Ossification in the patellar tendon and patella alta following sports injuries in children. Complications of sleeve fractures after conservative treatment

Management and subsequent outcomes of patellar sleeve injuries: A retrospective case series of 90 pediatric and adolescent patients

Purpose

This study aims to report the epidemiology of patellar sleeve injuries, describe diagnostic findings and treatment, and assess functional outcomes following different treatments.

Methods

A medical database was queried from 1990 to 2016 to identify patients ≤18 years presenting to a single pediatric institution with a patellar sleeve injury. Patients with significant comorbidities or previously operatively treated for ipsilateral knee injuries were excluded. Standard demographic data, mechanism of injury, skeletal maturity, injury-related radiographic parameters, along with treatment paradigms, post-treatment clinical and radiographic findings, and patient-reported outcomes were collected.

Results

A total of 90 patients, mean age of 10.7 years (range: 7-17) was included, of which 69 (77%) were male. Seventy-three percent of all injuries occurred while playing sports (particularly football/basketball/soccer), with "direct blow" or "landing" being the most prevalent mechanisms of injury. Twenty-six (29%) underwent operative treatment, with transosseous suture fixation being the most popular surgical technique (73%). Of the 64 (71%) non-operatively treated patients, 18 (39%) were placed in a hinged knee brace locked in extension with the remainder split between casting and standard knee immobilizer. Compared to the non-operative cohort, a higher percentage of the operative group had a pre-treatment extensor lag (p < 0.001) and greater fragment displacement (p < 0.001) with patella alta (p < 0.001) on imaging. There was no difference in outcome scores (Pedi-IKDC/Lysholm) or patella alta on radiographs between groups. Post-treatment surveys indicated no difference in residual pain or ability to return to sport.

Conclusion

This large case series provides valuable epidemiologic, clinical, and radiographic data describing patellar sleeve fractures, along with outcomes following non-operative and operative treatments.

Level of evidence

IV.

Patellar Tendon Rupture During Postoperative Physiotherapy for Crouch Gait: A Case Report

INTRODUCTION

A 14-year-old adolescent girl with spastic diplegic cerebral palsy underwent bilateral distal femur extension osteotomy and patellar tendon plication. Two and a half months after surgery, during physiotherapy, she sustained mid-substance tear of the left patellar tendon. The girl was successfully managed with patellar tendon repair and augmentation with tensor fascia lata autograft.

CONCLUSION

Patellar tendon rupture during rehabilitative physiotherapy after patellar tendon plication surgery is rare. Postoperative protocols in patients with cerebral palsy are crucial and should progress gradually to improve knee range of motion. This report highlights that patellar tendon repair with fascia lata augmentation yields good outcome.

Synovectomy induced patellar tendon ossification in patient with rheumatoid arthritis: A case report and review of the literature

INTRODUCTION

Patellar tendon ossification is a rare complication that primarily occurs following a knee injury. This article aims to describe, for the first time, a case of patellar tendon ossification following synovectomy.

CASE PRESENTATION

A 48-year-old male with a diagnosis of rheumatoid arthritis presented with swelling in his left knee following a synovectomy procedure. After a thorough physical examination, radiographic assessment, and computed tomography, the patient was diagnosed with total patellar tendon ossification. Subsequently, the patient underwent excision of the ossified mass and tendon reconstruction using an Achilles allograft.

DISCUSSION

The primary causes of patellar tendon ossification are iatrogenic and traumatic injuries. The presence of rheumatoid arthritis, which negatively affects tissue healing, may exacerbate this condition. Smaller lesions can be managed conservatively or through resection and repair. In cases of extensive ossification, resection and reconstruction are necessary. A comprehensive literature review is also provided.

CONCLUSION

The occurrence of patellar tendon swelling following trauma or surgery should raise suspicion of patellar tendon ossification. Rheumatoid arthritis is a risk factor for the development of patellar tendon ossification. In cases of extensive ossification, successful treatment can be achieved through reconstruction using an Achilles allograft.

