PFATS Articles
Rehabilitation Program for Arthroscopic Monopolar Radiofrequency Treatment of a Posterior Cruciate Ligament Insufficiency: A case study
Geoff Kaplan ATC, PT, SCS, CSCS
Assistant Athletic Trainer
Tennessee Titans
Michael L. Voight DPT, OCS, SCS, ATC
Belmont School of Physical Therapy
Introduction
Posterior cruciate ligament (PCL) injuries are probably more common than once thought. Depending on the setting, PCL injuries are reported to account for 3% to 37% of knee ligament injuries 1;2. To date, there are no data that accurately describe the incidence of PCL injuries in athletics. Given that the most common mechanism of injury is falling on a flexed knee, the incidence would be expected to vary according to sport. Following injury to the PCL, patients have two treatment options; surgical and non-surgical. Patients with posterior cruciate deficient knees tend to decrease their level of activity to accommodate the degree of instability. Non-surgical treatment includes activity modification, therapeutic exercise to strengthen the dynamic restraints to abnormal posterior tibial translation, and external bracing. When patients are either unable to modify their activity or exceed the capacity of their body to stabilize the knee, functional instability occurs. The surgical goals of PCL reconstruction are threefold: prevent repetitive episodes of on knee instability and subsequent secondary damage, normalize joint kinematics, and allow a return to normal activities of daily living including high-demand sports 3.
PCL insufficiency secondary to ligamentous disruption traditionally has been managed by reconstruction. As the function and disability associated with PCL have become more evident, the indications for surgery have become more uniform. Reconstructive methods vary from surgeon to surgeon because there are many technical details that require consideration. These include graft choice, type of fixation, and number of bundles. There are many adequate graft choices that include the use of autograft bone patellar tendon bone, quadrupled hamstring (gracilis and semi tendonosis), allograft bone patellar-tendon bone, allograft achilles tendon, autograft quadriceps tendon, contralateral bone patellar-tendon bone, contralateral hamstring, and contralateral quadriceps tendon. Controversy regarding timing and type of reconstruction still exists, because there are no long-term studies to determine which, if any is best. Surgical techniques are technically demanding and are associated with a variety of complications, including the recurrence of instability, stiffness, and neurovascular injury. Failures of PCL reconstruction include the loss of fixation, interstitial ligamentous creep, and gross disruption.
The use of thermal energy to modify collagenous soft tissues has been applied to and successfully treated patients with glenohumeral instability4-9. Shrinkage of attenuated ligamentous and capsular soft tissue has restored functional stability in these patients. In addition, multiple in vivo and in vitro studies have explored the interaction between therapeutic heat, collagen shrinkage, and healing10-15. These in vitro and in vivo studies provide the basic science foundation on which the clinical hypothesis that the therapeutic application on nonablative thermal energy can shrink the attenuated PCL and thereby restore objective and subjective instability. The primary contraindication for this radiofrequency-mediated ligament repair is discontinuity of the ligament. Detachment proximally, distally, or in the mid portion makes it impossible to retension the ligament and would therefore doom the electrotherapeutic repair to failure. Therefore, in order to retain attenuated ligamentous soft tissues, the PCL structure to be tightened must be attached on both the femur and the tibia.
We are presenting this case to demonstrate the use of a focused rehabilitation program following a thermal shrinkage of the posterior cruciate ligament. Initial alterations in the biomechanics of heat-treated ligaments highlight the need for specialized post-operative rehabilitation protocols. The patient presented in this case was a professional football player who wanted to return too full unrestricted play as soon as possible. This is the first report, to our knowledge, of a patient who underwent monopolar radiofrequency treatment for the primary purpose of returning to full-unrestricted sports participation.
Subjective History
The patient was a 29 year old, 5’ 8” 188 lbs. professional football player who injured his left knee on September 6, 1998 while participating in a regular season football game.
Injury Mechanism:
At the time of injury, the athlete was covering a punt. In the process of engaging a defender, he fell on the artificial surface with his knee bent approximately 90 degrees landing on his anterior knee. While the athlete denied hearing an audible “pop”, he did report immediate severe pain and an inability to bear weight on the left knee. Review of the injury on videotape the following day revealed that in fact the athlete did land on his flexed knee.
