Failed Surgical Reconstruction of Patellar Tendon Aplasia: A Report of Two Cases

Kasten, Philip MD; Weiss, Stefan MD; Carstens, Claus MD, PhD; Thomsen, Marc MD, PhD

Journal of Bone & Joint Surgery - American Volume:
doi: 10.2106/JBJS.D.02333
Case Reports
Author Information

1 Department of Orthopaedic Surgery, University of Heidelberg, Schlierbacher Landstrasse 200a, 69118 Heidelberg, Germany. E-mail address for P. Kasten:

Article Outline

Aplasia of the patellar tendon rarely has been reported in the orthopaedic literature. In a MEDLINE search from 1963 through 2004, we found only four reported cases1-3: two had been detected with use of magnetic resonance imaging in patients with fibular or tibial hemimelia (noted in one patient each)3, one had been discovered with use of ultrasound in a nine-day-old girl with tibial hemimelia1, and one had been noted in a twenty-five-year-old woman with bilateral congenital absence of the patellar tendon2. None of these three reports described the indications for surgery or the results of attempted reconstruction.

We present the cases of two patients who had congenital aplasia of the patellar tendon associated with shortening of the involved limb. One patient underwent reconstruction of the patellar tendon; the other was treated nonoperatively. The parents of both patients were notified that data concerning the cases would be submitted for publication.

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Case Reports

CASE 1. An eight-year-old boy presented to our institution with lower-extremity limb-length inequality (with the left lower limb being shorter than the right).' This condition caused the boy to limp and interfered with activities of daily living and sports activities.

During pregnancy, the patient's mother had had eclampsia with severe hypertension. Ten weeks prior to the due date, it became necessary to deliver the child by cesarean section. The boy weighed 1250 g at birth and was monitored for ten weeks in the intensive care and intermediate care units. The family history was negative for musculoskeletal abnormalities, and an older brother was normal. When the child was two months of age, a skin depression developed over the lateral aspect of the left femoral condyle and an extension lag of the knee was observed. When the patient reached six months of age, the patella was found to be more proximally positioned than normal on both physical examination and ultrasonography. Plain radiographs showed no appreciable abnormalities of the knee; however, the patella was not yet ossified. The diagnosis was a knee flexion contracture due to an arthrogryposis-like disorder, and physical therapy was recommended. Annual clinical examinations, performed until the patient was seven years of age, revealed an active extension lag of 20° to 35°. Repeat radiographs demonstrated hypoplasia of the femoral condyles as well as a proximally positioned patella (patella alta).

Physical examination at our institution revealed that the left lower extremity was 6 cm shorter than the right (with a difference of 3 cm in the femur and 3 cm in the tibia) and that the knee extensor mechanism was insufficient. The patient had a unilateral crouched gait because of the shortening of the left lower extremity. An active extension lag of 40° was documented. Passive range of motion of the knee was from 10° to 130°, with a 10° flexion contracture. There was an absence of patellar engagement with the patellofemoral groove even with the knee in maximum flexion. No patellar tendon was palpable. Patellar mobility and stability were essentially normal, and the knee was stable and not painful. The anterior and posterior cruciate and collateral ligaments were palpated and were found to be intact and stable. Because of the flexion contracture of the involved knee, there was a compensatory flexion contracture of the hip as well as ankle equinus (each of which measured 10° to 15°). No other abnormalities of the affected or the contralateral extremity were observed during the physical examination. Repeat radiographs and magnetic resonance images demonstrated a hypoplastic patella in a more proximal position than normal. The patellar tendon was absent, and the quadriceps muscle was severely hypoplastic (Figs. 1-A, 1-B, 1-C, 1-D).

After a discussion of nonoperative and operative options, the parents decided to proceed with patellar tendon reconstruction. A limb-lengthening procedure was also discussed but was not performed.

Intraoperatively, the patellar tendon was absent and the quadriceps muscle was fibrotic, with adhesions to the femur. With use of a V-Y quadriceps mechanism reconstruction and dissection of the adhesions, the hypoplastic patella was mobilized distally to the patellofemoral groove. The patellar tendon was reconstructed by doubling the capsule distal to the patella and using a semitendinosus tendon autograft and a PDS (polydioxanone) cord (Ethicon, Norderstedt, Germany). Following reconstruction, the passive intraoperative knee motion was from 0° to 60° of flexion.