Transosseous Repair of Patellar Sleeve Fractures: A Case Series and Surgical Technique Guide

The purpose of this study is to describe the surgical technique and outcomes of transosseous repair of patellar sleeve fractures in a pediatric cohort. A retrospective review was performed on patients younger than 16 years undergoing transosseous repair of distal patellar sleeve fractures. A chart review was performed on demographics, surgical repair technique, and postoperative care. Primary outcomes included intact extensor mechanism function and range of motion (ROM) at final follow-up. In this study, 20 patients, 17 males and 3 females, with a mean age of 11.7 years were included. ROM was initiated at a median of 27.5 days following surgery. All patients had a healed patellar sleeve fracture and intact extensor function at final follow-up. Final mean knee ROM among the 18 patients with minimum 3-month follow-up was 132 degrees. Thirteen patients (72%) achieved full ROM (≥ 130 degrees) and 5 patients (28%) achieved less than 130 degrees knee flexion. Duration of initial immobilization was found to be the only variable strongly associated with final postoperative ROM. Mean duration of immobilization for patients achieving ≥ 130 degrees was 24 days versus 44 days in those patients achieving < 130 degrees, p = 0.009. All patients who began knee ROM within 21 days of surgery obtained full knee ROM. No patients experienced construct failure or extensor lag. Operative management of displaced patellar sleeve fractures with anatomic transosseous suture repair of the sleeve fracture, brief immobilization no more than 21 days, and initiation range of early ROM results in excellent outcomes.

Patellar Tendon Reconstruction Using Autologous Hamstring Tendons for the Treatment of Extensive Patellar Tendon Ossification

Background

Extensive patellar tendon ossification is very uncommon and requires surgical intervention when ossification significantly affects knee function. While various approaches and grafts are available for reconstructing ruptured patellar tendons, there is a paucity of literature regarding the management of joint ankylosis due to severely ossified patellar tendons.

Case Presentation

This is a case involving an extensively ossified patellar tendon after patellar and tibial tuberosity fracture fixation. Reconstruction of the patellar tendon was performed using ipsilateral semitendinosus and gracilis autografts. At the latest follow‐up of 12 months, the patient achieved knee flexion up to 120° with a slight extension lag and resumed daily activities.

Conclusions

Autograft hamstring reconstruction of the patellar tendon is suitable for extensive heterotopic ossification of the patellar tendon, resulting in significant improvement in postoperative knee function. Similar patients may be referred for this reconstruction technique.

Patella Sleeve Fracture with Medial Patellofemoral Ligament Tear and Lateral Femoral Condyle Fracture in an Adolescent: A Case Report

CASE

A 12-year-old boy sustained a patella sleeve fracture of the superior pole, medial patellofemoral ligament tear, and lateral femoral condyle fracture after a direct contact sledding injury. He was managed nonoperatively with 5 weeks of cylinder cast immobilization with transition to a hinged knee brace and physiotherapy. By 3 months, he returned to sport activity without patellar instability.

CONCLUSION

This is the first case to describe simultaneous development of these 3 injuries in an adolescent. We recommend that patients with patella sleeve fracture undergo magnetic resonance imaging to assess for local soft-tissue injury because this may influence treatment decisions.

Case Report on Sleeve Avulsion of Patella in Young Adult

Introduction:

Sleeve avulsion of patella is extremely rare, limited almost to children. However, few cases have been reported in adults. Rarity of this fracture makes the diagnosis and choice of treatment difficult. Inability to raise leg remains important clinical sign for quadriceps mechanism insufficiency. In the absence of standard treatment guidelines pullout sutures through patella provides a secure and stable fixation option. Our case remains the first to be reported ever in English literature in a 23-year-old male with a superior pole avulsion patella being treated with Krakow pullout suture.

