Abstract
Introduction
Nonunion after locked plating of distal femur fractures is not uncommon.
Authors wanted to assess if “Dynamic” locked plating using near-cortex over-Drilling technique would provide a mechanical environment the promotes callus formation, thereby avoiding non-union encountered when applying locked plates with the conventional method.
Methods
This study was conducted at an academic Level 1 Trauma Center.
This is a prospective study conducted from November 2015 to November 2016. Follow-up was 10 months on average (ranging from 8 to 12 months).
The study included 20 patients with 20 fractures (13 males, 7 females). The average patients’ age was 41.2 years (18–64 years). According to the Müller AO classification of distal femur fractures (33A-C) there were 15 cases with extra-articular fractures (AO 33A), 5 patients with intra-articular fractures (AO 33C).
Dynamic Locked plating using near-cortical over-drilling technique was done for all patients.
Two blinded observers assessed callus score on 6-week radiographs using a 4-point ordinal scale. A 2-tailed t-test. Two-way mixed intra-class correlation testing was performed to determine reliability of the callus measurements by the 2 observers.
Results
All patients achieved union, time to union was 13.4 weeks on average (range form 8–24 weeks). Delayed union was observed in 2 patients. The average callus score for fractures was 1.8 (SD 0.6). All fractures united in alignment except 1 fracture which united in valgus malalignment, the deformity was appreciated in the postoperative radiographs.
No wound related complications, no loss of reduction, no catastrophic implant failure or screw breakage were detected.
Conclusion
Dynamic locked plating using near-cortex over-drilling is a simple technique that uses standard locked plates that promotes callus formation when used for fixing distal femur fractures.
Keywords: Distal femur, Fracture, Fixation, Dynamic locked plate
1. Introduction
Fracture Healing is greatly influenced by the fixation method. Classis compression plate fixation requires the creation of a rigid plate/bone construct which involves soft-tissue stripping and devitalization of the underlying bone, this may lead to inhibited callus formation. Hence, the concept of bridge plating with minimal soft tissue stripping using locking plates has been promoted.1, 2
Locking plates allows for stable bridge plating in cases with short end segments, thus their use is becoming more common for fixing distal femur fractures.3
However recent data from multiple centers has demonstrated nonunion rates between 10% and 20% when using locked plates.4 Insufficient fracture site motion and nonunion has been attributed to the stiffness of these implants.5
The concept of “Dynamic” Locked Plates, has been proposed to decrease construct stiffness & improve callus formation, various biomechanical & animal studies,6, 7, 8 using special implant design, have been done & showed that this concept decreases stiffness of locked plates & promote callus formation. Near-cortical over-drilling technique has been proposed by Gardner et al. [9], is based on the same biomechanical concept of dynamic licked plating but uses standard Locking plates instead of a specially designed implant (Fig. 1).
Fig 1.
Illustration of the biomechanical concept of dynamic locked plating using near-cortical over-drilling technique.
Authors wanted to clinically validate if the near-cortical over-drilling technique will promote callus formation thus proving it’s a form of dynamic locked plating fixation using conventional locked plates & not the specially designed dynamic locked plates. Authors also wanted to see if the results achieved by Gardner et al. [9] are be reproducible.
2. Method
This is a prospective study conducted from November 2015 to November 2016 in an academic level 1 trauma center. Follow-up was 10 months on average (ranging from 8 to 12 months).
Inclusion criteria included, adult patients (18–65 years old) who suffered from closed fractures of the distal femur. Patients who had diabetes mellitus, associated vascular injury, open fractures or Pathological fractures were excluded.
Twenty patients with 20 fractures (13 males, 7 females) where included in the study who met the inclusion criteria & didn’t have of the exclusion criteria. The average patients’ age was 41.2 years (18–64 years).
Fractures were classified according to the Müller AO classification10 of distal femur fractures (33A-C) & authors found the following; 15 cases had extra-articular fractures (AO 33A), among them 5 patients were (AO 33-A1), 3 patients were (AO33-A2) & 7 patients were (AO 33-A3). Five patients had intra-articular fractures, among them 3 patients had simple articular component and complex metaphyseal component (AO 33-C2), 2 patients had complex articular, metaphyseal components (AO 33-C3). (Table 1).
