INJURY CLINIC
Sports Medicine 12 (5): 338-346, 1991 0112-1642/91/0011-0338/$04.50/0 © Adis International Limited. All rights reserved. SP0156a
Rehabilitation Concerns Following Anterior Cruciate Ligament Reconstruction Philip A. Frndak and Carl C. Berasi Doctors Hospital, Columbus, Ohio, USA
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Summary
Summary I. Early Motion 2. Protection of the Biological ACL Graft 3. Strength Recovery 4. Neuromuscular Re-Education 5. Knee Braces 6. Conclusion
Rehabilitation following anterior cruciate ligament reconstruction is a subject of controversy in the orthopaedic and rehabilitation literature. With an increasing number of these operations currently being performed and with the advent of arthroscopically assisted ACL reconstruction over the past several years, particular rehabilitation needs and problems have been identified in association with these patients. Various authors have stressed one or a combination of a few basic themes which outline the basic rehabilitation concerns following ACL reconstruction. The most fundamental concern is the need to initiate motion very soon after surgery. Prolonged postoperative immobilisation is known to cause serious complications after ACL reconstruction which can be avoided by early motion. Positions or activities which may apply excessive stress to a newly reconstructed ACL must also be considered. The amount of protection required by the graft will vary depending upon the type of graft used and the quality of fixation obtained intraoperatively. Most authors agree that nonweightbearing, active resistive quadriceps exercises should be avoided for an extended period, while closed chain exercises may be initiated much earlier_ Strength recovery is obviously important for the quadriceps postoperatively, but maximal strength returns of all of the muscles about the knee must be pursued. Hamstring strength is of particular concern as this may provide an active support to the reconstructed ACL. Sensory loss in the knee after ACL disruption should also be addressed during rehabilitation, prior to a patient's return to full athletic activity. Progressive neuromuscular re-education exercises which rely on sensory input from intact pericapsular structures are encouraged. A final concern is the role of bracing after ACL reconstruction. Rehabilitative braces are in common use postoperatively to limit the patient's knee motion to that dictated by the physician. The use of braces during heavy athletic activity following anterior cruciate ligament reconstruction is less well supported by the literature. Although the physician may choose to prescribe such
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a device, the role of a brace must be considered secondary in comparison to the need for a strong, agile lower extremity to protect the ACL graft. In conclusion, the trends in rehabilitation following ACL reconstruction are increasingly focused on maximising the rate of recovery and return to full function while achieving optimal results. To reach this goal, a thorough understanding of the rehabilitation approach is necessary. In addition, significant questions remain with respect to the amount of stress a newly reconstructed ACL is able to tolerate during the various phases of recovery.
The goal after anterior cruciate ligament reconstruction is a biomechanically normal knee with respect to motion, strength and stability. Current techniques in arthroscopic reconstruction restore passive stability assuming that the new ligament is well placed (Jackson & Jennings 1988; Melhorn et al. 1987; Penner et al. 1988), strong enough to withstand physiological stresses (Blackburn 1985; Graf & Uhr 1988; Noyes et al. 1984), and is permitted to heal in this position without disruption or displacement (Arms et al. 1984; Draganich et al. 1989; Graf & Uhr 1988; Grana & Muse 1988; Kurosaka et al. 1987; Maltry et al. 1989). Motion, strength and dynamic stability must be regained during postoperative rehabilitation. Large studies documenting the long term benefits after ACL reconstruction utilising current techniques are not in abundance, but those published offer encouraging data (Boden et al. 1990; Sandberg et al. 1988; Seto et al. 1988; Tibone & Antich 1988). The reconstructed knees appear to be stronger, more stable and better able to withstand the stresses of athletic performance than ACL-deficient knees (Clancy et al. 1982; Tibone & Antich 1988). Today, as in other areas of orthopaedics, emphasis is increasingly focused on maximising the rate of recovery and return to full function while achieving optimal results (Jackson & Jennings 1988). Various themes arise repeatedly in the literature which address rehabilitation approaches after ACL reconstruction. These include avoidance of the complications of prolonged immobilisation (Anderson & Lipscomb 1989; Graf & Uhr 1988; Huegel & Indelicato 1988; Jakson & Jennings 1988; Konh 1990; Noyes et al. 1984, 1987; Shelbourne & Nitz 1990; Sprague 1987; Wilcox et al. 1987),
avoidance of positions or actIVItIes which may compromise the integrity of a freshly placed graft (Anderson & Lipscomb 1989; Arms et al. 1984; Blackburn 1985; Delitto et al. 1988b; Graf & Uhr 1988; Grana & Muse 1988; Huegel & Indelicato 1988; Kain et al. 1988; Kurosaka et al. 1987; Noyes et al. 1984; Paulos et al. 1981; Steadman 1983; Wilcox et al. 1987), the need to regain muscular strength after surgery (Anderson & Lipscomb 1989; Baratta et al. 1988; Coughlin et al. 1987; Delitto et al. 1988b; Draganich et al. 1989; Elmqvist et al. 1989; Huegel & Indelicato 1988; Paulos et al. 1981; Sisk et al. 1987; Steadman 1983; Wilcox et al. 1987), the importance of neuromuscular re-education to maximise coordination and fine kinaesthetic control (Anderson & Lipscomb 1989; Baratta et al. 1988; Blackburn 1985; Draganich et al. 1989; Gerber et al. 1985; Huegel & Indelicato 1988; Paulos et al. 1981; Seto et al. 1988; Solomonow et al. 1987; Steadman 1983) and the role of bracing after surgery (American Academy of Orthopaedic Surgeons 1984; Bessette & Hunter 1990; Shelbourne & Nitz 1990). Presented below is a review of these concerns based on the current literature.