Postoperatively, the lower extremity was immobilized in an above-the-knee cast for ten days. Intermittent passive range-of-motion exercises (with a flexion arc of 0° to 40°) were then performed for twenty minutes, three times a day, for one week. To stimulate the quadriceps, a 2-Hz electric muscle stimulator (Microstim, Hamburg, Germany) with an impulse intensity of 10 to 30 mA and an impulse duration of 7 ms was applied for thirty minutes per day, starting at two weeks postoperatively and continuing for eight weeks. At 2.5 weeks postoperatively, 60° of passive flexion was allowed during physical therapy. When physical therapy or passive motion was not being performed, the lower extremity was immobilized in a custom-made above-the-knee posterior splint, which was used for six weeks postoperatively without weight-bearing. Subsequently, the patient received a commercially available knee sleeve with an incorporated silicone insert that applied no pressure to the patella (GenuTrain; Bauerfeind, Kempen, Germany). Partial weight-bearing was then allowed for four weeks, followed by full weight-bearing. The patient utilized a shoe-lift because of the limb-length inequality. Physical therapy was continued three times a week, with particular attention focused on quadriceps strengthening. Wound-healing was unimpaired.

One year postoperatively, the patient's gait had improved. There was still an active extension lag of 35°. The passive range of motion was from 0° to 90° of flexion. A repeat magnetic resonance imaging scan showed that the patella was positioned in the patellofemoral groove and that the reconstructed patellar tendon was intact.

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Two years postoperatively, when the patient was ten years old, the gait had deteriorated and was worse than it had been before the operation. It was characterized by a persistent short-leg limp with an insufficient quadriceps mechanism; concentric contraction of the quadriceps did not produce full knee extension. The patient compensated by swinging the affected limb forward to passively extend the knee, resulting in a limp. The parents and the patient were dissatisfied with the outcome of surgery. The child subsequently resumed physical therapy, and an electronic stimulator was used in an effort to strengthen the quadriceps muscle. Passive knee motion changed minimally, and there was a persistent extension lag of 60° (Fig. 1-E). The patella was palpable within the patellofemoral groove. The reconstructed patellar tendon was also palpable. The knee was otherwise stable and not painful. Additional magnetic resonance images showed that the reconstructed patellar tendon and the patella were in the physiologic position but that the quadriceps muscle remained atrophic (Figs. 1-F and 1-G).

CASE 2. A 7.5-year-old boy presented to our institution with a slightly impaired gait due to an insufficient knee extensor mechanism. He was not limited in activities of daily living or school-related sport activities, such as gymnastics; however, he could not participate in more vigorous sports, such as tennis or soccer. There was minimal pain after exertion.

The medical history revealed that, during pregnancy, the boy's mother had undergone amniocentesis that had resulted in leakage and that had been treated with bed rest for one week. The child was delivered vaginally on the expected date and without complications. The birth weight was 2800 g, and there were no postnatal problems. The family history was negative for pediatric musculoskeletal abnormalities except for idiopathic scoliosis, in the elder of two brothers, which had been treated nonoperatively. The patient walked independently at fourteen months of age. At two years of age, an insufficient knee quadriceps mechanism was observed on the right side; however, no radiographs or other studies were performed at that time. When the patient was four years of age, a developmental delay was diagnosed and, for the first time, patellar tendon aplasia of the right knee was documented on the basis of a physical examination and ultrasonographic testing. Radiographs of the right knee demonstrated that the patella was in a more proximal position than normal. The treating physicians recommended operative treatment without specifying their operative strategy.

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Physical examination revealed that the patient walked with the involved extremity externally rotated 30° to 40° and compensated for the insufficient extensor mechanism by swinging the affected limb forward to passively extend the knee. The right femur was 2 cm shorter than the left femur. The tibial lengths were equal. Passive range of motion of the right knee was from 5° to 150° of flexion, with an active extension lag of 30°. The patella was palpable and mobile, but it was positioned proximal to the patellofemoral groove (patella alta). No ligamentous instability was present. A magnetic resonance imaging scan demonstrated that the patella was of normal size but was lying in a more proximal position than normal and that the patellar tendon was absent. The quadriceps muscle appeared to be severely hypotrophic. The ranges of motion of the hip and ankle were normal. Neurologic examination revealed normal findings. The contralateral extremity was examined and was deemed normal.

