Most surgeons believe patients with a fixed flexion contracture pose specific problems during total knee arthroplasty. It is also generally believed restoration of full passive extension should be attempted during surgery, although there is evidence residual flexion contracture after surgery may improve with time.1,5,9,15
Optimal knee function requires maximal restoration of knee extension. A residual flexion contracture decreases the patient's ability to walk, increases the energy cost, and slows velocity during ambulation.7,13 To restore full extension, the surgeon should understand the pathogenesis of a flexion contracture and its contributing factors, and should have a plan to address this problem during surgery. The presence of a flexion contracture is usually the consequence of bone impingement and/or soft tissue shortening. Anterior osteophytes can cause direct abutment and block tibiofemoral extension, or may tether the posterior soft tissues and prevent full extension. Patients with longstanding inflammatory or degenerative knee deformity often have secondary contractures of collateral and posterior soft tissues develop because of a chronic tendency to assume the most comfortable position of the knee in 30° to 45° of flexion and avoid painful extension.7
Specific surgical algorithms for total knee arthroplasty in the presence of a fixed flexion contracture have been presented in the past by a few authors, and have evolved over time.4,6,8,11,17 Most published algorithms have suggested differential approaches toward patients with mild, intermediate, or severe flexion contractures.
We describe a relatively simple surgical algorithm consisting of four sequential steps used during the past decade. The primary question was how many steps were required in order to obtain correction with increasing severity of the flexion contracture. We further wanted to know whether correction was maintained at two years after surgery, and which complications occurred in relation to the different steps of the algorithm.
MATERIALS AND METHODS
Using a prospectively created database, we retrospectively reviewed all patients undergoing total knee arthroplasty (TKA) between 1992 and 2004 with a preoperative fixed flexion contracture. The flexion contractures of all patients were treated according to a standard surgical algorithm. Data for all 2593 patients (2898 knees) undergoing TKA were entered in the database beginning in 1992. We analyzed data of knees only with a preoperative flexion contracture of 5° or greater and with a minimum followup time of 2 years. We excluded 12 knees with ankylosis (range of motion < 10°). With these criteria we identified 863 patients (924 knees), representing 31.8% of the total number of knees in the database.
The recorded data include preoperative, intraoperative, and postoperative evaluation at standard intervals, and annual followup reports. Patients were routinely followed according to the database schedule and were contacted in case of noncompliance to the followup program. The database contained patient demographics including age, gender, preoperative diagnosis, preoperative limb alignment, and mean flexion contracture for every group (Table 1).
Patients were categorized as having mild, moderate, or severe flexion contracture. Flexion contractures between 5° and 15° were considered mild, contractures between 15° and 30° considered moderate, and contractures greater than 30° considered severe (Table 1). Knee range of motion (ROM) was measured in horizontal decubitus using standard clinical goniometers centered over the knee with the lateral malleolus and greater trochanter as distal and proximal reference. With these criteria, the flexion contracture was graded as mild in 794 knees (746 patients), as moderate in 95 knees (86 patients), and as severe in 35 knees (31 patients).
All operative procedures were performed by one of the authors (JB, HV, JVi, JVa) or under his/her direct supervision. We followed a four-step surgical algorithm in each patient until full passive flexion was achieved with the trial implants in situ. In Step 1, we performed mediolateral ligament balancing with meticulous resection of all osteophytes and overresection of the distal femur by up to 2 mm to increase the extension space in relation to the flexion space. In Step 2, we performed a progressive transverse posterior capsular release posteromedial and/or posterolateral with subperiosteal release of the medial and/or lateral gastrocnemius head off the posterior femur, usually by blunt dissection using a periosteal elevator. In case insufficient correction was obtained, the central part of the capsule was released from the posterior femur using electro-cautery, taking care not to violate the popliteal vessels or the posterior cruciate ligament. In Step 3 we included additional overresection of the distal femur to a maximum of 4 mm. In Step 4, we performed a sharp tenotomy of any residually tight medial or lateral flexor tendons. We recorded which steps were performed for each case and the maximal extension at the end of surgery. Two different types of prostheses (Genesis® [Smith and Nephew, Memphis, TN], and Profix®, [Smith and Nephew]) were used in this patient group, depending upon the surgeon's preference at the time. The posterior cruciate ligament was retained or excised depending on the surgeon's philosophy. In case it was excised, a posterior stabilized implant was used.