1. Early Motion Less than 10 years ago at least 6 weeks of strict immobilisation was the norm after ACL reconstruction (Anderson & Lipscomb 1989; Arms et al. 1984; Clancy et al. 1982; Huegel & Indelicato 1988; Malone et al. 1980; Paulos et al. 1981; Steadman 1983). Complications associated with this approach included intra-articular adhesions, infrapatellar adhesions, patellofemoral crepitation, joint stiffness and profound quadriceps atrophy (Anderson & Lipscomb 1989; Graf & Uhr 1988; Sprague
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1987; Wilcox et al. 1987}. Other complications associated with immobility are also well described and include declines in the biomedical properties of bone, ligament and cartilage (Anderson & Lipscomb 1989; Noyes et al. 1977; Salter et al. 1980). In the mid 1980s the literature began to reflect a thrust to move the freshly operated knee more quickly in an effort to avoid these complications (Noyes et al. 1984, 1987). The literature however, is not in complete agreement with respect to how soon the knee should be moved, or with what restrictions after an intra-articular reconstruction. Continuous passive motion has been utilised immediately after surgery by many (Anderson & Lipscomb 1989; Graf & Uhr 1988; Shelbourne & Nitz 1990), while others prefer early passive motion following a brief period of immobilisation, typically lasting 2 weeks or less (Huegel & Indelicato 1988). Frequently, motion is permitted very early although with restrictions in range. Anderson and Lipscomb (1989), for example, examined various protocols of rehabilitation following ACL reconstruction, including one which provided 2 weeks ofimmobilisation followed by limited passive motion from 35 to 70°. Full extension was delayed for 3 months in this protocol. On the other hand, Graf and Uhr (1988), Wilcox et al. (1987) and Shelbourne and Nitz (1990) encourage immediate full range of motion. The rationale for limiting extension and initiating only passive motion in the early postoperative phase (Huegel & Indelicato 1988) is discussed in the following section.
2. Protection of the Biological ACL Graft Investigation of the biomechanics of the knee has identified numerous positions and activities which induce a traction stress on the intact anterior cruciate ligament (Arms et al. 1984; Gerber et al. 1985; Henning et al. 1985; Jurst & Otis 1985; Kain et al. 1988; Maltry et al. 1989; Noyes et al. 1987). Examination of passive positioning has revealed that the maximally flexed and extended position of the knee cause increased stress on an intact ACL, in comparison to mid-range positions (Gerber et
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al.1985). For this reason some authors encourage avoidance of these postures in the early phases after ACL reconstruction. Active, isolated quadriceps contraction in a nonweightbearing position is also associated with a potentially undesirable anterior drawer force on the proximal tibia, particularly from 45" to full extension (Arms et al. 1984; Henning et al. 1985; Huegel & Indelicato 1988). The vector associated with this force increases steadily until full extention is achieved. This stress can be neutralised by the use of simultaneous isometric co-contractions of the hamstrings with the quadriceps (Anderson & Lipscomb 1989; Arms et al. 1984; Blackburn 1985; Nitz & Dobner 1987) or by disallowing extension beyond 60° when performing isolated quadriceps contractions (Anderson & Lipscomb 1989; Arms et al. 1984; Jurst & Otis 1985; Maltry et al. 1989). Isometric co-contraction of the hamstrings with the quadriceps adds a posterior drawer force to the proximal tibia to neutralise the anteriorly directed stress induced by the quadriceps. This technique is believed to protect the ACL from excessive traction stress except in full extension. Alternatively, by positioning the knee in 60° of flexion during the exercise, the vectors associated with isolated quadriceps contractions are altered to minimise any force towards anterior subluxation. Utilising techniques such as these allows the initiation of safe quadriceps strengthening exercises much earlier than is otherwise possible after ACL reconstruction. Typically, routine active resistive quadriceps strengthening exercises are delayed for several months following ACL reconstruction (Huegel & Indelicato 1988; Wilcox et al. 1987), and as long as a year in one report (Henning et al. 1985). The exercises discussed above are begun within the first 2 weeks after surgery (Delitto et al. 1988a,b). Other activities, such as weightbearing exercises and cycling, have been examined with respect to a reference stress manoeuvre. Such activities provide another means of safely strengthening the lower extremity during the early postoperative phases. Lower extremity weightbearing, in a position such as a I-leg half-squat, requires simultaneous quad-
Rehabilitation After ACL Reconstruction
riceps and hamstrings contractions (Tiberio & Gray 1989). The quadriceps group functions concentrically to extend the knee, isometrically, or eccentrically to limit further knee flexion. During this activity the hamstrings function concurrently as strong hip extensors. This simultaneous contraction of the hamstrings with the quadriceps, along with axial compression of the joint surfaces, effectively limits anterior translation of the proximal tibia on the femur which would etherwise occur with an isolated, nonweightbearing quadriceps contraction of equal intensity (Fanton 1987; Shelbourne & Nitz 1990). Biomechanical principles such as these can be applied to safely accelerate the rehabilitation approach after ACL reconstruction. To provide an illustration, Henning et al. (19S5) looked at ACL stresses compared to a reference 80lb Lachman manoeuvre. Cycling produced 7% as much elongation as an 80lb Lachman test. A I-leg half-squat produced 21 % and quadriceps contractions against a 20lb weight boot at 45" of knee flexion produced 50% as much elongation as the reference manoeuvre. Quadriceps contractions near the terminal ranges of knee extension produced elongation forces of 87 to 121 % of their reference 80lb Lachman manoeuvre. They believe that the proper order of a rehabilitation programme should be crutch walking, cycling, walking, slow running and faster running. The surgeon's choice of an ACL replacement and the type of fixation utilised are also major factors in considering the amount of protection necessary for a freshly placed ACL graft (Indelicato et al. 1989; Kurosaka et al. 1987; Noyes et al. 1984). The type of healing that the graft is expected to undergo, the specific strength of the graft chosen and the quality of fixation obtained at the time of surgery should all be considered in deciding how much stress on the graft to permit during the healing phases. Although insufficient research has been done in this area, some facts have been established. During the early stages of healing, failure of an ACL graft typically occurs at the fixation site (Noyes et al. 1984). The commonly utilised middle onethird patellar tendon graft is believed to become fixed in position via bony and or fibrous healing
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within 6 to 8 weeks of surgery (Huegel & Indelicato 1988), but some reports have stated that 3 to 4 months may be necessary for the reconstructed graft to have solid anchorage at the fixation site (Noyes et al. 1984). Revascularisation and remodelling of the graft is a longer process which may be just reaching its peak 6 months following surgery (Graf & Uhr 1988; Huegel & Indelicato 1988). During this time the integrity of a graft is particularly compromised. The mechanical strength of the revascularised and remodeled patellar tendon graft is less than 50% of the original ACL 3 to 4 months after surgery (Currier & Mann 1983; Noyes et al. 1984). On the other hand, this type of biological graft is considered the strongest of the commonly utilised ACL substitutes. A 14mm wide bone-patellar tendon-bone autograft measures 168% as strong as a healthy anterior cruciate ligament during in vitro testing (Kurosaka et al. 1987; Noyes et al. 1984). When compared to other tissues about the knee, this graft has been found to have the greatest strength within its substance (Noyes et al. 1984) as well as the greatest pullout strength when secured through interference fit with a large diameter cancellous screw (Kurosaka et al. 1987). The significance of this information is that each type of anterior cruciate ligament graft will have different inherent limitations in its ability to withstand stress. Depending on the specific graft which has been used to replace the normal ACL, the rehabilitation approach may require alteration to provide either increased protection or freedom of activity. Additionally, it is essential to understand the biological limitations of the healing process when planning a progressive rehabilitation programme. Although it may be tempting to initiate more advanced activities as soon as the patient 'feels ready', the state of healing of the graft should always be of primary consideration. Maximally stressful activities should be avoided until the substitute ACL is believed to be strong enough to withstand heavy forces. In summary, it appears that certain activities may be placed on a rough scale with respect to the amount of traction they tend to impart to the ACL. At one end of the spectrum the least amount of
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stress on the ligament" would be strict immobilisation in a position of 30 to 40° of flexion. Relatively minimal stress on the ligament occurs with passive motions from 60 to 30°. Full passive range of motion, cycling and crutch walking with partial weightbearing may be the next level of activity, followed by full weightbearing. Lower extremity strengthening through the use of weightbearing exercises should follow, while isolated nonweightbearing quadriceps contractions near the final degrees of extension should be near the top end of this scale. The maximum stress studied by Henning et al. (1985) and Arms et al. (1984) was apparently nonweightbearing, actively resisted knee joint extension to 0°. Although not specifically mentioned in these studies, all of the above would be much less stressful than the potential forces acting on the knee during certain athletic activities. Important information has been accumulated regarding the ways in which various biological ACL replacements compare with each other in the laboratory setting, as well as how much stress various activities induce within the normal ACL in comparison to one another. However, the exact amount of stress that is applied in vivo is unknown and exactly how much stress each graft can safely tolerate during postoperative healing remains in question.
