Extensor tendon rupture after total knee arthroplasty
The incidence of extensor tendon rupture (Figure 1) after TKA has been reported in a range of 1–12% [1, 2]. Their etiology is complex and multifactorial, and poor results emphasize the importance of prevention [3–5]. Often, the rupture occurs during a traumatic event, which may be obvious, eg, a fall on the flexed knee, or trivial, eg, arising from a chair or carrying a heavy weight. Usually, the event causes the rupture because of preexisting fragility in the tendon .
The underlying reasons can either be patient-related or structural factors. When patient-related factors are the cause, several years may elapse between the TKA and the tendon rupture. When structural factors are the cause, the rupture often occurs early in the recuperative period .
Patient factors include obesity and other comorbidities. Obesity will lead to higher loads on the extensor, which it may not be able to withstand. On the other hand, several systemic diseases have an effect on soft-tissue quality, be it through their impact on blood supply, or through triggering inflammatory processes. Many comorbidities have been implicated in extensor tendon ruptures, including hyperthyroidism, diabetes mellitus, rheumatoid arthritis (RA), connective tissue disorders like systemic lupus erythematosus, and chronic renal failure [6, 8]. Additionally, long-term high-dosage glucocorticoid or fluoroquinolone use, or repeated intraarticular glucocorticoid injections can weaken collagenous tissues, and thus predispose patients for tendon ruptures .
Structural factors are often related to prior knee surgeries. To maintain good tissue quality of the extensor tendons in the long run, an optimal blood supply is vital. However, multiple surgical interventions around the extensor mechanism, including distal realignment procedures, will weaken and contribute to reduction of the blood supply . The more extensive the dissection, the higher the compromise of the vascularization.
Yixin Zhou, Professor and Chairman of Department of Adult Reconstructive Surgery, Beijing Jishuitan Hospital, points out: “Patients with the known relevant comorbidities, with stiff knees and a weak extensor mechanism, as well as male patients over 40 with tendinopathy, should raise red flags for surgeons and make them doubly careful with every maneuver avoiding overtension of the extensor. It is obvious that an impairment of vascularization has deleterious effects on any patient. However, in patients suffering from these conditions, the risk of subsequent tendon failure is so much higher. Therefore, every effort should be undertaken to be as vascularization-sparing as possible.”
Upon performing the TKA surgery, various vascular structures are imperiled (Figure 2). First, the medial and descending genicular arteries are at risk during medial arthrotomy. Second, the lateral-inferior genicular artery and the anterior-tibial recurrent artery are at risk during fat-pad excision. Third, the lateral-superior genicular artery is at risk during release of the lateral retinaculum [6, 8–11].
The importance of tibiofemoral joint stability
Beyond the mere stretching of the leg, a major function of the extensor mechanism is to stabilize the tibiofemoral joint. Basically, the entire knee is primarily stabilized by soft tissues, ie, the cruciate and collateral ligaments as well as the tendons of the muscles that span the joint. If any of these structures is weakened, the remaining structures will have to take over. Depending on the severity of the damage, they may be subjected to stresses they cannot withstand. Particularly in TKA patients, soft-tissue integrity if often compromised. Fortunately, a wide range of prosthetic designs exist that can be matched to various degrees of knee stability. Adequate stability can be provided by constrained, ultraconstrained, or hinged knee prostheses.
Did you know?
In the early days of knee endoprosthetics, hinged knee prostheses connected tibia and femur in a manner that would subject the prosthesis-bone interface to tensile forces and no rotating platforms existed. The effects were devastating. As we know today, tensile forces on the implant-bone interface will lead to early loosening. Nowadays, condylar loading rotating platform-hinged prostheses are able to rotate, providing stability without subjecting the bone to tensile forces.
In the presence of tibiofemoral instability, the extensor mechanism has to overwork to stabilize the knee—in so doing, it is subjected to excessive, intolerable stresses.
