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This article is a description of the surgical treatment and rehabilitation of combined complex ligament injuries. A background will be provided, and information on the combined complex knee injuries, selected aspects of surgical treatments, and rehabilitation strategies will be presented. Combined complex ligament injuries are devastating injuries and are not very common compared to other knee injuries. No meta-analysis or systematic review studies exist regarding the best treatments for these patients. This article's emphasis is on the stages in the rehabilitation program with documentation of the scientific and clinical rationale for the treatment techniques in each stage. Treatment interventions are described and documented with the limited evidence available in treating these patients. Guidelines for treatment, surgery, and a clinical protocol for treating patients with combined complex ligament injuries are provided for the practicing clinician to use as a template for treating these complicated patients.
Historically, knee dislocation and traumatic multi-ligament knee injury (MLKI) was usually managed with prolonged immobilization. The tradeoff for stability was significant knee stiffness. Surgical intervention was performed, not to restore limb function, but as an attempt to avoid the gangrene and life-threatening sepsis which all too often followed vascular compromise in the pre-antibiotic era. In 1824, Sir Astley Cooper stated that “there are scarcely any accidents to which the body is liable, which more imperiously demand immediate amputation than these.”1
Although the first reported description of surgical repair was by Thomas Annandale in 1881,2 few advances were made for many decades. Improved techniques to address vascular injury evolved during the Korean and Vietnam Wars and made limb salvage possible. Then in 1963, Kennedy3 published the first attempt to systematically define the pathophysiology of the dislocated or multi-ligament injured knee, and his work stimulated interest in the problem. Initial reports suggested that reasonable outcomes could be obtained with non-operative management, and that those results were comparable to surgical intervention.3–11 However, during that era, the typical surgical treatment involved the re-approximation of the cruciate and collateral ligaments with suture, rather than reconstruction with grafts, as well as other techniques that are now of historical interest only. As the technique and success rate of single cruciate ligament reconstruction evolved, so too did application of reconstruction occur for patients with MLKI. More recent authors have consistently reported superior results with an approach combining reconstruction of cruciate ligament insufficiency with repair or reconstruction of collateral ligament disruption.12–37
The decision for surgical versus non-operative treatment must still be individualized, however, as not all patients are candidates for operative intervention. Success is dependent on not only that portion of treatment which occurs in the operating room, but also that which is related to patient enthusiasm and compliance afterward. Both the ability of the surgeon to manage a complex and demanding procedure and the full cooperation of the patient during a lengthy convalescence are mandatory. Elements such as patient age and fitness, associated injuries, pre-injury level of function, and availability of appropriate physical therapy must be considered. For example, MLKI's sustained during athletic participation typically occur in well-conditioned individuals who are already familiar with physical training and rehabilitation and are motivated to return to a level of function for which knee stability is crucial. In contrast, the risk/benefit ratio for multiple trauma patients is higher. The high-energy dislocations of motor vehicle injury are more likely to involve individuals with multi-system injury or those unaccustomed to regular physical exercise. These individuals may be unable or unmotivated to participate in the lengthy and arduous rehabilitation necessary to maximize their recovery. Rather than improving their prognosis, well-intentioned surgical stabilization may instead increase the likelihood of permanent disabling knee stiffness.
Four guiding principles apply to the elective surgical treatment of MLKI:
Although a detailed description of surgical technique is beyond the scope of this paper, some specific points that bear on postoperative recovery and rehabilitation merit emphasis. Most of the same principles also apply to patients where non-operative treatment is elected. Optimal treatment of the patient with MLKI requires a team approach. The physical therapist should read and understand the operative report, comprehend the ramifications of specific aspects of the surgical procedure, and communicate with the surgeon before beginning treatment.
