directed toward ampu-tations (4,5,6) . The amputation provides an excellent clinicallaboratory for wound healing study . All tissues of the limb aresevered in cross section ; each must heal in its specific mannerunder the broad canopy of general principles of tissue repair . Theamputation is terminal ; and this anatomical fact permits the appli-cation of an external environment which need not concern bodystructure distal to the site of surgery . Thus there is latitude formanipulation of the physical environment not present in segmentalor intercalary surgery and trauma.

A majority of amputations are performed for ischemia . Post-surgical circumstances favorable to healing are especially criticalwhen cell viability is less than optimum . Thus, amputations forischemia present a special challenge in the area of wound healing.Since residual limb function and prosthetic rehabilitation are soclosely related to amputation level, the surgeon must measure suc-cess against the dual yardsticks of distal amputation level and pri-mary wound healing . This is a particularly critical choice in the caseof a lower limb in a geriatric patient.

In 1964 we set out to clinically evaluate wound healing follow-ing amputation when using a rigid dressing with pressure interface(8). Early function was obtained, in both the upper and lowerlimbs, by use of detachable functional terminal units to allow re-stricted ambulation in lower limb amputations and terminal device

18


control in upper limb amputations . Our system was modified fromreported techniques dating back to World War I : e .g., Wilson (27)(Fig . I) and more recently by Weiss (26) and Berlemont et al . (2).It has come to be known as Immediate Postsurgical ProstheticFitting, or IPPF.

FIGURE 1 .- Forerunner of modern IPPF techniques as outlined by Wilson, 1922.(Illustration, reprinted courtesy Journal of Bone & Joint Surgery, appeared in Vol . IV,No . 2, April 1922, page 240 .)

The rigid dressing (IPPF) system, as we use it, is designed toprovide an improved postsurgical physical environment for ampu-tation wound healing . It incorporates wound support, immobili-zation, external pressure both constant and intermittent, non-occlusive dressings to control moisture and humidity, reasonablesterility, and active residual limb use consistent with the dressing.IPPF is now a relatively standard system of postsurgical manage-ment in many areas throughout the world (14,15,19,20,25).

The study reported here relates to a refinement and greaterdegree of control of the modalities just outlined . The method to bedescribed, i .e ., Controlled Environment Treatment (CET), usesequipment developed by the Biomechanical Research and Develop-ment Unit, Department of Health and Social Security, Roehamp-ton, England. Clinical investigation of CET in the United States

19


began in March 1974, at the VA Hospital, Seattle, Washington,under the supervision of the Prosthetics Research Study, and thisreport records our specific experience in the treatment of 20 below-knee amputations between March 1974 and December 1975, usingMark I equipment.

Then, during the summer of 1975, additional CET units wereprovided to the San Francisco VA Hospital (Vascular-SurgicalService), San Francisco, California, the Castle Point VA Hospital(Surgical Service), Castle Point, New York ; the Duke UniversityMedical Center (Departments of Orthopaedic and Hand Surgery),Durham, North Carolina ; the Rancho hos Amigos Hospital (Reha-bilitation Engineering Center), Downey, California ; and to theUniversity of Washington School of Medicine (Departments ofOrthopedics and Surgery), Seattle, Washington . Some of thepreliminary results of these efforts will also be presented in thisreport, though separate publications are anticipated when moreextensive series are completed.

At Seattle and elsewhere, the method also has been used in avariety of limb surgical procedures and trauma including burns,hand surgery, fractures, sprains and dislocations, crush syndromes,and for the relief of edema. Some results are presented in theseareas .

DESCRIPTION OF METHOD AND EQUIPMENT

CET uses filtered air as a dressing medium . Equipment in a con-trol console maintains air pressure, constant or varying, on theenclosed part of tl limb . The gas composition, duration and mag-

phases, temperature, and humidity can all be, together with its controlled gaseous environ-

ithin a polyvinyl chloride (PVC) treatment bag.>arency of this dressing allow inspection and=d site without disturbing the bacteriologicallych umber . A special seal where the limb enters

;triction that could impede circulation within

vironment Treatment Unit consists of threecontrol console, an interconnecting flexible hose,

,10,22) . Filtered air is used as a dressing medi--cles of alternating high and low air pressure are

gram under the operator's control.her with its controlled environment,

polyvinyl chloride (PVC) bag.with a lightweight webbed harness

nitude of pressurecontrolled . Thement, is containedPliability and tranpalpation of thesterile gas withthe bag ?vo~_~'the limb.

The Controbasic parts : anand a dressingum and tinused accor,The ,is hourBag posisanchored about the waist.

20


Equipment in the air control console (Fig. 2) includes severalstages of centrifugal air compression, several stages of air filtration,provision for temperature and humidity control, and the valves andtiming mechanisms needed to regulate the magnitude and durationof pressure phases (9,10,22) . The controls allow the operator topreset a cycle with alternating high and low pressure phases : pres-sures available are anywhere from 10 to 50 mm Hg, and phasedurations from 0 to 5 minutes are available .

4PRESSURE

CONTROL

FIRST

FILTER

I MAINBLOWER

HEAT

BACTERI-

[ XCHANC,

FLTCAL

FILTERR

AIRPRE-

FILTER

COOLING

BLOWER

HEATER

TO TREATMENT

FIGURE 2 . — Diagram of air flow system for CET.

Following final compression, air is cooled and blown through ahigh-efficiency filter capable of 99 .998 percent retention of parti-cles of 0 .6 p. or greater, thus providing sterility . The filtered air isthen passed over a heating element and raised to a preset tempera-ture . Temperature may be varied in a range from approximately4 deg Celsius above ambient room temperature to 40 deg Celsius(3 deg above body temperature) . Three separate thermal cutoutsare incorporated to switch off the heater in the event that airtemperature rises too high. This fail-safe feature is automatic andwill reset after the temperature returns to normal limits . Since airis cooled and re-warmed before delivery to the amputation site(Fig . 2), relative humidity is reduced, providing dry conditionswithin the dressing bag .