For a successful restoration of the extensor mechanism, it is imperative that the surrounding structures provide sufficient stability to avoid overloading. In case they are compromised, they should also be repaired or reconstructed. Often, however, their condition will not allow this. In this case, suitable prosthetic designs like constrained or hinged prostheses will perform the stabilizing function.
Yixin Zhou states: “Since extensor rupture is a severe complication which has significant clinical consequences, usually we don ’t hesitate to upgrade the prosthesis to a constrained condylar knee prosthesis (CCK) or a rotating hinge knee (RHK) whenever the tibiofemoral joint has been destabilized. But of course, with a fresh extensor rupture and no impairment of the tibiofemoral joint stability, the operator may well let the tibiofemoral joint be and just repair the extensor.”
Since conservative treatment has only been suggested in selected cases of partial quadriceps tendon disruption, surgery is the mainstay of treatment for most extensor disruptions.
There are two fundamentally different ways to surgically treat extensor ruptures. The first is direct repair, ie, approximating the remnants of the tendon or, in the case of bony avulsions, the bone, and fixing them. The repair may or may not be augmented with synthetic graft or an adjacent tendon.
The second is the tendon reconstruction. For a reconstruction, additional material is used, which takes over the function of the ruptured tendon.
To select the best treatment method, there are two major determinants: the time from injury and the location of the tear. When the injury is fresh, the remnants of the tendon can easily be approximated. Therefore, Yixin Zhou always attempts direct repair for acute ruptures. For end-to-end repair, he uses nonabsorbable sutures. For tendon avulsions, he prefers anchors, interference screws, and nonabsorbable sutures, which he uses to fix the tendon in bone tunnels. For chronic ruptures, especially when more than 6 weeks have passed since the injury, he recommends performing a reconstruction of the extensor mechanism using autograft, allograft, or synthetic graft.
Direct repair techniques
Simple repair can be performed by direct or transosseous suturing, using nonabsorbable sutures, anchors, or staples . Note that direct repair with suture anchors in the patella can be complicated by the presence of patellar resurfacing .
For direct suturing, usually the Krackow technique, a locking loop suture technique commonly applied in tendon repair, is used . The repair should be protected by a cerclage wire or thick nonabsorbable sutures. Care should be taken to position the patella at the normal height . Some authors have argued that direct repair hardly ever works unless it is augmented . Yixin Zhou explains: “If the injury is fresh and the tissue quality of the tendon is good, there is a good chance that direct repair may work without augmentation. However, I would advise to additionally put a cerclage wire through the patella and tibial tubercle to form a frame. This will offload the repair and thus improve soft-tissue healing. During recuperation, the knee should rest in a brace to avoid overstretching of the newly repaired ligament. However, if the tendon quality and strength are in doubt, I augment the repair. My favorite material is synthetic mesh. It is readily available, easy to cut and shape, and possesses adequate strength. When using synthetic mesh, it is important to bury it well in the native soft tissues. Only this will allow a good fibrous ingrowth, so the newly formed tissue can eventually take over the tendon's function. Moreover, the rough surface of the synthetic mesh may lead to pain and discomfort upon moving the knee. Burying it well will thus also help avoiding soft tissue irritation.”
Various techniques have been described for the direct repair of the patellar tendon to explain how tunnels can be oriented in the patella to fix sutures or anchors. Ode et al and Liu et al drilled longitudinal tunnels, whereas Meyer et al used a combination of longitudinal and oblique tunnels [17–19].
For the direct repair of the quadriceps tendon, Rosenberg et al distally fixed suture anchors in the superior pole of the patella or through drill holes . Jimenez et al described virtually the same technique, however, they augmented this with an autograft construct .
Tendon reconstruction techniques
Reconstruction can be performed with autograft (Figure 3), allograft (Figure 4), or synthetic graft (Figure 5).
The most commonly used autografts are semitendinosus, gracilis, and quadriceps tendon.