No uniformity of opinion exists with respect to the optimal timing of surgery and the specifics of ligament repair/reconstruction. Shelbourne and Carr31 have recommended initial non-operative treatment for anterior cruciate ligament (ACL)/posterior cruciate ligament (PCL)/medial collateral ligament (MCL) injuries when PCL laxity is grade II or less and PCL reconstruction alone if PCL laxity is grade III. Their approach is predicated on the belief that the PCL and MCL have “intrinsic” abilities to heal, that residual laxity is preferable to stiffness, and that ACL reconstruction can be performed electively if necessary as a secondary procedure once ROM is re-established.31 Others have recommended that most patients with MLKI be treated by initial brace immobilization followed by simultaneous arthroscopic bi-cruciate ligament reconstruction in 4 to 6 weeks.14,26,38–40 Any residual collateral ligament laxity is later treated with reconstructive techniques.
Currently, most authors recommend simultaneous bicruciate and collateral ligament reconstruction/repair performed at approximately 14 days from injury unless extenuating circumstances exist.16,17,24,25,28 By this time, post-injury edema and the acute post-traumatic inflammatory response will have largely subsided and the ROM will have been at least partially restored. However, anatomic definition of the collateral ligaments and capsule still remains possible. The senior author has consistently followed this approach and believes that bi-cruciate ligament reconstruction allows the most accurate centering of the tibia on the femur and minimizes stress on repaired collateral ligaments; that cruciate and collateral reconstructions are complimentary, and thus best performed during a single surgery; and that delayed reconstruction of significant structural injury to the posterior medial or posterior lateral corners can not consistently match the quality of the end result obtained with acute surgical treatment. However, this approach assumes exacting surgical technique, tissue fixation that will tolerate aggressive rehabilitation, and appropriate patient compliance.
Although the majority of patients with MLKI can be managed on an elective basis, immediate surgery is indicated when the injury is compound (a wound communicates through the skin with the deep tissue or joint);9,21,41 associated vascular injury occurs;42–44 displaced intra-articular fractures exist requiring open reduction and internal fixation;45–47 and a complex dislocation occurs (usually posterolateral), wherein interposed capsule prevents concentric reduction of the dislocation.48–51 In these instances, definitive attention to the ligament pathology is delayed to be treated on an elective basis once the health of the limb is assured.
Three additional scenarios may mandate surgical intervention earlier than usual.
First, abnormally displaced structures (locked meniscus, flipped collateral ligaments);28 second, cruciate ligament avulsions from bone (as apposed to the typical interstitial disruption);15,32,52 and third, extensor mechanism disruption (quadriceps or infrapatellar tendon rupture).28
When early definitive surgery is not advisable, application of an external fixator or a hinged cast brace may be recommended. The spanning external fixator is often the best choice for patients who will be treated non-operatively. This technique provides good stability of the knee joint, is readily adjustable, and allows excellent access to open wounds and assessment of neurovascular status. Fixation pins must be placed far enough away from the joint and in such a manner that the pin tracks will not compromise incision placement for future knee surgery. If a non-operative approach is elected as the definitive treatment, the external fixator is maintained in place for six weeks before ROM exercises are begun. Serial radiographs should be obtained to confirm that a perfectly concentric reduction has not been lost during the period of immobilization. Recently, articulated hinged external fixation has also been proposed as a routine supplement for post-operative protection.53
Several graft options are available for cruciate ligament reconstruction. Ipsilateral autografts (patellar tendon for the PCL and semitendenosis/gracilis for the ACL) can be used, but harvest of these grafts increases the morbidity of an already severely traumatized knee. Contralateral auto-grafts can be utilized, especially if the patient will not allow the use of allograft tissue, but their use does, at least theoretically, compromise a perfect knee and harvesting requires additional operative time. The success rates obtained using allograft tissue in the reconstruction of isolated ACL and PCL injuries has been documented to approach that of autografts, and their use in the multiple-ligament-injured knee has decided advantages.16,25,54–57 Donor site morbidity is eliminated and a second surgeon or assistant can prepare the grafts while the primary surgeon prepares the knee, thus saving significant operative time. The only drawbacks to allograft use are potential disease transmission, limited availability, and cost.54,58–60 The patellar tendon is frequently utilized for ACL reconstruction and the Achilles tendon for PCL reconstruction. However, quadriceps, tibialis anterior, tibialis posterior, and semitendenosis muscle tendon allografts are also commercially available and can be utilized for either cruciate or collateral ligament reconstructions.
