Surgical Treatment of Tibial Tubercle Fractures in Osteogenesis Imperfecta: A Restrospective Case Series

Abstract

Background

Osteogenesis imperfecta (OI) is a rare bone fragility disorder involving type I collagen. Although fragility fractures are common, tibial tubercle apophyseal fracture reporting is limited. This study evaluates our series of tibial tubercle operative fractures in OI patients.

Methods

Retrospective review of all operative tibial tubercle fractures from 2010 to 2022, at a level one pediatric trauma and osteogenesis imperfecta referral center identified four patients with concomitant OI. Demographic information, OI type, antecedent and subsequent fracture history, surgical treatment, and OI treatment method were collected. Comparison was made with non-OI operatively treated tibial tubercle patients (n = 183).

Results

The mean OI tibial tubercle surgical patient was 11 years (range 9-14). The mean non-OI tibial tubercle surgical patient was 14.5 years (range 8.5-17.0). Two out of four OI patients were female (50%) and 94.5% were male in the non-OI group. Within the OI group, one patient was diagnosed with OI after their tibial tubercle fracture (15 months later). OI types included: type I (n = 3) and type IV (n = 1). Before the tibial tubercle fracture, no patients were on bisphosphonate therapy and three were on vitamin D supplementation. All OI patients underwent open reduction with cannulated screw fixation. In two out of four (50%) OI patients, suture anchors were used. In the non-OI group 13.7% of patients were treated with suture anchors. Three OI patients were treated with a brace, and one patient was casted post-operatively. Immediate weight bearing was allowed in three OI (75%) patients and in 52.5% of non-OI patients. All OI patients returned to baseline activities at 5.4 months (IQR, 4.4, 6.2) and in 4.4 months (IQR, 3.4, 6.4) in the non-OI group.

Conclusions

Patients with OI and surgically treated tibial tubercle fractures were younger than those without OI. The OI group made up 2.1% of all tibial tubercle surgical fractures. Suture anchor augments were employed in 50% of the OI cases and in 13.7% in the non-OI group. All OI patients returned to their baseline function, which is comparable to the non-OI group.

Key Concepts

• (1)Traditional surgical fixation methods including suture anchors can be used in OI patients.
• (2)Post operative immediate weight bearing as tolerated in a locked extended knee brace can be successfully utilized in OI patients.
• (3)Recovery time to baseline function is comparable between OI patients and non-OI patients after tibial tubercle surgery.

Level of Evidence

Level III

Introduction

Osteogenesis imperfecta (OI) is a rare bone fragility disorder associated with abnormal or deficient type 1 collagen [1]. OI patients commonly suffer fractures of the humerus, olecranon, and long bones [2,3]. Tibial tubercle fractures comprise 0.4%–2.7% of all pediatric fractures and <1% of all physeal fractures [[4], [5], [6]]. Tibial tubercle fractures commonly occur with resisted quadriceps muscle contraction or rapid knee flexion seen in running and jumping [5,7,8].

With only a handful of case reports, limited information exists in terms of the demographic features, incidence, clinical presentation, surgical management, and outcomes of pediatric tibial tubercle fractures in OI patients [[9], [10], [11]]. As the only case series that we are aware of, this study was conducted to address this gap in knowledge. This study was also conducted to evaluate the similarities and differences between pediatric OI and non-OI tibial tubercle surgical patients.

Methods

After obtaining institutional review board approval, all tibial tubercle fractures treated from January 2010 to December 2022 at a level one pediatric trauma and OI referral center were retrospectively reviewed. Inclusion criteria included operatively treated tibial tubercle fractures. Patients were excluded if they had follow-up of less than three months or were greater than 19 years of age. Demographic data, treatment course, and outcomes were collected from the electronic medical records.

Following the initial data collection, detailed clinical information was extracted from electronic medical records for patients with OI. The clinical information was used to write a detailed summary of the individual cases. All OI patients were treated by three fellowship-trained pediatric orthopaedic surgeons. Two groups were created: a non-OI group and an OI group. Descriptive statistics were used to summarize patient demographics, fracture characteristics/management, and surgical outcomes. DEXA Z-scores were height adjusted for heights outside the 25-75 percentile ranges with normal considered between −2 and +2. Continuous variables were reported as means or medians, depending on the data distribution.