Case Report:

A 23-year-old Indian male was admitted with left knee pain and swelling following fall from bike. He had knee pain, swelling, and inability to bear weight. Active straight leg raising was not possible. On X-ray he had small bony sleeve visible near proximal pole of patella. Magnetic resonance imaging (MRI) was done which showed sleeve avulsion of patella at proximal pole. Under spinal anesthesia fracture was exposed through midline approach. Pullout Krakow sutures were taken through quadriceps tendon and fracture fragments using 3 no Polyester suture. Transosseous tunnels were drilled in patella and tied distally. At 4 months patient had no extension lag with full range of movements. At 14 months follow-up patient is asymptomatic and able to run, squat, sit cross legged, and do his day-to-day activities.

Conclusion:

Sleeve avulsion of patella in adults is extremely rare with only few cases reported in literature. MRI is not only useful for diagnosis but also for deciding treatment modality. Krackow technique with Polyester suture through quadriceps tendon incorporating fracture fragment passed through patellar transosseous tunnel provides secure fixation with excellent results. Also avoids any future hardware problems in this subcutaneous bone.

Nonoperative Management of Minimally Displaced Patellar Sleeve Fractures

Patellar sleeve fractures primarily occur in the adolescent population from a rapid contraction of the quadriceps with the knee in a flexed position. Several small case reports describe operative reduction and fixation for displaced fractures. However, there is sparse literature on nonoperative management of these injuries. Retrospective review and prospective follow-up of all patients diagnosed with patellar sleeve fracture between 1991 and 2014 at a single institution. Patients with superior pole avulsion fractures, history of prior knee surgery, and fractures managed operatively were excluded. Patients with a clinical diagnosis without support of advanced imaging were also excluded. Radiographs and magnetic resonance imaging (MRI) were reviewed for initial fracture displacement, time until fracture union, and the presence of patellar tendon ossification. Outcome was assessed using the Tegner's activity scale, Kujala's Score and the International Knee Documentation Committee (IKDC) subjective knee evaluation score at final follow-up. Eighteen nonoperatively treated distal patellar pole sleeve fractures were identified, while five patients had advanced imaging to support their diagnosis. All were males with a mean age of 15.1 (range: 12-18). Traumatic and sport-related injuries were noted in the majority of patients. Only one patient had any appreciable displacement, but still < 2 mm. Final radiographic evaluation revealed fracture healing without patellar tendon ossification in all patients. All five patients had full terminal knee extension and symmetric range of motion. Mean IKDC score was 96.4 (range: 82-100) mean Tegner's activity score was 60 (range: 5-8), and mean Kujala's score was 89.7 (range: 63-100) at final follow-up. Of the five cases, three patients presented in a delayed fashion, and all went on to have surgical treatment. Two required arthroscopic loose body removal, while the other had an open patellar debridement and platelet-rich plasma (PRP) injection. Minimally displaced patellar sleeve fractures can be successfully managed nonoperatively with excellent clinical outcomes. However, delayed in presentation may be associated with worse outcome. This study of case series reflects level of evidence IV.

Patellar sleeve avulsion fracture in a patient with Sinding-Larsen-Johansson syndrome: a case report

BACKGROUND

Patellar sleeve avulsion (PSA) fractures are rare injuries that occur in in skeletally immature patients. Initial diagnosis is key to a successful outcome, as these injuries are easily overlooked on plain radiographs with poor results well documented from delayed management. High index of suspicion from the mechanism of injury, thorough clinical examination and Magnetic Resonance Imaging (MRI) help to avoid misdiagnosis.

CASE PRESENTATION

The case of a 12-year-old male athlete with an acute PSA after a conservative treatment of a SLJ syndrome is described. The patient was referred to our clinic due to severe pain and loss of function after performing a high jump. Plain radiographs (X-ray) and MRI confirmed an inferior pole PSA which was fixed with double trans osseous ultra-high strength tapes. At the 3-month follow- up visit the patient was able to ambulate brace free. At 2-years follow up the patient was able to play soccer and ice hockey. To our knowledge, there are no case reports of inferior pole PSA with prior SLJ syndrome described in literature.