A wide range of techniques on how to reconstruct extensor tendons has been published. The basic principle for reconstruction of the patellar tendon is to distally fix the graft in the tibia and proximally, either fix it in the patella or in the quadricipital tendon. For quadriceps tendon ruptures, the basic principle is to distally, either fix the graft in the patella, the patellar tendon, or the tibia, and proximally, fix it in the remnants of the quadriceps tendon or the quadriceps muscle itself.
To choose the best treatment option for an individual patient, the acuity and location of the injury, the quality of the remaining tissue, the quality of potential autograft, as well as the physiological age and activity demands of the patient must be considered [8, 9].
For patellar ligament reconstruction, distal anchorage in the tibia has been performed with tunnels to accept autograft tendons, fixed with interference screws [26, 27] or by creating a trough in the tibia or tibial tubercle. A trough was either used to fix an allograft bone block  or, upon reconstructing the entire extensor mechanism, to secure a synthetic graft with bone cement . Proximally, grafts have been anchored in transverse patellar tunnels  or transverse in the quadriceps tendon [29–32]. The reconstructed ligaments were either crossed over in front of the patella or created a frame in a box fashion. Another technique for patellar ligament reconstruction is splitting of the graft, with half of it passing through a longitudinal tunnel in the patella, and the other half around the patella. Both graft ends are then sewn directly into the intact quadriceps tendon . For the use of semitendinosus autograft, a technique has been reported that passes the graft through a transverse patellar tunnel or through the quadriceps tendon, and then feed the graft back distally to sew it to itself close to its insertion point [6, 33].
For quadriceps tendon reconstruction, proximal anchorage of the graft is always by sutures to the remnant tendon or the quadriceps muscle. Distal anchorage in the tibia or tibial tubercle has been performed with transosseous sutures, screws, or, if the graft included a calcaneal bone block, by tamping the bone block into a cavity that had been chiseled into the tubercle and then fixing it with screws or wires [22, 34–36]. Another paper described anchoring the graft transversally in the patellar tendon just below the patella, after crossing it over in front of the patella .
Outcomes and conclusions
As we have seen in the last paragraph, the techniques that have been used for extensor tendon repair or reconstruction are highly variable. Unfortunately, the study populations are very small and there is a lack of randomized studies comparing the different treatment options. Therefore, it is no surprise that no consensus exists in the literature on which type of extensor mechanism reconstruction yields the best results .
Primary repair has shown rather unfavorable results with poor outcomes in most patients that had complete tendon ruptures. Rand et al reported that suturing failed in six of nine cases and stapling in two of four cases . Lynch et al reported that direct repair performed in four cases failed consistently and indicated that chronic rupture may increase the risk of failure . Likewise, in quadricipital tendon ruptures, Dobbs et al reported a high failure rate .
Reconstruction with autograft has shown variable results [5, 27, 33]. In a series of seven patients with reconstruction of the patellar tendon with semitendinosus autograft, Cadambi and Engh achieved satisfactory results . However, this often came at the expense of a limitation in flexion.
Allograft augmentation of a disrupted extensor mechanism after TKA has recently gained popularity . Achilles tendon allografts and extensor mechanism allografts have demonstrated satisfactory outcomes. Crossett et al reported on a series of nine patients with Achilles tendon allograft reconstruction . The results showed improved walking ability, decreased extensor lag, improved ROM, and improved knee stability. However, they also reported high rates of secondary patellar ascension, even though this did not appear to affect function. Diaz-Ledezma et al reported satisfactory results in nearly 60% of patients but more than a third of failures in a series of 29 knees in 27 patients . Malhota at al reported a series of four patients who had undergone reconstruction with an extensor mechanism composite allograft consisting of a patella-patellar tendon-tibial tubercle. The outcomes were satisfactory, with good active extension and healing of the grafts. Emerson et al reported on a series of 15 patients in which a complete extensor mechanism allograft was used to treat a rupture of the patellar tendon. The results demonstrated improved ambulatory ability, no loss of flexion, and improved extensor lag. However, graft complications included one early graft rupture, one early quadriceps junction failure, and one patellar component loosening. Moreover, one graft fractured after revision of a metal-backed patella . Brown et al reported on 50 consecutive complete extensor mechanism allograft reconstructions, performed in 47 patients. In spite of the highly significant improvement of the mean Knee Society score from 33.9 to 75.9, 19 reconstructions (38%) were considered failures, including four that were revised to a second extensor mechanism allograft due to failure of the allograft, five for deep infection, and ten considered clinical failures secondary to a Knee Society score of <60 points or an extensor lag of >30° .