Ethical considerations, including patient confidentiality and data protection, were strictly adhered to throughout the study. Patient confidentiality and data protection were strictly adhered to, with informed consent waived due to the retrospective design and minimal participant risk.

Results

OI and Non-OI tibial tubercle fractures

A total of 187 records of operatively treated tibial tubercle fractures were reviewed during the study period, of which four cases (2.1%) involved patients diagnosed with osteogenesis imperfecta (Table 1). The mean age of the OI group was 11.0 years (range 9-14), compared to 14.5 years (range 8.5-17.0) in the non-OI group. The OI group included two males and two females. The non-OI group was predominantly male (93.8%). Among the OI group, all patients had a history of previous fractures. Two out of the four patients in the OI group were injured participating in sports. Specific fixation techniques, including the use of suture anchor augments, were employed in 50% of the OI cases compared to 13.7% in the non-OI group. The median follow-up duration for OI patients was 154 weeks (IQR, 70.3, 155.3) compared to 27.3 weeks (IQR, 17.6, 52.4) in the non-OI group. Overall, the OI patients achieved full return to baseline activities at a median of 5.4 months (IQR, 4.4-6.2), compared to 4.4 months (IQR, 3.4-6.4) observed in the non-OI group.

Table 1.

Demographics and outcomes comparing Non-OI and OI tibial tubercle fractures.

Variables	Category Description	Non-OI (N = 183)	OI (N = 4)
Age (y)	Mean	14.5	11
Sex, n (%)	Male	172 (94.0)	2 (50.0)
	Female	11 (6.0)	2 (50.0)
Side, n (%)	Left	106 (57.9)	0
	Right	77 (42.1)	4 (100.0)
Sports, n (%)	Sports	147 (80.3)	2 (50.0)
	Non-sports	36 (19.7)	2 (50.0)
Time from injury to surgery (d)	Median [IQR]	1.0 [1.0, 1.0]	1.0 [1.0, 1.0]
Length of F/U (wk)	Median [IQR]	27.3 [17.6, 52.4]	154 [70.3, 155.3]
Ogden type, n (%)	Type I/II	48 (26.2)	2 (50.0)
	Type III	90 (49.2)	2 (50.0)
	Type IV	45 (24.6)	0
Initial Cast/Brace, n (%)	Brace	133 (72.7)	3 (75.0)
	Cast	50 (27.3)	1 (25.0)
Initial WB, n (%)	WB	96 (52.5)	3 (75.0)
	Non-WB	87 (47.5)	1 (25.0)
Time to return to activity (mo)	Median [IQR]	4.4 [3.4, 6.4]	5.4 [4.4, 6.2]
Return to OR, n (%)		37 (20.2)	1 (25.0)
Return to OR for symptomatic hardware, n (%)		31 (17)	0
Fracture displaced, n (%)		3 (1.6)	1 (25.0)
Implant displaced, n (%)		2 (1.1)	0

Case 1

A 9-year-old boy (Table 2) with type I OI (diagnosed at age 2) sustained a minimally displaced Ogden type III tibial tubercle fracture during a basketball jump (Fig. 1). His history included multiple fractures (thoracic/lumbar spine, tibia/fibula, elbow epicondyle, and radius/ulna), all treated nonoperatively. He had a Dual Energy Xray Absorptiometry (DEXA) lumbar height adjusted Z-score of −1.13 noted 8 months before the tibial tubercle fracture. He was on consistent vitamin D and calcium supplements with no prior history of bisphosphonate use.

Table 2.

Case series summary.