When the patient presented to our institution, we recommended observation because of the lack of symptoms and the relatively normal function of the limb. Two years later, when the boy was 9.5 years of age, physical examination revealed essentially no change in his condition: the gait was still slightly impaired by the deficient quadriceps muscle, and the knee extension lag was still 30°.

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The patellar tendon is formed during the early stages of fetal development. It begins to form as early as the sixth week of fetal life as a detachment from the lower part of the femur4. It descends by the third month to lie in the depression between the future femoral condyles4. The quadriceps mechanism is then seen coursing over the anterior surface of the anlage of the patella. According to a study by Gardner and O'Rahilly, a differentiating patellar tendon was seen in two of nine embryos by six weeks5. By seven weeks, the patellar tendon was evident in all nine embryos. At 7.5 weeks, the medial and lateral patellar retinacula were present, and, by eight weeks, the knee joint resembled that of an adult5.

In children, the patella can be difficult to visualize radiographically because it ossifies late. The ossification of the patella is visible radiographically by two to four years of age in girls and by three to seven years of age in boys6.

Our patients appeared to have a congenital distal femoral deficiency. Both lacked the patellar tendon and had a short femur, and one had a hypoplastic patella. To our knowledge, these findings have not occurred in association with any known syndromes. A common entity that includes a hypoplastic or absent patella is the nail-patella syndrome (onycho-osteodysplasia syndrome), which can be associated with hypoplasia of the ischiopubic component of the pelvis, but to our knowledge there have been no reports of associated patellar tendon aplasia4,7-11.

Our first patient had been diagnosed with arthrogryposis multiplex congenita at six months of age. At the time that the patient presented to our institution, we believed that this diagnosis was unlikely because the contracture of the hip, knee, and ankle seemed secondary to the absent patellar tendon and the short extremity. No dimpling of other joints was present, and the patient lacked the classic appearance of a “wooden doll.” However, in retrospect, it is possible that the patient had a monomelic form of this disorder. The quadriceps muscle was of a firm and fibrotic consistency, which would be consistent with the findings associated with the myopathic form of arthrogryposis12,13.

In the case of our second patient, the child's mother had undergone amniocentesis, which had resulted in leakage of amniotic fluid. Theoretically, the child's lower extremity could have been injured during this procedure; however, we could not find any reports of a similar case.

Patients with tibial or fibular hemimelia may have an absent patellar tendon1,3. The presence or absence of a functioning quadriceps mechanism has a considerable impact on the treatment of tibial hemimelia in that the decision to perform fibular centralization or knee disarticulation is made on the basis of whether there is a functioning quadriceps mechanism1,14,15. If the quadriceps mechanism is absent or insufficient, reconstructive procedures in which fibular centralization is performed are not recommended14,15. The rationale for this recommendation is that the success of centralization of the fibula depends on the function of the knee, which depends on an intact quadriceps mechanism. Quadriceps muscle insufficiency may result in a flexion deformity of the knee1.

To our knowledge, only four cases of patellar tendon aplasia have been reported1-3. Two cases were found on magnetic resonance imaging in patients with fibular or tibial hemimelia3. The third case was discovered with use of ultrasound in a nine-day-old girl with tibial hemimelia1. Clinically, the knee was flexed and no active extension was observed. Radiographs revealed shortening of the femur and absence of the tibia, and ultrasonography of the knee demonstrated no tibial anlage or patellar tendon. In that patient, disarticulation of the knee was performed because of a fixed flexion deformity of the knee and absence of the quadriceps tendon1. The fourth case, reported by Messina et al., was noted in a twenty-five-year-old woman who had bilateral congenital absence of the patellar tendon2. That patient had presented for the treatment of right knee pain that had begun two weeks earlier, after a twisting injury. She reported an acute onset of swelling, one episode of locking, and increasing fullness and pain along the lateral aspect of the knee. She had no history of knee trauma or knee problems and was an active dancer who practiced for as long as four hours each day. She was also active in sports, participating in both basketball and volleyball. The initial physical examination revealed a mild crouched gait. The quadriceps muscle had normal mass and tone. Marked bilateral patella alta was noted. Observation of patellar tracking revealed an absence of patellar engagement with the patellofemoral groove until the knee was in 120° of flexion. The passive range of motion of the knee was from 0° to 135° or 140° of flexion bilaterally. A bilateral active extensor lag of 8° to 12° was present. The absence of the patellar tendons was confirmed on magnetic resonance imaging2. No specific therapy was documented in that report2.