A suggested surgical algorithm for patients with MLKI is as follows:
The rehabilitation of patients with combined complex knee injuries has paralleled the advances in the surgical techniques of the MLKI. These techniques, which emphasize the anatomical restoration of injured tissue, present the therapy team with an unmatched opportunity for optimal functional rehabilitation. However, no two instances of MLKI are exactly alike. Therefore, rehabilitation programs must be “customized” to the individual patient, and ongoing communication between the surgeon and the rehabilitation team is imperative to assure successful outcomes.
Detailed rehabilitation protocols for patients with MLKI have seldom been published.113–115 Furthermore, due to the uniqueness of each MLKI, randomized trials have not been performed. The strategies in the rehabilitation of the patient with MLKI may seem to be diametrically opposed as in the case of protecting both the reconstructed ACL and PCL, thereby creating significant challenges for the clinician. The progression of rehabilitation should occur in a logical sequence and include the following considerations:
Clinicians should incorporate both open kinetic chain (OKC)116–124 and closed kinetic chain (CKC)125–132 exercises into the rehabilitation of patients with MLKI. No studies exist that have discussed the specific ligamentous strains with MLKI. Consequently, all studies have researched CKC and OKC forces in isolated ligament injuries; therefore, this information will be applied to the MLKI. Furthermore, co-contraction exercises, particularly for patients with MKLI, may be protective to all the healing structures by stabilizing the knee joint.125–127,133,134
The following is a list of recommended “safe” guidelines regarding isolated ACL and PCL initial OKC and CKC exercises. However, because of the complexity of MLKI, these guidelines will need to be customized based on concomitant injured structures, surgical procedures, and the patient's response to rehabilitation.114
These ROM restrictions will be combined to form the basis of the rehabilitation program. Obviously these restrictions may be lifted as soft tissue healing allows during the rehabilitation process.114
This early phase of the post-operative course is quite constant, irrespective of the specifics of the pattern of MLKI and the surgical technique employed. The priority is to protect the reconstructed and repaired tissues, while implementing strategies to reduce pain, effusion and edema, regain ROM, and initiate/facilitate muscle function. During this phase of rehabilitation, a long-leg brace is utilized. For the first 4–6 weeks, this brace is locked in extension while maintaining a strict non-weight bearing status. Dependent upon a variety of factors, including patient compliance and the type of reconstruction/repair, partial weight bearing status may be initiated during weeks 4–6. However, controlled non-weight bearing early is encouraged, generally beginning approximately one week after surgery, but with a proximal pad or counterforce support on the proximal tibia to minimize the effects of gravity and to prevent posterior tibial sag.114 Arms et al135 demonstrated increased strain on the PCL as the knee flexes, with maximum strain recorded at 100 degrees. Therefore, knee flexion past 90 degrees is not allowed during the first 6 weeks of the rehabilitation program.
A predictable progression of soft-tissue healing response occurs after severe trauma and surgical intervention. The initial phase of acute inflammation is followed within a week by phases that include collagen fibroplasia, maturation, and then remodeling. During the acute inflammatory phase, various physical therapy modalities are effective in decreasing the severity of pain and effusion and, thus, facilitate a healing response. Soft tissue healing is a long process, with the latter three stages each taking weeks at a time. During soft tissue healing, it is important that the appropriate stresses be imposed on injured tissues to promote physiologic healing responses, minimize negative changes, and facilitate the proliferation and alignment of collagen fibers.114
Both pain and the presence of an effusion significantly delay ROM gains and quadriceps muscle function. Spencer et al136 demonstrated that as little as 20–30 mL of fluid in the knee joint can retard the contraction of the vastus medialis oblique muscle. Various modalities (cryotherapy, interferential electrical stimulation, etc.) may supplement pharmacological therapy in decreasing post-surgical pain, effusion, and edema, and lead to improved neuromuscular control early in the rehabilitation process.