3. Strength Recovery Another theme frequently arising in the literature is the need for strength recovery after ACL reconstruction (Anderson & Lipscomb 1989; Baratta et al. 1988; Draganich et al. 1989; Elmqvist et al. 1989; Graf & Uhr 1988; Kain et al. 1988; Seto et al. 1988; Solomonow et al. 1987; Tibone & Antich 1988). Some of the issues in this topic have already been discussed above, but it is of importance to note that profound quadriceps atrophy occurs in association with an ACL tear (Huegel & Indelicato 1988). Most reports have failed to show complete normalisation of quadriceps strength in these patients when compared to their nonoperative side, in spite of postoperative assessments long after the index surgery (Elmqvist et al. 1989; Ti-
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bone & Antich 1988). Research has explored the types of quadriceps muscle fibres which could atrophy disproportionately in comparison to others in an effort to identify the rates of speed at which a patient should exercise preferentially in the rehabilitation phase. Histological studies have, however, shown a uniform reduction in type I and type II muscle fibres, indicating that strengthening at every speed of contraction is equally important (Gerber et al. 1985). The role of the hamstring musculature in the strength needs of this patient group is controversial (Antich & Brewster 1988; Baratta et al 1988; Barrack et al. 1989; Draganich et al. 1989; Paulos et al. 1981; Seto et al. 1988; Solomonow et al. 1987). The quadriceps are known to atrophy to a much greater extent than the hamstrings and for this reason some authors have encouraged emphasis on strengthening the knee extensors preferentially (Huegel & Indelicato 1988). Others have documented the role of the hamstrings as a dynamic stabiliser of the knee (Antich & Brewster 1988; Baratta et al. 1988; Solomonow et al. 1987). Reflex arcs from the intact ACL and the joint capsule have been identified which support the likelihood that the hamstrings normally function to prevent overload of the ACL (Solomonow et al. 1987). For this reason some authors have encouraged supernormal strength goals for the hamstring muscles in an effort to protect the reconstructed ACL and improve the ability of the patient to withstand the severe stresses placed on the ligament during athletic competition (Barrack et al. 1989; Tibone et al. 1986). Giove et al. (1983) have documented that higher levels of sports participation are found in ACL-deficient patients whose hamstring strength is equal to or more than their quadriceps strength. In these individuals the quadriceps strength was improved to near normal and the hamstrings to a higher than normal level when compared to their unaffected side. Electrical muscle stimulation (EMS) is a subtopic in the strengthening theme discussed in the literature (Currier & Mann 1983; Delitto et al. 1988a,b; Kain et al. 1988; Nitz & Dobner 1987; Selkowitz 1985; Sisk et al. 1987; Soo et al. 1988).
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The primary goal in the use of EMS is the minimisation of postoperative atrophy. Numerous articles have addressed this technique with somewhat conflicting results. Delitto et al. (l988a,b), Nitz & Dobner (1987) and others have described significant clinical benefits from the use of EMS in the thigh musculature of patients with an injured, immobilised lower extremity. The benefits reported include decreased strength loss in the early postoperative phase, more rapid gains in range of motion, and increased overall rate of return to athletic activity. Other authors have reported less optimistic results, stating that EMS was no more effective than volitional exercise in maintaining thigh muscle strength in their studies (Selkowitz 1985; Sisk et al. 1987). Due to the numerous variables involved in the use of EMS it is very difficult to compare individual studies. Several factors may contribute to greater effectiveness in the use of electrical muscle stimulation. These include the ability of some to tolerate greater intensities of stimulation and therefore greater strengths of contraction, the potential for direct electrical stimulation to overcome reflex muscle inhibition caused by painful periarticular structures and the possibility of a pain-blocking effect of electric stimulation (Delitto et al. 1988b; Kain et al. 1988; Selkowitz 1989). Studies which examined healthy subjects must be differentiated from those which dealt with postoperative patients. The use of EMS in healthy subjects is known to produce strength gains similar to those with volitional exercise (Selkowitz 1989). Direct electrical muscle stimulation may potentially be of greater benefit than volitional exercise alone to minimise strength losses in the immediate postoperative phase. This issue is controversial (Delitto et al. 1988a,b; Sisk et al. 1987).