CONCLUSIONS

Early clinical suspicion and distinguishing this PSA from other enchondral ossification disorders around the knee is critical to avoid misdiagnosis. Whether SLJ syndrome increases the risk of sustaining a PSA is still not clear. Trans osseous fixation with suture tapes leads to good functional results in a young athlete with inferior pole PSA.

Paediatric injuries around the knee: Bony injuries

The aim of this article is to discuss the diagnosis, management and pitfalls of bony injuries around the skeletally immature knee. Each within their own right is a relatively uncommon injury but associated with potential complications. Distal femoral physeal fractures can result in growth arrest and vascular injury. Tibial spine avulsions can result in an unstable knee. Tibial tubercle fractures can be associated with compartment syndrome and pose a risk to the extensor mechanism of the knee. Fixation can be complicated by growth arrest and subsequent recurvatum deformity. Finally, patella sleeve injuries are often missed and this can also threaten the extensor mechanism. We discuss the approach to clinical and radiological assessment of these injuries, and evidence based recommendations as to how they are best managed to avoid complications.

[Patellar sleeve fractures : Bracing and augmentation technique with suture tape]

OBJECTIVE

Transosseous augmentation of patellar sleeve fractures (PSF) with suture tape in young athletes.

INDICATIONS

Acute avulsions of the proximal or distal patellar pol with clinical relevant deficit of knee extension.

CONTRAINDICATIONS

Local infections, severe soft tissue damage (relative contraindication), fractures of the patella or tibial tuberosity.

SURGICAL TECHNIQUE

Direct longitudinal anterior approach to the patella. Debridement of the proximal patellar tendon insertion. Anatomic reduction of any osteochondral fragments. Transosseous augmentation of the tendon with FiberTapes® (Arthrex, Naples, FL, USA).

POSTOPERATIVE MANAGEMENT

Passive motion exercise to 30° of flexion from day 1; increase to 60° from week 3; 90° from week 5. Partial load-bearing of 20 kg with knee in locked full extension brace during first 2 weeks. Isometric exercises from week 3. Free active ROM and full weight bearing from week 7.

RESULTS

If diagnosis and treatment is early and sufficient augmentation of the tendon and periosteum is provided, good to excellent functional outcome can be expected.

Patellar tendon ossification after retrograde intramedullary nailing for distal femoral shaft fracture: A case report and review of the literature

RATIONALE

Retrograde femoral nailing was one of the most important treatment means for distal femoral shaft fracture. However, studies regarding heterotopic ossification of the patellar tendon after retrograde intramedullary nailing for distal femoral shaft fracture are limited. We herein present a rare complication, namely heterotopic ossification of the patellar tendon, after retrograde intramedullary nailing for displaced femoral shaft fracture.

PATIENT CONCERNS

We present a case of 25-year-old male with displaced femoral shaft fracture who was treated by retrograde intramedullary nailing.

DIAGNOSES

During the period of follow-up, the patient developed symptomatic heterotopic ossification of the patellar tendon with extensively hard ossification area.

INTERVENTIONS

Open surgery was recommended, but the patient has refused further treatment.

OUTCOMES

The patient resulted in pain and restricted the range of motion of the affected knee.

LESSONS

This case stresses the importance of longer-term follow-up and further attention into the possibility of heterotopic ossification of the patellar tendon.

Acute Traumatic Patellar Tendon Rupture at the Tibial Tuberosity Attachment without Avulsion Fracture

Patellar tendon rupture in children is especially rare. The fact that the area of traumatic rupture has wide variations makes surgical treatment difficult. We present an 11-year-old boy with acute traumatic patellar tendon rupture at the tibial tuberosity attachment without avulsion fracture. Primary end-to-end repair and reinforcement using 1.5 mm stainless steel wires as a surgical strategy were undertaken. Early range of motion began with a functional knee brace and the reinforced stainless wire was removed 3 months after surgery. Knee function at the final follow-up was satisfactory. We suggest that this strategy may provide a useful option for surgical treatment.