All followup examinations were performed by one of the authors (JB, HV, JVi, JVa) or under his/her direct supervision; none were blinded. The database included the amount of extension at 1 and 2 years after surgery. We noted all complications related to the surgery.
For mild contractures, Step 1 was sufficient to obtain full extension in 716 cases (91.2%), and 78 cases (9.8%) we obtained correct with the additional posterior release in Step 2 (Table 2). Complete extension in this group was obtained in all but seven cases (0.9%), which were left with a flexion contracture of less than 5° at surgery. By 2 years after surgery, none of the cases from this group had a residual flexion contracture greater than 5°, and no complications related to the algorithm occurred.
Moderate flexion contractures (between 15° and 30°) were corrected after Step 1 in 54 cases (56.8%) and after Steps 1 and 2 in 83 cases (87.4%). Additional overresection of the distal femur (Step 3) was necessary in 11 cases (11.6%). In one case (1%), tenotomy of the biceps tendon was performed to obtain full extension. At the end of surgery, 11 cases (11.5%) in this group were left with a residual flexion contracture less than 5°, and three cases (3.2%) were left with a residual flexion contracture between 5° and 10°. At 2 years after surgery, all had improved to less than 5°, except one remaining at 7°. No complications occurred in this group with respect to the surgical algorithm, although in 2 patients with preoperative varus deformity an overrelease of the medial soft tissues occurred and compensatory release of the iliotibial band was necessary. In two other patients in this group the use of a mediolateral constraining insert was necessary to compensate for unacceptable laxity. At two year followup, no cases with mediolateral instability or recurvatum exceeding 5° were noted.
Severe flexion contractures were corrected after Step 1 in nine cases (25.7%), and after Steps 1 and 2 in 17 cases (48.6%). Additional overresection of the distal femur (Step 3) was necessary in 10 cases (28.6%). In eight cases (22.9.0%), tenotomy of the flexor tendons was performed to obtain full extension. In six cases we performed under direct vision a transverse tenotomy of the biceps tendon at the level of the joint line with the knee in extension. In two cases the semimembranosus tendon was transected just proximal to its tibial insertion, while the knee was positioned in 90° flexion.
At the end of surgery, four cases (11.4%) in this group were left with a residual flexion contracture less than 5°, and two cases (5.7%) were left with a residual flexion contracture of 10° and 15°, respectively, which were unaltered at 2 years after surgery. In this group with severe flexion contractures, two patients (5.7%) sustained a peroneal nerve palsy, one of which was permanent. Both occurred in patients that had tenotomy of the biceps.
One patient with preoperative varus deformity had an overrelease of the medial soft tissues and we performed compensatory release of the iliotibial band. In three patients the use of a mediolateral constraining insert was necessary to compensate for unacceptable laxity. At two year followup, no cases with mediolateral instability or recurvatum exceeding 5 degrees were noted.
The correction of flexion contracture during total knee arthroplasty will improve functional status and ambulation capacity.7,13 Preoperative physiotherapy, casting, or stretch-bracing have been proposed as preoperative measures to reduce the contracture before the operation and make the surgery easier, although few published data are available on their effect before total knee arthroplasty.3,7
In this study we used data obtained from our prospective database to determine how effective our surgical algorithm was in correcting flexion contractures with increasing severity. Despite the fact such database information is meticulously collected, its use for retrospective data analysis has some intrinsic limitations. Because four surgeons (JB, HV, JVi, JVa) were involved in patient examination, surgery and data registration, it likely creates variability that could be avoided when studying a single surgeon's experience. Outcome measures were performed by the same group of surgeons, although not necessarily on their own operated patients, and may have created some bias towards the clinical result.
