Suture Anchor Repair for Superior Pole Patella Sleeve... : Techniques in Orthopaedics (original) (raw)
A sleeve fracture of the patella is a well-recognized pediatric osteochondral injury.1 Although most patellar sleeve avulsion fractures are seen at the inferior pole of the patella, superior pole fractures have also been reported.2–8 We present an unusual case of patella sleeve avulsion at the superior pole of the patella involving the undersurface of the extensor mechanism in an adolescent. Our patient and his family were informed that data concerning the case would be submitted for publication, and they consented.
PRESENTATION OF THE CASE
A 12-year-old boy fell on his flexed left knee while playing soccer, when his left foot got stuck in a pot hole as he was running. He experienced immediate discomfort and swelling over the left knee. He was otherwise healthy with no prior symptoms related to the left lower extremity. Clinical examination the next day revealed a moderate-sized effusion of the left knee with discrete tenderness over the superolateral aspect of the patella. He was unable to actively extend the injured knee despite lack of substantial knee pain. A palpable defect in the extensor mechanism, including the quadriceps and patellar tendons was not present. There was no joint line tenderness or ligamentous laxity noted on further examination of the injured knee.
Radiographs of the left knee demonstrated a small osseous fragment at the superior pole of the patella as well as a moderate-sized effusion (Fig. 1). A sleeve fracture of the superior pole of the patella was suspected. Magnetic resonance imaging (MRI) of the left knee demonstrated the periosteal sleeve to be detached from the patella and uplifted by the quadriceps tendon (Fig. 2). The avulsion involved approximately three fourths of the undersurface of the quadriceps tendon footprint. A small osteochondral fragment of the proximal pole of the patella was attached to the uplifted periosteum (Fig. 3). A large knee joint effusion was also noted. The remaining intra-articular structures including the menisci, collateral, and cruciate ligaments were intact.
Radiograph of the left knee demonstrates a small fracture fragment (arrow) at the superior pole of the patella as well as a moderate synovial effusion.
Sagittal proton density magnetic resonance image of the left knee demonstrating the periosteal sleeve to be detached from the patella (arrow) and uplifted by the quadriceps tendon.
Sagittal proton density magnetic resonance image of the left knee demonstrating a small associated bony avulsion (arrow) attached to the uplifted periosteum at the proximal pole of the patella. A large knee joint effusion is also noted.
On the basis of the above noted physical exam and imaging findings, a diagnosis of a sleeve fracture of the superior pole of the patella, involving the undersurface of the quadriceps tendon was made. Surgical repair of the sleeve fracture was recommended. At surgery, 6 days following the injury, a longitudinal incision centered over the superior pole of the patella was made. As the attachment of the superficial most fibers of the quadriceps were still in continuity with the anterior periosteum of the patella, this attachment was not disturbed. Instead, through the lateral parapatellar arthrotomy, the patella was partially everted and the fracture site visualized. Intraoperative findings confirmed a sleeve fracture of the superior pole of the patella with disruption of the deep three fourth attachment of the quadriceps with a small osteochondral fragment from the remaining patella (Fig. 4), periosteal stripping in the adjacent area of the proximal patella and torn medial and lateral retinaculum. Two bioabsorbable suture anchors with a #2 FiberWire (Arthrex, Naples, FL) were placed into the distal fragment through the exposed cancellous fracture area (Fig. 5) and the other end of the suture passed through the distal portion of the quadriceps tendon using a modified Bunnell stitch. With the knee in full extension, the sutures were tied and further repair of the soft-tissue sleeve was reinforced using heavy absorbable sutures. The medial and lateral retinaculum was also repaired. Following skin closure, the patient was placed in a long leg cast with the knee in full extension and allowed partial weight bearing with crutches.
Intraoperative view of the sleeve fracture of the superior pole of the patella demonstrating the small osteochondral fragment proximally (arrow) that was attached to the undersurface of the quadriceps tendon. The patella has been everted and a portion of the femoral condyle is visualized (star).
Intraoperative view demonstrating the passing of intraosseous suture anchors in the distal fragment. The first intraosseous suture has been placed (thin arrow) and the second anchor is being engaged in the distal fragment (thick arrow), before securing both sutures individually in the proximal fragment including the distal portion of the quadriceps tendon.