Patellar Sleeve Fracture With Ossification of the Patellar Tendon

Patellar sleeve fractures make up greater than 50% of all patellar fractures. They are essentially only seen in the pediatric population because of the thick periosteum and the distal patellar pole apophysis in this group. These fractures can lead to complications if not treated appropriately and in a timely fashion. Complications of missed or untreated patellar sleeve fractures include patella alta, anterior knee pain, and quadriceps atrophy. These can all result in severe limitations in activity. The authors describe a case of a 16-year-old boy who sustained a patellar sleeve fracture 3 years prior to presentation. On presentation, he had patella alta, diminished strength, 5° of extensor lag, and radiographs that revealed bone formation along the patellar tendon. Despite this, he was able to maintain a high level of activity. This case report explores how the patient could have maintained a high level of activity despite having a patellar sleeve fracture. Also, because of the delayed presentation, the patella was ossified and the quadriceps was retracted, which led to a novel approach to reconstructing his distal extensor mechanism. This approach included a V-Y advancement of the quadriceps tendon and patellar tendon reconstruction using the patient's hamstring tendon (semitendinosus). This technique, combined with physical therapy postoperatively, resulted in his return to varsity high school soccer. To the best of the authors' knowledge, this technique has not been reported for this rare condition. [Orthopedics. 2017; 40(2):e357-e359.].

Apophyseal injuries in children's and youth sports

INTRODUCTION

The authors reviewed the current English literature regarding apophyseal injuries affecting young athletes, to highlight the frequency and characteristics of these injuries, to clarify risk factors and specific prevention measures, and to identify future research objectives.

SOURCES OF DATA

The authors performed a comprehensive search of the medical literature, using the Medline database, including all English articles. Various combinations of the Keywords 'injury', 'sports', 'athletic injuries', 'avulsion fractures', 'physeal', 'physis', 'apophysis', 'apophysitis', 'growth plate' were used.

AREAS OF AGREEMENT

Growth benefits from a moderate physical activity.

AREAS OF CONTROVERSY

Growth deficit may occur in young athletes involved in intensive practice of sport following apophysitis.

GROWING POINTS

Apophyseal injuries occurring during sport are less common than overall rate of injuries affecting the adolescent population. Growth disturbance occurs only rarely after an apophyseal injury.

AREAS TIMELY FOR DEVELOPING RESEARCH

Further studies should consider analytical as well as descriptive components of apophyseal injuries, to allow the identification of new possible risk factors and preventive measures and to help early detection and proper treatment as well.

Sleeve fracture of the patella with lateral slip of the retinaculum: a case report in an 11-year-old child

Adolescents are susceptible to patellar sleeve fractures. We present an interesting case of a patellar sleeve fracture in an 11-year-old child with lateral slip of the retinacular sleeve. Clinical assessment was difficult; however, an MRI scan confirmed the diagnosis. Surgical repair was undertaken, and the retinacular sleeve was repaired along with repair of the patellar tendon. The patient recovered well after surgery and underwent physiotherapy. A patellar sleeve fracture should always be suspected in patients less than 16 years of age, particularly in those with indirect acute trauma to the knee. Prompt surgical repair is important to achieve full functional recovery.

Patellar tendon ossification after anterior cruciate ligament reconstruction using bone--patellar tendon--bone autograft

Background

Among the various complications described in literature, the patellar tendon ossification is an uncommon occurrence in anterior cruciate ligament (ACL) reconstruction using bone – patellar tendon – bone graft (BPTB). The heterotopic ossification is linked to knee traumatism, intramedullary nailing of the tibia and after partial patellectomy, but only two cases of this event linked to ACL surgery have been reported in literature.

Case presentation

We present a case of a 42-year-old Caucasian man affected by symptomatic extended heterotopic ossification of patellar tendon after 20 months from ACL reconstruction using BPTB. The clinical diagnosis was confirmed by Ultrasound, X-Ray and Computed Tomography studies, blood tests were performed to exclude metabolic diseases then the surgical removal of the lesion was performed. After three years from surgery, the patient did not report femoro-patellar pain, there was not range of motion limitation and the clinical-radiological examinations resulted negative.