Case	#1	#2	#3	#4
Age at surgery	9	14	9	12
Sex	M	M	F	F
OI diagnosed before tibial tubercle fracture (Yes/No)	Yes	Yes	Yes	No
Time from injury to surgery (d)	3	1	1	1
OI type	I	I	IV	I
Sport prior to injury	Noncontact martial arts	Weightlifting and Tennis	N/A	N/A
Mechanism of injury	Jumping	Running	Fall	Dog ran into knee
Side	Right	Right	Right	Right
Ogden type	III	III	II	II
Bisphosphonate treatment prior to tibial tubercle fracture	No	No	No	No
DEXA scan before tibial tubercle fracture (Yes/No)	Yes	Yes	Yes	No
History of prior fractures	Yes	Yes	Yes	Yes
History of Tib/fib fractures	Yes	Yes	Yes	No
Imaging (XR)	Soft tissue swelling along the patellar tendon, superior positioning of the patella, and irregularity along the anterior tibial tubercle concerning for avulsion injury	Tibial tubercle avulsion fracture with extension through the epiphysis as well as metaphyseal component. With overlying soft tissue swelling.	Displaced tibial tubercle avulsion fracture, without evidence of extension into the tibial plateau. Associated infrapatellar soft tissue reticulation and pretibial soft tissue swelling.	Tibial tubercle avulsion fracture with displacement and vertical rotation of the inferior fracture fragment with mild fragmentation, as well as superior displacement of the patella.
Imaging (MRI)	Elevation of the tibial tuberosity from its metaphyseal bed with an incomplete fracture of the tibial epiphysis near the cartilaginous junction	N/A	N/A	N/A
Fixation	ORIF, 2 × 4.5 mm metaphyseal partially threaded unicortical cannulated screws with washer	ORIF, 1 × 5.5 mm epiphyseal partially threaded unicortical screw. 2 × 5.5 mm metaphyseal partially threaded screw	ORIF, 1 × 5.5 mm metaphyseal fully threaded unicortical cannulated screw, Kraków stitch, and 2x suture anchors	ORIF, 2 × 5.5 mm metaphyseal fully/partially threaded unicortical cannulated screws Revision: ORIF, 2 × 4.0 mm metaphyseal fully threaded cannulated screws, Kraków stitch, and 2x suture anchors
Initial cast or brace	Cast	Brace	Brace	Brace
Duration of immobilization/Locked in extension (wk)	3	2	4	4
Initial weight bearing (WB)	WB	No	WB	WB
Complication	Superficial surgical site infection	None	None	Right tibial tubercle fracture, displacement after open reduction & internal fixation
ROM at final follow up	0 to 120	0 to 120	0 to 140	0 to 120
Time to return to activity (d)	145	97	180	208
Sports at follow up	Swimming and noncontact martial arts	Weightlifting	n/a	n/a
Bisphosphonate treatment after surgery	Yes	Yes	No	No
DEXA scan following tibial tubercle fracture (Yes/No)	Yes	Yes	Yes	Yes
Length of follow up (Weeks)	134	219	59	174
Fracture of another site	Yes	No	Yes	Yes

Figure 1.

Patient 1 (9-year-old male, jumping). (A) Initial injury lateral radiograph demonstrates patella alta and anterior tibial tubercle irregularity, suggesting avulsion injury. (B) Initial injury MRI, showing edema surrounding the patella tendon and tibial tubercle, and elevation of the tibial tuberosity from its metaphyseal bed. (C) X-ray at 50 days post-surgery demonstrates healing with 2 × 4.5 mm metaphyseal partially threaded unicortical cannulated screws with washer.

An open reduction and internal fixation (ORIF) with two 4.5 mm metaphyseal partially threaded unicortical cannulated screws was performed. Postoperatively, immediate weight bearing (WB) was allowed in a cylinder cast with a walker. One week later, due to ankle pain, the cylinder cast was discontinued for a hinge knee brace locked in extension. He had a superficial wound infection treated with antibiotics and wound care. Passive motion of the knee began at 4 weeks after fixation. Six weeks post-surgery, the brace and walker were discontinued and physical therapy (PT) was initiated. By 5 months post-surgery, the patient returned to swimming and noncontact martial arts. Bisphosphonate (Pamidronate (0.5 mg/kg)) therapy was also initiated at that time. Fourteen months after the tibial tubercle surgery, the patient had only received one infusion before sustaining a surgically treated olecranon fracture.