4. Neuromuscular Re-Education Another theme recurring in the literature of rehabilitation after ACL reconstruction is the need for neuromuscular re-education (Elmqvist et al. 1989; Huegel & Indelicato 1988). Preathletic training exercises have been suggested for several years
to help bridge the gap between routine postoperative rehabilitation and return to competitive athletic performance (Blackburn 1985; Huegel & Indelicato 1988; Paulos et al. 1981; Steadman 1983). Now it is known that the intact ACL had an important sensory function in the normal knee (Barrack et al. 1989; Draganich et al. 1989; Gerber et al. 1985; Solomonow et al. 1987). Mechanoreceptors have been demonstrated within the intact ACL which could be able to detect joint position as well as s.udden or slow joint position changes (Barrack et al. 1989; Draganich et al. 1989; Gerber et al. 1985). A decrease in overall neuromuscular drive may be responsible for the refractory strength and girth losses typically sustained by the quadriceps musculature after ACL disruption (Elmqvist et al. 1989). Correspondingly, there is information which indicates that the hamstrings are more active than usual in the ACL deficient knee, indicating the likelihood of additional reflex arcs between other pericapsular and capsular knee joint structures with the hamstrings (Draganich et al. 1989; Solomonow et al. 1987). This lends increased support to the role of the hamstrings as a dynamic knee joint stabiliser. The goal of preathletic training exercise is that through gradual introduction of increasingly complex knee joint activities the patient may be able to learn to rely more heavily on the knee's remaining proprioceptive structures (Draganich et al. 1989; Elmqvist et al. 1989; Solomonow et al. 1987). In general, these activities are begun late in the rehabilitation period prior to return to athletic activity, but passive cycling is one example of a proprioceptive training activity which could be initiated comparatively early.
5. Knee Braces Finally, the role of knee bracing following anterior cruciate ligament reconstruction requires comment. There are 3 basic categories of knee braces used today. Prophylactic knee braces are designed to prevent or reduce the severity of knee injuries. Rehabilitative knee braces are intended to allow protected motion of injured knees treated
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Table I. A typical patellar tendon graft rehabilitation programme Postoperative Immediately after surgery CPM 20 to 900 Don Joy rehabilitative brace 20 to 900 Active hamstring ROM Ankle AROM Crutches (nonweightbearing) 1 week CPM continued at home until ROM is full and easy Full ROM when supervised by the physical therapist Avoidance of hyperextension or active extension PREs ankle motions Cycling (operative extremity passive) Hamstring PREs Unrestricted hip exercises - avoid active quadriceps exercises 2 weeks All of the above continued throughout rehabilitation 25% partial weightbearing with crutches Begin closed chain quadriceps exercises 3 weeks 50% partial weightbearing with crutches Progress closed chain quadriceps exercises (include squats 45 to 900 ) 4 weeks 75% partial weightbearing with crutches 5 weeks Full weightbearing Discontinue rehabilitative brace B weeks Continue to progress all of the above Add isometric quadriceps exercises 45 to 900 (variable positions) Progress squats to full extension 4 months Start 00 for quadriceps activity (SLRs and 'short arc quads' without resistance) Begin pool running 6 months Isokinetic quadriceps exercises Begin aggressive cycling Emphasise maximal strength returns at all degrees of knee extension and at all speeds of contraction Begin normal running at 7.5 months Progress through agility drillS as strength and function progress Resume competitive athletics No earlier than 9 months Full ROM Quadriceps strength to at least 90% of uninvolved LE No pain or swelling Successful completion of preathletic agility training (general and sport-specific) Abbreviations: CPM = continuous passive motion; (A)ROM =
(active) range of motion; PRE = progressive resistive exercise; SLR = straight leg raise.
operatively or nonoperatively. Functional knee braces attempt to provide stability for unstable knees during strenuous activity (American Academy of Orthopaedic Surgeons 1984). Many surgeons will employ a rehabilitation brace immediately after surgery to permit a limited amount ofknee motion (Cawley et al. 1989). This approach was mentioned above. Several braces are available which can predictably limit flexion and extension. They are designed to permit the surgeon to prescribe the amount of knee joint excursion desired and enable this prescription to be altered as needed through simple adjustments. Functional braces are also utilised to protect a stable knee with a reconstructed ACL. Many physicians will encourage their patients to use a brace in this capacity during strenuous activity (Shelbourne & Nitz 1990), but it is understood that these devices are only effective at low levels of stress (American Academy of Orthopaedic Surgeons 1984; Bessette & Hunter 1990). The demands placed on the ACL during athletic performance far exceed the levels at which functional braces have been proven to be effective (Bessette & Hunter 1990). Patients must be encouraged and educated in the reasons for maintaining a maximally strong, agile lower extremity to protect their knee. A brace must be considered of secondary importance.
6. Conclusion In view of the recent literature, rehabilitation following reconstruction of the anterior cruciate ligament appears to be following specific trends. Table I outlines our basic postoperative approach as determined through review of the literature and personal experience. The recent literature has suggested a more accelerated rehabilitation approach which may also be effective in some circumstances. The goals of rehabilitation after ACL reconstruction are early motion postoperatively, maximal strength return and continued intensive rehabilitation efforts through advanced levels of activity. The need to avoid the complications of prolonged immobility has been discussed, in addition to the
Rehabilitation After ACL Reconstruction
importance of an aggressive strengthening and neuromuscular re-education programme. Many important questions remain unanswered regarding the optimal way to reach the goal of a maximally functional knee following anterior cruciate ligament reconstruction. Perhaps the most fundamental of these is simply how much stress can a reconstructed anterior cruciate ligament safely withstand during the various stages of healing? A better understanding of these constraints would enable optimal therapeutic efforts within the limits of the biological needs of an ACL graft.