Table 1.
Patients’ fracture pattern distribution.
| Type of fracture | Number of cases | Percentage |
|---|---|---|
| (AO 33-A1) | 5 | 25% |
| (AO 33-A2) | 3 | 15% |
| (AO 33-A3) | 7 | 35% |
| (AO 33-C2) | 3 | 15% |
| (AO 33-C3) | 2 | 10% |
The mechanism of trauma was high energy trauma (e.g. motor car accident, motor bike accident or hit by a motor vehicle) in 18 patients and low energy (e.g. direct blow or fall to the ground) in 2 patients (Table 2).
Table 2.
Mode of trauma.
| Mode of trauma | Number of cases | Percentage |
|---|---|---|
| Road traffic accident | 7 | 35% |
| Motor car accident | 3 | 15% |
| Motor bike accident | 8 | 40% |
| Low energy | 2 | 10% |
Seventeen patients had only distal femoral fractures, 3 patients had another ipsilateral fractured bone (1 fracture patella, 1 fracture proximal tibia, 1 fracture distal tibia).
Intervention: Dynamic Locked plating was done for all patients using near-cortical over-drilling method as described by Gardner et al. [9]. In this method, regular locking plates are used & both cortices are drilled first using a 3.2-mm drill through a standard centering sleeve mounted to the locking hole in the plate. Then a 5.0-mm drill is used to drill the near cortex only. A 4.0-mm standard locking screw is then inserted and locked to the plate. This over-drilling will allow some motion between the near cortex & the screw, thus decreasing the stiffness of fixation by the standard locking plate as shown in the study conducted by Gardner et al. [6]. Near-cortical over-drilling was done for the proximal screws only (4–6 screws were used proximally) (Fig. 2).
Fig. 2.
Shows radiographs of a case examples, A: post-operative radiograph, B: final follow up radiograph.
Twelve cases were managed using minimally invasive plate osteosynthesis (MIPO), the other 8 cases were managed by open reduction internal fixation. No bone graft was used in any case. All Surgeries were performed by the first author.
Postoperatively, partial weight bearing as tolerated by the patient was allowed. The 1st post-operative visit was a wound check after 2 weeks, then follow-up by X-ray is done at monthly intervals till complete union, then at final follow up. Weight bearing was allowed as tolerated by patients. Knee range was encouraged after surgery & formal physical therapy was started after wound was healed.
Callus formation was assessed using Plain x-ray (antero-posterior & lateral views of the femur). Authors thought using other imaging techniques like CT scan to evaluate callus formation would subject patients to more irradiation & may be difficult to interpret due to presence hardware.
Authors adopted the method proposes by Gardner et al. [9] for assessment of callus; 2 blinded observers assessed callus score on 6-week radiographs using a 4-point ordinal scale (0 = none, 1 = minimal, 2 = moderate, 3 = robust). A 2-tailed t-test. Two-way mixed intra-class correlation testing was performed to determine reliability of the callus measurements by the 2 observers.
Union was defined as painless weight bearing and radiographic bridging of 3 of 4 cortices on 2 radiographic views. A 16-weeks mark was considered for delayed union & a 24-weeks mark was considered for non-union.
3. Results
All patients achieved union, time to union was 13.4 weeks on average (range form 8–24 weeks). Delayed union was observed in 2 patients with slow union, both were smokers, both achieved full radiological union by 20 and 24 weeks respectively (Table 3).
Table 3.
Time of full radiological union.
| Time to union | Number |
|---|---|
| Eight weeks | 1 |
| Ten weeks | 1 |
| Twelve weeks | 11 |
| Fourteen weeks | 2 |
| Sixteen weeks | 20 |
| Twenty weeks | 1 |
| Twenty-four weeks | 1 |
The average callus score for the fractures was 1.8 (SD 0.6). Five cases had a callus score of (1), 13 cases had a callus score of (2) & 2 cases had a callus score of (3) 2 cases healed by 1ry intention & had a callus score of (0), they were the 2 patients who showed delayed union (Fig. 3, Fig. 4). (Table 4). The two-way mixed intra-class correlation analysis showed agreement amongst observers in both consistency (0.712) and absolute score (0.723).