Conclusion

The surgical removal of the ossifications followed by anti-inflammatory therapy, seems to be useful in order to relieve pain and to prevent relapses. Moreover, a thorough cleaning of the patellar tendon may reveal useful, in order to prevent bone fragments remain inside it and to reduce patellar tendon heterotopic ossification risk.

Bilateral sleeve fracture of the inferior poles of the patella in a healthy child: case report and review of the literature

The initial diagnosis of a sleeve fracture of the patella is key to a successful outcome with poor results well documented in the literature from delayed management. Diagnosis is difficult due to the rarity of this injury and thus the low likelihood the admitting junior doctor would think of this injury in their differential. They are very uncommon in incidence and have features on plain radiography that are difficult to interpret unless the surgeon is familiar with the anatomy of the immature patella. Missing the diagnosis can be disastrous for the patient. In this paper we describe the presentation of bilateral sleeve fractures in a healthy child, our initial investigations and subsequent management. We chose to repair with 5 Ethibond via 3 transosseous tunnels, initially reinforced with a circlage wire. On last review the boy maintains stable, pain-free knees with a full range of motion. The authors hope that this case and literature review will provide a valuable teaching aid and so assist in early, accurate diagnosis and cover the management options to achieve a positive outcome.

Patellar tendon ossification after partial patellectomy: a case report

Introduction

Patellar tendon ossification is a rare pathology that may be seen as a complication after sleeve fractures of the tibial tuberosity, total patellectomy during arthroplasty, intramedullary nailing of tibial fractures, anterior cruciate ligament reconstruction with patellar tendon autograft and knee injury without fracture. However, its occurrence after partial patellectomy surgery has never been reported in the literature.

Case presentation

We present the case of a 35-year-old Turkish man with a comminuted inferior patellar pole fracture that was treated with partial patellectomy. During the follow-up period, his patellar tendon healed with ossification and then ruptured from the inferior attachment to the tibial tubercle. The ossification was excised and the tendon was subsequently repaired.

Conclusion

To the best of our knowledge, this is the first report of patellar tendon ossification occurring after partial patellectomy. Orthopaedic surgeons are thus cautioned to be conscious of this rare complication after partial patellectomy.

Non-contact paediatric knee injuries, including patellar sleeve fractures

Different patterns of injury of the knee are seen in children and adults, particularly in non-contact injuries. Examples of these are given, including the important patella sleeve fracture.

The patellotrochlear index: a new index for assessing patellar height

The radiological methods to determine patellar height described in the literature are variable, not reliable and depend on the chosen ratio. The purpose of this paper is to describe another method of measuring patellar height on sagittal MRI using the true articular cartilage patellotrochlear relationship. An analysis of magnetic resonance (MR) examinations of 66 consecutive patients was performed. The most common diagnoses were meniscal or anterior cruciate ligament pathologies. No patient suffered from patellofemoral complaints. Measurements on sagittal MR images included different parameters using the articular cartilage of the patella and the trochlea. The ratio patella : trochlea of the cartilage baselines was measured in percentages and described as patellotrochlear index. The measurements were assessed at two different times by three raters under blinded conditions. The mean patellotrochlear index was 31.7% (CI: 12.5-50.0; range -5.0 to 61.1%; SD +/-11.6). The intraobserver variability showed only in the "second observer" a difference of the mean values of the two different measurements (t=2.189; P=0.032). The interobserver correlation was high and significant (0.663-0.893; P=0.000). Our results indicate that the patellotrochlear index is a reliable and precise method to determine the exact articular correlation of the patellofemoral joint and the patellar height. The results represent the average patellotrochlear index in the normal population without patellofemoral complaints. Measurements of the articular cartilage congruence can be helpful to define an underlying pathology of patellar height, such as patella alta or infera.