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and histological study in primates. Clinical Orthopedics 123: 210-242, 1977 Paulos L, et al. Knee rehabilitation after anterior cruciate ligament reconstruction and repair. American Journal of Sports Medicine 9: 140-149, 1981 Penner D, et al. An in vitro study of anterior cruciate ligament graft placement and isometry. American Journal of Sports Medicine 16: 238-243, 1988 Salter R, et al. The biological effects of continuous passive motion on the healing of full-thickness defects in articular cartilage. Journal of Bone and Joint Surgery 62A: 1232-1251, 1980 Sandberg R, et al. The durability of anterior cruciate ligament reconstruction with the patellar tendon. American Journal of Sports Medicine 16: 341-343, 1988 Selkowitz D. Improvement in isometric strength of the quadriceps femoris muscle after training with electrical stimulation. Physical Therapy 65: 186-195, 1985 Selkowitz D. High frequency electrical stimulation in muscle strengthening. American Journal of Sports Medicine 17: 103III, 1989 Seto J, et al. Assessment of quadriceps/hamstring strength, knee ligament stability, functional and sports activity levels five years after anterior cruciate ligament reconstruction. American Journal of Sports Medicine 16: 170-180, 1988 Shelbourne KD, Nitz P. Accelerated rehabilitation after anterior cruciate ligament reconstruction. American Journal of Sports Medicine 18: 292-298, 1990 Sisk T, et al. Effect of electrical stimulation on quadriceps strength
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after reconstructive surgery of the anterior cruciate ligament. American Journal of Sports Medicine 15: 215-220, 1987 Solomonow M, et al. The synergistic action of the anterior cruciate ligament and thigh muscles in maintaining joint stability. American Journal of Sports Medicine 15: 207-213, 1987 Soo C, et al. Augmenting voluntary torque of healthy muscle by optimization of electrical stimulation. Physical Therapy 68: 333337, 1988 Sprague N. Motion-limiting arthrofibrosis of the knee: the role of arthroscopic management. Oinical Sports Medicine 6: 537-549, 1987 Steadman 1. Rehabilitation of acute injuries of the anterior cruciate ligament. Clinical Orthopaedics and Related Research 12: 129-132, 1983 Tiberio D, Gray GW. Kinematics and kinetics during gait. Orthopaedic and Physical Therapy I: 186, 1989 Tibone J, et al. Functional analysis of anterior cruciate ligament instability. American Journal of Sports Medicine 14: 276-283, 1986 Tibone J, Antich T. A biomechanical analysis of anterior cruciate ligament reconstruction with the patellar tendon: a two year followup. American Journal of Sports Medicine 16: 332-335, .\988 Wilcox P, et al. Arthroscopic anterior cruciate ligament reconstruction. Clinics in Sports Medicine 6: 513-524, 1987 Correspondence and reprints: Philip A. Frndack, 1087 Dennison Ave, Columbus, OH 43201, USA.
Sports Medicine 12 (5): 338-346, 1991 0112-1642/91/0011-0338/$04.50/0 © Adis International Limited. All rights reserved. SP0156a
Rehabilitation Concerns Following Anterior Cruciate Ligament Reconstruction Philip A. Frndak and Carl C. Berasi Doctors Hospital, Columbus, Ohio, USA
Contents 338 339 340
342 343 343 344
Summary
Summary I. Early Motion 2. Protection of the Biological ACL Graft 3. Strength Recovery 4. Neuromuscular Re-Education 5. Knee Braces 6. Conclusion
Rehabilitation following anterior cruciate ligament reconstruction is a subject of controversy in the orthopaedic and rehabilitation literature. With an increasing number of these operations currently being performed and with the advent of arthroscopically assisted ACL reconstruction over the past several years, particular rehabilitation needs and problems have been identified in association with these patients. Various authors have stressed one or a combination of a few basic themes which outline the basic rehabilitation concerns following ACL reconstruction. The most fundamental concern is the need to initiate motion very soon after surgery. Prolonged postoperative immobilisation is known to cause serious complications after ACL reconstruction which can be avoided by early motion. Positions or activities which may apply excessive stress to a newly reconstructed ACL must also be considered. The amount of protection required by the graft will vary depending upon the type of graft used and the quality of fixation obtained intraoperatively. Most authors agree that nonweightbearing, active resistive quadriceps exercises should be avoided for an extended period, while closed chain exercises may be initiated much earlier_ Strength recovery is obviously important for the quadriceps postoperatively, but maximal strength returns of all of the muscles about the knee must be pursued. Hamstring strength is of particular concern as this may provide an active support to the reconstructed ACL. Sensory loss in the knee after ACL disruption should also be addressed during rehabilitation, prior to a patient's return to full athletic activity. Progressive neuromuscular re-education exercises which rely on sensory input from intact pericapsular structures are encouraged. A final concern is the role of bracing after ACL reconstruction. Rehabilitative braces are in common use postoperatively to limit the patient's knee motion to that dictated by the physician. The use of braces during heavy athletic activity following anterior cruciate ligament reconstruction is less well supported by the literature. Although the physician may choose to prescribe such
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a device, the role of a brace must be considered secondary in comparison to the need for a strong, agile lower extremity to protect the ACL graft. In conclusion, the trends in rehabilitation following ACL reconstruction are increasingly focused on maximising the rate of recovery and return to full function while achieving optimal results. To reach this goal, a thorough understanding of the rehabilitation approach is necessary. In addition, significant questions remain with respect to the amount of stress a newly reconstructed ACL is able to tolerate during the various phases of recovery.
The goal after anterior cruciate ligament reconstruction is a biomechanically normal knee with respect to motion, strength and stability. Current techniques in arthroscopic reconstruction restore passive stability assuming that the new ligament is well placed (Jackson & Jennings 1988; Melhorn et al. 1987; Penner et al. 1988), strong enough to withstand physiological stresses (Blackburn 1985; Graf & Uhr 1988; Noyes et al. 1984), and is permitted to heal in this position without disruption or displacement (Arms et al. 1984; Draganich et al. 1989; Graf & Uhr 1988; Grana & Muse 1988; Kurosaka et al. 1987; Maltry et al. 1989). Motion, strength and dynamic stability must be regained during postoperative rehabilitation. Large studies documenting the long term benefits after ACL reconstruction utilising current techniques are not in abundance, but those published offer encouraging data (Boden et al. 1990; Sandberg et al. 1988; Seto et al. 1988; Tibone & Antich 1988). The reconstructed knees appear to be stronger, more stable and better able to withstand the stresses of athletic performance than ACL-deficient knees (Clancy et al. 1982; Tibone & Antich 1988). Today, as in other areas of orthopaedics, emphasis is increasingly focused on maximising the rate of recovery and return to full function while achieving optimal results (Jackson & Jennings 1988). Various themes arise repeatedly in the literature which address rehabilitation approaches after ACL reconstruction. These include avoidance of the complications of prolonged immobilisation (Anderson & Lipscomb 1989; Graf & Uhr 1988; Huegel & Indelicato 1988; Jakson & Jennings 1988; Konh 1990; Noyes et al. 1984, 1987; Shelbourne & Nitz 1990; Sprague 1987; Wilcox et al. 1987),
avoidance of positions or actIVItIes which may compromise the integrity of a freshly placed graft (Anderson & Lipscomb 1989; Arms et al. 1984; Blackburn 1985; Delitto et al. 1988b; Graf & Uhr 1988; Grana & Muse 1988; Huegel & Indelicato 1988; Kain et al. 1988; Kurosaka et al. 1987; Noyes et al. 1984; Paulos et al. 1981; Steadman 1983; Wilcox et al. 1987), the need to regain muscular strength after surgery (Anderson & Lipscomb 1989; Baratta et al. 1988; Coughlin et al. 1987; Delitto et al. 1988b; Draganich et al. 1989; Elmqvist et al. 1989; Huegel & Indelicato 1988; Paulos et al. 1981; Sisk et al. 1987; Steadman 1983; Wilcox et al. 1987), the importance of neuromuscular re-education to maximise coordination and fine kinaesthetic control (Anderson & Lipscomb 1989; Baratta et al. 1988; Blackburn 1985; Draganich et al. 1989; Gerber et al. 1985; Huegel & Indelicato 1988; Paulos et al. 1981; Seto et al. 1988; Solomonow et al. 1987; Steadman 1983) and the role of bracing after surgery (American Academy of Orthopaedic Surgeons 1984; Bessette & Hunter 1990; Shelbourne & Nitz 1990). Presented below is a review of these concerns based on the current literature.