21


Once heated to the desired temperature, the processed air travelsthrough a length of flexible hose to a presterilized, pliable, trans-parent treatment bag enclosing the residual limb or other part tobe treated (Fig . 3) . The hose allows convenient placement of themachinery near the patient 's bed, and permits the patient to sit,or to stand beside the bed, or even to walk a few steps on theremaining foot with the aid of crutches or a walker.

FIGURE 3 . —CET polyvinyl chloride treatment bag illustrating cross sectional andfull view of proximal "flutter" seal.

22


Construction of this transparent, flexible yet tough dressingallows visual inspection and palpation of the wound through thebag. A thin pad supports the limb, but there is no rigid supportfor contouring.

A flexible, pleated seal at the proximal end of the bag main-tains the preset pressure within the chamber regardless of limbvolume changes and without the risk of a tourniquet effect, i .e .,pressure from the seal around the thigh is generated only by the airpressure inflating the pleats, so seal pressure never exceeds thatwithin the bag (22). (The seal is a modification of the Hovercraft®principle.) In addition, the seal 's "flutter" system provides a con-tinuous but slow escape of air, which serves to cool and to ventilatethe wound environment . Because of the positive pressure withinthe treatment bag, and the gradient through the seal about the thighto the atmosphere, only the warm, sterile air introduced is present.Unsterile air cannot gain entry against the pressure gradient andlow flow rate through the nominally open proximal end (23) . Con-sequently, risk of environmentally induced infection is minimal.

Bag design has been patented by the British Medical ResearchCouncil . Variations in types and sizes of treatment bags, includinga body surface or trunk "barnacle" dressing, are being studied atRoehampton and will be made available as needed.

APPLICATION OF CET

The CET unit used in the initial study is designated Mk I . It wasa large, heavy, moderately noisy, yet easily constructed devicewhich allowed convenient access to its internal machinery for re-pair and modification . As an evaluation prototype it has served itspurpose well . An improved, more compact device, CET Mk II(Fig. 4), is currently being used, and other variants are describedbelow.

Treatment of the first 20 amputee patients was initiated imme-diately following below-knee surgery and was continued for anaverage of 10 postoperative days . During that time wound healingprogress, incidence of infection and hematoma, degree of any limbedema, requirements for pain medication, and patient activity wereclinically observed . The drain, when used, was removed with asterile forceps through the proximal opening and seal of the dress-ing bag, normally within 72 hours following surgery . Upon comple-tion of Controlled Environment Treatment, the residual limb wasroutinely fitted with an Immediate Postsurgical Prosthesis andcarried on through the routine rigid dressing technique to defini-tive limb fitting .

23


FIGURE 4 . — Improved console (Mk II) now in use.

Pressures, Cycle Times, and Temperature Settings

Pressures, cycle times, and temperature were set within rangesrecommended by the Biomechanical Research and DevelopmentUnit, Roehampton, England (9,10) . The initial 12 cases managedwith CET were on a regimen with high pressure ranging from45 to 50 mm Hg for 30 s, and low pressure set at 10 mm Hg for60 to 90 s . In several instances, the high pressure setting was re-duced on or about the 7th postoperative day . The last eight casesin this study were managed with a somewhat reduced high pressurephase : in those cases, the high pressure phase was applied at30 mm Hg for 30 s, and low pressure was set at 10 mm Hg for 60 to90 s . Temperature was set at 38 deg Celsius for the first 12 cases,and reduced to 32 deg Celsius for the last 8 cases . Patients appearedto be more comfortable at the lower temperature.

The relatively arbitrary pressure, time, and temperature parame-ters were based on clinical and experimental observations relativeto dynamic limb blood flow . Ischemic limbs coming to amputationhave only one common and absolute characteristic, i .e ., the need toamputate . Individual variations in limb blood flow and limb hemo-


dynamics vary from patient to patient in different pathologicalstates. The treatment protocol was designed with sufficient latitudeof safety neither to harm nor to delay the wound healing process.

Adjustments to pressures and cycle times were in many instancesmade partially on the basis of patient comfort . For example, thetrial use of cycle with a 10-s low pressure phase produced notice-able discomfort in cases with both noinial and impaired vascularity.We currently use a program of approximately 30 mm Hg for 30 s onhigh pressure, and 10 mm Hg for 30 to 90 s on low pressure . Basicresearch on cycle pressure/time relationships is currently a subjectof investigation at our center (13,17) . It is possible that moreflexible treatment regimens will result from these studies.

EXPERIENCE ON FIRST 20 CASES

The 20 below-knee amputation surgeries here reported wereall treated by the Prosthetics Research Study staff at the VeteransAdministration Hospital, Seattle, Washington . Consecutive below-knee amputations, regardless of etiology, were placed in the ma-chine whenever it was available . Cases were not randomized nor wasa control group used, although the patient population could becompared with an experience of several hundred below-knee ampu-tations at this single hospital for similar pathologies.

Patient population consisted of all males, ranging in age from25 to 85 years (Table 1) . Nine patients, or 45 percent, hadperipheral vascular disease with diabetes ; another 7 (35 percent)underwent amputation for peripheral vascular disease without dia-betes ; and in the remaining 4 cases (20 percent) posttraumaticcomplications was the primary reason for amputation (Fig . 5).

Eighteen patients in this study were unilateral amputees, twowere bilateral . Both bilateral patients were amputated for peripheralvascular disease, one with diabetes and one without . All 20 casesinvolved primary wound closure with or without drainage . Thestandard long posterior myocutaneous flap was utilized in allinstances except one in which the flap was irregularly fashioned dueto skin loss from the original trauma.

Wound Healing Progress

Eighteen patients (90 percent) healed promptly and withoutincident at the below-knee level . The two cases which requiredrevision to the above-knee level failed to heal due to ischemic skinand muscle necrosis . This diagnosis was confirmed in both cases bytissue examination and culture . No infection was present in eitherpatient .

