Rupture of the patellar tendon after total knee replacement is a rare and typically devastating problem (Fig. 13.1). Unfortunately, the results of several methods of acute repair are almost uniformly
Numerous theories have been postulated to explain the etiology of late rupture of the patellar tendon following TKA. As mentioned previously, improper surgical technique that malaligns the knee or the position of any single component can play a contributory role. Some authors have found its occurrence more common in knees with limited motion.10,11 Others have suggested impingement of the prosthesis on the patella tendon to blame.12 Still others believe that compromise of the vascular supply to the patellar tendon is a critical component of its failure.12,13
The time of occurrence of post-arthroplasty patellar tendon rupture has been debated in the literature. In the series reported
by Cambi and Engh,10 six of eight ruptures occurred intraopera-tively or soon afterwards. in contrast, Gustillo and Thompson found most of the patellar tendon ruptures in their series to occur later.4 Regardless of when the disruption occurs, no difference in management has been suggested to be time dependent.
Several repair techniques for patellar tendon disruption have been described. However, because the numbers in all post-arthro-plasty case series have been low, no single technique can be considered a gold standard.
Predictably disappointing results have been noted with prolonged cast or brace immobilization alone as the sole means of management. This method of treatment may be adequate for partial tears, but the definitive diagnosis of an incomplete lesion is often difficult and not readily recognized. Therefore, open surgical repair is the preferred treatment. Reconstruction options include direct surgical repair, local autologous graft, distant autologous graft, synthetic graft, or various types of allograft.
Complete acute tendon tears may be managed with direct repair, but will most likely need some method of augmentation. in order to maximize the effectiveness of the repair and minimize ensuing stiffness, the repair should be carried out as soon as possible. if the tear occurs in the mid portion of the tendon, an end-to-end repair technique may be employed. Several means of enhancing the suture fixation during direct repair have been described including a Bunnell suture weave,7 or a tendon grabbing stitch. The tendon should be repaired with nonabsorbable suture materials and, if present, the paratenon closed with absorbable sutures. Unfortunately, mid-tendon tears are less common than tears near the tendon origin or insertion. These later injuries are far more difficult to treat.
Bony avulsion or patellar tendon tears at the inferior pole of the patella are best managed by a traditional Bunnell-type repair with sutures passed through drill holes at the apex of the patella. it is important to reproduce the original length of the patella tendon when tensioning the sutures. Patella position can be ensured by comparing measurement of tendon length or position on a lateral radiograph with the opposite knee. Patellar baja must be avoided. Many authors also recommend a reinforcing cerclage suture encircling the tibial tubercle and the quadriceps tendon to protect the repair postoperatively. it would be our preference to use a #5 nonabsorbable suture rather than a metallic wire. Postoperative rehabilitation protocols vary. Typically, however, the knee is kept in full extension for 4 to 8 weeks with quadriceps setting exercise begun immediately. After allowing adequate time for soft tissue healing (approximately 6 weeks), the knee is started on a progressive range-of-motion and strengthening program. Unrestricted weight-bearing and flexion activities are permitted at about 12 weeks.
Tendon tears in close proximity to the tibial tubercle insertion pose a far greater repair challenge. A similar scenario occurs when the integrity of the distal remains of the patellar tendon is inadequate for a secure repair. In these clinical settings, the surgeon must choose between one of several reconstructive procedures. Unfortunately, large clinical series that establish the efficacy of any one technique do not exist.
One of the earliest described repair techniques for a patellar tendon-deficient knee was described by Kelikian14 (Fig. 13.2). He utilized the semitendinosus tendon by harvesting the proximal extent of the tendon up to the musculotendinous junction while
leaving the distal insertion site intact. The freed proximal end of the tendon was then routed through holes drilled in the tibial tubercle and the patella before being secured back onto itself near its insertion site. If there is insufficient length, the gracilis tendon can also be harvested, detached, and sutured to the semitendinosis tendon. Ecker and associates15 described a modification of this technique employing skeletal traction with a Steinmann pin through the superior pole of the patella to regain length of the shortened tendon. However, this technique is not recommended when a total knee replacement is present.
A modification of the Kelikian technique was reported by Cadambi and Engh10 (Fig. 13.2). In a series of seven patients with a patellar tendon rupture following total knee replacement, the semitendinosus tendon was routed along the border of the remnant of the patellar tendon and then through a transverse hole in the inferior pole of the patella, anterior to the patellar implantbone interface. In two of their seven patients, the repair was augmented by harvesting the gracilis tendon and passing it through the patella drill hole as well. Postoperatively, weight-bearing was begun within 48 hours in a knee immobilizer or cast. Knee motion was then initiated at 6 weeks and progressed slowly over the next 10 weeks in a hinged knee brace. They reported that quadriceps strength and knee motion was restored in all patients.
Other authors have reported the successful use of allografts to manage disruptions of the extensor mechanism. Emerson and associates3 have published on the successful use of an extensor mechanism allograft in a series of 15 patients with a rupture of the patella tendon in association with a total knee arthroplasty. The allograft consisted of the tibial tubercle, patellar tendon, patella, and quadriceps tendon that was freeze-dried or fresh-frozen. The graft was secured to the tibia with two screws distally and by non-absorbable suture attachment to native quadriceps tendon proxi-mally. Motion was begun postoperatively as soon as the wound was sealed limiting flexion to 60 degrees in a hinged knee brace for the first 6 weeks, and progressed to 90 degrees by the end of the second 6 weeks. The authors reported that all but three patients received full active extension, with 66% of patients having no appreciable extensor lag.
More recently, Zanotti and colleagues16 have reported successful treatment of a patellar tendon-deficient knee in a single patient with the use of a bone-patellar tendon-bone allograft. Their technique employed an irradiated, freeze-dried patellar-patellar tendon-proximal tibial allograft from a fresh cadaver. The host patella was prepared to accept the graft by creating a bone-to-bone interference fit further secured by circumferential sutures. The host tibia was prepared to accept the bone block of the graft, then tibial fixation was secured with a cortical screw. The repair was protected postoperatively in a cast for 3 months, and progressed to ambula-tion with a KAFO orthosis. They reported the graft to be healed with full active extension at 2-year follow-up.
Our current technique for reconstruction of chronic tears of the patellar tendon utilizes fresh-frozen extensor mechanism allograft that includes the tibial tubercle, patellar tendon, patella, and quadriceps tendon (Fig. 13.3). This is our preference because of the substantial amount of tissue that is available. Because disruptions of the extensor mechanism can lead to flexion instability, it is desirable to use a posterior-stabilized prosthesis. If there is any doubt about stability, then the arthroplasty should be revised to a constrained prosthesis. This may require revision of all the components. Finally, in planning the reconstruction, consideration must be given to the skin and surrounding soft tissues. It is not unusual
to be referred a case for allograft reconstruction that has had several prior attempts at repair. Because the skin may be adherent or there may be multiple scars, soft tissue expanders have been shown to be helpful, and should be considered.12 This is also important because the tibial tubercle allograft does add bulk to the proximal tibia making closure difficult.
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