Bilateral patellar tendon rupture in a child: a case report

Patellar tendon rupture in children is very rare. When it occurs, patellar tendon is usually ruptured either from the upper end as a sleeve fracture of the patella or from lower end as an avulsion fracture of the tibial tuberosity. In this report, we present the case of an otherwise healthy 9-years-old boy who had subsequent bilateral patellar tendon ruptures through the midparts, which has not been published previously in the literature. Treatment was performed with primary end-to-end repair, reinforcement with cerclage wires and fresh-frozen achilles tendon augmentation for both sides.

Avulsionsfrakturen des unteren Patellapols

Fractures of the lower pole of the patella are rare and occur typically in children. In these types of fractures an extensive sleeve of cartilage is pulled off with a small bony fragment. The so-called sleeve fractures are often overlooked in plain radiographs. We describe the operative treatment and outcomes in two patients with sleeve fractures, one receiving early and one delayed treatment.A 12-year-old boy (case 1) sustained an indirect injury to the left knee while playing ball. Clinical examination showed a lag of active extension of the left knee without decrease in passive range of motion. At 9 years of age, a 12-year-old girl (case 2) sustained a direct blunt trauma to her right knee while playing ball. The lesion of the lower pole of the patella was not diagnosed in time. During the following 3 years a lag of extension of the right knee developed.The sleeve fracture diagnosed early was treated by open reduction and internal fixation with transosseous suturing. At the 6-month follow-up the knee had regained full range of motion. The sleeve fracture diagnosed late showed a nonunion of the patella resulting in a lag of extension. Even after 3 years a shortening osteotomy of the patella resulted in full range of motion of the right knee.

A review of sleeve fractures of the patella in children

Patella fractures are rare in children and the sleeve fracture is a particular form of fracture that only occurs in children where it is the most common patella fracture. It is caused by rapid muscle contraction. Diagnosis may be difficult both clinically and on the X-ray which may look normal if there is no bony fragment. Patella alta is the best sign and ultrasound is very helpful. Awareness of the existence of the injury is all important. This fracture differs from straightforward avulsion because of the "sleeve" of periosteum which is pulled off the patella and will continue to form bone if not treated thus enlarging or even duplicating the patella. Treatment involves prompt reduction and, usually, internal fixation of the disrupted patella tendon.

Repair of patellar tendon injuries using a cell-collagen composite

Collagen gels were seeded with rabbit bone marrow-derived mesenchymal stem cells (MSCs) and contracted onto sutures at initial cell densities of 1, 4, and 8 million cells/ml. These MSC-collagen composites were then implanted into full thickness, full length, central defects created in the patellar tendons of the animals providing the cells. These autologous repairs were compared to natural repair of identical defects on the contralateral side. Biomechanical, histological, and morphometric analyses were performed on both repair tissue types at 6, 12, and 26 weeks after surgery. Repair tissues containing the MSC-collagen composites showed significantly higher maximum stresses and moduli than natural repair tissues at 12 and 26 weeks postsurgery. However, no significant differences were observed in any dimensional or mechanical properties of the repair tissues across seeding densities at each evaluation time. By 26 weeks, the repairs grafted with MSC-collagen composites were one-fourth of the maximum stress of the normal central portion of the patellar tendon with bone ends. The modulus and maximum stress of the repair tissues grafted with MSC-collagen composites increased at significantly faster rates than did natural repairs over time. Unexpectedly, 28% of the MSC-collagen grafted tendons formed bone in the regenerating repair site. Except for increased repair tissue volume, no significant differences in cellular organization or histological appearance were observed between the natural repairs and MSC-collagen grafted repairs. Overall, these results show that surgically implanting tissue engineered MSC-collagen composites significantly improves the biomechanical properties of tendon repair tissues, although greater MSC concentrations produced no additional significant histological or biomechanical improvement.

Children's sports injuries

Sports injuries in children are common. They range from very serious and even, occasionally, fatal accidents, to trivial sprains and bruises. Sports medicine is a burgeoning field. Parallel with this there has been an increased understanding of the radiology of these lesions. Lesions in the immature skeleton differ greatly to those in the mature skeleton. This review describes the most frequent sports injuries in children.