25

TABLE 1

PatientNumber Age Etiology

Drain Hematoma

Type of medication

Pain medication

Days of medication

Revision

Cast and0 1 2 3 4 5 6 7 8 9 10

to AK

measurements

1

58

PVD

Yes

2

53 PVD

No

3

84

PVD with

Yesdiabetes

4

85 PVD

No

No

Ascriptin-oral

No

Demerol-injectedDemerol-oralPhenergan-injected

No

Demerol-injectedPhenergan-injectedDarvon-oral

No

Demerol-injectedPhenergan-injectedCodeine-oralCodeine-injected

X X X X X X X

X X XX X X

X X X

XX

X XX X

X X

No

39 POD

No

38 POD

No

None

Yes

45 POD(Post AK Rev.)

X

X X

X XX X

X X

X XX X

X X X X

X

X X

X X X X X X XX

X

5

53

Trauma

Yes

6

82

Trauma with YesPVD

7

25

Trauma

No

No

Demerol-injectedPhenergan-injectedTylenol-oral

No

Demerol-injectedPhenergan-injectedAscriptin

No

Demerol-injectedPercodan-oralCodeine-oral

No

39 POD

No

34 POD

No

60 POD

TABLE 1


Drain Hematoma

Type of medication

Pain medication

Days of medication

Revision

Cast and0 1 2 3 4 5 6 7 8 9 10

to AK

measurements

XX X X

X X X X X X X X

X X X X XX

X X X X X

X XX X

X X X

X

XX X X X X

XX

X

8

70 PVD

No

9

85

PVD with

Nodiabetes

10

62

PVD with

Nodiabetes

11

59

PVD with

Nodiabetes

12

59

PVD with

Yesdiabetes

13

40

PVD with

Yesdiabetes

14

62 PVD

No

15

33

Trauma

No

No

Demerol-injectedDemerol-oralCodeine-oral

No

Demerol-injectedDemerol-oral

No

Demerol-injectedCodeine-oral

No

Morphine-injectedCodeine-oral

No

Morphine-injected

No

Morphine-injected

No

Demerol-injectedDemerol-oral

Yes

Percodan-oralDemerol-injectedTylenol-oral

Yes

Expired 51 POD

No

41 POD

No

35 POD

No

41 POD

No

70 POD

No

46 POD

No

36 POD

No

41 POD

TABLE 1


Drain Hematoma

Type of medication

Pain medication

Days of medication

Revision

Cast and0 1 2 3 4 5 6 7 8 9 10

to AK

measurements

No

39 POD

No

65 POD

No

33 POD

16

85

PVD with

Yesdiabetes

19

58

PVD with

Yesdiabetes

No

Percodan-oral

No

Demerol-injectedTaiwin-oral

No

Morphine-injectedCodeine-oralTylenol-oral

Yes

Demerol-injectedPhenergan-injectedPercodan-oral

X X

X X X X

XX X X X X X

X XX X X XX X X X X X X X X

X X X X X X XX X X X X X X

X X

17

58

PVD

18a 58 PVD

Yes

Yes

39 POD

20a63

PVD with

Yesdiabetes

No

Demerol-injectedPhenergan-injectedCodeine-oral

No

NoneXXX X X

a Bilateral below-knee amputees .


AGE AND ETIOLOGY

TRAUMA

PVD WITH DIABETES

PVD WITHOUT DIABETES

AGE

20-39

40-59

60-79

FIGURE 5 . — Chart depicting age and etiology of 20 patients.

In addition to the two patients who required revision to theabove-knee level, there was one instance of mild wound separationat the suture line with delay in healing . This individual, a 59-year-old male with peripheral vascular disease and diabetes, had pre-viously been treated by bilateral aortofemoral and femoral-poplitealDacron grafts . The below-knee amputation was healing uneventfullyat the time of the patient 's removal from the CET unit and applica-tion of the first cast, which was on the 12th postoperative day.At the time of the second cast application, the 26th postoperativeday, it was noted that the skin was overlapped and that a smallarea of skin necrosis had occurred at the suture line. No additionalsurgery was necessary, and the patient proceeded to uneventfulwound healing without infection . He was fitted with a definitiveprosthesis on the 70th postoperative day with subsequent comple-tion of his rehabilitation .

29


Infection

There were no instances of postoperative wound infectionamong the 20 patients.

Hematoma

Wounds were drained by Penrose drain in 55 percent of thecases . There were two instances of postoperative hematoma . Oneoccurred during the first postoperative week subsequent to drainremoval, in a case of amputation for chronic, gangrenous footulcers with peripheral vascular disease and diabetes . Occurrenceof the small hematoma was, in our opinion, due to improper drainplacement . The drain was removed and wound healing progresseduneventfully.

The second hematoma occurred in a wound which was notdrained. This patient presented with a severely infected crushedright foot . An emergency open guillotine amputation was per-formed just proximal to the ankle and was managed postopera-tively with CET . A closed below-knee amputation revision wascarried out 10 days later, also followed with CET . A hematomaoccurred on the second day after definitive amputation ; twosutures were removed, the hematoma evacuated, and a new bagwas put in place . The wound subsequently healed promptly andwithout further difficulty, and the patient progressed rapidly tofull rehabilitation.

Edema Control

The CET was noticeably effective in controlling postoperativeresidual limb edema. In all 20 cases, edema was felt to be absentor significantly reduced from the preoperative state . A numberof photographic methods were used to measure edema, and weare currently in the process of refining a technique to quantitateresidual limb volume changes during Controlled EnvironmentTreatment . This technique, which makes use of a small straingage sutured adjacent to the operative site, was used in conjunc-tion with CET in 4 of the 20 cases . b This system of instrumenta-tion is based upon the hypothesis that skin tension adjacent tothe suture line is related to limb volume (7) . With the feasibilityphase of this method now completed, it is expected that CET

b See paper entitled, "A Proposed Technique for the Postoperative Monitoring ofSkin Tension in Below-Knee Amputees," by E . M . Burgess, M .D ., Craig A. Spolek,

M .S ., and A . ,James Moore, as presented elsewhere in this issue of the BPR. (Three ofthe four cases are described in detail . Data on the fourth, and on four others, wereinvalidated by various mechanical difficulties).

30


efficacy in edema control can be quantitatively demonstrated withmore accuracy in the future.