Examination:
Immediately following the injury, an on the field examination was conducted by the team physician. The athlete was tender to palpation posteriormedially and while there was no medial instability present, he was painful with a valgus stress test. Posterior drawer stress was painful with a grade 2 - 2+. In addition to the increased laxity with the posterior drawer test, a soft end point was also noted. All other ligamentous stability testing was unremarkable at this time.
Post game examination was similar to the on the field exam: joint line pain, grade 2-2+ post drawer test, and all other ligament stability tests normal. Patellofemoral crepitus was also noted. The athlete was placed in a compression sleeve and long leg brace.
Clinical exam the following day revealed a grade 2-3 effusion, 0-120 range of motion secondary to the effusion, antalgic gait with decreased hip and knee flexion, good quad tone, and a grade 2 posterior drawer test. Posterior drawer testing was difficult to perform due to the swelling and muscle guarding
Diagnostic Imaging
Radiographic examination was normal. A MRI revealed a partial tear of the PCL involving the posterior aspect of the ligament extending to the tibial attachment. In addition, a bone bruise on the anterior aspect of the lateral femoral condyle and chondral changes in the trochlear groove was noted.
Diagnosis
Partial tear of the PCL with associated chondromalacia.
Pre-operative Rehabilitation:
The rehabilitation program was initiated on day one post-injury. Initial treatment goals centered on the control of the inflammation. The athlete’s treatment program consisted off icing, compression, and elevation. In addition the athlete was instructed to continue with the long leg immobilization. Eventually, the athlete was allowed to discontinue the immobilizer as tolerated. As soon as the effusion was controlled, an aggressive quadriceps strengthening and proprioception rehabilitation program was implemented to maintain quadriceps strength and regain function. Hamstring exercises were avoided for 6-8 weeks in order to not stress the healing PCL and associated structures
Day 1-7 post injury
Throughout the first week post-injury, ice compression, elevation, and anti-inflammatory medications were used to reduced the effusion and pain. This was performed twice daily.
Quadriceps tone was maintained through isometric quad sets, straight leg raising, bilateral mini squats, and closed chain terminal knee extensions (TKE). Proprioception and balance training was progressed from bilateral to unilateral stance on uneven surfaces and foam matting. As soon as the effusion subsided, range of motion (ROM) was restored and maintained through bicycling and wall slides.
The athletes progressed to single leg mini squats with resistance tubing, single leg press strength training, wall squats, and side stepping against resistance tubing. Balance training was progressed from unilateral stance eyes open activities to single leg eyes closed training. Stable base training progressed to unstable surfaces. Functional activities such as step ups, stairmaster, slide board, fitter, and straight ahead field jogging were initiated without complication.
Days 11-14
The athletes functional activity program was increased to include sport specific drills and position specific (defensive back) drills. These included jogging, side stepping, carioca, back pedal, cutting drills, figure of eights, change of direction drills, and covering a receiver running routes. All of these were initiated without complication.
The athlete was cleared for return to play 14 days post-injury and participated in full unrestricted activity. Upon his return, this particular athlete completed the rest of the season and did not miss any game action because of the PCL injury. Throughout the season, he did have recurrent episodes of effusion and anterior knee pain. Due the combination of PCL laxity and associated chondromalacia, the team physician felt that surgery was indeed indicated. This decision was based on the premised that the increased PCL laxity was increasing the articular pressure in the trochlear groove and thus causing further damage with continued effusion and pain.
Surgical Treatment:
As soon as the season was completed, the athlete had athroscopic chondroplasty and radiofrequency probe tightening of his PCL. While thermal ligament shrinkage in the knee is not a common procedure, it was felt that it was the most viable option for this athlete. Type I collagen is the main constituent of both ligaments and joint capsule. The highly ordered dense collagen fibers serve to provide tissues with their mechanical stiffness and strength. It is a well known phenomenon that collagenous tissue shrinks when it is heated. When threshold levels of temperature are reached, the heat labile bonds in the collagen molecule break down and the collagen molecule contracts into a less organized random coil configuration 4. When enough collagen molecules are heated in this manner, a visible contraction of the treated tissue occurs.