Full physiologic ROM is necessary for normal function of the knee. Prolonged immobilization is associated with many detrimental effects to the joint and surrounding structures, including the development of intra-articular and peri-articular adhesions, arthrofibrosis with loss of joint motion, degradation of hyaline cartilage, and decreased bone mass. The goal is the steady and gradual return of motion.114
Obtaining extension must take precedence during the initial phases of rehabilitation. The goal is to gain at least neutral extension by the end of the second week. This goal will be most difficult when injury patterns involve MCL pathology. Additionally, the repaired or reconstructed PCL comes under increasing stress as the knee goes into hyperextension. The PCL/posterior lateral corner combination injuries are especially vulnerable, as the lateral structures also come under increasing tension with terminal extension secondary to the “screw-home” phenomena.114 To quantitatively document the ROM, a measurement of knee extension via heel height difference is taken, where 1 centimeter in heel height is equal to approximately 1 degree.137,138
Oftentimes, additional treatment interventions need to be performed to achieve full ROM. For patients with hypomobilities, utilization of the total end range time (TERT) stretching formula is instituted. The TERT formula is used to create plastic deformation of the non-contractile tissue.139–140 This formula is based on the product of intensity, duration, and frequency. The intensity is the maximal stretch intensity the patient can tolerate based on comfort.140
In the early stages of rehabilitation this is modified based on soft tissue healing constraints (active assistive range of motion (AROM), short arc exercises, etc).
The first TERT is applied.
Hypomobility of patella-femoral cephalic glide interferes with the normal function of the extensor mechanism which may lead to loss of active and passive ROM or a quadriceps muscle lag. Patella-femoral caudal glides are utilized to increase knee flexion. In the single cruciate ligament reconstruction surgeries, mobilization of the tibio-femoral articulation is rarely necessary for patients who have had MKLI surgeries.114
Oftentimes, the musculo-tendinous unit also adaptively shortens which also leads to flexibility deficits. The static portion of the stretches should be held for 30 seconds for younger patients.141–153 However, if the patient is older than 60, greater benefits are obtained maintaining the stretch position for 60 seconds.144 Moreover, PNF techniques, such as contract-relax/hold-relax, can be included as part of the treatment program.
Passive range of motion (PROM) can only be utilized and maintained if adequate neuromuscular control exists.
Dynamic stabilization exercises for the entire lower extremity should be performed, which also includes core stability exercises.
The second TERT is applied at the completion of the physical therapy treatment session.147
The patient will perform a third TERT.
Quadriceps muscle weakness and atrophy in the initial stages post-operatively is unavoidable, but must be addressed immediately in order for the patient to meet their rehabilitation goals. Isometric quadriceps sets are initiated post-operatively day one, with a progression to a straight leg raise without the brace once adequate neuromuscular control is obtained. As previously discussed, various modalities are utilized to decrease the post-operative pain and effusion which are inevitable in all patients with MLKI. Quadriceps muscle sets can be supplemented with electrical stimulation to augment strength.148 Additionally, the use of biofeedback may be particularly useful in this population.
Exercise progression forms the foundation of the exercise program. The continuum stages are as follows:149
During Phase I, the emphasis is on the first three stages of this exercise progression. Total leg strength145–146 can also be performed, but caution must be taken when using the entire lower extremity and long lever arms, since total leg strength may put stresses on the healing ligaments.114
Knee proprioception and kinesthesia are disrupted by injury.150 Mechanoreceptors within the cruciate ligaments are injured during the ligament failure of MLKI and do not regenerate into the reconstructed grafts. In addition, receptors within the collateral ligaments and capsule are damaged to varying degrees. Specific exercises that are safe for the healing structures early in the rehabilitation program may facilitate the remaining intact mechanoreceptors to compensate for those that are absent. Various exercises that may be used at this time include angular joint replication training, end ROM reproduction training, and perturbation training.114,151
In Phase II, continued protection of repaired and reconstructed tissue is necessary, although progressive guarded stresses are imposed as the rehabilitation program continues. The patient may generally be allowed full weightbearing in their post-surgical brace at the beginning of the sixth week. Patients must have at least active neutral extension and no evidence of a quad lag to assume full weight bearing. A normal gait pattern is necessary to dispense with crutches. The long-leg post-operative brace is discontinued when the patient begins to ambulate without crutches at approximately 6-8 weeks.114
A functional brace is worn for all activities of daily living until approximately 12 weeks post-operative. It is highly recommended that patients who plan to return to athletic activity or manual labor utilize the brace for those specific activities for at least 18 months after surgery. At the present time, no published studies exist that assess the efficacy of functional braces after MKLI. Nevertheless, it appears to be important to provide the patient with external support because muscle function and proprioception are deficient during the early stages of recovery from these devastating injuries.114
Neutral extension should have been obtained by the end of the sixth week. The goal of the second phase of rehabilitation is to achieve physiological knee extension of the involved extremity equal to the uninvolved. Application of the TERT formula is continued if needed. Ideally, flexion should gradually increase until ROM is symmetrical to the uninvolved side by weeks 8-12. However, consistently obtaining full flexion may be difficult. If neutral extension and flexion to 125 degrees have not been obtained by week 12 and gains in ROM have plateaued, surgical intervention in selective patients with MLKI is considered.