1. Early Motion Less than 10 years ago at least 6 weeks of strict immobilisation was the norm after ACL reconstruction (Anderson & Lipscomb 1989; Arms et al. 1984; Clancy et al. 1982; Huegel & Indelicato 1988; Malone et al. 1980; Paulos et al. 1981; Steadman 1983). Complications associated with this approach included intra-articular adhesions, infrapatellar adhesions, patellofemoral crepitation, joint stiffness and profound quadriceps atrophy (Anderson & Lipscomb 1989; Graf & Uhr 1988; Sprague
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1987; Wilcox et al. 1987}. Other complications associated with immobility are also well described and include declines in the biomedical properties of bone, ligament and cartilage (Anderson & Lipscomb 1989; Noyes et al. 1977; Salter et al. 1980). In the mid 1980s the literature began to reflect a thrust to move the freshly operated knee more quickly in an effort to avoid these complications (Noyes et al. 1984, 1987). The literature however, is not in complete agreement with respect to how soon the knee should be moved, or with what restrictions after an intra-articular reconstruction. Continuous passive motion has been utilised immediately after surgery by many (Anderson & Lipscomb 1989; Graf & Uhr 1988; Shelbourne & Nitz 1990), while others prefer early passive motion following a brief period of immobilisation, typically lasting 2 weeks or less (Huegel & Indelicato 1988). Frequently, motion is permitted very early although with restrictions in range. Anderson and Lipscomb (1989), for example, examined various protocols of rehabilitation following ACL reconstruction, including one which provided 2 weeks ofimmobilisation followed by limited passive motion from 35 to 70°. Full extension was delayed for 3 months in this protocol. On the other hand, Graf and Uhr (1988), Wilcox et al. (1987) and Shelbourne and Nitz (1990) encourage immediate full range of motion. The rationale for limiting extension and initiating only passive motion in the early postoperative phase (Huegel & Indelicato 1988) is discussed in the following section.
2. Protection of the Biological ACL Graft Investigation of the biomechanics of the knee has identified numerous positions and activities which induce a traction stress on the intact anterior cruciate ligament (Arms et al. 1984; Gerber et al. 1985; Henning et al. 1985; Jurst & Otis 1985; Kain et al. 1988; Maltry et al. 1989; Noyes et al. 1987). Examination of passive positioning has revealed that the maximally flexed and extended position of the knee cause increased stress on an intact ACL, in comparison to mid-range positions (Gerber et
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al.1985). For this reason some authors encourage avoidance of these postures in the early phases after ACL reconstruction. Active, isolated quadriceps contraction in a nonweightbearing position is also associated with a potentially undesirable anterior drawer force on the proximal tibia, particularly from 45" to full extension (Arms et al. 1984; Henning et al. 1985; Huegel & Indelicato 1988). The vector associated with this force increases steadily until full extention is achieved. This stress can be neutralised by the use of simultaneous isometric co-contractions of the hamstrings with the quadriceps (Anderson & Lipscomb 1989; Arms et al. 1984; Blackburn 1985; Nitz & Dobner 1987) or by disallowing extension beyond 60° when performing isolated quadriceps contractions (Anderson & Lipscomb 1989; Arms et al. 1984; Jurst & Otis 1985; Maltry et al. 1989). Isometric co-contraction of the hamstrings with the quadriceps adds a posterior drawer force to the proximal tibia to neutralise the anteriorly directed stress induced by the quadriceps. This technique is believed to protect the ACL from excessive traction stress except in full extension. Alternatively, by positioning the knee in 60° of flexion during the exercise, the vectors associated with isolated quadriceps contractions are altered to minimise any force towards anterior subluxation. Utilising techniques such as these allows the initiation of safe quadriceps strengthening exercises much earlier than is otherwise possible after ACL reconstruction. Typically, routine active resistive quadriceps strengthening exercises are delayed for several months following ACL reconstruction (Huegel & Indelicato 1988; Wilcox et al. 1987), and as long as a year in one report (Henning et al. 1985). The exercises discussed above are begun within the first 2 weeks after surgery (Delitto et al. 1988a,b). Other activities, such as weightbearing exercises and cycling, have been examined with respect to a reference stress manoeuvre. Such activities provide another means of safely strengthening the lower extremity during the early postoperative phases. Lower extremity weightbearing, in a position such as a I-leg half-squat, requires simultaneous quad-
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riceps and hamstrings contractions (Tiberio & Gray 1989). The quadriceps group functions concentrically to extend the knee, isometrically, or eccentrically to limit further knee flexion. During this activity the hamstrings function concurrently as strong hip extensors. This simultaneous contraction of the hamstrings with the quadriceps, along with axial compression of the joint surfaces, effectively limits anterior translation of the proximal tibia on the femur which would etherwise occur with an isolated, nonweightbearing quadriceps contraction of equal intensity (Fanton 1987; Shelbourne & Nitz 1990). Biomechanical principles such as these can be applied to safely accelerate the rehabilitation approach after ACL reconstruction. To provide an illustration, Henning et al. (19S5) looked at ACL stresses compared to a reference 80lb Lachman manoeuvre. Cycling produced 7% as much elongation as an 80lb Lachman test. A I-leg half-squat produced 21 % and quadriceps contractions against a 20lb weight boot at 45" of knee flexion produced 50% as much elongation as the reference manoeuvre. Quadriceps contractions near the terminal ranges of knee extension produced elongation forces of 87 to 121 % of their reference 80lb Lachman manoeuvre. They believe that the proper order of a rehabilitation programme should be crutch walking, cycling, walking, slow running and faster running. The surgeon's choice of an ACL replacement and the type of fixation utilised are also major factors in considering the amount of protection necessary for a freshly placed ACL graft (Indelicato et al. 1989; Kurosaka et al. 1987; Noyes et al. 1984). The type of healing that the graft is expected to undergo, the specific strength of the graft chosen and the quality of fixation obtained at the time of surgery should all be considered in deciding how much stress on the graft to permit during the healing phases. Although insufficient research has been done in this area, some facts have been established. During the early stages of healing, failure of an ACL graft typically occurs at the fixation site (Noyes et al. 1984). The commonly utilised middle onethird patellar tendon graft is believed to become fixed in position via bony and or fibrous healing