In the early 1900’s, the holmium laser was found to be a useful tool for thermally contracting the shoulder capsule and improving shoulder stability in a young active patient population. A pilot study by Thabit et al confirmed that the laser-assisted capsulorrhaphy was an effective and less invasive method of clinically tightening the shoulder capsule that achieved success rates equal to or better than other arthroscopic techniques 16.
Because of its superficial thermal effects, the holmium:YAG (Ho:YAG) laser is an inappropriate device for the treatment of this entity 3. However, the deeper heating effects of the monopolar radiofrequency device (Figure 2) makes it ideal for such a purpose. Studies have shown that the thermal heating of the joint capsule, ligament, and tendon resulted in significant shrinkage that is both temperature dependent and time dependent 4;6;17;18. The degree of tissue modification (shrinkage) is influenced by the quality of the tissue (e.g., collagen content crosslinks) and direction of the collagen fibers. Both animal and human tissue studies have confirmed that the temperature required for collagen contraction and stabilization of the human joint capsule is approximately 65 degrees C 4;14;17. Using a temperature of 67 degrees C and 40W of power, significant shrinkage and heating effects, up to 5 mm of depth, can be achieved 3.
Surgical rationale for this athlete was centered on the surgeons vast experience with radiofrequency thermal capsular shrinkage. In addition, the lower chance of morbidity (creating a hypo mobile knee, improper arthrokinematics, and accelerating the deterioration of the articular cartilage) and a faster rehabilitation time than with traditional PCL reconstruction was considered in the decision process. On 1/6/99, the patient underwent an arthroscope knee surgery which included chondroplasty and radiofrequency probe thermal shrinkage tightening of the PCL
Post-operative Rehabilitation:
0-10 days
Immediately post-operative, the athlete was placed into a Donjoy IROM knee immobilizer locked in full extension thereby not allowing any range of motion. Full weight bearing as tolerate was allowed. Rehabilitation exercises were initiaed the day following surgery. Specific exercises included: straight leg raises, hip abduction, hip adduction, hip extension, quad sets, single leg balance in immobilzer (proprioception training), ankle pumps and patella mobilization. The goal of the early rehabilitation program was to promote healing, decrease swelling, decrease pain, and maintain quad tone.
10 days-3 weeks
The basic rehabilitation program continue as outlined above however, prone passive knee flexion to 90 degrees was allowed. The rationale for prone knee flexion instead of supine is that in this position gravity against the PCL is eliminated. Rehabilitation goals were increased to include gradual increases in PROM, increasing quad tone, and promotion of an optimal healing environment for the PCL.
3 weeks-5 weeks
At three weeks the post-operative brace was discontinued and the athlete initiated onto gait training. Lower extremity strengthening and proprioception training were progressed in intensity. Specific rehabilitation included: Bicycling, AROM, PROM (wall slides), patella mobilizations, single leg press with elastic tubing, single leg proprioception on uneven surfaces, closed chain TKE, standing calf raises, bilateral mini squats progressing to single leg mini squats against elastic tubing, Precor EFX elliptical trainer, and a stairmaster climbing program.
5-8 weeks
During the second month post-operative, both range of motion and strengthening exercises were continued to progress in both intensity and duration. Proprioception and balance training was progressed from eyes open to eyes closed and from stable to unstable surfaces. Specific rehabilitation included a progression with the single leg leg press, step up (both forward and lateral steps), single leg squats (on a smith squat machine), forward and back ward walking on a treadmill. In addition, functional activity training was initiated utilized the following: side to side stepping against elastic resistance, slide board, fitter, mini stepper, elliptical trainer, stairmaster, and spinner bike classes. By the end of the second month, the athlete displayed full active painfree range of motion.
8 -12 weeks
During the 3rd month post-operative, the athletes’ rehabilitation program continued to emphasize lower quarter strengthening and proprioception training.