Approximately 10 days postoperatively, the cast was removed. His incision was healing well, and he was placed in a knee-immobilizer. Four weeks later, passive-assisted and active-assisted range-of-motion exercises of the knee was initiated and the knee-immobilizer was gradually weaned off over the next 3 weeks. Approximately 4 months after surgery, he had regained full mobility and strength of the injured knee and was able to perform 10 single-leg hops on each leg without any difficulty. Radiographs at that time revealed satisfactory healing of the osteochondral fracture of the superior pole of the patella (Fig. 6). He was allowed to return to sports at that time, with the use of a soft patellar sleeve during contact sports. He returned to playing soccer and baseball at a competitive level. At the most recent follow-up, 10 months postoperatively, he remained asymptomatic with regards to his left knee.
Lateral radiograph of the left knee 4 months after surgery demonstrating a healed osteochondral fracture of the superior pole of the patella.
DISCUSSION
We present an unusual case of a periosteal sleeve avulsion fracture involving the superior pole of the patella with intact superficial fibers of the entire width of the quadriceps tendon. On the basis of our review of the literature, at least 14 cases of superior pole patella sleeve avulsions have been previously reported.2,4–6 However, we were unable to find a similar case involving the undersurface of the entire width of the extensor mechanism.
A patella sleeve fracture is a peculiar type of pediatric osteochondral injury that also involves the adjacent articular cartilage and periosteum.1 The majority of sleeve avulsion fractures involves the inferior pole of the patella, and is most commonly due to injury to a flexed knee.3 On plain radiographs, an osseous fragment is often present at the superior or inferior pole of the patella. Advanced imaging such as an ultrasound1,7,8 or an MRI3,5,9 has been used to confirm the diagnosis of a sleeve fracture of the superior pole of the patella.8 The MRI aids in defining the true extent of injury to the articular cartilage and the disruption of the extensor mechanism, an important assessment when evaluating the need for surgical repair. The periosteum and avulsed articular cartilage are best identified on sagittal T2-weighted images of an MRI. There are different signal intensities of the patella cartilage and underlying bone with fluid being hyperintense (Figs. 2, 3).
The majority of cases in previous reports of sleeve fractures of the superior pole of the patella were treated with surgical fixation, with 4 to 6 weeks of postoperative immobilization.3,4,6,8 A few authors have noted satisfactory results with cast immobilization only for minimally displaced fractures of the superior pole.5,7,9 It can be debated whether our patient would have had similar outcome had he been treated nonoperatively with cast immobilization alone. On the basis of the intraoperative findings with involvement of the entire width of the osteochondral fragment attached to the undersurface of the quadriceps tendon with substantial disruption of the medial and lateral retinaculum, while this fracture may have healed with prolonged cast immobilization, it is likely that the patient may have had persistent weakness in his extensor mechanism, that could have negatively impacted his daily activities including participation in recreational sports.
Our case has unique diagnostic and therapeutic implications. First, given the lack of disruption of the superficial fibers of the quadriceps tendon with the adjacent periosteum of the anterior surface of the patella, a defect in the substance of the quadriceps tendon was not palpable. Thus, one needs to have a high index of suspicion for a sleeve fracture based on the typical mechanism of injury (falling on a flexed knee) in a skeletally immature individual along with local tenderness and inability to actively extend the knee. Besides a plain radiograph of the knee, an MRI scan can be very helpful in confirming the diagnosis and assessing the extent of disruption of the extensor mechanism, as well as rule out additional intra-articular pathology. Second, it can be challenging to approach the fracture site on the undersurface of the quadriceps tendon without disrupting the tenuous but intact superficial attachment of the tendon to the anterior periosteum of the proximal portion of the patella. Previous authors have described using a transverse incision to approach a sleeve fracture involving the superior pole of the patella.2,8 We found that by everting the patella using a longitudinal parapatellar arthrotomy, one could pass the bone anchor sutures into the distal fragment through the exposed cancellous surface of the proximal pole sleeve fracture site without disrupting the integrity of the superficial fibers of the adjacent quadriceps tendon.
On the basis of a relatively short follow-up, our patient regained full function and returned to regular activities including contact sports four months following primary repair of this unique sleeve fracture of the superior pole of the patella. Prompt diagnosis aided with an MRI can help delineate the extent of injury accurately and aid in preoperative planning. Surgical repair using a parapatellar arthrotomy without disrupting the superficial most fibers of the quadriceps mechanism is feasible and allows the patient to return to their functional activities in a short period.
REFERENCES
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Keywords:
sleeve fracture; superior pole; patella; adolescent; suture anchor
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