Case 2

A 14-year-old boy (Table 2) with type I osteogenesis imperfecta presented with a tibial tubercle avulsion consisting of an Ogden type III lesion with Salter-Harris (S–H) II posterior tibial metaphyseal extension, sustained while running in gym class (Fig. 2). This fracture demonstrating a “Y configuration,” has been previously described by McKoy et al,. [12] who proposed classifying it as a Type V tibial tubercle avulsion fracture. He was on daily vitamin D and calcium supplementation at the time of this injury. He had a history of multiple fractures: distal fibula, unclassified rib, and clavicle treated nonoperatively, and olecranon treated w/ORIF. A DEXA scan 4 months prior to injury showed a lumbar height adjusted Z-score of −0.41. No prior bisphosphonate history.

Figure 2.

Patient 2 (14-year-old male, running). (A) Initial injury lateral radiograph. The right knee demonstrates a tibial tubercle avulsion fracture with extension through the epiphysis, and separate extension across the posterior tibial metaphysis. (B) 50 days post-surgery radiograph demonstrates healing with 1 × 5.5 mm epiphyseal partially threaded unicortical screw and 2 × 5.5 mm metaphyseal partially threaded screws. (C) 3 years 3 months post-surgery radiograph demonstrates three posteriorly directed screws used to affix prior tibial tubercle avulsion fracture now healed.

ORIF was performed with three (1 epiphyseal and 2 metaphyseal) 5.5 mm partially threaded screws. The patient was non-weight bearing (NWB) in a hinge knee brace locked in extension for 2 weeks before transitioning to toe touch weight bearing (TTWB). Six weeks post-surgery, the brace was discontinued with full weight bearing (FWB). Three months post-surgery, full ambulation, motion, and strength were achieved. Bisphosphonate (1.7 mg of Zoledronate (0.025 mg/kg) therapy began 3 months post-injury for a total of two doses 6 months apart. Bisphosphonate was discontinued with DEXA normalization. Six months after surgery, he returned to strength training in gym class. He went on to suffer subsequent shoulder and patella dislocations.

Case 3

A 9-year-old girl (Table 2) with type IV OI presented with an Ogden type II tibial tuberosity avulsion after a fall in gym class (Fig. 3). A DEXA scan 2 months before the fracture showed a lumbar Z-score of −1.9. She had no prior bisphosphonate history but had been taking Vitamin D and calcium daily. She had a history of multiple non-operative fractures (ulna, spinal compression (T7), and fibula).

Figure 3.

Patient 3 (9-year-old female, fall). (A) Initial injury lateral radiograph. The right knee demonstrates a displaced tibial tubercle avulsion fracture. (B) 182 days post-surgery radiograph demonstrates complete healing with 1 × 5.5 mm metaphyseal fully threaded unicortical cannulated screw, Kraków stitch, and 2x suture anchors to supplement fixation to the small bone fragment.

ORIF was performed with one fully threaded cannulated screw, and, given the small size of the bone fragment, the construct was augmented with patella tendon and periosteum repair using two suture anchors. A post-surgical hinge knee brace was placed, and TTWB was allowed locked in extension for four weeks, after which PT was started and the knee brace was unlocked. Eleven weeks post-surgery, the brace was discontinued. Bisphosphonate therapy was recommended but not started as the family opted to focus on strength and conditioning with a personal trainer. DEXA results showed a lumbar Z-score of −1.2 measured 12 months after the tibial tubercle fracture, with multiple vertebral compression fractures diagnosed during this study.

Case 4

A 12-year-old girl (Table 2) with type I OI (diagnosed two years after tibial tubercle fracture) and Ehlers-Danlos (COL1A1), sustained an Ogden type II tibial tubercle fracture after a 100-pound dog ran into her right knee, causing a backward fall (Fig. 4). She had a history of multiple fractures (humerus, tarsal, fourth and fifth digit of the hand, and radius/ulna) that were treated non-operatively (see Fig. 3).

Figure 4.