Fig. 3.
Case number 1 of healing by 1ry intention, A: Pre-op AP radiographs, B: Final follow up AP radiograph, C: Pre-op lateral radiographs, D: Final follow up Lateral radiograph.
Fig. 4.
Case number 2 of healing by 1ry intention, A: Pre-op AP radiographs, B: Final follow up AP radiograph, C: Pre-op lateral radiographs, D: Final follow up Lateral radiograph.
Table 4.
Callus Score.
| Callus score | Number of cases |
|---|---|
| 0 | 2 |
| 1 | 5 |
| 2 | 11 |
| 3 | 2 |
All fractures united in alignment except 1 fracture (AO 33-A3) which united in valgus malalignment following indirect reduction using minimally invasive plate osteosynthesis, the deformity was appreciated in the postoperative radiographs but a revision surgery decision was not accepted by the patient.
No knee stiffness, no wound related complications, no loss of reduction, no catastrophic implant failure or screw breakage were detected. Patients who had associated fractures healed un-eventfully. All patients returned to their pre-injury activities & employments.
4. Discussion
For fracture healing to occur, fixation must permit an appropriate degree of inter-fragmentary motion. Excessive inter-fragmentary motion, will cause hypertrophic nonunion of the fracture, whereas a fracture with too little inter-fragmentary motion may become atrophic.11 Various reports in the literature have shown that when locked plates are used in the distal femur, fracture healing was problematic.4, 5 This may be attributed to the stiffness of these implants that allow too little inter-fragmentary motion at fracture site, to the point that callus formation will not occur. After enough time, the plate may fail or screws may cut out of the bone.12
One method used to decrease the axial stiffness of a locked plates, is to increase the working length (the unsupported plate length over the fracture); However, this mainly leads to plate bending.4
Alternatively, the concept of “dynamic” locked plating was recently introduced to decrease the axial stiffness of specially designed “dynamic” locked plates. Several biomechanical studies were conducted & showed that such fixation principle is associated with less axial stiffness, in the study conducetd by Gardner et al.7 they demonstrated that axial stiffness was reduced by nearly half when dynamic locked plating was used.
In the study conducted by Bottlang et al.13 on animal model, they demonstrated 36% increase in callus volume & a 44% increase in bone mineral content when dynamic locked plates were compared to regular locked plating & they also could re-produce similar results when conducted a clinical study14 on 32 consecutive patients with 33 distal femur fractures.
Another form of “dynamic” locked plating is the near-cortical slotted holes dynamic locked plates, various biomechanical studies like that of Gardner et al. [67], the study by Sellei et al. [8] as well as the study by Lenz et al. [15] which is different in that instead of the screw toggling at the screw-plate interface, the slotted whole in the near cortex would allow for some movement thus increasing axial motion. Special instruments are used to create the oval shaped hole in the near cortex.
Recently Gardner et al. [9] described a new method for dynamic locked plating by near-cortical over-drilling which follows the same biomechanical principle of the near-cortical slotted hole in allowing for some motion between the screw shaft and the near cortex thus decreasing construct stiffness. They included 14 patients in their study & showed enhanced callus formation with this technique. We reached similar results in our study.
The limitations to our study includes, the small numbers of patients. Callus scoring is subjective & is observer dependent. More sophisticated imaging method like CT scan could be used to evaluate callus formation but it involves subjecting patients to more irradiation & may be difficult to interpret due to presence of hardware. The authors believe further multi-center studies that includes greater number of patients & longer follow-up is needed to fully evaluate this method.
In conclusion, the authors believe the near-cortical over-drilling technique for dynamic locked plating is a simple technique that can promotes callus formation when used for fixing fractures of the distal femur.
Funding
No funding was received for this study.
Ethical approval
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Conflict of interest
The author has none to declare.