Pain

In general, patients were remarkably comfortable during GET.The amount of pain medication was monitored (Fig . 6) . It is inter-esting to note that one patient required only aspirin followingamputation . The majority of patients did not require injectablepain medication after the first postoperative day and took no oralnarcotics after the fourth postoperative day . More frequent andextended use of injectable or oral narcotics was required in a fewcases where there had been a previous history of drug abuse orexcessive preoperative pain medication . One patient who devel-oped a hematoma required larger amounts of pain medicationuntil the hematoma was evacuated . Diabetic patients appeared toexperience less postoperative discomfort than others in this series.

INJECTABLE NARCOTICS REQUIRED

No . OF PATIENTS

20 –

12-1

10

8

6

4

2-i

A0

A0

A0

A0

Ln

FIGURE 6 . — Injectable narcotics required for the first five postoperative days . Twopatients did not require injectable narcotics .

31


Time from Surgery to Definitive Prosthetic Prescription

Sixteen of the patients were successfully cast and measured fora definitive below-knee prosthesis . The average time from surgeryto cast and measurements for a definitive prosthesis was 43 days;of the 16 patients fitted, 12 averaged 37 postoperative days . Aver-age time was relatively the same in all three etiological groups.

Of the four additional patients, one was discharged to a nursinghome on a non-ambulatory basis with the below-knee amputationwell healed (this patient had been non-ambulatory for more than1 year prior to admission and had a severe left hemiparesis) . An-other patient expired from myocardial infarction before completionof his rehabilitation ; a third patient (a bilateral amputee) was, be-cause of associated disabilities, not included in the routine post-operative rehabilitation protocol ; and the fourth patient wassuccessfully fitted following revision to the above-knee level.

Case Studies

Case No . 1 : 58-year-old male with severe arteriosclerosis withoutdiabetes . Associated diagnoses included hypertension, cardiachypertrophy, glaucoma, arrested pulmonary tuberculosis, chronicrheumatoid arthritis, and carcinoma of the larynx (postsurgical).In 1972 a cross-pubic (femoral-femoral) vascular vein graft wasplaced in an attempt to relieve left lower limb ischemia . Pain wasdecreased, but chronic ischemic ulcers developed over the lateralaspect of the distal left foot, and the lateral three toes were ampu-tated . Superficial ischemic ulcers also developed over the distaldorsum of the right foot . The patient had not walked for 1 yearprior to admission on March 13, 1974 for amputation of theleft leg (Fig . 7).

A long-posterior-flap, closed, left below-knee amputation wasperformed on March 15, 1974, and the residual limb was placedimmediately in the Controlled Environment Treatment chamber.The high pressure reading was initially set at 50 mm fig for a 30 sinterval, and the low pressure at 11 mm Hg for 120 s interval, withthe pressure states alternating. The patient was comfortable post-operatively, requiring . nothing but salicylates for relief of pain.The low pressure state was gradually reduced over a 3-day periodfrom 120 s time duration to a 60 s time duration, and on theseventh postoperative day the high pressure was reduced to37 mm fig continuing at a 30 s duration (Fig . 8) . Temperatureremained at 30 deg Celsius.

Healing progressed uneventfully ; the patient remained afebrile,comfortable, and without demonstrable evidence of residual limb

32


33


PRESSURE MM HG

60

PRESSURE CYCLE

CASE NO, 1.HIGH PRESSURE

LOW PRESSURE

50

4®

30

20

10

B

B

a

0 1 2 3 4

POSTOPERATIVEDAYS

FIGURE S . - Case No . 1 : Pressure cycle during CET.

edema. On the 14th postoperative day the limb was removed fromthe CET unit and placed in a plaster of paris rigid ImmediatePostoperative type of prosthetic dressing. Assisted ambulation withtouchdown was then initiated, and weightbearing was graduallyincreased according to tolerance . Sutures were removed on the 27thpostoperative day with firm primary healing of the operative wound(Fig . 9).

The patient was measured and cast for a definitive prosthesis onthe 39th postoperative day . After it was delivered, he was dis-charged from the hospital (Fig . 10), walking independently withhis prosthesis and walkerette . At this time, the superficial ulcerson the right foot had healed.

Two years following amputation, he continues wearing his pros-thesis daily, ambulatory with external aids, and living at home. Noother surgical treatment has been required for ischemia of his lowerlimbs.

Case No. 2 (Case No . 5 on Table 1) : 53-year-old male who hadsustained severe compound fractures of the right distal tibia andfibula, secondary to missile wounds incurred in 1945 . Chronicosteomyelitis of the distal tibia developed, requiring 2½ years ofhospitalization and approximately 15 open surgical procedures.Fracture union was achieved but there was a 3 in leg length dis-cr4pancy, with a spontaneous arthrodesis of the ankle and limitedmotion throughout the tarsal and toe joints . The foot was fixed

12

34


FIGURE 9 . — Case No . 1 : Four weeks following surgery .

35


FIGURE 10 . Case No. 1 : Patient in definitive prosthesis after completion of rehabilita-tive care.

36


:J

0

C',

0z

in varus, and moderate hypesthesia and motor dysfunction sec-ondary to scarring were present (Fig . 11) . An orthopedic shoe andbrace had been required for many years, and the patient expe-rienced pain on weightbearing.

He was admitted to the Seattle Veterans Administration Hospitalon May 8, 1974, for the treatment of an acute flarcup of the osteo-myelitis, demonstrated by drainage, fever, chills, regional lymphadenopathy, and elevated white count and sedimentation rate.

37


EE

38


Pressures were set at 50 mm Hg for 30 s and 10 mm Hg for 50 s,alternating with the temperature set at 30 deg Celsius (Fig. 13).The drain placed at surgery was removed on the first postoperativeday, and the patient was allowed up in a chair.

Preoperatively, 50 mg of Demerol and 25 mg of Phenergan byintramuscular injection had been required for pain control . Thepatient was kept on this medication for one postoperative day,but at the end of the second postoperative day, only an occasionaloral analgesic was needed . No edema developed ; the patient wasallowed in a walkerette with the CET chamber in place, and nolocal or systemic evidence of infection followed the amputation.

Six days following amputation, because of the patient's rapidand excellent progress, his leg was removed from the CET chamberand placed in an immediate postsurgical prosthetic cast . He wasdischarged from the hospital, ambulatory on crutches, the follow-ing day.