12-16 weeks
During the 4th month, strengthening exercises exercises were advanced with an emphasis on sport specific drills for a return to sport. In is important to note that hamstring exercises were not initiated until the athlete started working out with an isokinetic machine after 16 weeks. The rational for restricting hamstring strengthening was that a strong and powerful hamstring contraction during the time of biological healing of the PCL would place increased tension on the PCL and possible stretch the ligament.
In vivo and in vitro animal studies have consistently documented a trade off between soft tissue shrinkage and maintenance of soft tissue strength immediately after the deposition of thermal energy 3. Longitudinal in vivo studies show a restoration of biomechanical tissue strength / stiffness by 8 weeks with the Ho:YAG laser and 12 weeks with the monopolar radiofrequency device in glenohumeral or patellofemoral joint capsule 16. Near normal histology appears by 3 months for both the Ho:YAG laser and radiofrequency devices3. Jackson et al suggests that devitalized ACL tissue treated by a freezing thermal stress rather than heated thermal stress becomes “normal” compared with controls somewhere between 6 weeks and 6 months 19. The basic science for our rehabilitation program was based on previous animal studies and our clinical experience with thermal radiofrequency shrinkage of the glenohumeral joint capsule. It is important to note that at this early developmental stage of our rehab program we tend to error on the side of conservatism.
Functional Progression:
Since our athlete was a professional football player who played defensive back, the functional progression drills were designed to incorporate the nesessary movement and skills needed to play that position. All field rehab and field sessions started with the following exercises: (Note: each exercise is performed 2x25 yards.)
Warm up: High knee jogs, butt kicks, side steps, carioca, back pedal, skipping. In the initial stages of the functional progression, these exercises were followed by straight line jogging and running. As soon as the athlete was able to perform these drills without any gait deviations, pain or swelling, he was progressed as follows: Warm up as before with the addition of double leg hops, single leg hops, bounding, and a back pedal weave. Additional drills were added to incorporate cutting and change of direction:
Forward weave the width of the field, zig- zag weave the length of the field, figure of eights starting larger and gradually making smaller and faster cuts. The speed, duration and intensity of each drill was adjusted to challenge the player and test the knee. Position specific drills were incorporated into the functional progression. These included speed drills covering different passing routes: both with and without a receiver present. The criteria for full unrestricted return to activity was the performance of the full array of drills without pain, swelling, or dysfunction. Throughout the functional training period the athlete did not utilize any supportive taping or bracing. The athlete did want to wear a neoprene sleeve for comfort and warmth.
Clinical Objective Outcome Findings (20 weeks post-operative)
- ROM: 0-135 (painfree)
- Strength: Isokinetic testing of the athletes quadriceps musculature at 90, 180, and 300 degrees/second reveal quad strength within 10% of the non involved side at each of the testing speeds.
- Arthrometer scores: Unfortunately, pre-operative and immediate post-operative KT 1000 test were not taken. At 20 weeks post-operative, his KT-1000 scores were compared to his pre-injury values. No difference or increased laxity was noted.
- Survey results: Lysholm Score – 100
Cincinnati Score - 94 - Ability to return to pre-injury status: The athlete has returned to full unrestricted participation in professional football with out any recurrence of PCL problems.
Conclusions:
The thermal repair of PCL-insufficient knees represents an emerging treatment alternative to standard PCL reconstruction techniques. The minimal morbidity of PCL thermal repair must be counter-balanced by the success rate of the well documented PCL repair techniques. Patients must be observed closely in the first 3-month period after surgery, both clinically and in the rehabilitation setting. A high degree of patient compliance is required to protect the healing ligament in its early stages. Ongoing basic science projects will help to further delineate the complex interaction between the therapeutic shrinking on the insufficient, unreconstructed PCL as well as failed reconstructions or repairs. The key question yet to be answered is not whether the PCL can be tightened, but when is the best time to release the athlete back to full, unrestricted sports. The animal data provided by Jackson et al suggest that a minimum of 6 weeks and a maximum of 6 months may be required to restore tissue structure and function. Our clinical experience to date suggests that a 4-month period of activity modification and rehabilitation is both prudent and successful.
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