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within 6 to 8 weeks of surgery (Huegel & Indelicato 1988), but some reports have stated that 3 to 4 months may be necessary for the reconstructed graft to have solid anchorage at the fixation site (Noyes et al. 1984). Revascularisation and remodelling of the graft is a longer process which may be just reaching its peak 6 months following surgery (Graf & Uhr 1988; Huegel & Indelicato 1988). During this time the integrity of a graft is particularly compromised. The mechanical strength of the revascularised and remodeled patellar tendon graft is less than 50% of the original ACL 3 to 4 months after surgery (Currier & Mann 1983; Noyes et al. 1984). On the other hand, this type of biological graft is considered the strongest of the commonly utilised ACL substitutes. A 14mm wide bone-patellar tendon-bone autograft measures 168% as strong as a healthy anterior cruciate ligament during in vitro testing (Kurosaka et al. 1987; Noyes et al. 1984). When compared to other tissues about the knee, this graft has been found to have the greatest strength within its substance (Noyes et al. 1984) as well as the greatest pullout strength when secured through interference fit with a large diameter cancellous screw (Kurosaka et al. 1987). The significance of this information is that each type of anterior cruciate ligament graft will have different inherent limitations in its ability to withstand stress. Depending on the specific graft which has been used to replace the normal ACL, the rehabilitation approach may require alteration to provide either increased protection or freedom of activity. Additionally, it is essential to understand the biological limitations of the healing process when planning a progressive rehabilitation programme. Although it may be tempting to initiate more advanced activities as soon as the patient 'feels ready', the state of healing of the graft should always be of primary consideration. Maximally stressful activities should be avoided until the substitute ACL is believed to be strong enough to withstand heavy forces. In summary, it appears that certain activities may be placed on a rough scale with respect to the amount of traction they tend to impart to the ACL. At one end of the spectrum the least amount of
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stress on the ligament" would be strict immobilisation in a position of 30 to 40° of flexion. Relatively minimal stress on the ligament occurs with passive motions from 60 to 30°. Full passive range of motion, cycling and crutch walking with partial weightbearing may be the next level of activity, followed by full weightbearing. Lower extremity strengthening through the use of weightbearing exercises should follow, while isolated nonweightbearing quadriceps contractions near the final degrees of extension should be near the top end of this scale. The maximum stress studied by Henning et al. (1985) and Arms et al. (1984) was apparently nonweightbearing, actively resisted knee joint extension to 0°. Although not specifically mentioned in these studies, all of the above would be much less stressful than the potential forces acting on the knee during certain athletic activities. Important information has been accumulated regarding the ways in which various biological ACL replacements compare with each other in the laboratory setting, as well as how much stress various activities induce within the normal ACL in comparison to one another. However, the exact amount of stress that is applied in vivo is unknown and exactly how much stress each graft can safely tolerate during postoperative healing remains in question.
3. Strength Recovery Another theme frequently arising in the literature is the need for strength recovery after ACL reconstruction (Anderson & Lipscomb 1989; Baratta et al. 1988; Draganich et al. 1989; Elmqvist et al. 1989; Graf & Uhr 1988; Kain et al. 1988; Seto et al. 1988; Solomonow et al. 1987; Tibone & Antich 1988). Some of the issues in this topic have already been discussed above, but it is of importance to note that profound quadriceps atrophy occurs in association with an ACL tear (Huegel & Indelicato 1988). Most reports have failed to show complete normalisation of quadriceps strength in these patients when compared to their nonoperative side, in spite of postoperative assessments long after the index surgery (Elmqvist et al. 1989; Ti-
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bone & Antich 1988). Research has explored the types of quadriceps muscle fibres which could atrophy disproportionately in comparison to others in an effort to identify the rates of speed at which a patient should exercise preferentially in the rehabilitation phase. Histological studies have, however, shown a uniform reduction in type I and type II muscle fibres, indicating that strengthening at every speed of contraction is equally important (Gerber et al. 1985). The role of the hamstring musculature in the strength needs of this patient group is controversial (Antich & Brewster 1988; Baratta et al 1988; Barrack et al. 1989; Draganich et al. 1989; Paulos et al. 1981; Seto et al. 1988; Solomonow et al. 1987). The quadriceps are known to atrophy to a much greater extent than the hamstrings and for this reason some authors have encouraged emphasis on strengthening the knee extensors preferentially (Huegel & Indelicato 1988). Others have documented the role of the hamstrings as a dynamic stabiliser of the knee (Antich & Brewster 1988; Baratta et al. 1988; Solomonow et al. 1987). Reflex arcs from the intact ACL and the joint capsule have been identified which support the likelihood that the hamstrings normally function to prevent overload of the ACL (Solomonow et al. 1987). For this reason some authors have encouraged supernormal strength goals for the hamstring muscles in an effort to protect the reconstructed ACL and improve the ability of the patient to withstand the severe stresses placed on the ligament during athletic competition (Barrack et al. 1989; Tibone et al. 1986). Giove et al. (1983) have documented that higher levels of sports participation are found in ACL-deficient patients whose hamstring strength is equal to or more than their quadriceps strength. In these individuals the quadriceps strength was improved to near normal and the hamstrings to a higher than normal level when compared to their unaffected side. Electrical muscle stimulation (EMS) is a subtopic in the strengthening theme discussed in the literature (Currier & Mann 1983; Delitto et al. 1988a,b; Kain et al. 1988; Nitz & Dobner 1987; Selkowitz 1985; Sisk et al. 1987; Soo et al. 1988).