Healing progressed uneventfully (Fig . 14), the definitive pros-thesis was delivered and fitted on the 39th postoperative day, andhe has become a successful, fully rehabilitated amputee, requiringno external aids and carrying out essentially a normal social andwork life.

PRESSURE MM60 -

PRESSURE CYCLE

CASE NO, 2

OW PRESSURE

50 ~

40

30

GH r RESSURE

20-

0

1ea3

5 6

FIGURE 13 . — Case No . 2 : Pressure cycle during CET .

39


0

ro04

V

15 on babk 1) : 33-year-old male,ed a crushing injury with partial mn

a railroad accident . He was taken tomulti

o ;

a debridernent was carried out on theof injury as

ti

)u `ation site closed at a transmetatarsal 1a

40


41


FIGURE 16 . — Case No . 3 : Pressure cycle during CET.

Severe infection with septicemia developed ; the patient was trans-ferred to the Seattle Veterans Administration Hospital, and onJuly 20, 1975, an emergency open amputation was performedjust above the ankle joint to control infection (Fig . 15) . Soft dress-ings were applied . Two days following amputation, the limb wasplaced in the CET bag with pressure readings at 30 mm Hg for 30 son high and 10 mm Hg for 60 s on low, with the temperature setat 32 deg Celsius (Fig . 16) . Local and systemic signs of infectionwere promptly controlled ; pain moderated rapidly.

Ten days following the guillotine amputation, a closed below-knee amputation 18 cm in length was performed, using a longposterior flap . No drain was placed because the wound was dryafter hemostasis and release of the tourniquet . The residual limbwas again placed in the CET chamber, with pressure gradients setat the same levels as previously . On the second postoperative day,a hematoma developed . The limb was removed from the chamber,two sutures were removed, the hematoma evacuated, and the limbreplaced in the CET . The patient then continued to heal unevent-fully with rapid elimination of the edema present at the time ofsurgery and with a comfortable postoperative course . A strain gagehad been applied at the suture line at the time of closure . Thiswas not disturbed, and continuous readings, indicating tissue ten-sion, were taken.

Nine days following amputation, the leg was removed from theCET chamber . Healing was progressing well without infection,

42


0zV

edema, or evidence of necrosis or wound disruption (Fig . 17).Further rehabilitation progressed uneventfully with the rigiddressing technique .

43


A cast and measurement were taken for a definitive prosthesis41 days following amputation . Amputee rehabilitation proceededuneventfully to an excellent functional result.

Case No, 4 : 85-year-old male, admitted to Seattle VeteransAdministration Hospital on March 25, 1974, with severe peripheralvascular disease, ischemia of the lower limbs, and gross edema(Fig. 18) . Associated diagnoses were generalized arterioscleroticcardiovascular disease, congestive heart failure, and severe anemia.

The chief complaint involving the lower limbs was severe restpain in the right foot, increasing over a 3-year period . The patientrequired daily nitroglycerin for control of angina . Four weeks ofmedical supervision were necessary after admittance to preparethe patient sufficiently to withstand a below-knee amputation.This surgery was performed on April 23, 1974, using the classicallong posterior flap technique . The wound was not drained ; CET

FIGURE 18 . -- Case No . 4 : Preoperative appearance of patient with severe peripheral

vascular disease.

44


FIGURE 19 . — Case No . 4 : Residual limb in CET immedial ly following surgery.

PRESSURE CYCLE

CASE NO . 4

HIGH PRESSURE

PRESSURES MM HG60 —

50

40

30

20

10

LOW PRESSURE

11111111%110 1 2 3 4 5 6 7 8 9 10 11 12

POSTOPERATIVEDAY

FIGURE 20 . — Case No . 4 : Pressure cycle during GET .

was initiated immediately (Fig . 19) with a high pressure readingat 50 mm Hg for 30 s, and low pressure at 10 mm Hg for 50 s,alternating, and with the temperature at 38 deg Celsius (Fig . 20).

Pain was minimal ; the patient moved the leg comfortably withinthe chamber, but on the second postoperative day, he experiencedincreasing substernal chest pain and shortness of breath, and devel-oped a recurrence of congestive heart failure . His cardiovascularstatus, including chest pain, was improved by further active medicaltreatment, but the below-knee amputation site did not heal(Fig . 21) ; marginal skin necrosis developed, and it was necessary torevise the amputation to the above-knee level 17 days followingthe initial surgery .

A rigid dressing was applied, tilt table positioning was graduallyinstituted, and the patient was discharged from the hospital 15 daysfollowing the above-knee amputation . Healing progressed unevent-fully (Fig . 22) and 30 days later, the patient was cast and measuredfor a definitive prosthesis . He continues to use the prosthesis athome with a walker and has had no further hospital admissions.He is ambulant for short distances with the prosthesis and walker,lives with his family, and requires no special nursing care.

,flowing amputation . Dry ischemialulitis or infection.

46


FIGURE 22 . — Case No . 4 : Completely healed above-knee amputation.

At the time of the above-knee amputation, the below-knee sitewas studied . There was no infection present ; the failure in healingwas clue to ischemia. This elderly patient was considered a failurein pre-operative level determination . He would normally have hadan above-knee amputation initially ; however, an attempt was madeto salvage the knee since he had been ambulatory prior to hospitali-zation . Judgment as to rehabilitation potential was, however, veri-fied by the fact that 1 yr following the amputation, he was walkingwith an above-knee prosthesis and living at home . This case repre-sented one of two healing failures, neither of which can be attrib-uted to the CET physical environment.

CET Mk II UNIT

following initial clinical trials at Roehampton and Seattle, asmaller, ligher-weight, and quieter version of the CET was con-structed . This unit, designated Mk II (Fig . 4), provides easier oper-ation and control . Of paramount importance is the replacement ofthe deadweight pressure regulator system with a gas-regulated

method. Simple adjustments in pressure, temperature, and cycletimes can be made with controls conveniently located in the frontpanel. The Mk II unit is now standardized equipment, availablecommercially (through the Cape Engineering Company Limited,Warwick, England) as the Cape Sterishield Controlled EnvironmentTreatment System ® .