Patient 4 (12-year-old female, dog ran into knee). (A) Initial injury lateral radiograph. (B) Intraoperative fluoroscopy: after reduction, two 5.5 mm cannulated, metaphyseal (one partial and one fully threaded) screws were placed. (C) 14 days post surgery, the patient sustained a fall on the right knee and felt a “pop”. Lateral radiograph shows interval loss of reduction. This was revised using two 4.0 mm fully threaded cannulated screws with washers and supplemental repair of the distal periosteal flap with a suture anchor. (D) Patient demonstrates complete healing by 4 months postop. (E) At 2 years 2 months post-revision surgery, the patient sustained a fall, and a lateral radiograph was obtained. No fracture was noted.

ORIF was performed with two 5.5 mm cannulated screws (partially threaded and fully threaded unicortical). A post-surgical hinge knee brace was placed locked in extension, with TTWB. Four days after surgery, she fell onto her knee and displaced the fracture (Fig. 4). The construct was revised to two 4.0 mm fully threaded unicortical screws with washers and supplemented with two suture anchors for tendon and periosteal fixation. After the revision, a knee brace was placed locked in extension and NWB restrictions for 4 weeks.

A DEXA scan three weeks post-revision surgery showed a lumbar Z-score of −1.6. She began taking vitamin D and consuming calcium-rich foods daily. Physical therapy started four weeks after the revision surgery. At five weeks post revision, she had limited knee flexion (6°) and twisted her ankle attempting to walk, sustaining an ipsilateral distal tibia fracture. Two months post-revision, she suffered a nondisplaced ipsilateral distal femur fracture treated nonoperatively. At four months post-revision surgery, she began to walk independently with an unlocked hinged knee brace. By seven months post-revision, she walked without a limp, regained full range of motion, and had no knee pain. At that time multiple fragility fractures of her spine and foot were noted. Subsequent DEXA scans showed lumbar Z-scores of −0.8 and −0.5 at 26 and 39 months, respectively. Two years later the patient sustained a fall where repeat radiographs were obtained (Fig. 4E). There was no fracture. The patient remained asymptomatic after a short period of bracing. Bisphosphonate therapy was never recommended due to her medical history and DEXA results.

Non-OI tibial tubercle fractures

The non-OI group comprised 183 fractures in 177 patients, 93.8% (166 patients) were male. 80.3% of patients (n = 147 cases) were active in sports before the fracture. The median time from injury to presentation was one day. Ogden type III was the most common, seen in 90 cases (49.2%), followed by types I/II (48, 26.2%) and IV (45, 24.6%). The median length of follow-up was 27.3 weeks (IQR, 17.6-52.4). Most patients were initially treated with a brace following surgery (72.7%, 133 cases), while 27.3% were initially treated with a cast (50 cases), and 52.5% were initially WB (FWB, TTWB, and partial). The median time to return to activity was 4.4 months (IQR, 3.4-6.4). Of the 183 knees in the non-OI group, 81 patients (44.3%) experienced at least one complication. 20 patients (10.9%) experienced nonoperative complications. Among these patients, 37 (20.2%) returned to the operating room, most commonly for symptomatic hardware removal. Additionally, 5 patients (2.7%) experienced fracture displacement, and 2 patients (1.1%) had implant displacement postoperatively.

Discussion

This series reports an OI incidence of 4 patients in 187 (2.1%) operatively treated tibial tubercle fractures. The mean injury age in the OI group was 11.0 compared to 14.5 years in the non-OI group. In the non-OI cohort, 52.5% were initially allowed to weight bear (FWB, TTWB, and partial) compared to 75% in the OI cohort. In this study, we found that tibial tubercle fractures in patients with osteogenesis imperfecta (OI) have similar outcomes to non-OI patients. However, due to the unique challenges posed by bone fragility in OI patients, specific fixation techniques may be necessary to ensure stability and prevent complications. For instance, in two of our cases, suture anchors were used to repair the patella tendon and distal periosteal flap to augment fixation, accommodating the poor bone quality seen in OI. This technique aligns with alternative approaches used in adults for tibial tubercle avulsion fractures with fragile bones or small fracture fragments, where standard screw fixation may be insufficient [[13], [14], [15]]. Immediate post-surgical WB restriction disparity was also noted in this study. In general, immobilization is used to protect the fracture site, but prolonged immobilization can also exacerbate osteoporosis in OI patients. Treating surgeons may have been predisposed to allow earlier WB in OI patients to avoid worsening bone density in the affected extremity.