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The primary goal in the use of EMS is the minimisation of postoperative atrophy. Numerous articles have addressed this technique with somewhat conflicting results. Delitto et al. (l988a,b), Nitz & Dobner (1987) and others have described significant clinical benefits from the use of EMS in the thigh musculature of patients with an injured, immobilised lower extremity. The benefits reported include decreased strength loss in the early postoperative phase, more rapid gains in range of motion, and increased overall rate of return to athletic activity. Other authors have reported less optimistic results, stating that EMS was no more effective than volitional exercise in maintaining thigh muscle strength in their studies (Selkowitz 1985; Sisk et al. 1987). Due to the numerous variables involved in the use of EMS it is very difficult to compare individual studies. Several factors may contribute to greater effectiveness in the use of electrical muscle stimulation. These include the ability of some to tolerate greater intensities of stimulation and therefore greater strengths of contraction, the potential for direct electrical stimulation to overcome reflex muscle inhibition caused by painful periarticular structures and the possibility of a pain-blocking effect of electric stimulation (Delitto et al. 1988b; Kain et al. 1988; Selkowitz 1989). Studies which examined healthy subjects must be differentiated from those which dealt with postoperative patients. The use of EMS in healthy subjects is known to produce strength gains similar to those with volitional exercise (Selkowitz 1989). Direct electrical muscle stimulation may potentially be of greater benefit than volitional exercise alone to minimise strength losses in the immediate postoperative phase. This issue is controversial (Delitto et al. 1988a,b; Sisk et al. 1987).
4. Neuromuscular Re-Education Another theme recurring in the literature of rehabilitation after ACL reconstruction is the need for neuromuscular re-education (Elmqvist et al. 1989; Huegel & Indelicato 1988). Preathletic training exercises have been suggested for several years
to help bridge the gap between routine postoperative rehabilitation and return to competitive athletic performance (Blackburn 1985; Huegel & Indelicato 1988; Paulos et al. 1981; Steadman 1983). Now it is known that the intact ACL had an important sensory function in the normal knee (Barrack et al. 1989; Draganich et al. 1989; Gerber et al. 1985; Solomonow et al. 1987). Mechanoreceptors have been demonstrated within the intact ACL which could be able to detect joint position as well as s.udden or slow joint position changes (Barrack et al. 1989; Draganich et al. 1989; Gerber et al. 1985). A decrease in overall neuromuscular drive may be responsible for the refractory strength and girth losses typically sustained by the quadriceps musculature after ACL disruption (Elmqvist et al. 1989). Correspondingly, there is information which indicates that the hamstrings are more active than usual in the ACL deficient knee, indicating the likelihood of additional reflex arcs between other pericapsular and capsular knee joint structures with the hamstrings (Draganich et al. 1989; Solomonow et al. 1987). This lends increased support to the role of the hamstrings as a dynamic knee joint stabiliser. The goal of preathletic training exercise is that through gradual introduction of increasingly complex knee joint activities the patient may be able to learn to rely more heavily on the knee's remaining proprioceptive structures (Draganich et al. 1989; Elmqvist et al. 1989; Solomonow et al. 1987). In general, these activities are begun late in the rehabilitation period prior to return to athletic activity, but passive cycling is one example of a proprioceptive training activity which could be initiated comparatively early.
5. Knee Braces Finally, the role of knee bracing following anterior cruciate ligament reconstruction requires comment. There are 3 basic categories of knee braces used today. Prophylactic knee braces are designed to prevent or reduce the severity of knee injuries. Rehabilitative knee braces are intended to allow protected motion of injured knees treated
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Table I. A typical patellar tendon graft rehabilitation programme Postoperative Immediately after surgery CPM 20 to 900 Don Joy rehabilitative brace 20 to 900 Active hamstring ROM Ankle AROM Crutches (nonweightbearing) 1 week CPM continued at home until ROM is full and easy Full ROM when supervised by the physical therapist Avoidance of hyperextension or active extension PREs ankle motions Cycling (operative extremity passive) Hamstring PREs Unrestricted hip exercises - avoid active quadriceps exercises 2 weeks All of the above continued throughout rehabilitation 25% partial weightbearing with crutches Begin closed chain quadriceps exercises 3 weeks 50% partial weightbearing with crutches Progress closed chain quadriceps exercises (include squats 45 to 900 ) 4 weeks 75% partial weightbearing with crutches 5 weeks Full weightbearing Discontinue rehabilitative brace B weeks Continue to progress all of the above Add isometric quadriceps exercises 45 to 900 (variable positions) Progress squats to full extension 4 months Start 00 for quadriceps activity (SLRs and 'short arc quads' without resistance) Begin pool running 6 months Isokinetic quadriceps exercises Begin aggressive cycling Emphasise maximal strength returns at all degrees of knee extension and at all speeds of contraction Begin normal running at 7.5 months Progress through agility drillS as strength and function progress Resume competitive athletics No earlier than 9 months Full ROM Quadriceps strength to at least 90% of uninvolved LE No pain or swelling Successful completion of preathletic agility training (general and sport-specific) Abbreviations: CPM = continuous passive motion; (A)ROM =
(active) range of motion; PRE = progressive resistive exercise; SLR = straight leg raise.
operatively or nonoperatively. Functional knee braces attempt to provide stability for unstable knees during strenuous activity (American Academy of Orthopaedic Surgeons 1984). Many surgeons will employ a rehabilitation brace immediately after surgery to permit a limited amount ofknee motion (Cawley et al. 1989). This approach was mentioned above. Several braces are available which can predictably limit flexion and extension. They are designed to permit the surgeon to prescribe the amount of knee joint excursion desired and enable this prescription to be altered as needed through simple adjustments. Functional braces are also utilised to protect a stable knee with a reconstructed ACL. Many physicians will encourage their patients to use a brace in this capacity during strenuous activity (Shelbourne & Nitz 1990), but it is understood that these devices are only effective at low levels of stress (American Academy of Orthopaedic Surgeons 1984; Bessette & Hunter 1990). The demands placed on the ACL during athletic performance far exceed the levels at which functional braces have been proven to be effective (Bessette & Hunter 1990). Patients must be encouraged and educated in the reasons for maintaining a maximally strong, agile lower extremity to protect their knee. A brace must be considered of secondary importance.
6. Conclusion In view of the recent literature, rehabilitation following reconstruction of the anterior cruciate ligament appears to be following specific trends. Table I outlines our basic postoperative approach as determined through review of the literature and personal experience. The recent literature has suggested a more accelerated rehabilitation approach which may also be effective in some circumstances. The goals of rehabilitation after ACL reconstruction are early motion postoperatively, maximal strength return and continued intensive rehabilitation efforts through advanced levels of activity. The need to avoid the complications of prolonged immobility has been discussed, in addition to the
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importance of an aggressive strengthening and neuromuscular re-education programme. Many important questions remain unanswered regarding the optimal way to reach the goal of a maximally functional knee following anterior cruciate ligament reconstruction. Perhaps the most fundamental of these is simply how much stress can a reconstructed anterior cruciate ligament safely withstand during the various stages of healing? A better understanding of these constraints would enable optimal therapeutic efforts within the limits of the biological needs of an ACL graft.
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