Capabilities of Equipment

1. Pressure - 0—50 mm Hg, constant pressure or alternatingcycles of high and low pressure.

2. Cycle Time — constant pressure, or a cycle made up of twoalternating periods, each of which may be set at 0-300 s(Mk I) or 0—999 (Mk II).

3. Temperature — from approximately 4 deg Celsius aboveambient room temperature to 40 deg Celsius (3 deg abovebody temperature).

4. Sterility — HEPA bacterial filter (99 .998 percent efficiencyon 0 .6 ,um particles).

5. Humidity — provides reduced relative humidity (air is cooledand rewarmed prior to entering the treatment bag).

6. Gas Composition — room air is routinely used ; however gascomposition may be altered by introduction of other gas;e .g ., Oz.

DEVELOPMENT OF RELATED MANAGEMENT SYSTEMS

The clinical application of GET has provided impetus for thedevelopment of related management systems. These units supplyelevated air pressure for control of edema states which do notrequire a sterile environment . Compared with CET, they cost andweigh less and are more compact.

First to design a related system was the Biomechanical Researchand Development Unit (BRADU), Roehampton, England . TheirPressure Environment Treatment (PET), incorporates all featuresof the CET, with Cm exception of sterility and temperature con-

s . The PRS

in, Modulated Air Controlled EnvironmentGE), has basic i?l y the same capabilities as the PET, with

slightly different treatment ranges and methods of adjustment.Both. the PET and the MACE employ the CET dressing bag.

A third unit, the Rancho Edema Control System, developed atthe Rancho Lo,

s Hospi J , employs a doughnut-shapedseal in its r, .ett

This

i -flated to only three-quartersof the

ded to avoid constriction but to

48

Pressure

High pressure externally

0-30 mm Hgselected for 20, 30, 40

Externally adjustable (no

0-50 mm Hg

0-5f

tie

mm Hg or higher ; low

pressure feedback)

Externally adjus

pressure 10 mm Hginternally adjustable

Continuous or alternating ;

nigh and

Continuous or alternating

0-999 s high and low pres-

le

-essure 0-300 s

high and/or low pressure

Continuous

sure

30, 60, 90 s

Yes

C r

Sterility

Yes

Seal

CET "Doughnut" type ; sealpressure 75% of bag(set) pressure

allow slow leakage from the bag . Unlike the CET, PET, and MACE,the Rancho System provides constant pressure only . A comparativesummary of these treatment systems is seen in Table 2.

CET TRIAL CENTER REPORTS

San Francisco VA Hospital; Wesley S . Moore, M .D.

As of February 25, 1977,8 patients had been managed with CET.Five of these cases were part of a controlled and randomized studyof lower-limb amputations in which CET is being compared withthe Immediate Postsurgical Prosthetic Fitting Technique . Threeadditional cases of venous stasis ulcers were treated with the device,and results were encouraging.

Dr . Moore will report his findings in a separate publication uponcompletion of a larger number of cases . At this time, he remainsenthusiastic about CET ; however he is not yet in a position to mea-sure the advantages or disadvantages in wound healing with eithermethod of postoperative management . His program using CET isongoing, carefully ordered in a scientific statistical manner, andrequires more time before additional conclusions can be drawn.

Dr. Moore was appointed Professor and Head, Section of Vascu-lar Surgery, The University of Arizona Health Sciences Center,College of Medicine, Department of Surgery, Tucson, Arizona, andwill serve as a consultant to the VAH, Tucson, Arizona.

Rancho Los Amigos Hospital ; Downey, California, F. WilliamWagner, Jr., 11I .D.

Between March 1, 1975 and March 31, 1976, CET was used inthe postsurgical management of the first stage of 13 two-stageSyme's amputations, performed for diabetic and dysvascular infec-tion and gangrene. A control group, comprising 41 patients, used abias-cut stocking as the method of postoperative treatment . Aver-age age of combined cases completed during this time period was60.4 years.

Dr. Wagner reported a 62 percent wound healing success in thetrial (CET) group and a 73 percent success in the control group.He feels that at this time it is not possible to determine the advan-tages or disadvantages of CET, as it relates to wound healing prog-ress, compared to conventional wound management systems.

Dr . Wagner is, however, interested in the use of CET as a thera-peutic tool, he has suggested monitoring tissue levels of antibioticsto determine the efficacy of the equipment in management of infec-tion prior to proposed amputation . Rancho Los Amigos Hospitalhas submitted a grant request for a wound healing study using CF,"T.

50


Additional cases involving the use of CET at this facility haveincluded treatment of edema states of the lower limbs, vascularulcers, and well-draining infections (primarily in the ischemic limb).At this time, the Rancho Edema Control System, developed underVeterans Administration financing and sponsorship, is being usedas well in treatment of edema states which do not necessarily re-quire a sterile environment.

Castle Point, New York, VA Hospital: Bok Y. Lee, M.D., Frieda S.Trainor, Ph .D., and David Kanner, Ph .D.

During a 15 month trial period, which began in December 1974,CET was r

in below-knee and distal amputations ' 3 cases) and inthe manager

it of ischemic ulcers (3 cask ) .

vrience hasbe

positive, and CET has been inco,

he treatmentrrr~r~ntarium of the Vascular-Surgi< d

Castle Point.s acility continues to use the equi

satisfied with,'ic .°chnique, particularly in control of ed

, the treatmentculatory and static ulcers

the lower

major interestproject is prevention of

,)utatio : S .

. scalar patients.of the low ampur it VA Hospital

(3

5 yearly), CET is pirn

management of1 4r

erfect of CET onand skin blood

date a flexed elbow.This facility plans to continue incorporation of CET into the care

of postsurgical and posttraumatic hand problems and, at present,is investigating use of the equipment for edema states which do notnecessitate a sterile environment . Hence, the simpler managementsystems (PET, MACE, and Rancho Edema Control S). stem) wouldbe helpful in these situations.

Prosthetics Research Study, Seattle, 11'ashington : Ernest M. Burgess,M.D.

The CET Technique was used by the Prosthetics Research Studyfor a period of approximately 3 years, treating lower-limb amputa-tions immediately postsurgically.