A systematic review of the literature performed by Pretell-Mazzini et al. [16] found that proximal tibial epiphyseal injuries predominantly occur in males, accounting for 97% of cases, with a mean patient age of 14.6 years. This has been attributed to higher male adolescent sports participation and later onset of physeal closure in males [12]. The tibial tubercle ossifies along these stages: cartilaginous, apophyseal, epiphyseal, and osseous [4,17]. The secondary ossification center emerges during the apophyseal stage (between ages 8-12 in girls, 9-14 in boys) and is composed of fibrocartilage, providing resilience against tensile forces [4,12]. As the secondary ossification progresses fibrocartilage is replaced with columnar cartilage increasing the risk of stress-induced fractures [4,7,12]. Patients with OI may be more susceptible to these fractures at a younger age, without sex-based differences in presentation, due to dysregulation of normal bone maturation, formation, and resorption processes, seen in osteogenesis imperfecta, regardless of the timing of physeal closure or participation in sports.

Previously published literature discussing tibial tubercle fractures in pediatric patients with osteogenesis imperfecta (OI) do not mention the use of suture anchor fixation of the patella tendon to supplement fixation [[9], [10], [11],18]. This highlights a gap in the existing literature regarding alternative fixation methods that may be particularly beneficial in patients with compromised bone quality. This approach may have provided additional reinforcement and stability, which may represent a valuable consideration for future management of these fractures in the setting of poor bone quality or fracture comminution.

Conclusion

Management of these patients requires consultation with anesthesia, pediatric hospitalists, nursing, and other subspecialists. OI can affect the airway, cervical spine (atlanto-axial instability/basilar invagination), pulmonary system (restrictive type), cardiovascular system (cardiac valve/aortic dilation), and temperature regulation pathway (fever/tachycardia/metabolic acidosis). Bone health status can be assessed through dietary, fracture, and bisphosphonate treatment history, along with prior DEXA scan review. Calcium, magnesium, phosphorus, albumin, and 25-hydroxy-vitamin D levels can guide supplementation for post-operative fracture healing. Increased bleeding can be associated with OI patients. Baseline CBC, type and screen, and coagulation studies can be considered. Due to iatrogenic fracture risk, tourniquet use should be minimized, but if used, avoid pressures more than 100 mm Hg above the systolic [19]. Carefully position and pad the patients including the spine (kyphoscoliosis). Have bone anchors and washers available. Early weightbearing (WBAT, TTWB, or partial) is encouraged in a locked extended brace to reduce disuse osteopenia. Range of motion should be individualized based on fixation strength. Patients should be referred for future DEXA and bisphosphonate treatment consideration.

The limitations of this study include the small cohort size. Comparisons between OI and non-OI groups should be interpreted cautiously as differences may reflect random variation.

To our knowledge, this is the largest case series of OI pediatric tibial tubercle fractures. Suture anchors can safely augment standard screw fixation technique. Early weight bearing (WBAT, PWB, or partial) with an extended brace appears to be safe. Pediatric OI patients, like their non-OI counterparts can undergo successful surgery with comparable recovery times. Future studies should be multi-center given the rarity of this condition.

Author contributions

Anthony Dure: Writing – review & editing, Writing – original draft, Formal analysis, Data curation, Conceptualization. Emily L. Niu: Writing – review & editing, Writing – original draft, Data curation, Conceptualization. Evan Sheppard: Writing – review & editing, Writing – original draft, Data curation, Conceptualization. Benjamin D. Martin: Writing – review & editing, Writing – original draft, Data curation, Conceptualization. Laura L. Tosi: Writing – review & editing, Writing – original draft, Investigation, Data curation, Conceptualization. Syed I. Ahmed: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Resources, Project administration, Methodology, Investigation, Formal analysis, Data curation, Conceptualization.

Ethics approval and consent

The author(s) declare that no patient consent was necessary as no images or identifying information are included in the article.

Funding

None.

Declaration of competing interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.