The effect of surgeon-controlled variables on construct stiffness in lateral locked plating of distal femoral fractures

Background

Nonunion following treatment of supracondylar femur fractures with lateral locked plates (LLP) has been reported to be as high as 21 %. Implant related and surgeon-controlled variables have been postulated to contribute to nonunion by modulating fracture-fixation construct stiffness. The purpose of this study is to evaluate the effect of surgeon-controlled factors on stiffness when treating supracondylar femur fractures with LLPs:

Does plate length affect construct stiffness given the same plate material, fracture working length and type of screws?

Does screw type (bicortical locking versus bicortical nonlocking or unicortical locking) and number of screws affect construct stiffness given the same material, fracture working length, and plate length?

Does fracture working length affect construct stiffness given the same plate material, length and type of screws?

Does plate material (titanium versus stainless steel) affect construct stiffness given the same fracture working length, plate length, type and number of screws?

Methods

Mechanical study of simulated supracondylar femur fractures treated with LLPs of varying lengths, screw types, fractureworking lenghts, and plate/screw material. Overall construct stiffness was evaluated using an Instron hydraulic testing apparatus.

Results

Stiffness was 15 % higher comparing 13-hole to the 5-hole plates (995 N/mm849N vs. /mm, p = 0.003). The use of bicortical nonlocking screws decreased overall construct stiffness by 18 % compared to bicortical locking screws (808 N/mm vs. 995 N/mm, p = 0.0001). The type of screw (unicortical locking vs. bicortical locking) and the number of screws in the diaphysis (3 vs. 10) did not appear to significantly influence construct stiffness (p = 0.76, p = 0.24). Similarly, fracture working length (5.4 cm vs. 9.4 cm, p = 0.24), and implant type (titanium vs. stainless steel, p = 0.12) did also not appear to effect stiffness.

Discussion

Using shorter plates and using bicortical nonlocking screws (vs. bicortical locking screws) reduced overall construct stiffness. Using more screws, using unicortical locking screws, increasing fracture working length and varying plate material (titanium vs. stainless steel) does not appear to significantly alter construct stiffness. Surgeons can adjust plate length and screw types to affect overall fracture-fixation construct stiffness; however, the optimal stiffness to promote healing remains unknown.

The Epidemiology of Adult Distal Femoral Shaft Fractures in a Central London Major Trauma Centre Over Five Years

Background:

Distal femoral fractures account for 3-6% of adult femoral fractures and 0.4% of all fractures and are associated with significant morbidity and mortality rates. As countries develop inter-hospital trauma networks and adapt healthcare policy for an aging population there is growing importance for research within this field.

Methods:

Hospital coding and registry records at the central London Major Trauma Center identified 219 patients with distal femoral shaft fractures that occurred between December 2010 and January 2016. CT-Scans were reviewed resulting in exclusion of 73 inappropriately coded, 10 pediatric and 12 periprosthetic cases. Demographics, mechanism of injury, AO/OTA fracture classification and management were analyzed for the remaining 124 patients with 125 fractures. Mann Whitney U and Chi Squared tests were used during analyses.

Results:

The cases show bimodal distribution with younger patients being male (median age 65.6) compared to female (median age 71). Injury caused through high-energy mechanisms were more common in men (70.5%) whilst women sustained injuries mainly from low-energy mechanisms (82.7%) (p<0.0001). Majority of fractures were 33-A (52.0%) followed by 33-B (30.4%) and 33-C (17.6%). Ninety-two (73.6%) underwent operative management. The most common operation was locking plates (64.1%) followed by intramedullary nailing (19.6%).

Interpretation:

The epidemiology of a rare fracture pattern with variable degrees of complexity is described. A significant correlation between biological sex and mechanism of injury was identified. The fixation technique favored was multidirectional locking plates. Technical requirements for fixation and low prevalence of 33-C fractures warrant consideration of locating treatment at centers with high caseloads and experience.