The original upper-limb dressing bags were too short. Modifiedbags have since been constructed to accommodate the entire armup to the axilla, however there is still a need for a banana-shapedbag to provide for elbow flexion.

Twenty below-knee amputations were managed with CETbetween March 1974 and December 1975 . The result of thatclinical study is incorporated in the first part of this paper.

Since December 1975, 20 additional below-knee amputationshave been treated with the equipment in Seattle. Use of the deviceduring the past 12 months has also included treatment of upperand lower limb edema states (5 cases) in which amputation was notinvolved. Application of CET concepts has been extended in modi-fied form, with the development of the MACE at ProstheticsResearch Study, for control of limb edema conditions and for theimmediate management of closed limb trauma, primarily about theknee and ankle.

At the present time, four CET units are available to this investi-gator . Two are stationed at the Seattle VA Hospital, principallyfor the postsurgical care of lower-limb amputations, and a thirdis located at Providence Hospital in Seattle for similar use . A fourthunit is situated at the Harborview Medical Center, Seattle (a Uni-versity of Washington affiliate) where a wide variety of freshtrauma, including compartmental syndromes, closed fractures, andjoint injuries, are available for study.

The simplified MACE unit has been loaned directly to the De-partment of Biomedical Engineering and Orthopaedics at theUniversity of Washington, where basic research is underway tostudy the effects of external pressure . Here, the device is being used(in conjunction with supplementary electronic equipment) to mea-sure surface and muscle blood flow in the limbs of a rabbit animalmodel . Data derived from these studies will be translated to clinical

52


application of the CET and related management systems.

Conclusions Reported from Investigating Centers

Advantages of CET:1 . CET is easy to apply and to operate.2 CET provides uniform pressure, regardless of limb volume

changes, there is no danger of a tourniquet effect or localizedpressure areas.

3. CET provides a dry wound surface and sterile environment,conducive to wound healing.

4. CET allows visual inspection and palpation of the wound sitewithout disturbing the sterile environment.

5. CET provides edema control.6. In the absence of postsurgical complications, patients report

minimal discomfort using CET.7. Patient acceptance of CET is positive.8. CET permits freedom to carry out knee flexion exercises.

Disadvantages of CET:1. Originally the noise disturbed patients . This problem is now

essentially eliminated with the quieter Mk II CET.2. Weightbearing is delayed with CET.3. Mobility is somewhat limited with CET ; some patients be-

come restless if treatment is extended for a long period oftime.

4. Careful nursing is required to prevent decubiti in debilitatedpatients.

5. CET does not provide residual limb contouring.6. Syme 's amputees have difficulty ambulating because the

dressing bag hose connection contacts the floor . (Redesignedtreatment bags have helped to alleviate this problem .)

Summary of CET Equipment Malfunctions

Mechanical problems encountered during use of the equipmentwere corrected through a joint effort on the part of the PRS engi-neering staff, BRADU, and appropriate personnel at the varioustrial centers . The most common equipment malfunction was cool-ing fan failure, which occurred at the Duke University MedicalCenter, the Castle Point VA Hospital, and in three of the four unitsat the Prosthetics Research Study . In addition, it was necessary torewind the main compressor motor at Castle Point and to replace aburned-out main blower bearing at the San Francisco VA Hospital.Current Mk II CET units employ an improved cooling fan model,which provides increased durability .

Recommendations from Investigating Centers

Overall experience with CET at the participating trial centershas been positive . All investigators view this system of managementas a viable technique and are enthusiastic about its continued useand extension into other areas of treatment . The following recom-mendations were suggested at an evaluation workshop held inSeattle in May 1976:

1. At this time, CET offers an alternative to conventional sys-tems of wound management . A long-range controlled and random-ized study is needed to ascertain the effectiveness of CET on woundhealing progress, i .e ., to determine where CET stands in relation toconventional techniques for managing ischemic ulcers, amputations,and hand pathology.

2. There is a need to extend the use of CET into several areasof treatment in order to define where CET can be most effectivelyused .

3. A jointly controlled study involving all investigating centers,will provide comparative results in a short period of time.

4. Further basic research should be carried out to determinethe effects of CET on tissue physiology . Particular emphasis shouldbe placed upon the nature of the CET cycle times and pressurephases as they relate to the status of peripheral circulation, tissuecompartment pressure changes, and tissue gas concentrations.

5. Immobilization of the limb within the treatment bag is animportant area to explore, e .g., the possibility of splints to supportfractures or the long posterior flap in below-knee amputationsurgery.

6. Protocols should be prepared for the above phases of CETinvestigation .

DISCUSSION AND CONCLUSIONS

Wound healing, a process of tissue regeneration and repair,relates directly to restoration of function . The external physicalenvironment in which tissues heal and the influence of these en-vironmental forces on clinical wound healing are the bases of thisstudy.

Thermal injury, i .e ., burn and frostbite, has attracted the mostinterest in external healing environment . There is need for improve-ment in understanding and treating all types of tissue trauma inan optimum physical environment during healing.

This study outlines our observations using a controlled systemof environmental management following the surgery of amputa-tion . Amputations were selected as a pilot clinical study because

54


this operation without distal tissue to support constitutes anexcellent, controllable wound healing model . Our experience in thefirst 20 below-knee amputations using this specific ControlledEnvironment Treatment technique has encouraged us to extend thismanagement system to a wide variety of types of trauma anddisease of the limbs . Contraindications to this management systemwould be those circumstances in which the application of externalpressures could be harmful . Posttraumatic compartmental syn-dromes unrelieved by fasciotomy, infections (particularly closedspace infections), undrained hematomas, and thromboembolicstates exemplify situations in which CET could possibly produceharm.

A major drawback of the CET device in the management ofamputees is the inability to ambulate these patients, except withdifficulty and with no terminal wound support . We are stronglycommitted to postsurgical immobilization, i .e ., a rigid dressing.It is of considerable advantage to be able to visually inspect thehealing amputation with CET, but we favor a rigid dressing forsupport . With these factors in mind, we are currently exploringmethods to immobilize the residual limb within the treatment bagin order to obtain the advantages of external wound support andtissue rest, as well as the modalities provided by the CET equip-ment.