Today most surgeons agree maximal correction of the flexion contracture should be attempted during surgery, despite any residual flexion contracture following knee arthroplasty improving considerably. Tanzer and Miller15 and McPherson et al9 reported an average improvement of approximately 10° of residual flexion contractures after total knee arthroplasty, from 10° to 15° after surgery, to less than 3° at 2 years. Aderinto et al1 recently demonstrated improvement may occur up to 3 years after surgery.
Specific surgical algorithms to correct flexion contracture during TKA have been proposed by several authors and have evolved over time.4,6,8,11,17 The algorithm we used is based on numerous principles that have gradually gained consensus among knee surgeons. First, it is important to realize the flexion and extension gap are relative to each other. When dealing with flexion contracture, it is helpful to consider this a situation where the extension space is too tight compared to the flexion space. Surgical actions potentially leading to an increased flexion gap should be avoided. Strict posterior referencing for femoral sizing and anteroposterior positioning of the femoral component with restoration of the condylar offset is mandatory.2 The extension space can be increased by resecting more distal bone on the femur. However, it is important to realize flexion contractures are not the consequence of distal overgrowth of the femur. This step should be undertaken with caution because excessive overresection of the distal femur will proximalize the joint line and may alter knee kinematics and function by changing effective quadriceps length and impingement in the back and the front of the knee.2,16 Therefore, our algorithm includes only 2 mm overresection in Step 1.
In addition, soft tissue releases to increase the extension space while maintaining the flexion space can help to obtain gap equality. Using this principle, Mihalko and Whiteside11 and Whiteside and Mihalko17 recently described the sequential release of ligaments effective primarily in extension as one of the most important steps treating flexion contracture in TKA. Our algorithm is in accordance with these concepts, where adequate mediolateral ligament balancing is considered the most important part of Step 1, together with meticulous removal of all osteophytes that may constrain surrounding soft tissues or act as a bony block. The posterior portion of the medial collateral ligament (posterior oblique ligament) in the varus knee and the iliotibial tract in the valgus knee require specific attention while performing ligament balancing in the presence of the knee with flexion contracture, because these structures will almost become shortened due to the combined coronal and flexion deformity.17
Our data suggest most flexion contractures less than 30° (98.6%) could be corrected with Steps 1 and 2. This confirms the importance of the principles mentioned previously, and demonstrates that, aside from these two simple steps, no overresection of the distal femur is required. This is important because distal resection of the femur is one of the first steps during surgery and should therefore never be exaggerated in the early stage of the procedure. For surgeons who use a ligament referencing technique, it is important to realize that before making the distal femoral cut, the soft tissue releases described in Steps 1 and 2 will greatly influence the level of the distal femoral resection and should therefore be performed with maximal attention.
Steps 3 and 4 of our algorithm were seldom required and almost only in severe contractures greater than 30° or more. To our knowledge, tenotomy of the hamstring tendons has not been reported in previously described algorithms, but we used it in 22.9% of cases with severe flexion contractures. Six of these were valgus knees in which tenotomy of the biceps tendon was successful in restoring full extension. Unfortunately two patients had a peroneal nerve palsy develop, one of which was permanent despite keeping the leg in flexion in the immediate postoperative period to facilitate nerve recovery.12,14 Tenotomy of the biceps should therefore only be considered with caution. Leaving the knee without full correction of the flexion contracture, instead of taking the risk for peroneal nerve palsy with biceps tenotomy, may be a worthwhile alternative in these situations.
Our algorithm does not include release of the posterior cruciate ligament, despite previous authors having included this in their strategy to treat flexion contractures.6 It has recently been shown the major result of posterior cruciate ligament release or sacrifice is the creation of a larger flexion space relative to the extension space, which therefore aggravates the flexion-extension gap discrepancy present in flexion contracture.10
Our data suggest by using a relatively simple surgical algorithm, full extension can be restored during the procedure in most cases. Adequate mediolateral ligament balancing, removal of all osteophytes, overresection of the distal femur by 2 mm, and posterior capsular release are sufficient for almost all cases with flexion contractures up to 30°.
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