One study deserves special attention because it compares different techniques and materials. Lamberti et al reported results of three different reconstructive techniques for chronic patellar tendon disruption, namely Achilles tendon allograft with a calcaneal block (Group I), autograft of the quadriceps tendon reinforced by the semitendinosus tendon (Group II), and a full extensor mechanism allograft consisting of the tibial tubercle, patellar tendon, patella, and quadriceps tendon (Group III). Each of the groups comprised seven patients, however, group allocation was according to surgeon's preference and not randomized. Statistically significant differences were seen in the mean postoperative Knee Score between groups I (87.7 ± 14.3 points) and II (70 ± 4.1 points), but not between groups I and III (78.9 ± 14.6 points) or between groups II and III. No significant differences in the postoperative extensor lag were seen .
The results reported with synthetic graft materials are reasonable. Aracil et al reported on five reconstructions of the patellar tendon where direct repair was augmented by a Leeds-Keio ligament. Active extension of −10° was achieved by all the patients and a flexion of 90° or more. However, one superficial infection developed. Over time, the reconstruction stretched less than 1 cm without significantly affecting the function . Fujikawa et al reported on 19 knees in 18 patients who had undergone extensor reconstruction with the Leeds-Keio ligament. They achieved an average range of motion of 146°. Four patients could squat fully in the Japanese style, but an extension lag <10° remained in four patients. No infection, persistent joint effusion, or rerupture of the extensor apparatus occurred . Browne and Hanssen reviewed 13 consecutive patients who underwent extensor mechanism reconstruction with the Marlex mesh for patellar tendon disruption . Nine patients had good outcomes with a significant improvement of the mean Knee Society score, slightly improved knee flexion, and an extensor lag of no greater than 10°. However, in three patients, the graft reconstruction failed within 6 months . Abdel et al reviewed 77 patients with extensor mechanism disruption who underwent reconstruction with the Marlex mesh. The Knee Society score results improved significantly, and the extensor lag improved by a mean of 26° with mean postoperative extensor lag of 9°. However, twelve patients experienced a failure that required mesh revision: five for patellar tendon rupture, five for quadriceps tendon rupture, and two for symptomatic lengthening. Four additional patients with mesh failure were treated with bracing .
In summary, a wide range of treatment options exists for extensor ruptures in TKA patients. Due to a lack of large and comparative unbiased clinical studies, there is no clinical evidence as regards which treatment works best for which patient. Moreover, the achieved outcomes are heterogeneous. Therefore, surgeons have to rely on their own judgement and experience to find the optimal treatment for each of their patients.
The known risk factors for extensor disruption are manifold and often related to the patient's history and to technical difficulties encountered during surgery. Accordingly, preoperative identification of patients at risk for extensor mechanism disruption and proper surgical planning is essential . The key to prevention lies in an indepth review of the patient's history along with a detailed physical examination. Paying close attention to surgical detail with appropriate knowledge of patients’ medical and surgical risk factors can help to prevent the problem before it arises.
This series of articles was created with the support of the following specialists (in alphabetical order):
This issue was written by Elke Rometsch, AO Innovation Translation Center, Clinical Science, Switzerland.
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