Treatment of an absent patellar tendon is of uncertain value. The patient with bilateral congenital patellar tendon aplasia who was described by Messina et al.2, for example, was well adapted to the defect. That patient was very active in sports, and the absence of the patellar tendons was unknown prior to the injury. In contrast, one of our patients (Case 1) was limited in activities of daily living and sports activities. He had 6 cm of lower-extremity shortening, hypoplasia of the patella, aplasia of the patellar tendon, and hypoplasia of the quadriceps muscle. The absence of the patellar tendon caused a knee extension lag and a flexion contracture. Because functional deficits were present, the patient was offered surgical treatment to improve the biomechanics of the knee joint. Intraoperatively, the quadriceps muscle appeared severely fibrotic and had fatty infiltration. Despite the fact that the patellar tendon was successfully reconstructed, as seen both clinically and on magnetic resonance imaging, the functional outcome two years after the operation was disappointing because the quadriceps muscle had not regained function. Postoperatively, the gait was worse than it had been before surgery, despite intensive physical therapy.

Observation was recommended for our second patient (Case 2), who was of a similar age but who had minimal symptoms. The clinical course of this patient was unchanged during two years of follow-up; however, the long-term outcome is unknown.

The two cases described in the present report should alert the clinician that a knee extension lag in a child may, in rare cases, be caused by an absent patellar tendon. If operative reconstruction is considered, functional recovery may fail as a result of long-standing atrophy of the quadriceps muscle and tendon. On the basis of these two cases, we cannot give a clear recommendation for surgical reconstruction as the treatment for this rare condition. We recommend that, before the decision is made to perform a surgical reconstruction, the clinician should thoroughly document the existence of a functioning quadriceps muscle, the presence of which will optimize the possibility of a satisfactory functional recovery. ▪

The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

Investigation performed at the Department of Orthopaedic Surgery, University of Heidelberg, Heidelberg, Germany

1. , Harcke HT, Kumar SJ. Sonography in the management of tibial hemimelia. Clin Orthop Relat Res. 1990;251: 266-70.
2. , Meister K, Montgomery WJ. Bilateral congenital absence of the patellar tendon. Am J Knee Surg. 1997;10: 23-6.
3. , Jaramillo D, Hoffer FA, Kasser JR. MR imaging in congenital lower limb deformities. Pediatr Radiol. 1996;26: 381-7.
4. , Thneibat WA. Ischio-pubic-patellar hypoplasia: is it a new syndrome? Pediatr Radiol. 1997;27: 430-1.
5. , O'Rahilly R. The early development of the knee joint in staged human embryos. J Anat. 1968;102: 289-99.
6. . Radiology of postnatal skeletal development. X. Patella and tibial tuberosity. Skeletal Radiol. 1984;11: 246-57.
7. , Taor WS. The “small patella” syndrome. J Bone Joint Surg Br. 1979;61: 172-5.
8. , Gubler MC, Knoers NV. Nail-patella syndrome. Overview on clinical and molecular findings. Pediatr Nephrol. 2002;17: 703-12.
9. , Nelson J. Small patella syndrome. Am J Med Genet. 1995;57: 558-61.
10. . Comments on the ischio-pubic-patellar syndrome. Pediatr Radiol. 1997;27: 428-9.
11. , Satterwhite Y, Ogden JA, Pugh L, Ganey T. Nail patella syndrome: a review of 44 orthopaedic patients. J Pediatr Orthop. 1991;11: 737-42.
12. . Arthrogryposis multiplex congenita: spectrum of pathologic changes. Hum Pathol. 1986;17: 656-72.
13. . Pediatric orthopedics. 2nd ed. Philadelphia: Saunders; 1990. Arthrogryposis multiplex congenita (multiple congenital contracture); p 2086-119.
14. , Ginsburg GM, Hall JE. Brown's procedure for congenital absence of the tibia revisited. J Pediatr Orthop. 1996;16: 85-9.
15. , Eilert RE. Fibular transfer for congenital absence of the tibia. Clin Orthop Relat Res. 1979;139: 97-101.
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