Informed consent
Informed consent was obtained from all individual participants included in the study
References
- 1.Perren S.M. Evolution of the internal fixation of long bone fractures: the scientific basis of biological internal fixation: choosing a new balance between stability and biology. J Bone Joint Surg Br. 2002;84:1093–1110. doi: 10.1302/0301-620x.84b8.13752. [DOI] [PubMed] [Google Scholar]
- 2.Perren S.M. Backgrounds of the technology of internal fixators. Injury. 2003;34(Suppl. 2):B1–B3. doi: 10.1016/j.injury.2003.09.018. [DOI] [PubMed] [Google Scholar]
- 3.Koval K.J., Hoehl J.J., Kummer F.J. Distal femoral fixation: a biomechanical comparison of the standard condylar buttress plate, a locked buttress plate, and the 95-degree blade plate. J Orthop Trauma. 1997;11:521–524. doi: 10.1097/00005131-199710000-00010. [DOI] [PubMed] [Google Scholar]
- 4.Ricci W.M., Streubel P.N., Morshed S. Risk factors for failure of locked plate fixation of distal femur fractures: an analysis of 335cases. J Orthop Trauma. 2014;28:83–89. doi: 10.1097/BOT.0b013e31829e6dd0. [DOI] [PubMed] [Google Scholar]
- 5.Lujan T.J., Henderson C.E., Madey S.M. Locked plating of distal femur fractures leads to inconsistent and asymmetric callus formation. J Orthop Trauma. 2010;24:156–162. doi: 10.1097/BOT.0b013e3181be6720. [DOI] [PubMed] [Google Scholar]
- 6.Gardner M.J., Nork S.E., Huber P. Stiffness modulation of locking plate constructs using near cortical slotted holes: a preliminary study. J Orthop Trauma. 2009;23:281–287. doi: 10.1097/BOT.0b013e31819df775. [DOI] [PubMed] [Google Scholar]
- 7.Gardner M.J., Nork S.E., Huber P. Less rigid stable fracture fixation in osteoporotic bone using locked plates with near cortical slots. Injury. 2010;41:652–656. doi: 10.1016/j.injury.2010.02.022. [DOI] [PubMed] [Google Scholar]
- 8.Sellei R.M., Garrison R.L., Kobbe P. Effects of near cortical slotted holes in locking plate constructs. J Orthop Trauma. 2011;25(Suppl. 1):S35–S40. doi: 10.1097/BOT.0b013e3182070f2d. [DOI] [PubMed] [Google Scholar]
- 9.Linn M.S., McAndrew C.M., Prusaczyk B., Brimmo O., Ricci W.M., Gardner M.J. Dynamic locked plating of distal femur fractures. J Orthop Trauma. 2015;29:447–450. doi: 10.1097/BOT.0000000000000315. [DOI] [PubMed] [Google Scholar]
- 10.Muller M.E., Nazarian S., Koch P., Schatzker J. Springer Verlag; 1990. The Comprehensive Classification of Fractures of Long Bones. [Google Scholar]
- 11.Claes L.E., Heigele C.A. Magnitudes of local stress and strain along bony surfaces predict the course and type of fracture healing. J Biomech. 1999;32:255–266. doi: 10.1016/s0021-9290(98)00153-5. [DOI] [PubMed] [Google Scholar]
- 12.Curtis R., Goldhahn J., Schwyn R. Fixation principles in metaphyseal bone–a patent based review. Osteoporos Int. 2005;16(Suppl. 2):S54–S64. doi: 10.1007/s00198-004-1763-6. [DOI] [PubMed] [Google Scholar]
- 13.Bottlang M., Lesser M., Koerber J. Far cortical locking can improve healing of fractures stabilized with locking plates. J Bone Joint Surg Am. 2010;92:1652–1660. doi: 10.2106/JBJS.I.01111. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Bottlang M., Fitzpatrick D.C., Sheerin D. Dynamic fixation of distal femur fractures using far cortical locking screws: a prospective observational study. J Orthop Trauma. 2014;28:181–188. doi: 10.1097/01.bot.0000438368.44077.04. [DOI] [PubMed] [Google Scholar]
- 15.Pohlemann T., Gueorguiev B., Agarwal Y. Dynamic locking screw improves fixation strength in osteoporotic bone: an in vitro study on an artificial bone model. Int Orthop. 2015;39(4):761–768. doi: 10.1007/s00264-014-2658-6. [DOI] [PubMed] [Google Scholar]