Proprioceptive/kinesthesia exercises are advanced in a systematic fashion. Unlike isolate ligamentous injuries, the rate of progression for these exercises varies considerably between patients with MLKI. Suggested progression is as follows:152–154
An important part of the rehabilitation program for the patient with a MKLI is dynamic stability, which helps protect the knee joint and compensates for any residual impairments. Core stability training can also be included for a comprehensive rehabilitation program. As previously described, the exercise progression forms the foundation of the exercise program. In Phase II, the emphasis to enhance neuromuscular dynamic stability is on stages 3-6 of the exercise progression continuum.114
After knee surgery, patients have a tendency to unload their surgical extremity. Neitzel et al155 have demonstrated that patients continued to unload the surgical limb for at least six months, and then normalized their weight bearing by one year. Based on these findings, patients are encouraged to begin single leg exercises earlier in the rehabilitation program.
Exercises from phase II are continued with the addition of more aggressive progressions such as perturbation training exercises. These exercises are progressed from submaximal to maximal, slow to fast, and known (proactive) to unknown (reactive) patterns. At approximately week 24, low intensity agility drills may be initiated. Exercises such as controlled acceleration and deceleration, slideboard, and jumping rope form the foundation of these exercises.114, 129
A combination of concentric and eccentric exercises should be included in the rehabilitation because most functional activities use both modes of muscle actions. To improve muscular power, the patient exercises at fast speeds with maximum effort activities. Progression may include faster speed isokinetic training and functional training activities using more dynamic exercises, such as low intensity plyometric exercises.114
Neuromuscular reactive training is important to provide dynamic stability of the knee. Development of normal functional patterns is one of the goals of the training program. During this phase, the primary motor learning responses re-develop and activities progress from a conscious to an unconscious level where the responses occur automatically. Primary muscles involved in the compensatory patterns (quadriceps, hamstrings, and gastrocnemius muscles) following ACL injuries are important in helping the patient return to various activities.159–163 Therefore, a patient with a MKLI may also need to rely on some of these compensatory patterns to create the dynamic stability for the knee. However, because of the complexity of the MKLI, differences exist in the way the patients are going to compensate to provide dynamic knee stability. Consequently, as previously discussed, the rehabilitation program needs to be customized to each individual patient.114
A functional testing algorithm (FTA) is used to evaluate and progress a patient through the rehabilitation program. This phase focuses on the last few stages of the exercise progression continuum. The details and specific criteria are described by Davies and Zillmer.163 The FTA progresses the athlete through a series of stages, with each one becoming progressively more difficult. The patient must pass through each stage in a systematic process in order to progress to higher levels of functional activities. If the patient fails a test of the FTA, the rehabilitation program is then focused upon that area until the deficit is adequately addressed.114
No randomized controlled trial studies exist regarding the optimum surgical and rehabilitation guidelines for a patient following MLKI. Furthermore, these studies would be difficult considering the complexity and uniqueness of each MLKI. Both surgery and rehabilitation are customized to meet the particular need of each patient with a MLKI. Guidelines regarding mechanisms and classifications of injuries, surgical procedures, and limited evidence-based literature on rehabilitation combined with our empirically based experience with patients with MLKI have been presented.