Good experience using this specific system of Controlled En-vironment Treatment has encouraged the cooperating centers notonly to continue it for amputations but to extend this managementtechnique to a wide variety of trauma and disease of the limbs.

Prosthetics Research Study anticipates extended use of the CET.We believe it fills a need in many areas of limb and, in fact, trunktrauma disease . We continue to document case results and plan torecord our experience with further publication.

ACKNOWLEDGMENT

The authors wish to acknowledge the dedicated assistance pro-vided in this research by Patricia A. Seth, CET Project Coordinator,Prosthetics Research Study, Seattle, Washington.

REFERENCES

1 . Ashton, H . : The Effect of Increased Tissue Pressure on Blood Flow . Clin . Orthop .,113 :15-26, 1975 .

2. Berlemont, IA., R . Weber, and J . P . Willot : Ten Years of Experience with the Imme-diate Application of Prosthetic Devices to Amputees of the Lower Extremities on theOperating Table . Pros . Int., 3(8) :8-18, 1969.

3. Blair, V. P . : The Influence of Mechanical Pressure on Wound Healing. Ill . Med. J .,46 :249-252, 1924 . (Reprinted in Plast . Reconstr . Surg., 43 :186-189, 1969 .)

4. Burgess, E . M . and F . W . Marsden : Major Lower Extremity Amputations FollowingArterial Reconstruction . Arch . Surg ., 108 :655-660, 1974.

5. Burgess, E . M . and R . L . Romano : The Management of Lower Extremity AmputeesUsing Immediate Postsurgical Prostheses . Clin . Orthop ., 56 :137-146, 1968.

6. Burgess, E . M ., R . L. Romano, J . H. Zeal, and R. D. Schrock : Amputations of theLeg for Peripheral Vascular Insufficiency . J . Bone and Joint Surg., 53-A :874-890,1971.

7. Burgess, E . M ., G . A . Spolek, and A . J . Moore : Postoperative Measurement of SkinTension . Bull. Prosth . Res ., BPR 10-28 : 4-15, Fall 1977.

8. Burgess, E . M ., J . E. Traub, and A . B . Wilson : Immediate Postsurgical Prosthetics inthe Management of Lower Extremity Amputees . TR 10-5, U .S . Government PrintingOffice, Washington, D .C., 1967.

9. Department of Health and Social Security, Biomechanical Research and DevelopmentUnit : Controlled Environment Wound Management Equipment . Roehampton,England, January 1974 . Unpublished.

10. Department of Health and Social Security, Biomechanical Research and DevelopmentUnit : The B .R .A.D .U . Controlled Environment Equipment, Mk 1B, U.S.A . Version,Instructions for Operation. Roehampton, England, September 1974 . Unpublished.

11. Devito, R . V . : Healing of Wounds . Surg . Clin. North America, 45 :441459, 1965.12. Dingman, R. O. : Factors of Clinical Significance Affecting Wound Healing . Laryngo-

scope, 83 :1540-1555, 1973.13. Holloway, G. A., C . H . Daly, D . Kennedy, and J . Chimoskey : Effects of External

Pressure Loading on Human Skin Blood Flow Measured by 133 Xe Clearance . J . Appl.Physiol ., 40 :597-600, 1976.

14. Klein, R . W. and D. J . Roebuck : The Immediate Weight-bearing Prosthesis . Med . J.Australia, 1 :56-61, 1967.

15. Matsen, F . A ., and D. K . Clawson : The Deep Posterior Compartmental Syndrome ofthe Leg . J . Bone and Joint Surg ., 57-A :34-39, January, 1975.

16. Matsen, F . A ., and R. B . Krugmire : The Effect of Externally Applied Pressure onPost-Fracture Swelling . J . Bone and Joint Surg ., 56-A :1586-1591, December 1974.

17. Matsen, F . A., K. A . Mayo, G . W . Sheridan, and R . B . Krugmire : Monitoring ofIntramuscular Pressure . Surgery , 79 :702-709, 1976.

18. Moore, W. S ., A. D. Hall, and R . C . Lim : Below the Knee Amputation for IschemicGangrene . Comparative Results of Conventional Operation and Immediate Postopera-tive Fitting Technic . Anil Surg ., 124 :127-134, 1972.

19. Moore, W. S ., A . D. Hall, and E . J . Wylie : Below Knee Amputation for VascularInsufficiency . Experience with Immediate Postoperative Fitting of Prosthesis . Arch.Surg ., 97 :886-893, 1968.

20. Murdoch, G . : Levels of Amputations and Limiting Factors . Ann . Roy . Coll . Surg.,40 :204-216, 1967.

21. Peacock, E . E . : Biologic Frontiers in the Control of Healing . Am . J . Surg ., 126 :708-713, 1973.

22. Redhead, R . G . : The Problems of the Postoperative "Stump/Environment Interface ."In Proceedings of the First International Congress on Prosthetic Techniques andFunctional Rehabilitation, pp . 65-73 . Vienna, Egermann Druckereigesellschaftm .b .H ., 1973.

23. Sabri, S ., V . C . Roberts, and L. T . Cotton : Effects of Externally Applied Pressure onthe Haemodynamics of the Lower Limb . British Med J ., 3 :503-508, 1971.

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24. Schilling, J . A . : Wound Healing. Physiol . Rev ., 48 :374423, 1968.25. Sisiruca-Quintero, H . and A . Gonzalez-Naves : Mioplastia, Miodesis, Periostioplastia.

Nueva Tecnica Quirurgica en la Rehabilitacion del Amputado por Encima de laRodilla . Tribuna Med ., 35 :A13-A16, 1972.

26. Weiss, M . : The Prosthesis on the Operating Table from the Neurophvsiological Pointof View . Report of Workshop Panel on Lower Extremity Prosthetic Fitting . NationalAcademy of Sciences, Committee on Prosthetics Research and Development, Febru-ary 1966.

27. Wilson, P . D . : Early Weightbearing in the Treatment of Amputations of the LowerLimbs. J . Bone and Joint Surg., 4 :224-247, April 1922 .

controlled environment treatment ernest m . burgess,;triction that could impede circulation within...

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